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Sample records for cu-doped cds nanocrystals

  1. Swift heavy ion irradiation effect on Cu-doped CdS nanocrystals embedded in PMMA

    Indian Academy of Sciences (India)

    Shweta Agrawal; Subodh Srivastava; Sumit Kumar; S S Sharma; B Tripathi; M Singh; Y K Vijay

    2009-12-01

    Semiconductor nanocrystals (NCs) have received much interest for their optical and electronic properties. When these NCs dispersed in polymer matrix, brightness of the light emission is enhanced due to their quantum dot size. The CdCuS NCs have been synthesized by chemical route method and then dispersed in PMMA matrix. These nanocomposite polymer films were irradiated by swift heavy ion (SHI) (100 MeV, Si+7 ions beam) at different fluences of 1 × 1010 and 1 × 1012 ions/cm2 and then compared their structural and optical properties by XRD, atomic force microscopy, photoluminescence, and UV-Vis spectroscopy before and after irradiation. The XRD spectra showed a broad hump around 2 ≈ 11.83° due to amorphous PMMA and other peaks corresponding to hexagonal structure of CdS nanocrystals in PMMA matrix. The photoluminescence spectra shows a broad peak at 530 nm corresponding to green emission due to Cu impurities in CdS. The UV-Vis measurement showed red shift in optical absorption and bandgap changed from 4.38–3.60 eV as the irradiation fluency increased with respect to pristine CdCuS nanocomposite polymer film.

  2. Effects of Different Doping Ratio of Cu Doped CdS on QDSCs Performance

    Directory of Open Access Journals (Sweden)

    Xiaojun Zhu

    2015-01-01

    Full Text Available We use the successive ionic layer adsorption and reaction (SILAR method for the preparation of quantum dot sensitized solar cells, to improve the performance of solar cells by doping quantum dots. We tested the UV-Vis absorption spectrum of undoped CdS QDSCs and Cu doped CdS QDSCs with different doping ratios. The doping ratios of copper were 1 : 100, 1 : 500, and 1 : 1000, respectively. The experimental results show that, under the same SILAR cycle number, Cu doped CdS quantum dot sensitized solar cells have higher open circuit voltage, short circuit current density photoelectric conversion efficiency than undoped CdS quantum dots sensitized solar cells. Refinement of Cu doping ratio are 1 : 10, 1 : 100, 1 : 200, 1 : 500, and 1 : 1000. When the proportion of Cu and CdS is 1 : 10, all the parameters of the QDSCs reach the minimum value, and, with the decrease of the proportion, the short circuit current density, open circuit voltage, and the photoelectric conversion efficiency are all increased. When proportion is 1 : 500, all parameters reach the maximum values. While with further reduction of the doping ratio of Cu, the parameters of QDSCs have a decline tendency. The results showed that, in a certain range, the lower the doping ratio of Cu, the better the performance of quantum dot sensitized solar cell.

  3. Cu doping concentration effect on the physical properties of CdS thin films obtained by the CBD technique

    Science.gov (United States)

    Albor Aguilera, M. L.; Flores Márquez, J. M.; Remolina Millan, A.; Matsumoto Kuwabara, Y.; González Trujillo, M. A.; Hernández Vásquez, C.; Aguilar Hernandez, J. R.; Hernández Pérez, M. A.; Courel-Piedrahita, M.; Madeira, H. T. Yee

    2017-08-01

    Cu(In, Ga)Se2 (CIGS) and Cu2ZnSnS4 (CZTS) semiconductors are direct band gap materials; when these types of material are used in solar cells, they provide efficiencies of 22.1% and 12.6%, respectively. Most traditional fabrication methods involve expensive vacuum processes including co-evaporation and sputtering techniques, where films and doping are conducted separately. On the other hand, the chemical bath deposition (CBD) technique allows an in situ process. Cu-doped CdS thin films working as a buffer layer on solar cells provide good performing devices and they may be deposited by low cost techniques such as chemical methods. In this work, Cu-doped CdS thin films were deposited using the CBD technique on SnO2:F (FTO) substrates. The elemental analysis and mapping reconstruction were conducted by EDXS. Morphological, optical and electrical properties were studied, and they revealed that Cu doping modified the CdS structure, band-gap value and the electrical properties. Cu-doped CdS films show high resistivity compared to the non-doped CdS. The appropriate parameters of Cu-doped CdS films were determined to obtain an adequate window or buffer layer on CIGS and CZTS photovoltaic solar cells.

  4. CdS quantum dots sensitized Cu doped ZnO nanostructured thin films for solar cell applications

    Science.gov (United States)

    Poornima, K.; Gopala Krishnan, K.; Lalitha, B.; Raja, M.

    2015-07-01

    ZnO nanorods and Cu doped ZnO nanorods thin films have been prepared by simple hydrothermal method. CdS quantum dots are sensitized with Cu doped ZnO nanorod thin films using successive ionic layer adsorption and reaction (SILAR) method. The X-ray diffraction study reveals that ZnO nanorods, and CdS quantum dot sensitized Cu doped ZnO nanorods exhibit hexagonal structure. The scanning electron microscope image shows the presence of ZnO nanorods. The average diameter and length of the aligned nanorod is 300 nm and 1.5 μm respectively. The absorption spectra shows that the absorption edge of CdS quantum dot sensitized ZnO nanorod thin film is shifted toward longer wavelength region when compared to the absorption edge of ZnO nanorods film. The conversion efficiency of the CdS quantum dot sensitized Cu doped ZnO nanorod thin film solar cell is 1.5%.

  5. Biomaterials supported CdS nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Balu, Alina M. [Institute of Physical Chemistry ' Ilie Murgulescu' , Spl. Independentei 202, 060021 Bucharest (Romania); Departamento de Quimica Organica, Campus de Rabanales, Edificio Marie Curie, Ctra Nnal IV, Km 396, Universidad de Cordoba, E-14014 Cordoba (Spain); Campelo, Juan M. [Departamento de Quimica Organica, Campus de Rabanales, Edificio Marie Curie, Ctra Nnal IV, Km 396, Universidad de Cordoba, E-14014 Cordoba (Spain); Luque, Rafael, E-mail: q62alsor@uco.es [Departamento de Quimica Organica, Campus de Rabanales, Edificio Marie Curie, Ctra Nnal IV, Km 396, Universidad de Cordoba, E-14014 Cordoba (Spain); Rajabi, Fatemeh [Department of Science, Payame Noor University, PO Box 878, Qazvin (Iran, Islamic Republic of); Romero, Antonio A. [Departamento de Quimica Organica, Campus de Rabanales, Edificio Marie Curie, Ctra Nnal IV, Km 396, Universidad de Cordoba, E-14014 Cordoba (Spain)

    2010-11-01

    CdS quantum dot materials were prepared through a simple room temperature deposition of CdS nanocrystals on biomaterials including starch and chitosan. Materials obtained were found to contain differently distributed CdS nanocrystals on the surface of the biopolymers, making them potentially interesting for biomedical applications as contrast agents and/or in photocatalysis.

  6. Cu-doped CdS and its application in CdTe thin film solar cell

    Science.gov (United States)

    Deng, Yi; Yang, Jun; Yang, Ruilong; Shen, Kai; Wang, Dezhao; Wang, Deliang

    2016-01-01

    Cu is widely used in the back contact formation of CdTe thin film solar cells. However, Cu is easily to diffuse from the back contact into the CdTe absorber layer and even to the cell junction interface CdS/CdTe. This phenomenon is generally believed to be the main factor affecting the CdTe solar cell stability. In this study Cu was intentionally doped in CdS thin film to study its effect on the microstructural, optical and electrical properties of the CdS material. Upon Cu doping, the VCd- and the surface-state-related photoluminescence emissions were dramatically decreased/quenched. The presence of Cu atom hindered the recrystallization/coalescence of the nano-sized grains in the as-deposited CdS film during the air and the CdCl2 annealing. CdTe thin film solar cell fabricated with Cu-doped CdS window layers demonstrated much decreased fill factor, which was induced by the increased space-charge recombination near the p-n junction and the worsened junction crystalline quality. Temperature dependent current-voltage curve measurement indicated that the doped Cu in the CdS window layer was not stable at both room and higher temperatures.

  7. Cu-doped CdS and its application in CdTe thin film solar cell

    Directory of Open Access Journals (Sweden)

    Yi Deng

    2016-01-01

    Full Text Available Cu is widely used in the back contact formation of CdTe thin film solar cells. However, Cu is easily to diffuse from the back contact into the CdTe absorber layer and even to the cell junction interface CdS/CdTe. This phenomenon is generally believed to be the main factor affecting the CdTe solar cell stability. In this study Cu was intentionally doped in CdS thin film to study its effect on the microstructural, optical and electrical properties of the CdS material. Upon Cu doping, the VCd− and the surface-state-related photoluminescence emissions were dramatically decreased/quenched. The presence of Cu atom hindered the recrystallization/coalescence of the nano-sized grains in the as-deposited CdS film during the air and the CdCl2 annealing. CdTe thin film solar cell fabricated with Cu-doped CdS window layers demonstrated much decreased fill factor, which was induced by the increased space-charge recombination near the p-n junction and the worsened junction crystalline quality. Temperature dependent current-voltage curve measurement indicated that the doped Cu in the CdS window layer was not stable at both room and higher temperatures.

  8. Cu-doped CdS and its application in CdTe thin film solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Yi [School of Automation, Wuhan University of Technology, Wuhan, Hubei 430070 (China); College of Electronic and Information Engineering, Hankou University, Wuhan, Hubei 430212 (China); Yang, Jun; Yang, Ruilong; Shen, Kai; Wang, Dezhao [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wang, Deliang, E-mail: eedewang@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Key Laboratory of Materials for Energy Conversion, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2016-01-15

    Cu is widely used in the back contact formation of CdTe thin film solar cells. However, Cu is easily to diffuse from the back contact into the CdTe absorber layer and even to the cell junction interface CdS/CdTe. This phenomenon is generally believed to be the main factor affecting the CdTe solar cell stability. In this study Cu was intentionally doped in CdS thin film to study its effect on the microstructural, optical and electrical properties of the CdS material. Upon Cu doping, the V{sub Cd{sup −}} and the surface-state-related photoluminescence emissions were dramatically decreased/quenched. The presence of Cu atom hindered the recrystallization/coalescence of the nano-sized grains in the as-deposited CdS film during the air and the CdCl{sub 2} annealing. CdTe thin film solar cell fabricated with Cu-doped CdS window layers demonstrated much decreased fill factor, which was induced by the increased space-charge recombination near the p-n junction and the worsened junction crystalline quality. Temperature dependent current-voltage curve measurement indicated that the doped Cu in the CdS window layer was not stable at both room and higher temperatures.

  9. Effect of Cu-doping on optical, electrical and magnetic properties of chemically synthesized MnS nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Veeramanikandasamy, T., E-mail: veeramaniks@gmail.com [Department of Electronics and Communication Systems, Sri Krishna Arts and Science College, Coimbatore 641 008 (India); Rajendran, K. [Department of Electronics, L.R.G Govt. Arts College for Women, Tirupur 641 604 (India); Sambath, K. [Department of Electronics and Communication Systems, Sri Krishna Arts and Science College, Coimbatore 641 008 (India); Rameshbabu, P. [Center for Crystal Growth, VIT University, Vellore 632 014 (India)

    2016-03-01

    Manganese sulfide and Cu-doped manganese sulfide nanocrystals have been synthesized by wet chemical technique. The structural, optical, electrical and magnetic properties of as-synthesized nanocrystals have been investigated. The average crystallite size and lattice strain of the samples have been calculated from powder X-ray diffraction patterns using the Williamson–Hall analysis. The results show that the average crystallite size decreased while both the lattice strain and the dislocation density values increased in the Cu-doped MnS nanocrystals. The surface morphology of Cu-doped MnS nanocrystals has lesser particle size than undoped sample and it shows spherical like structures with little agglomeration. The chemical composition of the prepared samples has been obtained from EDAX. It clearly indicates the presence of Cu ions in the MnS lattice. UV–visible spectroscopy shows a blue shift in the optical band gap with doping. The photoluminescence spectra on the doped sample show a quenching of the PL intensity due to strain induced by doping. The electrical conduction, dielectric and impedance properties of as-synthesized nanocrystals have been investigated in the frequency range 50 Hz–5 MHz and temperature range 323–473 K which are greatly affected by doping with Cu. The vibrating sample magnetometer measurement revealed that the undoped MnS has paramagnetic behavior while the Cu-doped MnS has superparamagnetic behavior. On Cu-doping, the saturation magnetization and remanence increases while the coercivity decreases. - Highlights: • Pure and Cu-doped MnS nanocrystals were synthesized by the wet chemical technique. • Optical band gap value is raised by the Burstein-Moss effect due to the introduction of Cu-dopant. • It is a potential material for violet-blue light emission. • Cu-doped MnS showed good electrical conductivity compared to pure γ-MnS. • Doping of Cu induces superparamagnetic behavior in the system.

  10. Structural and Photoelectrochemical Properties of Cu-Doped CdS Thin Films Prepared by Ultrasonic Spray Pyrolysis

    Directory of Open Access Journals (Sweden)

    Rui Xie

    2013-01-01

    Full Text Available Cu-doped CdS thin films of variable doping levels have been deposited on indium tin oxide-coated glass substrate by simple and cost-effective ultrasonic spray pyrolysis. The influences of doping concentration and annealing treatment on the structure and photoelectrochemical properties of the films were investigated. The deposited films were characterized by XRD, SEM, and UV-Vis spectra. Moreover, the films were investigated by electrochemical and photoelectrochemical measurements with regard to splitting water for solar energy conversion. The results showed that the Cu impurity can cause a structural change and red shift of absorption edge. It was found that the photocurrent can be improved by the Cu-doping process for the unannealed films under the weak illumination. The unannealed 5 at.% Cu-doped sample obtained the maximum IPCE, which achieved about 45% at 0.3 V versus SCE potential under 420 nm wavelength photoirradiation. In addition, the p-type CdS was formed with a doping of 4 at.%~10 at.% Cu after 450°C 2 h annealed in vacuum.

  11. Multicolored luminescent CdS nanocrystals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The observation of efficient blue, green, orange and red luminescence from CdS nanocrystals made by using a reverse micelle method was reported. The blue luminescence about 480 nm is attributed to the radiative recombination of electron-hole pairs.The red luminescence around 650 nm is due to the radiative recombination of the exciton trapped in the nanocrystal surface defect states. The combination of different portion of band-edge emission and surface trap state emission results in green and orange luminescence for the nanocrystals. The CdS nanocrystals with efficient multicolored luminescence may find potential application in full color displays and biolabelings.

  12. Simultaneous control of nanocrystal size and nanocrystal{nanocrystal separation in CdS nanocrystal assembly

    Indian Academy of Sciences (India)

    Sameer Sapra; D D Sarma

    2005-10-01

    We report an easy, one pot synthesis to prepare ordered CdS nanocrystals with varying inter-particle separation and characterize the particle separation using x-ray diffraction at low and wide angles.

  13. Enhanced photovoltaic performance of quantum dot-sensitized solar cells with a progressive reduction of recombination using Cu-doped CdS quantum dots

    Science.gov (United States)

    Muthalif, Mohammed Panthakkal Abdul; Lee, Young-Seok; Sunesh, Chozhidakath Damodharan; Kim, Hee-Je; Choe, Youngson

    2017-02-01

    In this article, we have systematically probed the effect of Cu-doping in CdS quantum dots (QDs) to enhance the photovoltaic performance of the quantum dot-sensitized solar cells (QDSSCs). The Cu-doped CdS photoanodes were prepared by successive ionic layer adsorption and reaction (SILAR) method and the corresponding cell devices were fabricated using CuS counter electrodes with a polysulfide electrolyte. The photovoltaic performance results demonstrate that 3 mM Cu-doped CdS QDs based QDSSCs exhibit the efficiency (η) of 3% including JSC = 9.40 mA cm-2, VOC = 0.637 V, FF = 0.501, which are higher than those with bare CdS (η = 2.05%, JSC = 7.12 mA cm-2, VOC = 0.588 V, FF = 0.489). The structural, topographical and optical properties of the thin films have been studied with the help of X-ray diffraction pattern (XRD), atomic force microscopy (AFM) and UV-vis spectrophotometer. Electrochemical impedance spectroscopy (EIS) and open circuit voltage decay (OCVD) measurements indicate that Cu-dopant can inhibit the charge recombination at the photoanode/electrolyte interface and extend the lifetime of electrons. These results reveal that incorporation of copper metal in CdS QDs is a simple and effective method to improve the photovoltaic properties of QDSSCs.

  14. Synthesis and characterization of Cu doped cobalt oxide nanocrystals as methane gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Sheikhi Mehrabadi, Z; Ahmadpour, A [Nanotechnology Research Center, Department of Chemical Engineering, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Shahtahmasebi, N [Nanotechnology Research Center, Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Bagheri Mohagheghi, M M, E-mail: m_mohagheghee@yahoo.co.uk [School of Physics, Damghan University, Damghan (Iran, Islamic Republic of)

    2011-07-01

    In this paper, nanoparticles of copper-cobalt compound oxide have been prepared by the sol-gel technique with different mole ratios of Cu/Co (ranging from 0.05 to 0.15) for the detection of methane gas, which is chemically a very stable hydrocarbon. The structural properties and morphology of the powders were studied by x-ray diffraction (XRD), Fourier transform infrared spectroscopy and transmission electron microscopy (TEM). By XRD analysis, we confirm that Co{sub 3}O{sub 4} and (CuO{sub 0.3}CoO{sub 0.7}) Co{sub 2}O{sub 4} phases are formed and mean grain size is decreased with increasing Cu doping (from 28 to 24 nm). On the basis of TEM images, it is found that these particles possess a cubic structure with nearly uniform distribution. Also, gas-sensing measurements reveal that the optimal operating temperature is 300 {sup 0}C, that the use of Cu as a dopant improved the sensing properties of cobalt oxide and that the sensitivity increased considerably with Cu concentration. The best sensitivity properties of nanosensors have been found at the mole ratios of Cu/Co of 0.125 and 0.15.

  15. Growth Mechanisms of CdS Nanocrystals in Aqueous Media

    Directory of Open Access Journals (Sweden)

    Loredana Latterini

    2012-06-01

    Full Text Available CdS nanocrystals were prepared in water-in-oil microemulsions. The nanocrystal properties, absorption and luminescence spectra and size distributions, were monitored at different times after mixing the microemulsions of the two precursors to obtain information on their growth mechanism. In particular, CdS nanocrystals were prepared using water-in-heptane or water-in-nonane microemulsions. The results obtained from the investigation of nanocrystals prepared using heptane as the organic phase, confirmed that nanocrystal nucleation is fast while their growth is determined by droplet exchange content rate. Size distribution histograms obtained from the sample at early time points after mixing presented a bimodal population having average sizes of 3.0 ± 0.1 and 5.8 ± 0.1 nm, thus indicating that surface process controls the nanocrystal growth. With longer reaction times the occurrence of water droplet coalescence is likely responsible for the formation of nanocrystal agglomerates. Using a water-in-nonane microemulsion, the droplet exchange rate can be modified, thus leading to smaller CdS nanocrystals. However, the development of structural defects cannot be excluded, as evidenced by the luminescence spectra of the suspension. In general, aging of the nanocrystal in the pristine microemulsion resulted in the development of cubic semiconductor nanostructures.

  16. Effect of Al3+ co-doping on the dopant local structure, optical properties, and exciton dynamics in Cu+-doped ZnSe nanocrystals.

    Science.gov (United States)

    Gul, Sheraz; Cooper, Jason Kyle; Glans, Per-Anders; Guo, Jinghua; Yachandra, Vittal K; Yano, Junko; Zhang, Jin Zhong

    2013-10-22

    The dopant local structure and optical properties of Cu-doped ZnSe (ZnSe:Cu) and Cu and Al co-doped ZnSe (ZnSe:Cu,Al) nanocrystals (NCs) were studied with an emphasis on understanding the impact of introducing Al as a co-dopant. Quantum-confined NCs with zinc blende crystal structure and particle size of 6 ± 0.6 Å were synthesized using a wet chemical route. The local structure of the Cu dopant, studied by extended X-ray absorption fine structure, indicated that Cu in ZnSe:Cu NCs occupies a site that is neither substitutional nor interstitial and is adjacent to a Se vacancy. Additionally, we estimated that approximately 25 ± 8% of Cu was located on the surface of the NC. Al(3+) co-doping aids in Cu doping by accounting for the charge imbalance originated by Cu(+) doping and consequently reduces surface Cu doping. The Cu ions remain distorted from the center of the tetrahedron to one of the triangular faces. The lifetime of the dopant-related photoluminescence was found to increase from 550 ± 60 to 700 ± 60 ns after Al co-doping. DFT calculations were used to obtain the density of states of a model system to help explain the optical properties and dynamics processes observed. This study demonstrates that co-doping using different cations with complementary oxidation states is an effective method to enhance optical properties of doped semiconductor NCs of interest for various photonics applications.

  17. Synthesis of Cu-doped InP nanocrystals (d-dots) with ZnSe diffusion barrier as efficient and color-tunable NIR emitters.

    Science.gov (United States)

    Xie, Renguo; Peng, Xiaogang

    2009-08-05

    Efficient Cu-doped InP quantum dots (Cu:InP d-dots) emitters were successfully synthesized by epitaxial growth of a ZnSe diffusion barrier for the dopants. The Cu dopant emission of the Cu:InP/ZnSe core/shell d-dots covered the important red and near-infrared (NIR) window for biomedical applicaitons, from 630 to 1100 nm, by varying the size of the InP host nanocrystals. These new d-dots emitters not only compensate for the emission wavelength of the existing noncadmium d-dots emitters, Cu- and Mn-doped ZnSe d-dots (450-610 nm), but also offer a complete series of efficient nanocrystal emitters based on InP nanocrystals. The one-pot synthetic scheme for the formation of Cu:InP/ZnSe core/shell d-dots was successfully established by systematically studying the doping process, the dopant concentration-dependent photophysical properties, and the dopant diffusion during shell epitaxy, etc. Complete elimination of InP bandgap emission and efficient pure dopant emission (with photoluminescence quantum yield as high as between 35-40%) of the core/shell d-dots were achieved by optimizing the final doping level and the diffusion barrier thickness.

  18. Luminescence in Mn-doped CdS nanocrystals

    Indian Academy of Sciences (India)

    Angshuman Nag; Sameer Sapra; Subhra Sen Gupta; Ankita Prakash; Ajit Ghangrekar; N Periasamy; D D Sarma

    2008-06-01

    We have synthesized Mn-doped CdS nanocrystals (NCs) with size ranging from 1.8–3 nm. Photoluminescence (PL) spectra of the doped NCs differ from that of the undoped NCs with an additional peak due to Mn – transitions. Electron paramagnetic resonance spectra along with X-ray absorption spectroscopy and PL spectra confirm the incorporation of Mn in the CdS lattice. The fact that emissions from surface states and the Mn levels occur at two different energies, allowed us to study the PL lifetime decay behaviour of both kinds of emissions.

  19. Hot-Injection Synthesis of Cu-Doped Cu₂ZnSnSe₄ Nanocrystals to Reach Thermoelectric zT of 0.70 at 450°C.

    Science.gov (United States)

    Chen, Dongsheng; Zhao, Yan; Chen, Yani; Wang, Biao; Wang, Yuanyuan; Zhou, Jun; Liang, Ziqi

    2015-11-11

    As a new class of potential midrange temperature thermoelectric materials, quaternary chalcogenides like Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) suffer from low electrical conductivity due to insufficient doping. In this work, Cu-doped CZTSe nanocrystals consisting of polygon-like nanoparticles are synthesized with sufficient Cu doping contents. The hot-injection synthetic method, rather than the traditional one-pot method, in combination with the hot-pressing method is employed to produce the CZTSe nanocrystals. In Cu-doped CZTSe nanocrystals, the electrical conductivity is enhanced by substitution of Zn(2+) with Cu(+), which introduces additional holes as charge carriers. Meanwhile, the existence of boundaries between nanoparticles in as-synthesized CZTSe nanocrystals collectively results in intensive phonon-boundary scatterings, which remarkably reduce the lattice thermal conductivity. As a result, an average thermoelectric figure of merit of 0.70 is obtained at 450 °C, which is significantly larger than that of the state-of-the-art quaternary chalcogenides thermoelectric materials. The theoretical calculations from the Boltzmann transport equations and the modified effective medium approximation are in good agreement with the experimental data.

  20. Facile Synthesis of Monodisperse CdS Nanocrystals via Microreaction

    Directory of Open Access Journals (Sweden)

    Zhou Xinggui

    2009-01-01

    Full Text Available Abstract CdS-based nanocrystals (NCs have attracted extensive interest due to their potential application as key luminescent materials for blue and white LEDs. In this research, the continuous synthesis of monodisperse CdS NCs was demonstrated utilizing a capillary microreactor. The enhanced heat and mass transfer in the microreactor was useful to reduce the reaction temperature and residence time to synthesize monodisperse CdS NCs. The superior stability of the microreactor and its continuous operation allowed the investigation of synthesis parameters with high efficiency. Reaction temperature was found to be a key parameter for balancing the reactivity of CdS precursors, while residence time was shown to be an important factor that governs the size and size distribution of the CdS NCs. Furthermore, variation of OA concentration was demonstrated to be a facile tuning mechanism for controlling the size of the CdS NCs. The variation of the volume percentage of OA from 10.5 to 51.2% and the variation of the residence time from 17 to 136 s facilitated the synthesis of monodisperse CdS NCs in the size range of 3.0–5.4 nm, and the NCs produced photoluminescent emissions in the range of 391–463 nm.

  1. A steady blue-emitting CdS nanocrystals-polystyrene composites

    Energy Technology Data Exchange (ETDEWEB)

    Xue, H.T. [Nanjing University of Posts and Telecommunications, Department of Applied Physics, Nanjing (China); Zhao, P.Q. [Nanjing University of Technology, Department of Applied Physics, Nanjing (China); Nanjing University, Department of Physics, Nanjing (China)

    2013-02-15

    CdS nanocrystals with narrow size distribution were synthesized in an organic solution and transparent CdS nanocrystals/polystyrene composite films were fabricated. Transmission electron microscopy, energy dispersive X-ray spectroscopy, photoluminescence and Raman spectra were adopted to investigate these samples. The result of photoluminescence measurement shows that the composite films exhibit distinct luminescence properties of more stable emission and a narrower full-width at half-maximum than that of CdS nanocrystals in solution. Detailed analysis of the Raman spectra has enabled us to identify the origin of the optimized optoelectronic properties of the CdS nanocrystals-polystyrene composites films. (orig.)

  2. Influence of the dopant concentration on structural, optical and photovoltaic properties of Cu-doped ZnS nanocrystals based bulk heterojunction hybrid solar cells

    Science.gov (United States)

    Jabeen, Uzma; Adhikari, Tham; Shah, Syed Mujtaba; Pathak, Dinesh; Wagner, Tomas; Nunzi, Jean-Michel

    2017-06-01

    Zinc sulphide (ZnS) and Cu-doped ZnS nanoparticles were synthesized by the wet chemical method. The nanoparticles were characterized by UV-visible, fluorescence, fourier transform infra-red (FTIR) spectrometry, X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). Scanning electron microscopy supplemented with EDAX was employed to observe the morphology and chemical composition of the un-doped and doped samples. A significant blue shift of the absorption band with respect to the un-doped zinc sulphide was sighted by increasing the Cu concentration in the doped sample with decreasing the size of nanoparticles. Consequently, the band gap was tuned from 3.13 to 3.49 eV due to quantum confinement. The green emission arises from the recombination between the shallow donor level (sulfur vacancy) and the t2 level of Cu2+. However, the fluorescence emission spectrum of the undoped ZnS nanoparticles was deconvoluted into two bands, which are centered at 419 and 468 nm. XRD analysis showed that the nanomaterials were in cubic crystalline state. XRD peaks show that there were no massive crystalline distortions in the crystal lattice when the Cu concentration (0.05-0.1 M) was increased in the ZnS lattice. However, in the case of Cu-doped samples (0.15-0.2 M), the XRD pattern showed an additional peak at 37° due to incomplete substitution occurring during the experimental reaction step. A comparative study of surfaces of undoped and Cu-doped ZnS nanoparticles were investigated using X-ray photoelectron spectroscopy (XPS). The synthesized nanomaterial in combination with poly(3-hexylthiophene) (P3HT) was used in the fabrication of solar cells. The devices with ZnS nanoparticles showed an efficiency of 0.31%. The overall power conversion efficiency of the solar cells at 0.1 M Cu content in doped ZnS nanoparticles was found to be 1.6 times higher than the

  3. Defect evolution and its impact on the ferromagnetism of Cu-doped ZnO nanocrystals upon thermal treatment: A positron annihilation study

    Science.gov (United States)

    Chen, Zhi-Yuan; Chen, Yuqian; Zhang, Q. K.; Qi, N.; Chen, Z. Q.; Wang, S. J.; Li, P. H.; Mascher, P.

    2017-01-01

    CuO/ZnO nanocomposites with 4 at. % CuO were annealed in air at various temperatures between 100 and 1200 °C to produce Cu-doped ZnO nanocrystals. X-ray diffraction shows that a CuO phase can be observed in the CuO/ZnO nanocomposites annealed at different temperatures, and the Cu-doped ZnO nanocrystals are identified to be of wurtzite structure. The main peak (101) appears at slightly lower diffraction angles with increasing annealing temperature from 400 up to 1200 °C, which confirms the successful doping of Cu into the ZnO lattice above 400 °C. Scanning electron microscopy indicates that most particles in the CuO/ZnO nanocomposites are isolated when annealing at 100-400 °C, but these particles have a tendency to form clusters or aggregates as the annealing temperature increases from 700 to 1000 °C. Positron annihilation measurements reveal a large number of vacancy defects in the interface region of the nanocomposites, and they are gradually recovered with increasing annealing temperature up to 1000 °C. Room-temperature ferromagnetism can be observed in the CuO/ZnO nanocomposites, and the magnetization decreases continuously with increasing annealing temperature. However, there may be several different origins of ferromagnetism in the CuO/ZnO nanocomposites. At low annealing temperatures, the ferromagnetism originates from the CuO nanograins, and the ferromagnetism of CuO nanograins decreases with an increase in the grain size after subsequent higher temperature annealing, which leads to the weakening of ferromagnetism in the CuO/ZnO nanocomposites. After annealing from 400 to 1000 °C, the ferromagnetism gradually vanishes. The ferromagnetism is probably induced by Cu substitution but is mediated by vacancy defects in the CuO/ZnO nanocomposites. The disappearance of ferromagnetism coincides well with the recovery of vacancy defects. It can be inferred that the ferromagnetism is mediated by vacancy defects that are distributed in the interface region.

  4. Observation of the nano-effect on the SHG in moderately Cu-doped CdI2 thin nanocrystals

    Indian Academy of Sciences (India)

    M I Miah

    2015-09-01

    Nanocrystals take into account the nano-sized quantum-confined effect, where k-space bulk-like dispersion disappears and discrete excitonic-like nanolevels occur within the forbidden energy gap of the material processes. Nanocrystals of cadmium iodide both un-doped and doped with copper, synthesized and grown by the standard Bridgman method, were analysed by scanning electron microscopy for the investigation of the nano-confined effect on the optical nonlinearity. The second harmonic generation (SHG) of the crystals was measured and studied. The second-order optical susceptibilities in dependences of the size of the nanocrystals and of their copper contents within low levels were calculated. The results showed a clear increase in the SHG with the decrease in the thickness of the nanocrystals. The observed size dependence, however, demonstrates the nano-confined effect or nano-effect on the SHG, where the quantum confinement dominates the material’s optical properties. A significant change in the second-order optical response with copper content of the nanocrystals was also observed. The observed results are discussed by exploring the photo-induced electron–phonon anharmonic interaction for the noncentrosymmetry of the nanocrystallite’s process.

  5. Synthesis and Characterization of CdSe Nanocrystals Capped by CdS

    Institute of Scientific and Technical Information of China (English)

    SU Xing-guang; LIN Zhang-bi; HU Hai; ZHANG Jia-hua; JIN Qin-han

    2003-01-01

    CdSe semiconductor nanocrystals capped by CdS were synthesized in the aqueous solution with 2-mercaptoethanol as the stabilizer. The CdS capping with a higher band-gap than that of the core crystallite has successfully eliminated the surface traps. Optical absorption and fluorescence emission spectra were used to probe the effect of CdS passivation on the electronic structure of the nanocrystals. The composite CdSe/CdS nanocrystals exhibit strong, narrow(FWHM≤40 nm) and stable band-edge photoluminescence. X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy were used to analyze the composite nanocrystals and determine their average size, size distribution, shape, internal structure and elemental composition.

  6. Effect of Sulfur Precursor on Dimensions of One-dimensional CdS Nanocrystals

    Institute of Scientific and Technical Information of China (English)

    M. Maleki; Sh. Mirdamadi; R.Ghasemzadeh; M.Sasani Ghamsari

    2009-01-01

    One-dimensional CdS nanocrystals have been prepared by solvothermal method using cadmium acetate as a cadmium precursor, elemental sulfur and Na2S, as a sulfur precursor, and ethylenediamine as a solvent at 150℃ for 5 h. The nanocrystals were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis absorption spectroscopy. XRD patterns indicate that both Na2S and elemental sulfur as the sulfur precursor result in CdS nanorods with wurtzite phase (hexagonal structure). SEM and TEM images show that diameter of CdS nanorods can be decreased using Na2S instead of elemental sulfur. For the growth of CdS nanorods, a mechanism has been proposed. Uv-Vis absorption of CdS nanorods (sulfur precursor: Na2S) was shown blue shift to 485 nm due to the quantum size effect.

  7. Noninjection Synthesis of CdS and Alloyed CdSxSe1−xNanocrystals Without Nucleation Initiators

    Directory of Open Access Journals (Sweden)

    Zou Yu

    2010-01-01

    Full Text Available Abstract CdS and alloyed CdSxSe1−x nanocrystals were prepared by a simple noninjection method without nucleation initiators. Oleic acid (OA was used to stabilize the growth of the CdS nanocrystals. The size of the CdS nanocrystals can be tuned by changing the OA/Cd molar ratios. On the basis of the successful synthesis of CdS nanocrystals, alloyed CdSxSe1−x nanocrystals can also be prepared by simply replacing certain amount of S precursor with equal amount of Se precursor, verified by TEM, XRD, EDX as well as UV–Vis absorption analysis. The optical properties of the alloyed CdSxSe1−x nanocrystals can be tuned by adjusting the S/Se feed molar ratios. This synthetic approach developed is highly reproducible and can be readily scaled up for potential industrial production.

  8. Enzyme mediated synthesis of phytochelatin-capped CdS nanocrystals

    Science.gov (United States)

    Liu, Fang; Kang, Seung Hyun; Lee, Young-In; Choa, Yong-ho; Mulchandani, Ashok; Myung, Nosang V.; Chen, Wilfred

    2010-09-01

    We reported the enzyme mediated synthesis of CdS nanocrystals by immobilized phytochelatin synthase, which converts glutathione into the metal-binding peptide phytochelatin (PC). Formation of CdS nanocrystals were observed upon the addition of CdCl2 and Na2S with PC as the capping agent. By varying the reaction times, different compositions of PCs (form PC2 to PC3) can be synthesized, resulting in the formation of highly stable nanocrystals with tunable sizes (from 2.0 to 1.6 nm diameter). This approach may be generalized to guide the in vitro self assembly of a wide range of nanocrystals with different compositions and sizes.

  9. Shape and phase control of CdS nanocrystals using cationic surfactant in noninjection synthesis

    Directory of Open Access Journals (Sweden)

    Zou Yu

    2011-01-01

    Full Text Available Abstract Monodispersed CdS nanocrystals with controllable shape and phase have been successfully synthesized in this study by adding cationic surfactant in noninjection synthesis system. With the increase of the amount of cetyltrimethylammonium chloride (CTAC added, the shape of the CdS nanocrystals changed from spherical to multi-armed, and the phase changed from zinc-blende to wurtzite. It was found that halide ion Cl- plays a key role in the transformation, and other halide ions such as Br- can also induce similar transformation. We proposed that the strong binding between Cd2+ and halide ions reduced the reactivity of the precursors, decreased the nuclei formed in the nucleation stage, and led to the high concentration of precursor in the growth stage, resulting in the increase of size and phase transformation of CdS nanocrystals. In addition, it was found that the multi-armed CdS nanocrystals lost quantum confinement effect because of the increase of the size with the increase of the concentration of CTAC.

  10. Ionic liquid-assisted synthesis, structural characterization, and photocatalytic performance of CdS nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Yao Kaisheng [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu 730000 (China); School of Chemical Engineering and Pharmaceutics, Henan University of Science and Technology, Luoyang, Henan 471003 (China); Lu Weiwei [School of Chemical Engineering and Pharmaceutics, Henan University of Science and Technology, Luoyang, Henan 471003 (China); Wang Jianji, E-mail: jwang@henannu.edu.cn [School of Chemistry and Environmental Sciences, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, Henan Normal University, Xinxiang, Henan 453007 (China)

    2011-11-01

    Highlights: {yields} Short nanorods, quasi-nanospheres and faceted CdS NPs were prepared with the assistance of an IL. {yields} The CdS samples show hexagonal phase structures. {yields} Shape, size and crystallinity of the products could be controllably synthesized. {yields} The samples demonstrated a highly photocatalytic activity in the degradation of methyl orange. - Abstract: With the assistance of the ionic liquid trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentylphosphinate), we have successfully synthesized short nanorods, quasi-nanospheres and faceted CdS nanoparticles via thermal decomposition of cadmium diethyldithiocarbamate complexes. It was shown that the shape, size and crystallinity of the products could be controlled through delicate regulation of the reaction temperature, monomer concentration, reaction time, and ionic liquid ratio. We found that higher temperature was beneficial to the good crystallinity, while the lower temperature and higher monomer concentration were in favor of anisotropic structures. The used ionic liquid contributed to the formation of hexagonal phase CdS nanocrystals, and its ratio played an important role in determining the ultimate morphology of products. The possible mechanism for the formation CdS nanocrystals was proposed. Furthermore, the as-prepared CdS samples demonstrated a highly photocatalytic activity in the degradation of methyl orange under visible light irradiation.

  11. Microstructure analysis of chemically synthesized wurtzite-type CdS nanocrystals

    Indian Academy of Sciences (India)

    DEKA KULDEEP; KALITA M P C

    2016-05-01

    Microstructure of chemically synthesized wurtzite-type CdS nanocrystals have been investigated by X-ray diffraction (XRD) peak profile analysis by applying different forms of Williamson–Hall (WH) method viz., uniform deformation model (UDM), uniform stress deformation model (USDM) and uniform deformation energy density model (UDEDM), and transmission electron microscope (TEM) observations. The WH methods show the average crystallite size to beabout 10 nm. Strain, stress and energy density of the nanocrystals are found to be $1.18 \\times 10^{−2}, 0.43$ GPa and $2.27$ kJ m$^{−3}$, respectively. High-resolution TEM (HRTEM) results show the nanocrystals to be in spherical shape with an average crystallite size of 10 nm, thereby complementing the size estimation by WH methods. Further, HRTEM observations reveal the presence of edge dislocations and twin boundaries within the nanocrystals.

  12. Phase transfer of CdS nanocrystals mediated by heptamine β-cyclodextrin.

    Science.gov (United States)

    Depalo, Nicoletta; Comparelli, Roberto; Huskens, Jurriaan; Ludden, Manon J W; Perl, Andras; Agostiano, Angela; Striccoli, Marinella; Curri, M Lucia

    2012-06-12

    A fundamental and systematic study on the fabrication of a supramolecularly assembled nanostructure of an organic ligand-capped CdS nanocrystal (NC) and multiple heptamine β-cyclodextrin ((NH(2))(7)βCD) molecules in aqueous solution has been here reported. The functionalization process of presynthesized hydrophobic CdS NCs by means of (NH(2))(7)βCD has been extensively investigated by using different spectroscopic and structural techniques, as a function of different experimental parameters, such as the composition and the concentration of CD, the concentration of CdS NCs, the nature of the NC surface capping ligand (oleic acid and octylamine), and the organic solvent. The formation of a complex based on the direct coordination of the (NH(2))(7)βCD amine groups at the NC surface has been demonstrated and found responsible for the CdS NC phase transfer process. The amine functional group in (NH(2))(7)βCD and the appropriate combination of pristine capping agent coordinating the NC surface and a suitable solvent have been found decisive for the success of the CdS NC phase transfer process. Furthermore, a layer-by-layer assembly experiment has indicated that the obtained (NH(2))(7)βCD functionalized CdS NCs are still able to perform the host-guest chemistry. Thus, they offer a model of a nanoparticle-based material with molecular receptors, useful for bio applications.

  13. White light emitting Ho{sup 3+}-doped CdS nanocrystal ingrained glass nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Dey, Chirantan; Karmakar, Basudeb, E-mail: basudebk@cgcri.res.in [Glass Science and Technology Section, Glass Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata 700032 (India); Goswami, Madhumita [Glass and Advanced Materials Division, Bhaba Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2015-02-23

    We report the generation of white light from Ho{sup 3+} ion doped CdS nanocrystal ingrained borosilicate glass nanocomposites prepared by the conventional melt-quench method. Near visible 405 nm diode laser excited white light emission is produced by tuning the blue emission from the Ho{sup 3+} ions, green band edge, and orange-red surface-state emissions of the nanocrystalline CdS, which are further controlled by the size of the nanocrystals. The absorption and emission spectra evidenced the excitation of Ho{sup 3+} ions by absorption of photons emitted by the CdS nanocrystals. The high color rendering index (CRI = 84–89) and befitting chromaticity coordinates (x = 0.308–0.309, y = 0.326–0.338) of white light emission, near visible harmless excitation wavelength (405 nm), and high absorbance values at excitation wavelength point out that these glass nanocomposites may serve as a prominent candidate for resin free high power white light emitting diodes.

  14. Patterned structures of in situ size controlled CdS nanocrystals in a polymer matrix under UV irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Fragouli, D; Pompa, P P; Caputo, G; Cingolani, R; Athanassiou, A [NNL-National Nanotechnology Laboratory, INFM, CNR, Via Arnesano, 73100 Lecce (Italy); Resta, V; Laera, A M; Tapfer, L [ENEA, Centro Ricerche Brindisi, SS7 Appia Km 706, I-72100 Brindisi (Italy)], E-mail: despina.fragouli@unile.it

    2009-04-15

    A method of in situ formation of patterns of size controlled CdS nanocrystals in a polymer matrix by pulsed UV irradiation is presented. The films consist of Cd thiolate precursors with different carbon chain lengths embedded in TOPAS polymer matrices. Under UV irradiation the precursors are photolyzed, driving to the formation of CdS nanocrystals in the quantum size regime, with size and concentration defined by the number of incident UV pulses, while the host polymer remains macroscopically/microscopically unaffected. The emission of the formed nanocomposite materials strongly depends on the dimensions of the CdS nanocrystals, thus, their growth at the different phases of the irradiation is monitored using spatially resolved photoluminescence by means of a confocal microscope. X-ray diffraction measurements verified the existence of the CdS nanocrystals, and defined their crystal structure for all the studied cases. The results are reinforced by transmission electron microscopy. It is proved that the selection of the precursor determines the efficiency of the procedure, and the quality of the formed nanocrystals. Moreover it is demonstrated that there is the possibility of laser induced formation of well-defined patterns of CdS nanocrystals, opening up new perspectives in the development of nanodevices.

  15. Unusual Blueshifting of Optical Band Gap of CdS Nanocrystals through a Chemical Bath Deposition Method

    Directory of Open Access Journals (Sweden)

    Shu Qing Yuan

    2015-01-01

    Full Text Available CdS nanocrystals are synthesized through a chemical bath deposition method. After annealing, these nanocrystals are enlarged according to Scherrer’s formula. Small nanocrystals display wide band gaps as a result of the quantum effect experienced by nanocrystals of a certain size. However, the absorption edge and green and red emissions of annealed CdS nanocrystals show obvious blueshift compared with the as-grown ones. After annealing, the intensity ratio of these green and red emissions increases, which indicated that the defect states are reduced. Therefore, the improvement in crystalline quality and the reduced strain contribute to the unusual blueshifting of the optical band gap and of the green and red emissions.

  16. Preparation of Photoluminescence Tunable Cu-doped AgInS2 and AgInS2/ZnS Nanocrystals and Their Application as Cellular Imaging Probes.

    Science.gov (United States)

    Chen, Siqi; Demillo, Violeta; Lu, Minggen; Zhu, Xiaoshan

    In this work, high-quality Cu doped AIS and AIS/ZnS NCs have been first synthesized via a surface doping approach. By varying Cu concentrations in doping, Cu doped AIS NCs exhibit a photoluminescence red-shift from around 600 nm to 660 nm with a decrease of quantum yield from around 30% to 20%. After ZnS coating or zinc etching on the Cu doped AIS NCs, Cu doped AIS/ZnS NCs present photoluminescence peaks from around 570 nm to 610 nm and high quantum yields in the range of 50 ~ 60%. Moreover, it is found that Cu doping can prolong the photoluminescence lifetime of NCs, and the average photoluminescence lifetime of Cu doped AIS and AIS/ZnS NCs is in the range of 300 ~ 500 ns. The resultant Cu doped AIS/ZnS NCs were further encapsulated with amphiphilic polymers and used as biocompatible photoluminescent probes in cellular imaging. The cellular imaging study shows that peptide-conjugated probes can specifically target U-87 brain tumor cells and thus they can be applied to the detection of endogenous targets expressed on brain tumor cells.

  17. Cu-Doped-CdS/In-Doped-CdS Cosensitized Quantum Dot Solar Cells

    Directory of Open Access Journals (Sweden)

    Lin Li

    2014-01-01

    Full Text Available Cu-doped-CdS and In-doped-CdS cosensitized (Cu-doped-CdS/In-doped-CdS quantum dot solar cells (QDSCs are introduced here. Different cosensitized sequences, doping ratios, and the thickness (SILAR cycles of Cu-doped-CdS and In-doped-CdS are discussed. Compared with undoped CdS QDSCs, the short circuit current density, UV-Vis absorption spectra, IPCE (monochromatic incident photon-to-electron conversion, open circuit voltage, and so on are all improved. The photoelectric conversion efficiency has obviously improved from 0.71% to 1.28%.

  18. Facile microwave-assisted aqueous synthesis of CdS nanocrystals with their photocatalytic activities under visible lighting

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Chonghai, E-mail: chdeng@mail.ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026 (China); Department of Chemical and Materials Engineering, Hefei University, Hefei 230022 (China); Tian, Xiaobo [Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026 (China)

    2013-10-15

    Graphical abstract: - Highlights: • Three kinds of CdS nanostructures have been controllably synthesized. • Ethanediamine acts as a phase and morphology controlling reagent. • Three CdS nanostructures display high visible light photocatalytic activities. • Cubic CdS-3 shows superior photocatalytic activity to the other hexagonal CdS. • The growth processes for fabrication of CdS nanocrystals are also discussed. - Abstract: Three kinds of CdS nanostructures, that is, hexagonal nanospheres (CdS-1), hierarchical caterpillar-fungus-like hexagonal nanorods (CdS-2) and hierarchical cubic microspheres (CdS-3), were controllably synthesized by a facile and one-pot microwave-assisted aqueous chemical method using ethanediamine as a phase and morphology controlling reagent. The as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. The results show that CdS-1 is mainly composed of monodispersed hexagonal nanospheres with average diameters of about 100 nm; hexagonal CdS-2 has lengths in the range of 600–800 nm and diameters of 40–60 nm, assembled by nanoparticles about 20 nm in diameter; and CdS-3 is pure cubic microspheres with diameters in the range of 0.8–1.3 μm, aggregated by tiny nanograins with size of 5.8 nm. The band gap energies of CdS products were calculated to be 2.30, 2.31 and 2.24 eV observed from UV–vis DRS for CdS-1, CdS-2 and CdS-3, respectively. PL spectra of CdS samples showed that sphalerite CdS-3 possesses a very weak fluorescence, while wurtzite CdS-2 has a strongest green near-band edge emission (NBE) at 550 nm. The visible light photodegradation of methylene blue and rhodamine B in the presence of CdS photocatalysts illustrates that all of them display high photocatalytic activities. Significantly, the cubic CdS-3 exhibits more excellent photocatalytic

  19. Synthesis and Characterizations of Bare CdS Nanocrystals Using Chemical Precipitation Method for Photoluminescence Application

    Directory of Open Access Journals (Sweden)

    H. L. Lee

    2009-01-01

    Full Text Available Bare cadmium sulfide (CdS nanocrystals were successfully synthesized by the thermolysis of a single-source organometallic precursor, cadmium chloride hemipentahydrate (CdCl2⋅2.5H2O with thiourea in ethanol. The microstructure of the CdS samples was characterized using XRD, TEM, and Raman spectroscopy. The XRD's results showed that there was a transformation from cubic to hexagonal crystalline phase when higher mass of CdCl2⋅2.5H2O was used. Further experimental with different Cd2+ source showed ion Cl− originated from CdCl2⋅2.5H2O attributed to this crystalline phase transformation. The UV-Visible analysis indicated that quantum confinement effect took place when compared to the bulk CdS. However, the photoluminescence experiments revealed that the red-light emission was observed in all samples. This finding could be ascribed to deep trap defects that were due to sulfur vacancies as suggested by XPS and also the fact that the bare CdS nanoparticles are in contact with each other as shown in the TEM images.

  20. Synthesis and white-light emission character of CdS magic-sized nanocrystals

    Institute of Scientific and Technical Information of China (English)

    Ji Dong Wang; Shu Min Han; Dan Dan Ke

    2012-01-01

    Family 373 and 406 of CdS magic-sized nanocrystals (MSNCs) were synthesized by a one-pot non-injection approach and white-light emission was generated from the coexistence of them.This light had excellent color characteristics,as defined by their pure white CIE (Commission Intemational de l'Eclairage) color coordinates (0.328,0.343),and it correlated with a color temperature of 5696 K.A probable thermodynamic equilibrium was proposed to explain the white-light emission behavior in this letter.

  1. Highly fluorescent semiconductor core shell CdTe CdS nanocrystals for monitoring living yeast cells activity

    Science.gov (United States)

    de Farias, P. M. A.; Santos, B. S.; Menezes, F. D.; Brasil, A. G., Jr.; Ferreira, R.; Motta, M. A.; Castro-Neto, A. G.; Vieira, A. A. S.; Silva, D. C. N.; Fontes, A.; Cesar, C. L.

    2007-12-01

    Fluorescent semiconductor nanocrystals in quantum confinement regime (quantum dots) present several well-known features which make them very useful tools for biological labeling purposes. Low photobleaching rates, high chemical stability and active surface allowing conjugation to living cells explain the success of this labeling procedure over the commonly used fluorescent dyes. In this paper we report the results obtained with highly fluorescent core shell CdTe CdS (diameter=3 7 nm) colloidal nanocrystals synthesized in aqueous medium and conjugated to glucose molecules. The conjugated nanocrystals were incubated with living yeast cells, in order to investigate their glucose up-take activity in real time, by confocal microscopy analysis.

  2. Effect of CdS nanocrystals on charge transport mechanism in poly(3-hexylthiophene)

    Science.gov (United States)

    Khan, Mohd Taukeer; Almohammedi, Abdullah

    2017-08-01

    The present manuscript demonstrates the optical and electrical characteristics of poly(3-hexylthiophene) (P3HT) and cadmium sulphide (CdS) hybrid nanocomposites. Optical results suggest that there is a formation of charge transfer complex (CTC) between host P3HT and guest CdS nanocrystals (NCs). Electrical properties of P3HT and P3HT-CdS thin films have been studied in hole only device configurations at different temperatures (290 K-150 K), and results were analysed by the space charge limited conduction mechanism. Density of traps and characteristic trap energy increase on incorporation of inorganic NCs in the polymer matrix, which might be due to the additional favourable energy states created by CdS NCs in the band gap of P3HT. These additional trap states assist charge carriers to move quicker which results in enhancement of hole mobility from 7 × 10-6 to 5.5 × 10-5 cm2/V s in nanocomposites. These results suggest that the P3HT-CdS hybrid system has desirable optical and electrical properties for its applications to photovoltaics devices.

  3. Synthesis of CdS nanocrystals in polymeric films studied by in-situ GID and GISAXS

    KAUST Repository

    Di Luccio, Tiziana

    2015-07-07

    In this work, we describe the synthesis of CdS nanocrystals in thin polymeric films by in-situ Grazing Incidence Diffraction (GID) and Grazing Incidence Small Angle Scattering (GISAXS). The 2D GISAXS patterns indicate how the precursor structure is altered as the temperature is varied from 25°C to 300°C. At 150°C, the CdS nanocrystals start to arrange themselves in a hexagonal lattice with a lattice parameter of 27 A. The diffraction intensity from the hexagonal lattice reaches a maximum at 170"C and decreases steadily upon further heating above 220°C indicating loss of symmetry. Correspondingly, the GID scans at 170°C show strong crystalline peaks from cubic CdS nanocrystals that are about 2 nm size. The results indicate that a temperature of 170°C is sufficient to synthesize CdS nanocrystals without degradation of the polymer matrix (Topas) in thin films (about 30nm). © 2015 Materials Research Society.

  4. Shape-controlled synthesis of protein-conjugated CdS nanocrystals (NCs) and study on the binding of Cd2+/CdS to trypsin

    Science.gov (United States)

    Qin, Dezhi; Wang, Li; Wang, Yabo; Du, Xian; Zhang, Li; Zhang, Qiuxia; He, Bingyu

    2017-07-01

    Protein-conjugated CdS nanocrystals (NCs) with different morphology have been synthesized under biomimetic condition using trypsin as capping agent in aqueous medium. The reaction parameters including concentration of trypsin, pH value, reaction time, and temperature have a major influence on the morphology and optical property of CdS NCs. XRD, selected area electron diffraction (SAED), TEM, HRTEM, and EDS characterizations were used to investigate the structure, composition, morphology, and size of as-prepared products. The binding reaction between Cd2+/CdS and trypsin was investigated systematically through various spectroscopic methods. UV-vis, FT-IR, photoluminescence (PL) spectra, and conductivity analysis of Cd2+-trypsin suggest that Cd2+ ions could coordinate with the functional groups of trypsin and induce the formation of unfolding and loosening structure in protein molecules, and the change of protein conformation was also verified by circular dichroism (CD) spectra. This interaction increased local supersaturation of Cd2+ ions around the groups of trypsin and reduced the nucleation activation energy of CdS nuclei, which favored heterogeneous nucleation in trypsin matrix and resulted in the formation of inorganic-organic hybrid materials. The functional integrity of the enzyme conjugated to CdS NCs was studied by monitoring the enzymatic activity of CdS-trypsin conjugates. The fluorescence of CdS NCs is dependent strongly on trypsin which passivates the surface of NCs.

  5. Direct anisotropic growth of CdS nanocrystals in thermotropic liquid crystal templates for heterojunction optoelectronics.

    Science.gov (United States)

    Yuan, Kai; Chen, Lie; Chen, Yiwang

    2014-09-01

    The direct growth of CdS nanocrystals in functional solid-state thermotropic liquid crystal (LC) small molecules and a conjugated LC polymer by in situ thermal decomposition of a single-source cadmium xanthate precursor to fabricate LC/CdS hybrid nanocomposites is described. The influence of thermal annealing temperature of the LC/CdS precursors upon the nanomorphology, photophysics, and optoelectronic properties of the LC/CdS nanocomposites is systematically studied. Steady-state PL and ultrafast emission dynamics studies show that the charge-transfer rates are strongly dependent on the thermal annealing temperature. Notably, annealing at liquid-crystal state temperature promotes a more organized nanomorphology of the LC/CdS nanocomposites with improved photophysics and optoelectronic properties. The results confirm that thermotropic LCs can be ideal candidates as organization templates for the control of organic/inorganic hybrid nanocomposites at the nanoscale level. The results also demonstrate that in situ growth of semiconducting nanocrystals in thermotropic LCs is a versatile route to hybrid organic/inorganic nanocomposites and optoelectronic devices.

  6. Rapid Fabrication of CdS Nanocrystals with Well Mesoporous Structure Under Ultrasound Irradiation at Room Temperature

    Institute of Scientific and Technical Information of China (English)

    YU Chang-lin; ZHOU Wan-qin; YU Jim-my; YANG Jian-gao; FAN Qi-zhe

    2012-01-01

    Sphere-like mesoporous CdS nanocrystals with high crystallinity and big surface area were successfully fabricated by ultrasound irradiation at room temperature.The as-synthesized CdS with and without ultrasound irradiation was investigated by the characterizations of X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and Brunauer-Emmett-Teller(BET) surface areas.The photocatalytic activity of the CdS was evaluated by photocatalytic degradation of methyl orange under visible light(λ>420 nm) irradiation.A possible mechanism for the formation of the CdS nanocrystals with mesoporous structure under ultrasound irradiation was proposed.The results show that both the template role of the triblock copolymer of P123 and the effect of ultrasound-induced aggregation are mainly responsible for the formation of mesoporous structure.On the other hand,the energy generated from acoustic cavitation can effectively accelerate the crystallization process of the amorphous CdS.

  7. Ion beam synthesis of CdS, ZnS, and PbS compound semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    White, C.W.; Budai, J.D.; Meldrum, A.L. [and others

    1997-12-01

    Sequential ion implantation followed by thermal annealing has been used to form encapsulated CdS, ZnS, and PbS nanocrystals in SiO{sub 2} and Al{sub 2}O{sub 3} matrices. In SiO{sub 2}, nanoparticles are nearly spherical and randomly oriented, and ZnS and PbS nanocrystals exhibit a bimodal size distribution. In Al{sub 2}O{sub 3}, nanoparticles are faceted and coherent with the matrix. Initial photoluminescence (PL) results are presented.

  8. Bright CuInS2/CdS nanocrystal phosphors for high-gain full-spectrum luminescent solar concentrators.

    Science.gov (United States)

    Knowles, Kathryn E; Kilburn, Troy B; Alzate, Dane G; McDowall, Stephen; Gamelin, Daniel R

    2015-06-04

    The performance of colloidal CuInS2/CdS nanocrystals as phosphors for full-spectrum luminescent solar concentrators has been examined. Their combination of large solar absorption, high photoluminescence quantum yields, and only moderate reabsorption produces the highest projected flux gains of any nanocrystal luminophore to date.

  9. CDS

    Science.gov (United States)

    Allen, Mark

    2015-12-01

    The Centre de Donnees de Strasbourg (CDS) is a reference data centre for Astronomy. The CDS services; SIMBAD, Vizier, Aladin and X-Match, provide added value to scientific content in order to support the astronomy research community. Data and information are curated from refereed journals, major surveys, observatories and missions with a strong emphasis on maintaining a high level of quality. The current status and plans of the CDS will be presented, highlighting how the recent innovations of the HiPS (Hierarchical Progressive surveys) and MOC (Multi-Order Coverage map) systems enable the visualisation of hundreds of surveys and data sets, and brings new levels of interoperability between catalogues, surveys images and data cubes.

  10. Synthesis of Co-Doped CdS Nanocrystals by Direct Thermolysis of Cadmium and Cobalt Thiolate Clusters

    Directory of Open Access Journals (Sweden)

    Jianing Zhao

    2015-01-01

    Full Text Available Co-doped CdS (Co:CdS nanocrystals with controllable morphology (quantum dots and nanorods were easily synthesized by direct thermolysis of (Me4N2[Co4(SC6H510] and (Me4N4[S4Cd10(SPh16] under different precursor concentration, in virtue of the ions exchange of molecular clusters. The Co:CdS quantum dots were produced under low precursor concentration, and the Co:CdS nanorods could be obtained under higher precursor concentration. The Co-doping effect on the structure, growth process, and property of CdS nanocrystals was also investigated. The results indicated that the Co-doping was favorable for the formation of the nanorod structures for a short reaction time. In addition, the Co-doping in the CdS lattice resulted in the ferromagnetic property of the Co:CdS quantum dots at room temperature. Moreover, compared with the CdS quantum dots, the Co:CdS quantum dots exhibited obvious quantum confinement effect and photoluminescence emission with slightly red-shift.

  11. Cu-doped ZnO nanoporous film for improved performance of CdS/CdSe quantum dot-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Myeong-Soo; Son, Min-Kyu; Kim, Soo-Kyoung; Park, Songyi; Prabakar, Kandasamy; Kim, Hee-Je, E-mail: heeje@pusan.ac.kr

    2014-11-03

    Copper (Cu) doped zinc oxide (ZnO) powders were synthesized by co-precipitation method with different at% (0 and 0.5 at%) of Cu dopant. Cu-doped ZnO nanoporous (NP) films were fabricated to enhance the performance of the ZnO based cadmium sulfide (CdS) and cadmium selenide (CdSe) quantum dot-sensitized solar cells (QDSSCs). The existence of Cu ions in the Cu-doped ZnO NP film was detected by X-ray fluorescence. The surface morphology, microstructure and crystal structure of Cu-doped ZnO NP films were analyzed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The optical property of CdS/CdSe co-sensitized Cu-doped ZnO NP film was studied by UV–vis absorption spectroscopy. The photovoltaic performance and electrical property of Cu-doped ZnO CdS/CdSe QDSSCs were studied by current–voltage characteristic curves and electrochemical impedance spectroscopy under air mass 1.5 condition. As a result, short circuit current density and fill factor increased from 9.074 mA/cm{sup 2} and 0.403 to 9.865 mA/cm{sup 2} and 0.427 respectively, based on the enhanced absorbance and electron transport by Cu-doping. This led to the increasing light conversion efficiency from 2.27% to 2.61%. - Highlights: • Cu-doped ZnO powders were synthesized by co-precipitation method. • Cu-doped ZnO nanoporous films with high crystallinity were uniformly deposited. • Absorbance of Cu-doped ZnO nanoporous film was enhanced. • Electron conductivity of Cu-doped ZnO nanoporous film was enhanced. • Performance of Cu-doped ZnO CdS/CdSe QDSSC was improved.

  12. 有机硫源溶剂热法合成CdS纳米晶体%Solvothermal Synthesis of CdS Nanocrystals with Organic Sulphur Source

    Institute of Scientific and Technical Information of China (English)

    胡晓丹; 潘力嘉; 张海黔

    2009-01-01

    CdS nanocrystals were synthesized by a solvothermal method with tetramethyl thiuram disulfide(TMTD) as a sulphur source in benzene or water-benzene solvent at different temperatures for different periods of time. The structure and formation mechanism of CdS nanocrystals were investigated by field emission -scanning electron microscope(FE-SEM), X-ray diffraction(XRD) and fourier transform infrared spectroscopy(FHR), respectively. The results indicated that the solvothermal temperature played a more important role than reaction time in formation of crystal morphology. CdS nanocrystals were found to be a mixed phase of cube and hexagon. Furthermore, the type of solvent was also an important influencing factor for the structure and formation of CdS nanocrystals. The cathodoluminescence(CL) of the obtained flower-like CdS nanocrystals was also studied.%以二硫化四甲基秋兰姆(TMTD)作为有机硫源,分别在苯、水-苯溶剂中于不同温度、不同时间溶剂热法合成了CdS纳米晶体.采用FE-SEM、XRD和FTIR对晶体的结构和成形机理进行了研究.结果表明,溶剂热温度比反应时间对晶体形貌的形成影响更大.CdS纳米晶体是立方与六角的混合晶型.此外,溶剂的种类也是影响CdS纳米晶体结构和成形的重要因素,并且对花形CdS纳米晶体进行了阴极发光(CL)光谱的研究.

  13. CdS nanocrystals/TiO{sub 2}/crosslinked chitosan composite: Facile preparation, characterization and adsorption-photocatalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Huayue [Key Laboratory for Biomass-Resource Chemistry and Environmental Biotechnology of Hubei Province, Colledge of Resource and Environment Science, Wuhan University, Wuhan 430072, Hubei (China); Laboratory of Resource Utilization and Pollution Control, College of Life Science, Taizhou University, Taizhou 318000, Zhejiang (China); Jiang, Ru [Laboratory of Resource Utilization and Pollution Control, College of Life Science, Taizhou University, Taizhou 318000, Zhejiang (China); Xiao, Ling, E-mail: xiaoling9119@yahoo.cn [Key Laboratory for Biomass-Resource Chemistry and Environmental Biotechnology of Hubei Province, Colledge of Resource and Environment Science, Wuhan University, Wuhan 430072, Hubei (China); Liu, Li; Cao, Chunhua [Key Laboratory for Biomass-Resource Chemistry and Environmental Biotechnology of Hubei Province, Colledge of Resource and Environment Science, Wuhan University, Wuhan 430072, Hubei (China); Zeng, Guangming [Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, Hunan (China)

    2013-05-15

    CdS nanocrystals deposited on TiO{sub 2}/crosslinked chitosan composite (CdS/TiO{sub 2}/CSC) were prepared in an attempt to photocatalyze decolorization of water soluble azo dye in aqueous solution under simulated solar light irradiation. CdS/TiO{sub 2}/CSC was characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The characterization results proved that CdS nanocrystals has successfully been deposited on/in TiO{sub 2}/crosslinked chitosan composite. The adsorption ability of CdS/TiO{sub 2}/CSC was approximately 2.66 mg methyl orange (a typical water soluble azo dye) per gram. The photocatalytic decolorization of methyl orange solution reached 99.1% by CdS/TiO{sub 2}/CSC after simulated solar light irradiation for 210 min. Kinetics analysis indicated that photocatalytic decolorization of methyl orange solution by CdS/TiO{sub 2}/CSC obeyed first-order kinetic Langmuir-Hinshelwood mechanism (R{sup 2} > 0.997). CdS/TiO{sub 2}/CSC exhibited enhanced photocatalytic activity under simulated solar light irradiation compared with photocatalysts reported before and the photocatalytic activity of CdS/TiO{sub 2}/CSC maintained at 89.0% of initial decolorization rate after five batch reactions. The presence of NO{sub 3}{sup −} accelerated the decolorization of methyl orange solution by CdS/TiO{sub 2}/CSC, while SO{sub 4}{sup 2−} and Cl{sup −} had an inhibitory effect on the decolorization of methyl orange. Therefore, present experimental results indicated to assess the applicability of CdS/TiO{sub 2}/CSC as a suitable and promising photocatalyst for effective decolorization treatment of dye-containing effluents.

  14. The surface engineering of CdS nanocrystal for photocatalytic reaction: A strategy of modulating the trapping states and radicals generation towards RhB degradation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shuo, E-mail: lishuochem@outlook.com; Meng, Dedong, E-mail: 1159594702@qq.com; Hou, Libo, E-mail: hlb2014332156@outlook.com; Wang, Dejun, E-mail: wangdj@jlu.edu.cn; Xie, Tengfeng, E-mail: xietf@jlu.edu.cn

    2016-05-15

    Highlights: • Surfactants were successfully used for the surface states engineering of CdS nanocrystal. • The existence and the location of surface hole traps and surface electron traps were investigated. • The surface states can modulate the generation of radicals. - Abstract: Cationic surfactant (CTAB) and anionic surfactant (sodium oleate) were used to modify CdS nanocrystals with different surface states. The surfactant CTAB led to surface states of hole traps, while sodium oleate induced surface states of electron traps on the surface of CdS. The photodegradation of rhodamine B (RhB) over these modified CdS nanocrystals was investigated under visible light irradiation. An efficient cycloreversion degradation of RhB occurred over the E-CdS nanocrystals. However, for H-CdS nanocrystals, an efficient N-deethylation reaction concomitant with a subsequent slow cycloreversion reaction of RhB was observed. The E-CdS sample showed a first-order kinetic rate for the cycloreversion degradation of RhB. By contrast, H-CdS sample shows a zero-order kinetic rate for the N-deethylation reaction of RhB followed by a first-order kinetic rate for the cycloreversion degradation. It is revealed that the different kinds of surface traps could significantly affect the dynamic properties of photogenerated charge carriers, which leads to different degradation mechanism of RhB. These findings demonstrate an alternative solution towards developing efficient photocatalysts with high selectivity by constructing different surface trap states.

  15. Raman Spectroscopy of SiO{sub 2}–Na{sub 2}O–Al{sub 2}O{sub 3}–B{sub 2}O{sub 3} glass doped with Nd{sup 3+} and CdS nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Serqueira, E.O.; Dantas, N.O. [Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, MG 38400-902 (Brazil); Anjos, V. [Grupo de Espectroscopia de Materiais, Departamento de Física, ICE – UFJF, Campus Universitário, Juiz de Fora, MG 36036-330 (Brazil); Bell, M.J.V., E-mail: mjvbell@yahoo.com.br [Grupo de Espectroscopia de Materiais, Departamento de Física, ICE – UFJF, Campus Universitário, Juiz de Fora, MG 36036-330 (Brazil)

    2014-01-05

    Highlights: • The formation of CdS nanocrystals in the glassy host is shown by Raman measurements. • Nd{sub 2}O{sub 3} modifies the growth of CdS nanocrystals in the SNAB glass. • Nd{sup 3+} ions are not incorporated inside the semiconductor nanocrystals. -- Abstract: We report the Raman spectroscopic characterization of a SNAB glass system doped with neodymium and CdS nanocrystals and fabricated by the fusion process. Raman spectra revealed CdS nanocrystals in the glass host and bands associated with Si–O vibrational modes with five structural configurations, boroxol modes of B{sub 2}O{sub 3}, Al–O and Cd–S vibrational modes. Additionally, Nd{sub 2}O{sub 3} modifies the growth of CdS nanocrystals in the SNAB glass and Nd{sup 3+} ions are not incorporated inside the semiconductor nanocrystals.

  16. A ceramic microreactor for the synthesis of water soluble CdS and CdS/ZnS nanocrystals with on-line optical characterization

    Science.gov (United States)

    Pedro, Sara Gómez-De; Puyol, Mar; Izquierdo, David; Salinas, Iñigo; de La Fuente, J. M.; Alonso-Chamarro, Julián

    2012-02-01

    In this paper, a computer controlled microreactor to synthesize water soluble CdS and CdS/ZnS nanocrystals with in situ monitoring of the reaction progress is developed. It is based on ceramic tapes and the Low-Temperature Co-fired Ceramics technology (LTCC). As well the microsystem set-up, the microreactor fluidic design has also been thoroughly optimized. The final device is based on a hydrodynamic focusing of the reagents followed by a three-dimensional micromixer. This generates monodispersed and stable CdS and core-shell CdS/ZnS nanocrystals of 4.5 and 4.2 nm, respectively, with reproducible optical properties in terms of fluorescence emission wavelengths, bandwidth, and quantum yields, which is a key requirement for their future analytical applications. The synthetic process is also controlled in real time with the integration of an optical detection system for absorbance and fluorescence measurements based on commercial miniaturized optical components. This makes possible the efficient managing of the hydrodynamic variables to obtain the desired colloidal suspension. As a result, a simple, economic, robust and portable microsystem for the well controlled synthesis of CdS and CdS/ZnS nanocrystals is presented. Moreover, the reaction takes place in aqueous medium, thus allowing the direct modular integration of this microreactor in specific analytical microsystems, which require the use of such quantum dots as labels.

  17. Preparation, morphology, size quantization effect and photocatalytic properties of CdS Q-nanocrystals

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Weiguang; (章伟光); ZHONG; Yun; (钟昀); FAN; Jun; (范军),; SUN; Siqiao; (孙姒巧); TANG; Ning; (唐宁); TAN; Minyu; (谭民裕); WU; Longmin; (吴隆民)

    2003-01-01

    CdS nanoclusters were synthesized by using n- octylthiol as a ligand and n- hexadecyl- trimethyl-ammonium bromide (or n-tetrabutylammonium bromide) as an organic cation. Size- selective precipitation techniques have enabled the preparation of different CdS Q-nanoparticles with narrow size distribution and mean diameters ranging from 2 to 5 nm. UV-Vis spectroscopy, transmission electron microscopy (TEM) and small-angle X-ray scattering were used to determine the mean cluster size. Their size quantization effect has been observed in UV-Vis spectra, fluorescence spectra and small-angle X-ray diffraction, but it became too weak to be observed for large particles (2r > 10 nm). Moreover, their photo-catalysis has been studied by ESR technique and the results revealed that the photo-catalytic reaction occurred in the solution system and some free radicals such as (CH2-OH in methanol, or CH3-CH-OH in ethanol were generated if some CdS Q-particles were added to methanol (or ethanol) and initiated by UV light at the same time, which may be very crucial in organic synthesis.

  18. Chemical bath deposition of CdS thin films doped with Zn and Cu

    Indian Academy of Sciences (India)

    A I Oliva; J E Corona; R Patiño; A I Oliva-Avilés

    2014-04-01

    Zn- and Cu-doped CdS thin films were deposited onto glass substrates by the chemical bath technique. ZnCl2 and CuCl2 were incorporated as dopant agents into the conventional CdS chemical bath in order to promote the CdS doping process. The effect of the deposition time and the doping concentration on the physical properties of CdS films were investigated. The morphology, thickness, bandgap energy, crystalline structure and elemental composition of Zn- and Cu-doped CdS films were investigated and compared to the undoped CdS films properties. Both Zn- and Cu-doped CdS films presented a cubic crystalline structure with (1 1 1) as the preferential orientation. Lower values of the bandgap energy were observed for the doped CdS films as compared to those of the undoped CdS films. Zn-doped CdS films presented higher thickness and roughness values than those of Cu-doped CdS films. From the photoluminescence results, it is suggested that the inclusion of Zn and Cu into CdS crystalline structure promotes the formation of acceptor levels above the CdS valence band, resulting in lower bandgap energy values for the doped CdS films.

  19. 微波水热法制备CdS纳米晶体的研究%Semiconductor Nanocrystals CdS Synthesized by Microwave-Hydrothermal Method

    Institute of Scientific and Technical Information of China (English)

    王悦虹; 刘岩

    2012-01-01

    利用微波水热技术合成CdS半导体纳米晶体,可以克服有机合成方法毒性大,成本高等问题,通过XRD、TEM表征,产物CdS半导体纳米晶体具有立方晶相,纯度较高。通过紫外吸收光谱和荧光光谱分析,发现该方法制备出的半导体CdS纳米晶体具有良好的光致发光性质,证明水相同样适合高质量CdS半导体纳米晶体的生长。%CdS semiconductor nanocrystals(NCs) were synthesized by microwave-hydrothermal method in water solution.In comparison,with the synthesis of NCs in organic solvents,the growth surroundings of aqueous NCs were more poisonous and costly.The XRD and TEM provided direct evidence for a cubic zinc blende structure of bulk CdS crystal.Moreover,the CdS NCs had excellent photoluminescence properties by the characterizations of absorption spectra and luminescence spectra.This method proved that CdS NCs suited to grow in aqueous condition.

  20. Modification of multi-walled carbon nanotubes by plasma treatment and further use as templates for growth of CdS nanocrystals.

    Science.gov (United States)

    Tseng, Chun-Hao; Wang, Cheng-Chien; Chen, Chuh-Yung

    2006-11-28

    In this study, we present a novel method for preparing multi-walled carbon nanotubes (MWCNTs) grafted with a poly(2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA)-cadmium sulfide complex (CNTs-G-ICdS complex) through plasma-induced grafting polymerization. The characteristics of the MWCNTs after being grafted with the GMA-IDA polymer were monitored by a Fourier transform infrared (FT-IR) spectroscope. Scanning electronic microscopy (SEM) shows that the amount of GMA-IDA grafted onto the MWCNTs increases with the concentration of GMA-IDA monomer. The complex resulting from GMA-IDA polymer grafting onto the MWCNTs, CNTs-G-I (15%), shows excellent dispersion properties in aqueous solution and has high Zeta potential values over a wide range of pH values, from 2 to 12. Moreover, Raman spectroscopy was used to confirm the successful chemical modification of MWCNTs through the plasma treatment. The chelating groups, -N(CH(2)COO(-))(2) in the GMA-IDA polymer grafted on the surface of the CNTs-G-I, are the coordination sites for chelating cadmium ions, and are further used as nano-templates for the growth of CdS nanocrystals (quantum dots). Moreover, TEM microscopy reveals that the size of the CdS nanocrystals on the CNT surfaces increases with increasing S(2-) concentration. In addition, high resolution x-ray photoelectron (XPS) spectroscopy was used to characterize the functional groups on the surface of the MWCNTs after chemical modification by the plasma treatment and grafting with GMA-IDA polymer.

  1. High-efficiency CdTe/CdS core/shell nanocrystals in water enabled by photo-induced colloidal hetero-epitaxy of CdS shelling at room temperature

    Institute of Scientific and Technical Information of China (English)

    Hakimeh Zare[1; Maziar Marandi[2; Somayeh Fardindoost[1; Vijay Kumar Sharma[3,4; Aydan Yeltik[3; Omid Akhavan[1,5; Hilmi Volkan Demir[3,4; Nima Taghavinia[1,5

    2015-01-01

    We report high-efficiency CdTe/CdS core/shell nanocrystals synthesized in water by epitaxially growing CdS shells on aqueous CdTe cores at room temperature, enabled by the controlled release of S species under low-intensity ultraviolet (UV) light illumination. The resulting photo-induced dissociation of S2O2- ions conveniently triggers the formation of critical two-dimensional CdS epitaxy on the CdTe surface at room temperature, as opposed to initiating the growth of individual CdS core-only nanocrystals. This controlled colloidal hetero-epitaxy leads to a substantial increase in the photoluminescence (PL) quantum yield (QY) of the shelled nanocrystals in water (reaching 64%). With a systematic set of studies, the maximum PL QY is found to be almost independent of the illuminating UV intensity, while the shell formation kinetics required for reaching the maximum QY linearly depends on the illuminating UV intensity. A stability study of the QD films in air at various temperatures shows highly improved thermal stability of the shelled QDs (up to 120 ℃ in ambient air). These results indicate that the proposed aqueous CdTe/CdS core/shell nanocrystals hold great promise for applications requiring efficiency and stability.

  2. Enhanced Photocatalytic Property of Cu Doped Sodium Niobate

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jianbin; Zhang, Feng; Sun, Bingyang; Du, Yingge; Li, Guoqiang; Zhang, Weifeng

    2015-09-29

    We investigate the photocatalytic activity of Cu doped NaNbO3 powder sample prepared by the modified polymer complex method. The photocatalytic activity of hydrogen evolution from methanol aqueous solution was improved by Cu 2.6 at% doping. The photocatalytic degradation of rhodamine B under visible light irradiation was enhanced in comparison with pure NaNbO3. Cu inctroduction improved the adsorption property of NaNbO3, judging from the Fourier transform infrared spectra. Moreover, the ultraviolet light excitation in Cu doped sample was found to accelerate the mineralized process.

  3. Enhanced Photocatalytic Property of Cu Doped Sodium Niobate

    Directory of Open Access Journals (Sweden)

    Jianbin Xu

    2015-01-01

    Full Text Available We investigate the photocatalytic activity of Cu doped NaNbO3 powder sample prepared by the modified polymer complex method. The photocatalytic activity of hydrogen evolution from methanol aqueous solution was improved by Cu 2.6 at% doping. The photocatalytic degradation of rhodamine B (RhB under visible light irradiation was enhanced in comparison with pristine NaNbO3. Cu introduction improved the adsorption property of NaNbO3, judging from the Fourier transform infrared spectra. Moreover, the ultraviolet light excitation in Cu doped sample would accelerate the mineralized process.

  4. «Green» Synthesis of Noble Metal Nanoparticles and CdS Semiconductor Nanocrystals Using Biological Material

    Directory of Open Access Journals (Sweden)

    Blume, Ya.B.

    2015-01-01

    Full Text Available The basic principles of synthesis of metal nanoparticles and semiconductor nanocrystals and its application prospects are considered. The relevance of the exploiting living systems and their components for the development of «green » synthesis technology for nano-objects with the unique properties and a wide range of applications is analyzed. The biotechnological synthesis of nanoparticles of silver, gold and bimetallic silver-gold nanoparticles using plant extracts of Magnolia denudata, M. stellata, Camellia sinensis var. sinensis, C. sinensis var. assamica, Orthosiphon stamineus and Hypericum perforatum is described. The results of cadmium sulfide fluorescent semiconductor nanocrystal synthesis using bacteria Escherichia coli, basidiomycete Pleurotus ostreatus and plant Linaria maroccana are reported. Morphological and optical characteristics of the synthesized nanoparticles are presented.

  5. PREPARATION OF MONODISPERSE CdS NANOCRYSTALS/PNIPAM HYDROGEL AND ITS THERMOSENSITIVE FLUORESCENCE%单分散CdS纳米晶/PNIPAM复合水凝胶的制备及其温敏荧光特性

    Institute of Scientific and Technical Information of China (English)

    宋秋生; 朱小飞; 杨洋

    2012-01-01

    In order to investigate the influence of polymer aggregate state and chemical environment on the fluorescent performance of nanocrystal, monodisperse CdS nanocrystal is prepared via liquid-solid-solution synthesis ( LSS ) strategy, and monodisperse CdS nanocrystals/poly(iV-isopropylacrylamide) ( PNIPAM ) complex hydrogel are prepared by radical polymerization. The microstructure and performance of the monodisperse CdS nanocrystal and the complexes hydrogel are characterized by high resolution transmission electron microscopy (HRTEM) ,X-ray diffraction (XRD) ,Fourier transformed infrared spectroscopy (FTIR) , differential scanning calorimetry (DSC) and photoluminescence (PL). As evidenced from the HRTEM photos and XRD patterns, CdS nanocrystals show well monodispersity, and their size is about 2. 8 nm. PL spectrum shows that CdS nanocrystal has a strong emitting peak around 533 nm and a weak emitting peak around 469 nm. DSC curves suggest that the complex hydrogel is thermosensitive,and LCST of which is higher than that ofPNIPAM hydrogel. The results of PL spectra and DSC curves indicate that the complex hydrogel shows well thermosensitive-fluorescent performance, the variation of the fluorescent intensity of the complex hydrogel is in good agreement with its phase transformation. With variation of environmental temperature from 20℃ to 45℃ , the complex hydrogel changes from swollen state to collapse state, and the chemical environment around CdS nanocrystal changes from hydrophilic to hydrophobic, quantum yield of CdS nanocrystal changes respectively. The lower the environmental temperature is kept, the lower fluorescent intensity of the complex hydrogel is observed,and the fluorescent intensity changes sharply around its LCST. Testing on PL intensity change of CdS/PNIPAM hydrogel as a function of cooling-heating cycles between 20t and 40t demonstrates that the thermosensitive-fluorescent performance of the CdS/PNIPAM hydrogel is reversible.%采用液体-固

  6. Convenient synthesis of magnetically recyclable Fe{sub 3}O{sub 4}@C@CdS photocatalysts by depositing CdS nanocrystals on carbonized ferrocene

    Energy Technology Data Exchange (ETDEWEB)

    Li, Dan [Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Xie, Jianjian [Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Zhang, Yong; Qiao, Ru [Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Li, Sheng [Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Li, Zhengquan, E-mail: zqli@zjnu.edu.cn [Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China)

    2015-10-15

    Development of magnetic visible-light-driven photocatalysts is desirable to the practical application of photocatalyts for collection and recycling use. Here we present a facile approach to synthesize Fe{sub 3}O{sub 4}@C@CdS magnetic photocatalysts which can avoid multi-step preparation process. Through one-step solvothermal carbonization of ferrocene, the produced carbon-coated Fe{sub 3}O{sub 4} clusters can serve as both magnetic cores and deposition substrates for in situ generating crystalline CdS nanocrystals on them by rapid microwave irradiation. The prepared Fe{sub 3}O{sub 4}@C@CdS nanoparticles exhibit a uniform core–shell structure and display good photocatalytic activity and recyclability in the degradation of organic dyes. These magnetic photocatalysts may find potential application in wastewater treatment for the future environment remedy. - Highlights: • A rapid strategy is presented to obtain multifunctional core–shell nanostructures. • Magnetic visible-light-driven Fe{sub 3}O{sub 4}@C@CdS nanophotocatalysts are synthesized. • Carbonized ferrocene can provide both magnetic cores and good deposition substrate. • Photocatalytic and recyclable properties of Fe{sub 3}O{sub 4}@C@CdS nanoparticles are explored.

  7. Excitation dependent multicolor emission and photoconductivity of Mn, Cu doped In2S3 monodisperse quantum dots

    Science.gov (United States)

    Ghosh, Sirshendu; Saha, Manas; Ashok, Vishal Dev; Chatterjee, Arijit; De, S. K.

    2016-04-01

    Indium sulphide (In2S3) quantum dots (QDs) of average size 6 ± 2 nm and hexagonal nanoplatelets of average size 37 ± 4 nm have been synthesized from indium myristate and indium diethyl dithiocarbamate precursors respectively. The absorbance and emission band was tuned with variation of nanocrytal size from very small in the strong confinement regime to very large in the weak confinement regime. The blue emission and its shifting with size has been explained with the donor-acceptor recombination process. The 3d element doping (Mn2+ and Cu2+) is found to be effective for formation of new emission bands at higher wavelengths. The characteristic peaks of Mn2+ and Cu2+ and the modification of In3+ peaks in the x-ray photoelectric spectrum (XPS) confirm the incorporation of Mn2+ and Cu2+ into the In2S3 matrix. The simulation of the electron paramagnetic resonance signal indicates the coexistence of isotropic and axial symmetry for In and S vacancies. Moreover, the majority of Mn2+ ions and sulphur vacancies (VS ) reside on the surface of nanocrystals. The quantum confinement effect leads to an enhancement of band gap up to 3.65 eV in QDs. The formation of Mn 3d levels between conduction band edge and shallow donor states is evidenced from a systematic variation of emission spectra with the excitation wavelength. In2S3 QDs have been established as efficient sensitizers to Mn and Cu emission centers. Fast and slow components of photoluminescence (PL) decay dynamics in Mn and Cu doped QDs are interpreted in terms of surface and bulk recombination processes. Fast and stable photodetctors with high photocurrent gain are fabricated with Mn and Cu doped QDs and are found to be faster than pure In2S3. The fastest response time in Cu doped QDs is an indication of the most suitable system for photodetector devices.

  8. Cadmium (II) pyrrolidine dithiocarbamate complex as single source precursor for the preparation of CdS nanocrystals by microwave irradiation and conventional heating process

    Science.gov (United States)

    Marx Nirmal, R.; Pandian, K.; Sivakumar, K.

    2011-01-01

    The complex of cadmium with pyrrolidine dithiocarbamate Cd(pdtc)2 has been used as single source precursor for the synthesis of CdS nanoparticles. The formation of CdS nanostructures was achieved by thermal decomposition of the complex under microwave irradiation and conventional heating in presence of hexadecylamine. The CdS nanoparticles with disordered close-packed structure were obtained under microwave irradiation, whereas wurtzite hexagonal phase CdS nanorods were obtained by conventional heating method (up to 150 °C). Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and high resolution transmission electron microscopy (HRTEM) studies also were carried out to study the structure and morphology of nanoparticles. The optical property of the CdS nanoparticles was studied by UV-visible and fluorescence emission spectral studies. Fluorescence measurements on the CdS nanoparticles show a strong emission spectrum with two sub bands that are attributed to band-edge and surface-defect emissions. The reduction of a suitable cadmium metal complex is considered to be one of the single pot methods to generate CdS semiconductor nanoparticles with different shapes and high yield.

  9. Cadmium (II) pyrrolidine dithiocarbamate complex as single source precursor for the preparation of CdS nanocrystals by microwave irradiation and conventional heating process

    Energy Technology Data Exchange (ETDEWEB)

    Marx Nirmal, R. [Department of Physics, Anna University Chennai, Chennai, Tamil Nadu 600025 (India); Pandian, K. [Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai 600025 (India); Sivakumar, K., E-mail: ksivakumar@annauniv.edu [Department of Physics, Anna University Chennai, Chennai, Tamil Nadu 600025 (India)

    2011-01-15

    The complex of cadmium with pyrrolidine dithiocarbamate Cd(pdtc){sub 2} has been used as single source precursor for the synthesis of CdS nanoparticles. The formation of CdS nanostructures was achieved by thermal decomposition of the complex under microwave irradiation and conventional heating in presence of hexadecylamine. The CdS nanoparticles with disordered close-packed structure were obtained under microwave irradiation, whereas wurtzite hexagonal phase CdS nanorods were obtained by conventional heating method (up to 150 deg. C). Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and high resolution transmission electron microscopy (HRTEM) studies also were carried out to study the structure and morphology of nanoparticles. The optical property of the CdS nanoparticles was studied by UV-visible and fluorescence emission spectral studies. Fluorescence measurements on the CdS nanoparticles show a strong emission spectrum with two sub bands that are attributed to band-edge and surface-defect emissions. The reduction of a suitable cadmium metal complex is considered to be one of the single pot methods to generate CdS semiconductor nanoparticles with different shapes and high yield.

  10. The effect of Cu doping concentration on resistive switching of HfO{sub 2} film

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Tingting; Tan, Tingting, E-mail: tantt@nwpu.edu.cn; Liu, Zhengtang

    2015-10-01

    Graphical abstract: - Highlights: • The Cu doped and undoped HfO{sub 2} films were fabricated. • The improved RS behaviors were observed for Cu doped HfO{sub 2} film with BRS. • The 9.7% doped HfO{sub 2}:Cu film showed both BRS and URS behaviors. • The related switching mechanisms were illustrated. - Abstract: The Cu-doped and undoped HfO{sub 2} films were fabricated and the effect of Cu doping concentration on resistive switching (RS) of HfO{sub 2} film was demonstrated. The X-ray photoelectron spectroscopy (XPS) was carried out to investigate the chemical bonding states of Cu in HfO{sub 2}:Cu film. The improved RS behaviors in terms of ON/OFF ratio and switching parameters were observed for Cu-doped HfO{sub 2} film with bipolar resistive switching (BRS) behavior. With the increase of Cu doping concentration, the 9.7% Cu-doped HfO{sub 2} film showed both BRS and unipolar resistive switching (URS) behaviors with large operating voltages. The space charge limited current (SCLC) effect was proposed to interpret the switching mechanism of HfO{sub 2}:Cu films with BRS behavior and the URS behavior can be explained by the migration of Cu ions.

  11. Synthesis of Ultra-Small Palladium Nanoparticles Deposited on CdS Nanorods by Pulsed Laser Ablation in Liquid: Role of Metal Nanocrystal Size in the Photocatalytic Hydrogen Production.

    Science.gov (United States)

    Park, Hanbit; Reddy, D Amaranatha; Kim, Yujin; Lee, Seunghee; Ma, Rory; Kim, Tae Kyu

    2017-09-21

    It is imperative to suppress the rate of recombination of photogenerated carriers to improve the semiconductor-catalyzed solar-driven production of hydrogen. To this end, photocatalysts comprising active sunlight-harvesting photo-absorbers and stable metal co-catalysts have attracted significant attention. However, the size, clean surface, and highly dispersed nature of the metal co-catalysts are crucial factors affecting catalyst performance and reaction rate. Nevertheless, most of the available metal nanocrystals have been synthesized by complex procedures using harmful organic templates and stabilizers, affording high-purity compounds with difficulty and high cost. To overcome these problems, in this study, the pulsed laser ablation in liquid approach was utilized to generate palladium and bimetallic palladium-platinum nanoparticles with an average size and distribution by adjusting the laser wavelength and fluence. A high rate of evolution of hydrogen of 130.33 mmol g(-1)  h(-1) was obtained by using the optimized CdS-PdPt catalyst under simulated sunlight irradiation. This value is 51.31 times greater than that observed for bare CdS nanostructures. Furthermore, the amount of hydrogen evolved was significantly better than that obtained by using several other noble-metal co-catalysts deposited on CdS. This proposed strategy is thought to open new avenues for the design of advanced photocatalytic materials for efficient solar-driven production of hydrogen. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. The electrical and optical properties of Cu-doped In{sub 2}O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Fan [School of Physical Science and Technology and Shenzhen Key Laboratory of Sensor Technology, Shenzhen University, Shenzhen, 518060 (China); Cai, Xing-Min, E-mail: caixm@graduate.hku.hk [School of Physical Science and Technology and Shenzhen Key Laboratory of Sensor Technology, Shenzhen University, Shenzhen, 518060 (China); Zhong, Xue; Tian, Xiao-Qing [School of Physical Science and Technology and Shenzhen Key Laboratory of Sensor Technology, Shenzhen University, Shenzhen, 518060 (China); Jing, Shou-Yong [The Institute of Optoelectronics, Shenzhen University, Shenzhen, 518060 (China); Huang, Long-Biao; Roy, V.A.L. [Center of Super-Diamond and Advanced Films (COSDAF)and Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, Hong Kong (China); Zhang, Dong-Ping; Fan, Ping; Luo, Jing-Tin; Zheng, Zhuang-Hao; Liang, Guang-Xing [School of Physical Science and Technology and Shenzhen Key Laboratory of Sensor Technology, Shenzhen University, Shenzhen, 518060 (China)

    2014-04-01

    To study the effect of Cu doping, In{sub 2}O{sub 3} and Cu-doped In{sub 2}O{sub 3} films were deposited on K9 glass and Si substrates with the same experimental parameters. All the films were found to be body centered cubic and have the same preferred orientation. No secondary phases were detected in Cu-doped In{sub 2}O{sub 3}. The atomic ratio of Cu to Cu plus In was approximately 18% in Cu-doped In{sub 2}O{sub 3} films which were found to be n-type. After Cu doping, the resistivity of the films increased by 3 to 4 orders of magnitude and the film with higher Cu content had larger resistivity, due to compensation. Cu doping is found to widen the optical band gap of In{sub 2}O{sub 3} films, possibly due to a metal–insulator transition. - Highlights: • Cu doping changes neither the structure nor the preferred orientation of the films. • Cu doped In{sub 2}O{sub 3} are n-type. • Cu doped In{sub 2}O{sub 3} films have much larger resistivity than undoped In{sub 2}O{sub 3}. • Cu doped In{sub 2}O{sub 3} films have larger optical band gaps than undoped In{sub 2}O{sub 3}.

  13. Structural, optical and ethanol sensing properties of Cu-doped SnO{sub 2} nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Johari, Anima, E-mail: animajohari@gmail.com; Sharma, Manish [Center for Applied Research in Electronics (CARE), IIT Delhi, Hauz khas, New Delhi-110016 (India); Johari, Anoopshi [THDC Institute of Hydropower Institute of Engineering and Technology, Tehri-249124 (India); Bhatnagar, M. C. [Physics Department, IIT Delhi, Hauz khas, New Delhi-110016 (India)

    2014-04-24

    In present work, one-dimensional nanostructure of Cu-doped Tin oxide (SnO{sub 2}) was synthesized by using thermal evaporation method in a tubular furnace under Nitrogen (N{sub 2}) ambience. The growth was carried out at atmospheric pressure. SEM and TEM images reveal the growth of wire-like nanostructures of Cu-doped SnO{sub 2} on Si substrate. The XRD analysis confirms that the synthesized SnO{sub 2} nanowires have tetragonal rutile structure with polycrystalline nature and X-ray diffraction pattern also showed that Cu gets incorporated into the SnO{sub 2} lattice. EDX spectra confirm the doping of Cu into SnO{sub 2} nanowires and atomic fraction of Cu in nanowires is ∼ 0.5 at%. The Vapor Liquid Solid (VLS) growth mechanism for Cu-doped SnO{sub 2} nanowires was also confirmed by EDX spectra. The optical properties of as grown Cu-doped SnO{sub 2} nanowires were studied by using UV-vis spectra which concludes the band gap of about 3.7 eV. As synthesized single Cu-doped SnO{sub 2} nanowire based gas sensor exhibit relatively good performance to ethanol gas. This sensing behaviour offers a suitable application of the Cu-doped SnO{sub 2} nanowire sensor for detection of ethanol gas.

  14. Thermo-stimulated evolution of crystalline structure and dopant distribution in Cu-doped Y-stabilized ZrO2 nanopowders

    Science.gov (United States)

    Korsunska, N.; Polishchuk, Yu; Kladko, V.; Portier, X.; Khomenkova, L.

    2017-03-01

    This work deals with the effect of Cu doping on thermal stability of the structural properties of Y-stabilized ZrO2 nanopowders and dopants’ spatial distribution. The powders were synthesized by a co-precipitation technique, calcinated at T c  =  500–1100 °C during 2 h and studied by x-ray diffraction (XRD) and transmission electron microscopy. Calcination at T c  =  500 °C results in the formation of ZrO2 nanocrystals with tetragonal phase predominantly. The shifts of XRD peak positions of Cu-doped powders to larger angles in comparison with those of Cu-free ones testify to the Cu presence inside nanocrystals. The T c increase results in two main processes: (i) the non-monotonic shift of XRD peak positions and (ii) the phase transformation (tetragonal to cubic and both of them to monoclinic). This observation was explained by, at first, Cu atoms incorporation into the nanocrystal volume from the surface complexes (T c  =  500–700 °C) and then their outward diffusion followed by the formation of crystalline CuO (T c  >  700 °C). Phase transformation sets in at T c  =  700 °C, when monoclinic phase appears. Its contribution rises till T c  =  1000 °C. The mechanism of monoclinic phase formation is supposed to be consisted of the out-diffusion of interstitial Cu ions due to their shift from lattice sites. This promotes an appearance of the channels for Y out-diffusion via cation vacancies and results in phase transformation. The sintering process stimulated by CuO formation is proposed to be responsible for appearance of cubic phase at 1000–1100 °C.

  15. Electron paramagnetic resonance in Cu-doped ZnO

    Science.gov (United States)

    Buchheit, R.; Acosta-Humánez, F.; Almanza, O.

    2016-04-01

    In this work, ZnO and Cu-doped ZnO nanoparticles (Zn1-xCuxO, x = 3%), with a calcination temperature of 500∘C were synthesized using the sol-gel method. The particles were analyzed using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) at X-band, measurement in a temperature range from 90 K to room temperature. AAS confirmed a good correspondence between the experimental doping concentration and the theoretical value. XRD reveals the presence of ZnO phase in hexagonal wurtzite structure and a nanoparticle size for the samples synthesized. EPR spectroscopy shows the presence of point defects in both samples with g-values of g = 1.959 for shallow donors and g = 2.004 for ionized vacancies. It is important when these materials are required have been used as catalysts, as suggested that it is not necessary prepare them at higher temperature. A simulation of the Cu EPR signal using an anisotropic spin Hamiltonian was performed and showed good coincidence with the experimental spectra. It was shown that Cu2+ ions enter interstitial octahedral sites of orthorhombic symmetry in the wurtzite crystal structure. Temperature dependence of the EPR linewidth and signal intensity shows a paramagnetic behavior of the sample in the measurement range. A Néel temperature TN = 78 ± 19 K was determined.

  16. Aqueous synthesis and characterization of bovine hemoglobin-conjugated cadmium sulfide nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Guangrui [Institute of Environmental and Municipal Engineering, North China University of Water Conservancy and Electric Power, Zhengzhou 450011 (China); Qin, Dezhi, E-mail: dezhiqin@163.com [College of Chemistry and Chemical Engineering, Pingdingshan University, Pingdingshan 467000 (China); Du, Xian; Zhang, Li; Zhao, Ganqing; Zhang, Qiuxia; Wu, Jiulin [College of Chemistry and Chemical Engineering, Pingdingshan University, Pingdingshan 467000 (China)

    2014-08-01

    Highlights: • CdS nanocrystals were synthesized by biomimetic method in bovine hemoglobin (BHb) solution. • The study of the interaction between Cd{sup 2+}/CdS and BHb. • The optical properties of BHb-conjugated CdS nanocrystals. • The synthesis process of BHb-conjugated CdS nanocrystals is facile, effective and environment friendly. • The change of secondary structure of BHb after binding to CdS nanocrystals. - Abstract: Cadmium sulfide (CdS) nanocrystals with average diameter about 5.5 nm were synthesized in aqueous solution of bovine hemoglobin (BHb) via simple biomimetic method. Powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) characterizations were used to determine the structure and morphology of CdS nanocrystals. It was revealed that amount of BHb, chelating of Cd{sup 2+} to BHb and reaction temperature were key factors in controlling shape and dispersion of CdS nanocrystals. The binding sites of BHb to CdS nanocrystals and the change of secondary structure of protein have been identified by Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopy. It was found that conjugating of BHb with Cd{sup 2+} and CdS could protect nanocrystals from agglomerating. Moreover, the thermostability of BHb enhanced after conjugating with CdS nanocrystals. The interaction mechanism of BHb with Cd{sup 2+}/CdS was also proposed. The quantum-confined effect of CdS nanocrystals was confirmed by ultraviolet–visible (UV–vis) spectrum. The nanocrystals exhibited a well-defined photoluminescence (PL) emission feature at about 510 nm with narrow full width at half maximum (FWHM)

  17. Aging effect of quantum dots on solar cells sensitized with nano-crystals of CdS and PbS

    Directory of Open Access Journals (Sweden)

    V Borhanifar

    2015-01-01

    Full Text Available In this research, solar cells sensitized with CdS and PbS Nanocrystalline metal sulfides, chemically grown by SILAR, were fabricated and characterized. PV experiments including I-V test in the presence of light and dark,Vocdecay, and Electrochemical impedance spectroscopy were performed on the Cells made through this method in the presence of light and dark and in the time period of 2, 3, 6 and 10 days. From these experiments, the changes in indicators including fill factor, efficiency, open-circuit voltage, short-circuit current, lifetime of electrons in nanostructured anode electrode, recombination resistance and capacitance of the anode electrode-electrolyte interface were observed. Also, mechanisms for some existing evidences within photovoltaic experiments such as the increase and decrease of recombination resistance were proposed.

  18. Depolymerization of organosolv lignin to aromatic compounds over Cu-doped porous metal oxides

    NARCIS (Netherlands)

    Barta, Katalin; Warner, Genoa R.; Beach, Evan S.; Anastas, Paul T.

    2014-01-01

    Isolated, solvent-extracted lignin from candlenut (Aleurites moluccana) biomass was subjected to catalytic depolymerization in methanol with an added pressure of H-2, using a porous metal oxide catalyst (PMO) derived from a Cu-doped hydrotalcite-like precursor. The Cu-PMO was effective in converting

  19. Depolymerization of organosolv lignin to aromatic compounds over Cu-doped porous metal oxides

    NARCIS (Netherlands)

    Barta, Katalin; Warner, Genoa R.; Beach, Evan S.; Anastas, Paul T.

    2014-01-01

    Isolated, solvent-extracted lignin from candlenut (Aleurites moluccana) biomass was subjected to catalytic depolymerization in methanol with an added pressure of H-2, using a porous metal oxide catalyst (PMO) derived from a Cu-doped hydrotalcite-like precursor. The Cu-PMO was effective in converting

  20. Scintillation characteristics of undoped and Cu+-doped Li2B4O7 single crystals

    CERN Document Server

    Kobayashi, Masaaki; Senguttuvan, Nachimuthu

    2015-01-01

    Scintillation characteristics of undoped and Cu+-doped lithium tetraborate Li2B4O7 (LTB) were studied including optical transmittance, photoluminescence, radioluminescence for X- and gamma-rays, alpha/gamma ratio, and decay kinetics. The total time-integrated LYs in undoped and Cu+-doped LTB for X-rays are ~600 and ~760 ph/MeV (photons/MeV), respectively. The decay kinetics in undoped and Cu+-doped LTB are similar to each other. Typical decay spectra for pulsed X-rays can be fitted with four exponentials: for fast (t1~0.8 ns, t2~25-50 ns), medium (t3~300-400 ns), and slow (t4~20-30 ms) components. The slow component occupies about 60% of the total LY, while the fast ones less than 10%. The 10-90% rise time was 163 ps. The alpha/gamma ratio was 0.18 for external 241Am alpha-rays. The obtained increase in LY due to Cu+ doping remains modest. The Cu+-induced emission contains both fast and slow components, requiring further studies of the emission mechanism to explain the fast component.

  1. Highly efficient photocatalytic degradation of organic dyes by Cu doped ZnO nanostructures.

    Science.gov (United States)

    Kuriakose, Sini; Satpati, Biswarup; Mohapatra, Satyabrata

    2015-10-14

    Copper doped ZnO nanostructures have been synthesized by a facile wet chemical method. Structural properties of as-synthesized nanomaterials have been studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy, while UV-visible absorption spectroscopy and Raman spectroscopy have been used to study their optical properties. Sunlight driven photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes in water was used to evaluate the photocatalytic activities of Cu doped ZnO nanostructures using UV-visible absorption spectroscopy. The results showed that there is an optimum Cu doping level which leads to the highly enhanced photocatalytic activity of Cu doped ZnO nanostructures, as compared to pure ZnO nanostructures. A mechanism for the enhanced photocatalytic activity of Cu-ZnO nanostructures is tentatively proposed. The enhanced photocatalytic activity of Cu-ZnO nanostructures is attributed to the combined effects of improved separation of photogenerated charge carriers due to optimal Cu doping in ZnO nanostructures and the formation of ZnO-CuO nanoheterojunctions.

  2. The effect of Cu doping into Oriza sativa L. indica dye as photosensitizer for dye sensitized solar cell (DSSC)

    Science.gov (United States)

    Fadli, U. M.; Prasada, A. B.; Cari; Supriyanto, A.

    2016-11-01

    The aims of the research to are know the effect of Cu doping into natural dye in increasing the efficiency of DSCC, to determine of the optical and electrical characteristic of natural dye Cu doping. Sandwich structures formed in the sample consisted of working electrode pair Titanium Oxide (TiO2) and the counter electrode Platina (Pt). Absorbance test is measure by using UV-Visible spectrophotometer Lambda 25, conductivity test by using a two- point probe El Kahfi/I-V Meter, and characterization of current and voltage (I-V) by using a Keithley 2602A. The Cu doping into dye was increasing the efficiency of 71%.

  3. Doped semiconductor nanocrystal based fluorescent cellular imaging probes.

    Science.gov (United States)

    Maity, Amit Ranjan; Palmal, Sharbari; Basiruddin, S K; Karan, Niladri Sekhar; Sarkar, Suresh; Pradhan, Narayan; Jana, Nikhil R

    2013-06-21

    Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity.

  4. Effect of Cu doping on the structure and phase transition of directly synthesized FePt nanoparticles

    Science.gov (United States)

    Wang, Hanbin; Li, Yang; Chen, Xu; Shu, Dan; Liu, Xiang; Wang, Xina; Zhang, Jun; Wang, Hao; Wang, Yi; Ruterana, Pierre

    2017-01-01

    In this work, ternary Cu doped FePt nanoparticles were prepared in hexadecylamine at 320 °C by choosing FeCl2 as the Fe source. The experimental results showed that without Cu doping the as-prepared FePt nanoparticles possessed fcc structure and gradually exhibited typical fct diffraction peaks after increasing the Cu doping concentration. TEM images showed that the FePt nanoparticles had larger size and wider size distribution after introducing Cu additive. Magnetic property measurement showed that a coercivity of 4800 Oe was obtained when the composition of the ternary nanoparticles reached Fe35Pt45Cu20, in which the content of Fe+Cu was higher than Pt. The research indicates that Cu doping promotes the phase transition of FePt nanoparticles at temperature as low as 320 °C.

  5. Effect of Annealing on Structural and Optical Properties of Cu Doped In2O3 Thin Films

    OpenAIRE

    S. Kaleemulla; N. Madhusudhana Rao; N. Sai Krishna; M. Kuppan; M. Rigana Begam; M. Shobana

    2014-01-01

    Cu-doped In2O3 thin films were prepared using flash evaporation method at different Cu-doping levels. The effect of annealing was studied on the structure, morphology and optical properties of the thin films. The films exhibited cubic structure and optical transmittance of the films increasing with annealing temperature. The highest optical transmittance of 78 % was observed with band gap of 4.09 eV.

  6. Photocatalytic Characterization of Fe- and Cu-Doped ZnO Nanorods Synthesized by Cohydrolysis

    Directory of Open Access Journals (Sweden)

    Young Rang Uhm

    2013-01-01

    Full Text Available Fe- and Cu-doped ZnO nanorods have been synthesized by a novel process employing a hydrolysis of metal powders. Zn, Fe, and Cu nanopowders were used as starting materials and incorporated into distilled water. The solution was refluxed at 60°C for 24 h to obtain the precipitates from the hydrolysis of Zn and dopants (Cu and Fe. The TEM results for ZnO with and without metal doping showed that the produced powders had a rod-like shape. The rod shape was attributable to the zinc oxide from the hydrolysis of Zn. With an increasing doping content, the UV-vis spectra were shifted to a long wavelength and this result indicates that the band gap was changed by the metal doping. The values of phenol degrading Fe- and Cu-doped ZnO by a solar simulator were measured to be 60 and 75%, respectively.

  7. Effects of annealing on the ferromagnetism and photoluminescence of Cu-doped ZnO nanowires

    Science.gov (United States)

    Xu, H. J.; Zhu, H. C.; Shan, X. D.; Liu, Y. X.; Gao, J. Y.; Zhang, X. Z.; Zhang, J. M.; Wang, P. W.; Hou, Y. M.; Yu, D. P.

    2010-01-01

    Room temperature ferromagnetic Cu-doped ZnO nanowires have been synthesized using the chemical vapor deposition method. By combining structural characterizations and comparative annealing experiments, it has been found that both extrinsic (CuO nanoparticles) and intrinsic (Zn1-xCuxO nanowires) sources are responsible for the observed ferromagnetic ordering of the as-grown samples. As regards the former, annealing in Zn vapor led to a dramatic decrease of the ferromagnetism. For the latter, a reversible switching of the ferromagnetism was observed with sequential annealings in Zn vapor and oxygen ambience respectively, which agreed well with previous reports for Cu-doped ZnO films. In addition, we have for the first time observed low temperature photoluminescence changed with magnetic properties upon annealing in different conditions, which revealed the crucial role played by interstitial zinc in directly mediating high Tc ferromagnetism and indirectly modulating the Cu-related structured green emission via different charge transfer transitions.

  8. Cu-doped photovoltaic glasses by ion exchange for sunlight down-shifting

    Science.gov (United States)

    Mardegan, M.; Cattaruzza, E.

    2016-11-01

    Ion exchange process is a widely studied synthesis technique for the controlled modification of silicate glass composition and properties, being moreover an easy and cheap approach. Silicate glasses containing copper are known to exhibit a broad luminescent band peaked around 500 nm, ascribed to 3d10-3d94s1 electronic transition of Cu+ ions; this band turns out to be much promising for the realization of down-shifting systems, being excited in the UV and near-UV region. Luminescent Cu-doped silicate glass sheets suitable as down-shifters to be used for covering solar cells have been prepared by thermal ion exchange. Synthesis of the Cu-doped glasses has been done by dipping pure silicate sheets (commercially used as cover of photovoltaic panels) into a fused copper salt mixture at temperature of 400 °C, for duration between a few minutes and some hours; two different types of copper chloride salt mixtures were explored, with the aim at obtaining luminescent glasses able to improve the Si cell yield. Absorption and luminescence glass features were collected and compared. The performance of the different samples was tested by a solar simulator, measuring the output power of a Si solar cell covered with the Cu-doped glass slides.

  9. Engineering of electronic and optical properties of ZnO thin films via Cu doping

    Institute of Scientific and Technical Information of China (English)

    Zhang Guo-Heng; Deng Xiao-Yan; Xue Hua; Xiang Gang

    2013-01-01

    ZnO thin films doped with different Cu concentrations are fabricated by reactive magnetron sputtering technique.XRD analysis indicates that the crystal quality of the ZnO:Cu film can be enhanced by a moderate level of Cu-doping in the sputtering process.The results of XPS spectra of zinc,oxygen,and copper elements show that Cu-doping has an evident and complicated effect on the chemical state of oxygen,but little effect on those of zinc and copper.Interestingly,further investigation of the optical properties of ZnO:Cu samples shows that the transmittance spectra exhibit both red shift and blue shift with the increase of Cu doping,in contrast to the simple monotonic behavior of the Burstein-Moss effect.Analysis reveals that this is due to the competition between oxygen vacancies and intrinsic and surface states of oxygen in the sample.Our result may suggest an effective way of tuning the bandgap of ZnO samples.

  10. Formulation and Characterization of Cu Doped ZnO Thick Films as LPG Gas Sensor

    Directory of Open Access Journals (Sweden)

    A. V. PATIL

    2010-12-01

    Full Text Available Thick films of pure and various concentrations (1 wt. %, 3 wt. %, 5 wt. %, 7 wt. % and 10 wt. % of Cu-doped ZnO were prepared on alumina substrates using a screen printing technique. These films were fired at a temperature of 700ºC for two hours in an air atmosphere. Morphological, compositional and structural properties of the samples were obtained using the scanning electron microscopy (SEM, Energy dispersive spectroscopy (EDAX and X-ray diffraction techniques respectively. The LPG gas sensing properties of these thick films were investigated at different operating temperatures and LPG gas concentrations. The surface resistance of thick films decreases when exposed to LPG gas. The Cu doped films show significant sensitivity to LPG gas than pure ZnO film. 5 wt. % Cu-doped ZnO film was found to be more sensitive (87.3 % to LPG gas exposed at 300 oC than other doping concentrations with fast response and recovery time.

  11. Engineering of electronic and optical properties of PbS thin films via Cu doping

    Science.gov (United States)

    Touati, Baligh; Gassoumi, Abdelaziz; Dobryden, Illia; Natile, Marta Maria; Vomiero, Alberto; Turki, Najoua Kamoun

    2016-09-01

    Copper-doped PbS polycrystalline thin films were deposited by chemical bath deposition by adding small amount of Cu (ysolution = [Cu2+]/[Pb2+]) between 0.5 and 2 at%. The composition, structure, morphology, optical and electrical properties of the films were investigated by means of X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), UV-visible-near infrared (UV-Vis-NIR) spectrophotometry and Hall effect measurements. The XRD studies showed that the undoped films have PbS face centered cubic structure with (111) preferential orientation, while preferential orientation changes to (200) plane with increasing Cu doping concentration. The AFM and SEM measurements indicated that the film surfaces consisted of nanosized grains with pyramidal shape. Optical band gap was blue shifted from 0.72 eV to 1.69 eV with the increase in Cu doping concentration. The film obtained with the [Cu2+]/[Pb2+] ratio equal to 1.5 at% Cu showed the minimum resistivity of 0.16 Ω cm at room temperature and optimum value of optical band gap close to 1.5 eV. 1.5 at% Cu-doped PbS thin films exhibit the best optical and electrical properties, suitable for solar cells applications.

  12. Photocatalytic degradation of humic substances in aqueous solution using Cu-doped ZnO nanoparticles under natural sunlight irradiation.

    Science.gov (United States)

    Maleki, Afshin; Safari, Mahdi; Shahmoradi, Behzad; Zandsalimi, Yahya; Daraei, Hiua; Gharibi, Fardin

    2015-11-01

    In this study, Cu-doped ZnO nanoparticles were investigated as an efficient synthesized catalyst for photodegradation of humic substances in aqueous solution under natural sunlight irradiation. Cu-doped ZnO nanocatalyst was prepared through mild hydrothermal method and was characterized using FT-IR, powder XRD and SEM techniques. The effect of operating parameters such as doping ratio, initial pH, catalyst dosage, initial concentrations of humic substances and sunlight illuminance were studied on humic substances degradation efficiency. The results of characterization analyses of samples confirmed the proper synthesis of Cu-doped ZnO nanocatalyst. The experimental results indicated the highest degradation efficiency of HS (99.2%) observed using 1.5% Cu-doped ZnO nanoparticles at reaction time of 120 min. Photocatalytic degradation efficiency of HS in a neutral and acidic pH was much higher than that at alkaline pH. Photocatalytic degradation of HS was enhanced with increasing the catalyst dosage and sunlight illuminance, while increasing the initial HS concentration led to decrease in the degradation efficiency of HS. Conclusively, Cu-doped ZnO nanoparticles can be used as a promising and efficient catalyst for degradation of HS under natural sunlight irradiation.

  13. Experimental and theoretical study of the electronic properties of Cu-doped anatase TiO2.

    Science.gov (United States)

    Navas, Javier; Sánchez-Coronilla, Antonio; Aguilar, Teresa; Hernández, Norge C; de los Santos, Desireé M; Sánchez-Márquez, Jesús; Zorrilla, David; Fernández-Lorenzo, Concha; Alcántara, Rodrigo; Martín-Calleja, Joaquín

    2014-02-28

    A good correlation was obtained between the electronic properties of Cu-doped anatase TiO2 by virtue of both physical chemistry characterization and theoretical calculations. Pure and Cu-doped TiO2 were synthesized. The composition, structural and electronic properties, and the band gap energy were obtained using several techniques. The method of synthesis used produces Cu-doped anatase TiO2, and XRD, XPS and Raman spectroscopy indicate that Cu atoms are incorporated in the structure by substitution of Ti atoms, generating a distortion of the structure and oxygen vacancies. In turn, the band gap energy of the synthesized samples decrease drastically with the Cu doping. Moreover, periodic density functional theory (DFT-periodic) calculations were carried out both to model the experimentally observed doped structures and to understand theoretically the experimental structures obtained, the formation of oxygen vacancies and the values of the band gap energy. From the analysis of density of states (DOS), projected density of states (PDOS) and the electron localization function (ELF) a decrease in the band gap is predicted upon increasing the Cu doping. Thus, the inclusion of Cu in the anatase structure implies a covalent character in the Cu-O interaction, which involves the appearance of new states in the valence band maximum with a narrowing in the band gap.

  14. Facile synthesis of 2-D Cu doped WO3 nanoplates with structural, optical and differential anti cancer characteristics

    Science.gov (United States)

    Mehmood, Faisal; Iqbal, Javed; Gul, Asma; Ahmed, Waqqar; Ismail, M.

    2017-04-01

    Simple chemical co-precipitation method has been employed to synthesize two dimensional copper (Cu) doped tungsten oxide (WO3) nanoplates. A numbers of characterization techniques have been used to investigate their structural, optical and biocompatible anti cancer properties. The XRD results have confirmed the monoclinic crystal structure of WO3 nanoplates, and also successful doping of Cu ions into the WO3 crystal lattice. The presence of functional groups and chemical bonding have been verified through FTIR and Raman spectroscopy. The SEM images demonstrate that both undoped and Cu doped WO3 samples have squares plate like morphology. The EDX spectra confirm the presence of Cu, W and O ions. Diffuse reflectance spectroscopy (DRS) analysis has revealed a substantial red-shift in the absorption edge and a decrease in the band gap energy of nanoplates with Cu doping. Photoluminescence spectroscopy has been used to study the presence of defects like oxygen vacancies. Furthermore, the differential cytotoxic properties of Cu doped WO3 samples have been evaluated against human breast (MCF-7) and liver (Hep-2) cancer cells with ectocervical epithelial (HECE) healthy cells. The present findings confirm that the Cu doped WO3 nanoplates can be used as an efficient biocompatible anti cancer agent.

  15. Preparation of CdS Nanocrystals Doped TiO2 Supported on Bamboo Charcoal and Photocatalytic Properties%竹炭负载纳米CdS掺杂TiO2光催化剂制备及光催化性能

    Institute of Scientific and Technical Information of China (English)

    张建军

    2012-01-01

    A photocatalyst of CdS nanocrystals doped with TiO2 supported bamboo charcoal was prepared by a hydrothermal method in the different temperature. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption in low temperature and UV-Vis diffuse reflectance spectra. The XRD and SEM results showed that the as -synthesized TiO2 was anatase phase and its size was about 20-40nm. The UV-Vis diffuse reflectance spectra indicated that in the visible region, the absorption edges of the CdS nanonrystals doping TiO2 supported on bamboo charcoal shifted to visible light region, thus largely enhancing the TiO2 absorption of visible light. A xenon lamp ( λ >420nm) was used as an illuminant in the degeneration experiment and Rhodamine B (Rh B) was chosen as the model substance to evaluate photocatalytic activity of the CdS nanocrystals doped with TiO2 supported bamboo charcoal. The results showed that the photocatalytic activity of the CdS nanocrystals doping TiO2 supported bamboo charcoal synthesized at 240℃ when the doping amount of CdS nanocrystals is 4% ( mol fraction) is best, the colour removal of Rh B is 98.2% in 200 minutes.%采用水热法在不同温度下制备了竹炭(BC)负载纳米CdS掺杂TiO2光催化剂;采用X-射线粉末衍射(XRD)、扫描电子显微镜(SEM)、氮气低温吸附和紫外-可见漫反射图谱等对竹炭(BC)负载纳米CdS掺杂TiO2光催化剂进行了表征,XRD和SEM结果表明,TiO2为锐钛矿相.粒径为20nm~ 40nm.紫外-可见漫反射图谱显示,竹炭负载纳米CdS掺杂的TiO2的样品吸收边发生了明显的红移,大大提高了TiO2对可见光吸收.以氙灯为光源(λ> 420nm)、罗丹明B(Rh B)为模型污染物进行降解实验,探索了不同条件下合成竹炭负载纳米CdS掺杂TiO2的可见光催化性能.结果表明,纳米CdS掺杂量为4%(摩尔分数)240℃时,制备的竹炭负载纳米CdS掺杂TiO2对RhB的降解效果最好,

  16. Martensitic transformation in Cu-doped NiMnGa magnetic shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    Li Pan-Pan; Wang Jing-Min; Jiang Cheng-Bao

    2011-01-01

    This paper studies the martensitic transformation in the Cu-doped NiMnGa alloys. The orthorhombic martensite transforms to L21 cubic austenite by Cu substituting for Ni in the Ni50-x:CuxMn31Ga19 (x=2-10) alloys, the martensitic transformation temperature decreases significantly with the rate of 40 K per Cu atom addition. The variation of the Fermi sphere radius (kF) is applied to evaluate the change of the martensitic transformation temperature. The increase of kF leads to the increase of the martensitic transformation temperature.

  17. The saturable absorption and reverse saturable absorption properties of Cu doped zinc oxide thin films

    Science.gov (United States)

    Yao, Cheng-Bao; Wen, Xin; Li, Qiang-Hua; Yan, Xiao-Yan; Li, Jin; Zhang, Ke-Xin; Sun, Wen-Jun; Bai, Li-Na; Yang, Shou-Bin

    2017-03-01

    We present the structure and nonlinear absorption (NLA) properties of Cu-doped ZnO (CZO) films prepared by magnetron sputtering. The films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the CZO films can maintain a wurtzite structure. Furthermore, the open-aperture (OA) Z-scan measurements of the film were carried out by nanosecond laser pulse. A transition from saturable absorption (SA) to reverse saturable absorption (RSA) was observed as the excitation intensity increasing. With good excellent nonlinear optical coefficient, the samples were expected to be the potential applications in optical devices.

  18. Cu-doped zinc oxide and its polythiophene composites: preparation and antibacterial properties.

    Science.gov (United States)

    Ma, Ge; Liang, Xiaoxi; Li, Liangchao; Qiao, Ru; Jiang, Donghua; Ding, Yan; Chen, Haifeng

    2014-04-01

    Cu-doped zinc oxide and its polythiophene nanocomposites were prepared by the Sol-Gel and in situ polymerization methods, respectively. The structures, morphologies and compositions of the samples were characterized. The antibacterial properties of the samples on three kinds of strains were determined by using powder inhibition zones, minimum inhibitory concentrations and minimal bactericidal concentrations. The study confirmed that the antibacterial activities of the composites were better than those of their each component. The antibacterial mechanisms of the samples were discussed further.

  19. Photovoltaic properties of Cu-doped CH3NH3PbI3 with perovskite structure

    Science.gov (United States)

    Shirahata, Yasuhiro; Oku, Takeo

    2017-01-01

    Photovoltaic properties of copper (Cu)-doped perovskite (CH3NH3PbCuxI3+x) photovoltaic devices with different Cu content were investigated. The CH3NH3PbCuxI3+x films were polycrystalline with a tetragonal system, and their lattice constants and crystallite size varied with Cu doping. Compared to conversion efficiencies of non-doped CH3NH3PbI3 photovoltaic device, those of CH3NH3PbCuxI3+x photovoltaic devises increased. The improvement of photovoltaic properties was attributed to partial substitution of Cu at the Pb sites.

  20. Cu-doped ZnO nanoparticles: Synthesis, structural and electrical properties

    Science.gov (United States)

    Singhal, Sonal; Kaur, Japinder; Namgyal, Tsering; Sharma, Rimi

    2012-04-01

    Pure and Cu doped ZnO nanopowders (5, 10, 15, 20, 25 and 30 at% Cu) have been synthesized using co-precipitation method. Transmission Electron Microscopic analysis has shown the morphology of ZnO nanopowders to be quasi-spherical. Powder X-ray Diffraction studies have revealed the systematic doping of Cu into the ZnO lattice up to 10% Cu, though the peaks corresponding to CuO in 10% Cu are negligibly very small. Beyond this level, there was segregation of a secondary phase corresponding to the formation of CuO. Fourier Transform Infrared spectra have shown a broad absorption band at ∼490 cm-1 for all the samples, which corresponds to the stretching vibration of Zn-O bond. DC electrical resistivity has been found to decrease with increasing Cu content. The activation energy has also been observed to decrease with copper doping i.e. from ∼0.67 eV for pure ZnO to ∼0.41 eV for 30 at% Cu doped ZnO.

  1. Hydrogen generation by photoelectrochemical effect of the Cu-doped TiO2 photoanode

    Science.gov (United States)

    Ly, Ngoc Tai; Hoa Dao, Thi; Hoang To, Le Hong; Vu, Dinh Lam; Le, Van Hong

    2014-09-01

    TiO2 film photoanodes with a size of 1 × 1 cm2 were fabricated by a spin coating method. Cu-doped TiO2 powder with various Cu concentrations (0.2, 0.4, 0.6 and 0.8 at%) and surfactant were used as starting materials in coating Cu-doped TiO2 thin films onto FTO/glass substrate. Crystalline structure of TiO2 material, microstructure of the photoanode films and their thickness were identified by x-ray diffraction and Raman scattering. Hydrogen generation from water by photoelectrochemical effect in the visible light was observed by recording I/V characteristics of the photoanode in dark and light regimes. The obtained results have shown that the hydrogen generation efficiency of photoanode nonlinearly depends on Cu concentration. The nonlinear dependence of the hydrogen generation efficiency may be due to a change of resistivity of the film photoanode that is related with the random distribution of the hetero-junction between interfaces of TiO2 and CuO nanoparticles.

  2. Cu-doped ZnO nanoparticles: Synthesis, structural and electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Singhal, Sonal, E-mail: sonal1174@gmail.com [Department of Chemistry, Panjab University, Chandigarh 160014 (India); Kaur, Japinder; Namgyal, Tsering; Sharma, Rimi [Department of Chemistry, Panjab University, Chandigarh 160014 (India)

    2012-04-15

    Pure and Cu doped ZnO nanopowders (5, 10, 15, 20, 25 and 30 at% Cu) have been synthesized using co-precipitation method. Transmission Electron Microscopic analysis has shown the morphology of ZnO nanopowders to be quasi-spherical. Powder X-ray Diffraction studies have revealed the systematic doping of Cu into the ZnO lattice up to 10% Cu, though the peaks corresponding to CuO in 10% Cu are negligibly very small. Beyond this level, there was segregation of a secondary phase corresponding to the formation of CuO. Fourier Transform Infrared spectra have shown a broad absorption band at {approx}490 cm{sup -1} for all the samples, which corresponds to the stretching vibration of Zn-O bond. DC electrical resistivity has been found to decrease with increasing Cu content. The activation energy has also been observed to decrease with copper doping i.e. from {approx}0.67 eV for pure ZnO to {approx}0.41 eV for 30 at% Cu doped ZnO.

  3. Structural and optoelectronic properties of glucose capped Al and Cu doped ZnO nanostructures

    Directory of Open Access Journals (Sweden)

    Patwari Gunjan

    2016-03-01

    Full Text Available Al and Cu doped ZnO nanoparticles are considered as appropriate for modulation of structural and optoelectronic properties. Al atoms are found to substitute the host Zn whereas Cu dopants mainly segregate in grain boundaries and thereby determine the optical properties. The undoped as well as Al and Cu doped ZnO exhibit spherical well defined particles. The spherical nanoparticles change to rod type structures on co-doping. The average particle size decreases on doping what consequently results in an increment in band gap. Blue shift in UV absorption is governed by the functional group of glucose; further blue shift occurring on metal doping may be attributed to Burstein-Moss effect. PL spectra of doped and undoped ZnO show a dominant near band gap UV emission along with visible emission owing to the defects. The PL peak intensity increases on doping with Cu and Al. The linear I-V characteristics indicate the ohmic behavior of ZnO nanostructures.

  4. Structural, electronic and optical properties of Cu-doped ZnO: experimental and theoretical investigation

    Science.gov (United States)

    Horzum, S.; Torun, E.; Serin, T.; Peeters, F. M.

    2016-06-01

    Experiments are supplemented with ab initio density functional theory (DFT) calculations in order to investigate how the structural, electronic and optical properties of zinc oxide (ZnO) thin films are modified upon Cu doping. Changes in characteristic properties of doped thin films, that are deposited on a glass substrate by sol-gel dip coating technique, are monitored using X-ray diffraction (XRD) and UV measurements. Our ab initio calculations show that the electronic structure of ZnO can be well described by DFT+U/? method and we find that Cu atom substitutional doping in ZnO is the most favourable case. Our XRD measurements reveal that the crystallite size of the films decrease with increasing Cu doping. Moreover, we determine the optical constants such as refractive index, extinction coefficient, optical dielectric function and optical energy band gap values of the films by means of UV-Vis transmittance spectra. The optical band gap of ZnO the thin film linearly decreases from 3.25 to 3.20 eV at 5% doping. In addition, our calculations reveal that the electronic defect states that stem from Cu atoms are not optically active and the optical band gap is determined by the ZnO band edges. Experimentally observed structural and optical results are in good agreement with our theoretical results.

  5. Unexpected strong magnetism of Cu doped single-layer MoS₂ and its origin.

    Science.gov (United States)

    Yun, Won Seok; Lee, J D

    2014-05-21

    The magnetism of the 3d transition-metal (TM) doped single-layer (1L) MoS2, where the Mo atom is partially replaced by the 3d TM atom, is investigated using the first-principles density functional calculations. In a series of 3d TM doped 1L-MoS2's, the induced spin polarizations are negligible for Sc, Ti, and Cr dopings, while the induced spin polarizations are confirmed for V, Mn, Fe, Co, Ni, Cu, and Zn dopings and the systems become magnetic. Especially, the Cu doped system shows unexpectedly strong magnetism although Cu is nonmagnetic in its bulk state. The driving force is found to be a strong hybridization between Cu 3d states and 3p states of neighboring S, which results in an extreme unbalanced spin-population in the spin-split impurity bands near the Fermi level. Finally, we also discuss further issues of the Cu induced magnetism of 1L-MoS2 such as investigation of additional charge states, the Cu doping at the S site instead of the Mo site, and the Cu adatom on the layer (i.e., 1L-MoS2).

  6. The design of Cu-doped ZnO thermoelectric module (simulation study)

    Science.gov (United States)

    Hadi, Syamsul; Suratwan, Agus; Kurniawan, Agus; Budiana, Eko Prasetya; Suyitno

    2016-03-01

    The p-type semiconductor of Cu-doped ZnO-based thermoelectric material has already been synthesized and studied as an energy harvester. The next challenge is manufacturing the thermoelectric module in the development of thermoelectric as an eco-friendly material in the future. This research aims to investigate the effect of thermoelectric geometric design on the electrical output power and voltage and to recommend the most appropriate thermoelectric geometric design. The design of thermoelectric generator (TEG) includes the determinations of dimension (width, length, and height), number of modules, and semiconductor materials. The simulation used the coupled-field analysis of ANSYS APDL 14.5 in the steady state condition. The p- and n- type thermoelectric material used Cu-doped ZnO and Al-doped ZnO, respectively. The width of element and the number of thermoelectric module were varied to obtain a thermoelectric design, which produces the largest current, power, and voltage. The result of research shows that the t hermoelectric generator with the element widths of 0.94 mm, 1.125 mm, 1.05 mm, and 1.2 mm generates the largest power output and voltage, namely: 0.32 W and 0.89 V, 0.38 W and 0.98 V, 0.45 W and 1.06 V, and 0.52 W and 1.13 V, respectively.

  7. Electrical and photovoltaic properties of Cu-doped p-GaSe/n-InSe heterojunction

    Science.gov (United States)

    Shigetomi, S.; Ikari, T.

    2000-08-01

    GaSe(Cu)/InSe heterojunctions have been formed by bringing the cleavage surface of undoped n-InSe and Cu-doped p-GaSe into direct contact. Transport and phototransport properties are studied by the measurements of capacitance-voltage, current-voltage, and the spectral response of short-circuit current. Moreover, the efficiency parameters under illumination are estimated by using the open-circuit voltage and short-circuit current. These characteristics of GaSe(Cu)/InSe heterojunctions are compared with those of GaSe(Un)/InSe heterojunctions fabricated by undoped p-GaSe and n-InSe. The series resistance of GaSe(Cu)/InSe heterojunctions is found, the value of which is about 103 times lower than the corresponding value of GaSe(Un)/InSe heterojunctions. A short-circuit current density of 9.0 mA/cm2 and an open-circuit voltage of 0.42 V on GaSe(Cu)/InSe heterojunctions are obtained under illumination of 120 mW/cm2 of a halogen lamp. The short-circuit current of GaSe(Cu)/InSe heterojunctions is about one order of magnitude lager than that of GaSe(Un)/InSe heterojunctions. These experimental results indicate that the low-resistivity of Cu-doped GaSe is effective for the electrical and photovoltaic properties of GaSe/InSe heterojunctions.

  8. Building Structural Complexity in Semiconductor Nanocrystals through Chemical Transformations

    OpenAIRE

    Sadtler, Bryce F

    2010-01-01

    Methods are presented for synthesizing nanocrystal heterostructures comprised of two semiconductor materials epitaxially attached within individual nanostructures. The chemical transformation of cation exchange, where the cations within the lattice of an ionic nanocrystal are replaced with a different metal ion species, is used to alter the chemical composition at specific regions of a nanocrystal. Partial cation exchange was performed in cadmium sulfide (CdS) nanorods of well-defined size an...

  9. The Effects of Cu-doped TiO2 Thin Films on Hyperplasia, Inflammation and Bacteria Infection

    Directory of Open Access Journals (Sweden)

    Linhua Li

    2015-11-01

    Full Text Available In the present work, different concentrations of Cu ion (1, 2, 5 and 10 wt % were doped in the TiO2 film by a sol-gel method and dip coating process. The morphology of the Cu-doped TiO2 films were characterized by scanning electron microscopy (SEM and the results showed that the doped Cu made no change to the TiO2 films. The nitric oxide (NO release experiment showed that these Cu-doped surfaces showed the ability of catalytic decomposition of exogenous donor S-nitroso-N-acetyl-penicillamine (SNAP to generate (NO. Based on fluorescence analysis and CCK-8 quantitative results, such films had the ability to inhibit smooth muscle cells adhesion, proliferation and migration with SNAP in vitro. The macrophage adhesion assay and anti-bacterial test proved that such Cu-doped TiO2 films also possessed anti-inflammatory and anti-bacterial abilities. All the abilities above showed positive correlation with the amounts of the doped Cu. This study suggested that the Cu-doped TiO2 films were capable of generating physiological levels of NO in the presence of endogenous donor S-nitrosothiols (RSNO, endowing the TiO2 films with anti-hyperplasia, anti-inflammatory and anti-bacterial abilities.

  10. Optical, phonon and efficient visible and infrared photocatalytic activity of Cu doped ZnS micro crystals

    Science.gov (United States)

    Prasad, Neena; Balasubramanian, Karthikeyan

    2017-02-01

    We report, the enhanced photocatalytic behaviour of Cu doped ZnS micro crystals. ZnS and different concentrations of Cu doped ZnS microcrystals were prepared. X-ray diffraction confirms the crystalline and phase of the particles. Morphology and sizes were studied using Scanning Electron Microscopy (SEM). Recorded optical absorption spectra show a band for around 365 nm for pure ZnS, but there is a broad band in the near infrared regime for the Cu-doped ZnS microcrystals which are attributed to the d-d transitions of Cu2 + ions. Phonon properties of as-prepared samples were investigated using Raman spectroscopy. Present work we investigate the potential of ZnS and Cu doped ZnS as a photocatalyst. For this from the degradation of methylene blue dye in aqueous media the photocatalytic activity of pure and highest doped ZnS samples with the irradiation of white light and infrared, enhanced photocatalytic activity were observed. Mechanism of white light an IR light based photocatalytic activity is explained based on the electron-hole pair production.

  11. Realization of Cu-Doped p-Type ZnO Thin Films by Molecular Beam Epitaxy.

    Science.gov (United States)

    Suja, Mohammad; Bashar, Sunayna B; Morshed, Muhammad M; Liu, Jianlin

    2015-04-29

    Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films, and the best conductivity is achieved with a high hole concentration of 1.54 × 10(18) cm(-3), a low resistivity of 0.6 Ω cm, and a moderate mobility of 6.65 cm(2) V(-1) s(-1) at room temperature. Metal oxide semiconductor capacitor devices have been fabricated on the Cu-doped ZnO films, and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as X-ray diffraction, X-ray photoelectron, Raman, and absorption spectroscopies are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO.

  12. Photoinduced superhydrophilicity of TiO2 thin film with hierarchical Cu doping

    Directory of Open Access Journals (Sweden)

    Zhifeng Liu, Yun Wang, Xinli Peng, Yabin Li, Zhichao Liu, Chengcheng Liu, Jing Ya and Yizhong Huang

    2012-01-01

    Full Text Available Hydrophilic Cu–TiO2 thin films with a gradient in the Cu concentration were prepared on glass by layer-by-layer dip-coating from TiO2 precursors. The effects of the Cu doping on the structure and properties of TiO2 self-cleaning thin films are discussed. The Cu gradient markedly affects the hydrophilicity of the films, with the water contact angle significantly reduced compared with those of the pure or uniformly doped TiO2 thin films. This enhanced hydrophilicity is explained by the more efficient absorption of the solar light and by the reduced recombination of photoexcited electrons and holes in the TiO2 films containing a gradient of Cu dopants.

  13. Synthesis and photocatalytic properties of Co- and Cu-doped Bi2Sn2O7

    Science.gov (United States)

    Zhuang, Jing; Hu, Chaohao; Zhu, Binqing; Zhong, Yan; Zhou, Huaiying

    2017-01-01

    Bi2Sn2O7 photocatalysts doped by Co and Cu ions were successfully synthesized by using the hydrothermal process and impregnation method. The products were characterized using X-ray diffraction analysis (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray detector (EDS), infrared spectroscopy (IR), the photoluminescence (PL) spectra and UV-visible diffuse reflectance spectroscopy (DRS). The photocatalytic properties were further evaluated by degrading rhodamine B (RhB) as a model pollution under visible-light irradiation. The results indicated that Co- and Cu-doped Bi2Sn2O7 photocatalysts have a cubic pyrochlore phase with the hybrid metals. The metal-loaded photocatalysts show the enhanced photocatalytic efficiency for degradation of RhB under visible-light (λ> 420 nm). The mechanism of improved photocatalytic activity is also discussed in detail.

  14. Stress reduction of Cu-doped diamond-like carbon films from ab initio calculations

    Directory of Open Access Journals (Sweden)

    Xiaowei Li

    2015-01-01

    Full Text Available Structure and properties of Cu-doped diamond-like carbon films (DLC were investigated using ab initio calculations. The effect of Cu concentrations (1.56∼7.81 at.% on atomic bond structure was mainly analyzed to clarify the residual stress reduction mechanism. Results showed that with introducing Cu into DLC films, the residual compressive stress decreased firstly and then increased for each case with the obvious deterioration of mechanical properties, which was in agreement with the experimental results. Structural analysis revealed that the weak Cu-C bond and the relaxation of both the distorted bond angles and bond lengths accounted for the significant reduction of residual compressive stress, while at the higher Cu concentration the increase of residual stress attributed to the existence of distorted Cu-C structures and the increased fraction of distorted C-C bond lengths.

  15. Stress reduction of Cu-doped diamond-like carbon films from ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaowei; Ke, Peiling; Wang, Aiying, E-mail: aywang@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2015-01-15

    Structure and properties of Cu-doped diamond-like carbon films (DLC) were investigated using ab initio calculations. The effect of Cu concentrations (1.56∼7.81 at.%) on atomic bond structure was mainly analyzed to clarify the residual stress reduction mechanism. Results showed that with introducing Cu into DLC films, the residual compressive stress decreased firstly and then increased for each case with the obvious deterioration of mechanical properties, which was in agreement with the experimental results. Structural analysis revealed that the weak Cu-C bond and the relaxation of both the distorted bond angles and bond lengths accounted for the significant reduction of residual compressive stress, while at the higher Cu concentration the increase of residual stress attributed to the existence of distorted Cu-C structures and the increased fraction of distorted C-C bond lengths.

  16. Anharmonicity effects in Cu-doped ZnO nanocombs by temperature-dependent Raman scattering

    Science.gov (United States)

    Kong, J. F.; Fan, D. H.; Shen, W. Z.

    2016-09-01

    Micro-Raman spectra of E 2(high) phonon mode in Cu-doped ZnO nanocombs have been presented in detail with different Cu compositions under the temperature ranging from 83 to 443 K grown by a simple catalyst-free chemical vapor deposition method. The alloy disorder effect has been investigated by analyzing the asymmetric broadening of E 2(high) phonon mode and Cu-induced localized vibration mode at room temperature. In addition, we resort to a theory model including the lattice thermal expansion and anharmonic phonon-phonon interaction, which can well describe the temperature dependence of Raman shift and linewidth of E 2(high) phonon. In combining with the theory model, we have revealed an increasing anharmonic effect on the Raman shift and linewidth behaviors with increasing Cu composition. Furthermore, it is found that the lifetime of E 2(high) phonon mode shortens with enhancing the anharmonicity.

  17. Synthesis of Cu doped ZnS nanostructures on flexible substrate using low cost chemical method

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Nitin, E-mail: nitinmishra97@gmail.com; Purohit, L. P., E-mail: lppurohit@gmail.com [Gurukula Kangari University, Haridwar UK (India); Goswami, Y. C., E-mail: y-goswami@yahoo.com [ITM University, Turari, Gwalior, MP (India)

    2015-08-28

    Flexible electronics is one of the emerging area of this era. In this paper we have reported synthesis of Cu doped Zinc sulphide nanostructures on filter paper flexible substrates. Zinc chloride and Thio urea were used as a precursor for Zinc and Sulphur. The structures were characterized by XRD, FE-SEM and UV visible spectrometer. All the peaks identified for cubic structure of ZnS. Appearance of small Cu peaks indicates incorporation of Cu into ZnS lattice. Zns nanostructures assembled as nanobelts and nanofibers as shown in FE-SEM micrographs. Compound Structures provide the reasonable electrical conductivity on filter paper. Absorption in UV region makes them suitable for flexible electronic devices.

  18. Room-temperature ferromagnetic properties of Cu-doped ZnO rod arrays

    Indian Academy of Sciences (India)

    C H Xia; C G Hu; C H Hu; Z Ping; F Wang

    2011-08-01

    We have investigated properties of the Cu-doped ZnO crystalline film synthesized by the hydrothermal method. X-ray diffraction and X-ray photoelectron spectroscopy results provide the evidence that Cu2+ is incorporated into the ZnO lattices. Photoluminescence spectrum of the rod arrays shows that the UV emission peak shifts a little to lower energy and its intensity decreased. There are another two emission peaks centred in blue and green regions because of the incorporation of Cu2+ ions. The rod arrays have exhibited room-temperature ferromagnetic behaviour with the remanence of 0.926 × 10-3 emu/cm3. We suggest that the exchange interaction between local spin-polarized electrons (such as the electrons of Cu2+ ions) and conductive electrons is the cause of room-temperature ferromagnetism.

  19. Designing multifunctional chemical sensors using Ni and Cu doped carbon nanotubes

    DEFF Research Database (Denmark)

    Mowbray, Duncan; García Lastra, Juan Maria; Thygesen, Kristian Sommer

    2010-01-01

    We demonstrate a “bottom up” approach to the computational design of a multifunctional chemical sensor. General techniques are employed for describing the adsorption coverage and resistance properties of the sensor based on density functional theory and non-equilibrium Green's function methodolog......We demonstrate a “bottom up” approach to the computational design of a multifunctional chemical sensor. General techniques are employed for describing the adsorption coverage and resistance properties of the sensor based on density functional theory and non-equilibrium Green's function...... methodologies, respectively. Specifically, we show how Ni and Cu doped metallic (6,6) single-walled carbon nanotubes may work as effective multifunctional sensors for both CO and NH3....

  20. CERN Document Server (CDS): Introduction

    CERN Document Server

    CERN. Geneva; Costa, Flavio

    2017-01-01

    A short online tutorial introducing the CERN Document Server (CDS). Basic functionality description, the notion of Revisions and the CDS test environment. Links: CDS Production environment CDS Test environment  

  1. Ag- and Cu-doped multifunctional bioactive nanostructured TiCaPCON films

    Energy Technology Data Exchange (ETDEWEB)

    Shtansky, D.V., E-mail: shtansky@shs.misis.ru [National University of Science and Technology “MISIS”, Leninsky prospekt 4, Moscow 119049 (Russian Federation); Batenina, I.V.; Kiryukhantsev-Korneev, Ph.V.; Sheveyko, A.N.; Kuptsov, K.A. [National University of Science and Technology “MISIS”, Leninsky prospekt 4, Moscow 119049 (Russian Federation); Zhitnyak, I.Y.; Anisimova, N.Yu.; Gloushankova, N.A. [N.N. Blokhin Russian Cancer Research Center of RAMS, Kashirskoe shosse 24, Moscow 115478 (Russian Federation)

    2013-11-15

    A key property of multicomponent bioactive nanostructured Ti(C,N)-based films doped with Ca, P, and O (TiCaPCON) that can be improved further is their antibacterial effect that should be achieved without compromising the implant bioactivity and biocompatibility. The present work is focused on the study of structure, chemical, mechanical, tribological, and biological properties of Ag- and Cu-doped TiCaPCON films. The films with Ag (0.4–4 at.%) and Cu (13 at.%) contents were obtained by simultaneous sputtering of a TiC{sub 0.5}–Ca{sub 3}(PO{sub 4}){sub 2} target and either an Ag or a Cu target. The film structure was studied using X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, and Raman-shift and IR spectroscopy. The films were characterized in terms of their hardness, elastic modulus, dynamic impact resistance, friction coefficient and wear rate (both in air and normal saline), surface wettability, electrochemical behavior and Ag or Cu ion release in normal saline. Particular attention was paid to the influence of inorganic bactericides (Ag and Cu ions) on the bactericidal activity against unicellular yeast fungus Saccharomyces cerevisiae and gram-positive bacteria Lactobacillus acidophilus, as well as on the attachment, spreading, actin cytoskeleton organization, focal adhesions, and early stages of osteoblastic cell differentiation. The obtained results show that the Ag-doped films are more suitable for the protection of metallic surfaces against bacterial infection compared with their Cu-doped counterpart. In particular, an excellent combination of mechanical, tribological, and biological properties makes Ag-doped TiCaPCON film with 1.2 at.% of Ag very attractive material for bioengineering and modification of load-bearing metal implant surfaces.

  2. Ag- and Cu-doped multifunctional bioactive nanostructured TiCaPCON films

    Science.gov (United States)

    Shtansky, D. V.; Batenina, I. V.; Kiryukhantsev-Korneev, Ph. V.; Sheveyko, A. N.; Kuptsov, K. A.; Zhitnyak, I. Y.; Anisimova, N. Yu.; Gloushankova, N. A.

    2013-11-01

    A key property of multicomponent bioactive nanostructured Ti(C,N)-based films doped with Ca, P, and O (TiCaPCON) that can be improved further is their antibacterial effect that should be achieved without compromising the implant bioactivity and biocompatibility. The present work is focused on the study of structure, chemical, mechanical, tribological, and biological properties of Ag- and Cu-doped TiCaPCON films. The films with Ag (0.4-4 at.%) and Cu (13 at.%) contents were obtained by simultaneous sputtering of a TiC0.5-Ca3(PO4)2 target and either an Ag or a Cu target. The film structure was studied using X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, and Raman-shift and IR spectroscopy. The films were characterized in terms of their hardness, elastic modulus, dynamic impact resistance, friction coefficient and wear rate (both in air and normal saline), surface wettability, electrochemical behavior and Ag or Cu ion release in normal saline. Particular attention was paid to the influence of inorganic bactericides (Ag and Cu ions) on the bactericidal activity against unicellular yeast fungus Saccharomyces cerevisiae and gram-positive bacteria Lactobacillus acidophilus, as well as on the attachment, spreading, actin cytoskeleton organization, focal adhesions, and early stages of osteoblastic cell differentiation. The obtained results show that the Ag-doped films are more suitable for the protection of metallic surfaces against bacterial infection compared with their Cu-doped counterpart. In particular, an excellent combination of mechanical, tribological, and biological properties makes Ag-doped TiCaPCON film with 1.2 at.% of Ag very attractive material for bioengineering and modification of load-bearing metal implant surfaces.

  3. Time and Temperature Dependence of CdS Nanoparticles Grown in a Polystyrene Matrix

    Directory of Open Access Journals (Sweden)

    F. Antolini

    2012-01-01

    Full Text Available Luminescent CdS nanocrystals embedded in a polystyrene matrix were successfully prepared. The in situ growth of CdS QDs was realized by thermal treatment of Cd bis(thiolate/polymer foil at different times and temperatures (240°C and 300°C of annealing, in order to evaluate their influence on the quantum dots growth process. As a general trend, the increasing of time and temperature of annealing induces a rise of the CdS nanocrystals size into the polymeric matrix. The size distribution, morphology, and structure of the CdS nanoparticles were analysed with HRTEM and XRD experiments. UV-Vis and PL data are strongly size-dependent and were used to investigate the particles' growth process, too. The CdS nanoparticles behavior in solution indicated a general trend of QDs to aggregation. This predisposition was clearly displayed by DLS measurements.

  4. Effect of Cu doping on the properties of ZnTe:Cu thin films and CdS/CdTe/ZnTe solar cells

    Science.gov (United States)

    Tang, J.; Mao, D.; Trefny, J. U.

    1997-02-01

    The effects of Cu doping concentration and post-deposition annealing treatment on the properties of ZnTe thin films were investigated in an effort to decrease the Cu doping concentration and improve the long-term stability of CdS/CdTe/ZnTe solar cells. The structural, compositional, and electrical properties were studied systematically using x-ray diffraction (XRD), electron microprobe, Hall effect and conductivity measurements. XRD measurements indicated that the crystalline phase of as-deposited and low-temperature annealed ZnTe films is dependent on Cu doping concentration. Low-Cu-doped films exhibited zincblende phase, whereas high-Cu-doped films showed wurtzite phase. After annealing at high temperature (⩾350 °C), all films exhibited zincblende structure. Electron probe microanalysis revealed a deficiency of cations in low-Cu-doped films and an excess of cations in high-Cu-doped films. Hall effect measurements revealed a dependence of hole mobility on Cu doping concentration with the highest mobility (20 cm2/Vṡs) obtained at a low Cu concentration. Carrier concentrations higher than mid-1016cm-3 were obtained at a Cu concentration of 2 at. % and relatively low annealing temperatures. Studies of the activation energy of dark conductivity suggested that intrinsic defects (e.g., Zn vacancies) are the dominant acceptors for Cu concentrations lower than 4.5 at. %. Finally, ZnTe films with Cu concentrations as low as 1 at. % were used successfully as a back contact layer in CdTe based solar cells. Fill factors over 0.70 were obtained using ZnTe films of low Cu concentrations.

  5. Effect of Cu doping on the magnetic and electrical properties of n=2 Ruddlesden-Popper manganates

    Institute of Scientific and Technical Information of China (English)

    Si Ji-Wei; Cao Qing-Qi; Gu Ben-Xi; Du You-Wei

    2005-01-01

    A series of polycrystalline Cu-doped n=2 Ruddlesden-Popper manganates La1.2Sr1.sCuxMn(2-x)O7 (x=0, 0.04,0.13) were synthesized by the solid state reaction method. The effect of Cu doping on the magnetic and transport properties has been studied. It is found that Cu substitution for Mn greatly affects the magnetic and electrical properties of the parent phase La1.2Sr1.8Mn2O7. With the increase of Cu content, the system undergoes a transition from longrange ferromagnetic order to the spin glass state and further to an antiferromagnetic order. A little of Cu dopant can lead to the samples showing semiconductor or insulator behaviour in the whole observed temperature range while the parent phase has a metal-insulator transition. These samples show colossal magnetoresistance at low temperatures and the value of it decreases with increasing Cu content.

  6. Structural and magnetic properties of pure and Cu doped In{sub 2}O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Krishna, N. Sai; Kaleemulla, S., E-mail: skaleemulla@gmail.com; Rao, N. Madhusudhana; Krishnamoorthi, C.; Begam, M. Rigana [Thin Films Laboratory, School of Advanced Sciences, VIT University, Vellore – 632014 (India); Amarendra, G. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam –603102 (India); UGC-DAE-CSR, Kalpakkam Node, Kokilamedu-603104 (India)

    2015-06-24

    Pure and Cu (7 at.%) doped In{sub 2}O{sub 3} thin films were prepared using an electron beam evaporation technique. A systematic study was carried out on the structural, chemical and magnetic properties of the thin films. X-ray diffraction analysis revealed that all the films were cubic in structure. The pure and Cu doped In{sub 2}O{sub 3} thin films showed ferromagnetism at room temperature. The Cu doped In{sub 2}O{sub 3} thin films showed the saturation magnetization, coercivity and retentivity of 38.71 emu/cm{sup 3}, 245 G and 5.54 emu/cm{sup 3}, respectively.

  7. Structural and optical properties of Cu-doped CdTe films with hexagonal phase grown by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    F. de Moure-Flores

    2012-06-01

    Full Text Available Cu-doped CdTe thin films were prepared by pulsed laser deposition on Corning glass substrates using powders as target. Films were deposited at substrate temperatures ranging from 100 to 300 °C. The X-ray diffraction shows that both the Cu-doping and the increase in the substrate temperature promote the presence of the hexagonal CdTe phase. For a substrate temperature of 300 °C a CdTe:Cu film with hexagonal phase was obtained. Raman and EDS analysis indicate that the films grew with an excess of Te, which indicates that CdTe:Cu films have p-type conductivity.

  8. First-principles investigation of Cu-doped ZnS with enhanced photocatalytic hydrogen production activity

    Science.gov (United States)

    Dong, Ming; Zhou, Peng; Jiang, Chuanjia; Cheng, Bei; Yu, Jiaguo

    2017-01-01

    The band structure and electronic properties of Cu-doped wurtzite ZnS were investigated by density functional theory calculations. According to the formation energies, the substitutional Cu and S vacancy defects are stable among the examined doping species. Particularly, the hybridization of substitutional Cu 3d and S 3p orbitals narrows the band gap of substitutional Cu-doped ZnS (CuZn-ZnS), while the high effective mass ratio of photogenerated holes and electrons (mh∗/me∗) in the CuZn-ZnS is beneficial for the separation and migration of the photogenerated charge carriers. Lab-synthesized CuZn-ZnS sample exhibited enhanced visible-light absorption and photocatalytic hydrogen production activity compared to pure ZnS.

  9. Microstructure and antibacterial properties of Cu-doped TiO2 coating on titanium by micro-arc oxidation

    Science.gov (United States)

    Yao, Xiaohong; Zhang, Xiangyu; Wu, Haibo; Tian, Linhai; Ma, Yong; Tang, Bin

    2014-02-01

    Infection associated with titanium implants remains the most common serious complication after surgery. In this work, Cu-doped antibacterial TiO2 coating was synthesized by micro-arc oxidation of titanium in an electrolyte bearing Cu nanoparticles. Surface morphology and structure of the coating were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that Cu nanoparticles were not only distributed on the surface and inside the pores but also embedded in the coating. Cu mainly exists in the Cu2+ state in the TiO2 coating. The Cu-doped coating exhibited excellent antibacterial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus).

  10. Thermoluminescence dependence on the wavelength of monochromatic UV-radiation in Cu-doped KCl and KBr at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Perez R, A.; Piters, T.; Aceves, R.; Rodriguez M, R.; Perez S, R., E-mail: rperez@cifus.uson.mx [Universidad de Sonora, Departamento de Investigaciones en Fisica, Apdo. Postal 5-088, 83190 Hermosillo, Sonora (Mexico)

    2014-08-15

    Thermoluminescence (Tl) dependence on the UV irradiation wavelengths from 200 to 500 nm in Cu-doped KCl and KBr crystals with different thermal treatment has been analyzed. Spectrum of the Tl intensity of each material show lower intensity at wavelengths longer than 420 nm. The Tl intensity depends on the irradiation wavelength. Structure of the Tl intensity spectrum of each sample is very similar to the structure of its optical absorption spectrum, indicating that at each wavelength, monochromatic radiation is absorbed to produce electronic transitions and electron hole pairs. Thermoluminescence of materials with thermal treatment at high temperature shows electron-hole trapping with less efficiency. The results show that Cu-doped alkali-halide materials are good detectors of a wide range of UV monochromatic radiations and could be used to measure UV radiation doses. (Author)

  11. Enhancement of photocatalytic activity of Cu-doped ZnO nanorods for the degradation of an insecticide: Kinetics and reaction pathways.

    Science.gov (United States)

    Shirzad-Siboni, Mehdi; Jonidi-Jafari, Ahmad; Farzadkia, Mahdi; Esrafili, Ali; Gholami, Mitra

    2017-01-15

    The photocatalytic degradation of organophosphorus pesticide such as diazinon was investigated by Cu-doped ZnO nanorods. Cu-doped ZnO nanorods were synthesized via a facile co-precipitation method. The catalyst was characterized by XRD, FESEM, EDX, VSM, XPS, and pHzpc techniques. The effects of some operational parameters such as solution pH, Cu-doped ZnO nanorods dosage, initial diazinon concentration, oxygen and nitrogen gases, H2O2 concentration, and type of organic compounds on the degradation efficiency were discussed through the photocatalytic experiments using the Cu-doped ZnO nanorods. Neutral pH was selected as an optimal pH condition due to a photo-corrosion of ZnO in acidic and basic conditions. As the Cu-doped ZnO nanorods dosage increased up to 0.2 g/L, degradation efficiency of diazinon was continuously enhanced. Pseudo-first-order rate constant (kobs) was decreased from 0.051 to 0.0052 min(-1) and electrical energy per order (EEo) was increased from 94.12 to 923.08 (kWh/m(3)) by increasing diazinon concentration from 10 to 50 mg/L, respectively. The efficiency of the UV/Cu-doped ZnO for diazinon removal was approximately 96.97%, which was more effective than the UV/ZnO process (58.52%). Photocatalytic activity was maintained even after five successive cycles.

  12. Near Band Edge Emission by Free Exciton Decay and Intrinsic Ferromagnetic Ordering of Cu-Doped SnO2 Hollow Nanofibers.

    Science.gov (United States)

    Mohanapriya, P; Jaya, N Victor

    2015-03-01

    High quality nanocrystalline pristine and Cu-doped SnO2 hollow nanofibers were successfully prepared through simple and effective electrospinning technique. Nanofibers calcined at 600 °C for 3 h were characterized with different analytical techniques such as X-ray diffraction (XRD), Transmission electron Microscope (TEM) and Vibrating sample magnetometer (VSM). Observed TEM images and XRD patterns were corroborate to the formation of tetragonal crystalline SnO2 hollow nanofibers with rutile phase. Excellent optical behaviour was observed for Cu-doped SnO2. Highly intense near band edge emission at 3.58 eV for Cu-doped SnO2 evidences the free exciton decay process in the hollow nanofibers. For the first time we have reported here the near band edge PL emission in Cu-doped SnO2 tubular hollow nanostructure. This study substantiates that material potential for UV-lasing application. In addition to the above, magnetic measurement ascribes that Cu-doped SnO2 exhibit the intrinsic room temperature ferromagnetism within the low field strength. The occurrence of ferromagnetism in Cu-doped SnO2 is directly related to the p-d ferromagnetic exchange coupling between the local magnetic moment of Cu2+ and the polarized valence electrons of surrounding oxygen. Over all this study provides the primary information about tunable multifunctionality of SnO2 hollow nanostructures by adding the non-magnetic Cu ions.

  13. Structural, chemical and optical evaluation of Cu-doped ZnO nanoparticles synthesized by an aqueous solution method

    Energy Technology Data Exchange (ETDEWEB)

    Iribarren, A., E-mail: augusto@imre.oc.uh.cu [Instituto de Ciencia y Tecnología de Materiales (IMRE), Universidad de La Habana, Zapata y G, Vedado, Plaza, La Habana 10400 (Cuba); Hernández-Rodríguez, E. [Instituto de Ciencia y Tecnología de Materiales (IMRE), Universidad de La Habana, Zapata y G, Vedado, Plaza, La Habana 10400 (Cuba); Maqueira, L. [Instituto de Ciencia y Tecnología de Materiales (IMRE), Universidad de La Habana, Zapata y G, Vedado, Plaza, La Habana 10400 (Cuba); Facultad de Química, Universidad de La Habana, Zapata y G, Vedado, Plaza, La Habana 10400 (Cuba)

    2014-12-15

    Highlights: • Cu-doped ZnO nanoparticles obtained by chemical synthesis. • Substitutional or interstitial Cu into ZnO lead specific structural, chemical, and optical changes. • Incorporation efficiency of Cu atoms in ZnO as a function of the Cu concentration in the precursor dissolution. - Abstract: In this work a study of ZnO and Cu-doped ZnO nanoparticles obtained by chemical synthesis in aqueous media was carried out. Structural analysis gave the dominant presence of wurtzite ZnO phase forming a solid solution Zn{sub 1−x}Cu{sub x}O. For high Cu doping CuO phase is also present. For low Cu concentration the lattice shrinks due to Cu atoms substitute Zn atoms. For high Cu concentration the lattice enlarges due to predominance of interstitial Cu. From elemental analysis we determined and analyzed the incorporation efficiency of Cu atoms in Zn{sub 1−x}Cu{sub x}O as a function of the Cu concentration in the precursor dissolution. Combining structural and chemical results we described the Cu/Zn precursor concentrations r{sub w} in which the solid solution of Cu in ZnO is predominant. In the region located at r{sub w} ≈ 0.2–0.3 it is no longer valid. For Cu/Zn precursor concentration r{sub w} > 0.3 interstitial Cu dominates, and some amount of copper oxide appears. As the Cu concentration increases, the effective size of nanoparticles decreases. Photoluminescence (PL) measurements of the Cu-doped ZnO nanoparticles were carried out and analyzed.

  14. Fabrication of folic acid sensor based on the Cu doped SnO2 nanoparticles modified glassy carbon electrode

    Science.gov (United States)

    Lavanya, N.; Radhakrishnan, S.; Sudhan, N.; Sekar, C.; Leonardi, S. G.; Cannilla, C.; Neri, G.

    2014-07-01

    A novel folic acid biosensor has been fabricated using Cu doped SnO2 nanoparticles (NPs) synthesized by a simple microwave irradiation method. Powder XRD and TEM studies confirmed that both the pure and Cu doped SnO2 (Cu: 0, 10, 20wt%) crystallized in tetragonal rutile-type structure with spherical morphology. The average crystallite size of pure SnO2 was estimated to be around 16 nm. Upon doping, the crystallite sizes decreased to 9 nm and 5 nm for 10 and 20wt% Cu doped SnO2 respectively. XPS studies confirmed the electronic state of Sn and Cu to be 4+ and 2+ respectively. Cu (20wt%) doped SnO2 NPs are proved to be a good sensing element for the determination of folic acid (FA). Cu-SnO2 NPs (20wt%) modified glassy carbon electrode (GCE) exhibited the lowest detection limit of 0.024 nM over a wide folic acid concentration range of 1.0 × 10-10 to 6.7 × 10-5 M at physiological pH of 7.0. The fabricated sensor is highly selective towards the determination of FA even in the presence of a 100 fold excess of common interferent ascorbic acid. The sensor proved to be useful for the estimation of FA content in pharmaceutical sample with satisfactory recovery.

  15. Preparation and structural, optical, magnetic, and electrical characterization of Mn{sup 2+}/Co{sup 2+}/Cu{sup 2+} doped hematite nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Srikrishna Ramya, S.I., E-mail: ramyaskr@gmail.com; Mahadevan, C.K.

    2014-03-15

    Pure and Mn{sup 2+} / Co{sup 2+} / Cu{sup 2+} doped (1 and 2 at.%) spherical hematite (α-Fe{sub 2}O{sub 3})nanocrystals have been synthesized by a simple solvothermal method using a domestic microwave oven. XRD measurements confirm that all the seven nanocrystals prepared consist of nanocrystalline hematite phase without any other phases. The energy dispersive X-ray and Fourier transform infrared spectral analyses confirm the phase purity of the nanocrystals prepared. TEM analysis shows the average particle sizes within the range 33–51 nm. Optical absorption measurements indicate that all the three dopants enhance the optical transmittance and reflectance. A red shift is observed in the bandgap energy values estimated from optical absorption and reflectance spectra. Results of magnetic measurements made at room temperature using a vibrating sample magnetometer indicate significant changes in the magnetic properties (coercivity, retentivity and saturationmagnetization) due to doping. Results of magnetic measurements indicate significant changes in the magnetic properties. Results of AC electrical measurements made at various temperatures in the range 40–130 °C and frequencies in the range 100 Hz –1 MHz indicate low dielectric constants and AC electrical conductivities and consequently show the occurrence of nanoconfined states. -- Graphical abstract: The indexed X-ray diffraction (XRD) patterns of all the seven nanocrystals indicate the rhombohedral structure of hematite (JCPDS card No.13-0534). No impurity phase like oxides of Mn or Co or Cu was detected above equipment limit. The average crystallite (grain) sizes estimated using the Scherrer's formula. Highlights: • Pure and Mn/Co/Cu-doped hematite nanocrystals have been prepared. • The method adopted for the preparation is simple, economical and scalable. • Prepared nanocrystals are spherical in shape with good crystallinity and phase purity. • Mn/Co/Cu-doping enhances the optical

  16. Simple and green synthesis of protein-conjugated CdS nanoparticles and spectroscopic study on the interaction between CdS and zein

    Science.gov (United States)

    Qin, Dezhi; Zhang, Li; Du, Xian; Wang, Yabo; Zhang, Qiuxia

    2016-09-01

    The present study demonstrates the role of zein molecules in synthesizing CdS nanoassemblies through protein-directed, green synthetic approach. Zein molecules can as capping ligand and stabilizing agent to regulate the nucleation and growth of CdS nanocrystals, and the obtained products are organic-inorganic nanocomposites. The analysis of surface charge and conductivity indicates that strong electrostatic force restricts mobility of ions, which creates a local supersaturation surrounding the binding sites of zein and reduces the activated energy of nucleation. The interaction between Cd2+/CdS and zein molecules was systematically investigated through spectroscopy techniques. Fourier transform infrared (FT-IR) spectra were used to envisage the binding of the functional groups of zein with the surface of CdS nanoparticles. Ultraviolet visible (UV-Vis) and photoluminescence (PL) spectra results show that Cd2+/CdS might interact with the aromatic amino acids of protein molecules and change its chemical microenvironment. The quantum-confined effect of nanocrystals is confirmed by optical absorption spectrum due to the small size (3-5 nm) of CdS particles. The data of circular dichroism (CD) spectra indicate that the formation of CdS nanocrystals could lead to the conformational change of zein molecules. Moreover, the possible mechanism of CdS nanocrystals growth in zein solution was also discussed. The weak interactions such as Van der Waals, hydrophobic forces and hydrogen bonds in zein molecules should play a crucial factor in the self-assembly of small nanoparticles.

  17. XRD and XANES study of some Cu-doped MnBi materials

    Science.gov (United States)

    Mishra, Ashutosh; Patil, Harsha

    2016-10-01

    High purity MnBi low temperature phase has been prepared and analyzed using X- ray diffraction (XRD) and X-ray absorption near edge structure (XANES) measurements. The X-ray diffraction measurements were carried out using Bruker D8 Advance X-ray diffractometer. The X-rays were produced using a sealed tube and the wavelength of X-ray was 154 nm (Cu K-alpha). and X-rays were detected using a fast counting detector based on Silicon strip technology (Bruker LynxEye detector)[1]. and the X-ray absorption spectra has emerged as a powerful technique for local structure determination, which can be applied to any type of material. The X-ray absorption measurements of two Cu-doped MnBi alloys have been performed at the recently developed BL-8 Dispersive EXAFS beam line at 2.5 GeV Indus-2 synchrotron at RRCAT, Indore, India[2]. The X-ray absorption near edge structure (XANES) data obtained has been processed using data analysis program Athena. The energies of the K absorption edge, chemical shifts, edge-widths, shifts of the principal absorption maximum in the alloys have been determined.

  18. Influence of Cu doping on the structural, electrical and optical properties of ZnO

    Indian Academy of Sciences (India)

    Arindam Ghosh; Navnita Kumari; Ayon Bhattacharjee

    2015-04-01

    Pure and Cu-doped zinc oxide (ZnO) nanoparticles were prepared using a chemical method. The dopant concentration (Cu/Zn in atomic percentage (wt%)) is varied from 0 to 3 wt%. Structural characterization of the samples performed using X-ray diffraction (XRD) confirmed that all the nanoparticles of zinc oxide are having polycrystalline nature. Morphological studies were conducted using field emission scanning electron microscopy (FESEM) to confirm the grain size and texture. Electrical measurements showed that the AC conductivity initially decreases and then rises with increasing Cu concentration. The UV–Vis studies showed absorbance peaks in the 200–800 nm region. It is found that the absorbance does not significantly change with doping. This fact is further confirmed from the band-gap calculations using the reflectance graphs. When analysed in terms of Burstein–Moss shift, an increase of band gap from 3.42 to 3.54 eV with increasing Cu concentration is observed. In the photoluminescence (PL) studies a red-shift is observed with increasing dopant concentration.

  19. Investigations on structural, vibrational and dielectric properties of nanosized Cu doped Mg-Zn ferrites

    Science.gov (United States)

    Yadav, Anand; Rajpoot, Rambabu; Dar, M. A.; Varshney, Dinesh

    2016-05-01

    Transition metal Cu2+ doped Mg-Zn ferrite [Mg0.5Zn0.5-xCuxFe2O4 (0.0 ≤ x ≤ 0.5)] were prepared by sol gel auto combustion (SGAC) method to probe the structural, vibrational and electrical properties. X-ray diffraction (XRD) pattern reveals a single-phase cubic spinel structure without the presence of any secondary phase corresponding to other structure. The average particle size of the parent Mg0.5Zn0.5Fe2O4 is found to be ~29.8 nm and is found to increase with Cu2+ doping. Progressive reduction in lattice parameter of Mg0.5Zn0.5Fe2O4 has been observed due to difference in ionic radii of cations with improved Cu doping. Spinel cubic structure is further confirmed by Raman spectroscopy. Small shift in Raman modes towards higher wave number has been observed in doped Mg-Zn ferrites. The permittivity and dielectric loss decreases at lower doping and increases at higher order doping of Cu2+.

  20. Improvements of dielectric properties of Cu doped LaTiO3 þδ

    Institute of Scientific and Technical Information of China (English)

    Yan Chen; Jianxun Xu; Yimin Cui; Guangyi Shang; Jianqiang Qian; Jun-en Yao

    2016-01-01

    The ceramic composites of Cu-doped La1?xCuxTiO3þδ (x¼0.05, 0.15, 0.3, 0.5) were synthesized by con-ventional solid-state reaction. The complex dielectric properties of the composites were investigated as a function of temperature (77 KrTr320 K) and frequency (100 Hzrfr1 MHz) separately. In all com-posites, the dielectric constants increase monotonously and the dielectric loss undulates with tem-perature. And it is clearly observed that extraordinarily high low-frequency dielectric constant ( ? 104) appear at room temperature in La0.5Cu0.5TiO3þδ, which is ?100 times larger than that of La0.95Cu0.05TiO3 þδ. Interestingly, the dielectric constants increase remarkably with the doped Cu con-tents, meanwhile the dielectric loss for all samples is ideal lower than 1 at room temperature in the measured frequency range. By means of complex impedance analysis, the improvements of dielectric properties are attributed to both bulk contribution and grain boundary effect, in which the bulk polaronic relaxation and the Maxwell–Wagner relaxation due to grain boundary response are heightened re-markably with the high doped Cu contents.

  1. Electron delocalization and relaxation behavior in Cu-doped B i2S e3 films

    Science.gov (United States)

    Li, Mingze; Wang, Zhenhua; Yang, Liang; Li, Da; Yao, Q. R.; Rao, G. H.; Gao, Xuan P. A.; Zhang, Zhidong

    2017-08-01

    C uxB i2S e3 is known for superconductivity due to Cu intercalation in the van der Waals gaps between the quintuple layers of B i2S e3 at x >0.10 . Here we report the synthesis and transport properties of Cu-doped C uxB i2S e3 films prepared by the chemical-vapor-deposition (CVD) method with 0.11 ≥x ≥0 . It is found that the insulatinglike temperature-dependent resistivity of polycrystalline C uxB i2S e3 films exhibits a marked metallic downturn and an increase of carrier concentration below ˜37 K. There is also a time-dependent slow relaxation behavior in the resistance at low temperature. These effects might be related to the strong hybridization between C u+ and C u2 + conduction bands from the intercalated C u+ and substituted C u2 + sites in B i2S e3 films. The findings here have important implications for the understanding and development of doping-induced superconductivity in topological insulators.

  2. Building Structural Complexity in Semiconductor Nanocrystals through Chemical Transformations

    Energy Technology Data Exchange (ETDEWEB)

    Sadtler, Bryce F [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2009-05-01

    Methods are presented for synthesizing nanocrystal heterostructures comprised of two semiconductor materials epitaxially attached within individual nanostructures. The chemical transformation of cation exchange, where the cations within the lattice of an ionic nanocrystal are replaced with a different metal ion species, is used to alter the chemical composition at specific regions ofa nanocrystal. Partial cation exchange was performed in cadmium sulfide (CdS) nanorods of well-defined size and shape to examine the spatial organization of materials within the resulting nanocrystal heterostructures. The selectivity for cation exchange to take place at different facets of the nanocrystal plays an important role in determining the resulting morphology of the binary heterostructure. The exchange of copper (I) (Cu+) cations in CdS nanorods occurs preferentially at the ends of the nanorods. Theoretical modeling of epitaxial attachments between different facets of CdS and Cu2S indicate that the selectivity for cation exchange at the ends of the nanorods is a result of the low formation energy of the interfaces produced. During silver (I) (Ag+) cation exchange in CdS nanorods, non-selective nucleation of silver sulfide (Ag2S), followed by partial phase segregation leads to significant changes in the spatial arrangement of CdS and Ag2S regions at the exchange reaction proceeds through the nanocrystal. A well-ordered striped pattern of alternating CdS and Ag2S segments is found at intermediate fractions of exchange. The forces mediating this spontaneous process are a combination of Ostwald ripening to reduce the interfacial area along with a strain-induced repulsive interaction between Ag2S segments. To elucidate why Cu+ and Ag+ cation exchange with CdS nanorods produce different morphologies, models for epitaxial attachments between various facets of CdS with Cu2S or

  3. Information in CDS Spreads

    NARCIS (Netherlands)

    L. Norden (Lars)

    2014-01-01

    textabstractWe investigate how public and private information drives corporate CDS spreads before rating announcements. We find that CDS spreads of firms with higher news intensity move significantly earlier and stronger before rating announcements, which can be explained with public information fro

  4. Nanocrystal synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Tisdale, William; Prins, Ferry; Weidman, Mark; Beck, Megan

    2016-11-01

    A method of preparing monodisperse MX semiconductor nanocrystals can include contacting an M-containing precursor with an X donor to form a mixture, where the molar ratio between the M containing precursor and the X donor is large. Alternatively, if additional X donor is added during the reaction, a smaller ratio between the M containing precursor and the X donor can be used to prepare monodisperse MX semiconductor nanocrystals.

  5. Influence of gamma-ray irradiation on Faraday effect of Cu-doped germano-silicate optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Youngwoong; Ju, Seongmin; Jeong, Seongmook; Jang, Myoung-Jin [Department of Physics and Photon Science, School of Information and Communications, Gwangju Institute of Science and Technology, 261 Cheomdan-gwagiro, Buk-Gu, Gwangju 500-712 (Korea, Republic of); Kim, Jong-Yeol; Lee, Nam-Ho; Jung, Hyun-Kyu [Nuclear Convergence Technology Development Department, Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon (Korea, Republic of); Han, Won-Taek, E-mail: wthan@gist.ac.kr [Department of Physics and Photon Science, School of Information and Communications, Gwangju Institute of Science and Technology, 261 Cheomdan-gwagiro, Buk-Gu, Gwangju 500-712 (Korea, Republic of)

    2015-02-01

    Influence of gamma-ray irradiation on the Faraday effect of the Cu-doped germano-silicate optical fiber was investigated. The Verdet constant of the gamma-ray irradiated optical fiber at 660 nm was measured to be 3.07 rad T{sup −1} m{sup −1}, 1.46 times larger than that of before the irradiation at total dose of 1200 Gy. Cu-related radiation-induced defect centers and Cu metal particles which were reduced from Cu{sup 2+} ions by the irradiation are thought to be responsible for the increase in the Verdet constant of the optical fiber.

  6. Studies on thermal analysis and optical parameters of Cu doped poly(vinyl acetate)/polyindole composites

    Science.gov (United States)

    Bhagat, D. J.; Dhokane, G. R.

    2015-05-01

    This article reports investigation on optical parameters and thermal analysis of Cu doped poly(vinyl acetate)/polyindole composites using cupric chloride as an oxidant. The study's complex optical parameters were determined through ultraviolet-visible (UV-vis) spectroscopy. Thermal analysis was done through thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The optical band gap values were found in the range 3.4381-4.8646 eV that reflects that synthesized composites have the potential to have application in optical devices and solar cells. The optical conductivity of composites is calculated to be 1.608 × 107 S-1.

  7. Surface charging at the (1 0 0) surface of Cu doped and undoped Li{sub 2}B{sub 4}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Jie [Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Theodore Jorgensen Hall 855 North 16th Street, Lincoln, NE 68588-0299 (United States); Lozova, N. [J. Bennett Johnston Sr. Center for Advanced Microstructures and Devices, Louisiana State University, 6980 Jefferson Highway, Baton Rouge, LA 70806 (United States); Losovyj, Ya.B. [Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Theodore Jorgensen Hall 855 North 16th Street, Lincoln, NE 68588-0299 (United States); J. Bennett Johnston Sr. Center for Advanced Microstructures and Devices, Louisiana State University, 6980 Jefferson Highway, Baton Rouge, LA 70806 (United States); Wooten, D. [Air Force Institute of Technology, 2950 Hobson Way, Wright Patterson Air Force Base, OH 45433-7765 (United States); Ketsman, I. [Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Theodore Jorgensen Hall 855 North 16th Street, Lincoln, NE 68588-0299 (United States); Swinney, M.W.; Petrosky, J.; McClory, J. [Air Force Institute of Technology, 2950 Hobson Way, Wright Patterson Air Force Base, OH 45433-7765 (United States); Burak, Ya.V.; Adamiv, V.T. [Institute of Physical Optics, 23 Dragomanov Str., Lviv 79005 (Ukraine); Brant, A.T. [Department of Engineering Physics, West Virginia University, Morgantown, WV 26506 (United States); Dowben, P.A., E-mail: pdowben@unl.edu [Department of Physics and Astronomy and the Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Theodore Jorgensen Hall 855 North 16th Street, Lincoln, NE 68588-0299 (United States)

    2011-02-01

    We have compared the photovoltaic charging of the (1 0 0) surface termination for Cu doped and undoped Li{sub 2}B{sub 4}O{sub 7}. While the surface charging at the (1 0 0) surface of Li{sub 2}B{sub 4}O{sub 7} is significantly greater than observed at (1 1 0) surface, the Cu doping plays a role in reducing the surface photovoltage effects. With Cu doping of Li{sub 2}B{sub 4}O{sub 7}, the surface photovoltaic charging is much diminished at the (1 0 0) surface. The density of states observed with combined photoemission and inverse photoemission remains similar to that observed for the undoped material, except in the vicinity of the conduction band edge.

  8. Literate Programming System CDS

    Institute of Scientific and Technical Information of China (English)

    曾云峰

    1991-01-01

    This paper presents a broad outline and some implementation techniques of the literate programming system CDS.Compared with the previous ones (e.g.WEB,Cweb),CDS has two main characteristics:1) A Chinese-English typesetting system was developed to produce the documentation.This makes the Chinese documentation possible.2) A suitable method for automatic formatting was introduced to generate the software documentation automatically.This frees the programmer from typesetting details while still allowing programmer's interference.

  9. Post-annealing effect on the room-temperature ferromagnetism in Cu-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yu-Min, E-mail: ymhu@nuk.edu.tw; Kuang, Chein-Hsiun; Han, Tai-Chun; Yu, Chin-Chung [Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan (China); Li, Sih-Sian [Institute of Electro-Optical Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

    2015-05-07

    In this work, we investigated the structural and magnetic properties of both as-deposited and post-annealed Cu-doped ZnO thin films for better understanding the possible mechanisms of room-temperature ferromagnetism (RT-FM) in ZnO-based diluted magnetic oxides. All of the films have a c-axis-oriented wurtzite structure and display RT-FM. X-ray photoelectron spectroscopy results showed that the incorporated Cu ions in as-deposited films are in 1+ valence state merely, while an additional 2+ valence state occurs in post-annealed films. The presence of Cu{sup 2+} state in post-annealed film accompanies a higher magnetization value than that of as-deposited film and, in particular, the magnetization curves at 10 K and 300 K of the post-annealed film separate distinctly. Since Cu{sup 1+} ion has a filled 3d band, the RT-FM in as-deposited Cu-doped ZnO thin films may stem solely from intrinsic defects, while that in post-annealed films is enhanced due to the presence of CuO crystallites.

  10. Electronic structure and optical properties of Cu-doping and Zn vacancy impurities in ZnTe.

    Science.gov (United States)

    Li, Qing-Fang; Hu, Ge; She, Qing; Yao, Jing; Feng, Wen-Jiang

    2013-09-01

    The geometric structures of perfect ZnTe, that with Zn vacancy (Zn0.875Te), and Cu-doped ZnTe (Zn0.875Cu0.125Te) were optimized using the pseudopotential plane wave (PP-PW) method based on the density functional theory (DFT) within generalized gradient approximation (GGA). The cohesive energy, band structure, density of states, and Mulliken populations were calculated and discussed in detail. On the other hand, an accurate calculation of linear optical functions (the dielectric function, refraction index, reflectivity, conductivity function, and energy-loss spectrum) was performed. The results demonstrated that compared to the perfect ZnTe, the lattice parameters of Zn0.875Te and Zn0.875Cu0.125Te were changed and the cell volumes decreased to some extent due to the vacancy and introduction of impurity. A vacancy acceptor level and an acceptor impurity level were produced in Zn0.875Te and Zn0.875Cu0.125Te, respectively. By comparison, Cu doping in the ZnTe system is relatively stable while the monovacancy system is not.

  11. Spectral features and antibacterial properties of Cu-doped ZnO nanoparticles prepared by sol-gel method

    Institute of Scientific and Technical Information of China (English)

    Alireza Samavati; A F Ismail; Hadi Nur; Z Othaman; M K Mustafa

    2016-01-01

    Zn1−x Cux O (x=0.00, 0.01, 0.03, and 0.05) nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacterial properties of these nanoparticles is demonstrated. Powder x-ray diffraction investigations have illustrated the organized Cu doping into ZnO nanoparticles up to Cu concentration of 5% (x=0.05). However, the peak corresponding to CuO for x=0.01 is not distinguishable. The images of field emission scanning electron microscopy demonstrate the existence of a nearly spherical shape with a size in the range of 30–52 nm. Doping Cu creates the Cu–O–Zn on the surface and results in a decrease in the crystallite size. Photoluminescence and absorption spectra display that doping Cu causes an increment in the energy band gap. The antibacterial activities of the nanoparticles are examined against Escherichia coli (Gram negative bacteria) cultures using optical density at 600 nm and a comparison of the size of inhibition zone diameter. It is found that both pure and doped ZnO nanoparticles indicate appropriate antibacterial activity which rises with Cu doping.

  12. Microstructures and optical properties of Cu-doped ZnO films prepared by radio frequency reactive magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Ma Ligang [College of physics and Electronics Engineering, Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, Northwest Normal University, Lanzhou, Gansu, 730070 (China); Ma Shuyi, E-mail: maligang186@163.com [College of physics and Electronics Engineering, Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, Northwest Normal University, Lanzhou, Gansu, 730070 (China); Chen Haixia; Ai Xiaoqian; Huang Xinli [College of physics and Electronics Engineering, Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, Northwest Normal University, Lanzhou, Gansu, 730070 (China)

    2011-09-15

    Pure and Cu-doped ZnO (ZnO:Cu) thin films were deposited on glass substrates using radio frequency (RF) reactive magnetron sputtering. The effect of substrate temperature on the crystallization behavior and optical properties of the ZnO:Cu films have been studied. The crystal structures, surface morphology and optical properties of the films were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and a fluorescence spectrophotometer, respectively. The results indicated that ZnO films showed a stronger preferred orientation toward the c-axis and a more uniform grain size after Cu-doping. As for ZnO:Cu films, the full width at half maxima (FWHM) of (0 0 2) diffraction peaks decreased first and then increased, reaching a minimum of about 0.42 deg. at 350 deg. C and the compressive stress of ZnO:Cu decreased gradually with the increase of substrate temperature. The photoluminescence (PL) spectra measured at room temperature revealed two blue and two green emissions. Intense blue-green luminescence was obtained from the sample deposited at higher substrate temperature. Finally, we discussed the influence of annealing temperature on the structural and optical properties of ZnO:Cu films. The quality of ZnO:Cu film was markedly improved and the intensity of blue peak ({approx}485 nm) and green peak ({approx}527 nm) increased noticeably after annealing. The origin of these emissions was discussed.

  13. The structural, optical, and electrical properties of vacuum evaporated Cu-doped ZnTe polycrystalline thin films

    Science.gov (United States)

    Feng, L.; Mao, D.; Tang, J.; Collins, R. T.; Trefny, J. U.

    1996-09-01

    We have studied the structural, optical, and electrical properties of thermally evaporated, Cu-doped, ZnTe thin films as a function of Cu concentration and post-deposition annealing temperature. X-ray diffraction measurements showed that the ZnTe films evaporated on room temperature substrates were characterized by an average grain size of 300Å with a (111) preferred orientation. Optical absorption measurements yielded a bandgap of 2.21 eV for undoped ZnTe. A bandgap shrinkage was observed for the Cu-doped films. The dark resistivity of the as-deposited ZnTe decreased by more than three orders of magnitude as the Cu concentration was increased from 4 to 8 at.% and decreased to less than 1 ohm-cm after annealing at 260°C. For films doped with 6 7 at.% Cu, an increase of resistivity was also observed during annealing at 150 200°C. The activation energy of the dark conductivity was measured as a function of Cu concentration and annealing temperature. Hall measurements yielded hole mobility values in the range between 0.1 and 1 cm2/V·s for both as-deposited and annealed films. Solar cells with a CdS/CdTe/ZnTe/metal structure were fabricated using Cudoped ZnTe as a back contact layer on electrodeposited CdTe. Fill factors approaching 0.75 and energy conversion efficiencies as high as 12.1% were obtained.

  14. Spectral features and antibacterial properties of Cu-doped ZnO nanoparticles prepared by sol-gel method

    Science.gov (United States)

    Alireza, Samavati; A, F. Ismail; Hadi, Nur; Z, Othaman; M, K. Mustafa

    2016-07-01

    Zn1-x Cu x O (x = 0.00, 0.01, 0.03, and 0.05) nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacterial properties of these nanoparticles is demonstrated. Powder x-ray diffraction investigations have illustrated the organized Cu doping into ZnO nanoparticles up to Cu concentration of 5% (x = 0.05). However, the peak corresponding to CuO for x = 0.01 is not distinguishable. The images of field emission scanning electron microscopy demonstrate the existence of a nearly spherical shape with a size in the range of 30-52 nm. Doping Cu creates the Cu-O-Zn on the surface and results in a decrease in the crystallite size. Photoluminescence and absorption spectra display that doping Cu causes an increment in the energy band gap. The antibacterial activities of the nanoparticles are examined against Escherichia coli (Gram negative bacteria) cultures using optical density at 600 nm and a comparison of the size of inhibition zone diameter. It is found that both pure and doped ZnO nanoparticles indicate appropriate antibacterial activity which rises with Cu doping. Project supported by the Universiti Teknologi Malaysia (UTM) (Grant No. R. J1300000.7809.4F626). Dr. Samavati is thankful to RMC for postdoctoral grants.

  15. Microstress, strain, band gap tuning and photocatalytic properties of thermally annealed and Cu-doped ZnO nanoparticles

    Science.gov (United States)

    Prasad, Neena; V. M. M, Saipavitra; Swaminathan, Hariharan; Thangaraj, Pandiyarajan; Ramalinga Viswanathan, Mangalaraja; Balasubramanian, Karthikeyan

    2016-06-01

    ZnO nanoparticles and Cu-doped ZnO nanoparticles were prepared by co-precipitation method. Also, a part of the pure ZnO nanoparticles were annealed at 750 °C for 3, 6, and 9 h. X-ray diffraction studies were carried out and the lattice parameters, unit cell volume, interplanar spacing, and Young's modulus were calculated for all the samples, and also the crystallite size was found using the Scherrer method. X-ray peak broadening analysis was used to estimate the crystallite sizes and the strain using the Williamson-Hall (W-H) method and the size-strain plot (SSP) method. Stress and the energy density were calculated using the W-H method assuming different models such as uniform deformation model, uniform strain deformation model, uniform deformation energy density model, and the SSP method. Optical absorption properties of the samples were understood from their UV-visible spectra. Photocatalytic activities of ZnO and 5 % Cu-doped ZnO were observed by the degradation of methylene blue dye in aqueous medium under the irradiation of 20-W compact fluorescent lamp for an hour.

  16. Synthesis and photovoltaic application of coper (I) sulfide nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yue; Wadia, Cyrus; Ma, Wanli; Sadtler, Bryce; Alivisatos, A.Paul

    2008-06-24

    We present the rational synthesis of colloidal copper(I) sulfide nanocrystals and demonstrate their application as an active light absorbing component in combination with CdS nanorods to make a solution-processed solar cell with 1.6percent power conversion efficiency on both conventional glass substrates and flexible plastic substrates with stability over a 4 month testing period.

  17. Synthesis and applications of heterostructured semiconductor nanocrystals

    Science.gov (United States)

    Khon, Elena

    Semiconductor nanocrystals (NCs) have been of great interest to researchers for several decades due to their unique optoelectronic properties. These nanoparticles are widely used for a variety of different applications. However, there are many unresolved issues that lower the efficiency and/or stability of devices which incorporate these NCs. Our research is dedicated to addressing these issues by identifying potential problems and resolving them, improving existing systems, generating new synthetic strategies, and/or building new devices. The general strategies for the synthesis of different nanocrystals were established in this work, one of which is the colloidal growth of gold domains onto CdS semiconductor nanocrystals. Control of shape and size was achieved simply by adjusting the temperature and the time of the reaction. Depending on the exact morphology of Au and CdS domains, fabricated nano-composites can undergo evaporation-induced self-assembly onto a substrate, which is very useful for building devices. CdS/Au heterostructures can assemble in two different ways: through end-to-end coupling of Au domains, resulting in the formation of one-dimensional chains; and via side-by-side packing of CdS nanorods, leading to the onset of two-dimensional superlattices. We investigated the nature of exciton-plasmon interactions in Au-tipped CdS nanorods using femtosecond transient absorption spectroscopy. The study demonstrated that the key optoelectronic properties of electrically coupled metal and semiconductor domains are significantly different from those observed in systems with weak inter-domain coupling. In particular, strongly-coupled nanocomposites promote mixing of electronic states at semiconductor-metal domain interfaces, which causes a significant suppression of both plasmon and exciton carrier excitations. Colloidal QDs are starting to replace organic molecules in many different applications, such as organic light emmiting diods (OLEDs), due to their

  18. Synthesis of Cu-Doped Mixed-Phase TiO2 with the Assistance of Ionic Liquid by Atmospheric-Pressure Cold Plasma

    Institute of Scientific and Technical Information of China (English)

    ZHAN Zhibin; DI Lanbo; ZHANG Xiuling; LI Yanchun

    2016-01-01

    An atmospheric-pressure dielectric barrier discharge (DBD) gas-liquid cold plasma was employed to synthesize Cu-doped TiO2 nanoparticles in an aqueous solution with the assistance of [C2MIM]BF4 ionic liquid (IL) and using air as the working gas.The influences of the discharge voltage,IL and the amount of copper nitrite were investigated.X-ray diffraction,N2 adsorption-desorption measurements and UV-Vis spectroscopy were adopted to characterize the samples.The results showed that the specific surface area of TiO2 was promoted with Cu-doping (from 57.6 m2·g-1 to 106.2 m2·g-1 with 3% Cu-doping),and the content of anatase was increased.Besides,the band gap energy of TiO2 with Cu-doping decreased according to the UV-Vis spectroscopy test.The 3%Cu-IL-TiO2 samples showed the highest efficiency in degrading methylene blue (MB) dye solutions under simulated sunlight with an apparent rate constant of 0.0223 min-1,which was 1.2 times higher than that of non-doped samples.According to the characterization results,the reasons for the high photocatalytic activity were discussed.

  19. Mechanochemically assisted solid-state and citric acid complex syntheses of Cu-doped sodium cobaltite ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Pršić, S., E-mail: sanjaprsic@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade (Serbia); Savić, S.M., E-mail: slavicas@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade (Serbia); Branković, Z., E-mail: zorica.brankovic@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade (Serbia); Vrtnik, S., E-mail: stane.vrtnik@ijs.si [Institute Jožef Stefan, Condensed Matter Physics, Jamova cesta 39, 1000 Ljubljana (Slovenia); Dapčević, A., E-mail: hadzi-tonic@tmf.bg.ac.rs [Department of General and Inorganic Chemistry, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade (Serbia); Branković, G., E-mail: goran.brankovic@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade (Serbia)

    2015-08-15

    Highlights: • Sodium cobaltite was synthesized by mechanochemically assisted solid-state reaction and citric acid complex (CAC) method. • We investigated effect of Cu-doping in NaCo{sub 2−x}Cu{sub x}O{sub 4} (x = 0, 0.01, 0.03, 0.05). • ICP analysis showed that the controlling of the samples composition is easier by the CAC method. • The Seebeck coefficient in Cu-doped samples was higher compared to the undoped one. • The highest figure of merit was observed in the sample with the lowest Cu concentration. - Abstract: In the last decade, the sodium cobaltite ceramic became a promising candidate for potential thermoelectric applications, because of its large thermopower and low resistivity. In this work, polycrystalline samples of NaCo{sub 2−x}Cu{sub x}O{sub 4} (x = 0, 0.01, 0.03, 0.05) were prepared using mechanochemically assisted solid-state reaction method (MASSR) and the citric acid complex method (CAC). Bulk samples were prepared by pressing into disc-shaped pellets and subsequently subjected to a thermal treatment at 880 °C in inert argon atmosphere. Changes in structural and microstructural characteristics of the samples, caused by the substitution of Cu for Co, were characterized using X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM), respectively. The results of inductively coupled plasma (ICP) analysis showed that the compositions of the final products correspond to γ-NaCo{sub 2}O{sub 4} and confirmed that desired compound was obtained in both syntheses procedures. The advantages and disadvantages of these two syntheses procedures have been observed and discussed: the CAC method enabled obtaining samples with higher density and fine microstructure compared to the MASSR method, thus better thermoelectric properties. The Cu{sup 2+} substitution led to the increase in Seebeck coefficient in both synthesis routes. The highest figure of merit of 0.022 at 300 K was observed for the sample doped with 1 mol% Cu, obtained by

  20. Enhancement in visible light-responsive photocatalytic activity by embedding Cu-doped ZnO nanoparticles on multi-walled carbon nanotubes

    Science.gov (United States)

    Ahmad, M.; Ahmed, E.; Hong, Z. L.; Jiao, X. L.; Abbas, T.; Khalid, N. R.

    2013-11-01

    Copper doped ZnO nanoparticles embedded on multi-walled carbon nanotubes (CNTs) were successfully synthesized using a facile, nontoxic sol method. The resulting visible light-responsive Cu-doped ZnO/CNTs composites were characterized using powder X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and Brunauer Emmett Teller (BET) surface area analyzer. Optical properties of Cu-doped ZnO/CNTs nanocomposites, studied using UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL), which exhibited extended light absorption in visible light region and possessed better charge separation capability, respectively as compared to Cu-doped ZnO, pure ZnO and ZnO/CNTs composite. The photocatalytic activity was tested by degradation of methyl orange (MO) dye under visible light irradiation. The results demonstrated that Cu-doped ZnO/CNTs nanocomposites effectively bleached out MO, showing an impressive photocatalytic enhancement over ZnO, commercial ZnO, Cu-doped ZnO nanoparticles and ZnO/CNTs nanocomposites. Chemical oxygen demand (COD) of textile wastewater was also measured before and after the photocatalysis experiment under sunlight to evaluate the mineralization of wastewater. The significant decrease in COD of the treated effluent revealed a complete destruction of the organic molecules along with color removal. This dramatically enhanced photoactivity of nanocomposite photocatalysts was attributed to greater adsorptivity of dyes, extended light absorption and increased charge separation efficiency due to excellent electrical properties of carbon nanotubes and the large surface area.

  1. Clinical Decision Support (CDS) Inventory

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Clinical Decision Support (CDS) Inventory contains descriptions of past and present CDS projects across the Federal Government. It includes Federal projects,...

  2. Studies on Ferromagnetic and Photoluminescence Properties of ITO and Cu-Doped ITO Nanoparticles Synthesized by Solid State Reaction

    Science.gov (United States)

    Babu, S. Harinath; Kaleemulla, S.; Rao, N. Madhusudhana; Krishnamoorthi, C.

    2016-11-01

    Cubic structured indium-tin-oxide (ITO) and copper-doped ITO nanoparticles were synthesized by solid state reaction. The structure, morphology, chemical, magnetic, and photoluminescence properties of the synthesized nanoparticles were studied by x-ray diffraction, field emission scanning electron microscopy, x-ray photoelectron spectroscopy, vibrating sample magnetometry, and photoluminescence spectrophotometry, respectively. Magnetic studies confirmed that the ITO nanoparticles were ferromagnetic at room temperature (300 K) and at 100 K, and it was believed that the observed ferromagnetism may be due to oxygen vacancies and defects present in the system. No hysteresis loop was observed in copper-doped ITO nanoparticles at room temperature and 100 K. The ITO and Cu-doped ITO nanoparticles exhibited two broad emission peaks in the visible region of the electromagnetic spectrum.

  3. Photoluminescence of Cu-doped CdTe and related stability issues in CdS/CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Grecu, D. [University of Toledo, Toledo, Ohio 43606-3390 (United States); Compaan, A. D. [University of Toledo, Toledo, Ohio 43606-3390 (United States); Young, D. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Jayamaha, U. [First Solar LLC., Perrysburg, Ohio 43551 (United States); Rose, D. H. [First Solar LLC., Perrysburg, Ohio 43551 (United States)

    2000-09-01

    We explore Cu electronic states in CdTe using photoluminescence as the main investigative method. Our results are consistent with some Cu atoms occupying substitutional positions on the Cd sublattice and with others forming Frenkel pairs of the type Cu{sub i}{sup +}-V{sub Cd}{sup -} involving an interstitial Cu and a Cd vacancy. In addition, we find that Cu-doped CdTe samples exhibit a significant ''aging'' behavior, attributable to the instability of Cu acceptor states as verified by our Hall measurements. The aging appears to be reversible by a 150-200 degree sign C anneal. Our results are used to explain efficiency degradation of some CdTe solar-cell devices which use Cu for the formation of a backcontact. (c) 2000 American Institute of Physics.

  4. Conduction behavior conversion for Cu-doped ZnS/n-type Si devices with different Cu contents

    Science.gov (United States)

    Ni, Wei-Shih; Lin, Yow-Jon

    2015-06-01

    Currents through Cu-doped ZnS (ZnCuS)/n-type Si structures were studied. The electrical conduction investigations suggest that the carrier transport behavior is governed by the Poole-Frenkel emission for ZnCuS/n-type Si devices having the low Cu concentration. However, the carrier transport behavior is governed by the thermionic emission for ZnCuS/n-type Si devices having the high Cu concentration. The photoluminescence result revealed that sulfur vacancy ( V S) is the origin of conduction behavior conversion. It is shown that the increased Cu concentration leads to the reduced formation probability of V S. The dependence of V S on the film composition was identified for providing a guide to control the current transport behavior of ZnCuS/n-type Si devices.

  5. Local structure and magnetization of ferromagnetic Cu-doped ZnO films: No magnetism at the dopant?

    Energy Technology Data Exchange (ETDEWEB)

    Vachhani, P.S., E-mail: prashjdg@gmail.com [School of Physics, University of Hyderabad, Hyderabad 500 046 (India); Department of Physics, University of Trento, 38123 Povo, Trento (Italy); Šipr, O. [Institute of Physics AS CR v. v. i., Cukrovarnická 10, Prague (Czech Republic); Bhatnagar, A.K. [School of Physics, University of Hyderabad, Hyderabad 500 046 (India); School of Engineering Sciences & Technology, University of Hyderabad, Hyderabad 500 046 (India); Ramamoorthy, R.K. [Department of Physics, University of Trento, 38123 Povo, Trento (Italy); School of Engineering Sciences & Technology, University of Hyderabad, Hyderabad 500 046 (India); Choudhary, R.J.; Phase, D.M. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452 017 (India); Dalba, G. [Department of Physics, University of Trento, 38123 Povo, Trento (Italy); Kuzmin, A. [Institute of Solid State Physics, University of Latvia, LV-1063 Riga (Latvia); Rocca, F. [IFN-CNR, Institute for Photonics and Nanotechnologies, Unit “FBK-Photonics” of Trento, 38123 Povo, Trento (Italy)

    2016-09-05

    Relationship between magnetism and structure of Cu-doped ZnO was investigated at macroscopic and microscopic levels. Thin Zn{sub 1−x}Cu{sub x}O films (x = 0.02, 0.04, 0.07 and 0.10) were prepared by a pulsed laser deposition and characterized via superconducting quantum interference device (SQUID) magnetometry, high-resolution x-ray diffraction, and Cu K-edge and Zn K-edge x-ray absorption, x-ray linear dichroism and x-ray circular magnetic dichroism spectroscopy. Even though the samples exhibit room-temperature ferromagnetism with magnetization that increases with Cu concentration, we did not detect signatures of local magnetic moments associated with Cu atoms, as evidenced by the lack of any XMCD signal. The host ZnO wurtzite lattice is not significantly altered by the addition of Cu. At the same time, most of the Cu atoms are not incorporated into the wurtzite lattice but rather have a CuO-like coordination. These results indicate that ferromagnetism of the investigated Zn{sub 1−x}Cu{sub x}O films is not directly linked to the doping atoms but rather is due to some other changes which have been introduced to the host ZnO by the dopants. - Highlights: • Ferromagnetic Cu doped ZnO films have been prepared. • Magnetic moments are not actually associated with Cu atoms. • Observed ferromagnetism can be devoted to doping induced yet unspecified changes.

  6. Photovoltaic Devices from Multi-Armed CdS Nanorods and Conjugated Polyme, Composites

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-Shan; WANG Li; QIN Dong-Huan; CAO Yong

    2006-01-01

    We demonstrate the preparation of composite photovoltaic devices by using the blends of multi-armed CdS nanorods with conjugated polymer, poly[2-methoxy-5-(2'-ethylhexyloxy)-l,4-phenylenevinylene] (MEH-PPV). Multi-armed CdS nanorods are prepared by thermolysing single precursor cadmium ethylxanthate [Cd(exan)2] in pure hexadecylamine solution under ambient conditions. The photoluminescence of MEH-PPV can be ef fectively quenched in the composites at high CdS nanocrystal (nc-CdS)/MEH-PPV ratios. Post-treatment of the multi-armed CdS nanorods by refluxing in pyridine significantly increases the performance of the composite photovoltaic devices. Power conversion efficiency is obtained to be 0.17% under AM 1.5 illumination for this composite device.

  7. A comparative study of pure and copper (Cu)-doped ZnO nanorods for antibacterial and photocatalytic applications with their mechanism of action

    Science.gov (United States)

    Bhuyan, Tamanna; Khanuja, Manika; Sharma, R.; Patel, S.; Reddy, M. R.; Anand, S.; Varma, A.

    2015-07-01

    The present study reports the synthesis of pure and Cu-doped ZnO nanorods for antibacterial and photocatalytic applications. The samples were synthesized by simple, low cost mechanical-assisted thermal decomposition process. The synthesized materials were characterized by scanning electron microscopy, UV-Visible spectroscopy, and photoluminescence studies. The antibacterial activity of characterized samples was determined against Gram-positive bacteria such as Staphylococcus aureus and Streptococcus pyogenes and Gram-negative bacteria such as Escherichia coli using shake flask method with respect to time. The significant antibacterial activity was perceived from scanning electron micrographs that clearly revealed bacterial cell lysis resulting in the release of cytoplasmic content followed by cell death. The degradation of methylene blue was used as a model organic dye for photocatalytic activity. The present study demonstrates the superior photocatalytic and antibacterial activity of Cu-doped ZnO nanorods with respect to pure ZnO nanorods.

  8. A comparative study of pure and copper (Cu)-doped ZnO nanorods for antibacterial and photocatalytic applications with their mechanism of action

    Energy Technology Data Exchange (ETDEWEB)

    Bhuyan, Tamanna [Amity University, Uttar Pradesh, Amity Institute of Microbial Technology (India); Khanuja, Manika, E-mail: manikakhanuja@gmail.com; Sharma, R.; Patel, S.; Reddy, M. R.; Anand, S. [Amity University, Uttar Pradesh, Amity Institute of Nanotechnology (India); Varma, A. [Amity University, Uttar Pradesh, Amity Institute of Microbial Technology (India)

    2015-07-15

    The present study reports the synthesis of pure and Cu-doped ZnO nanorods for antibacterial and photocatalytic applications. The samples were synthesized by simple, low cost mechanical-assisted thermal decomposition process. The synthesized materials were characterized by scanning electron microscopy, UV–Visible spectroscopy, and photoluminescence studies. The antibacterial activity of characterized samples was determined against Gram-positive bacteria such as Staphylococcus aureus and Streptococcus pyogenes and Gram-negative bacteria such as Escherichia coli using shake flask method with respect to time. The significant antibacterial activity was perceived from scanning electron micrographs that clearly revealed bacterial cell lysis resulting in the release of cytoplasmic content followed by cell death. The degradation of methylene blue was used as a model organic dye for photocatalytic activity. The present study demonstrates the superior photocatalytic and antibacterial activity of Cu-doped ZnO nanorods with respect to pure ZnO nanorods.

  9. Tuning of multifunctional Cu-doped ZnO films and nanowires for enhanced piezo/ferroelectric-like and gas/photoresponse properties.

    Science.gov (United States)

    Ong, Wei Li; Huang, Hejin; Xiao, Juanxiu; Zeng, Kaiyang; Ho, Ghim Wei

    2014-01-01

    The prospect of tuning and enhancing multiple properties of ZnO from optical, electrical, piezo to ferroelectricity/magnetism with Cu dopants will certainly spur the pursuit of facile doping methodology to immensely advance this field of research. Here, a one-step aqueous synthesis of Cu-doped ZnO nanostructured materials with effective controllability over the morphology (film to nanowire) and doping concentrations both on rigid and flexible substrates has been developed. High structural integrity Cu-doped ZnO films and nanowires were achieved without multiple/harsh post-processing which tends to degrade their functional properties. Comprehensive investigations of varying doping concentrations on the enhancement and tunability of room temperature piezo/ferroelectricity to gas/photosensing multifunctional properties were systematically reported for the first time.

  10. Biomolecularly capped uniformly sized nanocrystalline materials: glutathione-capped ZnS nanocrystals

    Science.gov (United States)

    Torres-Martínez, Claudia L.; Nguyen, Liem; Kho, Richard; Bae, Weon; Bozhilov, Krassimir; Klimov, Victor; Mehra, Rajesh K.

    1999-09-01

    Micro-organisms such as bacteria and yeasts form CdS to detoxify toxic cadmium ions. Frequently, CdS particles formed in yeasts and bacteria were found to be associated with specific biomolecules. It was later determined that these biomolecules were present at the surface of CdS. This coating caused a restriction in the growth of CdS particles and resulted in the formation of nanometre-sized semiconductors (NCs) that exhibited typical quantum confinement properties. Glutathione and related phytochelatin peptides were shown to be the biomolecules that capped CdS nanocrystallites synthesized by yeasts Candida glabrata and Schizosaccharomyces pombe. Although early studies showed the existence of specific biochemical pathways for the synthesis of biomolecularly capped CdS NCs, these NCs could be formed in vitro under appropriate conditions. We have recently shown that cysteine and cysteine-containing peptides such as glutathione and phytochelatins can be used in vitro to dictate the formation of discrete sizes of CdS and ZnS nanocrystals. We have evolved protocols for the synthesis of ZnS or CdS nanocrystals within a narrow size distribution range. These procedures involve three steps: (1) formation of metallo-complexes of cysteine or cysteine-containing peptides, (2) introduction of stoichiometric amounts of inorganic sulfide into the metallo-complexes to initiate the formation of nanocrystallites and finally (3) size-selective precipitation of NCs with ethanol in the presence of Na+. The resulting NCs were characterized by optical spectroscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction and electron diffraction. HRTEM showed that the diameter of the ZnS-glutathione nanocrystals was 3.45+/-0.5 nm. X-ray diffraction and electron diffraction analyses indicated ZnS-glutathione to be hexagonal. Photocatalytic studies suggest that glutathione-capped ZnS nanocrystals prepared by our procedure are highly efficient in degrading a test model

  11. Synthesis of CdS flower-like hierarchical microspheres as electrode material for electrochemical performance

    Energy Technology Data Exchange (ETDEWEB)

    Kaviyarasu, K., E-mail: Kaviyarasuloyolacollege@gmail.com [UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology Laboratories, College of Graduate Studies, University of South Africa (UNISA), Muckleneuk Ridge, P O Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), Materials Research Department (MSD), iThemba LABS-National Research Foundation - NRF, 1 Old Faure Road, 7129, P O Box 722, Somerset West, Western Cape Province (South Africa); Manikandan, E., E-mail: maniphysics@gmail.com [Nanosciences African Network (NANOAFNET), Materials Research Department (MSD), iThemba LABS-National Research Foundation - NRF, 1 Old Faure Road, 7129, P O Box 722, Somerset West, Western Cape Province (South Africa); Central Research Laboratory, Sree Balaji Medical College & Hospital, Bharath University, Chrompet, Chennai, 600044, Tamil Nadu (India); Maaza, M., E-mail: maaza@gmail.com [UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology Laboratories, College of Graduate Studies, University of South Africa (UNISA), Muckleneuk Ridge, P O Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), Materials Research Department (MSD), iThemba LABS-National Research Foundation - NRF, 1 Old Faure Road, 7129, P O Box 722, Somerset West, Western Cape Province (South Africa)

    2015-11-05

    We report in this paper, a facile hydrothermal route for the preparation of CdS nanocrystals at room temperature (RT). Composition, structure and morphology of the products were analyzed and characterized by X-ray diffraction (XRD) confirms that the hydrothermal treatment at 180 °C for periods ranging from 0 to 1440 min caused no significant modification of the long range order structure subjected to hydrothermal treatment. From the XRD analysis the diffraction peaks pertaining to 26.75°, 43.89° and 52.34° are attributed to the (111), (220) and (311) planes of cubic zinc blende structure. The Photoluminescence (PL) spectra are dominated by a strong narrow band edge emission tunable in the blue region of the visible spectra indicating the narrow size distribution of CdS nanocrystals. TEM observation shows that the CdS nanocrystals synthesized by hydrothermal synthesis are well dispersed and the average crystallite size was found to be ∼10 nm. The confocal microscopic studies reveal that each flower like spheres is due to Ostwald's ripening with numerous nanoparticles aggregating a surface. - Highlights: • The adjacent particle coalesces together forming spherical particles. • The average crystalline size of CdS nanoparticles was found to be ∼3 nm. • In the case of spherical crystallite, is given by L = 3/4 D. • The CdS nanocrystal exhibits a direct band gap of 2.4 eV. • The microspheres are dispersed with good monodispersity.

  12. Synthesis of Cu-Doped Mixed-Phase TiO2 with the Assistance of Ionic Liquid by Atmospheric-Pressure Cold Plasma

    Science.gov (United States)

    Zhan, Zhibin; Di, Lanbo; Zhang, Xiuling; Li, Yanchun

    2016-05-01

    An atmospheric-pressure dielectric barrier discharge (DBD) gas-liquid cold plasma was employed to synthesize Cu-doped TiO2 nanoparticles in an aqueous solution with the assistance of [C2MIM]BF4 ionic liquid (IL) and using air as the working gas. The influences of the discharge voltage, IL and the amount of copper nitrite were investigated. X-ray diffraction, N2 adsorption-desorption measurements and UV-Vis spectroscopy were adopted to characterize the samples. The results showed that the specific surface area of TiO2 was promoted with Cu-doping (from 57.6 m2·g-1 to 106.2 m2·g-1 with 3% Cu-doping), and the content of anatase was increased. Besides, the band gap energy of TiO2 with Cu-doping decreased according to the UV-Vis spectroscopy test. The 3%Cu-IL-TiO2 samples showed the highest efficiency in degrading methylene blue (MB) dye solutions under simulated sunlight with an apparent rate constant of 0.0223 min-1, which was 1.2 times higher than that of non-doped samples. According to the characterization results, the reasons for the high photocatalytic activity were discussed. supported by National Natural Science Foundation of China (Nos. 21173028, 11505019), the Science and Technology Research Project of Liaoning Provincial Education Department (No. L2013464), the Scientific Research Foundation for the Doctor of Liaoning Province (No. 20131004), the Program for Liaoning Excellent Talents in University (No. LR2012042), and Dalian Jinzhou New District Science and Technology Plan Project (No. KJCX-ZTPY-2014-0001)

  13. An optical study of the D-D neutron irradiation-induced defects in Co-and Cu-doped ZnO wafers

    Institute of Scientific and Technical Information of China (English)

    Wang Yun-Bo; Li Gong-Ping; Xu Nan-Nan; Pan Xiao-Dong

    2013-01-01

    Room-temperature photoluminescence and optical transmittance spectroscopy of Co-doped (1 × 1014,5 × 1016,and 1 × 1017 cm-2) and Cu-doped (5 × 1016 cm-2) ZnO wafers irradiated by D-D neutrons (fluence of 2.9 x 1010 cm-2) have been investigated.After irradiation,the Co or Cu metal and oxide clusters in doped ZnO wafers are dissolved,and the würtzite structure of ZnO substrate for each sample remains unchanged and keeps in high c-axis preferential orientation.The degree of irradiation-induced crystal disorder reflected from the absorption band tail parameter (E0) is far greater for doped ZnO than the undoped one.Under the same doping concentration,the Cu-doped ZnO wafer has much higher irradiation-induced disorder than the Co-doped one.Photoluminescence measurements indicate that the introduction rate of both the zinc vacancy and the zinc interstitial is much higher for the doped ZnO wafer with a high doping level than the undoped one.In addition,both crystal lattice distortion and defect complexes are suggested to be formed in doped ZnO wafers.Consequently,the Co-or Cu-doped ZnO wafer (especially with a high doping level) exhibits very low radiation hardness compared with the undoped one,and the Cu-doped ZnO wafer is much less radiation-hard than the Co-doped one.

  14. Intermixing of InGaAs/GaAs Quantum Well Using Multiple Cycles Annealing Cu-doped SiO2

    Energy Technology Data Exchange (ETDEWEB)

    Hongpinyo, V; Ding, Y H; Dimas, C E; Wang, Y; Ooi, B S; Qiu, W; Goddard, L L; Behymer, E M; Cole, G D; Bond, T C

    2008-06-11

    The authors investigate the effect of intermixing in InGaAs/GaAs quantum well structure using Cu-doped SiO{sub 2}. The incorporation of Cu into the silica film yields larger bandgap shift than typical impurity-free vacancy diffusion (IFVD) method at a lower activation temperature. We also observe enhancement of the photoluminescence (PL) signal from the intermixed InGaAs/GaAs quantum well structure after being cycle-annealed at 850 C.

  15. Synthesis of Cu-doped Li2O and its cathode properties for lithium-ion batteries based on oxide/peroxide redox reactions

    Science.gov (United States)

    Kobayashi, Hiroaki; Hibino, Mitsuhiro; Makimoto, Tetsuya; Ogasawara, Yoshiyuki; Yamaguchi, Kazuya; Kudo, Tetsuichi; Okuoka, Shin-ichi; Ono, Hironobu; Yonehara, Koji; Sumida, Yasutaka; Mizuno, Noritaka

    2017-02-01

    Cu-doped Li2O, synthesized by mechanochemical reactions between Li2O and CuO, is demonstrated as a cathode material for lithium-ion batteries. The X-ray diffraction and absorption analyses suggest that in the Cu-doped Li2O, Cu2+ ions are located at 48g sites less symmetrical than 8c sites for Li+ ions, distorting the arrangement of surrounding O2- ions slightly from tetrahedral to square-planar, while the Cu2+ ions are doped in an antifluorite-type Li2O. The Cu-doped Li2O cathode has a charge capacity of 360 mAh g-1 without an irreversible O2 gas evolution reaction and exhibits a reversible capacity of 300 mAh g-1. Cu K-edge XANES spectroscopy and quantitative analysis of peroxide species reveal that redox of copper ions, formation/neutralization of O 2p electron holes, and generation/annihilation of peroxide species take place during charge/discharge.

  16. Cu-Doped ZnO Thin Films Deposited by a Sol-Gel Process Using Two Copper Precursors: Gas-Sensing Performance in a Propane Atmosphere

    Directory of Open Access Journals (Sweden)

    Heberto Gómez-Pozos

    2016-01-01

    Full Text Available A study on the propane gas-sensing properties of Cu-doped ZnO thin films is presented in this work. The films were deposited on glass substrates by sol-gel and dip coating methods, using zinc acetate as a zinc precursor, copper acetate and copper chloride as precursors for doping. For higher sensitivity values, two film thickness values are controlled by the six and eight dippings, whereas for doping, three dippings were used, irrespective of the Cu precursor. The film structure was analyzed by X-ray diffractometry, and the analysis of the surface morphology and film composition was made through scanning electron microscopy (SEM and secondary ion mass spectroscopy (SIMS, respectively. The sensing properties of Cu-doped ZnO thin films were then characterized in a propane atmosphere, C3H8, at different concentration levels and different operation temperatures of 100, 200 and 300 °C. Cu-doped ZnO films doped with copper chloride presented the highest sensitivity of approximately 6 × 104, confirming a strong dependence on the dopant precursor type. The results obtained in this work show that the use of Cu as a dopant in ZnO films processed by sol-gel produces excellent catalysts for sensing C3H8 gas.

  17. Photoluminescence studies of CdS and CdS:Cu

    Science.gov (United States)

    Price, K. J.

    2000-03-01

    Copper plays an important role in CdS/CdTe heterojunction solar cells, both as a dopant and a back contact to the CdTe. However, Cu is also thought to be responsible for the unstable performance of some types of CdS/CdTe devices under extreme conditions. Recently, Cu has been shown to diffuse from the back contact of the CdTe all the way to the CdS/CdTe interface and into the CdS. We have used photoluminescence (PL) to examine the electrically active states of CdS and CdS:Cu single crystals and polycrystalline films. In undoped films, we detect an exitonic feature at 2.54 eV related to a Cd vacancy. This feature is dramatically reduced in Cu-doped samples, indicating Cu in the Cd vacancy site. In addition, we will present results of light-soaking at 1 sun on the stability of the photoluminescence spectra.

  18. Influence of Cu-doping on the structural and optical properties of CaTiO{sub 3} powders

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, L.H.; Moura, A.P. de [UNESP-Universidade Estadual Paulista, P.O. Box 355, 14801-907, Araraquara, SP (Brazil); La Porta, F.A., E-mail: felipe_laporta@yahoo.com.br [Department of Chemistry, Federal Technological University of Parana (UTFPR), PO Box 3131, 86036-370, Londrina/PR (Brazil); Nogueira, I.C. [DQ-UFSCar-Universidade Federal de São Carlos, P.O. Box 676, 13565-905, São Carlos, SP (Brazil); Aguiar, E.C.; Sequinel, T. [UNESP-Universidade Estadual Paulista, P.O. Box 355, 14801-907, Araraquara, SP (Brazil); Rosa, I.L.V. [DQ-UFSCar-Universidade Federal de São Carlos, P.O. Box 676, 13565-905, São Carlos, SP (Brazil); Longo, E.; Varela, J.A. [UNESP-Universidade Estadual Paulista, P.O. Box 355, 14801-907, Araraquara, SP (Brazil)

    2016-09-15

    Highlights: • Ca{sub 1−x}Cu{sub x}TiO{sub 3} powders were successfully synthesized via a polymeric precursor method. • Effects of Cu incorporated on the Ca-site into the CaTiO{sub 3} lattice as host matrix has been investigated. • The optical behavior reveals that the Ca{sub 1−x}Cu{sub x}TiO{sub 3} powders have potential applications in emerging technologies. - Abstract: Here, we report on the effect of chemical substitution on the structural and optical properties of Cu-doped CaTiO{sub 3} (CTO) polycrystalline powders synthesized by the polymeric precursor method. Our findings are discussed based on the structural order-disorder effects originating from the modification of the Ca{sub 1−x}Cu{sub x}TiO{sub 3} microcrystal matrix. These results may elucidate the compositional modulation and methods of controlling the structural design, as well as reveal the changes in the optical behavior of this system at an atomic level.

  19. Structural and optical properties of Cu doped SnO2 nanoparticles: An experimental and density functional study

    Science.gov (United States)

    Chetri, Pawan; Saikia, Bhamyarswa; Choudhury, Amarjyoti

    2013-06-01

    The paper investigates, both theoretically and experimentally, the structural and optical changes in SnO2 system brought about by introduction of Cu in a SnO2 system. On the experimental front, a cost effective sol-gel technique is used to prepare hexagonal shaped Cu doped SnO2 nanoparticles. The prepared pristine SnO2 nanoparticle is found to be of random shape by transmission electron microscope (TEM) studies. A structural and morphological study is carried out using X-ray diffraction and TEM techniques. The different phonon interaction in the system is observed by Raman spectroscopy while electron paramagnetic resonance and UV-Visible spectroscopy confirms the presence of Cu in 2+ state. First principle calculations have been performed using "density functional theory"-based MedeA Vienna Ab Initio Simulation package on a SnO2 system where Cu is introduced. The introduction of Cu in the SnO2 system brings distortion which is corroborated by the variation in the corresponding bond lengths. The Density of State calculation of Sn16O32 and CuSn15O32 is also performed. Finally, a correlation is established between the experiment and the theory.

  20. Cu-doped Cd{sub 1-x}Zn{sub x}S alloy: synthesis and structural investigations

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Indu; Ahlawat, Dharamvir Singh; Ahlawat, Rachna [Chaudhary Devi Lal University, Department of Physics, Sirsa, Haryana (India)

    2016-03-15

    Copper doped Cd{sub 1-x}Zn{sub x}S (x ≤ 1) quantum dots have been synthesized using chemical co-precipitation method. Structural investigation of the synthesized nanomaterials has been carried out by powder XRD method. The XRD results have confirmed that as-prepared Cu-doped Cd{sub 1-x}Zn{sub x}S quantum dots have hexagonal structure. The average nanocrystallite size was estimated in the range 2-12 nm using Debye-Scherrer formula. The lattice constants, lattice plane, d-spacing, unit cell volume, Lorentz factor and dislocation density were also calculated from XRD data. The change in particle size was observed with the change in Zn concentration. Furthermore, FTIR spectra of the prepared samples were observed for identification of COO- and O-H functional groups. The TEM study has also reported the same size range of nanoparticles. The increase in agglomeration has been observed with the increase in Zn concentration in the prepared samples. (orig.)

  1. The effect of Cu doping on the mechanical and optical properties of zinc oxide nanowires synthesized by hydrothermal route

    Science.gov (United States)

    Robak, Elżbieta; Coy, Emerson; Kotkowiak, Michał; Jurga, Stefan; Załęski, Karol; Drozdowski, Henryk

    2016-04-01

    Zinc oxide (ZnO) is a wide-bandgap semiconductor material with applications in a variety of fields such as electronics, optoelectronic and solar cells. However, much of these applications demand a reproducible, reliable and controllable synthesis method that takes special care of their functional properties. In this work ZnO and Cu-doped ZnO nanowires are obtained by an optimized hydrothermal method, following the promising results which ZnO nanostructures have shown in the past few years. The morphology of as-prepared and copper-doped ZnO nanostructures is investigated by means of scanning electron microscopy and high resolution transmission electron microscopy. X-ray diffraction is used to study the impact of doping on the crystalline structure of the wires. Furthermore, the mechanical properties (nanoindentation) and the functional properties (absorption and photoluminescence measurements) of ZnO nanostructures are examined in order to assess their applicability in photovoltaics, piezoelectric and hybrids nanodevices. This work shows a strong correlation between growing conditions, morphology, doping and mechanical as well as optical properties of ZnO nanowires.

  2. CDS User survey

    CERN Multimedia

    CERN Document Service

    2011-01-01

      The CERN Document Server is launching a user survey in order to collect information relative to its search engine, submission interfaces, collaborative features and content organisation. With the view of re-shaping its collections and interfaces and to better integrate with the new INSPIRE platform that serves all HEP literature, CERN Document Server team invites you to take part in the survey. Your input is essential to provide us with useful information before setting up the new service and improve your interactions with CDS. Thanks for participating !  

  3. Safe-haven CDS Premia

    DEFF Research Database (Denmark)

    Klingler, Sven; Lando, David

    We argue that Credit Default Swap (CDS) premia for safe-haven sovereigns, like Germany and the United States, are driven to a large extent by regulatory requirements under which derivatives dealing banks have an incentive to buy CDS to hedge counterparty credit risk of their counterparties. We...

  4. Safe-haven CDS Premia

    DEFF Research Database (Denmark)

    Klingler, Sven; Lando, David

    We argue that Credit Default Swap (CDS) premia for safe-haven sovereigns, like Germany and the United States, are driven to a large extent by regulatory requirements under which derivatives dealing banks have an incentive to buy CDS to hedge counterparty credit risk of their counterparties. We...

  5. Nanocrystal quantum dots

    CERN Document Server

    Klimov, Victor I

    2010-01-01

    ""Soft"" Chemical Synthesis and Manipulation of Semiconductor Nanocrystals, J.A. Hollingsworth and V.I. Klimov Electronic Structure in Semiconductor Nanocrystals: Optical Experiment, D.J. NorrisFine Structure and Polarization Properties of Band-Edge Excitons in Semiconductor Nanocrystals, A.L. EfrosIntraband Spectroscopy and Dynamics of Colloidal Semiconductor Quantum Dots, P. Guyot-Sionnest, M. Shim, and C. WangMultiexciton Phenomena in Semiconductor Nanocrystals, V.I. KlimovOptical Dynamics in Single Semiconductor Quantum Do

  6. Novel Nanocrystal Floating Gate Memory

    OpenAIRE

    Zhou, Huimei

    2012-01-01

    This work is devoted to investigating the feasibility of engineering nanocrystals and tunnel oxide layer with a novel structure. Several novel devices are demonstrated to improve the performance of the novel nanocrystal memories.A novel TiSi2 nanocrystal memory was demonstrated. TiSi2 nanocrystals were synthesized on SiO2 by annealing Ti covered Si nanocrystals. Compared to the reference Si nanocrystal memory, both experiment and simulation results show that TiSi2 nanocrystal memory exhibits ...

  7. Effects of Cu doping on the electronic structure and magnetic properties of MnCo2O4 nanostructures

    Science.gov (United States)

    Pramanik, Prativa; Thota, Subhash; Singh, Sobhit; Joshi, Deep Chandra; Weise, Bruno; Waske, Anja; Seehra, M. S.

    2017-10-01

    Reported here are the results and their analysis from our detailed investigations of the effects of Cu doping (x ≤slant 0.2 ) on the electronic structure and magnetic properties of the spinel MnCo2 O4. A detailed comparison is given for the x = 0 and x = 0.2 cases for both the bulk-like samples and nanoparticles. The electronic structure determined from x-ray photoelectron spectroscopy and Rietveld analysis of x-ray diffraction patterns shows the structure to be: (Co3+ )A [Mn3+ Co2+(1-x) Cu2+x ]B O4 i.e. Cu2+ substitutes for Co2+ on the octahedral B-sites. For the bulk samples, the ferrimagnetic T_C= 184 K for x = 0 is lowered to TC = 167 K for the x = 0.2 sample, this decrease being due to the effect of Cu doping. For the nanosize x = 0 (x = 0.2 ) sample, the lower TC = 165 K (TC = 155 K) is observed using \\partial (χdcT)/\\partial T analysis, this lowering being due to finite size effects. For T > TC , fits of dc paramagnetic susceptibility data of χ-1 versus T in nanosize samples to the Néel expression are used to determine the exchange interactions between the A and B sites with exchange constants: JAA / kB ∼ 8.4 K (4.1 K), JBB/kB ∼21.2 K (16.3 K) and JAB / kB ∼ 13.9 K (13.8 K) for x = 0 (0.2) . The temperature dependence of ac susceptibilities χ\\prime(T) and χ\\prime\\prime(T) at different frequencies shows that in bulk samples of x = 0 and x=0.2 , the transition at T C is the normal second order transition. But for the nanosize x = 0 and 0.2 samples, analysis of the ac susceptibilities shows that the ferrimagnetic transition at T C is followed by a re-entrant spin-glass transition at lower temperatures T_SG ∼ 162 K (138 K) for x = 0 (x = 0.20 ). Analysis of the ac susceptibilities, χ\\prime(T) and χ\\prime\\prime(T) , versus T data is done in terms of two scaling laws: (i) Vogel–Fulcher law [τ = τo \\exp(Ea/(kB(T-To)))] ; and (ii) power law of critical slowing-down τ / τo = [(TP/TSG)-1]-zν . These fits confirm the existence

  8. Strasbourg Astronomical Data Center (CDS

    Directory of Open Access Journals (Sweden)

    F Genova

    2013-01-01

    Full Text Available The Centre de Donnees astronomiques de Strasbourg (CDS, created in 1972, has been a pioneer in the dissemination of digital scientific data. Ensuring sustainability for several decades has been a major issue because science and technology evolve continuously and the data flow increases endlessly. The paper briefly describes CDS activities, major services, and its R&D strategy to take advantage of new technologies. The next frontiers for CDS are the new Web 2.0/3.0 paradigm and, at a more general level, global interoperability of astronomical on-line resources in the Virtual Observatory framework.

  9. Surface chemical modification of nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Helms, Brett Anthony; Milliron, Delia Jane; Rosen, Evelyn Louise; Buonsanti, Raffaella; Llordes, Anna

    2017-03-14

    Nanocrystals comprising organic ligands at surfaces of the plurality of nanocrystals are provided. The organic ligands are removed from the surfaces of the nanocrystals using a solution comprising a trialkyloxonium salt in a polar aprotic solvent. The removal of the organic ligands causes the nanocrystals to become naked nanocrystals with cationic surfaces.

  10. Role of dopant concentration, crystal phase and particle size on microbial inactivation of Cu-doped TiO2 nanoparticles.

    Science.gov (United States)

    Sahu, Manoranjan; Wu, Bing; Zhu, Liying; Jacobson, Craig; Wang, Wei-Ning; Jones, Kristen; Goyal, Yogesh; Tang, Yinjie J; Biswas, Pratim

    2011-10-14

    The properties of Cu-doped TiO(2) nanoparticles (NPs) were independently controlled in a flame aerosol reactor by varying the molar feed ratios of the precursors, and by optimizing temperature and time history in the flame. The effect of the physico-chemical properties (dopant concentration, crystal phase and particle size) of Cu-doped TiO(2) nanoparticles on inactivation of Mycobacterium smegmatis (a model pathogenic bacterium) was investigated under three light conditions (complete dark, fluorescent light and UV light). The survival rate of M. smegmatis (in a minimal salt medium for 2 h) exposed to the NPs varied depending on the light irradiation conditions as well as the dopant concentrations. In dark conditions, pristine TiO(2) showed insignificant microbial inactivation, but inactivation increased with increasing dopant concentration. Under fluorescent light illumination, no significant effect was observed for TiO(2). However, when TiO(2) was doped with copper, inactivation increased with dopant concentration, reaching more than 90% (>3 wt% dopant). Enhanced microbial inactivation by TiO(2) NPs was observed only under UV light. When TiO(2) NPs were doped with copper, their inactivation potential was promoted and the UV-resistant cells were reduced by over 99%. In addition, the microbial inactivation potential of NPs was also crystal-phase-and size-dependent under all three light conditions. A lower ratio of anatase phase and smaller sizes of Cu-doped TiO(2) NPs resulted in decreased bacterial survival. The increased inactivation potential of doped TiO(2) NPs is possibly due to both enhanced photocatalytic reactions and leached copper ions.

  11. Effects of Cu-doping on the magnetic state of Zn(0.9-x)Fe0.1Cu(x)O.

    Science.gov (United States)

    Ziq, Kh A; Ismail, A; Salem, A F; Ahmed, Shakeel; Ghannam, A

    2011-03-01

    Magnetization measurements were performed on a series of Zn(0.9-x)Fe0.1Cu(x)O samples (0 magnetization and enhances the hysteresis losses. Curie behavior of the susceptibility at high temperature indicates the presence of ferromagnetic exchange interaction. Moreover, we found that the exchange interaction and the molecular field coefficient are both ferromagnetic and greatly enhanced with Cu-doping; however, the Arrott-Belov-Kouvel plot did not reveal the presence of spontaneous magnetization down to 4.2 K.

  12. Preparation and characterization of ZnS:Fe/MX (M = Cd, Zn; X = S, Se) core-shell nanocrystals

    Science.gov (United States)

    Li, Lihua; Xie, Ruishi; Gu, Yongjun; Huang, Jinliang; Zhu, Jianguo

    2012-06-01

    ZnS:Fe/MX (M = Cd, Zn; X = S, Se) nanocrystals were synthesized by chemical precipitation method. Compared to ZnS:Fe nanocrystals, the diffraction peaks intensity of ZnS:Fe/ZnS nanocrystals reduced and the diffraction peaks of ZnS:Fe/ZnSe nanocrystals moved to lower angles. TEM photos show that ZnS:Fe and ZnS:Fe/ZnSe nanocrystals are spheroidal and the average particles size is about 2-4 nm. The selected-area electron diffraction pattern of ZnS:Fe/ZnSe nanocrystals shows the diffraction rings, indicating the ZnS:Fe/ZnSe nanocrystals have a polycrystalline structure. XPS shows that the divalent and trivalent of Fe ion are coexisted in ZnS:Fe nanocrystals. The emission peaks of ZnS:Fe nanocrystals were from S and Zn ions vacancy defects and surface defects for the range of 200-900 nm. The use of ZnS (CdS, ZnSe) as surface modifying reagent inhibited the luminescent intensity of ZnS:Fe nanocrystallines at 420 nm. The PL spectra of ZnS:Fe/CdS nanocrystals show a new peak at 554 nm.

  13. Structural, optical and electron paramagnetic resonance studies on Cu-doped ZnO nanoparticles synthesized using a novel auto-combustion method

    Science.gov (United States)

    Elilarassi, R.; Chandrasekaran, G.

    2013-06-01

    Nanocrystalline Zn1 - x Cu x O ( x = 0, 0.02, 0.04, 0.06, 0.08) samples were synthesized by a novel auto-combustion method using glycine as the fuel material. The structural, optical and magnetic properties of the samples were characterized using XRD, SEM, photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopies. The XRD spectra of samples reveal the hexagonal wurtzite structures of ZnO. As the copper content increases, a diffraction peak at 2 θ = 39° corresponding to secondary phase of CuO ([111] crystalline face) appears when x ⩽ 6 mol.%. PL spectra of the samples show a strong ultraviolet (UV) emission and defect related visible emissions. Cu-doping in ZnO can effectively adjust the energy level in ZnO, which leads to red shift in the emission peak position in UV region. The EPR spectra of Cu-doped ZnO nanoparticles show a distinct and broad signal at room temperature, suggesting that it may be attributed to the exchange interactions within Cu2+ ions.

  14. Improved performance of dye sensitized solar cells using Cu-doped TiO2 as photoanode materials: Band edge movement study by spectroelectrochemistry

    Science.gov (United States)

    Zhou, Li; Wei, Liguo; Yang, Yulin; Xia, Xue; Wang, Ping; Yu, Jia; Luan, Tianzhu

    2016-08-01

    Cu-doped TiO2 nanoparticles are prepared and used as semiconductor materials of photoanode to improve the performance of dye sensitized solar cells (DSSCs). UV-Vis spectroscopy and variable temperature spectroelectrochemistry study are used to characterize the influence of copper dopant with different concentrations on the band gap energies of TiO2 nanoparticles. The prepared Cu-doped TiO2 semiconductor has avoided the formation of CuO during hydrothermal process and lowered the conduction band position of TiO2, which contribute to increase the short circuit current density of DSSCs. At the optimum Cu concentration of 1.0 at.%, the short circuit current density increased from 12.54 to 14.98 mA cm-2, full sun solar power conversion efficiencies increased from 5.58% up to 6.71% as compared to the blank DSSC. This showed that the presence of copper in DSSCs leads to improvements of up to 20% in the conversion efficiency of DSSCs.

  15. First-principle calculation of the elastic, band structure, electronic states, and optical properties of Cu-doped ZnS nanolayers

    Science.gov (United States)

    Lahiji, Mohammadreza Askaripour; Ziabari, Ali Abdolahzadeh

    2016-11-01

    The structural, elastic, electronic, and optical properties of undoped and Cu-doped ZnS nanostructured layers have been studied in the zincblende (ZB) phase, by first-principle approach. Density functional theory (DFT) has been employed to calculate the fundamental properties of the layers using full-potential linearized augmented plane-wave (FPLAPW) method. Mechanical analysis revealed that the bulk modulus increases with the increase of Cu content. Cu doping was found to reduce the band gap value of the material. In addition, DOS effective mass of the electrons and heavy holes was evaluated. Adding Cu caused the decrement/increment of transmission/reflectance of nanolayers in the UV-vis region. The substitution by Cu increased the intensity of the peaks, and a slight red shift was observed in the absorption peak. Moreover, the static dielectric constant, and static refractive index increased with Cu content. The optical conductivity also followed a similar trend to that of the dielectric constants. Energy loss function of the modeled compounds was also evaluated. All calculated parameters were compared with the available experimental and other theoretical results.

  16. Efficient degradation of Methylene Blue dye over highly reactive Cu doped strontium titanate (SrTiO3) nanoparticles photocatalyst under visible light.

    Science.gov (United States)

    Rahman, Qazi Inamur; Ahmad, Musheer; Misra, Sunil Kumar; Lohani, Minaxi

    2012-09-01

    Visible light induced photocatalysts of Cu doped SrTiO3 (Cu/SrTiO3) nanoparticles with the size -60-75 nm were prepared via facile sol-gel method. The morphological, optical, crystalline properties and compositions of synthesized Cu/SrTiO3 nanoparticles were thoroughly characterized by field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), ultra violet-visible spectroscopy (UV-Vis) and energy dispersive X-ray (EDX). A significant red shift in the UV-diffused reflectance spectrum was observed and the absorption edge shifted to visible region by the Cu doping. Surprisingly, the band gap of SrTiO3 was changed from 3.2 eV drop to 2.96 eV. The photocatalytic activity of the synthesized Cu/SrTiO3 nanoparticles was demonstrated for the degradation of Methylene Blue dye under visible light irradiation. The formation of new acceptor region in Cu/SrTiO3 was responsible for high photocatalytic activity of Cu/SrTiO3 nanoparticles. The results showed that the Methylene Blue dye was degraded by -66% within time span of 2 h over the Cu/SrTiO3 nanoparticles. This dye degradation reaction followed the Langmuir-Hinshelwood kinetics and also exhibited first order reaction rate. The calculated rate constant for the degradation reaction following first order kinetics was k = 0.0016 min(-1).

  17. Effect of Ar ion irradiation on the room temperature ferromagnetism of undoped and Cu-doped rutile TiO2 single crystals

    Science.gov (United States)

    Xu, Nan-Nan; Li, Gong-Ping; Lin, Qiao-Lu; Liu, Huan; Bao, Liang-Man

    2016-11-01

    Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals (SCs). To tune their magnetism, Ar ion irradiation was quantitatively performed on the two crystals in which the saturation magnetizations for the samples were enhanced distinctively. The post-irradiation led to a spongelike layer in the near surface of the Cu-doped TiO2. Meanwhile, a new CuO-like species present in the sample was found to be dissolved after the post-irradiation. Analyzing the magnetization data unambiguously reveals that the experimentally observed ferromagnetism is related to the intrinsic defects rather than the exotic Cu ions, while these ions are directly involved in boosting the absorption in the visible region. Project supported by the National Natural Science Foundation of China (Grant No. 11575074), the Open Project of State Key laboratory of Crystal Material, Shandong University, China (Grant No. KF1311), the Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, China (Grant No. LZUMMM2012003), the Open Project of Key Laboratory of Beam Technology and Material Modification of Ministry of Education, Beijing Normal University, China (Grant No. 201204), and the Fundamental Research Funds for the Central Universities, China (Grant No. lzujbky-2015-240).

  18. Evaluation of surface energy state distribution and bulk defect concentration in DSSC photoanodes based on Sn, Fe, and Cu doped TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Ako, Rajour Tanyi [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Ekanayake, Piyaisiri, E-mail: piyasiri.ekanayake@ubd.edu.bn [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Young, David James [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research -A*STAR, 3 Research Link, 117602 (Singapore); Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, Queensland, 4558 (Australia); Hobley, Jonathan [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Chellappan, Vijila [Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research - A*STAR, 3 Research Link, 117602 (Singapore); Tan, Ai Ling [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Gorelik, Sergey; Subramanian, Gomathy Sandhya [Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research - A*STAR, 3 Research Link, 117602 (Singapore); Lim, Chee Ming [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam)

    2015-10-01

    Graphical abstract: - Highlights: • The structural, optical and optoelectronic properties of 1 mol.% Fe, Sn and Cu doped TiO{sub 2} have been compared. • Transient lifetimes for pure TiO{sub 2} and Sn doped TiO{sub 2} were considerably shorter than Fe and Cu doped TiO{sub 2}. • A good correlation between the bulk defects and transient decay for the doped TiO{sub 2} powders was observed. • Photon to current conversion efficiency of DSSC based on the metal doped TiO{sub 2} were in order Sn-TiO{sub 2} > Cu-TiO{sub 2} > Pure >> Fe-TiO{sub 2}. • DSSC based on Fe doped photoanodes is limited by a high concentration of surface free holes observed at 433 nm. - Abstract: Electron transfer dynamics in the oxide layers of the working electrodes in both dye-sensitized solar cells and photocatalysts greatly influences their performance. A proper understanding of the distribution of surface and bulk energy states on/in these oxide layers can provide insights into the associated electron transfer processes. Metal ions like Iron (Fe), Copper (Cu) and Tin (Sn) doped onto TiO{sub 2} have shown enhanced photoactivity in these processes. In this work, the structural, optical and transient properties of Fe, Cu and Sn doped TiO{sub 2} nanocrystalline powders have been investigated and compared using EDX, Raman spectroscopy, X-ray Photoelectron spectroscopy (XPS), and Transient Absorption spectroscopy (TAS). Surface free energy states distributions were probed using Electrochemical Impedance spectroscopy (EIS) on Dye Sensitized Solar Cells (DSSC) based on the doped TiO{sub 2} photoanodes. Raman and XPS Ti2p{sub 3/2} peak shifts and broadening showed that the concentration of defects were in the order: Cu doped TiO{sub 2} > Fe doped TiO{sub 2} > Sn doped TiO{sub 2} > pure TiO{sub 2}. Nanosecond laser flash photolysis of Fe and Cu doped TiO{sub 2} indicated slower transient decay kinetics than that of Sn doped TiO{sub 2} or pure TiO{sub 2}. A broad absorption peak and fast

  19. High-refractive Index Nanocomposite Films Of Polyvinyl-pyrolidone And CdS Nanoparticles By In-Situ Thermolysis

    Science.gov (United States)

    Chaudhuri, Tapas K.; Patel, Mitesh G.

    2010-12-01

    A simple and rapid process for deposition of high refractive index films of CdS/PVP nanocomposite is described. CdS/PVP films are prepared on glass substrate by dip coating a precursor film from methanolic solution of thio-organic complex of cadmium and PVP and subsequent heating at 180° C in air for 10 min. The transmission spectra of the films (thickness ˜700 nm) in the wavelength range 300 to 1000 nm showed an absorption edge near 500 nm due to CdS and high transmission of 85% beyond 500 nm. The refractive index is found to be 1.74 by Swanepoel method, which is between that of PVP (1.48) and CdS (2.5). Transmission Electron Microscopy showed that PVP matrix contains 5 to 10 nm CdS nanocrystals. X-ray and electron diffraction revealed the formation of cubic CdS nanoparticles in PVP. Fourier Transform Infrared spectroscopy of the composite showed that there is a strong interaction between CdS nanocrystals and PVP.

  20. MD SIMULATION FOR NANOCRYSTALS

    Institute of Scientific and Technical Information of China (English)

    马新玲; 杨卫

    2003-01-01

    Molecular dynamic (MD) provided an ab initio simulation for nano-scale mechanical behavior of materials, provided that the inter-atomic potential is accurately prescribed. MD is particularly suitable in simulating the formation, the deformation, and the evolution of nanocrystals under a fast strain rate. To tackle large scale system and nano-seconds time duration, parallel algorithm is desired. The present paper reviews the recent advances in MD simulation for nanocrystals with attention focused on the applications toward nanomechanics. The examined issues are: formation of nanocrystalline metals, nanoindentation on nanocrystals, fast deformation of nanocrystals, orderdisorder transition, and nano-particle impact.

  1. Nuclear magnetic relaxation studies of semiconductor nanocrystals and solids

    Energy Technology Data Exchange (ETDEWEB)

    Sachleben, J. R. [Lawrence Berkeley Lab., CA (United States); California Univ., Berkeley, CA (United States). Dept. of Chemistry

    1993-09-01

    Semiconductor nanocrystals, small biomolecules, and {sup 13}C enriched solids were studied through the relaxation in NMR spectra. Surface structure of semiconductor nanocrystals (CdS) was deduced from high resolution {sup 1}H and {sup 13}C liquid state spectra of thiophenol ligands on the nanocrystal surfaces. The surface coverage by thiophenol was found to be low, being 5.6 and 26% for nanocrystal radii of 11.8 and 19.2 {angstrom}. Internal motion is estimated to be slow with a correlation time > 10{sup {minus}8} s{sup {minus}1}. The surface thiophenol ligands react to form a dithiophenol when the nanocrystals were subjected to O{sub 2} and ultraviolet. A method for measuring {sup 14}N-{sup 1}H J-couplings is demonstrated on pyridine and the peptide oxytocin; selective 2D T{sub 1} and T{sub 2} experiments are presented for measuring relaxation times in crowded spectra with overlapping peaks in 1D, but relaxation effects interfere. Possibility of carbon-carbon cross relaxation in {sup 13}C enriched solids is demonstrated by experiments on zinc acetate and L-alanine.

  2. Surface modification-a novel way of attaching cocatalysts on CdS semiconductors for photocatalytic hydrogen evolution

    KAUST Repository

    Yu, Weili

    2014-08-22

    Noble metals as cocatalysts for hydrogen evolution are widely investigated for semiconductor photocatalytic water splitting. In this paper, we present a novel way to attach not only noble metals, but also transitional metals onto CdS nanocrystals as cocatalysts for hydrogen evolution. The hydrogen evolution performances for each metal were compared and result shows that Pd attached CdS gives the highest hydrogen evolution rate of 250 μmol/h. The amounts of metal ions attached on the surface were measured by inductively coupled plasma optical emission spectrometry (ICP-OES). This work confirms that surface modification is a promising way of attaching cocatalysts onto semiconductor photocatalysts.

  3. General shape control of colloidal CdS, CdSe, CdTe quantum rods and quantum rod heterostructures.

    Science.gov (United States)

    Shieh, Felice; Saunders, Aaron E; Korgel, Brian A

    2005-05-12

    We report a general synthetic method for the formation of shape-controlled CdS, CdSe and CdTe nanocrystals and mixed-semiconductor heterostructures. The crystal growth kinetics can be manipulated by changing the injection rate of the chalcogen precursor, allowing the particle shape-spherical or rodlike-to be tuned without changing the underlying chemistry. A single injection of precursor leads to isotropic spherical growth, whereas multiple injections promote epitaxial growth along the length of the c-axis. This method was extended to produce linear type I and type II semiconductor nanocrystal heterostructures.

  4. Inorganic cluster syntheses of TM2+-doped quantum dots (CdSe, CdS, CdSe/CdS): physical property dependence on dopant locale.

    Science.gov (United States)

    Archer, Paul I; Santangelo, Steven A; Gamelin, Daniel R

    2007-08-08

    A series of colloidal transition-metal-doped chalcogenide semiconductor nanocrystals (TM2+:CdSe, TM2+:CdS, etc.) has been prepared by thermal decomposition of inorganic cluster precursors. It is shown through extensive spectroscopic and structural characterization that the nanocrystals prepared following literature procedures for synthesis of TM2+:CdSe nanocrystals actually possess an unintended CdSe/TM2+:CdS core/shell morphology. The conditions required for successful formation of TM2+:CdSe and TM2+:CdS by cluster decomposition have been determined. Magneto-optical and photoluminescence spectroscopic results for this series of doped nanocrystals reveal major physical consequences of dopant localization within the shell and demonstrate the capacity to engineer dopant-carrier exchange interactions via core/shell doping strategies. The results presented here illustrate some of the remarkable and unexpected complexities that can arise in nanocrystal doping chemistries and emphasize the need for meticulous characterization to avoid false positives.

  5. Enriching The Metadata On CDS

    CERN Document Server

    Chhibber, Nalin

    2014-01-01

    The project report revolves around the open source software package called Invenio. It provides the tools for management of digital assets in a repository and drives CERN Document Server. Primary objective is to enhance the existing metadata in CDS with data from other libraries. An implicit part of this task is to manage disambiguation (within incoming data), removal of multiple entries and handle replications between new and existing records. All such elements and their corresponding changes are integrated within Invenio to make the upgraded metadata available on the CDS. Latter part of the report discuss some changes related to the Invenio code-base itself.

  6. Diorganyl dichalcogenides as useful synthons for colloidal semiconductor nanocrystals.

    Science.gov (United States)

    Brutchey, Richard L

    2015-11-17

    The ability to synthesize colloidal semiconductor nanocrystals in a well-controlled manner (i.e., with fine control over size, shape, size dispersion, and composition) has been mastered over the past 15 years. Much of this success stems from careful studies of precursor conversion and nanocrystal growth with respect to phosphine chalcogenide precursors for the synthesis of metal chalcogenide nanocrystals. Despite the high level of success that has been achieved with phosphine chalcogenides, there has been a longstanding interest in exploring alternate chalcogenide precursors because of issues associated with phosphine chalcogenide cost, purity, toxicity, etc. This has resulted in a large body of literature on the use of sulfur and selenium dissolved in octadecene or amines, thio- and selenoureas, and silyl chalcogenides as alternate chalcogenide precursors for metal chalcogenide nanocrystal synthesis. In this Account, emerging work on the use of diorganyl dichalcogenides (R-E-E-R, where E = S, Se, or Te and R = alkyl, allyl, benzyl, or aryl) as alternate chalcogenide precursors for the synthesis of metal chalcogenide nanocrystals is summarized. Among the benefits of these dichalcogenide synthons are the following: (i) they represent the first and only common precursor type that can function as chalcogen transfer reagents for each of the group VI elements (i.e., to make metal oxide, metal sulfide, metal selenide, and metal telluride nanocrystals); (ii) they possess relatively weak E-E bonds that can be readily cleaved under mild thermolytic or photolytic conditions; and (iii) the organic substituents can be tuned to affect the reactivity. These combined attributes have allowed dichalcogenide precursors to be employed for a wide range of metal chalcogenide nanocrystal syntheses, including those for In2S3, SnxGe1-xSe, SnTe, Cu2-xSySe1-y, ZnSe, CdS, CdSe, MoSe2, WSe2, BiSe, and CuFeS2. Interestingly, a number of metastable phases of compositionally complex

  7. Optimal Financing with CDS Markets

    NARCIS (Netherlands)

    R. Matta

    2013-01-01

    One could argue that CDSs improve risk sharing, hence credit supply and financing terms for firms. Accordingly, one would expect risky borrowers to benefit the most from CDS insurance. This is in contrast, however, with recent empirical evidence (Ashcraft and Santos (2009) and Hirtle (2009)). This p

  8. A novel approach for the fabrication of all-inorganic nanocrystal solids: Semiconductor matrix encapsulated nanocrystal arrays

    Science.gov (United States)

    Moroz, Pavel

    matrix-encapsulated PbS nanocrystal films containing a tunable fraction of insulating ZnS domains, we uniquely distinguish the dynamics of charge scattering on defects from other processes of exciton dissociation. The measured times are subsequently used to estimate the diffusion length and the carrier mobility for each film type within hopping transport regime. It is demonstrated that nanocrystal films encapsulated into semiconductor matrices exhibit a lower probability of charge scattering than nanocrystal solids cross-linked with either 3-mercaptopropionic acid or 1,2-ethanedithiol molecular linkers. The suppression of carrier scattering in matrix-encapsulated nanocrystal films is attributed to a relatively low density of surface defects at nanocrystal/matrix interfaces. High stability and low density of defects made it possible to fabricate infrared-emitting nanocrystal solids. Presently, an important challenge facing the development of nanocrystal infrared emitters concerns the fact that both the emission quantum yield and the stability of colloidal nanoparticles become compromised when nanoparticle solutions are processed into solids. Here, we address this issue by developing an assembly technique that encapsulates infrared-emitting PbS NCs into crystalline CdS matrices, designed to preserve NC emission characteristics upon film processing. Here, the morphology of these matrices was designed to suppress the nonradiative carrier decay, whereby increasing the exciton lifetime up to 1 mus, and boosting the emission quantum yield to an unprecedented 3.7% for inorganically encapsulated PbS NC solids.

  9. Nano-sized Domain Wall Pinning Effects in Dilute Cu-Doped Perovskite LaMn1-x CuxO3 Manganites

    Institute of Scientific and Technical Information of China (English)

    GAO Tian; CAO Shi-Xun; ZHANG Jin-Cang; YU Li-Ming; KANG Bao-Juan; YUAN Shu-Juan

    2008-01-01

    Magnetic properties of Cu-doped LaMn1-x Cux O3 (x =0.05-0.30) systems are carefully studied in the temperature range of 2-300 K. A visible unexpected drop is observed in the ac susceptibility and the zero-field cooled dc magnetization curves for the dilute x ≤0.10 near 100 K, which depends on the measuring frequency and magnetic field. Measurements on frequency dependence of ac susceptibility, observation of magnetic relaxation, and the existence of critical field indicate that the anomaly can be attributed to the domain wall pinning effects. This is directly proven by the results of ball milled nano-sized powder counterparts compared with the bulk materials.

  10. More Cu, more problems: Decreased CO2 conversion ability by Cu-doped La0.75Sr0.25FeO3 perovskite oxides

    Science.gov (United States)

    Daza, Yolanda A.; Maiti, Debtanu; Hare, Bryan J.; Bhethanabotla, Venkat R.; Kuhn, John N.

    2016-06-01

    The effect of Cu doping on the conversion of CO2 to CO was investigated on H2-reduced La0.75Sr0.25FeO3 perovskite oxides. Six La0.75Sr0.25Fe1 -YCuYO3 perovskites, labeled Cu100*Y (with Y = 0, 0.10, 0.25, 0.50, 0.75, and 1) were synthesized and characterized through X-ray diffraction (XRD), temperature-programmed oxygen vacancy formation, and temperature-programmed reduction (TPR). The incorporation of Cu facilitates the formation of oxygen vacancies at lower temperatures but also increased the instability of the perovskite. DFT simulations suggested that the Cu10 sample is favored to produce oxygen vacancies compared to Cu0 and Cu25 samples, which was consistent with experimental oxygen vacancy formation results. For the Cu0, Cu10, and Cu25 samples, temperature-programmed CO2 conversion (TPO-CO2) after isothermal H2-reduction at 450 °C and post-reduction XRD were performed to evaluate the ability of the materials to convert CO2 at low temperatures and to identify the crystalline phases active in the reaction. The peak conversion of CO2 to CO was achieved 30 °C lower on the Cu10 sample versus the Cu0, but less CO was produced, due to a decreased re-oxidation activity of the Cu-doped samples. CO production was inhibited in the Cu25 sample, likely due to a combined effect of poor CO2 dissociative chemisorption energies on metallic Cu and increased thermodynamic stability of the oxygen vacant perovskites. Control experiments (Cu deposited onto La0.75Sr0.25FeO3) indicated the stability of the copper-containing perovskite oxides phases was the primary limiting factor preventing CO formation from CO2.

  11. Synthesis and Microwave Absorbing Properties of Cu-Doped Nickel Zinc Ferrite/Pb(Zr0.52Ti0.48O3 Nanocomposites

    Directory of Open Access Journals (Sweden)

    Avinandan Mandal

    2013-01-01

    Full Text Available Nanocomposites based on Cu-doped nickel zinc ferrite and lead zirconium titanate exhibited significant microwave absorbing properties in the X-band (8.2–12.4 GHz region. Coprecipitation and homogeneous precipitation methods were utilized to synthesize Cu-doped nickel zinc ferrite (Cu0.2Ni0.4Zn0.4Fe2O4 and lead zirconium titanate (Pb(Zr0.52Ti0.48O3 nanoparticles, respectively. To develop nanocomposites, dispersion of these nanoparticles into epoxy resin (LY665 polymeric matrix was carried out by using mechanical stirrer. Phase analyses of the nanoparticles were done by X-ray diffraction (XRD. Moreover, morphological characterization was done by scanning electron microscopy (SEM and transmission electron microscopy (TEM. Energy dispersive X-ray spectroscopy (EDS confirmed the chemical constituents present in the nanocomposites. Complex relative permittivity and complex relative permeability values of the nanocomposites were measured in different microwave frequencies in the X-band (8.2–12.4 GHz region by employing vector network analyzer (model PNA E8364B, and return loss (dB values were calculated to identify the microwave absorbing performance of the present nanocomposites. Brilliant microwave absorbing properties have been achieved by the nanocomposites with the minimum return loss of −49.53 dB at 8.44 GHz when sample thickness was 3 mm. For the present nanocomposites, mainly dielectric loss was responsible for loss mechanism.

  12. Nanocrystal diffusion doping.

    Science.gov (United States)

    Vlaskin, Vladimir A; Barrows, Charles J; Erickson, Christian S; Gamelin, Daniel R

    2013-09-25

    A diffusion-based synthesis of doped colloidal semiconductor nanocrystals is demonstrated. This approach involves thermodynamically controlled addition of both impurity cations and host anions to preformed seed nanocrystals under equilibrium conditions, rather than kinetically controlled doping during growth. This chemistry allows thermodynamic crystal compositions to be prepared without sacrificing other kinetically trapped properties such as shape, size, or crystallographic phase. This doping chemistry thus shares some similarities with cation-exchange reactions, but proceeds without the loss of host cations and excels at the introduction of relatively unreactive impurity ions that have not been previously accessible using cation exchange. Specifically, we demonstrate the preparation of Cd(1-x)Mn(x)Se (0 ≤ x ≤ ∼0.2) nanocrystals with narrow size distribution, unprecedentedly high Mn(2+) content, and very large magneto-optical effects by diffusion of Mn(2+) into seed CdSe nanocrystals grown by hot injection. Controlling the solution and lattice chemical potentials of Cd(2+) and Mn(2+) allows Mn(2+) diffusion into the internal volumes of the CdSe nanocrystals with negligible Ostwald ripening, while retaining the crystallographic phase (wurtzite or zinc blende), shape anisotropy, and ensemble size uniformity of the seed nanocrystals. Experimental results for diffusion doping of other nanocrystals with other cations are also presented that indicate this method may be generalized, providing access to a variety of new doped semiconductor nanostructures not previously attainable by kinetic routes or cation exchange.

  13. Optimizing the synthesis of CdS/ZnS core/shell semiconductor nanocrystals for bioimaging applications

    Directory of Open Access Journals (Sweden)

    Li-wei Liu

    2014-06-01

    Full Text Available In this study, we report on CdS/ZnS nanocrystals as a luminescence probe for bioimaging applications. CdS nanocrystals capped with a ZnS shell had enhanced luminescence intensity, stronger stability and exhibited a longer lifetime compared to uncapped CdS. The CdS/ZnS nanocrystals were stabilized in Pluronic F127 block copolymer micelles, offering an optically and colloidally stable contrast agents for in vitro and in vivo imaging. Photostability test exhibited that the ZnS protective shell not only enhances the brightness of the QDs but also improves their stability in a biological environment. An in-vivo imaging study showed that F127-CdS/ZnS micelles had strong luminescence. These results suggest that these nanoparticles have significant advantages for bioimaging applications and may offer a new direction for the early detection of cancer in humans.

  14. Suppression of auger recombination in ""giant"" core/shell nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Santamaria, Florencio [Los Alamos National Laboratory; Vela, Javier [Los Alamos National Laboratory; Schaller, Richard D [Los Alamos National Laboratory; Hollingsworth, Jennifer A [Los Alamos National Laboratory; Klimov, Victor I [Los Alamos National Laboratory; Chen, Yongfen [NON LANL

    2009-01-01

    Many potential applications of semiconductor nanocrystals are hindered by nonradiative Auger recombination wherein the electron-hole (exciton) recombination energy is transferred to a third charge carrier. This process severely limits the lifetime and bandwidth of optical gain, leads to large nonradiative losses in light emitting diodes and photovoltaic cells, and is believed to be responsible for intermittency ('blinking') of emission from single nanocrystals. The development of nanostructures in which Auger recombination is suppressed has been a longstanding goal in colloidal nanocrystal research. Here, we demonstrate that such suppression is possible using so-called 'giant' nanocrystals that consist of a small CdSe core and a thick CdS shell. These nanostructures exhibit a very long biexciton lifetime ({approx}10 ns) that is likely dominated by radiative decay instead of non-radiative Auger recombination. As a result of suppressed Auger recombination, even high-order multiexcitons exhibit high emission efficiencies, which allows us to demonstrate optical amplification with an extraordinarily large bandwidth (>500 me V) and record low excitation thresholds.

  15. Nanocrystals for electronics.

    Science.gov (United States)

    Panthani, Matthew G; Korgel, Brian A

    2012-01-01

    Semiconductor nanocrystals are promising materials for low-cost large-area electronic device fabrication. They can be synthesized with a wide variety of chemical compositions and size-tunable optical and electronic properties as well as dispersed in solvents for room-temperature deposition using various types of printing processes. This review addresses research progress in large-area electronic device applications using nanocrystal-based electrically active thin films, including thin-film transistors, light-emitting diodes, photovoltaics, and thermoelectrics.

  16. Gold electrodes from recordable CDs

    Science.gov (United States)

    Angnes; Richter; Augelli; Kume

    2000-11-01

    Gold electrodes are widely used in electrochemistry and electroanalytical chemistry. The notable performance when used in stripping analysis of many ionic species and the extraordinary affinity of thio compounds for its surface make these electrodes very suitable for many applications. This paper reports a simple and novel way to construct gold electrodes (CDtrodes) using recordable CDs as the gold source. The nanometer thickness of the gold layer of recordable disks (50-100 nm) favors the construction of band nanoelectrodes with areas as small as 10(-6) cm2. The plane surface can be easily used for the construction of conventional-sized gold electrodes for batch or flow injection analysis or even to obtain electrodes as large as 100 cm2. The low price of commercial recordable CDs allows a "one way use". The evaluation and applicability of these electrodes in the form of nanoelectrodes, in batch and associated with flow cells, are illustrated in this paper.

  17. Highly luminescent ZnO and CdS nanostructures prepared by ionic liquid precursors

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The ionic liquids containing Cd and Zn,which served as the metal-chalcogenides precursors,were synthesized and reacted with Na2S to synthesize the ionic-liquid-capped semiconductors. The products were detected by XRD and TEM. The results demonstrated that the CdS was composed of 5―6 nm monodispersed nanocrystals. At the same time,the ZnO composed of 1 μm hexagonal-disk nanostructure was prepared under the same experimental condition. The difference of the morphology and structures between Zn and Cd systems was discussed by thermodynamics and crystallography. The fluorescence of as-prepared ZnO and CdS showed the excellent photoluminescence.

  18. Photoluminescent nanocomposite materials based on SBMA copolymer and CdS

    Science.gov (United States)

    Iovu, M.; Enachescu, M.; Culeac, I.; Verlan, V.; Robu, S.; Bojin, D.; Nistor, Iu.; Cojocaru, I.

    2015-02-01

    We present experimental results on copolymer-based nanocomposite made of styrene with butyl methacrylate (SBMA) (1:1) and inorganic semiconductor CdS. Thin film composite samples have been characterized by UV-Vis absorption and photoluminescent spectroscopy, as well as by transmission electron microscopy. Transmission electron microscope (TEM) examination confirms a relatively narrow distribution of CdS nanoclusters in the SBMA matrix, which covers the range 2-10 nm. On the other side, the average CdS particles size estimated from the position of first excitonic peak in the UV-Vis absorption spectrum was found to be 2.8 nm and 4.4 nm for two samples with different duration of thermal treatment, which is in good agreement with photoluminescence (PL) experimental data. The PL spectrum for CdS nanocrystals is dominated by near-band-edge emission. The relatively narrow line width (40-45 nm) of the main PL band suggests the nanoparticles having narrow size distribution. On the other side, relatively low PL emission from surface trap states at longer wavelengths were observed in the region 500-750 nm indicating on recombination on defects. Key words: nanocomposite, polymer matrix, photoluminescence,

  19. Fabrication of 2D and 3D dendritic nanoarchitectures of CdS

    Institute of Scientific and Technical Information of China (English)

    GU Li

    2008-01-01

    The controlled preparation of two-dimensional (2D) and three-dimensional (3D) dendritic nanostructures of CdS was reported. 2D dendritic patterns are obtained through the self-assembly of nanoparticles under the entropy-driven force. 3D dendritic needle-like nanocrystals are prepared through an aqueous solution synthesis regulated by oleic acid molecules. Their growth mechanism is presumed to be the selective binding of OA molecules onto growing crystal planes. Techniques such as SEM, TEM, XRD, and FT-IR were employed to characterize the morphologies and structures of the obtained products.

  20. A configurable CDS for the production laboratory

    CERN Document Server

    Meek, Irish

    2003-01-01

    Various aspects of a configurable chromatography data system (CDS) for the production laboratory are discussed. The Atlas CDS can be configured extensively to fit the production laboratory work flow and meet the needs of analysts. The CDS can also be configured to automatically create a sample sequence with the required number of injections and download methods to the dedicated instrument. The Atlas Quick Start wizard offers uses quick way of generating a sequence from a predefined template and starting a run. (Edited abstract).

  1. A Low-Temperature, Solution-Processable, Cu-Doped Nickel Oxide Hole-Transporting Layer via the Combustion Method for High-Performance Thin-Film Perovskite Solar Cells.

    Science.gov (United States)

    Jung, Jae Woong; Chueh, Chu-Chen; Jen, Alex K-Y

    2015-12-16

    Low-temperature, solution-processable Cu-doped NiOX (Cu:NiOx ), prepared via combustion chemistry, is demonstrated as an excellent hole-transporting layer (HTL) for thin-film perovskite solar cells (PVSCs). Its good crystallinity, conductivity, and hole-extraction properties enable the derived PVSC to have a high power conversion efficiency (PCE) of 17.74%. Its general applicability for various elecrode materials is also revealed.

  2. Nanocrystal Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Gur, Ilan [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    This dissertation presents the results of a research agenda aimed at improving integration and stability in nanocrystal-based solar cells through advances in active materials and device architectures. The introduction of 3-dimensional nanocrystals illustrates the potential for improving transport and percolation in hybrid solar cells and enables novel fabrication methods for optimizing integration in these systems. Fabricating cells by sequential deposition allows for solution-based assembly of hybrid composites with controlled and well-characterized dispersion and electrode contact. Hyperbranched nanocrystals emerge as a nearly ideal building block for hybrid cells, allowing the controlled morphologies targeted by templated approaches to be achieved in an easily fabricated solution-cast device. In addition to offering practical benefits to device processing, these approaches offer fundamental insight into the operation of hybrid solar cells, shedding light on key phenomena such as the roles of electrode-contact and percolation behavior in these cells. Finally, all-inorganic nanocrystal solar cells are presented as a wholly new cell concept, illustrating that donor-acceptor charge transfer and directed carrier diffusion can be utilized in a system with no organic components, and that nanocrystals may act as building blocks for efficient, stable, and low-cost thin-film solar cells.

  3. Tuning light emission of PbS nanocrystals from infrared to visible range by cation exchange

    KAUST Repository

    Binetti, Enrico

    2015-10-27

    Colloidal semiconductor nanocrystals, with intense and sharp-line emission between red and near-infrared spectral regions, are of great interest for optoelectronic and bio-imaging applications. The growth of an inorganic passivation layer on nanocrystal surfaces is a common strategy to improve their chemical and optical stability and their photoluminescence quantum yield. In particular, cation exchange is a suitable approach for shell growth at the expense of the nanocrystal core size. Here, the cation exchange process is used to promote the formation of a CdS passivation layer on the surface of very small PbS nanocrystals (2.3 nm in diameter), blue shifting their optical spectra and yielding luminescent and stable nanostructures emitting in the range of 700–850 nm. Structural, morphological and compositional investigation confirms the nanocrystal size contraction after the cation-exchange process, while the PbS rock-salt crystalline phase is retained. Absorption and photoluminescence spectroscopy demonstrate the growth of a passivation layer with a decrease of the PbS core size, as inferred by the blue-shift of the excitonic peaks. The surface passivation strongly increases the photoluminescence intensity and the excited state lifetime. In addition, the nanocrystals reveal increased stability against oxidation over time. Thanks to their absorption and emission spectral range and the slow recombination dynamics, such highly luminescent nano-objects can find interesting applications in sensitized photovoltaic cells and light-emitting devices.

  4. Eco-friendly intracellular biosynthesis of CdS quantum dots without changing Escherichia coli's antibiotic resistance.

    Science.gov (United States)

    Yan, Zheng-Yu; Du, Qing-Qing; Qian, Jing; Wan, Dong-Yu; Wu, Sheng-Mei

    2017-01-01

    In the paper, a green and efficient biosynthetical technique was reported for preparing cadmium sulfide (CdS) quantum dots, in which Escherichia coli (E. coli) was chosen as a biomatrix. Fluorescence emission spectra and fluorescent microscopic photographs revealed that as-produced CdS quantum dots had an optimum fluorescence emission peak located at 470nm and emitted a blue-green fluorescence under ultraviolet excitation. After extracted from bacterial cells and located the nanocrystals' foci in vivo, the CdS quantum dots showed a uniform size distribution by transmission electron microscope. Through the systematical investigation of the biosynthetic conditions, including culture medium replacement, input time point of cadmium source, working concentrations of raw inorganic ions, and co-cultured time spans of bacteria and metal ions in the bio-manufacture, the results revealed that CdS quantum dots with the strongest fluorescence emission were successfully prepared when E. coli cells were in stationary phase, with the replacement of culture medium and following the incubation with 1.0×10(-3)mol/L cadmium source for 2 days. Results of antimicrobial susceptibility testing indicated that the sensitivities to eight types of antibiotics of E. coli were barely changed before and after CdS quantum dots were prepared in the mild temperature environment, though a slight fall of antibiotic resistance could be observed, suggesting hinted the proposed technique of producing quantum dots is a promising environmentally low-risk protocol.

  5. Crystalline nanostructured Cu doped ZnO thin films grown at room temperature by pulsed laser deposition technique and their characterization

    Energy Technology Data Exchange (ETDEWEB)

    Drmosh, Qasem A. [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Rao, Saleem G.; Yamani, Zain H. [Laser Research Group, Department of Physics, Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Gondal, Mohammed A., E-mail: magondal@kfupm.edu.sa [Laser Research Group, Department of Physics, Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

    2013-04-01

    We report structural and optical properties of Cu doped ZnO (ZnO:Cu) thin films deposited on glass substrate at room temperature by pulsed laser deposition (PLD) method without pre and post annealing contrary to all previous reports. For preparation of (ZnO:Cu) composites pure Zn and Cu targets in special geometrical arrangements were exposed to 248 nm radiations generated by KrF exciter laser. The laser energy was 200 mJ with 10 Hz frequency and 20 ns pulse width. The effect of Cu concentration on crystal structure, morphology, and optical properties were investigated by XRD, FESEM and photoluminescence spectrometer respectively. A systematic shift in ZnO (0 0 2) peak with Cu concentration observed in XRD spectra demonstrated that Cu ion has been incorporated in ZnO lattice. Uniform film with narrow size range grains were observed in FESEM images. The photoluminescence (PL) spectra measured at room temperature revealed a systematic red shift in ZnO emission peak and decrease in the band gap with the increase in Cu concentration. These results entail that PLD technique can be realized to deposit high quality crystalline ZnO and ZnO:Cu thin films without pre and post heat treatment which is normally practiced worldwide for such structures.

  6. Development and analysis of Cu-doped ZnTe for use as a back contact interface for CdS/CdTe solar cells

    Science.gov (United States)

    Gessert, T. A.; Coutts, T. J.

    1994-06-01

    It is well known that the losses associated with the back contact of typical CdS/CdTe solar cell devices can be a substantial part of the total external loss. Previous modeling has indicated that these losses will be significant, unless the value of specific contact resistance (rc) at this interface is reduced to ˜0.10 Ω-cm2 or less. Although several studies have inferred values of rc near this level, few have attempted to measure directly the value of rc as a function of various processing conditions. One reason for this situation is the difficulty in fabricating the appropriate patterns for direct analysis of rc. In the following paper, initial characterization studies of sputter-deposited, Cu-doped ZnTe are documented. Additionally, recent attempts to measure directly the contact resistance associated with the two interfaces of the Ni/ZnTe/CdTe contact stack, are presented and discussed. Preliminary testing of these processes has been conducted using sputter-deposited test structures representing the individual interfaces of a typical Ni/ZnTe/CdTe contact stack. Contact resistance analysis of these structures has allowed for the estimation of rc suggesting that, for the conditions studied, the contact stack appears to meet the criterion of yielding an rc value <0.1 Ω-cm2.

  7. Doping effect on SILAR synthesized crystalline nanostructured Cu-doped ZnO thin films grown on indium tin oxide (ITO) coated glass substrates and its characterization

    Science.gov (United States)

    Dhaygude, H. D.; Shinde, S. K.; Velhal, Ninad B.; Takale, M. V.; Fulari, V. J.

    2016-08-01

    In the present study, a novel chemical route is used to synthesize the undoped and Cu-doped ZnO thin films in aqueous solution by successive ionic layer adsorption and reaction (SILAR) method. The synthesized thin films are characterized by x-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive x-ray analysis (EDAX), contact angle goniometer and UV-Vis spectroscopic techniques. XRD study shows that the prepared films are polycrystalline in nature with hexagonal crystal structure. The change in morphology for different doping is observed in the studies of FE-SEM. EDAX spectrum shows that the thin films consist of zinc, copper and oxygen elements. Contact angle goniometer is used to measure the contact angle between a liquid and a solid interface and after detection, the nature of the films is initiated from hydrophobic to hydrophilic. The optical band gap energy for direct allowed transition ranging between 1.60-2.91 eV is observed.

  8. Mutual Excitation in Eurozone Sovereign CDS

    NARCIS (Netherlands)

    Aït-Sahalia, Y.; Laeven, R.J.A.; Pelizzon, L.

    2013-01-01

    We study self- and cross-excitation of shocks in the sovereign CDS market, on the basis of a large database of Eurozone sovereign CDS spreads. We adopt a multivariate setting with credit default intensities driven by mutually exciting jump processes, to capture the salient features observed in the d

  9. Nanocrystal grain growth and device architectures for high-efficiency CdTe ink-based photovoltaics.

    Science.gov (United States)

    Crisp, Ryan W; Panthani, Matthew G; Rance, William L; Duenow, Joel N; Parilla, Philip A; Callahan, Rebecca; Dabney, Matthew S; Berry, Joseph J; Talapin, Dmitri V; Luther, Joseph M

    2014-09-23

    We study the use of cadmium telluride (CdTe) nanocrystal colloids as a solution-processable "ink" for large-grain CdTe absorber layers in solar cells. The resulting grain structure and solar cell performance depend on the initial nanocrystal size, shape, and crystal structure. We find that inks of predominantly wurtzite tetrapod-shaped nanocrystals with arms ∼5.6 nm in diameter exhibit better device performance compared to inks composed of smaller tetrapods, irregular faceted nanocrystals, or spherical zincblende nanocrystals despite the fact that the final sintered film has a zincblende crystal structure. Five different working device architectures were investigated. The indium tin oxide (ITO)/CdTe/zinc oxide structure leads to our best performing device architecture (with efficiency >11%) compared to others including two structures with a cadmium sulfide (CdS) n-type layer typically used in high efficiency sublimation-grown CdTe solar cells. Moreover, devices without CdS have improved response at short wavelengths.

  10. Laser-induced growth of nanocrystals embedded in porous materials

    Science.gov (United States)

    Capoen, Bruno; Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bouazaoui, Mohamed

    2013-06-01

    Space localization of the linear and nonlinear optical properties in a transparent medium at the submicron scale is still a challenge to yield the future generation of photonic devices. Laser irradiation techniques have always been thought to structure the matter at the nanometer scale, but combining them with doping methods made it possible to generate local growth of several types of nanocrystals in different kinds of silicate matrices. This paper summarizes the most recent works developed in our group, where the investigated nanoparticles are either made of metal (gold) or chalcogenide semiconductors (CdS, PbS), grown in precursor-impregnated porous xerogels under different laser irradiations. This review is associated to new results on silver nanocrystals in the same kind of matrices. It is shown that, depending on the employed laser, the particles can be formed near the sample surface or deep inside the silica matrix. Photothermal and/or photochemical mechanisms may be invoked to explain the nanoparticle growth, depending on the laser, precursor, and matrix. One striking result is that metal salt reduction, necessary to the production of the corresponding nanoparticles, can efficiently occur due to the thermal wrenching of electrons from the matrix itself or due to multiphoton absorption of the laser light by a reducer additive in femtosecond regime. Very localized semiconductor quantum dots could also be generated using ultrashort pulses, but while PbS nanoparticles grow faster than CdS particles due to one-photon absorption, this better efficiency is counterbalanced by a sensitivity to oxidation. In most cases where the reaction efficiency is high, particles larger than the pores have been obtained, showing that a fast diffusion of the species through the interconnected porosity can modify the matrix itself. Based on our experience in these techniques, we compare several examples of laser-induced nanocrystal growth in porous silica xerogels, which allows

  11. Chemistry of the Colloidal Group II-VI Nanocrystal Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Haitao [Univ. of California, Berkeley, CA (United States)

    2007-05-17

    In the last two decades, the field of nanoscience andnanotechnology has witnessed tremendous advancement in the synthesis andapplication of group II-VI colloidal nanocrystals. The synthesis based onhigh temperature decomposition of organometallic precursors has becomeone of the most successful methods of making group II-VI colloidalnanocrystals. This methodis first demonstrated by Bawendi and coworkersin 1993 to prepare cadmium chalcogenide colloidal quantum dots and laterextended by others to prepare other group II-VI quantum dots as well asanisotropic shaped colloidal nanocrystals, such as nanorod and tetrapod.This dissertation focuses on the chemistry of this type of nanocrystalsynthesis. The synthesis of group II-VI nanocrystals was studied bycharacterizing the molecular structures of the precursors and productsand following their time evolution in the synthesis. Based on theseresults, a mechanism was proposed to account for the 2 reaction betweenthe precursors that presumably produces monomer for the growth ofnanocrystals. Theoretical study based on density functional theorycalculations revealed the detailed free energy landscape of the precursordecomposition and monomerformation pathway. Based on the proposedreaction mechanism, a new synthetic method was designed that uses wateras a novel reagent to control the diameter and the aspect ratio of CdSeand CdS nanorods.

  12. Great improvement of photoelectric property from co-sensitization of TiO{sub 2} electrodes with CdS quantum dots and dye N719 in dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jing [Ministry-of-Education, Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Wuhan 430062 (China); Zhao, Li, E-mail: zhaoli7376@163.com [Ministry-of-Education, Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Wuhan 430062 (China); Wang, Shimin, E-mail: shiminwang@126.com [Ministry-of-Education, Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Wuhan 430062 (China); Hu, Jinghua [School of Science, Wuhan University of Technology, Wuhan 430070 (China); Dong, Binghai; Lu, Hongbing; Wan, Li [Ministry-of-Education, Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Wuhan 430062 (China); Wang, Ping [School of Science, Wuhan University of Technology, Wuhan 430070 (China)

    2013-07-15

    Graphical abstract: - Highlights: • TiO{sub 2} film electrodes have been successfully sensitized with CdS QDs. • DSSC based on CdS QDs-sensitized TiO{sub 2} film with 4 min has the highest efficiency. • CdS QDs can improve the electron transport and reduce the electron recombination. • Our work open up a new avenue for the development of DSSCs. - Abstract: The TiO{sub 2} film electrodes sensitized with CdS quantum dots (QDs) via chemical bath deposition method were successfully prepared as the photoanode of dye-sensitized solar cells (DSSCs). Microstructural characterizations by XRD, SEM, TEM and EDX show that the CdS nanocrystals with the cubic structure have intimate contact to the TiO{sub 2} films. The amount of CdS QDs can be controlled by varying the dipping time. The experiment results demonstrate that the CdS QDs-sensitized solar cells show a wider absorption in the solar spectrum and an enhanced surface photovoltage response. The maximal photoelectric conversion efficiency of 5.57% was achieved by the DSSC based on CdS QDs-sensitized TiO{sub 2} film with 4 min. The performance improvement is ascribed to the enhancement of electron transport, the reduction of electron recombination and the long electron lifetime.

  13. Sorting fluorescent nanocrystals with DNA

    Energy Technology Data Exchange (ETDEWEB)

    Gerion, Daniele; Parak, Wolfgang J.; Williams, Shara C.; Zanchet, Daniela; Micheel, Christine M.; Alivisatos, A. Paul

    2001-12-10

    Semiconductor nanocrystals with narrow and tunable fluorescence are covalently linked to oligonucleotides. These biocompounds retain the properties of both nanocrystals and DNA. Therefore, different sequences of DNA can be coded with nanocrystals and still preserve their ability to hybridize to their complements. We report the case where four different sequences of DNA are linked to four nanocrystal samples having different colors of emission in the range of 530-640 nm. When the DNA-nanocrystal conjugates are mixed together, it is possible to sort each type of nanoparticle using hybridization on a defined micrometer -size surface containing the complementary oligonucleotide. Detection of sorting requires only a single excitation source and an epifluorescence microscope. The possibility of directing fluorescent nanocrystals towards specific biological targets and detecting them, combined with their superior photo-stability compared to organic dyes, opens the way to improved biolabeling experiments, such as gene mapping on a nanometer scale or multicolor microarray analysis.

  14. Biotemplated preparation of CdS nanoparticles/bacterial cellulose hybrid nanofibers for photocatalysis application.

    Science.gov (United States)

    Yang, Jiazhi; Yu, Junwei; Fan, Jun; Sun, Dongping; Tang, Weihua; Yang, Xuejie

    2011-05-15

    In this work, we describe a novel facile and effective strategy to prepare micrometer-long hybrid nanofibers by deposition of CdS nanoparticles onto the substrate of hydrated bacterial cellulose nanofibers (BCF). Hexagonal phase CdS nanocrystals were achieved via a simple hydrothermal reaction between CdCl(2) and thiourea at relatively low temperature. The prepared pristine BCF and the CdS/BCF hybrid nanofibers were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), UV-vis absorption spectroscopy (UV-vis), and X-ray photoelectron spectroscopy (XPS). The results reveal that the CdS nanoparticles were homogeneously deposited on the BCF surface and stabilized via coordination effect. The CdS/BCF hybrid nanofibers demonstrated high-efficiency photocatalysis with 82% methyl orange (MO) degradation after 90 min irradiation and good recyclability. The results indicate that the CdS/BCF hybrid nanofibers are promising candidate as robust visible light responsive photocatalysts.

  15. Structural and optical characterization of mechanochemically synthesized copper doped CdS nanopowders

    Energy Technology Data Exchange (ETDEWEB)

    Reyes, P., E-mail: pireyes@cinvestav.mx [Departamento de Ingenieria Electrica-SEES, CINVESTAV-IPN, Zacatenco, D.F., C.P.07360, Mexico (Mexico); Velumani, S. [Departamento de Ingenieria Electrica-SEES, CINVESTAV-IPN, Zacatenco, D.F., C.P.07360, Mexico (Mexico)

    2012-09-20

    Incorporation of copper into CdS crystals has been successfully prepared by mechanical alloying using a planetary ball mill. The powders are prepared with different milling times at 300 rpm with various Cu/Cd ratios from 0.1 to 25 at%. X-ray diffraction (XRD) analysis of milled powders showed peaks corresponding to hexagonal structure with a detection of phase transition to a cubic structure with increasing milling time. Grain sizes varied from 21 to 30 nm corresponding to different Cu/Cd ratios. Field emission scanning electron microscopy (FESEM) images reveal agglomerated materials with particle size of approximately 28 nm (5 Cu at%) and layered structures caused due to the milling process. Powder composition by energy dispersive analysis of X-rays (EDAX) reveals the incorporation of copper into the CdS. Micro Raman spectroscopy showed peaks approximately at 301 and 585 cm{sup -1} corresponding to first and second order scatterings of longitudinal optical phonon mode. The LO mode at 301 cm{sup -1} shifted towards lower wave number due to decrease of grain size by increase in milling time. From high resolution transmission electron microscope (HRTEM), the dominant phase of individual CdS nanocrystals was found to be hexagonal structure along with cubic structure.

  16. What do we know about speculation in the CDS market?

    NARCIS (Netherlands)

    L. Norden (Lars); K. Radoeva (Kristina)

    2012-01-01

    textabstractWe measure speculation in the CDS market and investigate its determinants. The CDS volume on a firm that exceeds its outstanding debt (= naked CDS) indicates speculation since hedging can be ruled out. Using weekly CDS trading volume data for actively traded U.S. firms during 2008-2012,

  17. ⁶⁴Cu-Doped PdCu@Au Tripods: A Multifunctional Nanomaterial for Positron Emission Tomography and Image-Guided Photothermal Cancer Treatment.

    Science.gov (United States)

    Pang, Bo; Zhao, Yongfeng; Luehmann, Hannah; Yang, Xuan; Detering, Lisa; You, Meng; Zhang, Chao; Zhang, Lei; Li, Zhi-Yuan; Ren, Qiushi; Liu, Yongjian; Xia, Younan

    2016-03-22

    This article reports a facile synthesis of radiolabeled PdCu@Au core-shell tripods for use in positron emission tomography (PET) and image-guided photothermal cancer treatment by directly incorporating radioactive (64)Cu atoms into the crystal lattice. The tripod had a unique morphology determined by the PdCu tripod that served as a template for the coating of Au shell, in addition to well-controlled specific activity and physical dimensions. The Au shell provided the nanostructure with strong absorption in the near-infrared region and effectively prevented the Cu and (64)Cu atoms in the core from oxidization and dissolution. When conjugated with D-Ala1-peptide T-amide (DAPTA), the core-shell tripods showed great enhancement in targeting the C-C chemokine receptor 5 (CCR5), a newly identified theranostic target up-regulated in triple negative breast cancer (TNBC). Specifically, the CCR5-targeted tripods with an arm length of about 45 nm showed 2- and 6-fold increase in tumor-to-blood and tumor-to-muscle uptake ratios, respectively, relative to their nontargeted counterpart in an orthotopic mouse 4T1 TNBC model at 24 h postinjection. The targeting specificity was further validated via a competitive receptor blocking study. We also demonstrated the use of these targeted, radioactive tripods for effective photothermal treatment in the 4T1 tumor model as guided by PET imaging. The efficacy of treatment was confirmed by the significant reduction in tumor metabolic activity revealed through the use of (18)F-fluorodeoxyglucose PET/CT imaging. Taken together, we believe that the (64)Cu-doped PdCu@Au tripods could serve as a multifunctional platform for both PET imaging and image-guided photothermal cancer therapy.

  18. Hyperfine interaction and tuning of magnetic anisotropy of Cu doped CoFe{sub 2}O{sub 4} ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Batoo, Khalid Mujasam, E-mail: khalid.mujasam@gmail.com [King Abdullah Institute for Nanotechnology, King Saud University, P.O. Box-2455, Riyadh 11451 (Saudi Arabia); Salah, Dina [Department of Physics, Ain Shams University, Khalifa El-Maamon, Street, 11566 Cairo (Egypt); Kumar, Gagan; Kumar, Arun; Singh, Mahavir [Department of Physics, Himachal Pradesh University, Summer Hill, Shimla 171005 (India); Abd El-sadek, M. [Nanomaterials Lab, Physics Department, Faculty of Science, South Valley University, Qena 83523 (Egypt); Mir, Feroz Ahmad [University Science Instrumentation Centre, University of Kashmir, Srinagar 190006 (India); Imran, Ahamad [King Abdullah Institute for Nanotechnology, King Saud University, P.O. Box-2455, Riyadh 11451 (Saudi Arabia); Jameel, Daler Adil [School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Center, University of Nottingham, NG7 2RD (United Kingdom)

    2016-08-01

    Ferrimagnetic oxides may contain single or multi domain particles which get converted into superparamagnetic state near a critical size. To explore the existence of these particles, we have made Mössbauer and magnetic studies of Cu{sup 2+} substitution effect in CoFe{sub 2−x}O{sub 4} Ferrites (0.0, 0.1, 0.2, 0.3, 0.4, and 0.5). All the samples have a cubic spinel structure with lattice parameters increasing linearly with increase in Cu content. The hysteresis loops yield a saturation magnetization, coercive field, and remanent magnetization that vary significantly with Cu content. The magnetic hysteresis curves shows a reduction in saturation magnetization and an increase in coercitivity with Cu{sup 2+} ion substitution. The anisotropy constant, K{sub 1,} is found strongly dependent on the composition of Cu{sup 2+} ions. The variation of saturation magnetization with increasing Cu{sup 2+} ion content has been explained in the light of Neel's molecular field theory. Mössbauer spectra at room temperature shows two ferrimagnetically relaxed Zeeman sextets. The dependence of Mössbauer parameters such as isomer shift, quadrupole splitting, line width and hyperfine magnetic field on Cu{sup 2+} ion concentration have been discussed. - Highlights: • Synthesis of the nanoparticles of Cu doped CoFe{sub 2}O{sub 4} ferrite nanoparticles. • The samples were characterized for the structural, morphological and magnetic studies using XRD, TEM, VSM and Mossbauer spectroscopy. • It has been found that the all the magnetic and Mossbauer parameters are diluted with the addition of Cu content in the CoFe{sub 2}O{sub 4} matrix. • The Mossbauer and magnetic properties were studied in the light of size of nanoparticles and also with respect to the doping composition.

  19. Vacancy Generation and Oxygen Uptake in Cu-Doped Pr-CeO2 Materials using Neutron and in Situ X-ray Diffraction.

    Science.gov (United States)

    D'Angelo, Anita M; Webster, Nathan A S; Chaffee, Alan L

    2016-12-19

    The oxygen uptake ability of Pr-CeO2-based oxygen carriers, catalysts, and solid oxide fuel cells can be attributed to 3+ cation generation and the presence of vacant oxygen sites. Oxygen occupancies of CeO2, Pr-CeO2, and 5% Cu-doped Pr-CeO2 were investigated using neutron diffraction and related to the oxygen uptake as determined using thermogravimetric analysis (TGA). The presence of vacant tetrahedral oxygen sites at room temperature did not correspond to low-temperature oxygen uptake. The materials did not uptake oxygen at 420 °C, but oxygen uptake was observed at 600 °C, which indicated that a minimum temperature needs to be met to generate sufficient vacancies/3+ cations. Variations in the lattice parameter as a function of temperature were revealed using in situ X-ray diffraction (XRD). With increasing temperature the lattice parameter increased linearly due to thermal expansion and was followed by an exponential increase at ∼300-400 °C as cations were reduced. Despite segregation of Cu into CuO at high dopant concentration, at 600 °C a higher O2 uptake was obtained for Ce0.65Pr0.20Cu0.15O2-δ (120 μmol g(-1)), in comparison to Ce0.75Pr0.2Cu0.05O2-δ (92 μmol g(-1)), and was higher than that for Ce0.8Pr0.2O2-δ (55 μmol g(-1)). Both Pr and Cu introduce vacancies and promote the O2 uptake of CeO2.

  20. Enhanced visible photocatalytic activity of cotton ball like nano structured Cu doped ZnO for the degradation of organic pollutant.

    Science.gov (United States)

    Thennarasu, G; Sivasamy, A

    2016-12-01

    Stringent Environmental standards followed worldwide led to the emergence of advanced oxidation process for the removal of toxic contaminants from water and wastewater. Among all semiconductor photocatalysts have great potential in the degradation of organic and inorganic pollutants into lesser harmful products under visible light irradiations. The present research work describes the synthesis of Cu doped ZnO (CuDZ) via a co-precipitation method to attain high crystallized powder confirmed by XRD analysis. The FE-SEM images showed that the CuDZ has cotton ball like morphology with a uniform size ranged from 25 to 40nm. TEM, FT-IR and UV-DRS studies of the synthesized CuDZ are also discussed in detail. The photocatalytic activity of the as prepared CuDZ catalyst was tested for the degradation of Direct Blue 71 (DB 71) dye in aqueous phase under visible light irradiation. The degree of degradation was found to be dependent on aqueous phase pH, duration of irradiation time, amount of photocatalyst, the initial dye concentration and kinetics of photodegradation. The maximum photocatytic degradation of DB 71 dye was found to be effective at pH 6.8. The optimum amount of photocatalyst was found 3gL(-1) of CuDZ for the complete degradation of DB 71 dye (0.01gL(-1)). The reusability of the photocatalyst indicates that 96% of DB 71 dye was degraded up to 3rd cycles of use. The visible photodegradation of DB 71 dye was exhibited pseudo-first-order kinetics. Chemical oxygen demand and ESI-MS studies confirmed the complete mineralization of DB 71 dye molecules. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Cu doped TiO{sub 2}/GF for photocatalytic disinfection of Escherichia coli in bioaerosols under visible light irradiation: Application and mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Pham, Thanh-Dong; Lee, Byeong-Kyu, E-mail: bklee@ulsan.ac.kr

    2014-03-01

    Highlights: • Cu dopants enhanced electron-hole separation efficiency and capacity of TiO{sub 2}. • Cu-TiO{sub 2}/GF exhibited high bioaerosol disinfection even under visible light. • The disinfection enhancement is depended on Cu content in Cu-TiO{sub 2}/GF. • The moderate humidity was the optimum condition for the bioaerosol disinfection. - Abstract: This study investigated the role of Cu as a doping agent to enhance photocatalytic activity of TiO{sub 2} in Cu-doped TiO{sub 2}/glass fibers (Cu-TiO{sub 2}/GF) used for disinfection of Escherichia coli (E. coli) in aerosols under visible light irradiation. Glass fiber was used as a substrate to immobilize TiO{sub 2} for disinfection of E. coli in bioaerosols. Cu in the prepared photocatalyst acted as an intermediate agent for the transfer of photo-generated electrons from the valence band to the conduction band of TiO{sub 2}. Cu dopants increased the electron-hole pair separation efficiency, inhibited their recombination leading to a lifetime increase of the generated electrons, and thus improved photocatalytic activity even under visible light irradiation. Cu also defected the TiO{sub 2} lattice by producing Ti{sup 3+} ions, which can increase the electron-hole separation capacity of the photocatalyst, thereby increasing photocatalytic capacity. The optimal Cu content in Cu/TiO{sub 2} to enhance the photocatalytic activity of TiO{sub 2} was 5 wt.%. Among three humidity conditions (dry (40 ± 5%), moderate (60 ± 5%) and humid (80 ± 5%)), the moderate condition showed the highest disinfection efficiency of E. coli. When the 5% Cu-TiO{sub 2}/GF was used under a moderate level of humidity, the highest disinfection efficiency and disinfection capacity of E. coli were identified as 87.8% and 23 CFU/s cm{sup 2}, respectively.

  2. Nanocrystal synthesis and thin film formation for earth abundant photovoltaics

    Science.gov (United States)

    Carter, Nathaniel J.

    Providing access to on-demand energy at the global scale is a grand challenge of our time. The fabrication of solar cells from nanocrystal inks comprising earth abundant elements represents a scalable and sustainable photovoltaic technology with the potential to meet the global demand for electricity. Solar cells with Cu2ZnSn(S,Se)4 (CZTSSe) absorber layers are of particular interest due to the high absorption coefficient of CZTSSe, its band gap in the ideal range for efficient photovoltaic power conversion, and the relative abundance of its constituent elements in the earth's crust. Despite the promise of this material system, CZTSSe solar cell efficiencies reported throughout literature have failed to exceed 12.6%, principally due to the low open-circuit voltage (VOC) achieved in these devices compared to the absorber band gap. The work presented herein primarily aims to address the low VOC problem. First, the fundamental cause for such low VOC's is investigated. Interparticle compositional inhomogeneities identified in the synthesized CZTS nanocrystals and their effect on the absorber layer formation and device performance are characterized. Real-time energy-dispersive x-ray diffraction (EDXRD) elucidates the role of these inhomogeneities in the mechanism by which a film of CZTS nanocrystals converts into a dense absorber layer comprising micron-sized CZTSSe grains upon annealing in a selenium atmosphere (selenization). Additionally, a direct correlation between the nanocrystal inhomogeneities and the VOC in completed devices is observed. Detailed characterization of CZTSSe solar cells identifies electrical potential fluctuations in the CZTSSe absorber - due to spatial composition variations not unlike those observed in the nanocrystals - as a primary V OC inhibitor. Additional causes for low VOC's in CZTSSe solar cells proposed in the literature involve recombination at the interface between the CZTSSe absorber and: (1) the n-type, CdS buffer layer, or (2) the

  3. Improving the Formatting Tools of CDS Invenio

    CERN Document Server

    Caffaro, J; Pu Faltings, Pearl

    2006-01-01

    CDS Invenio is the web-based integrated digital library system developed at CERN. It is a strategical tool that supports the archival and open dissemination of documents produced by CERN researchers. This paper reports on my Master’s thesis work done on BibFormat, a module in CDS Invenio, which formats documents metadata. The goal of this project was to implement a completely new formatting module for CDS Invenio. In this report a strong emphasis is put on the user-centered design of the new BibFormat. The bibliographic formatting process and its requirements are discussed. The task analysis and its resulting interaction model are detailed. The document also shows the implemented user interface of BibFormat and gives the results of the user evaluation of this interface. Finally the results of a small usability study of the formats included in CDS Invenio are discussed.

  4. Managing an Institutional Repository with CDS Invenio

    CERN Document Server

    Robinson, N; Simko, T

    2007-01-01

    CERN has long been committed to the free dissemination of scientific research results and theories. Towards this end, CERN's own institutional repository, the CERN Document Server (CDS) offers access to CERN works and to all related scholarly literature in the HEP domain. Hosting over 500 document collections containing more than 900,000 records, CDS provides access to anything from preprints and articles, to multimedia information such as photographs, movies, posters and brochures. The software that powers this service, CDS Invenio, is distributed freely under the GNU GPL and is currently used in approximately 15 institutions worldwide. In this paper, we discuss the use of CDS Invenio to manage a repository of scientific literature. We outline some of the issues faced during the lifecycle of a document from acquisition, processing and indexing to dissemination. In particular, we focus on the features and technology developed to meet the complexities of managing scientific information in the LHC era of large ...

  5. The Einstein nanocrystal

    CERN Document Server

    Bertoldi, D S; Miranda, E N

    2016-01-01

    We study the simplest possible model of nanocrystal consisting in a simple cubic lattice with a small number of atoms (NA ~ 10-10^3), where each atom is linked to its nearest neighbor by a quantum harmonic potential. Some properties (entropy, temperature, specific heat) of the nanocrystal are calculated numerically but exactly within the framework of the microcanonical ensemble. We find that the presence of a surface in the nanocrystal modifies the thermostatistic properties to a greater extent than the small number of atoms in the system. The specific heat Cv behaves similarly to the Einstein solid, with an asymptotic value for high temperatures that differs from that of the Dulong-Petit law by a term of the order of NA^(-1/3) and that can be explained easily in terms of the surface. The entropy is non-additive, but this is due to the presence of the surface and we show that the additivity is recovered in the thermodynamic limit. Finally, we find that, when calculations follow the canonical ensemble, results...

  6. Synthesis and Doping of Silicon Nanocrystals for Versatile Nanocrystal Inks

    Science.gov (United States)

    Kramer, Nicolaas Johannes

    The impact of nanotechnology on our society is getting larger every year. Electronics are becoming smaller and more powerful, the "Internet of Things" is all around us, and data generation is increasing exponentially. None of this would have been possible without the developments in nanotechnology. Crystalline semiconductor nanoparticles (nanocrystals) are one of the latest developments in the field of nanotechnology. This thesis addresses three important challenges for the transition of silicon nanocrystals from the lab bench to the marketplace: A better understanding of the nanocrystal synthesis was obtained, the electronic properties of the nanocrystals were characterized and tuned, and novel silicon nanocrystal inks were formed and applied using simple coating technologies. Plasma synthesis of nanocrystals has numerous advantages over traditional solution-based synthesis methods. While the formation of nanoparticles in low pressure nonthermal plasmas is well known, the heating mechanism leading to their crystallization is poorly understood. A combination of comprehensive plasma characterization with a nanoparticle heating model presented here reveals the underlying plasma physics leading to crystallization. The model predicts that the nanoparticles reach temperatures as high as 900 K in the plasma as a result of heating reactions on the nanoparticle surface. These temperatures are well above the gas temperature and sufficient for complete nanoparticle crystallization. Moving the field of plasma nanoparticle synthesis to atmospheric pressures is important for lowering its cost and making the process attractive for industrial applications. The heating and charging model for silicon nanoparticles was adapted in Chapter 3 to study plasmas maintained over a wide range of pressures (10 -- 105 Pa). The model considers three collisionality regimes and determines the dominant contribution of each regime under various plasma conditions. Strong nanoparticle cooling at

  7. Crystal electric field splitting of R{sup 3+}-ions in pure and Co- and Cu-doped RNi{sub 2}B{sub 2}C (R=Ho, Er, Tm)

    Energy Technology Data Exchange (ETDEWEB)

    Gasser, U.; Allenspach, P.; Henggeler, W.; Zolliker, M.; Furrer, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    From the crystal-electric-field (CEF) splitting of the R{sup 3+}-ions, the CEF parameters of RNi{sub 2}B{sub 2}C (R=Ho, Er, Tm) were deduced. In order to get information about the influence of the variation of the density of states (DOS) at the Fermi level (E{sub F}), CEF spectroscopy measurements with Co- and Cu-doped ErNi{sub 2}B{sub 2}C-samples were performed. (author) 1 fig., 1 tab., 1 ref.

  8. Patterning nanocrystals using DNA

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Shara Carol

    2003-09-01

    One of the goals of nanotechnology is to enable programmed self-assembly of patterns made of various materials with nanometer-sized control. This dissertation describes the results of experiments templating arrangements of gold and semiconductor nanocrystals using 2'-deoxyribonucleic acid (DNA). Previously, simple DNA-templated linear arrangements of two and three nanocrystals structures have been made.[1] Here, we have sought to assemble larger and more complex nanostructures. Gold-DNA conjugates with 50 to 100 bases self-assembled into planned arrangements using strands of DNA containing complementary base sequences. We used two methods to increase the complexity of the arrangements: using branched synthetic doublers within the DNA covalent backbone to create discrete nanocrystal groupings, and incorporating the nanocrystals into a previously developed DNA lattice structure [2][3] that self-assembles from tiles made of DNA double-crossover molecules to create ordered nanoparticle arrays. In the first project, the introduction of a covalently-branched synthetic doubler reagent into the backbone of DNA strands created a branched DNA ''trimer.'' This DNA trimer templated various structures that contained groupings of three and four gold nanoparticles, giving promising, but inconclusive transmission electron microscopy (TEM) results. Due to the presence of a variety of possible structures in the reaction mixtures, and due to the difficulty of isolating the desired structures, the TEM and gel electrophoresis results for larger structures having four particles, and for structures containing both 5 and 10 nm gold nanoparticles were inconclusive. Better results may come from using optical detection methods, or from improved sample preparation. In the second project, we worked toward making two-dimensional ordered arrays of nanocrystals. We replicated and improved upon previous results for making DNA lattices, increasing the size of the lattices

  9. Surface modification of cellulose nanocrystals

    Science.gov (United States)

    Eyley, Samuel; Thielemans, Wim

    2014-06-01

    Chemical modification of cellulose nanocrystals is an increasingly popular topic in the literature. This review analyses the type of cellulose nanocrystal modification reactions that have been published in the literature thus far and looks at the steps that have been taken towards analysing the products of the nanocrystal modifications. The main categories of reactions carried out on cellulose nanocrystals are oxidations, esterifications, amidations, carbamations and etherifications. More recently nucleophilic substitutions have been used to introduce more complex functionality to cellulose nanocrystals. Multi-step modifications are also considered. This review emphasizes quantification of modification at the nanocrystal surface in terms of degree of substitution and the validity of conclusions drawn from different analysis techniques in this area. The mechanisms of the modification reactions are presented and considered with respect to the effect on the outcome of the reactions. While great strides have been made in the quality of analytical data published in the field of cellulose nanocrystal modification, there is still vast scope for improvement, both in data quality and the quality of analysis of data. Given the difficulty of surface analysis, cross-checking of results from different analysis techniques is fundamental for the development of reliable cellulose nanocrystal modification techniques.

  10. Nanocrystal/sol-gel nanocomposites

    Science.gov (United States)

    Petruska, Melissa A.; Klimov, Victor L.

    2007-06-05

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites.

  11. Doping of CdSe Nanocrystals

    Science.gov (United States)

    Jensen, John

    2003-10-01

    What happens to a nanocrystal when it is doped with electrons? We doped CdSe nanocrystals with potassium metal and sodium biphenyl, potassium and sodium acting as the charge carriers. In order to monitor the properties of the doped nanocrystals we used Electron Spin Resonance and luminescence techniques. In this poster we present findings and problems encountered in doping CdSe nanocrystals.

  12. Independent control of the shape and composition of ionic nanocrystals through sequential cation exchange reactions

    Energy Technology Data Exchange (ETDEWEB)

    Luther, Joseph Matthew; Zheng, Haimei; Sadtler, Bryce; Alivisatos, A. Paul

    2009-07-06

    Size- and shape-controlled nanocrystal growth is intensely researched for applications including electro-optic, catalytic, and medical devices. Chemical transformations such as cation exchange overcome the limitation of traditional colloidal synthesis, where the nanocrystal shape often reflects the inherent symmetry of the underlying lattice. Here we show that nanocrystals, with established synthetic protocols for high monodispersity, can be templates for independent composition control. Specifically, controlled interconversion between wurtzite CdS, chalcocite Cu2S, and rock salt PbS occurs while preserving the anisotropic dimensions unique to the as-synthesized materials. Sequential exchange reactions between the three sulfide compositions are driven by the disparate solubilites of the metal ion exchange pair in specific coordinating molecules. Starting with CdS, highly anisotropic PbS nanorods are created, which serve as an important material for studying strong 2-dimensional quantum confinement, as well as for optoelectronic applications. Furthermore, interesting nanoheterostructures of CdS|PbS are obtained by precise control over ion insertion and removal.

  13. Mechanical Properties of Nanocrystal Supercrystals

    Energy Technology Data Exchange (ETDEWEB)

    Tam, Enrico; Podsiadlo, Paul; Shevchenko, Elena; Ogletree, D. Frank; Delplancke-Ogletree, Marie-Paule; Ashby, Paul D.

    2009-12-30

    Colloidal nanocrystals attract significant interest due to their potential applications in electronic, magnetic, and optical devices. Nanocrystal supercrystals (NCSCs) are particularly appealing for their well ordered structure and homogeneity. The interactions between organic ligands that passivate the inorganic nanocrystal cores critically influence their self-organization into supercrystals, By investigating the mechanical properties of supercrystals, we can directly characterize the particle-particle interactions in a well-defined geometry, and gain insight into both the self-assembly process and the potential applications of nanocrystal supercrystals. Here we report nanoindentation studies of well ordered lead-sulfide (Pbs) nanocrystal supercrystals. Their modulus and hardness were found to be similar to soft polymers at 1.7 GPa and 70 MPa respectively and the fractures toughness was 39 KPa/m1/2, revealing the extremely brittle nature of these materials.

  14. Photoacoustic Study on a Photonic System CdS and Doped CdS

    Science.gov (United States)

    Sankar, N.; Ramachandran, K.; Sanjeeviraja, C.

    2002-12-01

    Using Photoacoustic spectroscopy thermal diffusion, thermal conductivity and energy band gap are studied on crystals of photonic system CdS and doped CdS grown by Physical Vapour transport. Optical band gap measured here agrees well with Photo current measurements. It is also found that the thermal diffusivity, effusivity, and optical band gap increases with increase of carrier concentration.

  15. Photodeposition of Pt on Colloidal CdS and CdSe/CdS Semiconductor Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Dukovic, Gordana; Merkle, Maxwell G.; Nelson, James H.; Hughes, Steven M.; Alivisatos, A. Paul

    2008-08-06

    colloidal CdS and CdSe/CdS core/shell nanocrystals. Among the II-VI semiconductors, CdS is of particular interest because it has the correct band alignment for water photolysis[2] and has been demonstrated to be photocatalytically active.[11-16] We have found that the photoexcitation of CdS and CdSe/CdS in the presence of an organometallic Pt precursor leads to deposition of Pt nanoparticles on the semiconductor surface. Stark differences are observed in the Pt nanoparticle location on the two substrates, and the photodeposition can be completely inhibited by the modification of the semiconductor surface. Our results suggest that tuning of the semiconductor band structure, spatial organization and surface chemistry should be crucial in the design of photocatalytic nanostructures.

  16. A comparative study on CdS: PEO and CdS: PMMA nanocomposite solid films

    Energy Technology Data Exchange (ETDEWEB)

    Padmaja, S. [Thin film centre, PSG College of Technology, Coimbatore (India); Jayakumar, S., E-mail: s_jayakumar_99@yahoo.com [Department of Physics, PSG Institute of Technology and Applied Research, Coimbatore (India); Balaji, R.; Vaideki, K. [Thin film centre, PSG College of Technology, Coimbatore (India)

    2016-08-15

    Cadmium Sulphide (CdS) nanoparticles were reinforced in Poly(ethylene Oxide) (PEO) and Poly(methyl methacrylate) (PMMA) matrices by in situ technique. The presence of CdS in PEO and PMMA matrix was confirmed using X-ray photoelectron spectroscopy (XPS). Fourier Transform Infrared spectroscopy (FTIR) analysis disclosed the co-ordination of CdS in the matrices. Thermal analysis of the nanocomposites was carried out using Differential Scanning calorimetric studies (DSC). The optical studies using UV–vis spectroscopy were carried out to find the band gap of the materials and the absorption onset. The CdS particle size in the matrices was found by Effective Mass Approximation (EMA) model using the band gap values and was confirmed by TEM studies. The surface trapped emissions of the nanocomposites were observed from the photoluminescence (PL) spectra. The distribution of CdS particles in the polymer matrices were presented by Atomic force microscopic studies (AFM).

  17. Silicon nanocrystal inks, films, and methods

    Energy Technology Data Exchange (ETDEWEB)

    Wheeler, Lance Michael; Kortshagen, Uwe Richard

    2015-09-01

    Silicon nanocrystal inks and films, and methods of making and using silicon nanocrystal inks and films, are disclosed herein. In certain embodiments the nanocrystal inks and films include halide-terminated (e.g., chloride-terminated) and/or halide and hydrogen-terminated nanocrystals of silicon or alloys thereof. Silicon nanocrystal inks and films can be used, for example, to prepare semiconductor devices.

  18. EPR identification of defects responsible for thermoluminescence in Cu-doped lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) crystals

    Energy Technology Data Exchange (ETDEWEB)

    Brant, A.T., E-mail: Adam.Brant.ctr@afit.edu [Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433 (United States); Buchanan, D.A.; McClory, J.W. [Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433 (United States); Dowben, P.A. [Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States); Adamiv, V.T.; Burak, Ya.V. [Institute of Physical Optics, 23 Dragomanov St., Lviv 79005 (Ukraine); Halliburton, L.E. [Department of Physics, West Virginia University, Morgantown, WV 26505 (United States)

    2013-07-15

    Electron paramagnetic resonance (EPR) is used to identify the electron and hole traps responsible for thermoluminescence (TL) peaks occurring near 100 and 200 °C in copper-doped lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) crystals. As-grown crystals have Cu{sup +} and Cu{sup 2+} ions substituting for lithium and have Cu{sup +} ions at interstitial sites. All of the substitutional Cu{sup 2+} ions in the as-grown crystals have an adjacent lithium vacancy and give rise to a distinct EPR spectrum. Exposure to ionizing radiation at room temperature produces a second and different Cu{sup 2+} EPR spectrum when a hole is trapped by substitutional Cu{sup +} ions that have no nearby defects. These two Cu{sup 2+} trapped-hole centers are referred to as Cu{sup 2+}-V{sub Li} and Cu{sub active}{sup 2+}, respectively. Also during the irradiation, two trapped-electron centers in the form of interstitial Cu{sup 0} atoms are produced when interstitial Cu{sup +} ions trap electrons. They are observed with EPR and are labeled Cu{sub A}{sup 0} and Cu{sub B}{sup 0}. When an irradiated crystal is warmed from 25 to 150 °C, the Cu{sub active}{sup 2+} centers have a partial decay step that correlates with the TL peak near 100 °C. The concentrations of Cu{sub A}{sup 0} and Cu{sub B}{sup 0} centers, however, increase as the crystal is heated through this range. As the crystal is further warmed between 150 and 250 °C, the EPR signals from the Cu{sub active}{sup 2+} hole centers and Cu{sub A}{sup 0} and Cu{sub B}{sup 0} electron centers decay simultaneously. This decay step correlates with the intense TL peak near 200 °C. -- Highlights: ► We use EPR to identify a Cu{sup 2+} center and two Cu{sup 0} defects in Cu-doped Li{sub 2}B{sub 4}O{sub 7}. ► These defects form when our crystal is irradiated with X-rays at room temperature. ► We also observe two above-room-temperature thermoluminescence (TL) peaks. ► A pulsed anneal experiment correlates the decay of the EPR signals to two

  19. Biomolecular Assembly of Gold Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Micheel, Christine Marya [Univ. of California, Berkeley, CA (United States)

    2005-05-20

    Over the past ten years, methods have been developed to construct discrete nanostructures using nanocrystals and biomolecules. While these frequently consist of gold nanocrystals and DNA, semiconductor nanocrystals as well as antibodies and enzymes have also been used. One example of discrete nanostructures is dimers of gold nanocrystals linked together with complementary DNA. This type of nanostructure is also known as a nanocrystal molecule. Discrete nanostructures of this kind have a number of potential applications, from highly parallel self-assembly of electronics components and rapid read-out of DNA computations to biological imaging and a variety of bioassays. My research focused in three main areas. The first area, the refinement of electrophoresis as a purification and characterization method, included application of agarose gel electrophoresis to the purification of discrete gold nanocrystal/DNA conjugates and nanocrystal molecules, as well as development of a more detailed understanding of the hydrodynamic behavior of these materials in gels. The second area, the development of methods for quantitative analysis of transmission electron microscope data, used computer programs written to find pair correlations as well as higher order correlations. With these programs, it is possible to reliably locate and measure nanocrystal molecules in TEM images. The final area of research explored the use of DNA ligase in the formation of nanocrystal molecules. Synthesis of dimers of gold particles linked with a single strand of DNA possible through the use of DNA ligase opens the possibility for amplification of nanostructures in a manner similar to polymerase chain reaction. These three areas are discussed in the context of the work in the Alivisatos group, as well as the field as a whole.

  20. Silicon nanocrystals as handy biomarkers

    Science.gov (United States)

    Fujioka, Kouki; Hoshino, Akiyoshi; Manabe, Noriyoshi; Futamura, Yasuhiro; Tilley, Richard; Yamamoto, Kenji

    2007-02-01

    Quantum dots (QDs) have brighter and longer fluorescence than organic dyes. Therefore, QDs can be applied to biotechnology, and have capability to be applied to medical technology. Currently, among the several types of QDs, CdSe with a ZnS shell is one of the most popular QDs to be used in biological experiments. However, when the CdSe QDs were applied to clinical technology, potential toxicological problems due to CdSe core should be considered. To eliminate the problem, silicon nanocrystals, which have the potential of biocompatibility, could be a candidate of alternate probes. Silicon nanocrystals have been synthesized using several techniques such as aerosol, electrochemical etching, laser pyrolysis, plasma deposition, and colloids. Recently, the silicon nanocrystals were reported to be synthesized in inverse micelles and also stabilized with 1-heptene or allylamine capping. Blue fluorescence of the nanocrystals was observed when excited with a UV light. The nanocrystals covered with 1-heptene are hydrophobic, whereas the ones covered with allylamine are hydrophilic. To test the stability in cytosol, the water-soluble nanocrystals covered with allylamine were examined with a Hela cell incorporation experiment. Bright blue fluorescence of the nanocrystals was detected in the cytosol when excited with a UV light, implying that the nanocrystals were able to be applied to biological imaging. In order to expand the application range, we synthesized and compared a series of silicon nanocrystals, which have variable surface modification, such as alkyl group, alcohol group, and odorant molecules. This study will provide a wider range of optoelectronic applications and bioimaging technology.

  1. Doped semiconductor nanocrystal junctions

    Energy Technology Data Exchange (ETDEWEB)

    Borowik, Ł.; Mélin, T., E-mail: thierry.melin@isen.iemn.univ-lille1.fr [Institut d’Electronique, de Microélectronique et de Nanotechnologie, CNRS-UMR8520, Avenue Poincaré, F-59652 Villeneuve d’Ascq (France); Nguyen-Tran, T.; Roca i Cabarrocas, P. [Laboratoire de Physique des Interfaces et des Couches Minces, CNRS-UMR7647, Ecole Polytechnique, F-91128 Palaiseau (France)

    2013-11-28

    Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (N{sub D}≈10{sup 20}−10{sup 21}cm{sup −3}) silicon nanocrystals (NCs) in the 2–50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple phenomenological law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as N{sub D}{sup −1/3}, and depleted charge linearly increasing with the NC diameter and varying as N{sub D}{sup 1/3}. We thus establish a “nanocrystal counterpart” of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.

  2. Photoresponsive Cellulose Nanocrystals

    Directory of Open Access Journals (Sweden)

    Dimitris S Argyropoulos

    2011-07-01

    Full Text Available In this communication a method for the creation of fluorescent cellulose nanoparticles using click chemistry and subsequent photodimerization of the installed side‐ chains is demonstrated. In the first step, the primary hydroxyl groups on the surface of the CNCs were converted to carboxylic acids by using TEMPO‐mediated hypohalite oxidation. The alkyne groups, essential for the click reaction, were introduced into the surface of TEMPO‐ oxidized CNCs via carbodiimide‐mediated formation of an amide linkage between monomers carrying an amine functionality and carboxylic acid groups on the surface of the TEMPO‐oxidized CNCs. Finally, the reaction of surface‐modified TEMPO‐oxidized cellulose nanocrystals and azido‐bearing coumarin and anthracene monomers were carried out by means of a click chemistry, i.e., Copper(I‐catalyzed Azide‐Alkyne Cycloaddition (CuAAC to produce highly photo‐responsive and fluorescent cellulose nanoparticles. Most significantly, the installed coumarin and/or anthracene side‐chains were shown to undergo UV‐induced [2+2] and [4+4] cycloaddition reactions, bringing and locking the cellulose nanocrystals together. This effort paves the way towards creating, cellulosic photo responsive nano‐arrays with the potential of photo reversibility since these reactions are known to be reversible at varying wavelengths.

  3. Understanding and Controlling the Growth of Monodisperse CdS Nanowires in Solution

    DEFF Research Database (Denmark)

    Xi, Lifei; Tan, Winnie Xiu Wen; Boothroyd, Chris;

    2008-01-01

    diffusion rate of the precursor and hence low reactivity. Therefore, ODPA is good for generating nearly monodisperse and high aspect ratio US nanowires. Our nanowires have a high degree of dispersibility and thus can be easily processed for potential applications as solar cells and transistors. Finally......Cadmium sulfide (CdS) nanowires with a monodisperse diameter of 3.5 nm and length of about 600 nm were successfully synthesized using a simple and reproducible hot coordination solvents method. Structural characterization showed that the one-dimensional nanowires grow along the [001] direction......, we propose that the ODPA-to-Cd mole ratio is the key factor affecting the morphology of the nanowires because it affects both the cleavage rate of the P=S double bond and the nucleation/growth rate of the anisotropic nanocrystals. In addition, it was found that Cd-ODPA complexes give rise to a low...

  4. Cellulose nanocrystal submonolayers by spin coating.

    Science.gov (United States)

    Kontturi, Eero; Johansson, Leena-Sisko; Kontturi, Katri S; Ahonen, Päivi; Thüne, Peter C; Laine, Janne

    2007-09-11

    Dilute concentrations of cellulose nanocrystal solutions were spin coated onto different substrates to investigate the effect of the substrate on the nanocrystal submonolayers. Three substrates were probed: silica, titania, and amorphous cellulose. According to atomic force microscopy (AFM) images, anionic cellulose nanocrystals formed small aggregates on the anionic silica substrate, whereas a uniform two-dimensional distribution of nanocrystals was achieved on the cationic titania substrate. The uniform distribution of cellulose nanocrystal submonolayers on titania is an important factor when dimensional analysis of the nanocrystals is desired. Furthermore, the amount of nanocrystals deposited on titania was multifold in comparison to the amounts on silica, as revealed by AFM image analysis and X-ray photoelectron spectroscopy. Amorphous cellulose, the third substrate, resulted in a somewhat homogeneous distribution of the nanocrystal submonolayers, but the amounts were as low as those on the silica substrate. These differences in the cellulose nanocrystal deposition were attributed to electrostatic effects: anionic cellulose nanocrystals are adsorbed on cationic titania in addition to the normal spin coating deposition. The anionic silica surface, on the other hand, causes aggregation of the weakly anionic cellulose nanocrystals which are forced on the repulsive substrate by spin coating. The electrostatically driven adsorption also influences the film thickness of continuous ultrathin films of cellulose nanocrystals. The thicker films of charged nanocrystals on a substrate of opposite charge means that the film thickness is not independent of the substrate when spin coating cellulose nanocrystals in the ultrathin regime (<100 nm).

  5. Unique Challenges Accompany Thick-Shell CdSe/nCdS (n > 10) Nanocrystal Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Y; Marchuk, K; Abraham, R; Sampat, S; Abraham, R.; Fang, N; Malko, AV; Vela, J

    2011-12-23

    Thick-shell CdSe/nCdS (n {ge} 10) nanocrystals were recently reported that show remarkably suppressed fluorescence intermittency or 'blinking' at the single-particle level as well as slow rates of Auger decay. Unfortunately, whereas CdSe/nCdS nanocrystal synthesis is well-developed up to n {le} 6 CdS monolayers (MLs), reproducible syntheses for n {ge} 10 MLs are less understood. Known procedures sometimes result in homogeneous CdS nucleation instead of heterogeneous, epitaxial CdS nucleation on CdSe, leading to broad and multimodal particle size distributions. Critically, obtained core/shell sizes are often below those desired. This article describes synthetic conditions specific to thick-shell growth (n {ge} 10 and n {ge} 20 MLs) on both small (sub2 nm) and large (>4.5 nm) CdSe cores. We find added secondary amine and low concentration of CdSe cores and molecular precursors give desired core/shell sizes. Amine-induced, partial etching of CdSe cores results in apparent shell-thicknesses slightly beyond those desired, especially for very-thick shells (n {ge} 20 MLs). Thermal ripening and fast precursor injection lead to undesired homogeneous CdS nucleation and incomplete shell growth. Core/shells derived from small CdSe (1.9 nm) have longer PL lifetimes and more pronounced blinking at single-particle level compared with those derived from large CdSe (4.7 nm). We expect our new synthetic approach will lead to a larger throughput of these materials, increasing their availability for fundamental studies and applications.

  6. Improving the catalytic activity of semiconductor nanocrystals through selective domain etching.

    Science.gov (United States)

    Khon, Elena; Lambright, Kelly; Khnayzer, Rony S; Moroz, Pavel; Perera, Dimuthu; Butaeva, Evgeniia; Lambright, Scott; Castellano, Felix N; Zamkov, Mikhail

    2013-05-01

    Colloidal chemistry offers an assortment of synthetic tools for tuning the shape of semiconductor nanocrystals. While many nanocrystal architectures can be obtained directly via colloidal growth, other nanoparticle morphologies require alternative processing strategies. Here, we show that chemical etching of colloidal nanoparticles can facilitate the realization of nanocrystal shapes that are topologically inaccessible by hot-injection techniques alone. The present methodology is demonstrated by synthesizing a two-component CdSe/CdS nanoparticle dimer, constructed in a way that both CdSe and CdS semiconductor domains are exposed to the external environment. This structural morphology is highly desirable for catalytic applications as it enables both reductive and oxidative reactions to occur simultaneously on dissimilar nanoparticle surfaces. Hydrogen production tests confirmed the improved catalytic activity of CdSe/CdS dimers, which was enhanced 3-4 times upon etching treatment. We expect that the demonstrated application of etching to shaping of colloidal heteronanocrystals can become a common methodology in the synthesis of charge-separating nanocrystals, leading to advanced nanoparticles architectures for applications in areas of photocatalysis, photovoltaics, and light detection.

  7. Nonclassical radiation from diamond nanocrystals

    CERN Document Server

    Beveratos, A; Gacoin, T; Poizat, J P; Grangier, P; Beveratos, Alexios; Brouri, Rosa; Gacoin, Thierry; Poizat, Jean-Philippe; Grangier, Philippe

    2001-01-01

    The quantum properties of the fluorescence light emitted by diamond nanocrystals containing a single nitrogen-vacancy (NV) colored center is investigated. We have observed photon antibunching with very low background light. This system is therefore a very good candidate for the production of single photon on demand. In addition, we have measured larger NV center lifetime in nanocrystals than in the bulk, in good agreement with a simple quantum electrodynamical model.

  8. Theoretical investigation of magnetic and optical properties of semiconductor nanocrystals

    Science.gov (United States)

    Proshchenko, Vitaly

    This thesis presents the theoretical investigation of physical properties of pure and transition metal doped semiconductor nanostructures. First we study optical and energy (the density of states) spectra for Cd mSem clusters of various sizes and shapes, such as spheres, cubes, nanorods, and nanotubes. This work requires a careful computational analysis where a proper exchange-correlation functional has to be chosen to fit the experimental data. The next part of the thesis deals with the magnetic properties of manganese doped CdSe, ZnSe, ZnS, and CdS quantum dots (QDs). We theoretically explain the effect of dual luminescence and show that in the case with CdSe quantum dots the luminescence becomes tunable by a QD size. We also study the concentration dependence of magnetic order and optical transitions in Mn doped CdSe nanocrystals. Room temperature d0 ferromagnetism is studied in ZnS quantum dots and nanowires in Chapter 4. To find the magnetization of the medium and large size nanocrystals we introduce the surface-bulk (SB) model. We show that the condensation of Zn vacancies into a single droplet takes place which leads to the week d0 ferromagnetism in ZnS nanocrystals. In the last Chapter we study electronic, optical, and charge transport properties of two new holey 2D materials, ELH-g-C2N-H and ELH-g-C2N-Br with hydrogen and bromine side-groups, respectively. Since the two 2D crystals under study have not been synthesized yet, we provide the stability analysis and prove that the calculated crystal structures correspond to the global energy minimum criterion.

  9. Mutual excitation in Eurozone sovereign CDS

    NARCIS (Netherlands)

    Aït-Sahalia, Y.; Laeven, R.J.A.; Pelizzon, L.

    2014-01-01

    We study self- and cross-excitation of shocks in the Eurozone sovereign CDS market. We adopt a multivariate setting with credit default intensities driven by mutually exciting jump processes, to capture the salient features observed in the data, in particular, the clustering of high default probabil

  10. Semiconductor nanocrystal-based phagokinetic tracking

    Science.gov (United States)

    Alivisatos, A Paul; Larabell, Carolyn A; Parak, Wolfgang J; Le Gros, Mark; Boudreau, Rosanne

    2014-11-18

    Methods for determining metabolic properties of living cells through the uptake of semiconductor nanocrystals by cells. Generally the methods require a layer of neutral or hydrophilic semiconductor nanocrystals and a layer of cells seeded onto a culture surface and changes in the layer of semiconductor nanocrystals are detected. The observed changes made to the layer of semiconductor nanocrystals can be correlated to such metabolic properties as metastatic potential, cell motility or migration.

  11. Spectroscopic studies on photoelectron transfer from 2-(furan-2-yl)-1-phenyl-1H-phenanthro[9,10-d]imidazole to ZnO, Cu-doped ZnO and Ag-doped ZnO.

    Science.gov (United States)

    Thanikachalam, V; Arunpandiyan, A; Jayabharathi, J; Karunakaran, C; Ramanathan, P

    2014-09-01

    The 2-(furan-2-yl)-1-phenyl-1H-phenanthro[9,10-d]imidazole [FPI] has been designed and synthesized as fluorescent sensor for nanoparticulate ZnO. The present work investigates the photoelectron transfer (PET) from FPI to ZnO, Cu-doped ZnO and Ag- doped ZnO nanoparticles using electronic and life time spectral measurements. Broad absorption along with red shift indicates the formation of charge-transfer complex [FPI-Nanoparticles]. The photophysical studies indicate lowering of HOMO and LUMO energy levels of FPI on adsorption on ZnO due to FPI- ZnO interaction. The obtained binding constant implies that the binding of FPI with nanoparticles was influenced by the surface modification of ZnO nanoparticles with Cu and Ag.

  12. Harvesting Solar Energy by Means of Charge-Separating Nanocrystals and Their Solids

    Science.gov (United States)

    Diederich, Geoffrey; O'Connor, Timothy; Moroz, Pavel; Kinder, Erich; Kohn, Elena; Perera, Dimuthu; Lorek, Ryan; Lambright, Scott; Imboden, Martene; Zamkov, Mikhail

    2012-01-01

    Conjoining different semiconductor materials in a single nano-composite provides synthetic means for the development of novel optoelectronic materials offering a superior control over the spatial distribution of charge carriers across material interfaces. As this study demonstrates, a combination of donor-acceptor nanocrystal (NC) domains in a single nanoparticle can lead to the realization of efficient photocatalytic1-5 materials, while a layered assembly of donor- and acceptor-like nanocrystals films gives rise to photovoltaic materials. Initially the paper focuses on the synthesis of composite inorganic nanocrystals, comprising linearly stacked ZnSe, CdS, and Pt domains, which jointly promote photoinduced charge separation. These structures are used in aqueous solutions for the photocatalysis of water under solar radiation, resulting in the production of H2 gas. To enhance the photoinduced separation of charges, a nanorod morphology with a linear gradient originating from an intrinsic electric field is used5. The inter-domain energetics are then optimized to drive photogenerated electrons toward the Pt catalytic site while expelling the holes to the surface of ZnSe domains for sacrificial regeneration (via methanol). Here we show that the only efficient way to produce hydrogen is to use electron-donating ligands to passivate the surface states by tuning the energy level alignment at the semiconductor-ligand interface. Stable and efficient reduction of water is allowed by these ligands due to the fact that they fill vacancies in the valence band of the semiconductor domain, preventing energetic holes from degrading it. Specifically, we show that the energy of the hole is transferred to the ligand moiety, leaving the semiconductor domain functional. This enables us to return the entire nanocrystal-ligand system to a functional state, when the ligands are degraded, by simply adding fresh ligands to the system4. To promote a photovoltaic charge separation, we use a

  13. Harvesting solar energy by means of charge-separating nanocrystals and their solids.

    Science.gov (United States)

    Diederich, Geoffrey; O'Connor, Timothy; Moroz, Pavel; Kinder, Erich; Kohn, Elena; Perera, Dimuthu; Lorek, Ryan; Lambright, Scott; Imboden, Martene; Zamkov, Mikhail

    2012-08-23

    Conjoining different semiconductor materials in a single nano-composite provides synthetic means for the development of novel optoelectronic materials offering a superior control over the spatial distribution of charge carriers across material interfaces. As this study demonstrates, a combination of donor-acceptor nanocrystal (NC) domains in a single nanoparticle can lead to the realization of efficient photocatalytic materials, while a layered assembly of donor- and acceptor-like nanocrystals films gives rise to photovoltaic materials. Initially the paper focuses on the synthesis of composite inorganic nanocrystals, comprising linearly stacked ZnSe, CdS, and Pt domains, which jointly promote photoinduced charge separation. These structures are used in aqueous solutions for the photocatalysis of water under solar radiation, resulting in the production of H2 gas. To enhance the photoinduced separation of charges, a nanorod morphology with a linear gradient originating from an intrinsic electric field is used. The inter-domain energetics are then optimized to drive photogenerated electrons toward the Pt catalytic site while expelling the holes to the surface of ZnSe domains for sacrificial regeneration (via methanol). Here we show that the only efficient way to produce hydrogen is to use electron-donating ligands to passivate the surface states by tuning the energy level alignment at the semiconductor-ligand interface. Stable and efficient reduction of water is allowed by these ligands due to the fact that they fill vacancies in the valence band of the semiconductor domain, preventing energetic holes from degrading it. Specifically, we show that the energy of the hole is transferred to the ligand moiety, leaving the semiconductor domain functional. This enables us to return the entire nanocrystal-ligand system to a functional state, when the ligands are degraded, by simply adding fresh ligands to the system. To promote a photovoltaic charge separation, we use a

  14. Cu掺杂ZnO纳米粒子的光学性能及铁磁性%Ferromagnetic and Optical Properties of Cu-doped ZnO Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    邢伯阳; 牛世峰

    2012-01-01

    Cu doped ZnO nanoparticles were prepared by the sol-gel method in order to study the origin of room temperature ferromagnetism and optical properties of ZnO-based diluted magnetic semiconductors. X- ray diffractometry (XRD) shows that Zna-xCu+O samples are single phase with ZnO-like wurtzite structure. Znl-CuxO was ferromagnetic at room temperature, which ,attributed to the exchange interaction between the defects of zinc oxide and the doped Cu ions. All the samples show two distinct emissions, a sharp peak in the UV region and a broad deep level peak in the visible light regiom Cu doping into the ZnO lattice can effectively enhance the visible emission. Therefore, Znl-CuO system'may be a potential candidate in splntronics and photocatalytic.%利用溶胶凝胶法制备了纳米结构的Cu掺杂ZnO基稀磁半导体,通过X射线衍射分析表明,样品为纯相ZnO纤锌矿结构,磁性测量表明样品在室温下呈室温铁磁性,铁磁性来源为氧化锌晶格中的缺陷与Cu2+离子之间的交换作用。室温光致发光(PL)谱观察到紫外带边和可见光区两个发射峰,且随着Cu掺杂量增加,紫外峰淬灭,可见峰发射增强。

  15. Cu-doping effect on dielectric properties of organic gel synthesized Ba{sub 4}YMn{sub 3−x}Cu{sub x}O{sub 11.5±δ}

    Energy Technology Data Exchange (ETDEWEB)

    Barbier, Tristan, E-mail: tristan.barbier@gmail.com [Université François Rabelais de Tours, CNRS, CEA, ENIVL, GREMAN UMR 7347, 37200 Tours (France); Autret-Lambert, Cécile [Université François Rabelais de Tours, CNRS, CEA, ENIVL, GREMAN UMR 7347, 37200 Tours (France); Andreazza, Pascal [Centre de Recherche sur la matière divisée (CRMD), Université d' Orléans, CNRS, FRE3520, 1B rue de la Férollerie, 45071 Orléans (France); Ruyter, Antoine; Honstettre, Christophe [Université François Rabelais de Tours, CNRS, CEA, ENIVL, GREMAN UMR 7347, 37200 Tours (France); Lambert, Sébastien [CEA—DAM, Le Ripault, 37260 Monts (France); Gervais, François; Lethiecq, Marc [Université François Rabelais de Tours, CNRS, CEA, ENIVL, GREMAN UMR 7347, 37200 Tours (France)

    2013-10-15

    Copper doped-Ba{sub 4}YMn{sub 3−x}Cu{sub x}O{sub 11.5±δ} samples were synthesized by an organic gel assisted citrate process. X-ray diffraction of compositions with x=0.002, 0.005, 0.01, 0.02 and 0.04 does not reveal any change of hexagonal perovskite structure on doping. The effects of Cu-doping on the microstructure and dielectric properties were investigated. Cu doping modifies the electrical properties at the level of the impedance characteristics of both grain and grain boundary and to understand these different behaviours, we have carried out high-resolution transmission electron microscopy analysis. Among the Ba{sub 4}YMn{sub 3−x}Cu{sub x}O{sub 11.5±δ} specimens studied, the composition x=0.002 shows a permittivity (ε′{sub r}) higher than the undoped compound and a lower loss tangent (tanδ) over several orders of magnitude of frequency. - Graphical abstract: Highlighting of many stacking faults (intergrowths) in substituted compounds with x>0.01 (right picture), which could explain the different dielectric properties observed in these compounds. However compounds with x>0.01 remain with a better stacking sequence as we can see on the left picture. Display Omitted - Highlights: • High permittivity of the Ba{sub 4}YMn{sub 3−x}Cu{sub x}O{sub 11.5±δ}. • Substitution leads to a mixed oxidation state for manganese: Mn{sup 4+}/Mn{sup 3+}. • Creation of oxygen vacancies which are responsible for stacking faults. • Highlighting relationship between Cu substitution and dielectric properties.

  16. Nanocrystal assembly for tandem catalysis

    Science.gov (United States)

    Yang, Peidong; Somorjai, Gabor; Yamada, Yusuke; Tsung, Chia-Kuang; Huang, Wenyu

    2014-10-14

    The present invention provides a nanocrystal tandem catalyst comprising at least two metal-metal oxide interfaces for the catalysis of sequential reactions. One embodiment utilizes a nanocrystal bilayer structure formed by assembling sub-10 nm platinum and cerium oxide nanocube monolayers on a silica substrate. The two distinct metal-metal oxide interfaces, CeO.sub.2--Pt and Pt--SiO.sub.2, can be used to catalyze two distinct sequential reactions. The CeO.sub.2--Pt interface catalyzed methanol decomposition to produce CO and H.sub.2, which were then subsequently used for ethylene hydroformylation catalyzed by the nearby Pt--SiO.sub.2 interface. Consequently, propanal was selectively produced on this nanocrystal bilayer tandem catalyst.

  17. Nanocrystals for luminescent solar concentrators.

    Science.gov (United States)

    Bradshaw, Liam R; Knowles, Kathryn E; McDowall, Stephen; Gamelin, Daniel R

    2015-02-11

    Luminescent solar concentrators (LSCs) harvest sunlight over large areas and concentrate this energy onto photovoltaics or for other uses by transporting photons through macroscopic waveguides. Although attractive for lowering solar energy costs, LSCs remain severely limited by luminophore reabsorption losses. Here, we report a quantitative comparison of four types of nanocrystal (NC) phosphors recently proposed to minimize reabsorption in large-scale LSCs: two nanocrystal heterostructures and two doped nanocrystals. Experimental and numerical analyses both show that even the small core absorption of the leading NC heterostructures causes major reabsorption losses at relatively short transport lengths. Doped NCs outperform the heterostructures substantially in this critical property. A new LSC phosphor is introduced, nanocrystalline Cd(1-x)Cu(x)Se, that outperforms all other leading NCs by a significant margin in both small- and large-scale LSCs under full-spectrum conditions.

  18. Injected nanocrystals for targeted drug delivery

    Directory of Open Access Journals (Sweden)

    Yi Lu

    2016-03-01

    Full Text Available Nanocrystals are pure drug crystals with sizes in the nanometer range. Due to the advantages of high drug loading, platform stability, and ease of scaling-up, nanocrystals have been widely used to deliver poorly water-soluble drugs. Nanocrystals in the blood stream can be recognized and sequestered as exogenous materials by mononuclear phagocytic system (MPS cells, leading to passive accumulation in MPS-rich organs, such as liver, spleen and lung. Particle size, morphology and surface modification affect the biodistribution of nanocrystals. Ligand conjugation and stimuli-responsive polymers can also be used to target nanocrystals to specific pathogenic sites. In this review, the progress on injected nanocrystals for targeted drug delivery is discussed following a brief introduction to nanocrystal preparation methods, i.e., top-down and bottom-up technologies.

  19. TOPICAL REVIEW: Biological applications of colloidal nanocrystals

    Science.gov (United States)

    Parak, Wolfgang J.; Gerion, Daniele; Pellegrino, Teresa; Zanchet, Daniela; Micheel, Christine; Williams, Shara C.; Boudreau, Rosanne; LeGros, Mark A.; Larabell, Carolyn A.; Alivisatos, A. Paul

    2003-07-01

    Due to their interesting properties, research on colloidal nanocrystals has moved in the last few years from fundamental research to first applications in materials science and life sciences. In this review some recent biological applications of colloidal nanocrystals are discussed, without going into biological or chemical details. First, the properties of colloidal nanocrystals and how they can be synthesized are described. Second, the conjugation of nanocrystals with biological molecules is discussed. And third, three different biological applications are introduced: (i) the arrangement of nanocrystal-oligonucleotide conjugates using molecular scaffolds such as single-stranded DNA, (ii) the use of nanocrystal-protein conjugates as fluorescent probes for cellular imaging, and (iii) a motility assay based on the uptake of nanocrystals by living cells.

  20. Semiconductor Nanocrystals for Biological Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Aihua; Gu, Weiwei; Larabell, Carolyn; Alivisatos, A. Paul

    2005-06-28

    Conventional organic fluorophores suffer from poor photo stability, narrow absorption spectra and broad emission feature. Semiconductor nanocrystals, on the other hand, are highly photo-stable with broad absorption spectra and narrow size-tunable emission spectra. Recent advances in the synthesis of these materials have resulted in bright, sensitive, extremely photo-stable and biocompatible semiconductor fluorophores. Commercial availability facilitates their application in a variety of unprecedented biological experiments, including multiplexed cellular imaging, long-term in vitro and in vivo labeling, deep tissue structure mapping and single particle investigation of dynamic cellular processes. Semiconductor nanocrystals are one of the first examples of nanotechnology enabling a new class of biomedical applications.

  1. Visible-light driven photoelectrochemical immunosensor for insulin detection based on MWCNTs@SnS2@CdS nanocomposites.

    Science.gov (United States)

    Liu, Yixin; Zhang, Yifeng; Wu, Dan; Fan, Dawei; Pang, Xuehui; Zhang, Yong; Ma, Hongmin; Sun, Xu; Wei, Qin

    2016-12-15

    In this work, a label-free photoelectrochemical (PEC) immunosensor was developed for ultrasensitive detection of insulin based on MWCNTs@SnS2@CdS nanocomposites. As graphene-like 2D nanomaterial, SnS2 nanosheets loaded on the conducting framework of multi-walled carbon nanotubes (MWCNTs) were adopted for the construction of immunosensor for the first time, providing a favorable substrate for in-situ growth of CdS nanocrystal that had suitable band structure matching well with SnS2. The well-matched band structure of these two metal sulfides effectively inhibited the recombination of photogenerated electron-hole pairs, thus improving the photo-to-current conversion efficiency. Besides, the introduction of MWCNTs facilitated electron transfer across the surface of electrodes, leading to a further increment of photocurrent. The as constructed label-free PEC immunosensor based on MWCNTs@SnS2@CdS nanocomposites exhibited excellent PEC performance for the detection of insulin. The concentrations of insulin could be directly detected based on the decrement of photocurrent that was brought by the increased steric hindrances due to the formation of antigen-antibody immunocomplexes. Under the optimal conditions, the PEC immunosensor had a sensitive response to insulin in a linear range of 0.1pgmL(-1) to 5ngmL(-1) with a detection limit of 0.03pgmL(-1). Meanwhile, good stability and selectivity were achieved as well. The design and fabrication of this PEC immunosensor based on MWCNTs@SnS2@CdS nanocomposites not only provided an ideal platform for the detection of insulin, but also opened up a new avenue for the development of immunosensor for some other biomarkers analysis.

  2. A digital CDS technique and the performance testing

    CERN Document Server

    Liu, Xiao-Yan; Yang, Yan-Ji; Lu, Bo; Wang, Yu-Sa; Xu, Yu-Peng; Cui, Wei-Wei; Li, Wei; Li, Mao-Shun; Wang, Juan; Han, Da-Wei; Chen, Tian-Xiang; Huo, Jia; Hu, Wei; Zhang, Yi; Zhu, Yue; Zhang, Zi-Liang; Yin, Guo-He; Wang, Yu; Zhao, Zhong-Yi; Fu, Yan-Hong; Zhang, Ya; Ma, Ke-Yan; Chen, Yong

    2014-01-01

    Readout noise is a critical parameter for characterizing the performance of charge-coupled devices (CCDs), which can be greatly reduced by the correlated double sampling (CDS) circuit. However, conventional CDS circuit inevitably introduces new noises since it consists of several active analog components such as operational amplifiers. This paper proposes a digital CDS circuit technique, which transforms the pre-amplified CCD signal into a train of digital presentations by a high-speed data acquisition card directly without the noisy CDS circuit first, then implement the digital CDS algorithm through numerical method. The readout noise of 3.3 e$^{-}$ and the energy resolution of 121 eV@5.9keV can be achieved via the digital CDS technique.

  3. The genomic CDS sandbox: An assessment among domain experts.

    Science.gov (United States)

    Aziz, Ayesha; Kawamoto, Kensaku; Eilbeck, Karen; Williams, Marc S; Freimuth, Robert R; Hoffman, Mark A; Rasmussen, Luke V; Overby, Casey L; Shirts, Brian H; Hoffman, James M; Welch, Brandon M

    2016-04-01

    Genomics is a promising tool that is becoming more widely available to improve the care and treatment of individuals. While there is much assertion, genomics will most certainly require the use of clinical decision support (CDS) to be fully realized in the routine clinical setting. The National Human Genome Research Institute (NHGRI) of the National Institutes of Health recently convened an in-person, multi-day meeting on this topic. It was widely recognized that there is a need to promote the innovation and development of resources for genomic CDS such as a CDS sandbox. The purpose of this study was to evaluate a proposed approach for such a genomic CDS sandbox among domain experts and potential users. Survey results indicate a significant interest and desire for a genomic CDS sandbox environment among domain experts. These results will be used to guide the development of a genomic CDS sandbox.

  4. Surface oxidation and water desorption of CdS

    Institute of Scientific and Technical Information of China (English)

    陈正石; 李庆霖; 金振声

    1996-01-01

    The surface oxidation and HP desorption of powder CdS were studied by means of X-ray photoetectron spectroscopy (XPS), quadrupole mass spectrometry (QMS) and in-situ FTIR. The results show that with the changes of surface composition and the elongation of store time of CdS there are four types of H2O thermally desorbed at different temperatures. It has also been found that through high-temperature air treatment for a short time the oxidized surface layer of CdS can prevent O2 and H2O in air from further attacking the inner CdS molecules.

  5. Formation and Characterization of CdS Hollow Structures

    Institute of Scientific and Technical Information of China (English)

    HU Peng; YU Haihu; DENG Jinyang; JIANG Desheng

    2008-01-01

    CdS hollow structures were built up by using the one pot method and using carbon disulfide (CS2) and ethylenediamine as starting materials. CS2 is insoluble in water and could form metastable oil droplets in the water at a moderate temperature. The oil droplets formed chains in the circumvolving water. CdS crystals grew and mineralized on the surfaces of the CS2 droplet chains, forming CdS shells around the unreacted CS2 cores. After the surrounding temperature was raised above the boiling point of CS2, the unreacted CS2 cores vaporized, leaving the CdS shelled hollow structures. The CdS hollow structures were characterized by using a transmission electron microscope, an X-ray diffractometer, a UV-Visible spectrophotometer and a fluorescence spectrophotometer. The CdS hollow structures were mainly tubes with closed ends. The exterior diameter and the interior diameter of tubes were about 50nm and about 15nm, respectively. Compared with the absorption onset wavelength of the bulk CdS, the CdS hollow structures exhibited a blue shift of about 57nm. While excited at 213nm. the CdS hollow structures emitted greenish blue light centered at 470nm.

  6. "Nanocrystal bilayer for tandem catalysis"

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Yusuke; Tsung, Chia Kuang; Huang, Wenyu; Huo, Ziyang; E.Habas, Susan E; Soejima, Tetsuro; Aliaga, Cesar E; Samorjai, Gabor A; Yang, Peidong

    2011-01-24

    Supported catalysts are widely used in industry and can be optimized by tuning the composition and interface of the metal nanoparticles and oxide supports. Rational design of metal-metal oxide interfaces in nanostructured catalysts is critical to achieve better reaction activities and selectivities. We introduce here a new class of nanocrystal tandem catalysts that have multiple metal-metal oxide interfaces for the catalysis of sequential reactions. We utilized a nanocrystal bilayer structure formed by assembling platinum and cerium oxide nanocube monolayers of less than 10 nm on a silica substrate. The two distinct metal-metal oxide interfaces, CeO2-Pt and Pt-SiO2, can be used to catalyse two distinct sequential reactions. The CeO2-Pt interface catalysed methanol decomposition to produce CO and H2, which were subsequently used for ethylene hydroformylation catalysed by the nearby Pt-SiO2 interface. Consequently, propanal was produced selectively from methanol and ethylene on the nanocrystal bilayer tandem catalyst. This new concept of nanocrystal tandem catalysis represents a powerful approach towards designing high-performance, multifunctional nanostructured catalysts

  7. Exciton polarizability in semiconductor nanocrystals.

    Science.gov (United States)

    Wang, Feng; Shan, Jie; Islam, Mohammad A; Herman, Irving P; Bonn, Mischa; Heinz, Tony F

    2006-11-01

    The response of charge to externally applied electric fields is an important basic property of any material system, as well as one critical for many applications. Here, we examine the behaviour and dynamics of charges fully confined on the nanometre length scale. This is accomplished using CdSe nanocrystals of controlled radius (1-2.5 nm) as prototype quantum systems. Individual electron-hole pairs are created at room temperature within these structures by photoexcitation and are probed by terahertz (THz) electromagnetic pulses. The electronic response is found to be instantaneous even for THz frequencies, in contrast to the behaviour reported in related measurements for larger nanocrystals and nanocrystal assemblies. The measured polarizability of an electron-hole pair (exciton) amounts to approximately 10(4) A(3) and scales approximately as the fourth power of the nanocrystal radius. This size dependence and the instantaneous response reflect the presence of well-separated electronic energy levels induced in the system by strong quantum-confinement effects.

  8. Nanocrystal bilayer for tandem catalysis.

    Science.gov (United States)

    Yamada, Yusuke; Tsung, Chia-Kuang; Huang, Wenyu; Huo, Ziyang; Habas, Susan E; Soejima, Tetsuro; Aliaga, Cesar E; Somorjai, Gabor A; Yang, Peidong

    2011-05-01

    Supported catalysts are widely used in industry and can be optimized by tuning the composition and interface of the metal nanoparticles and oxide supports. Rational design of metal-metal oxide interfaces in nanostructured catalysts is critical to achieve better reaction activities and selectivities. We introduce here a new class of nanocrystal tandem catalysts that have multiple metal-metal oxide interfaces for the catalysis of sequential reactions. We utilized a nanocrystal bilayer structure formed by assembling platinum and cerium oxide nanocube monolayers of less than 10 nm on a silica substrate. The two distinct metal-metal oxide interfaces, CeO(2)-Pt and Pt-SiO(2), can be used to catalyse two distinct sequential reactions. The CeO(2)-Pt interface catalysed methanol decomposition to produce CO and H(2), which were subsequently used for ethylene hydroformylation catalysed by the nearby Pt-SiO(2) interface. Consequently, propanal was produced selectively from methanol and ethylene on the nanocrystal bilayer tandem catalyst. This new concept of nanocrystal tandem catalysis represents a powerful approach towards designing high-performance, multifunctional nanostructured catalysts.

  9. Energy transfer with semiconductor nanocrystals

    NARCIS (Netherlands)

    Rogach, A.L.; Klar, T.A.; Lupton, J.M.; Meijerink, A.; Feldmann, J.

    2009-01-01

    Fo¨ rster (or fluorescence) resonant energy transfer (FRET) is a powerful spectroscopic technique to study interactions, conformational and distance changes, in hybrid nanosystems. Semiconductor nanocrystals, also known as colloidal quantum dots, are highly efficient fluorophores with a strong band-

  10. Nanocrystals Research for Energy Efficient and Clean Energy Technologies:

    Energy Technology Data Exchange (ETDEWEB)

    Rosenthal, Sandra J

    2013-12-17

    Efforts centered on: nanocrystal photovoltaic fabrication, ultrafast dynamics and aberration-corrected STEM characterization of II-VI core, core/shell and alloyed nanocrystals, and fundamental investigation and applications of ultrasmall white light-emitting CdSe nanocrystal.

  11. Structural Investigations of Surfaces and Orientation-SpecificPhenomena in Nanocrystals and Their Assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Aruguete, Deborah Michiko [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    Studies of colloidal nanocrystals and their assemblies are presented. Two of these studies concern the atomic-level structural characterization of the surfaces, interfaces, and interiors present in II-VI semiconductor nanorods. The third study investigates the crystallographic arrangement of cobalt nanocrystals in self-assembled aggregates. Crystallographically-aligned assemblies of colloidal CdSe nanorods are examined with linearly-polarized Se-EXAFS spectroscopy, which probes bonding along different directions in the nanorod. This orientation-specific probe is used, because it is expected that the presence of specific surfaces in a nanorod might cause bond relaxations specific to different crystallographic directions. Se-Se distances are found to be contracted along the long axis of the nanorod, while Cd-Se distances display no angular dependence, which is different from the bulk. Ab-initio density functional theory calculations upon CdSe nanowires indicate that relaxations on the rod surfaces cause these changes. ZnS/CdS-CdSe core-shell nanorods are studied with Se, Zn, Cd, and S X-ray absorption spectroscopy (XAS). It is hypothesized that there are two major factors influencing the core and shell structures of the nanorods: the large surface area-to-volume ratio, and epitaxial strain. The presence of the surface may induce bond rearrangements or relaxations to minimize surface energy; epitaxial strain might cause the core and shell lattices to contract or expand to minimize strain energy. A marked contraction of Zn-S bonds is observed in the core-shell nanorods, indicating that surface relaxations may dominate the structure of the nanorod (strain might otherwise drive the Zn-S lattice to accommodate the larger CdS or CdSe lattices via bond expansion). EXAFS and X-ray diffraction (XRD) indicate that Cd-Se bond relaxations might be anisotropic, an expected phenomenon for a rod-shaped nanocrystal. Ordered self-assembled aggregates of cobalt nanocrystals are

  12. Cu掺杂SnO2/TiO2复合薄膜的制备及性能研究%Preparation and Properties of Cu-doped SnO2/TiO2 Film

    Institute of Scientific and Technical Information of China (English)

    王国栋; 魏长平; 何瑞英; 伞靖; 彭春佳

    2015-01-01

    制备Cu掺杂的纳米SnO2/TiO2溶胶,采用旋涂法在载玻片上镀膜,经干燥、煅烧制得Cu掺杂的SnO2/TiO2薄膜,通过对比实验探讨掺杂比例、条件、复合形式等对结构和性能的影响。采用XRD、SEM、EDS、UV-Vis等测试手段对样品进行表征,并以甲基橙为探针考察了其光催化降解性能。 XRD测试结果显示薄膜的晶型为锐钛矿型,结晶度较高。 SEM谱图显示薄膜表面无明显开裂,粒子分布均匀,粒径约为20 nm。 EDS测试结果表明薄膜材料中含有Cu元素,谱形一致。 UV-Vis吸收光谱表明Cu掺杂以及SnO2/TiO2的复合使得在近紫外区的光吸收比纯TiO2明显增强。光催化实验表明Cu掺杂后使得SnO2/TiO2复合薄膜对甲基橙的光催化降解效率进一步提高,SnO2/TiO2复合薄膜的光催化活性在10%Cu掺杂时达到最高。%Cu-doped nano-SnO2 TiO2 gelatins were prepared and coated onto glass substrates by spin coating method, followed by drying at low temperature and calcined at high temperature. The films were characterized by XRD, SEM, EDS, and UV-Vis. The photocatalysis degradation efficiency was studied by using methyl orange as probe. XRD patterns show that the films are anatase structure. SEM images show that the surfaces of the films are flat without obvious crack, and the average diam-eter is about 20 nm. EDS results indicate that Cu has been introduced to SnO2/TiO2 films. UV-Vis absorption spectra show that the absorbance of Cu-doped SnO2/TiO2 films at visible region increase comparing to pure TiO2 film. The degradation experiment under UV light shows that the photocataly-sis degradation efficiency of Cu-doped SnO2/TiO2 film is higher than that of pure TiO2 film. The photocatalysis degradation efficiency is the biggest when the doping mole fraction of Cu is 10%.

  13. Optimizing Photovoltaic Response by Tuning Light-Harvesting Nanocrystal Shape Synthesized Using a Quick Liquid-Gas Phase Reaction.

    Science.gov (United States)

    Mazumdar, Sayantan; Tamilselvan, Muthusamy; Bhattacharyya, Aninda J

    2015-12-30

    The electron recombination lifetime in a sensitized semiconductor assembly is greatly influenced by the crystal structure and geometric form of the light-harvesting semiconductor nanocrystal. When such light harvesters with varying structural characteristics are configured in a photoanode, its interface with the electrolyte becomes equally important and directly influences the photovoltaic efficiency. We have systematically probed here the influence of nanocrystal crystallographic structure and shape on the electron recombination lifetime and its eventual influence on the light to electricity conversion efficiency of a liquid junction semiconductor sensitized solar cell. The light-harvesting cadmium sulfide (CdS) nanocrystals of distinctly different and controlled shapes are obtained using a novel and simple liquid-gas phase synthesis method performed at different temperatures involving very short reaction times. High-resolution synchrotron X-ray diffraction and spectroscopic studies respectively exhibit different crystallographic phase content and optical properties. When assembled on a mesoscopic TiO2 film by a linker molecule, they exhibit remarkable variation in electron recombination lifetime by 1 order of magnitude, as determined by ac-impedance spectroscopy. This also drastically affects the photovoltaic efficiency of the differently shaped nanocrystal sensitized solar cells.

  14. Cu掺杂ZnSe高效量子点的合成及其光学特性研究%Synthesis of Effective and Qualified Cu-doped ZnSe Quantum Dots and Their Optical Properties

    Institute of Scientific and Technical Information of China (English)

    郑金桔; 曹盛; 高凤梅; 尉国栋; 贾龙; 杨为佑

    2013-01-01

    Effective Cu-doped ZnSe quantum dots (ZnSe:Cu d-dots) with high qualities were synthesized by a growth-doping strategy. The effect of the ratios of Zn to Se precursor within the raw materials on the quality of the ZnSe cores and ZnSerCu d-dots was studied. The photoluminescence (PL) properties of ZnSe:Cu d-dots in Cu doping process were investigated systematically. The results suggested that the optical performance and stability of the d-dots could be remarkably improved by further coated with a homogeneous ZnSe shell on the fabricated surface-doped ZnSe:Cu d-dots. In addition, the obtained ZnSe:Cu d-dots could be changed to be water-soluble by ligand exchange. It implied that these novel d-dots could be a promising candidate to substitute for the conventional quantum dots containing Cd elements, suggesting their potentially environment-friendly applications in the fields of solid state lighting and diagnostics.%采用生长掺杂方式制备出了Cu掺杂ZnSe高效量子点,探索了不同Zn、Se前驱体配比对ZnSe晶核以及ZnSe:Cu量子点质量的影响,并研究了Cu离子掺杂过程中的光谱特征.研究表明,进一步通过在表面掺杂的ZnSe:Cu量子点上同质包覆ZnSe壳层,能够实现其发光效率和稳定性的有效提高;采用配体交换能够实现ZnSe:Cu量子点由油溶性到水溶性的转变.这种新型的掺杂量子点有望替代传统含Cd量子点应用于环境友好型固体发光器件和生物标记.

  15. Water-Soluble CdTe/CdS Core/Shell Semiconductor Nanocrystals: How Their Optical Properties Depend on the Synthesis Methods

    Directory of Open Access Journals (Sweden)

    Brener R. C. Vale

    2016-10-01

    Full Text Available We conducted a comparative synthesis of water-soluble CdTe/CdS colloidal nanocrystalline semiconductors of the core/shell type. We prepared the CdS shell using two different methods: a one-pot approach and successive ionic layer adsorption and reaction (SILAR; in both cases, we used 3-mercaptopropionic acid (MPA as the surface ligand. In the one-pot approach, thiourea was added over the freshly formed CdTe dispersion, and served as the sulfur source. We achieved thicker CdS layers by altering the Cd:S stoichiometric ratio (1:1, 1:2, 1:4, and 1:8. The Cd:S ratios 1:1 and 1:2 furnished the best optical properties; these ratios also made the formation of surface defects less likely. For CdTe/CdS obtained using SILAR, we coated the surface of three differently sized CdTe cores (2.17, 3.10, and 3.45 nm with one to five CdS layers using successive injections of the Cd2+ and S2– ions. The results showed that the core size influenced the optical properties of the materials. The deposition of three to five layers over the surface of smaller CdTe colloidal nanocrystals generated strain effects on the core/shell structure.

  16. Regime-dependent determinants of Euro area sovereign CDS spreads

    NARCIS (Netherlands)

    Blommestein, H.J.; Eijffinger, Sylvester; Qian, Zongxin

    2016-01-01

    We study the determinants of sovereign CDS spreads of five Euro area countries (Greece, Ireland, Italy, Portugal, and Spain) after the collapse of Lehman Brothers. We find that global and/or European Monetary Union (EMU)-wide factors are the main drivers of changes in the sovereign CDS spreads in ou

  17. Electronic structure of cobalt nanocrystals suspended inliquid

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hongjian; Guo, Jinghua; Yin, Yadong; Augustsson, Andreas; Dong, Chungli; Nordgren, Joseph; Chang, Chinglin; Alivisatos, Paul; Thornton, Geoff; Ogletree, D. Frank; Requejo, Felix G.; de Groot, Frank; Salmeron, Miquel

    2007-07-16

    The electronic structure of cobalt nanocrystals suspended in liquid as a function of size has been investigated using in-situ x-ray absorption and emission spectroscopy. A sharp absorption peak associated with the ligand molecules is found that increases in intensity upon reducing the nanocrystal size. X-ray Raman features due to d-d and to charge-transfer excitations of ligand molecules are identified. The study reveals the local symmetry of the surface of {var_epsilon}-Co phase nanocrystals, which originates from a dynamic interaction between Co nanocrystals and surfactant + solvent molecules.

  18. Anisotropic Gold Nanocrystals:. Synthesis and Characterization

    Science.gov (United States)

    Stiufiuc, R.; Toderas, F.; Iosin, M.; Stiufiuc, G.

    In this letter we report on successful preparation and characterization of anisotropic gold nanocrystals bio-synthesized by reduction of aqueous chloroaurate ions in pelargonium plant extract. The nanocrystals have been characterized by means of Transmission Electron Microscopy (TEM), UV-VIS absorption spectroscopy and tapping mode atomic force microscopy (TM-AFM). Using these investigation techniques, the successful formation of anisotropic single nanocrystals with the preferential growth direction along the gold (111) plane has been confirmed. The high detail phase images could give us an explanation concerning the growth mechanism of the nanocrystals.

  19. Spectroscopic Analysis of Impurity Precipitates in CdS Films

    Energy Technology Data Exchange (ETDEWEB)

    Webb, J. D.; Keane, J.; Ribelin, R.; Gedvilas, L.; Swartzlander, A.; Ramanathan, K.; Albin, D. S.; Noufi, R.

    1999-10-31

    Impurities in cadmium sulfide (CdS) films are a concern in the fabrication of copper (indium, gallium) diselenide (CIGS) and cadmium telluride (CdTe) photovoltaic devices. Devices incorporating chemical-bath-deposited (CBD) CdS are comparable in quality to devices incorporating purer CdS films grown using vacuum deposition techniques, despite the higher impurity concentrations typically observed in the CBD CdS films. In this paper, we summarize and review the results of Fourier transform infrared (FTIR), Auger, electron microprobe, and X-ray photoelectron spectroscopic (XPS) analyses of the impurities in CBD CdS films. We show that these impurities differ as a function of substrate type and film deposition conditions. We also show that some of these impurities exist as 10{sup 2} micron-scale precipitates.

  20. Optical characterization of CdS nanorods capped with starch

    Science.gov (United States)

    Roy, J. S.; Pal Majumder, T.; Schick, C.

    2015-05-01

    Well crystalline uniform CdS nanorods were grown by changing the concentration of maize starch. The highly polymeric (branched) structure of starch enhances the growth of CdS nanorods. The average diameter of the nanorods is 20-25 nm while length is of 500-600 nm as verified from SEM and XRD observations. The optical band gaps of the CdS nanorods are varying from 2.66 eV to 2.52 eV depending on concentration of maize starch. The photoluminescence (PL) emission bands are shifted from 526 nm to 529 nm with concentration of maize starch. We have also observed the enhanced PL intensity in CdS nanorods capped with starch. The Fourier transform infrared (FTIR) spectroscopy shows the significant effect of starch on CdS nanorods.

  1. Large-scale synthesis of nearly monodisperse CdSe/CdS core/shell nanocrystals using air-stable reagents via successive ion layer adsorption and reaction.

    Science.gov (United States)

    Li, J Jack; Wang, Y Andrew; Guo, Wenzhuo; Keay, Joel C; Mishima, Tetsuya D; Johnson, Matthew B; Peng, Xiaogang

    2003-10-15

    Successive ion layer adsorption and reaction (SILAR) originally developed for the deposition of thin films on solid substrates from solution baths is introduced as a technique for the growth of high-quality core/shell nanocrystals of compound semiconductors. The growth of the shell was designed to grow one monolayer at a time by alternating injections of air-stable and inexpensive cationic and anionic precursors into the reaction mixture with core nanocrystals. The principles of SILAR were demonstrated by the CdSe/CdS core/shell model system using its shell-thickness-dependent optical spectra as the probes with CdO and elemental S as the precursors. For this reaction system, a relatively high temperature, about 220-240 degrees C, was found to be essential for SILAR to fully occur. The synthesis can be readily performed on a multigram scale. The size distribution of the core/shell nanocrystals was maintained even after five monolayers of CdS shell (equivalent to about 10 times volume increase for a 3.5 nm CdSe nanocrystal) were grown onto the core nanocrystals. The epitaxial growth of the core/shell structures was verified by optical spectroscopy, TEM, XRD, and XPS. The photoluminescence quantum yield (PL QY) of the as-prepared CdSe/CdS core/shell nanocrystals ranged from 20% to 40%, and the PL full-width at half-maximum (fwhm) was maintained between 23 and 26 nm, even for those nanocrystals for which the UV-vis and PL peaks red-shifted by about 50 nm from that of the core nanocrystals. Several types of brightening phenomena were observed, some of which can further boost the PL QY of the core/shell nanocrystals. The CdSe/CdS core/shell nanocrystals were found to be superior in comparison to the highly luminescent CdSe plain core nanocrystals. The SILAR technique reported here can also be used for the growth of complex colloidal semiconductor nanostructures, such as quantum shells and colloidal quantum wells.

  2. Lead sulphide nanocrystal photodetector technologies

    Science.gov (United States)

    Saran, Rinku; Curry, Richard J.

    2016-02-01

    Light detection is the underlying principle of many optoelectronic systems. For decades, semiconductors including silicon carbide, silicon, indium gallium arsenide and germanium have dominated the photodetector industry. They can show excellent photosensitivity but are limited by one or more aspects, such as high production cost, high-temperature processing, flexible substrate incompatibility, limited spectral range or a requirement for cryogenic cooling for efficient operation. Recently lead sulphide (PbS) nanocrystals have emerged as one of the most promising new materials for photodetector fabrication. They offer several advantages including low-cost manufacturing, solution processability, size-tunable spectral sensitivity and flexible substrate compatibility, and they have achieved figures of merit outperforming conventional photodetectors. We review the underlying concepts, breakthroughs and remaining challenges in photodetector technologies based on PbS nanocrystals.

  3. Flexible Photonic Cellulose Nanocrystal Films

    OpenAIRE

    Guidetti, G.; Atifi, S; Vignolini, S; Hamad, WY

    2016-01-01

    The fabrication of self-assembled cellulose nanocrystal (CNC) films of tunable photonic and mechanical properties using a facile, green approach is demonstrated. The combination of tunable flexibility and iridescence can dramatically expand CNC coating and film barrier capabilities for paints and coating applications, sustainable consumer packaging products, as well as effective templates for photonic and optoelectronic materials and structures. CelluForce Inc., Biotechnology and Biologica...

  4. Luminophores of tunable colors from ternary Ag-In-S and quaternary Ag-In-Zn-S nanocrystals covering the visible to near-infrared spectral range.

    Science.gov (United States)

    Gabka, Grzegorz; Bujak, Piotr; Kotwica, Kamil; Ostrowski, Andrzej; Lisowski, Wojciech; Sobczak, Janusz W; Pron, Adam

    2017-01-04

    Ternary Ag-In-S or quaternary Ag-In-Zn-S nanocrystals were prepared from simple precursors (silver nitrate, indium(iii) chloride, zinc stearate in a mixture of DDT and ODE) by injecting a solution of elemental sulfur into OLA. Ternary nanocrystals were modified by depositing either a ZnS or a CdS shell, yielding type I and type II core/shell systems exhibiting photoluminescence QY in the range of 12-16%. Careful optimization of the reaction conditions allowed alloyed quaternary Ag-In-Zn-S nanocrystals exhibiting tunable photoluminescence in the spectral range of 520-720 nm with a QY of 48% and 59% for green and red radiations, respectively, to be obtained. (1)H NMR analysis of the nanocrystal organic shell, after dissolution of its inorganic core, indicated that surfacial sulfur atoms were covalently bonded to aliphatic chains whereas surfacial cations were coordinated by amines and carboxylate anions. No thiol-type ligands were detected. Transfer of the prepared nanocrystals to water could be achieved in one step by exchanging the initial ligands for 11-mercaptoundecanoic ones resulting in a QY value of 31%. A new Ag-In-Zn-S nanocrystal preparation method was elaborated in which indium and zinc salts of fatty acids were used as cation precursors and DDT was replaced by thioacetamide. This original DDT-free method enabled similar tuning of the photoluminescence properties of the nanocrystals as in the previous method; however the measured photoluminescence QYs were three times lower. Hence, further optimization of the new method is required.

  5. Technical training: CERN Document Server (CDS), Inspire and Library Services

    CERN Multimedia

    IT & GS Departments

    2012-01-01

    A new training course, “CERN Document Server (CDS), Inspire and Library Services”, is available since the beginning of the year. The training course is given by members of CERN’s CDS Team (IT-CIS group) and the Library Services (GIS SIS group) and is intended for all members of personnel of CERN. This course will present CDS and inspirehep.net and the content, scope and scientific information available in or with CDS, as much as the classification and organization of the documents. It is intended to give you the training needed to know how to use CDS most efficiently and in particular covers: the main characteristics and advanced features for the search of documents (scientific, multimedia, etc). the collaborative tools : baskets, alerts, comments, evaluation, etc. the submission of documents in CDS and examples of workflows. An important part of the training is composed of various exercises, designed to acquire practical ability to work with CDS in cases similar to re...

  6. Aqueous foams stabilized by chitin nanocrystals

    NARCIS (Netherlands)

    Tzoumaki, M.; Karefyllakis, D.; Moschakis, T.; Biliaderis, C.G.; Scholten, E.

    2015-01-01

    The aim of the present study was to explore the potential use of chitin nanocrystals, as colloidal rod-like particles, to stabilize aqueous foams. Chitin nanocrystals (ChN) were prepared by acid hydrolysis of crude chitin and foams were generated mainly by sonicating the respective dispersions. The

  7. Synthesis, spectroscopy and simulation of doped nanocrystals

    NARCIS (Netherlands)

    Suyver, Jan Frederik

    2003-01-01

    This thesis deals with the properties of semiconductor nanocrystals (ZnS or ZnSe) in the size range (diameter) of 2 nm to 10 nm. The nanocrystals under investigation are doped with the transition metal ions manganese or copper. The goal is to study photoluminescence and electroluminescence from

  8. Synthesis, spectroscopy and simulation of doped nanocrystals

    NARCIS (Netherlands)

    Suyver, Jan Frederik

    2003-01-01

    This thesis deals with the properties of semiconductor nanocrystals (ZnS or ZnSe) in the size range (diameter) of 2 nm to 10 nm. The nanocrystals under investigation are doped with the transition metal ions manganese or copper. The goal is to study photoluminescence and electroluminescence from dope

  9. Emission efficiency limit of Si nanocrystals

    NARCIS (Netherlands)

    Limpens, R.; Luxembourg, S.L.; Weeber, A.W.; Gregorkiewicz, T.

    2016-01-01

    One of the important obstacles on the way to application of Si nanocrystals for development of practical devices is their typically low emissivity. In this study we explore the limits of external quantum yield of photoluminescence of solid-state dispersions of Si nanocrystals in SiO2. By making use

  10. Cellulose nanocrystals: synthesis, functional properties, and applications

    OpenAIRE

    George J.; Sabapathi SN

    2015-01-01

    Johnsy George, SN Sabapathi Food Engineering and Packaging Division, Defence Food Research Laboratory, Siddarthanagar, Mysore, Karnataka, India Abstract: Cellulose nanocrystals are unique nanomaterials derived from the most abundant and almost inexhaustible natural polymer, cellulose. These nanomaterials have received significant interest due to their mechanical, optical, chemical, and rheological properties. Cellulose nanocrystals primarily obtained from naturally occurring cellulose fibers...

  11. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    Science.gov (United States)

    Weiss, Shimon; Schlamp, Michael C.; Alivisatos, A. Paul

    2011-09-27

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit light of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  12. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    Science.gov (United States)

    Weiss, Shimon; Schlam, Michael C; Alivisatos, A. Paul

    2014-03-25

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit tight of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  13. ZnO nanorod/CdS nanocrystal core/shell-type heterostructures for solar cell applications

    Science.gov (United States)

    Guerguerian, Gariné; Elhordoy, Fernando; Pereyra, Carlos J.; Marotti, Ricardo E.; Martín, Francisco; Leinen, Dietmar; Ramos-Barrado, José R.; Dalchiele, Enrique A.

    2011-12-01

    ZnO/CdS core/shell nanorod arrays were fabricated by a two-step method. Single-crystalline ZnO nanorod arrays were first electrochemically grown on SnO2:F (FTO) glass substrates. Then, CdS nanocrystals were deposited onto the ZnO nanorods, using the successive ion layer adsorption and reaction (SILAR) technique, to form core/shell nanocable architectures. Structural, morphological and optical properties of the nanorod heterojunctions were investigated. The results indicate that CdS single-crystalline domains with a mean diameter of about 7 nm are uniformly and conformally covered on the surface of the single-crystalline ZnO nanorods. ZnO absorption with a bandgap energy value of 3.30 ± 0.02 eV is present in all optical transmittance spectra. Another absorption edge close to 500 nm corresponding to CdS with bandgap energy values between 2.43 and 2.59 eV is observed. The dispersion in this value may originate in quantum confinement inside the nanocrystalline material. The appearance of both edges corresponds with the separation of ZnO and CdS phases and reveals the absorption increase due to CdS sensitizer. The photovoltaic performance of the resulting ZnO/CdS core/shell nanorod arrays has been investigated as solar cell photoanodes in a photoelectrochemical cell under white illumination. In comparison with bare ZnO nanorod arrays, a 13-fold enhancement in photoactivity was observed using the ZnO/CdS coaxial heterostructures.

  14. Hydroxyapatite nanocrystal coating on biodegradable microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Masahiro [Department of Bioengineering, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka 565-8565 (Japan); Furuzono, Tsutomu, E-mail: furuzono@ri.ncvc.go.jp [Department of Bioengineering, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka 565-8565 (Japan)

    2010-10-15

    Nano-sized single crystals of calcined hydroxyapatite (HAp) were uniformly coated on poly(L-lactic acid) (PLLA) microspheres through the ionic interaction between calcium ions on the HAp nanocrystal and carboxyl groups on the PLLA microsphere. In order to coat the substrate with HAp nanocrystals through ionic interaction, the surfaces of the PLLA microspheres were hydrolyzed in an alkaline aqueous solution at pH 11.0 for 1 h at room temperature. The interaction between the HAp nanocrystals and the carboxyl groups originating from PLLA end groups was estimated by Fourier transform infrared spectroscopy. The alkali-treated PLLA microspheres were coated with HAp nanocrystals by immersing the microspheres in an ethanol dispersion of HAp nanocrystals followed by washing in an ultrasonic bath.

  15. Measuring the Valence of Nanocrystal Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Owen, Jonathan Scharle [Columbia Univ., New York, NY (United States)

    2016-11-30

    The goal of this project is to understand and control the interplay between nanocrystal stoichiometry, surface ligand binding and exchange, and the optoelectronic properties of semiconductor nanocrystals in solution and in thin solid films. We pursued three research directions with this goal in mind: 1) We characterized nanocrystal stoichiometry and its influence on the binding of L-type and X-type ligands, including the thermodynamics of binding and the kinetics of ligand exchange. 2) We developed a quantitative understanding of the relationship between surface ligand passivation and photoluminescence quantum yield. 3) We developed methods to replace the organic ligands on the nanocrystal with halide ligands and controllably deposit these nanocrystals into thin films, where electrical measurements were used to investigate the electrical transport and internanocrystal electronic coupling.

  16. Exploiting the colloidal nanocrystal library to construct electronic devices

    Science.gov (United States)

    Choi, Ji-Hyuk; Wang, Han; Oh, Soong Ju; Paik, Taejong; Sung, Pil; Sung, Jinwoo; Ye, Xingchen; Zhao, Tianshuo; Diroll, Benjamin T.; Murray, Christopher B.; Kagan, Cherie R.

    2016-04-01

    Synthetic methods produce libraries of colloidal nanocrystals with tunable physical properties by tailoring the nanocrystal size, shape, and composition. Here, we exploit colloidal nanocrystal diversity and design the materials, interfaces, and processes to construct all-nanocrystal electronic devices using solution-based processes. Metallic silver and semiconducting cadmium selenide nanocrystals are deposited to form high-conductivity and high-mobility thin-film electrodes and channel layers of field-effect transistors. Insulating aluminum oxide nanocrystals are assembled layer by layer with polyelectrolytes to form high-dielectric constant gate insulator layers for low-voltage device operation. Metallic indium nanocrystals are codispersed with silver nanocrystals to integrate an indium supply in the deposited electrodes that serves to passivate and dope the cadmium selenide nanocrystal channel layer. We fabricate all-nanocrystal field-effect transistors on flexible plastics with electron mobilities of 21.7 square centimeters per volt-second.

  17. TiO2-CdS Nanocomposites: Effect of CdS Oxidation on the Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    A. Hamdi

    2016-01-01

    Full Text Available Nanocomposites TiO2-CdS with different relative contents of CdS (molar ratios Cd/Ti = 0.02, 0.03, 0.05, 0.1, 0.2, and 0.5 were studied. The structural, photophysical, and chemical properties were investigated using XRD, Raman spectroscopy, XPS, GSDR, and LIL. XRD and Raman results confirmed the presence of TiO2 and CdS with intensities dependent on the ratio Cd/Ti. The presence of CdSO4 was detected by XPS at the surface of all TiO2-CdS composites. The relative amount of sulphate was dependent on the CdS loading. Luminescence time-resolved spectra clearly proved the existence of an excitation transfer process from CdS to TiO2 through the luminescence emission from TiO2 after excitation of CdS at λexc=410 nm, where no direct excitation of TiO2 occurs. Photodegradation of a series of aromatic carboxylic acids—benzoic, salicylic, 4-bromobenzoic, 3-phenylpropionic, and veratric acids—showed a great enhancement in the photocatalytic efficiency of the TiO2-CdS composites, which is due, mainly, to the effect of the charge carriers’ increased lifetime. In addition, it was shown that the oxidation of CdS to CdSO4 did not result in the deactivation of the photocatalytic properties and even contributed to enhance the degradation efficiency.

  18. Noncovalent functionalization of graphene by CdS nanohybrids for electrochemical applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Li [Chemical Engineering Research Center, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Qi, Wei, E-mail: qiwei@tju.edu.cn [Chemical Engineering Research Center, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072 (China); Su, Rongxin [Chemical Engineering Research Center, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072 (China); He, Zhimin [Chemical Engineering Research Center, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072 (China)

    2014-10-01

    Graphene–CdS (GR–CdS) nanocomposites were synthesized via a noncovalent functionalization process. To retain the intrinsic electronic and mechanical properties of graphene, the pristine graphene was firstly modified with 1-aminopyrene based on a strong π–π bond between the pyrenyl groups and the carbon rings of the graphene. Then the CdS nanocrystals were uniformly grown on the amino-graphene. The GR–CdS nanocomposites were characterized by UV–vis spectroscopy and scanning electron microscopy. A glucose biosensor was then fabricated based on the as-prepared GR–CdS nanocomposite by immobilizing glucose oxidase (GOD) in a chitosan thin film on a glassy carbon electrode. Direct electron transfer between GOD and the electrode was achieved and the biosensor showed good electrocatalytic activity with glucose ranging from 0.5 to 7.5 mM and a sensitivity of 45.4 μA mM{sup −1} cm{sup −2}. This work provided a simple and nondestructive functionalization strategy to fabricate graphene-based hybrid nanomaterials and it is expected that this composite film may find more potential applications in biosensors and biocatalysis. - Highlights: • A simple noncovalent approach to synthesize graphene–CdS (GR–CdS) nanocomposites • Direct electrochemistry of glucose oxidase based on synergistic effect of GR–CdS • A sensitive glucose biosensor was fabricated based on the GR–CdS hybrids.

  19. Strain-dependent photoluminescence behavior in three geometries of CdSe/CdS nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Charina L; Koski, Kristie J; Sivasankar, Sanjeevi; Alivisatos, A Paul

    2009-05-26

    In recent years, a new generation of quantum confined colloidal semiconductor structures has emerged, with more complex shapes than simple quantum dots1, 2. These include nanorods3 and tetrapods4. Beyond shape, it is also now possible to spatially vary the electron and hole potentials within these nanoparticles by varying the composition. Examples of these new structures include seeded dots, rods, and tetrapods, which contain a CdSe core embedded within a CdS shell5, 6. These structures may have many uses beyond those envisioned for simple quantum dots, which are frequently employed in luminescent applications7. This paper is concerned with changes in the optoelectronic properties of tetrapods when the arms are bent. We demonstrate that seeded tetrapods can serve as an optical strain gauge, capable of measuring forces on the order of nanonewtons. We anticipate that a nanocrystal strain gauge with optical readout will be useful for applications ranging from sensitive optomechanical devices to biological force investigations.

  20. Radiative and nonradiative pathways in multiexciton recombination in giant nanocrystal quantum dots

    Science.gov (United States)

    Malko, Anton; Sampat, Siddharth; Htoon, Han; Vela-Becerra, Javier; Chen, Yongfen; Hollingsworth, Jennifer; Klimov, Victor

    2010-03-01

    Recently,footnotetextY. Chen et al., JACS 130, 5026 (2008) we developed ``giant'' nanocrystal quantum dots (g-NQDs), in which a small emitting core of CdSe is overcoated with a thick shell of a wider-gap CdS. We conduct room-temp measurements of photoluminescence (PL) lifetimes in such g-NQDs as a function of excitation power and a number of shell monolayers. At low pump levels, corresponding to excitation of less than 1 exciton per dot on average (>1, fast (˜1ns) PL component appeared, accompanied by a transition to a sub-linear scaling of PL intensity with . Our findings indicate that while g-NQDs indeed produce suppression of nonradiative Auger recombination,footnotetextF. Garcia-Santamaria et al., Nanoletters 9, 3482 (2009) this suppression is incomplete. We conduct systematic studies of relative efficiencies of nonradiative and radiative processes in these nanostructures.

  1. Photocatalytic efficiency analysis of CdS nanoparticles with modified electronic states

    Directory of Open Access Journals (Sweden)

    Weon-Sik Chae

    2010-03-01

    Full Text Available For the photooxidative reaction of olefin, colloidal CdS nanoparticles (NPs show enhanced efficiency of photocatalytic activity compared to bulk CdS. We find that the enhanced activity is due to the enlarged surface area of the colloidal CdS NPs as well as enhanced energetic coupling between the colloidal CdS NPs and the olefin molecules. Photocatalytic activity is reduced in the case that CdS NPs are encapsulated in mesoporous silica nanopores.

  2. Hot electron induced NIR detection in CdS films.

    Science.gov (United States)

    Sharma, Alka; Kumar, Rahul; Bhattacharyya, Biplab; Husale, Sudhir

    2016-03-11

    We report the use of random Au nanoislands to enhance the absorption of CdS photodetectors at wavelengths beyond its intrinsic absorption properties from visible to NIR spectrum enabling a high performance visible-NIR photodetector. The temperature dependent annealing method was employed to form random sized Au nanoparticles on CdS films. The hot electron induced NIR photo-detection shows high responsivity of ~780 mA/W for an area of ~57 μm(2). The simulated optical response (absorption and responsivity) of Au nanoislands integrated in CdS films confirms the strong dependence of NIR sensitivity on the size and shape of Au nanoislands. The demonstration of plasmon enhanced IR sensitivity along with the cost-effective device fabrication method using CdS film enables the possibility of economical light harvesting applications which can be implemented in future technological applications.

  3. Photoelectrochemical glucose biosensor incorporating CdS nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Jinjie Sun; Yihua Zhu; Xiaoling Yang; Chunzhong Li

    2009-01-01

    A novel photoelectrochemical biosensor incorporating nanosized CdS semiconductor crystals with enzyme to enhance photochemical reaction has been investigated. CdS nanoparticles were synthesized by using dendrimer PAMAM as inner templates. The CdS nanoparticles and glucose oxidase (GOD) were immobilized on Pt electrode via layer-by-layer (LbL) technique to fabricate a biological-inorganic hybrid system. Under ultraviolet light, the photo-effect of the CdS nanoparticles showed enhancement of the biosensor to detect glucose. Pt nanoparticles were mixed into the Nation film to immobilize the CdS/enzyme composites and to improve the charge transfer of the hybrid, Experimental results demonstrate the desirable characteristics of this biosensing system, e.g. a sensitivity of 1.83 μA/(mM cm~2), lower detection limit (1 μM), and acceptable reproducibility and stability.

  4. Ordered Mesostructured CdS Nanowire Arrays with Rectifying Properties

    Directory of Open Access Journals (Sweden)

    Yuan Na

    2009-01-01

    Full Text Available Abstract Highly ordered mesoporous CdS nanowire arrays were synthesized by using mesoporous silica as hard template and cadmium xanthate (CdR2 as a single precursor. Upon etching silica, mesoporous CdS nanowire arrays were produced with a yield as high as 93 wt%. The nanowire arrays were characterized by XRD, N2adsorption, TEM, and SEM. The results show that the CdS products replicated from the mesoporous silica SBA-15 hard template possess highly ordered hexagonal mesostructure and fiber-like morphology, analogous to the mother template. The current–voltage characteristics of CdS nanoarrays are strongly nonlinear and asymmetrical, showing rectifying diode-like behavior.

  5. ZnO tetrapod nanocrystals

    Directory of Open Access Journals (Sweden)

    Marcus C. Newton

    2007-05-01

    Full Text Available ZnO has received considerable attention because of its unique optical, piezoelectric, and magnetic properties. It also readily self-assembles into a family of nanocrystalline structures. We review the current status of research into ZnO tetrapod nanocrystals. These crystals consist of a ZnO core in the zinc blende structure from which four ZnO arms in the wurtzite structure radiate. The arms are cylinders of hexagonal cross section, with each arm of equal length and diameter. Possible applications in optoelectronics, photovoltaics, spintronics, and piezoelectricity are discussed.

  6. Effect of Cu doping on the optical properties of ZnO/PS nanocomposite systems%Cu掺杂浓度对ZnO/PS纳米复合体系光学性能的影响

    Institute of Scientific and Technical Information of China (English)

    马书懿; 杨付超; 张小雷; 黄新丽; 马李刚; 李发明; 刘静; 赵强

    2012-01-01

    ZnO films doped with different Cu concentration are prepared on porous silicon(PS) substrate by RF magnetron sputtering technique. PS samples are formed by electrochemical anodization on p-type(lOO) silicon wafer. The influence of different Cu doping concentration on the microstructure and optical properties of ZnO films are investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence. The results of XRD show that all the samples have a strong diffraction peak and high preferential orientation in the (002) crystallographic direction. From the SEM images, it can be found that the ZnO nanoparticles sputtered from the target cover the porous silicon surface, exhibiting a smooth surface and obvious grain boundaries. The transmission spectrum show that all these films have a high transmittance ratio in the visible region and the transmittance ratio decreases with the incorporation Cu ion concentration increasing. The optical band edge decreases from 3. 22 eV to 3. 15 eV. The photoluminescence spectrum show that ZnO/PS nanocomposite formes a broad PL band including theblue, green emissions and red-orange emission. With the increase of Cu doping concentration, the intensity of the samples' emission peak decreases sharply. The blue and green emission from ZnO and red emission from PS are combined, thereby producing broad white light.%用电化学阳极氧化法腐蚀p型(100)的单晶硅片制成多孔硅(PS)衬底,然后采用射频反应磁控溅射技术在PS衬底上沉积了不同Cu掺杂浓度的ZnO薄膜.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外分光光度计和荧光分光光度计研究了不同Cu掺杂浓度对薄膜结构和光学性能的影响.XRD结果显示:所有样品都呈现出较强的(002)衍射峰,有很好的c轴择优取向;SEM形貌显示:ZnO晶粒覆盖了PS的孔洞,薄膜表面平整,晶界较明显;透射吸收谱显示:ZnO薄膜有较高的平均透射率,并随着Cu掺杂

  7. LAMDA at TREC CDS track 2015: Clinical Decision Support Track

    Science.gov (United States)

    2015-11-20

    biomedical literature retrieval for clinical cases: a survey of the TREC 2014 CDS track," Information Retrieval Journal , pp. 1-36. [2] M. S. Simpson and...LAMDA at TREC CDS track 2015 Clinical Decision Support Track Moon Soo Cha, Woo-Jin Han, Garam Lee, Minsung Kim, Kyung-Ah Sohn* Department of...Information and Computer Engineering Ajou University Suwon, Republic of Korea (ckanstnzja; data; piratekl; kimmsql; kasohn)@ajou.ac.kr Abstract

  8. Intraday dynamics of euro area sovereign CDS and bonds

    OpenAIRE

    Jacob Gyntelberg; Peter Hördahl; Kristyna Ters; Jörg Urban

    2013-01-01

    The recent sovereign debt crisis in the euro area has seen credit spreads on sovereign bonds and credit default swaps (CDS) surge for a number of member states. While these events have increased interest in understanding the dynamics of sovereign spreads in bond and CDS markets, there is little agreement in the literature as to whether one of the two markets is more important than the other in terms of price discovery of sovereign credit risk.

  9. Summer Student Project: Collecting and disseminating CDS KPIs

    CERN Document Server

    Alvarez Perez, Carmen

    2010-01-01

    CDS (CERN Document Server) stores over 900,000 bibliographic records, including 360,000 fulltext documents, of interest to people working in particle physics and related areas. My project consisted on extracting KPIs (Key Performance Indicators) from it and feeding them to a central IT KPI system. To achieve this, I learned the CDS-Invenio open source digital library software, and worked with its statistic module.

  10. Cu掺杂TiO2作为SERS基底的研究%Study of enhanced Raman scattering for molecules adsorbed on Cu-doped TiO2 nanoparticles

    Institute of Scientific and Technical Information of China (English)

    薛向欣; 纪伟; 毛竹; 阮伟东; 赵冰; MA Stephen; LOMBARDI John R

    2011-01-01

    本文采用溶胶-水热法制备了TiO2及Cu掺杂的TiO2纳米粒子作为表面增强拉曼光谱(SERS)活性基底,观察到当4-巯基苯甲酸吸附在3%Cu掺杂的TiO2表面上时,其SERS信号得到了最大程度的增强.Cu离子掺杂进TiO2晶格时会使TiO2表面的缺陷浓度(表面态)得到增加,一定量的缺陷浓度对TiO2-to-Molecule的电荷转移机理起到促进作用,进一步证明了化学增强机理在SERS现象的贡献.%A series of Cu-doped TiO2 (Cu-TiO2) nanoparticles (NPs) have been synthesized for the application as surface-enhanced Raman scattering (SERS) substrates.Significant SERS signals were observed when the probing molecules of 4-mercaptobenzoic acid were adsorbed on the surface of these substrates.Transmission electron microscopy (TEM), UV-vis spectrophotometer, X-ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the TiO2 and Cu-TiO2 nanaoparticles.The crystalline defects of the Cu-TiO2 NPs caused by Cu dopants affected the SERS activity.In these defect areas, the electrons transfer from the valance band of TiO2 NPs and then transfers to the surface state energy levels.The inner-particle charge-transfers also contributed to the particle-to-molecule charge-transfers, which played a very important role in the enhancements of SERS signals.

  11. 共溅射法制备Cu掺杂ZnO薄膜结构及性能的研究%Study on the structure and properties of Cu-doped ZnO films prepared by co-sputtering

    Institute of Scientific and Technical Information of China (English)

    郝嘉伟; 叶伏秋; 肖立娟; 李长山; 赵鹤平

    2014-01-01

    采用直流与射频双靶共溅射的方法在玻璃衬底上制备Cu掺杂的ZnO薄膜,并研究了Cu的溅射功率以及氧分压对薄膜结构和光电性能的影响,利用 X 射线衍射仪(XRD)、紫外可见光分光光度计(UV-VIS)以及霍尔测试仪(HALL8800)分别对样品的结构、光学特性以及电学特性进行表征,结果表明,薄膜的结晶质量随Cu溅射功率的增大有所提高,超过一定范围开始降低,而透过率则一直减小,增大氧分压可以改善样品的透过率。 Cu的掺入使薄膜发生了由n型向p型的转变,且富氧条件下有利于这种转变。%We used double target co-sputtering of DC and RF to prepare Cu-doped thin ZnO films , and the effects of sputtering power and oxygen partial pressure on the film structure and photoelectric properties were studied . Structure , optical and electrical characteristics of the samples were characterized with XRD , UV-VIS , and HALL8800 . As the results show , the crystal quality of the film first increase with the increase of the Cu sputtering power , and then decrease , while the transmittance keeps decreasing . The transmittance of samples can be improved by increasing the oxygen partial pressure . Doping Cu transforms n-type film to p-type , and enriched oxygen conditions can benefit such transformations .

  12. Quantum theory of electroabsorption in semiconductor nanocrystals.

    Science.gov (United States)

    Tepliakov, Nikita V; Leonov, Mikhail Yu; Baranov, Alexander V; Fedorov, Anatoly V; Rukhlenko, Ivan D

    2016-01-25

    We develop a simple quantum-mechanical theory of interband absorption by semiconductor nanocrystals exposed to a dc electric field. The theory is based on the model of noninteracting electrons and holes in an infinitely deep quantum well and describes all the major features of electroabsorption, including the Stark effect, the Franz-Keldysh effect, and the field-induced spectral broadening. It is applicable to nanocrystals of different shapes and dimensions (quantum dots, nanorods, and nanoplatelets), and will prove useful in modeling and design of electrooptical devices based on ensembles of semiconductor nanocrystals.

  13. Size quantization in Cu2Se nanocrystals

    Science.gov (United States)

    Govindraju, S.; Kalenga, M. P.; Airo, M.; Moloto, M. J.; Sikhwivhilu, L. M.; Moloto, N.

    2014-12-01

    Herein we report on the synthesis of size quantized copper selenide nanocrystals via the colloidal method. Different colours of the sample were obtained at different time intervals indicative of the sizes of the nanocrystals. The absorption band edges were blue-shifted from bulk indicative of quantum confinement. This was corroborated by the TEM results that showed very small particles ranging from 2 nm to 7 nm. This work therefore shows a phenomenon readily observed in cadmium chalcogenide nanocrystals but has never been reported for copper based chalcogenides.

  14. Sigmoidal diagnostics with SOHO/CDS

    Science.gov (United States)

    Del Zanna, G.; Gibson, S. E.; Mason, H. E.; Pike, C. D.; Mandrini, C. H.

    During the third Whole Sun Month Campaign (August 18 - September 14, 1999), the evolution of the active region NOAA 8668 was followed during its meridian passage and at the limb (Sigmoid JOP 106), with simultaneous observations with the Solar and Heliospheric Observatory (SOHO), and with other instruments, both satellite and ground-based. On August 21st, a small flare, associated with a brightening of the sigmoidal structure, occurred. SOHO Coronal Diagnostic Spectrometer (CDS) observations of this small flare are presented. Coronal temperatures and densities of the sigmoid are estimated. High transition region densities (in the range 2.5-7 × 10 11 cm -3), obtained using O IV, are present in the brightenings associated with the flare. At coronal level, high temperatures of at least 8 MK were reached, as shown by strong Fe XIX emission. After this small flare, relatively strong blue-shifts (⋍ 30 km/s) are observed in coronal lines, located at the two ends of a small loop system associated with the sigmoid.

  15. Storage of optical excitations in colloidal semiconductor nanocrystals; Speicherung optischer Anregungen in kolloidalen Halbleiter-Nanokristallen

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, Robert

    2009-07-22

    In the present theis it is described, how colloidal semiconductor nanocrystals can be used under influence of an electric field to store optical excitation energy at room temperature, to alter, and to supply controlledly. For this the photoluminescence emission of an ensemble of heterogeneous nanocrystals was manipulated and spectroscopically studied. The applied od-shaped particles consist of a spherical core of CdSe, on which an elongated shell of CdS is monocrystallinely be grown. The electron is in such an asymmetric geometry delocalized over the hole nanorod, whereas the hole because of the high potential barrier remains bound in the CdSe core. The wave-function overlap of the charge carriers can therefore be influenced both by the length of the nanorod and by an external electric field. In the regime of prompt fluorescence the manipulation of the charge-carrier separation by an electric field led to a suppression of the radiative recombination. As consequence a fluorescence suppression of about 40% could be observed. After the removal of the electric field the separation was reduced and the stored energy is in an fluorescence increasement directedly liberated again. The strength of the storage efficiency lies with the strength of the electric field in a linear connection. Furthermore in this time range a quantum-confined Stark effect of upt o 14 meV could be detected at room temperature, although the effect is complicated by the different orientations and sizes of the nanorods in the ensemble. Hereby it is of advance to can adress with the applied detection technique a subensemble of nanocrystals. Furthermore a significant storage of the ensmble emission by up to 100 {mu}s conditioned by the electric electric fieldcould be demonstrated, which exceeds the fluorescence lifetime of these particles by the 10{sup 5} fold. As also could be shown by experiments on CdSe/ZnS nanocrystals surface states play a relevent role for the emission dynamics of nanocrystals

  16. Doped Colloidal ZnO Nanocrystals

    Directory of Open Access Journals (Sweden)

    Yizheng Jin

    2012-01-01

    Full Text Available Colloidal ZnO nanocrystals are promising for a wide range of applications due to the combination of unique multifunctional nature and remarkable solution processability. Doping is an effective approach of enhancing the properties of colloidal ZnO nanocrystals in well-controlled manners. In this paper, we analyzed two synthetic strategies for the doped colloidal ZnO nanocrystals, emphasizing our understanding on the critical factors associated with the high temperature and nonaqueous approach. Latest advances of three topics, bandgap engineering, n-type doping, and dilute magnetic semiconductors related to doped ZnO nanocrystals were discussed to reveal the effects of dopants on the properties of the nanocrystalline materials.

  17. Photoluminescence of Silicon Nanocrystals in Silicon Oxide

    Directory of Open Access Journals (Sweden)

    L. Ferraioli

    2007-01-01

    Full Text Available Recent results on the photoluminescence properties of silicon nanocrystals embedded in silicon oxide are reviewed and discussed. The attention is focused on Si nanocrystals produced by high-temperature annealing of silicon rich oxide layers deposited by plasma-enhanced chemical vapor deposition. The influence of deposition parameters and layer thickness is analyzed in detail. The nanocrystal size can be roughly controlled by means of Si content and annealing temperature and time. Unfortunately, a technique for independently fine tuning the emission efficiency and the size is still lacking; thus, only middle size nanocrystals have high emission efficiency. Interestingly, the layer thickness affects the nucleation and growth kinetics so changing the luminescence efficiency.

  18. Tunable mid IR plasmon in GZO nanocrystals.

    Science.gov (United States)

    Hamza, M K; Bluet, J-M; Masenelli-Varlot, K; Canut, B; Boisron, O; Melinon, P; Masenelli, B

    2015-07-28

    Degenerate metal oxide nanoparticles are promising systems to expand the significant achievements of plasmonics into the infrared (IR) range. Among the possible candidates, Ga-doped ZnO nanocrystals are particularly suited for mid IR, considering their wide range of possible doping levels and thus of plasmon tuning. In the present work, we report on the tunable mid IR plasmon induced in degenerate Ga-doped ZnO nanocrystals. The nanocrystals are produced by a plasma expansion and exhibit unprotected surfaces. Tuning the Ga concentration allows tuning the localized surface plasmon resonance. Moreover, the plasmon resonance is characterized by a large damping. By comparing the plasmon of nanocrystal assemblies to that of nanoparticles dispersed in an alumina matrix, we investigate the possible origins of such damping. We demonstrate that it partially results from the self-organization of the naked particles and also from intrinsic inhomogeneity of dopants.

  19. Size-Dependent Raman Shifts for nanocrystals.

    Science.gov (United States)

    Gao, Yukun; Zhao, Xinmei; Yin, Penggang; Gao, Faming

    2016-04-22

    Raman spectroscopy is a very sensitive tool for probing semiconductor nanocrystals. The underlying mechanism behind the size-dependent Raman shifts is still quite controversial. Here we offer a new theoretical method for the quantum confinement effects on the Raman spectra of semiconductor nanocrystals. We propose that the shift of Raman spectra in nanocrystals can result from two overlapping effects: the quantum effect shift and surface effect shift. The quantum effect shift is extracted from an extended Kubo formula, the surface effect shift is determined via the first principles calculations. Fairly good prediction of Raman shifts can be obtained without the use of any adjustable parameter. Closer analysis shows that the size-dependent Raman shifts in Si nanocrystals mainly result from the quantum effect shifts. For nanodiamond, the proportion of surface effect shift in Raman shift is up to about 40%. Such model can also provide a good baseline for using Raman spectroscopy as a tool to measure size.

  20. Giant Raman gain in silicon nanocrystals

    National Research Council Canada - National Science Library

    Sirleto, Luigi; Ferrara, Maria Antonietta; Nikitin, Timur; Novikov, Sergei; Khriachtchev, Leonid

    2012-01-01

    ... of next generation nonlinear photonic devices. Here we report the first observation of stimulated Raman scattering in silicon nanocrystals embedded in a silica matrix under non-resonant excitation at infrared wavelengths (~1.5 μm...

  1. Gas phase grown silicon germanium nanocrystals

    Science.gov (United States)

    Mohan, A.; Tichelaar, F. D.; Kaiser, M.; Verheijen, M. A.; Schropp, R. E. I.; Rath, J. K.

    2016-09-01

    We report on the gas phase synthesis of highly crystalline and homogeneously alloyed Si1-xGex nanocrystals in continuous and pulsed plasmas. Agglomerated nanocrystals have been produced with remarkable control over their composition by altering the precursor GeH4 gas flow in a continuous plasma. We specially highlight that in the pulsed plasma mode, we obtain quantum-sized free standing alloy nanocrystals with a mean size of 7.3 nm. The presence of Si1-xGex alloy particles is confirmed with multiple techniques, i.e. Raman spectroscopy, XRD (Xray diffraction) and HRTEM (high resolution transmission electron microscopy) studies, with each of these methods consistently yielding the same composition. The nanocrystals synthesized here have potential applications in band-gap engineering for multijunction solar cells.

  2. Heavily Doped Semiconductor Nanocrystal Quantum Dots

    National Research Council Canada - National Science Library

    David Mocatta; Guy Cohen; Jonathan Schattner; Oded Millo; Eran Rabani; Uri Banin

    2011-01-01

    ... of fundamental understanding of this heavily doped limit under strong quantum confinement. We developed a method to dope semiconductor nanocrystals with metal impurities, enabling control of the band gap and Fermi energy...

  3. Zirconia nanocrystals as submicron level biological label

    Science.gov (United States)

    Smits, K.; Liepins, J.; Gavare, M.; Patmalnieks, A.; Gruduls, A.; Jankovica, D.

    2012-08-01

    Inorganic nanocrystals are of increasing interest for their usage in biology and pharmacology research. Our interest was to justify ZrO2 nanocrystal usage as submicron level biological label in baker's yeast Saccharomyces cerevisia culture. For the first time (to our knowledge) images with sub micro up-conversion luminescent particles in biologic media were made. A set of undoped as well as Er and Yb doped ZrO2 samples at different concentrations were prepared by sol-gel method. The up-conversion luminescence for free standing and for nanocrystals with baker's yeast cells was studied and the differences in up-conversion luminescence spectra were analyzed. In vivo toxic effects of ZrO2 nanocrystals were tested by co-cultivation with baker's yeast.

  4. Charge transport in semiconductor nanocrystal quantum dots

    Science.gov (United States)

    Mentzel, Tamar Shoshana

    In this thesis, we study charge transport in arrays of semiconductor nanocrystal quantum dots. Nanocrystals are synthesized in solution, and an organic ligand on the surface of the nanocrystal creates a potential barrier that confines charges in the nanocrystal. Optical absorption measurements reveal discrete electronic energy levels in the nanocrystals resulting from quantum confinement. When nanocrystals are deposited on a surface, they self-assemble into a close-packed array forming a nanocrystal solid. We report electrical transport measurements of a PbSe nanocrystal solid that serves as the channel of an inverted field-effect transistor. We measure the conductance as a function of temperature, source-drain bias and. gate voltage. The data indicates that holes are the majority carriers; the Fermi energy lies in impurity states in the bandgap of the nanocrystal; and charges hop between the highest occupied valence state in the nanocrystals (the 1S h states). At low source-drain voltages, the activation energy for hopping is given by the energy required to generate holes in the 1Sh state plus activation over barriers resulting from site disorder. The barriers from site disorder are eliminated with a sufficiently high source-drain bias. From the gate effect, we extract the Thomas-Fermi screening length and a density of states that is consistent with the estimated value. We consider variable-range hopping as an alternative model, and find no self-consistent evidence for it. Next, we employ charge sensing as an alternative to current measurements for studying transport in materials with localized sites. A narrow-channel MOSFET serves as a charge sensor because its conductance is sensitive to potential fluctuations in the nearby environment caused by the motion of charge. In particular, it is sensitive to the fluctuation of single electrons at the silicon-oxide interface within the MOSFET. We pattern a strip of amorphous germanium within 100 nm of the transistor. The

  5. Synthesis of new nanocrystal materials

    Science.gov (United States)

    Hassan, Yasser Hassan Abd El-Fattah

    Colloidal semiconductor nanocrystals (NCs) have sparked great excitement in the scientific community in last two decades. NCs are useful for both fundamental research and technical applications in various fields owing to their size and shape-dependent properties and their potentially inexpensive and excellent chemical processability. These NCs are versatile fluorescence probes with unique optical properties, including tunable luminescence, high extinction coefficient, broad absorption with narrow photoluminescence, and photobleaching resistance. In the past few years, a lot of attention has been given to nanotechnology based on using these materials as building blocks to design light harvesting assemblies. For instant, the pioneering applications of NCs are light-emitting diodes, lasers, and photovoltaic devices. Synthesis of the colloidal stable semiconductor NCs using the wet method of the pyrolysis of organometallic and chalcogenide precursors, known as hot-injection approach, is the chart-topping preparation method in term of high quality and monodisperse sized NCs. The advancement in the synthesis of these artificial materials is the core step toward their applications in a broad range of technologies. This dissertation focuses on exploring various innovative and novel synthetic methods of different types of colloidal nanocrystals, both inorganic semiconductors NCs, also known as quantum dots (QDs), and organic-inorganic metal halide-perovskite materials, known as perovskites. The work presented in this thesis focuses on pursuing fundamental understanding of the synthesis, material properties, photophysics, and spectroscopy of these nanostructured semiconductor materials. This thesis contains 6 chapters and conclusions. Chapters 1?3 focus on introducing theories and background of the materials being synthesized in the thesis. Chapter 4 demonstrates our synthesis of colloidal linker--free TiO2/CdSe NRs heterostructures with CdSe QDs grown in the presence of Ti

  6. Cellulose nanocrystals: synthesis, functional properties, and applications

    Directory of Open Access Journals (Sweden)

    George J

    2015-11-01

    Full Text Available Johnsy George, SN Sabapathi Food Engineering and Packaging Division, Defence Food Research Laboratory, Siddarthanagar, Mysore, Karnataka, India Abstract: Cellulose nanocrystals are unique nanomaterials derived from the most abundant and almost inexhaustible natural polymer, cellulose. These nanomaterials have received significant interest due to their mechanical, optical, chemical, and rheological properties. Cellulose nanocrystals primarily obtained from naturally occurring cellulose fibers are biodegradable and renewable in nature and hence they serve as a sustainable and environmentally friendly material for most applications. These nanocrystals are basically hydrophilic in nature; however, they can be surface functionalized to meet various challenging requirements, such as the development of high-performance nanocomposites, using hydrophobic polymer matrices. Considering the ever-increasing interdisciplinary research being carried out on cellulose nanocrystals, this review aims to collate the knowledge available about the sources, chemical structure, and physical and chemical isolation procedures, as well as describes the mechanical, optical, and rheological properties, of cellulose nanocrystals. Innovative applications in diverse fields such as biomedical engineering, material sciences, electronics, catalysis, etc, wherein these cellulose nanocrystals can be used, are highlighted. Keywords: sources of cellulose, mechanical properties, liquid crystalline nature, surface modification, nanocomposites 

  7. Polyimide Cellulose Nanocrystal Composite Aerogels

    Science.gov (United States)

    Nguyen, Baochau N.; Meador, Mary Ann; Rowan, Stuart; Cudjoe, Elvis; Sandberg, Anna

    2014-01-01

    Polyimide (PI) aerogels are highly porous solids having low density, high porosity and low thermal conductivity with good mechanical properties. They are ideal for various applications including use in antenna and insulation such as inflatable decelerators used in entry, decent and landing operations. Recently, attention has been focused on stimuli responsive materials such as cellulose nano crystals (CNCs). CNCs are environmentally friendly, bio-renewable, commonly found in plants and the dermis of sea tunicates, and potentially low cost. This study is to examine the effects of CNC on the polyimide aerogels. The CNC used in this project are extracted from mantle of a sea creature called tunicates. A series of polyimide cellulose nanocrystal composite aerogels has been fabricated having 0-13 wt of CNC. Results will be discussed.

  8. A luminescent nanocrystal stress gauge

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Charina; Koski, Kristie; Olson, Andrew; Alivisatos, Paul

    2010-10-25

    Microscale mechanical forces can determine important outcomes ranging from the site of material fracture to stem cell fate. However, local stresses in a vast majority of systems cannot be measured due to the limitations of current techniques. In this work, we present the design and implementation of the CdSe/CdS core/shell tetrapod nanocrystal, a local stress sensor with bright luminescence readout. We calibrate the tetrapod luminescence response to stress, and use the luminescence signal to report the spatial distribution of local stresses in single polyester fibers under uniaxial strain. The bright stress-dependent emission of the tetrapod, its nanoscale size, and its colloidal nature provide a unique tool that may be incorporated into a variety of micromechanical systems including materials and biological samples to quantify local stresses with high spatial resolution.

  9. Surface modification of cellulose nanocrystals

    Institute of Scientific and Technical Information of China (English)

    WANG Neng; DING Enyong; CHENG Rongshi

    2007-01-01

    In order to improve the dispersibility of cellulose nanocrystal(CNC) particles,three difierent grafted reactions of acetylation,hydroxyethylation and hydroxypropylation were introduced to modify the CNC surface.The main advantages of these methods were the simple and easily controlled reaction conditions,and the dispersibility of the resulting products was distinctly improved.The properties of the modified CNC were characterized by means of Fourier transform infrared spectroscopy(FT-IR),13 C nuclear magnetic resonance(NMR),transmission electron microscopy(TEM)and thermogravimetric analyses(TGA).The results indicated mat after desiccation,the modification products could be dispersed again in the proper solvents by ultrasonic treatments,and the diameter of their particles had no obvious changes.However,their thermal degradation behaviors were quite different.The initial decomposition temperature of the modified products via hydroxyethylation or hydroxypropylation was lower than that of modified products via acetylation.

  10. 2009 Clusters, Nanocrystals & Nanostructures GRC

    Energy Technology Data Exchange (ETDEWEB)

    Lai-Sheng Wang

    2009-07-19

    For over thirty years, this Gordon Conference has been the premiere meeting for the field of cluster science, which studies the phenomena that arise when matter becomes small. During its history, participants have witnessed the discovery and development of many novel materials, including C60, carbon nanotubes, semiconductor and metal nanocrystals, and nanowires. In addition to addressing fundamental scientific questions related to these materials, the meeting has always included a discussion of their potential applications. Consequently, this conference has played a critical role in the birth and growth of nanoscience and engineering. The goal of the 2009 Gordon Conference is to continue the forward-looking tradition of this meeting and discuss the most recent advances in the field of clusters, nanocrystals, and nanostructures. As in past meetings, this will include new topics that broaden the field. In particular, a special emphasis will be placed on nanomaterials related to the efficient use, generation, or conversion of energy. For example, we anticipate presentations related to batteries, catalysts, photovoltaics, and thermoelectrics. In addition, we expect to address the controversy surrounding carrier multiplication with a session in which recent results addressing this phenomenon will be discussed and debated. The atmosphere of the conference, which emphasizes the presentation of unpublished results and lengthy discussion periods, ensures that attendees will enjoy a valuable and stimulating experience. Because only a limited number of participants are allowed to attend this conference, and oversubscription is anticipated, we encourage all interested researchers from academia, industry, and government institutions to apply as early as possible. An invitation is not required. We also encourage all attendees to submit their latest results for presentation at the poster sessions. We anticipate that several posters will be selected for 'hot topic' oral

  11. Solvothermal growth of single-crystal CdS nanowires

    Indian Academy of Sciences (India)

    M A Mahdi; J J Hassan; S J Kasim; S S Ng; Z Hassan

    2014-04-01

    Cadmium sulfide (CdS) nanowires (NWs) were prepared by the solvothermal method using ethylenedi-amine as a solvent. Two sets of CdS NWs were synthesized at 160 and 200° C for various reaction durations (3.5, 7 and 24 h). Scanning/tunneling electron microscopy was used to examine the surface morphology of the grown NWs. Their dimensions are found to depend on the reaction temperature and duration. The CdS NWs grown at 200° C for all durations are longer than those prepared at 160° C, with diameters ranging from 15 to 40 nm. A three-armed structure is exhibited by all the samples. The grown CdS NWs display a hexagonal wurtzite phase and grows along the 001 direction. The optical absorption of the grown NWs shows a sharp absorption edge with a blueshift, which indicates an expansion of the optical band gap. All prepared samples show two emission peaks in their photoluminescence spectra. The emission peak location depends on the reaction temperature and duration. The CdS NWs prepared at 160° C show a sharp band–band emission compared with those prepared at 200° C. Raman analysis indicates that the optical properties of the grown NWs are enhanced with increased temperature and reaction duration.

  12. Optical switches based on CdS single nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Yi [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States); Hu, Chenguo, E-mail: hucg@cqu.edu.cn [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China); Zheng, Chunhua; Zhang, Hulin [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China); Yang, Rusen [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States); Tian, Yongshu [Chongqing Communication College, Chongqing 400035 (China)

    2010-10-15

    CdS nanowires have been synthesized by a composite-hydroxide-mediated approach. The characterization of the nanowire with X-ray diffraction, scanning electron microscopy, and transmission electron microscopy indicated a single-crystalline hexagonal structure growing along [21-bar 1-bar 0] direction with length up to 100 {mu}m. The UV-visible reflection spectrum demonstrated a band gap of 2.36 eV. A strong light emission centered at 543 nm was observed under different excitation wavelengths of 300, 320, 360 and 400 nm, which was further confirmed by a bright fluorescent imaging of a single CdS nanowire. The photocurrent response based on a single CdS nanowire showed distinct optical switch under the intermittent illumination of white light. The rise and decay time were less than 1.0 and 0.2 s, respectively, indicating high crystallization with fewer trap centers in the CdS nanowires. It is possible that the undesirable trapping effects on grain-boundaries for photoconductors could be avoided thanks to the single-crystalline nature of the CdS nanowires.

  13. Synthesis of nanocrystals and nanocrystal self-assembly

    Science.gov (United States)

    Chen, Zhuoying

    Chapter 1. A general introduction is presented on nanomaterials and nanoscience. Nanoparticles are discussed with respect to their structure and properties. Ferroelectric materials and nanoparticles in particular are highlighted, especially in the case of the barium titanate, and their potential applications are discussed. Different nanocrystal synthetic techniques are discussed. Nanoparticle superlattices, the novel "meta-materials" built from self-assembly at the nanoscale, are introduced. The formation of nanoparticle superlattices and the importance and interest of synthesizing these nanostructures is discussed. Chapter 2. Advanced applications for high k dielectric and ferroelectric materials in the electronics industry continues to demand an understanding of the underlying physics in decreasing dimensions into the nanoscale. The first part of this chapter presents the synthesis, processing, and electrical characterization of nanostructured thin films (thickness ˜100 nm) of barium titanate BaTiO3 built from uniform nanoparticles (properties. We observe the BaTiO3 nanocrystals crystallize with evidence of tetragonality. Electric field dependent polarization measurements show spontaneous polarization and hysteresis, indicating ferroelectric behavior for the BaTiO 3 nanocrystalline films with grain sizes in the range of 10--30 nm. Dielectric measurements of the films show dielectic constants in the range of 85--90 over the 1 kHz--100 kHz, with low loss. We present nanocrystals as initial building blocks for the preparation of thin films which exhibit uniform nanostructured morphologies and grain sizes. In the second part of this chapter, a nonhydrolytic alcoholysis route to study the preparation of well-crystallized size-tunable BaTiO3 nanocrystals is presented. Different surfactants of amines, carboxylic acids, and alcohols were used to study the effect of size and morphological control over the nanocrystals. Techniques including X-ray diffraction, transmission

  14. PENERAPAN MICRO CDS/ISIS UNTUK PENGELOLAAN INFORMASI

    Directory of Open Access Journals (Sweden)

    Rukasih Dardjat

    2011-12-01

    Full Text Available Penggunaan komputer untuk penyimpanan dan pencarian kembali informasi sudah banyak dilakukan oleh beberapa perpustakaan, pusat informasi, pusat dokumentasi, dan lain-lain.CDS/ISIS (Computerized Documentation Systems/Integrated Set of Information Systems, adalah suatu sistem penyimpanan dan pencarian kembali informasi pada umumnya, yang dirancang secara khusus untuk pengelolaan pangkalan data yang bukan numerik (non-numerical data base dengan menggunakan komputer.Micro CDS/ISIS Software Package merupakan paket piranti lunak yang dikembangkan oleh Unesco (Copyright Unesco, 1985, yang sistem pengelolaannya dapat dioperasikan dengan menggunakan komputer mikro (IBM PC XT/AT, IBM Compatible, Olivetti PC, dan lain-lain.Paket perangkat lunak Nicro CDS/ISIS terdiri dari satu set program-program komputer yang setiap program mempunyai fungsi khusus untuk mengolah serta memproses elemen-elemen data yang berbeda sama sekali untuk menjadi suatu informasi tertentu yang sesuai dengan keinginan para pengguna.

  15. Photoluminescence studies of CdS layers for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Gemain, Frederique; Robin, Ivan-Christophe; Renet, Sebastien; Bernardi, Sergio [Commissariat a l' Energie Atomique et aux Energies Alternatives, CEA-LETI, Minatec Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2012-08-15

    Photoluminescence (PL) measurements were performed on polycrystalline CdS films grown by close space sublimation (CSS) or by chemical bath deposition (CBD) in order to observe the evolution of emission features according to the deposition technique and post-deposition treatments. CdS is naturally n-type because of the presence of sulphur vacancies and in most of the observed samples, a donor-acceptor pair involving the sulfur vacancies could be identified at 1.65 eV. Different complexes emissions could be identified depending on the deposition technique and post-growth treatment. The best efficiencies were measured on CdTe/CdS based solar cells for which the CdS layer presents an excitonic donor bound PL peak as well as an emission corresponding to interstitial cadmium (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Optical sensor based on a single CdS nanobelt.

    Science.gov (United States)

    Li, Lei; Yang, Shuming; Han, Feng; Wang, Liangjun; Zhang, Xiaotong; Jiang, Zhuangde; Pan, Anlian

    2014-04-23

    In this paper, an optical sensor based on a cadmium sulfide (CdS) nanobelt has been developed. The CdS nanobelt was synthesized by the vapor phase transportation (VPT) method. X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) results revealed that the nanobelt had a hexagonal wurtzite structure of CdS and presented good crystal quality. A single nanobelt Schottky contact optical sensor was fabricated by the electron beam lithography (EBL) technique, and the device current-voltage results showed back-to-back Schottky diode characteristics. The photosensitivity, dark current and the decay time of the sensor were 4 × 10⁴, 31 ms and 0.2 pA, respectively. The high photosensitivity and the short decay time were because of the exponential dependence of photocurrent on the number of the surface charges and the configuration of the back to back Schottky junctions.

  17. Optical Sensor Based on a Single CdS Nanobelt

    Directory of Open Access Journals (Sweden)

    Lei Li

    2014-04-01

    Full Text Available In this paper, an optical sensor based on a cadmium sulfide (CdS nanobelt has been developed. The CdS nanobelt was synthesized by the vapor phase transportation (VPT method. X-Ray Diffraction (XRD and Transmission Electron Microscopy (TEM results revealed that the nanobelt had a hexagonal wurtzite structure of CdS and presented good crystal quality. A single nanobelt Schottky contact optical sensor was fabricated by the electron beam lithography (EBL technique, and the device current-voltage results showed back-to-back Schottky diode characteristics. The photosensitivity, dark current and the decay time of the sensor were 4 × 104, 31 ms and 0.2 pA, respectively. The high photosensitivity and the short decay time were because of the exponential dependence of photocurrent on the number of the surface charges and the configuration of the back to back Schottky junctions.

  18. Nanocrystal Bioassembly: Asymmetry, Proximity, and Enzymatic Manipulation

    Energy Technology Data Exchange (ETDEWEB)

    Claridge, Shelley A. [Univ. of California, Berkeley, CA (United States)

    2008-05-01

    Research at the interface between biomolecules and inorganic nanocrystals has resulted in a great number of new discoveries. In part this arises from the synergistic duality of the system: biomolecules may act as self-assembly agents for organizing inorganic nanocrystals into functional materials; alternatively, nanocrystals may act as microscopic or spectroscopic labels for elucidating the behavior of complex biomolecular systems. However, success in either of these functions relies heavily uponthe ability to control the conjugation and assembly processes.In the work presented here, we first design a branched DNA scaffold which allows hybridization of DNA-nanocrystal monoconjugates to form discrete assemblies. Importantly, the asymmetry of the branched scaffold allows the formation of asymmetric2assemblies of nanocrystals. In the context of a self-assembled device, this can be considered a step toward the ability to engineer functionally distinct inputs and outputs.Next we develop an anion-exchange high performance liquid chromatography purification method which allows large gold nanocrystals attached to single strands of very short DNA to be purified. When two such complementary conjugates are hybridized, the large nanocrystals are brought into close proximity, allowing their plasmon resonances to couple. Such plasmon-coupled constructs are of interest both as optical interconnects for nanoscale devices and as `plasmon ruler? biomolecular probes.We then present an enzymatic ligation strategy for creating multi-nanoparticle building blocks for self-assembly. In constructing a nanoscale device, such a strategy would allow pre-assembly and purification of components; these constructs can also act as multi-label probes of single-stranded DNA conformational dynamics. Finally we demonstrate a simple proof-of-concept of a nanoparticle analog of the polymerase chain reaction.

  19. The CDS and the Government Bonds Markets During the Last Financial Crisis

    Directory of Open Access Journals (Sweden)

    Križanič France

    2015-11-01

    Full Text Available Financial market had developed a special instrument to insure the buyers of bonds. This instrument is so called Credit Default Swap (CDS. The CDS price is a kind of insurance premium that the buyer of CDS pays to the seller of CDS in exchange for compensation of possible loss in operation. Paper analyses causality between CDS price and dynamics of bond yields and influence of macroeconomic factors on it in four selected countries during the last financial crisis. Analysis results show that there is no important macroeconomic variable included in the analysis that preceded the CDS prices connected with German government bonds. Sellers of CDS were apparently aware of the systemic nature of the financial crisis in the euro area. In the case of the United Kingdom, Russia and Slovenia we can observe the unemployment rate as the most important macroeconomic variable that preceded the CDS prices for government bonds.

  20. Growth and characterization of CdS crystals

    Science.gov (United States)

    Su, Ching-Hua; Lehoczky, S. L.; Szofran, F. R.

    1990-01-01

    A growth method for the physical vapor transport of compound semiconductors in closed ampoules is described. With the unique techniques applied in the heat treatment of the starting materials and the temperature profiles provided by the three-zone translational furnace, large crystals of CdS have been grown successfully by the method at lower temperatures than previously used. Both unseeded and seeded growth have been investigated. The CdS crystals were examined using optical and scanning electron microscopies (SEM) to study the microstructure and the dislocation etch-pits. The crystals were further characterized by infrared (IR) and ultraviolet (UV) transmission measurements.

  1. A CDO option market model on standardized CDS index tranches

    DEFF Research Database (Denmark)

    Dorn, Jochen

    We provide a market model which implies a dynamic for standardized CDS index tranche spreads. This model is useful for pricing options on tranches with future Issue Dates as well as for modeling emerging options on struc- tured credit derivatives. With the upcoming regulation of the CDS market...... in perspective, the model presented here is also an attempt to face the e ects on pricing approaches provoked by an eventual Clearing Chamber . It becomes also possible to calibrate Index Tranche Options with bespoke tenors/tranche subordination to market data obtained by more liquid Index Tranche Options...

  2. Tuning of copper nanocrystals optical properties with their shapes.

    Science.gov (United States)

    Salzemann, C; Brioude, A; Pileni, M-P

    2006-04-13

    Copper nanocrystals are obtained by chemical reduction of copper ions in mixed reverse micelles. A large excess of reducing agent favors producing a new generation of shaped copper nanocrystals as nanodisks, elongated nanocrystals, and cubes. By using UV-Visible spectroscopy and numerical optical simulations we demonstrate that the optical properties are tuned by the relative proportions of spheres and nanodisks.

  3. Metal halide solid-state surface treatment for nanocrystal materials

    Energy Technology Data Exchange (ETDEWEB)

    Luther, Joseph M.; Crisp, Ryan; Beard, Matthew C.

    2016-04-26

    Methods of treating nanocrystal and/or quantum dot devices are described. The methods include contacting the nanocrystals and/or quantum dots with a solution including metal ions and halogen ions, such that the solution displaces native ligands present on the surface of the nanocrystals and/or quantum dots via ligand exchange.

  4. A simple synthesis and characterization of CuS nanocrystals

    Indian Academy of Sciences (India)

    Ujjal K Gautam; Bratindranath Mukherjee

    2006-02-01

    Water-soluble CuS nanocrystals and nanorods were prepared by reacting copper acetate with thioacetamide in the presence of different surfactants and capping agents. The size of the nanocrystals varied from 3–20 nm depending on the reaction parameters such as concentration, temperature, solvent and the capping agents. The formation of nanocrystals was studied by using UV-visible absorption spectroscopy.

  5. Iron Oxide Nanocrystals for Magnetic Hyperthermia Applications

    Directory of Open Access Journals (Sweden)

    Dale L. Huber

    2012-05-01

    Full Text Available Magnetic nanocrystals have been investigated extensively in the past several years for several potential applications, such as information technology, MRI contrast agents, and for drug conjugation and delivery. A specific property of interest in biomedicine is magnetic hyperthermia—an increase in temperature resulting from the thermal energy released by magnetic nanocrystals in an external alternating magnetic field. Iron oxide nanocrystals of various sizes and morphologies were synthesized and tested for specific losses (heating power using frequencies of 111.1 kHz and 629.2 kHz, and corresponding magnetic field strengths of 9 and 25 mT. Polymorphous nanocrystals as well as spherical nanocrystals and nanowires in paramagnetic to ferromagnetic size range exhibited good heating power. A remarkable 30 °C temperature increase was observed in a nanowire sample at 111 kHz and magnetic field of 25 mT (19.6 kA/m, which is very close to the typical values of 100 kHz and 20 mT used in medical treatments.

  6. Titanium nitride: A new Ohmic contact material for n-type CdS

    NARCIS (Netherlands)

    Didden, A.; Battjes, H.; Machunze, R.; Dam, B.; Van de Krol, R.

    2011-01-01

    In devices based on CdS, indium is often used to make Ohmic contacts. Since indium is scarce and expensive, suitable replacement materials need to be found. In this work, we show that sputtered titanium nitride forms an Ohmic contact with n-type CdS. The CdS films, deposited with chemical bath depos

  7. Designer Nanocrystal Materials for Photovoltaics

    Science.gov (United States)

    Kagan, Cherie

    Advances in synthetic methods allow a wide range of semiconductor nanocrystals (NCs) to be tailored in size and shape and to be used as building blocks in the design of NC solids. However, the long, insulating ligands commonly employed in the synthesis of colloidal NCs inhibit strong interparticle coupling and charge transport once NCs are assembled into the solids state as NC arrays. We will describe the range of short, compact ligand chemistries we employ to exchange the long, insulating ligands used in synthesis and to increase interparticle coupling. These ligand exchange processes can have a dramatic influence on NC surface chemistry as well as NC organization in the solids, showing examples of short-range order. Synergistically, we use 1) thermal evaporation and diffusion and 2) wet-chemical methods to introduce extrinsic impurities and non-stoichiometry to passivate surface traps and dope NC solids. NC coupling and doping provide control over the density of states and the carrier type, concentration, mobility, and lifetime, which we characterize by a range of electronic and spectroscopic techniques. We will describe the importance of engineering device interfaces to design NC materials for solar photovoltaics.

  8. Prospects of nanoscience with nanocrystals.

    Science.gov (United States)

    Kovalenko, Maksym V; Manna, Liberato; Cabot, Andreu; Hens, Zeger; Talapin, Dmitri V; Kagan, Cherie R; Klimov, Victor I; Rogach, Andrey L; Reiss, Peter; Milliron, Delia J; Guyot-Sionnnest, Philippe; Konstantatos, Gerasimos; Parak, Wolfgang J; Hyeon, Taeghwan; Korgel, Brian A; Murray, Christopher B; Heiss, Wolfgang

    2015-02-24

    Colloidal nanocrystals (NCs, i.e., crystalline nanoparticles) have become an important class of materials with great potential for applications ranging from medicine to electronic and optoelectronic devices. Today's strong research focus on NCs has been prompted by the tremendous progress in their synthesis. Impressively narrow size distributions of just a few percent, rational shape-engineering, compositional modulation, electronic doping, and tailored surface chemistries are now feasible for a broad range of inorganic compounds. The performance of inorganic NC-based photovoltaic and light-emitting devices has become competitive to other state-of-the-art materials. Semiconductor NCs hold unique promise for near- and mid-infrared technologies, where very few semiconductor materials are available. On a purely fundamental side, new insights into NC growth, chemical transformations, and self-organization can be gained from rapidly progressing in situ characterization and direct imaging techniques. New phenomena are constantly being discovered in the photophysics of NCs and in the electronic properties of NC solids. In this Nano Focus, we review the state of the art in research on colloidal NCs focusing on the most recent works published in the last 2 years.

  9. CdS films deposited by chemical bath under rotation

    Energy Technology Data Exchange (ETDEWEB)

    Oliva-Aviles, A.I., E-mail: aoliva@mda.cinvestav.mx [Centro de Investigacion y de Estudios Avanzados Unidad Merida, Departamento de Fisica Aplicada. A.P. 73-Cordemex, 97310 Merida, Yucatan (Mexico); Patino, R.; Oliva, A.I. [Centro de Investigacion y de Estudios Avanzados Unidad Merida, Departamento de Fisica Aplicada. A.P. 73-Cordemex, 97310 Merida, Yucatan (Mexico)

    2010-08-01

    Cadmium sulfide (CdS) films were deposited on rotating substrates by the chemical bath technique. The effects of the rotation speed on the morphological, optical, and structural properties of the films were discussed. A rotating substrate-holder was fabricated such that substrates can be taken out from the bath during the deposition. CdS films were deposited at different deposition times (10, 20, 30, 40 and 50 min) onto Corning glass substrates at different rotation velocities (150, 300, 450, and 600 rpm) during chemical deposition. The chemical bath was composed by CdCl{sub 2}, KOH, NH{sub 4}NO{sub 3} and CS(NH{sub 2}){sub 2} as chemical reagents and heated at 75 deg. C. The results show no critical effects on the band gap energy and the surface roughness of the CdS films when the rotation speed changes. However, a linear increase on the deposition rate with the rotation energy was observed, meanwhile the stoichiometry was strongly affected by the rotation speed, resulting a better 1:1 Cd/S ratio as speed increases. Rotation effects may be of interest in industrial production of CdTe/CdS solar cells.

  10. SOHO/CDS observations of waves above the network

    NARCIS (Netherlands)

    Gömöry, P.; Rybák, J.; Kucera, A.; Curdt, W.; Wöhl, H.

    2006-01-01

    We analyze temporal variations in the intensities and the Doppler shifts of He i 584.33 Å (chromosphere), Ov 629.73 Å (transition region), and Mg ix 368.07 Å (corona) measured in and above chromospheric network near disk center with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Hel

  11. The Learning Management System Evolution. CDS Spotlight Report. Research Bulletin

    Science.gov (United States)

    Lang, Leah; Pirani, Judith A.

    2014-01-01

    This Spotlight focuses on data from the 2013 Core Data Service (CDS) to better understand how higher education institutions approach learning management systems (LMSs). Information provided for this Spotlight was derived from Module 8 of the Core Data Service, which contains several questions regarding information systems and applications.…

  12. Ag nanoparticle mediated growth of CdS nanobelts

    Energy Technology Data Exchange (ETDEWEB)

    Sreejith, K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai (India)]. E-mail: ksreeju@rediffmail.com; Nuwad, J. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai (India); Thinaharan, C. [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai (India); Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai (India); Pillai, C.G.S. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai (India)

    2007-06-30

    Catalytic growth of CdS have been carried out on large scale by evaporation of bulk CdS on Ag deposited Si (1 1 1) at atmospheric pressure. The as prepared CdS had wurtzite structure as evidenced by X-ray diffraction. The nanostructures were beltlike with several tens of micrometers length, several micrometers width and few nanometers to tens of nanometers thick as seen by scanning electron microscope and confirmed by TEM studies. The nanobelts were single crystalline in nature and showed reflection corresponding to (1 1 2) and (0 0 2) planes in SAED. The PL studies revealed the green band due to band gap emission and red band due to emission from the surface states. The higher intensity of the defect emission indicated the presence of considerable concentration of surface defects in the as prepared sample. The deposition of CdS could be explained on the basis of catalyst assisted vapor-liquid-solid and vapor-solid mechanism.

  13. Ag nanoparticle mediated growth of CdS nanobelts

    Science.gov (United States)

    Sreejith, K.; Nuwad, J.; Thinaharan, C.; Dey, G. K.; Pillai, C. G. S.

    2007-06-01

    Catalytic growth of CdS have been carried out on large scale by evaporation of bulk CdS on Ag deposited Si (1 1 1) at atmospheric pressure. The as prepared CdS had wurtzite structure as evidenced by X-ray diffraction. The nanostructures were beltlike with several tens of micrometers length, several micrometers width and few nanometers to tens of nanometers thick as seen by scanning electron microscope and confirmed by TEM studies. The nanobelts were single crystalline in nature and showed reflection corresponding to (1 1 2) and (0 0 2) planes in SAED. The PL studies revealed the green band due to band gap emission and red band due to emission from the surface states. The higher intensity of the defect emission indicated the presence of considerable concentration of surface defects in the as prepared sample. The deposition of CdS could be explained on the basis of catalyst assisted vapor-liquid-solid and vapor-solid mechanism.

  14. Gold nanocrystals with DNA-directed morphologies

    Science.gov (United States)

    Ma, Xingyi; Huh, June; Park, Wounjhang; Lee, Luke P.; Kwon, Young Jik; Sim, Sang Jun

    2016-09-01

    Precise control over the structure of metal nanomaterials is important for developing advanced nanobiotechnology. Assembly methods of nanoparticles into structured blocks have been widely demonstrated recently. However, synthesis of nanocrystals with controlled, three-dimensional structures remains challenging. Here we show a directed crystallization of gold by a single DNA molecular regulator in a sequence-independent manner and its applications in three-dimensional topological controls of crystalline nanostructures. We anchor DNA onto gold nanoseed with various alignments to form gold nanocrystals with defined topologies. Some topologies are asymmetric including pushpin-, star- and biconcave disk-like structures, as well as more complex jellyfish- and flower-like structures. The approach of employing DNA enables the solution-based synthesis of nanocrystals with controlled, three-dimensional structures in a desired direction, and expands the current tools available for designing and synthesizing feature-rich nanomaterials for future translational biotechnology.

  15. Shaping metal nanocrystals through epitaxial seeded growth

    Energy Technology Data Exchange (ETDEWEB)

    Habas, Susan E.; Lee, Hyunjoo; Radmilovic, Velimir; Somorjai,Gabor A.; Yang, Peidong

    2008-02-17

    Morphological control of nanocrystals has becomeincreasingly important, as many of their physical and chemical propertiesare highly shape-dependent. Nanocrystal shape control for both single andmultiple material systems, however, remains fairly empirical andchallenging. New methods need to be explored for the rational syntheticdesign of heterostructures with controlled morphology. Overgrowth of adifferent material on well-faceted seeds, for example, allows for the useof the defined seed morphology to control nucleation and growth of thesecondary structure. Here, we have used highly faceted cubic Pt seeds todirect the epitaxial overgrowth of a secondary metal. We demonstrate thisconcept with lattice matched Pd to produce conformal shape-controlledcore-shell particles, and then extend it to lattice mismatched Au to giveanisotropic growth. Seeding with faceted nanocrystals may havesignificant potential towards the development of shape-controlledheterostructures with defined interfaces.

  16. The structure and morphology of semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Kadavanich, Andreas V. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1997-11-01

    Colloidal semiconductor nanocrystals were studied using High Resolution Transmission Electron Microscopy (HRTEM). Organically capped nanocrystals were found to have faceted shapes consistent with Wulff polyhedra after the effects of capping ligands on surface energies were taken into account. The basic shape thus derived for wurtzite (WZ) structure CdSe nanocrystals capped by tri-octyl phosphine oxide (TOPO) was a truncated hexagonal prism, elongated alone the <001> axis with (100) and (002) facets. This structure has C{sub 3v} point group symmetry. The main defect in this structure is a stacking fault (a single layer of zinc blende type stacking), which does not significantly affect the shape (does not alter the point group).

  17. Crystallization and Growth of Colloidal Nanocrystals

    CERN Document Server

    Leite, Edson Roberto

    2012-01-01

    Since the size, shape, and microstructure of nanocrystalline materials strongly impact physical and chemical properties, the development of new synthetic routes to  nanocrystals with controlled composition and morphology is a key objective of the nanomaterials community. This objective is dependent on control of the nucleation and growth mechanisms that occur during the synthetic process, which in turn requires a fundamental understanding of both classical nucleation and growth and non-classical growth processes in nanostructured materials.  Recently, a novel growth process called Oriented Attachment (OA) was identified which appears to be a fundamental mechanism during the development of nanoscale  materials. OA is a special case of aggregation that provides an important route by which nanocrystals grow, defects are formed, and unique—often symmetry-defying—crystal morphologies can be produced. This growth mechanism involves reversible self-assembly of primary nanocrystals followed by reorientati...

  18. Developing New Nanoprobes from Semiconductor Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Aihua [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    In recent years, semiconductor nanocrystal quantum dots havegarnered the spotlight as an important new class of biological labelingtool. Withoptical properties superior to conventional organicfluorophores from many aspects, such as high photostability andmultiplexing capability, quantum dots have been applied in a variety ofadvanced imaging applications. This dissertation research goes along withlarge amount of research efforts in this field, while focusing on thedesign and development of new nanoprobes from semiconductor nanocrystalsthat are aimed for useful imaging or sensing applications not possiblewith quantum dots alone. Specifically speaking, two strategies have beenapplied. In one, we have taken advantage of the increasing capability ofmanipulating the shape of semiconductor nanocrystals by developingsemiconductor quantum rods as fluorescent biological labels. In theother, we have assembled quantum dots and gold nanocrystals into discretenanostructures using DNA. The background information and synthesis,surface manipulation, property characterization and applications of thesenew nanoprobes in a few biological experiments are detailed in thedissertation.

  19. The Intercalibration of SOHO EIT, CDS-NIS, and TRACE

    Science.gov (United States)

    Brooks, David H.; Warren, Harry P.

    2006-05-01

    Using coordinated observations of a quiet coronal region, we study the intercalibration of the CDS and EIT instruments on board the Solar and Heliospheric Observatory (SOHO) and the Transition Region and Coronal Explorer (TRACE). We derive the differential emission measure (DEM) distribution from CDS spectral line intensities and convolve it with EIT and TRACE temperature response functions, calculated with the latest atomic data from the CHIANTI database, to predict count rates in their observing channels. We examine different analysis methods and briefly discuss some more advanced aspects of atomic modeling such as the density dependence of the ionization fractions. We investigate the implications for our study using data from the ADAS database. We find that our CDS DEM can predict the TRACE and EIT 171 and 195 Å channel count rates to within 25%. However, the accuracy of the predictions depends on the ionization fractions and elemental abundances used. The TRACE 284 Å and EIT 284 and 304 Å filter predictions do not agree well with the observations, even after taking the contribution from the optically thick He II 304 Å line to the TRACE 284 Å channel into account. The different CDS DEM solutions we derive using different ionization fractions produce fairly similar results: the majority of the CDS line intensities used are reproduced to within 20% with only around one-fifth reproduced to worse than 50%. However, the comparison provides us with further clues with which to explain the discrepancies found for some lines, and highlights the need for accurate equilibrium ionization balance calculations even at low density.

  20. Cloning nanocrystal morphology with soft templates

    Science.gov (United States)

    Thapa, Dev Kumar; Pandey, Anshu

    2016-08-01

    In most template directed preparative methods, while the template decides the nanostructure morphology, the structure of the template itself is a non-general outcome of its peculiar chemistry. Here we demonstrate a template mediated synthesis that overcomes this deficiency. This synthesis involves overgrowth of silica template onto a sacrificial nanocrystal. Such templates are used to copy the morphologies of gold nanorods. After template overgrowth, gold is removed and silver is regrown in the template cavity to produce a single crystal silver nanorod. This technique allows for duplicating existing nanocrystals, while also providing a quantifiable breakdown of the structure - shape interdependence.

  1. Aerosol printing of colloidal nanocrystals by aerodynamic focusing

    Science.gov (United States)

    Qi, Lejun

    Colloidal semiconductor nanocrystals, or quantum dots, have shown promise as the active material in electronic and optoelectronic applications, because of their high quantum yield, narrow spectral emission band, size-tunable bandgap, chemical stability, and easy processibility. Meanwhile, it is still challenging to print patterns of nanocrystal films with desired linewidth and thickness, which is a critical step in fabrication of nanocrystal-based devices. In this thesis, a direct-write method of colloidal semiconductor nanocrystals has been developed. Like other direct-write techniques, this aerosol based method simplifies printing process and reduces the manufacturing cost, as it avoids mask screening, lithography, and pre-patterning of the substrate. Moreover, the aerosol printing with aerodynamic lenses needs neither microscale nozzles nor sheath gases, and is able to incorporate into the vacuum systems currently used in microelectronic fabrication. This thesis research presents systematic efforts to develop an aerosol-based method to directly write patterns of semiconductor nanocrystals from colloidal dispersions by aerodynamic focusing. First, the synthesized colloidal nanocrystals in hexane were nebulized into compact and spherical agglomerates suspending in the carrier gas. The details about the impact dynamics of individual aerosolized nanocrystal agglomerates were investigated. As building blocks of printed nanocrystal films, the agglomerate exhibited cohesive and granular behaviors during impact deformation on the substrate. The strength of cohesion between nanocrystals in the agglomerates could be adjusted by tuning the number concentration of colloidal nanocrystal dispersion. Second, ultrathin films of nanocrystals were obtained by printing monodisperse nanocrystal agglomerates. As the result of the granular property of nanocrystal agglomerates, it was found that the thickness of deposited agglomerates strongly depended on the size of agglomerates. A

  2. The fluorescence quenching mechanism of coumarin 120 with CdS nanoparticles in aqueous suspension

    Energy Technology Data Exchange (ETDEWEB)

    Acar, Murat; Bozkurt, Ebru; Meral, Kadem; Arık, Mustafa; Onganer, Yavuz, E-mail: yonganer@atauni.edu.tr

    2015-01-15

    The interaction of coumarin 120 (C120) with CdS nanoparticles (CdS NPs) in aqueous suspension was examined by using UV–vis absorption, steady-state, time-resolved fluorescence, and electron paramagnetic resonance (EPR) spectroscopy techniques. The fluorescence intensity of C120 was quenched with increasing the amount of CdS NPs in the aqueous suspension. The spectroscopic data revealed that the C120 molecules adsorbed on CdS NPs via electrostatic interactions. The apparent association constant (K{sub app}) and the degree of association (α) for C120/CdS NPs were determined as 130.3 M{sup −1} and 0.51 for 4 nm CdS NPs and 624.3 M{sup −1} and 0.71 for 8 nm CdS NPs, respectively. The photoinduced EPR studies exhibited that no electron transfers between CdS and C120 taking place. The results revealed that the fluorescence quenching of C120 with different CdS NPs is due to the formation of a non-fluorescent complex. - Highlights: • Interaction of C120 with CdS NPs in aqueous solution was spectroscopically examined. • Nonfluorescent C120–CdS NPs complexes in aqueous solution were formed. • In the system, CdS NPs in aqueous solution acted as a fluorescence quencher.

  3. An optimized multilayer structure of CdS layer for CdTe solar cells application

    Energy Technology Data Exchange (ETDEWEB)

    Han Junfeng, E-mail: pkuhjf@gmail.com [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Road Yiheyuan 5, Beijing 100871 (China); Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany); Liao Cheng, E-mail: Cliao@pku.edu.cn [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Road Yiheyuan 5, Beijing 100871 (China); Jiang Tao [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Road Yiheyuan 5, Beijing 100871 (China); Spanheimer, C.; Haindl, G.; Fu, Ganhua; Krishnakumar, V. [Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany); Zhao Kui [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Road Yiheyuan 5, Beijing 100871 (China); Klein, A.; Jaegermann, W. [Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany)

    2011-04-28

    Research highlights: > Two different methods to prepare CdS films for CdTe solar cells. > A new multilayer structure of window layer for the CdTe solar cell. > Thinner CdS window layer for the solar cell than the standard CdS layer. > Higher performance of solar cells based on the new multilayer structure. - Abstract: CdS layers grown by 'dry' (close space sublimation) and 'wet' (chemical bath deposition) methods are deposited and analyzed. CdS prepared with close space sublimation (CSS) has better crystal quality, electrical and optical properties than that prepared with chemical bath deposition (CBD). The performance of CdTe solar cell based on the CSS CdS layer has higher efficiency than that based on CBD CdS layer. However, the CSS CdS suffers from the pinholes. And consequently it is necessary to prepare a 150 nm thin film for CdTe/CdS solar cell. To improve the performance of CdS/CdTe solar cells, a thin multilayer structure of CdS layer ({approx}80 nm) is applied, which is composed of a bottom layer (CSS CdS) and a top layer (CBD CdS). That bi-layer film can allow more photons to pass through it and significantly improve the short circuit current of the CdS/CdTe solar cells.

  4. Comportamiento óptico no-lineal de nanocristales semiconductores de CdS en una matriz de gel de sílice

    Directory of Open Access Journals (Sweden)

    de la Rosa-Fox, N.

    2000-06-01

    Full Text Available Nanocrystals embedded in a dielectric matrix can be obtained through sol-gel method, it permits the control of several kinetic parameters during the nanocrystal growth. The size and size distribution have been studied by means small-angle neutron scattering techniques (SANS, that allow a spatial resolution from 1 to 50 nm. High intensity optical excitation from a Nd:YAG laser (6 ns pulse at 10 Hz repetition rate was focused on the sample to study the photoluminescence yield at rigth angle. The spectrum shows radiative process from intrinsic transitions (2.76 eV and a broad band in the lower energy side (1.65 eV that correspond to crystal surface traps. The photoluminescence yield grows superlineary giving rise to amplified intensity (60 cm-1 due to biexciton species, this fact can be interpreted as a non-linear optical behaviour coming from the CdS nanocrystals.

    La inclusión de nanocristales en una matriz dieléctrica puede realizarse mediante el método sol-gel, permitiendo el control de parámetros cinéticos en el crecimiento de los cristales. El tamaño y distribución de dichos nanocristales se han estudiado por medio de difusión de neutrones a bajo ángulo (SANS, con una resolución espacial entre 1 y 50 nm. Bajo excitación óptica de alta intensidad, usando un láser (Nd:YAG con pulsos de 6 ns y una frecuencia de repetición de 10 Hz, se focalizó en la muestra para registrar la señal de fotoluminiscencia en la dirección perpendicular. El espectro indica procesos radiativos debidos a transiciones intrínsecas (2.76 eV y una banda ancha a más baja energía (1.65 eV correspondiente a recombinaciones en los defectos superficiales. La señal de fotoluminiscencia crece superlinealmente dando lugar a una amplificación (60 cm-1 debida principalmente a biexcitones que indican un comportamiento óptico no-lineal de los nanocristales de CdS.

  5. Epitaxial overgrowth of platinum on palladium nanocrystals

    Science.gov (United States)

    Jiang, Majiong; Lim, Byungkwon; Tao, Jing; Camargo, Pedro H. C.; Ma, Chao; Zhu, Yimei; Xia, Younan

    2010-11-01

    This paper describes a systematic study on the epitaxial overgrowth of Pt on well-defined Pd nanocrystals with different shapes (and exposed facets), including regular octahedrons, truncated octahedrons, and cubes. Two different reducing agents, i.e., citric acid and L-ascorbic acid, were evaluated and compared for the reduction of K2PtCl4 in an aqueous solution in the presence of Pd nanocrystal seeds. When citric acid was used as a reducing agent, conformal overgrowth of octahedral Pt shells on regular and truncated octahedrons of Pd led to the formation of Pd-Pt core-shell octahedrons, while non-conformal overgrowth of Pt on cubic Pd seeds resulted in the formation of an incomplete octahedral Pt shell. On the contrary, localized overgrowth of Pt branches was observed when L-ascorbic acid was used as a reducing agent regardless of the facets expressed on the surface of Pd nanocrystal seeds. This work shows that both the binding affinity of a reducing agent to the Pt surface and the reduction kinetics for a Pt precursor play important roles in determining the mode of Pt overgrowth on Pd nanocrystal surface.

  6. Thick-shell nanocrystal quantum dots

    Science.gov (United States)

    Hollingsworth, Jennifer A.; Chen, Yongfen; Klimov, Victor I.; Htoon, Han; Vela, Javier

    2011-05-03

    Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes.

  7. Organization of 'nanocrystal molecules' using DNA

    Science.gov (United States)

    Alivisatos, A. Paul; Johnsson, Kai P.; Peng, Xiaogang; Wilson, Troy E.; Loweth, Colin J.; Bruchez, Marcel P.; Schultz, Peter G.

    1996-08-01

    PATTERNING matter on the nanometre scale is an important objective of current materials chemistry and physics. It is driven by both the need to further miniaturize electronic components and the fact that at the nanometre scale, materials properties are strongly size-dependent and thus can be tuned sensitively1. In nanoscale crystals, quantum size effects and the large number of surface atoms influence the, chemical, electronic, magnetic and optical behaviour2-4. 'Top-down' (for example, lithographic) methods for nanoscale manipulation reach only to the upper end of the nanometre regime5; but whereas 'bottom-up' wet chemical techniques allow for the preparation of mono-disperse, defect-free crystallites just 1-10 nm in size6-10, ways to control the structure of nanocrystal assemblies are scarce. Here we describe a strategy for the synthesis of'nanocrystal molecules', in which discrete numbers of gold nanocrystals are organized into spatially defined structures based on Watson-Crick base-pairing interactions. We attach single-stranded DNA oligonucleotides of defined length and sequence to individual nanocrystals, and these assemble into dimers and trimers on addition of a complementary single-stranded DNA template. We anticipate that this approach should allow the construction of more complex two-and three-dimensional assemblies.

  8. Atomic force microscopy characterization of cellulose nanocrystals

    Science.gov (United States)

    Roya R. Lahiji; Xin Xu; Ronald Reifenberger; Arvind Raman; Alan Rudie; Robert J. Moon

    2010-01-01

    Cellulose nanocrystals (CNCs) are gaining interest as a “green” nanomaterial with superior mechanical and chemical properties for high-performance nanocomposite materials; however, there is a lack of accurate material property characterization of individual CNCs. Here, a detailed study of the topography, elastic and adhesive properties of individual wood-derived CNCs...

  9. Silicon nanocrystal films for electronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Lechner, Robert W.

    2009-02-06

    Whether nanoparticles of silicon are really suited for such applications, whether layers fabricated from this exhibit semiconducting properties, whether they can be doped, and whether for instance via the doping the conductivity can be tuned, was studied in the present thesis. Starting material for this were on the one hand spherical silicon nanocrystals with a sharp size distribution and mean diameters in the range from 4-50 nm. Furthermore silicon particle were available, which are with 50-500 nm distinctly larger and exhibit a broad distribution of the mean size and a polycrystalline fine structure with strongly bifurcated external morphology. The small conductivities and tje low mobility values of the charge carriers in the layers of silicon nanocrystals suggest to apply suited thermal after-treatment procedures. So was found that the aluminium-induced layer exchange (ALILE) also can be transferred to the porous layers of nanocrystals. With the deuteron passivation a method was available to change the charge-carrier concentration in the polycrystalline layers. Additionally to ALILE laser crystallization as alternative after-treatment procedure of the nanocrystal layers was studied.

  10. Effects of Cu-Doped on Structure and Photoluminescence of CdS Thin Films and Property of CdS/CdTe Solar Cells%Cu掺杂对CdS薄膜结构、光致发光及CdS/CdTe电池性能的影响

    Institute of Scientific and Technical Information of China (English)

    杨军; 杨瑞龙; 白治中; 王德亮

    2013-01-01

    采用化学浴沉积(CBD)法在FTO(SnO2∶F)/Glass衬底上制备了Cu掺杂的CdS薄膜.用电感耦合等离子体-原子发射光谱(ICP-AES)测得不同Cu掺杂浓度的薄膜中Cu/Cd原子比分别为0.5%、1.5%、5%.分别用X射线衍射(XRD)、扫描电镜(SEM)、光致发光谱(PL)、紫外-可见-近红外反射透射谱对薄膜样品进行表征.研究了Cu掺杂对CdS薄膜的晶体结构,微观形貌以及体内点缺陷的影响.用Cu掺杂的CdS薄膜作为N型层制备CdTe太阳能电池,研究了CdS层中Cu对电池性能的影响.

  11. Dielectric Properties of CDS Nanoparticles Synthesized by Soft Chemical Route

    Indian Academy of Sciences (India)

    R Tripathi; A Kumar; T P Sinha

    2009-06-01

    CdS nanoparticles have been synthesized by a chemical reaction route using thiophenol as a capping agent. The frequency-dependent dielectric dispersion of cadmium sulphide (CdS) is investigated in the temperature range of 303–413 K and in a frequency range of 50 Hz–1 MHz by impedance spectroscopy. An analysis of the complex per-mittivity ( and ) and loss tangent (tan ) with frequency is performed by assuming a distribution of relaxation times. The scaling behaviour of dielectric loss spectra sug- gests that the relaxation describes the same mechanism at various temperatures. The frequency-dependent electrical data are analysed in the framework of conductivity and modulus formalisms. The frequency-dependent conductivity spectra obey the power law.

  12. Studies of heat treated CSS CdS films

    Science.gov (United States)

    Marinskiy, D.; Marinskaya, S.; Viswanathan, V.; Morel, D. L.; Ferekides, C. S.

    1999-03-01

    Cadmium sulfide continues to be the most successful and widely used n-type heterojunction partner in thin film CdTe solar cells. In most cases solar cell performance is enhanced if the CdS films are heat treated prior to the deposition of the CdTe. This paper discusses the effect of H2 annealing on the resistivity of CSS-CdS films and the use of a mobility activation model to explain the observed changes in resistivity. Photoluminescence measurements of CSS CdS films heat-treated in He and in CdCl2 vapor have also been carried out. In all cases the heat treatments lead to an increase in the intensity of a photoluminescence band believed to be associated with sulfur vacancies.

  13. Novel applications of semiconductor nanocrystals

    Science.gov (United States)

    Lau, Pick Chung

    We have investigated ways of modifying a common water soluble CdTe NCs to become non-photobleaching. Such NCs are capable of responding reversibly to an inter-switching of the oxygen and argon environments over multiple hours of photoexcitation. They are found to quench upon exposure to oxygen, but when the system is purged with argon, their photoluminescence (PL) revives to the original intensity. Such discovery could potentially be used as oxygen nanosensors. These PL robust CdTe NCs immobilized on glass substrates also exhibit significant changes in their PL when certain organic/bio molecules are placed in their vicinity (nanoscale). This novel technique also known as NC-organic molecule close proximity imaging (NC-cp imaging) has found to provide contrast ratio greater by a factor of 2-3 compared to conventional fluorescence imaging technique. PL of NCs is recoverable upon removal of these organic molecules, therefore validating these NCs as potential all-optical organic molecular nanosensors and, upon optimization, ultimately serving as point detectors for purposes of super-resolution microscopy (with proper instrumentation). No solvents are required for this sensing mechanism since all solutions were dried under argon flow. Furthermore, core graded shell CdSe/CdSexS1-x/CdS giant nanocrystal (g-NCs) were found to have very robust PL temperature response. At a size of 10.2 nm in diameter, these g-NCs undergo PL drop of only 30% at 355K (normalized to PL intensity at 85K). In comparison, the core step shells CdSe/CdS g-NCs at the same diameter exhibit 80% PL drop at 355K. Spectral shifting and broadening were acquired and found to be 5-10 times and 2-4 times smaller respectively than the standard CdSe core and CdSe/CdS core shell NCs. It is also discovered that these core graded shell g-NCs are largely nonblinking and have insignificant photoluminescence decay even after exciting the samples at very high irradiance (44 kW/cm2) for over an hour. These types of g

  14. Re-dispersible Li+ and Eu3+ co-doped CdS nanoparticles: Luminescence studies

    Indian Academy of Sciences (India)

    N S Gajbhiye; Raghumani Singh Ninghoujam; Asar Ahmed; D K Panda; S S Umare; S J Sharma

    2008-02-01

    Re-dispersible CdS, 5 at.% Eu3+-doped CdS, 2 at.% Li+ and 5 at.% Eu3+ co-doped CdS nanoparticles in organic solvent are prepared by urea hydrolysis in ethylene glycol medium at a low temperature of 170°C. CdS nanoparticles have spherical shape with a diameter of ∼ 80 nm. The asymmetric ratio (21) of the integrated intensities of the electrical dipole transition to the magnetic dipole transition for 5 at.% Eu3+-doped CdS is found to be 3.8 and this ratio is significantly decreased for 2 at.% Li+ and 5 at.% Eu3+ co-doped CdS (21 = 2.6). It establishes that the symmetry environment of Eu3+ ion is more favored by Li-doping. Extra peak at 550 nm (green emission) could be seen for 2 and 5 at.% Eu3+ co-doped CdS. Also, the significant energy transfer from host CdS to Eu3+ is found for 5 at.% Eu3+-doped CdS compared to that for 2 at.% Li+ and 5 at.% Eu3+ co-doped CdS.

  15. CDS/ISIS系统的输出

    Institute of Scientific and Technical Information of China (English)

    冯汇波

    1995-01-01

    介绍利用CDS/ISIS PASCAL语言开发的一个显示打印模块,它具有随意浏览、联机打印功能,并对ISIS PASCAL语言中一些资料中未说明而在程序设计中需要加以注意的问题作了阐述.

  16. The liquidity premium in CDS transaction prices: Do frictions matter?

    OpenAIRE

    Gehde-Trapp, Monika; Gündüz, Yalin; Nasev, Julia

    2015-01-01

    Based on individual CDS transactions cleared by the Depository Trust & Clearing Corporation, we show that illiquidity strongly affects credit default swap premiums. We identify the following effects: First, transaction direction affects prices, as buy (sell) orders lead to premium increases (decreases). Second, larger transactions have a higher price impact. This finding stands in stark contrast to corporate bond markets. Third, traders charge higher premiums as a price for liquidity provisio...

  17. Nonradiative and Radiative Recombination in CdS Polycrystalline Structures

    Directory of Open Access Journals (Sweden)

    E. Gaubas

    2013-01-01

    Full Text Available Properties of polycrystalline CdS layers, employed in formation of the CdS-Cu2S heterostructures, have been studied by combining contactless techniques of the time and spectrally resolved photoluminescence (TR-PL spectroscopy and microwave-probed photoconductivity (MW-PC transients. The confocal microscopy has been employed to correlate the homogeneity of photoluminescence and grain size in CdS layers. Three types of samples with crystallite grain size of <1 μm (the I-type and of 2–10 μm of homogeneous (II-type and inhomogeneous (III-type grain distribution have been separated. The simultaneous record of MW-PC and TR-PL responses ensures the same sampling area on the layer under investigation, as both (MW-PC and TR-PL signals are generated by the same UV laser excitation beam. Two PL bands peaked at 500 and 700 nm were revealed. It has been demonstrated that photoluminescence intensity strongly depends on the properties of the polycrystalline 15–26 μm thick CdS layers with equilibrium carrier density of about 1.5×1013 cm−3, which serve as the substrates to form CdS-Cu2S junctions. The different carrier decay components were ascribed to different microareas with characteristic MW-PC and PL decay lifetimes of 2–10 ns, ascribed to microcrystallites with PL instantaneous decay lifetimes of 40–200 ns, and MW-PC decay lifetimes in the range of 100–1000 μs attributed to the inter-crystallite areas of CdS polycrystalline material.

  18. Structure and transformation of tactoids in cellulose nanocrystal suspensions

    Science.gov (United States)

    Wang, Pei-Xi; Hamad, Wadood Y.; MacLachlan, Mark J.

    2016-05-01

    Cellulose nanocrystals obtained from natural sources are of great interest for many applications. In water, cellulose nanocrystals form a liquid crystalline phase whose hierarchical structure is retained in solid films after drying. Although tactoids, one of the most primitive components of liquid crystals, are thought to have a significant role in the evolution of this phase, they have evaded structural study of their internal organization. Here we report the capture of cellulose nanocrystal tactoids in a polymer matrix. This method allows us to visualize, for the first time, the arrangement of cellulose nanocrystals within individual tactoids by electron microscopy. Furthermore, we can follow the structural evolution of the liquid crystalline phase from tactoids to iridescent-layered films. Our insights into the early nucleation events of cellulose nanocrystals give important information about the growth of cholesteric liquid crystalline phases, especially for cellulose nanocrystals, and are crucial for preparing photonics-quality films.

  19. Performance and Reliability of Multilayer Silicon Nanocrystal Nonvolatile Memory

    Institute of Scientific and Technical Information of China (English)

    WANG Liudi; ZHANG Zhigang; ZHAO Yue; MAO Ping; PAN Liyang

    2009-01-01

    Nonvolatile memories (NVMs) with triple layers of silicon nanocrystals were fabricated with conventional CMOS technology.This paper explores the program/erase performance and reliability of NVMs with three layers of nanocrystals.The results indicate that the nanocrystals in the triple-layer nanocrystal NVM (NCNVM) are difficult to fully charge during the programming process.The programming speed of the triple-layer NCNVMs is quicker than that of single-layer NCNVMs,which means that the second and third layers of nanocrystals in the triple-layer NCNVM affect the charge of the first layer nanocrystals.Reliability tests show that the memory window has little degradation after 1×104 cycles.

  20. Nonthermal Plasma Synthesis of Nanocrystals: Fundamental Principles, Materials, and Applications.

    Science.gov (United States)

    Kortshagen, Uwe R; Sankaran, R Mohan; Pereira, Rui N; Girshick, Steven L; Wu, Jeslin J; Aydil, Eray S

    2016-09-28

    Nonthermal plasmas have emerged as a viable synthesis technique for nanocrystal materials. Inherently solvent and ligand-free, nonthermal plasmas offer the ability to synthesize high purity nanocrystals of materials that require high synthesis temperatures. The nonequilibrium environment in nonthermal plasmas has a number of attractive attributes: energetic surface reactions selectively heat the nanoparticles to temperatures that can strongly exceed the gas temperature; charging of nanoparticles through plasma electrons reduces or eliminates nanoparticle agglomeration; and the large difference between the chemical potentials of the gaseous growth species and the species bound to the nanoparticle surfaces facilitates nanocrystal doping. This paper reviews the state of the art in nonthermal plasma synthesis of nanocrystals. It discusses the fundamentals of nanocrystal formation in plasmas, reviews practical implementations of plasma reactors, surveys the materials that have been produced with nonthermal plasmas and surface chemistries that have been developed, and provides an overview of applications of plasma-synthesized nanocrystals.

  1. Hydrophobic starch nanocrystals preparations through crosslinking modification using citric acid.

    Science.gov (United States)

    Zhou, Jiang; Tong, Jin; Su, Xingguang; Ren, Lili

    2016-10-01

    Biodegradable starch nanocrystals prepared by an acid treatment process were modified through crosslinking modification using citric acid as reactant by a dry reaction method. The occurrence of crosslinking modification was evaluated by Fourier transform infrared spectroscopy and swelling degree. X-ray diffraction, wettability tests and contact angle measurements were used to characterize the modified starch nanocrystals. It was found that the crosslinked starch nanocrystals displayed a higher affinity for low polar solvents such as dichloromethane. The surface of starch nanocrystals became more roughness after crosslinking modification with citric acid and the size decreased as revealed by scanning electron microscopy and dynamic light scattering results. XRD analysis showed that the crystalline structure of starch nanocrystals was basically not changed after the crosslinking modification with shorter heating time. The resulting hydrophobic starch nanocrystals are versatile precursors to the development of nanocomposites.

  2. Observation of Single Colloidal Platinum Nanocrystal Growth Trajectories

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Haimei; Smith, Rachel; Jun, Young-wook; Kisielowski, Christian; Dahmen, Ulrich; Alivisatos, A. Paul

    2009-02-09

    It is conventionally assumed that the growth of monodisperse colloidal nanocrystals requires a temporally discrete nucleation followed by monomer attachment onto the existing nuclei. However, recent studies have reported violations of this classical growth model, and have suggested that inter-particle interactions are also involved during the growth. Mechanisms of nanocrystal growth still remain controversial. Using in situ transmission electron microscopy, we show that platinum nanocrystals can grow either by monomer attachment from solution onto the existing particles or by coalescence between the particles. Surprisingly, an initially broad size distribution of the nanocrystals can spontaneously narrow. We suggest that nanocrystals take different pathways of growth based on their size- and morphology-dependent internal energies. These observations are expected to be highly relevant for other nanocrystal systems.

  3. Synthesis and Surface Modification of CdTe Nanocrystals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    CdTe nanocrystals were prepared in aqueous solution via the reaction between Cd2+ and NaHTe in the presence of mercaptoacetic acid. Interactions between CdTe nanocrystals and phenylalanine were formed via electrostatic/coordinate self-assembly. The photoluminescence intensity of CdTe nanocrystals was improved obviously. The interaction mechanism was discussed and was considered to be surface passivation.

  4. Positron studies of surfaces, structure and electronic properties of nanocrystals

    OpenAIRE

    Eijt, S. W. H.; Barbiellini, B.; Houtepen, A.J.; Vanmaekelbergh, D.; Mijnarends, P. E.; Bansil, A.

    2007-01-01

    A brief review is given of recent positron studies of metal and semiconductor nanocrystals. The prospects offered by positron annihilation as a sensitive method to access nanocrystal (NC) properties are described and compared with other experimental methods. The tunability of the electronic structure of nanocrystals underlies their great potential for application in many areas. Owing to their large surface-to-volume ratio, the surfaces and interfaces of NCs play a crucial role in determining ...

  5. Electroluminescence of Si Nanocrystal-Doped SiO2

    Institute of Scientific and Technical Information of China (English)

    CHEN Dan; XIE Zhi-Qiang; WU Qian; ZHAO You-Yuan; LU Ming

    2007-01-01

    @@ We perform a comparative study on the electroluminescence (EL) and photoluminescence (PL) of Si nanocrystaldoped SiO2 (nc-Si:SiO2) and SiO2, and clarify whether the contribution from Si nanocrystals in the EL of nc-Si:SiO2 truly exists. The results unambiguously indicate the presence of EL of Si nanocrystals. The difference of peak positions between the EL and PL spectra are discussed. It is found that the normal method of passivation to enhance the PL of Si nanocrystals is not equally effective for the EL, hence new methods need to be explored to promote the EL of Si nanocrystals.

  6. Spectroscopy of intraband optical transitions in anisotropic semiconductor nanocrystals

    Science.gov (United States)

    Turkov, Vadim K.; Baimuratov, Anvar S.; Rukhlenko, Ivan D.; Baranov, Alexander V.; Fedorov, Anatoly V.

    2013-09-01

    We propose a new type of optical spectroscopy of anisotropic semiconductor nanocrystals, which is based on the welldeveloped stationary pump-probe technique, where the pump and probe fields are absorbed upon, respectively, interband and intraband transitions of the nanocrystals' electronic subsystem. We develop a general theory of intraband absorption based on the density matrix formalism. This theory can be applied to study degenerate eigenstates of electrons in semiconductor nanocrystals of different shapes and dimentions. We demonstrate that the angular dependence of intraband absorption by nonspherical nanocrystals enables investigating their shape and orientation, as well as the symmetry of quantum states excited by the probe field and selection rules of electronic transitions.

  7. Ultrasound-assisted microwave preparation of Ag-doped CdS nanoparticles.

    Science.gov (United States)

    Ma, Jun; Tai, Guo'an; Guo, Wanlin

    2010-03-01

    Ag-doped CdS nanoparticles were synthesized by an ultrasound-assisted microwave synthesis method. The X-ray diffraction patterns reveal a structural evolution from cubic to hexagonal with increasing molar ratios of Ag(+)/Cd(2+) from 0% to 5%. It shows that the Ag-doped hexagonal CdS nanoparticles are polycrystal. The X-ray photoelectron spectroscopy of the CdS nanoparticles doping with 5% Ag(+) shows that the doped Ag in CdS is metallic. Simultaneously, the characteristic Raman peaks of the CdS nanoparticles enhance with increasing Ag(+) concentrations. The photocatalytic activity of different Ag-doped samples show a reasonable change due to different ratios of Ag which doped into CdS. Copyright 2009 Elsevier B.V. All rights reserved.

  8. Extracellular Synthesis of Luminescent CdS Quantum Dots Using Plant Cell Culture

    Science.gov (United States)

    Borovaya, Mariya N.; Burlaka, Olga M.; Naumenko, Antonina P.; Blume, Yaroslav B.; Yemets, Alla I.

    2016-02-01

    The present study describes a novel method for preparation of water-soluble CdS quantum dots, using bright yellow-2 (BY-2) cell suspension culture. Acting as a stabilizing and capping agent, the suspension cell culture mediates the formation of CdS nanoparticles. These semiconductor nanoparticles were determined by means of an UV-visible spectrophotometer, photoluminescence, high-resolution transmission electron microscopy (HRTEM), and XRD. Followed by the electron diffraction analysis of a selected area, transmission electron microscopy indicated the formation of spherical, crystalline CdS ranging in diameter from 3 to 7 nm and showed wurtzite CdS quantum dots. In the present work, the toxic effect of synthesized CdS quantum dots on Nicotiana tabacum protoplasts as a very sensitive model was under study. The results of this research revealed that biologically synthesized CdS nanoparticles in low concentrations did not induce any toxic effects.

  9. Photo current generation in RGO - CdS nanorod thin film device

    Science.gov (United States)

    Chakraborty, Koushik; Chakrabarty, Sankalpita; Ibrahim, Sk.; Pal, Tanusri; Ghosh, Surajit

    2016-05-01

    Herein, we report the synthesis and characterization of reduced graphene oxide (RGO) - cadmium sulfide (CdS) nanocomposite materials. The reduction of GO, formation of CdS and decoration of CdS onto RGO sheets were done in a one- pot solvothermal process. We have observed that the PL intensity for CdS nanorods remarkably quenched after the attachment of RGO, which established the photo induced charge transformation from the CdS nanorod to RGO sheets through the RGO-CdS interface. The optoelectronic transport properties of our fabricated large area thin film device exhibits excellent photo induced charge generation under simulated solar light illumination. The photo sensitivity of the device increases linearly with the increase of illuminated light intensity. The RGO-CdS composite exhibits enhance photocatalytic dye degradation efficiency in compare to control CdS under simulated solar light illumination.

  10. Modification of optical and electrical properties of chemical bath deposited CdS using plasma treatments

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, G. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Krishnan, B. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Avellaneda, D.; Castillo, G. Alan; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Shaji, S., E-mail: sshajis@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

    2011-08-31

    Cadmium sulphide (CdS) is a well known n-type semiconductor that is widely used in solar cells. Here we report preparation and characterization of chemical bath deposited CdS thin films and modification of their optical and electrical properties using plasma treatments. CdS thin films were prepared from a chemical bath containing Cadmium chloride, Triethanolamine and Thiourea under various deposition conditions. Good quality thin films were obtained during deposition times of 5, 10 and 15 min. CdS thin films prepared for 10 min. were treated using a glow discharge plasma having nitrogen and argon carrier gases. The changes in morphology, optical and electrical properties of these plasma treated CdS thin films were analyzed in detail. The results obtained show that plasma treatment is an effective technique in modification of the optical and electrical properties of chemical bath deposited CdS thin films.

  11. Time-varying credit risk and liquidity premia in bond and CDS markets

    OpenAIRE

    Bühler, Wolfgang; Trapp, Monika

    2009-01-01

    We develop a reduced-form model that allows us to decompose bond spreads and CDS premia into a pure credit risk component, a pure liquidity component, and a component measuring the relation between credit risk and liquidity. CDS liquidity has important consequences for the bond credit risk and liquidity components. Besides the credit risk link, we document a liquidity link between the bond and the CDS market. Liquidity in both markets dries up as credit risk increases, and higher bond market ...

  12. Tunable plasmonic lattices of silver nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Andrea; Sinsermsuksakul, Prasert; Yang, Peidong

    2008-02-18

    Silver nanocrystals are ideal building blocks for plasmonicmaterials that exhibit a wide range of unique and potentially usefuloptical phenomena. Individual nanocrystals display distinct opticalscattering spectra and can be assembled into hierarchical structures thatcouple strongly to external electromagnetic fields. This coupling, whichis mediated by surface plasmons, depends on their shape and arrangement.Here we demonstrate the bottom-up assembly of polyhedral silvernanocrystals into macroscopic two-dimensional superlattices using theLangmuir-Blodgett technique. Our ability to control interparticlespacing, density, and packing symmetry allows for tunability of theoptical response over the entire visible range. This assembly strategyoffers a new, practical approach to making novel plasmonic materials forapplication in spectroscopic sensors, sub-wavelength optics, andintegrated devices that utilize field enhancement effects.

  13. Active Optical Fibers Doped with Ceramic Nanocrystals

    Directory of Open Access Journals (Sweden)

    Jan Mrazek

    2014-01-01

    Full Text Available Erbium-doped active optical fiber was successfully prepared by incorporation of ceramic nanocrystals inside a core of optical fiber. Modified chemical vapor deposition was combined with solution-doping approach to preparing preform. Instead of inorganic salts erbium-doped yttrium-aluminium garnet nanocrystals were used in the solution-doping process. Prepared preform was drawn into single-mode optical fiber with a numerical aperture 0.167. Optical and luminescence properties of the fiber were analyzed. Lasing ability of prepared fiber was proofed in a fiber-ring set-up. Optimal laser properties were achieved for a fiber length of 20~m. The slope efficiency of the fiber-laser was about 15%. Presented method can be simply extended to the deposition of other ceramic nanomaterials.

  14. Microwave assisted synthesis of CdS nanoparticles and their size evolution

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, I. A.; Vazquez, A.; Gomez, I., E-mail: idaliagomezmx@yahoo.com.mx [Universidad Autonoma de Nuevo Leon, Facultad de Ciencias Quimicas, Laboratorio de Materiales I, Av. Universidad, Cd. Universitaria, 66451 San Nicolas de los Garza, Nuevo Leon (Mexico)

    2013-05-01

    The study of the size evolution of CdS nanoparticles in aqueous dispersion is presented in this paper. The sodium citrate was employed as stabilizer of CdS nanoparticles synthesized by microwave assisted synthesis. Analysis of this study was carried out by UV-Vis spectrophotometry, by comparison of the band gap energy using theoretical and empirical models. Results obtained show that the synthesis conditions produce CdS nanoparticles with diameters below of 6 nm, which remains stabilized by at least 14 days. These characteristics were confirmed by transmission electron microscopy. The X-ray diffraction pattern confirms cubic phase of the CdS nanoparticles. (Author)

  15. Luminescence properties of Eu3+/CDs/PVA composite applied in light conversion film

    Science.gov (United States)

    He, Jiangling; He, Youling; Zhuang, Jianle; Zhang, Haoran; Lei, Bingfu; Liu, Yingliang

    2016-12-01

    In this work, blue-light-emitting carbon dots (CDs) were composited with red-light-emitting europium ions (Eu3+) solutions under the synergistic reaction of polyvinyl alcohol (PVA) to prepare the light conversion film. The formation mechanism of Eu3+/CDs/PVA film was detailedly discussed. It is the first report that this composite was synthesized through direct recombination of CDs and Eu3+ solutions instead of traditional methods based on Eu3+ coordination compound. Furthermore, tunable photoluminescence property can be successfully achieved by controlling the ratio of CDs to doped Eu3+, this property can meet the variable light component requirements for different species of plants.

  16. Digital Color in Cellulose Nanocrystal Films

    OpenAIRE

    Dumanli, Ahu Gümrah; van der Kooij, Hanne M.; Kamita, Gen; Reisner, Erwin; Baumberg, Jeremy J.; Steiner, Ullrich; Vignolini, Silvia

    2014-01-01

    This is the final published version. It first appeared at http://pubs.acs.org/doi/abs/10.1021/am501995e. Cellulose nanocrystals (CNCs) form chiral nematic phases in aqueous suspensions that can be preserved upon evaporation of water. The resulting films show an intense directional coloration determined by their microstructure. Here, microreflection experiments correlated with analysis of the helicoidal nanostructure of the films reveal that the iridescent colors and the ordering of the ind...

  17. Extracting hot carriers from photoexcited semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang

    2014-12-10

    This research program addresses a fundamental question related to the use of nanomaterials in solar energy -- namely, whether semiconductor nanocrystals (NCs) can help surpass the efficiency limits, the so-called “Shockley-Queisser” limit, in conventional solar cells. In these cells, absorption of photons with energies above the semiconductor bandgap generates “hot” charge carriers that quickly “cool” to the band edges before they can be utilized to do work; this sets the solar cell efficiency at a limit of ~31%. If instead, all of the energy of the hot carriers could be captured, solar-to-electric power conversion efficiencies could be increased, theoretically, to as high as 66%. A potential route to capture this energy is to utilize semiconductor nanocrystals. In these materials, the quasi-continuous conduction and valence bands of the bulk semiconductor become discretized due to confinement of the charge carriers. Consequently, the energy spacing between the electronic levels can be much larger than the highest phonon frequency of the lattice, creating a “phonon bottleneck” wherein hot-carrier relaxation is possible via slower multiphonon emission. For example, hot-electron lifetimes as long as ~1 ns have been observed in NCs grown by molecular beam epitaxy. In colloidal NCs, long lifetimes have been demonstrated through careful design of the nanocrystal interfaces. Due to their ability to slow electronic relaxation, semiconductor NCs can in principle enable extraction of hot carriers before they cool to the band edges, leading to more efficient solar cells.

  18. Fabrication and electronic transport studies of single nanocrystal systems

    Energy Technology Data Exchange (ETDEWEB)

    Klein, David Louis [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-05-01

    Semiconductor and metallic nanocrystals exhibit interesting electronic transport behavior as a result of electrostatic and quantum mechanical confinement effects. These effects can be studied to learn about the nature of electronic states in these systems. This thesis describes several techniques for the electronic study of nanocrystals. The primary focus is the development of novel methods to attach leads to prefabricated nanocrystals. This is because, while nanocrystals can be readily synthesized from a variety of materials with excellent size control, means to make electrical contact to these nanocrystals are limited. The first approach that will be described uses scanning probe microscopy to first image and then electrically probe surfaces. It is found that electronic investigations of nanocrystals by this technique are complicated by tip-sample interactions and environmental factors such as salvation and capillary forces. Next, an atomic force microscope technique for the catalytic patterning of the surface of a self assembled monolayer is described. In principle, this nano-fabrication technique can be used to create electronic devices which are based upon complex arrangements of nanocrystals. Finally, the fabrication and electrical characterization of a nanocrystal-based single electron transistor is presented. This device is fabricated using a hybrid scheme which combines electron beam lithography and wet chemistry to bind single nanocrystals in tunneling contact between closely spaced metallic leads. In these devices, both Au and CdSe nanocrystals show Coulomb blockade effects with characteristic energies of several tens of meV. Additional structure is seen the transport behavior of CdSe nanocrystals as a result of its electronic structure.

  19. CdS/ZnS core-shell nanocrystal photosensitizers for visible to UV upconversion.

    Science.gov (United States)

    Gray, Victor; Xia, Pan; Huang, Zhiyuan; Moses, Emily; Fast, Alexander; Fishman, Dmitry A; Vullev, Valentine I; Abrahamsson, Maria; Moth-Poulsen, Kasper; Lee Tang, Ming

    2017-08-01

    Herein we report the first example of nanocrystal (NC) sensitized triplet-triplet annihilation based photon upconversion from the visible to ultraviolet (vis-to-UV). Many photocatalyzed reactions, such as water splitting, require UV photons in order to function efficiently. Upconversion is one possible means of extending the usable range of photons into the visible. Vis-to-UV upconversion is achieved with CdS/ZnS core-shell NCs as the sensitizer and 2,5-diphenyloxazole (PPO) as annihilator and emitter. The ZnS shell was crucial in order to achieve any appreciable upconversion. From time resolved photoluminescence and transient absorption measurements we conclude that the ZnS shell affects the NC and triplet energy transfer (TET) from NC to PPO in two distinct ways. Upon ZnS growth the surface traps are passivated thus increasing the TET. The shell, however, also acts as a tunneling barrier for TET, reducing the efficiency. This leads to an optimal shell thickness where the upconversion quantum yield (Φ'UC) is maximized. Here the maximum Φ'UC was determined to be 5.2 ± 0.5% for 4 monolayers of ZnS shell on CdS NCs.

  20. Synthesis of Copper-Antimony-Sulfide Nanocrystals for Solution-Processed Solar Cells.

    Science.gov (United States)

    Suehiro, Satoshi; Horita, Keisuke; Yuasa, Masayoshi; Tanaka, Tooru; Fujita, Katsuhiko; Ishiwata, Yoichi; Shimanoe, Kengo; Kida, Tetsuya

    2015-08-17

    The p-type nanocrystals (NCs) of copper-based chalcogenides, such as CuInSe2 and Cu2ZnSnS4, have attracted increasing attention in photovoltaic applications due to their potential to produce cheap solution-processed solar cells. Herein, we report the synthesis of copper-antimony-sulfide (CAS) NCs with different crystal phases including CuSbS2, Cu3SbS4, and Cu12Sb4S13. In addition, their morphology, crystal phase, and optical properties were characterized using transmission electron microscopy, X-ray diffractometry, UV-vis-near-IR spectroscopy, and photoemission yield spectroscopy. The morphology, crystal phase, and electronic structure were significantly dependent on the chemical composition in the CAS system. Devices were fabricated using particulate films consisting of CAS NCs prepared by spin coating without a high-temperature treatment. The CAS NC-based devices exhibited a diode-like current-voltage characteristic when coupled with an n-type CdS layer. In particular, the CuSbS2 NC devices exhibited photovoltaic responses under simulated sunlight, demonstrating its applicability for use in solution-processed solar cells.

  1. Morphological variations in cadmium sulfide nanocrystals without phase transformation

    Directory of Open Access Journals (Sweden)

    Colorado Henry

    2011-01-01

    Full Text Available Abstract A very novel phenomenon of morphological variations of cadmium sulfide (CdS nanorods under the transmission electron microscopy (TEM beam was observed without structural phase transformation. Environmentally stable and highly crystalline CdS nanorods have been obtained via a chemical bath method. The energy of the TEM beam is believed to have a significant influence on CdS nanorods and may melt and transform them into smaller nanowires. Morphological variations without structural phase transformation are confirmed by recording selected area electron diffraction at various stages. The prepared CdS nanorods have been characterized by X-ray powder diffraction, TEM, UV-Vis spectroscopy, and photoluminescence spectroscopy. The importance of this phenomenon is vital for the potential application for CdS such as smart materials.

  2. Hydrogen evolution from water using CdS as photosensitizer

    OpenAIRE

    Tatiana Oncescu; M. Contineanu; Lucia Meahcov

    1999-01-01

    Colloidal chemical approaches are increasingly utilised for the preparation and stabilization of semiconductor nanoparticles.We prepared a colloidal CdS in excess of Na2S using a method described in the literature and determined the particle size from its absorption spectrum by Brus equation. A diameter of about 50Å was calculated. For the stabilization of colloid we choosed from various tested polymers a 1% in weight copolymer (1/1), styrene/maleic anhydride. As redox catalyst we used colloi...

  3. Chemical effects of size quantization of CdS nanoparticles

    Institute of Scientific and Technical Information of China (English)

    陈德文; 王素华

    1996-01-01

    The behaviour of photoreaction occurring on the superfine duster interface of semiconductor CdS has been studied. The results indicated that the size quantization effect of semiconductor nanoparticles was obviously reflected not only in their physical properties, but also in the interfacial photocatalysis reactions initiated by superfine nanopartides. This means that the direction and mechanisms in photoreactions of the compounds adsorbed on the surface of nanopartides could vary with the alteration of particle size because the redox potential values of semiconductor particles could be changed with the variation of particle size. Doubtlessly, this effect could play an important role in controlling the interfacial reaction mechanisms and raising the selectivity to photoreaction paths.

  4. Tying loan interest rates to borrowers' CDS spreads

    OpenAIRE

    Ivanov, Ivan T.; Santos, Joao A. C.; Vo, Thu

    2014-01-01

    We investigate how the introduction of market-based pricing, the practice of tying loan interest rates to credit default swaps, has affected borrowing costs. We find that CDS-based loans are associated with lower interest rates, both at origination and during the life of the loan. Our results also indicate that banks simplify the covenant structure of market-based pricing loans, suggesting that the decline in the cost of bank debt is explained, at least in part, by a reduction in monitoring c...

  5. Synthesis and Photovoltaic Application of Coper (I) Sulfide Nanocrystals

    Science.gov (United States)

    2008-12-22

    Cu2S ( JCPDS 026-1116, Fig. 1a red lines). Low-resolution transmission electron microscopy (TEM) studies (Fig. 1b) show nanocrystals with an average...a, XRD diffraction pattern of Cu2S nanocrystals, which can be indexed to hexagonal Cu2S ( JCPDS 026-1116, red lines). b, TEM image of Cu2S

  6. Characterization of Ge-nanocrystal films with photoelectron spectroscopy

    CERN Document Server

    Bostedt, C; Willey, T M; Nelson, A J; Franco, N; Möller, T; Terminello, L J

    2003-01-01

    The Ge 3d core-levels of germanium nanocrystal films have been investigated by means of photoelectron spectroscopy. The experiments indicate bulk-like coordinated atoms in the nanocrystals and suggest structured disorder on the nanoparticle surface. The results underline the importance of the surface on the overall electronic structure of this class of nanostructured materials.

  7. Synthesis and preservation of graphene-supported uranium dioxide nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Hanyu [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556 (United States); Wang, Haitao [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556 (United States); Department of Civil, Environmental, and Construction Engineering, Texas Tech University, 911 Boston Ave., Lubbock, TX 79409 (United States); Burns, Peter C. [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); McNamara, Bruce K.; Buck, Edgar C. [Nuclear Chemistry & Engineering Group, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA 99352 (United States); Na, Chongzheng, E-mail: chongzheng.na@gmail.com [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556 (United States); Department of Civil, Environmental, and Construction Engineering, Texas Tech University, 911 Boston Ave., Lubbock, TX 79409 (United States)

    2016-07-15

    Graphene-supported uranium dioxide (UO{sub 2}) nanocrystals are potentially important fuel materials. Here, we investigate the possibility of synthesizing graphene-supported UO{sub 2} nanocrystals in polar ethylene glycol compounds by the polyol reduction of uranyl acetylacetone under boiling reflux, thereby enabling the use of an inexpensive graphene precursor graphene oxide into a one-pot process. We show that triethylene glycol is the most suitable solvent with an appropriate reduction potential for producing nanometer-sized UO{sub 2} crystals compared to monoethylene glycol, diethylene glycol, and polyethylene glycol. Graphene-supported UO{sub 2} nanocrystals synthesized with triethylene glycol show evidence of heteroepitaxy, which can be beneficial for facilitating heat transfer in nuclear fuel particles. Furthermore, we show that graphene-supported UO{sub 2} nanocrystals synthesized by polyol reduction can be readily stored in alcohols, impeding oxidation from the prevalent oxygen in air. Together, these methods provide a facile approach for preparing and storing graphene-supported UO{sub 2} nanocrystals for further investigation and development under ambient conditions. - Highlights: • UO{sub 2} nanocrystals are synthesized using polyol reduction method. • Triethylene glycol is the best reducing agent for nano-sized UO{sub 2} crystals. • UO{sub 2} nanocrystals grow on graphene through heteroepitaxy. • Graphene-supported UO{sub 2} nanocrystals can be stored in alcohols to prevent oxidation.

  8. Isolating and moving single atoms using silicon nanocrystals

    Science.gov (United States)

    Carroll, Malcolm S.

    2010-09-07

    A method is disclosed for isolating single atoms of an atomic species of interest by locating the atoms within silicon nanocrystals. This can be done by implanting, on the average, a single atom of the atomic species of interest into each nanocrystal, and then measuring an electrical charge distribution on the nanocrystals with scanning capacitance microscopy (SCM) or electrostatic force microscopy (EFM) to identify and select those nanocrystals having exactly one atom of the atomic species of interest therein. The nanocrystals with the single atom of the atomic species of interest therein can be sorted and moved using an atomic force microscope (AFM) tip. The method is useful for forming nanoscale electronic and optical devices including quantum computers and single-photon light sources.

  9. Biocomposites reinforced with cellulose nanocrystals derived from potato peel waste.

    Science.gov (United States)

    Chen, D; Lawton, D; Thompson, M R; Liu, Q

    2012-09-01

    This study investigated the effectiveness of cellulose nanocrystals derived from potato peel waste as a reinforcement and vapor barrier additive. The nanocrystals were derived from cellulosic material in the potato peel by alkali treatment and subsequently acid hydrolysis. TEM images revealed the average fiber length of the nanocrystals was 410 nm with an aspect ratio of 41; its aspect ratio being considerably larger than cotton-derived nanocrystals prepared using similar reaction conditions. Cellulose nanocrystals (CNC)-filled polyvinyl alcohol (PVA) and thermoplastic starch (TPS) films were prepared by solution casting method to maintain uniform dispersion of the 1-2% (w/w) filler content. An increase of 19% and 33% (starch composite) and 38% and 49% (PVA composite) in tensile modulus was observed for the 1% and 2% CNC-reinforced composites, respectively. Water vapor transmission measurements showed a marginal reduction of water permeability for the PVA composite, whereas no effect was observed for the thermoplastic starch composite.

  10. Synthesis of tungsten carbide nanocrystals and their electrochemical properties

    Institute of Scientific and Technical Information of China (English)

    Jianghua ZENG; Dingsheng YUAN; Yingliang LIU; Jingxing CHEN; Sanxiang TAN

    2009-01-01

    Tungsten carbide (WC) nanocrystals have been prepared by a solvothermal method with Mg as the reductant and WO3 and anhydrous ethanol as the precursors. The effects of time and temperature on the synthesis of WC were investigated and a probable formation mechanism was discussed. The obtained WC nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, energy dispersive spec-troscopy and electrochemical methods. Hexagonal close-packed WC was successfully synthesized when the temperature was as low as 500°C. The content of carbon was more than that of W, indicating that the composition of the treated sample was C and WC only. The diameters of WC nanocrystals were ranged from 40 nm to 70 nm and the nanocrystals were dispersed on carbon films. The electrochemical measurements reveal that WC nanocrystals obviously promote Pt/C electrocatalytic ability for the oxygen reduction reaction.

  11. Facile synthesis of water-soluble curcumin nanocrystals

    Directory of Open Access Journals (Sweden)

    Marković Zoran M.

    2015-01-01

    Full Text Available In this paper, facile synthesis of water soluble curcumin nanocrystals is reported. Solvent exchange method was applied to synthesize curcumin nanocrystals. Different techniques were used to characterize the structural and photophysical properties of curcumin nanocrystals. We found that nanocurcumin prepared by this method had good chemical and physical stability, could be stored in the powder form at room temperature, and was freely dispersible in water. It was established that the size of curcumin nanocrystals was varied in the range of 20-500 nm. Fourier transform infrared spectroscopy and UV-Vis analyses showed the presence of tetrahydrofuran inside the curcumin nanocrystals. Also, it was found that nanocurcumin emitted photoluminescencewith yellow-green colour. [Projekat Ministarstva nauke Republike Srbije, br. 172003

  12. Synthesis, Growing Processes and Physical Properties of CdS Nanoclusters in Y-Zeolite Studied by Positron Annihilation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Direct synthesis of CdS nanoclusters within the pore structure of Y zeolite was made. The location of CdS nanoclusters inside Y zeolite hosts was confirmed by the blue-shifted reflection absorption spectra with respected to that of bulk CdS materials. In this paper, we conducted Positron Annihilation Lifetime Spectrum (PALS) measurements on a series of CdS/Y zeolite samples and concluded that CdS clusters were not located in supercages but in smaller sodalite cages; as the CdS loading concentration increases to 5 wt%, the discrete CdS cubes begin to form bigger superclusters through interaction. The stability of CdS clusters inside the so- dalite units is due to the coordination of Cd atoms with the framework oxygen atoms of the double six-ring windows. Moreover, PALS reveals some important information of surface states existing on the interfacial layers between CdS clusters and Y zeolite.

  13. The Financial Management System: A Pivotal Tool for Fiscal Viability. CDS Spotlight. ECAR Research Bulletin

    Science.gov (United States)

    Lang, Leah; Pirani, Judith A.

    2014-01-01

    This spotlight focuses on data from the 2013 CDS to better understand how higher education institutions approach financial management systems. Information provided for this spotlight was derived from Module 8 of Core Data Service (CDS), which asked several questions regarding information systems and applications. Responses from 525 institutions…

  14. BI Reporting, Data Warehouse Systems, and Beyond. CDS Spotlight Report. Research Bulletin

    Science.gov (United States)

    Lang, Leah; Pirani, Judith A.

    2014-01-01

    This Spotlight focuses on data from the 2013 Core Data Service [CDS] to better understand how higher education institutions approach business intelligence (BI) reporting and data warehouse systems (see the Sidebar for definitions). Information provided for this Spotlight was derived from Module 8 of CDS, which contains several questions regarding…

  15. Structural properties of dopping metallic impurities on CdS thin layers

    Directory of Open Access Journals (Sweden)

    S. Ghasemzadeh

    2016-12-01

    Full Text Available (Cu,Zn-dopped CdS thin layers were deposited on glass substrates by chemical bath deposition technique. The effects of the doping on the structural properties of CdS thin layers were studied by SEM and EDAX analysis. Hetero junction layers were produced with different nano structures and different fraction of voids and metallic ions.

  16. Structural properties of dopping metallic impurities on CdS thin layers

    OpenAIRE

    S. Ghasemzadeh; H. kangarlou

    2016-01-01

    (Cu,Zn)-dopped CdS thin layers were deposited on glass substrates by chemical bath deposition technique. The effects of the doping on the structural properties of CdS thin layers were studied by SEM and EDAX analysis. Hetero junction layers were produced with different nano structures and different fraction of voids and metallic ions.

  17. DEFECTS IN CDS - IN DETECTED BY PERTURBED ANGULAR-CORRELATION SPECTROSCOPY (PAC)

    NARCIS (Netherlands)

    MAGERLE, R; DEICHER, M; DESNICA, U; KELLER, R; PFEIFFER, W; PLEITER, F; SKUDLIK, H; WICHERT, T

    1991-01-01

    The local lattice environment of the donor In in CdS is investigated measuring the electric-field gradient at the site of the radioactive probe atom In-111 by the perturbed gamma-gamma angular correlation technique. It is shown that implantation of In into CdS with subsequent annealing drives 100% o

  18. BI Reporting, Data Warehouse Systems, and Beyond. CDS Spotlight Report. Research Bulletin

    Science.gov (United States)

    Lang, Leah; Pirani, Judith A.

    2014-01-01

    This Spotlight focuses on data from the 2013 Core Data Service [CDS] to better understand how higher education institutions approach business intelligence (BI) reporting and data warehouse systems (see the Sidebar for definitions). Information provided for this Spotlight was derived from Module 8 of CDS, which contains several questions regarding…

  19. A comparative study of CdS thin films deposited by different techniques

    Energy Technology Data Exchange (ETDEWEB)

    Pérez-Hernández, G., E-mail: german.perez@ujat.mx [Universidad Juárez Autónoma de Tabasco, Avenida Universidad s/n, Col. Magisterial, Villahermosa, Tabasco 86040 (Mexico); Pantoja-Enríquez, J. [Centro de Investigación y Desarrollo Tecnológico en Energías Renovables, UNICACH, Libramiento Norte No 1150, Tuxtla Gutiérrez, Chiapas 29039 (Mexico); Escobar-Morales, B. [Instituto Tecnológico de Cancún, Avenida Kábah Km 3, Cancún, Quintana Roo 77500 (Mexico); Martinez-Hernández, D.; Díaz-Flores, L.L.; Ricardez-Jiménez, C. [Universidad Juárez Autónoma de Tabasco, Avenida Universidad s/n, Col. Magisterial, Villahermosa, Tabasco 86040 (Mexico); Mathews, N.R.; Mathew, X. [Centro de Investigación en Energía, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico)

    2013-05-01

    Cadmium sulfide thin-films were deposited on glass slides and SnO{sub 2}:F coated glass substrates by chemical bath deposition, sputtering and close-spaced sublimation techniques. The films were studied for the structural and opto-electronic properties after annealing in an ambient identical to that employed in the fabrication of CdTe/CdS devices. Quantum efficiency of the CdTe/CdS solar cells fabricated with CdS buffer films prepared by the three methods were investigated to understand the role of CdS film preparation method on the blue response of the devices. The higher blue response observed for the devices fabricated with chemical bath deposited CdS film is discussed. - Highlights: ► CdS films were prepared by different techniques. ► Role of CdS on the blue response of device was studied. ► Structural and optical properties of CdS were analyzed. ► Chemically deposited CdS has high blue transmittance. ► CdS deposition method influences diffusion of S and Te.

  20. An alternative route towards monodisperse CdS quantum dots for hybrid solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Fengfeng; Wang, Hao [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Xia, Zhouhui [Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123 (China); Dai, Xiao; Cong, Shan [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Dong, Chao [Department of Chemistry and Biology, University of New Mexico, ABQ 87120 (United States); Sun, Baoquan [Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123 (China); Lou, Yanhui, E-mail: yhlou@suda.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Sun, Yinghui; Zhao, Jie [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Zou, Guifu, E-mail: zouguifu@suda.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China)

    2015-01-15

    Monodisperse CdS quantum dots (QDs) are synthesized by thermal decomposition of organic complexes in the system of the cost-effective commercial 0{sup #} diesel at 200 °C. The prepared CdS QDs have a good dispersion and high crystallization. When the CdS QDs are doped into the blends of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6, 6)C61 (PCBM) for hybrid solar cells (HSCs), the HSCs achieve about 25% increase of power conversion efficiency in comparison to the reference device without the CdS QDs. The improvement of the cell performance mainly attributes to the increased short-circuit current density arising from the absorption enhancement in the wavelength range of 350–550 nm by introducing the synthesized CdS QDs into the P3HT: PCBM active layer. - Highlights: • Monodisperse CdS quantum dots. • A cost-effective route to synthesize crystalline CdS quantum dots. • CdS quantum dots based hybrid solar cells with power conversion efficiency enhancement.

  1. The Financial Management System: A Pivotal Tool for Fiscal Viability. CDS Spotlight. ECAR Research Bulletin

    Science.gov (United States)

    Lang, Leah; Pirani, Judith A.

    2014-01-01

    This spotlight focuses on data from the 2013 CDS to better understand how higher education institutions approach financial management systems. Information provided for this spotlight was derived from Module 8 of Core Data Service (CDS), which asked several questions regarding information systems and applications. Responses from 525 institutions…

  2. Controlling the assembly of CdS nanorods via solvent and acidity

    NARCIS (Netherlands)

    Koster, L. J. A.; Khodabakhsh, S.; Greenham, N. C.

    2014-01-01

    We report control over the phase behavior of CdS nanorods via the solvent and acidity. CdS nanorods were synthesized using alkane phosphonic acid ligands, which were replaced after synthesis by a series of aromatic ligands. Change of ligand enabled us to cast films from different solvents. By replac

  3. Effects of bacteria on CdS thin films used in technological devices

    Science.gov (United States)

    Alpdoğan, S.; Adıgüzel, A. O.; Sahan, B.; Tunçer, M.; Metin Gubur, H.

    2017-04-01

    Cadmium sulfide (CdS) thin films were fabricated on glass substrates by the chemical bath deposition method at 70 {}^\\circ \\text{C} considering deposition times ranging from 2 h to 5 h. The optical band gaps of CdS thin films were found to be in the 2.42-2.37 eV range. CdS thin films had uniform spherical nano-size grains which had polycrystalline, hexagonal and cubic phases. The films had a characteristic electrical resistivity of the order of {{10}5} Ω \\text{cm} and n-type conductivity at room condition. CdS thin films were incubated in cultures of B.domonas aeruginosa and Staphylococcus aureus, which exist abundantly in the environment, and form biofilms. SEM images showed that S. aureus and K. pneumonia were detected significantly on the film surfaces with a few of P. aeruginosa and B. subtilis cells attached. CdS thin film surface exhibits relatively good resistance to the colonization of P. aeruginosa and B. subtilis. Optical results showed that the band gap of CdS thin films which interacted with the bacteria is 2.42 \\text{eV} . The crystal structure and electrical properties of CdS thin films were not affected by bacterial adhesion. The antimicrobial effect of CdS nanoparticles was different for different bacterial strains.

  4. Microstructural, optical and photocatalytic properties of CdS doped TiO2 thin films

    Science.gov (United States)

    Mohamed, S. H.; Shaaban, E. R.

    2011-11-01

    CdS doped TiO2 thin films (with CdS content=0, 3, 6, 9 and 12 at%) were grown on glass substrates. The X-ray diffraction analysis revealed that the films are polycrystalline of monoclinic TiO2 structure. The microstructure parameters of the films such as crystallite size (Dν) and microstrain (e) are calculated. Both the crystallites size and the microstrain are decreased with increasing CdS content. The optical constants have been determined in terms of Murmann's exact equations. The refractive index and extinction coefficient are increased with increasing CdS content. The optical band gap is calculated in the strong absorption region. The possible optical transition in these films is found to be an allowed direct transition. The values of Egopt are found to decrease as the CdS content increased. The films with 3 at% CdS content have better decomposition efficiency than undoped TiO2. The films with 6 at% and 9 at% CdS content have decomposition efficiency comparable to that of undoped TiO2, although they have lower band gap. The CdS doped TiO2 could have a better impact on the decomposing of organic wastes.

  5. A new synthesis strategy for chiral CdS nanotubes based on a homochiral MOF template.

    Science.gov (United States)

    Kuang, Xuan; Ma, Yu; Zhang, Caiyun; Su, Hao; Zhang, Jine; Tang, Bo

    2015-04-07

    We describe for the first time a convenient technique to prepare helical CdS nanotubes, with a MOF as the template. The prepared helical CdS nanotubes were remarkably sensitive to D/L-aspartic acid (Asp) and can be used as a potential sensor for enantioselective recognition of D/L-Asp.

  6. TRACE and CDS: JOP 146 Data Analysis Part I

    Science.gov (United States)

    Scott, J. T.; Cirtain, J. W.; Martens, P. C. H.

    2003-05-01

    Joint Observing Program 146 was designed to collect data on coronal loops using the Coronal Diagnostic Spectrometer on SoHO and the Transition Region and Coronal Explorer. These two instruments collectively provide high spatial, temporal and temperature resolution. Calibration of the 171 Å filter on TRACE to spectral line intensities collected by CDS combines these qualities to produce the most detailed data currently available for the solar corona. We have determined an absolute value for the wavelengths of ions in data collected on September 18, 2001. This wavelength was then used to determine the Doppler shifts for many points along a coronal loop. The resulting values for velocity and intensity of Mg IX were then compared to the flux measured by the TRACE 171 Å filter. We find a appreciable correlation between the 171 Å filter and Mg IX. We use this determination to develop method of Differential Emission Measure analysis that provides a DEM for any pixel along a loop at nearly the same instant in time. This is uncharacteristic of DEM curves typically created from CDS data, as these curves are highly time dependant.

  7. Spectral Dependent Photoelectrochemical Behaviors of CdS Sensitized ZnO Nanorods.

    Science.gov (United States)

    Majumder, T; Hmar, J J L; Roy, J N; Mondal, S P

    2016-04-01

    CdS decorated ZnO nanorods have been grown by a combination of hydrothermal method and successive ion layer absorption and reaction (SILAR) method. Optical absorption and emission properties of ZnO nanorods have been studied after sensitization with CdS nanoparticles. Current-voltage characteristics of ZnO nanorods and CdS sensitized ZnO nanorods have been studied in an electrochemical cell. The spectral dependent photocurrent and photopotential behaviors of ZnO nanorods and CdS sensitized ZnO nanorods have been investigated using monochromatic light of wavelength 300-700 nm. The photopotential recovery time have been estimated for CdS sensitized nanorods and pristine nanorods.

  8. Mesoporous structured MIPs@CDs fluorescence sensor for highly sensitive detection of TNT.

    Science.gov (United States)

    Xu, Shoufang; Lu, Hongzhi

    2016-11-15

    A facile strategy was developed to prepare mesoporous structured molecularly imprinted polymers capped carbon dots (M-MIPs@CDs) fluorescence sensor for highly sensitive and selective determination of TNT. The strategy using amino-CDs directly as "functional monomer" for imprinting simplify the imprinting process and provide well recognition sites accessibility. The as-prepared M-MIPs@CDs sensor, using periodic mesoporous silica as imprinting matrix, and amino-CDs directly as "functional monomer", exhibited excellent selectivity and sensitivity toward TNT with detection limit of 17nM. The recycling process was sustainable for 10 times without obvious efficiency decrease. The feasibility of the developed method in real samples was successfully evaluated through the analysis of TNT in soil and water samples with satisfactory recoveries of 88.6-95.7%. The method proposed in this work was proved to be a convenient and practical way to prepare high sensitive and selective fluorescence MIPs@CDs sensors.

  9. Optical Properties of CdS Nanobelts and Nanosaws Synthesized by Thermal Evaporation Method

    Institute of Scientific and Technical Information of China (English)

    Zhi-wei Peng; Bing-suo Zou

    2012-01-01

    By a simple one-step H2-assisted thermal evaporation method,high quality CdS nanostructures have been successfully fabricated on Au coated Si substrates in large scale.The as-synthesized CdS nanostructures consisted of sword-like nanobelts and toothed nanosaws with a single-crystal hexagonal wurtzite structure.The deposition temperature played an important role in determining the size and morphology of the CdS nanostructures.A combination of vapor-liquid-solid and vapor-solid growth mechanisms were proposed to interpret the formation of CdS nanostructures.Photoluminescence measurement indicated that the nanobelts and nanosaws have a prominent green emission at about 512 nm,which is the band-to-band emission of CdS.The waveguide characteristics of both types of CdS nanostructures were observed and discussed.

  10. Preparation of CdS nanoparticles by hydrothermal method in microemulsion

    Institute of Scientific and Technical Information of China (English)

    ZANG Jinxin; ZHAO Gaoling; HAN Gaorong

    2007-01-01

    CdS nanoparticles with good crystallinity were prepared by hydrothermal method in microemulsion composed of polyoxyethylene laurylether/water/cyclohexane/butanol.The structure and the size of the CdS nanoparticles were analyzed by TEM and XRD.The UV-Vis optical absorption of the samples was also investigated.The results show that hydrothermal treatment is an effective method to prepare CdS nanoparticles of hexagonal structure at lower temperature.The particles were in dimensional uniformity.The diameter of the CdS nanoparticles decreased with the increase of the molar ratio of water to surfactant.The minimum diameter of the CdS nanoparticles prepared in this work was about 10 nm.Obvious blue shift appeared in the UV-Vis absorption spectra.

  11. Structural and Optical Properties of CdS Thin Film Grown by Chemical Bath Deposition

    Directory of Open Access Journals (Sweden)

    S. Rajpal

    2013-07-01

    Full Text Available In this work we report synthesis and optical characterization of CdS thin films coated on glass substrate. The films were deposited using chemical bath deposition method. Scanning Electron microscopy shows a uniform film of CdS film at particular concentration and dipping time. The Energy Dispersive spectroscopy reveals the presence of Cd and S in the CdS film. X-Ray diffraction confirms the cubic structure of CdS deposited on glass and amorphous nature of glass. Optical and photoluminescence studies were done using UV-Visible spectroscopy and Photoluminescence spectroscopy respectively. We have determined bandgap by analyzing UV-Visible spectra results. Wettability studies were done using Optical Contact Angle, which confirms the hydrophobic nature of the CdS films.

  12. Formation of noble metal nanocrystals in the presence of biomolecules

    Science.gov (United States)

    Burt, Justin Lockheart

    One of the most promising, yet least studied routes for producing biocompatible nanostructures involves synthesis in the presence of biomolecules. I hypothesized that globular proteins could provide a suitable framework to regulate the formation of noble metal nanocrystals. As proof of concept, I designed two novel synthesis protocols utilizing bovine serum albumin (BSA) protein to regulate the formation of gold nanocrystals. In the first case, the standard protocol for polyol reduction was modified by replacing ethylene glycol with glycerin, replacing synthetic polymers with BSA as protecting agent, and decreasing the reaction temperature. In the second case, the Brust-Schiffrin two-phase reduction was modified by replacing alkylthiols with BSA as protecting agent, which facilitated a strictly aqueous phase synthesis. Due to superior product yield and rapid reduction at room temperature, the aqueous protocol became the foundation for subsequent studies. I extended this approach to produce well-dispersed ˜2nm silver, gold, and platinum nanocrystals. Having demonstrated the feasibility of BSA-functionalized nanocrystals, some potential uses were explored. BSA-functionalized silver nanocrystals were employed in a broader study on the interaction of silver nanocrystals with HIV. BSA-functionalized gold nanocrystals were utilized for in vivo dosage of a contrast enhancing agent to bacteria. BSA-functionalized platinum nanocrystals were studied as hydrogenation catalysts. Since many intriguing uses for protein-functionalized nanocrystals involve incorporation into biosystems, I sought to enhance biocompatibility by using ascorbic acid as reducing agent. Initial experiments revealed elongated and branched nanocrystals. Such structures were not observed in previous synthesis protocols with BSA, so I hypothesized ascorbic acid was driving their formation. To test my assertion, I reduced ionic gold in an aqueous solution of ascorbic acid, thereby discovering a new method

  13. Synthesis and Characterization of Colloidal Metal and Photovoltaic Semiconductor Nanocrystals

    KAUST Repository

    Abulikemu, Mutalifu

    2014-11-05

    Metal and semiconducting nanocrystals have received a great deal of attention from fundamental scientists and application-oriented researchers due to their physical and chemical properties, which differ from those of bulk materials. Nanocrystals are essential building blocks in the development of nanostructured devices for energy conversion. Colloidal metals and metal chalcogenides have been developed for use as nanocrystal inks to produce efficient solar cells with lower costs. All high-performing photovoltaic nanocrystals contain toxic elements, such as Pb, or scarce elements, such as In; thus, the production of solution-processable nanocrystals from earth-abundant materials using environmentally benign synthesis and processing methods has become a major challenge for the inorganic semiconductor-based solar field. This dissertation, divided into two parts, addresses several aspects of these emerging challenges. The first portion of the thesis describes the synthesis and characterization of nanocrystals of antimony sulfide, which is composed of non-scarce and non-toxic elements, and examines their performance in photovoltaic devices. The effect of various synthetic parameters on the final morphology is explored. The structural, optical and morphological properties of the nanocrystals were investigated, and Sb2S3 nanocrystal-based solid-state semiconductor-sensitized solar cells were fabricated using different deposition processes. We achieved promising power conversion efficiencies of 1.48%. The second part of the thesis demonstrates a novel method for the in situ synthesis and patterning of nanocrystals via reactive inkjet printing. The use of low-cost manufacturing approaches for the synthesis of nanocrystals is critical for many applications, including photonics and electronics. In this work, a simple, low-cost method for the synthesis of nanocrystals with minimum size variation and waste using reactive inkjet printing is introduced. As a proof of concept, the

  14. Toxicity of cadmium sulfide (CdS) nanoparticles against Escherichia coli and HeLa cells

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, Sk Tofajjen; Mukherjee, Samir Kumar, E-mail: dr.samirmukherjee@gmail.com

    2013-09-15

    Highlights: • Toxic effect of CdS NPs on the growth and cell division in E. coli was studied. • CdS NPs affected cell surface topology and cell division. • Downregulation of both FtsZ and FtsQ was observed due to NPs exposure. • CdS NPs affected HeLa cell morphology with fragmented nuclei. • All such effects might be due to elevated oxidative stress. -- Abstract: The present study endeavours to assess the toxic effect of synthesized CdS nanoparticles (NPs) on Escherichia coli and HeLa cells. The CdS NPs were characterized by DLS, XRD, TEM and AFM studies and the average size of NPs was revealed as ∼3 nm. On CdS NPs exposure bacterial cells changed morphological features to filamentous form and damage of the cell surface was found by AFM study. The expression of two conserved cell division components namely ftsZ and ftsQ in E. coli was decreased both at transcriptional and translational levels upon CdS NPs exposure. CdS NPs inhibited proper cell septum formation without affecting the nucleoid segregation. Viability of HeLa cells declined with increasing concentration of CdS NPs and the IC{sub 50} value was found to be 4 μg/mL. NPs treated HeLa cells showed changed morphology with condensed and fragmented nuclei. Increased level of reactive oxygen species (ROS) was found both in E. coli and HeLa cells on CdS NPs exposure. The inverse correlation between declined cell viabilities and elevated ROS level suggested that oxidative stress seems to be the key event by which NPs induce toxicity both in E. coli and HeLa cells.

  15. Synthesis of Silicon Nanocrystals in Microplasma Reactor

    Science.gov (United States)

    Nozaki, Tomohiro; Sasaki, Kenji; Ogino, Tomohisa; Asahi, Daisuke; Okazaki, Ken

    Nanocrystalline silicon particles with a grain size of at least less than 10 nm are widely recognized as one of the key materials in optoelectronic devices, electrodes of lithium battery, bio-medical labels. There is also important character that silicon is safe material to the environment and easily gets involved in existing silicon technologies. To date, several synthesis methods such as sputtering, laser ablation, and plasma enhanced chemical vapor deposition (PECVD) based on low-pressure silane chemistry (SiH4) have been developed for precise control of size and density distributions of silicon nanocrystals. We explore the possibility of microplasma technologies for the efficient production of mono-dispersed nanocrystalline silicon particles in a micrometer-scale, continuous-flow plasma reactor operated at atmospheric pressure. Mixtures of argon, hydrogen, and silicon tetrachloride were activated using very high frequency (VHF = 144 MHz) power source in a capillary glass tube with a volume of less than 1 μ-liter. Fundamental plasma parameters of VHF capacitively coupled microplasma were characterized by optical emission spectroscopy, showing electron density of approximately 1015 cm-3 and rotational temperature of 1500 K, respectively. Such high-density non-thermal reactive plasma has a capability of decomposing silicon tetrachloride into atomic silicon to produce supersaturated atomic silicon vapor, followed by gas phase nucleation via three-body collision. The particle synthesis in high-density plasma media is beneficial for promoting nucleation process. In addition, further growth of silicon nuclei was able to be favorably terminated in a short-residence time reactor. Micro Raman scattering spectrum showed that as-deposited particles were mostly amorphous silicon with small fraction of silicon nanocrystals. Transmission electron micrograph confirmed individual silicon nanocrystals of 3-15 nm size. Although those particles were not mono-dispersed, they were

  16. Silicon Nanocrystal Synthesis in Microplasma Reactor

    Science.gov (United States)

    Nozaki, Tomohiro; Sasaki, Kenji; Ogino, Tomohisa; Asahi, Daisuke; Okazaki, Ken

    Nanocrystalline silicon particles with grains smaller than 5 nm are widely recognized as a key material in optoelectronic devices, lithium battery electrodes, and bio-medical labels. Another important characteristic is that silicon is an environmentally safe material that is used in numerous silicon technologies. To date, several synthesis methods such as sputtering, laser ablation, and plasma-enhanced chemical vapor deposition (PECVD) based on low-pressure silane chemistry (SiH4) have been developed for precise control of size and density distributions of silicon nanocrystals. In this study, we explore the possibility of microplasma technologies for efficient production of mono-dispersed nanocrystalline silicon particles on a micrometer-scale, continuous-flow plasma reactor operated at atmospheric pressure. Mixtures of argon, hydrogen, and silicon tetrachloride were activated using a very-high-frequency (144 MHz) power source in a capillary glass tube with volume of less than 1 μl. Fundamental plasma parameters of the microplasma were characterized using optical emission spectroscopy, which respectively indicated electron density of 1015 cm-3, argon excitation temperature of 5000 K, and rotational temperature of 1500 K. Such high-density non-thermal reactive plasma can decompose silicon tetrachloride into atomic silicon to produce supersaturated silicon vapor, followed by gas-phase nucleation via three-body collision: particle synthesis in high-density plasma media is beneficial for promoting nucleation processes. In addition, further growth of silicon nuclei can be terminated in a short-residence-time reactor. Micro-Raman scattering spectra showed that as-deposited particles are mostly amorphous silicon with a small fraction of silicon nanocrystals. Transmission electron micrography confirmed individual 3-15 nm silicon nanocrystals. Although particles were not mono-dispersed, they were well separated and not coagulated.

  17. Luminescence properties of p-type thin CdS films prepared by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Ullrich, B. [Tokyo Univ. (Japan). Dept. of Physics; Ezumi, H. [Department of Electrical Engineering, Hiroshima-Denki Institute of Technology, Hiroshima 739-03 (Japan); Keitoku, S. [Hiroshima Women`s University, Hiroshima 734 (Japan); Kobayashi, T. [Tokyo Univ. (Japan). Dept. of Physics

    1995-12-01

    Investigations of the luminescence of p-type CdS:Cu thin (less than or equal to 2 {mu}m) films on glass substrate prepared by laser ablation were performed for the first time. The dependences of the luminescence on the Cu content in the thin films were studied at 300 K with argon laser lines at 457.9 nm, 488.0 nm and 514.5 nm. It is demonstrated that the luminescence excited with the 514.5 nm line corresponds to the donor-acceptor transition. Furthermore, it is shown that the intensity of the red emission of CdS:Cu films can be efficiently bleached by Cu doping. (orig.)

  18. Galvanic displacement of metals on semiconductor nanocrystals

    Science.gov (United States)

    Johnson, Melanie; Kelly, Joel A.; Henderson, Eric J.; Veinot, Jonathan G. C.

    2009-11-01

    We report the galvanic displacement (GD) of germanium from germanium nanocrystals (Ge-NCs) with silver. The Ge-NCs are synthesized by reductive thermal processing of germanium suboxide sol-gel prepolymers. Thermal processing yields size-controlled oxide-embedded Ge-NCs, which are liberated by dissolution of the germanium oxide matrix in water. Subsequent exposure of the freestanding Ge-NCs to aqueous solutions of AgNO3 leads to deposition of silver nanostructures by GD. The resulting metal structures were analyzed by XRD, XPS, TEM and EDX, confirming deposition of elemental silver in a variety of shapes and sizes.

  19. Galvanic displacement of metals on semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Melanie; Kelly, Joel A; Henderson, Eric J; Veinot, Jonathan G C, E-mail: jveinot@ualberta.ca [University of Alberta, Department of Chemistry, Edmonton, AB, T6G 2G2 (Canada)

    2009-11-15

    We report the galvanic displacement (GD) of germanium from germanium nanocrystals (Ge-NCs) with silver. The Ge-NCs are synthesized by reductive thermal processing of germanium suboxide sol-gel prepolymers. Thermal processing yields size-controlled oxide-embedded Ge-NCs, which are liberated by dissolution of the germanium oxide matrix in water. Subsequent exposure of the freestanding Ge-NCs to aqueous solutions of AgNO{sub 3} leads to deposition of silver nanostructures by GD. The resulting metal structures were analyzed by XRD, XPS, TEM and EDX, confirming deposition of elemental silver in a variety of shapes and sizes.

  20. Photoassisted tuning of silicon nanocrystal photoluminescence.

    Science.gov (United States)

    Choi, Jonghoon; Wang, Nam Sun; Reipa, Vytas

    2007-03-13

    Silicon is a rather inefficient light emitter due to the indirect band gap electronic structure, requiring a phonon to balance the electron momentum during the interband transition. Fortunately, momentum requirements are relaxed in the 1-5 nm diameter Si crystals as a result of quantum confinement effects, and bright photoluminescence (PL) in the UV-vis range is achieved. Photoluminescent Si nanocrystals along with the C- and SiC-based nanoparticles are considered bioinert and may lead to the development of biocompatible and smaller probes than the well-known metal chalcogenide-based quantum dots. Published Si nanocrystal production procedures typically do not allow for the fine control of the particle size. An accepted way to make the H-terminated Si nanocrystals consists of anodic Si wafer etching with the subsequent breakup of the porous film in an ultrasound bath. Resulting H-termination provides a useful platform for further chemical derivatization and conjugation to biomolecules. However, a rather polydisperse mixture is produced following the ultrasonic treatment, leading to the distributed band gap energies and the extent of surface passivation. From the technological point of view, a homogeneous nanoparticle size mixture is highly desirable. In this study, we offer an efficient way to reduce the H-terminated Si nanocrystal diameter and narrow size distribution through photocatalyzed dissolution in a HF/HNO3 acid mixture. Si particles were produced using the lateral etching of a Si wafer in a HF/EtOH/H2O bath followed by sonication in deaerated methanol. Initial suspensions exhibited broad photoluminescence in the red spectral region. Photoassisted etching was carried out by adding the HF/HNO3 acid mixture to the suspension and exposing it to a 340 nm light. Photoluminescence and absorbance spectra, measured during dissolution, show the gradual particle size decrease as confirmed by the photoluminescence blue shift. The simultaneous narrowing of the

  1. Structure and Magnetic Properties of Lanthanide Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Dickerson, James Henry [Vanderbilt Univ., Nashville, TN (United States)

    2014-06-01

    We have had considerable success on this project, particularly in the understanding of the relationship between nanostructure and magnetic properties in lanthanide nanocrystals. We also have successfully facilitated the doctoral degrees of Dr. Suseela Somarajan, in the Department of Physics and Astronomy, and Dr. Melissa Harrison, in the Materials Science Program. The following passages summarize the various accomplishments that were featured in 9 publications that were generated based on support from this grant. We thank the Department of Energy for their generous support of our research efforts in this area of materials science, magnetism, and electron microscopy.

  2. Semiconductor nanocrystals photosensitize C60 crystals.

    Science.gov (United States)

    Biebersdorf, Andreas; Dietmüller, Roland; Susha, Andrei S; Rogach, Andrey L; Poznyak, Sergey K; Talapin, Dmitri V; Weller, Horst; Klar, Thomas A; Feldmann, Jochen

    2006-07-01

    Semiconductor nanocrystals (SCNCs) made of CdSe, CdTe, and InP are used to photosensitize needlelike C(60) crystals. The photocurrent is increased by up to 3 orders of magnitude as compared with C(60) crystals without SCNCs. The photocurrent spectrum can be tuned precisely by the SCNC size and material, rendering the SCNC-functionalized C(60) crystals an excellent material for spectrally tuneable photodetectors. We explain the increased photocurrent as a result of photoexcited electrons transferring from the SCNCs to the C(60) crystals and causing photoconductivity, while the complementary holes remain trapped in the SCNCs.

  3. Enantioselective cellular uptake of chiral semiconductor nanocrystals

    Science.gov (United States)

    Martynenko, I. V.; Kuznetsova, V. A.; Litvinov, I. K.; Orlova, A. O.; Maslov, V. G.; Fedorov, A. V.; Dubavik, A.; Purcell-Milton, F.; Gun'ko, Yu K.; Baranov, A. V.

    2016-02-01

    The influence of the chirality of semiconductor nanocrystals, CdSe/ZnS quantum dots (QDs) capped with L- and D-cysteine, on the efficiency of their uptake by living Ehrlich Ascite carcinoma cells is studied by spectral- and time-resolved fluorescence microspectroscopy. We report an evident enantioselective process where cellular uptake of the L-Cys QDs is almost twice as effective as that of the D-Cys QDs. This finding paves the way for the creation of novel approaches to control the biological properties and behavior of nanomaterials in living cells.

  4. The influence of dopant distribution on the optoelectronic properties of tin-doped indium oxide nanocrystals and nanocrystal films

    Science.gov (United States)

    Lounis, Sebastien Dahmane

    Colloidally prepared nanocrystals of transparent conducting oxide (TCO) semiconductors have emerged in the past decade as an exciting new class of plasmonic materials. In recent years, there has been tremendous progress in developing synthetic methods for the growth of these nanocrystals, basic characterization of their properties, and their successful integration into optoelectronic and electrochemical devices. However, many fundamental questions remain about the physics of localized surface plasmon resonance (LSPR) in these materials, and how their optoelectronic properties derive from their underlying structural properties. In particular, the influence of the concentration and distribution of dopant ions and compensating defects on the optoelectronic properties of TCO nanocrystals has seen little investigation. Indium tin oxide (ITO) is the most widely studied and commercially deployed TCO. Herein we investigate the role of the distribution of tin dopants on the optoelectronic properties of colloidally prepared ITO nanocrystals. Owing to a high free electron density, ITO nanocrystals display strong LSPR absorption in the near infrared. Depending on the particular organic ligands used, they are soluble in various solvents and can readily be integrated into densely packed nanocrystal films with high conductivities. Using a combination of spectroscopic techniques, modeling and simulation of the optical properties of the nanocrystals using the Drude model, and transport measurements, it is demonstrated herein that the radial distribution of tin dopants has a strong effect on the optoelectronic properties of ITO nanocrystals. ITO nanocrystals were synthesized in both surface-segregated and uniformly distributed dopant profiles. Temperature dependent measurements of optical absorbance were first combined with Drude modeling to extract the internal electrical properties of the ITO nanocrystals, demonstrating that they are well-behaved degenerately doped semiconductors

  5. Surface and Core Electronic Structure of Oxidized Silicon Nanocrystals

    Directory of Open Access Journals (Sweden)

    Noor A. Nama

    2010-01-01

    Full Text Available Ab initio restricted Hartree-Fock method within the framework of large unit cell formalism is used to simulate silicon nanocrystals between 216 and 1000 atoms (1.6–2.65 nm in diameter that include Bravais and primitive cell multiples. The investigated properties include core and oxidized surface properties. Results revealed that electronic properties converge to some limit as the size of the nanocrystal increases. Increasing the size of the core of a nanocrystal resulted in an increase of the energy gap, valence band width, and cohesive energy. The lattice constant of the core and oxidized surface parts shows a decreasing trend as the nanocrystal increases in a size that converges to 5.28 Ǻ in a good agreement with the experiment. Surface and core convergence to the same lattice constant reflects good adherence of oxide layer at the surface. The core density of states shows highly degenerate states that split at the oxygenated (001-(1×1 surface due to symmetry breaking. The nanocrystal surface shows smaller gap and higher valence and conduction bands when compared to the core part, due to oxygen surface atoms and reduced structural symmetry. The smaller surface energy gap shows that energy gap of the nanocrystal is controlled by the surface part. Unlike the core part, the surface part shows a descending energy gap that proves its obedience to quantum confinement effects. Nanocrystal geometry proved to have some influence on all electronic properties including the energy gap.

  6. Luminescent Colloidal Semiconductor Nanocrystals Containing Copper: Synthesis, Photophysics, and Applications.

    Science.gov (United States)

    Knowles, Kathryn E; Hartstein, Kimberly H; Kilburn, Troy B; Marchioro, Arianna; Nelson, Heidi D; Whitham, Patrick J; Gamelin, Daniel R

    2016-09-28

    Copper-doped semiconductors are classic phosphor materials that have been used in a variety of applications for many decades. Colloidal copper-doped semiconductor nanocrystals have recently attracted a great deal of interest because they combine the solution processability and spectral tunability of colloidal nanocrystals with the unique photoluminescence properties of copper-doped semiconductor phosphors. Although ternary and quaternary semiconductors containing copper, such as CuInS2 and Cu2ZnSnS4, have been studied primarily in the context of their photovoltaic applications, when synthesized as colloidal nanocrystals, these materials have photoluminescence properties that are remarkably similar to those of copper-doped semiconductor nanocrystals. This review focuses on the luminescent properties of colloidal copper-doped, copper-based, and related copper-containing semiconductor nanocrystals. Fundamental investigations into the luminescence of copper-containing colloidal nanocrystals are reviewed in the context of the well-established luminescence mechanisms of bulk copper-doped semiconductors and copper(I) molecular coordination complexes. The use of colloidal copper-containing nanocrystals in applications that take advantage of their luminescent properties, such as bioimaging, solid-state lighting, and luminescent solar concentrators, is also discussed.

  7. Charge transport in metal oxide nanocrystal-based materials

    Science.gov (United States)

    Runnerstrom, Evan Lars

    There is probably no class of materials more varied, more widely used, or more ubiquitous than metal oxides. Depending on their composition, metal oxides can exhibit almost any number of properties. Of particular interest are the ways in which charge is transported in metal oxides: devices such as displays, touch screens, and smart windows rely on the ability of certain metal oxides to conduct electricity while maintaining visible transparency. Smart windows, fuel cells, and other electrochemical devices additionally rely on efficient transport of ionic charge in and around metal oxides. Colloidal synthesis has enabled metal oxide nanocrystals to emerge as a relatively new but highly tunable class of materials. Certain metal oxide nanocrystals, particularly highly doped metal oxides, have been enjoying rapid development in the last decade. As in myriad other materials systems, structure dictates the properties of metal oxide nanocrystals, but a full understanding of how nanocrystal synthesis, the processing of nanocrystal-based materials, and the structure of nanocrystals relate to the resulting properties of nanocrystal-based materials is still nascent. Gaining a fundamental understanding of and control over these structure-property relationships is crucial to developing a holistic understanding of metal oxide nanocrystals. The unique ability to tune metal oxide nanocrystals by changing composition through the introduction of dopants or by changing size and shape affords a way to study the interplay between structure, processing, and properties. This overall goal of this work is to chemically synthesize colloidal metal oxide nanocrystals, process them into useful materials, characterize charge transport in materials based on colloidal metal oxide nanocrystals, and develop ways to manipulate charge transport. In particular, this dissertation characterizes how the charge transport properties of metal oxide nanocrystal-based materials depend on their processing and

  8. Singly and Doubly Occupied Higher Quantum States in Nanocrystals.

    Science.gov (United States)

    Jeong, Juyeon; Yoon, Bitna; Kwon, Young-Wan; Choi, Dongsun; Jeong, Kwang Seob

    2017-02-08

    Filling the lowest quantum state of the conduction band of colloidal nanocrystals with a single electron, which is analogous to the filling the lowest unoccupied molecular orbital in a molecule with a single electron, has attracted much attention due to the possibility of harnessing the electron spin for potential spin-based applications. The quantized energy levels of the artificial atom, in principle, make it possible for a nanocrystal to be filled with an electron if the Fermi-energy level is optimally tuned during the nanocrystal growth. Here, we report the singly occupied quantum state (SOQS) and doubly occupied quantum state (DOQS) of a colloidal nanocrystal in steady state under ambient conditions. The number of electrons occupying the lowest quantum state can be controlled to be zero, one (unpaired), and two (paired) depending on the nanocrystal growth time via changing the stoichiometry of the nanocrystal. Electron paramagnetic resonance spectroscopy proved the nanocrystals with single electron to show superparamagnetic behavior, which is a direct evidence of the SOQS, whereas the DOQS of the two- or zero-electron occupied nanocrystals in the 1Se exhibit diamagnetic behavior. In combination with the superconducting quantum interference device measurement, it turns out that the SOQS of the HgSe colloidal quantum dots has superparamagnetic property. The appearance and change of the steady-state mid-IR intraband absorption spectrum reflect the sequential occupation of the 1Se state with electrons. The magnetic property of the colloidal quantum dot, initially determined by the chemical synthesis, can be tuned from diamagnetic to superparamagnetic and vice versa by varying the number of electrons through postchemical treatment. The switchable magnetic property will be very useful for further applications such as colloidal nanocrystal based spintronics, nonvolatile memory, infrared optoelectronics, catalyst, imaging, and quantum computing.

  9. Formation of hollow nanocrystals through the nanoscale kirkendall effect

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Yadong; Rioux, Robert M.; Erdonmez, Can K.; Hughes, Steven; Somorjai, Gabor A.; Alivisatos, A. Paul

    2004-03-11

    We demonstrate that hollow nanocrystals can be synthesized through a mechanism analogous to the Kirkendall Effect, in which pores form due to the difference in diffusion rates between two components in a diffusion couple. Cobalt nanocrystals are chosen as a primary example to show that their reaction in solution with oxygen, sulfur or selenium leads to the formation of hollow nanocrystals of the resulting oxide and chalcogenides. This process provides a general route to the synthesis of hollow nanostructures of large numbers of compounds. A simple extension of this process yields platinum-cobalt oxide yolk-shell nanostructures which may serve as nanoscale reactors in catalytic applications.

  10. Size-Dependence of Infrared Spectra in Niobium Carbide Nanocrystals

    Science.gov (United States)

    Shubert, V. Alvin; Lewis, Steven P.

    2012-08-01

    Niobium carbide nanocrystals of 1:1 stoichiometry have recently been observed for particle sizes ranging from Nb4C4 to Nb50C50. Infrared (IR) spectroscopic measurements show that a new band of IR vibrational modes appears with increasing particle size at Nb9C9. Using density-functional theory, we show that the vibrational modes in the new band involve structural features present only in nanocrystals with three or more atomic layers in every direction. The Nb9C9 nanocrystal is right at this structural threshold.

  11. Controlled Chemical Doping of Semiconductor Nanocrystals Using Redox Buffers

    Energy Technology Data Exchange (ETDEWEB)

    Engel, Jesse H. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Surendranath, Yogesh [Univ. of California, Berkeley, CA (United States); Alivisatos, Paul [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2013-07-20

    Semiconductor nanocrystal solids are attractive materials for active layers in next-generation optoelectronic devices; however, their efficient implementation has been impeded by the lack of precise control over dopant concentrations. Herein we demonstrate a chemical strategy for the controlled doping of nanocrystal solids under equilibrium conditions. Exposing lead selenide nanocrystal thin films to solutions containing varying proportions of decamethylferrocene and decamethylferrocenium incrementally and reversibly increased the carrier concentration in the solid by 2 orders of magnitude from their native values. This application of redox buffers for controlled doping provides a new method for the precise control of the majority carrier concentration in porous semiconductor thin films.

  12. Colloidal nanocrystal synthesis and the organic-inorganicinterface

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Yadong; Alivisatos, A. Paul

    2005-05-12

    Colloidal nanocrystals are nanometer-sized, solution-grown inorganic particles stabilized by a layer of surfactants attached to their surface. The inorganic cores exhibit useful properties controlled by composition as well as size and shape, while the surfactant coating ensures that these structures are easy to fabricate and process. It is this combination of features that makes colloidal nanocrystals attractive and promising building blocks for advanced materials and devices. But their full potential can only be exploited if we achieve exquisite control over their composition, size, shape, crystal structure and surface properties. Here we review what is known about nanocrystal growth and outline strategies for controlling it.

  13. Optical activity of chirally distorted nanocrystals

    Science.gov (United States)

    Tepliakov, Nikita V.; Baimuratov, Anvar S.; Baranov, Alexander V.; Fedorov, Anatoly V.; Rukhlenko, Ivan D.

    2016-05-01

    We develop a general theory of optical activity of semiconductor nanocrystals whose chirality is induced by a small perturbation of their otherwise achiral electronic subsystems. The optical activity is described using the quantum-mechanical expressions for the rotatory strengths and dissymmetry factors introduced by Rosenfeld. We show that the rotatory strengths of optically active transitions are decomposed on electric dipole and magnetic dipole contributions, which correspond to the electric dipole and magnetic dipole transitions between the unperturbed quantum states. Remarkably, while the two kinds of rotatory strengths are of the same order of magnitude, the corresponding dissymmetry factors can differ by a factor of 105. By maximizing the dissymmetry of magnetic dipole absorption one can significantly enhance the enantioselectivity in the interaction of semiconductor nanocrystals with circularly polarized light. This feature may advance chiral and analytical methods, which will benefit biophysics, chemistry, and pharmaceutical science. The developed theory is illustrated by an example of intraband transitions inside a semiconductor nanocuboid, whose rotatory strengths and dissymmetry factors are calculated analytically.

  14. A general strategy for nanocrystal synthesis

    Science.gov (United States)

    Wang, Xun; Zhuang, Jing; Peng, Qing; Li, Yadong

    2005-09-01

    New strategies for materials fabrication are of fundamental importance in the advancement of science and technology. Organometallic and other organic solution phase synthetic routes have enabled the synthesis of functional inorganic quantum dots or nanocrystals. These nanomaterials form the building blocks for new bottom-up approaches to materials assembly for a range of uses; such materials also receive attention because of their intrinsic size-dependent properties and resulting applications. Here we report a unified approach to the synthesis of a large variety of nanocrystals with different chemistries and properties and with low dispersity; these include noble metal, magnetic/dielectric, semiconducting, rare-earth fluorescent, biomedical, organic optoelectronic semiconducting and conducting polymer nanoparticles. This strategy is based on a general phase transfer and separation mechanism occurring at the interfaces of the liquid, solid and solution phases present during the synthesis. We believe our methodology provides a simple and convenient route to a variety of building blocks for assembling materials with novel structure and function in nanotechnology.

  15. Reusable hydroxyapatite nanocrystal sensors for protein adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Tagaya, Motohiro; Ikoma, Toshiyuki; Hanagata, Nobutaka [Biomaterials Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Chakarov, Dinko; Kasemo, Bengt [Department of Applied Physics, Chalmers University of Technology, Goeteberg S-41296 (Sweden); Tanaka, Junzo, E-mail: tikoma@ceram.titech.ac.j [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, Tokyo, Tokyo 152-8550 (Japan)

    2010-08-15

    The repeatability of the adsorption and removal of fibrinogen and fetal bovine serum on hydroxyapatite (HAp) nanocrystal sensors was investigated by Fourier transform infrared (FTIR) spectroscopy and quartz crystal microbalance with dissipation (QCM-D) monitoring technique. The HAp nanocrystals were coated on a gold-coated quartz sensor by electrophoretic deposition. Proteins adsorbed on the HAp sensors were removed by (i) ammonia/hydrogen peroxide mixture (APM), (ii) ultraviolet light (UV), (iii) UV/APM, (iv) APM/UV and (v) sodium dodecyl sulfate (SDS) treatments. FTIR spectra of the reused surfaces revealed that the APM and SDS treatments left peptide fragments or the proteins adsorbed on the surfaces, whereas the other methods successfully removed the proteins. The QCM-D measurements indicated that in the removal treatments, fibrinogen was slowly adsorbed in the first cycle because of the change in surface wettability revealed by contact angle measurements. The SDS treatment was not effective in removing proteins. The APM or UV treatment decreased the frequency shifts for the reused HAp sensors. The UV/APM treatment did not induce the frequency shifts but decreased the dissipation shifts. Therefore, we conclude that the APM/UV treatment is the most useful method for reproducing protein adsorption behavior on HAp sensors.

  16. MIS diode structure in As/+/ implanted CdS

    Science.gov (United States)

    Hutchby, J. A.

    1977-01-01

    Structure made by As implantation of carefully prepared high-conductivity CdS surfaces followed by Pt deposition and 450 C anneal display rectifying, although substantially different, I-V characteristics in the dark and during illumination with subband-gap light. Structures prepared in the same way on an unimplanted portion of the substrate have similar I-V characteristics, except that the forward turnover voltage for an illuminated unimplanted diode is much smaller than that for an implanted diode. It is suggested that the charge conduction in both structures is dominated by hole and/or electron tunneling through a metal-semiconductor potential barrier. The tunneling processes appear to be quite sensitive to subband-gap illumination, which causes the dramatic decreases of turnover voltages and apparent series resistances. The difference in turnover voltage appears to be caused by interface states between the Pt electrode and the implanted layer, which suggests a MIS model.

  17. Characterization of chemically synthesized CdS nanoparticles

    Indian Academy of Sciences (India)

    Rajeev R Prabhu; M Abdul Khadar

    2005-11-01

    II–VI semiconductor nanoparticles are presently of great interest for their practical applications such as zero-dimensional quantum confined materials and for their applications in optoelectronics and photonics. The optical properties get modified dramatically due to the confinement of charge carriers within the nanoparticles. Similar to the effects of charge carriers on optical properties, confinement of optical and acoustic phonons leads to interesting changes in the phonon spectra. In the present work, we have synthesized nanoparticles of CdS using chemical precipitation technique. The crystal structure and grain size of the particles are studied using XRD. The UV–visible absorption, photoluminescence and Raman spectra of the sample are recorded and discussed briefly.

  18. Optical properties of CdS sintered film

    Indian Academy of Sciences (India)

    D Patidar; R Sharma; N Jain; T P Sharma; N S Saxena

    2006-02-01

    Chemical method has been used to prepare cadmium sulphide by using cadmium, hydrochloric acid and H2S. The reflection spectra of covered and uncovered sintered films of CdS have been recorded by ‘Hitachi spectrophotometer’ over the wavelength range 300–700 nm. The energy band gaps of these films have been calculated from reflection spectra. It is found that the energy band gap of both films is same as 2.41 eV. It is indicated that energy band gap of these films does not change. This value of band gap is in good agreement with the value reported by other workers. The measurement of photocurrent has also been carried out using Keithley High Resistance meter/ Electrometer. This film shows the high photosensitivity and high photocurrent decay. Thus so obtained films are suitable for fabrication of photo detectors and solar cells.

  19. Nonlinear optical properties of semiconductor nanocrystals

    Science.gov (United States)

    Ricard, Gianpiero Banfi Vittorio Degiorgio Daniel

    1998-05-01

    This review is devoted to the description of recent experimental results concerning the nonlinear optical properties of semiconductor-doped glasses SDGs with particular emphasis on the regime in which the energy of the incident photon is smaller than the energy gap. A considerable theoretical and experimental effort has been devoted in the last 10years to the fundamental aspects of quantumconfined structures, which have properties somewhat intermediate between the bulk crystals and atoms or molecules. From this point of view, SDGs represent an easily available test system, and optical techniques have been a major diagnostic tool. Luminescence and absorption spectroscopy were extensively used to characterize the electronic states. The experiments aimed at the measurement of the real and imaginary parts of the third-order optical susceptibility of SDGs below the bandgap are described in some detail, and the results obtained with different techniques are compared. Besides the intrinsic fast nonlinearity due to bound electrons, SDGs may present a larger but much slower nonlinearity due to the free carriers generated by two-photon absorption. This implies that experiments have to be properly designed for separation of the two effects. In this article we stress the importance of a detailed structural characterization of the samples. Knowledge of the volume fraction occupied by the nanocrystals is necessary in order to derive from the experimental data the intrinsic nonlinearity and to compare it with the bulk nonlinearity. We discuss recent experiments in which the dependence of the intrinsic nonlinearity on the crystal size is derived by performing, on the samples, measurements of the real part and imaginary part of the nonlinear optical susceptibility and measurements of crystal size and volume fraction. Structural characterization is of interest also for a better understanding of the physical processes underlying the growth of crystallites in SDGs. The average size of

  20. Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes

    Science.gov (United States)

    Weiss, Shimon; Bruchez, Jr., Marcel; Alivisatos, Paul

    2008-01-01

    A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) an affinity molecule linked to the semiconductor nanocrystal. The semiconductor nanocrystal is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Exposure of the semiconductor nanocrystal to excitation energy will excite the semiconductor nanocrystal causing the emission of electromagnetic radiation. Further described are processes for respectively: making the luminescent semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.

  1. Broad spectral response photodetector based on individual tin-doped CdS nanowire

    Directory of Open Access Journals (Sweden)

    Weichang Zhou

    2014-12-01

    Full Text Available High purity and tin-doped 1D CdS micro/nano-structures were synthesized by a convenient thermal evaporation method. SEM, EDS, XRD and TEM were used to examine the morphology, composition, phase structure and crystallinity of as-prepared samples. Raman spectrum was used to confirm tin doped into CdS effectively. The effect of impurity on the photoresponse properties of photodetectors made from these as-prepared pure and tin-doped CdS micro/nano-structures under excitation of light with different wavelength was investigated. Various photoconductive parameters such as responsivity, external quantum efficiency, response time and stability were analyzed to evaluate the advantage of doped nanowires and the feasibility for photodetector application. Comparison with pure CdS nanobelt, the tin-doped CdS nanowires response to broader spectral range while keep the excellect photoconductive parameters. Both trapped state induced by tin impurity and optical whispering gallery mode microcavity effect in the doped CdS nanowires contribute to the broader spectral response. The micro-photoluminescence was used to confirm the whispering gallery mode effect and deep trapped state in the doped CdS nanowires.

  2. Broad spectral response photodetector based on individual tin-doped CdS nanowire

    Science.gov (United States)

    Zhou, Weichang; Peng, Yuehua; Yin, Yanling; Zhou, Yong; Zhang, Yong; Tang, Dongsheng

    2014-12-01

    High purity and tin-doped 1D CdS micro/nano-structures were synthesized by a convenient thermal evaporation method. SEM, EDS, XRD and TEM were used to examine the morphology, composition, phase structure and crystallinity of as-prepared samples. Raman spectrum was used to confirm tin doped into CdS effectively. The effect of impurity on the photoresponse properties of photodetectors made from these as-prepared pure and tin-doped CdS micro/nano-structures under excitation of light with different wavelength was investigated. Various photoconductive parameters such as responsivity, external quantum efficiency, response time and stability were analyzed to evaluate the advantage of doped nanowires and the feasibility for photodetector application. Comparison with pure CdS nanobelt, the tin-doped CdS nanowires response to broader spectral range while keep the excellect photoconductive parameters. Both trapped state induced by tin impurity and optical whispering gallery mode microcavity effect in the doped CdS nanowires contribute to the broader spectral response. The micro-photoluminescence was used to confirm the whispering gallery mode effect and deep trapped state in the doped CdS nanowires.

  3. Microwave Synthesized Monodisperse CdS Spheres of Different Size and Color for Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Carlos A. Rodríguez-Castañeda

    2015-01-01

    Full Text Available Monodisperse CdS spheres of size of 40 to 140 nm were obtained by microwave heating from basic solutions. It is observed that larger CdS spheres were formed at lower solution pH (8.4–8.8 and smaller ones at higher solution pH (10.8–11.3. The color of CdS products changed with solution pH and reaction temperature; those synthesized at lower pH and temperature were of green-yellow color, whereas those formed at higher pH and temperature were of orange-yellow color. A good photovoltage was observed in CdS:poly(3-hexylthiophene solar cells with spherical CdS particles. This is due to the good dispersion of CdS nanoparticles in P3HT solution that led to a large interface area between the organic and inorganic semiconductors. Higher photocurrent density was obtained in green-yellow CdS particles of lower defect density. The efficient microwave chemistry accelerated the hydrolysis of thiourea in pH lower than 9 and produced monodisperse spherical CdS nanoparticles suitable for solar cell applications.

  4. Cowrie-shell architectures: Low temperature growth of Ni doped CdS film

    Energy Technology Data Exchange (ETDEWEB)

    Thool, Gautam Sheel; Sraveen, K. [Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007 (India); Singh, Ajaya Kumar [Department of Chemistry, Govt. VYT PG. Autonomous College, Durg 491001, Chhattisgarh (India); Pal, Ujjwal [Central Mechanical Engineering Research Institute, M. G. Avenue, Durgapur 713209 (India); Singh, Surya Prakash, E-mail: spsingh@iict.res.in [Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007 (India)

    2015-11-15

    In this work, we report the synthesis of Ni doped CdS cowrie-shell architectures and submicron balls like structures via low temperature chemical bath deposition method. The as-synthesized materials were systematically characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDAX), Raman spectroscopy and FTIR spectra. XRD results revealed the existence of cubic phase of CdS based material. SEM pictures depicted the growth of well define morphologies i.e. cowries-shell and submicron balls. Deposition time and dopant played significant role in the growth of CdS based different architectures. The EDAX spectra confirmed the presence of Ni into the CdS lattice. Surface structure of synthesized material was derived by FTIR analysis. - Highlights: • Ni doped CdS cowrie-shell like architectures were synthesized using low temperature aqueous solution method. • We demonstrated the deposition time and dopant played significant role in the growth of CdS based different architectures. • The formation of Ni doped CdS submicron balls has taken place by simple over growth on cowrie-shell particles. • FTIR spectra showed that the surface Cd{sup 2+} ions probably coordinated to triethanol amine molecules.

  5. Synthesis, Characterization, Fluorescence, Photocatalytic and Antibacterial Activity of CdS Nanoparticles Using Schiff Base.

    Science.gov (United States)

    Ayodhya, Dasari; Venkatesham, M; Kumari, A Santoshi; Reddy, G Bhagavanth; Ramakrishna, D; Veerabhadram, G

    2015-09-01

    Cadmium sulfide nanoparticles (CdS NPs) were successfully prepared using sonochemical method by employing Schiff-base, (2-[(4-methoxy-phenylimino)-methyl]-4-nitro phenol) as a complexing agent. Here, SB is used as a ligand to control the morphology of NPs. XRD patterns and TEM images show that the synthesized CdS NPs have cubic structures with a diameter of about 2-10 nm. The formation of CdS NPs and their optical, structure, thermal and morphologies were studied by means of UV-vis DRS, fluorescence, FTIR, zeta potential, XRD, SEM and TEM. The interactions between CdS NPs and SB were investigated in an aqueous solution using fluorescence spectroscopy. The fluorescence quenching studies suggest that SB quenches the fluorescence of CdS NPs effectively. The degradation kinetics of methyl red (MR) by the photocatalyst was followed by Langmuir-Hinshelwood model. The results revealed that photocatalytic degradation of MR by SB capped CdS NPs could be considered as a practical and reliable technique for the removal of environmental pollutants. The antibacterial activity of samples was evaluated against E. coli, S. aureus and P. aeruginosa and the results were compared. SB and SB capped CdS NPs could be a potential antibacterial compounds after further investigation.

  6. Toxicity of cadmium sulfide (CdS) nanoparticles against Escherichia coli and HeLa cells.

    Science.gov (United States)

    Hossain, Sk Tofajjen; Mukherjee, Samir Kumar

    2013-09-15

    The present study endeavours to assess the toxic effect of synthesized CdS nanoparticles (NPs) on Escherichia coli and HeLa cells. The CdS NPs were characterized by DLS, XRD, TEM and AFM studies and the average size of NPs was revealed as ∼3 nm. On CdS NPs exposure bacterial cells changed morphological features to filamentous form and damage of the cell surface was found by AFM study. The expression of two conserved cell division components namely ftsZ and ftsQ in E. coli was decreased both at transcriptional and translational levels upon CdS NPs exposure. CdS NPs inhibited proper cell septum formation without affecting the nucleoid segregation. Viability of HeLa cells declined with increasing concentration of CdS NPs and the IC₅₀ value was found to be 4 μg/mL. NPs treated HeLa cells showed changed morphology with condensed and fragmented nuclei. Increased level of reactive oxygen species (ROS) was found both in E. coli and HeLa cells on CdS NPs exposure. The inverse correlation between declined cell viabilities and elevated ROS level suggested that oxidative stress seems to be the key event by which NPs induce toxicity both in E. coli and HeLa cells.

  7. The influence of surface passivation on electronic energy relaxation dynamics of CdSe and CdSe/CdS nanocrystals studied using visible and near infrared transient absorption spectroscopy.

    Science.gov (United States)

    Yi, Chongyue; Knappenberger, Kenneth L

    2015-03-19

    Charge carrier relaxation dynamics of electronically excited CdSe and CdSe/CdS core/shell nanocrystals (NCs) were studied using femtosecond time-resolved transient absorption spectroscopy, employing both visible and near-infrared (NIR) probe laser pulses. Following 400 nm excitation, the combination of visible and NIR laser probe pulses were used to determine the influence of surface passivation on electronic relaxation dynamics for nanocrystals overcoated with either organic ligands or inorganic semiconductors. In particular, low-energy NIR photons were used to isolate transient absorption signals due to either electron and hole intraband transitions. Four relaxation components were detected for CdSe NCs passivated by organic molecules: (1) picosecond hole relaxation; (2) electron deep trapping; (3) electron surface trapping; and (4) exciton radiative recombination. Based on TA data collected over a broad energy range, electron deep trapping at Se(2-) sites was suppressed for CdSe NCs passivated by inorganic (CdS) semiconducting materials. By comparing the time-dependent transient absorption data of a series of CdSe/CdS NCs with different shell thicknesses, evidence for the transition from Type-I to quasi Type-II NCs was obtained. These data illustrate the sensitivity of femtosecond time-resolved transient absorption measurements carried out over visible and near infrared probe energies for determining the influence of nanocrystal structure on electronic relaxation dynamics.

  8. Efficiently Enhancing Visible Light Photocatalytic Activity of Faceted TiO2 Nanocrystals by Synergistic Effects of Core-Shell Structured Au@CdS Nanoparticles and Their Selective Deposition.

    Science.gov (United States)

    Tong, Ruifeng; Liu, Chang; Xu, Zhenkai; Kuang, Qin; Xie, Zhaoxiong; Zheng, Lansun

    2016-08-24

    Integrating wide bandgap semiconductor photocatalysts with visible-light-active inorganic nanoparticles (such as Au and CdS) as sensitizers is one of the most efficient methods to improve their photocatalytic activity in the visible light region. However, as for all such composite photocatalysts, a rational design and precise control over their architecture is often required to achieve optimal performance. Herein, a new TiO2-based ternary composite photocatalyst with superior visible light activity was designed and synthesized. In this composite photocatalyst, the location of the visible light sensitizers was engineered according to the intrinsic facet-induced effect of well-faceted TiO2 nanocrystals on the spatial separation of photogenerated carriers. Experimentally, core-shell structured Au@CdS nanoparticles acting as visible light sensitizers were selectively deposited onto photoreductive {101} facets of well-faceted anatase TiO2 nanocrystals through a two-step in situ photodeposition route. Because the combination of Au@CdS and specific {101} facets of TiO2 nanocrystals facilitates the transport of charges photogenerated under visible light irradiation, this well-designed ternary composite photocatalyst exhibited superior activity in visible-light-driven photocatalytic H2 evolution, as expected.

  9. Selective staining of CdS on ZnO biolabel for ultrasensitive sandwich-type amperometric immunoassay of human heart-type fatty-acid-binding protein and immunoglobulin G.

    Science.gov (United States)

    Qin, Xiaoli; Xu, Aigui; Liu, Ling; Sui, Yuyun; Li, Yunlong; Tan, Yueming; Chen, Chao; Xie, Qingji

    2017-05-15

    We report on an ultrasensitive metal-labeled amperometric immunoassay of proteins, which is based on the selective staining of nanocrystalline cadmium sulfide (CdS) on ZnO nanocrystals and in-situ microliter-droplet anodic stripping voltammetry (ASV) detection on the immunoelectrode. Briefly, antibody 1 (Ab1), bovine serum albumin (BSA), antigen and ZnO-multiwalled carbon nanotubes (MWCNTs) labeled antibody 2 (Ab2-ZnO-MWCNTs) were successively anchored on a β-cyclodextrin-graphene sheets (CD-GS) nanocomposite modified glassy carbon electrode (GCE), forming a sandwich-type immunoelectrode (Ab2-ZnO-MWCNTs/antigen/BSA/Ab1/CD-GS/GCE). CdS was selectively grown on the catalytic ZnO surfaces through chemical reaction of Cd(NO3)2 and thioacetamide (ZnO-label/CdS-staining), due to the presence of an activated cadmium hydroxide complex on ZnO surfaces that can decompose thioacetamide. A beforehand cathodic "potential control" in air and then injection of 7μL of 0.1M aqueous HNO3 on the immunoelectrode allow dissolution of the stained CdS and simultaneous cathodic preconcentration of atomic Cd onto the electrode surface, thus the following in-situ ASV detection can be used for immunoassay with enhanced sensitivity. Under optimized conditions, human immunoglobulin G (IgG) and human heart-type fatty-acid-binding protein (FABP) are analyzed by this method with ultrahigh sensitivity, excellent selectivity and small reagent-consumption, and the limits of detection (LODs, S/N=3) are 0.4fgmL(-1) for IgG and 0.3fgmL(-1) for FABP (equivalent to 73 FABP molecules in the 6μL sample employed).

  10. The Photocatalytic Degradation Proformance of CdS Nanomaterials%硫化镉纳米材料对罗丹明B溶液的光催化降解性能

    Institute of Scientific and Technical Information of China (English)

    段莉梅; 崔海洋; 赵伟强

    2013-01-01

    Under solvothermal synthesis condition, the hexagonal cadmium sulphide nanomaterial was obtained by heating at 120oC for 12h, using ethylenediamine and water as mixed solvent. The sample was charaeterized by XRD and TEM technologies. The photocatalytic property of CdS nanocrystal was studied by adoptting the degradation of rho-damine B as the model reaction, and the factors influencing degradation efficiency of rhodamine B were discussed in-cluding the dosage of CdS sample, acidity of the degradation system and the type of light source. The degradation effect of CdS samples increased with the acidity decreased, and the degradation effect was better when rhodamine B solution was irradiated under sunlight than under 250 W mercury lamp.%  以氯化镉和硫脲为原料,以乙二胺和水为混合溶剂,采用溶剂热合成方法,在120oC和12h条件下,制得了六方相硫化镉样品,对其进行了XRD和TEM表征。以罗丹明B的降解为模型反应,对硫化镉纳米材料的光催化性能进行了研究,讨论了硫化镉的用量、降解体系的酸度及光源类型等因素对降解效果的影响。随着降解体系酸度的增加,硫化镉对罗丹明B溶液的光催化降解效果呈增大的趋势;太阳光照射下,罗丹明B溶液的降解效果好于250 W汞灯照射时的降解效果。

  11. REVERSE MICROEMULSION OF IGEPAL Co-720 SYSTEM AS MICROREACTOR FOR CdS SYNTHESIS

    Directory of Open Access Journals (Sweden)

    Fitria Rahmawati

    2016-08-01

    Full Text Available A Research on CdS synthesis in reverse microemulsion of Igepal CO-720 system has been conducted at various weight ratio of water to surfactant. Igepal CO-720 naturally forms oil in water (o/w emulsion type due to its high HLB (Hydrophilic -Lipophilic Balance value. Therefore, in this research the Igepal CO-720 system was inversed into water in oil (w/o system before it was used as microreactor for CdS synthesis. As comparison, a system of AOT (Aerosol OT; sodium bis (2-ethylhexyl sulfosuccinate which is naturally w/o system was also used as microreactor for CdS synthesis. The prepared CdS was analyzed by X-ray diffraction for crystal identification, scanning electron microscope for morphological analysis, UV-Vis for absorption edge determination and photoelectrochemical testing for photoactivity. The results show that the Igepal CO -720 system can be inverted into w/o system and can be used as microreactor for CdS synthesis. The prepared CdS is in nanosize with the average diameter of 2.517 ± 0.014 nm and the average gap energy of 3.805 ± 0.178 eV. The prepared CdS in Igepal CO-720 system has less regular form in comparison with morphology of the prepared CdS in AOT system. As the ω values decreases the particle diameter decreases, the gap energy increases and the % IPCE increases. It indicates that high surfactant concentration allows small size micelles formation and produced smaller CdS particle that has high surface area and therefore provide higher photocatalytic activity which was indicated by high value of its % IPCE.

  12. Facile method to prepare CdS nanostructure based on the CdTe films

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Ligang; Chen, Yuehui; Wei, Zelu; Cai, Hongling; Zhang, Fengming; Wu, Xiaoshan, E-mail: xswu@nju.edu.cn

    2015-09-15

    Graphical abstract: - Highlights: • CdS nanostructure is directly fabricated on CdTe film only by heating treatment under H{sub 2}S/N{sub 2} mixed atmosphere at a relatively low temperature (450 °C) with gold layer as the intermediate. • Nanostructure of CdS layer, varying from nanowires to nanosheets, may be controlled by the thickness of gold film. • The change of morphology adjusts its luminescence properties. - Abstract: Nanostructured cadmium sulfide (CdS) plays critical roles in electronics and optoelectronics. In this paper, we report a method to fabricate CdS nanostructure directly on CdTe film, via a thermal annealing method in H{sub 2}S/N{sub 2} mixed gas flow at a relatively low temperature (450 °C). The microstructure and optical properties of CdS nanostructure are investigated by X-ray diffraction, transmission electron microscopy, Raman, and photoluminescence. The morphology of CdS nanostructure, evolving from nanowires to nanosheets, can be controlled by the thickness of Au film deposited on the CdTe film. And CdS nanostructures are single crystalline with the hexagonal wurtzite structure. Raman spectroscopy under varying the excitation wavelengths confirm that synthesized CdS-CdTe films contain two layers, i.e., CdS nanostructure (top) and CdTe layer (bottom). The change of morphology modifies its luminescence properties. Obviously, through simply thermal annealing in H{sub 2}S/N{sub 2} mixed gas, fabricating CdS nanostructure on CdTe film can open up the new possibility for obtaining high efficient CdTe solar cell.

  13. Sol-gel derived precursors to Group 14 semiconductor nanocrystals - Convenient materials for enabling nanocrystal-based applications

    Energy Technology Data Exchange (ETDEWEB)

    Veinot, Jonathan G C; Henderson, Eric J; Hessel, Colin M, E-mail: jveinot@ualberta.ca [Department of Chemistry, University of Alberta, Edmonton, Alberta (Canada)

    2009-11-15

    Semiconductor nanocrystals are intriguing because of their electronic, optical, and chemical characteristics. Silicon nanocrystals (Si-NCs) of sub-5 nm dimension are of particular interest due to their intense photoluminescent response and the promise of linking silicon photonics and electronics. Other related nanomaterials of technological importance include SiC and Ge. The following contribution describes key experimental findings pertaining to synthetic methodology, investigation of nanodomain formation and growth, as determined by X-ray powder diffraction (XRD) and photoluminescence (PL) spectroscopy for a series of sol-gel derived prepolymers suitable for preparing Group 14 based nanocrystal containing composites.

  14. Sol-gel derived precursors to Group 14 semiconductor nanocrystals - Convenient materials for enabling nanocrystal-based applications

    Science.gov (United States)

    Veinot, Jonathan G. C.; Henderson, Eric J.; Hessel, Colin M.

    2009-11-01

    Semiconductor nanocrystals are intriguing because of their electronic, optical, and chemical characteristics. Silicon nanocrystals (Si-NCs) of sub-5 nm dimension are of particular interest due to their intense photoluminescent response and the promise of linking silicon photonics and electronics. Other related nanomaterials of technological importance include SiC and Ge. The following contribution describes key experimental findings pertaining to synthetic methodology, investigation of nanodomain formation and growth, as determined by X-ray powder diffraction (XRD) and photoluminescence (PL) spectroscopy for a series of sol-gel derived prepolymers suitable for preparing Group 14 based nanocrystal containing composites.

  15. Preparation and Structural Analysis of CdS Nanoparticle Embedded Polyurethane Nanocomposites

    Science.gov (United States)

    Indolia, Ajay Pal; Kumar, Purushottam; Gaur, M. S.

    2011-07-01

    Polymer nanocomposite samples of different weight ratio of CdS were developed by solution embedding of nanoparticles in polyurethane. XRD and Scanning Electron Microscopy (SEM) were used to understand the structural properties of polymer nanocomposite samples. SEM micrograph demonstrates the dispersion of CdS nanoparticles in polymer matrix. It has been observed that crystallinity of PU decreases with increase in concentration of CdS nanoparticles. The XRD data show the characteristic peaks of nanoparticles (i.e.CdS) in nanocomposite samples, which confirm the nanostructure formation in polymer matrix.

  16. Photoacoustic Study of CdS QDs for Application in Quantum-Dot-Sensitized Solar Cells

    OpenAIRE

    Abdallah, S.; N. Al-Hosiny; Ali Badawi

    2012-01-01

    The optical properties and photovoltaic characterization of CdS quantum dots sensitized solar cells (QDSSCs) were studied. CdS QDs were prepared by the chemical solution deposition (CD) technique. Photoacoustic spectroscopy (PA) was employed to study the optical properties of the prepared samples. The sizes of the CdS QDs were estimated from transmission electron microscope (TEM) micrographs gives radii ranged from 1.57 to 1.92 nm. The current density-voltage (J-V) characteristic curves of th...

  17. Growth of CdS nanoparticles by chemical method and its characterization

    Indian Academy of Sciences (India)

    R Bhattacharya; S Saha

    2008-07-01

    In the present work a simple chemical reduction method is followed to grow CdS nanoparticles at room temperature. The grown sample is ultrasonicated in acetone. The dispersed sample is characterized using electron diffraction technique. Simultaneously optical absorption of this sample is studied in the range of 400–700 nm. The photoluminescence spectrum of the sample is also studied. Results show the formation of nanoparticles. Hence an increase in band gap compared to bulk CdS and the as-prepared CdS nanoparticles have surface sulphur vacancies.

  18. Synthesis of CdS nanoparticles for photocatalytic application of methyleneblue degradation

    Science.gov (United States)

    Muthuraj, V.; Umadevi, M.; Sankarasubramanian, K.; Kajamuhideen, M. S.

    2014-04-01

    CdS nanoparticles were prepared by the reaction of cadmium acetate with thiourea in the presence and absence of methylene blue dye (MB). The nanoparticles were characterized by, XRD, FT-IR, UV-Vis. XRD study shows the presence of hexagonal phase for the nanoparticles whereas in case of the bulk samples only the hexagonal phase is observed. Fourier transform infrared spectroscopy (FT-IR) showed a strong interaction of methyl groups with CdS nanoparticles. The degradation of methylene blue was analysed using UV-Vis absorbance spectrum. Thus the results authenticate that methylene blue dye influences the structural and optical properties of the CdS nanoparticles.

  19. Chemical surface deposition of cds thin films from CdI2 aqueous solution

    Directory of Open Access Journals (Sweden)

    G. Il’chuk

    2009-01-01

    Full Text Available For the first time using CdI2 solution CdS films on glass and ITO coated glass substrates were produced by the method of layerwise chemical surface deposition (ChSD. CdS thin films with the widths from 40 nm to 100 nm were obtained for windows in solar cells based on CdS/CdTe heterojunctions. Changes of the structural and optical properties of CdS films due to air annealing are shown.

  20. Raman spectroscopy of optical properties in CdS thin films

    Directory of Open Access Journals (Sweden)

    Trajić J.

    2015-01-01

    Full Text Available Properties of CdS thin films were investigated applying atomic force microscopy (AFM and Raman spectroscopy. CdS thin films were prepared by using thermal evaporation technique under base pressure 2 x 10-5 torr. The quality of these films was investigated by AFM spectroscopy. We apply Raman scattering to investigate optical properties of CdS thin films, and reveal existence of surface optical phonon (SOP mode at 297 cm-1. Effective permittivity of mixture were modeled by Maxwell - Garnet approximation. [Projekat Ministarstva nauke Republike Srbije, br. 45003