Rheological and thermo-mechanical properties of poly(lactic acid)/lignin-coated cellulose nanocrystal composites

Science.gov (United States)

Anju Gupta; William Simmons; Gregory T. Schueneman; Donald Hylton; Eric A. Mintz

2017-01-01

Improving the processability and physical properties of sustainable biobased polymers and biobased fillers is essential to preserve its biodegradability and make them suitable for different end user applications. Herein, we report the use of spray-dried lignin-coated cellulose nanocrystals (L-CNCs), a biobased filler, to modify the rheological and thermos-mechanical...

Toxicity assessment of zebrafish following exposure to CdTe QDs

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wei, E-mail: wzhang@ecust.edu.cn [State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237 (China); Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology, Shanghai 200237 (China); School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai 200237 (China); Lin, Kuangfei, E-mail: kflin@ecust.edu.cn [State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237 (China); Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology, Shanghai 200237 (China); School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai 200237 (China); Miao, Youna [State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237 (China); Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology, Shanghai 200237 (China); School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai 200237 (China); Dong, Qiaoxiang; Huang, Changjiang; Wang, Huili [Zhejiang Provincial Key Lab for Technology and Application of Model Organisms, Wenzhou Medical College, Wenzhou 325035 (China); Guo, Meijin [State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237 (China); Cui, Xinhong [Shanghai Institute of Landscape Gardening, Shanghai 200233 (China)

2012-04-30

Highlights: Black-Right-Pointing-Pointer The LC{sub 50} of TGA-CdTe for zebrafish at 120 hpf was 185.9 nM. Black-Right-Pointing-Pointer Zebrafish exposed to TGA-CdTe resulted in lower hatch rate and more malformation. Black-Right-Pointing-Pointer Body length and heart beat of zebrafish declined after exposure to TGA-CdTe. Black-Right-Pointing-Pointer Larvae exposure to TGA-CdTe elicited a higher basal swimming rate. Black-Right-Pointing-Pointer Abnormal vascular of FLI-1 transgenic zebrafish larvae exposed to TGA-CdTe occurred. - Abstract: CdTe quantum dots (QDs) are nanocrystals of unique composition and properties that have found many new commercial applications; therefore, their potential toxicity to aquatic organisms has become a hot research topic. The lab study was performed to determine the developmental and behavioral toxicities to zebrafish under continuous exposure to low concentrations of CdTe QDs (1-400 nM) coated with thioglycolic acid (TGA). The results show: (1) the 120 h LC{sub 50} of 185.9 nM, (2) the lower hatch rate and body length, more malformations, and less heart beat and swimming speed of the exposed zebrafish, (3) the brief burst and a higher basal swimming rate of the exposed zebrafish larvae during a rapid transition from light-to-dark, and (4) the vascular hyperplasia, vascular bifurcation, vascular crossing and turbulence of the exposed FLI-1 transgenic zebrafish larvae.

Enhancement of open-circuit voltage and the fill factor in CdTe nanocrystal solar cells by using interface materials

International Nuclear Information System (INIS)

Zhu, Jiaoyan; Yang, Yuehua; Gao, Yuping; Qin, Donghuan; Wu, Hongbin; Huang, Wenbo; Hou, Lintao

2014-01-01

Interface states influence the operation of nanocrystal (NC) solar cell carrier transport, recombination and energetic mechanisms. In a typical CdTe NC solar cell with a normal structure of a ITO/p-CdTe NCs/n-acceptor (or without)/Al configuration, the contact between the ITO and CdTe is a non-ohm contact due to a different work function (for an ITO, the value is ∼4.7 eV, while for CdTe NCs, the value is ∼5.3 eV), which results in an energetic barrier at the ITO/CdTe interface and decreases the performance of the NC solar cells. This work investigates how interface materials (including Au, MoO x and C 60 ) affect the performance of NC solar cells. It is found that devices with interface materials have shown higher V oc than those without interface materials. For the case in which we used Au as an interface, we obtained a high open-circuit voltage of 0.65 V, coupled with a high fill factor (62%); this resulted in a higher energy conversion efficiency (ECE) of 5.3%, which showed a 30% increase in the ECE compared with those without the interlayer. The capacitance measurements indicate that the increased V oc in the case in which Au was used as the interface is likely due to good ohm contact between the Au’s and the CdTe NCs’ thin film, which decreases the energetic barrier at the ITO/CdTe interface. (paper)

Synthesis of Colloidal Quantum Dots Coated with Mercaptosuccinic Acid for Early Detection and Therapeutics of Oral Cancers

Science.gov (United States)

Jocelin, G.; Arivarasan, A.; Ganesan, M.; Prasad, N. Rajendra; Sasikala, G.

2016-04-01

Quantum dots (QDs) are gaining widespread recognition for its luminescence behavior and unique photo physical properties as a bio-marker and inorganic fluorophore. In spite of such rampant advantages, its application is clinically hampered depending on the surface coating decreasing its luminescence efficiency. The present study reports preparation of CdTe QDs capped with biologically active thiol based material, mercaptosuccinic acid (MSA) for diagnosis of oral cancer (KB) cells by acting as a fluorophore marking targeted tumor cells and at the same time exhibiting certain cytotoxic effects. Synthesized MSA coated CdTe QDs is spherical in shape with an average particle size of 3-5nm. In vitro, the rapid uptake of MSA CdTe QDs in oral cancer cell lines were assessed through fluorescence microscopy. Further, this study evaluates the therapeutic efficiency of MSA CdTe QDs in human oral cancer cell lines using MTT analysis. MSA CdTe QDs exhibit significant cytotoxicity in oral cancer cells in a dose dependent manner with low IC50 when compared with other raw CdTe QDs. MSA CdTe QDs were also treated with human lymphocytes (normal cells) to assess and compare the toxicity profile of QDs in normal and oral tumors. The results of our present study strengthen our hypothesis of using MSA CdTe QDs as detector for tracking and fluorescence imaging of oral cancer cells and exhibiting sufficient cytotoxicity in them.

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.

CdTe aggregates in KBr crystalline matrix

International Nuclear Information System (INIS)

Bensouici, A.; Plaza, J.L.; Dieguez, E.; Halimi, O.; Boudine, B.; Addala, S.; Guerbous, L.; Sebais, M.

2009-01-01

In this work, we report the experimental results on the fabrication and optical characterization of Czochralski (Cz) grown KBr single crystals doped with CdTe crystallites. The results of the optical absorption have shown two bands, the first one located at 250 nm demonstrates the incorporation of cadmium atoms in the KBr host followed by a partial chemical decomposition of CdTe, the second band located at 585 nm shows an optical response of CdTe aggregates. Photoluminescence spectra at room temperature before annealing showed a band located at 520 nm (2.38 eV), with a blue shift from the bulk gap of 0.82 eV (E g (CdTe)=1.56 eV). While the photoluminescence spectra after annealing at 600 deg. C showed a band situated at 640 nm (1.93 eV), these bands are due to band-to-band transitions of CdTe nanocrystals with a blue shift from the bulk gap at 0.38 eV. Blue shift in optical absorption and photoluminescence spectra confirm nanometric size of dopant. X-ray diffraction (XRD) spectra have shown the incorporation of CdTe aggregates in KBr.

CdTe aggregates in KBr crystalline matrix

Energy Technology Data Exchange (ETDEWEB)

Bensouici, A., E-mail: bensouicia@yahoo.f [Laboratory of Crystallography, Department of Physics, Mentouri-Constantine University, Constantine 25000 (Algeria); Plaza, J.L., E-mail: joseluis.plaza@uam.e [Crystal Growth Laboratory (CGL), Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, Madrid (Spain); Dieguez, E. [Crystal Growth Laboratory (CGL), Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, Madrid (Spain); Halimi, O.; Boudine, B.; Addala, S. [Laboratory of Crystallography, Department of Physics, Mentouri-Constantine University, Constantine 25000 (Algeria); Guerbous, L. [Centre de recherche nucleaire d' Alger (CRNA), Alger 16000 (Algeria); Sebais, M. [Laboratory of Crystallography, Department of Physics, Mentouri-Constantine University, Constantine 25000 (Algeria)

2009-09-15

In this work, we report the experimental results on the fabrication and optical characterization of Czochralski (Cz) grown KBr single crystals doped with CdTe crystallites. The results of the optical absorption have shown two bands, the first one located at 250 nm demonstrates the incorporation of cadmium atoms in the KBr host followed by a partial chemical decomposition of CdTe, the second band located at 585 nm shows an optical response of CdTe aggregates. Photoluminescence spectra at room temperature before annealing showed a band located at 520 nm (2.38 eV), with a blue shift from the bulk gap of 0.82 eV (E{sub g} (CdTe)=1.56 eV). While the photoluminescence spectra after annealing at 600 deg. C showed a band situated at 640 nm (1.93 eV), these bands are due to band-to-band transitions of CdTe nanocrystals with a blue shift from the bulk gap at 0.38 eV. Blue shift in optical absorption and photoluminescence spectra confirm nanometric size of dopant. X-ray diffraction (XRD) spectra have shown the incorporation of CdTe aggregates in KBr.

Hydroxyapatite nanocrystals functionalized with alendronate as bioactive components for bone implant coatings to decrease osteoclastic activity

Science.gov (United States)

Bosco, Ruggero; Iafisco, Michele; Tampieri, Anna; Jansen, John A.; Leeuwenburgh, Sander C. G.; van den Beucken, Jeroen J. J. P.

2015-02-01

The integration of bone implants within native bone tissue depends on periprosthetic bone quality, which is severely decreased in osteoporotic patients. In this work, we have synthesized bone-like hydroxyapatite nanocrystals (nHA) using an acid-base neutralization reaction and analysed their physicochemical properties. Subsequently, we have functionalized the nHA with alendronate (nHAALE), a well-known bisphosphonate drug used for the treatment of osteoporosis. An in vitro osteoclastogenesis test was carried out to evaluate the effect of nHAALE on the formation of osteoclast-like cells from monocytic precursor cells (i.e. RAW264.7 cell line) showing that nHAALE significantly promoted apoptosis of osteoclast-like cells. Subsequently, nHA and nHAALE were deposited on titanium disks using electrospray deposition (ESD), for which characterisation of the deposited coatings confirmed the presence of alendronate in nHAALE coatings with nanoscale thickness of about 700 nm. These results indicate that alendronate linked to hydroxyapatite nanocrystals has therapeutic potential and nHAALE can be considered as an appealing coating constituent material for orthopaedic and oral implants for application in osteoporotic patients.

In situ functionalization and PEO coating of iron oxide nanocrystals using seeded emulsion polymerization.

Science.gov (United States)

Kloust, Hauke; Schmidtke, Christian; Feld, Artur; Schotten, Theo; Eggers, Robin; Fittschen, Ursula E A; Schulz, Florian; Pöselt, Elmar; Ostermann, Johannes; Bastús, Neus G; Weller, Horst

2013-04-16

Herein we demonstrate that seeded emulsion polymerization is a powerful tool to produce multiply functionalized PEO coated iron oxide nanocrystals. Advantageously, by simple addition of functional surfactants, functional monomers, or functional polymerizable linkers-solely or in combinations thereof-during the seeded emulsion polymerization process, a broad range of in situ functionalized polymer-coated iron oxide nanocrystals were obtained. This was demonstrated by purposeful modulation of the zeta potential of encapsulated iron oxide nanocrystals and conjugation of a dyestuff. Successful functionalization was unequivocally proven by TXRF. Furthermore, the spatial position of the functional groups can be controlled by choosing the appropriate spacers. In conclusion, this methodology is highly amenable for combinatorial strategies and will spur rapid expedited synthesis and purposeful optimization of a broad scope of nanocrystals.

Intensely emitting CdTe nanocrystals retained initial photoluminescence efficiency in sol-gel derived Si1-xZrxO2 glass

International Nuclear Information System (INIS)

Yang, P.; Murase, N.

2007-01-01

Emitting CdTe nanocrystals (NCs) were embedded in pure glass matrices (Si 1-x Zr x O 2 , x≤0.15) using a controlled sol-gel method, where the pre-hydrolyzed condition, the molar ratio of Zr/Si, the gelation time, the pH, and the amount of alcohol were judiciously optimized considering the surface condition of the NCs and the mechanism of the glass formation. As a result, the prepared glass phosphor exhibited high photoluminescence efficiencies (40% for green and 60% for red when Zr/Si was 5-10%) by retaining their initial values as in CdTe colloidal solution. To our knowledge, these values are the highest among those ever obtained for any solid matrices containing NCs. Because of the existence of Zr, the prepared glasses exhibit much better resistance against the ambient atmosphere, heat-treatment, and boiling water compared with pure silica glass (x=0) or the glass prepared from our other methods using a silane coupling agent. Thus, the obtained glass is promising for applications such as optical devices. (orig.)

Enhanced electrochemiluminescence quenching of CdS:Mn nanocrystals by CdTe QDs-doped silica nanoparticles for ultrasensitive detection of thrombin

Science.gov (United States)

Shan, Yun; Xu, Jing-Juan; Chen, Hong-Yuan

2011-07-01

This work reports an aptasensor for ultrasensitive detection of thrombin based on remarkably efficient energy-transfer induced electrochemiluminescence (ECL) quenching from CdS:Mn nanocrystals (NCs) film to CdTe QDs-doped silica nanoparticles (CdTe/SiO2 NPs). CdTe/SiO2 NPs were synthesized via the Stöber method and showed black bodies' strong absorption in a wide spectral range without excitonic emission, which made them excellent ECL quenchers. Within the effective distance of energy scavenging, the ECL quenching efficiency was dependent on the number of CdTe QDs doped into the silica NPs. Using ca. 200 CdTe QDs doped silica NPs on average of 40 nm in diameter as ECL quenching labels, attomolar detection of thrombin was successfully realized. The protein detection involves a competition binding event, based on thrombin replacing CdTe/SiO2 NPs labeled probing DNA which is hybridized with capturing aptamer immobilized on a CdS:Mn NCs film modified glassy carbon electrode surface by specific aptamer-protein affinity interactions. It results in the displacement of ECL quenching labels from CdS:Mn NCs film and concomitant ECL signal recovery. Owing to the high-content CdTe QDs in silica NP, the increment of ECL intensity (ΔIECL) and the concentration of thrombin showed a double logarithmic linear correlation in the range of 5.0 aM~5.0 fM with a detection limit of 1aM. And, the aptasensor hardly responded to antibody, bovine serum albumin (BSA), haemoglobin (Hb) and lysozyme, showing good detection selectivity for thrombin. This long-distance energy scavenging could have a promising application perspective in the detection of biological recognition events on a molecular level.This work reports an aptasensor for ultrasensitive detection of thrombin based on remarkably efficient energy-transfer induced electrochemiluminescence (ECL) quenching from CdS:Mn nanocrystals (NCs) film to CdTe QDs-doped silica nanoparticles (CdTe/SiO2 NPs). CdTe/SiO2 NPs were synthesized via

Glutathione-capped CdTe nanocrystals as probe for the determination of fenbendazole

Science.gov (United States)

Li, Qin; Tan, Xuanping; Li, Jin; Pan, Li; Liu, Xiaorong

2015-04-01

Water-soluble glutathione (GSH)-capped CdTe quantum dots (QDs) were synthesized. In pH 7.1 PBS buffer solution, the interaction between GSH-capped CdTe QDs and fenbendazole (FBZ) was investigated by spectroscopic methods, including fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, and resonance Rayleigh scattering (RRS) spectroscopy. In GSH-capped CdTe QDs solution, the addition of FBZ results in the fluorescence quenching and RRS enhancement of GSH-capped CdTe QDs. And the quenching intensity (enhanced RRS intensity) was proportional to the concentration of FBZ in a certain range. Investigation of the interaction mechanism, proved that the fluorescence quenching and RRS enhancement of GSH-capped CdTe QDs by FBZ is the result of electrostatic attraction. Based on the quenching of fluorescence (enhancement of RRS) of GSH-capped CdTe QDs by FBZ, a novel, simple, rapid and specific method for FBZ determination was proposed. The detection limit for FBZ was 42 ng mL-1 (3.4 ng mL-1) and the quantitative determination range was 0-2.8 μg mL-1 with a correlation of 0.9985 (0.9979). The method has been applied to detect FBZ in real simples and with satisfactory results.

Enhanced electrochemiluminescence quenching of CdS:Mn nanocrystals by CdTe QDs-doped silica nanoparticles for ultrasensitive detection of thrombin.

Science.gov (United States)

Shan, Yun; Xu, Jing-Juan; Chen, Hong-Yuan

2011-07-01

This work reports an aptasensor for ultrasensitive detection of thrombin based on remarkably efficient energy-transfer induced electrochemiluminescence (ECL) quenching from CdS:Mn nanocrystals (NCs) film to CdTe QDs-doped silica nanoparticles (CdTe/SiO(2) NPs). CdTe/SiO(2) NPs were synthesized via the Stöber method and showed black bodies' strong absorption in a wide spectral range without excitonic emission, which made them excellent ECL quenchers. Within the effective distance of energy scavenging, the ECL quenching efficiency was dependent on the number of CdTe QDs doped into the silica NPs. Using ca. 200 CdTe QDs doped silica NPs on average of 40 nm in diameter as ECL quenching labels, attomolar detection of thrombin was successfully realized. The protein detection involves a competition binding event, based on thrombin replacing CdTe/SiO(2) NPs labeled probing DNA which is hybridized with capturing aptamer immobilized on a CdS:Mn NCs film modified glassy carbon electrode surface by specific aptamer-protein affinity interactions. It results in the displacement of ECL quenching labels from CdS:Mn NCs film and concomitant ECL signal recovery. Owing to the high-content CdTe QDs in silica NP, the increment of ECL intensity (ΔI(ECL)) and the concentration of thrombin showed a double logarithmic linear correlation in the range of 5.0 aM∼5.0 fM with a detection limit of 1aM. And, the aptasensor hardly responded to antibody, bovine serum albumin (BSA), haemoglobin (Hb) and lysozyme, showing good detection selectivity for thrombin. This long-distance energy scavenging could have a promising application perspective in the detection of biological recognition events on a molecular level.

Supercritical synthesis and in situ deposition of PbS nanocrystals with oleic acid passivation for quantum dot solar cells

Energy Technology Data Exchange (ETDEWEB)

Tavakoli, M.M. [Department of Materials Science and Engineering, Sharif University of Technology, 14588 Tehran (Iran, Islamic Republic of); Simchi, A., E-mail: simchi@sharif.edu [Department of Materials Science and Engineering, Sharif University of Technology, 14588 Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, 14588 Tehran (Iran, Islamic Republic of); Aashuri, H. [Department of Materials Science and Engineering, Sharif University of Technology, 14588 Tehran (Iran, Islamic Republic of)

2015-04-15

Colloidal quantum dot solar cells have recently attracted significant attention due to their low-processing cost and surging photovoltaic performance. In this paper, a novel, reproducible, and simple solution-based process based on supercritical fluid toluene is presented for in situ growth and deposition PbS nanocrystals with oleic-acid passivation. A lead precursor containing sulfur was mixed with oleic acid in toluene and processed in a supercritical fluid condition at different temperatures of 140, 270 and 330 °C for 20 min. The quantum dots were deposited on a fluorine-doped tin oxide glass substrate inside the supercritical reactor. Transmission electron microscopy, X-ray diffraction, absorption and dynamic light scattering showed that the nanocrystals processed at the supercritical condition (330 °C) are fully crystalline with a narrow size distribution of ∼3 nm with an absorption wavelength of 915 nm (bandgap of 1.3 eV). Fourier transform infrared spectroscopy indicated that the PbS quantum dots are passivated by oleic acid molecules during the growth. Photovoltaic characteristics of Schottky junction solar cells showed an improvement over devices prepared by spin-coating. - Highlights: • Supercritical fluid processing and in situ deposition of PbS QDs are presented. • The prepared nanocrystals are mono-dispersed with an optical bandgap of 1.3 eV. • Photovoltaic performance of the in situ deposited nanocrystals is reported. • An improved PV performance compared to spin coated Schottky solar cells is shown.

Solution-processing of ultra-thin CdTe/ZnO nanocrystal solar cells

International Nuclear Information System (INIS)

MacDonald, Brandon I.; Gengenbach, Thomas R.; Watkins, Scott E.; Mulvaney, Paul; Jasieniak, Jacek J.

2014-01-01

We have carried out a detailed study into how modifications of the physical, chemical and optical properties of solution-processed, nanocrystalline CdTe layers influence the photovoltaic performance of sintered CdTe/ZnO nanocrystal solar cells. Such solar cells are fabricated through layer-by-layer assembly, which is enabled through an inter layer chemical and thermal treatment cycle. In this manner we are able to fabricate working solar cells with sintered CdTe layers as low as 90 nm, provided that grain size is precisely controlled. We show that the extent of grain growth achieved during the CdTe sintering process is strongly dependent on nanocrystal surface chemistry and chemical environment, with the removal of the organic capping ligands and the introduction of CdCl 2 prior to annealing leading to greatly enhanced growth. Due to the air processing involved and the nanocrystalline nature of the CdTe, the overall performance of these solar cells is shown to be strongly dependent on both annealing temperature and time, with optimal results requiring a balance between crystal growth and degradation due to oxidation. Using this simple bi-layer device structure, optimized treatment conditions result in power conversion efficiencies of up to 7.7% and peak internal quantum efficiencies in excess of 95%. - Highlights: • We study the growth of nanocrystalline CdTe thin films from colloidal nanocrystals. • We examine the CdTe growth profiles as a function of surface chemistry. • We show that nanocrystalline CdTe is susceptible to oxidation under air annealing. • We show how this oxidation influences performance in CdTe/ZnO solar cells. • We demonstrate CdTe/ZnO solar cells with an efficiency of 7.7% fabricated in air

Microfluidic Fabrication of Hydrocortisone Nanocrystals Coated with Polymeric Stabilisers

Directory of Open Access Journals (Sweden)

David F. Odetade

2016-12-01

Full Text Available Hydrocortisone (HC nanocrystals intended for parenteral administration of HC were produced by anti-solvent crystallisation within coaxial assemblies of pulled borosilicate glass capillaries using either co-current flow of aqueous and organic phases or counter-current flow focusing. The organic phase was composed of 7 mg/mL of HC in a 60:40 (v/v mixture of ethanol and water and the anti-solvent was milli-Q water. The microfluidic mixers were fabricated with an orifice diameter of the inner capillary ranging from 50 µm to 400 µm and operated at the aqueous to organic phase flow rate ratio ranging from 5 to 25. The size of the nanocrystals decreased with increasing aqueous to organic flow rate ratio. The counter-current flow microfluidic mixers provided smaller nanocrystals than the co-current flow devices under the same conditions and for the same geometry, due to smaller diameter of the organic phase stream in the mixing zone. The Z-average particle size of the drug nanocrystals increased from 210–280 nm to 320–400 nm after coating the nanocrystals with 0.2 wt % aqueous solution of hydroxypropyl methylcellulose (HPMC in a stirred vial. The differential scanning calorimetry (DSC and X-ray powder diffraction (XRPD analyses carried out on the dried nanocrystals stabilized with HPMC, polyvinyl pyrrolidone (PVP, and sodium lauryl sulfate (SLS were investigated and reported. The degree of crystallinity for the processed sample was lowest for the sample stabilised with HPMC and the highest for the raw HC powder.

Plasmonic light-sensitive skins of nanocrystal monolayers

Science.gov (United States)

Akhavan, Shahab; Gungor, Kivanc; Mutlugun, Evren; Demir, Hilmi Volkan

2013-04-01

We report plasmonically coupled light-sensitive skins of nanocrystal monolayers that exhibit sensitivity enhancement and spectral range extension with plasmonic nanostructures embedded in their photosensitive nanocrystal platforms. The deposited plasmonic silver nanoparticles of the device increase the optical absorption of a CdTe nanocrystal monolayer incorporated in the device. Controlled separation of these metallic nanoparticles in the vicinity of semiconductor nanocrystals enables optimization of the photovoltage buildup in the proposed nanostructure platform. The enhancement factor was found to depend on the excitation wavelength. We observed broadband sensitivity improvement (across 400-650 nm), with a 2.6-fold enhancement factor around the localized plasmon resonance peak. The simulation results were found to agree well with the experimental data. Such plasmonically enhanced nanocrystal skins hold great promise for large-area UV/visible sensing applications.

Emission switching in carbon dots coated CdTe quantum dots driving by pH dependent hetero-interactions

Energy Technology Data Exchange (ETDEWEB)

Dai, Xiao; Wang, Hao; Yi, Qinghua; Wang, Yun; Cong, Shan; Zhao, Jie; Sun, Yinghui; Zou, Guifu, E-mail: zouguifu@suda.edu.cn, E-mail: jiexiong@uestc.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Qian, Zhicheng [School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Huang, Jianwen; Xiong, Jie, E-mail: zouguifu@suda.edu.cn, E-mail: jiexiong@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Luo, Hongmei [Department of Chemical and Materials Engineering, New Mexico State University, Las Cruces, New Mexico 88003 (United States)

2015-11-16

Due to the different emission mechanism between fluorescent carbon dots and semiconductor quantum dots (QDs), it is of interest to explore the potential emission in hetero-structured carbon dots/semiconducting QDs. Herein, we design carbon dots coated CdTe QDs (CDQDs) and investigate their inherent emission. We demonstrate switchable emission for the hetero-interactions of the CDQDs. Optical analyses indicate electron transfer between the carbon dots and the CdTe QDs. A heterojunction electron process is proposed as the driving mechanism based on N atom protonation of the carbon dots. This work advances our understanding of the interaction mechanism of the heterostructured CDQDs and benefits the future development of optoelectronic nanodevices with new functionalities.

Synthesis of surface molecular imprinting polymer on SiO{sub 2}-coated CdTe quantum dots as sensor for selective detection of sulfadimidine

Energy Technology Data Exchange (ETDEWEB)

Zhou, Zhiping; Ying, Haiqin; Liu, Yanyan [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Xu, Wanzhen, E-mail: xwz09@ujs.edu.cn [School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013 (China); Yang, Yanfei; Luan, Yu [Zhenjiang Institute for Drug Control of Jiangsu Province, Zhenjiang 212003 (China); Lu, Yi; Liu, Tianshu [Zhenjiang Entry-Exit Inspection Quarantine Bureau, Zhenjiang 212008 (China); Yu, Shui [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Yang, Wenming, E-mail: ywm@ujs.edu.cn [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China)

2017-05-15

Highlights: • Surface molecular imprinting technology and SiO{sub 2}-coated CdTe QDs were combined to prepare a novel fluorescent sensor for selective detection of sulfadimidine. • The relative fluorescent intensity weakened in a linear way with the increasing concentration of sulfadimidine in the range of 10–60 μmol L{sup −1}. • The practical application of the fluorescent MIP sensor was evaluated by means of analyzing sulfadimidine in the real milk samples. The recoveries were at the range of 90.3–99.6% and the relative standard deviation ranged from 1.9 to 3.1%. - Abstract: This paper demonstrates a facile method to synthesize surface molecular imprinting polymer (MIP) on SiO{sub 2}-coated CdTe QDs for selective detection of sulfadimidine (SM{sub 2}). The fluorescent MIP sensor was prepared using cadmium telluride quantum dots (CdTe QDs) as the material of fluorescent signal readout, sulfadimidine as template molecule, 3-aminopropyltriethoxysilane (APTES) as functional monomer and tetraethyloxysilane (TEOS) as cross-linking agent. The CdTe cores were embed in the silicon shells by a sol-gel reaction and then the molecular imprinting layers were immobilized on the surface of the SiO{sub 2}-coated CdTe QDs. Under the optimized conditions, the relative fluorescent intensity weakened in a linear way with the increasing concentration of sulfadimidine in the range of 10–60 μmol L{sup −1}. The practical application of the fluorescent MIP sensor was evaluated by means of analyzing sulfadimidine in the real milk samples. The recoveries were at the range of 90.3–99.6% and the relative standard deviation (RSD) ranged from 1.9 to 3.1%, which indicates the successful synthesis of the fluorescent MIP sensor. This sensor provides an alternative solution for selective determination of sulfadimidine from real milk samples.

Intensely emitting CdTe nanocrystals retained initial photoluminescence efficiency in sol-gel derived Si{sub 1-x}Zr{sub x}O{sub 2} glass

Energy Technology Data Exchange (ETDEWEB)

Yang, P.; Murase, N. [National Institute of Advanced Industrial Science and Technology, Photonics Research Institute, Osaka (Japan)

2007-10-15

Emitting CdTe nanocrystals (NCs) were embedded in pure glass matrices (Si{sub 1-x}Zr{sub x}O{sub 2}, x{<=}0.15) using a controlled sol-gel method, where the pre-hydrolyzed condition, the molar ratio of Zr/Si, the gelation time, the pH, and the amount of alcohol were judiciously optimized considering the surface condition of the NCs and the mechanism of the glass formation. As a result, the prepared glass phosphor exhibited high photoluminescence efficiencies (40% for green and 60% for red when Zr/Si was 5-10%) by retaining their initial values as in CdTe colloidal solution. To our knowledge, these values are the highest among those ever obtained for any solid matrices containing NCs. Because of the existence of Zr, the prepared glasses exhibit much better resistance against the ambient atmosphere, heat-treatment, and boiling water compared with pure silica glass (x=0) or the glass prepared from our other methods using a silane coupling agent. Thus, the obtained glass is promising for applications such as optical devices. (orig.)

Solution-processed efficient CdTe nanocrystal/CBD-CdS hetero-junction solar cells with ZnO interlayer

International Nuclear Information System (INIS)

Tian, Yiyao; Zhang, Yijie; Lin, Yizhao; Gao, Kuo; Zhang, Yunpeng; Liu, Kaiyi; Yang, Qianqian; Zhou, Xiao; Qin, Donghuan; Wu, Hongbin; Xia, Yuxin; Hou, Lintao; Lan, Linfeng; Chen, Junwu; Wang, Dan; Yao, Rihui

2013-01-01

CdTe nanocrystal (NC)/CdS p–n hetero-junction solar cells with an ITO/ZnO-In/CdS/CdTe/MoO x /Ag-inverted structure were prepared by using a layer-by-layer solution process. The CdS thin films were prepared by chemical bath deposition on top of ITO/ZnO-In and were found to be very compact and pin-hole free in a large area, which insured high quality CdTe NCs thin-film formation upon it. The device performance was strongly related to the CdCl 2 annealing temperature and annealing time. Devices exhibited power conversion efficiency (PCE) of 3.08 % following 400 °C CdCl 2 annealing for 5 min, which was a good efficiency for solution processed CdTe/CdS NC-inverted solar cells. By carefully designing and optimizing the CdCl 2 -annealing conditions (370 °C CdCl 2 annealing for about 15 min), the PCE of such devices showed a 21 % increase, in comparison to 400 °C CdCl 2 -annealing conditions, and reached a better PCE of 3.73 % while keeping a relatively high V OC of 0.49 V. This PCE value, to the best of our knowledge, is the highest PCE reported for solution processed CdTe–CdS NC solar cells. Moreover, the inverted solar cell device was very stable when kept under ambient conditions, less than 4 % degradation was observed in PCE after 40 days storage

Formic acid-assisted synthesis of palladium nanocrystals and their electrocatalytic properties.

Science.gov (United States)

Wang, Qinchao; Wang, Yiqian; Guo, Peizhi; Li, Qun; Ding, Ruixue; Wang, Baoyan; Li, Hongliang; Liu, Jingquan; Zhao, X S

2014-01-14

Palladium (Pd) nanocrystals have been synthesized by using formic acid as the reducing agent at room temperature. When the concentration of formic acid was increased continuously, the size of Pd nanocrystals first decreased to a minimum and then increased slightly again. The products have been investigated by a series of techniques, including X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), UV-vis absorption, and electrochemical measurements. The formation of Pd nanocrystals is proposed to be closely related to the dynamical imbalance of the growth and dissolution rate of Pd nanocrystals associated with the adsorption of formate ions onto the surface of the intermediates. It is found that small Pd nanocrystals showed blue-shifted adsorption peaks compared with large ones. Pd nanocrystals with the smallest size display the highest electrocatalytic activity for the electrooxidation of formic acid and ethanol on the basis of cyclic voltammetry and chronoamperometric data. It is suggested that both the electrochemical active surface area and the small size effect are the key roles in determining the electrocatalytic performances of Pd nanocrystals. A "dissolution-deposition-aggregation" process is proposed to explain the variation of the electrocatalytic activity during the electrocatalysis according to the HRTEM characterization.

Hybrid nanocrystal/polymer solar cells based on tetrapod-shaped CdSexTe1-x nanocrystals

International Nuclear Information System (INIS)

Zhou Yi; Li Yunchao; Zhong Haizheng; Hou Jianhui; Ding Yuqin; Yang Chunhe; Li Yongfang

2006-01-01

A series of ternary tetrapodal nanocrystals of CdSe x Te 1-x with x = 0 (CdTe), 0.23, 0.53, 0.78, 1 (CdSe) were synthesized and used to fabricate hybrid nanocrystal/polymer solar cells. Herein, the nanocrystals acted as electron acceptors, and poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) was used as an electron donor. It was found that the open circuit voltage (V oc ), short-circuit current (J sc ) and power conversion efficiency (η) of the devices all increased with increasing Se content in the CdSe x Te 1-x nanocrystals under identical experimental conditions. The solar cell based on the blend of tetrapodal CdSe nanocrystals and MEH-PPV (9:1 w/w) showed the highest power conversion efficiency of 1.13% under AM 1.5, 80 mW cm -2 , and the maximum incident photon to converted current efficiency (IPCE) of the device reached 47% at 510 nm. The influence of nanocrystal composition on the photovoltaic properties of the hybrid solar cells was explained by the difference of the band level positions between MEH-PPV and the nanocrystals

Impact of nanocrystal spray deposition on inorganic solar cells.

Science.gov (United States)

Townsend, Troy K; Yoon, Woojun; Foos, Edward E; Tischler, Joseph G

2014-05-28

Solution-synthesized inorganic cadmium telluride nanocrystals (∼4 nm; 1.45 eV band gap) are attractive elements for the fabrication of thin-film-based low-cost photovoltaic (PV) devices. Their encapsulating organic ligand shell enables them to be easily dissolved in organic solvents, and the resulting solutions can be spray-cast onto indium-tin oxide (ITO)-coated glass under ambient conditions to produce photoactive thin films of CdTe. Following annealing at 380 °C in the presence of CdCl2(s) and evaporation of metal electrode contacts (glass/ITO/CdTe/Ca/Al), Schottky-junction PV devices were tested under simulated 1 sun conditions. An improved PV performance was found to be directly tied to control over the film morphology obtained by the adjustment of spray parameters such as the solution concentration, delivery pressure, substrate distance, and surface temperature. Higher spray pressures produced thinner layers (spray-cast Schottky devices rivaled those prepared by conventional spin-coating, showing Jsc = 14.6 ± 2.7 mA cm(-2), Voc = 428 ± 11 mV, FF = 42.8 ± 1.4%, and Eff. = 2.7 ± 0.5% under 1 sun illumination. This optimized condition of CdTe spray deposition was then applied to heterojunction devices (ITO/CdTe/ZnO/Al) to reach 3.0% efficiency after light soaking under forward bias. The film thickness, surface morphology, and light absorption were examined with scanning electron microscopy, optical profilometry, and UV/vis spectroscopy.

Anode property of carbon coated LiFePO4 nanocrystals

Science.gov (United States)

Ni, Jiangfeng; Jiang, Jiaxing; Savilov, S. V.; Aldoshin, S. M.

2016-10-01

Nanostructured LiFePO4 is appealing cathode material for rechargeable lithium batteries. Herein, however, we report the intriguing anode properties of carbon coated LiFePO4 nanocrystals. In the potential range of 0-3.0 V, the LiFePO4 nanocrystal electrodes afford high reversible capacity of 373 mAhg-1 at a current rate of 0.05 Ag-1 and retains 239 mAhg-1 at a much higher rate of 1.25 Ag-1. In addition, it is capable of sustaining 1000 cycles at 1.25 Ag-1 without any capacity fading. Such superior properties indicate that nanostructured LiFePO4 could also be promising anode for rechargeable battery applications.

Nonlinear optical effect and excited electron dynamics of semiconductor nanocrystals; Handotai nano kessh no hisenkei kogaku koka to reiki denshi dynamics

Energy Technology Data Exchange (ETDEWEB)

Goto, T. [Tohoku University, Sendai (Japan)

1996-08-20

Investigations were given on nanocrystals of CuCl and CdTe with regard to their nonlinear optical mechanism. The experiment used a femto-second pump probe spectroscope. The experiment on CuCl nanocrystals revealed the following facts: in the case where one photon is absorbed into one nanocrystal, cascade mitigation occurs to the pair of electrons and holes, and exciters; and in the case where two photons are absorbed into one nanocrystal, exciter molecules are made via the pair of electrons and holes and the exciters. Thus, it was found that the optical nonlinearity occurs when more than two photons are absorbed into one nanocrystal, and inter-exciter interactions and formation of the exciter molecules are the physical causes thereof. The experiment on CdTe nanocrystals indicated that electrons and holes produced by laser beam are distributed instantaneously between the size-quantized discrete levels, and that temperature in the electron system drops with lapse of time. 9 refs., 6 figs.

Solution-processed efficient CdTe nanocrystal/CBD-CdS hetero-junction solar cells with ZnO interlayer

Energy Technology Data Exchange (ETDEWEB)

Tian, Yiyao; Zhang, Yijie; Lin, Yizhao; Gao, Kuo; Zhang, Yunpeng; Liu, Kaiyi; Yang, Qianqian [South China University of Technology, School of Materials Science and Engineering (China); Zhou, Xiao; Qin, Donghuan, E-mail: qindh@scut.edu.cn; Wu, Hongbin [South China University of Technology, Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices (China); Xia, Yuxin; Hou, Lintao [Jinan University, College of Science and Engineering (China); Lan, Linfeng; Chen, Junwu; Wang, Dan; Yao, Rihui [South China University of Technology, Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices (China)

2013-11-15

CdTe nanocrystal (NC)/CdS p–n hetero-junction solar cells with an ITO/ZnO-In/CdS/CdTe/MoO{sub x}/Ag-inverted structure were prepared by using a layer-by-layer solution process. The CdS thin films were prepared by chemical bath deposition on top of ITO/ZnO-In and were found to be very compact and pin-hole free in a large area, which insured high quality CdTe NCs thin-film formation upon it. The device performance was strongly related to the CdCl{sub 2} annealing temperature and annealing time. Devices exhibited power conversion efficiency (PCE) of 3.08 % following 400 °C CdCl{sub 2} annealing for 5 min, which was a good efficiency for solution processed CdTe/CdS NC-inverted solar cells. By carefully designing and optimizing the CdCl{sub 2}-annealing conditions (370 °C CdCl{sub 2} annealing for about 15 min), the PCE of such devices showed a 21 % increase, in comparison to 400 °C CdCl{sub 2}-annealing conditions, and reached a better PCE of 3.73 % while keeping a relatively high V{sub OC} of 0.49 V. This PCE value, to the best of our knowledge, is the highest PCE reported for solution processed CdTe–CdS NC solar cells. Moreover, the inverted solar cell device was very stable when kept under ambient conditions, less than 4 % degradation was observed in PCE after 40 days storage.

Hydrophilic ionic liquid-passivated CdTe quantum dots for mercury ion detection.

Science.gov (United States)

Chao, Mu-Rong; Chang, Yan-Zin; Chen, Jian-Lian

2013-04-15

A hydrophilic ionic liquid, 1-ethyl-3-methylimidazolium dicyanamide (EMIDCA), was used as a medium for the synthesis of highly luminescent CdTe nanocrystals (NCs) capped with thioglycolic acid (TGA). The synthesis was performed for 8 h at 130 °C, was similar to nanocrystal preparation in an aqueous medium, and used safe, low-cost inorganic salts as precursors. After the reaction, the photoluminescence quantum yield of the CdTe NCs (NC(IL-130)) prepared in EMIDCA was significantly higher than that of the nanocrystals prepared in water (NC(w)) at 100 °C (86% vs. 35%). Moreover, the emission wavelength and particle size of NC(IL-130) were smaller than NC(w) (450 nm vs. 540 nm and 4.0 nm vs. 5.2 nm, respectively). The activation of NC(IL-130) was successful due to the coordinated action of two ligands, EMIDCA and TGA, in the primary steps of the NC formation pathway. An increase or decrease in the synthesis temperature, to 160 °C or 100 °C, respectively, was detrimental to the luminescence quality. However, the quenching effect of Hg²⁺ on the fluorescence signals of the NC(IL-130) was distinctively unique, whereas certain interfering ions, such as Pb²⁺, Fe³⁺, Co²⁺, Ni²⁺, Ag⁺, and Cu²⁺, could also quench the emission of the NC(w). Based on the Perrin model, the quenching signals of NC(w) and NC(IL-130) were well correlated with the Hg²⁺ concentrations in the phosphate buffer (pH 7.5, 50 mM). In comparison with the NC(w), the NC(IL-130) had a high tolerance of the interfering ions coexisting with the Hg²⁺ analyte, high recovery of Hg²⁺ spiked in the BSA- or FBS-containing medium, and high stability of fluorescence quenching signals between trials and days. The NC(IL-130) nanocrystals can potentially be used to develop a probe system for the determination of Hg²⁺ in physiological samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Advanced Branching Control and Characterization of Inorganic Semiconducting Nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Hughes, Steven Michael [Univ. of California, Berkeley, CA (United States)

2007-01-01

The ability to finely tune the size and shape of inorganic semiconducting nanocrystals is an area of great interest, as the more control one has, the more applications will be possible for their use. The first two basic shapes develped in nanocrystals were the sphere and the anistropic nanorod. the II_VI materials being used such as Cadmium Selenide (CdSe) and Cadmium Telluride (CdTe), exhibit polytypism, which allows them to form in either the hexagonally packed wurtzite or cubically packed zinc blende crystalline phase. The nanorods are wurtzite with the length of the rod growing along the c-axis. As this grows, stacking faults may form, which are layers of zinc blende in the otherwise wurtzite crystal. Using this polytypism, though, the first generation of branched crystals were developed in the form of the CdTe tetrapod. This is a nanocrystal that nucleates in the zincblend form, creating a tetrahedral core, on which four wurtzite arms are grown. This structure opened up the possibility of even more complex shapes and applications. This disseration investigates the advancement of branching control and further understanding the materials polytypism in the form of the stacking faults in nanorods.

Ultrasound-assisted synthesis of zinc molybdate nanocrystals and molybdate-doped epoxy/PDMS nanocomposite coatings for Mg alloy protection.

Science.gov (United States)

Eduok, Ubong; Szpunar, Jerzy

2018-06-01

Zinc molybdate (ZM) is a safer anticorrosive additive for cooling systems when compared with chromates and lead salts, due to its insolubility in aqueous media. For most molybdate pigments, their molybdate anion (MoO 4 -2 ) acts as an anionic inhibitor and its passivation capacity is comparable with chromate anion (CrO 4 -2 ). To alleviate the environmental concerns involving chromates-based industrial protective coatings, we have proposed new alternative in this work. We have synthesized ZM nanocrystals via ultrasound-assisted process and encapsulated them within an epoxy/PDMS coating towards corrosion protection. The surface morphology and mechanical properties of these ZM doped epoxy/PDMS nanocomposite coatings is exhaustively discussed to show the effect of ZM content on protective properties. The presence of ZM nanocrystals significantly contributed to the corrosion barrier performance of the coating while the amount of ZM nanocrystals needed to prepare an epoxy coating with optimum barrier performance was established. Beyond 2 wt% ZM concentration, the siloxane-structured epoxy coating network became saturated with ZM pigments. This further broadened inherent pores channels, leading to the percolation of corrosion chloride ions through the coating. SEM evidence has revealed proof of surface delamination on ZM3 coating. A model mechanism of corrosion resistance has been proposed for ZM doped epoxy/PDMS nanocomposite coatings from exhaustive surface morphological investigations and evidence. This coating matrix may have emerging applications in cooling systems as anticorrosive surface paints as well as create an avenue for environmental corrosion remediation. Copyright © 2018 Elsevier B.V. All rights reserved.

Unravelling the surface chemistry of metal oxide nanocrystals, the role of acids and bases.

Science.gov (United States)

De Roo, Jonathan; Van den Broeck, Freya; De Keukeleere, Katrien; Martins, José C; Van Driessche, Isabel; Hens, Zeger

2014-07-09

We synthesized HfO2 nanocrystals from HfCl4 using a surfactant-free solvothermal process in benzyl alcohol and found that the resulting nanocrystals could be transferred to nonpolar media using a mixture of carboxylic acids and amines. Using solution (1)H NMR, FTIR, and elemental analysis, we studied the details of the transfer reaction and the surface chemistry of the resulting sterically stabilized nanocrystals. As-synthesized nanocrystals are charge-stabilized by protons, with chloride acting as the counterion. Treatment with only carboxylic acids does not lead to any binding of ligands to the HfO2 surface. On the other hand, we find that the addition of amines provides the basic environment in which carboxylic acids can dissociate and replace chloride. This results in stable, aggregate-free dispersions of HfO2 nanocrystals, sterically stabilized by carboxylate ligands. Moreover, titrations with deuterated carboxylic acid show that the charge on the carboxylate ligands is balanced by coadsorbed protons. Hence, opposite from the X-type/nonstoichiometric nanocrystals picture prevailing in literature, one should look at HfO2/carboxylate nanocrystals as systems where carboxylic acids are dissociatively adsorbed to bind to the nanocrystals. Similar results were obtained with ZrO2 NCs. Since proton accommodation on the surface is most likely due to the high Brønsted basicity of oxygen, our model could be a more general picture for the surface chemistry of metal oxide nanocrystals with important consequences on the chemistry of ligand exchange reactions.

MC3T3-E1 cell response of amorphous phase/TiO{sub 2} nanocrystal composite coating prepared by microarc oxidation on titanium

Energy Technology Data Exchange (ETDEWEB)

Zhou, Rui [Department of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wei, Daqing, E-mail: daqingwei@hit.edu.cn [Department of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Yang, Haoyue; Feng, Wei [Department of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Cheng, Su [Department of Mechanical Engineering, School of Architecture and Civil Engineering, Harbin University of Science and Technology, Harbin 150001 (China); Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu [Department of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2014-06-01

Bioactive amorphous phase/TiO{sub 2} nanocrystal (APTN) composite coatings were fabricated by microarc oxidation (MAO) on Ti. The APTN coatings are composed of much amorphous phase with Si, Na, Ca, Ti and O elements and a few TiO{sub 2} nanocrystals. With increasing applied voltage, the micropore density of the APTN coating decreases and the micropore size of the APTN coating increases. The results indicate that less MC3T3-E1 cells attach on the APTN coatings as compared to Ti. However, the APTN coatings greatly enhance the cell proliferation ability and the activity of alkaline phosphatase. The amorphous phase and the concentrations of the released Ca and Si from the APTN coatings during cell culture have significant effects on the cell response. - Highlights: • Amorphous phase/TiO2 nanocrystal (APTN) composite coatings were fabricated. • The MC3T3-E1 cell response of the APTN coatings was evaluated. • The APTN coatings greatly enhanced the cell proliferation ability.

A novel ascorbic acid sensor based on the Fe3+/Fe2+ modulated photoluminescence of CdTe quantum dots@SiO2 nanobeads.

Science.gov (United States)

Ma, Qiang; Li, Yang; Lin, Zi-Han; Tang, Guangchao; Su, Xing-Guang

2013-10-21

In this paper, CdTe quantum dot (QD)@silica nanobeads were used as modulated photoluminescence (PL) sensors for the sensing of ascorbic acid in aqueous solution for the first time. The sensor was developed based on the different quenching effects of Fe(2+) and Fe(3+) on the PL intensity of the CdTe QD@ silica nanobeads. Firstly, the PL intensity of the CdTe QDs was quenched in the presence of Fe(3+). Although both Fe(2+) and Fe(3+) could quench the PL intensity of the CdTe QDs, the quenching efficiency were quite different for Fe(2+) and Fe(3+). The PL intensity of the CdTe QD@silica nanobeads can be quenched by about 15% after the addition of Fe(3+) (60 μmol L(-1)), while the PL intensity of the CdTe QD@silica nanobeads can be quenched about 49% after the addition of Fe(2+) (60 μmol L(-1)). Therefore, the PL intensity of the CdTe QD@silica nanobeads decreased significantly when Fe(3+) was reduced to Fe(2+) by ascorbic acid. To confirm the strategy of PL modulation in this sensing system, trace H2O2 was introduced to oxidize Fe(2+) to Fe(3+). As a result, the PL intensity of the CdTe QD@silica nanobeads was partly recovered. The proposed sensor could be used for ascorbic acid sensing in the concentration range of 3.33-400 μmol L(-1), with a detection limit (3σ) of 1.25 μmol L(-1) The feasibility of the proposed sensor for ascorbic acid determination in tablet samples was also studied, and satisfactory results were obtained.

Reducing Water Vapor Permeability of Poly(lactic acid Film and Bottle through Layer-by-Layer Deposition of Green-Processed Cellulose Nanocrystals and Chitosan

Directory of Open Access Journals (Sweden)

Katalin Halász

2015-01-01

Full Text Available Layer-by-layer electrostatic self-assembly technique was applied to improve the barrier properties of poly(lactic acid (PLA films and bottles. The LbL process was carried out by the alternate adsorption of chitosan (CH (polycation and cellulose nanocrystals (CNC produced via ultrasonic treatment. Four bilayers (on each side of chitosan and cellulose nanocrystals caused 29 and 26% improvement in barrier properties in case of films and bottles, respectively. According to the results the LbL process with CH and CNC offered a transparent “green” barrier coating on PLA substrates.

Removal of CdTe in acidic media by magnetic ion-exchange resin: A potential recycling methodology for cadmium telluride photovoltaic waste

Energy Technology Data Exchange (ETDEWEB)

Zhang, Teng, E-mail: zhangteng@mail.iee.ac.cn; Dong, Zebin; Qu, Fei; Ding, Fazhu; Peng, Xingyu; Wang, Hongyan; Gu, Hongwei

2014-08-30

Highlights: • Sulfonated magnetic microsphere was prepared as one strong acid cation-exchange resin. • Cd and Te can be removed directly from the highly acidic leaching solution of CdTe. • Good chemical stability, fast adsorbing rate and quick magnetic separation in strong acidic media. • A potential path for recycling CdTe photovoltaic waste. - Abstract: Sulfonated magnetic microspheres (PSt-DVB-SNa MPs) have been successfully prepared as adsorbents via an aqueous suspension polymerization of styrene-divinylbenzene and a sulfonation reaction successively. The resulting adsorbents were confirmed by means of Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS) and vibrating sample magnetometer (VSM). The leaching process of CdTe was optimized, and the removal efficiency of Cd and Te from the leaching solution was investigated. The adsorbents could directly remove all cations of Cd and Te from a highly acidic leaching solution of CdTe. The adsorption process for Cd and Te reached equilibrium in a few minutes and this process highly depended on the dosage of adsorbents and the affinity of sulfonate groups with cations. Because of its good adsorption capacity in strong acidic media, high adsorbing rate, and efficient magnetic separation from the solution, PSt-DVB-SNa MPs is expected to be an ideal material for the recycling of CdTe photovoltaic waste.

Intense pulsed light annealing of copper zinc tin sulfide nanocrystal coatings

Energy Technology Data Exchange (ETDEWEB)

Williams, Bryce A.; Smeaton, Michelle A.; Holgate, Collin S.; Trejo, Nancy D.; Francis, Lorraine F., E-mail: francis@umn.edu; Aydil, Eray S., E-mail: aydil@umn.edu [Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Avenue SE, Minneapolis, Minnesota 55455 (United States)

2016-09-15

A promising method for forming the absorber layer in copper zinc tin sulfide [Cu{sub 2}ZnSnS{sub 4} (CZTS)] thin film solar cells is thermal annealing of coatings cast from dispersions of CZTS nanocrystals. Intense pulsed light (IPL) annealing utilizing xenon flash lamps is a potential high-throughput, low-cost, roll-to-roll manufacturing compatible alternative to thermal annealing in conventional furnaces. The authors studied the effects of flash energy density (3.9–11.6 J/cm{sup 2}) and number of flashes (1–400) during IPL annealing on the microstructure of CZTS nanocrystal coatings cast on molybdenum-coated soda lime glass substrates (Mo-coated SLG). The annealed coatings exhibited cracks with two distinct linear crack densities, 0.01 and 0.2 μm{sup −1}, depending on the flash intensity and total number of flashes. Low density cracking (0.01 μm{sup −1}, ∼1 crack per 100 μm) is caused by decomposition of CZTS at the Mo-coating interface. Vapor decomposition products at the interface cause blisters as they escape the coating. Residual decomposition products within the blisters were imaged using confocal Raman spectroscopy. In support of this hypothesis, replacing the Mo-coated SLG substrate with quartz eliminated blistering and low-density cracking. High density cracking is caused by rapid thermal expansion and contraction of the coating constricted on the substrate as it is heated and cooled during IPL annealing. Finite element modeling showed that CZTS coatings on low thermal diffusivity materials (i.e., SLG) underwent significant differential heating with respect to the substrate with rapid rises and falls of the coating temperature as the flash is turned on and off, possibly causing a build-up of tensile stress within the coating prompting cracking. Use of a high thermal diffusivity substrate, such as a molybdenum foil (Mo foil), reduces this differential heating and eliminates the high-density cracking. IPL annealing in presence of sulfur

CdTe magic-sized clusters and the use as building blocks for assembling two-dimensional nanoplatelets

Science.gov (United States)

Xu, Hu; Hou, Yumei; Zhang, Hua

2017-06-01

A facile one-pot noninjection synthesis of CdTe magic-sized clusters (MSCs) and their use as building blocks for assembling two-dimensional (2D) quantum confined nanoplatelets (NPLs) are reported. Four distinct MSC families, with the first exciton absorption peaks at 447 nm (F447), 485 nm (F485), 535 nm (F535), and 555 nm (F555), are synthesized by the reaction between cadmium oleate and trioctylphosphine tellurium (TOP-Te) in octadecene media containing primary amine and TOP at appropriate intermediate temperatures. Especially, F447 is obtained in pure form and can self-assemble in situ into 2D NPLs in the reaction solution. The formation, growth, and transformation of CdTe MSCs are monitored mainly by UV-Vis absorption spectroscopy. The pure F447 and its assembled 2D NPLs are further characterized using transmission electron microscopy. The influence of various experimental variables, including reaction temperature, the nature, and amount of capping ligands, on the stability and growth kinetics of the obtained MSC families has been systematically investigated. Experimental results indicate that the appropriate reaction temperature and the presence of long hydrocarbon chain primary amines play a crucial role in the formation of MSCs and the subsequent assembly into 2D NPLs. Primary amines can also promote ultra-small sized CdTe regular nanocrystals to transform into MSCs, and therefore, CdTe MSCs can be obtained indirectly from regularly sized nanocrystals. [Figure not available: see fulltext.

The influence of capping thioalkyl acid on the growth and photoluminescence efficiency of CdTe and CdSe quantum dots

International Nuclear Information System (INIS)

Aldeek, Fadi; Lambert, Jacques; Balan, Lavinia; Schneider, Raphael

2008-01-01

The influence of thioalkyl acid ligand was evaluated during aqueous synthesis at 100 deg. C and under hydrothermal conditions (150 deg. C) of CdTe and CdSe quantum dots (QDs). Experiments performed with 3-mercaptopropionic acid (MPA), 6-mercaptohexanoic acid (MHA) and 11-mercaptoundecanoic acid (MUA) demonstrated that the use of MHA and MUA allowed for the preparation of very small nanoparticles (0.6-2.5 nm) in carrying out the reaction under atmospheric pressure or in an autoclave and that the photophysical properties of QDs were dependent on the ligand and on the synthesis conditions. The influence of various experimental conditions, including the Te-to-Cd ratio, temperature, and precursor concentration, on the growth rate of CdTe or CdSe QDs has been systematically investigated. The fluorescence intensities of CdTe QDs capped with MPA, MHA, or MUA versus pH were also found to be related to the surface coverage of the nanoparticles.

Effect of Annealing Temperature and Spin Coating Speed on Mn-Doped ZnS Nanocrystals Thin Film by Spin Coating

Directory of Open Access Journals (Sweden)

Noor Azie Azura Mohd Arif

2017-01-01

Full Text Available ZnS:Mn nanocrystals thin film was fabricated at 300°C and 500°C via the spin coating method. Its sol-gel was spin coated for 20 s at 3000 rpm and 4000 rpm with metal tape being used to mold the shape of the thin film. A different combination of these parameters was used to investigate their influences on the fabrication of the film. Optical and structural characterizations have been performed. Optical characterization was analyzed using UV-visible spectroscopy and photoluminescence spectrophotometer while the structural and compositional analysis of films was measured via field emission scanning electron microscopy and energy dispersive X-ray. From UV-vis spectra, the wavelength of the ZnS:Mn was 250 nm and the band gap was within the range 4.43 eV–4.60 eV. In room temperature PL spectra, there were two emission peaks centered at 460 nm and 590 nm. Under higher annealing temperature and higher speed used in spin coating, an increase of 0.05 eV was observed. It was concluded that the spin coating process is able to synthesize high quality spherical ZnS:Mn nanocrystals. This conventional process can replace other high technology methods due to its synthesis cost.

Synthesis and Doping of Silicon Nanocrystals for Versatile Nanocrystal Inks

Science.gov (United States)

Kramer, Nicolaas Johannes

materials which is very interesting for certain applications. Finally the boron atoms were used to form a Lewis acidic nanocrystal surface chemistry allowing for the creation of ligand-less silicon nanocrystal solutions. This represents an immense step towards an abundant, non-toxic alternative to Pb and Cd-based nanocrystal technologies. The lack of long ligand chains enables the production of dense films with excellent electrical conductivity. This was demonstrated by forming uniform nanocrystal thin-films using simple and inexpensive spray coating techniques.

Influence of heavy nanocrystals on spermatozoa and fertility of mammals

Energy Technology Data Exchange (ETDEWEB)

Akhavan, Omid, E-mail: oakhavan@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of); Hashemi, Ehsan [National Research Center for Transgenic Mouse, National Institute of Genetic Engineering and Biotechnology, P.O. Box 14965-161, Tehran (Iran, Islamic Republic of); Zare, Hakimeh [Physics Department, Yazd University, Yazd, P.O. Box 89195-741 (Iran, Islamic Republic of); Shamsara, Mehdi [National Research Center for Transgenic Mouse, National Institute of Genetic Engineering and Biotechnology, P.O. Box 14965-161, Tehran (Iran, Islamic Republic of); Taghavinia, Nima [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of); Heidari, Farid [National Research Center for Transgenic Mouse, National Institute of Genetic Engineering and Biotechnology, P.O. Box 14965-161, Tehran (Iran, Islamic Republic of)

2016-12-01

In recent years, quantum dots (QDs) have been widely used in upcoming nanotechnology-based solar cells, light-emitting diodes and even bioimaging, due to their tunable optical properties and excellent quantum yields. But, such nanostructures are currently constituted by heavy elements which can threat the human health and living environment. Hence, in this work, the in vivo effects of CdTe nanocrystals (NCs) (as one of the promising QDs) on spermatozoa of male mice and subsequently on fertility of female mice were investigated, for the first time. To do this, CdTe NCs were synthesized through an environment-friendly (aqueous-based solution) method. The sperm cells presented a high potential for uptake of the heavy QDs. Meantime, the NCs exhibited concentration-dependent adverse effects on morphology, viability, kinetic characteristics and DNA of the spermatozoa. At low concentration of 0.1 μg/mL, the NCs showed a moderate toxicity (~ 25% reduction in viability and motility of the spermatozoa), while remarkable toxicities were observed at higher concentrations of 1.0–100 μg/mL (~ 67% reduction in viability and motility for 100 μg/mL). Furthermore, significant in vitro DNA fragmentation of the spermatozoa was observed at CdTe concentrations ≥ 10 μg/mL. In vivo toxicity of the NCs was found lower than the in vitro toxicity. Nevertheless, the in vivo destructive effects of the NCs still caused ~ 34% reduction in viability as well as motility and ~ 5% damages in DNA of male mice spermatozoa. These resulted in ~ 26% decrease in fertility and gestation of female mice, along with an overall hormone secretion during the pregnancy, and ~ 39% reduction in viability of pups/pregnant females. - Highlights: • The cytotoxic effects of CdTe nanocrystals on spermatozoa of male mice • High uptake of CdTe by spermatozoa, resulting in inactivation of spermatozoa or pollution of the others • The adverse effects of polluted spermatozoa on fertility/gestation of female mice

Density-controllable nonvolatile memory devices having metal nanocrystals through chemical synthesis and assembled by spin-coating technique

International Nuclear Information System (INIS)

Wang Guangli; Chen Yubin; Shi Yi; Pu Lin; Pan Lijia; Zhang Rong; Zheng Youdou

2010-01-01

A novel two-step method is employed, for the first time, to fabricate nonvolatile memory devices that have metal nanocrystals. First, size-averaged Au nanocrystals are synthesized chemically; second, they are assembled into memory devices by a spin-coating technique at room temperature. This attractive approach makes it possible to tailor the diameter and control the density of nanocrystals individually. In addition, processes at room temperature prevent Au diffusion, which is a main concern for the application of metal nanocrystal-based memory. The experimental results, both the morphology characterization and the electrical measurements, reveal that there is an optimum density of nanocrystal monolayer to balance between long data retention and a large hysteresis memory window. At the same time, density-controllable devices could also feed the preferential emphasis on either memory window or retention time. All these facts confirm the advantages and novelty of our two-step method. (semiconductor devices)

Mechanochemistry of Chitosan-Coated Zinc Sulfide (ZnS) Nanocrystals for Bio-imaging Applications

Science.gov (United States)

Bujňáková, Zdenka; Dutková, Erika; Kello, Martin; Mojžiš, Ján; Baláž, Matej; Baláž, Peter; Shpotyuk, Oleh

2017-05-01

The ZnS nanocrystals were prepared in chitosan solution (0.1 wt.%) using a wet ultra-fine milling. The obtained suspension was stable and reached high value of zeta potential (+57 mV). The changes in FTIR spectrum confirmed the successful surface coating of ZnS nanoparticles by chitosan. The prepared ZnS nanocrystals possessed interesting optical properties verified in vitro. Four cancer cells were selected (CaCo-2, HCT116, HeLa, and MCF-7), and after their treatment with the nanosuspension, the distribution of ZnS in the cells was studied using a fluorescence microscope. The particles were clearly seen; they passed through the cell membrane and accumulated in cytosol. The biological activity of the cells was not influenced by nanoparticles, they did not cause cell death, and only the granularity of cells was increased as a consequence of cellular uptake. These results confirm the potential of ZnS nanocrystals using in bio-imaging applications.

Origins of visible-light emissions in hydrogen-coated silicon nanocrystals: Role of passivating coating

International Nuclear Information System (INIS)

Tit, Nacir; Yamani, Z.H.; Graham, J.; Ayesh, A.

2010-01-01

We present a theoretical investigation of the electronic and optical properties of hydrogen-coated silicon nanocrystals (Si:H NCs). On one hand, the density-functional theory (DFT) is used to both calculate the total energy and relax the NCs. On a second hand, the tight-binding method, which includes the minimal sp 3 -basis set within the second-nearest-neighbor interaction scheme, is applied to calculate the electronic structures, oscillator strength (OS) and recombination rate (RR) versus the NC size, coating and atomic relaxation. Three main findings are reported: (i) The quantum confinement in these NCs do follow similar rule to the case of a single-particle in a box, where the confinement energy decays in power-law with the increasing NC's size. (ii) The coating is shown to play the essential role in creation of large band-gap energy lying within the visible-light energy spectrum. (iii) The surface atomic relaxation is found to reduce the band-gap energy by about 150 meV and enhance both OS and RR. Our claims are corroborated by the available experimental data.

Structure of CdTe nanoparticles in glass

Science.gov (United States)

Hayes, T. M.; Nagpal, Swati; Persans, P. D.

2000-03-01

Optical long-pass wavelength filters are generally made by growing small crystallites of appropriate semiconductors in a transparent glass matrix. Depending on the semiconductor, these systems are candidates for interesting and important nonlinear optical switching applications. The structure of these nanocrystals has been shown to be a valuable indicator of the chemical and thermodynamic processes during crystallite growth and dissolution. We have used x-ray absorption spectroscopy to study the structure of the crystallites produced during heat treatment of filter glasses containing Cd and Te and producing optical absorption edges at the band gap of bulk CdTe. The results will be discussed.

Folic acid modified gelatine coated quantum dots as potential reagents for in vitro cancer diagnostics

LENUS (Irish Health Repository)

Gerard, Valerie A

2011-11-10

Abstract Background Gelatine coating was previously shown to effectively reduce the cytotoxicity of CdTe Quantum Dots (QDs) which was a first step towards utilising them for biomedical applications. To be useful they also need to be target-specific which can be achieved by conjugating them with Folic Acid (FA). Results The modification of QDs with FA via an original "one-pot" synthetic route was proved successful by a range of characterisation techniques including UV-visible absorption spectroscopy, Photoluminescence (PL) emission spectroscopy, fluorescence life-time measurements, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). The resulting nanocomposites were tested in Caco-2 cell cultures which over-express FA receptors. The presence of FA on the surface of QDs significantly improved the uptake by targeted cells. Conclusions The modification with folic acid enabled to achieve a significant cellular uptake and cytotoxicity towards a selected cancer cell lines (Caco-2) of gelatine-coated TGA-CdTe quantum dots, which demonstrated good potential for in vitro cancer diagnostics.

Thermal degradation kinetics of polylactic acid/acid fabricated cellulose nanocrystal based bionanocomposites.

Science.gov (United States)

Monika; Dhar, Prodyut; Katiyar, Vimal

2017-11-01

Cellulose nanocrystals (CNC) are fabricated from filter paper (as cellulosic source) by acid hydrolysis using different acids such as sulphuric (H 2 SO 4 ), phosphoric (H 3 PO 4 ), hydrochloric (HCl) and nitric (HNO 3 ) acid. The resulting acid derived CNC are melt mixed with Polylactic acid (PLA) using extruder at 180°C. Thermogravimetric (TGA) result shows that increase in 10% and 50% weight loss (T 10 , T 50 ) temperature for PLA-CNC film fabricated with HNO 3 , H 3 PO 4 and HCl derived CNC have improved thermal stability in comparison to H 2 SO 4 -CNC. Nonisothermal kinetic studies are carried out with modified-Coats-Redfern (C-R), Ozawa-Flynn-Wall (OFW) and Kissinger method to predict the kinetic and thermodynamic parameters. Subsequently prediction of these parameter leads to the proposal of thermal induced degradation mechanism of nanocomposites using Criado method. The distribution of E a calculated from OFW model are (PLA-H 3 PO 4 -CNC: 125-139 kJmol -1 ), (PLA-HNO 3 -CNC: 126-145 kJmol -1 ), (PLA-H 2 SO 4 -CNC: 102-123 kJmol -1 ) and (PLA-HCl-CNC: 140-182 kJmol -1 ). This difference among E a for the decomposition of PLA-CNC bionanocomposite is probably due to various acids used in this study. The E a calculated by these two methods are found in consonance with that observed from Kissinger method. Further, hyphenated TG-Fourier transform infrared spectroscopy (FTIR) result shows that gaseous products such as CO 2 , CO, lactide, aldehydes and other compounds are given off during the thermal degradation of PLA-CNC nanocomposite. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of surface organic coatings of cellulose nanocrystals on the viability of mammalian cell lines

Directory of Open Access Journals (Sweden)

Jimenez AS

2017-09-01

Full Text Available Ambar S Jimenez,1 Francesca Jaramillo,1 Usha D Hemraz,2 Yaman Boluk,3 Karina Ckless,1 Rajesh Sunasee1 1Department of Chemistry, State University of New York at Plattsburgh, Plattsburgh, NY, USA; 2National Research Council, Montreal, QC, Canada, 3Department of Civil & Environmental Engineering, University of Alberta and National Institute for Nanotechnology, National Research Council, Edmonton, AB, Canada Abstract: Cellulose nanocrystals (CNCs have emerged as promising candidates for a number of bio-applications. Surface modification of CNCs continues to gain significant research interest as it imparts new properties to the surface of the nanocrystals for the design of multifunctional CNCs-based materials. A small chemical surface modification can potentially lead to drastic behavioral changes of cell-material interactions thereby affecting the intended bio-application. In this work, unmodified CNCs were covalently decorated with four different organic moieties such as a diaminobutane fragment, a cyclic oligosaccharide (β-cyclodextrin, a thermoresponsive polymer (poly[N-isopropylacrylamide], and a cationic aminomethacrylamide-based polymer using different synthetic covalent methods. The effect of surface coatings of CNCs and the respective dose-response of the above organic moieties on the cell viability were evaluated on mammalian cell cultures (J774A.1 and MFC-7, using 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide and lactate dehydrogenase assays. Overall, the results indicated that cells exposed to surface-coated CNCs for 24 h did not display major changes in cell viability, membrane permeability as well as cell morphology. However, with longer exposure, all these parameters were somewhat affected, which appears not to be correlated with either anionic or cationic surface coatings of CNCs used in this study. Keywords: cellulose nanocrystals, surface coating, cell viability, MTT, LDH

Thermodynamic Study of the Interaction of Bovine Serum Albumin and Amino Acids with Cellulose Nanocrystals.

Science.gov (United States)

Lombardo, Salvatore; Eyley, Samuel; Schütz, Christina; van Gorp, Hans; Rosenfeldt, Sabine; Van den Mooter, Guy; Thielemans, Wim

2017-06-06

The interaction of bovine serum albumin (BSA) with sulfated, carboxylated, and pyridinium-grafted cellulose nanocrystals (CNCs) was studied as a function of the degree of substitution by determining the adsorption isotherm and by directly measuring the thermodynamics of interaction. The adsorption of BSA onto positively charged pyridinium-grafted cellulose nanocrystals followed Langmuirian adsorption with the maximum amount of adsorbed protein increasing linearly with increasing degree of substitution. The binding mechanism between the positively charged pyridinum-grafted cellulose nanocrystals and BSA was found to be endothermic and based on charge neutralization. A positive entropy of adsorption associated with an increase of the degree of disorder upon addition of BSA compensated for the unfavorable endothermic enthalpy and enabled formation of pyridinium-g-CNC-BSA complexes. The endothermic enthalpy of adsorption was further found to decrease as a function of increasing degree of substitution. Negatively charged cellulose nanocrystals bearing sulfate and/or carboxylic functionalities were found to not interact significantly with the BSA protein. To investigate in more detail the role of single amino acids in the adsorption of proteins onto cellulose nanocrystals, we also studied the interaction of different types of amino acids with CNCs, i.e., charged (lysine, aspartic acid), aromatic (tryptophan, tyrosine), and polar (serine) amino acids. We found that none of the single amino acids bound with CNCs irrespective of surface charge and that therefore the binding of proteins with CNCs appears to require larger amino acid sequences that induce a greater entropic contribution to stabilize binding. Single amino acids are thus not adsorbed onto cellulose nanocrystals.

Colloidal infrared reflective and transparent conductive aluminum-doped zinc oxide nanocrystals

Science.gov (United States)

Buonsanti, Raffaella; Milliron, Delia J

2015-02-24

The present invention provides a method of preparing aluminum-doped zinc oxide (AZO) nanocrystals. In an exemplary embodiment, the method includes (1) injecting a precursor mixture of a zinc precursor, an aluminum precursor, an amine, and a fatty acid in a solution of a vicinal diol in a non-coordinating solvent, thereby resulting in a reaction mixture, (2) precipitating the nanocrystals from the reaction mixture, thereby resulting in a final precipitate, and (3) dissolving the final precipitate in an apolar solvent. The present invention also provides a dispersion. In an exemplary embodiment, the dispersion includes (1) nanocrystals that are well separated from each other, where the nanocrystals are coated with surfactants and (2) an apolar solvent where the nanocrystals are suspended in the apolar solvent. The present invention also provides a film. In an exemplary embodiment, the film includes (1) a substrate and (2) nanocrystals that are evenly distributed on the substrate.

The size control of silver nanocrystals with different polyols and its application to low-reflection coating materials

Energy Technology Data Exchange (ETDEWEB)

Park, Keum Hwan; Park, O Ok [Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Im, Sang Hyuk, E-mail: imromy@krict.re.kr, E-mail: ookpark@kaist.ac.kr [Korea Research Institute of Chemical Technology (KRICT), 19 Singsungno, Yuseong-gu, Daejeon 305-600 (Korea, Republic of)

2011-01-28

The size of silver nanocrystals in polyol synthesis can be simply controlled by tuning the viscosity of the reaction medium such as ethylene glycol, 1,2-propanediol, 1,4-butanediol and 1,5-pentanediol. We found that a higher viscose medium (1,5-pentanediol) led to monodispersed smaller particles thanks to the slow addition of silver atoms into the nuclei. Size-controlled silver nanocrystals of 30 nm were obtained in a viscosity controlled medium of 1,5-pentanediol to synthesize a low refractive index filler by coating with silica and subsequent etching of the silver core. The coated low-reflection layer from the hollow silica nanoparticles on polyethylene terephthalate (PET) film can greatly reduce the reflection of the PET film from 10% to 2% over the entire visible region.

All-inorganic perovskite nanocrystal assisted extraction of hot electrons and biexcitons from photoexcited CdTe quantum dots.

Science.gov (United States)

Mondal, Navendu; De, Apurba; Samanta, Anunay

2018-01-03

Excitation of semiconductor quantum dots (QDs) by photons possessing energy higher than the band-gap creates a hot electron-hole pair, which releases its excess energy as waste heat or under certain conditions (when hν > 2E g ) produces multiple excitons. Extraction of these hot carriers and multiple excitons is one of the key strategies for enhancing the efficiency of QD-based photovoltaic devices. However, this is a difficult task as competing carrier cooling and relaxation of multiple excitons (through Auger recombination) are ultrafast processes. Herein, we study the potential of all-inorganic perovskite nanocrystals (NCs) of CsPbX 3 (X = Cl, Br) as harvesters of these short-lived species from photo-excited CdTe QDs. The femtosecond transient absorption measurements show CsPbX 3 mediated extraction of both hot and thermalized electrons of the QDs (under a low pump power) and (under a high pump fluence) extraction of multiple excitons prior to their Auger assisted recombination. A faster timescale of thermalized electron transfer (∼2 ps) and a higher extraction efficiency of hot electrons (∼60%) are observed in the presence of CsPbBr 3 . These observations demonstrate the potential of all-inorganic perovskite NCs in the extraction of these short-lived energy rich species implying that complexes of the QDs and perovskite NCs are better suited for improving the efficiency of QD-sensitized solar cells.

Intracellular delivery of peptide nucleic acid and organic molecules using zeolite-L nanocrystals.

Science.gov (United States)

Bertucci, Alessandro; Lülf, Henning; Septiadi, Dedy; Manicardi, Alex; Corradini, Roberto; De Cola, Luisa

2014-11-01

The design and synthesis of smart nanomaterials can provide interesting potential applications for biomedical purposes from bioimaging to drug delivery. Manufacturing multifunctional systems in a way to carry bioactive molecules, like peptide nucleic acids able to recognize specific targets in living cells, represents an achievement towards the development of highly selective tools for both diagnosis and therapeutics. This work describes a very first example of the use of zeolite nanocrystals as multifunctional nanocarriers to deliver simultaneously PNA and organic molecules into living cells. Zeolite-L nanocrystals are functionalized by covalently attaching the PNA probes onto the surface, while the channel system is filled with fluorescent guest molecules. The cellular uptake of the PNA/Zeolite-L hybrid material is then significantly increased by coating the whole system with a thin layer of biodegradable poly-L-lysine. The delivery of DAPI as a model drug molecule, inserted into the zeolite pores, is also demonstrated to occur in the cells, proving the multifunctional ability of the system. Using this zeolite nanosystem carrying PNA probes designed to target specific RNA sequences of interest in living cells could open new possibilities for theranostic and gene therapy applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of CdTe QDs/single-walled aluminosilicate nanotubes hybrid compound and their antimicrobial activity on bacteria

Energy Technology Data Exchange (ETDEWEB)

Geraldo, Daniela A., E-mail: daniela.geraldo@unab.cl [Universidad Andres Bello, Departamento de Ciencias Quimicas (Chile); Arancibia-Miranda, Nicolas [CEDENNA, Center for the Development of Nanoscience and Nanotechnology (Chile); Villagra, Nicolas A. [Universidad Andres Bello, Laboratorio de Microbiologia, Facultad de Ciencias Biologicas (Chile); Mora, Guido C. [Universidad Andres Bello, Unidad de Microbiologia, Facultad de Medicina (Chile); Arratia-Perez, Ramiro [Universidad Andres Bello, Departamento de Ciencias Quimicas (Chile)

2012-12-15

The use of molecular conjugates of quantum dots (nanocrystalline fluorophores) for biological purposes have received much attention due to their improved biological activity. However, relatively, little is known about the synthesis and application of aluminosilicate nanotubes decorated with quantum dots (QDs) for imaging and treatment of pathogenic bacteria. This paper describes for a first time, the use of single-walled aluminosilicate nanotubes (SWNT) (imogolite) as a one-dimensional template for the in situ growth of mercaptopropionic acid-capped CdTe QDs. This new nanohybrid hydrogel was synthesized by a simple reaction pathway and their enhanced optical properties were monitored by fluorescence and UV-Vis spectroscopy, confirming that the use of these nanotubes favors the confinement effects of net CdTe QDs. In addition, studies of FT-IR spectroscopy and transmission electron microscopy confirmed the non-covalent functionalization of SWNT. Finally, the antimicrobial activity of SWNT coated with CdTe QDs toward three opportunistic multi-resistant pathogens such as Salmonella typhimurium, Acinetobacter baumannii, and Pseudomonas aeruginosa were tested. Growth inhibition tests were conducted by exposing growing bacteria to CdTe QDs/SWNT hybrid compound showing that the new nano-structured composite is a potential antimicrobial agent for heavy metal-resistant bacteria.

Synthesis of CdTe QDs/single-walled aluminosilicate nanotubes hybrid compound and their antimicrobial activity on bacteria

International Nuclear Information System (INIS)

Geraldo, Daniela A.; Arancibia-Miranda, Nicolás; Villagra, Nicolás A.; Mora, Guido C.; Arratia-Perez, Ramiro

2012-01-01

The use of molecular conjugates of quantum dots (nanocrystalline fluorophores) for biological purposes have received much attention due to their improved biological activity. However, relatively, little is known about the synthesis and application of aluminosilicate nanotubes decorated with quantum dots (QDs) for imaging and treatment of pathogenic bacteria. This paper describes for a first time, the use of single-walled aluminosilicate nanotubes (SWNT) (imogolite) as a one-dimensional template for the in situ growth of mercaptopropionic acid-capped CdTe QDs. This new nanohybrid hydrogel was synthesized by a simple reaction pathway and their enhanced optical properties were monitored by fluorescence and UV–Vis spectroscopy, confirming that the use of these nanotubes favors the confinement effects of net CdTe QDs. In addition, studies of FT-IR spectroscopy and transmission electron microscopy confirmed the non-covalent functionalization of SWNT. Finally, the antimicrobial activity of SWNT coated with CdTe QDs toward three opportunistic multi-resistant pathogens such as Salmonella typhimurium, Acinetobacter baumannii, and Pseudomonas aeruginosa were tested. Growth inhibition tests were conducted by exposing growing bacteria to CdTe QDs/SWNT hybrid compound showing that the new nano-structured composite is a potential antimicrobial agent for heavy metal-resistant bacteria.

Synthesis of CdTe QDs/single-walled aluminosilicate nanotubes hybrid compound and their antimicrobial activity on bacteria

Science.gov (United States)

Geraldo, Daniela A.; Arancibia-Miranda, Nicolás; Villagra, Nicolás A.; Mora, Guido C.; Arratia-Perez, Ramiro

2012-12-01

The use of molecular conjugates of quantum dots (nanocrystalline fluorophores) for biological purposes have received much attention due to their improved biological activity. However, relatively, little is known about the synthesis and application of aluminosilicate nanotubes decorated with quantum dots (QDs) for imaging and treatment of pathogenic bacteria. This paper describes for a first time, the use of single-walled aluminosilicate nanotubes (SWNT) (imogolite) as a one-dimensional template for the in situ growth of mercaptopropionic acid-capped CdTe QDs. This new nanohybrid hydrogel was synthesized by a simple reaction pathway and their enhanced optical properties were monitored by fluorescence and UV-Vis spectroscopy, confirming that the use of these nanotubes favors the confinement effects of net CdTe QDs. In addition, studies of FT-IR spectroscopy and transmission electron microscopy confirmed the non-covalent functionalization of SWNT. Finally, the antimicrobial activity of SWNT coated with CdTe QDs toward three opportunistic multi-resistant pathogens such as Salmonella typhimurium, Acinetobacter baumannii, and Pseudomonas aeruginosa were tested. Growth inhibition tests were conducted by exposing growing bacteria to CdTe QDs/SWNT hybrid compound showing that the new nano-structured composite is a potential antimicrobial agent for heavy metal-resistant bacteria.

Simple down conversion nano-crystal coatings for enhancing Silicon-solar cells efficiency

Directory of Open Access Journals (Sweden)

Gur Mittelman

2016-09-01

Full Text Available Utilizing self-assembled nano-structured coatings on top of existing solar cells has thepotential to increase the total quantum efficiency of the cell using a simple and cheap process. In ourwork we have exploited the controlled absorption of nano-crystal with different band gaps to realizedown conversion artificial antennas that self-assembled on the device surface. The UV sun light isconverted to the visible light enhancing the solar cell performance in two complementary routes; a.protecting the solar cell and coatings from the UV illumination and therefore reducing the UVradiation damage. b. enhancing the total external quantum efficiency of the cell by one percent. Thisis achieved using a simple cheap process that can be adjusted to many different solar cells.

Precipitação seletiva de tamanhos em nanopartículas semicondutoras coloidais de CdTe e CdSe: um estudo por espectroscopia UV-VIS

Directory of Open Access Journals (Sweden)

Lívia Cristina de Souza Viol

2011-01-01

Full Text Available The post-preparative size-selective precipitation technique was applied in CdTe and CdSe semiconductor nanocrystals prepared via colloidal route in water. The synthesis of CdTe and CdSe nanoparticles and the effect of the post-preparative size-selective precipitation have been characterized mainly by mean of ultraviolet and visible absorption spectroscopy (UV-Vis. It was demonstrated that the size-selective precipitation are able to isolate particles of different sizes and purify the nanoparticles as well.

Biocompatible fluorescence-enhanced ZrO2-CdTe quantum dot nanocomposite for in vitro cell imaging

Science.gov (United States)

Lu, Zhisong; Zhu, Zhihong; Zheng, Xinting; Qiao, Yan; Guo, Jun; Li, Chang Ming

2011-04-01

With advances of quantum dots (QDs) in bioimaging applications, various materials have been used to coat QDs to reduce their nanotoxicity; however, the coating could introduce new toxic sources and quench the fluorescence in bioimaging applications. In this work, ZrO2, an excellent ceramic material with low extinction coefficient and good biocompatibility, is utilized to coat CdTe QDs for the first time. Experimental results show that ZrO2-QD nanocomposites with the size of ~ 30 nm possess enhanced fluorescence emission, lower nanotoxicity and gradually increased fluorescence under 350 nm light illumination. After functionalization with folic acid, they were applied to label cultured HeLa cells effectively. Therefore, the ZrO2-QD nanocomposites could be promising biocompatible nanomaterials with strong fluorescence emission to replace or complement QDs in biomedical applications.

Biocompatible fluorescence-enhanced ZrO2-CdTe quantum dot nanocomposite for in vitro cell imaging

International Nuclear Information System (INIS)

Lu Zhisong; Zhu Zhihong; Zheng Xinting; Qiao Yan; Li Changming; Guo Jun

2011-01-01

With advances of quantum dots (QDs) in bioimaging applications, various materials have been used to coat QDs to reduce their nanotoxicity; however, the coating could introduce new toxic sources and quench the fluorescence in bioimaging applications. In this work, ZrO 2 , an excellent ceramic material with low extinction coefficient and good biocompatibility, is utilized to coat CdTe QDs for the first time. Experimental results show that ZrO 2 -QD nanocomposites with the size of ∼ 30 nm possess enhanced fluorescence emission, lower nanotoxicity and gradually increased fluorescence under 350 nm light illumination. After functionalization with folic acid, they were applied to label cultured HeLa cells effectively. Therefore, the ZrO 2 -QD nanocomposites could be promising biocompatible nanomaterials with strong fluorescence emission to replace or complement QDs in biomedical applications.

A computational ab initio study of surface diffusion of sulfur on the CdTe (111) surface

Energy Technology Data Exchange (ETDEWEB)

Naderi, Ebadollah, E-mail: enaderi42@gmail.com [Department of Physics, Savitribai Phule Pune University (SPPU), Pune-411007 (India); Ghaisas, S. V. [Department of Electronic Science, Savitribai Phule Pune University (SPPU), Pune-411007 (India)

2016-08-15

In order to discern the formation of epitaxial growth of CdS shell over CdTe nanocrystals, kinetics related to the initial stages of the growth of CdS on CdTe is investigated using ab-initio methods. We report diffusion of sulfur adatom on the CdTe (111) A-type (Cd-terminated) and B-type (Te-terminated) surfaces within the density functional theory (DFT). The barriers are computed by applying the climbing Nudge Elastic Band (c-NEB) method. From the results surface hopping emerges as the major mode of diffusion. In addition, there is a distinct contribution from kick-out type diffusion in which a CdTe surface atom is kicked out from its position and is replaced by the diffusing sulfur atom. Also, surface vacancy substitution contributes to the concomitant dynamics. There are sites on the B- type surface that are competitively close in terms of the binding energy to the lowest energy site of epitaxy on the surface. The kick-out process is more likely for B-type surface where a Te atom of the surface is displaced by a sulfur adatom. Further, on the B-type surface, subsurface migration of sulfur is indicated. Furthermore, the binding energies of S on CdTe reveal that on the A-type surface, epitaxial sites provide relatively higher binding energies and barriers than on B-type.

A computational ab initio study of surface diffusion of sulfur on the CdTe (111) surface

Science.gov (United States)

Naderi, Ebadollah; Ghaisas, S. V.

2016-08-01

In order to discern the formation of epitaxial growth of CdS shell over CdTe nanocrystals, kinetics related to the initial stages of the growth of CdS on CdTe is investigated using ab-initio methods. We report diffusion of sulfur adatom on the CdTe (111) A-type (Cd-terminated) and B-type (Te-terminated) surfaces within the density functional theory (DFT). The barriers are computed by applying the climbing Nudge Elastic Band (c-NEB) method. From the results surface hopping emerges as the major mode of diffusion. In addition, there is a distinct contribution from kick-out type diffusion in which a CdTe surface atom is kicked out from its position and is replaced by the diffusing sulfur atom. Also, surface vacancy substitution contributes to the concomitant dynamics. There are sites on the B- type surface that are competitively close in terms of the binding energy to the lowest energy site of epitaxy on the surface. The kick-out process is more likely for B-type surface where a Te atom of the surface is displaced by a sulfur adatom. Further, on the B-type surface, subsurface migration of sulfur is indicated. Furthermore, the binding energies of S on CdTe reveal that on the A-type surface, epitaxial sites provide relatively higher binding energies and barriers than on B-type.

A computational ab initio study of surface diffusion of sulfur on the CdTe (111) surface

International Nuclear Information System (INIS)

Naderi, Ebadollah; Ghaisas, S. V.

2016-01-01

In order to discern the formation of epitaxial growth of CdS shell over CdTe nanocrystals, kinetics related to the initial stages of the growth of CdS on CdTe is investigated using ab-initio methods. We report diffusion of sulfur adatom on the CdTe (111) A-type (Cd-terminated) and B-type (Te-terminated) surfaces within the density functional theory (DFT). The barriers are computed by applying the climbing Nudge Elastic Band (c-NEB) method. From the results surface hopping emerges as the major mode of diffusion. In addition, there is a distinct contribution from kick-out type diffusion in which a CdTe surface atom is kicked out from its position and is replaced by the diffusing sulfur atom. Also, surface vacancy substitution contributes to the concomitant dynamics. There are sites on the B- type surface that are competitively close in terms of the binding energy to the lowest energy site of epitaxy on the surface. The kick-out process is more likely for B-type surface where a Te atom of the surface is displaced by a sulfur adatom. Further, on the B-type surface, subsurface migration of sulfur is indicated. Furthermore, the binding energies of S on CdTe reveal that on the A-type surface, epitaxial sites provide relatively higher binding energies and barriers than on B-type.

Evaluation of Biological Toxicity of CdTe Quantum Dots with Different Coating Reagents according to Protein Expression of Engineering Escherichia coli

Directory of Open Access Journals (Sweden)

Wei Xu

2015-01-01

Full Text Available The results obtained from toxicity assessment of quantum dots (QDs can be used to establish guidelines for the application of QDs in bioimaging. This paper focused on the design of a novel method to evaluate the toxicity of CdTe QDs using engineering Escherichia coli as a model. The toxicity of mercaptoacetic acid (MPA, glutathione (GSH, and L-cysteine (Cys capped CdTe QDs was analyzed according to the heterologous protein expression in BL21/DE3, engineering Escherichia coli extensively used for protein expression. The results showed that the MPA-CdTe QDs had more serious toxicity than the other two kinds of CdTe QDs. The microscopic images and SEM micrographs further proved that both the proliferation and the protein expression of engineering Escherichia coli were inhibited after treatment with MPA-CdTe QDs. The proposed method is important to evaluate biological toxicity of both QDs and other nanoparticles.

Photoluminescence properties of a novel conjugate of water-soluble CdTe quantum dots to guanine

Energy Technology Data Exchange (ETDEWEB)

Feng Xuejiao [North-East Normal University, Changchun 130024 (China); Shang, Qingkun, E-mail: shangqk995@nenu.edu.c [North-East Normal University, Changchun 130024 (China); Liu Hongjian [Relia Diagnostic Systems, Burlingame, CA 94010 (United States); Wang Wenlan; Wang Zhidan; Liu Junyu [North-East Normal University, Changchun 130024 (China)

2010-04-15

A novel conjugate of water-soluble CdTe quantum dots to a small biomolecule guanine has been obtained in aqueous phase. The photoluminescence property and the stability of the conjugate increased comparing to CdTe QDs. The interaction between CdTe QDs and guanine was studied by TEM, fluorescence microscope and photoluminescence (PL), IR, UV-Vis spectra. The effects of reflux time, pH value, ionic strength, and the ratio of CdTe QDs to guanine on the photoluminescence properties of conjugate were investigated in detail. The results show that guanine has a great influence on both the photoluminescence property and stability of thioglycolic acid-stabilized CdTe QDs. The formation of coordination and hydrogen bond between guanine molecules and CdTe including thioglycolic acid on its surface may effectively enhance the PL intensity and stability of CdTe QDs. The maximum PL intensity of the conjugate was obtained on the condition with lower ionic strength, less than 30 min reflux time, neutral pH value and 6/1 as molar ratio of guanine to CdTe.

Engineering of lipid-coated PLGA nanoparticles with a tunable payload of diagnostically active nanocrystals for medical imaging.

Science.gov (United States)

Mieszawska, Aneta J; Gianella, Anita; Cormode, David P; Zhao, Yiming; Meijerink, Andries; Langer, Robert; Farokhzad, Omid C; Fayad, Zahi A; Mulder, Willem J M

2012-06-14

Polylactic-co-glycolic acid (PLGA) based nanoparticles are biocompatible and biodegradable and therefore have been extensively investigated as therapeutic carriers. Here, we engineered diagnostically active PLGA nanoparticles that incorporate high payloads of nanocrystals into their core for tunable bioimaging features. We accomplished this through esterification reactions of PLGA to generate polymers modified with nanocrystals. The PLGA nanoparticles formed from modified PLGA polymers that were functionalized with either gold nanocrystals or quantum dots exhibited favorable features for computed tomography and optical imaging, respectively.

Improving the interfacial and mechanical properties of short glass fiber/epoxy composites by coating the glass fibers with cellulose nanocrystals

Science.gov (United States)

A. Asadi; M. Miller; Robert Moon; K. Kalaitzidou

2016-01-01

In this study, the interfacial and mechanical properties of cellulose nanocrystals (CNC) coated glass fiber/epoxy composites were investigated as a function of the CNC content on the surface of glass fibers (GF). Chopped GF rovings were coated with CNC by immersing the GF in CNC (0–5 wt%) aqueous suspensions. Single fiber fragmentation (SFF) tests showed that the...

Phase- and size-controllable synthesis of hexagonal upconversion rare-earth fluoride nanocrystals through an oleic acid/ionic liquid two-phase system.

Science.gov (United States)

He, Meng; Huang, Peng; Zhang, Chunlei; Ma, Jiebing; He, Rong; Cui, Daxiang

2012-05-07

Herein, we introduce a facile, user- and environmentally friendly (n-octanol-induced) oleic acid (OA)/ionic liquid (IL) two-phase system for the phase- and size-controllable synthesis of water-soluble hexagonal rare earth (RE = La, Gd, and Y) fluoride nanocrystals with uniform morphologies (mainly spheres and elongated particles) and small sizes (size are discussed in detail. More importantly, the mechanism of the (n-octanol-induced) OA/IL two-phase system, the formation of the RE fluoride nanocrystals, and the distinctive size- and morphology-controlling capacity of the system are presented. BmimPF(6) is versatile in term of crystal-phase manipulation, size and shape maintenance, and providing water solubility in a one-step reaction. The luminescent properties of Er(3+)-, Ho(3+)-, and Tm(3+)-doped LaF(3), NaGdF(4), and NaYF(4) nanocrystals were also studied. It is worth noting that the as-prepared products can be directly dispersed in water due to the hydrophilic property of Bmim(+) (cationic part of the IL) as a capping agent. This advantageous feature has made the IL-capped products favorable in facile surface modifications, such as the classic Stober method. Finally, the cytotoxicity evaluation of NaYF(4):Yb,Er nanocrystals before and after silica coating was conducted for further biological applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interaction of porphyrins with CdTe quantum dots

International Nuclear Information System (INIS)

Zhang Xing; Liu Zhongxin; Ma Lun; Hossu, Marius; Chen Wei

2011-01-01

Porphyrins may be used as photosensitizers for photodynamic therapy, photocatalysts for organic pollutant dissociation, agents for medical imaging and diagnostics, applications in luminescence and electronics. The detection of porphyrins is significantly important and here the interaction of protoporphyrin-IX (PPIX) with CdTe quantum dots was studied. It was observed that the luminescence of CdTe quantum dots was quenched dramatically in the presence of PPIX. When CdTe quantum dots were embedded into silica layers, almost no quenching by PPIX was observed. This indicates that PPIX may interact and alter CdTe quantum dots and thus quench their luminescence. The oxidation of the stabilizers such as thioglycolic acid (TGA) as well as the nanoparticles by the singlet oxygen generated from PPIX is most likely responsible for the luminescence quenching. The quenching of quantum dot luminescence by porphyrins may provide a new method for photosensitizer detection.

Composite material including nanocrystals and methods of making

Science.gov (United States)

Bawendi, Moungi G.; Sundar, Vikram C.

2010-04-06

Temperature-sensing compositions can include an inorganic material, such as a semiconductor nanocrystal. The nanocrystal can be a dependable and accurate indicator of temperature. The intensity of emission of the nanocrystal varies with temperature and can be highly sensitive to surface temperature. The nanocrystals can be processed with a binder to form a matrix, which can be varied by altering the chemical nature of the surface of the nanocrystal. A nanocrystal with a compatibilizing outer layer can be incorporated into a coating formulation and retain its temperature sensitive emissive properties.

Morphological and luminescent evolution of near-infrared-emitting CdTe{sub x}Se{sub 1-x} nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Zhang Ruili; Yang Ping, E-mail: mse_yangp@ujn.edu.cn [University of Jinan, School of Material Science and Engineering (China)

2012-08-15

A facile organic route has been developed to synthesize CdTe{sub x}Se{sub 1-x} nanocrystals (NCs) using stearic acid as a capping agent. Because of growth kinetics of CdTe and CdSe, the molar ratio of Te/Se enables CdTe{sub x}Se{sub 1-x} NCs with various morphologies. By increasing the Te/Se ratio, the morphology of the NCs can be adjusted from tetrahedron to tetrapod. This is ascribed to the energy difference between wurtzite and the zinc-blende structures, which determines the nucleation and growth processes of the NCs. The diameters of the branches of tetrapod were 4-6 nm and their lengths were 7-20 nm. The CdTe{sub x}Se{sub 1-x} NCs revealed near-infrared (NIR) range (700-800 nm) photoluminescence (PL). The PL properties of the resulting NCs are strongly dependent on preparation conditions such as the molar ratio of Te/Se as well as the reaction temperature and time. In the cases of various reaction temperature (120-260 Degree-Sign C), the NCs revealed adjusted PL peak wavelength from visible to NIR range and narrow PL spectra. In addition, even though a high Te/Se molar ratio (0.67) was used, the CdTe{sub x}Se{sub 1-x} NCs revealed improved stability compared with CdTe NCs. Being coated with a composite Cd{sub y}Zn{sub 1-y}S shell, the PL intensity was drastically enhanced. The approach described here is utilizable to the fabrication of other semiconductor NCs with various morphologies. Because of the adjusted morphologies, tunable NIR range emission, and high stability of these composite NCs, we will focus on their applications such as solar cell and biolabeling.

Novel {beta}-cyclodextrin modified CdTe quantum dots as fluorescence nanosensor for acetylsalicylic acid and metabolites

Energy Technology Data Exchange (ETDEWEB)

Algarra, M. [Centro de Geologia do Porto, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Campos, B.B.; Aguiar, F.R.; Rodriguez-Borges, J.E. [Centro de Investigacao em Quimica (CIQ-UP), Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 169-007 Porto (Portugal); Esteves da Silva, J.C.G., E-mail: jcsilva@fc.up.pt [Centro de Investigacao em Quimica (CIQ-UP), Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 169-007 Porto (Portugal)

2012-05-01

{beta}-Cyclodextrin was modified with 11-[(ethoxycarbonyl)thio]undecanoic acid and used as a capping agent, together with mercaptosuccinic acid, to prepare water-stable CdTe quantum dots. The water soluble quantum dot obtained displays fluorescence with a maximum emission at 425 nm (under excitation at 300 nm) with lifetimes of 0.53, 4.8, 181, and 44.1 ns, respectively. The S-{beta}CD-MSA-CdTe can act as a nanoprobe that is due to the affinity of the cyclodextrin moiety for selected substances such as acetylsalicylic acid (ASA) and its metabolites as foreign species. The fluorescence of the S-{beta}CD-MSA-CdTe is enhanced on addition of ASA. Linear calibration plots are observed with ASA in concentrations between 0 and 1 mg/l, with a limit of detection at 8.5 Multiplication-Sign 10{sup -9} mol/l (1.5 ng/ml) and a precision as relative standard deviation of 1% (0.05 mg/l). The interference effect of certain compounds as ascorbic acid and its main metabolites such as salicylic, gentisic and salicyluric acid upon the obtained procedure was studied. Highlights: Black-Right-Pointing-Pointer Nanosensors constituted by CdTe quantum dots capped with modified cyclodextrin. Black-Right-Pointing-Pointer This nanomaterial shows fluorescence properties compatible with a semiconductor quantum dot. Black-Right-Pointing-Pointer The nanosensor shows fluorescence enhancement when inclusion complexes are formed with acetylsalicylic acid. Black-Right-Pointing-Pointer This nanomaterial has nanosensor potential taking into consideration the formation stability of the inclusion complex.

The Antifungal Activity of Functionalized Chitin Nanocrystals in Poly (Lactid Acid Films

Directory of Open Access Journals (Sweden)

Asier M. Salaberria

2017-05-01

Full Text Available As, in the market, poly (lactic acid (PLA is the most used polymer as an alternative to conventional plastics, and as functionalized chitin nanocrystals (CHNC can provide structural and bioactive properties, their combination sounds promising in the preparation of functional nanocomposite films for sustainable packaging. Chitin nanocrystals were successfully modified via acylation using anhydride acetic and dodecanoyl chloride acid to improve their compatibility with the matrix, PLA. The nanocomposite films were prepared by extrusion/compression approach using different concentrations of both sets of functionalized CHNC. This investigation brings forward that both sets of modified CHNC act as functional agents, i.e., they slightly improved the hydrophobic character of the PLA nanocomposite films, and, very importantly, they also enhanced their antifungal activity. Nonetheless, the nanocomposite films prepared with the CHNC modified with dodecanoyl chloride acid presented the best properties.

Biocompatible fluorescence-enhanced ZrO{sub 2}-CdTe quantum dot nanocomposite for in vitro cell imaging

Energy Technology Data Exchange (ETDEWEB)

Lu Zhisong; Zhu Zhihong; Zheng Xinting; Qiao Yan; Li Changming [School of Chemical and Biomedical Engineering, Nanyang Technological University, 70 Nanyang Drive, 637457 (Singapore); Guo Jun, E-mail: ecmli@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 (Singapore)

2011-04-15

With advances of quantum dots (QDs) in bioimaging applications, various materials have been used to coat QDs to reduce their nanotoxicity; however, the coating could introduce new toxic sources and quench the fluorescence in bioimaging applications. In this work, ZrO{sub 2}, an excellent ceramic material with low extinction coefficient and good biocompatibility, is utilized to coat CdTe QDs for the first time. Experimental results show that ZrO{sub 2}-QD nanocomposites with the size of {approx} 30 nm possess enhanced fluorescence emission, lower nanotoxicity and gradually increased fluorescence under 350 nm light illumination. After functionalization with folic acid, they were applied to label cultured HeLa cells effectively. Therefore, the ZrO{sub 2}-QD nanocomposites could be promising biocompatible nanomaterials with strong fluorescence emission to replace or complement QDs in biomedical applications.

Green synthesis of water soluble semiconductor nanocrystals and their applications

Science.gov (United States)

Wang, Ying

II-VI semiconductor nanomaterials, e.g. CdSe and CdTe, have attracted great attention over the past decades due to their fascinating optical and electrical properties. The research presented here focuses on aqueous semiconductor nanomaterials. The work can be generally divided into three parts: synthesis, property study and application. The synthetic work is devoted to develop new methods to prepare shape- and structure-controlled II-VI semiconductor nanocrystals including nanoparticles and nanowires. CdSe and CdSe CdS semiconductor nanocrystals have been synthesized using sodium citrate as a stabilizer. Upon prolonged illumination with visible light, photoluminescence quantum yield of those quantum dots can be enhanced up to 5000%. The primary reason for luminescence enhancement is considered to be the removing of specific surface states (photocorrosion) and the smoothing of the CdSe core surface (photoannealing). CdTe nanowires are prepared through self-organization of stabilizer-depleted CdTe nanoparticles. The dipolar-dipolar attraction is believed to be the driving force of nanowire formation. The rich surface chemistry of CdTe nanowire is reflected by the formation of silica shell with different morphologies when nanowires with different capping ligands are used. Te and Se nanowires are prepared by chemical decomposition of CdTe and CdSe nanoparticles in presence of an external chemical stimulus, EDTA. These results not only provide a new example of NP→NW transformation, but also lead to a better understanding of the molecular process occurring in the stabilizer-depleted nanoparticles. The applications of those semiconductor materials are primarily based on the construction of nano-structured ultrathin films with desirable functions by using layer-by-layer technique (LBL). We demonstrate that light-induced micro-scale multicolor luminescent patterns can be obtained on photoactivable CdSe/CdS nanoparticles thin films by combining the advantages of LBL as

High quality zinc-blende CdSe nanocrystals synthesized in a hexadecylamine-oleic acid-paraffin liquid mixture

Energy Technology Data Exchange (ETDEWEB)

Wang Lan, E-mail: lwang322@yahoo.com.cn [Department of Applied Physics, Harbin Institute of Technology, Harbin 150001 (China); Department of Physics, Harbin Medical University, Harbin 150081 (China); Sun Xiudong, E-mail: xdsun@hit.edu.cn [Department of Applied Physics, Harbin Institute of Technology, Harbin 150001 (China); Liu Wenjing [Department of Astronautic Science and Mechanics, Harbin Institute of Technology, Harbin 150001 (China); Liu Bingyi [Laboratory Center for the School of Pharmacy, Harbin Medical University, Harbin 150081 (China)

2010-03-15

Safe, common, and low-cost compounds were used as solvents for the non-tri-n-octylphosphine (TOP) synthesis of high quality CdSe nanocrystals (NCs) in open air. In oleic acid-paraffin liquid system, CdSe nanocrystals in the less common zinc-blende (ZB, cubic) crystal structure have been obtained. The effects of adding n-hexadecylamine (HDA) to different solutions were discussed. Stable, highly homogeneous and luminescent CdSe nanocrystals were formed by adding n-hexadecylamine to Cd solution rather than to Se solution. Without any size sorting, the size distribution of the nanocrystals can be readily controlled and the highest photoluminescence (PL) quantum efficiency (QE) of the nanocrystals was up to 20-30%.

High quality zinc-blende CdSe nanocrystals synthesized in a hexadecylamine-oleic acid-paraffin liquid mixture

International Nuclear Information System (INIS)

Wang Lan; Sun Xiudong; Liu Wenjing; Liu Bingyi

2010-01-01

Safe, common, and low-cost compounds were used as solvents for the non-tri-n-octylphosphine (TOP) synthesis of high quality CdSe nanocrystals (NCs) in open air. In oleic acid-paraffin liquid system, CdSe nanocrystals in the less common zinc-blende (ZB, cubic) crystal structure have been obtained. The effects of adding n-hexadecylamine (HDA) to different solutions were discussed. Stable, highly homogeneous and luminescent CdSe nanocrystals were formed by adding n-hexadecylamine to Cd solution rather than to Se solution. Without any size sorting, the size distribution of the nanocrystals can be readily controlled and the highest photoluminescence (PL) quantum efficiency (QE) of the nanocrystals was up to 20-30%.

Interaction of Water-Soluble CdTe Quantum Dots with Bovine Serum Albumin

Science.gov (United States)

2011-01-01

Semiconductor nanoparticles (quantum dots) are promising fluorescent markers, but it is very little known about interaction of quantum dots with biological molecules. In this study, interaction of CdTe quantum dots coated with thioglycolic acid (TGA) with bovine serum albumin was investigated. Steady state spectroscopy, atomic force microscopy, electron microscopy and dynamic light scattering methods were used. It was explored how bovine serum albumin affects stability and spectral properties of quantum dots in aqueous media. CdTe–TGA quantum dots in aqueous solution appeared to be not stable and precipitated. Interaction with bovine serum albumin significantly enhanced stability and photoluminescence quantum yield of quantum dots and prevented quantum dots from aggregating. PMID:27502633

Translocation and neurotoxicity of CdTe quantum dots in RMEs motor neurons in nematode Caenorhabditis elegans

International Nuclear Information System (INIS)

Zhao, Yunli; Wang, Xiong; Wu, Qiuli; Li, Yiping; Wang, Dayong

2015-01-01

Graphical abstract: - Highlights: • We investigated in vivo neurotoxicity of CdTe QDs on RMEs motor neurons in C. elegans. • CdTe QDs in the range of μg/L caused neurotoxicity on RMEs motor neurons. • Bioavailability of CdTe QDs may be the primary inducer for CdTe QDs neurotoxicity. • Both oxidative stress and cell identity regulate the CdTe QDs neurotoxicity. • CdTe QDs were translocated and deposited into RMEs motor neurons. - Abstract: We employed Caenorhabditis elegans assay system to investigate in vivo neurotoxicity of CdTe quantum dots (QDs) on RMEs motor neurons, which are involved in controlling foraging behavior, and the underlying mechanism of such neurotoxicity. After prolonged exposure to 0.1–1 μg/L of CdTe QDs, abnormal foraging behavior and deficits in development of RMEs motor neurons were observed. The observed neurotoxicity from CdTe QDs on RMEs motor neurons might be not due to released Cd 2+ . Overexpression of genes encoding Mn-SODs or unc-30 gene controlling cell identity of RMEs neurons prevented neurotoxic effects of CdTe QDs on RMEs motor neurons, suggesting the crucial roles of oxidative stress and cell identity in regulating CdTe QDs neurotoxicity. In nematodes, CdTe QDs could be translocated through intestinal barrier and be deposited in RMEs motor neurons. In contrast, CdTe@ZnS QDs could not be translocated into RMEs motor neurons and therefore, could only moderately accumulated in intestinal cells, suggesting that ZnS coating might reduce neurotoxicity of CdTe QDs on RMEs motor neurons. Therefore, the combinational effects of oxidative stress, cell identity, and bioavailability may contribute greatly to the mechanism of CdTe QDs neurotoxicity on RMEs motor neurons. Our results provide insights into understanding the potential risks of CdTe QDs on the development and function of nervous systems in animals

Facile template-directed synthesis of carbon-coated SnO2 nanotubes with enhanced Li-storage capabilities

International Nuclear Information System (INIS)

Zhu, Xiaoshu; Zhu, Jingyi; Yao, Yinan; Zhou, Yiming; Tang, Yawen; Wu, Ping

2015-01-01

Herein, a novel type of carbon-coated SnO 2 nanotubes has been designed and synthesized through a facile two-step hydrothermal approach by using ZnO nanorods as templates. During the synthetic route, SnO 2 nanocrystals and carbon layer have been uniformly deposited on the rod-like templates in sequence, meanwhile ZnO nanorods could be in situ dissolved owing to the generated alkaline and acidic environments during hydrothermal coating of SnO 2 nanocrystals and hydrothermal carbonization of glucose, respectively. When utilized as an anode material in lithium-ion batteries, the carbon-coated SnO 2 nanotubes manifests markedly enhanced Li-storage capabilities in terms of specific capacity and cycling stability in comparison with bare SnO 2 nanocrystals. - Graphical abstract: Display Omitted - Highlights: • C-coated SnO 2 nanotubes prepared via facile ZnO-nanorod-templated hydrothermal route. • Unique morphological and structural features toward lithium storage. • Enhanced Li-storage performance in terms of specific capacity and cycling stability

Rapid detection of malachite green in fish based on CdTe quantum dots coated with molecularly imprinted silica.

Science.gov (United States)

Wu, Le; Lin, Zheng-Zhong; Zhong, Hui-Ping; Peng, Ai-Hong; Chen, Xiao-Mei; Huang, Zhi-Yong

2017-08-15

A sensitive fluorescence sensor for the detection of malachite green (MG) was fabricated by grafting molecularly imprinted polymers (MIPs) onto the surface of CdTe quantum dots (QDs). The MIP-coated QDs were synthesized via a reverse microemulsion method using (3-aminopropyl)triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) as functional monomer and cross-linker, respectively. The optimum molar ratio of MG, functional monomer and cross-linker was 1:3:10. The MIP-coated QDs exhibited uniform spheres with diameter around 49nm and excellent fluorescence emission at λ ex 370nm. A linear relationship with two segments between the relative fluorescence intensities and the MG concentrations ranging from 0.08 to 20μmol·L -1 could be obtained with a detection limit of 12μg·kg -1 . The fluorescent probe was successfully applied to the determination of MG in fish samples with the spiked recoveries ranging from 94.3% to 109.5% which were in accordance with those of the measurement by HPLC-UV. Copyright © 2017 Elsevier Ltd. All rights reserved.

Translocation and neurotoxicity of CdTe quantum dots in RMEs motor neurons in nematode Caenorhabditis elegans

Energy Technology Data Exchange (ETDEWEB)

Zhao, Yunli; Wang, Xiong; Wu, Qiuli; Li, Yiping; Wang, Dayong, E-mail: dayongw@seu.edu.cn

2015-02-11

Graphical abstract: - Highlights: • We investigated in vivo neurotoxicity of CdTe QDs on RMEs motor neurons in C. elegans. • CdTe QDs in the range of μg/L caused neurotoxicity on RMEs motor neurons. • Bioavailability of CdTe QDs may be the primary inducer for CdTe QDs neurotoxicity. • Both oxidative stress and cell identity regulate the CdTe QDs neurotoxicity. • CdTe QDs were translocated and deposited into RMEs motor neurons. - Abstract: We employed Caenorhabditis elegans assay system to investigate in vivo neurotoxicity of CdTe quantum dots (QDs) on RMEs motor neurons, which are involved in controlling foraging behavior, and the underlying mechanism of such neurotoxicity. After prolonged exposure to 0.1–1 μg/L of CdTe QDs, abnormal foraging behavior and deficits in development of RMEs motor neurons were observed. The observed neurotoxicity from CdTe QDs on RMEs motor neurons might be not due to released Cd{sup 2+}. Overexpression of genes encoding Mn-SODs or unc-30 gene controlling cell identity of RMEs neurons prevented neurotoxic effects of CdTe QDs on RMEs motor neurons, suggesting the crucial roles of oxidative stress and cell identity in regulating CdTe QDs neurotoxicity. In nematodes, CdTe QDs could be translocated through intestinal barrier and be deposited in RMEs motor neurons. In contrast, CdTe@ZnS QDs could not be translocated into RMEs motor neurons and therefore, could only moderately accumulated in intestinal cells, suggesting that ZnS coating might reduce neurotoxicity of CdTe QDs on RMEs motor neurons. Therefore, the combinational effects of oxidative stress, cell identity, and bioavailability may contribute greatly to the mechanism of CdTe QDs neurotoxicity on RMEs motor neurons. Our results provide insights into understanding the potential risks of CdTe QDs on the development and function of nervous systems in animals.

Processing of Copper Zinc Tin Sulfide Nanocrystal Dispersions for Thin Film Solar Cells

Science.gov (United States)

Williams, Bryce Arthur

A scalable and inexpensive renewable energy source is needed to meet the expected increase in electricity demand throughout the developed and developing world in the next 15 years without contributing further to global warming through CO2 emissions. Photovoltaics may meet this need but current technologies are less than ideal requiring complex manufacturing processes and/or use of toxic, rare-earth materials. Copper zinc tin sulfide (Cu 2ZnSnS4, CZTS) solar cells offer a true "green" alternative based upon non-toxic and abundant elements. Solution-based processes utilizing CZTS nanocrystal dispersions followed by high temperature annealing have received significant research attention due to their compatibility with traditional roll-to-roll coating processes. In this work, CZTS nanocrystal (5-35 nm diameters) dispersions were utilized as a production pathway to form solar absorber layers. Aerosol-based coating methods (aerosol jet printing and ultrasonic spray coating) were optimized for formation of dense, crack-free CZTS nanocrystal coatings. The primary variables underlying determination of coating morphology within the aerosol-coating parameter space were investigated. It was found that the liquid content of the aerosol droplets at the time of substrate impingement play a critical role. Evaporation of the liquid from the aerosol droplets during coating was altered through changes to coating parameters as well as to the CZTS nanocrystal dispersions. In addition, factors influencing conversion of CZTS nanocrystal coatings into dense, large-grained polycrystalline films suitable for solar cell development during thermal annealing were studied. The roles nanocrystal size, carbon content, sodium uptake, and sulfur pressure were found to have pivotal roles in film microstructure evolution. The effects of these parameters on film morphology, grain growth rates, and chemical makeup were analyzed from electron microscopy images as well as compositional analysis

Effect of a gelatin-based edible coating containing cellulose nanocrystals (CNC) on the quality and nutrient retention of fresh strawberries during storage

Science.gov (United States)

Fakhouri, F. M.; Casari, A. C. A.; Mariano, M.; Yamashita, F.; Innocnentini Mei, L. H.; Soldi, V.; Martelli, S. M.

2014-08-01

Strawberry is a non-climacteric fruit with a very short postharvest shelf-life. Loss of quality in this fruit is mostly due to its relatively high metabolic activity and sensitivity to fungal decay, meanly grey mold (Botrytis cinerea). In this study, the ability of gelatin coatings containing cellulose nanocrystals (CNC) to extend the shelf-life of strawberry fruit (Fragaria ananassa) over 8 days were studied. The filmogenic solution was obtained by the hydration of 5 g of gelatin (GEL) in 100 mL of distillated water containing different amounts of CNC dispersion (10 mg CNC/g of GEL or 50 mg of CNC/g of GEL) for 1 hour at room temperature. After this period, the solution was heated to 70 °C and maintained at this temperature for 10 minutes. The plasticizer (glycerol) (10g/100g of the GEL) was then added with constant, gentle stirring in order to avoid forming air bubbles and also to avoid gelatin denaturation until complete homogenization. Strawberries (purchased at the local market) were immersed in the filmogenic solution for 1 minute and after coated were dried at 15 °C by 24 hours. The strawberries were then kept under refrigeration and characterized in terms of their properties (weight loss, ascorbic acid content, titratable acidity, water content). The results have shown that samples covered with GEL/CNC had a significant improvement in its shelf- life. For instance, for the control sample (without coating) the weight loss after 8 days of storage was around 65%, while covered samples loss in the range of 31-36%. Edible coating was also effective in the retention of ascorbic acid (AA) in the strawberries, while control sample presented a fast decay in the AA content, covered samples showed a slow decay in the AA concentration. Moreover, the use of GEL/CNC edible coating had an antimicrobial effect in the fruits.

Effect of a gelatin-based edible coating containing cellulose nanocrystals (CNC) on the quality and nutrient retention of fresh strawberries during storage

International Nuclear Information System (INIS)

Fakhouri, F M; Casari, A C A; Martelli, S M; Mariano, M; Soldi, V; Yamashita, F; Mei, L H Innocnentini

2014-01-01

Strawberry is a non-climacteric fruit with a very short postharvest shelf-life. Loss of quality in this fruit is mostly due to its relatively high metabolic activity and sensitivity to fungal decay, meanly grey mold (Botrytis cinerea). In this study, the ability of gelatin coatings containing cellulose nanocrystals (CNC) to extend the shelf-life of strawberry fruit (Fragaria ananassa) over 8 days were studied. The filmogenic solution was obtained by the hydration of 5 g of gelatin (GEL) in 100 mL of distillated water containing different amounts of CNC dispersion (10 mg CNC/g of GEL or 50 mg of CNC/g of GEL) for 1 hour at room temperature. After this period, the solution was heated to 70 °C and maintained at this temperature for 10 minutes. The plasticizer (glycerol) (10g/100g of the GEL) was then added with constant, gentle stirring in order to avoid forming air bubbles and also to avoid gelatin denaturation until complete homogenization. Strawberries (purchased at the local market) were immersed in the filmogenic solution for 1 minute and after coated were dried at 15 °C by 24 hours. The strawberries were then kept under refrigeration and characterized in terms of their properties (weight loss, ascorbic acid content, titratable acidity, water content). The results have shown that samples covered with GEL/CNC had a significant improvement in its shelf- life. For instance, for the control sample (without coating) the weight loss after 8 days of storage was around 65%, while covered samples loss in the range of 31-36%. Edible coating was also effective in the retention of ascorbic acid (AA) in the strawberries, while control sample presented a fast decay in the AA content, covered samples showed a slow decay in the AA concentration. Moreover, the use of GEL/CNC edible coating had an antimicrobial effect in the fruits

Biopolymer coated gold nanocrystals prepared using the green chemistry approach and their shape-dependent catalytic and surface-enhanced Raman scattering properties.

Science.gov (United States)

Chou, Chih-Wei; Hsieh, Hui-Hsuan; Hseu, You-Cheng; Chen, Ko-Shao; Wang, Gou-Jen; Chang, Hsien-Chang; Pan, Yong-Li; Wei, Yi-Syuan; Chang, Ko Hsin; Harn, Yeu-Wei

2013-07-21

This study deals with the preparation of multi-shaped nanoscale gold crystals under synthetically simple, green, and efficient conditions using a seed-mediated growth approach in the presence of hyaluronic acid (HA). These highly biocompatible multi-shaped gold nanocrystals were examined to evaluate their catalytic and surface enhanced Raman scattering (SERS) properties. The results show that the size and shape of the nanocrystals are mainly correlated to the amount of seed, seed size, HA concentration, and reaction temperature. Gold seeds accelerate the reduction of the gold precursor to form gold nanocrystals using HA. The HA serves as a reducing agent and a growth template for the reduction of Au(III) and nanocrystal stabilization. The multi-shaped gold nanocrystals showed superior catalytic properties and higher SERS performance. The simple, green approach efficiently controls the nanocrystals and creates many opportunities for future applications.

Ultrafast synthesis of flower-like ordered Pd3Pb nanocrystals with superior electrocatalytic activities towards oxidation of formic acid and ethanol

Science.gov (United States)

Jana, Rajkumar; Subbarao, Udumula; Peter, Sebastian C.

2016-01-01

Ordered intermetallic nanocrystals with high surface area are highly promising as efficient catalysts for fuel cell applications because of their unique electrocatalytic properties. The present work discusses about the controlled synthesis of ordered intermetallic Pd3Pb nanocrystals in different morphologies at relatively low temperature for the first time by polyol and hydrothermal methods both in presence and absence of surfactant. Here for the first time we report surfactant free synthesis of ordered flower-like intermetallic Pd3Pb nanocrystals in 10 s. The structural characteristics of the nanocrystals are confirmed by powder X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The as synthesized ordered Pd3Pb nanocrystals exhibit far superior electrocatalytic activity and durability towards formic acid and ethanol oxidation over commercially available Pd black (Pd/C). The morphological variation of nanocrystals plays a crucial role in the electrocatalytic oxidation of formic acid and ethanol. Among the catalysts, the flower-like Pd3Pb shows enhanced activity and stability in electrocatalytic formic acid and ethanol oxidation. The current density and mass activity of flower-like Pd3Pb catalyst are higher by 2.5 and 2.4 times than that of Pd/C for the formic acid oxidation and 1.5 times each for ethanol oxidation.

Using silicon-coated gold nanoparticles to enhance the fluorescence of CdTe quantum dot and improve the sensing ability of mercury (II)

Science.gov (United States)

Zhu, Jian; Chang, Hui; Li, Jian-Jun; Li, Xin; Zhao, Jun-Wu

2018-01-01

The effect of silicon-coated gold nanoparticles with different gold core diameter and silica shell thickness on the fluorescence emission of CdTe quantum dots (QDs) was investigated. For gold nanoparticles with a diameter of 15 nm, silica coating can only results in fluorescence recover of the bare gold nanoparticle-induced quenching of QDs. However, when the size of gold nanoparticle is increased to 60 nm, fluorescence enhancement of the QDs could be obtained by silica coating. Because of the isolation of the silica shell-reduced quenching effect and local electric field effect, the fluorescence of QDs gets intense firstly and then decreases. The maximum fluorescence enhancement takes place as the silica shell has a thickness of 30 nm. This enhanced fluorescence from silicon-coated gold nanoparticles is demonstrated for sensing of Hg2 +. Under optimal conditions, the enhanced fluorescence intensity decreases linearly with the concentration of Hg2 + ranging from 0 to 200 ng/mL. The limit of detection for Hg2 + is 1.25 ng/mL. Interference test and real samples detection indicate that the influence from other metal ions could be neglected, and the Hg2 + could be specifically detected.

Matrix-Assisted Laser Desorption Ionization Mass Spectrometry of Compounds Containing Carboxyl Groups Using CdTe and CuO Nanoparticles

OpenAIRE

Megumi Sakurai; Taro Sato; Jiawei Xu; Soichi Sato; Tatsuya Fujino

2018-01-01

Matrix-assisted laser desorption ionization mass spectrometry of compounds containing carboxyl groups was carried out by using semiconductor nanoparticles (CdTe and CuO) as the matrix. Salicylic acid (Sal), glucuronic acid (Glu), ibuprofen (Ibu), and tyrosine (Tyr) were ionized as deprotonated species (carboxylate anions) by using electrons ejected from CdTe after the photoexcitation. When CuO was used as the matrix, the peak intensity of Tyr became high compared with that obtained with CdTe....

Effect of cellulose nanocrystals (CNC) addition and citric acid as co-plasticizer on physical properties of sago starch biocomposite

Science.gov (United States)

Nasution, Halimatuddahliana; Afandy, Yayang; Al-fath, M. Thoriq

2018-04-01

Cellulose has potential applications in new high-performance materials with low environmental impact. Rattan biomass is a fiber waste from processing industry of rattan which contains 37,6% cellulose. The high cellulose contents of rattan biomass make it a source of cellulose nanocrystals as a filler in biocomposite. Isolation of alpha cellulose from biomass rattan was prepared by using three stages: delignification, alkalization, and bleaching. It was delignificated with 3,5% HNO3 and NaNO2, precipitated with 17,5% NaOH, bleaching process with 10% H2O2. Nanocrystals obtained through the hydrolysis of alpha cellulose using 45% H2SO4 and followed by mechanical processes of ultrasonication, centrifugation, and filtration with a dialysis membrane. Sago starch biocomposites were prepared using a solution casting method, which includes 1-4 wt % cellulose nanocrystals rattan biomass as fillers, 10-40 wt% citric acid as co-plasticizer and 30 wt% glycerol as plasticizer. The results of TEM and FTIR characteristic of cellulose nanocrystals show spherical like shape FTIR and chemical composition analysis demonstrated that lignin and hemicellulose structures were successfully removed. Biocomposite characteristic consists of density and water absorption. The results showed the highest density values were 0,266 gram/cm3 obtained at an additional of 3% cellulose nanocrystals rattan biomass and 30% citric acid. The lowest water absorption was 7,893% obtained at an additional of 4% cellulose nanocrystals rattan biomass and 10% citric acid.

Effect of shells on photoluminescence of aqueous CdTe quantum dots

International Nuclear Information System (INIS)

Yuan, Zhimin; Yang, Ping

2013-01-01

Graphical abstract: Size-tunable CdTe coated with several shells using an aqueous solution synthesis. CdTe/CdS/ZnS quantum dots exhibited high PL efficiency up to 80% which implies the promising applications for biomedical labeling. - Highlights: • CdTe quantum dots were fabricated using an aqueous synthesis. • CdS, ZnS, and CdS/ZnS shells were subsequently deposited on CdTe cores. • Outer ZnS shells provide an efficient confinement of electron and hole inside the QDs. • Inside CdS shells can reduce the strain on the QDs. • Aqueous CdTe/CdS/ZnS QDs exhibited high stability and photoluminescence efficiency of 80%. - Abstract: CdTe cores with various sizes were fabricated in aqueous solutions. Inorganic shells including CdS, ZnS, and CdS/ZnS were subsequently deposited on the cores through a similar aqueous procedure to investigate the effect of shells on the photoluminescence properties of the cores. In the case of CdTe/CdS/ZnS quantum dots, the outer ZnS shell provides an efficient confinement of electron and hole wavefunctions inside the quantum dots, while the middle CdS shell sandwiched between the CdTe core and ZnS shell can be introduced to obviously reduce the strain on the quantum dots because the lattice parameters of CdS is situated at the intermediate-level between those of CdTe and ZnS. In comparison with CdTe/ZnS core–shell quantum dots, the as-prepared water-soluble CdTe/CdS/ZnS quantum dots in our case can exhibit high photochemical stability and photoluminescence efficiency up to 80% in an aqueous solution, which implies the promising applications in the field of biomedical labeling

Surface chemical functionalisation of epoxy photoresist-based microcantilevers with organic-coated TiO2 nanocrystals

DEFF Research Database (Denmark)

Ingrosso, C.; Sardella, E.; Keller, S. S.

2012-01-01

In this Letter, a solution-based approach has been used for chemically immobilising oleic acid (OLEA)-capped TiO2 nanocrystals (NCs) on the surface of microcantilevers formed of SU-8, a negative tone epoxy photoresist. The immobilisation has been carried out at room temperature, under visible lig...

Highly thermal-stable and functional cellulose nanocrystals and nanofibrils produced using fully recyclable organic acids

Science.gov (United States)

Liheng Chen; Junyong Zhu; Carlos Baez; Peter Kitin; Thomas Elder

2016-01-01

Here we report the production of highly thermal stable and functional cellulose nanocrystals (CNC) and nanofibrils (CNF) by hydrolysis using concentrated organic acids. Due to their low water solubility, these solid organic acids can be easily recovered after hydrolysis reactions through crystallization at a lower or ambient temperature. When dicarboxylic acids were...

The use of castor oil and ricinoleic acid in lead chalcogenide nanocrystal synthesis

Science.gov (United States)

Kyobe, Joseph W. M.; Mubofu, Egid B.; Makame, Yahya M. M.; Mlowe, Sixberth; Revaprasadu, Neerish

2016-08-01

A green solution-based thermolysis method for the synthesis of lead chalcogenide (PbE, E = S, Se, Te) nanocrystals in castor oil (CSTO) and its isolate ricinoleic acid (RA) is described. The blue shift observed from the optical spectra of CSTO and RA-capped PbE nanocrystals (NCs) confirmed the evidence of quantum confinement. The dimensions of PbE NCs obtained from NIR absorption spectra, transmission electron microscopy (TEM), and X-ray diffraction (XRD) studies were in good agreement. The particle sizes estimated were in the range of 20, 25, and 130 nm for castor oil-capped PbS, PbSe, and PbTe, respectively. Well-defined close to cubic-shaped particles were observed in the scanning electron microscopy (SEM) images of PbSe and PbTe nanocrystals. The high-resolution TEM and selective area electron diffraction (SAED) micrographs of the as-synthesized crystalline PbE NCs showed distinct lattice fringes with d-spacing distances corroborating with the standard values reported in literature.

Comparative study of CdTe sources used for deposition of CdTe thin films by close spaced sublimation technique

Directory of Open Access Journals (Sweden)

Wagner Anacleto Pinheiro

2006-03-01

Full Text Available Unlike other thin film deposition techniques, close spaced sublimation (CSS requires a short source-substrate distance. The kind of source used in this technique strongly affects the control of the deposition parameters, especially the deposition rate. When depositing CdTe thin films by CSS, the most common CdTe sources are: single-crystal or polycrystalline wafers, powders, pellets or pieces, a thick CdTe film deposited onto glass or molybdenum substrate (CdTe source-plate and a sintered CdTe powder. In this work, CdTe thin films were deposited by CSS technique from different CdTe sources: particles, powder, compact powder, a paste made of CdTe and propylene glycol and source-plates (CdTe/Mo and CdTe/glass. The largest deposition rate was achieved when a paste made of CdTe and propylene glycol was used as the source. CdTe source-plates led to lower rates, probably due to the poor heat transmission, caused by the introduction of the plate substrate. The results also showed that compacting the powder the deposition rate increases due to the better thermal contact between powder particles.

Self-Catalyzed CdTe Wires

Directory of Open Access Journals (Sweden)

Tom Baines

2018-04-01

Full Text Available CdTe wires have been fabricated via a catalyst free method using the industrially scalable physical vapor deposition technique close space sublimation. Wire growth was shown to be highly dependent on surface roughness and deposition pressure, with only low roughness surfaces being capable of producing wires. Growth of wires is highly (111 oriented and is inferred to occur via a vapor-solid-solid growth mechanism, wherein a CdTe seed particle acts to template the growth. Such seed particles are visible as wire caps and have been characterized via energy dispersive X-ray analysis to establish they are single phase CdTe, hence validating the self-catalysation route. Cathodoluminescence analysis demonstrates that CdTe wires exhibited a much lower level of recombination when compared to a planar CdTe film, which is highly beneficial for semiconductor applications.

Study of the interaction of flavonoids with 3-mercaptopropionic acid modified CdTe quantum dots mediated by cetyltrimethyl ammonium bromide in aqueous medium

Science.gov (United States)

Aucelio, Ricardo Q.; Carvalho, Juliana M.; Real, Juliana T.; Maqueira-Espinosa, Luis; Pérez-Gramatges, Aurora; da Silva, Andrea R.

2017-02-01

Flavonoids are polyphenols that help the maintenance of health, aiding the prevention of diseases. In this work, CdTe QDs coated with 3-mercaptopropionic acid (3MPA), with an average size of 2.7 nm, were used as photoluminescence probe for flavonoids in different conditions. The interaction between 14 flavonoids and QDs was evaluated in aqueous dispersions in the absence and in the presence of cetyltrimethylammonium bromide (CTAB). To establish a relationship between photoluminescence quenching and the concentration of flavonoids, the Stern-Volmer model was used. In the absence of CTAB, the linear ranges for quercetin, morin and rutin were from 5.0 × 10- 6 mol L- 1 to 6.0 × 10- 5 mol L- 1 and from 1.0 × 10- 5 mol L- 1 to 6.0 × 10- 4 mol L- 1 for kaempferol. The sensibility of the Stern-Volmer curves (Ks) indicated that quercetin interacts more strongly with the probe: Ks quercetin > Ks kaempferol > Ks rutin > Ks morin. The conjugation extension in the 3 rings, and the acidic hydroxyl groups (positions 3ʹand 4ʹ) in the B-ring enhanced the interaction with 3MPA-CdTe QDs. The other flavonoids do not interact with the probe at 10- 5 mol L- 1 level. In CTAB organized dispersions, Ks 3-hydroxyflavone > Ks 7-hydroxyflavone > Ks flavona > Ks rutin in the range from 1.0 × 10- 6 mol L- 1 to 1.2 × 10- 5 mol L- 1 for flavones and of 1.0 × 10- 6 mol L- 1 to 1.0 × 10- 5 mol L- 1 for rutin. Dynamic light scattering, conductometric measurements and microenvironment polarity studies were employed to elucidate the QDs-flavonoids interaction in systems containing CTAB. The quenching can be attributed to the preferential solubility of hydrophobic flavonoid in the palisade layer of the CTAB aggregates adsorbed on the surface of the 3MPA CdTe QDs.

Inhibition of palm oil oxidation by zeolite nanocrystals.

Science.gov (United States)

Tan, Kok-Hou; Awala, Hussein; Mukti, Rino R; Wong, Ka-Lun; Rigaud, Baptiste; Ling, Tau Chuan; Aleksandrov, Hristiyan A; Koleva, Iskra Z; Vayssilov, Georgi N; Mintova, Svetlana; Ng, Eng-Poh

2015-05-13

The efficiency of zeolite X nanocrystals (FAU-type framework structure) containing different extra-framework cations (Li(+), Na(+), K(+), and Ca(2+)) in slowing the thermal oxidation of palm oil is reported. The oxidation study of palm oil is conducted in the presence of zeolite nanocrystals (0.5 wt %) at 150 °C. Several characterization techniques such as visual analysis, colorimetry, rheometry, total acid number (TAN), FT-IR spectroscopy, (1)H NMR spectroscopy, and Karl Fischer analyses are applied to follow the oxidative evolution of the oil. It was found that zeolite nanocrystals decelerate the oxidation of palm oil through stabilization of hydroperoxides, which are the primary oxidation product, and concurrently via adsorption of the secondary oxidation products (alcohols, aldehydes, ketones, carboxylic acids, and esters). In addition to the experimental results, periodic density functional theory (DFT) calculations are performed to elucidate further the oxidation process of the palm oil in the presence of zeolite nanocrystals. The DFT calculations show that the metal complexes formed with peroxides are more stable than the complexes with alkenes with the same ions. The peroxides captured in the zeolite X nanocrystals consequently decelerate further oxidation toward formation of acids. Unlike the monovalent alkali metal cations in the zeolite X nanocrystals (K(+), Na(+), and Li(+)), Ca(2+) reduced the acidity of the oil by neutralizing the acidic carboxylate compounds to COO(-)(Ca(2+))1/2 species.

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

Solution blow spun nanocomposites of poly(lactic acid)/cellulose nanocrystals from Eucalyptus kraft pulp

Science.gov (United States)

Cellulose nanocrystals (CNCs) were extracted from Eucalyptus kraft pulp by sulfuric acid hydrolysis, and esterified with maleic anhydride (CNCMA). The incorporation of sulfate ester groups on the cellulose surface resulted in higher stability of the nanoparticles in aqueous suspensions and lower the...

Eco-friendly approach towards green synthesis of zinc oxide nanocrystals and its potential applications.

Science.gov (United States)

Velmurugan, Palanivel; Park, Jung-Hee; Lee, Sang-Myeong; Yi, Young-Joo; Cho, Min; Jang, Jum-Suk; Myung, Hyun; Bang, Keuk-Soo; Oh, Byung-Taek

2016-09-01

In the present study, we investigated a novel green route for synthesis of zinc oxide (ZnO) nanocrystals using Prunus × yedoensis Matsumura leaf extract as a reducing agent without using any surfactant or external energy. Standard characterization studies were carried out to confirm the obtained product using UV-Vis spectra, SEM-EDS, FTIR, TEM, and XRD. In addition, the synthesized ZnO nanocrystals were coated onto fabric and leather samples to study their bacteriostatic effect against odor-causing bacteria Brevibacterium linens and Staphylococcus epidermidis. Zinc oxide nanocrystal-coated fabric and leather showed good activity against both bacteria.

Cellulose nanocrystals obtained from office waste paper and their potential application in PET packing materials.

Science.gov (United States)

Lei, Wanqing; Fang, Changqing; Zhou, Xing; Yin, Qian; Pan, Shaofei; Yang, Rong; Liu, Donghong; Ouyang, Yun

2018-02-01

Annually a tremendous amount of office waste paper (OWP) is discarded creating environmental pollution. Therefore, how to make this paper from waste to wealth and use it in new approaches have become a meaningful and challenging work. In this work, OWP being a cellulose rich biomass was employed for the production of cellulose nanocrystals (CNCs) by acid hydrolysis with different acid concentrations but without subjecting OWP to alkali and bleaching treatments. The testing results showed that CNCs prepared using sulfuric acid concentration of 59% with respect to OWP had the highest crystallinity and this concentration was the transition concentration for the production of opaque CNCs film with convoluted nanofibers to transparent one with orientated nanofibers. Besides, CNCs prepared using acid concentration of 65% coated on PET sheet not only had a better water vapor barrier property but also was on a par with the transparency of PET, which was hopeful to be used as coating materials in packaging materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

Vapor transport deposition of large-area polycrystalline CdTe for radiation image sensor application

Energy Technology Data Exchange (ETDEWEB)

Yang, Keedong; Cha, Bokyung; Heo, Duchang; Jeon, Sungchae [Korea Electrotechnology Research Institute, 111 Hanggaul-ro, Ansan-si, Gyeonggi-do 426-170 (Korea, Republic of)

2014-07-15

Vapor transport deposition (VTD) process delivers saturated vapor to substrate, resulting in high-throughput and scalable process. In addition, VTD can maintain lower substrate temperature than close-spaced sublimation (CSS). The motivation of this work is to adopt several advantages of VTD for radiation image sensor application. Polycrystalline CdTe films were obtained on 300 mm x 300 mm indium tin oxide (ITO) coated glass. The polycrystalline CdTe film has columnar structure with average grain size of 3 μm ∝ 9 μm, which can be controlled by changing the substrate temperature. In order to analyze electrical and X-ray characteristics, ITO-CdTe-Al sandwich structured device was fabricated. Effective resistivity of the polycrystalline CdTe film was ∝1.4 x 10{sup 9}Ωcm. The device was operated under hole-collection mode. The responsivity and the μτ product estimated to be 6.8 μC/cm{sup 2}R and 5.5 x 10{sup -7} cm{sup 2}/V. The VTD can be a process of choice for monolithic integration of CdTe thick film for radiation image sensor and CMOS/TFT circuitry. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Cellulose Nanocrystal/Poly(ethylene glycol) Composite as an Iridescent Coating on Polymer Substrates: Structure-Color and Interface Adhesion.

Science.gov (United States)

Gu, Mingyue; Jiang, Chenyu; Liu, Dagang; Prempeh, Nana; Smalyukh, Ivan I

2016-11-30

The broad utility as an environmentally friendly and colorful coating of cellulose nanocrystal (CNC) was limited by its instability of coloration, brittleness, and lack of adhesion to a hydrophobic surface. In the present work, a neutral polymer, poly(ethylene glycol) (PEG) was introduced into CNC coatings through evaporation-induced self-assembly (EISA) on polymer matrices. The structure-color and mechanical properties of the composite coating or coating film were characterized by UV-vis spectroscopy, polarized light microscopy (PLM), scanning electron microscopy (SEM), wide-angle X-ray diffraction (WXRD), and tensile tests. Results showed that the reflective wavelength of the iridescent CNCs could be finely tuned by incorporation of PEG with varied loadings from 2.5 to 50 wt %, although the high loading content of PEG would produce some side effects because of the severe microphase separation. Second, PEG played an effective plasticizer to improve the ductility or flexibility of the CNC coating or coating film. Furthermore, as a compatibilizer, PEG could effectively and tremendously enhance the adhesion strength between CNCs and neutral polymer matrices without destroying the chiral nematic mesophases of CNCs. Environmentally friendly CNC/PEG composites with tunable iridescence, good flexibility, and high bonding strength to hydrophobic polymer matrices are expected to be promising candidates in the modern green paint industry.

Cellular interactions of lauric acid and dextran-coated magnetite nanoparticles

International Nuclear Information System (INIS)

Pradhan, Pallab; Giri, Jyotsnendu; Banerjee, Rinti; Bellare, Jayesh; Bahadur, Dhirendra

2007-01-01

In vitro cytocompatibility and cellular interactions of lauric acid and dextran-coated magnetite nanoparticles were evaluated with two different cell lines (mouse fibroblast and human cervical carcinoma). Lauric acid-coated magnetite nanoparticles were less cytocompatible than dextran-coated magnetite nanoparticles and cellular uptake of lauric acid-coated magnetic nanoparticles was more than that of dextran-coated magnetite nanoparticles. Lesser cytocompatibility and higher uptake of lauric acid-coated magnetite nanoparticles as compared to dextran-coated magnetic nanoparticles may be due to different cellular interactions by coating material. Thus, coating plays an important role in modulation of biocompatibility and cellular interaction of magnetic nanoparticles

One-pot synthesis of Pd-Pt@Pd core-shell nanocrystals with enhanced electrocatalytic activity for formic acid oxidation

KAUST Repository

Yuan, Qiang

2014-01-01

Well-defined Pd-Pt@Pd core-shell nanocrystals with a Pd-Pt alloy core and a conformal Pd shell of ~2-3 nm were directly synthesized through a one-pot, aqueous solution approach without any preformed Pd or Pt seeds. These Pd-Pt@Pd core-shell nanocrystals show an enhanced electrocatalytic activity for formic acid oxidation compared with commercial Pd black. This journal is © 2014 The Royal Society of Chemistry.

Hydrazine-mediated construction of nanocrystal self-assembly materials.

Science.gov (United States)

Zhou, Ding; Liu, Min; Lin, Min; Bu, Xinyuan; Luo, Xintao; Zhang, Hao; Yang, Bai

2014-10-28

Self-assembly is the basic feature of supramolecular chemistry, which permits to integrate and enhance the functionalities of nano-objects. However, the conversion of self-assembled structures to practical materials is still laborious. In this work, on the basis of studying one-pot synthesis, spontaneous assembly, and in situ polymerization of aqueous semiconductor nanocrystals (NCs), NC self-assembly materials are produced and applied to design high performance white light-emitting diode (WLED). In producing self-assembly materials, the additive hydrazine (N2H4) is curial, which acts as the promoter to achieve room-temperature synthesis of aqueous NCs by favoring a reaction-controlled growth, as the polyelectrolyte to weaken inter-NC electrostatic repulsion and therewith facilitate the one-dimensional self-assembly, and in particular as the bifunctional monomers to polymerize with mercapto carboxylic acid-modified NCs via in situ amidation reaction. This strategy is versatile for mercapto carboxylic acid-modified aqueous NCs, for example CdS, CdSe, CdTe, CdSe(x)Te(1-x), and Cd(y)Hg(1-y)Te. Because of the multisite modification with carboxyl, the NCs act as macromonomers, thus producing cross-linked self-assembly materials with excellent thermal, solvent, and photostability. The assembled NCs preserve strong luminescence and avoid unpredictable fluorescent resonance energy transfer, the main problem in design WLED from multiple NC components. These advantages allow the fabrication of NC-based WLED with high color rendering index (86), high luminous efficacy (41 lm/W), and controllable color temperature.

Surface passivation for CdTe devices

Energy Technology Data Exchange (ETDEWEB)

Reese, Matthew O.; Perkins, Craig L.; Burst, James M.; Gessert, Timothy A.; Barnes, Teresa M.; Metzger, Wyatt K.

2017-08-01

In one embodiment, a method for surface passivation for CdTe devices is provided. The method includes adjusting a stoichiometry of a surface of a CdTe material layer such that the surface becomes at least one of stoichiometric or Cd-rich; and reconstructing a crystalline lattice at the surface of the CdTe material layer by annealing the adjusted surface.

CdTe Quantum Dots Embedded in Multidentate Biopolymer Based on Salep: Characterization and Optical Properties

Directory of Open Access Journals (Sweden)

Ghasem Rezanejade Bardajee

2013-01-01

Full Text Available This paper describes a novel method for surface modification of water soluble CdTe quantum dots (QDs by using poly(acrylic acid grafted onto salep (salep-g-PAA as a biopolymer. As-prepared CdTe-salep-g-PAA QDs were characterized by Fourier transform infrared (FT-IR spectrum, thermogravimetric (TG analysis, and transmission electron microscopy (TEM. The absorption and fluorescence emission spectra were measured to investigate the effect of salep-g-PAA biopolymer on the optical properties of CdTe QDs. The results showed that the optical properties of CdTe QDs were significantly enhanced by using salep-g-PAA-based biopolymer.

Grain boundaries at the surface of consolidated MgO nanocrystals and acid-base functionality.

Science.gov (United States)

Vingurt, Dima; Fuks, David; Landau, Miron V; Vidruk, Roxana; Herskowitz, Moti

2013-09-21

The increase of the surface basicity-acidity of MgO material by factors of 1.8-3.0 due to consolidation of its nanocrystals was demonstrated by the indicator titration. It was shown that the parallel increase of surface acidity and basicity is attributed to the formation of grain boundaries (GB) after MgO aerogel densification. A simple model predicting the increase of surface acidity-basicity of MgO that correlates with the results of direct measurements was proposed. The model is based on the study of the fine atomic structure at GB surface areas in consolidated MgO nanocrystals in the framework of Density Functional Theory. It is found that the displacements of coordinatively unsaturated surface ions near the GB are significant at the distances ~3-4 atomic layers from the geometrical contact plane between nanocrystals. The detailed analysis of atomic positions inside GB demonstrated the coordination deficiency of surface atoms at the GB areas leading to the formation of stretched bonds and to creation of low coordinated surface ions due to splitting of coordination numbers of surface atoms belonging to GB areas. Density of states for electrons shows the existence of additional states in the band gap close to the bottom of the conduction band. The adsorption energy of CO2 molecules atop oxygen atoms exposed at surface GB areas is of the same order of magnitude as that reported for oxygen atoms at crystallographic edges and corners of MgO crystals. It provides additional options for bonding of molecules at the surface of nanocrystalline MgO increasing the adsorption capacity and catalytic activity.

Novel green synthetic strategy to prepare ZnO nanocrystals using rambutan (Nephelium lappaceum L.) peel extract and its antibacterial applications.

Science.gov (United States)

Yuvakkumar, R; Suresh, J; Nathanael, A Joseph; Sundrarajan, M; Hong, S I

2014-08-01

In the present investigation, we report a sustainable novel green synthetic strategy to synthesis zinc oxide nanocrystals. This is the first report on sustainable biosynthesis of zinc oxide nanocrystals employing Nephelium lappaceum L., peel extract as a natural ligation agent. Green synthesis of zinc oxide nanocrystals was carried out via zinc-ellagate complex formation using rambutan peel wastes. The successful formation of zinc oxide nanocrystals was confirmed employing standard characterisation studies. A possible mechanism for the formation of ZnO nanocrystals with rambutan peel extract was also proposed. The prepared ZnO nanocrystals were coated on the cotton fabric and their antibacterial activity were analyzed. ZnO nanocrystals coated cotton showed good antibacterial activity towards Escherichia coli (E. coli), gram negative bacteria and Staphylococcus aureus (S. aureus), gram positive bacteria. Copyright © 2014 Elsevier B.V. All rights reserved.

A novel quantum dot-laccase hybrid nanobiosensor for low level determination of dopamine.

Science.gov (United States)

Shamsipur, Mojtaba; Shanehasz, Maryam; Khajeh, Khosro; Mollania, Nasrin; Kazemi, Sayyed Habib

2012-12-07

This work reports a novel nanobiosensor based on a thioglycolic acid (TGA)-capped CdTe quantum dot-laccase (Lac) enzyme system for sensitive detection of dopamine (DA). The enzyme used catalyzes the oxidation of DA to dopamine-o-quinone (DOQ), which can selectively quench the strong luminescence of CdTe nanocrystals at neutral pH. The relationship between luminescence intensity of CdTe nanocrystals and DA concentration is nicely described by the Stern-Volmer equation. At an optimum pH of 7.4, the proposed sensor gives a linear calibration over a DA concentration range of 0.3 to 100 μM, with a limit of detection of 0.16 μM and a response time of 2 min. The relative standard deviation for seven replicate determinations of 6.0 μM of DA was found to be 3.7%. The sensor was successfully applied to the determination of DA in a blood plasma sample and in a DA injection formulation.

Enhancing Docetaxel Delivery to Multidrug-Resistant Cancer Cells with Albumin-Coated Nanocrystals.

Science.gov (United States)

Gad, Sheryhan F; Park, Joonyoung; Park, Ji Eun; Fetih, Gihan N; Tous, Sozan S; Lee, Wooin; Yeo, Yoon

2018-01-29

Intravenous delivery of poorly water-soluble anticancer drugs such as docetaxel (DTX) is challenging due to the low bioavailability and the toxicity related to solubilizing excipients. Colloidal nanoparticles are used as alternative carriers, but low drug loading capacity and circulation instability limit their clinical translation. To address these challenges, DTX nanocrystals (NCs) were prepared using Pluronic F127 as an intermediate stabilizer and albumin as a functional surface modifier, which were previously found to be effective in producing small and stable NCs. We hypothesize that the albumin-coated DTX NCs (DTX-F-alb) will remain stable in serum-containing medium so as to effectively leverage the enhanced permeability and retention effect. In addition, the surface-bound albumin, in its native form, may contribute to cellular transport of NCs through interactions with albumin-binding proteins such as secreted protein acidic and rich in cysteine (SPARC). DTX-F-alb NCs showed sheet-like structure with an average length, width, and thickness of 284 ± 96, 173 ± 56, and 40 ± 8 nm and remained stable in 50% serum solution at a concentration greater than 10 μg/mL. Cytotoxicity and cellular uptake of DTX-F-alb and unformulated (free) DTX were compared on three cell lines with different levels of SPARC expression and DTX sensitivity. While the uptake of free DTX was highly dependent on DTX sensitivity, DTX-F-alb treatment resulted in relatively consistent cellular levels of DTX. Free DTX was more efficient in entering drug-sensitive B16F10 and SKOV-3 cells than DTX-F-alb, with consistent cytotoxic effects. In contrast, multidrug-resistant NCI/ADR-RES cells took up DTX-F-alb more than free DTX with time and responded better to the former. This difference was reduced by SPARC knockdown. The high SPARC expression level of NCI/ADR-RES cells, the known affinity of albumin for SPARC, and the opposing effect of SPARC knockdown support that DTX-F-alb have exploited the

Confocal microscopy and spectroscopy of nanocrystals on a high-Q microsphere resonator

International Nuclear Information System (INIS)

Goetzinger, S; Menezes, L de S; Benson, O; Talapin, D V; Gaponik, N; Weller, H; Rogach, A L; Sandoghdar, V

2004-01-01

We report on experiments where we used a home-made confocal microscope to excite single nanocrystals on a high-Q microsphere resonator. In that way spectra of an individual quantum emitter could be recorded. The Q factor of the microspheres coated with nanocrystals was still up to 10 9 . We also demonstrate the use of a prism coupler as a well-defined output port to collect the fluorescence of an ensemble of nanocrystals coupled to whispering-gallery modes

Interaction of different thiol-capped CdTe quantum dots with bovine serum albumin

International Nuclear Information System (INIS)

Wang Qisui; Zhang Xiaolei; Zhou Xiaolan; Fang Tingting; Liu Pengfei; Liu Peng; Min Xinmin; Li, Xi

2012-01-01

Due to their unique optical properties, quantum dots (QDs) are rapidly revolutionizing many areas of medicine and biology. Despite the remarkable speed of development of nanoscience, relatively little is known about the interaction of nanoscale objects with organism. In this work, interaction of CdTe QDs coated with mercaptopropanoic acid (MPA), L-cysteine (L-cys), and glutathione (GSH) with bovine serum albumin (BSA) was investigated. Fluorescence (FL), UV–vis absorption, and circular dichroism (CD) spectra methods were used. The Stern-Volmer quenching constant (K sv ) at different temperatures, corresponding thermodynamic parameters (ΔH, ΔG and ΔS), and information of the structural features of BSA were gained. We found that QDs can effectively quench the FL of BSA in a ligand-dependent manner, electrostatic interactions play a major role in the binding reaction, and the nature of quenching is static, resulting in forming QDs-BSA complexes. The CD spectra showed that the secondary and tertiary structure of BSA was changed. This study contributes to a better understanding of the ligand effects on QDs-proteins interactions, which is a critical issue for the applications in vivo. - Highlights: ► The interaction between three thiol-capped QDs and BSA by UV–vis, FL, and CD spectra. ► The bio-effect of CdTe QDs on BSA was a ligand-dependent manner. ► The thermodynamic parameters and the structural features of BSA were gained.

Photoinduced interaction between MPA capped CdTe QDs and certain anthraquinone dyes

Energy Technology Data Exchange (ETDEWEB)

Jagadeeswari, S.; Asha Jhonsi, M.; Kathiravan, A. [School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Renganathan, R., E-mail: rrengas@gmail.co [School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)

2011-04-15

Photoinduced interaction of mercapto propionic acid (MPA) capped CdTe quantum dots (QDs) with certain anthraquinone dyes namely alizarin, alizarin red S, acid blue 129 and uniblue has been studied by steady state and time resolved fluorescence measurements. Addition of anthraquinone dyes to CdTe QDs results in the reduction of electron hole recombination has been observed (i.e., fluorescence quenching). The Stern-Volmer constant (K{sub SV}), quenching rate constant (k{sub q}) and association constants (K) were obtained from fluorescence quenching data. The interaction of anthraquinone dyes with QDs occurs through static quenching was confirmed by unaltered fluorescence lifetime. The occurrence of electron transfer quenching mechanism has been proved by the negative free energy change ({Delta}G{sub et}) obtained as per the Rehm-Weller equation.

Growth and optical characterization of colloidal CdTe nanoparticles capped by a bifunctional molecule

Energy Technology Data Exchange (ETDEWEB)

Abd El-sadek, M.S., E-mail: el_sadek_99@email.co [Nanomaterial Laboratory, Physics Department, Faculty of Science, South Valley University, Qena-83523 (Egypt); Crystal Growth Centre, Anna University Chennai, Chennai-600025 (India); Moorthy Babu, S. [Crystal Growth Centre, Anna University Chennai, Chennai-600025 (India)

2010-08-15

Thiol-capped CdTe nanoparticles were synthesized in aqueous solution by wet chemical route. CdTe nanoparticles with bifunctional molecule mercaptoacetic acid as a stabilizer were synthesized at pH{approx}11.2 and using potassium tellurite as tellurium source. The effect of refluxing time on the preparation of these samples was measured using UV-vis absorption and photoluminescence analysis. By increasing the refluxing time the UV-vis absorption and photoluminescence results show that the band edge emission is redshifted. The synthesized thiol-capped CdTe were characterized with FT-IR, TEM and TG-DTA. The particle size was calculated by the effective mass approximation (EMA). The role of precursors, their composition, pH and reaction procedure on the development of nanoparticles are analyzed.

Review of CdTe medical applications

Energy Technology Data Exchange (ETDEWEB)

Entine, G; Garcia, D A; Tow, D E

1977-02-01

CdTe sensors are now being used in several areas of nuclear medicine. CdTe probe technics, originally developed to study dental pathology in dog models, are being used clinically to diagnose venous thrombosis of the legs and to detect occult dental infections in patients scheduled for prosthetic cardiovascular and orthopedic surgery. Similar instrumentation is in use in animal research of myocardial infarction and synthetic tooth substitutes. Transmission technics have also been developed to diagnose pulmonary edema and to measure bone mineral changes in space flight. Investigations are also underway in the use of linear or two-dimensional arrays of CdTe gamma sensors for medical imaging. Economic considerations have slowed this work, but the technology appears to be available. Development of photoconductive CdTe X-ray detectors for scintigraphic scanners has also begun. Rapid detector improvement will be needed for success in this field, but the potential usefulness is very great. Together, the present application results are encouraging and wide use of CdTe detectors should occur within only a few years.

Micromagnetic study of single-domain FePt nanocrystals overcoated with silica

International Nuclear Information System (INIS)

Hyun, Changbae; Lee, Doh C; Korgel, Brian A; Lozanne, Alex de

2007-01-01

Chemically-synthesized FePt nanocrystals must be annealed at a high temperature (>550 deg. C) to induce the hard ferromagnetic L 1 0 phase. Unfortunately, the organic stabilizer covering these nanocrystals degrades at these temperatures and the nanocrystals sinter, resulting in the loss of control over nanocrystal size and separation in the film. We have developed a silica overcoating strategy to prevent nanocrystal sintering. In this study, 6 nm diameter FePt nanocrystals were coated with 17 nm thick shells of silica using an inverse micelle process. Magnetization measurements of the annealed FePt-SiO 2 nanocrystals indicate ferromagnetism with a high coercivity at room temperature. Magnetic force microscopy (MFM) results show that the film composed of nanocrystals behaves as a dipole after magnetization by an 8 T external field. The individual nanocrystals are modelled as single-domain particles with random crystallographic orientations. We propose that the interparticle magnetic dipole interaction is weaker than the magnetocrystalline energy in the remanent state, leading to an unusual material with no magnetic anisotropy and no domains. Films of these nanoparticles are promising candidates for magnetic media with a data storage density of ∼Tb/in 2

Impairments of spatial learning and memory following intrahippocampal injection in rats of 3-mercaptopropionic acid-modified CdTe quantum dots and molecular mechanisms.

Science.gov (United States)

Wu, Tianshu; He, Keyu; Ang, Shengjun; Ying, Jiali; Zhang, Shihan; Zhang, Ting; Xue, Yuying; Tang, Meng

2016-01-01

With the rapid development of nanotechnology, quantum dots (QDs) as advanced nanotechnology products have been widely used in neuroscience, including basic neurological studies and diagnosis or therapy for neurological disorders, due to their superior optical properties. In recent years, there has been intense concern regarding the toxicity of QDs, with a growing number of studies. However, knowledge of neurotoxic consequences of QDs applied in living organisms is lagging behind their development, even if several studies have attempted to evaluate the toxicity of QDs on neural cells. The aim of this study was to evaluate the adverse effects of intrahippocampal injection in rats of 3-mercaptopropionic acid (MPA)-modified CdTe QDs and underlying mechanisms. First of all, we observed impairments in learning efficiency and spatial memory in the MPA-modified CdTe QD-treated rats by using open-field and Y-maze tests, which could be attributed to pathological changes and disruption of ultrastructure of neurons and synapses in the hippocampus. In order to find the mechanisms causing these effects, transcriptome sequencing (RNA-seq), an advanced technology, was used to gain the potentially molecular targets of MPA-modified CdTe QDs. According to ample data from RNA-seq, we chose the signaling pathways of PI3K-Akt and MPAK-ERK to do a thorough investigation, because they play important roles in synaptic plasticity, long-term potentiation, and spatial memory. The data demonstrated that phosphorylated Akt (p-Akt), p-ERK1/2, and c-FOS signal transductions in the hippocampus of rats were involved in the mechanism underlying spatial learning and memory impairments caused by 3.5 nm MPA-modified CdTe QDs.

Mechanism of charge transport in ligand-capped crystalline CdTe nanoparticles according to surface photovoltaic and photoacoustic results

Energy Technology Data Exchange (ETDEWEB)

Li Kuiying, E-mail: kuiyingli@ysu.edu.cn [National Laboratory of Metastable Materials Manufacture Technology and Science, Yanshan University, Hebei Str. 438, Qinhuangdao, Hebei Province 066004 (China); Zhang Hao [Key Laboratory for Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 (China); Yang Weiyong; Wei Sailing [National Laboratory of Metastable Materials Manufacture Technology and Science, Yanshan University, Hebei Str. 438, Qinhuangdao, Hebei Province 066004 (China); Wang Dayang, E-mail: dayang@mpikg-golm.mpg.de [Max Planck Institute of Colloids and Interfaces, Potsdam 14424 (Germany)

2010-09-01

By combining surface photovoltaic and photoacoustic techniques, we probed the photogenerated charge transport channels of 3-mercaptopropionic acid (MPA)- and 2-mercaptoethylamine (MA)-capped crystalline CdTe nanoparticles on illumination with UV-near IR light. The results experimentally confirmed the presence of a CdS shell outside the CdTe core that formed through the self-assembly and decomposition of mercapto ligands during CdTe preparation. The data revealed that the CdS layer was partly responsible for the deexcitation behavior of the photogenerated carriers, which is related to the quantum tunnel effect. Experiments demonstrated that two quantum wells were located at wavelengths of 440 and 500 nm in buried interfacial space-charge regions, whereas the formation of a ligand layer obstructed charge transfer transitions of the core CdTe nanoparticles to a certain extent.

Synthesis and characterization of electrochemically deposited nanocrystalline CdTe thin films

Energy Technology Data Exchange (ETDEWEB)

Singh, Ragini Raj, E-mail: raginirajsingh@gmail.com [Department of Physics, Bhopal University, Bhopal-462026 (India); Department of Physical Electronics, Iby and Aladar Fleishman Faculty of Engineering, Tel-Aviv University, Tel-Aviv-69978 (Israel); Painuly, Diksha [Centre for Nanoscience and Nanotechnology, University of Kerala, Thiruanantpuram, Kerala (India); Pandey, R.K. [Department of Physics, Bhopal University, Bhopal-462026 (India)

2009-07-15

Electrodeposition is emerging as a method for the synthesis of semiconductor thin films and nanostructures. In this work we prepared the nanocrystalline CdTe thin films on indium tin oxide coated glass substrate from aqueous acidic bath at the deposition temperature 50 {+-} 1 deg. C. The films were grown potentiostatically from -0.60 V to -0.82 V with respect to saturated calomel reference electrode. The structural, compositional, morphological and optical properties were investigated using X-ray diffraction (XRD), energy dispersive analysis by X-rays (EDAX), atomic force microscopy (AFM), and UV-vis spectroscopy respectively and cyclic voltammetery. The structural and optical studies revealed that films are nanocrystalline in nature and possess cubic phase, also the films are preferentially oriented along the cubic (1 1 1) plane. The effect of cadmium composition on the deposited morphology was also investigated. The size dependent blue shift in the experimentally determined absorption edge has been compared with the theoretical predictions based on the effective mass approximation and tight binding approximation. It is shown that the experimentally determined absorption edges depart from the theoretically calculated values.

Emissions and encapsulation of cadmium in CdTe PV modules during fires

Energy Technology Data Exchange (ETDEWEB)

Fthenakis, V.M.; Fuhrmann, M.; Heiser, J.; Fitts, J.; Wang, W. [Brookhaven National Laboratory, Upton, NY (United States). Environmental Sciences Dept.; Lanzirotti, A. [University of Chicago, Chicago, IL (United States). Consortium for Advanced Radiation Resources

2005-12-15

Fires in residential and commercial properties are not uncommon. If such fires involve the roof, photovoltaic arrays mounted on the roof will be exposed to the flames. The amount of cadmium that can be released in fires involving CdTe PV and the magnitude of associated health risks has been debated. The current study aims in delineating this issue. Previous thermogravimetric studies of CdTe, involved pure CdTe and single-glass PV modules. The current study is based on glass-glass CdTe PV modules which are the only ones in the market. Pieces of commercial CdTe photovoltaic (PV) modules, sizes 25x3 cm, were heated to temperatures up to 1100{sup o}C to simulate exposure to residential and commercial building fires. The temperature rate and duration in these experiments were defined according to standard protocols. Four different types of analysis were performed to investigate emissions and redistribution of elements in the matrix of heated CdTe PV modules: (1) measurements of sample weight loss as a function of temperature; (2) analyses of Cd and Te in the gaseous emissions; (3) Cd distribution in the heated glass using synchrotron X-ray fluorescence microprobe analysis; and (4) chemical analysis for Cd and Te in the acid-digested glass. These experiments showed that almost all (i.e., 99.5%) of the cadmium content of CdTe PV modules was encapsulated in the molten glass matrix; a small amount of Cd escaped from the perimeter of the samples before the two sheets of glass melted together. Adjusting for this loss in full-size modules, results in 99.96% retention of Cd. Multiplying this with the probability of occurrence for residential fires in wood-frame houses in the US (e.g., 10{sup -4}), results in emissions of 0.06 mg/GWh; the probability of sustained fires and subsequent emissions in adequately designed and maintained utility systems appears to be zero. (Author)

Study on response function of CdTe detector

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyunduk; Cho, Gyuseong [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); Kang, Bo-Sun [Department of Radiological Science, Catholic University of Daegu, Kyoungsan, Kyoungbuk 712-702 (Korea, Republic of)], E-mail: bskang@cu.ac.kr

2009-10-21

So far the origin of the mechanism of light emission in the sonoluminescence has not elucidated whether it is due to blackbody radiation or bremsstrahlung. The final goal of our study is measuring X-ray energy spectrum using high-sensitivity cadmium telluride (CdTe) detector in order to obtain information for understanding sonoluminescence phenomena. However, the scope of this report is the measurement of X-ray spectrum using a high-resolution CdTe detector and determination of CdTe detector response function to obtain the corrected spectrum from measured soft X-ray source spectrum. In general, the measured spectrum was distorted by the characteristics of CdTe detector. Monte Carlo simulation code, MCNP, was used to obtain the reference response function of the CdTe detector. The X-ray spectra of {sup 57}Co, {sup 133}Ba, and {sup 241}Am were obtained by a 4x4x1.0(t) mm{sup 3} CdTe detector at room temperature.

Sono-chemical synthesis of cellulose nanocrystals from wood sawdust using Acid hydrolysis.

Science.gov (United States)

Shaheen, Th I; Emam, Hossam E

2018-02-01

Cellulose nanocrystal (CNC) is a unique material obtained from naturally occurring cellulose fibers. Owing to their mechanical, optical, chemical, and rheological properties, CNC gained significant interest. Herein, we investigate the potential of commercially non-recyclable wood waste, in particular, sawdust as a new resource for CNC. Isolation of CNC from sawdust was conducted as per acid hydrolysis which induced by ultrasonication technique. Thus, sawdust after being alkali delignified prior sodium chlorite bleaching, was subjected to sulfuric acid with concentration of 65% (w/w) at 60 ° C for 60min. After complete reaction, CNC were collected by centrifugation followed by dialyzing against water and finally dried via using lyophilization technique. The CNC yield attained values of 15% from purified sawdust. Acid hydrolysis mechanism exactly referred that, the amorphous regions along with thinner as well as shorter crystallites spreaded throughout the cellulose structure are digested by the acid leaving CNC suspension. The latter was freeze-dried to produce CNC powder. A thorough investigation pertaining to nanostructural characteristics of CNC was performed. These characteristics were monitored using TEM, SEM, AFM, XRD and FTIR spectra for following the changes in functionality. Based on the results obtained, the combination of sonication and chemical treatment was great effective in extraction of CNC with the average dimensions (diameter×length) of 35.2±7.4nm×238.7±81.2nm as confirmed from TEM. Whilst, the XRD study confirmed the crystal structure of CNC is obeyed cellulose type I with crystallinity index ∼90%. Cellulose nanocrystals are nominated as the best candidate within the range studied in the area of reinforcement by virtue of their salient textural features. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhanced microwave absorption properties of graphite nanoflakes by coating hexagonal boron nitride nanocrystals

KAUST Repository

Zhong, Bo; Liu, Wei; Yu, Yuanlie; Xia, Long; Zhang, Jiulin; Chai, Zhenfei; Wen, Guangwu

2017-01-01

We report herein the synthesis of a novel hexagonal boron nitride nanocrystal/graphite nanoflake (h-BNNC/GNF) composite through a wet-chemistry coating of graphite nanoflakes and subsequent in-situ thermal treatment process. The characterization results of X-ray diffraction, scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectrum, and X-ray photoelectron spectroscopy demonstrate that h-BNNCs with diameter of tens of nanometers are highly crystallized and anchored on the surfaces of graphite nanoflakes without obvious aggregation. The minimum reflection loss (RL) value of the h-BNNC/GNF based absorbers could reach −32.38dB (>99.99% attenuation) with the absorber thickness of 2.0mm. This result is superior to the other graphite based and some dielectric loss microwave absorption materials recently reported. Moreover, the frequency range where the RL is less than −10dB is 3.49-17.28GHz with the corresponding thickness of 5.0 to 1.5mm. This reveals a better electromagnetic microwave absorption performance of h-BNNC/GNFs from the X-band to the Ku-band. The remarkable enhancement of the electromagnetic microwave absorption properties of h-BNNC/GNFs can be assigned to the increase of multiple scattering, interface polarization as well as the improvement of the electromagnetic impedance matching of graphite nanoflakes after being coated with h-BNNCs.

Enhanced microwave absorption properties of graphite nanoflakes by coating hexagonal boron nitride nanocrystals

KAUST Repository

Zhong, Bo

2017-05-31

We report herein the synthesis of a novel hexagonal boron nitride nanocrystal/graphite nanoflake (h-BNNC/GNF) composite through a wet-chemistry coating of graphite nanoflakes and subsequent in-situ thermal treatment process. The characterization results of X-ray diffraction, scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectrum, and X-ray photoelectron spectroscopy demonstrate that h-BNNCs with diameter of tens of nanometers are highly crystallized and anchored on the surfaces of graphite nanoflakes without obvious aggregation. The minimum reflection loss (RL) value of the h-BNNC/GNF based absorbers could reach −32.38dB (>99.99% attenuation) with the absorber thickness of 2.0mm. This result is superior to the other graphite based and some dielectric loss microwave absorption materials recently reported. Moreover, the frequency range where the RL is less than −10dB is 3.49-17.28GHz with the corresponding thickness of 5.0 to 1.5mm. This reveals a better electromagnetic microwave absorption performance of h-BNNC/GNFs from the X-band to the Ku-band. The remarkable enhancement of the electromagnetic microwave absorption properties of h-BNNC/GNFs can be assigned to the increase of multiple scattering, interface polarization as well as the improvement of the electromagnetic impedance matching of graphite nanoflakes after being coated with h-BNNCs.

Acetic acid-confined synthesis of uniform three-dimensional (3D) bismuth telluride nanocrystals consisting of few-quintuple-layer nanoplatelets

KAUST Repository

Yuan, Qiang; Radar, Kelly; Hussain, Muhammad Mustafa

2011-01-01

High-selectivity, uniform three-dimensional (3D) flower-like bismuth telluride (Bi2Te3) nanocrystals consisting of few-quintuple-layer nanoplatelets with a thickness down to 4.5 nm were synthesized for the first time by a facile, one-pot polyol method with acetic acid as the structure-director. Micrometre-sized 2D films and honeycomb-like spheres can be obtained using the uniform 3D Bi2Te3 nanocrystals as building blocks. © The Royal Society of Chemistry 2011.

Processing and Characterization of Cellulose Nanocrystals/Polylactic Acid Nanocomposite Films

Directory of Open Access Journals (Sweden)

Erin M. Sullivan

2015-12-01

Full Text Available The focus of this study is to examine the effect of cellulose nanocrystals (CNC on the properties of polylactic acid (PLA films. The films are fabricated via melt compounding and melt fiber spinning followed by compression molding. Film fracture morphology, thermal properties, crystallization behavior, thermo-mechanical behavior, and mechanical behavior were determined as a function of CNC content using scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, dynamic mechanical analysis, and tensile testing. Film crystallinity increases with increasing CNC content indicating CNC act as nucleating agents, promoting crystallization. Furthermore, the addition of CNC increased the film storage modulus and slightly broadened the glass transition region.

Interfacial interactions between calcined hydroxyapatite nanocrystals and substrates.

Science.gov (United States)

Okada, Masahiro; Furukawa, Keiko; Serizawa, Takeshi; Yanagisawa, Yoshihiko; Tanaka, Hidekazu; Kawai, Tomoji; Furuzono, Tsutomu

2009-06-02

Interfacial interactions between calcined hydroxyapatite (HAp) nanocrystals and surface-modified substrates were investigated by measuring adsorption behavior and adhesion strength with a quartz crystal microbalance (QCM) and a contact-mode atomic force microscope (AFM), respectively. The goal was to develop better control of HAp-nanocrystal coatings on biomedical materials. HAp nanocrystals with rodlike or spherical morphology were prepared by a wet chemical process followed by calcination at 800 degrees C with an antisintering agent to prevent the formation of sintered polycrystals. The substrate surface was modified by chemical reaction with a low-molecular-weight compound, or graft polymerization with a functional monomer. QCM measurement showed that the rodlike HAp nanocrystals adsorbed preferentially onto anionic COOH-modified substrates compared to cationic NH2- or hydrophobic CH3-modified substrates. On the other hand, the spherical nanocrystals adsorbed onto NH2- and COOH-modified substrates, which indicates that the surface properties of the HAp nanocrystals determined their adsorption behavior. The adhesion strength, which was estimated from the force required to move the nanocrystal in contact-mode AFM, on a COOH-grafted substrate prepared by graft polymerization was almost 9 times larger than that on a COOH-modified substrate prepared by chemical reaction with a low-molecular-weight compound, indicating that the long-chain polymer grafted on the substrate mitigated the surface roughness mismatch between the nanocrystal and the substrate. The adhesion strength of the nanocrystal bonded covalently by the coupling reaction to a Si(OCH3)-grafted substrate prepared by graft polymerization was approximately 1.5 times larger than that when adsorbed on the COOH-grafted substrate.

Flexible and fragmentable tandem photosensitive nanocrystal skins

Science.gov (United States)

Akhavan, S.; Uran, C.; Bozok, B.; Gungor, K.; Kelestemur, Y.; Lesnyak, V.; Gaponik, N.; Eychmüller, A.; Demir, H. V.

2016-02-01

We proposed and demonstrated the first account of large-area, semi-transparent, tandem photosensitive nanocrystal skins (PNSs) constructed on flexible substrates operating on the principle of photogenerated potential buildup, which avoid the need for applying an external bias and circumvent the current-matching limitation between junctions. We successfully fabricated and operated the tandem PNSs composed of single monolayers of colloidal water-soluble CdTe and CdHgTe nanocrystals (NCs) in adjacent junctions on a Kapton polymer tape. Owing to the usage of a single NC layer in each junction, noise generation was significantly reduced while keeping the resulting PNS films considerably transparent. In each junction, photogenerated excitons are dissociated at the interface of the semi-transparent Al electrode and the NC layer, with holes migrating to the contact electrode and electrons trapped in the NCs. As a result, the tandem PNSs lead to an open-circuit photovoltage buildup equal to the sum of those of the two single junctions, exhibiting a total voltage buildup of 128.4 mV at an excitation intensity of 75.8 μW cm-2 at 350 nm. Furthermore, we showed that these flexible PNSs could be bent over 3.5 mm radius of curvature and cut out in arbitrary shapes without damaging the operation of individual parts and without introducing any significant loss in the total sensitivity. These findings indicate that the NC skins are promising as building blocks to make low-cost, flexible, large-area UV/visible sensing platforms with highly efficient full-spectrum conversion.We proposed and demonstrated the first account of large-area, semi-transparent, tandem photosensitive nanocrystal skins (PNSs) constructed on flexible substrates operating on the principle of photogenerated potential buildup, which avoid the need for applying an external bias and circumvent the current-matching limitation between junctions. We successfully fabricated and operated the tandem PNSs composed of

Atoms diffusion-induced phase engineering of platinum-gold alloy nanocrystals with high electrocatalytic performance for the formic acid oxidation reaction.

Science.gov (United States)

Li, Fu-Min; Kang, Yong-Qiang; Liu, Hui-Min; Zhai, Ya-Nan; Hu, Man-Cheng; Chen, Yu

2018-03-15

Bimetallic noble metal nanocrystals have been widely applied in many fields, which generally are synthesized by the wet-chemistry reduction method. This work presents a purposely designed atoms diffusion induced phase engineering of PtAu alloy nanocrystals on platy Au substrate (PtAu-on-Au nanostructures) through simple hydrothermal treatment. Benefitting from the synergistic effects of component and structure, PtAu-on-Au nanostructures remarkably enhance the dehydrogenation pathway of the formic acid oxidation reaction (FAOR), and thus exhibit much higher FAOR activity and durability compared with Pt nanocrystals on platy Au substrate (Pt-on-Au nanostructures) and commercial Pd black due to an excellent stability of platy Au substrate and a high oxidation resistance of PtAu alloy nanocrystals. The atoms diffusion-induced phase engineering demonstrated in this work builds a bridge between the traditional metallurgy and modern nanotechnologies, which also provides some useful insights in developing noble metals based alloyed nanostructures for the energy and environmental applications. Copyright © 2017 Elsevier Inc. All rights reserved.

Predicting Nanocrystal Shape through Consideration of Surface-Ligand Interactions

KAUST Repository

Bealing, Clive R.

2012-03-27

Density functional calculations for the binding energy of oleic acid-based ligands on Pb-rich {100} and {111} facets of PbSe nanocrystals determine the surface energies as a function of ligand coverage. Oleic acid is expected to bind to the nanocrystal surface in the form of lead oleate. The Wulff construction predicts the thermodynamic equilibrium shape of the PbSe nanocrystals. The equilibrium shape is a function of the ligand surface coverage, which can be controlled by changing the concentration of oleic acid during synthesis. The different binding energy of the ligand on the {100} and {111} facets results in different equilibrium ligand coverages on the facets, and a transition in the equilibrium shape from octahedral to cubic is predicted when increasing the ligand concentration during synthesis. © 2012 American Chemical Society.

CdTe Photovoltaics for Sustainable Electricity Generation

Science.gov (United States)

Munshi, Amit; Sampath, Walajabad

2016-09-01

Thin film CdTe (cadmium telluride) is an important technology in the development of sustainable and affordable electricity generation. More than 10 GW of installations have been carried out using this technology around the globe. It has been demonstrated as a sustainable, green, renewable, affordable and abundant source of electricity. An advanced sublimation tool has been developed that allows highly controlled deposition of CdTe films onto commercial soda lime glass substrates. All deposition and treatment steps can be performed without breaking the vacuum within a single chamber in an inline process that can be conveniently scaled to a commercial process. In addition, an advanced cosublimation source has been developed to allow the deposition of ternary alloys such as Cd x Mg1- x Te to form an electron reflector layer which is expected to address the voltage deficits in current CdTe devices and to achieve very high efficiency. Extensive materials characterization, including but not limited to scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, high resolution transmission electron microscopy and electron back-scatter diffraction, has been performed to get a better understanding of the effects of processing conditions on CdTe thin film photovoltaics. This combined with computer modeling such as density function theory modeling gives a new insight into the mechanism of CdTe photovoltaic function. With all these efforts, CdTe photovoltaics has seen great progress in the last few years. Currently, it has been recorded as the cheapest source of electricity in the USA on a commercial scale, and further improvements are predicted to further reduce the cost while increasing its utilization. Here, we give an overview of the advantages of thin film CdTe photovoltaics as well as a brief review of the challenges that need to be addressed. Some fundamental studies of processing conditions for thin film CdTe are also presented

Hydrothermal synthesis of thiol-capped CdTe nanoparticles and their optical properties.

Science.gov (United States)

Bu, Hang-Beom; Kikunaga, Hayato; Shimura, Kunio; Takahasi, Kohji; Taniguchi, Taichi; Kim, DaeGwi

2013-02-28

Water soluble nanoparticles (NPs) with a high emission property were synthesized via hydrothermal routes. In this report, we chose thiol ligand N-acetyl-L-cysteine as the ideal stabilizer and have successfully employed it to synthesize readily size-controllable CdTe NPs in a reaction of only one step. Hydrothermal synthesis of CdTe NPs has been carried out in neutral or basic conditions so far. We found out that the pH value of precursor solutions plays an important role in the uniformity of the particle size. Actually, high quality CdTe NPs were synthesized under mild acidic conditions of pH 5. The resultant NPs indicated good visible light-emitting properties and stability. Further, the experimental results showed that the reaction temperature influenced significantly the growth rate and the maximum size of the NPs. The CdTe NPs with a high photoluminescence quantum yield (the highest value: 57%) and narrower half width at half maximum (the narrowest value: 33 nm) were attained in very short time, within 40 minutes, reaching diameters of 2.3 to 4.3 nm. The PL intensity was increased with an increase in the reaction time, reflecting the suppression of nonradiative recombination processes. Furthermore, the formation of CdTe/CdS core-shell structures was discussed from the viewpoint of PL dynamics and X-ray diffraction studies.

High-quality CdTe films from nanoparticle precursors

Energy Technology Data Exchange (ETDEWEB)

Schulz, D.L.; Pehnt, M.; Urgiles, E. [National Renewable Energy Lab., Golden, CO (United States)] [and others

1996-05-01

In this paper the authors demonstrate that nanoparticulate precursors coupled with spray deposition offers an attractive route into electronic materials with improved smoothness, density, and lower processing temperatures. Employing a metathesis approach, cadmium iodide was reacted with sodium telluride in methanol solvent, resulting in the formation of soluble NaI and insoluble CdTe nanoparticles. After appropriate chemical workup, methanol-capped CdTe colloids were isolated. CdTe thin film formation was achieved by spray depositing the nanoparticle colloids (25-75 {Angstrom} diameter) onto substrates at elevated temperatures (T = 280-440{degrees}C) with no further thermal treatment. These films were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Cubic CdTe phase formation was observed by XRD, with a contaminant oxide phase also detected. XPS analysis showed that CdTe films produced by this one-step method contained no Na or C and substantial O. AFM gave CdTe grain sizes of {approx}0.1-0.3 {mu}m for film sprayed at 400{degrees}C. A layer-by-layer film growth mechanism proposed for the one-step spray deposition of nanoparticle precursors will be discussed.

Solvothermal synthesis and characterization of CZTS nanocrystals

Science.gov (United States)

Dumasiya, Ajay; Shah, N. M.

2017-05-01

Cu2ZnSnS4 (CZTS) is a promising thin film absorber material for low cost solar cell applications. CZTS nanoparticle ink synthesized using solvothermal route is an attractive option to deposit absorber layer using screen printing or spin coating method in CZTS thin film solar cell. In this study we have synthesized CZTS nanocrystals using solvothermal method from aqueous solution of Copper nitrate [Cu(NO3)2], Zinc nitrate [Zn(NO3)2], tin chloride [SnCl4] and thiourea with varying concentration of Cu(NO3)2 (viz 0.82 mmol,1.4 mmol, 1.7 mmol) keeping concentrations of rest of solutions constant. As synthesized CZTS nanocrystals are characterized using Energy Dispersive Analysis of X-rays (EDAX) to verify stoichiometry of elements. Analysis of EDAX data suggests that CZTS nanocrystals having Copper nitrate [Cu (NO3)2] concentration of 1.4 m mole is near stoichiometric. X-ray diffraction analysis study of CZTS nanocrystals having Copper nitrate [Cu (NO3)2] concentration of 1.4 m mole reveals the preferred orientation of the grains in (112), (220) and (312) direction confirming Kesterite structure of CZTS.

Modification of cellulose nanocrystals (CNCs) for use in poly(lactic acid) (PLA)-CNC composite packaging products

Science.gov (United States)

Liqing Wei; Nicole M. Stark; Ronald C. Sabo; Laurent Matuana

2016-01-01

There is growing interest in developing bio-based materials for packaging. Bio-derived materials such as cellulose nanocrystals (CNCs) and poly(lactic acid) (PLA) can be used to develop sustainable packaging applications. Incorporating CNCs into PLA can increase the crystallinity and barrier properties of PLA. The challenge lies in both increasing the flexibility of...

Water-resistant, monodispersed and stably luminescent CsPbBr3/CsPb2Br5 core-shell-like structure lead halide perovskite nanocrystals

Science.gov (United States)

Qiao, Bo; Song, Pengjie; Cao, Jingyue; Zhao, Suling; Shen, Zhaohui; Gao, Di; Liang, Zhiqin; Xu, Zheng; Song, Dandan; Xu, Xurong

2017-11-01

Lead halide perovskite materials are thriving in optoelectronic applications due to their excellent properties, while their instability due to the fact that they are easily hydrolyzed is still a bottleneck for their potential application. In this work, water-resistant, monodispersed and stably luminescent cesium lead bromine perovskite nanocrystals coated with CsPb2Br5 were obtained using a modified non-stoichiometric solution-phase method. CsPb2Br5 2D layers were coated on the surface of CsPbBr3 nanocrystals and formed a core-shell-like structure in the synthetic processes. The stability of the luminescence of the CsPbBr3 nanocrystals in water and ethanol atmosphere was greatly enhanced by the photoluminescence-inactive CsPb2Br5 coating with a wide bandgap. The water-stable enhanced nanocrystals are suitable for long-term stable optoelectronic applications in the atmosphere.

Chronotherapeutically Modulated Pulsatile System of Valsartan Nanocrystals-an In Vitro and In Vivo Evaluation.

Science.gov (United States)

Biswas, Nikhil; Kuotsu, Ketousetuo

2017-02-01

The objective was to improve the dissolution of valsartan by developing valsartan nanocrystals and design a pulsed release system for the chronotherapy of hypertension. Valsartan nanocrystals were prepared by sonication-anti-solvent precipitation method and lyophilized to obtain dry powder. Nanocrystals were directly compressed to minitablets and coated to achieve pulsatile valsartan release. Pharmacokinetic profiles of optimized and commercial formulations were compared in rabbit model. The mean particle size and PDI of the optimized nanocrystal batch V4 was reported as 211 nm and 0.117, respectively. DSC and PXRD analysis confirmed the crystalline nature of valsartan in nanocrystals. The dissolution extent of valsartan was markedly enhanced with both nanocrystals and minitablets as compared to pure valsartan irrespective of pH of the medium. Core minitablet V4F containing 5% w/w polyplasdone XL showed quickest release of valsartan, over 90% within 15 min. Coated formulation CV4F showed two spikes in release profile after successive lag times of 235 and 390 min. The pharmacokinetic study revealed that the bioavailability of optimized formulation (72.90%) was significantly higher than the commercial Diovan tablet (30.18%). The accelerated stability studies showed no significant changes in physicochemical properties, release behavior, and bioavialability of CV4F formulation. The formulation was successfully designed to achieve enhanced bioavailability and dual pulsatile release. Bedtime dosing will more efficiently control the circadian spikes of hypertension in the morning.

Deposition kinetics of quantum dots and polystyrene latex nanoparticles onto alumina: role of water chemistry and particle coating.

Science.gov (United States)

Quevedo, Ivan R; Olsson, Adam L J; Tufenkji, Nathalie

2013-03-05

A clear understanding of the factors controlling the deposition behavior of engineered nanoparticles (ENPs), such as quantum dots (QDs), is necessary for predicting their transport and fate in natural subsurface environments and in water filtration processes. A quartz crystal microbalance with dissipation monitoring (QCM-D) was used to study the effect of particle surface coatings and water chemistry on the deposition of commercial QDs onto Al2O3. Two carboxylated QDs (CdSe and CdTe) with different surface coatings were compared with two model nanoparticles: sulfate-functionalized (sPL) and carboxyl-modified (cPL) polystyrene latex. Deposition rates were assessed over a range of ionic strengths (IS) in simple electrolyte (KCl) and in electrolyte supplemented with two organic molecules found in natural waters; namely, humic acid and rhamnolipid. The Al2O3 collector used here is selected to be representative of oxide patches found on the surface of aquifer or filter grains. Deposition studies showed that ENP deposition rates on bare Al2O3 generally decreased with increasing salt concentration, with the exception of the polyacrylic-acid (PAA) coated CdTe QD which exhibited unique deposition behavior due to changes in the conformation of the PAA coating. QD deposition rates on bare Al2O3 were approximately 1 order of magnitude lower than those of the polystyrene latex nanoparticles, likely as a result of steric stabilization imparted by the QD surface coatings. Adsorption of humic acid or rhamnolipid on the Al2O3 surface resulted in charge reversal of the collector and subsequent reduction in the deposition rates of all ENPs. Moreover, the ratio of the two QCM-D output parameters, frequency and dissipation, revealed key structural information of the ENP-collector interface; namely, on bare Al2O3, the latex particles were rigidly attached as compared to the more loosely attached QDs. This study emphasizes the importance of considering the nature of ENP coatings as well

Synthesis of cysteamine-coated CdTe quantum dots and its application in mercury (II) detection

Energy Technology Data Exchange (ETDEWEB)

Pei Jiying [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Department of Chemistry, University of Science and Technology of China (USTC), Hefei 230026 (China); Zhu Hui; Wang Xiaolei [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhang Hanchang [Department of Chemistry, University of Science and Technology of China (USTC), Hefei 230026 (China); Yang Xiurong, E-mail: xryang@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

2012-12-13

Highlights: Black-Right-Pointing-Pointer High-quality CA-CdTe QDs were synthesized with a kinetic-growth strategy. Black-Right-Pointing-Pointer The synthesis procedures were very simple. Black-Right-Pointing-Pointer The obtained QDs were used to detect Hg{sup 2+} without the interference of Cu{sup 2+}. - Abstract: High-quality cysteamine-coated CdTe quantum dots (CA-CdTe QDs) were successfully synthesized in aqueous phase by a facile one-pot method. Through hydroxylamine hydrochloride-promoted kinetic growth strategy, water-soluble CA-CdTe QDs could be obtained conveniently in a conical flask by a stepwise addition of raw materials. The photoluminescence quantum yield (PL QY) of the obtained QDs reached 9.2% at the emission peak of 520 nm. The optical property and the morphology of the QDs were characterized by UV-vis absorption spectra, photoluminescence spectra (PL) and transmission electron microscopy (TEM) respectively. Furthermore, the fluorescence of the resultant QDs was quenched by copper (II) (Cu{sup 2+}) and mercury (II) (Hg{sup 2+}) meanwhile. It is worthy of note that to separately detect Hg{sup 2+}, cyanide ion could be used to eliminate the interference of Cu{sup 2+}. Under the optimal conditions, the response was linearly proportional to the logarithm of Hg{sup 2+} concentration over the range of 0.08-3.33 {mu}M with a limit of detection (LOD) of 0.07 {mu}M.

Inorganic Nanocrystals Functionalized Mesoporous Silica Nanoparticles: Fabrication and Enhanced Bio-applications

Directory of Open Access Journals (Sweden)

Tiancong Zhao

2017-12-01

Full Text Available Mesoporous SiO2 nanoparticles (MSNs are one of the most promising materials for bio-related applications due to advantages such as good biocompatibility, tunable mesopores, and large pore volume. However, unlike the inorganic nanocrystals with abundant physical properties, MSNs alone lack functional features. Thus, they are not sufficiently suitable for bio-applications that require special functions. Consequently, MSNs are often functionalized by incorporating inorganic nanocrystals, which provide a wide range of intriguing properties. This review focuses on inorganic nanocrystals functionalized MSNs, both their fabrication and bio-applications. Some of the most utilized methods for coating mesoporous silica (mSiO2 on nanoparticles were summarized. Magnetic, fluorescence and photothermal inorganic nanocrystals functionalized MSNs were taken as examples to demonstrate the bio-applications. Furthermore, asymmetry of MSNs and their effects on functions were also highlighted.

Corrosion behavior of niobium coated 304 stainless steel in acid solution

Energy Technology Data Exchange (ETDEWEB)

Pan, T.J., E-mail: tjpan@cczu.edu.cn [School of Material Science and Engineering, Jiangsu Collaborative Innovation Center for Photovolatic Science and Engineering, Changzhou University, Changzhou 213164 (China); Jiangsu Key Laboratory of Material Surface Technology, Changzhou 213164 (China); Chen, Y.; Zhang, B. [School of Material Science and Engineering, Jiangsu Collaborative Innovation Center for Photovolatic Science and Engineering, Changzhou University, Changzhou 213164 (China); Hu, J. [School of Material Science and Engineering, Jiangsu Collaborative Innovation Center for Photovolatic Science and Engineering, Changzhou University, Changzhou 213164 (China); Jiangsu Key Laboratory of Material Surface Technology, Changzhou 213164 (China); Li, C. [Light Industry College of Liaoning University, Shenyang 110036 (China)

2016-04-30

Highlights: • The Nb coating produced by HEMAA offers good protection for 304SS in acid solution. • The coating increases corrosion potential and induces decrease of corrosion rate. • The protection of coating is ascribed to the stability of Nb in acid solution. - Abstract: The niobium coating is fabricated on the surface of AISI Type 304 stainless steel (304SS) by using a high energy micro arc alloying technique in order to improvecorrosion resistance of the steel against acidic environments. The electrochemical corrosion resistance of the niobium coating in 0.7 M sulfuric acid solutions is evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization and the open circuit potential versus time. Electrochemical measurements indicate that the niobium coating increases the free corrosion potential of the substrate by 110 mV and a reduction in the corrosion rate by two orders of magnitude compared to the substrate alone. The niobium coating maintains large impedance and effectively offers good protection for the substrate during the long-term exposure tests, which is mainly ascribed to the niobium coating acting inhibiting permeation of corrosive species. Finally, the corresponding electrochemical impedance models are proposed to elucidate the corrosion resistance behavior of the niobium coating in acid solutions.

Corrosion behavior of niobium coated 304 stainless steel in acid solution

International Nuclear Information System (INIS)

Pan, T.J.; Chen, Y.; Zhang, B.; Hu, J.; Li, C.

2016-01-01

Highlights: • The Nb coating produced by HEMAA offers good protection for 304SS in acid solution. • The coating increases corrosion potential and induces decrease of corrosion rate. • The protection of coating is ascribed to the stability of Nb in acid solution. - Abstract: The niobium coating is fabricated on the surface of AISI Type 304 stainless steel (304SS) by using a high energy micro arc alloying technique in order to improvecorrosion resistance of the steel against acidic environments. The electrochemical corrosion resistance of the niobium coating in 0.7 M sulfuric acid solutions is evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization and the open circuit potential versus time. Electrochemical measurements indicate that the niobium coating increases the free corrosion potential of the substrate by 110 mV and a reduction in the corrosion rate by two orders of magnitude compared to the substrate alone. The niobium coating maintains large impedance and effectively offers good protection for the substrate during the long-term exposure tests, which is mainly ascribed to the niobium coating acting inhibiting permeation of corrosive species. Finally, the corresponding electrochemical impedance models are proposed to elucidate the corrosion resistance behavior of the niobium coating in acid solutions.

Au nanocrystals grown on a better-defined one-dimensional tobacco mosaic virus coated protein template genetically modified by a hexahistidine tag

International Nuclear Information System (INIS)

Liu Nan; Zhang Wei; Luo Zhaopeng; Zhai Niu; Zhang Hongfei; Li Zhonghao; Jiang Xingyi; Tang Gangling; Hu Qingyuan; Wang Chong; Tian Dandan

2012-01-01

In this paper, tobacco mosaic virus (TMV) coated protein (CP) was genetically modified by introducing a hexahistidine tag into it for a well-defined one-dimensional template, on which Au nanocrystals (NCs) were grown. The results showed that genetic modification could not only ameliorate the one-dimensional structure of the template, but also improve the growth density of Au NCs on the template. This indicated that genetic modification could be an effective method to modulate the structure of the TMVCP template-based nanocomposites allowing for a broader application of them. (paper)

Design Strategies for High-Efficiency CdTe Solar Cells

Science.gov (United States)

Song, Tao

With continuous technology advances over the past years, CdTe solar cells have surged to be a leading contributor in thin-film photovoltaic (PV) field. While empirical material and device optimization has led to considerable progress, further device optimization requires accurate device models that are able to provide an in-depth understanding of CdTe device physics. Consequently, this thesis is intended to develop a comprehensive model system for high-efficiency CdTe devices through applying basic design principles of solar cells with numerical modeling and comparing results with experimental CdTe devices. The CdTe absorber is central to cell performance. Numerical simulation has shown the feasibility of high energy-conversion efficiency, which requires both high carrier density and long minority carrier lifetime. As the minority carrier lifetime increases, the carrier recombination at the back surface becomes a limitation for cell performance with absorber thickness cell performance, since it can induce a large valence-band bending which suppresses the hole injection near the interface for the electron-hole recombination, but too large a spike is detrimental to photocurrent transport. In a heterojunction device with many defects at the emitter/absorber interface (high SIF), a thin and highly-doped emitter can induce strong absorber inversion and hence help maintain good cell performance. Performance losses from acceptor-type interface defects can be significant when interface defect states are located near mid-gap energies. In terms of specific emitter materials, the calculations suggest that the (Mg,Zn)O alloy with 20% Mg, or a similar type-I heterojunction partner with moderate DeltaE C (e.g., Cd(S,O) or (Cd,Mg)Te with appropriate oxygen or magnesium ratios) should yield higher voltages and would therefore be better candidates for the CdTe-cell emitter. The CdTe/substrate interface is also of great importance, particularly in the growth of epitaxial

Highly phosphorescent hollow fibers inner-coated with tungstate nanocrystals

Science.gov (United States)

Ng, Pui Fai; Bai, Gongxun; Si, Liping; Lee, Ka I.; Hao, Jianhua; Xin, John H.; Fei, Bin

2017-12-01

In order to develop luminescent microtubes from natural fibers, a facile biomimetic mineralization method was designed to introduce the CaWO4-based nanocrystals into kapok lumens. The structure, composition, and luminescence properties of resultant fibers were investigated with microscopes, x-ray diffraction, thermogravimetric analysis, and fluorescence spectrometry. The yield of tungstate crystals inside kapok was significantly promoted with a process at high temperature and pressure—the hydrothermal treatment. The tungstate crystals grown on the inner wall of kapok fibers showed the same crystal structure with those naked powders, but smaller in crystal size. The resultant fiber assemblies demonstrated reduced phosphorescence intensity in comparison to the naked tungstate powders. However, the fibers gave more stable luminescence than the naked powders in wet condition. This approach explored the possibility of decorating natural fibers with high load of nanocrystals, hinting potential applications in anti-counterfeit labels, security textiles, and even flexible and soft optical devices.

Magnetoresistance of drop-cast film of cobalt-substituted magnetite nanocrystals.

Science.gov (United States)

Kohiki, Shigemi; Nara, Koichiro; Mitome, Masanori; Tsuya, Daiju

2014-10-22

An oleic acid-coated Fe2.7Co0.3O4 nanocrystal (NC) self-assembled film was fabricated via drop casting of colloidal particles onto a three-terminal electrode/MgO substrate. The film exhibited a large coercivity (1620 Oe) and bifurcation of the zero-field-cooled and field-cooled magnetizations at 300 K. At 10 K, the film exhibited both a Coulomb blockade due to single electron charging as well as a magnetoresistance of ∼-80% due to spin-dependent electron tunneling. At 300 K, the film also showed a magnetoresistance of ∼-80% due to hopping of spin-polarized electrons. Enhanced magnetic coupling between adjacent NCs and the large coercivity resulted in a large spin-polarized current flow even at 300 K.

Evolution of oxygenated cadmium sulfide (CdS:O) during high-temperature CdTe solar cell fabrication

Energy Technology Data Exchange (ETDEWEB)

Meysing, Daniel M.; Reese, Matthew O.; Warren, Charles W.; Abbas, Ali; Burst, James M.; Mahabaduge, Hasitha P.; Metzger, Wyatt K.; Walls, John M.; Lonergan, Mark C.; Barnes, Teresa M.; Wolden, Colin A.

2016-12-01

Oxygenated cadmium sulfide (CdS:O) produced by reactive sputtering has emerged as a promising alternative to conventional CdS for use as the n-type window layer in CdTe solar cells. Here, complementary techniques are used to expose the window layer (CdS or CdS:O) in completed superstrate devices and combined with a suite of materials characterization to elucidate its evolution during high temperature device processing. During device fabrication amorphous CdS:O undergoes significant interdiffusion with CdTe and recrystallization, forming CdS1-yTey nanocrystals whose Te fraction approaches solubility limits. Significant oxygen remains after processing, concentrated in sulfate clusters dispersed among the CdS1-yTey alloy phase, accounting for ~30% of the post-processed window layer based on cross-sectional microscopy. Interdiffusion and recrystallization are observed in devices with un-oxygenated CdS, but to a much lesser extent. Etching experiments suggest that the CdS thickness is minimally changed during processing, but the CdS:O window layer is reduced from 100 nm to 60-80 nm, which is confirmed by microscopy. Alloying reduces the band gap of the CdS:O window layer to 2.15 eV, but reductions in thickness and areal density improve its transmission spectrum, which is well matched to device quantum efficiency. The changes to the window layer in the reactive environments of device fabrication are profoundly different than what occurs by thermal annealing in an inert environment, which produced films with a band gap of 2.4 eV for both CdS and CdS:O. These results illustrate for the first time the significant changes that occur to the window layer during processing that are critical to the performance of CdTe solar cells.

Fractal features of CdTe thin films grown by RF magnetron sputtering

Energy Technology Data Exchange (ETDEWEB)

Hosseinpanahi, Fayegh, E-mail: f.hosseinpanahi@yahoo.com [Department of Physics, Payame Noor University, P.O. Box 19395-4697, Tehran (Iran, Islamic Republic of); Raoufi, Davood [Department of Physics, University of Bu Ali Sina, P.O. Box 65174, Hamedan (Iran, Islamic Republic of); Ranjbarghanei, Khadijeh [Department of Physics, Plasma Physics Research Center, Science & Research Branch Islamic Azad University, Tehran (Iran, Islamic Republic of); Karimi, Bayan [Department of Physics, Payame Noor University, P.O. Box 19395-4697, Tehran (Iran, Islamic Republic of); Babaei, Reza [Department of Physics, Plasma Physics Research Center, Science & Research Branch Islamic Azad University, Tehran (Iran, Islamic Republic of); Hasani, Ebrahim [Department of Physics, University of Bu Ali Sina, P.O. Box 65174, Hamedan (Iran, Islamic Republic of)

2015-12-01

Graphical abstract: - Highlights: • CdTe thin films were deposited on glass substrates by RF magnetron sputtering at room temperature with different deposition time 5, 10 and 15 min. • Nanostructure of CdTe layer indicates that CdTe films are polycrystalline and have zinc blende structure, irrespective of their deposition time. • Complexity and roughness of the CdTe films and strength of multifractality increase with increasing deposition time. • Detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe films have multifractal nature. - Abstract: Cadmium telluride (CdTe) thin films were prepared by RF magnetron sputtering on glass substrates at room temperature (RT). The film deposition was performed for 5, 10, and 15 min at power of 30 W with a frequency of 13.56 MHz. The crystal structure of the prepared CdTe thin films was studied by X-ray diffraction (XRD) technique. XRD analyses indicate that the CdTe films are polycrystalline, having zinc blende structure of CdTe irrespective of their deposition time. All CdTe films showed a preferred orientation along (1 1 1) crystalline plane. The surface morphology characterization of the films was studied using atomic force microscopy (AFM). The quantitative AFM characterization shows that the RMS surface roughness of the prepared CdTe thin films increases with increasing the deposition time. The detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe thin films have multifractal nature. The complexity, roughness of the CdTe thin films and strength of the multifractality increase as deposition time increases.

Fractal features of CdTe thin films grown by RF magnetron sputtering

International Nuclear Information System (INIS)

Hosseinpanahi, Fayegh; Raoufi, Davood; Ranjbarghanei, Khadijeh; Karimi, Bayan; Babaei, Reza; Hasani, Ebrahim

2015-01-01

Graphical abstract: - Highlights: • CdTe thin films were deposited on glass substrates by RF magnetron sputtering at room temperature with different deposition time 5, 10 and 15 min. • Nanostructure of CdTe layer indicates that CdTe films are polycrystalline and have zinc blende structure, irrespective of their deposition time. • Complexity and roughness of the CdTe films and strength of multifractality increase with increasing deposition time. • Detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe films have multifractal nature. - Abstract: Cadmium telluride (CdTe) thin films were prepared by RF magnetron sputtering on glass substrates at room temperature (RT). The film deposition was performed for 5, 10, and 15 min at power of 30 W with a frequency of 13.56 MHz. The crystal structure of the prepared CdTe thin films was studied by X-ray diffraction (XRD) technique. XRD analyses indicate that the CdTe films are polycrystalline, having zinc blende structure of CdTe irrespective of their deposition time. All CdTe films showed a preferred orientation along (1 1 1) crystalline plane. The surface morphology characterization of the films was studied using atomic force microscopy (AFM). The quantitative AFM characterization shows that the RMS surface roughness of the prepared CdTe thin films increases with increasing the deposition time. The detrended fluctuation analysis (DFA) and also multifractal detrended fluctuation analysis (MFDFA) methods showed that prepared CdTe thin films have multifractal nature. The complexity, roughness of the CdTe thin films and strength of the multifractality increase as deposition time increases.

Acid-resistant organic coatings for the chemical industry: a review

DEFF Research Database (Denmark)

Møller, Victor Buhl; Dam-Johansen, Kim; Frankær, Sarah Maria Grundahl

2017-01-01

Industries that work with acidic chemicals in their processes need to make choices on how to properly contain the substances and avoid rapid corrosion of equipment. Certain organic coatings and linings can be used in such environments, either to protect vulnerable construction materials, or......, in combination with fiber reinforcement, to replace them. However, degradation mechanisms of organic coatings in acid service are not thoroughly understood and relevant quantitative investigations are scarce. This review describes the uses and limitations of acid-resistant coatings in the chemical industry...

CdTe quantum dots with daunorubicin induce apoptosis of multidrug-resistant human hepatoma HepG2/ADM cells: in vitro and in vivo evaluation

Directory of Open Access Journals (Sweden)

Shi Lixin

2011-01-01

Full Text Available Abstract Cadmium telluride quantum dots (Cdte QDs have received significant attention in biomedical research because of their potential in disease diagnosis and drug delivery. In this study, we have investigated the interaction mechanism and synergistic effect of 3-mercaptopropionic acid-capped Cdte QDs with the anti-cancer drug daunorubicin (DNR on the induction of apoptosis using drug-resistant human hepatoma HepG2/ADM cells. Electrochemical assay revealed that Cdte QDs readily facilitated the uptake of the DNR into HepG2/ADM cells. Apoptotic staining, DNA fragmentation, and flow cytometry analysis further demonstrated that compared with Cdte QDs or DNR treatment alone, the apoptosis rate increased after the treatment of Cdte QDs together with DNR in HepG2/ADM cells. We observed that Cdte QDs treatment could reduce the effect of P-glycoprotein while the treatment of Cdte QDs together with DNR can clearly activate apoptosis-related caspases protein expression in HepG2/ADM cells. Moreover, our in vivo study indicated that the treatment of Cdte QDs together with DNR effectively inhibited the human hepatoma HepG2/ADM nude mice tumor growth. The increased cell apoptosis rate was closely correlated with the enhanced inhibition of tumor growth in the studied animals. Thus, Cdte QDs combined with DNR may serve as a possible alternative for targeted therapeutic approaches for some cancer treatments.

Effect of capping agent on selectivity and sensitivity of CdTe quantum dots optical sensor for detection of mercury ions

Science.gov (United States)

Labeb, Mohmed; Sakr, Abdel-Hamed; Soliman, Moataz; Abdel-Fettah, Tarek M.; Ebrahim, Shaker

2018-05-01

Cadmium telluride (CdTe) quantum dots (QDs) were prepared from an aqueous solution containing CdCl2 and Te precursor in the presence of thioglycolic acid (TGA) or L-cysteine as capping agents. Two optical sensors have been developed for Hg2+ ions with very low concentration in the range of nanomolar (nM) or picomolar (pM) depending on the type of capping agents and based on photoluminescence (PL) quenching of CdTe QDs. It was observed that low concentrations of Hg2+ ions quench the fluorescence spectra of CdTe QDs and TGA capped CdTe QDs exhibited a linear response to Hg2+ ions in the concentration range from 1.25 to 10 nM. Moreover, it was found that L-cysteine capped CdTe QDs optical sensor with a sensitivity of 6 × 109 M-1, exhibited a linear coefficient of 0.99 and showed a detection limit of 2.7 pM in range from 5 to 25 pM of Hg2+ ions was achieved. In contrast to the significant response that was observed for Hg2+, a weak signal response was noted upon the addition of other metal ions indicating an excellent selectivity of CdTe QDs towards Hg2+.

Synthesis of non-aggregated nicotinic acid coated magnetite nanorods via hydrothermal technique

Energy Technology Data Exchange (ETDEWEB)

Attallah, Olivia A., E-mail: olivia.adly@hu.edu.eg [Center of Nanotechnology, Nile University, 12677 Giza (Egypt); Pharmaceutical Chemistry Department, Heliopolis University, 11777 El Salam, Cairo (Egypt); Girgis, E. [Solid State Physics Department, National Research Center, 12622 Dokki, Giza (Egypt); Advanced Materials and Nanotechnology Lab, CEAS, National Research Center, 12622 Dokki, Giza (Egypt); Abdel-Mottaleb, Mohamed M.S.A. [Center of Nanotechnology, Nile University, 12677 Giza (Egypt)

2016-02-01

Non-aggregated magnetite nanorods with average diameters of 20–30 nm and lengths of up to 350 nm were synthesized via in situ, template free hydrothermal technique. These nanorods capped with different concentrations (1, 1.5, 2 and 2.5 g) of nicotinic acid (vitamin B3); possessed good magnetic properties and easy dispersion in aqueous solutions. Our new synthesis technique maintained the uniform shape of the nanorods even with increasing the coating material concentration. The effect of nicotinic acid on the shape, particle size, chemical structure and magnetic properties of the prepared nanorods was evaluated using different characterization methods. The length of nanorods increased from 270 nm to 350 nm in nicotinic acid coated nanorods. Goethite and magnetite phases with different ratios were the dominant phases in the coated samples while a pure magnetite phase was observed in the uncoated one. Nicotinic acid coated magnetic nanorods showed a significant decrease in saturation magnetization than uncoated samples (55 emu/g) reaching 4 emu/g in 2.5 g nicotinic acid coated sample. The novel synthesis technique proved its potentiality to prepare coated metal oxides with one dimensional nanostructure which can function effectively in different biological applications. - Highlights: • We synthesize nicotinic acid coated magnetite nanorods via hydrothermal technique • Effect of nicotinic acid concentration on the nanorods properties was significant • Nanorods maintained uniform shape with increased concentration of nicotinic acid • Alterations occurred in particle size, mineral phases and magnetics of coated samples.

Synthesis of non-aggregated nicotinic acid coated magnetite nanorods via hydrothermal technique

International Nuclear Information System (INIS)

Attallah, Olivia A.; Girgis, E.; Abdel-Mottaleb, Mohamed M.S.A.

2016-01-01

Non-aggregated magnetite nanorods with average diameters of 20–30 nm and lengths of up to 350 nm were synthesized via in situ, template free hydrothermal technique. These nanorods capped with different concentrations (1, 1.5, 2 and 2.5 g) of nicotinic acid (vitamin B3); possessed good magnetic properties and easy dispersion in aqueous solutions. Our new synthesis technique maintained the uniform shape of the nanorods even with increasing the coating material concentration. The effect of nicotinic acid on the shape, particle size, chemical structure and magnetic properties of the prepared nanorods was evaluated using different characterization methods. The length of nanorods increased from 270 nm to 350 nm in nicotinic acid coated nanorods. Goethite and magnetite phases with different ratios were the dominant phases in the coated samples while a pure magnetite phase was observed in the uncoated one. Nicotinic acid coated magnetic nanorods showed a significant decrease in saturation magnetization than uncoated samples (55 emu/g) reaching 4 emu/g in 2.5 g nicotinic acid coated sample. The novel synthesis technique proved its potentiality to prepare coated metal oxides with one dimensional nanostructure which can function effectively in different biological applications. - Highlights: • We synthesize nicotinic acid coated magnetite nanorods via hydrothermal technique • Effect of nicotinic acid concentration on the nanorods properties was significant • Nanorods maintained uniform shape with increased concentration of nicotinic acid • Alterations occurred in particle size, mineral phases and magnetics of coated samples.

Characterization and photoluminescence studies of CdTe ...

Indian Academy of Sciences (India)

Administrator

Abstract. The major objective of this work was to detect the change of photoluminescence (PL) intensity of. CdTe nanoparticles (NPs) before and after transfer from liquid phase to polystyrene (PS) matrix by electro- spinning technique. Thio-stabilized CdTe NPs were first synthesized in aqueous, then enwrapped by cetyl-.

Stability studies of CdSe nanocrystals in an aqueous environment

DEFF Research Database (Denmark)

Xi, Lifei; Lek, Jun Yan; Liang, Yen Nan

2011-01-01

In this paper, CdSe nanocrystal dissolution in an aqueous solution was studied. It was found that light is a key factor affecting the dissolution of nanocrystals. In the presence of light, the electrons generated from CdSe nanocrystals reduce water to hydrogen and hydroxide ions (OH − ) while photo......-generated holes oxidize CdSe to Cd2 + and elemental Se. The dissolution was accelerated in an acidic medium while moderate alkalinity (pH = 10.3) can slow down the dissolution possibly due to precipitation of nanocrystals. This study has strong implications for the use of these crystals in aqueous environments...

Synthesis of highly faceted multiply twinned gold nanocrystals stabilized by polyoxometalates

International Nuclear Information System (INIS)

Yuan Junhua; Chen Yuanxian; Han Dongxue; Zhang Yuanjian; Shen Yanfei; Wang Zhijuan; Niu Li

2006-01-01

A novel and facile chemical synthesis of highly faceted multiply twinned gold nanocrystals is reported. The gold nanocrystals are hexagonal in transmission electron microscopy and icosahedral in scanning electron microscopy. Phosphotungstic acid (PTA), which was previously reduced, serves as a reductant and stabilizer for the synthesis of gold nanocrystals. The PTA-gold nanocomposites are quite stable in aqueous solutions, and electrochemically active towards the hydrogen evolution reaction

Adsorption and spectroscopic characterization of lactoferrin on hydroxyapatite nanocrystals.

Science.gov (United States)

Iafisco, Michele; Di Foggia, Michele; Bonora, Sergio; Prat, Maria; Roveri, Norberto

2011-01-28

Lactoferrin (LF), a well-characterized protein of blood plasma and milk with antioxidant, cariostatic, anticarcinogenic and anti-inflammatory properties, has been adsorbed onto biomimetic hydroxyapatite (HA) nanocrystals at two different pH values (7.4 and 9.0). The interaction was herein investigated by spectroscopic, thermal and microscopic techniques. The positive electrostatic surface potential of LF at pH 7.4 allows a strong surface interaction with the slightly negative HA nanocrystals and avoids the protein-protein interaction, leading to the formation of a coating protein monolayer. In contrast, at pH 9.0 the surface potential of LF is a mix of negative and positive zones favouring the protein-protein interaction and reducing the interaction with HA nanocrystals; as a result a double layer of coating protein was formed. These experimental findings are supported by the good fittings of the adsorption isotherms by different theoretical models according to Langmuir, Freundlich and Langmuir-Freundlich models. The nanosized HA does not appreciably affect the conformation of the adsorbed protein. In fact, using FT-Raman and FT-IR, we found that after adsorption the protein was only slightly unfolded with a small fraction of the α-helix structure being converted into turn, while the β-sheet content remained almost unchanged. The bioactive surface of HA functionalized with LF could be utilized to improve the material performance towards the biological environment for biomedical applications.

Hydrogen storage in Pd nanocrystals covered with a metal-organic framework

Science.gov (United States)

Li, Guangqin; Kobayashi, Hirokazu; Taylor, Jared M.; Ikeda, Ryuichi; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki; Yamamoto, Tomokazu; Toh, Shoichi; Matsumura, Syo; Kitagawa, Hiroshi

2014-08-01

Hydrogen is an essential component in many industrial processes. As a result of the recent increase in the development of shale gas, steam reforming of shale gas has received considerable attention as a major source of H2, and the more efficient use of hydrogen is strongly demanded. Palladium is well known as a hydrogen-storage metal and an effective catalyst for reactions related to hydrogen in a variety of industrial processes. Here, we present remarkably enhanced capacity and speed of hydrogen storage in Pd nanocrystals covered with the metal-organic framework (MOF) HKUST-1 (copper(II) 1,3,5-benzenetricarboxylate). The Pd nanocrystals covered with the MOF have twice the storage capacity of the bare Pd nanocrystals. The significantly enhanced hydrogen storage capacity was confirmed by hydrogen pressure-composition isotherms and solid-state deuterium nuclear magnetic resonance measurements. The speed of hydrogen absorption in the Pd nanocrystals is also enhanced by the MOF coating.

The hydrodynamic size of polymer stabilized nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Krueger, Karl M; Al-Somali, Ali M; Mejia, Michelle; Colvin, Vicki L [Department of Chemistry, Rice University, MS-60 6100 Main Street, Houston, TX 77005 (United States)

2007-11-28

For many emerging applications, nanocrystals are surface functionalized with polymers to control self-assembly, prevent aggregation, and promote incorporation into polymer matrices and biological systems. The hydrodynamic diameter of these nanoparticle-polymer complexes is a critical factor for many applications, and predicting this size is complicated by the fact that the structure of the grafted polymer at a nanocrystalline interface is not generally established. In this work we evaluate using size-exclusion chromatography the overall hydrodynamic diameter of nanocrystals (Au, CdSe, d<5 nm) surface coated with polystyrene of varying molecular weight. The polymer is tethered to the nanoparticles via a terminal thiol to provide strong attachment. Our data show that at full coverage the polymer assumes a brush conformation and is 44% longer than the unbound polymer in solution. The brush conformation is confirmed by comparison with models used to describe polymer brushes at flat interfaces. From this work, we suggest an empirical formula which predicts the hydrodynamic diameter of polymer coated nanoparticles based on the size of the nanoparticle core and the size of the randomly coiled unbound polymer in solution.

The effect of excitons on CdTe solar cells

International Nuclear Information System (INIS)

Karazhanov, S. Zh.; Zhang, Y.; Mascarenhas, A.; Deb, S.

2000-01-01

Temperature and doping-level dependence of CdTe solar cells is investigated, taking into account the involvement of excitons on photocurrent transport. We show that the density of excitons in CdTe is comparable with that of minority carriers at doping levels ≥10 15 cm -3 . From the investigation of the dark-saturation current, we show that the product of electron and hole concentrations at equilibrium is several orders of magnitude more than the square of the intrinsic carrier concentration. With this assumption, we have studied the effect of excitons on CdTe solar cells, and the effect is negative. CdTe solar cell performance with excitons included agrees well with existing experimental results. (c) 2000 American Institute of Physics

Photostimulated changes of properties of CdTe films

Energy Technology Data Exchange (ETDEWEB)

Dzhafarov, T.D. [Institute of Physics, Azerbaijan National Academy of Sciences, AZ-1143 Baku (Azerbaijan); Yesilkaya, S.S. [Department of Physics, Yildiz Technical University, 34210 Esenler/Istanbul (Turkey)

2007-08-15

The effect of illumination during the close-spaced sublimation (CSS) growth on composition, structural, electrical, optical and photovoltaic properties of CdTe films and CdTe/CdS solar cells were investigated. Data on comparative study by using X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption spectra and conductivity-temperature measurements of CdTe films prepared by CSS method in dark (CSSD) and under illumination (CSSI) were presented. It is shown that the growth rate and the grain size of CdTe films grown under illumination is higher (by factor about of 1.5 and 3 respectively) than those for films prepared without illumination. The energy band gap of CdTe films fabricated by both technology, determined from absorption spectra, is same (about of 1.50 eV), however conductivity of the CdTe films produced by CSSI is considerably greater (by factor of 10{sup 7}) than that of films prepared by CSSD. The photovoltaic parameters of pCdTe/nCdS solar cells fabricated by photostimulated CSSI technology (J{sub sc}=28 mA/cm{sup 2}, V{sub oc}=0.63 V) are considerably larger than those for cells prepared by CSSD method (J{sub sc}=22 mA/cm{sup 2}, V{sub oc}=0.52 V). A mechanism of photostimulated changes of properties of CdTe films and improvement of photovoltaic parameters of CdTe/CdS solar cells is suggested. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Stability studies of CdSe nanocrystals in an aqueous environment

Energy Technology Data Exchange (ETDEWEB)

Xi Lifei; Lek, Jun Yan; Liang, Yen Nan; Zhou Wenwen; Yan Qingyu; Hu Xiao; Chiang, Freddy Boey Yin; Lam, Yeng Ming [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 (Singapore); Boothroyd, Chris, E-mail: ymlam@ntu.edu.sg [Center for Electron Nanoscopy, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark)

2011-07-08

In this paper, CdSe nanocrystal dissolution in an aqueous solution was studied. It was found that light is a key factor affecting the dissolution of nanocrystals. In the presence of light, the electrons generated from CdSe nanocrystals reduce water to hydrogen and hydroxide ions (OH{sup -}) while photo-generated holes oxidize CdSe to Cd{sup 2+} and elemental Se. The dissolution was accelerated in an acidic medium while moderate alkalinity (pH = 10.3) can slow down the dissolution possibly due to precipitation of nanocrystals. This study has strong implications for the use of these crystals in aqueous environments (bioimaging and dye-sensitized solar cells).

An innovative zinc oxide-coated zeolite adsorbent for removal of humic acid

Energy Technology Data Exchange (ETDEWEB)

Wang, Lingling, E-mail: lasier_wang@hotmail.com [College of Chemical Engineering and Materials, Quanzhou Normal University, Quanzhou 362000, Fujian (China); Environmental Engineering and Science Program, 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012 (United States); Han, Changseok [ORISE Post-doctoral Fellow, The U.S. Environmental Protection Agency, ORD, NRMRL, STD, CPB, 26 W. Martin Luther King Jr. Drive, Cincinnati, OH 45268 (United States); Nadagouda, Mallikarjuna N. [The U.S. Environmental Protection Agency, ORD, NRMRL, WSWRD, WQMB, 26 W. Martin Luther King Jr. Drive, Cincinnati, OH 45268 (United States); Dionysiou, Dionysios D., E-mail: dionysios.d.dionysiou@uc.edu [Environmental Engineering and Science Program, 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012 (United States); Nireas-International Water Research Centre, School of Engineering, University of Cyprus, PO Box 20537, 1678, Nicosia (Cyprus)

2016-08-05

Highlights: • An innovative adsorbent was successfully synthesized to remove humic acid. • The adsorbent possessed high adsorption capacity for humic acid. • The adsorption capacity remarkably increased after an acid modification. • The adsorption capacity was proportional to the amount of ZnO coated on zeolite. • Electrostatic interactions are a major factor at the first stage of the process. - Abstract: Zinc oxide (ZnO)-coated zeolite adsorbents were developed by both nitric acid modification and Zn(NO{sub 3}){sub 2}·6H{sub 2}O functionalization of zeolite 4A. The developed adsorbents were used for the removal of humic acid (HA) from aqueous solutions. The synthesized materials were characterized by porosimetry analysis, scanning electron microscopy, X-Ray diffraction analysis, and high resolution transmission electron microscopy. The maximum adsorption capacity of the adsorbents at 21 ± 1 °C was about 60 mgC g{sup −1}. The results showed that the positive charge density of ZnO-coated zeolite adsorbents was proportional to the amount of ZnO coated on zeolite and thus, ZnO-coated zeolite adsorbents exhibited a greater affinity for negatively charged ions. Furthermore, the adsorption capacity of ZnO-coated zeolite adsorbents increased markedly after acid modification. Adsorption experiments demonstrated ZnO-coated zeolite adsorbents possessed high adsorption capacity to remove HA from aqueous solutions mainly due to strong electrostatic interactions between negative functional groups of HA and the positive charges of ZnO-coated zeolite adsorbents.

An innovative zinc oxide-coated zeolite adsorbent for removal of humic acid

International Nuclear Information System (INIS)

Wang, Lingling; Han, Changseok; Nadagouda, Mallikarjuna N.; Dionysiou, Dionysios D.

2016-01-01

Highlights: • An innovative adsorbent was successfully synthesized to remove humic acid. • The adsorbent possessed high adsorption capacity for humic acid. • The adsorption capacity remarkably increased after an acid modification. • The adsorption capacity was proportional to the amount of ZnO coated on zeolite. • Electrostatic interactions are a major factor at the first stage of the process. - Abstract: Zinc oxide (ZnO)-coated zeolite adsorbents were developed by both nitric acid modification and Zn(NO_3)_2·6H_2O functionalization of zeolite 4A. The developed adsorbents were used for the removal of humic acid (HA) from aqueous solutions. The synthesized materials were characterized by porosimetry analysis, scanning electron microscopy, X-Ray diffraction analysis, and high resolution transmission electron microscopy. The maximum adsorption capacity of the adsorbents at 21 ± 1 °C was about 60 mgC g"−"1. The results showed that the positive charge density of ZnO-coated zeolite adsorbents was proportional to the amount of ZnO coated on zeolite and thus, ZnO-coated zeolite adsorbents exhibited a greater affinity for negatively charged ions. Furthermore, the adsorption capacity of ZnO-coated zeolite adsorbents increased markedly after acid modification. Adsorption experiments demonstrated ZnO-coated zeolite adsorbents possessed high adsorption capacity to remove HA from aqueous solutions mainly due to strong electrostatic interactions between negative functional groups of HA and the positive charges of ZnO-coated zeolite adsorbents.

Growth of CdTe: Al films; Crecimiento de peliculas de CdTe: Al

Energy Technology Data Exchange (ETDEWEB)

Gonzalez A, M.; Zapata T, M. [CICATA-IPN, 89600 Altamira, Tamaulipas (Mexico); Melendez L, M. [CINVESTAV-IPN, A.P. 14-740, 07000 Mexico D.F. (Mexico); Pena, J.L. [CINVESTAV-IPN, A.P. 73 Cordemex, 97310 Merida, Yucatan (Mexico)

2006-07-01

CdTe: AI films were grown by the close space vapor transport technique combined with free evaporation (CSVT-FE). The Aluminum (Al) evaporation was made by two kinds of sources: one made of graphite and the other of tantalum. The films were deposited on glass substrates. The Al source temperature was varied maintaining the CdTe source temperature fixed as well as the substrate temperature. The films were characterized by x-ray energy dispersive analysis (EDAX), x-ray diffraction and optical transmission. The results showed for the films grown with the graphite source for Al evaporation, the Al did not incorporate in the CdTe matrix, at least to the level of EDAX sensitivity; they maintained the same crystal structure and band gap. For the samples grown with the tantalum source, we were able to incorporate the Al. The x-ray diffraction patterns show that the films have a crystal structure that depends on Al concentration. They were cubic up to 2.16 at. % Al concentration; for 19.65 at. % we found a mixed phase; for Al concentration higher than 21 at. % the films were amorphous. For samples with cubic structure it was found that the lattice parameter decreases and the band gap increases with Al concentration. (Author)

On the doping problem of CdTe films: The bismuth case

Energy Technology Data Exchange (ETDEWEB)

Vigil-Galan, O. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico); Brown, M. [Department of Physics and Astronomy, The University of Toledo, 43606 Toledo, OH (United States); Ruiz, C.M. [Depto. Fisica de Materiales, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Vidal-Borbolla, M.A. [Instituto de Investigacion en Comunicacion Optica, Av. Karakorum 1470, Lomas 4a. Secc., 78210 San Luis Potosi, SLP (Mexico); Ramirez-Bon, R. [CINVESTAV-IPN, U. Queretaro, Libramiento Norponiente No. 2000, Fracc. Real de Juriquilla, 76230 Santiago de Queretaro, Qro. (Mexico); Sanchez-Meza, E. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico); Tufino-Velazquez, M. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico)], E-mail: mtufinovel@yahoo.com.mx; Calixto, M. Estela [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico); Compaan, A.D. [Department of Physics and Astronomy, The University of Toledo, 43606 Toledo, OH (United States); Contreras-Puente, G. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico)

2008-08-30

The controlled increase of hole concentration is an important issue and still an unsolved problem for polycrystalline CdTe-based solar cells. The typical hole concentration of as-grown CdTe thin-films goes up to 10{sup 13} cm{sup -3}, depending on the specific growth technique. The highest electron concentration obtained for CdS, the suitable window partner material of CdTe, is around 10{sup 15} cm{sup -3}. Thus, the PV-performance of a CdS/CdTe device can be optimized if the hole concentration in CdTe is increased. We have faced up this problem by studying the electrical properties of two types of CdTe films: CdTe films grown by Close Space Vapor Transport using a CdTe:Bi powder as the starting material and CdTe sputtered films doped by implantation with different Bi-doses. Temperature-dependent resistivity and Hall effect measurements and a discussion on the efficiency of both doping processes are presented.

On the doping problem of CdTe films: The bismuth case

International Nuclear Information System (INIS)

Vigil-Galan, O.; Brown, M.; Ruiz, C.M.; Vidal-Borbolla, M.A.; Ramirez-Bon, R.; Sanchez-Meza, E.; Tufino-Velazquez, M.; Calixto, M. Estela; Compaan, A.D.; Contreras-Puente, G.

2008-01-01

The controlled increase of hole concentration is an important issue and still an unsolved problem for polycrystalline CdTe-based solar cells. The typical hole concentration of as-grown CdTe thin-films goes up to 10 13 cm -3 , depending on the specific growth technique. The highest electron concentration obtained for CdS, the suitable window partner material of CdTe, is around 10 15 cm -3 . Thus, the PV-performance of a CdS/CdTe device can be optimized if the hole concentration in CdTe is increased. We have faced up this problem by studying the electrical properties of two types of CdTe films: CdTe films grown by Close Space Vapor Transport using a CdTe:Bi powder as the starting material and CdTe sputtered films doped by implantation with different Bi-doses. Temperature-dependent resistivity and Hall effect measurements and a discussion on the efficiency of both doping processes are presented

Study of CdTe and HgCdTe thin films obtained by electrochemical methods

International Nuclear Information System (INIS)

Guillen, C.

1990-01-01

Cadmium telluride polycrystalline thin films were fabricated on SnO 2 -coated glass substrates by potentiostatic electrodeposition and characterized by X-ray diffraction, energy dispersive X-ray analyses (EDAX), optical and electrical measurements. The films dseposited at potentials more positive than -0.65 V vs.SCE were p-type but those deposited at more negative potentials were n-type. All CdTe thin films showed a band-gap energy about 1.45 eV and a large absorption coeffici-ent (a=10 5 cm -1 ) above de band edge. The addition of even small amounts of mercury to the CdTe produces higuer conductivity values and lower band-gap energies. We have prepared HgCdTe thin films where the band-gap energies ranged between 0.93 and 0.88 eV depending on the ratio of mercury to cadmium. Heat treatment at 300 0 C increases the crystalline diameter and alter the composition of the electrodeposited films, a decrease of the resistivity values was also observed. (Author)

Synthesis of freestanding water-soluble indium oxide nanocrystals capped by alanine nitric acid via ligand exchange for thin film transistors and effects of ligands on the electrical properties

International Nuclear Information System (INIS)

Choi, Jin-Kyu; Koh, Ye-Seul; Jeong, Hyun-Dam

2015-01-01

We demonstrate synthesis of freestanding water-soluble indium oxide nanocrystals (In 2 O 3 NCs) by ligand exchange to β-alanine nitric acid (Ala·HNO 3 ) and its application for active channel layer in thin film transistors (TFTs), with investigation of the effect of curing temperatures on the TFT properties in terms of thermal behaviour of the ligand molecules at 150, 300, and 350 °C. After ligand exchange from long alkyl ligand (myristic acid, MA) to short Ala·HNO 3 , the mobility of NC TFTs cured at 150 °C increased by over 1 order of magnitude, from 1.3 × 10 −4 cm 2 V -1 s −1 to 4.5 × 10 −3 cm 2 V -1 s −1 , due to enhanced tunnelling rate (Γ) between adjective NCs. Higher curing temperatures such as 300 and 350 °C, inducing thermal decomposition of the organic ligands, led to further enhancement of the mobility, particularly up to 2.2 cm 2 V -1 s −1 for the In 2 O 3 NC-Ala·HNO 3 TFT cured at 350 °C. It is also found that the ligand exchange of In 2 O 3 NC in acidic condition (e.g. HNO 3 ) would be simple and effective to reduce the surface defects by surface etching, which may lead to better device performances. - Graphical abstract: Display Omitted - Highlights: • Freestanding water-soluble In 2 O 3 nanocrystals (NCs) were synthesized by ligand exchange. • Thin film transistors (TFTs) of colloidal NCs were fabricated by spin-coating method. • Water-soluble In 2 O 3 NC TFTs showed higher mobilities due to shorter ligand length. • Surface defects of NCs were notably reduced by surface etching during ligand exchange

Photo-crosslinked hyaluronic acid coated upconverting nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Mrazek, Jiri, E-mail: jiri.mrazek@contipro.com; Kettou, Sofiane; Matuska, Vit; Svozil, Vit; Huerta-Angeles, Gloria; Pospisilova, Martina; Nesporova, Kristina; Velebny, Vladimir [Contipro a. s. (Czech Republic)

2017-02-15

Hyaluronic acid (HA)-coated inorganic nanoparticles display enhanced interaction with the CD44 receptors which are overexpressed in many types of cancer cells. Here, we describe a modification of core-shell β-NaY{sub 0.80}Yb{sub 0.18}Er{sub 0.02}F{sub 4}@NaYF{sub 4} nanoparticles (UCNP) by HA derivative bearing photo-reactive groups. UCNP capped with oleic acid were firstly transferred to aqueous phase by an improved protocol using hydrochloric acid or lactic acid treatment. Subsequently, HA bearing furanacryloyl moieties (HA-FU) was adsorbed on the nanoparticle surface and crosslinked by UV irradiation. The crosslinking resulted in stable HA coating, and no polymer desorption was observed. As-prepared UCNP@HA-FU show a hydrodynamic diameter of about 180 nm and are colloidally stable in water and cell culture media. The cellular uptake by normal human fibroblasts and MDA MB-231 cancer cell line was investigated by upconversion luminescence imaging.

Radiative and interfacial recombination in CdTe heterostructures

Energy Technology Data Exchange (ETDEWEB)

Swartz, C. H., E-mail: craig.swartz@txstate.edu; Edirisooriya, M.; LeBlanc, E. G.; Noriega, O. C.; Jayathilaka, P. A. R. D.; Ogedengbe, O. S.; Hancock, B. L.; Holtz, M.; Myers, T. H. [Materials Science, Engineering, and Commercialization Program, Texas State University, 601 University Dr., San Marcos, Texas 78666 (United States); Zaunbrecher, K. N. [National Renewable Energy Laboratory, 15013 Denver West Parkway, Mississippi RSF200, Golden, Colorado 80401 (United States)

2014-12-01

Double heterostructures (DH) were produced consisting of a CdTe film between two wide band gap barriers of CdMgTe alloy. A combined method was developed to quantify radiative and non-radiative recombination rates by examining the dependence of photoluminescence (PL) on both excitation intensity and time. The measured PL characteristics, and the interface state density extracted by modeling, indicate that the radiative efficiency of CdMgTe/CdTe DHs is comparable to that of AlGaAs/GaAs DHs, with interface state densities in the low 10{sup 10 }cm{sup −2} and carrier lifetimes as long as 240 ns. The radiative recombination coefficient of CdTe is found to be near 10{sup −10} cm{sup 3}s{sup −1}. CdTe film growth on bulk CdTe substrates resulted in a homoepitaxial interface layer with a high non-radiative recombination rate.

Colloidal CuInSe2 nanocrystals thin films of low surface roughness

International Nuclear Information System (INIS)

Kergommeaux, Antoine de; Fiore, Angela; Faure-Vincent, Jérôme; Pron, Adam; Reiss, Peter

2013-01-01

Thin-film processing of colloidal semiconductor nanocrystals (NCs) is a prerequisite for their use in (opto-)electronic devices. The commonly used spin-coating is highly materials consuming as the overwhelming amount of deposited matter is ejected from the substrate during the spinning process. Also, the well-known dip-coating and drop-casting procedures present disadvantages in terms of the surface roughness and control of the film thickness. We show that the doctor blade technique is an efficient method for preparing nanocrystal films of controlled thickness and low surface roughness. In particular, by optimizing the deposition conditions, smooth and pinhole-free films of 11 nm CuInSe 2 NCs have been obtained exhibiting a surface roughness of 13 nm root mean square (rms) for a 350 nm thick film, and less than 4 nm rms for a 75 nm thick film. (paper)

Quantum Dots Microstructured Optical Fiber for X-Ray Detection

Science.gov (United States)

DeHaven, Stan; Williams, Phillip; Burke, Eric

2015-01-01

Microstructured optical fibers containing quantum dots scintillation material comprised of zinc sulfide nanocrystals doped with magnesium sulfide are presented. These quantum dots are applied inside the microstructured optical fibers using capillary action. The x-ray photon counts of these fibers are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The results of the fiber light output and associated effects of an acrylate coating and the quantum dot application technique are discussed.

Influence of phytic acid concentration on performance of phytic acid conversion coatings on the AZ91D magnesium alloy

International Nuclear Information System (INIS)

Cui Xiufang; Li Ying; Li Qingfen; Jin Guo; Ding Minghui; Wang Fuhui

2008-01-01

In this study, the phytic acid conversion coating, a new environmentally friendly chemical protective coating for magnesium alloys, was prepared. The influences of phytic acid concentration on the formation process, microstructure, chemical state and corrosion resistance of the conversion coatings on AZ91D magnesium alloy were investigated by means of weight gain measurement, field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS), respectively. And the depth profile of all elements in the optimal conversion coatings was analyzed by auger electron spectroscopy (AES). The results show that the growth, microstructure, chemical state and corrosion resistance of the conversion coatings are all obviously affected by the phytic acid concentration. The concentration of 5 g l -1 corresponds to the maximum weight gain. The main elements of the coating are Mg, Al, O, P, and C, which are distributed gradually in depth. The functional groups of conversion coatings formed in higher concentration phytic acid solution are closer to the constituent of phytic acid than those formed in lower concentration phytic acid solution. The coatings formed in 1-5 g l -1 are integrated and uniform. However, those formed in 20-50 g l -1 have some micro-cracks on the α phase. The coating formed in 5 g l -1 has the best corrosion resistance, whose open circuit current density decreases about six orders than that of the untreated sample, although the coatings deposited in 1-20 g l -1 can all improve the corrosion resistance of AZ91D

Electrophoretic properties of BSA-coated quantum dots.

Science.gov (United States)

Bücking, Wendelin; Massadeh, Salam; Merkulov, Alexei; Xu, Shu; Nann, Thomas

2010-02-01

Low toxic InP/ZnS quantum dots (QDs), ZnS:Mn(2+)/ZnS nanocrystals and CdSe/ZnS nanoparticles were rendered water-dispersible by different ligand-exchange methods. Eventually, they were coated with bovine serum albumin (BSA) as a model protein. All particles were characterised by isotachophoresis (ITP), laser Doppler velocimetry (LDV) and agarose gel electrophoresis. It was found that the electrophoretic mobility and colloidal stability of ZnS:Mn(2+)/ZnS and CdSe/ZnS nanoparticles, which bore short-chain surface ligands, was primarily governed by charges on the nanoparticles, whereas InP/ZnS nanocrystals were not charged per se. BSA-coated nanoparticles showed lower electrophoretic mobility, which was attributed to their larger size and smaller overall charge. However, these particles were colloidally stable. This stability was probably caused by steric stabilisation of the BSA coating.

Cellulose nanocrystals from acacia bark-Influence of solvent extraction.

Science.gov (United States)

Taflick, Ticiane; Schwendler, Luana A; Rosa, Simone M L; Bica, Clara I D; Nachtigall, Sônia M B

2017-08-01

The isolation of cellulose nanocrystals from different lignocellulosic materials has shown increased interest in academic and technological research. These materials have excellent mechanical properties and can be used as nanofillers for polymer composites as well as transparent films for various applications. In this work, cellulose isolation was performed following an environmental friendly procedure without chlorine. Cellulose nanocrystals were isolated from the exhausted acacia bark (after the industrial process of extracting tannin) with the objective of evaluating the effect of the solvent extraction steps on the characteristics of cellulose and cellulose nanocrystals. It was also assessed the effect of acid hydrolysis time on the thermal stability, morphology and size of the nanocrystals, through TGA, TEM and light scattering analyses. It was concluded that the extraction step with solvents was important in the isolation of cellulose, but irrelevant in the isolation of cellulose nanocrystals. Light scattering experiments indicated that 30min of hydrolysis was long enough for the isolation of cellulose nanocrystals. Copyright © 2017 Elsevier B.V. All rights reserved.

Polymer-coated quantum dots

NARCIS (Netherlands)

Tomczak, N.; Liu, Rongrong; Vancso, Gyula J.

2013-01-01

Quantum Dots (QDs) are semiconductor nanocrystals with distinct photophysical properties finding applications in biology, biosensing, and optoelectronics. Polymeric coatings of QDs are used primarily to provide long-term colloidal stability to QDs dispersed in solutions and also as a source of

Luminous composite ultrathin films of CdTe quantum dots/silk fibroin co-assembled with layered doubled hydroxide: Enhanced photoluminescence and biosensor application

Directory of Open Access Journals (Sweden)

Muhammad Sohail Haroone

2018-06-01

Full Text Available Quantum dots (QDs luminescent films are extensively applied to optoelectronics and optical devices. However, QDs aggregation results in the quenching of their fluorescence property which limits their practical applications to a greater extent. In order to resolve this issue, 3-mercaptopropionic acid (3-MPA functionalized Cadmium Tellurium (CdTe QDs were stabilized by silk fibroin (SB and co-assembled with layered doubled hydroxide (LDH to form (QDs@SF/LDHn ultrathin films (UTFs via the layer-by-layer (LBL technique. UV–Vis absorption and fluorescence spectroscopy showed a stepwise and normal growth of the films upon increasing the number of deposition cycles. XRD and AFM studies confirmed the formation of a periodic layered structure and regular surface morphology of the thin films. As compared to (CdTe QDs/LDHnUTFs, the (CdTe QDs@SF/LDHnUTFs displayed fluorescence enhancement and longer fluorescent lifetime, both in solid states and aqueous solutions. Furthermore compared with the solution state, the fluorescence enhancement of SF-RC and SF-β are, respectively, 7 times and 17 times in the (CdTe QDs@SF/LDHn UTFs, indicating that the LDH nanosheets favor the fluorescence enhancement effect on the CdTe QDs@SF. The fabricated materials displayed fluorescence response to a biological molecule such as immune globulin, lgG. Thus, the (CdTe QDs@SF/LDHn UTFs has a potential to be used as biosensor. Keywords: CdTe quantum dots, Silk fibroin, Layered doubled hydroxide, Co-assembly, Fluorescence enhancement

Synthesis of Pd-Au bimetallic nanocrystals via controlled overgrowth.

Science.gov (United States)

Lim, Byungkwon; Kobayashi, Hirokazu; Yu, Taekyung; Wang, Jinguo; Kim, Moon J; Li, Zhi-Yuan; Rycenga, Matthew; Xia, Younan

2010-03-03

This paper describes the synthesis of Pd-Au bimetallic nanocrystals with controlled morphologies via a one-step seeded-growth method. Two different reducing agents, namely, L-ascorbic acid and citric acid, were utilized for the reduction of HAuCl(4) in an aqueous solution to control the overgrowth of Au on cubic Pd seeds. When L-ascorbic acid was used as the reducing agent, conformal overgrowth of Au on the Pd nanocubes led to the formation of Pd-Au nanocrystals with a core-shell structure. On the contrary, localized overgrowth of Au was observed when citric acid was used as the reducing agent, producing Pd-Au bimetallic dimers. Through this morphological control, we were able to tune the localized surface plasmon resonance peaks of Pd-Au bimetallic nanostructures in the visible region.

Optimization of cellulose nanocrystal length and surface charge density through phosphoric acid hydrolysis

Science.gov (United States)

Vanderfleet, Oriana M.; Osorio, Daniel A.; Cranston, Emily D.

2017-12-01

Cellulose nanocrystals (CNCs) are emerging nanomaterials with a large range of potential applications. CNCs are typically produced through acid hydrolysis with sulfuric acid; however, phosphoric acid has the advantage of generating CNCs with higher thermal stability. This paper presents a design of experiments approach to optimize the hydrolysis of CNCs from cotton with phosphoric acid. Hydrolysis time, temperature and acid concentration were varied across nine experiments and a linear least-squares regression analysis was applied to understand the effects of these parameters on CNC properties. In all but one case, rod-shaped nanoparticles with a high degree of crystallinity and thermal stability were produced. A statistical model was generated to predict CNC length, and trends in phosphate content and zeta potential were elucidated. The CNC length could be tuned over a relatively large range (238-475 nm) and the polydispersity could be narrowed most effectively by increasing the hydrolysis temperature and acid concentration. The CNC phosphate content was most affected by hydrolysis temperature and time; however, the charge density and colloidal stability were considered low compared with sulfuric acid hydrolysed CNCs. This study provides insight into weak acid hydrolysis and proposes `design rules' for CNCs with improved size uniformity and charge density. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

Brilliant molecular nanocrystals emerging from sol-gel thin films: towards a new generation of fluorescent biochips

International Nuclear Information System (INIS)

Dubuisson, E; Monnier, V; Sanz-Menez, N; Ibanez, A; Boury, B; Usson, Y; Pansu, R B

2009-01-01

To develop highly sensitive biosensors, we made directly available to biological aqueous solutions organic nanocrystals previously grown in the pores of sol-gel films. Through the controlled dissolution of the sol-gel surface, we obtained emerging nanocrystals that remained strongly anchored to the sol-gel coating for good mechanical stability of the final sensing device. We demonstrated that in the presence of a solution of DNA functionalized with a molecular probe, the nanocrystal fluorescence is strongly quenched by Foerster resonance energy transfer thus opening the way towards very sensitive fluorescent biosensors through biomolecules grafted onto fluorescent nanocrystals. Finally, this controlled dissolution, involving weak concentrated NaOH solution, is a generic process that can be used for the thinning of any kind of sol-gel layer.

Se-Se isoelectronic centers in high purity CdTe

Energy Technology Data Exchange (ETDEWEB)

Najjar, Rita; Andre, Regis; Mariette, Henri [CEA-CNRS, Nanophysique et Semiconducteurs, Institut Neel, 25 rue des martyrs, 38042 Grenoble (France); Golnik, Andrzej; Kossacki, Piotr; Gaj, Jan A. [Institute of Experimental Physics, University of Warsaw, Hoza 69, 00-681 Warsaw (Poland)

2010-06-15

We evidence zero-dimensional exciton states trapped on isoelectronic Se centers in CdTe quantum wells, {delta}-doped with Se. Thanks to special precautions taken to have very high purity CdTe heterostructures, it is possible to observe, in photoluminescence spectra, sharp discrete lines arising from individual centers related to the Se doping. These emission lines appear at about 40 meV below the CdTe band gap energy. The most prominent lines are attributed to the recombination of excitons bound to nearest-neighbor selenium pairs in a tetrahedral CdTe environment. This assignment is confirmed by a common linear polarization direction of the emitted light, parallel to <110>. These excitons localized on individual isoelectronic traps are good candidates as single photon emitters (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Influence of EDTA2− on the hydrothermal synthesis of CdTe nanocrystallites

International Nuclear Information System (INIS)

Gong Haibo; Hao Xiaopeng; Wu Yongzhong; Cao Bingqiang; Xu Hongyan; Xu Xiangang

2011-01-01

Transformation from Te nanorods to CdTe nanoparticles was achieved with the assistance of EDTA as a ligand under hydrothermal conditions. Experimental results showed that at the beginning of reaction Te nucleated and grew into nanorods. With the proceeding of reaction, CdTe nucleus began to emerge on the surface, especially on the tips of Te nanorods. Finally, nearly monodispersed hexagonal CdTe nanoparticles with diameters of about 200 nm were obtained. The effects of EDTA on the morphology and formation of CdTe nanoparticles were discussed in consideration of the strong ligand-effect of EDTA, which greatly decreased the concentration of Cd 2+ . Furthermore, the possible formation process of CdTe nanoparticles from Te nanorods was further proposed. The crystal structure and morphology of the products were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). - Graphical Abstract: Firstly, Te nucleated and grew into nanorods in the presence of EDTA 2− . Then CdTe nucleus began to emerge on Te nanorods and finally monodispersed CdTe nanoparticles were obtained. Highlights: ► EDTA serves as a strong ligand with Cd 2+ . ► The existence of EDTA constrains the nucleation of CdTe and promotes the formation of Te nanorods. ► With the proceeding of reaction, CdTe nucleus began to emerge on the surface, especially on the tips of Te nanorods. ► Nearly monodispersed hexagonal CdTe nanoparticles with diameters of about 200 nm were finally obtained.

Reusable hydroxyapatite nanocrystal sensors for protein adsorption

International Nuclear Information System (INIS)

Tagaya, Motohiro; Ikoma, Toshiyuki; Hanagata, Nobutaka; Chakarov, Dinko; Kasemo, Bengt; Tanaka, Junzo

2010-01-01

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.

Reusable hydroxyapatite nanocrystal sensors for protein adsorption

Directory of Open Access Journals (Sweden)

Motohiro Tagaya, Toshiyuki Ikoma, Nobutaka Hanagata, Dinko Chakarov, Bengt Kasemo and Junzo Tanaka

2010-01-01

Full Text Available 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.

Band structure of CdTe under high pressure

International Nuclear Information System (INIS)

Jayam, Sr. Gerardin; Nirmala Louis, C.; Amalraj, A.

2005-01-01

The band structures and density of states of cadmium telluride (CdTe) under various pressures ranging from normal to 4.5 Mbar are obtained. The electronic band structure at normal pressure of CdTe (ZnS structure) is analyzed and the direct band gap value is found to be 1.654 eV. CdTe becomes metal and superconductor under high pressure but before that it undergoes structural phase transition from ZnS phase to NaCl phase. The equilibrium lattice constant, bulk modulus and the phase transition pressure at which the compounds undergo structural phase transition from ZnS to NaCl are predicted from the total energy calculations. The density of states at the Fermi level (N(E F )) gets enhanced after metallization, which leads to the superconductivity in CdTe. In our calculation, the metallization pressure (P M = 1.935 Mbar) and the corresponding reduced volume ((V/V 0 ) M = 0.458) are estimated. Metallization occurs via direct closing of band gap at Γ point. (author)

Low-Temperature Processed Ga-Doped ZnO Coatings from Colloidal Inks

KAUST Repository

Della Gaspera, Enrico

2013-03-06

We present a new colloidal synthesis of gallium-doped zinc oxide nanocrystals that are transparent in the visible and absorb in the near-infrared. Thermal decomposition of zinc stearate and gallium nitrate after hot injection of the precursors in a mixture of organic amines leads to nanocrystals with tunable properties according to gallium amount. Substitutional Ga3+ ions trigger a plasmonic resonance in the infrared region resulting from an increase in the free electrons concentration. These nanocrystals can be deposited by spin coating, drop casting, and spray coating resulting in homogeneous and high-quality thin films. The optical transmission of the Ga-ZnO nanoparticle assemblies in the visible is greater than 90%, and at the same time, the near-infrared absorption of the nanocrystals is maintained in the films as well. Several strategies to improve the films electrical and optical properties have been presented, such as UV treatments to remove the organic compounds responsible for the observed interparticle resistance and reducing atmosphere treatments on both colloidal solutions and thin films to increase the free carriers concentration, enhancing electrical conductivity and infrared absorption. The electrical resistance of the nanoparticle assemblies is about 30 kΩ/sq for the as-deposited, UV-exposed films, and it drops down to 300 Ω/sq after annealing in forming gas at 450 °C, comparable with state of the art tin-doped indium oxide coatings deposited from nanocrystal inks. © 2013 American Chemical Society.

Synthesis and characterization of CdTe quantum dots by one-step method

Directory of Open Access Journals (Sweden)

H. Li

2013-09-01

Full Text Available L-Cysteine (Cys-capped CdTe quantum dots (QDs were prepared when sodium tellurite worked as a tellurium source and sodium borohydride acted as a reductant. The influences of various experimental variables, including pH values, Cd/Te and Cd/Cys molar ratios, on the photoluminescence (PL quantum yield (QY of the obtained CdTe QDs have been systematically investigated. Experimental results indicated that green to red emitting CdTe QDs with maximum quantum yield of 19.4% can be prepared at pH 11.5 and n(Cd2+:n(Te2−:n(Cys = 1:0.07:2.0. X-Ray powder diffraction (XRD and transmission electron microscopy (TEM were used to characterize the crystal structure and shape of CdTe QDs. The results showed that the prepared CdTe QDs were of cubic zinc blend crystal structure in a sphere-like shape.DOI: http://dx.doi.org/10.4314/bcse.v27i3.7

Structure/Processing Relationships of Highly Ordered Lead Salt Nanocrystal Superlattices

KAUST Repository

Hanrath, Tobias; Choi, Joshua J.; Smilgies, Detlef-M.

2009-01-01

We investigated the influence of processing conditions, nanocrystal/substrate interactions and solvent evaporation rate on the ordering of strongly interacting nanocrystals by synergistically combining electron microscopy and synchrotron-based small-angle X-ray scattering analysis. Spin-cast PbSe nanocrystal films exhibited submicrometer-sized supracrystals with face-centered cubic symmetry and (001)s planes aligned parallel to the substrate. The ordering of drop-cast lead salt nanocrystal films was sensitive to the nature of the substrate and solvent evaporation dynamics. Nanocrystal films drop-cast on rough indium tin oxide substrates were polycrystalline with small grain size and low degree of orientation with respect to the substrate, whereas films drop-cast on flat Si substrates formed highly ordered face-centered cubic supracrystals with close-packed (111)s planes parallel to the substrate. The spatial coherence of nanocrystal films drop-cast in the presence of saturated solvent vapor was significantly improved compared to films drop-cast in a dry environment. Solvent vapor annealing was demonstrated as a postdeposition technique to modify the ordering of nanocrystals in the thin film. Octane vapor significantly improved the long-range order and degree of orientation of initially disordered or polycrystalline nanocrystal assemblies. Exposure to 1,2-ethanedithiol vapor caused partial displacement of surface bound oleic acid ligands and drastically degraded the degree of order in the nanocrystal assembly. © 2009 American Chemical Society.

Structure/Processing Relationships of Highly Ordered Lead Salt Nanocrystal Superlattices

KAUST Repository

Hanrath, Tobias

2009-10-27

We investigated the influence of processing conditions, nanocrystal/substrate interactions and solvent evaporation rate on the ordering of strongly interacting nanocrystals by synergistically combining electron microscopy and synchrotron-based small-angle X-ray scattering analysis. Spin-cast PbSe nanocrystal films exhibited submicrometer-sized supracrystals with face-centered cubic symmetry and (001)s planes aligned parallel to the substrate. The ordering of drop-cast lead salt nanocrystal films was sensitive to the nature of the substrate and solvent evaporation dynamics. Nanocrystal films drop-cast on rough indium tin oxide substrates were polycrystalline with small grain size and low degree of orientation with respect to the substrate, whereas films drop-cast on flat Si substrates formed highly ordered face-centered cubic supracrystals with close-packed (111)s planes parallel to the substrate. The spatial coherence of nanocrystal films drop-cast in the presence of saturated solvent vapor was significantly improved compared to films drop-cast in a dry environment. Solvent vapor annealing was demonstrated as a postdeposition technique to modify the ordering of nanocrystals in the thin film. Octane vapor significantly improved the long-range order and degree of orientation of initially disordered or polycrystalline nanocrystal assemblies. Exposure to 1,2-ethanedithiol vapor caused partial displacement of surface bound oleic acid ligands and drastically degraded the degree of order in the nanocrystal assembly. © 2009 American Chemical Society.

Spin dynamics in bulk CdTe at room temperature

International Nuclear Information System (INIS)

Nahalkova, P.; Nemec, P.; Sprinzl, D.; Belas, E.; Horodysky, P.; Franc, J.; Hlidek, P.; Maly, P.

2006-01-01

In this paper, we report on the room temperature dynamics of spin-polarized carriers in undoped bulk CdTe. Platelets of CdTe with different concentration of preparation-induced dislocations were prepared by combining the mechanical polishing and chemical etching. Using the polarization-resolved pump-probe experiment in transmission geometry, we have observed a systematic decrease of both the signal polarization and the electron spin dephasing time (from 52 to 36 ps) with the increased concentration of defects. We have suggested that the Elliot-Yafet mechanism might be the dominant spin dephasing mechanism in platelets of CdTe at room temperature

A facile route to shape controlled CdTe nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Mntungwa, Nhlakanipho; Rajasekhar, Pullabhotla V.S.R. [Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa 3886, Empangeni, KZN (South Africa); Revaprasadu, Neerish, E-mail: nrevapra@pan.uzulu.ac.za [Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa 3886, Empangeni, KZN (South Africa)

2011-04-15

Research highlights: {yields} A facile hybrid solution based/thermolysis route has been used for the synthesis of hexadecylamine capped CdTe nanoparticles. {yields} This method involves the reaction by the addition of an aqueous suspension of a cadmium salt to a freshly prepared NaHTe solution. {yields} The cadmium salt plays an important role in the growth mechanism of the particles and hence its final morphology. - Abstract: Hexadecylamine (HDA) capped CdTe nanoparticles have been synthesized using a facile hybrid solution based/thermolysis route. This method involves the reaction by the addition of an aqueous suspension or solution of a cadmium salt (chloride, acetate, nitrate or carbonate) to a freshly prepared NaHTe solution. The isolated CdTe was then dispersed in tri-octylphosphine (TOP) and injected into pre-heated HDA at temperatures of 190, 230 and 270 deg. C for 2 h. The particle growth and size distribution of the CdTe particles synthesized using cadmium chloride as the cadmium source were monitored using absorption and photoluminescence spectroscopy. The final morphology of the CdTe nanoparticles synthesized from the various cadmium sources was studied by transmission electron microscopy (TEM) and high resolution TEM. The cadmium source has an influence on the final morphology of the particles.

A facile route to shape controlled CdTe nanoparticles

International Nuclear Information System (INIS)

Mntungwa, Nhlakanipho; Rajasekhar, Pullabhotla V.S.R.; Revaprasadu, Neerish

2011-01-01

Research highlights: → A facile hybrid solution based/thermolysis route has been used for the synthesis of hexadecylamine capped CdTe nanoparticles. → This method involves the reaction by the addition of an aqueous suspension of a cadmium salt to a freshly prepared NaHTe solution. → The cadmium salt plays an important role in the growth mechanism of the particles and hence its final morphology. - Abstract: Hexadecylamine (HDA) capped CdTe nanoparticles have been synthesized using a facile hybrid solution based/thermolysis route. This method involves the reaction by the addition of an aqueous suspension or solution of a cadmium salt (chloride, acetate, nitrate or carbonate) to a freshly prepared NaHTe solution. The isolated CdTe was then dispersed in tri-octylphosphine (TOP) and injected into pre-heated HDA at temperatures of 190, 230 and 270 deg. C for 2 h. The particle growth and size distribution of the CdTe particles synthesized using cadmium chloride as the cadmium source were monitored using absorption and photoluminescence spectroscopy. The final morphology of the CdTe nanoparticles synthesized from the various cadmium sources was studied by transmission electron microscopy (TEM) and high resolution TEM. The cadmium source has an influence on the final morphology of the particles.

Predicting Nanocrystal Shape through Consideration of Surface-Ligand Interactions

KAUST Repository

Bealing, Clive R.; Baumgardner, William J.; Choi, Joshua J.; Hanrath, Tobias; Hennig, Richard G.

2012-01-01

Density functional calculations for the binding energy of oleic acid-based ligands on Pb-rich {100} and {111} facets of PbSe nanocrystals determine the surface energies as a function of ligand coverage. Oleic acid is expected to bind

Preparation of Rhodamine B Fluorescent Poly(methacrylic acid) Coated Gelatin Nanoparticles

OpenAIRE

Gan, Zhenhai; Ju, Jianhui; Zhang, Ting; Wu, Daocheng

2011-01-01

Poly(methacrylic acid) (PMAA)-coated gelatin nanoparticles encapsulated with fluorescent dye rhodamine B were prepared by the coacervation method with the aim to retard the release of rhodamine B from the gelatin matrix. With sodium sulfate as coacervation reagent for gelatin, a kind of biopolymer with excellent biocompatibility, the formed gelatin nanoparticles were cross-linked by formaldehyde followed by the polymerization of methacrylic acid coating. The fluorescent poly(methacrylic acid)...

Interaction and energy transfer studies between bovine serum albumin and CdTe quantum dots conjugates: CdTe QDs as energy acceptor probes.

Science.gov (United States)

Kotresh, M G; Inamdar, L S; Shivkumar, M A; Adarsh, K S; Jagatap, B N; Mulimani, B G; Advirao, G M; Inamdar, S R

2017-06-01

In this paper, a systematic investigation of the interaction of bovine serum albumin (BSA) with water-soluble CdTe quantum dots (QDs) of two different sizes capped with carboxylic thiols is presented based on steady-state and time-resolved fluorescence measurements. Efficient Förster resonance energy transfer (FRET) was observed to occur from BSA donor to CdTe acceptor as noted from reduction in the fluorescence of BSA and enhanced fluorescence from CdTe QDs. FRET parameters such as Förster distance, spectral overlap integral, FRET rate constant and efficiency were determined. The quenching of BSA fluorescence in aqueous solution observed in the presence of CdTe QDs infers that fluorescence resonance energy transfer is primarily responsible for the quenching phenomenon. Bimolecular quenching constant (k q ) determined at different temperatures and the time-resolved fluorescence data provide additional evidence for this. The binding stoichiometry and various thermodynamic parameters are evaluated by using the van 't Hoff equation. The analysis of the results suggests that the interaction between BSA and CdTe QDs is entropy driven and hydrophobic forces play a key role in the interaction. Binding of QDs significantly shortened the fluorescence lifetime of BSA which is one of the hallmarks of FRET. The effect of size of the QDs on the FRET parameters are discussed in the light of FRET parameters obtained. Copyright © 2016 John Wiley & Sons, Ltd.

Cellulose nanocrystal-filled poly(acrylic acid) nanocomposite fibrous membranes

International Nuclear Information System (INIS)

Lu Ping; Hsieh, You-Lo

2009-01-01

Nanocomposite fibrous membranes have been fabricated by electrospinning cellulose nanocrystal (CNC)-loaded poly(acrylic acid) (PAA) ethanol mixtures. Incorporating CNC in PAA significantly reduced fiber diameters and improved fiber uniformity. The average diameters of the as-spun nanocomposite fibers were significantly reduced from 349 nm to 162 nm, 141 nm, 90 nm and 69 nm at 5%, 10%, 15% and 20% CNC loading (by weight of a constant 4% PAA solution), respectively. CNC was well dispersed in the fibers as isolated rods oriented along the fiber axis and as spheres in the PAA matrix. The Young modulus and stress of the PAA/CNC nanocomposite fibers were significantly improved with increasing CNC loadings by up to 35-fold and 16-fold, respectively. Heat-induced esterification between the CNC surface hydroxyls and PAA carboxyl groups produced covalent crosslinks at the CNC-PAA interfaces, rendering the nanocomposite fibrous membranes insoluble in water, more thermally stable and far more superior in tensile strength. With 20% CNC, the crosslinked nanocomposite fibrous membrane exhibited a very impressive 77-fold increase in modulus and 58-fold increase in stress.

[Oxidative damage effects induced by CdTe quantum dots in mice].

Science.gov (United States)

Xie, G Y; Chen, W; Wang, Q K; Cheng, X R; Xu, J N; Huang, P L

2017-07-20

Objective: To investigate Oxidative damage effects induced by CdTe Quantum Dots (QDs) in mice. Methods: 40 ICR mice were randomly divided into 5 groups: one control group (normal saline) ; four CdTe QDs (exposed by intravenous injection of 0.2 ml of CdTe QDs at the concentration of 0、0.5、5.0、50.0 and 500.0 nmol/ml respectively) . After 24 h, the mice were decapitated and the blood was collected for serum biochemically indexes、hematology indexes, the activities of SOD、GSH-Px and the concentration of MDA were all detected. Results: The results showed in the four CdTe QDs exposure groups, the level of CRE、PLT and the concentration of MDA were all significantly lower than those of the control group ( P control group ( P <0.01) . Conclusion: It was suggested that CdTe QDs at 0.5 nmol/ml could induce Oxidative damage effects in mice.

A comparative guide to controlled hydrophobization of cellulose nanocrystals via surface esterification

Science.gov (United States)

Shane X. Peng; Huibin Chang; Satish Kumar; Robert J. Moon; Jeffrey P. Youngblood

2016-01-01

Surface esterification methods of cellulose nanocrystals (CNC) using acid anhydrides, acid chlorides, acid catalyzed carboxylic acids, and 101-carbonyldiimidazole (CDI) activated carboxylic acids were evaluated with acetyl-, hexanoyl-, dodecanoyl-, oleoyl-, and methacryloyl-functionalization. Their grafting efficiency was investigated using Fouriertransform infrared...

Semiconductor nanocrystals dispersed in imidazolium-based ionic liquids: a spectroscopic and morphological investigation

International Nuclear Information System (INIS)

Panniello, Annamaria; Binetti, Enrico; Ingrosso, Chiara; Curri, M. Lucia; Agostiano, Angela; Tommasi, Raffaele; Striccoli, Marinella

2013-01-01

A growing interest is devoted to the study of imidazolium-based ionic liquids as innovative materials to combine with functional elements for advanced technological applications. Materials based on semiconductor and oxide nanocrystals in ionic liquids can be promising for their integration in lithium batteries, as well as in innovative solar cells. Although the physical chemical properties and the solvation dynamics of bare ionic liquids have been extensively studied, their combination with colloidal nanocrystals still remains almost unexplored. Here, the optical properties of organic-capped luminescent cadmium selenide nanocrystals coated by a shell of zinc sulfide (CdSe(ZnS)) dispersed in 1,3-dialkyl imidazolium ionic liquids have been investigated, also in dependence of the alkyl chain length on the imidazolium ring and of the anion nature, by using both time-integrated and time-resolved optical spectroscopy. The observed variations in decay profiles of the ionic liquid in presence of colloidal nanocrystals suggest that the dispersion of the nanostructures induces modifications in the ionic liquid structural order. Finally, atomic force microscopy analysis has provided insight into the topography of the investigated dispersions deposited as film, confirming the organization of the ionic liquids in super-structures, also upon nanocrystal incorporation.

Colloidal CuInSe2 nanocrystals thin films of low surface roughness

Science.gov (United States)

de Kergommeaux, Antoine; Fiore, Angela; Faure-Vincent, Jérôme; Pron, Adam; Reiss, Peter

2013-03-01

Thin-film processing of colloidal semiconductor nanocrystals (NCs) is a prerequisite for their use in (opto-)electronic devices. The commonly used spin-coating is highly materials consuming as the overwhelming amount of deposited matter is ejected from the substrate during the spinning process. Also, the well-known dip-coating and drop-casting procedures present disadvantages in terms of the surface roughness and control of the film thickness. We show that the doctor blade technique is an efficient method for preparing nanocrystal films of controlled thickness and low surface roughness. In particular, by optimizing the deposition conditions, smooth and pinhole-free films of 11 nm CuInSe2 NCs have been obtained exhibiting a surface roughness of 13 nm root mean square (rms) for a 350 nm thick film, and less than 4 nm rms for a 75 nm thick film. Invited talk at the 6th International Workshop on Advanced Materials Science and Nanotechnology, 30 October-2 November 2012, Ha Long, Vietnam.

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 (alcohols were used to study the effect of size and morphological control over the nanocrystals. Techniques including X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and high-resolution electron microscopy are used to examine crystallinity and morphology. Chapter 3. By investigating the self-assembly of cadmium selenide-gold (CdSe-Au) nanoparticle mixtures by transmission electron microscopy after solvent evaporation, the effect of solvents in the formation process of CdSe-Au binary nanoparticle superlattices (BNSLs) was studied. 1-dodecanethiol was found to be critical in generating conditions necessary for superlattice formation, prior to the other factors that likely determine structure, highlighting the dual role of this organic polar molecule as both ligand and high boiling point/crystallization solvent. The influence of thiol was investigated under various concentrations (and also

Leaching of cadmium and tellurium from cadmium telluride (CdTe) thin-film solar panels under simulated landfill conditions

Science.gov (United States)

Ramos-Ruiz, Adriana; Wilkening, Jean V.; Field, James A.; Sierra-Alvarez, Reyes

2017-01-01

A crushed non-encapsulated CdTe thin-film solar cell was subjected to two standardized batch leaching tests (i.e., Toxicity Characteristic Leaching Procedure (TCLP) and California Waste Extraction Test (WET)) and to a continuous-flow column test to assess cadmium (Cd) and tellurium (Te) dissolution under conditions simulating the acidic- and the methanogenic phases of municipal solid waste landfills. Low levels of Cd and Te were solubilized in both batch leaching tests (leaching behavior of CdTe in the columns is related to different aqueous pH and redox conditions promoted by the microbial communities in the columns, and is in agreement with thermodynamic predictions. PMID:28472709

Research on fabrication technology for thin film solar cells for practical use. Research on low-cost fabrication technology for large-area modules (CdS/CdTe solar cell modules); Usumaku taiyo denchi seizo gijutsu no jitsuyoka kenkyu. Daimenseki module no tei cost seizo gijutsu (CdTe taiyo denchi module seizo no gijutsu kaihatsu)

Energy Technology Data Exchange (ETDEWEB)

Tatsuta, M [New Energy and Industrial Technology Development Organization, Tokyo (Japan)

1994-12-01

This paper reports the study results on the fabrication technology of CdS/CdTe solar cell modules in fiscal 1994. (1) On the fabrication technology for high-efficiency large-area solar cells, high-quality CdTe active layer was studied. S content taken in the active layer at sintering of CdTe decreased with an increase in formed CdTe, resulting in improvement of Voc of cells. (2) On the window layer with wide band gap, the solar cell superior in collection efficiency and photoelectric characteristics could be obtained using the newly developed mixed crystal film of Cd(1-x)Zn(x)S. (3) On the forming technology of large-area coating/sintering films, improvement of CdS film quality was studied by pressurized processing of printed CdS films. As a result, improvement of film density and light transmissivity was confirmed. (4) On the leveling process technology of CdTe films, smooth surface films were obtained by experiment using an equipment simultaneously exciting samples in all directions as one of uniform coating methods of films. 7 figs.

Diffusion cell investigations into the acidic degradation of organic coatings

DEFF Research Database (Denmark)

Møller, Victor Buhl; Wang, Ting; Dam-Johansen, Kim

2018-01-01

Protective organic coatings work by preventing contact between an aggressive environment and a vulnerable substrate. However, the long required lifetime of a barrier coating provides a challenge when attempting to evaluate coating performance. Diffusion cells can be used as a tool to estimate...... coating barrier properties and lifetime. In this work, a diffusion cell array was designed, constructed, and compared to previous designs, with simplicity being the most important design parameter. Sulfuric acid diffusion through five different coatings was monitored using a battery of cells...

Simultaneous acid exposure and erosive particle wear of thermoset coatings

DEFF Research Database (Denmark)

Møller, Victor Buhl; Dam-Johansen, Kim; Frankær, Sarah Maria

2018-01-01

, similar to the erosion/corrosion-type phenomena found in metals. A vinyl ester-based coating was the most resistant to the simultaneous erosive/acidic exposure, with a maximum polishing rate of 3.24±0.61 μm/week, while novolac epoxy and polyurethane coatings showed high polishing rates of 11.7±1.50 and 13.4±0......Handling acidic chemicals is a challenge in the chemical industry, requiring a careful choice of contact material. Certain thermoset organic coatings are applicable in low pH environments, but when particulate erosion is also present the performance demand is increased. This is the case in, e...

Anti-reflection coatings applied by acid leaching process

Science.gov (United States)

Pastirik, E.

1980-01-01

The Magicote C process developed by S.M. Thompsen was evaluated for use in applying an antireflective coating to the cover plates of solar panels. The process uses a fluosilicic acid solution supersaturated with silica at elevated temperature to selectively attack the surface of soda-lime glass cover plates and alter the physical and chemical composition of a thin layer of glass. The altered glass layer constitutes an antireflective coating. The process produces coatings of excellent optical quality which possess outstanding resistance to soiling and staining. The coatings produced are not resistant to mechanical abrasion and are attacked to some extent by glass cleansers. Control of the filming process was found to be difficult.

Revealing the nanostructure of calcium phosphate coatings using HRTEM/FIB techniques

International Nuclear Information System (INIS)

Solla, E.L.; Rodríguez-González, B.; Aguiar, H.; Rodríguez-Valencia, C.; Serra, J.; González, P.

2016-01-01

Herein, we report on the micro- and nanostructure of the calcium phosphate coating produced by pulsed laser deposition (PLD), using focused ion beam (FIB) lamella sample preparation and transmission electron microscopy (TEM) as the characterization technique. The initial selected area electron diffraction (SAED) data demonstrated the presence of hydroxyapatite (HA) over any other possible calcium phosphate crystalline structure and the polycrystalline nature of the coating. Moreover, the SAED analyses showed clear textured ring patterns coherent with the presence of a preferred orientation in the HA nano-crystal growth. The SAED data also indicated that the coating appears to be textured in the 〈002〉 crystalline direction. Dark-field images obtained using 002 as the working reflection showed a clear oriented crystal growth in columns, from bottom to top. These columns have a peculiar arrangement of nano-crystals since, in some cases, the preferred orientation appears to start at a certain distance from the substrate. Direct d-spacing measurements on high-resolution TEM images provided further proof of the presence of an HA nano-crystal structure. The reported data may be of interest in the future to adjust the microstructure of the HA coatings. - Highlights: •The FIB lift-out technique allows a very site-specific sample preparation method for HRTEM analysis. •It also permits a fast assessment of the HA coating thickness and elemental composition (EDS). •The coatings exhibit a nano-crystalline nature, with a texturing effect along the 002 planes. •PLD is suitable for the production of crystalline c-axis oriented hydroxyapatite coatings. •The crystalline HA phase in the PLD coating is very similar to the present in bone.

Revealing the nanostructure of calcium phosphate coatings using HRTEM/FIB techniques

Energy Technology Data Exchange (ETDEWEB)

Solla, E.L., E-mail: esolla@uvigo.es [Servicio de Microscopía Electrónica, CACTI, University of Vigo, Campus As Lagoas-Marcosende, 36310 Vigo (Spain); Rodríguez-González, B. [Servicio de Microscopía Electrónica, CACTI, University of Vigo, Campus As Lagoas-Marcosende, 36310 Vigo (Spain); Aguiar, H.; Rodríguez-Valencia, C.; Serra, J.; González, P. [Applied Physics Department, School of Industrial Engineering, University of Vigo, Campus As Lagoas-Marcosende, 36310 Vigo (Spain)

2016-12-15

Herein, we report on the micro- and nanostructure of the calcium phosphate coating produced by pulsed laser deposition (PLD), using focused ion beam (FIB) lamella sample preparation and transmission electron microscopy (TEM) as the characterization technique. The initial selected area electron diffraction (SAED) data demonstrated the presence of hydroxyapatite (HA) over any other possible calcium phosphate crystalline structure and the polycrystalline nature of the coating. Moreover, the SAED analyses showed clear textured ring patterns coherent with the presence of a preferred orientation in the HA nano-crystal growth. The SAED data also indicated that the coating appears to be textured in the 〈002〉 crystalline direction. Dark-field images obtained using 002 as the working reflection showed a clear oriented crystal growth in columns, from bottom to top. These columns have a peculiar arrangement of nano-crystals since, in some cases, the preferred orientation appears to start at a certain distance from the substrate. Direct d-spacing measurements on high-resolution TEM images provided further proof of the presence of an HA nano-crystal structure. The reported data may be of interest in the future to adjust the microstructure of the HA coatings. - Highlights: •The FIB lift-out technique allows a very site-specific sample preparation method for HRTEM analysis. •It also permits a fast assessment of the HA coating thickness and elemental composition (EDS). •The coatings exhibit a nano-crystalline nature, with a texturing effect along the 002 planes. •PLD is suitable for the production of crystalline c-axis oriented hydroxyapatite coatings. •The crystalline HA phase in the PLD coating is very similar to the present in bone.

Synthesis and characterization of TGA-capped CdTe nanoparticles embedded in PVA matrix

Energy Technology Data Exchange (ETDEWEB)

Tripathi, S.K.; Kaur, Ramneek; Sharma, Mamta [Panjab University, Department of Physics, Center of Advanced Study in Physics, Chandigarh (India)

2014-10-25

This paper reports the synthesis and characterization of TGA-capped CdTe nanoparticles and its nanocomposite in a PVA matrix prepared by ex situ technique. The crystallite sizes of the CdTe nanoparticles and nanocomposite calculated from X-ray diffraction patterns are 6.07 and 7.75 nm with hexagonal structure, respectively. The spherical nature of the CdTe nanoparticles is confirmed from transmission electron microscopy measurements. Fourier transform infrared spectroscopy shows good interaction between the CdTe nanoparticles and PVA matrix. The absorption and emission spectra have also been studied. The stability of the TGA-capped CdTe nanoparticles increases after dispersion in a PVA matrix. In electrical measurements, the dark conductivity and the steady-state photoconductivity of CdTe nanocomposite thin films have been studied. The effect of temperature and intensity on the transient photoconductivity of CdTe nanocomposite is also studied. The values of differential life time have been calculated from the decay of photocurrent with time. The non-exponential decay of photoconductivity is observed indicating that the traps exist at all the energies in the band gap, making these materials suitable for various optoelectronic devices. (orig.)

Synthesis and characterization of TGA-capped CdTe nanoparticles embedded in PVA matrix

International Nuclear Information System (INIS)

Tripathi, S.K.; Kaur, Ramneek; Sharma, Mamta

2015-01-01

This paper reports the synthesis and characterization of TGA-capped CdTe nanoparticles and its nanocomposite in a PVA matrix prepared by ex situ technique. The crystallite sizes of the CdTe nanoparticles and nanocomposite calculated from X-ray diffraction patterns are 6.07 and 7.75 nm with hexagonal structure, respectively. The spherical nature of the CdTe nanoparticles is confirmed from transmission electron microscopy measurements. Fourier transform infrared spectroscopy shows good interaction between the CdTe nanoparticles and PVA matrix. The absorption and emission spectra have also been studied. The stability of the TGA-capped CdTe nanoparticles increases after dispersion in a PVA matrix. In electrical measurements, the dark conductivity and the steady-state photoconductivity of CdTe nanocomposite thin films have been studied. The effect of temperature and intensity on the transient photoconductivity of CdTe nanocomposite is also studied. The values of differential life time have been calculated from the decay of photocurrent with time. The non-exponential decay of photoconductivity is observed indicating that the traps exist at all the energies in the band gap, making these materials suitable for various optoelectronic devices. (orig.)

Aqueous-Processed Inorganic Thin-Film Solar Cells Based on CdSe(x)Te(1-x) Nanocrystals: The Impact of Composition on Photovoltaic Performance.

Science.gov (United States)

Zeng, Qingsen; Chen, Zhaolai; Zhao, Yue; Du, Xiaohang; Liu, Fangyuan; Jin, Gan; Dong, Fengxia; Zhang, Hao; Yang, Bai

2015-10-21

Aqueous processed nanocrystal (NC) solar cells are attractive due to their environmental friendliness and cost effectiveness. Controlling the bandgap of absorbing layers is critical for achieving high efficiency for single and multijunction solar cells. Herein, we tune the bandgap of CdTe through the incorporation of Se via aqueous process. The photovoltaic performance of aqueous CdSexTe1-x NCs is systematically investigated, and the impacts of charge generation, transport, and injection on device performance for different compositions are deeply discussed. We discover that the performance degrades with the increasing Se content from CdTe to CdSe. This is mainly ascribed to the lower conduction band (CB) of CdSexTe1-x with higher Se content, which reduces the driving force for electron injection into TiO2. Finally, the performance is improved by mixing CdSexTe1-x NCs with conjugated polymer poly(p-phenylenevinylene) (PPV), and power conversion efficiency (PCE) of 3.35% is achieved based on ternary NCs. This work may provide some information to further optimize the aqueous-processed NC and hybrid solar cells.

Luminescence of polyethylene glycol coated CdSeTe/ZnS and InP/ZnS nanoparticles in the presence of copper cations.

Science.gov (United States)

Beaune, Grégory; Tamang, Sudarsan; Bernardin, Aude; Bayle-Guillemaud, Pascale; Fenel, Daphna; Schoehn, Guy; Vinet, Françoise; Reiss, Peter; Texier, Isabelle

2011-08-22

The use of click chemistry for quantum dot (QD) functionalization could be very promising for the development of bioconjugates dedicated to in vivo applications. Alkyne-azide ligation usually requires copper(I) catalysis. The luminescence response of CdSeTe/ZnS nanoparticles coated with polyethylene glycol (PEG) is studied in the presence of copper cations, and compared to that of InP/ZnS QDs coated with mercaptoundecanoic acid (MUA). The quenching mechanisms appear different. Luminescence quenching occurs without any wavelength shift in the absorption and emission spectra for the CdSeTe/ZnS/PEG nanocrystals. In this case, the presence of copper in the ZnS shell is evidenced by energy-filtered transmission electron microscopy (EF-TEM). By contrast, in the case of InP/ZnS/MUA nanocrystals, a redshift of the excitation and emission spectra, accompanied by an increase in absorbance and a decrease in photoluminescence, is observed. For CdSeTe/ZnS/PEG nanocrystals, PL quenching is enhanced for QDs with 1) smaller inorganic-core diameter, 2) thinner PEG shell, and 3) hydroxyl terminal groups. Whereas copper-induced PL quenching can be interesting for the design of sensitive cation sensors, copper-free click reactions should be used for the efficient functionalization of nanocrystals dedicated to bioapplications, in order to achieve highly luminescent QD bioconjugates. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of Rhodamine B Fluorescent Poly(methacrylic acid Coated Gelatin Nanoparticles

Directory of Open Access Journals (Sweden)

Zhenhai Gan

2011-01-01

Full Text Available Poly(methacrylic acid (PMAA-coated gelatin nanoparticles encapsulated with fluorescent dye rhodamine B were prepared by the coacervation method with the aim to retard the release of rhodamine B from the gelatin matrix. With sodium sulfate as coacervation reagent for gelatin, a kind of biopolymer with excellent biocompatibility, the formed gelatin nanoparticles were cross-linked by formaldehyde followed by the polymerization of methacrylic acid coating. The fluorescent poly(methacrylic acid coated gelatin (FPMAAG nanoparticles had a uniform spherical shape and a size distribution of 60±5 nm. Infrared spectral analysis confirmed the formation of PMAA coating on the gelatin nanoparticles. Based on UV-Vis spectra, the loading efficiency of rhodamine B for the FPMAAG nanoparticles was 0.26 μg per mg nanoparticles. The encapsulated rhodamine B could sustain for two weeks. Favorable fluorescence property and fluorescence imaging of cells confirmed that the FPMAAG nanoparticles have promising biochemical, bioanalytical, and biomedical applications.

Investigation of the photoluminescence properties of thermochemically synthesized CdS nanocrystals

Directory of Open Access Journals (Sweden)

M. Molaei

2011-03-01

Full Text Available In this work we have synthesized CdS nanocrystals with thermochemical method. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA was used as capping agent molecule. The structure and optical property of the nanocrystals were characterized by means of XRD, TEM, UV-visible optical spectroscopy and photoluminescence (PL. X-ray diffraction (XRD and TEM analyses demonstrated hexagonal phase CdS nanocrystals with an average size around 2 nm. Synthesized nanocrystals exhibited band gap of about 3.2 eV and showed a broad band emission from 400-750 nm centered at 504 nm with a (0.27, 0.39 CIE coordinate. This emission can be attributed to recombination of an electron in conduction band with a hole trapped in Cd vacancies near to the valance band of CdS. The best attained photoluminescence quantum yield of the nanocrystals was about 12%, this amount is about 20 times higher than that for thioglycerol (TG capped CdS nanocrystals.

Thermoset coatings from epoxidized sucrose soyate and blocked, bio-based dicarboxylic acids.

Science.gov (United States)

Kovash, Curtiss S; Pavlacky, Erin; Selvakumar, Sermadurai; Sibi, Mukund P; Webster, Dean C

2014-08-01

A new 100% bio-based thermosetting coating system was developed from epoxidized sucrose soyate crosslinked with blocked bio-based dicarboxylic acids. A solvent-free, green method was used to block the carboxylic acid groups and render the acids miscible with the epoxy resin. The thermal reversibility of this blocking allowed for the formulation of epoxy-acid thermoset coatings that are 100% bio-based. This was possible due to the volatility of the vinyl ethers under curing conditions. These systems have good adhesion to metal substrates and perform well under chemical and physical stress. Additionally, the hardness of the coating system is dependent on the chain length of the diacid used, making it tunable. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Doping of polycrystalline CdTe for high-efficiency solar cells on flexible metal foil.

Science.gov (United States)

Kranz, Lukas; Gretener, Christina; Perrenoud, Julian; Schmitt, Rafael; Pianezzi, Fabian; La Mattina, Fabio; Blösch, Patrick; Cheah, Erik; Chirilă, Adrian; Fella, Carolin M; Hagendorfer, Harald; Jäger, Timo; Nishiwaki, Shiro; Uhl, Alexander R; Buecheler, Stephan; Tiwari, Ayodhya N

2013-01-01

Roll-to-roll manufacturing of CdTe solar cells on flexible metal foil substrates is one of the most attractive options for low-cost photovoltaic module production. However, various efforts to grow CdTe solar cells on metal foil have resulted in low efficiencies. This is caused by the fact that the conventional device structure must be inverted, which imposes severe restrictions on device processing and consequently limits the electronic quality of the CdTe layer. Here we introduce an innovative concept for the controlled doping of the CdTe layer in the inverted device structure by means of evaporation of sub-monolayer amounts of Cu and subsequent annealing, which enables breakthrough efficiencies up to 13.6%. For the first time, CdTe solar cells on metal foil exceed the 10% efficiency threshold for industrialization. The controlled doping of CdTe with Cu leads to increased hole density, enhanced carrier lifetime and improved carrier collection in the solar cell. Our results offer new research directions for solving persistent challenges of CdTe photovoltaics.

A facile single injection Hydrothermal method for the synthesis of thiol capped CdTe Quantum dots as light harvesters

Energy Technology Data Exchange (ETDEWEB)

Jai Kumar, B.; Sumanth Kumar, D.; Mahesh, H.M., E-mail: hm_mahesh@rediffmail.com

2016-10-15

A facile, Single Injection Hydrothermal (SIH) method has been developed to synthesize high quality 3-Mercaptopropionic Acid (MPA) stabilized aqueous CdTe QDs, entirely in ambient environment. The synthesis protocol eliminates the use of inert atmosphere for reducing elemental Tellurium powder to Te precursor avoiding the oxidation of Te powder. The XRD result revealed that the synthesized QDs are in cubic zincblende type crystalline structure, without signature of Te oxidation. FTIR spectra have confirmed the attachment of short chained organic compound MPA to the surface of QDs by covalent bond. The Quantum confinement effect was clearly evident by shift in Longitudinal Optic (LO) peak of Raman spectra and absorption peak wavelength with respect to bulk CdTe materials. The optical direct band gap energy of CdTe QDs is between 3.63 eV to 1.96 eV and QDs size below 6 nm, confirm the QDs are well under strong Quantum confinement regime. Also, photoluminescence spectra depict a stable and high luminescence emission from green to dark red color. All these results corroborate that the synthesis of CdTe QDs procedure is very advantageous and present a simple, economical and easily up scalable method for large scale production.

Facile Synthesis of Colloidal CuO Nanocrystals for Light-Harvesting Applications

KAUST Repository

Lim, Yee-Fun; Choi, Joshua J.; Hanrath, Tobias

2012-01-01

CuO is an earth-abundant, nontoxic, and low band-gap material; hence it is an attractive candidate for application in solar cells. In this paper, a synthesis of CuO nanocrystals by a facile alcohothermal route is reported. The nanocrystals are dispersible in a solvent mixture of methanol and chloroform, thus enabling the processing of CuO by solution. A bilayer solar cell comprising of CuO nanocrystals and phenyl-C61-butyric acid methyl ester (PCBM) achieved a power conversion efficiency of 0.04%, indicating the potential of this material for light-harvesting applications.

Photoluminescence of hydrophilic silicon nanocrystals in aqueous solutions

International Nuclear Information System (INIS)

Prtljaga, Nikola; D'Amato, Elvira; Pitanti, Alessandro; Guider, Romain; Froner, Elena; Larcheri, Silvia; Scarpa, Marina; Pavesi, Lorenzo

2011-01-01

Stable aqueous solutions of undecylenic-acid-grafted silicon nanocrystals (Si-nc) were prepared. The time evolution of the photoluminescence properties of these hydrophilic silicon nanocrystals has been followed on different timescales (hours and days). On a short timescale (hours), Si-nc tend to agglomerate while the PL lineshape and intensity are stable. Agglomeration can be reduced by using suitable surfactants. On a long timescale (days), oxidation of Si-nc occurs even in the presence of surfactants. These two observations render Si-nc very useful as a labeling agent for biosensing.

Photoluminescence of hydrophilic silicon nanocrystals in aqueous solutions

Science.gov (United States)

Prtljaga, Nikola; D'Amato, Elvira; Pitanti, Alessandro; Guider, Romain; Froner, Elena; Larcheri, Silvia; Scarpa, Marina; Pavesi, Lorenzo

2011-05-01

Stable aqueous solutions of undecylenic-acid-grafted silicon nanocrystals (Si-nc) were prepared. The time evolution of the photoluminescence properties of these hydrophilic silicon nanocrystals has been followed on different timescales (hours and days). On a short timescale (hours), Si-nc tend to agglomerate while the PL lineshape and intensity are stable. Agglomeration can be reduced by using suitable surfactants. On a long timescale (days), oxidation of Si-nc occurs even in the presence of surfactants. These two observations render Si-nc very useful as a labeling agent for biosensing.

Photoluminescence of hydrophilic silicon nanocrystals in aqueous solutions

Energy Technology Data Exchange (ETDEWEB)

Prtljaga, Nikola; D' Amato, Elvira; Pitanti, Alessandro; Guider, Romain; Froner, Elena; Larcheri, Silvia; Scarpa, Marina; Pavesi, Lorenzo, E-mail: nikolap@science.unitn.it [Department of Physics, University of Trento, Via Sommarive 14, I-38123 Trento (Italy)

2011-05-27

Stable aqueous solutions of undecylenic-acid-grafted silicon nanocrystals (Si-nc) were prepared. The time evolution of the photoluminescence properties of these hydrophilic silicon nanocrystals has been followed on different timescales (hours and days). On a short timescale (hours), Si-nc tend to agglomerate while the PL lineshape and intensity are stable. Agglomeration can be reduced by using suitable surfactants. On a long timescale (days), oxidation of Si-nc occurs even in the presence of surfactants. These two observations render Si-nc very useful as a labeling agent for biosensing.

Synthesis of freestanding water-soluble indium oxide nanocrystals capped by alanine nitric acid via ligand exchange for thin film transistors and effects of ligands on the electrical properties

Energy Technology Data Exchange (ETDEWEB)

Choi, Jin-Kyu; Koh, Ye-Seul; Jeong, Hyun-Dam, E-mail: hdjeong@chonnam.ac.kr

2015-07-15

We demonstrate synthesis of freestanding water-soluble indium oxide nanocrystals (In{sub 2}O{sub 3} NCs) by ligand exchange to β-alanine nitric acid (Ala·HNO{sub 3}) and its application for active channel layer in thin film transistors (TFTs), with investigation of the effect of curing temperatures on the TFT properties in terms of thermal behaviour of the ligand molecules at 150, 300, and 350 °C. After ligand exchange from long alkyl ligand (myristic acid, MA) to short Ala·HNO{sub 3}, the mobility of NC TFTs cured at 150 °C increased by over 1 order of magnitude, from 1.3 × 10{sup −4} cm{sup 2}V{sup -1}s{sup −1} to 4.5 × 10{sup −3} cm{sup 2}V{sup -1}s{sup −1}, due to enhanced tunnelling rate (Γ) between adjective NCs. Higher curing temperatures such as 300 and 350 °C, inducing thermal decomposition of the organic ligands, led to further enhancement of the mobility, particularly up to 2.2 cm{sup 2}V{sup -1}s{sup −1} for the In{sub 2}O{sub 3} NC-Ala·HNO{sub 3} TFT cured at 350 °C. It is also found that the ligand exchange of In{sub 2}O{sub 3} NC in acidic condition (e.g. HNO{sub 3}) would be simple and effective to reduce the surface defects by surface etching, which may lead to better device performances. - Graphical abstract: Display Omitted - Highlights: • Freestanding water-soluble In{sub 2}O{sub 3} nanocrystals (NCs) were synthesized by ligand exchange. • Thin film transistors (TFTs) of colloidal NCs were fabricated by spin-coating method. • Water-soluble In{sub 2}O{sub 3} NC TFTs showed higher mobilities due to shorter ligand length. • Surface defects of NCs were notably reduced by surface etching during ligand exchange.

Effects of hydrazine on the solvothermal synthesis of Cu2ZnSnSe4 and Cu2CdSnSe4 nanocrystals for particle-based deposition of films

International Nuclear Information System (INIS)

Chiang, Ming-Hung; Fu, Yaw-Shyan; Shih, Cheng-Hung; Kuo, Chun-Cheng; Guo, Tzung-Fang; Lin, Wen-Tai

2013-01-01

The effects of hydrazine on the synthesis of Cu 2 ZnSnSe 4 (CZTSe) and Cu 2 CdSnSe 4 (CCTSe) nanocrystals in an autoclave as a function of temperature and time were explored. On heating at 190 °C for 24-72 h, pure CZTSe and CCTSe nanocrystals could readily grow in the hydrazine-added solution, while in the hydrazine-free solution the intermediate phases such as ZnSe, Cu 2 Se, and Cu 2 SnSe 3 , and Cu 2 SnSe 3 and CdSe associated with the CZTSe and CCTSe nanocrystals grew, respectively. This result reveals that hydrazine can speed up the synthesis of pure CZTSe and CCTSe nanocrystals via a solvothermal process. The mechanisms for the hydrazine-enhanced growth of CZTSe and CCTSe nanocrystals were discussed. The pure CZTSe and CCTSe nanocrystals were subsequently fabricated to the smooth films by spin coating without further annealing in selenium atmosphere. This processing may be beneficial to the fabrication of the absorber layer for solar cells and thermoelectric devices. - Highlights: • Hydrazine enhances the growth of pure Cu 2 ZnSnSe 4 and Cu 2 CdSnSe 4 nanocrystals. • The nanocrystals can be fabricated to films by spin coating without annealing. • This solvothermal processing is promising for the fabrication of thin film devices

Quantitative analysis of polarization phenomena in CdTe radiation detectors

International Nuclear Information System (INIS)

Toyama, Hiroyuki; Higa, Akira; Yamazato, Masaaki; Maehama, Takehiro; Toguchi, Minoru; Ohno, Ryoichi

2006-01-01

Polarization phenomena in a Schottky-type CdTe radiation detector were studied. We evaluated the distribution of electric field in a biased CdTe detector by measuring the progressive change of Schottky barrier lowering with time. The parameters of deep acceptors such as detrapping time, concentration, and the depth of the energy level were quantitatively evaluated. In the case of applying the conventional model of charge accumulation, the obtained result shows that the CdTe bulk is never undepleted. We modified the charge accumulation model by taking account of the occupation state of the deep acceptor level. When a modified model is applied, the time that the depletion width in the bulk begins to diminish closely fits the time that the photopeak position begins to shift in radiation measurements. In this paper, we present a distribution of electric field during biasing and a simple method for the evaluation of the parameters of deep acceptors in CdTe bulk. (author)

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

RHEED studies of MBE growth mechanisms of CdTe and CdMnTe

Energy Technology Data Exchange (ETDEWEB)

Waag, A.; Behr, T.; Litz, T.; Kuhn-Heinrich, B.; Hommel, D.; Landwehr, G. (Physikalisches Inst., Univ. Wuerzburg (Germany))

1993-01-30

We report on reflection high energy electron diffraction (RHEED) studies of molecular beam epitaxy (MBE) growth of CdTe and CdMnTe on (100) oriented CdTe substrates. RHEED oscillations were measured for both the growth and desorption of CdTe and CdMnTe as a function of flux and temperature. For the first time, the influence of laser and electron irradiation on the growth rate, as well as desorption, of CdTe is studied in detail using RHEED oscillations. We found a very small effect on the growth rate as well as on the CdTe desorption rate. The growth rate of CdTe was determined for different temperatures and CdTe flux ratios. The obtained experimental results are compared with a kinetic growth model to get information on the underlying growth processes, taking into account the influence of a precursor by including surface diffusion. From the comparison between model and experimental results the sticking coefficients of Cd and Te are determined. The growth rate of CdMnTe increases with Mn flux. This dependence can be used to calibrate the Mn content during growth by comparing the growth rate of CdTe with the growth rate of CdMnTe. The change in growth rate has been correlated with Mn content via photoluminescence measurements. In addition, the sticking coefficient of Mn is derived by comparing experimental results with a kinetic growth model. For high manganese content a transition to three-dimensional growth occurs. (orig.).

CdTe polycrystalline films on Ni foil substrates by screen printing and their photoelectric performance

International Nuclear Information System (INIS)

Yao, Huizhen; Ma, Jinwen; Mu, Yannan; Su, Shi; Lv, Pin; Zhang, Xiaoling; Zhou, Liying; Li, Xue; Liu, Li; Fu, Wuyou; Yang, Haibin

2015-01-01

Highlights: • The sintered CdTe polycrystalline films by a simple screen printing. • The flexible Ni foil was chose as substrates to reduce the weight of the electrode. • The compact CdTe film was obtained at 550 °C sintering temperature. • The photoelectric activity of the CdTe polycrystalline films was excellent. - Abstract: CdTe polycrystalline films were prepared on flexible Ni foil substrates by sequential screen printing and sintering in a nitrogen atmosphere for the first time. The effect of temperature on the quality of the screen-printed film was investigated in our work. The high-quality CdTe films were obtained after sintering at 550 °C for 2 h. The properties of the sintered CdTe films were characterized by scanning electron microscopy, X-ray diffraction pattern and UV–visible spectroscopy. The high-quality CdTe films have the photocurrent was 2.04 mA/cm 2 , which is higher than that of samples prepared at other temperatures. Furthermore, CdCl 2 treatment reduced the band gap of the CdTe film due to the larger grain size. The photocurrent of photoelectrode based on high crystalline CdTe polycrystalline films after CdCl 2 treatment improved to 2.97 mA/cm 2 , indicating a potential application in photovoltaic devices

Electropolymerization of camphorsulfonic acid doped conductive polypyrrole anti-corrosive coating for 304SS bipolar plates

Science.gov (United States)

Jiang, Li; Syed, Junaid Ali; Gao, Yangzhi; Zhang, Qiuxiang; Zhao, Junfeng; Lu, Hongbin; Meng, Xiangkang

2017-12-01

Conductive polymer coating doped with large molecular organic acid is an alternative method used to protect stainless steel (SS) bipolar plates in proton exchange membrane fuel cells (PEMFCs). However, it is difficult to select the proper doping acid, which improves the corrosion resistance of the coating without affecting its conductivity. In this study, large spatial molecular group camphorsulfonic acid (CSA) doped polypyrrole (PPY) conductive coating was prepared by galvanostatic electropolymerization on 304SS. The electrochemical properties of the coating were evaluated in 0.1 M H2SO4 solution in order to simulate the PEMFC service environment. The results indicate that the coating increased the corrosion potential and shifted Ecorr towards more positive value, particularly the jcorr value of PPY-CSA coated 304SS was dropped from 97.3 to 0.00187 μA cm-2. The long-term immersion tests (660 h) show that the PPY-CSA coating exhibits better corrosion resistance in comparison with the small acid (SO42-) doped PPY-SO42- or PPY/PPY-SO42- coatings. Moreover, the PPY-CSA coating presents low contact resistance and maintains strong corrosion resistance during the prolonged exposure time due to barrier effect and anodic protection.

Spin-coating: A new approach for improving dispersion of cellulose nanocrystals and mechanical properties of poly (lactic acid) composites.

Science.gov (United States)

Shojaeiarani, Jamileh; Bajwa, Dilpreet S; Stark, Nicole M

2018-06-15

This study systematically evaluated the influence of masterbatch preparation techniques, solvent casting and spin-coating methods, on composite properties. Composites were manufactured by combining CNCs masterbatches and PLA resin using twin screw extruder followed by injection molding. Different microscopy techniques were used to investigate the dispersion of CNCs in masterbatches and composites. Thermal, thermomechanical, and mechanical properties of composites were evaluated. Scanning electron microscopy (SEM) images showed superior dispersion of CNCs in spin-coated masterbatches compared to solvent cast masterbatches. At lower CNCs concentrations, both SEM and optical microscope images confirmed more uniform CNCs dispersion in spin-coated composites than solvent cast samples. Degree of crystallinity of PLA exhibited a major enhancement by 147% and 380% in solvent cast and spin-coated composites, respectively. Spin-coated composites with lower CNCs concentration exhibited a noticeable improvement in mechanical properties. However, lower thermal characteristics in spin-coated composites were observed, which could be attributed to the residual solvents in masterbatches. Copyright © 2018 Elsevier Ltd. All rights reserved.

Fluorescence enhancement of CdTe MPA-capped quantum dots by glutathione for hydrogen peroxide determination.

Science.gov (United States)

Rodrigues, S Sofia M; Ribeiro, David S M; Molina-Garcia, L; Ruiz Medina, A; Prior, João A V; Santos, João L M

2014-05-01

The manipulation of the surface chemistry of semiconductor nanocrystals has been exploited to implement distinct sensing strategies in many analytical applications. In this work, reduced glutathione (GSH) was added at reaction time, as an electron-donor ligand, to markedly increase the quantum yield and the emission efficiency of MPA-capped CdTe quantum dots. The developed approach was employed in the implementation of an automated flow methodology for hydrogen peroxide determination, as this can oxidize GSH preventing its surface passivating effect and producing a manifest fluorescence quenching. After optimization, linear working calibration curve for hydrogen peroxide concentrations between 0.0025% and 0.040% were obtained (n=6), with a correlation coefficient of 0.9975. The detection limit was approximately 0.0012%. The developed approach was employed in the determination of H₂O₂ in contact lens preservation solutions and the obtained results complied with those furnished by the reference method, with relative deviations comprised between -1.18 and 4.81%. Copyright © 2014 Elsevier B.V. All rights reserved.

Development of polylactic acid nanocomposite films reinforced with cellulose nanocrystals derived from coffee silverskin.

Science.gov (United States)

Sung, Soo Hyun; Chang, Yoonjee; Han, Jaejoon

2017-08-01

Bio-nanocomposite films based on polylactic acid (PLA) matrix reinforced with cellulose nanocrystals (CNCs) were developed using a twin-screw extruder. The CNCs were extracted from coffee silverskin (CS), which is a by-product of the coffee roasting process. They were extracted by alkali treatment followed by sulfuric acid hydrolysis. They were used as reinforcing agents to obtain PLA/CNC nanocomposites by addition at different concentrations (1%, 3%, and 5% CNCs). Morphological, tensile, and barrier properties of the bio-nanocomposites were analyzed. The tensile strength and Young's modulus increased with both 1% and 3% CNCs. The water vapor permeability decreased gradually with increasing addition of CNCs up to 3% and good oxygen barrier properties were found for all nanocomposites. These results suggest that CNCs from CS can improve the physical properties of PLA-based biopolymer film. The developed PLA/CNC bio-nanocomposite films can potentially be used for biopolymer materials with enhanced barrier and mechanical properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Photoluminescence studies on Cd(1-x)Zn(x)S:Mn2+ nanocrystals.

Science.gov (United States)

Sethi, Ruchi; Kumar, Lokendra; Pandey, A C

2009-09-01

Highly monodispersed, undoped and doped with Mn2+, binary and ternary (CdS, ZnS, Cd(1-x)Zn(x)S) compound semiconductor nanocrystals have been synthesized by co-precipitation method using citric acid as a stabilizer. As prepared sample are characterized by X-ray diffraction, Small angle X-ray scattering, Transmission electron microscope, Optical absorption and Photoluminescence spectroscopy, for their optical and structural properties. X-ray diffraction, Small angle X-ray scattering and Transmission electron microscope results confirm the preparation of monodispersed nanocrystals. Photoluminescence studies show a significant blue shift in the wavelength with an increasing concentration of Zn in alloy nanocrystals.

Processing of Polymer Nanocomposites Reinforced with Polysaccharide Nanocrystals

Directory of Open Access Journals (Sweden)

Alain Dufresne

2010-06-01

Full Text Available Aqueous suspensions of polysaccharide (cellulose, chitin or starch nanocrystals can be prepared by acid hydrolysis of biomass. The main problem with their practical use is related to the homogeneous dispersion of these nanoparticles within a polymeric matrix. Water is the preferred processing medium. A new and interesting way for the processing of polysaccharide nanocrystals-based nanocomposites is their transformation into a co-continuous material through long chain surface chemical modification. It involves the surface chemical modification of the nanoparticles based on the use of grafting agents bearing a reactive end group and a long compatibilizing tail.

Preparation and corrosion resistance of magnesium phytic acid/hydroxyapatite composite coatings on biodegradable AZ31 magnesium alloy.

Science.gov (United States)

Zhang, Min; Cai, Shu; Zhang, Feiyang; Xu, Guohua; Wang, Fengwu; Yu, Nian; Wu, Xiaodong

2017-06-01

In this work, a magnesium phytic acid/hydroxyapatite composite coating was successfully prepared on AZ31 magnesium alloy substrate by chemical conversion deposition technology with the aim of improving its corrosion resistance and bioactivity. The influence of hydroxyapatite (HA) content on the microstructure and corrosion resistance of the coatings was investigated. The results showed that with the increase of HA content in phytic acid solution, the cracks on the surface of the coatings gradually reduced, which subsequently improved the corrosion resistance of these coated magnesium alloy. Electrochemical measurements in simulated body fluid (SBF) revealed that the composite coating with 45 wt.% HA addition exhibited superior surface integrity and significantly improved corrosion resistance compared with the single phytic acid conversion coating. The results of the immersion test in SBF showed that the composite coating could provide more effective protection for magnesium alloy substrate than that of the single phytic acid coating and showed good bioactivity. Magnesium phytic acid/hydroxyapatite composite, with the desired bioactivity, can be synthesized through chemical conversion deposition technology as protective coatings for surface modification of the biodegradable magnesium alloy implants. The design idea of the new type of biomaterial is belong to the concept of "third generation biomaterial". Corrosion behavior and bioactivity of coated magnesium alloy are the key issues during implantation. In this study, preparation and corrosion behavior of magnesium phytic acid/hydroxyapatite composite coatings on magnesium alloy were studied. The basic findings and significance of this paper are as follows: 1. A novel environmentally friendly, homogenous and crack-free magnesium phytic acid/hydroxyapatite composite coating was fabricated on AZ31 magnesium alloy via chemical conversion deposition technology with the aim of enhancing its corrosion resistance and

Effectiveness of incorporating citric acid in cassava starch edible coatings to preserve quality of Martha tomatoes

Science.gov (United States)

Ambarsari, I.; Oktaningrum, G. N.; Endrasari, R.

2018-01-01

Tomato as an agricultural product is extremely perishable. Coatings of tomatoes with edible starch extend quality and storage life of the fruits. Incorporation of citric acid as antimicrobial agent in the edible starch coatings is expected to preserve the quality of tomatoes during storage. The aim of this study was to verify the effectiveness of citric acid incorporated in cassava starch coating to preserve quality of tomatoes. The edible coatings formula consisted of cassava starch solutions (1; 2; 3%), citric acid (0.5; 1.0%) and glycerol (10%). Tomatoes were dipped to the coating solution for 10 seconds, then air-dried and stored at room temperature during 18 days. All the treatments were carried out in triplicates. Experimental data were analyzed using One Way ANOVA. The results showed that coating treatments did not affect the weight loss, moisture content, color characteristic, carotene and vitamin C content on Martha tomatoes. The low concentration of starch coating on Martha tomatoes are indicated to be the reason why there was no significant difference between coated and coated tomatoes for some parameters. However, incorporating citric acid in cassava starch-based coatings could prevent tomato fruits from firmness reduction and spoilage during storage.

Thrombus detection using 125I-fibrinogen and a CdTe probe

International Nuclear Information System (INIS)

Garcia, D.A.; Frisbie, J.H.; Tow, D.E.; Sasahara, A.A.; Entine, G.

1976-01-01

A compact CdTe detector system was developed for use in a clinical screening test for venous thrombosis of the legs. Patients given intravenously administered autologous 125 I-fibrinogen were probed externally at selected points on the thighs and calves for abnormal accumulations of radioactivity. Measurements made with the CdTe probe were compared to those obtained with a standard portable NaI detector system. The CdTe probe was the equal of the NaI detector in diagnostic capability. The compact design of the semiconductor system considerably eased the probing procedure, especially in bedridden patients with limited mobility of the extremities

Degradation rates and mechanisms of acid-resistant coatings in copper-leaching tanks

DEFF Research Database (Denmark)

Møller, Victor Buhl

coating where the lifetime was estimated to 1:6 ± 0:2 and 1:4 ± 0:1 years, respectively. Part IV A series of newly designed and constructed diffusion cells were used to measure sulfuric acid diffusion rates through the coatings. A mathematical model was developed to simulate the experimental data...... potential in the mineral industry has not yet been thoroughly investigated. This particular industry poses unique challenges, with high operational temperatures (around 75 °C) and combined acidicerosive environments. The use of organic coatings to protect tanks, pipes, and secondary exposure areas, may....... Part I An in-depth literature study was performed to uncover and review uses and limitations ofacid-resistant coatings in the chemical industry, with a comparison to alternative resistant materialsbased on metals and ceramics. In addition, coating degradation phenomena caused by acid exposure, were...

Fluorescence Determination of Warfarin Using TGA-capped CdTe Quantum Dots in Human Plasma Samples.

Science.gov (United States)

Dehbozorgi, A; Tashkhourian, J; Zare, S

2015-11-01

In this study, some effort has been performed to provide low temperature, less time consuming and facile routes for the synthesis of CdTe quantum dots using ultrasound and water soluble capping agent thioglycolic acid. TGA-capped CdTe quantum dots were characterized through x-ray diffraction, transmission electron microscopy, Fourier transform infrared, ultraviolet-visible and fluorescence spectroscopy. The prepared quantum dots were used for warfarin determination based on the quenching of the fluorescence intensity in aqueous solution. Under the optimized conditions, the linear range of quantum dots fluorescence intensity versus the concentration of warfarin was 0.1-160.0 μM, with the correlation coefficient of 0.9996 and a limit of detection of 77.5 nM. There was no interference to coexisting foreign substances. The selectivity of the sensor was also tested and the results show that the developed method possesses a high selectivity for warfarin.

Effect of gallic acid/chitosan coating on fresh pork quality in modified atmosphere packaging.

Science.gov (United States)

Fang, Zhongxiang; Lin, Daniel; Warner, Robyn Dorothy; Ha, Minh

2018-09-15

Fresh meat safety and quality is a major concern of consumers in the current food market. The objective of this research was to investigate a newly developed gallic acid/chitosan edible coating on the preservation of fresh pork quality in modified atmosphere package (MAP) stored at 4 °C. The pork loins were coated with 2% chitosan (CHI), 0.2% gallic acid in 2% chitosan (CHI/0.2G), or 0.4% gallic acid in 2% chitosan (CHI/0.4G). Results showed that the antimicrobial activity of the chitosan coating was increased with the incorporation of gallic acid. The CHI/0.2G and CHI/0.4G pork loins also had lower lipid oxidation and myoglobin oxidation. However, the CHI/0.4G sample exhibited a pro-protein oxidation effect, suggesting an optimal concentration of gallic acid should be incorporated. This research provides a practical method in application of gallic acid/chitosan coatings on preservation of fresh pork to improve the safety and quality in MAP environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

CdTe quantum dots for an application in the life sciences

International Nuclear Information System (INIS)

Thuy, Ung Thi Dieu; Toan, Pham Song; Chi, Tran Thi Kim; Liem, Nguyen Quang; Khang, Dinh Duy

2010-01-01

This report highlights the results of the preparation of semiconductor CdTe quantum dots (QDs) in the aqueous phase. The small size of a few nm and a very high luminescence quantum yield exceeding 60% of these materials make them promisingly applicable to bio-medicine labeling. Their strong, two-photon excitation luminescence is also a good characteristic for biolabeling without interference with the cell fluorescence. The primary results for the pH-sensitive CdTe QDs are presented in that fluorescence of CdTe QDs was used as a proton sensor to detect proton flux driven by adenosine triphosphate (ATP) synthesis in chromatophores. In other words, these QDs could work as pH-sensitive detectors. Therefore, the system of CdTe QDs on chromatophores prepared from the cells of Rhodospirillum rubrum and the antibodies against the beta-subunit of F0F1–ATPase could be a sensitive detector for the avian influenza virus subtype A/H5N1

Mechanistic Study of Monodisperse Iron Oxide Nanocrystals ...

African Journals Online (AJOL)

To gain better insight into the formation of iron oxide nanocrystals from the solution phase thermal decomposition of iron (III) oleate complex, different reaction conditions including time, heating ramp, as well as concentrations of iron oleate precursor and oleic acid ligand were systematically varied and the resulting ...

Experimental investigation of coating degradation during simultaneous acid and erosive particle exposure

DEFF Research Database (Denmark)

Møller, Victor Buhl; Dam-Johansen, Kim; Frankær, Sarah Maria

When used in industrial processes, such as stirred acid leaching in the mineral industry, thermoset coatings are exposed to a combination of aggressive chemicals and erosive particlewear. While each exposure condition has been studied separately, no research has been presented on the effects...... of a simultaneous exposure. To investigate this, a pilot-scale stirred acid leaching tank, containing erosive particles and acidic solutions, has been designed and constructed. Resin types considered are amine-cured novolac epoxy and vinyl ester. Transient coating degradation is mapped through visual inspection...

Production of CdTe Semiconductor Thin Films by Electrodeposition Technique for Solar Cell Applications

Directory of Open Access Journals (Sweden)

Ahmet PEKSÖZ

2016-08-01

Full Text Available Electro-deposited cadmium tellurite (CuTe thin film was grown onto ITO-coated glass substrate for 120 seconds at the room temperature and a constant cathodic potential of -0.85 V. Deposition solution was prepared from cadmium chloride (CdCl2, sodium tellurite (Na2TeO3 and pure water. The pH value of the deposition solution was adjusted to 2.0 by adding HCl. The EDX analysis shows that the film has 52% Cd and 48% Te elemental compositions. Film thickness was found to be 140 nm. The CdTe thin film exhibits p-type semiconductor character, and has an energy bandgap of 1.47 eV. 

Improved electrochromical properties of sol-gel WO3 thin films by doping gold nanocrystals

International Nuclear Information System (INIS)

Naseri, N.; Azimirad, R.; Akhavan, O.; Moshfegh, A.Z.

2010-01-01

In this investigation, the effect of gold nanocrystals on the electrochromical properties of sol-gel Au doped WO 3 thin films has been studied. The Au-WO 3 thin films were dip-coated on both glass and indium tin oxide coated conducting glass substrates with various gold concentrations of 0, 3.2 and 6.4 mol%. Optical properties of the samples were studied by UV-visible spectrophotometry in a range of 300-1100 nm. The optical density spectra of the films showed the formation of gold nanoparticles in the films. The optical bandgap energy of Au-WO 3 films decreased with increasing the Au concentration. Crystalline structure of the doped films was investigated by X-ray diffractometry, which indicated formation of gold nanocrystals in amorphous WO 3 thin films. X-ray photoelectron spectroscopy (XPS) was used to study the surface chemical composition of the samples. XPS analysis indicated the presence of gold in metallic state and the formation of stoichiometric WO 3 . The electrochromic properties of the Au-WO 3 samples were also characterized using lithium-based electrolyte. It was found that doping of Au nanocrystals in WO 3 thin films improved the coloration time of the layer. In addition, it was shown that variation of Au concentration led to color change in the colored state of the Au-WO 3 thin films.

Nicotinic acid as a nontoxic corrosion inhibitor for hot dipped Zn and Zn-Al alloy coatings on steels in diluted hydrochloric acid

Energy Technology Data Exchange (ETDEWEB)

Ju Hong [Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 (China); Graduate School, Chinese Academy of Sciences, Beijing 100039 (China); Li Yan [Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 (China)], E-mail: yanlee@ms.qdio.ac.cn

2007-11-15

The inhibition effect of nicotinic acid for corrosion of hot dipped Zn and Zn-Al alloy coatings in diluted hydrochloric acid was investigated using quantum chemistry analysis, weight loss test, electrochemical measurement, and scanning electronic microscope (SEM) analysis. Quantum chemistry calculation results showed that nicotinic acid possessed planar structure with a number of active centers, and the populations of the Mulliken charge, the highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) were found mainly focused around oxygen and nitrogen atoms, and the cyclic of the benzene as well. The results of weight loss test and electrochemical measurement indicated that inhibition efficiency (IE%) increased with inhibitor concentration, and the highest inhibition efficiency was up to 96.7%. The corrosion inhibition of these coatings was discussed in terms of blocking the electrode reaction by adsorption of the molecules at the active centers on the electrode surface. It was found that the adsorption of nicotinic acid on coating surface followed Langmuir adsorption isotherm with single molecular layer, and nicotinic acid adsorbed on the coating surface probably by chemisorption. Nicotinic acid, therefore, can act as a good nontoxic corrosion inhibitor for hot dipped Zn and Zn-Al alloy coatings in diluted hydrochloric acid solution.

Study on de-coating used beverage cans with thick sulfuric acid for recycle

International Nuclear Information System (INIS)

Wang, Minghua; Woo, Kee-Do; Kim, Dong-Keon; Ma, Lirong

2007-01-01

More than 1800 hundreds of millions of beverage cans are manufactured yearly over the world, which will pollute the globe environment without recycle. The recycle and regeneration estates of used beverage cans are highly profitable enterprises. Vacuum technologies are mature on a large scale today, and therefore, the re-melting process of used beverage cans (UBCs) does not have to use flux. Furthermore, the coating on UBCs becomes the key factor causing poor product quality. The present paper concerns removing the coating of UBCs and compares two different kinds of methods to remove the coating: a thermal method and a chemical reagent method. A new kind of reagent, thick sulfuric acid, was employed in the chemical reagent de-coating process. The de-coating ratio in the thermal method reached 93% at most, but the de-coating ratio reached 100% within 30 min in the chemical reagent method by using thick sulfuric acid. Recycling the used thick sulfuric acid was also supplied. A titanium yellow product can be simultaneously obtained. The experiments show that the chemical reagent method is more available than the thermal method, which will enhance the purity of the regeneration product enormously

Insights into the microstructural and physical properties of colloidal Fe:ZnSe nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Xie, Ruishi, E-mail: rxie@foxmail.com [Analytical and Testing Center, Southwest University of Science and Technology, Mianyang 621010 (China); Li, Yuanli [Department of Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Jiang, Linhai; Zhang, Xingquan [Analytical and Testing Center, Southwest University of Science and Technology, Mianyang 621010 (China)

2014-10-30

Highlights: • We present a facile and environmentally friendly protocol to fabricate Fe:ZnSe nanocrystals. • The microstructural and physical properties of Fe:ZnSe nanocrystals were systematically investigated. • The current synthesis is dramatically simple and highly reproducible, it will facilitate the commercial scale synthesis of highly luminescent water-soluble nanocrystals with surface functionality in the near future. - Abstract: Here, we present a facile and environmentally friendly synthetic protocol to fabricate highly luminescent and water-soluble Fe:ZnSe nanocrystals in aqueous solution at low temperature. The microstructure and various physical properties (e.g., crystal structure, interplanar spacing, lattice parameter, crystalline size, lattice microstrain, intrinsic stress, X-ray density, specific surface area, dislocation density, porosity, agglomeration number) of the Fe:ZnSe nanocrystals were systematically investigated using X-ray diffraction. The particle size and morphology of the Fe:ZnSe nanocrystals were determined by transmission electron microscopy. The optical properties (e.g., absorption and photoluminescence) of the fabricated nanocrystals were explored using ultraviolet–visible absorption and photoluminescence spectroscopies, respectively. The surface functionalization of the Fe:ZnSe nanocrystals by mercaptoacetic acid ligand was evidenced by Fourier transform infrared spectroscopy. To confirm the elementary composition of the obtained nanocrystals, Energy dispersive X-ray spectroscopy was performed. To further shed light upon elemental distribution of the resulting nanocrystals, elemental mapping measurements were conducted. Moreover, the underlying mechanisms were also elucidated. As a consequence, the current investigation not only provides a deep insight into exploring the physical properties of doped nanocrystals, but also demonstrates a useful synthetic strategy for producing water-soluble and highly fluorescent doped

One-step synthesis of CdTe branched nanowires and nanorod arrays

International Nuclear Information System (INIS)

Hou Junwei; Yang Xiuchun; Lv Xiaoyi; Peng Dengfeng; Huang Min; Wang Qingyao

2011-01-01

Single crystalline CdTe branched nanowires and well-aligned nanorod arrays were simultaneously synthesized by a simple chemical vapor deposition (CVD) technique. X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and selected area electronic diffraction (SAED) were used to study the crystalline structure, composition and morphology of different samples. Vapor-liquid-solid (VLS) and vapor-solid (VS) processes were proposed for the formation of the CdTe branched nanowires and nanorod arrays, respectively. As-grown CdTe nanorod arrays show a strong red emission band centered at about 620 nm, which can be well fitted by two Gaussian curves centered at 610 nm and 635 nm, respectively.

Hydrothermal synthesis, characterization and up/down-conversion luminescence of barium rare earth fluoride nanocrystals

International Nuclear Information System (INIS)

Jia, Li-Ping; Zhang, Qiang; Yan, Bing

2014-01-01

Graphical abstract: Lanthanide ions doped bare earth rare earth fluoride nanocrystals are synthesized by hydrothermal technology and characterized. The down/up-conversion luminescence of them are discussed. - Highlights: • Mixed hydrothermal system H 2 O–OA (EDA)–O-A(LO-A) is used for synthesis. • Barium rare earth fluoride nanocrystals are synthesized comprehensively. • Luminescence for down-conversion and up-conversion are obtained for these systems. - Abstract: Mixed hydrothermal system H 2 O–OA (EDA)–O-A(LO-A) is developed to synthesize barium rare earth fluorides nanocrystals (OA = oleylamine, EDA = ethylenediamine, O-A = oleic acid and LO-A = linoleic acid). They are presented as BaREF 5 (RE = Ce, Pr, Nd, Eu, Gd, Tb, Dy, Y, Tm, Lu) and Ba 2 REF 7 (RE = La, Sm, Ho, Er, Yb). The influence of reaction parameters (rare earth species, hydrothermal system and temperature) is checked on the phase and shape evolution of the fluoride nanocrystals. It is found that reaction time and temperature of these nanocrystals using EDA (180 °C, 6 h) is lower than those of them using OA (220 °C, 10 h). The photoluminescence properties of these fluorides activated by some rare earth ions (Nd 3+ , Eu 3+ , Tb 3+ ) are studied, and especially up-conversion luminescence of the four fluoride nanocrystal systems (Ba 2 LaF 7 :Yb, Tm(Er), Ba 2 REF 7 :Yb, Tm(Er) (RE = Gd, Y, Lu)) is observed

Studying nanotoxic effects of CdTe quantum dots in Trypanosoma cruzi

Directory of Open Access Journals (Sweden)

Cecilia Stahl Vieira

2011-03-01

Full Text Available Semiconductor nanoparticles, such as quantum dots (QDs, were used to carry out experiments in vivo and ex vivo with Trypanosoma cruzi. However, questions have been raised regarding the nanotoxicity of QDs in living cells, microorganisms, tissues and whole animals. The objective of this paper was to conduct a QD nanotoxicity study on living T. cruzi protozoa using analytical methods. This was accomplished using in vitro experiments to test the interference of the QDs on parasite development, morphology and viability. Our results show that after 72 h, a 200 μM cadmium telluride (CdTe QD solution induced important morphological alterations in T. cruzi, such as DNA damage, plasma membrane blebbing and mitochondrial swelling. Flow cytometry assays showed no damage to the plasma membrane when incubated with 200 μM CdTe QDs for up to 72 h (propidium iodide cells, giving no evidence of classical necrosis. Parasites incubated with 2 μM CdTe QDs still proliferated after seven days. In summary, a low concentration of CdTe QDs (2 μM is optimal for bioimaging, whereas a high concentration (200 μM CdTe could be toxic to cells. Taken together, our data indicate that 2 μM QD can be used for the successful long-term study of the parasite-vector interaction in real time.

Patterning nanocrystals using DNA

Energy Technology Data Exchange (ETDEWEB)

Williams, Shara Carol [Univ. of California, Berkeley, CA (United States)

2003-01-01

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

Controlled synthesis of novel octapod platinum nanocrystals under microwave irradiation

International Nuclear Information System (INIS)

Dai, Lei; Chi, Quan; Zhao, Yanxi; Liu, Hanfan; Zhou, Zhongqiang; Li, Jinlin; Huang, Tao

2014-01-01

Graphical abstract: Under microwave irradiation, novel octapod Pt nanocrystals were synthesized by reducing H 2 PtCl 6 in TEG with PVP as a stabilizer. The as-prepared Pt nanocrystals displayed a unique octapod nanostructure with five little mastoids in each concave center. The use of KI was crucial to the formation of novel Pt octapods. Novel Octapod Platinum Nanocrystals. - Highlights: • A novel octapod Pt nanocrystals different from the common octapod were obtained. • The use of KI was crucial to the formation of the novel Pt octapods. • Microwave was readily employed in controlled synthesis of the novel Pt octapods. - Abstract: Microwave was employed in the shape-controlled synthesis of Pt nanoparticles. Novel octapod Pt nanocrystals enclosed with (1 1 1) facets were readily synthesized with H 2 PtCl 6 as a precursor, tetraethylene glycol (TEG) as both a solvent and a reducing agent, polyvinylpyrrolidone (PVP) as a stabilizer in the presence of an appropriate amount of KI under microwave irradiation for 140 s. The as-prepared Pt nanocrystals displayed a unique octapod nanostructure with five little mastoids in each concave center and exhibited higher electrocatalytic activity than commercial Pt black in the electro-oxidations of methanol and formic acid. The results demonstrated that the use of KI was crucial to the formation of Pt octapods. KI determined the formation of the novel octapod Pt nanocrystals by tuning up the reduction kinetics and adsorbing on the surfaces of growing Pt nanoparticles. The optimum molar ratio of H 2 PtCl 6 /KI/PVP was 1/30/45

Probing Lipid Coating Dynamics of Quantum Dot Core Micelles via Forster Resonance Energy Transfer

NARCIS (Netherlands)

Zhao, Yiming; Schapotschnikow, Philipp; Skajaa, Torjus; Vlugt, Thijs J. H.; Mulder, Willem J. M.; de Mello Donegá, Celso; Meijerink, Andries

2014-01-01

Lipid coated nanocrystal assemblies are among the most extensively investigated nanoparticle platforms for biomedical imaging and therapeutic purposes. However, very few efforts have been addressed to the lipid coating exchange dynamics in such systems, which is key to our understanding of the

Advanced processing of CdTe pixel radiation detectors

Science.gov (United States)

Gädda, A.; Winkler, A.; Ott, J.; Härkönen, J.; Karadzhinova-Ferrer, A.; Koponen, P.; Luukka, P.; Tikkanen, J.; Vähänen, S.

2017-12-01

We report a fabrication process of pixel detectors made of bulk cadmium telluride (CdTe) crystals. Prior to processing, the quality and defect density in CdTe material was characterized by infrared (IR) spectroscopy. The semiconductor detector and Flip-Chip (FC) interconnection processing was carried out in the clean room premises of Micronova Nanofabrication Centre in Espoo, Finland. The chip scale processes consist of the aluminum oxide (Al2O3) low temperature thermal Atomic Layer Deposition (ALD), titanium tungsten (TiW) metal sputtering depositions and an electroless Nickel growth. CdTe crystals with the size of 10×10×0.5 mm3 were patterned with several photo-lithography techniques. In this study, gold (Au) was chosen as the material for the wettable Under Bump Metalization (UBM) pads. Indium (In) based solder bumps were grown on PSI46dig read out chips (ROC) having 4160 pixels within an area of 1 cm2. CdTe sensor and ROC were hybridized using a low temperature flip-chip (FC) interconnection technique. The In-Au cold weld bonding connections were successfully connecting both elements. After the processing the detector packages were wire bonded into associated read out electronics. The pixel detectors were tested at the premises of Finnish Radiation Safety Authority (STUK). During the measurement campaign, the modules were tested by exposure to a 137Cs source of 1.5 TBq for 8 minutes. We detected at the room temperature a photopeak at 662 keV with about 2 % energy resolution.

Direct synthesis of antimicrobial coatings based on tailored bi-elemental nanoparticles

Directory of Open Access Journals (Sweden)

Giulio Benetti

2017-03-01

Full Text Available Ultrathin coatings based on bi-elemental nanoparticles (NPs are very promising to limit the surface-related spread of bacterial pathogens, particularly in nosocomial environments. However, tailoring the synthesis, composition, adhesion to substrate, and antimicrobial spectrum of the coating is an open challenge. Herein, we report on a radically new nanostructured coating, obtained by a one-step gas-phase deposition technique, and composed of bi-elemental Janus type Ag/Ti NPs. The NPs are characterized by a cluster-in-cluster mixing phase with metallic Ag nano-crystals embedded in amorphous TiO2 and present a promising antimicrobial activity including also multidrug resistant strains. We demonstrate the flexibility of the method to tune the embedded Ag nano-crystals dimension, the total relative composition of the coating, and the substrate type, opening the possibility of tailoring the dimension, composition, antimicrobial spectrum, and other physical/chemical properties of such multi-elemental systems. This work is expected to significantly spread the range of applications of NPs coatings, not only as an effective tool in the prevention of healthcare-associated infections but also in other technologically relevant fields like sensors or nano-/micro joining.

Direct synthesis of antimicrobial coatings based on tailored bi-elemental nanoparticles

Science.gov (United States)

Benetti, Giulio; Cavaliere, Emanuele; Canteri, Adalberto; Landini, Giulia; Rossolini, Gian Maria; Pallecchi, Lucia; Chiodi, Mirco; Van Bael, Margriet J.; Winckelmans, Naomi; Bals, Sara; Gavioli, Luca

2017-03-01

Ultrathin coatings based on bi-elemental nanoparticles (NPs) are very promising to limit the surface-related spread of bacterial pathogens, particularly in nosocomial environments. However, tailoring the synthesis, composition, adhesion to substrate, and antimicrobial spectrum of the coating is an open challenge. Herein, we report on a radically new nanostructured coating, obtained by a one-step gas-phase deposition technique, and composed of bi-elemental Janus type Ag/Ti NPs. The NPs are characterized by a cluster-in-cluster mixing phase with metallic Ag nano-crystals embedded in amorphous TiO2 and present a promising antimicrobial activity including also multidrug resistant strains. We demonstrate the flexibility of the method to tune the embedded Ag nano-crystals dimension, the total relative composition of the coating, and the substrate type, opening the possibility of tailoring the dimension, composition, antimicrobial spectrum, and other physical/chemical properties of such multi-elemental systems. This work is expected to significantly spread the range of applications of NPs coatings, not only as an effective tool in the prevention of healthcare-associated infections but also in other technologically relevant fields like sensors or nano-/micro joining.

Isolation of thermally stable cellulose nanocrystals by phosphoric acid hydrolysis.

Science.gov (United States)

Camarero Espinosa, Sandra; Kuhnt, Tobias; Foster, E Johan; Weder, Christoph

2013-04-08

On account of their intriguing mechanical properties, low cost, and renewable nature, high-aspect-ratio cellulose nanocrystals (CNCs) are an attractive component for many nanomaterials. Due to hydrogen bonding between their surface hydroxyl groups, unmodified CNCs (H-CNCs) aggregate easily and are often difficult to disperse. It is shown here that on account of ionic repulsion between charged surface groups, slightly phosphorylated CNCs (P-CNCs, average dimensions 31 ± 14 × 316 ± 127 nm, surface charge density = 10.8 ± 2.7 mmol/kg cellulose), prepared by controlled hydrolysis of cotton with phosphoric acid, are readily dispersible and form stable dispersions in polar solvents such as water, dimethyl sulfoxide, and dimethylformamide. Thermogravimetric analyses reveal that these P-CNCs exhibit a much higher thermal stability than partially sulfated CNCs (S-CNCs), which are frequently employed, but suffer from limited thermal stability. Nanocomposites of an ethylene oxide-epichlorohydrin copolymer and H-CNCs, S-CNCs, and P-CNCs were prepared, and their mechanical properties were studied by dynamic mechanical thermal analysis. The results show that P-CNCs offer a reinforcing capability that is comparable to that of H-CNCs or S-CNCs.

Physical vapor deposition of CdTe thin films at low temperature for solar cell applications

Energy Technology Data Exchange (ETDEWEB)

Heisler, Christoph; Brueckner, Michael; Lind, Felix; Kraft, Christian; Reisloehner, Udo; Ronning, Carsten; Wesch, Werner [Institute of Solid State Physics, University of Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)

2012-07-01

Cadmium telluride is successfully utilized as an absorber material for thin film solar cells. Industrial production makes use of high substrate temperatures for the deposition of CdTe absorber layers. However, in order to exploit flexible substrates and to simplify the manufacturing process, lower deposition temperatures are beneficial. Based on the phase diagram of CdTe, predictions on the stoichiometry of CdTe thin films grown at low substrate temperatures are made in this work. These predictions were verified experimentally using additional sources of Cd and Te during the deposition of the CdTe thin films at different substrate temperatures. The deposited layers were analyzed with energy-dispersive X-ray spectroscopy. In case of CdTe layers which were deposited at substrate temperatures lower than 200 C without usage of additional sources we found a non-stoichiometric growth of the CdTe layers. The application of the additional sources leads to a stoichiometric growth for substrate temperatures down to 100 C which is a significant reduction of the substrate temperature during deposition.

Preparation of biodegradable magnetic microspheres with poly(lactic acid)-coated magnetite

Energy Technology Data Exchange (ETDEWEB)

Zhao Hong; Saatchi, Katayoun [Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 East Mall, Vancouver, BC, 6T 1Z3 (Canada); Haefeli, Urs O. [Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 East Mall, Vancouver, BC, V6T 1Z3 (Canada)], E-mail: uhafeli@interchange.ubc.ca

2009-05-15

Poly(lactic acid) (PLA)-coated magnetic nanoparticles were made using uncapped PLA with free carboxylate groups. The physical properties of these particles were compared to those of oleate-coated or oleate/sulphonate bilayer (W40) coated magnetic particles. Magnetic microspheres (MMS) with the matrix material poly(lactide-co-glycolide) (PLGA) or PLA were then formed by the emulsion solvent extraction method with encapsulation efficiencies of 40%, 83% and 96% for oleate, PLA and oleate/sulfonate-coated magnetic particles, respectively. MMS made from PLA-coated magnetite were hemocompatible and produced no hemolysis, whereas the other MMS were hemolytic above 0.3 mg/mL of blood.

Preparation of biodegradable magnetic microspheres with poly(lactic acid)-coated magnetite

International Nuclear Information System (INIS)

Zhao Hong; Saatchi, Katayoun; Haefeli, Urs O.

2009-01-01

Poly(lactic acid) (PLA)-coated magnetic nanoparticles were made using uncapped PLA with free carboxylate groups. The physical properties of these particles were compared to those of oleate-coated or oleate/sulphonate bilayer (W40) coated magnetic particles. Magnetic microspheres (MMS) with the matrix material poly(lactide-co-glycolide) (PLGA) or PLA were then formed by the emulsion solvent extraction method with encapsulation efficiencies of 40%, 83% and 96% for oleate, PLA and oleate/sulfonate-coated magnetic particles, respectively. MMS made from PLA-coated magnetite were hemocompatible and produced no hemolysis, whereas the other MMS were hemolytic above 0.3 mg/mL of blood.

Nanocrystals Technology for Pharmaceutical Science.

Science.gov (United States)

Cheng, Zhongyao; Lian, Yumei; Kamal, Zul; Ma, Xin; Chen, Jianjun; Zhou, Xinbo; Su, Jing; Qiu, Mingfeng

2018-05-17

Nanocrystals technology is a promising method for improving the dissolution rate and enhancing the bioavailability of poorly soluble drugs. In recent years, it has been developing rapidly and applied to drug research and engineering. Nanocrystal drugs can be formulated into various dosage forms. This review mainly focused on the nanocrystals technology and its application in pharmaceutical science. Firstly, different preparation methods of nanocrystal technology and the characterization of nanocrystal drugs are briefly described. Secondly, the application of nanocrystals technology in pharmaceutical science is mainly discussed followed by the introduction of sustained release formulations. Then, the scaling up process, marketed nanocrystal drug products and regulatory aspects about nanodrugs are summarized. Finally, the specific challenges and opportunities of nanocrystals technology for pharmaceutical science are summarized and discussed. This review will provide a comprehensive guide for scientists and engineers in the field of pharmaceutical science and biochemical engineering. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Influence of the layer parameters on the performance of the CdTe solar cells

Science.gov (United States)

Haddout, Assiya; Raidou, Abderrahim; Fahoume, Mounir

2018-03-01

Influence of the layer parameters on the performances of the CdTe solar cells is analyzed by SCAPS-1D. The ZnO: Al film shows a high efficiency than SnO2:F. Moreover, the thinner window layer and lower defect density of CdS films are the factor in the enhancement of the short-circuit current density. As well, to increase the open-circuit voltage, the responsible factors are low defect density of the absorbing layer CdTe and high metal work function. For the low cost of cell production, ultrathin film CdTe cells are used with a back surface field (BSF) between CdTe and back contact, such as PbTe. Further, the simulation results show that the conversion efficiency of 19.28% can be obtained for the cell with 1-μm-thick CdTe, 0.1-μm-thick PbTe and 30-nm-thick CdS.

The next generation CdTe technology- Substrate foil based solar cells

Energy Technology Data Exchange (ETDEWEB)

Ferekides, Chris [Univ. of South Florida, Tampa, FL (United States)

2017-03-22

The main objective of this project was the development of one of the most promising Photovoltaic (PV) materials CdTe into a versatile, cost effective, and high throughput technology, by demonstrating substrate devices on foil substrates using high throughput fabrication conditions. The typical CdTe cell is of the superstrate configuration where the solar cell is fabricated on a glass superstrate by the sequential deposition of a TCO, n-type heterojunction partner, p-CdTe absorber, and back contact. Large glass modules are heavy and present significant challenges during manufacturing (uniform heating, etc.). If a substrate CdTe cell could be developed (the main goal of this project) a roll-to-toll high throughput technology could be developed.

Defect complexes formed with Ag atoms in CDTE, ZnTe, and ZnSe

CERN Document Server

Wolf, H; Ostheimer, V; Hamann, J; Lany, S; Wichert, T

2000-01-01

Using the radioactive acceptor $^{111}\\!$Ag for perturbed $\\gamma$-$\\gamma$-angular correlation (PAC) spectroscopy for the first time, defect complexes formed with Ag are investigated in the II-VI semiconductors CdTe, ZnTe and ZnSe. The donors In, Br and the Te-vacancy were found to passivate Ag acceptors in CdTe via pair formation, which was also observed in In-doped ZnTe. In undoped or Sb-doped CdTe and in undoped ZnSe, the PAC experiments indicate the compensation of Ag acceptors by the formation of double broken bond centres, which are characterised by an electric field gradient with an asymmetry parameter close to h = 1. Additionally, a very large electric field gradient was observed in CdTe, which is possibly connected with residual impurities.

Synthesis and characterization of MgO nanocrystals for biosensing applications

Energy Technology Data Exchange (ETDEWEB)

Li, Hongji [Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry & Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Li, Mingji, E-mail: limingji@163.com [Tianjin Key Laboratory of Film Electronic and Communication Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China); Qiu, Guojun [Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry & Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Li, Cuiping; Qu, Changqing; Yang, Baohe [Tianjin Key Laboratory of Film Electronic and Communication Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China)

2015-05-25

Highlights: • MgO nanocrystals were prepared using DC arc plasma jet CVD method. • The growth time does not exceed 10 min in process of the synthesis. • The samples were found to consist of cubic MgO nanobelts and nanosheets. • Nanocrystals contain contacts, rough edges, vacancies, and doping defects. • The samples exhibited excellent electrochemical biosensing properties. - Abstract: MgO nanocrystals were prepared using a simple direct current arc plasma jet chemical vapor deposition method. Magnesium nitrate was used as source material and Mo film was used as a substrate and catalyst. The high-temperature plasma produced ensured rapid synthesis of the MgO nanocrystals. The as-prepared nanocrystals were characterized by field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, energy-dispersive spectroscopy, Fourier transform infrared spectrometry, ultraviolet–visible spectrophotometry, and photoluminescence measurements. The as-synthesized samples were found to consist of cubic MgO nanobelts and nanosheets with large surface areas and low coordination oxide ions, and contained numerous contacts, rough edges, vacancies, and doping defects. The nanostructures exhibited excellent electrochemical sensing properties with high-sensing sensitivity toward ascorbic acid. Their high electrocatalytic activity was attributed to the effect of defects and the surface electron transfer ability of the one-dimensional MgO nanobelts.

Magnesium ferrite nanocrystal clusters for magnetorheological fluid with enhanced sedimentation stability

Science.gov (United States)

Wang, Guangshuo; Ma, Yingying; Li, Meixia; Cui, Guohua; Che, Hongwei; Mu, Jingbo; Zhang, Xiaoliang; Tong, Yu; Dong, Xufeng

2017-01-01

In this study, magnesium ferrite (MgFe2O4) nanocrystal clusters were synthesized using an ascorbic acid-assistant solvothermal method and evaluated as a candidate for magnetorheological (MR) fluid. The morphology, microstructure and magnetic properties of the MgFe2O4 nanocrystal clusters were investigated in detail by field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetric analyzer (TGA), X-ray diffraction (XRD) and superconducting quantum interference device (SQUID). The MgFe2O4 nanocrystal clusters were suspended in silicone oil to prepare MR fluid and the MR properties were tested using a Physica MCR301 rheometer fitted with a magneto-rheological module. The prepared MR fluid showed typical Bingham plastic behavior, changing from a liquid-like to a solid-like structure under an external magnetic field. Compared with the conventional carbonyl iron particles, MgFe2O4 nanocrystal clusters-based MR fluid demonstrated enhanced sedimentation stability due to the reduced mismatch in density between the particles and the carrier medium. In summary, the as-prepared MgFe2O4 nanocrystal clusters are regarded as a promising candidate for MR fluid with enhanced sedimentation stability.

The cell-type specific uptake of polymer-coated or micelle-embedded QDs and SPIOs does not provoke an acute pro-inflammatory response in the liver

Directory of Open Access Journals (Sweden)

Markus Heine

2014-09-01

Full Text Available Semiconductor quantum dots (QD and superparamagnetic iron oxide nanocrystals (SPIO have exceptional physical properties that are well suited for biomedical applications in vitro and in vivo. For future applications, the direct injection of nanocrystals for imaging and therapy represents an important entry route into the human body. Therefore, it is crucial to investigate biological responses of the body to nanocrystals to avoid harmful side effects. In recent years, we established a system to embed nanocrystals with a hydrophobic oleic acid shell either by lipid micelles or by the amphiphilic polymer poly(maleic anhydride-alt-1-octadecene (PMAOD. The goal of the current study is to investigate the uptake processes as well as pro-inflammatory responses in the liver after the injection of these encapsulated nanocrystals. By immunofluorescence and electron microscopy studies using wild type mice, we show that 30 min after injection polymer-coated nanocrystals are primarily taken up by liver sinusoidal endothelial cells. In contrast, by using wild type, Ldlr-/- as well as Apoe-/- mice we show that nanocrystals embedded within lipid micelles are internalized by Kupffer cells and, in a process that is dependent on the LDL receptor and apolipoprotein E, by hepatocytes. Gene expression analysis of pro-inflammatory markers such as tumor necrosis factor alpha (TNFα or chemokine (C-X-C motif ligand 10 (Cxcl10 indicated that 48 h after injection internalized nanocrystals did not provoke pro-inflammatory pathways. In conclusion, internalized nanocrystals at least in mouse liver cells, namely endothelial cells, Kupffer cells and hepatocytes are at least not acutely associated with potential adverse side effects, underlining their potential for biomedical applications.

Extraction and characterisation of cellulose nanocrystals from pineapple peel

Directory of Open Access Journals (Sweden)

Ana Raquel Madureira

2018-04-01

Full Text Available The potential of pineapple peel as a source of cellulose nanocrystals was evaluated. Peels skin from fresh-cut fruit was used as raw material. These residues were purified to remove pigments, lipids and hemicellulose, and a bleaching process for delignification was carried out for 4-6 h. All resulting products were characterised for their lignin, hemicellulose, cellulose and ash contents using standard techniques. Dry matter at the end was low (ca. 50% compared with the raw material (ca. 90%. The process applied resulted in ca. 20% (m/m of purified cellulose (ca. 80% purity, with ineligible levels of lignin and hemicellulose present, especially when using 6h of bleaching. The purified cellulose was subject to acid hydrolysis for nanocrystal extraction with two testing times, 30 and 60 minutes. These cellulose nanocrystals had small sizes (< 1000 nm, with high variability and negative zeta potential values. The time of extraction did not affect the nanocrystals’ chemical and physical properties. The use of 6 h of bleaching treatment during purification was shown to be more effective than 4 h. Pineapple peel was demonstrated to be a good source of cellulose for the production of cellulose nanocrystals.

Effects of substitute coated with hyaluronic acid or poly-lactic acid on implant fixation. Experimental study in ovariectomized and glucocorticoid treated sheep

DEFF Research Database (Denmark)

Andreasen, Christina M; Ding, Ming; Andersen, Thomas L

2018-01-01

Investigated in healthy animal models, hyaluronic acid (HyA) and poly-D,L -lactic acid (PDLLA) demonstrate osteoconductive properties when coated onto hydroxyapatite (HA) and β-tricalcium phosphate (βTCP) scaffolds. In this study, we examined the efficacy of HA/βTCP granules coated with HyA or PD...... formation, HyA and PDDLA are indeed considered valuable as new coating materials for composite ceramics when tested in a sheep model - even in bones of a compromised quality.......Investigated in healthy animal models, hyaluronic acid (HyA) and poly-D,L -lactic acid (PDLLA) demonstrate osteoconductive properties when coated onto hydroxyapatite (HA) and β-tricalcium phosphate (βTCP) scaffolds. In this study, we examined the efficacy of HA/βTCP granules coated with Hy...... allograft obtained from a healthy donor sheep (control), pure HA/βTCP, HA/βTCP-HyA or HA/βTCP-PDLLA. After 12 weeks, the bone formation adjacent to the implant surface was evaluated by histology and histomorphometry, while the implant fixation was measured by a push-out test. The investigation showed a bone...

Effect of acetic acid on rice seeds coated with rice husk ash

Directory of Open Access Journals (Sweden)

Lizandro Ciciliano Tavares

2013-06-01

Full Text Available Flooded rice cultivation promotes anaerobic conditions, favoring the formation of short chain organic acids such as acetic acid, which may be toxic to the crop. The objective of this study was to evaluate the effect of acetic acid on rice seeds coated with rice husk ash. The experiment was arranged in a 2 x 5 x 5 factorial randomized design, with two cultivars (IRGA 424 and BRS Querência, five doses of coating material (0, 2, 3,4 e 5 g kg-1 seed and five concentrations of acetic acid (0, 3, 6, 9 and 12 mM, with 4 replications, totaling 50 treatments. The variables first count of germination, germination, shoot and root length, dry weight of shoots and roots were recorded. The results showed that coating rice seeds with rice husk ash up to 5 g kg-1 seed does not influence the performance of rice seeds of cultivars IRGA 424 and BRS Querência when exposed to concentrations of 12 mM acetic acid. The presence of acetic acid in the substrates used for seed germination reduced the vigor and viability of seeds of cultivars IRGA 424 and BRS Querência, as well as seedling development, affecting mainly the roots of BRS Querência.

Deciphering ligands' interaction with Cu and Cu2O nanocrystal surfaces by NMR solution tools.

Science.gov (United States)

Glaria, Arnaud; Cure, Jérémy; Piettre, Kilian; Coppel, Yannick; Turrin, Cédric-Olivier; Chaudret, Bruno; Fau, Pierre

2015-01-12

The hydrogenolysis of [Cu2{(iPrN)2(CCH3)}2] in the presence of hexadecylamine (HDA) or tetradecylphosphonic acid (TDPA) in toluene leads to 6-9 nm copper nanocrystals. Solution NMR spectroscopy has been used to describe the nanoparticle surface chemistry during the dynamic phenomenon of air oxidation. The ligands are organized as multilayered shells around the nanoparticles. The shell of ligands is controlled by both their intermolecular interactions and their bonding strength on the nanocrystals. Under ambient atmosphere, the oxidation rate of colloidal copper nanocrystals closely relies on the chemical nature of the employed ligands (base or acid). Primary amine molecules behave as soft ligands for Cu atoms, but are even more strongly coordinated on surface Cu(I) sites, thus allowing a very efficient corrosion protection of the copper core. On the contrary, the TDPA ligands lead to a rapid oxidation rate of Cu nanoparticles and eventually to the re-dissolution of Cu(II) species at the expense of the nanocrystals. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced washing durability of hydrophobic coating on cellulose fabric using polycarboxylic acids

International Nuclear Information System (INIS)

Huang Wenqi; Xing Yanjun; Yu Yunyi; Shang Songmin; Dai Jinjin

2011-01-01

Nine polycarboxylic acids were used to improve washing durability of hydrophobic cellulose fabric finished by sol-gel method. By simultaneous forming ester-bridge between cellulose and silica layer by ester bond, polycarboxylic acids could anchor silica coating onto cellulose fabric to strengthen the adhesion of organic-inorganic hybrid coating. The wettability of treated fabrics was characterized by water contact angle, spray test and hydrostatic pressure test. The results showed that all investigated polycarboxylic acids could improve the durability. The polycarboxylic acid with proper distance between terminal carboxylic acid groups and number of carboxylic acid groups showed the highest durability. 1,2,3,4-butanetetracarboxylic acid (BTCA) led to the best durability of hydrophobic cellulose fabric with water contact angle of 137.6 o (recovery percentage of 94.2%) after 30 washing times. The effect of BTCA on durability was characterized by scanning electron microscopy. This study demonstrated that the surface treatment using polycarboxylic acids and mixed organosilanes is a promising alternative for achieving durable hydrophobic fabrics.

Effects of hydrazine on the solvothermal synthesis of Cu{sub 2}ZnSnSe{sub 4} and Cu{sub 2}CdSnSe{sub 4} nanocrystals for particle-based deposition of films

Energy Technology Data Exchange (ETDEWEB)

Chiang, Ming-Hung [Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan 701 (China); Fu, Yaw-Shyan, E-mail: ysfu@mail.nutn.edu.tw [Department of Greenergy, National University of Tainan, Tainan, Taiwan 700 (China); Shih, Cheng-Hung; Kuo, Chun-Cheng [Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan 701 (China); Guo, Tzung-Fang [Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan 701 (China); Lin, Wen-Tai, E-mail: wtlin@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan 701 (China)

2013-10-01

The effects of hydrazine on the synthesis of Cu{sub 2}ZnSnSe{sub 4} (CZTSe) and Cu{sub 2}CdSnSe{sub 4} (CCTSe) nanocrystals in an autoclave as a function of temperature and time were explored. On heating at 190 °C for 24-72 h, pure CZTSe and CCTSe nanocrystals could readily grow in the hydrazine-added solution, while in the hydrazine-free solution the intermediate phases such as ZnSe, Cu{sub 2}Se, and Cu{sub 2}SnSe{sub 3}, and Cu{sub 2}SnSe{sub 3} and CdSe associated with the CZTSe and CCTSe nanocrystals grew, respectively. This result reveals that hydrazine can speed up the synthesis of pure CZTSe and CCTSe nanocrystals via a solvothermal process. The mechanisms for the hydrazine-enhanced growth of CZTSe and CCTSe nanocrystals were discussed. The pure CZTSe and CCTSe nanocrystals were subsequently fabricated to the smooth films by spin coating without further annealing in selenium atmosphere. This processing may be beneficial to the fabrication of the absorber layer for solar cells and thermoelectric devices. - Highlights: • Hydrazine enhances the growth of pure Cu{sub 2}ZnSnSe{sub 4} and Cu{sub 2}CdSnSe{sub 4} nanocrystals. • The nanocrystals can be fabricated to films by spin coating without annealing. • This solvothermal processing is promising for the fabrication of thin film devices.

Deposition of tellurium films by decomposition of electrochemically-generated H{sub 2}Te: application to radiative cooling devices

Energy Technology Data Exchange (ETDEWEB)

Engelhard, T.; Jones, E.D.; Viney, I. [Coventry Univ. (United Kingdom). Centre for Data Storage Mater.; Mastai, Y.; Hodes, G. [Department of Materials and Interfaces, Weizmann Institute of Science, 76100, Rehovot (Israel)

2000-07-17

The preparation of homogenous, large area thin layers of tellurium on thin polyethylene foils is described. The tellurium was formed by room temperature decomposition of electrochemically generated H{sub 2}Te. Pre-treatment of the polyethylene substrates with KMnO{sub 4} to give a Mn-oxide layer was found to improve the Te adhesion and homogeneity. Optical characterization of the layers was performed using UV/VIS/NIR spectroscopy. Such coatings have favorable characteristics for use as solar radiation shields in radiative cooling devices. The simplicity of generation of the very unstable H{sub 2}Te was also exploited to demonstrate formation of size-quantized CdTe nanocrystals. (orig.)

Electrodeposition of CdTe thin film from acetate-based ionic liquid bath

Science.gov (United States)

Waldiya, Manmohansingh; Bhagat, Dharini; Mukhopadhyay, Indrajit

2018-05-01

CdTe being a direct band gap semiconductor, is mostly used in photovoltaics. Here we present, the synthesis of CdTe thin film on fluorine doped tin oxide (FTO) substrate potentiostatically using 1-butyl-3-methylimidazolium acetate ([Bmim][Ac]) ionic liquid (IL) bath at 90 °C. Major advantages of using electrodeposition involves process simplicity, large scalability & economic viability. Some of the benefits offered by IL electrolytic bath are low vapour pressure, wide electrochemical window, and good ionic mobility. Cd(CH3COO)2 (anhydrous) and TeO2 were used as the source precursors. The IL electrolytic bath temperature was kept at 90 °C for deposition, owing to the limited solubility of TeO2 in [Bmim][Ac] IL at room temperature. Cathodic electrodeposition was carried out using a three electrode cell setup at a constant potential of -1.20 V vs. platinum (Pt) wire. The CdTe/FTO thin film were annealed in argon (Ar) atmosphere. Optical study of nanostructured CdTe film were done using UV-Vis-IR and Raman spectroscopy. Raman analysis confirms the formation of CdTe having surface optics (SO) mode at 160.6 cm-1 and transverse optics (TO) mode at 140.5 cm-1. Elemental Te peaks at 123, 140.5 and 268 cm-1 were also observed. The optical band gap of Ar annealed CdTe thin film were found to be 1.47 eV (absorbance band edge ˜ 846 nm). The optimization of deposition parameters using acetate-based IL electrolytic bath to get nearly stoichiometric CdTe thin film is currently being explored.

Ultrasensitive fluorescence immunoassay for detection of ochratoxin A using catalase-mediated fluorescence quenching of CdTe QDs

Science.gov (United States)

Huang, Xiaolin; Zhan, Shengnan; Xu, Hengyi; Meng, Xianwei; Xiong, Yonghua; Chen, Xiaoyuan

2016-04-01

Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to perform a dynamic linear detection of OTA ranging from 0.05 pg mL-1 to 10 pg mL-1. The half maximal inhibitory concentration was 0.53 pg mL-1 and the limit of detection was 0.05 pg mL-1. These values were approximately 283- and 300-folds lower than those of horseradish peroxidase (HRP)-based conventional ELISA, respectively. The reported method is accurate, highly reproducible, and specific against other mycotoxins in agricultural products as well. In summary, the developed fluorescence immunoassay based on H2O2-induced fluorescence quenching of CdTe QDs can be used for the rapid and highly sensitive detection of mycotoxins or haptens in food safety monitoring.Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to

An Experimental Study on the Shape Changes of TiO2 Nanocrystals Synthesized by Microemulsion-Solvothermal Method

Directory of Open Access Journals (Sweden)

Wei Kong

2011-01-01

Full Text Available Titanium dioxide (TiO2 nanocrystals of different shape were successfully synthesized in a new microemulsion system through a solvothermal process. The TiO2 nanocrystals were prepared from the reaction of tetrabutyl titanate (TBT, H2O, and oleic acid (OA, which were used as solvent and surfactant at 300∘C and 240∘C in a stainless steel autoclave. The sphere, polygon, and rhombus-shaped nanocrystals have been prepared at 300∘C and the dot- and- rod shaped nanocrystals have been synthesized at 240∘C. The effect of the reaction time on the shape and size of TiO2 nanocrystals in this method was studied in the present paper. The size distribution of TiO2 nanocrystals prepared at 300∘C for different hours is also studied. In addition, an attempt to describe the mechanism of shape change of TiO2 nanocrystals was presented in this paper.

CDTE alloys and their application for increasing solar cell performance

Science.gov (United States)

Swanson, Drew E.

Cadmium Telluride (CdTe) thin film solar is the largest manufactured solar cell technology in the United States and is responsible for one of the lowest costs of utility scale solar electricity at a purchase agreement of $0.0387/kWh. However, this cost could be further reduced by increasing the cell efficiency. To bridge the gap between the high efficiency technology and low cost manufacturing, a research and development tool and process was built and tested. This fully automated single vacuum PV manufacturing tool utilizes multiple inline close space sublimation (CSS) sources with automated substrate control. This maintains the proven scalability of the CSS technology and CSS source design but with the added versatility of independent substrate motion. This combination of a scalable deposition technology with increased cell fabrication flexibility has allowed for high efficiency cells to be manufactured and studied. The record efficiency of CdTe solar cells is lower than fundamental limitations due to a significant deficit in voltage. It has been modeled that there are two potential methods of decreasing this voltage deficiency. The first method is the incorporation of a high band gap film at the back contact to induce a conduction-band barrier that can reduce recombination by reflecting electrons from the back surface. The addition of a Cd1-x MgxTe (CMT) layer at the back of a CdTe solar cell should induce this desired offset and reflect both photoelectrons and forward-current electrons away from the rear surface. Higher collection of photoelectrons will increase the cells current and the reduction of forward current will increase the cells voltage. To have the optimal effect, CdTe must have reasonable carrier lifetimes and be fully depleted. To achieve this experimentally, CdTe layers have been grown sufficiently thin to help produce a fully depleted cell. A variety of measurements including performance curves, transmission electron microscopy, x

A strategy for prediction of the elastic properties of epoxy-cellulose nanocrystal-reinforced fiber networks

Science.gov (United States)

Johnathan E. Goodsell; Robert J. Moon; Alionso Huizar; R. Byron Pipes

2014-01-01

The reinforcement potential of cellulose nanocrystal (CNC) additions on an idealized 2-dirmensional (2-D) fiber network structure consisting of micron sized fiber elements was investigated. The reinforcement mechanism considered in this study was through the stiffening of the micron sized fiber elements via a CNC-epoxy coating. A hierarchical analytical modeling...

Comparative Study on the Efficiency of the Photodynamic Inactivation of Candida albicans Using CdTe Quantum Dots, Zn(II Porphyrin and Their Conjugates as Photosensitizers

Directory of Open Access Journals (Sweden)

Osnir S. Viana

2015-05-01

Full Text Available The application of fluorescent II-VI semiconductor quantum dots (QDs as active photosensitizers in photodymanic inactivation (PDI is still being evaluated. In the present study, we prepared 3 nm size CdTe QDs coated with mercaptosuccinic acid and conjugated them electrostatically with Zn(II meso-tetrakis (N-ethyl-2-pyridinium-2-yl porphyrin (ZnTE-2-PyP or ZnP, thus producing QDs-ZnP conjugates. We evaluated the capability of the systems, bare QDs and conjugates, to produce reactive oxygen species (ROS and applied them in photodynamic inactivation in cultures of Candida albicans by irradiating the QDs and testing the hypothesis of a possible combined contribution of the PDI action. Tests of in vitro cytotoxicity and phototoxicity in fibroblasts were also performed in the presence and absence of light irradiation. The overall results showed an efficient ROS production for all tested systems and a low cytotoxicity (cell viability >90% in the absence of radiation. Fibroblasts incubated with the QDs-ZnP and subjected to irradiation showed a higher cytotoxicity (cell viability <90% depending on QD concentration compared to the bare groups. The PDI effects of bare CdTe QD on Candida albicans demonstrated a lower reduction of the cell viability (~1 log10 compared to bare ZnP which showed a high microbicidal activity (~3 log10 when photoactivated. The QD-ZnP conjugates also showed reduced photodynamic activity against C. albicans compared to bare ZnP and we suggest that the conjugation with QDs prevents the transmembrane cellular uptake of the ZnP molecules, reducing their photoactivity.

Nitrogen-Doped Nanoporous Carbon Membranes with Co/CoP Janus-Type Nanocrystals as Hydrogen Evolution Electrode in Both Acidic and Alkaline Environments

KAUST Repository

Wang, Hong

2017-03-31

Self-supported electrocatalysts being generated and employed directly as electrodes for energy conversion has been intensively pursued in the fields of materials chemistry and energy. Herein, we report a synthetic strategy to prepare freestanding hierarchically structured, nitrogen-doped nanoporous graphitic carbon membranes functionalized with Janus-type Co/CoP nanocrystals (termed as HNDCM-Co/CoP), which were successfully applied as a highly efficient, binder-free electrode in the hydrogen evolution reaction (HER). Benefited from multiple structural merits, such as a high degree of graphitization, three-dimensionally interconnected micro/meso/macropores, uniform nitrogen doping, well-dispersed Co/CoP nanocrystals, as well as the confinement effect of the thin carbon layer on the nanocrystals, HNDCM-Co/CoP exhibited superior electrocatalytic activity and long-term operation stability for HER under both acidic and alkaline conditions. As a proof-of-concept of practical usage, a 5.6 cm × 4 cm × 60 μm macroscopic piece of HNDCM-Co/CoP was prepared in our laboratory. Driven by a solar cell, electroreduction of water in alkaline conditions (pH 14) was performed, and H was produced at a rate of 16 mL/min, demonstrating its potential as real-life energy conversion systems.

Microstructure, thermal properties and crystallinity of amadumbe starch nanocrystals.

Science.gov (United States)

Mukurumbira, Agnes; Mariano, Marcos; Dufresne, Alain; Mellem, John J; Amonsou, Eric O

2017-09-01

Amadumbe (Colocasia esculenta), commonly known as taro is a tropical tuber that produces starch-rich underground corms. In this study, the physicochemical properties of starch nanocrystals (SNC) prepared by acid hydrolysis of amadumbe starches were investigated. Two varieties of amadumbe corms were used for starch extraction. Amadumbe starches produced substantially high yield (25%) of SNC's. These nanocrystals appeared as aggregated and individual particles and possessed square-like platelet morphology with size: 50-100nm. FTIR revealed high peak intensities corresponding to OH stretch, CH stretch and H 2 O bending vibrations for SNCs compared to their native starch counterparts. Both the native starch and SNC exhibited the A-type crystalline pattern. However, amadumbe SNCs showed higher degree of crystallinity and slightly reduced melting temperatures than their native starches. Amadumbe SNCs presented similar thermal decomposition property as their native starches. Amadumbe starch nanocrystals may have potential application in biocomposite films due to their square-like platelet morphology. Copyright © 2017 Elsevier B.V. All rights reserved.

Cytotoxicity assessment of functionalized CdSe, CdTe and InP quantum dots in two human cancer cell models

International Nuclear Information System (INIS)

Liu, Jing; Hu, Rui; Liu, Jianwei; Zhang, Butian; Wang, Yucheng; Liu, Xin; Law, Wing-Cheung; Liu, Liwei; Ye, Ling; Yong, Ken-Tye

2015-01-01

The toxicity of quantum dots (QDs) has been extensively studied over the past decade. Some common factors that originate the QD toxicity include releasing of heavy metal ions from degraded QDs and the generation of reactive oxygen species on the QD surface. In addition to these factors, we should also carefully examine other potential QD toxicity causes that will play crucial roles in impacting the overall biological system. In this contribution, we have performed cytotoxicity assessment of four types of QD formulations in two different human cancer cell models. The four types of QD formulations, namely, mercaptopropionic acid modified CdSe/CdS/ZnS QDs (CdSe-MPA), PEGylated phospholipid encapsulated CdSe/CdS/ZnS QDs (CdSe-Phos), PEGylated phospholipid encapsulated InP/ZnS QDs (InP-Phos) and Pluronic F127 encapsulated CdTe/ZnS QDs (CdTe-F127), are representatives for the commonly used QD formulations in biomedical applications. Both the core materials and the surface modifications have been taken into consideration as the key factors for the cytotoxicity assessment. Through side-by-side comparison and careful evaluations, we have found that the toxicity of QDs does not solely depend on a single factor in initiating the toxicity in biological system but rather it depends on a combination of elements from the particle formulations. More importantly, our toxicity assessment shows different cytotoxicity trend for all the prepared formulations tested on gastric adenocarcinoma (BGC-823) and neuroblastoma (SH-SY5Y) cell lines. We have further proposed that the cellular uptake of these nanocrystals plays an important role in determining the final faith of the toxicity impact of the formulation. The result here suggests that the toxicity of QDs is rather complex and it cannot be generalized under a few assumptions reported previously. We suggest that one have to evaluate the QD toxicity on a case to case basis and this indicates that standard procedures and comprehensive

Cytotoxicity assessment of functionalized CdSe, CdTe and InP quantum dots in two human cancer cell models

Energy Technology Data Exchange (ETDEWEB)

Liu, Jing [Institute of Gerontology and Geriatrics & Beijing Key Lab of Aging and Geriatrics, Chinese PLA General Hospital, Beijing 100853 (China); Hu, Rui [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Liu, Jianwei [Institute of Gerontology and Geriatrics & Beijing Key Lab of Aging and Geriatrics, Chinese PLA General Hospital, Beijing 100853 (China); Zhang, Butian; Wang, Yucheng [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Liu, Xin [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Law, Wing-Cheung [Department of Industrial and System Engineering, The Hang Kong Polytechnic University, Hung Hom (Hong Kong); Liu, Liwei [School of Science, Changchun University of Science and Technology, Changchun 130022 (China); Ye, Ling, E-mail: lye_301@163.com [Institute of Gerontology and Geriatrics & Beijing Key Lab of Aging and Geriatrics, Chinese PLA General Hospital, Beijing 100853 (China); Yong, Ken-Tye, E-mail: ktyong@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

2015-12-01

The toxicity of quantum dots (QDs) has been extensively studied over the past decade. Some common factors that originate the QD toxicity include releasing of heavy metal ions from degraded QDs and the generation of reactive oxygen species on the QD surface. In addition to these factors, we should also carefully examine other potential QD toxicity causes that will play crucial roles in impacting the overall biological system. In this contribution, we have performed cytotoxicity assessment of four types of QD formulations in two different human cancer cell models. The four types of QD formulations, namely, mercaptopropionic acid modified CdSe/CdS/ZnS QDs (CdSe-MPA), PEGylated phospholipid encapsulated CdSe/CdS/ZnS QDs (CdSe-Phos), PEGylated phospholipid encapsulated InP/ZnS QDs (InP-Phos) and Pluronic F127 encapsulated CdTe/ZnS QDs (CdTe-F127), are representatives for the commonly used QD formulations in biomedical applications. Both the core materials and the surface modifications have been taken into consideration as the key factors for the cytotoxicity assessment. Through side-by-side comparison and careful evaluations, we have found that the toxicity of QDs does not solely depend on a single factor in initiating the toxicity in biological system but rather it depends on a combination of elements from the particle formulations. More importantly, our toxicity assessment shows different cytotoxicity trend for all the prepared formulations tested on gastric adenocarcinoma (BGC-823) and neuroblastoma (SH-SY5Y) cell lines. We have further proposed that the cellular uptake of these nanocrystals plays an important role in determining the final faith of the toxicity impact of the formulation. The result here suggests that the toxicity of QDs is rather complex and it cannot be generalized under a few assumptions reported previously. We suggest that one have to evaluate the QD toxicity on a case to case basis and this indicates that standard procedures and comprehensive

Solvothermal synthesis of TiO2 nanocrystals with {001} facets using titanic acid nanobelts for superior photocatalytic activity

Science.gov (United States)

Cao, Yuhui; Zong, Lanlan; Li, Qiuye; Li, Chen; Li, Junli; Yang, Jianjun

2017-01-01

Anatase TiO2 nanocrystals exposed with {001} facets were fabricated by solvothermal strategy in HF-C4H9OH mixed solution, using titanic acid nanobelts (TAN) as a precursor. The shape of TAN is a long flat plane with a high aspect ratio, and F- is easily adsorbed on the surface of the nanobelts, inducing a higher exposure of {001} facet of TiO2 nanoparticles during the structure reorganization. The exposed percentage of {001} facets could vary from 40 to 77% by adjusting the amount of HF. The as-prepared samples were characterized by transmission electron microscopy, N2 adsorption-desorption isotherms, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscope. The photocatalytic measurement showed that TiO2 nanocrystals with 77% {001} facets exhibited much superior photocatalytic activity for photodegradation of methyl orange, methylene blue, and rhodamine B. And what's more, the mineralization rate of methyl orange was as high as 96% within 60 min. The photocatalytic enhancement is due to a large amount of the high energetic {001} facets exposing, the special truncated octahedral morphology and a stronger ability for dyes adsorption.

Preparation, characterization and catalytic effects of copper oxalate nanocrystals

International Nuclear Information System (INIS)

Singh, Gurdip; Kapoor, Inder Pal Singh; Dubey, Reena; Srivastava, Pratibha

2012-01-01

Graphical abstract: Prepared copper oxalate nanocrystals were characterized by FE-SEM and bright field TEM micrographs. Its catalytic activity was evaluated on the thermal decomposition of ammonium perchlorate using TG and TG-DSC techniques. Highlights: ► Preparation of nanocrystals (∼9.0 nm) of copper oxalate using Cu(NO 3 ) 2 ·2H 2 O, oxalic acid and acetone under thermal conditions. ► Method is simple and novel. ► Characterization using XRD, SEM, TEM, HRTEM and ED pattern. ► Catalytic activity of copper oxalate nanocrystals on AP thermal decomposition using thermal techniques (TG, TG-DSC and ignition delay). ► Kinetics of thermal decomposition of AP + CONs using isoconversional and model fitting kinetic approaches. - Abstract: Recent work has described the preparation and characterization of copper oxalate nanocrystals (CONs). It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and electron diffraction pattern (ED). The catalytic activity of CONs on the thermal decomposition of ammonium perchlorate (AP) and composite solid propellants (CSPs) has been done by thermogravimetry (TG), differential scanning calorimetry (DSC) and ignition delay measurements. Burning rate of CSPs was also found to be enhanced in presence of copper oxalate nanocrystals. Kinetics of thermal decomposition of AP with and without CONs has also been investigated. The model free (isoconversional) and model-fitting kinetic approaches have been applied to data for isothermal TG decomposition.

Probing lipid coating dynamics of quantum dot core micelles via förster resonance energy transfer

NARCIS (Netherlands)

Zhao, Yiming; Schapotschnikow, Philipp; Skajaa, Torjus; Vlugt, Thijs J H; Mulder, Willem J M; De Mello Donegá, Celso; Meijerink, A

2014-01-01

Lipid coated nanocrystal assemblies are among the most extensively investigated nanoparticle platforms for biomedical imaging and therapeutic purposes. However, very few efforts have been addressed to the lipid coating exchange dynamics in such systems, which is key to our understanding of the

Thermodynamic Study of the Interaction of Bovine Serum Albumin and Amino Acids with Cellulose Nanocrystals

OpenAIRE

Lombardo, Salvatore; Eyley, Sam; Schütz, Christina; Van Gorp, Hans; Rosenfeldt, Sabine; Van den Mooter, Guy; Thielemans, Wim

2017-01-01

The interaction of bovine serum albumin (BSA) with sulfated, carboxylated, and pyridinium-grafted cellulose nanocrystals (CNCs) was studied as a function of the degree of substitution by determining the adsorption isotherm and by directly measuring the thermodynamics of interaction. The adsorption of BSA onto positively charged pyridinium-grafted cellulose nanocrystals followed Langmuirian adsorption with the maximum amount of adsorbed protein increasing linearly with increasing degree of sub...

Performance and Metastability of CdTe Solar Cells with a Te Back-Contact Buffer Layer

Science.gov (United States)

Moore, Andrew

Thin-film CdTe photovoltaics are quickly maturing into a viable clean-energy solution through demonstration of competitive costs and performance stability with existing energy sources. Over the last half decade, CdTe solar technology has achieved major gains in performance; however, there are still aspects that can be improved to progress toward their theoretical maximum efficiency. Perhaps equally valuable as high photovoltaic efficiency and a low levelized cost of energy, is device reliability. Understanding the root causes for changes in performance is essential for accomplishing long-term stability. One area for potential performance enhancement is the back contact of the CdTe device. This research incorporated a thin-film Te-buffer layer into the contact structure, between the CdTe and contact metal. The device performance and characteristics of many different back contact configurations were rigorously studied. CdTe solar cells fabricated with the Te-buffer contact showed short-circuit current densities and open-circuit voltages that were on par with the traditional back-contacts used at CSU. However, the Te-buffer contact typically produced 2% larger fill-factors on average, leading to greater conversation efficiency. Furthermore, using the Te buffer allowed for incorporation of 50% less Cu, which is used for p-type doping but is also known to decrease lifetime and stability. This resulted in an additional 3% fill-factor gain with no change in other parameters compared to the standard-Cu treated device. In order to better understand the physical mechanisms of the Te-buffer contact, electrical and material properties of the Te layer were extracted and used to construct a simple energy band diagram. The Te layer was found to be highly p-type (>1018 cm-3) and possess a positive valence-band offset of 0.35-0.40 eV with CdTe. An existing simulation model incorporating the Te-layer properties was implemented and validated by comparing simulated results of CdTe

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.

Rapid synthesis of CdSe nanocrystals in aqueous solution at room ...

Indian Academy of Sciences (India)

Administrator

Water-soluble thioglycolic acid-capped CdSe nanocrystals (NCs) were prepared in aqueous solu- tion at room temperature. We investigated the ... NCs dispersed in buffer solution (pH = 4⋅0). FTIR spectra were recorded on a ... the theory of acid-base equilibrium, the initial pH value of original solution determines the ...

CCN activation experiments with adipic acid: effect of particle phase and adipic acid coatings on soluble and insoluble particles

Directory of Open Access Journals (Sweden)

S. S. Hings

2008-07-01

Full Text Available Slightly soluble atmospherically relevant organic compounds may influence particle CCN activity and therefore cloud formation. Adipic acid is a frequently employed surrogate for such slightly soluble organic materials. The 11 published experimental studies on the CCN activity of adipic acid particles are not consistent with each other nor do they, in most cases, agree with the Köhler theory. The CCN activity of adipic acid aerosol particles was studied over a significantly wider range of conditions than in any previous single study. The work spans the conditions of the previous studies and also provides alternate methods for producing "wet" (deliquesced solution droplets and dry adipic acid particles without the need to produce them by atomization of aqueous solutions. The experiments suggest that the scatter in the previously published CCN measurements is most likely due to the difficulty of producing uncontaminated adipic acid particles by atomization of solutions and possibly also due to uncertainties in the calibration of the instruments. The CCN activation of the small (d_m<150 nm initially dry particles is subject to a deliquescence barrier, while for the larger particles the activation follows the Köhler curve. Wet adipic acid particles follow the Köhler curve over the full range of particle diameters studied. In addition, the effect of adipic acid coatings on the CCN activity of both soluble and insoluble particles has also been studied. When a water-soluble core is coated by adipic acid, the CCN-hindering effect of particle phase is eliminated. An adipic acid coating on hydrophobic soot yields a CCN active particle. If the soot particle is relatively small (d_core≤102 nm, the CCN activity of the coated particles approaches the deliquescence line of adipic acid, suggesting that the total size of the particle determines CCN activation and the soot core acts as a scaffold.

Optimizing colloidal nanocrystals for applications

International Nuclear Information System (INIS)

Sytnyk, M.

2015-01-01

In the scientific literature colloidal nanocrystals are presented as promising materials for multiple applications, in areas covering optoelectronics, photovoltaics, spintronics, catalysis, and bio-medicine. On the marked are, however, only a very limited number of examples found, indeed implementing colloidal nanocrystals. Thus the scope of this thesis was to modify nanocrystals and to tune their properties to fulfill specific demands. While some modifications could be achieved by post synthetic treatments, one key problem of colloidal nanocrystals, hampering there widespread application is the toxicity of their constituents. To develop nanocrystals from non-toxic materials has been a major goal of this thesis as well. Roughly, the results in this thesis could be subdivided into three parts: (i) the development of ion exchange methods to tailor the properties of metallic and metal-oxide based nanocrystal heterostructures, (ii), the synthesis of semiconductor nanocrystals from non-toxic materials, and (iii) the characterization of the nanocrystals by measurements of their morphology, chemical composition, magnetic-, optical-, and electronic properties. In detail, the thesis is subdivided into an introductory chapter, 4 chapters reporting on scientific results, a chapter reporting the used methods, and the conclusions. The 4 chapters devoted to the scientific results correspond to manuscripts, which are either currently in preparation, or have been published in highly ranked scientific journals such as NanoLetters (chapter 2), ACS Nano (chapter 4), or JACS (chapter 5). Thus, these chapters provide also an extra introduction and conclusion section, as well as separate reference lists. Chapter 2 describes a cation exchange process which is used to tune and improve the magnetic properties of different iron-oxide based colloidal nanocrystal-heterostructures. The superparamagnetic blocking temperature, magnetic remanence, and coercivity is tuned by replacing Fe2+ by Co2

Tests of UFXC32k chip with CdTe pixel detector

Science.gov (United States)

Maj, P.; Taguchi, T.; Nakaye, Y.

2018-02-01

The paper presents the performance of the UFXC32K—a hybrid pixel detector readout chip working with CdTe detectors. The UFXC32K has a pixel pitch of 75 μm and can cope with both input signal polarities. This functionality allows operating with widely used silicon sensors collecting holes and CdTe sensors collecting electrons. This article describes the chip focusing on solving the issues connected to high-Z sensor material, namely high leakage currents, slow charge collection time and thick material resulting in increased charge-sharring effects. The measurements were conducted with higher X-ray energies including 17.4 keV from molybdenum. Conclusions drawn inside the paper show the UFXC32K's usability for CdTe sensors in high X-ray energy applications.

Composite biodegradable biopolymer coatings of silk fibroin - Poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) for biomedical applications

Science.gov (United States)

Miroiu, Floralice Marimona; Stefan, Nicolaie; Visan, Anita Ioana; Nita, Cristina; Luculescu, Catalin Romeo; Rasoga, Oana; Socol, Marcela; Zgura, Irina; Cristescu, Rodica; Craciun, Doina; Socol, Gabriel

2015-11-01

Composite silk fibroin-poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) (SF-PHBV) biodegradable coatings were grown by Matrix Assisted Pulsed Laser Evaporation on titanium substrates. Their physico-chemical properties and particularly the degradation behavior in simulated body fluid at 37 °C were studied as first step of applicability in local controlled release for tissue regeneration applications. SF and PHBV, natural biopolymers with excellent biocompatibility, but different biodegradability and tensile strength properties, were combined in a composite to improve their properties as coatings for biomedical uses. FTIR analyses showed the stoichiometric transfer from targets to coatings by the presence in the spectra of the main absorption maxima characteristic of both polymers. XRD investigations confirmed the FTIR results showing differences in crystallization behavior with respect to the SF and PHBV content. Contact angle values obtained through wettability measurements indicated the MAPLE deposited coatings were highly hydrophilic; surfaces turning hydrophobic with the increase of the PHBV component. Degradation assays proved that higher PHBV contents resulted in enhanced resistance and a slower degradation rate of composite coatings in SBF. Distinct drug-release schemes could be obtained by adjusting the SF:PHBV ratio to controllably tuning the coatings degradation rate, from rapid-release formulas, where SF predominates, to prolonged sustained ones, for larger PHBV content.

CdTe deposition by successive ionic layer adsorption and reaction (SILAR) technique onto ZnO nanowires

Energy Technology Data Exchange (ETDEWEB)

Salazar, Raul; Delamoreanu, Alexandru; Saidi, Bilel; Ivanova, Valentina [CEA, LETI, MINATEC Campus, 17 Rue des Martyrs, 38054, Grenoble (France); Levy-Clement, Claude [CNRS, Institut de Chimie et des Materiaux de Paris-Est, 94320, Thiais (France)

2014-09-15

In this study is reported CdTe deposition by Successive Ionic Layer Adsorption and reaction (SILAR) at room temperature onto ZnO nanowires (NWs). The as-deposited CdTe layer exhibits poor crystalline quality and not well defined optical transition which is probably result of its amorphous nature. The implementation of an annealing step and chemical treatment by CdCl{sub 2} to the classical SILAR technique improved significantly the CdTe film quality. The XRD analysis showed that the as treated layers are crystallized in the cubic zinc blende structure. The full coverage of ZnO nanowires and thickness of the CdTe shell, composed of small crystallites, was confirmed by STEM and TEM analysis. The layer thickness could be controlled by the number of SILAR cycles. The sharper optical transitions for the annealed and CdCl{sub 2} treated heterostructures additionally proves the enhancement of the layer crystalline quality. For comparison CdTe was also deposited by close space sublimation (CSS) method onto ZnO nanowires. It is shown that the SILAR deposited CdTe exhibits equal crystalline and optical properties to that prepared by CSS. These results demonstrate that SILAR technique is more suitable for conformal thin film deposition on nanostructures. CdTe extremely thin film deposited by SILAR method onto ZnO nanowire. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

CdTe deposition by successive ionic layer adsorption and reaction (SILAR) technique onto ZnO nanowires

International Nuclear Information System (INIS)

Salazar, Raul; Delamoreanu, Alexandru; Saidi, Bilel; Ivanova, Valentina; Levy-Clement, Claude

2014-01-01

In this study is reported CdTe deposition by Successive Ionic Layer Adsorption and reaction (SILAR) at room temperature onto ZnO nanowires (NWs). The as-deposited CdTe layer exhibits poor crystalline quality and not well defined optical transition which is probably result of its amorphous nature. The implementation of an annealing step and chemical treatment by CdCl 2 to the classical SILAR technique improved significantly the CdTe film quality. The XRD analysis showed that the as treated layers are crystallized in the cubic zinc blende structure. The full coverage of ZnO nanowires and thickness of the CdTe shell, composed of small crystallites, was confirmed by STEM and TEM analysis. The layer thickness could be controlled by the number of SILAR cycles. The sharper optical transitions for the annealed and CdCl 2 treated heterostructures additionally proves the enhancement of the layer crystalline quality. For comparison CdTe was also deposited by close space sublimation (CSS) method onto ZnO nanowires. It is shown that the SILAR deposited CdTe exhibits equal crystalline and optical properties to that prepared by CSS. These results demonstrate that SILAR technique is more suitable for conformal thin film deposition on nanostructures. CdTe extremely thin film deposited by SILAR method onto ZnO nanowire. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Metastability and reliability of CdTe solar cells

Science.gov (United States)

Guo, Da; Brinkman, Daniel; Shaik, Abdul R.; Ringhofer, Christian; Vasileska, Dragica

2018-04-01

Thin-film modules of all technologies often suffer from performance degradation over time. Some of the performance changes are reversible and some are not, which makes deployment, testing, and energy-yield prediction more challenging. Manufacturers devote significant empirical efforts to study these phenomena and to improve semiconductor device stability. Still, understanding the underlying reasons of these instabilities remains clouded due to the lack of ability to characterize materials at atomistic levels and the lack of interpretation from the most fundamental material science. The most commonly alleged causes of metastability in CdTe devices, such as ‘migration of Cu’, have been investigated rigorously over the past fifteen years. Still, the discussion often ended prematurely with stating observed correlations between stress conditions and changes in atomic profiles of impurities or CV doping concentration. Multiple hypotheses suggesting degradation of CdTe solar cell devices due to interaction and evolution of point defects and complexes were proposed, and none of them received strong theoretical or experimental confirmation. It should be noted that atomic impurity profiles in CdTe provide very little intelligence on active doping concentrations. The same elements could form different energy states, which could be either donors or acceptors, depending on their position in crystalline lattice. Defects interact with other extrinsic and intrinsic defects; for example, changing the state of an impurity from an interstitial donor to a substitutional acceptor often is accompanied by generation of a compensating intrinsic interstitial donor defect. Moreover, all defects, intrinsic and extrinsic, interact with the electrical potential and free carriers so that charged defects may drift in the electric field and the local electrical potential affects the formation energy of the point defects. Such complexity of interactions in CdTe makes understanding of temporal

Bionanocomposite films based on plasticized PLA-PHB/cellulose nanocrystal blends.

Science.gov (United States)

Arrieta, M P; Fortunati, E; Dominici, F; López, J; Kenny, J M

2015-05-05

Optically transparent plasticized poly(lactic acid) (PLA) based bionanocomposite films intended for food packaging were prepared by melt blending. Materials were plasticized with 15wt% of acetyl(tributyl citrate) (ATBC) to improve the material processability and to obtain flexibile films. Poly(hydroxybutyrate) (PHB) was used to increase PLA crystallinity. The thermal stability of the PLA-PHB blends was improved by the addition of 5 wt% of cellulose nanocrystals (CNC) or modified cellulose nanocrystals (CNCs) synthesized from microcrystalline cellulose. The combination of ATBC and cellulose nanocrystals, mainly the better dispersed CNCs, improved the interaction between PLA and PHB. Thus, an improvement on the oxygen barrier and stretchability was achieved in PLA-PHB-CNCs-ATBC which also displayed somewhat UV light blocking effect. All bionanocomposite films presented appropriate disintegration in compost suggesting their possible applications as biodegradable packaging materials. Copyright © 2014 Elsevier Ltd. All rights reserved.

Application of CdTe for the NeXT mission

International Nuclear Information System (INIS)

Takahashi, Tadayuki; Nakazawa, Kazuhiro; Watanabe, Shin; Sato, Goro; Mitani, Takefumi; Tanaka, Takaaki; Oonuki, Kousuke; Tamura, Ken'ichi; Tajima, Hiroyasu; Kamae, Tuneyoshi; Madejski, Greg; Nomachi, Masaharu; Fukazawa, Yasushi; Makishima, Kazuo; Kokubun, Motohide; Terada, Yukikatsu; Kataoka, Jun; Tashiro, Makoto

2005-01-01

Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) have been regarded as promising semiconductor materials for hard X-ray and γ-ray detection. The high-atomic number of the materials (Z Cd =48,Z Te =52) gives a high quantum efficiency in comparison with Si. The large band-gap energy (E g =1.5eV) allows to operate the detector at room temperature. Based on recent achievements in high-resolution CdTe detectors, in the technology of ASICs and in bump-bonding, we have proposed the novel hard X-ray and γ-ray detectors for the NeXT mission in Japan. The high-energy response of the super mirror onboard NeXT will enable us to perform the first sensitive imaging observations up to 80keV. The focal plane detector, which combines a fully depleted X-ray CCD and a pixellated CdTe detector, will provide spectra and images in the wide energy range from 0.5 to 80keV. In the soft γ-ray band up to ∼ 1MeV, a narrow field-of-view Compton γ-ray telescope utilizing several tens of layers of thin Si or CdTe detector will provide precise spectra with much higher sensitivity than present instruments. The continuum sensitivity will reach several x10 -8 photons -1 keV -1 cm -2 in the hard X-ray region and a few x10 -7 photons -1 keV -1 cm -2 in the soft γ-ray region

Influence of reductant and germanium concentration on the growth and stress development of germanium nanocrystals in silicon oxide matrix

International Nuclear Information System (INIS)

Chew, H G; Zheng, F; Choi, W K; Chim, W K; Foo, Y L; Fitzgerald, E A

2007-01-01

Germanium (Ge) nanocrystals have been synthesized by annealing co-sputtered SiO 2 -Ge samples in N 2 or forming gas (90% N 2 +10% H 2 ) at temperatures ranging from 700 to 1000 deg. C. We concluded that the annealing ambient, temperature and Ge concentration have a significant influence on the formation and evolution of the nanocrystals. We showed that a careful selective etching of the annealed samples in hydrofluoric acid solution enabled the embedded Ge nanocrystals to be liberated from the SiO 2 matrix. From the Raman results of the as-grown and the liberated nanocrystals, we established that the nanocrystals generally experienced compressive stress in the oxide matrix and the evolution of these stress states was intimately linked to the distribution, density, size and quality of the Ge nanocrystals

Understanding shape and morphology of unusual tubular starch nanocrystals.

Science.gov (United States)

Gong, Bei; Liu, Wenxia; Tan, Hua; Yu, Dehai; Song, Zhaoping; Lucia, Lucian A

2016-10-20

Starch nanocrystals (SNC) are aptly described as the insoluble degradation byproducts of starch granules that purportedly display morphologies that are platelet-like, round, square, and oval-like. In this work, we reported the preparation of SNC with unprecedented tubular structures through sulfuric acid hydrolysis of normal maize starch, subsequent exposure to ammonia and relaxation at 4°C. High-resolution transmission electron microscopy observation clearly proved that the SNCs possess tubular nanostructures with polygonal cross-section. After further reviewing the transformations of SNC by acid hydrolysis, ammonia treatment, and curing time at 4°C, a mechanism for T-SNC formation is suggested. It is conjectured that T-SNC gradually self-assembles by combination of smaller platelet-like/square nanocrystals likely loosely aggregated by starch molecular chains from residual amorphous regions. This work paves the way for the pursuit of new approaches for the preparation of starch-based nanomaterials possessing unique morphologies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Hydrogen production over Au-loaded mesoporous-assembled SrTiO3 nanocrystal photocatalyst: Effects of molecular structure and chemical properties of hole scavengers

International Nuclear Information System (INIS)

Puangpetch, Tarawipa; Chavadej, Sumaeth; Sreethawong, Thammanoon

2011-01-01

Graphical abstract: Formic acid, which is the smallest and completely-dissociated water-soluble carboxylic acid, exhibited the highest hydrogen production enhancement ability over the 1 wt.% Au-loaded mesoporous-assembled SrTiO 3 nanocrystal photocatalyst. Display Omitted Research highlights: → The 1 wt.% Au-loaded mesoporous-assembled SrTiO 3 nanocrystal photocatalyst was synthesized. → The molecular structure and chemical properties of hole scavengers affected H 2 production rate. → Formic acid exhibited the highest photocatalytic H 2 production enhancement ability. -- Abstract: The hydrogen production via the photocatalytic water splitting under UV irradiation using different compounds as hole scavengers (including methanol, formic acid, acetic acid, propanoic acid, hydrochloric acid, and sulfuric acid) under a low concentration range ( 3 nanocrystal photocatalyst. The results indicated that the hydrogen production efficiency greatly depended on the molecular structure, chemical properties, and concentration of the hole scavengers. Formic acid, which is the smallest and completely-dissociated water-soluble carboxylic acid, exhibited the highest hydrogen production enhancement ability. The 2.5 vol.% aqueous formic acid solution system provided the highest photocatalytic hydrogen production rate.

Current simulation of symmetric contacts on CdTe

International Nuclear Information System (INIS)

Ruzin, A.

2011-01-01

This article presents the calculated current-voltage characteristics of symmetric Metal-Semiconductor-Metal configurations for Schottky, Ohmic, and injecting-Ohmic contacts on high resistivity CdTe. The results clearly demonstrate that in the wide band-gap, semi-insulating semiconductors, such as high resistivity CdTe, the linearity of the I-V curves cannot be considered a proof of the ohmicity of the contacts. It is shown that the linear I-V curves are expected for a wide range of contact barriers. Furthermore, the slope of these linear curves is governed by the barrier height, rather than the bulk doping concentration. Therefore the deduction of bulk's resistivity from the I-V curves may be false.

Current simulation of symmetric contacts on CdTe

Energy Technology Data Exchange (ETDEWEB)

Ruzin, A., E-mail: aruzin@post.tau.ac.il [School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, 69978 Tel Aviv (Israel)

2011-12-01

This article presents the calculated current-voltage characteristics of symmetric Metal-Semiconductor-Metal configurations for Schottky, Ohmic, and injecting-Ohmic contacts on high resistivity CdTe. The results clearly demonstrate that in the wide band-gap, semi-insulating semiconductors, such as high resistivity CdTe, the linearity of the I-V curves cannot be considered a proof of the ohmicity of the contacts. It is shown that the linear I-V curves are expected for a wide range of contact barriers. Furthermore, the slope of these linear curves is governed by the barrier height, rather than the bulk doping concentration. Therefore the deduction of bulk's resistivity from the I-V curves may be false.

Inorganic photovoltaic devices fabricated using nanocrystal spray deposition.

Science.gov (United States)

Foos, Edward E; Yoon, Woojun; Lumb, Matthew P; Tischler, Joseph G; Townsend, Troy K

2013-09-25

Soluble inorganic nanocrystals offer a potential route to the fabrication of all-inorganic devices using solution deposition techniques. Spray processing offers several advantages over the more common spin- and dip-coating procedures, including reduced material loss during fabrication, higher sample throughput, and deposition over a larger area. The primary difference observed, however, is an overall increase in the film roughness. In an attempt to quantify the impact of this morphology change on the devices, we compare the overall performance of spray-deposited versus spin-coated CdTe-based Schottky junction solar cells and model their dark current-voltage characteristics. Spray deposition of the active layer results in a power conversion efficiency of 2.3 ± 0.3% with a fill factor of 45.7 ± 3.4%, Voc of 0.39 ± 0.06 V, and Jsc of 13.3 ± 3.0 mA/cm(2) under one sun illumination.

Fluorescent cellulose nanocrystals via supramolecular assembly of terpyridine-modified cellulose nanocrystals and terpyridine-modified perylene

International Nuclear Information System (INIS)

Hassan, Mohammad L.; Moorefield, Charles M.; Elbatal, Hany S.; Newkome, George R.; Modarelli, David A.; Romano, Natalie C.

2012-01-01

Highlights: ► Surfaces of cellulose nanocrystals were modified with terpyridine ligands. ► Fluorescent nanocrystals could be obtained via self-assembly of terpyridine-modified perylene dye onto the terpyridine-modified cellulose nanocrystals. ► Further self-assembly of azide-functionalized terpyridine onto the fluorescent cellulose nanocrystals was possible to obtain nanocellulosic material with expected use in bioimaging. - Abstract: Due to their natural origin, biocompatibility, and non-toxicity, cellulose nanocrystals are promising candidates for applications in nanomedicine. Highly fluorescent nanocellulosic material was prepared via surface modification of cellulose nanocrystals with 2,2′:6′,2″-terpyridine side chains followed by supramolecular assembly of terpyridine-modified perylene dye onto the terpyridine-modified cellulose nanocrystals (CTP) via Ru III /Ru II reduction. The prepared terpyridine-modified cellulose-Ru II -terpyridine-modified perylene (CTP-Ru II -PeryTP) fluorescent nanocrystals were characterized using cross-polarized/magic angle spin 13 C nuclear magnetic resonance (CP/MAS 13 C NMR), Fourier transform infrared (FTIR), UV–visible, and fluorescence spectroscopy. In addition, further self-assembly of terpyridine units with azide functional groups onto CTP-Ru II -PeryTP was possible via repeating the Ru III /Ru II reduction protocol to prepare supramolecular fluorescent nanocrystals with azide functionality (CTP-Ru II -PeryTP-Ru II -AZTP). The prepared derivative may have potential application in bio-imaging since the terminal azide groups can be easily reacted with antigens via “Click” chemistry reaction.

Enhanced glutathione content allows the in vivo synthesis of fluorescent CdTe nanoparticles by Escherichia coli.

Directory of Open Access Journals (Sweden)

Juan P Monrás

Full Text Available The vast application of fluorescent semiconductor nanoparticles (NPs or quantum dots (QDs has prompted the development of new, cheap and safer methods that allow generating QDs with improved biocompatibility. In this context, green or biological QDs production represents a still unexplored area. This work reports the intracellular CdTe QDs biosynthesis in bacteria. Escherichia coli overexpressing the gshA gene, involved in glutathione (GSH biosynthesis, was used to produce CdTe QDs. Cells exhibited higher reduced thiols, GSH and Cd/Te contents that allow generating fluorescent intracellular NP-like structures when exposed to CdCl(2 and K(2TeO(3. Fluorescence microscopy revealed that QDs-producing cells accumulate defined structures of various colors, suggesting the production of differently-sized NPs. Purified fluorescent NPs exhibited structural and spectroscopic properties characteristic of CdTe QDs, as size and absorption/emission spectra. Elemental analysis confirmed that biosynthesized QDs were formed by Cd and Te with Cd/Te ratios expected for CdTe QDs. Finally, fluorescent properties of QDs-producing cells, such as color and intensity, were improved by temperature control and the use of reducing buffers.

Photoemission studies of semiconductor nanocrystals

International Nuclear Information System (INIS)

Hamad, K.S.; Roth, R.; Alivisatos, A.P.

1997-01-01

Semiconductor nanocrystals have been the focus of much attention in the last ten years due predominantly to their size dependent optical properties. Namely, the band gap of nanocrystals exhibits a shift to higher energy with decreasing size due to quantum confinement effects. Research in this field has employed primarily optical techniques to study nanocrystals, and in this respect this system has been investigated extensively. In addition, one is able to synthesize monodisperse, crystalline particles of CdS, CdSe, Si, InP, InAs, as well as CdS/HgS/CdS and CdSe/CdS composites. However, optical spectroscopies have proven ambiguous in determining the degree to which electronic excitations are interior or surface admixtures or giving a complete picture of the density of states. Photoemission is a useful technique for understanding the electronic structure of nanocrystals and the effects of quantum confinement, chemical environments of the nanocrystals, and surface coverages. Of particular interest to the authors is the surface composition and structure of these particles, for they have found that much of the behavior of nanocrystals is governed by their surface. Previously, the authors had performed x-ray photoelectron spectroscopy (XPS) on CdSe nanocrystals. XPS has proven to be a powerful tool in that it allows one to determine the composition of the nanocrystal surface

Long-term exposure of CdTe quantum dots on PC12 cellular activity and the determination of optimum non-toxic concentrations for biological use

Directory of Open Access Journals (Sweden)

Gérard Valérie A

2010-03-01

Full Text Available Abstract Background The unique and tuneable photonic properties of Quantum Dots (QDs have made them potentially useful tools for imaging biological entities. However, QDs though attractive diagnostic and therapeutic tools, have a major disadvantage due to their inherent cytotoxic nature. The cellular interaction, uptake and resultant toxic influence of CdTe QDs (gelatinised and non-gelatinised Thioglycolic acid (TGA capped have been investigated with pheochromocytoma 12 (PC12 cells. In conjunction to their analysis by confocal microscopy, the QD - cell interplay was explored as the QD concentrations were varied over extended (up to 72 hours co-incubation times. Coupled to this investigation, cell viability, DNA quantification and cell proliferation assays were also performed to compare and contrast the various factors leading to cell stress and ultimately death. Results Thioglycolic acid (TGA stabilised CdTe QDs (gel and non - gel were co-incubated with PC12 cells and investigated as to how their presence influenced cell behaviour and function. Cell morphology was analysed as the QD concentrations were varied over co-incubations up to 72 hours. The QDs were found to be excellent fluorophores, illuminating the cytoplasm of the cells and no deleterious effects were witnessed at concentrations of ~10-9 M. Three assays were utilised to probe how individual cell functions (viability, DNA quantification and proliferation were affected by the presence of the QDs at various concentrations and incubation times. Cell response was found to not only be concentration dependant but also influenced by the surface environment of the QDs. Gelatine capping on the surface acts as a barrier towards the leaking of toxic atoms, thus reducing the negative impact of the QDs. Conclusion This study has shown that under the correct conditions, QDs can be routinely used for the imaging of PC12 cells with minimal adverse effects. We have found that PC12 cells are highly

Long-term exposure of CdTe quantum dots on PC12 cellular activity and the determination of optimum non-toxic concentrations for biological use

LENUS (Irish Health Repository)

Prasad, Babu R

2010-03-25

Abstract Background The unique and tuneable photonic properties of Quantum Dots (QDs) have made them potentially useful tools for imaging biological entities. However, QDs though attractive diagnostic and therapeutic tools, have a major disadvantage due to their inherent cytotoxic nature. The cellular interaction, uptake and resultant toxic influence of CdTe QDs (gelatinised and non-gelatinised Thioglycolic acid (TGA) capped) have been investigated with pheochromocytoma 12 (PC12) cells. In conjunction to their analysis by confocal microscopy, the QD - cell interplay was explored as the QD concentrations were varied over extended (up to 72 hours) co-incubation times. Coupled to this investigation, cell viability, DNA quantification and cell proliferation assays were also performed to compare and contrast the various factors leading to cell stress and ultimately death. Results Thioglycolic acid (TGA) stabilised CdTe QDs (gel and non - gel) were co-incubated with PC12 cells and investigated as to how their presence influenced cell behaviour and function. Cell morphology was analysed as the QD concentrations were varied over co-incubations up to 72 hours. The QDs were found to be excellent fluorophores, illuminating the cytoplasm of the cells and no deleterious effects were witnessed at concentrations of ~10-9 M. Three assays were utilised to probe how individual cell functions (viability, DNA quantification and proliferation) were affected by the presence of the QDs at various concentrations and incubation times. Cell response was found to not only be concentration dependant but also influenced by the surface environment of the QDs. Gelatine capping on the surface acts as a barrier towards the leaking of toxic atoms, thus reducing the negative impact of the QDs. Conclusion This study has shown that under the correct conditions, QDs can be routinely used for the imaging of PC12 cells with minimal adverse effects. We have found that PC12 cells are highly susceptible to

Stable Water Oxidation in Acid Using Manganese-Modified TiO2 Protective Coatings.

Science.gov (United States)

Siddiqi, Georges; Luo, Zhenya; Xie, Yujun; Pan, Zhenhua; Zhu, Qianhong; Röhr, Jason A; Cha, Judy J; Hu, Shu

2018-06-06

Accomplishing acid-stable water oxidation is a critical matter for achieving both long-lasting water-splitting devices and other fuel-forming electro- and photocatalytic processes. Because water oxidation releases protons into the local electrolytic environment, it becomes increasingly acidic during device operation, which leads to corrosion of the photoactive component and hence loss in device performance and lifetime. In this work, we show that thin films of manganese-modified titania, (Ti,Mn)O x , topped with an iridium catalyst, can be used in a coating stabilization scheme for acid-stable water oxidation. We achieved a device lifetime of more than 100 h in pH = 0 acid. We successfully grew (Ti,Mn)O x coatings with uniform elemental distributions over a wide range of manganese compositions using atomic layer deposition (ALD), and using X-ray photoelectron spectroscopy, we show that (Ti,Mn)O x films grown in this manner give rise to closer-to-valence-band Fermi levels, which can be further tuned with annealing. In contrast to the normally n-type or intrinsic TiO 2 coatings, annealed (Ti,Mn)O x films can make direct charge transfer to a Fe(CN) 6 3-/4- redox couple dissolved in aqueous electrolytes. Using the Fe(CN) 6 3-/4- redox, we further demonstrated anodic charge transfer through the (Ti,Mn)O x films to high work function metals, such as iridium and gold, which is not previously possible with ALD-grown TiO 2 . We correlated changes in the crystallinity (amorphous to rutile TiO 2 ) and oxidation state (2+ to 3+) of the annealed (Ti,Mn)O x films to their hole conductivity and electrochemical stability in acid. Finally, by combining (Ti,Mn)O x coatings with iridium, an acid-stable water-oxidation anode, using acid-sensitive conductive fluorine-doped tin oxides, was achieved.

Simultaneous detection of folic acid and methotrexate by an optical sensor based on molecularly imprinted polymers on dual-color CdTe quantum dots.

Science.gov (United States)

Ensafi, Ali A; Nasr-Esfahani, Parisa; Rezaei, B

2017-12-15

In this work, molecularly imprinted polymers (MIPs) were used on the surface of cadmium telluride quantum dots (CdTe QDs) for the simultaneous determination of folic acid (FA) and methotrexate (MTX). For this purpose, two different sizes of CdTe QDs with emission peaks in the yellow (QD Y ) and orange (QD O ) spectral regions were initially synthesized and capped with MIPs. FA and MTX were used as templates for the synthesis of the two composites and designated as QD Y -MIPs and QD O -MIPs, respectively. Fourier transform infrared spectroscopy, transmission electron microscopy, and fluorescence spectroscopy were employed to characterize the composites. QD Y -MIPs and QD O -MIPs were then mixed (to form QDs-MIPs) and excited at identical excitation wavelengths; they emitted two different emission wavelengths without any spectral overlap. The fluorescence signals of QD Y -MIPs and QD O -MIPs diminished in intensity with increasing concentration of the corresponding template molecules. Under optimal conditions, the dynamic range was 0.5-20 μmol L -1 for FA and MTX, and the detection limits for FA and MTX were 32.0 nmol L -1 and 34.0 nmol L -1 , respectively. The reproducibility of the method was checked for 12.5 μmol L -1 of FA and MTX to find RSD values of 4.2% and 6.3%, respectively. Finally, the applicability of the method was checked using human blood plasma samples. Results indicated the successful application of the method as a fluorescent probe for the rapid and simultaneous detection of FA and MTX in real samples. Copyright © 2017 Elsevier B.V. All rights reserved.

A 90 element CdTe array detector

Energy Technology Data Exchange (ETDEWEB)

Iwase, Y.; Onozuka, A.; Ohmori, M. (Nippon Mining Co. Ltd., Toda, Saitama (Japan). Electronic Material and Components Labs.); Funaki, M. (Nippon Mining Co. Ltd., Toda, Saitama (Japan). Materials Development Research Labs.)

1992-11-15

The fabrication of a CdTe array radiation detector and its radiation detection characteristics are described. In order to obtain high efficiency of charge collection and realize uniform detection sensitivity, current-voltage characteristics with the combination of large and small barrier height contacts and three kinds of CdTe crystals have been investigated. It was found that the Schottky barrier height of electroless Pt deposition was 0.97 eV, which effectively suppressed electron injection. By using the crystal grown by the travelling heater method with a Cl concentration of 2 ppm, carrier lifetimes for electrons and holes of 1.0 and 0.5 [mu]s, respectively, were achieved. A 90 element array detector exhibited an energy resolution as low as 4.5 keV and a count rate variation of less than 5% for 60 keV [gamma]-rays. (orig.).

A 90 element CdTe array detector

Science.gov (United States)

Iwase, Y.; Funaki, M.; Onozuka, A.; Ohmori, M.

1992-11-01

The fabrication of a CdTe array radiation detector and its radiation detection characteristics are described. In order to obtain high efficiency of charge collection and realize uniform detection sensitivity, current-voltage characteristics with the combination of large and small barrier height contacts and three kinds of CdTe crystals have been investigated. It was found that the Schottky barrier height of electroless Pt deposition was 0.97 eV, which effectively suppressed electron injection. By using the crystal grown by the travelling heater method with a Cl concentration of 2 ppm, carrier lifetimes for electrons and holes of 1.0 and 0.5 μs, respectively, were achieved. A 90 element array detector exhibited an energy resolution as low as 4.5 keV and a count rate variation of less than 5% for 60 keV γ-rays.

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.

Cellulose nanocrystal from pomelo (C. Grandis osbeck) albedo: Chemical, morphology and crystallinity evaluation

Energy Technology Data Exchange (ETDEWEB)

Zain, Nor Fazelin Mat; Yusop, Salma Mohamad [Food Science Program, School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Selangor (Malaysia); Ahmad, Ishak [Polymer Research Centre (PORCE), School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Selangor (Malaysia)

2013-11-27

Citrus peel is one of the under-utilized waste materials that have potential in producing a valuable fibre, which are cellulose and cellulose nanocrystal. Cellulose was first isolated from pomelo (C. Grandis Osbeck) albedo by combination of alkali treatment and bleaching process, followed by acid hydrolysis (65% H{sub 2}SO{sub 4}, 45 °C, 45min) to produce cellulose nanocrystal. The crystalline, structural, morphological and chemical properties of both materials were studied. Result reveals the crystallinity index obtained from X-ray diffraction for cellulose nanocrystal was found higher than extracted cellulose with the value of 60.27% and 57.47%, respectively. Fourier transform infrared showed that the chemical treatments removed most of the hemicellulose and lignin from the pomelo albedo fibre. This has been confirmed further by SEM and TEM for their morphological studies. These results showed that cellulose and cellulose nanocrystal were successfully obtained from pomelo albedo and might be potentially used in producing functional fibres for food application.

Cellulose nanocrystal from pomelo (C. Grandis osbeck) albedo: Chemical, morphology and crystallinity evaluation

International Nuclear Information System (INIS)

Zain, Nor Fazelin Mat; Yusop, Salma Mohamad; Ahmad, Ishak

2013-01-01

Citrus peel is one of the under-utilized waste materials that have potential in producing a valuable fibre, which are cellulose and cellulose nanocrystal. Cellulose was first isolated from pomelo (C. Grandis Osbeck) albedo by combination of alkali treatment and bleaching process, followed by acid hydrolysis (65% H 2 SO 4 , 45 °C, 45min) to produce cellulose nanocrystal. The crystalline, structural, morphological and chemical properties of both materials were studied. Result reveals the crystallinity index obtained from X-ray diffraction for cellulose nanocrystal was found higher than extracted cellulose with the value of 60.27% and 57.47%, respectively. Fourier transform infrared showed that the chemical treatments removed most of the hemicellulose and lignin from the pomelo albedo fibre. This has been confirmed further by SEM and TEM for their morphological studies. These results showed that cellulose and cellulose nanocrystal were successfully obtained from pomelo albedo and might be potentially used in producing functional fibres for food application

Determination of hyperin in seed of Cuscuta chinensis Lam. by enhanced chemiluminescence of CdTe quantum dots on calcein/K3Fe(CN)6 system.

Science.gov (United States)

Kang, Jing; Li, Xuwen; Geng, Jiayang; Han, Lu; Tang, Jieli; Jin, Yongri; Zhang, Yihua

2012-10-15

In this paper, 3-mercaptocarboxylic acid (MPA) modified CdTe quantum dots (QDs) were used as sensitizers, to enhance the chemiluminescence (CL) of the calcein/K(3)Fe(CN)(6) system. A new CL system of CdTe/calcein/K(3)Fe(CN)(6) was developed. The effects of reactant concentrations and the particle sizes of CdTe QDs on the CL emission were investigated in detail. The possible enhancement mechanism of the CL was also further investigated based on the photoluminescence (PL) and CL spectra. Polyphenols such as chlorogenic acid, quercetin, hyperin, catechin and kaempferol, were observed to inhibit the CL signal of the CdTe/calcein/K(3)Fe(CN)(6) system and determined by the proposed method. The proposed method was applied to the determination of hyperin in seed of Cuscuta chinensis Lam. and the results obtained were satisfactory. Copyright © 2012 Elsevier Ltd. All rights reserved.

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.

Polymer-grafted cellulose nanocrystals as pH-responsive reversible flocculants.

Science.gov (United States)

Kan, Kevin H M; Li, Jian; Wijesekera, Kushlani; Cranston, Emily D

2013-09-09

Cellulose nanocrystals (CNCs) are a sustainable nanomaterial with applications spanning composites, coatings, gels, and foams. Surface modification routes to optimize CNC interfacial compatibility and functionality are required to exploit the full potential of this material in the design of new products. In this work, CNCs have been rendered pH-responsive by surface-initiated graft polymerization of 4-vinylpyridine with the initiator ceric(IV) ammonium nitrate. The polymerization is a one-pot, water-based synthesis carried out under sonication, which ensures even dispersion of the cellulose nanocrystals during the reaction. The resultant suspensions of poly(4-vinylpyridine)-grafted cellulose nanocrystals (P4VP-g-CNCs) show reversible flocculation and sedimentation with changes in pH; the loss of colloidal stability is visible by eye even at concentrations as low as 0.004 wt %. The presence of grafted polymer and the ability to tune the hydrophilic/hydrophobic properties of P4VP-g-CNCs were characterized by Fourier transform infrared spectroscopy, elemental analysis, electrophoretic mobility, mass spectrometry, transmittance spectroscopy, contact-angle measurements, thermal analysis, and various microscopies. Atomic force microscopy showed no observable changes in the CNC dimensions or degree of aggregation after polymer grafting, and a liquid crystalline nematic phase of the modified CNCs was detected by polarized light microscopy. Controlled stability and wettability of P4VP-g-CNCs is advantageous both in composite design, where cellulose nanocrystals generally have limited dispersibility in nonpolar matrices, and as biodegradable flocculants. The responsive nature of these novel nanoparticles may offer new applications for CNCs in biomedical devices, as clarifying agents, and in industrial separation processes.

CdTe amplification nanoplatforms capped with thioglycolic acid for electrochemical aptasensing of ultra-traces of ATP

Energy Technology Data Exchange (ETDEWEB)

Shamsipur, Mojtaba, E-mail: mshamsipur@yahoo.com [Department of Chemistry, Razi University, P.O. Box 67149-67346, Kermanshah (Iran, Islamic Republic of); Farzin, Leila [Department of Analytical Chemistry, School of Chemistry, College of Science, University of Tehran, P.O. Box 14174-66191, Tehran (Iran, Islamic Republic of); Tabrizi, Mahmoud Amouzadeh [Research Center for Science and Technology in Medicine,Tehran University of Medical Sciences, P.O. Box 14197-33131, Tehran (Iran, Islamic Republic of); Shanehsaz, Maryam [Analytical Chemistry Research Laboratory, Mobin Shimi Azma Company, P.O. Box 14768-44949, Tehran (Iran, Islamic Republic of)

2016-12-01

A “signal off” voltammetric aptasensor was developed for the sensitive and selective detection of ultra-low levels of adenosine triphosphate (ATP). For this purpose, a new strategy based on the principle of recognition-induced switching of aptamers from DNA/DNA duplex to DNA/target complex was designed using thioglycolic acid (TGA)-capped CdTe quantum dots (QDs) as the signal amplifying nano-platforms. Owing to the small size, high surface-to-volume ratio and good conductivity, quantum dots were immobilized on the electrode surface for signal amplification. In this work, methylene blue (MB) adsorbed to DNA was used as a sensitive redox reporter. The intensity of voltammetric signal of MB was found to decrease linearly upon ATP addition over a concentration range of 0.1 nM to 1.6 μM with a correlation coefficient of 0.9924. Under optimized conditions, the aptasensor was able to selectively detect ATP with a limit of detection of 45 pM at 3σ. The results also demonstrated that the QDs-based amplification strategy could be feasible for ATP assay and presented a potential universal method for other small biomolecular aptasensors. - Highlights: • A “signal off” voltammetric aptasensor has been reported. • The DPV technique was used for the determination of ATP. • The determination of ATP up to 1.6 μM with a detection limit 45 pM, respectively.

SYNTHESIS AND CHARACTERIZATION OF CdTe QUANTUM ...

African Journals Online (AJOL)

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variables, including pH values, Cd/Te and Cd/Cys molar ratios, on the ... QDs requires nitrogen as the protective gas at the initial stage. ... three-fold volume isopropyl alcohol, and the sediment was collected after centrifugation at 4000.

Excitons in tunnel coupled CdTe and (Cd,Mn)Te quantum wells

Energy Technology Data Exchange (ETDEWEB)

Terletskii, Oleg; Ryabchenko, Sergiy; Tereshchenko, Oleksandr [Institute of Physics NASU, pr. Nauki 46, 03680 Kyiv (Ukraine); Sugakov, Volodymyr; Vertsimakha, Ganna [Institute for Nuclear Research NASU, pr. Nauki 47, 03680 Kyiv (Ukraine); Karczewski, Grzegorz [Institute of Physics PAS, Al. Lotnikow 32/46, PL-02-668 Warsaw (Poland)

2017-05-15

The photoluminescence (PL) from structures containing Cd{sub 0.95}Mn{sub 0.05}Te and CdTe quantum wells (QWs) separated by a narrow (1.94 nm) barrier was studied. The PL lines of comparable intensities from several possible exciton states were observed simultaneously at energy distances substantially exceeding kT. This means that the energy transfer in the studied systems is slower than the radiative recombination of the confined excitons. For the CdTe QW width of about 8.7-9 nm, indirect excitons with the electron and heavy hole chiefly localized in the CdTe and Cd{sub 1-x}Mn{sub x}Te QWs, respectively, were detected in the magnetic field. These indirect excitons have PL energy of about 10-20 meV above the PL line of the direct excitons in the CdTe QW. The observation of the PL from the indirect excitons which are not the lowest excitations in the structure is a distinctive feature of the system. Photoluminescence intensity dependence on the energy and the magnetic field. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Photoluminescence measurement of polycrystalline CdTe made of high purity source material

Energy Technology Data Exchange (ETDEWEB)

Hempel, Hannes; Kraft, Christian; Heisler, Christoph; Geburt, Sebastian; Ronning, Carsten; Wesch, Werner [Institute of Solid State Physics, Friedrich Schiller Universitaet Jena, Helmholtzweg 3, 07743 Jena (Germany)

2012-07-01

CdTe is a common material for thin film solar cells. However, the mainly used CdTe source material is known to contain a high number of intrinsic defects and impurities. In this work we investigate the defect structure of high purity CdTe by means of Photoluminescence, which is a common method to detect the energy levels of defects in the band gap of semiconductors. We used a 633 nm HeNe-Laser at sample temperatures of 8 K. The examined samples were processed in a new vacuum system based on the PVD method. They yield significantly different spectra on as-grown samples compared to those measured on samples which are grown by the standard process, since the double peak at 1.55 eV was hardly detectable and the A-center correlated transition vanished. Instead a peak at 1.50 eV with pronounced phonon coupling was observed. The 1.50 eV peak is known from other measurements but has not been characterized so far. The intention of this work is to characterize this new feature and the influence of post deposition treatments of the CdTe layers on the PL spectra.

In situ capping for size control of monochalcogenide (ZnS, CdS and SnS) nanocrystals produced by anaerobic metal-reducing bacteria

International Nuclear Information System (INIS)

Jang, Gyoung Gug; Datskos, Panos G; Jacobs, Christopher B; Ivanov, Ilia N; Joshi, Pooran C; Meyer, Harry M III; Armstrong, Beth L; Kidder, Michelle; Graham, David E; Moon, Ji-Won

2015-01-01

Metal monochalcogenide quantum dot nanocrystals of ZnS, CdS and SnS were prepared by anaerobic, metal-reducing bacteria using in situ capping by oleic acid or oleylamine. The capping agent preferentially adsorbs on the surface of the nanocrystal, suppressing the growth process in the early stages, thus leading to production of nanocrystals with a diameter of less than 5 nm. (paper)

Investigation of the chlorine A-Center in polycrystalline CdTe layers by photoluminescence spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Kraft, Christian; Metzner, Heiner; Haedrich, Mathias [Institut fuer Festkoerperphysik, Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Schley, Pascal [Institut fuer Physik, Technische Universitaet Ilmenau, 98684 Ilmenau (Germany); Goldhahn, Ruediger [Institut fuer Experimentelle Physik, Universitaet Magdeburg, 39016 Magdeburg (Germany)

2012-07-01

Polycrystalline CdTe is a well known absorber material for thin film solar cells. However, the improvement of CdTe-based solar cells for industrial application is mainly based on empirical enhancements of certain process steps which are not concerning the absorber itself. Hence, the defect structure of CdTe is still not understood in detail. One of the most discussed defects in CdTe is the so called chlorine A-center. In general, the A-Center describes a defect complex of the intrinsic cadmium vacancy defect and an extrinsic impurity. By means of photoluminescence spectroscopy at temperatures of 5 K we investigated the behavior of the chlorine A-center under different CdTe activation techniques. Therefore, we were able to determine the electronic level of that defect and to analyze its influence on the crystal quality and the functionality of solar cells that were prepared of the corresponding samples.

Cellulose nanocrystal properties and their applications

Directory of Open Access Journals (Sweden)

mahdi jonoobi

2015-05-01

Full Text Available The main purpose of this work is to provide an overview of recent research in the area of cellulose nonmaterials production from different sources. Due to their abundance, their renewability, high strength and stiffness, being eco-friendly, and low weight; numerous studies have been reported on the isolation of cellulose nanomaterials from different cellulosic sources and their use in high performance applications. This work covers an introduction into the nano cellulose definition as well as used methods for isolation of nanomaterials (nanocrystals from various sources. The rod-like cellulose nanocrystals (CNC can be isolated from sources like wood, plant fibers, agriculture and industrial bio residues, tunicates, and bacterial cellulose using acid hydrolysis process. Following this, the paper focused on characterization methods, materials properties and structure. The current review is a comprehensive literature regarding the nano cellulose isolation and demonstrates the potential of cellulose nanomaterials to be used in a wide range of high-tech applications.

Separation of water and oil by poly (acrylic acid)-coated stainless steel mesh prepared by radiation crosslinking

Energy Technology Data Exchange (ETDEWEB)

Nho, Young Chang; Shin, Jung Woong; Park, Jong Seok; Lim, Young Mook; Jeun, Joon Pyo; Kang, Phil Hyun [Research Division for Industry and Environment, Korea Atomic Energy Research Institute, Jeongeup (Korea, Republic of)

2015-05-15

The stainless steel mesh coated with poly(acrylic acid) hydrogel was fabricated and applied for the separation of water and oil. The stainless steel mesh was immersed in aqueous poly (acrylic acid) solution, and then irradiated by radiation to introduce poly(acrylic acid) hydrogel on the surface of mesh by crosslinking. It was possible to separate oil and water from mixtures of oil/water effectively using the hydrogel-coated mesh. The effect of irradiation dose, coating thickness, size of mesh on the separation efficiency was examined.

Facile aqueous synthesis and growth mechanism of CdTe nanorods

International Nuclear Information System (INIS)

Gong Haibo; Hao Xiaopeng; Gao Chang; Wu Yongzhong; Du Jie; Xu Xiangang; Jiang Minhua

2008-01-01

Single-crystal CdTe nanorods with diameters of 50-100 nm were synthesized under a surfactant-assisted hydrothermal condition. The experimental results indicated that with a temporal dependence the morphologies of CdTe nanocrystallites changed from nanoparticles to smooth surface nanorods. The crystal structure, morphology and optical properties of the products were investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and fluorescence spectrophotometer. Furthermore, the formation mechanisms of the nanorods were investigated and discussed on the basis of the experimental results.

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.

Preparation and characterization of bifunctional dendrimer modified Fe{sub 3}O{sub 4}/CdTe nanoparticles with both luminescent and superparamagnetic properties

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiuling, E-mail: wxling_self@163.com [Department of Chemical and Biological Engineering, Suzhou University of Science and Technology, Suzhou 215009 (China); Gu, Yinjun; Dong, Shuling [Department of Chemical and Biological Engineering, Suzhou University of Science and Technology, Suzhou 215009 (China); Zhao, Qin [School of Chemistry and Chemical Engineering, Nantong University, Nantong, Jiangsu 226019 (China); Liu, Yongjian [Department of Chemical and Biological Engineering, Suzhou University of Science and Technology, Suzhou 215009 (China)

2015-10-15

Highlights: • The fluorescent superparamagnetic dendrimeric Fe{sub 3}O{sub 4}/CdTe nanoparticles are synthesized in this paper. • The synthesized nanocomposites maintain excellent magnetic properties. • The synthesized nanocomposites maintain highly luminescent markers with narrow emission bands. - Abstract: Magnetic nanoparticles Fe{sub 3}O{sub 4} were prepared by hydrothermal coprecipitation of ferric and ferrous ions using NaOH. The surface modification of Fe{sub 3}O{sub 4} nanoparticle by dendrimers has rendered the nanoparticle surface with enriched amine groups which facilitated the adsorption and conjugation of thioglycolic acid (TGA) modified CdTe quantum dots to form a stable hybrid nanostructure. Three generations (first generation: G0F, second generation: G1F, third generation: G3F) of bifunctional dendrimeric Fe{sub 3}O{sub 4}/CdTe nanoparticles were successfully prepared using this technique and characterized by microscopy. The optical and magnetic properties of the dendrimeric Fe{sub 3}O{sub 4}/CdTe nanoparticle were also investigated. The microscopic study reveals 3 different sizes for 3 generations, 16 nm (G0F), 31 nm (G1F) and 47 nm (G3F). Among three generations of nanoparticles, the G1F has the best optical property with a luminescent quantum yield of 25.6% and the G0F has the best magnetic property with a saturation magnetization of 19.3 emμ/g.

Electrophoretic deposition and electrochemical behavior of novel graphene oxide-hyaluronic acid-hydroxyapatite nanocomposite coatings

International Nuclear Information System (INIS)

Li, Ming; Liu, Qian; Jia, Zhaojun; Xu, Xuchen; Shi, Yuying; Cheng, Yan; Zheng, Yufeng; Xi, Tingfei; Wei, Shicheng

2013-01-01

Novel ternary graphene oxide-hyaluronic acid-hydroxyapatite (GO-HY-HA) nanocomposite coatings were prepared on Ti substrate using anodic electrophoretic deposition (EPD). Hyaluronic acid was employed as charging additive and dispersion agent during EPD. The kinetics and mechanism of the deposition, and the microstructure of the coated samples were investigated using scanning electron microscopy, X-ray diffraction, Raman spectrum, thermo-gravimetric analysis, and microscopic Fourier transform infrared analysis. The results showed that the addition of GO sheets into the HY-HA suspensions could increase the deposition rate and inhibit cracks creation and propagation in the coatings. The corrosion resistant of the resulting samples were evaluated using potentiodynamic polarization method in simulated body fluid, and the GO-HY-HA coatings could effectively improve the anti-corrosion property of the Ti substrate

Electrophoretic deposition and electrochemical behavior of novel graphene oxide-hyaluronic acid-hydroxyapatite nanocomposite coatings

Science.gov (United States)

Li, Ming; Liu, Qian; Jia, Zhaojun; Xu, Xuchen; Shi, Yuying; Cheng, Yan; Zheng, Yufeng; Xi, Tingfei; Wei, Shicheng

2013-11-01

Novel ternary graphene oxide-hyaluronic acid-hydroxyapatite (GO-HY-HA) nanocomposite coatings were prepared on Ti substrate using anodic electrophoretic deposition (EPD). Hyaluronic acid was employed as charging additive and dispersion agent during EPD. The kinetics and mechanism of the deposition, and the microstructure of the coated samples were investigated using scanning electron microscopy, X-ray diffraction, Raman spectrum, thermo-gravimetric analysis, and microscopic Fourier transform infrared analysis. The results showed that the addition of GO sheets into the HY-HA suspensions could increase the deposition rate and inhibit cracks creation and propagation in the coatings. The corrosion resistant of the resulting samples were evaluated using potentiodynamic polarization method in simulated body fluid, and the GO-HY-HA coatings could effectively improve the anti-corrosion property of the Ti substrate.

Size- and dose-dependent toxicity of cellulose nanocrystals (CNC) on human fibroblasts and colon adenocarcinoma.

Science.gov (United States)

Hanif, Zahid; Ahmed, Farrukh R; Shin, Seung Won; Kim, Young-Kee; Um, Soong Ho

2014-07-01

A controlled preparation of cellulose nanocrystals of different sizes and shapes has been carried out by acid hydrolysis of microcrystalline cellulose. The size- and concentration-dependent toxicity effects of the resulting cellulose nanocrystals were evaluated against two different cell lines, NIH3T3 murine embryo fibroblasts and HCT116 colon adenocarcinoma. It could serve as a therapeutic platform for cancer treatment. Copyright © 2014 Elsevier B.V. All rights reserved.

Lanthanide-doped Na xScF 3+ x nanocrystals: Crystal structure evolution and multicolor tuning

KAUST Repository

Teng, Xue

2012-05-23

Rare-earth-based nanomaterials have recently drawn considerable attention because of their unique energy upconversion (UC) capabilities. However, studies of Sc 3+-based nanomaterials are still absent. Herein we report the synthesis and fine control of Na xScF 3+x nanocrystals by tuning of the ratio of oleic acid (OA, polar surfactant) to 1-octadecene (OD, nonpolar solvent). When the OA:OD ratio was increased from low (3:17) to high (3:7), the nanocrystals changed from pure monoclinic phase (Na 3ScF 6) to pure hexagonal phase (NaScF 4) via a transition stage at an intermediate OA:OD ratio (3:9) where a mixture of nanocrystals in monoclinic and hexagonal phases was obtained and the coexistence of the two phases inside individual nanocrystals was also observed. More significantly, because of the small radius of Sc 3+, Na xScF 3+x:Yb/Er nanocrystals show different UC emission from that of NaYF 4:Yb/Er nanocrystals, which broadens the applications of rare-earth-based nanomaterials ranging from optical communications to disease diagnosis. © 2012 American Chemical Society.

Heavy doping of CdTe single crystals by Cr ion implantation

Science.gov (United States)

Popovych, Volodymyr D.; Böttger, Roman; Heller, Rene; Zhou, Shengqiang; Bester, Mariusz; Cieniek, Bogumil; Mroczka, Robert; Lopucki, Rafal; Sagan, Piotr; Kuzma, Marian

2018-03-01

Implantation of bulk CdTe single crystals with high fluences of 500 keV Cr+ ions was performed to achieve Cr concentration above the equilibrium solubility limit of this element in CdTe lattice. The structure and composition of the implanted samples were studied using secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) to characterize the incorporation of chromium into the host lattice and to investigate irradiation-induced damage build-up. It was found that out-diffusion of Cr atoms and sputtering of the targets alter the depth distribution and limit concentration of the projectile ions in the as-implanted samples. Appearance of crystallographically oriented, metallic α-Cr nanoparticles inside CdTe matrix was found after implantation, as well as a strong disorder at the depth far beyond the projected range of the implanted ions.

Protective Performance of Polyaniline-Sulfosalicylic Acid/Epoxy Coating for 5083 Aluminum

Science.gov (United States)

Liu, Suyun; Liu, Li; Meng, Fandi; Li, Ying; Wang, Fuhui

2018-01-01

Epoxy coatings incorporating different content of sulfosalicylic acid doped polyaniline (PANI-SSA) have been investigated for corrosion protection of 5083 aluminum alloy in 3.5% NaCl solution. The performance of the coatings is studied using a combination of electrochemical impedance spectroscopy (EIS), open circuit potential (OCP), gravimetric tests, adhesion tests, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the content of PANI-SSA not only affects the coating compactness and the transportation of aggressive medium, but also has a significant influence on the-based aluminum. The coating with 2 wt. % PANI-SSA exhibits the best corrosion inhibition due to its good protective properties and the formation of a complete PANI-SSA induced oxide layer. PMID:29438304

A stacked CdTe pixel detector for a compton camera

International Nuclear Information System (INIS)

Oonuki, Kousuke; Tanaka, Takaaki; Watanabe, Shin; Takeda, Shin'ichiro; Nakazawa, Kazuhiro; Ushio, Masayoshi; Mitani, Takefumi; Takahashi, Tadayuki; Tajima, Hiroyasu

2007-01-01

We are developing a semiconductor Compton telescope to explore the universe in the energy band from several tens of keV to a few MeV. A detector material of combined Si strip and CdTe pixel is used to cover the energy range around 60keV. For energies above several hundred keV, in contrast, the higher detection efficiency of CdTe semiconductor in comparison with Si is expected to play an important role as both an absorber and a scatterer. In order to demonstrate the spectral and imaging capability of a CdTe-based Compton camera, we developed a Compton telescope consisting of a stack of CdTe pixel detectors as a small scale prototype. With this prototype, we succeeded in reconstructing images and spectra by solving the Compton kinematics within the energy band from 122 to 662keV. The energy resolution (FWHM) of reconstructed spectra is 7.3keV at 511keV. The angular resolution obtained at 511keV is measured to be 12.2 deg. (FWHM)

Size-Controlled TiO{sub 2} nanocrystals with exposed {001} and {101} facets strongly linking to graphene oxide via p-Phenylenediamine for efficient photocatalytic degradation of fulvic acids

Energy Technology Data Exchange (ETDEWEB)

Yan, Wen-Yuan; Zhou, Qi [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Chen, Xing, E-mail: xingchen@iim.ac.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Laboratory of Nanomaterials and Environmental Detection, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei 230031 (China); Yang, Yong [State Key Laboratory of High Performance Ceramics and Superfine Microstructure,Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhang, Yong [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Huang, Xing-Jiu [Laboratory of Nanomaterials and Environmental Detection, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei 230031 (China); Wu, Yu-Cheng, E-mail: ycwu@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Anhui Key Laboratory of Advanced Functional Materials and Devices, Hefei 230009 (China)

2016-08-15

Highlights: • N-RGO/TiO{sub 2} nanocomposites were prepared via one-step hydrothermal method. • Facets of TiO{sub 2} nanocrystals were modulated with addition of HF. • Sizes of TiO{sub 2} nanocrystals were controlled by the contents of RGO-NH{sub 2.} • Obtained N-RGO/TiO{sub 2} nanocomposites exhibited excellent photocatalytic activity and stability. - Abstract: Photocatalytic degradation is one of the most promising methods for removal of fulvic acids (FA), which is a typical category of natural organic contamination in groundwater. In this paper, TiO{sub 2}/graphene nanocomposites (N-RGO/TiO{sub 2}) were prepared via simple chemical functionalization and one-step hydrothermal method for efficient photodegradation of FA under illumination of a xenon lamp as light source. Here, p-phenylenediamine was used as not only the linkage chemical agent between TiO{sub 2} nanocrystals and graphene, but also the nitrogen dopant for TiO{sub 2} nanocrystals and graphene. During the hydrothermal process, facets of TiO{sub 2} nanocrystals were modulated with addition of HF, and sizes of TiO{sub 2} nanocrystals were controlled by the contents of graphene oxide functionalized with p-phenylenediamine (RGO-NH{sub 2}). The obtained N-RGO/TiO{sub 2} nanocomposites exhibited a much higher photocatalytic activity and stability for degradation of methyl blue (MB) and FA compared with other TiO{sub 2} samples under xenon lamp irradiation. For the third cycle, the 10wt%N-RGO/TiO{sub 2} catalyst maintains high photoactivity (87%) for the degradation of FA, which is much better than the TiO{sub 2}-N/F (61%) in 3 h. This approach supplies a new strategy to design and synthesize metal oxide and graphene oxide nanocomposites with highly efficient photocatalytic performance.

Increased short circuit current in organic photovoltaic using high-surface area electrode based on ZnO nanowires decorated with CdTe quantum dots.

Science.gov (United States)

Aga, R S; Gunther, D; Ueda, A; Pan, Z; Collins, W E; Mu, R; Singer, K D

2009-11-18

A photosensitized high-surface area transparent electrode has been employed to increase the short circuit current of a photovoltaic device with a blend of poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM) as the active layer. This is achieved by directly growing ZnO nanowires on indium tin oxide (ITO) film via a physical vapor method. The nanowire surface is then decorated with CdTe quantum dots by pulsed electron-beam deposition (PED). The nanowires alone provided a 20-fold increase in the short circuit current under visible light illumination. This was further increased by a factor of approximately 1.5 by the photosensitization effect of CdTe, which has an optical absorption of up to 820 nm.

Poly (lactic acid organoclay nano composites for paper coating applications

Directory of Open Access Journals (Sweden)

Tatcha Sonjui

2014-10-01

Full Text Available Poly(lactic acid or PLA is a well-known biodegradable polymer derived from renewable resources such as corn strach, tapioca strach, and sugar cane. PLA is the most extensively utilized biodegradable polyester with potential to replace conventional petrochemical-based polymers. However, PLA has some drawbacks, such as brittleness and poor gas barrier properties. Nano composite polymers have experience and increasing interest due to their characteristics, especially in mechanical and thermal properties. The objectives of this research were to prepare PLA formulations using three different PLAs. The formulas giving high gloss coating film were selected to prepare nano composite film by incorporated with different amount of various types of organoclays. The physical properties of the PLA coating films were studied and it was found that the PLA 7000D with 0.1%w/w of Cloisite 30B provided decent viscosity for coating process. In addition, the nano composite coating films showed good physical properties such as high gloss, good adhesion, and good hardness. There is a possibility of using the obtained formulation as a paper coating film.

Impedance spectroscopy of CdTe thin film solar cells

Energy Technology Data Exchange (ETDEWEB)

Weiss, Charlotte; Heisler, Christoph; Reisloehner, Udo; Ronning, Carsten; Wesch, Werner [Institute of Solid State Physics, University of Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)

2012-07-01

Impedance Spectroscopy (IS) is a widely used method to analyze dielectric properties of specimen as a function of frequency. Typically this characterization method delivers an equivalent circuit diagram of the device under examination to describe its electrical properties. Traditionally IS is used in coating evaluation, corrosion monitoring and in electrochemistry. During the last years the method became more important also in the field of electrical characterization of solar cells. In our work we use IS for the electrical characterization of thin film CdTe solar cells. The measurement is done at room temperature without illumination in a frequency domain from 20 Hz to 2 MHz. The samples are measured under variable forward bias. The results match insufficiently with the model of two resistor-capacitor circuits in series which is commonly used to describe the p-n junction and the blocking back contact. For better consistency, other models from the literature are used and discussed. From the results a conclusion is drawn about the properties of the solar cell such as the nature of the p-n junction or the performance of the back contact.

Hydrogen-Bonded Organic Semiconductor Micro- And Nanocrystals: From Colloidal Syntheses to (Opto-)Electronic Devices

Science.gov (United States)

2014-01-01

Organic pigments such as indigos, quinacridones, and phthalocyanines are widely produced industrially as colorants for everyday products as various as cosmetics and printing inks. Herein we introduce a general procedure to transform commercially available insoluble microcrystalline pigment powders into colloidal solutions of variously sized and shaped semiconductor micro- and nanocrystals. The synthesis is based on the transformation of the pigments into soluble dyes by introducing transient protecting groups on the secondary amine moieties, followed by controlled deprotection in solution. Three deprotection methods are demonstrated: thermal cleavage, acid-catalyzed deprotection, and amine-induced deprotection. During these processes, ligands are introduced to afford colloidal stability and to provide dedicated surface functionality and for size and shape control. The resulting micro- and nanocrystals exhibit a wide range of optical absorption and photoluminescence over spectral regions from the visible to the near-infrared. Due to excellent colloidal solubility offered by the ligands, the achieved organic nanocrystals are suitable for solution processing of (opto)electronic devices. As examples, phthalocyanine nanowire transistors as well as quinacridone nanocrystal photodetectors, with photoresponsivity values by far outperforming those of vacuum deposited reference samples, are demonstrated. The high responsivity is enabled by photoinduced charge transfer between the nanocrystals and the directly attached electron-accepting vitamin B2 ligands. The semiconducting nanocrystals described here offer a cheap, nontoxic, and environmentally friendly alternative to inorganic nanocrystals as well as a new paradigm for obtaining organic semiconductor materials from commercial colorants. PMID:25253644

Polylactic acid coating on a biodegradable magnesium alloy: An in vitro degradation study by electrochemical impedance spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Alabbasi, Alyaa; Liyanaarachchi, S.; Kannan, M. Bobby, E-mail: bobby.mathan@jcu.edu.au

2012-09-30

Polylactic acid (PLA) was coated on a biodegradable magnesium alloy, AZ91, using spin coating technique for temporary implant applications. The degradation behaviour of the coated alloy samples was evaluated using electrochemical impedance spectroscopy (EIS) method in simulated body fluid (SBF). EIS results suggested that the PLA coating enhanced the degradation resistance of the alloy significantly. Increase in the PLA coating thickness was found to increase the degradation resistance, but resulted in poor adhesion. Long-term EIS experiments of the PLA coated samples suggested that their degradation resistance gradually decreased with increase in SBF exposure time. However, the degradation resistance of the PLA coated samples was significantly higher than that of the bare metal even after a 48 h exposure to SBF. - Highlights: Black-Right-Pointing-Pointer Polylactic acid (PLA) was coated on a magnesium-based alloy. Black-Right-Pointing-Pointer PLA coating enhanced the in vitro degradation resistance of the alloy. Black-Right-Pointing-Pointer Increase in the PLA coating thickness improved the alloy degradation resistance. Black-Right-Pointing-Pointer Thin film PLA coating exhibited both good degradation resistance and adhesion.

Polylactic acid coating on a biodegradable magnesium alloy: An in vitro degradation study by electrochemical impedance spectroscopy

International Nuclear Information System (INIS)

Alabbasi, Alyaa; Liyanaarachchi, S.; Kannan, M. Bobby

2012-01-01

Polylactic acid (PLA) was coated on a biodegradable magnesium alloy, AZ91, using spin coating technique for temporary implant applications. The degradation behaviour of the coated alloy samples was evaluated using electrochemical impedance spectroscopy (EIS) method in simulated body fluid (SBF). EIS results suggested that the PLA coating enhanced the degradation resistance of the alloy significantly. Increase in the PLA coating thickness was found to increase the degradation resistance, but resulted in poor adhesion. Long-term EIS experiments of the PLA coated samples suggested that their degradation resistance gradually decreased with increase in SBF exposure time. However, the degradation resistance of the PLA coated samples was significantly higher than that of the bare metal even after a 48 h exposure to SBF. - Highlights: ► Polylactic acid (PLA) was coated on a magnesium-based alloy. ► PLA coating enhanced the in vitro degradation resistance of the alloy. ► Increase in the PLA coating thickness improved the alloy degradation resistance. ► Thin film PLA coating exhibited both good degradation resistance and adhesion.

Corrosion Performance of Nano-ZrO₂ Modified Coatings in Hot Mixed Acid Solutions.

Science.gov (United States)

Xu, Wenhua; Wang, Zhenyu; Han, En-Hou; Wang, Shuai; Liu, Qian

2018-06-01

A nano-ZrO₂ modified coating system was prepared by incorporation of nano-ZrO₂ concentrates into phenolic-epoxy resin. The corrosion performance of the coatings was evaluated in hot mixed acid solution, using electrochemical methods combined with surface characterization, and the effects of nano-ZrO₂ content were specially focused on. The results showed that 1% and 3% nano-ZrO₂ addition enhanced the corrosion resistance of the coatings, while 5% nano-ZrO₂ addition declined it. The coating with 3% nano-ZrO₂ presented the minimum amount of species diffusion, the lowest average roughness (5.94 nm), and the highest C/O ratio (4.55) and coating resistance, and it demonstrated the best corrosion performance among the coating specimens.

Surface chemical compositions and dispersity of starch nanocrystals formed by sulfuric and hydrochloric acid hydrolysis.

Science.gov (United States)

Wei, Benxi; Xu, Xueming; Jin, Zhengyu; Tian, Yaoqi

2014-01-01

Surface chemical compositions of starch nanocrystals (SNC) prepared using sulfuric acid (H2SO4) and hydrochloric acid (HCl) hydrolysis were analyzed by X-ray photoelectron spectroscopy (XPS) and FT-IR. The results showed that carboxyl groups and sulfate esters were presented in SNC after hydrolysis with H2SO4, while no sulfate esters were detected in SNC during HCl-hydrolysis. TEM results showed that, compared to H2SO4-hydrolyzed sample, a wider size distribution of SNC prepared by HCl-hydrolysis were observed. Zeta-potentials were -23.1 and -5.02 mV for H2SO4- and HCl-hydrolyzed SNC suspensions at pH 6.5, respectively. Nevertheless, the zeta-potential values decreased to -32.3 and -10.2 mV as the dispersion pH was adjusted to 10.6. After placed 48 h at pH 10.6, zeta-potential increased to -24.1 mV for H2SO4-hydrolyzed SNC, while no change was detected for HCl-hydrolyzed one. The higher zeta-potential and relative small particle distribution of SNC caused more stable suspensions compared to HCl-hydrolyzed sample.

Surface chemical compositions and dispersity of starch nanocrystals formed by sulfuric and hydrochloric acid hydrolysis.

Directory of Open Access Journals (Sweden)

Benxi Wei

Full Text Available Surface chemical compositions of starch nanocrystals (SNC prepared using sulfuric acid (H2SO4 and hydrochloric acid (HCl hydrolysis were analyzed by X-ray photoelectron spectroscopy (XPS and FT-IR. The results showed that carboxyl groups and sulfate esters were presented in SNC after hydrolysis with H2SO4, while no sulfate esters were detected in SNC during HCl-hydrolysis. TEM results showed that, compared to H2SO4-hydrolyzed sample, a wider size distribution of SNC prepared by HCl-hydrolysis were observed. Zeta-potentials were -23.1 and -5.02 mV for H2SO4- and HCl-hydrolyzed SNC suspensions at pH 6.5, respectively. Nevertheless, the zeta-potential values decreased to -32.3 and -10.2 mV as the dispersion pH was adjusted to 10.6. After placed 48 h at pH 10.6, zeta-potential increased to -24.1 mV for H2SO4-hydrolyzed SNC, while no change was detected for HCl-hydrolyzed one. The higher zeta-potential and relative small particle distribution of SNC caused more stable suspensions compared to HCl-hydrolyzed sample.

Surface Chemical Compositions and Dispersity of Starch Nanocrystals Formed by Sulfuric and Hydrochloric Acid Hydrolysis

Science.gov (United States)

Wei, Benxi; Xu, Xueming; Jin, Zhengyu; Tian, Yaoqi

2014-01-01

Surface chemical compositions of starch nanocrystals (SNC) prepared using sulfuric acid (H2SO4) and hydrochloric acid (HCl) hydrolysis were analyzed by X-ray photoelectron spectroscopy (XPS) and FT-IR. The results showed that carboxyl groups and sulfate esters were presented in SNC after hydrolysis with H2SO4, while no sulfate esters were detected in SNC during HCl-hydrolysis. TEM results showed that, compared to H2SO4-hydrolyzed sample, a wider size distribution of SNC prepared by HCl-hydrolysis were observed. Zeta-potentials were −23.1 and −5.02 mV for H2SO4- and HCl-hydrolyzed SNC suspensions at pH 6.5, respectively. Nevertheless, the zeta-potential values decreased to −32.3 and −10.2 mV as the dispersion pH was adjusted to 10.6. After placed 48 h at pH 10.6, zeta-potential increased to −24.1 mV for H2SO4-hydrolyzed SNC, while no change was detected for HCl-hydrolyzed one. The higher zeta-potential and relative small particle distribution of SNC caused more stable suspensions compared to HCl-hydrolyzed sample. PMID:24586246

A new MBE CdTe photoconductor array detector for X-ray applications

International Nuclear Information System (INIS)

Yoo, S.S.; Sivananthan, S.; Faurie, J.P.; Rodricks, B.; Bai, J.; Montano, P.A.; Argonne National Lab., IL

1994-10-01

A CdTe photoconductor array x-ray detector was grown using Molecular Beam Epitaxially (MBE) on a Si (100) substrate. The temporal response of the photoconductor arrays is as fast as 21 psec risetime and 38 psec Full Width Half Maximum (FWHM). Spatial and energy responses were obtained using x-rays from a rotating anode and synchrotron radiation source. The spatial resolution of the photoconductor was good enough to provide 75 microm FWHM using a 50 microm synchrotron x-ray beam. A substantial number of x-ray photons are absorbed effectively within the MBE CdTe layer as observed from the linear response up to 15 keV. These results demonstrate that MBE grown CdTe is a suitable choice of the detector materials to meet the requirements for x-ray detectors in particular for the new high brightness synchrotron sources

A novel biodegradable nicotinic acid/calcium phosphate composite coating on Mg-3Zn alloy

Energy Technology Data Exchange (ETDEWEB)

Song, Yingwei, E-mail: ywsong@imr.ac.cn; Shan, Dayong; Han, En-Hou

2013-01-01

A novel biodegradable composite coating is prepared to reduce the biodegradation rate of Mg-3Zn alloy. The Mg-3Zn substrate is first immersed into 0.02 mol L{sup -1} nicotinic acid (NA) solution, named as vitamin B{sub 3}, to obtain a pretreatment film, and then the electrodeposition of calcium phosphate coating with ultrasonic agitation is carried out on the NA pretreatment film to obtain a NA/calcium phosphate composite coating. Surface morphology is observed by scanning electron microscopy (SEM). Chemical composition is determined by X-ray diffraction (XRD) and EDX. Protection property of the coatings is evaluated by electrochemical tests. The biodegradable behavior is investigated by immersion tests. The results indicate that a thin but compact bottom layer can be obtained by NA pretreatment. The electrodeposition calcium phosphate coating consists of many flake particles and ultrasonic agitation can greatly improve the compactness of the coating. The composite coating is biodegradable and can reduce the biodegradation rate of Mg alloys in stimulated body fluid (SBF) for twenty times. The biodegradation process of the composite coating can be attributed to the gradual dissolution of the flake particles into chippings. - Highlights: Black-Right-Pointing-Pointer NA/calcium phosphate composite coating is prepared to protect Mg-3Zn alloy implant. Black-Right-Pointing-Pointer Nicotinic acid (vitamin B{sub 3}) is available to obtain a protective bottom film. Black-Right-Pointing-Pointer Ultrasonic agitation greatly improves the compactness of calcium phosphate coating. Black-Right-Pointing-Pointer The composite coating can reduce the biodegradation rate of Mg-3Zn twenty times. Black-Right-Pointing-Pointer The composite coating is biodegraded by the dissolution of flakes into chippings.

Enriching Silver Nanocrystals with a Second Noble Metal.

Science.gov (United States)

Wu, Yiren; Sun, Xiaojun; Yang, Yin; Li, Jumei; Zhang, Yun; Qin, Dong

2017-07-18

Noble-metal nanocrystals have received considerable interests owing to their fascinating properties and promising applications in areas including plasmonics, catalysis, sensing, imaging, and medicine. As demonstrated by ample examples, the performance of nanocrystals in these and related applications can be augmented by switching from monometallic to bimetallic systems. The inclusion of a second metal can enhance the properties and greatly expand the application landscape by bringing in new capabilities. Seeded growth offers a powerful route to bimetallic nanocrystals. This approach is built upon the concept that preformed nanocrystals with uniform, well-controlled size, shape, and structure can serve as seeds to template and direct the deposition of metal atoms. Seeded growth is, however, limited by galvanic replacement when the deposited metal is less reactive than the seed. The involvement of galvanic replacement not only makes it difficult to control the outcome of seeded growth but also causes degradation to some properties. We have successfully addressed this issue by reducing the salt precursor(s) into atoms with essentially no galvanic replacement. In the absence of self-nucleation, the atoms are preferentially deposited onto the seeds to generate bimetallic nanocrystals with controlled structures. In this Account, we use Ag nanocubes as an example to demonstrate the fabrication of Ag@M and Ag@Ag-M (M = Au, Pd, or Pt) nanocubes with a core-frame or core-shell structure by controlling the deposition of M atoms. A typical synthesis involves the titration of M n+ (a precursor to M) ions into an aqueous suspension containing Ag nanocubes, ascorbic acid, and poly(vinylpyrrolidone) under ambient conditions. In one approach, aqueous sodium hydroxide is introduced to increase the initial pH of the reaction system. At pH = 11.9, ascorbic acid is dominated by ascorbate monoanion, a much stronger reductant, to suppress the galvanic replacement between M n+ and Ag. In

Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

Directory of Open Access Journals (Sweden)

M. M. Aliyu

2012-01-01

Full Text Available This study investigates the key issues in the fabrication of CdTe solar cells on metallic substrates, their trends, and characteristics as well as effects on solar cell performance. Previous research works are reviewed while the successes, potentials, and problems of such technology are highlighted. Flexible solar cells offer several advantages in terms of production, cost, and application over glass-based types. Of all the metals studied as substrates for CdTe solar cells, molybdenum appears the most favorable candidate, while close spaced sublimation (CSS, electrodeposition (ED, magnetic sputtering (MS, and high vacuum thermal evaporation (HVE have been found to be most common deposition technologies used for CdTe on metal foils. The advantages of these techniques include large grain size (CSS, ease of constituent control (ED, high material incorporation (MS, and low temperature process (MS, HVE, ED. These invert-structured thin film CdTe solar cells, like their superstrate counterparts, suffer from problems of poor ohmic contact at the back electrode. Thus similar strategies are applied to minimize this problem. Despite the challenges faced by flexible structures, efficiencies of up to 13.8% and 7.8% have been achieved in superstrate and substrate cell, respectively. Based on these analyses, new strategies have been proposed for obtaining cheaper, more efficient, and viable flexible CdTe solar cells of the future.

pH studies in the synthesis of amino acid coated hydrophilic MNPs

Science.gov (United States)

Saxena, Namita; Dube, Charu Lata

2018-04-01

Magnetic iron oxide nanoparticles magnetite and maghemite (MNPs) are specially useful in various fields like biomedical, waste disposal, catalysis etc. because of their biocompatibility and magnetic properties. They can be manipulated by applying magnetic field and hence their easier separation, wider applications and unending scope in the field of research. They are inherently hydrophobic, and aggregate easily mainly due to magnetic and nanosize effects. The present work reports the synthesis of hydrophilic, stably dispersed MNPs coated by different amino acids at different pH values. Lower concentration of amino acids, 1/3 (moles by moles) of Iron salts concentration was used in the study. Crystallites were found to be approximately 6-7 nm in size, as determined by XRD and also found to have good magnetization values in VSM studies. The effects of coating are mainly studied by FTIR and TG. Higher/lower pH values have been studied for better coating, and it is observed that higher pH is more helpful in getting better results, on bare MNPs synthesized under a pH of approximately 13.3. The effects of net charge on coating efficiency were also studied.

One-pot size-controlled growth of graphene-encapsulated germanium nanocrystals

Science.gov (United States)

Lee, Jae-Hyun; Lee, Eun-Kyung; Kang, Seog-Gyun; Jung, Su-Ho; Son, Seok-Kyun; Nam, Woo Hyun; Kim, Tae-Hoon; Choi, Byong Lyong; Whang, Dongmok

2018-05-01

To realize graphene-encapsulated semiconductor nanocrystals (NCs), an additional graphene coating process, which causes shape destruction and chemical contamination, has so far been inevitable. We report herein one-pot growth of uniform graphene-germanium core-shell nanocrystals (Ge@G NCs) in gram scale by the addition of methane as a carbon source during the thermal pyrolysis of germane. The methane plays a critical role in the growth of the graphene shell, as well as in the determination of the nucleation density and diameter of the NCs, similar to a surfactant in the liquid-phase growth of monodisperse NCs. By adjusting the gas ratio of precursors, a mixture of germane and methane, we can control the size of the Ge@G NCs in the range of ∼5-180 nm. The Ge@G NCs were characterized by various microscopic and spectroscopic tools, which indicated that the Ge core is single crystalline, and is completely covered by the graphene shell. We further investigated the merits of the graphene shell, which can enhance the electrical conductivity of nanocrystalline materials.

Numerical Analysis of Novel Back Surface Field for High Efficiency Ultrathin CdTe Solar Cells

Directory of Open Access Journals (Sweden)

M. A. Matin

2013-01-01

Full Text Available This paper numerically explores the possibility of high efficiency, ultrathin, and stable CdTe cells with different back surface field (BSF using well accepted simulator AMPS-1D (analysis of microelectronics and photonic structures. A modified structure of CdTe based PV cell SnO2/Zn2SnO4/CdS/CdTe/BSF/BC has been proposed over reference structure SnO2/Zn2SnO4/CdS/CdTe/Cu. Both higher bandgap materials like ZnTe and Cu2Te and low bandgap materials like As2Te3 and Sb2Te3 have been used as BSF to reduce minority carrier recombination loss at the back contact in ultra-thin CdTe cells. In this analysis the highest conversion efficiency of CdTe based PV cell without BSF has been found to be around 17% using CdTe absorber thickness of 5 μm. However, the proposed structures with different BSF have shown acceptable efficiencies with an ultra-thin CdTe absorber of only 0.6 μm. The proposed structure with As2Te3 BSF showed the highest conversion efficiency of 20.8% ( V,  mA/cm2, and . Moreover, the proposed structures have shown improved stability in most extents, as it was found that the cells have relatively lower negative temperature coefficient. However, the cell with ZnTe BSF has shown better overall stability than other proposed cells with temperature coefficient (TC of −0.3%/°C.

Characterization of a pixelated CdTe Timepix detector operated in ToT mode

International Nuclear Information System (INIS)

Billoud, T.; Leroy, C.; Papadatos, C.; Roux, J.S.; Pichotka, M.; Pospisil, S.

2017-01-01

A 1 mm thick CdTe sensor bump-bonded to a Timepix readout chip operating in Time-over-Threshold (ToT) mode has been characterized in view of possible applications in particle and medical physics. The CdTe sensor layer was segmented into 256 × 256 pixels, with a pixel pitch of 55  μm. This CdTe Timepix device, of ohmic contact type, has been exposed to alpha-particles and photons from an 241 Am source, photons from a 137 Cs source, and protons of different energies (0.8–10 MeV) delivered by the University of Montreal Tandem Accelerator. The device was irradiated on the negatively biased backside electrode. An X-ray per-pixel calibration commonly used for this type of detector was done and its accuracy and resolution were assessed and compared to those of a 300  μm thick silicon Timepix device. The electron mobility-lifetime product (μ e τ e ) of CdTe for protons of low energy has been obtained from the Hecht equation. Possible polarization effects have been also investigated. Finally, information about the homogeneity of the detector was obtained from X-ray irradiation.

Phase transitions and doping in semiconductor nanocrystals

Science.gov (United States)

Sahu, Ayaskanta

Colloidal semiconductor nanocrystals are a promising technological material because their size-dependent optical and electronic properties can be exploited for a diverse range of applications such as light-emitting diodes, bio-labels, transistors, and solar cells. For many of these applications, electrical current needs to be transported through the devices. However, while their solution processability makes these colloidal nanocrystals attractive candidates for device applications, the bulky surfactants that render these nanocrystals dispersible in common solvents block electrical current. Thus, in order to realize the full potential of colloidal semiconductor nanocrystals in the next-generation of solid-state devices, methods must be devised to make conductive films from these nanocrystals. One way to achieve this would be to add minute amounts of foreign impurity atoms (dopants) to increase their conductivity. Electronic doping in nanocrystals is still very much in its infancy with limited understanding of the underlying mechanisms that govern the doping process. This thesis introduces an innovative synthesis of doped nanocrystals and aims at expanding the fundamental understanding of charge transport in these doped nanocrystal films. The list of semiconductor nanocrystals that can be doped is large, and if one combines that with available dopants, an even larger set of materials with interesting properties and applications can be generated. In addition to doping, another promising route to increase conductivity in nanocrystal films is to use nanocrystals with high ionic conductivities. This thesis also examines this possibility by studying new phases of mixed ionic and electronic conductors at the nanoscale. Such a versatile approach may open new pathways for interesting fundamental research, and also lay the foundation for the creation of novel materials with important applications. In addition to their size-dependence, the intentional incorporation of

Synthesis and characterization of KTiOPO4 nanocrystals and their PMMA nanocomposites

International Nuclear Information System (INIS)

Galceran, M; Pujol, M C; Carvajal, J J; Diaz, F; Aguilo, M; Tkaczyk, S; Kityk, I V

2009-01-01

KTiOPO 4 (KTP) nanocrystals have been synthesized by the modified Pechini method using ethylenediaminetetraacetic acid (EDTA) and ethylene glycol (EG) as chelating and sterification agents, respectively. Orthorhombic KTP has been obtained by calcination at 1073 K for several hours. Differential thermal and thermogravimetric (DTA-TG) analyses have been used to study the optimized heat treatment used on the precursor powder to obtain KTP nanocrystals. X-ray powder diffraction (XRD) studies on the thermally treated precursor powders indicated that nanocrystals began to crystallize at 923 K. Nanocrystals with a size dispersion distribution that fit to a lognormal function centered at 25 nm were observed by electronic microscopy. KTP nanocomposites were prepared by embedding nanocrystals in poly(methyl methacrylate) (PMMA). The photoinduced second-order susceptibility parameter and the piezo-optical coefficient were measured for the KTP nanocomposites. The optimal conditions for the generation of the frequency-doubled second harmonic generation were recorded at 391 K, and at a fundamental laser wavelength of 1064 nm and under additional treatment by polarized UV light, provided the maximum value obtained of 3.23 pm V -1 . The piezo-optical coefficients were recorded at room temperature under photoinduced treatment by a UV laser beam; the maximum value achieved was 0.673 x 10 -14 m 2 N -1 at a pump-probe delaying time of 160 s.

Ecotoxicity of CdTe quantum dots to freshwater mussels: Impacts on immune system, oxidative stress and genotoxicity

International Nuclear Information System (INIS)

Gagne, F.; Auclair, J.; Turcotte, P.; Fournier, M.; Gagnon, C.; Sauve, S.; Blaise, C.

2008-01-01

The purpose of this study was to examine the toxic effects of cadmium-telluride (CdTe) quantum dots on freshwater mussels. Elliption complanata mussels were exposed to increasing concentrations of CdTe (0, 1.6, 4 and 8 mg/L) and cadmium sulfate (CdSO 4 , 0.5 mg/L) for 24 h at 15 o C. After the exposure period, they were removed for assessments of immunocompetence, oxidative stress (lipid peroxidation) and genotoxicity (DNA strand breaks). Preliminary experiments revealed that CdTe dissolved in aquarium water tended to aggregate in the particulate phase (85%) while 15% of CdTe was found in the dissolved phase. Immunotoxicity was characterized by a significant decrease in the number of hemocytes capable of ingesting fluorescent beads, and hemocyte viability. The cytotoxic capacity of hemocytes to lyse mammalian K-562 cells was significantly increased, but the number of circulating hemocytes remained unchanged. Lipid peroxidation was significantly increased at a threshold concentration of 5.6 mg/L in gills and significantly reduced in digestive glands at a threshold concentration <1.6 mg/L CdTe. The levels of DNA strand breaks were significantly reduced in gills at <1.6 mg/L CdTe. In digestive glands, a transient but marginal increase in DNA strand breaks occurred at the lowest concentration and dropped significantly at the higher concentrations. A multivariate analysis revealed that the various response patterns differed based on the concentration of CdTe, thus permitting the identification of biomarkers associated with the form (colloidal vs. molecular) of cadmium

Ecotoxicity of CdTe quantum dots to freshwater mussels: Impacts on immune system, oxidative stress and genotoxicity

Energy Technology Data Exchange (ETDEWEB)

Gagne, F. [Fluvial Ecosystem Research, Environment Canada, 105 McGill Street, Montreal, Quebec, H2Y 2E7 (Canada)], E-mail: francois.gagne@ec.gc.ca; Auclair, J.; Turcotte, P. [Fluvial Ecosystem Research, Environment Canada, 105 McGill Street, Montreal, Quebec, H2Y 2E7 (Canada); Fournier, M. [INRS-Institut Armand-Frappier, 245 Hymus, Pointe-Claire, Quebec, H9R 3G6 (Canada); Gagnon, C. [Fluvial Ecosystem Research, Environment Canada, 105 McGill Street, Montreal, Quebec, H2Y 2E7 (Canada); Sauve, S. [Departement de Chimie, Universite de Montreal, C.P. 6128, Succursale Centre-ville, Montreal, Quebec, H3C 3J7 (Canada); Blaise, C. [Fluvial Ecosystem Research, Environment Canada, 105 McGill Street, Montreal, Quebec, H2Y 2E7 (Canada)

2008-02-18

The purpose of this study was to examine the toxic effects of cadmium-telluride (CdTe) quantum dots on freshwater mussels. Elliption complanata mussels were exposed to increasing concentrations of CdTe (0, 1.6, 4 and 8 mg/L) and cadmium sulfate (CdSO{sub 4}, 0.5 mg/L) for 24 h at 15 {sup o}C. After the exposure period, they were removed for assessments of immunocompetence, oxidative stress (lipid peroxidation) and genotoxicity (DNA strand breaks). Preliminary experiments revealed that CdTe dissolved in aquarium water tended to aggregate in the particulate phase (85%) while 15% of CdTe was found in the dissolved phase. Immunotoxicity was characterized by a significant decrease in the number of hemocytes capable of ingesting fluorescent beads, and hemocyte viability. The cytotoxic capacity of hemocytes to lyse mammalian K-562 cells was significantly increased, but the number of circulating hemocytes remained unchanged. Lipid peroxidation was significantly increased at a threshold concentration of 5.6 mg/L in gills and significantly reduced in digestive glands at a threshold concentration <1.6 mg/L CdTe. The levels of DNA strand breaks were significantly reduced in gills at <1.6 mg/L CdTe. In digestive glands, a transient but marginal increase in DNA strand breaks occurred at the lowest concentration and dropped significantly at the higher concentrations. A multivariate analysis revealed that the various response patterns differed based on the concentration of CdTe, thus permitting the identification of biomarkers associated with the form (colloidal vs. molecular) of cadmium.

An innovative zinc oxide-coated zeolite adsorbent for removal of humic acid

Science.gov (United States)

Zinc oxide (ZnO)-coated zeolite adsorbents were developed by both nitric acid modification and Zn(NO3)2•6H2O functionalization of zeolite. The developed adsorbents were used for the removal of humic acid (HA) from aqueous solutions. The adsorption capacity of the adsorbents at 21...

A computational study on the energy bandgap engineering in performance enhancement of CdTe thin film solar cells

Directory of Open Access Journals (Sweden)

Ameen M. Ali

Full Text Available In this study, photovoltaic properties of CdTe thin film in the configuration of n-SnO2/n-CdS/p-CdTe/p-CdTe:Te/metal have been studied by numerical simulation software named “Analysis of Microelectronic and Photonic Structure” (AMPS-1D. A modified structure for CdTe thin film solar cell has been proposed by numerical analysis with the insertion of a back contact buffer layer (CdTe:Te. This layer can serve as a barrier that will decelerate the copper diffusion in CdTe solar cell. Four estimated energy bandgap relations versus the Tellurium (Te concentrations and the (CdTe:Te layer thickness have been examined thoroughly during simulation. Correlation between energy bandgap with the CdTe thin film solar cell performance has also been established. Keywords: Numerical modelling, CdTe thin film, Solar cell, AMPS-1D, Bandgap

Characterization of point defects in CdTe by positron annihilation spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Elsharkawy, M. R. M. [Carnegie Laboratory of Physics, SUPA, School of Science and Engineering, University of Dundee, Dundee DD1 4HN (United Kingdom); Physics Department, Faculty of Science, Minia University, P.O. Box 61519, Minia (Egypt); Kanda, G. S.; Keeble, D. J., E-mail: d.j.keeble@dundee.ac.uk [Carnegie Laboratory of Physics, SUPA, School of Science and Engineering, University of Dundee, Dundee DD1 4HN (United Kingdom); Abdel-Hady, E. E. [Physics Department, Faculty of Science, Minia University, P.O. Box 61519, Minia (Egypt)

2016-06-13

Positron lifetime measurements on CdTe 0.15% Zn-doped by weight are presented, trapping to monovacancy defects is observed. At low temperatures, localization at shallow binding energy positron traps dominates. To aid defect identification density functional theory, calculated positron lifetimes and momentum distributions are obtained using relaxed geometry configurations of the monovacancy defects and the Te antisite. These calculations provide evidence that combined positron lifetime and coincidence Doppler spectroscopy measurements have the capability to identify neutral or negative charge states of the monovacancies, the Te antisite, A-centers, and divacancy defects in CdTe.

Laser fabrication nanocrystalline coatings using simultaneous powders/wire feed

Science.gov (United States)

Li, Jianing; Zhai, Tongguang; Zhang, Yuanbin; Shan, Feihu; Liu, Peng; Ren, Guocheng

2016-07-01

Laser melting deposition (LMD) fabrication is used to investigate feasibilty of simultaneously feeding TC17 wire and the Stellite 20-Si3N4-TiC-Sb mixed powders in order to increase the utilization ratio of materials and also quality of LMD composite coatings on the TA1 substrate. SEM images indicated that such LMD coating with metallurgical joint to substrate was formed free of the obvious defects. Lots of the ultrafine nanocrystals (UNs) were produced, which distributed uniformly in some coating matrix location, retarding growth of the ceramics in a certain extent; UNs were intertwined with amorphous, leading the yarn-shape materials to be produced. Compared with substrate, an improvement of wear resistance was achieved for such LMD coating.

Microstructural, optical and electrical properties of Cl-doped CdTe single crystals

Directory of Open Access Journals (Sweden)

Choi Hyojeong

2016-09-01

Full Text Available Microstructural, optical and electrical properties of Cl-doped CdTe crystals grown by the low pressure Bridgman (LPB method were investigated for four different doping concentrations (unintentionally doped, 4.97 × 1019 cm−3, 9.94 × 1019 cm−3 and 1.99 × 1020 cm−3 and three different locations within the ingots (namely, samples from top, middle and bottom positions in the order of the distance from the tip of the ingot. It was shown that Cl dopant suppressed the unwanted secondary (5 1 1 crystalline orientation. Also, the average size and surface coverage of Te inclusions decreased with an increase in Cl doping concentration. Spectroscopic ellipsometry measurements showed that the optical quality of the Cl-doped CdTe single crystals was enhanced. The resistivity of the CdTe sample doped with Cl at the 1.99 × 1020 cm−3 was above 1010 Ω.cm.

Preliminary study of CdTe and CdTe:Cu thin films nanostructures deposited by using DC magnetron sputtering

Energy Technology Data Exchange (ETDEWEB)

Marwoto, Putut; Made, D. P. Ngurah; Sugianto [Departement of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Semarang, Gunungpati, Semarang 50229 Jawa Tengah (Indonesia); Wibowo, Edy; Astuti, Santi Yuli; Aryani, Nila Prasetya [Materials Research Group, Laboratory of Thin Film, Department of Physics, Universitas Negeri Semarang, Gunungpati, Semarang 50229 Jawa Tengah (Indonesia); Othaman, Zulkafli [Departement of Physics, Universiti Teknologi Malaysia (UTM), Skudai, Johor Bahru (Malaysia)

2013-09-03

Growth and properties of CdTe and CdTe:Cu thin films nanostrucures deposited by using dc magnetron sputtering are reported. Scanning electron microscope (SEM) was used to observe the surface morphologies of the thin films. At growth conditions of 250 °C and 14 W, CdTe films did not yet evenly deposited. However, at growth temperature and plasma power of 325 °C and 43 W, both CdTe and CdTe:Cu(2%) have deposited on the substrates. In this condition, the morphology of the films indicate that the films have a grain-like nanostructures. Grain size diameter of about 200 nm begin to appear on top of the films. Energy Dispersive X-rays spectroscopy (EDX) was used to investigate chemical elements of the Cu doped CdTe film deposited. It was found that the film deposited consist of Cd, Te and Cu elements. XRD was used to investigate the full width at half maximum (FWHM) values of the thin films deposited. The results show that CdTe:Cu(2%) thin film has better crystallographic properties than CdTe thin film. The UV-Vis spectrometer was used to investigate the optical properties of thin films deposited. The transmittance spectra showed that transmittance of CdTe:Cu(2%) film is lower than CdTe film. It was found that the bandgap energy of CdTe and CdTe:Cu(2%) thin films of about 1.48 eV.

NaGd(MoO4)2 nanocrystals with diverse morphologies: controlled synthesis, growth mechanism, photoluminescence and thermometric properties.

Science.gov (United States)

Li, Anming; Xu, Dekang; Lin, Hao; Yang, Shenghong; Shao, Yuanzhi; Zhang, Yueli

2016-08-10

Pure tetragonal phase, uniform and well-crystallized sodium gadolinium molybdate (NaGd(MoO4)2) nanocrystals with diverse morphologies, e.g. nanocylinders, nanocubes and square nanoplates have been selectively synthesized via oleic acid-mediated hydrothermal method. The phase, structure, morphology and composition of the as-synthesized products are studied. Contents of both sodium molybdate and oleic acid of the precursor solutions are found to affect the morphologies of the products significantly, and oleic acid plays a key role in the morphology-controlled synthesis of NaGd(MoO4)2 nanocrystals with diverse morphologies. Growth mechanism of NaGd(MoO4)2 nanocrystals is proposed based on time-dependent morphology evolution and X-ray diffraction analysis. Morphology-dependent down-shifting photoluminescence properties of NaGd(MoO4)2: Eu(3+) nanocrystals, and upconversion photoluminescence properties of NaGd(MoO4)2: Yb(3+)/Er(3+) and Yb(3+)/Tm(3+) nanoplates are investigated in detail. Charge transfer band in the down-shifting excitation spectra shows a slight blue-shift, and the luminescence intensities and lifetimes of Eu(3+) are decreased gradually with the morphology of the nanocrystals varying from nanocubes to thin square nanoplates. Upconversion energy transfer mechanisms of NaGd(MoO4)2: Yb(3+)/Er(3+), Yb(3+)/Tm(3+) nanoplates are proposed based on the energy level scheme and power dependence of upconversion emissions. Thermometric properties of NaGd(MoO4)2: Yb(3+)/Er(3+) nanoplates are investigated, and the maximum sensitivity is determined to be 0.01333 K(-1) at 285 K.

Effects of acid and alkaline based surface preparations on spray deposited cerium based conversion coatings on Al 2024-T3

Energy Technology Data Exchange (ETDEWEB)

Pinc, W. [Department of Materials Science Engineering, Materials Research Center, Missouri University of Science and Technology, Rolla, MO 65409 (United States)], E-mail: wrphw5@mst.edu; Geng, S.; O' Keefe, M.; Fahrenholtz, W.; O' Keefe, T. [Department of Materials Science Engineering, Materials Research Center, Missouri University of Science and Technology, Rolla, MO 65409 (United States)

2009-01-15

Cerium based conversion coatings were spray deposited on Al 2024-T3 and characterized to determine the effect of surface preparation on the deposition rate and surface morphology. It was found that activation of the panel using a 1-wt.% sulfuric acid solution increased the coating deposition rate compared to alkaline cleaning alone. Analysis of the surface morphology of the coatings showed that the coatings deposited on the acid treated panels exhibited fewer visible cracks compared to coatings on alkaline cleaned panels. Auger electron spectroscopy depth profiling showed that the acid activation decreased the thickness of the aluminum oxide layer and the concentration of magnesium on the surface of the panels compared to the alkaline treatment. Additionally, acid activation increased the copper concentration at the surface of the aluminum substrate. Based on the results, the acid based surface treatment appeared to expose copper rich intermetallics, thus increasing the number of cathodic sites on the surface, which led to an overall increase in the deposition rate.

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.

The response of quartz crystals coated with thin fatty acid film to organic gases

CERN Document Server

Jin, C N; Kim, K H; Kwon, Y S

1999-01-01

We tried to apply a quartz crystal as a sensor by using the resonant frequency and the resistance properties of quartz crystals. Four kinds of fatty acids that have the same head groups were coated on the surfaces of the quartz crystals, and the shift of the resonant frequency and the resistance were observed based on the lengths of the tail groups. Myristic acid (C sub 1 sub 4), palmitic acid (C sub 1 sub 6), stearic acid (C sub 1 sub 8), and arachidic acid (C sub 2 sub 0) were deposited on the surfaces of quartz crystals by using the Langmuir-Blodgett (LB) method. As a result, the resonant frequency change was more sensitive to high molecular-weight fatty acids than to low molecular-weight ones. We also observed the effect of temperature on stearic acid LB films, and the response properties of quartz crystals coated with stearic-acid LB films to organic gases were investigated. As a result, the sensitivity of quartz crystals to organic gases was higher for higher molecular-weight gas, and we found that quar...

Effects of various deposition times and RF powers on CdTe thin film growth using magnetron sputtering

Science.gov (United States)

Ghorannevis, Z.; Akbarnejad, E.; Ghoranneviss, M.

2016-09-01

Cadmium telluride (CdTe) is a p-type II-VI compound semiconductor, which is an active component for producing photovoltaic solar cells in the form of thin films, due to its desirable physical properties. In this study, CdTe film was deposited using the radio frequency (RF) magnetron sputtering system onto a glass substrate. To improve the properties of the CdTe film, effects of two experimental parameters of deposition time and RF power were investigated on the physical properties of the CdTe films. X-ray Diffraction (XRD), atomic force microscopy (AFM) and spectrophotometer were used to study the structural, morphological and optical properties of the CdTe samples grown at different experimental conditions, respectively. Our results suggest that film properties strongly depend on the experimental parameters and by optimizing these parameters, it is possible to tune the desired structural, morphological and optical properties. From XRD data, it is found that increasing the deposition time and RF power leads to increasing the crystallinity as well as the crystal sizes of the grown film, and all the films represent zinc blende cubic structure. Roughness values given from AFM images suggest increasing the roughness of the CdTe films by increasing the RF power and deposition times. Finally, optical investigations reveal increasing the film band gaps by increasing the RF power and the deposition time.

Engineering the bio-nano interface using a multi-functional polymer coating

Science.gov (United States)

Wang, Wentao

Interfacing inorganic nanoparticles with biological systems to develop a variety of novel imaging, sensing and diagnostic tools has generated great interest and much activity over the past two decades. However, the effectiveness of this approach hinges on the ability to prepare water dispersible nanoparticles, with compact size and long term colloidal stability in biological environments, and the development of controlled conjugation to various biomolecules. The primary focus of this dissertation is the design and synthesis, characterization and use of a series of new multidentate and multifunctional coordinating polymers as ligands that render various inorganic nanocrystals water soluble, In Chapter 1 we introduce the basic physical properties of quantum dots (QDs), gold nanocrystals and magnetic nanocrystals along with brief description of their syntheses. We then provide an overview of surface functionalization strategies and recent progress in the ligand chemistry, followed by highlights of a few conjugation approaches applied to nanoparticles in biology. We then discuss modulation of the optical and spectroscopic properties of QDs via energy and charge transfer interactions. We conclude by presenting a few related examples on the incorporation of QD-conjugates into sensor design and intracellular imaging. In Chapter 2, we report the design of a series of multifunctional polymers as ligands for surface engineering of QDs and facilitating their use in bioconjugation. First, we introduce a novel PEGylated polymer that combines the synergies of metal-chelation promoted by lipoic acid and imidazole groups, as effective coating for the surface functionalization of QDs; one of the goals was to address the problems associated with thiol oxidation and weak imidazole affinity. Second, to minimize the hydrodynamic radius of the QDs without sacrificing aqueous solubility, a set of polymer ligands appended with zwitterion and imidazole motifs have been synthesized applied

Laser surface treatment of S235JRC carbon steel with Co{sub 2}B nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Simsek, Tuncay [Hacettepe Univ., Ankara (Turkey). Dept. of Physics Engineering; Baris, Mustafa [Eti Maden Works General Management, Ankara (Turkey). Dept. of Technology Development; Akkurt, Adnan [Gazi Univ., Ankara (Turkey). Dept. of Industrial Design Engineering

2017-06-15

In this study, Co{sub 2}B nanocrystals, which were synthesized in a planetary type mill by using the mechanochemical method, were pre-coated on the surface of S235JRC low carbon steel substrates, and then the surfaces were clad using a CO{sub 2} laser. In the experiments, laser scan speed was kept constant and laser power was specified as the variable parameter. The microstructure and phases of the coatings were investigated by using X-ray diffractometry, scanning electron microscopy, and optical microscopy. The mechanical properties of the coatings were characterized using micro-hardness, ball-on-disc wear, and scratch testing. The thickness of the coatings depending on the laser power was measured in the range 35-71 μm. The hardness and the wear resistance of the coatings were approximately 3 times higher compared to the base metal due to FeN{sub 0.0760}, Fe{sub 15.1}C, FeCo, and B{sub 2}C{sub 5}N{sub 2} phases of the coatings. The most durable coatings against wear were obtained at 174 W and 220 W laser powers.

Nanocrystal/sol-gel nanocomposites

Science.gov (United States)

Petruska, Melissa A [Los Alamos, NM; Klimov, Victor L [Los Alamos, NM

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.

About the use of photoacoustic spectroscopy for the optical characterization of semiconductor thin films: CdTe

International Nuclear Information System (INIS)

Marin, E.; Calderon, A.; Vigil G, O.; Sastre, J.; Contreras P, G.; Aguilar H, J.; Saucedo, E.; Ruiz, C.M.

2006-01-01

CdTe has been used satisfactorily in multiple and diverse technological applications such as detectors of X and gamma rays that operate at room temperature, for digital imagenology of X rays with medical and industrial applications and as active part in CdTe/CdS solar cells. In form of films, CdTe is generally grown with thicknesses ranging between 3 and 15 μm, for which it is difficult to measure, by means of optical techniques, absorption coefficients greater than 10 3 cm -1 because nearly full absorption of light should occur below 800 nm. The exact determination of the optical absorption coefficient in detectors on the basis of CdTe is very important since this parameter determines the absorption length at which 90% of the photons with energies over the forbidden zone of the CdTe will be absorbed by this. In CdS/CdTe polycrystalline solar cells the greater efficiency of conversion have been reported for film thicknesses of 10 mm, however, the optimal value of this parameter depends strongly on the method and the variables of growth. The optical absorption coefficient spectrum can be determined by several methods, often involving several approximations and the knowledge of some minority carrier related electronic parameters that reduce their application in general way. In this work we propose to determine the absorption coefficient in CdTe thin films by photoacoustic spectroscopy (PAS), because this technique allow us to obtain the optical absorption spectra in thicker layers and therefore the study of the influence of the several growth and post-growth processes in the optical properties of this thin films. We measure by PAS the optical-absorption coefficients of CdTe thin films in the spectral region near the fundamental absorption edge ranging from 1.0 to 2.4 eV using an open cell in the transmission configuration. The films were deposited on different substrates by the CSVT-HW (hot wall) technique. In order to study the influence of several growth

Z-Contrast STEM Imaging and EELS of CdSe Nanocrystals: Towards the Analysis of Individual Nanocrystal Surfaces

International Nuclear Information System (INIS)

Erwin, M.; Kadavanich, A.V.; Kippeny, T.; Pennycook, S.J.; Rosenthal, S.J.

1999-01-01

We have applied Atomic Number Contract Scanning Transmission Electron Microscopy (Z-Contrast STEM) and STEM/EELS (Electron Energy Loss Spectroscopy) towards the study of colloidal CdSe semiconductor nanocrystals embedded in MEH-PPV polymer films. Unlike the case of conventional phase-contrast High Resolution TEM, Z-Contrast images are direct projections of the atomic structure. Hence they can be interpreted without the need for sophisticated image simulation and the image intensity is a direct measure of the thickness of a nanocrystal. Our thickness measurements are in agreement with the predicted faceted shape of these nanocrystals. Our unique 1.3A resolution STEM has successfully resolve3d the sublattice structure of these CdSe nanocrystals. In [010] projection (the polar axis in the image plane) we can distinguish Se atom columns from Cd columns. Consequently we can study the effects of lattice polarity on the nanocrystal morphology. Furthermore, since the STEM technique does not rely on diffraction, it is superbly suited to the study of non-periodic detail, such as the surface structure of the nanocrystals. EELS measurements on individual nanocrystals indicate a significant amount (equivalet to 0.5-1 surface monolayers) of oxygen on the nanocrystals, despite processing in an inert atmosphere. Spatially resolved measurements at 7A resolution suggest a surface oxide layer. However, the uncertainty in the measurement precludes definitive assignment at this time. The source of the oxygen is under investigation as well

CdTe QDs-based prostate-specific antigen probe for human prostate cancer cell imaging

International Nuclear Information System (INIS)

Dong Wei; Guo Li; Wang Meng; Xu Shukun

2009-01-01

L-glutathione (GSH) stabilized CdTe quantum dots (QDs) were directly prepared in aqueous solution. The as-prepared QDs were linked to prostate-specific antigen (PSA) for the direct labeling and linked to immunoglobulin G (IgG) for the indirect labeling of fixed prostate cancer cells. The results indicated that QD-based probes were ideal fluorescent markers with excellent spectral properties and photostability and much better than organic dyes making them very suitable in target detection. Meanwhile, the indirect labeling showed much better specificity than the direct labeling. Furthermore, the prepared CdTe QDs did not show detectable effect on cell growth after having cultured for three days, which suggested that the L-glutathione capped CdTe had scarcely cytotoxicity.

In Situ PDF Study of the Nucleation and Growth of Intermetallic PtPb Nanocrystals

DEFF Research Database (Denmark)

Saha, Dipankar; Bojesen, Espen D.; Mamakhel, Mohammad Aref Hasen

2017-01-01

The mechanism of Pt and PtPb nanocrystal formation under supercritical ethanol conditions has been investigated by means of in situ X-ray total scattering and pair distribution function (PDF) analysis. The metal complex structures of two different platinum precursor solutions, chloroplatinic acid...... supercritical ethanol process for obtaining phase-pure hexagonal PtPb nanocrystals. The study thus highlights the importance of in situ studies in revealing atomic-scale information about nucleation mechanisms, which can be used in design of specific synthesis pathways, and the new continuous-flow process...

Optimization of material/device parameters of CdTe photovoltaic for solar cells applications

Science.gov (United States)

Wijewarnasuriya, Priyalal S.

2016-05-01

Cadmium telluride (CdTe) has been recognized as a promising photovoltaic material for thin-film solar cell applications due to its near optimum bandgap of ~1.5 eV and high absorption coefficient. The energy gap is near optimum for a single-junction solar cell. The high absorption coefficient allows films as thin as 2.5 μm to absorb more than 98% of the above-bandgap radiation. Cells with efficiencies near 20% have been produced with poly-CdTe materials. This paper examines n/p heterostructure device architecture. The performance limitations related to doping concentrations, minority carrier lifetimes, absorber layer thickness, and surface recombination velocities at the back and front interfaces is assessed. Ultimately, the paper explores device architectures of poly- CdTe and crystalline CdTe to achieve performance comparable to gallium arsenide (GaAs).

Thermal stability of substitutional ag in CdTe

NARCIS (Netherlands)

Jahn, SG; Hofsass, H; Restle, M; Ronning, C; Quintel, H; BharuthRam, K; Wahl, U

The thermal stability of substitutional Ag in CdTe was deduced from lattice location measurements at different temperatures. Substitutional Ag probe atoms were generated via transmutation doping from radioactive Cd isotopes. The lattice sites of Ag isotopes were determined by measuring the

Plasmon-assisted photoluminescence enhancement of SiC nanocrystals by proximal silver nanoparticles

International Nuclear Information System (INIS)

Zhang, N.; Dai, D.J.; Fan, J.Y.

2012-01-01

Highlights: ► We studied metal surface plasmon-enhanced photoluminescence in SiC nanocrystals. ► The integrated emission intensity can be enhanced by 17 times. ► The coupling between SiC emission and Ag plasmon oscillation induces the enhancement. ► The enhancement is tunable with varied spacing thickness of electrolytes. - Abstract: Plasmon-enhanced photoluminescence has wide application potential in many areas, whereas the underlying mechanism is still in debate. We report the photoluminescence enhancement in SiC nanocrystal–Ag nanoparticle coupled system spaced by the poly(styrene sulfonic acid) sodium salt/poly(allylamine hydrochloride) polyelectrolyte bilayers. The integrated luminescence intensity can be improved by up to 17 times. Our analysis indicates that the strong coupling between the SiC nanocrystals and the surface plasmon oscillation of the silver nanoparticles is the major cause of the luminescence enhancement. These findings will help to understand the photoluminescence enhancement mechanism as well as widen the applications of the SiC nanocrystals in photonics and life sciences.

Growth of wurtzite CdTe nanowires on fluorine-doped tin oxide glass substrates and room-temperature bandgap parameter determination

Science.gov (United States)

Choi, Seon Bin; Song, Man Suk; Kim, Yong

2018-04-01

The growth of CdTe nanowires, catalyzed by Sn, was achieved on fluorine-doped tin oxide glass by physical vapor transport. CdTe nanowires grew along the 〈0001〉 direction, with a very rare and phase-pure wurtzite structure, at 290 °C. CdTe nanowires grew under Te-limited conditions by forming SnTe nanostructures in the catalysts and the wurtzite structure was energetically favored. By polarization-dependent and power-dependent micro-photoluminescence measurements of individual nanowires, heavy and light hole-related transitions could be differentiated, and the fundamental bandgap of wurtzite CdTe at room temperature was determined to be 1.562 eV, which was 52 meV higher than that of zinc-blende CdTe. From the analysis of doublet photoluminescence spectra, the valence band splitting energy between heavy hole and light hole bands was estimated to be 43 meV.

Nanocrystal thin film fabrication methods and apparatus

Science.gov (United States)

Kagan, Cherie R.; Kim, David K.; Choi, Ji-Hyuk; Lai, Yuming

2018-01-09

Nanocrystal thin film devices and methods for fabricating nanocrystal thin film devices are disclosed. The nanocrystal thin films are diffused with a dopant such as Indium, Potassium, Tin, etc. to reduce surface states. The thin film devices may be exposed to air during a portion of the fabrication. This enables fabrication of nanocrystal-based devices using a wider range of techniques such as photolithography and photolithographic patterning in an air environment.

Citric acid-coated gold nanoparticles for visual colorimetric recognition of pesticide dimethoate

Energy Technology Data Exchange (ETDEWEB)

Dar, Aqib Iqbal; Walia, Shanka; Acharya, Amitabha, E-mail: amitabhachem@gmail.com, E-mail: amitabha@ihbt.res.in [CSIR-Institute of Himalayan Bioresource Technology, Biotechnology Division (India)

2016-08-15

A colorimetric chemo-sensor based on citric acid-coated gold NPs (C-GNP) showed a linear increase in fluorescence intensity with increasing concentration of pesticide dimethoate (DM). The limit of detection was found to be between ~8.25± 0.3 and 20 ± 9.5 ppm. The increase in fluorescence intensity was suggested to have originated from the soft–soft interaction between C-GNPs and DM via sulfur group which is absent in pesticide dicofol (DF). Similar studies with citric acid-coated silver NPs (C-SNPs) did not result any change in the fluorescence intensity. The microscopic studies suggested aggregation of C-GNPs in the presence of DM but not in case of DF.Graphical Abstract.

Pressure-induced drastic structural change in liquid CdTe

International Nuclear Information System (INIS)

Kinoshita, T.; Hattori, T.; Narushima, T.; Tsuji, K.

2005-01-01

We investigate the structure of liquid CdTe at pressures up to 6 GPa by synchrotron x-ray diffraction. The structure factor, S(Q), and the pair distribution function, g(r), change drastically within a small pressure interval of about 1 GPa (between 1.8 and 3 GPa). The S(Q),g(r), and other structural parameters, such as the average coordination number, CN, and the ratios of peak positions in S(Q) or g(r), reveal that the change originates from the pressure-induced modification in the local structure from the zinc-blende-like form into the rocksaltlike one. The liquid CdTe shows a high-pressure behavior similar to that in the crystalline counterpart in terms of the sharpness of the structural change and the high-pressure sequence in the local structure

Synthesis and transport characterization of electrochemically deposited CdTe nanowires

Science.gov (United States)

Kaur, Jaskiran; Kaur, Harmanmeet; Singh, R. C.

2018-04-01

This paper reports the synthesis and characterization of CdTe nanowires. A thin polymeric films were irradiated with 80MeV Ag ions at a fluence of 8E7 ions/cm2, followed by UV irradiation and chemically etching in aqueous NaOH. Nanosizes go-through pores so formed were filled using a specially designed cell via electrodeposition. Nanowires so formed were further studied using SEM, I-V, UV and XRD analysis. SEM images show very smooth and uniform CdTe nanowires freely standing on the substrate. The in-situ I-V characteristics of nano-/micro structures was carried out at room temperature by leaving the structures embedded in the insulating template membrane itself.

Electro-Plating and Characterisation of CdTe Thin Films Using CdCl2 as the Cadmium Source

Directory of Open Access Journals (Sweden)

Nor A. Abdul-Manaf

2015-09-01

Full Text Available Cadmium telluride (CdTe thin films have been successfully prepared from an aqueous electrolyte bath containing cadmium chloride (CdCl2·H2O and tellurium dioxide (TeO2 using an electrodeposition technique. The structural, electrical, morphological and optical properties of these thin films have been characterised using X-ray diffraction (XRD, Raman spectroscopy, optical profilometry, DC current-voltage (I-V measurements, photoelectrochemical (PEC cell measurement, scanning electron microscopy (SEM, atomic force microscopy (AFM and UV-Vis spectrophotometry. It is observed that the best cathodic potential is 698 mV with respect to standard calomel electrode (SCE in a three electrode system. Structural analysis using XRD shows polycrystalline crystal structure in the as-deposited CdTe thin films and the peaks intensity increase after CdCl2 treatment. PEC cell measurements show the possibility of growing p-, i- and n-type CdTe layers by varying the growth potential during electrodeposition. The electrical resistivity of the as-deposited layers are in the order of 104 Ω·cm. SEM and AFM show that the CdCl2 treated samples are more roughness and have larger grain size when compared to CdTe grown by CdSO4 precursor. Results obtained from the optical absorption reveal that the bandgap of as-deposited CdTe (1.48–1.52 eV reduce to (1.45–1.49 eV after CdCl2 treatment. Full characterisation of this material is providing new information on crucial CdCl2 treatment of CdTe thin films due to its built-in CdCl2 treatment during the material growth. The work is progressing to fabricate solar cells with this material and compare with CdTe thin films grown by conventional sulphate precursors.

Atmospheric photochemistry at a fatty acid-coated air-water interface

Science.gov (United States)

Rossignol, Stéphanie; Tinel, Liselotte; Bianco, Angelica; Passananti, Monica; Brigante, Marcello; Donaldson, D. James; George, Christian

2016-08-01

Although fatty acids are believed to be photochemically inert in the actinic region, complex volatile organic compounds are produced during illumination of an air-water interface coated solely with a monolayer of carboxylic acid. When aqueous solutions containing nonanoic acid (NA) at bulk concentrations that give rise to just over a monolayer of NA coverage are illuminated with actinic radiation, saturated and unsaturated aldehydes are seen in the gas phase, and more highly oxygenated products appear in the aqueous phase. This chemistry is probably initiated by triplet-state NA molecules excited by direct absorption of actinic light at the water surface. Because fatty acids-covered interfaces are ubiquitous in the environment, such photochemical processing will have a substantial impact on local ozone and particle formation.

Novel Contact Materials for Improved Performance CdTe Solar Cells Final Report

Energy Technology Data Exchange (ETDEWEB)

Rockett, Angus [Colorado School of Mines, Golden, CO (United States); Marsillac, Sylvain [Old Dominion Univ., Norfolk, VA (United States); Collins, Robert [Univesity of Toledo

2018-04-15

This program has explored a number of novel materials for contacts to CdTe solar cells in order to reduce the back contact Schottky barrier to zero and produce an ohmic contact. The project tested a wide range of potential contact materials including TiN, ZrN, CuInSe2:N, a-Si:H and alloys with C, and FeS2. Improved contacts were achieved with FeS2. As part of understanding the operation of the devices and controlling the deposition processes, a number of other important results were obtained. In the process of this project and following its conclusion it led to research that resulted in seven journal articles, nine conference publications, 13 talks presented at conferences, and training of eight graduate students. The seven journal articles were published in 2015, 2016, and 2017 and have been cited, as of March 2018, 52 times (one cited 19 times and two cited 11 times). We demonstrated high levels of doping of CIS with N but electrical activity of the resulting N was not high and the results were difficult to reproduce. Furthermore, even with high doping the contacts were not good. Annealing did not improve the contacts. A-Si:H was found to produce acceptable but unstable contacts, degrading even over a day or two, apparently due to H incorporation into the CdTe. Alloying with C did not improve the contacts or stability. The transition metal nitrides produced Schottky type contacts for all materials tested. While these contacts were found to be unsatisfactory, we investigated FeS2 and found this material to be effective and comparable to the best contacts currently available. The contacts were found to be chemically stable under heat treatment and preferable to Cu doped contacts. Thus, we demonstrated an improved contact material in the course of this project. In addition, we developed new ways of controlling the deposition of CdTe and other materials, demonstrated the nature of defects in CdTe, and studied the distribution of conductivity and carrier type in CdTe

Edge effects in a small pixel CdTe for X-ray imaging

Science.gov (United States)

Duarte, D. D.; Bell, S. J.; Lipp, J.; Schneider, A.; Seller, P.; Veale, M. C.; Wilson, M. D.; Baker, M. A.; Sellin, P. J.; Kachkanov, V.; Sawhney, K. J. S.

2013-10-01

Large area detectors capable of operating with high detection efficiency at energies above 30 keV are required in many contemporary X-ray imaging applications. The properties of high Z compound semiconductors, such as CdTe, make them ideally suitable to these applications. The STFC Rutherford Appleton Laboratory has developed a small pixel CdTe detector with 80 × 80 pixels on a 250 μm pitch. Historically, these detectors have included a 200 μm wide guard band around the pixelated anode to reduce the effect of defects in the crystal edge. The latest version of the detector ASIC is capable of four-side butting that allows the tiling of N × N flat panel arrays. To limit the dead space between modules to the width of one pixel, edgeless detector geometries have been developed where the active volume of the detector extends to the physical edge of the crystal. The spectroscopic performance of an edgeless CdTe detector bump bonded to the HEXITEC ASIC was tested with sealed radiation sources and compared with a monochromatic X-ray micro-beam mapping measurements made at the Diamond Light Source, U.K. The average energy resolution at 59.54 keV of bulk and edge pixels was 1.23 keV and 1.58 keV, respectively. 87% of the edge pixels present fully spectroscopic performance demonstrating that edgeless CdTe detectors are a promising technology for the production of large panel radiation detectors for X-ray imaging.

Growth and analysis of micro and nano CdTe arrays for solar cell applications

Science.gov (United States)

Aguirre, Brandon Adrian

CdTe is an excellent material for infrared detectors and photovoltaic applications. The efficiency of CdTe/CdS solar cells has increased very rapidly in the last 3 years to ˜20% but is still below the maximum theoretical value of 30%. Although the short-circuit current density is close to its maximum of 30 mA/cm2, the open circuit voltage has potential to be increased further to over 1 Volt. The main limitation that prevents further increase in the open-circuit voltage and therefore efficiency is the high defect density in the CdTe absorber layer. Reducing the defect density will increase the open-circuit voltage above 1 V through an increase in the carrier lifetime and concentration to tau >10 ns and p > 10 16 cm-3, respectively. However, the large lattice mismatch (10%) between CdTe and CdS and the polycrystalline nature of the CdTe film are the fundamental reasons for the high defect density and pose a difficult challenge to solve. In this work, a method to physically and electrically isolate the different kinds of defects at the nanoscale and understand their effect on the electrical performance of CdTe is presented. A SiO2 template with arrays of window openings was deposited between the CdTe and CdS to achieve selective-area growth of the CdTe via close-space sublimation. The diameter of the window openings was varied from the micro to the nanoscale to study the effect of size on nucleation, grain growth, and defect density. The resulting structures enabled the possibility to electrically isolate and individually probe micrometer and nanoscale sized CdTe/CdS cells. Electron back-scattered diffraction was used to observe grain orientation and defects in the miniature cells. Scanning and transmission electron microscopy was used to study the morphology, grain boundaries, grain orientation, defect structure, and strain in the layers. Finally, conducting atomic force microscopy was used to study the current-voltage characteristics of the solar cells. An

Induced Recrystallization of CdTe Thin Films Deposited by Close-Spaced Sublimation

International Nuclear Information System (INIS)

Mayo, B.

1998-01-01

We have deposited CdTe thin films by close-spaced sublimation at two different temperature ranges. The films deposited at the lower temperature partially recrystallized after CdCl2 treatment at 350C and completely recrystallized after the same treatment at 400C. The films deposited at higher temperature did not recrystallize at these two temperatures. These results confirmed that the mechanisms responsible for changes in physical properties of CdTe films treated with CdCl2 are recrystallization and grain growth, and provided an alternative method to deposit CSS films using lower temperatures

Electronic displays using optically pumped luminescent semiconductor nanocrystals

Science.gov (United States)

Weiss, Shimon [Pinole, CA; Schlamp, Michael C [Plainsboro, NJ; Alivisatos, A Paul [Oakland, CA

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.

The large-area CdTe thin film for CdS/CdTe solar cell prepared by physical vapor deposition in medium pressure

Energy Technology Data Exchange (ETDEWEB)

Luo, Run; Liu, Bo; Yang, Xiaoyan; Bao, Zheng; Li, Bing, E-mail: libing70@126.com; Zhang, Jingquan; Li, Wei; Wu, Lili; Feng, Lianghuan

2016-01-01

Graphical abstract: - Highlights: • The large-area CdTe film has been prepared by PVD under the pressure of 0.9 kPa. • The as-prepared CdTe thin film processes excellent photovoltaic properties. • This technique is suitable for depositing large-area CdTe thin film. • The 14.6% champion efficiency CdS/CdTe cell has been achieved. - Abstract: The Cadmium telluride (CdTe) thin film has been prepared by physical vapor deposition (PVD), the Ar + O{sub 2} pressure is about 0.9 kPa. This method is a newer technique to deposit CdTe thin film in large area, and the size of the film is 30 × 40 cm{sup 2}. This method is much different from the close-spaced sublimation (CSS), as the relevance between the source temperature and the substrate temperature is weak, and the gas phase of CdTe is transferred to the substrate by Ar + O{sub 2} flow. Through this method, the compact and uniform CdTe film (30 × 40 cm{sup 2}) has been achieved, and the performances of the CdTe thin film have been determined by transmission spectrum, SEM and XRD. The film is observed to be compact with a good crystallinity, the CdTe is polycrystalline with a cubic structure and a strongly preferred (1 1 1) orientation. Using the CdTe thin film (3 × 5 cm{sup 2}) which is taken from the deposited large-area film, the 14.6% efficiency CdS/CdTe thin film solar cell has been prepared successfully. The structure of the cell is glass/FTO/CdS/CdTe/graphite slurry/Au, short circuit current density (J{sub sc}) of the cell is 26.9 mA/cm{sup 2}, open circuit voltage (V{sub oc}) is 823 mV, and filling factor (FF) is 66.05%. This technique can be a quite promising method to apply in the industrial production, as it has great prospects in the fabricating of large-area CdTe film.

A Facile Fabrication of Silver-Coated Copper Nanowires by Galvanic Replacement

Directory of Open Access Journals (Sweden)

Xin He

2016-01-01

Full Text Available We demonstrated a general strategy to fabricate silver-coated copper nanowires by a galvanic replacement, which is guided by the chemical principle that metal ions (silver ions with a relatively high reduction potential can galvanically etch nanostructure made from a less metal (copper. Well-dispersed and high-yielded copper nanowires were initially synthesized and then introduced into silver-ammonia solution for the growth of silver nanocrystals on the nanowire surfaces under vigorous oscillation. The results of X-ray diffraction, scanning electron microscope, and transmission electron microscope revealed that the silver nanocrystals were uniformly distributed on the copper nanowire surfaces to form Cu-Ag heterostructures. The concentration of silver-ammonia solution and the time of replacement reaction determine the size and density of the silver nanocrystals. Our investigation might pave the way to the synthesis of other bimetallic nanostructures via a facile, fast, and economical route.

Blue-Emitting Small Silica Particles Incorporating ZnSe-Based Nanocrystals Prepared by Reverse Micelle Method

Directory of Open Access Journals (Sweden)

Masanori Ando

2007-01-01

Full Text Available ZnSe-based nanocrystals (ca. 4-5 nm in diameter emitting in blue region (ca. 445 nm were incorporated in spherical small silica particles (20–40 nm in diameter by a reverse micelle method. During the preparation, alkaline solution was used to deposit the hydrolyzed alkoxide on the surface of nanocrystals. It was crucially important for this solution to include Zn2+ ions and surfactant molecules (thioglycolic acid to preserve the spectral properties of the final silica particles. This is because these substances in the solution prevent the surface of nanocrystals from deterioration by dissolution during processing. The resultant silica particles have an emission efficiency of 16% with maintaining the photoluminescent spectral width and peak wavelength of the initial colloidal solution.

Effect of visible and UV irradiation on the aggregation stability of CdTe quantum dots

International Nuclear Information System (INIS)

Tsipotan, Aleksei S.; Gerasimova, Marina A.; Aleksandrovsky, Aleksandr S.; Zharkov, Sergey M.; Slabko, Vitaliy V.

2016-01-01

The possibility of controlling the aggregation stability of CdTe quantum dots (QDs) stabilized by thioglycolic acid (TGA) is important for implementation of quasi-resonant laser-induced self-assembly. This study examines the influence of irradiation by the UV as well as by the visible light on the photostimulated aggregation of QDs. Different photochemical mechanisms are identified, depending on whether light wavelength falls into an interband transition or the first exciton transition. Irradiation by visible light does not lead to changes in the absorption spectra but decreases luminescence intensity through the detachment of TGA and the formation of dangling bonds, leading to the creation of radiativeless relaxation centers. UV irradiation (in the 300–370 nm range), at an intensity of 0.4 W/cm"2, initially (during the first 75 min) leads to the degradation of the stabilizer and QDs’ surface. After 75 min of combined UV and visible light irradiation, a gradual increase in spontaneous aggregation takes place, testifying excessive decrease in stabilizing potential barrier height. Hence, the laser-induced self-assembly of CdTe QDs is recommended to be performed over a time period of between 80 and 100 min after the beginning of low-intensity UV irradiation under conditions equivalent to those applied in this study.

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

Influence of high loading of cellulose nanocrystals in polyacrylonitrile composite films

Science.gov (United States)

Jeffrey Luo; Huibin Chang; Amir A. Bakhtiary Davijani; H. Clive Liu; Po-Hsiang Wang; Robert J. Moon; Satish Kumar

2017-01-01

Polyacrylonitrile-co-methacrylic acid (PAN-co-MAA) and cellulose nanocrystal (CNC) composite films were produced with up to 40 wt% CNC loading through the solution casting method. The rheological properties of the solution/suspensions and the structural, optical, thermal, and mechanical properties of the resulting films were investigated. The viscosity of the composite...

A pH dependence study of CdTe quantum dots fluorescence quantum yields using eclipsing thermal lens spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Estupiñán-López, C. [Laboratory of Biomedical Optics and Imaging, Federal University of Pernambuco, Recife, PE (Brazil); Dominguez, C. Tolentino [Laboratory of Biomedical Optics and Imaging, Federal University of Pernambuco, Recife, PE (Brazil); Centre for Telecommunication Studies, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro, RJ (Brazil); Filho, P.E. Cabral [Laboratory of Biomedical Optics and Imaging, Federal University of Pernambuco, Recife, PE (Brazil); Biophysics and Radiobiology Department, Federal University of Pernambuco, Recife, PE (Brazil); Santos, B.S. [Laboratory of Biomedical Optics and Imaging, Federal University of Pernambuco, Recife, PE (Brazil); Pharmaceutical Sciences Department, Federal University of Pernambuco, Recife, PE (Brazil); Fontes, A., E-mail: adriana.fontes.biofisica@gmail.com [Laboratory of Biomedical Optics and Imaging, Federal University of Pernambuco, Recife, PE (Brazil); Biophysics and Radiobiology Department, Federal University of Pernambuco, Recife, PE (Brazil); Araujo, R.E. de, E-mail: renato.earaujo@ufpe.br [Laboratory of Biomedical Optics and Imaging, Federal University of Pernambuco, Recife, PE (Brazil)

2016-06-15

In this study we evaluated the absolute fluorescence quantum yield (Φ) of hydrophilic CdTe QDs in function of different pHs, modified from the alkaline to acid, by using two different chemicals compounds, the mercaptosuccinic acid (MSA-the stabilizing agent of the QDs synthesis) or hydrochloric acid (HCl). The pH control of QDs suspensions is essential for the use of fluorescent nanoparticles in biological systems. We used the eclipsing thermal lens spectroscopy technique to determine the absolute fluorescence quantum yield values. The results showed variations on the Φ values as a function of the pH, which allowed a better understanding of QDs emission characteristics, establishing parameters for their use in biomedical applications such as optical images of biological systems, immunoassays, flow cytometry, biosensors and others.

Functionalized antibiofilm thin coatings based on PLA–PVA microspheres loaded with usnic acid natural compounds fabricated by MAPLE

Energy Technology Data Exchange (ETDEWEB)

Grumezescu, Valentina [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, PO Box MG-36, Bucharest-Magurele, Bucharest (Romania); University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, Department of Science and Engineering of Oxidic Materials and Nanomaterials, Polizu Street no 1-7, 011061 Bucharest (Romania); Socol, Gabriel [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, PO Box MG-36, Bucharest-Magurele, Bucharest (Romania); Grumezescu, Alexandru Mihai, E-mail: grumezescu@yahoo.com [University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, Department of Science and Engineering of Oxidic Materials and Nanomaterials, Polizu Street no 1-7, 011061 Bucharest (Romania); Holban, Alina Maria [Faculty of Biology, University of Bucharest, Microbiology Immunology Department, Aleea Portocalelor 1-3, Sector 5, 77206 Bucharest (Romania); Ficai, Anton [University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, Department of Science and Engineering of Oxidic Materials and Nanomaterials, Polizu Street no 1-7, 011061 Bucharest (Romania); Truşcǎ, Roxana [S.C. Metav-CD S.A., 31Rosetti Str., 020015 Bucharest (Romania); Bleotu, Coralia [Stefan S Nicolau Institute of Virology, Bucharest (Romania); Balaure, Paul Cǎtǎlin [Department of Organic Chemistry, Faculty of Applied Chemistry and Materials Science, Politehnica Universitiy of Bucharest, Polizu Street no 1-7, 011061 Bucharest (Romania); Cristescu, Rodica [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, PO Box MG-36, Bucharest-Magurele, Bucharest (Romania); Chifiriuc, Mariana Carmen [Faculty of Biology, University of Bucharest, Microbiology Immunology Department, Aleea Portocalelor 1-3, Sector 5, 77206 Bucharest (Romania)

2014-05-01

We report the fabrication of thin coatings of PLA–PVA microspheres loaded with usnic acid by matrix assisted pulsed laser evaporation (MAPLE) onto Ti substrate. The obtained coatings have been physico-chemically characterized by scanning electron microscopy (SEM) and infrared microscopy (IRM). In vitro biological assays have been performed in order to evaluate the influence of fabricated microsphere thin coatings on the Staphylococcus aureus biofilm development as well as their biocompatibility. SEM micrographs have revealed a uniform morphology of thin coatings, while IRM investigations have proved both the homogeneity and functional groups integrity of prepared thin coatings. The obtained microsphere-based thin coatings have proved to be efficient vehicles for usnic acid natural compound with antibiofilm activity, as demonstrated by the inhibitory activity on S. aureus mature biofilm development, opening new perspectives for the prevention and therapy associated to biofilm related infections.

The effects of anode material type on the optoelectronic properties of electroplated CdTe thin films and the implications for photovoltaic application

Science.gov (United States)

Echendu, O. K.; Dejene, B. F.; Dharmadasa, I. M.

2018-03-01

The effects of the type of anode material on the properties of electrodeposited CdTe thin films for photovoltaic application have been studied. Cathodic electrodeposition of two sets of CdTe thin films on glass/fluorine-doped tin oxide (FTO) was carried out in two-electrode configuration using graphite and platinum anodes. Optical absorption spectra of films grown with graphite anode displayed significant spread across the deposition potentials compared to those grown with platinum anode. Photoelectrochemical cell result shows that the CdTe grown with graphite anode became p-type after post-deposition annealing with prior CdCl2 treatment, as a result of carbon incorporation into the films, while those grown with platinum anode remained n-type after annealing. A review of recent photoluminescence characterization of some of these CdTe films reveals the persistence of a defect level at (0.97-0.99) eV below the conduction band in the bandgap of CdTe grown with graphite anode after annealing while films grown with platinum anode showed the absence of this defect level. This confirms the impact of carbon incorporation into CdTe. Solar cell made with CdTe grown with platinum anode produced better conversion efficiency compared to that made with CdTe grown using graphite anode, underlining the impact of anode type in electrodeposition.

Photoactivation by visible light of CdTe quantum dots for inline generation of reactive oxygen species in an automated multipumping flow system

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, David S.M.; Frigerio, Christian; Santos, Joao L.M. [Requimte, Department of Chemical Sciences, Laboratory of Applied Chemistry, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira no. 228, 4050-313 Porto (Portugal); Prior, Joao A.V., E-mail: joaoavp@ff.up.pt [Requimte, Department of Chemical Sciences, Laboratory of Applied Chemistry, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira no. 228, 4050-313 Porto (Portugal)

2012-07-20

Highlights: Black-Right-Pointing-Pointer CdTe quantum dots generate free radical species upon exposure to visible radiation. Black-Right-Pointing-Pointer A high power visible LED lamp was used as photoirradiation element. Black-Right-Pointing-Pointer The laboratory-made LED photocatalytic unit was implemented inline in a MPFS. Black-Right-Pointing-Pointer Free radical species oxidize luminol producing a strong chemiluminescence emission. Black-Right-Pointing-Pointer Epinephrine scavenges free radical species quenching chemiluminescence emission. - Abstract: Quantum dots (QD) are semiconductor nanocrystals able to generate free radical species upon exposure to an electromagnetic radiation, usually in the ultraviolet wavelength range. In this work, CdTe QD were used as highly reactive oxygen species (ROS) generators for the control of pharmaceutical formulations containing epinephrine. The developed approach was based on the chemiluminometric monitoring of the quenching effect of epinephrine on the oxidation of luminol by the produced ROS. Due to the relatively low energy band-gap of this chalcogenide a high power visible light emitting diode (LED) lamp was used as photoirradiation element and assembled in a laboratory-made photocatalytic unit. Owing to the very short lifetime of ROS and to ensure both reproducible generation and time-controlled reaction implementation and development, all reactional processes were implemented inline by using an automated multipumping micro-flow system. A linear working range for epinephrine concentration of up to 2.28 Multiplication-Sign 10{sup -6} mol L{sup -1} (r = 0.9953; n = 5) was verified. The determination rate was about 79 determinations per hour and the detection limit was about 8.69 Multiplication-Sign 10{sup -8} mol L{sup -1}. The results obtained in the analysis of epinephrine pharmaceutical formulations by using the proposed methodology were in good agreement with those furnished by the reference procedure, with

About the use of photoacoustic spectroscopy for the optical characterization of semiconductor thin films: CdTe

Energy Technology Data Exchange (ETDEWEB)

Marin, E.; Calderon, A. [CICATA-IPN, Av. Legaria 694, 11500 Mexico D.F. (Mexico); Vigil G, O.; Sastre, J.; Contreras P, G.; Aguilar H, J. [ESFM-IPN, 07738 Mexico D.F. (Mexico); Saucedo, E.; Ruiz, C.M. [Departamento de Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, 28049 Madrid (Spain)

2006-07-01

CdTe has been used satisfactorily in multiple and diverse technological applications such as detectors of X and gamma rays that operate at room temperature, for digital imagenology of X rays with medical and industrial applications and as active part in CdTe/CdS solar cells. In form of films, CdTe is generally grown with thicknesses ranging between 3 and 15 {mu}m, for which it is difficult to measure, by means of optical techniques, absorption coefficients greater than 10{sup 3} cm{sup -1} because nearly full absorption of light should occur below 800 nm. The exact determination of the optical absorption coefficient in detectors on the basis of CdTe is very important since this parameter determines the absorption length at which 90% of the photons with energies over the forbidden zone of the CdTe will be absorbed by this. In CdS/CdTe polycrystalline solar cells the greater efficiency of conversion have been reported for film thicknesses of 10 mm, however, the optimal value of this parameter depends strongly on the method and the variables of growth. The optical absorption coefficient spectrum can be determined by several methods, often involving several approximations and the knowledge of some minority carrier related electronic parameters that reduce their application in general way. In this work we propose to determine the absorption coefficient in CdTe thin films by photoacoustic spectroscopy (PAS), because this technique allow us to obtain the optical absorption spectra in thicker layers and therefore the study of the influence of the several growth and post-growth processes in the optical properties of this thin films. We measure by PAS the optical-absorption coefficients of CdTe thin films in the spectral region near the fundamental absorption edge ranging from 1.0 to 2.4 eV using an open cell in the transmission configuration. The films were deposited on different substrates by the CSVT-HW (hot wall) technique. In order to study the influence of several

X-ray diffraction study of epitaxial heterostructures of II-VI CdTe and ZnTe semiconductors; Etude par diffraction de rayons X d`heterostructures epitaxiees a base des semi-conducteurs II-VI CdTe et ZnTe

Energy Technology Data Exchange (ETDEWEB)

Bouchet-Boudet, N.

1996-10-07

This work deals with the structural study of II-VI semiconductor (CdTe and ZnTe) heterostructures by X-ray diffraction and reflectivity. These heterostructures have a high lattice parameter misfit and are grown by Molecular Beam Epitaxy. Two main subjects are developed: the characterization of ZnTe wires, grown by step propagation on a CdTe (001) vicinal surface, and the study of the vertical correlations in Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattices and superlattices made of ZnTe fractional layers spaced by CdTe. The growth of organised system is up to date; its aim is to realize quantum boxes (or wires) superlattices which are laterally and vertically ordered. The deformation along the growth axis induced by a ZnTe fractional layer inserted in a CdTe matrix is modelled, in the kinematical approximation, to reproduce the reflectivity measured around the substrate (004) Bragg peak. The lateral periodicity of the wires, deposited on a vicinal surface is a new and difficult subject. Some results are obtained on a vertical superlattice grown on a 1 deg. mis-cut surface. The in-plane and out-of-plane correlation lengths of a Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattice are deduced from the diffused scattered intensity measured at grazing incidence. The calculations are made within the `distorted Wave Born Approximation`. The vertical correlation in ZnTe boxes (or wines) superlattices can be measured around Bragg peaks. It is twice bigger in a superlattice grown on a 2 deg. mis-cut substrate than a nominal one. (author). 74 refs.

Bright trions in direct-bandgap silicon nanocrystals revealed bylow-temperature single-nanocrystal spectroscopy

Czech Academy of Sciences Publication Activity Database

Kůsová, Kateřina; Pelant, Ivan; Valenta, J.

2015-01-01

Roč. 4, Oct (2015), e336 ISSN 2047-7538 R&D Projects: GA ČR(CZ) GBP108/12/G108; GA ČR GPP204/12/P235 Institutional support: RVO:68378271 Keywords : silicon nanocrystals * single-nanocrystal spectroscopy * luminescing trions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 13.600, year: 2015

Development Considerations for Nanocrystal Drug Products.

Science.gov (United States)

Chen, Mei-Ling; John, Mathew; Lee, Sau L; Tyner, Katherine M

2017-05-01

Nanocrystal technology has emerged as a valuable tool for facilitating the delivery of poorly water-soluble active pharmaceutical ingredients (APIs) and enhancing API bioavailability. To date, the US Food and Drug Administration (FDA) has received over 80 applications for drug products containing nanocrystals. These products can be delivered by different routes of administration and are used in a variety of therapeutic areas. To aid in identifying key developmental considerations for these products, a retrospective analysis was performed on the submissions received by the FDA to date. Over 60% of the submissions were for the oral route of administration. Based on the Biopharmaceutics Classification System (BCS), most nanocrystal drugs submitted to the FDA are class II compounds that possess low aqueous solubility and high intestinal permeability. Impact of food on drug bioavailability was reduced for most nanocrystal formulations as compared with their micronized counterparts. For all routes of administration, dose proportionality was observed for some, but not all, nanocrystal products. Particular emphasis in the development of nanocrystal products was placed on the in-process tests and controls at critical manufacturing steps (such as milling process), mitigation and control of process-related impurities, and the stability of APIs or polymorphic form (s) during manufacturing and upon storage. This emphasis resulted in identifying challenges to the development of these products including accurate determination of particle size (distribution) of drug substance and/or nanocrystal colloidal dispersion, identification of polymorphic form (s), and establishment of drug substance/product specifications.

Atmospheric Pressure Chemical Vapor Deposition of CdTe for High-Efficiency Thin-Film PV Devices; Annual Report, 26 January 1998-25 January 1999

Energy Technology Data Exchange (ETDEWEB)

Meyers, P. V. [ITN Energy Systems, Wheat Ridge, Colorado (US); Kee, R.; Wolden, C.; Raja, L.; Kaydanov, V.; Ohno, T.; Collins, R.; Aire, M.; Kestner, J. [Colorado School of Mines, Golden, Colorado (US); Fahrenbruch, A. [ALF, Inc., Stanford, California (US)

1999-09-30

ITN's 3-year project, titled ''Atmospheric Pressure Chemical Vapor Deposition (APCVD) of CdTe for High-Efficiency Thin-Film Photovoltaic (PV) Devices,'' has the overall objectives of improving thin-film CdTe PV manufacturing technology and increasing CdTe PV device power conversion efficiency. CdTe deposition by APCVD employs the same reaction chemistry as has been used to deposit 16%-efficient CdTe PV films, i.e., close-spaced sublimation, but employs forced convection rather than diffusion as a mechanism of mass transport. Tasks of the APCVD program center on demonstrating APCVD of CdTe films, discovering fundamental mass-transport parameters, applying established engineering principles to the deposition of CdTe films, and verifying reactor design principles that could be used to design high-throughput, high-yield manufacturing equipment. Additional tasks relate to improved device measurement and characterization procedures that can lead to a more fundamental understanding of CdTe PV device operation, and ultimately, to higher device conversion efficiency and greater stability. Specifically, under the APCVD program, device analysis goes beyond conventional one-dimensional device characterization and analysis toward two-dimension measurements and modeling. Accomplishments of the first year of the APCVD subcontract include: selection of the Stagnant Flow Reactor design concept for the APCVD reactor, development of a detailed reactor design, performance of detailed numerical calculations simulating reactor performance, fabrication and installation of an APCVD reactor, performance of dry runs to verify reactor performance, performance of one-dimensional modeling of CdTe PV device performance, and development of a detailed plan for quantification of grain-boundary effects in polycrystalline CdTe devices.

Facile synthesis of uniform large-sized InP nanocrystal quantum dots using tris(tert-butyldimethylsilyl)phosphine

Science.gov (United States)

2012-01-01

Colloidal III-V semiconductor nanocrystal quantum dots [NQDs] have attracted interest because they have reduced toxicity compared with II-VI compounds. However, the study and application of III-V semiconductor nanocrystals are limited by difficulties in their synthesis. In particular, it is difficult to control nucleation because the molecular bonds in III-V semiconductors are highly covalent. A synthetic approach of InP NQDs was presented using newly synthesized organometallic phosphorus [P] precursors with different functional moieties while preserving the P-Si bond. Introducing bulky side chains in our study improved the stability while facilitating InP formation with strong confinement at a readily low temperature regime (210°C to 300°C). Further shell coating with ZnS resulted in highly luminescent core-shell materials. The design and synthesis of P precursors for high-quality InP NQDs were conducted for the first time, and we were able to control the nucleation by varying the reactivity of P precursors, therefore achieving uniform large-sized InP NQDs. This opens the way for the large-scale production of high-quality Cd-free nanocrystal quantum dots. PMID:22289352