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Sample records for high photoluminescence quantum

  1. Highly Photoluminescent and Stable Aqueous ZnS Quantum Dots

    Science.gov (United States)

    Li, Hui; Shih, Wan Y.; Shih, Wei-Heng

    2009-01-01

    We report an all-aqueous synthesis of highly photoluminescent and stable ZnS quantum dots (QDs) with water as the medium, i.e. first synthesizing ZnS QDs with 3-mercaptopropionic acid (MPA) as the capping molecule, followed by replacing some of MPA with (3-mercaptopropyl) trimethoxysilane (MPS). The resultant MPS-replaced ZnS QDs were about 5 nm in size with a cubic zinc blende crystalline structure, and had both MPA and MPS on the surface as confirmed by the Fourier Transform Infrared (FTIR) spectroscopy. They exhibited blue trap-state emissions around 415 nm and a quantum yield (QY) of 75% with Rhodamine 101 as the reference, and remained stable for more than 60 days under the ambient conditions. Through the capping molecule replacement procedure, the MPS-replaced ZnS QDs avoided the shortcomings of both the MPA-ZnS QDs and the MPS-ZnS QDs, and acquired the advantages of strong photoluminescence and good stability, which are important to the QDs’ applications especially for bioimaging. PMID:21954321

  2. Highly Luminescent Carbon-​Nanoparticle-​Based Materials: Factors Influencing Photoluminescence Quantum Yield

    NARCIS (Netherlands)

    Qu, S.; Shen, D.; Liu, X.; Jing, P.; Zhang, L.; Ji, W.; Zhao, H.; Fan, X.; Zhang, H.

    2014-01-01

    Unravelling the factors influencing photoluminescence (PL) quantum yield of the carbon nanoparticles (CNPs) is the prerequisite for prepg. highly luminescent CNP-​based materials. In this work, an easy and effective method is reported for prepg. highly luminescent CNP-​based materials. Water-​sol.

  3. High-resolution photoluminescence studies of single semiconductor quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Østergaard, John Erland; Jensen, Jacob Riis

    2000-01-01

    Semiconductor quantum dots, especially those formed by self-organized growth, are considered a promising material system for future optical devices [1] and the optical properties of quantum dot ensembles have been investigated in detail over the past years. Recently, considerable interest has dev...

  4. Graphene quantum dots: Highly active bifunctional nanoprobes for nonenzymatic photoluminescence detection of hydroquinone.

    Science.gov (United States)

    He, Yuezhen; Sun, Jian; Feng, Dexiang; Chen, Hongqi; Gao, Feng; Wang, Lun

    2015-12-15

    In this paper, a simple and sensitive photoluminescence method is developed for the hydroquinone quantitation by using graphene quantum dots which simultaneously serve as a peroxidase-mimicking catalyst and a photoluminescence indicator. In the presence of dissolved oxygen, graphene quantum dots with intrinsic peroxidase-mimicking catalytic activity can catalyze the oxidation of hydroquinone to produce p-benzoquinone, an intermediate, which can efficiently quench graphene quantum dots' photoluminescence. Based on this effect, a novel fluorescent platform is proposed for the sensing of hydroquinone, and the detection limit of 5 nM is found. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Photoluminescence under high-electric field of PbS quantum dots

    Directory of Open Access Journals (Sweden)

    B. Ullrich

    2012-12-01

    Full Text Available The effect of a laterally applied electric field (≤10 kV/cm on the photoluminescence of colloidal PbS quantum dots (diameter of 2.7 nm on glass was studied. The field provoked a blueshift of the emission peak, a reduction of the luminescent intensity, and caused an increase in the full width at half maximum of the emission spectrum. Upon comparison with the photoluminescence of p-type GaAs exhibits the uniqueness of quantum dot based electric emission control with respect to bulk materials.

  6. Origin of high photoluminescence efficiencies in CdSe quantum belts.

    Science.gov (United States)

    Liu, Yi-Hsin; Wayman, Virginia L; Gibbons, Patrick C; Loomis, Richard A; Buhro, William E

    2010-01-01

    CdSe quantum belts (QBs) having lengths of 0.5-1.5 microm and thicknesses of 1.5-2.0 nm exhibit high photoluminescence (PL) efficiencies of approximately 30%. Epifluorescence studies establish the PL spectra to be uniform along single QBs, and nearly the same from QB to QB. Photogenerated excitons are shown to be effectively delocalized over the entire QBs by position-selective excitation. Decoration of the QBs with gold nanoparticles indicates a low density of surface-trap sites, located primarily on the thin belt edges. The high PL efficiencies and effective exciton delocalization are attributed to the minimization of defective {1100} edge surface area or edge-top/bottom (face) line junctions in QBs relative to quantum wires having roughly isotropic cross sections, for which very low PL quantum efficiencies have been reported. The results suggest that trap sites can be minimized in pseudo-one-dimensional nanocrystals, such that the facile transport of energy and charge along their long axes becomes possible.

  7. Highly Luminescent Phase-Stable CsPbI3 Perovskite Quantum Dots Achieving Near 100% Absolute Photoluminescence Quantum Yield.

    Science.gov (United States)

    Liu, Feng; Zhang, Yaohong; Ding, Chao; Kobayashi, Syuusuke; Izuishi, Takuya; Nakazawa, Naoki; Toyoda, Taro; Ohta, Tsuyoshi; Hayase, Shuzi; Minemoto, Takashi; Yoshino, Kenji; Dai, Songyuan; Shen, Qing

    2017-10-24

    Perovskite quantum dots (QDs) as a new type of colloidal nanocrystals have gained significant attention for both fundamental research and commercial applications owing to their appealing optoelectronic properties and excellent chemical processability. For their wide range of potential applications, synthesizing colloidal QDs with high crystal quality is of crucial importance. However, like most common QD systems such as CdSe and PbS, those reported perovskite QDs still suffer from a certain density of trapping defects, giving rise to detrimental nonradiative recombination centers and thus quenching luminescence. In this paper, we show that a high room-temperature photoluminescence quantum yield of up to 100% can be obtained in CsPbI3 perovskite QDs, signifying the achievement of almost complete elimination of the trapping defects. This is realized with our improved synthetic protocol that involves introducing organolead compound trioctylphosphine-PbI2 (TOP-PbI2) as the reactive precursor, which also leads to a significantly improved stability for the resulting CsPbI3 QD solutions. Ultrafast kinetic analysis with time-resolved transient absorption spectroscopy evidence the negligible electron or hole-trapping pathways in our QDs, which explains such a high quantum efficiency. We expect the successful synthesis of the "ideal" perovskite QDs will exert profound influence on their applications to both QD-based light-harvesting and -emitting devices.

  8. Efficient Synthesis of Highly Photoluminescent Short Dendritic CdSeS/ZnS Quantum Dots for Biolabeling.

    Science.gov (United States)

    Kong, Peng; Zhou, Guangjun; Zhou, Haifeng; Zhou, Juan; Zhang, Xingshuang; Yu, Zhichao

    2016-03-01

    A convenient and efficient approach is reported to synthesize CdSeS with low-cost and low-toxic materials. The influence of the Se/S ratio and reaction time on the photoluminescent properties of CdSeS QDs is investigated through researching the temporal evolution of the absorption and the emission. Following, the high photoluminescent short dendritic green-emitting CdSeS/ZnS QDs are prepared using the method inspired by the successive ion layer adsorption and reaction procedure, which are composed of a CdSeS core and ZnS branches. Transmission electronic microscopy and X-ray diffraction show that the CdSeS/ZnS QDs is in a cubic zinc blende structure. The photoluminescence intensity increase significantly when the ZnS branches form as a result of the charge carriers being confined in the core. The photoluminescence quantum yield of the obtained CdSeS/ZnS core-shell QDs can be up to 90%, which is much higher than that of initial CdSeS QDs (39%). In addition, CdSeS/ZnS QDs have good photoluminescence intensity after they are transferred from organic solvent into aqueous media through ligand replacement using mercaptoacetic acid. Afterwards, the E. Coli O-157 are not only successfully conjugated with CdSeS/ZnS QDs but also present clear images under UV irradiation.

  9. Photoluminescence properties of highly dispersed ZnO quantum dots in polyvinylpyrrolidone nanotubes prepared by a single capillary electrospinning.

    Science.gov (United States)

    Li, X H; Shao, C L; Liu, Y C; Chu, X Y; Wang, C H; Zhang, B X

    2008-09-21

    Highly dispersed ZnO quantum dots (QDs) in polyvinylpyrrolidone (PVP) nanotubes have been prepared by a single capillary electrospinning. The structure and optical properties characterizations were performed by x-ray diffraction, scanning and transmission electron microscopy, absorption, photoluminescence, and resonant Raman spectra. In the composites, PVP molecules passivate the surface defects of ZnO QDs and prevent the aggregations of ZnO QDs. As a result, the composites exhibit narrower band edge emissions and less laser thermal effects. Blueshifted band gap, enlarged exciton energy, and less exciton-longitudinal optical (LO) phonon interaction due to the quantum confinement effect have also been observed.

  10. High Photoluminescence Quantum Yields in Organic Semiconductor-Perovskite Composite Thin Films.

    Science.gov (United States)

    Longo, Giulia; La-Placa, Maria-Grazia; Sessolo, Michele; Bolink, Henk J

    2017-10-09

    One of the obstacles towards efficient radiative recombination in hybrid perovskites is a low exciton binding energy, typically in the orders of tens of meV. It has been shown that the use of electron-donor additives can lead to a substantial reduction of the non-radiative recombination in perovskite films. Herein, the approach using small molecules with semiconducting properties, which are candidates to be implemented in future optoelectronic devices, is presented. In particular, highly luminescent perovskite-organic semiconductor composite thin films have been developed, which can be processed from solution in a simple coating step. By tuning the relative concentration of methylammonium lead bromide (MAPbBr3 ) and 9,9spirobifluoren-2-yl-diphenyl-phosphine oxide (SPPO1), it is possible to achieve photoluminescent quantum yields (PLQYs) as high as 85 %. This is attributed to the dual functions of SPPO1 that limit the grain growth while passivating the perovskite surface. The electroluminescence of these materials was investigated by fabricating multilayer LEDs, where charge injection and transport was found to be severely hindered for the perovskite/SPPO1 material. This was alleviated by partially substituting SPPO1 with a hole-transporting material, 1,3-bis(N-carbazolyl)benzene (mCP), leading to bright electroluminescence. The potential of combining perovskite and organic semiconductors to prepare materials with improved properties opens new avenues for the preparation of simple lightemitting devices using perovskites as the emitter. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. High Photoluminescence Quantum Yield in Band Gap Tunable Bromide Containing Mixed Halide Perovskites

    OpenAIRE

    Carolin M. Sutter-Fella Yanbo Li Matin Amani Joel W. Ager III Francesca M. Toma; Eli Yablonovitch Ian D. Sharp and Ali Javey

    2016-01-01

    Hybrid organic–inorganic halide perovskite based semiconductor materials are attractive for use in a wide range of optoelectronic devices because they combine the advantages of suitable optoelectronic attributes and simultaneously low cost solution processability. Here we present a two step low pressure vapor assisted solution process to grow high quality homogeneous CH3NH3PbI3–xBrx perovskite films over the full band gap range of 1.6–2.3 eV. Photoluminescence light in versus light out charac...

  12. Freestanding carbon nanodots/poly (vinyl alcohol) films with high photoluminescent quantum yield realized by inverted-pyramid structure

    Science.gov (United States)

    Pang, Linna; Ba, Lixiang; Pan, Wei; Shen, Wenzhong

    2017-02-01

    Carbon nanodots (C-dots) have attracted great attention for their biocompatibility and strong tunable photoluminescence (PL). However, aggregation-induced PL quenching blocks their practical application in solid-state optoelectronics. Here, we report a luminescent C-dots freestanding film with a substantially enhanced high quantum yield (QY) of 72.3%. A facile template method, rather than complicate lithography and etching technique is proposed to fabricate the C-dots composite films with large-area (8 inch × 8 inch) ordered micro-scale inverted-pyramid patterns on the surface. The control experiment and theoretical analysis demonstrate the key success to QY enhancement lies in the separation of C-dots and the pattern of surface inverted-pyramid structure. This work realizes the QY enhancement simply by geometrical optics, not the chemical treatment of luminescent particles. It provides a general approach to fabricate large-area freestanding luminescent composite film with high QY.

  13. Highly enhanced photoluminescence of AgInS2/ZnS quantum dots by hot-injection method

    Science.gov (United States)

    Liao, Shenghua; Huang, Yu; Zhang, Ying; Shan, Xiaohui; Yan, Zhengyu; Shen, Weiyang

    2015-01-01

    Highly photoluminescent and air-stable AgInS2 quantum dots (AIS QDs) were synthesized by a hot-injection route in N2 atmosphere and dark environment. The as-synthesized AIS QDs were further capped with ZnS shell by one-pot method in order to enhance the photoluminescence (PL) intensity. The photo-electronic property and the morphology of AIS QDs and AIS/ZnS QDs were characterized by ultraviolet-visible spectroscopy (UV), PL spectroscopy and transmission electronic microscopy (TEM). The results indicated that the narrow and symmetrical PL spectra of AIS QDs was time-dependent, and the emission wavelength of AIS QDs could be tunable within 436-610 nm by altering the initial Ag/In ratios. After being capped with ZnS shell, the AIS QDs showed excellent optical characteristics, including PL QYs up to 15%. The TEM results indicated that the spherical AIS/ZnS QDs were nearly monodispersed and homogeneous with an average particle size of 8 nm. The heavy metal free and high luminous AIS/ZnS QDs have great potential in biological application.

  14. Photoluminescence studies of single InGaAs quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1999-01-01

    Semiconductor quantum dots are considered a promising material system for future optical devices and quantum computers. We have studied the low-temperature photoluminescence properties of single InGaAs quantum dots embedded in GaAs. The high spatial resolution required for resolving single dots...... is obtained by exciting and detecting the photoluminescence through a microscope objective which is located inside the cryostat. Furthermore, e-beam lithography and mesa etching have been used to reduce the size of the detection area to a few hundred nanometers in diameter. These techniques allow us...

  15. Electrostatic Stabilized InP Colloidal Quantum Dots with High Photoluminescence Efficiency.

    Science.gov (United States)

    Mnoyan, Anush N; Kirakosyan, Artavazd Gh; Kim, Hyunki; Jang, Ho Seong; Jeon, Duk Young

    2015-06-30

    Electrostatically stabilized InP quantum dots (QDs) showing a high luminescence yield of 16% without any long alkyl chain coordinating ligands on their surface are demonstrated. This is achieved by UV-etching the QDs in the presence of fluoric and sulfuric acids. Fluoric acid plays a critical role in selectively etching nonradiative sites during the ligand-exchange process and in relieving the acidity of the solution to prevent destruction of the QDs. Given that the InP QDs show high luminescence without any electrical barriers, such as long alkyl ligands or inorganic shells, this method can be applied for QD treatment for application to highly efficient QD-based optoelectronic devices.

  16. Highly photoluminescent amino-functionalized graphene quantum dots used for sensing copper ions.

    Science.gov (United States)

    Sun, Hanjun; Gao, Nan; Wu, Li; Ren, Jinsong; Wei, Weili; Qu, Xiaogang

    2013-09-27

    Herein, we report a new kind of highly fluorescent probe for Cu(2+) sensing generated by hydrothermal treatment of graphene quantum dots (GQDs). After hydrothermal treatment in ammonia, the greenish-yellow fluorescent GQDs (gGQDs) with a low quantum yield (QY, 2.5%) are converted to amino-functionalized GQDs (afGQDs) with a high QY (16.4%). Due to the fact that Cu(2+) ions have a higher binding affinity and faster chelating kinetics with N and O on the surface of afGQDs than other transition-metal ions, the selectivity of afGQDs for Cu(2+) is much higher than that of gGQDs. Furthermore, afGQDs are biocompatible and eco-friendly, and the afGQDs with a positive charge can be easily taken up by cells, which makes it possible to sense Cu(2+) in living cells. The strategy presented here is simple in design, economical, and offers a "mix-and-detect" protocol without dye-modified oligonucleotides or complex chemical modification. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Infrared photoluminescence of high In-content InN/InGaN multiple-quantum-wells

    Energy Technology Data Exchange (ETDEWEB)

    Valdueza-Felip, Sirona; Naranjo, Fernando B.; Gonzalez-Herraez, Miguel [Electronics Department, University of Alcala, Alcala de Henares (Spain); Rigutti, Lorenzo; Julien, Francois H. [Institut d' Electronique Fondamentale, University of Paris Sud XI, UMR 8622 CNRS, Orsay (France); Lacroix, Bertrand; Ruterana, Pierre [Centre de Recherche sur les Ions les Materiaux et la Photonique (CIMAP), UMR 6252, CNRS, ENSICAEN, CEA, UCBN, Caen (France); Fernandez, Susana [Departamento de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Madrid (Spain); Monroy, Eva [CEA Grenoble, INAC/SP2M, Grenoble (France)

    2012-01-15

    We report on the thermal evolution of the photoluminescence (PL) from high In-content InN/In{sub 0.9}Ga{sub 0.1}N multiple-quantum wells (MQWs) synthesized by plasma-assisted molecular-beam epitaxy on GaN-on-sapphire templates. The structural quality and the well/barrier thickness uniformity in the MQW structure are assessed by X-ray diffraction and transmission electron microscopy measurements. PL results are compared with the luminescence from a 1-{mu}m-thick InN reference sample. In both cases, the dominant low-temperature (5 K) PL emission peaks at {proportional_to}0.73 eV with a full width at half maximum of {proportional_to}86 meV. The InN layer displays an S-shape evolution of the emission peak energy with temperaure, explained in terms of carrier localization. A carrier localization energy of {proportional_to}12 meV is estimated for the InN layer, in good agreement with the expected carrier concentration. In the case of the MQW structure, an enhancement of the carrier localization associated to the piezoelectric field results in an improved thermal stability of the PL intensity, reaching an internal quantum efficiency of {proportional_to}16%. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Synthesis of highly luminescent water stable ZnO quantum dots as photoluminescent sensor for picric acid

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Kulvinder; Chaudhary, G.R.; Singh, Sukhjinder; Mehta, S.K., E-mail: skmehta@pu.ac.in

    2014-10-15

    Highly luminescent, water stable (3-aminopropyl) triethoxysilane capped ZnO quantum dots (QDs) have been synthesized using a simple solution route. The synthesized ZnO QDs have been characterized using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Particle size analyzer (PSA), UV–visible (UV–vis), Photoluminescence (PL) and Fourier transform infrared (FTIR) spectroscopy. The PL studies demonstrate that the particles synthesized are highly luminescent in nature emitting yellow color on exposure to UV radiation. Further, PL emission of ZnO QDs in the presence of picric acid (PA) shows their high sensitivity and selectivity for PA. The superior response of ZnO QDs in the presence of PA makes them very effective PL sensors. The limit of detection comes out to be 2.86 µM. - Highlights: • ZnO QDs act as photoluminiscent sensor for picric acid in aqueous medium. • Sensor shows high selectivity and sensitivity with a detection limit of 2.86 μM. • More the number of nitro groups, more is the quenching in PL emission of ZnO QDs.

  19. Highly photoluminescent MoO{sub x} quantum dots: Facile synthesis and application in off-on Pi sensing in lake water samples

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Sai Jin [Jiangxi Key Laboratory of Mass Spectrometry and Instrumentation, East China University of Technology (ECUT), Nanchang 330013 (China); School of Chemistry, Biology and Material Science, ECUT, Nanchang 330013 (China); Zhao, Xiao Jing; Zuo, Jun [School of Chemistry, Biology and Material Science, ECUT, Nanchang 330013 (China); Huang, Hai Qing [State Key Laboratory Breeding Base of Nuclear Resources and Environment, ECUT, Nanchang 330013 (China); Zhang, Li, E-mail: zhangli8@ncu.edu.cn [College of Chemistry, Nanchang University, Nanchang 330031 (China)

    2016-02-04

    Molybdenum oxide (MoO{sub x}) is a well-studied transition-metal semiconductor material, and has a wider band gap than MoS{sub 2} which makes it become a promising versatile probe in a variety of fields, such as gas sensor, catalysis, energy storage ect. However, few MoO{sub x} nanomaterials possessing photoluminescence have been reported until now, not to mention the application as photoluminescent probes. Herein, a one-pot method is developed for facile synthesis of highly photoluminescent MoO{sub x} quantum dots (MoO{sub x} QDs) in which commercial molybdenum disulfide powder and hydrogen peroxide (H{sub 2}O{sub 2}) are involved as the precursor and oxidant, respectively. Compared with current synthesis methods, the proposed one has the advantages of rapid, one-pot, easily prepared, environment friendly as well as strong photoluminescence. The obtained MoO{sub x} QDs is further utilized as an efficient photoluminescent probe, and a new off-on sensor has been constructed for phosphate (Pi) determination in complicated lake water samples, attributed to the fact that the binding affinity of Eu{sup 3+} ions to the oxygen atoms from Pi is much higher than that from the surface of MoO{sub x} QDs. Under the optimal conditions, a good linear relationship was found between the enhanced photoluminescence intensity and Pi concentration in the range of 0.1–160.0 μM with the detection limit of 56 nM (3σ/k). The first application of the photoluminescent MoO{sub x} nanomaterials for ion photochemical sensing will open the gate of employing MoO{sub x} nanomaterials as versatile probes in a variety of fields, such as chemi-/bio-sensor, cell imaging, biomedical and so on. - Highlights: • Though increasing effort has been devoted to MoO{sub x} nanomaterials synthesis, only a few reports mentioning its photoluminescence property are available, while even no evidence has shown its applications in chemical and biological sensing. • Herein, a one-pot method possessing the

  20. Using quantum dot photoluminescence for load detection

    Directory of Open Access Journals (Sweden)

    M. Moebius

    2016-08-01

    Full Text Available We propose a novel concept for an integrable and flexible sensor capable to visualize mechanical impacts on lightweight structures by quenching the photoluminescence (PL of CdSe quantum dots. Considering the requirements such as visibility, storage time and high optical contrast of PL quenching with low power consumption, we have investigated a symmetrical and an asymmetrical layer stack consisting of semiconductor organic N,N,N′,N′-Tetrakis(3-methylphenyl-3,3′-dimethylbenzidine (HMTPD and CdSe quantum dots with elongated CdS shell. Time-resolved series of PL spectra from layer stacks with applied voltages of different polarity and simultaneous observation of power consumption have shown that a variety of mechanisms such as photo-induced charge separation and charge injection, cause PL quenching. However, mechanisms such as screening of external field as well as Auger-assisted charge ejection is working contrary to that. Investigations regarding the influence of illumination revealed that the positive biased asymmetrical layer stack is the preferred sensor configuration, due to a charge carrier injection at voltages of 10 V without the need of coincident illumination.

  1. High-temperature photoluminescence and photoluminescence excitation spectroscopy of Al0.60Ga0.40N/Al0.70Ga0.30N multiple quantum wells

    Science.gov (United States)

    Murotani, Hideaki; Nakamura, Katsuto; Fukuno, Tomonori; Miyake, Hideto; Hiramatsu, Kazumasa; Yamada, Yoichi

    2017-02-01

    The excitonic optical properties of an Al0.60Ga0.40N/Al0.70Ga0.30N multiple quantum well (MQW) structure were studied using photoluminescence (PL) and PL excitation (PLE) spectroscopy at high temperatures. Clear excitonic PL was observed at temperatures up to 750 K. Biexciton luminescence was clearly observed even at this high temperature. These observations unambiguously demonstrated the extremely high thermal stability of biexcitons in this MQW. Furthermore, additional PL peaks were observed on the low-energy side of the biexciton luminescence. The observation of biexciton two-photon resonance in the PLE spectra of these peaks indicates that these peaks can be explained by processes involving inelastic scattering of excitons and biexcitons.

  2. Solvothermal tuning of photoluminescent graphene quantum dots: from preparation to photoluminescence mechanism

    Science.gov (United States)

    Qi, Bao-Ping; Zhang, Xiaoru; Shang, Bing-Bing; Xiang, Dongshan; Zhang, Shenghui

    2018-02-01

    Solvothermal synthesis was employed to tune the surface states of graphene quantum dots (GQDs). Two series of GQDs with the particle sizes from 2.6 to 4.5 nm were prepared as follows: (I) GQDs with the same size but different oxygen degrees; (II) GQDs with different core sizes but the similar surface chemistry. Both the large sizes and the high surface oxidation degrees led to the redshift photoluminescence (PL) of GQDs. Electrochemiluminescence (ECL) spectra from two series of GQDs were all in accordance with their PL spectra, respectively, which provided good evidence for the conjugated structures in GQDs responsible for PL. [Figure not available: see fulltext.

  3. Effect of boron incorporation on the structural and photoluminescence properties of highly-strained InxGa1-xAs/GaAs multiple quantum wells

    Directory of Open Access Journals (Sweden)

    Qi Wang

    2013-07-01

    Full Text Available In this research, 5-period highly-strained BInGaAs/GaAs multiple quantum wells (MQWs have been successfully grown at 480-510ºC by LP-MOCVD. Room-temperature photoluminescence (RT-PL measurements of BInGaAs/GaAs MQWs showed the peak wavelength as long as 1.17 μm with full-width at half maximum (FWHM of only 29.5 meV. In addition, a slight blue-shift (∼18 meV of PL peak energy of InxGa1-xAs/GaAs MQWs was observed after boron incorporation. It has been found boron incorporation ( 40%, the positive effect of boron incorporation prevailed, i.e., boron incorporation completely suppressed the thickness undulation and lead to the improvement of PL properties.

  4. Solid state photoluminescence thermoplastic starch film containing graphene quantum dots.

    Science.gov (United States)

    Javanbakht, Siamak; Namazi, Hassan

    2017-11-15

    Fluorescent polymer films, a matrix of thermoplastic starch (TPS) based bio-polymer and graphene quantum dots (GQDs) were fabricated by a casting method. The GQDs provide solid state fluorescent properties to the prepared thermoplastic starch graphene quantum dots (TPS/GQD). The fluorescent, thermal, mechanical and optical properties of TPS/GQD were investigated. High optical transparency (88-91%) and well dispersion of GQDs (1-17wt%) in the polymeric matrix of TPS/GQD nanocomposite was observed. The maximum photoluminescence intensity of materials has been obtained at 50wt% of GQD content. These materials have great potential to use in flexible electronic displays, light emitting diodes (LED), GQD-LED packaging and other optoelectronics applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Near-unity photoluminescence quantum yield in MoS₂.

    Science.gov (United States)

    Amani, Matin; Lien, Der-Hsien; Kiriya, Daisuke; Xiao, Jun; Azcatl, Angelica; Noh, Jiyoung; Madhvapathy, Surabhi R; Addou, Rafik; KC, Santosh; Dubey, Madan; Cho, Kyeongjae; Wallace, Robert M; Lee, Si-Chen; He, Jr-Hau; Ager, Joel W; Zhang, Xiang; Yablonovitch, Eli; Javey, Ali

    2015-11-27

    Two-dimensional (2D) transition metal dichalcogenides have emerged as a promising material system for optoelectronic applications, but their primary figure of merit, the room-temperature photoluminescence quantum yield (QY), is extremely low. The prototypical 2D material molybdenum disulfide (MoS2) is reported to have a maximum QY of 0.6%, which indicates a considerable defect density. Here we report on an air-stable, solution-based chemical treatment by an organic superacid, which uniformly enhances the photoluminescence and minority carrier lifetime of MoS2 monolayers by more than two orders of magnitude. The treatment eliminates defect-mediated nonradiative recombination, thus resulting in a final QY of more than 95%, with a longest-observed lifetime of 10.8 ± 0.6 nanoseconds. Our ability to obtain optoelectronic monolayers with near-perfect properties opens the door for the development of highly efficient light-emitting diodes, lasers, and solar cells based on 2D materials. Copyright © 2015, American Association for the Advancement of Science.

  6. Effect of defects on quantum yield in blue emitting photoluminescent nitrogen doped graphene quantum dots

    Science.gov (United States)

    Kharangarh, Poonam R.; Umapathy, Siva; Singh, Gurmeet

    2017-10-01

    This paper presents a comprehensive study of the impact of defects on quantum yield in Nitrogen doped graphene quantum dots (N-GQDs). The facile and high yielding hydrothermal method was used to process the N-GQDs by selecting two different nitrogen containing powders, that is, NH4Cl (sample-I) and (NH4)2SO4(sample-II). Initially, the synthesized samples were characterized by using High Resolution Transmission Electron Microscope (HRTEM), Powdered X-Ray Diffraction, Raman Spectroscopy, and UV-Visible spectroscopy, Fourier Transform Infrared Spectroscopy, and Photoluminescence (PL) for sample integrity. HRTEM images suggest that the majority of the both sample types were in the narrow range of 5-20 nm in diameter. The samples show blue photoluminescence and excitation dependent PL emission characteristics. As expected, by using the different excitation energy in PL, appearance of peak introduces additional energy levels between π and π* that provide alternative electron transition pathways. The most remarkable finding is that the fluorescence quantum yield is up to 28% for sample-I and is 49.8% for sample-II, which is higher than that of reported GQDs (less than 25%). This clearly suggests that the defect states related to Nitrogen, Chlorine, and Sulfur that alter the band gap of the GQDs determine the PL characteristics and the quantum yield.

  7. Red shift in the photoluminescence of colloidal carbon quantum dots induced by photon reabsorption

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wenxia; Dai, Dejian; Chen, Xifang; Guo, Xiaoxiao; Fan, Jiyang, E-mail: jyfan@seu.edu.cn [Department of Physics, Southeast University, Nanjing 211189 (China)

    2014-03-03

    We synthesize the colloidal carbon/graphene quantum dots 1–9 nm in diameter and study their photoluminescence properties. Surprisingly, the luminescence properties of a fixed collection of colloidal carbon quantum dots can be systematically changed as the concentration varies. A model based on photon reabsorption is proposed which explains well the experiment. Infrared spectral study indicates that the surfaces of the carbon quantum dots are substantially terminated by oxygen atoms, which causes their ultra-high hydrophilicity. Our result clarifies the mystery of distinct emission colors in carbon quantum dots and indicates that photon reabsorption can strongly affect the luminescence properties of colloidal nanocrystals.

  8. Tuning the photoluminescence of graphene quantum dots by co-doping of nitrogen and sulfur

    Science.gov (United States)

    Luo, Yi; Li, Ming; Sun, Lang; Xu, Yongjie; Hu, Guanghui; Tang, Tao; Wen, Jianfeng; Li, Xinyu

    2017-11-01

    Nitrogen and sulfur co-doped graphene quantum dots (NS-GQDs) were successfully synthesized using a facile, inexpensive, and environmentally friendly hydrothermal reaction of aqueous ammonia, S powder, and graphene quantum dots. The NS-GQDs with oxygen-rich functional groups have a high quantum yield of 41% and a diameter of 1-5 nm. The photoluminescence (PL) properties of the nitrogen-doped graphene quantum dots (N-GQDs) and NS-GQD were investigated. The results showed that the PL emission of the NS-GQD exhibits a clear blue shift of 54 nm compared to that of the N-GQDs.

  9. Photoluminescence spectroscopy of CdSe/CdS(/ZnS) quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Menke, Torben; Chilla, Gerwin; Kipp, Tobias; Heitmann, Detlef [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany); Nikolic, Marija [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade (RS); Froemsdorf, Andreas; Weller, Horst; Foerster, Sephan [Institut fuer Physikalische Chemie, Universitaet Hamburg, Grindelallee 117, 20146 Hamburg (Germany)

    2007-07-01

    We investigate chemically synthesized nanocrystal quantum dots by photoluminescence (PL) spectroscopy. Our CdSe-core nanocrystals, fabricated as core-shell and core-shell-shell variants, are embedded in a thin polymer matrix on silicon substrates or spin coated directly on sapphire substrates. The nanocrystal density on the substrate is chosen to be so low, that both, ensemble and single nanocrystal PL experiments are possible. In our ensemble measurements, we have in particular studied the photostability of the photoluminescence signal for temperatures T=4-300 K and for different excitation densities. We found the expected red-shift of the photoluminescence with increasing temperature and indication for a high stability of the photon efficiency. In microscopic photoluminescence measurements on single nanocrystals we found crystals with an impressive stability concerning photobleaching. The blinking behavior shows that these nanocrystals are predominantly in the on-state.

  10. Polarization of the photoluminescence of quantum dots incorporated into quantum wires

    Energy Technology Data Exchange (ETDEWEB)

    Platonov, A. V., E-mail: alexei.platonov@mail.ioffe.ru; Kochereshko, V. P.; Kats, V. N.; Cirlin, G. E.; Bouravleuv, A. D.; Avdoshina, D. V. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Delga, A.; Besombes, L.; Mariette, H. [CEA, INAC, SP2M, and Institut Néel, CEA-CNRS group “Nanophysique et Semiconducteurs” (France)

    2016-12-15

    The photoluminescence spectra of individual quantum dots incorporated into a quantum wire are studied. From the behavior of the spectra in a magnetic field, it is possible to estimate the exciton binding energy in a quantum dot incorporated into a quantum wire. It is found that the exciton photoluminescence signal emitted from a quantum dot along the direction of the nanowire axis is linearly polarized. At the same time, the photoluminescence signal propagating in the direction orthogonal to the nanowire axis is practically unpolarized. The experimentally observed effect is attributed to the nonaxial arrangement of the dot in the wire under conditions of a huge increase in the exciton binding energy due to the effect of the image potential on the exciton.

  11. Synthesis of AgInS2 quantum dots with tunable photoluminescence for sensitized solar cells

    Science.gov (United States)

    Cai, Chunqi; Zhai, Lanlan; Ma, Yahui; Zou, Chao; Zhang, Lijie; Yang, Yun; Huang, Shaoming

    2017-02-01

    Synthesis of quantum dots (QDs) with high photoluminescence is critical for quantum dot sensitized solar cells (QDSCs). A series of high quality AgInS2 QDs were synthesized under air circumstance by the organometallic high temperature method. Feature of tunable photoluminescence of AgInS2 QDs with long lifetime and quantum yields beyond 40% has been achieved, which was mainly attributed to the donor-acceptor pair recombination, contributed above 91% to the whole emission profiles. After ligand exchange with bifunctional linker, water-soluble AgInS2 QDs were adopted as light harvesters to fabricate QDSCs, achieved best PCE of 2.91% (short-circuit current density of 13.78 mA cm-2, open-circuit voltage of 0.47 V, and fill factor of 45%) under one full sun illumination. The improved photovoltaic performance of AgInS2 QDs-based QDSCs is mainly originated from broadened optoelectronic response range up to ∼900 nm, and enhanced photoluminescence with long lifetime and high quantum yield beyond 40%, which provide strong photoresponse ∼40% over the window below 750 nm. The synthetic approach combined with intrinsic defects created by intentionally composition modulation introduces a new approach towards the goal of high performance QDSCs.

  12. Photoluminescence intermittency of semiconductor quantum dots in dielectric environments

    Energy Technology Data Exchange (ETDEWEB)

    Isaac, A.

    2006-08-11

    The experimental studies presented in this thesis deal with the photoluminescence intermittency of semiconductor quantum dots in different dielectric environments. Detailed analysis of intermittency statistics from single capped CdSe/ZnS, uncapped CdSe and water dispersed CdSe/ZnS QDs in different matrices provide experimental evidence for the model of photoionization with a charge ejected into the surrounding matrix as the source of PL intermittency phenomenon. We propose a self-trapping model to explain the increase of dark state lifetimes with the dielectric constant of the matrix. (orig.)

  13. Tuning the Photoluminescence of Graphene Quantum Dots by Fluorination

    Directory of Open Access Journals (Sweden)

    Yi Luo

    2017-01-01

    Full Text Available Fluorinated graphene quantum dots (F-GQDs were prepared by mixing GQDs and XeF2 in a facile gaseous phase heating method. The F-GQDs with excellent water solubility have a F/C atomic ratio of 84.25% and a diameter of 2–6 nm. The photoluminescence (PL properties of GQDs and F-GQDs were investigated systematically. The results showed that the PL emission of the F-GQDs exhibited an obvious blue-shift of 90 nm compared to that of the GQDs.

  14. Synthesis and unique photoluminescence properties of nitrogen-rich quantum dots and their applications.

    Science.gov (United States)

    Chen, Xiuxian; Jin, Qingqing; Wu, Lizhu; Tung, ChenHo; Tang, Xinjing

    2014-11-10

    Nitrogen-rich quantum dots (N-dots) were serendipitously synthesized in methanol or aqueous solution at a reaction temperature as low as 50 °C. These N-dots have a small size (less than 10 nm) and contain a high percentage of the element nitrogen, and are thus a new member of quantum-dot family. These N-dots show unique and distinct photoluminescence properties with an increasing percentage of nitrogen compared to the neighboring carbon dots. The photoluminescence behavior was adjusted from blue to green simply through variation of the reaction temperature. Furthermore, the detailed mechanism of N-dot formation was also proposed with the trapped intermediate. These N-dots have also shown promising applications as fluorescent ink and biocompatible staining in C. elegans. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Asymmetrical quantum well degradation of InGaN/GaN blue laser diodes characterized by photoluminescence

    Science.gov (United States)

    Wen, Pengyan; Liu, Jianping; Zhang, Shuming; Zhang, Liqun; Ikeda, Masao; Li, Deyao; Tian, Aiqin; Zhang, Feng; Cheng, Yang; Zhou, Wei; Yang, Hui

    2017-11-01

    The temperature, power, and voltage dependent photoluminescence spectra are studied in InGaN/GaN double quantum well blue laser diodes. Emissions from the two quantum wells can be distinguished at low temperature at low excitation power density due to the different built-in electric field in the two quantum wells. This finding is utilized to study the degradation of InGaN/GaN blue laser diodes. Two peaks are observed for the non-aged laser diode (LD), while one peak for the aged LD which performed 3200 h until no laser output is detected. The disappearance of the high energy peak in the photoluminescence spectra indicates a heavier degradation of the quantum well on the p-side, which agrees with our previous observation that both the linewidth and the potential fluctuation of InGaN quantum wells (QWs) reduced for the aged LDs.

  16. Synthesis, Photoluminescence and Bio-Targeting Applications of Blue Graphene Quantum Dots.

    Science.gov (United States)

    Wang, Jigang; Zhou, Ji; Zhou, Wenhua; Shi, Jilong; Ma, Lun; Chen, Wei; Wang, Yongsheng; He, Dawei; Fu, Ming; Zhang, Yongna

    2016-04-01

    Chemical derived graphene oxide, an atomically thin sheet of graphite with two-dimensional construction, offers interesting physical, electronic, thermal, chemical, and mechanical properties that are currently being explored for advanced physics electronics, membranes, and composites. Herein, we study graphene quantum dots (GQD) with the blue photoluminescence under various parameters. The GQD samples were prepared at different temperatures, and the blue photoluminescence intensity of the solution improved radically as the heating temperatures increased. Concerning PL peak and intensity of the quantum dots, the results demonstrated dependence on time under heating, temperature of heating, and pH adjusted by the addition of sodium hydroxide. After hydrothermal synthesis routes, the functional groups of graphene oxide were altered the morphology showed the stacking configuration, and self-assembled structure of the graphene sheets with obvious wrinkles appeared at the edge structures. In addition, absorption, PL, and PLE spectra of the graphene quantum dots increase with different quantities of sodium hydroxide added. Finally, using GQD to target PNTIA cells was carried out successfully. High uptake efficiency and no cytotoxic effects indicate graphene quantum dots can be suitable for bio-targeting.

  17. Photoluminescence quenching of CdSe core/shell quantum dots by hole transporting materials

    NARCIS (Netherlands)

    Zhang, Y.; Jing, P.; Zeng, Q.; Sun, Y.; Su, H.; Wang, Y.A.; Kong, X.; Zhao, J.; Zhang, H.

    2009-01-01

    Photoluminescence quenching of colloidal CdSe core/shell quantum dots (QDs) with CdS, ZnS and CdS/CdZnS/ZnS shells in the presence of hole-transporting materials (HTMs) is studied by means of steady-state and time-resolved photoluminescence spectroscopy. Static quenching is surprisingly found to

  18. Near-unity photoluminescence quantum yield in MoS.sub.2

    Energy Technology Data Exchange (ETDEWEB)

    Amani, Matin; Lien, Der-Hsien; Kiriya, Daisuke; Bullock, James; Javey, Ali

    2017-12-26

    Two-dimensional (2D) transition-metal dichalcogenides have emerged as a promising material system for optoelectronic applications, but their primary figure-of-merit, the room-temperature photoluminescence quantum yield (QY) is extremely poor. The prototypical 2D material, MoS.sub.2 is reported to have a maximum QY of 0.6% which indicates a considerable defect density. We report on an air-stable solution-based chemical treatment by an organic superacid which uniformly enhances the photoluminescence and minority carrier lifetime of MoS.sub.2 monolayers by over two orders of magnitude. The treatment eliminates defect-mediated non-radiative recombination, thus resulting in a final QY of over 95% with a longest observed lifetime of 10.8.+-.0.6 nanoseconds. Obtaining perfect optoelectronic monolayers opens the door for highly efficient light emitting diodes, lasers, and solar cells based on 2D materials.

  19. Dewetting-Induced Photoluminescent Enhancement of Poly(lauryl methacrylate)/Quantum Dot Thin Films.

    Science.gov (United States)

    Geldmeier, Jeffrey; Rile, Lexy; Yoon, Young Jun; Jung, Jaehan; Lin, Zhiqun; Tsukruk, Vladimir V

    2017-12-19

    A new method for enhancing photoluminescence from quantum dot (QD)/polymer nanocomposite films is proposed. Poly(lauryl methacrylate) (PLMA) thin films containing embedded QDs are intentionally allowed to undergo dewetting on substrates by exposure to a nonsolvent vapor. After controlled dewetting, films exhibited typical dewetting morphologies with increased amounts of scattering that served to outcouple photoluminescence from the film and reduce internal light propagation within the film. Up to a 5-fold enhancement of the film emission was achieved depending on material factors such as the initial film thickness and QD concentration within the film. An increase in initial film thickness was shown to increase the dewetted maximum feature size and its characteristic length until a critical thickness was reached where dewetting became inhibited. A unique light exposure-based photopatterning method is also presented for the creation of high contrast emissive patterns as guided by spatially controlled dewetting.

  20. Time-resolved photoluminescence of sub-monolayer InGaAs/GaAs quantum-dot-quantum-well heterostructures

    DEFF Research Database (Denmark)

    Xu, Zhangcheng; Jia, G.Z.; Sun, L.

    2005-01-01

    Time-resolved photoluminescence (PL) of sub-monolayer (SML) InGaAs/GaAs quantum-dot-quantum-well heterostructures was measured at 5 K for the first time. The radiative lifetime of SML quantum dots (QDs) increases from 500 ps to 800 ps with the increase of the size of QDs, which is related...

  1. Photoluminescence Properties Research on Graphene Quantum Dots/Silver Composites.

    Science.gov (United States)

    Wang, Jun; Li, Yan; Zhang, Bo-Ping; Xie, Dan-Dan; Ge, Juan; Liu, Hui

    2016-04-01

    Graphene quantum dots (GQDs) possess unique properties of graphene and exhibit a series of new phenomena of 0 dimension (D) carbon materials. Thus, GQDs have attracted much attention from researchers and have shown great promise for many applications. Recently, many works focus on GQDs-metal ions and metal nanoparticles (NPs). Although, many researches point out that metal ions and metal NPs have significant effect on photoluminescence (PL) feature of GQDs, mainly focus on PL intensity. Here, for the first time, we reported that metal NPs also affected PL peak position which was dependent on the mix mechanism of metal and GQDs. When GQDs-silver (Ag) composite mixed by physical method and excited at a wavelength of 320 nm, PL peak position of composites first showed blue-shifted then red-shifted with increasing of Ag content. However, if GQDs-Ag composite prepared by chemical method, PL peak position of the composites blue-shifted. Furthermore, the shift of PL peak position of GQDs-Ag prepared both for physical and chemical method displayed excitation-dependent feature. When the excitation wavelength approached to Ag SPR peaks, no obvious PL shift was observed. The mechanism for different PL shifts and the phenomenon of excitation-dependent PL shift as well as the formation mechanism of GQDs-Ag composite by chemical method are discussed in detail in this paper.

  2. Photoluminescence response of colloidal quantum dots on VO2 film across metal to insulator transition.

    Science.gov (United States)

    Kuznetsov, Sergey N; Cheremisin, Alexander B; Stefanovich, Genrikh B

    2014-01-01

    We have proposed a method to probe metal to insulator transition in VO2 measuring photoluminescence response of colloidal quantum dots deposited on the VO2 film. In addition to linear luminescence intensity decrease with temperature that is well known for quantum dots, temperature ranges with enhanced photoluminescence changes have been found during phase transition in the oxide. Corresponding temperature derived from luminescence dependence on temperature closely correlates with that from resistance measurement during heating. The supporting reflectance data point out that photoluminescence response mimics a reflectance change in VO2 across metal to insulator transition. Time-resolved photoluminescence study did not reveal any significant change of luminescence lifetime of deposited quantum dots under metal to insulator transition. It is a strong argument in favor of the proposed explanation based on the reflectance data. 71.30. + h; 73.21.La; 78.47.jd.

  3. The emission wavelength dependent photoluminescence lifetime of the N-doped graphene quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Xingxia [Research Center of Quantum Macro-Phenomenon and Application, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China); School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Sun, Jing; Yang, Siwei; Ding, Guqiao, E-mail: gqding@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shen, Hao; Zhou, Wei; Lu, Jian [Research Center of Quantum Macro-Phenomenon and Application, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China); Wang, Zhongyang, E-mail: wangzy@sari.ac.cn [Research Center of Quantum Macro-Phenomenon and Application, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China); School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210 (China)

    2015-12-14

    Aromatic nitrogen doped graphene quantum dots were investigated by steady-state and time-resolved photoluminescence (PL) techniques. The PL lifetime was found to be dependent on the emission wavelength and coincident with the PL spectrum, which is different from most semiconductor quantum dots and fluorescent dyes. This result shows the synergy and competition between the quantum confinement effect and edge functional groups, which may have the potential to guide the synthesis and expand the applications of graphene quantum dots.

  4. Homogeneous linewidth of self-assembled III-V quantum dots observed in single-dot photoluminescence

    DEFF Research Database (Denmark)

    Leosson, K.; Birkedal, Dan; Magnúsdóttir, Ingibjörg

    2003-01-01

    We report photoluminescence emission from single self-assembled InAlGaAs quantum dots, which is broadened purely by dephasing processes. We observe linewidths as low as 6+/-3@meV at 10K, which agrees with the homogeneous linewidth derived from four-wave mixing experiments. By selecting dots...... that are not affected by local field fluctuations and using high-energy excitation, we avoid additional sources of linewidth broadening typically present in single-dot photoluminescence spectra. We observe a strong LO-phonon coupling in InAlGaAs and InGaAs dots, which becomes the dominating contribution...

  5. Tuning the Photoluminescence of Graphene Quantum Dots by Photochemical Doping with Nitrogen.

    Science.gov (United States)

    Xu, Xiaofen; Gao, Fuhua; Bai, Xiaohua; Liu, Fuchi; Kong, Wenjie; Li, Ming

    2017-11-20

    Nitrogen-doped graphene quantum dots (NGQDs) were synthesized by irradiating graphene quantum dots (GQDs) in an NH₃ atmosphere. The photoluminescence (PL) properties of the GQDs and the NGQDs samples were investigated. Compared with GQDs, a clear PL blue-shift of NGQDs could be achieved by regulating the irradiating time. The NGQDs obtained by irradiation of GQDs for 70 min had a high N content of 15.34 at % and a PL blue-shift of about 47 nm. This may be due to the fact that photochemical doping of GQDs with nitrogen can significantly enhance the contents of pyridine-like nitrogen, and also effectively decrease the contents of oxygen functional groups of NGQDs, thus leading to the observed obvious PL blue-shift.

  6. Tuning the Photoluminescence of Graphene Quantum Dots by Photochemical Doping with Nitrogen

    Directory of Open Access Journals (Sweden)

    Xiaofen Xu

    2017-11-01

    Full Text Available Nitrogen-doped graphene quantum dots (NGQDs were synthesized by irradiating graphene quantum dots (GQDs in an NH3 atmosphere. The photoluminescence (PL properties of the GQDs and the NGQDs samples were investigated. Compared with GQDs, a clear PL blue-shift of NGQDs could be achieved by regulating the irradiating time. The NGQDs obtained by irradiation of GQDs for 70 min had a high N content of 15.34 at % and a PL blue-shift of about 47 nm. This may be due to the fact that photochemical doping of GQDs with nitrogen can significantly enhance the contents of pyridine-like nitrogen, and also effectively decrease the contents of oxygen functional groups of NGQDs, thus leading to the observed obvious PL blue-shift.

  7. Photoluminescent Ti3 C2 MXene Quantum Dots for Multicolor Cellular Imaging.

    Science.gov (United States)

    Xue, Qi; Zhang, Huijie; Zhu, Minshen; Pei, Zengxia; Li, Hongfei; Wang, Zifeng; Huang, Yang; Huang, Yan; Deng, Qihuang; Zhou, Jie; Du, Shiyu; Huang, Qing; Zhi, Chunyi

    2017-04-01

    The fabrication of photoluminescent Ti3 C2 MXene quantum dots (MQDs) by a facile hydrothermal method is reported, which may greatly extend the applications of MXene-based materials. Interestingly, the as-prepared MQDs show excitation-dependent photoluminescence spectra with quantum yields of up to ≈10% due to strong quantum confinement. The applications of MQDs as biocompatible multicolor cellular imaging probes and zinc ion sensors are demonstrated. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Photo-luminescent quantum dots used for security identification

    Science.gov (United States)

    Chang, Shoude; Yu, Kui; Liu, Jiaren

    2007-10-01

    Information retrieval is critical in security technologies such as those for status identification and documentation authentication. Ideally, coding materials should be difficult to locate, impossible to counterfeit, and easy to process. This presentation addresses a novel information retrieval technology with these ideal features of its coding materials: the photo-luminescent (PL) quantum-dots (QD) synthesized via wet-chemistry approaches. As compared to traditional PL materials, they exhibit emission with narrower full width at half maximum, greater brightness, and higher photo-stability; also, their PL wavelength can be easily and accurately tuned via their size, structure, and composition. Due to such a feasible tune-ability, mainly, QDs have demonstrated enormous potential applications in security and defense. When QDs are excited, they can provide coded information with their PL wavelength and intensity. If the coding wavelengths from the QD PL are designed as the Fraunhofer lines, i.e. black lines in solar spectrum, the retrieval system can extract the useful information even under sunshine covering areas. Multi-photon excitation (MPE) technologies can further extend applications of QDs to multi-layer information extraction. For an info-label of 2-millimeter in depth, a MPE system with the depth resolution less than one micro-meter can thus achieve 2 GB resolutions, when a coding material exhibiting 6 PL wavelengths with 10 intensity levels. In general, transparent thin-film coating of QDs can be applied to various substrates, such as documents, fingernails, and military helmets and vehicles. Moreover, QD based security information can be easily destroyed by preset expiration in the presence of timing agents.

  9. Power density and temperature effects on the photoluminescence spectra of InAlAs/GaAlAs quantum dots

    Science.gov (United States)

    Ben Daly, A.; Riahi, H.; Bernardot, F.; Barisien, T.; Galopin, E.; Lemaître, A.; Maaref, M. A.; Testelin, C.

    2017-04-01

    Photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurement techniques are used to characterize the size and the density of In1-xAlxAs/Ga0.67Al0.33As quantum dots (QDs) for different QD aluminium compositions. The integrated photoluminescence intensity (IPL) depends on an excitation light power, decreases with increasing the aluminium proportion emphasizing the QDs surface density decreasing. In TRPL experiments, the influence of QD lateral coupling is evidence in high QD density sample, the radiative lifetime increases with increasing temperatures for sample with a low aluminium proportion, instead, the observed radiative lifetime keep constant for samples with a high aluminium proportions in agreement with the QD zero-dimensional confinement.

  10. Green and fast synthesis of amino-functionalized graphene quantum dots with deep blue photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Blanco, E., E-mail: eduardo.blanco@uca.es; Blanco, G.; Gonzalez-Leal, J. M.; Barrera, M. C.; Domínguez, M.; Ramirez-del-Solar, M. [University of Cádiz, Institute of Electron Microscopy and Materials (Spain)

    2015-05-15

    Graphene quantum dots (GQDs) were prepared using a top-down approach with a green microwave-assisted hydrothermal synthesis from ultrathin graphite, previously ultrasound delaminated. Results obtained by transmission electron microscopy and atomic force microscopy indicate that the so-fabricated GQDs are plates with 6 nm of average diameter, mostly single- or bi-layered. Photoluminescence characterization shows that the strongest emission occurs at 410–415 nm wavelength when the samples are excited at 310–320 nm wavelength. In addition to these down-conversion features, GQDs also exhibit up-conversion photoluminescence when excited in the range 560–800 nm wavelength, with broad emission peaks at 410–450 nm wavelength. Analysis of X-ray photoelectron spectroscopy measurements indicates a higher proportion of C–C sp{sup 2} than sp{sup 3} bonds, with the sp{sup 3} ones mainly located at the GQD surfaces. Also evidences of C–O and C–N bonds at the GQD surface have been observed. The combination of these results with Raman and ultraviolet–visible absorption experiments allows envisaging the GQDs to be composed of amino-functionalized sp{sup 2} islands with a high degree of surface oxidation. This would explain the photoluminescent properties observed in the samples under study. The combined up- and down-conversion photoluminescence processes would made these GQDs a powerful energy-transfer component in GQDs–TiO{sub 2} nanocomposite systems, which could be used in photocatalyst devices with superior performance compared to simple TiO{sub 2} systems.

  11. Green and fast synthesis of amino-functionalized graphene quantum dots with deep blue photoluminescence

    Science.gov (United States)

    Blanco, E.; Blanco, G.; Gonzalez-Leal, J. M.; Barrera, M. C.; Domínguez, M.; Ramirez-del-Solar, M.

    2015-05-01

    Graphene quantum dots (GQDs) were prepared using a top-down approach with a green microwave-assisted hydrothermal synthesis from ultrathin graphite, previously ultrasound delaminated. Results obtained by transmission electron microscopy and atomic force microscopy indicate that the so-fabricated GQDs are plates with 6 nm of average diameter, mostly single- or bi-layered. Photoluminescence characterization shows that the strongest emission occurs at 410-415 nm wavelength when the samples are excited at 310-320 nm wavelength. In addition to these down-conversion features, GQDs also exhibit up-conversion photoluminescence when excited in the range 560-800 nm wavelength, with broad emission peaks at 410-450 nm wavelength. Analysis of X-ray photoelectron spectroscopy measurements indicates a higher proportion of C-C sp2 than sp3 bonds, with the sp3 ones mainly located at the GQD surfaces. Also evidences of C-O and C-N bonds at the GQD surface have been observed. The combination of these results with Raman and ultraviolet-visible absorption experiments allows envisaging the GQDs to be composed of amino-functionalized sp2 islands with a high degree of surface oxidation. This would explain the photoluminescent properties observed in the samples under study. The combined up- and down-conversion photoluminescence processes would made these GQDs a powerful energy-transfer component in GQDs-TiO2 nanocomposite systems, which could be used in photocatalyst devices with superior performance compared to simple TiO2 systems.

  12. Efficiency droop suppression of distance-engineered surface plasmon-coupled photoluminescence in GaN-based quantum well LEDs

    Directory of Open Access Journals (Sweden)

    Yufeng Li

    2017-11-01

    Full Text Available Ag coated microgroove with extreme large aspect-ratio of 500:1 was fabricated on p-GaN capping layer to investigate the coupling behavior between quantum wells and surface plasmon in highly spatial resolution. Significant photoluminescence enhancement was observed when the distance between Ag film and QWs was reduced from 220 nm to about 20 nm. A maximum enhancement ratio of 18-fold was achieved at the groove bottom where the surface plasmonic coupling was considered the strongest. Such enhancement ratio was found highly affected by the excitation power density. It also shows high correlation to the internal quantum efficiency as a function of coupling effect and a maximum Purcell Factor of 1.75 was estimated at maximum coupling effect, which matches number calculated independently from the time-resolved photoluminescence measurement. With such Purcell Factor, the efficiency was greatly enhanced and the droop was significantly suppressed.

  13. Temperature-dependent photoluminescence of cadmium-free Cu-Zn-In-S quantum dot thin films as temperature probes.

    Science.gov (United States)

    Wang, Lan; Kang, Xiaojiao; Huang, Lijian; Pan, Daocheng

    2015-12-21

    We reported temperature-dependent photoluminescence (PL) studies on Cu-Zn-In-S quantum dot (QD) thin films. In this paper, cadmium-free and luminescent Cu-Zn-In-S quantum dot thin films were in situ formed by thermal decomposition of molecular-based precursors in the open air, without need of the complicated quantum dot synthesis. Molecular-based precursor solutions were prepared by dissolving Cu2O, ZnO, and In(OH)3 in the ethanol solution of butylamine and carbon disulfide. The effects of sintering temperature, sintering time, and the concentration of capping agents on the photoluminescence properties of Cu-Zn-In-S QD thin films have been systematically investigated. It was found that alkali metal ions play an important role in enhancing the PL quantum yield of quantum dot thin films. The as-prepared QD thin films show composition-tunable emission in the range of 535 nm to 677 nm, and the absolute PL quantum yields can reach as high as 22.1%. All of the as-deposited QD thin films show a single-exponential decay to temperature, indicating that these cadmium-free QD thin films have high potential as temperature probes.

  14. Temperature dependence of photoluminescence from submonolayer deposited InGaAs/GaAs quantum dots

    DEFF Research Database (Denmark)

    Xu, Zhangcheng; Leosson, K.; Birkedal, Dan

    2002-01-01

    The temperature dependence of photoluminescence (PL) from self-assembled InGaAs quantum dots (QD's) grown by submonolayer deposition mode (non-SK mode), is investigated. It is found that the PL spectra are dominated by the ground-state transitions at low temperatures, but increasingly by the exci......The temperature dependence of photoluminescence (PL) from self-assembled InGaAs quantum dots (QD's) grown by submonolayer deposition mode (non-SK mode), is investigated. It is found that the PL spectra are dominated by the ground-state transitions at low temperatures, but increasingly...

  15. Perovskite Quantum Dots with Near Unity Solution and Neat-Film Photoluminescent Quantum Yield by Novel Spray Synthesis.

    Science.gov (United States)

    Dai, Shu-Wen; Hsu, Bo-Wei; Chen, Chien-Yu; Lee, Chia-An; Liu, Hsiao-Yun; Wang, Hsiao-Fang; Huang, Yu-Ching; Wu, Tien-Lin; Manikandan, Arumugam; Ho, Rong-Ming; Tsao, Cheng-Si; Cheng, Chien-Hong; Chueh, Yu-Lun; Lin, Hao-Wu

    2018-02-01

    In this study, a novel perovskite quantum dot (QD) spray-synthesis method is developed by combining traditional perovskite QD synthesis with the technique of spray pyrolysis. By utilizing this new technique, the synthesis of cubic-shaped perovskite QDs with a homogeneous size of 14 nm is demonstrated, which shows an unprecedented stable absolute photoluminescence quantum yield ≈100% in the solution and even in the solid-state neat film. The highly emissive thin films are integrated with light emission devices (LEDs) and organic light emission displays (OLEDs). The color conversion type QD-LED (ccQD-LED) hybrid devices exhibit an extremely saturated green emission, excellent external quantum efficiency of 28.1%, power efficiency of 121 lm W -1 , and extraordinary forward-direction luminescence of 8 500 000 cd m -2 . The conceptual ccQD-OLED hybrid display also successfully demonstrates high-definition still images and moving pictures with a 119% National Television System Committee 1931 color gamut and 123% Digital Cinema Initiatives-P3 color gamut. These very-stable, ultra-bright perovskite QDs have the properties necessary for a variety of useful applications in optoelectronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. One-pot green synthesis of high quantum yield oxygen-doped, nitrogen-rich, photoluminescent polymer carbon nanoribbons as an effective fluorescent sensing platform for sensitive and selective detection of silver(I) and mercury(II) ions.

    Science.gov (United States)

    Wang, Zhong-Xia; Ding, Shou-Nian

    2014-08-05

    This work reports on a facile, economical, and green preparative strategy toward water-soluble, fluorescent oxygen-doped, nitrogen-rich, photoluminescent polymer carbon nanoribbons (ONPCRs) with a quantum yield of approximately 25.61% by the hydrothermal process using uric acid as a carbon-nitrogen source for the first time. The as-prepared fluorescent ONPCRs showed paddy leaf-like structure with 80-160 nm length and highly efficient fluorescent quenching ability in the presence of mercury(II) (Hg(2+)) or silver (Ag(+)) ions due to the formed nonfluorescent metal complexes via robust Hg(2+)-O or Ag(+)-N interaction with the O and N of fluorescent ONPCRs, which allowed the analysis of Hg(2+) and Ag(+) ions in a very simple method. By employing this sensor, excellent linear relationships existed between the quenching degree of the ONPCRs and the concentrations of Hg(2+) and Ag(+) ions in the range of 2.0 nM to 60 μM and 5.0 nM to 80 μM, respectively. By using ethylenediaminetetraacetate and ammonia as the masking agent of Hg(2+) and Ag(+) ions, respectively, Hg(2+) or Ag(+) ions were exclusively detected in coexistence with Ag(+) or Hg(2+) ions with high sensitivity, and the detection limits as low as 0.68 and 1.73 nM (3σ) were achieved, respectively, which also provided a reusable detection method for Hg(2+) and Ag(+) ions. Therefore, the easily synthesized fluorescent ONPCRs may have great potential applications in the detection of Hg(2+) and Ag(+) ions for biological assay and environmental protection.

  17. Photoluminescence enhancement of quantum dots on Ag nanoneedles.

    Science.gov (United States)

    Ahmed, Syed Rahin; Cha, Hee Ryoung; Park, Jung Youn; Park, Enoch Y; Lee, Dongyun; Lee, Jaebeom

    2012-08-07

    Noble metal nanostructure allows us to tune optical and electrical properties, which has high utility for real-world application. We studied surface plasmon-induced emission of semiconductor quantum dots (QDs) on engineered metallic nanostructures. Highly passive organic ZnS-capped CdSe QDs were spin-coated on poly-(methyl methacrylate)-covered Ag films, which brought QDs near the metallic surface. We obtained the enhanced electromagnetic field and reduced fluorescence lifetimes from CdSe/ZnS QDs due to the strong coupling of emitter wave function with the Ag plasmon resonance. Observed changes include a six-fold increase in the fluorescence intensity and striking reduction in fluorescence lifetimes of CdSe/ZnS QDs on rough Ag nanoneedle compared to the case of smooth surfaces. The advantages of using those nanocomposites are expected for high-efficiency light-emitting diodes, platform fabrication of biological and environmental monitoring, and high-contrast imaging.

  18. Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots

    Directory of Open Access Journals (Sweden)

    Lin Chien-Hung

    2011-01-01

    Full Text Available Abstract In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states on photoluminescence excitation (PLE spectra of InAs quantum dots (QDs was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T were compared. Our findings show that the profile of the PLE resonances associated with the bound transitions disintegrated and broadened. This was attributed to the coupling of the localized QD excited states to the crossed states and scattering of longitudinal acoustical (LA phonons. The degree of spectral linewidth broadening was larger for the excited state in smaller QDs because of the higher crossed joint density of states and scattering rate.

  19. The mechanisms for linear polarization loss of in-plane photoluminescence of InGaAs/GaAs quantum well and quantum dot structures

    NARCIS (Netherlands)

    Aleshkin, VY; Zvonkov, BN; Malkina, IG; Chernov, AL; Romanov, YA

    1999-01-01

    The mechanisms for linear polarization loss of photoluminescence from quantum wells and quantum dots in InGaAs/GaAs structures observed from cleavages have been investigated. It is found that the mechanisms for polarization loss of in-plane photoluminescence are different for OD and 2D hole states.

  20. Near-unity photoluminescence quantum yield in MoS2

    Science.gov (United States)

    Amani, Matin; Lien, Der-Hsien; Kiriya, Daisuke; Xiao, Jun; Azcatl, Angelica; Noh, Jiyoung; Madhvapathy, Surabhi R.; Addou, Rafik; KC, Santosh; Dubey, Madan; Cho, Kyeongjae; Wallace, Robert M.; Lee, Si-Chen; He-Hau, Jr.; Ager, Joel W.; Zhang, Xiang; Yablonovitch, Eli; Javey, Ali

    2015-11-01

    Two-dimensional (2D) transition metal dichalcogenides have emerged as a promising material system for optoelectronic applications, but their primary figure of merit, the room-temperature photoluminescence quantum yield (QY), is extremely low. The prototypical 2D material molybdenum disulfide (MoS2) is reported to have a maximum QY of 0.6%, which indicates a considerable defect density. Here we report on an air-stable, solution-based chemical treatment by an organic superacid, which uniformly enhances the photoluminescence and minority carrier lifetime of MoS2 monolayers by more than two orders of magnitude. The treatment eliminates defect-mediated nonradiative recombination, thus resulting in a final QY of more than 95%, with a longest-observed lifetime of 10.8 ± 0.6 nanoseconds. Our ability to obtain optoelectronic monolayers with near-perfect properties opens the door for the development of highly efficient light-emitting diodes, lasers, and solar cells based on 2D materials.

  1. Near-unity photoluminescence quantum yield in MoS2

    KAUST Repository

    Amani, Matin

    2015-11-26

    Two-dimensional (2D) transition metal dichalcogenides have emerged as a promising material system for optoelectronic applications, but their primary figure of merit, the room-temperature photoluminescence quantum yield (QY), is extremely low.The prototypical 2D material molybdenum disulfide (MoS2) is reported to have a maximum QYof 0.6%, which indicates a considerable defect density. Herewe report on an air-stable, solution-based chemical treatment by an organic superacid, which uniformly enhances the photoluminescence and minority carrier lifetime of MoS2 monolayers by more than two orders of magnitude.The treatment eliminates defect-mediated nonradiative recombination, thus resulting in a finalQYofmore than 95%, with a longest-observed lifetime of 10.8 0.6 nanoseconds. Our ability to obtain optoelectronic monolayers with near-perfect properties opens the door for the development of highly efficient light-emitting diodes, lasers, and solar cells based on 2D materials.

  2. Enhanced quantum yield of photoluminescent porous silicon prepared by supercritical drying

    Energy Technology Data Exchange (ETDEWEB)

    Joo, Jinmyoung [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093 (United States); Biomedical Engineering Research Center, Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505 (Korea, Republic of); Defforge, Thomas; Gautier, Gael, E-mail: msailor@ucsd.edu, E-mail: gael.gautier@univ-tours.fr, E-mail: lcanham@psivida.com [Universite Francois Rabelais de Tours, CNRS CEA, INSA-CVL, GREMAN UMR 7347, 37071 Tours Cedex 2 (France); Loni, Armando [pSiMedica Ltd., Malvern Hills Science Park, Geraldine Road, Malvern, Worcestershire WR14 3SZ (United Kingdom); Kim, Dokyoung; Sailor, Michael J., E-mail: msailor@ucsd.edu, E-mail: gael.gautier@univ-tours.fr, E-mail: lcanham@psivida.com [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093 (United States); Li, Z. Y. [Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Canham, Leigh T., E-mail: msailor@ucsd.edu, E-mail: gael.gautier@univ-tours.fr, E-mail: lcanham@psivida.com [pSiMedica Ltd., Malvern Hills Science Park, Geraldine Road, Malvern, Worcestershire WR14 3SZ (United Kingdom); Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

    2016-04-11

    The effect of supercritical drying (SCD) on the preparation of porous silicon (pSi) powders has been investigated in terms of photoluminescence (PL) efficiency. Since the pSi contains closely spaced and possibly interconnected Si nanocrystals (<5 nm), pore collapse and morphological changes within the nanocrystalline structure after common drying processes can affect PL efficiency. We report the highly beneficial effects of using SCD for preparation of photoluminescent pSi powders. Significantly higher surface areas and pore volumes have been realized by utilizing SCD (with CO{sub 2} solvent) instead of air-drying. Correspondingly, the pSi powders better retain the porous structure and the nano-sized silicon grains, thus minimizing the formation of non-radiative defects during liquid evaporation (air drying). The SCD process also minimizes capillary-stress induced contact of neighboring nanocrystals, resulting in lower exciton migration levels within the network. A significant enhancement of the PL quantum yield (>32% at room temperature) has been achieved, prompting the need for further detailed studies to establish the dominant causes of such an improvement.

  3. Surface-plasmon-enhanced photoluminescence of quantum dots based on open-ring nanostructure array

    Science.gov (United States)

    Kannegulla, Akash; Liu, Ye; Cheng, Li-Jing

    2016-03-01

    Enhanced photoluminescence (PL) of quantum dots (QD) in visible range using plasmonic nanostructures has potential to advance several photonic applications. The enhancement effect is, however, limited by the light coupling efficiency to the nanostructures. Here we demonstrate experimentally a new open-ring nanostructure (ORN) array 100 nm engraved into a 200 nm thick silver thin film to maximize light absorption and, hence, PL enhancement at a broadband spectral range. The structure is different from the traditional isolated or through-hole split-ring structures. Theoretical calculations based on FDTD method show that the absorption peak wavelength can be adjusted by their period and dimension. A broadband absorption of about 60% was measured at the peak wavelength of 550 nm. The emission spectrum of CdSe/ZnS core-shell quantum dots was chosen to match the absorption band of the ORN array to enhance its PL. The engraved silver ORN array was fabricated on a silver thin film deposited on a silicon substrate using focus ion beam (FIB) patterning. The device was characterized by using a thin layer of QD water dispersion formed between the ORN substrate and a cover glass. The experimental results show the enhanced PL for the QD with emission spectrum overlapping the absorption band of ORN substrate and quantum efficiency increases from 50% to 70%. The ORN silver substrate with high absorption over a broadband spectrum enables the PL enhancement and will benefit applications in biosensing, wavelength tunable filters, and imaging.

  4. UV and air stability of high-efficiency photoluminescent silicon nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jihua, E-mail: yangj@umn.edu [Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Liptak, Richard [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Department of Physics and Optical Engineering, Rose-Hulman Institute of Technology, 5500 Wabash Ave, Terre Haute, IN 47803 (United States); Rowe, David; Wu, Jeslin [Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Casey, James; Witker, David [Dow Corning Corporation, 2200 W. Salzburg Road, Midland, MI 48686 (United States); Campbell, Stephen A. [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Kortshagen, Uwe, E-mail: kortshagen@umn.edu [Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455 (United States)

    2014-12-30

    The effects of UV light and air exposure on the photoluminescent properties of nonthermal plasma-synthesized silicon nanocrystals (Si NCs) were investigated. Si NCs with high-efficiency photoluminescence (PL) have been achieved via a post-synthesis hydrosilylation process. Photobleaching is observed within the first few hours of ultra-violet (UV) irradiation. Equilibrium is reached after ∼4 h of UV exposure wherein the Si NCs are able to retain 52% of the initially measured PL quantum yield (PLQY). UV-treated Si NCs showed recovery of PL with time. Gas-phase passivation of Si NCs by hydrogen afterglow injection improves PLQY and PL stability against UV and air exposure. Additionally, phosphorous doping can also improve UV stability of photoluminescent Si NCs.

  5. Homogeneous linewidth of single InGaAs quantum dot photoluminescence

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Langbein, Wolfgang; Jensen, Jacob Riis

    2000-01-01

    We have used m-photoluminescence spectroscopy with a spectral resolution of 20 meV to measure homogeneous linewidths of single emission lines within an inhomogeneously broadened ensemble of In0.5Ga0.5As/GaAs self-assembled quantum dots. At 10K, a distribution of linewidths peaking around 50 me...

  6. Detection of CdSe quantum dot photoluminescence for security label on paper

    Science.gov (United States)

    Isnaeni, Sugiarto, Iyon Titok; Bilqis, Ratu; Suseno, Jatmiko Endro

    2016-02-01

    CdSe quantum dot has great potential in various applications especially for emitting devices. One example potential application of CdSe quantum dot is security label for anti-counterfeiting. In this work, we present a practical approach of security label on paper using one and two colors of colloidal CdSe quantum dot, which is used as stamping ink on various types of paper. Under ambient condition, quantum dot is almost invisible. The quantum dot security label can be revealed by detecting emission of quantum dot using photoluminescence and cnc machine. The recorded quantum dot emission intensity is then analyzed using home-made program to reveal quantum dot pattern stamp having the word 'RAHASIA'. We found that security label using quantum dot works well on several types of paper. The quantum dot patterns can survive several days and further treatment is required to protect the quantum dot. Oxidation of quantum dot that occurred during this experiment reduced the emission intensity of quantum dot patterns.

  7. Detection of CdSe quantum dot photoluminescence for security label on paper

    Energy Technology Data Exchange (ETDEWEB)

    Isnaeni,, E-mail: isnaeni@lipi.go.id; Sugiarto, Iyon Titok [Research Center for Physics, Indonesian Institute of Science, Building 442 Puspiptek Serpong, South Tangerang, Banten, Indonesia 15314 (Indonesia); Bilqis, Ratu; Suseno, Jatmiko Endro [Department of Physics, Diponegoro University, Jl. Prof. Soedarto, Tembalang, Semarang, Indonesia 50275 (Indonesia)

    2016-02-08

    CdSe quantum dot has great potential in various applications especially for emitting devices. One example potential application of CdSe quantum dot is security label for anti-counterfeiting. In this work, we present a practical approach of security label on paper using one and two colors of colloidal CdSe quantum dot, which is used as stamping ink on various types of paper. Under ambient condition, quantum dot is almost invisible. The quantum dot security label can be revealed by detecting emission of quantum dot using photoluminescence and cnc machine. The recorded quantum dot emission intensity is then analyzed using home-made program to reveal quantum dot pattern stamp having the word ’RAHASIA’. We found that security label using quantum dot works well on several types of paper. The quantum dot patterns can survive several days and further treatment is required to protect the quantum dot. Oxidation of quantum dot that occurred during this experiment reduced the emission intensity of quantum dot patterns.

  8. Photoluminescent (PL) or electroluminescent (EL) quantum dots for display, lighting, and photomedicine (Conference Presentation)

    Science.gov (United States)

    Dong, Yajie

    2017-02-01

    Quantum dots (QDs) have gone through a long journey before finding their ways into the display field. This talk will briefly touch on the history before trying to answer several key questions related to QDs applications in display: What are QDs? How are they made? What properties do they have and Why? How can these properties be used to improve color and efficiency of display, in either photoluminescence (PL) or electroluminescence (EL) mode? And what are the remaining challenges for QDs wide adoption in display industry? Lastly, some most recent progresses in our UCF lab at both PL and EL fronts will be highlighted. For PL, a cadmium-free perovskite-polymer composite films with exceptionally narrow emission green peaks (FWHM 20 nm) and good water and thermal stability will be reported. Together with red quantum dots or PFS/KSF phosphors as down-converters for blue LEDs, a white-light source with 95% Rec. 2020 color gamut was demonstrated [1]. For EL, red quantum dot light emitting devices (QLEDs) with record luminance of 165,000 Cd/m2 has been obtained at a current density of 1000 mA/cm2 with a low driving voltage of 5.8 V and CIE coordinates of (0.69, 0.31). [2] The potential of using these QLEDs for light sources for integrated sensing platform [3] or high efficiency, high color quality hybrid white OLED [4] will be discussed. [1] Y. N. Wang, J. He, H. Chen, J. S. Chen, R. D. Zhu, P. Ma, A. Towers, Y. Lin, A. J. Gesquiere, S. T. Wu, Y. J. Dong. Ultrastable, Highly Luminescent Organic-Inorganic Perovskite - Polymer Composite Films, Advanced Materials, accepted, (2016). [2] Y. J. Dong, J.M. Caruge, Z. Q. Zhou, C. Hamilton, Z. Popovic, J. Ho, M. Stevenson, G. Liu, V. Bulovic, M. Bawendi, P. T. Kazlas, S. Coe-Sullivan, and J. Steckel Ultra-bright, Highly Efficient, Low Roll-off Inverted Quantum-Dot Light Emitting Devices (QLEDs). SID Symp. Dig. Tech. Pap. 46, 270-273 (2015). [3] J. He, H. Chen, S. T. Wu, and Y. J. Dong, Integrated Sensing Platform Based on Quantum

  9. Photoluminescent graphene quantum dots for in vivo imaging of apoptotic cells

    Science.gov (United States)

    Roy, Prathik; Periasamy, Arun Prakash; Lin, Chiu-Ya; Her, Guor-Mour; Chiu, Wei-Jane; Li, Chi-Lin; Shu, Chia-Lun; Huang, Chih-Ching; Liang, Chi-Te; Chang, Huan-Tsung

    2015-01-01

    Apoptosis (programmed cell death) is linked to many incurable neurodegenerative, cardiovascular and cancer causing diseases. Numerous methods have been developed for imaging apoptotic cells in vitro; however, there are few methods available for imaging apoptotic cells in live animals (in vivo). Here we report a novel method utilizing the unique photoluminescence properties of plant leaf-derived graphene quantum dots (GQDs) modified with annexin V antibody (AbA5) to form (AbA5)-modified GQDs (AbA5-GQDs) enabling us to label apoptotic cells in live zebrafish (Danio rerio). The key is that zebrafish shows bright red photoluminescence in the presence of apoptotic cells. The toxicity of the GQDs has also been investigated with the GQDs exhibiting high biocompatibility as they were excreted from the zebrafish's body without affecting its growth significantly at a concentration lower than 2 mg mL-1 over a period of 4 to 72 hour post fertilization. The GQDs have further been used to image human breast adenocarcinoma cell line (MCF-7 cells), human cervical cancer cell line (HeLa cells), and normal human mammary epithelial cell line (MCF-10A). These results are indispensable to further the advance of graphene-based nanomaterials for biomedical applications.Apoptosis (programmed cell death) is linked to many incurable neurodegenerative, cardiovascular and cancer causing diseases. Numerous methods have been developed for imaging apoptotic cells in vitro; however, there are few methods available for imaging apoptotic cells in live animals (in vivo). Here we report a novel method utilizing the unique photoluminescence properties of plant leaf-derived graphene quantum dots (GQDs) modified with annexin V antibody (AbA5) to form (AbA5)-modified GQDs (AbA5-GQDs) enabling us to label apoptotic cells in live zebrafish (Danio rerio). The key is that zebrafish shows bright red photoluminescence in the presence of apoptotic cells. The toxicity of the GQDs has also been investigated with

  10. Origin of low quantum efficiency of photoluminescence of InP/ZnS nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Shirazi, Roza, E-mail: rozas@fotonik.dtu.dk [Department of Photonics Engineering, Technical University of Denmark, Oersted Plads 343, 2800 Kgs Lyngby (Denmark); Kovacs, Andras [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Peter Grunberg Institute, Forschungszentrum Julich, 52425 Julich (Germany); Dan Corell, Dennis [Department of Photonics Engineering, Technical University of Denmark, Riso, Frederiksborgvej 399, 4000 Roskilde (Denmark); Gritti, Claudia [Department of Photonics Engineering, Technical University of Denmark, Oersted Plads 343, 2800 Kgs Lyngby (Denmark); Thorseth, Anders; Dam-Hansen, Carsten; Michael Petersen, Paul [Department of Photonics Engineering, Technical University of Denmark, Riso, Frederiksborgvej 399, 4000 Roskilde (Denmark); Kardynal, Beata [Department of Photonics Engineering, Technical University of Denmark, Oersted Plads 343, 2800 Kgs Lyngby (Denmark); PGI-9, Forschungszentrum Julich, JARA FIT, 52425 Julich (Germany)

    2014-01-15

    In this paper, we study the origin of a strong wavelength dependence of the quantum efficiency of InP/ZnS nanocrystals. We find that while the average size of the nanocrystals increased by 50%, resulting in longer emission wavelength, the quantum efficiency drops more than one order of magnitude compared to the quantum efficiency of the small nanocrystals. By correlating this result with the time-resolved photoluminescence we find that the reduced photoluminescence efficiency is caused by a fast growing fraction of non-emissive nanocrystals while the quality of the nanocrystals that emit light is similar for all samples. Transmission electron microscopy reveals the polycrystalline nature of many of the large nanocrystals, pointing to the grain boundaries as one possible site for the photoluminescence quenching defects. -- Highlights: • We investigate drop of quantum efficiency of InP/ZnS nanocrystals emitting at longer wavelengths. • We correlate quantum efficiency measurements with time-resolved carrier dynamics. • We find that only a small fraction of larger nanocrystals is optically active.

  11. AgCl-doped CdSe quantum dots with near-IR photoluminescence

    Directory of Open Access Journals (Sweden)

    Pavel A. Kotin

    2017-05-01

    Full Text Available We report the synthesis of colloidal CdSe quantum dots doped with a novel Ag precursor: AgCl. The addition of AgCl causes dramatic changes in the morphology of synthesized nanocrystals from spherical nanoparticles to tetrapods and finally to large ellipsoidal nanoparticles. Ellipsoidal nanoparticles possess an intensive near-IR photoluminescence ranging up to 0.9 eV (ca. 1400 nm. In this article, we explain the reasons for the formation of the ellipsoidal nanoparticles as well as the peculiarities of the process. The structure, Ag content, and optical properties of quantum dots are also investigated. The optimal conditions for maximizing both the reaction yield and IR photoluminescence quantum yield are found.

  12. Physico-chemical mechanism for the vapors sensitivity of photoluminescent InP quantum dots

    Science.gov (United States)

    Prosposito, P.; De Angelis, R.; De Matteis, F.; Hatami, F.; Masselink, W. T.; Zhang, H.; Casalboni, M.

    2016-03-01

    InP/InGaP surface quantum dots are interesting materials for optical chemical sensors since they present an intense emission at room temperature, whose intensity changes rapidly and reversibly depending on the composition of the environmental atmosphere. We present here their emission properties by time resolved photoluminescence spectroscopy investigation and we discuss the physico-chemical mechanism behind their sensitivity to the surrounding atmosphere. Photoluminescence transients in inert atmosphere (N2) and in solvent vapours of methanol, clorophorm, acetone and water were measured. The presence of vapors of clorophorm, acetone and water showed a very weak effect on the transient times, while an increase of up to 15% of the decay time was observed for methanol vapour exposure. On the basis of the vapor molecule nature (polarity, proticity, steric hindrance, etc.) and of the interaction of the vapor molecules with the quantum dots surface a sensing mechanism involving quantum dots non-radiative surface states is proposed.

  13. Improved photoluminescence characteristics of order-disorder AlGaInP quantum wells at room and elevated temperatures

    Science.gov (United States)

    Mukherjee, Kunal; Deotare, Parag B.; Fitzgerald, Eugene A.

    2015-04-01

    A set of nominally undoped CuPt-B type ordered (AlxGa1-x)0.5In0.5P quantum-wells with disordered (Al0.7Ga0.3)0.5In0.5P barriers were grown and characterized using transmission electron microscopy and photoluminescence spectroscopy. Such structures are potentially beneficial for light emitting devices due to the possibility of greater carrier confinement, reduced scattering into the indirect valleys, and band-offset adjustment beyond what is possible with strain and composition. Furthermore, the possibility of independently tuning the composition and the order-parameter of the quantum-well allows for the decoupling of the carrier confinement and the aluminum content and aids in the identification of carrier loss mechanisms. In this study, sharp order-disorder interfaces were achieved via the control of growth temperature between 650 °C and 750 °C using growth pauses. Improved high-temperature (400 K) photoluminescence intensity was obtained from quantum-wells with ordered Ga0.5In0.5P as compared to disordered Ga0.5In0.5P due to greater confinement. Additionally, in the ordered samples with a higher Al/Ga ratio to counter the band-gap reduction, the photoluminescence intensity at high temperature was as bright as that from conventional disordered heterostructures and had slightly improved wavelength stability. Room-temperature time-resolved luminescence measurements indicated a longer radiative lifetime in the ordered quantum-well with reduced scattering into the barrier. These results show that in samples of good material quality, the property controlling the luminescence intensity is the carrier confinement and not the presence of ordering or the aluminum content.

  14. Improved photoluminescence characteristics of order-disorder AlGaInP quantum wells at room and elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Kunal; Fitzgerald, Eugene A. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Deotare, Parag B. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2015-04-06

    A set of nominally undoped CuPt-B type ordered (Al{sub x}Ga{sub 1−x}){sub 0.5}In{sub 0.5}P quantum-wells with disordered (Al{sub 0.7}Ga{sub 0.3}){sub 0.5}In{sub 0.5}P barriers were grown and characterized using transmission electron microscopy and photoluminescence spectroscopy. Such structures are potentially beneficial for light emitting devices due to the possibility of greater carrier confinement, reduced scattering into the indirect valleys, and band-offset adjustment beyond what is possible with strain and composition. Furthermore, the possibility of independently tuning the composition and the order-parameter of the quantum-well allows for the decoupling of the carrier confinement and the aluminum content and aids in the identification of carrier loss mechanisms. In this study, sharp order-disorder interfaces were achieved via the control of growth temperature between 650 °C and 750 °C using growth pauses. Improved high-temperature (400 K) photoluminescence intensity was obtained from quantum-wells with ordered Ga{sub 0.5}In{sub 0.5}P as compared to disordered Ga{sub 0.5}In{sub 0.5}P due to greater confinement. Additionally, in the ordered samples with a higher Al/Ga ratio to counter the band-gap reduction, the photoluminescence intensity at high temperature was as bright as that from conventional disordered heterostructures and had slightly improved wavelength stability. Room-temperature time-resolved luminescence measurements indicated a longer radiative lifetime in the ordered quantum-well with reduced scattering into the barrier. These results show that in samples of good material quality, the property controlling the luminescence intensity is the carrier confinement and not the presence of ordering or the aluminum content.

  15. Hydrothermal synthesis of two photoluminescent nitrogen-doped graphene quantum dots emitted green and khaki luminescence

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaohua; Zuo, Xiaoxi; Hu, Ruiping; Xiao, Xin; Liang, Yong; Nan, Junmin, E-mail: jmnan@scnu.edu.cn

    2014-10-15

    A simple and effective chemical synthesis of the photoluminescent nitrogen-doped graphene quantum dots (N-GQDs) biomaterial is reported. Using the hydrothermal treatment of graphene oxide (GO) in the presence of hydrogen peroxide (H{sub 2}O{sub 2}) and ammonia, the N-GQDs are synthesized through H{sub 2}O{sub 2} exfoliating the GO into nanocrystals with lateral dimensions and ammonia passivating the generated active surface. Then, after a dialytic separation, two water-soluble N-GQDs with average size of about 2.1 nm/6.2 nm, which emit green/khaki luminescence and exhibit excitation dependent/independent photoluminescence (PL) behaviors, are obtained. In addition, it is also demonstrated that these two N-GQDs are stable over a broad pH range and have the upconversion PL property, showing this approach provides a simple and effective method to synthesize the functional N-GQDs. - Highlights: • Nitrogen-doped graphene quantum dots (N-GQDs) are prepared by hydrothermal routine. • Two N-GQDs with different size distribution emit green/khaki photoluminescence. • Two N-GQDs exhibit excitation-dependent/independent photoluminescence behaviors.

  16. Brightly photoluminescent phosphor materials based on silicon quantum dots with oxide shell passivation.

    Science.gov (United States)

    Tu, Chang-Ching; Zhang, Qifeng; Lin, Lih Y; Cao, Guozhong

    2012-01-02

    We demonstrate silicon-based phosphor materials which exhibit bright photoluminescence from near-infra-red to green. The colloidal composites which are composed of silicon quantum dots (SiQDs) attached on micro-size silicon particles are synthesized by electrochemical etching of silicon wafers and then dispersed in ethanol. Subsequently, isotropic etching by HF/HNO3 mixture controls the size so as the emission wavelength of SiQDs, and forms an oxide passivating shell. The phosphors can further react with alkoxysilanes to form a stable suspension in non-polar solvents for solution-processing. The resulting red-light-emitting SiQD-based phosphors in chloroform exhibit photoluminescence external quantum efficiency of 15.9%. Their thin films can be efficiently excited by InGaN light-emitting diodes and are stable in room condition.

  17. Femtosecond pulsed laser ablation in microfluidics for synthesis of photoluminescent ZnSe quantum dots

    Science.gov (United States)

    Yang, Chao; Feng, Guoying; Dai, Shenyu; Wang, Shutong; Li, Guang; Zhang, Hua; Zhou, Shouhuan

    2017-08-01

    A simple but new toxic chemical free method, Femtosecond Laser Ablation in Microfluidics (FLAM) was proposed for the first time. ZnSe quantum dots of 4-6 nm were synthesized and with the use of hyperbranched Polyethyleneimine (PEI) as both structural and functional coated layer. These aqueous nanosized micelles consisting of quantum dots exhibit deep defect states emission of bright green light centered at 500 nm. A possible mechanism for the enhanced board band emission was discussed. The properties of toxic matters free and enhanced photoluminescence without doped transition metal ions demonstrate an application potential for biomedical imaging.

  18. Anisotropic carrier and exciton confinement in T-shaped quantum wires revealed by magneto-photoluminescence

    DEFF Research Database (Denmark)

    Langbein, Wolfgang Werner; Gislason, Hannes; Hvam, Jørn Märcher

    1998-01-01

    The realization of one-dimensional (1D) semiconductor nanostructures with large confinement energies is of importance for device applications. Different techniques such as growth on tilted substrates (Serpentine superlattices) or prepatterned substrates (V-groove quantum wires) and the cleaved-ed...... was revealed by magneto-photoluminescence. We determine here the extension of the T-shaped quantum wire (T-QWR) state in both confining directions [110] and [001] to verify its 1D character, as shown for crescent-shaped wires...

  19. Plasmon resonance-induced photoluminescence enhancement of CdTe/Cds quantum dots thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongyu [Nanjing University of Posts and Telecommunications, Nanjing 210003 (China); National Laboratory of Solid State Microstructure and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Xu, Ling, E-mail: xuling@nju.edu.cn [National Laboratory of Solid State Microstructure and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Wu, Yangqing; Xu, Jun; Ma, Zhongyuan; Chen, Kunji [National Laboratory of Solid State Microstructure and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China)

    2016-11-30

    Highlights: • CdTe/CdS quantum dots/Au nano-rods nano-composite films were fabricated. • PL intensity of the quantum dots films was enhanced due to Au nanorods. • Internal quantum efficiency increased due to localized surface plasmon resonance. • The lifetimes of quantum dots films decreased after interaction with Au nano-rods. - Abstract: CdTe/CdS quantum dots/Au nano-rods nano-composite films were fabricated on planar Si substrates. The optical properties of all samples were investigated and the corresponding simulations were studied. It was found that the photoluminescence intensity of the CdTe/CdS quantum dots films was enhanced about 9-fold after the incorporation of Au nano-rods, the internal quantum efficiency increased from 24.3% to 35.2% due to the localized surface plasmon resonance. The time-resolved luminescence decay curves showed that the lifetimes of CdTe/CdS quantum dots films decreased to 2.8 ns after interaction with Au nano-rods. The results of finite-difference time-domain simulation indicated that Au nano-rods induced the localization of electric field, which enhanced the PL intensity of quantum dots films in the vicinity of Au nano-rods.

  20. Synthesis of silicon quantum dots showing high quantum efficiency.

    Science.gov (United States)

    Cho, Bomin; Baek, Sangsoo; Woo, Hee-Gweon; Sohn, Honglae

    2014-08-01

    Quantum efficiencies of Si quantum dots (QDs) have been investigated from the reaction of magnesium silicide and ammonium chloride. The change of quantum yield and optical characterization of Si QDs are measured depending on the reaction time. Highly luminescent Si QDs were obtained as the reaction time increased. Absorption measurement indicated that the Si QDs consisted of only silicon and hydrogen atom. Optical characterizations of Si QDs were measured by UV-Vis and PL spectroscopy. The size distribution and orientation of Si QDs were measured by TEM and XRD. TEM image displays the spherical Si QDs with the size of 3-4 nm. As the reaction time increased, Si QDs grew and their emission wavelength shifted to the longer wavelength. The monotonic shift of the PL as a function of excitation wavelength resulted in the excitation of different sizes of QDs that had different optical transition energies. Photoluminescence quantum yields exceeding 60% have been achieved.

  1. Facile synthesis and photoluminescence mechanism of graphene quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ping; Zhou, Ligang; Zhang, Shenli; Pan, Wei, E-mail: sjtushelwill@sjtu.edu.cn; Shen, Wenzhong, E-mail: wzshen@sjtu.edu.cn [Laboratory of Condensed Matter Spectroscopy and Opto-Electronic Physics, and Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Wan, Neng [SEU-FEI Nano Pico Center, Key Laboratory of MEMS of Ministry of Education, School of Electronics Science and Engineering, Southeast University, Nanjing 210096 (China)

    2014-12-28

    We report a facile hydrothermal synthesis of intrinsic fluorescent graphene quantum dots (GQDs) with two-dimensional morphology. This synthesis uses glucose, concentrate sulfuric acid, and deionized water as reagents. Concentrated sulfuric acid is found to play a key role in controlling the transformation of as-prepared hydrothermal products from amorphous carbon nanodots to well-crystallized GQDs. These GQDs show typical absorption characteristic for graphene, and have nearly excitation-independent ultraviolet and blue intrinsic emissions. Temperature-dependent PL measurements have demonstrated strong electron-electron scattering and electron-phonon interactions, suggesting a similar temperature behavior of GQDs to inorganic semiconductor quantum dots. According to optical studies, the ultraviolet emission is found to originate from the recombination of electron-hole pairs localized in the C=C bonds, while the blue emission is from the electron transition of sp{sup 2} domains.

  2. Nanoscale characterization of GaN/InGaN multiple quantum wells on GaN nanorods by photoluminescence spectroscopy

    Science.gov (United States)

    Chen, Weijian; Wen, Xiaoming; Latzel, Michael; Yang, Jianfeng; Huang, Shujuan; Shrestha, Santosh; Patterson, Robert; Christiansen, Silke; Conibeer, Gavin

    2017-02-01

    GaN/InGaN multiple quantum wells (MQW) and GaN nanorods have been widely studied as a candidate material for high-performance light emitting diodes. In this study, GaN/InGaN MQW on top of GaN nanorods are characterized in nanoscale using confocal microscopy associated with photoluminescence spectroscopy, including steady-state PL, timeresolved PL and fluorescence lifetime imaging (FLIM). Nanorods are fabricated by etching planar GaN/InGaN MQWs on top of a GaN layer on a c-plane sapphire substrate. Photoluminescence efficiency from the GaN/InGaN nanorods is evidently higher than that of the planar structure, indicating the emission improvement. Time-resolved photoluminescence (TRPL) prove that surface defects on GaN nanorod sidewalls have a strong influence on the luminescence property of the GaN/InGaN MWQs. Such surface defects can be eliminated by proper surface passivation. Moreover, densely packed nanorod array and sparsely standing nanorods have been studied for better understanding the individual property and collective effects from adjacent nanorods. The combination of the optical characterization techniques guides optoelectronic materials and device fabrication.

  3. Photoluminescence from quantum dots in cubic GaN/InGaN/GaN double heterostructures

    Science.gov (United States)

    Husberg, O.; Khartchenko, A.; As, D. J.; Vogelsang, H.; Frey, T.; Schikora, D.; Lischka, K.; Noriega, O. C.; Tabata, A.; Leite, J. R.

    2001-08-01

    We have measured photoluminescence spectra of molecular-beam-epitaxy-grown cubic GaN/InxGa1-xN/GaN double heterostructures with x between 0.09 and 0.33. We observe a luminescence peak at about 2.3-2.4 eV which is almost independent of the InGaN layer composition. High-resolution x-ray diffraction measurements revealed a pseudomorphic In-rich phase with x=0.56±0.02 embedded in the InGaN layers. Including strain effects we calculate a gap energy Eg=2.13 eV of this phase. In cubic InGaN, spontaneous polarization and strain-induced piezoelectric fields are negligible. Therefore, the observed difference between the luminescence energy and the gap of the In-rich phase is assumed to be due to the localization of excitons at quantum-dot-like structures with a size of about 15 nm.

  4. Exploration of CdTe quantum dots as mesoscale pressure sensors via time-resolved shock-compression photoluminescent emission spectroscopy

    Science.gov (United States)

    Kang, Zhitao; Banishev, Alexandr A.; Lee, Gyuhyon; Scripka, David A.; Breidenich, Jennifer; Xiao, Pan; Christensen, James; Zhou, Min; Summers, Christopher J.; Dlott, Dana D.; Thadhani, Naresh N.

    2016-07-01

    The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as particulate media. In this work, the time-resolved laser-excited photoluminescence response of QDs to shock-compression was investigated to explore their utilization as mesoscale sensors for pressure measurements and in situ diagnostics during shock loading experiments. Laser-driven shock-compression experiments with steady-state shock pressures ranging from 2.0 to 13 GPa were performed on nanocomposite films of CdTe QDs dispersed in a soft polyvinyl alcohol polymer matrix and in a hard inorganic sodium silicate glass matrix. Time-resolved photoluminescent emission spectroscopy was used to correlate photoluminescence changes with the history of shock pressure and the dynamics of the matrix material surrounding the QDs. The results revealed pressure-induced blueshifts in emitted wavelength, decreases in photoluminescent emission intensity, reductions in peak width, and matrix-dependent response times. Data obtained for these QD response characteristics serve as indicators for their use as possible time-resolved diagnostics of the dynamic shock-compression response of matrix materials in which such QDs are embedded as in situ sensors.

  5. Exploration of CdTe quantum dots as mesoscale pressure sensors via time-resolved shock-compression photoluminescent emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Zhitao [Georgia Tech Research Institute, Georgia Institute of Technology, Atlanta, Georgia 30332-0826 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States); Banishev, Alexandr A.; Christensen, James; Dlott, Dana D. [School of Chemical Sciences and Fredrick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Lee, Gyuhyon; Scripka, David A.; Breidenich, Jennifer; Summers, Christopher J.; Thadhani, Naresh N., E-mail: naresh.thadhani@mse.gatech.edu [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States); Xiao, Pan [LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States); Zhou, Min [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States)

    2016-07-28

    The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as particulate media. In this work, the time-resolved laser-excited photoluminescence response of QDs to shock-compression was investigated to explore their utilization as mesoscale sensors for pressure measurements and in situ diagnostics during shock loading experiments. Laser-driven shock-compression experiments with steady-state shock pressures ranging from 2.0 to 13 GPa were performed on nanocomposite films of CdTe QDs dispersed in a soft polyvinyl alcohol polymer matrix and in a hard inorganic sodium silicate glass matrix. Time-resolved photoluminescent emission spectroscopy was used to correlate photoluminescence changes with the history of shock pressure and the dynamics of the matrix material surrounding the QDs. The results revealed pressure-induced blueshifts in emitted wavelength, decreases in photoluminescent emission intensity, reductions in peak width, and matrix-dependent response times. Data obtained for these QD response characteristics serve as indicators for their use as possible time-resolved diagnostics of the dynamic shock-compression response of matrix materials in which such QDs are embedded as in situ sensors.

  6. Investigation of reactive-ion-etch-induced damage of InP/InGaAs multiple quantum wells by photoluminescence

    DEFF Research Database (Denmark)

    Steffensen, O. M.; Birkedal, Dan; Hanberg, J.

    1995-01-01

    The effects of CH4/H2 reactive ion etching (RIE) on the optical properties of an InP/InGaAs multiple-quantum-well structure have been investigated by low-temperature photoluminescence (PL). The structure consisted of eight InGaAs quantum wells, lattice matched to InP, with nominal thicknesses of 0...

  7. Magnetic enhancement of photoluminescence from blue-luminescent graphene quantum dots

    Science.gov (United States)

    Chen, Qi; Shi, Chentian; Zhang, Chunfeng; Pu, Songyang; Wang, Rui; Wu, Xuewei; Wang, Xiaoyong; Xue, Fei; Pan, Dengyu; Xiao, Min

    2016-02-01

    Graphene quantum-dots (GQDs) have been predicted and demonstrated with fascinating optical and magnetic properties. However, the magnetic effect on the optical properties remains experimentally unexplored. Here, we conduct a magneto-photoluminescence study on the blue-luminescence GQDs at cryogenic temperatures with magnetic field up to 10 T. When the magnetic field is applied, a remarkable enhancement of photoluminescence emission has been observed together with an insignificant change in circular polarization. The results have been well explained by the scenario of magnetic-field-controlled singlet-triplet mixing in GQDs owing to the Zeeman splitting of triplet states, which is further verified by temperature-dependent experiments. This work uncovers the pivotal role of intersystem crossing in GQDs, which is instrumental for their potential applications such as light-emitting diodes, photodynamic therapy, and spintronic devices.

  8. Femtosecond pulsed laser ablation in microfluidics for synthesis of photoluminescent ZnSe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chao, E-mail: chaoyangscu@gmail.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Feng, Guoying, E-mail: guoing_feng@scu.edu.cn [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Dai, Shenyu, E-mail: 232127079@qq.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Wang, Shutong, E-mail: wangshutong.scu@gmail.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Li, Guang, E-mail: 632524844@qq.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Zhang, Hua [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Zhou, Shouhuan, E-mail: zhoush@scu.edu.cn [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); North China Research Institute of Electro-Optics, 4 Jiuxianqiao Street, Chaoyang District, Beijing 100015 (China)

    2017-08-31

    Highlights: • A novel method for synthesis and coating of quantum dots by ultrafast laser pulses. • Mild and “green” synthesis method without toxic chemicals. • Enhanced bright green light emission without doped transition metal ions. • Ultrafast laser and coating layer enhanced the emission originated from defects. - Abstract: A simple but new toxic chemical free method, Femtosecond Laser Ablation in Microfluidics (FLAM) was proposed for the first time. ZnSe quantum dots of 4–6 nm were synthesized and with the use of hyperbranched Polyethyleneimine (PEI) as both structural and functional coated layer. These aqueous nanosized micelles consisting of quantum dots exhibit deep defect states emission of bright green light centered at 500 nm. A possible mechanism for the enhanced board band emission was discussed. The properties of toxic matters free and enhanced photoluminescence without doped transition metal ions demonstrate an application potential for biomedical imaging.

  9. In-situ Evidence of the Redox-State Dependence of Photoluminescence in Graphene Quantum Dots.

    Science.gov (United States)

    Barrera, Joaquin; Ibañez, David; Heras, Aranzazu; Ruiz, Virginia; Colina, Alvaro

    2017-01-19

    Changes in the optical properties of graphene quantum dots (GQD) during electrochemical reduction and oxidation were investigated by photoluminescence (PL) spectroelectrochemistry, which provided direct in situ evidence of the dependence of GQD luminescence on their redox state. We demonstrated that GQD PL intensity was enhanced upon reduction (quantum yield increased from 0.44 to 0.55) and substantially bleached during oxidation (quantum yield ∼0.12). Moreover, PL emission blue/red-shifted upon GQD reduction/oxidation, rendering information about electronic transitions involved in the redox processes, namely, the π → π* and the n → π* transitions between energy levels of the aromatic sp 2 domains and the functional groups, respectively. PL intensity changes during GQD reduction/oxidation resulted from a variation in structural changes in GQD as a result of charge injection, as corroborated by in situ Raman spectroelectrochemistry.

  10. Self-assembly and photoluminescence evolution of hydrophilic and hydrophobic quantum dots in sol–gel processes

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ping, E-mail: mse_yangp@ujn.edu.cn [School of Material Science and Engineering, University of Jinan, Jinan 250022 (China); Matras-Postolek, Katarzyna [Faculty of Chemical Engineering and Technology, Cracow University of Technology, Krakow 31-155 (Poland); Song, Xueling; Zheng, Yan; Liu, Yumeng; Ding, Kun; Nie, Shijie [School of Material Science and Engineering, University of Jinan, Jinan 250022 (China)

    2015-10-15

    Graphical abstract: Highly luminescent quantum dots (QDs) with tunable photoluminescence (PL) wavelength were assembled into various morphologies including chain, hollow spheres, fibers, and ring structures through sol–gel processes. The PL properties during assembly as investigated. - Highlights: • Highly luminescent quantum dots (QDs) were synthesized from several ligands. • The evolution of PL in self-assembly via sol–gel processes was investigated. • CdTe QDs were assembled into a chain by controlling hydrolysis and condensation reactions. • Hollow spheres, fibers, and ring structures were created via CdSe/ZnS QDs in sol–gel processes. - Abstract: Highly luminescent quantum dots (QDs) with tunable photoluminescence (PL) wavelength were synthesized from several ligands to investigate the PL evolution in QD self-assembly via sol–gel processes. After ligand exchange, CdTe QDs were assembled into a chain by controlling the hydrolysis and condensation reaction of 3-mercaptopropyl-trimethoxysilane. The chain was then coated with a SiO{sub 2} shell from tetraethyl orthosilicate (TEOS). Hollow spheres, fibers, and ring structures were created from CdSe/ZnS QDs via various sol–gel processes. CdTe QDs revealed red-shifted and narrowed PL spectrum after assembly compared with their initial one. In contrast, the red-shift of PL spectra of CdSe/ZnS QDs is small. By optimizing experimental conditions, SiO{sub 2} spheres with multiple CdSe/ZnS QDs were fabricated using TEOS and MPS. The QDs in these SiO{sub 2} spheres retained their initial PL properties. This result is useful for application because of their high stability and high PL efficiency of 33%.

  11. AgCl-doped CdSe quantum dots with near-IR photoluminescence

    OpenAIRE

    Kotin, Pavel Aleksandrovich; Bubenov, Sergey Sergeevich; Mordvinova, Natalia Evgenievna; Dorofeev, Sergey Gennadievich

    2017-01-01

    We report the synthesis of colloidal CdSe quantum dots doped with a novel Ag precursor: AgCl. The addition of AgCl causes dramatic changes in the morphology of synthesized nanocrystals from spherical nanoparticles to tetrapods and finally to large ellipsoidal nanoparticles. Ellipsoidal nanoparticles possess an intensive near-IR photoluminescence ranging up to 0.9 eV (ca. 1400 nm). In this article, we explain the reasons for the formation of the ellipsoidal nanoparticles as well as the peculia...

  12. Dilute nitride InNP quantum dots: Growth and photoluminescence mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Kuang, Y. J. [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States); Takabayashi, K.; Kamiya, I. [Quantum Interface Laboratory, Toyota Technological Institute, Nagoya 468-8511 (Japan); Sukrittanon, S. [Material Science and Engineering Program, University of California, San Diego, La Jolla, California 92093 (United States); Pan, J. L.; Tu, C. W. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States)

    2014-10-27

    Self-assembled dilute nitride InNP quantum dots (QDs) in GaP matrix grown under the Stranski-Krastanov mode by gas-source molecular beam epitaxy are studied. The N-related localized states inside the InNP QDs provide a spatially direct recombination channel, in contrast to the spatially indirect channel through the strained In(N)P QDs/GaP interface states. The N incorporation into InP QDs therefore causes a blueshift and double-peak features in photoluminescence, which are not observed in other dilute nitride materials.

  13. Coupling effects on photoluminescence of exciton states in asymmetric quantum dot molecules.

    Science.gov (United States)

    Fino, Nelson R; Camacho, Angela S; Ramírez, Hanz Y

    2014-01-01

    We present a theoretical study of photoluminescence from exciton states in InAs/GaAs asymmetric dot pairs, where interdot coupling is reached via magnetic field in the Faraday configuration. Electronic structure is obtained by finite element calculations, and Coulomb effects are included using a perturbative approach. According to our simulated spectra, bright excited states may become optically accessible at low temperatures in hybridization regimes where intermixing with the ground state is achieved. Our results show effective magnetic control on the energy, polarization and intensity of emitted light, and suggest these coupled nanostructures as relevant candidates for implementation of quantum optoelectronic devices.

  14. Time-resolved photoluminescence properties of semiconductor quantum dot superlattices of different microcrystal shapes

    Energy Technology Data Exchange (ETDEWEB)

    Chae, Weon-Sik, E-mail: wschae@kbsi.re.kr; Choi, Eunjin; Ku Jung, Yun [Korea Basic Science Institute, Gangneung 210-702 (Korea, Republic of); Jung, Jin-Seung [Department of Chemistry, Gangneung-Wonju National University, Gangneung 210-702 (Korea, Republic of); Lee, Jin-Kyu [Department of Chemistry, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-04-14

    We report time-resolved photoluminescence properties on semiconductor quantum dot (QD) superlattices (SLs) using PL lifetime imaging microscopy at a single particle level. PL lifetime imaging technique clearly reveals that different shaped QD SL microcrystals have different time-resolved PL characteristics. The faceted SL microcrystals consisted of well-organized QDs showed faster recombination rates than those of the spherical microparticles including randomly organized QDs, which can be explained by the different degree of energetic couplings among component QDs due to different packing fraction.

  15. Studying of the photoluminescence characteristics of AgInS2 quantum dots

    Science.gov (United States)

    Yang, Fan; Wang, Yinghui; Gao, Jiechao; Sui, Ning; Liu, Qinghui; Wang, Yue; Liu, Liwei; Zou, Lu; Kang, Zhihui; Zhang, Hanzhuang

    2015-03-01

    The optical properties of AgInS2 quantum dots (QDs), with the average size being 5 nm, are studied in detail. The photoluminescence (PL) of AgInS2 QDs in solution and aggregation state exhibits an unusual temperature-dependent peak shift behaviour. Therefore, the relaxation process of excited QDs is detected using transient absorption technique, which shows that two kinds of emission states (involving the exciton state and trapping state) participate in the PL process of QDs. The emission of trapping state is expected to play an important role in the temperature-dependent evolution of PL peak.

  16. The dual roles of functional groups in the photoluminescence of graphene quantum dots

    Science.gov (United States)

    Wang, Shujun; Cole, Ivan S.; Zhao, Dongyuan; Li, Qin

    2016-03-01

    The photoluminescent properties of graphene nanoparticle (named graphene quantum dots) have attracted significant research attention in recent years owing to their profound application potential. However, the photoluminescence (PL) origin of this class of nanocarbons is still unclear. In this paper, combining direct experimental evidence enabled by a facile size-tunable oxygenated graphene quantum dots (GQDs) synthesis method and theoretical calculations, the roles of the aromatic core, functional groups and disordered structures (i.e. defects and sp3 carbon) in the PL of oxygenated GQDs are elucidated in detail. In particular, we found that the functional groups on GQDs play dual roles in the overall emission: (1) they enable π* --> n and σ* --> n transitions, resulting in a molecular type of PL, spectrally invariable with change of particle size or excitation energy; (2) similar to defects and sp3 carbon, functional groups also induce structural deformation to the aromatic core, leading to mid-gap states or, in other words, energy traps, causing π* --> mid-gap states --> π transitions. Therefore, functional groups contribute to both the blue edge and the red shoulder of GQDs' PL spectra. The new insights on the role of functional groups in PL of fluorescent nanocarbons will enable better designs of this new class of materials.The photoluminescent properties of graphene nanoparticle (named graphene quantum dots) have attracted significant research attention in recent years owing to their profound application potential. However, the photoluminescence (PL) origin of this class of nanocarbons is still unclear. In this paper, combining direct experimental evidence enabled by a facile size-tunable oxygenated graphene quantum dots (GQDs) synthesis method and theoretical calculations, the roles of the aromatic core, functional groups and disordered structures (i.e. defects and sp3 carbon) in the PL of oxygenated GQDs are elucidated in detail. In particular, we found

  17. Excitation density dependence of the photoluminescence from Cd{sub x}Hg{sub 1-x}Te multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Tonheim, C R; Selvig, E; Nicolas, S; Breivik, M; Haakenaasen, R [Norwegian Defence Research Establishment, PO Box 25, N-2027 Kjeller (Norway); Gunnaes, A E [Department of Physics, University of Oslo, Boks 1048 Blindern, N-0316 Oslo (Norway)], E-mail: celin.tonheim@ffi.no

    2008-03-15

    A study of the photoluminescence from a four-period Cd{sub x}Hg{sub 1-x}Te multiple quantum well structure at 11 K as a function of excitation density is presented. High-resolution X-ray diffraction and transmission electron microscopy revealed that the quantum well structure is of high quality. This was supported by the narrow photoluminescence peak originating in the ground state electron - heavy hole transition, with a full width at half maximum of only 7.4 meV for an excitation density of 1.3 W/cm{sup 2}. When the excitation density was increased from 1.3 to 23.4 W/cm{sup 2}, the peak position was shifted toward higher energy by 2.6 meV and the full width at half maximum increased from 7.4 to 10.9 meV.

  18. Excitation wavelength dependence of the photoluminescence quantum yield and decay behavior of CdSe/CdS quantum dot/quantum rods with different aspect ratios.

    Science.gov (United States)

    Geißler, D; Würth, C; Wolter, C; Weller, H; Resch-Genger, U

    2017-05-17

    The excitation wavelength (λexc) dependence of the photoluminescence (PL) quantum yield (ΦPL) and decay behavior (τPL) of a series of CdSe/CdS quantum dot/quantum rods (QDQRs), consisting of the same spherical CdSe core and rod-shaped CdS shells, with aspect ratios ranging from 2 to 20 was characterized. λexc between 400-565 nm were chosen to cover the first excitonic absorption band of the CdSe core material, the onset of absorption of the CdS shell, and the region of predominant shell absorption. A strong λexc dependence of relative and absolutely measured ΦPL and τPL was found particularly for the longer QDQRs with higher aspect ratios. This is attributed to combined contributions from a length-dependent shell-to-core exciton localization efficiency, an increasing number of defect states within the shell for the longest QDQRs, and probably also the presence of absorbing, yet non-emitting shell material. Although the ΦPL values of the QDQRs decrease at shorter wavelength, the extremely high extinction coefficients introduced by the shell outweigh this effect, leading to significantly higher brightness values at wavelengths below the absorption onset of the CdS shell compared with direct excitation of the CdSe cores. Moreover, our results present also an interesting example for the comparability of absolutely measured ΦPL using an integrating sphere setup and ΦPL values measured relative to common ΦPL standards, and underline the need for a correction for particle scattering for QDQRs with high aspect ratios.

  19. Photoluminescence study of InGaN/GaN double quantum wells with varying barrier widths

    CERN Document Server

    Ryu, M Y; Shin, E J; Lee, J I; Yu, S K; Oh, E S; Park, Y J; Park, H S; Kim, T I

    2000-01-01

    We report the results of photoluminescence (PL) and time-resolved PL studies on InGaN/GaN double quantum well (DQW) samples with different barrier widths. The barrier-width dependence of the PL emission energy and intensity are discussed. The PL as a function of excitation density can be well explained in terms of the quantum-confined Stark effect (QCSE). The temporal behavior of the PL was also studied. As the barrier width increases, the decay times tau sub 1 and tau sub 2 , decrease from 1.02 ns and 6.99 ns to 0.32 ns and 1.09 ns, respectively. The PL efficiency and the decay lifetime depend on the barrier width.

  20. Temperature dependence of the photoluminescence of MnS/ZnS core—shell quantum dots

    Science.gov (United States)

    Fang, Dai-Feng; Ding, Xing; Dai, Ru-Cheng; Zhao, Zhi; Wang, Zhong-Ping; Zhang, Zeng-Ming

    2014-12-01

    The temperature dependence of the photoluminescence (PL) from MnS/ZnS core—shell quantum dots is investigated in a temperature range of 8 K-300 K. The orange emission from the 4T1 → 6A1 transition of Mn2+ ions and the blue emission related to the trapped surface state are observed in the MnS/ZnS core—shell quantum dots. As the temperature increases, the orange emission is shifted toward a shorter wavelength while the blue emission is shifted towards the longer wavelength. Both the orange and blue emissions reduce their intensities with the increase of temperature but the blue emission is quenched faster. The temperature-dependent luminescence intensities of the two emissions are well explained by the thermal quenching theory.

  1. Wavelength-tunable photoluminescence of ZnSe quantum dot micelles synthesized by femtosecond laser ablation in microfluidics

    Science.gov (United States)

    Yang, Chao; Feng, Guoying; Wang, Shutong; Dai, Jiangyun; Zhang, Yuqin; Zhou, Shouhuan

    2017-09-01

    Aqueous ZnSe quantum dots were synthesized by femtosecond laser ablation in microfluidics (FLAM). Hyperbranched polyethylenimine (PEI) was used to form quantum dot micelles which exhibited wavelength-tunable photoluminescence of bright visible light with the variation of pH values. The emission was attributed to the radiative deep levels introduced by the defect states. The emission peak center exhibited a blue shift as much as 25 nm to the shorter band. A possible band gap expansion mechanism for the photoluminescence wavelength tunability was discussed.

  2. Photoluminescence Study of Plasma-Induced Damage of GaInN Single Quantum Well

    Science.gov (United States)

    Izumi, Shouichiro; Minami, Masaki; Kamada, Michiru; Tatsumi, Tetsuya; Yamaguchi, Atsushi A.; Ishikawa, Kenji; Hori, Masaru; Tomiya, Shigetaka

    2013-08-01

    Plasma-induced damage (PID) due to Cl2/SiCl4/Ar plasma etching of the GaN capping layer (CAP)/GaInN single quantum well (SQW)/GaN structure was investigated by conventional photoluminescence (PL), transmission electron microscopy (TEM), and time-resolved and temperature-dependent photoluminescence (TRPL). SQW PL intensity remained constant initially, although plasma etching of the CAP layer proceeded, but when the etching thickness reached a certain amount (˜60 nm above the SQW), PL intensity started to decrease sharply. On the other hand, TEM observations show that the physical damage (structural damage) was limited to the topmost surface region. These findings can be explained by the results of TRPL studies, which revealed that there exist two different causes of PID. One is an increase in the number of nonradiative recombination centers, which mainly affects the PL intensity. The other is an increase in the quantum level fluctuation owing mainly to physical damage.

  3. Quantum-confined photoluminescence from size-controlled boron doped nanocrystalline-Si:H/a-SiC{sub x}:H superlattice

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jun; Ni, Jian, E-mail: elsevier_jianni@163.com; Zhang, JianJun; Liu, Qun; Zhang, XiaoDan; Zhao, Ying

    2014-12-31

    Boron doped nanocrystalline-Si:H/a-SiC{sub x}:H (nc-Si:H/a-SiC{sub x}:H) quantum dot superlattice has been prepared by plasma enhanced chemical vapor deposition at a low temperature of 150 °C. This method for fabricating superlattice allows controlling both the size and density of Si quantum dots in potential well and the characteristics of potential barrier without subsequent annealing treatment. Cross-section high resolution transmission electron microscopy investigations confirm the periodic multi-layer structure of silicon quantum dots (∼ 2 nm diameter) separated by a-SiC{sub x}:H matrix (2–3 nm thickness) with sharp interface. With strong blue photoluminescence and high perpendicular conductivity, boron doped nc-Si:H/a-SiC{sub x}:H quantum dot superlattice shows great advantages in obtaining applicable blue light emission. - Highlights: • Boron-doped nanocrystalline-Si:H/a-SiC{sub x}:H superlattice was fabricated by PECVD. • Sharp well/barrier interface and relatively high density of Si QDs achieved simultaneously. • Room temperature blue photoluminescence is imputable of the quantum confinement effects.

  4. Carrier trapping induced abnormal temperature dependent photoluminescence properties of novel sandwiched structure InGaN quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    He, Juan; Li, Ding; Rajabi, K.; Yang, Wei; Hu, Xiaodong [State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Liu, Lei [Suzhou Institute of Nano-tech and Nano-bionics, CAS, Suzhou 215125 (China)

    2014-04-15

    A dual-wavelength LED sample with novel sandwiched structure in high-In-content MQWs is studied by temperature dependent photoluminescence (TDPL) and the abnormal temperature dependence of emission intensity is obtained. The novel MQWs structure which contains staggered quantum wells and an ultra-thin InN interlayer in the wells shows better luminescence property than the reference sample which has conventional quantum wells. Under 325 nm continuous wave laser excitation the LED sample of novel structure exhibits unexpected increasing luminescence intensity as temperature goes up from 140 K to 220 K and reaches its maximum at 220 K. This could be attributed to (1) the carrier redistribution and the novel sandwiched MQWs' high carrier trapping capability; (2) the intrinsic emission property of the MQWs enhanced by improvement of electron-hole overlap and reduction of quantum confined Stark effect (QCSE) and compositional fluctuation. TDPL under 405 nm laser excitation is also measured to support this view. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Control of the external photoluminescent quantum yield of emitters coupled to nanoantenna phased arrays

    Science.gov (United States)

    Guo, Ke; Lozano, Gabriel; Verschuuren, Marc A.; Gómez Rivas, Jaime

    2015-08-01

    Optical losses in metals represent the largest limitation to the external quantum yield of emitters coupled to plasmonic antennas. These losses can be at the emission wavelength, but they can be more important at shorter wavelengths, i.e., at the excitation wavelength of the emitters, where the conductivity of metals is usually lower. We present accurate measurements of the absolute external photoluminescent quantum yield of a thin layer of emitting material deposited over a periodic nanoantenna phased array. Emission and absorptance measurements of the sample are performed using a custom-made setup including an integrating sphere and variable angle excitation. The measurements reveal a strong dependence of the external quantum yield on the angle at which the optical field excites the sample. Such behavior is attributed to the coupling between far-field illumination and near-field excitation mediated by the collective resonances supported by the array. Numerical simulations confirm that the inherent losses associated with the metal can be greatly reduced by selecting an optimum angle of illumination, which boosts the light conversion efficiency in the emitting layer. This combined experimental and numerical characterization of the emission from plasmonic arrays reveals the need to carefully design the illumination to achieve the maximum external quantum yield.

  6. Synthesis of highly photoluminescent carbon dots via citric acid and Tris for iron(III) ions sensors and bioimaging.

    Science.gov (United States)

    Zhou, Ming; Zhou, Zhulong; Gong, Aihua; Zhang, Yan; Li, Qijun

    2015-10-01

    In this work, high quantum yield and strong photoluminescent carbon quantum dots (C-QDs) are successfully synthesized via a facile and green hydrothermal method using citric acid and Tris as precursors. The as-synthesized C-QDs with a quantum yield (QY) as high as 52% were characterized by UV, FT-IR, TEM, XPS and fluorescence spectroscope. TEM results show that C-QDs are mono-dispersed spherical particles and the diameter distribution of C-QDs is 2.8±1.1 nm. The extraordinary photoluminescent properties and low cytotoxicity of C-QDs were obtained through optical property characterization and cytotoxicity assay. In addition, we found that the as-prepared C-QDs had a high affinity for Fe(3+) ions and the response toward Fe(3+) ions was highly linear (R(2)=0.997) over the concentration range from 2 to 50 μM, which could provide an effective platform for portable detection of Fe(3+) ions. Also, it is demonstrated that the photoluminescent C-QDs display hypotoxicity and are biocompatible for use as biosensors in living cells. Copyright © 2015. Published by Elsevier B.V.

  7. Role of C–N Configurations in the Photoluminescence of Graphene Quantum Dots Synthesized by a Hydrothermal Route

    Science.gov (United States)

    Permatasari, Fitri Aulia; Aimon, Akfiny Hasdi; Iskandar, Ferry; Ogi, Takashi; Okuyama, Kikuo

    2016-01-01

    Graphene quantum dots (GQDs) containing N atoms were successfully synthesized using a facile, inexpensive, and environmentally friendly hydrothermal reaction of urea and citric acid, and the effect of the GQDs’ C–N configurations on their photoluminescence (PL) properties were investigated. High-resolution transmission electron microscopy (HR-TEM) images confirmed that the dots were spherical, with an average diameter of 2.17 nm. X-ray photoelectron spectroscopy (XPS) analysis indicated that the C–N configurations of the GQDs substantially affected their PL intensity. Increased PL intensity was obtained in areas with greater percentages of pyridinic-N and lower percentages of pyrrolic-N. This enhanced PL was attributed to delocalized π electrons from pyridinic-N contributing to the C system of the GQDs. On the basis of energy electron loss spectroscopy (EELS) and UV-Vis spectroscopy analyses, we propose a PL mechanism for hydrothermally synthesized GQDs. PMID:26876153

  8. Enhanced photoluminescence of corrugated Al2O3 film assisted by colloidal CdSe quantum dots.

    Science.gov (United States)

    Bai, Zhongchen; Hao, Licai; Zhang, Zhengping; Huang, Zhaoling; Qin, Shuijie

    2017-05-19

    We present the enhanced photoluminescence (PL) of a corrugated Al2O3 film enabled by colloidal CdSe quantum dots. The colloidal CdSe quantum dots are fabricated directly on a corrugated Al2O3 substrate using an electrochemical deposition (ECD) method in a microfluidic system. The photoluminescence is excited by using a 150 nm diameter ultraviolet laser spot of a scanning near-field optical microscope. Owing to the electron transfer from the conduction band of the CdSe quantum dots to that of Al2O3, the enhanced photoluminescence effect is observed, which results from the increase in the recombination rate of electrons and holes on the Al2O3 surface and the reduction in the fluorescence of the CdSe quantum dots. A periodically-fluctuating fluorescent spectrum was exhibited because of the periodical wire-like corrugated Al2O3 surface serving as an optical grating. The spectral topographic map around the fluorescence peak from the Al2O3 areas covered with CdSe quantum dots was unique and attributed to the uniform deposition of CdSe QDs on the corrugated Al2O3 surface. We believe that the microfluidic ECD system and the surface enhanced fluorescence method described in this paper have potential applications in forming uniform optoelectronic films of colloidal quantum dots with controllable QD spacing and in boosting the fluorescent efficiency of weak PL devices.

  9. Interface and photoluminescence characteristics of graphene-(GaN/InGaN){sub n} multiple quantum wells hybrid structure

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liancheng, E-mail: wanglc@semi.ac.cn, E-mail: lzq@semi.ac.cn, E-mail: zh.zhang@hebut.edu.cn [Engineering Product Development Pillar (EPD), Singapore University of Technology & Design (SUTD), 8 Somapah Road, Singapore 487372 (Singapore); Semiconductor Lighting Technology Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Mind Star (Beijing) Technology Co., Ltd., Zhongguancun South Street, Haidian District, No. 45 Hing Fat Building 1001, Beijing 100872 (China); Liu, Zhiqiang, E-mail: wanglc@semi.ac.cn, E-mail: lzq@semi.ac.cn, E-mail: zh.zhang@hebut.edu.cn; Tian, Ying Dong; Yi, Xiaoyan; Wang, Junxi; Li, Jinmin; Wang, Guohong [Semiconductor Lighting Technology Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Zhang, Zi-Hui, E-mail: wanglc@semi.ac.cn, E-mail: lzq@semi.ac.cn, E-mail: zh.zhang@hebut.edu.cn [Key Laboratory of Electronic Materials and Devices of Tianjin, School of Electronics and Information Engineering, Hebei University of Technology, Tianjin 300401 (China)

    2016-04-14

    The effects of graphene on the optical properties of active system, e.g., the InGaN/GaN multiple quantum wells, are thoroughly investigated and clarified. Here, we have investigated the mechanisms accounting for the photoluminescence reduction for the graphene covered GaN/InGaN multiple quantum wells hybrid structure. Compared to the bare multiple quantum wells, the photoluminescence intensity of graphene covered multiple quantum wells showed a 39% decrease after excluding the graphene absorption losses. The responsible mechanisms have been identified with the following factors: (1) the graphene two dimensional hole gas intensifies the polarization field in multiple quantum wells, thus steepening the quantum well band profile and causing hole-electron pairs to further separate; (2) a lower affinity of graphene compared to air leading to a weaker capability to confine the excited hot electrons in multiple quantum wells; and (3) exciton transfer through non-radiative energy transfer process. These factors are theoretically analysed based on advanced physical models of semiconductor devices calculations and experimentally verified by varying structural parameters, such as the indium fraction in multiple quantum wells and the thickness of the last GaN quantum barrier spacer layer.

  10. Photoluminescence spectrum changes of GaN quantum wells caused by the strong piezoelectric fields

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, H.; Calderon, A. [CICATA-IPN, Av. Legaria 694, Col. Irrigacion, 11500 Mexico D.F. (Mexico); Gonzalez de la Cruz, G. [CINVESTAV-IPN, A.P. 14-740, 07000 Mexico D.F. (Mexico)

    2006-07-01

    Spontaneous and piezoelectric fields are known to be the key to understanding the optical properties of nitride heterostructures. This effect modifies the electronic states in the quantum well (QW) and the emission energy in the photoluminescence (PL) spectrum. These fields induce a reduction of the oscillator strength on the transition energy between the confined electron and hole states in GaN/Al{sub x}Ga{sub 1-x}N QW's and dramatically increase the carrier life time as the QW thickness increases. In this work, we solve analytically the Schroedinger equation for moderate electric fields when the electron-hole transition energy in the QW is larger than the energy gap of the GaN. Furthermore, the large redshifts of the PL energy position and the spatial separation of the electron and hole by several times of the Bohr radius caused by the strong piezoelectric fields are explained using a triangular potential in the Schrodinger equation. The transition energy calculations between the electron-hole pair as a function of the well width with the electric field as a fitting parameter are in agreement with the measured photoluminescence energy peaks. (Author)

  11. Origin of tunable photoluminescence from graphene quantum dots synthesized via pulsed laser ablation.

    Science.gov (United States)

    Santiago, S R M; Lin, T N; Yuan, C T; Shen, J L; Huang, H Y; Lin, C A J

    2016-08-10

    A one-step synthesis of graphene quantum dots (GQDs) has been implemented using pulsed laser ablation (PLA) with carboxyl-functionalized multiwalled carbon nanotubes (MWCNTs). The synthesized GQDs with an average size smaller than 3 nm were obtained by the fragmentation of MWCNTs via oxidative cutting. The GQDs can generate tunable photoluminescence (PL) ranging from green to blue by controlling the PLA time. The PL spectrum (decay time) of the green GQDs remains unchanged under different excitation energies (emission energies), while that of the blue GQDs correlates with the excitation energy (emission energy). On the basis of the pH and temperature dependence of PL, we suggest that the localized intrinsic states associated with the sp(2) nanodomains and delocalized extrinsic states embedded on the GQD surface are responsible for blue and green emission in GQDs, respectively.

  12. Two beam photoluminescence of PbS quantum dots in polyvinyl alcohol

    Science.gov (United States)

    Babu Pendyala, Naresh; Koteswara Rao, K. S. R.

    2010-11-01

    We report the effect of dual beam excitation on the photoluminescence (PL) from PbS quantum dots in polyvinyl alcohol by using two excitation lasers, namely Ar + (514.5 nm) and He-Ne laser (670 nm). Both sources of excitation gave similar PL spectra around 1.67 eV (related to shallow traps) and 1.1 eV (related to deep traps). When both lasers were used at the same time, we found that the PL induced by each of the lasers was partly quenched by the illumination of the other laser. The proposed mechanism of this quenching effect involves traps that are populated by one specific laser excitation, being photo-ionized by the presence of the other laser. Temperature, laser intensity and modulation frequency dependent quenching efficiencies are presented in this paper. This reversible modulation has potential for optical switching and memory device applications.

  13. Highly tunable photoluminescent properties of amphiphilic conjugated block copolymers.

    Science.gov (United States)

    Park, Sang-Jae; Kang, Seung-Gu; Fryd, Michael; Saven, Jeffery G; Park, So-Jung

    2010-07-28

    We report a novel class of amphiphilic conjugated block copolymers composed of poly(3-octylthiophene) and poly(ethylene oxide) (POT-b-PEO) that exhibit highly tunable photoluminescence colors spanning from blue to red. POT-b-PEO self-assembles into various well-defined core/shell-type nanostructures as a result of its amphiphilicity. The self-assembly structure can be readily controlled by altering the solvent composition or by other external stimuli. The color change was completely reversible, demonstrating that the strategy can be used to manipulate the light-emission properties of conjugated polymers in a highly controllable manner without having to synthesize entirely new sets of molecules.

  14. Highly Photoluminescent Nitrogen-Doped Carbon Nanodots and Their Protective Effects against Oxidative Stress on Cells.

    Science.gov (United States)

    Xu, Zi-Qiang; Lan, Jia-Yi; Jin, Jian-Cheng; Dong, Ping; Jiang, Feng-Lei; Liu, Yi

    2015-12-30

    Highly photoluminescent (PL) (quantum yield = 54%) nitrogen doped carbon nanodots (C-dots) have been prepared through one-step carbonizing citric acid and tris(hydroxymethyl)aminomethane and using oleic acid as solvent. The synthesized C-dots are monodisperse with narrow size distribution (average 1.7 nm). The PL properties of C-dots are pH dependent, and hence, using C-dots as sophisticated pH sensor to detect pH values between 7 and 9 can be expected. In addition, the PL intensity of C-dots remains stable under high ionic strength. The C-dots can protect cells from oxidative stress, which shows potential to expand the biological application of C-dots, especially in medical treatment. The protective mechanism is associated with intracellular reactive oxygen species elimination and the intracellular superoxide dismutase production.

  15. Violet-to-Blue Gain and Lasing from Colloidal CdS Nanoplatelets: Low-Threshold Stimulated Emission Despite Low Photoluminescence Quantum Yield

    Energy Technology Data Exchange (ETDEWEB)

    Diroll, Benjamin T.; Talapin, Dmitri V.; Schaller, Richard D.

    2017-02-13

    Amplified spontaneous emission (ASE) and lasing from solution-processed materials are demonstrated in the challenging violet-to-blue (430–490 nm) spectral region for colloidal nanoplatelets of CdS and newly synthesized core/shell CdS/ZnS nanoplatelets. Despite modest band-edge photoluminescence quantum yields of 2% or less for single excitons, which we show results from hole trapping, the samples exhibit low ASE thresholds. Furthermore, four-monolayer CdS samples show ASE at shorter wavelengths than any reported film of colloidal quantum-confined material. This work underlines that low quantum yields for single excitons do not necessarily lead to a poor gain medium. The low ASE thresholds originate from negligible dispersion in thickness, large absorption cross sections of 2.8 × 10–14 cm–2, and rather slow (150 to 300 ps) biexciton recombination. We show that under higher-fluence excitation, ASE can kinetically outcompete hole trapping. Using nanoplatelets as the gain medium, lasing is observed in a linear optical cavity. This work confirms the fundamental advantages of colloidal quantum well structures as gain media, even in the absence of high photoluminescence efficiency.

  16. Graphene Quantum Dots-based Photoluminescent Sensor: A Multifunctional Composite for Pesticide Detection.

    Science.gov (United States)

    Zor, Erhan; Morales-Narváez, Eden; Zamora-Gálvez, Alejandro; Bingol, Haluk; Ersoz, Mustafa; Merkoçi, Arben

    2015-09-16

    Due to their size and difficulty to obtain, cost/effective biological or synthetic receptors (e.g., antibodies or aptamers, respectively), organic toxic compounds (e.g., less than 1 kDa) are generally challenging to detect using simple platforms such as biosensors. This study reports on the synthesis and characterization of a novel multifunctional composite material, magnetic silica beads/graphene quantum dots/molecularly imprinted polypyrrole (mSGP). mSGP is engineered to specifically and effectively capture and signal small molecules due to the synergy among chemical, magnetic, and optical properties combined with molecular imprinting of tributyltin (291 Da), a hazardous compound, selected as a model analyte. Magnetic and selective properties of the mSGP composite can be exploited to capture and preconcentrate the analyte onto its surface, and its photoluminescent graphene quantum dots, which are quenched upon analyte recognition, are used to interrogate the presence of the contaminant. This multifunctional material enables a rapid, simple and sensitive platform for small molecule detection, even in complex mediums such as seawater, without any sample treatment.

  17. Optical absorption, photoluminescence and structural analysis of CdS quantum dots in weak confinement

    Science.gov (United States)

    Mishra, Rakesh K.; Vedeshwar, A. G.; Tandon, R. P.

    2014-02-01

    The diffusion-controlled growth of CdS quantum dots (QDs) dispersed in a silicate glass matrix was investigated. It was found that the size of CdS QDs can be controlled by either heat treatment at various temperatures for a fixed duration or varying times at a constant temperature. Pastel yellow colored glass samples were obtained due to the presence of CdS petite crystals. X-ray diffraction (XRD) was used for determining the average dot size which varied from 3.8 to 30 nm. The typical quantum confinement effect was clearly observed from the blue shift measured in the optical absorption edge with decreasing dot size in the absorption spectroscopy. The band gap of CdS QDs ranges from 2.41 to 2.82 eV. Measured photoluminescence (PL) at an excitation wavelength of 350 nm showed the red shift of emission wavelength with increasing thermal treatment time and temperature in agreement with the increasing dot sizes. The half-width of PL spectra seems to indicate qualitatively the size distribution of dots and is consistent with the treatment parameters.

  18. Photoluminescent Hybrids of Cellulose Nanocrystals and Carbon Quantum Dots as Cytocompatible Probes for in Vitro Bioimaging.

    Science.gov (United States)

    Guo, Jiaqi; Liu, Dongfei; Filpponen, Ilari; Johansson, Leena-Sisko; Malho, Jani-Markus; Quraishi, Sakeena; Liebner, Falk; Santos, Hélder A; Rojas, Orlando J

    2017-07-10

    We present an approach to construct biocompatible and photoluminescent hybrid materials comprised of carbon quantum dots (CQDs) and TEMPO-oxidized cellulose nanocrystals (TO-CNCs). First, the amino-functionalized carbon quantum dots (NH2-CQDs) were synthesized using a simple microwave method, and the TO-CNCs were prepared by hydrochloric acid (HCl) hydrolysis followed by TEMPO-mediated oxidation. The conjugation of NH2-CQDs and TO-CNCs was conducted via carbodiimide-assisted coupling chemistry. The synthesized TO-CNC@CQD hybrid nanomaterials were characterized using X-ray photoelectron spectroscopy, cryo-transmittance electron microscopy, confocal microscopy, and fluorescence spectroscopy. Finally, the interactions of TO-CNC@CQD hybrids with HeLa and RAW 264.7 macrophage cells were investigated in vitro. Cell viability tests suggest the surface conjugation with NH2-CQDs not only improved the cytocompatibility of TO-CNCs, but also enhanced their cellular association and internalization on both HeLa and RAW 264.7 cells after 4 and 24 h incubation.

  19. Nonradiative centers in InAs quantum dots revealed by two-wavelength excited photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Kamata, N. [Department of Functional Materials Science, Saitama University, 255 Shimo-Ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570 (Japan)]. E-mail: kamata@fms.saitama-u.ac.jp; Saravanan, S. [Department of Nonlinear Science, ATR Wave Engineering. Laboratories, Kyoto 619-0288 (Japan); Zanardi Ocampo, J.M. [Department of Nonlinear Science, ATR Wave Engineering. Laboratories, Kyoto 619-0288 (Japan); Vaccaro, P.O. [Department of Nonlinear Science, ATR Wave Engineering. Laboratories, Kyoto 619-0288 (Japan); Arakawa, Y. [Research Center for Advanced Science and Technology, University of Tokyo, Tokyo 153-8505 (Japan)

    2006-04-01

    We studied nonradiative recombination centers in MBE-grown InAs/GaAs quantum dot (QD) structures with photoluminescence (PL) peak energies between 1.12 and 1.29 eV by the scheme of two-wavelength excitation. Temporally chopped below-gap excitation (BGE) light of 0.75 eV was superposed on a CW above-gap excitation light of 1.59 eV on the sample surface, and the resultant PL intensity change due to the BGE (BGE effect) was measured. Observed 25-35% decrease in PL intensity at 80-90 K implies a first discrimination of a pair of nonradiative centers activated at 0.75 eV inside the band gap of the QD region. Due to trap-filling, the BGE effect showed saturation with increasing BGE power. Its temperature dependence below 50 K was different from that of quantum wells, reflecting carrier dynamics peculiar to the QD.

  20. Composition-dependent photoluminescence properties of CuInS{sub 2}/ZnS core/shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Hua, Jie [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China); College of Information Technology, Jilin Normal University, Siping 136000, Jilin (China); Du, Yuwei; Wei, Qi [College of Information Technology, Jilin Normal University, Siping 136000, Jilin (China); Yuan, Xi; Wang, Jin [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China); College of Information Technology, Jilin Normal University, Siping 136000, Jilin (China); Zhao, Jialong [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China); Li, Haibo, E-mail: lihaibo@jlnu.edu.cn [Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, Jilin (China)

    2016-06-15

    CuInS{sub 2}/ZnS (CIS/ZnS) core/shell quantum dots (QDs) with various Cu/In ratios were synthesized using the hot-injection method, and their photoluminescence (PL) properties were investigated by measuring steady-state and time-resolved PL spectroscopy. The emission peak of the CIS/ZnS QDs were tuned from 680 to 580 nm by decreasing the Cu/In precursor ratio from 1/1 to 1/9. As the Cu/In ratio decreases, the PL lifetimes and PL quantum yields (QYs) of CIS/ZnS core/shell QDs increased firstly and then decreased. Two dominant radiative recombination processes were postulated to analyze composition-dependent PL properties, including the recombination from a quantized conduction band to deep defects state and donor-acceptor pair (DAP) recombination. The decrease of PL efficiency resulted from high density defects and traps, which formed at the interface between CIS core and ZnS shell due to the large off-stoichiometry composition. The PL intensity and peak energy for CIS/ZnS core/shell QDs as a function of temperature were also provided. The thermal quenching further confirmed that the PL emission of CIS/ZnS QDs did not come from the recombination of excitons but from the recombination of many kinds of intrinsic defects inside the QDs as emission centers.

  1. Mechanism for excitation-dependent photoluminescence from graphene quantum dots and other graphene oxide derivates: consensus, debates and challenges

    Science.gov (United States)

    Gan, Zhixing; Xu, Hao; Hao, Yanling

    2016-04-01

    Luminescent nanomaterials, with wide applications in biosensing, bioimaging, illumination and display techniques, have been consistently garnering enormous research attention. In particular, those with wavelength-controllable emissions could be highly beneficial. Carbon nanostructures, including graphene quantum dots (GQDs) and other graphene oxide derivates (GODs), with excitation-dependent photoluminescence (PL), which means their fluorescence color could be tuned simply by changing the excitation wavelength, have attracted lots of interest. However the intrinsic mechanism for the excitation-dependent PL is still obscure and fiercely debated presently. In this review, we attempt to summarize the latest efforts to explore the mechanism, including the quantum confinement effect, surface traps model, giant red-edge effect, edge states model and electronegativity of heteroatom model, as well as the newly developed synergistic model, to seek some clues to unravel the mechanism. Meanwhile the controversial difficulties for each model are further discussed. Besides this, the challenges and potential influences of the synthetic methodology and development of the materials are illustrated extensively to elicit more thought and constructive attempts toward their application.

  2. High-amplitude THz and GHz strain waves, generated by ultrafast screening of piezoelectric fields in InGaN/GaN multiple quantum wells

    DEFF Research Database (Denmark)

    Porte, Henrik; van Capel, P.J.S.; Turchinovich, Dmitry

    2010-01-01

    Screening of large built-in piezoelectric fields in InGaN/GaN quantum wells leads to high-amplitude acoustic emission. We will compare acoustic emission by quantum wells with different thicknesses with photoluminescence; indicating screening.......Screening of large built-in piezoelectric fields in InGaN/GaN quantum wells leads to high-amplitude acoustic emission. We will compare acoustic emission by quantum wells with different thicknesses with photoluminescence; indicating screening....

  3. Tunable photoluminescence of Cd free AgInS2 quantum dots: Synthesis and application for light emitting diodes

    Science.gov (United States)

    Lv, Jiufang; Liang, Xiao

    2017-10-01

    I-III-VI semiconductor quantum dots (QDs) without Cd element have attracted considerable attention in the optoelectronics device areas. Herein, we demonstrated that AgInS2 QDs with tunable photoluminescence were used for light emitting diodes (LEDs). With the increase of reaction temperature, the photoluminescence (PL) peak was monotonically red shifted from 600 to 750 nm. The temperature-dependent lifetime of the photoluminescence emission could reach to 900 ns. The successful synthesis of the AgInS2 nanocrystals with long PL lifetime provided a potential application in LEDs. The fabricated QDs LEDs exhibited a relative low turn-on voltage of 2.9 V and a maximum luminance intensity of 122 cd/m2.

  4. Photoluminescent sensing for acidic amino acids based on the disruption of graphene quantum dots/europium ions aggregates.

    Science.gov (United States)

    Zhang, Qi; Song, Chan; Zhao, Ting; Fu, Hai-Wei; Wang, Hui-Zhen; Wang, Yong-Jian; Kong, De-Ming

    2015-03-15

    A simple mix-and-detect photoluminescence method was developed for the turn-on detection of acidic amino acids. To achieve this, graphene quantum dots (GQDs), which emit both down-conversion and up-conversion photoluminescence were prepared by solvothermal synthesis. The carboxylic acid-rich surface not only increases the water solubility of the prepared GQDs, but also makes Eu(3+)-triggered GQDs aggregation possible, thus causing the photoluminescence quenching of GQDs. The quenched photoluminescence can be recovered by the competition between acidic amino acids and GQDs for Eu(3+). Under optimized conditions, sensitive and specific acidic amino acids quantitation can be achieved by utilizing the changes in either down-conversion or up-conversion photoluminescence. Up-conversion mode gives a little lower detection limit than the down-conversion one. Nearly overlapped calibration curves were obtained for the two acidic amino acids, glutamic acid (Glu) and aspartic acid (Asp), thus suggesting that the proposed method can be used not only for the quantitation of individual acidic amino acids, but also for the detection of total amount of them. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Modulation of intersubband light absorption and interband photoluminescence in double GaAs/AlGaAs quantum wells under strong lateral electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Balagula, R. M., E-mail: rmbal@spbstu.ru; Vinnichenko, M. Ya., E-mail: mvin@spbstu.ru; Makhov, I. S.; Firsov, D. A.; Vorobjev, L. E. [Peter the Great Saint-Petersburg Polytechnic University (Russian Federation)

    2016-11-15

    The effect of a lateral electric field on the mid-infrared absorption and interband photoluminescence spectra in double tunnel-coupled GaAs/AlGaAs quantum wells is studied. The results obtained are explained by the redistribution of hot electrons between quantum wells and changes in the space charge in the structure. The hot carrier temperature is determined by analyzing the intersubband light absorption and interband photoluminescence modulation spectra under strong lateral electric fields.

  6. Simultaneous Gene Delivery and Tracking through Preparation of Photo-Luminescent Nanoparticles Based on Graphene Quantum Dots and Chimeric Peptides

    OpenAIRE

    Ghafary, Soroush Moasses; Nikkhah, Maryam; Hatamie, Shadie; Hosseinkhani, Saman

    2017-01-01

    Designing suitable nano-carriers for simultaneous gene delivery and tracking is in the research priorities of the molecular medicine. Non-toxic graphene quantum dots (GQDs) with two different (green and red) emission colors are synthesized by Hummer?s method and characterized by UV-Vis, Photoluminescence (PL), Fourier Transform Infrared (FTIR) and Raman spectroscopies, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The GQDs are co...

  7. Effect of exciton oscillator strength on upconversion photoluminescence in GaAs/AlAs multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, Osamu, E-mail: kojima@phoenix.kobe-u.ac.jp; Okumura, Shouhei; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan); Akahane, Kouichi [National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei, Tokyo 184-8795 (Japan)

    2014-11-03

    We report upconversion photoluminescence (UCPL) in GaAs/AlAs multiple quantum wells. UCPL from the AlAs barrier is caused by the resonant excitation of the excitons in the GaAs well. When the quantum well has sufficient miniband width, UCPL is hardly observed because of the small exciton oscillator strength. The excitation-energy and excitation-density dependences of UCPL intensity show the exciton resonant profile and a linear increase, respectively. These results demonstrate that the observed UCPL caused by the saturated two-step excitation process requires a large number of excitons.

  8. Combined atomic force microscopy and photoluminescence imaging to select single InAs/GaAs quantum dots for quantum photonic devices.

    Science.gov (United States)

    Sapienza, Luca; Liu, Jin; Song, Jin Dong; Fält, Stefan; Wegscheider, Werner; Badolato, Antonio; Srinivasan, Kartik

    2017-07-24

    We report on a combined photoluminescence imaging and atomic force microscopy study of single, isolated self-assembled InAs quantum dots. The motivation of this work is to determine an approach that allows to assess single quantum dots as candidates for quantum nanophotonic devices. By combining optical and scanning probe characterization techniques, we find that single quantum dots often appear in the vicinity of comparatively large topographic features. Despite this, the quantum dots generally do not exhibit significant differences in their non-resonantly pumped emission spectra in comparison to quantum dots appearing in defect-free regions, and this behavior is observed across multiple wafers produced in different growth chambers. Such large surface features are nevertheless a detriment to applications in which single quantum dots are embedded within nanofabricated photonic devices: they are likely to cause large spectral shifts in the wavelength of cavity modes designed to resonantly enhance the quantum dot emission, thereby resulting in a nominally perfectly-fabricated single quantum dot device failing to behave in accordance with design. We anticipate that the approach of screening quantum dots not only based on their optical properties, but also their surrounding surface topographies, will be necessary to improve the yield of single quantum dot nanophotonic devices.

  9. Biodegradable, Elastomeric, and Intrinsically Photoluminescent Poly(Silicon-Citrates) with high Photostability and Biocompatibility for Tissue Regeneration and Bioimaging.

    Science.gov (United States)

    Du, Yuzhang; Xue, Yumeng; Ma, Peter X; Chen, Xiaofeng; Lei, Bo

    2016-02-04

    Biodegradable polymer biomaterials with intrinsical photoluminescent properties have attracted much interest, due to their potential advantages for tissue regeneration and noninvasive bioimaging. However, few of current biodegradable polymers possess tunable intrinsically fluorescent properties, such as high photostability, fluorescent lifetime, and quantum field, and strong mechanical properties for meeting the requirements of biomedical applications. Here, by a facile one-step thermal polymerization, elastomeric poly(silicone-citrate) (PSC) hybrid polymers are developed with controlled biodegradability and mechanical properties, tunable inherent fluorescent emission (up to 600 nm), high photostability (beyond 180 min for UV and six months for natural light), fluorescent lifetime (near 10 ns) and quantum yield (16%-35%), high cellular biocompatibility, and minimal inflammatory response in vivo, which provide advantages over conventional fluorescent dyes, quantum dots, and current fluorescent polymers. The promising applications of PSC hybrids for cell and implants imaging in vitro and in vivo are successfully demonstrated. The development of elastomeric PSC polymer may provide a new strategy in synthesizing new inorganic-organic hybrid photo-luminescent materials for tissue regeneration and bioimaging applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Facile synthesis and step by step enhancement of blue photoluminescence from Ag-doped ZnS quantum dots.

    Science.gov (United States)

    Sahai, Sonal; Husain, Mushahid; Shanker, Virendra; Singh, Nahar; Haranath, D

    2011-05-15

    Our results pertaining to the step by step enhancement of photoluminescence (PL) intensity from ZnS:Ag,Al quantum dots (QDs) are presented. Initially, these QDs were synthesized using a simple co-precipitation technique involving a surfactant, polyvinylpyrrolidone (PVP), in de-ionised water. It was observed that the blue PL originated from ZnS:Ag,Al QDs was considerably weak and not suitable for any practical display application. Upon UV (365 nm) photolysis, the PL intensity augmented to ~170% and attained a saturation value after ~100 min of exposure. This is attributed to the photo-corrosion mechanism exerted by high-flux UV light on ZnS:Ag,Al QDs. Auxiliary enhancement of PL intensity to 250% has been evidenced by subjecting the QDs to high temperatures (200 °C) and pressures (~120 bars) in a sulphur-rich atmosphere, which is due to the improvement in crystallanity of ZnS QDs. The origin of the bright-blue PL has been discussed. The results were supported by X-ray phase analysis, high-resolution electron microscopy and compositional evaluation. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Photoluminescence of ZnS: Mn quantum dot by hydrothermal method

    Directory of Open Access Journals (Sweden)

    Yun Hu

    2018-01-01

    Full Text Available ZnS: Mn quantum dots (QDs with the average grain size from 4.2 to 7.2 nm were synthesized by a hydrothermal method. All samples were cubic zinc blende structure (β-ZnS measured using X-ray diffraction (XRD. And the main diffraction peaks of ZnS: Mn shifted slightly towards higher angle in comparison with the intrinsic ZnS because of the substitution of Mn2+ for Zn2+. Due to the small grain size (4-7 nm effect, the poor dispersion and serious reunion phenomenon for the samples were observed from transmission electron microscopy (TEM. ZnS: Mn QDs had four peaks centered at 466, 495, 522, and 554 nm, respectively, in the photoluminescence (PL spectra, in which the band at 554 nm absent in the intrinsic ZnS: Mn is attributed to the doping of Mn2+ in the lattice sites. As the concentration of Mn2+ increasing from 0% to 0.6 at%, the intensity of the PL emission also increased. But the concentration reached 0.9 at%, quenching of PL emission occurred. The peak in ZnS: Mn QDs observed at 490 cm-1 was originated from the stretching vibration of the Mn–O bonds in the Fourier transform infrared (FTIR spectra. And the small changes about this peak compared with the previous reports at 500 cm-1 can be attributed to the formation of quantum dots. This method we utilized to synthesize ZnS: Mn QDs is very simple, low cost, and applicable for other semiconductor QD materials.

  12. Photoluminescence Quenching of CdTe Quantum Dots Generated via Glutathione-Capped Au Nanocrystals.

    Science.gov (United States)

    Zhu, Yuanna; Yang, Ping; Miao, Yanping; Cao, Yongqiang; Yang, Yang

    2015-06-01

    The photoluminescence (PL) quenching of thioglycolic acid (TGA)-capped CdTe quantum dots (QDs) by glutathione (GSH)-capped Au nanocrystals (NCs) were investigated via PL degradated measurement. It was found that the PL of the QDs with several sizes can be effectively quenched by GSH-Au NCs. The size and PL peak wavelengths of QDs have no significant impact on the quenching processing. Through the characterizations of UV-visble absorption spectrum, Zeta potential and steady-state, and time-resolved fluorescence spectroscopy, it was proved that the PL quenching of the QDs by GSH-Au NCs was attributed to static quenching caused by the formation of a QDs-Au complex. The binding parameters calculated from modified Stern-Volmer equation showed that the binding affinities between the GSH-Au NCs and CdTe QDs was in the order of 10(5) L x mol(-1), which indicated that the binding force was larger and the effective quenching occurred. The thermodynamic parameters studies revealed that the binding was characterized by positive enthalpy and positive entropy changes and hydrophobic force played a major role for QDs-Au association. In addition, all the quenching experiments were conducted in the phosphate-buffered saline (PBS) buffer solution at pH 7.4 and the investigation is expected to be applied in the biology.

  13. Effect of graphene on photoluminescence properties of graphene/GeSi quantum dot hybrid structures

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y. L.; Ma, Y. J.; Wang, W. Q.; Ding, K.; Wu, Q.; Fan, Y. L.; Yang, X. J.; Zhong, Z. Y.; Jiang, Z. M., E-mail: zmjiang@fudan.edu.cn [State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education) and Department of Physics, Fudan University, Shanghai 200433 (China); Chen, D. D.; Xu, F. [SHU-SolarE R and D Lab, Department of Physics, College of Science, Shanghai University, Shanghai 200444 (China)

    2014-07-14

    Graphene has been discovered to have two effects on the photoluminescence (PL) properties of graphene/GeSi quantum dot (QD) hybrid structures, which were formed by covering monolayer graphene sheet on the multilayer ordered GeSi QDs sample surfaces. At the excitation of 488 nm laser line, the hybrid structure had a reduced PL intensity, while at the excitation of 325 nm, it had an enhanced PL intensity. The attenuation in PL intensity can be attributed to the transferring of electrons from the conducting band of GeSi QDs to the graphene sheet. The electron transfer mechanism was confirmed by the time resolved PL measurements. For the PL enhancement, a mechanism called surface-plasmon-polariton (SPP) enhanced absorption mechanism is proposed, in which the excitation of SPP in the graphene is suggested. Due to the resonant excitation of SPP by incident light, the absorption of incident light is much enhanced at the surface region, thus leading to more exciton generation and a PL enhancement in the region. The results may be helpful to provide us a way to improve optical properties of low dimensional surface structures.

  14. Temporally and spatially resolved photoluminescence investigation of (112{sup ¯}2) semi-polar InGaN/GaN multiple quantum wells grown on nanorod templates

    Energy Technology Data Exchange (ETDEWEB)

    Liu, B.; Smith, R.; Athanasiou, M.; Yu, X.; Bai, J.; Wang, T., E-mail: t.wang@sheffield.ac.uk [Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2014-12-29

    By means of time-resolved photoluminescence (PL) and confocal PL measurements, temporally and spatially resolved optical properties have been investigated on a number of In{sub x}Ga{sub 1−x}N/GaN multiple-quantum-well (MQW) structures with a wide range of indium content alloys from 13% to 35% on (112{sup ¯}2) semi-polar GaN with high crystal quality, obtained through overgrowth on nanorod templates. With increasing indium content, the radiative recombination lifetime initially increases as expected, but decreases if the indium content further increases to 35%, corresponding to emission in the green spectral region. The reduced radiative recombination lifetime leads to enhanced optical performance for the high indium content MQWs as a result of strong exciton localization, which is different from the behaviour of c-plane InGaN/GaN MQWs, where quantum confined Stark effect plays a dominating role in emission process.

  15. The relation between photoluminescence properties and gas pressure with [0001] InGaN single quantum well systems

    Energy Technology Data Exchange (ETDEWEB)

    Tsutsumi, Toshiaki [Department of Nanosystem Sciences, Yokohama City University, Yokohama 236-0027 (Japan); Alfieri, Giovanni; Kawakami, Yoichi [Department of Electronic Science and Engineering, Kyoto University, Kyotodaigaku-katsura, Nishikyo, Kyoto 615-8510 (Japan); Micheletto, Ruggero, E-mail: ruggero@yokohama-cu.ac.jp [Department of Nanosystem Sciences, Yokohama City University, Yokohama 236-0027 (Japan)

    2017-01-15

    Highlights: • Photoluminescence of InGaN device is variable, there is no clear explanation for this. • We perform an ad-hoc absorption procedure, found that gases on the surface reduce emission. • We found that variability is related to the pressure of the gas in which the sample is immersed. • We point out the role of oxygen as major player in the reduction of photoluminescence. • A model is proposed and explains successfully the dynamical optical processes observed. - Abstract: We show for the first time that photoluminescence of InGaN single quantum wells (SQW) devices is related to the gas pressure in which the sample is immersed, also we give a model of the phenomena to suggest a possible cause. Our model shows a direct relation between experimental behavior and molecular coverage dynamics. This strongly suggests that the driving force of photoluminescence decrease is oxygen covering the surface of the device with a time dynamics that depends on the gas pressure. This aims to contribute to the understanding of the physical mechanism of the so-called optical memory effect and blinking phenomenon observed in these devices.

  16. Charging and Discharging Channels in Photoluminescence Intermittency of Single Colloidal CdSe/CdS Core/Shell Quantum Dot.

    Science.gov (United States)

    Meng, Renyang; Qin, Haiyan; Niu, Yuan; Fang, Wei; Yang, Sen; Lin, Xing; Cao, Hujia; Ma, Junliang; Lin, Wanzhen; Tong, Limin; Peng, Xiaogang

    2016-12-15

    Understanding photoluminescence (PL) intermittency of single quantum dots (QDs) (intensity blinking by randomly switching between distinguishable brightness states under continuous excitation) has been a long-standing fundamental challenge and potential roadblock for their applications. Here we introduce a new analysis method for single-molecule spectroscopy that treats the blinking as photochemical/chemical processes (switching between neutral/bright and charged/dim states). It uncovers the channels for charging (bright to dim) and discharging (dim to bright) involved in PL blinking of single CdSe/CdS core/shell QDs. Both charging and discharging of the single CdSe/CdS core/shell QD possess a photochemical channel (∼10(-5) to 10(-6) events/photon) that linearly depends on excitation in both single- and multi-exciton regime. These two linear channels coupled to a spontaneous discharging channel (∼2 events/s) to dictate the QDs from nonblinking to gradually blinking under increasing excitation. For high-quality CdSe/CdS core/shell QDs, Auger ionization of multiexciton for both charging and discharging is negligible.

  17. Simultaneous Gene Delivery and Tracking through Preparation of Photo-Luminescent Nanoparticles Based on Graphene Quantum Dots and Chimeric Peptides.

    Science.gov (United States)

    Ghafary, Soroush Moasses; Nikkhah, Maryam; Hatamie, Shadie; Hosseinkhani, Saman

    2017-08-25

    Designing suitable nano-carriers for simultaneous gene delivery and tracking is in the research priorities of the molecular medicine. Non-toxic graphene quantum dots (GQDs) with two different (green and red) emission colors are synthesized by Hummer's method and characterized by UV-Vis, Photoluminescence (PL), Fourier Transform Infrared (FTIR) and Raman spectroscopies, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The GQDs are conjugated with MPG-2H1 chimeric peptide and plasmid DNA (pDNA) by non-covalent interactions. Following conjugation, the average diameter of the prepared GQDs increased from 80 nm to 280 nm in complex structure, and the ζ-potential of the complex increased (from -36.87 to -2.56 mV). High transfection efficiency of the nano-carrier and results of confocal microscopy demonstrated that our construct can be considered as a nontoxic carrier with dual functions for gene delivery and nuclear targeting.

  18. Magnetic field-induced dynamics of the photoluminescence bands of the II-VI semimagnetic quantum structures

    Energy Technology Data Exchange (ETDEWEB)

    Zayachuk, D.M., E-mail: zayachuk@polynet.lviv.ua [Lviv Polytechnic National University, 12 Bandera St., 79013 Lviv (Ukraine)

    2011-08-15

    The problem of quantitative analysis of photoluminescence (PL) spectra of semimagnetic quantum structures formed by superposition of a certain number of elementary components is examined. It is shown that the method of averaging can be advantageously used in such analysis. It ensures a precision in determining the single component energy sufficient for quantitative analysis. A precision of determination of both the band full width at half maximum (FWHM) and the intensity of the components is sufficient at least for qualitative analysis. - Highlights: > Method of averaging was used in analysis of photoluminescence spectra. > It ensures a precision of the single component energy sufficient for quantitative analysis. > Precision of determination of the other characteristics is sufficient for qualitative analysis.

  19. Study of MBE-grown GaN/AlGaN quantum well structures by two wavelength excited photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Zanardi Ocampo, J.M.; Hirasawa, M.; Kamata, N.; Yamada, K. [Saitama Univ., Urawa (Japan). Dept. of Functional Materials Science; Klausing, H.; Semchinova, O.; Stemmer, J. [Hannover Univ. (Germany). Lab. fuer Informationstechnologie

    2001-01-01

    We report experimental results of two wavelength excited photoluminescence (TWEPL) applied to GaN/Al{sub 0.2}Ga{sub 0.8}N multiple quantum well structures grown by plasma assisted molecular beam epitaxy. An increase or a decrease in photoluminescence (PL) indicate the presence of trap centers with dissimilar characteristics for each case. In these samples, a spatial inhomogeneity of trap distribution originating from the growth process was detected due to different change in PL for distinct regions. Also a time-dependent phenomenon in PL was observed: after a continuous mid-term irradiation with UV light (4.12 eV), the amount of change in PL, which is characteristic of TWEPL, became nil. We argue this phenomenon is a complex issue that can be due to migration of native defects or a kind of saturation process involving trap centers. (orig.)

  20. Probing the Quenching of Quantum Dot Photoluminescence by Peptide-Labeled Ruthenium(II) Complexes.

    Science.gov (United States)

    Scott, Amy M; Algar, W Russ; Stewart, Michael H; Trammell, Scott A; Blanco-Canosa, Juan B; Dawson, Philip E; Deschamps, Jeffrey R; Goswami, Ramasis; Oh, Eunkeu; Huston, Alan L; Medintz, Igor L

    2014-05-01

    Charge transfer processes with semiconductor quantum dots (QDs) have generated much interest for potential utility in energy conversion. Such configurations are generally nonbiological; however, recent studies have shown that a redox-active ruthenium(II)-phenanthroline complex (Ru(2+)-phen) is particularly efficient at quenching the photoluminescence (PL) of QDs, and this mechanism demonstrates good potential for application as a generalized biosensing detection modality since it is aqueous compatible. Multiple possibilities for charge transfer and/or energy transfer mechanisms exist within this type of assembly, and there is currently a limited understanding of the underlying photophysical processes in such biocomposite systems where nanomaterials are directly interfaced with biomolecules such as proteins. Here, we utilize redox reactions, steady-state absorption, PL spectroscopy, time-resolved PL spectroscopy, and femtosecond transient absorption spectroscopy (FSTA) to investigate PL quenching in biological assemblies of CdSe/ZnS QDs formed with peptide-linked Ru(2+)-phen. The results reveal that QD quenching requires the Ru(2+) oxidation state and is not consistent with Förster resonance energy transfer, strongly supporting a charge transfer mechanism. Further, two colors of CdSe/ZnS core/shell QDs with similar macroscopic optical properties were found to have very different rates of charge transfer quenching, by Ru(2+)-phen with the key difference between them appearing to be the thickness of their ZnS outer shell. The effect of shell thickness was found to be larger than the effect of increasing distance between the QD and Ru(2+)-phen when using peptides of increasing persistence length. FSTA and time-resolved upconversion PL results further show that exciton quenching is a rather slow process consistent with other QD conjugate materials that undergo hole transfer. An improved understanding of the QD-Ru(2+)-phen system can allow for the design of more

  1. Probing the Quenching of Quantum Dot Photoluminescence by Peptide-Labeled Ruthenium(II) Complexes

    Science.gov (United States)

    2015-01-01

    Charge transfer processes with semiconductor quantum dots (QDs) have generated much interest for potential utility in energy conversion. Such configurations are generally nonbiological; however, recent studies have shown that a redox-active ruthenium(II)–phenanthroline complex (Ru2+-phen) is particularly efficient at quenching the photoluminescence (PL) of QDs, and this mechanism demonstrates good potential for application as a generalized biosensing detection modality since it is aqueous compatible. Multiple possibilities for charge transfer and/or energy transfer mechanisms exist within this type of assembly, and there is currently a limited understanding of the underlying photophysical processes in such biocomposite systems where nanomaterials are directly interfaced with biomolecules such as proteins. Here, we utilize redox reactions, steady-state absorption, PL spectroscopy, time-resolved PL spectroscopy, and femtosecond transient absorption spectroscopy (FSTA) to investigate PL quenching in biological assemblies of CdSe/ZnS QDs formed with peptide-linked Ru2+-phen. The results reveal that QD quenching requires the Ru2+ oxidation state and is not consistent with Förster resonance energy transfer, strongly supporting a charge transfer mechanism. Further, two colors of CdSe/ZnS core/shell QDs with similar macroscopic optical properties were found to have very different rates of charge transfer quenching, by Ru2+-phen with the key difference between them appearing to be the thickness of their ZnS outer shell. The effect of shell thickness was found to be larger than the effect of increasing distance between the QD and Ru2+-phen when using peptides of increasing persistence length. FSTA and time-resolved upconversion PL results further show that exciton quenching is a rather slow process consistent with other QD conjugate materials that undergo hole transfer. An improved understanding of the QD–Ru2+-phen system can allow for the design of more sophisticated

  2. Temperature dependence and quantum efficiency of ultrabroad NIR photoluminescence from Ni2+centers in nanocrystalline Ba-Al titanate glass ceramics

    OpenAIRE

    Gao, Guojun; Peng, Mingying; Wondraczek, Lothar

    2012-01-01

    Ultrabroad near-infrared (NIR) photoluminescence from Ni2+-centers in nanocrystalline Ba-Al titanate glass ceramics was studied by temperature-dependent static and dynamic photoluminescence spectroscopy in the regime of 10 to 300 K. Photoluminescence covers the spectral range of about 1100 nm to >1600  nm with a typical bandwidth (FWHM) greater than 300 nm. For UV-LED excitation at 352 nm, an internal quantum efficiency of 65% is obtained. The excited state lifetime τ at room temperature is 3...

  3. Room temperature photoluminescence (lambda = 1.3 mu m) of InGaAs quantum dots in Si(001) substrate

    CERN Document Server

    Burbaev, T M; Kurbatov, V A; Rzaev, M M; Tsvetkov, V A; Tsekhosh, V I

    2002-01-01

    A heterostructure with GaAs/In sub x Ga sub 1 sub - sub x As quantum dots has exhibit intense photoluminescence in the range of 1.3 mu m at room temperature. It was grown on Si(001) substrate with Si sub 1 sub - sub x Ge sub x buffer layer. The growth process was performed consecutively in two molecular beam epitaxy systems with over loading through out the atmosphere. Results of growth process study by the fast electron diffraction method are presented

  4. Optical properties of type-II AlInAs/AlGaAs quantum dots by photoluminescence studies

    Energy Technology Data Exchange (ETDEWEB)

    Saïdi, I.; Neffati, R.; Ben Radhia, S.; Boujdaria, K., E-mail: kais.boujdaria@fsb.rnu.tn [Laboratoire de Physique des Matériaux: Structure et Propriétés, Faculté des Sciences de Bizerte, Université de Carthage, 7021 Zarzouna, Bizerte (Tunisia); Lemaître, A. [Laboratoire de Photonique et Nanostructures, CNRS, UPR 20, Route de Nozay, F-91460 Marcoussis (France); Bernardot, F.; Testelin, C. [Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris (France)

    2016-07-21

    We report photoluminescence (PL) characterization and model simulation of AlInAs/AlGaAs type-II quantum dots (QDs). A thorough and precise determination of the band parameters for QD and matrix materials is given, focusing on the effects of alloy composition and strain state on the electronic properties. Origins of experimentally observed PL emission peaks are identified through a comparison with the band lineup theoretically determined in this work. We interpret the QD emission as originating from indirect type-II transitions involving electrons in the barrier X valley and heavy holes with S and P symmetry.

  5. Redshifted and blueshifted photoluminescence emission of InAs/InP quantum dots upon amorphization of phase change material.

    Science.gov (United States)

    Humam, Nurrul Syafawati Binti; Sato, Yu; Takahashi, Motoki; Kanazawa, Shohei; Tsumori, Nobuhiro; Regreny, Philippe; Gendry, Michel; Saiki, Toshiharu

    2014-06-16

    We present the mechanisms underlying the redshifted and blueshifted photoluminescence (PL) of quantum dots (QDs) upon amorphization of phase change material (PCM). We calculated the stress and energy shift distribution induced by volume expansion using finite element method. Simulation result reveals that redshift is obtained beneath the flat part of amorphous mark, while blueshift is obtained beneath the edge region of amorphous mark. Simulation result is accompanied by two experimental studies; two-dimensional PL intensity mapping of InAs/InP QD sample deposited by a layer of PCM, and an analysis on the relationship between PL intensity ratio and energy shift were performed.

  6. High Performance Photoluminescent Carbon Dots for In Vitro and In Vivo Bioimaging: Effect of Nitrogen Doping Ratios.

    Science.gov (United States)

    Wang, Junqing; Zhang, Pengfei; Huang, Chao; Liu, Gang; Leung, Ken Cham-Fai; Wáng, Yì Xiáng J

    2015-07-28

    Photoluminescent carbon dots (CDs) have received ever-increasing attention in the application of optical bioimaging because of their low toxicity, tunable fluorescent properties, and ultracompact size. We report for the first time on enhanced photoluminescence (PL) performance influenced by structure effects among the various types of nitrogen doped (N-doped) PL CDs. These CDs were facilely synthesized from condensation carbonization of linear polyethylenic amine (PEA) analogues and citric acid (CA) of different ratios. Detailed structural and property studies demonstrated that either the structures or the molar ratio of PEAs altered the PL properties of the CDs. The content of conjugated π-domains with C═N in the carbon backbone was correlated with their PL Quantum Yield (QY) (up to 69%). The hybridization between the surface/molecule state and the carbon backbone synergistically affected the chemical/physical properties. Also, long-chain polyethylenic amine (PEA) molecule-doped CDs exhibit increasing photostability, but at the expense of PL efficiency, proving that the PL emission of high QY CDs arise not only from the sp(2)/sp(3) carbon core and surface passivation of CDs, but also from the molecular fluorophores integrated in the CDs. In vitro and in vivo bioimaging of these N-doped CDs showed strong photoluminescence signals. Good biocompatibility demonstrates their potential feasibility for bioimaging applications. In addition, the overall size profile of the as-prepared CDs is comparable to the average size of capillary pores in normal living tissues (∼5 nm). Our study provides valuable insights into the effects of the PEA doping ratios on photoluminescence efficiency, biocompatibility, cellular uptake, and optical bioimaging of CDs.

  7. Photoluminescence of p-doped quantum wells with strong spin splitting

    OpenAIRE

    Kossacki, P.; Boukari, H.; Bertolini, M; Ferrand, D.; Cibert, J.; Tatarenko, S.; Gaj, J. A.; Deveaud, B.; Ciulin, V.; Potemski, M.

    2004-01-01

    The spectroscopic properties of a spin polarized two-dimensional hole gas are studied in modulation doped (Cd,Mn)Te quantum wells. The giant Zeeman effect induces a significant spin splitting even at very small values of the applied field. Several methods of measuring the carrier density (Hall effect, filling factors of the Landau levels at high field, various manifestations of Moss-Burstein shifts) are described and calibrated. The value of the spin splitting needed to fully polarize the hol...

  8. Substrate- and time-dependent photoluminescence of quantum dots inside the ultrathin polymer LbL film.

    Science.gov (United States)

    Zimnitsky, Dmitry; Jiang, Chaoyang; Xu, Jun; Lin, Zhiqun; Tsukruk, Vladimir V

    2007-04-10

    The photoluminescence of CdSe/ZnS quantum dots (QDs) in different configurations at solid surfaces (glass, silicon, PDMS, and metals) is considered for three types of organization: QDs directly adsorbed on solid surfaces, separated from the solid surface by a nanoscale polymer film with different thickness, and encapsulated into a polymer film. The complete suppression of photoluminescence for QDs on conductive metal surfaces (copper, gold) indicated a strong quenching effect. The temporal variation of the photoluminescent intensity on other substrates (glass, silicon, and PDMS) can be tuned by placing the nanoscale (3-50 nm) LbL polymer film between QDs and the substrate. The photooxidation and photobleaching processes of QD nanoparticles in the vicinity of the solid surface can be tuned by proper selection of the substrate and the dielectric nanoscale polymer film placed between the substrate and QDs. Moreover, the encapsulation of QD nanoparticles into the polymer film resulted in a dramatic initial increase in the photoemission intensity due to the accelerated photooxidation process. The phenomenon of enhanced photoemission of QDs encapsulated into the ultrathin polymer film provides not only the opportunity for making flexible, ultrathin, QD-containing polymer films, transferable to any microfabricated substrate, but also improved light emitting properties.

  9. Phenyl-Modified Carbon Nitride Quantum Dots with Distinct Photoluminescence Behavior.

    Science.gov (United States)

    Cui, Qianling; Xu, Jingsan; Wang, Xiaoyu; Li, Lidong; Antonietti, Markus; Shalom, Menny

    2016-03-07

    A novel type of quantum dot (Ph-CN) is manufactured from graphitic carbon nitride by "lining" the carbon nitride structure with phenyl groups through supramolecular preorganization. This approach requires no chemical etching or hydrothermal treatments like other competing nanoparticle syntheses and is easy and safe to use. The Ph-CN nanoparticles exhibit bright, tunable fluorescence, with a high quantum yield of 48.4 % in aqueous colloidal suspensions. Interestingly, the observed Stokes shift of approximately 200 nm is higher than the maximum values reported for carbon nitride based fluorophores. The high quantum yield and the large Stokes shift are related to the structural surface organization of the phenyl groups, which affects the π-electron delocalization in the conjugated carbon nitride networks and induces colloidal stability. The remarkable performance of the Ph-CN nanoparticles in imaging is demonstrated by a simple incubation study with HeLa cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Impact of light polarization on photoluminescence intensity and quantum efficiency in AlGaN and AlInGaN layers

    Science.gov (United States)

    Netzel, C.; Knauer, A.; Weyers, M.

    2012-12-01

    We analyzed emission intensity, quantum efficiency, and emitted light polarization of c-plane AlGaN and AlInGaN layers (λ = 320-350 nm) by temperature dependent photoluminescence. Low indium content in AlInGaN structures causes a significant intensity increase by change of the polarization of the emitted light. Polarization changes from E ⊥ c to E ‖ c with increasing aluminum content. It switches back to E ⊥ c with the incorporation of indium. The polarization degree decreases with temperature. This temperature dependence can corrupt internal quantum efficiency determination by temperature dependent photoluminescence.

  11. Influence of near-field coupling from Ag surface plasmons on InGaN/GaN quantum-well photoluminescence

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Iida, Daisuke; Chen, Yuntian

    2016-01-01

    We have investigated the borderline between photoluminescence quenching and enhancement of InGaN/GaN quantum-wells due to Ag nanoparticles and their surface plasmon modes. By embedding Ag nanoparticles inside nanohole structures on the p-type layer GaN, luminescence quenching is observed.Increasi......We have investigated the borderline between photoluminescence quenching and enhancement of InGaN/GaN quantum-wells due to Ag nanoparticles and their surface plasmon modes. By embedding Ag nanoparticles inside nanohole structures on the p-type layer GaN, luminescence quenching is observed...

  12. Photoluminescence probing of interface evolution with annealing in InGa(N)As/GaAs single quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Jun, E-mail: jshao@mail.sitp.ac.cn; Qi, Zhen; Zhu, Liang; Chen, Xiren; Guo, Shaoling [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 200083 Shanghai (China); Zhao, H. [Department of Microtechnology and Nanoscience, Chalmers University of Technology, S-41296 Göteborg (Sweden); Song, Yuxin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China); Zha, F.-X. [Physics Department, Shanghai University, 200444 Shanghai (China); Wang, S. M., E-mail: shumin@mail.sim.ac.cn [Department of Microtechnology and Nanoscience, Chalmers University of Technology, S-41296 Göteborg (Sweden); State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 200050 Shanghai (China)

    2015-10-28

    The effects of thermal annealing on the interfaces of InGa(N)As/GaAs single quantum wells (SQWs) are investigated by excitation-, temperature-, and magnetic field-dependent photoluminescence (PL). The annealing at 750 °C results in more significant blueshift and narrowing to the PL peak than that at 600 °C. Each of the PL spectra can be reproduced with two PL components: (i) the low-energy component (LE) keeps energetically unchanged, while the high-energy component (HE) moves up with excitation and shows at higher energy for the In{sub 0.375}Ga{sub 0.625}As/GaAs but crosses over with the LE at a medium excitation power for the In{sub 0.375}Ga{sub 0.625}N{sub 0.012}As{sub 0.988}/GaAs SQWs. The HE is broader than the corresponding LE, the annealing at 750 °C narrows the LE and HE and shrinks their energetic separation; (ii) the PL components are excitonic, and the InGaNAs shows slightly enhanced excitonic effects relative to the InGaAs SQW; (iii) no typical S-shape evolution of PL energy with temperature is detectable, and similar blueshift and narrowing are identified for the same annealing. The phenomena are mainly from the interfacial processes. Annealing improves the intralayer quality, enhances the interfacial In-Ga interdiffusion, and reduces the interfacial fluctuation. The interfacial interdiffusion does not change obviously by the small N content and hence similar PL-component narrowing and blueshift are observed for the SQWs after a nominally identical annealing. Comparison with previous studies is made and the PL measurements under different conditions are shown to be effective for probing the interfacial evolution in QWs.

  13. Rapid thermal annealing and modulation-doping effects on InAs/GaAs quantum dots photoluminescence dependence on excitation power

    Energy Technology Data Exchange (ETDEWEB)

    Chaâbani, W. [Laboratoire Matériaux-Molécules et Applications, Institut Préparatoire aux Etudes Scientifiques et Techniques, Université de Carthage, La Marsa 2070 (Tunisia); Melliti, A., E-mail: adnenmelliti@yahoo.fr [Laboratoire Matériaux-Molécules et Applications, Institut Préparatoire aux Etudes Scientifiques et Techniques, Université de Carthage, La Marsa 2070 (Tunisia); Maaref, M.A. [Laboratoire Matériaux-Molécules et Applications, Institut Préparatoire aux Etudes Scientifiques et Techniques, Université de Carthage, La Marsa 2070 (Tunisia); Testelin, C. [Institut des NanoSciences de Paris, UPMC Univ., Paris 06, UMR 7588, F-75005 Paris (France); CNRS, UMR 7588, INSP, F-75005 Paris (France); Lemaître, A. [Laboratoire de Photonique et Nanostructures (LPN), CNRS, Route de Nozay, F-91460 Marcoussis (France)

    2016-07-15

    The optical properties of p-doped and annealed InAs/GaAs quantum dots (QDs) was investigated by photoluminescence (PL) as a function of temperature and excitation power density (P{sub exc}). At low-T, PL spectra of rapid thermal annealing (RTA) and p-modulation doped QDs show an energy blueshift and redshift, respectively. A superlinear dependence of integrated PL intensity on P{sub exc} at high-T was found only for undoped QD. The superlinearity was suppressed by modulation-doping and RTA effects. A linear dependence of I{sub PL} at all temperatures and a decrease of the carrier-carrier Coulomb interaction at high-T was found after RTA.

  14. Optical excitation and external photoluminescence quantum efficiency of Eu3+ in GaN

    NARCIS (Netherlands)

    de Boer, W.D.A.M.; McGonigle, C.; Gregorkiewicz, T.; Fujiwara, Y.; Stallinga, P.

    2014-01-01

    We investigate photoluminescence of Eu-related emission in a GaN host consisting of thin layers grown by organometallic vapor-phase epitaxy. By comparing it with a reference sample of Eu-doped Y2O3, we find that the fraction of Eu3+ ions that can emit light upon optical excitation is of the order of

  15. Photoluminescence of Diamondoid Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Clay, William; /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /Stanford U., Geballe Lab.; Sasagawa, Takao; Iwasa, Akio; /TIT, Nagatsuta; Liu, Zhi; /LBNL, ALS; Dahl, Jeremy E.; /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /Stanford U., Geballe Lab.; Carlson, Robert M.K.; /Molecular Diamond Technologies, Chevron Technology Ventures; Kelly, Michael; Melos, Nicholas; /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /Stanford U., Geballe Lab.; Shen, Zhi-Xun; /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /Stanford U., Geballe Lab. /SIMES, Stanford

    2012-04-03

    The photoluminescence of diamondoids in the solid state is examined. All of the diamondoids are found to photoluminesce readily with initial excitation wavelengths ranging from 233 nm to 240 nm (5.3 eV). These excitation energies are more than 1 eV lower than any previously studied saturated hydrocarbon material. The emission is found to be heavily shifted from the absorption, with emission wavelengths of roughly 295 nm (4.2 eV) in all cases. In the dissolved state, however, no uorescence is observed for excitation wavelengths as short as 200 nm. We also discuss predictions and measurements of the quantum yield. Our predictions indicate that the maximum yield may be as high as 25%. Our measurement of one species, diamantane, gives a yield of 11%, the highest ever reported for a saturated hydrocarbon, even though it was likely not at the optimal excitation wavelength.

  16. Enhanced photoluminescence of Co{sup 2+} ions in ZnCoO/ZnMgO multiple quantum wells and the fluorescence energy transfer mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Ashfaq, J.M.; Hu, B.C.; Zhou, N.; Li, X.L.; Ma, C.Y.; Zhang, Q.Y., E-mail: qyzhang@dlut.edu.cn

    2015-02-15

    Using a pulsed laser deposition system, ZnCoO/ZnMgO multiple quantum well (MQW) samples were grown on c-plane sapphire substrate with a ∼20 nm thick ZnO buffer layer. Compared with monolayer ZnCoO film, the MQW samples exhibited obviously enhanced Co{sup 2+} photoluminescence (PL) at ∼1.80 eV and multiple-phonon resonant Raman scattering (RRS). The enhancement in multiple-phonon RRS was due to the introduction of ZnMgO barrier layer. The enhanced Co{sup 2+} PL was assigned to the quantum confinement effect (QCE) of MQW samples. However, QCE was found not helpful to prevent the band-gap PL quenching. Co{sup 2+} 3d electronic states were proved to be highly localized and a mechanism of fluorescence resonance energy transfer (FRET) between ZnO excitons and the localized Co{sup 2+} 3d states was proposed. - Highlights: • Enhanced Co{sup 2+} PL and multiple-phonon RRS have been observed in ZnCoO/ZnMgO MQW samples. • Quantum confinement effect and ZnMgO barrier layers are responsible for the enhancement of Co{sup 2+} PL and multiple-phonon RRS, respectively. • Band-gap PL quenching is suggested to be due to the fluorescence resonance energy transfer from the excitons to the localized Co{sup 2+} 3d states.

  17. Impact of doping on InAs/GaAs quantum-dot solar cells: A numerical study on photovoltaic and photoluminescence behavior

    OpenAIRE

    Cappelluti, F.; Gioannini, M.; A Khalili

    2016-01-01

    We investigate the effect of doping on quantum dot (QD) solar cells by analysing their behavior in terms of photovoltaic characteristic, external quantum efficiency, and photoluminescence (PL) at room temperature. The analysis addresses the two most widespread methods for QD selective doping, namely modulation and direct doping, to gain a comprehensive device-level assessment of the impact of doping profile and density on the solar cell behavior. Devices are simulated using a physics-based mo...

  18. Highly Controlled Synthesis and Super-Radiant Photoluminescence of Plasmonic Cube-in-Cube Nanoparticles.

    Science.gov (United States)

    Park, Jeong-Eun; Kim, Sungi; Son, Jiwoong; Lee, Yeonhee; Nam, Jwa-Min

    2016-12-14

    The plasmonic properties of metal nanostructures have been heavily utilized for surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF), but the direct photoluminescence (PL) from plasmonic metal nanostructures, especially with plasmonic coupling, has not been widely used as much as SERS and MEF due to the lack of understanding of the PL mechanism, relatively weak signals, and the poor availability of the synthetic methods for the nanostructures with strong PL signals. The direct PL from metal nanostructures is beneficial if these issues can be addressed because it does not exhibit photoblinking or photobleaching, does not require dye-labeling, and can be employed as a highly reliable optical signal that directly depends on nanostructure morphology. Herein, we designed and synthesized plasmonic cube-in-cube (CiC) nanoparticles (NPs) with a controllable interior nanogap in a high yield from Au nanocubes (AuNCs). In synthesizing the CiC NPs, we developed a galvanic void formation (GVF) process, composed of replacement/reduction and void formation steps. We unraveled the super-radiant character of the plasmonic coupling-induced plasmon mode which can result in highly enhanced PL intensity and long-lasting PL, and the PL mechanisms of these structures were analyzed and matched with the plasmon hybridization model. Importantly, the PL intensity and quantum yield (QY) of CiC NPs are 31 times and 16 times higher than those of AuNCs, respectively, which have shown the highest PL intensity and QY reported for metallic nanostructures. Finally, we confirmed the long-term photostability of the PL signal, and the signal remained stable for at least 1 h under continuous illumination.

  19. High resolution quantum metrology via quantum interpolation

    Science.gov (United States)

    Ajoy, Ashok; Liu, Yixiang; Saha, Kasturi; Marseglia, Luca; Jaskula, Jean-Christophe; Cappellaro, Paola

    2016-05-01

    Nitrogen Vacancy (NV) centers in diamond are a promising platform for quantum metrology - in particular for nanoscale magnetic resonance imaging to determine high resolution structures of single molecules placed outside the diamond. The conventional technique for sensing of external nuclear spins involves monitoring the effects of the target nuclear spins on the NV center coherence under dynamical decoupling (the CPMG/XY8 pulse sequence). However, the nuclear spin affects the NV coherence only at precise free evolution times - and finite timing resolution set by hardware often severely limits the sensitivity and resolution of the method. In this work, we overcome this timing resolution barrier by developing a technique to supersample the metrology signal by effectively implementing a quantum interpolation of the spin system dynamics. This method will enable spin sensing at high magnetic fields and high repetition rate, allowing significant improvements in sensitivity and spectral resolution. We experimentally demonstrate a resolution boost by over a factor of 100 for spin sensing and AC magnetometry. The method is shown to be robust, versatile to sensing normal and spurious signal harmonics, and ultimately limited in resolution only by the number of pulses that can be applied.

  20. Theory of phonon-modified spontaneous emission and photoluminescence intensity from quantum dots coupled to structured photonic reservoirs

    Science.gov (United States)

    Roy Choudhury, Kaushik; Hughes, S.

    2015-08-01

    We present a general theory for calculating the spontaneous emission (SE) rate and the photoluminescence intensity of a quantum dot (QD) exciton coupled to an arbitrary structured photonic reservoir and a bath of acoustic phonons. We describe a polaron master equation (ME) approach which includes phonon interaction nonperturbatively and assume a weak coupling with the photon reservoir which is valid in the Purcell coupling regime. As examples of structured photonic reservoirs, we choose the cases of a Lorentzian cavity and a slow-light coupled-cavity waveguide. In analogy with a simple atom, the SE rate of a QD is expected to be proportional to the local density of photon states (LDOS) of the structured reservoir at the resonant frequency of a QD exciton. However, using a polaron ME theory, we show how the phonon-dressed SE rate of a QD is determined by a broad bandwidth of the photonic LDOS, in violation of the well known Fermi's golden rule. This broadband frequency dependence results in rich spontaneous emission enhancement and suppression, manifesting in significant changes in the Purcell factor and photoluminescence intensity as a function of frequency.

  1. Energy spectrum of quantum wells in PbTe/PbEuTe type structures based on photoluminescence data

    CERN Document Server

    Zasavitskij, I I; Abramof, E

    2002-01-01

    The effect of the dimensional quantization and temperature on the energy spectrum of structures with the quantum wells of the PbTe/PbEuTe-type is studied. The calculated spectrum is compared with the data on the photoluminescence spectra, measured at 4.2 and 77.4 K. The energies of the emitting transitions are well described within the frames of the two-zone model with an account of the nonparabolicity, anisotropy and PbTe multivalley structure as well as by the uniaxial deformation, available in the heterostructures. It is established, that by decrease in the E sub g forbidden zone width the dE sub g /dT temperature coefficient in the two-dimensional heterostructure decreases, which is explained by weakening the electron-phonon interaction

  2. The influence of bio-conjugation on photoluminescence of CdSe/ZnS quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Torchynska, Tetyana V. [ESFM Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional, México, D.F. 07738 (Mexico); Vorobiev, Yuri V. [Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV) Querétaro, Libramiento Norponiente 2000, Fracc. Real de Juriquilla, 76230 Querétaro (Mexico); Makhniy, Victor P. [Yuri Fedkovych Chernivtsi National University, 2 Kotsyubynsky Str., 58012 Chernivtsi (Ukraine); Horley, Paul P., E-mail: paul.horley@cimav.edu.mx [Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Chihuahua/Monterrey, 120 Avenida Miguel de Cervantes, 31109 Chihuahua (Mexico)

    2014-11-15

    We report a considerable blue shift in the luminescence spectra of CdSe/ZnS quantum dots conjugated to anti-interleukin-10 antibodies. This phenomenon can be explained theoretically by accounting for bio-conjugation as a process causing electrostatic interaction between a quantum dot and an antibody, which reduces effective volume of the dot core. To solve the Schrödinger equation for an exciton confined in the quantum dot, we use mirror boundary conditions that were successfully tested for different geometries of quantum wells.

  3. Red-shift of the photoluminescent emission peaks of CdTe quantum dots due to the synergistic interaction with carbon quantum dot mixtures

    Science.gov (United States)

    Pelayo, E.; Zazueta, A.; López-Delgado, R.; Saucedo, E.; Ruelas, R.; Ayón, A.

    2016-11-01

    We report the relatively large red-shift effect observed in down-shifting carbon quantum dots (CQDs) that is anticipated to have a positive impact on the power conversion efficiency of solar cells. Specifically, with an excitation wavelength of 390 nm, CQDs of different sizes, exhibited down-shifted emission peaks centered around 425 nm. However, a solution comprised of a mixture of CQDs of different sizes, was observed to have an emission peak red-shifted to 515 nm. The effect could arise when larger carbon quantum dots capture the photons emitted by their smaller counterparts followed by the subsequent re-emission at longer wavelengths. Furthermore, the red-shift effect was also observed in CdTe QDs when added to a solution with the aforementioned mixture of Carbon QDs. Thus, whereas a solution solely comprised of a collection of CdTe QDs of different sizes, exhibited a down-shifted photoluminescence centered around 555 nm, the peak was observed to be further red-shifted to 580 nm when combined with the solution of CQDs of different sizes. The quantum dot characterization included crystal structure analysis as well as photon absorption and photoluminescence wavelengths. Subsequently, the synthesized QDs were dispersed in a polymeric layer of poly-methyl-methacrylate (PMMA) and incorporated on functional and previously characterized solar cells, to quantify their influence in the electrical performance of the photovoltaic structures. We discuss the synthesis and characterization of the produced Carbon and CdTe QDs, as well as the observed improvement in the power conversion efficiency of the fabricated photovoltaic devices.

  4. Towards highly multimode optical quantum memory for quantum repeaters

    OpenAIRE

    Jobez, Pierre; Timoney, Nuala; Laplane, Cyril; Etesse, Jean; Ferrier, Alban; Goldner, Philippe; Gisin, Nicolas; Afzelius, Mikael

    2015-01-01

    Long-distance quantum communication through optical fibers is currently limited to a few hundreds of kilometres due to fiber losses. Quantum repeaters could extend this limit to continental distances. Most approaches to quantum repeaters require highly multimode quantum memories in order to reach high communication rates. The atomic frequency comb memory scheme can in principle achieve high temporal multimode storage, without sacrificing memory efficiency. However, previous demonstrations hav...

  5. Origin of low quantum efficiency of photoluminescence of InP/ZnS nanocrystals

    DEFF Research Database (Denmark)

    Shirazi, Roza; Kovacs, Andras; Corell, Dennis Dan

    2013-01-01

    In this paper, we study the origin of a strong wavelength dependence of the quantum efficiency of InP/ZnS nanocrystals. We find that while the average size of the nanocrystals increased by 50%, resulting in longer emission wavelength, the quantum efficiency drops more than one order of magnitude...

  6. Easy synthesis of highly fluorescent carbon dots from albumin and their photoluminescent mechanism and biological imaging applications

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xiaohua; An, Xueqin, E-mail: anxueqin@ecust.edu.cn; Li, Lielie

    2016-01-01

    A simple and green approach was developed to synthesize highly fluorescent carbon dots (CDs) using albumin as a carbon source in aqueous solution at room temperature. The CDs were characterized by excellent monodispersion, superior photostability, pH-independent emission, long fluorescence lifetime and high quantum yield (QY). The photoluminescent (PL) mechanism of CDs was explored by means of time-resolved PL decay, and the results revealed that PL originated from the emission of both defect state and intrinsic state. In addition, biological imaging with the application of CDs was carried out in human breast cancer Bcap-37 cell, which demonstrated that CDs were provided with an excellent biocompatiblity, low cytotoxicity and good transmembrane ability. Besides, CDs could be considered as a potential substitute for organic dyes or semiconductor quantum dots (SQDs) in biological imaging. - Highlights: • High fluorescent CDs have been synthesized at room temperature. • The CDs showed superior photostability and low cytotoxicity. • The good biocompatibility of the CDs was conformed. • The CDs manifest potential for cell imaging and fluorescent staining.

  7. A robust ligand exchange approach for preparing hydrophilic, biocompatible photoluminescent quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Sujuan; Zhou, Changhua [Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004 (China); Yuan, Hang [Life Science Division, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Shen, Huaibin [Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004 (China); Zhao, Wenxiu [Life Science Division, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Ma, Lan, E-mail: malan@sz.tsinghua.edu.cn [Life Science Division, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Li, Lin Song, E-mail: lsli@henu.edu.cn [Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004 (China)

    2013-08-01

    Graphical abstract: - Highlights: • Aqueous CdSe/ZnS QDs were prepared using polymaleic anhydrides as capping ligand. • Effect of reaction temperature and time were systematically studied in the synthesis process. • Water-soluble QDs exhibited a good stability in physiological relevant environment. • The aqueous QDs were applied as biological probe to detect human embryonic stem cell. - Abstract: This paper describes a robust ligand exchange approach for preparing biocompatible CdSe/ZnS quantum dots (QDs) to make bioprobe for effective cell imaging. In this method, polymaleic anhydride (PMA) ligand are first used to replace original hydrophobic ligand (oleic acid) and form a protection shell with multiple hydrophilic groups to coat and protect CdSe/ZnS QDs. The as-prepared aqueous QDs exhibit small particle size, good colloidal stability in aqueous solutions with a wide range of pH, salt concentrations and under thermal treatment, which are necessary for biological applications. The use of this new class of aqueous QDs for effective cell imaging shows strong fluorescence signal to human embryonic stem cell, which demonstrate that PMA coated QDs are fully satisfied with the requirements of preparing high quality biological probe.

  8. Temperature dependence and quantum efficiency of ultrabroad NIR photoluminescence from Ni2+ centers in nanocrystalline Ba-Al titanate glass ceramics.

    Science.gov (United States)

    Gao, Guojun; Peng, Mingying; Wondraczek, Lothar

    2012-04-01

    Ultrabroad near-infrared (NIR) photoluminescence from Ni2+-centers in nanocrystalline Ba-Al titanate glass ceramics was studied by temperature-dependent static and dynamic photoluminescence spectroscopy in the regime of 10 to 300 K. Photoluminescence covers the spectral range of about 1100 nm to >1600 nm with a typical bandwidth (FWHM) greater than 300 nm. For UV-LED excitation at 352 nm, an internal quantum efficiency of 65% is obtained. The excited state lifetime τ at room temperature is 39 μs. The stimulated emission cross section σ(em) is 8.5×10(-20) cm2, resulting in a practical figure of merit, σ(em) * τ, of 3.3×10(-24) cm2 s at room temperature. These properties suggest suitability as a broadband gain medium for tunable lasers and optical amplifiers.

  9. Photoluminescence up-conversion in five Inx(Al0.17Ga0.83)1-xAs/ Al0.17Ga0.83As quantum wells with different x values

    DEFF Research Database (Denmark)

    Machida, S.; Tadakuma, T.; Satake, A.

    Photoluminescence (PL) up-conversion in a unique system with five different quantum wells has been investigated. Anti-Stokes PL intensity observed shows dramatic dependence on where carriers are resonantly photoexcited, indicating nonlinear processes with spatial position dependence.......Photoluminescence (PL) up-conversion in a unique system with five different quantum wells has been investigated. Anti-Stokes PL intensity observed shows dramatic dependence on where carriers are resonantly photoexcited, indicating nonlinear processes with spatial position dependence....

  10. Utilization of down-shifting photoluminescent ZnO quantum dots on solar cells

    Science.gov (United States)

    Zazueta-Raynaud, A.; Lopez-Delgado, R.; Pelayo-Ceja, J. E.; Alvarez-Ramos, M. E.; Ayon, A.

    2017-07-01

    We report on the synthesis of photo luminescent zinc oxide (ZnO) quantum dots, their deployment on the window side of photovoltaic structures and the measured influence on the power conversion efficiency. Down-shifting effects were characterized by exciting the synthesized nanostructures with photons in the 340-350 nm range, and measuring the wavelength of the emitted photons observed to be ~500 nm. The colloidal ZnO quantum dots were synthesized in an ethanol-based solution, obtaining different sized nanostructures centered at 4 nm, optically recognizable by their emission in various colors. Subsequently, different concentrations of zinc oxide quantum dots were prepared and dispersed in poly-methyl-methacrylate (PMMA) to be spin cast on the window side of previously characterized solar cells. The observations made to date indicate an improvement of ~4.8% in the PCE. In this work, we discuss the results obtained and suggest pathways to further increase the power conversion efficiency of photovoltaic devices employing quantum dots.

  11. High-dimensional quantum cloning and applications to quantum hacking.

    Science.gov (United States)

    Bouchard, Frédéric; Fickler, Robert; Boyd, Robert W; Karimi, Ebrahim

    2017-02-01

    Attempts at cloning a quantum system result in the introduction of imperfections in the state of the copies. This is a consequence of the no-cloning theorem, which is a fundamental law of quantum physics and the backbone of security for quantum communications. Although perfect copies are prohibited, a quantum state may be copied with maximal accuracy via various optimal cloning schemes. Optimal quantum cloning, which lies at the border of the physical limit imposed by the no-signaling theorem and the Heisenberg uncertainty principle, has been experimentally realized for low-dimensional photonic states. However, an increase in the dimensionality of quantum systems is greatly beneficial to quantum computation and communication protocols. Nonetheless, no experimental demonstration of optimal cloning machines has hitherto been shown for high-dimensional quantum systems. We perform optimal cloning of high-dimensional photonic states by means of the symmetrization method. We show the universality of our technique by conducting cloning of numerous arbitrary input states and fully characterize our cloning machine by performing quantum state tomography on cloned photons. In addition, a cloning attack on a Bennett and Brassard (BB84) quantum key distribution protocol is experimentally demonstrated to reveal the robustness of high-dimensional states in quantum cryptography.

  12. Synthesis of Luminescent Graphene Quantum Dots with High Quantum Yield and Their Toxicity Study.

    Directory of Open Access Journals (Sweden)

    Dan Jiang

    Full Text Available High fluorescence quantum yield graphene quantum dots (GQDs have showed up as a new generation for bioimaging. In this work, luminescent GQDs were prepared by an ameliorative photo-Fenton reaction and a subsequent hydrothermal process using graphene oxide sheets as the precursor. The as-prepared GQDs were nanomaterials with size ranging from 2.3 to 6.4 nm and emitted intense green luminescence in water. The fluorescence quantum yield was as high as 24.6% (excited at 340 nm and the fluorescence was strongest at pH 7. Moreover, the influences of low-concentration (12.5, 25 μg/mL GQDs on the morphology, viability, membrane integrity, internal cellular reactive oxygen species level and mortality of HeLa cells were relatively weak, and the in vitro imaging demonstrated GQDs were mainly in the cytoplasm region. More strikingly, zebrafish embryos were co-cultured with GQDs for in vivo imaging, and the results of heart rate test showed the intake of small amounts of GQDs brought little harm to the cardiovascular of zebrafish. GQDs with high quantum yield and strong photoluminescence show good biocompatibility, thus they show good promising for cell imaging, biolabeling and other biomedical applications.

  13. Synthesis of Luminescent Graphene Quantum Dots with High Quantum Yield and Their Toxicity Study

    Science.gov (United States)

    Jiang, Dan; Chen, Yunping; Li, Na; Li, Wen; Wang, Zhenguo; Zhu, Jingli; Zhang, Hong; Liu, Bin; Xu, Shan

    2015-01-01

    High fluorescence quantum yield graphene quantum dots (GQDs) have showed up as a new generation for bioimaging. In this work, luminescent GQDs were prepared by an ameliorative photo-Fenton reaction and a subsequent hydrothermal process using graphene oxide sheets as the precursor. The as-prepared GQDs were nanomaterials with size ranging from 2.3 to 6.4 nm and emitted intense green luminescence in water. The fluorescence quantum yield was as high as 24.6% (excited at 340 nm) and the fluorescence was strongest at pH 7. Moreover, the influences of low-concentration (12.5, 25 μg/mL) GQDs on the morphology, viability, membrane integrity, internal cellular reactive oxygen species level and mortality of HeLa cells were relatively weak, and the in vitro imaging demonstrated GQDs were mainly in the cytoplasm region. More strikingly, zebrafish embryos were co-cultured with GQDs for in vivo imaging, and the results of heart rate test showed the intake of small amounts of GQDs brought little harm to the cardiovascular of zebrafish. GQDs with high quantum yield and strong photoluminescence show good biocompatibility, thus they show good promising for cell imaging, biolabeling and other biomedical applications. PMID:26709828

  14. Photoluminescence of InAs quantum dots embedded in AlGaAs/InGaAs quantum wells with strain reducing layer

    Science.gov (United States)

    Cisneros Tamayo, R.; Torchynska, T. V.; Polupan, G.; Guerrero Moreno, I. J.; Velázquez Lozada, E.; Shcherbyna, L.

    2014-07-01

    Photoluminescence (PL) of InAs quantum dots (QDs) embedded in the Al0.30Ga0.70As/In0.15Ga0.85As/InGaAlAs/GaAs quantum wells (QWs) have been investigated in the temperature range of 10-500 K for as grown samples and after thermal annealing at 640 °C or 710 °C for two hours. QD samples with the different InAlGaAs capping layers (GaAs or Al0.1Ga0.75 In0.15As) have been studied. The higher PL intensity and lower energy of ground state (GS) emission are detected in the structure with Al0.1Ga0.75 In0.15As layer. This QD structure in as grown state has smaller PL thermal decay in comparison with this parameter in the structure with GaAs layer. The variation of PL intensities and peak positions at annealing are more essential in the QD structure with Al0.1Ga0.75 In0.15As capping layer, apparently, due to more efficient Ga(Al)/In intermixing.

  15. Highly luminescent water-soluble CdTe quantum dots

    NARCIS (Netherlands)

    Wuister, SF; Swart, A.N.; van Driel, F; Hickey, SG; Donega, CD; Swart, Ingmar|info:eu-repo/dai/nl/304837652

    Colloidal CdTe quantum dots prepared in TOP/DDA (trioctylphosphine/dodecylamine) are transferred into water by the use of aminoethanethiol.HCl (AET) or mercaptopropionic acid (MPA). This results in an increase in the photoluminescence quantum efficiency and a longer exciton lifetime. For the first

  16. Photoluminescence of monocrystalline and stain-etched porous silicon doped with high temperature annealed europium

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero-Lemus, R; Montesdeoca-Santana, A; Gonzalez-Diaz, B; Diaz-Herrera, B; Hernandez-Rodriguez, C; Jimenez-Rodriguez, E [Departamento de Fisica Basica, Universidad de La Laguna (ULL), Avenida AstrofIsico Francisco Sanchez, 2. 38206 La Laguna, Tenerife (Spain); Velazquez, J J, E-mail: rglemus@ull.es [Departamento de Fisica Fundamental y Experimental, Electronica y Sistemas, Universidad de La Laguna (ULL), Avenida Astrofisico Francisco Sanchez, 2. 38206 La Laguna, Tenerife (Spain)

    2011-08-24

    In this work, for the first time, the photoluminescent emission and excitation spectra of non-textured layers and stain-etched porous silicon layers (PSLs) doped with high temperature annealed europium (Eu) are evaluated. The PSLs are evaluated as a host for rare earth ions and as an antireflection coating. The applied doping process, which consists in a simple impregnation method followed by a high-temperature annealing step, is compatible with the standard processes in the fabrication of solar cells. The results show down-shifting processes with a maximum photoluminescent intensity at 615 nm, related to the transition {sup 5}D{sub 0} {yields} {sup 7}F{sub 2}. Different initial concentrations of Eu(NO{sub 3}){sub 3} are evaluated to study the influence of the rare earth concentration on the photoluminescent intensity. The chemical composition and the morphology of Eu-doped PSLs are examined by means of x-ray dispersion spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy. These Eu-doped layers are considered to be applied as energy converters in silicon-based third generation solar cells.

  17. Study of optical absorption and photoluminescence of quantum dots of CdS formed in borosilicate glass matrix

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Jitender; Verma, A; Pandey, P K; Bhatnagar, P K; Mathur, P C [Department of Electronic Science, University of Delhi South Campus, Benito Juarez Road, New Delhi-110021 (India); Liu, W; Tang, S H [Department of Physics, National University of Singapore, 119243 (Singapore)], E-mail: jitender_does@yahoo.co.in

    2009-06-15

    Optical absorption and photoluminescence (PL) measurements have been made on the quantum dots (QDs) of CdS grown in a borosilicate glass matrix using a two-step annealing technique. The absorption measurements, made in the energy range of 1.3-3.2 eV, indicate the presence of nonradiative trap centers located in the forbidden gap at an energy level near 1.5 eV. The origin of these traps is attributed to the impurities present in the glass matrix. The PL measurements have been made at an excitation energy of 2.75 eV and it is concluded that the origin of PL is not due to either direct recombination of electrons and holes or deep traps, but that it is the shallow traps which are responsible for the observed PL. The shallow traps are attributed to sulfur vacancies formed at the glass-QD interface. The reason for the observed decrease in PL peak intensity with the increase of annealing time is due to the decrease of surface to volume ratio for QDs of higher size.

  18. Measurement procedure for absolute broadband infrared up-conversion photoluminescent quantum yields: correcting for absorption/re-emission.

    Science.gov (United States)

    MacDougall, Sean K W; Ivaturi, Aruna; Marques-Hueso, Jose; Richards, Bryce S

    2014-06-01

    The internal photoluminescent quantum yield (iPLQY)--defined as the ratio of emitted photons to those absorbed--is an important parameter in the evaluation and application of luminescent materials. The iPLQY is rarely reported due to the complexities in the calibration of such a measurement. Herein, an experimental method is proposed to correct for re-emission, which leads to an underestimation of the absorption under broadband excitation. Although traditionally the iPLQY is measured using monochromatic sources for linear materials, this advancement is necessary for nonlinear materials with wavelength dependent iPLQY, such as the application of up-conversion to solar energy harvesting. The method requires an additional measurement of the emission line shape that overlaps with the excitation and absorption spectra. Through scaling of the emission spectrum, at the long wavelength edge where an overlap of excitation does not occur, it is possible to better estimate the value of iPLQY. The method has been evaluated for a range of nonlinear material concentrations and under various irradiances to analyze the necessity and boundary conditions that favor the proposed method. Use of this refined method is important for a reliable measurement of iPLQY under a broad illumination source such as the Sun.

  19. Enhancement of photoluminescence efficiency from semi-polar InGaN/GaN multiple quantum wells with silver metal

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyoung Su; Lee, Dong Uk; Kim, Eun Kyu, E-mail: ek-kim@hanyang.ac.kr

    2015-06-15

    We have studied the effect of surface plasmon polariton (SPP) and localized surface plasmon (LSP) on the emission of semi-polar InGaN/GaN light emitting diode (LED) with multi-quantum wells structure. From the photoluminescence (PL) measurement at room temperature, spectrally-integrated enhancements of semi-polar SPP LEDs with 15 and 40-nm-thick Ag films were 1.7 and 2.9, respectively. The absorbance peak of Ag nanoparticles was red-shifted as diameter of Ag nanoparticles increases. However, the absorbance peak of Au nanoparticles was not related with their diameters. Spectrally-integrated enhancement of semi-polar LSP LED with 250-nm-diameter Ag nanoparticles was shown to 1.3. These results showed that the blue emission of semi-polar InGaN/GaN LED can be improved by SPP and LSP. - Highlights: • The enhancement of blue emission from semi-polar LED has been investigated. • The integrated PL intensity of semi-polar LED with 40-nm-thick Ag film was about 2.9. • The integrated PL intensity of semi-polar LED with Ag nanoparticles was about 1.3.

  20. Preparation and characterization of multi stimuli-responsive photoluminescent nanocomposites of graphene quantum dots with hyperbranched polyethylenimine derivatives

    Science.gov (United States)

    Liu, Xing; Liu, Hua-Ji; Cheng, Fa; Chen, Yu

    2014-06-01

    Oxidized graphene sheets (OGS) were treated with a hyperbranched polyethylenimine (PEI) under hydrothermal conditions to generate nanocomposites of graphene quantum dots (GQDs) functionalized with PEI (GQD-PEIs). The influence of the reaction temperature and the PEI/OGS feed ratio on the photoluminescence properties of the GQD-PEIs was studied. The obtained GQD-PEIs were characterized by TEM, dynamic light scattering, elemental analysis, FTIR, zeta potential measurements and 1H NMR spectroscopy, from which their structural information was inferred. Subsequently, isobutyric amide (IBAm) groups were attached to the GQD-PEIs through the amidation reaction of isobutyric anhydride with the PEI moieties, which resulted in GQD-PEI-IBAm nanocomposites. GQD-PEI-IBAm was not only thermoresponsive, but also responded to other stimuli, including inorganic salts, pH, and loaded organic guests. The cloud point temperature (Tcp) of aqueous solutions of GQD-PEI-IBAm could be modulated through changing the number of IBAm units in GQD-PEI-IBAm, by varying the type and concentration of the inorganic salts and loaded organic guests, or by varying the pH. All the obtained GQD-PEI-IBAm nanocomposites were photoluminescent, and their maximum emission wavelengths were not influenced by outside stimuli. Their emission intensities were influenced a little or negligibly by pH, traditional salting-out anions (Cl- and SO42-), and the relatively polar aspirin guest. However, the traditional salting-in I- anion and the more hydrophobic 1-pyrenebutyric acid (PBA) guest could effectively quench their fluorescence. 2D NOESY 1H NMR spectra verified that GQD-PEI-IBAm accommodated the relatively polar aspirin guest using the PEI-IBAm shell, but adsorbed the relatively hydrophobic PBA guest through the nanographene core. The release rate of the guest encapsulated by the thermoresponsive GQD is different below and above Tcp.Oxidized graphene sheets (OGS) were treated with a hyperbranched

  1. ZnO photoluminescent quantum dots with down-shifting effect applied in solar cells.

    Science.gov (United States)

    Zazueta-Raynaud, A.; Pelayo-Ceja, J. E.; Lopez-Delgado, R.; Ayon, A.

    2016-11-01

    We report the synthesis of Zinc Oxide (ZnO) quantum dots (QDs) and their influence on the power conversion efficiency of photovoltaic devices. With an excitation wavelength of 340 nm the down-shifted emission peaks were observed to be located at 510 and 540 nm for colloidal solutions with pH values of 10 and 12, respectively. The largest PCE variation was observed to increase from 14.60% to 15.49% when dispersing the QDs extracted from a 4 mL colloidal solution that were subsequently dispersed in PMMA. This represents an improvement of ∼6.1%.

  2. Quantification of thyroxine by the selective photoluminescence quenching of L-cysteine–ZnS quantum dots in aqueous solution containing hexadecyltrimethylammonium bromide

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Sarzamin; Carneiro, Leonardo S.A. [Chemistry Department, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900 Rio de Janeiro-RJ (Brazil); Romani, Eric C.; Larrudé, Dunieskys G. [Physics Department, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900, Rio de Janeiro-RJ (Brazil); Aucelio, Ricardo Q., E-mail: aucelior@puc-rio.br [Chemistry Department, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900 Rio de Janeiro-RJ (Brazil)

    2014-12-15

    The determination of L-thyroxine is proposed based on the photoluminescence quenching effect caused on the L-cysteine modified ZnS quantum dots (L-cysteine ZnS QDs) aqueous dispersion. Under optimum conditions, the analytical response followed a Stern–Volmer model and the experimental conditions were adjusted to enable a robust and reproducible photoluminescence signal. The linear response observed in the quantum dots aqueous dispersion covered the L-thyroxine concentration from the LOQ (2.0×10{sup −8} mol L{sup −1}) to 4.0×10{sup −6} mol L{sup −1}. The approach was tested in the determination of L-thyroxine in pharmaceutical formulations used to treat patients with thyroid gland disorder. The percent recoveries in controlled samples were between 93.3 and 103%. Analyte fortified saliva was also evaluated as a possible sample for L-thyroxine monitoring of a patient under treatment. It was identified a static type of photoluminescence quenching caused by L-thyroxine. - Highlights: • L-cysteine ZnS QDs were used as a photoluminescent probe to detect L-thyroxine. • Intensity of probe decreases following a Stern–Volmer model. • The method can detect down ng L{sup −1} levels of L-thyroxine in the probe dispersion. • Method was used to determinate of L-thyroxine in saliva and in pharmaceuticals. • Mechanism of interaction between L-thyroxine and quantum dots was studied.

  3. A Tunable Photoluminescent Composite of Cellulose Nanofibrils and CdS Quantum Dots

    Directory of Open Access Journals (Sweden)

    Qinwen Wang

    2016-09-01

    Full Text Available The preparation of fluorescent nanocomposite materials with tunable emission wavelengths by combining cellulose nanofibrils (CNFs with inorganic nanoparticles is important for promoting CNFs applications. A CNF/CdS nanocomposite was prepared via in situ compositing at room temperature on oxidized CNFs with CdS quantum dots. By controlling the –COOH/Cd2+ ratio on the CNF, the feeding time of Na2S and the ultrasonic maturing time, the size of the CdS quantum dots on the CNF surface could be adjusted so that to obtain the CNF/CdS nanocomposite material with different fluorescent colors. The results indicated that the CdS particles quantized were evenly distributed on the CNF. The maximum average size of the CdS nanoparticles glowed red under the excitation of UV light was 5.34 nm, which could be obtained with a –COOH/Cd2+ ratio of 1.0, a Na2S feeding time of 20 min, and an ultrasonic maturing time of 60 min. A series of CNF/CdS nanocomposite materials were obtained with CdS nanoparticle sizes varying from 3.44 nm to 5.34 nm, the emission wavelength of which varied from 546 nm to 655 nm, and their fluorescence color changed from green to yellow to red. This is the first time the fluorescence-tunable effect of the CNF/CdS nanocomposite has been realized.

  4. High-speed quantum networking by ship.

    Science.gov (United States)

    Devitt, Simon J; Greentree, Andrew D; Stephens, Ashley M; Van Meter, Rodney

    2016-11-02

    Networked entanglement is an essential component for a plethora of quantum computation and communication protocols. Direct transmission of quantum signals over long distances is prevented by fibre attenuation and the no-cloning theorem, motivating the development of quantum repeaters, designed to purify entanglement, extending its range. Quantum repeaters have been demonstrated over short distances, but error-corrected, global repeater networks with high bandwidth require new technology. Here we show that error corrected quantum memories installed in cargo containers and carried by ship can provide a exible connection between local networks, enabling low-latency, high-fidelity quantum communication across global distances at higher bandwidths than previously proposed. With demonstrations of technology with sufficient fidelity to enable topological error-correction, implementation of the quantum memories is within reach, and bandwidth increases with improvements in fabrication. Our approach to quantum networking avoids technological restrictions of repeater deployment, providing an alternate path to a worldwide Quantum Internet.

  5. Synthesis and photochemical applications of processable polymers enclosing photoluminescent carbon quantum dots.

    Science.gov (United States)

    Mosconi, Dario; Mazzier, Daniela; Silvestrini, Simone; Privitera, Alberto; Marega, Carla; Franco, Lorenzo; Moretto, Alessandro

    2015-04-28

    Herein, we propose convenient routes to produce hybrid-polymers that covalently enclosed, or confined, N-doped carbon quantum dots (CQDs). We focus our attention on polyamide, polyurea-urethane, polyester, and polymethylmetacrylate polymers, some of the most common resources used to create everyday materials. These hybrid materials can be easily prepared and processed to obtain macroscopic objects of different shapes, i.e., fibers, transparent sheets, and bulky forms, where the characteristic luminescence properties of the native N-doped CQDs are preserved. More importantly we explore the potential use of these hybrid composites to achieve photochemical reactions as those of photoreduction of silver ions to silver nanoparticles (under UV-light), the selective photo-oxidation of benzylalcohol to the benzaldehyde (under vis-light), and the photocatalytic generation of H2 (under UV-light).

  6. Photoluminescence studies on self-organized 1.55-μm InAs/InGaAsP/InP quantum dots under hydrostatic pressure

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, P. Y.; Dou, X. M.; Wu, X. F.; Ding, K.; Jiang, D. S.; Sun, B. Q., E-mail: bqsun@semi.ac.cn [State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Luo, S.; Yang, T.; Zhu, H. J. [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

    2014-07-14

    We report an experimental study on the optical properties of the self-organized 1.55-μm InAs/InGaAsP/InP quantum dots (QDs) under hydrostatic pressure up to 9.5 GPa at 10 K. The obtained pressure coefficients of emissions from InGaAsP to InAs QDs are 92 meV/GPa and 76 meV/GPa, respectively. Their photoluminescence intensities are found to decrease significantly with increasing pressure due to the pressure-induced Γ-X mixing of InGaAsP at about 8.5 GPa. The lifetime of excitonic emission from QDs decreases from about 1.15 at zero pressure to about 1.05 ns at 7.41 GPa. The wavelength of QD emission was tuned from 1.55 to 0.9 μm by applying a pressure of 8 GPa, displaying the feasibility for indirectly characterizing the individual InAs/InGaAsP/InP QDs of 1.55-μm emission (at zero pressure) under high-pressure using silicon avalanche photodiode.

  7. Highly efficient photoluminescence of SiO2 and Ce-SiO2 microfibres and microspheres.

    Science.gov (United States)

    Ruso, Juan M; Gravina, A Noel; D'Elía, Noelia L; Messina, Paula V

    2013-06-14

    Semiconductor nanocrystals and nanostructures have been extensively studied in the last few years due to their interesting optical and optoelectronic properties. Nevertheless, combining precise photoluminescence properties with controlled morphologies of SiO2 is a major hurdle for a broad range of basic research and technological applications. Here, we demonstrate that microemulsion droplet interfacial elasticity can be manipulated to induce definite morphologies associated with specific intrinsic and extrinsic photoluminescent defects in the silica matrix. Thus, under precise experimental conditions hollow crystalline and compact amorphous SiO2 spheres showing ultraviolet-photoluminescence and helicoidal fibrils of Ce-doped amorphous silica with violet-blue emissions are obtained. Overall, it is demonstrated that the combination of microemulsions and doping represents an easy strategy for the design of specific nanoscale structures with high efficiency photoluminescence. The detailed structural analysis provided in the present work is expected to be useful as accurate information on assessment of technological nanostructures.

  8. High resolution STEM of quantum dots and quantum wires

    DEFF Research Database (Denmark)

    Kadkhodazadeh, Shima

    2013-01-01

    This article reviews the application of high resolution scanning transmission electron microscopy (STEM) to semiconductor quantum dots (QDs) and quantum wires (QWRs). Different imaging and analytical techniques in STEM are introduced and key examples of their application to QDs and QWRs...

  9. Composition-dependent trap distributions in CdSe and InP quantum dots probed using photoluminescence blinking dynamics

    Science.gov (United States)

    Chung, Heejae; Cho, Kyung-Sang; Koh, Weon-Kyu; Kim, Dongho; Kim, Jiwon

    2016-07-01

    Although Group II-VI quantum dots (QDs) have attracted much attention due to their wide range of applications in QD-based devices, the presence of toxic ions in II-VI QDs raises environmental concerns. To fulfill the demands of nontoxic QDs, synthetic routes for III-V QDs have been developed. However, only a few comparative analyses on optical properties of III-V QDs have been performed. In this study, the composition-related energetic trap distributions have been explored by using three different types of core/multishell QDs: CdSe-CdS (CdSe/CdS/ZnS), InP-ZnSe (InP/ZnSe/ZnS), and InP-GaP (InP/GaP/ZnS). It was shown that CdSe-CdS QDs have much larger trap densities than InP-shell QDs at higher energy states (at least 1Eg (band gap energy) above the lowest conduction band edge) based on probability density plots and Auger ionization efficiencies which are determined by analyses of photoluminescence blinking dynamics. This result suggests that the composition of encapsulated QDs is closely associated with the charge trapping processes, and also provides an insight into the development of more environmentally friendly QD-based devices.Although Group II-VI quantum dots (QDs) have attracted much attention due to their wide range of applications in QD-based devices, the presence of toxic ions in II-VI QDs raises environmental concerns. To fulfill the demands of nontoxic QDs, synthetic routes for III-V QDs have been developed. However, only a few comparative analyses on optical properties of III-V QDs have been performed. In this study, the composition-related energetic trap distributions have been explored by using three different types of core/multishell QDs: CdSe-CdS (CdSe/CdS/ZnS), InP-ZnSe (InP/ZnSe/ZnS), and InP-GaP (InP/GaP/ZnS). It was shown that CdSe-CdS QDs have much larger trap densities than InP-shell QDs at higher energy states (at least 1Eg (band gap energy) above the lowest conduction band edge) based on probability density plots and Auger ionization

  10. Photoluminescence and photocurrent from InP nanowires with InAsP quantum dots grown on Si by molecular beam epitaxy

    Science.gov (United States)

    Kuyanov, P.; LaPierre, R. R.

    2015-08-01

    InP nanowires with InAsP quantum dots (QDs) were grown by molecular beam epitaxy on a Si (111) substrates. The structure of the InAsP QDs were studied using transmission electron microscopy, allowing the development of a model where QD growth occurs by group V desorption from the surrounding substrate surface. Micro-photoluminescence was performed at 10 K showing emission at 1.47-1.49 eV from the InP wurtzite structure, and various emission peaks between 0.93 and 1.33 eV attributed to the QDs. The emission was tuned by the QD composition. The effectiveness of an AlInP passivation shell was demonstrated via an improvement in the photoluminescence intensity. Spectrally-resolved photocurrent measurements at room temperature demonstrated infrared response due to absorption within the QDs. The absorption red-shifted with increasing As composition of the QD.

  11. Photoluminescence of anti-modulation doped near-surface GaAs/AlGaAs single quantum well structures exposed to hydrogen plasma

    CERN Document Server

    Bumaj, Y A; Goldkhan, R; Shtajn, N; Golombek, A; Nakov, V; Cheng, T S

    2002-01-01

    The anti-modulation Si-doped GaAs/AlGaAs structures with near-surface single quantum wells grown by molecular-beam epitaxy were exposed to hydrogen plasma at 260 deg C and investigated by low-temperature photoluminescence, photoluminescence excitation and photoreflectance spectroscopy. After hydrogenation, the quenching of the exciton luminescence for the below AlGaAs band gap excitation due to the increase of electric field in the structure has been observed. The effect is consistent with unpinning of Fermi level from mid gap of nominally undoped (p-type) GaAs cap layer due to passivation of surface states by hydrogen without neutralization of shallow impurities in the epilayers

  12. Intersublevel infrared photodetector with strain-free GaAs quantum dot pairs grown by high-temperature droplet epitaxy.

    Science.gov (United States)

    Wu, Jiang; Shao, Dali; Dorogan, Vitaliy G; Li, Alvason Z; Li, Shibin; DeCuir, Eric A; Manasreh, M Omar; Wang, Zhiming M; Mazur, Yuriy I; Salamo, Gregory J

    2010-04-14

    Normal incident photodetection at mid infrared spectral region is achieved using the intersublevel transitions from strain-free GaAs quantum dot pairs in Al(0.3)Ga(0.7)As matrix. The GaAs quantum dot pairs are fabricated by high temperature droplet epitaxy, through which zero strain quantum dot pairs are obtained from lattice matched materials. Photoluminescence, photoluminescence excitation optical spectroscopy, and visible-near-infrared photoconductivity measurement are carried out to study the electronic structure of the photodetector. Due to the intersublevel transitions from GaAs quantum dot pairs, a broadband photoresponse spectrum is observed from 3 to 8 microm with a full width at half-maximum of approximately 2.0 microm.

  13. High quantum yield ZnO quantum dots synthesizing via an ultrasonication microreactor method.

    Science.gov (United States)

    Yang, Weimin; Yang, Huafang; Ding, Wenhao; Zhang, Bing; Zhang, Le; Wang, Lixi; Yu, Mingxun; Zhang, Qitu

    2016-11-01

    Green emission ZnO quantum dots were synthesized by an ultrasonic microreactor. Ultrasonic radiation brought bubbles through ultrasonic cavitation. These bubbles built microreactor inside the microreactor. The photoluminescence properties of ZnO quantum dots synthesized with different flow rate, ultrasonic power and temperature were discussed. Flow rate, ultrasonic power and temperature would influence the type and quantity of defects in ZnO quantum dots. The sizes of ZnO quantum dots would be controlled by those conditions as well. Flow rate affected the reaction time. With the increasing of flow rate, the sizes of ZnO quantum dots decreased and the quantum yields first increased then decreased. Ultrasonic power changed the ultrasonic cavitation intensity, which affected the reaction energy and the separation of the solution. With the increasing of ultrasonic power, sizes of ZnO quantum dots first decreased then increased, while the quantum yields kept increasing. The effect of ultrasonic temperature on the photoluminescence properties of ZnO quantum dots was influenced by the flow rate. Different flow rate related to opposite changing trend. Moreover, the quantum yields of ZnO QDs synthesized by ultrasonic microreactor could reach 64.7%, which is higher than those synthesized only under ultrasonic radiation or only by microreactor. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Highly Efficient Near-IR Photoluminescence of Er3+ Immobilized in Mesoporous SBA-15

    Directory of Open Access Journals (Sweden)

    Wu P

    2010-01-01

    Full Text Available Abstract SiO2 mesoporous molecular sieve SBA-15 with the incorporation of erbium ions is studied as a novel type of nanoscopic composite photoluminescent material in this paper. To enhance the photoluminescence efficiency, two schemes have been used for the incorporation of Er3+ where (1 Er3+ is ligated with bis-(perfluoromethylsulfonyl-aminate (PMS forming Er(PMSx-SBA-15 and (2 Yb3+ is codoped with Er3+ forming Yb-Er-SBA-15. As high as 11.17 × 10−21cm2 of fluorescent cross section at 1534 nm and 88 nm of “effective bandwidth” have been gained. It is a 29.3% boost in fluorescent cross section compared to what has been obtained in conventional silica. The upconversion coefficient in Yb-Er-SBA-15 is relatively small compared to that in other ordinary glass hosts. The increased fluorescent cross section and lowered upconversion coefficient could benefit for the high-gain optical amplifier. Finally, the Judd–Ofelt theory has also been used for the analyses of the optical spectra of Er(PMSx-SBA-15.

  15. High Quantum Yield Blue Emission from Lead-Free Inorganic Antimony Halide Perovskite Colloidal Quantum Dots.

    Science.gov (United States)

    Zhang, Jian; Yang, Ying; Deng, Hui; Farooq, Umar; Yang, Xiaokun; Khan, Jahangeer; Tang, Jiang; Song, Haisheng

    2017-09-26

    Colloidal quantum dots (QDs) of lead halide perovskite have recently received great attention owing to their remarkable performances in optoelectronic applications. However, their wide applications are hindered from toxic lead element, which is not environment- and consumer-friendly. Herein, we utilized heterovalent substitution of divalent lead (Pb(2+)) with trivalent antimony (Sb(3+)) to synthesize stable and brightly luminescent Cs3Sb2Br9 QDs. The lead-free, full-inorganic QDs were fabricated by a modified ligand-assisted reprecipitation strategy. A photoluminescence quantum yield (PLQY) was determined to be 46% at 410 nm, which was superior to that of other reported halide perovskite QDs. The PL enhancement mechanism was unraveled by surface composition derived quantum-well band structure and their large exciton binding energy. The Br-rich surface and the observed 530 meV exciton binding energy were proposed to guarantee the efficient radiative recombination. In addition, we can also tune the inorganic perovskite QD (Cs3Sb2X9) emission wavelength from 370 to 560 nm via anion exchange reactions. The developed full-inorganic lead-free Sb-perovskite QDs with high PLQY and stable emission promise great potential for efficient emission candidates.

  16. High-Sensitive Sensor of Dopamine Based on Photoluminescence Quenching of Hierarchical CdS Spherical Aggregates

    Directory of Open Access Journals (Sweden)

    Binjie Sun

    2012-01-01

    Full Text Available Hierarchical CdS spherical aggregates have been fabricated by an assembling strategy starting from nanoparticles, which opens a general way to obtain hierarchical spherical aggregates of different types of materials. The hierarchical CdS spherical aggregates are of high porosity and high surface area, which give rise to unique photoluminescence properties. The desirable properties we report here will spur further developments of novel dopamine photoluminescence sensors based on the high surface area hierarchical CdS spherical aggregates fabricated with our unique assembling strategy. The novel dopamine photoluminescence sensor has a low detection limit of 1.0×10−8 M, which is much lower than those reported previously.

  17. Effect of bismuth surfactant on InP-based highly strained InAs/InGaAs triangular quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Y.; Zhang, Y. G., E-mail: ygzhang@mail.sim.ac.cn; Chen, X. Y.; Xi, S. P.; Du, B.; Ma, Y. J. [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2015-11-23

    We report the effect of Bi surfactant on the properties of highly strained InAs/InGaAs triangular quantum wells grown on InP substrates. Reduced surface roughness, improved heterostructure interfaces and enhanced photoluminescence intensity at 2.2 μm are observed by moderate Bi-mediated growth. The nonradiative processes are analysed based on temperature-dependent photoluminescence. It is confirmed that Bi incorporation is insignificant in the samples, whereas excessive Bi flux during the growth results in deteriorated performance. The surfactant effect of Bi is promising to improve InP-based highly strained structures while the excess of Bi flux needs to be avoided.

  18. Strong Photoluminescence Enhancement in All-Dielectric Fano Metasurface with High Quality Factor.

    Science.gov (United States)

    Yuan, Shuai; Qiu, Xingzhi; Cui, Chengcong; Zhu, Liangqiu; Wang, Yuxi; Li, Yi; Song, Jinwen; Huang, Qingzhong; Xia, Jinsong

    2017-11-28

    All-dielectric metamaterials offer great flexibility for controlling light-matter interaction, owing to their strong electric and magnetic resonances with negligible loss at wavelengths above the material bandgap. Here, we propose an all-dielectric asymmetric metasurface structure exhibiting high quality factor and prominent Fano line shape. Over three-orders photoluminescence enhancement is demonstrated in the fabricated all-dielectric metasurface with record-high quality factor of 1011. We find this strong emission enhancement is attributed to the coherent Fano resonances, which originate from the destructive interferences of antisymmetric displacement currents in the asymmetric all-dielectric metasurface. Our observations show a promising approach to realize light emitters based on all-dielectric metasurfaces.

  19. Direct measurement of the hole-nuclear spin interaction in single InP/GaInP quantum dots using photoluminescence spectroscopy.

    Science.gov (United States)

    Chekhovich, E A; Krysa, A B; Skolnick, M S; Tartakovskii, A I

    2011-01-14

    We measure the hyperfine interaction of the valence band hole with nuclear spins in single InP/GaInP semiconductor quantum dots. Detection of photoluminescence (PL) of both "bright" and "dark" excitons enables direct measurement of the Overhauser shift of states with the same electron but opposite hole spin projections. We find that the hole hyperfine constant is ≈11% of that of the electron and has the opposite sign. By measuring the degree of circular polarization of the PL, an upper limit to the contribution of the heavy-light hole mixing to the measured value of the hole hyperfine constant is deduced. Our results imply that environment-independent hole spins are not realizable in III-V semiconductor, a result important for solid-state quantum information processing using hole spin qubits.

  20. Photoluminescence energy transitions in GaAs-Ga{sub 1-x}Al{sub x}As double quantum wells: Electric and magnetic fields and hydrostatic pressure effects

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, S.Y. [Grupo de Educacion en Ciencias Experimentales y Matematicas-GECEM, Facultad de Educacion, Universidad de Antioquia, AA 1226 Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque@fisica.udea.edu.c [Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia)

    2009-12-15

    The photoluminescence energy transitions in GaAs-Ga{sub 1-x}Al{sub x}As coupled double quantum wells are presented by considering the simultaneous effects of applied electric and magnetic fields and hydrostatic pressure. Calculations have been made in the framework of the effective mass and parabolic band approximations and using a variational procedure. The electric field is taken to be oriented along the growth direction of the heterostructure whereas for the magnetic field both in-plane and in-growth directions have been considered. The results show that the hydrostatic pressure and the applied electric field are two useful tools to tune the direct and indirect exciton transitions in such heterostructures. Our results are in good agreement with previous experimental findings in double quantum wells under applied electric field and hydrostatic pressure.

  1. Bidentate Ligand-passivated CsPbI3 Perovskite Nanocrystals for Stable Near-unity Photoluminescence Quantum Yield and Efficient Red Light-emitting Diodes

    KAUST Repository

    Pan, Jun

    2017-12-17

    Although halide perovskite nanocrystals (NCs) are promising materials for optoelectronic devices, they suffer severely from chemical and phase instabilities. Moreover, the common capping ligands like oleic acid and oleylamine that encapsulate the NCs will form an insulating layer, precluding their utility in optoelectronic devices. To overcome these limitations, we develop a post-synthesis passivation process for CsPbI3 NCs by using a bidentate ligand, namely 2,2’-Iminodibenzoic acid. Our passivated NCs exhibit narrow red photoluminescence with exceptional quantum yield (close to unity) and substantially improved stability. The passivated NCs enabled us to realize red light-emitting diodes (LEDs) with 5.02% external quantum efficiency and 748 cd/m2 luminance, surpassing by far LEDs made from the non-passivated NCs.

  2. High-fidelity quantum driving

    DEFF Research Database (Denmark)

    Bason, Mark George; Viteau, Matthieu; Malossi, Nicola

    2011-01-01

    Accurately controlling a quantum system is a fundamental requirement in quantum information processing and the coherent manipulation of molecular systems. The ultimate goal in quantum control is to prepare a desired state with the highest fidelity allowed by the available resources and the experi......Accurately controlling a quantum system is a fundamental requirement in quantum information processing and the coherent manipulation of molecular systems. The ultimate goal in quantum control is to prepare a desired state with the highest fidelity allowed by the available resources...... with the Heisenberg uncertainty principle. In the opposite limit, we realize the recently proposed transitionless superadiabatic protocols in which the system follows the instantaneous adiabatic ground state nearly perfectly. We demonstrate that superadiabatic protocols are extremely robust against control parameter...

  3. Preparation of highly aligned silicon oxide nanowires with stable intensive photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Duraia, El-Shazly M., E-mail: duraia_physics@yahoo.co [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Al-Farabi Kazakh National University, Almaty (Kazakhstan); Institute of Physics and Technology, 11 Ibragimov Street, 050032 Almaty (Kazakhstan); Mansurov, Z.A. [Al-Farabi Kazakh National University, Almaty (Kazakhstan); Tokmolden, S. [Institute of Physics and Technology, 11 Ibragimov Street, 050032 Almaty (Kazakhstan); Beall, Gary W. [Texas State University-San Marcos, Department of Chemistry and Biochemistry, 601 University Dr., San Marcos, TX 78666 (United States)

    2010-02-15

    In this work we report the successful formation of highly aligned vertical silicon oxide nanowires. The source of silicon was from the substrate itself without any additional source of silicon. X-ray measurement demonstrated that our nanowires are amorphous. Photoluminescence measurements were conducted through 18 months and indicated that there is a very good intensive emission peaks near the violet regions. The FTIR measurements indicated the existence of peaks at 463, 604, 795 and a wide peak at 1111 cm{sup -1} and this can be attributed to Si-O-Si and Si-O stretching vibrations. We also report the formation of the octopus-like silicon oxide nanowires and the growth mechanism of these structures was discussed.

  4. High photoluminescent metal-organic frameworks as optical markers for the identification of gunshot residues.

    Science.gov (United States)

    Weber, Ingrid Távora; de Melo, Adenaule James Geber; Lucena, Marcella Auxiliadora de Melo; Rodrigues, Marcelo Oliveira; Alves, Severino

    2011-06-15

    Gunshot residue (GSR) are solid particles produced when a firearm is discharged, and its detection is important evidence in forensic investigations. Currently, scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS) is the standard technique adopted for the analysis and identification of GSR; however, this methodology is inefficient for lead-free ammunition. Herein, we report the inclusion of high photoluminescent metal-organic frameworks in ammunition to allow for the visual detection of GSR. The tests indicated that marked GSR is easily visible in proportions above 5.0 wt %. A total of 1 g of marker suffices to tag 100 0.38 mm bullets or 62 0.40 mm bullets.

  5. Radio-photoluminescence of highly irradiated LiF:Mg,Ti and LiF:Mg,Cu,P detectors

    OpenAIRE

    Mrozik, Anna; Bilski, Paweł; Marczewska, Barbara; Obryk, Barbara; Hodyr, Krzysztof; Gieszczyk, Wojciech

    2014-01-01

    The radio-photoluminescent (RPL) characteristics of LiF:Mg,Ti (MTS) and LiF:Mg,Cu,P (MCP) thermoluminescent detectors, routinely used in radiation protection dosimetry, were investigated after irradiation with ultra-high electron doses ranging up to 1 MGy. The photoluminescence of both types of LiF detectors was stimulated by a blue light (460 nm) and measured within a spectral window around 530 nm. The RPL dose response was found to be linear up to 50 kGy and sublinear in the range of 50 kGy...

  6. Size-Dependent Non-FRET Photoluminescence Quenching in Nanocomposites Based on Semiconductor Quantum Dots CdSe/ZnS and Functionalized Porphyrin Ligands

    Directory of Open Access Journals (Sweden)

    Eduard I. Zenkevich

    2012-01-01

    Full Text Available We review recent experimental work to utilize the size dependence of the luminescence quenching of colloidal semiconductor quantum dots induced by functionalized porphyrin molecules attached to the surface to describe a photoluminescence (PL quenching process which is different from usual models of charge transfer (CT or Foerster resonant energy transfer (FRET. Steady-state and picosecond time-resolved measurements were carried out for nanocomposites based on colloidal CdSe/ZnS and CdSe quantum dots (QDs of various sizes and surfacely attached tetra-mesopyridyl-substituted porphyrin molecules (“Quantum Dot-Porphyrin” nanocomposites, in toluene at 295 K. It was found that the major part of the observed strong quenching of QD PL in “QD-Porphyrin” nanocomposites can neither be assigned to FRET nor to photoinduced charge transfer between the QD and the chromophore. This PL quenching depends on QD size and shell and is stronger for smaller quantum dots: QD PL quenching rate constants scale inversely with the QD diameter. Based on the comparison of experimental data and quantum mechanical calculations, it has been concluded that QD PL quenching in “QD-Porphyrin” nanocomposites can be understood in terms of a tunneling of the electron (of the excited electron-hole pair followed by a (self- localization of the electron or formation of trap states. The major contribution to PL quenching is found to be proportional to the calculated quantum-confined exciton wave function at the QD surface. Our findings highlight that single functionalized molecules can be considered as one of the probes for the complex interface physics and dynamics of colloidal semiconductor QD.

  7. Ratiometric two-photon excited photoluminescence of quantum dots triggered by near-infrared-light for real-time detection of nitric oxide release in situ

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Hui [Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, College of Chemistry and Chemical Engineering, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Shandong 266071 (China); Gui, Rijun, E-mail: guirijun@qdu.edu.cn [Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, College of Chemistry and Chemical Engineering, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Shandong 266071 (China); Sun, Jie; Wang, Yanfeng [Institute of Materia Medica, Shandong Academy of Medical Sciences, Jinan 250062 (China)

    2016-05-30

    Probe-donor integrated nanocomposites were developed from conjugating silica-coated Mn{sup 2+}:ZnS quantum dots (QDs) with MoS{sub 2} QDs and photosensitive nitric oxide (NO) donors (Fe{sub 4}S{sub 3}(NO){sub 7}{sup −}, RBS). Under excitation with near-infrared (NIR) light at 808 nm, the Mn{sup 2+}:ZnS@SiO{sub 2}/MoS{sub 2}-RBS nanocomposites showed the dual-emissive two-photon excited photoluminescence (TPEPL) that induced RBS photolysis to release NO in situ. NO caused TPEPL quenching of Mn{sup 2+}:ZnS QDs, but it produced almost no impact on the TPEPL of MoS{sub 2} QDs. Hence, the nanocomposites were developed as a novel QDs-based ratiometric TPEPL probe for real-time detection of NO release in situ. The ratiometric TPEPL intensity is nearly linear (R{sup 2} = 0.9901) with NO concentration in the range of 0.01∼0.8 μM, which corresponds to the range of NO release time (0∼15 min). The detection limit was calculated to be approximately 4 nM of NO. Experimental results confirmed that this novel ratiometric TPEPL probe possessed high selectivity and sensitivity for the detection of NO against potential competitors, and especially showed high detection performance for NIR-light triggered NO release in tumor intracellular microenvironments. These results would promote the development of versatile probe-donor integrated systems, also providing a facile and efficient strategy to real-time detect the highly controllable drug release in situ, especially in physiological microenvironments. - Highlights: • Mn{sup 2+}:ZnS@SiO{sub 2}/MoS{sub 2}-RBS nanocomposites were developed as a novel ratiometric two-photon excited fluorescence probe. • This probe could conduct real-time detection of nitric oxide release in situ. • High feasibility of this probe was confirmed in tumor intracellular microenvironments.

  8. Silica-coated S(2-)-enriched manganese-doped ZnS quantum dots as a photoluminescence probe for imaging intracellular Zn2+ ions.

    Science.gov (United States)

    Ren, Hu-Bo; Wu, Bo-Yue; Chen, Jia-Tong; Yan, Xiu-Ping

    2011-11-01

    Detection of intracellular Zn(2+) has gained great attention because of its biological significances. Here we show the fabrication of silica-coated S(2-)-enriched Mn-doped ZnS quantum dots (SiO(2)-S-Mn-ZnS QDs) by enriching S(2-) with a silica shell on the surface of Mn-doped ZnS QDs via a sol-gel process for imaging intracellular Zn(2+) ions. The developed probe gave a good linearity for the calibration plot (the recovered PL intensity of the SiO(2)-S-Mn-ZnS QDs against the concentration of Zn(2+) from 0.3 to 15.0 μM), excellent reproducibility (1.2% relative standard deviation for 11 replicate measurements of Zn(2+) at 3 μM), and low detection limit (3s; 80 nM Zn(2+)). The SiO(2)-S-Mn-ZnS QDs showed negligible cytotoxicity, good sensitivity, and selectivity for Zn(2+) in a photoluminescence turn-on mode, being a promising probe for photoluminescence imaging of intracellular Zn(2+).

  9. Change point analysis of matrix dependent photoluminescence intermittency of single CdSe/ZnS quantum dots with intermediate intensity levels

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Robert [Institute of Physics and Center for Nanostructured Materials and Analytics, Chemnitz University of Technology, Reichenhainer Str. 70, D 09107 Chemnitz (Germany); Krasselt, Cornelius, E-mail: cornelius.krasselt@physik.tu-chemnitz.de [Institute of Physics and Center for Nanostructured Materials and Analytics, Chemnitz University of Technology, Reichenhainer Str. 70, D 09107 Chemnitz (Germany); Borczyskowski, Christian von [Institute of Physics and Center for Nanostructured Materials and Analytics, Chemnitz University of Technology, Reichenhainer Str. 70, D 09107 Chemnitz (Germany)

    2012-10-08

    Highlights: Black-Right-Pointing-Pointer We study single blinking CdSe/ZnS quantum dots in polystyrene and polyvinyl alcohol. Black-Right-Pointing-Pointer The blinking dynamics were analysed with respect to intermediate intensity levels. Black-Right-Pointing-Pointer The On-times show a matrix dependent deviation from a truncated power law. Black-Right-Pointing-Pointer Deviation relates to well defined intensities, intensity jumps and state dwell times. Black-Right-Pointing-Pointer Quantum dots are coupled to hydroxyl groups which induce hole traps. -- Abstract: Blinking dynamics of single CdSe/ZnS quantum dots are analyzed by change point analysis, which gives access to intermediate photoluminescence (PL) intensities observed during PL intermittency. The on-times show systematic deviations from a (truncated) power law. This deviation is manifested in variations of the PL intensity distribution and is related with well defined PL intensity jumps. Varying the matrix from polystyrene (PS) to polyvinyl alcohol (PVA) changes the on-time blinking dynamics and reveals coupling of the QDs either to OH-groups of the SiO{sub x} interface or to OH-groups of PVA. Analysis of dwell times in respective intensity correlated traps reveals that OH-related traps are strongly stabilized with much longer dwell times as compared to otherwise broadly distributed trap states.

  10. Enhanced room-temperature 3.5 µm photoluminescence in stress-balanced metamorphic In(Sb,As)/In(Ga,Al)As/GaAs quantum wells

    Science.gov (United States)

    Chernov, Mikhail Yu.; Solov’ev, Victor A.; Komkov, Oleg S.; Firsov, Dmitriy D.; Meltser, Boris Ya.; Yagovkina, Maria A.; Baidakova, Marina V.; Kop’ev, Petr S.; Ivanov, Sergey V.

    2017-12-01

    In this Letter, we report on the design optimization of metamorphic InSb/InAs/In(Ga,Al)As/GaAs heterostructures with type-II-in-type-I quantum well (QW) active regions, aimed at the enhancement of their room-temperature photoluminescence (PL). The strong influence of the design of the convex-graded metamorphic buffer layer (MBL) and the value of the MBL inverse step in the range from 2 to 14 mol % In on stresses in such heterostructures, as well as their PL intensity, are discussed. The optimized metamorphic In(Sb,As)/In0.63Ga0.37As/In0.75Al0.25As/MBL/GaAs structure with the inverse step of 10 mol % demonstrates 3.2–3.5 µm mid-IR PL intensity quenching from liquid-nitrogen to room temperature by a factor of 12.

  11. Carrier redistribution between different potential sites in semipolar (202¯1) InGaN quantum wells studied by near-field photoluminescence

    KAUST Repository

    Marcinkevičius, S.

    2014-09-15

    © 2014 AIP Publishing LLC. Scanning near-field photoluminescence (PL) spectroscopy at different excitation powers was applied to study nanoscale properties of carrier localization and recombination in semipolar (202¯1) InGaN quantum wells (QWs) emitting in violet, blue, and green-yellow spectral regions. With increased excitation power, an untypical PL peak energy shift to lower energies was observed. The shift was attributed to carrier density dependent carrier redistribution between nm-scale sites of different potentials. Near-field PL scans showed that in (202¯1) QWs the in-plane carrier diffusion is modest, and the recombination properties are uniform, which is advantageous for photonic applications.

  12. High quantum yield graphene quantum dots decorated TiO{sub 2} nanotubes for enhancing photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Ailan, E-mail: qal67@163.com; Xie, Haolong; Xu, Xinmei; Zhang, Yangyu; Wen, Shengwu; Cui, Yifan

    2016-07-01

    Highlights: • High concentration yellow GQDs and TiO{sub 2} nanotubes were achieved by a simple and green method. • High quantum yield GQDs enhanced the photodegradation capacity of TiO{sub 2} nanotube. • The catalytic performance of GQDs/TiO{sub 2} depends on the GQDs loading. • The improved photocatalytic activity of GQDs/TiO{sub 2} was attributed to three aspects. - Abstract: Graphene quantum dots (GQDs) with high quantum yield (about 23.6% at an excitation wavelength of 320 nm) and GQDs/TiO{sub 2} nanotubes (GQDs/TiO{sub 2} NTs) composites were achieved by a simple hydrothermal method at low temperature. Photoluminescence characterization showed that the GQDs exhibited the down-conversion PL features at excitation from 300 to 420 nm and up-conversion photoluminescence in the range of 600–800 nm. The photocatalytic activity of prepared GQDs/TiO{sub 2} NTs composites on the degradation of methyl orange (MO) was significantly enhanced compared with that of pure TiO{sub 2} nanotubes (TiO{sub 2} NTs). For the composites coupling with 1.5%, 2.5% and 3.5% GQDs, the degradation of MO after 20 min irradiation under UV–vis light irradiation (λ = 380–780 nm) were 80.52%, 94.64% and 51.91%, respectively, which are much higher than that of pure TiO{sub 2} NTs (35.41%). It was inferred from the results of characterization that the improved photocatalytic activity of the GQDs/TiO{sub 2} NTs composites was attributed to the synergetic effect of up-conversion properties of the GQDs, enhanced visible light absorption and efficient separation of photogenerated electron-holes of the GQDs/TiO{sub 2} composite.

  13. Photoluminescence and reflectivity studies of high energy light ions irradiated polymethyl methacrylate films

    Science.gov (United States)

    Bharti, Madhu Lata; Singh, Fouran; Ramola, R. C.; Joshi, Veena

    2017-11-01

    The self-standing films of non-conducting polymethyl methacrylate (PMMA) were irradiated in vacuum using high energy light ions (HELIs) of 50 MeV Lithium (Li+3) and 80 MeV Carbon (C+5) at various ion dose to induce the optical changes in the films. Upon HELI irradiation, films exhibit a significant enhancement in optical reflectivity at the highest dose. Interestingly, the photoluminescence (PL) emission band with green light at (514.5 nm) shows a noticeable increase in the intensity with increasing ion dose for both ions. However, the rate of increase in PL intensity is different for both HELI and can be correlated with the linear energy transfer by these ions in the films. Origin of PL is attributed to the formation of carbon cluster and hydrogenated amorphous carbon in the polymer films. HAC clusters act as PL active centres with optical reflectivity. Most of the harmful radiation like UV are absorbed by the material and is becoming opaque after irradiation and this PL active material are useful in fabrication of optoelectronic devices, UV-filter, back-lit components in liquid crystal display systems, micro-components for integrate optical circuits, diffractive elements, advanced materials and are also applicable to the post irradiation laser treatment by means of ion irradiation.

  14. Photoluminescence of highly porous nanostructured Si-based thin films deposited by pulsed laser ablation

    Science.gov (United States)

    Yang, D.-Q.; Ethier, V.; Sacher, E.; Meunier, M.

    2005-07-01

    Nanostructured, Si-based cottonlike, highly porous thin films of Si, SiNx, and SiOx were deposited by the excimer laser ablation of Si targets in He, He /N2, and He /O2 ambients, respectively. Photoluminescence (PL), x-ray photoelectron spectroscopy, and photoacoustic Fourier transform IR have been used to characterize these deposits. After exposure to air, broad PL bands appear at 1.7eV (Si), 2.0eV (SiNx), and 2.3eV (SiOx); air oxidation causes the separation of the PL spectra into two identical component peaks, at 1.5 and 2.3eV, whose relative ratios differ with film composition. The present results indicate that the red PL peak at 1.5eV is due to the localized states at the oxidized surfaces of these materials, while the green PL peak at 2.3eV is due to oxygen-related defects in their local disordered nanostructures.

  15. Classification and control of the origin of photoluminescence from Si nanocrystals.

    Science.gov (United States)

    Godefroo, S; Hayne, M; Jivanescu, M; Stesmans, A; Zacharias, M; Lebedev, O I; Van Tendeloo, G; Moshchalkov, V V

    2008-03-01

    Silicon dominates the electronics industry, but its poor optical properties mean that III-V compound semiconductors are preferred for photonics applications. Photoluminescence at visible wavelengths was observed from porous Si at room temperature in 1990, but the origin of these photons (do they arise from highly localized defect states or quantum confinement effects?) has been the subject of intense debate ever since. Attention has subsequently shifted from porous Si to Si nanocrystals, but the same fundamental question about the origin of the photoluminescence has remained. Here we show, based on measurements in high magnetic fields, that defects are the dominant source of light from Si nanocrystals. Moreover, we show that it is possible to control the origin of the photoluminescence in a single sample: passivation with hydrogen removes the defects, resulting in photoluminescence from quantum-confined states, but subsequent ultraviolet illumination reintroduces the defects, making them the origin of the light again.

  16. Effect of band alignment on photoluminescence and carrier escape from InP surface quantum dots grown by metalorganic chemical vapor deposition on Si

    Energy Technology Data Exchange (ETDEWEB)

    Halder, Nripendra N. [Advanced Technology Development Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Biswas, Pranab; Banerji, P., E-mail: pallab@matsc.iitkgp.ernet.in [Materials Science Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Dhabal Das, Tushar; Das, Sanat Kr.; Chattopadhyay, S. [Department of Electronic Science, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Biswas, D. [Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology, Kharagpur 721 302 (India)

    2014-01-28

    A detailed analysis of photoluminescence (PL) from InP quantum dots (QDs) grown on Si has been carried out to understand the effect of substrate/host material in the luminescence and carrier escape process from the surface quantum dots. Such studies are required for the development of monolithically integrated next generation III-V QD based optoelectronics with fully developed Si microelectronics. The samples were grown by atmospheric pressure metalorganic chemical vapor deposition technique, and the PL measurements were made in the temperature range 10–80 K. The distribution of the dot diameter as well as the dot height has been investigated from atomic force microscopy. The origin of the photoluminescence has been explained theoretically. The band alignment of InP/Si heterostructure has been determined, and it is found be type II in nature. The positions of the conduction band minimum of Si and the 1st excited state in the conduction band of InP QDs have been estimated to understand the carrier escape phenomenon. A blue shift with a temperature co-efficient of 0.19 meV/K of the PL emission peak has been found as a result of competitive effect of different physical processes like quantum confinement, strain, and surface states. The corresponding effect of blue shift by quantum confinement and strain as well as the red shift by the surface states in the PL peaks has been studied. The origin of the luminescence in this heterojunction is found to be due to the recombination of free excitons, bound excitons, and a transition from the 1st electron excited state in the conduction band (e{sub 1}) to the heavy hole band (hh{sub 1}). Monotonic decrease in the PL intensity due to increase of thermally escaped carriers with temperature has been observed. The change in barrier height by the photogenerated electric-field enhanced the capture of the carriers by the surface states rather than their accumulation in the QD excited state. From an analysis of the dependence of

  17. Spatially and spectrally resolved photoluminescence of InGaN MQWs grown on highly Si doped a-plane GaN buffer

    Energy Technology Data Exchange (ETDEWEB)

    Thunert, Martin; Wieneke, Matthias; Dempewolf, Anja; Bertram, Frank; Dadgar, Armin; Krost, Alois; Christen, Juergen [Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg (Germany)

    2011-07-01

    A set of InGaN multi quantum well (MQW) samples grown by MOVPE on highly Si doped a-plane GaN on r-plane sapphire templates has been investigated using spatially resolved photoluminescence spectroscopy ({mu}-PL). The Si doping level of nominal about 10{sup 20} cm{sup -3} leads to three dimensionally grown crystallites mostly terminated by m-facets. The MQW thickness has been systematically varied from nominally 2.1 to 4.2 nm, as well as the InGaN growth temperature, which was varied from 760 C to 700 C. The growth of a-plane GaN based devices leads to a non-polar growth direction avoiding the polarization field affected Quantum-Confined-Stark-Effect. Spatially resolved PL studies show for all samples low near band edge (NBE) GaN emission intensity over the whole area under investigation accompanied by highly intense InGaN MQW emission for single crystallites. The MQW luminescence shows a systematic blueshift with increasing InGaN growth temperature due to lower In incorporation as well as a systematic redshift with increasing MQW thickness. Excitation power dependent spectra at 4 K as well as temperature dependent PL spectra will be presented.

  18. Quantum entanglement of high angular momenta.

    Science.gov (United States)

    Fickler, Robert; Lapkiewicz, Radek; Plick, William N; Krenn, Mario; Schaeff, Christoph; Ramelow, Sven; Zeilinger, Anton

    2012-11-02

    Single photons with helical phase structures may carry a quantized amount of orbital angular momentum (OAM), and their entanglement is important for quantum information science and fundamental tests of quantum theory. Because there is no theoretical upper limit on how many quanta of OAM a single photon can carry, it is possible to create entanglement between two particles with an arbitrarily high difference in quantum number. By transferring polarization entanglement to OAM with an interferometric scheme, we generate and verify entanglement between two photons differing by 600 in quantum number. The only restrictive factors toward higher numbers are current technical limitations. We also experimentally demonstrate that the entanglement of very high OAM can improve the sensitivity of angular resolution in remote sensing.

  19. High-density excitation effect on photoluminescence in ZnO nanoparticles

    Science.gov (United States)

    Suzuki, Keigo; Inoguchi, Masashi; Fujita, Koji; Murai, Shunsuke; Tanaka, Katsuhisa; Tanaka, Nobuhiko; Ando, Akira; Takagi, Hiroshi

    2010-06-01

    In this study, photoluminescence (PL) under high excitation intensity as a function of crystalline size was systematically investigated through ZnO nanocrystalline films prepared by spin-coating a colloidal solution of ZnO nanoparticles obtained using the microemulsion method. Annealing of the films at 723, 633, and 593 K allowed us to tune the crystalline radius R. PL studies distinguished different regimes of crystalline size according to the ratio of R to the effective Bohr radius aB(R /aB). For the sample annealed at 723 K (R /aB=7.2), the peak of stimulated emission due to the exciton-exciton collisions appeared on the low-energy side of the exciton emission with an increase in excitation intensity. A further increase in excitation intensity eventually resulted in the occurrence of an electron-hole plasma (EHP) accompanied by consequent band gap renormalization, which indicates that high excitation intensity provokes the dissociation of excitons. For the sample annealed at 633 K (R /aB=4.7), the stimulated emission was observed while the transition to EHP was obscure. For the sample annealed at 593 K (R /aB=2.1), only emissions due to the recombination of the electron-hole pair were observed, and stimulated emission did not appear even when the excitation intensity was increased. The transition from free-exciton emission to donor-bound exciton emission was observed in temperature dependence of PL only for the sample with R /aB=7.2. The origin of annihilation of the stimulated emission with a size reduction is discussed based on nonradiative Auger recombination.

  20. Transmission electron microscopy and photoluminescence characterization of InGaAs strained quantum wires on GaAs vicinal (110) substrates

    CERN Document Server

    Shim, B R; Ota, T; Kobayashi, K; Maehashi, K; Nakashima, H; Lee, S Y

    1999-01-01

    We have used transmission electron microscopy (TEM) and photoluminescence (PL) to study InGaAs/AlGaAs strained quantum wires (QWRs) grown by molecular beam epitaxy (MBE) on GaAs vicinal (110) substrates. The cross-sectional TEM image reveals that InGaAs QWRs structures are naturally formed on AlGaAs giant steps. In the plan-view TEM images, the fringe pattern in the giant-step region is observed for In sub x Ga sub 1 sub - sub x As layers with x<= 0.4 We measured the separation of the fringe in the plan-view TEM images and compared the result with the calculated fringe separation. From this result, we conclude that the fringes observed in the plan-view TEM images are moire fringes. PL spectra of the InGaAs QWRs samples reveal 80-meV shifts to lower energy with respect to the spectrum of a quantum well (QWL) grown on a (001) substrate under the same conditions. We also measured the polarization anisotropy of the PL spectra from the QWRs. The PL peak shifts systematically toward higher energy with decreasing...

  1. Photoluminescence of double core/shell infrared (CdSeTe)/ZnS quantum dots conjugated to Pseudo rabies virus antibodies

    Science.gov (United States)

    Torchynska, T. V.; Casas Espinola, J. L.; Jaramillo Gómez, J. A.; Douda, J.; Gazarian, K.

    2013-06-01

    Double core CdSeTe/ZnS quantum dots (QDs) with emission at 800 nm (1.60 eV) have been studied by photoluminescence (PL) and Raman scattering methods in the non-conjugated state and after the conjugation to the Pseudo rabies virus (PRV) antibodies. The transformation of PL spectra, stimulated by the electric charge of antibodies, has been detected for the bioconjugated QDs. Raman scattering spectra are investigated with the aim to reveal the CdSeTe core compositions. The double core QD energy diagrams were designed that help to analyze the PL spectra and their transformation at the bioconjugation. It is revealed that the interface in double core QDs has the type II quantum well character that permits to explain the near IR optical transition (1.60 eV) in the double core QDs. It is shown that the essential transformation of PL spectra is useful for the study of QD bioconjugation with specific antibodies and can be a powerful technique in early medical diagnostics.

  2. CdSe/ZnS quantum dot films for high performance flexible lighting and display applications.

    Science.gov (United States)

    Altintas, Yemliha; Genc, Sinan; Talpur, Mohammad Younis; Mutlugun, Evren

    2016-07-22

    Colloidal quantum dots have attracted significant interest in recent years for lighting and display applications and have recently appeared in high-end market products. The integration of quantum dots with light emitting diodes has made them promising candidates for superior lighting applications with tunable optical characteristics. In this work we propose and demonstrate high quality colloidal quantum dots in their novel free-standing film forms to allow high quality white light generation to address flexible lighting and display applications. High quality quantum dots have been characterized using transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, steady state and time resolved photoluminescence and dynamic light scattering methods. The engineering of colloidal quantum dot composition and its optical properties in stand-alone film form has led to the experimentally high NTSC color gamut of 122.5 (CIE-1931) for display applications, color rendering index of 88.6, luminous efficacy of optical radiation value of 290 lm/Wopt and color temperature of 2763 K for lighting applications.

  3. High pressure effects on the photoluminescence intensity of sexithiophene single crystals

    NARCIS (Netherlands)

    Loi, M.A.; Bongiovanni, G.; Mura, A.; Cai, Q.; Martin, C.; Chandrasekhar, H.R.; Chandrasekhar, M.; Graupner, W.; Garnier, F.

    2001-01-01

    We report on the influence of interchain interactions on the light emission properties of a sexithiophene single crystal. The strength of the intermolecular interactions is controlled by applying hydrostatic pressure. The combined use of both steady-state and time-resolved photoluminescence

  4. Towards quantum dot and FRET-based optical DNA biosensor technology: surface chemistry and photoluminescence of CdSe/ZnS and Si quantum dots

    Science.gov (United States)

    Algar, W. Russ; Zhou, Yuehui; Zeng, Jiang; Krull, Ulrich J.

    2007-06-01

    Quantum dots (QDs) are nanostructures that are highly attractive to optical biosensing. We have developed a nucleic acid biosensing strategy based on the use of quantum dots as energy donors in FRET. One of the challenges in such an approach is avoiding the non-specific adsorption of oligonucleotides. In this report, we describe our efforts to develop poly(ethylene glycol) (PEG)-based hydrophilic surface chemistry and hexanethiol based hydrophobic surface chemistry to alleviate non-specific adsorption. With respect to the former, it was found that the PEG surface chemistry strongly quenched the band-edge luminescence of CdSe/ZnS QDs and yielded significant band-gap luminescence. Furthermore, the PEG chemistry proved ineffective in preventing adsorption. With respect to hexanethiol capped CdSe/ZnS QDs, it was found that good QD luminescence was retained in organic solvent but was quenched in aqueous solution. The use of hydrophobic hexanethiol QDs in aqueous solution required the immobilization of QDs. To achieve this, we used thiol modified biotin and avidin coated fused silica optical fibers. Despite the quenching of the QDs, minimal adsorption was observed suggesting the methodology has good potential. In addition, we describe the development of a one-pot method for both the synthesis and capping of silicon QDs. Our approach also allows versatile post-synthetic modification of the silicon QD capping to produce a variety of functional groups. Silicon QDs are of interest in biosensing due to their biocompatibility and much lower toxicity compared to II-VI semiconductors.

  5. High spatial dynamics-photoluminescence imaging reveals the metallurgy of the earliest lost-wax cast object

    Science.gov (United States)

    Thoury, M.; Mille, B.; Séverin-Fabiani, T.; Robbiola, L.; Réfrégiers, M.; Jarrige, J.-F.; Bertrand, L.

    2016-11-01

    Photoluminescence spectroscopy is a key method to monitor defects in semiconductors from nanophotonics to solar cell systems. Paradoxically, its great sensitivity to small variations of local environment becomes a handicap for heterogeneous systems, such as are encountered in environmental, medical, ancient materials sciences and engineering. Here we demonstrate that a novel full-field photoluminescence imaging approach allows accessing the spatial distribution of crystal defect fluctuations at the crystallite level across centimetre-wide fields of view. This capacity is illustrated in archaeology and material sciences. The coexistence of two hitherto indistinguishable non-stoichiometric cuprous oxide phases is revealed in a 6,000-year-old amulet from Mehrgarh (Baluchistan, Pakistan), identified as the oldest known artefact made by lost-wax casting and providing a better understanding of this fundamental invention. Low-concentration crystal defect fluctuations are readily mapped within ZnO nanowires. High spatial dynamics-photoluminescence imaging holds great promise for the characterization of bulk heterogeneous systems across multiple disciplines.

  6. High spatial dynamics-photoluminescence imaging reveals the metallurgy of the earliest lost-wax cast object.

    Science.gov (United States)

    Thoury, M; Mille, B; Séverin-Fabiani, T; Robbiola, L; Réfrégiers, M; Jarrige, J-F; Bertrand, L

    2016-11-15

    Photoluminescence spectroscopy is a key method to monitor defects in semiconductors from nanophotonics to solar cell systems. Paradoxically, its great sensitivity to small variations of local environment becomes a handicap for heterogeneous systems, such as are encountered in environmental, medical, ancient materials sciences and engineering. Here we demonstrate that a novel full-field photoluminescence imaging approach allows accessing the spatial distribution of crystal defect fluctuations at the crystallite level across centimetre-wide fields of view. This capacity is illustrated in archaeology and material sciences. The coexistence of two hitherto indistinguishable non-stoichiometric cuprous oxide phases is revealed in a 6,000-year-old amulet from Mehrgarh (Baluchistan, Pakistan), identified as the oldest known artefact made by lost-wax casting and providing a better understanding of this fundamental invention. Low-concentration crystal defect fluctuations are readily mapped within ZnO nanowires. High spatial dynamics-photoluminescence imaging holds great promise for the characterization of bulk heterogeneous systems across multiple disciplines.

  7. Effects of thickness layer on the photoluminescence properties of InAlAs/GaAlAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Daly, A. Ben; Maaref, M.A. [Universite de Carthage, Laboratoire Materiaux, Molecules et Applications, Institut Preparatoire aux Etudes Scientifiques et Techniques, Tunis (Tunisia); Bernardot, F.; Barisien, T.; Testelin, C. [Sorbonne Universites, UPMC Universite Paris 06, UMR 7588, Institut des NanoSciences de Paris, Paris (France); CNRS, UMR 7588, INSP, Paris (France); Galopin, E.; Lemaitre, A. [Laboratoire de Photonique et Nanostructures, CNRS, Marcoussis (France)

    2016-09-15

    We investigated the effect of InAlAs layer thickness on exciton-spin relaxation and optical properties of In{sub 0.62}Al{sub 0.38}As/Al{sub 0.67}Ga{sub 0.33}As QDs. The luminescence properties and carrier dynamics of QDs were studied by the temperature-dependent photoluminescence (PL) and pump-probe measurements. As the total amount of deposited In0.62Al0.38As alloy increased, the central position of the low-energy PL signal decreases, while its full width at half maximum (FWHM) increases. A monotonous redshift of the PL peak was observed with increasing temperature due to the electron-phonon scattering. From the pump-probe measurement, the spin relaxation time decreases with the monolayers at higher temperatures, in agreement with the phonon energy determinate by PL measurements. (orig.)

  8. Rapid solid-phase microwave synthesis of highly photoluminescent nitrogen-doped carbon dots for Fe3+ detection and cellular bioimaging

    Science.gov (United States)

    He, Guili; Xu, Minghan; Shu, Mengjun; Li, Xiaolin; Yang, Zhi; Zhang, Liling; Su, Yanjie; Hu, Nantao; Zhang, Yafei

    2016-09-01

    Recently, carbon dots (CDs) have been playing an increasingly important role in industrial production and biomedical field because of their excellent properties. As such, finding an efficient method to quickly synthesize a large scale of relatively high purity CDs is of great interest. Herein, a facile and novel microwave method has been applied to prepare nitrogen doped CDs (N-doped CDs) within 8 min using L-glutamic acid as the sole reaction precursor in the solid phase condition. The as-prepared N-doped CDs with an average size of 1.64 nm are well dispersed in aqueous solution. The photoluminescence of N-doped CDs is pH-sensitive and excitation-dependent. The N-doped CDs show a strong blue fluorescence with relatively high fluorescent quantum yield of 41.2%, which remains stable even under high ionic strength. Since the surface is rich in oxygen-containing functional groups, N-doped CDs can be applied to selectively detect Fe3+ with the limit of detection of 10-5 M. In addition, they are also used for cellular bioimaging because of their high fluorescent intensity and nearly zero cytotoxicity. The solid-phase microwave method seems to be an effective strategy to rapidly obtain high quality N-doped CDs and expands their applications in ion detection and cellular bioimaging.

  9. "High Quantum Efficiency of Band-Edge Emission from ZnO Nanowires"

    Energy Technology Data Exchange (ETDEWEB)

    GARGAS, DANIEL; GAO, HANWEI; WANG, HUNGTA; PEIDONG, YANG

    2010-12-01

    External quantum efficiency (EQE) of photoluminescence as high as 20 percent from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher than those reported for ZnO materials in forms of bulk, thin films or powders. Additional insight on the radiative extraction factor of one-dimensional nanostructures was gained by measuring the internal quantum efficiency of individual nanowires. Such quantitative EQE measurements provide a sensitive, noninvasive method to characterize the optical properties of low-dimensional nanostructures and allow tuning of synthesis parameters for optimization of nanoscale materials.

  10. High quantum yield III-V photoanodes

    Energy Technology Data Exchange (ETDEWEB)

    Erne, B.H.

    1995-09-01

    The morphological and electrochemical aspects of the (photo)anodic etching of the n-type 3-5 semiconductors GaP, GaAs, and InP are examined. The etched surfaces are characterized experimentally by electrochemical and other methods. Particular attention is paid to the anodic photocurrent quantum yield. The processes investigated lead to a large enhancement of the quantum yield or give a quantum yield in excess of unity, hence the title of the thesis. The quantum yield of a photoanode is determined by processes both in the bulk and at the surface of the semiconductor. The competition between charge separation and recombination in the bulk of the semiconductor determines the fraction of the photogenerated holes which reaches the surface, and surface processes determine the fraction of those holes which contributes to current in the external circuit. Chapter 2 examines the increased effective absorption due to surface roughness and the increase in the diffusion length of holes associated with photocurrent flow, two effects which can cause charge separation to compete more effectively with bulk recombination. Chapter 3 considers the influence of the wavelength of the light used for photoanodic etching on the morphology. Chapter 4 demonstrates that porous etching may lead to an enormous enhancement of the photoresponse. The influence of surface (electro)chemistry on the quantum yield is investigated for n-type InP electrodes by means of optoelectrical impedance spectroscopy. Even in indifferent electrolyte, InP photoanodes have remarkably high quantum yields in excess of unity, due to electron injection by dissolution intermediates (Chapter 5). Interaction with a chemical etchant can increase the quantum yield even further (Chapter 6). The main conclusions of the thesis are summarized in Chapter 7. 52 figs., 180 refs., 1 appendix

  11. Surface plasmon inhibited photo-luminescence activation in CdSe/ZnS core-shell quantum dots

    Czech Academy of Sciences Publication Activity Database

    Chen, J.; Žídek, Karel; Abdellah, M.; Al-Marri, M.J.; Zheng, K.; Pullerits, T.

    2016-01-01

    Roč. 28, č. 25 (2016), č. článku 254001. ISSN 0953-8984 Institutional support: RVO:61389021 Keywords : surface plasmon * gold nanorods * quantum dots * energy transfer * photoactivation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.649, year: 2016 http://dx.doi.org/10.1088/0953-8984/28/25/254001

  12. Highly sensitive detection of ionizing radiations by a photoluminescent uranyl organic framework

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Jian; Wang, Yaxing; Liu, Wei; Yin, Xuemiao; Chen, Lanhua; Diwu, Juan; Chai, Zhifang; Wang, Shuao [School for Radiological and interdisciplinary Sciences (RAD-X) and Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou (China); Zou, Youming [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui (China); Albrecht-Schmitt, Thomas E. [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL (United States); Liu, Guokui [Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL (United States)

    2017-06-19

    Precise detection of low-dose X- and γ-radiations remains a challenge and is particularly important for studying biological effects under low-dose ionizing radiation, safety control in medical radiation treatment, survey of environmental radiation background, and monitoring cosmic radiations. We report here a photoluminescent uranium organic framework, whose photoluminescence intensity can be accurately correlated with the exposure dose of X- or γ-radiations. This allows for precise and instant detection of ionizing radiations down to the level of 10{sup -4} Gy, representing a significant improvement on the detection limit of approximately two orders of magnitude, compared to other chemical dosimeters reported up to now. The electron paramagnetic resonance analysis suggests that with the exposure to radiations, the carbonyl double bonds break affording oxo-radicals that can be stabilized within the conjugated uranium oxalate-carboxylate sheet. This gives rise to a substantially enhanced equatorial bonding of the uranyl(VI) ions as elucidated by the single-crystal structure of the γ-ray irradiated material, and subsequently leads to a very effective photoluminescence quenching through phonon-assisted relaxation. The quenched sample can be easily recovered by heating, enabling recycled detection for multiple runs. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Stokes and anti-Stokes photoluminescence towards five different In-x(Al0.17Ga0.83)(1-x)As/Al0.17Ga0.83As quantum wells

    DEFF Research Database (Denmark)

    Machida, S.; Tadakuma, T.; Satake, A.

    2005-01-01

    Stokes and anti-Stokes photoluminescence (AS-PL) has been investigated in a step-graded Inx(Al0.17Ga0.83)1–xAs/Al0.17Ga0.83As quantum-well (QW) heterostructure consisting of five QWs with different x values. Stokes PL spectra of this sample show a significant difference in PL intensity between...

  14. A highly bioactive poly (amido amine)/70S30C bioactive glass hybrid with photoluminescent and antimicrobial properties for bone regeneration.

    Science.gov (United States)

    Akbari Dourbash, Fakhraddin; Alizadeh, Parvin; Nazari, Shahram; Farasat, Alireza

    2017-09-01

    The field of tissue engineering constantly calls for novel biomaterials that possess intrinsically multifunctional properties such as bioactivity, bioimaging ability and antibacterial properties. In this paper, poly (amido amine) generation 5/bioactive glass inorganic-organic hybrids have been developed through direct hybridization by 3-glycidoxypropyltrimethoxysilane (GPTMS) as coupling agent. Results indicated that the degree of covalent coupling by GPTMS and the weight percent of inorganic and organic constituents highly influence hybrids properties. It was found that nanoscale integration of inorganic and organic chains by GPTMS significantly endows hybrids with high thermal stability. Furthermore, hybrids exhibited photoluminescent ability (emission 400-600nm and 700nm) without incorporating of any organic dyes or quantum dots. In addition, hydrophilicity of our hybrids indicated good cell/material interaction. The biological apatite was formed on the surface of calcium containing hybrids when soaked in simulated body fluid (SBF) for 1week. Hybrids also showed linear biodegradation behavior in SBF that could be controlled by the degree of covalent crosslinking which was indicative of their stable biodegradation ability. High inherent antibacterial properties against Staphylococcus aureus was also observed from poly (amido amine)/silica hybrids. No adverse cytotoxicity for human gingival fibroblast cell lines (HGF) was detected after 4days. It is envisaged that our novel multifunctional hybrid system will confer intriguing potential in advancing the field of tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Photoluminescence characteristics of CdSe quantum dots: role of exciton-phonon coupling and defect/trap states

    Science.gov (United States)

    Kushavah, Dushyant; Mohapatra, P. K.; Ghosh, Pintu; Singh, Mamraj; Vasa, P.; Bahadur, D.; Singh, B. P.

    2017-07-01

    In this paper, we report temperature dependent photoluminescence (PL) characteristics of CdSe colloidal QDs with average diameter ~2.8 nm. Temperature dependence of strongly confined exciton PL peak position, linewidth and intensity were investigated in 30 K to 300 K temperature range. Our studies reveal nearly four times weaker exciton-LO phonon coupling than bulk CdSe crystal. Theoretically, it should be vanishingly small due to near identical electron and hole charge distributions in strongly confined QDs. On the other hand, exciton-acoustic phonon coupling is an order of magnitude larger than its bulk counterpart. Observed finite value of exciton-LO phonon coupling and enhanced exciton-acoustic phonon coupling are due to piezoelectric strain fields. PL intensity exhibits anomalous behavior in the temperature range 100-230 K. This has been explained by thermally activated detrapping of the charge carriers trapped in the potential wells formed at the interface adjoining dislocations/stacking faults developed during the synthesis process. Above 230 K, PL is partially quenched by thermal escape of charge carriers from luminescing exciton state to higher lying nonluminescing states.

  16. Absence of quantum confinement effects in the photoluminescence of Si{sub 3}N{sub 4}–embedded Si nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Hiller, D., E-mail: daniel.hiller@imtek.uni-freiburg.de; Zelenina, A.; Gutsch, S.; Zacharias, M. [Faculty of Engineering, IMTEK, Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg (Germany); Dyakov, S. A. [Department of Electronic and Electrical Engineering, Trinity College Dublin, Dublin 2 (Ireland); Optics and Photonics, School of Information and Communication Technology, Royal Institute of Technology (KTH), Electrum 229, Kista SE-16440 (Sweden); López-Conesa, L.; López-Vidrier, J.; Peiró, F.; Garrido, B. [MIND-IN2UB, Departament d' Electrònica, Universitat de Barcelona, C. Martí i Franquès, 1, 08028 Barcelona (Spain); Estradé, S. [MIND-IN2UB, Departament d' Electrònica, Universitat de Barcelona, C. Martí i Franquès, 1, 08028 Barcelona (Spain); CCiT, Scientific and Technical Centers, Universitat de Barcelona, C/Lluís Solé i Sabaris 1, 08028 Barcelona (Spain); Valenta, J.; Kořínek, M.; Trojánek, F.; Malý, P. [Faculty of Mathematics and Physics, Department of Chemical Physics and Optics, Charles University in Prague, Ke Karlovu 3, CZ-12116 Prague 2 (Czech Republic); Schnabel, M.; Weiss, C.; Janz, S. [Fraunhofer-Institut für Solare Energiesysteme ISE, Heidenhofstr. 2, 79110 Freiburg (Germany)

    2014-05-28

    Superlattices of Si-rich silicon nitride and Si{sub 3}N{sub 4} are prepared by plasma-enhanced chemical vapor deposition and, subsequently, annealed at 1150 °C to form size-controlled Si nanocrystals (Si NCs) embedded in amorphous Si{sub 3}N{sub 4}. Despite well defined structural properties, photoluminescence spectroscopy (PL) reveals inconsistencies with the typically applied model of quantum confined excitons in nitride-embedded Si NCs. Time-resolved PL measurements demonstrate 10{sup 5} times faster time-constants than typical for the indirect band structure of Si NCs. Furthermore, a pure Si{sub 3}N{sub 4} reference sample exhibits a similar PL peak as the Si NC samples. The origin of this luminescence is discussed in detail on the basis of radiative defects and Si{sub 3}N{sub 4} band tail states in combination with optical absorption measurements. The apparent absence of PL from the Si NCs is explained conclusively using electron spin resonance data from the Si/Si{sub 3}N{sub 4} interface defect literature. In addition, the role of Si{sub 3}N{sub 4} valence band tail states as potential hole traps is discussed. Most strikingly, the PL peak blueshift with decreasing NC size, which is often observed in literature and typically attributed to quantum confinement (QC), is identified as optical artifact by transfer matrix method simulations of the PL spectra. Finally, criteria for a critical examination of a potential QC-related origin of the PL from Si{sub 3}N{sub 4}-embedded Si NCs are suggested.

  17. Photoluminescence Study of the Interface Fluctuation Effect for InGaAs/InAlAs/InP Single Quantum Well with Different Thickness.

    Science.gov (United States)

    Wang, Ying; Sheng, Xinzhi; Guo, Qinglin; Li, Xiaoli; Wang, Shufang; Fu, Guangsheng; Mazur, Yuriy I; Maidaniuk, Yurii; Ware, Morgan E; Salamo, Gregory J; Liang, Baolai; Huffaker, Diana L

    2017-12-01

    Photoluminescence (PL) is investigated as a function of the excitation intensity and temperature for lattice-matched InGaAs/InAlAs quantum well (QW) structures with well thicknesses of 7 and 15 nm, respectively. At low temperature, interface fluctuations result in the 7-nm QW PL exhibiting a blueshift of 15 meV, a narrowing of the linewidth (full width at half maximum, FWHM) from 20.3 to 10 meV, and a clear transition of the spectral profile with the laser excitation intensity increasing four orders in magnitude. The 7-nm QW PL also has a larger blueshift and FWHM variation than the 15-nm QW as the temperature increases from 10 to ~50 K. Finally, simulations of this system which correlate with the experimental observations indicate that a thin QW must be more affected by interface fluctuations and their resulting potential fluctuations than a thick QW. This work provides useful information on guiding the growth to achieve optimized InGaAs/InAlAs QWs for applications with different QW thicknesses.

  18. Photoluminescence and AFM characterisation of photochemically etched highly resistive n-type silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hadjersi, T.; Gabouze, N. [Unite de Developpement de la Technologie du Silicium (UDTS), 2, Bd. Frantz Fanon, B.P. 399 Alger-Gare, Alger (Algeria); Kooij, E.S. [Solid State Physics, MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Eschede (Netherlands); Yamamoto, N. [Communications Research Laboratory, Basic and Advanced Research, Division, 4-2-1, Nukui- kitamachi, Koganei,Tokyo, 184-8795 (Japan); Sakamaki, K.; Takai, H. [Tokyo Denki University, Department of Electrical Engineering, 2-2 Kanda-Nishiki-cyo, Chiyoda-ku, Tokyo, 101-8457 (Japan)

    2005-06-01

    A light-emitting layer has been made on highly resistive n-type silicon (6.4 k and ohm;cm) using photochemical etching in a mixture of HF with H{sub 2}O{sub 2}. The morphology of the porous films grown after exposure to a He-Ne laser (633 nm) at normal incidence was analysed by Atomic Force Microscopy (AFM). The results show that the film obtained are porous and the morphology of the porous layer obtained are shown to be similar to that obtained by the electrochemical method on highly doped silicon. Furthermore, excitation of the porous silicon layer formed on highly resistive silicon samples under He-Cd laser (325 nm) irradiation shows that the PL intensity increases with increasing etching time. The maximum PL spectrum peaked at 636 nm with a FWHM of about 0.3 eV. Finally, the quantum confinement effect has been invoked to explain the bright, visible, room temperature PL of porous silicon (PS). (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. High-density quantum sensing with dissipative first order transitions

    OpenAIRE

    Raghunandan, Meghana; Wrachtrup, Jörg; Weimer, Hendrik

    2017-01-01

    The sensing of external fields using quantum systems is a prime example of an emergent quantum technology. Generically, the sensitivity of a quantum sensor consisting of $N$ independent particles is proportional to $\\sqrt{N}$. However, interactions invariably occuring at high densities lead to a breakdown of the assumption of independence between the particles, posing a severe challenge for quantum sensors operating at the nanoscale. Here, we show that interactions in quantum sensors can be t...

  20. Quantum chromodynamics at high energy

    CERN Document Server

    Kovchegov, Yuri V

    2012-01-01

    Filling a gap in the current literature, this book is the first entirely dedicated to high energy QCD including parton saturation. It presents groundbreaking progress on the subject and describes many of the problems at the forefront of research, bringing postgraduate students, theorists and advanced experimentalists up to date with the current status of the field. A broad range of topics in high energy QCD are covered, most notably on the physics of parton saturation and the Color Glass Condensate (CGC). The material is presented in a pedagogical way, with numerous examples and exercises. Discussion ranges from the quasi-classical McLerran–Venugopalan model to the linear and non-linear BFKL/BK/JIMWLK small-x evolution equations. The authors adopt both a theoretical and experimental outlook and present the physics of strong interactions in a universal way, making it useful to physicists from various sub-communities and applicable to processes studied at high energy accelerators around the world.

  1. Fe(III)-functionalized carbon dots—Highly efficient photoluminescence redox catalyst for hydrogenations of olefins and decomposition of hydrogen peroxide

    KAUST Repository

    Bourlinos, Athanasios B.

    2017-03-21

    We present the first bottom-up approach to synthesize Fe(III)-functionalized carbon dots (CDs) from molecular precursors without the need of conventional thermal or microwave treatment and additional reagents. Specifically, sonication of xylene in the presence of anhydrous FeCl3 results in oxidative coupling of the aromatic substrate towards Fe(III)-functionalized CDs. The as-prepared CDs are spherical in shape with a size of 3–8 nm, highly dispersible in organic solvents and display wavelength-dependent photoluminescence (PL). The iron ions attached to the surface endow the CDs with superior catalytic activity for olefin hydrogenation with excellent conversion and selectivity (up to 100%). The Fe(III)-CDs are more effective in the hydrogenation of a series of electron donating or withdrawing olefin substrates compared to conventional homogeneous or heterogeneous Fe(III)-based catalysts. The as-prepared heterogeneous nanocatalyst can be used repeatedly without any loss of catalytic activity. Importantly, the stability of the new catalysts can be easily monitored by PL intensity or quantum yield measurements, which certainly opens the doors for real time monitoring in a range of applications. Additionally, to the best of our knowledge, for the first time, the oxidative property of Fe-CDs was also explored in decomposition of hydrogen peroxide in water with the first order rate constant of 0.7 × 10−2 min−1, proving the versatile catalytic properties of such hybrid systems.

  2. Synthesis of blue-photoluminescent graphene quantum dots/polystyrenic anion-exchange resin for Fe(III) detection

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wenjun, E-mail: wjzhang@hebut.edu.cn; Gan, Jie

    2016-05-30

    Highlights: • GQD/PS-AER was prepared as a solid fluorescent sensor with millimeter size. • The GQD/PS-AER sensor could detect Fe{sup 3+} ions selectively. • The GQD/PS-AER sensor could be reusable. • This method is simple and economical. - Abstract: A novel solid fluorescent sensor with millimeter size, based on graphene quantum dots/polystyrenic anion-exchange resin (GQDs/PS-AER) was obtained for the detection of Fe{sup 3+}. The linear response range of Fe{sup 3+} was obtained from 1 μM to 7 μM and the detection limit was as low as 0.65 μM. In addition, the sensor could be regenerated by adding complexing agent EDTA and be separated by using simple filtration.

  3. Observation and tunability of room temperature photoluminescence of GaAs/GaInAs core-multiple-quantum-well shell nanowire structure grown on Si (100) by molecular beam epitaxy.

    Science.gov (United States)

    Park, Kwang Wook; Park, Chang Young; Ravindran, Sooraj; Jang, Ja-Soon; Jo, Yong-Ryun; Kim, Bong-Joong; Lee, Yong Tak

    2014-01-01

    We report the observation of room temperature photoluminescence (PL) emission from GaAs/GaInAs core-multiple-quantum-well (MQW) shell nanowires (NWs) surrounded by AlGaAs grown by molecular beam epitaxy (MBE) using a self-catalyzed technique. PL spectra of the sample show two PL peaks, originating from the GaAs core NWs and the GaInAs MQW shells. The PL peak from the shell structure red-shifts with increasing well width, and the peak position can be tuned by adjusting the width of the MQW shell. The GaAs/GaInAs core-MQW shell NW surrounded by AlGaAs also shows an enhanced PL intensity due to the improved carrier confinement owing to the presence of an AlGaAs clad layer. The inclined growth of the GaAs NWs produces a core-MQW shell structure having a different PL peak position than that of planar QWs. The PL emission by MQW shell and the ability to tune the PL peak position by varying the shell width make such core-shell NWs highly attractive for realizing next generation ultrasmall light sources and other optoelectronics devices. 81.07.Gf; 81.15.Hi; 78.55.Cr.

  4. Photoluminescence close to V-shaped pits in the quantum wells and enhanced output power for InGaN light emitting diode

    Science.gov (United States)

    Han, Dan; Ma, Shufang; Jia, Zhigang; Jia, Wei; Liu, Peizhi; Dong, Hailiang; Shang, Lin; Zhang, Aiqin; Zhai, Guangmei; Li, Xuemin; Liu, Xuguang; Xu, Bingshe

    2017-11-01

    Unlike the typical ‘S-shaped’ temperature dependent behavior for InGaN/GaN light emitting diodes (LEDs), the emission of the c-plane MQWs (C-QWs) close to V-shaped pits (V-pits) broadens across the short-wavelength band and exhibits a blue-shift as temperature increases by temperature-dependent micro photoluminescence (µ-TDPL). The phenomenon can be mainly attributed to a higher proportion carriers generate high-energy radiative transition in C-QWs close to V-pits because of augmented carrier mobility, in which the mechanism of carriers absorbed in sidewall MQWs (S-QWs) move to the C-QWs close to V-pits acts as a significant process. The sizes of V-pits can be enlarged as increasing the thickness of low temperature GaN interlayer (LT-GaN interlayer), leading to improved output power for LEDs.

  5. Blue photoluminescence of sponge-like highly porous alumina synthesized in hydrofluoric acid based electrolytes

    Science.gov (United States)

    Ilin, D. O.; Vokhmintsev, A. S.; Martemyanov, N. A.; Weinstein, I. A.

    2017-11-01

    For the first time nanostructures of anodized aluminum oxide (AAO) were synthesized using hydrofluoric acid based electrolytes under potentiostatic mode with varied oxidation conditions. As-grown oxide layers were amorphous and had sponge-like disordered structure with ramified pores system of 50 to 300 nm diameters. All samples under daylight demonstrated blue emission with power up to 10 μW that was seen by naked eye. It was shown that integral intensity of photoluminescence (PL) emission band in 350 – 650 range increases up to 7 – 60 times depending on synthesis details. Observed PL spectra were approximated by superposition of two components with Emax = 2.74 and 2.44 eV, FWHM = 0.63 and 0.53 eV. It was substantiated that studied emission have intrinsic origin and can be attributed to F2 2+ - and F2-centers.

  6. A novel approach to obtain highly intense self-activated photoluminescence emissions in hydroxyapatite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Machado, Thales R. [CDMF-UFSCar, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, São Paulo (Brazil); QIO-UJI, Universitat Jaume I, 12071 Castellón (Spain); Sczancoski, Júlio C. [CDMF-UFSCar, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, São Paulo (Brazil); Beltrán-Mir, Héctor [QIO-UJI, Universitat Jaume I, 12071 Castellón (Spain); Nogueira, Içamira C. [PPGEM-IFMA, Instituto Federal de Educação, Ciência e Tecnologia do Maranhão, 65030-005 São Luís, MA (Brazil); Li, Máximo S. [IFSC-USP, Universidade de São Paulo, P.O. Box 369, 13560-970 São Carlos, SP (Brazil); Andrés, Juan [QFA-UJI, Universitat Jaume I, 12071 Castellón (Spain); Cordoncillo, Eloisa [QIO-UJI, Universitat Jaume I, 12071 Castellón (Spain); Longo, Elson, E-mail: elson.liec@gmail.com [CDMF-UFSCar, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, São Paulo (Brazil)

    2017-05-15

    Defect-related photoluminescence (PL) in materials have attracted interest for applications including near ultraviolet (NUV) excitable light-emitting diodes and in biomedical field. In this paper, hydroxyapatite [Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}] nanorods with intense PL bands (bluish- and yellowish-white emissions) were obtained when excited under NUV radiation at room temperature. These nanoparticles were synthesized via chemical precipitation at 90 °C followed by distinct heat treatments temperatures (200–800 °C). Intense and broad emission profiles were achieved at 350 °C (380–750 nm) and 400 °C (380–800 nm). UV–Vis spectroscopy revealed band gap energies (5.58–5.78 eV) higher than the excitation energies (~3.54 and ~2.98 eV at 350 and 415 nm, respectively), confirming the contribution of defect energy levels within the forbidden zone for PL emissions. The structural features were characterized by X-ray diffraction, Rietveld refinement, thermogravimetric analysis, and Fourier transform infrared spectroscopy. By means of these techniques, the relation between structural order-disorder induced by defects, chemical reactions at both lattice and surface of the materials as well as the PL, without activator centers, was discussed in details. - Graphical abstract: The self-activated photoluminescence emissions of chemically precipitated hydroxyapatite nanorods were improved by different heat treatment temperatures. - Highlights: • HA nanorods were synthesized with improved self-activated PL at room temperature. • PL profile and intensity dependents on the temperature of posterior heat treatments. • Bluish- and yellowish-white emissions under NUV excitation (350 and 415 nm). • Broad and intense profiles achieved at 350 °C (380–750 nm) and 400 °C (380–800 nm). • PL from the e′–h{sup •} recombination between defect energy levels within the band gap.

  7. Visible photoluminescence in polycrystalline terbium doped aluminum nitride (Tb:AlN) ceramics with high thermal conductivity

    Science.gov (United States)

    Wieg, A. T.; Kodera, Y.; Wang, Z.; Imai, T.; Dames, C.; Garay, J. E.

    2012-09-01

    Thermal management continues to be one of the major challenges in the development of high powered light sources such as solid state lasers. In particular, the relatively low thermal conductivity of standard photoluminescent (PL) materials limits the overall power output and/or duty cycle. We present a method based on current activated pressure assisted densification for the fabrication of high thermal conductivity PL materials: rare earth doped polycrystalline bulk aluminum nitride. Specifically, the ceramics are translucent and are doped with Tb3+, allowing for emission in the visible. Remarkably, the ceramics have a room temperature thermal conductivity of 94 W/(m K) which is almost seven times higher than that of the state of the art host material, Nd-doped yttrium aluminum garnet. These light emitting properties coupled with very high thermal conductivity should enable the development of a wide variety of more powerful light sources.

  8. Quantum Phenomena in High Energy Density Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Murnane, Margaret [Univ. of Colorado, Boulder, CO (United States); Kapteyn, Henry [Univ. of Colorado, Boulder, CO (United States)

    2017-05-10

    The possibility of implementing efficient (phase matched) HHG upconversion of deep- UV lasers in multiply-ionized plasmas, with potentially unprecedented conversion efficiency is a fascinating prospect. HHG results from the extreme nonlinear response of matter to intense laser light:high harmonics are radiated as a result of a quantum coherent electron recollision process that occurs during laser field ionization of an atom. Under current support from this grant in work published in Science in 2015, we discovered a new regime of bright HHG in highly-ionized plasmas driven by intense UV lasers, that generates bright harmonics to photon energies >280eV

  9. Photoinduced spectral changes of photoluminescent gold nanoclusters

    Science.gov (United States)

    Matulionytė, Marija; Marcinonytė, Raminta; Rotomskis, Ričardas

    2015-05-01

    Ultrasmall photoluminescent gold nanoclusters (Au NCs), composed of several atoms with sizes up to a few nanometers, have recently stimulated extensive interest. Unique molecule-like behaviors, low toxicity, and facile synthesis make photoluminescent Au NCs a very promising alternative to organic fluorophores and semiconductor quantum dots (QDs) in broad ranges of biomedical applications. However, using gold nanoparticles (Au NPs) for bioimaging might cause their degradation under continuous excitation with UV light, which might result in toxicity. We report spectral changes of photoluminescent 2-(N-morpholino) ethanesulfonic acid (MES)-coated (Au-MES) NCs under irradiation with UV/blue light. Photoluminescent water soluble Au-MES NCs with a photoluminescence (PL) band maximum at 476 nm (λex=420 nm) were synthesized. Under irradiation with 402 nm wavelength light the size of photoluminescent Au-MES NCs decreased (λem=430 nm). Irradiating the sample solution with 330 nm wavelength light, nonluminescent Au NPs were disrupted, and photoluminescent Au NCs (λem=476 nm) were formed. Irradiation with 330 nm wavelength light did not directly affect photoluminescent Au-MES NCs, however, increase in PL intensity indicated the formation of photoluminescent Au NCs from the disrupted nonluminescent Au NPs. This study gives a good insight into the photostability of MES-coated Au NPs under continuous excitation with UV/blue light.

  10. Poly(vinylpyrrolidone) supported copper nanoclusters: glutathione enhanced blue photoluminescence for application in phosphor converted light emitting devices

    Science.gov (United States)

    Wang, Zhenguang; Susha, Andrei S.; Chen, Bingkun; Reckmeier, Claas; Tomanec, Ondrej; Zboril, Radek; Zhong, Haizheng; Rogach, Andrey L.

    2016-03-01

    Poly(vinylpyrrolidone) supported Cu nanoclusters were synthesized by reduction of Cu(ii) ions with ascorbic acid in water, and initially showed blue photoluminescence with a quantum yield of 8%. An enhancement of the emission quantum yield has been achieved by treatment of Cu clusters with different electron-rich ligands, with the most pronounced effect (photoluminescence quantum yield of 27%) achieved with glutathione. The bright blue emission of glutathione treated Cu NCs is fully preserved in the solid state powder, which has been combined with commercial green and red phosphors to fabricate down-conversion white light emitting diodes with a high colour rendering index of 92.Poly(vinylpyrrolidone) supported Cu nanoclusters were synthesized by reduction of Cu(ii) ions with ascorbic acid in water, and initially showed blue photoluminescence with a quantum yield of 8%. An enhancement of the emission quantum yield has been achieved by treatment of Cu clusters with different electron-rich ligands, with the most pronounced effect (photoluminescence quantum yield of 27%) achieved with glutathione. The bright blue emission of glutathione treated Cu NCs is fully preserved in the solid state powder, which has been combined with commercial green and red phosphors to fabricate down-conversion white light emitting diodes with a high colour rendering index of 92. Electronic supplementary information (ESI) available: The optical spectra of control experiments for Cu NC synthesis, optimization of the reaction conditions, and spectra for LEDs chips and blue LEDs. See DOI: 10.1039/c6nr00806b

  11. High-rate measurement-device-independent quantum cryptography

    DEFF Research Database (Denmark)

    Pirandola, Stefano; Ottaviani, Carlo; Spedalieri, Gaetana

    2015-01-01

    Quantum cryptography achieves a formidable task - the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum cryptography is now headed towards solving the practical problem of constructing scalable and secure quantum networks. A significant step in this direction...... than those currently achieved. Our protocol could be employed to build high-rate quantum networks where devices securely connect to nearby access points or proxy servers....

  12. Electronic structure of InAs/GaAs self-assembled quantum dots studied by high-excitation luminescence in magnetic fields up to 73 T

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, D.; Raymond, S.; Studenikin, S.; Babinski, A.; Leotin, J.; Frings, P.; Potemski, M.; Sachrajda, A

    2004-04-30

    We report on high-excitation photoluminescence (PL) measurements of an ensemble of InAs/GaAs self-assembled quantum dots with large inter-shell spacing (75 meV) in magnetic fields up to 73 T. The PL spectra show a complex picture of levels splitting and crossings. A simple two-band single-particle model provides a good approximation to explain the observed magneto-PL spectra.

  13. Photoluminescence properties of graphene versus other carbon nanomaterials.

    Science.gov (United States)

    Cao, Li; Meziani, Mohammed J; Sahu, Sushant; Sun, Ya-Ping

    2013-01-15

    Photoluminescent nanomaterials continue to garner research attention because of their many applications. For many years, researchers have focused on quantum dots (QDs) of semiconductor nanocrystals for their excellent performance and predictable fluorescence color variations that depend on the sizes of the nanocrystals. Even with these advantages, QDs can present some major limitations, such as the use of heavy metals in the high-performance semiconductor QDs. Therefore, researchers continue to be interested in developing new QDs or related nanomaterials. Recently, various nanoscale configurations of carbon have emerged as potential new platforms in the development of brightly photoluminescent materials. As a perfect π-conjugated single sheet, graphene lacks electronic bandgaps and is not photoluminescent. Therefore, researchers have created energy bandgaps within graphene as a strategy to impart fluorescence emissions. Researchers have explored many experimental techniques to introduce bandgaps, such as cutting graphene sheets into small pieces or manipulating the π electronic network to form quantum-confined sp(2) "islands" in a graphene sheet, which apparently involve the formation or exploitation of structural defects. In fact, defects in graphene materials not only play a critical role in the creation of bandgaps for emissive electronic transitions, but also contribute directly to the bright photoluminescence emissions observed in these materials. Researchers have found similar defect-derived photoluminescence in carbon nanotubes and small carbon nanoparticles, dubbed carbon "quantum" dots or "carbon dots". However, they have not systematically examined the emissions properties of these different yet related carbon nanomaterials toward understanding their mechanistic origins. In this Account, we examine the spectroscopic features of the observed photoluminescence emissions in graphene materials. We associate the structural characteristics in the underlying

  14. High quality factor of AlN microdisks embedding GaN quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Mexis, M.; Guillet, T.; Brimont, C.; Bretagnon, T.; Gil, B. [GES, Universite des Sciences et Techniques du Languedoc, Place Eugene Bataillon, 34095 Montpellier (France); Sergent, S. [CHREA-CNRS, 06560 Valbonne (France); Universite de Nice Sophia Antipolis, Parc Valrose, 06102 Nice (France); Semond, F.; Leroux, M. [CHREA-CNRS, 06560 Valbonne (France); Neel, D.; David, S.; Checoury, X.; Boucaud, P. [Institut d' Electronique Fondamentale, CNRS - Universite Paris Sud, 91405 Orsay (France)

    2011-07-15

    We report the observation of high quality (Q) factor whispering gallery modes for GaN/AlN quantum dot based microdisks. Room temperature photoluminescence measurements show a large number of high Q modes on the whole PL spectral range. For the first time we report Q values up to 6000 for nitride based cavities. We attribute this improvement of the Q factor to the etching quality and to the relatively low cavity loss by inserting dots into the microdisks. The uniformity of the resonant modes with respect to a wide range of energies allows us to identify the different radial mode families. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Quantum interpolation for high-resolution sensing.

    Science.gov (United States)

    Ajoy, Ashok; Liu, Yi-Xiang; Saha, Kasturi; Marseglia, Luca; Jaskula, Jean-Christophe; Bissbort, Ulf; Cappellaro, Paola

    2017-02-28

    Recent advances in engineering and control of nanoscale quantum sensors have opened new paradigms in precision metrology. Unfortunately, hardware restrictions often limit the sensor performance. In nanoscale magnetic resonance probes, for instance, finite sampling times greatly limit the achievable sensitivity and spectral resolution. Here we introduce a technique for coherent quantum interpolation that can overcome these problems. Using a quantum sensor associated with the nitrogen vacancy center in diamond, we experimentally demonstrate that quantum interpolation can achieve spectroscopy of classical magnetic fields and individual quantum spins with orders of magnitude finer frequency resolution than conventionally possible. Not only is quantum interpolation an enabling technique to extract structural and chemical information from single biomolecules, but it can be directly applied to other quantum systems for superresolution quantum spectroscopy.

  16. Highly luminescent S,N co-doped carbon quantum dots-sensitized chemiluminescence on luminol-H2 O2 system for the determination of ranitidine.

    Science.gov (United States)

    Chen, Jianqiu; Shu, Juan; Chen, Jiao; Cao, Zhiran; Xiao, An; Yan, Zhengyu

    2017-05-01

    S,N co-doped carbon quantum dots (N,S-CQDs) with super high quantum yield (79%) were prepared by the hydrothermal method and characterized by transmission electron microscopy, photoluminescence, UV-Vis spectroscopy and Fourier transformed infrared spectroscopy. N,S-CQDs can enhance the chemiluminescence intensity of a luminol-H2 O2 system. The possible mechanism of the luminol-H2 O2 -(N,S-CQDs) was illustrated by using chemiluminescence, photoluminescence and ultraviolet analysis. Ranitidine can quench the chemiluminescence intensity of a luminol-H2 O2 -N,S-CQDs system. So, a novel flow-injection chemiluminescence method was designed to determine ranitidine within a linear range of 0.5-50 μg ml(-1) and a detection limit of 0.12 μg ml(-1) . The method shows promising application prospects. Copyright © 2016 John Wiley & Sons, Ltd.

  17. Quantum wells for high-efficiency photovoltaics

    Science.gov (United States)

    Alonso-Álvarez, Diego; Ekins-Daukes, Nicholas

    2016-03-01

    Over the last couple of decades, there has been an intense research on strain balanced semiconductor quantum wells (QW) to increase the efficiency of multi-junction solar (MJ) solar cells grown monolithically on germanium. So far, the most successful application of QWs have required just to tailor a few tens of nanometers the absorption edge of a given subcell in order to reach the optimum spectral position. However, the demand for higher efficiency devices requiring 3, 4 or more junctions, represents a major difference in the challenges QWs must face: tailoring the absorption edge of a host material is not enough, but a complete new device, absorbing light in a different spectral region, must be designed. Among the most important issues to solve is the need for an optically thick structure to absorb enough light while keeping excellent carrier extraction using highly strained materials. Improvement of the growth techniques, smarter device designs - involving superlattices and shifted QWs, for example - or the use of quantum wires rather than QWs, have proven to be very effective steps towards high efficient MJ solar cells based on nanostructures in the last couple of years. But more is to be done to reach the target performances. This work discusses all these challenges, the limitations they represent and the different approaches that are being used to overcome them.

  18. Förster Resonance Energy Transfer Mediated Photoluminescence Quenching in Stoichiometrically Assembled CdSe/ZnS Quantum Dot-Peptide Labeled Black Hole Quencher Conjugates for Matrix Metalloproteinase-2 Sensing.

    Science.gov (United States)

    Pillai, Sreenadh Sasidharan; Yukawa, Hiroshi; Onoshima, Daisuke; Biju, Vasudevanpillai; Baba, Yoshinobu

    2017-01-01

    The steady state and time-resolved photoluminescence quenching of streptavidin modified CdSe/ZnS quantum dots (QDs) instigated by biotin-peptide-BHQ-1 (biotin-pep-BHQ-1) molecule was investigated. Here, we have achieved an efficient photoluminescence (PL) quenching of QDs with the conjugation of dark quencher (black hole quencher-BHQ) molecules intermediated with the GPLGVRGK peptide. The luminescence of streptavidin-QDs585 was decreased upon titration with a nano molar concentration of the biotin-GPLGVRGK-BHQ-1 molecule. It has been suggested that the decrease of QDs PL occurred through a Förster resonance energy transfer (FRET) mechanism from the analysis of steady state photoluminescence intensity measurements as well as time resolved lifetime measurements of streptavidin-QDs and QDs-(pep-BHQ-1)n conjugates. The sequence of intermediate peptide GPLG↓VRGK can act as a target material for matrix metalloproteinases-2 (MMP-2) produced by cancer cells at its Gly and Val region, shown by the down-headed arrow. Interestingly, here the reported self-assembled QDs-(pep-BHQ-1)n conjugates could detect the presence MMP-2 at a detection limit of 1 ng/mL with a clear luminescence recovery.

  19. Aptamer and 5-fluorouracil dual-loading Ag2S quantum dots used as a sensitive label-free probe for near-infrared photoluminescence turn-on detection of CA125 antigen.

    Science.gov (United States)

    Jin, Hui; Gui, Rijun; Gong, Jun; Huang, Wenxue

    2017-06-15

    In this article, Ag 2 S quantum dots (QDs) were prepared by a facile aqueous synthesis method, using thiourea as a new sulfur precursor. Based on electrostatic interactions, 5-fluorouracil (5-Fu) was combined with the aptamer of CA125 antigen to fabricate aptamer/5-Fu complex. The surface of as-prepared Ag 2 S QDs was modified with polyethylenimine, followed by combination with the aptamer/5-Fu complex to form Ag 2 S QDs/aptamer/5-Fu hybrids. During the combination of Ag 2 S QDs with aptamer/5-Fu complex, near-infrared (NIR) photoluminescence (PL) of QDs (peaked at 850nm) was markedly reduced under excitation at 625nm, attributed to photo-induced electron transfer from QDs to 5-Fu. However, the addition of CA125 induced obvious NIR PL recovery, which was ascribed to the strong binding affinity of CA125 with its aptamer, and the separation of aptamer/5-Fu complex from the surface of QDs. Hence, the Ag 2 S QDs/aptamer/5-Fu hybrids were developed as a novel NIR PL turn-on probe of CA125. In the concentration range of [CA125] from 0.1 to 10 6 ngmL -1 , there were a good linear relationship between NIR PL intensities of Ag 2 S QDs and Log[CA125], and a low limit of detection of 0.07ngmL -1 . Experimental results revealed the highly selective and sensitive NIR PL responses of this probe to CA125, over other potential interferences. In real human body fluids, this probe also exhibited superior analytical performance, together with high detection recoveries. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Facile and highly effective synthesis of controllable lattice sulfur-doped graphene quantum dots via hydrothermal treatment of durian.

    Science.gov (United States)

    Wang, Gang; Guo, Qinglei; Chen, Da; Liu, Zhiduo; Zheng, Xiaohu; Xu, Anli; Yang, Siwei; Ding, Guqiao

    2018-01-19

    Recently, the biomass "bottom-up" approach for the synthesis of graphene quantum dots have attracted broad interest because of the outstanding features, including low-cost, rapid and environmentally friendly nature. However, the low crystalline quality of products, substitutional doping with heteroatoms in lattice and ambiguous reaction mechanism strongly challenge the further development of this technique. Herein, we proposed a facile and effective strategy to prepare controllable sulfur (S) doping in graphene quantum dots, occurring in a lattice substitution manner, by hydrothermal treatment of durian with platinum catalyst. S atoms in graphene quantum dots are demonstrated to exist in the thiophene structure, resulting good optical and chemical stabilities, as well as ultrahigh quantum yield. Detailed mechanism of the hydrothermal reaction progress was investigated. High-efficiency reforming-cyclization provided by platinum was evidenced by the co-existence of diversified sp2 fused heterocyclic compounds and thiophene derivatives. Moreover, we also demonstrated that saccharides in durian with small molecular weight (graphene quantum dots. Due to the desulfurizing process, controllable photoluminescence properties could be achieved in as-prepared graphene quantum dots via tuning doping concentrations.

  1. Feshbach shape resonance for high Tc pairing in superlattices of quantum stripes and quantum wells

    Directory of Open Access Journals (Sweden)

    A Bianconi

    2006-09-01

    Full Text Available   The Feshbach shape resonances in the interband pairing in superconducting superlattices of quantum wells or quantum stripes is shown to provide the mechanism for high Tc superconductivity. This mechanism provides the Tc amplification driven by the architecture of material: superlattices of quantum wells (intercalated graphite or diborides and superlattices of quantum stripes (doped high Tc cuprate perovskites where the chemical potential is tuned to a Van Hove-Lifshitz singularity (vHs in the electronic energy spectrum of the superlattice associated with the change of the Fermi surface dimensionality in one of the subbands.

  2. Highly Efficient Light-Emitting Diodes of Colloidal Metal-Halide Perovskite Nanocrystals beyond Quantum Size.

    Science.gov (United States)

    Kim, Young-Hoon; Wolf, Christoph; Kim, Young-Tae; Cho, Himchan; Kwon, Woosung; Do, Sungan; Sadhanala, Aditya; Park, Chan Gyung; Rhee, Shi-Woo; Im, Sang Hyuk; Friend, Richard H; Lee, Tae-Woo

    2017-07-25

    Colloidal metal-halide perovskite quantum dots (QDs) with a dimension less than the exciton Bohr diameter DB (quantum size regime) emerged as promising light emitters due to their spectrally narrow light, facile color tuning, and high photoluminescence quantum efficiency (PLQE). However, their size-sensitive emission wavelength and color purity and low electroluminescence efficiency are still challenging aspects. Here, we demonstrate highly efficient light-emitting diodes (LEDs) based on the colloidal perovskite nanocrystals (NCs) in a dimension > DB (regime beyond quantum size) by using a multifunctional buffer hole injection layer (Buf-HIL). The perovskite NCs with a dimension greater than DB show a size-irrespective high color purity and PLQE by managing the recombination of excitons occurring at surface traps and inside the NCs. The Buf-HIL composed of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) and perfluorinated ionomer induces uniform perovskite particle films with complete film coverage and prevents exciton quenching at the PEDOT:PSS/perovskite particle film interface. With these strategies, we achieved a very high PLQE (∼60.5%) in compact perovskite particle films without any complex post-treatments and multilayers and a high current efficiency of 15.5 cd/A in the LEDs of colloidal perovskite NCs, even in a simplified structure, which is the highest efficiency to date in green LEDs that use colloidal organic-inorganic metal-halide perovskite nanoparticles including perovskite QDs and NCs. These results can help to guide development of various light-emitting optoelectronic applications based on perovskite NCs.

  3. High Efficiency Colloidal Quantum Dot Phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Kahen, Keith

    2013-12-31

    The project showed that non-Cd containing, InP-based nanocrystals (semiconductor materials with dimensions of ~6 nm) have high potential for enabling next-generation, nanocrystal-based, on chip phosphors for solid state lighting. Typical nanocrystals fall short of the requirements for on chip phosphors due to their loss of quantum efficiency under the operating conditions of LEDs, such as, high temperature (up to 150 °C) and high optical flux (up to 200 W/cm2). The InP-based nanocrystals invented during this project maintain high quantum efficiency (>80%) in polymer-based films under these operating conditions for emission wavelengths ranging from ~530 to 620 nm. These nanocrystals also show other desirable attributes, such as, lack of blinking (a common problem with nanocrystals which limits their performance) and no increase in the emission spectral width from room to 150 °C (emitters with narrower spectral widths enable higher efficiency LEDs). Prior to these nanocrystals, no nanocrystal system (regardless of nanocrystal type) showed this collection of properties; in fact, other nanocrystal systems are typically limited to showing only one desirable trait (such as high temperature stability) but being deficient in other properties (such as high flux stability). The project showed that one can reproducibly obtain these properties by generating a novel compositional structure inside of the nanomaterials; in addition, the project formulated an initial theoretical framework linking the compositional structure to the list of high performance optical properties. Over the course of the project, the synthetic methodology for producing the novel composition was evolved to enable the synthesis of these nanomaterials at a cost approximately equal to that required for forming typical conventional nanocrystals. Given the above results, the last major remaining step prior to scale up of the nanomaterials is to limit the oxidation of these materials during the tens of

  4. Strong blue photoluminescence from single-crystalline bismuth oxychloride nanoplates

    Energy Technology Data Exchange (ETDEWEB)

    Deng Zhengtao; Tang Fangqiong [Laboratory of Controllable Preparation and Application of Nanomaterials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Muscat, Anthony J [Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ 85721 (United States)], E-mail: tangfq@mail.ipc.ac.cn

    2008-07-23

    Single-crystalline bismuth oxychloride (BiOCl) nanoplates with in-plane sizes of 200-500 nm and a thickness of 15-25 nm are synthesized by a simple solution route. Strong blue photoluminescence centred at 455 nm ({approx}2.72 eV) with very high quantum yields ({phi}{sub PL}{approx}0.4) has been observed at room temperature, representing the first report of strong room temperature photoluminescence from bismuth oxyhalide nanomaterials. It is envisaged that bismuth oxychloride could join the family of non-cadmium based high-efficiency emitters; it has promising applications in various fields, especially in light emitting diodes, lasers and solar cells.

  5. High-Temperature Luminescence Quenching of Colloidal Quantum Dots

    NARCIS (Netherlands)

    Zhao, Y.|info:eu-repo/dai/nl/355358352; Riemersma, C.; Pietra, F|info:eu-repo/dai/nl/355358395; de Mello Donega, C.|info:eu-repo/dai/nl/125593899; Meijerink, A.|info:eu-repo/dai/nl/075044986

    2012-01-01

    Thermal quenching of quantum dot (QD) luminescence is important for application in luminescent devices. Systematic studies of the quenching behavior above 300 K are, however, lacking. Here, high-temperature (300–500 K) luminescence studies are reported for highly efficient CdSe core–shell quantum

  6. Quantum effects in condensed matter at high pressure

    CERN Document Server

    Stishov, S M

    2001-01-01

    Experimental data on the influence of quantum effects on the equation of state and melting at high pressure are reviewed. It is shown that quantum isotopic effects tend to increase upon compression of substances with predominately Coulomb interaction, whereas compression of the van der Waals substances reveals the opposite trend. The cold melting of Coulomb substances at high pressure is discussed

  7. Long-range ordered self-assembled InAs quantum dots epitaxially grown on (110) GaAs

    Science.gov (United States)

    Bauer, J.; Schuh, D.; Uccelli, E.; Schulz, R.; Kress, A.; Hofbauer, F.; Finley, J. J.; Abstreiter, G.

    2004-11-01

    We report on a promising approach for positioning of self-assembled InAs quantum dots on (110) GaAs with nanometer precision. By combining self-assembly of quantum dots with molecular beam epitaxy on previously grown and in situ cleaved substrates (cleaved-edge overgrowth), arrays of long-range ordered InAs quantum dots have been fabricated. Both atomic force microscopy and micro-photoluminescence measurements demonstrate the ability to control size, position, and ordering of the quantum dots. Furthermore, single dot photoluminescence investigations confirm the high optical quality of the quantum dots fabricated.

  8. Quantum Accelerators for High-performance Computing Systems

    Energy Technology Data Exchange (ETDEWEB)

    Humble, Travis S. [ORNL; Britt, Keith A. [ORNL; Mohiyaddin, Fahd A. [ORNL

    2017-11-01

    We define some of the programming and system-level challenges facing the application of quantum processing to high-performance computing. Alongside barriers to physical integration, prominent differences in the execution of quantum and conventional programs challenges the intersection of these computational models. Following a brief overview of the state of the art, we discuss recent advances in programming and execution models for hybrid quantum-classical computing. We discuss a novel quantum-accelerator framework that uses specialized kernels to offload select workloads while integrating with existing computing infrastructure. We elaborate on the role of the host operating system to manage these unique accelerator resources, the prospects for deploying quantum modules, and the requirements placed on the language hierarchy connecting these different system components. We draw on recent advances in the modeling and simulation of quantum computing systems with the development of architectures for hybrid high-performance computing systems and the realization of software stacks for controlling quantum devices. Finally, we present simulation results that describe the expected system-level behavior of high-performance computing systems composed from compute nodes with quantum processing units. We describe performance for these hybrid systems in terms of time-to-solution, accuracy, and energy consumption, and we use simple application examples to estimate the performance advantage of quantum acceleration.

  9. Effect of annealing on the structure and optical properties of InGaAs/GaAs quantum dots

    DEFF Research Database (Denmark)

    Xu, Zhangcheng; Leosson, Kristjan; Birkedal, Dan

    2002-01-01

    We report the effect of annealing on self-assembled InGaAs/GaAs quantum dots, as investigated by means of resonant photoluminescence (PL), resonant Raman scattering, polarization dependent PL, and high resolution X-ray diffraction.......We report the effect of annealing on self-assembled InGaAs/GaAs quantum dots, as investigated by means of resonant photoluminescence (PL), resonant Raman scattering, polarization dependent PL, and high resolution X-ray diffraction....

  10. Bright and high-photostable inner-Mn-doped core/giant-shell quantum dots

    Science.gov (United States)

    Xu, Ruilin; Huang, Bo; Wang, Tian; Yuan, Yufen; Zhang, Lei; Lu, Changgui; Cui, Yiping; Zhang, Jiayu

    2017-11-01

    Compared with quantum-dot (QD) displays, QD lighting possesses higher demand of photostability. Owing to high photostability from the combination of inner independent luminescence center and thick shell (≥15 monolayers (MLs)), inner-Mn-doped core/giant-shell QDs with bright wide emission are a promising candidate for QD lighting. Aiming at bright and high-photostable giant QDs with low time cost (giant-shell growth time: within 20 min), we put forward the perfect combination strategy of hot-injection nucleation doping and optimized ;flash; synthesis, going beyond the combination strategy of one-pot growth doping and typical ;flash; synthesis, which led to an increase in photoluminescence (PL) quantum yield (QY) of giant Mn-doped CdS/ZnS QDs (ZnS shell: ∼18 MLs) from ≤20% to 40%. The PLQY was enhanced to 45% by light annealing. Using traditional LED as the reference, these simply-encapsulated QDs can exhibit the high photostability, throwing light of the application of these inner-Mn-doped core/giant-shell QDs even for QD lighting.

  11. Highly Sensitive and Selective Detection of Nanomolar Ferric Ions Using Dopamine Functionalized Graphene Quantum Dots.

    Science.gov (United States)

    Dutta Chowdhury, Ankan; Doong, Ruey-An

    2016-08-17

    The good stability, low cytotoxicity, and excellent photoluminescence property of graphene quantum dots (GQDs) make them an emerging class of promising materials in various application fields ranging from sensor to drug delivery. In the present work, the dopamine-functionalized GQDs (DA-GQDs) with stably bright blue fluorescence were successfully synthesized for low level Fe(3+) ions detection. The as-synthesized GQDs are uniform in size with narrow-distributed particle size of 4.5 ± 0.6 nm and high quantum yield of 10.2%. The amide linkage of GQDs with dopamine, confirmed by using XPS and FTIR spectra, results in the specific interaction between Fe(3+) and catechol moiety of dopamine at the interfaces for highly sensitive and selective detection of Fe(3+). A linear range of 20 nM to 2 μM with a detection limit of 7.6 nM is obtained for Fe(3+) detection by DA-GQDs. The selectivity of DA-GQDs sensing probe is significantly excellent in the presence of other interfering metal ions. In addition, the reaction mechanism for Fe(3+) detection based on the complexation and oxidation of dopamine has been proposed and validated. Results obtained in this study clearly demonstrate the superiority of surface functionalized GQDs to Fe(3+) detection, which can pave an avenue for the development of high performance and robust sensing probes for detection of metal ions and other organic metabolites in environmental and biomedical applications.

  12. Tough photoluminescent hydrogels doped with lanthanide.

    Science.gov (United States)

    Wang, Mei Xiang; Yang, Can Hui; Liu, Zhen Qi; Zhou, Jinxiong; Xu, Feng; Suo, Zhigang; Yang, Jian Hai; Chen, Yong Mei

    2015-03-01

    Photoluminescent hydrogels have emerged as novel soft materials with potential applications in many fields. Although many photoluminescent hydrogels have been fabricated, their scope of usage has been severely limited by their poor mechanical performance. Here, a facile strategy is reported for preparing lanthanide (Ln)-alginate/polyacrylamide (PAAm) hydrogels with both high toughness and photoluminescence, which has been achieved by doping Ln(3+) ions (Ln = Eu, Tb, Eu/Tb) into alginate/PAAm hydrogel networks, where Ln(3+) ions serve as both photoluminescent emitters and physical cross-linkers. The resulting hydrogels exhibit versatile advantages including excellent mechanical properties (∼ MPa strength, ≈ 20 tensile strains, ≈ 10(4) kJ m(-3) energy dissipation), good photoluminescent performance, tunable emission color, excellent processability, and cytocompatibility. The developed tough photoluminescent hydrogels hold great promises for expanding the usage scope of hydrogels. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Photoluminescence studies of Mn{sup 4+} ions in YAlO{sub 3} crystals at ambient and high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Zhydachevskii, Ya [Lviv Polytechnic National University, 12 Bandera, Lviv 79646 (Ukraine); Galanciak, D [Department of Physics, University of Bydgoszcz, Weyssenhoffa 11, 85-072, Bydgoszcz (Poland); Kobyakov, S [Institute of Physics, Polish Academy of Sciences, 32/46 Aleja Lotnikow, 02-668 Warsaw (Poland); Berkowski, M [Institute of Physics, Polish Academy of Sciences, 32/46 Aleja Lotnikow, 02-668 Warsaw (Poland); Kaminska, A [Institute of Physics, Polish Academy of Sciences, 32/46 Aleja Lotnikow, 02-668 Warsaw (Poland); Suchocki, A [Institute of Physics, Polish Academy of Sciences, 32/46 Aleja Lotnikow, 02-668 Warsaw (Poland); Zakharko, Ya [I. Franko Lviv National University, 107 Tarnavskogo Street, Lviv 79017 (Ukraine); Durygin, A [CeSMEC, Florida International University, University Park, Miami, FL 33199 (United States)

    2006-12-13

    Detailed investigations of the photoluminescence properties of Mn{sup 4+} (3d{sup 3}) ions in YAlO{sub 3} have been performed in the temperature range 10-600 K. The luminescence of Mn{sup 4+} ions due to the {sup 2}E {yields}{sup 4}A{sub 2} transition consists of two zero-phonon lines (R lines) at 691.3 and 692.7 nm, which became visible only at low temperature, and their vibronic sidebands that cover the range of 660-740 nm. The thermal quenching of the luminescence intensity due to the non-radiative decay occurs at temperatures above 420 K. The temperature dependence of the luminescence decay time shows a quasi-linear decrease from {tau} = 4.9 to 1.6 ms in the temperature range from 90 to 420 K (with a temperature coefficient -0.01 ms K{sup -1}) that makes YAlO{sub 3}:Mn a potentially good phosphor for a fibre optic fluorescence thermometer in this temperature range. The high-pressure low-temperature luminescence measurements in a diamond-anvil cell reveal similar pressure coefficients for Mn{sup 4+} and Cr{sup 3+} dopant ions in YAlO{sub 3}, equal to 1.16 cm{sup -1} kbar{sup -1} and 1.08 cm{sup -1} kbar{sup -1}, respectively.

  14. Efficient Luminescence from Perovskite Quantum Dot Solids

    KAUST Repository

    Kim, Younghoon

    2015-11-18

    © 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals\\' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

  15. Photoluminescent properties of single crystal diamond microneedles

    Science.gov (United States)

    Malykhin, Sergey A.; Ismagilov, Rinat R.; Tuyakova, Feruza T.; Obraztsova, Ekaterina A.; Fedotov, Pavel V.; Ermakova, Anna; Siyushev, Petr; Katamadze, Konstantin G.; Jelezko, Fedor; Rakovich, Yury P.; Obraztsov, Alexander N.

    2018-01-01

    Single crystal needle-like diamonds shaped as rectangular pyramids were produced by combination of chemical vapor deposition and selective oxidation with dimensions and geometrical characteristics depending on the deposition process parameters. Photoluminescence spectra and their dependencies on wavelength of excitation radiation reveal presence of nitrogen- and silicon-vacancy color centers in the diamond crystallites. Photoluminescence spectra, intensity mapping, and fluorescence lifetime imaging microscopy indicate that silicon-vacancy centers are concentrated at the crystallites apex while nitrogen-vacancy centers are distributed over the whole crystallite. Dependence of the photoluminescence on excitation radiation intensity demonstrates saturation and allows estimation of the color centers density. The combination of structural parameters, geometry and photoluminescent characteristics are prospective for advantageous applications of these diamond crystallites in quantum information processing and optical sensing.

  16. Shape-Uniform, High-Quality Monolayered MoS2 Crystals for Gate-Tunable Photoluminescence.

    Science.gov (United States)

    Zhang, Xiumei; Nan, Haiyan; Xiao, Shaoqing; Wan, Xi; Ni, Zhenhua; Gu, Xiaofeng; Ostrikov, Kostya

    2017-11-21

    Two-dimensional molybdenum disulfide (MoS2) has recently drawn major attention due to its promising applications in electronics and optoelectronics. Chemical vapor deposition (CVD) is a scalable method to produce large-area MoS2 monolayers, yet it is challenging to achieve shape-uniform, high-quality monolayered MoS2 grains as random, diverse crystallographic orientations and various shapes are produced in the same CVD process. Here, we report the growth of high-quality MoS2 monolayers with uniform triangular shapes dominating (up to 89%) over other shapes on both SiO2/Si and sapphire substrates. The new confined-space CVD process prevents contamination and helps regulate the Mo/S ratio during the deposition. The as-grown triangular MoS2 monolayers exhibit grain sizes up to 150 μm and possess better crystalline properties and lighter n-type doping concentration than those of the monolayers grown by common CVD methods. The corresponding field effect transistor devices show high electron mobilities of 50-60 cm(2) V(-1) s(-1) and positive threshold voltages of 21-35 V. This mild n-type behavior makes it possible to regulate the formation of excitons by back-gate voltage due to the interaction of excitons with free charge carriers in the MoS2 channel. As a result, gate-tunable photoluminescence (PL) effect, which is rarely achievable for MoS2 samples prepared by common CVD or mechanical exfoliation, is demonstrated. This study provides a simple versatile approach to fabricating monolayered crystals of MoS2 and other high-quality transition metal dichalcogenides and could lead to new optoelectronic devices based on gate-tunable PL effect.

  17. Demonstration of deterministic and high fidelity squeezing of quantum information

    DEFF Research Database (Denmark)

    Yoshikawa, J-I.; Hayashi, T-; Akiyama, T.

    2007-01-01

    , and an ancillary squeezed vacuum state, thus direct interaction between a strong pump and the quantum state is circumvented. We demonstrate three different squeezing levels for a coherent state input. This scheme is highly suitable for the fault-tolerant squeezing transformation in a continuous variable quantum...

  18. High Spin Baryons in Quantum Mechanical Chromodynamics

    Science.gov (United States)

    Kirchbach, M.; Compean, C. B.

    2009-04-01

    A framework of quantum mechanical chromodynamics (QMCD) is developed with the aim to place the description of the nucleon on a comparable footing with Schrödinger's quantum mechanical treatment of the hydrogen atom. Such indeed turns out to be possible upon replacing the (e--p) by a (q-qq) system, on the one hand, and the Coulomb potential by the recently reported by us exactly solvable trigonometric extension of the Cornell (TEC) potential, on the other. The TEC potential translates the inverse distance potential in ordinary flat space to a space of constant positive curvature, the 3D hypersphere, a reason for which both potentials have the SO(4) and SO(2, 1) symmetries in common. In effect, the nucleon spectrum, inclusive its Δ branch, acquire the degeneracy patterns of the electron excitations with spin in 1H without copying them, however. There are two essential differences between the N(Δ) and H atom spectra. The first concerns the parity of the states which can be unnatural for the N and Δ excitations due to compositeness of the diquark, the second refers to the level splittings in the baryon spectra which contain besides the Balmer term also its inverse of opposite sign. Our scheme reproduces the complete number of states (except the hybrid Δ(1600)), predicts a total of 33 new resonances, and explains the splittings of the N and Δ levels containing high-spin resonances. It also describes accurately the proton electric charge form factor. We here calculate the potential in momentum space (instantaneous effective gluon propagator) as a Fourier transform of the TEC potential and show that the concept of curvature allows to avoid the integral divergences suffered by schemes based on power potentials. We find a propagator that is finite at origin, likely to produce confinement. The advocated new potential picture allows for deconfinement too as effect of space flattening in the limit of infinite radius of the 3D hypersphere. The potential's SO(4)/SO(2, 1

  19. High fluorescent water soluble CdTe quantum dots—a promising system for light harvesting applications

    Science.gov (United States)

    de Sa, Arsenio; Moura, Isabel; Abreu, Ana S.; Oliveira, Manuel; Ferreira, Miguel F.; Machado, Ana V.

    2017-05-01

    The entrapment of quantum dots (QDs) in the inner part of micelles formed by surfactant polymers is a powerful methodology to prepare stable and photoluminescent core nanoparticles with enhanced optical properties. These features are crucial for the application of QDs in the design of hybrid assemblies for light harvesting applications, where energy transfer processes are required. The present work was focused on the synthesis of a surfactant homopolymer, poly (acrylic acid) (PAA) macroRAFT, to be used as a stabilizer of hydrophobic cadmium telluride (CdTe) QDs in aqueous solution. PAA macroRAFT was synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization in a single chemical reaction. Its micelles were used to entangle and entrap hydrophobic CdTe QDs, with different molar ratio of polymer and QDs. The morphology and optical properties of the entrapped QDs were determined. The results showed that PAA macroRAFT is able to form micelles with a critical micelle concentration of 2.08 mg/mL. It was also noticed that the molar ratio of polymer and QDs have high influence on the QDs' morphology and their optical properties. The QDs' photoluminescence quantum yield was enhanced approximately 23% upon their entrapment in PAA macroRAFT micelles, using 60 equivalents of polymer. Moreover, while in solution, QDs are well-dispersed, having a 3.5 nm diameter, upon being entrapped in the micelles, tend to form clusters with a size around 100 nm.

  20. High Color-Purity Green, Orange, and Red Light-Emitting Didoes Based on Chemically Functionalized Graphene Quantum Dots

    Science.gov (United States)

    Kwon, Woosung; Kim, Young-Hoon; Kim, Ji-Hee; Lee, Taehyung; Do, Sungan; Park, Yoonsang; Jeong, Mun Seok; Lee, Tae-Woo; Rhee, Shi-Woo

    2016-04-01

    Chemically derived graphene quantum dots (GQDs) to date have showed very broad emission linewidth due to many kinds of chemical bondings with different energy levels, which significantly degrades the color purity and color tunability. Here, we show that use of aniline derivatives to chemically functionalize GQDs generates new extrinsic energy levels that lead to photoluminescence of very narrow linewidths. We use transient absorption and time-resolved photoluminescence spectroscopies to study the electronic structures and related electronic transitions of our GQDs, which reveals that their underlying carrier dynamics is strongly related to the chemical properties of aniline derivatives. Using these functionalized GQDs as lumophores, we fabricate light-emitting didoes (LEDs) that exhibit green, orange, and red electroluminescence that has high color purity. The maximum current efficiency of 3.47 cd A-1 and external quantum efficiency of 1.28% are recorded with our LEDs; these are the highest values ever reported for LEDs based on carbon-nanoparticle phosphors. This functionalization of GQDs with aniline derivatives represents a new method to fabricate LEDs that produce natural color.

  1. High Color-Purity Green, Orange, and Red Light-Emitting Didoes Based on Chemically Functionalized Graphene Quantum Dots

    Science.gov (United States)

    Kwon, Woosung; Kim, Young-Hoon; Kim, Ji-Hee; Lee, Taehyung; Do, Sungan; Park, Yoonsang; Jeong, Mun Seok; Lee, Tae-Woo; Rhee, Shi-Woo

    2016-01-01

    Chemically derived graphene quantum dots (GQDs) to date have showed very broad emission linewidth due to many kinds of chemical bondings with different energy levels, which significantly degrades the color purity and color tunability. Here, we show that use of aniline derivatives to chemically functionalize GQDs generates new extrinsic energy levels that lead to photoluminescence of very narrow linewidths. We use transient absorption and time-resolved photoluminescence spectroscopies to study the electronic structures and related electronic transitions of our GQDs, which reveals that their underlying carrier dynamics is strongly related to the chemical properties of aniline derivatives. Using these functionalized GQDs as lumophores, we fabricate light-emitting didoes (LEDs) that exhibit green, orange, and red electroluminescence that has high color purity. The maximum current efficiency of 3.47 cd A−1 and external quantum efficiency of 1.28% are recorded with our LEDs; these are the highest values ever reported for LEDs based on carbon-nanoparticle phosphors. This functionalization of GQDs with aniline derivatives represents a new method to fabricate LEDs that produce natural color. PMID:27048887

  2. Highly photoluminescent polysilsesquioxane hybrids based on weakly fluorescent 1,8-naphthalic anhydride derivatives

    Science.gov (United States)

    Pan, Fei; Huang, Miao; Song, Jianhui; Wu, Meng; Xu, Min

    2016-07-01

    A series of highly fluorescent polysilsesquioxane materials based on 1,8-naphthalic anhydride derivatives(XNA) have been prepared. The XNAs were chemically bonded with the polysiloxane. Though the fluorescent intensities of the solution of XNAs with different substitutes make a great difference, some of them are even very weakly emissive, the fluorescent intensities of the corresponding solid polysilsesquioxane materials are strong. In this case, the electronic effect of the substitute became non-important. With restricted molecular motion and J-aggregation, some traditionally weakly fluorescent or non-fluorescent chromophoric organics due to the substituent effect may be used to prepare highly fluorescent materials.

  3. Preparation of carbon quantum dots based high photostability luminescent membranes.

    Science.gov (United States)

    Zhao, Jinxing; Liu, Cui; Li, Yunchuan; Liang, Jiyuan; Liu, Jiyan; Qian, Tonghui; Ding, Jianjun; Cao, Yuan-Cheng

    2017-06-01

    Urethane acrylate (UA) was used to prepare carbon quantum dots (C-dots) luminescent membranes and the resultants were examined with FT-IR, mechanical strength, scanning electron microscope (SEM) and quantum yields (QYs). FT-IR results showed the polyurethane acrylate (PUA) prepolymer -C = C-vibration at 1101 cm-1 disappeared but there was strong vibration at1687cm-1 which was contributed from the-C = O groups in cross-linking PUA. Mechanical strength results showed that the different quantity of C-dots loadings and UV-curing time affect the strength. SEM observations on the cross-sections of the membranes are uniform and have no structural defects, which prove that the C-dots are compatible with the water-soluble PUA resin. The C-dot loading was increased from 0 to 1 g, the maximum tensile stress was nearly 2.67 MPa, but the tensile strain was decreased from 23.4% to 15.1% and 7.2% respectively. QYs results showed that the C-dots in the membrane were stable after 120 h continuous irradiation. Therefore, the C-dots photoluminescent film is the promising material for the flexible devices in the future applications. Copyright © 2016 John Wiley & Sons, Ltd.

  4. Synthesis and photoluminescence property of silicon carbide ...

    Indian Academy of Sciences (India)

    Administrator

    blue shift may be ascribed to morphology, quantum size confinement effects of the nanomaterials and abundant structure defects that existed in the nanowires. Keywords. SiC nanowires; nanocrystalline diamond; crystal growth; photoluminescence. 1. Introduction. SiC has been widely recognized as a versatile material.

  5. Synthesis and photoluminescence property of silicon carbide ...

    Indian Academy of Sciences (India)

    The -SiC nanowires thin films exhibit the strong photoluminescence (PL) peak at a wavelength of 400 nm, which is significantly shifted to the blue compared with the reported PL results of SiC materials. The blue shift may be ascribed to morphology, quantum size confinement effects of the nanomaterials and abundant ...

  6. Triggered high-purity telecom-wavelength single-photon generation from p-shell-driven InGaAs/GaAs quantum dot.

    Science.gov (United States)

    Dusanowski, Ł; Holewa, P; Maryński, A; Musiał, A; Heuser, T; Srocka, N; Quandt, D; Strittmatter, A; Rodt, S; Misiewicz, J; Reitzenstein, S; Sęk, G

    2017-12-11

    We report on the experimental demonstration of triggered single-photon emission at the telecom O-band from In(Ga)As/GaAs quantum dots (QDs) grown by metal-organic vapor-phase epitaxy. Micro-photoluminescence excitation experiments allowed us to identify the p-shell excitonic states in agreement with high excitation photoluminescence on the ensemble of QDs. Hereby we drive an O-band-emitting GaAs-based QD into the p-shell states to get a triggered single photon source of high purity. Applying pulsed p-shell resonant excitation results in strong suppression of multiphoton events evidenced by the as measured value of the second-order correlation function at zero delay of 0.03 (and ~0.005 after background correction).

  7. High Color-Purity Green, Orange, and Red Light-Emitting Didoes Based on Chemically Functionalized Graphene Quantum Dots

    OpenAIRE

    Woosung Kwon; Young-Hoon Kim; Ji-Hee Kim; Taehyung Lee; Sungan Do; Yoonsang Park; Mun Seok Jeong; Tae-Woo Lee; Shi-Woo Rhee

    2016-01-01

    Chemically derived graphene quantum dots (GQDs) to date have showed very broad emission linewidth due to many kinds of chemical bondings with different energy levels, which significantly degrades the color purity and color tunability. Here, we show that use of aniline derivatives to chemically functionalize GQDs generates new extrinsic energy levels that lead to photoluminescence of very narrow linewidths. We use transient absorption and time-resolved photoluminescence spectroscopies to study...

  8. Photocatalytic synthesis of intensely photoluminescent gold nanoclusters and application in cell imaging

    Science.gov (United States)

    Wei, Ming; Tian, Ye; Wang, Lijun; Hong, Yuankai; Sha, Yinlin

    2017-07-01

    In this article, a facile and rapid method was developed to synthesize intensely photoluminescent gold nanoclusters (AuNCs) based on photocatalytic reduction. Using (5-mercapto-1,3,4-thiadiazol-2-ylthio)acetic acid (TMT) that is a photosensitive material as the ligands, AuNC@TMT, with high photoluminescence quantum yield (19.7%), were prepared. The average diameter of gold core is 1.69 ± 0.22 nm. The maximum excitation and emission wavelengths of AuNC@TMT are at 422 and 516 nm, respectively. The mechanism of photocatalytic reduction is preliminarily understood. Under UV lamp with 365 nm irradiation, Au(Ι)-TMT complex occurred with electron transfer from TMT to Au(Ι), which was reduced to Au(0) as the gold core of AuNC. Thus, it indicates that the photosensitive and electron transport materials with a thiol group will be superior ligands for synthesis of intensely photoluminescent AuNCs.

  9. Synthesis and characterization of Ag doped ZnS quantum dots for enhanced photocatalysis of Strychnine asa poison: Charge transfer behavior study by electrochemical impedance and time-resolved photoluminescence spectroscopy.

    Science.gov (United States)

    Gupta, Vinod Kumar; Fakhri, Ali; Azad, Mona; Agarwal, Shilpi

    2018-01-15

    In this study, the photocatalytic degradation of Strychnine was investigated by ZnS quantum dots and doped with silver in UV systems. ZnS and Ag-ZnS quantum dots were synthesized by chemical method and characterized by powder X-ray diffraction, transmission electron microscopy, UV-vis spectra and photoluminescence. The charge transfer process on the semicon-ductor/electrolyte interface was investigated via electrochemical impedance spectroscopy (EIS) and time-resolved photoluminescence. The average diameters of ZnS and Ag doped ZnS QDs were 3.0-5.0nm and 3.0-5.3nm, respectively. The band gap of ZnS and Ag-ZnS QDs was computed as 3.47 and 3.1eV, respectively. The surface area values of ZnS and Ag-ZnS QDs have been found as 78.25 and 89.54m2/g, respectively. The influences of key operating parameters such as initial pH, catalyst dosage, UV radiation intensity, reaction time as well as the effect of initial Strychnine concentration on mineralization extents were studied. The results of the study showed that the maximum removal efficiency of Strychnine had been achieved by un-doped and Ag-doped ZnS QDs at radiation intensity of 100W/m2, at time of 60min, pH of 3 and initial Strychnine concentration of 20mg/ml. Also the observations clearly showed that the photocatalysis process with Ag doped ZnS QDs are more effective than un-doped ZnS QDs. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Highly luminescent water-soluble quaternary Zn–Ag–In–S quantum dots and their unique precursor S/In ratio-dependent spectral shifts

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Dawei, E-mail: david597300@163.com [Department of Biomedical Engineering, School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009 (China); Qu, Lingzhi [Department of Biomedical Engineering, School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009 (China); Cheng, Zhiqiang [College of Resources and Environment, Jilin Agricultural University, Changchun 130118 (China); Achilefu, Samuel, E-mail: achilefus@mir.wustl.edu [Department of Radiology, School of Medicine, Washington University, St. Louis, MO 63110 (United States); Gu, Yueqing, E-mail: guyueqingsubmission@hotmail.com [Department of Biomedical Engineering, School of Life Science and Technology, China Pharmaceutical University, Nanjing 210009 (China)

    2014-02-15

    Quaternary I–II–III–VI semiconductor quantum dots (QDs) containing less toxic elements are receiving increasing attention because of their promising applications in solar cells, light-emitting diode (LED), and biological labeling. Despite its advantages, the quaternary system is more complex than the binary and ternary analogues. This is reflected in the difficulty to control the size, size distribution, elemental composition, and optical properties of quaternary I–II–III–VI QDs, especially in aqueous medium. In this work, we have synthesized new aqueous quaternary Zn–Ag–In–S (ZAIS) QDs with tunable photoluminescence (PL) for the first time, giving the highest PL quantum yield (QY) of 30%, which is close to those of the conventional well-developed aqueous II–VI QDs. Most importantly, three unique spectral shifts depending on precursor S/In ratio were observed in this quaternary system. The spectral were characterized by diverse analytical methods to systematically establish distinct features of the quaternary nanomaterials. The results demonstrate the potential utility of this new water-soluble system in fundamental and applied researches with quaternary QDs. -- Highlights: • The synthesis of water-soluble quaternary Zn–Ag–In–S quantum dots. • The high photoluminescence quantum yield, 30%. • The three unique precursor S/In ratio-dependent spectral shifts.

  11. High-field spin dynamics of antiferromagnetic quantum spin chains

    DEFF Research Database (Denmark)

    Enderle, M.; Regnault, L.P.; Broholm, C.

    2000-01-01

    The characteristic internal order of macroscopic quantum ground states in one-dimensional spin systems is usually not directly accessible, but reflected in the spin dynamics and the field dependence of the magnetic excitations. In high magnetic fields quantum phase transitions are expected. We...... present recent work on the high-field spin dynamics of the S = I antiferromagnetic Heisenberg chains NENP (Haldane ground state) and CsNiCl3 (quasi-1D HAF close to the quantum critical point), the uniform S = 1/2 chain CTS, and the spin-Peierls system CuGeO3. (C) 2000 Elsevier Science B,V. All rights...

  12. High Efficiency Quantum Well Waveguide Solar Cells Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The long-term objective of this program is to develop flexible, lightweight, single-junction solar cells using quantum structured designs that can achieve ultra-high...

  13. High-Temperature Luminescence Quenching of Colloidal Quantum Dots

    OpenAIRE

    Zhao, Y.; Riemersma, C.; Pietra, F; de Mello Donega, C.; Meijerink, A.

    2012-01-01

    Thermal quenching of quantum dot (QD) luminescence is important for application in luminescent devices. Systematic studies of the quenching behavior above 300 K are, however, lacking. Here, high-temperature (300–500 K) luminescence studies are reported for highly efficient CdSe core–shell quantum dots (QDs), aimed at obtaining insight into temperature quenching of QD emission. Through thermal cycling (yoyo) experiments for QDs in polymer matrices, reversible and irreversible luminescence quen...

  14. High-dimensional quantum state transfer through a quantum spin chain

    Science.gov (United States)

    Qin, Wei; Wang, Chuan; Long, Gui Lu

    2013-01-01

    In this paper, we investigate a high-dimensional quantum state transfer protocol. An arbitrary unknown high-dimensional state can be transferred with high fidelity between two remote registers through an XX coupling spin chain of arbitrary length. The evolution of the state transfer is determined by the natural dynamics of the chain without external modulation and coupling strength engineering. As a consequence, entanglement distribution with a high efficiency can be achieved. Also the strong field and high spin quantum number can partly counteract the effect of finite temperature to ensure the high fidelity of the protocol when the quantum data bus is in the thermal equilibrium state under an external magnetic field.

  15. Bright photoluminescent hybrid mesostructured silica nanoparticles.

    Science.gov (United States)

    Miletto, Ivana; Bottinelli, Emanuela; Caputo, Giuseppe; Coluccia, Salvatore; Gianotti, Enrica

    2012-07-28

    Bright photoluminescent mesostructured silica nanoparticles were synthesized by the incorporation of fluorescent cyanine dyes into the channels of MCM-41 mesoporous silica. Cyanine molecules were introduced into MCM-41 nanoparticles by physical adsorption and covalent grafting. Several photoluminescent nanoparticles with different organic loadings have been synthesized and characterized by X-ray powder diffraction, high resolution transmission electron microscopy and nitrogen physisorption porosimetry. A detailed photoluminescence study with the analysis of fluorescence lifetimes was carried out to elucidate the cyanine molecules distribution within the pores of MCM-41 nanoparticles and the influence of the encapsulation on the photoemission properties of the guests. The results show that highly stable photoluminescent hybrid materials with interesting potential applications as photoluminescent probes for diagnostics and imaging can be prepared by both methods.

  16. Enhanced conversion efficiency in Si solar cells employing photoluminescent down-shifting CdSe/CdS core/shell quantum dots.

    Science.gov (United States)

    Lopez-Delgado, R; Zhou, Y; Zazueta-Raynaud, A; Zhao, H; Pelayo, J E; Vomiero, A; Álvarez-Ramos, M E; Rosei, F; Ayon, A

    2017-10-26

    Silicon solar cells have captured a large portion of the total market of photovoltaic devices mostly due to their relatively high efficiency. However, Silicon exhibits limitations in ultraviolet absorption because high-energy photons are absorbed at the surface of the solar cell, in the heavily doped region, and the photo-generated electron-hole pairs need to diffuse into the junction region, resulting in significant carrier recombination. One of the alternatives to improve the absorption range involves the use of down-shifting nano-structures able to interact with the aforementioned high energy photons. Here, as a proof of concept, we use downshifting CdSe/CdS quantum dots to improve the performance of a silicon solar cell. The incorporation of these nanostructures triggered improvements in the short circuit current density (Jsc, from 32.5 to 37.0 mA/cm2). This improvement led to a ∼13% increase in the power conversion efficiency (PCE), from 12.0 to 13.5%. Our results demonstrate that the application of down-shifting materials is a viable strategy to improve the efficiency of Silicon solar cells with mass-compatible techniques that could serve to promote their widespread utilization.

  17. Synthesis of biocompatible and highly photoluminescent nitrogen doped carbon dots from lime: Analytical applications and optimization using response surface methodology

    Energy Technology Data Exchange (ETDEWEB)

    Barati, Ali [Faculty of Chemistry, Institute for Advanced Studies in Basic Sciences, Zanjan (Iran, Islamic Republic of); Shamsipur, Mojtaba, E-mail: mshamsipur@yahoo.com [Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Arkan, Elham [Nano Drug Delivery Research Center Kermanshah University of Medical Sciences, Kermanshah (Iran, Islamic Republic of); Hosseinzadeh, Leila [Novel Drug Delivery Research Center, Faculty of Pharmacy, Kermanshah University of Medical Sciences, Kermanshah (Iran, Islamic Republic of); Abdollahi, Hamid, E-mail: abd@iasbs.ac.ir [Faculty of Chemistry, Institute for Advanced Studies in Basic Sciences, Zanjan (Iran, Islamic Republic of)

    2015-02-01

    Herein, a facile hydrothermal treatment of lime juice to prepare biocompatible nitrogen-doped carbon quantum dots (N-CQDs) in the presence of ammonium bicarbonate as a nitrogen source has been presented. The resulting N-CQDs exhibited excitation and pH independent emission behavior; with the quantum yield (QY) up to 40%, which was several times greater than the corresponding value for CQDs with no added nitrogen source. The N-CQDs were applied as a fluorescent probe for the sensitive and selective detection of Hg{sup 2+} ions with a detection limit of 14 nM. Moreover, the cellular uptake and cytotoxicity of N-CQDs at different concentration ranges from 0.0 to 0.8 mg/ml were investigated by using PC12 cells as a model system. Response surface methodology was used for optimization and systematic investigation of the main variables that influence the QY, including reaction time, reaction temperature, and ammonium bicarbonate weight. - Highlights: • High fluorescent N-doped CQDs from lime juice have been prepared. • Response surface methodology was used to optimize and model the main factors. • N-doped CQDs were used in the selective and sensitive detection of Hg(II). • The biocompatibility of prepared N-doped CQDs was conformed using PC12 cells.

  18. Growth and characterization of high strain InGaAs/GaAs quantum well by molecular beam epitaxy

    Science.gov (United States)

    Shan, Rui; Liu, Yu; Guo, Jie; Wang, Guowei; Xu, Yingqiang

    2016-10-01

    High indium composition InxGa1-xAs/GaAs quantum wells (x˃0.4) in which the well width reached to 7 nm without relaxing were grown on (100) GaAs substrates by MBE. The good crystal quality and optical properties of the high strained InGaAs/GaAs QW were obtained by controlling quasi-2D growth model and optimizing the growth condition including the growth temperature, growth rate, and V/III BEP ratio. Photoluminescence (PL) showed that the cutoff wavelength was about 1.3μm at room temperature with narrow full width at half maximum below 30meV. Dilute nitrogen and high In composition InGaAsN/GaAs QW extended wavelength infrared photodetectors at 1.3 and 1.55 μm were also realized.

  19. Near-infrared light controlled photocatalytic activity of carbon quantum dots for highly selective oxidation reaction

    Science.gov (United States)

    Li, Haitao; Liu, Ruihua; Lian, Suoyuan; Liu, Yang; Huang, Hui; Kang, Zhenhui

    2013-03-01

    Selective oxidation of alcohols is a fundamental and significant transformation for the large-scale production of fine chemicals, UV and visible light driven photocatalytic systems for alcohol oxidation have been developed, however, the long wavelength near infrared (NIR) and infrared (IR) light have not yet fully utilized by the present photocatalytic systems. Herein, we reported carbon quantum dots (CQDs) can function as an effective near infrared (NIR) light driven photocatalyst for the selective oxidation of benzyl alcohol to benzaldehyde. Based on the NIR light driven photo-induced electron transfer property and its photocatalytic activity for H2O2 decomposition, this metal-free catalyst could realize the transformation from benzyl alcohol to benzaldehyde with high selectivity (100%) and conversion (92%) under NIR light irradiation. HO&z.rad; is the main active oxygen specie in benzyl alcohol selective oxidative reaction confirmed by terephthalic acid photoluminescence probing assay (TA-PL), selecting toluene as the substrate. Such metal-free photocatalytic system also selectively converts other alcohol substrates to their corresponding aldehydes with high conversion, demonstrating a potential application of accessing traditional alcohol oxidation chemistry.Selective oxidation of alcohols is a fundamental and significant transformation for the large-scale production of fine chemicals, UV and visible light driven photocatalytic systems for alcohol oxidation have been developed, however, the long wavelength near infrared (NIR) and infrared (IR) light have not yet fully utilized by the present photocatalytic systems. Herein, we reported carbon quantum dots (CQDs) can function as an effective near infrared (NIR) light driven photocatalyst for the selective oxidation of benzyl alcohol to benzaldehyde. Based on the NIR light driven photo-induced electron transfer property and its photocatalytic activity for H2O2 decomposition, this metal-free catalyst could realize

  20. QSPIN: A High Level Java API for Quantum Computing Experimentation

    Science.gov (United States)

    Barth, Tim

    2017-01-01

    QSPIN is a high level Java language API for experimentation in QC models used in the calculation of Ising spin glass ground states and related quadratic unconstrained binary optimization (QUBO) problems. The Java API is intended to facilitate research in advanced QC algorithms such as hybrid quantum-classical solvers, automatic selection of constraint and optimization parameters, and techniques for the correction and mitigation of model and solution errors. QSPIN includes high level solver objects tailored to the D-Wave quantum annealing architecture that implement hybrid quantum-classical algorithms [Booth et al.] for solving large problems on small quantum devices, elimination of variables via roof duality, and classical computing optimization methods such as GPU accelerated simulated annealing and tabu search for comparison. A test suite of documented NP-complete applications ranging from graph coloring, covering, and partitioning to integer programming and scheduling are provided to demonstrate current capabilities.

  1. Non-Bleaching Photoluminescent Magnetic Nanoparticles

    Science.gov (United States)

    Zou, Lu; Kim, Chanjoong; Girgis, Emad; Khalil, Wagdy K. B.

    2013-03-01

    We report a new type of photoluminescent magnetic nanoparticles produced by a very simple process. The nanoparticle consists of an ordinary magnetic nanoparticle as core and a non-toxic polymer shell. The biocompatibility is evaluated using in-vivo tests on mice. They are non-bleaching photoluminescent without any addition of fluorophores, such as quantum dots or fluorescent dyes that can be toxic and easily photobleached, respectively. This work provides a low-cost, bio-safe, non-bleaching alternative of conventional fluoroscent magnetic nanoparticles which covers a wide range of applications, from bio-imaging to biomedical diagnostics and therapeutics, such as hyperthermia.

  2. Microwave formation and photoluminescence mechanisms of multi-states nitrogen doped carbon dots

    Science.gov (United States)

    He, Guili; Shu, Mengjun; Yang, Zhi; Ma, Yujie; Huang, Da; Xu, Shusheng; Wang, Yanfang; Hu, Nantao; Zhang, Yafei; Xu, Lin

    2017-11-01

    In recent years, carbon dots (CDs) have attracted much attention in the material field because of their remarkable performance in various aspects. Therefore, the exploration of complex and variable photoluminescence mechanisms shows great significance. Herein, we present a systematic study on the correlation between the formation process and photoluminescence mechanisms through the characterization and analysis of three states of nitrogen doped carbon dots (N-CDs) obtained by microwave irradiation. At low temperature of 160 °C, the small organic molecule polymer nanodots whose photoluminescence center is molecule state are obtained with superior quantum yield of about 51.61%. Increasing the reaction temperature up to 200 °C, the intermediate transition products named carbon nanodots begin to appear. Prolonging the holding time, the typical carbon quantum dots with a special stable optical properties are finally generated, and their most photoluminescence arises from the carbon cores which are gained through the polymerization, dehydration, carbonation of organic fluorescent molecules. Furthermore, N-CDs have been applied in metal ions detection as well as animal and plant cell fluorescence imaging owing to their excellent water solubility and low cytotoxicity. Our exploration provides the theoretical basis for synthesis of CDs with different properties and purposes. In the near future, more high-quality CDs will be developed in order to better benefit the various fields of mankind.

  3. The effect of stimulated interband emission on the impurity-assisted far-infrared photoluminescence in GaAs/AlGaAs quantum wells

    Science.gov (United States)

    Makhov, I. S.; Panevin, V. Yu.; Sofronov, A. N.; Firsov, D. A.; Vorobjev, L. E.; Vinnichenko, M. Ya.; Vasil'ev, A. P.; Maleev, N. A.

    2017-12-01

    Emission of far- and near-infrared radiations in the n-GaAs/AlGaAs quantum well nanostructures under interband photoexcitation of electron-hole pairs is studied at low lattice temperatures. Optical transitions of nonequilibrium electrons involving donor impurity states in quantum wells are revealed in far- and near-infrared emission spectra. Intensive optical pumping allows to observe near-infrared stimulated emission related to the radiative recombination of electrons from the ground donor state and holes from the valence subband in quantum wells. The possibility of the intensity increase of impurity-assisted far-infrared radiation due to effective depopulation of donor states with interband stimulated emission in quantum wells is demonstrated.

  4. Growth of Bi2Te3 quantum dots/rods in glass: a unique highly stable nanosystem with novel functionality for high performance magneto optical devices.

    Science.gov (United States)

    Panmand, Rajendra P; Kumar, Ganapathy; Mahajan, Satish M; Shroff, Niloufer; Kale, Bharat B; Gosavi, Suresh W

    2012-12-21

    Magneto optical materials are currently of great interest, primarily for modern applications in optical isolation, modulation and switching in telecommunication. However, single crystals are the benchmark materials still used in these devices which are rather expensive and very difficult to fabricate. In this context, we are reporting herewith a stable and novel Bi(2)Te(3) quantum dot-glass nanosystem obtained using a controlled thermo-chemical method. The Q-dots of hexagonal Bi(2)Te(3) of size 4 to 14 nm were grown along the direction. Surprisingly, we obtained quantum rods of Bi(2)Te(3) of size 6 × 10 nm for the first time. The strong quantum confinement in the nanosystem is clearly shown by the optical study. The band gap of the host glass was drastically reduced (from 4.00 to 1.88 eV) due to the growth of Bi(2)Te(3) quantum dots whereas photoluminescence showed a Stokes shift ~175 meV. Faraday Rotation (FR) investigations of the Bi(2)Te(3) quantum dot-glass nanosystem show a nonlinear response in Verdet constant with a decrease in the Bi(2)Te(3) dot sizes. The Bi(2)Te(3) Q-dot-glass nanosystem with ~4 nm dots shows significant enhancement (70 times) in Verdet constant compared to the host glass and more radically better than conventional single crystal (TGG). This is the first time that such a type of unique nanosystem has been architectured and has given extremely good magneto-optical performance. We strongly feel that this novel nanosystem has tremendous applications in magneto-optical devices. It is noteworthy that expensive single crystals can be replaced with this cost effective novel glass nanosystem. Interestingly, the present quantum dot-glass nanosystem can be transformed into optical fibers very easily, which will have an exceptionally high impact on the fabrication of high performance magneto optical devices.

  5. Near-infrared InN quantum dots on high-In composition InGaN

    Energy Technology Data Exchange (ETDEWEB)

    Soto Rodriguez, Paul E. D.; Gomez, Victor J.; Kumar, Praveen; Calleja, Enrique; Noetzel, Richard [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2013-04-01

    We report the growth of InN quantum dots (QDs) on thick InGaN layers with high In composition (>50%) by molecular beam epitaxy. Optimized growth conditions are identified for the InGaN layers at reduced growth temperature and increased active N flux resulting in minimized phase separation and defect generation. The InN QDs grown on top of the optimized InGaN layer exhibit small size, high density, and photoluminescence up to room temperature. The InN/InGaN QDs reveal excellent potential for intermediate band solar cells with the InGaN and InN QD bandgap energies tuned to the best match of absorption to the solar spectrum.

  6. High Performance PbS Quantum Dot/Graphene Hybrid Solar Cell with Efficient Charge Extraction

    Science.gov (United States)

    2016-01-01

    Hybrid colloidal quantum dot (CQD) solar cells are fabricated from multilayer stacks of lead sulfide (PbS) CQD and single layer graphene (SG). The inclusion of graphene interlayers is shown to increase power conversion efficiency by 9.18%. It is shown that the inclusion of conductive graphene enhances charge extraction in devices. Photoluminescence shows that graphene quenches emission from the quantum dot suggesting spontaneous charge transfer to graphene. CQD photodetectors exhibit increased photoresponse and improved transport properties. We propose that the CQD/SG hybrid structure is a route to make CQD thin films with improved charge extraction, therefore resulting in improved solar cell efficiency. PMID:27213219

  7. Synthesis of Pyridinic-Rich N, S Co-doped Carbon Quantum Dots as Effective Enzyme Mimics

    Science.gov (United States)

    Liu, Teng; Cui, Zhi-wei; Zhou, Jun; Wang, Ying; Zou, Zhi-gang

    2017-05-01

    N and S co-doped carbon quantum dots (N, S-CQDs) with high N- and S-doping level were synthesized by microwave solid-phase pyrolysis within 50 s. Owing to the dominant pyridinic N injection into the conjugated framework, both high enzyme mimics catalytic activity and photoluminescence quantum yield are achieved simultaneously.

  8. Formation mechanism of highly luminescent silica capsules incorporating multiple hydrophobic quantum dots with various emission wavelengths.

    Science.gov (United States)

    Li, Chunliang; Murase, Norio

    2013-12-01

    A synthesis process was reconsidered for encapsulating hydrophobic quantum dots (QDs) into silica capsules with high photoluminescent (PL) efficiency. The process comprises three steps: silanization of QD surfaces, seed formation by assembly of the QDs, and coating of the QD seeds with a silica shell. Analysis of the encapsulation mechanism enabled this process to be adapted for application to CdSe-based core-shell QDs with various organic ligands such as oleic acid and with various emission wavelengths. Formation of the seeds is the key step in synthesizing the silica capsules, so that they have high PL efficiency. Due to the differences in QD size and in the affinity of the ligands on their surfaces, the concentration of QDs used in the synthesis must be optimized to maximize emission efficiency. Contrary to an initial assumption, several ligands remained on the QD surfaces even after the QDs were transferred from organic solution to water. This greatly affected the size and PL efficiency of the seeds. Judicious selection of the conditions for seed and silica capsule synthesis resulted in seeds with PL efficiency greater than 70% and in silica capsules encapsulating multiple CdSe/CdZnS QDs with PL efficiency as high as 41%. Silica capsules incorporating QDs with various emission peak wavelengths from green to red were also prepared. The process presented serves as a guideline for encapsulating various types of hydrophobic QDs into silica capsules for biological tagging applications. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. High Crystallinity CuScO2 Delafossite Films Exhibiting Ultraviolet Photoluminescence Grown by Vapor-Liquid-Solid Tri-phase Epitaxy

    Science.gov (United States)

    Matsubara, Yuya; Makino, Takayuki; Hiraga, Hiroki; Chen, Chunlin; Tsukimoto, Susumu; Ueno, Kazunori; Kozuka, Yusuke; Ikuhara, Yuichi; Kawasaki, Masashi

    2012-01-01

    We have grown direct wide-bandgap CuScO2 thin films on MgAl2O4(111) substrates by tri-phase epitaxy employing molten Bi-O flux on the growth surface. The full width at half maximum of (0006) rocking curve is as narrow as 0.005 degrees, an order of magnitude narrower than those grown by conventional pulsed laser deposition (PLD). Transmission electron microscopy confirms the scarcity of defect structures or precipitates, which are of high density in PLD films. The films exhibit sharp near-bandedge photoluminescence at 3.3 eV, which is absent in PLD films.

  10. Aqueous synthesis of highly luminescent AgInS2-ZnS quantum dots and their biological applications

    Science.gov (United States)

    Regulacio, Michelle D.; Win, Khin Yin; Lo, Seong Loong; Zhang, Shuang-Yuan; Zhang, Xinhai; Wang, Shu; Han, Ming-Yong; Zheng, Yuangang

    2013-02-01

    Highly emissive and air-stable AgInS2-ZnS quantum dots (ZAIS QDs) with quantum yields of up to 20% have been successfully synthesized directly in aqueous media in the presence of polyacrylic acid (PAA) and mercaptoacetic acid (MAA) as stabilizing and reactivity-controlling agents. The as-prepared water-dispersible ZAIS QDs are around 3 nm in size, possess the tetragonal chalcopyrite crystal structure, and exhibit long fluorescence lifetimes (>100 ns). In addition, these ZAIS QDs are found to exhibit excellent optical and colloidal stability in physiologically relevant pH values as well as very low cytotoxicity, which render them particularly suitable for biological applications. Their potential use in biological labelling of baculoviral vectors is demonstrated.Highly emissive and air-stable AgInS2-ZnS quantum dots (ZAIS QDs) with quantum yields of up to 20% have been successfully synthesized directly in aqueous media in the presence of polyacrylic acid (PAA) and mercaptoacetic acid (MAA) as stabilizing and reactivity-controlling agents. The as-prepared water-dispersible ZAIS QDs are around 3 nm in size, possess the tetragonal chalcopyrite crystal structure, and exhibit long fluorescence lifetimes (>100 ns). In addition, these ZAIS QDs are found to exhibit excellent optical and colloidal stability in physiologically relevant pH values as well as very low cytotoxicity, which render them particularly suitable for biological applications. Their potential use in biological labelling of baculoviral vectors is demonstrated. Electronic supplementary information (ESI) available: Quantum yields, EDX spectrum and photoluminescence decay curves. See DOI: 10.1039/c3nr34159c

  11. Photoluminescent reduced graphene oxide quantum dots from latex of Calotropis gigantea for metal sensing, radical scavenging, cytotoxicity, and bioimaging in Artemia salina: A greener route.

    Science.gov (United States)

    Murugesan, Balaji; Sonamuthu, Jegatheeswaran; Pandiyan, Nithya; Pandi, Boomi; Samayanan, Selvam; Mahalingam, Sundrarajan

    2018-01-01

    In this work, we report the fabrication of green fluorescent reduced graphene oxide quantum dots (rGOQDs) from the latex of Calotropis gigantea by simple one-step microwave assisted greener route. The latex of Calotropis gigantea calcined at 300°C and its ethanolic extract is used for the synthesis of QDs, The rGOQDs showed particle size ranging from 2 to 8nm and it exhibited green fluorescent in longer UV region at 360-520nm. The rGOQDs graphitic nature was confirmed by RAMAN and XRD analysis. The FTIR, XPS demonstrate that presence of functional groups such as CO, COC, -OH, hence it's addressing them as rGOQDs. It is used to design the greener and economically adopted fluorescent probe for the detection of Pb2+ ions. It provides simple and appropriate for the selective and sensitive detection of Pb2+ ions in water purification process. It also trapped the free radicals and neutralized that and act as an excellent radical scavenger in DPPH radical scavenging assessment. These rGOQDs showed excellent biocompatibility on brine shrimp nauplii (Artemia salina) up to 160μg/mL for 24h incubation. Furthermore, rGOQDS were demonstrated as fluorescent bioimaging probe selectively in the inner digestion part of Artemia salina. In summary, stable, economically viable, highly biocompatible, greener method based rGOQDs were prepared for heavy metal ion detecting, radical scavenging, bioimaging applications which can play a vital role in the future nanotechnology-based biomedical field. Copyright © 2017. Published by Elsevier B.V.

  12. Nanobio applications of quantum dots in cancer: imaging, sensing, and targeting.

    Science.gov (United States)

    SalmanOgli, Ahmad

    In this article, the syntheses and optical properties of core/shell quantum dot (CdSe/ZnS) and their applications are reviewed. Nevertheless, the main focus is to provide an overview on biological applications of quantum dots that contain imaging, targeting, and sensing. We discuss the different synthetic methods, optical properties (photoluminescence intensity, absorption, and fluorescence spectra), and their dependence on shape, size, and inner structure of quantum dots. Also, the different mechanisms of quantum dots bio-targeting (passive and active mechanisms) are discussed. The impact of quantum dots in bioimaging is reviewed regarding its photoluminescence intensity, absorption and emission spectrum, and photo-stability on high-quality and sensitivity imaging. Further, the difference between near infrared and visible emission quantum dots in deep tissue imaging will be reviewed and some of done works are considered and compared with each other. And finally, the biosensing potential/application of quantum dots in medical diagnosis is going to be highlighted.

  13. Quantum dot amplifiers with high output power and low noise

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Mørk, Jesper

    2003-01-01

    Quantum dot semiconductor optical amplifiers have been theoretically investigated and are predicted to achieve high saturated output power, large gain, and low noise figure. We discuss the device dynamics and, in particular, show that the presence of highly inverted barrier states does not limit...

  14. Quantum emitters coupled to circular nanoantennas for high-brightness quantum light sources

    Science.gov (United States)

    Abudayyeh, Hamza A.; Rapaport, Ronen

    2017-09-01

    Engineering the directionality and emission rate of quantum light sources is essential in the development of modern quantum applications. In this work we use numerical calculations to optimise the brightness of a broadband quantum emitter positioned in a hybrid metal-dielectric circular periodic nanoantenna. The optimised structure features a photon collection efficiency of 74 % (82 % ) and a photon flux enhancement of over 10 (6) into a numerical aperture of 0.22 (0.50), respectively, corresponding to a direct coupling into two types of multi-mode fibres. To enhance the emission rate, we present a new circular nanoantenna design where a quantum emitter is attached to a silver nanocone at the centre of the antenna. After optimisation, we find a collection efficiency of 61 % (78 % ) into a numerical aperture of 0.22 (0.50), giving a brightness enhancement of 1000 (600) for an unpolarised emitter. The enhancements in both structures are broadband due to the low-quality factor of the device and are therefore ideal for room-temperature sources. This type of a scalable design can be utilised towards on-chip, high-brightness quantum light sources operating at room temperature.

  15. Photoluminescent-dielectric duple switch in a perovskite-type high-temperature phase transition compound: [(CH3)3PCH2OCH3][PbBr3].

    Science.gov (United States)

    Geng, Fu-Juan; Wu, De-Hong; Zhou, Lin; Shi, Ping-Ping; Li, Peng-Fei; Gao, Ji-Xing; Zheng, Xuan; Fu, Da-Wei; Ye, Qiong

    2017-07-25

    A bistable optical-electrical duple switch belongs to a class of highly satisfying intelligent materials that can transform optical and electrical responses simultaneously in one device. A perovskite-type high-temperature phase transition compound with one-dimensional chain-like crystal structure, ([(CH3)3PCH2OCH3][PbBr3], 1), displays remarkable bistable photoluminescent-dielectric duple switching behaviors. The noteworthy order-disorder transition of the phosphonium cation and the motions of anions contribute to the phase transition, leading to the space group P21/c at a low temperature phase to C2/c at a high temperature phase. 1 exhibits a prominent step-like dielectric anomaly at 401.0 K and demonstrates novel optical properties with a band gap of 3.54 eV. The photoluminescence intensity suddenly declines from 398 K to 408 K, which may be attributed to the occurrence of phase transition. The electron cloud distributions of the frontier orbital in compound 1 have been calculated using a DFT program.

  16. Droplet epitaxial growth of highly symmetric quantum dots emitting at telecommunication wavelengths on InP(111)A

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Neul; Kuroda, Takashi [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Graduate School of Engineering, Kyushu University, NIMS, Tsukuba 305-0044 (Japan); Liu, Xiangming; Mano, Takaaki, E-mail: mano.takaaki@nims.go.jp; Mitsuishi, Kazutaka; Noda, Takeshi; Sakuma, Yoshiki; Sakoda, Kazuaki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Castellano, Andrea [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Dip. di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 55, I-20125 Milano (Italy); Sanguinetti, Stefano [Dip. di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 55, I-20125 Milano (Italy)

    2014-04-07

    We demonstrate the formation of InAs quantum dots (QDs) on InAlAs/InP(111)A by means of droplet epitaxy. The C{sub 3v} symmetry of the (111)A substrate enabled us to realize highly symmetric QDs that are free from lateral elongations. The QDs exhibit a disk-like truncated shape with an atomically flat top surface. Photoluminescence signals show broad-band spectra at telecommunication wavelengths of 1.3 and 1.5 μm. Strong luminescence signals are retained up to room temperature. Thus, our QDs are potentially useful for realizing an entangled photon-pair source that is compatible with current telecommunication fiber networks.

  17. High-NOON states by mixing quantum and classical light.

    Science.gov (United States)

    Afek, Itai; Ambar, Oron; Silberberg, Yaron

    2010-05-14

    Precision measurements can be brought to their ultimate limit by harnessing the principles of quantum mechanics. In optics, multiphoton entangled states, known as NOON states, can be used to obtain high-precision phase measurements, becoming more and more advantageous as the number of photons grows. We generated "high-NOON" states (N = 5) by multiphoton interference of quantum down-converted light with a classical coherent state in an approach that is inherently scalable. Super-resolving phase measurements with up to five entangled photons were produced with a visibility higher than that obtainable using classical light only.

  18. Photoluminescence study of high energy proton irradiation on Cu(In,Ga)Se{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Bonhyeong [Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, June Hyuk [Neutron Science Division, Korea Atomic Energy Research Institute (KAERI), 989-111 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Shin, Donghyeop [Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708 (United States); Ahn, Byung Tae, E-mail: btahn@kaist.ac.kr [Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Shin, Byungha, E-mail: byungha@kaist.ac.kr [Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2016-03-31

    We have studied the effect of proton irradiation on Cu(In,Ga)Se{sub 2} (CIGS) thin films using photoluminescence (PL). We used a 10 MeV proton beam with varying doses from 10{sup 9} to 10{sup 12} cm{sup −2}. Intensity-dependent low temperature PL measurements suggest that the proton irradiation does not create a new defect level but instead changes the number of preexisting defects in the detection range of the PL system. By comparing PL spectra after the proton irradiation with those obtained after thermal annealing under inert gas as well as under hydrogen gas ambient, we find that the irradiation-induced change in the defect structure does not originate from the incorporation of hydrogen but from energetics of the irradiating particles. Electrical resistivity of the proton irradiated CIGS thin films is shown to decrease after the proton irradiation, and this is explained by the reduction of the concentration of compensating donor-like defects, specifically selenium vacancies, based on the PL results. - Highlights: • Photoluminescence study of 10 MeV proton irradiation on CIGS at 10 K. • Irradiation modified population of existing defects without introducing new levels. • Changes in CIGS by 10 MeV irradiation are due to energetics of irradiating protons.

  19. High excitation photoluminescence effects as a probing tool for the growth of Cu(In,Ga)Se2

    Science.gov (United States)

    Moret, Matthieu; Briot, Olivier; Gil, Bernard; Lepetit, Thomas; Arzel, Ludovic; Barreau, Nicolas

    2015-03-01

    Copper Indium Gallium deSelenide (Cu(In,Ga)Se2, CIGS) is a promising material for cost-efficient solar cells. Efficiencies above 20% have already been demonstrated in laboratory, and large area CIGS solar panels are already on the market. However, it is still an interesting issue to find efficient characterization techniques that can be used to validate the quality of the different layers at any step of the process, without having to process a complete cell and measure its electrical properties. In this work, we have deposited CIGS onto Mo coated soda lime glass by co-evaporation, using the so-called three step deposition process. Then, photoluminescence (PL) measurements were made on the samples, in the range of 10K to the room temperature, and the excitation intensity was varied in a very large range, in order to reach non-linear regime. We report the first observation of stimulated emission in mechanisms are discussed. The threshold at which sample photoluminescence changes from spontaneous to stimulated is well known to be sensitive to overall sample quality, and we propose to use this measurement as a probing tool for sample quality. This opens an interesting perspective for characterization of CIGS during solar cell processing.

  20. Facile Synthesis of pH-sensitive Germanium Nanocrystals with High Quantum Yield for Intracellular Acidic Compartment Imaging.

    Science.gov (United States)

    Li, Feng; Wang, Jing; Sun, Shuqing; Wang, Hai; Tang, Zhiyong; Nie, Guangjun

    2015-04-24

    A green-light emitting germanium nanocrystal-based biosensor to monitor lysosomal pH changes is developed. The Ge nanocrystals are synthesized in an aqueous solution with a significantly enhanced photoluminescence quantum yield of 26%. This synthesis involves a facile solution based route which avoided the use of toxic or environmentally unfriendly agents. Importantly, the photoluminescence intensity of the synthesized Ge nanocrystals is particularly sensitive to changes in pH between 5 and 6. When incubated with cultured cells, the nanocrystals are internalized and subsequently translocated via the lysosomal pathway, and the Ge nanocrystals' fluorescence are greatly enhanced, even when the lysosomal pH is only slightly increased. These results reveal that the Ge nanocrystals possess high pH sensitivity compared to a commercially available dye, LysoSensor Green DND-189. The fluorescent properties of the Ge nanocrystals are demonstrated to be dependent on both the crystal form and their surface chemistry. The superior fluorescence properties and bioapplicability of the Ge nanocrystals makes them a promising intracellular bioimaging probe for monitoring various pH-sensitive processes in cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Blue photoluminescent carbon nanodots from limeade.

    Science.gov (United States)

    Suvarnaphaet, Phitsini; Tiwary, Chandra Sekhar; Wetcharungsri, Jutaphet; Porntheeraphat, Supanit; Hoonsawat, Rassmidara; Ajayan, Pulickel Madhavapanicker; Tang, I-Ming; Asanithi, Piyapong

    2016-12-01

    Carbon-based photoluminescent nanodot has currently been one of the promising materials for various applications. The remaining challenges are the carbon sources and the simple synthetic processes that enhance the quantum yield, photostability and biocompatibility of the nanodots. In this work, the synthesis of blue photoluminescent carbon nanodots from limeade via a single-step hydrothermal carbonization process is presented. Lime carbon nanodot (L-CnD), whose the quantum yield exceeding 50% for the 490nm emission in gram-scale amounts, has the structure of graphene core functionalized with the oxygen functional groups. The micron-sized flake of the as-prepared L-CnD powder exhibits multicolor emission depending on an excitation wavelength. The L-CnDs are demonstrated for rapidly ferric-ion (Fe(3+)) detection in water compared to Fe(2+), Cu(2+), Co(2+), Zn(2+), Mn(2+) and Ni(2+) ions. The photoluminescence quenching of L-CnD solution under UV light is used to distinguish the Fe(3+) ions from others by naked eyes as low concentration as 100μM. Additionally, L-CnDs provide exceptional photostability and biocompatibility for imaging yeast cell morphology. Changes in morphology of living yeast cells, i.e. cell shape variation, and budding, can be observed in a minute-period until more than an hour without the photoluminescent intensity loss. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties.

    Science.gov (United States)

    Stoumpos, Constantinos C; Malliakas, Christos D; Kanatzidis, Mercouri G

    2013-08-05

    A broad organic-inorganic series of hybrid metal iodide perovskites with the general formulation AMI3, where A is the methylammonium (CH3NH3(+)) or formamidinium (HC(NH2)2(+)) cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of 1-4 classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100-400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that 1-4 behave as direct-gap semiconductors with energy band gaps distributed in the range of 1.25-1.75 eV. The compounds exhibit an intense near-IR photoluminescence (PL) emission in the 700-1000 nm range (1.1-1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH3NH3Sn(1-x)Pb(x)I3 (5). The charge transport type in these materials was characterized by Seebeck coefficient and Hall-effect measurements. The compounds behave as p- or n-type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are n-type; p

  3. Chemical sensitivity of InP/In0.48Ga0.52P surface quantum dots studied by time-resolved photoluminescence spectroscopy

    NARCIS (Netherlands)

    De Angelis, R.; Casalboni, M.; De Matteis, F.; Hatami, F.; Masselink, W.T.; Zhang, H.; Prosposito, P.

    2015-01-01

    InP/InGaP surface quantum dots represent an attractive material for optical chemical sensors since they show a remarkable near infra-red emission at room temperature, whose intensity increases rapidly and reversibly depending on the composition of the environmental atmosphere. We show here their

  4. New development in carbon quantum dots technical applications.

    Science.gov (United States)

    Shen, Li-Ming; Liu, Jing

    2016-08-15

    As a newly emerged member in carbon nanomaterials family, carbon quantum dots (CQDs) attracted everincreasing attention owing to their ultracompact size, excellent photoluminescence, favorable biocompatibility, versatile surface and superior electron transfer ability. The past decade has witnessed continuous advancements in the production of CQDs with high photoluminescence quantum yields for various applications. Herein, we track the newest development of CQDs with advanced physicochemical properties and their applications in sensing, bioimaging, nanomedicine and catalysis, and propose the challenges and perspectives in this exciting and promising field. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Progress in high-performance quantum cascade lasers

    Science.gov (United States)

    Lyakh, Arkadiy; Maulini, Richard; Tsekoun, Alexei G.; Patel, C. Kumar N.

    2010-11-01

    Because of their compact size, reliability, tunability, and convenience of direct electrical pumping, quantum cascade lasers have found a number of important civilian and defense applications in the midwave infrared and long-wave-infrared spectral range. Most of these applications would benefit from higher laser optical power and higher wall-plug efficiency. We describe some of the most important features of high-efficiency quantum cascade laser design and realization of high-power quantum cascade laser systems. Specifically, optimization of the active region and waveguide, thermal management on the chip level, and impact of the laser facet coating on laser efficiency and scaling of optical power with cavity length are discussed. Also, we present experimental results demonstrating multiwatt operation with reliability of at least several thousands of hours on a system level.

  6. Full quantum trajectories resolved high-order harmonic generation.

    Science.gov (United States)

    Ye, Peng; He, Xinkui; Teng, Hao; Zhan, Minjie; Zhong, Shiyang; Zhang, Wei; Wang, Lifeng; Wei, Zhiyi

    2014-08-15

    We use a carrier-envelope-phase stabilized sub-2-cycle laser pulse to generate high-order harmonics and study how the two-dimensional spectrum of harmonics, with the resolutions in temporal frequency and spatial frequency, is shaped by the laser phase. An arrowlike spectrum obtained experimentally when the gas cell is located in front of the laser focus point shows a resolution of full quantum trajectories; i.e., harmonics from different trajectories stand on different positions in this spectrum. In particular, due to the laser phase combined with the classical-like action, the harmonics from short and long trajectories differ maximally in their curvatures of wave fronts in the generation area, and so occupy very different ranges of spatial frequency at the far field. The result directly gives a full map of quantum trajectories in high-order harmonic generation. The conclusion is supported by an analytical model and quantum mechanics simulations.

  7. High-capacity quantum Fibonacci coding for key distribution

    Science.gov (United States)

    Simon, David S.; Lawrence, Nate; Trevino, Jacob; Dal Negro, Luca; Sergienko, Alexander V.

    2013-03-01

    Quantum cryptography and quantum key distribution (QKD) have been the most successful applications of quantum information processing, highlighting the unique capability of quantum mechanics, through the no-cloning theorem, to securely share encryption keys between two parties. Here, we present an approach to high-capacity, high-efficiency QKD by exploiting cross-disciplinary ideas from quantum information theory and the theory of light scattering of aperiodic photonic media. We propose a unique type of entangled-photon source, as well as a physical mechanism for efficiently sharing keys. The key-sharing protocol combines entanglement with the mathematical properties of a recursive sequence to allow a realization of the physical conditions necessary for implementation of the no-cloning principle for QKD, while the source produces entangled photons whose orbital angular momenta (OAM) are in a superposition of Fibonacci numbers. The source is used to implement a particular physical realization of the protocol by randomly encoding the Fibonacci sequence onto entangled OAM states, allowing secure generation of long keys from few photons. Unlike in polarization-based protocols, reference frame alignment is unnecessary, while the required experimental setup is simpler than other OAM-based protocols capable of achieving the same capacity and its complexity grows less rapidly with increasing range of OAM used.

  8. Large-scale synthesis of high quality InP quantum dots in a continuous flow-reactor under supercritical conditions.

    Science.gov (United States)

    Ippen, Christian; Schneider, Benjamin; Pries, Christopher; Kröpke, Stefan; Greco, Tonino; Holländer, Andreas

    2015-02-27

    The synthesis of indium phosphide quantum dots (QDs) in toluene under supercritical conditions was carried out in a macroscopic continuous flow reaction system. The results of first experiments are reported in comparison with analogous reactions in octadecene. The reaction system is described and details are provided about special procedures that are enabled by the continuous flow system for the screening of reaction conditions. The produced QDs show very narrow emission peaks with full width at half maximum down to 45 nm and reasonable photoluminescence quantum yields. The subsequent purification process is facilitated by the ease of removal of toluene, and the productivity of the system is increased by high temperature and high pressure conditions.

  9. Development of aliphatic biodegradable photoluminescent polymers.

    Science.gov (United States)

    Yang, Jian; Zhang, Yi; Gautam, Santosh; Liu, Li; Dey, Jagannath; Chen, Wei; Mason, Ralph P; Serrano, Carlos A; Schug, Kevin A; Tang, Liping

    2009-06-23

    None of the current biodegradable polymers can function as both implant materials and fluorescent imaging probes. The objective of this study was to develop aliphatic biodegradable photoluminescent polymers (BPLPs) and their associated cross-linked variants (CBPLPs) for biomedical applications. BPLPs are degradable oligomers synthesized from biocompatible monomers including citric acid, aliphatic diols, and various amino acids via a convenient and cost-effective polycondensation reaction. BPLPs can be further cross-linked into elastomeric cross-linked polymers, CBPLPs. We have shown representatively that BPLP-cysteine (BPLP-Cys) and BPLP-serine (BPLP-Ser) offer advantages over the traditional fluorescent organic dyes and quantum dots because of their preliminarily demonstrated cytocompatibility in vitro, minimal chronic inflammatory responses in vivo, controlled degradability and high quantum yields (up to 62.33%), tunable fluorescence emission (up to 725 nm), and photostability. The tensile strength of CBPLP-Cys film ranged from 3.25 +/- 0.13 MPa to 6.5 +/- 0.8 MPa and the initial Modulus was in a range of 3.34 +/- 0.15 MPa to 7.02 +/- 1.40 MPa. Elastic CBPLP-Cys could be elongated up to 240 +/- 36%. The compressive modulus of BPLP-Cys (0.6) (1:1:0.6 OD:CA:Cys) porous scaffold was 39.60 +/- 5.90 KPa confirming the soft nature of the scaffolds. BPLPs also possess great processability for micro/nano-fabrication. We demonstrate the feasibility of using BPLP-Ser nanoparticles ("biodegradable quantum dots") for in vitro cellular labeling and noninvasive in vivo imaging of tissue engineering scaffolds. The development of BPLPs and CBPLPs represents a new direction in developing fluorescent biomaterials and could impact tissue engineering, drug delivery, bioimaging.

  10. Development of aliphatic biodegradable photoluminescent polymers

    Science.gov (United States)

    Yang, Jian; Zhang, Yi; Gautam, Santosh; Liu, Li; Dey, Jagannath; Chen, Wei; Mason, Ralph P.; Serrano, Carlos A.; Schug, Kevin A.; Tang, Liping

    2009-01-01

    None of the current biodegradable polymers can function as both implant materials and fluorescent imaging probes. The objective of this study was to develop aliphatic biodegradable photoluminescent polymers (BPLPs) and their associated cross-linked variants (CBPLPs) for biomedical applications. BPLPs are degradable oligomers synthesized from biocompatible monomers including citric acid, aliphatic diols, and various amino acids via a convenient and cost-effective polycondensation reaction. BPLPs can be further cross-linked into elastomeric cross-linked polymers, CBPLPs. We have shown representatively that BPLP-cysteine (BPLP-Cys) and BPLP-serine (BPLP-Ser) offer advantages over the traditional fluorescent organic dyes and quantum dots because of their preliminarily demonstrated cytocompatibility in vitro, minimal chronic inflammatory responses in vivo, controlled degradability and high quantum yields (up to 62.33%), tunable fluorescence emission (up to 725 nm), and photostability. The tensile strength of CBPLP-Cys film ranged from 3.25 ± 0.13 MPa to 6.5 ± 0.8 MPa and the initial Modulus was in a range of 3.34 ± 0.15 MPa to 7.02 ± 1.40 MPa. Elastic CBPLP-Cys could be elongated up to 240 ± 36%. The compressive modulus of BPLP-Cys (0.6) (1:1:0.6 OD:CA:Cys) porous scaffold was 39.60 ± 5.90 KPa confirming the soft nature of the scaffolds. BPLPs also possess great processability for micro/nano-fabrication. We demonstrate the feasibility of using BPLP-Ser nanoparticles (“biodegradable quantum dots”) for in vitro cellular labeling and noninvasive in vivo imaging of tissue engineering scaffolds. The development of BPLPs and CBPLPs represents a new direction in developing fluorescent biomaterials and could impact tissue engineering, drug delivery, bioimaging. PMID:19506254

  11. High-dimensional quantum channel estimation using classical light

    CSIR Research Space (South Africa)

    Mabena, Chemist M

    2017-11-01

    Full Text Available A method is proposed to characterize a high-dimensional quantum channel with the aid of classical light. It uses a single nonseparable input optical field that contains correlations between spatial modes and wavelength to determine the effect...

  12. Rapid single flux quantum logic in high temperature superconductor technology

    NARCIS (Netherlands)

    Shunmugavel, K.

    2006-01-01

    A Josephson junction is the basic element of rapid single flux quantum logic (RSFQ) circuits. A high operating speed and low power consumption are the main advantages of RSFQ logic over semiconductor electronic circuits. To realize complex RSFQ circuits in HTS technology one needs a reproducible

  13. High-Efficiency Perovskite Quantum-Dot Light-Emitting Devices by Effective Washing Process and Interfacial Energy Level Alignment.

    Science.gov (United States)

    Chiba, Takayuki; Hoshi, Keigo; Pu, Yong-Jin; Takeda, Yuya; Hayashi, Yukihiro; Ohisa, Satoru; Kawata, So; Kido, Junji

    2017-05-31

    All inorganic perovskites quantum dots (PeQDs) have attracted much attention for used in thin film display applications and solid-state lighting applications, owing to their narrow band emission with high photoluminescence quantum yields (PLQYs), color tunability, and solution processability. Here, we fabricated low-driving-voltage and high-efficiency CsPbBr3 PeQDs light-emitting devices (PeQD-LEDs) using a PeQDs washing process with an ester solvent containing butyl acetate (AcOBu) to remove excess ligands from the PeQDs. The CsPbBr3 PeQDs film washed with AcOBu exhibited a PLQY of 42%, and a narrow PL emission with a full width at half-maximum of 19 nm. We also demonstrated energy level alignment of the PeQD-LED in order to achieve effective hole injection into PeQDs from the adjacent hole injection layer. The PeQD-LED with AcOBu-washed PeQDs exhibited a maximum power efficiency of 31.7 lm W-1 and EQE of 8.73%. Control of the interfacial PeQDs through ligand removal and energy level alignment in the device structure are promising methods for obtaining high PLQYs in film state and high device efficiency.

  14. Towards a new family of photoluminescent organozinc 8-hydroxyquinolinates with a high propensity to form noncovalent porous materials.

    Science.gov (United States)

    Sokołowski, Kamil; Justyniak, Iwona; Sliwiński, Witold; Sołtys, Katarzyna; Tulewicz, Adam; Kornowicz, Arkadiusz; Moszyński, Robert; Lipkowski, Janusz; Lewiński, Janusz

    2012-04-27

    We report on investigations of reactions of tBu(2)Zn with 8-hydroxyquinoline (q-H) and the influence of water on the composition and structure of the final product. A new synthetic approach to photoluminescent zinc complexes with quinolinate ligands was developed that allowed the isolation of a series of structurally diverse and novel alkylzinc 8-hydroxyquinolate complexes: the trinuclear alkylzinc aggregate [tBuZn(q)](3) (1(3)), the pentanuclear oxo cluster [(tBu)(3)Zn(5)(μ(4) -O)(q)(5)] (2), and the tetranuclear hydroxo cluster [Zn(q)(2)](2)[tBuZn(OH)](2) (3). All compounds were characterized in solution by (1)H NMR, IR, UV/Vis, and photoluminescence (PL) spectroscopy, and in the solid state by X-ray diffraction, TGA, and PL studies. Density functional theory calculations were also carried out for these new Zn(II) complexes to rationalize their luminescence behavior. A detailed analysis of the supramolecular structures of 2 and 3 shows that the unique shape of the corresponding single molecules leads to the formation of extended 3D networks with 1D open channels. Varying the stoichiometry, shape, and supramolecular structure of the resulting complexes leads to changes in their spectroscopic properties. The close-packed crystal structure of 1(3) shows a redshifted emission maximum in comparison to the porous crystal structure of 2 and the THF-solvated structure of 3. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. High-Rate Strong-Signal Quantum Cryptography

    Science.gov (United States)

    Yuen, Horace P.

    1996-01-01

    Several quantum cryptosystems utilizing different kinds of nonclassical lights, which can accommodate high intensity fields and high data rate, are described. However, they are all sensitive to loss and both the high rate and the strong-signal character rapidly disappear. A squeezed light homodyne detection scheme is proposed which, with present-day technology, leads to more than two orders of magnitude data rate improvement over other current experimental systems for moderate loss.

  16. A Lattice-Trapped and Cavity-Enhanced High-Quality Quantum Memory

    Science.gov (United States)

    Yang, Sheng-Jun; Wang, Xu-Jie; Bao, Xiao-Hui; Pan, Jian-Wei

    2015-05-01

    Quantum memory plays an increasing essential part in many applications of quantum information science. Currently, the intense research and crucial challenge is that integration of a full functional quantum memory with various high-performance properties in a single system. Storage lifetime and retrieval efficiency are the two most important qualities of quantum memory, especially indispensable for quantum repeater and long-distance quantum communication. Here based on techniques of magic optical lattice trap and ring cavity enhancement, we experimentally achieved a high-quality cold atom quantum memory. The initial intrinsic retrieval efficiency is up to 77(5)%, with an e-1-storage lifetime about 0.25 sec for the first time. Such high effective and long-lived quantum memory should be significantly important for quantum communication and cryptography, and would truly stimulate a first practical demonstration of long distance quantum repeaters in the near future.

  17. Nontrivial transition of transmission in a highly open quantum point contact in the quantum Hall regime

    Science.gov (United States)

    Hong, Changki; Park, Jinhong; Chung, Yunchul; Choi, Hyungkook; Umansky, Vladimir

    2017-11-01

    Transmission through a quantum point contact (QPC) in the quantum Hall regime usually exhibits multiple resonances as a function of gate voltage and high nonlinearity in bias. Such behavior is unpredictable and changes sample by sample. Here, we report the observation of a sharp transition of the transmission through an open QPC at finite bias, which was observed consistently for all the tested QPCs. It is found that the bias dependence of the transition can be fitted to the Fermi-Dirac distribution function through universal scaling. The fitted temperature matches quite nicely to the electron temperature measured via shot-noise thermometry. While the origin of the transition is unclear, we propose a phenomenological model based on our experimental results that may help to understand such a sharp transition. Similar transitions are observed in the fractional quantum Hall regime, and it is found that the temperature of the system can be measured by rescaling the quasiparticle energy with the effective charge (e*=e /3 ). We believe that the observed phenomena can be exploited as a tool for measuring the electron temperature of the system and for studying the quasiparticle charges of the fractional quantum Hall states.

  18. High-Sensitivity Charge Detection with a Single-Lead Quantum Dot for Scalable Quantum Computation

    Science.gov (United States)

    House, Matthew; Bartlett, Ian; Pakkiam, Prasanna; Koch, Matthias; Peretz, Eldad; van der Heijden, Joost; Kobayashi, Takashi; Rogge, Sven; Simmons, Michelle

    We report the development of a high sensitivity semiconductor charge sensor based on a quantum dot coupled to a single lead, designed to minimize the geometric requirements of a charge sensor for scalable quantum computing architectures. The quantum dot is fabricated in Si:P using atomic precision lithography and its charge transitions are measured with rf reflectometry. A second quantum dot with two leads placed 42 nm away serves as both a charge for the sensor to measure and as a conventional rf single electron transistor (rf-SET) with which to make a comparison of the charge detection sensitivity. We demonstrate sensitivity equivalent to an integration time of 550 ns to detect a single charge with a signal-to-noise ratio of 1, compared with an integration time of 55 ns for the rf-SET. This level of sensitivity is suitable for fast (Communication Technology (Project No. CE110001027) and the U.S. Army Research Office under Contract No. W911NF-13-1-0024.

  19. Photoluminescent and biodegradable polycitrate-polyethylene glycol-polyethyleneimine polymers as highly biocompatible and efficient vectors for bioimaging-guided siRNA and miRNA delivery.

    Science.gov (United States)

    Wang, Min; Guo, Yi; Yu, Meng; Ma, Peter X; Mao, Cong; Lei, Bo

    2017-05-01

    Development of biodegradable and biocompatible non-viral vectors with intrinsical multifunctional properties such as bioimaging ability for highly efficient nucleic acids delivery still remains a challenge. Here, a biodegradable poly (1,8-octanedio-citric acid)-co-polyethylene glycol grafted with polyethyleneimine (PEI) (POCG-PEI) polymers with the photoluminescent capacity were synthesized for nucleic acids delivery (siRNA and miRNA). POCG-PEI polymers can efficiently bind various nucleic acids, protect them against enzymatic degradation and release the genes in the presence of polyanionic heparin. POCG-PEI also showed a significantly low cytotoxicity, enhanced cellular uptake and high transfection efficiency of nucleic acids, as compared to commercial transfection agents, lipofectamine 2000 (Lipo) and polyethylenimine (PEI 25K). POCG-PEI polymers demonstrate an excellent photostability, which allows for imaging the cells and real-time tracking the nucleic acids delivery. The photoluminescent property, low cytotoxicity, biodegradation, good gene binding and protection ability and high genes delivery efficiency make POCG-PEI highly competitive as a non-virus vector for genes delivery and real-time bioimaging applications. Our results may be also an important step for designing biodegradable biomaterials with multifunctional properties towards bioimaging-guided genes therapeutic applications. Here, a biodegradable poly (1,8-octanedio-citric acid)-co-polyethylene glycol grafted with polyethyleneimine (PEI) (POCG-PEI) polymers with controlled photoluminescent capacity were synthesized for nucleic acids delivery (siRNA and miRNA). POCG-PEI polymers can efficiently bind various nucleic acids, protect them against enzymatic degradation and release the genes in the presence of polyanionic heparin. POCG-PEI also showed a significantly low cytotoxicity, enhanced cellular uptake and high transfection efficiency of nucleic acids, as compared to commercial transfection agents

  20. Electro-optic properties of GaInAsSb/GaAs quantum well for high-speed integrated optoelectronic devices

    Science.gov (United States)

    Thoma, Jiri; Liang, Baolai; Reyner, Charles; Ochalski, Tomasz; Williams, David; Hegarty, Stephen P.; Huffaker, Diana; Huyet, Guillaume

    2013-01-01

    The electro-optic properties of strained GaInAsSb/GaAs quantum wells (QWs) are investigated. A single QW p-i-n sample was grown by molecular beam epitaxy with antimony (Sb) pre-deposition technique. We numerically predict and experimentally verify a strong quantum confined Stark shift of 40 nm. We also predict a fast absorption recovery times crucial of high-speed optoelectronic devices mainly due to strong electron tunneling and thermionic emission. Predicted recovery times are corroborated by bias and temperature dependent time-resolved photoluminescence measurements indicating (≤30 ps) recovery times. This makes GaInAsSb QW an attractive material particularly for electroabsorption modulators and saturable absorbers.

  1. Hydrothermal synthesis of highly luminescent blue-emitting ZnSe(S) quantum dots exhibiting low toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Mirnajafizadeh, Fatemeh; Ramsey, Deborah; McAlpine, Shelli [School of Chemistry, University of New South Wales, Sydney, NSW 2052 (Australia); Wang, Fan; Reece, Peter [School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia); Stride, John Arron, E-mail: j.stride@unsw.edu.au [School of Chemistry, University of New South Wales, Sydney, NSW 2052 (Australia); Bragg Institute, Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234 (Australia)

    2016-07-01

    Highly luminescent quantum dots (QDs) that emit in the visible spectrum are of interest to a number of imaging technologies, not least that of biological samples. One issue that hinders the application of luminescent markers in biology is the potential toxicity of the fluorophore. Here we show that hydrothermally synthesized ZnSe(S) QDs have low cytotoxicity to both human colorectal carcinoma cells (HCT-116) and human skin fibroblast cells (WS1). The QDs exhibited a high degree of crystallinity, with a strong blue photoluminescence at up to 29% quantum yield relative to 4′,6-diamidino-2-phenylindole (DAPI) without post-synthetic UV-irradiation. Confocal microscopy images obtained of HCT-116 cells after incubation with the QDs highlighted the stability of the particles in cell media. Cytotoxicity studies showed that both HCT-116 and WS1 cells retain 100% viability after treatment with the QDs at concentrations up to 0.5 g/L, which makes them of potential use in biological imaging applications. - Highlights: • Highly luminescent ZnSe(S) QDs were synthesized using a simple, one-step hydrothermal method. • The as-synthesized QDs were found to be nontoxic in the presence of biological cells. • The QDs were stable in biological media with identical emission profile to that in water.

  2. Fabrication, spectroscopy, and dynamics of highly luminescent core-shell InP@ZnSe quantum dots.

    Science.gov (United States)

    Kim, Mee Rahn; Chung, Jae Hun; Lee, Mihee; Lee, Seonghoon; Jang, Du-Jeon

    2010-10-01

    InP quantum dots of 3 nm in diameter have been prepared using a dehalosilylation reaction and passivated with ZnSe to enhance photoluminescence by 6.8 times. Core-shell InP@ZnSe quantum dots dispersed in n-hexane have then been investigated using time-resolved spectroscopy to understand their photoluminescence dynamics. The observed decay times of 0.1, 7, and 1100 ns have been attributed to the relaxation times of electrons in the conduction band, trap sites, and surface states. The surface-state luminescence of core-shell InP@ZnSe quantum dots having the maximum at 760 nm has been distinguished spectrally and dynamically from their band-edge emission having the maximum at 620 nm or from their trap-site emission having the maximum at 660 nm. Copyright 2010 Elsevier Inc. All rights reserved.

  3. High mobility and quantum well transistors design and TCAD simulation

    CERN Document Server

    Hellings, Geert

    2013-01-01

    For many decades, the semiconductor industry has miniaturized transistors, delivering increased computing power to consumers at decreased cost. However, mere transistor downsizing does no longer provide the same improvements. One interesting option to further improve transistor characteristics is to use high mobility materials such as germanium and III-V materials. However, transistors have to be redesigned in order to fully benefit from these alternative materials. High Mobility and Quantum Well Transistors: Design and TCAD Simulation investigates planar bulk Germanium pFET technology in chapters 2-4, focusing on both the fabrication of such a technology and on the process and electrical TCAD simulation. Furthermore, this book shows that Quantum Well based transistors can leverage the benefits of these alternative materials, since they confine the charge carriers to the high-mobility material using a heterostructure. The design and fabrication of one particular transistor structure - the SiGe Implant-Free Qu...

  4. Detection of bioconjugated quantum dots passivated with different ligands for bio-applications.

    Science.gov (United States)

    Singh, Gurpal; Zaidi, Neelam Hazoor; Soni, Udit; Gautam, Manoj; Jackeray, Richa; Singh, Harpal; Sapra, Sameer

    2011-05-01

    Bioconjugation of quantum dots has resulted in a significant increase in resolution of biological fluorescent labeling. This intrinsic property of quantum dots can be utilized for sensitive detection of target analytes with high sensitivity; including pathogenic bacteria and cancer monitoring. The quantum dots and quantum dot doped silica nanoparticles exhibit prominent emission peaks when excited at 400 nm but on conjugation to model rabbit antigoat antibodies exhibit diminished intensity of emission peak at 600 nm. It shows that photoluminescence intensity of conjugated quantum dots and quantum dot doped silica nanoparticles could permit the detection of bioconjugation. Samples of conjugated and unconjugated quantum dots and quantum dot doped silica nanoparticles were subjected to enzyme linked immunosorbent assay for further confirmation of bioconjugation. In the present study ligand exchange, bioconjugation, fluorescence detection of bioconjugated quantum dots and quantum dot doped silica nanoparticles and further confirmation of bioconjugation by enzyme linked immunosorbent assay has been described.

  5. Spontaneous emission of quantum dots in disordered photonic crystal waveguides

    DEFF Research Database (Denmark)

    Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren

    2010-01-01

    We report on the enhancement of the spontaneous emission rate of single semiconductor quantum dots embedded in a photonic crystal waveguide with engineered disorder. Random high-Q cavities, that are signature of Anderson localization, are measured in photoluminescence experiments and appear...

  6. Continuous wave laser for tailoring the photoluminescence of silicon nanoparticles produced by laser ablation in liquid

    Science.gov (United States)

    Popovic, Dusan M.; Kushima, Akihiro; Bogdanovic, Milena I.; Chai, Jong Seo; Kasalica, Becko; Trtica, Milan; Stasic, Jelena; Zekic, Andrijana A.

    2017-09-01

    Silicon nanoparticles (SiNPs) are attracting attention for applications in various fields, from energy storage to bio-imaging. One of their main advantages is good photoluminescence (PL) properties combined with the relatively high bio-compatibility. Here, we fabricated SiNPs by the laser ablation of silicon single crystal in de-ionized water, employing simultaneously the picosecond pulse laser (150 ps, 1064 nm, 7 mJ/pulse) and a continuous wave (CW) laser (532 nm, 270 mW). TEM analysis (bright field TEM, HRTEM, HAADF, EDS) clearly shows that the introduction of the CW laser significantly increases the crystallinity of the produced nanoparticles, which may be crucial for many optical and electronic applications. The obtained SiNPs exhibit good blue photoluminescence properties, and the introduction of the CW laser into the fabrication process leads to the considerable increases in the photoluminescence. Additionally, we conducted a detailed analysis on the aging-time dependence and the excitation wavelength-dependent PL. The results indicate that the blue photoluminescence may be ascribed to quantum confinement effect, interface related states, and defect in the O-containing layer (shell) of the nanoparticles. We demonstrate that the relative share of these mechanisms in overall PL is significantly affected by the introduction of the CW laser to the pulse laser ablation and it may improve the applicability of the Si nanoparticles produced to a wide variety of fields.

  7. Small Iminocoumarin Derivatives as Red Emitters: From Biological Imaging to Highly Photoluminescent Non-doped Micro- and Nanofibres.

    Science.gov (United States)

    Khemakhem, Kacem; Soulié, Marine; Brousses, Rémy; Ammar, Houcine; Abid, Souhir; Fery-Forgues, Suzanne

    2015-05-18

    The fluorescence properties of four derivatives of 3-thienyl-2-(N-dicyanovinyl)iminocoumarin, bearing a diethylamino group in the 7-position or a methoxy group in the 6, 7 and 8 positions, were compared in solution and in the solid state. The 7-diethylamino derivative was strongly fluorescent in various solvents, with marked solvatochromism. Its fluorescence was quenched by aggregation. In contrast, the methoxy derivatives were only moderately or weakly fluorescent in solution, but two of them were strongly photoluminescent in the crystalline state, owing to favourable molecular packing. The 6-methoxy derivative even exhibited spectacular crystallization-enhanced emission, examples of which are particularly rare for this type of dyes. Dyes were tested for biological use. The 7-diethylamino derivative led to particularly strong fluorescence staining of the cytoplasm of HCT-116 colon cancer cells. No fading was observed over prolonged illumination by the microscope light beam, but a phototoxic effect was detected. The use of the dyes as red-emitting materials was also investigated. Using easy-to-implement preparation methods, the compounds self- assembled to give one-dimensional nano- and microsized particles, including millimeter-long microfibres that exhibited clear wave-guiding properties. This study shows the value of these low molecular-weight molecules for the preparation of new orange and red-emitting fluorescent materials based on totally pure dye. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Catastrophic degradation in high-power InGaAs-AlGaAs strained quantum well lasers and InAs-GaAs quantum dot lasers

    Science.gov (United States)

    Sin, Yongkun; LaLumondiere, Stephen; Foran, Brendan; Ives, Neil; Presser, Nathan; Lotshaw, William; Moss, Steven C.

    2013-03-01

    Reliability and degradation processes in broad-area InGaAs-AlGaAs strained quantum well (QW) lasers are under investigation because these lasers are indispensible as pump lasers for fiber lasers and amplifiers that have found an increasing number of industrial applications in recent years. Extensive efforts by a number of groups to develop InAs-GaAs quantum dot (QD) lasers have recently led to significant improvement in performance characteristics, but due to a short history of commercialization, high power QD lasers lacks studies in reliability and degradation processes. For the present study, we investigated reliability and degradation processes in MOCVD-grown broad-area InGaAs-AlGaAs strained QW lasers as well as in MBE-grown broad-area InAs-GaAs QD lasers using various failure mode analysis (FMA) techniques. Dots for the QD lasers were formed via a self-assembly process during MBE growth. We employed two different methods to degrade lasers during accelerated life-testing: commercial lifetester and our newly developed time-resolved electroluminescence (TR-EL) set-up. Our TR-EL set-up allows us to observe formation of a hot spot and subsequent formation and progression of dark spots and dark lines through windowed n-contacts during entire accelerated life-tests. Deep level transient spectroscopy (DLTS) and time resolved photoluminescence (TR-PL) techniques were employed to study trap characteristics and carrier dynamics in pre- and post-stressed QW and QD lasers to identify the root causes of catastrophic degradation processes in these lasers. We also employed electron beam induced current (EBIC), focused ion beam (FIB), and high resolution TEM to study dark line defects and crystal defects in post-aged QW and QD lasers at different stages of degradation.

  9. High Quantum Efficiency OLED Lighting Systems

    Energy Technology Data Exchange (ETDEWEB)

    Shiang, Joseph [General Electric (GE) Global Research, Fairfield, CT (United States)

    2011-09-30

    The overall goal of the program was to apply improvements in light outcoupling technology to a practical large area plastic luminaire, and thus enable the product vision of an extremely thin form factor high efficiency large area light source. The target substrate was plastic and the baseline device was operating at 35 LPW at the start of the program. The target LPW of the program was a >2x improvement in the LPW efficacy and the overall amount of light to be delivered was relatively high 900 lumens. Despite the extremely difficult challenges associated with scaling up a wet solution process on plastic substrates, the program was able to make substantial progress. A small molecule wet solution process was successfully implemented on plastic substrates with almost no loss in efficiency in transitioning from the laboratory scale glass to large area plastic substrates. By transitioning to a small molecule based process, the LPW entitlement increased from 35 LPW to 60 LPW. A further 10% improvement in outcoupling efficiency was demonstrated via the use of a highly reflecting cathode, which reduced absorptive loss in the OLED device. The calculated potential improvement in some cases is even larger, ~30%, and thus there is considerable room for optimism in improving the net light coupling efficacy, provided absorptive loss mechanisms are eliminated. Further improvements are possible if scattering schemes such as the silver nanowire based hard coat structure are fully developed. The wet coating processes were successfully scaled to large area plastic substrate and resulted in the construction of a 900 lumens luminaire device.

  10. High-efficiency reconciliation for continuous variable quantum key distribution

    Science.gov (United States)

    Bai, Zengliang; Yang, Shenshen; Li, Yongmin

    2017-04-01

    Quantum key distribution (QKD) is the most mature application of quantum information technology. Information reconciliation is a crucial step in QKD and significantly affects the final secret key rates shared between two legitimate parties. We analyze and compare various construction methods of low-density parity-check (LDPC) codes and design high-performance irregular LDPC codes with a block length of 106. Starting from these good codes and exploiting the slice reconciliation technique based on multilevel coding and multistage decoding, we realize high-efficiency Gaussian key reconciliation with efficiency higher than 95% for signal-to-noise ratios above 1. Our demonstrated method can be readily applied in continuous variable QKD.

  11. Progress in quantum electrodynamics theory of highly charged ions

    OpenAIRE

    Volotka, A. V.; Glazov, D. A.; Plunien, G.; Shabaev, V. M.

    2013-01-01

    Recent progress in quantum electrodynamics (QED) calculations of highly charged ions is reviewed. The theoretical predictions for the binding energies, the hyperfine splittings, and the g factors are presented and compared with available experimental data. Special attention is paid to tests of bound-state QED at strong field regime. Future prospects for tests of QED at the strongest electric and magnetic fields as well as for determination of the fine structure constant and the nuclear magnet...

  12. High-Efficiency InGaN/GaN Quantum Well-Based Vertical Light-Emitting Diodes Fabricated on β-Ga2O3 Substrate

    KAUST Repository

    Muhammed, Mufasila

    2017-09-11

    We demonstrate a state-of-the-art high-efficiency GaN-based vertical light-emitting diode (VLED) grown on a transparent and conductive (-201)-oriented (β-Ga2O3) substrate, obtained using a straightforward growth process that does not require a high cost lift-off technique or complex fabrication process. The high-resolution scanning transmission electron microscopy (STEM) images confirm that we produced high quality upper layers, including a multi-quantum well (MQW) grown on the masked β-Ga2O3 substrate. STEM imaging also shows a well-defined MQW without InN diffusion into the barrier. Electroluminescence (EL) measurements at room temperature indicate that we achieved a very high internal quantum efficiency (IQE) of 78%; at lower temperatures, IQE reaches ~ 86%. The photoluminescence (PL) and time-resolved PL analysis indicate that, at a high carrier injection density, the emission is dominated by radiative recombination with a negligible Auger effect; no quantum-confined Stark effect is observed. At low temperatures, no efficiency droop is observed at a high carrier injection density, indicating the superior VLED structure obtained without lift-off processing, which is cost-effective for large-scale devices.

  13. Dynamics of quantum liquids at high momentum

    Energy Technology Data Exchange (ETDEWEB)

    Tanatar, B.; Talbot, E.F.; Glyde, H.R.

    1987-12-01

    The dynamic form factor S(Q,..omega..) in liquid /sup 3/He and /sup 4/He is evaluated in the wave-vector transfer range 3less than or equal toQless than or equal to15 A/sup -1/. The input is the pair interatomic potential, developed by Aziz et al. The S(Q,..omega..) is calculated within the random-phase approximation (RPA) which becomes valid when h-dash-barQ is much larger than the average momentum in the liquid. A T-matrix approximation represents the interaction appearing in the RPA. The aim is to explore how well S(Q,..omega..) can be described for 3less than or equal toQless than or equal to15 A/sup -1/ from first principles. In /sup 3/He, we find S(Q,..omega..) is a broad, nearly Gaussian function, centered just below the recoil frequency having a width and shape that agrees well with experiment. It does, however, have tails at high frequency which make important contributions to its moments. In /sup 4/He, S(Q,..omega..) is a more sharply peaked function which also agrees quite well with experiment. We are able to reproduce the oscillations in the peak position and in the width of S(Q,..omega..) with Q in liquid /sup 4/He observed by Martel et al. In the present model, these oscillations originate from oscillations in the magnitude of the T-matrix interaction with Q. The corresponding oscillations are predicted to be very small and probably unobservable in liquid /sup 3/He.

  14. Quantum Dot Spectrum Converters for Enhanced High Efficiency Photovoltaics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This research proposes to enhance solar cell efficiency, radiation resistance and affordability. The Quantum Dot Spectrum Converter (QDSC) disperses quantum dots...

  15. Photoluminescence properties of the high-brightness Eu3+-doped KNaCa2(PO4)2 phosphors

    Science.gov (United States)

    jin, Cheng; Ma, Hengxin; Liu, Qingbo; Li, Xu; Liu, Pengfei

    2014-03-01

    A series of red-emitting phosphors Eu3+-doped KNaCa2(PO4)2 were synthesized by solid-state reaction, and the photoluminescence (PL) properties were also investigated. The excitation spectrum is composed of charge-transfer (CT) of Eu-O and excitation lines of Eu3+ ions. The strongest excitation lines appeared at 393 nm. The emission spectra of KNaCa2(PO4)2:Eu3+ phosphors exhibit five peaks assigned to the 5D0-7FJ (J = 0, 1, 2, 3, 4) transitions of Eu3+ and have dominating emission peak at 621 nm under 393 nm excitation. The luminescence intensity enhanced with increasing Eu3+ content and the emission reached the maximum intensity at x = 0.02 in KNaCa2-x(PO4)2:xEu3+. The effect of the charge compensators on the emission intensity of the phosphors was investigated. The integral intensity of the emission spectrum of KNaCa1.96(PO4)2:0.02Eu3+, 0.02Na+ excited at 393 nm is about 2.4 times as strong as that of Y2O3:0.05Eu3+ commercial red phosphor. The color coordinates for KNaCa1.96(PO4)2:0.02Eu3+,0.02Na+ were measured. The results indicate that KNaCa2(PO4)2:Eu3+ might be a promising phosphor for w-LEDs.

  16. Controllable synthesis of dual emissive Ag:InP/ZnS quantum dots with high fluorescence quantum yield

    Science.gov (United States)

    Yang, Wu; He, Guoxing; Mei, Shiliang; Zhu, Jiatao; Zhang, Wanlu; Chen, Qiuhang; Zhang, Guilin; Guo, Ruiqian

    2017-11-01

    Dual emissive Cd-free quantum dots (QDs) are in great demand for various applications. However, their synthesis has been faced with challenges. Here, we demonstrate the dual emissive Ag:InP/ZnS core/shell QDs with the excellent photoluminescence quantum yield (PL QY) up to 75% and their PL dependence on the reaction temperature, reaction time, the different ZnX2 (X = I, Cl, and Br) precursors, the ratio of In/Zn and the Ag dopant concentration. The as-prepared Ag:InP/ZnS QDs exhibit dual emission with one peak position of about 492 nm owing to the intrinsic emission, and the other peak position of about 575 nm resulting from Ag-doped emission. These dual emissive QDs are integrated with the commercial GaN-based blue LEDs, and the simulation results show that the Ag:InP/ZnS QDs-based white LEDs could realize bright natural white-lights with the luminous efficacy (LE) of 94.2-98.4 lm/W, the color rendering index (CRI) of 82-83 and the color quality scale (CQS) of 82-83 at different correlated color temperatures (CCT). This unique combination of the above properties makes this new class of dual emissive QDs attractive for white LED applications.

  17. Tomography of the quantum state of photons entangled in high dimensions

    CSIR Research Space (South Africa)

    Agnew, M

    2011-12-01

    Full Text Available Systems entangled in high dimensions have recently been proposed as important tools for various quantum information protocols, such as multibit quantum key distribution and loophole-free tests of nonlocality. It is therefore important to have...

  18. CsSnI3: Semiconductor or metal? High electrical conductivity and strong near-infrared photoluminescence from a single material. High hole mobility and phase-transitions.

    Science.gov (United States)

    Chung, In; Song, Jung-Hwan; Im, Jino; Androulakis, John; Malliakas, Christos D; Li, Hao; Freeman, Arthur J; Kenney, John T; Kanatzidis, Mercouri G

    2012-05-23

    CsSnI(3) is an unusual perovskite that undergoes complex displacive and reconstructive phase transitions and exhibits near-infrared emission at room temperature. Experimental and theoretical studies of CsSnI(3) have been limited by the lack of detailed crystal structure characterization and chemical instability. Here we describe the synthesis of pure polymorphic crystals, the preparation of large crack-/bubble-free ingots, the refined single-crystal structures, and temperature-dependent charge transport and optical properties of CsSnI(3), coupled with ab initio first-principles density functional theory (DFT) calculations. In situ temperature-dependent single-crystal and synchrotron powder X-ray diffraction studies reveal the origin of polymorphous phase transitions of CsSnI(3). The black orthorhombic form of CsSnI(3) demonstrates one of the largest volumetric thermal expansion coefficients for inorganic solids. Electrical conductivity, Hall effect, and thermopower measurements on it show p-type metallic behavior with low carrier density, despite the optical band gap of 1.3 eV. Hall effect measurements of the black orthorhombic perovskite phase of CsSnI(3) indicate that it is a p-type direct band gap semiconductor with carrier concentration at room temperature of ∼ 10(17) cm(-3) and a hole mobility of ∼585 cm(2) V(-1) s(-1). The hole mobility is one of the highest observed among p-type semiconductors with comparable band gaps. Its powders exhibit a strong room-temperature near-IR emission spectrum at 950 nm. Remarkably, the values of the electrical conductivity and photoluminescence intensity increase with heat treatment. The DFT calculations show that the screened-exchange local density approximation-derived band gap agrees well with the experimentally measured band gap. Calculations of the formation energy of defects strongly suggest that the electrical and light emission properties possibly result from Sn defects in the crystal structure, which arise

  19. Quantum Electrodynamics with Semiconductor Quantum Dots Coupled to Anderson‐localized Random Cavities

    DEFF Research Database (Denmark)

    Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren

    2011-01-01

    of the spontaneous emission decay rate by up to a factor 15 and an efficiency of channeling single photons into Anderson-localized modes reaching values as high as 94%. These results prove that disordered photonic media provide an efficient platform for quantum electrodynamics, offering a novel route to quantum......We demonstrate that the spontaneous emission decay rate of semiconductor quantum dots can be strongly modified by the coupling to disorder-induced Anderson-localized photonic modes. We experimentally measure, by means of time-resolved photoluminescence spectroscopy, the enhancement...

  20. Quantum creep in a highly crystalline two-dimensional superconductor

    Science.gov (United States)

    Saito, Yu; Kasahara, Yuichi; Ye, Jianting; Iwasa, Yoshihiro; Nojima, Tsutomu

    Conventional studies on quantum phase transitions, especially on superconductor-insulator or superconductor-metal-insulator transitions have been performed in deposited metallic thin films such as Bismuth or MoGe. Although the techniques of thin films deposition have been considerably improved, unintentional disorder such as impurities and deficiencies, generating the pinning centers, seems to still exist in such systems. The mechanical exfoliated highly crystalline two-dimensional material can be a good candidate to realize a less-disordered 2D superconductor with extremely weak pinning, combined with transfer method or ionic-liquid gating. We report on the quantum metal, namely, magnetic-field-induced metallic state observed in an ion-gated two-dimensional superconductor based on an ultra-highly crystalline layered band insulator, ZrNCl. We found that the superconducting state is extremely fragile against external magnetic fields; that is, zero resistance state immediately disappears, once an external magnetic field switches on. This is because the present system is relatively clean and the pinning potential is extremely weak, which cause quantum tunneling and flux flow of vortices, resulting in metallic ground state.

  1. Synthesis of biocompatible and highly photoluminescent nitrogen doped carbon dots from lime: analytical applications and optimization using response surface methodology.

    Science.gov (United States)

    Barati, Ali; Shamsipur, Mojtaba; Arkan, Elham; Hosseinzadeh, Leila; Abdollahi, Hamid

    2015-02-01

    Herein, a facile hydrothermal treatment of lime juice to prepare biocompatible nitrogen-doped carbon quantum dots (N-CQDs) in the presence of ammonium bicarbonate as a nitrogen source has been presented. The resulting N-CQDs exhibited excitation and pH independent emission behavior; with the quantum yield (QY) up to 40%, which was several times greater than the corresponding value for CQDs with no added nitrogen source. The N-CQDs were applied as a fluorescent probe for the sensitive and selective detection of Hg(2+) ions with a detection limit of 14 nM. Moreover, the cellular uptake and cytotoxicity of N-CQDs at different concentration ranges from 0.0 to 0.8 mg/ml were investigated by using PC12 cells as a model system. Response surface methodology was used for optimization and systematic investigation of the main variables that influence the QY, including reaction time, reaction temperature, and ammonium bicarbonate weight. Copyright © 2014. Published by Elsevier B.V.

  2. Influence of Electron–Acoustic-Phonon Scattering on Intensity Power Broadening in a Coherently Driven Quantum-Dot–Cavity System

    OpenAIRE

    C. Roy; S. Hughes

    2011-01-01

    We present a quantum optics formalism to study the intensity power broadening of a semiconductor quantum dot interacting with an acoustic-phonon bath and a high-Q microcavity. Power broadening is investigated using a time-convolutionless master equation in the polaron frame, which allows for a nonperturbative treatment of the interaction of the quantum dot with the phonon reservoir. We calculate the full non-Lorentzian photoluminescence (PL) line shapes and numerically extract the intensity l...

  3. Quantum

    CERN Document Server

    Al-Khalili, Jim

    2003-01-01

    In this lively look at quantum science, a physicist takes you on an entertaining and enlightening journey through the basics of subatomic physics. Along the way, he examines the paradox of quantum mechanics--beautifully mathematical in theory but confoundingly unpredictable in the real world. Marvel at the Dual Slit experiment as a tiny atom passes through two separate openings at the same time. Ponder the peculiar communication of quantum particles, which can remain in touch no matter how far apart. Join the genius jewel thief as he carries out a quantum measurement on a diamond without ever touching the object in question. Baffle yourself with the bizzareness of quantum tunneling, the equivalent of traveling partway up a hill, only to disappear then reappear traveling down the opposite side. With its clean, colorful layout and conversational tone, this text will hook you into the conundrum that is quantum mechanics.

  4. Absorption and photoluminescence in organic cavity QED

    Science.gov (United States)

    Herrera, Felipe; Spano, Frank C.

    2017-05-01

    Organic microcavities can be engineered to reach exotic quantum regimes of strong and ultrastrong light-matter coupling. However, the microscopic interpretation of their spectroscopic signals can be challenging due to the competition between coherent and dissipative processes involving electrons, vibrations, and cavity photons. We develop here a theoretical framework based on the Holstein-Tavis-Cummings model and a Markovian treatment of dissipation to account for previously unexplained spectroscopic features of organic microcavities consistently. We identify conditions for the formation of dark vibronic polaritons, a class of light-matter excitations that are not visible in absorption but lead to strong photoluminescence lines. We show that photon leakage from dark vibronic polaritons can be responsible for enhancing photoluminescence at the lower polariton frequency, and also can explain the apparent breakdown of reciprocity between absorption and emission in the vicinity of the bare molecular transition frequency. Successful comparison with experimental data demonstrates the applicability of our theory.

  5. Photoluminescence and structural studies of Tb and Eu implanted at high temperatures into SiO{sub 2} films

    Energy Technology Data Exchange (ETDEWEB)

    Bregolin, F.L. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501-970, Porto Alegre-RS (Brazil); Sias, U.S., E-mail: uilson.sias@gmail.com [Instituto Federal Sul-rio-grandense, Campus Pelotas, Praca 20 de Setembro 455, 96015-360, Pelotas-RS (Brazil); Behar, M. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501-970, Porto Alegre-RS (Brazil)

    2013-03-15

    The present work deals with the photoluminescence (PL) emitted from Eu and Tb ions implanted at room temperature (RT) up to 350 Degree-Sign C in a SiO{sub 2} matrix, followed by a further anneal process. The ions were implanted with energy of 100 keV and a fluence of 3 Multiplication-Sign 10{sup 15} ions/cm Superscript-Two . Further anneals were performed in atmospheres of N{sub 2} or O{sub 2} with temperatures ranging from 500 up to 800 Degree-Sign C. PL measurements were performed at RT and structural measurements were done via transmission electron microscopy (TEM). In addition, the Rutherford backscattering technique (RBS) was used to investigate the corresponding ion depth profiles. For Tb, the optimal implantation temperature was 200 Degree-Sign C, and the anneal one was of 500 Degree-Sign C. Under these conditions, the PL yield of the sharp band centered at 550 nm was significatively higher than the one obtained with RT implants. The PL spectra corresponding to the Eu ions show two bands, one narrow centered around 650 nm and a second broad one in the blue-green region. The implantation temperature plays a small influence on the PL shape and yield. However, the annealing atmosphere has a strong influence on it. Samples annealed in N{sub 2} present a broad PL band, ranging from 370 up to 840 nm. On the other hand, the O{sub 2} anneal conserves the original as-implanted spectrum, that is: a broad PL band in the blue-green region together with sharp PL band in the red one. For both ions, Tb and Eu, the TEM analyses indicate the formation of nanoclusters in the hot as-implanted samples. - Highlights: Black-Right-Pointing-Pointer Eu and Tb nanoparticles were obtained by hot ion implantation into SiO{sub 2} matrix. Black-Right-Pointing-Pointer TEM results indicate the formation of nanoclusters in the hot as-implanted samples. Black-Right-Pointing-Pointer Samples annealed in N{sub 2} presented a broad PL band (from 370 up to 840 nm). Black-Right-Pointing-Pointer O

  6. Microscopic theory of spatially resolved photoluminescence in disordered nanostructures

    Directory of Open Access Journals (Sweden)

    Di Stefano, O

    2005-11-01

    Full Text Available Quantum dots have become objects of extensive research activity because of their applications such as advanced electronic and optoelectronic devices. Here we analyse theoretically the optical properties of dots naturally formed by interface fluctuations in GaAs narrow quantum wells. Specifically we present the simulations of local optical spectroscopy and spatially resolved photoluminescence in quantum wells with interface fluctuations. The theory includes light quantization, acoustic phonon scattering, and inhomogeneous sample-excitation and/or light-detection. Such theoretical framework provides a general basis for the description of spectroscopic imaging. Numerically calculated absorption and photoluminescence images clarify the impact of the near-field optical setup and put forward the potentials of the method for the understanding of near-field light emission from semiconductor quantum structures.

  7. Formation Mechanism of Carbogenic Nanoparticles with Dual Photoluminescence Emission

    KAUST Repository

    Krysmann, Marta J.

    2012-01-18

    We present a systematic investigation of the formation mechanism of carbogenic nanoparticles (CNPs), otherwise referred to as C-dots, by following the pyrolysis of citric acid (CA)-ethanolamine (EA) precursor at different temperatures. Pyrolysis at 180 °C leads to a CNP molecular precursor with a strongly intense photoluminescence (PL) spectrum and high quantum yield formed by dehydration of CA-EA. At higher temperatures (230 °C) a carbogenic core starts forming and the PL is due to the presence of both molecular fluorophores and the carbogenic core. CNPs that exhibit mostly or exclusively PL arising from carbogenic cores are obtained at even higher temperatures (300 and 400 °C, respectively). Since the molecular fluorophores predominate at low pyrolysis temperatures while the carbogenic core starts forming at higher temperatures, the PL behavior of CNPs strongly depends on the conditions used for their synthesis. © 2011 American Chemical Society.

  8. A high-temperature quantum spin liquid with polaron spins

    Science.gov (United States)

    Klanjšek, Martin; Zorko, Andrej; Žitko, Rok; Mravlje, Jernej; Jagličić, Zvonko; Biswas, Pabitra Kumar; Prelovšek, Peter; Mihailovic, Dragan; Arčon, Denis

    2017-11-01

    The existence of a quantum spin liquid (QSL) in which quantum fluctuations of spins are sufficiently strong to preclude spin ordering down to zero temperature was originally proposed theoretically more than 40 years ago, but its experimental realization turned out to be very elusive. Here we report on an almost ideal spin liquid state that appears to be realized by atomic-cluster spins on the triangular lattice of a charge-density wave state of 1T-TaS2. In this system, the charge excitations have a well-defined gap of ~0.3 eV, while nuclear quadrupole resonance and muon-spin-relaxation experiments reveal that the spins show gapless QSL dynamics and no long-range magnetic order at least down to 70 mK. Canonical T2 power-law temperature dependence of the spin relaxation dynamics characteristic of a QSL is observed from 200 K to Tf = 55 K. Below this temperature, we observe a new gapless state with reduced density of spin excitations and high degree of local disorder signifying new quantum spin order emerging from the QSL.

  9. A highly efficient single-photon source based on a quantum dot in a photonic nanowire

    DEFF Research Database (Denmark)

    Claudon, Julien; Bleuse, Joel; Malik, Nitin Singh

    2010-01-01

    –4 or a semiconductor quantum dot5–7. Achieving a high extraction efficiency has long been recognized as a major issue, and both classical solutions8 and cavity quantum electrodynamics effects have been applied1,9–12. We adopt a different approach, based on an InAs quantum dot embedded in a GaAs photonic nanowire...

  10. High quantum efficiency S-20 photocathodes in photon counting detectors

    Science.gov (United States)

    Orlov, D. A.; DeFazio, J.; Duarte Pinto, S.; Glazenborg, R.; Kernen, E.

    2016-04-01

    Based on conventional S-20 processes, a new series of high quantum efficiency (QE) photocathodes has been developed that can be specifically tuned for use in the ultraviolet, blue or green regions of the spectrum. The QE values exceed 30% at maximum response, and the dark count rate is found to be as low as 30 Hz/cm2 at room temperature. This combination of properties along with a fast temporal response makes these photocathodes ideal for application in photon counting detectors, which is demonstrated with an MCP photomultiplier tube for single and multi-photoelectron detection.

  11. Quantum Key Distribution with High Loss: Toward Global Secure Communication

    Science.gov (United States)

    Hwang, Won-Young

    2003-08-01

    We propose a decoy-pulse method to overcome the photon-number-splitting attack for Bennett-Brassard 1984 quantum key distribution protocol in the presence of high loss: A legitimate user intentionally and randomly replaces signal pulses by multiphoton pulses (decoy pulses). Then they check the loss of the decoy pulses. If the loss of the decoy pulses is abnormally less than that of signal pulses, the whole protocol is aborted. Otherwise, to continue the protocol, they estimate the loss of signal multiphoton pulses based on that of decoy pulses. This estimation can be done with an assumption that the two losses have similar values. We justify that assumption.

  12. Gain in a quantum wire laser of high uniformity

    OpenAIRE

    Akiyama, Hidefumi; Pfeiffer, Loren N.; Yoshita, Masahiro; Pinczuk, Aron; Littlewood, Peter B.; West, Ken W.; Matthews, Manyalibo J.; Wynn, James

    2002-01-01

    A multi-quantum wire laser operating in the 1-D ground state has been achieved in a very high uniformity structure that shows free exciton emission with unprecedented narrow width and low lasing threshold. Under optical pumping the spontaneous emission evolves from a sharp free exciton peak to a red-shifted broad band. The lasing photon energy occurs about 5 meV below the free exciton. The observed shift excludes free excitons in lasing and our results show that Coulomb interactions in the 1-...

  13. Quantum Transport Simulation of High-Power 4.6-μm Quantum Cascade Lasers

    Directory of Open Access Journals (Sweden)

    Olafur Jonasson

    2016-06-01

    Full Text Available We present a quantum transport simulation of a 4.6- μ m quantum cascade laser (QCL operating at high power near room temperature. The simulation is based on a rigorous density-matrix-based formalism, in which the evolution of the single-electron density matrix follows a Markovian master equation in the presence of applied electric field and relevant scattering mechanisms. We show that it is important to allow for both position-dependent effective mass and for effective lowering of very thin barriers in order to obtain the band structure and the current-field characteristics comparable to experiment. Our calculations agree well with experiments over a wide range of temperatures. We predict a room-temperature threshold field of 62 . 5 kV/cm and a characteristic temperature for threshold-current-density variation of T 0 = 199 K . We also calculate electronic in-plane distributions, which are far from thermal, and show that subband electron temperatures can be hundreds to thousands of degrees higher than the heat sink. Finally, we emphasize the role of coherent tunneling current by looking at the size of coherences, the off-diagonal elements of the density matrix. At the design lasing field, efficient injection manifests itself in a large injector/upper lasing level coherence, which underscores the insufficiency of semiclassical techniques to address injection in QCLs.

  14. High-efficiency "green" quantum dot solar cells.

    Science.gov (United States)

    Pan, Zhenxiao; Mora-Seró, Iván; Shen, Qing; Zhang, Hua; Li, Yan; Zhao, Ke; Wang, Jin; Zhong, Xinhua; Bisquert, Juan

    2014-06-25

    Semiconductor quantum dots (QDs) are extremely interesting materials for the development of photovoltaic devices, but currently the present the drawback is that the most efficient devices have been prepared with toxic heavy metals of Cd or Pb. Solar cells based on "green" QDs--totally free of Cd or Pb--present a modest efficiency of 2.52%. Herein we achieve effective surface passivation of the ternary CuInS2 (CIS) QDs that provides high photovoltaic quality core/shell CIS/ZnS (CIS-Z) QDs, leading to the development of high-efficiency green QD solar cells that surpass the performance of those based on the toxic cadmium and lead chalcogenides QDs. Using wide absorption range QDs, CIS-Z-based quantum dot sensitized solar cell (QDSC) configuration with high QD loading and with the benefit of the recombination reduction with type-I core/shell structure, we boost the power conversion efficiency of Cd- and Pb-free QDSC to a record of 7.04% (with certified efficiency of 6.66%) under AM 1.5G one sun irradiation. This efficiency is the best performance to date for QDSCs and also demonstrates that it is possible to obtain comparable or even better photovoltaic performance from green CIS QDs to the toxic cadmium and lead chalcogenides QDs.

  15. Room- and low-temperature assessment of pseudomorphic AlGaAs/InGaAs/GaAS high-electron-mobility transistor structures by photoluminescence spectroscopy

    Science.gov (United States)

    Gilperez, J. M.; Sanchez-Rojas, J. L.; Munoz, E.; Calleja, E.; David, J. P. R.; Reddy, M.; Hill, G.; Sanchez-Dehesa, J.

    1994-11-01

    The use of room- and low-temperature photoluminescence (PL) spectroscopy for the assessment of n-type pseudomorphic AlGaAs/InGaAs/GaAs high-electron-mobility transistor stransitor structures is reported. We describe a method to determine the InAs mole fraction x, the channel layer thickness L, and the confined two-dimensional electron gas density (n(sub s)), based on the comparison between the PL transitions and the recombination energies derived from self-consistent calculations of the subband structure. A detailed analysis of the optical transitions and their dependence on the Fermi level position and temperature is performed. It is shown that, in real devices, the high sensitivity of the recombination energies and intensities on small changes of the parameters x, L, and n(sub s) allows us to detect deviations from their nominal structural parameters within the uncertainty of the molecular beam epitaxy growth technique. The present assessment procedure has been applied to a significant number of samples, and it has been backed by independent measurements of these parameters by more sophisticated techniques such as Shubnikov-de Haas and PL excitation in standard and gated samples, and by physical techniques like transmission electron microscopy and Auger spectroscopy.

  16. Tailoring quantum structures for active photonic crystals

    DEFF Research Database (Denmark)

    Kuznetsova, Nadezda

    This work is dedicated to the tailoring of quantum structures, with particular attention to the integration of selective area grown (SAG) active material into photonic crystal (PhC) slabs. The platform based on active PhC is vital to the realization of highly efficient elements with low energy......; in particular, the emission control of SAG QW matched the operating wavelength of photonic crystals. A strong photoluminescence signal in the slow light regime with the group index of 18 was demonstrated....

  17. High-fidelity quantum state preparation using neighboring optimal control

    Science.gov (United States)

    Peng, Yuchen; Gaitan, Frank

    2017-10-01

    We present an approach to single-shot high-fidelity preparation of an n-qubit state based on neighboring optimal control theory. This represents a new application of the neighboring optimal control formalism which was originally developed to produce single-shot high-fidelity quantum gates. To illustrate the approach, and to provide a proof-of-principle, we use it to prepare the two-qubit Bell state |β _{01}\\rangle = (1/√{2})[ |01\\rangle + |10\\rangle ] with an error probability ɛ ˜ 10^{-6} (10^{-5}) for ideal (non-ideal) control. Using standard methods in the literature, these high-fidelity Bell states can be leveraged to fault-tolerantly prepare the logical state |\\overline{β }_{01}\\rangle.

  18. Investigation of biocompatible and protein sensitive highly luminescent quantum dots/nanocrystals of CdSe, CdSe/ZnS and CdSe/CdS

    Science.gov (United States)

    Ratnesh, R. K.; Mehata, Mohan Singh

    2017-05-01

    The size and shape dependent semiconductor quantum dots (0D nanoparticles) with color tunability demonstrating significant influence in a biological system and considered as ideal probes. Here, a non-coordinated colloidal approach was used for the synthesis of CdSe, CdSe/ZnS and CdSe/CdS core-shell quantum dots (QDs) of 3-4 nm. The synthesized nanocrystals show a high crystallinity, examined by X-ray diffraction (XRD) and high-resolution electron microscopy (HRTEM). The core-shell semiconductor QDs exhibit stronger photoluminescence (PL) as compared to the core QDs. The strong PL with small full-width half maximum (FWHM) indicates that the prepared QDs have a nearly uniform size distribution and well dispersibility. The quantum yield (QY) of core-shell QDs increases due to the surface passivation. Further, the PL of BSA is quenched strongly by the presence of core-shell QDs and follows the well-known Stern-Volmer (S-V) relation, whereas the PL lifetime does not follow the S-V relation, demonstrating that the observed quenching is predominantly static in nature. Among CdSe core, CdSe/ZnS and CdSe/CdS core-shell QDs, the CdSe/ZnS QDs shows the least cytotoxicity and most biocompatibility. Thus, the prepared core-shell QDs are biocompatible and exhibit strong sensing ability.

  19. Highly luminescent and ultrastable CsPbBr{sub 3} perovskite quantum dots incorporated into a silica/alumina monolith

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhichun; Kong, Long; Huang, Shouqiang; Li, Liang [School of Environmental Science and Engineering, Shanghai Jiao Tong University (China)

    2017-07-03

    We successfully prepared QDs incorporated into a silica/alumina monolith (QDs-SAM) by a simple sol-gel reaction of an Al-Si single precursor with CsPbBr{sub 3} QDs blended in toluene solution, without adding water and catalyst. The resultant transparent monolith exhibits high photoluminescence quantum yields (PLQY) up to 90 %, and good photostability under strong illumination of blue light for 300 h. We show that the preliminary ligand exchange of didodecyl dimethyl ammonium bromide (DDAB) was very important to protect CsPbBr{sub 3} QDs from surface damages during the sol-gel reaction, which not only allowed us to maintain the original optical properties of CsPbBr{sub 3} QDs but also prevented the aggregation of QDs and made the monolith transparent. The CsPbBr{sub 3} QDs-SAM in powder form was easily mixed into the resins and applied as color-converting layer with curing on blue light-emitting diodes (LED). The material showed a high luminous efficacy of 80 lm W{sup -1} and a narrow emission with a full width at half maximum (FWHM) of 25 nm. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Highly Luminescent and Ultrastable CsPbBr3 Perovskite Quantum Dots Incorporated into a Silica/Alumina Monolith.

    Science.gov (United States)

    Li, Zhichun; Kong, Long; Huang, Shouqiang; Li, Liang

    2017-07-03

    We successfully prepared QDs incorporated into a silica/alumina monolith (QDs-SAM) by a simple sol-gel reaction of an Al-Si single precursor with CsPbBr3 QDs blended in toluene solution, without adding water and catalyst. The resultant transparent monolith exhibits high photoluminescence quantum yields (PLQY) up to 90 %, and good photostability under strong illumination of blue light for 300 h. We show that the preliminary ligand exchange of didodecyl dimethyl ammonium bromide (DDAB) was very important to protect CsPbBr3 QDs from surface damages during the sol-gel reaction, which not only allowed us to maintain the original optical properties of CsPbBr3 QDs but also prevented the aggregation of QDs and made the monolith transparent. The CsPbBr3 QDs-SAM in powder form was easily mixed into the resins and applied as color-converting layer with curing on blue light-emitting diodes (LED). The material showed a high luminous efficacy of 80 lm W-1 and a narrow emission with a full width at half maximum (FWHM) of 25 nm. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Coupled Double Quantum Wells

    Directory of Open Access Journals (Sweden)

    Élder Mantovani Lopes

    2010-12-01

    Full Text Available The progress of the semiconductor growth techniques allows the opportunity to produce new semiconductors devices that may contribute to the development of the nanotechnology. The fabrication of semiconductor heterostructures with high quality allows the obtaining of new effects based on the quantum properties of those systems, which have stimulated great technological interest, especially on the optoelectronic and telecommunications fields. In this work some basic concepts related to one of those heterostructures are discussed: the Coupled Double Quantum Well (CDQW. The deduction of the expression for the determination of the energy levels in CDQWs is presented in details. The results obtained through this expression are compared with experimental results obtained through photoluminescence (PL measurements, complementing the work.

  2. Structure and optical anisotropy of vertically correlated submonolayer InAs/GaAs quantum dots

    DEFF Research Database (Denmark)

    Xu, Zhangcheng; Birkedal, Dan; Hvam, Jørn Märcher

    2003-01-01

    A vertically correlated submonolayer (VCSML) InAs/GaAs quantum-dot (QD) heterostructure was studied using transmission electron microscopy, high-resolution x-ray diffraction (HRXRD) and polarization-dependent photoluminescence. The HRXRD (004) rocking curve was simulated using the Tagaki-Taupin e......A vertically correlated submonolayer (VCSML) InAs/GaAs quantum-dot (QD) heterostructure was studied using transmission electron microscopy, high-resolution x-ray diffraction (HRXRD) and polarization-dependent photoluminescence. The HRXRD (004) rocking curve was simulated using the Tagaki...... with respect to GaAs is around 1.4%, while the lattice mismatch in the QW is negligible. The photoluminescence is transverse magnetic-polarized in the edge geometry....

  3. Size-controlled synthesis of ZnO quantum dots in microreactors

    Science.gov (United States)

    Schejn, Aleksandra; Frégnaux, Mathieu; Commenge, Jean-Marc; Balan, Lavinia; Falk, Laurent; Schneider, Raphaël

    2014-04-01

    In this paper, we report on a continuous-flow microreactor process to prepare ZnO quantum dots (QDs) with widely tunable particle size and photoluminescence emission wavelengths. X-ray diffraction, electron diffraction, UV-vis, photoluminescence and transmission electron microscopy measurements were used to characterize the synthesized ZnO QDs. By varying operating conditions (temperature, flow rate) or the capping ligand, ZnO QDs with diameters ranging from 3.6 to 5.2 nm and fluorescence maxima from 500 to 560 nm were prepared. Results obtained show that low reaction temperatures (20 or 35 °C), high flow rates and the use of propionic acid as a stabilizing agent are favorable for the production of ZnO QDs with high photoluminescence quantum yields (up to 30%).

  4. Atomically precise, coupled quantum dots fabricated by cleaved edge overgrowth

    Science.gov (United States)

    Wegscheider, W.; Schedelbeck, G.; Bichler, M.; Abstreiter, G.

    Recent progress in the fabrication of quantum dots by molecular beam epitaxy along three directions in space is reviewed. The optical properties of different sample structures consisting of individual quantum dots, pairs of coupled dots as well as of linear arrays of dots are studied by microscopic photoluminescence spectroscopy. The high degree of control over shape, composition and position of the 7×7×7 nm3 size GaAs quantum dots, which form at the intesection of three orthogonal quantum wells, allows a detailed investigation of the influence of coupling between almost identical zero-dimensional objects. In contrast to the inhomogeneously broadened quantum well and quantum wire signals originating from the complex twofold cleaved edge overgrowth structure, the photoluminescence spetrum of an individual quantum dot exhibits a single sharp line (full width at half maximum denomination "artificial atoms" for the quantum dots. It is further demonstrated that an "artifical molecule", characterized by the existence of bonding and antibonding states can be assembled from two of such "artificial atoms". The coupling strength between the "artificial atoms" is adjusted by the "interatomic" distance and is reflected in the energetic separation of the bonding and antibonding levels and the linewidths of the corresponding interband transitions.

  5. Storing single photons emitted by a quantum memory on a highly excited Rydberg state.

    Science.gov (United States)

    Distante, Emanuele; Farrera, Pau; Padrón-Brito, Auxiliadora; Paredes-Barato, David; Heinze, Georg; de Riedmatten, Hugues

    2017-01-19

    Strong interaction between two single photons is a long standing and important goal in quantum photonics. This would enable a new regime of nonlinear optics and unlock several applications in quantum information science, including photonic quantum gates and deterministic Bell-state measurements. In the context of quantum networks, it would be important to achieve interactions between single photons from independent photon pairs storable in quantum memories. So far, most experiments showing nonlinearities at the single-photon level have used weak classical input light. Here we demonstrate the storage and retrieval of a paired single photon emitted by an ensemble quantum memory in a strongly nonlinear medium based on highly excited Rydberg atoms. We show that nonclassical correlations between the two photons persist after retrieval from the Rydberg ensemble. Our result is an important step towards deterministic photon-photon interactions, and may enable deterministic Bell-state measurements with multimode quantum memories.

  6. Controlled positioning of self-assembled InAs quantum dots on (1 1 0) GaAs

    Science.gov (United States)

    Schuh, D.; Bauer, J.; Uccelli, E.; Schulz, R.; Kress, A.; Hofbauer, F.; Finley, J. J.; Abstreiter, G.

    2005-02-01

    We report on a new approach for positioning of self-assembled InAs quantum dots on (1 1 0) GaAs with nanometer precision. By combining self-assembly of quantum dots with molecular beam epitaxy on in situ cleaved surfaces (cleaved-edge overgrowth) we have successfully fabricated arrays of long-range ordered InAs quantum dots. Both atomic force microscopy and micro-photoluminescence measurements demonstrate the ability to control position and ordering of the quantum dots with epitaxial precision as well as size and size homogeneity. Furthermore, photoluminescence investigations on dot ensembles and on single dots confirm the high homogeneity and the excellent optical quality of the quantum dots fabricated.

  7. Graphene Quantum Capacitors for High Frequency Tunable Analog Applications.

    Science.gov (United States)

    Moldovan, Clara F; Vitale, Wolfgang A; Sharma, Pankaj; Tamagnone, Michele; Mosig, Juan R; Ionescu, Adrian M

    2016-08-10

    Graphene quantum capacitors (GQC) are demonstrated to be enablers of radio-frequency (RF) functions through voltage-tuning of their capacitance. We show that GQC complements MEMS and MOSFETs in terms of performance for high frequency analog applications and tunability. We propose a CMOS compatible fabrication process and report the first experimental assessment of their performance at microwaves frequencies (up to 10 GHz), demonstrating experimental GQCs in the pF range with a tuning ratio of 1.34:1 within 1.25 V, and Q-factors up to 12 at 1 GHz. The figures of merit of graphene variable capacitors are studied in detail from 150 to 350 K. Furthermore, we describe a systematic, graphene specific approach to optimize their performance and predict the figures of merit achieved if such a methodology is applied.

  8. High power and single mode quantum cascade lasers.

    Science.gov (United States)

    Bismuto, Alfredo; Bidaux, Yves; Blaser, Stéphane; Terazzi, Romain; Gresch, Tobias; Rochat, Michel; Muller, Antoine; Bonzon, Christopher; Faist, Jerome

    2016-05-16

    We present a single mode quantum cascade laser with nearly 1 W optical power. A buried distributed feedback reflector is used on the back section for wavelength selection. The laser is 6 mm long, 3.5 μm wide, mounted episide-up and the laser facets are left uncoated. Laser emission is centered at 4.68 μm. Single-mode operation with a side mode suppression ratio of more than 30 dB is obtained in whole range of operation. Farfield measurements prove a symmetric, single transverse-mode emission in TM00-mode with typical divergences of 41° and 33° in the vertical and horizontal direction respectively. This work shows the potential for simple fabrication of high power lasers compatible with standard DFB processing.

  9. Film quantum yields of EUV& ultra-high PAG photoresists

    Energy Technology Data Exchange (ETDEWEB)

    Hassanein, Elsayed; Higgins, Craig; Naulleau, Patrick; Matyi, Richard; Gallatin, Greg; Denbeaux, Gregory; Antohe, Alin; Thackery, Jim; Spear, Kathleen; Szmanda, Charles; Anderson, Christopher N.; Niakoula, Dimitra; Malloy, Matthew; Khurshid, Anwar; Montgomery, Cecilia; Piscani, Emil C.; Rudack, Andrew; Byers, Jeff; Ma, Andy; Dean, Kim; Brainard, Robert

    2008-01-10

    Base titration methods are used to determine C-parameters for three industrial EUV photoresist platforms (EUV-2D, MET-2D, XP5496) and twenty academic EUV photoresist platforms. X-ray reflectometry is used to measure the density of these resists, and leads to the determination of absorbance and film quantum yields (FQY). Ultrahigh levels ofPAG show divergent mechanisms for production of photo acids beyond PAG concentrations of 0.35 moles/liter. The FQY of sulfonium PAGs level off, whereas resists prepared with iodonium PAG show FQY s that increase beyond PAG concentrations of 0.35 moles/liter, reaching record highs of 8-13 acids generatedlEUV photons absorbed.

  10. Highly luminescent metal-organic frameworks through quantum dot doping.

    Science.gov (United States)

    Buso, Dario; Jasieniak, Jacek; Lay, Matthew D H; Schiavuta, Piero; Scopece, Paolo; Laird, Jamie; Amenitsch, Heinz; Hill, Anita J; Falcaro, Paolo

    2012-01-09

    The incorporation of highly luminescent core-shell quantum dots (QDs) within a metal-organic framework (MOF) is achieved through a one-pot method. Through appropriate surface functionalization, the QDs are solubilized within MOF-5 growth media. This permits the incorporation of the QDs within the evolving framework during the reaction. The resulting QD@MOF-5 composites are characterized using X-ray fluorescence, cross-sectional confocal microscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and small-angle X-ray scattering. The synergistic combination of luminescent QDs and the controlled porosity of MOF-5 in the QD@MOF-5 composites is harnessed within a prototype molecular sensor that can discriminate on the basis of molecular size. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Interface between path and orbital angular momentum entanglement for high-dimensional photonic quantum information.

    Science.gov (United States)

    Fickler, Robert; Lapkiewicz, Radek; Huber, Marcus; Lavery, Martin P J; Padgett, Miles J; Zeilinger, Anton

    2014-07-30

    Photonics has become a mature field of quantum information science, where integrated optical circuits offer a way to scale the complexity of the set-up as well as the dimensionality of the quantum state. On photonic chips, paths are the natural way to encode information. To distribute those high-dimensional quantum states over large distances, transverse spatial modes, like orbital angular momentum possessing Laguerre Gauss modes, are favourable as flying information carriers. Here we demonstrate a quantum interface between these two vibrant photonic fields. We create three-dimensional path entanglement between two photons in a nonlinear crystal and use a mode sorter as the quantum interface to transfer the entanglement to the orbital angular momentum degree of freedom. Thus our results show a flexible way to create high-dimensional spatial mode entanglement. Moreover, they pave the way to implement broad complex quantum networks where high-dimensionally entangled states could be distributed over distant photonic chips.

  12. Influence of GaAsSb structural properties on the optical properties of InAs/GaAsSb quantum dots

    Science.gov (United States)

    Zhang, Zewen; Huang, Yidan; Reece, Peter J.; Bremner, Stephen P.

    2017-10-01

    The optical properties of InAs quantum dots with GaAsSb buffer, capping and cladding layers of different alloy compositions are studied by photoluminescence techniques. Fully strained GaAsSb layers show that the inclusion of a buffer layer gives a blue-shift to quantum dot emission, while for quantum dots capped with GaAsSb a clear red-shift is seen. Power-dependent photoluminescence suggests a transition from type-I to type-II can be achieved by GaAsSb at Sb composition between 11-13%, while the transition for the GaAsSb cladding layer occurs at around 11%. At low Sb composition, good crystal quality and energy barrier are detected by temperature-dependent photoluminescence, while high-level dislocation and defects exist under high antimony content, as evidenced by X-Ray Diffraction and Transmission Electron Microscopy.

  13. Device Characterization of High Performance Quantum Dot Comb Laser

    KAUST Repository

    Rafi, Kazi

    2012-02-01

    The cost effective comb based laser sources are considered to be one of the prominent emitters used in optical communication (OC) and photonic integrated circuits (PIC). With the rising demand for delivering triple-play services (voice, data and video) in FTTH and FTTP-based WDM-PON networks, metropolitan area network (MAN), and short-reach rack-to-rack optical computer communications, a versatile and cost effective WDM transmitter design is required, where several DFB lasers can be replaced by a cost effective broadband comb laser to support on-chip optical signaling. Therefore, high performance quantum dot (Q.Dot) comb lasers need to satisfy several challenges before real system implementations. These challenges include a high uniform broadband gain spectrum from the active layer, small relative intensity noise with lower bit error rate (BER) and better temperature stability. Thus, such short wavelength comb lasers offering higher bandwidth can be a feasible solution to address these challenges. However, they still require thorough characterization before implementation. In this project, we briefly characterized the novel quantum dot comb laser using duty cycle based electrical injection and temperature variations where we have observed the presence of reduced thermal conductivity in the active layer. This phenomenon is responsible for the degradation of device performance. Hence, different performance trends, such as broadband emission and spectrum stability were studied with pulse and continuous electrical pumping. The tested comb laser is found to be an attractive solution for several applications but requires further experiments in order to be considered for photonic intergraded circuits and to support next generation computer-communications.

  14. Experimental observation of spatially resolved photo-luminescence intensity distribution in dual mode upconverting nanorod bundles

    Science.gov (United States)

    Kumar, Pawan; Singh, Satbir; Singh, V. N.; Singh, Nidhi; Gupta, R. K.; Gupta, Bipin Kumar

    2017-02-01

    A novel method for demonstration of photoluminescence intensity distribution in upconverting nanorod bundles using confocal microscopy is reported. Herein, a strategy for the synthesis of highly luminescent dual mode upconverting/downshift Y1.94O3:Ho3+0.02/Yb3+0.04 nanorod bundles by a facile hydrothermal route has been introduced. These luminescent nanorod bundles exhibit strong green emission at 549 nm upon excitations at 449 nm and 980 nm with quantum efficiencies of ~6.3% and ~1.1%, respectively. The TEM/HRTEM results confirm that these bundles are composed of several individual nanorods with diameter of ~100 nm and length in the range of 1-3 μm. Furthermore, two dimensional spatially resolved photoluminescence intensity distribution study has been carried out using confocal photoluminescence microscope throughout the nanorod bundles. This study provides a new direction for the potential use of such emerging dual mode nanorod bundles as photon sources for next generation flat panel optical display devices, bio-medical applications, luminescent security ink and enhanced energy harvesting in photovoltaic applications.

  15. Ultrafast Method for Selective Design of Graphene Quantum Dots with Highly Efficient Blue Emission

    Science.gov (United States)

    Kang, Suk Hyun; Mhin, Sungwook; Han, Hyuksu; Kim, Kang Min; Jones, Jacob L.; Ryu, Jeong Ho; Kang, Ju Seop; Kim, Shin Hee; Shim, Kwang Bo

    2016-12-01

    Graphene quantum dots (GQDs) have attractive properties and potential applications. However, their various applications are limited by a current synthetic method which requires long processing time. Here, we report a facile and remarkably rapid method for production of GQDs exhibiting excellent optoelectronic properties. We employed the pulsed laser ablation (PLA) technique to exfoliate GQDs from multi-wall carbon nanotube (MWCNTs), which can be referred to as a pulsed laser exfoliation (PLE) process. Strikingly, it takes only 6 min to transform all MWCNTs precursors to GQDs by using PLE process. Furthermore, we could selectively produce either GQDs or graphene oxide quantum dots (GOQDs) by simply changing the organic solvents utilized in the PLE processing. The synthesized GQDs show distinct blue photoluminescence (PL) with excellent quantum yield (QY) up to 12% as well as sufficient brightness and resolution to be suitable for optoelectronic applications. We believe that the PLE process proposed in this work will further open up new routes for the preparation of different optoelectronic nanomaterials.

  16. One-step synthesis of photoluminescent carbon dots with excitation-independent emission for selective bioimaging and gene delivery.

    Science.gov (United States)

    Yang, Xudong; Wang, Yang; Shen, Xiran; Su, Chunyan; Yang, Jinghua; Piao, Mingjun; Jia, Fei; Gao, Guanghui; Zhang, Long; Lin, Quan

    2017-04-15

    Photoluminescent carbon dots (C-dots), as new members of the quantum sized carbon analogues have attracted significant attention due to their unique size, less toxicity, good compatibility and relatively easy surface modification. In this work, we report a simple, low-cost and one-step hydrothermal carbonization approach to synthesize the positively charged C-dots using PEI and FA. From the photoluminescence (PL) measurements, the as-prepared C-dots exhibit good stability and intense PL with the high quantum yield (QY) at Ca. 42%. Significantly, The as-prepared C-dots integrate the advantages of C-dots and PEI: the presence of C-dots can effectively decrease the cytotoxicity of PEI, the C-dots can be applied in biological system for selective imaging of folate receptor (FR)-positive cancerous cells from normal cells, while the cationic PEI with positive charges can make them link to plasmid DNA and efficiently transfect the therapeutic plasmid into cells. Therefore, the as-prepared with the facile synthesis method can be a promising photoluminescent probe for cancer diagnosis and gene therapy. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Highly aqueous soluble CaF2:Ce/Tb nanocrystals: effect of surface functionalization on structural, optical band gap, and photoluminescence properties.

    Science.gov (United States)

    Ansari, Anees A; Parchur, Abdul K; Kumar, Brijesh; Rai, S B

    2016-12-01

    decomposition rout shows high dispersibility in aqueous solvents with enhanced photoluminescence. The epitaxial growth of inert CaF2 shell and further amorphous silica, respectively, enhanced their optical and luminescence properties, which is highly usable for luminescent biolabeling, and optical bioprobe etc.

  18. Highly selective detection of phosphate ion based on a single-layered graphene quantum dots-Al3+ strategy.

    Science.gov (United States)

    Chen, Bin Bin; Sheng Li, Rong; Li Liu, Meng; Yan Zou, Hong; Liu, Hui; Huang, Cheng Zhi

    2018-02-01

    Determination of phosphate ion (PO43-) is important in biomedical and environmental arrays because its controlling concentrations are associated with different pathologies or the quality of water. Herein, we report a new type of photoluminescence (PL) probe for highly selective detection of PO43- based on a single-layered graphene quantum dots chelating with aluminium ions (s-GQDs-Al3+) system. The PL of s-GQDs can be enhanced by Al3+ through the aggregation-induced emission enhancement (AIEE) effect. With the addition of PO43-, the PL of the s-GQDs-Al3+ system is faded away because PO43- has stronger coordination with Al3+ which results in the elimination of AIEE effect and the decrease in the PL intensity of the s-GQDs-Al3+ system. Therefore, the s-GQDs-Al3+ system can behave as an on-off type PL probe for PO43- detection. It is found that the PL intensity ratio (I/I0) of s-GQDs in the presence of Al3+ at 463nm is proportional to the concentration of PO43- in the range of 0.25-7.5μM with the limit of detection as low as 0.1μM. This selective assay has a great application prospect in the complex matrixes owing to its simplicity and specificity for PO43- detection. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. One-pot synthesis of highly luminescent carbon quantum dots and their nontoxic ingestion by zebrafish for in vivo imaging.

    Science.gov (United States)

    Huang, Yi-Fan; Zhou, Xin; Zhou, Rong; Zhang, Hong; Kang, Kai-Bin; Zhao, Min; Peng, Yong; Wang, Qiang; Zhang, Hao-Li; Qiu, Wen-Yuan

    2014-05-05

    Photoluminescent carbon and/or silicon-based nanodots have attracted ever increasing interest. Accordingly, a myriad of synthetic methodologies have been developed to fabricate them, which unfortunately, however, frequently involve relatively tedious steps, such as initial surface passivation and subsequent functionalization. Herein, we describe a green and sustainable synthetic strategy to combine these procedures into one step and to produce highly luminescent carbon quantum dots (CQDs), which can also be easily fabricated into flexible thin films with intense luminescence for future roll-to-roll manufacturing of optoelectronic devices. The as-synthesized CQDs exhibited enhanced cellular permeability and low or even noncytotoxicity for cellular applications, as corroborated by confocal fluorescence imaging of HeLa cells as well as cell viability measurements. Most strikingly, zebrafish were directly fed with CQDs for in vivo imaging, and mortality and morphologic analysis indicated ingestion of the CQDs posed no harm to the living organisms. Hence, the multifunctional CQDs potentially provide a rich pool of tools for optoelectronic and biomedical applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

    Science.gov (United States)

    Morrison, C.; Casteleiro, C.; Leadley, D. R.; Myronov, M.

    2016-09-01

    The complex quantum transport of a strained Ge quantum well (QW) modulation doped heterostructure with two types of mobile carriers has been observed. The two dimensional hole gas (2DHG) in the Ge QW exhibits an exceptionally high mobility of 780 000 cm2/Vs at temperatures below 10 K. Through analysis of Shubnikov de-Haas oscillations in the magnetoresistance of this 2DHG below 2 K, the hole effective mass is found to be 0.065 m0. Anomalous conductance peaks are observed at higher fields which deviate from standard Shubnikov de-Haas and quantum Hall effect behaviour due to conduction via multiple carrier types. Despite this complex behaviour, analysis using a transport model with two conductive channels explains this behaviour and allows key physical parameters such as the carrier effective mass, transport, and quantum lifetimes and conductivity of the electrically active layers to be extracted. This finding is important for electronic device applications, since inclusion of highly doped interlayers which are electrically active, for enhancement of, for example, room temperature carrier mobility, does not prevent analysis of quantum transport in a QW.

  1. Steady-state photoluminescent excitation characterization of semiconductor carrier recombination

    Energy Technology Data Exchange (ETDEWEB)

    Bhosale, J. S. [Intel Corporation, Hillsboro, Oregon 97124 (United States); Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Moore, J. E.; Wang, X.; Bermel, P.; Lundstrom, M. S. [Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2016-01-15

    Photoluminescence excitation spectroscopy is a contactless characterization technique that can provide valuable information about the surface and bulk recombination parameters of a semiconductor device, distinct from other sorts of photoluminescent measurements. For this technique, a temperature-tuned light emitting diode (LED) has several advantages over other light sources. The large radiation density offered by LEDs from near-infrared to ultraviolet region at a low cost enables efficient and fast photoluminescence measurements. A simple and inexpensive LED-based setup facilitates measurement of surface recombination velocity and bulk Shockley-Read-Hall lifetime, which are key parameters to assess device performance. Under the right conditions, this technique can also provide a contactless way to measure the external quantum efficiency of a solar cell.

  2. High-dimensional quantum key distribution based on multicore fiber using silicon photonic integrated circuits

    DEFF Research Database (Denmark)

    Ding, Yunhong; Bacco, Davide; Dalgaard, Kjeld

    2017-01-01

    -dimensional quantum states, and enables breaking the information efficiency limit of traditional quantum key distribution protocols. In addition, the silicon photonic circuits used in our work integrate variable optical attenuators, highly efficient multicore fiber couplers, and Mach-Zehnder interferometers, enabling......Quantum key distribution provides an efficient means to exchange information in an unconditionally secure way. Historically, quantum key distribution protocols have been based on binary signal formats, such as two polarization states, and the transmitted information efficiency of the quantum key...... is intrinsically limited to 1 bit/photon. Here we propose and experimentally demonstrate, for the first time, a high-dimensional quantum key distribution protocol based on space division multiplexing in multicore fiber using silicon photonic integrated lightwave circuits. We successfully realized three mutually...

  3. Large Stokes Shift and High Efficiency Luminescent Solar Concentrator Incorporated with CuInS2/ZnS Quantum Dots.

    Science.gov (United States)

    Li, Chen; Chen, Wei; Wu, Dan; Quan, Dunhang; Zhou, Ziming; Hao, Junjie; Qin, Jing; Li, Yiwen; He, Zhubing; Wang, Kai

    2015-12-08

    Luminescent solar concentrator (LSC) incorporated with quantum dots (QDs) have been widely regarded as one of the most important development trends of cost-effective solar energy. In this study, for the first time we report a new QDs-LSC integrated with heavy metal free CuInS2/ZnS core/shell QDs with large Stokes shift and high optical efficiency. The as-prepared CuInS2/ZnS QDs possess advantages of high photoluminescence quantum yield of 81% and large Stocks shift more than 150 nm. The optical efficiency of CuInS2/ZnS QDs-LSC reaches as high as 26.5%. Moreover, the power conversion efficiency of the QDs-LSC-PV device reaches more than 3 folds to that of pure PMMA-PV device. Furthermore, the PV device is able to harvest 4.91 folds solar energy with the assistance of this new CuInS2/ZnS QDs-LSC for the same size c-Si PV cell. The results demonstrate that this new CuInS2/ZnS QDs-LSC provides a promising way for the high efficiency, nonhazardous and low cost solar energy.

  4. Photoluminescent carbogenic nanoparticles directly derived from crude biomass

    KAUST Repository

    Krysmann, Marta J.

    2012-01-01

    We present an environmentally benign, energy efficient and readily scalable approach to synthesize photoluminescent carbogenic nanoparticles directly from soft tissue biomass. Our approach relies on the pyrolytic decomposition of grass that gives rise to the formation of well-defined nanoparticles. The carbogenic nanoparticles can be readily surface modified, generating a series of highly selective photoluminescent materials that exhibit remarkable stability upon prolonged exposure to aggressive, high-temperature, high-salinity environment. © 2012 The Royal Society of Chemistry.

  5. Highly luminescent hybrid SiO2-coated CdTe quantum dots: synthesis and properties.

    Science.gov (United States)

    Liu, Ning; Yang, Ping

    2013-01-01

    Novel hybrid SiO2-coated CdTe quantum dots (QDs) were created using CdTe QDs coated with a hybrid SiO2 shell containing Cd(2+) ions and a sulfur source via a sol-gel process in aqueous solution. Aqueous CdTe QDs with tunable emitting color created through a reaction between cadmium chloride and sodium hydrogen telluride was used as cores for the preparation of hybrid SiO2-coated CdTe QDs. In our experiments we found that the surface state of the cores and preparation conditions that affect the formation of the hybrid SiO2 shell also greatly affect photoluminescence of the hybrid SiO2-coated CdTe QDs. The generation of CdS-like clusters in the vicinity of the CdTe QDs, caused the quantum size effect of the QDs to be greatly reduced, which changes photoluminescence properties of the hybrid QDs fundamentally. Namely, the novel hybrid SiO2 shell played an important role in generating a series of specific optical properties. In addition, the novel hybrid SiO2 shell can be created if no CdTe QD is added. In order to gain an insight into the inter structure of the hybrid shell, we characterized the hybrid SiO2-coated CdTe QDs using X-ray diffraction analysis and discuss the formation mechanism of such a hybrid structure. This work is significant because the novel hybrid SiO2-coated CdTe QDs with its excellent properties can be used in many applications, such as biolabeling and optoelectronic devices. Copyright © 2013 John Wiley & Sons, Ltd.

  6. Photoluminescence Properties of β-Ga2O3 Thin Films Produced by Ion-Plasma Sputtering

    Science.gov (United States)

    Bordun, O. M.; Bordun, B. O.; Kukharskyy, I. Yo.; Medvid, I. I.

    2017-03-01

    Photoluminescence and photoexcitation spectra of β-Ga2O3 thin films prepared by high-frequency ion-plasma sputtering in an Ar atmosphere were investigated. Photoluminescence spectra were deconvoluted by the Alentsev—Fock method into ultimate constituents. The nature of two strong bands with maxima at 2.95 and 3.14 eV and two weak bands with maxima at 3.90 and 4.25 eV was discussed. The two strong bands were attributed to an associate originating from the interaction of oxygen and gallium vacancies; the weak ones, recombination of excitons in quantum wells formed by acceptor clusters. It was found that the damping time constant for the 3.14-eV band was 105 μs; for the 2.95-eV band, 114 μs. The similarity of the decay time constants for these bands confirmed their relationship to a common associate.

  7. Highly Luminescent Water-Dispersible NIR-Emitting Wurtzite CuInS2/ZnS Core/Shell Colloidal Quantum Dots

    Science.gov (United States)

    2017-01-01

    Copper indium sulfide (CIS) quantum dots (QDs) are attractive as labels for biomedical imaging, since they have large absorption coefficients across a broad spectral range, size- and composition-tunable photoluminescence from the visible to the near-infrared, and low toxicity. However, the application of NIR-emitting CIS QDs is still hindered by large size and shape dispersions and low photoluminescence quantum yields (PLQYs). In this work, we develop an efficient pathway to synthesize highly luminescent NIR-emitting wurtzite CIS/ZnS QDs, starting from template Cu2-xS nanocrystals (NCs), which are converted by topotactic partial Cu+ for In3+ exchange into CIS NCs. These NCs are subsequently used as cores for the overgrowth of ZnS shells (≤1 nm thick). The CIS/ZnS core/shell QDs exhibit PL tunability from the first to the second NIR window (750–1100 nm), with PLQYs ranging from 75% (at 820 nm) to 25% (at 1050 nm), and can be readily transferred to water upon exchange of the native ligands for mercaptoundecanoic acid. The resulting water-dispersible CIS/ZnS QDs possess good colloidal stability over at least 6 months and PLQYs ranging from 39% (at 820 nm) to 6% (at 1050 nm). These PLQYs are superior to those of commonly available water-soluble NIR-fluorophores (dyes and QDs), making the hydrophilic CIS/ZnS QDs developed in this work promising candidates for further application as NIR emitters in bioimaging. The hydrophobic CIS/ZnS QDs obtained immediately after the ZnS shelling are also attractive as fluorophores in luminescent solar concentrators. PMID:28638177

  8. On-chip generation of high-dimensional entangled quantum states and their coherent control.

    Science.gov (United States)

    Kues, Michael; Reimer, Christian; Roztocki, Piotr; Cortés, Luis Romero; Sciara, Stefania; Wetzel, Benjamin; Zhang, Yanbing; Cino, Alfonso; Chu, Sai T; Little, Brent E; Moss, David J; Caspani, Lucia; Azaña, José; Morandotti, Roberto

    2017-06-28

    Optical quantum states based on entangled photons are essential for solving questions in fundamental physics and are at the heart of quantum information science. Specifically, the realization of high-dimensional states (D-level quantum systems, that is, qudits, with D > 2) and their control are necessary for fundamental investigations of quantum mechanics, for increasing the sensitivity of quantum imaging schemes, for improving the robustness and key rate of quantum communication protocols, for enabling a richer variety of quantum simulations, and for achieving more efficient and error-tolerant quantum computation. Integrated photonics has recently become a leading platform for the compact, cost-efficient, and stable generation and processing of non-classical optical states. However, so far, integrated entangled quantum sources have been limited to qubits (D = 2). Here we demonstrate on-chip generation of entangled qudit states, where the photons are created in a coherent superposition of multiple high-purity frequency modes. In particular, we confirm the realization of a quantum system with at least one hundred dimensions, formed by two entangled qudits with D = 10. Furthermore, using state-of-the-art, yet off-the-shelf telecommunications components, we introduce a coherent manipulation platform with which to control frequency-entangled states, capable of performing deterministic high-dimensional gate operations. We validate this platform by measuring Bell inequality violations and performing quantum state tomography. Our work enables the generation and processing of high-dimensional quantum states in a single spatial mode.

  9. Ionization effects on spectral signatures of quantum-path interference in high-harmonic generation.

    Science.gov (United States)

    Holler, M; Zaïr, A; Schapper, F; Auguste, T; Cormier, E; Wyatt, A; Monmayrant, A; Walmsley, I A; Gallmann, L; Salières, P; Keller, U

    2009-03-30

    The interference between the emission originating from the short and long electron quantum paths is intrinsic to the high harmonic generation process. We investigate the universal properties of these quantum-path interferences in various generation media and discuss how ionization effects influence the observed interference structures. Our comparison of quantum-path interferences observed in xenon, argon, and neon demonstrates that our experimental tools are generally applicable and should also allow investigating more complex systems such as molecules or clusters.

  10. On-chip generation of high-dimensional entangled quantum states and their coherent control

    Science.gov (United States)

    Kues, Michael; Reimer, Christian; Roztocki, Piotr; Cortés, Luis Romero; Sciara, Stefania; Wetzel, Benjamin; Zhang, Yanbing; Cino, Alfonso; Chu, Sai T.; Little, Brent E.; Moss, David J.; Caspani, Lucia; Azaña, José; Morandotti, Roberto

    2017-06-01

    Optical quantum states based on entangled photons are essential for solving questions in fundamental physics and are at the heart of quantum information science. Specifically, the realization of high-dimensional states (D-level quantum systems, that is, qudits, with D > 2) and their control are necessary for fundamental investigations of quantum mechanics, for increasing the sensitivity of quantum imaging schemes, for improving the robustness and key rate of quantum communication protocols, for enabling a richer variety of quantum simulations, and for achieving more efficient and error-tolerant quantum computation. Integrated photonics has recently become a leading platform for the compact, cost-efficient, and stable generation and processing of non-classical optical states. However, so far, integrated entangled quantum sources have been limited to qubits (D = 2). Here we demonstrate on-chip generation of entangled qudit states, where the photons are created in a coherent superposition of multiple high-purity frequency modes. In particular, we confirm the realization of a quantum system with at least one hundred dimensions, formed by two entangled qudits with D = 10. Furthermore, using state-of-the-art, yet off-the-shelf telecommunications components, we introduce a coherent manipulation platform with which to control frequency-entangled states, capable of performing deterministic high-dimensional gate operations. We validate this platform by measuring Bell inequality violations and performing quantum state tomography. Our work enables the generation and processing of high-dimensional quantum states in a single spatial mode.

  11. Highly Efficient Perovskite-Quantum-Dot Light-Emitting Diodes by Surface Engineering

    KAUST Repository

    Pan, Jun

    2016-08-16

    A two-step ligand-exchange strategy is developed, in which the long-carbon-chain ligands on all-inorganic perovskite (CsPbX3, X = Br, Cl) quantum dots (QDs) are replaced with halide-ion-pair ligands. Green and blue light-emitting diodes made from the halide-ion-paircapped quantum dots exhibit high external quantum efficiencies compared with the untreated QDs.

  12. Matrix Sputtering Method: A Novel Physical Approach for Photoluminescent Noble Metal Nanoclusters.

    Science.gov (United States)

    Ishida, Yohei; Corpuz, Ryan D; Yonezawa, Tetsu

    2017-12-19

    variety of photoluminescent monometallic nanoclusters of Au, Ag, and Cu, all of which showed stable emission in both solution and solid form via our matrix sputtering method with the induction of cationic-, neutral-, and anionic-charged thiol ligands. We also succeeded in synthesizing photoluminescent bimetallic Au-Ag nanoclusters that showed tunable emission within the UV-NIR region by controlling the composition of the atomic ratio by a double-target sputtering technique. Most importantly, we have revealed the formation mechanism of these unique photoluminescent nanoclusters by sputtering, which had relatively larger diameters (ca. 1-3 nm) as determined using TEM and stronger emission quantum yield (max. 16.1%) as compared to typical photoluminescent nanoclusters prepared by chemical means. We believe the high tunability of sputtering systems presented here has significant advantages for creating novel photoluminescent nanoclusters as a complementary strategy to common chemical methods. This Account highlights our journey toward understanding the photophysical properties and formation mechanism of photoluminescent noble metal nanoclusters via the sputtering method, a novel strategy that will contribute widely to the body of scientific knowledge of metal nanoparticles and nanoclusters.

  13. Storing quantum information in spins and high-sensitivity ESR.

    Science.gov (United States)

    Morton, John J L; Bertet, Patrice

    2018-02-01

    Quantum information, encoded within the states of quantum systems, represents a novel and rich form of information which has inspired new types of computers and communications systems. Many diverse electron spin systems have been studied with a view to storing quantum information, including molecular radicals, point defects and impurities in inorganic systems, and quantum dots in semiconductor devices. In these systems, spin coherence times can exceed seconds, single spins can be addressed through electrical and optical methods, and new spin systems with advantageous properties continue to be identified. Spin ensembles strongly coupled to microwave resonators can, in principle, be used to store the coherent states of single microwave photons, enabling so-called microwave quantum memories. We discuss key requirements in realising such memories, including considerations for superconducting resonators whose frequency can be tuned onto resonance with the spins. Finally, progress towards microwave quantum memories and other developments in the field of superconducting quantum devices are being used to push the limits of sensitivity of inductively-detected electron spin resonance. The state-of-the-art currently stands at around 65 spins per Hz, with prospects to scale down to even fewer spins. Copyright © 2017. Published by Elsevier Inc.

  14. High threshold distributed quantum computing with three-qubit nodes

    Science.gov (United States)

    Li, Ying; Benjamin, Simon C.

    2012-09-01

    In the distributed quantum computing paradigm, well-controlled few-qubit ‘nodes’ are networked together by connections which are relatively noisy and failure prone. A practical scheme must offer high tolerance to errors while requiring only simple (i.e. few-qubit) nodes. Here we show that relatively modest, three-qubit nodes can support advanced purification techniques and so offer robust scalability: the infidelity in the entanglement channel may be permitted to approach 10% if the infidelity in local operations is of order 0.1%. Our tolerance of network noise is therefore an order of magnitude beyond prior schemes, and our architecture remains robust even in the presence of considerable decoherence rates (memory errors). We compare the performance with that of schemes involving nodes of lower and higher complexity. Ion traps, and NV-centres in diamond, are two highly relevant emerging technologies: they possess the requisite properties of good local control, rapid and reliable readout, and methods for entanglement-at-a-distance.

  15. Submonolayer Quantum Dots for High Speed Surface Emitting Lasers

    Directory of Open Access Journals (Sweden)

    Zakharov ND

    2007-01-01

    Full Text Available AbstractWe report on progress in growth and applications of submonolayer (SML quantum dots (QDs in high-speed vertical-cavity surface-emitting lasers (VCSELs. SML deposition enables controlled formation of high density QD arrays with good size and shape uniformity. Further increase in excitonic absorption and gain is possible with vertical stacking of SML QDs using ultrathin spacer layers. Vertically correlated, tilted or anticorrelated arrangements of the SML islands are realized and allow QD strain and wavefunction engineering. Respectively, both TE and TM polarizations of the luminescence can be achieved in the edge-emission using the same constituting materials. SML QDs provide ultrahigh modal gain, reduced temperature depletion and gain saturation effects when used in active media in laser diodes. Temperature robustness up to 100 °C for 0.98 μm range vertical-cavity surface-emitting lasers (VCSELs is realized in the continuous wave regime. An open eye 20 Gb/s operation with bit error rates better than 10−12has been achieved in a temperature range 25–85 °Cwithout current adjustment. Relaxation oscillations up to ∼30 GHz have been realized indicating feasibility of 40 Gb/s signal transmission.

  16. Highly Efficient Inverted Structural Quantum Dot Solar Cells.

    Science.gov (United States)

    Wang, Ruili; Wu, Xun; Xu, Kaimin; Zhou, Wenjia; Shang, Yuequn; Tang, Haoying; Chen, Hao; Ning, Zhijun

    2018-01-08

    Highly efficient PbS colloidal quantum dot (QD) solar cells based on an inverted structure have been missing for a long time. The bottlenecks are the construction of an effective p-n heterojunction at the illumination side with smooth band alignment and the absence of serious interface carrier recombination. Here, solution-processed nickel oxide (NiO) as the p-type layer and lead sulfide (PbS) QDs with iodide ligand as the n-type layer are explored to build a p-n heterojunction at the illumination side. The large depletion region in the QD layer at the illumination side leads to high photocurrent. Interface carrier recombination at the interface is effectively prohibited by inserting a layer of slightly doped p-type QDs with 1,2-ethanedithiol as ligands, leading to improved voltage of the device. Based on this graded device structure design, the efficiency of inverted structural heterojunction PbS QD solar cells is improved to 9.7%, one time higher than the highest efficiency achieved before. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Theoretical Study of Operational Limits of High-Speed Quantum Dot Lasers

    Science.gov (United States)

    2012-09-09

    strained -layer InGaAs quantum - well improvement of an InAs quantum dot AlGaAs –GaAs– InGaAs –InAs... AlGaAs –GaAs– InGaAs heterostructure diode laser operation Appl. Phys. Lett. 80 1126–8 [20] Walter G, Chung T and Holonyak N 2002 Coupled-stripe quantum - well ...8] Tokranov V, Yakimov M, van Eisden J and Oktyabrsky S 2006 Tunnel quantum well -on-dots InGaAs –InAs high-gain medium for laser diodes Proc.

  18. Engineering two-photon high-dimensional states through quantum interference.

    Science.gov (United States)

    Zhang, Yingwen; Roux, Filippus S; Konrad, Thomas; Agnew, Megan; Leach, Jonathan; Forbes, Andrew

    2016-02-01

    Many protocols in quantum science, for example, linear optical quantum computing, require access to large-scale entangled quantum states. Such systems can be realized through many-particle qubits, but this approach often suffers from scalability problems. An alternative strategy is to consider a lesser number of particles that exist in high-dimensional states. The spatial modes of light are one such candidate that provides access to high-dimensional quantum states, and thus they increase the storage and processing potential of quantum information systems. We demonstrate the controlled engineering of two-photon high-dimensional states entangled in their orbital angular momentum through Hong-Ou-Mandel interference. We prepare a large range of high-dimensional entangled states and implement precise quantum state filtering. We characterize the full quantum state before and after the filter, and are thus able to determine that only the antisymmetric component of the initial state remains. This work paves the way for high-dimensional processing and communication of multiphoton quantum states, for example, in teleportation beyond qubits.

  19. Development of a photomultiplier tube with high quantum efficiency

    CERN Document Server

    Shima, T

    1999-01-01

    We propose a new method to significantly increase the quantum efficiency of a photomultiplier tube by employing a multi-photocathode and a mirror to produce photoelectrons by reusing photons transmitted by a single photocathode. In order to estimate the expected performance of the new photomultiplier, we studied the spectral responses of the reflectance, transmittance, and quantum efficiency of a K sub 2 CsSb photocathode as a function of the wavelength of incident light. A large enhancement of the quantum efficiency is expected in the regions between lambda=280 and 650 nm. (author)

  20. Creating high yield water soluble luminescent graphene quantum dots via exfoliating and disintegrating carbon nanotubes and graphite flakes.

    Science.gov (United States)

    Lin, Liangxu; Zhang, Shaowei

    2012-10-21

    We have developed an effective method to exfoliate and disintegrate multi-walled carbon nanotubes and graphite flakes. With this technique, high yield production of luminescent graphene quantum dots with high quantum yield and low oxidization can be achieved.

  1. Macroscopic quantum electrodynamics of high-Q cavities

    Energy Technology Data Exchange (ETDEWEB)

    Khanbekyan, Mikayel

    2009-10-27

    In this thesis macroscopic quantum electrodynamics in linear media was applied in order to develop an universally valid quantum theory for the description of the interaction of the electromagnetic field with atomic sources in high-Q cavities. In this theory a complete description of the characteristics of the emitted radiation is given. The theory allows to show the limits of the applicability of the usually applied theory. In order to establish an as possible generally valid theory first the atom-field interaction was studied in the framework of macroscopic quantum electrodynamics in dispersive and absorptive media. In order to describe the electromagnetic field from Maxwell's equations was started, whereby the noise-current densities, which are connected with the absorption of the medium, were included. The solution of these equations expresses the electromagnetic field variables by the noise-current densities by means of Green's tensor of the macroscopic Maxwell equations. The explicit quantization is performed by means of the noise-current densities, whereby a diagonal Hamiltonian is introduced, which then guarantees the time development according to Maxwell's equation and the fulfillment of the fundamental simultaneous commutation relations of the field variables. In the case of the interaction of the medium-supported field with atoms the Hamiltonian must be extended by atom-field interactions energies, whereby the canonical coupling schemes of the minimal or multipolar coupling can be used. The dieelectric properties of the material bodies as well as their shape are coded in the Green tensor of the macroscopic Maxwell equations. As preparing step first the Green tensor was specified in order to derive three-dimensional input-output relations for the electromagnetic field operators on a plane multilayer structure. Such a general dewscription of the electromagnetic field allows the inclusion both of dispersion and absorption of the media and the

  2. 2-(2-Hydroxyphenyl)benzimidazole-based four-coordinate boron-containing materials with highly efficient deep-blue photoluminescence and electroluminescence.

    Science.gov (United States)

    Zhang, Zhenyu; Zhang, Houyu; Jiao, Chuanjun; Ye, Kaiqi; Zhang, Hongyu; Zhang, Jingying; Wang, Yue

    2015-03-16

    Two novel four-coordinate boron-containing emitters 1 and 2 with deep-blue emissions were synthesized by refluxing a 2-(2-hydroxyphenyl)benzimidazole ligand with triphenylborane or bromodibenzoborole. The boron chelation produced a new π-conjugated skeleton, which rendered the synthesized boron materials with intense fluorescence, good thermal stability, and high carrier mobility. Both compounds displayed deep-blue emissions in solutions with very high fluorescence quantum yields (over 0.70). More importantly, the samples showed identical fluorescence in the solution and solid states, and the efficiency was maintained at a high level (approximately 0.50) because of the bulky substituents between the boron atom and the benzimidazole unit, which can effectively separate the flat luminescent units. In addition, neat thin films composed of 1 or 2 exhibited high electron and hole mobility in the same order of magnitude 10(-4), as determined by time-of-flight. The fabricated electroluminescent devices that employed 1 or 2 as emitting materials showed high-performance deep-blue emissions with Commission Internationale de L'Eclairage (CIE) coordinates of (X = 0.15, Y = 0.09) and (X = 0.16, Y = 0.08), respectively. Thus, the synthesized boron-containing materials are ideal candidates for fabricating high-performance deep-blue organic light-emitting diodes.

  3. High-density 1.54 μm InAs/InGaAlAs/InP(100) based quantum dots with reduced size inhomogeneity

    Science.gov (United States)

    Banyoudeh, Saddam; Reithmaier, Johann Peter

    2015-09-01

    Self-assembled InAs quantum dots (QDs) were grown by solid source molecular beam epitaxy. The impact of the growth parameters like the growth temperature of the InGaAlAs nucleation layer, V/III ratio and growth rate during growth of QD layers were carefully investigated by using atomic force microscopy and photoluminescence spectroscopy. The excellent size uniformity of InAs QDs grown on InP substrates are verified by narrow photoluminescence line widths of 17 meV for single QD layers and 26 meV for stacked QD layers, respectivaly. Both values measured at 10 K.

  4. Theoretical analysis of quantum dot amplifiers with high saturation power and low noise figure

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Mørk, Jesper

    2002-01-01

    Semiconductor quantum dot amplifiers are predicted to exhibit superior characteristics such as high gain, and output power and low noise. The analysis provides criteria and design guidelines for the realization of high quality amplifiers.......Semiconductor quantum dot amplifiers are predicted to exhibit superior characteristics such as high gain, and output power and low noise. The analysis provides criteria and design guidelines for the realization of high quality amplifiers....

  5. Glycerol-regulated facile synthesis and targeted cell imaging of highly luminescent Ag2Te quantum dots with tunable near-infrared emission.

    Science.gov (United States)

    Jin, Hui; Gui, Rijun; Sun, Jie; Wang, Yanfeng

    2016-07-01

    In this work, highly luminescent and emission tunable Ag2Te quantum dots (QDs) were facilely prepared by using water-dispersed glycerol as viscous solvent and CH3COOAg/Na2TeO3 as Ag/Te precursors. Viscous glycerol was utilized to slow the nucleation and growth of QDs at 200°C, and enabled the isolation of QDs with different emission wavelengths. Experimental results revealed that the as-prepared Ag2Te QDs exhibited tunable near-infrared emission from 930 to 1084nm, high photoluminescence (PL) quantum yields (QYs, more than 20%), good photostability and low cytotoxicity. After surface coating of a thin silica shell (∼1.4nm), the resulting NH2 terminated Ag2Te@SiO2-NH2 displayed enhanced PL QYs, higher photostability and biocompatibility when compared with the original Ag2Te QDs. Through a facile carboxy-amine coupling, folic acid (FA) was grafted with Ag2Te@SiO2-NH2 to form Ag2Te@SiO2-FA nanocomposites, which were used for targeted PL imaging of folate receptor over-expressed tumor cells. Copyright © 2016. Published by Elsevier B.V.

  6. High performance tunnel injection InGaN/GaN quantum Dot light emitting diodes emitting in the green (λ=495nm)

    KAUST Repository

    Zhang, Meng

    2011-05-01

    InGaN/GaN self-organized quantum dots with density of (2-5)×10 10 cm-2, internal quantum efficiency of 32% and a reduced recombination lifetime of 0.6 ns were grown by plasma assisted molecular beam epitaxy. The photoluminescence spectra of the dots peak at 495 nm at 300 K. The characteristics of tunnel injection InGaN/GaN quantum dot light emitting diodes are presented. The current density at maximum efficiency is 90.2 A/cm 2, which is superior to equivalent multiquantum well devices. © 2010 Elsevier B.V. All rights reserved.

  7. High-performance shortwave-infrared light-emitting devices using core-shell (PbS-CdS) colloidal quantum dots.

    Science.gov (United States)

    Supran, Geoffrey J; Song, Katherine W; Hwang, Gyu Weon; Correa, Raoul E; Scherer, Jennifer; Dauler, Eric A; Shirasaki, Yasuhiro; Bawendi, Moungi G; Bulović, Vladimir

    2015-02-25

    Core-shell PbS-CdS quantum dots enhance the peak external quantum efficiency of shortwave-infrared light-emitting devices by up to 50-100-fold (compared with core-only PbS devices). This is more than double the efficiency of previous quantum-dot light-emitting devices operating at wavelengths beyond 1 μm, and results from the passivation of the PbS cores by the CdS shells against in situ photoluminescence quenching. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Design of Quantum Dot-Conjugated Lipids for Long-Term, High-Speed Tracking Experiments on Cell Surfaces

    Science.gov (United States)

    Murcia, Michael J.; Minner, Daniel. E.; Mustata, Gina-Mirela; Ritchie, Kenneth; Naumann, Christoph A.

    2009-01-01

    The current study reports the facile design of quantum dot (QD)-conjugated lipids and their application to high-speed tracking experiments on cell surfaces. CdSe/ZnS core/shell QDs with two types of hydrophilic coatings, 2-(2-aminoethoxy)ethanol (AEE-coating) and a 60:40 molar mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol-2000] (LIPO-coating), are conjugated to sulfhydryl lipids via maleimide reactive groups on the QD surface. Prior to lipid conjugation, the colloidal stability of both types of coated QDs in aqueous solution is confirmed using fluorescence correlation spectroscopy. A sensitive assay based on single lipid tracking experiments on a planar solid-supported phospholipid bilayer is presented that establishes conditions of monovalent conjugation of QDs to lipids. The QD lipids are then employed as single molecule tracking probes in plasma membranes of several cell types. Initial tracking experiments at a frame rate of 30 fps corroborate that QD-lipids diffuse like dye-labeled lipids in the plasma membrane of COS-7, HEK-293, 3T3, and NRK cells, thus confirming monovalent labeling. Finally, QD-lipids are applied for the first time to high-speed single molecule imaging by tracking their lateral mobility in the plasma membrane of NRK fibroblasts with up to 1000 fps. Our high-speed tracking data, which are in excellent agreement to previous tracking experiments with larger 40nm Au labels, not only push the time resolution in long-time, continuous fluorescence-based single molecule tracking, but also show that highly photostable, photoluminescent nanoprobes of 10nm size can be employed (AEE-coated QDs). These probes are also attractive because, unlike Au nanoparticles, they facilitate complex multicolor experiments. PMID:18937457

  9. Coupling of erbium dopants to yttrium orthosilicate photonic crystal cavities for on-chip optical quantum memories

    Energy Technology Data Exchange (ETDEWEB)

    Miyazono, Evan; Zhong, Tian; Craiciu, Ioana; Kindem, Jonathan M.; Faraon, Andrei, E-mail: faraon@caltech.edu [T. J. Watson Laboratory of Applied Physics, California Institute of Technology, 1200 E California Blvd, Pasadena, California 91125 (United States)

    2016-01-04

    Erbium dopants in crystals exhibit highly coherent optical transitions well suited for solid-state optical quantum memories operating in the telecom band. Here, we demonstrate coupling of erbium dopant ions in yttrium orthosilicate to a photonic crystal cavity fabricated directly in the host crystal using focused ion beam milling. The coupling leads to reduction of the photoluminescence lifetime and enhancement of the optical depth in microns-long devices, which will enable on-chip quantum memories.

  10. High-speed linear optics quantum computing using active feed-forward.

    Science.gov (United States)

    Prevedel, Robert; Walther, Philip; Tiefenbacher, Felix; Böhi, Pascal; Kaltenbaek, Rainer; Jennewein, Thomas; Zeilinger, Anton

    2007-01-04

    As information carriers in quantum computing, photonic qubits have the advantage of undergoing negligible decoherence. However, the absence of any significant photon-photon interaction is problematic for the realization of non-trivial two-qubit gates. One solution is to introduce an effective nonlinearity by measurements resulting in probabilistic gate operations. In one-way quantum computation, the random quantum measurement error can be overcome by applying a feed-forward technique, such that the future measurement basis depends on earlier measurement results. This technique is crucial for achieving deterministic quantum computation once a cluster state (the highly entangled multiparticle state on which one-way quantum computation is based) is prepared. Here we realize a concatenated scheme of measurement and active feed-forward in a one-way quantum computing experiment. We demonstrate that, for a perfect cluster state and no photon loss, our quantum computation scheme would operate with good fidelity and that our feed-forward components function with very high speed and low error for detected photons. With present technology, the individual computational step (in our case the individual feed-forward cycle) can be operated in less than 150 ns using electro-optical modulators. This is an important result for the future development of one-way quantum computers, whose large-scale implementation will depend on advances in the production and detection of the required highly entangled cluster states.

  11. Formation mechanism and optimization of highly luminescent N-doped graphene quantum dots

    Science.gov (United States)

    Qu, Dan; Zheng, Min; Zhang, Ligong; Zhao, Haifeng; Xie, Zhigang; Jing, Xiabin; Haddad, Raid E.; Fan, Hongyou; Sun, Zaicheng

    2014-01-01

    Photoluminescent graphene quantum dots (GQDs) have received enormous attention because of their unique chemical, electronic and optical properties. Here a series of GQDs were synthesized under hydrothermal processes in order to investigate the formation process and optical properties of N-doped GQDs. Citric acid (CA) was used as a carbon precursor and self-assembled into sheet structure in a basic condition and formed N-free GQD graphite framework through intermolecular dehydrolysis reaction. N-doped GQDs were prepared using a series of N-containing bases such as urea. Detailed structural and property studies demonstrated the formation mechanism of N-doped GQDs for tunable optical emissions. Hydrothermal conditions promote formation of amide between –NH2 and –COOH with the presence of amine in the reaction. The intramoleculur dehydrolysis between neighbour amide and COOH groups led to formation of pyrrolic N in the graphene framework. Further, the pyrrolic N transformed to graphite N under hydrothermal conditions. N-doping results in a great improvement of PL quantum yield (QY) of GQDs. By optimized reaction conditions, the highest PL QY (94%) of N-doped GQDs was obtained using CA as a carbon source and ethylene diamine as a N source. The obtained N-doped GQDs exhibit an excitation-independent blue emission with single exponential lifetime decay. PMID:24938871

  12. Characteristics of exciton photoluminescence kinetics in low-dimensional silicon structures

    CERN Document Server

    Sachenko, A V; Manojlov, E G; Svechnikov, S V

    2001-01-01

    The time-resolved visible photoluminescence of porous nanocrystalline silicon films obtained by laser ablation have been measured within the temperature range 90-300 K. A study has been made of the interrelationship between photoluminescence characteristics (intensity, emission spectra, relaxation times, their temperature dependencies and structural and dielectric properties (size and shapes of Si nanocrystals, oxide phase of nanocrystal coating, porosity). A photoluminescence model is proposed that describes photon absorption and emission occurring in quantum-size Si nanocrystals while coupled subsystems of electron-hole pairs and excitons take part in the recombination. Possible excitonic Auger recombination mechanism in low-dimensional silicon structures is considered

  13. Internal quantum efficiency enhancement of GaInN/GaN quantum-well structures using Ag nanoparticles

    DEFF Research Database (Denmark)

    Iida, Daisuke; Fadil, Ahmed; Chen, Yuntian

    2015-01-01

    We report internal quantum efficiency enhancement of thin p-GaN green quantumwell structure using self-assembled Ag nanoparticles. Temperature dependent photoluminescence measurements are conducted to determine the internal quantum efficiency. The impact of excitation power density...

  14. Strain-Dependent Photoluminescence Behavior of CdSe/CdS Nanocrystals with Spherical, Linear, and Branched Topologies

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-08-13

    The photoluminescence of CdSe/CdS core/shell quantum dots, nanorods, and tetrapods is investigated as a function of applied hydrostatic and non-hydrostatic pressure. The optoelectronic properties of all three nanocrystal morphologies are affected by strain. Furthermore, it is demonstrated that the unique morphology of a tetrapod is highly sensitive to non-isotropic stress environments. Seeded tetrapods can thereby serve as an optical strain gauge, capable of measuring forces on the order of nanonewtons. We anticipate that a nanocrystal strain gauge with optical readout will be useful for applications ranging from sensitive optomechanical devices to investigations of biomechanical processes.

  15. A new switching characteristics of highly doped multi-quantum well

    CERN Document Server

    Song, C K

    1999-01-01

    A new type of hysteretic current-voltage characteristics, which switched from a low conductance off-state into a high conductance on-state at a threshold voltage and the high conductance state was sustained even when the bias voltage reduced below the threshold voltage, was experimentally observed for the highly doped multi-quantum well structure. The characteristics were attributed to confinement of electrons and impact ionization of the confined electrons out of the quantum wells. The test devices employing 10 periods of quantum wells were fabricated by using AlGaAs/GaAs semiconductor heterostructure and I-V characteristics were examined.

  16. Structure and photoluminescence properties of red-emitting apatite-type phosphor NaY9(SiO4)6O2:Sm3+ with excellent quantum efficiency and thermal stability for solid-state lighting.

    Science.gov (United States)

    Mei, Lefu; Liu, Haikun; Liao, Libing; Zhang, Yuanyuan; Kumar, R Vasant

    2017-11-09

    A novel red-emitting phosphor NaY9(SiO4)6O2:Sm3+ (NYS:Sm3+) was synthesized and the X-ray diffraction and high-resolution TEM testified that the NYS compound belongs to the apatite structure which crystallized in a hexagonal unit cell with space group P63/m. The novel phosphor boasts of such three advantageous properties as perfect compatible match with the commercial UV chips, 73.2% quantum efficiency and 90.9% thermal stability at 150 °C. Details are as follows. NYS:Sm3+ phosphor showed obvious absorption in the UV regions centered at 407 nm, which can be perfectly compatible with the commercial UV chips. The property investigations showed that NYS:Sm3+ phosphor emitted reddish emission with CIE coordination of (0.563, 0.417). The optimum quenching concentration of Sm3+ in NYS phosphor was about 10%mol, and the corresponding concentration quenching mechanism was verified to be the electric dipole-dipole interaction. Upon excitation at 407 nm, the composition-optimized NYS:0.10Sm3+ exhibited a high quantum efficiency of 73.2%, and its luminescence intensity at 150 °C decreased simply to 90.9% of the initial value at room temperature. All of the results indicated that NYS:Sm3+ is a promising candidate as a reddish-emitting UV convertible phosphor for application in white light emitting diodes (w-LEDs).

  17. High density InAlAs/GaAlAs quantum dots for non-linear optics in microcavities

    Energy Technology Data Exchange (ETDEWEB)

    Kuszelewicz, R.; Benoit, J.-M.; Barbay, S.; Lemaitre, A.; Patriarche, G.; Meunier, K. [Laboratoire de Photonique et Nanostructures, Route de Nozay, Marcoussis 91460 (France); Tierno, A.; Ackemann, T. [University of Strathclyde, Glasgow (United Kingdom)

    2012-02-15

    Structural and optical properties of InAlAs/GaAlAs quantum dots grown by molecular beam epitaxy are studied using transmission electron microscopy and temperature- and time-resolved photoluminescence. The control of the recombination lifetime (50 ps-1.25 ns) and of the dot density (5.10{sup -8}-2.10{sup 11} cm{sup -3}) strongly suggest that these material systems can find wide applications in opto-electronic devices as focusing non-linear dispersive materials as well as fast saturable absorbers.

  18. High-Dimensional Single-Photon Quantum Gates: Concepts and Experiments

    Science.gov (United States)

    Babazadeh, Amin; Erhard, Manuel; Wang, Feiran; Malik, Mehul; Nouroozi, Rahman; Krenn, Mario; Zeilinger, Anton

    2017-11-01

    Transformations on quantum states form a basic building block of every quantum information system. From photonic polarization to two-level atoms, complete sets of quantum gates for a variety of qubit systems are well known. For multilevel quantum systems beyond qubits, the situation is more challenging. The orbital angular momentum modes of photons comprise one such high-dimensional system for which generation and measurement techniques are well studied. However, arbitrary transformations for such quantum states are not known. Here we experimentally demonstrate a four-dimensional generalization of the Pauli X gate and all of its integer powers on single photons carrying orbital angular momentum. Together with the well-known Z gate, this forms the first complete set of high-dimensional quantum gates implemented experimentally. The concept of the X gate is based on independent access to quantum states with different parities and can thus be generalized to other photonic degrees of freedom and potentially also to other quantum systems.

  19. High-Dimensional Single-Photon Quantum Gates: Concepts and Experiments.

    Science.gov (United States)

    Babazadeh, Amin; Erhard, Manuel; Wang, Feiran; Malik, Mehul; Nouroozi, Rahman; Krenn, Mario; Zeilinger, Anton

    2017-11-03

    Transformations on quantum states form a basic building block of every quantum information system. From photonic polarization to two-level atoms, complete sets of quantum gates for a variety of qubit systems are well known. For multilevel quantum systems beyond qubits, the situation is more challenging. The orbital angular momentum modes of photons comprise one such high-dimensional system for which generation and measurement techniques are well studied. However, arbitrary transformations for such quantum states are not known. Here we experimentally demonstrate a four-dimensional generalization of the Pauli X gate and all of its integer powers on single photons carrying orbital angular momentum. Together with the well-known Z gate, this forms the first complete set of high-dimensional quantum gates implemented experimentally. The concept of the X gate is based on independent access to quantum states with different parities and can thus be generalized to other photonic degrees of freedom and potentially also to other quantum systems.

  20. Versatile Tri(pyrazolyl)phosphanes as Phosphorus Precursors for the Synthesis of Highly Emitting InP/ZnS Quantum Dots.

    Science.gov (United States)

    Panzer, René; Guhrenz, Chris; Haubold, Danny; Hübner, René; Gaponik, Nikolai; Eychmüller, Alexander; Weigand, Jan J

    2017-08-22

    Tri(pyrazolyl)phosphanes (5(R1,R2) ) are utilized as an alternative, cheap and low-toxic phosphorus source for the convenient synthesis of InP/ZnS quantum dots (QDs). From these precursors, remarkably long-term stable stock solutions (>6 months) of P(OLA)3 (OLAH=oleylamine) are generated from which the respective pyrazoles are conveniently recovered. P(OLA)3 acts simultaneously as phosphorus source and reducing agent in the synthesis of highly emitting InP/ZnS core/shell QDs. These QDs are characterized by a spectral range between 530-620 nm and photoluminescence quantum yields (PL QYs) between 51-62 %. A proof-of-concept white light-emitting diode (LED) applying the InP/ZnS QDs as a color-conversion layer was built to demonstrate their applicability and processibility. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Origin of the green photoluminescence from zinc sulfide nanobelts

    Science.gov (United States)

    Ye, Changhui; Fang, Xiaosheng; Li, Guanghai; Zhang, Lide

    2004-10-01

    ZnS nanobelts with a pure wurtzite phase have been synthesized by a thermal evaporation method with the assistance of H2S in an Ar atmosphere. Photoluminescence band centered at about 535nm has been observed under excitation in the range of 250-480nm with decay rate as short as 860ps. The origin of this intense photoluminescence is related to elemental sulfur species on the surface of the ZnS nanobelts. This assignment is substantiated by structural analysis by high-resolution electron microscopy, x-ray photoelectron spectroscopy, and photoluminescence and excitation technique. ZnS nanobelts with intense surface photoluminescence could be used as effective green light emitters, humid sensors, and UV light detectors.

  2. Nano-patterned superconducting surface for high quantum efficiency cathode

    Science.gov (United States)

    Hannon, Fay; Musumeci, Pietro

    2017-03-07

    A method for providing a superconducting surface on a laser-driven niobium cathode in order to increase the effective quantum efficiency. The enhanced surface increases the effective quantum efficiency by improving the laser absorption of the surface and enhancing the local electric field. The surface preparation method makes feasible the construction of superconducting radio frequency injectors with niobium as the photocathode. An array of nano-structures are provided on a flat surface of niobium. The nano-structures are dimensionally tailored to interact with a laser of specific wavelength to thereby increase the electron yield of the surface.

  3. Luminescent carbon quantum dots with high quantum yield as a single white converter for white light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Feng, X. T.; Zhang, Y.; Liu, X. G., E-mail: liuxuguang@tyut.edu.cn [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Zhang, F.; Wang, Y. L.; Yang, Y. Z., E-mail: yyztyut@126.com [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China)

    2015-11-23

    Carbon quantum dots (CQDs) with high quantum yield (51.4%) were synthesized by a one-step hydrothermal method using thiosalicylic acid and ethylenediamine as precursor. The CQDs have the average diameter of 2.3 nm and possess excitation-independent emission wavelength in the range from 320 to 440 nm excitation. Under an ultraviolet (UV) excitation, the CQDs aqueous solutions emit bright blue fluorescence directly and exhibit broad emission with a high spectral component ratio of 67.4% (blue to red intensity to total intensity). We applied the CQDs as a single white-light converter for white light emitting diodes (WLEDs) using a UV-LED chip as the excitation light source. The resulted WLED shows superior performance with corresponding color temperature of 5227 K and the color coordinates of (0.34, 0.38) belonging to the white gamut.

  4. Photovoltaic infrared photoresponse of the high-mobility graphene quantum Hall system due to cyclotron resonance

    Science.gov (United States)

    Masubuchi, Satoru; Onuki, Masahiro; Arai, Miho; Yamaguchi, Takehiro; Watanabe, Kenji; Taniguchi, Takashi; Machida, Tomoki

    2013-09-01

    We report on the infrared photoresponse of high-mobility graphene in high magnetic fields. Two types of photoresponse signals were observed that were due to photovoltaic and bolometric effects. The photovoltaic signal was observed in the quantum Hall regime, whereas the bolometric signal was dominant in the quantum Hall transition regime. The photovoltaic effect, which was induced by cyclotron resonance, was observable up to 180 K. The polarity of the photovoltaic photoresponse was shown to be systematically reversed on reversal of the applied magnetic field direction and measurement geometry, suggesting that the photovoltage signals were generated along the quantum Hall edge channel.

  5. Theoretical/Computational Studies of High-Temperature Superconductivity from Quantum Magnetism

    Science.gov (United States)

    2016-06-09

    AFRL-AFOSR-VA-TR-2016-0204 Theoretical/Computational Studies of High-Temperature Superconductivity from Quantum Magnetism Jose Rodriguez CALIFORNIA...TITLE AND SUBTITLE Theoretical/Computational Studies of High-Temperature Superconductivity from Quantum Magnetism 5a.  CONTRACT NUMBER 5b.  GRANT...SUBJECT TERMS quantum magnetism , HTS, superconductivity 16.  SECURITY CLASSIFICATION OF: 17.  LIMITATION OF       ABSTRACT UU 18.  NUMBER        OF

  6. Experimental ladder proof of Hardy's nonlocality for high-dimensional quantum systems

    Science.gov (United States)

    Chen, Lixiang; Zhang, Wuhong; Wu, Ziwen; Wang, Jikang; Fickler, Robert; Karimi, Ebrahim

    2017-08-01

    Recent years have witnessed a rapidly growing interest in high-dimensional quantum entanglement for fundamental studies as well as towards novel applications. Therefore, the ability to verify entanglement between physical qudits, d -dimensional quantum systems, is of crucial importance. To show nonclassicality, Hardy's paradox represents "the best version of Bell's theorem" without using inequalities. However, so far it has only been tested experimentally for bidimensional vector spaces. Here, we formulate a theoretical framework to demonstrate the ladder proof of Hardy's paradox for arbitrary high-dimensional systems. Furthermore, we experimentally demonstrate the ladder proof by taking advantage of the orbital angular momentum of high-dimensionally entangled photon pairs. We perform the ladder proof of Hardy's paradox for dimensions 3 and 4, both with the ladder up to the third step. Our paper paves the way towards a deeper understanding of the nature of high-dimensionally entangled quantum states and may find applications in quantum information science.

  7. High Quantum Efficiency Type II SLS FPAs for Space-Based Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I SBIR proposes to develop high quantum efficiency (QE) and low dark current infrared epitaxy materials based on Type II Strained Layer Superlattice (SLS)...

  8. High Efficiency Quantum Dot III-V Multijunction Solar Cell for Space Power Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We are proposing to utilize quantum dots to develop a super high-efficiency multijunction III-V solar cell for space. In metamorphic triple junction space solar...

  9. High Quantum Efficiency Type II SLS FPAs for Space-Based Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase II SBIR proposes to develop high quantum efficiency (QE) and low dark current infrared epitaxy materials based on Type II Strained Layer Superlattice...

  10. High Quantum Efficiency 1024x1024 Longwave Infrared SLS FPA and Camera Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a high quantum efficiency (QE) 1024x1024 longwave infrared focal plane array (LWIR FPA) and CAMERA with ~ 12 micron cutoff wavelength made from...

  11. Optimizing Decoy State Enabled Quantum Key Distribution Systems to Maximize Quantum Throughput and Detect Photon Number Splitting Attacks with High Confidence

    OpenAIRE

    Mailloux, Logan O.; Grimaila, Michael R.; Hodson, Douglas D.; Engle, Ryan D.; McLaughlin, Colin V.; Gerald B. Baumgartner

    2016-01-01

    Quantum Key Distribution (QKD) is an innovative quantum communications protocol which exploits the laws of quantum mechanics to generate unconditionally secure cryptographic keying material between two geographically separated parties. The unique nature of QKD shows promise for high-security applications such as those found in banking, government, and military environments. However, QKD systems contain implementation non-idealities which can negatively impact their performance and security.In...

  12. Photoluminescence of nanocoral ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Borysiewicz, M.A., E-mail: mbory@ite.waw.pl [Institute of Electron Technology, Al. Lotników 32/46, Warsaw 02-668 (Poland); Wzorek, M. [Institute of Electron Technology, Al. Lotników 32/46, Warsaw 02-668 (Poland); Wojciechowski, T.; Wojtowicz, T. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, Warsaw 02-668 (Poland); Kamińska, E.; Piotrowska, A. [Institute of Electron Technology, Al. Lotników 32/46, Warsaw 02-668 (Poland)

    2014-03-15

    Photoluminescence studies of nanocoral ZnO nanostructures, fabricated using magnetron sputter deposition of porous Zn films with subsequent oxidation by RTP annealing at 400–800 °C is presented. Structural characterization of the films performed using electron microscopy techniques show the nanocoral morphology of the films with individual coral branches constituting of bunched single crystal ZnO grains of 30–100 nm in dimensions. High resolution images confirm the high quality of individual grains. The features in the photoluminescence spectra are identified using temperature-dependent and power-dependent measurements, with rich features observed in the excitonic region at 5 K, as well as zinc vacancy lines and surface-state recombination lines being present. It is found, that the spectra significantly depend on the annealing temperatures of the samples, with the spectra acquired for the sample annealed at 800 °C exhibiting stronger excitonic emission by 2 orders of magnitude than any other features, thus proving the highest structural quality of the nanostructures. -- Highlights: • Photoluminescence (PL) of nanocoral ZnO nanostructures is studied. • Nanocoral ZnO fabricated by sputtering with post deposition oxidation at 400–800 °C. • PL spectra taken at 300 K and 5 K exhibit excitonic and intrinsic defect lines. • Rich excitonic features identified in temperature- /power-dependent spectra. • Structures fabricated at 800 °C show significantly dominating excitonic emission.

  13. Highly indistinguishable and strongly entangled photons from symmetric GaAs quantum dots.

    Science.gov (United States)

    Huber, Daniel; Reindl, Marcus; Huo, Yongheng; Huang, Huiying; Wildmann, Johannes S; Schmidt, Oliver G; Rastelli, Armando; Trotta, Rinaldo

    2017-05-26

    The development of scalable sources of non-classical light is fundamental to unlocking the technological potential of quantum photonics. Semiconductor quantum dots are emerging as near-optimal sources of indistinguishable single photons. However, their performance as sources of entangled-photon pairs are still modest compared to parametric down converters. Photons emitted from conventional Stranski-Krastanov InGaAs quantum dots have shown non-optimal levels of entanglement and indistinguishability. For quantum networks, both criteria must be met simultaneously. Here, we show that this is possible with a system that has received limited attention so far: GaAs quantum dots. They can emit triggered polarization-entangled photons with high purity (g(2)(0) = 0.002±0.002), high indistinguishability (0.93±0.07 for 2 ns pulse separation) and high entanglement fidelity (0.94±0.01). Our results show that GaAs might be the material of choice for quantum-dot entanglement sources in future quantum technologies.

  14. Highly indistinguishable and strongly entangled photons from symmetric GaAs quantum dots

    Science.gov (United States)

    Huber, Daniel; Reindl, Marcus; Huo, Yongheng; Huang, Huiying; Wildmann, Johannes S.; Schmidt, Oliver G.; Rastelli, Armando; Trotta, Rinaldo

    2017-01-01

    The development of scalable sources of non-classical light is fundamental to unlocking the technological potential of quantum photonics. Semiconductor quantum dots are emerging as near-optimal sources of indistinguishable single photons. However, their performance as sources of entangled-photon pairs are still modest compared to parametric down converters. Photons emitted from conventional Stranski–Krastanov InGaAs quantum dots have shown non-optimal levels of entanglement and indistinguishability. For quantum networks, both criteria must be met simultaneously. Here, we show that this is possible with a system that has received limited attention so far: GaAs quantum dots. They can emit triggered polarization-entangled photons with high purity (g(2)(0) = 0.002±0.002), high indistinguishability (0.93±0.07 for 2 ns pulse separation) and high entanglement fidelity (0.94±0.01). Our results show that GaAs might be the material of choice for quantum-dot entanglement sources in future quantum technologies. PMID:28548081

  15. Two High-Dimensional Cartesian Bases for Quantum Key Distribution

    NARCIS (Netherlands)

    Tentrup, Tristan Bernhard Horst; Luiten, Willemijn; Hooijschuur, Peter; van der Meer, Reinier; Pinkse, Pepijn W.H.

    2017-01-01

    Quantum Key Distribution (QKD) provides a secure way of generating shared cryptographic keys between a sender (Alice) and a receiver (Bob). The original BB84 protocol uses a two-dimensional polarization basis, limiting the information content of a single photon to 1 bit. Using the transverse

  16. High Photovoltaic Quantum Efficiency in Ultrathin van der Waals Heterostructures.

    Science.gov (United States)

    Wong, Joeson; Jariwala, Deep; Tagliabue, Giulia; Tat, Kevin; Davoyan, Artur R; Sherrott, Michelle C; Atwater, Harry A

    2017-07-25

    We report experimental measurements for ultrathin (van der Waals heterostructures exhibiting external quantum efficiencies exceeding 50% and show that these structures can achieve experimental absorbance >90%. By coupling electromagnetic simulations and experimental measurements, we show that pn WSe 2 /MoS 2 heterojunctions with vertical carrier collection can have internal photocarrier collection efficiencies exceeding 70%.

  17. High-order noise filtering in nontrivial quantum logic gates

    CSIR Research Space (South Africa)

    Green, T

    2012-07-01

    Full Text Available that must be accounted for in order to understand total average error rates. We develop a treatment based on effective Hamiltonian theory that allows us to efficiently model the effect of classical noise on nontrivial single-bit quantum logic operations...

  18. Monodisperse Formamidinium Lead Bromide Nanocrystals with Bright and Stable Green Photoluminescence.

    Science.gov (United States)

    Protesescu, Loredana; Yakunin, Sergii; Bodnarchuk, Maryna I; Bertolotti, Federica; Masciocchi, Norberto; Guagliardi, Antonietta; Kovalenko, Maksym V

    2016-11-02

    Bright green emitters with adjustable photoluminescence (PL) maxima in the range of 530-535 nm and full-width at half-maxima (fwhm) of <25 nm are particularly desirable for applications in television displays and related technologies. Toward this goal, we have developed a facile synthesis of highly monodisperse, cubic-shaped formamidinium lead bromide nanocrystals (FAPbBr 3 NCs) with perovskite crystal structure, tunable PL in the range of 470-540 nm by adjusting the nanocrystal size (5-12 nm), high quantum yield (QY) of up to 85% and PL fwhm of <22 nm. High QYs are also retained in films of FAPbBr 3 NCs. In addition, these films exhibit low thresholds of 14 ± 2 μJ cm -2 for amplified spontaneous emission.

  19. Ultrafast spontaneous emission modulation of graphene quantum dots interacting with Ag nanoparticles in solution

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jianwei [Department of Physics, Shanghai University, Shanghai 200444 (China); Research Center of Quantum Macro-Phenomenon and Application, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China); Lu, Jian, E-mail: luj@sari.ac.cn; Wang, Zhongyang, E-mail: wangzy@sari.ac.cn [Research Center of Quantum Macro-Phenomenon and Application, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China); Wang, Liang [School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444 (China); Institute of Nanochemistry and Nanobiology, Shanghai University, Shanghai 200444 (China); Tian, Linfan [Research Center of Quantum Macro-Phenomenon and Application, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China); School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210 (China); Deng, Xingxia [Research Center of Quantum Macro-Phenomenon and Application, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China); School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Tian, Lijun [Department of Physics, Shanghai University, Shanghai 200444 (China); Pan, Dengyu [School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444 (China)

    2016-07-11

    We investigated the strong interaction between graphene quantum dots and silver nanoparticles in solution using time-resolved photoluminescence techniques. In solution, the silver nanoparticles are surrounded by graphene quantum dots and interacted with graphene quantum dots through exciton-plasmon coupling. An ultrafast spontaneous emission process (lifetime 27 ps) was observed in such a mixed solution. This ultrafast lifetime corresponds to the emission rate exceeding 35 GHz, with the purcell enhancement by a factor of ∼12. These experiment results pave the way for the realization of future high speed light sources applications.

  20. Stimuli-responsive photoluminescent liquid crystals.

    Science.gov (United States)

    Yamane, Shogo; Tanabe, Kana; Sagara, Yoshimitsu; Kato, Takashi

    2012-01-01

    We describe mechanochromic and thermochromic photoluminescent liquid crystals. In particular, mechanochromic photoluminescent liquid crystals found recently, which are new stimuli-responsive materials are reported. For example, photoluminescent liquid crystals having bulky dendritic moieties with long alkyl chains change their photoluminescent colors by mechanical stimuli associated with isothermal phase transitions. The photoluminescent properties of molecular assemblies depend on their assembled structures. Therefore, controlling the structures of molecular assemblies with external stimuli leads to the development of stimuli-responsive luminescent materials. Mechanochromic photoluminescent properties are also observed for a photoluminescent metallomesogen and a liquid-crystalline polymer. We also show thermochromic photoluminescent liquid crystals based on origo-(p-phenylenevinylene) and anthracene moieties and a thermochromic photoluminescent metallocomplex.

  1. Optical and structural properties of MOVPE-grown GaInSb/GaSb quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Wagener, Viera, E-mail: viera.wagener@nmmu.ac.z [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Olivier, E.J.; Botha, J.R. [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

    2009-12-15

    This paper reports on the optical and structural properties of strained type-I Ga{sub 1-x}In{sub x}Sb quantum wells embedded in GaSb from a metal-organic vapour phase epitaxial growth perspective. Photoluminescence measurements and transmission electron microscopy were used to evaluate the effect of the growth temperature on the quality of Ga{sub 1-x}In{sub x}Sb strained layers with varied alloy compositions and thicknesses. Although the various factors contributing to the overall quality of the strained layers are difficult to separate, the quantum well characteristics are significantly altered by the growth temperature. Despite the high growth rates (approx2 nm/s), quantum wells grown at 607 deg. C display photoluminescence emissions with full-width at half-maximum of 3.5-5.0 meV for an indium solid content (x) up to 0.15.

  2. Quantum Computers and Quantum Computer Languages: Quantum Assembly Language and Quantum C

    OpenAIRE

    Blaha, Stephen

    2002-01-01

    We show a representation of Quantum Computers defines Quantum Turing Machines with associated Quantum Grammars. We then create examples of Quantum Grammars. Lastly we develop an algebraic approach to high level Quantum Languages using Quantum Assembly language and Quantum C language as examples.

  3. Quantum Computers and Quantum Computer Languages: Quantum Assembly Language and Quantum C Language

    OpenAIRE

    Blaha, Stephen

    2002-01-01

    We show a representation of Quantum Computers defines Quantum Turing Machines with associated Quantum Grammars. We then create examples of Quantum Grammars. Lastly we develop an algebraic approach to high level Quantum Languages using Quantum Assembly language and Quantum C language as examples.

  4. Type II InAs/GaAsSb quantum dots: Highly tunable exciton geometry and topology

    Energy Technology Data Exchange (ETDEWEB)

    Llorens, J. M.; Wewior, L.; Cardozo de Oliveira, E. R.; Alén, B., E-mail: benito.alen@csic.es [IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, E-28760 Tres Cantos, Madrid (Spain); Ulloa, J. M.; Utrilla, A. D.; Guzmán, A.; Hierro, A. [Institute for Systems based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2015-11-02

    External control over the electron and hole wavefunctions geometry and topology is investigated in a p-i-n diode embedding a dot-in-a-well InAs/GaAsSb quantum structure with type II band alignment. We find highly tunable exciton dipole moments and largely decoupled exciton recombination and ionization dynamics. We also predicted a bias regime where the hole wavefunction topology changes continuously from quantum dot-like to quantum ring-like as a function of the external bias. All these properties have great potential in advanced electro-optical applications and in the investigation of fundamental spin-orbit phenomena.

  5. Ultrafast, high repetition rate, ultraviolet, fiber based laser source: application towards Yb+ fast quantum-logic

    OpenAIRE

    Hussain, Mahmood Irtiza; Petrasiunas, Matthew Joseph; Bentley, Christopher D. B.; Taylor, Richard L.; Carvalho, Andre R. R.; Hope, Joseph J.; Streed, Erik W.; Lobino, Mirko; Kielpinski, David

    2016-01-01

    Trapped ions are one of the most promising approaches for the realization of a universal quantum computer. Faster quantum logic gates could dramatically improve the performance of trapped-ion quantum computers, and require the development of suitable high repetition rate pulsed lasers. Here we report on a robust frequency upconverted fiber laser based source, able to deliver 2.5 ps ultraviolet (UV) pulses at a stabilized repetition rate of 300.00000 MHz with an average power of 190 mW. The la...

  6. Analysis of Eu-effect on stabilization of the TiO2-anatase structure in high temperature and photoluminescence efficiency for the coatings as-deposited in magnetron sputtering process

    Science.gov (United States)

    Wojcieszak, D.

    2017-11-01

    In this work the influence of annealing on structural properties and photoluminescence efficiency of TiO2 thin films doped with 0.2 at.% of Eu was described. Coatings were as-deposited in magnetron sputtering process and additionally annealed at 800 °C. Due to application of 'high energy' process the undoped titanium dioxide had fine crystalline rutile structure directly after deposition. In the case of TiO2:Eu film the situation was different. Doping with europium resulted in receiving of nanocrystalline anatase form. Moreover, Eu-dopant was stabilizing the anatase structure in high temperature (at 800 °C) and the phase transformation effect did not occurred. The influence of europium on the microstructure of TiO2 thin films was determined by X-ray diffraction, transmission electron microscope and Raman spectroscopy. The analysis was correlated with photoluminescence measurements. It was found that the crystal form of the TiO2 matrix as well as presence of defect states had a direct impact on PL efficiency. Moreover, the excitation mechanism of photo-generate electrons from TiO2 conduction band via matrix defect states into europium ions was discussed with the respect to location of Eu2+ and Eu3+ ions and its surrounding in the film.

  7. Quantum theoretical study of hydrogen under high pressure

    CERN Document Server

    Biermann, S

    2001-01-01

    In the first chapter we will review our knowledge of the phase diagram of hydrogen. Chapter 2 is a summary of the standard density functional and molecular dynamics methods and shows how these are combined in the Car-Parrinello method. Here the nuclei are still treated as classical particles obeying Newtonian mechanics. In chapter 3 we drop this approximation. The path integral description of quantum statistics is added on top of the classical Car-Parrinello method and yields a formalism that includes quantum effects due to the finite de Broglie wavelength of the nuclei. Some technical aspects, namely the parallel implementation of the Path Integral Car-Parrinello (PICP) method, are discussed in chapter 4. In chapter 5 we present the results of our PICP calculations and compare them with prior calculations using the classical Car-Parrinello method as described in chapter 2.

  8. High quantum yield Ag2S quantum dot@polypeptide-engineered hybrid nanogels for targeted second near-infrared fluorescence/photoacoustic imaging and photothermal therapy.

    Science.gov (United States)

    Zhao, Dong-Hui; Yang, Jie; Xia, Rui-Xue; Yao, Ming-Hao; Jin, Rui-Mei; Zhao, Yuan-Di; Liu, Bo

    2018-01-11

    A high quantum yield (4.3%) hybrid nanogel system based on engineered polypeptides and Ag2S quantum dots has been developed as a multifunctional diagnostic and therapeutic agent for targeted second near-infrared fluorescence, photoacoustic imaging, and photothermal therapy.

  9. High-fidelity quantum state evolution in imperfect photonic integrated circuits

    Science.gov (United States)

    Mower, Jacob; Harris, Nicholas C.; Steinbrecher, Gregory R.; Lahini, Yoav; Englund, Dirk

    2015-09-01

    We propose and analyze the design of a programmable photonic integrated circuit for high-fidelity quantum computation and simulation. We demonstrate that the reconfigurability of our design allows us to overcome two major impediments to quantum optics on a chip: it removes the need for a full fabrication cycle for each experiment and allows for compensation of fabrication errors using numerical optimization techniques. Under a pessimistic fabrication model for the silicon-on-insulator process, we demonstrate a dramatic fidelity improvement for the linear optics controlled-not and controlled-phase gates and, showing the scalability of this approach, the iterative phase estimation algorithm built from individually optimized gates. We also propose and simulate an experiment that the programmability of our system would enable: a statistically robust study of the evolution of entangled photons in disordered quantum walks. Overall, our results suggest that existing fabrication processes are sufficient to build a quantum photonic processor capable of high-fidelity operation.

  10. High-resolution hard x-ray spectroscopy of high-temperature plasmas using an array of quantum microcalorimeters.

    Science.gov (United States)

    Thorn, Daniel B; Gu, Ming F; Brown, Greg V; Beiersdorfer, Peter; Porter, F Scott; Kilbourne, Caroline A; Kelley, Richard L

    2008-10-01

    Quantum microcalorimeters show promise in being able to fully resolve x-ray spectra from heavy highly charged ions, such as would be found in hot plasmas with temperatures in excess of 50 keV. Quantum microcalorimeter arrays are able to achieve this as they have a high-resolving power and good effective quantum efficiency for hard x-ray photons up to 60 keV. To demonstrate this, we present a measurement using an array of thin HgTe quantum microcalorimeters to measure the K-shell spectrum of hydrogenlike through carbonlike praseodymium (Z=57). With this device we are able to attain a resolving power, E/DeltaE, of 1000 at a photon energy of 37 keV.

  11. Solvatochromism in highly luminescent environmental friendly carbon quantum dots for sensing applications: Conversion of bio-waste into bio-asset.

    Science.gov (United States)

    Pramanik, A; Biswas, S; Kumbhakar, P

    2018-02-15

    Recently studies on synthesis and fluorescence based sensing in biocompatible carbon quantum dots (CQDs) have become a widely spoken topic of research due to the several advantageous properties of CQDs in compared to semiconductor quantum dots. In this work, we have reported the rarely reported solvatochromism along-with a high photoluminescence (PL) quantum yield (PLQY) of 22%. Samples have been synthesized by using a simple process of hydrothermal carbonization of a naturally occurring bio-waste i.e. Aegle marmelos leaves powder. The linear absorption and PL emission characteristics of CQDs have been studied in different solvent environments to explore the origin of the observed excitation dependent PL emissions characteristics of the sample. The interesting solvatochromic PL (SPL) behavior of CQDs are observed at an excitation wavelength of 325nm by dispersing them in different polar protic and aprotic solvents, which suggest their possible applications as a replacement of solvatochromic dye molecules for sensing applications. Different polarity functions and molecular-microscopic solvent polarity parameter (ETN) are used to calculate the change in dipole moment (Δδ) of the solute-solvent system and the origin of SPL in CQDs has been explained. The SPL behavior of CQDs has been utilized for fluorescence sensing of organic liquids (Ethanol and Tetrahydrofuran) in water. Whereas, the photo-induced electron transfer mediated quenching in PL of aqueous dispersion of CQDs has led to development of "turn off" fluorescence Fe3+ ion sensor with a detection limit of 0.12μM. Therefore, this work may open a new avenue of conversion of a bio-waste into a fluorescent bio-asset. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Solvatochromism in highly luminescent environmental friendly carbon quantum dots for sensing applications: Conversion of bio-waste into bio-asset

    Science.gov (United States)

    Pramanik, A.; Biswas, S.; Kumbhakar, P.

    2018-02-01

    Recently studies on synthesis and fluorescence based sensing in biocompatible carbon quantum dots (CQDs) have become a widely spoken topic of research due to the several advantageous properties of CQDs in compared to semiconductor quantum dots. In this work, we have reported the rarely reported solvatochromism along-with a high photoluminescence (PL) quantum yield (PLQY) of 22%. Samples have been synthesized by using a simple process of hydrothermal carbonization of a naturally occurring bio-waste i.e. Aegle marmelos leaves powder. The linear absorption and PL emission characteristics of CQDs have been studied in different solvent environments to explore the origin of the observed excitation dependent PL emissions characteristics of the sample. The interesting solvatochromic PL (SPL) behavior of CQDs are observed at an excitation wavelength of 325 nm by dispersing them in different polar protic and aprotic solvents, which suggest their possible applications as a replacement of solvatochromic dye molecules for sensing applications. Different polarity functions and molecular-microscopic solvent polarity parameter (ETN) are used to calculate the change in dipole moment (Δδ) of the solute-solvent system and the origin of SPL in CQDs has been explained. The SPL behavior of CQDs has been utilized for fluorescence sensing of organic liquids (Ethanol and Tetrahydrofuran) in water. Whereas, the photo-induced electron transfer mediated quenching in PL of aqueous dispersion of CQDs has led to development of ;turn off; fluorescence Fe3 + ion sensor with a detection limit of 0.12 μM. Therefore, this work may open a new avenue of conversion of a bio-waste into a fluorescent bio-asset.

  13. High-Rate Field Demonstration of Large-Alphabet Quantum Key Distribution

    Science.gov (United States)

    2017-05-22

    Public Release ∗To whom correspondence should be addressed; E-mail: englund@mit.edu. May 22, 2017 A central goal of quantum information science is to...distribution field test, using photons encoded in a high-dimensional alphabet to increase the secure information yield per de- 1 tected photon. By adjusting the...fiber networks. Introduction Quantum key distribution (QKD) allows two parties, Alice and Bob, to establish provably se- cure encryption keys at a

  14. Possibility of high performance quantum computation by superluminal evanescent photons in living systems.

    Science.gov (United States)

    Musha, Takaaki

    2009-06-01

    Penrose and Hameroff have suggested that microtubules in living systems function as quantum computers by utilizing evanescent photons. On the basis of the theorem that the evanescent photon is a superluminal particle, the possibility of high performance computation in living systems has been studied. From the theoretical analysis, it is shown that the biological brain can achieve large quantum bits computation compared with the conventional processors at room temperature.

  15. High Efficiency Quantum Dot Solar Cells Based on Multiple Exciton Generation

    Energy Technology Data Exchange (ETDEWEB)

    Breeze, Alison [Solexant Corp., San Jose, CA (United States)

    2011-04-15

    The objective of this project was to demonstrate that efficient multiple exciton generation observed in quantum dot materials could be harvested in nanostructured solar cells to dramatically improve the maximum power efficiency obtainable in photovoltaic modules. This proposal aimed to develop a high efficiency solar cell through a combination of quantum dot materials, nanostructured surfaces and atomic layer deposition for fabricating conformal and ultrathin films.

  16. Quantum non-demolition and high-efficiency detection of traveling microwave photons - part 1

    Science.gov (United States)

    Royer, Baptiste; Grimsmo, Arne L.; Bourassa, Jerome; Didier, Nicolas; Blais, Alexandre

    Optical photon detectors are indispensable tools for quantum optics experiments. Realizing their microwave counterparts has, however, remained an elusive task due in part to the energy scale difference between the two frequency ranges. In this talk, we will present a possible solution to this problem by adapting a scheme for qubit readout to allow high-efficiency measurement of traveling photons. Having such photon detectors would enable a wide variety of applications ranging from quantum information processing to mesoscopic physics.

  17. The excitation power density effect on the Si nanocrystals photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Sias, U.S. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul (UFRGS), C.P. 15051, 91501-970 Porto Alegre, Rio Grande do Sul (Brazil) and Centro Federal de Educacao Tecnologica-Rio Grande do Sul (CEFET-RS), 96015-360 Pelotas, Rio Grande do Sul (Brazil)]. E-mail: uilson@if.ufrgs.br; Amaral, L. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul (UFRGS), C.P. 15051, 91501-970 Porto Alegre, Rio Grande do Sul (RS) (Brazil); Behar, M. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul (UFRGS), C.P. 15051, 91501-970 Porto Alegre, Rio Grande do Sul (RS) (Brazil); Boudinov, H. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul (UFRGS), C.P. 15051, 91501-970 Porto Alegre, Rio Grande do Sul (RS) (Brazil); Moreira, E.C. [Centro Universitario Franciscano (UNIFRA), 97010-032 Santa Maria, RS (Brazil)

    2006-09-15

    In the present work we have studied the photoluminescence (PL) behavior from Si nanocrystals (NCs) as a function of the excitation power density and annealing time. The NCs were produced in a SiO{sub 2} matrix by Si implantations from room temperature (RT) up to 700 deg. C, followed by post-annealing in N{sub 2} atmosphere at high temperature. With this aim we have changed the excitation power density (from 2 x 10{sup -3} W/cm{sup 2} up to 15 W/cm{sup 2}) and the annealing time (from 10 min up to 15 h). The strong PL signal, which at 15 W/cm{sup 2} is composed by a single-peak structure (650-1000 nm) centered at around 780 nm, expands up to 1200 nm showing a two-peak structure when measured at 20 x 10{sup -3} W/cm{sup 2}. The peak structure located at the short wavelength side is kept at {approx}780 nm, while the second peak, starting at around 900 nm, redshifts and increases its intensity with the implantation temperature and annealing time. The effect of the annealing time on the PL spectra behavior measured at low excitation power agrees by the first time with the Si NC growth according to quantum confinement effects.

  18. Thermodynamic of photoluminescence far from the radiative limit

    CERN Document Server

    Manor, Assaf; Rotschild, Carmel

    2016-01-01

    The radiance of thermal emission, as described by Plancks law, depends only on the emissivity and temperature of a body, and increases monotonically with temperature rise at any emitted wavelength. Nonthermal radiation, such as photoluminescence (PL), is a fundamental light matter interaction that conventionally involves the absorption of an energetic photon, thermalization, and the emission of a redshifted photon. Until recently, the role of rate conservation when thermal excitation is significant, has not been studied in any nonthermal radiation. A question: What is the overall emission rate if a high quantum efficiency (QE), PL material, is heated to a temperature where it thermally emits a rate of 50 photons/sec at its bend edge, while in parallel is PL excited at a rate of 100 photons/sec. Recently, we discovered that the answer is an overall rate of 100 blueshifted photons/sec. In contrast to thermal emission, the PL rate is conserved with temperature increase, while each photon is blueshifted. Further ...

  19. Preparation and biological evaluation of photoluminescent carbonaceous nanospheres.

    Science.gov (United States)

    Qian, Jun; Chen, Jiantao; Ruan, Shaobo; Shen, Shun; He, Qin; Jiang, Xinguo; Zhu, Jianhua; Gao, Huile

    2014-09-01

    Carbon nanospheres (CNP) possess several unique properties that render CNP superior to traditional organic dyes and quantum dots in the biological application. However, the interaction of CNP with biological systems was far from well-known. In this study, a simple method using cocoon silk was used to synthesize photoluminescent CNP. The particle size of CNP was 100.6 nm with well dispersity. The excitation/emission wavelength was 340 nm and 442 nm. Cellular uptake demonstrated the uptake of CNP by A549 cells was a time-, concentration- and energy-dependent procedure. Endosome was involved in the uptake rather than mitochondria. Through several uptake inhibitors, it showed the uptake was energy-dependent and mainly mediated by clathrin-mediated endocytosis. In vivo, CNP were mainly distributed in heart and lung, while only a modest amount of CNP was distributed in spleen, liver and kidney. The distribution in tumor was relatively low, which made CNP a candidate for heart cell imaging. At as high as 2mg/mL, CNP showed no obvious toxicity to cells. The hemolysis rate of CNP was also lower than 10%. These results suggested CNP was relatively safe in biological application. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Confinement enhancing barriers for high performance quantum dots-in-a-well infrared detectors

    Science.gov (United States)

    Barve, A. V.; Sengupta, S.; Kim, J. O.; Sharma, Y. D.; Adhikary, S.; Rotter, T. J.; Lee, S. J.; Kim, Y. H.; Krishna, S.

    2011-11-01

    We demonstrate the use of thin AlGaAs barrier layers in the quantum dots in a well heterostructure to enhance the quantum confinement of carriers in the excited energy level, while maintaining high escape probability. This is achieved by controlling the excited state energy between the confinement enhancing (CE) barriers and the continuum level. Responsivity of ˜0.1 A/W, detectivity of 6.5 × 1010 cmHz1/2 W-1 (77 K, 0.6 V, 7.5 µm, f/2), and a factor of 10 improvement over a control sample without the CE barriers have been measured. The effect of changing the quantum well thickness and quantum dot size is also reported.

  1. High efficiency frequency upconversion of photons carrying orbital angular momentum for a quantum information interface.

    Science.gov (United States)

    Tang, Ruikai; Li, Xiongjie; Wu, Wenjie; Pan, Haifeng; Zeng, Heping; Wu, E

    2015-04-20

    The orbital angular momentum (OAM) of light shows great potential in quantum communication. The transmission wavelength for telecom is usually around 1550 nm, while the common quantum information storage and processing devices based on atoms, ions or NV color centers are for photons in visible regime. Here we demonstrate a quantum information interface based on the frequency upconversion for photons carrying OAM states from telecom wavelength to visible regime by sum-frequency generation with high quantum conversion efficiency. The infrared photons at 1558 nm carrying different OAM values were converted to the visible regime of 622.2 nm, and the OAM value of the signal photons was well preserved in the frequency upconversion process with pump beam in Gaussian profile.

  2. High-Fidelity Preservation of Quantum Information During Trapped-Ion Transport

    Science.gov (United States)

    Kaufmann, Peter; Gloger, Timm F.; Kaufmann, Delia; Johanning, Michael; Wunderlich, Christof

    2018-01-01

    A promising scheme for building scalable quantum simulators and computers is the synthesis of a scalable system using interconnected subsystems. A prerequisite for this approach is the ability to faithfully transfer quantum information between subsystems. With trapped atomic ions, this can be realized by transporting ions with quantum information encoded into their internal states. Here, we measure with high precision the fidelity of quantum information encoded into hyperfine states of a Yb171 + ion during ion transport in a microstructured Paul trap. Ramsey spectroscopy of the ion's internal state is interleaved with up to 4000 transport operations over a distance of 280 μ m each taking 12.8 μ s . We obtain a state fidelity of 99.9994 (-7+6) % per ion transport.

  3. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation

    Science.gov (United States)

    Ge, Jiechao; Lan, Minhuan; Zhou, Bingjiang; Liu, Weimin; Guo, Liang; Wang, Hui; Jia, Qingyan; Niu, Guangle; Huang, Xing; Zhou, Hangyue; Meng, Xiangmin; Wang, Pengfei; Lee, Chun-Sing; Zhang, Wenjun; Han, Xiaodong

    2014-08-01

    Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen (1O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce 1O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of 1O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility.

  4. Highly mobile gapless excitations in a two-dimensional candidate quantum spin liquid.

    Science.gov (United States)

    Yamashita, Minoru; Nakata, Norihito; Senshu, Yoshinori; Nagata, Masaki; Yamamoto, Hiroshi M; Kato, Reizo; Shibauchi, Takasada; Matsuda, Yuji

    2010-06-04

    The nature of quantum spin liquids, a novel state of matter where strong quantum fluctuations destroy the long-range magnetic order even at zero temperature, is a long-standing issue in physics. We measured the low-temperature thermal conductivity of the recently discovered quantum spin liquid candidate, the organic insulator EtMe3Sb[Pd(dmit)2]2. A sizable linear temperature dependence term is clearly resolved in the zero-temperature limit, indicating the presence of gapless excitations with an extremely long mean free path, analogous to excitations near the Fermi surface in pure metals. Its magnetic field dependence suggests a concomitant appearance of spin-gap-like excitations at low temperatures. These findings expose a highly unusual dichotomy that characterizes the low-energy physics of this quantum system.

  5. A graphene quantum dot photodynamic therapy agent with high singlet oxygen generation

    Science.gov (United States)

    Ge, Jiechao; Lan, Minhuan; Zhou, Bingjiang; Liu, Weimin; Guo, Liang; Wang, Hui; Jia, Qingyan; Niu, Guangle; Huang, Xing; Zhou, Hangyue; Meng, Xiangmin; Wang, Pengfei; Lee, Chun-Sing; Zhang, Wenjun; Han, Xiaodong

    2014-01-01

    Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen (1O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce 1O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of 1O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility. PMID:25105845

  6. Provably secure and high-rate quantum key distribution with time-bin qudits.

    Science.gov (United States)

    Islam, Nurul T; Lim, Charles Ci Wen; Cahall, Clinton; Kim, Jungsang; Gauthier, Daniel J

    2017-11-01

    The security of conventional cryptography systems is threatened in the forthcoming era of quantum computers. Quantum key distribution (QKD) features fundamentally proven security and offers a promising option for quantum-proof cryptography solution. Although prototype QKD systems over optical fiber have been demonstrated over the years, the key generation rates remain several orders of magnitude lower than current classical communication systems. In an effort toward a commercially viable QKD system with improved key generation rates, we developed a discrete-variable QKD system based on time-bin quantum photonic states that can generate provably secure cryptographic keys at megabit-per-second rates over metropolitan distances. We use high-dimensional quantum states that transmit more than one secret bit per received photon, alleviating detector saturation effects in the superconducting nanowire single-photon detectors used in our system that feature very high detection efficiency (of more than 70%) and low timing jitter (of less than 40 ps). Our system is constructed using commercial off-the-shelf components, and the adopted protocol can be readily extended to free-space quantum channels. The security analysis adopted to distill the keys ensures that the demonstrated protocol is robust against coherent attacks, finite-size effects, and a broad class of experimental imperfections identified in our system.

  7. High-Yield Fabrication of Entangled Photon Emitters for Hybrid Quantum Networking Using High-Temperature Droplet Epitaxy.

    Science.gov (United States)

    Basso Basset, Francesco; Bietti, Sergio; Reindl, Marcus; Esposito, Luca; Fedorov, Alexey; Huber, Daniel; Rastelli, Armando; Bonera, Emiliano; Trotta, Rinaldo; Sanguinetti, Stefano

    2018-01-10

    Several semiconductor quantum dot techniques have been investigated for the generation of entangled photon pairs. Among the other techniques, droplet epitaxy enables the control of the shape, size, density, and emission wavelength of the quantum emitters. However, the fraction of the entanglement-ready quantum dots that can be fabricated with this method is still limited to around 5%, and matching the energy of the entangled photons to atomic transitions (a promising route toward quantum networking) remains an outstanding challenge. Here, we overcome these obstacles by introducing a modified approach to droplet epitaxy on a high symmetry (111)A substrate, where the fundamental crystallization step is performed at a significantly higher temperature as compared with previous reports. Our method drastically improves the yield of entanglement-ready photon sources near the emission wavelength of interest, which can be as high as 95% due to the low values of fine structure splitting and radiative lifetime, together with the reduced exciton dephasing offered by the choice of GaAs/AlGaAs materials. The quantum dots are designed to emit in the operating spectral region of Rb-based slow-light media, providing a viable technology for quantum repeater stations.

  8. Magnetic field effect on the visible photoluminescence of porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Torchynska, T.V.; Diaz Cano, A. [ESFM, National Polytechnic Institute of Mexico, U.P.A.L.M., Ed. 9 (Mexico); Khomenkova, L.Y. [Institute of Semiconductor Physics of Ukraine, National Academy of Sciences, Kiev 252028 (Ukraine); Zakharchenko, V.N. [National Polytechnic Institute KPI, Dept. of General and Experimental Physics, Kiev 252056 (Ukraine); Zakharchenko, R.V. [National Polytechnic Institute KPI, Dept. of General and Experimental Physics, Kiev 252056 (Ukraine); CINVESTAV-IPN, Unidad Queretaro, Libramiento Norponiente 2000, Juriquilla, Queretaro (Mexico); Gonzalez-Hernandez, J. [CIMAV, Miguel de Cervantes 120, Chihuahua (Mexico); Vorobiev, Y.V. [CINVESTAV-IPN, Unidad Queretaro, Libramiento Norponiente 2000, Juriquilla, Queretaro (Mexico)

    2005-06-01

    The excitation and emission spectra of red photoluminescence of Si wire nanostructures were studied in dependence on surface morphology and influence of magnetic field. The magnetic field of 0.5 T reduced the emission intensity by 10% at all emission spectral range. Comparison of the two photoluminescence models - the quantum confinement and the hot carrier ballistic ones - favours the second model based on the assumption of the excitation of interface oxide defect related luminescence by hot quasi-ballistic carriers created by illumination. The effective mobility of hot electrons is estimated as 6000 cm{sup 2}/Vs, which greatly exceeds normal electron mobility (1900 cm{sup 2}/Vs) in Si and thus confirms the presence of hot carrier ballistic motion. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Structural and optical properties of size controlled Si nanocrystals in Si{sub 3}N{sub 4} matrix: The nature of photoluminescence peak shift

    Energy Technology Data Exchange (ETDEWEB)

    Zelenina, A., E-mail: anastasia.zelenina@imtek.uni-freiburg.de; Hiller, D.; Gutsch, S.; Zacharias, M. [Faculty of Engineering, IMTEK, Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg (Germany); Dyakov, S. A. [Department of Electronic and Electrical Engineering, Trinity College Dublin, Dublin 2 (Ireland); Optics and Photonics, School of Information and Communication Technology, Royal Institute of Technology (KTH), Electrum 229, Kista SE-16440 (Sweden); Trouillet, V.; Bruns, M. [Institute for Applied Materials (IAM) and Karlsruhe Nano Micro Facility, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Mirabella, S. [MATIS IMM-CNR, Universita' di Catania, Via S. Sofia 64, I-95123 Catania (Italy); Löper, P. [Fraunhofer-Institut für Solare Energiesysteme ISE Heidenhofstr. 2, 79110 Freiburg (Germany); López-Conesa, L.; López-Vidrier, J.; Peiró, F.; Garrido, B. [MIND-IN2UB, Departament d’Electrònica, Universitat de Barcelona, C/Martí i Franquès, 1, 08028 Barcelona (Spain); Estradé, S. [MIND-IN2UB, Departament d’Electrònica, Universitat de Barcelona, C/Martí i Franquès, 1, 08028 Barcelona (Spain); CCiT, Scientific and Technical Centers, Universitat de Barcelona, C/Lluís Solé i Sabaris 1, 08028 Barcelona (Spain); and others

    2013-11-14

    Superlattices of Si{sub 3}N{sub 4} and Si-rich silicon nitride thin layers with varying thickness were prepared by plasma enhanced chemical vapor deposition. After high temperature annealing, Si nanocrystals were formed in the former Si-rich nitride layers. The control of the Si quantum dots size via the SiN{sub x} layer thickness was confirmed by transmission electron microscopy. The size of the nanocrystals was well in agreement with the former thickness of the respective Si-rich silicon nitride layers. In addition X-ray diffraction evidenced that the Si quantum dots are crystalline whereas the Si{sub 3}N{sub 4} matrix remains amorphous even after annealing at 1200 °C. Despite the proven Si nanocrystals formation with controlled sizes, the photoluminescence was 2 orders of magnitude weaker than for Si nanocrystals in SiO{sub 2} matrix. Also, a systematic peak shift was not found. The SiN{sub x}/Si{sub 3}N{sub 4} superlattices showed photoluminescence peak positions in the range of 540–660 nm (2.3–1.9 eV), thus quite similar to the bulk Si{sub 3}N{sub 4} film having peak position at 577 nm (2.15 eV). These rather weak shifts and scattering around the position observed for stoichiometric Si{sub 3}N{sub 4} are not in agreement with quantum confinement theory. Therefore theoretical calculations coupled with the experimental results of different barrier thicknesses were performed. As a result the commonly observed photoluminescence red shift, which was previously often attributed to quantum-confinement effect for silicon nanocrystals, was well described by the interference effect of Si{sub 3}N{sub 4} surrounding matrix luminescence.

  10. Electrical And Optical Properties Of Colloidal Quantum Dots And Quantum Dot Networks: Role Of Surface States And Using Biomolecular Links In Network Assembly

    National Research Council Canada - National Science Library

    Stroscio, Michael A; Dutta, Mitra; Ramadurai, Dinakar; Shi, Peng; Li, Yang; Alexson, Dimitri; Kohanpour, Babak; Sethuraman, Akil; Saini, Vikas; Raichura, Amit; Yang, Jianyong

    2004-01-01

    .... Absorption spectra and photoluminescence (PL) spectra of colloidal cadmium sulfide (CdS) quantum dots are analyzed to investigate the role of surface states in determining the electrical and optical properties of these semiconductor quantum dots...

  11. Strained-graphene-based highly efficient quantum heat engine operating at maximum power

    Science.gov (United States)

    Mani, Arjun; Benjamin, Colin

    2017-09-01

    A strained graphene monolayer is shown to operate as a highly efficient quantum heat engine delivering maximum power. The efficiency and power of the proposed device exceeds that of recent proposals. The reason for these excellent characteristics is that strain enables complete valley separation in transmittance through the device, implying that increasing strain leads to very high Seebeck coefficient as well as lower conductance. In addition, since time-reversal symmetry is unbroken in our system, the proposed strained graphene quantum heat engine can also act as a high-performance refrigerator.

  12. Thermally stimulated luminescence and photoluminescence ...

    Indian Academy of Sciences (India)

    2012-01-13

    Eu3+ and SrBPO5:Eu2+ phosphors were carried out in the temperature range of 300–650 K. In order to characterize the phosphors, X-ray diffraction and photoluminescence (PL) techniques were used. The emission spectrum of ...

  13. Thermally stimulated luminescence and photoluminescence ...

    Indian Academy of Sciences (India)

    Thermally stimulated luminescence (TSL) investigations of SrBPO5:Eu3+ and SrBPO5:Eu2+ phosphors were carried out in the temperature range of 300–650 K. In order to characterize the phosphors, X-ray diffraction and photoluminescence (PL) techniques were used. The emission spectrum of air heated SrBPO5:Eu3+ ...

  14. Photoluminescence and thermoluminescence properties of ...

    Indian Academy of Sciences (India)

    ... of Materials Science; Volume 30; Issue 5. Photoluminescence and thermoluminescence properties of tricalcium phosphate phosphors doped with dysprosium and europium. K Madhukumar H K Varma Manoj Komath T S Elias V Padmanabhan C M K Nair. Thermal Properties Volume 30 Issue 5 October 2007 pp 527-534 ...

  15. Photoluminescence, thermally stimulated luminescence and ...

    Indian Academy of Sciences (India)

    Photoluminescence, thermally stimulated luminescence and electron paramagnetic resonance studies of U. 6+ doped BaSO4. M K BHIDE, T K SESHAGIRI. ∗. , SASHIKALA OJHA† and S V GODBOLE. Radiochemistry Division, †Radiation Safety Systems Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.

  16. Synthesis, characterization, photoluminescence and thermally ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Sm3+-doped ZnAl2O4 phosphor was synthesized by citrate sol–gel method and characterized using. X-ray diffraction and scanning electron microscopy to identify the crystalline phase and determine the parti- cle size. Photoluminescence (PL) studies on the sample showed emission peaks at 563, 601, 646 and ...

  17. Quantum efficiency and oscillator strength of site-controlled InGaAs quantum dots

    DEFF Research Database (Denmark)

    Albert, F.; Schneider, C.; Stobbe, Søren

    2010-01-01

    We report on time-resolved photoluminescence spectroscopy to determine the oscillator strength (OS) and the quantum efficiency (QE) of site-controlled In(Ga)As quantum dots nucleating on patterned nanoholes. These two quantities are determined by measurements on site-controlled quantum dot (SCQD...

  18. Quantum efficiency and oscillator strength of site-controlled InAs quantum dots

    DEFF Research Database (Denmark)

    Albert, F.; Stobbe, Søren; Schneider, C.

    2010-01-01

    We report on time-resolved photoluminescence spectroscopy to determine the oscillator strength (OS) and the quantum efficiency (QE) of site-controlled InAs quantum dots nucleating on patterned nanoholes. These two quantities are determined by measurements on site-controlled quantum dot (SCQD...

  19. The effect of two additional Eu3+ lumophors in two novel trinuclear europium complexes on their photoluminescent properties.

    Science.gov (United States)

    Yang, Chaolong; Xu, Jing; Ma, Jianying; Zhu, Dongyu; Zhang, Yunfei; Liang, Liyan; Lu, Mangeng

    2013-02-01

    Two novel trinuclear europium complexes based on trisphen(1,3,5-tris{4-((1,10-phenanthroline-[5,6-d]imidazol-2yl)phenoxy)methyl}-2,4,6-trimethyl-benzene) as a second ligand were designed, synthesized, and characterized by FT-IR, (1)H NMR, UV-visible, photoluminescence (PL) spectroscopy, elemental analysis (EA) and ESI-MS. The geometries of these two trinuclear europium complexes were predicted using the Sparkle/PM3 model and suggested a chemical environment of very low symmetry around the lanthanide ions (C(1)), which is in agreement with the luminescent spectra. CV analysis demonstrated that the trinuclear complexes possessed excellent electro-injection abilities. The effects of two additional Eu(3+) lumophors in these trinuclear europium complexes on their photoluminescent properties were investigated in detail. The results indicated that these trinuclear europium complexes exhibited highly luminescent quantum efficiencies and experimental intensity parameters in the solid state. Especially, due to the contribution of the two additional Eu(3+) lumophors in the trinuclear europium complexes, the quantum efficiency of the trinuclear complex Eu(3)(TTA)(9)trisphen was higher (ca. 34%) than the mononuclear europium complex Eu(TTA)(3)imidazophen.

  20. Solution-processed, high-performance light-emitting diodes based on quantum dots

    Science.gov (United States)

    Dai, Xingliang; Zhang, Zhenxing; Jin, Yizheng; Niu, Yuan; Cao, Hujia; Liang, Xiaoyong; Chen, Liwei; Wang, Jianpu; Peng, Xiaogang

    2014-11-01

    Solution-processed optoelectronic and electronic devices are attractive owing to the potential for low-cost fabrication of large-area devices and the compatibility with lightweight, flexible plastic substrates. Solution-processed light-emitting diodes (LEDs) using conjugated polymers or quantum dots as emitters have attracted great interest over the past two decades. However, the overall performance of solution-processed LEDs--including their efficiency, efficiency roll-off at high current densities, turn-on voltage and lifetime under operational conditions--remains inferior to that of the best vacuum-deposited organic LEDs. Here we report a solution-processed, multilayer quantum-dot-based LED with excellent performance and reproducibility. It exhibits colour-saturated deep-red emission, sub-bandgap turn-on at 1.7 volts, high external quantum efficiencies of up to 20.5 per cent, low efficiency roll-off (up to 15.1 per cent of the external quantum efficiency at 100 mA cm-2), and a long operational lifetime of more than 100,000 hours at 100 cd m-2, making this device the best-performing solution-processed red LED so far, comparable to state-of-the-art vacuum-deposited organic LEDs. This optoelectronic performance is achieved by inserting an insulating layer between the quantum dot layer and the oxide electron-transport layer to optimize charge balance in the device and preserve the superior emissive properties of the quantum dots. We anticipate that our results will be a starting point for further research, leading to high-performance, all-solution-processed quantum-dot-based LEDs ideal for next-generation display and solid-state lighting technologies.