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Sample records for sensitive cdte quantum

  1. A simple and sensitive label-free fluorescence sensing of heparin based on Cdte quantum dots.

    PubMed

    Rezaei, B; Shahshahanipour, M; Ensafi, Ali A

    2016-06-01

    A rapid, simple and sensitive label-free fluorescence method was developed for the determination of trace amounts of an important drug, heparin. This new method was based on water-soluble glutathione-capped CdTe quantum dots (CdTe QDs) as the luminescent probe. CdTe QDs were prepared according to the published protocol and the sizes of these nanoparticles were verified through transmission electron microscopy (TEM), X-ray diffraction (XRD) and dynamic light scattering (DLS) with an average particle size of about 7 nm. The fluorescence intensity of glutathione-capped CdTe QDs increased with increasing heparin concentration. These changes were followed as the analytical signal. Effective variables such as pH, QD concentration and incubation time were optimized. At the optimum conditions, with this optical method, heparin could be measured within the range 10.0-200.0 ng mL(-1) with a low limit of detection, 2.0 ng mL(-1) . The constructed fluorescence sensor was also applied successfully for the determination of heparin in human serum. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  2. Structural, optical and photovoltaic properties of co-doped CdTe QDs for quantum dots sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Ayyaswamy, Arivarasan; Ganapathy, Sasikala; Alsalme, Ali; Alghamdi, Abdulaziz; Ramasamy, Jayavel

    2015-12-01

    Zinc and sulfur alloyed CdTe quantum dots (QDs) sensitized TiO2 photoelectrodes have been fabricated for quantum dots sensitized solar cells. Alloyed CdTe QDs were prepared in aqueous phase using mercaptosuccinic acid (MSA) as a capping agent. The influence of co-doping on the structural property of CdTe QDs was studied by XRD analysis. The enhanced optical absorption of alloyed CdTe QDs was studied using UV-vis absorption and fluorescence emission spectra. The capping of MSA molecules over CdTe QDs was confirmed by the FTIR and XPS analyses. Thermogravimetric analysis confirms that the prepared QDs were thermally stable up to 600 °C. The photovoltaic performance of alloyed CdTe QDs sensitized TiO2 photoelectrodes were studied using J-V characteristics under the illumination of light with 1 Sun intensity. These results show the highest photo conversion efficiency of η = 1.21%-5% Zn & S alloyed CdTe QDs.

  3. Quantum dot sensitized solar cells. A tale of two semiconductor nanocrystals: CdSe and CdTe.

    PubMed

    Bang, Jin Ho; Kamat, Prashant V

    2009-06-23

    CdSe and CdTe nanocrystals are linked to nanostructured TiO2 films using 3-mercaptopropionic acid as a linker molecule for establishing the mechanistic aspects of interfacial charge transfer processes. Both these quantum dots are energetically capable of sensitizing TiO2 films and generating photocurrents in quantum dot solar cells. These two semiconductor nanocrystals exhibit markedly different external quantum efficiencies ( approximately 70% for CdSe and approximately 0.1% for CdTe at 555 nm). Although CdTe with a more favorable conduction band energy (E(CB) = -1.0 V vs NHE) is capable of injecting electrons into TiO2 faster than CdSe (E(CB) = -0.6 V vs NHE), hole scavenging by a sulfide redox couple remains a major bottleneck. The sulfide ions dissolved in aqueous solutions are capable of scavenging photogenerated holes in photoirradiated CdSe system but not in CdTe. The anodic corrosion and exchange of Te with S dominate the charge transfer at the CdTe interface. Factors that dictate the efficiency and photostability of CdSe and CdTe quantum dots are discussed.

  4. Sensitive arginine sensing based on inner filter effect of Au nanoparticles on the fluorescence of CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Liu, Haijian; Li, Ming; Jiang, Linye; Shen, Feng; Hu, Yufeng; Ren, Xueqin

    2017-02-01

    Arginine plays an important role in many biological functions, whose detection is very significant. Herein, a sensitive, simple and cost-effective fluorescent method for the detection of arginine has been developed based on the inner filter effect (IFE) of citrate-stabilized gold nanoparticles (AuNPs) on the fluorescence of thioglycolic acid-capped CdTe quantum dots (QDs). When citrate-stabilized AuNPs were mixed with thioglycolic acid-capped CdTe QDs, the fluorescence of CdTe QDs was significantly quenched by AuNPs via the IFE. With the presence of arginine, arginine could induce the aggregation and corresponding absorption spectra change of AuNPs, which then IFE-decreased fluorescence could gradually recover with increasing amounts of arginine, achieving fluorescence "turn on" sensing for arginine. The detection mechanism is clearly illustrated and various experimental conditions were also optimized. Under the optimum conditions, a decent linear relationship was obtained in the range from 16 to 121 μg L- 1 and the limit of detection was 5.6 μg L- 1. And satisfactory results were achieved in arginine analysis using arginine injection, compound amino acid injection, even blood plasma as samples. Therefore, the present assay showed various merits, such as simplicity, low cost, high sensitivity and selectivity, making it promising for sensing arginine in biological samples.

  5. Sensitive detection of sodium cromoglycate with glutathione-capped CdTe quantum dots as a novel fluorescence probe.

    PubMed

    Hao, Chenxia; Liu, Shaopu; Li, Dan; Yang, Jidong; He, Youqiu

    2015-11-01

    A sensitive and simple analytical strategy for the detection of sodium cromoglycate (SCG) has been established based on a readily detectable fluorescence quenching effect of SCG for glutathione-capped (GSH-capped) CdTe quantum dots (QDs). The fluorescence of GSH-capped CdTe QDs could be efficiently quenched by SCG through electron transfer from GSH-capped CdTe QDs to SCG. Under optimum conditions, the response was linearly proportional to the concentration of SCG between 0.6419 and 100 µg/mL, with a correlation coefficient (R) of 0.9964; the detection limit (3δ/K) was 0.1926 µg/mL. The optimum conditions and the influence of coexisting foreign substances on the reaction were also investigated. The very effective and simple method reported here has been successfully applied to the determination of SCG in synthetic and real samples. It is believed that the established approach could have good prospects for application in the fields of clinical diseases diagnosis and treatment.

  6. Permethylated-β-Cyclodextrin Capped CdTe Quantum Dot and its Sensitive Fluorescence Analysis of Malachite Green.

    PubMed

    Cao, Yujuan; Wei, Jiongling; Wu, Wei; Wang, Song; Hu, Xiaogang; Yu, Ying

    2015-09-01

    In the present work, the CdTe quantum dots were covalently conjugated with permethylated-β-cyclodextrin (OMe-β-CD) using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride as cross-linking reagent. The obtained functional quantum dots (OMe-β-CD/QDs) showed highly luminescent, water solubility and photostability as well as good inclusion ability to malachite green. A sensitive fluorescence method was developed for the analysis of malachite green in different samples. The good linearity was 2.0 × 10(-7)-1.0 × 10(-5) mol/L and the limit of detect was 1.7 × 10(-8) mol/L. The recoveries for three environmental water samples were 92.0-108.2 % with relative standard deviation (RSD) of 0.24-1.87 %, while the recovery for the fish sample was 94.3 % with RSD of 1.04 %. The results showed that the present method was sensitive and convenient to determine malachite green in complex samples. Graphical Abstract The analytical mechanism of OMe-β-CD/QDs and its linear response to MG.

  7. Temperature Sensitivity of Water-Soluble CdTe and CdSe/ZnS Quantum Dots Incorporated into Biopolymer Submicron Particles

    NASA Astrophysics Data System (ADS)

    Slyusarenko, N. V.; Gerasimova, M. A.; Slabko, V. V.; Slyusareva, E. A.

    2017-07-01

    Polymer particles with sizes 0.3-0.4 μm are synthesized based on chitosan and chondroitin sulfate with incorporated CdTe (core) and CdSe/ZnS (core-shell) quantum dots. Their morphological and spectral properties are investigated by the methods of dynamic scattering, electron microscopy, and absorption and luminescence spectroscopy at temperatures from 10 to 80°C. Spectral effects associated with a change in temperature (a red shift and a decrease in the amplitude of the photoluminescence spectrum) can be explained by the temperature expansion of the quantum dots and activation of surface traps. It is shown that the temperature sensitivity of spectra of the quantum dots incorporated into the biopolymer particles is not less than in water. To develop an optical temperature sensor, the core quantum dots are more preferable than the core-shell quantum dots.

  8. A sensitive fluorescent nanosensor for chloramphenicol based on molecularly imprinted polymer-capped CdTe quantum dots.

    PubMed

    Amjadi, Mohammad; Jalili, Roghayeh; Manzoori, Jamshid L

    2016-05-01

    A novel fluorescent nanosensor using molecularly imprinted silica nanospheres embedded CdTe quantum dots (CdTe@SiO2 @MIP) was developed for detection and quantification of chloramphenicol (CAP). The imprinted sensor was prepared by synthesis of molecularly imprinting polymer (MIP) on the hydrophilic CdTe quantum dots via reverse microemulsion method using small amounts of solvents. The resulting CdTe@SiO2 @MIP nanoparticles were characterized by fluorescence, UV-vis absorption and FT-IR spectroscopy and transmission electron microscopy. They preserved 48% of fluorescence quantum yield of the parent quantum dots. CAP remarkably quenched the fluorescence of prepared CdTe@SiO2 @MIP, probably via electron transfer mechanism. Under the optimal conditions, the relative fluorescence intensity of CdTe@SiO2 @MIP decreased with increasing CAP by a Stern-Volmer type equation in the concentration range of 40-500 µg L(-1). The corresponding detection limit was 5.0 µg L(-1). The intra-day and inter-day values for the precision of the proposed method were all <4%. The developed sensor had a good selectivity and was applied to determine CAP in spiked human and bovine serum and milk samples with satisfactory results. Copyright © 2015 John Wiley & Sons, Ltd.

  9. Highly-sensitive organophosphorus pesticide biosensors based on CdTe quantum dots and bi-enzyme immobilized eggshell membranes.

    PubMed

    Xue, Gao; Yue, Zhao; Bing, Zhang; Yiwei, Tang; Xiuying, Liu; Jianrong, Li

    2016-02-07

    An optical biosensing method using CdTe quantum dots (QDs) and bi-enzyme-immobilized eggshell membranes for the determination of organophosphorus pesticides (OPs) has been developed. Increasing amounts of OPs led to a decrease of the enzymatic activity and thus a decrease in the production of hydrogen peroxide (H2O2), which can quench the fluorescence of the CdTe QDs. Under the optimum conditions, there was a good linear relationship between the enzyme inhibition percentage and the logarithm of paraoxon or parathion concentration in the range of 1.0 × 10(-11)-1.0 × 10(-6) mol L(-1). The detection limit (S/N = 3) of the proposed biosensors were as low as 4.30 × 10(-12) mol L(-1) for paraoxon and 2.47 × 10(-12) mol L(-1) for parathion. The bi-enzyme-immobilized eggshell membrane demonstrated a long shelf-life of at least 2 months and the results showed good repeatability. The proposed method was successfully applied to the determination of the OPs in real fruit samples with satisfactory results.

  10. Determination of Captopril Based on the Photoluminescence Quenching of the pH Sensitive Mercaptopropanoic Acid Capped CdTe Quantum Dots

    NASA Astrophysics Data System (ADS)

    Khan, S.; Lima, A. A.; Aucelio, R. Q.

    2017-01-01

    The determination of captopril was performed by measuring the photoluminescence quenching of pH sensitive mercaptopropanoic acid capped CdTe quantum dots. Under optimum conditions, the calibration model (log F0/F as a function of the concentration of captopril) was linear up to 8 × 10-6 mol/L (1.7 μg/mL) and the limit of detection (xb - 3sb) was 2.7 × 10-7 mol/L (18 ng/mL). A possible mechanism for quenching is proposed. The method was applied in the determination of captopril in two commercial pharmaceutical formulations, indicating that it can be used for simple and fast quantitative control of commercial medicines or pharmaceutical preparations.

  11. Sensitive determination of enoxacin in pharmaceutical formulations by its quench effect on the fluorescence of glutathione-capped CdTe quantum dots.

    PubMed

    Yang, Qiong; Tan, Xuanping; Yang, Jidong

    2016-02-01

    A sensitive and simple method for the determination of enoxacin (ENX) was developed based on the fluorescence quenching effect of ENX for glutathione (GSH)-capped CdTe quantum dots (QDs). Under optimum conditions, a good linear relationship was obtained from 4.333 × 10(-9)  mol⋅L(-1) to 1.4 × 10(-5)  mol⋅L(-1) with a correlation coefficient (R) of 0.9987, and the detection limit (3σ/K) was 1.313 × 10(-9)  mol⋅L(-1). The corresponding mechanism has been proposed on the basis of electron transfer supported by ultraviolet-visible (UV) light absorption, fluorescence spectroscopy, and the measurement of fluorescence lifetime. The method has been applied to the determination of ENX in pharmaceutical formulations (enoxacin gluconate injections and commercial tablets) with satisfactory results. The proposed method manifested several advantages such as high sensitivity, short analysis time, low cost and ease of operation.

  12. Surface Molecular Imprinting on Silica-Coated CdTe Quantum Dots for Selective and Sensitive Fluorescence Detection of p-aminophenol in Water.

    PubMed

    Lu, Xialin; Wei, Fangdi; Xu, Guanhong; Wu, Yanzi; Yang, Jing; Hu, Qin

    2017-01-01

    In this paper, a selective and sensitive sensor for the determination of p-aminophenol (PAP) was developed by grafting molecularly imprinted polymers (MIPs) on the surface of silica-coated CdTe quantum dots (CdTe@SiO2@MIPs). The obtained CdTe@SiO2@MIPs were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and fluorescence spectroscopy. The fluorescence intensity of CdTe@SiO2@MIPs was more strongly quenched by PAP than that of the structural analogues of PAP. Under the optimal conditions, the fluorescence intensity of the CdTe@SiO2@MIPs decreased sensitively with the increase of PAP concentration in the range of 0.05-50 μM. The limit of detection was 0.02 μM (3σ/K sv). The sensor was successfully used to determine PAP in tap and lake water samples, and the average recoveries of PAP at various spiking levels ranged from 97.33 % to 103.3 % with relative standard deviations below 20 %.

  13. Fluorescence enhancement of CdTe quantum dots by HBcAb-HRP for sensitive detection of H2O2 in human serum.

    PubMed

    Gong, Tingting; Liu, Junfeng; Wu, Yiwei; Xiao, Yao; Wang, Xuehan; Yuan, Siqi

    2017-06-15

    A simple, high selective, ultra-sensitive and stable biosensor based on hepatitis B core antibody labeled with horseradish peroxidase (HBcAb-HRP) induced fluorescent enhancement of CdTe QDs for recognition of H2O2 have been constructed. In this assay, sulfurs in HBcAb-HRP, which possess a strong affinity towards Cd(2+), can improve greatly the recombination fluorescence of CdTe QDs by creating more radiative centers at CdTe/Cd-SR complex. Then, H2O2 oxidizes Cd-S bonds in CdTe QDs to organic disulfide product (RS-SR), causing thioglycolic acid (TGA) and HBcAb-HRP detach from surface of CdTe QDs and thus leading to fluorescence quenching. Just with the addition of HBcAb-HRP, sensitivity of the new biosensor has been improved by near one order of magnitude as compared with CdTe QDs probe. Detection limit of HBcAb-HRP-CdTe QDs biosensor for determination of H2O2 was 6.9×10(-8)mol L(-1) (3σ/slope), and the excellent linear range was 1.0×10(-7)~1.5×10(-4)molL(-1). By using sodium diethyldithiocarbamate (DDTC) and NH4OH as masking agents of Ag(+), Hg(2+) and Cu(2+), H2O2 can be selectively detected in coexistence with Ag(+), Hg(2+) and Cu(2+), and the biosensor has been used to detect H2O2 in human serum with satisfactory results. The superior properties of this biosensor showed great potential usage in more chemical and biological researches.

  14. Interaction of porphyrins with CdTe quantum dots.

    PubMed

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

    2011-05-13

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

  15. Immobilization of pH-sensitive CdTe Quantum Dots in a Poly(acrylate) Hydrogel for Microfluidic Applications

    NASA Astrophysics Data System (ADS)

    Franke, M.; Leubner, S.; Dubavik, A.; George, A.; Savchenko, T.; Pini, C.; Frank, P.; Melnikau, D.; Rakovich, Y.; Gaponik, N.; Eychmüller, A.; Richter, A.

    2017-04-01

    Microfluidic devices present the basis of modern life sciences and chemical information processing. To control the flow and to allow optical readout, a reliable sensor material that can be easily utilized for microfluidic systems is in demand. Here, we present a new optical readout system for pH sensing based on pH sensitive, photoluminescent glutathione capped cadmium telluride quantum dots that are covalently immobilized in a poly(acrylate) hydrogel. For an applicable pH sensing the generated hybrid material is integrated in a microfluidic sensor chip setup. The hybrid material not only allows in situ readout, but also possesses valve properties due to the swelling behavior of the poly(acrylate) hydrogel. In this work, the swelling property of the hybrid material is utilized in a microfluidic valve seat, where a valve opening process is demonstrated by a fluid flow change and in situ monitored by photoluminescence quenching. This discrete photoluminescence detection (ON/OFF) of the fluid flow change (OFF/ON) enables upcoming chemical information processing.

  16. Immobilization of pH-sensitive CdTe Quantum Dots in a Poly(acrylate) Hydrogel for Microfluidic Applications.

    PubMed

    Franke, M; Leubner, S; Dubavik, A; George, A; Savchenko, T; Pini, C; Frank, P; Melnikau, D; Rakovich, Y; Gaponik, N; Eychmüller, A; Richter, A

    2017-12-01

    Microfluidic devices present the basis of modern life sciences and chemical information processing. To control the flow and to allow optical readout, a reliable sensor material that can be easily utilized for microfluidic systems is in demand. Here, we present a new optical readout system for pH sensing based on pH sensitive, photoluminescent glutathione capped cadmium telluride quantum dots that are covalently immobilized in a poly(acrylate) hydrogel. For an applicable pH sensing the generated hybrid material is integrated in a microfluidic sensor chip setup. The hybrid material not only allows in situ readout, but also possesses valve properties due to the swelling behavior of the poly(acrylate) hydrogel. In this work, the swelling property of the hybrid material is utilized in a microfluidic valve seat, where a valve opening process is demonstrated by a fluid flow change and in situ monitored by photoluminescence quenching. This discrete photoluminescence detection (ON/OFF) of the fluid flow change (OFF/ON) enables upcoming chemical information processing.

  17. Hydride Generation for Headspace Solid-Phase Extraction with CdTe Quantum Dots Immobilized on Paper for Sensitive Visual Detection of Selenium.

    PubMed

    Huang, Ke; Xu, Kailai; Zhu, Wei; Yang, Lu; Hou, Xiandeng; Zheng, Chengbin

    2016-01-05

    A low-cost, simple, and highly selective analytical method was developed for sensitive visual detection of selenium in human urine both outdoors and at home, by coupling hydride generation with headspace solid-phase extraction using quantum dots (QDs) immobilized on paper. The visible fluorescence from the CdTe QDs immobilized on paper was quenched by H2Se from hydride generation reaction and headspace solid-phase extraction. The potential mechanism was investigated by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) as well as Density Functional Theory (DFT). Potential interferences from coexisting ions, particularly Ag(+), Cu(2+), and Zn(2+), were eliminated. The selectivity was significantly increased because the selenium hydride was effectively separated from sample matrices by hydride generation. Moreover, due to the high sampling efficiency of hydride generation and headspace solid phase extraction, the sensitivity and the limit of detection (LOD) were significantly improved compared to conventional methods. A LOD of 0.1 μg L(-1) and a relative standard deviation (RSD, n = 7) of 2.4% at a concentration of 20 μg L(-1) were obtained when using a commercial spectrofluorometer as the detector. Furthermore, a visual assay based on the proposed method was developed for the detection of Se, 5 μg L(-1) of selenium in urine can be discriminated from the blank solution with the naked eye. The proposed method was validated by analysis of certified reference materials and human urine samples with satisfactory results.

  18. Optical measurements for excitation of CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Vladescu, Marian; Feies, Valentin; Schiopu, Paul; Craciun, Alexandru; Grosu, Neculai; Manea, Adrian

    2016-12-01

    The paper presents the experimental results obtained using a laboratory setup installation for fluorescence excitation of CdTe QDs used as biomarkers for clinical diagnostics. Quantum Dots (QDs) made of Cadmium Telluride (CdTe), are highly fluorescent and they are used as robust biomarkers. Generally, QDs are referred to as the zero-dimensional colloidal crystals that possess strong size dependence and multi-colored luminescence properties. Along with its intrinsic features, such as sharp and symmetric emission, photo-stability and high quantum yields, QDs play a vital role in various applications, namely the identification of the chemical moieties, clinical diagnostics, optoelectronics, bio-imaging and bio-sensing1.

  19. Turn-on electrochemiluminescence sensing of Cd2+ based on CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Song, Honglei; Yang, Miao; Fan, Xinxin; Wang, Haiyan

    2014-12-01

    A simple and sensitive method for the detection of cadmium ion was proposed based on the electrochemiluminescence (ECL) of thioglycolic acid capped-CdTe quantum dots (CdTe QDs). The ECL of CdTe QDs was firstly quenched by introduction of S2- and was restored due to following addition of Cd2+, on the basis of which, a "turn-on" ECL method for the detection of Cd2+ was demonstrated. The ECL of CdTe QDs exhibited linear response toward Cd2+ concentration in the range from 6.3 nM to 3.4 μM (R = 0.999) with a detection limit of 2.1 nM. The proposed assay was simple, sensitive, selective, and practicable in real water samples.

  20. CdTe quantum dots for an application in the life sciences

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  1. An NMR quantum computer of the semiconductor CdTe

    NASA Astrophysics Data System (ADS)

    Shimizu, T.; Goto, A.; Hashi, K.; Ohki, S.

    2002-12-01

    We propose a method to implement a quantum computer by solid-state NMR. We can use the J-coupling for the quantum gate in CdTe. Both Cd and Te have two isotopes with spin 1/2, then we can have 4-qubits. The decoherence by dipole interaction may be minimized by preparing the isotope superlattice grown in the order of— 111Cd- 123Te- 113Cd- 125Te—in the [111] direction and by applying the magnetic field in the direction of [100], the magic angle of the dipole interaction. The optical pumping technique can be used in CdTe to make the initialization of the qubits.

  2. CdTe quantum dot-based fluorescent probes for selective detection of Hg (II): The effect of particle size

    NASA Astrophysics Data System (ADS)

    Zhu, Jian; Zhao, Zhu-Jun; Li, Jian-Jun; Zhao, Jun-Wu

    2017-04-01

    Mercury ions-induced fluorescence quenching properties of CdTe quantum dots (QDs) have been studied using the fluorescence spectroscopic techniques. By using the hydrothermal method, the CdTe QDs with different particles sizes from 1.98 to 3.68 nm have been prepared, and the corresponding fluorescence emission wavelength is changed from 518 to 620 nm. The fluorescence of QDs is enhanced after linking Bovine serum albumin (BSA) onto the surface of the QDs. Experimental results show that the fluorescence intensity of BSA-coated CdTe QDs could be effectively quenched when Hg2 + react with BSA-coated CdTe QDs. Interestingly, both the sensing sensitivity and selectivity of this fluorescence probe could be improved when the particle size of the QDs decreases. Thus the BSA-coated CdTe QDs with green fluorescence emission have better advantages than the BSA-coated CdTe QDs with red fluorescence for Hg2 + detection. Interference experiment results indicate that the influence from other metal ions could be neglected in the detection, and the Hg2 + could be specifically detected. By using this BSA-coated CdTe QDs-based fluorescence probe, the Hg2 + could be detected with an ultra-low detection limit of nanomole level, and the linear range spans a scope from 0.001 to 1 μmol/L.

  3. CdTe quantum dot as a fluorescence probe for vitamin B(12) in dosage form.

    PubMed

    Vaishnavi, E; Renganathan, R

    2013-11-01

    We here report the CdTe quantum dot (CdTe QDs)-based sensor for probing vitamin B12 derivatives in aqueous solution. In this paper, simple and sensitive fluorescence quenching measurements has been employed. The Stern-Volmer constant (KSV), quenching rate constant (kq) and binding constant (K) were rationalized from fluorescence quenching measurement. Furthermore, the fluorescence resonance energy transfer (FRET) mechanism was discussed. This method was applicable over the concentration ranging from 1 to 14μg/mL (VB12) with correlation coefficient of 0.993. The limit of detection (LOD) of VB12 was found to be 0.15μg/mL. Moreover, the present approach opens a simple pathway for developing cost-effective, sensitive and selective QD-based fluorescence sensors/probes for biologically significant VB12 in pharmaceutical sample with mean recoveries in the range of 100-102.1%.

  4. CdTe quantum dot as a fluorescence probe for vitamin B12 in dosage form

    NASA Astrophysics Data System (ADS)

    Vaishnavi, E.; Renganathan, R.

    2013-11-01

    We here report the CdTe quantum dot (CdTe QDs)-based sensor for probing vitamin B12 derivatives in aqueous solution. In this paper, simple and sensitive fluorescence quenching measurements has been employed. The Stern-Volmer constant (KSV), quenching rate constant (kq) and binding constant (K) were rationalized from fluorescence quenching measurement. Furthermore, the fluorescence resonance energy transfer (FRET) mechanism was discussed. This method was applicable over the concentration ranging from 1 to 14 μg/mL (VB12) with correlation coefficient of 0.993. The limit of detection (LOD) of VB12 was found to be 0.15 μg/mL. Moreover, the present approach opens a simple pathway for developing cost-effective, sensitive and selective QD-based fluorescence sensors/probes for biologically significant VB12 in pharmaceutical sample with mean recoveries in the range of 100-102.1%.

  5. Interfacial charge transfer between CdTe quantum dots and Gram negative vs. Gram positive bacteria.

    SciTech Connect

    Dumas, E.; Gao, C.; Suffern, D.; Bradforth, S. E.; Dimitrejevic, N. M.; Nadeau, J. L.; McGill Univ.; Univ. of Southern California

    2010-01-01

    Oxidative toxicity of semiconductor and metal nanomaterials to cells has been well established. However, it may result from many different mechanisms, some requiring direct cell contact and others resulting from the diffusion of reactive species in solution. Published results are contradictory due to differences in particle preparation, bacterial strain, and experimental conditions. It has been recently found that C{sub 60} nanoparticles can cause direct oxidative damage to bacterial proteins and membranes, including causing a loss of cell membrane potential (depolarization). However, this did not correlate with toxicity. In this study we perform a similar analysis using fluorescent CdTe quantum dots, adapting our tools to make use of the particles fluorescence. We find that two Gram positive strains show direct electron transfer to CdTe, resulting in changes in CdTe fluorescence lifetimes. These two strains also show changes in membrane potential upon nanoparticle binding. Two Gram negative strains do not show these effects - nevertheless, they are over 10-fold more sensitive to CdTe than the Gram positives. We find subtoxic levels of Cd{sup 2+} release from the particles upon irradiation of the particles, but significant production of hydroxyl radicals, suggesting that the latter is a major source of toxicity. These results help establish mechanisms of toxicity and also provide caveats for use of certain reporter dyes with fluorescent nanoparticles which will be of use to anyone performing these assays. The findings also suggest future avenues of inquiry into electron transfer processes between nanomaterials and bacteria.

  6. Apparent quantum efficiency effects in CdTe solar cells

    NASA Astrophysics Data System (ADS)

    Gloeckler, M.; Sites, J. R.

    2004-04-01

    Quantum efficiency measurements of n-CdS/p-CdTe solar cells performed under nonstandard illumination, voltage bias, or both can be severely distorted by photogeneration and contact-barrier effects. In this work we will discuss the effects that are typically observed, the requirements needed to reproduce these effects with modeling tools, and the potential applications of apparent quantum efficiency analysis. Recently published experimental results are interpreted and reproduced using numerical simulation tools. The suggested model explains large negative apparent quantum efficiencies (≫100%) seen in the spectral range of 350-550 nm, modestly large negative apparent quantum efficiencies (>100%) in the spectral range of 800-850 nm, enhanced positive or negative response observed under red, blue, and white light bias, and photocurrent gain significantly different from unity. Some of these effects originate from the photogeneration in the highly compensated CdS window layer, some from photogeneration within the CdTe, and some are further modified by the height of the CdTe back-contact barrier.

  7. Fabrication of CdTe quantum dots-apoferritin arrays for detection of dopamine

    NASA Astrophysics Data System (ADS)

    Le, Thi Hoa; Kim, Ji Hyeon; Park, Sang Joon

    2017-06-01

    A method was proposed for detecting dopamine using a two-dimensional CdTe quantum dots (QDs)-apoferritin array fabricated on a modified silicon (Si) surface. First, CdTe QDs were synthesized in the cavity of horse spleen apoferritin (HsAFr). Then, the characterization of CdTe QDs in apoferritin was performed using photoluminescence (PL) spectroscopy. Transmission electron microscopy was used to analyze the size and structure of CdTe QDs. An atomic force microscopy image was obtained to evaluate the topography of the Si surface. In addition, the PL change resulting from the conjugation reaction of the CdTe QDs-apoferritin array with dopamine was investigated. When the array was linked to dopamine, a significant quenching of fluorescence was observed. Accordingly, the CdTe QDs-apoferritin arrays could be employed as useful sensing media for dopamine detection.

  8. Radiation detection with CdTe quantum dots in sol-gel glass and polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Manickaraj, Kavin; Wagner, Brent K.; Kang, Zhitao

    2013-05-01

    Optically based radiation detectors in various fields of science still suffer from low resolution, sensitivity and efficiency that restrict their overall performance. Quantum dots (QD) are well-suited for such detectors due to their unique optical properties. CdTe QDs show fast luminescence decay times, high conversion efficiencies, and have band gaps strongly dependent on the particle radius. Since QD particle sizes are well below the wavelengths of their emissions, they remain optically transparent when incorporated in both polymer and sol-gel based silica glass due to negligible optical scattering. In addition, as these composite materials can greatly improve the mechanical robustness of alpha-particle detectors, conventionally known to have delicate components, CdTe QDs show high promise for radiation sensing applications. These properties are especially advantageous for alpha-particle and potentially neutron detection. In this work, CdTe QD-based glass or polymer matrix nanocomposites were synthesized for use as alpha-particle detection scintillators.. The fast photo-response and decay times provide excellent time resolution. The radiation responses of such nanocomposites in polymer or glass matrices were investigated.

  9. Aqueous phase synthesis of CdTe quantum dots for biophotonics.

    PubMed

    Yong, Ken-Tye; Law, Wing-Cheung; Roy, Indrajit; Jing, Zhu; Huang, Huijie; Swihart, Mark T; Prasad, Paras N

    2011-01-01

    Over the past few years, CdTe quantum dots have been demonstrated as powerful probes for biophotonics applications. The aqueous phase synthesis technique remains the best approach to make high quality CdTe QDs in a single-pot process. CdTe QDs prepared directly in the aqueous phase can have quantum yield as high as 80%. In addition, the surface of CdTe QDs prepared using the aqueous phase technique is functionalized with reactive groups that enable them to be directly conjugated with specific ligands for targeted delivery and sensing. In this contribution, we review recent progress in fabricating aqueous CdTe QDs and exploiting their optical properties in novel approaches to biomedical imaging and sensing applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Laser ablation synthesis route of CdTe colloidal quantum dots for biological applications

    NASA Astrophysics Data System (ADS)

    Almeida, D. B.; Rodriguez, E.; Moreira, R. S.; Agouram, S.; Barbosa, L. C.; Jimenez, E.; Cesar, C. L.

    2009-07-01

    In this work we report a novel technique for obtain thiol capped CdTe colloidal quantum dots in one step. These nanoparticles are compatible for silica capping indicating their possible use as fluorescent markers.

  11. Systematic study of the interaction of cobalt ions with different-sized CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Zhong, Wenying; Liang, Jiaran; Yu, Junsheng

    2009-10-01

    Five sizes of water-dispersed CdTe quantum dots (QDs) stabilized by thioglycolic acid (TGA) with a high photoluminescence (PL) quantum yield were synthesized and a size dependent quenching of the fluorescence by cobalt ions was also observed. No matter for smaller or larger particles, obvious quenching effect was observed, and the fluorescence quenching of CdTe nanoparticles depended on the concentration of cobalt ions solution. However, CdTe QDs with different size showed dramatically different quenching efficiency, sensitivity, linear range and selectivity. With the increase of size, the quenching efficiency reduced correspondingly. The smallest particle was the most sensitive with the limit of detection for cobalt ions is 7.3 × 10 -9 mol L -1 Co 2+. For larger particles, the sensitivity was much lower, but the linear range was relatively wide, under optimal conditions, the quenched fluorescence intensity increased linearly with the concentration of cobalt ions ranging from 3.32 × 10 -8 to 3.62 × 10 -6 mol L -1. Besides, the influence on the fluorescence signal of foreign cations, including Ca 2+, Mg 2+, Ni 2+, Ba 2+, Zn 2+, Cu 2+, Fe 3+ and Ag + were also studied, results showed a high selectivity of the smaller QDs towards cobalt ions. According to Stern-Volmer-type equation, quenching of quantum dot luminescence was most effective for the smallest particles with the highest Ksv.

  12. Super fast detection of latent fingerprints with water soluble CdTe quantum dots.

    PubMed

    Cai, Kaiyang; Yang, Ruiqin; Wang, Yanji; Yu, Xuejiao; Liu, Jianjun

    2013-03-10

    A new method based on the use of highly fluorescent water-soluble cadmium telluride (CdTe) quantum dots (QDs) capped with mercaptosuccinic acid (MSA) was explored to develop latent fingerprints. After optimized the effectiveness of QDs method contains pH value and developing time, super fast detection was achieved. Excellent fingerprint images were obtained in 1-3s after immersed the latent fingerprints into quantum dots solution on various non-porous surfaces, i.e. adhesive tape, transparent tape, aluminum foil and stainless steel. High sensitivity of the new latent fingerprints develop method was obtained by developing the fingerprints pressed on aluminum foil successively with the same finger. Compared with methyl violet and rhodamine 6G, the MSA-CdTe QDs showed the higher develop speed and fingerprint image quality. Clear image can be maintained for months by extending exposure time of CCD camera, storing fingerprints in a low temperature condition and secondary development.

  13. The role of stress in CdTe quantum dot doped glasses

    NASA Astrophysics Data System (ADS)

    de Thomaz, A. A.; Almeida, D. B.; Pelegati, V. B.; Carvalho, H. F.; Moreira, S. G. C.; Barbosa, L. C.; Cesar, C. L.

    2016-11-01

    In this work, we unequivocally demonstrate the influence of matrix-related stresses on quantum dots by measuring, side by side, a CdTe quantum dot doped glass and a colloidal sample with similar sizes. We measured the fluorescence spectra and fluorescence lifetime for both samples as a function of the temperature. We show that the expansion coefficient mismatch between CdTe quantum dots and the glass host causes stresses and drastically changes its behavior compared to its colloidal counterpart, even leading to phase transitions. This finding indicates that most experimental data on glass-doped quantum dots used to validate confinement models should be revised, taking stress into account.

  14. The interactions of glutathione-capped CdTe quantum dots with trypsin.

    PubMed

    Yang, Bingjun; Liu, Rutao; Hao, Xiaopeng; Wu, Yongzhong; Du, Jie

    2012-06-01

    Due to their unique fluorescent properties, quantum dots present a great potential for biolabelling applications; however, the toxic interactions of quantum dots with biopolymers are little known. The toxic interactions of glutathione-capped CdTe quantum dots with trypsin were studied in this paper using synchronous fluorescence spectroscopy, fluorescence emission spectra, and UV-vis absorption spectra. The interaction between CdTe quantum dots and trypsin resulted in structure changes of trypsin and inhibited trypsin's activity. Fluorescence emission spectra revealed that the quenching mechanism of trypsin by CdTe quantum dots was a static quenching process. The binding constant and the number of binding sites at 288 and 298 K were calculated to be 1.98 × 10(6) L mol(-1) and 1.37, and 6.43 × 10(4) L mol(-1) and 1.09, respectively. Hydrogen bonds and van der Waals' forces played major roles in this process.

  15. Study on CdTe Quantum Dots Electrochemiluminescent Sensor Supported by Carbon Nano-tubes With ITO Basal Electrode

    NASA Astrophysics Data System (ADS)

    Caixia, Yu; Jilin, Yan; Yifeng, Tu

    2011-05-01

    The water soluble CdTe quantum dots (QDs) was synthesized with modified method. Its quantum yield was characterized for higher than 54%. Therefore a novel sensitive electrochemiluminescent (ECL) sensor was constructed based on the modification of composite of CdTe QDs, carbon nanotubes (CNTs) and chitosan (CHIT) on indium tin oxide (ITO) glass. After heat-treatment by infrared radiation, meanwhile with the co-reactant, triethylamine (TEA), the proposed sensor showed excellent anodic ECL efficiency and stability. This ECL sensor responded the dopamine (DA) in a wide linear range from 50 pM to 10 nM with a detection limit of 24 pM due to the quenching effect from DA. The DA contents in practical biological samples of cerebro-spinal fluid were detected with satisfactory recovery of average 95.7%.

  16. Hydrothermal synthetic mercaptopropionic acid stabled CdTe quantum dots as fluorescent probes for detection of Ag⁺.

    PubMed

    Gan, Ting-Ting; Zhang, Yu-Jun; Zhao, Nan-Jing; Xiao, Xue; Yin, Gao-Fang; Yu, Shao-Hui; Wang, Huan-Bo; Duan, Jing-Bo; Shi, Chao-Yi; Liu, Wen-Qing

    2012-12-01

    Mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) with particle size 3 nm have been successfully synthesized in aqueous medium by hydrothermal synthesis method. And the effects of different metal ions on MPA capped CdTe QDs fluorescence were studied using fluorescence spectrometry. The results demonstrated that at the same concentration level, Ag(+) could strongly quench CdTe QDs fluorescence, and the other metal ions had little effect on CdTe QDs fluorescence except Cu(2+). On the basis of this fact, a rapid, simple, highly sensitive and selective method based on fluorescence quenching principle for Ag(+) detection in aqueous solution was proposed. Under optimal conditions, the quenched fluorescence intensity (F(0)-F) increased linearly with the concentration of Ag(+) ranging from 4 × 10(-7) to 32 × 10(-7)mol L(-1). The limit of detection for Ag(+) was 4.106 × 10(-8)mol L(-1). The obtained plot of F(0)/F versus [Ag(+)] was an upward curvature, concave towards the y-axis, rather than a straight line. The modified form of the Stern-Volmer equation was third order in Ag(+) concentration. According to the modified Stern-Volmer equation, it can be inferred that dynamic quenching and static quenching simultaneously occurred when Ag(+) interacted with MPA capped CdTe QDs. At the same time other factors might also influence the quenching process. Based on this study, hydrothermal synthesized MPA capped CdTe QDs with particle size 3 nm may be used as a novel fluorescence probe to quantificationally and selectively detect Ag(+).

  17. CdTe quantum dots@luminol as signal amplification system for chrysoidine with chemiluminescence-chitosan/graphene oxide-magnetite-molecularly imprinting sensor

    NASA Astrophysics Data System (ADS)

    Duan, Huimin; Li, Leilei; Wang, Xiaojiao; Wang, Yanhui; Li, Jianbo; Luo, Chuannan

    2016-01-01

    A sensitive chemiluminescence (CL) sensor based on chemiluminescence resonance energy transfer (CRET) in CdTe quantum dots@luminol (CdTe QDs@luminol) nanomaterials combined with chitosan/graphene oxide-magnetite-molecularly imprinted polymer (Cs/GM-MIP) for sensing chrysoidine was developed. CdTe QDs@luminol was designed to not only amplify the signal of CL but also reduce luminol consumption in the detection of chrysoidine. On the basis of the abundant hydroxy and amino, Cs and graphene oxide were introduced into the GM-MIP to improve the adsorption ability. The adsorption capacities of chrysoidine by both Cs/GM-MIP and non-imprinted polymer (Cs/GM-NIP) were investigated, and the CdTe QDs@luminol and Cs/GM-MIP were characterized by UV-vis, FTIR, SEM and TEM. The proposed sensor can detect chrysoidine within a linear range of 1.0 × 10- 7 - 1.0 × 10- 5 mol/L with a detection limit of 3.2 × 10- 8 mol/L (3δ) due to considerable chemiluminescence signal enhancement of the CdTe quantum dots@luminol detector and the high selectivity of the Cs/GM-MIP system. Under the optimal conditions of CL, the CdTe QDs@luminol-Cs/GM-MIP-CL sensor was used for chrysoidine determination in samples with satisfactory recoveries in the range of 90-107%.

  18. CdTe quantum dots and YAG hybrid phosphors for white light-emitting diodes.

    PubMed

    Yin, Yanchun; Wang, Rongfang; Zhou, Liya

    2014-09-01

    CdTe quantum dots, 3.28 nm in size, were synthesized using a one-step method in an aqueous medium. The CdTe quantum dots were successfully employed as hybrid phosphors for white light-emitting diode (LED) devices by combining them with yellow-emitting YAG:Ce phosphor. The color-rendering index value and International Commission on illumination coordinates for hybrid phosphor white LEDs were 75 and (x = 0.30, y = 0.29), respectively. Compared with conventional phosphors, semiconductor quantum dots have larger band gap energy and broader absorption features, and can be excited more efficiently by optical pumping sources. The results confirmed that the high color-rendering index value of the white LED was due to the CdTe quantum dots introduced in the hybrid phosphor system.

  19. Photo-induced interaction of thioglycolic acid (TGA)-capped CdTe quantum dots with cyanine dyes.

    PubMed

    Abdelbar, Mostafa F; Fayed, Tarek A; Meaz, Talaat M; Ebeid, El-Zeiny M

    2016-11-05

    The photo-induced interaction of three different sizes of thioglycolic acid (TGA)-capped CdTe quantum dots (CdTe QDs) with two monomethine cyanine dyes belonging to the thiazole orange (TO) family has been studied. Positively charged cyanines interact with QDs surface which is negatively charged due to capping agent carboxylate ions. The energy transfer parameters including Stern-Volmer constant, Ksv, number of binding sites, n, quenching sphere radius, r, the critical energy transfer distance, R0, and energy transfer efficiencies, E have been calculated. The effect of structure and the number of aggregating molecules have been studied as a function of CdTe QDs particle size. Combining organic and inorganic semiconductors leads to increase of the effective absorption cross section of the QDs which can be utilized in novel nanoscale designs for light-emitting, photovoltaic and sensor applications. A synthesized triplet emission of the studied dyes was observed using CdTe QDs as donors and this is expected to play a potential role in molecular oxygen sensitization and in photodynamic therapy (PDT) applications.

  20. Photo-induced interaction of thioglycolic acid (TGA)-capped CdTe quantum dots with cyanine dyes

    NASA Astrophysics Data System (ADS)

    Abdelbar, Mostafa F.; Fayed, Tarek A.; Meaz, Talaat M.; Ebeid, El-Zeiny M.

    2016-11-01

    The photo-induced interaction of three different sizes of thioglycolic acid (TGA)-capped CdTe quantum dots (CdTe QDs) with two monomethine cyanine dyes belonging to the thiazole orange (TO) family has been studied. Positively charged cyanines interact with QDs surface which is negatively charged due to capping agent carboxylate ions. The energy transfer parameters including Stern-Volmer constant, Ksv, number of binding sites, n, quenching sphere radius, r, the critical energy transfer distance, R0, and energy transfer efficiencies, E have been calculated. The effect of structure and the number of aggregating molecules have been studied as a function of CdTe QDs particle size. Combining organic and inorganic semiconductors leads to increase of the effective absorption cross section of the QDs which can be utilized in novel nanoscale designs for light-emitting, photovoltaic and sensor applications. A synthesized triplet emission of the studied dyes was observed using CdTe QDs as donors and this is expected to play a potential role in molecular oxygen sensitization and in photodynamic therapy (PDT) applications.

  1. Fluorescence-tagged metallothionein with CdTe quantum dots analyzed by the chip-CE technique

    NASA Astrophysics Data System (ADS)

    Guszpit, Ewelina; Krizkova, Sona; Kepinska, Marta; Rodrigo, Miguel Angel Merlos; Milnerowicz, Halina; Kopel, Pavel; Kizek, Rene

    2015-11-01

    Quantum dots (QDs) are fluorescence nanoparticles (NPs) with unique optic properties which allow their use as probes in chemical, biological, immunological, and molecular imaging. QDs linked with target ligands such as peptides or small molecules can be used as tumor biomarkers. These particles are a promising tool for selective, fast, and sensitive tagging and imaging in medicine. In this study, an attempt was made to use QDs as a marker for human metallothionein (MT) isoforms 1 and 2. Four kinds of CdTe QDs of different sizes bioconjugated with MT were analyzed using the chip-CE technique. Based on the results, it can be concluded that MT is willing to interact with QDs, and the chip-CE technique enables the observation of their complexes. It was also observed that changes ranging roughly 6-7 kDa, a value corresponding to the MT monomer, depend on the hydrodynamic diameters of QDs; also, the MT sample without cadmium interacted stronger with QDs than MT saturated with cadmium. Results show that MT is willing to interact with smaller QDs (blue CdTe) rather than larger ones QDs (red CdTe). To our knowledge, chip-CE has not previously been applied in the study of CdTe QDs interaction with MT.

  2. Determination of 2-methoxyestradiol by chemiluminescence based on luminol-KMnO4-CdTe quantum dots system

    NASA Astrophysics Data System (ADS)

    Du, Bin; Wang, Tiantian; Han, Shuping; Cao, Xiaohui; Qu, Tiantian; Zhao, Feifei; Guo, Xinhong; Yao, Hanchun

    2015-02-01

    In this study, water-soluble CdTe quantum-dots (QDs) capped with glutathione (GSH) was synthesized. It was found that CdTe QDs could greatly enhance the chemiluminescence (CL) emission from the luminol-KMnO4 system in alkaline medium, and 4 nm CdTe QDs was used as catalysts to enhance the reaction sensitivity. The CL intensity of CdTe QDs-luminol-KMnO4 was strongly inhibited in the presence of 2-methoxyestradiol (2-ME) and the relative CL intensity was in linear correlation with the concentration of 2-ME. Based on this inhibition, a novel CL method with a lower detection limit and wider linear range was developed for the determination of 2-ME. The detection limit of plasma samples was 3.07 × 10-10 g mL-1 with a relative standard deviation of 0.24% for 8.0 × 10-9 g mL-1 2-ME. The method was successfully applied for determination of 2-ME in plasma samples. The possible CL reaction mechanism was also discussed briefly.

  3. Determination of 2-methoxyestradiol by chemiluminescence based on luminol-KMnO4-CdTe quantum dots system.

    PubMed

    Du, Bin; Wang, Tiantian; Han, Shuping; Cao, Xiaohui; Qu, Tiantian; Zhao, Feifei; Guo, Xinhong; Yao, Hanchun

    2015-02-05

    In this study, water-soluble CdTe quantum-dots (QDs) capped with glutathione (GSH) was synthesized. It was found that CdTe QDs could greatly enhance the chemiluminescence (CL) emission from the luminol-KMnO4 system in alkaline medium, and 4 nm CdTe QDs was used as catalysts to enhance the reaction sensitivity. The CL intensity of CdTe QDs-luminol-KMnO4 was strongly inhibited in the presence of 2-methoxyestradiol (2-ME) and the relative CL intensity was in linear correlation with the concentration of 2-ME. Based on this inhibition, a novel CL method with a lower detection limit and wider linear range was developed for the determination of 2-ME. The detection limit of plasma samples was 3.07×10(-10) g mL(-1) with a relative standard deviation of 0.24% for 8.0×10(-9) g mL(-1) 2-ME. The method was successfully applied for determination of 2-ME in plasma samples. The possible CL reaction mechanism was also discussed briefly. Copyright © 2014. Published by Elsevier B.V.

  4. Enhanced chemiluminescence of CdTe quantum dots-H2O2 by horseradish peroxidase-mimicking DNAzyme

    NASA Astrophysics Data System (ADS)

    Zhang, Junli; Li, Baoxin

    In this study, it was found that horseradish peroxidase (HRP)-mimicking DNAzyme could effectively enhance the CL emission of CdTe quantum dots (QDs)-H2O2 system, whereas HRP could not enhance the CL intensity. The CL enhancement mechanism was investigated, and the CL enhancement was supposed to originate from the catalysis of HRP-mimicking DNAzyme on the CL reaction between CdTe QDs and H2O2. Meantime, compared with CdTe QDs-H2O2 CL system, H2O2 concentration was markedly decreased in QDs-H2O2-HRP-mimicking DNAzyme CL system, improving the stability of QDs-H2O2 CL system. The QDs-based CL system was used to detect sensitively CdTe QDs and HRP-mimicking DNAzyme (as biologic labels). This work gives a path for enhancing CL efficiency of QDs system, and will be helpful to promote the step of QDs application in various fields such as bioassay and trace detection of analyte.

  5. Glucose biosensor based on nanocomposite films of CdTe quantum dots and glucose oxidase.

    PubMed

    Li, Xinyu; Zhou, Yunlong; Zheng, Zhaozhu; Yue, Xiuli; Dai, Zhifei; Liu, Shaoqin; Tang, Zhiyong

    2009-06-02

    A blood glucose sensor has been developed based on the multilayer films of CdTe semiconductor quantum dots (QDs) and glucose oxidase (GOD) by using the layer-by-layer assembly technique. When the composite films were contacted with glucose solution, the photoluminescence of QDs in the films was quickly quenched because the enzyme-catalyzed reaction product (H2O2) of GOD and glucose gave rise to the formation of surface defects on QDs. The quenching rate was a function of the concentration of glucose. The linear range and sensitivity for glucose determination could be adjusted by controlling the layers of QDs and GOD. The biosensor was used to successfully determine the concentration of blood glucose in real serum samples without sample pretreatment and exhibited satisfactory reproducibility and accuracy.

  6. Temperature-Dependent Exciton and Trap-Related Photoluminescence of CdTe Quantum Dots Embedded in a NaCl Matrix: Implication in Thermometry.

    PubMed

    Kalytchuk, Sergii; Zhovtiuk, Olga; Kershaw, Stephen V; Zbořil, Radek; Rogach, Andrey L

    2016-01-27

    Temperature-dependent optical studies of semiconductor quantum dots (QDs) are fundamentally important for a variety of sensing and imaging applications. The steady-state and time-resolved photoluminescence properties of CdTe QDs in the size range from 2.3 to 3.1 nm embedded into a protective matrix of NaCl are studied as a function of temperature from 80 to 360 K. The temperature coefficient is found to be strongly dependent on QD size, with the highest sensitivity obtained for the smallest size of QDs. The emission from solid-state CdTe QD-based powders is maintained with high color purity over a wide range of temperatures. Photoluminescence lifetime data suggest that temperature dependence of the intrinsic radiative lifetime in CdTe QDs is rather weak, and it is mostly the temperature-dependent nonradiative decay of CdTe QDs which is responsible for the thermal quenching of photoluminescence intensity. By virtue of the temperature-dependent photoluminescence behavior, high color purity, photostability, and high photoluminescence quantum yield (26%-37% in the solid state), CdTe QDs embedded in NaCl matrices are useful solid-state probes for thermal imaging and sensing over a wide range of temperatures within a number of detection schemes and outstanding sensitivity, such as luminescence thermochromic imaging, ratiometric luminescence, and luminescence lifetime thermal sensing. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. [The quantification of gemifloxacin by fluorescence quenching method using chitosan-coated CdTe quantum dots].

    PubMed

    Zhong, Wen-Ying; Wang, Yan; Huang, Bin; Shu, Chang

    2012-06-01

    Chitosan-coated CdTe quantum dots can reduce QDs toxicity and enhance its stability in aqueous solution. Chitosan-coated CdTe QDs were used as fluorescence probes to determine Gemifloxacin on the basis of fluorescence quenching method. The results indicated that the relative fluorescence intensity was linearly proportional to the Gemifloxacin concentration in the range of 3.46 x 10(-9)-3.46 x 10(-7) g x L(-1) with a linear fitting equation of F0/F= 1.0637 + 0.016 7c(g x L(-1)) and the RSD was 2.7%. On the basis of fluorescence quenching method theory, it was concluded that the interaction between QDs and Gemifloxacin was a kind of static quenching through hydrogen bonding and Van der Waals force, and the binding sites value was 0.8. This method with high sensitivity and broad linear range provided a new approach to determining Gemifloxacin.

  8. Optical properties and charge carrier dynamics of CdTe quantum dots in silicate glasses

    NASA Astrophysics Data System (ADS)

    Li, Wenke; Zhang, Wenchao; Xia, Mengling; Liu, Chao; Wang, Jing

    2017-05-01

    CdTe quantum dots (QDs) in silicate glasses were fabricated through conventional melt-quenching and heat-treatment; steady-state and transient optical properties of CdTe QDs were investigated. CdTe QDs with diameters of 2.3-5.9 nm with photoluminescence in the range of 553-768 nm were precipitated in the glasses. Time-resolved photoluminescence and transient absorption analysis showed that photoluminescence of CdTe QDs was composed of intrinsic emission and defect emission. Oxidation of Te2- and formation of Te2 during thermal treatment led to the unpassivated Cd2+ on the surface of CdTe QDs and formation of shallow trapping states. The photo-generated electrons were trapped by the shallow surface states of CdTe QDs within 0.4±0.03 ps, and Auger recombination processes occurred within a timescale of 3.2±0.35 ps. Both intrinsic emission and defect emission with effective lifetimes of several nanoseconds and dozens of nanoseconds were observed.

  9. Position-sensitive CdTe detector using improved crystal growth method

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The feasibility of developing a position-sensitive CdTe detector array for astronomical observations in the hard X-ray, soft gamma ray region is demonstrated. In principle, it was possible to improve the resolution capability for imaging measurements in this region by orders of magnitude over what is now possible through the use of CdTe detector arrays. The objective was to show that CdTe crystals of the quality, size and uniformity required for this application can be obtained with a new high pressure growth technique. The approach was to fabricate, characterize and analyze a 100 element square array and several single-element detectors using crystals from the new growth process. Results show that detectors fabricated from transversely sliced, 7 cm diameter wafers of CdTe exhibit efficient counting capability and a high degree of uniformity over their entire areas. A 100 element square array of 1 sq mm detectors was fabricated and operated.

  10. Facile preparation of highly luminescent CdTe quantum dots within hyperbranched poly(amidoamine)s and their application in bio-imaging

    PubMed Central

    2014-01-01

    A new strategy for facile preparation of highly luminescent CdTe quantum dots (QDs) within amine-terminated hyperbranched poly(amidoamine)s (HPAMAM) was proposed in this paper. CdTe precursors were first prepared by adding NaHTe to aqueous Cd2+ chelated by 3-mercaptopropionic sodium (MPA-Na), and then HPAMAM was introduced to stabilize the CdTe precursors. After microwave irradiation, highly fluorescent and stable CdTe QDs stabilized by MPA-Na and HPAMAM were obtained. The CdTe QDs showed a high quantum yield (QY) up to 58%. By preparing CdTe QDs within HPAMAM, the biocompatibility properties of HPAMAM and the optical, electrical properties of CdTe QDs can be combined, endowing the CdTe QDs with biocompatibility. The resulting CdTe QDs can be directly used in biomedical fields, and their potential application in bio-imaging was investigated. PMID:24624925

  11. Near-Unity Quantum Yields from Chloride Treated CdTe Colloidal Quantum Dots

    PubMed Central

    Page, Robert C; Espinobarro-Velazquez, Daniel; Leontiadou, Marina A; Smith, Charles; Lewis, Edward A; Haigh, Sarah J; Li, Chen; Radtke, Hanna; Pengpad, Atip; Bondino, Federica; Magnano, Elena; Pis, Igor; Flavell, Wendy R; O'Brien, Paul; Binks, David J

    2015-01-01

    Colloidal quantum dots (CQDs) are promising materials for novel light sources and solar energy conversion. However, trap states associated with the CQD surface can produce non-radiative charge recombination that significantly reduces device performance. Here a facile post-synthetic treatment of CdTe CQDs is demonstrated that uses chloride ions to achieve near-complete suppression of surface trapping, resulting in an increase of photoluminescence (PL) quantum yield (QY) from ca. 5% to up to 97.2 ± 2.5%. The effect of the treatment is characterised by absorption and PL spectroscopy, PL decay, scanning transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. This process also dramatically improves the air-stability of the CQDs: before treatment the PL is largely quenched after 1 hour of air-exposure, whilst the treated samples showed a PL QY of nearly 50% after more than 12 hours. PMID:25348200

  12. A selective determination of copper ions in water samples based on the fluorescence quenching of thiol-capped CdTe quantum dots.

    PubMed

    Nurerk, Piyaluk; Kanatharana, Proespichaya; Bunkoed, Opas

    2016-03-01

    CdTe quantum dots (QDs) capped with different stabilizers, i.e. thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA) and glutathione (GSH) were investigated as fluorescent probes for the determination of Cu(2+). The stabilizer was shown to play an important role in both the sensitivity and selectivity for the determination of Cu(2+). TGA-capped CdTe QDs showed the highest sensitivity, followed by the MPA and GSH-capped CdTe QDs, respectively. The TGA- and MPA-capped CdTe QDs were not selective for Cu(2+) that was affected by Ag(+). The GSH-capped CdTe QDs were insensitive to Ag(+) and were used to determine Cu(2+) in water samples. Under optimal conditions, quenching of the fluorescence intensity (F0/F) increased linearly with the concentration of Cu(2+) over a range of 0.10-4.0 µg/mL and the detection limit was 0.06 µg/mL. The developed method was successfully applied to the determination of Cu(2+) in water samples. Good recoveries of 93-104%, with a relative standard deviation of < 6% demonstrated that the developed simple method was accurate and reliable. The quenching mechanisms were also described.

  13. Evidence of Quantum Resonance in Periodically-Ordered Three-Dimensional Superlattice of CdTe Quantum Dots.

    PubMed

    Kim, DaeGwi; Tomita, Shougo; Ohshiro, Kazuma; Watanabe, Taichi; Sakai, Takenobu; Chang, I-Ya; Hyeon-Deuk, Kim

    2015-07-08

    Semiconductor quantum dot (QD) superlattices, which are periodically ordered three-dimensional (3D) array structures of QDs, are expected to exhibit novel photo-optical properties arising from the resonant interactions between adjacent QDs. Since the resonant interactions such as long-range dipole-dipole Coulomb coupling and short-range quantum resonance strongly depend on inter-QD nano space, precise control of the nano space is essential for physical understanding of the superlattice, which includes both of nano and bulk scales. Here, we study the pure quantum resonance in the 3D CdTe QD superlattice deposited by a layer-by-layer assembly of positively charged polyelectrolytes and negatively charged CdTe QDs. From XRD measurements, existence of the periodical ordering of QDs both in the lamination and in-plane directions, that is, the formation of the 3D periodic QD superlattice, was confirmed. The lowest excitation energy decreases exponentially with decreasing the nano space between the CdTe QD layers and also with decreasing the QD size, which is apparently indicative of the quantum resonance between the QDs rather than a dipole-dipole Coulomb coupling. The quantum resonance was also computationally demonstrated and rationalized by the orbital delocalization to neighboring CdTe QDs in the superlattice.

  14. Graphene-amplified electrogenerated chemiluminescence of CdTe quantum dots for H2O2 sensing.

    PubMed

    Wang, Zhonghui; Song, Hongjie; Zhao, Huihui; Lv, Yi

    2013-01-01

    Electrogenerated chemiluminescence (ECL) of thiol-capped CdTe quantum dots (QDs) in aqueous solution was greatly enhanced by PDDA-protected graphene (P-GR) film that were used for the sensitive detection of H2 O2 . When the potential was cycled between 0 and -2.3 V, two ECL peaks were observed at -1.1 (ECL-1) and -1.4 V (ECL-2) in pH 11.0, 0.1 M phosphate buffer solution (PBS), respectively. The electron-transfer reaction between individual electrochemically-reduced CdTe nanocrystal species and oxidant coreactants (H2 O2 or reduced dissolved oxygen) led to the production of ECL-1. While mass nanocrystals packed densely in the film were reduced electrochemically, assembly of reduced nanocrystal species reacted with coreactants to produce an ECL-2 signal. ECL-1 showed higher sensitivity for the detection of H2 O2 concentrations than that of ECL-2. Further, P-GR film not only enhanced ECL intensity of CdTe QDs but also decreased its onset potential. Thus, a novel CdTe QDs ECL sensor was developed for sensing H2O2. Light intensity was linearly proportional to the concentration of H2 O2 between 1.0 × 10(-5) and 2.0 x 10(-7) mol L(-1) with a detection limit of 9.8 x 10(-8) mol L(-1). The P-GR thin-film modified glassy carbon electrode (GCE) displayed acceptable reproducibility and long-term stability.

  15. Hot electron extraction from CdTe quantum dots via beta carotene molecular energy levels

    NASA Astrophysics Data System (ADS)

    Pazhanivel, T.; Nataraj, D.; Devarajan, V. P.; Senthil, K.; Seol, M.; Yong, K.

    2012-06-01

    We report our findings related to hot electron extraction from CdTe quantum dots, and we were able to do this by using beta carotene as an electron acceptor. Transient absorption spectra with two slow recovering negative bleaches at the absorption maximum of the molecule and quantum dot have indicated the slowing down of cooling process and the existence of hot carriers in this hybrid system.

  16. Origins of photoluminescence decay kinetics in CdTe colloidal quantum dots.

    PubMed

    Califano, Marco

    2015-03-24

    Recent experimental studies have identified at least two nonradiative components in the fluorescence decay of solutions of CdTe colloidal quantum dots (CQDs). The lifetimes reported by different groups, however, differed by orders of magnitude, raising the question of whether different types of traps were at play in the different samples and experimental conditions and even whether different types of charge carriers were involved in the different trapping processes. Considering that the use of these nanomaterials in biology, optoelectronics, photonics, and photovoltaics is becoming widespread, such a gap in our understanding of carrier dynamics in these systems needs addressing. This is what we do here. Using the state-of-the-art atomistic semiempirical pseudopotential method, we calculate trapping times and nonradiative population decay curves for different CQD sizes considering up to 268 surface traps. We show that the seemingly discrepant experimental results are consistent with the trapping of the hole at unsaturated Te bonds on the dot surface in the presence of different dielectric environments. In particular, the observed increase in the trapping times following air exposure is attributed to the formation of an oxide shell on the dot surface, which increases the dielectric constant of the dot environment. Two types of traps are identified, depending on whether the unsaturated bond is single (type I) or part of a pair of dangling bonds on the same Te atom (type II). The energy landscape relative to transitions to these traps is found to be markedly different in the two cases. As a consequence, the trapping times associated with the different types of traps exhibit a strikingly contrasting sensitivity to variations in the dot environment. Based on these characteristics, we predict the presence of a sub-nanosecond component in all photoluminescence decay curves of CdTe CQDs in the size range considered here if both trap types are present. The absence of such a

  17. Studying nanotoxic effects of CdTe quantum dots in Trypanosoma cruzi.

    PubMed

    Vieira, Cecilia Stahl; Almeida, Diogo Burigo; de Thomaz, André Alexandre; Menna-Barreto, Rubem Figueredo Sadok; dos Santos-Mallet, Jacenir Reis; Cesar, Carlos Lenz; Gomes, Suzete Araujo Oliveira; Feder, Denise

    2011-03-01

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

  18. Effect of surface ligands on the optical properties of aqueous soluble CdTe quantum dots

    PubMed Central

    2012-01-01

    We investigate systematically the influence of the nature of thiol-type capping ligands on the optical and structural properties of highly luminescent CdTe quantum dots synthesized in aqueous media, comparing mercaptopropionic acid (MPA), thioglycolic acid (TGA), 1-thioglycerol (TGH), and glutathione (GSH). The growth rate, size distribution, and quantum yield strongly depend on the type of surface ligand used. While TGH binds too strongly to the nanocrystal surface inhibiting growth, the use of GSH results in the fastest growth kinetics. TGA and MPA show intermediate growth kinetics, but MPA yields a much lower initial size distribution than TGA. The obtained fluorescence quantum yields range from 38% to 73%. XPS studies unambiguously put into evidence the formation of a CdS shell on the CdTe core due to the thermal decomposition of the capping ligands. This shell is thicker when GSH is used as ligand, as compared with TGA ligands. PMID:23017183

  19. Synthesis and characterization of surface-modified colloidal CdTe Quantum Dots

    SciTech Connect

    Rajh, T. ); Micic, O.I.; Nozik, A.J. )

    1993-11-18

    The controlled synthesis of quantized colloidal CdTe nanocrystals (in aqueous solutions) with narrow size distributions and stabilized against rapid oxidation was achieved by capping the quantum dot particles with 3-mercapto-1,2-propanediol. Nanocrystals (i.e., quantum dots) with mean diameters of 20, 25, 35, and 40 A were produced. Optical absorption spectra showed strong excitonic peaks at the smallest size; the absorption coefficient was shown to follow an inverse cube dependence on particle diameter, while the extinction coefficient per particle remained constant. The quantum yield for photoluminescence increased with decreasing particle size and reached 20% at 20 A. The valence band edges of the CdTe quantum dots were determined by pulse radiolysis experiments (hole injection from oxidizing radicals); the bandgaps were estimated from pulse radiolysis data (redox potentials of hole and electron injecting radicals) and from the optical spectra. The dependence of the CdTe bandgap on quantum dot size was found to be much weaker than predicted by the effective mass approximation; this result is consistent with recently published theoretical calculations by several groups. 36 refs., 5 figs., 1 tab.

  20. Assembly of light-emitting diode based on hydrophilic CdTe quantum dots incorporating dehydrated silica gel.

    PubMed

    Du, Jinhua; Wang, Chunlei; Xu, Xiaojing; Wang, Zhuyuan; Xu, Shuhong; Cui, Yiping

    2016-03-01

    Stable photoluminescence QD light-emitting diodes (QD-LEDs) were made based on hydrophilic CdTe quantum dots (QDs). A quantum dot-inorganic nanocomposite (hydrophilic CdTe QDs incorporating dehydrated silica gel) was prepared by two methods (rotary evaporation and freeze drying). Taking advantage of its viscosity, plasticity and transparency, dehydrated silica gel could be coated on the surface of ultraviolet (UV) light LEDs to make photoluminescence QD-LEDs. This new photoluminescence QD-LED, which is stable, environmentally non-toxic, easy to operate and low cost, could expand the applications of hydrophilic CdTe QDs in photoluminescence.

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

    PubMed Central

    2011-01-01

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

  2. Novel synthesis of β-cyclodextrin functionalized CdTe quantum dots as luminescent probes

    NASA Astrophysics Data System (ADS)

    Chen, Xiao-Feng; Zhou, Min; Chang, Yan-Ping; Ren, Cui-Ling; Chen, Hong-Li; Chen, Xing-Guo

    2012-12-01

    A novel, inexpensive procedure for the preparation of highly fluorescent and water-soluble CdTe quantum dots (QDs) using β-cyclodextrin (β-CD) as surface-coating agents was fabricated through the substitution reaction at the C-6 position of mono-6-deoxy-6-(p-tolylsulfonyl)-cyclodextrin (6-TsO-β-CD) by the sbnd NH2 of (3-aminopropyl)triethoxysilane-coated CdTe QDs (APTES/CdTe QDs) under mild conditions. X-ray powder diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), ultraviolet and visible (UV-vis) spectrophotometer, and fluorescence (FL) spectrophotometer were used to characterize the obtained nanoparticles, which proved that the CdTe QDs have been effectively modified by β-CD. The quantum yields (QYs) of CdTe QDs, APTES/CdTe QDs and β-CD/APTES/CdTe QDs in water comparative to Rhodamine 6G were about 17%, 12%, and 9%, respectively. A pair of isomer o,p'-DDT and p,p'-DDT was chosen as the template molecules to evaluate the molecular recognition properties of β-CD/APTES/CdTe QDs. The results revealed that β-CD/APTES/CdTe QDs simultaneously possessed unique optical properties of QDs and excellent molecules recognition ability of β-CD through combining their individual distinct advantages.

  3. CdTe quantum dots@luminol as signal amplification system for chrysoidine with chemiluminescence-chitosan/graphene oxide-magnetite-molecularly imprinting sensor.

    PubMed

    Duan, Huimin; Li, Leilei; Wang, Xiaojiao; Wang, Yanhui; Li, Jianbo; Luo, Chuannan

    2016-01-15

    A sensitive chemiluminescence (CL) sensor based on chemiluminescence resonance energy transfer (CRET) in CdTe quantum dots@luminol (CdTe QDs@luminol) nanomaterials combined with chitosan/graphene oxide-magnetite-molecularly imprinted polymer (Cs/GM-MIP) for sensing chrysoidine was developed. CdTe QDs@luminol was designed to not only amplify the signal of CL but also reduce luminol consumption in the detection of chrysoidine. On the basis of the abundant hydroxy and amino, Cs and graphene oxide were introduced into the GM-MIP to improve the adsorption ability. The adsorption capacities of chrysoidine by both Cs/GM-MIP and non-imprinted polymer (Cs/GM-NIP) were investigated, and the CdTe QDs@luminol and Cs/GM-MIP were characterized by UV-vis, FTIR, SEM and TEM. The proposed sensor can detect chrysoidine within a linear range of 1.0×10(-7) - 1.0×10(-5) mol/L with a detection limit of 3.2×10(-8) mol/L (3δ) due to considerable chemiluminescence signal enhancement of the CdTe quantum dots@luminol detector and the high selectivity of the Cs/GM-MIP system. Under the optimal conditions of CL, the CdTe QDs@luminol-Cs/GM-MIP-CL sensor was used for chrysoidine determination in samples with satisfactory recoveries in the range of 90-107%. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Cyclodextrin capped CdTe quantum dots as versatile fluorescence sensors for nitrophenol isomers.

    PubMed

    Zhang, Zhixing; Zhou, Jie; Liu, Yun; Tang, Jian; Tang, Weihua

    2015-12-14

    Cyclodextrin (CD) capped CdTe quantum dots (QDs) were prepared with uniform dimension (average diameter ∼5 nm) and high quantum yield (ca. 65%). By taking advantage of the inclusion complexation of CD, β-CD-CdTe QDs exhibited strong fluorescence quenching in a linear relationship with the concentration of o-, m- and p-nitrophenol in the range of 20-100 μM. The detection limit reached 0.05 μM for o-/p-nitrophenol and 0.3 μM for m-nitrophenol. The fluorescence decay study revealed the stabilization effect of CD covering on CdTe QDs and fine-tuning of the fluorescence for selective ultrasensitive detection of nitrophenol isomers.

  5. Monolithic ZnTe-based pillar microcavities containing CdTe quantum dots.

    PubMed

    Kruse, Carsten; Pacuski, Wojciech; Jakubczyk, Tomasz; Kobak, Jakub; Gaj, Jan A; Frank, Kristian; Schowalter, Marco; Rosenauer, Andreas; Florian, Matthias; Jahnke, Frank; Hommel, Detlef

    2011-07-15

    Micropillars of different diameters have been prepared by focused ion beam milling out of a planar ZnTe-based cavity. The monolithic epitaxial structure, deposited on a GaAs substrate, contains CdTe quantum dots embedded in a ZnTe λ-cavity delimited by two distributed Bragg reflectors (DBRs). The high refractive index material of the DBR structure is ZnTe, while for the low index material a short-period triple MgTe/ZnTe/MgSe superlattice is used. The CdTe quantum dots are formed by a novel Zn-induced formation process and are investigated by scanning transmission electron microscopy. Micro-photoluminescence measurements show discrete optical modes for the pillars, in good agreement with calculations based on a vectorial transfer matrix method. The measured quality factor reaches a value of 3100.

  6. Monolithic ZnTe-based pillar microcavities containing CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Kruse, Carsten; Pacuski, Wojciech; Jakubczyk, Tomasz; Kobak, Jakub; Gaj, Jan A.; Frank, Kristian; Schowalter, Marco; Rosenauer, Andreas; Florian, Matthias; Jahnke, Frank; Hommel, Detlef

    2011-07-01

    Micropillars of different diameters have been prepared by focused ion beam milling out of a planar ZnTe-based cavity. The monolithic epitaxial structure, deposited on a GaAs substrate, contains CdTe quantum dots embedded in a ZnTe λ-cavity delimited by two distributed Bragg reflectors (DBRs). The high refractive index material of the DBR structure is ZnTe, while for the low index material a short-period triple MgTe/ZnTe/MgSe superlattice is used. The CdTe quantum dots are formed by a novel Zn-induced formation process and are investigated by scanning transmission electron microscopy. Micro-photoluminescence measurements show discrete optical modes for the pillars, in good agreement with calculations based on a vectorial transfer matrix method. The measured quality factor reaches a value of 3100.

  7. Cathodic stripping synthesis and cytotoxity studies of glutathione-capped CdTe quantum dots.

    PubMed

    Ge, Cunwang; Zhao, Yu; Hui, Jie; Zhang, Tianyi; Miao, Wujian; Yu, Wei

    2011-08-01

    A cathodic stripping of Te precursor in the presence of Cd2+ and biocompatible glutathione (GSH) was reported for facile synthesis of lowly cytotoxic and highly luminescent CdTe quantum dots (QDs) in aqueous solution. The photoluminescence, electrogenerated chemiluminescence (ECL), toxicity, and cyto-osmosis of the QDs were evaluated to reveal their potential bio-applications. The morphology and composition of as-prepared QDs were investigated by HRTEM and powder XRD spectroscopy, which indicated that the QDs consisted of a CdTe core coated with a CdS shell. The obtained CdTe/CdS core/shell QDs possessed good crystallinity, narrow monodispersity and long-term stability. These QDs showed high fluorescence quantum yields of 49% to 63% over a broad spectral range of 540-650 nm. Efficient and stable ECL of QDs was observed on the anodic potential region upon the electrode potential cycled between 1.5 and -2.0 V versus Ag/AgCl. Furthermore, human liver cancer HepG2 cells were chosen as model cells for toxicity assay of QDs. Effects of the concentration, size, and incubation time of CdTe QDs capped with GSH or mercaptoacetic acid (MAA) on the cell metabolic viability and cyto-osmosis were evaluated. GSH-capped CdTe QDs could infiltrate cytomembrane and karyothecas, and were less cytotoxic than MAA-capped ones under the same experimental conditions. The reported CdTe QDs could be good candidates of fluorescent and ECL probes for biosensing and cell imaging.

  8. Selective optosensing of clenbuterol and melamine using molecularly imprinted polymer-capped CdTe quantum dots.

    PubMed

    The Huy, Bui; Seo, Min-Ho; Zhang, Xinfeng; Lee, Yong-Ill

    2014-07-15

    A novel procedure for the optosensing of clenbuterol and melamine was developed using molecularly imprinted polymer-capped CdTe quantum dots (MIP-CdTe QDs). The MIP-CdTe QDs were synthesized by a radical polymerization process among CdTe QDs, a template, 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS). The sizes of the MIP-CdTe particles were controlled by the speed of polymerization, concentration of the template, concentration of the quantum dots, and the ratio of template, monomer and cross-linker. Excellent selectivity and high sensitivity of MIP-CdTe QDs toward clenbuterol/melamine molecules were observed based on the fluorescence quenching of QDs. Experimental results showed that the optimum molar ratios of template, monomer, and cross-linker were 1:8:20 and 1:4:20 for analyzing clenbuterol and melamine, respectively. Under optimum conditions, these MIP-CdTe QDs showed a limit of detection of 0.4 μM (120 ng/mL) for clenbuterol and 0.6 μM (75 ng/mL) for melamine. The feasibility of the developed method in real samples was successfully evaluated through the analysis of clenbuterol and melamine in milk and liver samples with satisfactory recoveries of 92-97%. The MIP-CdTe QDs could be easily regenerated for subsequent sample analysis with water.

  9. Synthesis and enhanced fluorescence of Ag doped CdTe semiconductor quantum dots.

    PubMed

    Ding, Si-Jing; Liang, Shan; Nan, Fan; Liu, Xiao-Li; Wang, Jia-Hong; Zhou, Li; Yu, Xue-Feng; Hao, Zhong-Hua; Wang, Qu-Quan

    2015-02-07

    Doping with intentional impurities is an intriguing way to tune the properties of semiconductor nanocrystals. However, the synthesis of some specific doped semiconductor nanocrystals remains a challenge and the doping mechanism in this strongly confined system is still not clearly understood. In this work, we report, for the first time, the synthesis of stable and water-soluble Ag-doped CdTe semiconductor quantum dots (SQDs) via a facile aqueous approach. Experimental characterization demonstrated the efficient doping of the Ag impurities into the CdTe SQDs with an appropriate reaction time. By doping 0.3% Ag impurities, the Stokes shift is decreased by 120 meV, the fluorescence intensity is enhanced more than 3 times, the radiative rate is enhanced 4.2 times, and the non-radiative rate is efficiently suppressed. These observations reveal that the fluorescence enhancement in Ag-doped CdTe SQDs is mainly attributed to the minimization of surface defects, filling of the trap states, and the enhancement of the radiative rate by the silver dopants. Our results suggest that the silver doping is an efficient method for tuning the optical properties of the CdTe SQDs.

  10. Photodegradation of Mercaptopropionic Acid- and Thioglycollic Acid-Capped CdTe Quantum Dots in Buffer Solutions.

    PubMed

    Miao, Yanping; Yang, Ping; Zhao, Jie; Du, Yingying; He, Haiyan; Liu, Yunshi

    2015-06-01

    CdTe quantum dots (QDs) were synthesized by 3-mercaptopropionic acid (MPA) and thioglycollic acid (TGA) as capping agents. It is confirmed that TGA and MPA molecules were attached on the surface of the QDs using Fourier transform infrared (FT-IR) spectra. The movement of the QDs in agarose gel electrophoresis indicated that MPA-capped CdTe QDs had small hydrodynamic diameter. The photoluminescence (PL) intensity of TGA-capped QDs is higher than that of MPA-capped QDs at same QD concentration because of the surface passivation of TGA. To systemically investigate the photodegradation, CdTe QDs with various PL peak wavelengths were dispersed in phosphate buffered saline (PBS) and Tris-borate-ethylenediaminetetraacetic acid (TBE) buffer solutions. It was found that the PL intensity of the QDs in PBS decreased with time. The PL peak wavelengths of the QDs in PBS solutions remained unchanged. As for TGA-capped CdTe QDs, the results of PL peak wavelengths in TBE buffer solutions indicated that S(2-) released by TGA attached to Cd(2+) and formed CdS-like clusters layer on the surface of aqueous CdTe QDs. In addition, the number of TGA on the CdTe QDs surface was more than that of MPA. When the QDs were added to buffer solutions, agents were removed from the surface of CdTe QDs, which decreased the passivation of agents thus resulted in photodegradation of CdTe QDs in buffer solutions.

  11. Near-unity quantum yields from chloride treated CdTe colloidal quantum dots.

    PubMed

    Page, Robert C; Espinobarro-Velazquez, Daniel; Leontiadou, Marina A; Smith, Charles; Lewis, Edward A; Haigh, Sarah J; Li, Chen; Radtke, Hanna; Pengpad, Atip; Bondino, Federica; Magnano, Elena; Pis, Igor; Flavell, Wendy R; O'Brien, Paul; Binks, David J

    2015-04-01

    Colloidal quantum dots (CQDs) are promising materials for novel light sources and solar energy conversion. However, trap states associated with the CQD surface can produce non-radiative charge recombination that significantly reduces device performance. Here a facile post-synthetic treatment of CdTe CQDs is demonstrated that uses chloride ions to achieve near-complete suppression of surface trapping, resulting in an increase of photoluminescence (PL) quantum yield (QY) from ca. 5% to up to 97.2 ± 2.5%. The effect of the treatment is characterised by absorption and PL spectroscopy, PL decay, scanning transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. This process also dramatically improves the air-stability of the CQDs: before treatment the PL is largely quenched after 1 hour of air-exposure, whilst the treated samples showed a PL QY of nearly 50% after more than 12 hours. © 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Near-unity quantum yields from chloride treated CdTe colloidal quantum dots

    DOE PAGES

    Page, Robert C.; Espinobarro-Velazquez, Daniel; Leontiadou, Marina A.; ...

    2014-10-27

    Colloidal quantum dots (CQDs) are promising materials for novel light sources and solar energy conversion. However, trap states associated with the CQD surface can produce non-radiative charge recombination that significantly reduces device performance. Here a facile post-synthetic treatment of CdTe CQDs is demonstrated that uses chloride ions to achieve near-complete suppression of surface trapping, resulting in an increase of photoluminescence (PL) quantum yield (QY) from ca. 5% to up to 97.2 ± 2.5%. The effect of the treatment is characterised by absorption and PL spectroscopy, PL decay, scanning transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. We find thismore » process also dramatically improves the air-stability of the CQDs: before treatment the PL is largely quenched after 1 hour of air-exposure, whilst the treated samples showed a PL QY of nearly 50% after more than 12 hours.« less

  13. Temperature induced stress phase transition in CdTe quantum dots observed by dielectric constant and thermal diffusivity measurements

    NASA Astrophysics Data System (ADS)

    Moreira, S. G. C.; da Silva, E. C.; Mansanares, A. M.; Barbosa, L. C.; Cesar, C. L.

    2007-07-01

    The authors measured the dielectric constant by capacitance method and the thermal diffusivity by thermal lens technique in the temperature range from 20to300K for CdTe quantum dot doped borosilicate glass samples. Results show a huge difference between the thermal behavior of the pure glass matrix, without quantum dots, and of the doped glass, especially around 90 and 250K. The authors attributed this difference to the phase transition experienced by the CdTe nanocrystals due to the high pressure exerted by the glass matrix over the CdTe quantum dots. The temperature induced stress is caused by the thermal expansion coefficient mismatch between the quantum dot and the glass matrix.

  14. Fabrication of fluorescent composite with ultrafast aqueous synthesized high luminescent CdTe quantum dots

    SciTech Connect

    Zhang, Lei Chen, Haibin E-mail: mejswu@ust.hk; Wu, Jingshen E-mail: mejswu@ust.hk; Bi, Xianghong

    2014-05-15

    Without precursor preparation, inert gas protection and enormous amount of additives and reductants, CdTe quantum dots (QDs) can be rapidly synthesized with high quality. A 600 nm photoluminescence peak wavelength could be obtained within 1 hour's refluxing through minimal addition of 1,2-diaminoethane (DAE). The theoretical design for the experiments are illustrated and further proved by the characterization results with different concentrations and reagents. On the other hand, generation of CdTe QDs was found even under room temperature by applying droplet quantity of DAE. This indicates that QDs can be synthesized with simply a bottle and no enormous additives required. The QDs were mixed into the epoxy matrix through solution casting method with cetyltrimethylammonium (CTA) capping for phase transfer. The acquired epoxy based nanocomposite exhibits good transparency, compatibility and fluorescence.

  15. In situ preparation of fluorescent CdTe quantum dots with small thiols and hyperbranched polymers as co-stabilizers

    PubMed Central

    2014-01-01

    A new strategy for in situ preparation of highly fluorescent CdTe quantum dots (QDs) with 3-mercaptopropionic acid (MPA) and hyperbranched poly(amidoamine)s (HPAMAM) as co-stabilizers was proposed in this paper. MPA and HPAMAM were added in turn to coordinate Cd2+. After adding NaHTe and further microwave irradiation, fluorescent CdTe QDs stabilized by MPA and HPAMAM were obtained. Such a strategy avoids the aftertreatment of thiol-stabilized QDs in their bioapplication and provides an opportunity for direct biomedical use of QDs due to the existence of biocompatible HPAMAM. The resulting CdTe QDs combine the mechanical, biocompatibility properties of HPAMAM and the optical, electrical properties of CdTe QDs together. PMID:24636234

  16. ZnS shell growth on thiol capped CdTe quantum dots using gamma irradiation

    NASA Astrophysics Data System (ADS)

    Raju, S. P.; Hareesh, K.; Pai, S. Chethan; Dhole, S. D.; Sanjeev, Ganesh

    2017-05-01

    The formation of ZnS shell on 3-Mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) using gamma radiation has been reported in this study. Hydrothermally synthesized CdTe QDs were exposed to gamma radiation before and after introducing shell source materials (Zn+MPA complex). The gamma rays exposed samples were characterized using UV-Vis spectroscopy, Photoluminescence spectroscopy (PL) and X-Ray Diffraction (XRD) techniques. The redshift in absorption spectra for gamma irradiated samples indicates the formation of bigger nanoparticles as the shell stretched the core size. The shift in the XRD peaks (cubic zinc blade structure) towards higher angle reveals the formation of MPA capped CdTe/ZnS core/shell QDs against gamma radiation. The variation in PL spectra also followed the same redshift corroborating the UV-Vis and XRD results. The increase in PL intensity only after introducing shell source material against gamma radiation clearly confirms ZnS shell saturated the surface dangling bonds by increasing radiative decay mechanism over CdTe core surface.

  17. Probing the interactions of CdTe quantum dots with pseudorabies virus

    PubMed Central

    Du, Ting; Cai, Kaimei; Han, Heyou; Fang, Liurong; Liang, Jiangong; Xiao, Shaobo

    2015-01-01

    Quantum dots (QDs) have become one of the most promising luminescent materials for tracking viral infection in living cells. However, several issues regarding how QDs interact with the virus remain unresolved. Herein, the effects of Glutathione (GSH) capped CdTe QDs on virus were investigated by using pseudorabies virus (PRV) as a model. One-step growth curve and fluorescence colocalization analyses indicate that CdTe QDs inhibit PRV multiplication in the early stage of virus replication cycle by suppressing the invasion, but have no significant effect on the PRV penetration. Fluorescence spectrum analysis indicates that the size of QDs is reduced gradually after the addition of PRV within 30 min. Release of Cd2+ was detected during the interaction of QDs and PRV, resulting in a decreased number of viruses which can infect cells. Further Raman spectra and Circular Dichroism (CD) spectroscopy analyses reveal that the structure of viral surface proteins is altered by CdTe QDs adsorbed on the virus surface, leading to the inhibition of virus replication. This study facilitates an in-depth understanding of the pathogenic mechanism of viruses and provides a basis for QDs-labeled virus research. PMID:26552937

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

    PubMed

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

    2012-10-15

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

  19. Subcellular Localization of Thiol-Capped CdTe Quantum Dots in Living Cells

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Mi, Lan; Xiong, Rongling; Wang, Pei-Nan; Chen, Ji-Yao; Yang, Wuli; Wang, Changchun; Peng, Qian

    2009-07-01

    Internalization and dynamic subcellular distribution of thiol-capped CdTe quantum dots (QDs) in living cells were studied by means of laser scanning confocal microscopy. These unfunctionalized QDs were well internalized into human hepatocellular carcinoma and rat basophilic leukemia cells in vitro. Co-localizations of QDs with lysosomes and Golgi complexes were observed, indicating that in addition to the well-known endosome-lysosome endocytosis pathway, the Golgi complex is also a main destination of the endocytosed QDs. The movement of the endocytosed QDs toward the Golgi complex in the perinuclear region of the cell was demonstrated.

  20. Voltammetry as a Tool for Characterization of CdTe Quantum Dots

    PubMed Central

    Sobrova, Pavlina; Ryvolova, Marketa; Hubalek, Jaromir; Adam, Vojtech; Kizek, Rene

    2013-01-01

    Electrochemical detection of quantum dots (QDs) has already been used in numerous applications. However, QDs have not been well characterized using voltammetry, with respect to their characterization and quantification. Therefore, the main aim was to characterize CdTe QDs using cyclic and differential pulse voltammetry. The obtained peaks were identified and the detection limit (3 S/N) was estimated down to 100 fg/mL. Based on the convincing results, a new method for how to study stability and quantify the dots was suggested. Thus, the approach was further utilized for the testing of QDs stability. PMID:23807507

  1. Fluorescence-based CdTe nanosensor for sensitive detection of cytochrome C.

    PubMed

    Amin, Rehab M; Elfeky, Souad A; Verwanger, Thomas; Krammer, Barbara

    2017-12-15

    Cytochrome c (Cyt c) is commonly used as intrinsic biomarker for several characteristics of the cell such as respiration, energy level and apoptosis. In the present study a simple colorimetric sensor should be developed and tested for the real-time detection of Cyt c in living cells. We synthesized cadmium telluride quantum dots (CdTe QDs) capped with thioglycolic acid (TGA) as a fluorometric Cyt c nanosensor. The synthesized TGA/CdTe QDs nanosensor was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and absorption as well as fluorescence spectrophotometry. We investigated the developed TGA/CdTe QDs sensor with regard to its applicability in the fluorometric detection of Cyt c. Results showed that the TGA/CdTe QDs could be used as a sensitive fluorescence probe for the quantification of different concentrations of Cyt c ranging from 0.5 - 2.5μM. Increased binding of QDs to Cyt c results in decreasing fluorescence. The fluorescence of the QDs is inversely correlated to the Cyt c concentration. Based on these data, a standard curve up to 2.5μM Cyt c was established. Moreover, the developed nanosensor was applied in different concentrations on primary human dermal fibroblasts. Results showed that TGA/CdTe QDs were taken up by cells and could be visualized by fluorescence microscopy. Quantification of Cyt c within living cells via QDs is, however, influenced by various factors such as cell damage, QD aggregation or the level of reactive oxygen species, which have to be taken into account. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Studying nanotoxic effects of CdTe quantum dots in Trypanosoma cruzi

    NASA Astrophysics Data System (ADS)

    Stahl, C. V.; Almeida, D. B.; de Thomaz, A. A.; Fontes, A.; Menna-Barreto, R. F. S.; Santos-Mallet, J. R.; Cesar, C. L.; Gomes, S. A. O.; Feder, D.

    2010-02-01

    Many studies have been done in order to verify the possible nanotoxicity of quantum dots in some cellular types. Protozoan pathogens as Trypanosoma cruzi, etiologic agent of Chagas1 disease is transmitted to humans either by blood-sucking triatomine vectors, blood transfusion, organs transplantation or congenital transmission. The study of the life cycle, biochemical, genetics, morphology and others aspects of the T. cruzi is very important to better understand the interactions with its hosts and the disease evolution on humans. Quantum dot, nanocrystals, highly luminescent has been used as tool for experiments in in vitro and in vivo T. cruzi life cycle development in real time. We are now investigating the quantum dots toxicity on T. cruzi parasite cells using analytical methods. In vitro experiments were been done in order to test the interference of this nanoparticle on parasite development, morphology and viability (live-death). Ours previous results demonstrated that 72 hours after parasite incubation with 200 μM of CdTe altered the development of T. cruzi and induced cell death by necrosis in a rate of 34%. QDs labeling did not effect: (i) on parasite integrity, at least until 7 days; (ii) parasite cell dividing and (iii) parasite motility at a concentration of 2 μM CdTe. This fact confirms the low level of cytotoxicity of these QDs on this parasite cell. In summary our results is showing T. cruzi QDs labeling could be used for in vivo cellular studies in Chagas disease.

  3. Interactions between N-acetyl-L-cysteine protected CdTe quantum dots and doxorubicin through spectroscopic method

    SciTech Connect

    Yang, Xiupei; Lin, Jia; Liao, Xiulin; Zong, Yingying; Gao, Huanhuan

    2015-06-15

    Highlights: • CdTe quantum dots with the diameter of 3–5 nm were synthesized in aqueous solution. • The modified CdTe quantum dots showed well fluorescence properties. • The interaction between the CdTe quantum dots and doxorubicin (DR) was investigated. - Abstract: N-acetyl-L-cysteine protected cadmium telluride quantum dots with a diameter of 3–5 nm were synthesized in aqueous solution. The interaction between N-acetyl-L-cysteine/cadmium telluride quantum dots and doxorubicin was investigated by ultraviolet–visible absorption and fluorescence spectroscopy at physiological conditions (pH 7.2, 37 °C). The results indicate that electron transfer has occurred between N-acetyl-L-cysteine/cadmium telluride quantum dots and doxorubicin under light illumination. The quantum dots react readily with doxorubicin to form a N-acetyl-L-cysteine/cadmium telluride-quantum dots/doxorubicin complex via electrostatic attraction between the −NH{sub 3}{sup +} moiety of doxorubicin and the −COO{sup −} moiety of N-acetyl-L-cysteine/cadmium telluride quantum dots. The interaction of N-acetyl-L-cysteine/cadmium telluride-quantum dots/doxorubicin complex with bovine serum albumin was studied as well, showing that the complex might induce the conformation change of bovine serum due to changes in microenvironment of bovine serum.

  4. Chiral recognition of phenylglycinol enantiomers based on N-acetyl-L-cysteine capped CdTe quantum dots in the presence of Ag+

    NASA Astrophysics Data System (ADS)

    Guo, Yuan; Zeng, Xiaoqing; Yuan, Haiyan; Huang, Yunmei; Zhao, Yanmei; Wu, Huan; Yang, Jidong

    2017-08-01

    In this study, a novel method for chiral recognition of phenylglycinol (PG) enantiomers was proposed. Firstly, water-soluble N-acetyl-L-cysteine (NALC)-capped CdTe quantum dots (QDs) were synthesized and experiment showed that the fluorescence intensity of the reaction system slightly enhancement when added PG enantiomers to NALC-capped CdTe quantum dots (QDs), but the R-PG and S-PG could not be distinguished. Secondly, when there was Ag+ presence in the reaction system, the experiment result was extremely interesting, the PG enantiomers cloud make NALC-capped CdTe QDs produce different fluorescence signal, in which the fluorescence of S-PG + Ag+ + NALC-CdTe system was significantly enhanced, and the fluorescence of R-PG + Ag+ + NALC-CdTe system was markedly decreased. Thirdly, all the enhanced and decreased of the fluorescence intensity were directly proportional to the concentration of R-PG and S-PG in the linearly range 10- 5-10- 7 mol·L- 1, respectively. So, the new method for simultaneous determination of the PG enantiomers was built too. The experiment result of the method was satisfactory with the detection limit of PG can reached 10- 7 mol·L- 1 and the related coefficient of S-PG and R-PG are 0.995 and 0.980, respectively. The method was highly sensitive, selective and had wider detection range compared with other methods.

  5. Liver Toxicity of Cadmium Telluride Quantum Dots (CdTe QDs) Due to Oxidative Stress in Vitro and in Vivo

    PubMed Central

    Zhang, Ting; Hu, Yuanyuan; Tang, Meng; Kong, Lu; Ying, Jiali; Wu, Tianshu; Xue, Yuying; Pu, Yuepu

    2015-01-01

    With the applications of quantum dots (QDs) expanding, many studies have described the potential adverse effects of QDs, yet little attention has been paid to potential toxicity of QDs in the liver. The aim of this study was to investigate the effects of cadmium telluride (CdTe) QDs in mice and murine hepatoma cells alpha mouse liver 12 (AML 12). CdTe QDs administration significantly increased the level of lipid peroxides marker malondialdehyde (MDA) in the livers of treated mice. Furthermore, CdTe QDs caused cytotoxicity in AML 12 cells in a dose- and time-dependent manner, which was likely mediated through the generation of reactive oxygen species (ROS) and the induction of apoptosis. An increase in ROS generation with a concomitant increase in the gene expression of the tumor suppressor gene p53, the pro-apoptotic gene Bcl-2 and a decrease in the anti-apoptosis gene Bax, suggested that a mitochondria mediated pathway was involved in CdTe QDs’ induced apoptosis. Finally, we showed that NF-E2-related factor 2 (Nrf2) deficiency blocked induced oxidative stress to protect cells from injury induced by CdTe QDs. These findings provide insights into the regulatory mechanisms involved in the activation of Nrf2 signaling that confers protection against CdTe QDs-induced apoptosis in hepatocytes. PMID:26404244

  6. Light Scattering Induced Giant Red-Shift in Photoluminescence from CdTe Quantum Dots Encapsulated in Polyacrylamide Gel Nanospheres

    NASA Astrophysics Data System (ADS)

    Garner, Brett W.; Cai, Tong; Hu, Zhibing; Kim, Moon; Neogi, Arup

    2009-07-01

    The photoluminescence emission from CdTe quantum dots embedded in hydrogel nanospheres based on poly(N-isopropylacrylamide) (PNIPAM) polymer is observed to be modified by the random light scattering within the colloidal medium. Photoluminescence emission from CdTe quantum dots of various size has been observed making the gel fluorescent. The optical properties of the quantum dots entrapped within the gel microspheres can be modified due to change in refractive index, volume density of the surrounding hydrogel medium. A red-shift of ˜100 nm has been observed from quantum dots emitting in the green wavelength region as the cell length is increased. This shift is due to secondary scattering and energy transfer induced by the larger scattering cross-section within the medium which results in a re-excitation of larger sized quantum dots.

  7. Luminescence temperature antiquenching of water-soluble CdTe quantum dots: role of the solvent.

    PubMed

    Wuister, Sander F; de Mello Donegá, Celso; Meijerink, Andries

    2004-08-25

    Luminescence temperature antiquenching (LTAQ) is observed for water-soluble CdTe quantum dots (QDs) capped with aminoethanethiol (AET). The efficient exciton emission (quantum efficiency of approximately 40% at 300 K) is quenched almost completely as the QD solutions are cooled to below 230 K and is fully recovered around 270 K upon warming up to room temperature (LTAQ). Temperature-dependent lifetime measurements show that the quenching rate is high, resulting in an on/off behavior. No LTAQ is observed for CdTe QDs capped with aminoundecanethiol (AUT). The LTAQ is explained by the influence of solvent freezing on the surface of the QD core. Freezing of the solvation water molecules surrounding the QD will induce strain in the capping shell, due to the interaction between water and the charged heads of the capping molecules. Short carbon chains (AET) will propagate the strain to the QD surface, creating surface quenching states, whereas long and flexible chains (AUT) will dissipate the strain, thus avoiding surface distortion. Freezing-point depression by the addition of methanol results in a lowering of the transition temperature. Additional support is provided by the size dependence of the LTAQ: smaller particles, with higher local ionic strength due to a higher density of charged NH(3)(+) surface groups, experience a lower transition temperature due to stronger local freezing-point depression.

  8. Thiol capped colloidal CdTe quantum dots synthesized using laser ablation

    NASA Astrophysics Data System (ADS)

    Almeida, D. B.; Rodriguez, E.; Moreira, R. S.; Agouram, S.; Barbosa, L. C.; Jimenez, E.; Cesar, C. L.

    2009-08-01

    Semiconductor quantum dots [QD] have shown a great number of applications from fluorescent markers to solar cell devices. Colloidal systems have been usually obtained through chemical synthesis, that have to be devoleped for each material. The best quality QDs have been obtained with non-aqueous solution and non-physiological pH, requiring a posterior processing to be used in biology, for example. In contrast, the same physical synthetic method, such as laser ablation, would be applied to any semiconductor, metallic or dielectric material. Colloidal QD can be obtained by laser ablation of a target inside any solvent, given this method a very large flexibility. The fluorescence efficiency, however, depend on the surface traps and stability of colloids. The usual method to avoid surface traps is to grow a cap layer to passivate its surface and, at the same time, stabilize the colloid, sterically or electrostatically. In this work we report a novel technique for obtain thiol capped CdTe colloidal quantum dots in one step. A target immerse in a solution of ethanol and 3-mercaptopropyltrimethoxysilane (MPS), or thiol, was hit by a nanosecond 532 nm laser. With this assembly CdTe luminescent QDs were obtained. The colloid photoluminescence and other optical and structural properties are studied.

  9. Crystallization from amorphous structure to hexagonal quantum dots induced by an electron beam on CdTe thin films

    NASA Astrophysics Data System (ADS)

    Becerril, M.; Zelaya-Angel, O.; Medina-Torres, A. C.; Aguilar-Hernández, J. R.; Ramírez-Bon, R.; Espinoza-Beltran, F. J.

    2009-02-01

    Amorphous cadmium-telluride films were prepared by rf sputtering on Corning 7059 glass substrates at room temperature. The deposition time was 10 and 12 h with a thickness of 400 and 480 (±40 nm), respectively. As-prepared films were amorphous according to X-ray diffraction (XRD) patterns, but a win-fit-software analysis of the main XRD broad band suggests a wurtzite structure at short range. Transmission electron microscopy (TEM) at 200 keV produces crystallization of the amorphous CdTe. The TEM-electron beam induces the formation of CdTe quantum dots with the wurtzite hexagonal structure (the metastable structure of CdTe) and with ˜6 nm of average grain size. As effect of a probable distortion of the CdTe crystalline lattice, the unit cell volume (UCV) shrinks to about 30% with respect to the bulk-UCV of CdTe. Besides, the energy band gap increases as expected, according to literature data on quantum confinement.

  10. CdTe and CdSe Quantum Dots Cytotoxicity: A Comparative Study on Microorganisms

    PubMed Central

    Gomes, Suzete A.O.; Vieira, Cecilia Stahl; Almeida, Diogo B.; Santos-Mallet, Jacenir R.; Menna-Barreto, Rubem F. S.; Cesar, Carlos L.; Feder, Denise

    2011-01-01

    Quantum dots (QDs) are colloidal semiconductor nanocrystals of a few nanometers in diameter, being their size and shape controlled during the synthesis. They are synthesized from atoms of group II–VI or III–V of the periodic table, such as cadmium telluride (CdTe) or cadmium selenium (CdSe) forming nanoparticles with fluorescent characteristics superior to current fluorophores. The excellent optical characteristics of quantum dots make them applied widely in the field of life sciences. Cellular uptake of QDs, location and translocation as well as any biological consequence, such as cytotoxicity, stimulated a lot of scientific research in this area. Several studies pointed to the cytotoxic effect against micoorganisms. In this mini-review, we overviewed the synthesis and optical properties of QDs, and its advantages and bioapplications in the studies about microorganisms such as protozoa, bacteria, fungi and virus. PMID:22247686

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

    PubMed

    Dehbozorgi, A; Tashkhourian, J; Zare, S

    2015-11-01

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

  12. Chemiluminescence of CdTe nanocrystals catalyzed by sodium hexametaphosphate and its sensitive application for determination of estrogens.

    PubMed

    Wang, Lun; Yuan, Fei; Chen, Hong-Qi; Ling, Bo; Xu, Juan

    2012-06-01

    A novel flow injection nanocrystals (NCs) chemiluminescence (CL) analysis method has been established for the determination of estradiol, estriol and estrone based on the enhancement of CdTe NCs-KMnO(4) CL reaction catalyzed by sodium hexametaphosphate. Glutathione (GSH)-capped CdTe nanocrystals were synthesized in aqueous medium, and the CdTe NCs emitted at around 555 nm was selected as the light emitter in CdTe NCs-KMnO(4) chemiluminescence (CL) system. It has been found that sodium hexametaphosphate (SHMP) enhanced the CL of the CdTe NCs-KMnO(4) system and estrogens increased these CL signals again in near neutral solution. UV-visible spectra, photoluminescence (PL) spectra, transmission electron microscopy (TEM) and CL spectra were used to characterize CdTe nanoparticles and investigate the mechanism of the CL reaction. On the basis of the enhancement, a novel flow-injection CL method has been established for the determination of estrogens. Under the optimum experimental conditions, three linear relationships were obtained. The method described is simple, sensitive, and has been successfully utilized for the determination of estrogens in tap water samples. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Chemiluminescence of CdTe nanocrystals catalyzed by sodium hexametaphosphate and its sensitive application for determination of estrogens

    NASA Astrophysics Data System (ADS)

    Wang, Lun; Yuan, Fei; Chen, Hong-Qi; Ling, Bo; Xu, Juan

    2012-06-01

    A novel flow injection nanocrystals (NCs) chemiluminescence (CL) analysis method has been established for the determination of estradiol, estriol and estrone based on the enhancement of CdTe NCs-KMnO4 CL reaction catalyzed by sodium hexametaphosphate. Glutathione (GSH)-capped CdTe nanocrystals were synthesized in aqueous medium, and the CdTe NCs emitted at around 555 nm was selected as the light emitter in CdTe NCs-KMnO4 chemiluminescence (CL) system. It has been found that sodium hexametaphosphate (SHMP) enhanced the CL of the CdTe NCs-KMnO4 system and estrogens increased these CL signals again in near neutral solution. UV-visible spectra, photoluminescence (PL) spectra, transmission electron microscopy (TEM) and CL spectra were used to characterize CdTe nanoparticles and investigate the mechanism of the CL reaction. On the basis of the enhancement, a novel flow-injection CL method has been established for the determination of estrogens. Under the optimum experimental conditions, three linear relationships were obtained. The method described is simple, sensitive, and has been successfully utilized for the determination of estrogens in tap water samples.

  14. Mercaptopropionic acid-capped CdTe quantum dots as fluorescence probe for the determination of salicylic acid in pharmaceutical products.

    PubMed

    Bunkoed, Opas; Kanatharana, Proespichaya

    2015-11-01

    Mercaptopropionic acid (MPA)-capped cadmium telluride (CdTe) quantum dot (QDs) fluorescent probes were synthesized in aqueous solution and used for the determination of salicylic acid. The interaction between the MPA-capped CdTe QDs and salicylic acid was studied using fluorescence spectroscopy and some parameters that could modify the fluorescence were investigated to optimize the measurements. Under optimum conditions, the quenched fluorescence intensity of MPA-capped CdTe QDs was linearly proportional to the concentration of salicylic acid in the range of 0.5-40 µg mL(-1) with a coefficient of determination of 0.998, and the limit of detection was 0.15 µg mL(-1). The method was successfully applied to the determination of salicylic acid in pharmaceutical products, and satisfactory results were obtained that were in agreement with both the high pressure liquid chromatography (HPLC) method and the claimed values. The recovery of the method was in the range 99 ± 3% to 105 ± 9%. The proposed method is simple, rapid, cost effective, highly sensitivity and eminently suitable for the quality control of pharmaceutical preparation. The possible mechanisms for the observed quenching reaction was also discussed.

  15. Effect of visible and UV irradiation on the aggregation stability of CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Tsipotan, Aleksei S.; Gerasimova, Marina A.; Aleksandrovsky, Aleksandr S.; Zharkov, Sergey M.; Slabko, Vitaliy V.

    2016-11-01

    The possibility of controlling the aggregation stability of CdTe quantum dots (QDs) stabilized by thioglycolic acid (TGA) is important for implementation of quasi-resonant laser-induced self-assembly. This study examines the influence of irradiation by the UV as well as by the visible light on the photostimulated aggregation of QDs. Different photochemical mechanisms are identified, depending on whether light wavelength falls into an interband transition or the first exciton transition. Irradiation by visible light does not lead to changes in the absorption spectra but decreases luminescence intensity through the detachment of TGA and the formation of dangling bonds, leading to the creation of radiativeless relaxation centers. UV irradiation (in the 300-370 nm range), at an intensity of 0.4 W/cm2, initially (during the first 75 min) leads to the degradation of the stabilizer and QDs' surface. After 75 min of combined UV and visible light irradiation, a gradual increase in spontaneous aggregation takes place, testifying excessive decrease in stabilizing potential barrier height. Hence, the laser-induced self-assembly of CdTe QDs is recommended to be performed over a time period of between 80 and 100 min after the beginning of low-intensity UV irradiation under conditions equivalent to those applied in this study.

  16. High-throughput and rapid fluorescent visualization sensor of urinary citrate by CdTe quantum dots.

    PubMed

    Zhuo, Shujuan; Gong, Jiajia; Zhang, Ping; Zhu, Changqing

    2015-08-15

    In this paper, we have presented a novel CdTe quantum dots (QDs) based fluorescent sensor for visual and turn-on sensing of citrate in human urine samples. The europium ion (Eu(3+)) can lead to the fluorescence quenching of thioglycollic acid (TGA) modified CdTe QDs due to photoinduced electron transfer accompanied by the change of emission color from yellow to orange. Next, addition of citrate breaks the preformed assembly because citrate can replace the CdTe QDs, based on the fact that the Eu(3+) ion displays higher affinity with citrate than the CdTe QDs. Thus the photoinduced electron transfer is switched off, and the fluorescence emission of CdTe QDs is rapidly (within 5min) recovered, simultaneously, the orange emission color restores to yellow. Such proposed strategy may conveniently discriminate the patient of renal stone from normal person by naked eyes. In addition to visualization detection, the fluorescence responses can be used for well quantifying citrate in the range of 0.67-133μM. So, the present, simple, low-cost and visualized citrate fluorescence sensor has great potential in the applications for earlier screening in clinical detection.

  17. Aptamer-based fluorescent screening assay for acetamiprid via inner filter effect of gold nanoparticles on the fluorescence of CdTe quantum dots.

    PubMed

    Guo, Jiajia; Li, Ying; Wang, Luokai; Xu, Jingyue; Huang, Yanjun; Luo, Yeli; Shen, Fei; Sun, Chunyan; Meng, Rizeng

    2016-01-01

    This paper reports a novel aptamer-based fluorescent detection method for small molecules represented by acetamiprid based on the specific binding of aptamers with acetamiprid, and the inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (CdTe QDs). When CdTe QDs were mixed with AuNPs, the fluorescence of CdTe QDs was significantly quenched via IFE. The IFE efficiency could be readily modulated by the absorption and the aggregation state of AuNPs. The presence of salt could easily induce the aggregation of AuNPs, resulting in the fluorescence recovery of the quenched QDs. Acetamiprid-binding aptamer (ABA) could adsorb on the negatively charged AuNPs through the coordination interaction to protect AuNPs from salt-induced aggregation, so the fluorescence of CdTe QDs would be quenched by the IFE of AuNPs. However, the specific binding of ABA with acetamiprid could release the ABA from the surfaces of AuNPs and decrease the salt tolerance of AuNPs, so the IFE-decreased fluorescence of CdTe QDs was regained with the presence of acetamiprid, and the fluorescence enhancement efficiency was driven by the concentration of acetamiprid. Based on this principle, the aptamer-based fluorescent method for acetamiprid has been established and optimized. The assay exhibited excellent selectivity towards acetamiprid over its analogues and other pesticides which may coexist with acetamiprid. Under the optimum experiment conditions, the established method could be applied for the determination of acetamiprid with a wide linear range from 0.05 to 1.0 μM, and a low detection limit of 7.29 nM (3σ). Furthermore, this IFE-based method has been successfully utilized to detect acetamiprid in six types of vegetables, and the results were in full agreement with those from HPLC and LC-MS. The proposed method displays remarkable advantages of high sensitivity, rapid analysis, excellent selectivity, and would be suitable for the practical application

  18. Tuning optical properties of water-soluble CdTe quantum dots for biological applications

    NASA Astrophysics Data System (ADS)

    Schulze, Anne S.; Tavernaro, Isabella; Machka, Friederike; Dakischew, Olga; Lips, Katrin S.; Wickleder, Mathias S.

    2017-02-01

    In this study, two different synthetic methods in aqueous solution are presented to tune the optical properties of CdTe and CdSe semiconductor nanoparticles. Additionally, the influence of different temperatures, pressures, precursor ratios, surface ligands, bases, and core components in the synthesis was investigated with regard to the particle sizes and optical properties. As a result, a red shift of the emission and absorption maxima with increasing reaction temperature (100 to 220°C), pressure (1 to 25 bar), and different ratios of core components of alloyed semiconductor nanoparticles could be observed without a change of the particle size. An increase in particle size from 2.5 to 5 nm was only achieved by variation of the mercaptocarboxylic acid ligands in combination with the reaction time and used base. To get a first hint on the cytotoxic effects and cell uptake of the synthesized quantum dots, in vitro tests mesenchymal stem cells (MSCs) were carried out.

  19. Determination of captopril using selective photoluminescence enhancement of 2-mercaptopropionic modified CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Khan, Sarzamin; Lima, Alex A.; Larrudé, Dunieskys G.; Romani, Eric C.; Aucelio, Ricardo Q.

    2014-04-01

    A photoluminescent probe for the determination of captopril is proposed based on the enhancement of luminescence from 2-mercaptopropionic modified CdTe quantum dots (2-MPA-CdTe QDs). Under optimum conditions, the calibration model (the Langmuir binding isotherm) was linear up to 4.8 × 10-4 mol L-1 with equilibrium binding constant of 3.2 × 104 L mol-1 and limit of detection (xb + 3 sb) of 2.7 × 10-7 mol L-1 (59 ng mL-1). The approach was tested in the determination of captopril in pharmaceutical formulations and the results were in agreement with the ones obtained using reference method. The possible mechanism of interaction is also investigated by Raman and electronic absorption spectroscopy and dynamic light scattering.

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

    PubMed Central

    2011-01-01

    Cadmium telluride quantum dots (Cdte QDs) have received significant attention in biomedical research because of their potential in disease diagnosis and drug delivery. In this study, we have investigated the interaction mechanism and synergistic effect of 3-mercaptopropionic acid-capped Cdte QDs with the anti-cancer drug daunorubicin (DNR) on the induction of apoptosis using drug-resistant human hepatoma HepG2/ADM cells. Electrochemical assay revealed that Cdte QDs readily facilitated the uptake of the DNR into HepG2/ADM cells. Apoptotic staining, DNA fragmentation, and flow cytometry analysis further demonstrated that compared with Cdte QDs or DNR treatment alone, the apoptosis rate increased after the treatment of Cdte QDs together with DNR in HepG2/ADM cells. We observed that Cdte QDs treatment could reduce the effect of P-glycoprotein while the treatment of Cdte QDs together with DNR can clearly activate apoptosis-related caspases protein expression in HepG2/ADM cells. Moreover, our in vivo study indicated that the treatment of Cdte QDs together with DNR effectively inhibited the human hepatoma HepG2/ADM nude mice tumor growth. The increased cell apoptosis rate was closely correlated with the enhanced inhibition of tumor growth in the studied animals. Thus, Cdte QDs combined with DNR may serve as a possible alternative for targeted therapeutic approaches for some cancer treatments. PMID:21711951

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

    PubMed

    Zhang, Gen; Shi, Lixin; Selke, Matthias; Wang, Xuemei

    2011-06-13

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

  2. Anodic electrochemiluminescence of CdTe quantum dots and its energy transfer for detection of catechol derivatives.

    PubMed

    Liu, Xuan; Jiang, Hui; Lei, Jianping; Ju, Huangxian

    2007-11-01

    This work reported for the first time the anodic electrochemiluminescence (ECL) of CdTe quantum dots (QDs) in aqueous system and its analytical application based on the ECL energy transfer to analytes. The CdTe QDs were modified with mercaptopropionic acid to obtain water-soluble QDs and stable and intensive anodic ECL emission with a peak value at +1.17 V (vs Ag/AgCl) in pH 9.3 PBS at an indium tin oxide (ITO) electrode. The ECL emission was demonstrated to involve the participation of superoxide ion produced at the ITO surface, which could inject an electron into the 1Se quantum-confined orbital of CdTe to form QDs anions. The collision between these anions and the oxidation products of QDs led to the formation of the excited state of QDs and ECL emission. The ECL energy transfer from the excited CdTe QDs to quencher produced a novel methodology for detection of catechol derivatives. Using dopamine and L-adrenalin as model analytes, this ECL method showed wide linear ranges from 50 nM to 5 microM and 80 nM to 30 microM for these species. Both ascorbic acid and uric acid, which are common interferences, did not interfere with the detection of catechol derivatives in practical biological samples.

  3. Extracellular biosynthesis of CdTe quantum dots by the fungus Fusarium oxysporum and their anti-bacterial activity

    NASA Astrophysics Data System (ADS)

    Syed, Asad; Ahmad, Absar

    2013-04-01

    The growing demand for semiconductor [quantum dots (Q-dots)] nanoparticles has fuelled significant research in developing strategies for their synthesis and characterization. They are extensively investigated by the chemical route; on the other hand, use of microbial sources for biosynthesis witnessed the highly stable, water dispersible nanoparticles formation. Here we report, for the first time, an efficient fungal-mediated synthesis of highly fluorescent CdTe quantum dots at ambient conditions by the fungus Fusarium oxysporum when reacted with a mixture of CdCl2 and TeCl4. Characterization of these biosynthesized nanoparticles was carried out by different techniques such as Ultraviolet-visible (UV-Vis) spectroscopy, Photoluminescence (PL), X-ray Diffraction (XRD), X-ray Photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Fourier Transformed Infrared Spectroscopy (FTIR) analysis. CdTe nanoparticles shows antibacterial activity against Gram positive and Gram negative bacteria. The fungal based fabrication provides an economical, green chemistry approach for production of highly fluorescent CdTe quantum dots.

  4. A one-dimensional model for the growth of CdTe quantum dots on Si substrates

    NASA Astrophysics Data System (ADS)

    Ferreira, S. C.; Ferreira, S. O.

    2006-03-01

    Recent experiments involving CdTe films grown on Si(111) substrates by hot wall epitaxy revealed features not previously observed [S.O. Ferreira, et al., J. Appl. Phys. 93 (2003) 1195]. This system, which follows the Volmer Weber growth mode with nucleation of isolated 3D islands for less than one monolayer of evaporated material, was described by a peculiar behavior of the quantum dot (QD) size distributions. In this work, we proposed a kinetic deposition model to reproduce these new features. The model, which includes thermally activated diffusion and evaporation of CdTe, qualitatively reproduced the experimental QD size distributions. Moreover, the model predicts a transition from Stranski Krastanow growth mode at lower temperatures to Volmer Weber growth mode at higher ones characterized through the QD width distributions.

  5. Development of a novel deltamethrin sensor based on molecularly imprinted silica nanospheres embedded CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Ge, Shenguang; Lu, Juanjuan; Ge, Lei; Yan, Mei; Yu, Jinghua

    2011-09-01

    A novel procedure for the determination of deltmethrin (DM) is reported. The water-soluble CdTe quantum dots (QDs) and highly fluorescent silica molecularly imprinted nanospheres embedded CdTe QDs (CdTe-SiO 2-MIPs) were prepared and characterized by fluorescence spectroscopy, UV-vis spectroscopy, TEM and IR. The fluorescence nanosensor based CdTe-SiO 2-MIPs is developed. The possible quenching mechanism is discussed by DM. Under optimal conditions, the relative fluorescence intensity of CdTe-SiO 2-MIPs decreased with increasing DM by a Stern-Volmer type equation in the concentration range of 0.5-35.0 μg mL -1, the corresponding detection limit is 0.16 μg mL -1. The developed sensor based on CdTe-SiO 2-MIPs was applied to determine DM in fruit and vegetable samples.

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

    SciTech Connect

    Dai, Xiao; Wang, Hao; Yi, Qinghua; Wang, Yun; Cong, Shan; Zhao, Jie; Sun, Yinghui; Zou, Guifu E-mail: jiexiong@uestc.edu.cn; Qian, Zhicheng; Huang, Jianwen; Xiong, Jie E-mail: jiexiong@uestc.edu.cn; Luo, Hongmei

    2015-11-16

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

  7. Blinking suppression of CdTe quantum dots on epitaxial graphene and the analysis with Marcus electron transfer

    SciTech Connect

    Hirose, Takuya; Tamai, Naoto; Kutsuma, Yasunori; Kurita, Atsusi; Kaneko, Tadaaki

    2014-08-25

    We have prepared epitaxial graphene by a Si sublimation method from 4H-SiC. Single-particle spectroscopy of CdTe quantum dots (QDs) on epitaxial graphene covered with polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG) showed the suppression of luminescence blinking and ∼10 times decreased luminescence intensity as compared with those on a glass. The electronic coupling constant, H{sub 01}, between CdTe QDs and graphene was calculated to be (3.3 ± 0.4) × 10{sup 2 }cm{sup −1} in PVP and (3.7 ± 0.8) × 10{sup 2 }cm{sup −1} in PEG based on Marcus theory of electron transfer and Tang-Marcus model of blinking with statistical distribution.

  8. Cheat sensitive quantum bit commitment.

    PubMed

    Hardy, Lucien; Kent, Adrian

    2004-04-16

    We define cheat sensitive cryptographic protocols between mistrustful parties as protocols which guarantee that, if either cheats, the other has some nonzero probability of detecting the cheating. We describe an unconditionally secure cheat sensitive nonrelativistic bit commitment protocol which uses quantum information to implement a task which is classically impossible; we also describe a simple relativistic protocol.

  9. Infrared magneto-transmission studies of the 2DEGs in (CdMn)Te and CdTe Quantum wells

    NASA Astrophysics Data System (ADS)

    Tanveer, Imtiaz; Wiater, Maciej; Karczewski, Grzegorz; Wojtowicz, Tomasz; McCombe, B. D.

    We are probing quantum hall ferromagnetism (QHF) in the 2DEG of Modulation-doped quantum wells (QWs) in the (CdMn)Te/(CdMg)Te (with 1.5% Mn) heterostructure system by THz cyclotron resonance. Samples with CdTe QWs are also studied. Both structures have the same QW width (30 nm), very similar electron densities in the wells ~3.0 x 1011 cm-2 and mobilities of 450,000 (CdTe) and 66,000 cm2/Vs ((CdMn)Te) at 1.6 K. The electron effective masses (m*/m0) from cyclotron resonance measurements at 5K are 0.110 +/- 0.001 for CdTe and 0.114 +/- 0.003 for (CdMn)Te . Linear fits to the resonance positions in frequency vs. field give small non-zero intercepts which may result from small non-parabolicity or bound magneto-plasmon effects. The FWHM linewidths from Lorentzian fits of the transmission minima are ~2 cm-1(CdTe) and ~8 cm-1((CdMn)Te). Our present focus is on detailed studies of the CR positions and linewidths in the magnetic field region around the cusp-like behavior in the Rxx oscillations, which indicates the presence of the QHF state. The field position of this state is tuned via electron density in the QWs varied incrementally by a photon-dose method with an in-situ green LED. Work at UB was supported in part by the Office of the Provost, and work in Poland was supported in part by the National Science Centre through Grant DEC-2012/06/A/ST3/00247.

  10. CdTe quantum dots and gold nanoparticle based spectral methods for determination of lincomycin

    NASA Astrophysics Data System (ADS)

    Ge, Baoyu; Li, Zhigang; Xie, Yuanzhe; Yang, Lingling; Wang, Ruiyong

    2015-05-01

    Two novel and convenient methods for the determination of lincomycin (LCM) in aqueous solutions have been developed. The first method was based on the enhanced fluorescence of thioglycolic acidcapped CdTe quantum dots (TGA-CdTe QDs) by LCM. For the second method, the introduction of LCM could induce the aggregation of gold nanoparticles (AuNPs), displaying distinct changes in color and in UVvis spectra. Under optimal conditions, the enhanced fluorescence intensity was linearly proportional to LCM concentration in the range of 1-240 μg mL-1 with a detection limit of 2.63 × 10-1 μg mL-1. The second platform is capable of determining LCM in ranges from 1.00 × 10-3 to 2.00 × 10-2 μg mL-1 and from 3.00 × 10-2 to 1.20 × 10-1 μg mL-1 with a detection limit of 1.27 × 10-4 μg mL-1. Both methods were used for rapid detection of LCM in real samples with satisfactory results. Comparisons between the two methods were made.

  11. Mechanisms underlying toxicity induced by CdTe quantum dots determined in an invertebrate model organism.

    PubMed

    Ambrosone, Alfredo; Mattera, Lucia; Marchesano, Valentina; Quarta, Alessandra; Susha, Andrei S; Tino, Angela; Rogach, Andrey L; Tortiglione, Claudia

    2012-03-01

    A systematic and thorough quantitative analysis of the in vivo effects of inorganic nanoparticles is extremely important for the design of functional nanomaterials for diagnostic and therapeutic applications, better understanding of their non-specificity toward tissues and cell types, and for assessments of their toxicity. This study was undertaken to examine the impact of CdTe quantum dots (QDs) on an invertebrate freshwater model organism, Hydra vulgaris, for assessment of long term toxicity effects. The continuous exposure of living polyps to sub-lethal doses of QDs caused time and dose dependent morphological damages more severe than Cd(2+) ions at the same concentrations, impaired both reproductive and regenerative capability, activated biochemical and molecular responses. Of remarkable interest, low QD doses, apparently not effective, caused early changes in the expression of general stress responsive and apoptotic genes. The occurrence of subtle genetic variations, in the absence of morphological damages, indicates the importance of genotoxicity studies for nanoparticle risk assessment. The versatility in morphological, cellular, biochemical and molecular responses renders Hydra a perfect model system for high-throughput screening of toxicological and ecotoxicological impact of nanomaterials on human and environmental health.

  12. Graphite oxide-dispersed CdTe quantum dots nanocomposite for flexible display luminescent membranes.

    PubMed

    Liu, Cui; Du, Lei; Lin, Yongjun; Liang, Jiyuan; Liu, Jun'an; Cao, Yuan-Cheng

    2017-03-08

    A quantum dot (QD) dispersant material was prepared using graphite oxide (GO). Luminescent films were prepared using polyvinyl alcohol as the polymer matrix. First, water-soluble CdTe QDs were prepared by wet chemistry and GO was synthesized using a modified Hummers method. X-Ray diffraction tests showed that the GO reflection peak [001] was 11.9°, which indicates that the d-spacing is 0.7431 nm; atomic force microscopy showed a GO thickness of 200 nm. Fourier transform infrared spectra showed vibrations at 1624 cm(-1) for the carbonyl groups, and 3260 cm(-1) for the GO samples; the -C-O vibration was at 1320 cm(-1) and -COOH, -OH vibrations were at 950 cm(-1) . Fluorescent tests showed that pH had an impact on the QD colloidal stability. GO was neutralized before use as the host media for the GO/QDs nanocomposite. The results proved that the resultant nanocomposite is promising for use in brightness enhancement films in flexible displays.

  13. Quantum Dot Sensitized Photoelectrodes

    PubMed Central

    Macdonald, Thomas J.; Nann, Thomas

    2011-01-01

    Quantum Dots (QDs) are promising alternatives to organic dyes as sensitisers for photocatalytic electrodes. This review article provides an overview of the current state of the art in this area. More specifically, different types of QDs with a special focus on heavy-metal free QDs and the methods for preparation and adsorption onto metal oxide electrodes (especially titania and zinc oxide) are discussed. Eventually, the key areas of necessary improvements are identified and assessed.

  14. Highly efficient nonradiative energy transfer mediated light harvesting in water using aqueous CdTe quantum dot antennas.

    PubMed

    Mutlugun, Evren; Samarskaya, Olga; Ozel, Tuncay; Cicek, Neslihan; Gaponik, Nikolai; Eychmüller, Alexander; Demir, Hilmi Volkan

    2010-05-10

    We present light harvesting of aqueous colloidal quantum dots to nonradiatively transfer their excitonic excitation energy efficiently to dye molecules in water, without requiring ligand exchange. These as-synthesized CdTe quantum dots that are used as donors to serve as light-harvesting antennas are carefully optimized to match the electronic structure of Rhodamine B molecules used as acceptors for light harvesting in aqueous medium. By varying the acceptor to donor concentration ratio, we measure the light harvesting factor, along with substantial lifetime modifications of these water-soluble quantum dots, from 25.3 ns to 7.2 ns as a result of their energy transfer with efficiency levels up to 86%. Such nonradiative energy transfer mediated light harvesting in aqueous medium holds great promise for future quantum dot multiplexed dye biodetection systems.

  15. Monoclonal antibody-quantum dots CdTe conjugate-based fluoroimmunoassay for the determination of aflatoxin B1 in peanuts.

    PubMed

    Zhang, Zhaowei; Li, Yuanyuan; Li, Peiwu; Zhang, Qi; Zhang, Wen; Hu, Xiaofeng; Ding, Xiaoxia

    2014-03-01

    A fluoroimmunoassay towards aflatoxin B1 (AFB1) was presented using quantum dots as the fluorescent label. The CdTe QDs were successfully linked to the monoclonal antibody against AFB1. Based on the conjugated complexes, a novel direct competitive fluorescence-linked immunosorbent assay (cFLISA) was developed for AFB1 detection. The 50% inhibition value (IC50) of the cFLISA was 0.149ng/mL in peanuts matrix. The method performance included the limit of detection (LOD) of 0.016ng/mL and considerable recoveries of 85-117% at three fortification levels (0.075, 0.15, and 0.3ng/g) from spiked AFB1 blank peanuts samples, along with coefficients of variation (CVs) below 10%. The cFLISA provided an alternative of rapid and sensitive detection for AFB1 and, moreover provided great potential for multiplexed mycotoxins determination simultaneously.

  16. Distributed Bragg reflectors obtained by combining Se and Te compounds: Influence on the luminescence from CdTe quantum dots

    SciTech Connect

    Rousset, J.-G. Kobak, J.; Janik, E.; Slupinski, T.; Golnik, A.; Kossacki, P.; Nawrocki, M.; Pacuski, W.; Parlinska-Wojtan, M.

    2016-05-14

    We report on the optical properties of structures containing self assembled CdTe quantum dots (QDs) combined with Te and Se based distributed Bragg reflectors either in a half cavity geometry with a relatively broad cavity mode or in a full cavity geometry where the cavity mode is much narrower. We show that for both structures the extraction coefficient of the light emitted from the QDs ensemble is enhanced by more than one order of magnitude with respect to the QDs grown on a ZnTe buffer. However, a single QD line broadening is observed and attributed to an unintentional incorporation of Se in the vicinity of the CdTe QDs. We show that postponing the QDs growth for 24 h after the distributed Bragg reflector deposition allows recovering sharp emission lines from individual QDs. This two step growth method is proven to be efficient also for the structures with CdTe QDs containing a single Mn{sup 2+} ion.

  17. Study on the interaction between bovine serum albumin and CdTe quantum dots with spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Liang, Jiangong; Cheng, Yanping; Han, Heyou

    2008-12-01

    The interaction between bovine serum albumin (BSA) and CdTe quantum dots (QDs) was studied by fluorescence, UV-vis and Raman spectroscopic techniques. The results showed that the fluorescence of BSA was strongly quenched by CdTe QDs. The quenching mechanism was discussed to be a static quenching procedure, which was proved by the quenching rate constant ( Kq) and UV-vis absorption spectra. According to Lineweaver-Burk equations at different temperatures, the thermodynamic parameters, Δ H θ, Δ S θ and Δ G θ were observed to be -23.69 kJ mol -1, 48.39 J mol -1 K -1 and -38.04 kJ mol -1, respectively. The binding constant ( KA) and the number of binding sites ( n) were obtained by Scatchard equation. It was found that hydrophobic force and sulfhydryl group played a key role in the interaction process. Further results from Raman spectra indicated that the α-helical content in BSA reduced after binding with CdTe QDs.

  18. Enhanced Specificity of Multiplex Polymerase Chain Reaction via CdTe Quantum Dots

    NASA Astrophysics Data System (ADS)

    Liang, Gaofeng; Ma, Chao; Zhu, Yanliang; Li, Shuchun; Shao, Youhua; Wang, Yong; Xiao, Zhongdang

    2011-12-01

    Nanoparticles were recently reported to be able to improve both efficiency and specificity in polymerase chain reaction (PCR). Here, CdTe QDs were introduced into multi-PCR systems. It was found that an appropriate concentration of CdTe QDs could enhance the performance of multi-PCR by reducing the formation of nonspecific products in the complex system, but an excessive amount of CdTe QDs could suppress the PCR. The effects of QDs on PCR can be reversed by increasing the polymerase concentration or by adding bovine serum albumin (BSA). The mechanisms underlying these effects were also discussed. The results indicated that CdTe QDs could be used to optimize the amplification products of the PCR, especially in the multi-PCR system with different primers annealing temperatures, which is of great significance for molecular diagnosis.

  19. Adhesion of CdTe quantum dots on model membranes and internalization into RBL-2H3 cells.

    PubMed

    Zhang, Mengmeng; Wei, Xiaoran; Ding, Lei; Hu, Jingtian; Jiang, Wei

    2017-03-08

    Quantum dots (QDs) have attracted broad attention due to their special optical properties and promising prospect in medical and biological applications. However, the process of QDs on cell membrane is worth further investigations because such process may lead to harmful effects on organisms and also important for QD application. In this study, adhesion of amino- and carboxyl-coated CdTe QDs (A-QDs and C-QDs) on cell membrane and the subsequent internalization are studied using a series of endocytosis-free model membranes, including giant and small unilamellar vesicles, supported lipid bilayers and giant plasma membrane vesicles (GPMVs). The adhered QD amounts on model membranes are quantified by a quartz crystal microbalance. The CdTe QD adhesion on model membranes is governed by electrostatic forces. Positively charged A-QDs adhere on GPMV surface and passively penetrate the plasma membrane via endocytosis-free mechanism, but negatively charged C-QDs cannot. Rat basophilic leukemia (RBL-2H3) cells are exposed to CdTe QDs to monitor the QD internalization process. Both A- and C-QDs are internalized by RBL-2H3 cells mainly via endocytosis. CdTe QDs do not accumulate on the plasma membrane of living cells due to the fast endocytosis and the weakened electrostatic attraction in biological medium, resulting in low chance of passive penetration. The suspended cells after trypsin digestion take more QDs than the adherent cells. A-QDs cause lower cell viability than C-QDs, probably because the approach of positively charged QDs to cells is favored and the smaller aggregates of A-QDs.

  20. A simple and rapid label-free fluorimetric biosensor for protamine detection based on glutathione-capped CdTe quantum dots aggregation.

    PubMed

    Ensafi, Ali A; Kazemifard, N; Rezaei, B

    2015-09-15

    A novel fluorescent biosensor is developed, based on glutathione-capped CdTe quantum dots aggregation, for the determination of trace amount of an important drug, protamine. In this method with increasing the protamine concentration, the fluorescence of the quantum dots was quenched due to their aggregation. Different parameters affect the sensitivity, such as pH and the amount of the quantum dots, were optimized. Using the new optical biosensor, under the optimized conditions, protamine could be measured in the range of 2.0-200 ng mL(-1) with a detection limit of 1.0 ng mL(-)(1). The relative standard deviation for five replicates determination of 30.0 ng mL(-)(1) protamine was 1.26%. The influence of common interfering species on the protamine detection was studied. The results showed that the biosensor is highly selective and sensitive for the detection of protamine. The optical biosensor was successfully used for the determination of protamine in real samples.

  1. A simple fluorescence quenching method for berberine determination using water-soluble CdTe quantum dots as probes

    NASA Astrophysics Data System (ADS)

    Cao, Ming; Liu, Meigui; Cao, Chun; Xia, Yunsheng; Bao, Linjun; Jin, Yingqiong; Yang, Song; Zhu, Changqing

    2010-03-01

    A novel method for the determination of berberine has been developed based on quenching of the fluorescence of thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) by berberine in aqueous solutions. Under optimum conditions, the relative fluorescence intensity was linearly proportional to the concentration of berberine between 2.5 × 10 -8 and 8.0 × 10 -6 mol L -1 with a detection limit of 6.0 × 10 -9 mol L -1. The method has been applied to the determination of berberine in real samples, and satisfactory results were obtained. The mechanism of the proposed reaction was also discussed.

  2. Efficient fluorescence energy transfer system between fluorescein isothiocyanate and CdTe quantum dots for the detection of silver ions.

    PubMed

    Feng, Yueshu; Liu, Liwei; Hu, Siyi; Zou, Peng; Zhang, Jiaqi; Huang, Chen; Wang, Yue; Wang, Sihan; Zhang, Xihe

    2016-03-01

    We report a fluorescence resonance energy transfer (FRET) system in which the fluorescent donor is fluorescein isothiocyanate (FITC) dye and the fluorescent acceptor is CdTe quantum dot (QDs). Based on FRET quenching theory, we designed a method to detect the concentration of silver ions (Ag(+)). The results revealed a good linear trend over Ag(+) concentrations in the range 0.01-8.96 nmol/L, a range that was larger than with other methods; the quenching coefficient is 0.442. The FRET mechanism and physical mechanisms responsible for dynamic quenching are also discussed.

  3. Biocompatibility of hydrophilic silica-coated CdTe quantum dots and magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Ruan, Jing; Wang, Kan; Song, Hua; Xu, Xin; Ji, Jiajia; Cui, Daxiang

    2011-12-01

    Fluorescent magnetic nanoparticles exhibit great application prospects in biomedical engineering. Herein, we reported the effects of hydrophilic silica-coated CdTe quantum dots and magnetic nanoparticles (FMNPs) on human embryonic kidney 293 (HEK293) cells and mice with the aim of investigating their biocompatibility. FMNPs with 150 nm in diameter were prepared, and characterized by high-resolution transmission electron microscopy and photoluminescence (PL) spectra and magnetometer. HEK293 cells were cultured with different doses of FMNPs (20, 50, and 100μ g/ml) for 1-4 days. Cell viability and adhesion ability were analyzed by CCK8 method and Western blotting. 30 mice were randomly divided into three groups, and were, respectively, injected via tail vein with 20, 60, and 100 μg FMNPs, and then were, respectively, raised for 1, 7, and 30 days, then their lifespan, important organs, and blood biochemical parameters were analyzed. Results show that the prepared water-soluble FMNPs had high fluorescent and magnetic properties, less than 50 μg/ml of FMNPs exhibited good biocompatibility to HEK293 cells, the cell viability, and adhesion ability were similar to the control HEK293 cells. FMNPs primarily accumulated in those organs such as lung, liver, and spleen. Lung exposed to FMNPs displayed a dose-dependent inflammatory response, blood biochemical parameters such as white blood cell count (WBC), alanine aminotransferase (ALT), and aspartate aminotransferase (AST), displayed significant increase when the FMNPs were injected into mice at dose of 100μg. In conclusion, FMNPs exhibit good biocompatibility to cells under the dose of less than 50 μg/ml, and to mice under the dose of less than 2mg/kg body weight. The FMNPs' biocompatibility must be considered when FMNPs are used for in vivo diagnosis and therapy.

  4. Blood group antigen studies using CdTe quantum dots and flow cytometry

    PubMed Central

    Cabral Filho, Paulo E; Pereira, Maria IA; Fernandes, Heloise P; de Thomaz, Andre A; Cesar, Carlos L; Santos, Beate S; Barjas-Castro, Maria L; Fontes, Adriana

    2015-01-01

    New methods of analysis involving semiconductor nanocrystals (quantum dots [QDs]) as fluorescent probes have been highlighted in life science. QDs present some advantages when compared to organic dyes, such as size-tunable emission spectra, broad absorption bands, and principally exceptional resistance to photobleaching. Methods applying QDs can be simple, not laborious, and can present high sensibility, allowing biomolecule identification and quantification with high specificity. In this context, the aim of this work was to apply dual-color CdTe QDs to quantify red blood cell (RBC) antigen expression on cell surface by flow cytometric analysis. QDs were conjugated to anti-A or anti-B monoclonal antibodies, as well as to the anti-H (Ulex europaeus I) lectin, to investigate RBCs of A1, B, A1B, O, A2, and Aweak donors. Bioconjugates were capable of distinguishing the different expressions of RBC antigens, both by labeling efficiency and by flow cytometry histogram profile. Furthermore, results showed that RBCs from Aweak donors present fewer amounts of A antigens and higher amounts of H, when compared to A1 RBCs. In the A group, the amount of A antigens decreased as A1 > A3 > AX = Ael, while H antigens were AX = Ael > A1. Bioconjugates presented stability and remained active for at least 6 months. In conclusion, this methodology with high sensibility and specificity can be applied to study a variety of RBC antigens, and, as a quantitative tool, can help in achieving a better comprehension of the antigen expression patterns on RBC membranes. PMID:26185442

  5. Red Light-Emitting Diode Based on Blue InGaN Chip with CdTe x S(1 - x) Quantum Dots

    NASA Astrophysics Data System (ADS)

    Wang, Rongfang; Wei, Xingming; Qin, Liqin; Luo, Zhihui; Liang, Chunjie; Tan, Guohang

    2017-01-01

    Thioglycolic acid-capped CdTe x S(1 - x) quantum dots (QDs) were synthesized through a one-step approach in an aqueous medium. The CdTe x S(1 - x) QDs played the role of a color conversion center. The structural and luminescent properties of the obtained CdTe x S(1 - x) QDs were investigated. The fabricated red light-emitting hybrid device with the CdTe x S(1 - x) QDs as the phosphor and a blue InGaN chip as the excitation source showed a good luminance. The Commission Internationale de L'Eclairage coordinates of the light-emitting diode (LED) at (0.66, 0.29) demonstrated a red LED. Results showed that CdTe x S(1 - x) QDs can be excited by blue or near-UV regions. This feature presents CdTe x S(1 - x) QDs with an advantage over wavelength converters for LEDs.

  6. Red Light-Emitting Diode Based on Blue InGaN Chip with CdTe x S(1 - x) Quantum Dots.

    PubMed

    Wang, Rongfang; Wei, Xingming; Qin, Liqin; Luo, Zhihui; Liang, Chunjie; Tan, Guohang

    2017-12-01

    Thioglycolic acid-capped CdTe x S(1 - x) quantum dots (QDs) were synthesized through a one-step approach in an aqueous medium. The CdTe x S(1 - x) QDs played the role of a color conversion center. The structural and luminescent properties of the obtained CdTe x S(1 - x) QDs were investigated. The fabricated red light-emitting hybrid device with the CdTe x S(1 - x) QDs as the phosphor and a blue InGaN chip as the excitation source showed a good luminance. The Commission Internationale de L'Eclairage coordinates of the light-emitting diode (LED) at (0.66, 0.29) demonstrated a red LED. Results showed that CdTe x S(1 - x) QDs can be excited by blue or near-UV regions. This feature presents CdTe x S(1 - x) QDs with an advantage over wavelength converters for LEDs.

  7. Hydrothermal synthesis of GSH-TGA co-capped CdTe quantum dots and their application in labeling colorectal cancer cells.

    PubMed

    Yu, Yongli; Xu, Linru; Chen, Jing; Gao, Huanyu; Wang, Shuo; Fang, Jin; Xu, Shukun

    2012-06-15

    We have successfully synthesized GSH and TGA co-capped CdTe quantum dots (QDs) with good biological compatibility and high fluorescence intensity. The effects of different reaction time, temperature, pH value, ligand concentration and the molar ratio of GSH/TGA were carefully investigated to optimize the synthesis condition. The optical properties of as-prepared CdTe QDs were studied by UV-visible absorption spectrum and fluorescence spectrum, meanwhile their structure and morphology were characterized using transmission electron microscope (TEM), Fourier transform infrared spectra (FT-IR) and X-ray powder diffraction (XRD). Compared with the CdTe QDs that are single-capped with either GSH or TGA, the GSH-TGA co-capped CdTe QDs demonstrated significantly improved fluorescence intensity and optical stability. In addition, GSH-TGA co-capped CdTe QDs were conjugated to amonoclonal antibody ND-1. The GSH-TGA co-capped CdTe QDs-antibody probe was successfully used to label colorectal cancer cells, CCL187, in vitro. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. CdTe and CdSe quantum dots: synthesis, characterizations and applications in agriculture

    NASA Astrophysics Data System (ADS)

    Dieu Thuy Ung, Thi; Tran, Thi Kim Chi; Nga Pham, Thu; Nghia Nguyen, Duc; Khang Dinh, Duy; Liem Nguyen, Quang

    2012-12-01

    This paper highlights the results of the whole work including the synthesis of highly luminescent quantum dots (QDs), characterizations and testing applications of them in different kinds of sensors. Concretely, it presents: (i) the successful synthesis of colloidal CdTe and CdSe QDs, their core/shell structures with single- and/or double-shell made by CdS, ZnS or ZnSe/ZnS; (ii) morphology, structural and optical characterizations of the synthesized QDs; and (iii) testing examples of QDs as the fluorescence labels for agricultural-bio-medical objects (for tracing residual pesticide in agricultural products, residual clenbuterol in meat/milk and for detection of H5N1 avian influenza virus in breeding farms). Overall, the results show that the synthesized QDs have very good crystallinity, spherical shape and strongly emit at the desired wavelengths between ˜500 and 700 nm with the luminescence quantum yield (LQY) of 30-85%. These synthesized QDs were used in fabrication of the three testing fluorescence QD-based sensors for the detection of residual pesticides, clenbuterol and H5N1 avian influenza virus. The specific detection of parathion methyl (PM) pesticide at a content as low as 0.05 ppm has been realized with the biosensors made from CdTe/CdS and CdSe/ZnSe/ZnS QDs and the acetylcholinesterase (AChE) enzymes. Fluorescence resonance energy transfer (FRET)-based nanosensors using CdTe/CdS QDs conjugated with 2-amino-8-naphthol-6-sulfonic acid were fabricated that enable detection of diazotized clenbuterol at a content as low as 10 pg ml-1. For detection of H5N1 avian influenza virus, fluorescence biosensors using CdTe/CdS QDs bound on the surface of chromatophores extracted and purified from bacteria Rhodospirillum rubrum were prepared and characterized. The specific detection of H5N1 avian influenza virus in the range of 3-50 ng μl-1 with a detection limit of 3 ng μL-1 has been performed based on the antibody-antigen recognition.

  9. Density of Trap States and Auger-mediated Electron Trapping in CdTe Quantum-Dot Solids.

    PubMed

    Boehme, Simon C; Azpiroz, Jon Mikel; Aulin, Yaroslav V; Grozema, Ferdinand C; Vanmaekelbergh, Daniël; Siebbeles, Laurens D A; Infante, Ivan; Houtepen, Arjan J

    2015-05-13

    Charge trapping is an ubiquitous process in colloidal quantum-dot solids and a major limitation to the efficiency of quantum dot based devices such as solar cells, LEDs, and thermoelectrics. Although empirical approaches led to a reduction of trapping and thereby efficiency enhancements, the exact chemical nature of the trapping mechanism remains largely unidentified. In this study, we determine the density of trap states in CdTe quantum-dot solids both experimentally, using a combination of electrochemical control of the Fermi level with ultrafast transient absorption and time-resolved photoluminescence spectroscopy, and theoretically, via density functional theory calculations. We find a high density of very efficient electron traps centered ∼0.42 eV above the valence band. Electrochemical filling of these traps increases the electron lifetime and the photoluminescence quantum yield by more than an order of magnitude. The trapping rate constant for holes is an order of magnitude lower that for electrons. These observations can be explained by Auger-mediated electron trapping. From density functional theory calculations we infer that the traps are formed by dicoordinated Te atoms at the quantum dot surface. The combination of our unique experimental determination of the density of trap states with the theoretical modeling of the quantum dot surface allows us to identify the trapping mechanism and chemical reaction at play during charge trapping in these quantum dots.

  10. Synthesis of AS1411-aptamer-conjugated CdTe quantum dots with high fluorescence strength for probe labeling tumor cells.

    PubMed

    Alibolandi, Mona; Abnous, Khalil; Ramezani, Mohammad; Hosseinkhani, Hossein; Hadizadeh, Farzin

    2014-09-01

    In this paper, we report microwave-assisted, one-stage synthesis of high-quality functionalized water-soluble cadmium telluride (CdTe) quantum dots (QDs). By selecting sodium tellurite as the Te source, cadmium chloride as the Cd source, mercaptosuccinic acid (MSA) as the capping agent, and a borate-acetic acid buffer solution with a pH range of 5-8, CdTe nanocrystals with four colors (blue to orange) were conveniently prepared at 100 °C under microwave irradiation in less than one hour (reaction time: 10-60 min). The influence of parameters such as the pH, Cd:Te molar ratio, and reaction time on the emission range and quantum yield percentage (QY%) was investigated. The structures and compositions of the prepared CdTe QDs were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, selective area electron diffraction, and X-ray powder diffraction experiments. The formation mechanism of the QDs is discussed in this paper. Furthermore, AS1141-aptamer-conjugated CdTe QDs in the U87MG glioblastoma cell line were assessed with a fluorescence microscope. The obtained results showed that the best conditions for obtaining a high QY of approximately 87% are a pH of 6, a Cd:Te molar ratio of 5:1, and a 30-min reaction time at 100 °C under microwave irradiation. The results showed that AS1141-aptamer-conjugated CdTe QDs could enter tumor cells efficiently. It could be concluded that a facile high-fluorescence-strength QD conjugated with a DNA aptamer, AS1411, which can recognize the extracellular matrix protein nucleolin, can specifically target U87MG human glioblastoma cells. The qualified AS1411-aptamer-conjugated QDs prepared in this study showed excellent capabilities as nanoprobes for cancer targeting and molecular imaging.

  11. A CdTe position sensitive detector for a hard X- and gamma-ray wide field camera

    SciTech Connect

    Caroli, E.; Cesare, G. de; Donati, A.; Dusi, W.; Landini, G.; Stephen, J.B.; Perotti, F.

    1998-12-31

    An important region of the electromagnetic spectrum for astrophysics is the hard X- and gamma ray band between 10 keV and a few MeV, where several processes occur in a wide variety of objects and with different spatial distribution and time scales. In order to fulfill the observational requirements in this energy range and taking into account the opportunities given by small/medium size missions (e.g., on the ISS), the authors have proposed a compact, wide field camera based on a thick (1 cm) position sensitive CdTe detector (PSD). The detector is made of an array of 128x96 CdTe microspectrometers with a pixel size of 2x2 mm{sup 2}. The basic element of the PSD is the linear module that is an independent detection unit with 32 CdTe crystals and monolithic front-electronics (ASIC) supported by a thin (300 {micro}m) ceramic layer. The expected performance of the PSD over the operative energy range and some of the required ASIC functionality are presented and discussed.

  12. Microcalorimetric, spectroscopic and microscopic investigation on the toxic effects of CdTe quantum dots on Halobacterium halobium R1.

    PubMed

    Li, Ran; Jiang, Fenglei; Xiao, Qi; Li, Jiahan; Liu, Xiaorong; Yu, Qiuliyang; Liu, Yi; Zeng, Chi

    2010-11-26

    The biological effect of CdTe quantum dots (QDs) on Halobacterium halobium R1 (H. halobium R1) growth was analyzed by a microcalorimetric technique. By using a TAM air eight channels microcalorimeter, the thermogenic curves of H. halobium R1 growth were obtained at 37 °C. To analyze the results, the maximum heat power (P(m)) and the growth rate constants (k) were determined, which showed that they were correlated to the concentration of QDs. The addition of quantum dots caused a gradual increase of P(m) and k at low concentrations of QDs, and a conspicuous decrease at high concentrations. For confirmation, the turbidity (OD(600)) and respiratory rate at different concentrations of QDs were studied. The morphology of H. halobium R1 cells both in the absence and presence of QDs was examined by transmission electron microscopy (TEM). The results of these studies were corroborated with ones derived from microcalorimetry. In this work, the mechanism of cytotoxicity of QDs was explored through fluorescence spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS) and microcalorimetry. It was clear that metabolic mechanism of H. halobium R1 growth was changed by the addition of QDs. To the best of our knowledge, the thermokinetics and toxicology of CdTe QDs against H. halobium R1 were obtained for the first time by microcalorimetry.

  13. Microcalorimetric, spectroscopic and microscopic investigation on the toxic effects of CdTe quantum dots on Halobacterium halobium R1

    NASA Astrophysics Data System (ADS)

    Li, Ran; Jiang, Fenglei; Xiao, Qi; Li, Jiahan; Liu, Xiaorong; Yu, Qiuliyang; Liu, Yi; Zeng, Chi

    2010-11-01

    The biological effect of CdTe quantum dots (QDs) on Halobacterium halobium R1 (H. halobium R1) growth was analyzed by a microcalorimetric technique. By using a TAM air eight channels microcalorimeter, the thermogenic curves of H. halobium R1 growth were obtained at 37 °C. To analyze the results, the maximum heat power (Pm) and the growth rate constants (k) were determined, which showed that they were correlated to the concentration of QDs. The addition of quantum dots caused a gradual increase of Pm and k at low concentrations of QDs, and a conspicuous decrease at high concentrations. For confirmation, the turbidity (OD600) and respiratory rate at different concentrations of QDs were studied. The morphology of H. halobium R1 cells both in the absence and presence of QDs was examined by transmission electron microscopy (TEM). The results of these studies were corroborated with ones derived from microcalorimetry. In this work, the mechanism of cytotoxicity of QDs was explored through fluorescence spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS) and microcalorimetry. It was clear that metabolic mechanism of H. halobium R1 growth was changed by the addition of QDs. To the best of our knowledge, the thermokinetics and toxicology of CdTe QDs against H. halobium R1 were obtained for the first time by microcalorimetry.

  14. Effects of multi-walled carbon nanotubes on the electrogenerated chemiluminescence and fluorescence of CdTe quantum dots.

    PubMed

    Wusimanjiang, Yiliyasi; Meyer, Alexander; Lu, Liping; Miao, Wujian

    2016-10-01

    Effects of multi-walled carbon nanotubes (CNTs) that were immobilized on glassy carbon electrode (GCE) on the electrogenerated chemiluminescence (ECL) of CdTe quantum dots (QDs) using tri-n-propylamine (TPrA) and 2-(dibutylamino)ethanol (DBAE) as the anodic coreactant are reported. Depending on the solution concentration of coreactant and QDs, the surface-confined CNTs could either quench or enhance the ECL intensity. Lowering the solution concentration of QDs was found to be beneficial for enhancing ECL. A V-shaped profile of ECL intensity ratio (at CNTs over bare GCE) versus coreactant concentration suggested that either low or high concentrations of coreactant were needed for effective ECL generation. The ECL quenching by CNTs was believed to follow the typical dynamic quenching mechanism, which was confirmed by fluorescent data that provided a Stern-Volmer and an estimated quenching constant of 11.7 g/L and 1.2 × 10(9) L/g•s, respectively, for the excited state CdTe* quenching by CNTs in solution. Furthermore, the ECL performance at CNTs was also affected by the type of the coreactant used, where up to 30 times enhancement in ECL was observed from the CdTe/DBAE system under the given experimental conditions. Graphical Abstract Illustration of anodic quantum dots ECL enhancement and quenching by multi-walled carbon nanotubes.

  15. Efficient quenching of TGA-capped CdTe quantum dot emission by a surface-coordinated europium(III) cyclen complex.

    PubMed

    Gallagher, Shane A; Comby, Steve; Wojdyla, Michal; Gunnlaugsson, Thorfinnur; Kelly, John M; Gun'ko, Yurii K; Clark, Ian P; Greetham, Gregory M; Towrie, Michael; Quinn, Susan J

    2013-04-15

    Extremely efficient quenching of the excited state of aqueous CdTe quantum dots (QDs) by photoinduced electron transfer to a europium cyclen complex is facilitated by surface coordination to the thioglycolic acid capping ligand. The quenching dynamics are elucidated using steady-state emission and picosecond transient absorption.

  16. PbTe and SnTe quantum dot precipitates in a CdTe matrix fabricated by ion implantation

    SciTech Connect

    Kaufmann, E.; Schwarzl, T.; Groiss, H.; Hesser, G.; Schaeffler, F.; Palmetshofer, L.; Springholz, G.; Heiss, W.

    2009-08-15

    We present rock-salt IV-VI semiconductor quantum dots fabricated by implantation of Pb{sup +}, Te{sup +}, or Sn{sup +} ions into epitaxial zinc-blende CdTe layers. PbTe and SnTe nanoprecipitates of high structural quality are formed after implantation by thermal annealing due to the immiscibility of dot and matrix materials. For samples implanted only with Pb{sup +}, intense continuous-wave photoluminescence peaked at 1.6 mum at 300 K is found. In contrast, for PbTe quantum dots fabricated by coimplantation of Pb{sup +} and Te{sup +}, the 300 K emission peak is observed at 2.9 mum, indicating luminescence from much larger dots.

  17. One- and two-photon photoluminescence excitation spectra of CdTe quantum dots in a cryogenic confocal microscopy platform.

    PubMed

    Almeida, Diogo B; de Thomaz, André A; Carvalho, Hernandes F; Cesar, Carlos L

    2015-07-27

    In this work we describe a method to obtain photoluminescente excitation spectra, through one and two photon absorption, of CdTe quantum dots, based on a confocal microscope platform. This system becomes an analytical multipurpose characterization platform with spatial, and spectral resolution with temperature control. The capabilities of such platform were demonstrated by photoluminescence and second harmonic generation spectra acquisition as a function of temperature from 10 K to room temperature. The differences for one and two photons transition selection rules between the quantum dot confined levels provide access to intra and inter band, forbidden in one photon transitions, information that could be used to validate confinement models. The results agree well with the transition selection rules calculated with a parabolic model.

  18. Photodynamic therapy potential of thiol-stabilized CdTe quantum dot-group 3A phthalocyanine conjugates (QD-Pc).

    PubMed

    Tekdaş, Duygu Aydın; Durmuş, Mahmut; Yanık, Hülya; Ahsen, Vefa

    2012-07-01

    Thiol stabilized CdTe quantum dot (QD) nanoparticles were synthesized in aqueous phase and were used as energy donors to tetra-triethyleneoxythia substituted aluminum, gallium and indium phthalocyanines through fluorescence resonance energy transfer (FRET). Energy transfer occurred from the QDs to phthalocyanines upon photoexcitation of the QDs. An enhancement in efficiency of energy transfer with the nature of the carboxylic thiol stabilizer on the QDs was observed. As a result of the nanoparticle and the phthalocyanine mixing, the photoluminescence efficiency of the phthalocyanine moieties in the mixtures does not strictly follow the quantum yields of the bare phthalocyanines. The photochemistry study of phthalocyanines in the presence of the QDs revealed high singlet oxygen quantum yield, hence the possibility of using QDs in combination with phthalocyanines as photosensitizers in photodynamic therapy of cancer. The fluorescence of the CdTe quantum dots-phthalocyanine conjugates (QDs-Pc) were effectively quenched by addition of 1,4-benzoquinone.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. High-sensitivity brain SPECT system using cadmium telluride (CdTe) semiconductor detector and 4-pixel matched collimator.

    PubMed

    Suzuki, Atsuro; Takeuchi, Wataru; Ishitsu, Takafumi; Tsuchiya, Katsutoshi; Morimoto, Yuichi; Ueno, Yuichiro; Kobashi, Keiji; Kubo, Naoki; Shiga, Tohru; Tamaki, Nagara

    2013-11-07

    For high-sensitivity brain imaging, we have developed a two-head single-photon emission computed tomography (SPECT) system using a CdTe semiconductor detector and 4-pixel matched collimator (4-PMC). The term, '4-PMC' indicates that the collimator hole size is matched to a 2 × 2 array of detector pixels. By contrast, a 1-pixel matched collimator (1-PMC) is defined as a collimator whose hole size is matched to one detector pixel. The performance of the higher-sensitivity 4-PMC was experimentally compared with that of the 1-PMC. The sensitivities of the 1-PMC and 4-PMC were 70 cps/MBq/head and 220 cps/MBq/head, respectively. The SPECT system using the 4-PMC provides superior image resolution in cold and hot rods phantom with the same activity and scan time to that of the 1-PMC. In addition, with half the usual scan time the 4-PMC provides comparable image quality to that of the 1-PMC. Furthermore, (99m)Tc-ECD brain perfusion images of healthy volunteers obtained using the 4-PMC demonstrated acceptable image quality for clinical diagnosis. In conclusion, our CdTe SPECT system equipped with the higher-sensitivity 4-PMC can provide better spatial resolution than the 1-PMC either in half the imaging time with the same administered activity, or alternatively, in the same imaging time with half the activity.

  1. High-sensitivity brain SPECT system using cadmium telluride (CdTe) semiconductor detector and 4-pixel matched collimator

    NASA Astrophysics Data System (ADS)

    Suzuki, Atsuro; Takeuchi, Wataru; Ishitsu, Takafumi; Tsuchiya, Katsutoshi; Morimoto, Yuichi; Ueno, Yuichiro; Kobashi, Keiji; Kubo, Naoki; Shiga, Tohru; Tamaki, Nagara

    2013-11-01

    For high-sensitivity brain imaging, we have developed a two-head single-photon emission computed tomography (SPECT) system using a CdTe semiconductor detector and 4-pixel matched collimator (4-PMC). The term, ‘4-PMC’ indicates that the collimator hole size is matched to a 2 × 2 array of detector pixels. By contrast, a 1-pixel matched collimator (1-PMC) is defined as a collimator whose hole size is matched to one detector pixel. The performance of the higher-sensitivity 4-PMC was experimentally compared with that of the 1-PMC. The sensitivities of the 1-PMC and 4-PMC were 70 cps/MBq/head and 220 cps/MBq/head, respectively. The SPECT system using the 4-PMC provides superior image resolution in cold and hot rods phantom with the same activity and scan time to that of the 1-PMC. In addition, with half the usual scan time the 4-PMC provides comparable image quality to that of the 1-PMC. Furthermore, 99mTc-ECD brain perfusion images of healthy volunteers obtained using the 4-PMC demonstrated acceptable image quality for clinical diagnosis. In conclusion, our CdTe SPECT system equipped with the higher-sensitivity 4-PMC can provide better spatial resolution than the 1-PMC either in half the imaging time with the same administered activity, or alternatively, in the same imaging time with half the activity.

  2. Cytotoxicity of CdTe quantum dots in human umbilical vein endothelial cells: the involvement of cellular uptake and induction of pro-apoptotic endoplasmic reticulum stress

    PubMed Central

    Yan, Ming; Zhang, Yun; Qin, Haiyan; Liu, Kezhou; Guo, Miao; Ge, Yakun; Xu, Mingen; Sun, Yonghong; Zheng, Xiaoxiang

    2016-01-01

    Cadmium telluride quantum dots (CdTe QDs) have been proposed to induce oxidative stress, which plays a crucial role in CdTe QDs-mediated mitochondrial-dependent apoptosis in human umbilical vein endothelial cells (HUVECs). However, the direct interactions of CdTe QDs with HUVECs and their potential impairment of other organelles like endoplasmic reticulum (ER) in HUVECs are poorly understood. In this study, we reported that the negatively charged CdTe QDs (−21.63±0.91 mV), with good dispersity and fluorescence stability, were rapidly internalized via endocytosis by HUVECs, as the notable internalization could be inhibited up to 95.52% by energy depletion (NaN3/deoxyglucose or low temperature). The endocytosis inhibitors (methyl-β-cyclodextrin, genistein, sucrose, chlorpromazine, and colchicine) dramatically decreased the uptake of CdTe QDs by HUVECs, suggesting that both caveolae/raft- and clathrin-mediated endocytosis were involved in the endothelial uptake of CdTe QDs. Using immunocytochemistry, a striking overlap of the internalized CdTe QDs and ER marker was observed, which indicates that QDs may be transported to ER. The CdTe QDs also caused remarkable ER stress responses in HUVECs, confirmed by significant dilatation of ER cisternae, upregulation of ER stress markers GRP78/GRP94, and activation of protein kinase RNA-like ER kinase-eIF2α-activating transcription factor 4 pathway (including phosphorylation of both protein kinase RNA-like ER kinase and eIF2α and elevated level of activating transcription factor 4). CdTe QDs further promoted an increased C/EBP homologous protein expression, phosphorylation of c-JUN NH2-terminal kinase, and cleavage of ER-resident caspase-4, while the specific inhibitor (SP600125, Z-LEVD-fmk, or salubrinal) significantly attenuated QDs-triggered apoptosis, indicating that all three ER stress-mediated apoptosis pathways were activated and the direct participation of ER in the CdTe QDs-caused apoptotic cell death in HUVECs

  3. A sensitive and selective sensing platform based on CdTe QDs in the presence of l-cysteine for detection of silver, mercury and copper ions in water and various drinks.

    PubMed

    Gong, Tingting; Liu, Junfeng; Liu, Xinxin; Liu, Jie; Xiang, Jinkun; Wu, Yiwei

    2016-12-15

    Water soluble CdTe quantum dots (QDs) have been prepared simply by one-pot method using potassium tellurite as stable tellurium source and thioglycolic acid (TGA) as stabilizer. The fluorescence of CdTe QDs can be improved 1.3-fold in the presence of l-cysteine (Cys), however, highly efficiently quenched in the presence of silver or mercury or copper ions. A sensitive and selective sensing platform for analysis of silver, mercury and copper ions has been simply established based on CdTe QDs in the presence of l-cysteine. Under the optimum conditions, excellent linear relationships exist between the quenching degree of the sensing platform and the concentrations of Ag(+), Hg(2+) and Cu(2+) ranging from 0.5 to 40ngmL(-1). By using masking agents of sodium diethyldithiocarbamate (DDTC) for Ag(+) and Cu(2+), NH4OH for Ag(+) and Hg(2+) and 1-(2-Pyridylazo)-2-naphthol (PAN) for Hg(2+) and Cu(2+), Hg(2+), Cu(2+) and Ag(+) can be exclusively detected in coexistence with other two ions, and the detection limits (3σ) were 0.65, 0.063 and 0.088ngmL(-1) for Ag(+), Hg(2+) and Cu(2+), respectively. This effective sensing platform has been used to detection of Ag(+), Hg(2+) and Cu(2+) in water and various drinks with satisfactory results.

  4. Preparation of highly luminescent hybrid gel incorporating NAC-capped CdTe quantum dots through sol-gel processing

    NASA Astrophysics Data System (ADS)

    Bu, Hang-Beom; Watanabe, Taichi; Hizume, Masayuki; Takagi, Tomomi; Sobue, Susumu; Kawai, Shoichi; Okuno, Eiichi; Kim, DaeGwi

    2015-03-01

    Highly photoluminescent gel was prepared by embedding water soluble quantum dots (QDs) in an inorganic-organic hybrid gel matrix using a conventional sol-gel process. Aminopropyltrimethoxysilane and citric acid (CA) were found to be the best combination for the gel preparation. 13C-NMR and FT-IR studies indicated hydrogen bond formation between the amine group of APS and the carboxyl group of CA. IR-light radiation curing was comparable to thermal curing and reduced the gelation time to a considerable extent (71 %). The resulting composite formed a hybrid gel phosphor with excellent transparency by embedding CdTe QDs into the matrix and emitted light of various colors with high photoluminescence efficiency (40 %). The gel phosphor retained the PL properties after storage in air for one year. In addition, the strength of the hybrid phosphor was demonstrated by a coin-flipping test.

  5. Fluorescence biosensor based on CdTe quantum dots for specific detection of H5N1 avian influenza virus

    NASA Astrophysics Data System (ADS)

    Hoa Nguyen, Thi; Dieu Thuy Ung, Thi; Hien Vu, Thi; Tran, Thi Kim Chi; Quyen Dong, Van; Khang Dinh, Duy; Liem Nguyen, Quang

    2012-09-01

    This report highlights the fabrication of fluorescence biosensors based on CdTe quantum dots (QDs) for specific detection of H5N1 avian influenza virus. The core biosensor was composed of (i) the highly luminescent CdTe/CdS QDs, (ii) chromatophores extracted from bacteria Rhodospirillum rubrum, and (iii) the antibody of β-subunit. This core part was linked to the peripheral part of the biosensor via a biotin-streptavidin-biotin bridge and finally connected to the H5N1 antibody to make it ready for detecting H5N1 avian influenza virus. Detailed studies of each constituent were performed showing the image of QDs-labeled chromatophores under optical microscope, proper photoluminescence (PL) spectra of CdTe/CdS QDs, chromatophores and the H5N1 avian influenza viruses.

  6. Concentration-dependent optical properties of TGA stabilized CdTe Quantum dots synthesized via the single injection hydrothermal method in the ambient environment

    NASA Astrophysics Data System (ADS)

    Jai Kumar, B.; Mahesh, H. M.

    2017-04-01

    Thioglycolic acid (TGA) stabilized aqueous CdTe Quantum dots (QDs) were synthesized using a facile, cost efficient Single Injection Hydrothermal (SIH) method. The complete preparation of precursors and growth of QDs was carried out in the ambient environment without inter gas protection. The Cadmium and Tellurium precursors were prepared from cadmium nitrate and elemental tellurium powder with sodium borohydride as reducing agent respectively. A systematic investigation was carried out in order to study the effect of 0.04M and 0.08M TGA concentration on ease synthesis, stability and size-tunable optical absorbance, bandgap, photoluminescence (PL) and Quantum yield (QY) of CdTe QDs. The Structure of QDs was verified by XRD and optical properties by absorbance and PL spectra. Experimental results revealed that the 0.08M TGA QDs possess good chemical and optical stability with high luminescence and decent QY, ready to use in optoelectronics, photovoltaic and biological application.

  7. A novel density-tunable nanocomposites of CdTe quantum dots linked to dendrimer-tethered multi-wall carbon nanotubes.

    PubMed

    Zeng, Yunlong; Tang, Chunran; Wang, Haowen; Jiang, Jianhui; Tian, Meina; Shen, Guoli; Yu, Ruqin

    2008-10-01

    A novel nanocomposite of CdTe-PAMAM-MWNT was synthesized by covalently linking CdTe quantum dots (QDs) onto highly water-soluble multi-wall carbon nanotubes (MWNTs) functionalized with dendritic poly(amidoamine) (PAMAM). The IR, UV-vis and TEM methods has been used for the characterization of the composites. A facile method for controlling the density of QDs in the composite by simply changing the ratio of CdTe QDs/PAMAM-MWNT, as was verified by the TEM images. The experiments revealed that PAMAM and PAMAM-MWNT, once covalently linked with CdTe QDs, had remarkable effect on their fluorescence property. The fluorescence intensity of the CdTe-PAMAM hybrid was substantially enhanced as a compared to that of QDs, and the fluorescence was quenched greatly when QDs reacted with PAMAM-MWNT. The experimentally observed phenomena indicate that electron and energy transfer took place efficiently between CdTe QDs, PAMAM and MWNTs in the novel composite. These nanocomposits might hold great potential in photoelectron device and biotechnology applications.

  8. Effects of N-acetyl-L-cysteine-capped CdTe quantum dots on bovine serum albumin and bovine hemoglobin: isothermal titration calorimetry and spectroscopic investigations.

    PubMed

    Sun, Haoyu; Cui, Erqian; Tan, Zhigang; Liu, Rutao

    2014-12-01

    The interactions of N-acetyl-L-cysteine-capped CdTe quantum dots (QDs) with bovine serum albumin (BSA) and bovine hemoglobin (BHb) were investigated by isothermal titration calorimetry (ITC), fluorescence, synchronous fluorescence, fluorescence lifetime, ultraviolet-visible absorption, and circular dichroism techniques. Fluorescence data of BSA-QDs and BHb-QDs revealed that the quenching was static in every system. While CdTe QDs changed the microenvironment of tryptophan in BHb, the microenvironment of BSA kept unchanged. Adding CdTe QDs affected the skeleton and secondary structure of the protein (BSA and BHb). The ITC results indicated that the interaction between the protein (BSA and BHb) and QDs-612 was spontaneous and the predominant force was hydrophobic interaction. In addition, the binding constants were determined to be 1.19 × 10(5) L mol(-1) (BSA-QDs) and 2.19 × 10(5) L mol(-1) (BHb-QDs) at 298 K. From these results, we conclude that CdTe QDs have a larger impact on the structure of BHb than BSA.

  9. The behaviors of metal ions in the CdTe quantum dots-H2O2 chemiluminescence reaction and its sensing application.

    PubMed

    Sheng, Zonghai; Han, Heyou; Liang, Jiangong

    2009-01-01

    The behaviors of 15 kinds of metal ions in the thiol-capped CdTe quantum dots (QDs)-H2O2 chemiluminescence (CL) reaction were investigated in detail. The results showed that Ag+, Cu2+ and Hg2+ could inhibit CdTe QDs and H2O2 CL reaction. A novel CL method for the selective determination of Ag+, Cu2+ and Hg2+ was developed, based on their inhibition of the reaction of CdTe QDs and H2O2. Under the optimal conditions, good linear relationships were realized between the CL intensity and the logarithm of concentrations of Ag+, Cu2+ and Hg2+. The linear ranges were from 2.0 x 10(-6) to 5.0 x 10(-8) mol L(-1) for Ag+, from 5.0 x 10-6 to 7.0 x 10(-8) mol L(-1) for Cu2+ and from 2.0 x 10(-5) to 1.0 x 10(-7) mol L(-1) for Hg2+, respectively. The limits of detection (S/N = 3) were 3.0 x 10(-8), 4.0 x 10(-8) and 6.7 x 10(-8) mol L(-1) for Ag+, Cu2+ and Hg2+, respectively. A possible mechanism for the inhibition of CdTe QDs and H2O2 CL reaction was also discussed.

  10. Synthesis of surface molecular imprinting polymer on SiO2-coated CdTe quantum dots as sensor for selective detection of sulfadimidine

    NASA Astrophysics Data System (ADS)

    Zhou, Zhiping; Ying, Haiqin; Liu, Yanyan; Xu, Wanzhen; Yang, Yanfei; Luan, Yu; Lu, Yi; Liu, Tianshu; Yu, Shui; Yang, Wenming

    2017-05-01

    This paper demonstrates a facile method to synthesize surface molecular imprinting polymer (MIP) on SiO2-coated CdTe QDs for selective detection of sulfadimidine (SM2). The fluorescent MIP sensor was prepared using cadmium telluride quantum dots (CdTe QDs) as the material of fluorescent signal readout, sulfadimidine as template molecule, 3-aminopropyltriethoxysilane (APTES) as functional monomer and tetraethyloxysilane (TEOS) as cross-linking agent. The CdTe cores were embed in the silicon shells by a sol-gel reaction and then the molecular imprinting layers were immobilized on the surface of the SiO2-coated CdTe QDs. Under the optimized conditions, the relative fluorescent intensity weakened in a linear way with the increasing concentration of sulfadimidine in the range of 10-60 μmol L-1. The practical application of the fluorescent MIP sensor was evaluated by means of analyzing sulfadimidine in the real milk samples. The recoveries were at the range of 90.3-99.6% and the relative standard deviation (RSD) ranged from 1.9 to 3.1%, which indicates the successful synthesis of the fluorescent MIP sensor. This sensor provides an alternative solution for selective determination of sulfadimidine from real milk samples.

  11. A highly selective and simple fluorescent sensor for mercury (II) ion detection based on cysteamine-capped CdTe quantum dots synthesized by the reflux method.

    PubMed

    Ding, Xiaojie; Qu, Lingbo; Yang, Ran; Zhou, Yuchen; Li, Jianjun

    2015-06-01

    Cysteamine (CA)-capped CdTe quantum dots (QDs) (CA-CdTe QDs) were prepared by the reflux method and utilized as an efficient nano-sized fluorescent sensor to detect mercury (II) ions (Hg(2+) ). Under optimum conditions, the fluorescence quenching effect of CA-CdTe QDs was linear at Hg(2+) concentrations in the range of 6.0-450 nmol/L. The detection limit was calculated to be 4.0 nmol/L according to the 3σ IUPAC criteria. The influence of 10-fold Pb(2+) , Cu(2+) and Ag(+) on the determination of Hg(2+) was < 7% (superior to other reports based on crude QDs). Furthermore, the detection sensitivity and selectivity were much improved relative to a sensor based on the CA-CdTe QDs probe, which was prepared using a one-pot synthetic method. This CA-CdTe QDs sensor system represents a new feasibility to improve the detection performance of a QDs sensor by changing the synthesis method.

  12. Fluorescence quenching studies on the interaction of catechin-quinone with CdTe quantum dots. Mechanism elucidation and feasibility studies.

    PubMed

    Dwiecki, Krzysztof; Neunert, Grażyna; Nogala-Kałucka, Małgorzata; Polewski, Krzysztof

    2015-01-01

    Changes of the photoluminescent properties of QD in the presence of oxidized catechin (CQ) were investigated by absorption, steady-state fluorescence, fluorescence lifetime and dynamic light scattering measurements. Photoluminescence intensity and fluorescence lifetime was decreasing with increasing CQ concentration. Dynamic light scattering technique found the hydrodynamic diameter of QD suspension in water is in range of 45 nm, whereas in presence of CQ increased to mean values of 67 nm. Calculated from absorption peak position of excition band indicated on average QD size of 3.2 nm. Emission spectroscopy and time-resolved emission studies confirmed preservation of electronic band structure in QD-CQ aggregates. On basis of the presented results, the elucidated mechanism of QD fluorescence quenching is a result of the interaction between QD and CQ due to electron transfer and electrostatic attraction. The results of fluorescence quenching of water-soluble CdTe quantum dot (QD) capped with thiocarboxylic acid were used to implement a simple and fast method to determine the presence of native antioxidant quinones in aqueous solutions. Feasibility studies on this method carried out with oxidized catechin showed a linear relation between the QD emission and quencher concentration, in range from 1 up to 200 μM. The wide linear range of concentration dependence makes it possible to apply this method for the fast and sensitive detection of quinones in solutions.

  13. Spectroscopic investigations on the effect of N-Acetyl-L-cysteine-Capped CdTe Quantum Dots on catalase

    NASA Astrophysics Data System (ADS)

    Sun, Haoyu; Yang, Bingjun; Cui, Erqian; Liu, Rutao

    2014-11-01

    Quantum dots (QDs) are recognized as some of the most promising semiconductor nanocrystals in biomedical applications. However, the potential toxicity of QDs has aroused wide public concern. Catalase (CAT) is a common enzyme in animal and plant tissues. For the potential application of QDs in vivo, it is important to investigate the interaction of QDs with CAT. In this work, the effect of N-Acetyl-L-cysteine-Capped CdTe Quantum Dots with fluorescence emission peak at 612 nm (QDs-612) on CAT was investigated by fluorescence, synchronous fluorescence, fluorescence lifetime, ultraviolet-visible (UV-vis) absorption and circular dichroism (CD) techniques. Binding of QDs-612 to CAT caused static quenching of the fluorescence, the change of the secondary structure of CAT and the alteration of the microenvironment of tryptophan residues. The association constants K were determined to be K288K = 7.98 × 105 L mol-1 and K298K = 7.21 × 105 L mol-1. The interaction between QDs-612 and CAT was spontaneous with 1:1 stoichiometry approximately. The CAT activity was also inhibited for the bound QDs-612. This work provides direct evidence about enzyme toxicity of QDs-612 to CAT in vitro and establishes a new strategy to investigate the interaction between enzyme and QDs at a molecular level, which is helpful for clarifying the bioactivities of QDs in vivo.

  14. Ultrafast optical generation of coherent phonons in CdTe1-xSex quantum dots

    NASA Astrophysics Data System (ADS)

    Bragas, A. V.; Aku-Leh, C.; Costantino, S.; Ingale, Alka; Zhao, J.; Merlin, R.

    2004-05-01

    We report on the impulsive generation of coherent optical phonons in CdTe0.68Se0.32 nanocrystallites embedded in a glass matrix. Pump-probe experiments using femtosecond laser pulses were performed by tuning the laser central energy to resonate with the absorption edge of the nanocrystals. We identify two longitudinal optical phonons, one longitudinal acoustic phonon and a fourth mode of a mixed longitudinal-transverse nature. The amplitude of the optical phonons as a function of the laser central energy exhibits a resonance that is well described by a model based on impulsive stimulated Raman scattering. The phases of the coherent phonons reveal coupling between different modes. At low power density excitations, the frequency of the optical coherent phonons deviates from values obtained from spontaneous Raman scattering. This behavior is ascribed to the presence of electronic impurity states which modify the nanocrystal dielectric function and, thereby, the frequency of the infrared-active phonons.

  15. A sensitive quantum dots-based "OFF-ON" fluorescent sensor for ruthenium anticancer drugs and ctDNA.

    PubMed

    Huang, Shan; Zhu, Fawei; Qiu, Hangna; Xiao, Qi; Zhou, Quan; Su, Wei; Hu, Baoqing

    2014-05-01

    In this contribution, a simple and sensitive fluorescent sensor for the determination of both the three ruthenium anticancer drugs (1 to 3) and calf thymus DNA (ctDNA) was established based on the CdTe quantum dots (QDs) fluorescence "OFF-ON" mode. Under the experimental conditions, the fluorescence of CdTe QDs can be effectively quenched by ruthenium anticancer drugs because of the surface binding of these drugs on CdTe QDs and the subsequent photoinduced electron transfer (PET) process from CdTe QDs to ruthenium anticancer drugs, which render the system into fluorescence "OFF" status. The system can then be "ON" after the addition of ctDNA which brought the restoration of CdTe QDs fluorescence intensity, since ruthenium anticancer drugs broke away from the surface of CdTe QDs and inserted into double helix structure of ctDNA. The fluorescence quenching effect of the CdTe QDs-ruthenium anticancer drugs systems was mainly concentration dependent, which could be used to detect three ruthenium anticancer drugs. The limits of detection were 5.5 × 10(-8) M for ruthenium anticancer drug 1, 7.0 × 10(-8) M for ruthenium anticancer drug 2, and 7.9× 10(-8) M for ruthenium anticancer drug 3, respectively. The relative restored fluorescence intensity was directly proportional to the concentration of ctDNA in the range of 1.0 × 10(-8) M ∼ 3.0 × 10(-7) M, with a correlation coefficient (R) of 0.9983 and a limit of detection of 1.1 × 10(-9) M. The relative standard deviation (RSD) for 1.5 × 10(-7) M ctDNA was 1.5% (n = 5). There was almost no interference to some common chemical compounds, nucleotides, amino acids, and proteins. The proposed method was applied to the determination of ctDNA in three synthetic samples with satisfactory results. The possible reaction mechanism of CdTe QDs fluorescence "OFF-ON" was further investigated. This simple and sensitive approach possessed some potential applications in the investigation of interaction between drug molecules and DNA

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

    PubMed

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

    2005-05-12

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

  17. Parallel comparative studies on the toxic effects of unmodified CdTe quantum dots, gold nanoparticles, and carbon nanodots on live cells as well as green gram sprouts.

    PubMed

    Song, Yanchao; Feng, Duan; Shi, Wen; Li, Xiaohua; Ma, Huimin

    2013-11-15

    By using confocal fluorescence microscopy and direct visualization, a parallel comparative investigation has been systematically made on the relative toxicity of three common nanomaterials, such as unmodified CdTe quantum dots (QDs), Au nanoparticles (Au NPs) and carbon nanodots (C-dots), to live cells as well as green gram sprouts. Bare CdTe QDs exert the most toxic effect on a variety of cell lines (HeLa, MCF-7, NIH/3T3 cells) as well as live plants (green gram sprouts). For cells, this toxic effect leads to the partial death of cells, the decrease of cell metabolic activity, the shrinkage of cells, the breakage of chromatin, the damage of cell membrane integrity, and the fragmentation of mitochondria; for green gram sprouts, the presence of CdTe QDs markedly inhibits their growth. Moreover, the toxic behaviors of CdTe QDs are dose- and time-dependent. Under the same conditions, Au NPs only decrease the metabolic activity of cells to a small extent, and do not affect the appearance of cellular/subcellular structures and the plant growth; interestingly, C-dots exert no obvious toxicity to both live cells and the growth of green gram sprouts, showing good biocompatibility. These parallel comparative studies clearly reveal that the relative toxicity of the three nanomaterials in their native forms is bare CdTe QDs>Au NPs>C-dots, whose IC50 values for normal NIH/3T3 cells are 0.98 μg/mL, 62 μg/mL, and >250 μg/mL, respectively. This quantitative information is of great importance for right choice of the nanomaterials in their practical applications.

  18. Accurate analysis of electron transfer from quantum dots to metal oxides in quantum dot sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Javad Fahimi, Mohammad; Fathi, Davood; Ansari-Rad, Mehdi

    2015-09-01

    Electron transfer rate from quantum dot (QD) to metal oxide (MO) in quantum dot sensitized solar cells (QDSSCs) has an important role in the efficiency. In this work, we analyse the electron transfer rate from CdSe, CdS and CdTe QDs to TiO2, ZnO and SnO2 MOs by extending the related equations with considering various effects, based on the Marcus theory. In this regard, the effects of QD diameter, QD-MO spacing, the crystalline defects, temperature, and the reorganizational energy, on the electron transfer rate are investigated. The results show that, the maximum electron transfer rate is achieved for CdTe QD with the mentioned three MOs. Moreover, in order to direct the designer to reach the appropriate QDs-MOs combinations for obtaining the maximum electron transfer rate, the average electron transfer rate for various combinations is calculated. For the verification of simulation method, a part of work has been compared with the previous experimental and theoretical results, which indicates the correctness of our simulation algorithm.

  19. Effect of Controlled Deposition of ZnS Shell on the Photostability of CdTe Quantum Dots as Studied by Conventional Fluorescence and FCS Techniques.

    PubMed

    Patra, Satyajit; Seth, Sudipta; Samanta, Anunay

    2015-12-21

    The effect of one and two monolayers of ZnS shells on the photostability of CdTe quantum dots (QDs) in aqueous and nonaqueous media has been studied by monitoring the fluorescence behavior of the QDs under ensemble and single-molecule conditions. ZnS capping of the CdTe QDs leads to significant enhancement of the fluorescence brightness of these QDs. Considerable enhancement of the photostability of the shell-protected QDs, including the suppression of photoactivation, is also observed. Fluorescence correlation spectroscopy measurements reveal an increase in the number of particles undergoing reversible fluorescent on-off transitions in the volume under observation with increasing excitation power; this effect is found to be more pronounced in the case of core-only QDs than for core-shell QDs.

  20. Two-photon-excited fluorescence resonance energy transfer in an aqueous system of CdTe quantum dots and Rhodamine B

    SciTech Connect

    Li, Muye; Lu, Peixiang; Li, Fang He, Zhicong; Zhang, Junpei; Han, Junbo

    2014-12-21

    Two-photon excited fluorescence resonance energy transfer (FRET) between CdTe quantum dots with different emission peaks and Rhodamine B in aqueous solution are investigated both experimentally and theoretically. The photoluminescence and lifetime are measured using a time-resolved fluorescence test system. The two-photon excited FRET efficiency is found to increase as the degree of spectral overlap of the emission spectrum of CdTe and the absorption spectrum of Rhodamine B increases, which is due to the increase of Forster radius of the sample. Moreover, FRET efficiency increases when the ratio of acceptor/donor concentration increases. The two-photon excited FRET efficiency was found to reach 40%.

  1. A novel method for fabricating hybrid biobased nanocomposites film with stable fluorescence containing CdTe quantum dots and montmorillonite-chitosan nanosheets.

    PubMed

    Guo, Yawen; Ge, Xuesong; Guan, Jing; Wu, Lin; Zhao, Fuhua; Li, Hui; Mu, Xindong; Jiang, Yijun; Chen, Aibing

    2016-07-10

    A method was presented for fabricating the fluorescent nanocomposites containing CdTe quantum dots (QDs) and montmorillonite (MMT)-chitosan (CS). MMT-CS/CdTe QDs nanocomposites were prepared via a simple, versatile and robust approach combination of covalent and electrostatic assembly methods (Scheme 1). The negatively charged MMT was initially modified with positively charged CS through electrostatic assembly, followed by incorporation of CdTe-QDs into the MMT-CS nanosheets by covalent connections between the amino groups of CS and the carboxylic acid groups of thioglycollic acid (TGA). The X-ray diffraction (XRD), High resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and the FTIR were used to prove the QDs have intercalated into the MMT-CS matrix. The fluorescence emission spectra showed that the MMT-CS/CdTe QDs nanocomposites had the best fluorescence intensity compared with the bare CdTe QDs and CS-QDs.

  2. Quantum dot-sensitized solar cells incorporating nanomaterials.

    PubMed

    Yang, Zusing; Chen, Chia-Ying; Roy, Prathik; Chang, Huan-Tsung

    2011-09-14

    Quantum dot-sensitized solar cells (QDSSCs) are interesting energy devices because of their (i) impressive ability to harvest sunlight and generate multiple electron/hole pairs, (ii) ease of fabrication, and (iii) low cost. The power conversion efficiencies (η) of most QDSSCs (typically <4%) are, however, less than those (up to 12%) of dye-sensitized solar cells, mainly because of narrow absorption ranges and charge recombination occurring at the QD-electrolyte and TiO(2)-electrolyte interfaces. To further increase the values of η of QDSSCs, it will be necessary to develop new types of working electrodes, sensitizers, counter electrodes and electrolytes. This Feature Article describes the nanomaterials that have been used recently as electronic conductors, sensitizers and counter electrodes in QDSSCs. The nature, size, morphology and quantity of these nanomaterials all play important roles affecting the efficiencies of electron injection and light harvesting. We discuss the behavior of several important types of semiconductor nanomaterials (sensitizers, including CdS, Ag(2)S, CdSe, CdTe, CdHgTe, InAs and PbS) and nanomaterials (notably TiO(2), ZnO and carbon-based species) that have been developed to improve the electron transport efficiency of QDSSCs. We point out the preparation of new generations of nanomaterials for QDSSCs and the types of electrolytes, particularly iodide/triiodide electrolytes (I(-)/I(3)(-)), polysulfide electrolytes (S(2-)/S(x)(2-)), and cobalt redox couples ([Co(o-phen)(3)(2+)/(3+)]), that improve their lifetimes. With advances in nanotechnology, we foresee significant improvements in the efficiency (η > 6%) and durability (>3000 h) of QDSSCs.

  3. Photostability of thiol-capped CdTe quantum dots in living cells: the effect of photo-oxidation

    NASA Astrophysics Data System (ADS)

    Ma, J.; Chen, Ji-Yao; Guo, J.; Wang, C. C.; Yang, W. L.; Xu, L.; Wang, P. N.

    2006-05-01

    The photostability of thiol-capped CdTe quantum dots (QDs) in Euglena gracilis (EG 277) and human embryonic kidney (HEK 293) cells was studied. The photobleaching for the cellular QDs is dependent both on the irradiation power density and the QD local concentration. The photostability of cellular QDs is better than that of chlorophyll in EG 277 cells and of green fluorescence protein (GFP) in HEK 293 cells, and is much better than that of FITC when the local concentration of QDs is not too low. The photobleaching of cellular QDs was remarkably reduced in the nitrogen treated EG 277 cells, indicating that photobleaching in living cells mainly results from photo-oxidation. The effect of photo-oxidation on QD photobleaching was further confirmed by comparing the situations in oxygen treated and nitrogen treated QD aqueous solutions. The photobleaching rate is related to the irradiation power density and the local density of QDs. The higher irradiation power density and oxygen abundance and lower QD concentration will result in a higher photobleaching rate.

  4. Laser-excited optical emission response of CdTe quantum dot/polymer nanocomposite under shock compression

    SciTech Connect

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

    2016-01-04

    Laser-driven shock compression experiments and corresponding finite element method simulations are carried out to investigate the blueshift in the optical emission spectra under continuous laser excitation of a dilute composite consisting of 0.15% CdTe quantum dots by weight embedded in polyvinyl alcohol polymer. This material is a potential candidate for use as internal stress sensors. The analyses focus on the time histories of the wavelength blue-shift for shock loading with pressures up to 7.3 GPa. The combined measurements and calculations allow a relation between the wavelength blueshift and pressure for the loading conditions to be extracted. It is found that the blueshift first increases with pressure to a maximum and subsequently decreases with pressure. This trend is different from the monotonic increase of blueshift with pressure observed under conditions of quasistatic hydrostatic compression. Additionally, the blueshift in the shock experiments is much smaller than that in hydrostatic experiments at the same pressure levels. The differences in responses are attributed to the different stress states achieved in the shock and hydrostatic experiments and the time dependence of the mechanical response of the polymer in the composite. The findings offer a potential guide for the design and development of materials for internal stress sensors for shock conditions.

  5. Systematically investigations of conformation and thermodynamics of HSA adsorbed to different sizes of CdTe quantum dots.

    PubMed

    Xiao, Qi; Huang, Shan; Su, Wei; Li, Peiyuan; Ma, Jianqiang; Luo, Fenping; Chen, Jing; Liu, Yi

    2013-02-01

    Fluorescent quantum dots (QDs) have attracted great attention in biological and biomedical fields. In particular, for any potential application, the interaction of QDs with some biomolecules is much important. Herein, the interactions between QDs with different sizes and human serum albumin (HSA) were systematically investigated by UV-vis absorption spectra, fluorescence spectra and circular dichroism (CD) spectra under the physiological conditions. Four sizes of CdTe QDs with maximum emission of 520 nm (green QDs, GQDs), 568 nm (yellow QDs, YQDs), 620 nm (red QDs, RQDs) and 680 nm (crimson QDs, CQDs) were tested. The fluorescence spectra results indicated that QDs could quench the fluorescence intensity of HSA effectively with a size-dependent relationship. The binding of QDs and HSA is a result of the formation of QDs-HSA complex and the electrostatic interaction plays a major role in stabilizing the complex. The modified Stern-Volmer quenching constants K(a) at different temperatures and corresponding thermodynamic parameters ΔH, ΔG and ΔS were calculated. The conformational changes of HSA induced by QDs have been analyzed by CD spectra, and the results indicated that the biological activity of HSA was weakened in the present of QDs with bigger size. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. High Sensitivity Optically Pumped Quantum Magnetometer

    PubMed Central

    Tiporlini, Valentina; Alameh, Kamal

    2013-01-01

    Quantum magnetometers based on optical pumping can achieve sensitivity as high as what SQUID-based devices can attain. In this paper, we discuss the principle of operation and the optimal design of an optically pumped quantum magnetometer. The ultimate intrinsic sensitivity is calculated showing that optimal performance of the magnetometer is attained with an optical pump power of 20 μW and an operation temperature of 48°C. Results show that the ultimate intrinsic sensitivity of the quantum magnetometer that can be achieved is 327 fT/Hz1/2 over a bandwidth of 26 Hz and that this sensitivity drops to 130 pT/Hz1/2 in the presence of environmental noise. The quantum magnetometer is shown to be capable of detecting a sinusoidal magnetic field of amplitude as low as 15 pT oscillating at 25 Hz. PMID:23766716

  7. High sensitivity optically pumped quantum magnetometer.

    PubMed

    Tiporlini, Valentina; Alameh, Kamal

    2013-01-01

    Quantum magnetometers based on optical pumping can achieve sensitivity as high as what SQUID-based devices can attain. In this paper, we discuss the principle of operation and the optimal design of an optically pumped quantum magnetometer. The ultimate intrinsic sensitivity is calculated showing that optimal performance of the magnetometer is attained with an optical pump power of 20 μW and an operation temperature of 48°C. Results show that the ultimate intrinsic sensitivity of the quantum magnetometer that can be achieved is 327 fT/Hz(½) over a bandwidth of 26 Hz and that this sensitivity drops to 130 pT/Hz(½) in the presence of environmental noise. The quantum magnetometer is shown to be capable of detecting a sinusoidal magnetic field of amplitude as low as 15 pT oscillating at 25 Hz.

  8. Epitope imprinted polymer coating CdTe quantum dots for specific recognition and direct fluorescent quantification of the target protein bovine serum albumin.

    PubMed

    Yang, Ya-Qiong; He, Xi-Wen; Wang, Yi-Zhi; Li, Wen-You; Zhang, Yu-Kui

    2014-04-15

    A novel epitope molecularly imprinted polymer (EMIP) for specific recognition and direct fluorescent quantification of the target protein bovine serum albumin (BSA) was demonstrated where polymerization was performed on the surface of silica nanospheres embedded CdTe quantum dots (QDs). The synthetic peptide derived from the surface-exposed C-terminus of bovine serum albumin (BSA, residues 599-607) was selected as the template molecule. The resulting EMIP film was able to selectively capture the template peptide and the corresponding target protein BSA via the recognition cavities. Based on the fluorescence quenching, the EMIP-coated QDs (molecular imprinted polymer coating CdTe QDs using epitope as the template) nanospheres were successfully applied to the direct fluorescence quantification of BSA. Compared with BMIP-coated QDs (molecular imprinted polymer coating CdTe QDs using BSA as the template), the imprinting factor and adsorption capacity of EMIP-coated QDs were greatly increased. The prepared EMIP-coated QDs can also discriminate even one mismatched sequences from the original sequences of the epitope of the BSA. The practical analytical performance of the EMIP-coated QDs was examined by evaluating the detection of BSA in the bovine calf serum sample with satisfactory results. In addition, the resulting EMIP-coated QDs nanospheres were also successfully applied to separating BSA from the bovine blood sample. © 2013 Published by Elsevier B.V.

  9. Tandem Solar Cells from Solution-Processed CdTe and PbS Quantum Dots Using a ZnTe-ZnO Tunnel Junction.

    PubMed

    Crisp, Ryan W; Pach, Gregory F; Kurley, J Matthew; France, Ryan M; Reese, Matthew O; Nanayakkara, Sanjini U; MacLeod, Bradley A; Talapin, Dmitri V; Beard, Matthew C; Luther, Joseph M

    2017-02-08

    We developed a monolithic CdTe-PbS tandem solar cell architecture in which both the CdTe and PbS absorber layers are solution-processed from nanocrystal inks. Due to their tunable nature, PbS quantum dots (QDs), with a controllable band gap between 0.4 and ∼1.6 eV, are a promising candidate for a bottom absorber layer in tandem photovoltaics. In the detailed balance limit, the ideal configuration of a CdTe (Eg = 1.5 eV)-PbS tandem structure assumes infinite thickness of the absorber layers and requires the PbS band gap to be 0.75 eV to theoretically achieve a power conversion efficiency (PCE) of 45%. However, modeling shows that by allowing the thickness of the CdTe layer to vary, a tandem with efficiency over 40% is achievable using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first step toward developing this technology, we explore CdTe-PbS tandem devices by developing a ZnTe-ZnO tunnel junction, which appropriately combines the two subcells in series. We examine the basic characteristics of the solar cells as a function of layer thickness and bottom-cell band gap and demonstrate open-circuit voltages in excess of 1.1 V with matched short circuit current density of 10 mA/cm(2) in prototype devices.

  10. Enhancing quantum sensing sensitivity by a quantum memory

    NASA Astrophysics Data System (ADS)

    Zaiser, Sebastian; Rendler, Torsten; Jakobi, Ingmar; Wolf, Thomas; Lee, Sang-Yun; Wagner, Samuel; Bergholm, Ville; Schulte-Herbrüggen, Thomas; Neumann, Philipp; Wrachtrup, Jörg

    2016-08-01

    In quantum sensing, precision is typically limited by the maximum time interval over which phase can be accumulated. Memories have been used to enhance this time interval beyond the coherence lifetime and thus gain precision. Here, we demonstrate that by using a quantum memory an increased sensitivity can also be achieved. To this end, we use entanglement in a hybrid spin system comprising a sensing and a memory qubit associated with a single nitrogen-vacancy centre in diamond. With the memory we retain the full quantum state even after coherence decay of the sensor, which enables coherent interaction with distinct weakly coupled nuclear spin qubits. We benchmark the performance of our hybrid quantum system against use of the sensing qubit alone by gradually increasing the entanglement of sensor and memory. We further apply this quantum sensor-memory pair for high-resolution NMR spectroscopy of single 13C nuclear spins.

  11. Enhancing quantum sensing sensitivity by a quantum memory.

    PubMed

    Zaiser, Sebastian; Rendler, Torsten; Jakobi, Ingmar; Wolf, Thomas; Lee, Sang-Yun; Wagner, Samuel; Bergholm, Ville; Schulte-Herbrüggen, Thomas; Neumann, Philipp; Wrachtrup, Jörg

    2016-08-10

    In quantum sensing, precision is typically limited by the maximum time interval over which phase can be accumulated. Memories have been used to enhance this time interval beyond the coherence lifetime and thus gain precision. Here, we demonstrate that by using a quantum memory an increased sensitivity can also be achieved. To this end, we use entanglement in a hybrid spin system comprising a sensing and a memory qubit associated with a single nitrogen-vacancy centre in diamond. With the memory we retain the full quantum state even after coherence decay of the sensor, which enables coherent interaction with distinct weakly coupled nuclear spin qubits. We benchmark the performance of our hybrid quantum system against use of the sensing qubit alone by gradually increasing the entanglement of sensor and memory. We further apply this quantum sensor-memory pair for high-resolution NMR spectroscopy of single (13)C nuclear spins.

  12. Enhancing quantum sensing sensitivity by a quantum memory

    PubMed Central

    Zaiser, Sebastian; Rendler, Torsten; Jakobi, Ingmar; Wolf, Thomas; Lee, Sang-Yun; Wagner, Samuel; Bergholm, Ville; Schulte-Herbrüggen, Thomas; Neumann, Philipp; Wrachtrup, Jörg

    2016-01-01

    In quantum sensing, precision is typically limited by the maximum time interval over which phase can be accumulated. Memories have been used to enhance this time interval beyond the coherence lifetime and thus gain precision. Here, we demonstrate that by using a quantum memory an increased sensitivity can also be achieved. To this end, we use entanglement in a hybrid spin system comprising a sensing and a memory qubit associated with a single nitrogen-vacancy centre in diamond. With the memory we retain the full quantum state even after coherence decay of the sensor, which enables coherent interaction with distinct weakly coupled nuclear spin qubits. We benchmark the performance of our hybrid quantum system against use of the sensing qubit alone by gradually increasing the entanglement of sensor and memory. We further apply this quantum sensor-memory pair for high-resolution NMR spectroscopy of single 13C nuclear spins. PMID:27506596

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

    PubMed Central

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

    2016-01-01

    With the rapid development of nanotechnology, quantum dots (QDs) as advanced nanotechnology products have been widely used in neuroscience, including basic neurological studies and diagnosis or therapy for neurological disorders, due to their superior optical properties. In recent years, there has been intense concern regarding the toxicity of QDs, with a growing number of studies. However, knowledge of neurotoxic consequences of QDs applied in living organisms is lagging behind their development, even if several studies have attempted to evaluate the toxicity of QDs on neural cells. The aim of this study was to evaluate the adverse effects of intrahippocampal injection in rats of 3-mercaptopropionic acid (MPA)-modified CdTe QDs and underlying mechanisms. First of all, we observed impairments in learning efficiency and spatial memory in the MPA-modified CdTe QD-treated rats by using open-field and Y-maze tests, which could be attributed to pathological changes and disruption of ultrastructure of neurons and synapses in the hippocampus. In order to find the mechanisms causing these effects, transcriptome sequencing (RNA-seq), an advanced technology, was used to gain the potentially molecular targets of MPA-modified CdTe QDs. According to ample data from RNA-seq, we chose the signaling pathways of PI3K–Akt and MPAK–ERK to do a thorough investigation, because they play important roles in synaptic plasticity, long-term potentiation, and spatial memory. The data demonstrated that phosphorylated Akt (p-Akt), p-ERK1/2, and c-FOS signal transductions in the hippocampus of rats were involved in the mechanism underlying spatial learning and memory impairments caused by 3.5 nm MPA-modified CdTe QDs. PMID:27358562

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

    PubMed

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

    2016-01-01

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

  15. Designed short RGD peptides for one-pot aqueous synthesis of integrin-binding CdTe and CdZnTe quantum dots.

    PubMed

    He, Hua; Feng, Min; Hu, Jing; Chen, Cuixia; Wang, Jiqian; Wang, Xiaojuan; Xu, Hai; Lu, Jian R

    2012-11-01

    We have designed a series of short RGD peptide ligands and developed one-pot aqueous synthesis of integrin-binding CdTe and CdZnTe quantum dots (QDs). We first examined the effects of different RGD peptides, including RGDS, CRGDS, Ac-CRGDS, CRGDS-CONH₂, Ac-CRGDS-CONH₂, RGDSC, CCRGDS, and CCCRGDS, on the synthesis of CdTe QDs. CRGDS were found to be the optimal ligand, providing the CdTe QDs with well-defined wavelength ranges (500-650 nm) and relatively high photoluminescence quantum yields (up to 15%). The key synthesis parameters (the pH value of the Cd²⁺-RGD precursors and the molar ratio of RGD/Cd²⁺) were assessed. In order to further improve the optical properties of the RGD-capped QDs, zinc was then incorporated by the simultaneous reaction of Cd²⁺ and Zn²⁺ with NaHTe. By using a mixture of CRGDS and cysteine as the stabilizer, the quantum yields of CdZnTe alloy QDs reached as high as 60% without any post-treatment, and they also showed excellent stability against time, pH, and salinity. Note that these properties could not be obtained with CRGDS or cysteine alone as the stabilizer. Finally, we demonstrated that the RGD-capped QDs preferentially bind to cell surfaces because of the specific recognition of the RGD sequence to cell surface integrin receptors. Our synthesis strategy based on RGD peptides thus represents a convenient route for opening up QD technologies for cell-specific tagging and labeling applicable to a wide range of diagnostics and therapy.

  16. Enhanced electrochemiluminescence of RuSi nanoparticles for ultrasensitive detection of ochratoxin A by energy transfer with CdTe quantum dots.

    PubMed

    Wang, Qingling; Chen, Miaomiao; Zhang, Haiqing; Wen, Wei; Zhang, Xiuhua; Wang, Shengfu

    2016-05-15

    This paper develops a new approach to enhance the electrochemiluminescence (ECL) emission of the Ru(bpy)3(2+)-tripropyl amine (TPrA) system for ultrasensitive determination of ochratoxin A (OTA). Ru(bpy)3(2+)-doped silica nanoparticles (RuSi NPs) act as ECL materials, which are immobilized on the surface of electrode by chitosan to fabricate a solid-state ECL sensor. CdTe quantum dots (QDs) can enhance the ECL emission of the Ru(bpy)3(2+)-TPrA ECL system by energy transfer. This strategy can improve the sensitivity of the sensor. In this assay, we combine the ECL with molecular imprinting technique to improve the selectivity of this sensor. The template molecule could be eluted from the molecularly imprinted polymer (MIP), and the formed cavities could then selectively recognize the target. The cavities could also work as the tunnel for the transfer of coreactant TPrA to produce responsive signal. With the increase of the concentration of OTA in samples, more cavities were filled because of the rebinding of OTA to the MIP surface, resulting in a gradual decrease in ECL intensity. The results showed that the ECL decrease value depended linearly on the logarithm of the OTA concentration in the range from 1.00×10(-5) to 11.13 ng mL(-1) with lower detection limit of 3.0 fg mL(-1) (S/N=3). This ECL sensor has also been applied to detect OTA concentration in the real samples with satisfied results, and the recoveries range from 85.1% to 107.9%.

  17. Porous ZnS/ZnO microspheres prepared through the spontaneous organization of nanoparticles and their application as supports of holding CdTe quantum dots

    SciTech Connect

    Cao Xuebo Lan Xianmei; Zhao Cui; Shen Wenjun; Yao Dan

    2008-05-06

    This manuscript describes a self-organization method for the large-scale production of porous ZnS/ZnO composite microspheres and their application as supports of CdTe quantum dots. Through the reaction of Zn{sup 2+} and urea and thioacetamide at 85 deg. C for 10 min, nanoparticles of cubic ZnS and amorphous ZnO were formed and they present a strong tendency to organize into regular microspheres. The formation of nanopores within the microspheres is related to Ostwald ripening: some small nanoparticles within the microspheres were merged by the larger ones, and as a result, numerous nanopores were generated. Furthermore, when a solvothermal ripening is applied for the porous microspheres, the components within them can be transformed into hexagonal ZnS and ZnO. CdTe quantum dots were introduced into the nanopores to achieve luminescent microspheres through in situ nucleation and growth. And it is expected that, besides semiconducting quantum dots, other functional units, such as magnetic and catalytically activated nanoparticles, can also be introduced into them.

  18. Sensitive chemical compass assisted by quantum criticality

    NASA Astrophysics Data System (ADS)

    Cai, C. Y.; Ai, Qing; Quan, H. T.; Sun, C. P.

    2012-02-01

    A radical-pair-based chemical reaction might be used by birds for navigation via the geomagnetic direction. The inherent physical mechanism is that the quantum coherent transition from a singlet state to triplet states of the radical pair could respond to a weak magnetic field and be sensitive to the direction of such a field; this then results in different photopigments to be sensed by the avian eyes. Here, we propose a quantum bionic setup, inspired by the avian compass, as an ultrasensitive probe of a weak magnetic field based on the quantum phase transition of the environments of the two electrons in the radical pair. We prove that the yield of the chemical products via recombination from the singlet state is determined by the Loschmidt echo of the environments with interacting nuclear spins. Thus quantum criticality of environments could enhance the sensitivity of detection of weak magnetic fields.

  19. CdTe quantum dots conjugated to concanavalin A as potential fluorescent molecular probes for saccharides detection in Candida albicans.

    PubMed

    Tenório, Denise P L A; Andrade, Camila G; Cabral Filho, Paulo E; Sabino, Caetano P; Kato, Ilka T; Carvalho, Luiz B; Alves, Severino; Ribeiro, Martha S; Fontes, Adriana; Santos, Beate S

    2015-01-01

    Semiconductor colloidal quantum dots (QDs) have been applied in biological analysis due to their unique optical properties and their versatility to be conjugated to biomolecules, such as lectins and antibodies, acquiring specificity to label a variety of targets. Concanavalin A (Con A) lectin binds specifically to α-d-mannose and α-d-glucose regions of saccharides that are usually expressed on membranes of mammalian cells and on cell walls of microbials. Candida albicans is the most common fungal opportunistic pathogen present in humans. Therefore, in this work, this fungus was chosen as a model for understanding cells and biofilm-forming organisms. Here, we report an efficient bioconjugation process to bind CdTe (Cadmium Telluride) QDs to Con A, and applied the bioconjugates to label saccharide structures on the cellular surface of C. albicans suspensions and biofilms. By accomplishing hemagglutination experiments and circular dichroism, we observed that the Con A structure and biochemical properties were preserved after the bioconjugation. Fluorescence microscopy images of yeasts and hyphae cells, as well as biofilms, incubated with QDs-(Con A) showed a bright orange fluorescence profile, indicating that the cell walls were specifically labeled. Furthermore, flow cytometry measurements confirmed that over 93% of the yeast cells were successfully labeled by QD-(Con A) complex. In contrast, non-conjugated QDs or QDs-(inhibited Con A) do not label any kind of biological system tested, indicating that the bioconjugation was specific and efficient. The staining pattern of the cells and biofilms demonstrate that QDs were effectively bioconjugated to Con A with specific labeling of saccharide-rich structures on C. albicans. Consequently, this work opens new possibilities to monitor glucose and mannose molecules through fluorescence techniques, which can help to optimize phototherapy protocols for this kind of fungus.

  20. Detective quantum efficiency, modulation transfer function and energy resolution comparison between CdTe and silicon sensors bump-bonded to XPAD3S.

    PubMed

    Medjoubi, Kadda; Bucaille, Thierry; Hustache, Stéphanie; Bérar, Jean François; Boudet, Nathalie; Clemens, Jean Claude; Delpierre, Pierre; Dinkespiler, Bernard

    2010-07-01

    XPAD3S is a single-photon-counting chip developed in collaboration by SOLEIL Synchrotron, the Institut Louis Néel and the Centre de Physique de Particules de Marseille. The circuit, designed in the 0.25 microm IBM technology, contains 9600 square pixels with 130 microm side giving a total size of 1 cm x 1.5 cm. The main features of each pixel are: single threshold adjustable from 4.5 keV up to 35 keV, 2 ms frame rate, 10(7) photons s(-1) mm(-2) maximum local count rate, and a 12-bit internal counter with overflow allowing a full 27-bit dynamic range to be reached. The XPAD3S was hybridized using the flip-chip technology with both a 500 microm silicon sensor and a 700 microm CdTe sensor with Schottky contacts. Imaging performances of both detectors were evaluated using X-rays from 6 keV up to 35 keV. The detective quantum efficiency at zero line-pairs mm(-1) for a silicon sensor follows the absorption law whereas for CdTe a strong deficit at low photon energy, produced by an inefficient entrance layer, is measured. The modulation transfer function was evaluated and it was shown that both detectors present an ideal modulation transfer function at 26 keV, limited only by the pixel size. The influence of the Cd and Te K-edges of the CdTe sensor was measured and simulated, establishing that fluorescence photons reduce the contrast transfer at the Nyquist frequency from 60% to 40% which remains acceptable. The energy resolution was evaluated at 6% with silicon using 16 keV X-rays, and 8% with CdTe using 35 keV X-rays. A 7 cm x 12 cm XPAD3 imager, built with eight silicon modules (seven circuits per module) tiled together, was successfully used for X-ray diffraction experiments. A first result recently obtained with a new 2 cm x 3 cm CdTe imager is also presented.

  1. Fine structure of a resonantly excited p -shell exciton in a CdTe quantum dot

    NASA Astrophysics Data System (ADS)

    Smoleński, T.; Kazimierczuk, T.; Goryca, M.; Wojnar, P.; Kossacki, P.

    2016-05-01

    We present a polarization-resolved photoluminescence excitation study of the absorption spectrum of a p -shell neutral exciton in a single CdTe/ZnTe quantum dot. We find that the fine structure of the p -shell exciton is completely analogous to the fine structure of the s -shell exciton, including the selection rules and the effects of a magnetic field applied in Faraday and Voigt configurations. The energy spectrum of the p -shell exciton is found to be well described by introducing respective isotropic and anisotropic constants of the exchange interaction between a p -shell electron and a p -shell hole. The typical values of these exchange constants averaged over several randomly selected quantum dots yield δ0p p=(0.92 ±0.16 ) meV and δ1p p=(0.58 ±0.25 ) meV. Additionally, we demonstrate that the nonresonant relaxation of the p -shell exciton conserves the exciton spin to a very high degree for both bright and dark exciton configurations.

  2. CdTe quantum dots induce activation of human platelets: implications for nanoparticle hemocompatibility.

    PubMed

    Samuel, Stephen P; Santos-Martinez, Maria J; Medina, Carlos; Jain, Namrata; Radomski, Marek W; Prina-Mello, Adriele; Volkov, Yuri

    2015-01-01

    New nanomaterials intended for systemic administration have raised concerns regarding their biocompatibility and hemocompatibility. Quantum dots (QD) nanoparticles have been used for diagnostics, and recent work suggests their use for in vivo molecular and cellular imaging. However, the hemocompatibility of QDs and their constituent components has not been fully elucidated. In the present study, comprehensive investigation of QD-platelet interactions is presented. These interactions were shown using transmission electron microscopy. The effects of QDs on platelet function were investigated using light aggregometry, quartz crystal microbalance with dissipation, flow cytometry, and gelatin zymography. Platelet morphology was also analyzed by phase-contrast, immunofluorescence, atomic-force and transmission electron microscopy. We show that the QDs bind to platelet plasma membrane with the resultant upregulation of glycoprotein IIb/IIIa and P-selectin receptors, and release of matrix metalloproteinase-2. These findings unravel for the first time the mechanism of functional response of platelets to ultrasmall QDs in vitro.

  3. Combining ligand-induced quantum-confined stark effect with type II heterojunction bilayer structure in CdTe and CdSe nanocrystal-based solar cells.

    PubMed

    Yaacobi-Gross, Nir; Garphunkin, Natalia; Solomeshch, Olga; Vaneski, Aleksandar; Susha, Andrei S; Rogach, Andrey L; Tessler, Nir

    2012-04-24

    We show that it is possible to combine several charge generation strategies in a single device structure, the performance of which benefits from all methods used. Exploiting the inherent type II heterojunction between layered structures of CdSe and CdTe colloidal quantum dots, we systematically study different ways of combining such nanocrystals of different size and surface chemistry and with different linking agents in a bilayer solar cell configuration. We demonstrate the beneficial use of two distinctly different sizes of NCs not only to improve the solar spectrum matching but also to reduce exciton binding energy, allowing their efficient dissociation at the interface. We further make use of the ligand-induced quantum-confined Stark effect in order to enhance charge generation and, hence, overall efficiency of nanocrystal-based solar cells.

  4. Comparative syntheses of tetracycline-imprinted polymeric silicate and acrylate on CdTe quantum dots as fluorescent sensors.

    PubMed

    Chao, Mu-Rong; Hu, Chiung-Wen; Chen, Jian-Lian

    2014-11-15

    The amphoteric drug molecule tetracycline, which contains groups with pKa 3.4-9.9, was used as a template for conjugating molecularly imprinted polymers (MIPs) and as a quencher for CdTe quantum dot (QD) fluorescence. Two MIP-QD composites were synthesized by a sol-gel method using a silicon-based monomer and a monomer linker between the MIP and QD, i.e., tetraethoxylsilane/3-mercaptopropyltriethoxysilane (MPS) and tetraethoxylsilane/3-aminopropyltriethoxysilane (APS). Another MIP-QD composite was synthesized by the chain-growth polymerization of methacrylic acid (MAA) and an allyl mercaptan linker. The prepared MIP-QDs were characterized by FTIR and SEM and utilized at 0.33 mg/mL to determine the tetracycline content in phosphate buffers (pH 7.4, 50mM) through the Perrin and Stern-Volmer models of quenching fluorometry. The Perrin model was applied to tetracycline concentrations of 7.4 μM-0.37 mM for MIP-MPS-QD, 7.4 μM-0.12 mM for MIP-APS-QD, and 7.4 μM-0.10mM for MIP-MAA-QD (R(2)=0.9988, 0.9978, and 0.9931, respectively). The Stern-Volmer model was applied to tetracycline concentrations of 0.12-0.37 mM for MIP-APS-QD (R(2)=0.9983) and 0.10-0.37 mM for MIP-MAA-QD (R(2)=0.9970). The detection limits were 0.45 μM, 0.54 μM, and 0.50 μM for MIP-MPS-QD, MIP-APS-QD, and MIP-MAA-QD, respectively. Equilibrium times, differences between imprinted and nonimprinted polymers, and MIP-QD quenching mechanisms were discussed. Finally, specificity studies demonstrated that MIP-MAA-QD exhibited optimal recoveries of 96% from bovine serum albumin (n=5, RSD=3.6%) and 91% from fetal bovine serum (n=5, RSD=4.8%). Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Novel fluorescent CdTe quantum dot-thymine conjugate—synthesis, properties and possible application

    NASA Astrophysics Data System (ADS)

    Rodzik, Łucja; Lewandowska-Łańcucka, Joanna; Szuwarzyński, Michał; Szczubiałka, Krzysztof; Nowakowska, Maria

    2017-01-01

    Novel, highly fluorescent cadmium telluride quantum dots conjugated with thymine and stabilized with thioglycolic acid were obtained and characterized. Successful formation of the conjugate was confirmed by elemental analysis, and UV-vis, fluorescence and Fourier transform infrared spectroscopies. Crystal structure and composition of the conjugates were characterized with xray diffraction and x-ray photoelectron spectroscopy. The size of the conjugates was 4-6 nm as demonstrated using atomic force microscopy and high resolution transmission electron microscopy imaging. The plasmon resonance fluorescence band at 540 nm on excitation at 351 nm was observed for these nanoparticles. The intensity of this band increased with the increase in the amount of conjugated thymine with no shift in its position. Based on the fluorescence measurements it was found that the CdTe-thymine conjugate interacted efficiently and selectively not only with adenine, a nucleobase complementary to thymine, but also with adenine-containing modified nucleosides, i.e., 5‧-deoxy-5‧-(methylthio)adenosine and 2‧-O-methyladenosine, the urinary tumor markers which allow monitoring of the disease progression. To the best of our knowledge, as yet, there have been no studies presented in literature on that type of the interaction with CdTe-thymine conjugates. Therefore, the system presented can be considered as a working component of a selective adenine/adenosine biosensor with potential application in cancer diagnosis.

  6. Tandem Solar Cells from Solution-Processed CdTe and PbS Quantum Dots Using a ZnTe–ZnO Tunnel Junction

    DOE PAGES

    Crisp, Ryan W.; Pach, Gregory F.; Kurley, J. Matthew; ...

    2017-01-10

    We developed a monolithic CdTe-PbS tandem solar cell architecture in which both the CdTe and PbS absorber layers are solution-processed from nanocrystal inks. Due to their tunable nature, PbS quantum dots (QDs), with a controllable band gap between 0.4 and ~1.6 eV, are a promising candidate for a bottom absorber layer in tandem photovoltaics. In the detailed balance limit, the ideal configuration of a CdTe (Eg = 1.5 eV)-PbS tandem structure assumes infinite thickness of the absorber layers and requires the PbS band gap to be 0.75 eV to theoretically achieve a power conversion efficiency (PCE) of 45%. However, modelingmore » shows that by allowing the thickness of the CdTe layer to vary, a tandem with efficiency over 40% is achievable using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first step toward developing this technology, we explore CdTe-PbS tandem devices by developing a ZnTe-ZnO tunnel junction, which appropriately combines the two subcells in series. We examine the basic characteristics of the solar cells as a function of layer thickness and bottom-cell band gap and demonstrate open-circuit voltages in excess of 1.1 V with matched short circuit current density of 10 mA/cm2 in prototype devices.« less

  7. Quantum dots (QDs) based fluorescence probe for the sensitive determination of kaempferol

    NASA Astrophysics Data System (ADS)

    Tan, Xuanping; Liu, Shaopu; Shen, Yizhong; He, Youqiu; Yang, Jidong

    2014-12-01

    In this work, using the quenching of fluorescence of thioglycollic acid (TGA)-capped CdTe quantum dots (QDs), a novel method for the determination of kaempferol (KAE) has been developed. Under optimum conditions, a linear calibration plot of the quenched fluorescence intensity at 552 nm against the concentration of KAE was observed in the range of 4-44 μg mL-1 with a detection limit (3σ/K) of 0.79 μg mL-1. In addition, the detailed reaction mechanism has also been proposed on the basis of electron transfer supported by ultraviolet-visible (UV-vis) absorption and fluorescence (FL) spectroscopy. The method has been applied for the determination of KAE in pharmaceutical preparations with satisfactory results. The proposed method manifested several advantages such as high sensitivity, short analysis time, low cost and ease of operation.

  8. CLAVATA3 Dodecapeptide Modified CdTe Nanoparticles: A Biocompatible Quantum Dot Probe for In Vivo Labeling of Plant Stem Cells

    PubMed Central

    Yu, Guanghui; Tan, Yanping; He, Xiangzhu; Qin, Yonghua; Liang, Jiangong

    2014-01-01

    CLAVATA3 (CLV3) dodecapeptides function in plant stem cell maintenance, but CLV3 function in cell-cell communication remains less clear. Here, we coupled CLV3 dodecapeptides to synthesized CdTe nanoparticles to track their bioactivity on stem cells in the root apical meristem. To achieve this, we first synthesized CdTe quantum dots (QDs) using a one-pot method, and then evaluated the cytotoxicity of the QDs in BY-2 cells. The results showed that QDs in plant cells must be used at low concentrations and for short treatment time. To make biocompatible probes to track stem cell fate, we conjugated CLV3 dodecapeptides to the QDs by the zero-coupling method; this modification greatly reduced the cytotoxicity of the QDs. Furthermore, we detected CLV3-QDs localized on the cell membrane, consistent with the known localization of CLV3. Our results indicate that using surface-modified QDs at low concentrations and for short time treatment can improve their utility for plant cell imaging. PMID:24586624

  9. CLAVATA3 dodecapeptide modified CdTe nanoparticles: a biocompatible quantum dot probe for in vivo labeling of plant stem cells.

    PubMed

    Yu, Guanghui; Tan, Yanping; He, Xiangzhu; Qin, Yonghua; Liang, Jiangong

    2014-01-01

    CLAVATA3 (CLV3) dodecapeptides function in plant stem cell maintenance, but CLV3 function in cell-cell communication remains less clear. Here, we coupled CLV3 dodecapeptides to synthesized CdTe nanoparticles to track their bioactivity on stem cells in the root apical meristem. To achieve this, we first synthesized CdTe quantum dots (QDs) using a one-pot method, and then evaluated the cytotoxicity of the QDs in BY-2 cells. The results showed that QDs in plant cells must be used at low concentrations and for short treatment time. To make biocompatible probes to track stem cell fate, we conjugated CLV3 dodecapeptides to the QDs by the zero-coupling method; this modification greatly reduced the cytotoxicity of the QDs. Furthermore, we detected CLV3-QDs localized on the cell membrane, consistent with the known localization of CLV3. Our results indicate that using surface-modified QDs at low concentrations and for short time treatment can improve their utility for plant cell imaging.

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

    SciTech Connect

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

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Observation of Distinct Two-Photon Transition Channels in CdTe Quantum Dots in a Regime of Very Strong Confinement.

    PubMed

    Gonçalves Vivas, Marcelo; Leandro De Sousa, José Carlos; De Boni, Leonardo; Schiavon, Marco Antônio; Mendonca, Cleber Renato

    2017-03-30

    We report here on the direct observation of distinct two-photon transition channels in glutathione-capped (GSH) CdTe quantum dots (QDs) in a very strong confinement regime. CdTe-GSH QDs with different average diameters (2.5, 3.0, and 3.3 nm) were synthesized through the one-pot method and their two-photon absorption (2PA) spectrum determined by a femtosecond wavelength-tunable Z-scan. Our results show that the two lower-energy one-photon-allowed excitonic transitions, 1S3/2(h) → 1S(e) and 2S3/2(h) → 1S(e), are also accessed via 2PA. These results were ascribed to the relaxation of the parity selection rules due to the noncentrosymmetric structure of the CdTe QDs (zinc-blended structure), whose magnitude are determined by surface defects and structural irregularities present in CdTe-GSH QDs, in the strong confinement regime.

  13. Plasma kinetics and biodistribution of water-soluble CdTe quantum dots in mice: a comparison between Cd and Te

    NASA Astrophysics Data System (ADS)

    Han, Ying; Xie, Guangyun; Sun, Zhiwei; Mu, Ying; Han, Sihai; Xiao, Yang; Liu, Na; Wang, Hui; Guo, Caixia; Shi, Zhixiong; Li, Yanbo; Huang, Peili

    2011-10-01

    Water-soluble quantum dots (QDs) have shown potential as tumor diagnostic agents. However, little is known about their biological behaviors in vivo. Male ICR mice were intravenously given a single dose (2.5 μmol kg-1 body weight) of water-soluble cadmium-telluride (CdTe) QDs (the QDs are approximately 4 nm in diameter and have maximal emission at 630 nm). Inductively coupled plasma mass spectrometry (ICP-MS) was used for measuring the kinetic action of 111Cd and 125Te for 7 days. The plasma kinetics of Cd and Te followed a two-compartment model, in which Cd exhibited greater apparent volume of distribution, greater clearance, faster distribution half-life, and significantly slower elimination half-life compared to Te. Contrary to its relatively transient fate in the plasma, high levels of Cd persisted in the liver and kidneys. Te accumulated primarily in the spleen. The different plasma kinetics and distribution patterns of Cd and Te imply that CdTe QDs have been part of the degradation or aggregation in vivo.

  14. Macromolecular Systems with MSA-Capped CdTe and CdTe/ZnS Core/Shell Quantum Dots as Superselective and Ultrasensitive Optical Sensors for Picric Acid Explosive.

    PubMed

    Dutta, Priyanka; Saikia, Dilip; Adhikary, Nirab Chandra; Sarma, Neelotpal Sen

    2015-11-11

    This work reports the development of highly fluorescent materials for the selective and efficient detection of picric acid explosive in the nanomolar range by fluorescence quenching phenomenon. Poly(vinyl alcohol) grafted polyaniline (PPA) and its nanocomposites with 2-mercaptosuccinic acid (MSA)-capped CdTe quantum dots (PPA-Q) and with MSA-capped CdTe/ZnS core/shell quantum dots (PPA-CSQ) are synthesized in a single step free radical polymerization reaction. The thermal stability and photo stability of the polymer increases in the order of PPA < PPA-Q < PPA-CSQ. The polymers show remarkably high selectivity and efficient sensitivity toward picric acid, and the quenching efficiency for PPA-CSQ reaches up to 99%. The detection limits of PPA, PPA-Q, and PPA-CSQ for picric acid are found to be 23, 1.6, and 0.65 nM, respectively, which are remarkably low. The mechanism operating in the quenching phenomenon is proposed to be a combination of a strong inner filter effect and ground state electrostatic interaction between the polymers and picric acid. A portable and cost-effective electronic device for the visual detection of picric acid by the sensory system is successfully fabricated. The device is further employed for quantitative detection of picric acid in real water samples.

  15. Microfluidic assisted synthesis of multi-functional polycaprolactone microcapsules: incorporation of CdTe quantum dots, Fe3O4 superparamagnetic nanoparticles and tamoxifen anticancer drugs.

    PubMed

    Yang, C-H; Huang, K-S; Lin, Y-S; Lu, K; Tzeng, C-C; Wang, E-C; Lin, C-H; Hsu, W-Y; Chang, J-Y

    2009-04-07

    This paper demonstrates a proof-of-concept approach for encapsulating the anticancer drug tamoxifen, Fe3O4 nanoparticles (NPs) and CdTe quantum dots (QDs) into size-controlled polycaprolactone (PCL) microcapsules utilizing microfluidic emulsification, which combined magnetic targeting, fluorescence imaging and drug controlled release properties into one drug delivery system. Cross-linking the composite PCL microcapsules with poly(vinyl alcohol) (PVA) tailored their size, morphology, optical and magnetic properties and drug release behaviors. The flow conditions of the two immiscible solutions were adjusted in order to successfully generate various sizes of polymer droplets. The result showed superparamagnetic and fluorescent properties, and was used as a controlled drug release vehicle. The composite magnetic and fluorescent PCL microcapsules are potential candidates for a smart drug delivery system.

  16. Deep level transient spectroscopy of hole traps related to CdTe self-assembled quantum dots embedded in ZnTe matrix

    NASA Astrophysics Data System (ADS)

    Zielony, E.; Placzek-Popko, E.; Dyba, P.; Gumienny, Z.; Dobaczewski, L.; Karczewski, G.

    2011-12-01

    The capacitance—voltage (C-V) and deep level transient spectroscopy (DLTS) measurements have been performed on a Schottky structure containing self-assembled CdTe quantum dots (QDs) embedded in ZnTe (p-type) matrix. A characteristic step on the C-V curve due to charge accumulation on QD states as well as QD related DLTS signal were found. Thermal activation energy of 0.1 eV was obtained from Arrhenius plot related to the signal. This energy level can be related either to the hole emission from the defects accompanying QD formation or to the hole emission from the QD states to the ZnTe valence band.

  17. Effect of CdTe quantum dots size on the conformational changes of human serum albumin: results of spectroscopy and isothermal titration calorimetry.

    PubMed

    Yang, Bingjun; Liu, Rutao; Hao, Xiaopeng; Wu, Yongzhong; Du, Jie

    2013-10-01

    Quantum dots (QDs) are recognized as some of the most promising candidates for future applications in biomedicine. However, concerns about their safety have delayed their widespread application. Human serum albumin (HSA) is the main protein component of the circulatory system. It is important to explore the interaction of QDs with HSA for the potential in vivo application of QDs. Herein, using spectroscopy and isothermal titration calorimetry (ITC), the effect of glutathione-capped CdTe quantum dots of different sizes on the HSA was investigated. After correction for the inner filter effect, the fluorescence emission spectra and synchronous fluorescence spectra showed that the microenvironment of aromatic acid residues in the protein was slightly changed when the glutathione (GSH)-cadmium telluride (CdTe) QDs was added, and GSH-CdTe QDs with larger particle size exhibited a much higher effect on HSA than the small particles. Although a ground-state complex between HSA and GSH-CdTe QDs was formed, the UV-vis absorption and circular dichroism spectroscopic results did not find appreciable conformational changes of HSA. ITC has been used for the first time to characterize the binding of QDs with HSA. The ITC results revealed that the binding was a thermodynamically spontaneous process mainly driven by hydrophobic interactions, and the binding constant tended to increase as the GSH-CdTe QDs size increased. These findings are helpful in understanding the bioactivities of QDs in vivo and can be used to assist in the design of biocompatible and stable QDs.

  18. Semiconductor quantum dot-sensitized solar cells

    PubMed Central

    Tian, Jianjun; Cao, Guozhong

    2013-01-01

    Semiconductor quantum dots (QDs) have been drawing great attention recently as a material for solar energy conversion due to their versatile optical and electrical properties. The QD-sensitized solar cell (QDSC) is one of the burgeoning semiconductor QD solar cells that shows promising developments for the next generation of solar cells. This article focuses on recent developments in QDSCs, including 1) the effect of quantum confinement on QDSCs, 2) the multiple exciton generation (MEG) of QDs, 3) fabrication methods of QDs, and 4) nanocrystalline photoelectrodes for solar cells. We also make suggestions for future research on QDSCs. Although the efficiency of QDSCs is still low, we think there will be major breakthroughs in developing QDSCs in the future. PMID:24191178

  19. Semiconductor quantum dot-sensitized solar cells.

    PubMed

    Tian, Jianjun; Cao, Guozhong

    2013-10-31

    Semiconductor quantum dots (QDs) have been drawing great attention recently as a material for solar energy conversion due to their versatile optical and electrical properties. The QD-sensitized solar cell (QDSC) is one of the burgeoning semiconductor QD solar cells that shows promising developments for the next generation of solar cells. This article focuses on recent developments in QDSCs, including 1) the effect of quantum confinement on QDSCs, 2) the multiple exciton generation (MEG) of QDs, 3) fabrication methods of QDs, and 4) nanocrystalline photoelectrodes for solar cells. We also make suggestions for future research on QDSCs. Although the efficiency of QDSCs is still low, we think there will be major breakthroughs in developing QDSCs in the future.

  20. CdTe and graphene co-sensitized TiO2 nanotube array photoanodes for protection of 304SS under visible light.

    PubMed

    Li, Hong; Wang, Xiutong; Zhang, Liang; Hou, Baorong

    2015-04-17

    CdTe/graphene/TiO2 films that served as photoanodes for cathodic protection application were prepared by an electrochemical deposition method. The deposition of graphene and CdTe nanoparticles (NPs) on the surface of the TiO2 nanotubes was confirmed by scanning electron microscope and transmission electron microscopy. The composites exhibited high light absorption in both the UV and visible light region. The results indicated that TiO2 nanotube photoelectrodes sensitized by 20-cycle graphene and 30-cycle CdTe NPs exhibited effective photocathodic protection properties for 304 stainless steel (304SS) under the visible-light illumination, with an photopotential of -750 mV versus saturated calomel electrode and a current density of 560 μA cm(-2). Due to the efficient photogenerated charge separation, the three-component CdTe/graphene/TiO2 showed stronger photoresponse than pure TiO2 under visible-light illumination. In summary, the CdTe/graphene could improve the photocathodic protection properties of TiO2 films.

  1. Quantum Confinement Regimes in CdTe Nanocrystals Probed by Single Dot Spectroscopy: From Strong Confinement to the Bulk Limit.

    PubMed

    Tilchin, Jenya; Rabouw, Freddy T; Isarov, Maya; Vaxenburg, Roman; Van Dijk-Moes, Relinde J A; Lifshitz, Efrat; Vanmaekelbergh, Daniel

    2015-08-25

    Sufficiently large semiconductor nanocrystals are a useful model system to characterize bulk-like excitons, with the electron and hole bound predominantly by Coulomb interaction. We present optical characterization of excitons in individual giant CdTe nanocrystals with diameters up to 25.5 nm at 4.2 K under varying excitation power and magnetic field strength. We determine values for the biexciton binding energy, diamagnetic shift constant, and Landé g-factor, which approach the bulk values with increasing nanocrystal size.

  2. Quantum control of electron spins in the two-dimensional electron gas of a CdTe quantum well with a pair of Raman-resonant phase-locked laser pulses

    NASA Astrophysics Data System (ADS)

    Sweeney, Timothy M.; Phelps, Carey; Wang, Hailin

    2011-08-01

    We demonstrated optical spin control of a two-dimensional electron gas in a modulation-doped CdTe quantum well by driving a spin-flip Raman transition with a pair of phase-locked laser pulses. In contrast to single-pulse optical spin control, which features a fixed spin-rotation axis, manipulation of the initial relative phase of the pulse pair enables us to control the axis of the optical spin rotation. We show that the Raman pulse pair acts like an effective microwave field, mapping the relative optical phase onto the phase of the electron spin polarization and making possible ultrafast, all-optical, and full quantum control of the electron spins.

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

    PubMed

    Viana, Osnir S; Ribeiro, Martha S; Rodas, Andréa C D; Rebouças, Júlio S; Fontes, Adriana; Santos, Beate S

    2015-05-18

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

  4. Fabrication of l-cysteine-capped CdTe quantum dots based ratiometric fluorescence nanosensor for onsite visual determination of trace TNT explosive.

    PubMed

    Qian, Jing; Hua, Mengjuan; Wang, Chengquan; Wang, Kan; Liu, Qian; Hao, Nan; Wang, Kun

    2016-11-23

    New strategies for onsite determination of trace 2,4,6-trinitrotoluene (TNT) explosives have become a research hotspot for homeland security needs against terrorism and environmental concerns. Herein, we designed a ratiometric fluorescence nanohybrid comprising 3-mercaptopropionic acid-capped green-emitting CdTe quantum dots (gQDs) encapsulated into SiO2 sphere and l-cysteine (Lcys)-capped red-emitting CdTe QDs (rQDs) conjugated onto SiO2 surface. The surface Lcys can be used as not only the stabilizer of the rQDs but also the primary amine provider which can react with TNT to form Meisenheimer complexes. Without any additional surface modification procedure, the fluorescence of rQDs equipped with Lcys was selectively quenched by TNT because electrons of the rQDs transferred to TNT molecules due to the formation of Meisenheimer complexes. Meanwhile, the embedded gQDs always remained constant. Upon exposure to increasing amounts of TNT, the fluorescence of rQDs could be gradually quenched and consequently the logarithm of the dual emission intensity ratios exhibited a good linear negative correlation with TNT concentration over a range of 10 nM-8 μM with a low detection limit of 3.3 nM. One can perform onsite visual determination of TNT with high resolution because the ratiometric fluorescence nanosensing system exhibited obvious fluorescence color changes. This sensing strategy has been successfully applied in real samples and already integrated in a filter paper-based assay, which enables potential fields use application featuring easy handling and cost-effectiveness. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. MPA-capped CdTe quantum dots exposure causes neurotoxic effects in nematode Caenorhabditis elegans by affecting the transporters and receptors of glutamate, serotonin and dopamine at the genetic level, or by increasing ROS, or both

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    As quantum dots (QDs) are widely used in biomedical applications, the number of studies focusing on their biological properties is increasing. While several studies have attempted to evaluate the toxicity of QDs towards neural cells, the in vivo toxic effects on the nervous system and the molecular mechanisms are unclear. The aim of the present study was to investigate the neurotoxic effects and the underlying mechanisms of water-soluble cadmium telluride (CdTe) QDs capped with 3-mercaptopropionic acid (MPA) in Caenorhabditis elegans (C. elegans). Our results showed that exposure to MPA-capped CdTe QDs induced behavioral defects, including alterations to body bending, head thrashing, pharyngeal pumping and defecation intervals, as well as impaired learning and memory behavior plasticity, based on chemotaxis or thermotaxis, in a dose-, time- and size-dependent manner. Further investigations suggested that MPA-capped CdTe QDs exposure inhibited the transporters and receptors of glutamate, serotonin and dopamine in C. elegans at the genetic level within 24 h, while opposite results were observed after 72 h. Additionally, excessive reactive oxygen species (ROS) generation was observed in the CdTe QD-treated worms, which confirmed the common nanotoxicity mechanism of oxidative stress damage, and might overcome the increased gene expression of neurotransmitter transporters and receptors in C. elegans induced by long-term QD exposure, resulting in more severe behavioral impairments.

  6. Recombination in quantum dot sensitized solar cells.

    PubMed

    Mora-Seró, Iván; Giménez, Sixto; Fabregat-Santiago, Francisco; Gómez, Roberto; Shen, Qing; Toyoda, Taro; Bisquert, Juan

    2009-11-17

    Quantum dot sensitized solar cells (QDSCs) have attracted significant attention as promising third-generation photovoltaic devices. In the form of quantum dots (QDs), the semiconductor sensitizers have very useful and often tunable properties; moreover, their theoretical thermodynamic efficiency might be as high as 44%, better than the original 31% calculated ceiling. Unfortunately, the practical performance of these devices still lags behind that of dye-sensitized solar cells. In this Account, we summarize the strategies for depositing CdSe quantum dots on nanostructured mesoporous TiO(2) electrodes and discuss the methods that facilitate improvement in the performance and stability of QDSCs. One particularly significant factor for solar cells that use polysulfide electrolyte as the redox couple, which provides the best performance among QDSCs, is the passivation of the photoanode surface with a ZnS coating, which leads to a dramatic increase of photocurrents and efficiencies. However, these solar cells usually show a poor current-potential characteristic, so a general investigation of the recombination mechanisms is required for improvements. A physical model based on recombination through a monoenergetic TiO(2) surface state that takes into account the effect of the surface coverage has been developed to better understand the recombination mechanisms of QDSCs. The three main methods of QD adsorption on TiO(2) are (i) in situ growth of QDs by chemical bath deposition (CBD), (ii) deposition of presynthesized colloidal QDs by direct adsorption (DA), and (iii) deposition of presynthesized colloidal QDs by linker-assisted adsorption (LA). A systematic investigation by impedance spectroscopy of QDSCs prepared by these methods showed a decrease in the charge-transfer resistance and increased electron lifetimes for CBD samples; the same result was found after ZnS coating because of the covering of the TiO(2) surface. The increase of the lifetime with the ZnS treatment

  7. One-pot aqueous synthesis of gadolinium doped CdTe quantum dots with dual imaging modalities.

    PubMed

    Jiang, Chunli; Shen, Zhitao; Luo, Chunhua; Lin, Hechun; Huang, Rong; Wang, Yiting; Peng, Hui

    2016-08-01

    A facile one-pot strategy has been developed for the aqueous synthesis of Gd doped CdTe (Gd:CdTe) QDs as fluorescence and magnetic resonance imaging dual-modal agent. The prepared Gd:CdTe QDs showed narrow size distribution and the average size was less than 5nm. The amount of Gd(3+) dopant in Gd:CdTe QDs significantly affected the optical properties of obtained QDs. The highest PL QY for the prepared Gd:CdTe QDs was up to 42.5%. The QDs showed the weak toxicity and significant enhancement in MRI signal. The specific relaxivity value (r1) was determined to be 4.22mM(-1)s(-1). These properties make the prepared Gd:CdTe QDs be an effective dual-modal imaging agent and have great potential applications in biomedical field.

  8. Selective and Sensitive Detection of Silver(I) Ion Based on Tetracationic Complex and TGA/GSH Co-capped Quantum Dots as an Effective Fluorescent Sensing Platform.

    PubMed

    Liu, Xue-Wen; Shu, Jun-Shi; Xiao, Yang; Yang, Yang; Zhang, Song-Bai

    2017-01-01

    CdTe quantum dots capped with glutathione (GSH) and thioglycolic acid (TGA) were synthesized and the interaction between QDs and tetracationic Fe complex was investigated. Based on the specific interaction between Ag(+) and cytosine bases (C), we designed a label-free DNA sensor for the detection of Ag(+) in aqueous solution. Furthermore, tetracationic Fe complex with a higher positive charge is demonstrated to improve the sensitivity of the sensor. A detection limit of 3.3 nmol dm(-3) was obtained, which was lower than in previous reports. This sensor also exhibits promising potential for real sample analysis.

  9. Influence of Cu2+ dopant in optical property of CdTe quantum dots and photoelectrochemical performance of CdTe:Cu2+/TiO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Chen, Qian; Geng, Yue; Zhou, Chunyan; Song, Jiahui; Zhou, Liya

    2016-05-01

    A novel one-step synthesis process was used to prepare CdTe:Cu2+/TiO2 nanotube arrays (TNTAs). X-ray powder diffraction and high-resolution transmission electron microscopy analyses confirmed that the obtained CdTe:Cu2+ quantum dots (QDs) possess cubic structures, which are approximately spherical, and a small particle size (2.95 nm). The photoluminescent and UV-visible absorption spectra of CdTe:Cu2+ QDs also display an obvious redshift, which was attributed to the replacement of Cd2+ with Cu2+. Compared with that of the TNTAs and CdTe/TNTAs, the photoelectric conversion efficiency of CdTe:5% Cu2+/TNTAs increased by 785.7% and 103.3%, respectively. The incident photo-to-current conversion efficiency of CdTe:5% Cu2+/TNTAs was 50.6%, which indicated the potential use of QDs in photochemical solar cells.

  10. The relationship between the length of surface ligand and effects of CdTe quantum dots on the physiological functions of isolated mitochondria.

    PubMed

    Xiang, Xun; Wu, Can; Zhang, Bo-Rui; Gao, Tao; Zhao, Jie; Ma, Long; Jiang, Feng-Lei; Liu, Yi

    2017-10-01

    The potential toxicity of Quantum dots (QDs) should be assessed comprehensively for their fast spreading applications. Many studies have shown the toxicity of QDs is associated with their surface ligands. In this work, two analog ligands with one carbon difference, 2-mercaptoacetic acid (TGA) and 3-mercaptopropionic acid (MPA) were used as coating materials in the syntheses of two types of CdTe QDs with similar physicochemical properties. Then the biological effects of QDs on isolated mitochondria were studied. It was found that the two types of QDs could impair mitochondrial respiration and induce mitochondrial permeability transition (MPT). However, as compared with TGA-CdTe QDs, MPA-CdTe QDs had a stronger effect on MPT. The weaker effect of TGA-CdTe QDs on MPT might be owing to their better stability and thus less amount of released Cd(2+), which could be further explained by the stronger affinity between the ligand (TGA) and the cadmium complexes in the crystal growth of QDs. These results highlighted the importance of ligands responsible for the toxicity of QDs at the sub-cellular level. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. A molecularly imprinted polymer-coated CdTe quantum dot nanocomposite for tryptophan recognition based on the Förster resonance energy transfer process

    NASA Astrophysics Data System (ADS)

    Tirado-Guizar, Antonio; Paraguay-Delgado, Francisco; Pina-Luis, Georgina E.

    2016-12-01

    A new ‘turn-on’ Förster resonance energy transfer (FRET) nanosensor for l-tryptophan based on molecularly imprinted quantum dots (QDs) is proposed. The approach combines the advantages of the molecular imprinting technique, the fluorescent characteristics of the QDs and the energy transfer process. Silica-coated CdTe QDs were first synthesized and then molecularly imprinted using a sol-gel process without surfactants. The final composite presents stable fluorescence which increases with the addition of l-tryptophan. This ‘turn-on’ response is due to a FRET mechanism from the l-tryptophan as donor to the imprinted QD as acceptor. QDs are rarely applied as acceptors in FRET systems. The nanosensor shows selectivity towards l-tryptophan in the presence of other amino acids and interfering ions. The l-tryptophan nanosensor exhibits a linear range between 0 and 8 µM concentration, a detection limit of 350 nM and high selectivity. The proposed sensor was successfully applied for the detection of l-tryptophan in saliva. This novel sensor may offer an alternative approach to the design of a new generation of imprinted nanomaterials for the recognition of different analytes.

  12. Fluorescent "on-off-on" switching sensor based on CdTe quantum dots coupled with multiwalled carbon nanotubes@graphene oxide nanoribbons for simultaneous monitoring of dual foreign DNAs in transgenic soybean.

    PubMed

    Li, Yaqi; Sun, Li; Qian, Jing; Long, Lingliang; Li, Henan; Liu, Qian; Cai, Jianrong; Wang, Kun

    2017-06-15

    With the increasing concern of potential health and environmental risk, it is essential to develop reliable methods for transgenic soybean detection. Herein, a simple, sensitive and selective assay was constructed based on homogeneous fluorescence resonance energy transfer (FRET) between CdTe quantum dots (QDs) and multiwalled carbon nanotubes@graphene oxide nanoribbons (MWCNTs@GONRs) to form the fluorescent "on-off-on" switching for simultaneous monitoring dual target DNAs of promoter cauliflower mosaic virus 35s (P35s) and terminator nopaline synthase (TNOS) from transgenic soybean. The capture DNAs were immobilized with corresponding QDs to obtain strong fluorescent signals (turning on). The strong π-π stacking interaction between single-stranded DNA (ssDNA) probes and MWCNTs@GONRs led to minimal background fluorescence due to the FRET process (turning off). The targets of P35s and TNOS were recognized by dual fluorescent probes to form double-stranded DNA (dsDNA) through the specific hybridization between target DNAs and ssDNA probes. And the dsDNA were released from the surface of MWCNTs@GONRs, which leaded the dual fluorescent probes to generate the strong fluorescent emissions (turning on). Therefore, this proposed homogeneous assay can be achieved to detect P35s and TNOS simultaneously by monitoring the relevant fluorescent emissions. Moreover, this assay can distinguish complementary and mismatched nucleic acid sequences with high sensitivity. The constructed approach has the potential to be a tool for daily detection of genetically modified organism with the merits of feasibility and reliability. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Probing the interaction of a new synthesized CdTe quantum dots with human serum albumin and bovine serum albumin by spectroscopic methods.

    PubMed

    Bardajee, Ghasem Rezanejade; Hooshyar, Zari

    2016-05-01

    A novel CdTe quantum dots (QDs) were prepared in aqueous phase via a facile method. At first, poly (acrylic amide) grafted onto sodium alginate (PAAm-g-SA) were successfully synthesized and then TGA capped CdTe QDs (CdTe-TGA QDs) were embed into it. The prepared CdTe-PAAm-g-SA QDs were optimized and characterized by transmission electron microscopy (TEM), thermo-gravimetric (TG) analysis, Fourier transform infrared (FT-IR), UV-vis and fluorescence spectroscopy. The characterization results indicated that CdTe-TGA QDs, with particles size of 2.90 nm, were uniformly dispersed on the chains of PAAm-g-SA biopolymer. CdTe-PAAm-g-SA QDs also exhibited excellent UV-vis absorption and high fluorescence intensity. To explore biological behavior of CdTe-PAAm-g-SA QDs, the interactions between CdTe-PAAm-g-SA QDs and human serum albumin (HSA) (or bovine serum albumin (BSA)) were investigated by cyclic voltammetry, FT-IR, UV-vis, and fluorescence spectroscopic. The results confirmed the formation of CdTe-PAAm-g-SA QDs-HSA (or BSA) complex with high binding affinities. The thermodynamic parameters (ΔG<0, ΔH<0 and ΔS<0) were indicated that binding reaction was spontaneous and van der Waals interactions and hydrogen-bond interactions played a major role in stabilizing the CdTe-PAAm-g-SA QDs-HSA (or BSA) complexes. The binding distance between CdTe-PAAm-g-SA QDs and HSA (or BSA)) was calculated about 1.37 nm and 1.27 nm, respectively, according to Forster non-radiative energy transfer theory (FRET). Analyzing FT-IR spectra showed that the formation of QDs-HSA and QDs-BSA complexes led to conformational changes of the HSA and BSA proteins. All these experimental results clarified the effective transportation and elimination of CdTe-PAAm-g-SA QDs in the body by binding to HSA and BSA, which could be a useful guideline for the estimation of QDs as a drug carrier.

  14. CdTe quantum dots: aqueous phase synthesis, stability studies and protein conjugation for development of biosensors

    NASA Astrophysics Data System (ADS)

    Borse, Vivek; Sadawana, Mayur; Srivastava, Rohit

    2016-04-01

    Synthesis of quantum dots (QDs) in aqueous medium is advantageous as compared to the organic solvent mediated synthesis, as the aqueous synthesis is less toxic, reagent effective, easily reproducible and importantly, synthesized QDs have biological compatibility. The QDs should be aqueous in nature for use in cell imaging, drug labeling, tracking and delivery. Structural modifications are necessary to enable their use in biosensing application. In this work, mercaptopropionic acid capped cadmium telluride QDs (MPA-CdTe QDs) were synthesized by hydrothermal method and characterized by various techniques. Water and various biochemical buffers were used to study the fluorescence intensity stability of the QDs at different physicochemical conditions. QDs stored in 4° C showed excellent stability of fluorescence intensity values as compared to the samples stored at room temperature. Staphylococcal protein A (SPA) was conjugated with the QDs (SPA-QDs) and characterized using UV and fluorescence spectroscopy, zeta potential, HRTEM, FTIR, and AFM. Blue shift was observed in the fluorescence emission spectra that may be due to reduction in the surface charge as carboxyl groups on QDs were replaced by amino groups of SPA. This SPA conjugated to QDs enables binding of the C-terminal of antibodies on its surface allowing N-terminal binding site remain free to bind with antigenic biomarkers. Thus, the biosensor i.e. antibody bound on SPA-QDs would bind to the antigenic biomarkers in sample and the detection system could be developed. As QDs have better fluorescence properties than organic dyes, this biosensor will provide high sensitivity and quantitative capability in diagnostics.

  15. Sensitivity of quantum-dot semiconductor lasers to optical feedback.

    PubMed

    O'Brien, D; Hegarty, S P; Huyet, G; Uskov, A V

    2004-05-15

    The sensitivity of quantum-dot semiconductor lasers to optical feedback is analyzed with a Lang-Kobayashi approach applied to a standard quantum-dot laser model. The carriers are injected into a quantum well and are captured by, or escape from, the quantum dots through either carrier-carrier or phonon-carrier interaction. Because of Pauli blocking, the capture rate into the dots depends on the carrier occupancy level in the dots. Here we show that different carrier capture dynamics lead to a strong modification of the damping of the relaxation oscillations. Regions of increased damping display reduced sensitivity to optical feedback even for a relatively large alpha factor.

  16. The Influence of Surface Modification on the Photoluminescence of CdTe Quantum Dots: Realization of Bio-Imaging via Cost-Effective Polymer.

    PubMed

    Jin, Gan; Jiang, Li-Ming; Yi, Dong-Mei; Sun, Hai-Zhu; Sun, Hong-Chen

    2015-12-01

    To impart biocompatibility, stability, and specificity to quantum dots (QDs)-and to reduce their toxicity-it is essential to carry out surface modification. However, most surface-modification processes are costly, complicated, and time-consuming. In addition, the modified QDs often have a large size, which leads to easy aggregation in biological environments, making it difficult to excrete them from in vivo systems. To solve these problems, three kinds of conventional polymers, namely, polyvinyl alcohol (PVA, neutral), sodium polystyrene sulfonate (PSS, negative charged), and poly(diallyl dimethyl ammonium chloride) (PDDA, positive charged) were selected to modify the surface of QDs at low cost via a simple process in which the size of the QDs was kept small after modification. The effect of polymer modification on the photoluminescence (PL) properties of the QDs was systematically investigated. High quantum yields (QYs) of 65 % were reached, which is important for the realization of bio-imaging. Then, the cytotoxicity of CdTe QD-polymer composites was systematically investigated via MTT assay using the Cal27 and HeLa cell lines, especially for high concentrations of QD-polymer composites in vitro. The experimental results showed that the cytotoxicity decreased in the order CdTe-PDDA>CdTe>CdTe-PSS>CdTe-PVA, indicating that PSS and PVA can reduce the toxicity of the QDs. An obvious cytotoxicity of CdTe-PVA and CdTe-PSS was present until 120 h for the Cal27 cell line and until 168 h for the HeLa cell line. At last, the Cal27 cell line was selected to realize bio-imaging using CdTe-PSS and CdTe-PVA composites with different emission colors under one excitation wavelength. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Impact of D2O/H2O Solvent Exchange on the Emission of HgTe and CdTe Quantum Dots: Polaron and Energy Transfer Effects.

    PubMed

    Wen, Qiannan; Kershaw, Stephen V; Kalytchuk, Sergii; Zhovtiuk, Olga; Reckmeier, Claas; Vasilevskiy, Mikhail I; Rogach, Andrey L

    2016-04-26

    We have studied light emission kinetics and analyzed carrier recombination channels in HgTe quantum dots that were initially grown in H2O. When the solvent is replaced by D2O, the nonradiative recombination rate changes highlight the role of the vibrational degrees of freedom in the medium surrounding the dots, including both solvent and ligands. The contributing energy loss mechanisms have been evaluated by developing quantitative models for the nonradiative recombination via (i) polaron states formed by strong coupling of ligand vibration modes to a surface trap state (nonresonant channel) and (ii) resonant energy transfer to vibration modes in the solvent. We conclude that channel (i) is more important than (ii) for HgTe dots in either solution. When some of these modes are removed from the relevant spectral range by the H2O to D2O replacement, the polaron effect becomes weaker and the nonradiative lifetime increases. Comparisons with CdTe quantum dots (QDs) served as a reference where the resonant energy loss (ii) a priori was not a factor, also confirmed by our experiments. The solvent exchange (H2O to D2O), however, is found to slightly increase the overall quantum yield of CdTe samples, probably by increasing the fraction of bright dots in the ensemble. The fundamental study reported here can serve as the foundation for the design and optimization principles of narrow bandgap quantum dots aimed at applications in long wavelength colloidal materials for infrared light emitting diodes and photodetectors.

  18. Exponential Sensitivity and its Cost in Quantum Physics.

    PubMed

    Gilyén, András; Kiss, Tamás; Jex, Igor

    2016-02-10

    State selective protocols, like entanglement purification, lead to an essentially non-linear quantum evolution, unusual in naturally occurring quantum processes. Sensitivity to initial states in quantum systems, stemming from such non-linear dynamics, is a promising perspective for applications. Here we demonstrate that chaotic behaviour is a rather generic feature in state selective protocols: exponential sensitivity can exist for all initial states in an experimentally realisable optical scheme. Moreover, any complex rational polynomial map, including the example of the Mandelbrot set, can be directly realised. In state selective protocols, one needs an ensemble of initial states, the size of which decreases with each iteration. We prove that exponential sensitivity to initial states in any quantum system has to be related to downsizing the initial ensemble also exponentially. Our results show that magnifying initial differences of quantum states (a Schrödinger microscope) is possible; however, there is a strict bound on the number of copies needed.

  19. Exponential Sensitivity and its Cost in Quantum Physics

    NASA Astrophysics Data System (ADS)

    Gilyén, András; Kiss, Tamás; Jex, Igor

    2016-02-01

    State selective protocols, like entanglement purification, lead to an essentially non-linear quantum evolution, unusual in naturally occurring quantum processes. Sensitivity to initial states in quantum systems, stemming from such non-linear dynamics, is a promising perspective for applications. Here we demonstrate that chaotic behaviour is a rather generic feature in state selective protocols: exponential sensitivity can exist for all initial states in an experimentally realisable optical scheme. Moreover, any complex rational polynomial map, including the example of the Mandelbrot set, can be directly realised. In state selective protocols, one needs an ensemble of initial states, the size of which decreases with each iteration. We prove that exponential sensitivity to initial states in any quantum system has to be related to downsizing the initial ensemble also exponentially. Our results show that magnifying initial differences of quantum states (a Schrödinger microscope) is possible; however, there is a strict bound on the number of copies needed.

  20. Exponential Sensitivity and its Cost in Quantum Physics

    PubMed Central

    Gilyén, András; Kiss, Tamás; Jex, Igor

    2016-01-01

    State selective protocols, like entanglement purification, lead to an essentially non-linear quantum evolution, unusual in naturally occurring quantum processes. Sensitivity to initial states in quantum systems, stemming from such non-linear dynamics, is a promising perspective for applications. Here we demonstrate that chaotic behaviour is a rather generic feature in state selective protocols: exponential sensitivity can exist for all initial states in an experimentally realisable optical scheme. Moreover, any complex rational polynomial map, including the example of the Mandelbrot set, can be directly realised. In state selective protocols, one needs an ensemble of initial states, the size of which decreases with each iteration. We prove that exponential sensitivity to initial states in any quantum system has to be related to downsizing the initial ensemble also exponentially. Our results show that magnifying initial differences of quantum states (a Schrödinger microscope) is possible; however, there is a strict bound on the number of copies needed. PMID:26861076

  1. Near-infrared emitting CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots: synthesis and bright luminescence

    PubMed Central

    2012-01-01

    We present how CdTe0.5Se0.5 cores can be coated with Cd0.5Zn0.5S shells at relatively low temperature (around 200°C) via facile synthesis using organic ammine ligands. The cores were firstly fabricated via a less toxic procedure using CdO, trioctylphosphine (TOP), Se, Te, and trioctylamine. The cores with small sizes (3.2-3.5 nm) revealed green and yellow photoluminescence (PL) and spherical morphologies. Hydrophobic core/shell CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots (QDs) with tunable PL between green and near-infrared (a maximum PL peak wavelength of 735 nm) were then created through a facile shell coating procedure using trioctylphosphine selenium with cadmium and zinc acetate. The QDs exhibited high PL efficiencies up to 50% because of the formation of a protective Cd0.5Zn0.5S shell on the CdTe0.5Se0.5 core, even though the PL efficiency of the cores is low (≤1%). Namely, the slow growth process of the shell plays an important role for getting high PL efficiencies. The properties of the QDs are largely determined by the properties of CdTe0.5Se0.5 cores and shells preparation conditions such as reaction temperature and time. The core/shell QDs exhibited a small size diameter. For example, the average diameter of the QDs with a PL peak wavelength of 735 nm is 6.1 nm. Small size and tunable bright PL makes the QDs utilizable as bioprobes because the size of QD-based bioprobes is considered as the major limitation for their broad applications in biological imaging. PMID:23130948

  2. Application of hybrid SiO2-coated CdTe nanocrystals for sensitive sensing of Cu2+ and Ag+ ions.

    PubMed

    Cao, Yongqiang; Zhang, Aiyu; Ma, Qian; Liu, Ning; Yang, Ping

    2013-01-01

    A new ion sensor based on hybrid SiO2 -coated CdTe nanocrystals (NCs) was prepared and applied for sensitive sensing of Cu(2+) and Ag(+) for the selective quenching of photoluminescence (PL) of NCs in the presence of ions. As shown by ion detection experiments conducted in pure water rather than buffer solution, PL responses of NCs were linearly proportional to concentrations of Cu(2+) and Ag(+) ions < 3 and 7 uM, respectively. Much lower detection limits of 42.37 nM for Cu(2+) and 39.40 nM for Ag(+) were also observed. In addition, the NC quenching mechanism was discussed in terms of the characterization of static and transient optical spectra. The transfer and trapping of photoinduced charges in NCs by surface energy levels of CuS and Ag2 S clusters as well as surface defects generated by the exchange of Cu(2+) and Ag(+) ions with Cd(2+) ion in NCs, resulted in PL quenching and other optical spectra changes, including steady-state absorption and transient PL spectra. It is our hope that these results will be helpful in the future preparation of new ion sensors.

  3. Dummy molecularly imprinted polymers-capped CdTe quantum dots for the fluorescent sensing of 2,4,6-trinitrotoluene.

    PubMed

    Xu, Shoufang; Lu, Hongzhi; Li, Jinhua; Song, Xingliang; Wang, Aixiang; Chen, Lingxin; Han, Shaobo

    2013-08-28

    Molecularly imprinted polymers (MIPs) with trinitrophenol (TNP) as a dummy template molecule capped with CdTe quantum dots (QDs) were prepared using 3-aminopropyltriethoxy silane (APTES) as the functional monomer and tetraethoxysilane (TEOS) as the cross linker through a seed-growth method via a sol-gel process (i.e., DMIP@QDs) for the sensing of 2,4,6-trinitrotoluene (TNT) on the basis of electron-transfer-induced fluorescence quenching. With the presence and increase of TNT in sample solutions, a Meisenheimer complex was formed between TNT and the primary amino groups on the surface of the QDs. The energy of the QDs was transferred to the complex, resulting in the quenching of the QDs and thus decreasing the fluorescence intensity, which allowed the TNT to be sensed optically. DMIP@QDs generated a significantly reduced fluorescent intensity within less than 10 min upon binding TNT. The fluorescence-quenching fractions of the sensor presented a satisfactory linearity with TNT concentrations in the range of 0.8-30 μM, and its limit of detection could reach 0.28 μM. The sensor exhibited distinguished selectivity and a high binding affinity to TNT over its possibly competing molecules of 2,4-dinitrophenol (DNP), 4-nitrophenol (4-NP), phenol, and dinitrotoluene (DNT) because there are more nitro groups in TNT and therefore a stronger electron-withdrawing ability and because it has a high similarity in shape and volume to TNP. The sensor was successfully applied to determine the amount of TNT in soil samples, and the average recoveries of TNT at three spiking levels ranged from 90.3 to 97.8% with relative standard deviations below 5.12%. The results provided an effective way to develop sensors for the rapid recognition and determination of hazardous materials from complex matrices.

  4. Synthesis of CdSe quantum dots for quantum dot sensitized solar cell

    SciTech Connect

    Singh, Neetu Kapoor, Avinashi; Kumar, Vinod; Mehra, R. M.

    2014-04-24

    CdSe Quantum Dots (QDs) of size 0.85 nm were synthesized using chemical route. ZnO based Quantum Dot Sensitized Solar Cell (QDSSC) was fabricated using CdSe QDs as sensitizer. The Pre-synthesized QDs were found to be successfully adsorbed on front ZnO electrode and had potential to replace organic dyes in Dye Sensitized Solar Cells (DSSCs). The efficiency of QDSSC was obtained to be 2.06 % at AM 1.5.

  5. Cheat sensitive quantum bit commitment via pre- and post-selected quantum states

    NASA Astrophysics Data System (ADS)

    Li, Yan-Bing; Wen, Qiao-Yan; Li, Zi-Chen; Qin, Su-Juan; Yang, Ya-Tao

    2014-01-01

    Cheat sensitive quantum bit commitment is a most important and realizable quantum bit commitment (QBC) protocol. By taking advantage of quantum mechanism, it can achieve higher security than classical bit commitment. In this paper, we propose a QBC schemes based on pre- and post-selected quantum states. The analysis indicates that both of the two participants' cheat strategies will be detected with non-zero probability. And the protocol can be implemented with today's technology as a long-term quantum memory is not needed.

  6. Efficient energy transfer from inserted CdTe quantum dots to YVO₄:Eu³⁺ inverse opals: a novel strategy to improve and expand visible excitation of rare earth ions.

    PubMed

    Zhu, Yongsheng; Cui, Shaobo; Chen, Xu; Xu, Wen; Zhou, Pingwei; Wang, Yunfeng; Xu, Lin; Song, Hongwei; Huang, Ling; Huang, Wei

    2014-07-21

    Rare earth (RE)-based phosphors demonstrate sharp emission lines, long lifetimes and high luminescence quantum yields; thus, they have been employed in various photoelectric devices, such as light-emitting diodes (LEDs) and solar spectral converters. However, their applications are largely confined by their narrow excitation bands and small absorption cross sections of 4f-4f transitions. In this paper, we demonstrate a novel strategy to improve and expand the visible excitation bands of Eu(3+) ions through the interface energy transfer (ET) from CdTe quantum dots (QDs) to YVO₄:Eu(3+) inverse opal photonic crystals (IOPCs). The significant effects observed in the CdTe QDs/YVO₄:Eu(3+) IOPCs composites were that the excitation of Eu(3+) ions was continuously extended from 450 to 590 nm and that the emission intensity of the (5)D₀-(7)FJ transitions was enhanced ∼20-fold, corresponding to the intrinsic (7)F₁-(5)D₁ excitation at 538 nm. Furthermore, in the IOPC network, the ET efficiency from the QDs to YVO₄:Eu(3+) was greatly improved because of the suppression of energy migration among the CdTe QDs, which gave an optimum ET efficiency as high as 47%. Besides, the modulation of photonic stop bands (PSBs) on the radiative transition rates of the QDs and Eu(3+) ions was studied, which showed that the decay lifetime constants for Eu(3+) ions were independent of PSBs, while those of QDs demonstrated a suppression in the PSBs. Their physical nature was explained theoretically.

  7. Efficient energy transfer from inserted CdTe quantum dots to YVO4:Eu3+ inverse opals: a novel strategy to improve and expand visible excitation of rare earth ions

    NASA Astrophysics Data System (ADS)

    Zhu, Yongsheng; Cui, Shaobo; Chen, Xu; Xu, Wen; Zhou, Pingwei; Wang, Yunfeng; Xu, Lin; Song, Hongwei; Huang, Ling; Huang, Wei

    2014-06-01

    Rare earth (RE)-based phosphors demonstrate sharp emission lines, long lifetimes and high luminescence quantum yields; thus, they have been employed in various photoelectric devices, such as light-emitting diodes (LEDs) and solar spectral converters. However, their applications are largely confined by their narrow excitation bands and small absorption cross sections of 4f-4f transitions. In this paper, we demonstrate a novel strategy to improve and expand the visible excitation bands of Eu3+ ions through the interface energy transfer (ET) from CdTe quantum dots (QDs) to YVO4:Eu3+ inverse opal photonic crystals (IOPCs). The significant effects observed in the CdTe QDs/YVO4:Eu3+ IOPCs composites were that the excitation of Eu3+ ions was continuously extended from 450 to 590 nm and that the emission intensity of the 5D0-7FJ transitions was enhanced ~20-fold, corresponding to the intrinsic 7F1-5D1 excitation at 538 nm. Furthermore, in the IOPC network, the ET efficiency from the QDs to YVO4:Eu3+ was greatly improved because of the suppression of energy migration among the CdTe QDs, which gave an optimum ET efficiency as high as 47%. Besides, the modulation of photonic stop bands (PSBs) on the radiative transition rates of the QDs and Eu3+ ions was studied, which showed that the decay lifetime constants for Eu3+ ions were independent of PSBs, while those of QDs demonstrated a suppression in the PSBs. Their physical nature was explained theoretically.

  8. A RGB-Type Quantum Dot-based Sensor Array for Sensitive Visual Detection of Trace Formaldehyde in Air.

    PubMed

    Xia, Hui; Hu, Jing; Tang, Jie; Xu, Kailai; Hou, Xiandeng; Wu, Peng

    2016-11-10

    A simple colorimetric sensor array based on red-emitting CdTe QDs and green-colored fluorescein that exhibited RGB-type color change was proposed for visual detection of trace formaldehyde. In the presence of formaldehyde, the red fluorescence from CdTe QDs was quenched while the green fluorescein was inert thus as a reference. Through harvesting the varied quenching efficiency of different ligand-capped CdTe QDs by formaldehyde, a simple sensor array can be constructed for both selective detection of formaldehyde with high sensitivity (LOD of 0.08 ppm) and identification of the existence of potential interference from acetaldehyde. The quenching mechanisms of formaldehyde toward different ligand capped CdTe QDs were studied with fluorescence lifetime, zeta potential, and also theoretical calculations. The results from theoretical calculations were in good agreement with the experimental results. The proposed sensor array was successfully explored for visual analysis of formaldehyde in indoor air samples.

  9. A RGB-Type Quantum Dot-based Sensor Array for Sensitive Visual Detection of Trace Formaldehyde in Air

    NASA Astrophysics Data System (ADS)

    Xia, Hui; Hu, Jing; Tang, Jie; Xu, Kailai; Hou, Xiandeng; Wu, Peng

    2016-11-01

    A simple colorimetric sensor array based on red-emitting CdTe QDs and green-colored fluorescein that exhibited RGB-type color change was proposed for visual detection of trace formaldehyde. In the presence of formaldehyde, the red fluorescence from CdTe QDs was quenched while the green fluorescein was inert thus as a reference. Through harvesting the varied quenching efficiency of different ligand-capped CdTe QDs by formaldehyde, a simple sensor array can be constructed for both selective detection of formaldehyde with high sensitivity (LOD of 0.08 ppm) and identification of the existence of potential interference from acetaldehyde. The quenching mechanisms of formaldehyde toward different ligand capped CdTe QDs were studied with fluorescence lifetime, zeta potential, and also theoretical calculations. The results from theoretical calculations were in good agreement with the experimental results. The proposed sensor array was successfully explored for visual analysis of formaldehyde in indoor air samples.

  10. Highly sensitive detection of caspase-3 activities via a nonconjugated gold nanoparticle-quantum dot pair mediated by an inner-filter effect.

    PubMed

    Li, Jingwen; Li, Xinming; Shi, Xiujuan; He, Xuewen; Wei, Wei; Ma, Nan; Chen, Hong

    2013-10-09

    We describe here a simple fluorometric assay for the highly sensitive detection of caspase-3 activities on the basis of the inner-filter effect of gold nanoparticles (AuNPs) on CdTe quantum dots (QDs). The method takes advantage of the high molar absorptivity of the plasmon band of gold nanoparticles as well as the large absorption band shift from 520 to 680 nm upon nanoparticle aggregation. When labeled with a peptide possessing the caspase-3 cleavage sequence (DEVD), the monodispersed Au-Ps (peptide-modified AuNPs) exhibited a tendency to aggregate when exposed to caspase-3, which induced the absorption band transition from 520 to 680 nm and turned on the fluorescence of the CdTe QDs for caspase-3 sensing. Under optimum conditions, a high sensitivity towards caspase-3 was achieved with a detection limit as low as 18 pM, which was much lower than the corresponding assays based on absorbance or other approaches. Overall, we demonstrated a facile and sensitive approach for caspase-3 detection, and we expected that this method could be potentially generalized to design more fluorescent assays for sensing other bioactive entities.

  11. Fabrication of transparent TiO2 nanotube-based photoanodes for CdS/CdTe quantum co-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Gualdrón-Reyes, A. F.; Cárdenas-Arenas, A.; Martínez, C. A.; Kouznetsov, V. V.; Meléndez, A. M.

    2017-01-01

    In order to fabricate a solar cell, ordered TiO2 nanotube (TNT) arrays were prepared by double anodization. TNT arrays with variable lengths were obtained by changing the duration of the anodizing process of up to 3h. TNT membranes were transferred to indium tin oxide substrates and attached with a B-TiO2 sol. TNT photoanode with the best photoelectrochemical performance was sensitized with CdS by SILAR method. On other hand, CdTe quantum dots prepared via colloidal synthesis were deposited on TNT photoanodes for 2h, 4h and 6h. In addition, TNT/CdS was loaded with CdTe quantum dots for 4 h. Morphology and chemical modification of TiO2 were characterized by FESEM and XPS, while their photoelectrochemical performance was measured by open-circuit photopotential and photovoltammetry under visible light. TiO2 nanotubes grown during 2.5h showed the highest photocurrent due to presence of Ti3+ donor states by N and F co-doping, increasing the number of photogenerated electrons transported to back collector. TNT/CdS/CdTe photoanode reach the highest conversion efficiency under AM 1.5G simulated solar illumination.

  12. Highly Luminescent Hybrid SiO2-Coated CdTe Quantum Dots Retained Initial Photoluminescence Efficiency in Sol-Gel SiO2 Film.

    PubMed

    Sun, Hongsheng; Xing, Yugui; Wu, Qinan; Yang, Ping

    2015-02-01

    A highly luminescent silica film was fabricated using tetraethyl orthosilicate (TEOS) and 3-aminopropyltrimethoxysilane (APS) through a controlled sol-gel reaction. The pre-hydrolysis of TEOS and APS which resulted in the mixture of TEOS and APS in a molecular level is a key for the formation of homogenous films. The aminopropyl groups in APS play an important role for obtaining homogeneous film with high photoluminescence (PL). Red-emitting hybrid SiO2-coated CdTe nano-crystals (NCs) were fabricated by a two-step synthesis including a thin SiO2 coating via a sol-gel process and a subsequent refluxing using green-emitting CdTe NCs. The hybrid SiO2-coated CdTe NCs were embedded in a functional SiO2 film via a two-step process including adding the NCs in SiO2 sol with a high viscosity and almost without ethanol and a subsequent spinning coating. The hybrid SiO2-coated CdTe NCs retained their initial PL efficiency (54%) in the film. Being encapsulated with the hybrid NCs in the film, no change on the absorption and PL spectra of red-emitting CdTe NCs (632 nm) was observed. This indicates the hybrid NCs is stable enough during preparation. This phenomenon is ascribed to the controlled sol-gel process and a hybrid SiO2 shell on CdTe NCs. Because these films exhibited high PL efficiency and stability, they will be utilizable for potential applications in many fields.

  13. Quantum dot bio-conjugate: as a western blot probe for highly sensitive detection of cellular proteins

    NASA Astrophysics Data System (ADS)

    Kale, Sonia; Kale, Anup; Gholap, Haribhau; Rana, Abhimanyu; Desai, Rama; Banpurkar, Arun; Ogale, Satishchandra; Shastry, Padma

    2012-03-01

    In the present study, we report a quantum dot (QD)-tailored western blot analysis for a sensitive, rapid and flexible detection of the nuclear and cytoplasmic proteins. Highly luminescent CdTe and (CdTe)ZnS QDs are synthesized by aqueous method. High resolution transmission electron microscopy, Raman spectroscopy, fourier transform infrared spectroscopy, fluorescence spectroscopy and X-ray diffraction are used to characterize the properties of the quantum dots. The QDs are functionalized with antibodies of prostate apoptosis response-4 (Par-4), poly(ADP-ribose) polymerases and β actin to specifically bind with the proteins localized in the nucleus and cytoplasm of the cells, respectively. The QD-conjugated antibodies are used to overcome the limitations of conventional western blot technique. The sensitivity and rapidity of protein detection in QD-based approach is very high, with detection limits up to 10 pg of protein. In addition, these labels provide the capability of enhanced identification and localization of marker proteins in intact cells by confocal laser scanning microscopy.

  14. Cyclic voltammetry as a sensitive method for in situ probing of chemical transformations in quantum dots.

    PubMed

    Osipovich, Nikolai P; Poznyak, Sergei K; Lesnyak, Vladimir; Gaponik, Nikolai

    2016-04-21

    The application of electrochemical methods for the characterization of colloidal quantum dots (QDs) attracts considerable attention as these methods may allow for monitoring of some crucial parameters, such as energetic levels of conduction and valence bands as well as surface traps and ligands under real conditions of colloidal solution. In the present work we extend the applications of cyclic voltammetry (CV) to in situ monitoring of degradation processes of water-soluble CdTe QDs. This degradation occurs under lowering of pH to the values around 5, i.e. under conditions relevant to bioimaging applications of these QDs, and is accompanied by pronounced changes of their photoluminescence. Observed correlations between characteristic features of CV diagrams and the fluorescence spectra allowed us to propose mechanisms responsible for evolution of the photoluminescence properties as well as degradation pathway of CdTe QDs at low pH.

  15. Excitons and multi-excitons in single CdTe quantum dots probed by near-field spectroscopy

    NASA Astrophysics Data System (ADS)

    Brun, M.; Huant, S.; Woehl, J. C.; Motte, J.-F.; Marsal, L.; Mariette, H.

    2002-03-01

    A near-field optical spectroscopy study of a single CdTe/ZnTe quantum dot at low temperatures is presented. While the photoluminescence spectrum at low excitation power reveals only one single sharp peak due to the radiative recombination of excitons (X) in the single dot, several additional sharp peaks appear with increasing excitation density. The dominant features are ascribed to exciton complexes and charged exciton complexes such as negatively charged excitons (X -), neutral (2X and 3X) and negative (2X - and 3X -) biexcitons and triexcitons. Exciton charging arises due to efficient hole trapping by residual acceptors in the barrier material. This partly inhibits the formation of biexcitons and triexcitons. A spectral feature appearing close to the X - peak is tentatively assigned to X 2- negative excitons. This feature is found to shift to the red with increasing power: two possible explanations for this unexpected behaviour are proposed.

  16. Synthesis and application of intercellular Ca2+-sensitive fluorescent probe based on quantum dots.

    PubMed

    Xia, Jinzhi; Yu, Ying; Liao, Qiumei; Cao, Yujuan; Lin, Bixia; Hu, Xiaogang; Wu, Jianzhong

    2013-01-01

    A novel Ca(2+)-sensitive fluorescent probe was synthesized and characterized with a coupled method that coupled di[2-(N,N-dicarboxylmethyl)amino]ethyl ether (EGTA) to the surface of mercaptoethylamine-modified CdTe quantum dots (CdTe/MA-EGTA QDs). The application of this probe to detect intercellular Ca(2+) change in the leaf cells of Arabidopsis thaliana was studied. Results from transmission electron micrographs showed that the particle size of CdTe/MA-EGTA was about 3-4 nm; the fluorescent spectrum indicated that the excitation spectral ranged from 350 to 490 nm with a narrow and symmetric emission spectral peak at 565 nm when excited by 400 nm, and capillary electrophoresis demonstrated that CdTe/MA-EGTA was obtained by a coupling reaction. When the detected conditions were set as an excitation wavelength of 514 nm and detection wavelength of 561-604 nm, the increase of Ca(2+) in A. thaliana leaf cells and the rapidly quenching effect of fluorescence signal induced by exogenous treatment of jasmonate acid (JA) could be measured using laser scanning confocal microscopy. The quenching rate of traditional Ca(2+)-sensitive fluorescent probe Fluo-3 reached about 80% within a minute when exciting at 488 nm, which was much faster than the novel fluorescent probe CdTe/MA-EGTA. CdTe/MA-EGTA, however, was better at resisting photo bleaching and was more suitable for long-term tracking and monitoring than Fluo-3. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. Thiol-capped CdTe quantum dots with two-photon excitation for imaging high autofluorescence background living cells.

    PubMed

    Wang, Tao; Chen, Ji-Yao; Zhen, Shen; Wang, Pei-Nan; Wang, Chang-Chun; Yang, Wu-Li; Peng, Qian

    2009-07-01

    To effectively image living cells with quantum dots (QDs), particularly for those cells containing high content of native fluorophores, the two-photon excitation (TPE) with a femto-second 800 nm laser was employed and compared with the single-photon excitations (SPE) of 405 nm and 488 nm in BY-2 Tobacco (BY-2-T) and human hepatocellular carcinoma (QGY) cells, respectively. The 405 nm SPE produced the bright photoluminescence (PL) signals of cellular QDs but also induced a strong autofluorescence(AF) from the native fluorophores like flavins in cells. The AF occupied about 30% and 13% of the total signals detected in QD imaging channel in the BY-2-T and QGY cells, respectively. With the excitation of 488 nm SPE, the PL signals were lower than those excited with the 405 nm SPE, although the AF signals were also reduced. The 800 nm TPE generated the best PL images of intracellular QDs with the highest signal ratio of PL to AF, because the two-photon absorption cross section of QDs is much higher than that of the native fluorophores. By means of the TPE, the reliable cellular imaging with QDs, even for the cells having the high AF background, can be achieved.

  18. Sensitivity to small perturbations in systems of large quantum spins

    NASA Astrophysics Data System (ADS)

    Elsayed, Tarek A.; Fine, Boris V.

    2015-10-01

    We investigate the sensitivity of nonintegrable large-spin quantum lattices to small perturbations with a particular focus on the time reversal experiments known in statistical physics as ‘Loschmidt echoes’ and in nuclear magnetic resonance (NMR) as ‘magic echoes.’ Our numerical simulations of quantum spin-7\\frac{1}{2} clusters indicate that there is a regime where Loschmidt echoes exhibit nearly exponential sensitivity to small perturbations with characteristic constant approximately equal to twice the value of the largest Lyapunov exponent of the corresponding classical spin clusters. The above theoretical results are verifiable by NMR experiments on solids containing large-spin nuclei.

  19. Amplified solid-state electrochemiluminescence detection of cholesterol in near-infrared range based on CdTe quantum dots decorated multiwalled carbon nanotubes@reduced graphene oxide nanoribbons.

    PubMed

    Huan, Juan; Liu, Qian; Fei, Airong; Qian, Jing; Dong, Xiaoya; Qiu, Baijing; Mao, Hanping; Wang, Kun

    2015-11-15

    An amplified solid-state electrochemiluminescence (ECL) biosensor for detection of cholesterol in near-infrared (NIR) range was constructed based on CdTe quantum dots (QDs) decorated multiwalled carbon nanotubes@reduced graphene nanoribbons (CdTe-MWCNTs@rGONRs), which were prepared by electrostatic interactions. The CdTe QDs decorated on the MWCNTs@rGONRs resulted in the amplified ECL intensity by ~4.5 fold and decreased onset potential by ~100 mV. By immobilization of the cholesterol oxidase (ChOx) and NIR CdTe-MWCNTs@rGONRs on the electrode surface, a solid-state ECL biosensor for cholesterol detection was constructed. When cholesterol was added to the detection solution, the immobilized ChOx catalyzed the oxidation of cholesterol to generate H2O2, which could be used as the co-reactant in the ECL system of CdTe-MWCNTs@rGONRs. The as-prepared biosensor exhibited good performance for cholesterol detection including good reproducibility, selectivity, and acceptable linear range from 1 μM to 1mM with a relative low detection limit of 0.33 μM (S/N=3). The biosensor was successfully applied to the determination of cholesterol in biological fluid and food sample, which would open a new possibility for development of solid-state ECL biosensors with NIR emitters.

  20. Evaluation of current sensitivity of quantum flux parametron

    NASA Astrophysics Data System (ADS)

    Yamanashi, Yuki; Matsushima, Takashi; Takeuchi, Naoki; Yoshikawa, Nobuyuki; Ortlepp, Thomas

    2017-08-01

    Current sensitivity of a quantum flux parametron (QFP) was evaluated by measuring gray zone width on the basis of both circuit simulation and measurements, for superconducting sensing systems composed of a superconducting sensor array and superconducting read-out and signal processing circuits. Simulation results indicate a narrow gray zone width can be obtained by decreasing inductances comprising the QFP. Moreover, both high-sensitivity and low-power operation of the QFP can be realized by using optimized circuit parameters with an excitation current that has long rise time. A gray zone width of approximately 0.5 μA, which is smaller than that of the Josephson current comparator based on a single flux quantum circuit, was obtained experimentally, using a trapezoidal excitation current with rise time of 50 μs. These results indicate the QFP is promising for the read-out circuit in superconducting sensing systems, due to its high sensitivity and low power consumption.

  1. Interfacial Engineering for Quantum-Dot-Sensitized Solar Cells.

    PubMed

    Shen, Chao; Fichou, Denis; Wang, Qing

    2016-04-20

    Quantum-dot-sensitized solar cells (QDSCs) are promising solar-energy-conversion devices, as low-cost alternatives to the prevailing photovoltaic technologies. Compared with molecular dyes, nanocrystalline quantum dot (QD) light absorbers exhibit higher molar extinction coefficients and a tunable photoresponse. However, the power-conversion efficiencies (PCEs) of QDSCs are generally below 9.5 %, far behind their molecular sensitizer counterparts (up to 13 %). These low PCEs have been attributed to a large free-energy loss during sensitizer regeneration, energy loss during the charge-carrier transport and transfer processes, and inefficient charge separation at the QD/electrolyte interfaces, and various interfacial engineering strategies for enhancing the PCE and cell stability have been reported. Herein, we review recent progress in the interfacial engineering of QDSCs and discuss future prospects for the development of highly efficient and stable QDSCs.

  2. The relationship between photoluminescence (PL) decay and crystal growth kinetics in thioglycolic acid (TGA) capped CdTe quantum dots (QDs).

    PubMed

    Lv, Xiangying; Xue, Xiaogang; Huang, Yang; Zhuang, Zanyong; Lin, Zhang

    2014-06-21

    The PL lifetime optimization of CdTe QDs capped with TGA has yet to be understood from a perspective of growth kinetics. In this work, the growth kinetics and PL properties of CdTe QDs growing in aqueous solutions of two TGA concentrations, 0 mM and 57 mM, were systematically investigated using UV, TEM, and PL methods. CdTe QDs in 0 mM TGA solution were found to follow the mixed OA (Oriented Attachment)-OR (Ostwald Ripening) growth kinetics. The PL peaks experienced a red-shift with almost unchanged intensity and the PL lifetimes increased gradually. In 57 mM TGA solution, the QDs followed the OA dominated growth mechanism. The PL peak broadened greatly with a red-shift and its intensity decreased significantly. The PL lifetime increased much higher than that in 0 mM TGA solution. Based on the different growth kinetic models of the two systems, we suggest that in the low (0 mM) TGA solution, the increased surface defects induced by TGA desorption and the existence of partial internal defects caused by OA growth were the main reasons for the gradual increase of PL lifetime, while in high (57 mM) TGA solution, the increase of PL lifetime was ascribed to the abundant internal defects produced by OA collision. Finally, kinetic data showed the effect of the TGA concentration on crystal growth and PL lifetime of CdTe QDs. The results might provide guidance for understanding the mechanism behind the phenomena of ligand-related PL properties.

  3. High-Sensitivity Charge Detection with a Single-Lead Quantum Dot for Scalable Quantum Computation

    NASA Astrophysics Data System (ADS)

    House, M. G.; Bartlett, I.; Pakkiam, P.; Koch, M.; Peretz, E.; van der Heijden, J.; Kobayashi, T.; Rogge, S.; Simmons, M. Y.

    2016-10-01

    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 (<15 μ s ) single-spin readout in quantum-information applications, with a significantly reduced geometric footprint compared to the rf SET.

  4. Carbon nanotube quantum dots as highly sensitive THz spectrometers

    NASA Astrophysics Data System (ADS)

    Rinzan, Mohamed; Jenkins, Greg; Drew, Dennis; Shafranjuk, Serhii; Barbara, Paola

    2012-02-01

    We show that carbon nanotube quantum dots (CNT-Dots) coupled to antennas are extremely sensitive, broad-band, terahertz quantum detectors. Their response is due to photon-assisted single-electron tunneling (PASET)[1], but cannot be fully understood with orthodox PASET models[2]. We consider intra-dot excitations and non-equilibrium cooling to explain the anomalous response. REFERENCES: [1] Y. Kawano, S. Toyokawa, T. Uchida and K. Ishibashi, THz photon assisted tunneling in carbon-nanotube quantum dots, Journal of Applied Physics 103, 034307 (2008). [2] P. K. Tien and J. P. Gordon, Multiphoton Process Observed in the Interaction of Microwave Fields with the Tunneling between Superconductor Films, Phys. Rev. 129, 647 (1963).

  5. Highly sensitive humidity sensing properties of carbon quantum dots films

    SciTech Connect

    Zhang, Xing; Ming, Hai; Liu, Ruihua; Han, Xiao; Kang, Zhenhui; Liu, Yang; Zhang, Yonglai

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► A humidity sensing device was fabricated based on carbon quantum dots (CQDs) films. ► The conductivity of the CQDs films shows a linear and rapid response to atmosphere humidity. ► The humidity sensing property was due to the hydrogen bonds between the functional groups on CQDs. -- Abstract: We reported the fabrication of a humidity sensing device based on carbon quantum dots (CQDs) film. The conductivity of the CQDs film has a linear and rapid response to relative humidity, providing the opportunity for the fabrication of humidity sensing devices. The mechanism of our humidity sensor was proposed to be the formation of hydrogen bonds between carbon quantum dots and water molecules in the humidity environment, which significantly promote the electrons migration. In a control experiment, this hypothesis was confirmed by comparing the humidity sensitivity of candle soot (i.e. carbon nanoparticles) with and without oxygen containing groups on the surfaces.

  6. Enhancing sensitivity in quantum metrology by Hamiltonian extensions

    NASA Astrophysics Data System (ADS)

    Fraïsse, Julien Mathieu Elias; Braun, Daniel

    2017-06-01

    A well-studied scenario in quantum parameter estimation theory arises when the parameter to be estimated is imprinted on the initial state by a Hamiltonian of the form θ G . For such "phase-shift Hamiltonians" it has been shown that one cannot improve the channel quantum Fisher information by adding ancillas and letting the system interact with them. Here we investigate the general case, where the Hamiltonian is not necessarily a phase shift, and show that in this case in general it is possible to increase the quantum channel information and to reach an upper bound. This can be done by adding a term proportional to the derivative of the Hamiltonian, or by subtracting a term from the original Hamiltonian. Neither method makes use of any ancillas, which shows that, for quantum channel estimation with an arbitrary parameter-dependent Hamiltonian, entanglement with an ancillary system is not necessary to reach the best possible sensitivity. By adding an operator to the Hamiltonian we can also modify the time scaling of the channel quantum Fisher information. We illustrate our techniques with nitrogen vacancy center magnetometry and the estimation of the direction of a magnetic field in a given plane using a single spin-1 as probe.

  7. Quantum protocol for cheat-sensitive weak coin flipping.

    PubMed

    Spekkens, R W; Rudolph, Terry

    2002-11-25

    We present a quantum protocol for the task of weak coin flipping. We find that, for one choice of parameters in the protocol, the maximum probability of a dishonest party winning the coin flip if the other party is honest is 1/sqrt[2]. We also show that if parties restrict themselves to strategies wherein they cannot be caught cheating, their maximum probability of winning can be even smaller. As such, the protocol offers additional security in the form of cheat sensitivity.

  8. Development of a H2 O2 -sensitive quantum dots-based fluorescent sandwich ELISA for sensitive detection of bovine β-lactoglobulin by monoclonal antibody.

    PubMed

    He, Shengfa; Li, Xin; Gao, Jinyan; Tong, Ping; Chen, Hongbing

    2017-06-16

    Bovine β-lactoglobulin (BLG) is the major allergen in cows' milk, and the specific epitope plays a key role in food allergy. Developing a method specifically bind to the IgE epitope is necessary for testing BLG and its allergenic residues. The monoclonal antibody (1G9) specific to the IgE linear epitope for BLG was identified as high affinity and specificity. Based on 1G9, a sensitive fluorescent sandwich enzyme-linked immunosorbent assay (sELISA) was successfully developed using catalase-mediated fluorescence quenching of thiolated CdTe quantum dots in the presence of hydrogen peroxide as fluorescent signal output. The fluorescent sELISA showed high sensitivity and specificity, the limit of detection was 0.49 ng mL(-1) , which was 16-fold lower than horseradish peroxidase (HRP)-based sELISA. The linear range for BLG detection were 125-4000 ng mL(-1) (r = 0.9939) and 0.48-62.5 ng mL(-1) (r = 0.9919). The recoveries and coefficients of variation were 94.25-109.83% and 4.38-20.29%, respectively. Allergenic residues were also detected in hydrolysed infant formulas. The results of fluorescent sELISA showed good performance as HRP-based sELISA and commercial sELISA kit. This proposed fluorescent sELISA could be employed to detect BLG and its allergenic residues in food with highly sensitivity, reliability, and recovery. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  9. Acquisition of a Recondensing Cryostat for Ultra-Sensitive Charge Detection of Quantum Systems

    DTIC Science & Technology

    2014-10-21

    Acquisition of a Recondensing Cryostat for Ultra - Sensitive Charge Detection of Quantum Systems The funding provided by this grant was used to...accelerate our efforts to develop cavity-embedded Cooper pair transistors for ultra sensitive charge detection of quantum systems such as quantum dots and...reviewed journals: Final Report: Acquisition of a Recondensing Cryostat for Ultra -Sensitive Charge Detection of Quantum Systems Report Title The funding

  10. Constructive and destructive quantum interference sensitive to quantum vacuum mode structure in a metallic waveguide

    SciTech Connect

    Shen Jianqi

    2011-12-15

    Quantum vacuum mode structure can be changed due to length scale fluctuation of the cross section of a metallic waveguide. Such a structure change in vacuum modes (particularly in cutoff vacuum modes) would lead to dramatic enhancement or inhibition of spontaneous emission decay of atoms and, if the waveguide is filled with a dilute atomic vapor consisting of quantum-coherent atoms of a four-level tripod-configuration system, an optical wave propagating inside the waveguide can be coherently manipulated by tunable constructive and destructive quantum interference between two control transitions (driven by two control fields) in a quite unusual way (e.g., the optical response, in which a three-level dark state is involved, is sensitive to the waveguide dimension variations at certain positions of resonance of the atomic spontaneous emission decay rate). Therefore, an intriguing effect that can be employed to designs of new photonic and quantum optical devices could be achieved based on the present mechanisms of quantum-vacuum manipulation and quantum coherence control.

  11. Photoisomerization of alfa calcidol by a sensitized quantum chain reaction.

    PubMed

    Estruch, Gastón A; Aramendía, Pedro F

    2012-01-01

    The production of vitamin D3 is a pharmaceutically relevant process, producing high added-value products. Precursors are extracts from vegetal origin but bearing mainly an E geometry in the 5,6 double bond. The synthesis of vitamin D3 (5-E-α-calcidol) with the correct Z stereochemistry in the 5,6 double bond from the E isomer using anthracene and triethylamine (TEA) as the sensitizer system was studied from the kinetic and mechanistic point of view. The sensitized isomerization of E-calcidol by irradiation of anthracene takes place only in deoxygenated solution and yields the Z isomer in ca 5% yield in the photostationary state. When TEA is added to the system, the E-Z reaction is not inhibited by oxygen any more, the quantum yield of photoisomerization to the Z isomer grows linearly with the concentration of E-calcidol, while conversions higher than 95% to the Z isomer are reached in the photostationary state and E-Z quantum yields as high as 45 at [E-calcidol] = 25 mM are reached. If TEA is replaced by 1,4-diazabicyclo[2.2.2]octane, the reaction rate drops to one-third at the same amine concentration. The observations can be explained by a quantum chain reaction mechanism. The high conversion achieved eliminates the need of isomer separation. © 2011 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2011 The American Society of Photobiology.

  12. Enhanced anodic electrochemiluminescence of CdTe quantum dots based on electrocatalytic oxidation of a co-reactant by dendrimer-encapsulated Pt nanoparticles and its application for sandwiched immunoassays.

    PubMed

    Ren, Lu-Lu; Dong, Hao; Han, Ting-Ting; Chen, Yun; Ding, Shou-Nian

    2017-09-21

    Herein, we synthesized Pt dendrimer-encapsulated nanoparticles (Pt DENs) using amine-terminated sixth-generation polyamidoamine dendrimers. The enhanced and stable anodic electrochemiluminescence (ECL) of 3-mercaptopropionic acid-capped CdTe quantum dots (QDs) in a tripropylamine solution was achieved owing to Pt DENs. The reason may be that Pt DENs exhibit high catalytic electrochemical oxidation in the presence of tripropylamine and excellent conductive property. Inspired by this, Pt DENs were conjugated with Fe3O4@SiO2 nanoparticles and served as nano-carriers. The capture antibodies were immobilized on the Fe3O4@SiO2-Pt DEN nanocomposites, which possess many attractive advantages such as the ease of bioconjugation, large specific surface area, and convenience of magnetic separation. Fluorescence microscopy images and UV-vis spectra were used to verify the immobilization of capture antibodies on the nanocomposites. The CdTe QDs were applied as signal labels for conjugation of nanocomposites with detection antibodies, which were characterized by agarose gel electrophoresis. Electrochemical impedance spectroscopy and cyclic voltammetry demonstrated the successful preparation of an ECL immunosensor. Under the optimal conditions, the proposed immunosensor provided a wide linear range from 0.005 ng mL(-1) to 150 ng mL(-1) with a detection limit of 0.2 pg mL(-1) (S/N = 3) for the detection of carcinoembryonic antigen. Moreover, the immunosensor showed good performance for the detection of carcinoembryonic antigen in serum samples as well as great potential in clinical bioassay.

  13. Security bound of cheat sensitive quantum bit commitment

    PubMed Central

    He, Guang Ping

    2015-01-01

    Cheat sensitive quantum bit commitment (CSQBC) loosens the security requirement of quantum bit commitment (QBC), so that the existing impossibility proofs of unconditionally secure QBC can be evaded. But here we analyze the common features in all existing CSQBC protocols, and show that in any CSQBC having these features, the receiver can always learn a non-trivial amount of information on the sender's committed bit before it is unveiled, while his cheating can pass the security check with a probability not less than 50%. The sender's cheating is also studied. The optimal CSQBC protocols that can minimize the sum of the cheating probabilities of both parties are found to be trivial, as they are practically useless. We also discuss the possibility of building a fair protocol in which both parties can cheat with equal probabilities. PMID:25796977

  14. Security bound of cheat sensitive quantum bit commitment.

    PubMed

    He, Guang Ping

    2015-03-23

    Cheat sensitive quantum bit commitment (CSQBC) loosens the security requirement of quantum bit commitment (QBC), so that the existing impossibility proofs of unconditionally secure QBC can be evaded. But here we analyze the common features in all existing CSQBC protocols, and show that in any CSQBC having these features, the receiver can always learn a non-trivial amount of information on the sender's committed bit before it is unveiled, while his cheating can pass the security check with a probability not less than 50%. The sender's cheating is also studied. The optimal CSQBC protocols that can minimize the sum of the cheating probabilities of both parties are found to be trivial, as they are practically useless. We also discuss the possibility of building a fair protocol in which both parties can cheat with equal probabilities.

  15. Security bound of cheat sensitive quantum bit commitment

    NASA Astrophysics Data System (ADS)

    He, Guang Ping

    2015-03-01

    Cheat sensitive quantum bit commitment (CSQBC) loosens the security requirement of quantum bit commitment (QBC), so that the existing impossibility proofs of unconditionally secure QBC can be evaded. But here we analyze the common features in all existing CSQBC protocols, and show that in any CSQBC having these features, the receiver can always learn a non-trivial amount of information on the sender's committed bit before it is unveiled, while his cheating can pass the security check with a probability not less than 50%. The sender's cheating is also studied. The optimal CSQBC protocols that can minimize the sum of the cheating probabilities of both parties are found to be trivial, as they are practically useless. We also discuss the possibility of building a fair protocol in which both parties can cheat with equal probabilities.

  16. Development of dual-emission ratiometric probe-based on fluorescent silica nanoparticle and CdTe quantum dots for determination of glucose in beverages and human body fluids.

    PubMed

    Zhai, Hong; Feng, Ting; Dong, Lingyu; Wang, Liyun; Wang, Xiangfeng; Liu, Hailing; Liu, Yuan; Chen, Luan; Xie, MengXia

    2016-08-01

    A novel dual emission ratiometric fluorescence probe for determination of glucose has been developed. The reference dye fluorescence isothiocyanate (FITC) has been encapsulated in the silica nanoparticles and then the red emission CdTe QDs were grafted on the surface of the silica particles to obtain the fluorescence probe. With glucose and dopamine as substrates, the glucose level was proportional to the fluorescence ratio change of above probe caused by dopamine oxidation, which was produced via bienzyme catalysis (glucose oxidase and horseradish peroxidase). The established approach was sensitive and selective, and has been applied to determine the glucose in beverage, urine and serum samples. The average recoveries of the glucose at various spiking levels ranged from 95.5% to 108.9% with relative standard deviations from 1.5% to 4.3%. The results provided a clue to develop sensors for rapid determination of the target analytes from complex matrices.

  17. Efficient eco-friendly inverted quantum dot sensitized solar cells.

    PubMed

    Park, Jinhyung; Sajjad, Muhammad T; Jouneau, Pierre-Henri; Ruseckas, Arvydas; Faure-Vincent, Jérôme; Samuel, Ifor D W; Reiss, Peter; Aldakov, Dmitry

    2016-01-21

    Recent progress in quantum dot (QD) sensitized solar cells has demonstrated the possibility of low-cost and efficient photovoltaics. However, the standard device structure based on n-type materials often suffers from slow hole injection rate, which may lead to unbalanced charge transport. We have fabricated efficient p-type (inverted) QD sensitized cells, which combine the advantages of conventional QD cells with p-type dye sensitized configurations. Moreover, p-type QD sensitized cells can be used in highly promising tandem configurations with n-type ones. QDs without toxic Cd and Pb elements and with improved absorption and stability were successfully deposited onto mesoporous NiO electrode showing good coverage and penetration according to morphological analysis. Detailed photophysical charge transfer studies showed that high hole injection rates (10(8) s(-1)) observed in such systems are comparable with electron injection in conventional n-type QD assemblies. Inverted solar cells fabricated with various QDs demonstrate excellent power conversion efficiencies of up to 1.25%, which is 4 times higher than the best values for previous inverted QD sensitized cells. Attempts to passivate the surface of the QDs show that traditional methods of reduction of recombination in the QD sensitized cells are not applicable to the inverted architectures.

  18. Quantum bit commitment with cheat sensitive binding and approximate sealing

    NASA Astrophysics Data System (ADS)

    Li, Yan-Bing; Xu, Sheng-Wei; Huang, Wei; Wan, Zong-Jie

    2015-04-01

    This paper proposes a cheat-sensitive quantum bit commitment scheme based on single photons, in which Alice commits a bit to Bob. Here, Bob’s probability of success at cheating as obtains the committed bit before the opening phase becomes close to \\frac{1}{2} (just like performing a guess) as the number of single photons used is increased. And if Alice alters her committed bit after the commitment phase, her cheating will be detected with a probability that becomes close to 1 as the number of single photons used is increased. The scheme is easy to realize with present day technology.

  19. Quantum-Dot-Sensitized Solar Cell with Unprecedentedly High Photocurrent

    PubMed Central

    Lee, Jin-Wook; Son, Dae-Yong; Ahn, Tae Kyu; Shin, Hee-Won; Kim, In Young; Hwang, Seong-Ju; Ko, Min Jae; Sul, Soohwan; Han, Hyouksoo; Park, Nam-Gyu

    2013-01-01

    The reported photocurrent density (JSC) of PbS quantum dot (QD)-sensitized solar cell was less than 19 mA/cm2 despite the capability to generate 38 mA/cm2, which results from inefficient electron injection and fast charge recombination. Here, we report on a PbS:Hg QD-sensitized solar cell with an unprecedentedly high JSC of 30 mA/cm2. By Hg2+ doping into PbS, JSC is almost doubled with improved stability. Femtosecond transient study confirms that the improved JSC is due to enhanced electron injection and suppressed charge recombination. EXAFS reveals that Pb-S bond is reinforced and structural disorder is reduced by interstitially incorporated Hg2+, which is responsible for the enhanced electron injection, suppressed recombination and stability. Thanks to the extremely high JSC, power conversion efficiency of 5.6% is demonstrated at one sun illumination. PMID:23308343

  20. A RGB-Type Quantum Dot-based Sensor Array for Sensitive Visual Detection of Trace Formaldehyde in Air

    PubMed Central

    Xia, Hui; Hu, Jing; Tang, Jie; Xu, Kailai; Hou, Xiandeng; Wu, Peng

    2016-01-01

    A simple colorimetric sensor array based on red-emitting CdTe QDs and green-colored fluorescein that exhibited RGB-type color change was proposed for visual detection of trace formaldehyde. In the presence of formaldehyde, the red fluorescence from CdTe QDs was quenched while the green fluorescein was inert thus as a reference. Through harvesting the varied quenching efficiency of different ligand-capped CdTe QDs by formaldehyde, a simple sensor array can be constructed for both selective detection of formaldehyde with high sensitivity (LOD of 0.08 ppm) and identification of the existence of potential interference from acetaldehyde. The quenching mechanisms of formaldehyde toward different ligand capped CdTe QDs were studied with fluorescence lifetime, zeta potential, and also theoretical calculations. The results from theoretical calculations were in good agreement with the experimental results. The proposed sensor array was successfully explored for visual analysis of formaldehyde in indoor air samples. PMID:27830733

  1. Computational studies of quantum dot sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kolesov, Grigory

    This thesis presents a computational study of quantum dot (QD) sensitized solar cells. First part deals with the non-equilibrium many-body theory or non-equilibrium Green's function (NEGF) theory. In this approach I study electron dynamics in the quantum-dot sensitized solar cell subjected to time-dependent fields. NEGF theory, because it does not impose any conditions on a perturbation, is the fundamental one to describe ultrafast processes in small, strongly correlated systems and/or in strong fields. In this research I do not only perform analytical derivation, but also design and implement spectral numerical solution for the resulting complex system of partial integrodifferential equations. This numerical solution yielded an order of magnitude speedup over the methods used previously in the field. The forth chapter of this thesis deals with calculation of optical properties and the ground state configuration of Zn2SnO4 (ZTO). ZTO is used by experimentalists in UW to grow nanorods which are then sensitized by QDs. ZTO is a challenging material for computational analysis because of its inverse spinel structure; thus it has an immense number of configurations matching the X-ray diffraction experiments. I've applied a cluster expansion method and have found the ground state configuration and phase diagram for ZTO. Calculations of optical properties of ground state bulk ZTO were done with a recently developed DFT functional. The optical band gap obtained in these calculations matched the experimental value. The last chapter describes development of the general simulator for interdigitated array electrodes. The application of this simulation together with the experiments may lead to understanding of reaction parameters and mechanisms important for development of electrochemical solar cells.

  2. A carbon dots-CdTe quantum dots fluorescence resonance energy transfer system for the analysis of ultra-trace chlortoluron in water.

    PubMed

    Tao, Huilin; Liao, Xiufen; Sun, Chao; Xie, Xiangli; Zhong, Fuxin; Yi, Zhongsheng; Huang, Yipeng

    2015-02-05

    In this paper, a fluorescence resonance energy transfer (FRET) system between fluorescence carbon dots (CDs, donor) and CdTe quantum dots (CdTe, acceptor) was constructed, and a novel platform for sensitive and selective determination of chlortoluron was accordingly proposed. It was found that in Tris-HCl buffer solution at pH=8.7, energy transfer from CDs to CdTe occurred, which resulted in a great enhancement of the fluorescence intensity of CdTe. Upon the addition of chlortoluron, in terms of strong interaction between chlortoluron and CdTe QDs through the formation of chlortoluron-CdTe ground state complex, resulted in CdTe fluorescence quenching. Under optimal conditions, in range of 2.4×10(-10)molL(-1)-8.5×10(-8)molL(-1), the change of CdTe fluorescence intensity was in good linear relationship with the chlortoluron concentration, and the detection limit was 7.8×10(-11)molL(-1) (S/N=3). Most of common relevant substance, cations and anions did not interfere with the detection of chlortoluron. The proposed method was applied to determine chlortoluron in water samples with satisfactory results. Published by Elsevier B.V.

  3. Theory and development of position-sensitive quantum calorimeters

    NASA Astrophysics Data System (ADS)

    Figueroa Feliciano, Enectali

    Quantum calorimeters are being developed as imaging spectrometers for future X-ray astrophysics observatories. Much of the science to be done by these instruments could benefit greatly from larger focal-plane coverage of the detector (without increasing pixel size). An order of magnitude more area will greatly increase the science throughput of these future instruments. One of the main deterrents to achieving this goal is the complexity of the readout schemes involved. We devised a way to increase the number of pixels from the current baseline designs by an order of magnitude without increasing the number of channels required for readout. The instrument is a high energy resolution, distributed-readout imaging spectrometer called a Position-Sensitive Transition-Edge Sensor (PoST). A PoST is a quantum calorimeter consisting of two Transition-Edge Sensors (TESs) on the ends of a long absorber to do one-dimensional imaging spectroscopy. Comparing rise time and energy information, the position of the event in the PoST is determined. Energy is inferred from the sum of the two pulses. We develop a generalized theoretical formalism for distributed-readout calorimeters and apply it to our devices. We derive the noise theory and calculate the theoretical energy resolution of a PoST. Our calculations show that a 7-pixel PoST with 6˜keV saturation energy can achieve 2.3˜eV resolution, making this a competitive design for future quantum calorimeter instruments. For this thesis we fabricated 7- and 15-pixel PoSTs using Mo/Au TESs and gold absorbers, and moved from concept drawings on scraps of napkins to a 32 eV at 1.5 keV energy resolution 7-pixel PoST calorimeter.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

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

    PubMed

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

    2017-02-05

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

  6. Enhancing reactive species generation upon photo-activation of CdTe quantum dots for the chemiluminometric determination of unreacted reagent in UV/S2O8(2-) drug degradation process.

    PubMed

    Santana, Rodolfo M M; Oliveira, Thaís D; Rodrigues, S Sofia M; Frigerio, Christian; Santos, João L M; Korn, Mauro

    2015-04-01

    A new chemiluminescence (CL) flow method for persulfate determination was developed based on luminol oxidation by in-line generated radicals. Reactive oxygen species (ROS) generated by CdTe quantum dots (QDs) under a low energetic radiation (visible light emitted by LEDs) promoted the decomposition of persulfate ion (S2O8(2-)) into sulfate radical (SO4(∙-)), leading to subsequent radical chain reactions that yield the emission of light. Due to the inherent radical short lifetimes and the transient behavior of CL phenomena an automated multi-pumping flow system (MPFS) was proposed to improve sample manipulation and reaction zone implementation ensuring reproducible analysis time and high sampling rate. The developed approach allowed up to 60 determinations per hour and determine S2O8(2-) concentrations between 0.1 and 1 mmol with good linearity (R=0.9999). The method has shown good repeatability with relative standard deviations below 2.5% (n=3) for different persulfate concentrations (0.1 and 0.625 mmol L(-1)). Limits of detection (3σ) and quantification (10σ) were 2.7 and 9.1 µmol L(-1), respectively. The MPFS system was applied to persulfate determination in bench scale UV/S2O8(2-) drug degradation processes of model samples showing good versatility and providing real time information on the persulfate consumption in photo-chemical degradation methodologies.

  7. Characterization of the interaction of a mono-6-thio-β-cyclodextrin-capped CdTe quantum dots-methylene blue/methylene green system with herring sperm DNA using a spectroscopic approach.

    PubMed

    Shen, Yizhong; Liu, Shaopu; Wang, Lei; Yin, Pengfei; He, Youqiu

    2014-11-01

    Novel, water-soluble CdTe quantum dots (QDs) capped with β-cyclodextrin (β-CD) and ~ 4.0 nm in diameter were synthesized in aqueous solution, and characterized using transmission electron microscopy (TEM). A fluorescence-sensing system based on the photoinduced electron transfer (PET) of (mono-6-thio-β-CD)-CdTe QDs was then designed to measure the interaction of phenothiazine dyes [methylene blue (MB) and methylene green (MG)] with herring sperm DNA (hsDNA). This fluorescence-sensing system was based on a fluorescence "OFF-ON" mode. First, MB/MG adsorbed on the surface of (mono-6-thio-β-CD)-CdTe QDs effectively quenches the fluorescence of (mono-6-thio-β-CD)-CdTe QDs through PET. Then, addition of hsDNA restores the fluorescence intensity of (mono-6-thio-β-CD)-CdTe QDs, because hsDNA can bind with MB/MG and remove it from the as-prepared (mono-6-thio-β-CD)-CdTe QDs. In addition, detailed reaction mechanisms of the (mono-6-thio-β-CD)-CdTe QDs-MB/MG-hsDNA solution system were studied using optical methods, by comparison with the TGA-CdTe QDs-MB/MG-hsDNA solution system. Copyright © 2014 John Wiley & Sons, Ltd.

  8. Reaching the quantum limit of sensitivity in electron spin resonance

    SciTech Connect

    Bienfait, A.; Pla, J. J.; Kubo, Y.; Stern, M.; Zhou, X.; Lo, C. C.; Weis, C. D.; Schenkel, T.; Thewalt, M. L. W.; Vion, D.; Esteve, D.; Julsgaard, B.; Mølmer, K.; Morton, J. J. L.; Bertet, P.

    2015-12-14

    The detection and characterization of paramagnetic species by electron spin resonance (ESR) spectroscopy is widely used throughout chemistry, biology and materials science, from in vivo imaging to distance measurements in spin-labelled proteins. ESR relies on the inductive detection of microwave signals emitted by the spins into a coupled microwave resonator during their Larmor precession. However, such signals can be very small, prohibiting the application of ESR at the nanoscale (for example, at the single-cell level or on individual nanoparticles). Here in this work, using a Josephson parametric microwave amplifier combined with high-quality-factor superconducting microresonators cooled at millikelvin temperatures, we improve the state-of-the-art sensitivity of inductive ESR detection by nearly four orders of magnitude. We demonstrate the detection of 1,700 bismuth donor spins in silicon within a single Hahn echo with unit signal-to-noise ratio, reduced to 150 spins by averaging a single Carr-Purcell-Meiboom-Gill sequence. This unprecedented sensitivity reaches the limit set by quantum fluctuations of the electromagnetic field instead of thermal or technical noise, which constitutes a novel regime for magnetic resonance. In conclusion, the detection volume of our resonator is ~0.02nl, and our approach can be readily scaled down further to improve sensitivity, providing a new versatile toolbox for ESR at the nanoscale.

  9. Reaching the quantum limit of sensitivity in electron spin resonance

    DOE PAGES

    Bienfait, A.; Pla, J. J.; Kubo, Y.; ...

    2015-12-14

    The detection and characterization of paramagnetic species by electron spin resonance (ESR) spectroscopy is widely used throughout chemistry, biology and materials science, from in vivo imaging to distance measurements in spin-labelled proteins. ESR relies on the inductive detection of microwave signals emitted by the spins into a coupled microwave resonator during their Larmor precession. However, such signals can be very small, prohibiting the application of ESR at the nanoscale (for example, at the single-cell level or on individual nanoparticles). Here in this work, using a Josephson parametric microwave amplifier combined with high-quality-factor superconducting microresonators cooled at millikelvin temperatures, we improvemore » the state-of-the-art sensitivity of inductive ESR detection by nearly four orders of magnitude. We demonstrate the detection of 1,700 bismuth donor spins in silicon within a single Hahn echo with unit signal-to-noise ratio, reduced to 150 spins by averaging a single Carr-Purcell-Meiboom-Gill sequence. This unprecedented sensitivity reaches the limit set by quantum fluctuations of the electromagnetic field instead of thermal or technical noise, which constitutes a novel regime for magnetic resonance. In conclusion, the detection volume of our resonator is ~0.02nl, and our approach can be readily scaled down further to improve sensitivity, providing a new versatile toolbox for ESR at the nanoscale.« less

  10. Reaching the quantum limit of sensitivity in electron spin resonance.

    PubMed

    Bienfait, A; Pla, J J; Kubo, Y; Stern, M; Zhou, X; Lo, C C; Weis, C D; Schenkel, T; Thewalt, M L W; Vion, D; Esteve, D; Julsgaard, B; Mølmer, K; Morton, J J L; Bertet, P

    2016-03-01

    The detection and characterization of paramagnetic species by electron spin resonance (ESR) spectroscopy is widely used throughout chemistry, biology and materials science, from in vivo imaging to distance measurements in spin-labelled proteins. ESR relies on the inductive detection of microwave signals emitted by the spins into a coupled microwave resonator during their Larmor precession. However, such signals can be very small, prohibiting the application of ESR at the nanoscale (for example, at the single-cell level or on individual nanoparticles). Here, using a Josephson parametric microwave amplifier combined with high-quality-factor superconducting microresonators cooled at millikelvin temperatures, we improve the state-of-the-art sensitivity of inductive ESR detection by nearly four orders of magnitude. We demonstrate the detection of 1,700 bismuth donor spins in silicon within a single Hahn echo with unit signal-to-noise ratio, reduced to 150 spins by averaging a single Carr-Purcell-Meiboom-Gill sequence. This unprecedented sensitivity reaches the limit set by quantum fluctuations of the electromagnetic field instead of thermal or technical noise, which constitutes a novel regime for magnetic resonance. The detection volume of our resonator is ∼ 0.02 nl, and our approach can be readily scaled down further to improve sensitivity, providing a new versatile toolbox for ESR at the nanoscale.

  11. Ligand-Capped CdTe Quantum Dots as a Fluorescent Nanosensor for Detection of Copper Ions in Environmental Water Sample.

    PubMed

    Elmizadeh, Hamideh; Soleimani, Majid; Faridbod, Farnoush; Bardajee, Ghasem Rezanejade

    2017-09-21

    In this work, as a novel fluorescent nano-sensor, a ligand-capped CdTe QDs (CdTe-L QDs) was designed for the detection and quantification of Cu(2+) ions in environmental water samples. The synthesized QDs were characterized by transmission electron microscopy (TEM), thermo-gravimetric (TG) analysis, Fourier transform infrared (FTIR), UV-Vis spectrophotometry and fluorescence spectroscopy. Optical properties of the produced nanosensor were monitored by UV-Vis and fluorescence spectrophotometry. It was observed that fluorescence intensity of the produced nano-sensor selectively quenched by adding Cu(2+) ions in comparison to other metal ions tested. Using CdTe-L QDs, a rapid and facile analytical method was developed to determine Cu(2+) ions in the concentration range of 5.16 ± 0.07 × 10(- 8) mol L(- 1)-1.50 ± 0.03 × 10(- 5) mol L(- 1) with a detection limit of 1.55 ± 0.05 × 10(- 8) mol L(- 1). The nanosensor was successfully applied for the determination of Cu(2+) ions in various water samples, and the results were compared with the standard method. Graphical Abstract.

  12. Efficient CdSe quantum dot-sensitized solar cells prepared by an improved successive ionic layer adsorption and reaction process.

    PubMed

    Lee, Hyojoong; Wang, Mingkui; Chen, Peter; Gamelin, Daniel R; Zakeeruddin, Shaik M; Grätzel, Michael; Nazeeruddin, Md K

    2009-12-01

    In pursuit of efficient quantum dot (QD)-sensitized solar cells based on mesoporous TiO(2) photoanodes, a new procedure for preparing selenide (Se(2-)) was developed and used for depositing CdSe QDs in situ over TiO(2) mesopores by the successive ionic layer adsorption and reaction (SILAR) process in ethanol. The sizes and density of CdSe QDs over TiO(2) were controlled by the number of SILAR cycles applied. After some optimization of these QD-sensitized TiO(2) films in regenerative photoelectrochemical cells using a cobalt redox couple [Co(o-phen)(3)(2+/3+)], including addition of a final layer of CdTe, over 4% overall efficiencies were achieved at 100 W/m(2) with about 50% IPCE at its maximum. Light-harvesting properties and transient voltage decay/impedance measurements confirmed that CdTe-terminated CdSe QD cells gave better charge-collection efficiencies and kinetic parameters than corresponding CdSe QD cells. In a preliminary study, a CdSe(Te) QD-sensitized TiO(2) film was combined with an organic hole conductor, spiro-OMeTAD, and shown to exhibit a promising efficiency of 1.6% at 100 W/m(2) in inorganic/organic hybrid all-solid-state cells.

  13. Reflection sensitivity of 1.3 μm quantum dot lasers epitaxially grown on silicon.

    PubMed

    Liu, Alan Y; Komljenovic, Tin; Davenport, Michael L; Gossard, Arthur C; Bowers, John E

    2017-05-01

    We present measurements of relative intensity noise versus various levels of optical feedback for 1.3 μm quantum dot lasers epitaxially grown on silicon for the first time. A systematic comparison is made with heterogeneously integrated 1.55 μm quantum well lasers on silicon. Our results indicate up to 20 dB reduced sensitivity of the quantum dot lasers on silicon compared to the quantum wells.

  14. High Efficiency Quantum Dot Sensitized Solar Cells Based on Direct Adsorption of Quantum Dots on Photoanodes.

    PubMed

    Wang, Wenran; Jiang, Guocan; Yu, Juan; Wang, Wei; Pan, Zhenxiao; Nakazawa, Naoki; Shen, Qing; Zhong, Xinhua

    2017-07-12

    Unambiguously direct adsorption (DA) of initial oil-soluble quantum dots (QDs) on TiO2 film electrode is a convenient and simple approach in the construction of quantum dot sensitized solar cells (QDSCs). Regrettably, low QD loading amount and poor reproducibility shadow the advantages of DA route and constrain its practical application. Herein, the influence of experimental variables in DA process on QD loading amount as well as on the photovoltaic performance of the resultant QDSCs was investigated and optimized systematically, including the choice of solvent, purification of QDs, and sensitization time, as well as QD concentration. Experimental results demonstrated that it is essential to choose appropriate solvent as well as control purification cycles of original QD suspensions so as to realize satisfactory QD loading amount and ensure the high reproducibility. In addition, DA mode renders efficient electron injection from QD to TiO2, yet low QD loading amount and adverse QD agglomeration in comparison with the well-developed capping ligand induced self-assembly (CLIS) deposition approach. Mg(2+) treatment on TiO2 photoanodes can promote the QD loading amount in DA mode. The optimized QDSCs based on DA mode exhibited efficiencies of 6.90% and 9.02% for CdSe and Zn-Cu-In-Se QDSCs, respectively, which were comparable to the best results based on CLIS mode (6.88% and 9.56%, respectively).

  15. Device Fabrication using Crystalline CdTe and CdTe Ternary Alloys Grown by MBE

    SciTech Connect

    Zaunbrecher, Katherine; Burst, James; Seyedmohammadi, Shahram; Malik, Roger; Li, Jian V.; Gessert, Timothy A.; Barnes, Teresa

    2015-06-14

    We fabricated epitaxial CdTe:In/CdTe:As homojunction and CdZnTe/CdTe and CdMgTe/CdTe heterojunction devices grown on bulk CdTe substrates in order to study the fundamental device physics of CdTe solar cells. Selection of emitter-layer alloys was based on passivation studies using double heterostructures as well as band alignment. Initial results show significant device integration challenges, including low dopant activation, high resistivity substrates and the development of low-resistance contacts. To date, the highest open-circuit voltage is 715 mV in a CdZnTe/CdTe heterojunction following anneal, while the highest fill factor of 52% was attained in an annealed CdTe homojunction. In general, all currentvoltage measurements show high series resistance, capacitancevoltages measurements show variable doping, and quantum efficiency measurements show low collection. Ongoing work includes overcoming the high resistance in these devices and addressing other possible device limitations such as non-optimum junction depth, interface recombination, and reduced bulk lifetime due to structural defects.

  16. Sensitivity of Heterointerfaces on Emission Wavelength in Quantum Cascade Lasers

    DTIC Science & Technology

    2016-10-31

    Pflügl, A. M. Andrews, W. Schrenk, and G. Strasser, "X-ray investigation of quantum well intermixing after postgrowth rapid thermal processing," Journal...Metalorganic vapor phase epitaxy; A3. Quantum wells ; B2. Semiconducting III-V materials; B3. Infrared devices. 1. Introduction Quantum cascade lasers...of a coupled quantum - well structure, where the energy separation for a given material system and strain state is dependent on the thickness of the

  17. Multiplex electrochemiluminescence DNA sensor for determination of hepatitis B virus and hepatitis C virus based on multicolor quantum dots and Au nanoparticles.

    PubMed

    Liu, Linlin; Wang, Xinyan; Ma, Qiang; Lin, Zihan; Chen, Shufan; Li, Yang; Lu, Lehui; Qu, Hongping; Su, Xingguang

    2016-04-15

    In this work, a novel multiplex electrochemiluminescence (ECL) DNA sensor has been developed for determination of hepatitis B virus (HBV) and hepatitis C virus (HCV) based on multicolor CdTe quantum dots (CdTe QDs) and Au nanoparticles (Au NPs). The electrochemically synthesized graphene nanosheets (GNs) were selected as conducting bridge to anchor CdTe QDs551-capture DNA(HBV) and CdTe QDs607-capture DNA(HCV) on the glassy carbon electrode (GCE). Then, different concentrations of target DNA(HBV) and target DNA(HCV) were introduced to hybrid with complementary CdTe QDs-capture DNA. Au NPs-probe DNA(HBV) and Au NPs-probe DNA(HCV) were modified to the above composite film via hybrid with the unreacted complementary CdTe QDs-capture DNA. Au NPs could quench the electrochemiluminescence (ECL) intensity of CdTe QDs due to the inner filter effect. Therefore, the determination of target DNA(HBV) and target DNA(HCV) could be achieved by monitoring the ECL DNA sensor based on Au NPs-probe DNA/target DNA/CdTe QDs-capture DNA/GNs/GCE composite film. Under the optimum conditions, the ECL intensity of CdTe QDs551 and CdTe QDs607 and the concentration of target DNA(HBV) and target DNA(HCV) have good linear relationship in the range of 0.0005-0.5 nmol L(-1) and 0.001-1.0 nmol L(-1) respectively, and the limit of detection were 0.082 pmol L(-1) and 0.34 pmol L(-1) respectively (S/N = 3). The DNA sensor showed good sensitivity, selectivity, reproducibility and acceptable stability. The proposed DNA sensor has been employed for the determination of target DNA(HBV) and target DNA(HCV) in human serum samples with satisfactory results.

  18. Influence of surface states of CuInS2 quantum dots in quantum dots sensitized photo-electrodes

    NASA Astrophysics Data System (ADS)

    Peng, Zhuoyin; Liu, Yueli; Wu, Lei; Zhao, Yinghan; Chen, Keqiang; Chen, Wen

    2016-12-01

    Surface states are significant factor for the enhancement of electrochemical performance in CuInS2 quantum dot sensitized photo-electrodes. DDT, OLA, MPA, and S2- ligand capped CuInS2 quantum dot sensitized photo-electrodes are prepared by thermolysis, solvethermal and ligand-exchange processes, respectively, and their optical properties and photoelectrochemical properties are investigated. The S2- ligand enhances the UV-vis absorption and electron-hole separation property as well as the excellent charge transfer performance of the photo-electrodes, which is attributed to the fact that the atomic S2- ligand for the interfacial region of quantum dots may improve the electron transfer rate. These S2--capped CuInS2 quantum dot sensitized photo-electrodes exhibit the excellent photoelectrochemical efficiency and IPCE peak value, which is higher than that of the samples with DDT, OLA and MPA ligands.

  19. pH sensitive quantum dot-anthraquinone nanoconjugates

    NASA Astrophysics Data System (ADS)

    Ruedas-Rama, Maria Jose; Hall, Elizabeth A. H.

    2014-05-01

    Semiconductor quantum dots (QDs) have been shown to be highly sensitive to electron or charge transfer processes, which may alter their optical properties. This feature can be exploited for different sensing applications. Here, we demonstrate that QD-anthraquinone conjugates can function as electron transfer-based pH nanosensors. The attachment of the anthraquinones on the surface of QDs results in the reduction of electron hole recombination, and therefore a quenching of the photoluminescence intensity. For some anthraquinone derivatives tested, the quenching mechanism is simply caused by an electron transfer process from QDs to the anthraquinone, functioning as an electron acceptor. For others, electron transfer and energy transfer (FRET) processes were found. A detailed analysis of the quenching processes for CdSe/ZnS QD of two different sizes is presented. The photoluminescence quenching phenomenon of QDs is consistent with the pH sensitive anthraquinone redox chemistry. The resultant family of pH nanosensors shows pKa ranging ˜5-8, being ideal for applications of pH determination in physiological samples like blood or serum, for intracellular pH determination, and for more acidic cellular compartments such as endosomes and lysosomes. The nanosensors showed high selectivity towards many metal cations, including the most physiologically important cations which exist at high concentration in living cells. The reversibility of the proposed systems was also demonstrated. The nanosensors were applied in the determination of pH in samples mimicking the intracellular environment. Finally, the possibility of incorporating a reference QD to achieve quantitative ratiometric measurements was investigated.

  20. Quantum limits on the detection sensitivity of a linear detector with feedback

    NASA Astrophysics Data System (ADS)

    Gao, Yang

    2017-03-01

    We show that the detection sensitivity of a linear detector is lower bounded by some quantum limits. For the force sensitivity, which is relevant for atomic force microscopes, the lower bound is given by the so-called ultimate quantum limit (UQL). For the displacement sensitivity, which is relevant for detecting gravitational waves, a generalized lower bound that can overcome the usual UQL is obtained.

  1. Melt-growth dynamics in CdTe crystals

    DOE PAGES

    Zhou, X. W.; Ward, D. K.; Wong, B. M.; ...

    2012-06-01

    We use a new, quantum-mechanics-based bond-order potential (BOP) to reveal melt growth dynamics and fine scale defect formation mechanisms in CdTe crystals. Previous molecular dynamics simulations of semiconductors have shown qualitatively incorrect behavior due to the lack of an interatomic potential capable of predicting both crystalline growth and property trends of many transitional structures encountered during the melt → crystal transformation. Here, we demonstrate successful molecular dynamics simulations of melt growth in CdTe using a BOP that significantly improves over other potentials on property trends of different phases. Our simulations result in a detailed understanding of defect formation during themore » melt growth process. Equally important, we show that the new BOP enables defect formation mechanisms to be studied at a scale level comparable to empirical molecular dynamics simulation methods with a fidelity level approaching quantum-mechanical methods.« less

  2. CdSe quantum-dot-sensitized solar cell with ∼100% internal quantum efficiency.

    PubMed

    Fuke, Nobuhiro; Hoch, Laura B; Koposov, Alexey Y; Manner, Virginia W; Werder, Donald J; Fukui, Atsushi; Koide, Naoki; Katayama, Hiroyuki; Sykora, Milan

    2010-11-23

    We have constructed and studied photoelectrochemical solar cells (PECs) consisting of a photoanode prepared by direct deposition of independently synthesized CdSe nanocrystal quantum dots (NQDs) onto a nanocrystalline TiO(2) film (NQD/TiO(2)), aqueous Na(2)S or Li(2)S electrolyte, and a Pt counter electrode. We show that light harvesting efficiency (LHE) of the NQD/TiO(2) photoanode is significantly enhanced when the NQD surface passivation is changed from tri-n-octylphosphine oxide (TOPO) to 4-butylamine (BA). In the PEC the use of NQDs with a shorter passivating ligand, BA, leads to a significant enhancement in both the electron injection efficiency at the NQD/TiO(2) interface and charge collection efficiency at the NQD/electrolyte interface, with the latter attributed mostly to a more efficient diffusion of the electrolyte through the pores of the photoanode. We show that by utilizing BA-capped NQDs and aqueous Li(2)S as an electrolyte, it is possible to achieve ∼100% internal quantum efficiency of photon-to-electron conversion, matching the performance of dye-sensitized solar cells.

  3. A strategy of combining SILAR with solvothermal process for In2S3 sensitized quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Yang, Peizhi; Tang, Qunwei; Ji, Chenming; Wang, Haobo

    2015-12-01

    Pursuit of an efficient strategy for quantum dot-sensitized photoanode has been a persistent objective for enhancing photovoltaic performances of quantum dot-sensitized solar cell (QDSC). We present here the fabrication of the indium sulfide (In2S3) quantum dot-sensitized titanium dioxide (TiO2) photoanode by combining successive ionic layer adsorption and reaction (SILAR) with solvothermal processes. The resultant QDSC consists of an In2S3 sensitized TiO2 photoanode, a liquid polysulfide electrolyte, and a Co0.85Se counter electrode. The optimized QDSC with photoanode prepared with the help of a SILAR method at 20 deposition cycles and solvothermal method yields a maximum power conversion efficiency of 1.39%.

  4. Sensitivity of Heterointerfaces on Emission Wavelength in Quantum Cascade Lasers

    DTIC Science & Technology

    2016-08-18

    mW and pulsed efficiencies of ~8.5 to 10%. Keywords: A1. Interfaces, A1. Segregation, A3. Metalorganic vapor phase epitaxy, A3. Quantum wells ... quantum - well structure, where the energy separation for a given material system and strain state is dependent on the thickness of the quantum wells and...AlInAs/GaInAs multiple- quantum - well (MQW) structures, along with QCL modeling are presented. It was found that decreasing the AlInAs thickness (with

  5. Quantum Dot Sensitized Nanotubes for Full Solar Spectrum Photovoltaic Cell

    NASA Astrophysics Data System (ADS)

    Khanal, Sohana

    The demand for energy with limited non-renewable sources of energy has called researchers to find clean renewable energy sources. Solar light is considered good choice of the alternate energy. Our effort in this work was to investigate efficient photovoltaic (PV) systems by designing a hybrid photoelectrode with good absorption as well as charge transport properties. A coupled semiconductor material, one-dimensional TiO2 nanotubes (1D TiO2-NTs), filled with low band semiconductor quantum dots (QDs), PbS QDs, for better charge carrier transport was prepared and investigated. The vertically standing self assembled nanotubular array was attained by anodizing the Ti metal in two different solutions: (1) Ethylene Glycol with 0.5 wt% NH4F and 3 vol percent water and (2) 0.5M H3PO4 with 0.5 wt% NH4F. The anodized samples were annealed and then filled with the nanoparticles of other low band gap semiconductor materials. The CdS nanoparticles were used for the better understanding of the sensitizing process. The material was then switched to the PbS. As in the hypothesis, if PbS quantum dots are uniformly distributed in the 1D TiO2 Multiple Charge Carrier Generation can be created since PbS has a small band gap. A chemical bath deposition process in the presence of ultrasonic waves was adopted for the deposition of the QDs. Saturated lead sulfide solution was used as the lead source and the 0.2 M Na2S solution for the sulfur source. The process resulted in the successful uniform deposition of the PbS QDs onto the 1D TiO2 NTs. The deposited compound obeyed the stoichiometric ratio of 1:1 as desired. Photocurrent densities of 4.5 mA/cm2 was obtained, which is higher than the TiO2 alone in a polysulfide solution. PbS-TiO2 can be a suitable candidate for harvesting a broad solar spectrum as the UV-vis study proved that they absorb the light in the UV range.

  6. Covalent Coupling of Organophosphorus Hydrolase Loaded Quantum Dots to Carbon Nanotube/Au Nanocomposite for Enhanced Detection of Methyl Parathion

    SciTech Connect

    Du, Dan; Chen, Wenjuan; Zhang, Weiying; Liu, Deli; Li, Haibing; Lin, Yuehe

    2010-02-15

    An amperometric biosensor for highly selective and sensitive determination of methyl parathion (MP) was developed based on dual signal amplification: (1) a large amount of introduced enzyme on the electrode surface and (2) synergistic effects of nanoparticles towards enzymatic catalysis. The fabrication process includes (1) electrochemical deposition of gold nanoparticles by a multi-potential step technique at multiwalled carbon nanotube (MWCNT) film pre-cast on a glassy carbon electrode and (2) immobilization of methyl parathion degrading enzyme (MPDE) onto a modified electrode through CdTe quantum dots (CdTe QDs) covalent attachment. The introduced MWCNT and gold nanoparticles significantly increased the surface area and exhibited synergistic effects towards enzymatic catalysis. CdTe QDs are further used as carriers to load a large amount of enzyme. As a result of these two important enhancement factors, the proposed biosensor exhibited extremely sensitive, perfectly selective, and rapid response to methyl parathion in the absence of a mediator.

  7. Size controlled preparation of CdTe nanoparticles by apoferritin

    NASA Astrophysics Data System (ADS)

    Peng, Shasha; Kim, Ji Hyeon; Park, Sang Joon

    2017-06-01

    Cadmium telluride quantum dots (CdTe QDs) were synthesized in the cavity of horse spleen apoferritin and CdTe-apoferritin complex was fluorescent. Apoferritin is a popular bio-template to prepare various nanoparticles with narrow size distribution due to the confinement of the hollow protein shell. In this work, we controlled the diameters of CdTe NPs by changing the reaction conditions. Altering the molar ratio of Cd to Te from 1:0.05 to 1:0.2 and pH can change the diameters of NPs cores. The synthesized QDs were characterized by photoluminescence (PL) spectroscopy, UV-vis spectroscopy and transmission electron microscopy (TEM). The results showed that the PL intensity decreased when the Cd/Te molar ratio was decreased from 1:0.05 to 1:0.3 and pH was increased from 9.01 to 9.96. In addition, it was proven that the existence of apoferritin is necessary for the present synthetic method and the formation of CdTe QDs in the inner cavity of apoferritin.

  8. Characterization of CdTe Nanoparticles Fabricated by Pulsed Electron Deposition Technique at Different Ablation Parameters

    NASA Astrophysics Data System (ADS)

    Jackson, E.; Aga, R.; Steigerwald, A.; Ueda, A.; Pan, Z.; Collins, W. E.; Mu, R.

    2008-03-01

    Telluride (CdTe) is a front-runner photovoltaic (PV) material because it has already attained efficiencies above 16%. The fabrication of CdTe nanoparticles has aroused considerable interest because of their potential application as active layer in organic/inorganic hybrid solar cells. They can also be used for sensitisation of wide band gap semiconductors. In this work, we explore pulsed electron beam deposition (PED) technique to fabricate CdTe nanoparticles. Two ablation parameters, namely background gas pressure and electron energy were varied to investigate their effects on the nanoparticle formation. AFM and optical transmission measurements indicate that we have fabricated CdTe nanocrystalline films exhibiting quantum confinement effect. These films contain scattered nanoparticles with diameters varying from 40 nm to 500 nm, which contribute to the optical absorption near the bulk bandgap energy. However, increasing the background pressure to 19 mTorr improves the nanocrystalline film uniformity.

  9. Noise-immune laser receiver - transmitters with the quantum sensitivity limit

    SciTech Connect

    Kutaev, Yu F; Mankevich, S K; Nosach, O Yu; Orlov, E P

    2009-11-30

    We consider the operation principles of noise-immune near-IR receiver - transmitters with the quantum sensitivity limit, in which active quantum filters based on iodine photodissociation quantum amplifiers and iodine lasers are used. The possible applications of these devices in laser location, laser space communication, for the search for signals from extraterrestrial civilisations and sending signals to extraterrestrial civilisations are discussed. (invited paper)

  10. L-cysteine-capped CdTe QD-based sensor for simple and selective detection of trinitrotoluene.

    PubMed

    Chen, Yufang; Chen, Zhang; He, Yejuan; Lin, Hailan; Sheng, Pengtao; Liu, Chengbin; Luo, Shenglian; Cai, Qingyun

    2010-03-26

    Trinitrotoluene, usually known as TNT, is a kind of chemical explosive with hazardous and toxic effects on the environment and human health. National and societal security concerns have dictated an increasing need for the analytical detection of TNT with rapidity, high sensitivity and low cost. This work demonstrates a novel method using L-cysteine-capped CdTe quantum dots (QDs) to assay TNT, based on the formation of a Meisenheimer complex between TNT and cysteine. The fluorescence (FL) of quantum dots quench because electrons of the QDs transfer to the TNT molecules via the formation of a Meisenheimer complex. TNT can be detected with a low detection limit of 1.1 nM. Studies on the selectivity of this method show that only TNT can generate an intense signal response. The synthesized QDs are excellent nanomaterials for TNT detection. In addition, TNT in soil samples is also analyzed by the proposed method.

  11. Electrostatic assembles and optical properties of Au CdTe QDs and Ag/Au CdTe QDs

    NASA Astrophysics Data System (ADS)

    Yang, Dongzhi; Wang, Wenxing; Chen, Qifan; Huang, Yuping; Xu, Shukun

    2008-09-01

    Au-CdTe and Ag/Au-CdTe assembles were firstly investigated through the static interaction between positively charged cysteamine-stabilized CdTe quantum dots (QDs) and negatively charged Au or core/shell Ag/Au nano-particles (NCs). The CdTe QDs synthesized in aqueous solution were capped with cysteamine which endowed them positive charges on the surface. Both Au and Ag/Au NCs were prepared through reducing precursors with gallic acid obtained from the hydrolysis of natural plant poly-phenols and favored negative charges on the surface of NCs. The fluorescence spectra of CdTe QDs exhibited strong quenching with the increase of added Au or Ag/Au NCs. Railey resonance scattering spectra of Au or Ag/Au NCs increased firstly and decreased latter with the concentration of CdTe QDs, accompanied with the solution color changing from red to purple and colorless at last. Experimental results on the effects of gallic acid, chloroauric acid tetrahydrate and other reagents demonstrated the static interaction occurred between QDs and NCs. This finding reveals the possibilities to design and control optical process and electromagnetic coupling in hybrid structures.

  12. Graphene Quantum Dots Electrochemistry and Sensitive Electrocatalytic Glucose Sensor Development.

    PubMed

    Gupta, Sanju; Smith, Tyler; Banaszak, Alexander; Boeckl, John

    2017-09-29

    Graphene quantum dots (GQDs), derived from functionalized graphene precursors are graphene sheets a few nanometers in the lateral dimension having a several-layer thickness. They are zero-dimensional materials with quantum confinement and edge site effects. Intense research interest in GQDs is attributed to their unique physicochemical phenomena arising from the sp²-bonded carbon nanocore surrounded with edged plane functional moieties. In this work, GQDs are synthesized by both solvothermal and hydrothermal techniques, with the optimal size of 5 nm determined using high-resolution transmission electron microscopy, with additional UV-Vis absorption and fluorescence spectroscopy, revealing electronic band signatures in the blue-violet region. Their potential in fundamental (direct electron transfer) and applied (enzyme-based glucose biosensor) electrochemistry has been practically realized. Glucose oxidase (GOx) was immobilized on glassy carbon (GC) electrodes modified with GQDs and functionalized graphene (graphene oxide and reduced form). The cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy are used for characterizing the direct electron transfer kinetics and electrocatalytical biosensing. The well-defined quasi-reversible redox peaks were observed under various electrochemical environment and conditions (pH, concentration, scan rate) to determine the diffusion coefficient (D) and first-order electron transfer rate (kET). The cyclic voltammetry curves showed homogeneous ion transport behavior for GQD and other graphene-based samples with D ranging between 8.45 × 10(-9) m² s(-1) and 3 × 10(-8) m² s(-1) following the order of GO < rGO < GQD < GQD (with FcMeOH as redox probe) < GOx/rGO < GOx/GO < HRP/GQDs < GOx/GQDs. The developed GOx-GQDs biosensor responds efficiently and linearly to the presence of glucose over concentrations ranging between 10 μM and 3 mM with a limit of detection of 1.35 μM and sensitivity of

  13. Photonic Quantum Metrologies Using Photons: Phase Super-sensitivity and Entanglement-Enhanced Imaging

    NASA Astrophysics Data System (ADS)

    Takeuchi, Shigeki

    Quantum information science has been attracting significant attention recently. It harnesses the intrinsic nature of quantum mechanics such as quantum superposition, the uncertainty principle, and quantum entanglement to realize novel functions. Recently, quantum metrology has been emerging as an application of quantum information science. Among the many physical quanta, photons are an indispensable tool for metrology, as light-based measurements are applicable to fields ranging from astronomy to life science. In quantum metrology, quantum entanglement between photons is the phenomenon utilized.In this chapter, we will try to give a brief overview of this emerging field mainly focusing on two topics: Optical phase measurements beyond the standard quantum limit (SQL) and quantum optical coherence tomography (QOCT). The sensitivity of an optical phase measurement for a given photon number N is usually limited by N sqrt{N} , which is called the SQL or shot noise limit. However, the SQL can be overcome when non-classical light is used. We explain the basic concepts and the recent experimental results that exceed the SQL, and an application of this technology for microscopy. QOCT harnesses the quantum entanglement of photons in frequency to cancel out the dispersion effect, which degrades the resolution of conventional OCT. The mechanism of the dispersion cancellation and the latest experimental results will be given.

  14. A sensitive and selective fluorimetric method of quick determination of sialic acids in egg products by lectin-CdTe quantum dots as nanoprobe.

    PubMed

    Wang, Qi; Wang, Beibei; Ma, Meihu; Cai, Zhaoxia

    2014-12-01

    Sialic acids (SA) are widely found as components of oligosaccharide units in mucins, glycoproteins and other microbial polymers in nature food. The aim of this study is to create a new fluorimetric detection method applied for determinating SA in egg products by using a sensitive lectin-CdTe quantum dots (QDs) nanoprobe. Water-soluble and high luminescent CdTe QDs were conjugated with sambucus nigra bark lectin (SNA) as probe for SA detection. As a result of specific interaction between SA and SNA-CdTe QDs, the conjugations finally lead to the change of a fluorescent signal. Under optimal conditions, fluorescence intensity increase linearly with the increase of the concentration of SA ranging from 12 to 680 ng/mL. The low detection limit is 0.67 ng/mL. This quick and selective analysis method for SA detection has been used in synthetic samples and egg products with recovery between 97.92% and 110.42%, which demonstrates the application of this assay is feasible and practical.

  15. A highly sensitive quantum dots-DNA nanobiosensor based on fluorescence resonance energy transfer for rapid detection of nanomolar amounts of human papillomavirus 18.

    PubMed

    Shamsipur, Mojtaba; Nasirian, Vahid; Mansouri, Kamran; Barati, Ali; Veisi-Raygani, Asad; Kashanian, Soheila

    2017-03-20

    A very sensitive and convenient nanobiosensor based on fluorescence resonance energy transfer (FRET) was developed for the detection of a 22-mer oligonucleotides sequence in Human Papillomavirus 18 virus (HPV18) gene. For this purpose, water-soluble CdTe quantum dots (QDs) were synthesized and, subsequently, amino-modified 11-mer oligonucleotide as one of the two necessary probes was attached to QDs surface to form functional QDs-DNA conjugates. Right after addition of the QDs-DNA and a second Cyanine5 (Cy5)-labeled 11-mer oligonucleotide probe to the DNA target solution, the sandwiched hybrids were formed. The resulting hybridization brings the Cy5 fluorophore as the acceptor to close proximity of the QDs as donor, so that an effective transfer of energy from the excited QDs to the Cy5 probe would occur via FRET processing. The fluorescence intensity of Cy5 found to linearly enhance by increasing the DNA target concentration from 1.0 to 50.0nM, with a detection limit of 0.2nM. This homogeneous DNA detection method does not require excessive washing and separation steps of un-hybridized DNA, due to the fact that no FRET can be observed when the probes are not ligated. Finally, feasibility and selectivity of the proposed one-spot DNA detection nanobiosensor were investigated by analysis of derived nucleotides from HPV18 and mismatched sequences. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Phase-sensitive cascaded four-wave-mixing processes for generating three quantum correlated beams

    NASA Astrophysics Data System (ADS)

    Wang, Li; Wang, Hailong; Li, Sijin; Wang, Yaxian; Jing, Jietai

    2017-01-01

    Theoretical studies and experimental implementations of quantum correlation are the important contents of continuous variables quantum optics and quantum information science. There are various systems for the study of quantum correlation. Here, we study an experimental scheme for generating three quantum correlated beams based on phase-sensitive cascaded four-wave-mixing (FWM) processes in rubidium vapor. Quantum correlation including intensity difference or sum squeezing, two other combinatorial squeezing, and quantum entanglement among the three output light fields are theoretically analyzed in this paper. Also, the comparison of the quantum correlations have been made between the phase-sensitive cascaded FWM processes and the phase-insensitive cascaded FWM processes. By changing the phases and intensities of the input beams, it is interesting to find that the maximum degrees of various combinatorial squeezing are equal when the two FWM processes share a common intensity gain. When the common intensity gain of the two FWM processes changes, the maximum degrees of different combinatorial squeezing will be synchronously controlled. At last we discuss the genuine tripartite entanglement and steering in our phase-sensitive cascaded scheme, and compare them with the cases of the phase-insensitive cascaded scheme.

  17. CdS/CdSe co-sensitized SnO2 photoelectrodes for quantum dots sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Lin, Yibing; Lin, Yu; Meng, Yongming; Tu, Yongguang; Zhang, Xiaolong

    2015-07-01

    SnO2 nanoparticles were synthesized by hydrothermal method and applied to photo-electrodes of quantum dots-sensitized solar cells (QDSSCs). After sensitizing SnO2 films via CdS quantum dots, CdSe quantum dots was decorated on the surface of CdS/SnO2 photo-electrodes to further improve the power conversion efficiency. CdS and CdSe quantum dots were deposited by successive ionic layer absorption and reaction method (SILAR) and chemical bath deposition method (CBD) respectively. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to identify the surface profile and crystal structure of SnO2 photo-electrodes before and after deposited quantum dots. After CdSe co-sensitized process, an overall power conversion efficiency of 1.78% was obtained in CdSe/CdS/SnO2 QDSSC, which showed 66.4% improvement than that of CdS/SnO2 QDSSC.

  18. Dynamic sensitivity of photon-dressed atomic ensemble with quantum criticality

    SciTech Connect

    Huang Jinfeng; Kuang Leman; Li Yong; Liao Jieqiao; Sun, C. P.

    2009-12-15

    We study the dynamic sensitivity of an atomic ensemble dressed by a single-mode cavity field (called a photon-dressed atomic ensemble), which is described by the Dicke model near the quantum critical point. It is shown that when an extra atom in a pure initial state passes through the cavity, the photon-dressed atomic ensemble will experience a quantum phase transition showing an explicit sudden change in its dynamics characterized by the Loschmidt echo of this quantum critical system. With such dynamic sensitivity, the Dicke model can resemble the cloud chamber for detecting a flying particle by the enhanced trajectory due to the classical phase transition.

  19. Nanocrystalline TiO2 solar cells sensitized with InAs quantum dots.

    PubMed

    Yu, Pingrong; Zhu, Kai; Norman, Andrew G; Ferrere, Suzanne; Frank, Arthur J; Nozik, Arthur J

    2006-12-21

    We report nanocrystalline TiO2 solar cells sensitized with InAs quantum dots. InAs quantum dots of different sizes were synthesized and incorporated in solar cell devices. Efficient charge transfer from InAs quantum dots to TiO2 particles was achieved without deliberate modification of the quantum dot capping layer. A power conversion efficiency of about 1.7% under 5 mW/cm2 was achieved; this is relatively high for a nanocrystalline metal oxide solar cell sensitized with presynthesized quantum dots, but this efficiency could only be achieved at low light intensity. At one sun, the efficiency decreased to 0.3%. The devices are stable for at least weeks under room light in air.

  20. Experimental study of the effect of addition of gold nanoparticles on CdSe quantum dots sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Indayani, Wahyu; Huda, Ichsanul; Herliansyah, Khuzaimah, Fasya; Musyaro'ah, Gunawan, Bodi; Endarko

    2017-01-01

    The effect of the gold nanoparticles on the quantum dots sensitized solar cells has been investigated. Gold nanoparticles were added in quantum dot CdSe before used as a sensitizer. The result showed that addition of colloidal gold nanoparticles could be enhanced the absorbance of quantum dot CdSe sensitizer. In this research, the QDSCs were arranged in the sandwich structure consecutively TiO2 as photoelectrode, gold nanoparticle, and quantum dot CdSe as a sensitizer, KI as electrolyte and black carbon as counter-electrode. The use of gold nanoparticles and quantum dot improved the average efficiency of the QDSC by about 104%.

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

    PubMed

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

    2015-04-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  3. Synthesis of CdTe quantum dot-conjugated CC49 and their application for in vitro imaging of gastric adenocarcinoma cells

    PubMed Central

    2013-01-01

    The purpose of this experiment was to investigate the visible imaging of gastric adenocarcinoma cells in vitro by targeting tumor-associated glycoprotein 72 (TAG-72) with near-infrared quantum dots (QDs). QDs with an emission wavelength of about 550 to 780 nm were conjugated to CC49 monoclonal antibodies against TAG-72, resulting in a probe named as CC49-QDs. A gastric adenocarcinoma cell line (MGC80-3) expressing high levels of TAG-72 was cultured for fluorescence imaging, and a gastric epithelial cell line (GES-1) was used for the negative control group. Transmission electron microscopy indicated that the average diameter of CC49-QDs was 0.2 nm higher compared with that of the primary QDs. Also, fluorescence spectrum analysis indicated that the CC49-QDs did not have different optical properties compared to the primary QDs. Immunohistochemical examination and in vitro fluorescence imaging of the tumors showed that the CC49-QDs probe could bind TAG-72 expressed on MGC80-3 cells. PMID:23800369

  4. Synthesis of CdTe quantum dot-conjugated CC49 and their application for in vitro imaging of gastric adenocarcinoma cells

    NASA Astrophysics Data System (ADS)

    Zhang, Yun-Peng; Sun, Peng; Zhang, Xu-Rui; Yang, Wu-Li; Si, Cheng-Shuai

    2013-06-01

    The purpose of this experiment was to investigate the visible imaging of gastric adenocarcinoma cells in vitro by targeting tumor-associated glycoprotein 72 (TAG-72) with near-infrared quantum dots (QDs). QDs with an emission wavelength of about 550 to 780 nm were conjugated to CC49 monoclonal antibodies against TAG-72, resulting in a probe named as CC49-QDs. A gastric adenocarcinoma cell line (MGC80-3) expressing high levels of TAG-72 was cultured for fluorescence imaging, and a gastric epithelial cell line (GES-1) was used for the negative control group. Transmission electron microscopy indicated that the average diameter of CC49-QDs was 0.2 nm higher compared with that of the primary QDs. Also, fluorescence spectrum analysis indicated that the CC49-QDs did not have different optical properties compared to the primary QDs. Immunohistochemical examination and in vitro fluorescence imaging of the tumors showed that the CC49-QDs probe could bind TAG-72 expressed on MGC80-3 cells.

  5. "Turn-off" fluorescent sensor for highly sensitive and specific simultaneous recognition of 29 famous green teas based on quantum dots combined with chemometrics.

    PubMed

    Liu, Li; Fan, Yao; Fu, Haiyan; Chen, Feng; Ni, Chuang; Wang, Jinxing; Yin, Qiaobo; Mu, Qingling; Yang, Tianming; She, Yuanbin

    2017-04-22

    Fluorescent "turn-off" sensors based on water-soluble quantum dots (QDs) have drawn increasing attention owing to their unique properties such as high fluorescence quantum yields, chemical stability and low toxicity. In this work, a novel method based on the fluorescence "turn-off" model with water-soluble CdTe QDs as the fluorescent probes for differentiation of 29 different famous green teas is established. The fluorescence of the QDs can be quenched in different degrees in light of positions and intensities of the fluorescent peaks for the green teas. Subsequently, with aid of classic partial least square discriminant analysis (PLSDA), all the green teas can be discriminated with high sensitivity, specificity and a satisfactory recognition rate of 100% for training set and 98.3% for prediction set, respectively. Especially, the "turn-off" fluorescence PLSDA model based on second-order derivatives (2nd der) with reduced least complexity (LVs = 3) was the most effective one for modeling. Most importantly, we further demonstrated the established "turn-off" fluorescent sensor mode has several significant advantages and appealing properties over the conventional fluorescent method for large-class-number classification (LCNC) of green teas. This work is, to the best of our knowledge, the first report on the rapid and effective identification of so many kinds of famous green teas based on the "turn-off" model of QDs combined with chemometrics, which also implies other potential applications on complex LCNC classification system with weak fluorescence or even without fluorescence to achieve higher detective response and specificity.

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

    PubMed

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  8. Confinement sensitivity in quantum dot singlet-triplet relaxation.

    PubMed

    Wesslen, Carl; Lindroth, Eva

    2017-09-08

    Spin-orbit mediated phonon relaxation in a two-dimensional quantum dot is investigated using different confining potentials. Elliptical harmonic oscillator and cylindrical well results are compared to each other in the case of a two-electron GaAs quantum dot subjected to a tilted magnetic field. The lowest energy set of two-body singlet and triplet states are calculated including spin-orbit and magnetic effects. These are used to calculate the phonon induced transition rate from the excited triplet to the ground state singlet for magnetic fields up to where the states cross. The roll of the cubic Dresselhaus effect, which is found to be much more important than previously assumed, and the positioning of "spin hot-spots" are discussed and relaxation rates for a few different systems are exhibited. © 2017 IOP Publishing Ltd.

  9. CdTe devices and method of manufacturing same

    DOEpatents

    Gessert, Timothy A.; Noufi, Rommel; Dhere, Ramesh G.; Albin, David S.; Barnes, Teresa; Burst, James; Duenow, Joel N.; Reese, Matthew

    2015-09-29

    A method of producing polycrystalline CdTe materials and devices that incorporate the polycrystalline CdTe materials are provided. In particular, a method of producing polycrystalline p-doped CdTe thin films for use in CdTe solar cells in which the CdTe thin films possess enhanced acceptor densities and minority carrier lifetimes, resulting in enhanced efficiency of the solar cells containing the CdTe material are provided.

  10. Enhancement of quantum-enhanced LADAR receiver in nonideal phase-sensitive amplification

    NASA Astrophysics Data System (ADS)

    Zhang, Shuan; Liu, Hongjun; Huang, Nan; Wang, Zhaolu; Han, Jing

    2017-07-01

    The phase-sensitive amplification (PSA) with an injected squeezed vacuum field is theoretically investigated in quantum-enhanced laser detection and ranging (LADAR) receiver. The theoretical model of the amplified process is derived to investigate the quantum fluctuations in detail. A new method of mitigating the unflat gain of nonideal PSA is proposed by adjusting the squeezed angle of the squeezed vacuum field. The simulation results indicate that signal-noise ratio (SNR) of system can be efficiently improved and close to the ideal case by this method. This research will provide an important potential in the applications of quantum-enhanced LADAR receiver.

  11. Phase-sensitive coherence and the classical-quantum boundary in ghost imaging

    NASA Astrophysics Data System (ADS)

    Erkmen, Baris I.; Hardy, Nicholas D.; Venkatraman, Dheera; Wong, Franco N. C.; Shapiro, Jeffrey H.

    2011-10-01

    The theory of partial coherence has a long and storied history in classical statistical optics. The vast majority of this work addresses fields that are statistically stationary in time, hence their complex envelopes only have phase-insensitive correlations. The quantum optics of squeezed-state generation, however, depends on nonlinear interactions producing baseband field operators with phase-insensitive and phase-sensitive correlations. Utilizing quantum light to enhance imaging has been a topic of considerable current interest, much of it involving biphotons, i.e., streams of entangled-photon pairs. Biphotons have been employed for quantum versions of optical coherence tomography, ghost imaging, holography, and lithography. However, their seemingly quantum features have been mimicked with classical-state light, questioning wherein lies the classical-quantum boundary. We have shown, for the case of Gaussian-state light, that this boundary is intimately connected to the theory of phase-sensitive partial coherence. Here we present that theory, contrasting it with the familiar case of phase-insensitive partial coherence, and use it to elucidate the classical-quantum boundary of ghost imaging. We show, both theoretically and experimentally, that classical phase-sensitive light produces ghost images most closely mimicking those obtained with biphotons, and we derive the spatial resolution, image contrast, and signal-to-noise ratio of a standoff-sensing ghost imager, taking into account target-induced speckle.

  12. Phase-Sensitive Coherence and the Classical-Quantum Boundary in Ghost Imaging

    NASA Technical Reports Server (NTRS)

    Erkmen, Baris I.; Hardy, Nicholas D.; Venkatraman, Dheera; Wong, Franco N. C.; Shapiro, Jeffrey H.

    2011-01-01

    The theory of partial coherence has a long and storied history in classical statistical optics. the vast majority of this work addresses fields that are statistically stationary in time, hence their complex envelopes only have phase-insensitive correlations. The quantum optics of squeezed-state generation, however, depends on nonlinear interactions producing baseband field operators with phase-insensitive and phase-sensitive correlations. Utilizing quantum light to enhance imaging has been a topic of considerable current interest, much of it involving biphotons, i.e., streams of entangled-photon pairs. Biphotons have been employed for quantum versions of optical coherence tomography, ghost imaging, holography, and lithography. However, their seemingly quantum features have been mimicked with classical-sate light, questioning wherein lies the classical-quantum boundary. We have shown, for the case of Gaussian-state light, that this boundary is intimately connected to the theory of phase-sensitive partial coherence. Here we present that theory, contrasting it with the familiar case of phase-insensitive partial coherence, and use it to elucidate the classical-quantum boundary of ghost imaging. We show, both theoretically and experimentally, that classical phase-sensitive light produces ghost imaging most closely mimicking those obtained in biphotons, and we derived the spatial resolution, image contrast, and signal-to-noise ratio of a standoff-sensing ghost imager, taking into account target-induced speckle.

  13. Phase-Sensitive Coherence and the Classical-Quantum Boundary in Ghost Imaging

    NASA Technical Reports Server (NTRS)

    Erkmen, Baris I.; Hardy, Nicholas D.; Venkatraman, Dheera; Wong, Franco N. C.; Shapiro, Jeffrey H.

    2011-01-01

    The theory of partial coherence has a long and storied history in classical statistical optics. the vast majority of this work addresses fields that are statistically stationary in time, hence their complex envelopes only have phase-insensitive correlations. The quantum optics of squeezed-state generation, however, depends on nonlinear interactions producing baseband field operators with phase-insensitive and phase-sensitive correlations. Utilizing quantum light to enhance imaging has been a topic of considerable current interest, much of it involving biphotons, i.e., streams of entangled-photon pairs. Biphotons have been employed for quantum versions of optical coherence tomography, ghost imaging, holography, and lithography. However, their seemingly quantum features have been mimicked with classical-sate light, questioning wherein lies the classical-quantum boundary. We have shown, for the case of Gaussian-state light, that this boundary is intimately connected to the theory of phase-sensitive partial coherence. Here we present that theory, contrasting it with the familiar case of phase-insensitive partial coherence, and use it to elucidate the classical-quantum boundary of ghost imaging. We show, both theoretically and experimentally, that classical phase-sensitive light produces ghost imaging most closely mimicking those obtained in biphotons, and we derived the spatial resolution, image contrast, and signal-to-noise ratio of a standoff-sensing ghost imager, taking into account target-induced speckle.

  14. Surface passivation for CdTe devices

    DOEpatents

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

    2017-08-01

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

  15. Nanostructured titania films sensitized by quantum dot chalcogenides.

    PubMed

    Kontos, Athanassios G; Likodimos, Vlassis; Vassalou, Eleni; Kapogianni, Ioanna; Raptis, Yannis S; Raptis, Costas; Falaras, Polycarpos

    2011-03-29

    The optical and structural properties of cadmium and lead sulfide nanocrystals deposited on mesoporous TiO2 substrates via the successive ionic layer adsorption and reaction method were comparatively investigated by reflectance, transmittance, micro-Raman and photoluminescence measurements. Enhanced interfacial electron transfer is evidenced upon direct growth of both CdS and PbS on TiO2 through the marked quenching of their excitonic emission. The optical absorbance of CdS/TiO2 can be tuned over a narrow spectral range. On the other side PbS/TiO2 exhibits a remarkable band gap tunability extending from the visible to the near infrared range, due to the distinct quantum size effects of PbS quantum dots. However, PbS/TiO2 suffers from severe degradation upon air exposure. Degradation effects are much less pronounced for CdS/TiO2 that is appreciably more stable, though it degrades readily upon visible light illumination.

  16. Nanostructured titania films sensitized by quantum dot chalcogenides

    PubMed Central

    2011-01-01

    The optical and structural properties of cadmium and lead sulfide nanocrystals deposited on mesoporous TiO2 substrates via the successive ionic layer adsorption and reaction method were comparatively investigated by reflectance, transmittance, micro-Raman and photoluminescence measurements. Enhanced interfacial electron transfer is evidenced upon direct growth of both CdS and PbS on TiO2 through the marked quenching of their excitonic emission. The optical absorbance of CdS/TiO2 can be tuned over a narrow spectral range. On the other side PbS/TiO2 exhibits a remarkable band gap tunability extending from the visible to the near infrared range, due to the distinct quantum size effects of PbS quantum dots. However, PbS/TiO2 suffers from severe degradation upon air exposure. Degradation effects are much less pronounced for CdS/TiO2 that is appreciably more stable, though it degrades readily upon visible light illumination. PMID:21711770

  17. Design Rules for High-Efficiency Quantum-Dot-Sensitized Solar Cells: A Multilayer Approach.

    PubMed

    Shalom, Menny; Buhbut, Sophia; Tirosh, Shay; Zaban, Arie

    2012-09-06

    The effect of multilayer sensitization in quantum-dot (QD)-sensitized solar cells is reported. A series of electrodes, consisting of multilayer CdSe QDs were assembled on a compact TiO2 layer. Photocurrent measurements along with internal quantum efficiency calculation reveal similar electron collection efficiency up to a 100 nm thickness of the QD layers. Moreover, the optical density and the internal quantum efficiency measurements reveal that the desired surface area of the TiO2 electrode should be increased only by a factor of 17 compared with a compact electrode. We show that the sensitization of low-surface-area TiO2 electrode with QD layers increases the performance of the solar cell, resulting in 3.86% efficiency. These results demonstrate a conceptual difference between the QD-sensitized solar cell and the dye-based system in which dye multilayer decreases the cell performance. The utilization of multilayer QDs opens new opportunities for a significant improvement of quantum-dot-sensitized solar cells via innovative cell design.

  18. Reprint of : Flux sensitivity of quantum spin Hall rings

    NASA Astrophysics Data System (ADS)

    Crépin, F.; Trauzettel, B.

    2016-08-01

    We analyze the periodicity of persistent currents in quantum spin Hall loops, partly covered with an s-wave superconductor, in the presence of a flux tube. Much like in normal (non-helical) metals, the periodicity of the single-particle spectrum goes from Φ0 = h / e to Φ0 / 2 as the length of the superconductor is increased past the coherence length of the superconductor. We further analyze the periodicity of the persistent current, which is a many-body effect. Interestingly, time reversal symmetry and parity conservation can significantly change the period. We find a 2Φ0-periodic persistent current in two distinct regimes, where one corresponds to a Josephson junction and the other one to an Aharonov-Bohm setup.

  19. Singlet exciton fission-sensitized infrared quantum dot solar cells.

    PubMed

    Ehrler, Bruno; Wilson, Mark W B; Rao, Akshay; Friend, Richard H; Greenham, Neil C

    2012-02-08

    We demonstrate an organic/inorganic hybrid photovoltaic device architecture that uses singlet exciton fission to permit the collection of two electrons per absorbed high-energy photon while simultaneously harvesting low-energy photons. In this solar cell, infrared photons are absorbed using lead sulfide (PbS) nanocrystals. Visible photons are absorbed in pentacene to create singlet excitons, which undergo rapid exciton fission to produce pairs of triplets. Crucially, we identify that these triplet excitons can be ionized at an organic/inorganic heterointerface. We report internal quantum efficiencies exceeding 50% and power conversion efficiencies approaching 1%. These findings suggest an alternative route to circumvent the Shockley-Queisser limit on the power conversion efficiency of single-junction solar cells.

  20. A facile and green preparation of high-quality CdTe semiconductor nanocrystals at room temperature

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Shen, Qihui; Yu, Dongdong; Shi, Weiguang; Li, Jixue; Zhou, Jianguang; Liu, Xiaoyang

    2008-06-01

    One chemical reagent, hydrazine hydrate, was discovered to accelerate the growth of semiconductor nanocrystals (cadmium telluride) instead of additional energy, which was applied to the synthesis of high-quality CdTe nanocrystals at room temperature and ambient conditions within several hours. Under this mild condition the mercapto stabilizers were not destroyed, and they guaranteed CdTe nanocrystal particle sizes with narrow and uniform distribution over the largest possible range. The CdTe nanocrystals (photoluminescence emission range of 530-660 nm) synthesized in this way had very good spectral properties; for instance, they showed high photoluminescence quantum yield of up to 60%. Furthermore, we have succeeded in detecting the living Borrelia burgdorferi of Lyme disease by its photoluminescence image using CdTe nanocrystals.

  1. Quantum dot sensitized solar cells with improved efficiency prepared using electrophoretic deposition.

    PubMed

    Salant, Asaf; Shalom, Menny; Hod, Idan; Faust, Adam; Zaban, Arie; Banin, Uri

    2010-10-26

    Quantum dot sensitized solar cells (QDSSC) may benefit from the ability to tune the quantum dot optical properties and band gap through the manipulation of their size and composition. Moreover, the inorganic nanocrystals may provide increased stability compared to organic sensitizers. We report the facile fabrication of QDSSC by electrophoretic deposition of CdSe QDs onto conducting electrodes coated with mesoporous TiO(2). Unlike prior chemical linker-based methods, no pretreatment of the TiO(2) was needed, and deposition times as short as 2 h were sufficient for effective coating. Cross-sectional chemical analysis shows that the Cd content is nearly constant across the entire TiO(2) layer. The dependence of the deposition on size was studied and successfully applied to CdSe dots with diameters between 2.5 and 5.5 nm as well as larger CdSe quantum rods. The photovoltaic characteristics of the devices are greatly improved compared with those achieved for cells prepared with a linker approach, reaching efficiencies as high as 1.7%, under 1 sun illumination conditions, after treating the coated electrodes with ZnS. Notably, the absorbed photon to electron conversion efficiencies did not show a clear size-dependence indicating efficient electron injection even for the larger QD sizes. The electrophoretic deposition method can be easily expanded and applied for preparations of QDSSCs using diverse colloidal quantum dot and quantum rod materials for sensitization.

  2. Quantum dot-sensitized hierarchical micro/nanowire architecture for photoelectrochemical water splitting.

    PubMed

    Sheng, Wenjun; Sun, Bo; Shi, Tielin; Tan, Xianhua; Peng, Zhengchun; Liao, Guanglan

    2014-07-22

    We report the fabrication of quantum dot-sensitized hierarchical structure and the application of the structure as a photoanode for photoelectrochemical water splitting. The structure is synthesized by hydrothermally growing ZnO nanowires on silicon microwires grown with the vapor-liquid-solid method. Then the hierarchical structure is further sensitized with CdS and CdSe quantum dots and modified with IrOx quantum dots. As a result, the silicon microwires, ZnO nanowires, and the quantum dot/ZnO core/shell structure form a multiple-level hierarchical heterostructure, which is remarkably beneficial for light absorption and charge carrier separation. Our experimental results reveal that the photocurrent density of our multiple-level hierarchical structure achieves a surprising 171 times enhancement compared to that from simple ZnO nanowires on a planar substrate. In addition, the photoanode shows high stability during the water-splitting experiment. These results prove that the quantum dot-sensitized hierarchical structure is an ideal candidate for a photoanode in solar water splitting applications. Importantly, the modular design approach we take to produce the photoanode allows for the integration of future discoveries for further improvement of its performance.

  3. High open circuit voltages of solar cells based on quantum dot and dye hybrid-sensitization

    SciTech Connect

    Zhao, Yujie; Zhao, Wanyu; Chen, Jingkuo; Li, Huayang; Fu, Wuyou E-mail: fuwy56@163.com; Sun, Guang; Cao, Jianliang; Zhang, Zhanying; Bala, Hari E-mail: fuwy56@163.com

    2014-01-06

    A type of solar cell based on quantum dot (QD) and dye hybrid-sensitized mesoporous TiO{sub 2} film electrode was designed and reported. The electrode was consisted of a TiO{sub 2} nanoparticle (NP) thin film layer sensitized with CdS quantum dot (QD) and an amorphous TiO{sub 2} coated TiO{sub 2} NP thin film layer that sensitized with C106 dye. The amorphous TiO{sub 2} layer was obtained by TiCl{sub 4} post-treatment to improve the properties of solar cells. Research showed that the solar cells fabricated with as-prepared hybrid-sensitized electrode exhibited excellent photovoltaic performances and a fairly high open circuit voltage of 796 mV was achieved.

  4. Broadband energy transfer to sensitizing dyes by mobile quantum dot mediators in solar cells.

    PubMed

    Adhyaksa, Gede Widia Pratama; Lee, Ga In; Baek, Se-Woong; Lee, Jung-Yong; Kang, Jeung Ku

    2013-01-01

    The efficiency of solar cells depends on absorption intensity of the photon collectors. Herein, mobile quantum dots (QDs) functionalized with thiol ligands in electrolyte are utilized into dye-sensitized solar cells. The QDs serve as mediators to receive and re-transmit energy to sensitized dyes, thus amplifying photon collection of sensitizing dyes in the visible range and enabling up-conversion of low-energy photons to higher-energy photons for dye absorption. The cell efficiency is boosted by dispersing QDs in electrolyte, thereby obviating the need for light scattering or plasmonic structures. Furthermore, optical spectroscopy and external quantum efficiency data reveal that resonance energy transfer due to the overlap between QD emission and dye absorption spectra becomes dominant when the QD bandgap is higher than the first excitonic peak of the dye, while co-sensitization resulting in a fast reduction of oxidized dyes is pronounced in the case of lower QD band gaps.

  5. Broadband energy transfer to sensitizing dyes by mobile quantum dot mediators in solar cells

    PubMed Central

    Adhyaksa, Gede Widia Pratama; Lee, Ga In; Baek, Se-Woong; Lee, Jung-Yong; Kang, Jeung Ku

    2013-01-01

    The efficiency of solar cells depends on absorption intensity of the photon collectors. Herein, mobile quantum dots (QDs) functionalized with thiol ligands in electrolyte are utilized into dye–sensitized solar cells. The QDs serve as mediators to receive and re–transmit energy to sensitized dyes, thus amplifying photon collection of sensitizing dyes in the visible range and enabling up–conversion of low-energy photons to higher-energy photons for dye absorption. The cell efficiency is boosted by dispersing QDs in electrolyte, thereby obviating the need for light scattering1 or plasmonic2 structures. Furthermore, optical spectroscopy and external quantum efficiency data reveal that resonance energy transfer due to the overlap between QD emission and dye absorption spectra becomes dominant when the QD bandgap is higher than the first excitonic peak of the dye, while co–sensitization resulting in a fast reduction of oxidized dyes is pronounced in the case of lower QD band gaps. PMID:24048384

  6. Quantum Zeno effect explains magnetic-sensitive radical-ion-pair reactions.

    PubMed

    Kominis, I K

    2009-11-01

    Chemical reactions involving radical-ion pairs are ubiquitous in biology, since not only are they at the basis of the photosynthetic reaction chain, but are also assumed to underlie the biochemical magnetic compass used by avian species for navigation. Recent experiments with magnetic-sensitive radical-ion-pair reactions provided strong evidence for the radical-ion-pair magnetoreception mechanism, verifying the expected magnetic sensitivities and chemical product yield changes. It is here shown that the theoretical description of radical-ion-pair reactions used since the 70s cannot explain the observed data, because it is based on phenomenological equations masking quantum coherence effects. The fundamental density-matrix equation derived here from basic quantum measurement theory considerations naturally incorporates the quantum Zeno effect and readily explains recent experimental observations on low- and high magnetic-field radical-ion-pair reactions.

  7. Quantum Zeno effect explains magnetic-sensitive radical-ion-pair reactions

    NASA Astrophysics Data System (ADS)

    Kominis, I. K.

    2009-11-01

    Chemical reactions involving radical-ion pairs are ubiquitous in biology, since not only are they at the basis of the photosynthetic reaction chain, but are also assumed to underlie the biochemical magnetic compass used by avian species for navigation. Recent experiments with magnetic-sensitive radical-ion-pair reactions provided strong evidence for the radical-ion-pair magnetoreception mechanism, verifying the expected magnetic sensitivities and chemical product yield changes. It is here shown that the theoretical description of radical-ion-pair reactions used since the 70s cannot explain the observed data, because it is based on phenomenological equations masking quantum coherence effects. The fundamental density-matrix equation derived here from basic quantum measurement theory considerations naturally incorporates the quantum Zeno effect and readily explains recent experimental observations on low- and high magnetic-field radical-ion-pair reactions.

  8. Controlled optical properties of water-soluble CdTe nanocrystals via anion exchange.

    PubMed

    Li, Jing; Jia, Jianguang; Lin, Yuan; Zhou, Xiaowen

    2016-02-01

    We report a study on anion exchange reaction of CdTe nanocrystals with S(2-) in aqueous solution under ambient condition. We found that the optical properties of CdTe nanocrystals can be well tuned by controlling the reaction conditions, in which the reaction temperature is crucially important. At low reaction temperature, the product nanocrystals showed blue-shifts in both absorption and PL spectra, while the photoluminescence quantum yield (PLQY) was significantly enhanced. When anion exchanges were carried out at higher reaction temperature, on the other hand, obvious red shifts in absorption and PL spectra accompanied by a fast increase followed by gradual decrease in PLQY were observed. On variation of S(2-) concentration, it was found that the overall kinetics of Te(2-) for S(2-) exchanges depends also on [S(2-)] when anion exchanges were performed at higher temperature. A possible mechanism for anion exchanges in CdTe NCs was proposed.

  9. Sensitivity of heterointerfaces on emission wavelength of quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Wang, C. A.; Schwarz, B.; Siriani, D. F.; Connors, M. K.; Missaggia, L. J.; Calawa, D. R.; McNulty, D.; Akey, A.; Zheng, M. C.; Donnelly, J. P.; Mansuripur, T. S.; Capasso, F.

    2017-04-01

    The measured emission wavelengths of AlInAs/GaInAs/InP quantum cascade lasers (QCLs) grown by metal organic vapor phase epitaxy (MOVPE) have been reported to be 0.5-1 μm longer than the designed QCL wavelength. This work clarifies the origin of the red-shifted wavelength. It was found that AlInAs/GaInAs heterointerfaces are compositionally graded over 2.5-4.5 nm, and indium accumulates at the AlInAs-to-GaInAs interface. Thus, the as-grown QCLs are far from the ideal abrupt interfaces used in QCL modeling. When graded layers are incorporated in QCL band structure and wavefunction calculations, the emission wavelengths are red shifted. Furthermore, we demonstrate that QCLs with graded interfaces can be designed without compromising performance and show greatly improved correlation between designed and measured emission wavelength. QCLs were designed for emission between 7.5 and 8.5 μm. These structures were grown and wet-etched ridge devices were fabricated. The QCLs exhibit room temperature peak powers exceeding 900 mW and pulsed efficiencies of 8 to 10%.

  10. Quantum-dot-sensitized TiO2 inverse opals for photoelectrochemical hydrogen generation.

    PubMed

    Cheng, Chuanwei; Karuturi, Siva Krishna; Liu, Lijun; Liu, Jinping; Li, Hongxing; Su, Liap Tat; Tok, Alfred Iing Yoong; Fan, Hong Jin

    2012-01-09

    A new nanoarchitecture photoelectrode design comprising CdS quantum-dot-sensitized, optically and electrically active TiO(2) inverse opals is developed for photoelectrochemical water splitting. The photoelectrochemical performance shows high photocurrent density (4.84 mA cm(-2) at 0 V vs. Ag/AgCl) under simulated solar-light illumination.

  11. Elimination of Zero-Quantum artifacts and sensitivity enhancement in perfect echo based 2D NOESY.

    PubMed

    Baishya, Bikash; Verma, Ajay

    2015-03-01

    Zero-Quantum artifacts seriously degrade the performance of 2D NOESY. Homonuclear J-evolution during t(1) period generates Zero-Quantum and other higher quantum coherences which represent the magnetization loss and the artifacts created. We demonstrate that creation of such artifacts itself can be prevented for shorter t1 period by a perfect echo based decoupling technique during t1 period in a single scan. This is in contrast to existing methods that create unwanted coherence, and subsequently suppress that to produce a clean spectrum with a sensitivity penalty. Although decoupling performance of the present scheme remains robust for echo time 2τ short compared to 1/2J, we show that even a partial decoupling effect for extended t(1) (=2τ) period up to 100 ms along with a Zero-Quantum filter generates NOE spectrum from Cyclosporine A, in which majority of the cross peaks displayed partial sensitivity enhancement with few exceptions. However, in crowded proton spin systems like menthol, the enhancements were not observed and perfect echo NOESY displays similar performance as Zero-Quantum filtered NOESY.

  12. Quantum dot sensitized solar cells: Light harvesting versus charge recombination, a film thickness consideration

    NASA Astrophysics Data System (ADS)

    Wang, Xiu Wei; Wang, Ye Feng; Zeng, Jing Hui; Shi, Feng; Chen, Yu; Jiang, Jiaxing

    2017-08-01

    Sensitizer loading level is one of the key factors determined the performance of sensitized solar cells. In this work, we systemically studied the influence of photo-anode thicknesses on the performance of the quantum-dot sensitized solar cells. It is found that the photo-to-current conversion efficiency enhances with increased film thickness and peaks at around 20 μm. The optimal value is about twice as large as the dye counterparts. Here, we also uncover the underlying mechanism about the influence of film thickness over the photovoltaic performance of QDSSCs from the light harvesting and charge recombination viewpoint.

  13. Sensitivity Enhancement in Static Solid-State NMR Experiments VIA Single and Multiple Quantum Dipolar Coherences

    PubMed Central

    Gopinath, T.; Veglia, Gianluigi

    2012-01-01

    We present a new method to enhance the sensitivity in static solid-state NMR for a gain in signal-to-noise ratio up to 40%. This sensitivity enhancement is different from the corresponding solution NMR sensitivity enhancement schemes and is achieved by combining single and multiple quantum dipolar coherences. While this new approach is demonstrated for the PISEMA (polarization inversion spin exchange at magic angle) experiment, it can be generalized to the other separated local field experiments for solid-state NMR spectroscopy. This method will have a direct impact on solid-state NMR spectroscopy of liquid crystals as well as membrane proteins aligned in lipid membranes. PMID:19351170

  14. Optimizing timing performance of CdTe detectors for PET

    NASA Astrophysics Data System (ADS)

    Nakhostin, M.

    2017-10-01

    Despite several attractive properties, the poor timing performance of compound semiconductor detectors such as CdTe and CdZnTe has hindered their use in commercial PET imaging systems. The standard method of pulse timing with such detectors is to employ a constant-fraction discriminator at the output of a timing filter which is fed by the pulses from a charge-sensitive preamplifier. The method has led to a time resolution of about 10 ns at full-width at half-maximum (FWHM) with 1 mm thick CdTe detectors. This paper presents a detailed investigation on the parameters limiting the timing performance of Ohmic contact planar CdTe detectors with the standard pulse timing method. The jitter and time-walk errors are studied through simulation and experimental measurements and it is revealed that the best timing results obtained with the standard timing method suffer from a significant loss of coincidence events (~50%). In order to improve the performance of the detectors with full detection efficiency, a new digital pulse timing method based on a simple pattern recognition technique was developed. A time resolution of 3.29  ±  0.10 ns (FWHM) in the energy range of 300–650 keV was achieved with an Ohmic contact planar CdTe detector (5  ×  5  ×  1 mm3). The digital pulse processing method was also used to correct for the charge-trapping effect and an improvement in the energy resolution from 4.83  ±  0.66% to 2.780  ±  0.002% (FWHM) at 511 keV was achieved. Further improvement of time resolution through a moderate cooling of the detector and the application of the method to other detector structures are also discussed.

  15. Metal oxide semiconductors for dye- and quantum-dot-sensitized solar cells.

    PubMed

    Concina, Isabella; Vomiero, Alberto

    2015-04-17

    This Review provides a brief summary of the most recent research developments in the synthesis and application of nanostructured metal oxide semiconductors for dye sensitized and quantum dot sensitized solar cells. In these devices, the wide bandgap semiconducting oxide acts as the photoanode, which provides the scaffold for light harvesters (either dye molecules or quantum dots) and electron collection. For this reason, proper tailoring of the optical and electronic properties of the photoanode can significantly boost the functionalities of the operating device. Optimization of the functional properties relies with modulation of the shape and structure of the photoanode, as well as on application of different materials (TiO2, ZnO, SnO2) and/or composite systems, which allow fine tuning of electronic band structure. This aspect is critical because it determines exciton and charge dynamics in the photoelectrochemical system and is strictly connected to the photoconversion efficiency of the solar cell. The different strategies for increasing light harvesting and charge collection, inhibiting charge losses due to recombination phenomena, are reviewed thoroughly, highlighting the benefits of proper photoanode preparation, and its crucial role in the development of high efficiency dye sensitized and quantum dot sensitized solar cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. [The impact of ZnS/CdS composite window layer on the quantun efficiency of CdTe solar cell in short wavelength].

    PubMed

    Zhang, Li-xiang; Feng, Liang-huan; Wang, Wen-wu; Xu, Hang; Wu, Li-li; Zhang, Jing-quan; Li, Wei; Zeng, Guang-gen

    2015-02-01

    ZnS/CdS composite window layer was prepared by magnetron sputtering method and then applied to CdTe solar cell. The morphology and structure of films were measured. The data of I-V in light and the quantum efficiency of CdTe solar cells with different window layers were also measured. The effect of ZnS films prepared in different conditions on the performance of CdTe solar cells was researched. The effects of both CdS thickness and ZnS/CdS composite layer on the transmission in short wavelength were studied. Particularly, the quantum efficiency of CdTe solar cells with ZnS/CdS window layer was measured. The results show as follows. With the thickness of CdS window layer reducing from 100 to 50 nm, the transmission increase 18.3% averagely in short wavelength and the quantum efficiency of CdTe solar cells increase 27.6% averagely. The grain size of ZnS prepared in 250 degrees C is smaller than prepared at room temperature. The performance of CdTe solar cells with ZnS/CdS window layer is much better if ZnS deposited at 250 degrees C. This indicates grain size has some effect on the electron transportation. When the CdS holds the same thickness, the transmission of ZnS/CdS window layer was improved about 2% in short wavelength compared with CdS window layer. The quantum efficiency of CdTe solar cells with ZnS/CdS window layer was also improved about 2% in short wavelength compared with that based on CdS window layer. These indicate ZnS/CdS composite window layer can increase the photon transmission in short wavelength so that more photons can be absorbed by the absorbent layer of CdTe solar cells.

  17. Fluorescent graphene quantum dot nanoprobes for the sensitive and selective detection of mercury ions.

    PubMed

    Wang, Baojuan; Zhuo, Shujuan; Chen, Luyang; Zhang, Yongjun

    2014-10-15

    Graphene quantum dots were prepared by ultrasonic route and served as a highly selective water-soluble probe for sensing of Hg(2+). The fluorescence emission spectrum of graphene quantum dots was at about 430nm. In the presence of Hg(2+), the fluorescence of the quantum dots significantly quenched. And the fluorescence intensity gradually decreased with the increasing concentration of Hg(2+). The change of fluorescence intensity is directly proportional to the concentration of Hg(2+). Under optimum conditions, the linear range for the detection of Hg(2+) was 8.0×10(-7) to 9×10(-6)M with a detection limit of 1.0×10(-7)M. In addition, the preliminary mechanism of fluorescence quenching was discussed in the paper. The constructed sensor with high sensitivity and selectivity, simple, rapid properties makes it valuable for further application. Copyright © 2014 Elsevier B.V. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Highly Sensitive Electrochemical Determination of Alfatoxin B1 Using Quantum Dots-Assembled Amplification Labels.

    PubMed

    Zeng, Xiaoqun; Gao, Huiju; Pan, Daodong; Sun, Yangying; Cao, Jinxuan; Wu, Zhen; Pan, Zhenyu

    2015-08-20

    A competitive electrochemical immunoassay for highly sensitive detection of AFB1 is demonstrated using layer-by-layer (LBL) assembled quantum dots (QDs) as labels. To investigate the effects of the higher sensitivity of square wave voltammetric stripping (SWV) and of the LBL technique on the proposed immunoassays, the proposed assay was compared to electrochemical (EC) and fluorescent immunoassays, which did not use LBL technology. Peanut samples were analyzed using the three immunoassays. The limits of detection (LODs) were 0.018, 0.046 and 0.212 ng/mL, respectively, while the sensitivities were 0.308, 1.011 and 4.594 ng/mL, respectively. The proposed electrochemical immunoassay displayed a significant improvement in sensitivity, thereby providing a simple and sensitive alternative strategy for determining AFB1 levels in peanut samples.

  20. Green synthesis of highly efficient CdSe quantum dots for quantum-dots-sensitized solar cells

    SciTech Connect

    Gao, Bing; Shen, Chao; Zhang, Mengya; Yuan, Shuanglong; Yang, Yunxia E-mail: grchen@ecust.edu.cn; Chen, Guorong E-mail: grchen@ecust.edu.cn; Zhang, Bo

    2014-05-21

    Green synthesis of CdSe quantum dots for application in the quantum-dots-sensitized solar cells (QDSCs) is investigated in this work. The CdSe QDs were prepared with glycerol as the solvent, with sharp emission peak, full width at half maximum around 30 nm, and absorption peak from 475 nm to 510 nm. The reaction is environmental friendly and energy saving. What's more, the green synthesized CdSe QDs are coherence to the maximum remittance region of the solar spectrum and suitable as sensitizers to assemble onto TiO{sub 2} electrodes for cell devices application. What's more, the dynamic procedure of the carriers' excitation, transportation, and recombination in the QDSCs are discussed. Because the recombination of the electrons from the conduction band of TiO{sub 2}'s to the electrolyte affects the efficiency of the solar cells greatly, 3-Mercaptopropionic acid capped water-dispersible QDs were used to cover the surface of TiO{sub 2}. The resulting green synthesized CdSe QDSCs with Cu{sub 2}S as the electrode show a photovoltaic performance with a conversion efficiency of 3.39%.

  1. Alloying Strategy in Cu-In-Ga-Se Quantum Dots for High Efficiency Quantum Dot Sensitized Solar Cells.

    PubMed

    Peng, Wenxiang; Du, Jun; Pan, Zhenxiao; Nakazawa, Naoki; Sun, Jiankun; Du, Zhonglin; Shen, Gencai; Yu, Juan; Hu, Jin-Song; Shen, Qing; Zhong, Xinhua

    2017-02-15

    I-III-VI2 group "green" quantum dots (QDs) are attracting increasing attention in photoelectronic conversion applications. Herein, on the basis of the "simultaneous nucleation and growth" approach, Cu-In-Ga-Se (CIGSe) QDs with light harvesting range of about 1000 nm were synthesized and used as sensitizer to construct quantum dot sensitized solar cells (QDSCs). Inductively coupled plasma atomic emission spectrometry (ICP-AES), wild-angle X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses demonstrate that the Ga element was alloyed in the Cu-In-Se (CISe) host. Ultraviolet photoelectron spectroscopy (UPS) and femtosecond (fs) resolution transient absorption (TA) measurement results indicate that the alloying strategy could optimize the electronic structure in the obtained CIGSe QD material, thus matching well with TiO2 substrate and favoring the photogenerated electron extraction. Open circuit voltage decay (OCVD) and impedance spectroscopy (IS) tests indicate that the intrinsic recombination in CIGSe QDSCs was well suppressed relative to that in CISe QDSCs. As a result, CIGSe based QDSCs with use of titanium mesh supported mesoporous carbon counter electrode exhibited a champion efficiency of 11.49% (Jsc = 25.01 mA/cm(2), Voc = 0.740 V, FF = 0.621) under the irradiation of full one sun in comparison with 9.46% for CISe QDSCs.

  2. An integrated approach to realizing high-performance liquid-junction quantum dot sensitized solar cells.

    PubMed

    McDaniel, Hunter; Fuke, Nobuhiro; Makarov, Nikolay S; Pietryga, Jeffrey M; Klimov, Victor I

    2013-01-01

    Solution-processed semiconductor quantum dot solar cells offer a path towards both reduced fabrication cost and higher efficiency enabled by novel processes such as hot-electron extraction and carrier multiplication. Here we use a new class of low-cost, low-toxicity CuInSexS2-x quantum dots to demonstrate sensitized solar cells with certified efficiencies exceeding 5%. Among other material and device design improvements studied, use of a methanol-based polysulfide electrolyte results in a particularly dramatic enhancement in photocurrent and reduced series resistance. Despite the high vapour pressure of methanol, the solar cells are stable for months under ambient conditions, which is much longer than any previously reported quantum dot sensitized solar cell. This study demonstrates the large potential of CuInSexS2-x quantum dots as active materials for the realization of low-cost, robust and efficient photovoltaics as well as a platform for investigating various advanced concepts derived from the unique physics of the nanoscale size regime.

  3. An integrated approach to realizing high-performance liquid-junction quantum dot sensitized solar cells

    PubMed Central

    McDaniel, Hunter; Fuke, Nobuhiro; Makarov, Nikolay S.; Pietryga, Jeffrey M.; Klimov, Victor I.

    2013-01-01

    Solution-processed semiconductor quantum dot solar cells offer a path towards both reduced fabrication cost and higher efficiency enabled by novel processes such as hot-electron extraction and carrier multiplication. Here we use a new class of low-cost, low-toxicity CuInSexS2−x quantum dots to demonstrate sensitized solar cells with certified efficiencies exceeding 5%. Among other material and device design improvements studied, use of a methanol-based polysulfide electrolyte results in a particularly dramatic enhancement in photocurrent and reduced series resistance. Despite the high vapour pressure of methanol, the solar cells are stable for months under ambient conditions, which is much longer than any previously reported quantum dot sensitized solar cell. This study demonstrates the large potential of CuInSexS2−x quantum dots as active materials for the realization of low-cost, robust and efficient photovoltaics as well as a platform for investigating various advanced concepts derived from the unique physics of the nanoscale size regime. PMID:24322379

  4. Wavelength sensitive detector based on ICD in two coupled quantum wells

    NASA Astrophysics Data System (ADS)

    Goldzak, Tamar; Gilary, Ido; Moiseyev, Nimrod

    2014-05-01

    We design a wavelength sensitive detector based on inter coulombic decay (ICD) mechanism in a two-quantum well nano-structure. The two coupled quantum wells are designed to satisfy the specific conditions which allow the ICD to occur. In this setup, by absorbing light an electron in one well is excited. Its relaxation back to the ground state is a non-radiative process which transfers the excess energy to the ionization of the electron in the neighboring well into the continuum. Only radiation with a specific wavelength will be absorbed, when the wavelength matches the excitation energy in the quantum well. By applying a weak bias a current is obtained even when light with a very low intensity is absorbed. For the ICD to be dominant decay mechanism it must prevail over all other possible competitive decay processes. We have found that the lifetime of the ICD is on the timescale of picoseconds. Control over the ICD lifetime can be achieved by variation of different parameters in the two quantum well nano-structure. The most useful parameter is the distance between the two quantum wells. We show that as the distance decreases the decay rate of the ICD increases. Furthermore the distance can be tuned such that the emitted electron would be in a metastable state in the continuum (a resonance state); this causes the life time of the ICD to be an order of magnitude smaller, and improves the efficiency of the ICD.

  5. Antimony diffusion in CdTe

    DOE PAGES

    Colegrove, Eric; Harvey, Steven P.; Yang, Ji -Hui; ...

    2017-02-08

    Group V dopants may be used for next-generation high-voltage cadmium telluride (CdTe) solar photovoltaics, but fundamental defect energetics and kinetics need to be understood. Here, antimony (Sb) diffusion is studied in single-crystal and polycrystalline CdTe under Cd-rich conditions. Diffusion profiles are determined by dynamic secondary ion mass spectroscopy and analyzed with analytical bulk and grain-boundary diffusion models. Slow bulk and fast grain-boundary diffusion are found. Density functional theory is used to understand formation energy and mechanisms. Lastly, the theory and experimental results create new understanding of group V defect kinetics in CdTe.

  6. Giant photocurrent enhancement by transition metal doping in quantum dot sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Rimal, Gaurab; Pimachev, Artem K.; Yost, Andrew J.; Poudyal, Uma; Maloney, Scott; Wang, Wenyong; Chien, TeYu; Dahnovsky, Yuri; Tang, Jinke

    2016-09-01

    A huge enhancement in the incident photon-to-current efficiency of PbS quantum dot (QD) sensitized solar cells by manganese doping is observed. In the presence of Mn dopants with relatively small concentration (4 at. %), the photoelectric current increases by an average of 300% (up to 700%). This effect cannot be explained by the light absorption mechanism because both the experimental and theoretical absorption spectra demonstrate several times decreases in the absorption coefficient. To explain such dramatic increase in the photocurrent we propose the electron tunneling mechanism from the LUMO of the QD excited state to the Zn2SnO4 (ZTO) semiconductor photoanode. This change is due to the presence of the Mn instead of Pb atom at the QD/ZTO interface. The ab initio calculations confirm this mechanism. This work proposes an alternative route for a significant improvement of the efficiency for quantum dot sensitized solar cells.

  7. Giant photocurrent enhancement by transition metal doping in quantum dot sensitized solar cells

    SciTech Connect

    Rimal, Gaurab; Pimachev, Artem K.; Yost, Andrew J.; Poudyal, Uma; Maloney, Scott; Wang, Wenyong; Chien, TeYu; Dahnovsky, Yuri E-mail: jtang2@uwyo.edu; Tang, Jinke E-mail: jtang2@uwyo.edu

    2016-09-05

    A huge enhancement in the incident photon-to-current efficiency of PbS quantum dot (QD) sensitized solar cells by manganese doping is observed. In the presence of Mn dopants with relatively small concentration (4 at. %), the photoelectric current increases by an average of 300% (up to 700%). This effect cannot be explained by the light absorption mechanism because both the experimental and theoretical absorption spectra demonstrate several times decreases in the absorption coefficient. To explain such dramatic increase in the photocurrent we propose the electron tunneling mechanism from the LUMO of the QD excited state to the Zn{sub 2}SnO{sub 4} (ZTO) semiconductor photoanode. This change is due to the presence of the Mn instead of Pb atom at the QD/ZTO interface. The ab initio calculations confirm this mechanism. This work proposes an alternative route for a significant improvement of the efficiency for quantum dot sensitized solar cells.

  8. Study on the Fabrication of Paint-Type Si Quantum Dot-Sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Seo, Hyunwoong; Son, Min-Kyu; Kim, Hee-Je; Wang, Yuting; Uchida, Giichiro; Kamataki, Kunihiro; Itagaki, Naho; Koga, Kazunori; Shiratani, Masaharu

    2013-10-01

    Quantum dots (QDs) have attracted much attention with their quantum characteristics in the research field of photochemical solar cells. Si QD was introduced as one of alternatives to conventional QD materials. However, their large particles could not penetrate inside TiO2 layer. Therefore, this work proposed the paint-type Si QD-sensitized solar cell. Its heat durability was suitable for the fabrication of paint-type solar cell. Si QDs were fabricated by multihollow discharge plasma chemical vapor deposition and characterized. The paste type, sintering temperature, and Si ratio were controlled and analyzed for better performance. Finally, its performance was enhanced by ZnS surface modification and the whole process was much simplified without sensitizing process.

  9. A structure of CdS/CuxS quantum dots sensitized solar cells.

    PubMed

    Shen, Ting; Bian, Lu; Li, Bo; Zheng, Kaibo; Pullerits, Tönu; Tian, Jianjun

    2016-05-23

    This work introduces a type of CdS/CuxS quantum dots (QDs) as sensitizers in quantum dot sensitized solar cells by in-situ cationic exchange reaction method where CdS photoanode is directly immersed in CuCl2 methanol solution to replace Cd(2+) by Cu(2+). The p-type CuxS layer on the surface of the CdS QDs can be considered as hole transport material, which not only enhances the light harvesting of photoanode but also boosts the charge separation after photo-excitation. Therefore, both the electron collection efficiency and power conversion efficiency of the solar cell are improved from 80% to 92% and from 1.21% to 2.78%, respectively.

  10. A structure of CdS/Cu{sub x}S quantum dots sensitized solar cells

    SciTech Connect

    Shen, Ting; Bian, Lu; Li, Bo; Tian, Jianjun; Zheng, Kaibo; Pullerits, Tönu

    2016-05-23

    This work introduces a type of CdS/Cu{sub x}S quantum dots (QDs) as sensitizers in quantum dot sensitized solar cells by in-situ cationic exchange reaction method where CdS photoanode is directly immersed in CuCl{sub 2} methanol solution to replace Cd{sup 2+} by Cu{sup 2+}. The p-type Cu{sub x}S layer on the surface of the CdS QDs can be considered as hole transport material, which not only enhances the light harvesting of photoanode but also boosts the charge separation after photo-excitation. Therefore, both the electron collection efficiency and power conversion efficiency of the solar cell are improved from 80% to 92% and from 1.21% to 2.78%, respectively.

  11. Sensitive Radio-Frequency Measurements of a Quantum Dot by Tuning to Perfect Impedance Matching

    NASA Astrophysics Data System (ADS)

    Ares, N.; Schupp, F. J.; Mavalankar, A.; Rogers, G.; Griffiths, J.; Jones, G. A. C.; Farrer, I.; Ritchie, D. A.; Smith, C. G.; Cottet, A.; Briggs, G. A. D.; Laird, E. A.

    2016-03-01

    Electrical readout of spin qubits requires fast and sensitive measurements, which are hindered by poor impedance matching to the device. We demonstrate perfect impedance matching in a radio-frequency readout circuit, using voltage-tunable varactors to cancel out parasitic capacitances. An optimized capacitance sensitivity of 1.6 aF /√{Hz } is achieved at a maximum source-drain bias of 170 -μ V root-mean-square and with a bandwidth of 18 MHz. Coulomb blockade in a quantum-dot is measured in both conductance and capacitance, and the two contributions are found to be proportional as expected from a quasistatic tunneling model. We benchmark our results against the requirements for single-shot qubit readout using quantum capacitance, a goal that has so far been elusive.

  12. Has the Sun Set on Quantum Dot-Sensitized Solar Cells?

    DOE PAGES

    Wrenn, Toshia L.; McBride, James R.; Smith, Nathanael J.; ...

    2015-01-01

    This is a reminder, a review and a look toward the future prospects for quantum dot-sensitized solar cells - a reminder of the highly viable, energy-efficient solar cells achievable. This is also a review of ground-breaking devices and their similarities to the near unity photon-to-electron mechanisms of photosynthesis; a look toward architectures that capitalize on the advances observed in previous work.

  13. Biomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cells.

    PubMed

    Briscoe, Joe; Marinovic, Adam; Sevilla, Marta; Dunn, Steve; Titirici, Magdalena

    2015-04-07

    New hybrid materials consisting of ZnO nanorods sensitized with three different biomass-derived carbon quantum dots (CQDs) were synthesized, characterized, and used for the first time to build solid-state nanostructured solar cells. The performance of the devices was dependent on the functional groups found on the CQDs. The highest efficiency was obtained using a layer-by-layer coating of two different types of CQDs.

  14. Ultrafast interfacial charge transfer dynamics in dye-sensitized and quantum dot solar cell

    NASA Astrophysics Data System (ADS)

    Ghosh, Hirendra N.

    2013-02-01

    Dye sensitized solar cell (DSSC) appeared to be one of the good discovery for the solution of energy problem. We have been involved in studying ultrafast interfacial electron transfer dynamics in DSSC using femtosecond laser spectroscopy. However it has been realized that it is very difficult to design and develop higher efficient one, due to thermodynamic limitation. Again in DSSC most of the absorbed photon energy is lost as heat within the cell, which apart from decreasing the efficiency also destabilizes the device. It has been realized that quantum dot solar cell (QDSC) are the best bet where the sensitizer dye molecules can be replaced by suitable quantum dot (QD) materials in solar cell. The quantum-confinement effect in semiconductors modifies their electronic structure, which is a very important aspect of these materials. For photovoltaic applications, a long-lived charge separation remains one of the most essential criteria. One of the problems in using QDs for photovoltaic applications is their fast charge recombination caused by nonradiative Auger processes, which occur predominantly at lower particle sizes due to an increase in the Coulomb interaction between electrons and holes. Various approaches, such as the use of metal-semiconductor composites, semiconductor-polymer composite, and semiconductor core-shell heterostructures, have been attempted to minimize the fast recombination between electrons and holes. To make higher efficient solar devices it has been realised that it is very important to understand charge carrier and electron transfer dynamics in QD and QD sensitized semiconductor nanostructured materials. In the present talk, we are going to discuss on recent works on ultrafast electron transfer dynamics in dye-sensitized TiO2 nanoparticles/film [1-12] and charge (electron/hole) transfer dynamics in quantum dot core-shell nano-structured materials [13-17].

  15. Elucidating triplet-sensitized photolysis mechanisms of sulfadiazine and metal ions effects by quantum chemical calculations.

    PubMed

    Wang, Se; Song, Xuedan; Hao, Ce; Gao, Zhanxian; Chen, Jingwen; Qiu, Jieshan

    2015-03-01

    Sulfadiazine (SDZ) mainly proceeds triplet-sensitized photolysis with dissolved organic matter (DOM) in the aquatic environment. However, the mechanisms underlying the triplet-sensitized photolysis of SDZ with DOM have not been fully worked out. In this study, we investigated the mechanisms of triplet-sensitized photolysis of SDZ(0) (neutral form) and SDZ(-) (anionic form) with four DOM analogues, i.e., fluorenone (FL), thioxanthone (TX), 2-acetonaphthone (2-AN), and 4-benzoylbenzoic acid (CBBP), and three metal ions (i.e., Mg(2+), Ca(2+), and Zn(2+)) effects using quantum chemical calculations. Results indicated that the triplet-sensitized photolysis mechanism of SDZ(0) with FL, TX, and 2-AN was hydrogen transfer, and with CBBP was electron transfer along with proton transfer (for complex SDZ(0)-CBBP2) and hydrogen transfer (for complex SDZ(0)-CBBP1). The triplet-sensitized photolysis mechanisms of SDZ(-) with FL, TX, and CBBP was electron transfer along with proton transfer, and with 2-AN was hydrogen transfer. The triplet-sensitized photolysis product of both SDZ(0) and SDZ(-) was a sulfur dioxide extrusion product (4-(2-iminopyrimidine-1(2H)-yl)aniline), but the formation routs of the products for SDZ(0) and SDZ(-) were different. In addition, effects of the metal ions on the triplet-sensitized photolysis of SDZ(0) and SDZ(-) were different. The metal ions promoted the triplet-sensitized photolysis of SDZ(0), but inhibited the triplet-sensitized photolysis of SDZ(-).

  16. Ligand displacement-induced fluorescence switch of quantum dots for ultrasensitive detection of cadmium ions.

    PubMed

    Hu, Xianyun; Zhu, Kao; Guo, Qingsheng; Liu, Yuqian; Ye, Mingfu; Sun, Qingjiang

    2014-02-17

    This paper reports the construction of a simple CdTe quantum dots (QDs)-based sensor with 1,10-phenanthroline (Phen) as ligand, and the demonstration of a novel ligand displacement-induced fluorescence switch strategy for sensitive and selective detection of Cd(2+) in aqueous phase. The complexation of Phen at the surface quenches the green photoluminescence (PL) of QDs dominated by a photoinduced hole transfer (PHT) mechanism. In the presence of Cd(2+), the Phen ligands are readily detached from the surface of CdTe QDs, forming [Cd(Phen)2(H2O)2](2+) in solution, and as a consequence the PL of CdTe QDs switches on. The detection limit for Cd(2+) is defined as ∼0.01 nM, which is far below the maximum Cd(2+) residue limit of drinking water allowed by the U.S. Environmental Protection Agency (EPA). Two consecutive linear ranges allow a wide determination of Cd(2+) from 0.02 nM to 0.6 μM. Importantly, this CdTe QDs-based sensor features to distinctly discriminate between Cd(2+) and Zn(2+), and succeeds in real water samples. This extremely simple strategy reported here represents an attempt for the development of fluorescent sensors for ultrasensitive chemo/biodetection.

  17. Panchromatic quantum-dot-sensitized solar cells based on a parallel tandem structure.

    PubMed

    Zhou, Na; Yang, Yueyong; Huang, Xiaoming; Wu, Huijue; Luo, Yanhong; Li, Dongmei; Meng, Qingbo

    2013-04-01

    A tandem-structure sensitized solar cell, comprising different inorganic semiconductor quantum dots (QDs) as sensitizers in two different compartments, has been designed for the first time with the aim of extending the light-absorption range of current technologies. In this system, the CdS/CdSe co-sensitized quantum-dot solar cell (QDSC) is in the upper part, whereas the PbS/CdS co-sensitized QDSC is in the lower part; these are connected in parallel with each other. In the middle of the tandem solar cell, a Cu2 S mesh counter electrode is employed. By optimizing the electrode thickness and QD-deposition time, short-circuit photocurrent density values of as high as 25.12 mA cm(-2) have been achieved; this value is nearly equal to the sum of the two constituent QD-sensitized devices and gives rise to a solar power-conversion efficiency of 5.06 %.

  18. CDTE alloys and their application for increasing solar cell performance

    NASA Astrophysics Data System (ADS)

    Swanson, Drew E.

    -gap structure demonstrated higher current collection and increased quantum efficiency at longer wavelengths. Material characterization shows the diffusion of selenium through the CdTe during passivation resulting in improved in lifetime and a reduced voltage deficit at lower band gaps.

  19. Increased Quantum Dot Loading by pH Control Reduces Interfacial Recombination in Quantum-Dot-Sensitized Solar Cells.

    PubMed

    Roelofs, Katherine E; Herron, Steven M; Bent, Stacey F

    2015-08-25

    The power conversion efficiency of quantum-dot-sensitized solar cells (QDSSCs) hinges on interfacial charge transfer. Increasing quantum dot (QD) loading on the TiO2 anode has been proposed as a means to block recombination of electrons in the TiO2 to the hole transport material; however, it is not known whether a corresponding increase in QD-mediated recombination processes might lead to an overall higher rate of recombination. In this work, a 3-fold increase in PbS QD loading was achieved by the addition of an aqueous base to negatively charge the TiO2 surface during Pb cation deposition. Increased QD loading improved QDSSC device efficiencies through both increased light absorption and an overall reduction in recombination. Unexpectedly, we also found increased QD size had the detrimental effect of increasing recombination. Kinetic modeling of the effect of QD size on interfacial charge transfer processes provided qualitative agreement with the observed variation in recombination lifetimes. These results demonstrate a robust method of improving QD loading, identify the specific mechanisms by which increased QD deposition impacts device performance, and provide a framework for future efforts optimizing the device architecture of QDSSCs.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. The sensitivity analysis of propagator for path independent quantum finance model

    NASA Astrophysics Data System (ADS)

    Kim, Min Jae; Hwang, Dong Il; Lee, Sun Young; Kim, Soo Yong

    2011-03-01

    Quantum finance successfully implements the imperfectly correlated fluctuation of forward interest rates at different maturities, by replacing the Wiener process with a two-dimensional quantum field. Interest rate derivatives can be priced at a more realistic value under this new framework. The quantum finance model requires three main ingredients for pricing: the initial forward interest rates, the volatility of forward interest rates, and the correlation of forward interest rates at different maturities. However, the hedging strategy only focused on fluctuation of forward interest rates. This hedging method is based on the assumption that the propagator, the covariance of forward interest rates, has an ergodic property. Since inserting the propagator is the main characteristic that distinguishes quantum finance from the Libor market model (LMM) and the Heath, Jarrow and Morton (HJM) model, understanding the impact of propagator dynamics on the price of interest rate derivatives is crucial. This research is the first step in developing a hedge strategy with respect to the evolution of the propagator. We analyze the dynamics of the propagator from Libor futures data and the integrated propagator from zero-coupon bond rate data. Then we study the sensitivity of the implied volatility of caplets and swaptions according to the three dominant dynamics of the propagator, and the change of the zero-coupon bond option price according to the two dominant dynamics of the integrated propagator.

  2. Improving the performance of colloidal quantum-dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Giménez, Sixto; Mora-Seró, Iván; Macor, Lorena; Guijarro, Nestor; Lana-Villarreal, Teresa; Gómez, Roberto; Diguna, Lina J.; Shen, Qing; Toyoda, Taro; Bisquert, Juan

    2009-07-01

    Solar cells based on a mesoporous structure of TiO2 and the polysulfide redox electrolyte were prepared by direct adsorption of colloidal CdSe quantum dot light absorbers onto the oxide without any particular linker. Several factors cooperate to improve the performance of quantum-dot-sensitized solar cells: an open structure of the wide bandgap electron collector, which facilitates a higher covering of the internal surface with the sensitizer, a surface passivation of TiO2 to reduce recombination and improved counter electrode materials. As a result, solar cells of 1.83% efficiency under full 1 sun illumination intensity have been obtained. Despite a relatively large short circuit current (Jsc = 7.13 mA cm-2) and open circuit voltage (Voc = 0.53 V), the colloidal quantum dot solar cell performance is still limited by a low fill factor of 0.50, which is believed to arise from charge transfer of photogenerated electrons to the aqueous electrolyte.

  3. Quantum noise reduction in intensity-sensitive surface-plasmon-resonance sensors

    NASA Astrophysics Data System (ADS)

    Lee, Joong-Sung; Huynh, Trung; Lee, Su-Yong; Lee, Kwang-Geol; Lee, Jinhyoung; Tame, Mark; Rockstuhl, Carsten; Lee, Changhyoup

    2017-09-01

    We investigate the use of twin-mode quantum states of light with symmetric statistical features in their photon number for improving intensity-sensitive surface plasmon resonance (SPR) sensors. For this purpose, one of the modes is sent into a prism setup where the Kretschmann configuration is employed as a sensing platform and the analyte to be measured influences the SPR excitation conditions. This influence modifies the output state of light that is subsequently analyzed by an intensity-difference measurement scheme. We show that quantum noise reduction is achieved not only as a result of the sub-Poissonian statistical nature of a single mode, but also as a result of the nonclassical correlation of the photon number between the two modes. When combined with the high sensitivity of the SPR sensor, we show that the use of twin-mode quantum states of light notably enhances the estimation precision of the refractive index of an analyte. With this we are able to identify a clear strategy to further boost the performance of SPR sensors, which are already a mature technology in biochemical and medical sensing applications.

  4. Preparation of pH-stimuli-responsive PEG-TGA/TGH-capped CdTe QDs and their application in cell labeling.

    PubMed

    Du, Yan; Yang, Dongzhi; Sun, Shian; Zhao, Ziming; Tang, Daoquan

    2015-08-01

    A pH-sensitive and double functional nanoprobe was designed and synthesized in a water-soluble system using thioglycolic acid (TGA) and mercapto-acetohydrazide (TGH) as the stabilizers. TGA is biocompatible because the carboxyl group is easily linked to biological macromolecules. At the same time, the hydrazide on TGH reacts with the aldehyde on poly(ethylene glycol) (PEG) and forms a hydrazone bond. The hydrazone bond ruptured at specific pH values and exhibited pH-stimuli-responsive characteristics. As an optical imaging probe, the PEG-TGA/TGH-capped CdTe quantum dots (QDs) had high quality, with a fluorescence efficiency of 25-30%, and remained stable for at least five months. This pH-responsive factor can be used for the effective release of CdTe QDs under the acidic interstitial extracellular environment of tumor cells. This allows the prepared pH-stimuli-responsive nanoprobes to show fluorescence signals for use in cancer cell imaging. Copyright © 2014 John Wiley & Sons, Ltd.

  5. Quantum dot-mediated photoproduction of reactive oxygen species for cancer cell annihilation.

    PubMed

    Chen, Ji-Yao; Lee, Yee-Man; Zhao, Dan; Mak, Nai-Ki; Wong, Ricky Ngok-Shun; Chan, Wing-Hong; Cheung, Nai-Ho

    2010-01-01

    While semiconductor quantum dots produce little singlet oxygen, they may undergo Type I photoreactions to produce other reactive oxygen species (ROS) to kill cells. CdTe quantum dots coated with thioglycolic acid were used to test that possibility. Some thiol ligands were purposely removed to regenerate the surface electron traps that were passivated by the ligand. This allowed photoinduced electrons to dwell on the surface long enough to be gathered by nearby oxygen molecules to produce ROS. The photocytotoxicity of these quantum dots was tested on nasopharyngeal carcinoma cells. Photokilling was shown to be drug and light dose dependent. Using 0.6 mum quantum dots for incubation and 4.8 J cm(-2) for irradiation, about 80% of the cells were annihilated. These quantum dots promised to be potent sensitizers for photoannihilation of cancer cells.

  6. Improving Sensitivity and Bandwidth of an Atomic Magnetometer using Quantum Non-Demolition Measurement

    NASA Astrophysics Data System (ADS)

    Shah, Vishal; Vasilakis, Georgios; Romalis, Michael

    2009-05-01

    The fundamental sensitivity of an atomic magnetometer is limited by spin projection noise. In the case of uniform spin relaxation, it is well understood that it is not possible to improve the sensitivity using spin squeezing induced by quantum non-demolition (QND) measurement for measurement time scales longer than spin relaxation time [1, 2]. It is however possible to increase the bandwidth of the magnetometer using QND measurement. Here we experimentally demonstrate, in excellent agreement with the theory, an improvement in the bandwidth of our scalar alkali vapor atomic magnetometer using continuous QND measurement. We also investigate the possibility of improving sensitivity of our magnetometer in the special case in which the spin relaxation is time dependent. The case of time dependent spin relaxation naturally arises in high polarization regime in an alkali-alkali spin-exchange relaxation dominated atomic sample. [1] S. F. Huelga, Phys. Rev. Lett. 79, 3865 -- 3868, 1997. [2] M. Auzinsh, Phys. Rev. Lett. 93, 173002, 2004.

  7. Core/shell colloidal quantum dot exciplex states for the development of highly efficient quantum-dot-sensitized solar cells.

    PubMed

    Wang, Jin; Mora-Seró, Iván; Pan, Zhenxiao; Zhao, Ke; Zhang, Hua; Feng, Yaoyu; Yang, Guang; Zhong, Xinhua; Bisquert, Juan

    2013-10-23

    Searching suitable panchromatic QD sensitizers for expanding the light-harvesting range, accelerating charge separation, and retarding charge recombination is an effective way to improve power conversion efficiency (PCE) of quantum-dot-sensitized solar cells (QDSCs). One possible way to obtain a wide absorption range is to use the exciplex state of a type-II core/shell-structured QDs. In addition, this system could also provide a fast charge separation and low charge-recombination rate. Herein, we report on using a CdTe/CdSe type-II core/shell QD sensitizer with an absorption range extending into the infrared region because of its exciplex state, which is covalently linked to TiO2 mesoporous electrodes by dropping a bifunctional linker molecule mercaptopropionic acid (MPA)-capped QD aqueous solution onto the film electrode. High loading and a uniform distribution of QD sensitizer throughout the film electrode thickness have been confirmed by energy dispersive X-ray (EDX) elemental mapping. The accelerated electron injection and retarded charge-recombination pathway in the built CdTe/CdSe QD cells in comparison with reference CdSe QD-based cells have been confirmed by impedance spectroscopy, fluorescence decay, and intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) analysis. With the combination of the high QD loading and intrinsically superior optoelectronic properties of type-II core/shell QD (wide absorption range, fast charge separation, and slow charge recombination), the resulting CdTe/CdSe QD-based regenerative sandwich solar cells exhibit a record PCE of 6.76% (J(sc) = 19.59 mA cm(-2), V(oc) = 0.606 V, and FF = 0.569) with a mask around the active film under a full 1 sun illumination (simulated AM 1.5), which is the highest reported to date for liquid-junction QDSCs.

  8. Carrier transport dynamics in Mn-doped CdSe quantum dot sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Poudyal, Uma; Maloney, Francis S.; Sapkota, Keshab; Wang, Wenyong

    2017-10-01

    In this work quantum dot sensitized solar cells (QDSSCs) were fabricated with CdSe and Mn-doped CdSe quantum dots (QDs) using the SILAR method. QDSSCs based on Mn-doped CdSe QDs exhibited improved incident photon-to-electron conversion efficiency. Carrier transport dynamics in the QDSSCs were studied using the intensity modulated photocurrent/photovoltage spectroscopy technique, from which transport and recombination time constants could be derived. Compared to CdSe QDSSCs, Mn–CdSe QDSSCs exhibited shorter transport time constant, longer recombination time constant, longer diffusion length, and higher charge collection efficiency. These observations suggested that Mn doping in CdSe QDs could benefit the performance of solar cells based on such nanostructures.

  9. Quantum dot-based western blot for sensitive detection of pig serum antibody to actinobacillus pleuropneumoniae

    NASA Astrophysics Data System (ADS)

    Cişmileanu, Ana; Sima, Cornelia; Grigoriu, Constantin

    2007-08-01

    A quantum dot - immunoglobulin conjugate specific for pig IgG, was obtained by carbodiimide chemistry. We used a Western blot technique for detecting specific antibodies against Actinobacillus pleuropneumoniae (A. pp), which cause porcine pleuropneumonia. The antigen used in this technique was Apx haemolysin which is an important virulence factor of A. pp and it induces protective immunity in vaccined pigs. The detection on Western blot membrane was possible at 1/50 dilution of quantum dot conjugate at a dilution of pig serum till 1/6400. The results for pig serum demonstrated a higher sensitivity of QD-based Western blot technique for the presence of antibodies specific for Apx haemolysin in comparison with similar classical techniques (with coloured substrate for enzyme present in secondary antibody conjugate).

  10. Modified surface loading process for achieving improved performance of the quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Jin, Zhongxiu; Zhu, Jun; Xu, Yafeng; Zhou, Li; Dai, Songyuan

    2016-06-01

    Achieving high surface coverage of the colloidal quantum dots (QDs) on TiO2 films has been challenging for quantum dot-sensitized solar cells (QDSCs). Herein, a general surface engineering approach was proposed to increase the loading of these QDs. It was found that S2- treatment/QD re-uptake process can significantly improve the attachment of the QDs on TiO2 films. Surface concentration of the QDs was improved by ∼60%, which in turn greatly enhances light absorption and decreases carrier recombination in QDSCs. Ensuing QDSCs with optimized QD loading exhibit a power conversion efficiency of 3.66%, 83% higher than those fabricated with standard procedures.

  11. Performance characteristics of CdTe drift ring detector

    NASA Astrophysics Data System (ADS)

    Alruhaili, A.; Sellin, P. J.; Lohstroh, A.; Veeramani, P.; Kazemi, S.; Veale, M. C.; Sawhney, K. J. S.; Kachkanov, V.

    2014-03-01

    CdTe and CdZnTe material is an excellent candidate for the fabrication of high energy X-ray spectroscopic detectors due to their good quantum efficiency and room temperature operation. The main material limitation is associated with the poor charge transport properties of holes. The motivation of this work is to investigate the performance characteristics of a detector fabricated with a drift ring geometry that is insensitive to the transport of holes. The performance of a prototype Ohmic CdTe drift ring detector fabricated by Acrorad with 3 drift rings is reported; measurements include room temperature current voltage characteristics (IV) and spectroscopic performance. The data shows that the energy resolution of the detector is limited by leakage current which is a combination of bulk and surface leakage currents. The energy resolution was studied as a function of incident X-ray position with an X-ray microbeam at the Diamond Light Source. Different ring biasing schemes were investigated and the results show that by increasing the lateral field (i.e. the bias gradient across the rings) the active area, evaluated by the detected count rate, increased significantly.

  12. Controllable synthesis of thiol-capped CdTe nanoparticles for optical sensing of triethylenetetramine dihydrochloride.

    PubMed

    Huy, Bui The; Kumar, Avvaru Praveen; Seo, Min-Ho; Kim, Jan-Di; Lee, Yong-Ill

    2014-10-01

    Highly luminescent CdTe quantum dots (QDs) were synthesized through a co-precipitation route in aqueous salt solutions using different thiols as stabilizers. The synthetic procedure was simple, efficient, and stable. It could also allow controlling the emission wavelength by varying the experimental conditions such as reaction time and pH values. The strong luminescence of the QDs was observed under UV-excitation and emission colors could be adjusted. The interaction between CdTe QDs and triethylenetetramine dihydrochloride (TETA) which is a candidate treatment for diabetic cardiovascular complication was investigated by fluorescence spectroscopy. Based on the quenching effect on CdTe photoluminescence intensity by TETA, a simple assay system for analyzing the content of TETA in aqueous samples was developed. The linearity was maintained in the range of 0.2 μM to 1.2 μM (R2 = 0.994) with a limit of detection (LOD; S/N = 3) at 28 nM. The results showed that CdTe QDs capped with diverse thiols has a potential for the quantitative analysis of TETA in urine samples.

  13. 14%-efficient flexible CdTe solar cells on ultra-thin glass substrates

    SciTech Connect

    Rance, W. L.; Burst, J. M.; Reese, M. O.; Gessert, T. A.; Metzger, W. K.; Barnes, T. M.; Meysing, D. M.; Wolden, C. A.; Garner, S.; Cimo, P.

    2014-04-07

    Flexible glass enables high-temperature, roll-to-roll processing of superstrate devices with higher photocurrents than flexible polymer foils because of its higher optical transmission. Using flexible glass in our high-temperature CdTe process, we achieved a certified record conversion efficiency of 14.05% for a flexible CdTe solar cell. Little has been reported on the flexibility of CdTe devices, so we investigated the effects of three different static bending conditions on device performance. We observed a consistent trend of increased short-circuit current and fill factor, whereas the open-circuit voltage consistently dropped. The quantum efficiency under the same static bend condition showed no change in the response. After storage in a flexed state for 24 h, there was very little change in device efficiency relative to its unflexed state. This indicates that flexible glass is a suitable replacement for rigid glass substrates, and that CdTe solar cells can tolerate bending without a decrease in device performance.

  14. Fluorescence Quenching of CdTe Nanocrystals by Bound Gold Nanoparticles in Aqueous Solution

    PubMed Central

    Zhang, Jian; Badugu, Ramachandram; Lakowicz, Joseph R.

    2009-01-01

    Water-soluble gold nanoparticles with an average diameter of 5 nm were prepared with carboxylic acid terminated thiol ligands. These ligands contain zero to eight methylene moieties. CdTe nanocrystals with an average diameter of 5 nm were synthesized with aminoethanethiol capping. These nanocrystals displayed characteristic absorption and emission spectra of quantum dots. The amine terminated CdTe nanocrystals and carboxylic-acid-terminated gold nanoparticles were conjugated in aqueous solution at pH 5.0 by electrostatic interaction, and the conjugation was monitored with fluorescence spectroscopy. The CdTe nanocrystals were significantly quenched upon binding with gold nanoparticles. The quenching efficiency was affected by both the concentration of gold nanoparticles in the complex and the length of spacer between the CdTe nanocrystal and Au nanoparticle. The observed quenching was explained using Förster resonance energy transfer (FRET) mechanism, and the Förster distance was estimated to be 3.8 nm between the donor-acceptor pair. PMID:19890452

  15. Application of Lithium Chloride Dopant in Fabrication of CdTe Solar Cells

    NASA Astrophysics Data System (ADS)

    Xu, Hang; Zeng, Guanggen; Feng, Lianghuan; Wu, Lili; Liu, Cai; Ren, Shengqiang; Li, Kang; Li, Bing; Li, Wei; Wang, Wenwu; Zhang, Jingquan

    2017-02-01

    We report use of lithium chloride (LiCl) as a non-Cd dopant to deal with the environmental issues associated with use of traditional CdCl2 dopant in CdTe solar cells. It has been found that, after LiCl treatment, device performance parameters including external quantum efficiency and conversion efficiency were improved considerably, being comparable to those of a counterpart treated with CdCl2. The optimal efficiency of 9.58% was obtained at 405°C, and V oc as high as ˜737.3 mV was obtained at 385°C. Thorough study of the properties of the CdTe film treated by LiCl by x-ray diffraction analysis, scanning electron microscopy, x-ray photoelectron spectroscopy, and secondary-ion mass spectroscopy further verified the feasibility of posttreatment with nontoxic LiCl for fabrication of CdTe photovoltaic devices. The doping level of p-type CdTe thin film was improved by lithium. This represents a nontoxic approach for fabrication of commercial CdS/CdTe thin-film solar cells with better performance.

  16. Preparation of bioconjugates of CdTe nanocrystals for cancer marker detection

    NASA Astrophysics Data System (ADS)

    Hu, Fengqin; Ran, Yuliang; Zhou, Zhuan; Gao, Mingyuan

    2006-06-01

    Highly fluorescent CdTe quantum dots (Q-dots) stabilized by 3-mercaptopropionic acid (MPA) were prepared by an aqueous solution approach and used as fluorescent labels in detecting a cancer marker, carcinoembryonic antigen (CEA), expressed on human colon carcinoma cell line LS 180. Nonspecific adsorptions of CdTe Q-dots on carcinoma cells were observed and effectively eliminated by replacing MPA with a thiolated PEG (poly(ethylene glycol), Mn = 750) synthesized according to literature. It was unexpectedly found out that the PEG-coated CdTe Q-dots exhibited very strong and specific affinity to anti-CEA monoclonal antibody rch 24 (rch 24 mAb). The resultant CdTe-(rch 24 mAb) conjugates were successfully used in detections of CEA expressed on the surface of cell line LS 180. Further experiments demonstrated that the fluorescent CdTe Q-dots exhibited much better photostability and a brighter fluorescence than FITC, which consequently led to a higher efficiency in the cancer marker detection.

  17. Charging of quantum dots by sulfide redox electrolytes reduces electron injection efficiency in quantum dot sensitized solar cells.

    PubMed

    Zhu, Haiming; Song, Nianhui; Lian, Tianquan

    2013-08-07

    In quantum dot (QD) sensitized solar cells (QDSSCs), redox electrolytes act as hole scavengers to regenerate the QD ground state from its oxidized form, thus enabling a continuous device operation. However, unlike molecular sensitizers, QDs also have redox-active trap states within the band gap, which can be charged in the presence of redox electrolyte. The effects of electrolyte induced charging of QDs on the performance of QDSSCs have not been reported. Here, using steady-state and time-resolved absorption and emission spectroscopy, we show that CdSe/CdS3MLZnCdS2MLZnS2ML core/multishell QDs are charged in the presence of sulfide electrolytes due to the reduction of surface states. As a result, exciton lifetimes in these QDs are shortened due to an Auger recombination process. Such charging induced fast Auger recombination can compete effectively with electron transfer from QDs to TiO2 and reduce the electron injection efficiency in QDSSCs. We believe that the reported charging effects are present for most colloidal nanocrystals in the presence of redox media and have important implications for designing QD-based photovoltaic and photocatalytic devices.

  18. Quantifying Magnetic Sensitivity of Radical Pair Based Compass by Quantum Fisher Information.

    PubMed

    Guo, Li-Sha; Xu, Bao-Ming; Zou, Jian; Shao, Bin

    2017-07-19

    The radical pair (RP) based compass is considered as one of the principal models of avian magnetoreception. Different from the conventional approach where the sensitivity of RP based compass is described by the singlet yield, we introduce the quantum Fisher information (QFI), which represents the maximum information about the magnetic field's direction extracted from the RP state, to quantify the sensitivity of RP based compass. The consistency between our results and experimental observations suggests that the QFI may serve as a measure to describe the sensitivity of RP based compass. Besides, within the framework of quantum metrology, we give two specific possible measurement schemes and find that the conventional singlet yield is corresponding to the measurement of total angular momentum. Moreover, we show that the measurement of fluctuation of the total magnetic moment is much more accurate than the singlet yield measurement, and is close to the optimal measurement scheme. Finally, the effects of entanglement and decoherence are also discussed in the spirit of our approach.

  19. Quantum Dots Sensitized Solar Cell: Effect of CdSe Nanoparticles Purification Procedure of QD Sensitized Photoanodes

    NASA Astrophysics Data System (ADS)

    Yaacob, K. A.; Ishak, M. N.; Alias, N. N.

    2013-04-01

    In this research the effect of purification of CdSe nanoparticles for application in quantum dots sensitized solar cells (QDSSC) photoanodes are studied. The CdSe nanoparticles are attached to the titanium dioxide surface using a linker based approached (CdSe nanoparticles disperse in toluene) and direct mode attachment (CdSe re-disperse in dichloromethane (DCM)). Colloidal CdSe nanoparticles with estimated size of 3.0 nm were synthesized by hot injection method in trioctylphosphine oxide (TOPO) as stabilizing solvent. Prior to the sensitization, the CdSe nanoparticles were purified using a common purification step involving the alternate cycles of precipitation / redispersion in non-polar solvent and polar solvent. With increasing the number of purification, the concentrations of CdSe nanoparticles attached to the titanium dioxide were also increased; from 2.47 × 1015 dots/cc for 3 × wash CdSe nanoparticles to 3.70 × 1015 dots/cc for 4 × wash CdSe nanoparticles. Polysulfide electrolyte and Cu2S counterelectrodes were used to assemble a complete QDSSC. The highest efficiency of 0.05% was obtained from 4 × wash CdSe nanoparticles; Voc = 0.2V, Jsc = 0.34 mA/cm2 and FF = 0.07).

  20. A novel carboxymethyl chitosan-quantum dot-based intracellular probe for Zn2+ ion sensing in prostate cancer cells.

    PubMed

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

    2014-02-01

    In this paper, we fabricated novel carboxymethyl chitosan-coated CdTe quantum dots (CMC-CdTe QDs) via the electrostatic interaction between amino groups in the carboxymethyl chitosan polymeric chains and carboxyl groups of the CdTe QDs. Carboxymethyl chitosan on the surface of CdTe QDs had strong binding ability with Zn(2+), resulting in the obvious enhancement of the photoluminescence of CdTe QDs. The photoluminescence intensity of CMC-CdTe QDs probe was proportional to the concentration of Zn(2+) in the range of 5.0 × 10(-6) to 5.0 × 10(-3) mol l(-1). The detection limit for Zn(2+) was 4.5 × 10(-6) mol l(-1). The experimental results indicate that the CMC-CdTe QDs possess favorable cell compatibility, good sensitivity and selectivity for intracellular Zn(2+) sensing, and are promising candidates for cellular imaging and sensing in prostate cancer cells. The present study also provides an approach for the further development of nanoprobes dedicated to intracellular sensing. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  1. Classical versus quantum dynamical chaos: Sensitivity to external perturbations, stability and reversibility

    NASA Astrophysics Data System (ADS)

    Sokolov, Valentin V.; Zhirov, Oleg V.; Kharkov, Yaroslav A.

    The extraordinary complexity of classical trajectories of typical nonlinear systems that manifest stochastic behavior is intimately connected with exponential sensitivity to small variations of initial conditions and/or weak external perturbations. In rigorous terms, such classical systems are characterized by positive algorithmic complexity described by the Lyapunov exponent or, alternatively, by the Kolmogorov-Sinai entropy. The said implies that, in spite of the fact that, formally, any however complex trajectory of a perfectly isolated (closed) system is unique and differentiable for any certain initial conditions and the motion is perfectly reversible, it is impractical to treat that sort of classical systems as closed ones. Inevitably, arbitrary weak influence of an environment crucially impacts the dynamics. This influence, that can be considered as a noise, rapidly effaces the memory of initial conditions and turns the motion into an irreversible random process. In striking contrast, the quantum mechanics of the classically chaotic systems exhibit much weaker sensitivity and strong memory of the initial state. Qualitatively, this crucial difference could be expected in view of a much simpler structure of quantum states as compared to the extraordinary complexity of random and unpredictable classical trajectories. However the very notion of trajectories is absent in quantum mechanics so that the concept of exponential instability seems to be irrelevant in this case. The problem of a quantitative measure of complexity of a quantum state of motion, that is a very important and nontrivial issue of the theory of quantum dynamical chaos, is the one of our concern. With such a measure in hand, we quantitatively analyze the stability and reversibility of quantum dynamics in the presence of external noise. To solve this problem we point out that individual classical trajectories are of minor interest if the motion is chaotic. Properties of all of them are alike in

  2. An oleic acid-capped CdSe quantum-dot sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Chen, Jing; Song, J. L.; Sun, X. W.; Deng, W. Q.; Jiang, C. Y.; Lei, W.; Huang, J. H.; Liu, R. S.

    2009-04-01

    In this letter, we report an oleic acid (OA)-capped CdSe quantum-dot sensitized solar cell (QDSSC) with an improved performance. The TiO2/OA-CdSe photoanode in a two-electrode device exhibited a photon-to-current conversion efficiency of 17.5% at 400 nm. At AM1.5G irradiation with 100 mW/cm2 light intensity, the QDSSCs based on OA-capped CdSe showed a power conversion efficiency of about 1%. The function of OA was to increase QD loading, extend the absorption range and possibly suppress the surface recombination.

  3. Highly efficient yttrium-doped ZnO nanorods for quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Soo-Kyoung; Gopi, Chandu V. V. M.; Srinivasa Rao, S.; Punnoose, Dinah; Kim, Hee-Je

    2016-03-01

    Yttrium-doped ZnO nanorod arrays were applied to photoanodes of quantum dot-sensitized solar cells (QDSCs). The introduction of yttrium to ZnO nanostructures facilitates the growth of ZnO nanorods and increases the amount of QD deposition with a large surface area. Furthermore, lower electrical resistance and longer electron lifetime were achieved with yttrium-doping owing to fewer defects and trap sites on the surface of yttrium-doped ZnO nanorods. As a result, the conversion efficiency of 3.3% was achieved with the optimized concentration of yttrium.

  4. Sensitivity Enhancement in Multiple-Quantum NMR Experiments with CPMG Detection

    NASA Astrophysics Data System (ADS)

    Lim, Kwang Hun; Nguyen, Tuan; Mazur, Tanya; Wemmer, David E.; Pines, Alexander

    2002-07-01

    We present a modified multiple-quantum (MQ) experiment, which implements the Carr-Purcell-Meiboom-Gill (CPMG) detection scheme in the static MQ NMR experiment proposed by W. S. Warren et al. (1980, J. Chem. Phys.73, 2084-2099) and exploited further by O. N. Antzutkin and R. Tycko (1999, J. Chem. Phys.110, 2749-2752). It is demonstrated that a significant enhancement in the sensitivity can be achieved by acquiring echo trains in the MQ experiments for static powder samples. The modified scheme employing the CPMG detection was superior to the original MQ experiment, in particular for the carbonyl carbon with a very large chemical shift anisotropy.

  5. An oleic acid-capped CdSe quantum-dot sensitized solar cell

    SciTech Connect

    Chen Jing; Song, J. L.; Deng, W. Q.; Sun, X. W.; Jiang, C. Y.; Lei, W.; Huang, J. H.; Liu, R. S.

    2009-04-13

    In this letter, we report an oleic acid (OA)-capped CdSe quantum-dot sensitized solar cell (QDSSC) with an improved performance. The TiO{sub 2}/OA-CdSe photoanode in a two-electrode device exhibited a photon-to-current conversion efficiency of 17.5% at 400 nm. At AM1.5G irradiation with 100 mW/cm{sup 2} light intensity, the QDSSCs based on OA-capped CdSe showed a power conversion efficiency of about 1%. The function of OA was to increase QD loading, extend the absorption range and possibly suppress the surface recombination.

  6. Porous CdTe nanocrystal assemblies: ligation effects on the gelation process and the properties of resultant aerogels.

    PubMed

    Yao, Qinghong; Brock, Stephanie L

    2011-10-17

    Highly porous CdTe nanoarchitectures (aerogels) were prepared by sol-gel assembly of discrete nanocrystals followed by supercritical CO(2) drying. CdTe nanocrystal surface functionalization (either phosphine oxide or thiolate) is found to be immaterial to oxidation induced gel formation suggesting that the standard thiolate capping procedure is not a necessary step in the gelation process. On the basis of this observation, and reduction induced dispersion of the gel network, the exposure of reactive sites and the subsequent surface oxidation reaction to form polychalcogenide linkages are key steps in the gelation mechanism. Consequently, CdTe aerogels exhibit similar physicochemical properties, regardless of original ligating functionality. The aerogels are mesoporous, with surface area >100 m(2)/g, and exhibit an optical bandgap of 1.92 eV, consistent with quantum confinement within the 3-D linked network. Photoluminescence is suppressed in the aerogels, but can be partially recovered upon heating.

  7. Capping Ligand-Induced Self-Assembly for Quantum Dot Sensitized Solar Cells.

    PubMed

    Li, Wenjie; Zhong, Xinhua

    2015-03-05

    Quantum dot-sensitized solar cells (QDSCs), having the advantages of low-cost assembling process, economically viable materials and intrinsic optoelectronic properties of QD sensitizers, are regarded as attractive candidates for the third-generation solar cells. In spite of the previous unsatisfied performance resulted from poor sensitization, an increasing power conversion efficiency has been experimentally confirmed with the development of effective deposition approaches in the last five years. In this Perspective article, we present an overview on versatile QD deposition methods, regarding mainly the effective loading of QDs and surface chemistry issues. Linker-assisted assembly, a most efficient sensitizer deposition approach to achieve fast, uniform and dense coverage of the sensitizers on mesoporous TiO2 film electrode, will be discussed with emphasis. Recent advances based on this deposition technique in achieving high efficiency are presented. Also, combined efforts regarding the overall improvement of the device have been discussed to provide more possible access to higher power conversion efficiencies of the QDSCs.

  8. Gravitational wave radiation by LIGO-type detectors and its reciprocity relation with the detector's fundamental quantum limited sensitivity

    NASA Astrophysics Data System (ADS)

    Pang, Belinda; Ma, Yiqiu; Miao, Haixing; Chen, Yanbei

    2017-01-01

    We relate the radiation of gravitational waves (GW) by a light interferometer with cavity arms (such as LIGO) to its quantum limited sensitivity as a detector of GW's, thereby demonstrating a reciprocity relation between the interferometer's function as a detector and emitter. We derive the pairwise interactions among the cavity optical field, the cavity end mirror, and the gravitational perturbation from the action principle. We quantize these degrees of freedom to calculate the GW's generated by a quantum object. We find that the rate of gravitational wave generation is related to the so-called quantum Cramer Rao bound of the detector, which is a general result from linear measurement theory that gives the fundamental limit to a detector's sensitivity. We show that increasing the maximal sensitivity for the interferometer also increases its GW radiation. This finding may point towards a new paradigm for improving detector sensitivity by maximizing GW radiator.

  9. Tuning the external optical feedback-sensitivity of a passively mode-locked quantum dot laser

    SciTech Connect

    Raghunathan, R. Kovanis, V.; Lester, L. F.; Grillot, F.; Mee, J. K.; Murrell, D.

    2014-07-28

    The external optical feedback-sensitivity of a two-section, passively mode-locked quantum dot laser operating at elevated temperature is experimentally investigated as a function of absorber bias voltage. Results show that the reverse-bias voltage on the absorber has a direct impact on the damping rate of the free-running relaxation oscillations of the optical signal output, thereby enabling interactive external control over the feedback-response of the device, even under the nearly resonant cavity configuration. The combination of high temperature operation and tunable feedback-sensitivity is highly promising from a technological standpoint, in particular, for applications requiring monolithic integration of multi-component architectures on a single chip in order to accomplish, for instance, the dual-objectives of stable pulse quality and isolation from parasitic reflections.

  10. Co-sensitized quantum dot solar cell based on ZnO nanowire

    NASA Astrophysics Data System (ADS)

    Chen, J.; Wu, J.; Lei, W.; Song, J. L.; Deng, W. Q.; Sun, X. W.

    2010-10-01

    An efficient photoelectrode is fabricated by sequentially assembled CdS and CdSe quantum dots (QDs) onto a ZnO-nanowire film. As revealed by UV-vis absorption spectrum and scanning electron microscopy (SEM), CdS and CdSe QDs can be effectively adsorbed on ZnO-nanowire array. Electrochemical impedance spectroscopy (EIS) measured demonstrates that the electron lifetime for ZnO/CdS/CdSe (13.8 ms) is calculated longer than that of ZnO/CdS device (6.2 ms), which indicates that interface charge recombination rate is reduced by sensitizing CdSe QDs. With broader light absorption range and longer electron lifetime, a power conversion efficiency of 1.42% is achieved for ZnO based CdS/CdSe co-sensitized solar cell under the illumination of one Sun (AM 1.5G, 100 mW cm -2).

  11. Mn(II/III) complexes as promising redox mediators in quantum-dot-sensitized solar cells.

    PubMed

    Haring, Andrew J; Pomatto, Michelle E; Thornton, Miranda R; Morris, Amanda J

    2014-09-10

    The advancement of quantum dot sensitized solar cell (QDSSC) technology depends on optimizing directional charge transfer between light absorbing quantum dots, TiO2, and a redox mediator. The nature of the redox mediator plays a pivotal role in determining the photocurrent and photovoltage from the solar cell. Kinetically, reduction of oxidized quantum dots by the redox mediator should be rapid and faster than the back electron transfer between TiO2 and oxidized quantum dots to maintain photocurrent. Thermodynamically, the reduction potential of the redox mediator should be sufficiently positive to provide high photovoltages. To satisfy both criteria and enhance power conversion efficiencies, we introduced charge transfer spin-crossover Mn(II/III) complexes as promising redox mediator alternatives in QDSSCs. High photovoltages ∼ 1 V were achieved by a series of Mn poly(pyrazolyl)borates, with reduction potentials ∼ 0.51 V vs Ag/AgCl. Back electron transfer (recombination) rates were slower than Co(bpy)3, where bpy = 2,2'-bipyridine, evidenced by electron lifetimes up to 4 orders of magnitude longer. This is indicative of a large barrier to electron transport imposed by spin-crossover in these complexes. Low solubility prevented the redox mediators from sustaining high photocurrent due to mass transport limits. However, with high fill factors (∼ 0.6) and photovoltages, they demonstrate competitive efficiencies with Co(bpy)3 redox mediator at the same concentration. More positive reduction potentials and slower recombination rates compared to current redox mediators establish the viability of Mn poly(pyrazolyl)borates as promising redox mediators. By capitalizing on these characteristics, efficient Mn(II/III)-based QDSSCs can be achieved with more soluble Mn-complexes.

  12. A frequency and sensitivity tunable microresonator array for high-speed quantum processor readout

    NASA Astrophysics Data System (ADS)

    Whittaker, J. D.; Swenson, L. J.; Volkmann, M. H.; Spear, P.; Altomare, F.; Berkley, A. J.; Bumble, B.; Bunyk, P.; Day, P. K.; Eom, B. H.; Harris, R.; Hilton, J. P.; Hoskinson, E.; Johnson, M. W.; Kleinsasser, A.; Ladizinsky, E.; Lanting, T.; Oh, T.; Perminov, I.; Tolkacheva, E.; Yao, J.

    2016-01-01

    Superconducting microresonators have been successfully utilized as detection elements for a wide variety of applications. With multiplexing factors exceeding 1000 detectors per transmission line, they are the most scalable low-temperature detector technology demonstrated to date. For high-throughput applications, fewer detectors can be coupled to a single wire but utilize a larger per-detector bandwidth. For all existing designs, fluctuations in fabrication tolerances result in a non-uniform shift in resonance frequency and sensitivity, which ultimately limits the efficiency of bandwidth utilization. Here, we present the design, implementation, and initial characterization of a superconducting microresonator readout integrating two tunable inductances per detector. We demonstrate that these tuning elements provide independent control of both the detector frequency and sensitivity, allowing us to maximize the transmission line bandwidth utilization. Finally, we discuss the integration of these detectors in a multilayer fabrication stack for high-speed readout of the D-Wave quantum processor, highlighting the use of control and routing circuitry composed of single-flux-quantum loops to minimize the number of control wires at the lowest temperature stage.

  13. A frequency and sensitivity tunable microresonator array for high-speed quantum processor readout

    SciTech Connect

    Whittaker, J. D. Swenson, L. J.; Volkmann, M. H.; Spear, P.; Altomare, F.; Berkley, A. J.; Bunyk, P.; Harris, R.; Hilton, J. P.; Hoskinson, E.; Johnson, M. W.; Ladizinsky, E.; Lanting, T.; Oh, T.; Perminov, I.; Tolkacheva, E.; Yao, J.; Bumble, B.; Day, P. K.; Eom, B. H.; and others

    2016-01-07

    Superconducting microresonators have been successfully utilized as detection elements for a wide variety of applications. With multiplexing factors exceeding 1000 detectors per transmission line, they are the most scalable low-temperature detector technology demonstrated to date. For high-throughput applications, fewer detectors can be coupled to a single wire but utilize a larger per-detector bandwidth. For all existing designs, fluctuations in fabrication tolerances result in a non-uniform shift in resonance frequency and sensitivity, which ultimately limits the efficiency of bandwidth utilization. Here, we present the design, implementation, and initial characterization of a superconducting microresonator readout integrating two tunable inductances per detector. We demonstrate that these tuning elements provide independent control of both the detector frequency and sensitivity, allowing us to maximize the transmission line bandwidth utilization. Finally, we discuss the integration of these detectors in a multilayer fabrication stack for high-speed readout of the D-Wave quantum processor, highlighting the use of control and routing circuitry composed of single-flux-quantum loops to minimize the number of control wires at the lowest temperature stage.

  14. A quasi-quantum well sensitized solar cell with accelerated charge separation and collection.

    PubMed

    Yan, Keyou; Zhang, Lixia; Qiu, Jianhang; Qiu, Yongcai; Zhu, Zonglong; Wang, Jiannong; Yang, Shihe

    2013-06-26

    Semiconductor-sensitized solar cell (SSSC) represents a new generation of device aiming to achieve easy fabrication and cost-effective performance. However, the power of the semiconductor sensitizers has not been fully demonstrated in SSSC, making it actually overshadowed by dye-sensitized solar cell (DSSC). At least part of the problem is related to the inefficient charge separation and severe recombination with the current technologies, which calls on rethinking about how to better engineer the semiconductor sensitizer structure in order to enhance the power conversion efficiency (PCE). Herein we report on using for the first time a quasi-quantum well (QW) structure (ZnSe/CdSe/ZnSe) as the sensitizer, which is quasi-epitaxially deposited on ZnO tetrapods. Such a novel photoanode architecture has attained 6.20% PCE, among the highest reported to date for this type of SSSCs. Impedance spectra have revealed that the ZnSe/CdSe/ZnSe QW structure has a transport resistance only a quarter that of, but a recombination resistance twice that of the ZnSe/CdSe heterojunction (HJ) structure, yielding much longer electron diffusion length, consistent with the resulting higher photovoltage, photocurrent, and fill factor. Time-resolved photoluminescence spectroscopy indicates dramatically reduced electron transfer from ZnO to the QW sensitizer, a feature which is conducive to charge separation and collection. This study together with the impedance spectra and intensity modulated photocurrent spectroscopies supports a core/shell two-channel transport mechanism in this type of solar cells and further suggests that the electron transport along sensitizer can be considerably accelerated by the QW structure employed.

  15. Recent progress in all-solid-state quantum dot-sensitized TiO2 nanotube array solar cells

    NASA Astrophysics Data System (ADS)

    Wang, Qingyao; Chen, Chao; Liu, Wei; Gao, Shanmin; Yang, Xiuchun

    2016-01-01

    All-solid-state quantum dot-sensitized TiO2 nanotube array solar cells have been drawing great attention to solar energy conversion, which break through restrictions in traditional solar cells, such as the high recombination at interfaces of porous TiO2 films/sensitizers/hole conductors/counter electrodes, instability of dyes, and leakage of solution electrolyte, and so the novel solar cells exhibit promising applications in the future. In this Minireview article, the assembling of solar cells including the preparation of TiO2 nanotube array photoanodes, quantum dot preparation and sensitization on photoanodes, filling of hole conductors in TiO2 nanotubes, and selection of counter electrodes are overviewed, and the development course of all-solid-state quantum dot-sensitized TiO2 nanotube array solar cells in recent years are summarized in detail. Moreover, the influences of TiO2 nanotube array photoanodes, quantum dots, solid electrolyte, and counter electrodes on photon-to-current efficiencies of solar cells are summarized. In addition, current problems of solid-state quantum dot-sensitized TiO2 nanotube array solar cells are analyzed, and the corresponding improvements, such as multisensitizers and passivation layers, are proposed to improve the photoelectric conversion efficiency. Finally, this Minireview provides a perspective for the future development of this novel solar cell.

  16. Assembly of CdS Quantum Dots onto Hierarchical TiO2 Structure for Quantum Dots Sensitized Solar Cell Applications

    PubMed Central

    Ali, Syed Mansoor; Aslam, Mohamed; Farooq, W. A.; Fatehmulla, Amanullah; Atif, M.

    2015-01-01

    Quantum dot (QD) sensitized solar cells based on Hierarchical TiO2 structure (HTS) consisting of spherical nano-urchins on transparent conductive fluorine doped tin oxide glass substrate is fabricated. The hierarchical TiO2 structure consisting of spherical nano-urchins on transparent conductive fluorine doped tin oxide glass substrate synthesized by hydrothermal route. The CdS quantum dots were grown by the successive ionic layer adsorption and reaction deposition method. The quantum dot sensitized solar cell based on the hierarchical TiO2 structure shows a current density JSC = 1.44 mA, VOC = 0.46 V, FF = 0.42 and η = 0.27%. The QD provide a high surface area and nano-urchins offer a highway for fast charge collection and multiple scattering centers within the photoelectrode.

  17. Quantum dots and ionic liquid-sensitized effect as an efficient and green catalyst for the sensitive determination of glucose

    NASA Astrophysics Data System (ADS)

    Azizi, Seyed Naser; Chaichi, Mohammad Javad; Shakeri, Parmis; Bekhradnia, Ahmadreza

    2015-07-01

    A novel fluorescence (FL) method using water-soluble CdSe quantum dots (QDs) is proposed for the fluorometric determination of hydrogen peroxide and glucose. Water-soluble CdSe QDs were synthesized by using thioglycolic acid as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy, photoluminescence (PL) emission spectroscopy and transmission electron microscope (TEM). Ionic liquid-sensitized effect in aqueous solution was then investigated. In the presence of ionic liquid as catalyst, H2O2 was decomposed into radical that could quench the fluorescence of CdSe QDs more efficiently and rapidly. Then the oxidization of glucose by glucose oxidase was coupled with the fluorescence quenching of CdSe QDs by H2O2 producer with ionic liquid catalyst, which can be used to detect glucose. Therefore, a new FL analysis system was developed for the determination of glucose. Under the optimum conditions, there is a good linear relationship between the relative PL emission intensity and the concentration of glucose in the range of 5.0 × 10-7-1.0 × 10-4 M of glucose with a correlation coefficient (R2) of 0.9973. The limit of detection of this system was found to be 1.0 × 10-7 M. This method is not only simple, sensitive and low cost, but also reliable for practical applications.

  18. Decorating CdTe QD-Embedded Mesoporous Silica Nanospheres with Ag NPs to Prevent Bacteria Invasion for Enhanced Anticounterfeit Applications.

    PubMed

    Gao, Yangyang; Dong, Qigeqi; Lan, Shi; Cai, Qian; Simalou, Oudjaniyobi; Zhang, Shiqi; Gao, Ge; Chokto, Harnoode; Dong, Alideertu

    2015-05-13

    Quantum dots (QDs) as potent candidates possess advantageous superiority in fluorescence imaging applications, but they are susceptible to the biological circumstances (e.g., bacterial environment), leading to fluorescence quenching or lose of fluorescent properties. In this work, CdTe QDs were embedded into mesoporous silica nanospheres (m-SiO2 NSs) for preventing QD agglomeration, and then CdTe QD-embedded m-SiO2 NSs (m-SiO2/CdTe NSs) were modified with Ag nanoparticles (Ag NPs) to prevent bacteria invasion for enhanced anticounterfeit applications. The m-SiO2 NSs, which serve as intermediate layers to combine CdTe QDs with Ag NPs, help us establish a highly fluorescent and long-term antibacterial system (i.e., m-SiO2/CdTe/Ag NSs). More importantly, CdTe QD-embedded m-SiO2 NSs showed fluorescence quenching when they encounter bacteria, which was avoided by attaching Ag NPs outside. Ag NPs are superior to CdTe QDs for preventing bacteria invasion because of the structure (well-dispersed Ag NPs), size (small diameter), and surface charge (positive zeta potentials) of Ag NPs. The plausible antibacterial mechanisms of m-SiO2/CdTe/Ag NSs toward both Gram-positive and Gram-negative bacteria were established. As for potential applications, m-SiO2/CdTe/Ag NSs were developed as fluorescent anticounterfeiting ink for enhanced imaging applications.

  19. Synthesis and characterization of chitosan-based polyelectrolyte complexes, doped by quantum dots

    NASA Astrophysics Data System (ADS)

    Abuzova, N. V.; Gerasimova, M. A.; Slabko, V. V.; Slyusareva, E. A.

    2015-12-01

    Doping of polymer particles by a fluorophores results in the sensitization within the visible spectral region becoming very promising materials for sensor applications. Colloids of biocompatible chitosan-based polyelectrolyte complexes (PECs) doped with quantum dots (QD) of CdTe and CdSe/ZnS (with sizes of 2.0-2.4 nm) were synthesized and characterized by scanning electron microscopy, dynamic light scattering, ζ-potential measurements, absorption and luminescence (including time-resolved) spectroscopy. The influence of ionic strength (0.02-1.5 M) on absorption and photoluminescence properties of encapsulated into PEC and unencapsulated quantum dots was investigated. The stability of the emission intensity of the encapsulated quantum dots has been shown to be strongly dependent on concentration of quantum dots.

  20. ISGRI: a CdTe array imager for INTEGRAL

    NASA Astrophysics Data System (ADS)

    Lebrun, Francois; Blondel, Claire; Fondeur, Irene; Goldwurm, Andrea; Laurent, Phillipe; Leray, Jean P.

    1996-10-01

    The INTEGRAL soft gamma-ray imager (ISGRI) is a large and thin CdTe array. Operating at room temperature, this gamma camera covers the lower part (below 200 keV) of the energy domain (20 keV - 10 MeV) of the imager on board the INTEGRAL Satellite (IBIS). The ASIC's front-end electronics features particularly a low noise preamplifier, allowing a threshold below 20 keV and a pulse rise-time measurement which permits a charge loss correction. The charge loss correction and its performances are presented as well as the results of various studies on CdTe thermal behavior and radiation hardness. At higher energy (above 200 keV) ISGRI will operate in conjunction with PICsIT, the IBIS CsI gamma camera. A selection among the events in coincidence performed on the basis of the Compton scattering properties reduces strongly the background. This allows an improvement of the sensitivity and permits short term imaging and spectral studies (high energy pulsars) which otherwise would not have fit within the IBIS telemetry allocation.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  2. Nanoscale Imaging of Band Gap and Defects in Polycrystalline CdTe Photovoltaic Devices

    NASA Astrophysics Data System (ADS)

    Zhitenev, Nikolai; Yoon, Yohan; Chae, Jungseok; Katzenmeyer, Aaron; Yoon, Heayoung; An, Sangmin; Shumacher, Joshua; Centrone, Andrea

    To further increase the power efficiency of polycrystalline thin film photovoltaic (PV) technology, a detailed understanding of microstructural properties of the devices is required. In this work, we investigate the microstructure of CdTe PV devices using two optical spectroscopies. Sub-micron thickness lamella samples were cut out from a PV device, either in cross-section or in-plane, by focused ion beam. The first technique is the photothermal induced resonance (PTIR) used to obtain absorption spectra over a broad range of wavelengths. In PTIR, a wavelength tunable pulsed laser is combined with an atomic force microscope to detect the local thermal expansion of lamella CdTe sample induced by light absorption. The second technique based on a near-field scanning optical microscope maps the local absorption at fixed near-IR wavelengths with energies at or below CdTe band-gap energy. The variation of the band gap throughout the CdTe absorber determined from PTIR spectra is ~ 20 meV. Both techniques detect strong spatial variation of shallow defects over different grains. The spatial distribution of mid-gap defects appears to be more uniform. The resolution, the sensitivity and the applicability of these two approaches are compared.

  3. Position sensitive photon detectors using epitaxial InGaAs/InAlAs quantum wells

    NASA Astrophysics Data System (ADS)

    Ganbold, T.; Antonelli, M.; Biasiol, G.; Cautero, G.; Jark, H.; Eichert, D. M.; Cucini, R.; Menk, R. H.

    2014-12-01

    This work deals with the investigation of novel position-sensitive devices based on InGaAs/InAlAs quantum wells, which could be applied to several applications of either synchrotron or conventional light sources. Such devices may be used as fast and efficient detectors due to the direct, low-energy band gap and high electron mobility at room temperature. Metamorphic In0.75Ga0.25As/In0.75Al0.25As quantum wells containing a two-dimensional electron gas were grown by molecular beam epitaxy. Two devices with size of 5 × 5 mm2 were prepared by using optical lithography. In the first, the active layers were segmented into four electrically insulated quadrants. Indium ohmic contacts were realized on the corner of each quadrant (for readout) and on the back surface (for bias). In the second, the quantum well was left unsegmented and covered by 400 nm of Al providing a single bias electrode, while four readout electrodes were fabricated on the back side by depositing and segmenting a Ni/Ge/Au layer. Photo-generated carriers can be collected at the readout electrodes by biasing from either the QW side or the back side of the devices during beam exposure. Individual currents obtained from each electrode allow monitoring of both the position and the intensity of the impinging beam for photon energies ranging from visible to hard X-ray. Such detector prototypes were tested with synchrotron radiation. Moreover, the position of the beam can be estimated with a precision of 800 nm in the segmented QW. A lower precision of 10 μm was recorded in the unsegmented QW due to the charge diffusion through the 500-μm-thick wafer, with however a lower electronic noise due to the better uniformity of the contacts.

  4. Theory and Development of Position-Sensitive Quantum Calorimeters. Degree awarded by Stanford Univ.

    NASA Technical Reports Server (NTRS)

    Figueroa-Feliciano, Enectali; White, Nicholas E. (Technical Monitor)

    2001-01-01

    Quantum calorimeters are being developed as imaging spectrometers for future X-ray astrophysics observatories. Much of the science to be done by these instruments could benefit greatly from larger focal-plane coverage of the detector (without increasing pixel size). An order of magnitude more area will greatly increase the science throughput of these future instruments. One of the main deterrents to achieving this goal is the complexity of the readout schemes involved. We have devised a way to increase the number of pixels from the current baseline designs by an order of magnitude without increasing the number of channels required for readout. The instrument is a high energy resolution, distributed-readout imaging spectrometer called a Position-Sensitive Transition-Edge Sensor (POST). A POST is a quantum calorimeter consisting of two Transition-Edge Sensors (TESS) on the ends of a long absorber capable of one-dimensional imaging spectroscopy. Comparing rise time and energy information from the two TESS, the position of the event in the POST is determined. The energy of the event is inferred from the sum of the two pulses. We have developed a generalized theoretical formalism for distributed-readout calorimeters and apply it to our devices. We derive the noise theory and calculate the theoretical energy resolution of a POST. Our calculations show that a 7-pixel POST with 6 keV saturation energy can achieve 2.3 eV resolution, making this a competitive design for future quantum calorimeter instruments. For this thesis we fabricated 7- and 15-pixel POSTS using Mo/Au TESs and gold absorbers, and moved from concept drawings on scraps of napkins to a 32 eV energy resolution at 1.5 keV, 7-pixel POST calorimeter.

  5. Field enhanced plexitonic coupling between InAs quantum dot and silver film: highly sensitive plasmonic composite

    NASA Astrophysics Data System (ADS)

    Dillu, Venus; Rani, Preeti; Sinha, Ravindra Kumar

    2014-09-01

    In this work we propose and study a highly sensitive quantum dot (QD)-metal film plasmonic composite. The system comprises of indium arsenide (InAs) QDs on silver film. The intensity is traced by scanning the absorption spectra for the system. We found that the behaviour of the plasmonic composite changes by varying the thickness of metal film. It is observed that the sensitivity of the composite varies with the thickness of metallic film and the quantum size effects dominate at sub-nanometer gap. The proposed system shows promising applications in lasing, sensing and spectroscopy.

  6. Size-dependent active effect of cadmium telluride quantum dots on luminol-potassium periodate chemiluminescence system for levodopa detection.

    PubMed

    Wang, Jianbo; Cui, Lijuan; Han, Suqin; Hao, Fang

    2015-06-01

    It was found that cadmium telluride (CdTe) quantum dots (QDs) with different sizes can have a great sensitizing effect on chemiluminescence (CL) emission from luminol-potassium periodate (KIO4) system. Levodopa, a widely prescribed drug in the treatment of Parkinson's disease, could inhibit luminol-KIO4-CdTe QDs CL reaction in alkaline solution. The inhibited CL intensity was proportional to the concentration of levodopa in the range from 8.0 nM to 10.0 μM. The detection limit was 3.8 nM. This method has been successfully applied to determine levodopa in pharmaceutical preparation and human urine and plasma samples with recoveries of 94.1-105.4%. This was the first work for inhibition effect determination of levodopa using a QD-based CL method.

  7. Quantum dot-sensitized solar cells based on directly adsorbed zinc copper indium sulfide colloids.

    PubMed

    Guijarro, Néstor; Guillén, Elena; Lana-Villarreal, Teresa; Gómez, Roberto

    2014-05-21

    Heavy metal-based quantum dots (QDs) have been demonstrated to behave as efficient sensitizers in QD-sensitized solar cells (QDSSCs), as attested by the countless studies and encouraging efficiencies reported so far. However, their intrinsic toxicity has arisen as a major issue for the prospects of commercialization. Here, we examine the potential of environmentally friendly zinc copper indium sulfide (ZCIS) QDs for the fabrication of liquid-junction QDSSCs by means of photoelectrochemical measurements. A straightforward approach to directly adsorb ZCIS QDs on TiO2 from a colloidal dispersion is presented. Incident photon-to-current efficiency (IPCE) spectra of sensitized photoanodes show a marked dependence on adsorption time, with longer times leading to poorer performances. Cyclic voltammograms point to a blockage of the channels of the mesoporous TiO2 film by the agglomeration of QDs as the main reason for the decrease in efficiency. Photoanodes were also subjected to the ZnS treatment. Its effects on electron recombination with the electrolyte are analyzed through electrochemical impedance spectroscopy and photopotential measurements. The corresponding results bring out the role of the ZnS coating as a barrier layer in preventing electron leakage toward the electrolyte, as argued in other QD-sensitized systems. The beneficial effect of the ZnS coating is ultimately reflected in the power conversion efficiency of complete devices, reaching values of 2%. In a more general vein, through these findings, we aim to call the attention to the potentiality of this quaternary alloy, virtually unexplored as a light harvester for sensitized devices.

  8. States of maximum polarization for a quantum light field and states of a maximum sensitivity in quantum interferometry

    NASA Astrophysics Data System (ADS)

    Peřinová, Vlasta; Lukš, Antonín

    2015-06-01

    The SU(2) group is used in two different fields of quantum optics, the quantum polarization and quantum interferometry. Quantum degrees of polarization may be based on distances of a polarization state from the set of unpolarized states. The maximum polarization is achieved in the case where the state is pure and then the distribution of the photon-number sums is optimized. In quantum interferometry, the SU(2) intelligent states have also the property that the Fisher measure of information is equal to the inverse minimum detectable phase shift on the usual simplifying condition. Previously, the optimization of the Fisher information under a constraint was studied. Now, in the framework of constraint optimization, states similar to the SU(2) intelligent states are treated.

  9. Highly Sensitive Homogeneous Immunoassays Based on Construction of Silver Triangular Nanoplates-Quantum Dots FRET System

    NASA Astrophysics Data System (ADS)

    Zeng, Qinghui; Li, Qin; Ji, Wenyu; Bin, Xue; Song, Jie

    2016-05-01

    With growing concerns about health issues worldwide, elegant sensors with high sensitivity and specificity for virus/antigens (Ag) detection are urgent to be developed. Homogeneous immunoassays (HIA) are an important technique with the advantages of small sample volumes requirement and pretreatment-free process. HIA are becoming more favorable for the medical diagnosis and disease surveillance than heterogeneous immunoassays. An important subset of HIA relies on the effect of fluorescence resonance energy transfer (FRET) via a donor-acceptor (D-A) platform, e.g., quantum dots (QDs) donor based FRET system. Being an excellent plasmonic material, silver triangular nanoplates (STNPs) have unique advantages in displaying surface plasmon resonance in the visible to near infrared spectral region, which make them a better acceptor for pairing with QDs in a FRET-based sensing system. However, the reported STNPs generally exhibited broad size distributions, which would greatly restrict their application as HIA acceptor for high detection sensitivity and specificity purpose. In this work, uniform STNPs and red-emitting QDs are firstly applied to construct FRET nanoplatform in the advanced HIA and further be exploited for analyzing virus Ag. The uniform STNPs/QDs nanoplatform based medical sensor provides a straightforward and highly sensitive method for Ag analysis in homogeneous form.

  10. First principles DFT study of dye-sensitized CdS quantum dots

    SciTech Connect

    Jain, Kalpna; Singh, Kh. S.; Kishor, Shyam; Josefesson, Ida; Odelius, Michael; Ramaniah, Lavanya M.

    2014-04-24

    Dye-sensitized quantum dots (QDs) are considered promising candidates for dye-sensitized solar cells. In order to maximize their efficiency, detailed theoretical studies are important. Here, we report a first principles density functional theory (DFT) investigation of experimentally realized dye - sensitized QD / ligand systems, viz., Cd{sub 16}S{sub 16}, capped with acetate molecules and a coumarin dye. The hybrid B3LYP functional and a 6−311+G(d,p)/LANL2dz basis set are used to study the geometric, energetic and electronic properties of these clusters. There is significant structural rearrangement in all the clusters studied - on the surface for the bare QD, and in the positions of the acetate / dye ligands for the ligated QDs. The density of states (DOS) of the bare QD shows states in the band gap, which disappear on surface passivation with the acetate molecules. Interestingly, in the dye-sensitised QD, the HOMO is found to be localized mainly on the dye molecule, while the LUMO is on the QD, as required for photo-induced electron injection from the dye to the QD.

  11. Plasmonic Silicon Quantum Dots Enabled High-Sensitivity Ultrabroadband Photodetection of Graphene-Based Hybrid Phototransistors.

    PubMed

    Ni, Zhenyi; Ma, Lingling; Du, Sichao; Xu, Yang; Yuan, Meng; Fang, Hehai; Wang, Zhen; Xu, Mingsheng; Li, Dongsheng; Yang, Jianyi; Hu, Weida; Pi, Xiaodong; Yang, Deren

    2017-09-22

    Highly sensitive photodetection even approaching the single-photon level is critical to many important applications. Graphene-based hybrid phototransistors are particularly promising for high-sensitivity photodetection because they have high photoconductive gain due to the high mobility of graphene. Given their remarkable optoelectronic properties and solution-based processing, colloidal quantum dots (QDs) have been preferentially used to fabricate graphene-based hybrid phototransistors. However, the resulting QD/graphene hybrid phototransistors face the challenge of extending the photodetection into the technologically important mid-infrared (MIR) region. Here, we demonstrate the highly sensitive MIR photodetection of QD/graphene hybrid phototransistors by using plasmonic silicon (Si) QDs doped with boron (B). The localized surface plasmon resonance (LSPR) of B-doped Si QDs enhances the MIR absorption of graphene. The electron-transition-based optical absorption of B-doped Si QDs in the ultraviolet (UV) to near-infrared (NIR) region additionally leads to photogating for graphene. The resulting UV-to-MIR ultrabroadband photodetection of our QD/graphene hybrid phototransistors features ultrahigh responsivity (up to ∼10(9) A/W), gain (up to ∼10(12)), and specific detectivity (up to ∼10(13) Jones).

  12. Improved performance of colloidal CdSe quantum dot-sensitized solar cells by hybrid passivation.

    PubMed

    Huang, Jing; Xu, Bo; Yuan, Chunze; Chen, Hong; Sun, Junliang; Sun, Licheng; Agren, Hans

    2014-11-12

    A hybrid passivation strategy is employed to modify the surface of colloidal CdSe quantum dots (QDs) for quantum dot-sensitized solar cells (QDSCs), by using mercaptopropionic acid (MPA) and iodide anions through a ligand exchange reaction in solution. This is found to be an effective way to improve the performance of QDSCs based on colloidal QDs. The results show that MPA can increase the coverage of the QDs on TiO2 electrodes and facilitate the hole extraction from the photoxidized QDs, and simultaneously, that the iodide anions can remedy the surface defects of the CdSe QDs and thus reduce the recombination loss in the device. This hybrid passivation treatment leads to a significant enhancement of the power conversion efficiency of the QDSCs by 41%. Furthermore, an optimal ratio of iodide ions to MPA was determined for favorable hybrid passivation; results show that excessive iodine anions are detrimental to the loading of the QDs. This study demonstrates that the improvement in QDSC performance can be realized by using a combination of different functional ligands to passivate the QDs, and that ligand exchange in solution can be an effective approach to introduce different ligands.

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

    PubMed

    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.

  14. Hierarchically structured ZnO nanorods-nanosheets for improved quantum-dot-sensitized solar cells.

    PubMed

    Tian, Jianjun; Uchaker, Evan; Zhang, Qifeng; Cao, Guozhong

    2014-03-26

    ZnO nanorods (NRs) and nanosheets (NSs) were fabricated by adjusting the growth orientation of ZnO crystals in the reaction solution, respectively. The thin ZnO NSs were slowly assembled on the surface of NRs to form a hierarchically structured NR-NS photoelectrode for constructing CdS/CdSe quantum-dot-sensitized solar cells (QDSCs). This hierarchical structure had two advantages in improving the power conversion efficiency (PCE) of the solar cells: (a) it increased the surface area and modified the surface profile of the ZnO NRs to aid in harvesting more quantum dots, which leads to a high short-current density (Jsc); (b) it facilitated transportation of the electrons in this compact structure to reduce the charge recombination, which led to enhancement of the open-circuit voltage (Voc) and fill factor (FF). As a result, the QDSC assembled with the hierarchical NR-NS photoelectrode exhibited a high PCE of 3.28%, which is twice as much as that of the NR photoelectrode (1.37%).

  15. Visual and sensitive fluorescent sensing for ultratrace mercury ions by perovskite quantum dots.

    PubMed

    Lu, Li-Qiang; Tan, Tian; Tian, Xi-Ke; Li, Yong; Deng, Pan

    2017-09-15

    Mercury ions sensing is an important issue for human health and environmental safety. A novel fluorescence nanosensor was designed for rapid visual detection of ultratrace mercury ions (Hg(2+)) by using CH3NH3PbBr3 perovskite quantum dots (QDs) based on the surface ion-exchange mechanism. The synthesized CH3NH3PbBr3 QDs can emitt intense green fluorescence with high quantum yield of 50.28%, and can be applied for Hg(2+) sensing with the detection limit of 0.124 nM (24.87 ppt) in the range of 0 nM-100 nM. Furthermore, the interfering metal ions have no any influence on the fluorescence intensity of QDs, showing the perovskite QDs possess the high selectivity and sensitivity for Hg(2+) detection. The sensing mechanism of perovskite QDs for Hg(2+) is has also been investigated by XPS, EDX studies, showing Pb(2+) on the surface of perovskite QDs has been partially replaced by Hg(2+). Spot plate test shows that the perovskite QDs can also be used for visual detection of Hg(2+). Our research indicated the perovskite QDs are promising candidates for the visual fluorescence detection of environmental micropollutants. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Center-of-mass motion as a sensitive convergence test for variational multimode quantum dynamics

    NASA Astrophysics Data System (ADS)

    Cosme, Jayson G.; Weiss, Christoph; Brand, Joachim

    2016-10-01

    Multimode expansions in computational quantum dynamics promise convergence toward exact results upon increasing the number of modes. Convergence is difficult to ascertain in practice due to the unfavorable scaling of required resources for many-particle problems and therefore a simplified criterion based on a threshold value for the least occupied mode function is often used. Here we show how the separable quantum motion of the center of mass can be used to sensitively detect unconverged numerical multiparticle dynamics in harmonic potentials. Based on an experimentally relevant example of attractively interacting bosons in one dimension, we demonstrate that the simplified convergence criterion fails to assure qualitatively correct results. Furthermore, the numerical evidence for the creation of two-hump fragmented bright soliton-like states presented by A. I. Streltsov et al. [Phys. Rev. Lett. 100, 130401 (2008), 10.1103/PhysRevLett.100.130401] is shown to be inconsistent with exact results. Implications for understanding dynamical fragmentation in attractive boson systems are briefly discussed.

  17. Tuning electron transfer rates through molecular bridges in quantum dot sensitized oxides.

    PubMed

    Wang, Hai; McNellis, Erik R; Kinge, Sachin; Bonn, Mischa; Cánovas, Enrique

    2013-11-13

    Photoinduced electron transfer processes from semiconductor quantum dots (QDs) molecularly bridged to a mesoporous oxide phase are quantitatively surveyed using optical pump-terahertz probe spectroscopy. We control electron transfer rates in donor-bridge-acceptor systems by tuning the electronic coupling strength through the use of n-methylene (SH-[CH2]n-COOH) and n-phenylene (SH-[C6H4](n)-COOH) molecular bridges. Our results show that electron transfer occurs as a nonresonant quantum tunneling process with characteristic decay rates of β(n) = 0.94 ± 0.08 and β(n) = 1.25 per methylene and phenylene group, respectively, in quantitative agreement with reported conductance measurements through single molecules and self-assembled monolayers. For a given QD donor-oxide acceptor separation distance, the aromatic n-phenylene based bridges allow faster electron transfer processes when compared with n-methylene based ones. Implications of these results for QD sensitized solar cell design are discussed.

  18. Hybrid polymer/ZnO solar cells sensitized by PbS quantum dots.

    PubMed

    Wang, Lidan; Zhao, Dongxu; Su, Zisheng; Shen, Dezhen

    2012-02-07

    Poly[2-methoxy-5-(2-ethylhexyloxy-p-phenylenevinylene)]/ZnO nanorod hybrid solar cells consisting of PbS quantum dots [QDs] prepared by a chemical bath deposition method were fabricated. An optimum coating of the QDs on the ZnO nanorods could strongly improve the performance of the solar cells. A maximum power conversion efficiency of 0.42% was achieved for the PbS QDs' sensitive solar cell coated by 4 cycles, which was increased almost five times compared with the solar cell without using PbS QDs. The improved efficiency is attributed to the cascade structure formed by the PbS QD coating, which results in enhanced open-circuit voltage and exciton dissociation efficiency.

  19. Semiconductor nanowires for highly sensitive, room-temperature detection of terahertz quantum cascade laser emission

    NASA Astrophysics Data System (ADS)

    Vitiello, Miriam S.; Viti, Leonardo; Romeo, Lorenzo; Ercolani, Daniele; Scalari, G.; Faist, J.; Beltram, F.; Sorba, L.; Tredicucci, A.

    2012-06-01

    We report on the development of nanowire-based field-effect transistors operating as high sensitivity terahertz (THz) detectors. By feeding the 1.5 THz radiation field of a quantum cascade laser (QCL) at the gate-source electrodes with a wide band dipole antenna, we record a photovoltage signal corresponding to responsivity values >10 V/W, with impressive noise equivalent power levels <6 × 10-11 W/√Hz at room temperature and a wide modulation bandwidth. The potential scalability to even higher frequencies and the technological feasibility of realizing multi-pixel arrays coupled with QCL sources make the proposed technology highly competitive for a future generation of THz detection systems.

  20. Effect of Organic and Inorganic Passivation in Quantum-Dot-Sensitized Solar Cells.

    PubMed

    de la Fuente, Mauricio Solis; Sánchez, Rafael S; González-Pedro, Victoria; Boix, Pablo P; Mhaisalkar, S G; Rincón, Marina E; Bisquert, Juan; Mora-Seró, Iván

    2013-05-02

    The effect of semiconductor passivation on quantum-dot-sensitized solar cells (QDSCs) has been systematically characterized for CdS and CdS/ZnS. We have found that passivation strongly depends on the passivation agent, obtaining an enhancement of the solar cell efficiency for compounds containing amine and thiol groups and, in contrast, a decrease in performance for passivating agents with acid groups. Passivation can induce a change in the position of TiO2 conduction band and also in the recombination rate and nature, reflected in a change in the β parameter. Especially interesting is the finding that β, and consequently the fill factor can be increased with the passivation treatment. Applying this strategy, record cells of 4.65% efficiency for PbS-based QDSCs have been produced.

  1. Circular-polarization-sensitive metamaterial based on triple-quantum-dot molecules.

    PubMed

    Kotetes, Panagiotis; Jin, Pei-Qing; Marthaler, Michael; Schön, Gerd

    2014-12-05

    We propose a new type of chiral metamaterial based on an ensemble of artificial molecules formed by three identical quantum dots in a triangular arrangement. A static magnetic field oriented perpendicular to the plane breaks mirror symmetry, rendering the molecules sensitive to the circular polarization of light. By varying the orientation and magnitude of the magnetic field one can control the polarization and frequency of the emission spectrum. We identify a threshold frequency Ω, above which we find strong birefringence. In addition, Kerr rotation and circular-polarized lasing action can be implemented. We investigate the single-molecule lasing properties for different energy-level arrangements and demonstrate the possibility of circular-polarization conversion. Finally, we analyze the effect of weak stray electric fields or deviations from the equilateral triangular geometry.

  2. Improved measurement of two-mode quantum correlations using a phase-sensitive amplifier

    NASA Astrophysics Data System (ADS)

    Li, Tian; Anderson, Brian E.; Horrom, Travis; Schmittberger, Bonnie L.; Jones, Kevin M.; Lett, Paul D.

    2017-09-01

    We demonstrate the ability of a phase-sensitive amplifier (PSA) to pre-amplify a selected quadrature of one mode of a two-mode squeezed state in order to improve the measurement of two-mode quantum correlations that exist before degradation due to optical and detection losses. We use four-wave mixing (4WM) in $^{85}$Rb vapor to generate bright beams in a two-mode squeezed state. One of these two modes then passes through a second 4WM interaction in a PSA configuration to noiselessly pre-amplify the desired quadrature of the mode before loss is intentionally introduced. We demonstrate an enhancement in the measured degree of intensity correlation and intensity-difference squeezing between the two modes.

  3. Highly Sensitive Ultraviolet Photodetectors Fabricated from ZnO Quantum Dots/Carbon Nanodots Hybrid Films

    PubMed Central

    Guo, Deng-Yang; Shan, Chong-Xin; Qu, Song-Nan; Shen, De-Zhen

    2014-01-01

    Ultraviolet photodetectors have been fabricated from ZnO quantum dots/carbon nanodots hybrid films, and the introduction of carbon nanodots improves the performance of the photodetectors greatly. The photodetectors can be used to detect very weak ultraviolet signals (as low as 12 nW/cm2). The detectivity and noise equivalent power of the photodetector can reach 3.1 × 1017 cmHz1/2/W and 7.8 × 10−20 W, respectively, both of which are the best values ever reported for ZnO-based photodetectors. The mechanism for the high sensitivity of the photodetectors has been attributed to the enhanced carrier-separation at the ZnO/C interface. PMID:25502422

  4. CdSe quantum dot sensitized solar cell based hierarchical branched ZnO nanoarrays

    NASA Astrophysics Data System (ADS)

    Xu, Gang; Deng, Jianping

    2015-05-01

    The hierarchical branched ZnO nanoarrays (NAs) photoanode was prepared by a two-step hydrothermal method. Vertically aligned long ZnO NWs were first synthesized using as the backbone of hierarchical branched ZnO NAs structure and high quality ZnO NAs branches were grown on the surface of backbone ZnO NAs. The structured films enhance the optical path length through the light scatting effect of branched ZnO NAs and prove the larger internal surface area in NAs film to increase quantum dots (QDs) sensitizer loadings, so the light absorption has an optimization. Compared with the cell based conventional 1D ZnO NAs, the efficiency of the new cells has a great improvement due to the increase of the short circuit current density.

  5. Quantum-dot-sensitized solar cells: understanding linker molecules through theory and experiment.

    PubMed

    Margraf, Johannes T; Ruland, Andrés; Sgobba, Vito; Guldi, Dirk M; Clark, Timothy

    2013-02-19

    We have investigated the role of linker molecules in quantum-dot-sensitized solar cells (QDSSCs) using density-functional theory (DFT) and experiments. Linkers not only govern the number of attached QDs but also influence charge separation, recombination, and transport. Understanding their behavior is therefore not straightforward. DFT calculations show that mercaptopropionic acid (MPA) and cysteine (Cys) exhibit characteristic binding configurations on TiO(2) surfaces. This information is used to optimize the cell assembly process, yielding Cys-based cells that significantly outperform MPA cells, and reach power conversion efficiencies (PCE) as high as 2.7% under AM 1.5 illumination. Importantly, the structural information from theory also helps understand the cause for this improved performance.

  6. Investigation of II-VI Semiconductor Quantum Dots for Sensitized Solar Cell Applications

    NASA Astrophysics Data System (ADS)

    Horoz, Sabit

    Semiconductor nanocrystals, also referred to as quantum dots (QDs) which have advantages of low-cost, photostability, high molar extinction coefficients and size-dependent optical properties, have been the focus of great scientific and technological efforts in solar cells development. Due to the multi-electron generation effect, the theoretical maximum efficiency of quantum dots sensitized solar cells (QDSSCs) is much higher than that of dye sensitized solar cells (DSSCs). Thus QDSSCs have a clear potential to overtake the efficiency of other kinds of solar cells. Doped semiconductor QDs can not only retain nearly all advantages of intrinsic QDs, but also have additional absorption bands for improved efficiency. This approach is particularly important for wide band gap semiconductors, for example, zinc based QDs. Zinc based are desirable candidates as they are inexpensive, earth abundant and nontoxic. When doped, they can cover a broad range of visible spectrum. In my project, I aim at developing novel methods for the preparation of II-VI QDs and investigating the effects of doping on the properties and performances of QDSSCs. Cadmium selenide (CdSe), manganese doped cadmium selenide (Mn:CdSe), and manganese doped zinc sulfide (Mn:ZnS) QDs have been synthesized by laser ablation in water. The structural and luminescent properties of the QDs have been investigated. In addition, QDSSC performances of the samples have been measured using nanowire electrode made of ZnO and Zn2SnO 4. I have also successfully synthesized europium doped zinc sulfide (Eu:ZnS) and manganese doped cadmium sulfide (Mn:CdS) nanoparticles by wet chemical method, and analyzed structural, optical, and magnetic properties as well as the device performance of the nanoparticles.

  7. Boosting the efficiency of quantum dot sensitized solar cells through modulation of interfacial charge transfer.

    PubMed

    Kamat, Prashant V

    2012-11-20

    The demand for clean energy will require the design of nanostructure-based light-harvesting assemblies for the conversion of solar energy into chemical energy (solar fuels) and electrical energy (solar cells). Semiconductor nanocrystals serve as the building blocks for designing next generation solar cells, and metal chalcogenides (e.g., CdS, CdSe, PbS, and PbSe) are particularly useful for harnessing size-dependent optical and electronic properties in these nanostructures. This Account focuses on photoinduced electron transfer processes in quantum dot sensitized solar cells (QDSCs) and discusses strategies to overcome the limitations of various interfacial electron transfer processes. The heterojunction of two semiconductor nanocrystals with matched band energies (e.g., TiO(2) and CdSe) facilitates charge separation. The rate at which these separated charge carriers are driven toward opposing electrodes is a major factor that dictates the overall photocurrent generation efficiency. The hole transfer at the semiconductor remains a major bottleneck in QDSCs. For example, the rate constant for hole transfer is 2-3 orders of magnitude lower than the electron injection from excited CdSe into oxide (e.g., TiO(2)) semiconductor. Disparity between the electron and hole scavenging rate leads to further accumulation of holes within the CdSe QD and increases the rate of electron-hole recombination. To overcome the losses due to charge recombination processes at the interface, researchers need to accelerate electron and hole transport. The power conversion efficiency for liquid junction and solid state quantum dot solar cells, which is in the range of 5-6%, represents a significant advance toward effective utilization of nanomaterials for solar cells. The design of new semiconductor architectures could address many of the issues related to modulation of various charge transfer steps. With the resolution of those problems, the efficiencies of QDSCs could approach those of dye

  8. Infra-red photoresponse of mesoscopic NiO-based solar cells sensitized with PbS quantum dot

    NASA Astrophysics Data System (ADS)

    Raissi, Mahfoudh; Pellegrin, Yann; Jobic, Stéphane; Boujtita, Mohammed; Odobel, Fabrice

    2016-04-01

    Sensitized NiO based photocathode is a new field of investigation with increasing scientific interest in relation with the development of tandem dye-sensitized solar cells (photovoltaic) and dye-sensitized photoelectrosynthetic cells (solar fuel). We demonstrate herein that PbS quantum dots (QDs) represent promising inorganic sensitizers for NiO-based quantum dot-sensitized solar cells (QDSSCs). The solar cell sensitized with PbS quantum dot exhibits significantly higher photoconversion efficiency than solar cells sensitized with a classical and efficient molecular sensitizer (P1 dye = 4-(Bis-{4-[5-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl}-amino)-benzoic acid). Furthermore, the system features an IPCE (Incident Photon-to-Current Efficiency) spectrum that spreads into the infra-red region, reaching operating wavelengths of 950 nm. The QDSSC photoelectrochemical device works with the complexes tris(4,4‧-ditert-butyl-2,2‧-bipyridine)cobalt(III/II) redox mediators, underscoring the formation of a long-lived charge-separated state. The electrochemical impedance spectrocopy measurements are consistent with a high packing of the QDs upon the NiO surface, the high density of which limits the access of the electrolyte and results in favorable light absorption cross-sections and a significant hole lifetime. These notable results highlight the potential of NiO-based photocathodes sensitized with quantum dots for accessing and exploiting the low-energy part of the solar spectrum in photovoltaic and photocatalysis applications.

  9. Infra-red photoresponse of mesoscopic NiO-based solar cells sensitized with PbS quantum dot

    PubMed Central

    Raissi, Mahfoudh; Pellegrin, Yann; Jobic, Stéphane; Boujtita, Mohammed; Odobel, Fabrice

    2016-01-01

    Sensitized NiO based photocathode is a new field of investigation with increasing scientific interest in relation with the development of tandem dye-sensitized solar cells (photovoltaic) and dye-sensitized photoelectrosynthetic cells (solar fuel). We demonstrate herein that PbS quantum dots (QDs) represent promising inorganic sensitizers for NiO-based quantum dot-sensitized solar cells (QDSSCs). The solar cell sensitized with PbS quantum dot exhibits significantly higher photoconversion efficiency than solar cells sensitized with a classical and efficient molecular sensitizer (P1 dye = 4-(Bis-{4-[5-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl}-amino)-benzoic acid). Furthermore, the system features an IPCE (Incident Photon-to-Current Efficiency) spectrum that spreads into the infra-red region, reaching operating wavelengths of 950 nm. The QDSSC photoelectrochemical device works with the complexes tris(4,4′-ditert-butyl-2,2′-bipyridine)cobalt(III/II) redox mediators, underscoring the formation of a long-lived charge-separated state. The electrochemical impedance spectrocopy measurements are consistent with a high packing of the QDs upon the NiO surface, the high density of which limits the access of the electrolyte and results in favorable light absorption cross-sections and a significant hole lifetime. These notable results highlight the potential of NiO-based photocathodes sensitized with quantum dots for accessing and exploiting the low-energy part of the solar spectrum in photovoltaic and photocatalysis applications. PMID:27125454

  10. Infra-red photoresponse of mesoscopic NiO-based solar cells sensitized with PbS quantum dot.

    PubMed

    Raissi, Mahfoudh; Pellegrin, Yann; Jobic, Stéphane; Boujtita, Mohammed; Odobel, Fabrice

    2016-04-29

    Sensitized NiO based photocathode is a new field of investigation with increasing scientific interest in relation with the development of tandem dye-sensitized solar cells (photovoltaic) and dye-sensitized photoelectrosynthetic cells (solar fuel). We demonstrate herein that PbS quantum dots (QDs) represent promising inorganic sensitizers for NiO-based quantum dot-sensitized solar cells (QDSSCs). The solar cell sensitized with PbS quantum dot exhibits significantly higher photoconversion efficiency than solar cells sensitized with a classical and efficient molecular sensitizer (P1 dye = 4-(Bis-{4-[5-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl}-amino)-benzoic acid). Furthermore, the system features an IPCE (Incident Photon-to-Current Efficiency) spectrum that spreads into the infra-red region, reaching operating wavelengths of 950 nm. The QDSSC photoelectrochemical device works with the complexes tris(4,4'-ditert-butyl-2,2'-bipyridine)cobalt(III/II) redox mediators, underscoring the formation of a long-lived charge-separated state. The electrochemical impedance spectrocopy measurements are consistent with a high packing of the QDs upon the NiO surface, the high density of which limits the access of the electrolyte and results in favorable light absorption cross-sections and a significant hole lifetime. These notable results highlight the potential of NiO-based photocathodes sensitized with quantum dots for accessing and exploiting the low-energy part of the solar spectrum in photovoltaic and photocatalysis applications.

  11. Quantum dot-based immunochromatography test strip for rapid, quantitative and sensitive detection of alpha fetoprotein.

    PubMed

    Yang, Qiuhua; Gong, Xiaoqun; Song, Tao; Yang, Jiumin; Zhu, Shengjiang; Li, Yunhong; Cui, Ye; Li, Yingxin; Zhang, Bingbo; Chang, Jin

    2011-12-15

    Rapid, quantitative detection of tumor markers with high sensitivity and specificity is critical to clinical diagnosis and treatment of cancer. We describe here a novel portable fluorescent biosensor that integrates quantum dot (QD) with an immunochromatography test strip (ICTS) and a home-made test strip reader for detection of tumor markers in human serum. Alpha fetoprotein (AFP), which is valuable for diagnosis of primary hepatic carcinoma, is used as a model tumor marker to demonstrate the performance of the proposed immunosensor. The principle of this sensor is on the basis of a sandwich immunoreaction that was performed on an ICTS. The fluorescence intensity of captured QD labels on the test line and control line served as signals was determined by the home-made test strip reader. The strong luminescence and robust photostability of QDs combined with the promising advantages of an ICTS and sensitive detection with the test strip reader result in good performance. Under optimal conditions, this biosensor is capable of detecting as low as 1 ng/mL AFP standard analyte in 10 min with only 50 μL sample volume. Furthermore, 1000 clinical human serum samples were tested by both the QD-based ICTS and a commercial electrochemiluminescence immunoassay AFP kit simultaneously to estimate the sensitivity, specificity and concordance of the assays. Results showed high consistency except for 24 false positive cases (false positive rate 3.92%) and 17 false negative cases (false negative rate 4.38%); the error rate was 4.10% in all. This demonstrates that the QD-based ICTS is capable of rapid, sensitive, and quantitative detection of AFP and shows a great promise for point-of-care testing of other tumor markers. Copyright © 2011 Elsevier B.V. All rights reserved.

  12. Quantum-dot submicrobead-based immunochromatographic assay for quantitative and sensitive detection of zearalenone.

    PubMed

    Duan, Hong; Chen, Xuelan; Xu, Wei; Fu, Jinhua; Xiong, Yonghua; Wang, Andrew

    2015-01-01

    Mycotoxin pollutants are commonly related to cereal products and cause fatal threats in food safety, and therefore require simple and sensitive detection. In this work, quantum-dot (QD) submicrobeads (QBs) were synthesized by encapsulating CdSe/ZnS QDs using the microemulsion technique. The resultant QBs, with approximately 2800 times brighter luminescence than the corresponding QDs, were explored as novel fluorescent probes in the immunochromatographic assay (ICA) for sensitive and quantitative detection of zearalenone (ZEN) in corns. Various parameters that influenced the sensitivity and stability of QB-based ICA (QB-ICA) were investigated and optimized. The optimal QB-ICA exhibits good dynamic linear detection for ZEN over the range of 0.125 ng/mL to 10 ng/mL with a median inhibitory concentration of 1.01±0.09 ng/mL (n=3). The detection limits for ZEN in a standard solution and real corn sample (dilution ratio of 1:30) are 0.0625 ng/mL and 3.6 µg/kg, respectively, which is much better than that of a previously reported gold nanoparticle-based ICA method. Forty-six natural corn samples are assayed using both QB-ICA and enzyme-linked immunosorbent assay. The two methods show a highly significant correlation (R(2)=0.92). Nine ZEN-contaminated samples were further confirmed with liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the QB-ICA results also exhibited good agreement with LC-MS/MS method. In brief, this work demonstrates that QB-ICA is capable of rapid, sensitive screening of toxins in food analysis, and shows great promise for point-of-care testing of other analytes.

  13. Synthesis of Bi{sub 2}S{sub 3} quantum dots for sensitized solar cells by reverse SILAR

    SciTech Connect

    Singh, Navjot; Sharma, J.; Tripathi, S. K. E-mail: surya-tr@yahoo.com

    2016-05-06

    Quantum Dot Sensitized Solar cells (QDSSC) have great potential to replace silicon-based solar cells. Quantum dots of various materials and sizes could be used to convert most of the visible light into the electrical current. This paper put emphasis on the synthesis of Bismuth Sulphide quantum dots and selectivity of the anionic precursor by Successive Ionic Layer Adsorption Reaction (SILAR). Bismuth Sulfide (Bi{sub 2}S{sub 3}) (group V – Vi semiconductor) is strong contestant for cadmium free solar cells due to its optimum band gap for light harvesting. Optical, structural and electrical measurements are reported and discussed. Problem regarding the choice of precursor for anion extraction is discussed. Band gap of the synthesized quantum dots is 1.2 eV which does not match with the required energy band gap of bismuth sulfide that is 1.7 eV.

  14. Sensitivity of absorption spectra to surface segregation in InGaN/GaN quantum well structures

    SciTech Connect

    Klymenko, M. V.; Shulika, O. V.; Sukhoivanov, I. A.

    2014-05-15

    We investigate the influence of the indium surface segregation on absorption spectra in InGaN/GaN quantum well structures having different indium amount. Results of the mathematical modeling show that such influence is more pronounced in quantum well structures with high indium amounts. The origin of this effect is related to the interplay between the indium surface segregation and internal electrostatic fields. Our theoretical analysis is performed using semiconductor Bloch equations within the Hartree-Fock approximation including into consideration excitonic effects. Results of the global sensitivity analysis evidence that the influence of the indium surface segregation is less than one order of magnitude in comparison with the impact of the quantum-well width and indium molar fraction. Also, the influence of the indium surface segregation is not the same for each interface of the quantum well.

  15. Ligand capping effect for dye solar cells with a CdSe quantum dot sensitized ZnO nanorod photoanode.

    PubMed

    Sun, Xiao Wei; Chen, Jing; Song, Jun Ling; Zhao, De Wei; Deng, Wei Qiao; Lei, Wei

    2010-01-18

    We report a quantum dot sensitized solar cell (QDSSC) with a thioglycolic acid (TGA) capped CdSe quantum dot (QD) sensitized ZnO nanorod photoanode. As revealed by UV-Vis absorption spectrum and transmission electron microscopy, the quantum dots can be effectively adsorbed onto ZnO nanorods. By studying the emission decay, the quenching of the CdSe QDs by ZnO nanorod was verified, and an electron transfer (from QD to ZnO) rate constant of 1 x 10(8) s(-1) was obtained. The efficiency of the as-prepared QDSSC was 0.66% and an incident power conversion efficiency of 22% at 400 nm was achieved.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  17. Highly sensitive polymerase chain reaction-free quantum dot-based quantification of forensic genomic DNA.

    PubMed

    Tak, Yu Kyung; Kim, Won Young; Kim, Min Jung; Han, Eunyoung; Han, Myun Soo; Kim, Jong Jin; Kim, Wook; Lee, Jong Eun; Song, Joon Myong

    2012-04-06

    Forensic DNA samples can degrade easily due to exposure to light and moisture at the crime scene. In addition, the amount of DNA acquired at a criminal site is inherently limited. This limited amount of human DNA has to be quantified accurately after the process of DNA extraction. The accurately quantified extracted genomic DNA is then used as a DNA template in polymerase chain reaction (PCR) amplification for short tandem repeat (STR) human identification. Accordingly, highly sensitive and human-specific quantification of forensic DNA samples is an essential issue in forensic study. In this work, a quantum dot (Qdot)-labeled Alu sequence was developed as a probe to simultaneously satisfy both the high sensitivity and human genome selectivity for quantification of forensic DNA samples. This probe provided PCR-free determination of human genomic DNA and had a 2.5-femtogram detection limit due to the strong emission and photostability of the Qdot. The Qdot-labeled Alu sequence has been used successfully to assess 18 different forensic DNA samples for STR human identification.

  18. Engineered band structure for an enhanced performance on quantum dot-sensitized solar cells

    SciTech Connect

    Jin, Bin Bin; Wang, Ye Feng; Wei, Dong; Chen, Yu; Zeng, Jing Hui; Cui, Bin

    2016-06-20

    A photon-to-current efficiency of 2.93% is received for the Mn-doped CdS (MCdS)-quantum dot sensitized solar cells (QDSSCs) using Mn:ZnO (MZnO) nanowire as photoanode. Hydrothermal synthesized MZnO are spin-coated on fluorine doped tin oxide (FTO) glass with P25 paste to serve as photoanode after calcinations. MCdS was deposited on the MZnO film by the successive ionic layer adsorption and reaction method. The long lived excitation energy state of Mn{sup 2+} is located inside the conduction band in the wide bandgap ZnO and under the conduction band of CdS, which increases the energetic overlap of donor and acceptor states, reducing the “loss-in-potential,” inhibiting charge recombination, and accelerating electron injection. The engineered band structure is well reflected by the electrochemical band detected using cyclic voltammetry. Cell performances are evidenced by current density-voltage (J-V) traces, diffuse reflectance spectra, transient PL spectroscopy, and incident photon to current conversion efficiency characterizations. Further coating of CdSe on MZnO/MCdS electrode expands the light absorption band of the sensitizer, an efficiency of 4.94% is received for QDSSCs.

  19. Highly sensitive detection of DNA methylation levels by using a quantum dot-based FRET method.

    PubMed

    Ma, Yunfei; Zhang, Honglian; Liu, Fangming; Wu, Zhenhua; Lu, Shaohua; Jin, Qinghui; Zhao, Jianlong; Zhong, Xinhua; Mao, Hongju

    2015-11-07

    DNA methylation is the most frequently studied epigenetic modification that is strongly involved in genomic stability and cellular plasticity. Aberrant changes in DNA methylation status are ubiquitous in human cancer and the detection of these changes can be informative for cancer diagnosis. Herein, we reported a facile quantum dot-based (QD-based) fluorescence resonance energy transfer (FRET) technique for the detection of DNA methylation. The method relies on methylation-sensitive restriction enzymes for the differential digestion of genomic DNA based on its methylation status. Digested DNA is then subjected to PCR amplification for the incorporation of Alexa Fluor-647 (A647) fluorophores. DNA methylation levels can be detected qualitatively through gel analysis and quantitatively by the signal amplification from QDs to A647 during FRET. Furthermore, the methylation levels of three tumor suppressor genes, PCDHGB6, HOXA9 and RASSF1A, in 20 lung adenocarcinoma and 20 corresponding adjacent nontumorous tissue (NT) samples were measured to verify the feasibility of the QD-based FRET method and a high sensitivity for cancer detection (up to 90%) was achieved. Our QD-based FRET method is a convenient, continuous and high-throughput method, and is expected to be an alternative for detecting DNA methylation as a biomarker for certain human cancers.

  20. Transport studies of quantum dots sensitized single Mn-ZnO nanowire field effect transistors

    NASA Astrophysics Data System (ADS)

    Sapkota, Keshab R.; Maloney, Francis Scott; Rimal, Gaurab; Poudyal, Uma; Tang, Jinke; Wang, Wenyong

    We present opto-electrical transport properties of Mn-CdSe quantum dots (QDs) sensitized single Mn-ZnO nanowire (NW) field effect transistors (FET). The ZnO NWs with 2 atomic % of Mn doping are grown by chemical vapor deposition. The NWs are ferromagnetic at low temperature. The as grown nanowires are transferred to clean SiO2/Si substrate and single nanowire field effect transistors (FET) are fabricated by standard e-beam lithography. Mobility and carrier concentration of Mn-ZnO NWs are estimated from FET device measurement which shows NWs are n-type semiconductors. Pulse laser deposition of Mn-CdSe QDs on the single NW FET significantly increases carrier concentration of the QD-NW system in dark where the QD monolayer conduction is negligibly small. The photoconductivity study of QD sensitized NW FET enlightens the conduction spectrum of QD-NW system and QD to NW carrier transfer mechanism. This work has been supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-10ER46728.

  1. Engineered band structure for an enhanced performance on quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Jin, Bin Bin; Wang, Ye Feng; Wei, Dong; Cui, Bin; Chen, Yu; Zeng, Jing Hui

    2016-06-01

    A photon-to-current efficiency of 2.93% is received for the Mn-doped CdS (MCdS)-quantum dot sensitized solar cells (QDSSCs) using Mn:ZnO (MZnO) nanowire as photoanode. Hydrothermal synthesized MZnO are spin-coated on fluorine doped tin oxide (FTO) glass with P25 paste to serve as photoanode after calcinations. MCdS was deposited on the MZnO film by the successive ionic layer adsorption and reaction method. The long lived excitation energy state of Mn2+ is located inside the conduction band in the wide bandgap ZnO and under the conduction band of CdS, which increases the energetic overlap of donor and acceptor states, reducing the "loss-in-potential," inhibiting charge recombination, and accelerating electron injection. The engineered band structure is well reflected by the electrochemical band detected using cyclic voltammetry. Cell performances are evidenced by current density-voltage (J-V) traces, diffuse reflectance spectra, transient PL spectroscopy, and incident photon to current conversion efficiency characterizations. Further coating of CdSe on MZnO/MCdS electrode expands the light absorption band of the sensitizer, an efficiency of 4.94% is received for QDSSCs.

  2. Quantum dots based mesoporous structured imprinting microspheres for the sensitive fluorescent detection of phycocyanin.

    PubMed

    Zhang, Zhong; Li, Jinhua; Wang, Xiaoyan; Shen, Dazhong; Chen, Lingxin

    2015-05-06

    Phycocyanin with important physiological/environmental significance has attracted increasing attention; versatile molecularly imprinted polymers (MIPs) have been applied to diverse species, but protein imprinting is still quite difficult. Herein, using phycocyanin as template via a sol-gel process, we developed a novel fluorescent probe for specific recognition and sensitive detection of phycocyanin by quantum dots (QDs) based mesoporous structured imprinting microspheres (SiO2@QDs@ms-MIPs), obeying electron-transfer-induced fluorescence quenching mechanism. When phycocyanin was present, a Meisenheimer complex would be produced between phycocyanin and primary amino groups of QDs surface, and then the photoluminescent energy of QDs would be transferred to the complex, leading to the fluorescence quenching of QDs. As a result, the fluorescent intensity of the SiO2@QDs@ms-MIPs was significantly decreased within 8 min, and accordingly a favorable linearity within 0.02-0.8 μM and a high detectability of 5.9 nM were presented. Excellent recognition specificity for phycocyanin over its analogues was displayed, with a high imprinting factor of 4.72. Furthermore, the validated probe strategy was successfully applied to seawater and lake water sample analysis, and high recoveries in the range of 94.0-105.0% were attained at three spiking levels of phycocyanin, with precisions below 5.3%. The study provided promising perspectives to develop fluorescent probes for convenient, rapid recognition and sensitive detection of trace proteins from complex matrices, and further pushed forward protein imprinting research.

  3. Ternary CuBiS2 nanoparticles as a sensitizer for quantum dot solar cells.

    PubMed

    Suriyawong, Nipapon; Aragaw, Belete; Shi, Jen-Bin; Lee, Ming-Way

    2016-07-01

    This work investigates the synthesis and application in solar cells of a novel solar absorber material CuBiS2. Ternary copper chalcogenide CuBiS2 nanoparticles were grown on a mesoporous TiO2 electrode by the chemical bath deposition (CBD) method. The synthesized CuBiS2 nanoparticles, size 5-10nm, have an energy gap Eg of 2.1eV. Liquid-junction quantum dot-sensitized solar cells were fabricated from the CuBiS2-sensitized electrode using a polysulfide electrolyte. Three types of counter electrodes (CEs) - Pt, Au and Cu2S - were tested. The photovoltaic performance depends on the CBD reaction time and the CE. The best cell, obtained with the Cu2S CE, exhibited the photovoltaic performance of a short-circuit current density Jsc of 6.87mA/cm(2), an open-circuit voltage Voc of 0.25V, a fill factor FF of 36% and a power conversion efficiency η of 0.62%. The present work demonstrates the feasibility of CuBiS2 as a solar energy material.

  4. Surface treatment properties of CdS quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Razzaq, Abdul; Lee, Jun Young; Bhattacharya, Bhaskar; Park, Jung-Ki

    2014-08-01

    The dye-sensitized solar cells (DSSCs) are attractive due to their low cost and promising efficiency. One of the research perspectives in the respective field is to replace the expensive and photodegradable ruthenium metal-based dyes. Present work describes a simple, modified in situ route designed by mimicking the adsorption principle of dyes in DSSCs for surface modification and linking of CdS-Quantum Dots (QDs) to TiO2 electrode. An organic compound 2-mercaptoethanol (ME) was used as a surface modifying and linking agent. By following this route it was expected to get a well assembled layer of CdS QDs for better cell performance but performances were not as expected. The main reason for low photocurrent density is the partial coverage of QDs surface by ME and the spatial distance between QDs and TiO2 electrode. Additional surface treatment of the CdS QDs sensitized TiO2 electrode resulted in an increase in the photocurrent density and photovoltage. This indicates that ME is not an effective capping agent and thus partially covers the QDs surface. The remaining sites, not covered by ME were passivated by sulfur ions in the ionic solution.

  5. Colloidal graphene quantum dots incorporated with a Cobalt electrolyte in a dye sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Lim, Hyuna

    The utilization of sun light as a renewable energy source has been pursued for a long time, but the ultimate goal of developing inexpensive and highly efficient photovoltaic devices remains elusive. To address this problem, colloidal graphene quantum dots (GQDs) were synthesized and used as a new sensitizer in dye sensitized solar cells (DSCs). Not only do the GQDs have a well-defined structure, but their large absorptivity, tunable bandgap, and size- and functional group-dependent redox potentials make them promising candidates for photovoltaic applications. Because volatile organic solvents in electrolyte solutions hinder long-term use and mass production of DSC devices, imidazolium based ionic liquids (ILs) were investigated. Cobalt-bipyridine complexes were successfully synthesized and characterized for use as new redox shuttles in DSCs. In the tested DSCs, J-V (current density-voltage) curves illustrate that the short circuit current and fill factor decrease significantly as the active area in the TiO2 photo anode increases. Dark current measurement indicated that the diode factor is bigger than one, which is different from the conventional p-n junction type solar cells, due to the high efficiency of photoelectron injection. The variation of the diode factor in dark and in light would show various types of recombination behaviors in DSCs. The performance of the DSC stained by GQDs incorporated with the cobalt redox couple was tested, but further study to improve the efficiency and to understand photochemical reaction in the DSCs is needed.

  6. Folic acid-CdTe quantum dot conjugates and their applications for cancer cell targeting

    SciTech Connect

    Suriamoorthy, Preethi; Zhang, Xing; Hao, Guiyang; Joly, Alan G.; Singh, S.; Hossu, Marius; Sun, Xiankai; Chen, Wei

    2010-12-01

    In this study, we report the preparation,luminescence, and targeting properties of folic acid- CdTe quantum dot conjugates. Water-soluble CdTe quantum dots were synthesized and conjugated with folic acid using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide-N-hydroxysuccinimide chemistry. The in-fluence of folic acid on the luminescence properties of CdTe quantum dots was investigated, and no energy transfer between them was observed. To investigate the efficiency of folic acid-CdTe nanoconjugates for tumor targeting, pure CdTe quantum dots and folic acid-coated CdTe quantum dots were incubated with human naso- pharyngeal epidermal carcinoma cell line with positive expressing folic acid receptors (KB cells) and lung cancer cells without expression of folic acid receptors (A549 cells). For the cancer cells with positive folate receptors (KB cells), the uptake for CdTe quantum dots is very low, but for folic acid-CdTe nanoconjugates, the uptake is very high. For the lung cancer cells without folate receptors (A549 cells), the uptake for folic acid- CdTe nanoconjugates is also very low. The results indicate that folic acid is an effective targeting molecule for tumor cells with overexpressed folate receptors.

  7. Quantum

    NASA Astrophysics Data System (ADS)

    Elbaz, Edgard

    This book gives a new insight into the interpretation of quantum mechanics (stochastic, integral paths, decoherence), a completely new treatment of angular momentum (graphical spin algebra) and an introduction to Fermion fields (Dirac equation) and Boson fields (e.m. and Higgs) as well as an introduction to QED (quantum electrodynamics), supersymmetry and quantum cosmology.

  8. An ultralow noise current amplifier based on superconducting quantum interference device for high sensitivity applications

    NASA Astrophysics Data System (ADS)

    Granata, C.; Vettoliere, A.; Russo, M.

    2011-01-01

    An integrated ultrahigh sensitive current amplifier based on a niobium dc superconducting quantum interference device (SQUID) has been developed. The sensor design is based on a multiturn signal coil coupled to a suitable SQUID magnetometer. The signal coil consists of 60 square niobium turns tightly coupled to a superconducting flux transformer of a SQUID magnetometer. The primary coil (pick-up coil) of the flux transformer has been suitably designed in order to accommodate the multiturn input coil. It has a side length of 10 mm and a width of 2.4 mm. In such a way we have obtained a signal current to magnetic flux transfer coefficient (current sensitivity) as low as 62 nA/Φ0. The sensor has been characterized in liquid helium by using a direct coupling low noise readout electronic and a standard modulated electronic in flux locked loop configuration for the noise measurements. Beside the circuit complexity, the sensor has exhibited a smooth and free resonance voltage-flux characteristic guaranteeing a reliable and a stable working operation. Considering a SQUID magnetic flux noise of SΦ1/2 = 1.8 μΦ0/Hz1/2 at T = 4.2 K, a current noise as low as 110 fA/Hz1/2 is obtained. Such a value is about a factor two less than the noise of other SQUIDs of the same category. As an application, Nyquist noise measurements of integrated test resistors using the current sensing noise thermometer technique are reported. Due to its high performance such a sensor can be employed in all applications requiring an extremely current sensitivity like the readout of the gravitational wave detectors and the current sensing noise thermometry.

  9. An ultralow noise current amplifier based on superconducting quantum interference device for high sensitivity applications.

    PubMed

    Granata, C; Vettoliere, A; Russo, M

    2011-01-01

    An integrated ultrahigh sensitive current amplifier based on a niobium dc superconducting quantum interference device (SQUID) has been developed. The sensor design is based on a multiturn signal coil coupled to a suitable SQUID magnetometer. The signal coil consists of 60 square niobium turns tightly coupled to a superconducting flux transformer of a SQUID magnetometer. The primary coil (pick-up coil) of the flux transformer has been suitably designed in order to accommodate the multiturn input coil. It has a side length of 10 mm and a width of 2.4 mm. In such a way we have obtained a signal current to magnetic flux transfer coefficient (current sensitivity) as low as 62 nA∕Φ(0). The sensor has been characterized in liquid helium by using a direct coupling low noise readout electronic and a standard modulated electronic in flux locked loop configuration for the noise measurements. Beside the circuit complexity, the sensor has exhibited a smooth and free resonance voltage-flux characteristic guaranteeing a reliable and a stable working operation. Considering a SQUID magnetic flux noise of S(Φ)(1∕2) = 1.8 μΦ(0)∕Hz(1∕2) at T = 4.2 K, a current noise as low as 110 fA∕Hz(1∕2) is obtained. Such a value is about a factor two less than the noise of other SQUIDs of the same category. As an application, Nyquist noise measurements of integrated test resistors using the current sensing noise thermometer technique are reported. Due to its high performance such a sensor can be employed in all applications requiring an extremely current sensitivity like the readout of the gravitational wave detectors and the current sensing noise thermometry.

  10. Open-Path High Sensitivity Atmospheric Ammonia Sensing with a Quantum Cascade Laser Instrument

    NASA Astrophysics Data System (ADS)

    Miller, D. J.; Dirisu, A.; Rafferty, K.; Parkes, B.; Zondlo, M. A.

    2009-12-01

    Atmospheric trace-gas sensing with quantum cascade laser (QCL) spectroscopy offers the potential for high sensitivity, fast, selective mid-infrared absorption measurements of atmospheric species such as ammonia (NH3). As the third most abundant nitrogen species and most gaseous base in the atmosphere, ammonia plays important roles in neutralizing acidic species and as a gas-phase precursor to ammoniated fine particulate matter. High precision gas phase measurements are necessary to constrain highly uncertain emission sources and sinks with implications for understanding how chemical components of fine particulate matter affect air quality and climate as well as nitrogen deposition to ecosystems. Conventional ammonia sensors employing chemical ionization, denuder or filter techniques are labor-intensive, not gas-selective and exhibit low time resolution. As an advantageous alternative to conventional measurement techniques, we develop an open-path quantum cascade laser-based ammonia sensor operating at 9.06 μm for ground-based measurements. A continuous wave, thermoelectrically cooled quantum cascade laser is used to perform wavelength modulation absorption spectroscopy (WMS). Room-temperature, unattended operation with minimal surface adsorption effects due to the open-path configuration represent significant improvements over cryogenically cooled, closed path systems. The feasibility of a cylindrical mirror multi-pass optical cell for achieving long path lengths near 50 m in a compact design is also assessed. Meaningful ammonia measurements require fast sub-ppbv detection limits due to ammonia’s large dynamic range and temporal and spatial atmospheric variability. When fully developed, our instrument will achieve high time resolution (up to 10 Hz) measurements with ammonia detection limits in the 100 pptv range. Initial results include ambient laboratory ammonia detection at 58 ppbv relative to a 0.4% ammonia reference cell based on the WMS signal integrated

  11. The use of Schottky CdTe detectors for high-energy astronomy: application to the detection plane of the instrument SVOM/ECLAIRs

    NASA Astrophysics Data System (ADS)

    Nasser, G.; Godet, O.; Atteia, J.-L.; Amoros, C.; Barret, D.; Bordon, S.; Cordier, B.; Gevin, O.; Gonzalez, F.; Houret, B.; Lacombe, K.; Mandrou, P.; Marty, W.; Mercier, K.; Pons, R.; Rambaud, D.; Ramon, P.; Rouaix, G.; Waegebaert, V.

    2014-07-01

    Ohmic CdZnTe and CdTe detectors have been successfully used in high-energy missions such as IBIS on-board INTEGRAL and the Swift-BAT in the past two decades. Such detectors provide very good quantum efficiency in the hard X-ray band. For the future generation of hard X-ray coded mask detectors, a higher sensitivity will be required. A way to achieve this is to increase the effective area of the pixilated detection plane, to change the mask pattern and/or the properties of the semi-conductors paving the detection plane. For the future Chinese-French Gamma-ray burst mission SVOM, the GRB trigger camera ECLAIRs will make use of a new type of high-energy detectors, the Schottky CdTe detectors. Such detectors, when reversely biased, are known to present very low leakage current, resulting in lower values of the low-energy threshold (down to 4 keV or less) than for previous missions (i.e. > 10 keV for the Swift-BAT and INTEGRAL/IBIS). Such low values will enable ECLAIRs with a moderate geometrical area of 1024 cm2 and a low-energy threshold of 4 keV to be more sensitive to high-redshift GRBs (emitting mainly in X-rays) than the Swift-BAT with a higher effective area and low-energy threshold. However, the spectral performance of such detectors are known to degrade over time, once polarized, due to the polarization effect that strongly depends on the temperature and the bias voltage applied to the detectors. In this paper, we present an intensive study of the properties of Schottky CdTe detectors as used on SVOM/ECLAIRs such as I-V characteristics, polarization effect, activation energy and low temperature annealing effects. We discuss the implications of these measurements on the use of this type of detectors in future high-energy instruments.

  12. Quantum-Dot-Sensitized Solar Cells: Effect of Nanostructured TiO2 Morphologies on Photovoltaic Properties.

    PubMed

    Toyoda, Taro; Shen, Qing

    2012-07-19

    There is a great deal of interest in dye-sensitized solar cells (DSCs) fabricated with nanostructured TiO2 electrodes. Many different dye molecules have been designed and synthesized to achieve high photovoltaic conversion efficiency. Recently, as an alternative to organic dyes, semiconductor quantum dots (QDs) have been studied for their light-harvesting capability compared with other sensitizers. Accordingly, an attractive configuration to exploit these fascinating properties of semiconductor QDs is the quantum-dot-sensitized solar cell (QDSC) due to their high photoactivity, process realization, and low cost of production. The morphology of TiO2 electrodes included with surface orientation is important for satisfactory assembly of QDSCs in order to improve the efficiency. Breakthroughs allowing an increase in efficiency will advance on two areas of electrode morphology control, namely, (A) TiO2 nanotube electrodes and (B) inverse opal TiO2 electrodes.

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

    NASA Astrophysics Data System (ADS)

    Xu, Hu; Hou, Yumei; Zhang, Hua

    2017-06-01

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

  14. Covalent coupling of organophosphorus hydrolase loaded quantum dots to carbon nanotube/Au nanocomposite for enhanced detection of methyl parathion.

    PubMed

    Du, Dan; Chen, Wenjuan; Zhang, Weiying; Liu, Deli; Li, Haibing; Lin, Yuehe

    2010-02-15

    An amperometric biosensor for highly selective and sensitive determination of methyl parathion (MP) was developed based on dual-signal amplification: (1) a large amount of introduced enzyme on the electrode surface and (2) synergistic effects of nanoparticles towards enzymatic catalysis. The fabrication process includes (1) electrochemical deposition of gold nanoparticles by a multi-potential step technique at multiwalled carbon nanotube (MWCNT) film pre-cast on a glassy carbon electrode and (2) immobilization of methyl parathion degrading enzyme (MPDE) onto a modified electrode through CdTe quantum dots (CdTe QDs) covalent attachment. The introduced MWCNT and gold nanoparticles significantly increased the surface area and exhibited synergistic effects towards enzymatic catalysis. CdTe QDs are further used as carriers to load a large amount of enzyme. As a result of these two important enhancement factors, the proposed biosensor exhibited extremely sensitive, perfectly selective, and rapid response to methyl parathion in the absence of a mediator. The detection limit was 1.0 ng/mL. Moreover, since MPDE hydrolyzes pesticides containing the P-S bond, it showed high selectivity for detecting MP and many interfering compounds, such as carbamate pesticides. Other organophosphorous pesticides and oxygen-containing inorganic ions (SO(4)(2-), NO(3)(-)) did not interfere with the determination. The proposed MPDE biosensor presents good reproducibility and stability, and the MPDE is not poisoned by organophosphate pesticides. Unlike cholinesterase-based biosensor, the MPDE biosensor can be potentially reused and is suitable for continuous monitoring.

  15. Recycling of CdTe photovoltaic waste

    DOEpatents

    Goozner, Robert E.; Long, Mark O.; Drinkard, Jr., William F.

    1999-01-01

    A method for extracting and reclaiming metals from scrap CdTe photovoltaic cells and manufacturing waste by leaching the waste with a leaching solution comprising nitric acid and water, skimming any plastic material from the top of the leaching solution, separating the glass substrate from the liquid leachate and electrolyzing the leachate to separate Cd from Te, wherein the Te is deposits onto a cathode while the Cd remains in solution.

  16. Highly sensitive detection of DNA methylation levels by using a quantum dot-based FRET method

    NASA Astrophysics Data System (ADS)

    Ma, Yunfei; Zhang, Honglian; Liu, Fangming; Wu, Zhenhua; Lu, Shaohua; Jin, Qinghui; Zhao, Jianlong; Zhong, Xinhua; Mao, Hongju

    2015-10-01

    DNA methylation is the most frequently studied epigenetic modification that is strongly involved in genomic stability and cellular plasticity. Aberrant changes in DNA methylation status are ubiquitous in human cancer and the detection of these changes can be informative for cancer diagnosis. Herein, we reported a facile quantum dot-based (QD-based) fluorescence resonance energy transfer (FRET) technique for the detection of DNA methylation. The method relies on methylation-sensitive restriction enzymes for the differential digestion of genomic DNA based on its methylation status. Digested DNA is then subjected to PCR amplification for the incorporation of Alexa Fluor-647 (A647) fluorophores. DNA methylation levels can be detected qualitatively through gel analysis and quantitatively by the signal amplification from QDs to A647 during FRET. Furthermore, the methylation levels of three tumor suppressor genes, PCDHGB6, HOXA9 and RASSF1A, in 20 lung adenocarcinoma and 20 corresponding adjacent nontumorous tissue (NT) samples were measured to verify the feasibility of the QD-based FRET method and a high sensitivity for cancer detection (up to 90%) was achieved. Our QD-based FRET method is a convenient, continuous and high-throughput method, and is expected to be an alternative for detecting DNA methylation as a biomarker for certain human cancers.DNA methylation is the most frequently studied epigenetic modification that is strongly involved in genomic stability and cellular plasticity. Aberrant changes in DNA methylation status are ubiquitous in human cancer and the detection of these changes can be informative for cancer diagnosis. Herein, we reported a facile quantum dot-based (QD-based) fluorescence resonance energy transfer (FRET) technique for the detection of DNA methylation. The method relies on methylation-sensitive restriction enzymes for the differential digestion of genomic DNA based on its methylation status. Digested DNA is then subjected to PCR

  17. Non-toxic silver iodide (AgI) quantum dots sensitized solar cells

    SciTech Connect

    Moosakhani, S.; Sabbagh Alvani, A.A.; Sarabi, A.A.; Sameie, H.; Salimi, R.; Kiani, S.; Ebrahimi, Y.

    2014-12-15

    Highlights: • We have demonstrated AgI sensitized solar cell for the first time. • Obtained mesoporous titania powders possessed small crystallite size, high purity and surface area, and developed mesopores with a narrow pore size distribution. • Photovoltaic measurements revealed the electron injection from AgI to TiO{sub 2}. • The assembled AgI-QD solar cells yielded a power conversion efficiency of 0.64% under one sun illumination. • AgI may be a suitable candidate material for use as a non-toxic sensitizer in QDSSC. - Abstract: The present study reports the performance of a new photosensitizer -AgI quantum dots (QDs)- and mesoporous titania (TiO{sub 2}) nanocrystals synthesized by sol–gel (SG) method for solar cells. Furthermore, the effects of n-heptane on the textural properties of TiO{sub 2} nanocrystals were comprehensively investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N{sub 2} adsorption–desorption measurements, and UV–vis spectroscopy. TiO{sub 2} powders exhibited an anatase-type mesoporous structure with a high surface area of 89.7 m{sup 2}/g. Afterwards, the QDs were grown on mesoporous TiO{sub 2} surface to fabricate a TiO{sub 2}/AgI electrode by a successive ionic layer adsorption and reaction (SILAR) deposition route. Current–voltage characteristics and electrochemical impedance spectroscopy (EIS) data demonstrated that the injection of photoexcited electrons from AgI QDs into the TiO{sub 2} matrix produces photocurrents. The assembled AgI-QD solar cells yielded a power conversion efficiency of 0.64% and a short-circuit current of 2.13 mA/cm{sup 2} under one sun illumination.

  18. FRET-based quantum dot immunoassay for rapid and sensitive detection of Aspergillus amstelodami.

    PubMed

    Kattke, Michele D; Gao, Elizabeth J; Sapsford, Kim E; Stephenson, Larry D; Kumar, Ashok

    2011-01-01

    In this study, a fluorescence resonance energy transfer (FRET)-based quantum dot (QD) immunoassay for detection and identification of Aspergillus amstelodami was developed. Biosensors were formed by conjugating QDs to IgG antibodies and incubating with quencher-labeled analytes; QD energy was transferred to the quencher species through FRET, resulting in diminished fluorescence from the QD donor. During a detection event, quencher-labeled analytes are displaced by higher affinity target analytes, creating a detectable fluorescence signal increase from the QD donor. Conjugation and the resulting antibody:QD ratios were characterized with UV-Vis spectroscopy and QuantiT protein assay. The sensitivity of initial fluorescence experiments was compromised by inherent autofluorescence of mold spores, which produced low signal-to-noise and inconsistent readings. Therefore, excitation wavelength, QD, and quencher were adjusted to provide optimal signal-to-noise over spore background. Affinities of anti-Aspergillus antibody for different mold species were estimated with sandwich immunoassays, which identified A. fumigatus and A. amstelodami for use as quencher-labeled- and target-analytes, respectively. The optimized displacement immunoassay detected A. amstelodami concentrations as low as 10(3) spores/mL in five minutes or less. Additionally, baseline fluorescence was produced in the presence of 10(5) CFU/mL heat-killed E. coli O157:H7, demonstrating high specificity. This sensing modality may be useful for identification and detection of other biological threat agents, pending identification of suitable antibodies. Overall, these FRET-based QD-antibody biosensors represent a significant advancement in detection capabilities, offering sensitive and reliable detection of targets with applications in areas from biological terrorism defense to clinical analysis.

  19. Flow-injection chemiluminescence analysis for sensitive determination of atenolol using cadmium sulfide quantum dots.

    PubMed

    Khataee, Alireza; Lotfi, Roya; Hasanzadeh, Aliyeh; Iranifam, Mortaza; Joo, Sang Woo

    2016-03-15

    A sensitive, rapid and simple flow-injection chemiluminescence (CL) system based on the light emitted from KMnO4-cadmium sulfide quantum dots (CdS QDs) reaction in the presence of cetyltrimethylammonium bromide (CTAB) in acidic medium was developed as a CL probe for the sensitive determination of atenolol. Optical and structural features of CdS QDs capped with l-cysteine, which synthesized via hydrothermal approach, were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and UV-Vis spectroscopy. The CL intensity of KMnO4-CdS QDs-CTAB was remarkably enhanced in the presence of trace level of atenolol. Under optimum experimental conditions, there is a linear relationship between the increase in CL intensity of KMnO4-CdS QDs-CTAB system and atenolol concentration in a range of 0.001 to 4.0 mg L(-1) and 4.0 to 18.0 mg L(-1), with a detection limit (3σ) of 0.0010 mg L(-1). A possible mechanism for KMnO4-CdS QDs-CTAB-atenolol CL reaction is proposed. To prove the practical application of the KMnO4-CdS QDs-CTAB CL method, the method was applied for the determination of atenolol in spiked environmental water samples and commercial pharmaceutical formulation. Furthermore, corona discharge ionization ion mobility spectrometry (CD-IMS) technique was utilized for determination of atenolol. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Quantum-dot-embedded silica nanotubes as nanoprobes for simple and sensitive DNA detection

    NASA Astrophysics Data System (ADS)

    Liu, Yi-Hsin; Tsai, Yi-Yun; Chien, Hsiao-Ju; Chen, Chien-Ying; Huang, Yu-Feng; Chen, Jinn-Shiun; Wu, Yi-Chun; Chen, Chia-Chun

    2011-04-01

    We have developed a new technique using fluorescent silica nanotubes for simple and sensitive DNA detection. The quantum-dot-embedded silica nanotubes (QD-SNTs) were fabricated by a sol-gel reaction using anodic aluminum silica oxide (AAO) as a template. The fluorescent QD-SNTs of different colors were then immobilized with single-stranded DNA and used as nanoprobes for DNA detection. The optical and structural properties of QD-SNT nanoprobes were examined using photoluminescence spectroscopy, confocal microscopy and transmission electron microscopy (TEM). The QD-SNT nanoprobes were applied to detect dye-labeled target DNA in a solution phase. The obvious color change of the QD-SNT nanoprobes was observed visually under a simple microscope after the successful detection with target DNA. The quantitative analyses indicated that ~ 100 attomole of target DNA in one nanoprobe can generate a distinguishable and observable color change. The detection results also demonstrated that our assay exhibited high specificity, high selectivity and very low nonspecific adsorption. Our simple DNA assay based on QD-SNT nanoprobes is expected to be quite useful for the needs of fast DNA screening and detection applications.

  1. Use of titanium dioxide nanoparticles biosynthesized by Bacillus mycoides in quantum dot sensitized solar cells

    PubMed Central

    2014-01-01

    Background One of the major challenges of nanotechnology during the last decade has been the development of new procedures to synthesize nanoparticles. In this context, biosynthetic methods have taken hold since they are simple, safe and eco-friendly. Results In this study, we report the biosynthesis of TiO2 nanoparticles by an environmental isolate of Bacillus mycoides, a poorly described Gram-positive bacterium able to form colonies with novel morphologies. This isolate was able to produce TiO2 nanoparticles at 37°C in the presence of titanyl hydroxide. Biosynthesized nanoparticles have anatase polymorphic structure, spherical morphology, polydisperse size (40–60 nm) and an organic shell as determined by UV–vis spectroscopy, TEM, DLS and FTIR, respectively. Also, conversely to chemically produced nanoparticles, biosynthesized TiO2 do not display phototoxicity. In order to design less expensive and greener solar cells, biosynthesized nanoparticles were evaluated in Quantum Dot Sensitized Solar Cells (QDSSCs) and compared with chemically produced TiO2 nanoparticles. Solar cell parameters such as short circuit current density (ISC) and open circuit voltage (VOC) revealed that biosynthesized TiO2 nanoparticles can mobilize electrons in QDSSCs similarly than chemically produced TiO2. Conclusions Our results indicate that bacterial extracellular production of TiO2 nanoparticles at low temperatures represents a novel alternative for the construction of green solar cells. PMID:25027643

  2. Quantum dots and p-phenylenediamine based method for the sensitive determination of glucose.

    PubMed

    Lv, Xiaoxiao; Wang, Xiaoyu; Huang, Dawei; Niu, Chenggang; Zeng, Guangming; Niu, Qiuya

    2014-11-01

    By introducing p-phenylenediamine (PPD) to the hybrid system of Mn-doped CdS/ZnS quantum dots (QDs) and glucose oxidase (GOD), a sensitive label-free method was proposed for direct detection of glucose. With glucose and PPD as substrates, 2,5-diamino-N,N'-di-(4-aminophenyl)-2,5-cyclohexadiene-1,4-diimine (DDACD) that intensively quenches the fluorescence of QDs can be produced by the catalysis of GOD. A detection limit as low as 3.2 μM was obtained with the high-efficient fluorescence quencher. Two linear ranges, from 5.0 μM to 1000 μM and from 1.0 mM to 10.0 mM, were identified between time-gated fluorescence intensity and the concentration of glucose. It is shown that the newly proposed methods have high selectivity for glucose over other saccharides and coexisting biological species in serum. The method can be used directly to determine glucose in normal adult human serum without any complicated sample pretreatments. The recovery rate and repeatability of the method were also shown to be satisfactory.

  3. Heterodyne Phase-Sensitive Dispersion Spectroscopy in the Mid-Infrared with a Quantum Cascade Laser.

    PubMed

    Martín-Mateos, Pedro; Hayden, Jakob; Acedo, Pablo; Lendl, Bernhard

    2017-06-06

    Molecular dispersion spectroscopy encompasses a group of spectroscopic techniques for gas analysis that retrieve the characteristics of the sample from the measurement of the profile of its refractive index in the vicinity of molecular resonances. This approach, which is in clear contrast to traditional methods based on the detection of absorption, provides inherent immunity to power fluctuations, calibration-free operation, and an output that is linearly dependent on gas concentration. Heterodyne phase-sensitive dispersion spectroscopy (HPSDS) is a very recently proposed technique for molecular dispersion spectroscopy based on tunable lasers that is characterized by a very simple architecture in which data processing and concentration retrieval are straightforward. Different HPSDS implementations have been experimentally validated in the near-IR. Here, we present the first demonstration of HPSDS in the mid-IR using a directly modulated quantum cascade laser for the measurement of CO. The setup is put under test to characterize its response to changing concentrations, pressures, and levels of optical intensity on the detector, and the limit of detection is estimated. Besides this, an experimental comparison with wavelength modulation spectroscopy with second-harmonic detection (2f-WMS) is performed and discussed in detail in order to offer a clear view of the benefits and drawbacks that HPSDS can provide over what we could consider the reference method for gas analysis based on tunable laser spectroscopy.

  4. Wire-shaped quantum dots-sensitized solar cells based on nanosheets and nanowires.

    PubMed

    Chen, Haining; Zhu, Liqun; Wang, Meng; Liu, Huicong; Li, Weiping

    2011-11-25

    Wire-shaped quantum dots-sensitized solar cells (WS-QDSCs) based on nanosheets and nanowires were fabricated and investigated for this paper. The nanosheets grown on stainless steel (SS) wire by electrodeposition were mainly composed of Zn₅(OH)₈Cl₂·H₂O and most of the Zn₅(OH)₈Cl₂·H₂O was converted to ZnO by post-treatment, and ZnO nanowires were directly grown on SS wire by the hydrothermal method. CdS QDs were deposited on nanosheets and nanowires by successive ionic layer adsorption and reaction method. The results of photoelectrochemical performance indicated that WS-QDSCs showed a similar conversion efficiency in polysulfide and Na₂SO₄ electrolytes, while the WS-QDSCs based on the Cu2S counter electrode achieved much higher performance than those based on SS and Cu counter electrodes. By optimizing electrodeposition duration, the WS-QDSCs based on nanosheets presented the highest conversion efficiency of 0.60% for the duration of 20 min. Performance comparison indicated that the WS-QDSC based on nanosheets showed very superior performance to that based on the nanowires with similar film thickness.

  5. Nanocomposite of europium organic framework and quantum dots for highly sensitive chemosensing of trinitrotoluene.

    PubMed

    Kaur, Rajnish; Paul, A K; Deep, Akash

    2014-09-01

    Luminescent metal-organic frameworks (MOFs) are considered as next-generation sensor materials for small molecules and explosives. In the present work, a nanocomposite of luminescent europium organic framework (EuOF) and CdSe quantum dots (QDs) has been first time investigated for photoluminescence (PL) based highly sensitive detection of trinitrotoluene (TNT). The nanocomposite EuOF/QD has been synthesized by initiating the growth of EuOF in the presence of QDs. The successful synthesis of the product has been verified with the help of electron microscopy, X-ray diffraction analysis, and surface area measurements. Compared to EuOF alone, the EuOF/QD nanocomposite offers reproducible and stable measurements. The linear range of PL quenching based detection of TNT with EuOF/QD nanocomposite is 5-1000 ppb with the detection limit of 3 ppb. The detection of TNT with EuOF/QD is selective with respect to some other investigated aromatic compounds, such as phenol, o-cresol, toluene, benzene, nitrobenzene and nitrophenol. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  6. Use of titanium dioxide nanoparticles biosynthesized by Bacillus mycoides in quantum dot sensitized solar cells.

    PubMed

    Ordenes-Aenishanslins, Nicolás Alexis; Saona, Luis Alberto; Durán-Toro, Vicente María; Monrás, Juan Pablo; Bravo, Denisse Margarita; Pérez-Donoso, José Manuel

    2014-07-16

    One of the major challenges of nanotechnology during the last decade has been the development of new procedures to synthesize nanoparticles. In this context, biosynthetic methods have taken hold since they are simple, safe and eco-friendly. In this study, we report the biosynthesis of TiO2 nanoparticles by an environmental isolate of Bacillus mycoides, a poorly described Gram-positive bacterium able to form colonies with novel morphologies. This isolate was able to produce TiO2 nanoparticles at 37 ° C in the presence of titanyl hydroxide. Biosynthesized nanoparticles have anatase polymorphic structure, spherical morphology, polydisperse size (40-60 nm) and an organic shell as determined by UV-vis spectroscopy, TEM, DLS and FTIR, respectively. Also, conversely to chemically produced nanoparticles, biosynthesized TiO2 do not display phototoxicity. In order to design less expensive and greener solar cells, biosynthesized nanoparticles were evaluated in Quantum Dot Sensitized Solar Cells (QDSSCs) and compared with chemically produced TiO2 nanoparticles. Solar cell parameters such as short circuit current density (ISC) and open circuit voltage (VOC) revealed that biosynthesized TiO2 nanoparticles can mobilize electrons in QDSSCs similarly than chemically produced TiO2. Our results indicate that bacterial extracellular production of TiO2 nanoparticles at low temperatures represents a novel alternative for the construction of green solar cells.

  7. Effect of photoanode surface coverage by a sensitizer on the photovoltaic performance of titania based CdS quantum dot sensitized solar cells.

    PubMed

    Prasad, Rajendra M B; Pathan, Habib M

    2016-04-08

    In spite of the promising design and architecture, quantum dot sensitized solar cells (QDSSCs) have a long way to go before they attain the actual projected photoconversion efficiencies. Such an inferior performance displayed by QDSSCs is primarily because of many unwanted recombination losses of charge carriers at various interfaces of the cell. Electron recombination due to back electron transfer at the photoanode/electrolyte interface is an important one that needs to be addressed, to improve the efficiency of these third generation nanostructured solar cells. The present work highlights the importance of conformal coverage of CdS quantum dots (QDs) on the surface of the nanocrystalline titania photoanode in arresting such recombinations, leading to improvement in the performance of the cells. Using the successive ionic layer adsorption and reaction (SILAR) process, photoanodes are subjected to different amounts of CdS QD sensitization by varying the number of cycles of deposition. The sensitized electrodes are characterized using UV-visible spectroscopy, cyclic voltammetry and transmission electron microscopy to evaluate the extent of surface coverage of titania electrodes by QDs. Sandwich solar cells are then fabricated using these electrodes and characterized employing electrochemical impedance spectroscopy and J-V characteristics. It is observed that maximum solar cell efficiency is obtained for photoanodes with conformal coating of QDs and any further deposition of sensitizer leads to QD aggregation and so reduces the performance of the solar cells.

  8. Sensitive fluorimetric assays for α-glucosidase activity and inhibitor screening based on β-cyclodextrin-coated quantum dots.

    PubMed

    Liu, Si-Yao; Wang, Huan; He, Tian; Qi, Liang; Zhang, Zhi-Qi

    2016-02-01

    A fluorescence method was established for a α-glucosidase activity assay and inhibitor screening based on β-cyclodextrin-coated quantum dots. p-Nitrophenol, the hydrolysis product of the α-glucosidase reaction, could quench the fluorescence of β-cyclodextrin-coated quantum dots via an electron transfer process, leading to fluorescence turn-off, whereas the fluorescence of the system turned on in the presence of α-glucosidase inhibitors. Taking advantage of the excellent properties of quantum dots, this method provided a very simple, rapid and sensitive screening method for α-glucosidase inhibitors. Two α-glucosidase inhibitors, 2,4,6-tribromophenol and acarbose, were used to evaluate the feasibility of this screening model, and IC50 values of 24 μM and 0.55 mM were obtained respectively, which were lower than those previously reported. The method may have potential application in screening α-glucosidase inhibitors.

  9. Fast monolayer adsorption and slow energy transfer in CdSe quantum dot sensitized ZnO nanowires.

    PubMed

    Zheng, Kaibo; Žídek, Karel; Abdellah, Mohamed; Torbjörnsson, Magne; Chábera, Pavel; Shao, Shuyan; Zhang, Fengling; Pullerits, Tõnu

    2013-07-25

    A method for CdSe quantum dot (QD) sensitization of ZnO nanowires (NW) with fast adsorption rate is applied. Photoinduced excited state dynamics of the quantum dots in the case of more than monolayer coverage of the nanowires is studied. Transient absorption kinetics reveals an excitation depopulation process of indirectly attached quantum dots with a lifetime of ~4 ns. Photoluminescence and incident photon-to-electron conversion efficiency show that this process consists of both radiative e-h recombination and nonradiative excitation-to-charge conversion. We argue that the latter occurs via interdot energy transfer from the indirectly attached QDs to the dots with direct contact to the nanowires. From the latter, fast electron injection into ZnO occurs. The energy transfer time constant is found to be around 5 ns.

  10. Dipolar Molecular Capping in Quantum Dot-Sensitized Oxides: Fermi Level Pinning Precludes Tuning Donor-Acceptor Energetics.

    PubMed

    Wang, Hai I; Lu, Hao; Nagata, Yuki; Bonn, Mischa; Cánovas, Enrique

    2017-05-23

    Reducing the donor-acceptor excess energy (ΔGET) associated with electron transfer (ET) across quantum dot (QD)/oxide interfaces can boost photoconversion efficiencies in sensitized solar cell and fuel architectures. One proposed path for engineering ΔGET losses at interfaces refers to the tuning of sensitizer workfunction by exploiting QD dipolar molecular capping treatments. However, the change in workfunction per debye in QD solids has been reported to be ∼20-fold larger when compared to the effect achieved in QD-sensitized architectures. The origin behind the modest workfunction tunability in QD-sensitized oxides remains unclear. Here, we investigate the interplay between QD dipolar molecular capping, interfacial QD-oxide ET rates, and QD workfunction in PbS QD/SnO2-sensitized interfaces. We find that interfacial QD-to-oxide ET is invariant to both the nature and strength of the specific QD dipolar capping treatment. Photoelectron spectroscopy reveals that the resolved invariance in ET rates is the result of a lack of QD workfunction (and hence ΔGET) tuning, despite effective molecular dipolar capping. We therefore conclude that Fermi level pinning precludes tuning donor-acceptor energetics by dipolar molecular capping in strongly coupled quantum dot-sensitized oxides.

  11. Sensitivity of quantum yield for O(/sup 1/D) production from ozone photolysis

    SciTech Connect

    Wuebbles, D.J.; Tarp, R.L.

    1980-06-01

    Recent laboratory studies have indicated that the quantum yield for O(/sup 1/D) production from photolysis of ozone may be less than unity at wavelengths shorter than 300 nm (below the fall off region). Previously it had been assumed that the quantum yield was unity at these wavelengths. Based on the recent work of Brock and Watson (who measured the quantum yield at 266 nm), the effect of assuming a quantum yield of 0.9 for O(/sup 1/D) production at wavelengths less than 300 nm in the LLL 1-d model was tested. Since measurements of the quantum yield fall off at longer wavelength also assume unity quantum yield below the fall off region, we also multiplied the O(/sup 1/D) quantum yield through this region by 0.9. The remaining quantum yield from the photolysis reaction is assumed to produce O(/sup 3/P) at all wavelengths so that the total quantum yield is unity.

  12. Influence of Quantum Dot Concentration on Carrier Transport in ZnO:TiO₂ Nano-Hybrid Photoanodes for Quantum Dot-Sensitized Solar Cells.

    PubMed

    Maloney, Francis S; Poudyal, Uma; Chen, Weimin; Wang, Wenyong

    2016-10-25

    Zinc oxide nanowire and titanium dioxide nanoparticle (ZnO:TiO₂ NW/NP) hybrid films were utilized as the photoanode layer in quantum dot-sensitized solar cells (QDSSCs). CdSe quantum dots (QDs) with a ZnS passivation layer were deposited on the ZnO:TiO₂ NW/NP layer as a photosensitizer by successive ion layer adsorption and reaction (SILAR). Cells were fabricated using a solid-state polymer electrolyte and intensity-modulated photovoltage and photocurrent spectroscopy (IMVS/PS) was carried out to study the electron transport properties of the cell. Increasing the SILAR coating number enhanced the total charge collection efficiency of the cell. The electron transport time constant and diffusion length were found to decrease as more QD layers were added.

  13. Influence of Quantum Dot Concentration on Carrier Transport in ZnO:TiO2 Nano-Hybrid Photoanodes for Quantum Dot-Sensitized Solar Cells

    PubMed Central

    Maloney, Francis S.; Poudyal, Uma; Chen, Weimin; Wang, Wenyong

    2016-01-01

    Zinc oxide nanowire and titanium dioxide nanoparticle (ZnO:TiO2 NW/NP) hybrid films were utilized as the photoanode layer in quantum dot-sensitized solar cells (QDSSCs). CdSe quantum dots (QDs) with a ZnS passivation layer were deposited on the ZnO:TiO2 NW/NP layer as a photosensitizer by successive ion layer adsorption and reaction (SILAR). Cells were fabricated using a solid-state polymer electrolyte and intensity-modulated photovoltage and photocurrent spectroscopy (IMVS/PS) was carried out to study the electron transport properties of the cell. Increasing the SILAR coating number enhanced the total charge collection efficiency of the cell. The electron transport time constant and diffusion length were found to decrease as more QD layers were added. PMID:28335319

  14. Resonantly enhanced optical nonlinearity in hybrid semiconductor quantum dot - metal nanoparticle structures

    NASA Astrophysics Data System (ADS)

    Fu, Ming; Wang, Kai; Long, Hua; Yang, Guang; Lu, Peixiang; Hetsch, Frederik; Susha, Andrei S.; Rogach, Andrey L.

    2012-02-01

    The optical nonlinearity of hybrid structures composed of CdTe quantum dots and periodical particle array of gold is studied using Z-scan method. The optical nonlinearity is dramatically affected by the interaction between exciton in CdTe quantum dots and surface plasmons in Au periodical particle array. When the Au surface plasmon is tuned to be in resonance with the exciton transition in CdTe quantum dots, the largest nonlinear refractive index and the smallest two-photon absorption coefficient, n2 = -0.53 cm2/GW and β = 25 cm/GW, which are about 8 times larger and 50 times smaller than that of bare CdTe quantum dots, can be achieved.

  15. Quantum-Noise-Limited Sensitivity Enhancement of a Passive Optical Cavity by a Fast-Light Medium

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Luckay, H. A.; Chang, Hongrok; Myneni, Krishna

    2016-01-01

    We demonstrate for a passive optical cavity containing a dispersive atomic medium, the increase in scale factor near the critical anomalous dispersion is not cancelled by mode broadening or attenuation, resulting in an overall increase in the predicted quantum-noise-limited sensitivity. Enhancements of over two orders of magnitude are measured in the scale factor, which translates to greater than an order-of-magnitude enhancement in the predicted quantum-noise-limited measurement precision, by temperature tuning a low-pressure vapor of non-interacting atoms in a low-finesse cavity close to the critical anomalous dispersion condition. The predicted enhancement in sensitivity is confirmed through Monte-Carlo numerical simulations.

  16. Boronic acid functionalized N-doped carbon quantum dots as fluorescent probe for selective and sensitive glucose determination

    NASA Astrophysics Data System (ADS)

    Jiang, Guohua; Jiang, Tengteng; Li, Xia; Wei, Zheng; Du, Xiangxiang; Wang, Xiaohong

    2014-04-01

    Nitrogen doped carbon quantum dots (NCQDs) of about 10 nm in diameter have been obtained by hydrothermal reaction from collagen. Because of the superiority of water dispersion, low toxicity and ease of functionlization, the NCQDs were designed as a glucose sensor after covalent grafting by 3-aminophenylboronic (APBA) (APBA-NCQDs). The as-prepared APBA-NCQDs were imparted with glucose sensitivity and selectivity from other saccharides via fluorescence (FL) quenching effect at physiological pH and at room temperature, which show high sensitivity and specificity for glucose determination with a wide range from 1 mM to 14 mM. FL quenching mechanism of APBA-NCQDs was also investigated by adding an external quencher. The APBA-NCQDs-based platform is an environmentally friendly way to substitute inorganic quantum dots containing heavy metals which offer a facile and low cost detection method.

  17. High sensitivity detection of NO2 employing cavity ringdown spectroscopy and an external cavity continuously tunable quantum cascade laser.

    PubMed

    Rao, Gottipaty N; Karpf, Andreas

    2010-09-10

    A trace gas sensor for the detection of nitrogen dioxide based on cavity ringdown spectroscopy (CRDS) and a continuous wave external cavity tunable quantum cascade laser operating at room temperature has been designed, and its features and performance characteristics are reported. By measuring the ringdown times of the cavity at different concentrations of NO(2), we report a sensitivity of 1.2 ppb for the detection of NO(2) in Zero Air.

  18. Graphene Quantum Dot-Sensitized ZnO Nanorod/Polymer Schottky Junction UV Detector with Superior External Quantum Efficiency, Detectivity, and Responsivity.

    PubMed

    Dhar, Saurab; Majumder, Tanmoy; Mondal, Suvra Prakash

    2016-11-23

    Graphene quantum dot (GQD)-sensitized ZnO nanorods/poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) Schottky junction has been fabricated for visible-blind ultraviolet (UV) photodetector applications. Schottky diode parameters such as ideality factor, effective work function, and series resistance have been studied for GQD-modified and pristine ZnO nanorod-based devices. Under illumination of broadband light of intensity 80 mW/cm(2), GQD-sensitized samples showed 11 times higher photocurrent value compared to pristine ZnO at -0.75 V external bias. GQD-modified detector demonstrated maximum photocurrent at UV region (wavelength ∼340 nm) for all reverse bias voltages. ZnO nanorods/polymer Schottky junction UV detectors revealed high external quantum efficiency (EQE) more than 100%. Interestingly, GQD sensitized nanorod-based device demonstrated high EQE value of 13,161% at -1 V bias (wavelength ∼340 nm), which is eight times higher than pristine ZnO NR-based detector. GQD-modified detectors also showed superior responsivity (36 A/W), detectivity (1.3 × 10(12) Hz(1/2)/W) at -1 V bias under incident of light of wavelength 340 nm. Even at very low intensity of UV light (0.07 mW/cm(2)), GQD-modified UV detectors showed high photocurrent (∼7.0 mA/cm(2)).

  19. Enhanced Internal Quantum Efficiency in Dye-Sensitized Solar Cells: Effect of Long-Lived Charge-Separated State of Sensitizers.

    PubMed

    Sun, Haiya; Liu, Dongzhi; Wang, Tianyang; Lu, Ting; Li, Wei; Ren, Siyao; Hu, Wenping; Wang, Lichang; Zhou, Xueqin

    2017-03-22

    Effective charge separation is one of the key determinants for the photovoltaic performance of the dye-sensitized solar cells (DSSCs). Herein, two charge-separated (CS) sensitizers, MTPA-Pyc and YD-Pyc, have been synthesized and applied in DSSCs to investigate the effect of the CS states of the sensitizers on the device's efficiency. The CS states with lifetimes of 64 and 177 ns for MTPA-Pyc and YD-Pyc, respectively, are formed via the photoinduced electron transfer (PET) from the 4-styryltriphenylamine (MTPA) or 4-styrylindoline (YD) donor to the pyrimidine cyanoacrylic acid (Pyc) acceptor. DSSCs based on MTPA-Pyc and YD-Pyc exhibit high internal quantum efficiency (IQE) values of over 80% from 400 to 600 nm. In comparison, the IQEs of the charge transfer (CT) sensitizer cells are 10-30% lower in the same wavelength range. The enhanced IQE values in the devices based on the CS sensitizers are ascribed to the higher electron injection efficiencies and slower charge recombination. The results demonstrate that taking advantage of the CS states in the sensitizers can be a promising strategy to improve the IQEs and further enhance the overall efficiencies of the DSSCs.

  20. Towards Visible Light Hydrogen Generation: Quantum Dot-Sensitization via Efficient Light Harvesting of Hybrid-TiO2

    PubMed Central

    Kim, Kwanghyun; Kim, Myeong-Jong; Kim, Sun-I; Jang, Ji-Hyun

    2013-01-01

    We report pronounced enhancement of photoelectrochemical hydrogen generation of a quantum dot-sensitized hybrid-TiO2 (QD/H-TiO2) electrode that is composed of a mesoporous TiO2 layer sandwiched by a double sided energy harvesting layer consisting of a surface-textured TiO2 inverse opals layer on the bottom and a patterned mesoporous TiO2 layer on the top. CdSe/H-TiO2 exhibits a maximum photocurrent density of ~16.2 mA/cm2, which is 35% higher than that of the optimized control sample (CdSe/P25), achieved by matching of the bandgap of quantum dot-sensitization with the wavelength where light harvesting of H-TiO2 is observed. Furthermore, CdSe/H-TiO2 under filtered exposure conditions recorded current density of ~14.2 mA/cm2, the greatest value in the visible range. The excellent performance of the quantum dot-sensitized H-TiO2 suggests that alteration of the photoelectrodes to suitable nanostructures with excellent light absorption may offer optimal strategies for attaining maximum efficiency in a variety of photoconversion systems. PMID:24270426

  1. Towards Visible Light Hydrogen Generation: Quantum Dot-Sensitization via Efficient Light Harvesting of Hybrid-TiO2

    NASA Astrophysics Data System (ADS)

    Kim, Kwanghyun; Kim, Myeong-Jong; Kim, Sun-I.; Jang, Ji-Hyun

    2013-11-01

    We report pronounced enhancement of photoelectrochemical hydrogen generation of a quantum dot-sensitized hybrid-TiO2 (QD/H-TiO2) electrode that is composed of a mesoporous TiO2 layer sandwiched by a double sided energy harvesting layer consisting of a surface-textured TiO2 inverse opals layer on the bottom and a patterned mesoporous TiO2 layer on the top. CdSe/H-TiO2 exhibits a maximum photocurrent density of ~16.2 mA/cm2, which is 35% higher than that of the optimized control sample (CdSe/P25), achieved by matching of the bandgap of quantum dot-sensitization with the wavelength where light harvesting of H-TiO2 is observed. Furthermore, CdSe/H-TiO2 under filtered exposure conditions recorded current density of ~14.2 mA/cm2, the greatest value in the visible range. The excellent performance of the quantum dot-sensitized H-TiO2 suggests that alteration of the photoelectrodes to suitable nanostructures with excellent light absorption may offer optimal strategies for attaining maximum efficiency in a variety of photoconversion systems.

  2. Quantum-Noise-Limited Sensitivity-Enhancement of a Passive Optical Cavity by a Fast-Light Medium

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Luckay, H. A.; Chang, Hongrok; Myneni, Krishna

    2016-01-01

    We demonstrate for a passive optical cavity containing an intracavity dispersive atomic medium, the increase in scale factor near the critical anomalous dispersion is not cancelled by mode broadening or attenuation, resulting in an overall increase in the predicted quantum-noiselimited sensitivity. Enhancements of over two orders of magnitude are measured in the scale factor, which translates to greater than an order-of-magnitude enhancement in the predicted quantumnoise- limited measurement precision, by temperature tuning a low-pressure vapor of noninteracting atoms in a low-finesse cavity close to the critical anomalous dispersion condition. The predicted enhancement in sensitivity is confirmed through Monte-Carlo numerical simulations.

  3. Hollow fiber based quantum cascade laser spectrometer for fast and sensitive drug identification

    NASA Astrophysics Data System (ADS)

    Herbst, J.; Scherer, B.; Ruf, A.; Erb, J.; Lambrecht, A.

    2012-01-01

    Sensitive and fast identification of drugs or drug precursors is important and necessary in scenarios like baggage or container check by customs or police. Fraunhofer IPM is developing a laser spectrometer using external cavity quantum cascade lasers (EC-QCL) to obtain mid-infrared (IR) absorption spectra in the wavelength range of the specific vibrational bands of amphetamines and their precursors. The commercial EC-QCL covers a tuning range of about 225 cm-1 within 1.4 s. The system could be used for different sample types like bulk samples or liquid solutions. A sampling unit evaporates the sample. Because of small sample amounts a 3 m long hollow fiber with an inner volume smaller than 1ml is used as gas cell and wave guide for the laser beam. This setup is suitable as a detector of a gas chromatograph instead of a standard detector (TCD or FID). The advantage is the selective identification of drugs by their IR spectra in addition to the retention time in the gas chromatographic column. In comparison to Fourier Transform IR systems the EC-QCL setup shows a good mechanical robustness and has the advantage of a point light source. Because of the good fiber incoupling performance of the EC-QCL it is possible to use hollow fibers. So, a good absorption signal is achieved because of the long optical path in the small cell volume without significant dilution. In first laboratory experiments a detection limit in the microgram range for pseudo ephedrine is achieved.

  4. Influence of annealing on composition and optical properties of CdTe nanoparticle layer-by-layer films.

    PubMed

    Briscoe, Joe; Gallardo, Diego E; Lesnyak, Vladimir; Dunn, Steve

    2011-06-01

    CdTe nanoparticle-polymer composite films were deposited conformally using a layer-by-layer (LbL) process onto planar or ZnO nanorod-coated substrates. Films were annealed between 150-450 degrees C. Under air this led to oxidation of the nanoparticles while under vacuum their composition was retained. Annealing at 450 degrees C led to complete removal of the polymer with a loss of quantum confinement as shown by UV-vis spectroscopy. Annealing at 350 degrees C gave partial removal of the polymer and retained quantum confinement. Such annealed nanoparticle composite systems may have application in photovoltaics.

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

  6. Wearable and sensitive heart-rate detectors based on PbS quantum dot and multiwalled carbon nanotube blend film

    NASA Astrophysics Data System (ADS)

    Gao, Liang; Dong, Dongdong; He, Jungang; Qiao, Keke; Cao, Furong; Li, Min; Liu, Huan; Cheng, Yibing; Tang, Jiang; Song, Haisheng

    2014-10-01

    Wearable and sensitive photodetectors (PDs) have been demonstrated based on a blend film of PbS quantum dots (QDs) and QDs modified multiwalled carbon nanotubes (MWCNTs). Owing to the synergetic effect from high light sensitivity of PbS QDs and excellent conductive and mechanical properties of MWCNTs, the blend PDs show high sensitivity and flexibility performance: device responsivity and detectivity reach 583 mA/W and 3.25 × 1012 Jones, respectively, and could stand large number (at least 10 000 cycles) and wide angle (up to 80°) bending. Furthermore, the wearable and sensitive PDs have been applied to measure the heart rate in both red and near infrared (NIR) ranges. The presented PDs are expected to work as sensor candidates in integrated electronic skin.

  7. Wearable and sensitive heart-rate detectors based on PbS quantum dot and multiwalled carbon nanotube blend film

    SciTech Connect

    Gao, Liang; Dong, Dongdong; Qiao, Keke; Cheng, Yibing; Tang, Jiang E-mail: songhs-wnlo@mail.hust.edu.cn; Song, Haisheng E-mail: songhs-wnlo@mail.hust.edu.cn; He, Jungang; Li, Min; Liu, Huan; Cao, Furong

    2014-10-13

    Wearable and sensitive photodetectors (PDs) have been demonstrated based on a blend film of PbS quantum dots (QDs) and QDs modified multiwalled carbon nanotubes (MWCNTs). Owing to the synergetic effect from high light sensitivity of PbS QDs and excellent conductive and mechanical properties of MWCNTs, the blend PDs show high sensitivity and flexibility performance: device responsivity and detectivity reach 583 mA/W and 3.25 × 10{sup 12 }Jones, respectively, and could stand large number (at least 10 000 cycles) and wide angle (up to 80°) bending. Furthermore, the wearable and sensitive PDs have been applied to measure the heart rate in both red and near infrared (NIR) ranges. The presented PDs are expected to work as sensor candidates in integrated electronic skin.

  8. Achieving effective terminal exciton delivery in quantum dot antenna-sensitized multistep DNA photonic wires.

    PubMed

    Spillmann, Christopher M; Ancona, Mario G; Buckhout-White, Susan; Algar, W Russ; Stewart, Michael H; Susumu, Kimihiro; Huston, Alan L; Goldman, Ellen R; Medintz, Igor L

    2013-08-27

    Assembling DNA-based photonic wires around semiconductor quantum dots (QDs) creates optically active hybrid architectures that exploit the unique properties of both components. DNA hybridization allows positioning of multiple, carefully arranged fluorophores that can engage in sequential energy transfer steps while the QDs provide a superior energy harvesting antenna capacity that drives a Förster resonance energy transfer (FRET) cascade through the structures. Although the first generation of these composites demonstrated four-sequential energy transfer steps across a distance >150 Å, the exciton transfer efficiency reaching the final, terminal dye was estimated to be only ~0.7% with no concomitant sensitized emission observed. Had the terminal Cy7 dye utilized in that construct provided a sensitized emission, we estimate that this would have equated to an overall end-to-end ET efficiency of ≤ 0.1%. In this report, we demonstrate that overall energy flow through a second generation hybrid architecture can be significantly improved by reengineering four key aspects of the composite structure: (1) making the initial DNA modification chemistry smaller and more facile to implement, (2) optimizing donor-acceptor dye pairings, (3) varying donor-acceptor dye spacing as a function of the Förster distance R0, and (4) increasing the number of DNA wires displayed around each central QD donor. These cumulative changes lead to a 2 orders of magnitude improvement in the exciton transfer efficiency to the final terminal dye in comparison to the first-generation construct. The overall end-to-end efficiency through the optimized, five-fluorophore/four-step cascaded energy transfer system now approaches 10%. The results are analyzed using Förster theory with various sources of randomness accounted for by averaging over ensembles of modeled constructs. Fits to the spectra suggest near-ideal behavior when the photonic wires have two sequential acceptor dyes (Cy3 and Cy3.5) and

  9. Improved performance of silicon nanowire/cadmium telluride quantum dots/organic hybrid solar cells

    NASA Astrophysics Data System (ADS)

    Ge, Zhaoyun; Xu, Ling; Zhang, Renqi; Xue, Zhaoguo; Wang, Hongyu; Xu, Jun; Yu, Yao; Su, Weining; Ma, Zhongyuan; Chen, Kunji

    2015-04-01

    We fabricated silicon nanowire/cadmium telluride quantum dots (CdTe QDs)/organic hybrid solar cells and investigated their structure and electrical properties. Transmission electron microscope revealed that CdTe QDs were uniformly distributed on the surface of the silicon nanowires, which made PEDOT:PSS easily filled the space between SiNWs. The current density-voltage (J-V) characteristics of hybrid solar cells were investigated both in dark and under illumination. The result shows that the performance of the hybrid solar cells with CdTe QDs layer has an obvious improvement. The optimal short-circuit current density (Jsc) of solar cells with CdTe QDs layer can reach 33.5 mA/cm2. Compared with the solar cells without CdTe QDs, Jsc has an increase of 15.1%. Power conversion efficiency of solar cells also increases by 28.8%. The enhanced performance of the hybrid solar cells with CdTe QDs layers are ascribed to down-shifting effect of CdTe QDs and the modification of the silicon nanowires surface with CdTe QDs. The result of our experiments suggests that hybrid solar cells with CdTe QDs modified are promising candidates for solar cell application.

  10. Highly sensitive colorimetric and fluorescent sensor for cyanazine based on the inner filter effect of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Dong, Liang; Hou, Changjun; Yang, Mei; Fa, Huanbao; Wu, Huixiang; Shen, Caihong; Huo, Danqun

    2016-06-01

    Cyanazine residue poses a great threat to human health and its derivatives would remain in soils, natural waters, and other environmental domains for a long time. Herein, a simple, rapid, and ultra-sensitive analytical method for the determination of cyanazine (CZ) based on inner filter effect (IFE) of Au nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs) is first described in this study. With the presence of citrate-stabilized AuNPs, the fluorescence of GSH-capped CdTe QDs was remarkably quenched by AuNPs via IFE. The fluorescence of the AuNP-CdTe QD system was recovered upon addition of CZ. CZ can adsorb on to the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on CdTe QDs was weakened, and the fluorescence intensity of CdTe QDs was recovered accordingly. A good linear correlation for detection of CZ was exhibited from 0.05 to 9 μM, and the detection limit reached 0.1568 μM, which was much lower than the safety limit required by the USA, the UK, and China. In order to probe into the selectivity of AuNPs towards CZ over other pesticides, various frequently used pesticides were mixed with AuNPs. AuNP composite solution shows good selectivity towards CZ among other pesticides. This method was successfully carried out for the assessment of CZ in real samples with satisfactory results, which revealed many advantages such as high sensitivity, low cost, and non-time-consuming compared with traditional methods.

  11. Modeling skin sensitization potential of mechanistically hard-to-be-classified aniline and phenol compounds with quantum mechanistic properties.

    PubMed

    Ouyang, Qin; Wang, Lirong; Mu, Ying; Xie, Xiang-Qun

    2014-12-24

    Advanced structure-activity relationship (SAR) modeling can be used as an alternative tool for identification of skin sensitizers and in improvement of the medical diagnosis and more effective practical measures to reduce the causative chemical exposures. It can also circumvent ethical concern of using animals in toxicological tests, and reduce time and cost. Compounds with aniline or phenol moieties represent two large classes of frequently skin sensitizing chemicals but exhibiting very variable, and difficult to predict, potency. The mechanisms of action are not well-understood. A group of mechanistically hard-to-be-classified aniline and phenol chemicals were collected. An in silico model was established by statistical analysis of quantum descriptors for the determination of the relationship between their chemical structures and skin sensitization potential. The sensitization mechanisms were investigated based on the features of the established model. Then the model was utilized to analyze a subset of FDA approved drugs containing aniline and/or phenol groups for prediction of their skin sensitization potential. A linear discriminant model using the energy of the highest occupied molecular orbital (ϵHOMO) as the descriptor yielded high prediction accuracy. The contribution of ϵHOMO as a major determinant may suggest that autoxidation or free radical binding could be involved. The model was further applied to predict allergic potential of a subset of FDA approved drugs containing aniline and/or phenol moiety. The predictions imply that similar mechanisms (autoxidation or free radical binding) may also play a role in the skin sensitization caused by these drugs. An accurate and simple quantum mechanistic model has been developed to predict the skin sensitization potential of mechanistically hard-to-be-classified aniline and phenol chemicals. The model could be useful for the skin sensitization potential predictions of a subset of FDA approved drugs.

  12. Enhanced electrogenerated chemiluminescence of tris(2,2'-bipyridyl)ruthenium(II) system by l-cysteine-capped CdTe quantum dots and its application for the determination of nitrofuran antibiotics.

    PubMed

    Taokaenchan, Narin; Tangkuaram, Tanin; Pookmanee, Pusit; Phaisansuthichol, Sirirat; Kuimalee, Surasak; Satienperakul, Sakchai

    2015-04-15

    This paper reports a new approach to enhance the electrogenerated chemiluminescence (ECL) of the tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3(2+)) system using resonance energy transfer with l-cysteine-capped cadmium telluride quantum dots (CdTe-QDs) in aqueous solution. The oxidative peak signal of Ru(bpy)3(2+) occurred at a voltage of 1.10V when the potential was cycled between 0.4 and 1.6V using cyclic voltammetry with a carbon screen-printed electrode (SPE) in a 0.11M phosphate buffer at pH 7.50. The l-cysteine-capped CdTe-QDs were synthesized and added into the solution of Ru(bpy)3(2+) to magnify the ECL signal. The ECL emission signal was investigated and the extreme enhancement of the ECL intensity was achieved due to the energy transfer by the l-cysteine-capped CdTe-QDs. It was found that the induced ECL from the Ru(bpy)3(2+) CdTe-QDs system was inhibited by the presence of selected nitrofurans. This quenching effect of nitrofuran antibiotics on the anodic ECL of Ru(bpy)3(2+) CdTe-QDs was found to be selective and concentration dependent and was observed to have a linear relationship over the concentration range 10-100×10(-6)M. The detection limits were found to be 0.40, 0.73 and 0.60µM for furaltadone (FTD), furazolidone (FZD) and nitrofurantoin (NFT). In addition, the proposed ECL method was successfully applied to detect the total residuals of selected nitrofuran residues in animal feed samples with satisfactory results. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Evaluation of XRI-UNO CdTe detector for nuclear medical imaging

    NASA Astrophysics Data System (ADS)

    Jambi, L. K.; Lees, J. E.; Bugby, S. L.; Tipper, S.; Alqahtani, M. S.; Perkins, A. C.

    2015-06-01

    Over the last two decades advances in semiconductor detector technology have reached the point where they are sufficiently sensitive to become an alternative to scintillators for high energy gamma ray detection for application in fields such as medical imaging. This paper assessed the Cadmium-Telluride (CdTe) XRI-UNO semiconductor detector produced by X-RAY Imatek for photon energies of interest in nuclear imaging. The XRI-UNO detector was found to have an intrinsic spatial resolution of <0.5mm and a high incident count rate capability up to at least 1680cps. The system spatial resolution, uniformity and sensitivity characteristics are also reported.

  14. Reaction analysis on Yb(3+) and DNA based on quantum dots: The design of a fluorescent reversible off-on mode.

    PubMed

    Wang, Linlin; Song, Jing; Liu, Shaopu; Hao, Chenxia; Kuang, Nianxi; He, Youqiu

    2015-11-01

    Even though various strategies have reported for DNA detection, development of a simple, time-saving and specific fluorescent sensing platform still remains a desired goal. In this work, a quantum dots (QDs) based fluorescent reversible "off-on" mode was developed for sensitively recognition of herring sperm DNA (hsDNA). Firstly, in the "turn off" stage, the fluorescence of glutathione (GSH) capped CdTe QDs could be effectively quenched by ytterbium ion (Yb(3+)) was due to the occurrence of the electron transfer between Yb(3+) and the photoexcited QDs. And then, in the following "turn on" stage, with the effective binding reaction of Yb(3+) to hsDNA, the fluorescence intensity of GSH-capped CdTe QDs enhanced. Under the optimal conditions, the linear range of fluorescence versus the concentration of hsDNA was 0.010-12 μg/mL, and the detection limit was 3.033 ng/mL. In addition, the reaction mechanism among GSH-capped CdTe QDs, Yb(3+) and hsDNA were investigated by fluorescence spectroscopy, UV-vis spectrophotometry, fluorescence lifetime measurement and viscosity measurements. This analytical fluorescent reversible "off-on" pattern offered a way with good sensitivity and selectivity for the detection of hsDNA.

  15. Quantum-dot-sensitized solar cells: Assembly of CdS-quantum-dots coupling techniques of self-assembled monolayer and chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Lin, Sheng-Chih; Lee, Yuh-Lang; Chang, Chi-Hsiu; Shen, Yu-Jen; Yang, Yu-Min

    2007-04-01

    Two methods, coupling self-assembled monolayer and chemical bath deposition (CBD), were utilized to assemble cadmium sulfide (CdS) quantum dots (QDs) onto mesoporous TiO2 films for dye-sensitized solar cell (DSSC) applications. Colloidal CdS QDs were first self-assembled on the TiO2 surface. CBD was then introduced to replenish the incorporated amount and increase the coverage ratio of CdS QDs on the TiO2 surface. The preassembled CdS QDs act as nucleation sites in the CBD process, forming a CdS nanofilm with an interfacial structure capable of inhibiting the recombination of injected electrons. An efficiency as high as 1.35% for the QD-sensitized DSSC was achieved using the present strategy.

  16. Recycling of CdTe photovoltaic waste

    DOEpatents

    Goozner, Robert E.; Long, Mark O.; Drinkard, Jr., William F.

    1999-04-27

    A method for extracting and reclaiming metals from scrap CdTe photovoltaic cells and manufacturing waste by leaching the metals in dilute nitric acid, leaching the waste with a leaching solution comprising nitric acid and water, skimming any plastic material from the top of the leaching solution, separating the glass substrate from the liquid leachate, adding a calcium containing base to the leachate to precipitate Cd and Te, separating the precipitated Cd and Te from the leachate, and recovering the calcium-containing base.

  17. Recycling of CdTe photovoltaic waste

    DOEpatents

    Goozner, R.E.; Long, M.O.; Drinkard, W.F. Jr.

    1999-04-27

    A method for extracting and reclaiming metals from scrap CdTe photovoltaic cells and manufacturing waste by leaching the metals in dilute nitric acid, leaching the waste with a leaching solution comprising nitric acid and water, skimming any plastic material from the top of the leaching solution, separating the glass substrate from the liquid leachate, adding a calcium containing base to the leachate to precipitate Cd and Te, separating the precipitated Cd and Te from the leachate, and recovering the calcium-containing base. 3 figs.

  18. Synthesis and Characterizations of Pb-modified CdSe Aqueous Quantum Dots and Their Applications in Quantum Dot-Sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Lu, Cheng-Hsin

    Quantum Dots (QDs) are semiconductor nanocrystals with typical size ranges around 1-20 nm. They exhibit distinctive size-dependent photoluminescence (PL) properties due to the quantum confinement effect. QDs have great potentials in display, lighting, lasing, bioimaging, fluorescent label, sensor, photodetector, and photovoltaic applications, and have been widely studied in the past decades. Cadmium selenide (CdSe) QDs have been synthesized using an environmentally friendly, aqueous method under low temperature. While traditional QDs synthesized by hot injection method using organic solvent generally exhibit edge-state emission with narrow peaks, aqueous quantum dots (AQDs) tend to have trap-state emissions with broad peaks. The objective of this thesis is to investigate how Pb modifications in CdSe AQDs synthesis can affect the optoelectronic properties of the QDs and how these modifications affect their corresponding photovoltaic performance in quantum dot-sensitized solar cell (QDSSC) applications. Lead (Pb) precursor has been introduced either during the synthesis or after the synthesis of CdSe AQDs forming either Pb-doped or Pb-coated CdSe QDs, respectively. Pb-doped CdSe QDs exhibit red-shift in both absorption and emission spectra while Pb-coated CdSe QDs exhibit blue-shift in both absorption and emission spectra along with the generation of more surface defects. Although blue-shifted absorption indicating a narrower absorption range and the surface defects providing undesired recombination pathways are detrimental to solar cell performance, however surprisingly, we found that QDSSCs made from Pb-coated CdSe QDs actually had better solar cell performance than that made from Pb-doped CdSe QDs. We attributed this finding to a protection/passivation layer formed in-situ when the coated Pb react with the iodide/triiodide electrolyte during solar cell operation resulting in QDSSCs with better charge injection and stability.

  19. Broadband Ce(III)-Sensitized Quantum Cutting in Core-Shell Nanoparticles: Mechanistic Investigation and Photovoltaic Application.

    PubMed

    Sun, Tianying; Chen, Xian; Jin, Limin; Li, Ho-Wa; Chen, Bing; Fan, Bo; Moine, Bernard; Qiao, Xvsheng; Fan, Xianping; Tsang, Sai-Wing; Yu, Siu Fung; Wang, Feng

    2017-10-05

    Quantum cutting in lanthanide-doped luminescent materials is promising for applications such as solar cells, mercury-free lamps, and plasma panel displays because of the ability to emit multiple photons for each absorbed higher-energy photon. Herein, a broadband Ce(3+)-sensitized quantum cutting process in Nd(3+) ions is reported though gadolinium sublattice-mediated energy migration in a NaGdF4:Ce@NaGdF4:Nd@NaYF4 nanostructure. The Nd(3+) ions show downconversion of one ultraviolet photon through two successive energy transitions, resulting in one visible photon and one near-infrared (NIR) photon. A class of NaGdF4:Ce@NaGdF4:Nd/Yb@NaYF4 nanoparticles is further developed to expand the spectrum of quantum cutting in the NIR. When the quantum cutting nanoparticles are incorporated into a hybrid crystalline silicon (c-Si) solar cell, a 1.2-fold increase in short-circuit current and a 1.4-fold increase in power conversion efficiency is demonstrated under short-wavelength ultraviolet irradiation. These insights should enhance our ability to control and utilize spectral downconversion with lanthanide ions.

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

    SciTech Connect

    Wang, Xiuling; Gu, Yinjun; Dong, Shuling; Zhao, Qin; Liu, Yongjian

    2015-10-15

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