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Quantum dot

Zhihua Xie, Yannick Lefier, Miguel Angel Suarez, Mathieu Mivelle, Roland Salut, Jean-Marc Merolla, Thierry Grosjean
Colloidal quantum dots (CQDs) have drawn strong interest in the past for their high prospects in scientific, medical, and industrial applications. However, the full characterization of these quantum emitters is currently restricted to the visible wavelengths, and it remains a key challenge to optically probe single CQDs operating in the infrared spectral domain, which is targeted by a growing number of applications. Here, we report the first experimental detection and imaging at room temperature of single infrared CQDs operating at telecommunication wavelengths...
March 24, 2017: Nano Letters
F Pelayo García de Arquer, Xiwen Gong, Randy P Sabatini, Min Liu, Gi-Hwan Kim, Brandon R Sutherland, Oleksandr Voznyy, Jixian Xu, Yuangjie Pang, Sjoerd Hoogland, David Sinton, Edward Sargent
Quantum dot and well architectures are attractive for infrared optoelectronics, and have led to the realization of compelling light sensors. However, they require well-defined passivated interfaces and rapid charge transport, and this has restricted their efficient implementation to costly vacuum-epitaxially grown semiconductors. Here we report solution-processed, sensitive infrared field-emission photodetectors. Using quantum-dots-in-perovskite, we demonstrate the extraction of photocarriers via field emission, followed by the recirculation of photogenerated carriers...
March 24, 2017: Nature Communications
Ding Jiang, Xiaojiao Du, Lei Zhou, Henan Li, Kun Wang
Deeply understanding the internal mechanism of photoelectrohemical (PEC) process is conducive to fabricate high-performances PEC biosensors. In this work, we proposed a new insight towards efficient charge separation mechanism in high-performances PEC biosensors. Specifically, we disclosed that the lifetimes of photogenerated charge carriers of ultrathin MoS2 nanosheets could be prolonged by approximately millisecond timescales after a proper mole ratio of NGQDs were coupled, leading to the promoted charge separation, and giant photocurrent signal-magnify...
March 24, 2017: Analytical Chemistry
Saradh Prasad, Hanan Saleh AlHesseny, Mohamad S AlSalhi, Durairaj Devaraj, Vadivel Masilamai
Tunable lasers are essential for medical, engineering and basic science research studies. Most conventional solid-state lasers are capable of producing a few million laser shots, but limited to specific wavelengths, which are bulky and very expensive. Dye lasers are continuously tunable, but exhibit very poor chemical stability. As new tunable, efficient lasers are always in demand, one such laser is designed with various sized CdSe/ZnS quantum dots. They were used as a colloid in tetrahydrofuran to produce a fluorescent broadband emission from 520 nm to 630 nm...
January 30, 2017: Nanomaterials
Li Liu, Yao Fan, Haiyan Fu, Feng Chen, Chuang Ni, Jinxing Wang, Qiaobo Yin, Qingling Mu, Tianming Yang, Yuanbin She
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...
April 22, 2017: Analytica Chimica Acta
Melinda Varga
With the aim of constructing an S-layer fusion protein that combines both excellent self-assembly and specific ligand i.e., biotin binding ability, streptavidin (aa 16-133) was fused to the S-layer protein of Sporosarcina ureae ATCC 13881 (SslA) devoid of its N-terminal 341 and C-terminal 172 amino acids. The genetically engineered chimeric protein could be successfully produced in E. coli, isolated, and purified via Ni affinity chromatography. In vitro recrystallisation experiments performed with the purified chimeric protein in solution and on a silicon wafer have demonstrated that fusion of the streptavidin domain does not interfere with the self-assembling properties of the S-layer part...
November 4, 2016: Nanomaterials
Noor-Ul-Ain, Martin O Eriksson, Susann Schmidt, M Asghar, Pin-Cheng Lin, Per Olof Holtz, Mikael Syväjärvi, G Reza Yazdi
Tuning the emission energy of graphene quantum dots (GQDs) and understanding the reason of tunability is essential for the GOD function in optoelectronic devices. Besides material-based challenges, the way to realize chemical doping and band gap tuning also pose a serious challenge. In this study, we tuned the emission energy of GQDs by substitutional doping using chlorine, nitrogen, boron, sodium, and potassium dopants in solution form. Photoluminescence data obtained from (Cl- and N-doped) GQDs and (B-, Na-, and K-doped) GQDs, respectively exhibited red- and blue-shift with respect to the photoluminescence of the undoped GQDs...
November 3, 2016: Nanomaterials
Francis S Maloney, Uma Poudyal, Weimin Chen, Wenyong Wang
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...
October 25, 2016: Nanomaterials
Qinwen Wang, Aimin Tang, Yuan Liu, Zhiqiang Fang, Shiyu Fu
The preparation of fluorescent nanocomposite materials with tunable emission wavelengths by combining cellulose nanofibrils (CNFs) with inorganic nanoparticles is important for promoting CNFs applications. A CNF/CdS nanocomposite was prepared via in situ compositing at room temperature on oxidized CNFs with CdS quantum dots. By controlling the -COOH/Cd(2+) ratio on the CNF, the feeding time of Na₂S and the ultrasonic maturing time, the size of the CdS quantum dots on the CNF surface could be adjusted so that to obtain the CNF/CdS nanocomposite material with different fluorescent colors...
September 7, 2016: Nanomaterials
Sofia Paulo, Emilio Palomares, Eugenia Martinez-Ferrero
Graphene and carbon quantum dots have extraordinary optical and electrical features because of their quantum confinement properties. This makes them attractive materials for applications in photovoltaic devices (PV). Their versatility has led to their being used as light harvesting materials or selective contacts, either for holes or electrons, in silicon quantum dot, polymer or dye-sensitized solar cells. In this review, we summarize the most common uses of both types of semiconducting materials and highlight the significant advances made in recent years due to the influence that synthetic materials have on final performance...
August 25, 2016: Nanomaterials
Guanying Chen, Zhijun Ning, Hans Ågren
We are glad to announce the Special Issue "Nanostructured Solar Cells", published in Nanomaterials. This issue consists of eight articles, two communications, and one review paper, covering major important aspects of nanostructured solar cells of varying types. From fundamental physicochemical investigations to technological advances, and from single junction solar cells (silicon solar cell, dye sensitized solar cell, quantum dots sensitized solar cell, and small molecule organic solar cell) to tandem multi-junction solar cells, all aspects are included and discussed in this issue to advance the use of nanotechnology to improve the performance of solar cells with reduced fabrication costs...
August 9, 2016: Nanomaterials
Chunze Yuan, Lin Li, Jing Huang, Zhijun Ning, Licheng Sun, Hans Ågren
Ternary alloy PbxCd1-xS quantum dots (QDs) were explored as photosensitizers for quantum-dot-sensitized solar cells (QDSCs). Alloy PbxCd1-xS QDs (Pb0.54Cd0.46S, Pb0.31Cd0.69S, and Pb0.24Cd0.76S) were found to substantially improve the photocurrent of the solar cells compared to the single CdS or PbS QDs. Moreover, it was found that the photocurrent increases and the photovoltage decreases when the ratio of Pb in PbxCd1-xS is increased. Without surface protecting layer deposition, the highest short-circuit current density reaches 20 mA/cm² under simulated AM 1...
May 25, 2016: Nanomaterials
Jiupeng Cao, Yifan Zhao, Yatong Zhu, Xiaoyu Yang, Peng Shi, Hongdi Xiao, Na Du, Wanguo Hou, Genggeng Qi, Jianqiang Liu
The present study reports a new type of quantum dot sensitized solar cells (QDSSCs) using the zinc tin mixed metal oxides (MMO) as the anode materials, which were obtained from the layered double hydroxide (LDH) precursor. The successive ionic layer adsorption and reaction (SILAR) method is applied to deposit CdS quantum dots. The effects of sensitizing cycles on the performance of CdS QDSSC are studied. Scanning electron microscopy (SEM), Transmission electron microscope (TEM) and X-ray diffraction (XRD) are used to identify the surface profile and crystal structure of the mixed metal oxides anode...
March 16, 2017: Journal of Colloid and Interface Science
Helena Montón, Mariana Medina-Sánchez, Joan Antoni Soler, Andrzej Chałupniak, Carme Nogués, Arben Merkoçi
Despite all the efforts made over years to study the cancer expression and the metastasis event, there is not a clear understanding of its origins and effective treatment. Therefore, more specialized and rapid techniques are required for studying cell behaviour under different drug-based treatments. Here we present a quantum dot signalling-based cell assay carried out in a segmental microfluidic device that allows studying the effect of anti-cancer drugs in cultured cell lines by monitoring phosphatidylserine translocation that occurs in early apoptosis...
March 18, 2017: Biosensors & Bioelectronics
Nikhil R Jana, Chumki Dalal
Although trans-activating transcription (TAT)-peptide functionalized nanoparticle/polymer/liposome is widely used for cellular transfection applications, the multivalency (number of attached peptide per particle) effect on cell uptake mechanism and subcellular targeting performance is largely unexplored. Here we show that multivalency of nanoparticle controls the cellular interaction, cellular entry/exit mechanism and subcellular targeting performance. We have synthesized TAT peptide functionalized quantum dot (QD) of 30-35 nm hydrodynamic diameter with varied multivalency from 10 to 75 (e...
March 23, 2017: Journal of Physical Chemistry. B
Fabienne Michelini, Adeline Crépieux, Katawoura Beltako
We discuss some thermodynamic aspects of energy conversion in electronic nanosystems able to convert light energy into electrical or/and thermal energy using the non-equilibrium Green's function formalism. In a first part, we derive the photon energy and particle currents inside a nanosystem interacting with light and in contact with two electron reservoirs at different temperatures. Energy conservation is verified, and radiation laws are discussed from electron non-equilibrium Green's functions. We further use the photon currents to formulate the rate of entropy production for steady-state nanosystems, and we recast this rate in terms of efficiency for specific photovoltaic-thermoelectric nanodevices...
March 23, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Qi Ding, Kyle J Czech, Yuzhou Zhao, Jianyuan Zhai, Robert J Hamers, John C Wright, Song Jin
Molybdenum disulfide (MoS2) is a two-dimensional material promising for electronic, optical, and catalytic applications. To fully harness its potential, functionalization is essential to control its properties. However, MoS2 functionalization has been mostly limited to either 1T-phase MoS2 or the edges of 2H-phase MoS2, and the chemistry of covalent functionalization on the basal plane of 2H-MoS2 is poorly understood. Here we report a facile approach to covalently functionalize chemical vapor deposition (CVD) grown 2H-MoS2 monolayers (MLs), as well as mechanically exfoliated MoS2, via thiol conjugation at sulfur vacancies on the basal plane...
March 23, 2017: ACS Applied Materials & Interfaces
Zhi Zheng, Lin Gan, Jianbing Zhang, Fuwei Zhuge, Tianyou Zhai
ZnO nanostructure-based photodetectors have a wide applications in many aspects, however, the response range of which are mainly restricted in the UV region dictated by its bandgap. Herein, UV-vis-NIR sensitive ZnO photodetectors consisting of ZnO nanowires (NW) array/PbS quantum dots (QDs) heterostructures are fabricated through modified electrospining method and an exchanging process. Besides wider response region compared to pure ZnO NWs based photodetectors, the heterostructures based photodetectors have faster response and recovery speed in UV range...
March 2017: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Yan Zhao, Yue Zhang, Gaofeng Qin, Jinjun Cheng, Wenhao Zeng, Shuchen Liu, Hui Kong, Xueqian Wang, Qingguo Wang, Huihua Qu
The unique features of quantum dots (QDs) make them desirable fluorescent tags for cell and developmental biology applications that require long-term, multitarget, and highly sensitive imaging. In this work, we imaged fluorescent cadmium telluride/zinc sulfide (CdTe/ZnS) QDs in organs, tissues, and cells, and analyzed the mechanism of their lymphatic uptake and cellular distribution. We observed that the fluorescent CdTe/ZnS QDs were internalized by lymph nodes in four cell lines from different tissue sources...
2017: International Journal of Nanomedicine
E N Bodunov, Yu A Antonov, A L Simões Gamboa
The non-exponential room temperature luminescence decay of colloidal quantum dots is often well described by a stretched exponential function. However, the physical meaning of the parameters of the function is not clear in the majority of cases reported in the literature. In this work, the room temperature stretched exponential luminescence decay of colloidal quantum dots is investigated theoretically in an attempt to identify the underlying physical mechanisms associated with the parameters of the function...
March 21, 2017: Journal of Chemical Physics
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