Synergistic photoluminescent interaction of Si and CdTe quantum dots

Microsystem Technologies - We report the synergistic photoluminescent effect observed in heterogeneous colloidal solutions comprising different volumetric concentrations of Si and CdTe quantum dots...     

Anomalous Stokes shift of colloidal quantum dots and their influence on solar cell performance

Microsystem Technologies - We report an anomalous Stokes shift effect observed in colloidal solutions containing down-shifting Carbon quantum dots (CQDs) of different sizes that is expected to have...     

Layer-by-layer self-assembly CdTe quantum dots and molecularly imprinted polymers modified chemiluminescence sensor for deltamethrin detection

A novel chemiluminescence sensor for determination deltamethrin was firstly reported based on CdTe quantum dots and deltamethrin imprinted polymers by layer-by-layer assembly modified on the surface of slide glass, whose shape was the same as the bottom of 96 well micro-plate. The binding characteristic of the imprinted polymers to deltamethrin was evaluated by equilibrium binding experiments and the morphology was studied by scanning electronic microscope. Scatchard analysis was carried out to estimate the binding parameters of the imprinted polymers. The water-soluble TGA-capped CdTe quantum dots were prepared. NaHTe was used as the Te precursor for CdTe quantum dots synthesis. Under the optimum conditions, the chemiluminescence intensity had a linear relationship against the concentration of deltamethrin over the range of 0.053-46.5 μg mL⁻¹ with a lower detection limit of 0.018 μg mL⁻¹. The regression equation was ΔI = 2225 + 107c (c: μg mL⁻¹) with a correlation coefficient of 0.9973. The relative standard deviation was 4.7%. The presented method was applied successfully to the determination of deltamethrin in real samples with satisfactory results.     

石墨烯量子点和量子比特

本文主要回顾了石墨烯量子点的制备以及基于石墨烯量子点自旋和电荷量子比特操作的研究进展,由于石墨烯材料相对较轻的原子重量使其具有较小的自旋轨道相互作用,另外含有核自旋的碳同位素13C在自然界中的含量大约只占1%,这使得超精细相互作用(即核自旋和电子自旋相互作用)较弱,所以石墨烯比其他材料具有较长的自旋退相干时间,在量子计算和量子信息中有非常好的应用前景.本文计算了5种静电约束制备的石墨烯量子点:1)扶手型单层石墨烯纳米条带,2)单层石墨烯圆盘,3)双层石墨烯圆盘,4)ABC堆积型三层石墨烯圆盘,5)ABA堆积型三层石墨烯圆盘.石墨烯量子点中自旋比特应用的关键是破坏谷简并,在1)中,主要是利用边界条件破坏谷简并,而2)–5)中是利用外磁场破坏谷简并.文章进一步介绍了自旋轨道相互作用和超精细相互作用对石墨烯量子点中自旋操作的影响.     

发光纳米材料和量子点化学传感及其机理

介绍了荧光和磷光纳米材料的种类,如无机半导体量子点,金属离子掺杂的半导体量子点,金属纳米粒子或纳米簇,硅点,碳点和石墨烯点等。接着阐述了这些纳米材料的光致发光的光物理机制和猝灭或增强的一般性原理。最后简要综述了量子点或纳米材料发光的猝灭或增强现象在化学传感中的应用和具体的响应机理。     

量子点荧光标记技术在生物医学领域的应用

量子点作为一种新型的纳米荧光材料在生物学领域的应用已引起国际上的普遍关注,量子点独特的荧光性能使其在这一领域的应用有着无可比拟的优越性.该文主要就量子点的荧光性能,基于量子点标记的生物荧光探针的制备及其在生物医学领域中的应用研究进展作一概述.     

Effects of ITO film annealing temperature on hybrid solar cell performance

The effects of indium tin oxide (ITO) film annealing temperature on the performance of organic solar cells are investigated. The roughness of the ITO film surface morphology increased with increasing annealing temperature. The optical penetration and rate of exciton generation both increased with increasing ITO film annealing temperature, enhancing the short-circuit current density. The maximum efficiency (2.62 %) was obtained with an annealing temperature of about 500 °C. The incident-photon-to-current efficiency value for a hybrid photovoltaic device with an ITO film annealed temperature at 500 °C was 45 % at 475 nm.     

Modified genetic programming combining with particle swarm optimization and performance criterion in solar cell fabrication

This study describes the design and development of the novel model for the process optimization of solar cell fabrication. The model performance can affect the result of the physical experiment in the solar cell fabrication because the high accuracy model can provide the closer result to the output efficiency of the physical experiment. In this study, genetic programming (GP) based modeling technique was developed for the process simulation. GP is a global modeling technique, so it is suitable for process data modeling. This study describes the modified GP algorithm to solve the constant terminal problem. In the traditional GP, the constant term can be randomly selected within the fixed range when the structure is changed. Therefore, the variation ratio of the constant is too low to fit the model well. In this study, the novel GP is proposed. The method includes particle swarm optimization (PSO) to optimize the constant term in the terminals. PSO is a strong searching algorithm without a high computation cost. Actually, through the simulation results, the modeling performance and speed can be improved by the proposed GP. Because by the proposed modeling method, the structure and parameters of the model can be optimized simultaneously, the proposed method can be used as the new global modeling approach.     

Monochromatic LEDs based on perovskite quantum dots: Opportunities and challenges

Perovskite quantum dots (QDs) are emerging as one of the most promising candidates for the monochromatic light‐emitting diodes (LEDs) approaching the Rec. 2020 color gamut due to their extremely narrow emission bandwidth. Another important aspect are the high photoluminescence quantum yield (PLQY) values that can be obtained either in solution or thin films making these materials as promising candidates for optoelectronic applications such as LEDs or solar cells. Considerable research efforts in chemistry, chemical engineering, solid‐state physics, and material sciences have been made in the past years. The new opportunity in the field of semiconductor quantum dots is still in the beginning phase and is expected to remain active in the following years. Here, in this invited commentary, we briefly discuss and summarize the opportunities and challenges in both fundamental and technological aspects, based on our work and the recent work in this field.     

Cathodoluminescence and electron microscopy of red quantum dots used for display applications

Cathodoluminescent imaging of the visible light emitted from quantum dots is reported. The shape and uniformity of individual particles is observed in the scanning transmission electron microscope image, and the image of the particles created from their visible light collected simultaneously is shown. Visible light images of the 13 nm sized particles are reported for clusters of particles. The emission spectrum collected from small clusters of quantum dots is also reported.     

Automatic segmentation of clustered quantum dots based on improved watershed transformation

Automated analysis of the quantum dots (QDs) images is very important in the field of material science. In this frame, efficient QDs segmentation is prerequisite. In this paper, we propose an algorithm of automatic detection and segmentation of the QDs, especially the clustered ones. We depend on fuzzy c-means (FCM) method for initial segmentation of the QDs from the substrate background. Then we present a modified watershed algorithm with markers and a novel marking function. The markers are extracted by adaptive H-minima transformation. Then a marking function based on Quasi-Euclidean distance transform is introduced to accurately and rapidly separate the clustered QDs. We demonstrate the comparisons of our method with the existing approaches. The experimental results show that the proposed method is efficient and accurate with very little running time and has a high quality on QDs segmentation.     

Numerical implementation of the ellipsoidal wave equation and application to ellipsoidal quantum dots

We present a full implementation of the algorithm of Arscott et al. [Math. Comp. 40 (1983) 367] in order to evaluate the discrete eigenvalue spectrum and associated eigenfunctions of the Laplacian operator in a three-dimensional ellipsoidal region subject to Dirichlet boundary condition. The results were applied to provide the first solution to the triaxial ellipsoidal infinite-barrier quantum-dot problem in quantum mechanics.     

Improving performance of ZnO flexible dye sensitized solar cell by incorporation of graphene oxide

At today great interest has been paid to hydrogen production by water electrolysis due to their simplicity and low cost. Dye sensitized solar cell are promising devices as renewable electrical power source to achieve water electrolysis because they possess high theoretical efficiency compared with Si based solar cells. In this research, ZnO photo catalyst was modified with graphene oxide (GO) by means of high energy milling. The anode of the flexible dye-sensitized solar cell was fabricated by electrophoretic deposition of the photo catalyst onto flexible electrodes. The obtained materials were characterized by FTIR, XRD, XPS and SEM–EDS. The efficiency and fill factor of ZnO and ZnO–GO cells were estimated from the I–V curve, measured under simulated sunlight. The obtained results demonstrate that ZnO–GO cell have higher efficiency compared with the ZnO cell. The latter can be explained by the better dispersion of ZnO that enlace the dye adsorption onto the fabricated anode and by the presence of GO that improve the absorption of photons from the light.

     

基于CdSe/ZnS量子点荧光生物传感器构建与应用

设计了一种由CdSe/ZnS量子点和荧光染料Cy3(C31H37KN2O8S2)基于荧光共振能量转移(FRET)原理的生物传感器,并进行了该体系下不同浓度和不同pH溶液中荧光转移强度的实验。实验表明:CdSe/ZnS荧光半导体量子点作为供体对Cy3(C_(31)H_(37)KN_2O_8S_2)染料的荧光增强作用明显。在CdSe/ZnS量子点与Cy3的比例为1∶1.2时,荧光转移效率达到83.68%,对细胞外液p H值荧光变化敏感(pH=5.93～8.36)。此外,该生物传感器可以清楚地识别前列腺癌细胞。该实验结果对前列腺癌细胞的早期诊断和前列腺癌生物传感器的设计提供了一种新的方法。     

PVP／CdS量子点修饰电极的制备及其对肌红蛋白的直接电化学研究

该文采用溶胶-凝胶法制备了聚乙烯吡咯烷酮(PVP)表面修饰的硫化镉(CdS)半导体量子点,用透射电镜(TEM)、X射线衍射(XRD)等手段进行了表征;将其修饰在玻碳电极(GC)表面制得量子点修饰电极,并研究了肌红蛋白(Myoglobin,Mb)在该量子点修饰电极上的电化学行为.实验结果表明,PVP/CdS量子点修饰电极对肌红蛋白具有催化还原作用,且还原峰电流与被测蛋白质浓度呈良好线性关系.流动注射分析结果进一步表明该量子点修饰电极具有高的稳定性和好的重现性,检出限为2.0×10.mol/L,该电极可作为检测肌红蛋白的新型高灵敏度电化学传感器.     

ZnS掺Mn磷光量子点对金属离子传感机理的探讨

合成了以3-巯基丙酸或L-半胱氨酸修饰的水溶性ZnS掺Mn磷光量子点,磷光发射峰在590 nm,产生于Mn2+的4T1-6A1跃迁.磷光信号稳定,不易受溶解氧的影响.检测了七种常见金属离子对磷光性质的影响,结果表明:对于3-巯基丙酸修饰的ZnS:Mn量子点,Cu2+,Mn2+,Fe3+,Co2+,pb2和Hg2+离子能...     

Image charges in spherical quantum dots with an off-centered impurity: algorithm and numerical results

A computational scheme yielding exact (numerical) wave-functions and energies of a spherical nanocrystallite, with a shallow donor impurity located anywhere inside, is presented. Position-dependent effective mass, finite step-like spatial confining potential, coulombic and image potentials originating from the dielectric mismatch at the quantum dot edge are taken into account. Strategies to overcome mathematical divergences, low numerical convergence and computer cut-off errors are discussed. The resulting code is employed to carry out a comprehensive study on the influence of the impurity off-centering on the image charge contribution to the electronic energy. The highly non-additivity of the different contributions to this energy emphasizes the relevance of employing computational schemes like the one presented here, which incorporate all confining potentials in a balanced way.     

Survey of control performance in quantum information processing

There is a rich variety of physics underlying the fundamental gating operations for quantum information processing (QIP). A key aspect of a QIP system is how noise may enter during quantum operations and how suppressing or correcting its effects can best be addressed. Quantum control techniques have been developed to specifically address this effort, although a detailed classification of the compatibility of controls schemes with noise sources found in common quantum systems has not yet been performed. This work numerically examines the performance of modern control methods for suppressing decoherence in the presence of noise forms found in viable quantum systems. The noise-averaged process matrix for controlled one-qubit and two-qubit operations are calculated across noise found in systems driven by Markovian open quantum dynamics. Rather than aiming to describe the absolute best control scheme for a given physical circumstance, this work serves instead to classify quantum control behavior across a large class of noise forms so that opportunities for improving QIP performance may be identified.     

Entanglement generation of two quantum dots with Majorana fermions via optimal control

We propose schemes to entangle two quantum dots (QDs) with the aid of Majorana fermions via optimal control. Two paradigmatic cases, the teleportation and the intradot spin flip processes, are considered, respectively, in the charge and spin degrees of QDs. We demonstrate that optimal control techniques can be effectively used to prepare entanglement between two QDs through manipulating their chemical potentials. Significantly, our optimal control generation of entangled states has a prominent advantage: The runtime is much shorter than in adiabatic passage, providing a shortcut to adiabatic entanglement preparation.