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Phonon-Driven Energy Relaxation in PbS/CdS and PbSe/CdSe Core/Shell Quantum Dots
摘要： We study the impact of the chemical composition on phonon-mediated exciton relaxation in the core/shell quantum dots (QDs), with 1-nm core made of PbX and the monolayer shell made of CdX, where X=S and Se. For this, time-domain non-adiabatic dynamics (NAMD) based on Density Functional Theory (DFT) and Surface Hopping techniques are applied. Simulations reveal twice faster energy relaxation in PbS/CdS than PbSe/CdSe due to dominant couplings to higher-energy optical phonons in structures with sulfur anions. For both QDs, the long-living intermediate states associated with the core-shell interface govern the dynamics. Therefore, a simple exponential model is not appropriate, and the four-state irreversible kinetic model is suggested instead, predicting 0.9 ps and 0.5 ps relaxation rates in PbSe/CdSe and PbS/CdS QDs, respectively. Thus, 2-nm PdSe/CdSe QDs with a single monolayer shell exhibit the phonon-mediated relaxation time sufficient for carrier multiplications to outpace energy dissipation and benefit the solar conversion efficiency.
关键词： Density Functional Theory,phonon-driven energy relaxation,PbSe/CdSe,PbS/CdS,core/shell quantum dots,Surface Hopping techniques,non-adiabatic dynamics
更新于2025-09-23 15:21:01
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Controlled Synthesis of Ag <sub/>2</sub> Te@Ag <sub/>2</sub> S Corea??Shell Quantum Dots with Enhanced and Tunable Fluorescence in the Second Neara??Infrared Window
摘要： Fluorescence in the second near-infrared window (NIR-II, 900–1700 nm) has drawn great interest for bioimaging, owing to its high tissue penetration depth and high spatiotemporal resolution. NIR-II fluorophores with high photoluminescence quantum yield (PLQY) and stability along with high biocompatibility are urgently pursued. In this work, a Ag-rich Ag2Te quantum dots (QDs) surface with sulfur source is successfully engineered to prepare a larger bandgap of Ag2S shell to passivate the Ag2Te core via a facile colloidal route, which greatly enhances the PLQY of Ag2Te QDs and significantly improves the stability of Ag2Te QDs. This strategy works well with different sized core Ag2Te QDs so that the NIR-II PL can be tuned in a wide range. In vivo imaging using the as-prepared Ag2Te@Ag2S QDs presents much higher spatial resolution images of organs and vascular structures as compared with the same dose of Ag2Te nanoprobes administrated, suggesting the success of the core–shell synthetic strategy and the potential biomedical applications of core–shell NIR-II nanoprobes.
关键词： NIR-II nanoprobes,Ag2Te@Ag2S,bioimaging,core–shell quantum dots
更新于2025-09-23 15:19:57
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Ge/Si Core/Shell Quantum Dots in an Alumina Matrix: Influence of the Annealing Temperature on the Optical Properties
摘要： Structures with Ge/Si nanoparticles (quantum dots) in an aluminum-oxide matrix are of interest due to the combination of two basic semiconductors and the use of a matrix with a high permittivity and strong oxygen–metal bonding. In this study, multilayer nanoperiodic structures in the form of a substrate/Al2O3/Ge/Si/Al2O3…Al2O3 sequence of layers (with the period Al2O3/Ge/Si and the number of periods up to 20) are produced and then annealed at different temperatures. It is shown that, after annealing, the structures contain both Ge and Si crystalline particles, whose dimensions and number are defined by the deposited-layer thicknesses and the annealing temperature. The results obtained by different optical techniques suggest that the structures exhibit the quantum-confinement effect. This inference is supported by high-resolution microscopy.
关键词： Ge/Si,multilayer nanostructures,core–shell quantum dots
更新于2025-09-23 15:19:57
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68Ga CdTe/CdS fluorescent quantum dots for detection of tumors: investigation on the effect of nanoparticle size on stability and in vivo pharmacokinetics
摘要： Background: Quantum dots (QDs)-based theranostics offer exciting new approaches to diagnose and therapy of cancer. To take advantage of the unique properties of these fluorescent QDs for different biomedical applications, their structures, size and/or surface chemistry need to be optimized, allowing their stability and functionalities to be tailored for different biomedical applications. Methodology: Cadmium telluride/Cadmium sulfide QDs (CdTe/CdS QDs) were synthesized and their structure, size, photostability and functionalities as a bioprobe for detection of Fibrosarcoma tumors were studied and compared with Cadmium telluride (CdTe) QDs. Hence, CdTe/CdS QDs were labeled with 68Ga radionuclide for fast in vivo biological nuclear imaging. Using gamma paper chromatography (γ-PC), the physicochemical properties of the prepared labeled QDs were assessed. In vivo biodistribution and positron emission tomography (PET) imaging of the 68Ga@ CdTe/CdS QDs nanocrystals were investigated in Sprague Dawley? rats bearing Fibrosarcoma tumor. Results: CdS shell on the surface of CdTe core increases the size and photostability against high energy radiations; therefore, CdTe/CdS QDs show prolonged fluorescence as compared to CdTe QDs. Conclusion: Excellent accumulation in tumor was observed for core/shell quantum dots, but this study showed that small changes in the size of the QDs (+1 nm), after adding the CdS shell around CdTe core, greatly change their biodistribution (especially the liver uptake).
关键词： core/shell quantum dots,PET,tumor imaging,68Ga,Cadmium telluride/Cadmium sulfide
更新于2025-09-23 15:19:57
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Preparation of Highly Stable and Photoluminescent Cadmiuma??Free InP/GaP/ZnS Core/Shell Quantum Dots and Application to Quantitative Immunoassay
摘要： Indium phosphide (InP) quantum dots (QDs) are ideal substitutes for widely used cadmium-based QDs and have great application prospects in biological fields due to their environmentally benign properties and human safety. However, the synthesis of InP core/shell QDs with biocompatibility, high quantum yield (QY), uniform particle size, and high stability is still a challenging subject. Herein, high quality (QY up to 72%) thick shell InP/GaP/ZnS core/shell QDs (12.8 ± 1.4 nm) are synthesized using multiple injections of shell precursor and extension of shell growth time, with GaP serving as the intermediate layer and 1-octanethiol acting as the new S source. The thick shell InP/GaP/ZnS core/shell QDs still keep high QY and photostability after transfer into water. InP/GaP/ZnS core/shell QDs as fluorescence labels to establish QD-based fluorescence-linked immunosorbent assay (QD-FLISA) for quantitative detection of C-reactive protein (CRP), and a calibration curve is established between fluorescence intensity and CRP concentrations (range: 1–800 ng mL?1, correlation coefficient: R2 = 0.9992). The limit of detection is 2.9 ng mL?1, which increases twofold compared to previously reported cadmium-free QD-based immunoassays. Thus, InP/GaP/ZnS core/shell QDs as a great promise fluorescence labeling material, provide a new route for cadmium-free sensitive and specific immunoassays in biomedical fields.
关键词： cadmium-free,quantum dot-based fluorescence-linked immunosorbent assays,thick shell InP core/shell quantum dots,C-reactive proteins,quantitative detection
更新于2025-09-19 17:13:59
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Rational design of colloidal core/shell quantum dots for optoelectronic applications
摘要： Colloidal core/shell quantum dots (QDs) are promising for solar technologies because of their excellent optoelectronic properties including tunable light absorption/emission spectra, high photoluminescence quantum yield (PLQY), suppressed Auger recombination, efficient charge separation/transfer and outstanding photo-, thermal-/chemical stability. In this review, engineered core/shell QDs with various types of band structures and corresponding device performance in luminescent solar concentrators (LSCs), light-emitting diodes (LEDs), solar-driven photoelectrochemical (PEC) devices and QDs-sensitized solar cells (QDSCs) are summarized. In particular, the applications of interfacial layer engineering and eco-friendly, heavy metal-free core/shell QDs in optoelectronic device are highlighted. Finally, strategies towards the developments and practical perspectives of core/shell QDs are briefly mentioned to offer guidelines for achieving prospective high-efficiency and long-term stable QD devices.
关键词： Core/shell quantum dots,Photoelectrochemical cells,Light-emitting diodes,Solar cells,Luminescent solar concentrators
更新于2025-09-19 17:13:59
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Nonvolatile Resistive Switching Memory Device Employing CdSe/CdS Core/Shell Quantum Dots as an Electrode Modification Layer
摘要： Accompanied with great advantages in various fields of performance, memristors show huge potential in the next generation of mainstream storage devices. However, their random distribution of resistance switching voltage has always been one of the problems in applications. In this present work, a nonvolatile resistive switching memory device was proposed, which employed CdSe/CdS core/shell quantum dots (QDs) assembled as an electrode modification layer with the device configuration of Pt/CdSe-CdS QDs/TaOx/Ta. The device possesses multiple excellent resistance switching characteristics such as lower and more consistent set/reset threshold voltage and better endurance performance, which is considered as the effect of the electrode modification layer based CdSe/CdS core/shell QDs. A model with uneven QDs/Pt electrode interface was put forward to explain the different resistance switching behaviors, which may be beneficial to the development of existing research about memristors based on metal oxides and quantum dots.
关键词： Migration,Oxygen vacancy,Schottky interface,CdSe/CdS core/shell quantum dots,resistive switching
更新于2025-09-19 17:13:59
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Core/Shell Quantum Dots Solar Cells
摘要： Semiconductor nanocrystals, the so-called quantum dots (QDs), exhibit versatile optical and electrical properties. However, QDs possess high density of surface defects/traps due to the high surface-to-volume ratio, which act as nonradiative carrier recombination centers within the QDs, thereby deteriorating the overall solar cell performance. The surface passivation of QDs through the growth of an outer shell of different materials/compositions called “core/shell QDs” has proven to be an effective approach to reduce the surface defects and confinement potential, which can enable the broadening of the absorption spectrum, accelerate the carrier transfer, and reduce exciton recombination loss. Here, the recent research developments in the tailoring of the structure of core/shell QDs to tune exciton dynamics so as to improve solar cell performance are summarized. The role of band alignment of core and shell materials, core size, shell thickness/compositions, and interface engineering of core/thick shell called “giant” QDs on electron–hole spatial separation, carrier transport, and confinement potential, before and after grafting on the carrier scavengers (semiconductor/electrolyte), is described. Then, the solar cell performance based on core/shell QDs is introduced. Finally, an outlook for the rational design of core/shell QDs is provided, which can further promote the development of high-efficiency and stable QD sensitized solar cells.
关键词： core/shell quantum dots,carrier dynamics,solar cells,interface engineering
更新于2025-09-19 17:13:59
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A novel approach to coat silica on quantum dots: Forcing decomposition of tetraethyl orthosilicate in toluene at high temperature
摘要： The coating of silica (SiO2) on quantum dots (QDs) has been widely studied, because SiO2 can protect QDs from the damages of moisture, radiation, and heat. Conventional SiO2 coating methods for QDs are usually performed in aqueous or emulsion solutions, which require the addition of water for the hydrolysis of SiO2 precursors and lead to the photoluminescence (PL) quenching of QDs. To address this issue, a novel SiO2 coating approach on single particle level was developed by the thermally forcing decomposition of tetraethyl orthosilicate in toluene. The CdSe/CdS/ZnS:Al@SiO2 nanoparticles (NPs) were prepared without decreasing the original PL quantum yield (QY), which exhibited much better photo and thermal stability in comparison with uncoated CdSe/CdS/ZnS:Al QDs. Furthermore, due to the natural formation of silanol groups on the SiO2 shell, CdSe/CdS/ZnS:Al@SiO2 NPs present not only good solubility but also excellent room temperature stability in phosphate buffer saline solution for several months.
关键词： SiO2,TEOS,stability,core/shell quantum dots,water solubility
更新于2025-09-11 14:15:04