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Spectroscopic monitoring of the evolution of size and structural defects in kinetic growth of CdSe quantum dots
摘要： We report here on the exciton-phonon coupling and role of trap states formed at the interface of structural dislocations in CdSe quantum dots (QDs) synthesized by kinetic growth method. Even though non-luminescing, our studies recognize their signatures in the temperature dependent photoluminescence characteristics of lowest QD excitonic state and have some useful implications for structural quality of thus synthesized QDs. We have explained the observed temperature dependence of PL intensity in terms of a simple model taking account of different radiative and nonradiative recombination processes as well as carrier trapping/detrapping and determined the depth of potential well formed due to such long range defects. Our studies indicate the presence of such defect states only in QD samples size sorted by aliquoting at intermediate intervals during the reaction and do not appear when the reaction proceeds uninterrupted.
关键词： Temperature dependent photoluminescence,Exciton-phonon coupling,Thermal escape,CdSe Quantum Dots
更新于2025-09-16 10:30:52
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On-demand Milifluidic Synthesis of Quantum Dots in Digital Droplet Reactors
摘要： Colloidal quantum dots (QDs) offer dramatic potential due to their size-dependent optical properties. Lack of facile synthesis methods for precise and reproducible size and composition, however, present an extant barrier to their widespread use. Here we report the use of droplet microfluidics for the simple and highly reproducible synthesis of cadmium sulfide (CdS) and cadmium selenide (CdSe) QDs without the use of harsh solvents and in ambient conditions. Our approach uses a liquid-liquid barrier between two immiscible liquids to generate a digital droplet reactor. This reaction droplet is easily controlled and manipulated and offers enhanced mixing when coupled to a helical mixer, resulting in a significant reduction in size distribution compared to benchtop procedures. Furthermore, QD characteristics have modeled and predicted based on the parameters of the microfluidic device. We believe this method overcomes the current manufacturing challenges with synthesizing nanostructures, which is required for the next generation of nanosensors.
关键词： CdS,CdSe,quantum dots,microfluidics,nanosensors
更新于2025-09-12 10:27:22
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Semiconductor Quantum Dots Are Efficient and Recyclable Photocatalysts for Aqueous PET-RAFT Polymerization
摘要： This Letter describes the use of CdSe quantum dots (QDs) as photocatalysts for photoinduced electron transfer reversible addition?fragmentation chain transfer (PET-RAFT) polymerization of a series of aqueous acrylamides and acrylates. The high colloidal solubility and photostability of these QDs allowed polymerization to occur with high efficiency (>90% conversion in 2.5 h), low dispersity (PDI < 1.1), and ultralow catalyst loading (<0.5 ppm). The use of protein concentrators enabled the removal of the photocatalyst from the polymer and monomer with tolerable metal contamination (8.41 ug/g). These isolated QDs could be recycled for four separate polymerizations without a significant decrease in efficiency. By changing the pore size of the protein concentrators, the QDs and polymer could be separated from the remaining monomer, allowing for the synthesis of block copolymers using a single batch of QDs with minimal purification steps and demonstrating the fidelity of chain ends.
关键词： block copolymers,CdSe quantum dots,photocatalysts,aqueous acrylamides,acrylates,protein concentrators,PET-RAFT polymerization
更新于2025-09-12 10:27:22
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Three-dimensional ZnO/ZnxCd1?xS/CdS nanostructures modified by microwave hydrothermal reaction-deposited CdSe quantum dots for chemical solar cells
摘要： Effective interfaces composed of smart materials could play a critical role in the rapid transfer and separation of charges to achieve the high power-conversion efficiency of solar cells. In this work, we report an efficient chemical solar cell that uses a ZnO/ZnxCd1?xS/CdS structure, modified with CdSe deposited with a microwave hydrothermal technique, for rapid transport of charges using a frame construction to allow for reuse. The morphology, nanostructure, and reaction mechanisms of CdS nanorods and the ZnxCd1?xS layer were systematically investigated. The results indicated that light absorption expands from 550 nm of CdS to 700 nm because of the absorption of nearly all the visible light by deposited CdSe quantum dots. The effects of the compositional structure on cell performance are investigated to reveal the enhancement mechanism, which is mainly attributed to the suitable nano-branch structure, high light absorbability, low charge transfer resistance, and low recombination rate. This work demonstrates a potential universal method of designing an interface with a multi-component composite for efficient charge transport and separation, not only in chemical solar cells but with extensions to photocatalysis and water splitting uses as well.
关键词： Chemical solar cell,Composite structures,ZnO/ZnxCd1?xS/CdS,CdSe quantum dots,Microwave hydrothermal
更新于2025-09-12 10:27:22
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Simultaneous positive and negative optical patterning with dye-sensitized CdSe quantum dots
摘要： CdSe quantum dots are functionalized with the organic dye iron β-tetraaminophthalocyanine to reward a solution-processable hybrid material with two individually addressable optical resonances. We exploit this dual functionality during optical write/optical read patterning experiments and show that it is possible to simultaneously write complex optical patterns with positive and negative fluorescence contrast. This is enabled by a fluorescence enhancement under near-resonant excitation of the quantum dots in combination with a fluorescence bleaching during excitation of the singlet transition of the phthalocyanine. The presence of the organic dye not only enables negative optical patterning but also enhances the contrast during positive patterning. Furthermore, the patterning result is strongly dependent on the excitation wavelength during readout. Our results highlight the new possibilities that arise from combining inorganic quantum dots and organic π-systems into hybrid nanocomposites.
关键词： fluorescence contrast,optical patterning,iron β-tetraaminophthalocyanine,CdSe quantum dots,hybrid nanocomposites
更新于2025-09-12 10:27:22
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Enzyme-Catalyzed in Situ Synthesis of Temporally and Spatially Distinct CdSe Quantum Dots in Biological Backgrounds
摘要： The cellular machinery of metal metabolism is capable of making a wide range of inorganic nanoparticles and quantum dots. Individual enzymes from these metabolic pathways are being identified with metal reducing activity, and some have been isolated for in situ particle formation and labeling. We previously identified a glutathione reductase like metalloid reductase (GRLMR) from Pseudomonas moravenis stanleyae with a high affinity for the bioavailable selenium thiolate selenodiglutatione and exhibiting NADPH-dependent reduction of selenodiglutathione to Se(0), initiating the growth of pure selenium metal nanoparticles. In this study, we demonstrate that the GRLMR enzyme can further reduce selenium to a Se(2?) oxidative state, which is capable of nucleating with Cd(2+) to rapidly form CdSe quantum dots. We show that GRLMR can outcompete background sources of cellular selenium reduction (such as glutathione) and can control the kinetics of quantum dot formation in complex media. The resulting particles are of smaller diameter, with a distinguishingly shifted emission spectrum and superior full width at half-maximum. This study indicates that there is great potential for using GRLMR to study and design enzymes capable of controlled biosynthesis of nanoparticles and quantum dots, paving the way for cellularly assembled nanoparticle biosensors and reporters.
关键词： enzyme-catalyzed,CdSe quantum dots,nanoparticle biosynthesis,GRLMR,biological backgrounds,selenium reduction
更新于2025-09-12 10:27:22
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Time controlled growth of CdSe QDs for applications in white light emitting diodes
摘要： Semiconductor nanophosphors have the exceptional resources to demonstrate the quantum phenomenon due to their tailored-size dependent photoluminescence (PL). The work here is focused on the synthesis of highly luminescent Cadmium Selenide (CdSe) Quantum Dots (QDs) by a simple technique. This is a time dependent process where change in the size of CdSe QDs was observed at a reaction temperature of 100 °C without any inert atmosphere. The CdSe QDs were synthesised by using 3-Mercapto propionic acid (MPA) rather than using the typically utilized capping agent. All the samples were characterised for their optical properties. The size of QDs was calculated in a range up to 3 nm by UV–Vis Spectroscopy and con?rmed by High Resolution Transmission Electron Microscopy (HRTEM). It was clear from the UV studies that QDs exhibit size dependent tunable optical absorption. The broad Photoluminescence (PL) emission spectra depicts the presence of surface defects produced along with band edge spectrum. The absorbance and emission spectra were shifted to the red region due to the quantum con?nement e?ect occurred in QDs. The water soluble QDs were economical and easy to fabricate has applications in Light Emitting Diodes (LEDs).
关键词： 3-Mercapto propionic acid,Light Emitting Diodes,Quantum con?nement,Photoluminescence,CdSe Quantum Dots
更新于2025-09-11 14:15:04
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A TiO2/g-C3N4/CdS Nanocomposite-Based Photoelectrochemical Biosensor for Ultrasensitive Evaluation of T4 Polynucleotide Kinase Activity
摘要： Herein, an efficient photoelectrochemical (PEC) platform was constructed by a co-sensitization strategy with a cascade energy level arrangement for the ultrasensitive evaluation of T4 polynucleotide kinase (T4 PNK). Based on CdSe quantum dots (QDs) with an extremely narrow bandgap, this co-sensitization strategy offered a highly efficient sensitizer with a matching band-edge level of a ternary TiO2/g-C3N4/CdS nanocomposite. In this protocol, the ternary nanocomposite was first prepared to serve as the matrix to construct the PEC sensing platform. On the other hand, a well-designed hairpin DNA1 probe with 5’-hydroxyl termini was specifically phosphorylated by T4 PNK which would be selectively cleaved with lambda exonuclease (λ-Exo) outputting 3’-thiol end ssDNA2. After tagged with CdSe QDs, ssDNA2 was captured by the complementary capture DNA3 on the electrode surface. As a result, CdSe QDs were in close contact with the ternary nanocomposite matrix, leading to an enhanced photocurrent response. Therefore, this proposed PEC platform displayed an analytical performance with a wide linear range from 0.0001 to 0.02 U mL-1 and a low detection limit down to 6.9 × 10-5 U mL-1. Moreover, this ternary nanocomposite-based platform exhibited excellent selectivity, good reproducibility, and remarkable storage stability, which shows the great potential for the T4 PNK detection and inhibitor screening.
关键词： CdSe quantum dots,T4 polynucleotide kinase,ternary nanocomposite,co-sensitization strategy,photoelectrochemical biosensor
更新于2025-09-04 15:30:14