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Alleviating the toxicity of quantum dots to Phanerochaete chrysosporium by sodium hydrosulfide and cysteine
摘要： Quantum dots (QDs) have caused large challenges in clinical tests and biomedical applications due to their potential toxicity from nanosize effects and heavy metal components. In this study, the physiological responses of Phanerochaete chrysosporium (P. chrysosporium) to CdSe/ZnS QDs with either an inorganic sulfide NaHS or an organic sulfide cysteine as antidote have been investigated. Scanning electron microscope analysis showed that the hyphal structure and morphology of P. chrysosporium have obviously changed after exposure to 100 nM of COOH CdSe/ZnS 505, NH2 CdSe/ZnS 505, NH2 CdSe/ZnS 565, or NH2 CdSe/ZnS 625. Fourier transform infrared spectroscopy analysis indicated that the existence of hydroxyl, amino, and carboxyl groups on cell surface could possibly conduct the stabilization of QDs in an aqueous medium. However, after NaHS or cysteine treatment, the cell viability of P. chrysosporium exposed to CdSe/ZnS QDs increased as compared to control group, since NaHS and cysteine have assisted P. chrysosporium to alleviate oxidative damage by regulating lipid peroxidation and superoxide production. Meanwhile, NaHS and cysteine have also stimulated P. chrysosporium to produce more antioxidant enzymes (superoxide dismutase and catalase), which played significant roles in the defense system. In addition, NaHS and cysteine were used by P. chrysosporium as sulfide sources to promote the glutathione biosynthesis to relieve CdSe/ZnS QDs-induced oxidative stress. This work revealed that sulfide sources (NaHS and cysteine) exerted a strong positive effect in P. chrysosporium against the toxicity induced by CdSe/ZnS QDs.
关键词： Detoxification,Cysteine,CdSe/ZnS quantum dots,Sodium hydrosulfide,Antioxidant enzymes,Oxidative stress
更新于2025-09-23 15:19:57
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Incorporating graphene quantum dots to enhance the photoactivity of CdSe-sensitized TiO2 nanorods for solar hydrogen production
摘要： This work demonstrated that the incorporation of graphene quantum dots (GQDs) can greatly improve the photoelectrochemical (PEC) efficiency of CdSe-sensitized TiO2 nanorods (TiO2/CdSe), a TiO2-based visible light-responsive photoelectrode paradigm, for solar hydrogen production. For TiO2/CdSe, the accumulated holes at CdSe may induce photocorrosive oxidation to decompose CdSe, deteriorating the long-term stability of photoelectrode and degrading the PEC performance. With the introduction of GQDs, the delocalized holes can further transfer from CdSe to the GQDs, which eases the hole accumulation at the CdSe sites, thus retarding photocorrosion. Compared to the binary TiO2/CdSe photoanode, the ternary TiO2/CdSe/GQDs photoanode displays higher photocurrent and better photostability toward PEC hydrogen production. This superiority can be attributed to vectorial charge transfer and enhanced reaction kinetics provided by the introduction of GQDs. The findings from this work highlight the importance of the introduction of GQDs as a potential solution to the photocorrosion issue of chalcogenide-sensitized semiconductor photoelectrodes.
关键词： photocorrosion,photoelectrochemical efficiency,solar hydrogen production,CdSe-sensitized TiO2 nanorods,graphene quantum dots
更新于2025-09-23 15:19:57
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Coherent Exciton Dynamics in Ensembles of Size-Dispersed CdSe Quantum Dot Dimers Probed via Ultrafast Spectroscopy: A Quantum Computational Study
摘要： Interdot coherent excitonic dynamics in nanometric colloidal CdSe quantum dots (QD) dimers lead to interdot charge migration and energy transfer. We show by electronic quantum dynamical simulations that the interdot coherent response to ultrashort fs laser pulses can be characterized by pump-probe transient absorption spectroscopy in spite of the inevitable inherent size dispersion of colloidal QDs. The latter, leading to a broadening of the excitonic bands, induce accidental resonances that actually increase the efficiency of the interdot coupling. The optical electronic response is computed by solving the time-dependent Schrodinger equation including the interaction with the oscillating electric field of the pulses for an ensemble of dimers that differ by their size. The excitonic Hamiltonian of each dimer is parameterized by the QD size and interdot distance, using an effective mass approximation. Local and charge transfer excitons are included in the dimer basis set. By tailoring the QD size, the excitonic bands can be tuned to overlap and thus favor interdot coupling. Computed pump-probe transient absorption maps averaged over the ensemble show that the coherence of excitons in QD dimers that lead to interdot charge migration can survive size disorder and could be observed in fs pump-probe, four-wave mixing, or covariance spectroscopy.
关键词： coherent electronic dynamics,pump-probe transient absorption spectroscopy,CdSe quantum dots dimers,exciton dynamics,size dispersion effects
更新于2025-09-23 15:19:57
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Efficient Perovskite Solar Cells Based on CdSe/ZnS Quantum Dots Electron Transporting Layer with Superior UV Stability
摘要： Stability is the main challenge in the field of perovskite solar cells (PSCs). Finding new strategies is required to protect the PSCs from deteriorated agents such as humidity, heating, and illumination. In this study, we propose a new electron transporting layer (ETL), i.e., CdSe/ZnS quantum dots (QDs) for the fabrication of efficient and stable PSCs. CdSe/ZnS QDs layer not only works as an ETL but also has down-shifting property, which can improve both efficiency and stability of the PSCs. Using CdSe/ZnS QDs ETL with green emission, a PSC with maximum power conversion efficiency (PCE) of 18% is achieved. More importantly, our device shows great UV stability much better than the device with TiO2 ETL, where it retains 90% of its initial PCE value after 75 h under continuous UV illumination.
关键词： down-shifting layer,perovskite,solar cell,CdSe/ZnS QDs,stability,UV stability
更新于2025-09-23 15:19:57
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P-9.11: Synthesis and optical properties of CdSe <sub/>x</sub> S <sub/>1-x</sub> nanomaterials with different morphologies
摘要： The optical properties of colloidal nanometer quantum dots, including fluorescence peak position, fluorescence peak width, fluorescence quantum yield, fluorescence attenuation channel, fluorescence scintillation and brightness of single quantum dots, are determined by the properties of Exciton states, and the properties of Exciton states are closely related to their structure. During the synthesis of CdSexS1-x Nanomaterials, a series of different morphologies are obtained by controlling the reaction solvent, reaction temperature, reaction time, type and concentration of the reaction ligand and the precursor type CdSeXS1-x nanomaterial.
关键词： CdSe,Nanoplatelets,Nanorods,Quantum Dots
更新于2025-09-19 17:15:36
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Morphology of CdSe-Based Coatings Formed on Polyamide Substrate
摘要： Cadmium selenide (CdSe)-based layers were formed on the surface of polyamide 6 (PA) substrate film by treating PA film samples with potassium selenotrithionate (K2SeS2O6) solution (seleniumization) and then with cadmium(II) acetate, Cd(CH3COO)2, solution (cadmiumization). The morphology of CdSe-based layers was investigated by atomic force and scanning electron microscopies. It was determined that the formation of CdSe-based layers proceeds unevenly in the form of islands, which later tends to agglomerate. Therefore the surface of the layers formed is relatively uneven and rather rough. After seleniumization and cadmiumization procedures the average height of this layer have tendency to decrease from 337 after 1 h of seleniumization to 153 nm at 2.5 and 3.5 h of seleniumization. It was also determined that the RMS of formed layers slightly increases (from 32 to 42 nm) with the prolongation of PA seleniumization (from 1 to 2.5 hours) and it decreases (from 43 to 22 nm) with the increase of the temperature (from 50 °C to 70 °C) of seleniumized PA treatment by the solution containing Cd(II) salt. XPS data show that in coatings, substantial amounts of both cadmium hydroxide (Cd(OH)2) and cadmium oxide (CdO) are formed on the surface and within deeper layers of formed coatings. It was also determined that only a small fraction (～0.1%–2%) of cadmium selenide is present on the surface of formed coating after seleniumization and cadmiumization, while within in the deeper layers the concentrations of both Cd and Se were much higher and the fractions of Cd(OH)2 and CdO decreased.
关键词： SEM,Polyamide,Potassium Selenotrithionate,AFM,Morphology,CdSe-Based Layers
更新于2025-09-19 17:15:36
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Efficient electrochemical detection and extraction of copper ions using ZnSe-CdSe/SiO2 core-shell nanomaterial
摘要： Development of nanostructured materials has received tremendous attention nowadays due to their unique properties and efficacious in wide range of applications. Herein, we present a facile synthesis of ZnSe-CdSe/SiO2 core-shell nanomaterial for pollutants monitoring and environmental remediation purposes. The utility of ZnSe-CdSe/SiO2 core-shell nanomaterial was explored toward electrochemical detection and adsorptive removal of copper ions from aquatic system. Experimental results reveal that both electrochemical detection and adsorption of Cu(II) using ZnSe-CdSe/SiO2 nanomaterial strongly depends on the solution pH, with an optimum pH of 5. Based on the results, the amperometric sensor based on ZnSe-CdSe/SiO2 core-shell nanomaterial modified electrode exhibited a detection limit of 50 μgL?1. Moreover, ZnSe-CdSe/SiO2 core-shell nanomaterial as adsorbent demonstrated high uptake capacity equals to 126.25 mgg?1. Thus, ZnSe-CdSe/SiO2 core-shell nanomaterial can be employed as promising material for several environmental remediation purposes.
关键词： Core-shell,Adsorption,Copper,ZnSe-CdSe/SiO2,Electrochemical Sensor,Nanomaterial,Extraction
更新于2025-09-19 17:15:36
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Quantification of the Photon Absorption, Scattering, and On-resonance Emission Properties of CdSe/CdS Core/Shell Quantum Dots: Effect of Shell Geometry and Volumes
摘要： Reliable quantification of the optical properties of fluorescent quantum dots (QDs) is critical for their photo-chemical, -physical, and -biological applications. Presented herein is the experimental quantification of photon scattering, absorption, and on-resonance-fluorescence (ORF) activities of CdSe/CdS core/shell fluorescent QDs as a function of the shell sizes and geometries. Four spherical QDs (SQDs) with different diameters and four rod-like QDs (RQDs) with different aspect ratios (ARs) have been analyzed using UV-vis, fluorescence, and the recent polarized resonance synchronous spectroscopic (PRS2) methods. All quantum dots are simultaneous absorbers and scatterers in the UV-vis wavelength region, and they all exhibit strong ORF emission in the wavelength regions where the QDs both absorb and emit. The absorption and scattering cross-sections of the CdS shell are linearly and quadratically, respectively, proportional to the shell volume for both the SQDs and RQDs. However, the effects of CdS shell coating on the core optical properties are different between SQDs and RQDs. For RQDs, increasing the CdS shell volume through the length elongation has no effect on either the peak wavelength or intensity of the CdSe core UV-vis absorption and ORF, but it reduces the QD fluorescence depolarization. In contrast, increasing CdS shell volume in the SQDs induces red-shift in the CdSe core peak UV-vis absorption and ORF wavelengths, and increases their peak cross-sections, but it has no effect on the SQD fluorescence depolarization. The RQD ORF cross-sections and quantum yields are significantly higher than their respective counterparts for the SQDs with similar particle sizes (volumes). While these new insights should be significant for the QD design, characterization, and applications, the methodology presented in this work is directly applicable for quantifying the optical activities of optically complex materials where the common UV-vis spectrometry and fluorescence spectroscopy are inadequate.
关键词： quantum dots,CdSe/CdS,photon absorption,shell geometry,scattering,shell volumes,on-resonance fluorescence
更新于2025-09-19 17:13:59
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Thermodynamic Implications of the Ligand Exchange with Alkylamines on the Surface of CdSe Quantum Dots: The Importance of Ligand-Ligand Interactions
摘要： Ligand exchange is a critical step for tuning the properties of quantum dots (QDs), as well as functionalization for wide applications. Previous studies have categorized X-, L- and Z-types of ligands and classified the ligand exchange process accordingly. Many works have investigated the influences of ligand exchange on the optical properties of QDs. To date, however, the thermodynamic implications of ligand exchange are not well understood, and the mechanisms of distinct effects of the ligands of the same type are unclear. To address these issues, ligand exchange reactions of the oleate-capped CdSe QDs with alkylamines of different carbon chain length, namely n-butylamine (C4Am), n-octylamine (C8Am), n-dodecylamine (C12Am), were investigated using 1H nuclear magnetic resonance (1H NMR) spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), et al. 1H NMR studies showed that the equilibrium constants (Keq) for the desorption of the Z-type ligand (cadmium oleate) from the surface of CdSe QDs, as promoted by the L-type ligands (alkylamines), were in the order of C4Am > C8Am > C12Am, presumably highlighting the small steric barrier of ligands with short carbon chain. In addition, the ligand exchange was studied by fluorescence titration at varied temperatures from a perspective of ligand adsorption following the desorption of cadmium oleate. The binding constants were in the order of magnitude of 103 M-1. A “Two-step Ligand Exchange (TSLE)” model was developed to describe the ligand desorption-adsorption process with thermodynamic perspectives. The increased length of the carbon chain brought not only increasing steric barrier but also increasing van der Waals interactions, exhibiting a double-edged sword effect in ligand exchange. The ligand exchange with C8Am contributed the most negative value of ΔH and ΔS since the van der Waals interactions between C8Am and neighboring ligands was stronger than that for C4Am, whereas its steric barrier was weaker than that of C12Am. These demonstrated the importance of ligand-ligand interactions, relatively less documented in the previous studies, besides the predominance of the nanocrystal-ligand interactions. UV-vis absorption spectroscopic and fluorescence lifetime studies further showed that the ligand exchange with all three alkylamines affected optical properties of CdSe QDs to some extent. Powder X-ray diffraction (XRD) and transmission electron microscopic (TEM) results showed that the ligand exchange process basically did not affect the crystal structure and core size of the CdSe QDs. Our work had proposed a conceivable mechanism for ligand exchange, elucidated the thermodynamic implications and provided a reasonable guidance for selection of suitable ligands.
关键词： Quantum dots,Ligand exchange,Thermodynamics,CdSe,Alkylamines
更新于2025-09-19 17:13:59
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CdSe@CdS Dot@Platelet Nanocrystals: Controlled Epitaxy, Mono-Exponential Decay of Two-Dimensional Exciton, and Non-Blinking Photoluminescence of Single Nanocrystal
摘要： Wurtzite CdSe@CdS dot@platelet nanocrystals—a dot-shaped CdSe nanocrystal encased within an epitaxially-grown CdS nanoplatelet—are controllably synthesized with nearly monodisperse size/shape distribution and outstanding photoluminescence (PL) properties. The excellent size/shape control with their lateral to thickness dimension ratio up to 3 to 1 is achieved by systematically studying the synthetic parameters, which results in a simple, tunable yet reproducible epitaxy scheme. This special type of core/shell nanocrystals possess two-dimensional emission dipole with the ab plane of the wurtzite structure. While their near-unity PL quantum yield and mono-exponential PL decay dynamics are at the same level of the-state-of-art CdSe/CdS core/shell nanocrystals in dot shape, CdSe@CdS dot@platelet nanocrystals possess ~2 orders of magnitude lower probability for initiating PL blinking at single-nanocrystal level than the dot-shaped counterparts do.
关键词： dot@platelet nanocrystals,non-blinking,photoluminescence,CdSe@CdS,epitaxy
更新于2025-09-19 17:13:59