The two-photon photochemistry of CdSe quantum dots (QDs) has been systematically studied. We find that upon intense irradiation CdSe quantum dots that absorb two or more visible photons undergo photodarkening. The quantum yield for this process is on the order of 6% in chloroform and much smaller in nonpolar solvents, such as octane. An analysis of the energetics indicates that, following two-photon excitation, the biexciton undergoes an Auger process producing a hot hole. This hot hole is ejected to a surface-bound TOP ligand, forming a QD(-)/TOP(+) contact ion pair that separates in chloroform, but not in octane. The charged and deligated QD is dark, resulting in the overall photodarkening. This photodarkening reaction may or may not be reversible, depending on what other chemical components are in the irradiated solution. The quantum dot concentration dependence and PL decay kinetics indicate that charge recombination occurs rapidly, followed by ligand reattachment and reorganization on a longer (tens of minutes) time scale. The relation of this mechanism to one-photon photochemistry is also discussed.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1021/acsnano.5b04710 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Landau-Levich Scaling for Optimization of Quantum Dot Layer Morphology and Thickness in Quantum-Dot Light-Emitting Diodes.
ACS Nano
January 2025
Department of Chemical and Biomolecular Engineering, Lehigh University, 124 E. Morton Street, Bethlehem, Pennsylvania 18015, United States.
Quantum dot (QD) light-emitting diodes (QLEDs) are promising candidates for next-generation displays because of their high efficiency, brightness, broad color gamut, and solution-processability. Large-scale solution-processing of electroluminescent QLEDs poses significant challenges, particularly concerning the precise control of the active layer's thickness and uniformity. These obstacles directly impact charge transport, leading to current leakage and reduced overall efficiency.
View Article and Find Full Text PDFPhotodegradation of aqueous tetracycline using CuS@TiO₂ composite under solar-simulated light: Complete mineralization, catalyst efficiency, and reusability.
Heliyon
January 2025
Department of Chemistry, An-Najah National University, Nablus, Palestine.
While CuS/TiO₂ has been previously synthesized and employed in a limited number of photodegradation studies, the current study investigated its effectiveness for TC degradation under UV-visible light irradiation. CuS is known to be a nontoxic, environmentally friendly material; hence, it has great potential as an alternative to CdS and CdSe, which are used conventionally as sensitizers. In this work, the CuS/TiO₂ photocatalysts achieved a maximum 95 % removal of TC at an initial concentration of 20 ppm, confirming the good utilization of active sites.
View Article and Find Full Text PDFpH is an important physiological parameter within organisms, playing a crucial role in functional activities in cells and tissues. Among various pH sensing methods, optical fiber pH sensors have gained a wide attention due to their unique advantages. However, current silica optical fiber-based pH sensors face some challenges such as weak biocompatibility, low biological safety, complex or unstable surface modification.
View Article and Find Full Text PDFResearch Progress on Quantum Dot-Embedded Polymer Films and Plates for LCD Backlight Display.
Polymers (Basel)
January 2025
College of Engineering and Applied Sciences, Nanjing University, Nanjing 210023, China.
Quantum dot-polymer composites have the advantages of high luminescent quantum yield (PLQY), narrow emission half-peak full width (FWHM), and tunable emission spectra, and have broad application prospects in display and lighting fields. Research on quantum dots embedded in polymer films and plates has made great progress in both synthesis technology and optical properties. However, due to the shortcomings of quantum dots, such as cadmium selenide (CdSe), indium phosphide (InP), lead halide perovskite (LHP), poor water, oxygen, and light stability, and incapacity for large-scale synthesis, their practical application is still restricted.
View Article and Find Full Text PDFThe Temperature-Dependent Tight Binding Theory Modelling of Strain and Composition Effects on the Electronic Structure of CdSe- and ZnSe-Based Core/Shell Quantum Dots.
Materials (Basel)
January 2025
Nanoscience and Nanoengineering Programme, İstanbul Technical University, Maslak Campus, İstanbul 34469, Turkey.
We propose a temperature-dependent optimization procedure for the second-nearest neighbor (2NN) * tight-binding (TB) theory parameters to calculate the effects of strain, structure dimensions, and alloy composition on the band structure of heterostructure spherical core/shell quantum dots (QDs). We integrate the thermoelastic theory of solids with the 2NN * TB theory to calculate the strain, core and shell dimensions, and composition effects on the band structure of binary/ternary CdSe/Cd(Zn)S and ZnSe/Zn(Cd)S QDs at any temperature. We show that the 2NN * TB theory with optimized parameters greatly improves the prediction of the energy dispersion curve at and in the vicinity of L and X symmetry points.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!