Quantum Dot Size Effect on the Frontier Molecular Orbital Energies in the Presence of Different Aquatic Environmental Ligands

Abstract

One of the challenging tasks of the century is to clean up the contaminants of the environment by ecofriendly, sustainable and economically adoptable technologies. The application of quantum dots (QDs) is growing rapidly in to the field of nanotechnology. The electronic properties such as the energy of the highest occupied molecular orbital (E HOMO), the lowest unoccupied molecular orbital (E LUMO), the energy gap ΔE are correlated to the size of quantum dots (QDs) such as CdSe in the presence of different ligands. Linear regression equations were developed through statistical analysis using SPSS. In terms of correlation coefficient R 2 , both the size and nature of organic ligand capping affect the E HOMO , E LUMO and ΔE levels of QDs. Among all QDs, CdSe has the strongest correlation between its frontier molecular orbital energy levels with the QDs size. The R 2 value is greater than 0.63 for a regression equation with a coefficient value of −0.17 and a constant of 2.9. This result implies that a unit decrease of size in the range lower than 7 nm would increase the band gap ΔE by 17%. Potential environmental applications of QDs are presented.

Modeling and numerical simulation of electrical and optical characteristics of a quantum dot light-emitting diode based on the hopping mobility model: Influence of quantum dot concentration

“…Density, width, and the center of the Gaussian peak of the host and dopants are necessary to form the Gaussian energy distribution in the EML and can greatly affect the resulting hopping mobility. Based on the results of research on the size and ligand effects on the DOS of CdSe nanocrystals, [57][58][59] we deduce that the QDs used in this study have a Gaussianlike peak in the CB with an energy of E CB = 2.2 eV and a Gaussian-like peak in the VB with an energy of E VB = 5.6 eV. On the other hand, the PVK HOMO and LUMO energy levels are measured [60] at E HOMO = 5.5 eV and E LUMO = 2.2 eV.…”