Probing Absolute Electronic Energy Levels in Hg‐Doped CdTe Semiconductor Nanocrystals by Electrochemistry and Density Functional Theory

Abstract

The absolute electronic energy levels in Hg-doped CdTe semiconductor nanocrystals (CdHgTe NCs) with varying sizes/volumes and Hg contents are determined by using cyclic voltammetry (CV) measurements and density functional theory (DFT) -based calculations. The electrochemical measurements demonstrate several distinct characteristic features in the form of oxidation and reduction peaks in the voltammograms, where the peak positions are dependent on the volume of CdHgTe NCs as well as on their composition. The estimated absolute electronic energy levels for three different volumes, namely 22, 119 and 187 nm(3) with 2.7±0.3 % of Hg content, show strong volume dependence. The volume-dependent shift in the characteristic reduction and oxidation peak potential scan can be attributed to the alteration in the energetic band positions owing to the quantum confinement effect. Moreover, the composition (Cd/Hg=98.3/1.7 and 97.0/3.0) -dependent alteration in the electronic energy levels of CdHgTe NCs for two different samples with similar volumes (ca. 124±5 nm(3) ) are shown. Thus obtained electronic energy level values of CdHgTe NCs as a function of volume and composition demonstrate good congruence with the corresponding absorption and emission spectral data, as well as with DFT-based calculations. DFT calculations reveal that incorporation of Hg into CdTe NCs mostly affects the energy levels of conduction band edge, whereas the valence band edge remains almost unaltered.

Electrochemical Tuning of Localized Surface Plasmon Resonance in Copper Chalcogenide Nanocrystals

“…By simultaneous recording absorption spectra and the electric potential of the system we avoid possible rearrangements of the crystal structure, which may happen on a prolonged time scale, and thus exclude additional processes which might affect the plasmon response. Electrochemistry provides powerful approaches to probe semiconductor nanoparticles, although it has been mostly employed to investigate “classical” cadmium chalcogenide-based quantum dots. − Such electrochemical method as cyclic voltammetry is especially useful in studying redox processes in a wide range of different compounds . Our findings indicate that the two chosen types of nanoparticles (Cu 2– x Se and CuS NCs) behave differently upon similar experimental conditions of the measurements.…”

Cyclic voltammetry as a sensitive method for in situ probing of chemical transformations in quantum dots

“…[8][9][10][11][12][13][14][15] Lately, we have demonstrated the applicability of the CV for probing energy levels in Hg-doped CdTe QDs supported by density functional theory calculations. 16 This method is especially sensitive to surface related processes, in particular, to reactions of ligand molecules. To elucidate these processes we compared electrochemical behaviour of the QDs with that of bulk CdTe and Te films under similar conditions.…”