Surface and Quantum Confinement Effects in ZnO Nanocrystals

Abstract

ZnO nanocrystals are studied using theoretical calculations based on the density functional theory. The two main effects related to the reduced size of the nanocrystals are investigated: quantum confinement and a large surface:volume ratio. The effects of quantum confinement are studied by saturating the surface dangling bonds of the nanocrystals with hypothetical H atoms. To understand the effects of the surfaces of the nanocrystals, all saturation is removed and the system is relaxed to its minimum energy position. Several different surface motifs are reported, which should be observed experimentally. Spin-polarized calculations are performed in the nonsaturated nanocrystals, leading to different magnetic moments. We propose that this magnetic moment can be responsible for the intrinsic magnetism observed in ZnO nanostructures.

Cobalt-doped ZnO nanocrystals: quantum confinement and surface effects from ab initio methods

“…We have already reported the structural and electronic changes in pure ZnO nanocrystals when the surfaces of these nanocrystals were exposed. 43,44 Besides the changes in structure, through the creation of different types of reconstructions, we also observed the appearance of a spontaneous magnetization on the surface of these nanocrystals, which should be responsible for the ferromagnetic signal observed in undoped samples.…”

Surface photovoltage phase spectra for analysing the photogenerated charge transfer and photocatalytic activity of ZnFe2O4–TiO2 nanotube arrays

“…Compared to the bulk band gap value of 1.9 eV, 47 the absorption edge of ZnFe 2 O 4 on the ZFO-TNAs is blue shifted, which might be due to the quantum confinement effect arising from the small size regime. 48,49 The lock-in-based SPV measurements were carried out to explore the photovoltaic properties of the samples; the results (SPV and corresponding phase spectra) for the TNAs are shown in Fig. 4.…”

Defect rich seed mediated growth: a novel synthesis method to enhance defect emission in nanocrystals

“…The solvent used for synthesis was absolute ethanol (Analytical a Calculated using an approximation. 42 b Measured from PLE spectrum (Fig. S5).…”