Electronic Properties of MoS₂ Nanoparticles

TLDR

The study aims to explain the size‑dependent photoluminescence and STM spectra of MoS₂ nanoparticles and to propose design strategies for direct‑gap 3D layered particles or Mo‑doped metallic nanowires. The authors use first‑principles theoretical calculations to model the electronic structure of MoS₂ nanoparticles and predict how size, layer stacking, and interlayer distance affect their properties. The results show that single‑sheet MoS₂ nanoparticles up to ~3.4 nm exhibit no quantum confinement and are dominated by surface states, while in 3D particles the band gap and photoluminescence vary with the number of layers and their spacing, allowing the engineering of direct‑gap clusters and metallic nanowires with catalytic and thermoelectric functions.

Abstract

We present a first principle, theoretical study of MoS2 nanoparticles that provides a unified explanation of measured photoluminescence spectra and recent STM measurements as a function of size. In addition, our calculations suggest ways to engineer the electronic properties of these systems so as to obtain direct band gap 3D layered nanoparticles or Mo doped metallic nanowires. In particular, we show that single sheet MoS2 nanoparticles up to ∼3.4 nm show no appreciable quantum confinement effects. Instead, their electronic structure is entirely dominated by surface states near the Fermi level. In 3D nanoparticles, we found a strong dependence of their electronic properties on layer stacking and distance, and we suggest that the observed photoluminescence variation as a function of size originates from the number of planes composing the system. The number of these planes and their distance can be tuned to engineer clusters with direct band gaps, at variance with the bulk. Our results also suggest ways to take advantage of surface states to design metallic nanowires with novel catalytic and thermoelectric properties.