Elucidating the role of electron transfer in the photoluminescence of $\mathrm{MoS_{2}}$ quantum dots synthesized by fs-pulse ablation

TL;DR

This study synthesizes MoS2 quantum dots via femtosecond pulsed laser ablation, revealing how electron transfer between phases influences their photoluminescence and optoelectronic properties for potential use in advanced technologies.

Contribution

It uncovers the role of electron transfer between MoS2 and MoO3-x phases in determining the photoluminescence characteristics of the quantum dots.

Findings

Secondary phase MoO3-x causes large Stokes-shift and blue emission.

Electron transfer between phases modulates optoelectronic properties.

Laser parameters control quantum dot optical and structural features.

Abstract

Herein, $\mathrm{MoS_{2}}$ quantum dot (QDs) with controlled optical, structural, and electronic properties are synthesized using the femtosecond pulsed laser ablation in liquid (fs-PLAL) technique by varying pulse-width, ablation power, and ablation time to harness the potential for next-generation optoelectronics and quantum technology. Furthermore, this work elucidates key aspects of the mechanisms underlying the near-UV and blue emission, the accompanying large Stokes-shift, and the consequent change in sample color with laser exposure parameters pertaining to $\mathrm{MoS_{2}}$ QDs. Through spectroscopic analysis, including UV-visible absorption, photoluminescence, and Raman spectroscopy, we successfully unravelled the mechanisms for the change in optoelectronic properties of $\mathrm{MoS_{2}}$ QDs with laser parameters. We realize that the occurrence of a secondary phase, specifically $\mathrm{MoO_{3-x}}$, is responsible for the significant Stokes-shift and blue emission observed in this QDs system. The primary factor influencing these activities is the electron transfer observed between these two phases, as validated by excitation dependent photoluminescence, XPS and Raman spectroscopies.