Light-triggered reversible change of the electronic structure of MoO3 nanosheets via an excited-state proton transfer mechanism

Under supervision of Prof. Nadav Amdursky

In recent years, there has been an increasing interest in the development of light stimuli-responsive chemical systems, enabling control over chemical and physical processes. The processes we are after are related to the electronic structure, specifically, the redox state and the formation of a localized surface plasmonic resonance (LSPR), of molybdenum oxide (MoO3) nanostructures, which are important for a wide array of applications. We use light as a gating source for the control of the electronic properties in such nanostructures upon the excitation of pyranine (HPTS) that is used as a photoacid. We show that the excitation of HPTS triggers the initiation of the LSPR peak, associated with the reduced state of the MoO3-x nanosheets, and most importantly, in the absence of light, the LSPR peak disappear and the nanosheets return to their oxidized form, MoO3, in a reversible manner. We ascribe our finding to an excited-state proton transfer from HPTS to MoO3, a process that can control the reduction of the nanosheets, thus the formation of LSPR, resulting also in a change in the nanosheets size and morphology.