Coating of gallium-based liquid metal particles with molybdenum oxide and oxysulfide for electronic band structure modulation.

Liquid metal (LM) droplets are now used in many applications including catalysis, sensing, and flexible electronics. Consequently, the introduction of methods for on-demand alternating electronic properties of LMs is necessary. The active surface of LMs provides a unique environment for spontaneous chemical reactions that enable the formation of thin layers of functional materials for such modulations. Here, we showed the deposition of n-type MoO and MoOS semiconductors on the surface of EGaIn LM droplets under mechanical agitation to successfully modulate their electronic structures. The "liquid solution"-"liquid metal" interaction resulted in the formation of oxide and oxysulfide layers on the surface of LM droplets. The comprehensive study of electronic and optical properties revealed a decrease in the band gap of the droplets after surface decoration with MoO and MoOS, leading to deeper n-type doping of the materials. This method provides a facile procedure for engineering the electronic band structure of LM-based composites when they are necessary for various applications.