Sonication-assisted synthesis of gallium oxide suspensions featuring trap state absorption: test of photochemistry

Gallium is a near room temperature liquid metal with extraordinary properties that partly originate from the self-limiting oxide layer formed on its surface. Taking advantage of the surface gallium oxide (Ga2O3), this work introduces a novel technique to synthesize gallium oxide nanoflakes at high yield by harvesting the self-limiting native surface oxide of gallium. The synthesis process follows a facile two-step method comprising liquid gallium metal sonication in DI water and subsequent annealing. In order to explore the functionalities of the product, the obtained hexagonal α-Ga2O3 nanoflakes are used as a photocatalytic material to decompose organic model dyes. Excellent photocatalytic activity is observed under solar light irradiation. To elucidate the origin of these enhanced catalytic properties, the electronic band structure of the synthesized α-Ga2O3 is carefully assessed. Consequently, this excellent photocatalytic performance is associated with an energy bandgap reduction, due to the presence of trap states, which are located at ≈1.65 eV under the conduction band minimum. This work presents a novel route for synthesizing oxide nanostructures that can be extended to other low melting temperature metals and their alloys, with great prospects for scaling up and high yield synthesis.