Liquid metals (LMs) have emerged as promising functional
materials
that combine the properties of both liquid and metal. These characteristics
enabled them to find applications in many fields. However, the LMs
usually can only display a silver-white physical appearance, which
limits their further applications in the fields with the imposition
of stringent requirements for color and aesthetics. Herein, we report
that the surface of LMs was transformed directly from metal to fluorescent
semiconductor layer by an example of eutectic GaInSn (eGaInSn) induced
by thermal oxidation. Specifically, a core–shell structure
is formed from the fluorescent layer and the LMs. The shell endows
the LMs with fluorescence without affecting their interior fluidity
and conductivity. In particular, the formation process as well as
the degree of crystallization, phase transformation, and light emission
of the fluorescent oxide shell on the surface of LMs is regulated
by the component content. A thorough analysis of surface morphology,
composition, structure, and properties of the fluorescent shell suggests
that the Ga2O3 layer is formed on the surface
of gallium-based LMs after their immersion in deionized water. Subsequently,
thermal oxidation results in the formation of the β-Ga2O3 shell on the surface of liquid metals. Importantly,
abundant oxygen vacancies (VO) in β-Ga2O3 as the donors and the gallium vacancies (VGa), gallium–oxygen vacancy pairs (VO–VGa), defect energy levels, and intrinsic defects as the acceptors
enabled the light emission. The fluorescent LMs have promising potential
for flexible lighting and displays, anticounterfeiting measures, sensing,
and chameleon robots.