BiOBr-assisted hydrothermal synthesis of hierarchical Bi4(GeO4)3/Zn2GeO4 microspheres for optical sensor application

Dual-emitting hierarchical Bi4(GeO4)3/Zn2GeO4 hybrid microspheres have been prepared by a facile one-pot hydrothermal synthesis of Zn2GeO4 with the addition of pre-synthesized BiOBr nanoplates. The phase composition and morphology evolution of the Bi4(GeO4)3/Zn2GeO4 composites are investigated depending on the amounts of BiOBr precursor used in the hydrothermal process. The photoluminescence peaks at 412 and 532 nm for the as-prepared Bi4(GeO4)3/Zn2GeO4 are ascribed to Bi3+ emission and defect-related centers in the Zn2GeO4 component, respectively, and the features show a quenching response toward a temperature increase. The fluorescence intensity ratio (FIR) of Bi3+: 3P1–1S0 (412 nm) to the defect emission center of Zn2GeO4 (532 nm) can be exploited as a self-calibrated temperature index for potential thermometer applications. The maximum relative sensitivity (Sr) is 3.96% °C−1 in the temperature range of 20 °C to 100 °C. This work expands the rational design strategy for controllable particle morphology and structure modulation, and further explores their synergetic distinctive properties and potential optical sensor applications.