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

Abstract

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 (S_r) 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.