Luminescent Zn₂GeO₄:Mn²⁺ Nanoparticles with High Quantum Yield for Salivary Protein Detection

Zinc germanate doped with Mn²⁺ (Zn₂GeO₄:Mn²⁺) is known to be a green luminescence phosphor with many applications in biosensing and bioimaging. This study presents a simple method for creating small size Zn₂GeO₄:Mn²⁺ nanoparticles using a combination of the coprecipitation-molten salt synthesis method. These nanoparticles exhibit bright green luminescence under UV excitation. After surface functionalization, these nanoparticles were then used to develop a fluorescence resonance energy transfer (FRET)-based immunoassay. This immunoassay shows a detection range of 5-20 ng/mL of C-reactive protein (CRP), which suggests its potential for simple solution CRP detection and broader applications in protein biosensing.