Fluorescence decay dynamics of surface-functionalized nanoparticles

We report the fluorescence decay dynamics of surface-functionalized nanoparticles (NPs), poly(ethylene glycol) bis(carboxymethyl) ether coated LaF$_{3}$: Ce,Tb and thioglycolic acid coated ZnS:Mn, in solution and also in the surface-bound phase. The NPs exhibited high quantum yield and multi-component decays, and of average lifetime of 20-130 microseconds in solution, but 10-60 microseconds in the bound phase depending on the solid substrates. Our results suggest that the coated ZnS:Mn nanoparticles hold great promise as a non-toxic labeling agent for ultra-sensitive, time-gated, trace biomaterials detections in nano-forensic applications.