Controllable Doping for Tunable and Multimodal Emission in ZnS-Based Mechanoluminescent Nanocrystals

Scaling mechanoluminescent materials to the nanoscale enhances their potential for biomedical applications due to improved sensitivity, resolution, and biocompatibility. Here, we report a versatile strategy for synthesizing wavelength-tunable mechanoluminescent ZnS nanocrystals doped with Ag⁺, Cu²⁺, or Mn²⁺. The method involves coassembly of ZnS and metal sulfide nanocrystals within silica nanoreactors, followed by high-temperature calcination to induce solid-state doping and phase transformation. The resulting ZnS:Ag⁺, ZnS:Cu²⁺, and ZnS:Mn²⁺ nanocrystals exhibit focused ultrasound-induced mechanoluminescence at 480, 500, and 585 nm, respectively. Notably, ZnS:Ag⁺ also shows photoluminescence and afterglow upon UV excitation. The luminescence intensity is highly dependent on Ag⁺ concentration, with 0.15% yielding the optimal emission. These nanocrystals were further applied to stimulate neuronal cells, successfully inducing action potentials. This work highlights a scalable, dopant-tunable approach for fabricating multimodal luminescent nanomaterials with strong potential for noninvasive sono-optogenetic neuromodulation.