Ag photoionization-induced single-pass assembly of Ag2S nanodots in flowing thiol droplets

Photoinduced assembly of Ag2S nanodots with surface thiolates was achieved in a single-pass gas stream configuration. Ag nanoagglomerates were converted into aligned Ag2S nanodots without hydrothermal reaction, separation, or purification procedures. The proposed route to fabricate hybrid nanodroplets containing Ag nanoagglomerates and 1-hexanethiol resulted in electrostatic interactions between Ag surfaces and thiol groups to assemble Ag2S nanodots. Photoirradiation (185 nm wavelength UV light) onto the nanodroplets induced electron detachments from Ag via photons (photon energy: 6.2 eV) reaching the Ag (work function: 4.3 eV) surfaces. The positively charged Ag surfaces interacted with the negatively charged surrounding thiol groups, resulting in the formation of Ag2S nanodots. Continuous photoirradiation for 6.4 s resulted in complete phase transfer; thus, inducing the isolation of the nanodots (i.e., resulting in an aligned structure of the nanodots without random aggregation) by conjugated surface thiolates. The nanodots were stably dispersible for near-infrared-radiation-induced fluorescence bioimaging without significant cytotoxic effects; furthermore, merging the nanodots with TiO2 nanoparticles significantly enhanced photocurrent generation under simulated solar irradiation. The photoinduced assembly demonstrates a new feasible safe-by-design platform to continuously produce photoresponsive nanodots without optimization concerning chemically efficient and environmentally benign concepts.