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

Abstract

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.