Application of single-entity electrochemistry for ultraviolet detection using photoreduced silver nanoparticles

As an application of single-entity electrochemistry (SEE), ultraviolet (UV) detection by SEE of single silver (Ag) nanoparticles (NPs) has been conducted. In this study, silver chloride (AgCl) NPs are converted to Ag NPs through UV irradiation, catalyzed by citrate. The oxidation current of the photoreduced Ag NPs are detected using SEE, exhibiting variations dependent on the UV wavelength and irradiation time. AgCl NPs exposed to light at wavelengths of 600 and 730 nm do not produce any current signal in the SEE measurement. However, at wavelengths of 254 and 365 nm, current signals are observed for SEE, with the signal frequency increasing with longer irradiation times. Frequency analysis of the signal reveals a significant difference between irradiation at 254 and 365 nm, indicating that the photoreduction rate of AgCl NPs irradiated at 254 nm is approximately 34 times faster than at 365 nm. These findings demonstrate the feasibility of applying SEE to study photoreaction characteristics and underscore the potential application of SEE in fabricating ultra-small UV sensors using minimal NP solution