In situ generated plasmonic silver nanoparticles sensitized amorphous titanium dioxide for ultrasensitive photoelectrochemical sensing of formaldehyde.

Trace concentration of formaldehyde can damage human health and environment. Consequently, it is of great significance to develop an ultrasensitive sensor for its determination. Herein, an ingenious and efficient photoelectrochemical sensor for formaldehyde was constructed by amorphous TiO2 hollow spheres incorporated with Ag+ ions, which were brought about by silica templates etching and then the exchange of Ag+/Na+ ions. The amorphous TiO2 acted as the dual role of Ag+ ion probe carriers and photoelectric materials. Upon exposure to the increased concentration of formaldehyde, the Ag nanoparticles were produced in situ and photocurrent amplification was then achieved in a proportional manner. It is attributed to the injection of hot electrons from plasmonic Ag nanoparticles into the conduction band of amorphous titanium dioxide and enhanced the photocurrent therefore. The linear relationship between 1 and 400 pmol L-1 was resulted from the enhanced photocurrent and the increased concentration of formaldehyde, and the detection limit was 0.4 pmol L-1. Benefited from an in situ and unique sensitization strategy, this PEC sensor exhibited many advantages such as sensitivity, selectivity, cost-effectiveness, convenience of fabrication, low power consumption, and stability.