Ammonia sensing of silver nanoparticles synthesized using tannic acid combined with UV radiation: Effect of UV exposure time

Abstract

Green synthesis of silver nanoparticles were done using silver nitrate as a silver precursor and tannic acid as a reducing agent and a stabilizer with the assistance of UV radiation at room temperature and neutral condition. The aim of this research was to study the effect of UV exposure time on the synthesis and ammonia sensing ability of the obtained nanoparticles; therefore, UV exposure times were varied from 15, 30, 45, 60, 90 to 120 min. The intensities of the characteristic peak at around 370 and 425 nm in UV–vis spectra increased with increasing UV exposure time. The spherical nanoparticles having the diameters in the range of 8–30 nm were revealed by transmission electron microscope and its crystal structure was revealed by HRTEM. After adding ammonia, the color of all synthesized nanoparticles colloids changed from orange-yellow to yellowish-green which can be preliminary observed by the naked eyes. They also exhibited the absorbance peaks at around 320 nm and a decrease in the intensities of the absorbance peaks at 370 and 425 nm. The results suggested that UV exposure time of 60 min used in this system was suitable for synthesizing silver nanoparticles with high sensing ability to ammonia and the detection limit of 100 ppm.