PH Effect on Characteristics and Ammonia Sensing of Silver Nanoparticles Synthesized in the Presence of Tannic Acid

Abstract

Silver nanoparticles were synthesized using silver nitrate as a silver precursor in the presence of tannic acid under UV radiation for 60 minutes. Various pH conditions were employed in the synthesis in order to study its effect on characteristics and ammonia sensing of the synthesized nanoparticles. The images obtained from transmission electron microscope revealed the formation of the spherical particles with average diameters in the range of 10-40 nm depending on pH conditions. It was found that using acidic condition resulted in yellow silver nanoparticles colloids with bigger particles and exhibiting a UV-visible absorbance peak at around 435 nm whereas using other conditions yielded greenish-yellow colloids with smaller particles and having two absorbance peaks at around 370 and 430 nm. After adding 100 ppm of ammonia, TEM images revealed the aggregation and the changes in size and shape of the silver nanoparticles. The color of the silver nanoparticles colloids synthesized using acidic condition changed to orange-yellow color. However, other pH conditions caused the color of the colloids became darker. These color changes were observed by the naked eyes.