Optical and antibacterial properties of synthesised silver nanoparticles

In the present study, tri-sodium citrate has been used as both the reducing agent and stabiliser for the synthesis of silver nanoparticles (AgNPs). Sodium borohydride (NaBH4) was used in various concentrations. The absorbance of AgNP solution was measured after the addition of NaBH4. The samples were characterised by ultraviolet- visible spectroscopy after 5, 10, 15, 25, 60 and 120 min of synthesis to investigate the stability of AgNPs for different concentrations of NaBH4. Transmission electron microscopy revealed the nanostructure of the prepared samples with average sizes as 18, 20 and 29 nm. Photoluminescence spectra of these AgNPs showed maximum emission at wavelengths 473, 470 and 469 nm, respectively, when excited at 350 nm. Further, Disk diffusion test showed that all the prepared samples are good candidates for antibacterial activity while AgNPs of average size 18 nm were found most effective against the tested Grampositive and Gram-negative