In this paper, we report the synthesis and antibacterial activity of 4-[(E)-(5-ethyl-1,3,4-thiadiazol-2-yl)diazenyl]phenol-alkanethiol functionalized silver nanoparticle(Ag@Azodye). The synthesised nanoparticles were characterized by UV–Vis absorption spectroscopy, XRD spectra, SEM and TEM analysis. Results showed that the functionalized silver Nanoparticles to be spherical having size 9.5-16 nm, from UV-Vis absorption studies it can be observed that, the azodye undergoes photoisomerisation on the surface of silver nanoparticle upon irradiation of 365 nm UV light. The antibacterial activity of functionalized silver nanoparticles against E. coli was investigated in a nutrient broth supplemented with different concentrations of functionalized silver particles under dark and photo irradiated condition. These particles were found to be an effective bactericide and their activity increased upon irradiation of UVA light.