Colloidal silver nanoparticles (Ag NPs) of different sizes and shapes with tunable plasmonic absorptions within the entire 400-900 nm range are synthesized by simple photochemical reduction of AgNO3 in presence of a biocompatible polymer, chitosan, by varying the pH of the medium and/or light exposure conditions. Chitosan, a highly cationic and amine terminating polymer, is being used for its unique biocompatible and biodegradable properties for various biomedical applications. Stabilizing different size/shape silver nanoparticles in chitosan by avoiding harmful reducing agents will further enhance the biological significance of chitosan as well as silver nanoparticles. An interesting phenomenon of reversible pH-dependent gelation is observed such that the well-known Ag NP plasmonic absorption at ca. 410 nm is, most unusually, accompanied by additional absorption bands at near-IR wavelengths. This single step method provides a convenient recipe for formation of Ag NPs with tunable shape and size simply by an intricate interplay of pH and light exposure variations. These particles are characterized by UV-Vis, DLS, SEM, TEM and EDAX analyses. Preliminary results showed promising antimicrobial activity in prokaryotic plant pathogenic bacteria, Pseudomonas syringe DC 3000 and Pseudomonas syringe PV maculicola. Studies are in progress to exactly determine the antimicrobial effect depending on size, shape, concentration, and microbe type.

Antimicrobial studies of biocompatible colloidal silver nanoparticles with tunable visible to near-infrared plasmonic absorptions

240th National Meeting (2010)

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