Sunil K. Pillalamarri

Photolithographic synthesis of polyaniline nanofibres

Thin films of polyaniline nanofibres were synthesized using ultraviolet irradiation of aqueous solutions of aniline, nitric acid, and ammonium peroxydisulfate. The parent solution was spin coated on a planar substrate, and allowed to polymerize in the dark for 4–5 min. The substrate was then exposed to ultraviolet light for 6–10 min. Irradiation was carried out either with a frequency-tripled Nd:YAG laser, or with a mercury vapour lamp. The polyaniline fibres and films were characterized with scanning and transmission electron microscopy, and with Fourier transform infrared spectroscopy. Fibres had typical diameters between 20 and 150 nm, and lengths of the order of microns. Bulk polyaniline formed in the unirradiated portion of the samples. Using a masking technique, alternating stripes of bulk polyaniline and polyaniline nanofibres were produced.

Radiolytic Synthesis of Bimetallic Nanoparticles with High Aspect Ratio

Abstract : We present a technique to synthesize high aspect ratio metallic nanostructures based on the radiolysis method. In our experiments, we use gamma rays to irradiate aqueous solutions containing Ag and Pt ions and a water-soluble polymer. The aspect ratio of the nanoparticles is controlled by varying the radiation dose rate, the type of polymer, and the type of counter ions. Transmission electron microscopy shows that wire-like structures composed of grains with a face centered cubic (fcc) structure can be formed with a length of up to 3.5 micrometers and typical diameters between 5 and 12nm. X-Ray absorption spectroscopy shows that Ag and Pt do not form an alloy, but remain segregated.