Rishi Pal Chahal

Optical and structural properties of poly(vinyl alcohol) films embedded with citrate-stabilized gold nanoparticles

Hydrosol of Au nanoparticles was prepared by citrate reduction of chloroauric acid. The synthesized nanoparticles were characterized through transmission electron microscopy (TEM) and UV–Visible spectroscopy. The prepared nanoparticles were almost spherical in shape with their mean diameter ~6 nm and possessed face-centred-cubic (fcc) structure. The absorption spectrum of the as-prepared nanoparticles shows the SPR peak at 530 nm in agreement with that predicted from calculations based on Mie theory. These nanoparticles were dispersed in poly(vinyl alcohol) (PVA) using the sol–gel method to prepare PVA–Au nanocomposite films with different concentrations of Au. Optical and structural properties of these nanocomposites were studied using UV–Visible spectroscopy, x-ray diffraction (XRD) and FTIR spectroscopy. The value of optical band gap deduced from the UV–Visible absorption spectroscopy is found to be reduced from 4.98 eV (for pure PVA) to 3.85 eV after embedding 0.074 wt% of Au nanoparticles. Further, the refractive index behaviour for pure PVA and PVA–Au nanocomposite films was studied through transmission and reflection behaviour. The induced structural changes, revealed through XRD and FTIR spectroscopy, are responsible for the observed changes in optical behaviour of PVA after embedding Au nanoparticles in it.

Optical behaviour of swift heavy ions irradiated poly(vinyl alcohol) films

Polyvinyl alcohol films were irradiated to 90 MeV O 6+ and 150 MeV Si 14+ ions at fluence ranging from 1010 to 1012 ions/cm2. The observed changes in optical energy gap of this polymer have been investigated and results are tried to be explained in terms of energy transferred by the incident ions. It has been noticed that the value of optical energy gap decreases with increasing energy loss during the ion–polymer interaction process.

Study of Dielectric Behavior and Charge Conduction Mechanism of Poly(Vinyl Alcohol) (PVA)-Copper (Cu) and Gold (Au) Nanocomposites as a Bio-resorbable Material for Organic Electronics

Poly(vinyl alcohol) (PVA) embedded with varying concentrations of chemically synthesized copper (Cu) and gold (Au) nanoparticles (NPs) were prepared using ex situ sol–gel casting method. The addition of almost the same concentration of CuNPs in PVA improves the conducting properties, while that of AuNPs improves the dielectric nature of composite films. It has been found that addition of AuNPs up to ∼0.4 wt.% concentration enhaneces the capacitive nature due to the formation of small Coulomb tunneling knots as internal capacitors. The dielectric studies suggest the Maxwell–Wagner interfacial polarization as the dominant dielectric relaxation process, whereas the I–V characteristics indicate bulk limited Poole–Frenkel emission at high voltages as the dominant charge transport mechanism operating at room temperature in all specimens. These novel features lead to the conclusion that addition of a small quantity of metal nanoparticles can help tune the properties of PVA for desired applications in bio-compatible polymer-based organic electronic devices.

Synthesis and Characterization of Silver‐Poly(vinyl alcohol) Nanocomposites

Silver nanoparticles were synthesized by chemical reduction of silver salt in water with sodium borohydride as a reducing agent. The optical absorption spectrum shows the presence of characteristic SPR band peaking at ∼400 nm. The size of silver nanoparticles obtained through TEM measurements was found to be 9±2 nm. After embedding silver nanoparticles in PVA matrix, red shift in SPR band has been observed. The positions of SPR band of silver nanoparticles in aqueous medium and PVA matrix were reconstructed using Mie theory and found to be in good agreement with those obtained experimentally.

Photoluminescence and Refractive Index Behaviour of PMMA-PAni Blends

The optical properties of PMMA-PAni blends have been investigated. Increase in intensity of photoluminescence (PL) peak and decrease in refractive index have been observed with increase in the PAni concentration in PMMA-PAni blends prompting the utilization of such materials in various optical applications.

Thermal properties of PMMA doped with Polyaniline

PMMA‐PAni conducting blends have been prepared through solution blending of PMMA with different wt. % concentration of chemically synthesized PAni‐DBSA, taking chloroform as solvent. These blends were characterized through the UV‐Visible and TGA spectroscopy. UV‐Visible spectroscopic results show the interaction of PAni with PMMA. Further, as the concentration of PAni increases, the value of thermal activation energy of blended films increases, leading to the increased thermal stability of PMMA‐PAni blends with increasing concentration of PAni..