Advanced Materials Research Vol. 938

Abstract: Lot of research is going on to develop materials suitable for absorbing sound and reducing noise. By virtue of their superior vibration damping capability and attractive characteristics such as visco elasticity, simple processing and commercial availability, polyurethane foams are extensively applied not only in automotive seats but also in various acoustical parts. However, the sound absorption coefficient of polyurethane foams is high (0.8 1.0) in high frequencies in the range 300 to 10000Hz while it is found to be low (0 to 0.5) at low frequencies (10 to 200 Hz). In this study new polyurethane based porous composites were synthesized by in situ foam rising polymerization of polyol and diisocyanate in the presence of fillers such as nanosilica (NS) and nanoclay (NC). The effect of these fillers at various concentrations up to 2% was studied for sound absorption characteristics in the frequency range 100-200Hz. Sound absorption coefficient was determined using standing wave impedance tube method. The sound absorption coefficient of filled PU foams increases from 0.5 to 0.8 with frequency increase from 100 to 200 Hz at higher content of the nanofillers employed. This research work is further extended to study the sound absorption capacity of unfilled PU foam with varying thickness and also hybrid foams with woven glass (GFC) and polyester cloth (PEC). The unfilled foam with 60mm of thickness gives sound absorption value same as that of 15mm of filled foam. Further enhanced absorption value is achieved with PU/NS-GFC hybrid. The results obtained are explained based on the porosity of composite structure and foam cell size.Key words Polyurethane foam, sound absorption coefficient, nanosilica, nanoclay, low frequency sound.

Abstract: A novel Cadmium selenide Quantum dots MWCNTs nanocomposite modified electrode was achieved by simple drop casting method and its application towards the quantitative determination of epinephrine. The Cadmium selenide Quantum Dots was characterized by transmission electron microscopy and MWCNT was characterized by scanning electron microscopy. The electrochemical characteristics of the modified electrode were studied using cyclic voltammetry. The voltammetric response of the modified electrode was higher than that of the MWCNT and bare electrodes. The modified electrode exhibits excellent electrocatalytic activity towards the oxidation of epinephrine by enhancing its oxidation current in 0.1M phosphate buffer solution. The determination range of epinephrine is from 0.16 μM to 14 μM and the detection limit was 0.05 μM (S/N = 3). The proposed modified electrode exhibited good stability and reproducibility.

Abstract: A single step method for the synthesis of gold nanoparticles decorated graphene oxide nanocomposite using aniline as reducing agent has been developed. The composite was characterized using FE-SEM, UV-Vis and FT-IR and XRD analysis. The electron transfer behavior of the modified electrodes was investigated in a redox probe using cyclic voltammetry. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to evaluate the electrochemical properties of AuNPs/GO/GCE towards the electrochemical oxidation of tryptophan. A calibration graph was constructed by plotting the concentration of tryptophan against the peak current. Under the optimum experimental conditions, the oxidation peak currents were measured by varying the tryptophan concentrations. The resulting sensor displays an excellent repeatability and long-term stability.

Abstract: The nickel hexacyanoferrate decorated titanium oxide nanotube (NiHCF@TNT) was prepared by ion exchange method by mixing of nickel ion modified titanium oxide nanotube with a known amount of potassium ferricyanide under stirring over a period of 5 h. The resulting product was isolated and then characterized with XRD, FT-IR and SEM. The electrochemical behaviour of NiHCF@TNT was investigated by cyclic voltammetry using chitosan as stabilizing agent. The electrocatalytic property of chitosan protected NiHCF@TNT was carried out on electrochemical oxidation of paracetamol and caffeine simultaneously. The proposed method may be applied for the electrochemical detection of paracetamol in drug samples. _______________________________________________________________________________

Abstract: Multi-walled carbon nanotubes (MWCNTs)-Polyvinylidene fluoride (PVDF) superhydrophobic coatings were prepared by a facile phase separation and spray coating method. The effect of phase separation and stirring on wettability has been studied. A transformation of hydrophobic to super-hydrophobic state is achieved with increasing CNT content. In the absence of CNTs, the neat PVDF coatings exhibited water contact angle (WCA) of 105^o. A gradual increase in WCA is observed with increasing addition of CNTs, and reaches to super-hydrophobic state (WCA > 150^o) for CNT content of 33%. FTIR studies revealed a stronger interaction between PVDF and CNT with increasing stirring time. FESEM images and EDAX data show uniform morphology and higher fluorine content, respectively for samples stirred for longer time when compared to shorter stirring time, and the results are discussed in detail.

Abstract: In this study, we demonstrate dielectric properties of Natural rubber-TiO₂ (NR-TiO₂) nanocomposite. We fabricated a device by sandwiching NR-TiO₂ nanocomposite between two different work function electrodes aluminium and Indium Tin Oxide (ITO). Capacitance versus voltage analysis showed a nonlinear behavior as that of an organic Schottky diode. Variation of real and imaginary part of dielectric constant with different frequencies was studied by using Electrochemical Impedance spectroscopy (EIS). Validity of the impedance data was evaluated by using theoretical Kramers-Kronig relations and the obtained results showed an acceptable match with high degree of consistency.

Abstract: High temperature superconducting (SC) 2212 BiSrCaCuO nanoparticles were prepared by Sol-Gel method. Precursor was characterized by X-ray diffraction (XRD) and scanning Electron micrography. The superconductor nanocomposites were fabricated by nanoparticles of the SC powder with NR/LLDPE blends. The superconductive properties of the sintered samples and the nanocomposites were studied. Transition to a superconducting state around 88K appeared in the parent sample and in the composites. The scanning electron microscopic investigation of the nanostructures of SC polymer ceramic nanocomposites shown nanoscale dispersion of BSCCO in the polymer phase uniformly.

Abstract: Bismuth sulfide(Bi₂S₃) nanorods(NRs) decorated on uniform shape carbon sphere(CS)have been prepared by hydrothermal method, using single source precursorpolyvinyl pyrrolidone(PVP) as a capping agent. The nanoparticles were synthesized with different ratio of capping agent at different temperatures.The prepared nanoparticles were characterized by FTIR spectroscopy,thermo gravimetric and differential thermal analysis. The crystallinity, morphology and elemental composition of the synthesized nanocrystals have been confirmed through X-ray diffraction (XRD), HRSEMand EDX. The electrochemical catalytic activity on the reduction of catechol of the synthesized Bi₂S₃ NRs has been investigated.The electrocatalytic oxidation of catechol done with Bi₂S₃NRs coated CS/GCE modified by using CV and the effect of the scan rate also studied. The modified nanocomposites Bi₂S₃NRs on CS in GCE are act as a good sensor by detection of catechol in ultra trace level by using DPV techniques.

Abstract: Polyaniline (PANI) Nanocomposites are potential materials for actuators, EMI shielding, Fuel cells and components in non volatile memory. Silver nanoparticles have wide range of applications such as catalysis, microelectronics, biotechnology and silver-oxide batteries. This work reports the effect of thermal alteration [lowhigh temperatur on the electrical conductivity of green synthesized silver (Ag) nanoparticles-polyaniline composite. A simple low cost green synthesis using Azadirachta indica [Neem] extract is employed for synthesis of silver nanoparticles; Polyaniline is prepared by redox polymerization of aniline using ammonium per sulphate. The silver nanoparticles are incorporated into Polyaniline during polymerization. PANI and PANI-Ag composites are characterized by FTIR, UV-Vis, TGA, XRD, TEM and DC conductivity. The DC conductivity and UV-Vis spectral response were recorded for the samples at low temperatures [263K, 273K, and 283 and high temperatures [353K, 433K, and 533. The effect of thermal alteration showed a significant change in both conductivity and UV-Vis spectral response. UV-visible spectra show the transition occurring in PANI Emeraldine salt phase to Pernigraniline with increase in temperature. TGA analysis confirms the improved thermal stability for PANI-Ag composite. The mechanism of electrical conductivity with temperature in the system is investigated and reported. Thus, this work deals with an approach to analyze the electrical behavior of green synthesized silver nanoparticles composited with a conducting polymer. The results show that these composites can be suitable for temperature dependent semiconductors, bio sensors and catalytic reactions.

Abstract: Nanobiotechnology is a multidisciplinary branch of nanotechnology which includes fabrication of nanosized materials using biological approaches. Highly structured metallic and metal sulfide nanoparticles have been reported to be synthesized by numerous bacteria, fungi, yeasts and viruses. However, biosynthesis of nanoparticles by Haloarchaea (salt-loving archaea) of the third domain of life, Archaea, is in its nascent stages. In this study, we report the intracellular synthesis of stable, mostly spherical silver nanoparticles (SNPs) by the haloarchaeal isolate Halococcus salifodinae BK6. The isolate adapted to silver nitrate was found to exhibit growth kinetics similar to that of cells unexposed to silver nitrate. The nitrate reductase enzyme assay and the enzyme inhibitor studies showed the involvement of NADH dependent nitrate reductase in silver tolerance, reduction, and synthesis of SNPs. UV visible spectroscopy, XRD, TEM and EDAX were used for characterization of SNPs. The XRD exhibited characteristic Bragg peaks of face centered cubic silver with crystallite domain size of 26 nm and 12 nm for SNPs synthesized in NTYE and halophilic nitrate broth, respectively. TEM analysis exhibited an average particle size of 50.3 nm and 12 nm for SNPs synthesized in NTYE and halophilic nitrate broth (HNB), respectively. The as synthesized SNPs exhibited antimicrobial activity against both Gram positive and Gram negative organisms.