Highly Proton Conductive Poly(vinyl acetate)/Nafion® Composite Membrane for Proton Exchange Membrane Fuel Cell Application.

A novel blend of membranes made of cast Nafion® and poly(vinyl acetate) (PVAc) was prepared and its proton conductivity and ion exchange capacity (IEC) were characterized to investigate its applicability in proton exchange membrane fuel cells (PEMFCs). The intermolecular interactions and morphology of these membranes were assessed using Fourier-transform infrared spectroscopy (FT-IR) and field-emission scanning electron microscopy (FE-SEM). A twofold increase in the proton conductivity is observed for the PVAc/Nafion® composite membrane (2 × 10-2 Scm-1) compared to that of cast Nafion® (1.1 × 10-2 Scm-1). In addition to that, the composite membranes exhibited better mechanical strength and adequate water retention ability as well as IEC comparable to that of cast Nafion®. The thermal property and chemical degradation property were also investigated. The results indicate that the introduction of PVAc as a modifier played a vital role in improving the membrane performance. Accordingly, these polymer electrolyte membranes with suitable PVAc contents have prospect for use in low-temperature PEMFCs.

Physical and Antibacterial Properties of Gold-Poly(ethyl methacrylate) Nanocomposites Prepared by In-Situ Polymerization.

In this paper, the physical and antimicrobial properties of gold-poly(ethyl methacrylate) nanocomposites (Au-PEMA) are evaluated. Characterization of gold nanoparticles was carried out based on UV-Vis spectroscopy and transmission electron microscopy (TEM). The specimens were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscope (FE-SEM). We identified the thermal stability of Au-PEMA nanocomposites and the inhibitory effect of live bacterial attachment of Au-PEMA nanocomposites against S. mutans was also evaluated.

Antifungal and physical characteristics of modified denture base acrylic incorporated with silver nanoparticles.

OBJECTIVE: This study evaluated the antifungal and physical characteristics of denture base acrylic combined with silver nanoparticles. MATERIALS AND METHODS: Polymerized denture acrylic disc specimens containing 0 (control), 1.0, 5.0, 10.0, 20.0 and 30.0 wt% of silver nanoparticles were placed on separate culture plate dish and 100 ìL samples of yeast suspension of Candida albicans strain were inoculated on each specimens and incubated at 37°C, for 24 h. The antifungal effects were evaluated as a number of viable cells in retrieved fungal suspension. To characterize physical aspects, specimens were tested for elution of silver cation (Ag(+)) at 24 h and 30th day, thermal analysis (TG/DTA), scanning electron microscope and energy dispersed X-ray analysis (SEM/EDX) and color stability. RESULTS: Significant reduced CFU was exhibited at 20.0 and 30.0 wt% of silver nanoparticles incorporated (p < 0.01) and Ag(+) elution from specimens (maximum 0.356 ± 0.11 mg/L) contributed little to the antifungal activity considering MIC of Ag(+) in this study (3.0 mg/L). The successful synthesis of modified denture acrylic containing silver nanoparticles was accessed by TG/DTA and EDX analysis. CONCLUSION: The modified denture base acrylic combined with silver nanoparticles displayed antifungal properties and acted like latent antifungal material itself with low-releasing Ag(+), however, the improvement of poor color stability was still required.

Surface-enhanced Raman spectroscopy of omethoate adsorbed on silver surface.

We have investigated surface-enhanced Raman spectroscopy (SERS) spectrum of Omethoate (O,O-dimethyl-S-methylcarbamoylmethylthiophosphate). It is found significant signals in the ordinary Raman spectrum for solid-state Omethoate as well as strong vibrational signals absorbed on the silver sol surface which is prepared by γ-irradiation technique at a very low concentration. Effects of pH and anions (Cl-, Br-, I-) on the adsorption orientation are investigated as well. Two different adsorption mechanisms are deduced, depending on the experimental conditions. The sulfur atom or the sulfur and two oxygen atoms are adsorbed onto the silver sol surface. Among halide ions, Br- and I- are more strongly adsorbed onto the silver sol surface. As a result, the adsorption of Omethoate is less effective due to their steric hindrance.

Comparison of the adsorption orientation for 2-mercaptobenzothiazole and 2-mercaptobenzoxazole by SERS spectroscopy.

In this study, the adsorption orientation for 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzoxazole (MBO) on to silver mirror and silver sol substrates have been studied by surface enhanced Raman scattering (SERS). The MBT and MBO were chemisorbed on both silver mirror and silver sol after deprotonation with a tilted orientation to the silver surfaces. The surface enhanced properties of MBT and MBO showed that the substrate of silver mirror was superior to the sliver sol. The SERS spectra of MBT and MBO revealed that both of the MBT and MBO were adsorbed on silver surfaces strongly by a common sulfur molecule and a sulfur atom from MBT and an oxygen atom from MBO. Therefore, the adsorption orientation of MBT and MBO was little tilted perpendicularly to the silver surfaces. The adsorption geometry did not undergo any significant changes in acidic and basic solutions. It showed that the adsorption orientation for MBT and MBO were stable in the both solutions.