Highly Porous Polypyrrole (PPy) Hydrogel Support for the Design of a Co-N-C Electrocatalyst for Oxygen Reduction Reaction.

Atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts have emerged as one of the most promising platinum-group metal (PGM)-free cathode catalysts for oxygen reduction reaction (ORR). Among the various approaches to enhance the ORR performance of the catalysts, increasing the density of accessible active sites is of paramount importance. Thus, nitrogen-rich support with abundant porosity can be very propitious. Herein, we report a highly porous polypyrrole (PPy) hydrogel as a versatile support for the facile design of a Co-N-C electrocatalyst for ORR. The resulting Co-N-C catalyst with abundant micro- and mesoporous combinations demonstrates a half-wave potential (E1/2) of 0.825 V vs reversible hydrogen electrode (RHE) in O2-saturated 0.1M KOH with just 2.1 wt % Co content. The ORR performance reduces only 11 mV (E1/2) after 5000 cycles of accelerated durability test (ADT), portraying its excellent stability. The catalyst retains ≈83% of its original current during a short-term durability test at 0.8 V vs RHE for 25 h. Furthermore, the catalyst shows electron transfer approaching ≈4 with low H2O2 yield in the potential range 0.5-0.9 V vs RHE. This work provides a simple design strategy to synthesize M-N-C catalysts with increased accessible active site density and enhanced mass transport for ORR and other electrocatalytic applications.

Nanoporous imprinted polymers (nanoMIPs) for controlled release of cancer drug.

In this article, a new approach to directly synthesize drug molecule imbedded in the nanometer sized polymer particles is reported. Molecular imprinting is used to prepare polymers for drug specific for selectively loading of a desired drug. Computer simulations were performed to provide mechanistic insights on the binding modalities of model cancer drug, amygdalin with the polymer precursors. Controlled release of amygdalin from nanoMIPs was studied in vitro cell test and monitoring the absorbance at λem of 390 nm by fluorescence. The nanoparticles imprinted with amygdalin (nanoMIPs) showed high drug loading (0.98 mg g-1) and also releases drug in a controlled way without burst release. The polymer releases amygdalin 0.095 µg (5 min), 0.120 µg (30 min), 0.180 µg (180 min), 0.205 µg in 300 min in de-ionized water and similar pattern of release was observed in buffer 2 and 7. The sustained release of drug from nanoMIPs follows Fickian diffusion; and uniformity in nanoMIPs size have significant impact on release of drug. Swelling of nanoMIP is one of the dominant factors influencing the drug release patterns. The imprinting procedure and the studies reported in this study would be highly useful in future for cancer drug administration.

Growth, structural and optical characterization of wurtzite GaP nanowires.

Bulk gallium phosphide (GaP) crystallizes in the zinc-blende (ZB) structure and has an indirect bandgap. However, GaP nanowires (NWs) can be synthesized in the wurtzite (WZ) phase as well. The contradictory theoretical predictions and experimental reports on the band structure of WZ GaP suggest a direct or a pseudo-direct bandgap. There are only a few reports of the growth and luminescence from WZ and ZB GaP NWs. We first present a comprehensive study of the gold-catalyzed growth of GaP NWs via metalorganic vapor phase epitaxy on various crystalline and amorphous substrates. We optimized the growth parameters like temperature, pressure and reactant flow rates to grow WZ GaP NWs with minimal taper. These wires were characterized using electron microscopy, x-ray diffraction, Raman scattering and photoluminescence spectroscopy. The luminescence studies of bare GaP NWs and GaP/AlGaP core-shell heterostructures with WZ- and ZB-phase GaP cores suggest that the WZ-phase GaP has a pseudo-direct bandgap with weak near-band-edge luminescence intensity.

Growth of high-quality Bi2Sr2 CaCu2O8+δ whiskers and electrical properties of resulting exfoliated flakes.

In this work, we demonstrate a simple technique to grow high-quality whiskers of Bi2 Sr2 CaCu2 O8+δ - a high T c superconductor. Structural analysis shows the single-crystalline nature of the grown whiskers. To probe electrical properties, we exfoliate these whiskers into thin flakes (~50 nm thick) using the scotch-tape technique and develop a process to realize good electrical contacts. We observe a superconducting critical temperature, T c , of 86 K. We map the evolution of the critical current as a function of temperature. With 2-D materials emerging as an exciting platform to study low-dimensional physics, our work paves the way for future studies on two-dimensional high-T c superconductivity.

Central dopaminergic system plays a role in the analgesic action of paracetamol: Preclinical evidence.

OBJECTIVE: Even after 100 years of discovery, the exact mechanisms for the analgesic action of paracetamol are under scanner. It was recently proposed that paracetamol may act through different mechanisms, especially altering the serotoninergic system. The main objective of this preclinical study was to verify the role of drugs modulating dopaminergic system (l-dopa, bromocriptine, olanzapine) on the analgesic effect of paracetamol. MATERIALS AND METHODS: Thirty adult male albino mice were divided into five groups: distilled water (0.5 ml/25 g), paracetamol (200 mg/kg), levodopa (10 mg/kg) + paracetamol, bromocriptine (5 mg/kg) + paracetamol (200 mg/kg), and olanzapine (2 mg/kg) + paracetamol (200 mg/kg). All drugs were administered orally for 14 days. Eddy's hot plate and tail immersion tests were used to determine analgesic activity. Tests were conducted 1 h after the drug administration on the 14th day. After that, animals were sacrificed and brains were dissected out, to measure the levels of dopamine. Statistical comparisons among the groups were performed by one-way analysis of variance followed by Tukey-Kramer test. RESULTS: Coadministration of l-dopa and bromocriptine with paracetamol increased the antinociceptive activity of paracetamol significantly, whereas coadministration of olanzapine with paracetamol decreased the analgesic activity of paracetamol in the Eddy's hot plate and tail immersion tests considerably. There was a significant increase (P < 0.001) in the levels of dopamine in the brains of mice, which received levodopa, bromocriptine, and paracetamol. However, it was opposite in the brains of animals which received olanzapine. CONCLUSION: The results suggest that analgesic action of paracetamol is influenced by dopaminergic system.

The Mechanism of Ni-Assisted GaN Nanowire Growth.

Despite the numerous reports on the metal-catalyzed growth of GaN nanowires, the mechanism of growth is not well understood. Our study of the nickel-assisted growth of GaN nanowires using metalorganic chemical vapor deposition provides key insights into this process. From a comprehensive study of over 130 nanowires, we observe that as a function of thickness, the length of the nanowires initially increases and then decreases. We attribute this to an interplay between the Gibbs-Thomson effect dominant in very thin nanowires and a diffusion induced growth mode at larger thickness. We also investigate the alloy composition of the Ni-Ga catalyst particle for over 60 nanowires using energy dispersive X-ray spectroscopy, which along with data from electron energy loss spectroscopy and high resolution transmission electron microscopy suggests the composition to be Ni2Ga3. At the nanowire growth temperature, this alloy cannot be a liquid, even taking into account melting point depression in nanoparticles. We hence conclude that Ni-assisted GaN nanowire growth proceeds via a vapor-solid-solid mechanism instead of the conventional vapor-liquid-solid mechanism.

Novel molecularly imprinted polymeric microspheres for preconcentration and preservation of polycyclic aromatic hydrocarbons from environmental samples.

Molecularly imprinted polymer (MIP) microspheres with diameters in the range 60-500 µm were synthesized in a continuous segmented flow microfluidic reactor and used as packing material for microtraps for the selective separation of benzo[a]pyrene (BAP) from environmental aqueous samples. The synthesis involved the pumping of monodisperse droplets of acetonitrile containing methacrylic acid as the functional monomer, BAP as a template, and ethylene glycol dimethacrylate as the cross-linking monomer into the microchannels of the microfluidic reactor. The microspheres showed high adsorption capacity and selectivity for BAP in aqueous solutions; both are important for the environmental monitoring and analysis of BAP. The adsorption capacity for BAP of the smallest MIP microspheres (size range 60-80 µm), prepared as part of this study, was 75 mg g(-1) in aqueous solutions; furthermore, this adsorption capacity was close to 300 % higher than that of commercially used activated carbon. Microtraps packed with MIP retained BAP intact for at least 30 days, whereas microtraps packed with activated carbon for BAP showed 40 % reduction in BAP concentration for the same period. This study has demonstrated that MIP microtraps have significant potential for the selective enrichment and preservation of targeted polycyclic aromatic hydrocarbons from complex environmental samples.

Strains of Sarcocystis neurona exhibit differences in their surface antigens, including the absence of the major surface antigen SnSAG1.

A gene family of surface antigens is expressed by merozoites of Sarcocystis neurona, the primary cause of equine protozoal myeloencephalitis (EPM). These surface proteins, designated SnSAGs, are immunodominant and therefore excellent candidates for development of EPM diagnostics or vaccines. Prior work had identified an EPM isolate lacking the major surface antigen SnSAG1, thus suggesting there may be some diversity in the SnSAGs expressed by different S. neurona isolates. Therefore, a bioinformatic, molecular and immunological study was conducted to assess conservation of the SnSAGs. Examination of an expressed sequence tag (EST) database revealed several notable SnSAG polymorphisms. In particular, the EST information implied that the EPM strain SN4 lacked the major surface antigen SnSAG1. The absence of this surface antigen from the SN4 strain was confirmed by both Western blot and Southern blot. To evaluate SnSAG polymorphisms in the S. neurona population, 14 strains were examined by Western blots using monospecific polyclonal antibodies against the four described SnSAGs. The results of these analyses demonstrated that SnSAG2, SnSAG3, and SnSAG4 are present in all 14 S. neurona strains tested, although some variance in SnSAG4 was observed. Importantly, SnSAG1 was not detected in seven of the strains, which included isolates from four cases of EPM and a case of fatal meningoencephalitis in a sea otter. Genetic analyses by PCR using gene-specific primers confirmed the absence of the SnSAG1 locus in six of these seven strains. Collectively, the data indicated that there is heterogeneity in the surface antigen composition of different S. neurona isolates, which is an important consideration for development of serological tests and prospective vaccines for EPM. Furthermore, the diversity reported herein likely extends to other phenotypes, such as strain virulence, and may have implications for the phylogeny of the various Sarcocystis spp. that undergo sexual stages of their life cycle in opossums.