Molecular interactions of MnO2@RGO (manganese dioxide-reduced graphene oxide) nanocomposites with bovine serum albumin.

Graphene based materials have attracted global attention due to their excellent properties. GO-metal oxide nanocomposites have been conjugated with biomolecules for the development of novel materials and potentially used as biomarkers. Herein, a detailed study on the interaction of Bovine serum albumin (BSA) with MnO2@RGO (manganese dioxide-reduced graphene oxide) nanocomposites (NC) has been carried out. MnO2@RGO nanocomposites were prepared through a template/surfactant free hydrothermal route at 180 °C for 12 h by varying the graphene oxide (GO) concentration. Different biophysical experiments have been carried out to evaluate molecular interactions between BSA and NCs. Intrinsic fluorescence has been used to quantify the quenching efficiency of NCs and the binding association of BSA-NC complexes. NCs effectively quenched the intrinsic fluorescence of BSA via static and dynamic mechanism. Further, the results indicate that the molecular interactions of NC with BSA are dependent on the GO percentage in NC. Circular dichroism results demonstrate nominal changes in the secondary structure of BSA in presence of NCs. Also, the esterase-like activity of BSA was marginally affected after adsorption upon NCs. In addition, the FESEM micrographs reveal that the protein-NC complexes consist of nanorod and sheet-like morphologies are forming aggregates of different sizes. We hope that this study will provide a basis for the design of novel graphene based and other related nanomaterials for several biological applications.Communicated by Ramaswamy H. Sarma.

3 D Co3 (PO4 )2 -Reduced Graphene Oxide Flowers for Photocatalytic Water Splitting: A Type†II Staggered Heterojunction System.

The design, synthesis, and photoelectrochemical characterization of Co3 (PO4 )2 , a hydrogen evolving catalyst modified with reduced graphene oxide (RGO), is reported. The 3 D flowerlike Co3 (PO4 )2 heterojunction system, consisting of 3 D flowerlike Co3 (PO4 )2 and RGO sheets, was synthesized by a one-pot in situ photoassisted method under visible-light irradiation, which was achieved without the addition of surfactant or a structure-directing reagent. For the first time, Co3 (PO4 )2 is demonstrated to act as a hydrogen evolving catalyst rather than being used as an oxygen evolving photoanode. In particular, 3 D flowerlike Co3 (PO4 )2 anchored to RGO nanosheets is shown to possess dramatically improved photocatalytic activity. This enhanced photoactivity is mainly due to the staggered type II heterojunction system, in which photoinduced electrons from 3 D flowerlike Co3 (PO4 )2 transfer to the RGO sheets and result in decreased charge recombination, as evidenced by photoluminescence spectroscopy. The band gap of Co3 (PO4 )2 was calculated to be 2.35 eV by the Kubelka-Munk method. Again, the Co3 (PO4 )2 semiconductor displays n-type behavior, as observed from Mott-Schottky measurements. These RGO-Co3 (PO4 )2 conjugates are active in the visible range of solar light for water splitting and textile dye degradation, and can be used towards the development of greener and cheaper photocatalysts by exploiting solar light.

Physicochemical characterization and adsorption behavior of calcined Zn/Al hydrotalcite-like compound (HTlc) towards removal of fluoride from aqueous solution.

A Zn/Al hydrotalcite-like compound (HTlc) was prepared by co-precipitation (at constant pH) method and was characterized by XRD, TG/DTA, FTIR, and BET surface area. The ability of Zn/Al oxide to remove F- from aqueous solution was investigated. All the adsorption experiments were carried out as a function of time, pH, concentration of adsorbate, adsorbent dose, temperature etc. It was found that the maximum adsorption takes place within 4 h at pH 6.0. The percentage of adsorption increases with increase in the adsorbent dose, but decreases with increase in the adsorbate concentration. From the temperature variation it was found that the percentage of adsorption decreases with increase in temperature, which shows that the adsorption process is exothermic in nature. The adsorption data fitted well into the linearly transformed Langmuir equation. Sulfate and phosphate were found to have profound effects on fluoride removal. Thermodynamic parameters such as DeltaG0, DeltaH0, and DeltaS0 were calculated. The negative value of DeltaH0 indicates that the adsorption process is exothermic. The apparent equilibrium constants (Ka) are also calculated and found to decrease with increase in temperature. With 0.01 M NaOH the adsorbed F- could be completely desorbed from Zn/Al oxide in 6 h.