Development of an electrochemical enzyme-free glucose sensor based on self-assembled Pt-Pd bimetallic nanosuperlattices.

The huge demand for the clinical diagnosis of diabetes mellitus has prompted the development of great-performance sensing platforms for glucose detection. Non-enzymatic glucose sensors are getting closer to their use in realistic applications. In this work, polyvinylpyrrolidone (PVP)-conjugated bimetallic Pt-Pd nanosuperlattices were synthesized precisely through a simple synthesis procedure, leading to controllable spherical morphologies with significantly fine and precise nanostructures in a size range of ∼3-5 nm by the reduction of Pt and Pd precursors in ethylene glycol, using an ultrasonic method. High-resolution transmission electron microscopy (HRTEM) measurements evidenced the formation of Pt-Pd bimetallic nanosuperlattices (BMNSLs). The superlattice-fringe patterns (111) of bimetallic Pt-Pd NSLs were identified in the HRTEM images, clearly showing their crystalline nature. The prepared material was used in the electrochemical oxidation of glucose using voltammetry analyses. The experimental evidence indicates that the Pt-Pd BMNSL modified glassy carbon electrode is effective for the selective amperometric detection of glucose in the presence of galactose, sucrose, fructose, lactose, and ascorbic acid. Moreover, its application in the detection of glucose in real serum and urine samples was assessed and good recoveries are achieved. The results show that a Pt-Pd bimetallic nanosuperlattice with high surface area, catalytic activity, and superior selectivity could be a promising material in the generation of novel electrodes for low-cost non-enzymatic glucose sensors.

Cellulose Derived Graphenic Fibers for Capacitive Desalination of Brackish Water.

We describe a simple and inexpensive cellulose-derived and layer-by-layer stacked carbon fiber network electrode for capacitive deionization (CDI) of brackish water. The microstructure and chemical composition were characterized using spectroscopic and microscopic techniques; electrochemical/electrical performance was evaluated by cyclic voltammetry and 4-probe electrical conductivity and surface area by Brunauer-Emmett-Teller analysis, respectively. The desalination performance was investigated using a laboratory batch model CDI unit, under fixed applied voltage and varying salt concentrations. Electro-adsorption of NaCl on the graphite reinforced-cellulose (GrC) electrode reached equilibrium quickly (within 90 min) and the adsorbed salts were released swiftly (in 40 min) back into the solution, during reversal of applied potential. X-ray photoelectron spectroscopic studies clearly illustrate that sodium and chloride ions were physisorbed on the negative and positive electrodes, respectively during electro-adsorption. This GrC electrode showed an electro-adsorption capacity of 13.1 mg/g of the electrode at a cell potential of 1.2 V, with excellent recyclability and complete regeneration. The electrode has a high tendency for removal of specific anions, such as fluoride, nitrate, chloride, and sulfate from water in the following order: Cl->NO3->F->SO4(2-). GrC electrodes also showed resistance to biofouling with negligible biofilm formation even after 5 days of incubation in Pseudomonas putida bacterial culture. Our unique cost-effective methodology of layer-by-layer stacking of carbon nanofibers and concurrent reinforcement using graphite provides uniform conductivity throughout the electrode with fast electro-adsorption, rapid desorption, and extended reuse, making the electrode affordable for capacitive desalination of brackish water.

ZnO supported CoFe2O4 nanophotocatalysts for the mineralization of Direct Blue 71 in aqueous environments.

In this study, an attempt was made to render both the magnetic and photocatalytic properties in a semiconductor material to enhance the efficiency of degradation and recycling possibility of magnetic nanophotocatalysts. CoFe2O4 and CoFe2O4 loaded ZnO nanoparticles were prepared by a simple co-precipitation method and characterized using various analytical tools and in addition to check its visible light assisted photocatalytic activity. CoFe2O4/ZnO nanocatalyst coupled with acceptor, peroxomonosulphate (PMS) showed 1.69-fold enhancement in Direct Blue 71 (triazo dye; DB71) mineralization within 5h. The accomplished enrichment in decolorization was due to the production of more number of non-selective and active free radicals at the catalyst surface.