ABSTRACT
Perchlorate contamination in groundwater poses a serious threat to human health, owing to its interference with thyroid function. The high solubility and poor adsorption of perchlorate ions make perchlorate degradation a necessary technology in groundwater contaminant removal. Here, we demonstrate the perchlorate degradation by employing nano zero-valent iron (nZVI) embedded in biocompatible silica alginate hybrid beads fabricated using calcium chloride (1 wt%) as a crosslinker. The concentration of precursors (sodium alginate, sodium silicate) for bead formation was standardized by evaluating the thermal stability of beads prepared at different sodium silicate and alginate concentrations. Thermal degradation of silica alginate hybrid samples showed a stepwise weight loss during the thermal sweep, indicating different types of reactions that occur during the degradation process. The formation of the silica alginate hybrid structure was confirmed by FT-IR spectroscopy. Scanning electron microscopy (SEM) data revealed the surface morphology of silica alginate hybrid changes by varying sodium silicate and alginate concentrations. nZVI-loaded alginate-silicate polymer bead (nZVI-ASB) exhibited excellent perchlorate degradation efficiency by degrading 20 ppm of perchlorate within 4 h. Our study also showed the perchlorate degradation efficiency of nZVI-ASB is maximum at neutral pH conditions.
ABSTRACT
Tailoring metal oxide nanostructures with mesoporous architectures is vital to improve their electrocatalytic performance. Herein, we demonstrate the synthesis of 2D mesoporous Co3 O4 (meso-Co3 O4 ) nanobundles with uniform shape and size by employing a hard-template method. In this study, the incipient wetness impregnation technique has been chosen for loading metal precursor into the silica hard template (SBA-15). The results reveal that the concentration of a saturated precursor solution plays a vital role in mesostructured ordering, as well as the size and shape of the final meso-Co3 O4 product. The optimized precursor concentration allows us to synthesize ordered meso-Co3 O4 with four to seven nanowires in each particle. The meso-Co3 O4 structure exhibits excellent electrocatalytic activity for both glucose and water oxidation reactions.
ABSTRACT
Heteroatom doping is a powerful means to tune the optical and electronic properties of gold clusters at the atomic level. We herein report that doping a Au38 cluster with Pt and Pd atoms leads to core-doped [Pt2Au36(SC6H13)24]2- and [Pd2Au36(SC6H13)24]0, respectively. Voltammetric investigations show that these clusters exhibit drastically different electronic structures; whereas the HOMO-LUMO gap of [Pt2Au36(SC6H13)24]2- is found to be 0.95 V, that of [Pd2Au36(SC6H13)24]0 is drastically decreased to 0.26 V, suggesting Jahn-Teller distortion of the 12-electron cluster. Density functional investigations confirm that the HOMO-LUMO gap of the Pd-doped cluster is indeed reduced. Analysis of the optimized geometry for the 12-electron [Pd2Au36(SC6H13)24]0 reveals that the rod-like M2Au21 core becomes more flattened upon Pd-doping. Reversible geometrical interconversion between [Pt2Au36(SC6H13)24]0 and [Pt2Au36(SC6H13)24]2- is clearly demonstrated by manipulating the oxidation state of the cluster.
ABSTRACT
Charge transport in polymeric films bound by redox reagents is a topic of current interest. The dynamics of electroinactive ions across the interface is studied by immobilizing ferrocyanide anion in a polysilsesquioxanes (PSQs) modified electrode. Redox reagents can stay in the polymeric film by either physical forces or electrostatic binding. The present work describes the immobilization of ferro/ferricyanide redox couples in PSQ films possessing protonated amine functional groups by electrostatic interactions. Charge transport in [Fe(CN)6](4-)-PSQs film was found to be anion dependent, and its formal potential value varied with the relative hydrophilic or hydrophobic nature of the anion used in the supporting electrolyte, unlike the observed dependence on solution cation for electrodes modified with metal hexacyanoferrates (Prussian Blue analogues). The [Fe(CN)6](4-) bound PSQs films were extensively characterized by varying different supporting electrolytes anions using cyclic voltammetry. The redox peak currents were linearly proportional to the square root of the scan rate, implying that the transport of charge carriers is accompanied with redox ion diffusion and electron hopping in a confined space. dsDNA molecules were found to interact with this polymer matrix through anionic phosphate groups. Both voltammetry and A.C. impedance spectroscopy studies revealed that these interactions could be exploited for the determination of ultra-low level (0.5 attomolar) of dsDNA present in aqueous solution.
