No abstract

No abstract

Nafion resin, a perfluorinated ion-exchange polymer, has been used as a heterogeneous strong acid catalyst for a range of reactions; however, in nonpolar solvents or for gas phase reactions the activity is limited due to the extremely low surface area of the polymer beads (<0.02 m2 g-1). In this paper we describe a novel nanocomposite of Nafion resin, in which small (20−60 nm diameter) Nafion resin particles are entrapped within a porous silica network. This material combines the excellent solid acid catalyst properties of Nafion resin with the desirable porous support characteristics of silica. BET surface area is typically in the range of 150−500 m2 g-1 for the composite. Assuming the Nafion resin particles are dense spheres we estimate the effective surface area of the Nafion resin alone to be in the range of 153 (20 nm spheres) to 50 (60 nm spheres) m2 g-1. This new material has been developed using an in situ sol−gel technique wherein solutions of Nafion resin are mixed with soluble silicon sources to form a gel, which is dried to a clear hard glass-like material. These new porous nanocomposites offer the potential for significantly enhanced activity due to the increased accessibility of the Nafion resin-based acid sites. We show examples of catalytic reactions in which the activity per unit weight of Nafion resin has been found to be at least 100 times higher in the composite than the pure polymer.

CuO nanowires have been prepared and applied for the fabrication of glucose sensors with highly enhanced sensitivity. Cu(OH)(2) nanowires were initially synthesised by a simple and fast procedure, CuO nanowires were then formed simply by removing the water through heat treatment. The structures and morphologies of Cu(OH)(2) and CuO nanowires were characterised by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The direct electrocatalytic oxidation of glucose in alkaline medium at CuO nanowire modified electrodes has been investigated in detail. Compared to a bare Cu electrode, a substantial decrease in the overvoltage of the glucose oxidation was observed at the CuO nanowire electrodes with oxidation starting at ca. 0.10 V vs. Ag/AgCl (saturated KCl). At an applied potential of 0.33 V, CuO nanowire electrodes produce high and reproducible sensitivity to glucose with 0.49 microA/micromol dm(-3). Linear responses were obtained over a concentration range from 0.40 micromol dm(-3) to 2.0 mmol dm(-3) with a detection limit of 49 nmol dm(-3) (S/N = 3). The CuO nanowire modified electrode allows highly sensitive, low working potential, stable, and fast amperometric sensing of glucose, thus is promising for the future development of non-enzymatic glucose sensors.