Directly Grown K0.33WO3 Nanosheet Film Electrode for Fast Direct Electron Transfer of Protein

A potassium tungstate (K0.33WO3) nanosheet film grown directly on a conductive tungsten (W) substrate by a hotplate-heating approach effects direct electron transfer between the W electrode and a biocatalytic protein or microbe, a long-sought effect of both fundamental and practical importance. The K0.33WO3 forms into a 5-20 nm thick multilayered nanosheet with a number of steps along the surface. A single nanosheet of K0.33WO3 is hydrophilic and highly electron conducting (resistivity similar to 8.3 x 10(-3) Omega cm), characteristic of metallic behaviour. Glucose oxidase (GOD) immobilized on a K0.33WO3-nanosheet-coated electrode demonstrates facile direct electron transfer. The electron transfer rate constant (k(s)) is similar to 9.5 s(-1). This electrode has been used to construct a direct electrochemistry-based glucose sensor, which exhibits good sensitivity (as high as similar to 66.4 mu Amm(-1) cm(-2)), fast sensing response time (similar to 4 s), a low detection limit (0.5 mu m), high selectivity and good reliability in practical uses. Growing K0.33WO3 nanosheet on electrodes offers a promising general approach for effecting direct bioelectrochemistry for widespread uses in bioelectronic and bioenergy applications.