Glucose sensor based on nano-baskets of tin oxide templated in porous alumina by plasma enhanced CVD

A feasibility study of glucose oxidase (GOx) immobilized tin oxide thin films, consisting of nano-baskets, for glucose sensing is presented. The nano-baskets of SnO2 were grown on in-house fabricated anodized aluminum oxide pores of ∼80-nm diameter using plasma enhanced chemical vapor deposition (PECVD) at an RF power of 60 W. Hydrated stannic chloride was used as a precursor and O2 (20 sccm) as a reactant gas. The deposition was carried out from 350 to 450 °C at a pressure of 0.2 Torr for 15 min each. Deposition at 450 °C resulted in crystalline film with basket-like (nano-sized) structure. GOx was immobilized by physical adsorption (soaking films in GOx solution containing 1000 units for 3 h). Increase in film conductivity was noticed after GOx immobilization. The immobilized films were found sensitive to glucose (C2H12O6, dextrose) concentration from 10 to 360 mg/dl. Sensitivity increases linearly with glucose concentration. Nano-baskets resulted in higher sensitivity in comparison with other structures. From the elemental analyses of the films after GOx immobilization, GOx was found covalently attached with tin oxide, as evident by N 1s peak in the photoelectron spectra. A possible sensing mechanism is presented and discussed.