Tungsten oxide-Au nanosized film composites for glucose oxidation and sensing in neutral medium

Abstract

In this work, we report for the first time the use of tungsten oxide (WOx) as catalyst support for Au toward the direct electrooxidation of glucose. The nanostructured WOx/Au electrodes were synthesized by means of laser-ablation technique. Both micro-Raman spectroscopy and transmission electron microscopy showed that the produced WOx thin film is amorphous and made of ultrafine particles of subnanometer size. X-ray diffraction and X-ray photoelectron spectroscopy revealed that only metallic Au was present at the surface of the WOx/Au composite, suggesting that the WOx support did not alter the electronic structure of Au. The direct electrocatalytic oxidation of glucose in neutral medium such as phosphate buffered saline (pH 7.2) solution has been investigated with cyclic voltammetry, chronoamperometry, and square-wave voltammetry. Sensitivity as high as 65.7 μA cm⁻² mM⁻¹ up to 10 mM of glucose and a low detection limit of 10 μM were obtained with square-wave voltammetry. This interesting analytical performance makes the laser-fabricated WOx/Au electrode potentially promising for implantable glucose fuel cells and biomedical analysis as the evaluation of glucose concentration in biological fluids. Finally, owing to its unique capabilities proven in this work, it is anticipated that the laser-ablation technique will develop as a fabrication tool for chip miniature-sized sensors in the near future.

Keywords:

• Au
• tungsten oxide
• nanostructures
• pulsed laser deposition
• glucose oxidation and sensing

Supplementary materials

Figure S1 XPS survey scan of WOx deposited onto carbon paper.

Abbreviations: XPS, X-ray photoelectron spectroscopy; WOx, tungsten oxide.

Figure S2 XPS survey scan of Au deposited onto WOx.

Abbreviations: WOx, tungsten oxide; XPS, X-ray photoelectron spectroscopy.

Figure S3 Electrochemical studies of glucose detection and sensitivity.

Notes: (A) Voltammetry measurements recorded with 2 mV second⁻¹ at the Au-WOx electrode in argon-saturated 0.01 M PBS solution at pH 7.2 containing concentrations of glucose varying from 0.01 mM to 100 mM; (B) the dependence of the peak current density over the whole range of glucose concentration and (C) the linearity domain of peak current density. A linear relationship with a regression equation of y = 30.8 × + 0.34 (×: concentration/mM, y: current/μA cm⁻²) and a correlation coefficient of R² = 0.9987 was observed from 10 μM to 15 mM (C). The sensitivity was found to be 30.8 μA cm⁻² mM⁻¹ and a low detection limit 10 μM.

Abbreviations: WOx, tungsten oxide; PBS, phosphate-buffered saline.

Figure S4 Electrochemical studies of glucose detection and sensitivity.

Notes: (A) Chronoamperometry measurements at an applied potential of 0.25 V vs Ag/AgCl at the Au-WOx electrode in argon-saturated 0.01 M PBS solution at pH 7.2 containing concentrations of glucose varying from 0 mM to 100 mM; (B) the dependence of the steady-state current density over the whole range of glucose concentration and (C) the linearity domain of the steady-state current density. A linear relationship with a regression equation of y = 24.5 ×−2.1 (×: concentration/mM, y: current/μA cm⁻²) and a correlation coefficient of R² = 0.9961 was observed from 10 μM to 10 mM (C). The sensitivity was found to be 24.5 μA cm⁻² mM⁻¹ and a low detection limit 10 μM.

Abbreviations: WOx, tungsten oxide; PBS, phosphate-buffered saline.

Acknowledgments

This work was financially supported by the Natural Sciences Engineering Research Council of Canada and the Fonds Québécois pour la Recherche en Nature et Technologie.

Disclosure

The authors report no conflicts of interest in this work.