Open Access Nano Express

A nanoporous interferometric micro-sensor for biomedical detection of volatile sulphur compounds

Tushar Kumeria, Luke Parkinson and Dusan Losic*

Author Affiliations

Ian Wark Research Institute, University of South Australia, Mawson Lakes Boulevard, Adelaide, SA 5095, Australia

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Nanoscale Research Letters 2011, 6:634  doi:10.1186/1556-276X-6-634

Published: 16 December 2011

Abstract

This work presents the use of nanoporous anodic aluminium oxide [AAO] for reflective interferometric sensing of volatile sulphur compounds and hydrogen sulphide [H2S] gas. Detection is based on changes of the interference signal from AAO porous layer as a result of specific adsorption of gas molecules with sulphur functional groups on a gold-coated surface. A nanoporous AAO sensing platform with optimised pore diameters (30 nm) and length (4 ┬Ám) was fabricated using a two-step anodization process in 0.3 M oxalic, followed by coating with a thin gold film (8 nm). The AAO is assembled in a specially designed microfluidic chip supported with a miniature fibre optic system that is able to measure changes of reflective interference signal (Fabry-Perrot fringes). When the sensor is exposed to a small concentration of H2S gas, the interference signal showed a concentration-dependent wavelength shifting of the Fabry-Perot interference fringe spectrum, as a result of the adsorption of H2S molecules on the Au surface and changes in the refractive index of the AAO. A practical biomedical application of reflectometric interference spectroscopy [RIfS] Au-AAO sensor for malodour measurement was successfully shown. The RIfS method based on a nanoporous AAO platform is simple, easy to miniaturise, inexpensive and has great potential for development of gas sensing devices for a range of medical and environmental applications.

Keywords:
nanoporous alumina; reflectometric interference spectroscopy; volatile sulphur compounds; hydrogen sulphide sensor; oral malodour