Surface plasmon resonance imaging-based optoelectronic nose: fundamental study on the effects of temperature and humidity

The sensitive, selective and real-time detection of odors, in the form of volatile organic compounds (VOCs), remains an important challenge in modern science. As a result, in the field of artificial olfaction, subsequent advances in sensor technologies have given rise to a variety of gas sensors spanning to address a large plethora of applications such as medical diagnostics, quality control, environmental monitoring and etc. Currently, however, the development of electronic nose (eN) technology has garnered the most attention with its biomimetic approach of multi-sensor systems. This study focuses on such an opto-eN system, which utilises Surface Plasmon Resonance Imaging (SPRI) as its transduction technique, operating in gas phase. The immediate requirement, therein, lies on the robustness of these system, especially in their ability to produce reliable measurement during in situ/on field applications. In this regard, temperature and humidity variations, regionally and seasonally, have shown to cause the most significant impact. Their influence on the signal is integrated, with chemical and physical contributions arising from both the immobilized sensing receptors and the metallized SPRI prism, responsible for the plasmonic behavior. Accordingly, we began by optimizing the prism metallization through a complete numerical study on metal layer configurations and thickness choices. The chosen structures were then experimentally compared for optimum performance and stability. Finally, the selected Chromium/Gold (Cr/Au) prism sample was used to test the effect of humidity and temperature. The developed numerical model was demonstrated to be a useful technique, which was experimentally coupled at various temperatures to obtain a fundamental understanding of the adsorption of water on gold surfaces. We believe that the comprehension of this phenomenon and its possible implications will be transferable and thereby useful for sensors beyond the opto-eN application.