SnO₂ sensing performance toward volatile organic compounds

Metal oxide semiconductor (MOS) gas sensors are widely used for their numerous advantages, including simplicity of use, low cost, fast response and recovery time, high sensitivity and the capability to detect several analytes. Among MOS, doped or undoped tin oxide (SnO₂), was considered as a good candidate to develop a high-performance resistive sensor for the detection of volatile organic compounds (VOCs).

VOCs impact on the profile of flavours, that as known affect our senses of smell and taste, contributing to identify appealing and affordable foods and drinks, characterizing unambiguously the products quality.

As an example, diacetyl is the VOC that confers a butter‐like aroma in many foods and beverages; it is naturally produced in small quantities during the fermentation and the storage processes in many products such as beer, wine, brandy, balsamic vinegar, roasted coffee, honey, butter, yogurt, and several cheeses. However, if diacetyl threshold value is overcome its presence may indicate an issue in the production or storage processes. Therefore, the monitoring of diacetyl concentrations contributes to the quality of the final product.

In this work, SnO₂ was used as sensing layer for diacetyl detection. The metal oxide powder was obtained through a hydrothermal process and characterized by means of complementary investigation techniques. A thin film of SnO₂ was deposited on an alumina planar substrate supplied with interdigitated platinum electrodes and opportunely conditioned to promote its stabilization. The detection of diacetyl vapor, obtained by bubbling air in liquid diacetyl maintained at a controlled temperature, was performed in different working conditions. The effects of temperature, flow rate, humidity and analyte concentration of pure, aqueous and alcoholic diacetyl solutions were investigated.

From these preliminary results, SnO₂ showed promising sensing characteristics toward VOCs detection such as diacetyl. However, further investigations are necessary to improve the developed sensing system.