LOW-TEMPERATURE CHEMORESISTIVE SENSING OF ACETONE BY PORPHYRIN-SnO2 HYBRIDS

The sensing of gas molecules is of fundamental importance for the control of chemical processes, environmental monitoring, and non-invasive medical diagnostics based on human’s breath analysis.[1] Acetone is a biomarker of type I diabetes, since its concentration in breath varies from 300 to 900 ppb in healthy people to more than 1800 ppb for diabetics. Therefore, the development of small, hand-held devices for reliable and continuous real-time measurement at room temperature of acetone would be a desirable outcome, also from a commercial point of view. Chemoresistive gas sensors are promising candidates, due to their high sensitivity, portability, compactness, low costs, sufficient limit of detection and ease of fabrication. Currently, however, the most used materials for chemoresistive gas sensors are n-type and/or p-type Metal Oxides Semiconductors (MOS) which require high temperature to work properly.[2] Recently, the combination of MOS with porphyrin sensitizers has attracted increasing attention as an easy way to improve the sensitivity of the sensors by reducing the fast electron-hole recombination processes and consequently the working temperature of these devices.[3,4] The present contribution deals with the preparation of two Zn(II)porphyrin-SnO2 hybrids, and the investigation of their properties by electrochemical, spectroscopical and computational methods. After deposition of the composites on an interdigitated platinum electrode by air-brush, the sensing performances of the final devices are studied at mild temperatures after LED light photoactivation, to recognize the best combination for high-performing sensing materials able to reduce the acetone sensing temperature by guaranteeing acceptable LOD values. Our findings produce useful insights for the rational design of porphyrin complexes and the engineering of hybrid materials having specific surface features for enhanced sensing properties.