The electronic interaction of SnO2 with Ag and Pd particles dispersed on its surface was examined by means of X-ray photoelectron spectroscopy (XPS). The binding energies (BE) of Sn3d and O1s of Ag(1.5 wt%)-SnO2 and Pd(3.0 wt%)-SnO2, which were lower by 0.5–0.7 eV than those of pure SnO2 in the as-prepared state, shifted reversibly by reduction and oxidation treatments. These shifts in BE are shown to reflect the shifts of Fermi energy of SnO2 which are interacting electronically with the metal additives. The electronic interaction depended on the metal loading, being strongest at 1.5 wt% and 3.0 wt% loadings of Ag and Pb, respectively. The implication is that the electronic interaction is of primary importance to the inflammable gas detection by Ag-SnO2 sensors.

Electronic Interaction between Metal Additives and Tin Dioxide in Tin Dioxide-Based Gas Sensors : Surfaces, Interfaces and Films

Diversiform metal oxide-based hybrid nanostructures for gas sensing with versatile prospects

With the development of the Internet-of-Things (IoT) technology, the applications of gas sensors in the fields of smart homes, wearable devices, and smart mobile terminals have developed by leaps and bounds. In such complex sensing scenarios, the gas sensor shows the defects of cross sensitivity and low selectivity. Therefore, smart gas sensing methods have been proposed to address these issues by adding sensor arrays, signal processing, and machine learning techniques to traditional gas sensing technologies. This review introduces the reader to the overall framework of smart gas sensing technology, including three key points; gas sensor arrays made of different materials, signal processing for drift compensation and feature extraction, and gas pattern recognition including Support Vector Machine (SVM), Artificial Neural Network (ANN), and other techniques. The implementation, evaluation, and comparison of the proposed solutions in each step have been summarized covering most of the relevant recently published studies. This review also highlights the challenges facing smart gas sensing technology represented by repeatability and reusability, circuit integration and miniaturization, and real-time sensing. Besides, the proposed solutions, which show the future directions of smart gas sensing, are explored. Finally, the recommendations for smart gas sensing based on brain-like sensing are provided in this paper.

https://www.mdpi.com/1424-8220/19/17/3760/pdf

Review on Smart Gas Sensing Technology.

Abstract A carbon nanotube based gas sensor array was developed for discriminating gases and vapors. The sensor array was composed of 32 sensing elements with nanomaterials, e.g. pristine single walled carbon nanotubes (SWNTs), and SWNTs with different metal dopants and polymer coatings. This sensor array was exposed to NO 2 , HCN, HCl, Cl 2 , acetone and benzene in parts per million (ppm) concentration levels. The array data was normalized and autoscaled for eliminating concentration and background noise, and ignoring outliers. The post processed array data was then subjected to a principal component analysis, a pattern recognition technique, for gas and vapor discrimination. All tested gases and vapors can be discriminated by their chemical nature in the low gas/vapor concentration at ppm levels using this carbon nanotube based sensor array.

http://ma.ecsdl.org/content/MA2006-02/49/2162.full.pdf

A Carbon Nanotube Sensor Array for Sensitive Gas Discrimination Using Principal Component Analysis

Acetone is a well-known volatile organic compound that is widely used in different industrial and domestic areas. However, it can have dangerous effects on human life and health. Thus, the realization of sensitive and selective sensors for recognition of acetone is highly important. Among different gas sensors, resistive gas sensors based on nanostructured metal oxide with high surface area, have been widely reported for successful detection of acetone gas, owing to their high sensitivity, fast dynamics, high stability, and low price. Herein, we discuss different aspects of metal oxide-based acetone gas sensors in pristine, composite, doped, and noble metal functionalized forms. Gas sensing mechanisms are also discussed. This review is an informative document for those who are working in the field of gas sensors.

https://www.mdpi.com/1424-8220/20/11/3096/pdf

Nanostructured Metal Oxide-Based Acetone Gas Sensors: A Review

Finding a non-invasive, painless and simple method for monitoring of health parameters and early detection of physiological disorders is of utmost importance in today’s world. Breath analysis has been attracted tremendous attention as a potentially powerful tool for studying the medical diagnosis diseases because of its noninvasive nature and capability of real-time monitoring. For metabolic monitoring, several candidates are attractive. As an example, acetone has been considered as a main breath biomarker for diabetes. In addition to diabetes, fat burn monitoring is another application for breath acetone. This article provides a comprehensive study on the state of the art research activities in gas sensor field. It mainly focuses on the metal oxide semiconductor based acetone sensors such as WO3, ZnO, SnO2, Fe2O3, In2O3, TiO2, Co2O3, NiO and etc. Several different type of acetone sensor technologies such as polymer based chemiresistors, mixed potential, optical and mass sensitive devices are presented as well. The effect of nano structures and morphology on response of sensors are discussed. The advantages and disadvantages of different techniques used for metal oxide semiconductor synthesis are also discussed. Finally, sensor arrays with different receptor materials and transducers for breath analyzing are discussed.

Breath Acetone Sensors as Non-Invasive Health Monitoring Systems: A Review

In this paper, PPy-WO3 hybrid nanocomposites with different weight percentages of WO3 nanoparticles (5-40%wt) dispersed in polypyrrole (PPy) matrix were prepared and utilized as a new sensing material for acetone detection. PPy-WO3 hybrid nanocomposite were deposited on interdigitated electrode by the electrospinning technique. WO3 nanoparticles and PPy-WO3 nanocomposites sensor were characterized by X-ray diffraction and field emission scanning electron microscopy, respectively. The presence of WO3 in PPy matrix was confirmed by EDAX. The resistance changes of different nanocomposites in exposure to acetone and methanol in three temperature (70 °C, 90 °C, and 110 °C) was tested and the results were compared with polypyrrole-based sensor. It was found that enhanced acetone sensing properties of PPy-WO3 nanocomposite films strongly influenced by the WO3 weight percentage and temperature. Comparing with PPy-based sensor, prepared PPy-WO3 hybrid nanocomposite films exhibit excellent acetone vapor sensing properties at low temperature. The detection limit of PPy-WO3 (20%) hybrid nanocomposite sensor is about 16 times better than PPy sensor and it shows fast response (< 5 s) toward acetone vapor at operating temperature of 90 °C. As a result, PPy-WO3 hybrid nanocomposite sensor can be a good candidate for high performance acetone detection.

Enhanced Low-Temperature Response of PPy-WO 3 Hybrid Nanocomposite Based Gas Sensor Deposited by Electrospinning Method For Selective and Sensitive Acetone Detection

This paper presents a novel 4-element chemiresistive sensor array based on PPy-ZnO hybrid nanocomposites for identification and quantitative prediction of different amine vapors. PPy and PPy-ZnO hybrid nanocomposite films, with different ZnO loading levels (10, 20 and 40 wt%)were successfully prepared by electrospinning deposition method onto an interdigitated electrodes (IDEs).The synthesized ZnO particles and the hybrid nanocomposites were characterized in terms of their crystalline structures and morphologies by XRD and FE-SEM methods. The sensing performance of the sensor to various alkylamines such as methyl-, ethyl-, propyl- and n-butyl amine, alcohols, acetone and water vapor were investigated. The sensor exhibited high sensitivity to amine vapors. The discrimination ability of the array evaluated after a 3D principal component analysis (PCA), was proved to be very good. Moreover, the quantitativity of the sensor responses was well fitted with artificial neural network (ANN) model for all tested amine vapors in a wide range of concentrations. The electrospun hybrid nanocomposite sensors developed in this study appear to be very good candidates to design low cost sensor array for the identification and quantitative analysis of different amine vapors, with high sensitivity, short response time (

Detection of alkyl amine vapors using PPy-ZnO hybrid nanocomposite sensor array and artificial neural network

This paper successfully achieved the recognition and quantitative prediction of different amine vapors in high humid atmosphere through the combination of PPy-metal oxide semiconductor (MOS)-based sensor array and multiple linear regression (MLR)-based signal processing technique. PPy-MOS hybrid nanocomposite films with various metal oxide semiconductor materials, including WO3, NiO, ZnO-NiO, and SnO2-NiO were successfully prepared and deposited on interdigitated electrodes by electrospinning technique. The synthesized metal oxide particles and PPy-MOS hybrid nanocomposites were characterized in terms of their crystalline structures, morphologies, and compositional features by XRD, FE-SEM, and EDAX methods. The sensing performance of the designed array exposed to various alkyl amines, including methyl-, dimethyl-, ethyl- and propylamine, ethanol, acetone, and water vapors have been studied. The principal component analysis was utilized to test the ability of the proposed sensor array to recognize different gas classes. MLR technique was used for simultaneous determination of amine vapors in humid atmosphere. The results showed the capability of developed fabricated sensor array for identification and quantification of different amine vapors in humid atmosphere at low temperature.

Hoda Jamalabadi

Papers

Breath Acetone Sensors as Non-Invasive Health Monitoring Systems: A Review

Enhanced Low-Temperature Response of PPy-WO 3 Hybrid Nanocomposite Based Gas Sensor Deposited by Electrospinning Method For Selective and Sensitive Acetone Detection

Detection of alkyl amine vapors using PPy-ZnO hybrid nanocomposite sensor array and artificial neural network

PPy-Metal Oxide Hybrid Nanocomposite Sensor Array for Simultaneous Determination of Volatile Organic Amines in High Humid Atmosphere