Metal oxide semiconductor (MOS) gas sensors have poor selectivity, especially in volatile organic compounds (VOCs). Dynamic measurement method of gas sensors can bring a potential to resolve this problem. However, it is also a challenge to distinguish homologue gases with the same functional group. In this paper, four alcohol homologue gases were detected by a ZnO gas sensor. The period of triangular wave is changed to explore the optimal temperature range in dynamic interval temperature modulation mode for detecting ethyl alcohol, n-propyl alcohol, isopropyl alcohol and n-butyl alcohol. The experimental results show that only when the low temperature is lower than 180 °C and the high temperature is higher than 460 °C, the unsaturation phenomenon can be solved, so as to realize the qualitative and quantitative analysis of the four alcohol homologue gases. Under this experimental condition, the concentration gradient measurement of 100–400 ppm is carried out. After the optimization with the decision tree classification algorithm, the recognition accuracy of the four alcohol homologue gases is 97.62%. 

Detection of four alcohol homologue gases by ZnO gas sensor in dynamic interval temperature modulation mode

Metal oxide semiconductor (MOS) gas sensors have poor selectivity, especially in volatile organic compounds (VOCs). Dynamic measurement method of gas sensors can bring a potential to resolve this problem. However, it is also a challenge to distinguish homologue gases with the same functional group. In this paper, four alcohol homologue gases were detected by a ZnO gas sensor. The period of triangular wave is changed to explore the optimal temperature range in dynamic interval temperature modulation mode for detecting ethyl alcohol, n-propyl alcohol, isopropyl alcohol and n-butyl alcohol. The experimental results show that only when the low temperature is lower than 180 °C and the high temperature is higher than 460 °C, the unsaturation phenomenon can be solved, so as to realize the qualitative and quantitative analysis of the four alcohol homologue gases. Under this experimental condition, the concentration gradient measurement of 100–400 ppm is carried out. After the optimization with the decision tree classification algorithm, the recognition accuracy of the four alcohol homologue gases is 97.62%.

Preparation of SnO2/SiO2 nanocomposites by sol-gel method for enhancing the gas sensing performance to triethylamine

Ultrahigh sensitive and selective room-temperature carbon monoxide gas sensor based on polypyrrole/titanium dioxide nanocomposite

With the rampant drug crime, the detection of drug-producing chemicals has put forward the great demand of multi-type and multi-concentration on-line rapid detection. The rapid development of dynamic measurement for semiconductor gas sensors provides a solution to this problem. However, the mutual blend of type and concentration information negatively affects sensor performance. In this paper, principal component analysis (PCA) was used for weak separation of type and concentration; k-Nearest Neighbor (KNN) was used for qualitative recognition; polynomial regression was used for quantitative recognition. The physical meaning of the dynamic response signal after PCA transformation was first proposed: PC1 has a weak concentration meaning; the combination of PC2, PC3, and PC4 has a weak type meaning. Based on the weak separation, the stepwise recognition method of qualitative classification and quantitative regression was first used to improve the recognition rate, the resolution and the generalization performance of the sensor. Using the inverse transformation of PCA, the principle of PCA and the method of ideal data verified the feasibility of this method. The qualitative and quantitative recognition of various drug-producing chemicals had been realized, which is a new way of on-line rapid sensor detection for drug-producing chemicals.

Qualitative and quantitative recognition method of drug-producing chemicals based on SnO2 gas sensor with dynamic measurement and PCA weak separation

Semiconductor gas sensors have been widely applied to Volatile Organic Compounds (VOCs) detection. However, the poor selectivity in the actual complex gas environment has become a bottleneck to restrict the development of semiconductor gas sensors. In order to solve this problem, SnO2 gas sensor is prepared and temperature modulation measurement is carried out. In this paper, the method of zigzag-rectangular wave temperature modulation is first proposed, which improved the selectivity of the sensor and significantly increased the characteristic peak. Support vector machine (SVM) is used for pattern recognition, which proved the superior of the SVM in small sample size. The results demonstrate that the combination of zigzag-rectangular wave temperature modulation and SVM pattern recognition method can effectively improve the selectivity of the gas sensor.

Dynamic Measurement and Recognition Methods of SnO 2 Sensor to VOCs Under Zigzag-Rectangular Wave Temperature Modulation

Novel combined waveform temperature modulation method of NiO-In2O3 based gas sensor for measuring and identifying VOC gases

Acetic anhydride is an essential raw material for manufacturing the drug heroin. Its rapid detection using semiconductor sensors has great significance to curb the spread of drugs. However, there are few reports on the design of semiconductor sensors for acetic anhydride, and the sensing mechanism remains unclear. For this reason, the strategy enhancing the Lewis base sites on the ZnO surface via S-doped is proposed in view of the Lewis acid properties of acetic anhydride combined with Lewis acid base theory. The synthesized S-doped porous spherical ZnO (S-ZnO-600) sensor response (312.4) to 100 ppm acetic anhydride is 4.9 times than ZnO-600 (64.1) with a detection limit of 200 ppb. X-ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR) and the electron localization function (ELF) indicate that S-doped greatly modulates the electronic structure of ZnO through lattice defects. Meanwhile, the increase of Lewis basicity on the ZnO surface through S doping is further confirmed using CO2 temperature programmed desorption (CO2-TPD), the frontier molecular orbital and the charge density difference (CDD). Gas-phase mass spectrometry (GP-MS) combined with DFT further reveals the catalytic degradation of acetic anhydride sensing process. 

Hanyang Ji

Papers

Qualitative and quantitative recognition method of drug-producing chemicals based on SnO2 gas sensor with dynamic measurement and PCA weak separation

Detection of four alcohol homologue gases by ZnO gas sensor in dynamic interval temperature modulation mode

Dynamic Measurement and Recognition Methods of SnO 2 Sensor to VOCs Under Zigzag-Rectangular Wave Temperature Modulation

Novel combined waveform temperature modulation method of NiO-In2O3 based gas sensor for measuring and identifying VOC gases

Conductometric acetic anhydride gas sensors based on S-doped porous ZnO microspheres with enhanced Lewis base interaction