The influence of temperature on flow-induced forces on quartz-crystal-microbalance sensors in a Chinese liquor identification electronic-nose: three-dimensional computational fluid dynamics simulation and analysis

An electronic-nose is developed based on eight quartz-crystal-microbalance (QCM) gas sensors in a sensor box, and is used to detect Chinese liquors at room temperature. Each sensor is a highly-accurate and highly-sensitive oscillator that has experienced airflow disturbances under the condition of varying room temperatures due to unstable flow-induced forces on the sensors surfaces. The three-dimensional (3D) nature of the airflow inside the sensor box and the interactions of the airflow on the sensors surfaces at different temperatures are studied by computational fluid dynamics (CFD) tools. Higher simulation accuracy is achieved by optimizing meshes, meshing the computational domain using a fine unstructural tetrahedron mesh. An optimum temperature, 30 ℃, is obtained by analyzing the distributions of velocity streamlines and the static pressure, as well as the flow-induced forces over time, all of which may be used to improve the identification accuracy of the electronic-nose for achieving stable and repeatable signals by removing the influence of temperature.

Application of a Quartz Crystal Microbalance (QCM) System Coated with Chromatographic Adsorbents for the Detection of Olive Oil Volatile Compounds

A sensor based on the technique of a piezoelectric quartz crystal microbalance (QCM) is analyzed for the detection of six organic volatile compounds with high olive oil sensory significance, such as hexanal, acetic acid, Z-3-hexenyl acetate, undecane, 1-octen-3-ol and 2-butanone. Four sample concentrations have been exposed to each QCM sensor constructed. The detection system is based on the sample adsorption on the forty sensing films coated at the surfaces of forty AT-cut gold-coated quartz crystals. Each sensing film has been prepared with different solution concentrations of ten materials, usually used as chromatographic sta-tionary phases. Sensing film coating process shows excellent repeatability, with coefficient values less than 0.50%. The frequency shifts of the piezoelectric crystals due to the adsorption of the volatile compounds have been measured as sensor responses, using a static measurement system. The results show that only five QCM sensors, with high sensitivity values, are enough to the detection of the volatile compounds studied. Therefore, the developed detection system presented herein provides a rapid identification of organic volatile compounds with elevated olive oil sensory connotation and it could be a substitute technique to the analytical methods normally used for the analysis of the olive oil flavor.

Fabrication of high sensitivity 2-PEA sensor based on Aldehyde-functionalized mesoporous carbon

2-Phenylethylamine(2-PEA)is one of the main ingredients for stimulants.Therefore,it is necessary to limit its use and illegal trade by conveniently detecting 2-PEA vapour.Here,a QCM based 2-PEA gas sensor was constructed by using aldehyde functionalized mesoporous carbon(FDU-15-CHO)as sensing materials designed according to Schiff base adsorption role.The 2D hexagonal mesoporous structures of the sensing material have been confirmed by small-angle X-ray diffraction(SXRD),transmission electron microscopy(TEM),and N2adsorption-desorption isotherms.The covalent grafting of aldehyde group onto the FDU-15 was confirmed by Fourier transform infrared spectroscopy(FT-IR).FDU-15-CHO based Quartz Crystal Microbalance(QCM)sensor shows better sensitivity to 2-PEA than its parent FDU-15.Besides,the detection limit of FDU-15-CHO based sensor can reach down to 1 ppm,and its selectivity and reproducibility are satisfactory.The high concentrations of active sites in the mesopores of FDU-15 are believed to facilitate 2-PEA adsorption,and thus the presence of the-CHO group leading to sensitive and selective response,which is verified by Gaussian simulation.

Superhydrophobic hierarchical porous divinylbenzene polymer for BTEX sensing and toluene/water selective detection

This work reports a superhydrophobic divinylbenzene polymer with hierarchical porous structure as sensing material to modify the quartz crystal microbalance(QCM)to detect benzene,toluene,ethylbenzene,and xylene(BTEX)vapor.Notably,sensing results toward toluene vapor in different relative humidities indicates that this superhydrophobic polymer has favorable toluene/water selective detection performance.Besides,the limit of detection toward toluene is lower than 1 ppm.