VOCs Sensor And Array Technology Based On Composite Of Ionic Liquids And Nanoporous Materials

Volatile organic compounds (VOCs) are among the most common air pollutants, not only affect the environment air quality, but also greatly harm human health. There is a critical need for VOC qualitative and quantitative analysis and countries around the world pay great attention on the ideal VOC detection method.Therefore, the development of rapid, sensitive, stable and low-cost portable VOC sensor and the array-based electronic nose technology are of great signifieance for atmospheric pollution monitoring and human health. The progress in sensor technology depends very much on the sensing materials used. Ionic liquids (ILs) are ionic systems, which consist of salts that are liquid at ambient temperatures. Among many potential materials, ionic liquids should be promising a new class of sensing materials because of their negligible volatility and tunable chemical structures. And the nanoporous materials are also attractive VOC sensing materials due to their high surface area and specific nano-structured confinement properties. In the context of this work, we constructed the new optical and electrical VOC sensors with ionic liquids confined in nanopore channels of the porous materials. Meanwhile, we developed the electronic nose systems based on sensor array and pattern recognition technology, which were used to imitate the function of human olfaction system for VOC identification and detection. The main contents of this article are as follows:(1) This article reviewed the VOC concept with respect to its air quality and human health effects and the current research status of VOC sensor both at home and abroad. The development of porous silicon photonic crystal and ionic liquids as VOC sensing materials were summarized, respectively.(2) An optical VOC sensor based on the light scattering effect of condensed microdroplets was fabricated by infiltrating porous silicon with ionic liquids. Porous silicon photonic crystal has high surface area, active surface and a sharp resonance peak. The ionic liquids were confined in the nanopore channels of porous silicon and occupied a large fraction of the pore space. The formation of uniform microdroplets on the surface of porous silicon could be observed upon dosing with VOC, thereby leading to a significant decrease in peak intensity due to the light scattering effect of microdroplets.The working principles and response performance of the optical VOC sensor was studies based on unique confinement properties of ionic liquids in nano-pores, and specific surface tension, volume expansion effect of ionic liquids, as well as interactions with VOC. The VOC optical sensor was rapid, sensitive and stable. At optimum conditions, the full response time was only several seconds. The miniaturized, low-power VOC detector device was established with a simple electronic circuitry, a light-emitting diode and a phototransistor(3) A novel optical sensor array for VOC detection was constructed by infiltrating different ionic liquid into SU-8patterned porous silicon chip. The diverse set of IL/PSi studied shows cross responding pattern for each VOC due to structural differences. Classification or identification of VOC could be achieved by PCA, which solved the poor selectivity for a single gas sensor. And different IL/PSi sensor could be correctly classified in HCA, ionic liquids-based sensing materials with similar structure would be preferentially gathered in a cluster.(4) An innovative olfaction visualization system based on IL/PSi array was developed. The principle of VOC recognition is the utilization of gray change occurring in IL/PSi array upon exposed to VOC. Simply recording images of IL/PSi arrays before and after exposed to VOC respectively, and obtain unique gray-change signature for each VOC with image processing software. Every gray-change pattern is so different but unique to the VOC that is similar to the fingerprint of human.(5) chemiresistive VOC sensor and array technology based on ionic liquids entrapped in porous Al2O3nanopores were constructed. When the ionic liquid absorbs VOC, the viscosity decreases and conductivity increase. Monitoring current of ionic liquid sensing material allows for rapid, sensitive and stable detection of VOC in air samples. The chemiresistive sensor exhibited good relationship between the current change and concentration of VOC. This article also provided a design of multi-channel electrical detection device. Microelectrode arrays were located on the same chip. The ILs/PSi chemiresistive VOC sensor array was used to discriminate VOC with Artificial Neural Network date processing methods and established the electronic nose system.