Chemical sensors volatile organic compounds

DEVELOPMENT OF CHEMICAL SENSORS FOR VOLATILE ORGANIC COMPOUNDS DETERMINATION... 

Square-planar ds platinum complexes could perhaps be used as the chemically sensitive layer for a chemical sensor system. These complexes are robust and form colored solid-state materials that respond spectroscopically to a wide range of volatile organic compounds (VOCs) this process has been named vapochromism. The vapochromic shifts occur in the solid-state UV-vis,... 

Because of their electrical, optical, and redox properties as well as the thermal and chemical stability, the Pcs also have been tried in the detection of volatile organic compounds and poisonous gases, which is very important for environment and human health. In the past decades, the possible applications of Pc thin film as sensor for atmospheric gaseous pollutants have been extensively studied [73, 74], Langmuir-Blodgett films of some multinuclear and multidouble-decker lutetium Pcs have also been used for those measurements [75,76], More details about conductivity and sensing properties of Pcs can be found elsewhere [77,78]. 

Based on the optical thickness of films on porous silicon, this new generation of sensors relies on changes in the film to detect chemicals. In tests for volatile organic compounds, polycyclic aromatic hydrocarbons, explosives, and other chemicals, these sensors have been sensitive to ppb ranges (Sailor, 1997). 

Recently, organic conducting polymers have become the focus of much of the materials research in chemosensing devices. Synthetic flexibility allows the chemical and physical properties of polymers to be tailored over a broad range of values for any given application. In addition, polymers exhibit tunable specificity to volatile organic compounds, which makes them ideal candidates for replacing canonical sensor materials such as metal oxide semiconductors. 

Llobet, E., Brezmes, J., Vilanova, X., Sueiras, J.E., Correig, X. Qualitative and quantitative analysis of volatile organic compounds using transient and steady-state responses of a thick-film tin oxide gas sensor array. Sensors and Actuators B - Chemical 41, 13-21 (1997)... 

The development of a volatile organic compound sensor using SERS detection has also been reported. The SERS substrate is chemically modified with a... 

The same can be said for other pairs of metal oxides, for example SnO -CTO or SnOj-WOj. Titanium-substituted chromium oxide, Cr Ti Oj (CTO), with 0.01 chemical stability at its operating temperature, an easily measurable range of resistance, and good conductivity response (Williams 1999). In contrast to SnO -based sensors, the effect of water vapor on the parameters of CTO-based sensors, such as the baseline and sensitivity, is much less than that on the parameters of SnOj-based devices operating at the same temperatures. This has been the key to the successful commercial development of CTO-based sensors for detection of carbon monoxide and volatile organic compounds in the air. On the other hand, CTO sensors, unlike SnO sensors, are not sensitive to... 

The science of chemical sensors is being studied at Manchester University for the use and application of conducting polymers [4]. Derivatives of polyaniline, polythiophene, polypyrrole and poly(phenylene vinylene) doped with various ions have been investigated as chemical sensors for biosensors, volatile organic compounds, polymer field-effect gas-sensitive transistors and optical sensors based on electrochromic properties. 

Kessick, R. and G. Tepper (2006). Electrospun polymer composite fiber arrays for the detection and identification of volatile organic compounds. Sensors and Actuators B Chemical 117(1) 205-210. 

Environmental sensors capable of detecting specific pollutants such as volatile organic compounds and heavy metals (two of the largest classes of chemical pollutants)... 

Sensors using quartz crystal are very sensitive and can detect samples of the order of pg. Usually, an organic thin film is pasted on quartz surface since the crystal surface hardly absorbs any chemical species. The organic thin film provides the potential to detect various kinds of volatilities with high selectivity and sensitivity. The principle of the gas sensor is based on Eq. (1) [32]. The quartz oscillator has a specific resonance frequency with an oscillating circuit. Its frequency is decreased by the absorption of volatilities on the quartz surface due to the increase in mass. The frequency shift caused by exposure to a volatile depends on the amount adsorbed. With a 9 MHz quartz oscillator, the frequency is decreased by 400 Hz upon adsorption of 1 pg of a compound. A resonance oscillator with a higher resonance frequency can detect smaller amounts. 

There has recently been considerable interest in the detection and identification of air-borne volatile compounds in such diverse areas as quality control of perfume to detection of toxic gases. Miniaturization, the potential low cost of sensors and the variety of applications promise an enormous market (29, 30), Chemical sensors (29) for volatile compounds operate on varied principles and can be classified according to the method of functioning into basic groups such as electrical (field-effect transistors, metal oxide semiconductors and organic semiconductors), optical (spectrophotometric, luminescence, optothermal) and sensors that are sensitive to a change of mass (piezoelectric and acoustosurface). 

---