Hydrocarbon sensors thin-film

Conventional humidity sensors of the electric resistance variable type use hydrocarbon polyelectrolyte as a moisture sensing material. Therefore, the sensors usually have insufficient heat resistance, and cannot be used at temperatures of 60°C or more. Another problem is that they deteriorate when in contact with cigarette smoke and oil contained in the air [64,65]. When the fluorinated pitch-deposited coating was breathed upon, the electrical resistance quickly decreased, but electrical resistance quickly recovered when this action was stopped. Then, how to develop a humidity sensor excelling in humidity response sensitivity, heat resistance and durability was attempted [66]. Two kinds of comb-like electrodes with different electrode gaps were made, and a thin film was formed on the surfaces by vacuum deposition of fluorinated pitch. The obtained fluorinated pitch sensors were left at rest in a thermostatic chamber, and electrical resistance was determined under the following conditions. 

Zhao, Z., Arrandale, M., Vassiltsova, O. V., Petrukhina, M. A. and Carpenter, M. A. (2009) Sensing Mechanism Investigation on Semicondnctor Quantum Dot/polymer Thin Film Based Hydrocarbon Sensor. Sensor. Actual. B, 141, 26-33. 

Moseley P, Williams DE (1989) Gas sensors based on oxides of early transition meteds. Polyhedron 8 1615-1618 Mosley PT, Norris J, Williams DE (eds) (1991) Techniques and mechanisms in gas sensing. Adam Hilger, New York Moulson AJ, Herbert JM (1990) Electroceramics materieils, properties, applications. Chapman and Hall, London Mukundan R, Brosha E, Brown D, Garzon F (1999) Ceria-electrolyte-based mixed potential sensors for the detection of hydrocarbons and carbon monoxide. Electrochem Soc Lett 2(8) 412-414 MuUa IS, Ramgir NS, Hwang YK, Chang J-S (2004) Semiconductor tin oxide gas sensors from bulk to thin films. J Ind Eng Chem 10(7) 1242-1256... 

In particular, Alberti et al. (1991) proposed zeolite-based sensors for detection of hydrocarbons such as butane and Balkus et al. (1997) used thin film aluminophosphate (AlPO)-5 molecular sieve as the dielectric phase in a capacitance-type chemical sensor for CO and CO. AlPO-n is a family of phosphorus molecular sieves which, similar to zeolites, have ordered molecular-sized pores. The AlPO-5 structure used for the dielectric layer consists of four- and six-membered rings of alternating phosphate and aluminum ions bridged by oxygen. These rings are arranged to produce one-dimensional channels 0.73 nm in diameter. The properties of AlPO-n are reviewed in detail by Ishihara and Takita (1996), and one of the attractive properties of these materials is their heat stability. The properties of zeolites as they relate to zeolite-based gas sensors are discussed in a special section in Vol. 2. 

Recently, gas sensors based on organic-inorganic nanocomposite materials have also been investigated [196,317], The gas-sensing properties of the PANI/Ti02 thin film to NH3 and CO indicated that PANI/Ti02 thin film was an excellent candidate for NH3 detection, but not for the fabrication of a CO gas sensor [276], CdSe/PMMA nanocomposites have been also used as a chemical sensor for detection of aromatic hydrocarbons [196],... 

In early 1975 an idea about new gas sensitive MOS device was presented [4] by I Lundstrom et al Since then in Sweden a great deal of work has been done on gas-sensitive field-effect devices (see, for example, [5-7]) Hydrogen sensors are prepared by using a Pd thin film electrode (about 200 nm) as the gate material By using ultra thin catalytic metal layers (about 10 nm thick), sensitivity to ammonia is created and the sensitivity to gases like alcohols and unsaturated hydrocarbons is increased... 

Hydrogen sulfide (H S) can reversibly be quantified down to 10 ppm(v) with silicone thin films doped (after curing) with nanometer-sized CdSe/CdS luminescent quantum dots [12]. The sensor response is due to donor (H Sf-acceptor (QD) interactions. The indicator layer does not display any response to water, volatile hydrocarbons or alcohols, but shows some response to amines such as 1-butylamine, due to the higher nucleophihcity of the latter. 

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