Chemical sensors hydrogen

Real-time output of a solid-state hydrogen sensor that can be used in process refineries to improve efficiency. (Courtesy of Air Products and Chemicals, Inc., Allentown, PA.)... 

A thermopile can also be used as a chemical sensor if one of the two materials is a catalytic metal for a given volatile compound. In this case it is necessary to keep the warm and cold junctions at constant temperature. During absorption of the volatile compound on behalf of the catalytic material the thermoelectric power may change, giving rise to an output voltage which can be related to the concentration of the volatile compound. A typical example is the thermopile as hydrogen sensor, where one of the two materials is palladium, a standard hydrogen catalyzer. 

Chung, M.G., et al., Flexible hydrogen sensors using graphene with palladium nanoparticle decoration. Sensors and Actuators B Chemical, 2012.169(0) p. 387-392. 

The hydrogen sensitivity of palladinm-oxide-semiconductor (Pd-MOS) strnctnres was first reported hy Lnndstrom et al. in 1975 [61]. A variety of devices can he nsed as field-effect chemical sensor devices (Fignre 2.6) and these are introdnced in this section. The simplest electronic devices are capacitors and Schottky diodes. SiC chemical gas sensors based on these devices have been under development for several years. Capacitor devices with a platinum catalytic layer were presented in 1992 [62], and Schottky diodes with palladium gates the same year [63]. In 1999 gas sensors based on FET devices were presented [64, 65]. There are also a few publications where p-n junctions have been tested as gas sensor devices [66, 67]. 

Engstrom and Carlsson already introduced in 1983 an SLPT [119] for the characterisation of MIS structures, which was extended to chemical gas sensors by Lundstrom et al. [26]. Both SLPT and LAPS base upon the same technique and principle. However, due to the different fields of applications in history, one refers to LAPS for chemical sensors in electrolyte solutions and for biosensors, and the SLPT for gas sensors. A description of the development of a hydrogen sensor based on catalytic field-effect devices including the SLP technique can be found, e.g., in Refs. [120,121]. The SPLT consists of a metal surface as sensitive material which is heated by, for instance, underlying resistive heaters to a specific working-point temperature, and a prober tip replaces the reference electrode (see Fig. 5.10). 

Another important class of sensors is constituted by inorganic field-effect gas sensors, known as chemically sensitive field-effect transistors (CFIEMFETs) [28,31-35]. Their most successful application is in highly sensitive hydrogen sensors commercialized by Sensistor AB (Sweden) more than 15 years ago as leak detectors. They have proven over the years to be very reliable. A CHEMFET is essentially a... 

G.N. Chaudhari, A.M. Bende, A.B. Bodade, S.S. Patil, V.S. Sapkal, Structural and gas sensing properties of nanocrystalline Ti02 W03-based hydrogen sensors , Sensors and Actuators B Chemical, 115, 297-302, (2006). 

The structure, microstructure, and properties of these composite materials have been studied by X-Ray diffraction, AFM, TEM, and electrical measurements. Anticipated applications of the present composites are photanodes for hydrogen production, active lithium-ion rechargeable battery materials, and chemical gas sensors. An important aspect of these composite materials is the nature of the interfacial properties of the nanostructured particles and the PPX material. 

Kanungo, J.,Saha,H. and Basu, S. Room temperature metal-insulator-semiconductor (MIS) hydrogen sensors based on chemically surface modified porous silicon , (2009) Semor. Actual B. 140,65-72. 

Korotcenkov G, Han 8-D, 8tetter JR (2009) Review of electrochemical hydrogen sensors. Chem Rev 109(3) 1402-1433 Korotcenkov G, Cho BK, Narayanaswamy R, Sevilla F III (2011) Optical and fiber optic chemical sensors. In Korotcenkov G (ed) Chemical sensors comprehensive sensor technologies, vol 5, Electrochemical and optical sensors. Momentum Press, New York, pp 311-476... 

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