Paper-based gas sensors

There are a variety of paper materials available to the user, although the choice is based mainly on the fabrication steps required in developing a device and also on the specific application area. In the development of sensors and microfiuidic technologies, filter paper has seen widespread use in recent years for producing paper-based sensors due to its wicking ability (Li et al. 2010 Martinez et al. 2010). In particular, the Whatman cellulose range is popular with the important parameters of porosity, particle retention, and flow rate differentiating the filter paper types. 

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The explanations of observed gas-sensing effects in CNT-based devices are usually based on the analysis of adsorption/desorption phenomena taking place on the surface of CNTs (Peng and Cho 2000 Zhao et al. 2001, 2002 Bauschlicher and Ricca 2004). According to this approach, the resistance of CNT-based gas sensors is conditioned by the change of the CNT resistance caused by interaction with analyte. In particular, in many papers the interaction of NO with the nanotube was interpreted as strictly connected to a bulk doping effect. Actually, NO can be bound to a semiconducting nanotube... 

A number of review papers on zeoUte-based gas sensors are available in the literature (Moos et al. 2006, 2009 Xu et al. 2006 Walcarius 2008 Sahner et al. 2008 Zheng et al. 2012). They focus on various aspects of this materials class and mostly classify devices according to the analytes to be detected or the type of sensor transduction. When used in sensor elements, zeolites can take various roles, which fall into two major categories (see Fig. 8.7). 

Fig. 2.1 Literature review various types of metal oxide-based gas sensors discussed in 2007 (based on a total of 340 papers aveiilable via ISI Web of Science) (Reprinted with permission from Sahner and Tuller (2010). Copyright 2010 Springer)...

MIS, Schottky diode, and p-n-junction-based gas sensors can also be of capacitance type. The construction and principles of operation of such sensors can be found in the Introduction and review papers (Lundsfiom 1981). 

There are very few papers on a sol—gel Al203-based gas sensor. Saha et al. [15] developed a capacitive himiidity sensor based on a porous AI2O3 membrane obtained from alumimun sec-butoxide, with a detection Umit of 3 ppm. The same research group developed an ammonia conductometric sensor based on nanocomposites made of AI2O3 and carbon nanotubes [16]. 

Conducting polymers have shown very promising results for application in gas sensors [107] and are currently used in electronic nose systems [108]. Because of the insolubility of these materials, chemoresistors are, in general, prepared by electrodeposition [107aj. Especially considering the limited reproducibility of this method, there remains a need for alternative methods for the preparation of chemoresistors [108bj. The authors of the paper presented a simple, wafer-scale fabrication method based on a commercial polyaniline product (experimental details explained in Ref. [106]). 

Dossi N, Toniolo R, Pizzariello A, Carrilho E, Piccin E, Battiston S, Bontempelli G (2012) An electrochemical gas sensor based on paper supported room temperature ionic liquids. Lab Chip 12 153-158 Earle MJ, Seddon KR (2000) Ionic liquids. Green solvents for the future, re Appl Chem 72(7) 1391-1398 Fletcher KA, Pandey S, Storey IK, Hendricks AE, Pandey S (2002) Selective fluorescence quenching of polycyclic aromatic hydrocarbons by nitromethane within room temperature ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate. Antd Chim Acta 453 89-96... 

Sensors based on reactivity of gas Electrochemical sensors Semiconductor sensor Combustible gas sensor/microcalorimetric gas sensor/peUistor Colorimetric paper tape Chemiluminescence Schottky barrier/heterocontact sensor/FET-based sensors... 

Hydrogel membranes fulfill many of the important conditions for most of above-mentioned application fields. Therefore, we have focused our paper on the applications of PVA-based membranes in areas such as for separation membranar processes, fuel cells, sensors, biochemical/medical applications, catalyst or PVA derivatives membranes as gas and vapor barriers. 

In this paper we describe the application of an adaptive network based fuzzy inference system (ANFIS) predictor to the estimation of the product compositions in a binary methanol-water continuous distillation column from available on-line temperature measurements. This soft sensor is then applied to train an ANFIS model so that a GA performs the searching for the optimal dual control law applied to the distillation column. The performance of the developed ANFIS estimator is further tested by observing the performance of the ANFIS based control system for both set point tracking and disturbance rejection cases. 

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