Response chemical sensors

Fast-Response Chemical Sensors Used for Eddy Correlation Flux Measurements... 

Bukowski, R. M. Davenport, M. D. Titus, A. H. Bright, F. V., 02-responsive chemical sensors based on hybrid xerogels that contain fluorinated precursors. Applied spectroscopy 2006, 60(9), 951-957... 

May use slightly slower response chemical sensors compared with eddy correlation. 

In the field of chemical sensors, the revolution in software and inexpensive hardware means that not only nonlinear chemical responses can be tolerated, but incomplete selectivity to a variety of chemical species can also be handled. Arrays of imperfectly selective sensors can be used in conjunction with pattern recognition algorithms to sort out classes of chemical compounds and thek concentrations when the latter are mixed together. 

Moreover, the receptrode has an extremely rapid response time, requiring only two to three milliseconds to fully respond to a target concentration change. The response times of conventional chemical sensors (qv) are typically from several seconds to several minutes. The receptrode exhibits a response that follows the empirical relationship... 

In Chapter 2 we touch on theoretical models of adsorption response of electrophysical characteristics of real semiconductor adsorbents used as sensitive elements of chemical sensors. 

We scrutinize issues dealing with requirements of high sensitivity and response selectivity of electrophysical parameters in reference to the gas monitored or the type of active particles under study as well as other requirements put forward to adsorbents of chemical sensors. We discuss principles underlying the basis of solving these problems. We dwell on the issue of the type of crystal of adsorbents examined, which is directly linked to the character of intracrystallite contacts. 

The method proposed to deal with polycrystalline adsorbent is highly promising while considering polycrystalline composites, the latter being mixtures of various oxides used as adsorbents who made chemical sensors [175, 177]. It was established in above papers that mixtures of various oxides exhibit the highest sensitivity to specific gases. Moreover, in several cases the adsorption-caused response in electrophysical parameters of such composites exhibit anomalous behavior [58, 176, 177],... 

Over the last several years, the number of studies on application of artificial neural network for solving modeling problems in analytical chemistry and especially in optical fibre chemical sensor technology, has increase substantially69. The constructed sensors (e.g. the optical fibre pH sensor based on bromophenol blue immobilized in silica sol-gel film) are evaluated with respect to prediction of error of the artificial neural network, reproducibility, repeatability, photostability, response time and effect of ionic strength of the buffer solution on the sensor response. 

The history of ion-selective electrodes (ISEs) [1] starts from the discovery of the pH response of thin film glass membranes by Cremer in 1906, thus making ISEs the oldest class of chemical sensors. They still are superior over other sensor types in a variety... 

The number of chemical sensors based on LPGs coated with a chemo-sensitive overlay is still quite limited and even lower is the number of those sensors for which the phenomenon of the modal transition is knowingly used to enhance the performances of the devices. Some of them are based on overlays with low refractive index and/or on thick overlays, which have the drawback of slow diffusion limited response times. One application that seems to attract particular interest is the measurement of the relative humidity (RH). 

Patrick, H. J. Kersey, A. D. Bucholtz, F. Ewing, K. J. Judkins, J. B. Vengsarkar, A. M., Chemical sensor based on long period fibre grating response to index of refraction, Proc. Conf. Lasers Electro Opt. (CLEO 97) 1997, 11, 420 421... 

The response curve (RC) represents the calibrated output response of a sensor as a function of the measurand/s applied to its input. For instance, in the case of a chemical sensor based on conductivity (G), it is recommended to use one of the following notations [1] for the output response ... 

To define a feature extraction procedure it is necessary to consider that the output signal of a chemical sensor follows the variation of the concentration of gases at which it is exposed with a certain dynamics. The nontrivial handling of gas samples complicates the investigation of the dynamics of the sensor response. Generally, sensor response models based on the assumption of a very rapid concentration transition from two steady states results in exponential behaviour. 

As an example of the use of array methodology to study chemical sensor properties let us consider the thirteen molecular structures reported in Figure 5. To investigate the sensing properties of these molecules we studied the behaviour of the response of thickness shear mode resonators (TSMR) sensors, each coated with a molecular film, to different concentration of various volatile compounds (VOC). Analyte compounds were chosen in order to have different expected interaction mechanisms. 

Another distinction should be made (independently of the fluorescence aspects) between chemical sensors (also called chemosensors) and biosensors. In the former, the analyte-responsive moiety is of abiotic origin, whereas it is a biological macromolecule (e.g. protein) in the latter. 

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