Sensor chemical-sensing material

Use of computational methods in designing, selecting, and ultimately in optimizing chemical sensing materials and sensor sets for arrays is a growing field, which will assist in development of sensing devices for various applications. 

Because in zeolites the silver clusters change their color when in contact with water, it has been suggested that these compounds may be used as water-vapor-sensing materials. Ozin et al. observed the vapor-pressure chromic, cathode-ray chromic, water chromic, photochromic, and thermochromic properties for silver-sodalite, and they proposed that these compounds hold promise for use as sensors.[30] In addition, the silver clusters in zeolites are also sensitive to other molecules, and therefore, they have great potential as chemical-sensing materials. 

Sensors are instruments that are able to convert one form of energy to another, and are alternatively called transducers . In the particular case of environmental monitoring, chemical sensors are utilised because they constitute an active chemical sensing material that is able to convert a... 

As opposed to conventional analytical techniques, optical sensors and biosensors, particularly those employing absorption and fluorescence-based sensing materials potentially allow for measurement through transparent or semi-transparent materials in a non-destructive fashion4, 5> 9 10. Chemical sensor technology has developed rapidly over the past years and a number of systems for food applications have been introduced and evaluated with foods. 

Polymers are among the most widely used materials for chemical sensing since they are able to collect and concentrate molecules on sensor surfaces by reversible sorption they can be deposited on several substrates as thin adherent films with easy processing techniques they are available in many kinds having different chemical and sorption properties, which can be used to enhance the selectivity of the sensors last but not least, they are of low cost. 

We have shown a new concept for selective chemical sensing based on composite core/shell polymer/silica colloidal crystal films. The vapor response selectivity is provided via the multivariate spectral analysis of the fundamental diffraction peak from the colloidal crystal film. Of course, as with any other analytical device, care should be taken not to irreversibly poison this sensor. For example, a prolonged exposure to high concentrations of nonpolar vapors will likely to irreversibly destroy the composite colloidal crystal film. Nevertheless, sensor materials based on the colloidal crystal films promise to have an improved long-term stability over the sensor materials based on organic colorimetric reagents incorporated into polymer films due to the elimination of photobleaching effects. In the experiments... 

Bulk sensors certainly have a role in chemical sensing of explosives, but the subject of this book is the other basic type sensor, one that seeks molecules released from the bulk of the explosive material in an object. We will refer to these as trace chemical sensors. They are sometimes called vapor sensors, but that seems a less accurate description when they are applied to explosive molecules, which may not always be found in a vapor state. As we shall see in Chapter 5, that requires us to understand where and how to look for these molecules. It will become apparent upon a little reflection that the two types of sensors are complementary and are best used in different situations. Furthermore, even when trace sensors are used, in some situations sampling of particles of soil or vegetation or sampling from surfaces may prove to be more productive that vapor sampling. For underwater sources the term vapor sensing is also inappropriate. 

Although the construction of sensors for external physical stimuli, such as light, heat or pressure, is relatively simple, it becomes more complicated when the target stimuli come from atoms or molecules. These types of sensors are often referred to as chemical sensors or chemosensors and biochemical sensors or biosensors (see below in Sects. 1.2 and 1.3). For the latter types, a sensing material should be used that can respond to the presence of the target analyte. This response may or may not be obviously true with vague information. Hence, chemo- and biosensors should be... 

It is safe to say that any conventional spectrophotometric and colorimetric analysis can be performed in an optical sensing format. That makes the optical sensors probably the most universal type of chemical sensors. Miniaturization of optical components and rapid advances in the development of new optical materials and hardware support this fast-growing area of chemical sensing. 

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