Composites for optical sensors

Shang et al. (61) used microemulsion polymerization to synthesize MWCNT-PMMA composites for gas sensor applications. Better dispersion, enhanced electrical conductivity and better sensor response was observed for in-situ fabricated composites compared to composites prepared by solution mixing. Ma et al. (62) performed in-situ polymerization of MWCNT-PMMA composites in the presence of an AC electric field to study dispersion and alignment of MWCNT in PMMA matrix induced by the electric field. Experimental evidences from in-situ optical microscopy, Raman spectroscopy, SEM and electrical conductivity showed that both dispersion and alignment qualities were significantly enhanced for oxidized MWCNT compared to pristine MWCNT. 

Low temperature sol-gel technology is promising approach for preparation of modified with organic molecules silica (SG) thin films. Such films are perspective as sensitive elements of optical sensors. Incorporation of polyelectrolytes into SG sol gives the possibility to obtain composite films with ion-exchange properties. The addition of non-ionic surfactants as template agents into SG sol results formation of ordered mechanically stable materials with tunable pore size. 

These findings therefore suggest the possibility of using the information on the different absorption in the visible and the IR for a very quick, cheap and non-invasive determination of the ink composition using this optical sensor. 

As can be summarized from this survey dye-doped beads represent very versatile analytical tools which are applied in various fields of science and technology. The size of the particles is of the utmost importance here. The smallest beads are mostly designed for intracellular monitoring of analytes and much larger beads are often used in composite materials and sensor arrays. Sensing schemes for optical che-mosensors are established and are similarly realized on nano- and microscale. 

Nonlinear optical organic materials such as porphyrins, dyes, and phthalocyanines provide optical limiting properties for photonic devices to control light frequency and intensity in a predictable manner. The optical limit of CNTs composites is saturated at CNTs exceeding 3.8wt% relative to the polymer mass (Chen et al., 2002). Polymer/ CNT composites could also be used to protect human eyes, for example, optical elements, optical sensors, and optical switching (Cao et al., 2002). 

This technique has also been employed for the preparation of a catalytic imprinted membrane by coating a cellulose membrane with a polymer incorporating particles imprinted with the transition-state analogue of a dehydrofluorination reaction [264]. The application of such an MIP composite membrane as the recognition element in an optical sensor has been reported for digitoxin analysis in serum samples by embedding digitoxin-MIP particles in polyvinyl chloride film in presence of plasticizer by the dry inversion process [265],... 

Fibre Bragg grating sensors are a type of optical sensor that has received considerable attention in recent years. They are used for monitoring the structural condition of fibre-reinforced composites, concrete constructions or other construction materials. 

In conclusion, the proposed technologically improved IWAO made evident its appropriateness as a versatile platform for the development of ion-selective optical sensors, depending on the membrane composition, which also permits disposable transducers to be obtained. 

Table II (118) shows that the surface area, pore volume, and pore size of the deposited films vary consistently with the aging times. Thus the film structures may be tailored for such applications as surface passivation, sensors, membranes, or catalysts by a simple aging process prior to film deposition. In addition, multiple deposition schemes involving different compositions or structures or both allow the formation of complex layered architectures potentially useful for optics, electronics, or sensors.

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