Chemosensors optical

An r/rr/mnv -squaraine-based chemosensor 23a absorbing at 635 nm (eM = 260,000 M 1cm 1) and emitting at 665 nm signals alkaline and earth-alkaline metal ions in millimolar concentrations in acetonitrile [81]. In presence of Na+ ions, the fluorescence signal weakly increases while it significantly decreases in presence of Ca2+, Mg2+, and Ba2+ and does not change substantially upon addition of K+ ions. The same squaraine 23a and the azacrown-squaraine 23b [82] were used for Na+ and K+ sensing in a plasticized PVC matrix [83]. The squaraine derivatives exhibited fluorescence emission based optical responses to... 

Keywords Biofluids Chemosensors Emission spectroscopy Mechanosensors Optical properties Polarity Rheology Twisted intramolecular charge transfer Viscosity... 

Since the quality of a sensor and its application depends on all components of the sensor system, optical transduction, sensitive layers and chemometrics will be discussed in more detail in dependence on the different approaches. In the final chapter, quite a few applications will demonstrate the feasibility and the quality of such bio or chemosensors. Since miniaturisation and parallelisation are further essential topics in these applications, these approaches will be included. 

Based on these chemosensors, biosensors can be set up such as glucose or H2O2 sensors. In this case the appropriate biological compound (glucose oxidase or catalase) must be immobilized on the chemosensor. Different optical sensors are also used as transducer elements for the production of biosensors, especially of immuno-sensors. Here the affinity component is immobilized on the tip of the fiber and all available immuno-sensing assays can be performed using this transducer element. Since these sensors cannot be sterilized and used for on-line monitoring in a bioprocess we refer to other publications [25-27]. 

The present chapter critically encompasses developments and achievements reached in MIP-based selective sensing combined with optical, piezoelectric (PZ) and electrochemical signal transduction. General procedures of MIP preparation along with methods of MIP immobilization for chemosensor fabrication are presented. Protocols of analyte determination involving measurement complexities, like template presence or absence, have been addressed in detail. Moreover, analytical parameters, such as detectability, sensitivity, selectivity, linear dynamic... 

In principle, optical chemosensors make use of optical techniques to provide analytical information. The most extensively exploited techniques in this regard are optical absorption and photoluminescence. Moreover, sensors based on surface plasmon resonance (SPR) and surface enhanced Raman scattering (SERS) have recently been devised. 

This value is comparable to those for the luminescent ion chemosensor systems based on fibre optics or flow-through measurements. In general, the effect of other ions on MIP may be assumed to be negligible, as confirmed by the low MIP fluorescence measured during cross-reactivity tests. However, in toluene in the presence of Mg2+ the MIP fluorescence increased significantly ( 50% of the total intensity) as compared to that in the presence of Al3+. Moreover, Be2+ in ACN yielded almost equal response (90%) to that measured in the presence of Al3+. 

In situ polymerization, and electrochemical polymerization in particular [22], is an elegant procedure to form an ultra thin MIP film directly on the transducer surface. Electrochemical polymerization involves redox monomers that can be polymerized under galvanostatic, potentiostatic or potentiodynamic conditions that allow control of the properties of the MIP film being prepared. That is, the polymer thickness and its porosity can easily be adjusted with the amount of charge transferred as well as by selection of solvent and counter ions of suitable sizes, respectively. Except for template removal, this polymerization does not require any further film treatment and, in fact, the film can be applied directly. Formation of an ultrathin film of MIP is one of the attractive ways of chemosensor fabrication that avoids introduction of an excessive diffusion barrier for the analyte, thus improving chemosensor performance. This type of MIP is used to fabricate not only electrochemical [114] but also optical [59] and PZ [28] chemosensors. 

Figure 1 The 3R chemosensor strategy. An electrical or optical signal reports the noncovalent binding of analyte to a receptor site via a relay mechanism.

The incorporation of siloles in polymers is of interest and importance in chemistry and functionalities. Some optoelectronic properties, impossible to obtain in silole small molecules, may be realized with silole-containing polymers (SCPs). The first synthesis of SCPs was reported in 1992.21 Since then, different types of SCPs, such as main chain type 7r-conjugated SCPs catenated through the aromatic carbon of a silole, main chain type cr-conjugated SCPs catenated through the silicon atom of a silole, SCPs with silole pendants, and hyperbranched or dendritic SCPs (Fig. 2), have been synthesized.10 In this chapter, the functionalities of SCPs, such as band gap, photoluminescence, electroluminescence, bulk-heterojunction solar cells, field effect transistors, aggregation-induced emission, chemosensors, conductivity, and optical limiting, are summarized. 

Tusa JK, He H (2005) Critical care analyzer with fluorescent optical chemosensors for blood analytes. J Mat Chem 15 2640-2647... 

Gunnlaugsson T et al (2001) A novel optically based chemosensor for the detection of blood Na+. Tetrahedron Lett 42 4725-4728... 

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