Chemosensors sensors

Guan, G. Liu, B. Wang, Z. Zhang, Z. (2008). Impainting of Molecular Recognition Sites on Nanostructures and its Applications in Chemosensors. Sensors, 8, 8291-8320. 

G. Guan, B. Liu, Z. Wang, and Z. Zhang, Imprinting of molecular recognition sites on nanostructures and its apphcations in chemosensors. Sensors, 8,8291-8320,2008. 

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. 

In parallel with improvements in chemical sensor performance, analytical science has also seen tremendous advances in the development of compact, portable analytical instruments. For example, lab-on-a-chip (LOAC) devices enable complex bench processes (sampling, reagent addition, temperature control, analysis of reaction products) to be incorporated into a compact, device format that can provide reliable analytical information within a controlled internal environment. LOAC devices typically incorporate pumps, valves, micromachined flow manifolds, reagents, sampling system, electronics and data processing, and communications. Clearly, they are much more complex than the simple chemo-sensor described above. In fact, chemosensors can be incorporated into LOAC devices as a selective sensor, which enables the sensor to be contained within the protective internal environment. Figure 5... 

The combination of dyes with microporous materials opens-up a way to develop selective chemosensors microporous zeolites with an anchored squaraine 27 (Fig. 13) and some other types of dyes can be used as chemosensors for the chromogenic discrimination of amines [75], These dye-zeolite hosts are expected to be promising sensor materials allowing the visible discrimination of selected target guests by size and/or polarity within families or closely related molecules. It was found that the response of the solid to amines was basically governed by the three-dimensional architecture of the solid material. 

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. 

Valeur B., Badaoui F., Bardez E., Bourson J., Boutin P., Chatelain A., Devol I., Larrey B., Lefevre J. P. and Soulet A. (1997) Cation-Responsive Fluorescent Sensors. Understanding of Structural and Environmental Effects, in Desvergne J.-P. and Czarnik A. W. (Eds), Chemosensors of Ion and Molecule Recognition, NATO ASI Series, Kluwer Academic Publishers, Dordrecht, pp. 195-220. 

A new PET-based chemosensor for uronic and sialic acids utilizing the cooperative action of boronic acid and metal chelate was reported by Shinkai and co-workers. This group synthesized a novel fluorescent chemosensor molecule bearing both an o-aminomethylphenylboronic acid group for diol binding to a saccharide and a l,10-phenanthroline-Zn(II)chelate moiety for the carboxylate binding, which enables this sensor to discriminate between neutral monosaccharides and acidic compounds [110],... 

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]. 

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... 

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. 

Sandwich casting permits one to prepare an MIP film with uniform thickness [28, 106, 108, 109]. In this procedure, a drop of the solution containing a monomer, cross-linker, template and initiator is dispensed on the surface of a PZ transducer and covered with a microscope quartz slide. Then this assembly is exposed to UV light in order to initiate polymerization that results in a thin MIP film. The polymerization can be performed either on the activated immobilized initiator PZ transducer surface or on the bare transducer surface. For example, sialic acid has been determined with an MIP film immobilized on a platinum-film electrode of the quartz resonator using the former procedure [57]. That is, 1-butanethiol has been used for modification of the Pt surface. An indole-3-acetic acid plant hormone served as the template. An MIP-PZ chemosensor prepared that way operated reproducibly. That is, the coefficient of variation of the chemosensor performance was 9% for three different sensors. 

For gas-phase sensors, both remarkable selectivity and very low LOD are important. Sensors featuring MIP recognition combined with SAW transduction can meet these requirements. The MIP-PZ chemosensors operating in gases are devised for two main applications, namely for indoor gas inspection and online monitoring of volatile organic compounds. The latter is essential to protect humans from threats of environmental atmospheric pollutants. 

Selectivity of the MIP-PZ sensors can be improved by separately optimizing the binding and determination medium. MIPs combined with PZ transducers are unique in selectivity with respect to enantiomers. The proper choice of functional monomers used for imprinting can improve this selectivity at a very low LOD. For instance, paracetamol has been determined with the MIP-QCM chemosensor using VPD and MAA as the MIP functional monomers [109], Affinity of this... 

A potassium-ion-selective, dendritic, fluorescing chemosensor, bearing three crown ether moieties in the periphery, shows a linear increase in fluorescence intensity with increasing potassium concentration (in acetonitrile). An important criterion for potassium chemosensors is their mode of action (selectivity) in the presence of large amounts of sodium. The tris-crown ether sensor shown in Fig. 8.16 is able to detect very small traces of potassium ions, even if large quantities of sodium ions are present in the same solution - such as in body fluids [55]. 

Cyclenes are a useful component of metal sensor molecules. The common structure of such chemosensor is fluorophore - linker - sensor. Various fluorophores were connected to the cyclene which ensured the detection of the desired cation. These molecules were often water soluble and worked under physiological conditions what made them interesting from the biomedical point of view. 

A review on molecular machines useful for the design of chemosensors emphasizing, among others, modified CDs as molecular sensors, and on rotaxanes and catenanes is published [36],... 

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