Metals sensor molecules

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. 

Luminescent Sensor Molecules Based on Coordinated Metals A Review of Recent Developments, Coord. Chem. Rev. 

Protons are relatively simple targets for sensor molecules and do not require engineered receptors, however, achievement of selective interactions with other chemical species requires much more elaborate receptors. In the most cases cations are bound via electrostatic or coordinative interactions within the receptors alkali metal cations, which are rather poor central ions and form only very weak coordination bonds, are usually bound within crown ethers, azacrown macrocycles, cryptands, podands, and related types of receptor moieties with oxygen and nitrogen donor atoms [8], Most of the common cation sensors are based on the photoinduced electron transfer (PET) mechanism, so the receptor moiety must have its redox potential (HOMO energy) adjusted to quench luminescence of the fluorophore (Figure 16.3). 

Keefe MH, Benkstein KD, Hupp JT. Luminescent sensor molecules based on coordinated metals a review of recent developments. Coord Chem Rev 2000 205 201-28. 

Rurack, K. Flipping the light switch ON —The design of sensor molecules that show cation-induced fluorescence enhancement with heavy and transition metal ions. Spec-trochim. Acta, Part A Mol. Biomol. Spectrosc. 2001. 57. 2161-2195. 

Modification of electrode with conducting polymers can improve sensitivity, impart selectivity, and provide a support matrix for sensor molecules. These approaches are intensively studied for gas sensors, electroanalysis, and biosensors. The composite film of conducting polymers and metal nanoparticles on electrode often catalyzes electrode reactions (electrocatalysis). 

Justino CIL, Rocha-Santos TA, Duarte AC, Rocha-Santos TA (2010) Review of analytical figures of merit of sensors and biosensors in clinical applications. Trends Anal Chem 29(10) 172-1183 Keefe MK, Benkstein KD, Hup JT (2000) Luminescent sensor molecules based on coordinated metals a review of recent developments. Coord Chem Rev 205(l) 201-228 Kharitonov SA, Barnes PJ (2000) CUnical aspects of exhaled nitric oxide. Eur Respir J 16 781-792 King WH Jr (1964) Piezoelectric sorption detector. Anal Chem 36 1735-1739... 

In addition to being used for glucose detection, electrical sensors have been developed for pH, ions, heavy metals, small molecules, nucleotides, and enzymes/proteins. Proof of concept has also been demonstrated utilizing antibodies and whole cells as recognition elements. We discuss some characteristic examples below, by order of application as opposed to chronologically. 

Although insulators other than aluminum oxide have been tried, aluminum is still used almost universally because it is easy to evaporate and forms a limiting oxide layer of high uniformity. To be restricted, therefore, to adsorption of molecules on aluminum oxide might seem like a disadvantage of the technique, but aluminum oxide is very important in many technical fields. Many catalysts are supported on alumina in various forms, as are sensors, and in addition the properties of the oxide film on aluminum metal are of the greatest interest in adhesion and protection. 

Cyclophanes or 7r-spherands have played a central role in the development of supramolecular chemistry forming an important class of organic host molecules for the inclusion of metal ions or organic molecules via n-n interactions. Particular examples are provided by their applications in synthesis [80], in the development of molecular sensors [81], and the development of cavities adequate for molecular reactions with possible applications in catalysis [82]. The classical organic synthesis of cyclophanes can be quite complex [83], so that the preparation of structurally related molecules via coordination or organometallic chemistry might be an interesting alternative. 

The initial hurdle to overcome in the biosensor application of a nucleic acid is that involving its stable attachment on a transducing element which commonly includes a metallic electrode. In the first part of this chapter, we wish to introduce our approach for DNA immobilization (Scheme 1). A detailed characterization of the immobilization chemistry is also presented. In the second part, we follow the development of work from our laboratory on chemical sensor applications of the DNA-modified electrode involving a biosensor for DNA-binding molecules and an electrochemical gene sensor. 

To dissociate molecules in an adsorbed layer of oxide, a spillover (photospillover) phenomenon can be used with prior activation of the surface of zinc oxide by particles (clusters) of Pt, Pd, Ni, etc. In the course of adsorption of molecular gases (especially H2, O2) or more complex molecules these particles emit (generate) active particles on the surface of substrate [12], which are capable, as we have already noted, to affect considerably the impurity conductivity even at minor concentrations. Thus, the semiconductor oxide activated by cluster particles of transition metals plays a double role of both activator and analyzer (sensor). The latter conclusion is proved by a large number of papers discussed in detail in review [13]. The papers cited maintain that the particles formed during the process of activation are fairly active as to their influence on the electrical properties of sensors made of semiconductor oxides in the form of thin sintered films. 

---