Sensing Metal Ions

Scheme 14. Metal ion sensing based on the change of the hydration state of the Gdm complex.

A series of unsymmetrical porphyrazines with thio-ethoxy(ethoxy) ethanol groups (S-polyetherol) appended to the periphery, which both coordinate metals and impart solubility to the macrocycle have been reported (50). These macrocycles show selective optical changes in response to specific metal ions, thus are of potential use in metal ion sensing. 

Pond SJK, Tsutsumi O, Rumi M et al (2004) Metal-ion sensing lluorophores with large two-photon absorption cross sections aza-crown ether substituted donor-acceptor-donor distyryl benzenes. J Am Chem Soc 126 9291-9306... 

Liu B, Yu W-L, Pei J, Liu S-Y, Lai Y-H, Huang W (2001) Design and synthesis of bipyridyl-containing conjugated polymers effects of polymer rigidity on metal ion sensing. Macromolecules 34 7932-7940... 

Crowns with Polymethines Dyes. The ready synthesis, see Figure 3.18, of crown ethers attached to polymethines or hemicyanines has made these compounds a fertile area of research and application in metal ion sensing. AU of these polymethine derivatives are cation responsive e.g. (3.84b) forms complexes with Na, Mg, Ca, Sr and Ba with an increase in fluorescence intensity. 

Fig. 10.1. Schematic of the generic interface used to immobilise peptides on an electrode surfaces for metal ion sensing.

Schmittel M, Kalsani V, Mai P, Bats JW (2006) The HETTAP approach self-assembly and metal ion sensing of dumbbell-shaped molecules and clip molecules. Inorg Chem 45 6370... 

Szurdoki, F. Ren, D. Walt, D. R., A combinatorial approach to discover new chelators for optical metal ion sensing, Anal. Chem. 2000, 72, 5250-5257... 

Crego-Calama, M. Reinhoudt, D. N., New materials for metal ion sensing by self-assembled monolayers on glass, Adv. Mater. 2001, 13, 1171-1174... 

Fluorescent SAMs on glass have been developed by Crego-Calama et al. as new sensor materials. In 1999, the phenomenon of proximal but spatially separable receptor-fluorophore communication was recorded in solution by Tonellato et al.33 and in 2001 Crego et al. demonstrated for the first time that disconnection between fluorophore and receptor can be applied to the preparation of stable sensitive fluorescent materials for metal ion sensing.34 They used SAMs on glass substrates as a 2D scaffold to impart sufficient molecular orientation to separately deposit various binding functionalities (rather than the entire receptor molecule) and the fluorophore on the surface to achieve analyte selectivity. This approach avoids the synthesis and... 

Because the most interesting analytes are present in aqueous environment, sensing in water is very important, especially for medical and environmental applications. Thus, the extension of the approach to metal ion sensing in water was the next step. The synthesis of new fluorescent monolayers stable in water was performed, and their sensing abilities toward cations and anions in aqueous environment were investigated. 

Combinatorial Monolayer Array in a Microtiter Plate Format for Metal Ion Sensing... 

Basabe-Desmonts, L. van der Baan, F. Zimmerman, R. S. Reinhoudt, D. N. Crego-Calama, M. Cross-Reactive Sensor Array for Metal Ion Sensing Based on Fluorescent SAMs. Sensors 2007, 7, 1731-1746... 

Clearly, if metal-binding sites are required, one strategy is to prepare alternating copolymers where one monomer is based on a well-known ligand (e.g., bipyridine, phenanthroline, and acetylacetonate), which is capable of coordinating to a metal ion. One such example was a study carried out by Liu et al. In this case, three similar conjugated polymers 17 (R = Oct), 18, and 19 based on fluorene and bipyridine were prepared and tested for their metal ion sensing capabilities [55],... 

J. D. (2007). Entrapment of fluorescence signaling DNA enzymes in sol-gel-derived materials for metal ion sensing. Anal Chem 79, 3494-3503. 

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