Sensors combined anion/cation

Generally, dependent on the sensor design and working conditions, the optimum separation distance or optimum density of the immobilized ssDNA should be found in order to achieve a maximal hybridization signal. A twice increase in the hybridization signal can be obtained when combining a cation- and anion-sensitive FED in a differential measuring set-up. 

Imanaka, N., Kamikawa, M. and Adachi, G.-y. (2002) A carbon dioxide gas sensor by combination of multivalent cation and anion conductors with a water-insoluble oxycarbonate-based auxiliary electrode. Anal. Chem., 74 (18), 4800-4. 

There have been obtained macrocycles the framework of which also includes other heterocyclic systems, e.g., pyrrole, pyridine, imidazole, ferrocene, indolizine, triazolothiadiazole, and benzopyrazole except the quinoxaline moiety. As a rule, a constandy growing interest is attached to the mutual influence of the heterocyclic fragments closely located toward each other. This is due to interest in the ample opportunities they hold for their practical application. Thus, the quinoxaline macrocycles with imidazole, pyrrole, or ferrocene moieties are sensors for some anions and cations for the heavy metals. The combination in one molecule of macrocycles of quinoxaline, pyrrolidine, and benzopyrazolne fragments leads to the selective inhibition of the kinase, and the presence of pyrrolidine and amide fragments leads to an antihepatitis effect. Mono-, bis-, and tris- quinoxalinoporphyrins the macrocyclic skeleton of which included pyrrolequinoxaline and pyrrole moieties are attractive for the development of optical devices and materials. 

Conductive electrodes based on metal oxide, e.g., indium-tin oxide (TTO), are widely used in electrochemistry as a support for surface modification with the goal to develop sensors with electrochemical transduction or combined spectroscopic and electrochemical responses or electrochemiluminescence. Inorganic thin films can also be prepared from the assembly of two-dimensional layered inorganic solids, such as cationic clays and layered double hydroxides (LDHs, also defined as anionic clays). These materials can be used to preconcentrate species on the basis of ion-exchange reactions and applied to heavy metal determination or for the detection of organic pollutants. 

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