Chiral Electrochemical Recognition by Very Thin Molecularly Imprinted Sol−Gel Films

Abstract

Thin films with enantioselective properties for electrochemically active chiral probes were developed. Enantioselectivity was accomplished via molecular imprinting. The films were fabricated through the sol-gel technique and were spin-coated on ITO electrodes. The chiral selectivity recognition was detected using two enantiomer pairs: D- and L-3,4-dihydroxyphenylalanine (D- and L-dopa) and (R)- and (S)-N,N'-dimethylferrocenylethylamine [(R)-Fc and (S)-Fc]. A defined chiral cavity was obtained by selection of functional monomers that interact with the template molecule, followed by its removal. Chiral selection properties were measured by cyclic voltammetry and square wave voltammetry. For both template molecules, very good chiral recognition was revealed by electrochemical measurement. The nonspecific adsorption measured for reference nonimprinted films was negligible (less than 5%). Dopa imprinted films revealed both high sensitivity, by the detection of 1 nM (0.2 ppb) concentration, and excellent selectivity, when challenged with a series of catechol derivatives. Fc-imprinted films were able to detect ca. 2 ppm of the target molecule, with very good enantioselectivity and low nonspecific adsorption. To our knowledge, this is the first report of successful molecular imprinting of a ferrocene derivative.

Molecularly Imprinted Mesoporous Organosilica

“…Several reports of molecular imprinting in thin films of silica have confirmed that significantly improved target interaction can be achieved by reducing the diffusion length. 4,[8][9][10] Alternatively, surface imprinting on silica eliminates the need for diffusion altogether, 11,12 but in the case of organic molecules, this method does risk sacrificing the size and shape selectivity that can be achieved by creating a closed imprint cavity. Thin films may be useful for sensing and other analytical applications, but if molecularly imprinted silica is to be used for preparative applications or produced in larger quantities for industrial use, a better choice of morphology is silica powder; it can easily be packed into columns or other vessels, suspended in various solvents and then isolated by centrifugation or filtration, and washed and dried for reuse.…”

Biosensing Applications of Molecularly Imprinted Nanomaterials

“…Such a cross-linkable polymer in solution can be deposited more easily than a simple monomer mixture on a flat surface by spin-coating and other printing techniques. By combing sol-gel chemistry with spin-coating deposition, Marx et al [94] coated a thin MIP film (70 nm) on ITO electrodes to fabricate electrochemical sensors. The designed sensors displayed very high sensitivity and selectivity for the model analytes.…”

Formation, Characterization, and Applications of Organic and Inorganic Nanometric Films

“…[34,35] We have shown that imprinted sol-gel films composed of a mixture of hydrolyzed and polymerized trimethoxysilanes were able to selectively extract different templated species. For examples, we demonstrated this approach for the selective determination of low levels of parathion.…”