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The transduction of host-guest interactions into electronic signals by molecular systems

Authors

  • Prof. David N. Reinhoudt,

    1. Department of Chemistry, University of Twente P.O. Box 217, 7500 AE Enschede (The Netherlands)
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    • was born in 1942 in the Netherlands. He studied Chemical Technology at the Delft University of Technology and gained a Ph.D. in chemistry in 1969 for his work with Professor H. C. Beijerman on a thesis entitled: “On the synthesis of Cephalosporin C”. In 1970 he joined the Royal Dutch/Shell-Laboratories in Amsterdam as a research chemist in the department of Organic Chemsitry. He was actively involed in the start-up of a novel group in “Heterocyclic Chemsitry” at Shell and worked on thiepin chemistry and (2 + 2)-cycloadditions. In 1971 he started the crown ether research program at Shell and also worked on the physical-organic chemistry of crown ether complexation. In 1978 he was appointed full professor at Twente University. His research interests include the synthesis of heterocycles with biological activity such as β-lactams and bioreductive anti-tumor antibiotics (Mitomycins), and pericyclic reactions. The major part of his research deals with the synthesis of macrocyclic host molecules, e.g. crown ethers, calixarenes, and (hemi) spherands, complexation studies with neutral guest molecules and the application of macrocycles in catalysis, membrane transport, and in (electronic) sensor systems.

  • Dr. Ernst J. R. Sudhölter

    1. Department of Chemistry, University of Twente P.O. Box 217, 7500 AE Enschede (The Netherlands)
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  • The authors acknowledge the important contributions in this field made by Dr. A. v. d. Berg, Ir. P. D. v. d. Wal, Dr. M. Skowronska-Ptasinska, Dr. H. A. J. Holterman, Dr. M. L. M. Pennings, Dr. A. G. Talma and Mr. H. van Vossen from our research group and would like to thank Prof. P. Bergveld for stimulating discussions. Financial support from the CME Twente, and the Netherlands Technology Foundation (STW), and the Technology Science Branch of the Netherlands Organization for the Advancement of Pure Research (NWO) is gratefully acknowledged.

Abstract

Synthetic receptor molecules that selectively bind charged guests can store chemical information. The transduction of this information into electronic signals connects the chemical and electronic domains. Field effect transistors (FETs) are attractive transducing elements because these microdevices are able to register and amplify chemical changes at the gate oxide surface of the semiconductor chip.

Integration of molecular receptors and field effect transistors into one chemical system gives a device that can communicate-changes of substrate activities in aqueous solution. Simulations of a system in which the receptor molecules are directly attached to the FET gate oxide indicate serious limitations with respect to sensitivity, dynamic range and extreme requirements for complex stability. Therefore we have concentrated on the integration of covalently attached thin membranes.

The problem of the thermodynamically ill-defined oxidemembrane ipterface has been solved by applying a covalently linked hydrophilic polyhydroxyethylmethacrylate (polyHEMA) gel between the sensing membrane and the silylated gate oxide. A buffered aqueous electrolyte solution in the hydrogel renders the surface potential at the gate oxide constant via the dissociation equilibrium of the residual silanol groups. The subsequent attachment of a polysiloxane membrane that has the required dielectric constant, glass transition temperature Tg, and receptor molecule, provides a stable chemical system that transduces the complexation of cationic species into electronic signals (CHEMFET).

The response to changing K concentrations in a solution of 0.1 M NaCl is fast (<1 sec) and linear in the concentration range of 10−5–1.0 M (55–58 mV /decade). A reference FET (REFET) based on the same technology is obtained when the intrinsic sensitivity to changes in ion concentration is eliminated by the addition of 2.10−5 mol g−1 of didodecyldimethyl ammonium bromide to the ACE membrane. Differential measurements with a REFET/CHEMFET combination showed excellent linear K response over long periods of time.

All chemical reactions used are compatible with planar IC technology and allow fabrication on wafer scale.

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