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F4.4.1

Preparation and Electrochemical Characterization of DNA-modified Nanocrystalline Diamond Films Wensha Yang1, Orlando Auciello3, James E. Butler2, Wei Cai1, John A. Carlisle3, Jennifer E. Gerbi3, Dieter M. Gruen3, Tanya Knickerbocker1, Tami L. Lasseter1, John N. Russell, Jr.2, Lloyd M. Smith1, and Robert J. Hamers*1 1

Department of Chemistry University of Wisconsin-Madison 1101 University Avenue Madison, WI 53706 2

Naval Research Laboratory 4555 Overlook Ave. S.W. Washington, DC 20375 3

Materials Science Division Argonne National Laboratory 9700 S. Cass Ave. Argonne, Illinois 60439 ABSTRACT Nanocrystalline diamond thin films of sub-micron thickness have been covalently modified with DNA oligonucleotides. Quantitative studies of hybridization of surfacebound oligonucleotides with fluorescently tagged complementary and noncomplementary oligonucleotides were performed. The results show no detectable nonspecific adsorption, with extremely good selectivity between matched and mismatched sequences. Impedance spectroscopy measurements were made of DNA-modified borondoped nanocrystalline diamond films. The results show that exposure to noncomplementary sequences induce only small changes in impedance, while complementary DNA sequences produce a pronounced decrease in impedance. The combination of high stability, selectivity, and the ability to directly detect DNA hybridization via electrical means suggest that diamond may be an ideal substrate for continuously-monitoring biological sensors. INTRODUCTION Recent advances in biotechnology and molecular electronics have fueled an interest in fabrication of well-defined, highly stable interfaces between biomolecules and solid substrates.[1-4] The desire to link biomolecules to substrates compatible with current electronic technologies is leading to increased interest in substrates such as gold,[5] silicon,[3,4,6,7] and diamond.[8] Diamond is especially attractive since, in addition to having good electrical[9] and chemical properties,[10] it is also biocompatible, and can be deposited as a robust thin film on silicon and other substrates at moderate temperatures that are compatible with microelectronics processing.[11-13]

Downloaded from https://www.cambridge.org/core. UCSD University of California San Diego, on 24 Jun 2020 at 12:04:34, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-737-F4.4

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However, to achieve very thin, continuous, pinhole-free diamond films, the nucleation density during growth must be extremely high, producing diamond films with crystallites of nanometer dimensions. Recent advances in seeding processes and other techniques have made this readily obtainable on a variety of substrates. EXPERIMENT Experiments were performed using diamond thin films grown via two very different procedures. Nanocrystalline diamond (NCD) thin films were grown in a 2.45 GHz microwave plasma chamber under hydrogen-rich conditions, using purified hydrogen (900 sccm) and methane (99.999%,