Diamond and biology

Abstract

A summary of photo- and electrochemical surface modifications applied on single-crystalline chemical vapour deposition diamond films is given. The covalently bonded formation of amine and phenyl linker molecular layers is characterized using X-ray photoelectron spectroscopy, atomic force microscopy (AFM), cyclic voltammetry and field-effect transistor characterization experiments. Amine and phenyl layers are very different with respect to formation, growth, thickness and molecular arrangement. We deduce a sub-monolayer of amine linker molecules on diamond with approximately 10% coverage of 1.510(15) cm(-2) carbon bonds. Amine is bonded only on initially H-terminated surface areas. In the case of electrochemical deposition of phenyl layers, multilayer properties are detected with three-dimensional nitrophenyl growth properties. This leads to the formation of typically 25 A thick layers. The electrochemical bonding to boron-doped diamond works on H-terminated and oxidized surfaces. After reacting such films with heterobifunctional cross-linker molecules, thiol-modified ss-DNA markers are bonded to the organic system. Application of fluorescence and AFM on hybridized DNA films shows dense arrangements with densities up to 10(13) cm(-2). The DNA is tilted by an angle of approximately 35 degrees with respect to the diamond surface. Shortening the bonding time of thiol-modified ss-DNA to 10 min causes a decrease in DNA density to approximately 10(12) cm(-2). Application of AFM scratching experiments shows threshold removal forces of approximately 75 and 45 nN for the DNA bonded to the phenyl and the amine linker molecules, respectively. First, DNA sensor applications using Fe(CN6) 3-/4- mediator redox molecules and DNA field-effect transistor devices are introduced and discussed.

Boron-doped diamond electrode: synthesis, characterization, functionalization and analytical applications

“…Scanning electron microscopy (SEM) can be used to probe the morphology of doped diamond films prepared by CVD such as grain size, orientation, and surface coverage. 43 A comparison of the SEM micrographs of nanocrystalline versus polycrystalline boron-doped diamond electrodes is shown in Fig. 3.…”

Diamond nano-wires, a new approach towards next generation electrochemical gene sensor platforms

“…Details can be found in Ref. [39][40][41]. Electrochemical attachment has been selected as it gives rise to preferential attachment of phenyl-linker molecules to tips of wires which is schematically shown in Fig.…”

“…[38] 3) Reactive ion etching in O 2 /CF 4 gas mixture is applied to form patterns of vertically aligned diamond nano-wires. 4) These wires are functionalized by use of an electrochemical phenyl-linker molecule attachment schema, [39][40][41] which preferentially bonds phenyl linker-molecules to tips of wires. Such functionalized nano-wires are used to bond geometrically controlled oligonucleotide molecules to diamond, thereby combining the outstanding electrochemical properties of diamond as transducer with the advantages coming by dispersed and controlled bonding "like in aqueous solution" of DNA molecules.…”

Nanoindentation as a Tool to Clarify the Mechanism Causing Variable Stiffness of a Silane Layer on Diamond

“…Diamond is at present drawing attention as a material for biological applications because of its hardness, absence of toxicity, and potential conductivity. It is now used for electrodes and biosensors, DNA and protein chips, and for coating of implants [1][2][3]. Though it is known to be chemically inert, there are many approaches, which allow modification of its surface [2,4,5].…”