Electrochemical Grafting of Boron-Doped Single-Crystalline Chemical Vapor Deposition Diamond with Nitrophenyl Molecules

Abstract

The growth of covalently bonded nitrophenyl layers on atomically smooth boron-doped single-crystalline diamond surfaces is characterized using cyclic voltammetric attachment and constant-potential grafting by electrochemical reduction of aryl diazonium salts. We apply atomic force microscopy (AFM) in contact mode to remove phenyl layers and measure phenyl layer thicknesses by oscillatory AFM. Angle-resolved X-ray photoelectron spectroscopy is applied to reveal the bonding arrangement of phenyl molecules, and transient current measurements during the grafting are used to investigate the dynamics of chemical bonding. Nitrophenyl groups at an initial stage of attachment grow three-dimensional (3D), forming layers of varying heights and densities. Layer thicknesses of up to 80 A are detected for cyclic voltammetry attachment after five cycles, whereas the layer becomes denser and only about 25 A thick in the case of constant-potential attachment. No monomolecular closed layer can be detected. The data are discussed taking into account established growth models. Redox systems such as Fe(CN)63-/4- and Ru(NH3)62+/3+ are used to probe the electrochemical barrier properties of nitrophenyl groups grafted onto diamond.

Hydrogen termination of CVD diamond films by high-temperature annealing at atmospheric pressure

“…23,24 Figure 5(a) (solid line) shows the cyclic voltammogram of the electrochemical attachment of dodecylphenyl groups to the H 2 -treated diamond surface. The peak at −0.56 V is attributed to the electroreduction.…”

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 may be more biocompatible for direct protein immobilization than, for example, metal surfaces [22]. However, from our experience of single-molecule dynamics [23,24], as well as that of others' [10,[25][26][27][28][29][30], we still recommend the use of an intervening layer for preserving enzymatic activities. Polymer layers have a distinct advantage compared with flat solid surfaces in terms of retaining protein activity.…”

“…Several pioneering works, reporting the properties of polymer layers, formed on a diamond surface, describe testing of the layers on Hterminated diamond by scratching with an AFM cantilever [28,29,31,32]. Since different proteins require different treatments for maintaining their activities, an intervening layer needs the adjustment of thickness, roughness, and stiffness.…”