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Diamond is a promising candidate for bioapplications. Properties of hybridized DNA arrays on single-crystalline diamond are studied on a microscopic level by atomic force microscopy (AFM) in buffer solutions. Compact DNA layers in a thickness of 76 A are resolved by optimizing phase and height contrast in AFM. The height shows some long-range (30 nm) undulations of +/-5 A due to tip and DNA interactions. The axis of double helix DNA is oriented at about 36 degrees with respect to the diamond surface. DNA molecules can be removed by contact-mode AFM with forces >45 nN, indicating stronger DNA bonding than on gold substrates.

Immobilization of biomolecules on transducer surfaces depends on detailed characteristics of linker molecular layers. In this paper, we investigate amine layer growth on atomically smooth hydrogen-terminated diamond surfaces, applying a photochemical attachment process using ω-unsaturated 10-amino-dec-1-ene molecules protected with trifluoroacetic acid groups. The layer formation and growth is characterized by atomic force microscopy (AFM) in tapping and contact mode, X-ray photoelectron spectroscopy (XPS), and surface conductivity experiments. A two-dimensional (2D) formation of a mono-molecular amine-layer is revealed that needs about 8−10 h to form a closed layer on the surface of diamond. Application of photochemical attachment for longer times results in three-dimensional (3D) growth, governed by cross-polymerization and generation of layer protrusions. The diamond/amine interface remains basically hydrogen-terminated, which points toward low surface-defect generation by olefin addition. The 2D growth is discussed using a chain reaction model initiated at isolated carbon dangling bonds.

We prepared WO3 nanosponge photoanodes by nanoparticle/solution hybrid dispersion–deposition for production of “high-value-added” reagents.

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