Photochemical Amine Layer Formation on H-Terminated Single-Crystalline CVD Diamond

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.