One-dimensional array of Au nanoparticles fixed on nanofibers of organogelators by the Langmuir-blodgett method

The Langmuir-Blodgett (LB) method was applied to low molecular weight organogelator N-[N-(6-hydroxyhexyl)-3-carbamoylpropyl]-3,4,5-tris(dodecyloxy) benzamide (1) to form molecular-assembly fibers on a solid substrate. Molecule 1 formed a stable monolayer up to 40 mN/m at the air-water interface. The monolayer was transferred onto a mica surface at 35 mN/m. In the transferred film, fibrous structures with typical dimensions of 1.2 nm (height) × 50-100 nm (width) × 5-10 μm (length) were observed by atomic force microscopy. These structures were ordered in specific directions, reflecting the C₆ surface crystal symmetry of mica. Lateral modulation frictional force microscope measurements revealed that the fibrous structures had high crystallinity and that the surface groups were hydrophilic. These results enabled us to construct functional fibers by introducing functional units into the hydrophilic part of molecule 1. N-[N-(6-Aminoriexyl)-3-carbamoylpropyl]-3,4, 5-tris(dodecyloxy)benzamide hydrochloride (2) has an ammonium moiety instead of the terminal alcohol moiety of 1. By adding 2 to 1, we introduced adsorption sites for Au nanoparticles on the surface of the fibrous structure. By casting a Au nanoparticle suspension onto this fibrous structure, we successfully constructed Au nanoparticle arrays in which Au nanoparticles were adsorbed on a mixed fibrous structure of 1 and 2 on mica substrates.