Triangular, hexagonal, and truncated triangular single-crystal gold nanoplates are successfully synthesized under Langmuir monolayers of long-chain ionic liquid molecules 1-hexadecyl-3-methylimidazolium bromide (C 16 mimBr) through interfacial reduction of AuCl 4 -by formaldehyde gas. The Au nanoparticles are characterized using transmission electron microscopy (TEM), selected-area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and UV-vis spectroscopy. It is found that the size of the Au plates varies from several hundred nanometers to several micrometers, up to 20 µm, and the thickness is ca. 35 nanometers. The atomically flat planar surfaces of the Au nanoplates correspond to {111} planes and the lateral surfaces are {110} planes. The concentration of HAuCl 4 aqueous solution strongly influences the formation of the Au nanoplates. The formation of the nanoplates should be attributed to the preferential adsorption of 1-hexadecyl-3-methylimidazolium cations onto the {111} planes of Au nuclei and the connection of small, triangular nanoplates.

Three kinds of Langmuir monolayers formed by dipalmitoylphosphatidylcholine (DPPC), arachidic acid (AA), and octadecylamine (ODA) were used as templates to study the initial stage of nucleation and crystallization of calcium phosphates. It was demonstrated that the combination of calcium ions (or phosphates) to the monolayer/subphase interface is a prerequisite for subsequent nucleation. It was found that calcium phosphate dihydrate (DPCD) formed at 25.0 degrees C for 12 h has a biphasic structure containing both amorphous and crystalline phases. These results showed that calcium phosphates were formed through a multistage assembly process, during which an initial amorphous phase DPCD was followed by a phase transformation into a crystalline phase and then the most stable hydroxyapatite (HAp). This provided new insights into the template-biomineral interaction and a mechanism for biomineralization.

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