有機分子で安定化さわた粒径1～20nm程度の金属ナノ粒rn子は，金属が電子の閉じ込め，発光，線形・非線形光学特rn性，磁性などの物性を示す一方，周囲の有機配位子殻はナノrn粒子を粉末化させると同時に，溶媒に溶解させる役割を担っrnている（Fig.1）．高品質金属ナノ粒子の化学合成法は近年rn急激な進歩を見せており，一次構造（粒径，形状，結晶rn構造，組成，相構造）を極めて良く制御できるようになったrnおかけで，ナノ粒子の構造ー物性問の相関が議論可能となっrnた．%In order to reveal the electron transport properties of 2D superlattices of small nanoparticles, establishing a general fabrication technique of well-ordered small metal nanoparticle superlattices with narrow interparticle spacings (small tunneling resistance) is indispensable. We have succeeded in the fabrication of self-assembled 2D superlattices of small Au nanoparticles stabilized by bidentate thiolate ligands terminated with π-conjugated aromatic groups with tuning the interparticle spacings. The stable and monodisperse Au nanoparticles smaller than 2 nm are easily prepared by the reduction of HAuCl_4 · 4H_2O in DMF/H_2O in the presence of a series of bidentate ligands, 2,6-bis(1'-(n-thioalkyl)benzimidazol-2-yl)pyridine. These small nanoparticles form hexagonal close packed (hcp) 2D superlattices with tunable interparticle spacings (1.2 nm to 2.5 nm), produced by changing the length of the ligand at not only the hydrophobic amorphous carbon but also the air-water interface. Long-range ordered hcp 2D superlattices were fabricated through the cleavage and construction of interligand π-π interactions formed via an annealing process at the air-water interface.
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