The preparation and spectroscopic characterizations of size-controlled Pyridine-functionalized gold clusters formed self-assembled 2D superlattices with hexagonal packing were studied. The characterizations of pyridine-modified Au clusters using TEM, UV-vis, NMR and ESCA techniques are also reported. Pyridine-functionalized monolayer-protected Au clusters (MPCs) were prepared as illustrated in Scheme 1. The gold nanoparticles prepared by the reduction with NaBH4 have 3.2 ¡Ó 0.88 nm average core diameters established by TEM. The ~3 nm particles were used to induce size and shap evolution with heating treatment in toluene or in TOABr (tetraoctylammonium bromide). The pyridine-functionalized MPCs exhibit an identifiable plasmon resonance band at ~515 nm. The confirmation of the functionalization of pyridyl octanethiol in Au MPCs came from the downfield NMR resonances in the region of 120-150 ppm, which were established the resonances of the Py moiety.