2008 年 29 巻 9 号 p. 518-525
Two-dimensional chirality has attracted interest as an approach to develop novel chiral catalysts and sensors. However, there is no standard tool to distinguish and evaluate the chirality at surfaces and interfaces, since the number of chiral molecules or chiral sites are limited in the two-dimensional system. Linear chiroptical spectroscopy, such as circular dichroism (CD) and Raman optical activity (ROA), cannot be applied to the two dimensional system, because these methods are basing on the optical transition forbidden under the electric dipole approximation and, then, the chiral responses becomes much weak. Recently, one of the nonlinear spectroscopy, infrared-visible sum frequency generation (VSFG) has been established as a novel chiroptical tool to investigate the molecular and surface chirality. In the present study, this optical technique was applied to recognize the chirality at chiral molecules-modified surfaces under the nonelectronic resonant condition. For polycrystalline films of bi-naphthol (BINOL), chiral VSFG signal reached around 50% of achiral SFG signal and the chirality of the thin film could be successfully recognized. On the other hand, for submonolayer of binaphthyl molecules on Au, there was a limitation in the sensitivity and it was desired to introduce the doubly resonant VSFG enhancement for in situ monitoring of chiral recognition processes.