Selective observation of boundary water near a solid/water interface by variable-angle polarization specific attenuated total reflection infrared spectroscopy and principal-component analysis

An infrared spectrum of the boundary water near a solid/water interface has been observed, which is distinguished from the bulk water using a novel an alytical technique. The technique employs the variable-angle polarization s pecific (VAPS) attenuated total reflection (ATR) infrared spectrometry and a characteristic of principal component analysis (PCA). To date, near-field optical techniques or artificial polycrystalline water thin-layer formatio n technique have been used to study the structure of boundary-water molecul es below the limitations of spatial resolution. Here, however, we show that the combination technique of VAPS-ATR and PCA analytically overcomes the d ifficulty of spatial resolution and detection limit, so that we selectively observe the boundary water. The orientation of the boundary-water Molecule s has been evaluated using the resolved infrared spectra obtained as the PC A loadings. In addition, it was also suggested that there was an intermedia te layer between the boundary water layer and bulk water.