Takuji Ube

In situ transmission infrared spectroscopy of hydroxylation of aluminum thin film and subsequent dehydration processes

A transmission Fourier-transform infrared spectroscopy apparatus for the in situ observation of chemical reaction in an aqueous solution has been developed. Reforming from an aluminum film to aluminum hydroxide (boehmite) during hydrothermal treatment and a subsequent dehydration process from boehmite to gamma alumina by heating in vacuum are quantitatively observed. According to the absorption peaks of the Al–O–H vibration of boehmite and the H–O–H vibration of liquid water, the hydrothermal reaction of the Al film occurs through two stages: the formation of boehmite and the penetration of excess water into the boehmite crystal.

Refractive index susceptibility of palladium nanoplates with plasmonic resonance in the visible region

We synthesized anisotropic Pd nanoplates for use as a novel refractive index (RI) sensing material in the visible region. The nanoplates showed an extinction peak that was attributed to the excitation of the localized surface plasmon resonance at ~620 nm in the visible region. It was found that the peak was red-shifted with increasing the RI of the surrounding medium. The susceptibility was calculated to be 250 nm per RI unit, comparable to some anisotropic Au nanoparticles that are excellent RI sensing materials.

In situ Measurement of the pH-dependent Transmission Infrared Spectra of Aqueous Lactic Acid Solutions

The transmission infrared absorption spectra of an aqueous lactic acid solution was measured over a pH range of 2.66 - 1.59 using a cell with an optical path length of 12 μm. Absorption peaks were then identified by density functional theory (DFT) calculations. The observed pH-dependent changes in the absorbance spectra were consistent with the properties of the assigned functional groups. We therefore believe that the present method can be applied to the contactless and non-invasive quantitative evaluation of pH values in aqueous systems, such as bioprocesses and bioimaging.