Application of laser ionization mass spectrometry for the analysis of pyrolysis products from TiO2 nanoparticles treated with a silane coupling agent

摘要

Laser ionization time-of-flight mass spectrometry (LI/TOFMS) was applied to the analysis of pyrolysis products from TiO2 nanoparticles treated with phenyltriethoxysilane (PTES). The first step was to measure the decomposition products from silanized TiO2 nanoparticles by gradual heating in a gas chromatograph (GC) oven. As a result, a molecular ion peak was not observed for PTES, whereas a peak for the benzene ion was prominent. However, a molecular ion peak and some fragment ion peaks did appear in the mass spectrum of PTES, whereas a peak for the benzene ion did not. These results indicated the existence of compounds that were different from PTES on the surface of the silanized TiO2 nanoparticles that were used in the present study. In addition, a toluene ion peak was observed when heating in a GC oven, but that of phenol, rather than toluene, was confirmed when a pyrolyzer was used for rapid heating. A plausible explanation for these results could be the existence of water in the vicinity of silanized TiO2 nanoparticles when the pyrolysis products were generated. In the present study, the products generated by heating a glass filter paper or TiO2 nanoparticles on to which PTES had been dropped were also measured using a pyrolyzer in order to confirm whether the adsorption conditions could be identified. As a result, a peak for benzene, but not for PTES, was observed by heating TiO2 nanoparticles, whereas a molecular ion of PTES was prominent when a glass filter paper was heated. These results suggest that the present method can reveal the differences in silane coupling agents and can be used to evaluate whether these agents remain on the target sample or have been chemisorbed.