Laser ablation time-of-flight mass spectrometric diagnosis of the surface states of porous siliceous materials

Abstract

Zeolites and related siliceous porous solids are widely used in industrial sorptive, ion-exchange, and catalytic processes in which the effects of the inner surface states on the properties are important from both practical and theoretical aspects. In this paper, a novel surface diagnostic technique based on laser-induced cluster generation will be reported. Laser ablation has been widely used for the efficient generation of atomic and molecular clusters. We have performed the mass spectrometric study of cluster generation from high silica porous siliceous materials by XeCl excimer laser ablation time-of-flight mass spectrometry (TOF-MS). Several cluster sequences [(SiO/sub 2/)/sub n/X]/sup -/ with different X were observed. It is found that the compositions of the cluster sequences (i.e., X) and the abundance distributions are closely related to the surface states of the samples. The most prominent result is the effect of surface silanol group (SiOH) on the cluster formation.