Applications Of Laser-induced Fluorescence Spectroscopy In Heterogeneous Catalysis

Laser-induced fluorescence (LIF) spectroscopy is an extremely sensitivetechnique, not only giving the information of electronic states of molecule but alsoprobing the influence of surrounding environment on a molecule. LIF has beenwidely used in biology science as well as many other fields. But this technique hasnot been well used in catalysis area until recently.In order to study on heterogenous catalysis using LIF, we designed and built upan in situ laser-induced fluorescence spectroscopy setup. By using this technique, wehave detected the defect in catalyst, which is of the crucial subject concerning activesites. Using supported ZnO catalyst as an example, the results show that the visibleluminescence bands of samples sensitively characterize the changes in the density ofoxygen vacancies in ZnO according to the oxidizing-reducing properties of zincprecursors and calcination atmosphere, and the acid-base properties of supports. Onthe other hand, using aniline as fluorescent probe molecule for the first time, we havestudied the surface properties of the superacid sulfated zirconia catalysts, and theinfluences by the pore and the exchanged cations of zeolite on the adsorbateconfiguration. It is found that there is a very small amount of unique active sites onpure zirconia with tetragonal and monoclinic phase, the S-O groups in sulfatedzirconia are favorable for the generation of these unique active sites, which are likelyresponsible for the so-called superacid property of the sulfated zirconia catalyst. Onthe other hand, the electronic states levels of adsorbed probe molecule indicate thatboth the pores and the exchanged cations of zeolites exhibit solvent effect in theadsorption of polar aniline molecule.This work also demonstrates that LIF spectroscopy is a powerfulcharacterization technique for catalysis.