Photoluminescence (PL) Spectroscopy

This chapter deals with the fundamental of the photoluminescence (PL) spectroscopy and its applications to study the chemical reaction of molecules on solid surfaces and the reactivity of various heterogeneous solid catalysts in relation to their properties in adsorption, catalysis, and photocatalysis. After a short introduction, the basic principles of PL spectroscopy are explained in relation to the definitions of fluorescence and phosphorescence. And, the PL features of the semiconducting catalysts are discussed in relation to the surface band structures. Next, the practical aspects of static and dynamic PL with the spectral parameters including wavelength and spectral shape, lifetime and the Stern-Volmer expression, energy transfer and migration, and ultrafast time-resolved PL spectroscopy are discussed. In Sect. 14.4, which is one of the cores of this chapter, the characterization of the catalytically active sites by applying in situ PL spectroscopy are discussed with various single-sites heterogeneous catalysts such as Ti-oxide, V-oxide, and Mo-oxide single-site containing catalysts, and carbon containing catalysts such as polymeric carbon nitride. In Sect. 14.5, characterization of acidic and basic surface sites is discussed by means of luminescence probe molecules and in situ PL spectroscopy. In Sect. 14.6, in situ PL studies are discussed in relation to the photocatalytic reaction processes on inorganic and organic semiconducting catalysts. Especially, photo-generation of electron and holes, their lifetimes, and reaction dynamics are discussed. In Sect. 14.7, effects of temperature on PL spectra of their intensity and wavelength are discussed. In Sect. 14.8, effect of magnetic fields on PL spectra are discussed. Section 14.9 is the conclusion and outlook of the PL spectroscopy in catalysis and photocatalysis.