https://doi.org/10.1351/goldbook.14041
Surface centre, i.e., either a surface defect or a regular surface site, at which a chemical transformation takes place after converting the centre into an active state by a photophysical process, e.g., by photoexcitation.
Notes:
- The number of photoactive centres is very often difficult to establish, particularly on solid surfaces and in suspended particles.
- When the density of the active centres is unknown, the reaction rates may be related to the \(\rm{BET}(\ce{N2})\) area with the understanding that the parameter or property of the system will be a lower limit of the actual value, because the surface determined by \(\ce{N2}\) adsorption will be larger than that reached by the radiation. See Note 2 under the definition of Brunauer–Emmett–Teller (BET) surface area.
- The photophysical process may include one or several processes such as direct excitation of the photocatalytic centre via absorption of ultraviolet, visible, or infrared radiation, via photocarrier trapping, via interaction with excitons, or via energy and/or electron transfer from a photoexcited reagent or intermediate.
See: BET(N2), catalytic site