Determination of quantum yields in two-dimensional scattering systems

A simple method for the determination of photochemical quantum yields (Φ) in light scattering system is proposed. The method is applied for two-dimensional (2D) reactors, such as photocatalytic layers, where scattered light can exit only through the front or rear surfaces. The determination of Φ is based on the measurement of both product formation rate, R, and the transmitted light (IT) in the 2D system, comparing two 2D reactors (layers with thickness L1 and L2, or suspensions with concentration C1 and C2), respectively. A good approximation of the quantum yield can be derived from the equation: Φ(R2−R1)/(IT(1)–IT(2)), where the numbers in parenthesis refer to the given reactor. Satisfactory accuracy is obtained with “D1”=0.6–1 and “D2”=1.2–2, where “D1” and “D2” represent the respective apparent spectrophotometric absorbance of the 2D reactors. The method requires only a light intensity detector or a chemical actinometer. Systematic errors are discussed.