DT transmitted and reference spectra are collected with two spectrometers coupled to CMOS detectors, in differential configuration. The samples are analysed in form of solution, which is first sonicated for 15 minutes and then poured into a 1-mm thick quartz cuvette. The concentration of the composites is the same used for the photocatalytic measurements, i.e. 1g/L in the case of HER and 0.5g/L in the case of NH3 photofixation.