After successfully dip-coating the COP platelets with the photocatalyst, the transmission for all coated and lasered samples was measured using an Ocean Optics spectrometer (FLAME-S-UV-VIS-ES, FLMS01966). For this purpose, the coated platelets were placed in the sample chamber of the device. A UV-Vis light source shone light through the samples and a detector recorded the light intensity after passing through the coated surfaces to determine the transmittance. The transmission was measured for all coated and laser-treated samples.