Spectrokinetic Investigation of the Photochromic System Under Continuous Uv Irradiance Using Reflectance vs. Time Curves

The photochromic properties of the dye 5-chloro-1,3,3-trimethylspiro[indoline-2,3'-[3H] naphtho[2,1-b] [1,4]- oxazine] were investigated by exposing it to continuous monochromatic irradiation using 360 nm ultraviolet irradiation using photochromic prints at 293.15  2 K; it undergoes a photocoloration and photodecoloration state, thus following the dynamics of a photochromic cycle of growth and decay phase, respectively. Even if the isolated photo isomeric form of the photochromic dye structure is unavailable, one can quantitatively analyse the photo-induced kinetics of photochromic systems using the raw reflectance data. The quantum colour yield is represented by colour span values [K/S] obtained by converting reflectance data to Kubelka- Munk values. The dynamics of the photoreaction in a photochromic system can be examined by analysing the constants for the rate of colouration and decolouration caused by light. By employing first-order kinetics, the dependent dominant wavelength [max] can be determined by fitting the raw data obtained as a change in reflectance values from the FOTOCHROM3 spectrophotometer. The relationship between the colour span values and the concentration of the photochromic dye employed in the photochromic prints is linear.