No abstract

Organic dyes namely 1,3,3-trimethylindolino-naphtospirooxazine (TINS) and 3,3-diphenyl-3H-napthol [2,1-pyran DNP) were used in studies of photochromic transformation in ethanol solution. The samples were exposed to UV light ranging from 5, 10 and 15s respectively. TINS absorbs UV light at 613nm for multiple exposure time. The absorption initiated the opening of oxazine spirostructure with formation of open merocyanine species. Irradiation of DNP with UV at 5, 10 and 15s absorbs at 413nm with formation of opening cyclicstucture of naphthopyran, namely allenyl-naphtol. The intensity peaks of TINS and DNP were increased with increasing the period of irradiation time. TINS and DNP dyes exhibit normal photochromic in the polar protic solvent by displaying color changes form transparent to color blue and light orange under exposed UV light. The photochromic activity of these compounds is due to the reversible light-induced cleavage of the C-O bond between the heterocyclic oxygen atom and the quaternary carbon.

Photochromism behaviors of a spiropyran dye namely 5-bromo-8-methoxy-6-nitro BIPS (BNM) has been investigated in the present of papain as anti-oxidant at different H+ ions conditions. BNM has been dissolved and diluted in ethanol (EtOH) to a concentration of 1.0 x 10-5M. The hydrochloric acid (HCL) was used to alter the acidity of the solution to be pH2 and pH7. The fine dispersed transparent solutions were exposed to UV light at 365nm for 5s and the absorption spectra were measured using UV-Vis spectrometer. Upon UV light irradiation, BNM exhibits photochromic behaviors by displaying coloration changes from transparent to light purplish with maximum absorbance spectrum, λmax at 552nm with and without present of papain in both acidic (pH2) and neutral (pH7) conditions. It was found that incorporation of papain in both different pH conditions slightly decreased the intensities of absorbance spectrum for BNM photo-transformation activities. However, detection in time drive mode at 522nm with 5s UV irradiation showed that the addition of papain stabilize and prolongs the absorbance intensity. Incorporation of anti-oxidant molecules is significant in order to obtain long-life activities of the spiropyran in the photo-reversible activity of open-form merocyanine state to closed-form spiro state. This study reveals that the photo-transformation stability of BNM molecules is increased with addition of papain in neutral condition that acts as anti-oxidant agent towards the BNM photo-reversible process.

No abstract

No abstract