Temperature And Ph Sensitive Photoluminescence Of Riboflavin-Methyl Cellulose Hydrogel: Towards And Molecular Logic Gate Behaviour

The photoluminescence (PL) of riboflavin-methyl cellulose hydrogel is 93 fold enhanced in the gel state compared to that in the sol state at pH <= 7. AND molecular logic gate like behaviour is observed using temperature and pH as inputs and enhanced PL of riboflavin as the output. Thermal gelation of methyl cellulose at higher temperatures (>50 degrees C) produces hydrophobic core entrapping riboflavin molecules at the fibrillar junction points inhibiting the non-radiative decay of exitons by the solvent molecules. This causes a dramatic increase of PL intensity at pH <= 7 in the gel state compared to that of the sol state. But at pH 9 the PL intensity reduces to 1/3 of the value of that of pH 7 at 85 degrees C because the labile proton of imido group becomes ionized hampering the conjugation of isoalloxazine ring causing PL quenching. So below the gelation temperature (<50 degrees C) of methyl cellulose and pH higher than 7 are '0' state and temperature >50 degrees C and pH <= 7 are '1' state. Thus a semi solid AND logic gate like system is demonstrated using a riboflavin-methyl cellulose hydrogel and the reversibility of the logic gate action is examined with respect to both the temperature and pH of the system.