Swarup Manna

A two component thermoreversible hydrogel of riboflavin and melamine: Enhancement of photoluminescence in the gel form

A new thermoreversible hydrogel of riboflavin and melamine supramolecular complex (> or =0.02%, w/v) shows enhanced photoluminescence properties through H-bonding.

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 °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 °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 °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.

Low Molecular Weight Organogelators from Self-assembling Synthetic Tripeptides With Coded Amino Acids: Morphological, Structural, Thermodynamic and Spectroscopic Investigations

A series of self-assembling terminally blocked tripeptides (containing coded amino acids) form gels in various aromatic solvents including benzene, toluene, xylenes at low concentrations. However these tripeptides do not form gels in aliphatic hydrocarbons like n-hexane, cyclohexane, n-decane etc. Morphological studies of the dried gel indicate the presence of an entangled fibrous network, which is responsible for gelation. Differential scanning calorimetric (DSC) studies of the gels produced by peptide 1 clearly demonstrates thermoreversible nature of the gel and tripeptide–solvent complex may be produced during gel formation. FT-IR and 1H NMR studies of the gels demonstrate that an intermolecular hydrogen-bonding network is formed during gelation. Single crystal X-ray diffraction studies for peptides 1, 2 and 3 have been performed to investigate the molecular arrangement that might be responsible for forming the fibrous network of these self-assembling peptide gelators. It has been found that the morph responsible for gelation of peptides 1, 2 and 3 in benzene is somewhat different from that of its xerogel.