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Sowntharya C.,Dwaraka Doss Goverdhan Doss Vaishnav College Autonomous | Gayathri S.,Dwaraka Doss Goverdhan Doss Vaishnav College Autonomous | Dhenadayalan N.,National Taiwan University | Vasanthi R.,Dwaraka Doss Goverdhan Doss Vaishnav College Autonomous | And 2 more authors.
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2017

Photophysical and electrochemical studies of photoinduced electron transfer (PET) based acridinedione dye with water soluble food hydrocolloid, Gum Arabic (GA) were carried out in aqueous solution. Addition of GA to resorcinol based acridinedione dye (ADDR) which is a PET dye, results in a fluorescence quenching accompanied with a blue shift in the emission maximum (6 nm). The fluorescence quenching is attributed to the promotion of the PET process through space between the donor moiety (OCH3) and the acceptor moiety of basic acridinedione dye ring structure (C[dbnd]O). The fluorescence quenching of ADDR is found to be dynamic in nature. The fluorescence decay of ADDR in the presence of GA shows tri-exponential decay, which implies that there exists a heterogeneous micro environment around the vicinity of the dye with variation in the fluorescence lifetime and their relative distribution. The interaction of ADDR with GA in water is found to be largely hydrophobic, but GA containing several hydrogen-bonding functional groups (sugar moieties and amino acids) also influences the excited state spectral properties of ADDR dye. GA serves as an excellent promoter of electron transfer (ET) through space between the donor and acceptor moiety of ADDR. The variation in oxidation potential of ADDR on the addition of GA is elucidated from cyclic voltammetry studies and the existence of multi-environment of ADDR in GA is elucidated from time resolved fluorescence lifetime measurements. © 2017 Elsevier B.V.

Dhenadhayalan N.,National Taiwan University | Mythily R.,Dwaraka Doss Goverdhan Doss Vaishnav College Autonomous | Kumaran R.,Dwaraka Doss Goverdhan Doss Vaishnav College Autonomous
Journal of Luminescence | Year: 2014

Gum Arabic (GA), a food hydrocolloid is a natural composite obtained from the stems and branches of Acacia Senegal and Acacia Seyal trees. GA structure is made up of highly branched arabinogalactan polysaccharides. Steady-state absorption, fluorescence, and time-resolved fluorescence spectral studies of acid hydrolyzed GA solutions were carried out at various pH conditions. The fluorescence in GA is predominantly attributed to the presence of tyrosine and phenylalanine amino acids. The presence of multi-emissive peaks at different pH condition is attributed to the exposure of the fluorescing amino acids to the aqueous phase, which contains several sugar units, hydrophilic and hydrophobic moieties. Time-resolved fluorescence studies of GA exhibits a multi-exponential decay with different fluorescence lifetime of varying amplitude which confirms that tyrosine is confined to a heterogeneous microenvironment. The existence of multi-emissive peaks with large variation in the fluorescence intensities were established by 3D emission contour spectral studies. The probable location of the fluorophore in a heterogeneous environment was further ascertained by constructing a time-resolved emission spectrum (TRES) and time-resolved area normalized emission spectrum (TRANES) plots. Fluorescence spectral technique is used as an analytical tool in understanding the photophysical properties of a water soluble complex food hydrocolloid containing an intrinsic fluorophore located in a multiple environment is illustrated. © 2014 Elsevier B.V.

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