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Lignin was extracted from Sal leaves by treating with alkaline solution followed by acidification at room temperature. The extracted lignin was first purified by hot water extraction followed by soxhlet extraction with cyclohexane and ethanol mixture. This purified lignin was epoxidized with epichlorohydrin in alkaline medium. FTIR, UV-Visible, TGA and DTA techniques were used to characterize the lignin and its epoxidized form. FTIR spectra are comparable with other lignin structure in the literature. UV-Visible spectra show a long absorption band in the visible region other than the usual absorption in the UV region. The epoxidized form was mixed with epoxy based primer coating and coated on metal panel for corrosion studies by electrochemical analyzer. The Tafel plot shows that the corrosion rate increases with increase in lignin content in the paint composition.

Fluorescent conjugated materials exhibiting reasonable biocompatibility that are capable of interacting with biological molecules are of interest for bio-sensing and imaging applications. Traditional approaches do not allow for the synthesis of conjugated materials in the presence of biologically relevant substrates. Further conjugated polymers synthesized using conventional methods are doped and not fluorescent. Here we explore the possibility of synthesizing fluorescent oligomers of indole using enzymes as catalyst under mild conditions. The peroxidase catalyzed coupling reaction presented here creates a photoluminescent material that allows for direct utilization (without purification and separation of the dopant) in biosensing applications. The polymerization reaction proceeds smoothly in just deionized water and ethanol. Monitoring of the absorption and fluorescence spectra over one hour shows that the concentration of both absorbing and emitting species grows steadily over time. The presence of anionic buffers and templates is shown to effectively retard the development of light emitting species and instead leads to the formation of an electrically doped conjugated polymer. Structural characterization through FTIR and ¹H-NMR analysis suggests that the oligomer is coupled through the 2 and 3 positions on the indole ring.

Green synthesis of gold-zinc oxide (Au-ZnO) nanocomposite was successfully attempted under organic solvent–free conditions at room temperature. Prolonged stirring of the reaction mixture introduced crystallinity in the ZnO phase of Au-ZnO nanocomposites. Luminescence properties were observed in these crystalline Au-ZnO nanocomposites due to in situ embedding of gold nanoparticles (AuNP) of 5–6 nm diameter on the surface. This efficient strategy involved the reduction of Au(III) by Zn(0) powder in aqueous medium, where sodium citrate (NaCt) was the stabilizing agent. Reaction time and variation of reagent concentrations were investigated to control the Au:Zn ratio within the nanocomposites. The reaction with the least amount of NaCt for a long duration resulted in Au-ZnO/Zn(OH)2 nanocomposite. X-ray photoelectron spectroscopy (XPS) confirmed the formation of Zn(OH)2 and ZnO in the same nanocomposite. These nanocomposites were reconnoitered as bioimaging materials in human cells and applied for visible light–induced photodegradation of rhodamine-B dye.