This paper reports a microwave assisted one pot facile synthesis of ester derivatives of agarose (Agr-GAEst) through chemical reaction of agarose (Agr) with gallic acid (GA), an organic acid found in many plants employing carbodiimide chemistry. Agr-GAEst was characterised by FT-IR, 13C NMR spectroscopy, thermogravimetric analysis (TGA), DMA measurements, scanning electron microscopy (SEM), UV–vis spectrophotometry and rheometry. The native agarose was insoluble in ethylene glycol, but Agr-GAEst (obtained at an optimized molar ratio of 1: 0.5) formed good quality gel (tan δ ∼ 0.1) at 4% (w/v) concentration. The gel thus obtained exhibited substantial degree of thixotropy (hysteresis loop area = 38.73%), rapid self-healing ability (12 min) upon complete cleavage of the gel and excellent stretching ability (>20 times of its original length). These types of multifunctional gels would find applications in food and personal health care industries.

A novel in situ core@shell structure consisting of nanoparticles of Ag (Ag Nps) and AgI in agarose matrix (Ag@ AgI/agarose) has been synthesized as a hybrid, in order to have an efficient antibacterial agent for repetitive usage with no toxicity. The synthesized core@shell structure is very well characterized by XRD, UV−visible, photoluminescence, and TEM. A detailed antibacterial studies including repetitive cycles are carried out on Gram-negative Escherichia coli (E. coli) and Grampositive Staphylococcus aureus (S. aureus) bacteria in saline water, both in dark and on exposure to visible light. The hybrid could be recycled for the antibacterial activity and is nontoxic toward human cervical cancer cells (HeLa cells). The water insoluble Ag@AgI in agarose matrix forms a good coating on quartz, having good mechanical strength. EPR and TEM studies are carried out on the Ag@AgI/agarose and the bacteria, respectively, to elucidate a possible mechanism for killing of the bacteria.