Nanohybrid hydrogels based on pristine graphene with enhanced toughness and dual responsive drug delivery feature is opening a new era for smart materials. Here pristine graphene hydrogels are synthesized by in situ free radical polymerization where graphene platelets are the nanobuiliding blocks to withstand external stress and shows reversible ductility. Such uniqueness is a mere reflection of rubber-like elasticity on the hydrogels. These nanobuilding blocks serve also the extensive physisorption which enhances the physical crosslinking inside the gel matrix. Besides the pH-responsive drug release features, these hydrogels are also implemented as a pulsatile drug delivery device. The electric responsive drug release behaviours are noticed and hypothesized by the formation of conducting network in the polyelectrolytic hydrogel matrix. The hydrogels are also tested as good biocompatibility and feasible cell-attachment during live-dead cell adhesion study. The drug release characteristics can also be tuned by adjusting the conducting filler loading into the gel matrix. As of our knowledge, this type of hydrogels with rubber-like consistency, high mechanical property, tunable and dual responsive drug delivery feature and very good human cell compatible is the first to report.

In this study, facile hydrothermal synthesis of carbon dots was developed from seaweed-derived κ-carrageenan and lemon juice followed by surface quaternization with benzalkonium chloride for the first time to improve fluorescence properties. The as-prepared spherical carbon dots (KLBC-dots) exhibited excellent water solubility, significant upconversion photoluminescence and excellent photostability. We report small angle neutron scattering (SANS) experiments with the C-dots which illustrate their surface fractals and the proneness of the C-dots to coalescence before and after surface passivation. Selective monitoring of aquatic chromium is critically significant owing to its severe toxic and carcinogenic properties, which have a dramatic impact on health and the environment. It is a remarkable fact that these KLBC-dots can serve as an “on–off–on” fluorescent platform for the selective sensing of Cr(VI) based on the inner filter effect (IFE). Ascorbic acid was employed to validate the “off–on” type fluorescent probe. Using this phenomenon, a logic gate based on the novel KLBC-dots has been constructed. This bifunctional nanosensor affords a very low detection limit (7 nM) and has the obvious benefits of rapid response, simplicity, convenience, high sensitivity and selectivity in practical applications. In addition, these carbon dots showed intracellular Cr(VI) detection and interesting antibacterial activity towards the Gram-negative bacteria E. coli. This study delivers multifunctional applications of KLBC-dots, as an antibacterial agent and for Cr(VI) detection, in environmental fields.

Non-linear mechanical responses observed in networks of many biopolymers such as pectin are important for their functioning as biological systems. Additionally, pectins derived from plant sources are also used for several food and biomedical applications. In the present work, the possible contributions of egg-box bundles in the large deformation response of calcium crosslinked gels of low methoxy pectin are explored using large amplitude oscillatory shear (LAOS). The gels exhibit a significant overshoot in the loss modulus (G′′) and intra-cycle strain-stiffening, more prominent at greater extents of egg-box bundling. This observation signifies the dissipation characteristics of the egg-box bundles in pectin gels, hitherto not reported. The observed non-linear signatures diminish when the extent of bundling as well as the bundle radius decreases below a critical value. We identify different pectin/Ca concentration regimes based on the semi-flexible/flexible nature of the gel network and the non-linear signatures. Monovalent salt addition prior to crosslinking is shown to modify the extent of bundling, thereby influencing the magnitude of G′′ overshoot and strain-stiffening. The intensity of the G′′ overshoot and the extent of strain-stiffening are correlated with the radius of the egg-box bundles obtained from small angle neutron scattering (SANS) data. However, analysis using strain-stiffening models indicates the possible contributions from the semi-flexible nature of egg-box bundles and single chains.