Insight into a pure spinel Co3O4 and boron, nitrogen, sulphur (BNS) tri-doped Co3O4-rGO nanocomposite for the electrocatalytic oxygen reduction reaction.

The intricate problems concerning energy require innovative solutions. Herein, we propose a smart composite nano system that can be used in a sustainable and dichotomous manner to resolve energy crises. The current study describes a new way to synthesize a pure spinel cobalt oxide (Co3O4) and boron (B), nitrogen (N), and sulfur (S) tri-doped Co3O4-reduced graphite oxide (rGO) nanocomposite (CBNS). A hydrothermal method has been used for the synthesis of these nanomaterials. The synthesized nanocomposite was characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), X-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). The XRD results showed the formation of Co3O4 and B, N, S doped nanocomposite with high purity and crystallinity. XAS analysis elucidates the formation of spinel Co3O4 with tetrahedral and octahedral arrangement of cobalt ions. The peaks at 2.50 Å and 3.07 Å are due to the Co-Co bonding. The electrocatalytic oxygen reduction (ORR) was successfully implemented using these nanocomposites. The electrochemical study exhibits the better activity of the B, N, and S tri-doped Co3O4-rGO nanocomposite due to the mutual effect of B, N and S. The synthesized catalyst has maximum current density of 9.97 mA cm-2 with onset potential (Eonset) of 0.98 V in alkaline medium.

In situ reduced graphene-based aerogels embedded with gold nanoparticles for real-time humidity sensing and toxic dyes elimination.

Hybrid aerogels are promising candidates for energy storage, biosensing, and medical applications, but the conventional fabrication methods, being time-consuming and complex, limit their widespread utilization. The critical issues affecting their functionality include the un-controllable particle dispersity, loading of active materials, and the porosity. We report a simple and efficient method to synthesize in situ reduced Au nanoparticles@graphene (Au@graphene) hybrid aerogel using near-infrared radiation (NIR), resulting the uniform loading of well-dispersed Au nanoparticles (Au-NPs) as well as in situ reduction of graphene oxide (GO) with enhanced conductivity. The concentration of iso-propylacrylamide and GO can be adjusted to control the aerogel pore size during the freeze-drying process. Reduction of HAuCl4 and GO to high extent under NIR light was confirmed with advanced characterization techniques. Density functional theory based calculations with generalized gradient-corrected functional (GGA/PW91) in the hybrid aerogel system, and dnd basis sets are used for the confirmation of possible interactions between the GO, Au-NPs, and the polymer. The as-designed highly porous and conductive aerogel shows an excellent humidity response (30-97%) and successfully removes the methylene blue pollutant from the aqueous solution to a high extent (90%). Therefore, Au@graphene hybrid aerogel is potentially an exciting candidate for a wide range of applications in the humidity sensing and biomedical disease detection.

Cellulose Nanocrystals/Polyacrylamide Composites of High Sensitivity and Cycling Performance To Gauge Humidity.

Cellulose nanocrystals (CNCs) have attracted much interest due to their unique optical property, rich resource, environment friendliness, and templating potentials. CNCs have been reported as novel photonic humidity sensors, which are unfortunately limited by the dissolution and unideal moisture absorption of CNCs. We, in this study, developed a high-performance photonic humidity composite sensor that consisted of CNCs and polyacrylamide; chemical bonding was induced between the two components by using glutaraldehyde as a bridging agent. The composites inherited the chiral nematic structure of CNCs and maintained it well through a cycling test. A distinct color change was observed for these composites used as a humidity indicator; the change was caused by polyacrylamide swelling with water and thus enlarging the helical pitch of the chiral nematic structure. The composites showed no degradation of the sensing performance through cycling. The excellent cycling stability was attributed to the bonding between polyacrylamide and CNCs. This composite strategy can extend to the development of other photonic indicators.