: A simple microwave-assisted (MWI) wet chemical route to synthesize pure anatase phase titanium dioxide (TiO₂) nanoparticles (NPs) is reported here using titanium tetrachloride (TiCl₄) as starting material. The as-prepared TiO₂ NPs were characterized by electron microscopy, X-ray diffraction, UV/visible absorption spectroscopy, and infrared and Raman spectroscopic techniques. Further modification of the anatase TiO₂ NPs was carried out by incorporating plasmonic silver (Ag) NPs and graphene oxide (GO) in order to enhance the visible light absorption. The photocatalytic activities of the anatase TiO₂, Ag/TiO₂, and Ag/TiO₂/GO nanocomposites were evaluated under both ultraviolet (UV) and visible light irradiation using phenol as a model contaminant. The presence of Ag NPs was found to play a significant role to define the photocatalytic activity of the Ag/TiO₂/GO nanocomposite. It was found that the Ag performed like a sink under UV excitation and stored photo-generated electrons from TiO₂, whereas, under visible light excitation, the Ag acted as a photosensitizer enhancing the photocatalytic activity of the nanocomposite. The detailed mechanism was studied based on photocatalytic activities of Ag/TiO₂/GO nanocomposites. Therefore, the as-prepared Ag/TiO₂/GO nanocomposite was used as photocatalytic materials under both UV and visible light irradiation toward degradation of organic molecules.

Polymethylmethacrylate–graphene (PMMA/RGO) nanocomposites were prepared via in situ bulk polymerization using two different preparation techniques. In the first approach, a mixture of graphite oxide (GO) and methylmethacrylate monomers (MMA) were polymerized using a bulk polymerization method with a free radical initiator. After the addition of the reducing agent hydrazine hydrate (HH), the product was reduced via microwave irradiation (MWI) to obtain R-(GO-PMMA) composites. In the second approach, a mixture of graphite sheets (RGO) and MMA monomers were polymerized using a bulk polymerization method with a free radical initiator to obtain RGO-(PMMA) composites. The composites were characterized by FTIR, ¹H-NMR and Raman spectroscopy and XRD, SEM, TEM, TGA and DSC. The results indicate that the composite obtained using the first approach, which involved MWI, had a better morphology and dispersion with enhanced thermal stability compared with the composites prepared without MWI.

Well-designed noble metals and ceramic nanoarchitectures are significantly important for the development of high performance, selective, sensitive and cost effective electrochemical sensors. Here, we report gold (Au) nanoparticles (NPs) uniformly dispersed on hydroxyapatite (HAp) nanorods forming particles on rod nanoarchitectures for sensitive hydrazine sensors. The Au/HAp nanocomposites were prepared by a versatile hydrothermal precipitation method. The precipitated citrate-stabilized Au NPs were 6–8 nm in size and strongly anchored onto rod-shaped HAp with a diameter of 10 nm and length of 65 nm. The structural, chemical, and electrochemical properties and growth mechanism of the Au nanoparticles on the HAp nanorods (NRs) are presented. Progress toward the application of hybrid nanocomposites in electrochemical oxidation of hydrazine is reviewed. Compared to Au NPs, the incorporation of Au NPs into HAp NRs favored the adsorption of hydrazine, thus bringing hydrazine much closer to the catalytic sites of Au NPs and then increasing the efficiency of hydrazine oxidation in neutral solution. The amperometric (i–t) hydrazine sensor, using the as-prepared Au/HAp as the electrochemical catalyst, shows a wide linear response range of 0.5–1429 μM, a lower detection limit (0.017 μM) and very high sensitivity of 0.5 μA μM⁻¹ cm⁻². Furthermore, the Au/HAp nanocomposites showed an excellent anti-interference property towards the various organic and inorganic electroactive compounds, and good inter-electrode and intra-electrode reproducibility. Our present technique shows both qualitative and quantitative measurement of hydrazine in various water samples with high sensitivity, cost effectiveness and rapid analysis time.

With lithium-ion (li-ion) batteries as energy storage devices, operational safety from thermal runaway remains a major obstacle especially for applications in harsh environments such as in the oil industry. In this approach, a facile method via microwave irradiation technique (MWI) was followed to prepare Co₃O₄/reduced graphene oxide (RGO)/hexagonal boron nitride (h-BN) nanocomposites as anodes for high temperature li-ion batteries. Results showed that the addition ofh-BN not only enhanced the thermal stability of Co₃O₄/RGO nanocomposites but also enhanced the specific surface area. Co₃O₄/RGO/h-BN nanocomposites displayed the highest specific surface area of 191 m²/g evidencing the synergistic effects between RGO andh-BN. Moreover, Co₃O₄/RGO/h-BN also displayed the highest specific capacity with stable reversibility on the high performance after 100 cycles and lower internal resistance. Interestingly, this novel nanocomposite exhibits outstanding high temperature performances with excellent cycling stability (100% capacity retention) and a decreased internal resistance at 150 °C.

Two-dimensional atomically thick materials such as graphene and layered molybdenum disulfide (MoS₂) have been studied as potential energy storage materials because of their high specific surface area, potential redox activity, and mechanical flexibility. However, because of the layered structure restacking and poor electrical conductivity, these materials are unable to attain their full potential. Composite electrodes made of a mixture of graphene and MoS₂ have been shown to partially resolve these issues in the past, although their performance is still limited by inadequate mixing at the nanoscale. Herein, we report three composites via a simple ball-milling method and analyze supercapacitor electrodes. Compared with pristine graphene and MoS₂, the composites showed high capacitance. The as-obtained MoS₂@Graphene composite (1:9) possesses a high surface area and uniform dispersion of MoS₂ on the graphene sheet. The MoS₂@Graphene (1:9) composite electrode has a high specific capacitance of 248 F g^-1 at 5 A g^-1 in an electrochemical supercapacitor compared with the other two composites. Simultaneously, the flexible symmetric supercapacitor device prepared demonstrated superior flexibility and a long lifespan (93% capacitance retention after 8000 cycles) with no obvious changes in performance under different angles. In portable and wearable energy storage devices, the current experimental results will result in scalable, freestanding hybrid electrodes with improved, flexible, supercapacitive performance.

In this work, holey reduced graphene oxide (HRGO) was synthesized by the deposition of silver (Ag) nanoparticles onto the reduced graphene oxide (RGO) sheets followed by nitric acid treatment to remove Ag nanoparticles by microwave irradiation to form a porous structure. The HRGO were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultra violet-visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA) and Raman spectroscopy. These novel HRGO exhibited high rate capability with excellent cycling stability as an anode material for lithium-ion batteries. The results have shown an excellent electrochemical response in terms of charge/discharge capacity (423 mAh/g at 100 mA/g). The cyclic performance was also exceptional as a high reversible capacity (400 mAh/g at 100 mA/g) was retained for 100 charge/discharge cycles. This fascinating electrochemical performance can be ascribed to their specific porous structure (2–5 nm pores) and high surface area (457 m²/g), providing numerous active sites for Li⁺ insertion, high electrical conductivity, low charge-transfer resistance across the electrolyte–electrode interface and improved structural stability against the local volume change during Li⁺ insertion–extraction. Such electrodes are envisioned to be mass scalable with relatively simple and low-cost fabrication procedures, thereby providing a clear pathway toward commercialization.