Microbial infections are considered one of the most dangerous infections in humans due to their resistance to most antimicrobial agents. In this study, nanocomposites based on reduced graphene oxide (RGO) and metal oxides (NiO, AgO, and ZnO) were fabricated. The graphite precursor and RGO were characterized by XRD, Raman spectroscopy, SEM, and HRTEM, while SEM, XRD, and EDX mapping analysis validated the synthesized nanocomposites. In addition, ZOI and MIC were employed to test the antimicrobial potential, while their antibiofilm activity and the effect of UV illumination were also investigated. Finally, reaction mechanism determination was performed using SEM analysis. The results revealed that all the synthesized nanocomposites (RGO-NiO, RGO-AgO, and RGO-ZnO) had outstanding antimicrobial activity against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), unicellular fungi (Candida albicans and Cryptococcus neoformans) and multicellular fungi (Aspergillus niger, A. terreus, A. flavus and A. fumigatus). Moreover, the synthesized RGO-NiO nanocomposite exhibited antibiofilm activity (following 10.0 µg mL−1 RGO-NiO), with an inhibition percentage of 94.60% for B. subtilis, 91.74% for P. aeruginosa, and 98.03% for C. neoformans. The maximum percentage inhibition under UV illumination toward P. aeruginosa, B. subtilis and C. neoformans at the end of the experiment using RGO-NiO were 83.21%, 88.54%, and 91.15%, respectively, while the values of RGO-AgO were 64.85%, 68.0%, and 80.15%, respectively, and those of RGO-ZnO were 72.95%, 82.15%, and 79.25%, respectively. The SEM analysis of C. neoformans in the absence of the RGO-NiO nanocomposite showed the development of unicellular fungal cells by regular budding. In contrast, after RGO-NiO treatment, noticeable morphological differences were identified in C. neoformans, including the lysis of the outer surface with deformations of the fungal cells. In conclusion, the prepared nanocomposites are promising antimicrobial and antibiofilm agents and can be used to treat the pathogenic microbes at low concentrations and represent a new strategy for managing infectious diseases caused by pathogenic microorganisms.

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Promising antimicrobial and antibiofilm activities of reduced graphene oxide-metal oxide (RGO-NiO, RGO-AgO, and RGO-ZnO) nanocomposites

Structure Investigation by Neutron Diffraction and X-Ray Diffraction of Graphene Nanocomposite CuO–rGO Prepared by Low-Cost Method

A tin oxide (SnO2) and reduced graphene oxide (rGO) hybrid composite gas sensor for high-performance carbon dioxide (CO2) gas detection at room temperature was studied. Since it can be used independently from a heater, it emerges as a promising candidate for reducing the complexity of device circuitry, packaging size, and fabrication cost; furthermore, it favors integration into portable devices with a low energy density battery. In this study, SnO2-rGO was prepared via an in-situ chemical reduction route. Dedicated material characterization techniques including field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) were conducted. The gas sensor based on the synthesized hybrid composite was successfully tested over a wide range of carbon dioxide concentrations where it exhibited excellent response magnitudes, good linearity, and low detection limit. The synergistic effect can explain the obtained hybrid gas sensor’s prominent sensing properties between SnO2 and rGO that provide excellent charge transport capability and an abundance of sensing sites.

A Highly Sensitive Room Temperature CO2 Gas Sensor Based on SnO2-rGO Hybrid Composite.

Abstract Global food crisis due to climate change, pandemic COVID-19 outbreak, and Russia-Ukraine conflict leads to catastrophic consequences; almost 10 percent of the world’s population go to bed hungry daily. Narrative solution for green agriculture with high vegetation and crop yield is mandatory; novel nanomaterials can improve plant immunity and restrain plant diseases. Iron is fundamental nutrient element; it plays vital role in enzyme activity and RNA synthesis; furthermore it is involved in photosynthesis electron-transfer chains. This study reports on the facile synthesis of colloidal ferric oxide nanoparticles as novel nano-fertilizer to promote vegetation and to suppress Fusarium wilt disease in tomato plant. Disease index, protection percent, photosynthetic pigments, and metabolic indicators of resistance in plant as response to induction of systemic resistance (SR) were recorded. Results illustrated that Fe 2 O 3 NPs had antifungal activity against F . oxysporum . Fe 2 O 3 NPs (at 20 µg/mL) was the best treatment and reduced percent disease indexes by 15.62 and gave highly protection against disease by 82.15% relative to untreated infected plants. Fe 2 O 3 NPs treatments in either (non-infected or infected) plants showed improvements in photosynthetic pigments, osmolytes, and antioxidant enzymes activity. The beneficial effects of the synthesized Fe 2 O 3 NPs were extended to increase not only photosynthetic pigments, osmolytes contents but also the activities of peroxidase (POD), polyphenol oxidase (PPO), catalase (CAT) and superoxide dismutase (SOD), enzymes of the healthy and infected tomato plants in comparison with control. For, peroxidase and polyphenol oxidase activities it was found that, application of Fe 2 O 3 NPs (10 µg/mL) on challenged plants offered the best treatments which increased the activities of POD by (34.4%) and PPO by (31.24%). On the other hand, application of Fe 2 O 3 NPs (20 µg/mL) on challenged plants offered the best treatments which increased the activities of CAT by (30.9%), and SOD by (31.33%). 

/pdf/ferric-oxide-colloid-towards-green-nano-fertilizer-for-266be1bw.pdf

Ferric Oxide Colloid: Towards Green Nano-Fertilizer for Tomato Plant with Enhanced Vegetative Growth and Immune Response Against Fusarium Wilt Disease

Improving energy harvesting efficiency of dye sensitized solar cell by using cobalt-rGO co-doped TiO2 photoanode

Whereas ferric oxide particles are common catalyst for energetic oxidizers such as ammonium perchlorate (APC), reduced graphene oxide (RGO) with superior thermal conductivity as well as high interfacial surface area could be candidate substrate for advanced catalytic systems. This study reports on the facile synthesis of RGO-Fe2O3 nanocomposite as a novel catalyzing agent for APC oxidizer. GO was developed via oxidation of graphite using Hummer’s method, while RGO was developed via GO reduction with hydrazine hydrate. RGO-Fe2O3 nanocomposite was developed via direct precipitation method. Morphological characterization of RGO-Fe2O3 nanocomposite demonstrated the formation of hematite RGO-Fe2O3 nanocomposite in the form of rod-shaped crystals with average crystallite size 30 nm. The synthesized RGO-Fe2O3 nanocomposite was effectively-encapsulated into APC particles via co-precipitation technique. The catalytic performance of RGO-Fe2O3 nanocomposite on APC thermal behavior was evaluated using DSC and TGA. RGO-Fe2O3 nanocomposite demonstrated superior catalytic performance; APC initial endothermic decomposition was decreased by 16% which could be ascribed to enhance the thermal conductivity and catalytic efficiency of the developed hybrid. APC total heat release was enhanced by 83%; this could be ascribed to superior interfacial surface area. Gaseous products could be efficiently-adsorbed on the catalyst surface offering high combustion enthalpy.

Seham K. Abdel Aal

Papers

Facile synthesis of RGO-Fe 2 O 3 nanocomposite: A novel catalyzing agent for composite propellants