Preparation Of Graphene-based Nanocomposites Research Articles

Preparation of graphene-based nanocomposites with spinel ferrite nanoparticles: Their cytotoxic levels in different human cell lines and molecular docking studies

Nanocomposite-modified structures based on reduced graphene oxide (rGO) are preferred because of their excellent advantages. Here we assessed the comparative interaction of graphene oxide (GO), chemically reduced GO (rGO), copper and nickel spinel ferrite nanoparticles (CuFe2O4 NPs and NiFe2O4 NPs) and their nanocomposites with reduced graphene oxide (rGOCuFe2O4, rGONiFe2O4 NCs). The synthesized nanomaterials were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis. The cytotoxic analysis revealed a nontoxic behavior at concentrations below 50 µg/mL in human fetal lung fibroblast (MRC-5), human hepatocellular carcinoma (HepG2), and human glioblastoma (TG98) cell lines. The IC50 values were found to be lower in rGO than that of GO in MRC-5 and T98G cell lines. 50 µg/mL and higher concentrations of rGOCuFe2O4 NCs displayed more potent cytotoxic effects in MRC-5 and HepG2 cell lines compared with the CuFe2O4 NPs. Cytotoxicity was decreased in HepG2 and T98G cell lines treated with rGONiFe2O4 NCs compared to NiFe2O4 NPs but increased in MRC-5. According to the molecular docking results, DNA binding modes of all nanomaterials were found to be minor groove recognition, while their DNA binding affinities ranged between -4.78 and -12.89 kcal/mol. Docking results showed that, based on their sharp-edged conformations, GO and rGO, and rGO-MFe2O4 (M: Cu, Ni) composites may be promising shape-selective DNA minor groove binders, with the potential to cause specific DNA damage in cancer cells.

Edge Functionalized Graphene Layers for (Ultra) High Exfoliation in Carbon Papers and Aerogels in the Presence of Chitosan.

Ultra-high exfoliation in water of a nanosized graphite (HSAG) was obtained thanks to the synergy between a graphene layer edge functionalized with hydroxy groups and a polymer such as chitosan (CS). The edge functionalization of graphene layers was performed with a serinol derivative containing a pyrrole ring, serinol pyrrole (SP). The adduct between CS and HSAG functionalized with SP was formed simply with a mortar and pestle, then preparing water dispersions stable for months in the presence of acetic acid. Simple casting of such dispersions on a glass support led to carbon papers. Aerogels were prepared through the freeze-dry procedure. Exfoliation was observed in both these families of composites and ultra-high exfoliation was documented in aerogels swollen in water. Carbon papers and aerogels were stable for months in solvents in a wide range of solubility parameter and in a pretty wide range of pH. By considering that a moderately functionalized nanographite was straightforwardly exfoliated in water in the presence of one of the most abundant biobased polymers, the obtained results pave the way for the simple and sustainable preparation of graphene-based nanocomposites. HSAG–SP/CS adducts were characterized by wide angle X-ray diffraction (WAXD), scanning and transmission electron microscopy (SEM, TEM and HRTEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Thermal stability of the composites was studied by thermogravimetric analysis (TGA) and their direct electrical conductivity with the four-point probe method.

Acid-free co-operative self-assembly of graphene-ZnO nanocomposites and its defect mediated visible light photocatalytic activities

We propose an acid-free and environmental friendly surfactant based approach to anchor zinc oxide (ZnO) nanoparticles on graphene. Herein, liquid-phase exfoliated graphene in water by ultrasonic waves has been used to prepare graphene-ZnO (G-ZnO) nanocomposites that circumvent the use of various toxic acids and chemicals which are generally used in the preparation of graphene-based nanocomposites. Oxygen vacancy related defect peaks observed by Raman and photoluminescence confirm the formation of C–O–Zn bond due to the synergistic interaction of carbon and zinc via oxygen atoms in G-ZnO nanocomposites. The enhanced photocatalytic behavior of G-ZnO under visible light as evaluated using the dye Rhodamine B holds its genesis from the intrinsic oxygen defects in G-ZnO. Furthermore, graphene acts as electron sink for accumulation of charges from defect levels of ZnO, which controls recombination of charge carriers. It is envisaged that the acid-free and facile strategy can be a potential route for the preparation of graphene-based hybrid materials using liquid-phase exfoliation methodology.

A controllable synthetic route for preparing graphene-Cu and graphene-Cu2O nanocomposites using graphene oxide-Cuo as a precursor

The development of convenient method to obtain graphene-based nanocomposites is a key issue for their application. Herein, we described a facile route for synthesizing graphene-Cu and graphene-Cu2O nanocomposites using graphene oxide-CuO as a precursor. Remarkably, the different nanocomposites could be formed just by varying the reaction temperature and time. This work provides a feasible route for the preparation of graphene-based nanocomposites with various constituents.

Thermal Reduction of Graphene Oxide in Organic Solvents for Producing Colloidal Suspensions of Reduced Graphene Oxide Sheets

A new method for preparing graphene colloidal suspension is studied by thermal reducing graphene oxide in N-methylpyrrolidone (NMP) and γ-Butyrolactone (GBL) at 200°. Without assistance of polymeric or surfactant stabilizers, thermal reduction and dispersion of reduced graphene sheets are performed in one pot, and stable suspensions are confirmed by transmission electron microscope (TEM) and atomic force microscope (AFM) technic. Experimental results such as thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Raman indicate bulk cleavage of oxygen-containing functional groups and restoration of graphite structure on reduced graphene oxide sheets. The study contributes to the preparation of graphene-based nanocomposites using this quick and low-cost processing technique.

Stable aqueous dispersions of graphene prepared with hexamethylenetetramine as a reductant

Highly stable graphene aqueous dispersions were achieved by chemical reduction of graphene oxide with an environmentally friendly reagent of hexamethylenetetramine (HMTA). By this method, chemical reduction as well as dispersion of graphene can be carried out in one step without the need of organic stabilizers or pH control. The as-synthesized products were characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy, scanning and transmission electron microscopy, and thermogravimetry and differential scanning calorimetry. It is revealed that the bulk of the oxygen-containing functional groups were removed from graphene oxide via HMTA reduction, and stable aqueous colloidal dispersions of graphene have a concentration up to ca. 0.65 mg/mL. Moreover, it is found that the freshly precipitated graphene nanosheets can be re-dispersed in water with simple ultrasonic treatment. A mechanism for the formation of stable graphene colloidal dispersions is proposed. This simple and green approach should find practical applications in the preparation of graphene-based nanocomposites with a facile and low-cost solution processing technique.