Graphene-Cuprous Oxide nanocomposite

Synthesis and Characterization of Graphene-Cuprous oxide Nano-composite and its photo catalytic and anti-fungal (candida) application

Graphene, the purest form of carbon. It is exceptional material due to properties such as large theoretical surface area (2360 m²/g) , high intrinsic mobility (200,000 cm²v ⁻¹s ⁻¹), extremely high Young's Modulus (~1TPa), thermal Conductivity (∼5000Wm⁻¹K⁻¹), optical transmittance (~97.7 %) and robust and flexible membrane, which provides essentially infinite possibilities for the modification or functionalization of its carbon backbone. The last property is exploited to make Graphene composites which find application in catalysis, fuel cells, bio-sensors and optics. Graphene is a 2D building material for carbon materials of all other dimensionalities. It can be wrapped up into 0D buckyballs, rolled into 1D nanotubes or stacked into 3D graphite.

Cuprous oxide (Cu₂O) is attracting more and more research attention for its potential applications in hydrogen production, solar energy, catalysis, and anode material for lithium ion batteries. Apart from some research on the morphology of Cu₂O, several studies have been performed regarding the integration of Cu₂O on carbonaceous materials to obtain enhanced properties for applications, such as the stable catalytic activity of carbon nano-tubes Cu₂O cathodes in water treatment.

Objective and scope of this project work can be stated as follows:

1. To synthesize Graphene oxide from Graphite powder using modified Hummer‘s method.
2. To synthesize Graphene-Cuprous oxide nano-composite using copper acetate-adsorbed graphene oxide (GO) sheets as precursors.
3. To characterize the as synthesized nano-composite using optical techniques viz. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction, Fourier Transform Infrared (FTIR) Spectroscopy and thermal techniques viz. Thermogravimetric Analysis(TGA) techniques.
4. To study the photo catalytic activity of graphene-cuprous oxide nano-composite for the degradation of methyl orange aqueous solution under ultraviolet light irradiation.
5. To study the anticandidal action of graphene-cuprous oxide nano-composite against the growth of C. albicans077 in dose dependent manner.

Graphene Oxide synthesis

The route to prepare GO involves two main steps; Firstly, graphite powder is oxidized to produce graphite oxide, which can be readily dispersed in water or another polar solvent due to the presence of hydroxyl and epoxide groups across the basal planes of graphite oxide and carbonyl and carboxyl groups located at the edges. Secondly, the bulk graphite oxide can be exfoliated by sonication to form colloidal suspensions of mono layer, bi layer or few-layer GO sheets in different

Most popular methods to prepare Graphene Oxide:

However, all three reactions involve the liberation of toxic gas NOx and/or ClO2. Some modifications based on the Hummers method have been proposed.

1. Kovtyukhova added a pre-oxidized procedure using H2SO4, K2S2O8, and P2O5. The C/O ratio of the oxidation product was 4.0/3.1, illustrating that this was richer in oxygen than the graphite oxide prepared by the Hummers method. The method proposed by Kovtyukhova is defined as a typical "modified Hummers method".
2. Marcano found another method, which is named the “improved Hummers method”. Here, in the improved Hummers method, using KMnO4, H2SO4, and H3PO4 as the oxidizing agents, avoids the release of NOx and yields a greater amount of hydrophilic oxidized graphite material compared to the original Hummers method. Due to its simpler protocol and equivalent conductivity upon reduction, the improved Hummers method is attractive for preparing GO on a large scale. Recently, Li reported that GO prepared by the improved Hummers method could obtain a high grafting rate of poly (L-lactic acid) (30.8%) at a moderate condition.

Graphene-cuprous oxide nano composite synthesis (Thermal reduction of GO with sodium borohydride)

Characterization of Graphene-cuprous oxide nano composite

The following methods were used to characterize the Graphene-Cuprous nano-composite:

• UV-vis spectrophotometer
• X-ray Diffraction (XRD) (View XRD peak of Graphene: xrd pattern.JPG)
• Fourier Transform Infrared Microscopy (FTIR) (View FTIR pattern: FTIR pattern.pdf)
• Scanning Electron Microscopy (SEM) (View SEM images: SEM images.pdf)
• Transmission Electron microscopy (TEM) (View TEM images: TEM images.JPG)
• Frequency dependent dielectric spectroscopy

Anti-candida activity of Graphene-Cu₂O composite

The anti-candida activity was measured using C. Albicans 077 culture in agar medium. The below methods were used:

1. Agar disc diffusion assay: Different concentrations of graphene/Cu2O nanocomposite (0, 5, 10, and 15 μg/ml) were loaded onto the paper discs. The Petri plates were incubated at 37 0C for 40 h, after that zone of inhibition were determined by measuring the diameter of C. albicans077 cells clearance.
2. In-vitro killing assay: Various concentrations of graphene/Cu2O nanocomposite (0, 5, 10, and 15 μg/ml) diluted in 100 μl sterile SD broth medium was added and incubated at 37 0C for 2 h. Cytotoxicity was detected by the dose dependent reduction in number of colony forming units (CFUs).

View Anti-candida test results: Anti-candida test.pdf

Photo catalytic activity of graphene-Cu2O nanocomposite

The photocatalytic activity of graphene/Cu2O nanocomposites is measured against the methyl orange (MO) dye under UV light irradiation (365 nm). In the photocatalytic degradation experiment graphene/Cu2O nanocomposites catalyst was added to dye solution. Before irradiation, the suspensions containing MO dye and graphene/Cu2O nanocomposites were magnetically stirred in the dark to ensure the establishment of an adsorption/desorption equilibrium. At a fixed time interval aliquots were sampled and then magnetically separated to remove essentially all the graphene/Cu2O nanocomposite. The filtrate was analyzed by recording variations in the maximum absorption band (λmax ~465nm ) using a UV-vis spectrophotomete in the wavelength range of 200 to 800 nm. The degradation of the MO dye via the photocatalytic activity of graphene/Cu2O nanocomposites was calculated by measuring the MO dye initial concentration before degradation and the absorbance after the different time intervals.

View tests for photocatalytic activity: Photocatalytic test.pdf