The present study focuses on an efficient eco-friendly method for reducing graphene oxide (rGO) using Coffea arabica leaf extract for bio-medical applications for the first time to the best of our knowledge. The reduction of graphene oxide (GO) using Coffea arabica leaves was verified through Raman, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM). The XRD peaks corresponding to GO at 2 =10º have dissapeared on reduction of GO to rGO and the formation of rGO was verified through a new broad peak at 2 =26º. FTIR revealed functional group changes in reducing GO to rGO. The SEM images of rGO showed a ribbed form instead of the rigid appearance of the GO flakes. The analysis revealed that the current green method is a feasible method for reducing GO to rGO and formation of the Coffea arabica/rGO nanocomposite. The composite prepared from young coffee leave exhibited higher antioxidant capacity than matured leave against scavenging 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radicals. Fascinatingly, the Coffea arabica/rGO nanocomposite showed an anti-inflammatory activity as well suggesting that the Coffea arabica /rGO nanocomposite is promising candidate for bio-medical applications in near future.
Research was carried out to develop a wound dressing hydrogel using polyvinylpyrrolidone (PVP), kappa carrageenan and polyethylene glycol (PEG) by Co 60 gamma irradiation. The gel has a soothing effect and it is not necessary to change the dressing too often. This gel is suitable for the tropical conditions of Sri Lanka and has a comparatively long shelf-life. The cost is affordable. Aqueous solutions of PVP & kappa-carrageenan were mixed with low molecular weight PEG to form the pseudogel which was then subjected to 25kGy irradiation. Absorption behaviour in distilled water, 9% saline water and pseudoextracellular fluid, tensile properties, bioadhesion onto human skin and sterility/shelf-life were studied in comparison with commercial hydrogels. The chemical and physical behaviour of the PVP/carrageenan/PEG hydrogel were further studied by analyzing FTIR spectra and SEM images. The observations made in the study concluded that the properties of the developed hydrogel are comparable to that of the commercial hydrogels, to the level required to apply as a wound dressing. The results obtained from testing and analysis of the hydrogel further confirm that the PVP/carrageenan/PEG hydrogel has been developed to the point where it is ready to proceed to clinical trials.
After exfoliation of graphite and discovered graphene in 2004 by Novoselov and Geim, the attention of graphene by the global scientific community enhanced progressively as a multifunctional wonder material in the world due to its unique extraordinary properties.Numerous methods apart from the discovered method have been investigated to synthesize the graphene in mass scale for variety of applications. Consequently, we believe that an adequate knowledge is necessary to choose a proper method of synthesis for a particular application. The main objective of the present review is to summarize the feasible methods followed in synthesis of graphene, discussing their properties, applications, advantages, and disadvantages for future prospects.
The present study was aimed to obtain the optimum yield of graphene oxide (GO) from Kahatagaha graphite by optimizing oxidation time, and to effectively utilize hydrothermal microwave irradiation technique to produce high quality reduced graphene oxide (rGO) with the optimum level of reduction from Kahatagaha graphene oxide. Kahatagaha vein graphite was specifically selected for the study due to its remarkable morphological, structural, compositional and carbon isotropic variations from the other types of graphite. Oxidation time of Kahatagaha graphite was optimized and subsequently, microwave irradiation time was optimized to obtain maximumly reduced graphene oxide from the synthesized GO. XRD, SEM, FTIR and gravimetric analyses were employed to characterize the synthesized GO and rGO. The optimized oxidation time for the complete conversion of Kahatagaha graphite to GO was 5 hours that resulted in a yield of 170 % (w/w) with respect to the amount of graphite used. This level of yield would be highly beneficial for commercial productions of GO. The maximum level reduction of GO (production of rGO) was achieved in 20 minutes _________________________________________________________________________
This study was focused on evaluation of conducting and tensile properties of rGO/ Polybutylene adipate terephthalate (PBAT) nanocomposite intended to use in electronic applications which require biodegradability. This study was also considered to be worthwhile since very little work has been done in this regard so far. PBAT was specifically selected for the study as it is an extensively used biodegradable polymer for variety of applications. The solvent casting method was employed to prepare rGO/PBAT nanocomposites where rGO was dispersed in a solution of PBAT by ultrasonication followed by evaporation of the solvent components. Electrical conductivity (σ) of rGO/PBAT nanocomposites showed a percolation behavior as rGO content was increased from the 0.5 % to 1.5 % (σ increased drastically with the increase of rGO content). The percolation threshold was approximately 0.0045, (i.e., 0.75 w/w % of rGO). The average critical exponent (t) related to the percolation theory was 1.49 ± 0.19 which is well within the expected range 1< t < 2. According to impedance studies, the electrical impedance of GO/PBAT composites decreased with the increasing rGO content, which agreed well with the behavior of the electrical conductivity investigated previously. The same equivalent circuit was shown by each composite except the values for constant phase element CPE and resistor R; the equivalent electrical circuit was a parallel combination of CPE and R. The dielectric analysis of the composites indicated that dielectric parameters ϵ”, ϵ’ and dissipation factor increased significantly with increasing rGO content. The tensile strength of the composites was better than that of neat PBAT up to 1.5 % of rGO loading and decreased on further increasing of rGO. However, their tensile strain at break decreased with increasing rGO content. The results indicated that PBAT/rGO polymer composite is promising candidate for various electronic applications.
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