Viral filtration using carbon-based materials.

Viral infections alone are a significant cause of morbidity and mortality worldwide and have a detrimental impact on global healthcare and socio-economic development. The discovery of novel antiviral treatments has gained tremendous attention and support with the rising number of viral outbreaks. In this work, carbonaceous materials, including graphene nanoplatelets and graphene oxide nanosheets, were investigated for antiviral properties. The materials were characterized using scanning electron microscopy and transmission electron microscopy. Analysis showed the materials to be two-dimensional with lateral dimensions ranging between 1 and 4 µm for graphene oxide and 110 ± 0.11 nm for graphene nanoplatelets. Antiviral properties were assessed against a DNA virus model microorganism at concentrations of 0.5, 1.0 and 2.0 wt/v%. Both carbonaceous nanomaterials exhibited potent antiviral properties and gave rise to a viral reduction of 100% across all concentrations tested. Graphene oxide nanosheets were then incorporated into polymeric fibres, and their antiviral behaviour was examined after 3 and 24 hr. A viral reduction of 39% was observed after 24 hr of exposure. The research presented here showcases, for the first time, the antiviral potential of several carbonaceous nanomaterials, also included in a carrier polymer. These outcomes can be translated and implemented in many fields and devices to prevent viral spread and infection.

Breaking the Nanoparticle Loading-Dispersion Dichotomy in Polymer Nanocomposites with the Art of Croissant-Making.

The intrinsic properties of nanomaterials offer promise for technological revolutions in many fields, including transportation, soft robotics, and energy. Unfortunately, the exploitation of such properties in polymer nanocomposites is extremely challenging due to the lack of viable dispersion routes when the filler content is high. We usually face a dichotomy between the degree of nanofiller loading and the degree of dispersion (and, thus, performance) because dispersion quality decreases with loading. Here, we demonstrate a potentially scalable pressing-and-folding method (P & F), inspired by the art of croissant-making, to efficiently disperse ultrahigh loadings of nanofillers in polymer matrices. A desired nanofiller dispersion can be achieved simply by selecting a sufficient number of P & F cycles. Because of the fine microstructural control enabled by P & F, mechanical reinforcements close to the theoretical maximum and independent of nanofiller loading (up to 74 vol %) were obtained. We propose a universal model for the P & F dispersion process that is parametrized on an experimentally quantifiable " D factor". The model represents a general guideline for the optimization of nanocomposites with enhanced functionalities including sensing, heat management, and energy storage.

The effect of graphene-poly(methyl methacrylate) fibres on microbial growth.

A novel class of ultra-thin fibres, which affect microbial growth, were explored. The microbial properties of poly(methyl methacrylate) fibres containing 2, 4 and 8 wt% of graphene nanoplatelets (GNPs) were studied. GNPs were dispersed in a polymeric solution and processed using pressurized gyration. Electron microscopy was used to characterize GNP and fibre morphology. Scanning electron microscopy revealed the formation of beaded porous fibres. GNP concentration was found to dictate fibre morphology. As the GNP concentration increased, the average fibre diameter increased from 0.75 to 2.71 µm, while fibre porosity decreased. Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa were used to investigate the properties of 2, 4 and 8 wt% GNP-loaded fibres. GNP-loaded fibres (0 wt%) were used as the negative control. The fibres were incubated for 24 h with the bacteria; bacterial colony-forming units were enumerated by adopting the colony-counting method. The presence of 2 and 4 wt% GNP-loaded fibres promoted microbial growth, while 8 wt% GNP-loaded fibres showed antimicrobial activity. These results indicate that the minimum inhibitory concentration of GNPs required within a fibre is 8 wt%.

Salt Templating with Pore Padding: Hierarchical Pore Tailoring towards Functionalised Porous Carbons.

We propose a new synthetic route towards nanoporous functional carbon materials based on salt templating with pore-padding approach (STPP). STPP relies on the use of a pore-padding agent that undergoes an initial polymerisation/ condensation process prior to the formation of a solid carbon framework. The pore-padding agent allows tailoring hierarchically the pore-size distribution and controlling the amount of heteroatom (nitrogen in this case) functionalities as well as the type of nitrogen (graphitic, pyridinic, oxides of nitrogen) incorporated within the carbon framework in a single-step-process. Our newly developed STPP method offers a unique pathway and new design principle to create simultaneously high surface area, microporosity, functionality and pore hierarchy. The functional carbon materials produced by STPP showed a remarkable CO2 /N2 selectivity. At 273 K, a carbon with only micropores offered an exceptionally high CO2 adsorption capacity whereas a carbon with only mesopores showed promising CO2 -philicity with high CO2 /N2 selectivity in the range of 46-60 %, making them excellent candidates for CO2 capture from flue gas or for CO2 storage.

In Situ Exfoliation of Graphene in Epoxy Resins: A Facile Strategy to Efficient and Large Scale Graphene Nanocomposites.

Any industrial application aiming at exploiting the exceptional properties of graphene in composites or coatings is currently limited by finding viable production methods for large volumes of good quality and high aspect ratio graphene, few layer graphene (FLG) or graphite nanoplatelets (GNP). Final properties of the resulting composites are inherently related to those of the initial graphitic nanoparticles, which typically depend on time-consuming, resource-demanding and/or low yield liquid exfoliation processes. In addition, efficient dispersion of these nanofillers in polymer matrices, and their interaction, is of paramount importance. Here we show that it is possible to produce graphene/epoxy nanocomposites in situ and with high conversion of graphite to FLG/GNP through the process of three-roll milling (TRM), without the need of any additives, solvents, compatibilisers or chemical treatments. This readily scalable production method allows for more than 5 wt % of natural graphite (NG) to be directly exfoliated into FLG/GNP and dispersed in an epoxy resin. The in situ exfoliated graphitic nanoplatelets, with average aspect ratios of 300-1000 and thicknesses of 5-17 nm, were demonstrated to conferee exceptional enhancements in mechanical and electrical properties to the epoxy resin. The above conclusions are discussed and interpreted in terms of simple analytical models.

Novel Preparation, Microstructure, and Properties of Polyacrylonitrile-Based Carbon Nanofiber-Graphene Nanoplatelet Materials.

Polyacrylonitrile (PAN) fibers containing various concentrations of graphene nanoplatelets (GNPs) were prepared by pressurized gyration, and carbon nanofibers (CNFs) were obtained after subsequent heat treatment and spark plasma sintering (SPS). The influence of processing parameters such as rotational speed, working pressure, carbonization, and SPS temperature on the diameter of the nanofibers has been studied. Furthermore, the thermal properties, morphologies, and crystallization properties of the CNFs have been investigated by using thermogravimetry, scanning and transmission electron microscopy, and Raman spectroscopy. Also, the electrical conductivity and the mechanical properties of these samples have been studied. The results suggest that the gyration conditions and the loading concentration of the GNPs significantly modified the properties of the nanofibers.

45S5 Bioglass(®)-MWCNT composite: processing and bioactivity.

Multi-walled carbon nanotube (MWCNT)-Bioglass (BG) matrix composite was fabricated using a facile and scalable aqueous colloidal processing method without using any surfactants followed by spark plasma sintering (SPS) consolidation. The individual MWCNTs were initially uniformly dispersed in water and then entirely immobilized on the BG particles during the colloidal processing, avoiding their common re-agglomeration during the water-removal and drying step, which guaranteed their uniform dispersion within the dense BG matrix after the consolidation process. SPS was used as a fast sintering technique to minimise any damage to the MWCNT structure during the high-temperature consolidation process. The electrical conductivity of BG increased by 8 orders of magnitude with the addition of 6.35 wt% of MWCNTs compared to pure BG. Short-duration tests were used in the present study as a preliminary evaluation to understand the effect of incorporating MWCNTs on osteoblast-like cells. The analysed cell proliferation, viability and phenotype expression of MG-63 cells showed inhibition on 45S5 Bioglass(®)-MWCNT composite surfaces.

Processing and bioactivity of 45S5 Bioglass(®)-graphene nanoplatelets composites.

Well dispersed 45S5 Bioglass(®) (BG)-graphene nanoplatelets (GNP) composites were prepared after optimising the processing conditions. Fully dense BG nanocomposites with GNP loading of 1, 3 and 5 vol% were consolidated using Spark plasma sintering (SPS). SPS avoided any structural damage of GNP as confirmed using Raman spectroscopy. GNP increased the viscosity of BG-GNP composites resulting in an increase in the sintering temperature by ~50 °C compared to pure BG. Electrical conductivity of BG-GNP composites increased with increasing concentration of GNP. The highest conductivity of 13 S/m was observed for BG-GNP (5 vol%) composite which is ~9 orders of magnitude higher compared to pure BG. For both BG and BG-GNP composites, in vitro bioactivity testing was done using simulated body fluid for 1 and 3 days. XRD confirmed the formation of hydroxyapatite for BG and BG-GNP composites with cauliflower structures forming on top of the nano-composites surface. GNP increased the electrical conductivity of BG-GNP composites without affecting the bioactivity thus opening the possibility to fabricate bioactive and electrically conductive scaffolds for bone tissue engineering.

Improved adhesive strength and toughness of polyvinyl acetate glue on addition of small quantities of graphene.

We have prepared composites of polyvinyl acetate (PVAc) reinforced with solution exfoliated graphene. We observe a 50% increase in stiffness and a 100% increase in tensile strength on addition of 0.1 vol % graphene compared to the pristine polymer. As PVAc is commonly used commercially as a glue, we have tested such composites as adhesives. The adhesive strength and toughness of the composites were up to 4 and 7 times higher, respectively, than the pristine polymer.

Toughened and machinable glass matrix composites reinforced with graphene and graphene-oxide nano platelets.

The processing conditions for preparing well dispersed silica-graphene nanoplatelets and silica-graphene oxide nanoplatelets (GONP) composites were optimized using powder and colloidal processing routes. Fully dense silica-GONP composites with up to 2.5 vol% loading were consolidated using spark plasma sintering. The GONP aligned perpendicularly to the applied pressure during sintering. The fracture toughness of the composites increased linearly with increasing concentration of GONP and reached a value of ∼0.9 MPa m1/2 for 2.5 vol% loading. Various toughening mechanisms including GONP necking, GONP pull-out, crack bridging, crack deflection and crack branching were observed. GONP decreased the hardness and brittleness index (BI) of the composites by ∼30 and ∼50% respectively. The decrease in BI makes silica-GONP composites machinable compared to pure silica. When compared to silica-Carbon nanotube composites, silica-GONP composites show better process-ability and enhanced mechanical properties.

Solvent-exfoliated graphene at extremely high concentration.

We describe three related methods to disperse graphene in solvents with concentrations from 2 to 63 mg/mL. Simply sonicating graphite in N-methyl-2-pyrrolidinone, followed by centrifugation, gives dispersed graphene at concentrations of up to 2 mg/mL. Filtration of a sonicated but uncentrifuged dispersion gives a partially exfoliated powder that can be redispersed at concentrations of up to 20 mg/mL. However, this process can be significantly improved by removing any unexfolaited graphite from the starting dispersion by centrifugation. The centrifuged dispersion can be filtered to give a powder of exfoliated few-layer graphene. This powder can be redispersed at concentrations of at least 63 mg/mL. The dispersed flakes are ~1 µm long and ~3 to 4 layers thick on average. Although some sedimentation occurs, ~26-28 mg/mL of the dispersed graphene appears to be indefinitely stable.