A facile co-solvent strategy for preparation of graphene nanoplatelet powder: An industrially viable innovative approach

We report an industrially viable promising approach to produce micrometer-sized multilayer graphene nanoplatelet powder (MGNP) in a scalable quantity via microwave-assisted exfoliation of graphite (MEG) and fragmented into MGNP through liquid-phase exfoliation in the co-solvent mixture by kitchen mixer (KM). KM allows rapid delaminating MEG into MGNP by shear force dominated exfoliation. Majority of MGNPs are with a diameter of few micrometers and thickness is in nanometers. MGNP are crystalline with very limited defects was confirmed by Raman measurements and transmission electron microscopy. This process transforms, more than 86% of graphite flakes into MGNP. This advanced approach opens a new pathway to produce MGNP in bulk quantity as it is feasible, rapid, and cost-effective.     

Weak Delocalization in Graphene on a Ferromagnetic Insulating Film

Graphene has been predicted to develop a magnetic moment by proximity effect when placed on a ferromagnetic film, a promise that could open exciting possibilities in the fields of spintronics and magnetic data recording. In this work, the interplay between the magnetoresistance of graphene and the magnetization of an underlying ferromagnetic insulating film is studied in detail. A clear correlation between both magnitudes is observed but through a careful modeling of the magnetization and the weak localization measurements, that such correspondence can be explained by the effects of the magnetic stray fields arising from the ferromagnetic insulator is found. The results emphasize the complexity arising at the interface between magnetic and 2D materials.     

Interaction of graphene,MnOx, and Ca2+ for enhanced biomimetic, ‘bubble-free’ oxygen evolution reaction at mild pH

Water electrolysis powered by renewable electricity will likely be critical to a future hydrogen economy. However, the typical use of strongly acidic or alkaline electrolytes necessitates the use of expensive materials, while bubbles add to capital and operational costs, due to blocking of the electrode surface and the necessary use of pumps and gas-liquid separators. Here ‘bubble-free’ oxygen evolution at mild pH is carried out using an electrocatalyst that mimics photosystem II (PSII). The bubble-free electrode includes a gas-extracting Gore-Tex® membrane. Edge-functionalised graphene (EFG) is included to mimic the metal-binding local protein environment, and the tyrosine residue, in the oxygen evolving complex (OEC) of PSII, while MnO_x and Ca²⁺ are incorporated to mimic the Mn₄CaO₅ cluster. Interaction between EFG, MnO_x, and Ca²⁺ results in a significant, 130 mV fall in the overpotential required to drive electrocatalytic oxygen evolution at 10 mA cm⁻², compared to the electrode without these biomimetic components.     

Facile synthesis of Co0.5Zn0.5Fe2O4 nanoparticles decorated reduced graphene oxide hybrid nanocomposites with enhanced electromagnetic wave absorption properties

Herein, reduced graphene oxide/cobalt-zinc ferrite (RGO/Co_0.5Zn_0.5Fe₂O₄) hybrid nanocomposites were fabricated by a facile hydrothermal strategy. Results revealed that the contents of RGO could affect the micromorphology, electromagnetic parameters and electromagnetic wave absorption properties. As the contents of RGO increased in the as-synthesized hybrid nanocomposites, the dispersibility of the particles was improved. Meanwhile, numerously ferromagnetic Co_0.5Zn_0.5Fe₂O₄ particles were evenly anchored on the wrinkled surfaces of flaky RGO. Besides, the obtained hybrid nanocomposites exhibited superior electromagnetic absorption in both X and Ku bands, which was achieved by adjusting the RGO contents and matching thicknesses. Significantly, when the content of RGO was 7.4 wt%, the binary nanocomposites showed the optimal reflection loss of -73.9 dB at a thickness of 2.2 mm and broadest effective absorption bandwidth of 6.0 GHz (12.0–18.0 GHz) at a thin thickness of merely 2.0 mm. The enhanced electromagnetic absorption performance was primarily attributed to the multiple polarization effects, improved conduction loss caused by electron migration, and magnetic loss derived from ferromagnetic Co_0.5Zn_0.5Fe₂O₄ nanoparticles. Our results could provide inspiration for manufacturing graphene-based hybrid nanocomposites as high-efficient electromagnetic wave absorbers.     

Preparation of ZrC/SiC porous self-supporting monoliths via sol-gel process using polyethylene glycol as phase separation inducer

We present a straightforward method via sol-gel process using polyethylene glycol (PEG) as phase separation inducer to prepare zirconium carbide/silicon carbide (ZrC/SiC) porous monoliths. Organic/inorganic hybrid gels are prepared using zirconium oxychloride, furfuryl alcohol, and tetraethyl orthosilicate as major starting materials. In the presence of PEG, crack-free hybrid monoliths are obtained by drying the wet gels under ambient pressure, whereas in the absence of PEG, the wet gels break into pieces as expected. PEG plays a key role in maintaining the macroscopic shape of the monoliths. After ceramization at 1300–1500?°C, ZrC/SiC porous monoliths are obtained. SEM and mercury intrusion porosimetry data show that PEG also has strong influence on the microstructures of the monoliths. The compressive strengths of the ceramic monoliths are in the range of 0.3 to 0.7?MPa. And their compressive behavior starts to differ due to the changes in their microstructures, especially the pore structure.     

Nanocrystalline transition metal oxides and their composites with reduced graphene oxide and carbon nanotubes for photocatalytic applications

Transition metal oxide nanoparticles (CuO, ZnO & Fe₂O₃) and mixed metal oxides CuO. ZnO.Fe₂O₃ were fabricated by facile co-precipitation approach for photocatalytic treatment of organic dyes. The structural features, phase purity, crystallite size and morphology of individual and mixed metal oxides were analysed by X-rays diffraction patterns (XRD) and scanning electron microscopic (SEM) analysis. Electrical behaviour of CuO, ZnO, Fe₂O₃ and mixed metal oxides CuO. ZnO.Fe₂O₃ was explored by current-voltage (I-V) measurements. Functional groups present in the synthesized metal oxides were investigated by Fourier transform infrared spectroscopy (FTIR) which ensures the existence of M-O functional groups in the samples. The optical bandgap analysis was carried out by UV–visible spectroscopic technique which revealed that the blend of three different transition metal oxides reduced the bandgap energy of mixed metal oxides. The reason behind this reduced bandgap energy is formation of new electronic state which arises due to the metal-oxygen interactions. Moreover, the nanocomposites of CuO.ZnO.Fe₂O₃ with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) were prepared to study the effect of the carbonaceous materials on the rate of photodegradation. These carbonaceous nanomaterials have plethora properties which can bring advancement in sector of photocatalytic treatment of wastewater. The photocatalytic experiments were performed using methylene blue (MB) as standard dye for comparative study of metal oxides and their composites with rGO and CNTs. The percentage degradation of methylene blue (MB) by nanocomposite CuO.ZnO.Fe₂O₃/rGO is 87% which is prominent among all samples. This result ascribed the photocatalytic aspects of reduced graphene oxide along with mixed metal oxides.     

Decorating surface charge of graphite nanoplate using an electrostatic coupling agent for 3-dimensional polymer nanocomposite

Here, we report a facile approach to electrostatically couple the surface charges of graphite nanoplate (GNP) fillers and poly(methyl methacrylate) (PMMA) polymer particles using ethylene maleic anhydride (EMA) copolymer as an electrostatic coupling agent. Our strategy involved switching the intrinsic repulsive electrostatic interactions between the directly exfoliated GNPs fillers and the PMMA particles to attractive electrostatic surface interactions for preparing core(PMMA)-shell (GNP) precursor in order to optimizing 3-dimensionally dispersed polymer nanocomposite. As a result, the electrical conductivity of the composites dramatically increased by a factor of 16.7 in the EMA-coupled GNP/PMMA composites compared with that of the EMA-free GNP/PMMA composites. In addition, the percolation threshold was also notably reduced from 0.32 to 0.159 vol% after electrostatic coupling of the GNPs fillers and PMMA particles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48390.     

On‐the‐Spot Immobilization of Quantum Dots,Graphene Oxide,and Proteins via Hydrophobins

Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications.     

石墨烯热电器件栅控特性研究

为了获得一种稳定可控的能源，提出一种栅控石墨烯热电器件。通过对石墨烯通道的载流子输运机理的分析，获得了温度和栅压对通道电阻的影响。依据半经典Mott公式推导了石墨烯塞贝克系数的表达式，同时给出了石墨烯的电导率和热导率模型。最后通过有限元分析(FEA)建模获得不同栅压条件下的器件温度，当栅极电压V_B=0 V时，石墨烯热电器件热端和冷端温度差为30 K；当V_B=6 V时，最大温差达到50 K；当V_B=30 V时，最小温差只有10 K。结果表明，栅压对热电器件的性能有明显的调控性。该研究可为石墨烯热电器件的设计提供理论参考。