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In the present investigation, natural bone-derived hydroxyapatite (HA, 2 wt %) and/or exfoliated graphene (Gr, 0.1 wt %)-embedded polydimethylsiloxane (PDMS) elastomeric films were prepared using a vascular method. The morphology, mechanical properties, crystallinity, and chemical structure of the composite films were evaluated. The in vitro biodegradation kinetics of the films indicates their adequate physiological stability. Most of the results favored PDMS/HA/Gr as a best composite scaffold having more than 703% elongation. A simulation study of the microfluidic vascular channel of the PDMS/HA/Gr scaffold suggests that the pressure drop at the outlet became greater (from 1.19 to 0.067 Pa) unlike velocity output (from 0.071 to 0.089 m/s), suggesting a turbulence-free laminar flow. Our bioactive scaffold material, PDMS/HA/Gr, showed highest cytotoxicity toward the lung cancer and breast cancer cells through Runx3 protein-mediated cytotoxic T lymphocyte (CTL) generation. Our data and predicted mechanism also suggested that the PDMS/HA/Gr-supported peripheral blood mononuclear cells (PBMCs) not only increased the generation of CTL but also upregulated the expression of RUNX3. Since the PDMS/HA/Gr scaffold-supported Runx3 induced CTL generation caused maximum cell cytotoxicity of breast cancer (MCF-7) and lung cancer (A549) cells, PDMS/HA/Gr can be treated as an excellent potential candidate for CTL-mediated cancer therapy.

Biocompatible graphene quantum dots (GQDs), obtained from extracts of neem root, are found to be suitable for structured illumination microscopy and two-photon microscopy (TPM). Results of TPM and confocal luminescence microscopy ensure lysosome specificity in live cells and tissue-dependent localization in zebrafish, respectively, of GQDs.

Over the past decades, the synthesis of inorganic and organic nanocomposites has received much attention in the range of fields including electroanalysis of organic chemicals. In this regard, we have prepared copper oxide nanoparticle (CuO NPs) decorated graphene/β-cyclodextrin (GR-β-CD) composites using a simple electrochemical methodology, where the CuO NPs are electrodeposited on GR-β-CD composite modified electrodes. A stable GR-β-CD composite was prepared by sonication of GR in β-CD aqueous solution. As-prepared GR-β-CD/CuO NPs composites were characterized by the high-resolution scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Cyclic voltammetry results reveal that the GR-β-CD/CuO NPs composite modified electrode exhibits an excellent catalytic activity and lower reduction potential towards the electrochemical detection of metronidazole (MTZ) over other modified electrodes including GR, GR-β-CD, and CuO NPs. Under optimized conditions, amperometry was used for the determination of MTZ using GR-β-CD/CuO NPs composite modified electrodes. The response of MTZ using the composite electrodes was linear over the range from 0.002 to 210.0 µM. This sensor showed the lowest limit of detection of 0.6 nM and was much lower than the previously reported MTZ sensors. In addition, the sensor is highly sensitive, selective and durable in the presence of a range of potentially interfering electroactive compounds., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Recently, polymeric self-healing materials are tremendously being exploited in the fields of biomedical and other advanced engineering applications. However, mechanism of the self-healing materials is not very clear and the healing performance is very poor for the existed materials. Therefore in our present investigation, hydroxyapatite (HA) bioceramic, graphene (Gr) and polydimethysiloxane (PDMS) were used to develop a high performance novel self-healing composite. Here, we proposed a single step accessible preparation of short-layers graphene by the exfoliation of graphite layers via acid leaching method. Further, Gr/HA embedded PDMS membranes were prepared using a vascular method. We prepared the PDMS elastomer (resin:hardener ratio = 1:1) being mixed with 2 wt% HA and varying concentrations 0.1 wt%, 0.3 wt%, 0.5 wt% of Gr. The band gap, phase structure, crystalline and chemical structure of the Gr/HA composite films were characterized using UV-Vis, XRD and FTIR studies. A series of tensile tests were conducted to measure virgin and healed tensile specimens. The highest mechanical property was achieved at 2 wt% of HA. But best self-healing performance of the 0.1 wt%Gr composite was obtained from the recovery of tensile properties. The healing efficiency was found to depend on the curing properties of PDMS varied with HA/Gr reinforcement and quantity of healing agent delivered. [ABSTRACT FROM AUTHOR]

Polyamide 6 (PA6)-based composite materials have shown attractive mechanical properties for structural applications. However, their tribological properties have not been much improved till date. Therefore, influence of graphite (Grt) with variation of 1, 3, and 5 mass% on the mechanical and tribological behaviours of 5 mass% glass fibre (GF)-reinforced injection moulded PA6 composites has been studied. This study describes the fabrication and experimental evaluation of Grt-reinforced PA6/GF composites (e.g., PA6/5GF/1Grt, PA6/5GF/3Grt, and PA6/5GF/5Grt). The coefficient of friction (COF) and dry wear properties were evaluated under ambient conditions at variable rotating speeds of 200, 400 and 800 rpm, and normal loads of 10, 20 and 30 N for a fixed run-time of 30 min. SEM and optical microscopy revealed the morphology and wear mechanisms of worn surfaces. Among all the developed composites, 1 mass% of graphite-reinforced PA6/5GF composite had shown noticeably enhanced the tribological (0.20–0.26 COF) and mechanical (45 MPa tensile strength and HRB 47 hardness) characteristics compared to pure PA6, other prepared composites and also some other reported similar composite systems. The thermogravimetric analysis revealed that the optimal thermal stability can be achieved by PA6/5GF/1Grt composite, which, thus, can be used for further applications. [ABSTRACT FROM AUTHOR]

Uses of aluminium (Al)-based metal matrix composites (MMCs) have been emerging in variety of applications since several decades. Hence, in the present study, hybrid Al-MMCs were developed using rice husk-extracted highly pure silica (SiO2) and commercial graphite (Grt) as reinforcing materials by powder metallurgical route followed by unique re-sintering. Effect of reinforcements on mechanical as well as thermal properties of Al-MMCs has been determined in this study by various tests. The microscopy, spectroscopy, and X-ray diffraction studies were conducted to characterize the purity and homogeneity of the composites. The hybrid MMCs had shown excellent physical and mechanical properties in terms of surface strength along with being light mass. The Vickers hardness (up to 250 MPa) and compressive strength (up to 341 MPa) of the hybrid nanocomposites has increased significantly on the addition of reinforcements. Thermal properties, including conductivity and linear expansion, were found to be lower for the composites compared to pure Al. Hence, the newly developed rice husk-extracted pure silica and graphite-reinforced hybrid Al-MMCs, particularly the samples of 5SiO2/5Grt/90Al (mass%), can be used as reliable potential materials for several advanced applications including, engine piston, automobile, aviation, and spacecraft components where both mechanical and thermal properties play vital role. [ABSTRACT FROM AUTHOR]

Silica plays an important role in aluminium-based materials. However, role of silica in aluminium matrix composite is not clear so far. In the present study, pure silica was successfully extracted from rice husk by thermal and chemical treatments. The extracted silica had undergone FESEM, FTIR, and XRD for characterizing the purity of silica particles. The results showed that the obtained silica particles were highly pure. The rice husk-extracted pure silica was used as reinforcement in graphite/aluminium matrix hybrid composites. Composites were made using powder metallurgy process followed by sintering. Reinforcements of silica and graphite in aluminium matrix composites were done at different compositions to control the hardness in order to improve machinability. The aluminium matrix hybrid composites had shown excellent physical, mechanical, and thermal properties in terms of surface strength along with light mass as well as controlled thermal conductivity. The hardness of the hybrid composites had increased significantly compared to the single phase aluminium and also was controlled by the combined effect of added silica nanoparticle and graphite flake as reinforcements. Beside mechanical properties, these hybrid composites showed significantly desired thermal properties, particularly lower thermal expansion than that of pristine aluminium. Hence, the newly developed rice husk-extracted pure silica reinforced graphite/aluminium matrix hybrid composites can be used as potential materials for various advanced applications including microelectronic devices, engine piston, and automobile components. [ABSTRACT FROM AUTHOR]

Highlights Unique hybrid thermoplastic composites based on polyoxymethylene copolymer (POM C), 10 wt.% glass fiber (GF) and graphite (Grt) filler at 1, 3, and 5 wt.% were developed using injection molding technique. According to the Taguchi L16 orthogonal array, present experiments were carried out with the aim of determining the coefficient of friction (COF) and specific wear rate (SWR) under a range of loads (namely, 5, 10, 20, and 30 N), sliding speeds (namely, 200, 400, 600, and 800 rpm), and run times (namely, 15, 30, 45, and 60 min) with varying wt.% of Grt (namely, 1, 3, and 5 wt.%) throughout the experiment. Analysis of variance (ANOVA) was used to evaluate the most significant factors that affect the output functions (viz., COF and SWR). The findings demonstrated that POM C/10GF composites' tribo‐mechanical, structural, and thermal properties were considerably improved upon by including Grt. Various microscopical methods were also employed to study the wear mechanisms of the composites and the surface morphology of the worn samples. The POM C/10GF with a 3 wt.% of Grt exhibited superior tribological properties owing to its enhanced interfacial bonding characteristics, resulting to increased wear resistance. Injection molded POM C/10GF hybrid composites with 1, 3, and 5 wt.% graphite (Grt) Structural, thermal, chemical, tribo‐mechanical and microstructural studies Design of experiment with variable loads, times, speeds, and Grt compositions COF and specific wear resistance as response Optimization of hybrid composite composition using Taguchi L16 orthogonal array [ABSTRACT FROM AUTHOR]