Developing titania-hydroxyapatite-reduced graphene oxide nanocomposite coatings by liquid flame spray deposition for photocatalytic applications

Nanostructured titania has been extensively investigated for photocatalytic applications. Persistent challenge yet is how to effectively promote adhesion of microorganisms on the material surface for consequent enhanced photocatalytic disinfection. Here we report fabrication and characterization of titania-based nanocomposite coatings with addition of hydroxyapatite-reduced graphene oxide (HA-rGO). The nano features of TiO₂, HA, and rGO were well retained during liquid flame spray deposition. Photocatalytic activities of the coatings were examined by degradation of methylene blue and sterilization testing of Escherichia coli bacteria. Addition of HA-rGO effectively increased the specific surface area of the coatings and markedly enhanced adherence of the bacteria for subsequent extinguishment. The TiO₂–10 wt.% (HA-rGO) coating showed the best photocatalytic performances and further overloading of HA-rGO resulted in enwrapping of TiO₂ particles, resulting in deteriorated degradation activity. The results give clear insight into fabrication of novel photocatalytic nanocomposites by suspension thermal spray route for enhanced performances.     

Nano-hydroxyapatite reinforced zeolite ZSM composites: A comprehensive study on the structural and in vitro biological properties

The bioactive composite of hydroxyapatite and zeolite-ZSM5 was successfully synthesized via the cost effective microwave wet precipitation method. The structural and morphological features were studied by X-ray diffraction, FT-IR spectroscopy and TEM/EDX analysis. These tests revealed the presence of zeolite and hydroxyapatite in the zeolite–HA composites. Spherical particles, 76–88±20 nm in size, were visible on the TEM. The simulated body fluid SBF results in vitro verified the ability of the composites to support and accelerate the growth of the HA. Furthermore, the MTT assay showed the viability of normal human osteoblasts (NHOst) on the composite, up to seven days of culture. The cell adhesion and proliferation of the normal human osteoblast (NHOst) cells onto the disc surface was much higher than the control. Overall, the ZSM–HA samples composite nanostructure can be a considered potential candidate for biomedical application.     

聚合物基氧化石墨烯纳米复合材料研究进展

氧化石墨烯作为石墨烯的重要衍生物,原料来源广泛,制备过程简单,成本低廉,具有优异力学性能、耐磨性能以及吸附性能等,其还原产物具有优良的导电性能和导热性能等,是聚合物基纳米复合材料的理想填料。近年来,随着复合材料制备方法的不断革新,聚合物基氧化石墨烯纳米复合材料在储能、阻燃等领域实现了规模化应用,有助于引领聚合物基氧化石墨烯纳米复合材料相关产品的进一步开发和应用。该文系统介绍了氧化石墨烯的共价改性方法以及非共价改性方法,综述了聚合物基氧化石墨烯纳米复合材料的研究进展,展望了聚合物基氧化石墨烯纳米复合材料的发展前景。     

聚合物基氧化石墨烯纳米复合材料研究进展

氧化石墨烯作为石墨烯的重要衍生物,原料来源广泛,制备过程简单,成本低廉,具有优异力学性能、耐磨性能以及吸附性能等,其还原产物具有优良的导电性能和导热性能等,是聚合物基纳米复合材料的理想填料。近年来,随着复合材料制备方法的不断革新,聚合物基氧化石墨烯纳米复合材料得到了快速发展,并在储能、阻燃等领域实现了规模化应用,有助于引领聚合物基氧化石墨烯纳米复合材料相关产品的进一步开发和应用。本文系统介绍了氧化石墨烯的改性方法,综述了聚合物基氧化石墨烯纳米复合材料的研究进展,展望了聚合物基氧化石墨烯纳米复合材料的发展前景。     

Microwave assisted synthesis of rGO/ZnO composites for non-enzymatic glucose sensing and supercapacitor applications

Zinc oxide (ZnO) and Graphene Oxide (GO) are known to show good electrochemical properties. In this paper, rGO/ZnO nanocomposites have been synthesised using a simple microwave assisted method. The nanocomposites are characterized using XRD, Raman, SEM and TEM. XRD reveals the wurtzite structure of ZnO and TEM shows the heterogeneous nucleation of ZnO nanocrystals anchored onto graphene sheets. The electrochemical properties of the rGO/ZnO nanocomposite enhanced significantly for applications in glucose sensors and supercapacitors. The non-enzymatic glucose sensor of this nanocomposite tested using cyclic voltammetry (CV) and chronoamperometry, exhibits high sensitivity (39.78 mA cm⁻² mM⁻¹) and a lower detection limit of 0.2 nM. The supercapacitor electrode of rGO/ZnO nanocomposite exhibits a significant increase in specific capacitance.     

Progression from Graphene and Graphene Oxide to High Performance Polymer-Based Nanocomposite: A Review

In this article, various types of carbon nanofiller and modification of graphene oxide and graphene for the preparation of polymer-based nanocomposites are reviewed. Recently, polymer/graphene and graphene oxide-based materials have attracted tremendous interest due to high performance even at low filler content. The property enhancement is due to the high aspect ratio, high surface area and excellent electrical, thermal and mechanical properties of nanofiller. Different techniques have been employed to fabricate polymer/graphene and graphene oxide nanocomposite with uniform dispersion due to fine matrix/nanofiller interaction. Here we discuss the structure, properties and preparation of these nanocomposites.     

One-pot synthesis of CdS sensitized TiO2 decorated reduced graphene oxide nanosheets for the hydrolysis of ammonia-borane and the effective removal of organic pollutant from water

A hybrid material of reduced graphene oxide (RGO) sheets decorated with CdS-TiO₂ NPs was prepared through a facile one-pot hydrothermal method. The assembly of CdS-TiO₂ nanoparticles (NPs) on RGO sheets was in-situ produced. As-synthesized nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy disperse X-ray spectrum (EDS), fourier transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL). The obtained nanocomposites exhibited a good photocatalytic activity for the visible-light-induced decomposition of methylene blue (MB) dye and hydrolysis of ammonia borane. The results showed that by incorporation of CdS and TiO₂ NPs on graphene oxide sheets the photocatalytic efficiency was enhanced. The significant enhancement in the photocatalytic activity of CdS-TiO₂/RGO nanocomposites under visible light irradiation can be ascribed to the effect of CdS by acting as electron traps in TiO₂ band gap. Reduced graphene oxide worked as the adsorbent, electron acceptor and a photo-sensitizer to efficiently enhance the dye photo decomposition. Such nanocomposite photocatalyst might find potential application in a wide range of fields, including hydrogen energy generation, air purification, and wastewater treatment.     

Nano-sized graphene oxide as sole surfactant in miniemulsion polymerization for nanocomposite synthesis: Effect of pH and ionic strength

Miniemulsion polymerization of styrene using AIBN as initiator at 70 °C has been performed with nano-dimensional graphene oxide (GO) sheets as surfactant (no conventional surfactants employed) with a view to exploring the effects of pH and ionic strength (NaCl concentration). The pH value of the emulsion exerted a relatively minor influence on the polymerization, with a somewhat narrower particle size distribution being obtained at pH = 3.2 relative to pH = 2.4 and 5.2. The ionic strength had a more significant effect – the presence of a suitable concentration of NaCl resulted in increased colloidal stability and narrower particle size distribution. The results are explained in terms of the effects of pH on degree of ionization of COOH groups of GO and the influence of ionic strength on the electric double layer, and have implications with regards to synthesis of polymer/graphene nanocomposite materials for a variety of applications.     

Preparation and Characterization of Fluorescence Probe from Assembly Hydroxyapatite Nanocomposite

A new nanocomposite fluorescence probe with thioglycolic acid (TA) functional layers embedded inside the hydroxyapatite nanoribbon spherulites has been synthesized. The fluorescence intensity of the novel probe is about 1.5–3.3-fold increase compared with the probe containing no TA. When used to detect cadmium ion, the most of original assembly nanoribbon spherulites structure in the novel probe is found to have been damaged to new flake structures. The mechanism of determining cadmium ion in alcohol solution has been studied. The present systematic study provides significant information on the effect of assembly nanostructure on the metal-enhanced fluorescence phenomenon.     

Cobalt oxide nanocomposites and their electrocatalytic behavior for oxygen evolution reaction

In this work, we have described the simple preparation method of cobalt oxide nanocomposites where cobalt oxide nanoparticles were grown on the surface of carbon nanotube, graphene oxide and graphene (Co₃O₄@CNT, Co₃O₄@GO, Co₃O₄@G). The as-grown Co₃O₄@CNT, Co₃O₄@GO, Co₃O₄@G were investigated for H₂O oxidation. The nanoparticles displayed high activity toward oxygen evolution. Further, the stability of the catalysts were tested in alkaline solution, which exhibited good stability. Among all nanoparticles, Co₃O₄@G exhibited higher current density at lower overpotential and also exhibited lower Tafel slope (157.1 mV dec⁻¹) as compared to Co₃O₄@CNT and Co₃O₄@GO. The Co₃O₄@G delivered a current density of 10 mAcm⁻² at 0.8 V (overpotential 535 V versus Ag/AgCl) in 0.1 M KOH solution, which is superior than many electrocatalysts reported for oxygen evolution so far. The good electrocatalytic performance might be due to the structural features of Co₃O₄@G, which cause enhancement of oxygen evolution activity.     

Morphological,mechanical, and biological evolution of pure hydroxyapatite and its composites with titanium carbide for biomedical applications

Pure hydroxyapatite (HAp) was synthesized successfully via a wet chemical precipitation method. To study the influence of TiC (weight % of 5, 10, 15) substitution on the mechanical behavior of pure HAp, its composites with TiC were synthesized using a solid-state reaction method. Herein, detailed investigations of pure HAp and its composites using X-ray powder diffraction (XRD), FTIR spectroscopy, Raman spectroscopy, UV-VIS spectroscopy, SEM followed by EDAX and particle size analysis were carried out. XRD study reveals the phase stability of the prepared HAp and composite samples. However, FTIR and Raman spectroscopic studies revealed the bond formation among the various constituents. Mechanical behavior of HAp, and its composites with TiC were studied using numerous parameters like density, Young's modulus, fracture toughness, and load absorption capability. Based on these studies, it was revealed that the addition of 5 wt % substitution of TiC sintered at 1200 °C significantly enhanced the mechanical properties of pure HAp. Hence, 5 wt % of TiC composite 95HAp-5TiC showed the best mechanical characteristics such as density (2.3060 g/cm³), Young's modulus (14.53 MPa), fracture toughness (19.82 MPa m^1/2), maximum compressive strength (186 MPa) respectively. Cytotoxicity and osteogenic activities of the synthesized pure HAp and its composite, 95HAp-5TiC were performed using osteoblast cells (mouse calvarial) at different concentrations of the samples (0.01 μg, - 100 μg). From the above studies, the cell viability and ALP activities of the composite, 95HAp-5TiC found to be excellent than that of pure HAp. Hence, this composite sample may be utilized for bone implant applications.     

Structure-dependent re-dispersibility of graphene oxide powders prepared by fast spray drying

The graphene oxide powder (GOP) obtained from the spray drying process often exhibits poor re-dispersibility which is considered due to the partial reduction of GO sheets. The reduction of drying tem-perature can effectively increase the re-dispersibility of GOP, but result in a decreased drying efficiency. Herein, we found that the re-dispersibility of GOP is strongly affected by its microstructure, which is determined by the feed concentration. With the increase of feed concentration, the GO nanosheet assem-bly varies from the disordered stacking to relatively oriented assembly, making the morphology of the GOP transform from ball-like (the most crumpled one) to flake-like (the least crumpled one), and the 0.8 mg·ml-1 is the threshold concentration for the morphology, structure, and re-dispersibility change. Once the feed concentration reaches 0.8 mg·ml-1, the appearance of the nematic phase in droplet ensures the relatively oriented assembly of GO sheets to form the layered structure with a low crumpling degree, which greatly improves the polar parts surface tension of the solid GOP, making the GOP easier to form hydrogen bonding with water during the redispersion process, thus stabilizing dispersion. This work pro-vides useful information for understanding the relationships between the morphology, microstructure, and final re-dispersibility of GOPs.     

Fabrication of bifunctional nanocomposite for dye degradation

An effective photocatalytic system is designed to treat with methylene blue. Graphene oxide matrix was decorated with cobalt ferrite and zinc oxide nanoparticles, providing it with dual functionality. The nanocomposite was prepared via sonochemistry. Structural characterization was done by X-ray diffraction. Morphology was observed by scanning electron microscopy while elemental analysis confirmed the purity of the synthesized nanocomposite. The photocatalytic activity of nanocomposite was tested for denaturing methylene blue under solar conditions. Enhanced photocatalytic activity was observed due to trapped electron-hole pairs at graphene oxide surface and other interfaces of the nanocomposite. The efficiency of photocatalyst was calculated as 98% within 15 min which was further examined till 5 more repeated cycles.     

In vitro studies of hydrogen peroxide treated titanium for biomedical applications

Pure titanium substrate was subjected to chemical treatment with different concentrations of hydrogen peroxide and subsequently heat treated to produce a titania gel layer with anatase nature. The surface modified substrates were then immersed in simulated body fluid for the formation of calcium phosphate layer over the surface. Titanium treated with 15 wt.% of hydrogen peroxide produced a uniform porous layer, which was found to induce the calcium phosphate formation more easily. However, titanium treated with 5 wt.% and 25 wt.% of hydrogen peroxide exhibited inhomogeneous surface for the growth of calcium phosphate layer. Further, the corrosion behaviour of the untreated and hydrogen peroxide treated specimens in simulated body fluid was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy. The results have shown that the surface modified titanium using 15 wt.% of hydrogen peroxide exhibited higher corrosion resistance compared to specimens treated with other concentrations of hydrogen peroxide.     

Ternary hydroxyapatite/chitosan/graphene oxide composite coating on AZ91D magnesium alloy by electrophoretic deposition

In this work, ternary HA/chitosan/graphene oxide (GO) coating was applied via electrophoretic deposition on AZ91D magnesium alloy as bone implants, successfully. Subsequently, phase composition, surface morphology, hardness, corrosion behavior, bioactivity and antibacterial of the composite coatings were studied. Hardness and Young's modulus of the composite coatings increased from 40 ± 1.5 MPa and 3.1 ± 0.42 GPa to 60 ± 3.12 MPa and 8 ± 0.53 GPa for composite coatings with 0 and 2 wt% GO, respectively. The results of the SBF solution soaking of the composites after 24 days, indicated the improvement of HA growth due to the increasing of the GO addition in composite coating. New HA grains with leaf-like morphology grew uniformly at higher amounts of GO (1 and 2 %wt) in a perfectly balanced composition. Rate of the substrate corrosion significantly decreased from 4.3 to 0.2 (mpy), when the amount of GO increased from 0 to 2 wt% due to reduction of the surface cracks at the presence of the GO reinforcement. Also, there was no Escherichia coli and Staphylococcus aureus bacteria growth in broth medium after 24 h and OD₆₀₀ results at 24 h post inoculation for the 2%wt GO addition in coating.     

Simultaneous co-substitution of Sr2+/Fe3+ in hydroxyapatite nanoparticles for potential biomedical applications

In human, strontium (Sr) follows the same physiological pathway as calcium and thus could be used for improving the bioactivity and osteoconductivity of hydroxyapatite (HAp) in bone tissues. Similarly, iron (Fe) can potentially play an important role in bone remodeling due to its magnetic properties. Therefore, the current study was aimed to simultaneously co-substitute Sr²⁺/Fe³⁺ in HAp nanoparticles for various potential biomedical applications. The Sr²⁺/Fe³⁺ co-substituted HAp nanoparticles were systematically synthesized through sonication-assisted aqueous precipitation method. The as-synthesized nanoparticles were evaluated for different physicochemical and biological properties. X-ray diffraction (XRD) patterns of Sr²⁺/Fe³⁺ co-substituted HAp nanoparticles confirmed their phase purity and showed hexagonal-like structure. Scanning electron microscope (SEM) micrographs showed an agglomerated rod-like morphology of HAp nanoparticles which contained pores consisted of small spheroids. The nanoparticles displayed magnetization (Ms) reliance on the loading level of mole % (X?=?Fe³⁺) and exhibited tunable porosity and microhardness (Hv) upon heat treatment. The nanoparticles showed less than 5% hemolysis demonstrating high blood compatibility with high in vitro bioactivity performance. The multifunctional properties of synthesized nanoparticles make them a potential candidate for various biomedical applications; including bone grafting and guided bone regeneration, targeted drug delivery, magnetic resonance imaging, and hyperthermia based cancer treatment.     

Bioactive,luminescent erbium-doped hydroxyapatite nanocrystals for biomedical applications

Diagnosis and imaging play an essential key role in primary detection, screening, and image-guided smart nanomedicine for healthcare solutions. This study illustrates the successful fabrication of luminescent lanthanide (erbium)-doped hydroxyapatite (Er-HAp) by one step facile wet-chemical precipitation method. The chemical compositions, morphology, optical, and biological properties were systematically characterized using relevant different structural, compositional analytical instrumentation and cytotoxicity assays. After erbium doping, synthesized luminescent nano-structured materials exhibited elongated morphology, with well dispersed <50 nm size distribution. The photoluminescence (PL) study confirmed three emission bands assigned to ⁴F_3/2 → ⁴I_15/2 (purple), ⁴F_7/2 → ⁴I_15/2 (blue), and ⁴S_3/2 → ⁴I_15/2 (green) transition states, respectively. In vitro bioactivity and optical imaging studies conducted in osteoblast like MG-63 cells confirmed the nontoxic luminescent behavior of the synthesized nanomaterials.     

Preparation of Pectin–ZnO Nanocomposite

Pectin–ZnO nanocomposite was prepared in the aqueous solution condition at room temperature. The Fourier transform infrared, X-ray diffraction, and transmission electron microscope (TEM) measurements confirmed the nanoscaled structure of pectin–ZnO composite. According to the TEM observation, the average composite granules size was about 150 nm and the embedded ZnO nanoparticles were uniform with an average diameter of 70 nm.     

Preparation of WO3-reduced graphene oxide nanocomposites with enhanced photocatalytic property

In this work, WO₃-reduced graphene oxide (RGO) nanocomposite was synthesized via a simple one-pot hydrothermal method. The synthesized nanocomposite was characterized by SEM, XRD, EDX, UV–vis spectroscopy, N₂ adsorption/desorption, photocurrent response, electrochemical impedance spectroscopy and Raman spectroscopy. The superior contact between WO₃ and RGO sheets in the nanocomposite facilitates the photocatalytic degradation of methylene blue and evolution of oxygen. The cause of the enhanced photocatalytic performance could ascribe to the highly facilitated electron transport by the synergistic effect between WO₃ and RGO sheets, as well as suppressing the electron hole pair recombination in the nanocomposite.