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Water pollution has been a prevalent issue globally for some time. Some pollutants are released into the water system without treatment, making the water not suitable for consumption. This problem may lead to more grave problems in the future including the destruction of the ecosystem along with the organisms inhabiting it, and illness and diseases endangering human health. Conventional methods have been implemented to remove hazardous pollutants such as dyes, heavy metals, and oil but are incapable of doing so due to economic restraints and the inability to degrade the pollutants, leading to secondary pollution. Photocatalysis is a more recently applied concept and is proven to be able to completely remove and degrade pollutants into simpler organic compounds. Titanium dioxide (TiO

Background: Owing to their remarkable chemical, physical and biological properties, silver nanoparticles have been widely used in water purification, electronics, bio-sensing, clothing, food industry, paint and medical devices. Various approaches, such as using harsh reducing and stabilising agents for reverse micelle and thermal decomposition, were proposed for silver nanoparticle production. However, these methods are not eco-friendly. Thus, the aim of this paper is to synthesise silver nanoparticles through a cost-effective and environmentally friendly approach. Materials and Methods: A green approach was presented for the synthesis of silver nanoparticles. This approach involved the treatment of silver nitrate and hibiscus leaf extract, which acts as reducing and capping agent. The synthesis was performed at room temperature. The resulting silver nanoparticles were characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and Fourier transform infrared (FTIR) spectroscopy. Results: Spherical, rod-like, hexagonal and triangular silver nanoparticles were obtained through the proposed synthesis method. The crystalline nature of each nanoparticle was revealed by XRD and selected area electron diffraction (SAED). The average spherical size of the silver nanoparticles produced in this route was 44.3 nm. The obtained FTIR band at 1622 cm-1 corresponded to the C=O stretch in the amine I group, which is commonly found in protein. Thus, the protein was believed to serve as capping agent that was responsible for the stabilisation of silver nanoparticles. Conclusion: In conclusion, silver nanoparticles had been successfully synthesised using hibiscus leaf extract and a plausible formation mechanism of silver nanoparticles was proposed.

This work focuses on alkylation as an effective method to cope with mixing issue between both graphene oxide (GO) and reduced graphene oxide (RGO) with hydrophobic polymer such as polypropylene. Alkylation is an amidation reaction to graft alkyl groups onto GO and RGO surfaces. The successful grafting of alkyl groups on GO and RGO to form alkylated graphene oxide (AGO) and alkylated reduced graphene oxide (ARGO) were supported by several analysis. Scanning Electron Microscopy (SEM) micrographs showed the formation of wrinkle surfaces in higher degree for AGO and ARGO, as compared with GO. No agglomeration was seen on both surfaces as well. For Fourier Transform Infrared (FTIR) spectroscopy, the appearance of new peaks at around 2921 cm-1, 2850 cm-1 and 1424 cm-1 confirmed the alky chains were grafted successfully. Furthermore, ID/IG ratio for AGO and ARGO were almost similar, proving that no further amount of defect onto structure of AGO was formed in the reduction of AGO. Lastly, for AGO and ARGO, the X-ray Diffraction (XRD) spectra showed the presence of new peaks at 2θ = 20.26° and 20.18°, respectively. Several other peaks can be seen as well, to prove successful alkylation which implied the grafting of alkyl groups provides more reactive site for stronger interfacial reaction with polymer to improve mechanical properties.

In this work, reduced graphene oxide (rGO) was fabricated at different reduction temperatures via an environmentally friendly solvothermal approach. The rGO formed at 160 °C clearly showed the partial restoration of the sp2 hybridization brought about by the elimination of oxygenated functionalities from the surface. Owing to the augmented surface area and the band gap reduction, rGO-160 exhibited the best adsorption (29.26%) and photocatalytic activity (32.68%) towards the removal of MB dye. The effects of catalyst loading, initial concentration of dye, light intensity, and initial pH of solution were evaluated. It was demonstrated that rGO-160 could achieve a higher adsorptive removal (87.39%) and photocatalytic degradation (98.57%) of MB dye when 60 mg of catalyst, 50 ppm of dye at pH 11, and 60 W m−2 of UV-C light source were used. The MB photodegradation activity of rGO-160 displayed no obvious decrease after five successive cycles. This study provides a potential metal-free adsorbent-cum-photocatalyst for the decontamination of dyes from wastewater.

Background: The discharge of effluents from the textile and dyeing industries has been a worldwide concern. Although reduced graphene oxide/titanium dioxide (rGO/TiO2) nanocomposite is a potential candidate for wastewater treatment, the influence of graphene oxide (GO) content on its physico-chemical characteristics and its subsequent photocatalytic capabilities in degrading the organic contaminants has not been well established. Objective: The primary objective of this study was to assess the use of rGO/TiO2 nanocomposites with various GO contents for the removal of toxic methylene blue (MB) dye from aqueous solution. Method: In the present study, rGO/TiO2 nanocomposites were fabricated using various GO contents through a one-step solvothermal method. The effect of GO content on the nanocomposite formation was investigated by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The resulting nanocomposites were evaluated against MB degradation under artificial solar light illumination. Results: Based on the photocatalytic results, the highest removal percentage of MB was achieved by 0.15rGO/TiO2, which was about 1.7 times higher than that of 0.01rGO/TiO2. The enhanced removal efficiency of MB by the nanocomposite with the highest GO content (0.15 g) was attributed to the increased active adsorption sites, which greatly promoted the π- π interaction between the aromatic rings of MB dye and the graphitic skeleton of rGO, as well as the electrostatic interaction between the cationic center of MB molecules and the residual oxygen functionalities of rGO.

The purpose of this review is to reveal the lipid and protein contents in black soldier fly larvae (BSFL) for the sustainable production of protein and energy sources. It has been observed from studies in the literature that the larval lipid and protein contents vary with the rearing conditions as well as the downstream processing employed. The homogenous, heterogenous and microbial-treated substrates via fermentation are used to rear BSFL and are compared in this review for the simultaneous production of larval protein and biodiesel. Moreover, the best moisture content and the aeration rate of larval feeding substrates are also reported in this review to enhance the growth of BSFL. As the downstream process after harvesting starts with larval inactivation, various related methods have also been reviewed in relation to its impact on the quality/quantity of larval protein and lipids. Subsequently, the other downstream processes, namely, extraction and transesterification to biodiesel, are finally epitomized from the literature to provide a comprehensive review for the production of unconventional protein and lipid sources from BSFL feedstock. Incontrovertibly, the review accentuates the great potential use of BSFL biomass as a green source of protein and lipids for energy production in the form of biodiesel. The traditional protein and energy sources, preponderantly fishmeal, are unsustainable naturally, pressingly calling for immediate substitutions to cater for the rising demands. Accordingly, this review stresses the benefits of using BSFL biomass in detailing its production from upstream all the way to downstream processes which are green and economical at the same time.

This study investigates the effects of stirring duration on the synthesis of graphene oxide (GO) using an improved Hummers' method. Various samples are examined under different stirring durations (20, 40, 60, 72, and 80 h). The synthesized GO samples are evaluated through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The GO sample with 72 h stirring duration (GO72) has the highest d-spacing in the XRD results, highest atomic percentage of oxygen in EDX (49.57%), highest intensity of oxygen functional group in FTIR spectra, and highest intensity ratio in Raman analysis (ID/IG = 0.756). Results show that GO72 with continuous stirring has the highest degree of oxidation among other samples. Electrochemical impedance spectroscopy analysis shows that GO72-titanium dioxide (TiO2) exhibits smaller charge transfer resistance and higher electron lifetime compared with the TiO2-based photoanode. The GO72 sample incorporating TiO2 nanocomposites achieves 6.25% photoconversion efficiency, indicating an increase of more than twice than that of the mesoporous TiO2 sample. This condition is fully attributed to the efficient absorption rate of nanocomposites and the reduction of the recombination rate of TiO2 by GO in dye-sensitized solar cells.

Oily wastewater, especially water-oil emulsion has become serious environmental issue and received global attention. Chemical demulsifiers are widely used to treat oil-water emulsion, but the toxicity, non-recyclable and non-environmental friendly characteristic of chemical demulsifiers had limited their practical application in oil-water separation. Therefore, it is imperative to develop an efficient, simple, eco-friendly and recyclable demulsifiers for breaking up the emulsions from the oily wastewater. In this study, a magnetic demulsifier, magnetite-reduced graphene oxide (M-rGO) nanocomposites were proposed as a recyclable demulsifier to break up the surfactant stabilized crude oil-in-water (O/W) emulsion. M-rGO nanocomposites were prepared via in situ chemical synthesis by using only one type Fe salt and GO solid as precursor at room temperature. The prepared composites were fully characterized by various techniques. The effect of demulsifier dosage and pH of emulsion on demulsification efficiency (ED) has been studied in detailed. The demulsification mechanism was also proposed in this study. Results showed that M-rGO nanocomposites were able to demulsify crude O/W emulsion. The ED reaches 99.48% when 0.050 wt.% of M-rGO nanocomposites were added to crude O/W emulsion (pH = 4). Besides, M-rGO nanocomposites can be recycled up to 7 cycles without showing a significant change in terms of ED. Thus, M-rGO nanocomposite is a promising demulsifier for surfactant stabilized crude O/W emulsion.

Oil-in-water (O/W) emulsion has been a major concern for the petroleum industry. A cost-effective magnetite-reduced graphene oxide (MRGO) nanocomposite was synthesized to study the demulsification process of emulsion using said nanocomposite under solar illumination. Characterization data show that the magnetite was successfully deposited on reduced graphene oxide through redox reaction at varying loading amounts of magnetite. Demulsification of the O/W emulsion using MRGO nanocomposite shows that in general the demulsification efficiency was dependent on the loading amount of Fe3O4 on the RGO sheet. It was proposed that the surfactant hydroxyl groups have an affinity towards Fe3O4, which the loading amount was directly proportionate to available active site in Fe3O4. As the loading amount increases, charge recombination centers on the RGO sheet would increase, effectively affecting the charge distribution within MRGO structure.

The remarkable properties of graphene have directly accelerated the graphene research. Due to its unique and remarkable characteristics, graphene can be potentially used in various applications. Chemical Vapour Deposition (CVD) has been identified as a promising and important method for preparation and production of graphene due to its good film uniformity and large scale production. Herein, we demonstrated that reaction parameters including the reaction duration and reaction temperature could affect the quality, quantity and morphology of synthesized samples. Energy Dispersive X-ray (EDX) results indicated that the carbon content on the graphene-like samples increased with the increasing reaction duration. Scanning electron microscopy (SEM) images showed that thicker carbon clusters were grown when a longer reaction time was used. X-ray diffraction (XRD) pattern indicted carbon existed in the samples synthesized. The comparison between different reaction parameters can assist in selecting the optimum growth parameters of graphene-like samples.

Graphene has emerged as the most popular topic in the active research field since graphene's discovery in 2004 by Andrei Geim and Kostya Novoselov. Since then, graphene research has exponentially accelerated because of its extraordinary properties, which have attracted the interest of researchers all over the world. For example, among the key properties are its thermal conductivity, electrical conductivity, optical transparency, and mechanical properties. These remarkable properties of graphene show its promise for applications in different industries including optical electronics, photovoltaic systems and others. However, the large-scale production and transfer method onto target substrates of monolayer graphene for commercial and industrial applications are still under study in the improvement stage. Therefore, this review presents the state-of-the-art research activities and latest advancement in the synthesis of graphene using various carbon precursors including solid, liquid and gas carbon feedstocks. The characterization methods have also been critically discussed in this review. In addition, the advancement in the transfer methods onto target substrates for achieving clean and high-quality transferred graphene have been thoroughly reviewed. Furthermore, the current growth mechanisms of single and multilayer graphene have also been discussed.

Oily wastewater from the oil and gas industry negatively affects the environment. Oily wastewater typically exists in the form of an oil-in-water emulsion. Conventional methods to treat oily wastewater have low separation efficiency and long separation time and use large equipment. Therefore, a simple but effective method must be developed to separate oil-in-water emulsions with high separation efficiency and short separation times. Magnetite–reduced graphene oxide (M–RGO) nanocomposites were used as a demulsifier in this work. Magnetite nanoparticles (Fe3O4) were coated on reduced graphene oxide (rGO) nanosheets via an in situ chemical synthesis method. The synthesized M–RGO nanocomposites are environmentally friendly and can be recovered after demulsification by an external magnetic field. M–RGO characterization was performed using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning microscopy, Raman spectroscopy, and vibrating sample magnetometry. Demulsification performance was evaluated in terms of M–RGO dosage, effects of pH, and brine concentration. The demulsification capability of M–RGO was determined based on the residual oil content of the emulsion, which was measured with a UV-vis spectrometer. The response surface method was used to determine the optimum conditions of the input variables. The optimum demulsification efficiency achieved at pH 4 and M–RGO dosage of 29 g L−1 was approximately 96%. This finding demonstrates that M–RGO nanocomposites are potential magnetic demulsifiers for oily wastewater that contains oil-in-water emulsions. Also, the recyclability of this nanocomposite has been tested and the results shown that it is a good recyclable demulsifier.

Since graphene has been successfully synthesized in year 2004, graphene has become the highlight of the research study in the material science field because of its peculiar properties and attracted a large amount of research for its application. The extraordinary properties of graphene show some promising applications such as optical electronics, photovoltaic systems, composites and others. However, it is found that the production of single layer graphene for commercial application still under research for improvement of its quality, size and amount. It has been reported that single-layer graphene can be synthesized using several methods, but the most promising method to synthesize high quality single-layer graphene is chemical vapour deposition (CVD). In this review, current development of the synthesis of single layer graphene and its future prospects is presented and discussed.

Alkylation becomes one of the alternatives to cope with mixing compatibility issue that arises during melt mixing between graphene oxide (GO) and polypropylene (PP) by grafting linear alkyl chains onto GO surface. Alkylated (AGO-PP) and alkylated reduced (ARGO-PP) nanocomposites showed improvement in tensile strength and Young’s modulus values than neat PP as nanofillers loadings increased. However, the elongation at break for both AGO-PP and ARGO-PP nanocomposites displayed lower values than neat PP. This indicates that the interfacial interaction between nanofillers and PP was enhanced. On the contrary, the decrement in elongation at break in both nanocomposites than neat PP was found which caused by the restriction of movement at the interface layer between nanofillers and PP matrix.

Graphene oxide (GO) is known has some unique properties for various applications. GO is the oxidation form of graphene. It is synthesized from graphite through chemical oxidation. The structure of GO is different with graphite and graphene where the plane of the GO is attached with oxygen functional groups. In this research, GO was prepared by using improved Hummers’ method from natural graphite powder. In addition, the effects of different reaction time of 24 hours, 48 hours, 72 hours and 96 hours on the yields of GO were studied. Results indicated that different samples of GO possessed different morphologies, attachment of functionalized groups, crystallinity and absorption peaks in Ultraviolet Visible (UV-Vis) spectroscopy. GO was characterized by using a Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and UV-Vis. SEM result showed platelet-like surface that appeared on the surface of GO (48 hours) as compared with GO (72 hours) where wavy wrinkled and layered-flakes, and crumpled structures were seen on GO (96 hours) surface respectively. In FTIR results, the existence of higher amount of abundant oxygen-containing functional groups was confirmed in GO (96 hours) as compared with GO (24 hours) due to the longer oxidation time. Furthermore, the absorption peak of GO was noticed at around 230 nm and the intensity of peak was increased with reaction time. By comparing these results, the oxidation of graphite to form GO can be determined accurately. Therefore, this study is a great beneficial to provide more understanding for many researchers about how to control the quality and amount of GO by varying reaction times for various applications.

Researchers studied graphene oxide (GO) and reduced graphene oxide (rGO), to explore its usefulness in different fields and applications. To produce rGO using conventional method at low-cost and environmental-friendly is a huge challenge because it involves harmful and hazardous chemicals such as hydrazine hydrate. Therefore, scientists proposed several green reducing agents as an alternative method to produce a same product. This research presents an outline and discussion of green synthesis of rGO using green tea extract as the reducing agents by manipulating their reaction time. Besides, it also gives an overview on the characterization of GO and rGO by analysing them using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) with Energy-dispersive X-ray spectroscopy (EDX), Fourier Transmission Infrared (FTIR) and Ultraviolet-visible Spectroscopy (UV-Vis). XRD spectra has proven the GO and rGO were successfully synthesised by exhibiting the peak at 9.75 nm and 25.42 nm respectively. In SEM images, wrinkled and flaky structures were observed in both GO and rGO while the EDX showed the composition of them. Moreover, the FTIR analysis suggested that the amount of oxygen functional groups in GO were decreased when it was reduced to rGO whereas the UV-Vis spectra proved the presence of absorption peak of GO (230 nm) and rGO (280 nm) accurately at different locations. Thus, the objectives of this research were achieved, and this green method can be a substitution to lower down the rely on chemical substances.

Magnetite nanoparticles were synthesized through co-precipitation method, in which surfactant such as polyvinylpyrrolidone (PVP) and sodium dodecyl benzene sulfonate (SDBS) were applied as stabilizing agent. Various techniques were employed to characterize the synthesized magnetite nanoparticles. Magnetite nanoparticles with spinel structure are successfully synthesized and confirmed by X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results proved that surface of magnetite nanoparticles were successfully coated with PVP and SDBS. From the transmission electron microscope (TEM), it showed that surfactant coated magnetite nanoparticles possess smaller particle size than that of bare magnetite nanoparticles. In comparison with SDBS, PVP has a better capping efficiency and the PVP coated magnetite nanoparticles have an average particle size of 10.8 nm. In addition, surfactant coated magnetite nanoparticles also exhibited lower value of satura...

Graphene oxide (GO) and reduced graphene oxide (RGO) are known to have superior properties for various applications. This work compares the properties of GO and RGO with graphite. GO was prepared by using Improved Hummer’s method whereas the produced GO was subjected to chemical reduction with the use of hydrazine hydrate. Graphite, GO and RGO had different morphologies, quality, functionalized groups, UV-Vis absorption peaks and crystallinity. With the removal of oxygen-containing functional group during reduction for RGO, the quality of samples was decreased due to higher intensity of D band than G band was seen in Raman results. In addition, platelet-like surface can be observed on the surface of graphite as compared to GO and RGO where wrinkled and layered flakes, and crumpled thin sheets were observed on GO and RGO surface respectively. Fourier Transform Infra-Red (FTIR) analysis showed the presence of abundant oxygen-containing functional groups in GO as compared to RGO and graphite. The characteris...

Cobalt/gold hollow microspheres were successfully prepared through galvanic replacement in an organic solvent. The diameters of these hollow microspheres ranged from 800 nm to 1 μm. However, the surface of the hollow microsphere was very rough. Nanospikes of various lengths from about 40 to 100 nm were grown on the surface of these spheres. Initially, particles with "island-like" rough surfaces were found with the addition of 4 ml chloroauric acid (HAuCl4). When the volume of HAuCl4 increased from 4 to 5 ml, microspheres with a hollow structure were formed. Some broken microspheres were observed when HAuCl4 was further increased to 6 ml. X-ray diffraction results showed a high-intensity sharp peak of gold when the HAuCl4 in the sample increased. After the galvanic replacement reaction, the cobalt content in the sample decreased meanwhile the gold content increased. This can be seen from energy dispersive X-ray analysis spectroscopy and also evident from the thermo gravimetric analysis result. The hollow Au/Co microspheres showed two broad plasmonic peaks in the ultraviolet-visible measurement. The plasmonic peaks at longer wavelengths shifted to the near-infrared region with the addition of HAuCl4.

This work describes the effect of hydrazine hydrate on the formation of the raspberry-like morphology of the cobalt nanomaterials in a polyol route. In the synthesis, the molar ratio of N2H4 to Co2+was varied from 2.5 to 10. At the beginning with low molar ratio, spherical microspheres were formed. When the molar ratio was increased to 5 and above, final morphology of the cobalt nanomaterials became raspberry-like. This might be attributed to the absorption of the hydrazine complex of cobalt nanoparticles at certain facets during their growth stage and later self-assembled into the raspberry shaped microparticles. The plausible formation mechanism were proposed.

To produce thin-walled plastic items, injection molding process is one of the most widely used application tools. However, to set optimal process parameters is difficult as it may cause to produce faulty items on injected mold like shrinkage. This study aims at to determine such an optimum injection molding process parameters which can reduce the fault of shrinkage on a plastic cell phone cover items. Currently used setting of machines process produced shrinkage and mis-specified length and with dimensions below the limit. Thus, for identification of optimum process parameters, maintaining closer targeted length and width setting magnitudes with minimal variations, more experiments are needed. The mold temperature, injection pressure and screw rotation speed are used as process parameters in this research. For optimal molding process parameters the Response Surface Methods (RSM) is applied. The major contributing factors influencing the responses were identified from analysis of variance (ANOVA) technique. Through verification runs it was found that the shrinkage defect can be minimized with the optimal setting found by RSM.

Porous cobalt gold nanostructures with Au nanoflakes covering the top of their cobalt cores were synthesized through facile galvanic replacement reaction with the assistance of ultrasonic bath. The average thickness of the nanoflakes was around 50 nm–60 nm. The magnetic properties of the bimetallic particles were measured after galvanic replacement reaction. Compared with the as-prepared spherical cobalt core before the galvanic replacement reaction, this bimetallic nanostructure exhibited enhanced coercivity as a result of surface anisotropy. A possible mechanism for the formation of this flake-like nanostructure is proposed.

Graphene is a promising material due to its fascinating properties, such as mechanical, electronic and thermal properties. Graphene based hybrids materials also have been widely studied due to its wide applications, such as sensors, energy storage and conversion, electronic device and others. The current study presents the synthesis of magnetite-reduced graphene oxide (M-rGO) nanocomposites through in situ chemical synthesis at different stirring durations. This synthesis process involves the redox reaction between the iron(II) salts and graphene oxide (GO) sheets. Various techniques were employed to characterize the synthesized M-rGO nanocomposites. From X-ray diffraction (XRD) results, the crystal structure of M-rGO was found to be independent on the stirring duration. Three magnetite vibrations, D band and G band were observed in Raman spectrum of M-rGO with 24 hours stirring duration. From Fourier transform infrared (FTIR) analysis, M-rGO with 24 hours stirring duration showed the strong intensity of Fe-O vibration. Thus, this indicated that a large amount of magnetite nanoparticles were covered on the surface of rGO sheets. This result is further supported by the morphology of nanocomposites from scanning electron microscopy (SEM) and the elemental analysis (EDX). A monolayer of rGO sheet (C= 33.79 atomic %) with full coverage of magnetite nanoparticles (Fe= 30.20 atomic %) was found for the M-rGO with 24 hours stirring duration. Overall, M-rGO require 24 hours of continuous stirring to ensure full coverage of magnetite nanoparticles on the surface of rGO sheets.

Correction for ‘Review of the synthesis, transfer, characterization and growth mechanisms of single and multilayer graphene’ by H. Cheun Lee et al., RSC Adv., 2017, 7, 15644–15693.

Silver nanoparticles were successfully synthesised at room temperature from silver nitrate using unripe Carica papaya fruit extract as a reducing and capping agent. PH of the reaction solution was adjusted with the addition of sodium hydroxide from pH 5.6 (original pH of the broth) to pH 6.5, pH 7.5 and pH 8.5. Quasi spherical silver nanoparticles were obtained across the studied pH range. The average particle size obtained decreased from 34 nm to 15 nm as the pH of the solution increased from 5.6 to 8.5. From the observations and ultra violet-visible spectrophotometer analysis, the rate of reduction and formation of silver nanoparticles increased as the pH increased. The crystalline nature of the as-synthesised silver nanoparticles in a cubic structure was confirmed by the peaks in X-ray diffraction and selected area electron diffraction. From Fourier transform infrared spectra, it was found that proteins in unripe papaya fruit extract were strongly bounded to the surface of silver nanoparticles as a capping agent. The thin layer of protein coating also further confirmed under high resolution transmission electron microscope. A plausible formation mechanism has been briefly proposed.