Covalent polymer functionalized graphene oxide/poly(ether ether ketone) composites for fused deposition modeling: improved mechanical and tribological performance

This paper presents a novel method using poly(aryl ether ketone) containing pendant carboxyl groups to covalently functionalize graphene oxide. The functionalized graphene oxide (LFG) was used to prepare poly(ether ether ketone) (PEEK) composites through melt blending. It is found that LFG has great interface adhesion to the PEEK matrix, and just a small amount of it can simultaneously improve the strength and toughness of the composites, while unmodified graphene oxide could enhance strength but cause toughness damage. The tensile and impact strength of composite with 0.1 wt% LFG are 5.7% and 20.5% higher than that of neat PEEK, respectively. In addition, 0.5 wt% LFG composite shows great friction and wear performance with friction coefficient and specific wear rate 27.3% and 18.3% lower than that of PEEK. Furthermore, the composites can be used as practical high-performance additive manufacturing materials because LFG is able to improve the mechanical performance of the fused deposition modeling (FDM) composite samples significantly.

A polymer “bridge” was designed to connect graphene oxide and poly(ether ether ketone), making stronger and tougher composites.     

Melamine-based functionalized graphene oxide and zirconium phosphate for high performance removal of mercury and lead ions from water

Heavy metal ions are highly toxic and widely spread as environmental pollutants. This work reports the development of two novel chelating adsorbents, based on the chemical modifications of graphene oxide and zirconium phosphate by functionalization with melamine-based chelating ligands for the effective and selective extraction of Hg(ii) and Pb(ii) from contaminated water sources. The first adsorbent melamine, thiourea-partially reduced graphene oxide (MT-PRGO) combines the heavier donor atom sulfur with the amine and triazine nitrogen''s functional groups attached to the partially reduced GO nanosheets to effectively capture Hg(ii) ions from water. The MT-PRGO adsorbent shows high efficiency for the extraction of Hg(ii) with a capacity of 651 mg g⁻¹ and very fast kinetics resulting in a 100% removal of Hg(ii) from 500 ppb and 50 ppm concentrations in 15 second and 30 min, respectively. The second adsorbent, melamine zirconium phosphate (M-ZrP), is designed to combine the amine and triazine nitrogen''s functional groups of melamine with the hydroxyl active sites of zirconium phosphate to effectively capture Pb(ii) ions from water. The M-ZrP adsorbent shows exceptionally high adsorption affinity for Pb(ii) with a capacity of 681 mg g⁻¹ and 1000 mg g⁻¹ using an adsorbent dose of 1 g L⁻¹ and 2 g L⁻¹, respectively. The high adsorption capacity is also coupled with fast kinetics where the equilibrium time required for the 100% removal of Pb(ii) from 1 ppm, 100 ppm and 1000 ppm concentrations is 40 seconds, 5 min and 30 min, respectively using an adsorbent dose of 1 g L⁻¹. In a mixture of six heavy metal ions at a concentration of 10 ppm, the removal efficiency is 100% for Pb(ii), 99% for Hg(ii), Cd(ii) and Zn(ii), 94% for Cu(ii), and 90% for Ni(ii) while at a higher concentration of 250 ppm the removal efficiency for Pb(ii) is 95% compared to 23% for Hg(ii) and less than 10% for the other ions. Because of the fast adsorption kinetics, high removal capacity, excellent regeneration, stability and reusability, the MT-PRGO and M-ZrP are proposed as top performing remediation adsorbents for the solid phase extraction of Hg(ii) and Pb(ii), respectively from contaminated water.

Two novel chelating adsorbents are developed for the effective and selective extraction of Hg(ii) and Pb(ii) ions from contaminated water sources.     

Efficient removal of crystal violet dye using EDTA/graphene oxide functionalized corncob: a novel low cost adsorbent

In this study, EDTA functionalized corncob (EDTA-corncob) and EDTA/graphene oxide functionalized corncob (EDTA-GO/corncob) were prepared using disodium ethylenediamine tetraacetic acid and the graphene oxide immersion method. EDTA-corncob and EDTA-GO/corncob were characterized by SEM and FTIR spectroscopy. On this basis, the adsorption properties of EDTA-corncob and EDTA-GO/corncob were studied with crystal violet as the adsorbate. The optimum adsorption conditions were determined by the effect of samples on the adsorption properties of crystal violet at different times, temperatures and pH, and the reusability of the samples was studied. The results showed that adsorption capacity of crystal violet on EDTA-GO/corncob was higher compared with natural corncob and EDTA-corncob. The most suitable pH value of the solution is about 6.0, the adsorption equilibrium time is 200 min. EDTA-GO/corncob can be reused eight times. This study indicated that EDTA-GO/corncob is a reusable adsorbent for rapid, low-cost, and efficient removal of dye from waste water.

In this study, crystal violet dyes were adsorbed by EDTA functionalized corncob (EDTA-corncob) and EDTA/graphene oxide functionalized corncob (EDTA-GO/corncob), which were prepared using disodium ethylenediamine tetraacetic acid and the graphene oxide immersion method.     

Long-term stably dispersed functionalized graphene oxide as an oil additive

In oil lubrication systems, it is essential to continuously supply lubricant to the contact surface during practical applications. Herein, to realize its long-term stable dispersion in oil, graphene oxide was modified with polyisobutylene succinimide (PIBS, trade name T154), which is an effective dispersant for lubricating oils. Characterization of the T154-modified graphene oxide (GO-T154) by FTIR, XPS, and XRD revealed that the surface of the graphene platelets was covered by the T154 chains, and the dimensions of the graphene platelets had obviously decreased. The dispersion study demonstrated the long-term stability of a GO-T154/oil suspension, which could stand for more than a year without any significant precipitation. The lubricating property was greatly improved by the addition of GO-T154; more specifically, for the optimal performance, the friction coefficient decreased by 54%, and the wear rate decreased by 60%. Micro observation of the worn surfaces indicated that well-dispersed GO-T154 could enter the gap between the friction surfaces, forming a transfer film to separate the rubbing surface. With the long-term stability, high thermal stability and outstanding tribological properties of the suspension, GO-T154 promises to realize practical applications of graphene in lubricating oil.

T154 modified graphene oxide as an oil additive exhibited excellent tribological properties, long-term stable dispersity and high thermal properties.     

Hollow ZnO microspheres functionalized with electrochemical graphene oxide for the photodegradation of salicylic acid

Hollow ZnO microspheres were successfully synthesized by a hydrothermal method and then functionalized with graphene oxide (GO) flakes, previously obtained through electrochemical oxidation. Their photocatalytic activity toward the photodegradation of salicylic acid under UV light irradiation was evaluated by UV-Vis spectroscopy. Unfunctionalized microspheres and ZnO functionalized with chemically oxidized graphene were also studied as comparative terms. The hybrid materials of ZnO with both electrochemical and chemical GO gave a similar photodegradation yield of ∼28% against 18% of the non-functionalized microspheres. The similar degradation yields and rate constants obtained with the two GO synthetic methods indicate that electrochemical oxidation of GO represents an eco-friendly option over traditional methods for photocatalytic degradation systems.

Hollow ZnO microspheres were successfully synthesized by a hydrothermal method and then functionalized with graphene oxide (GO) flakes, previously obtained through electrochemical oxidation.     

Enhanced oxygen evolution reaction on amine functionalized graphene oxide in alkaline medium

Development of highly efficient oxygen evolution reaction (OER) electrocatalysts is a critical challenge in the cost-effective generation of clean fuels. Here, a metal-free tyramine functionalized graphene oxide (T-GO) electrocatalyst is proposed to use in alkaline electrolytes for enhanced OER. Moreover, the T-GO and GO nanomaterials are well characterized by SEM, XRD, FTIR, XPS and Raman spectroscopy. T-GO exhibits an electrocatalytic OER with a current density of 2 mA cm⁻² at a low onset potential of ∼1.39 V and a small Tafel slope of about 69 mV dec⁻¹ and GO exhibits an onset potential of 1.51 V and Tafel slope of about 92 mV dec⁻¹. Additionally, the current stability and RRDE based diffusion controlled response of the T-GO electrocatalyst are outstanding compared to GO. This study establishes metal free T-GO as an efficient electrocatalyst for the OER and used for cathodic production of hydrogen as a counter reaction in the field of water splitting.

Metal free tyramine functionalized graphene oxide (T-GO) is a promising electrocatalyst for oxygen evolution reaction (OER) in alkaline medium having high activity and stability, resulting from the tyramine active sites.     

Study on the thermal decomposition mechanism of graphene oxide functionalized with triaminoguanidine (GO-TAG) by molecular reactive dynamics and experiments

Graphene oxide (GO) has a catalytic effect on the thermal decomposition of energetic materials above the melting point. To further enhance the catalytic activity of GO, it has been functionalized with the high nitrogen ligand triaminoguanidine (TAG). However, theoretical studies on the reactivity of functionalized GO (e.g., GO-TAG) have not been carried out. Therefore, the thermal decomposition of each TAG, GO and GO-TAG is studied by molecular dynamic simulations using a reactive force-field (ReaxFF) with experimental verification, and the results are reported herein. The results show that the GO nanolayer has a tendency to aggregate into a large carbon cluster during its degradation. The main decomposition products of TAG are NH₃, N₂ and H₂. For GO-TAG, the main decomposition products are H₂O, NH₃, N₂ and H₂. GO has a significant acceleration effect on the decomposition process of TAG by decreasing the decomposition temperature of TAG. This phenomenon is in agreement with the experimental results. The initial decomposition of TAG is mainly caused by hydrogen transfer in the molecule. The edge carbon atoms of GO promote the decomposition of TAG molecules and reduce the decomposition activation energy of TAG by 15.4 kJ mol⁻¹. Therefore, TAG will quickly decompose due to the catalytic effect of GO. This process produces a “new” GO that catalyzes the decomposition of components such as TAG. At the same time, many free radicals (HN₂, H₂N and free H) are generated during the decomposition of TAG to catalyze the decomposition of other components, which in turn, enhance the catalytic capability of GO.

The edge carbon atoms on the GO promote the decomposition of TAG.     

Cerium oxide nanoparticle functionalized lignin as a nano-biosorbent for efficient phosphate removal

Removing excess phosphorus is a highly effective method to prevent eutrophication in contaminated water. However, the design and preparation of an efficient biosorbent for phosphate capture is still a great challenge. We fabricated a novel, and inexpensive nano-biosorbent, L-NH₂@Ce, by loading cerium oxide nanoparticles (nano-CeO₂) within the aminated lignin using a facile in situ precipitation approach for efficient phosphate removal. The as-designed nano-biosorbent L-NH₂@Ce exhibited a BET surface area (S_BET) of 89.8 m² g⁻¹, 3 times that of lignin, and a pore volume (V_p) of 0.23 cm³ g⁻¹. Owing to these results, the adsorption capacity of L-NH₂@Ce increased by 14-fold to 27.86 mg g⁻¹ compared with lignin (1.92 mg g⁻¹). Moreover, the L-NH₂@Ce can quickly reduce a high phosphate concentration of 10 ppm to well below the discharge standard of 0.5 ppm recommended by the World Health Organization (WHO) for drinking water. Importantly, a study of leaching tests indicated the negligible risk of Ce ion leakage during phosphate adsorption over the wide pH range of 4–9. Moreover, L-NH₂@Ce exhibits good reusability and retains 90% of removal efficiency after two adsorption–desorption cycles. The environmentally benignity of the raw material, the simple preparation process, and the high stability and reusability makes L-NH₂@Ce a promising nano-biosorbent for phosphate removal.

An inexpensive, high stability, and good reusability nano-biosorbent L-NH₂@Ce for efficient phosphate removal was fabricated by a facile method.     

Selective removal of lead ions from aqueous solutions using 1,8-dihydroxyanthraquinone (DHAQ) functionalized graphene oxide; isotherm,kinetic and thermodynamic studies

An anthraquinone – graphene structure was fabricated and applied for the removal of lead(ii) from aqueous solution. The equilibrium occurred in about 10 min revealing the high adsorption rate at the beginning of the process. The maximum Pb(ii) adsorption capacity of the Fe₃O₄@DHAQ_GO nanocomposite was about 283.5 mg g⁻¹ that was observed at 323 K and pH 5.5. The Pb(ii) adsorption ability increased with the increasing pH. The isotherm and kinetic studies indicated that the Sips isotherm model and the linear form of the pseudo-second kinetic model had a better fit with the experimental results. The positive value of ΔH⁰ indicated endothermic interactions between Pb(ii) and Fe₃O₄@DHAQ_GO. The negative ΔG⁰ indicated that the reactions are spontaneous with a high affinity for Pb(ii). The positive ΔS⁰ values indicated increasing randomness at the solid–solute interface during the adsorption process. The selective removal of Pb(ii) by the nanocomposite confirms the presence of higher-affinity binding sites for Pb(ii) than Cd(ii), Co(ii), Zn(ii), and Ni(ii) ions. Furthermore, the Fe₃O₄@DHAQ_GO nanocomposite revealed an excellent preferential adsorbent for Pb(ii) spiked in drinking water samples containing natural ion matrices. EDTA-2NA 0.01 N was found to be a better elution agent than HCl 0.1 M for the nanocomposite regeneration. After five adsorption/desorption cycles using EDTA-2NA 0.01 N, more than 84% of the adsorbed Pb(ii) was still desorbed in 30 min. Capturing sub-ppm initial concentrations of Pb(ii) and the capability to selectively remove lead from drinking water samples make the Fe₃O₄@DHAQ_GO nanocomposite practically convenient for water treatment purposes. High adsorption capacity and facile chemical synthesis route are the other advancements.

The Fe₃O₄@DHAQ_GO nanocomposite can serve as an efficient adsorbent for the selective removal of lead from polluted water.     

Electrochemical detection of C-reactive protein using functionalized iridium nanoparticles/graphene oxide as a tag

C-reactive protein (CRP) has become a recognized indicator of inflammation. CRP concentration in serum is an important indicator for monitoring early heart damage, and it is also a newly discovered coronary heart disease-associated inflammatory factor. A conductive nano-hybrid material composed of Au NPs and ionic liquid functionalized molybdenum disulfide (Au NPs/IL-MoS₂) was prepared and utilized to immobilize primary CRP antibodies. Subsequently, 1,5-diaminonaphthalene (DN) was adsorbed onto graphene oxide (GO) through π–π stacking, which was used to load iridium nanoparticles (Ir NPs) as a tag to label secondary CRP antibodies. The large surface area of Au NPs/IL-MoS₂ and the excellent electrocatalytic properties of Ir NPs/GO-DN toward the reduction of H₂O₂ resulted in a highly sensitive assay for CRP antigens. This immunosensor exhibited wide linear ranges from 0.01 to 100 ng mL⁻¹ and a lower detection of limit of 3.3 pg mL⁻¹ (S/N = 3). This CRP immunosensor can be applied in real serum sample analysis with satisfactory results, indicating that the immunosensor has potential applications in biomedical detection.

Ir NPs@GO-DN was used as a tag to label CRP antibody to construct a sandwich CRP immunosensor.     

Facile fabrication of long-chain alkyl functionalized ultrafine reduced graphene oxide nanocomposites for enhanced tribological performance

Due to their ultrathin 2D laminated structure as well as excellent mechanical and thermal stabilities, ultrafine graphene-based nanoparticles exhibit fascinating advantages as highly-efficient lubricant additives. However, it remains a daunting challenge to achieve good and durable dispersion of these graphene-based nanoparticles in lubricating oils. Herein, we report a facile and efficient integration strategy involving particle size miniaturization, surface grafting with octadecyl alcohol (OA), and partial chemical reduction to prepare a novel long-chain alkyl functionalized ultrafine reduced graphene oxide (RGO-g-OA) with highly-dispersive capacity and superior tribological performance. The chemical composition and structural characteristics, microstructural morphology, and particle size distribution of RGO-g-OA were systematically investigated. Combining significantly improved lipophilicity derived from the long-chain alkyl grafting and partial chemical reduction with the small-size effect gave rise to outstanding long-term dispersion stability (as long as one month) of RGO-g-OA in the finished oil. Moreover, the friction coefficient and wear volume of finished oil with merely 0.005 wt% RGO-g-OA greatly reduced to 0.065 and 10 316 μm³, decreased by 9.7% and 44%, respectively, compared to those of pristine finished oil, demonstrating remarkable friction reduction and anti-wear performances. Consequently, owing to the characteristics of facile fabrication, durable dispersion stability, and superior tribological performance at an extremely low content, this novel nanoadditive shows a promising application potential in the tribology field.

Long-chain alkyl functionalized ultrafine reduced graphene oxide nanocomposites with outstanding dispersibility and enhanced lubricating performances.     

Optimizing graphene oxide membranes for effective removal of dyes by modulating the reduction degree and doped nitrogen

The excellent mechanical and chemical characteristics of graphene oxide (GO) enable their potential application in the realm of membrane separation. However, the expansion and instability of GO nanosheets in water limit its application. In this work, nitrogen-doped GO (NGO) was obtained by a harmless hydrothermal reduction method. The obtained NGO films were attached to a polyvinylidene fluoride support membrane by vacuum filtration. By changing the hydrothermal reaction temperature, the reduction degree of GO and doping amount of nitrogen was adjusted to control the inter-layer structure and permeability of NGO. The defect of NGO nanosheets and the reduction of oxygen-containing functional groups could accelerate the transportation of water molecules through the inter-layer space of the hydrophobic graphene sheets. Significantly, the polarization and high adsorption energy of pyridine-N serve as a supplement to the exclusion mechanism of the inter-layer spacing. NGO membranes have better permeability than the initial GO membranes without sacrificing the rejection rate. The optimized NGO film has a significant rejection rate of above 99% for various dyes, such as methylene blue, Congo red and methyl blue.

The defect of NGO nanosheets and the reduction of oxygen-containing functional groups could accelerate the transportation of water molecules through the inter-layer space of the hydrophobic graphene sheets.     

Synergistic effect of functionalized graphene oxide and carbon nanotube hybrids on mechanical properties of epoxy composites

Epoxy resin was grafted to graphene oxide (GO) via esterification reaction and 3D structure hybrids were prepared by combining 1D carbon nanotube (CNT) and 2D functionalized GO through π-stacking interaction. Epoxy composites filled with 3D structure hybrids were fabricated. The results show that functionalized GO effectively improves the dispersibility of CNTs in epoxy matrix due to good compatibility. Excellent mechanical properties were achieved by epoxy composites filled with 3D structure hybrids. The fracture surface analysis indicated improved interfacial interaction between 3D structure hybrids and epoxy matrix, which may due to the covalent bonding formed between the epoxy molecular chain grafted on EGO and the hardener agent during the curing process. In the 3D structure filler network, the mechanisms of crack deflection/bifurcation induced by functionalized GO make the crack path tortuous, which causes the cracks to encounter more CNTs and then promote the mechanisms of CNT fracture and crack bridging, resulting in more energy dissipation. This is the key mechanism for its excellent reinforcing and toughening effects.

The 3D structure hybrids obtained by combining CNT and epoxy functionalized GO exhibit an obvious synergistic effect on the improvement of mechanical properties of epoxy composites.     

Visible-light-driven photocatalytic degradation of safranin-T dye using functionalized graphene oxide nanosheet (FGS)/ZnO nanocomposites

Photocatalysts suffer from a lack of separation of photogenerated excitons due to the fast recombination of charge carriers, so a strong synergistic effect exhibited by photocatalysts is promising for effective photocatalysis. Herein, we have synthesized efficient visible light functionalized graphene oxide nanosheet (FGS)/ZnO nanocomposite photocatalysts via a simple and economical approach with large scale production for practical applications. A series of nanocomposites (FGS/ZnO NCs) with different amounts by weight of graphene oxide (GO) have been synthesized via a facile solution route followed by calcination under environmental conditions. The phase, purity and morphological studies of the synthesized FGS/ZnO NCs were carried out using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The optical properties were studied using UV-visible diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). XRD results confirm the formation of a pure phase of ZnO in the FGS/ZnO NCs and TEM results show strongly adhered ZnO NPs on the surface of the FGS. DRS results confirm the extension of light absorption in the visible region while PL results confirm the effective separation of charge carriers in 0.09 wt% FGS/ZnO NCs. The synthesized photocatalyst efficiently degrades carcinogenic safranin-T dye under visible light illumination which is reported for the first time using FGS/ZnO nanocomposites. Photocatalytic studies confirm the higher photocatalytic activity of 0.09 wt% FGS/ZnO NCs (about 94.5%) towards the photodegradation of safranin-T dye in aqueous solution under visible light. The improved photocatalytic activity of 0.09 wt% FGS/ZnO NCs can be ascribed to the integrative synergistic effects of the enhanced adsorption capacity of safranin-T dye, effective separation of photogenerated excitons and effective interfacial hybridization of FGS and ZnO NCs. The generation of reactive oxygen species was confirmed using terephthalic acid as a probe molecule and a scavenger test was conducted in presence of histidine.

FGS/ZnO NCs with excellent photocatalytic activity towards photodegradation of safranin-T have been synthesized via a facile and economical solution route.     

Highly sensitive and wearable gas sensors consisting of chemically functionalized graphene oxide assembled on cotton yarn

Highly sensitive and wearable chemical sensors for the detection of toxic gas molecules are given significant attention for a variety of applications in human health care and environmental safety. Herein, we demonstrated fiber-type gas sensors based on graphene oxide functionalized with organic molecules such as heptafluorobutylamine (HFBA), 1-(2-methoxyphenyl)piperazine (MPP), and 4-(2-keto-1-benzimidazolinyl)piperidine (KBIP) by assembling functionalized graphene oxide (FGO) on a single yarn fabric. These gas sensors of FGO on yarn exhibited extraordinarily higher sensitivity upon exposure to gas molecules than chemically reduced graphene oxide due to many active functional groups on the GO surface. Furthermore, the mechanical stability and chemical durability of the resulting gas sensors are well-maintained. Based on these results, we expected that our sensors with high sensitive and wearability will provide a good premise for wearable chemical sensors-based multidisciplinary applications.

Functionalized-graphene-oxide-based gas sensors with KBIP-GO-Y showed extremely high sensitivity (∼70%) for exposure to gas molecules compared with rGO-based sensors (∼12%) in spite of relatively low gas concentrations (8 ppm NH₃ gas).     

Nanocomposite of graphene oxide decorated Al-waste sludge for removal of rhodamine B from water

The contamination of land and water resources is reaching its breaking point due to increased human activities. This research attempts to provide a smart solution based on the concept of waste to treat waste, in which solid waste from the aluminium anodizing industry is upcycled and used with graphene oxide to engineer a composite material to treat dye contaminated water. Here, highly porous upcycled aluminium waste sludge is combined with less than 1% (w/w) of graphene oxide and then thermally treated to partially reduce the graphene oxide within the nano matrix. Partial reduction enhances π–π interaction with dye molecules while preserving the hydrophilicity and porosity of the overall composite. Studies carried out with rhodamine B, a toxic dye with intense colour, show complete and efficient removal of the dye from water, independent of any pH adjustment. Moreover, the adsorbed material shows no leachate of the dye nor heavy metals back into water over a wide range of pH values. This facilitates alternative product developments such as building materials and eliminates secondary waste generation. Therefore, the composite described herein is sustainable in both material development and in its usage for wastewater treatment and solid waste management.

A nanocomposite of graphene oxide decorated Al-waste sludge is engineered to provide a sustainable and eco-friendly solution for wastewater treatment and waste disposal.     

Grafting and stabilization of ordered mesoporous silica COK-12 with graphene oxide for enhanced removal of methylene blue

Large-pore ordered mesoporous silica (OMS) COK-12, analogous to the well-known SBA-15, but synthesized in a more environmentally friendly way and exhibiting a shorter plate-like structure, was grafted with different amounts of graphene oxide (GO) for the first time in an inexpensive and rapid process, that was successfully upscaled. Samples were examined with nitrogen sorption analysis, SAXS, Raman spectroscopy, XPS, and zeta potential analysis. Adsorption experiments with the cationic dye methylene blue (MB) were conducted on the grafted materials and on pure COK-12, taking into account the influence of initial dye concentration (30–600 mg L⁻¹), adsorbent dosage (0.2–14 g L⁻¹), contact time (0.3–300 min), solution pH (4–10), and influence of salts and temperature (0–1 M NaCl, 80 °C) to simulate industrial dye effluent. The adsorption process was found to be represented best by the Langmuir isotherm model, i.e., adsorption is a monolayer process. The calculated maximum adsorption capacities were found to be 20.2 and 197.5 mg g⁻¹ at dosages of 5 and 0.5 g L⁻¹ for pure COK-12 and COK-12 grafted with 50 wt% GO, respectively, at pH 5.65 and MB concentration of 100 mg L⁻¹. Adsorption kinetics were found to follow the pseudo-second order model, i.e., chemisorption is the rate controlling step. The adsorption performances could be well preserved at simulated dye effluent. Desorption was found to be most effective with hydrochloric acid. The COK-12 grafted with GO presented in this work shows superior adsorption properties in comparison to other grafted OMS materials. In addition, grafting with GO remarkably improved the stability of COK-12 in aqueous solution.

Grafting of environmentally friendly produced ordered mesoporous silica (OMS) COK-12 with graphene oxide yields a superior OMS/GO adsorbent for methylene blue.     

Controllable reduction of graphene oxide by electron-beam irradiation

The oxygen content of graphene oxide (GO) is directly related to its physical and chemical properties, such as hydrophilicity, suspension stability, adsorption, and ion-sieving ability of GO membranes. Here, a series of reduced GO (rGO) with C/O atomic ratios from 1.6 to 4.8 were prepared conveniently by electron-beam irradiation (EBI) with irradiation-dose control. Moreover, a single oxygen-containing group, i.e., epoxy or carbonyl, could be retained mainly in the rGO. The interlayer spacing of rGO could be changed from 9.6 Å to 7.4 Å through control of the oxygen content. The prepared rGO exhibited an excellent adsorption effect on Pb(ii) ions, and the max adsorption capacity reached 194.76 mg g⁻¹ for rGO with a low irradiation dose (5 kGy), which showed that the ratio of oxygen-containing groups is important for improving the adsorption of rGO in aqueous solution. These results indicated that highly efficient, environmentally friendly, and advanced EBI technology has good potential prospects for use in the large-scale production of rGO with precise control of the oxygen content.

The oxygen content of graphene oxide (GO) is directly related to its physical and chemical properties, such as hydrophilicity, suspension stability, adsorption, and ion-sieving ability of GO membranes.     

Antimicrobial activity of multifaceted lactoferrin or graphene oxide functionalized silver nanocomposites biosynthesized using mushroom waste and chitosan

Hybrid nanoparticles designed to exert multiple mechanisms of antibacterial action offer a new approach to the fight against pathogenic resistant bacteria. In this study, nanomaterials with the dual actions of antibacterial and anti-biofilm activities were developed using silver nanoparticles (AgNPs) functionalized with either lactoferrin (LTF) or graphene oxide (GO). AgNPs were synthesized using mushroom waste as a reducing agent and chitosan (CS) as a stabilizing agent, prior to their surface functionalization with either GO (AgGO) or LTF (Ag-LTF). The AgNPs exhibited a surface plasmon resonance (SPR) band at 430 nm, as determined by UV-vis spectroscopy, whereas the absorption of AgGO and Ag-LTF occurred at 402 and 441 nm, respectively. Particle size analysis of AgNPs, AgGO, and Ag-LTF revealed sizes of 121.5 ± 10.5, 354.0 ± 1.6, and 130.8 ± 1.2 nm, respectively. All AgNPs, Ag-LTF, and AgGO inhibited selected Gram-positive bacteria and Gram-negative bacteria with comparable antibacterial performance, as determined by the agar diffusion method. Despite the absence of antibacterial activity by GO and LTF, a synergistic effect of AgGO and Ag-LTF was observed as they had a greater activity against P. aeruginosa. Moreover, Ag-LTF did not affect cell viability and migration rate of cells, suggesting the non-toxicity of Ag-LTF. In conclusion, AgNPs, Ag-LTF, and AgGO possess antibacterial activity, which may offer an alternative for future antibacterial agents.

Biosynthesis of multifaceted silver nanoparticles using waste mushroom and chitosan.     

Magnetite nanoparticle decorated reduced graphene oxide for adsorptive removal of crystal violet and antifungal activities

This work reports the synthesis and application of magnetic rGO/Fe₃O₄ NCs using a pod extract of Dolichos lablab L. as areducing agent. GO was synthesized by a modified Hummers method, however GO was reduced using the plant extract to produce rGO. The as-synthesized rGO/Fe₃O₄ NCs were characterized by UV-vis spectrophotometer, Fourier transform infrared (FT-IR) spectroscopy, FT-Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy supported with energy dispersed X-ray spectroscopy (FESEM-EDX), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The synthesis of magnetic rGO/Fe₃O₄ NCs was confirmed from characterization results of FT-Raman, TEM and VSM. The FT-Raman results showed the D and G bands at 1306.92 cm⁻¹ and 1591 cm⁻¹ due to rGO and a peak at around 589 cm⁻¹ due to Fe₃O₄ NPs that were anchored on rGO sheets; TEM results showed the synthesis of Fe₃O₄ with an average particle size of 8.86 nm anchored on the surface of rGO sheets. The VSM result confirmed the superparamagnetic properties of the rGO/Fe₃O₄ NCs with a saturation magnetization of 42 emu g⁻¹. The adsorption capacity of rGO/Fe₃O₄ NCs towards crystal violet (CV) dye was calculated to be 62 mg g⁻¹. The dye removal behavior fitted well with the Freundlich isotherm and the pseudo-second-order kinetic model implies possible chemisorption. Besides, rGO/Fe₃O₄ NCs showed antifungal activities against Trichophyton mentagrophytes and Candida albicans by agar-well diffusion method with a zone inhibition of 24 mm and 21 mm, respectively. Therefore, rGO/Fe₃O₄ NCs can be used as an excellent adsorbent to remove organic dye pollutants and kill pathogens.

This work reports synthesis of magnetic rGO/Fe₃O₄ NCs using pod extract of Dolichos lablab L. as a reducing agent and its applications.