Functionalized Graphene Oxide Nanosheets Research Articles

Intrinsically reactive hyperbranched interface governs graphene oxide dispersion and crosslinking in epoxy for enhanced flame retardancy

Enhancing the flame retardancy of epoxy (EP) resins typically entailed a trade-off with other physical properties. Herein, hyperbranched poly(amidoamine) (HPAA) and phytic acid (PA) were used to functionalize graphene oxide (GO) via electrostatic self-assembly in water to prepare a phosphorus-nitrogen functionalized graphene oxide nanosheet (PN-GOs), which could be utilized as high efficient flame-retardant additive of epoxy resin without sacrificing other properties. The PN-GOs demonstrated improved dispersion and compatibility within the EP matrix, which resulted in significant concurrent enhancements in both the mechanical performance and flame-retardant properties of the PN-GOs/EP nanocomposites over virgin EP. Notably, the incorporation of just 1.0 wt% PN-GOs yielded a 20.4, 6.4 and 42.7 % increases in flexural strength, flexural modulus and impact strength for the PN-GOs/EP nanocomposites, respectively. Furthermore, simultaneous reductions were achieved in the peak heat release rate (pHRR) by 60.0 %, total smoke production (TSP) by 43.0 %, peak CO production rate (pCOP) by 57.9 %, and peak CO2 production rate (pCO2P) by 63.9 %. This study presented a facile method for the design of GO-based nano flame retardants, expanding their application potential in polymer-matrix composites.

Catalytic membranes assembled by Co–Fe Prussian blue analogues functionalized graphene oxide nanosheets for rapid removal of contaminants

The catalytic membrane, combining confinement effect with advanced oxidation processes, exhibits great potential as an efficient technology for removing contaminants and mitigating membrane fouling. Herein, the Prussian blue analogues (PBAs) functionalized graphene oxide (GO) membranes, referred as PGMs, was successfully fabricated. It exhibited a package-like confined structure where Co–Fe PBAs were encapsulated within interconnected GO nanosheets. The surface properties, internal structure as well as the catalytic performance of PGMs were controlled by adjusting the amount of Co–Fe PBAs anchored on GO nanosheets. The designed PGM as efficient peroxymonosulfate activator exhibited exceptional catalytic performance, achieving complete removal of bisphenol A (BPA) with a retention time of 31 ms. The corresponding first-order rate constant was 6000 min−1, which surpassed conventional batch system by four orders of magnitude (0.2194 min−1). Moreover, the redox cycle involving Fe2+ and Co3+, coupled with the effective suppression of ion leaching from Co–Fe PBAs nanoparticles (<10 μg/L) through GO protective layers, ensured the stable catalytic performance of PGM over 144 h. This study employs a novel approach to confine catalytic nanoparticles within two-dimensional nanosheets, demonstrating the potential applications of the resulting confined membrane in water treatment.

Mechanistic evaluation of contrasting modulation in conformation and catalytic performance of urease by surface interaction of graphene oxide and amine- functionalized graphene oxide nanosheets

The increasing use of graphene-based nanomaterials raises concerns about their potential environmental impact as ecotoxicants. This article examines the interaction and effects of graphene oxide (GO) and its amine-derived (GONH2) 2-D nanosheets on urease dynamics, a crucial enzyme in soil nutrient cycling, through spectroscopic, microscopic, and computational analyses. The findings reveal the distinct interaction mechanisms: GO formed ground - and excited-state complexes with urease; thus, fluorescence quenching was static and dynamic via hydrophobic interaction. In contrast, GONH2 nanosheets formed a ground-state complex by static quenching involving Van der Waals and hydrogen bonding. These interactions were energetically favored and altered tryptophan (Trp) residues’ microenvironment more than tyrosine (Tyr). The average exciton lifetime of urease in the presence of GO have decreased from 4.34 ns to 3.647 ns at the mere concentration of 7.11 µM, while for GONH2, no discernable change (4.16 ns) was observed even at the concentration of 16.75 µM. Primarily, the strong interaction of GO leads to the rearrangement of polypeptide structure, reduced α-helices to 12 %, and increased β-sheets by six times. In contrast, with GONH2, α-helices were reduced to 79 %, and β-sheets were increased by 1.8 times at the similar concentration. Molecular docking revealed that neither GO nor GONH2 interacted with the active site of urease, and binding was primarily via hydrophobic, Van der Waals, and hydrogen bonding, concurrent with in-vitro incubation results. Positive total energy (3.85 kJ mol−1) during molecular docking analysis of urease-GO interaction and inhibition in enzyme activity to 62 %, altered Vmax value (0.04606 ± 0.001 mM/s), without affecting the Km (4.78045 ± 0.12 mM) suggested that inhibition was noncompetitive and steric clashes due to disruptive binding might drove the inhibition. Meanwhile, negative total internal energy (-3.97 kJ mol−1) during urease + GONH2 binding and enhanced enzymatic activity by 32 % in-vitro without altering Vmax (0.063091 ± 0.003 mM/s) and Km (4.953943 ± 0.2 mM) values suggested that urease's binding site was well-complemented by GONH2 nanosheets, serving as a redox-mediator and radical-quencher.

Design of quetiapine fumarate loaded polyethylene glycol decorated graphene oxide nanosheets: Invitro-exvivo characterization

Quetiapine Fumarate (QF) is an atypical antipsychotic with poor oral bioavailability (9%) due to its low permeability and pH-dependent solubility. Therefore, this study aims to design QF-loaded polyethylene glycol (PEG) functionalized graphene oxide nanosheets (GON) for nasal delivery of QF. In brief, GO was synthesized using a modified Hummers process, followed by ultra-sonication to produce GON. Subsequently, PEG-functionalized GON was prepared using carbodiimide chemistry (PEG-GON). QF was then decorated onto the cage of PEG-GON using the π-π stacking phenomenon (QF@PEG-GON). The QF@PEG-GON nanocomposite underwent several spectral characterizations, in vitro drug release, mucoadhesion study, ex vivo diffusion study, etc. The surface morphology of QF@PEG-GON nanocomposite validates the cracked nature of the nanocomposite, whereas the diffractograms and thermogram of nanocomposite confirm the conversion of QF into an amorphous form with uniform distribution in PEG-GON. Moreover, an ex vivo study of PEG-GON demonstrates superior mucoadhesion capacity due to its surface functional groups and hydrophilicity. The percent drug loading content and percent entrapment efficiency of the nanocomposite were found to be 9.2±0.62% and 92.3±1.02%, respectively. The developed nanocomposite exhibited 43.82±1.65% drug release within 24h, with the Korsemeyer-Peppas model providing the best-fit release kinetics (R2: 0.8614). Here, the interlayer spacing of PEG-GON prevented prompt diffusion of the buffer, leading to a delayed release pattern. In conclusion, the anticipated QF@PEG-GON nanocomposite shows promise as a nanocarrier platform for nasal delivery of QF.

An electrochemical sensor for the detection of arsenic using nanocomposite-modified electrode

The aim of this research is to develop an electrochemical sensor based on a conducting polymer, polyaniline, and a cationic polymer, poly(diallyldimethylammonium chloride), reinforced with graphene oxide nanosheets functionalized with acrylic acid. The two-dimensional nature of acrylic acid functionalized graphene oxide nanosheets and clusters made of conductive polymers and acrylic acid functionalized graphene oxide nanosheets were confirmed by microscopic tests. The prepared nanocomposite was deposited on the glassy carbon electrode in order to prepare an electrochemical sensor for the detection of arsenic by cyclic voltammetry and differential pulse voltammetry methods. It should be mentioned that the presence of acrylic acid functionalized graphene oxide nanosheets increases the surface area due to the nano size effect and better dispersion of this nanomaterial, poly(diallyldimethylammonium chloride), increases the adsorption capacity of the analyte due to electrostatic interaction between the negatively charged analyte and positively charged surface, and polyanilin increases the charge transfer rate due to the good conductivity. The results show that the prepared electrode has a sensitivity equal to 1.79 A/M with 0.12 μM as the detection limit. The proposed sensor could be used for the determination of total inorganic arsenic by first oxidative pretreatment for conversion of As(III) to As(V).

Effects of adding functionalized graphene oxide nanosheets on physical, mechanical, and anti-biofilm properties of acrylic resin: In vitro- experimental study

Background: Polymethyl methacrylate resin is widely used in orthodontic treatments. Graphene oxide (GO) has reactive functional groups on its surface that facilitate binding to various materials such as polymers, biomolecules, DNA, and proteins. This study aimed to investigate the impact of adding functionalized GO nanosheets on the physical, mechanical, cytotoxicity, and anti-biofilm properties of acrylic resin.Materials and Methods: In this experimental study, fifty samples (for each test) were divided into groups of 10, in the form of acrylic resin discs with concentrations of 0, 0.25, 0.5, 1, and 2 weight percentage (wt%) of functionalized GO nanosheets and also the control group. Samples were evaluated in terms of physical properties (surface hardness, surface roughness, compressive strength, fracture toughness, and flexural strength), anti-biofilm properties (On four groups of micro-organisms, including Streptococcus mutans, Streptococcus sanguis, Staphylococcus aureus, and Candida albicans), and cytotoxicity. Data were analyzed using SPSS software version 22, descriptive statistics, one-way analysis of variance test, and Tukey post hoc test. The significance level was considered P < 0.05.Results: No significant difference was observed between the different groups with weight percentages of 0.25, 0.5, 1, and 2% nano GO (nGO) and the control group (without nGO) in terms of surface roughness and toughness. However, compressive strength, three-point flexural strength, and surface hardness showed significant differences between the groups. Furthermore, the degree of cytotoxicity increased by increasing the weight percentage of nano-GO.Conclusion: The addition of functionalized nGO in appropriate concentrations to polymethyl methacrylate can improve the anti-bacterial and anti-fungal biofilm properties without changing or increasing their physical and mechanical properties.

Fabrication of Inorganic Coatings Incorporated with Functionalized Graphene Oxide Nanosheets for Improving Fire Retardancy of Wooden Substrates.

Flame-retardant chemicals are frequently used within consumer products and can even be employed as a treatment on the surface of different types of materials (e.g., wood, steel, and textiles) to prevent fire or limit the rapid spread of flames. Functionalized graphene oxide (FGO) nanosheets are a promising construction coating nanomaterial that can be blended with sodium metasilicate and gypsum to reduce the flammability of construction buildings. In this work, we designed and fabricated novel and halogen-free FGO sheets using the modified Hummers method; and subsequently functionalized them by pentaerythritol through a chemical impregnation process before dispersing them within the construction coating. Scanning electron microscopic images confirm that the FGO-filled coating was uniformly dispersed on the surface of wooden substrates. We identified that the FGO content is a critical factor affecting the fire retardancy. Thermogravimetric analysis of the FGO coating revealed that higher char residue can be obtained at 700 °C. Based on the differential scanning calorimetry, the exothermic peak contained a temperature delay in the presence of FGO sheets, primarily due to the formation of a thermal barrier. Such a significant improvement in the flame retardancy confirms that the FGO nanosheets are superior nanomaterials to be employed as a flame-retardant construction coating nanomaterial for improving thermal management within buildings.

Biological investigation of a novel nanocomposite based on functionalized graphene oxide nanosheets with pectin, silk fibroin and zinc chromite nanoparticles

For biotechnology applications, a novel nanobiocomposite was synthesized based on modification of graphene oxide (GO) by extracted silk fibroin (SF), natural polymer pectin (Pec) and zinc chromite (ZnCr2O4) nanoparticles (NPs). The structure and properties of hybrid nanobiocomposite GO-Pec/SF/ZnCr2O4 such as thermal stability, less toxicity, biocompatibility, antibacterial, and biodegradable were proved by using field emission scanning electron microscope (FE-SEM), Fourier-transformed infrared (FT-IR), Energy dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), and X-Ray diffraction (XRD). According to the biological features of substances, the GO-Pec/SF/ZnCr2O4 nanobiocomposite shows perfect results in MTT (83.71 %) and Hemolysis (16.52 %) assays. accordingly, mentioned properties of this nanobiocomposite can be used as a scaffold for medical applications.

Carbon Fiber Reinforced Polymer Composites with Enhanced Interfacial Properties Based on Electrostatic Assembled FGO / Oxidized CF

AbstractInterfacial properties play a critical role in the performance of carbon fiber‐reinforced composites (CFRPs). However, poor interfacial interactions between carbon fiber (CF) and polymer matrix often limit the performance improvement of CFRPs. In the present work, ethylenediamine functionalized graphene oxide (FGO) and oxidized‐carbon fiber (oxidized‐CF) are applied to prepare CFRPs through electrostatic self‐assembly. Results of Raman, TGA, SEM, and dynamic contact angle analyses confirm that FGO nanosheets are tightly bonded onto the oxidized‐CF surface. DMA results show a small increase of Tg of the oxidized‐CF‐FGO composites, as well as a great increment of energy storage modulus (E') compared to that of the untreated CF composites, which indicates an enhancement of interfacial properties. More importantly, the interfacial shear strength shows a great improvement of 30.4%, reaching 58.7 MPa. The interfacial enhancement mechanisms are further discussed based on the microstructure and performance evaluation results.

Edge and basal functionalized graphene oxide nanosheets: Two different behavior in improving electrical conductivity of epoxy nanocomposite coatings

Two different graphene nanosheets with different oxygen groups' localization were synthesized to investigate their effect on the electrical properties of graphene/epoxy nanocomposite coatings. Graphite natural flakes (NG) and expanded graphite (EG) were used as a carbon precursor to synthesize Edge functionalized (E-GO) and Basal Functionalized (B-GO) graphene nanosheets, respectively. Next, polymer nanocomposite coatings were fabricated by dispersing E-GO and B-GO into a waterborne epoxy matrix. Rheology was assisted in evaluating the dispersion state of the nanosheets in the epoxy matrix. B-GO exhibited better performance in network formation which can be related to the similarity of oxygen groups between B-GO and epoxy matrix. Next, the electrical conductivitie values of polymer nanocomposite coatings were measured after in-situ thermal reduction at 225 °C. The results indicated that polymeric coatings containing B-GO nanosheets represent higher electrical conductivity values compared to samples containing E-GO nanosheets despite the higher intrinsic electrical conductivity of E-GO compared to B-GO. This can be related to the improved ability of B-GO nanosheets to form an electrically conductive network inside the epoxy matrix. The electrical conductivity value of 0.5 S/m was obtained for polymeric coatings containing 0.8 vol% B-GO nanosheets with percolation thresholds of 0.17 vol%. The improved electrical conductivity can be correlated to the formation of the interphase region between the epoxy matrix and B-GO nanosheets which is the result of the similarity of the oxygen groups' nature in B-GO and epoxy.

Synergistically enhancing the performance of cardanol-rich epoxy anticorrosive coatings using cardanol-based reactive diluent and its functionalized graphene oxide

In this paper, a new anti-corrosion composite coating with high-volume fraction of cardanol-based components was prepared using epoxy, cardanol-based reactive diluent (602A), and 602A functionalized graphene oxide nanosheets (A-GO). A one-step, low-cost method was adopted to synthesize the A-GO. By synergistically enhancing the matrix compactness, filler dispersibility, and matrix hydrophobicity, the cardanol-rich epoxy composite coating (A-GO/602A/epoxy) shows high anti-corrosion performance in the long term. The morphology and structure analyses show that the A-GO/602A/epoxy composite coating has i. enhanced matrix compactness, ii. optimized filler dispersibility and filler/matrix bonding strength, and iii. improved matrix hydrophobicity. The electrochemical impedance spectroscopy (EIS) test was used to determine the anti-corrosion performance of the A-GO/602A/epoxy composite coating. After immersing in diluent NaCl solution (3.5 wt%) for 90 days, the increase of the impedance modulus of the A-GO/602A/epoxy composite coating maintains three orders of magnitude at low frequencies (0.01 Hz) compared to the pure petroleum-based epoxy coating, indicating that the corrosion properties of the composite coating can be significantly enhanced by synergistically optimization of the three factors. Our results show the high potential of cardanol-rich epoxy coatings in the field of anti-corrosion epoxy coatings, and may give a guide to the design of high-performance anti-corrosion epoxy coatings.

Electric Field Polarized Fe−N Functionalized Graphene Oxide Nanosheet Catalyst for Efficient Oxygen Reduction Reaction

AbstractLow‐cost noble‐metal‐free electrocatalysts for oxygen reduction reaction (ORR) are useful for future energy storage and conversion devices, and other technologies. In this work, iron (Fe)‐nitrogen (N) functionalized graphene oxide (Fe−N−GO) nanosheets have been synthesized and studied for ORR properties in alkaline solution. We utilized a multi‐layer/multi‐polarization method to study the DC electric field polarization effect on the electrocatalytic properties of the Fe−N−GO catalyst. The poling effect with DC electric field was created on the catalyst ink drop‐casted on a polished glassy carbon working electrode, resulting in more compact electrocatalyst electrode. Compared to the commercial Pt/C catalyst, the polarized Fe−N−GO catalyst exhibited similar ORR catalytic activity along with superior stability in alkaline media.

L-Cysteine functionalized graphene oxide nanoarchitectonics: A metal-free Hg2+ nanosensor with peroxidase-like activity boosted by competitive adsorption.

Developing non-noble metal, even metal-free chemical sensors for the detection of toxic heavy metal ions is significantly desirable for economically and environmentally sustainable application but has heretofore remained elusive. Herein, a L-cysteine functionalized graphene oxide nanosheet (CGO) nanoarchitectonics, greenly synthesized by a very simple method at room temperature, was utilized to realize the simultaneous enrichment and colorimetric detection of trace mercury ions (Hg2+). It was discovered that CGO, as a nanozyme mimic exhibited greatly enhanced peroxidase-like catalytic activity than the pristine graphene oxide. By exploring the interactions of CGO nanozyme with colorimetric substrate, 3,3',5,5'-tetramethylbenzidine (TMB) and target Hg2+ ions, we found that the sensing principle was based mainly on the competitive adsorption between Hg2+ ions and TMB over CGO. The pre-capture of Hg2+ ions hindered the TMB binding on CGO, resulting in the promoted oxidation of TMB by H2O2 to produce more colored oxidation products, from which the colorimetric sensing of Hg2+ was realized with a good detection effect on 5μgL-1 solution. As an enrichment-sensing integration platform, this metal-free sensor is cost-effective and sensitive, and presents considerable anti-interference ability over other metal ions. Overall, this work not only expands the application of graphene-based materials in colorimetric detection but also provides a general sensing principle to construct highly sensitive sensors.

Functionalized graphene oxide nanosheets with folic acid and silk fibroin as a novel nanobiocomposite for biomedical applications

In this paper, a novel graphene oxide-folic acid/silk fibroin (GO-FA/SF) nanobiocomposite scaffold was designed and fabricated using affordable and non-toxic materials. The GO was synthesized using the hummer method, covalently functionalized with FA, and then easily conjugated with extracted SF via the freeze-drying process. For characterization of the scaffold, several techniques were employed: Fourier-transform infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and thermogravimetric analysis (TGA). The cell viability method, hemolysis, and anti-biofilm assays were performed, exploring the biological capability of the nanobiocomposite. The cell viability percentages were 96.67, 96.35 and 97.23% for 24, 48, and 72 h, respectively, and its hemolytic effect was less than 10%. In addition, it was shown that this nanobiocomposite prevents the formation of Pseudomonas aeruginosa biofilm and has antibacterial activity.

Incorporating amino acids functionalized graphene oxide nanosheets into Pebax membranes for CO2 separation

Graphene oxide (GO) nanosheets, as versatile nanofillers, can create two-dimensional passageways in mixed matrixed membranes (MMMs), yet the flexible manipulation of GO nanosheets is hampered by the lack of appropriate chemical functional groups. In this study, we chose amino acids（arginine, histidine and cysteine）to modify GO nanosheets by direct crosslinking and the loading content of amino acids on GO nanosheets was more than 20%. The modified GO nanosheets were then filled into the Pebax matrix to prepare MMMs. The CO2 separation performance of MMMs with different nanofillers was compared and different amino acids modified GO nanosheets could fortify the solution mechanism for CO2 in the order of arginine@GO ＞ histidine@GO ＞ cysteine@GO. Density functional theory (DFT) calculations were conducted to further elucidate the interaction mechanism between gases molecules and amino acids. Under dry state, the complexation energy (Ec) between CO2 and amine groups was similar to the Ec between CO2 and carboxylic groups in amino acids. In particular, 0.4 wt% arg@GO nanosheets rendered the membranes with promising CO2 permeance of 169 Barrer and CO2/N2 selectivity of 70, and surpassed the 2008 upper bound. The amino acids modified GO nanosheets may enlighten an alternative way to explore CO2 transfer mechanism within MMMs and fabricate high separation performance membranes.

Antifouling and antibacterial β-cyclodextrin decorated graphene oxide/polyamide thin-film nanocomposite reverse osmosis membranes for desalination applications

• β-cyclodextrin-functionalized graphene oxide enhanced membrane properties. • Membrane with improved surface hydrophilicity and pure water permeability obtained. • Superior antibacterial and antifouling properties imparted on membrane. • Potentially a robust reverse osmosis membrane with an improved life-span. Incorporating functional nanomaterials in polyamide-based membranes has opened up new alternative ways to develop reverse osmosis membranes with excellent performance, biological stability, chemical stability and longer life-span. In this study, β-cyclodextrin functionalized graphene oxide nanosheets (β-CD-f-GO) were synthesized and used to fabricate polyamide thin film nanocomposite membranes possessing excellent reverse osmosis performance, antifouling and antibacterial properties. The β-CD functionalized graphene oxide nanosheets were prepared via an amide-mediated coupling reaction between ethylenediamine-grafted β-CD and graphene oxide. The fabricated nanosheets were then embedded in the polyamide thin film composite membranes via interfacial polymerization of m-phenylenediamine in an aqueous solution containing β-CD-f-GO nanosheets with trimesoyl chloride. The influence of the nanosheets on the membrane surface chemistry, permselectivity performance, antibacterial and antifouling properties was investigated. The results revealed that the water permeation flux and antibacterial activity of the β-CD-f-GO incorporated membranes showed an improvement by approximately 38% and 45.9%, respectively, relative to an unmodified polyamide membrane, with an insignificant change in salt rejection. In addition, the nanocomposite membranes exhibited improved antifouling properties with a lower total fouling ratio of 26.2% and a higher flux recovery ratio of 88.3% in comparison to the respective 46.8% and 74.1% obtained with the unmodified polyamide membrane. Additionally, the nanomposite membranes showed long term stability over a period of 144 h of reverse osmosis testing and improved chlorine resistance. With this study, it can be concluded that the β-cyclodextrin-functionalized graphene oxide nanocomposite has a good potential in the fabrication of membranes with improved stability and lifespan for desalination applications.

Highly selective heavy metal ions membranes combining sulfonated polyethersulfone and self-assembled manganese oxide nanosheets on positively functionalized graphene oxide nanosheets

This study presents the synthesis of a novel graphene oxide-manganese oxide (GO-MnO2) nanohybrid and its incorporation into sulfonated polyethersulfone (SPES) ultrafiltration (UF) membranes for wastewater treatment applications. The nanohybrid was first prepared by grafting ethylenediamine (ED) onto the edge of GO followed by direct mixing with the MnO2 nanosheets. The composite membranes were prepared via the phase inversion method and optimized by varying the concentration of the GO-MnO2 nanohybrid (0–6 wt%). The membranes were characterized using scanning electron microscopy, surface zeta potential, water flux, porosity, among others. The results showed that the pure water flux increased from 59.5 ± 2.5 L·m−2·h−1 in the pristine SPES membrane to 129.7 ± 4.1 L·m−2·h−1 in the SPGM4 (4 wt% GO-MnO2). Furthermore, the heavy metal ions rejection improved from 70.1, 49.1, and 55.8% for Cu2+, Zn2+, and Ni2+ ions, respectively, in the pristine SPES membrane to 81.1, 64.0, and 67.4% in the SPGM4 membrane. Also, the composite membranes revealed improvement in the anti-fouling properties over the pristine SPES membrane. For example, the SPGM4 membrane recovered 90.5 ± 2.9% of its initial flux compared to only 72.6 ± 3.1% in the pristine membrane after 4 cycles of heavy metal filtration and simple acid cleaning steps. Overall, the addition of GO-MnO2 nanohybrid enhanced the properties of the pristine SPES, creating new potential for such composite membranes in the wastewater treatment industry.

A MODIFYING GO AND DOPING IT IN WATERBORNE ACRYLIC COATINGS TO ENHANCE THEIR MECHANICAL PERFORMANCE AND CORROSION PROTECTION

With the development of science and technology and the ever-increasing focus of the environmental protection, waterborne acrylic resin based coating has been commonly used in a wide range of applications due to its high flexibility and good UV resistance. Continuous attempts have been extensively carried out to improve its corrosion resistance and mechanical properties through doping of different nanomaterials. In this study, Functionalized Graphene Oxide (FGO) nanosheets covalently bonded to hydroxylated acrylic resin was introduced into the Hydroxyacrylic Acid Dispersion (HAD) matrix to enhance the performance. To study the effect of grafted hydroxylated acrylic resin on morphology and properties of GO nanosheets, the GO and FGO nanosheets have been systematically characterized with various testing methods, such as FTIR, field emission-scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), Raman spectroscopy, X-ray diffraction (XRD) analysis, UV–vis analysis, and thermogravimetric analysis (TGA). The morphology, physical–mechanical, and anti-corrosion properties of the HAD coatings doped with GO and FGO nanosheets have been compared. The results confirmed that FGO’s dispersion behavior in the HAD matrix has been improved after modifification with the hydroxylated acrylic resin, and the interfacial bonds between the HAD-FGO nanosheets have been significantly enhanced.

Dimethyl carbonate production via transesterification reaction using nitrogen functionalized graphene oxide nanosheets

Nitrogen-functionalized graphene oxide (GO) nanocatalysts were prepared using ammonia, methylamine, ethylamine, and hydrazine hydrate as a nitrogen source. Nanocatalysts samples were thoroughly characterized using XRD, Raman, FTIR, XPS, FESEM, TEM, and TGA techniques. Quantitative and qualitative analyses of surface acidic and basic sites were done by NH3- and CO2-TPD techniques. Nanocatalysts were further examined for DMC production via transesterification reaction of propylene carbonate (PC) with CH3OH. Quantitative analysis of nitrogen-containing functional groups in the prepared sample with respect to other functional moieties was performed. Among various nanocatalysts, ammonia functionalized GO (AGO) was found to be the best for DMC production. At optimized reaction conditions of temperature (180 °C), time (6 h), and catalyst dose (1 wt% with respect PC), the highest DMC yield of ∼50% was observed. Reusability studies using AGO nanocatalyst were conducted up to four consecutive test cycles to evaluate catalysts' potentiality towards DMC synthesis. Thus, N-functionalized GO is a useful metal-free nanocatalyst that could also be explored for other chemical processes.

Zwitterion-decorated graphene oxide nanosheets with aliphatic amino acids under specific pH conditions

The chemical functionalization of graphene oxide nanosheets (GO) with aliphatic amino acids such as arginine and lysine (Arg and Lys), was studied to determine the zwitterionic behavior of nanomaterials under specific pH conditions (Arg at pH 8 and Lys at pH 9.8). For this purpose, the primary amine of each amino acid was previously activated, aiming to promote the formation of C-N bonds between the amino acid and the epoxide groups at the surface of GO nanosheets. Results showed significant changes in the crystalline structure and morphology of GO with this amino acid incorporation, associated with C-N bond formation and, corroborated by FTIR and XPS measurements. Consequently, Zeta potential of the functionalized graphene oxide nanosheets presented an isoelectric point ca. 2.14 for GO-Arg and 2.41 for GO-Lys, suggesting a zwitterionic behavior in aqueous solutions. Zwitterionic behavior of GO nanosheets decorated with aliphatic amino acids may act as a selective nanomaterial for organic dye removal.