Silane-functionalized Graphene Oxide Research Articles

Effect of EPD coated silanized graphene oxide on carbon fiber reinforced plastic: An emphasis on mechanical properties at cryogenic temperatures

The space industry is constantly exploring lightweight, high-strength materials, particularly carbon fiber reinforced polymer (CFRP) composites. Nonetheless, in some cryogenic space applications, neat CFRP fails miserably. Here, silane functionalized graphene oxide (SGO) was coated on the carbon fiber surface to modify its properties. SGO is deposited onto a PAN-based plain weave carbon fiber using the electrophoretic deposition (EPD) process. SGO coated carbon fiber, along with epoxy resin, was used to fabricate CFRP laminates. From mechanical studies of CFRP samples, tensile, flexural, and impact strength improved by 13.1 %, 26.6 %, and 3.9 %, respectively, at room temperature (RT). The improvements were 15.1 %, 35.3 %, and 13.5 %, respectively, at cryogenic temperatures (CT). FTIR studies confirmed the emergence of a flexible Si-O-Si bond, which is a key factor for improved strength. AFM and SEM analysis were conducted to investigate contact roughness improvement. Contact angle microscopy examined SGO-induced wettability of modified carbon fiber. Also, a fracture study showed that the failure mode of SGO-coated CFRP at CT had changed from interface failure to matrix failure.

Versatile selective absorption-based optical fiber toward epinephrine detection

A versatile lossy mode resonance (LMR) sensor is developed for Epinephrine monitoring based on the state-of-the-art molecular imprinting technique over an optical fiber. The optical absorption concept of the LMR-based sensor is proven by incorporating an amino silane-functionalized graphene oxide (SiO2-NH2@GO) as an adhesive layer for grafting Epinephrine imprinting polydopamine (Ep-IPDA) as a sensing layer onto the optical fiber curved surface. The accurate structural and morphological characterization confirmed the rough crystalline and spherical particles for Ep-IPDA and SiO2-NH2-GO onto optical fiber curved surface, while spectroscopic analysis confirms the formation of imprinting polymer and desirable absorbance characteristics. The optimized probe exhibits an excellent performance with the maximum sensitivity within two intervals of 0.3–1 µM and 1–90 µM along with the linearity coefficient of R2 = 0.99 possessing a low limit of detection of 0.07 µM. Additionally, this sensor selectively detects Ep in the presence of other species and showed good recovery in human urine and injection samples. This work opens a new avenue for developing bio-inspired LMR-based optical fiber biosensors and could be further extended to detect other catecholamine neurotransmitters.

Construction of vinyl ester resins composite coatings via introducing silane-functionalized graphene oxide for enhancing comprehensive performance

Vinyl ester resins (VERs) are often used as anti-corrosive coating due to their high curing speed and good mechanical property in most industrial fields. However, many small holes can be formed during the curing process of these resins, resulting in they are not suitable for heavy anti-corrosion applications. Herein, approximately 100% utilization rate of raw materials and solvent-free polyfunctional acrylates (AGO-VERs) with excellent anti-corrosive properties are synthesized by crosslinking VERs with silane decorated graphene oxide (AGO) using toluene diisocyanate as the crosslinking agent. Compared with GO-VERs, AGO-VERs show better dispersibility and higher degree of peeling in the resin systems. Furthermore, the cured coating containing AGO-VER-6 exhibits the maximum tensile strength (80.73 MPa), flexural strength (178.58 MPa), Young's modulus (669.53 MPa) and impedance modulus (2.43 × 108 Ω cm2 after soaking for 7 d). Finally, the possible corrosion protection mechanism of the modified VERs is clarified. Results demonstrate a simple and efficient approach for covalently combining VERs with GO well, which can achieve long-term corrosion protection of metal substrates in the field of heavy anti-corrosive coatings.

Investigation on the mechanical, thermal, structural and morphological properties of polypropylene/ethylene-vinyl acetate copolymer/graphene oxide nanocomposites: effect of nanofiller surface functionalization and compatibilizers

Rubber toughened PP nanocomposites with desirable thermal properties and tensile strength (TS) found applications in automotive and packaging industries. This article reports on the mechanical, thermal, structural, and morphological properties of polypropylene (PP)/ethylene-vinyl acetate copolymer (EVA) blend reinforced with graphene oxide (GO) and silane-functionalized GO (f-GO). GO was modified with two silanes: γ-glycidoxypropyltrimethoxysilane (GPTMS) and γ-mercaptopropyltrimethoxysilane (MPTMS). The influence of three compatibilizer systems: (PP-g-OH, PP-g-COOH, and PP-g-NH2) on the properties of the composites was also evaluated. The structure and thermal behavior of GO and f-GO were comparatively studied for the first time. The attenuated total reflectance Fourier transform infrared (ATR-FTIR), Raman spectroscopy measurements, and X-ray diffraction (XRD) brought evidence for the successful interactions of silanes with GO. Thermogravimetric analysis (TGA) showed that f-GO exhibited higher thermal stability compared to GO. According to the mechanical analysis, PP/EVA/GPTMS-GO/PP-g-NH2 displayed higher TS and stiffness than the other compatibilized nanocomposites. TGA results indicated that the presence of both f-GO and compatibilizers caused a drastic improvement in the thermal stability. DSC analyses revealed that the addition of nanoparticles led to an increase in PP melting and crystallization temperatures, as well as the degree of crystallinity. XRD patterns revealed the formation of intercalated-delaminated nanocomposites and the promotion of β-phase crystals of PP for the samples containing PP-g-COOH and PP-g-NH2. The scanning electron microscopy (SEM) showed that the addition of compatibilizers drastically reduces the domain size of the EVA particles. All results suggest that GO nanoparticles enhance the mechanical and thermal properties of PP/EVA blend.

Silane functionalized graphene oxide-bound polyelectrolyte layers for producing monovalent cation permselective membranes

This study reports a novel layer-by-layer (LbL) strategy for producing a monovalent cation perm-selective membrane with an improved antifouling property. LbL architectures were fabricated by using the polyvinyl chloride (PVC) based heterogeneous cation exchange membrane as the substrate and chitosan (CS) and polyacrylic acid (PAA) as the polycation and polyanion, respectively. The coating layers on the substrate consist of 1.5 bilayers with CS as the initiating and terminating layer and PAA blended with silane functionalized graphene oxide (S-f-GO) as the middle layer. Molecular electrostatic potential (MEP) of the utilized materials proved the availability of appropriate reactive sites in their structures. FTIR spectra, EDX analysis, zeta-potential measurement, and FESEM images verified successful LbL assembly of CS and PAA blended with S-f-GO. The presence of S-f-GO in the anionic layer of the LbL architectures caused more compactness of the terminating cationic layer and increased the porosity of the anionic layer. LbL membranes containing S-f-GO possessed lower surface roughness and more hydrophilic surface and provided higher antifouling property, monovalent selectivity, and electrical conductivity than LbL architecture without additive. Results showed that utilizing 2 wt% S-f-GO in the anionic layer led to increasing permselectivity (PMg2+Na+)from 1.03 to 6. Also, the incorporation of S-f-GO was found to enhance the regeneration ability of the LbL membranes. This novel strategy for producing the MCPM can open up a new insight into designing advanced monovalent selective ion exchange membranes.

Dispersion of silane-functionalized GO and its reinforcing effects in cement composites

The agglomeration of graphene oxide (GO) in alkaline media fundamentally restricts its reinforcement efficiency in cement composites . We investigate a method of enhancing the dispersion and reinforcement efficiency of GO via functionalization using 3-aminopropyltriethoxy silane (APTS). Our results indicated that functionalization improved the dispersion of GO in a pore solution by up to 60% primarily due to steric hindrance and electrostatic repulsive effects. Strong interactions between the silane-functionalized GO (FGO) and cement hydration products via residual oxygen functional groups on GO (confirmed by FTIR and XPS) could fundamentally improve reinforcing effects. FGO samples provided higher heat flow peaks due jointly to the nucleation effect of GO and the pozzolan reaction of silica in silane. At the similar loadings of 0.02%, FGO increased workability by up to 17%, alongside compressive and tensile strength increments of 19% and 31%, respectively at 28 days compared with the reference GO. These findings demonstrated the effectiveness and potential of enhancing nano-reinforcing effects of GO in cement composites by improving dispersion capacity while ensuring strong interactions between GO and cement hydration products. • Silane-functionalized GO (FGO) showed better dispersion capacity in an alkaline environment compared to GO. • The combination of the nucleation effect of GO and the pozzolan reaction between silane and CH promoted the hydration peaks. • Strong interactions between the FGO and cement hydration products could fundamentally improve reinforcing effects.

Deciphering the role of amine in amino silane-functionalized Pd/rGO catalyst for formic acid decomposition at room temperature

Additive free, selective decomposition of formic acid to hydrogen and carbon dioxide at room temperature is still a challenging catalytic process which often requires noble metal catalyst (Pd, AuPd, AuPt) and sodium formate as an additive. Till date, catalyst design is targeted towards minimum noble metal usage along with incorporation of basic functionalities to produce in situ formate ion (key intermediate for dehydrogenation) from formic acid. In this work, we have studied the catalytic behaviour of amino silane-functionalized graphene oxide (GO) containing palladium nanoparticles for formic acid decomposition in ambient condition. By varying amine functionalization on GO and palladium content, the best performing catalyst was obtained with 5 wt% palladium loading. Additionally, it was observed for the first time that along with stability of a catalyst in reaction medium, its interaction with decomposed products, i.e., carbon dioxide with amine functional groups plays a crucial role in recyclability of a catalyst.

SiO2-GO nanofillers enhance the corrosion resistance of waterborne polyurethane acrylic coatings

Corrosion to metal is a great challenge to major industries. Anticorrosive coatings can effectively prevent metal corrosion. In this study, we propose a novel method to prepare silica nanoparticles-covered graphene oxide (SiO2-GO) nanohybrids and anticorrosion SiO2-GO/waterborne polyurethane acrylic (WPUA) coatings. Firstly, we obtained silane-functionalized graphene oxide (A-GO) via a simple covalent functionalization of graphene oxide (GO) with 3-aminopropyltriethoxysilane. Secondly, SiO2-GO was synthesized by a simple sol–gel method with tetraethoxysilane in water–alcohol solution. Finally, the obtained SiO2-GO nanofillers were added into WPUA to prepare SiO2-GO/WPUA coatings. GO, A-GO, and SiO2-GO nanohybrids could be confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectra, and transmission electron microscope. SiO2-GO nanohybrids showed small size compared with the unfunctionalized GO. Meanwhile, GO, A-GO, and SiO2-GO nanofillers were added into WPUA. The electrochemical impedance spectroscopy and field emission scanning electron microscope indicate that SiO2-GO nanohybrids can be homogeneously dispersed in the WPUA coatings at 0.4% loading level and the SiO2-GO/WPUA film exhibits excellent anticorrosion performance. SiO2-GO nanoparticles can effectively utilize in the area of anticorrosive nanofiller industry. This study provides a convenient method of anticorrosive coating production.

Immobilized amino-containing basic ionic liquid on graphene oxide as an efficient and stable catalyst for transesterification

A basic ionic liquid containing aminopropylimidazolium moiety and OH‒ anion was immobilized on silane-functionalized graphene oxide (GO) by a condensation process, followed by an anion-exchange reaction. The properties of the resulting GO-[Ap-im]OH material were characterized using extensive techniques including FTIR, XPS, AFM, TGA, etc. The material could be used as a transesterification catalyst, affording the expected ester products in good yields under mild reaction conditions. This GO-[Ap-im]OH material with amino groups shows higher activity than GO-[Ap-im]Cl without amino groups. Furthermore, this catalyst could easily be separated from the reaction mixture by filtration and recycled at least 6 times without a noticeable decrease in the catalytic activity. The prominent performance of GO-[Ap-im]OH is attributed to the enhanced basicity of combining amine groups and OH‒ anions as well as less mass-transfer resistance of laminar GO.

Corrosion study of silane-functionalized graphene oxide coatings on copper

This research work aims to produce corrosion resistant silane-functionalized graphene oxide (GO) coatings on copper (Cu) metal. Two types of precursor graphite (flakes and powder) were utilized to synthesize GO following improved Hummers' method, and resulting GO was labelled as FGO and PGO, respectively. GO was deposited on copper metal, which was made anode and platinum was made cathode, from GO/water suspension by electrophoretic deposition (EPD). Silane functionalization was performed by immersing GO-coated samples in 3-aminopropyltriethoxy silane solution. The role of precursor graphite and post-coating treatment of GO coating with silane on corrosion protection ability of GO coatings was studied. Optimum EPD parameters for the development of uniform coatings were found to be 5 V and 30 s with GO/water concentration of 2:1. Characterization of GO and silane-functionalizedGO coatings was performed by atomic force microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Corrosion behavior of GO and silane-functionalizedGO-coated Cu samples was studied by Tafel analysis, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) in 3.5% NaCl solution. The results showed that precursor graphite effects quality of GO, and consequently the corrosion behavior of the GO coatings. PGO-coated Cu showed better corrosion protection compared to FGO-coated Cu as determined by Tafel analysis. Tafel analysis showed that PGO coating and silane-functionalizedPGO coating developed at optimized parameters enhanced corrosion resistance of Cu by ca. 3.45× and 23×, respectively, compared to bare Cu. Tafel results were well validated by EIS and CV.

Steel surface pre-treated by an advance and eco-friendly cerium oxide nanofilm modified by graphene oxide nanosheets; electrochemical and adhesion measurements

In this research the silane-functionalized graphene oxide (GO) nanosheets were utilized for modification of an eco-friendly cerium conversion coating and its effect on the cathodic disbonding, corrosion protection and adhesion properties of the epoxy coating was investigated. For this purpose, the cerium coating was modified by GO nanosheets functionalized with 3-(Triethoxysilyl) propyl isocyanate (TEPI, IGO nano-fillers). The Electrochemical Impedance Spectroscopy (EIS) showed that the addition of IGO nano-fillers in the cerium coating resulted in improved anti-corrosion properties of cerium coatings. The adhesion and anti-corrosion performance of the steel-cerium/epoxy system were also investigated. Results showed that inclusion of IGO nano-filler into the cerium matrix significantly improved the corrosion resistance, cathodic disbonding and adhesion properties of the top epoxy coating.

Corrosion protection of AA2024-T3 by sol-gel film modified with graphene oxide

Graphene oxide (GO) was introduced into sol-gel systems to enhance the corrosion protective properties of the obtained film on AA2024-T3 aluminum alloy. The characterization of morphology, microstructure and component of the films indicated that GO covalently reacted with silanol groups from hydrolyzed 3-glycidoxypropyl-trimethoxysilane (GPTMS) monomer, forming silane functionalized GO (SGO) by COSi covalent bonds. Corrosion protective properties of the films were evaluated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and immersion tests studies. The results showed that the addition of GO improved the corrosion protective properties of sol-gel film distinctly by providing the good barrier property of layered GO and enhancing the cross-linking density of the film. The significant improvement of GO on sol-gel film mainly focused on the resistance and capacitance of film itself. The optimal concentration of GO addition was 0.5 mg mL−1, at which the film was uniform and showed good corrosion protective properties in 0.05 M NaCl aqueous solution. The corrosion current density of the sol-gel film with 0.5 mg mL−1 GO was one order magnitude smaller than that of sol-gel film without GO. The protection efficiency of the film was up to 99.45%.

Corrosion Protective Properties of Silane Functionalized Graphene Oxide Film on AA2024-T3 Aluminum Alloy

3-glycidoxypropyl-trimethoxysilane (GPTMS) functionalized graphene oxide (GO) was used to synthesize graphene-based film for corrosion protection of AA2024-T3 aluminum alloy. GO covalently reacted with the silanol group from the hydrolyzed GPTMS monomer, forming silane functionalized GO (silane-GO) linked by C-O-Si covalent bonds. The silane coupling agents acted as a ‘bridge’ to link GO to adjacent GO and to the metal surface by covalent bonds. The corrosion protective properties of silane-GO film were determined by electrochemical measurements and immersion tests. Results indicated that silane-GO film provided effective protection for the metal substrate and the readily corrodible areas (at the periphery of protruding constituent particles). This was due to the good barrier property from layered GO, the filled defects and gaps between GO, and the enhanced adhesion strength of GO to adjacent GO and the film to the substrate. The protective efficiency of silane-GO film was up to 95.0%. The successful application of silane-GO film on AA2024-T3 aluminum alloy suggests that there is the considerable potential for broad application of graphene-based protective film on metals, even on the metals with corrosion-sensitive areas.

Silane functionalization of graphene oxide and its use as a reinforcement in bismaleimide composites

Silane-functionalized graphene oxide (GO) nanosheets were synthesized by chemically grafting γ-methacryloxypropyltrimethoxysilane (MPTS) onto GO sheets. The resulting MPTS-functionalized GO (MPTS-GO) nanosheets were characterized by Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, X-ray photoelectron spectra, X-ray diffraction, and Raman spectroscopy. Bismaleimide (BMI) composites filled with GO and MPTS-GO were prepared at different filler loading levels. The study showed that the exfoliation and dispersion of graphene sheets in BMI resin were significantly improved due to the surface functionalization effect. The tensile test indicated that the MPTS-GO/BMI nanocomposites showed higher tensile strength and modulus than the neat BMI resin and GO/BMI composites. Meanwhile, the impact strength of composites was also improved. The maximum increment of the tensile strength, tensile modulus, and impact strength of MPTS-GO/BMI nanocomposites were 22.17, 33.05, and 66.64 %, respectively. The fracture surface analysis revealed that the highly dispersed MPTS-GO nanosheets could trigger large-scale plastic deformation of resin matrix.

Use of silane-functionalized graphene oxide in organic photovoltaic cells and organic light-emitting diodes.

Graphene oxide (GO) and silane-functionalized GO (sGO) sheets obtained through a simple sonication exfoliation method are employed as hole transport layers to improve the efficiency of organic photovoltaic (OPV) cells and organic light-emitting diodes (OLED). GO was functionalized using (3-glycidyl oxypropyl)trimethoxysilane (GPTMS) and triethoxymethylsilane (MTES). The appearance of new peaks in the Fourier-transform infrared spectra of the sGOs indicates the formation of Si-O-C, Si-O-Si, Si-H, and Si-O-C moieties, which provide evidence of the addition of silane to the GO surface. Furthermore, the appearance of Si-O-Si bonds in the synchrotron radiation photoelectron spectra (SRPES) of the MTES-sGO and GPTMS-sGO samples suggests that silane groups were effectively functionalized onto the GO sheets. An OPV cell with GO layers showed a lower performance with a power conversion efficiency (PCE) of 2.06%; in contrast, OPV cells based on GPTMS-sGO and MTES-sGO have PCE values of 3.00 and 3.08%, respectively. The OLED devices based on GPTMS-sGO and MTES-sGO showed a higher maximum luminance efficiency of 13.91 and 12.77 cd A(-1), respectively, than PEDOT:PSS-based devices (12.34 cd A(-1)). The SRPES results revealed that the work functions of GO, GPTMS-sGO, and MTES-sGO were 4.8, 4.9, and 5.0 eV, respectively. Therefore, the increase in the PCE value is attributed to improved band-gap alignment. It is thought that sGO could be used as an interfacial layer in OPV and OLED devices.

Mechanical properties of epoxy composites filled with silane-functionalized graphene oxide

In this work, the effects of as-produced GO and silane functionalized GO (silane-f-GO) loading and silane functionalization on the mechanical properties of epoxy composites are investigated and compared. Such silane functionalization containing epoxy ended-groups is found to effectively improve the compatibility between the silane-f-GO and the epoxy matrix. Increased storage modulus, glass transition temperature, thermal stability, tensile and flexural properties and fracture toughness of epoxy composites filled with the silane-f-GO sheets are observed compared with those of the neat epoxy and GO/epoxy composites. These findings confirm the improved dispersion and interfacial interaction in the composites arising from covalent bonds between the silane-f-GO and the epoxy matrix. Moreover, several possible fracture mechanisms, i.e. crack pinning/deflection, crack bridging, and matrix plastic deformation initiated by the debonding/delamination of GO sheets, were identified and evaluated.