A novel fabrication of a high performance SiO2-graphene oxide (GO) nanohybrids: Characterization of thermal properties of epoxy nanocomposites filled with SiO2-GO nanohybrids

Quantum Chemical Model Calculations of Adhesion and Dissociation between Epoxy Resin and Si-Containing Molecules

There is no doubt that when solid surfaces are modified, the functional groups and atoms directly bonded to solid atoms play a major role in adsorption interactions with molecules or resins. In this study, the adhesion and dissociation between epoxy resin and molecules containing Si atoms were analyzed. The analysis, conducted in contact with the solid surface of silicon, utilized quantum chemical calculations based on a molecular model. We compared some Si-containing molecular models to test quantum chemical calculations that contribute to the study of adhesion and dissociation between epoxy resins and solid surfaces somehow other than simple potential energy curve calculations. The AFIR (artificial force induced reaction) method, implemented in the GRRM (global reaction route mapping) program, was employed to separate an epoxy resin model molecule and three types of silicon compounds (Si(CH3)2(OH)2, Si(CH3)4, and (CH3)2SiF2) in three directions, determining their minimum dissociation energy when changing the applied energy by 2.5 kJ/mol. In systems with weak hydrogen bonds, such as Si(CH3)4 or (CH3)2SiF2, the energy required for dissociation was not large; however, in systems with strong hydrogen bonds, such as Si(CH3)2(OH)2, dissociation was more difficult in the vertical direction. Although anisotropy due to hydroxyl groups was calculated in the horizontal direction, dissociation remained relatively easy.

Covalently hybridized carbon dots@mesoporous silica nanobeads as a robust and versatile phosphorescent probe for time-resolved biosensing and bioimaging

Phosphorescence analyses have attracted broad attention due to their remarkable merits of the elimination of auto-fluorescence and scattering light. However, it remains a great challenge to develop novel materials with uniform size and morphology, stability, long lifetime, and aqueous-phase room temperature phosphorescence (RTP) characteristics. Herein, monodisperse and uniform RTP nanobeads were fabricated by an in situ covalent hybridization of carbon dots (CDs) and dendritic mesoporous silicon nanoparticles (DMSNs) via silane hydrolysis. The formation of Si-O-C and Si-C/N covalent bonds is beneficial for the fixation of vibrations and rotations of the luminescent centers. Specially, the nanopores of DMSNs provide a confined area that can isolate the triplet state of CDs from water and oxygen and thus ensure the occurrence of aqueous-phase RTP with an ultra-long lifetime of 1.195 s (seen by the naked eye up to 9 seconds). Through surface modifying folic acid (FA), CDs@DMSNs can serve as a probe to distinguish different cell lines that feature varying FA receptor expression levels. In addition, taking MCF-7 as the model, highly sensitive and quantitative detection (linear range: 103-106 cells per mL) has been achieved via an RTP probe. Furthermore, their potential applications in cellular and in vivo time-gated phosphorescence imaging have been proposed and demonstrated, respectively. This work would provide a new route to design CD-based RTP composites and promote their further applications in the medical and biological fields.

Multifunctional cellulose-based aerogel for intelligent fire fighting

Multifunctional biomass-based aerogels with mechanically robust and high fire safety are urgently needed for the development of environmentally-friendly intelligent fire fighting but challenging. Herein, a novel polymethylsilsesquioxane (PMSQ)/cellulose/MXene composite aerogel (PCM) with superior comprehensive performance was fabricated by ice-induced assembly and in-situ mineralization. It exhibited light weight (16.2 mg·cm-3), excellent mechanical resilience, and rapidly recovered after being subjected to the pressure of 9000 times of its own weight. Moreover, PCM demonstrated outstanding thermal insulation, hydrophobicity and sensitive piezoresistive sensing. In addition, benefiting from the synergism of PMSQ and MXene, PCM displayed good flame retardancy and improved thermostability. The limiting oxygen index of PCM was higher than 45.0 %, and it quickly self-extinguished after being removed away from fire. More importantly, the rapid electrical resistance reduction of MXene at high temperature endowed PCM with sensitive fire-warning capability (trigger time was less than 1.8 s), which provided valuable time for people to evacuate and relief. This work provides new insights for the preparation and application of the next-generation high performance biomass-based aerogels.

Rice straw derived graphene-silica based nanocomposite and its application in improved co-fermentative microbial enzyme production and functional stability

Cellulases are the one of the most highly demanded industrial biocatalysts due to their versatile applications, such as in the biorefinery industry. However, relatively poor efficiency and high production costs are included as the key industrial constraints that hinder enzyme production and utilization at economic scale. Furthermore, the production and functional efficiency of the β-glucosidase (BGL) enzyme is usually found to be relatively low among the cellulase cocktail produced. Thus, the current study focuses on fungi-mediated improvement of BGL enzyme in the presence of a rice straw-derived graphene-silica-based nanocomposite (GSNCs), which has been characterized using various techniques to analyze its physicochemical properties. Under optimized conditions of solid-state fermentation (SSF), co-fermentation using co-cultured cellulolytic enzyme has been done, and maximum enzyme production of 42 IU/gds FP, 142 IU/gds BGL, and 103 IU/gds EG have been achieved at a 5 mg concentration of GSNCs. Moreover, at a 2.5 mg concentration of nanocatalyst, the BGL enzyme showed its thermal stability at 60°C and 70 °C by holding its half-life relative activity for 7 h, while the same enzyme demonstrated pH stability at pH 8.0 and 9.0 for the 10 h. This thermoalkali BGL enzyme might be useful for the long-term bioconversion of cellulosic biomass into sugar.

Dual char-forming strategy driven MXene-based fire-proofing epoxy resin coupled with good toughness

It is challenging that the functionalized MXene-based nanofillers are designed to modify the inherent flammability and poor toughness of epoxy polymeric materials and further to facilitate the application of EP composites. Herein, silicon-reinforced Ti₃C₂T_x MXene-based nanoarchitectures (MXene@SiO₂) are synthesized by simple self-growth method, and its enhancement effects on epoxy resin (EP) are investigated. The as-prepared nanoarchitectures realize homogeneous dispersion in EP matrix, indicating well performance-enhancing potential. The incorporation of MXene@SiO₂ achieves improved thermal stability for EP composites with higher T_-5% and lower R_max values. Moreover, EP/2 wt% MXene@SiO₂ composites obtain a 30.2% and 34.0% reduction in peak heat release rate (PHRR) and peak smoke production rate (PSPR) compared to those of pure EP, respectively, also achieving a 52.5% fall in smoke factor (SF) values and increased yield and stability of chars. The dual char-forming effects of MXene@SiO₂ nanoarchitectures, including the catalytic charring of MXene and the migration of SiO₂ to induce charring, are accounted for the results, as well as lamellar barrier effects. Additionally, EP/MXene@SiO₂ composites achieve an enhanced storage modulus of 51.5%, along with improved tensile strength and elongation at break, compared to those of pure EP.

Water-soluble long afterglow carbon dots/silica composites for dual-channel detection of alkaline phosphatase and multi-level information anti-counterfeiting

Water-soluble carbon dots/silica (CDs/SiO₂) composites with an ultra-long lifetime of 846.9 ms and an ultra-high afterglow quantum yield of 12.1% were successfully obtained by incorporating CDs into a SiO₂ network. Within the aqueous solution, the SiO₂ layer isolates CDs from the surrounding oxygen. Meanwhile, hydrogen bonds and covalent bonds are formed between the CDs and SiO₂, and these bonds restrict the movement and vibration of the CDs. Accordingly, the non-radiative inactivation rate of the triplet excitons of the CDs is reduced, thereby enhancing the room-temperature phosphorescence of the CDs and triggering thermally activated delayed fluorescence. The multiple properties of the material effectively protect the CDs from the external environment, making CDs/SiO₂ emit a long afterglow in the solid and liquid phases. The prepared CDs/SiO₂ composites have exceptional stability against strong oxidants, acids, bases, and polar solvents. The composites were successfully used in the dual-optical mode detection of alkaline phosphatase, as an anti-counterfeiting ink, and in multi-level information anti-counterfeiting and encryption.

Experimental and Theoretical Studies toward Superior Anti-corrosive Nanocomposite Coatings of Aminosilane Wrapped Layer-by-Layer Graphene Oxide@MXene/Waterborne Epoxy

Herein, layer-by-layer MXene/graphene oxide nanosheets wrapped with 3-aminopropyltriethoxy silane (abbreviated as F-GO@MXene) are proposed as an anti-corrosion promoter for waterborne epoxies. The GO@MXene nanohybrid is synthesized by a solvothermal reaction to produce a multi-layered 2D structure without defects. Then, the GO@MXene is modified by silane wrapping under a reflux reaction, in order to achieve chemical stability and to create active sites on the nanohybrid surface for reaction with the polymer matrix of the coating. The organic coating modified with 0.1 wt % F-GO@MXene has revealed superior corrosion protection efficiency than the organic coatings modified with either F-GO or F-MXene nanosheets. The impedance modulus at low frequency for the pure epoxy, epoxy/F-MXene, epoxy/F-GO, and epoxy/F-GO@MXene coatings is 4.17 × 10⁵, 5.5 × 10⁸, 4.46 × 10⁸, and 1.14 × 10¹⁰ Ω·cm² after 30 days of immersion in the corrosive media, respectively. The remarkable anti-corrosion property is assigned to the intense effect of the nanohybrid on the barrier performance, surface roughness, and adhesion strength of the epoxy coating. The complemental analysis based on first-principles density functional theory reveals that the adhesion strength related to the silane functional groups in its complexes follows the order F-GO@MXene > F-MXene > F-GO. The enhanced stabilization predicted on the GO@MXene nanohybrid ultimately stems from the combined role of the electrostatic and van der Waals forces, suggesting an increase in the penetration path of the corrosive media.

Silicon dioxide nanoparticles decorated on graphene oxide nanosheets and their application in poly(l-lactic acid) scaffold

INTRODUCTION

The aggregation of graphene oxide (GO) is considered as main challenge, although GO possesses excellent mechanical properties which arouses widespread attention as reinforcement for polymers.

OBJECTIVES

In this study, silicon dioxide (SiO₂) nanoparticles were decorated onto surface of GO nanosheets through in situ growth method for promoting dispersion of GO in poly(l-lactic acid) (PLLA) bone scaffold.

METHODS

Hydroxyl and carboxyl functional groups of GO provided sites for SiO₂ nucleation, and SiO₂ grew with hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) and finally formed nanoparticles onto surface of GO with covalent bonds. Then, the GO@ SiO₂ nanocomposite was blended with PLLA for the fabrication of bone scaffold by selective laser sintering (SLS).

RESULT

The results indicated that the obtained SiO₂ were distributed relatively uniformly on surface of GO under TEOS concentration of 0.10 mol/L (GO@SiO₂-10), and the covering of SiO₂ on GO could increase interlayer distance of GO nanosheets from 0.799 nm to 0.894 nm, thus reducing van der Waals forces between GO nanosheets and facilitating the dispersion. Tensile and compressive strength of scaffold containing GO@SiO₂ hybrids were significantly enhanced, especially for the scaffold containing GO@SiO₂-10 hybrids with enhancement of 30.95 % in tensile strength and 66.33 % in compressive strength compared with the scaffold containing GO. Additionally, cell adhesion and fluorescence experiments demonstrated excellent cytocompatibility of the scaffold.

CONCLUSIONS

The good dispersion of GO@SiO₂ enhances the mechanical properties and cytocompatibility of scaffold, making it a potential candidate for bone tissue engineering applications.

Synthesis and characterization of a novel composite of rice husk-derived graphene oxide with titania microspheres (GO-RH/TiO2) for effective treatment of cationic dye methylene blue in aqueous solutions

Graphene oxide (GO) was synthesized utilizing rice husk (RH) as the starting raw material via a modified Hummers' method. Ground pencil leads were used as a control powder of the starting raw material to monitor the consistency of the synthesis method. TiO₂ microspheres were synthesized via a precipitated method using the pluronic F127 solution as the pore template. GO derived from RH (GO-RH) was composited with TiO₂ microspheres as GO-RH/TiO₂ composites by an impregnation method with weight ratios of 3:1, 2:2, and 1:3. Characterized results revealed GO-RH formed a ternary phase material of graphene oxide, graphite oxide, and silica. A typical microstructure of the calcined TiO₂ microspheres was found as the agglomerated anatase nanoparticles. Furthermore, the composites belong to large surface areas and numerous oxygen-containing functionalities on their surfaces. Removal efficiencies of cationic dye methylene blue (MB) from aqueous solutions by the composites, GO-RH and TiO₂, were studied under UV illumination for 180 min. Due to the effective combination of adsorption and photodegradation for the MB removal, the composites provided the higher efficiencies (99-100%) faster than those of GO-RH and TiO₂ and could be reused at least 4 times. Finally, a mechanism of the MB removal by the composites was proposed.

Synchronously improved thermal conductivity and dielectric constant for epoxy composites by introducing functionalized silicon carbide nanoparticles and boron nitride microspheres

Polymer-based dielectrics with high thermal conductivity and superb dielectric properties hold great promising for advanced electronic packaging and thermal management application. However, integrating these properties into a single material remains challenging due to their mutually exclusive physical connotations. Here, an ideal dielectric thermally conductive epoxy composite is successfully prepared by incorporating multiscale hybrid fillers of boron nitride microsphere (BNMS) and silicon dioxide coated silicon carbide nanoparticles (SiC@SiO₂). In the resultant composites, the microscale BNMS serve as the principal building blocks to establish the thermally conductive network, while the nanoscale SiC@SiO₂ as bridges to optimize the heat transfer and suppress the interfacial phonon scattering. In addition, the special core-shell nanoarchitecture of SiC@SiO₂ can significantly impede the leakage current and generate a great deal of minicapacitors in the composites. Consequently, favorable thermal conductivity (0.76 W/mK) and dielectric constant (∼8.19) are simultaneously achieved in the BNMS/SiC@SiO₂/Epoxy composites without compromising the dielectric loss (∼0.022). The strategy described in this study provides important insights into the design of high-performance dielectric composites by capitalizing on the merits of different particles.

Highly sensitive and selective detection of glutathione using ultrasonic aided synthesis of graphene quantum dots embedded over amine-functionalized silica nanoparticles

Glutathione (GSH) is the most abundant antioxidant in the majority of cells and tissues; and its use as a biomarker has been known for decades. In this study, a facile electrochemical method was developed for glutathione sensing using voltammetry and amperometry analyses. In this study, a novel glassy carbon electrode composed of graphene quantum dots (GQDs) embedded on amine-functionalized silica nanoparticles (SiNPs) was synthesized. GQDs embedded on amine-functionalized SiNPs were physical-chemically characterized by different techniques that included high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction spectroscopy (XRD), UV-visible spectroscopy, Fourier-transform infrared spectroscopy(FTIR), and Raman spectroscopy. The newly developed electrode exhibits a good response to glutathione with a wide linear range (0.5-7 µM) and a low detection limit (0.5 µM) with high sensitivity(2.64 µA µM-1). The fabricated GQDs-SiNPs/GC electrode shows highly attractive electrocatalytic activity towards glutathione detection in the neutral media at low potential due to a synergistic surface effect caused by the incorporation of GQDs over SiNPs. It leads to higher surface area and conductivity, improving electron transfer and promoting redox reactions. Besides, it provides outstanding selectivity, reproducibility, long-term stability, and can be used in the presence of interferences typically found in real sample analysis.

Functional groups in graphene oxide

Graphene oxide consists of diverse surface chemistry which allows tethering GO with additional functionalities and tuning its intrinsic properties. This review summarizes recently advanced methods to covalently modify GO for specific applications.

Hyperbranched epoxy resin-grafted graphene oxide for efficient and all-purpose epoxy resin modification

Despite great efforts have been made on epoxy resins modification, development of additives that can be used to efficiently and universally modify epoxy composites remains a challenging task. Herein, graphene oxide (GO) sheets were covalently linked with hyperbranched epoxy resin (HBPEE-epoxy) to form HBPEE-epoxy functionalized GO (HPE-GO), which was then incorporated into epoxy resin (EP) matrix to achieve efficient and all-purpose enhancement of the properties of EPs. Compared with unmodified GO sheets, the functionalized HPE-GO sheets were better dispersed and exhibited better interfacial compatibility with the epoxy matrix, and consequently, the mechanical and thermal properties of HPE-GO/EP composites improved significantly compared to unmodified GO/EP composites. The tensile strength, flexural strength, impact strength, and fracture toughness (K_IC) of EP composites containing 0.5 wt% HPE-GO increased by 65.0%, 36.2%, 259.1%, and 178.9%, respectively, compared with those for the neat EP. The storage modulus (E'), glass transition temperature (T_g), and thermal stability (T_5%) also showed modest improvements. Furthermore, the HPE-GO/EP composites exhibited optimal thermal conductivities and thermal expansion properties, while maintaining higher volume resistivities compared with GO/EP composites. The results of this study support that HPE-GO is a promising, all-purpose modifier for EPs.

Preparation and characteristics of sepiolite-waterborne polyurethane composites

A kind of organic/inorganic composite material composed of waterborne polyurethane and sepiolite was prepared in this work. Sepiolite was organically modified by three kinds of silane coupling agents, and then compounded with waterborne polyurethane through layer-by-layer method in order to prepare composite materials. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) show the crystal and chemistry structure of sepiolite samples, and confirmed the preparation of organic sepiolite. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) showed the surface microstructure and elemental content of sepiolite and organic sepiolite, and was consistent with the XRD results. Transmission electron microscope (TEM) examination of waterborne polyurethane composites surfaces showed that sepiolite particles were regularly dispersed in the waterborne polyurethane matrix. Thermal resistance of waterborne polyurethane composites was determined by thermogravimetry analyzer (TG) and derivative thermogravimetry analyzer (DTG), differential scanning calorimetry (DSC), gas chromatography (GC), and mass chromatography (MS). Mechanical behavior was examined by tensile strength tester, showed higher break strength than that of the control waterborne polyurethane. Therefore, organically modified sepiolite was considered to be a kind of wonderful inorganic material that could be used to improve the thermal stability and mechanical property of polymer.

Nano-SiO2 and Silane Coupling Agent Co-Decorated Graphene Oxides with Enhanced Anti-Corrosion Performance of Epoxy Composite Coatings

Coatings are of great significance for irons and steels in regards to the harsh marine environment. Graphene oxides (GO) have been considered as an ideal filler material of epoxy coating. However, the undesired dispersion in the epoxy together with easy agglomeration and stacking remain great problems for practical application of GO composited epoxy coatings. A method that can effectively solve both self-aggregation and poor dispersion of GO is highly desired. Herein, we present a high dispersion strategy of graphene oxides in epoxy by co-decoration of nano-SiO₂ and silane coupling agent. The co-decorated GO filled epoxy coating exhibits high anti-corrosion performance, including high electrochemical impedance, high self-corrosive potential, low self-corrosive current, and superior electrochemical impedance stability for ten days to Q235 carbon steel. This work displays new possibilities for designing novel coating materials with high performance toward practical marine anti-corrosion applications.

Hydrothermal Synthesis of Zinc-Doped Silica Nanospheres Simultaneously Featuring Stable Fluorescence and Long-Lived Room-Temperature Phosphorescence

Fluorescence and phosphorescence are known as two kinds of fundamental optical signals, which have been used for myriad applications. To date, simultaneous activation of stable fluorescence and long-lived room-temperature phosphorescence (RTP) emission in the aqueous phase remains a big challenge. We prepare zinc-doped silica nanospheres (Zn@SiNSs) with fluorescence and RTP properties using a facile hydrothermal synthetic strategy. For the as-prepared Zn@SiNSs, the recombination of electrons and holes in defects and defect-stabilized excitons derived from oxygen vacancy/C=N bonds lead to the production of stable fluorescence and long-lived RTP (emission lasting for ≈9 s, quantum yield (QY): ≈33.6 %, RTP lifetime: ≈236 ms). The internal Si-O bonded networks and hydrophilic surface in Zn@SiNSs can reduce nonradiative decay to form self-protective RTP, and also provide high water solubility, excellent pH- and photostability.

Design, synthesis, and catalytic performance of modified graphene oxide based on a cobalt complex as a heterogenous catalyst for the preparation of aminonaphthoquinone derivatives

We are reporting a functionalized graphene oxide catalyst developed by modifying graphene oxide surface using the covalent attachment of an amino-functionalized SiO2 sphere/cobalt complex. Silica network has special characteristics including mechanical strength, high thermal and chemical stability with good dispersion in solvents. The silica/graphene oxide mixture provides improved properties and extends the scope of application. Graphene oxide was functionalized by spherical silica with the help of hybrid silane-containing nitrogen to coordinate with Co(ii) for increasing the catalytic activity. The catalyst was characterized by Fourier Transform Infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), Raman spectroscopy, and Thermal Gravimetric (TGA) analyses. The catalyst showed high catalytic activity for multi-component reactions in the synthesis of aminonaphthoquinones in ethanol solvent. The catalyst's ability to improve the yield (96-98%), reduce the reaction time (5-8 min), and recycling ability are important benefits for the catalyst.

Lipidomics phenotyping of clam (Corbicula fluminea) through graphene/fibrous silica nanohybrids based solid-phase extraction and HILIC-MS analysis

Polyunsaturated phospholipids are abundant in clam (Corbicula fluminea) but difficult to be fully extracted. Herein, graphene/fibrous silica (G/KCC-1) nanohybrids were synthesized, characterized, and applied for solid-phase extraction (SPE) of phospholipids in clam. The effectiveness of G/KCC-1 SPE was verified by hydrophilic interaction chromatography mass spectrometry (HILIC-MS) based lipidomics and statistical analysis. The ions of PE 16:0/18:1 (m/z 716.4), PC 16:0/20:5 (m/z 824.6) and etc. were regarded as the main difference among the crude lipids, acetone washed extract, and eluate of G/KCC-1 SPE. Finally, this method was validated in terms of linearity (R² 0.9965 to 0.9981), sensitivity (LOD 0.19-0.51 μg·mL^-1 and LOQ 0.48 - 1.47 μg·mL^-1), and precision (RSD_intra-day ≤ 7.16% and RSD_inter-day ≤ 7.30%). In conclusion, the G/KCC-1 SPE and HILIC-MS method was shown to be accurate and efficient in selective extracting and phenotyping phospholipids in C. fluminea.

Effect of High-Dispersible Graphene on the Strength and Durability of Cement Mortars

Graphene’s outstanding properties make it a potential material for reinforced cementitious composites. However, its shortcomings, such as easy agglomeration and poor dispersion, severely restrict its application in cementitious materials. In this paper, a highly dispersible graphene (TiO₂-RGO) with better dispersibility compared with graphene oxide (GO) is obtained through improvement of the graphene preparation method. In this study, both GO and TiO₂-RGO can improve the pore size distribution of cement mortars. According to the results of the mercury intrusion porosity (MIP) test, the porosity of cement mortar mixed with GO and TiO₂-RGO was reduced by 26% and 40%, respectively, relative to ordinary cement mortar specimens. However, the TiO₂-RGO cement mortars showed better pore size distribution and porosity than GO cement mortars. Comparative tests on the strength and durability of ordinary cement mortars, GO cement mortars, and TiO₂-RGO cement mortars were conducted, and it was found that with the same amount of TiO₂-RGO and GO, the TiO₂-RGO cement mortars have nearly twice the strength of GO cement mortars. In addition, it has far higher durability, such as impermeability and chloride ion penetration resistance, than GO cement mortars. These results indicate that TiO₂-RGO prepared by titanium dioxide (TiO₂) intercalation can better improve the strength and durability performance of cement mortars compared to GO.

Preparation and Phase Change Performance of Graphene Oxide and Silica Composite Na2SO4·10H2O Phase Change Materials (PCMs) as Thermal Energy Storage Materials

In this study, a novel nucleating agent composed of graphene oxide (GO) and silicon dioxide (SiO₂) (GO-SiO₂) is developed. GO is used as a skeleton material through which SiO₂ nanomaterials are absorbed and subsequently incorporated into Na₂SO₄·10H₂O phase change materials (PCMs). Furthermore, this study examines the phase change performance of the composite Na₂SO₄·10H₂O materials. Fourier-transform infrared (FTIR) spectra confirmed the physical combination of GO with a SiO₂ nanoparticles. Scanning electron microscope (SEM) results showed that the GO-SiO₂ composite exhibited a layered structure and excellent dispersibility. The GO-SiO₂ composite Na₂SO₄·10H₂O PCMs displayed a low level of supercooling, i.e., about 1.2 °C with the addition of GO-SiO₂ at 2.45 wt%. This was because the synergistic relation of the GO and the high dispersion SiO₂, imparted more nucleation sites for Na₂SO₄·10H₂O. Additionally, the prepared PCMs achieved high phase change latent heat and thermal conductivity, even under these conditions. The results show that the GO-SiO₂ in the Na₂SO₄·10H₂O exhibited advantageous application prospects for the improvement of the thermal performance of hydrate salts.

Hydroxyl-Terminated Triazine Derivatives Grafted Graphene Oxide for Epoxy Composites: Enhancement of Interfacial and Mechanical Properties

An effective approach to the fabrication of progressive epoxy nanocomposites by the incorporation of hydroxyl-terminated dendrimers functionalized graphene oxide (GO-TCT-Tris) is reported. The relationship between surface grafting, chemical construction, morphology, dispersion, and interfacial interaction as well as the corresponding mechanical properties of the composites were studied in detail. It was shown that hydroxyl-terminated triazine derivatives have been resoundingly bonded onto the GO surface through covalent bonding, which effectively improved the dispersion and compatibility of GO sheets in epoxy resin. The tensile and flexural tests manifested that the GO-TCT-Tris/epoxy composites exhibited greater tensile/flexural strength and modulus than either the pure epoxy or the GO/epoxy composites. For GO-TCT-Tris (0.10 wt%)/epoxy composite, the tensile strength and elastic modulus increased from 63 ± 4 to 89 ± 6 MPa (41.27%) and from 2.8 ± 0.1 to 3.6 ± 0.2 GPa (28.57%), and the flexural strength and modulus increased from 106 ± 5 to 158 ± 6 MPa (49.06%) and from 3.0 ± 0.1 to 3.5 ± 0.2 GPa (16.67%), respectively, compared to the pure epoxy matrix. Moreover, the fractographic analysis also illustrated the ameliorative interfacial interaction between GO-TCT-Tris and epoxy matrix.

Facile silane functionalization of graphene oxide

The facile silane functionalization of graphene oxide (GO) was achieved yielding vinyltrimethoxysilane-reduced graphene oxide (VTMOS-rGO) nanospheres located in the inter-layer spacing between rGO sheets via an acid-base reaction using aqueous media. The successful grafting of the silane agent with pendant vinyl groups to rGO was confirmed by a combination of Fourier-transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The structure and speciation of the silane-graphene network (nanosphere) and, the presence of free vinyl groups was verified from solid-state magic angle spinning (MAS) and solution 13C and 29Si nuclear magnetic resonance (NMR) measurements. Evidence from Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM) and TEM-High-Angle Annular Dark-Field (TEM-HAADF) imaging showed that these silane networks aided the exfoliation of the rGO layers preventing agglomeration, the interlayer spacing increased by 10 Å. The thermal stability (TGA/DTA) of VTMOS-rGO was significantly improved relative to GO, displaying just one degradation process for the silane network some 300 °C higher than either VTMOS or GO alone. The reduction of GO to VTMOS-rGO induced sp2 hybridization and enhanced the electrical conductivity of GO by 105 S m-1.