A New Filler for Epoxy Resin: Study on the Properties of Graphite Carbon Nitride (g-C3N4) Reinforced Epoxy Resin Composites

Fe3O4@gC3N4@Thiamine: a novel heterogeneous catalyst for the synthesis of heterocyclic compounds and microextraction of tebuconazole in food samples

Graphite carbon nitride (g-C3N4) is a two-dimensional nano-sheet with electronic properties, which shows unique characteristics with high chemical and thermal stability in its structure. The functionalization of these compounds through covalent bonding is an important step towards significantly improving their properties and capabilities. To achieve this goal, a novel strategy for the covalent functionalization of Fe3O4@g-C3N4 with thiamine hydrochloride (vitamin B1) via cyanuric chloride (TCT), which is a divalent covalent linker, was presented. The efficiency of Fe3O4@gC3N4@Thiamine as a heterogeneous organic catalyst in the synthesis of spirooxindole-pyran derivatives and 2-amino-4H-pyran under solvent-free conditions was evaluated and the yields of high-purity products were presented. In addition, easy recycling and reuse for seven consecutive cycles without significant reduction in catalytic activity are other features of this catalyst. Moreover, the performance of the prepared sorbent in the microextraction technique (herein, magnetic solid phase extraction) was studied. The tebuconazole was selected as the target analyte. The target analyte was extracted and determined by HPLC-UV. Under the optimum condition, the linear range of the method (LDR) was estimated in the range of 0.2-100 μg L-1 (the coefficient of determination of 0.9962 for tebuconazole). The detection limit (LOD) of the method for tebuconazole was calculated to be 0.05 µg L-1. The limit of quantification (LOQ) of the method was also estimated to be 0.16 µg L-1. In order to check the precision of the proposed method, the intra-day and inter-day relative standard deviations (RSD%) were calculated, which were in the range of 1.5- 2.8%. The method was used for the successful extraction and determination of tebuconazole in tomato, cucumber, and carrot samples.

Synthesis of graphitic carbon nitride-based nanocomposites and their mechanical properties in epoxy compositions

Thermoset epoxy resins are widely used in research and commercial applications. Zeolite imidazole framework-8 (ZIF-8), graphitic carbon nitride (GCN, g-C3N4), and S-doped graphitic carbon nitride (SCN, S-g-C3N4) composites were synthesized as accelerators and their effects on the physical properties of epoxies were examined. An ultrasound-assisted method was used to prepare ZIF-8/GCN and ZIF-8/SCN nanocomposites while g-C3N4 and S-g-C3N4 were prepared from the calcination of melamine and thiourea, respectively. The surface morphology, and particle size were characterized by scanning electron microscopy, and X-ray diffraction. The properties of synthesized nanocomposites were measured using Fourier-transform infrared spectroscopy. After the accelerator was added to the epoxy composites, their activation energies were calculated using differential scanning calorimetry. The tensile strength and flexural strength were measured using a universal testing machine and impact strength was measured by using an Izod impact strength tester. The impact strength of ZIF-8/SCN nanocomposites was enhanced by 45.2%. The storage stability of the epoxy compositions with different catalysts was evaluated by measuring the variation of viscosity with time at a constant temperature.

A green approach for preparation of chitosan/hydroxyapatite/graphitic carbon nitride hydrogel nanocomposite for improved 5-FU delivery

Reducing the side effects of cancer treatment methods is an important issue. The loading efficiency and sustained release of 5-Fluorouracil (5-FU) have been significantly improved by creating a new method. A nanocarrier with pH sensitivity has been developed through the w/o/w emulsification method. It is loaded with 5-FU and comprises of chitosan (CS), hydroxyapatite (HAp), and graphitic carbon nitride (g-C3N4). g-C3N4 nanosheets were incorporated in CS/HAp hydrogel to improve the entrapment and loading efficiency. Drug loading efficiency and entrapment efficiency reached 48 % and 87 %, respectively, and the FTIR and XRD tests verified evidence of the formation of chemical bonds among the drug and nanocarrier. Structural analysis was done using FE-SEM. DLS and zeta potential were employed to obtain average size distribution and surface charge. The release profile of 5-FU in various conditions shows the nanoparticles' pH dependence, and the nanocomposite's controlled release is consistent with the Korsmeyer-Peppas kinetic model. Cell apoptosis and cytotoxicity were evaluated in vitro using flow cytometry and MTT analysis. The biocompatibility of CS/HAp/g-C3N4 against MCF-7 cells was shown by the MTT method and confirmed by flow cytometry. CS/HAp/g-C3N4@5-FU led to the highest apoptosis rate in MCF-7 cells, indicating the nanocarrier's efficiency in killing cancer cells. These data indicate that the designed CS/HAp/g-C3N4@5-FU can be a potential drug for treating cancer cells.

Graphitic Carbon Nitride as Reinforcement of Photopolymer Resin for 3D Printing

Digital light processing (DLP) has the advantages of higher printing speed and product precision than other 3D printing technologies. However, DLP products have low mechanical strength owing to the inherent properties of photocurable materials. Graphitic carbon nitride (GCN), which is an abundant hydrogen bonding motif (-NH2, -NH), has low solubility in most solvents; thus, to use GCN as a reinforcement of the polymer matrix, optimal dispersion processes must be applied. In this study, GCN was proposed as a novel reinforcing material to improve the mechanical properties of photocurable epoxy acrylate (EA) resins for DLP. Herein, two-step (planetary mixing and ultrasonication) processes were applied to disperse GCN within EA, and the dispersion performance was identified by checking the degree of precipitation over time. To test the printability of the dispersed GCN/EA composites subjected to DLP 3D printing, cube specimens of GCN/EA composites were prepared, and the dispersed GCN/EA output had a low dimensional error of 0.3-1.3%, while the undispersed composite output showed larger dimensional errors of 27.7-36.2%. Additionally, in the mechanical test of the DLP-3D-printed sample (dispersed GCN/EA composite), the tensile strength and elastic modulus of the dispersed GCN/EA composite specimen were measured to be 75.56 MPa and 3396 MPa, respectively, which were improved by 22% (tensile strength) and 34% (modulus of elasticity) in relation to those of the neat EA specimen. This study is the first to use GCN as a reinforcement and manufacture a composite product for DLP with excellent performance (22% increased tensile strength) through the optimal dispersion of GCN. Considering the high mechanical performance, DLP products using the GCN/EA composites can be used in industries such as automobiles, shipbuilding, and aviation.

Dye Degradation, Antimicrobial Activity, and Molecular Docking Analysis of Samarium-Grafted Carbon Nitride Doped-Bismuth Oxobromide Quantum Dots

Various concentrations of samarium-grafted-carbon nitride (Sm-g-C3N4) doped-bismuth oxobromide (BiOBr) quantum dots (QDs) are prepared by the co-precipitation method. Elemental evaluation, morphological, optical, and functional group assessment are studied employing characterization techniques. Based on the XRD pattern analysis, it is determined that BiOBr exhibits a tetragonal crystal structure. The electronic spectroscopy revealed an absorption peak for BiOBr at 315 nm and the bandgap energy (E g) decreasing from 3.9 to 3.8 eV with the insertion of Sm-g-C3N4. The presence of vibrational modes related to BiOBr at 550 cm-1 is confirmed through FTIR spectra. TEM revealed that pure BiOBr possessed non-uniform QDS, and agglomeration increased with the addition of Sm-g-C3N4. The catalytic performance of Sm-g-C3N4 into BiOBr (6 mL) in a neutral medium toward rhodamine B exhibited excellent results (99.66%). The bactericidal activity is evaluated against multi-drug resistance (MDR) Escherichia coli once the surface area is increased by dopant and the measured inhibition zone is assessed to be 3.65 mm. Molecular docking results supported the in vitro bactericidal potential of Sm-g-C3N4 and Sm-g-C3N4 doped-BiOBr as DNA gyraseE. coli inhibitors. This study shows that the novel Sm-g-C3N4 doped-BiOBr is a better catalyst that increases specific semiconductor's catalytic activity (CA).

Impact- and Thermal-Resistant Epoxy Resin Toughened with Acacia Honey

High performance polymers with bio-based modifiers are promising materials in terms of applications and environmental impact. In this work, raw acacia honey was used as a bio-modifier for epoxy resin, as a rich source of functional groups. The addition of honey resulted in the formation of highly stable structures that were observed in scanning electron microscopy images as separate phases at the fracture surface, which were involved in the toughening of the resin. Structural changes were investigated, revealing the formation of a new aldehyde carbonyl group. Thermal analysis confirmed the formation of products that were stable up to 600 °C, with a glass transition temperature of 228 °C. An energy-controlled impact test was performed to compare the absorbed impact energy of bio-modified epoxy containing different amounts of honey with unmodified epoxy resin. The results showed that bio-modified epoxy resin with 3 wt% of acacia honey could withstand several impacts with full recovery, while unmodified epoxy resin broke at first impact. The absorbed energy at first impact was 2.5 times higher for bio-modified epoxy resin than it was for unmodified epoxy resin. In this manner, by using simple preparation and a raw material that is abundant in nature, a novel epoxy with high thermal and impact resistance was obtained, opening a path for further research in this field.

Simultaneous decolorization of anionic and cationic dyes by 3D metal-free easily separable visible light active photocatalyst

To overcome the hard and costly post-treatment separation of ultrathin graphitic carbon nitride nanosheets (UGCN), it was supported on polyurethane foam (PUF). The ratio of PUF/UGCN was optimized for the removal of a mixture of methylene blue (MB) and methyl orange (MO) dyes. The characteristics of the composite photocatalyst and its photocatalytic performance were detailly studied. The X-ray diffraction and Fourier transform infrared results proved the successful preparation of UGCN and PUF and that the PUF/UGCN composite combines the features of both pure materials. The transmission electron microscopy illustrated the ultrathin nanosheet shape of the UGCN, while the scanning electron microscope showed the highly porous 3D-hierarchical structure of PUF. Compared to the pure components, the composite photocatalyst with PUF/UGCN mass ratio of 4 achieved better decolorization of MO and almost same decolorization of MB as UGCN. Neutral pH and 1 g/L of the composite photocatalyst were the optimum conditions for MB/MO mixture decolorization. The composite photocatalyst kept its efficiency for five successive cycles. Hydroxyl radicals were the dominant in the degradation of MB, while superoxide radicals were the most influencer in MO degradation. Conclusively, supporting UGCN onto PUF kept the photocatalytic efficiency of UGCN toward MB decolorization and improved its efficiency toward MO. Moreover, it enabled the reuse of the composite photocatalyst and facilitated the post-treatment separation process.

Rheological and Electrical Study of a Composite Material Based on an Epoxy Polymer Containing Cyclotriphosphazene

In this work, we have studied, formulated, prepared, and characterized the rheological and electrical behavior of a composite material based on an epoxy resin Diglycidyl Ether of Bisphenol A (DGEBA) reinforced with hexaglycidyl cyclotriphosphazene (HGCP). The epoxy system was cured with 4,4’-methylene dianiline (MDA). DGEBA-HGCP-MDA epoxy composite materials with reinforced HGCP which varied from 5% to 10% by weight were prepared by mixing in the molten state. The morphology was evaluated by SEM. The rheological behavior was studied using small deformation rheology. The electrical characterization was carried out with a frequency variation range from 1 Hz to 100 KHz at room temperature. These measurements revealed that the rheological and electrical behaviors strongly depend on the quantity of HGCP in the DGEBA matrix. The linear viscoelastic properties study reveals that the modulus of elasticity G’ is dependent on the amount of HGCP present in the epoxy resin DGEBA. The capacitance-frequency measurements suggest a distribution of localized states in the band gap of the blends.

Experimental Characterization of the Torsional Damping in CFRP Disks by Impact Hammer Modal Testing

Composite materials are widely used for their peculiar combination of excellent structural, mechanical, and damping properties. This work presents an experimental study on the dissipation properties of disk-shaped composite specimens exploiting vibration tests. Two different polymer matrix composites with the same number of identical laminae, but characterized by different stacking sequences, namely unidirectional and quasi-isotropic configurations, have been evaluated. An ad-hoc steel structure was designed and developed to reproduce an in-plane torsional excitation on the specimen. The main idea of the proposed approach relies on deriving the damping properties of the disks by focusing on the modal damping of the overall vibrating structure and, in particular, using just the first in-plane torsional deformation mode. Experimental torsional damping evaluations were conducted by performing vibrational hammer excitation on the presented setup. Two methods were proposed and compared, both relying on a single-degree-of-freedom (SDOF) approximation of the measured frequency response function (FRF).