Frontiers of Materials Science最新文献

Graphene materials like turbostratic graphene exhibit remarkable promise for an array of applications, spanning from electronic devices to aerospace technologies. It is essential to develop a fabrication method that is not only economical and efficient, but also environmentally sustainable. In this study, the molten salt-assisted magnesiothermic reduction (MSAMR) method is proposed for the synthesis of few-layer turbostratic graphene. K₂CO₃ serves as both the carbon source and the catalyst for graphitization, facilitating the formation of the graphene structure, while in-situ generated MgO nanoparticles exert confinement and templating effects on the growth of graphene. The molten salts used effectively prevent the aggregation and the Bernal stacking of graphene sheets, ensuring the few-layer and turbostratic structure. The synergistic effects of K₂CO₃, in-situ generated MgO, and molten salts guarantee the formation of few-layer turbostratic graphene at a relatively low temperature, characterized with 4–8 stacking layers, a mesopore-dominated microstructure, and a high degree of graphitization.

The surface engineering has been testified to be an effective strategy for optimizing oxygen evolution reaction (OER) activity. Nevertheless, many of these techniques involve complex and multiple synthesis process, which leads to potential safety hazards, raises the cost of production, and hinders the scaled-up application. Herein, a facile strategy (i.e., quenching with lanthanum nitrate cold salt solution) was adopted to fabricate the surface of Co₃O₄ grown on nickel foam, and boost the electrocatalytic performance for OER. Analyses of the experimental results show that the surface engineering strategy can induce many defects on the surface of Co₃O₄, including microcracks and oxygen vacancies, which provides more active sites for electrochemical reaction. Consequently, the treated sample exhibits significantly improved OER electrocatalytic activity, requiring only 311 mV to deliver 100 mA·cm⁻² for OER in alkaline solution. This work highlights the feasibility of designing advanced electrocatalysts towards OER via quenching and extends the use of quenching chemistry in catalysis.

With the accelerated development of urbanization, it is urgent to develop new green and effective fungicides for water disinfection, which can effectively sterilize without causing bacterial drug resistance and environmental burden. In this work, the new ternary nanofiber (NF) heterojunctions, Ag/ZnO/g-C₃N₄ (Ag/ZCN), with high specific surface area were controllably fabricated through the photodeposition of different amounts of Ag quantum dots on electrospun ZCN NFs. Ag/ZCN with 6 wt.% Ag was found to exhibit the highest antibacterial activity superior to that of ZCN and ZnO NFs, which completely killed E. coli or S. aureus within 30 min under solar light. Moreover, it maintained high stability during four consecutive photocatalytic cycles. The photocatalytic Z-scheme charge transportation mechanism of Ag/ZCN was confirmed through structure characterization and free radical capture experiments. It was verified that the active oxygen substances such as ·OH, ¹O₂, and a certain amount of ·O₂⁻ were mainly produced in the photocatalytic sterilization process. Therefore, the Z-scheme NF heterojunction Ag/ZCN has great application potential in actual environmental water disinfection.

It is undoubtedly a challenge to design an efficient and recyclable photocatalyst for the degradation of tetracycline (TC). In this study, a MoS₂@C composite catalyst was fabricated through the simple sulfurization of alginate-based spheres encapsulating ammonium molybdate by thiourea. The incorporation of porous carbon as a co-catalyst significantly augmented reactive active sites, endowing it with great specific surface area and effectively preventing the aggregation of MoS₂ nanoparticles. While offering abundant catalytic sites for the reaction, the structure with interconnected channels promoted the adsorption of the reactant. The MoS₂@C composites showed excellent photocatalytic performance, achieving a photodegradation ratio of 87.01% for TC within 60 min, superior to that of pure MoS₂. Additionally, the photocatalytic mechanism for the degradation of TC was also investigated through free radical trapping experiments in combination with the electron spin resonance technique.

Conventional metal-oxide-semiconductor (MOS) gas sensors are limited in wearable gas detection due to their non-flexibility, high operating temperature, and less durability. In this study, a yarn-based superhydrophobic flexible wearable sensor for room-temperature ammonia gas detection was prepared based on the nano-size effect of both nanocore yarns prepared through electrostatic spinning and MOS gas-sensitive materials synthesized via a two-step hydrothermal synthesis approach. The yarn sensor has a response sensitivity of 13.11 towards 100 ppm (1 ppm = 10⁻⁶) ammonia at room temperature, a response time and a recovery time of 36 and 21 s, respectively, and a detection limit as low as 10 ppm with the sensitivity of up to 4.76 towards ammonia. In addition, it displays commendable linearity within the concentration range of 10–100 ppm, accompanied by remarkable selectivity and stability, while the hydrophobicity angle reaches 155.74°. Furthermore, its sensing performance still maintains stability even after repeated bending and prolonged operation. The sensor also has stable mechanical properties and flexibility, and can be affixed onto the fabric surface through sewing, which has a specific potential for clothing use.

We present an interesting low-cost, green, and scalable technique for direct ink writing for flexible electronic applications different from traditional fabrication techniques. In this work, a reduced graphene oxide (RGO)-bismuth oxide (Bi₂O₃)/carbon nanotube (CNT) (RGBC) ternary conductive ink was prepared by an initial synthesis of RGO-Bi₂O₃ (RGB) via a hydrothermal method. This was followed by the fabrication of conductive ink through homogenous mixing of the binary nanocomposite with CNTs in a mixture of ethanol, ethylene glycol, glycerol, and double-distilled water as the solvent. Electronic circuits were fabricated through directly writing the prepared ink on flexible nanocrystalline cellulose (NCC) thin film substrates. The nanocomposites consisted of rod-shaped nanoparticles that were grown on the surface of the nanographene sheet. The semiconductor nanocomposite exhibited excellent conductivity and further confirmed by applying it as an electrode in the electrical circuit to light a light-emitting diode (LED) bulb. The highest electrical conductivity achieved was 2.84 × 10³ S·m⁻¹ with a contact angle of 37°. The electronic circuit written using the conductive ink exhibited good homogeneity, uniformity, and adhesion. The LED experiment demonstrates the good conductivity of the electroconductive circuit and prepared ink. Hence, the NCC substrate and RGBC conductive ink showcase an excellent potential for flexible electronic applications.

A novel and eco-friendly ethyl acetate/water solvent system was employed to create stable water-in-oil (W/O) emulsions of curcumin (Cur)-loaded poly(ε-caprolactone) (PCL)/bovine serum albumin (BSA) without the need for surfactants. The size of emulsion droplets decreased with the rise of the BSA concentration but increased with the drop of the oil-to-water (OTW) volume ratio. Upon electrospinning, the morphology of Cur-loaded PCL/BSA composites transformed from bead-like structures to uniform fibers as the BSA concentration rose from 0% (w/v) to 10% (w/v). With the enhancement of the OTW volume ratio, the composite fibers displayed an increased diameter and a consistently uniform morphology. The highest modulus of elasticity (0.198 MPa) and the largest elongation at break (199%) of fibers were achieved at the OTW volume ratio of 7:3, while the maximum tensile strength (3.83 MPa) was obtained at 8:2. Notably, the presence of BSA resulted in the superhydrophilicity of composite fibers. Moreover, all composite fibers exhibited sustained drug release behaviors, especially for those with the OTW volume ratio of 7:3, the release behavior of which was the best to match the first-order model. This study is expected to improve biofunctions of hydrophobic PCL and expand its applications in biomedical fields.

Calcium ion-crosslinked alginate hydrogels are widely used as a materials system for investigating cell behavior in 3D environments in vitro. Suspensions of calcium sulfate particles are often used as the source of Ca²⁺ to control the rate of gelation. However, the instability of calcium sulfate suspensions can increase chances of reduced homogeneity of the resulting gel and requires researcher’s proficiency. Here, we show that ball-milled calcium sulfate microparticles (MPs) with smaller sizes can create more stable crosslinker suspensions than unprocessed or simply autoclaved calcium sulfate particles. In particular, 15 µm ball-milled calcium sulfate MPs result in gels that are more homogeneous with a balanced gelation rate, which facilitates fabrication of gels with consistent mechanical properties and reliable performance for 3D cell culture. Overall, these MPs represent an improved method for alginate hydrogel fabrication that can increase experimental reliability and quality for 3D cell culture.

In recent years, research on self-healing polymers for diverse biomedical applications has surged due to their resemblance to the native extracellular matrix. Here, we introduce a novel self-healing hydrogel scaffold made from collagen (Col) and nano-hydroxyapatite (nHA) via a one-pot-synthesis approach under the influence of heating in less than 10 min. Process parameters, including the quantities of Col, guar gum, solvent, nHA, borax, and glycerol in the system were optimized for the minimization of the self-healing time. The synthesized hydrogel and polymers underwent characterization via FTIR, SEM, EDS, TGA, and ¹³C-NMR. Additionally, the hydrogel showed hemocompatibility with only 6.76% hemolysis at 10 µg·mL⁻¹, while the scaffold maintained cellular metabolic activity at all concentrations for 24 h, with the optimal viability at 1 and 2.5 µg·mL⁻¹, sustaining 93.5% and 90% viability, respectively. Moreover, the hydrogel scaffold exhibited rapid self-healing within 30 s of damage, alongside a tough and flexible nature, as indicated by its swelling rate, biodegradation under various biological pH solutions, and tensile strength of 0.75 MPa. Hence, the innovative Col and nHA self-healing hydrogel scaffold emerges as an ideal, non-toxic, cost-effective, and easily synthesized material with promising potential in cartilage repair applications.