Three-dimensional Network Structure Research Articles

Electrical conduction properties of PP-based nanocomposite with high thermal conductivity for HVDC cable insulation

This paper reports on thermal and electrical conduction properties of polypropylene (PP)-based nanocomposite used for high voltage direct current cable insulation. To improve the thermal conductivity of the PP/propylene-based elastomer (PBE) blend (noted as PB), boron nitride (BN) nanosheets with high thermal conductivity are added. The pretreatment process through template method is to obtain a three-dimensional (3D) network structure composed of BN nanosheets (noted as 3DBN). Then the 3DBN is added into the PP/ PBE blend, in which the 3D networks are locally arranged and the other BN nanosheets are randomly dispersed. Thermal conductivity is estimated, while electrical conductivity is measured under electric fields of 5–40 kV mm−1 at various temperatures. Carrier trap distribution is derived from isothermal surface potential decay method. In addition, the microstructure and crystallization characteristics of the nanocomposites are measured. The results show that the thermal conductivity of the PP/PBE blend is improved obviously by the addition of the locally arranged 3DBN, and that of PB-3DBN-10 is increased by 16% compared with that of PB. Deep traps are introduced by the dispersed BN nanosheets and the electrical conduction is reduced, which becomes increasingly evident with the filler content and temperature. It is suggested that the introduction of thermal conductive fillers with a 3D network structure and well-dispersed state can synergistically enhance the thermal conductivity and insulation performances of the PP-based material.

Lightweight aramid nanofibers/carbon nanotubes/MnFe2O4 composite aerogel for highly efficient microwave absorption

With the booming development and wide applications of modern communication technology, wearable devices are becoming more and more popular in our life. Meanwhile, the pollution and radiation of electromagnetic wave (EMW) is becoming increasingly prominent and threating to human health, equipment operation and military security. Multi-component regulation and spatial microstructure design of microwave absorption materials is an effective strategy for solving the pollution and radiation of electromagnetic wave. Herein, aramid nanofibers/carbon nanotubes/MnFe2O4 (ACF) composite aerogel were prepared through the combination of freeze-drying technique and hydrothermal method. Impedance matching of aramid nanofibers/carbon nanotubes aerogel is improved by introducing MnFe2O4 particles, inducing to that EMW is more easily incident into aerogel and then attenuated by microwave absorber. In addition, the three-dimensional networks structure of aerogel can enhance the multiple reflection and scattering, and improve the loss capacity of EMW. ACF05 aerogel exhibits a minimum reflection loss of −64.6 dB at 12.0 GHz and broad effective absorption bandwidth of 5.0 GHz under thickness of 2.1 mm. The excellent microwave absorption (MA) performance of ACF aerogel mainly comes from the synergistic effect of three-dimensional networks structure, impedance matching, dielectric loss and magnetic loss.

Fabrication of nitrogen-doped reduced graphene oxide/tricobalt tetraoxide composite aerogels with high efficiency, broadband microwave absorption, and good compression recovery performance

The fabrication of advanced graphene-based microwave absorbing materials with thin thickness, wide bandwidth, strong absorption strength, and low filling ratio remains a huge challenge. In this paper, nitrogen-doped reduced graphene oxide/tricobalt tetraoxide (NRGO/Co3O4) composite aerogels were synthesized by a three-step method of solvothermal reaction, high-temperature calcination, and hydrothermal self-assembly. The results showed that the attained NRGO/Co3O4 composite aerogels had a unique three-dimensional porous network structure, extremely low bulk density, and good compression recovery. Furthermore, the effect of the addition amounts of flower-like Co3O4 on the complex dielectric constant and microwave absorption properties of NRGO/Co3O4 composite aerogels was investigated. When the addition amount of Co3O4 was equal to 15 mg, the prepared binary composite aerogel showed the strongest absorption strength of –62.78 dB and a wide absorption bandwidth of 5.5 GHz at a thin thickness of 2.13 mm and a low filling ratio of 15 wt.%. It was worth noting that the maximum absorption bandwidth could reach 6.32 GHz (11.68–18 GHz, spanning the entire Ku-band) at a thickness of 2.24 mm. In addition, the possible microwave absorption mechanism of NRGO/Co3O4 composite aerogels was also proposed. Therefore, this paper will provide a new and simple strategy for preparing RGO-based porous nanocomposites as lightweight, efficient, and broadband microwave absorbers.

Construction of gelatin/alginate hydrogels doped hemicyanine derivatives for photodynamic antibacterial application

Hydrogel systems based on natural polymer materials have provided alternative opportunities for preparing antimicrobial dressings. A composite antibacterial hydrogel system containing gelatin (Gel), alginate (Alg) and hemicyanine derivatives with different chain lengths (C3, C6 and C10) was constructed. The composite hydrogels have excellent swelling ability and low degradability due to the classical three-dimensional network structure. Because of the photosensitization ability of C3, C6 and C10, hydrogels containing these molecules can also effectively produce reactive oxygen species (ROS) under light. Importantly, the hydrogel containing C3 molecules that have higher spatial extension structure and shorter alkyl chain than C6 and C10 shows better photo-responsive antibacterial effect against drug-resistant Escherichia coli. The bacterial killing activity of the composite hydrogel system could be regulated by changing the alkyl chain length of the photosensitizers. This effective and photo-responsive composite hydrogel system is expected to be used for bacteria-infected wound repair and promoting wound healing.

Highly sensitive flexible SERS substrates with a sandwich structure for rapid detection of trace pesticide residues

Compared to rigid surface-enhanced Raman scatting (SERS) substrates, flexible SERS substrates offer significant advantages for the detection of pesticide residues on vegetable and fruit surfaces, primarily due to their convenient sampling process and shorter detection times. However, for paper-based SERS substrates, gold nanoparticles (AuNPs) are easy to form ineffective dispersion in the three-dimensional network structure of paper, resulting in unsatisfactory SERS enhancement. To address this challenge and achieve high-performance flexible SERS substrates, a novel sandwich structure is proposed. Specifically, AuNPs are aggregated on expanded graphite (EG) through a chemical enhancement process facilitated by LiCl. EG is found to improve the adsorption capacity of targeted molecules while preventing signal attenuation caused by filter papers. By employing an aggregating agent at specific concentrations, it is possible to significantly increase the amounts of hot spots to provide a more pronounced enhancement effect. Furthermore, the developed flexible SERS substrates are applied to qualitatively and quantitatively detect pesticide residues, including Thiram, Nitrofural and Dinotefuran. The flexible SERS substrates demonstrate high accuracy and robustness, making them easily storable and suitable for practical applications.

Porous Collagen Sponge Loaded with Large Efficacy-Potentiated Exosome-Mimicking Nanovesicles for Diabetic Skin Wound Healing.

Diabetic skin wounds are difficult to heal quickly due to insufficient angiogenesis and prolonged inflammation, which is an urgent clinical problem. To address this clinical problem, it becomes imperative to develop a dressing that can promote revascularization and reduce inflammation during diabetic skin healing. Herein, a multifunctional collagen dressing (CTM) was constructed by loading large efficacy-potentiated exosome-mimicking nanovesicles (L-Meseomes) into a porous collagen sponge with transglutaminase (TGase). L-Meseomes were constructed in previous research with the function of promoting cell proliferation, migration, and angiogenesis and inhibiting inflammation. CTM has a three-dimensional porous network structure with good biocompatibility, swelling properties, and degradability and could release L-Meseome slowly. In vitro experiments showed that CTM could promote the proliferation of fibroblasts and the polarization of macrophages to the anti-inflammatory phenotype. For in vivo experiments, on the 21st day after surgery, the wound healing rates of the control and CTM were 83.026 ± 4.17% and 93.12 ± 2.16%, respectively; the epidermal maturation and dermal differentiation scores in CTM were approximately four times that of the control group, and the skin epidermal thickness of the CTM group was approximately 20 μm, which was closest to that of normal rats. CTM could significantly improve wound healing in diabetic rats by promoting anti-inflammation, angiogenesis, epidermal recovery, and dermal collagen deposition. In summary, the multifunctional collagen dressing CTM could significantly promote the healing of diabetic skin wounds, which provides a new strategy for diabetic wound healing in the clinic.

A novel cobalt-based coordination polymer for rapid degradation of organic dyes in water by visible light assistance

It is crucial to construct an effective photocatalyst for the removal of dyes from aqueous environments. In the present work, a novel cobalt-based coordination polymer was synthesized and characterized with the molecular formula [Co(ipa)(ptt)]n (Co-CP), (ipa = isophthalic acid, ptt = 5-(4-Pyridyl)-1H-tetrazole). In Co-CP, each cobalt ion is in a six-coordination mode and is connected to two adjacent ligands to form a three-dimensional network structure. Furthermore, Co-CP excellent degradation properties and can effectively degrade methylene blue (MB) and rhodamine B (Rh B) under visible light with degradation efficiencies of 84.3 % and 94.6 %, respectively. Additionally, its PXRD patterns and FTIR spectra remained consistent with the original complex after three cycles, which proved that it was very stable, and there was no significant decrease in degradation ability after three cycling cycles, indicating its excellent reusability. The photocatalytic degradation mechanism was subsequently rationalized through free radical trapping experiments and analysis the energy band structure of Co-CP.

Effect of Fiber Content on Mechanical Properties of Fiber-Reinforced CGF All-Solid-Waste Binder-Solidified Soil.

In order to realize the resource utilization of solid waste and improve the tensile strength and toughness of soil, CCR-GGBS-FA all-solid-waste binder (CGF) composed of general industrial solid waste calcium carbide residue (CCR), ground granulated blast furnace slag (GGBS) and fly ash (FA) was used instead of cement and combined with polypropylene fiber to strengthen the silty soil taken from Dongying City, China. An unconfined compressive strength test (UCS test) and a uniaxial tensile test (UT test) were carried out on 10 groups of samples with five different fiber contents to uncover the effect of fiber content on tensile and compressive properties, and the reinforcement mechanism was studied using a scanning electron microscopy (SEM) test. The test results show that the unconfined compressive strength, the uniaxial tensile strength, the deformation modulus, the tensile modulus, the fracture energy and the residual strength of fiber-reinforced CGF-solidified soil are significantly improved compared with nonfiber-solidified soil. The compressive strength and the tensile strength of polypropylene-fiber-reinforced CGF-solidified soil reach the maximum value when the fiber content is 0.25%, as the unconfined compressive strength and the tensile strength are 3985.7 kPa and 905.9 kPa, respectively, which are 116.60% and 186.16% higher than those of nonfiber-solidified soil, respectively. The macro-micro tests identify that the hydration products generated by CGF improve the compactness through gelling and filling in solidified soil, and the fiber enhances the resistance to deformation by bridging and forming a three-dimensional network structure. The addition of fiber effectively improves the toughness and stiffness of solidified soil and makes the failure mode of CGF-solidified soil transition from typical brittle failure to plastic failure. The research results can provide a theoretical basis for the application of fiber-reinforced CGF-solidified soil in practical engineering.

Multifunction-balanced porous carbon and its application in sulfur-loading host and separator modification for lithium–sulfur batteries

Lithium–sulfur batteries have been researched extensively because of their high energy density and low price. However, the poor conductivity of sulfur, the shuttle effect of polysulfide, the slow redox kinetics of sulfur species, and the significant volume expansion and contraction during charging and discharging have hindered the commercial application of lithium–sulfur batteries. In this study, a simple, scalable, and cost-effective strategy was developed to control the balance of the porosity, specific surface area, graphitization, heteroatom co-doping, and polar-polar interactions of a biomass carbon source. With this strategy, multifunctional porous carbon materials with three-dimensional network structures were prepared to serve as sulfur-loading hosts with high specific surface area, strong adsorption activity, and good conductivity. Moreover, the optimal porous carbon material was directly coated on a commercial separator, and the modified separator was found to further improve the electrochemical performance of a lithium–sulfur battery. As a result, for the battery with GPCS-3 as cathode electrode and modified separator as separator, the initial discharge capacity at 1.0C is 926.2 mAh g−1. After 300 cycles, the discharge capacity is 712.7 mAh g−1, and the average capacity decay is only 0.077 % per cycle. Since the three-dimensional network structure material exhibits good performance as a sulfur-loading host as well as the ability to effectively modify a separator, this study provides a valuable strategy for the fabrication of high energy density lithium–sulfur batteries.

The three-dimensional culture of L929 and C2C12 cells based on SPI-SA interpenetrating network hydrogel scaffold with excellent mechanical properties.

Cell-cultured meat, which is obtained by adsorbing cells on the three-dimensional scaffold, is considered a potential solution to animal welfare issues. Edible and safe cell-cultured meat scaffolds are a key part of its research. Soy protein isolate (SPI) hydrogel has a three-dimensional network structure and has been studied for L929 cell culture because of its non-toxicity and biocompatibility. However, the toughness and mechanical properties of SPI hydrogel are not enough to bear the requirements of cell cultivation. In this paper, sodium alginate (SA) was added to SPI hydrogel, and the interpenetrating network (IPN) technology was used to construct SPI-SA IPN hydrogel by transglutaminase and Ca2+ double crosslinking method. SPI-SA IPN hydrogel has excellent mechanical properties, structural stability and biodegradable performance than SPI hydrogel. The bio-compatibility and degradability of L929 and C2C12 cells on SPI-SA IPN hydrogel were studied by cytotoxicity, trypan blue and living/dead cell staining, and the growth law of the hydrogel as a scaffold for cell culture was analyzed. The results showed that L929/C2C12 cells can proliferate normally and adhere in hydrogel and have good bio-compatibility. L929 cells with size about 20-50µm have better adhesion and growth abilities on SPI-SA IPN hydrogel than C2C12 cells with 100-300µm. Therefore, the SPI-SA IPN hydrogel is non-toxic and supports the growth of cells in the pores of the material. This study provides a reference for the application of SPI-SA IPN hydrogels in vitro cell growth.

Exploring the effect of polyacrylamide/graphene oxide composite hydrogel on the synthesis and application of ZSM-5 molecular sieves

Herein, we demonstrate the synthesis of coffin-shaped ZSM-5 molecular sieves in polyacrylamide (PAM)/graphene oxide (GO) composite hydrogel using the hydrothermal method. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), and Thermogravimetry analyses (TGA). The effect of PAM and GO addition on the morphology and structure of ZSM-5 was investigated. The results indicated that the introduction of PAM and GO promoted the growth of the ZSM-5 (101) plane. Moreover, samples synthesized in the PAM/GO hydrogel exhibited a longer c-axis and a more pronounced coffin-shaped morphology compared to samples synthesized solely in PAM hydrogel. The Si/Al ratio decreased with the addition of GO, possibly due to interface effects leading to the formation of ZSM-5 precursors with a higher Al content. TG, FT-IR, and XPS characterization revealed hydrogen bonding interactions between PAM and GO, and the addition of GO likely restricted the movement of polymers, improving cross-linking between monomers and forming a more uniform network structure. The sample G-15 (P-5) exhibited higher mesopore volume and average pore diameter, contributing to enhanced catalytic performance. However, with increasing GO content, the average pore diameter decreased, potentially due to functional groups on the surfaces of graphene oxide and polyacrylamide forming a more uniform and structurally stable three-dimensional network structure. This allowed for controlled modulation of the molecular sieve morphology and pore size. The introduction of PAM/GO hydrogel resulted in a moderate amount of weak acid and an increased amount of strong acid, both shifting to lower temperatures. The ZSM-5 molecular sieves synthesized in the PAM/GO composite hydrogel demonstrated outstanding MTO catalytic performance, exhibiting high selectivity for light olefins and an extended catalytic lifespan. This work is expected to provide new ideas and methods for developing efficient ZSM-5 catalysts.

Mechanical properties and microstructure of waterborne polyurethane-modified cement composites as concrete repair mortar

With the increase in service life, the durability of a large number of concrete structures deteriorates year by year under the influence of the external environment, requiring urgent repair and reinforcement. Ordinary cement concrete materials have disadvantages such as high brittleness, low tensile strength, poor bonding ability, and insufficient durability, making it difficult to meet the repair needs of high-quality building structures. Therefore, self-synthesized anion WPU was used to study its effect on the mechanical properties of cement-based repair mortar. The research found that waterborne polyurethane (WPU)-modified cementitious composite repair materials exhibit better bonding strength with old concrete substrates compared to traditional cement-based materials. Additionally, the incorporation of WPU significantly reduces the brittleness of the repair material, ensuring enhanced efficiency in the repair process. However, according to the hydration heat test results, the addition of WPU delays the hydration process of the composite repair materials. In addition, the addition of WPU enhances the flexibility and bonding ability of the materials, with flexural strength and tensile strength at the age of 28 days reaching 13 MPa and 6 MPa, respectively. Through stress‒strain curve analysis, it was found that the maximum strain amplification of WPU cement mortar can reach 134 %. Combined with SEM testing, it was observed that cured WPU films were present in specimens aged 28 days with P/C ratios of 10 % and 15 %. WPU and cement hydration products permeate each other, forming a three-dimensional polymer network structure, improving the pore structure, and fully exerting the flexibility of WPU. This also validates the experimental results of increased ultimate tensile strain. WPU cement-based composite repair materials have higher bonding strength at a high P/C ratio (15 %), and WPU alone, used as an interface agent for pretreating the interface of old concrete, can improve the interface bonding strength, up to twice that of the group without the surface agent.

Chitosan modified graphene oxide with MnO2 deposition for high energy density flexible supercapacitors

To obtain a flexible composite electrode material with excellent electrochemical performance, chitosan (CS)/graphene oxide (GO) composite pretreated from microwave hydrothermal is adopted as the carbon substrate, and MnO2 active material is uniformly deposited on their surface through anodic electrodeposition. In this composite system, CS penetrates into graphene sheets as small molecule units, forming NH-C=O groups with GO via dehydration condensation, which effectively inhibits the stacking of GO and improves the specific surface area, conductivity, as well as the wettability of the carbon support. MnO2 bonding with heteroatom N from CS enables high active material loadings and forms stable three-dimensional network structure, facilitating the enhanced electrochemical performance. Results indicate that increasing depositing MnO2 amount leads to more defective structures of the composite, which promotes their electrochemical performance when used as electrode material. The area specific capacitance of the optimal composite reaches 3553.74 mF/cm2 at 5 mA/cm2 in 1 M Na2SO4 electrolyte. Kinetic analysis shows the energy storage process is capacitance-dominated, with the redox reactions of MnO2 being the main contributor. The prepared asymmetric solid supercapacitor delivers an energy density high up to 0.585 mWh/cm2 at power density of 3000 mW/cm2, and their excellent flexibility makes them promising candidates as flexible sensor.

Integration of covalent organic frameworks and molecularly imprinted polymers for selective extraction of flavonoid naringenin from grapefruit (Citrus × paradisi Macf.) peels

Grapefruit (Citrus × paradisi Macf.) peel, a by-product of the citrus-processing industry, possesses an important economic value due to the richness of bioactive compounds. In this study, boron-linked covalent organic frameworks integrated with molecularly imprinted polymers (CMIPs) were developed via a facile one-pot bulk polymerization approach for the selective extraction of naringenin from grapefruit peel extract. The obtained CMIPs possessed a three-dimensional network structure with uniform pore size distribution, large surface areas (476 m2/g), and high crystallinity. Benefiting from the hybrid functional monomer APTES-MAA, the acylamino group can coordinate with the boronate ligands of the boroxine-based framework to form B-N bands, facilitating the integration of imprinted cavities with the aromatic skeleton. The composite materials exhibited a high adsorption capacity of 153.65 mg/g, and a short adsorption equilibrium time of 30 min for naringenin, together with favorable selectivity towards other flavonoid analogues. Additionally, the CMIPs captured the template molecules through π–π* interaction and hydrogen bonding, as verified by FT-IR and XPS. Furthermore, they had good performance when employed to enrich naringenin in grapefruit peels extract compared with the common adsorbent materials including AB-8, D101, cationic exchange resin, and active carbon. This research highlights the potential of CMIPs composite materials as a promising alternative adsorbent for naringenin extraction from grapefruit peel.

Geometry-based cross-linking algorithm for modeling resorcinol resins through united-atom molecular dynamics simulations

The addition-condensation polymerization (ACP) of resorcinol with formaldehyde and the electrochemical polymerization (ECP) of resorcinol were desirable to improve the performances of resins. To achieve computational design, a new geometry-based cross-linking modeling algorithm for three-dimensional (3D) cross-linked network structures of resorcinol resins was developed for molecular dynamics (MD) simulations using a united-atom model. The ACP and ECP of resorcinol were successfully modeled using one algorithm by changing the parameters of the reaction rate constants of methylene, ether, and biphenyl bond formations. Furthermore, reaction judgment was performed under a reaction probability function comprising the Gaussian functions based on the interatomic distance of the reaction candidate atom pairs and interior angles regarding the spatial arrangement of two resorcinol rings. This geometry-based cross-linking algorithm successfully generated strainless 3D cross-linked network structures of the ACP and ECP resorcinol resins without the formation of highly bent unstable structures, such as U-shaped biphenyls. The MD simulation results indicated that the cross-linking of the ACP resin comprising methylene linkages proceeded with a network structure formation mechanism similar to that of phenolic resins, where the cross-linked network structure was determined at the gel point and the reactions after the gel point were to fix and freeze the network structure. For the ECP resins comprising ether and biphenyl linkages, the molar ratio of ether to biphenyl bonds affected the elastic property of the resins, and the incorporation of rigid biphenyl structures into ether-linkage networks increased the elastic modulus. Moreover, an increase in rigidity was observed as a decrease in the Poisson's ratio.

Integrating with a tough framework and efficient self-healing behavior based on a flexible polymer skeleton for Si anode binders in lithium-ion cells

As a prospective and efficient strategy to address the volume expansion of the Si nanoparticles, the binder plays an increasingly significant role in the Si anode of lithium-ion batteries. Based on the inspiration of natural physics and cross-linked networks, a functional (named polyacrylic acid-citric acid-polyethyleneimine) binder that is similar to a flexible polymer skeleton integrated with a tough framework and efficient self-healing behavior is designed to achieve long cycling stability for Si anodes. The cross-linked network can be stabilized by the amide bonds, formed by polyethyleneimine (PEI) and polyacrylic acid (PAA). Based on this, citric acid (CA) can be added to form multiple hydrogen bonds, whose carboxyl groups can also establish a more reversible cross-linked network with Si particles. Then, PEI and CA molecules can connect with PAA to form a “rigid and flexible” structure. The expansion stress of Si nanoparticles is relieved by the protective buffer layer built by the addition of PEI and CA molecules. In addition, PAA, PEI, and CA work together to solve the problem that the action of CA and PAA alone cannot perform well under large currents. Hence, this water-based binder with a three-dimensional cross-linked network structure with self-healing ability has better performance during cycling: at a current density of 0.2C, it still has a capacity of 2017.4 mAh·g−1 after 200 cycles, with a capacity retention rate of 80.7 % (1745.3 mAh·g−1, 300 cycles, a capacity retention of 74.9 %).

A TA/Cu2+ Nanoparticle Enhanced Carboxymethyl Chitosan-Based Hydrogel Dressing with Antioxidant Properties and Promoting Wound Healing.

As the first line of immune defense and the largest organ of body, skin is vulnerable to damage caused by surgery, burns, collisions and other factors. Wound healing in the skin is a long and complex physiological process that is influenced by a number of different factors. Proper wound care can greatly improve the speed of wound healing and reduce the generation of scars. However, traditional wound dressings (bandages, gauze, etc.) often used in clinical practice have a single function, lack of active ingredients and are limited in use. Hydrogels with three-dimensional network structure are a potential biomedical material because of their physical and chemical environment similar to extracellular matrix. In particular, hydrogel dressings with low price, good biocompatibility, degradability, antibacterial and angiogenic activity are favored by the public. Here, a carboxymethyl chitosan-based hydrogel dressing (CMCS-TA/Cu2+) reinforced by copper ion crosslinked tannic acid (TA/Cu2+) nanoparticles was developed. This study investigated the physical and chemical characteristics, cytotoxicity, and angiogenesis of TA/Cu2+ nanoparticles and CMCS-TA/Cu2+ hydrogels. Furthermore, a full-thickness skin defect wound model was employed to assess the in vivo wound healing capacity of hydrogel dressings. The introduction of TA/Cu2+ nanoparticles not only could increase the mechanical properties of the hydrogel but also continuously releases copper ions to promote cell migration (the cell migration could reach 92% at 48 h) and tubule formation, remove free radicals and promote wound healing (repair rate could reach 90% at 9 days). Experiments have proved that CMCS-TA/Cu2+ hydrogel has good cytocompatibility, antioxidant and wound healing ability, providing an advantageous solution for skin repair.

A three-dimensional network structure of metal-based nanozymes for the construction of colorimetric sensors for the detection of antioxidants.

Although many excellent nanozymes have been developed, designing and synthesizing highly active nanozymes is still challenging. Here, we developed a metal-based nanozyme (metal = Co, Fe, Cu, Zn) with a three-dimensional network structure. It possesses excellent peroxidase activity and catalyzes the reaction between H2O2 and TMB to produce blue oxTMB, while antioxidants have different reducing power on the oxidation product of TMB (oxTMB), which leads to different absorbance and color changes. Using these color reactions, different nanozymes were used to form a colorimetric sensor array with seven antioxidants, and seven antioxidants were sensitively identified. And the differences between the three nanozymes were compared by density functional theory calculations and enzyme kinetic curve results. In conclusion, the colorimetric sensor array based on metal-based nanozymes provides a good strategy for the identification and detection of antioxidants, which has a broad application prospect.

3D net-like Co3O4@NiO nanostructures for high performance supercapacitors.

Co3O4@NiO composite electrode materials were successfully synthesized by a two-step hydrothermal method followed by annealing treatment. Due to their three-dimensional network structure, these composite materials exhibited a large specific surface area, enhancing their electrochemical performance. Consequently, the Co3O4@NiO electrode demonstrated a specific capacitance of 1306 F g-1 at a current density of 1 A g-1, an excellent specific capacitance retention rate of 95.5% after 3000 cycles even at 8 A g-1 and a coulombic efficiency approaching 100%. These outstanding properties make the Co3O4@NiO composite materials promising electrode materials for high performance supercapacitors.

Magnesium-Doped Nano-Hydroxyapatite/Polyvinyl Alcohol/Chitosan Composite Hydrogel: Preparation and Characterization.

Polyvinyl alcohol/Chitosan hydrogel is often employed as a carrier because it is non-toxic, biodegradable, and has a three-dimensional network structure. Meanwhile, Magnesium-doped nano-hydroxyapatite(Mg-nHA) demonstrated high characterization to promote the osteogenic differentiation of bone marrow derived mesenchymal stem cell(BMSCs). Therefore, in order to develop a porous hydrogel scaffold for the application of bone tissue engineering, an appropriate-type Mg-nHA hydrogel scaffold was developed and evaluated. A composite hydrogel containing magnesium-doped nano-hydroxyapatite (Mg-nHA/PVA/CS) was developed using a magnetic stirring-ion exchange method and cyclic freeze-thaw method design, with polyvinyl alcohol and chitosan as the main components. Fourier transform infrared spectra (FTIR), electron energy dispersive spectroscopy (EDS), X-ray photoelectron spectrometer (XPS) and scanning electron microscopy (SEM) were employed to analyze the chemical structure, porosity, and elemental composition of each hydrogels. The equilibrium swelling degree, moisture content, pH change, potential for biomineralization, biocompatibility, the osteogenic potential and magnesium ion release rate of the composite hydrogel were also evaluated. SEM analysis revealed a well-defined 3D spatial structure of micropores in the synthesised hydrogel. FTIR analysis showed that doping nanoparticles had little effect on the hydrogel's structure and both the 5% Mg-nHA/PVA/CS and 10% Mg-nHA/PVA/CS groups promoted amide bond formation. EDS observation indicated that the new material exhibited favourable biomineralization ability, with optimal performance seen in the 5% Mg-nHA/PVA/CS group. The composite hydrogel not only displayed favourable water content, enhanced biocompatibility, and porosity (similar to human cancellous bone), but also maintained an equilibrium swelling degree and released magnesium ions that created an alkaline environment around it. Additionally, it facilitated the proliferation of bone marrow mesenchymal stem cells and their osteogenic differentiation. The Mg-nHA/PVA/CS hydrogel demonstrates significant potential for application in the field of bone repair, making it an excellent composite material for bone tissue engineering.