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In order to improve Perccottus glenii myofibrillar protein (MP) gel properties, three treatments were evaluated: ultrasonic, transglutaminase (TGase) and combined ultrasonic-transglutaminase treatments. Combined ultrasonic-transglutaminase treatment altered protein structure and gel properties most dramatically. As compared with untreated control group protein, treated protein gels possessed decreased sulfhydryl group content and increases in water holding capacity, whiteness value and hydrophobic interactions that increased gel strength value by up to 3.79 times that of untreated protein gel. Protein structural and Differential scanning calorimetry (DSC) analyses revealed that combined ultrasonic-TGase treatment increased both protein thermal denaturation temperature and UV absorbance (as compared to control and other treatment groups) that supported formation of MP gels with desirable characteristics. These results provide a theoretical basis for development of superior MP gels to promote greater utilization of this fish protein resource by the food industry.

A rewritable photonic crystal (PC) paper as an environmentally friendly and low-resource-consuming material for information storage and spreading has gradually become a research hotspot. In this work, a novel rewritable PC paper with inkless writing and double-sided rewritability properties was developed. A double-sided epoxy resin PC paper exhibiting an inverse opal structure and a bright structural color was fabricated using the sacrificial template method. Carbon black was doped into the material to increase color saturation and purity while preventing light transmission and protecting the double-sided structural color from interference. The force of sliding friction and deformation triggered by capillary pressure as well as swelling-triggered recovery of the inverse opal structure led to an easy rewriting of the PC paper. The PC paper exhibited excellent rewritability even after 50 runs of the rewriting process. Given the inkless and double-sided rewriting, this study provides a new method for the preparation of rewritable PC papers.

Integrating nitrogen species into sp2-hybridized carbon materials has proved an efficient means to improve their electrochemical performance. Nevertheless, an inevitable mixture of nitrogen species in carbon materials, due to the uncontrolled conversion among different nitrogen configurations involved in synthesizing nitrogen-doped carbon materials, largely retards the precise identification of electrochemically active nitrogen configurations for specific reactions. Here, we report the preparation of single pyrrolic N-doped carbon materials (SPNCMs) with a tunable nitrogen content from 0 to 4.22 at.% based on a strategy of low-temperature dehalogenation-induced and subsequent alkaline-activated pyrolysis of 3-halogenated phenol-3-aminophenol-formaldehyde (X-APF) co-condensed resins. Additionally, considering that the pseudocapacitance of SPNCMs is positively dependent on the pyrrolic nitrogen content, it could be inferred that pyrrolic nitrogen species are highly active pseudocapacitive sites for nitrogen-doped carbon materials. This work gives an ideal model for understanding the contribution of pyrrolic nitrogen species in N-doped carbon materials. A mixture of nitrogen species in carbon materials typically hinders the precise identification of electrochemically active nitrogen configurations for specific reactions. Here the authors show single-site pyrrolic-nitrogen-doped sp2-hybridized carbon materials and their pseudocapacitive properties.

Heterogeneous Fe3O4 and Fe composites are highly desirable for microwave absorption application because of their complementary electromagnetic (EM) properties. With three-dimensional (3D) Fe2O3 as a sacrificing template, we realize the construction of Fe3O4/Fe composites with tunable chemical composition, and more importantly, these composites inherit the unique 3D microstructure from their precursor. The change in chemical composition produces significant impacts on the EM functions of these composites. On the one hand, dielectric loss can be improved greatly through positive interfacial polarization and reach the peak when the mass contents of Fe3O4 and Fe are 72.1 and 27.9 wt %, respectively. On the other hand, high Fe content slightly pulls down magnetic loss in the low-frequency range but favors strong magnetic loss in the high-frequency range because of the breakthrough of Snoek's limitation. The attenuation constant reveals that dielectric loss dominates overall consumption of incident EM waves. As a result, the optimized composite, F-350 (the reduction of Fe2O3 is conducted at 350 °C), shows the best microwave absorption performance, whose strongest reflection loss is -56.0 dB at 17.5 GHz and the effective bandwidth can cover the frequency range of 12.0-15.5 GHz with the thickness of 1.5 mm. Furthermore, an ultrawide effective bandwidth of 15.3 GHz can be achieved with the integrated thickness of 1.0-5.0 mm. Such a performance is superior to those of many reported Fe3O4/Fe composites, and a comparative analysis manifests that good microwave absorption of F-350 is also benefited from its unique 3D architecture.

Yolk-shell magnetic nanoparticles@nitrogen-enriched Carbon nanostructures with a magnetic core and a hollow nitrogen-enriched carbon shell exhibit considerable promise in various applications, such as drug delivery, heterogenous catalysts, removal of metal ions and organic pollutants, and screening of biomolecules, due to their strong magnetic response, unique cavities, and the selective absorption ability of nitrogen-enriched groups. However, their complicated synthesis always involves possible surface modification, layer-by-layer deposition of a sacrificial middle layer and an outer nitrogen-enriched layer on magnetic nanoparticles, subsequent carbonization, and final removal of the sacrificial middle layer. Herein, yolk-shell Fe

UV-triggered single-microcapsule self-healing materials have significant potential in effectively repairing microcracks and improving the reliability of polymer coatings on spacecraft with the aid of abundant UV radiation in space. Unfortunately, UV light can also cause undesirable curing of the repair agent within the microcapsules before self-repairing and make the latent UV-cured healing agent fail. Herein, we developed UV-triggered self-healing SiO2/polydopamine (PDA) hybrid microcapsules with enhanced UV-shielding ability and compatibility for epoxy resin coating. The microcapsules contain a liquid core of mixed epoxy resin (E-51 and A1815) and UV initiator (PI6992) and a novel UV-shielding SiO2/PDA hybrid shell with uniform embedment of an ultrathin PDA layer into the SiO2 mesoporous structure of the shell. As a UV absorber, PDA endows SiO2/PDA hybrid microcapsules with a UV-shielding hybrid shell and protects the core material from undesirable UV-cured behavior before self-repairing in space with abundant UV radiation. In addition, PDA containing benzene rings and polar groups, including hydroxyl, amino, and carbonyl groups, can enhance the compatibility of SiO2/PDA hybrid microcapsules with epoxy resin containing benzene rings and epoxy and hydroxyl groups due to π-π stacking interactions between abundant benzene rings and hydrogen bonding interactions between these polar groups. The epoxy coatings containing SiO2/PDA microcapsules aged for 192 h under UV irradiation maintained great self-repairing ability, which was attributed to the enhanced UV-shielding ability and compatibility.

Two-dimensional (2D) carbon nanomaterials generally display some limitations in adsorption applications due to easy agglomeration. To solve this problem, as-synthesized sandwiched nanocomposites made of Fe3O4 nanoparticles, poly(allylamine) hydrochloride molecules, and carboxylate graphene oxide sheets were prepared using a layer-by-layer (LbL) self-assembly method. The successfully synthesized sandwiched structures in the present nanocomposites have outstanding organic dye adsorption performance, stability, and recycling. The agglomeration of carboxylate graphene oxide was reduced with increased specific surface area because the Fe3O4 nanoparticles play important roles in interpenetrating and supporting graphene oxide sheets layers. In comparison with other kinds of composite adsorbents, the preparation process of the present new sandwiched composite materials is facile to operate and regulate, which demonstrates potential large-scale applications in wastewater treatment and dye removal.

Magnetically recoverable heteropoly acids (HPAs) exhibit high activity for oxidation reactions. However, HPA species immobilized onto magnetic supports commonly suffer from the loss of active species into reaction solutions due to the weak affinity of the supports for active species. Herein, core-shell Fe3O4@thermally crosslinked PANI@Tunstophoric acid (Fe3O4@TC-PANI@TPA) nanostructures were rationally synthesized based on a PVP-mediated surface polymerization strategy and a subsequent thermal treatment process. Uniform PANI shell and TPA species were successively deposited onto Fe3O4 nanoclusters, followed by a thermal crosslinked treatment of PANI shell. Spatial confinement of high dispersed TPA sites within thermally crosslinked PANI shell could largely enhance their solvent tolerance against the loss of active TPA sites accompanied by the dissolution of some non-crosslinked PANI chains during catalytic transformations. As expected, the Fe3O4@TC-PANI@TPA catalyst exhibited high activity, facile magnetic recoverability, and robust stability for green epoxidation of cis-cyclooctene using ethanol as a solvent and H2O2 as an oxidant.

Integrating nitrogen species into sp2-hybridized carbon materials has proved an efficient means to improve their electrochemical performance. Nevertheless, an inevitable mixture of nitrogen species in carbon materials, due to the uncontrolled conversion among different nitrogen configurations involved in synthesizing nitrogen-doped carbon materials, largely retards the precise identification of electrochemically active nitrogen configurations for specific reactions. Here, we report the preparation of single pyrrolic N-doped carbon materials (SPNCMs) with a tunable nitrogen content from 0 to 4.22 at.% based on a strategy of low-temperature dehalogenation-induced and subsequent alkaline-activated pyrolysis of 3-halogenated phenol-3-aminophenol-formaldehyde (X-APF) co-condensed resins. Additionally, considering that the pseudocapacitance of SPNCMs is positively dependent on the pyrrolic nitrogen content, it could be inferred that pyrrolic nitrogen species are highly active pseudocapacitive sites for nitrogen-doped carbon materials. This work gives an ideal model for understanding the contribution of pyrrolic nitrogen species in N-doped carbon materials., A mixture of nitrogen species in carbon materials typically hinders the precise identification of electrochemically active nitrogen configurations for specific reactions. Here the authors show single-site pyrrolic-nitrogen-doped sp2-hybridized carbon materials and their pseudocapacitive properties.

Heterogeneous Fe

With the development of computer networks, the management and operation of the library are gradually becoming networked. And the network management model has greatly improved the management efficiency of the library. Of course, the computer network also makes the library’s data have hidden dangers. This paper mainly analyzes the library computer network security problem and the improvement measures of the library computer network security problem.

UV-responsive single-microcapsule self-healing systems exhibit considerable potential to effectively repair the microcracks and then extend the service life and reliability of polymeric composite coatings on spacecraft because of abundant UV irradiation in space environment and the stable healing process based on an accurate stoichiometric ratio. Unfortunately, UV irradiation in space environment also could cause undesirable curing of healing agents in the microcapsules embedded into the coatings before the generation and UV-responsive self-healing of the microcracks in these coatings and therefore deactivation of healing agents. Herein, we propose a UV-responsive single-microcapsule self-healing system with epoxy resin core and enhanced UV-shielding SiO2/ZnO hybrid shell for polymer coatings through a layer-by-layer deposition strategy. Homogenous embedment of ultrasmall ZnO nanocrystals into the mesoporous SiO2 shell endows the microcapsules with excellent UV-shielding performance. Moreover, in contrast to conventional polymer shell, our stable inorganic SiO2 counterpart could avoid the degradation fate catalyzed by photo-responsive ZnO or TiO2 nanoparticles, thereby enhancing the stability of the microcapsule. As expected, when the SiO2/ZnO microcapsules after aging up to 21 days under UV radiation were embedded in the epoxy coating, the epoxy coating containing these aged microcapsules still displays good self-healing capability upon scratching and UV-induced self-healing, and then scratches are still filled and repaired, attributing to the shielding ability of ultrasmall ZnO nanocrystals highly dispersed into the SiO2 shell from undesirable UV-induced curing of epoxy resin core before self-healing behavior in the UV-sufficient space environment.

Two-dimensional microwave-absorbing materials (MAMs) with abundant preferable interfaces are highly desirable for high-performance microwave absorption. Herein, a leaf-like Fe/C structure, consisting of iron veins interpenetrated in amorphous carbon lamina, was fabricated by reducing a petal-like iron alkoxide in an H2/Ar atmosphere. The synthesized leaf-like Fe/C composites dissipate microwaves in an effectively similar process green to leaves absorbing sunlight. First, the unique leaf-like structure enables microwaves to pass into the composites because the 2D amorphous carbon, with its high BET surface area, provide adequate access for microwaves. Then, the incident microwave is attenuated by the distinctly improved dielectric loss caused by enhanced interface polarization and an effective magnetic loss from the natural resonance of iron. Therefore, the leaf- like Fe/C composite shows microwave absorption with a maximum reflection loss of − 59.7 dB, whose effective bandwidth (reflection loss ≤ − 10 dB) covers the whole Ku band and X band with thicknesses of only 1.5 mm and 2.0 mm, respectively.

Ni-based magnetic catalysts exhibited moderate activity, low cost, and magnetic reusability for hydrogenation reactions. However, Ni nanoparticles anchored on magnetic supports suffer commonly from undesirable agglomeration during catalytic reactions due to the relatively weak affinity of magnetic support to Ni nanoparticles. A hierarchically yolk-shell Fe@SiO2/Ni catalyst with an inner movable Fe core and an ultrathin SiO2/Ni nanosheets-assembled shell was synthesized via a self-templating reduction strategy with the hierarchically yolk-shell Fe3O4@nickel silicate nanocomposite as the precursor. Spatial confinement of highly dispersed Ni nanoparticles of the mean size of 4 nm into ultrathin SiO2 nanosheets of the 2.6-nm thickness could not only prevent their agglomeration during catalytic transformations but also expose abundant active Ni sites accessible to the reactants. Moreover, the large inner cavities and interlayer space among the assembled ultrathin SiO2/Ni nanosheets provide suitable mesoporous channels for the diffusion of the reactants toward active sites. As expected, the Fe@SiO2/Ni catalyst displays high activity, high stability and magnetic recoverability for the reduction of nitroaromatic compounds. In particular, the Ni-based catalyst maintained the conversion of 4-Nitroamine of over 98% and preserved the initial yolk-shell structure without any obvious aggregation of Ni nanoparticles after over ten catalytic cycles, confirming the high structural stability of the Ni-based catalyst.

A new crystalline silicon solar cell with Si nanocone arrays on the top and Al nanohemisphere arrays on bottom surface were proposed. The light-trapping ability were systematically studied by COMSOL Multiphysics. The nanocone arrays benefit light-trapping by introducing gradient change of refractive index and coupling the incoming light into optical modes. The metallic nanohemisphere arrays affect the light-harvesting by surface plasmon polaritons (SPPs) and scattering effect. The numerical simulations show that the optimal parameters for the periodic nanocone arrays are 350 nm in diameter and 1.1 of the pitch/diameter ratio. The optimal parameters for the nanohemisphere arrays are 160 nm in diameter, 1.3 of the pitch/diameter ratio respectively. Eliminating the Ohmic Loss in metallic nanohemisphere, a 700 nm thick silicon solar cell with the combination of these two nanostructures will contribute an average absorption of 72.928% and a 33.311 mA/cm2 short circuit photocurrent density in the wavelength of 310–1127 nm.

Yolk-shell magnetic nanoparticles@nitrogen-enriched Carbon nanostructures with a magnetic core and a hollow nitrogen-enriched carbon shell exhibit considerable promise in various applications, such as drug delivery, heterogenous catalysts, removal of metal ions and organic pollutants, and screening of biomolecules, due to their strong magnetic response, unique cavities, and the selective absorption ability of nitrogen-enriched groups. However, their complicated synthesis always involves possible surface modification, layer-by-layer deposition of a sacrificial middle layer and an outer nitrogen-enriched layer on magnetic nanoparticles, subsequent carbonization, and final removal of the sacrificial middle layer. Herein, yolk-shell Fe3 O4 @nitrogen-enriched carbon nanostructures are constructed based on NH4+ ion-induced one-step deposition of SiO2 and Resorcinol-3-aminophenol-formaldehyde cocondensed resin (R-APF) dual layers onto poly acrylic acid-modified Fe3 O4 nanoclusters without any extra surface modification. The N-Carbon shell thickness of the yolk-shell Fe3 O4 @Void@N-Carbon nanostructure can be finely tailored though tailoring the feeding amount of aminophenol and resorcinol to tune the thickness of the outer R-APF resin shell onto Fe3 O4 @SiO2 intermediate particles. This NH4+ ion-induced one-pot deposition of double layers can effectively promote synthesis efficiency of this kind of yolk-shell nanostructure.

In this work, various nickel cobalt double hydroxide nanoflowers with different Ni/Co ratios (denoted as NixCo(1−x)(OH)2), assembled by filmy nanoflakes, are prepared via a facile template-free hydrothermal process. The sizes of these nanoflowers are easily tuned by the Ni/Co ratio in the precursors. The formation mechanism of flower-like nickel cobalt hydroxide, based on the synergistic effect of ammonia complexation, Ni/Co ratios, precipitators and solvents in the template-free hydrothermal system, is demonstrated in detail. As the battery materials, the as prepared flower-like nickel cobalt double hydroxides exhibit excellent specific capacities and high rate performance. Ni0.28Co0.72(OH)2 displays the highest capacity of 206.7 mA h g−1 at 1 mV s−1 and 174.3 mA h g−1 at 1 A g−1, respectively. The capacity retention of Ni0.28Co0.72(OH)2 is 59.1% (from 206.7 to 122.2 mA h g−1) at the potential scan rate from 1 to 25 mV s−1. Due to the high rate performance corresponding to high power energy, Ni0.28Co0.72(OH)2 is used as positive material to assemble the hybrid device (asymmetric supercapacitor) with activated carbon as negative material. The as-prepared asymmetric supercapacitor exhibits 19.4 Wh kg−1 at 80.5 W kg−1, and even 20.6 Wh kg−1 at 3.93 kW kg−1.

A soft template-assisted simultaneous redox strategy has been developed to fabricate Fe3O4@polypyrrole/Pd (Fe3O4@PPy/Pd) nanocomposites with a single Fe3O4 core and multiple PPy satellites, into each of which multiple tiny Pd nanocrystals are uniformly confined. The dispersion of Pd nanocrystals into PPy satellites and the Pd loading of the nanocatalyst could be finely tuned by tailoring the polarity of the reaction medium and by changing the molar ratio of pyrrole monomer to Pd precursor, respectively. The Pd-based catalyst shows high activity, robust stability and magnetic recyclability for the reduction of nitroaromatic compounds. Superior activity could be attributed to the short transport route toward the active Pd nanocrystals within the small PPy satellite for the outer substitutes. Meanwhile, high stability could be ascribed to the confinement of Pd nanocrystals uniformly into PPy satellites against aggregation and even loss of active sites during catalytic transformations.

Functional polymer-grafting silica nanoparticles hold great promise in diverse applications such as molecule recognition, drug delivery, and heterogeneous catalysis due to high density and uniform distribution of functional groups and their tunable spatial distance. However, conventional grafting methods from monomers mainly consist of one or more extra surface modification steps and a subsequent surface polymerization step. A monomer protonation-dependent surface polymerization strategy is proposed to achieve one-step uniform surface grafting of cross-linked poly(4-vinylpyridine) (P4VP) onto core-shell Fe

The contact between Ni(OH)2 and graphene oxide (GO) determines the specific capacitance, high-rate performance, and stability of Ni(OH)2-GO composites when they were used as capacitive materials with high/ultrahigh material loading. To improve this contact, the exfoliated GO from Hummers’ method is oxidized twice for anchoring Ni(OH)2 nanoflakes. The X-ray photoelectron spectroscopy (XPS) results reveal that the further oxidation process increases the carbonyl (C–O) groups and oxygen content on the GO surface. The Ni(OH)2-GO composites were obtained through a simple hydrothermal process. Morphology and microstructure characterizations indicate that the further oxidation of GO improves the affinity of Ni(OH)2 and GO via the increased surface groups on the GO. Due to the high conductivity and suitable structure, the Ni(OH)2 anchored on the treated GO (Ni(OH)2/TGO) exhibits good capacitive performance and high areal specific capacitance. The Ni(OH)2/TGO exhibits high specific capacitance of 1236.4 F g–1 at 1...

We synthesized hierarchical Polystyrene/Polyaniline@Au (PS/PANI@Au) catalysts through a seeded swelling polymerization and in-situ reduction procedure. PS/PANI@Au catalysts possess a core of PS as seed and template, a PANI shell with fibers and uniform gold nanoparticles on the surface. The configuration changes of the PANI chains resulting from the doping/dedoping procedure led to various loading amounts of Au nanoparticles. Reduction of 4-nitrophenol was chosen as the probe reaction to evaluate the catalytic activity of supported Au nanocatalysts. The catalytic results indicated that dedoping treatment of the PS/PANI supports provides stronger coordinative ability to metal nanoparticles as well as more -N= groups, which results in a better catalytic performance towards the reduction of 4-nitrophenol.

Magnetite/poly(4-vinylpyridine) composite nanospheres with multiple Fe 3 O 4 cores embedded in a P4VP shell were first synthesized by miniemulsion polymerization and then used as recoverable supports for MoO 2 (acac) 2 complex. The supported complex, together with superparamagnetism and strong magnetic response, showed high efficiency for the catalytic epoxidation of cis-cyclooctene with aqueous H 2 O 2 in ethanol. The response strongly facilitated the easy recovery of the catalyst, which was stable in recycling tests.

Ni-based magnetic catalysts exhibit moderate activity, low cost, and magnetic reusability in hydrogenation reactions. However, Ni nanoparticles anchored on magnetic supports commonly suffer from undesirable agglomeration during catalytic reactions due to the relatively weak affinity of the magnetic support for the Ni nanoparticles. A hierarchical yolk-shell Fe@SiO

UV-triggered self-healing of single microcapsules has been a good candidate to enhance the life of polymer-based aerospace coatings because of its rapid healing process and healing chemistry based on an accurate stoichiometric ratio. However, free radical photoinitiators used in single microcapsules commonly suffer from possible deactivation due to the presence of oxygen in the space environment. Moreover, entrapment of polymeric microcapsules into coatings often involves elevated temperature or a strong solvent, probably leading to swelling or degradation of polymer shell, and ultimately the loss of active healing species into the host matrix. We herein describe the first single robust SiO2 microcapsule self-healing system based on UV-triggered cationic polymerization for potential application in aerospace coatings. On the basis of the similarity of solubility parameters of the active healing species and the SiO2 precursor, the epoxy resin and cationic photoinitiator are successfully encapsulated into a single SiO2 microcapsule via a combined interfacial/in situ polymerization. The single SiO2 microcapsule shows solvent resistance and thermal stability, especially a strong resistance for thermal cycling in a simulated space environment. In addition, the up to 89% curing efficiency of the epoxy resin in 30 min, and the obvious filling of scratches in the epoxy matrix demonstrate the excellent UV-induced healing performance of SiO2 microcapsules, attributed to a high load of healing species within the capsule (up to 87 wt %) and healing chemistry based on an accurate stoichiometric ratio of the photoinitiator and epoxy resin at 9/100. More importantly, healing chemistry based on a UV-triggered cationic polymerization mechanism is not sensitive to oxygen, extremely facilitating future embedment of this single SiO2 microcapsule in spacecraft coatings to achieve self-healing in a space environment with abundant UV radiation and oxygen.

Molybdenum complexes immobilized on core–shell–shell structured Fe 3 O 4 @SiO 2 @poly(4-vinylpyridine) microspheres have been successfully fabricated by grafting [3-(methacryloyloxy)propyl]trimethoxysilane on Fe 3 O 4 @SiO 2 followed by seeded emulsion polymerization of 4-vinylpyridine monomers. The synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), x-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectra (FT-IR) and magnetometer. Their catalytic property was investigated by epoxidation of alkenes, using environmentally friendly H 2 O 2 and ethanol as oxidant and solvent, respectively. The results show that Mo–Fe 3 O 4 @SiO 2 @P4VP catalyst possesses high conversion (99.0%) and selectivity (99.0%) in the epoxidation of cis -cyclooctene at 60 °C for 24 h, and the catalyst can be recovered using a magnet and still shows high conversion (95.0%) and selectivity (99.0%) after being recycled three times.

Porous SrTiO 3 spheres were successfully synthesized by a convenient hydrothermal method, employing SrCl 2 as Sr source and titanate nanotube as Ti precursor. In this reaction, when short titanate nanotube was used as Ti precursor, porous SrTiO 3 spheres were generated for the aggregation of the nanotube@SrTiO 3 heteronanostructure. Whereas long titanate nanowire was used as the Ti precursor, solid SrTiO 3 spheres were obtained due to the SrTiO 3 which grows up gradually on the titanate nanowire. The morphology and the pore size of the SrTiO 3 sphere structures can be easily controlled by simply adjusting the reaction time, reaction temperature and the Ti precursor. The porous SrTiO 3 spheres exhibited enhanced photocatalytic activity which could achieve 100% degradation of Rhodamine B with a UV irradiation for 20 min.

Polyaniline-modified Fe 3 O 4 /SiO 2 /TiO 2 composite microspheres have been successfully synthesized by sol–gel reactions on Fe 3 O 4 microspheres followed by the chemical oxidative polymerization of aniline. The synthesized multilayer-structured composites were characterized by TEM, XRD, TGA, UV–vis diffuse reflectance spectra and magnetometer. The photocatalytic activity was evaluated by the photodegradation of methylene blue under visible light. The effect of polyaniline (PANI) amounts on the photocatalytic activity was investigated. The photocatalytic activity results show that the Fe 3 O 4 /SiO 2 /TiO 2 composites with about 2.4 wt.%–4.1 wt.% PANI could show higher photocatalytic efficiency than that of Fe 3 O 4 /SiO 2 /TiO 2 . Furthermore, the PANI-Fe 3 O 4 /SiO 2 /TiO 2 photocatalyst could be easily recovered using a magnet.

Robust nitrogen-enriched Fe3O4@carbon nanospheres have been fabricated as a catalyst scaffold for Pt nanoparticles. In this work, core-shell Fe3O4@3-aminophenol/formaldehyde (APF) nanocomposites were first synthesized by a simple hydrothermal method, and subsequently carbonized to Fe3O4@N-Carbon nanospheres for in situ growth of Pt nanocrystals. Abundant amine groups were distributed uniformly onto Fe3O4@N-Carbon nanospheres, which not only improved the dispersity and stability of the Pt nanocrystals, but also endowed the Pt-based catalysts with good compatibility in organic solvents. The dense three-dimensional cross-linked carbon shell protects the Fe3O4 cores against damage from harsh chemical environments, even in aqueous HCl (up to 1.0 M) or NaOH (up to 1.0 M) solutions under ultrasonication for 24 hours, which indicates that it can be used as a robust catalyst scaffold. In the reduction of nitrobenzene compounds, the Fe3O4@N-Carbon@Pt nanocatalysts show outstanding catalytic activity, stability, and recoverability.

Functional polymer-grafting silica nanoparticles hold great promise in diverse applications such as molecule recognition, drug delivery, and heterogeneous catalysis due to high density and uniform distribution of functional groups and their tunable spatial distance. However, conventional grafting methods from monomers mainly consist of one or more extra surface modification steps and a subsequent surface polymerization step. A monomer protonation-dependent surface polymerization strategy is proposed to achieve one-step uniform surface grafting of cross-linked poly(4-vinylpyridine) (P4VP) onto core-shell Fe3 O4 @SiO2 nanostructures. At an approximate pH, partially protonated 4VP sites in aqueous solution can be strongly adsorbed onto deprotonated silanol groups (SiO- ) onto Fe3 O4 @SiO2 nanospheres to ensure prior polymerization of these protonated 4VP sites exclusively onto Fe3 O4 @SiO2 nanoparticles and subsequent polymerization of other 4VP and divinylbenzene monomers harvested by these protonated 4VP monomers onto Fe3 O4 @SiO2 nanoparticles, thereby achieving direct grafting of cross-linked P4VP macromolecules onto Fe3 O4 @SiO2 nanoparticles.

Gold nanoparticles (AuNPs) have attracted widespread attention for their excellent catalytic activity, as well as their unusual physical and chemical properties. The main challenges come from the agglomeration and time-consuming separation of gold nanoparticles, which have greatly baffled the development and application in liquid phase selective reduction. To solve these problems, we propose the preparation of polyvinyl alcohol(PVA)/poly(acrylic acid)(PAA)/Fe3O4 nanocomposites with loaded AuNPs. The obtained PVA/PAA/Fe3O4 composite membrane by electrospinning demonstrated high structural stability, a large specific surface area, and more active sites, which is conducive to promoting good dispersion of AuNPs on membrane surfaces. The subsequently prepared PVA/PAA/Fe3O4@AuNPs nanocomposites exhibited satisfactory nanostructures, robust thermal stability, and a favorable magnetic response for recycling. In addition, the PVA/PAA/Fe3O4@AuNPs nanocomposites showed a remarkable catalytic capacity in the catalytic reduction of p-nitrophenol and 2-nitroaniline solutions. In addition, the regeneration studies toward p-nitrophenol for different consecutive cycles demonstrate that the as-prepared PVA/PAA/Fe3O4@AuNPs nanocomposites have outstanding stability and recycling in catalytic reduction.

Hierarchical Fe3O4@SiO2@P(4VP-DVB)@Au nanostructures were prepared in which the slightly cross-linked, thin poly(4-vinylpyridine-co-divinylbenzene) (P(4VP-DVB)) shells were constructed onto Fe3O4@SiO2 nanospheres, followed by in situ embedding of gold nanocrystals homogeneously into the P4VP chains. These slightly cross-linked chains, easily swollen by the reactants, make the gold nanocrystals accessible to the reactants, and the thin shell (about 15 nm) reduces the diffusion distance of the reactants to the active gold nanocrystals (about 5 nm), thereby enhancing their catalytic activity and utility. At the same time, confinement of gold nanocrystals within the P4VP shells prevents their migration and coagulation during catalytic transformations. Hence the nanocomposites exhibit high activity (up to 4369.5 h(-1) of turnover frequency (TOF)) and controllable magnetic recyclability without any significant loss of gold species after ten runs of catalysis in the reduction of 4-nitrophenol.

Hierarchical Fe3O4@poly(4-vinylpyridine-co-divinylbenzene)@Au (Fe3O4@P(4-VP-DVB)@Au) nanostructures were fabricated successfully by means of a facile two-step synthesis process. In this study, well-defined core-shell Fe3O4@P(4-VP-DVB) microspheres were first prepared with a simple polymerization method, in which 4-VP was easily polymerized on the surface of Fe3O4 nanoparticles by means of strong hydrogen-bond interactions between -COOH groups on poly(acrylic acid)-modified Fe3O4 nanoparticles and a 4-VP monomer. HAuCl4 was adsorbed on the chains of a P(4-VP) shell and then reduced to Au nanoparticles by NaBH4, which were embedded into the P(4-VP) shell of the composite microspheres to finally form the Fe3O4@P(4-VP-DVB)@Au nanostructures. The obtained Fe3O4@P(4-VP-DVB)@Au catalysts with different Au loadings were applied in the reduction of 4-nitrophenol (4-NP) and exhibited excellent catalytic activity (up to 3025 h(-1) of turnover frequency), facile magnetic separation (up to 31.9 emu g(-1) of specific saturation magnetization), and good durability (over 98 % of conversion of 4-NP after ten runs of recyclable catalysis and almost negligible leaching of Au).