Au@Fe3O4@PANI hybrid shells with controllable polyaniline (PANI) coatings as advanced supported catalysts have been fabricated. Specifically, Fe3O4 and Au nanoparticles were assembled on SiO2 templates, followed by conducting polymer PANI coating, leading to the formation of Au@Fe3O4@PANI hybrid shells after the template removal. The resultant supported Au nanocatalysts not only maintain hollow structures but also possess high saturation magnetization (65.46 emu/g). Catalytic tests toward the reduction of 4-nitrophenol in the presence of NaBH4 indicate that PANI and Fe3O4 not only endow high stability and recyclability but also can largely improve the catalytic activity of Au nanoparticles because of their synergetic effects. It is believed that Fe3O4@PANI hybrid shells can be regarded as multifunctional supports for noble metal nanocatalysts with a remarkably improved catalytic performance.

Multifunctional nanocatalysts of Au@Fe3O4/m-SiO2 yolk@shell hybrids had been developed through a template-assisted synthesis, where Fe3O4 nanoparticles (∼12 nm) and m-SiO2 shells were sequentially assembled on surfaces of Au/SiO2 core/shell templates, followed by selective etching of the inner SiO2 cores, leading to the formation of Au@Fe3O4/m-SiO2 yolk@shell hybrids. The Fe3O4 nanoparticles were implanted in the inner surfaces of m-SiO2 shells with partially exposed surfaces to the inner cavity. The novel design not only ensures a high surface area (540.0 m2/g) and saturation magnetization (48.6 emu/g) of the hybrids but also enables interaction between Au and Fe3O4 nanoparticles. Catalytic tests toward the reduction of 4-nitrophenol in the presence of NaBH4 indicated that Au@Fe3O4/m-SiO2 yolk@shell nanocatalysts not only showed high stability and recyclability but also maintained improved catalytic activity as a result of the synergetic effect resulting from Au and Fe3O4 interactions.

Mesoporous C, N-codoped TiO2 (C/N-TiO2) hybrid shells incorporated with graphite carbon were synthesized using polystyrene spheres as templates, followed by polyaniline (PANI) and TiO2 coating, and then post-treatments of etching and calcination, where PANI functioned as both C and N doping sources and supplied the graphite carbon. Compared with pure TiO2 and C-doped TiO2 (C-TiO2) hybrid shells, C/N-TiO2 hybrid shells exhibited enhanced photocatalytic activity in the degradation of organic dyes and H2 production under visible light irradiation, which could be attributed to the enhanced visible light absorption and charge separation efficiency associated with the codoped-C and N and the presence of graphite carbon. It is believed that the strategy presented here will provide a promising route for the construction of other C/N-semiconductor hybrid shells for broader applications.

Poly(o-aminothiophenol) (PATP)-stabilized Pd nanoparticles with Pd nanoparticles embedded in a polymer matrix have been obtained through a facile one-step route by mixing o-aminothiophenol monomer and Pd(NO3)2 in an acidic aqueous solution without additional template or surfactant. The redox reaction between o-aminothiophenol and Pd(NO3)2 leads to the simultaneous formation of a PATP polymer and Pd nanoparticles. The PATP-stabilized Pd nanoparticles have been characterized by TEM, FTIR, XRD, ICP-MS and XPS. Catalytic results showed that PATP-stabilized Pd nanoparticles were highly stable and active catalysts for Suzuki cross-coupling reactions, where high yields could be achieved with arylboronic acid and aryl halides bearing a variety of substituents.

Multifunctional magnetic adsorbents containing MnO2 and polyaniline (PANI) with optimized adsorption properties toward heavy metal ions have been developed. In particular, Fe3O4 spheres were chosen as the magnetic core, followed by PANI and MnO2 coating, realizing the formation of Fe3O4/PANI/MnO2 core–shell hybrids. The as-synthesized Fe3O4/PANI/MnO2 core–shell hybrids showed a hierarchical structure with a large surface area and high magnetic saturation value. In comparison with Fe3O4/PANI and Fe3O4/MnO2 core–shell hybrids, Fe3O4/PANI/MnO2 core–shell hybrids displayed the highest adsorption capacity toward heavy metal ions (including Cd(II), Zn(II), Pb(II) and Cu(II)), thanks to the integrated physical and chemical adsorption behaviors resulting from MnO2 inorganic oxide and the PANI polymer. The developed multifunctional Fe3O4/PANI/MnO2 adsorbents synthesized by a facile and economic route are believed to show high potential in environmental remediation for heavy metal removal.

Recent research has established growing research interest in subject of conducting polymer (CP)-based hybrids due to their novel properties and potential applications in diverse fields. The incorporation of CPs with other materials can produce new hybrids showing distinct properties that are not observed in the individual components. Among numerous CP-based hybrids, CP and noble metal nanoparticle (NMNP) hybrids have attracted the most intensive attention in the past few years. The numerous functional groups and tunable chemical structures through redox in the main chains of CPs, make them as ideal supporters for NMNPs. The compact interactions and synergistic effects between CPs and NMNPs contribute to the increased performances in diverse applications. The purpose of this review focuses on state-of-the-art synthetic strategies, mechanisms and applications involved in CP-NMNP hybrids. Herein, CPs used are polyaniline (PANI), polypyrrole (PPY), polythiophene (PTH) and their derivatives; while NMNPs mainly refer to Au, Ag, Pt and Pd nanoparticles. Specifically, the topics include: 1) strategies and mechanisms involved in the synthesis of CP-NMNP hybrids; 2) potential applications of CP-NMNP hybrids in fields of catalysis, sensor, surface-enhanced Raman scattering (SERS), device and others. Finally, prospects and challenges for making advanced CP-NMNP hybrids are discussed.

We present a proof-of-concept demonstration of surface cavities for incorporation of noble metal nanoparticles with remarkable catalytic performance involved in liquid phase catalytic reactions. Mesoporous Ni(OH)2 (m-Ni(OH)2) nanowires with surface cavities have been chosen as multifunctional supports for Au nanoparticles with a well controlled size (2 nm) and high dispersity through a facile room-temperature in situ reduction process without any additional stabilizer. In addition to immobilizing Au nanoparticles, the cavities also can prevent aggregation of neighboring noble metal nanoparticles, thus ensuring high stability/recyclability for Au/m-Ni(OH)2 supported nanocatalysts. The results from catalytic reactions involved in the reduction of 4-nitrophenol in the presence of NaBH4 using Au/m-Ni(OH)2 as the catalyst demonstrated its remarkable catalytic performance due to its nanoscale configuration.

Mesoporous hybrid shells of carbonized polyaniline (CPANI)/Mn2O3 with well-controlled diameter and high surface area have been synthesized through surface protected calcination processes. Originating from polystyrene template, PANI, MnO2, and SiO2 were sequentially loaded, followed by template removal and calcination, resulting in the desired CPANI/Mn2O3 hybrid shells. The introduction of SiO2 shell was established to play the determining role in maintaining the configuration during calcination process under high temperature. The CPANI/Mn2O3 hybrid shells showed outstanding electrocatalytic activity toward oxygen reduction reaction (ORR), with the onset potential at +0.974 V (versus RHE), the specific current at 60.8 mA/mg, and an overall quasi 4-electron transfer, which are comparable to those of the benchmark Pt/C. The remarkable ORR performance was attributed to the high specific surface area, the surface oxidation state of Mn, and composition-codependent behavior.Keywords: carbonization; hollow spheres; Mn2O3; oxygen reduction reaction; polyaniline

Carbon-incorporated mesoporous NiO/TiO2 (NiO/TiO2/C) hybrid shells as low-cost and highly efficient visible light photocatalysts have been developed. The NiO/TiO2/C hybrid shells were synthesized by choosing polystyrene nanospheres as templates, followed by TiO2 and NiO coating, and finally the calcination post-treatment to carbonize PS with the aid of metal oxides. Polystyrene nanospheres serve dual purposes as both a template to ensure the hollow structure and the electrically conductive graphite carbon source. Evaluation of their photocatalytic activity by organic pollutes (rhodamine B, methylene blue, and phenol) degradation and H2 production under visible light demonstrated the superior photocatalytic performance, thanks to the enhanced visible-light absorption and exciton separation associated with the incorporation of electrically conductive graphite carbon.Keywords: carbon; mesoporous shells; NiO; photocatalyst; TiO2

In order to maximize supercapacitor performances, it is essential to engineer the electrode architecture with shortened ion-diffusion paths and high content of pseudocapacitive sites. By incorporating redox-active species into low-dimensional carbon materials, both the specific capacitances and rate capabilities can be improved. In this study, a self-sustaining, flexible mat consisting of nitrogen-enriched carbon fiber (NCF) network was successfully produced through the co-electrospinning of a polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP)/SiO2 blended solution, followed by pyrolysis and SiO2 removal processes. Despite its low surface area (<60 m2/g), the NCF exhibits high nitrogen content (17.3 wt%) and interconnected meso-macroporous nanostructure, resulting in high pseudocapacitance (242 F/g at 0.2 A/g), fast rate capability, and excellent cycling performance (99% of initial capacitance after 5000 cycles). The electrical double-layer capacitance and pseudocapacitance can be easily decoupled. The binder-free NCF based symmetric supercapacitor demonstrates a purely capacitive responses and high rate handling. We attribute the excellent electrochemical performances to the good conductivity and shortened ion diffusion paths of carbon fiber backbone, and pseudocapacitive edge-concentrated nitrogen species.

A facile hydrothermal process is developed for the synthesis of NiCo2S4/reduced graphene oxide (RGO) hybrid and NiCo2S4 hollow spheres. The morphology and microstructure are characterized by powder X-ray diffraction (XRD), Raman spectra, transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), and energy dispersive spectrometry (EDS) mapping. NiCo2S4 nanoparticles with the diameter of about 20–30 nm were in-situ grown on RGO sheets. NiCo2S4 hollow spheres were obtained with the diameter of about 300–400 nm and the width of shell in the range of 30–40 nm in the absence of graphene oxide (GO). GO as a substrate material can offer abundant active sites for nucleation of NiCo2S4 and can be reduced to RGO, providing excellent electron transfer path and high conduction, which enable the fast surface redox reaction. Supercapacitor based on NiCo2S4/RGO hybrid shows a high specific capacitance of 1804.7 F/g at a current density of 0.5 A/g. Due to the high capacitive performance of NiCo2S4/RGO hybrid, the NiCo2S4/RGO//AC asymmetric supercapacitor (ASC) possesses an extended voltage window of 1.5 V, high energy density of 24.4 W h/kg at a power density of 750 W/kg in 2 mol/L KOH electrolyte. NiCo2S4/RGO hybrid can serve as a promising electrode material for high performance supercapacitors.A facile hydrothermal route was developed to growth of NiCo2S4 nanoparticles on the RGO sheets with excellent capacitive performance for supercapacitors.

Three metallosurfactants Cn–Cu–Cn (n = 8, 12, 16) were synthesized via two-step in this paper. All of these surfactants were characterized by ultimate analysis, 1H NMR, FT-IR, LC-MS, elemental analysis. In addition, the three surfactants can form vesicles under sonication at a relatively high concentration, and their aggregation behavior and the stability of Cn–Cu–Cn vesicles were investigated by surface tension, electrical conductivity, FT-IR, negative staining–TEM. Results showed that C12–Cu–C12 vesicles with average size of ∼60 nm had good stability over inorganic salt, temperature, and aging time. Doxorubicin hydrochloride was incorporated into C12–Cu–C12 vesicles with a remarkably high efficiency of above 70 %, and the delivery system has obvious sustained release effect.

The NiCo2S4 hollow spheres were prepared by an oil/water (O/W) interface-assisted hydrothermal process using CoCl2 · 6H2O, NiCl2 · 6H2O, ethanediamine, and carbon disulfide (CS2) as raw materials. Powder X-ray diffraction (XRD), UV–Vis absorption spectrum, transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), energy dispersive spectrometry (EDS), N2 adsorption-desorption isotherm, and X-ray photoelectron spectroscopy (XPS) were measured to characterize the morphology and microstructure of the prepared NiCo2S4 hollow spheres. When applied as the electrode material for supercapacitor, the NiCo2S4 hollow spheres show outstanding performances. The specific capacitance of the NiCo2S4 hollow spheres is 1753.2 F/g at a current density of 1 A/g. Of the capacity, 77.8 % were retained when the current density increased from 1 to 10 A/g. At a current density of 3 A/g, the specific capacitance of the NiCo2S4 hollow sphere electrode is about 1350.5 F/g after suffering 1000 continuous cycles. The supercapacitor possesses high energy density of 39.0 Wh/kg at a power density of 200 W/kg. The as-prepared NiCo2S4 hollow sphere electrode exhibits high specific capacitance, rate capacity, energy density, and good cycle stability, making it a promising electrode material for high-performance supercapacitors.

The α-Ni(OH)2 nanowires (α-Ni(OH)2 NWs) and nanoparticles (α-Ni(OH)2 NPs) were grown on reduced graphene oxide (RGO) sheets by adjusting the reduction degree of the substrates. The α-Ni(OH)2 NWs/RGO composite was achieved by using graphene oxide (GO) as the substrate. In contrast, the α-Ni(OH)2 NPs/RGO composite was obtained when RGO was applied as the support. The difference in morphology can be attributed to the fact that the hydrophilic function of GO is larger than that of RGO, and sp2 carbon atom concentration in α-Ni(OH)2 NPs/RGO is higher than that in α-Ni(OH)2 NWs/RGO. When α-Ni(OH)2 NWs/RGO and α-Ni(OH)2 NPs/RGO composites were used as electrode materials for supercapacitors, the α-Ni(OH)2 NPs/RGO exhibits superior electrochemical performance than α-Ni(OH)2 NWs/RGO, which is attributed to the fact that the specific surface area, conductivity, and sp2 carbon atom concentration of α-Ni(OH)2 NPs/RGO are larger than those of α-Ni(OH)2 NWs/RGO. The α-Ni(OH)2 NPs/RGO composite is a promising candidate as electrode material for high performance supercapacitor.

Hydrophilic Fe3O4–Au Janus nanoparticles have been synthesized through a facile aqueous solution-based Fe3O4 seed-mediated chemical reduction route, where Au nanoparticles can be in situ formed on surfaces of PVP-modified Fe3O4 nanoparticles by adopting the well-known citrate reduction route. The diameter of Au nanoparticles can be controllably tuned in the range of 3–12 nm by simply changing the initial molar ratio between sodium citrate and auric acid. The as-fabricated hydrophilic Fe3O4–Au Janus nanoparticles have shown excellent catalytic performance with high catalytic activity and recyclability due to the synergetic effect between Au and Fe3O4 nanoparticles.

Nanostructured hybrid shells of r-GO/AuNP/m-TiO2 were synthesized using SiO2 spheres as templates, followed by graphene oxide (GO) and Au nanoparticle (AuNP) deposition and TiO2 coating, and then post-treatments of template removal and calcination. Evaluation of their photocatalytic activity by degradation of Rhodamine B (RhB) under the irradiation of UV, visible light, and simulated daylight demonstrated the superior photocatalytic performance of the sandwich-like hollow hybrid shells, which could be attributed to the porous nature of the hybrid shells and the enhanced charge separation and visible-light absorption of r-GO and AuNPs.Keywords: Au nanoparticle; graphene; hybrid shells; mesoporous; photocatalyst; TiO2

By exploiting a facile and controllable anion exchange strategy, mesoporous α-Ni(OH)2 nanowires with multinanocavities in surfaces have been successfully developed. The novel nanoscale morphology has been proven to be responsible for their excellent capacitive performances.

A highly viscoelastic fluid formed by the ionic liquid-type surfactant 1-hexadecyl-3-nonyl imidazolium bromide ([C16imC9]Br) in water in the absence of any additive was studied. The phase behavior and morphology of aggregates were studied by a combination of rheological techniques, small-angle X-ray scattering (SAXS), cryo-etch-scanning electron microscopy (cryo-etch-SEM) and freeze-fractured transmission electron microscopy (FF-TEM). [C16imC9]Br aqueous solutions showed interesting rheological behavior as a function of both concentration and temperature, which invoked a transition between wormlike micelles and hydrogels. With the increase in [C16imC9]Br concentration, the aqueous solution could form viscoelastic wormlike micelles (50–80 mM), hydrogels (90–110 mM) and wormlike micelles (120–180 mM). As the temperature increased, the hydrogels (90–110 mM) could also transit to wormlike micelles. The unusual phase transition between wormlike micelles and elastic hydrogels was postulated to be the change of the average micellar length.

A novel fabrication method for colloidal crystals has been proposed for the first time in this research. In this method, a suspension droplet containing colloidal particles was first spread onto a glass substrate placed in an ethanol vapor environment, and then the droplet was extracted from its center. In that case, the contact angle of the droplet reduced and the contact line receded toward the center, during which the colloidal particles self-assembled and immobilized forming a 2D colloidal crystal film on the substrate upon drying the liquid film. Alternately spreading and drying of suspension films could construct fine multi-layers of colloidal crystals, while the ethanol fraction in the suspension would be used to control roughly but rapidly the layer numbers of colloidal crystals. It was also found that the photonic properties of resultant colloidal crystal films were elevated by increasing their thickness.

Ni7S6 hollow spheres with mesoporous shells were successfully synthesized by a novel and facile hydrothermal process without any template or surfactant using nickel chloride hexahydrate and sodium thioglycolate as starting materials. The morphology and microstructure of the samples were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), energy dispersive spectroscopy (EDS), and N2 adsorption–desorption isotherm measurement. A bubble template-based ripening process was proposed for the formation of Ni7S6 hollow spheres with mesoporous shells. When applied as electrode materials for supercapacitors, the as-prepared Ni7S6 hollow spheres with mesoporous shells exhibited tremendous pseudocapacitance of 2329.5 F g−1 at 2 mV s−1 and 2283.2 F g−1 at 1 A g−1. A capacity retention of 97.1% was achieved even after 1000 cycles. The maximum energy density is 50.7 W h kg−1 at a current density of 1 A g−1. The excellent capacitive performance is attributed to their unique hollow structure with mesoporous shells providing fast ion and electron transfer, and high electronic conduction. These results suggest that the Ni7S6 hollow spheres with mesoporous shells are highly promising candidates for supercapacitor electrodes.

A nanoplate-based tower-like hierarchical architecture of aniline oligomers has been fabricated via the oxidation polymerization of aniline in NaOH aqueous solution at 35 °C, with ammonium peroxydisulfate as an oxidant. Experimental results indicated that the concentrations of NaOH and aniline, and temperature played important roles in the formation or the uniformity of such oligomer micro-towers. The offspring obtained at different reaction stages has been characterized by FESEM, FTIR and UV-vis techniques to gain insight into the morphological evolvement and chemical structure development of the tower-like product. Based on the results of these characterization techniques, the possible formation mechanism for the oligomer microtower was proposed. In addition, the adsorption properties of the aniline oligomer microtowers toward heavy metal ions (Cu(II) et al.) in water, as well as the sorption isotherms and kinetics were investigated carefully.

A novel oligoaniline with hierarchical flower-on-leaf microstructures has been fabricated via the oxidation of aniline in EtOH/water (3:7, v/v) mixtures. The as-prepared oligoaniline was characterized using the UV-vis, FTIR, 1H NMR and MALDI-TOF MS techniques for analyzing the chemical structures. A possible formation mechanism has been proposed to interpret the growth of such hierarchical microstructures, and several inter-molecular interactions were suggested to drive the supermolecular assembly. The effect of the ethanol content in the medium on the morphology of the product was discussed, and the functions of the ethanol in the synthesis were explored. Besides, the adsorption properties of the as-prepared product toward organic dyes (crystal violet etc.) in water, as well as the sorption isotherms and kinetics, have been investigated carefully. The realizable sorption capacity for crystal violet was found to be 181 mg g−1 which was higher than those of most of the sorbent.

The search for functional supramolecular aggregations with different structure has attracted interest of chemists because they have the potential in industrial and technological application. Hydrophobic interaction has great influence on the formation of these aggregations, such as hexagonal liquid crystals, wormlike micelles, hydrogels, etc. So a systematical investigation was done to investigate the influence of alkyl chain length of surfactants on the aggregation behavior in water. The aggregation behavior of 1-hexadecyl-3-alkyl imidazolium bromide and water has been systematically investigated. These ionic liquid surfactants are denoted as C16–Cn (n = 2, 3, 4, 6, 8, 9, 10, 12, 14, 16). The rheological behavior and microstructure were characterized via a combination of rheology, cryo-etch scanning electron microscopy, polarization optical microscopy, and X-ray crystallography. The alkyl chain has great influence on the formation of surfactant aggregates in water at the molecular level. With increasing alkyl chain length, different aggregates, such as hexagonal liquid crystals, wormlike micelles, and hydrogels can be fabricated: C16–C2 aqueous solution only forms hexagonal liquid crystal; C16–C3 aqueous solution forms wormlike micelle and hexagonal liquid crystal; C16–C4, C16–C6 and C16–C8 aqueous solutions only form wormlike micelle; C16–C9 aqueous solution experiences a transition between wormlike micelle and hydrogel; C16–C10, C16–C12, C16–C14 and C16–C16 only form hydrogel. The mechanism of the transition of different aggregation with increasing alkyl chain length was also proposed.

Fe3O4/polyaniline (PANI)/Pd nanoparticles as supported catalysts with high recyclability and durability have been developed. Fe3O4/PANI as reactive magnetic supporters have been firstly synthesized, followed by the addition of PdCl2 to initial redox reaction between PANI and Pd ions to form Pd nanoparticles on surfaces of Fe3O4/PANI cores, leading to the formation of Fe3O4/PANI/Pd nanoparticle-supported catalysts. The structures of Fe3O4/PANI/Pd nanoparticle-supported catalysts have been confirmed by TEM, energy dispersive X-ray spectroscopic (EDS) elemental mapping analysis, and XPS, and the formation mechanisms have been revealed by FTIR spectra. The catalytic activity of Fe3O4/PANI/Pd nanoparticle-supported catalysts involved in liquid phase reactions have been established through the model catalysis reaction involving reduction of nitroaromatic compounds by NaBH4. Furthermore, their high stability and reactivity for Suzuki cross-coupling reactions of aryl bromides with phenylboronic acids have also been investigated.

Yolk@shell nanostructures of Au@r-GO/TiO2 with mesoporous shells were prepared by a sol–gel coating process sequentially with GO and TiO2 on Au/SiO2 core/shell spheres, followed by calcination and template removal, where the silica interlayer acts as a template not only to produce the void space but also to promote the coating of the r-GO and TiO2 layer. The evaluation of visible light photocatalytic activities in dye decomposition and water-splitting H2 production demonstrated their superior photocatalytic performance, which indicates their potential as powerful photocatalysts.

The development of catalysts with improved stability and efficiency is increasingly important for both economic and environmental reasons. Herein, Fe3O4/PANI/m-SiO2 hybrid core/shell spheres have been successfully synthesized as novel and robust reactive catalyst supports to produce highly stable and recyclable noble metal nanocatalysts. Specifically, Fe3O4/PANI/m-SiO2 hybrid core/shell spheres were firstly fabricated, followed by the addition of noble metal ions to initiate the redox reaction between PANI and noble metal ions to yield noble metal nanoparticles on PANI surfaces. The Fe3O4 core and mesoporous SiO2 shell of the Fe3O4/PANI/m-SiO2 hybrid supports can significantly improve the recycling efficiency and greatly reinforce the stability of catalyst nanoparticles against coagulation, respectively. Various parameters, such as the thickness of the PANI coating and the etching time of the SiO2 dense shell, were considered in optimizing the catalyst supports. Furthermore, the high stability and recyclability of Fe3O4/PANI/Au/m-SiO2 hybrid catalysts involved in liquid phase reactions were established, implying their potential applications in the field of catalysis.

Novel Au–polymer hollow hybrids having a single Au nanoparticle encapsulated in each porous polymer shell with superior catalytic efficiency and recyclability have been demonstrated.

By exploiting a facile and controllable anion exchange strategy, mesoporous α-Ni(OH)2 nanowires with multinanocavities in surfaces have been successfully developed. The novel nanoscale morphology has been proven to be responsible for their excellent capacitive performances.

We present a proof-of-concept demonstration of surface cavities for incorporation of noble metal nanoparticles with remarkable catalytic performance involved in liquid phase catalytic reactions. Mesoporous Ni(OH)2 (m-Ni(OH)2) nanowires with surface cavities have been chosen as multifunctional supports for Au nanoparticles with a well controlled size (2 nm) and high dispersity through a facile room-temperature in situ reduction process without any additional stabilizer. In addition to immobilizing Au nanoparticles, the cavities also can prevent aggregation of neighboring noble metal nanoparticles, thus ensuring high stability/recyclability for Au/m-Ni(OH)2 supported nanocatalysts. The results from catalytic reactions involved in the reduction of 4-nitrophenol in the presence of NaBH4 using Au/m-Ni(OH)2 as the catalyst demonstrated its remarkable catalytic performance due to its nanoscale configuration.

Novel Au–polymer hollow hybrids having a single Au nanoparticle encapsulated in each porous polymer shell with superior catalytic efficiency and recyclability have been demonstrated.

The development of catalysts with improved stability and efficiency is increasingly important for both economic and environmental reasons. Herein, Fe3O4/PANI/m-SiO2 hybrid core/shell spheres have been successfully synthesized as novel and robust reactive catalyst supports to produce highly stable and recyclable noble metal nanocatalysts. Specifically, Fe3O4/PANI/m-SiO2 hybrid core/shell spheres were firstly fabricated, followed by the addition of noble metal ions to initiate the redox reaction between PANI and noble metal ions to yield noble metal nanoparticles on PANI surfaces. The Fe3O4 core and mesoporous SiO2 shell of the Fe3O4/PANI/m-SiO2 hybrid supports can significantly improve the recycling efficiency and greatly reinforce the stability of catalyst nanoparticles against coagulation, respectively. Various parameters, such as the thickness of the PANI coating and the etching time of the SiO2 dense shell, were considered in optimizing the catalyst supports. Furthermore, the high stability and recyclability of Fe3O4/PANI/Au/m-SiO2 hybrid catalysts involved in liquid phase reactions were established, implying their potential applications in the field of catalysis.

Multifunctional magnetic adsorbents containing MnO2 and polyaniline (PANI) with optimized adsorption properties toward heavy metal ions have been developed. In particular, Fe3O4 spheres were chosen as the magnetic core, followed by PANI and MnO2 coating, realizing the formation of Fe3O4/PANI/MnO2 core–shell hybrids. The as-synthesized Fe3O4/PANI/MnO2 core–shell hybrids showed a hierarchical structure with a large surface area and high magnetic saturation value. In comparison with Fe3O4/PANI and Fe3O4/MnO2 core–shell hybrids, Fe3O4/PANI/MnO2 core–shell hybrids displayed the highest adsorption capacity toward heavy metal ions (including Cd(II), Zn(II), Pb(II) and Cu(II)), thanks to the integrated physical and chemical adsorption behaviors resulting from MnO2 inorganic oxide and the PANI polymer. The developed multifunctional Fe3O4/PANI/MnO2 adsorbents synthesized by a facile and economic route are believed to show high potential in environmental remediation for heavy metal removal.