The imine condensation reaction of 5,5′‐(benzo[c][1,2,5]thiadiazole‐4,7‐diyl)diisophthalaldehyde with cyclohexanediamine resulted in a shape‐persistent multifunctional tubular organic cage (MTC1). It exhibits selective fluorescence sensing towards divalent Pd ions with a very low detection limit (38 ppb), suggesting effective complexation between these two species. Subsequent reduction of MTC1 and Pd(OAc)2 with NaBH4 afforded a cage‐supported catalyst with well‐dispersed ultrafine Pd nanoparticles (NPs) in a narrow size distribution (1.9±0.4 nm), denoted as Pd@MTC1‐1/5. Such ultrafine Pd NPs in Pd@MTC1‐1/5, in cooperation with photocatalytically active MTC1, enable efficient sequential reactions involving visible light‐induced aerobic hydroxylation of 4‐nitrophenylboronic acid to 4‐nitrophenol and the following hydride reduction with NaBH4. This is the first example of a multifunctional organic cage capable of sensing, directing nanoparticle growth, and catalyzing sequential reactions. 相似文献
A novel magnetic binary‐metal‐oxide‐coated nanocataly composing of a hollow Fe3O4 core and CeO2‐La2O3 shells with Au nanoparticles encapsulated has been created in this work. The structural features of catalysts were characterized by several techniques, including SEM, TEM, UV‐vis, FTIR, XRD, XPS and TGA analyses. After the coating of CeO2‐La2O3 layer, CeO2‐La2O3/Au/C/Fe3O4 microspheres showed a superior thermal stability and catalytic reactivity compared with a pure CeO2 or La2O3 layer. Accompanied by the burning of carbon layer, the specific surface could be increased by the formation of double‐shelled structure. Besides, the desired samples could be separated by magnet, implying the superior recycle performance. Using the reduction of 4‐nitrophenol by NaBH4 as a model reaction, the microspheres exhibited highly reusability, superior catalytic activity, thermal stability, which are attributed to the unique double‐shelled structure of the support, uniform distribution of Au nanoparticles, the highly thermal stability of CeO2‐La2O3 layer and mixed oxide synergistic effect. As a consequence, the unique nanocatalyst will open a promising way in the fabrication of the double‐shelled hollow binary‐metal‐oxide materials for future research and has great potential in other applications. 相似文献
Polystyrene (PS)/gold (Au) core-shell nanocomposites with tunable size, high stability, and excellent catalytic activity have been synthesized by a facile method that combines the ionic self-assembly with the in situ reduction. The composition and stoichiometry, as well as its morphology and optical properties of these nanocomposites have been examined and verified by various characterization techniques. The size and the coverage of gold nanoparticles (NPs) can be simply tailored by changing the amount of 3-aminopropyltrimethoxysilane (APTES), the functionalization time, the protonation time, and the amount of chloroauric acid (HAuCl4). The continuous red shifts of the localized surface plasmon resonance absorption of the Au NPs on the PS spheres are observed. Importantly, the obtained Au NPs with controllable and uniform size on the surfaces of amino-functionalized PS spheres exhibit excellent size-dependent catalytic properties for the reduction of 4-nitrophenol (4-NP) by NaBH4. 相似文献
Noble metals can be ionized by electrochemical corrosion and transported by electrospray ionization. Mass spectrometry (MS) showed solvated metal ions as the main ionic constituent of the sprayed droplets. Collection of the electrospray plume on a surface yielded noble metal nanoparticles (NPs) under ambient conditions. The NPs were characterized by several techniques. Under typical conditions, capped‐nanoparticle sizes averaged 2.2 nm for gold and 6.5 nm for silver. The gold nanoparticles showed high catalytic activity in the reduction of p‐nitrophenol by NaBH4. Efficient catalysis was also observed by simply directing the spray of solvated Au+ onto the surface of an aqueous p‐nitrophenol/NaBH4 mixture. Organometallic ions were generated by spiking ligands into the spray solvent: for example, CuI bipyridine cations dominated the spray during Cu electrocorrosion in acetonitrile containing bipyridine. This organometallic reagent was shown to be effective in the radical polymerization of styrene. 相似文献
Due to the high activity of Au nanoparticles (NPs) for various reactions, many researchers have tried to develop heterogeneous catalysts in order to prevent irreversible agglomeration of Au NPs. Herein, magnetic graphene oxide modified with polyaniline (PANI) was used as a support for Au NPs that brings together advantages including: uniform dispersal of the catalyst in water,alarge surface area related to the graphene oxide; easy electron transfer in chemical reactions and good attachment of Au NPs to the support associated with PANI; and finally facile recovery in the presence of a magnetic field. Catalytic reduction of different analytes (Congo red, methylene blue, rhodamine B and 4‐nitro phenol) was evaluated in the presence of NaBH4 and the results show high catalytic activity of the catalyst. The catalyst was thoroughly characterized using various methods including FTIR, XRD, XPS, FE‐SEM and HRTEM analyses while its catalytic activity was evaluated via reduction of different analytes. 相似文献
Supported noble bimetallic nanomaterials have attracted great interest owing to their applications in catalysis. Herein, polystyrene‐supported Ag@AgAu bimetallic nanocomposites were synthesized by using a seed‐growth route. The size and degree of coverage of the Ag@AgAu NPs could be controlled by changing the experimental parameters. SEM, TEM, STEM, EDS, and XPS analysis was used to characterize the morphology, structure, and composition of these nanocomposites. We found that the bimetallic nanoparticles on the polystyrene beads had a core–shell structure that was comprised of a Ag core and a AgAu alloy shell. The optical properties of the nanocomposites were also studied by UV/Vis/NIR spectroscopy, which indicated that the localized surface plasmon resonance (LSPR) absorptions of the nanocomposites could be tailored over a large scale from 450 nm to 950 nm. The catalytic properties of the nanocomposites were studied by using the reduction of 4‐nitrophenol (4‐NP) by NaBH4 as a model system. The results showed that the catalytic activity of the polystyrene‐supported Ag@AgAu bimetallic nanocomposites was remarkably superior to that of polystyrene‐supported monometallic Ag and Au nanocomposites with the same nanoparticle size. In addition, an investigation of the recycling catalytic activity of the PS‐Ag@AgAu nanocomposites revealed that the catalyst possessed good stability. The enhancement of the catalytic activity was proposed to be due to the ligand and strain effects between Ag and Au. 相似文献
The integration of metal/metal oxide nanoparticles (NPs) into metal–organic frameworks (MOFs) to form composite materials has attracted great interest due to the broad range of applications. However, to date, it has not been possible to encapsulate metastable NPs with high catalytic activity into MOFs, due to their instability during the preparation process. For the first time, we have successfully developed a template protection–sacrifice (TPS) method to encapsulate metastable NPs such as Cu2O into MOFs. SiO2 was used as both a protective shell for Cu2O nanocubes and a sacrificial template for forming a yolk–shell structure. The obtained Cu2O@ZIF‐8 composite exhibits excellent cycle stability in the catalytic hydrogenation of 4‐nitrophenol with high activity. This is the first report of a Cu2O@MOF‐type composite material. The TPS method provides an efficient strategy for encapsulating unstable active metal/metal oxide NPs into MOFs or maybe other porous materials. 相似文献
An efficient and facile method to synthesise silica nanorattles with multiple noble metal (Au and Pd) cores by a simultaneous etching and growth route has been developed. In this strategy, a dual‐functional alkylaminosilane was adopted to form the middle layer of solid organic–inorganic hybrid solid‐silica spheres (HSSSs), which enabled the selective etching of the middle hybrid layer of the HSSSs and the in situ growth of metal nanoparticles (NPs) inside the cavity in a one‐step hydrothermal reaction. By adjusting the pH values of the reaction system, the metal NPs could be grown exclusively inside the silica nanorattles, resulting in a high atomic utilisation of the noble metals. The size and number of Au cores were tunable by manipulating the initial concentration of HAuCl4. The prepared silica nanorattles with Au cores were successfully applied to the catalytic reduction of 4‐nitrophenol and showed high catalytic activity and cycle stability. Catalysts with multiple gold cores exhibited superior catalytic activity to those with a single gold core, probably because they possess smaller Au cores with greater surface area. 相似文献
Noble metal nanoparticles (NPs) with 1–5 nm diameter obtained from NaHB4 reduction possess high catalytic activity. However, they are rarely used directly. This work presents a facile, versatile, and efficient aerosol‐spray approach to deliver noble‐metal NPs into metal oxide supports, while maintaining the size of the NPs and the ability to easily adjust the loading amount. In comparison with the conventional spray approach, the size of the loaded noble‐metal nanoparticles can be significantly decreased. An investigation of the 4‐nitrophenol hydrogenation reaction catalyzed by these materials suggests that the NPs/oxides catalysts have high activity and good endurance. For 1 % Au/CeO2 and Pd/Al2O3 catalysts, the rate constants reach 2.03 and 1.46 min?1, which is much higher than many other reports with the same noble‐metal loading scale. Besides, the thermal stability of catalysts can be significantly enhanced by modifying the supports. Therefore, this work contributes an efficient method as well as some guidance on how to produce highly active and stable supported noble‐metal catalysts. 相似文献
The loading of noble‐metal nanoparticles (NMNPs) onto various carriers to obtain stable and highly efficient catalysts is currently an important strategy in the development of noble metal (NM)‐based catalytic reactions and their applications. We herein report a nanowire supramolecular assembly constructed from the surfactant‐encapsulating polyoxometalates (SEPs) CTAB‐PW12, which can act as new carriers for NMNPs. In this case, the Ag NPs are loaded onto the SEP nanowire assembly with a narrow size distribution from 5 to 20 nm in diameter; the average size is approximately 10 nm. The Ag NPs on the nanowire assemblies are well stabilized and the over agglomeration of Ag NPs is avoided owing to the existence of well‐arranged polyoxometalate (POM) units in the SEP assembly and the hydrophobic surfactant on the surface of the nanowire assembly. Furthermore, the loading amount of the Ag NPs can be adjusted by controlling the concentration of the AgNO3 aqueous solution. The resultant Ag/CTAB‐PW12 composite materials exhibit high activity and good stability for the catalytic reduction of 4‐nitrophenol (4‐NP) with NaBH4 in isopropanol/H2O solution. The NMNPs‐loaded SEP nanoassembly may represent a new composite catalyst system for application in NM‐based catalysis. 相似文献
Water‐soluble gold nanoparticles (Au NPs) stabilized by a nitrogen‐rich poly(ethylene glycol) (PEG)‐tagged substrate have been prepared by reduction of HAuCl4 with NaBH4 in water at room temperature. The morphology and size of the nanoparticles can be controlled by simply varying the gold/stabilizer ratio. The nanoparticles have been fully characterized by TEM, high‐resolution (HR) TEM, electron diffraction (ED), energy‐dispersive X‐ray spectroscopy (EDS), UV/Vis, powder XRD, and elemental analysis. The material is efficient as a recyclable catalyst for the selective reduction of nitroarenes with NaBH4 to yield the corresponding anilines in water at room temperature. Furthermore, the potential ability of the Au NPs as a refractive index sensor owing to their localized surface plasmon resonance (LSPR) effect has also been assessed. 相似文献
Although catalytic processes mediated by surface plasmon resonance (SPR) excitation have emerged as a new frontier in catalysis, the selectivity of these processes remains poorly understood. Here, the selectivity of the SPR‐mediated oxidation of p‐aminothiophenol (PATP) employing Au NPs as catalysts was controlled by the choice of catalysts (Au or TiO2‐Au NPs) and by the modulation of the charge transfer from UV‐excited TiO2 to Au. When Au NPs were employed as catalyst, the SPR‐mediated oxidation of PATP yielded p,p‐dimercaptobenzene (DMAB). When TiO2‐Au NPs were employed as catalysts under both UV illumination and SPR excitation, p‐nitrophenol (PNTP) was formed from PATP in a single step. Interestingly, PNTP molecules were further reduced to DMAB after the UV illumination was removed. Our data show that control over charge‐transfer processes may play an important role to tune activity, product formation, and selectivity in SPR‐mediated catalytic processes. 相似文献
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). 相似文献
Gold nanoparticle (Au‐NPs)‐Titanium oxide nanotube (TiO2‐NTs) electrodes are prepared by using galvanic deposition of gold nanoparticles on TiO2‐NTs electrodes as support. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy results indicate that nanotubular TiO2 layers consist of individual tubes of about 60–90 nm diameters and gold nanoparticles are well‐dispersed on the surface of TiO2‐NTs support. The electrooxidation of hydroquinone of Au‐NPs/TiO2‐NTs electrodes is investigated by different electrochemical methods. Au‐NPs/TiO2‐NTs electrode can be used repeatedly and exhibits stable electrocatalytic activity for the hydroquinone oxidation. Also, determination of hydroquinone in skin cream using this electrode was evaluated. Results were found to be satisfactory and no matrix effects are observed during the determination of hydroquinone content of the “skin cream” samples. 相似文献
In this article, a detailed electrochemical study of a novel 6‐ferrocenylhexanethiol (HS(CH2)6Fc) self‐assembled multiwalled carbon nanotubes‐Au nanoparticles (MWNTs/Au NPs) composite film was demonstrated. MWNTs/Au NPs were prepared by one‐step in situ synthesis using linear polyethyleneimine (PEI) as bifunctionalizing agent. HS(CH2)6Fc, which acted as the redox mediator, was self‐assembled to MWNTs/Au NPs via Au‐S bond. Transmission electron microscopy (TEM), energy‐dispersive X‐ray analysis (EDX), Fourier transformed infrared absorption spectroscopy (FT‐IR), UV‐visible absorption spectroscopy, and cyclic voltammetry were used to characterize the properties of the MWNTs/Au NPs/HS(CH2)6Fc nanocomposite. The preparation of the nanocomposite was very simple and effectively prevented the leakage of the HS(CH2)6Fc mediator during measurements. The electrooxidation of AA could be catalyzed by Fc/Fc+ couple as a mediator and had a higher electrochemical response due to the unique performance of MWNTs/Au NPs. The nanocomposite modified electrode exhibited excellent catalytic efficiency, high sensitivity, good stability, fast response (within 3 s) and low detection limit toward the oxidation of AA at a lower potential. 相似文献
Silver nanoparticles supported on polyhedral oligomeric silsesquioxane (OA‐POSS) nanocrosslinked poly (ethylene glycol)‐based hydrogels (PEG600‐POSS/Ag NPs) as novel nanohybrid catalysts were synthesized for the first time. The as‐prepared nanohybrid hydrogels were fully characterized by FT‐IR, SEM, EDX, XRD, TEM and TGA. PEG600‐POSS/Ag NPs exhibited excellent catalytic performance for the reduction of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) in water at room temperature in the presence of borohydride. 相似文献
The ability to capture, store, and use CO2 is important for remediating greenhouse‐gas emissions and combatting global warming. Herein, Au nanoparticles (Au‐NPs) are synthesized for effective electrochemical CO2 reduction and syngas production, using polyethylenimine (PEI) as a ligand molecule. The PEI‐assisted synthesis provides uniformly sized 3‐nm Au NPs, whereas larger irregularly shaped NPs are formed in the absence of PEI in the synthesis solution. The Au‐NPs synthesized with PEI (PEI?Au/C, average PEI Mw=2000) exhibit improved CO2 reduction activities compared to Au‐NPs formed in the absence of PEI (bare Au NPs/C). PEI?Au/C displays a 34 % higher activity toward CO2 reduction than bare Au NPs/C; for example, PEI?Au/C exhibits a CO partial current density (jCO) of 28.6 mA cm?2 at ?1.13 VRHE, while the value for bare Au NPs/C is 21.7 mA cm?2; the enhanced jCO is mainly due to the larger surface area of PEI?Au/C. Furthermore, the PEI?Au/C electrode exhibits stable performance over 64 h, with an hourly current degradation rate of 0.25 %. The developed PEI?Au/C is employed in a CO2‐reduction device coupled with an IrO2 water‐oxidation catalyst and a proton‐conducting perfluorinated membrane to form a PEI?Au/C|Nafion|IrO2 membrane‐electrode assembly. The device using PEI?Au/C as the CO2‐reduction catalyst exhibits a jCO of 4.47 mA/cm2 at 2.0 Vcell. Importantly, the resulted PEI?Au/C is appropriate for efficient syngas production with a CO ratio of around 30–50 %. 相似文献
Gold–nickel nanoparticles (NPs) of 3–4 nm diameter embedded in silica nanospheres of around 15 nm have been prepared by using [Au(en)2Cl3] and [Ni(NH3)6Cl2] as precursors in a NP‐5/cyclohexane reversed‐micelle system, and by in situ reduction in an aqueous solution of NaBH4/NH3BH3. Compared with monometallic Au@SiO2 and Ni@SiO2, the as‐synthesized Au–Ni@SiO2 catalyst shows higher catalytic activity and better durability in the hydrolysis of ammonia borane, generating a nearly stoichiometric amount of hydrogen. During the generation of H2, the synergy effect between gold and nickel is apparent: The nickel species stabilizes the gold NPs and the existence of gold helps to improve the catalytic activity and durability of the nickel NPs. 相似文献
As a typical photocatalyst for CO2 reduction, practical applications of TiO2 still suffer from low photocatalytic efficiency and limited visible‐light absorption. Herein, a novel Au‐nanoparticle (NP)‐decorated ordered mesoporous TiO2 (OMT) composite (OMT‐Au) was successfully fabricated, in which Au NPs were uniformly dispersed on the OMT. Due to the surface plasmon resonance (SPR) effect derived from the excited Au NPs, the TiO2 shows high photocatalytic performance for CO2 reduction under visible light. The ordered mesoporous TiO2 exhibits superior material and structure, with a high surface area that offers more catalytically active sites. More importantly, the three‐dimensional transport channels ensure the smooth flow of gas molecules, highly efficient CO2 adsorption, and the fast and steady transmission of hot electrons excited from the Au NPs, which lead to a further improvement in the photocatalytic performance. These results highlight the possibility of improving the photocatalysis for CO2 reduction under visible light by constructing OMT‐based Au‐SPR‐induced photocatalysts. 相似文献
Multifunctional nanostructures : By using 3‐aminopropyltrimethoxysilane as a linker, Au nanoparticles (NPs), Au shells, flowerlike Au/Pt hybrid NPs, and Ag or Au/Ag core/shell NPs could be supported on the surface of superparamagnetic Fe3O4 spheres to construct hybrid nanostructures that display near‐IR absorption, high catalytic activity towards an electron‐transfer reaction, or excellent surface‐enhanced Raman scattering activity. The picture shows SEM images of Fe3O4 spheres coated with Au shells (top) and with Au/Pt hybrid NPs (bottom).