Mesoporous Au/TiO2 Nanocomposite Microspheres for Visible‐Light Photocatalysis

Mesoporous Au/TiO₂ nanocomposite microspheres have been synthesized by using a microemulsion‐based bottom‐up self‐assembly (EBS) process starting from monodisperse gold and titania nanocrystals as building blocks. The microspheres had large surface areas (above 270 m² g^?1) and open mesopores (about 5 nm), which led to the adsorption‐driven concentration of organic molecules in the vicinity of the microspheres. Au nanoparticles, which were stably confined within the microspheres, enhanced the absorption over the broad UV/Vis/NIR spectroscopic range, owing to their strong surface plasmon resonance (SPR); as a result, the Au nanoparticles promoted the visible‐light photo‐induced degradation of organic compounds.     

Au Nanoparticles Loaded on Hollow TiO2 Microspheres with (001) Exposed Facets: a Strategy for Promoting Photocatalytic Performance

Au nanoparticles loaded TiO₂ hollow microspheres with exposed (001) facets(Au-HTFs) were synthesized through template-free hydrothermal process combined with a chemical reduction role. Au-HTFs displayed excellent photocatalytic activity in catalyzing oxidization reaction in organic pollutant system, which originates from the synergistic effect of the reactive (001) facets and Au nanoparticles with a wide range of absorption in visible region based on localized surface plasmon resonance effect. The unique synergistic effect could largely increase the photocatalytic performance resulting from the improvements of both the visible light aborption and the recombination of electron-hole pairs. Our findings revealed that among Au-HTFs with different Au loading percentages, Au-HTFs with 2%(mass fraction) Au loading possessed the superior photocatalytic activity.     

Synthesis and adsorption properties of gold nanoparticles within pores of surface‐functional porous polymer microspheres

Mesoporous polymer microspheres with gold (Au) nanoparticles inside their pores were prepared considering their surface functionality and porosity. The Au/polymer composite microspheres prepared were characterized by transmission electron microscope (TEM), X‐ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) techniques. The results showed that the adsorption of Au nanoparticles could be increased by imparting the pore structure and surface‐functional groups into the supporting polymer microspheres (in this study, poly (ethylene glycol dimethacrylate‐co‐acrylonitrile) and poly (EGDMA‐co‐AN) system). Above all, from this study, it was established that the porosity of the polymer microspheres is the most important factor that determines the distribution and adsorption amount of face‐centered cubic (fcc) Au nanoparticles in the final products. Our study showed that the continuous adsorption of Au nanoparticles with the aid of the large surface area and surface interaction sites formed more favorably the Au/polymer composite microspheres. The BET measurements of Au/poly(EGDMA‐co‐AN) composite microspheres reveals that the adsorption of Au nanoparticles into the pores kept the pore structure intact and made it more porous. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5627–5635, 2004     

SYNTHESIS OF POLY(DIVINYLBENZENE-co-ACRYLIC ACID) HOLLOW MICROSPHERES WITH GOLD NANOPARTICLES ON THE INTERIOR SURFACE

Poly(divinylbenzene-co-acrylic acid) (poly(DVB-co-AA)) hollow microspheres with gold nanoparticles on the interior surfaces were prepared from the gold nanoparticles-coated poly(methacrylic acid) (PMAA@Au@poly(DVB-co-AA)) core-shell microspheres by removal of the PMAA core in water.Au nanoparticles-coated PMAA microspheres were afforded by the in-situ reduction of gold trichloride with PMAA microsphere as stabilizer via the interaction between carboxylic acid groups and Au nanoparticles.Gold nanoparticle...     

In situ Deposition of ‘Naked’ Gold Nanoparticles Supported on Silica Spheres as Recyclable Catalysts in Styrene Epoxidation

Tlie rational designs of particle size, morphology and surface states of the Au nanoparticles(AuNPs) are crucial for Au nanocatalyst. We herein report a method to synthesize the silica microspheres supported AuNPs(ca.1 nm) and their application in controlling the reaction conversion and selectivity in styrene epoxidation. Surfactant-ftee AuNPs deposited on silica microspheres were in situ fabricated with aid of the Ag nanoparticles (AgNPs) as sacrificial template by galvanic replacement reaction, leading to AuNPs/SiO2 catalyst directly without any post-treatment to expose crystal facets.A high conversion of 46.7% and selectivity of 91.7% to styrene oxide was achieved with H2O2 as oxidant in ethanol. The solid catalyst could be reused at least 10 reaction cycles without significant decrease in activity and selectivity. This study not only supplies an active, recoverable catalyst for styrene oxidation with green oxidant and solvent, but also demonstrates that the silica microspheres functionalized with thiol groups have a superior ability in stabilizing noble metal nanoparticles even without any surfactant.     

Novel Au/La‐SrTiO3 microspheres: Superimposed Effect of Gold Nanoparticles and Lanthanum Doping in Photocatalysis

Novel multielement Au/La‐SrTiO₃ microspheres were synthesized by a solvothermal method using monodisperse gold and La‐SrTiO₃ nanocrystals as building blocks. The porous Au/La‐SrTiO₃ microspheres had a large surface area of 94.6 m² g^?1. The stable confined Au nanoparticles demonstrated strong surface plasmon resonance effect, leading to enhanced absorption in a broad UV/Vis/NIR range. Doping of rare‐earth metal La also broadened the absorption band to the visible region. Both the conduction and valence bands of Au/La‐SrTiO₃ microspheres thus show favorable potential for proton reduction under visible light. The superimposed effect of Au nanoparticles and La doping in Au/La‐SrTiO₃ microspheres led to high photocurrent density in photoelectrochemical water splitting and good photocatalytic activity in photodegradation of rhodamine B. The photocatalytic activities are in the order of the following: Au/La‐SrTiO₃ microspheres>Au/SrTiO₃ microspheres>La‐SrTiO₃ microspheres>SrTiO₃ microspheres.     

Growth mechanism of gold nanoparticles decorated on polystyrene spheres via self-regulated reduction

Uniform polystyrene (PS) microspheres prepared for deposition of metallic nanoparticles were synthesized using the surfactant-free emulsion polymerization based on styrene/potassium persulfate/water (St/KPS/H₂O) system. Owing to the presence of sulfate groups, the PS microspheres can be utilized to reduce gold nanoparticles without adding extra reducing agent into the mixture. The synthesis and characterization of metal-polystyrene nanocomposites are reported, and a possible reduction mechanism is proposed: by heating the aqueous solution in the presence of metal ions and PS, the sulfate chain end groups of the PS hydrolyzed and transformed to hydroxyl groups firstly. The hydroxyl groups function as a reducing agent, and carboxylic groups provide a site to adsorb the gold nuclei. The Au nanoparticles grow in size with the coalescence and dissolving of nuclei through the Ostwald ripening process. The PS microspheres and Au nanoparticles were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray power diffraction, and thermal gravimetric analysis.     

Au@PS纳米颗粒掺杂PDMS/(PVDF-TrFE)复合薄膜的制备及介电-疏水性能

结合乳液聚合和还原法在250 nm的聚苯乙烯(PS)微球表面均匀负载了Au纳米颗粒. 通过溶液共混法, 使Au@PS纳米颗粒与聚二甲基硅氧烷(PDMS)/聚偏氟乙烯-三氟乙烯[P(VDF-TrFE)](质量比为2∶3)均匀混合, 制备出结构致密、 Au@PS均匀分布的微突起的复合薄膜. 研究了不同Au@PS纳米颗粒掺杂量对复合薄膜的结构、 熔融结晶行为和介电疏水特性的影响. 研究发现, Au@PS纳米颗粒的引入阻碍了P(VDF-TrFE)的β相的产生, 但对PDMS/P(VDF-TrFE)复合薄膜的化学健结构没有显著影响; 随着Au@PS纳米颗粒含量的增多, 复合薄膜结晶温度和玻璃化转化温度升高, 熔点略有降低. 由于界面极化和微电容效应协同作用, 掺杂Au@PS复合薄膜的介电常数有显著提升. PS球表面均匀负载的Au纳米颗粒减少了导电网络的构成, 使介电损耗维持在较低值. 掺杂5%(质量分数)Au@PS的复合薄膜介电常数达到22(100 Hz), 分别为纯PDMS和PDMS/P(VDF-TrFE)的8.8倍和3.14倍, 同时具有优异的疏水特性, 接触角达到112.31°.     

Gold nanoparticle-decorated keggin ions/TiO2 photococatalyst for improved solar light photocatalysis

We demonstrate a facile localized reduction approach to synthesizing a Au nanoparticle-decorated Keggin ion/TiO(2) photococatalyst for improved solar light photocatalysis application. This has been achieved by exploiting the ability of TiO(2)-bound Keggin ions to act as a UV-switchable, highly localized reducing agent. Notably, the approach proposed here does not lead to contamination of the resultant cocatalyst with free metal nanoparticles during aqueous solution-based synthesis. The study shows that for Keggin ions (phosphotungstic acid, PTA), being photoactive molecules, the presence of both Au nanoparticles and PTA on the TiO(2) surface in a cocatalytic system can have a dramatic effect on increasing the photocatalytic performance of the composite system, as opposed to a TiO(2) surface directly decorated with metal nanoparticles without a sandwiched PTA layer. The remarkable increase in the photocatalytic performance of these materials toward the degradation of a model organic Congo red dye correlates to an increase of 2.7-fold over that of anatase TiO(2) after adding Au to it and 4.3-fold after introducing PTA along with Au to it. The generalized localized reduction approach to preparing TiO(2)-PTA-Au cocatalysts reported here can be further extended to other similar systems, wherein a range of metal nanoparticles in the presence of different Keggin ions can be utilized. The composites reported here may have wide potential implications toward the degradation of organic species and solar cell applications.     

Water-medium and solvent-free organic reactions over a bifunctional catalyst with Au nanoparticles covalently bonded to HS/SO3H functionalized periodic mesoporous organosilica

An operationally simple approach for the preparation of a new class of bifunctional Au nanoparticle-acid catalysts has been developed. In situ reduction of Au(3+) with HS-functionalized periodic mesoporous organosilicas (PMOs) creates robust, fine Au nanoparticles and concomitantly produces a sulfonic acid moiety strongly bonded to PMOs. Characterizations of the nanostructures reveal that Au nanoparticles are formed with uniformed, narrow size distribution around 1-2 nm, which is very critical for essential catalytic activities. Moreover, the Au nanoparticles are mainly attached onto the pore surface rather than onto the outer surface with ordered mesoporous channels, allowing for maximal exposure to reaction substrates while minimizing Au nanoparticle leaching. Their higher S(BET), V(P), and D(P) than either the Au-HS-PMO(Et) or the Au/SO(3)H-PMO(Et) render the catalyst with comparably even higher catalytic efficiency than its homogeneous counterparts. Furthermore, the unique amphiphilic compartment of the Au-HS/SO(3)H-PMO(Et) nanostructures enables organic reactions to proceed efficiently in a pure aqueous solution without using any organic solvents or even without water. As demonstrated experimentally, remarkably, the unique bifunctional Au-HS/SO(3)H-PMO(Et) catalyst displays higher efficiencies in promoting water-medium alkyne hydration, intramolecular hydroamination, styrene oxidation, and three-component coupling reactions and even the solvent-free alkyne hydration process than its homogeneous catalysts. The robust catalyst can be easily recycled and used repetitively at least 10 times without loss of catalytic efficiency. These features render the catalyst particularly attractive in the practice of organic synthesis in an environmentally friendly manner.     

Synthesis of a Au/silica/polymer trilayer composite and the corresponding hollow polymer microsphere with a movable Au core

Gold/silica/poly(N,N'-methylenebisacrylamide) (Au/SiO2/polyMBAAm) trilayer composite materials were prepared by distillation precipitation polymerization of N,N'-methylenebisacrylamide (MBAAm) in the presence of Au/SiO2 particles as seeds, in which the seeds were prepared by a combination of gold-complexing and silane coupling agent with a further modified St?ber method. The polymerization of MBAAm was performed in neat acetonitrile with 2,2'-azobisisobutyronitrile as an initiator to encapsulate the Au/SiO2 seeds driven by the hydrogen-bonding interaction between the hydroxyl group on the surface of the seeds and the amide unit of polyMBAAm without modification of the Au/SiO2 surface in the absence of any stabilizer or surfactant. Hollow polyMBAAm microspheres with movable Au cores were further developed by the selective removal of the middle silica layer with hydrofluoric acid. The resultant trilayer Au/SiO2/polyMBAAm composite and hollow polyMBAAm microspheres with movable Au cores were characterized by transmission electron microscopy. The diffusion of chemicals across the polyMBAAm shell was investigated by a catalytic reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride as a reductant.     

Facile preparation of Au nanoparticle-embedded polydopamine hollow microcapsule and its catalytic activity for the reduction of methylene blue

Abstract

Development of novel supported catalysts with high activity and stability is still a challenge. In this study, the Au-polydopamine (Au-PDA) hollow microcapsules with Au nanoparticles embedded into the PDA microcapsule shell have been synthesized through a simple template-induced covalent assembly method, where polystyrene (PS) nanospheres were used as templates to form core/shell structured PS/Au-PDA composites, followed by core removal through tetrahydrofuran etching. Their morphology and composition were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectra (FT-IR), UV-Vis spectrophotometer and X-ray diffraction (XRD), respectively. Results showed that the Au-PDA microcapsules possessed well-fined hollow structure and uniform sizes with inner diameter of about 385?nm, shell thickness of about 30?nm, and Au nanoparticles with diameter of about 17?nm incorporated. The catalytic performance of Au-PDA hollow microcapsules was evaluated through the reduction of methylene blue (MB) dye with NaBH₄ as a reducing agent. Compared to PDA/Au composites with Au nanoparticles loaded on the surface of PDA microspheres, as-prepared Au-PDA hollow microcapsules show good stability and recyclability in the catalytic experiments as the Au nanoparticles were firmly wrapped in PDA matrix, which makes the Au-PDA hollow microcapsules a practicable catalyst candidate for advanced catalytic systems.     

Fe3O4/PEI/Au@CdSe/CdS多功能复合材料的制备与表征

以共沉淀法制备出Fe₃O₄纳米粒子,通过聚乙烯亚胺(PEI)修饰Fe₃O₄纳米粒子,再原位复合上Au纳米粒子,制得Fe₃O₄/PEI/Au纳米颗粒微球。再将Fe₃O₄/PEI/Au纳米颗粒与巯基乙酸修饰的量子点CdSe/CdS连接,成功制备了Fe₃O₄/PEI/Au@CdSe/CdS多功能复合微球。经过傅里叶变换红外光谱仪(FTIR)、荧光分光光度计、荧光显微镜、X射线衍射(XRD)、透射电子显微镜(TEM)及振动样品磁强计(VSM)的表征。结果表明:多功能复合微球的粒径在40nm左右,具有超顺磁性,剩磁,矫顽力近似等于零,饱和磁化强度为28.83A·m₂·kg^-1,同时兼有优越的荧光性能和金纳米粒子的特性。     

Preparation and adsorption property of novel inverse-opal hierarchical porous N-doped carbon microspheres

The design of pore structure is the key factor for the performance of porous carbon spheres.In this wo rk,novel micron-sized colloidal crystal microspheres consisting of fibrous silica(F-SiO_2) nanoparticles are firstly prepared by water-evapo ration-induced self-assembly of F-SiO_2 nanoparticles in the droplets of an inverse emulsion system to be used as sacrificial templates.Acrylonitrile(AN) was infiltrated in the voids of the F-SiO_2 colloidal crystal microspheres,and in-situ induced by ~(60)Co y-ray to polymerize into polyacrylonitrile(PAN).After the PAN-infiltrated F-SiO_2 colloidal crystal microspheres were carbonized and etched with HF solution,novel micron-sized inverse-opal N-doped carbon(IO-NC) microspheres consisting of hollow carbon nanoparticles with a hierarchical macro/meso-porous inner surface were obtained.The IO-NC microspheres have a specific surface area as high as 266.4 m~2/g and a molar ratio of C/N of 5.They have a good dispersibility in water,and show a high adsorption capacity towards rhodamine B(RhB) up to 137.28 mg/(g microsphe re).This work offers a way to obtain novel micron-sized hierarchical macro/meso-porous N-doped carbon microspheres,which opens a new idea to prepare high-performance hierarchical porous carbon materials.     

Fe3O4/PEI/Au@CdSe/CdS多功能复合材料的制备与表征

以共沉淀法制备出Fe₃O₄纳米粒子,通过聚乙烯亚胺(PEI)修饰Fe₃O₄纳米粒子,再原位复合上Au纳米粒子,制得Fe₃O₄/PEI/Au纳米颗粒微球。再将Fe₃O₄/PEI/Au纳米颗粒与巯基乙酸修饰的量子点CdSe/CdS连接,成功制备了Fe₃O₄/PEI/Au@CdSe/CdS多功能复合微球。经过傅里叶变换红外光谱仪(FTIR)、荧光分光光度计、荧光显微镜、X射线衍射(XRD)、透射电子显微镜(TEM)及振动样品磁强计(VSM)的表征。结果表明:多功能复合微球的粒径在40 nm左右,具有超顺磁性,剩磁,矫顽力近似等于零,饱和磁化强度为28.83 A·m²·kg^-1,同时兼有优越的荧光性能和金纳米粒子的特性。     

Synthesis of Au nanoparticles with Bi adlayers using glucose as dispersant

Well-dispersed Au/Bi nanoparticles with average size below 10 nm were prepared by using NaBH₄ to reduce HAuCl₄ with glucose as dispersant. The obtained Au/Bi NPs were well characterized by UV-Vis spectra, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements. The electrochemical study found that Bi adlayers on the surface of Au nanoparticles owns two kinds of surface structures, including a low coverage (2 × 2)-Bi adlayer and a close-packed (p × √3)-2 Bi adlayer due to the strong interaction between the two Bi layers and the below Au atoms, which is same with that bulk on Au surface.     

控制自由基聚合制备Fe_3O_4/SiO_2/P(AA-MMA-St)磁性复合微球

用原硅酸乙酯对Fe3O4纳米粒子进行表面改性得到Fe3O4/SiO2磁流体.在Fe3O4/SiO2磁流体存在下,以1,1-二苯基乙烯(DPE)为自由基聚合控制剂,利用乳液聚合法制备了Fe3O4/SiO2/P(AA-MMA-St)核-壳磁性复合微球.用红外光谱(FTIR)、振动样品磁强计(VSM)、透射电镜(TEM)、X光电子能谱(XPS)、热重分析(TGA)、示差扫描量热仪(DSC)对所制备的磁流体、磁性高分子复合微球的结构、形态、性能进行了表征.研究发现,原硅酸乙酯水解后能在Fe3O4表面形成硅膜保护层从而避免Fe3O4的酸蚀,使Fe3O4/SiO2/P(AA-MMA-St)复合微球的比饱和磁化强度比同样条件下制备的Fe3O4/P(AA-MMA-St)微球提高了28%;DPE能有效控制自由基在Fe3O4/SiO2磁流体表面均匀地引发单体聚合,得到平均粒径为422 nm,无机粒子含量为40%,比饱和磁化强度为34.850 emu/g,表面羧基含量为0.176 mmol/g的磁性复合微球.     

Raman scattering of 4-aminobenzenethiol sandwiched between Ag/Au nanoparticle and macroscopically smooth Au substrate

Raman scattering measurements were conducted for a 4-aminobenzenethiol (4-ABT) monolayer assembled on a macroscopically smooth Au substrate. Although no peak was detected at the beginning, Raman peaks were distinctly observed by attaching Ag or Au nanoparticles onto the 4-ABT monolayer (Ag(Au)@4-ABT/Au(flat)). Considering the fact that no Raman signal is observed when Ag (Au) nanoparticles are adsorbed on a (4-aminophenyl)silane monolayer assembled on a silicon wafer, the Raman spectrum observed for Ag(Au)@4-ABT/Au(flat) must be a surface-enhanced Raman scattering (SERS) spectrum, derived from the electromagnetic coupling of the localized surface plasmon of Ag (Au) nanoparticles with the surface plasmon polariton of the underneath Au metal. The electromagnetic coupling responsible for SERS appeared to be governed more by the bulk Au substrate than the sparsely distributed Ag or Au nanoparticles. The chemical enhancement appeared on the other hand to be derived more from the formation of Au-S bonds than any charge-transfer interaction between the protonated amine group and the Au or Ag nanoparticles. The enhancement factors derived from the attachment of a single Ag or Au nanoparticle onto 4-ABT on Au were estimated to be as large as 8.3 x 10(5) and 5.0 x 10(5), respectively, (for the ring 3 band (b(2)) near 1390 cm(-1)) in which a factor of approximately 10(2) was presumed to be due to the chemical effect, with the remaining contributed by the electromagnetic effect.     

Controlled synthesis and enhanced bacteriostatic activity of Mg(OH)<Subscript>2</Subscript>/Ag nanocomposite

Silver nanoparticles have good sterilization performance due to their small size and large specific surface area, while the small size also brings about reunification and reduces the sterilization activity. To resolve the problem, magnesium hydroxide [Mg(OH)₂] microsphere was designed as a supported material to load silver particles on its surface. Mg(OH)₂ microspheres were successfully synthesized under the control of a biotemplate of eggshell membrane. X-ray diffraction, thermal gravimetric analysis/differential scanning calorimetry, and transmission electron microscopy were performed to characterize the Mg(OH)₂ microspheres. The results indicate that the Mg(OH)₂ microspheres of average size ~ 2 μm were formed from nanoflakes. The silver nanoparticles were loaded on the surface of Mg(OH)₂ microspheres to form Mg(OH)₂/Ag nanocomposite, which exhibited enhanced antibacterial effect compared to that of silver nanoparticles. The enhanced antibacterial mechanism was investigated in detail.     

Tunable surface-enhanced infrared absorption on au nanofilms on si fabricated by self-assembly and growth of colloidal particles

Au colloids were used to fabricate nanoscale-tunable Au nanofilms on silicon for surface-enhanced IR absorption bases in both ambient and electrochemical environments. This wet process incorporates the self-assembly of colloidal Au monolayer using 3-aminopropyl trimethoxysilane as the organic coupler with subsequent chemical plating in an Au(III)/hydroxylamine solution. FTIR spectroscopy in transmission mode of the probe species SCN- was used to evaluate the apparent surface enhancement in IR absorption of 2D Au colloid arrays and chemically plated Au particles. The nanostructure of Au films was examined by atomic force microscopy. The IR and AFM results show that the apparent surface enhancement factor (1-2 orders of magnitude) increases with increasing sizes and/or contact, and the severe aggregation of Au nanoparticles may cause the bipolar band shape. Cyclic voltammetry on the Au nanofilm obtained by the above nucleation and growth strategy exhibits a feasible electrochemical stability and behavior. In situ ATR-FTIR measurement of p-nitrobenzoic acid adsorption demonstrates that the as-grown Au film yields rather promising surface enhancement as well.