电化学沉积法制备金（核）-铜（壳）纳米粒子阵列

以组装在有机分子自组装膜/金基底电极上的Au纳米粒子阵列为电化学沉积模板,制备了金(核)-铜 (壳)纳米粒子阵列.选用巯基十一胺（AUDT）和巯基癸烷（DT）混合自组装膜作为基底电极与Au纳米粒子的耦联层,可以在一定的电位下实现金属Cu在Au纳米粒子上的选择性沉积.将沉积电位控制在－0.03 V（vs SCE）时,沉积初期（t ≤ 15 s,沉积粒子粒径 ≤ 20 nm ）金(核)-铜 (壳)粒子具有良好的单分散性和近似球形,而且粒径实验值同计算值非常吻合.     

Preparation and encapsulation of highly fluorescent conjugated polymer nanoparticles

A facile method has been developed to prepare aqueous dispersions of encapsulated conjugated polymer nanoparticles exhibiting high fluorescence brightness. Salient features of the nanoparticles include their small diameter and spherical morphology. Encapsulation of the nanoparticles with a silica shell reduces the rate of photooxidation and allows facile attachment of functional groups for subsequent bioconjugation and nanoparticle assembly. Functionalization of the nanoparticle with amine groups followed by the addition of Au nanoparticles resulted in the formation of nanoparticle assemblies, as evidenced by the efficient quenching of the conjugated polymer fluorescence by the Au nanoparticles.     

Adsorption mechanism of water molecules surrounding Au nanoparticles of different sizes

Molecular dynamic simulation is used to investigate the adsorption mechanism of water molecules surrounding Au nanoparticles with different sizes. Our results show that the adsorption mechanism of the water molecules in the first water shell will be influenced by the size of the Au nanoparticle. For the larger Au nanoparticles, the hydrogen bonding of water molecules adsorbed on the surface of the Au nanoparticles are arranged in a two-dimensional structure, while those adsorbed on the edge of the surface of the Au nanoparticles are arranged in a three-dimensional structure. However, in the case of the smallest Au nanoparticle, the hydrogen bonding of the water molecules on the first adsorbed layer are arranged only in a three-dimensional structure. The arrangement of the water molecules in the first water shell can be determined by orientation order parameter. The water molecules that adsorb on the larger Au nanoparticles tend to arrange in an irregular arrangement, while those adsorbed on the smallest Au nanoparticle tend to arrange a regular arrangement. Interestingly, the water molecules adsorbed on the smallest nanoparticle are arranged in a bulklike structure in the first shell.     

Photocatalytically Renewable Micro‐electrochemical Sensor for Real‐Time Monitoring of Cells

Electrode fouling and passivation is a substantial and inevitable limitation in electrochemical biosensing, and it is a great challenge to efficiently remove the contaminant without changing the surface structure and electrochemical performance. Herein, we propose a versatile and efficient strategy based on photocatalytic cleaning to construct renewable electrochemical sensors for cell analysis. This kind of sensor was fabricated by controllable assembly of reduced graphene oxide (RGO) and TiO₂ to form a sandwiching RGO@TiO₂ structure, followed by deposition of Au nanoparticles (NPs) onto the RGO shell. The Au NPs‐RGO composite shell provides high electrochemical performance. Meanwhile, the encapsulated TiO₂ ensures an excellent photocatalytic cleaning property. Application of this renewable microsensor for detection of nitric oxide (NO) release from cells demonstrates the great potential of this strategy in electrode regeneration and biosensing.     

铁氧化物/金磁性核壳纳米粒子的制备及其富集与SERS研究

本文用种子生长法制备铁氧化物/金磁性核壳纳米粒子, 并利用SERS对其磁场靶向性进行了检测.     

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.     

Observed Dramatically Improved Catalysis of Ag Shell on Au/Ag Core‐shell Nanorods is Due to Silver Impurities Released During Etching Process

Core/shell bimetallic nanoparticles are highly popular in electrocatalysis; it is argued that the core metal enhances the catalytic properties of the shell. We have investigated the electrocatalytic properties of Au/Ag core‐shell nanorods (Au/Ag NRs) where Ag shell was thinned by aging in the presence of cetyltrimethylammonium bromide. We observed excellent electrocatalysis toward hydrogen peroxide electroreduction upon decreasing the Ag shell thickness, which would, at first, appear to imply a strong synergistic effect of the Au core with the Ag shell for electrocatalysis. We show, however, that this electrocatalysis is not caused by particular Au/Ag core/shell structures but rather by the presence of residual silver impurities in the form of Ag nanoparticles (Ag NPs) formed during the preparation of the thin‐layer silver shell/gold core nanorods.     

Various Au nanoparticle organizations fabricated through SiO2 monomer induced self-assembly

A novel method has been developed to fabricate the assembly of Au colloidal nanoparticles (NPs) using SiO(2) monomers. The key strategy was the use of a controlled sol-gel procedure including hydrolysis, deposition, and condensation of tetraethyl orthosilicate (TEOS). Namely, the assembly of Au NPs was created by the anisotropic deposition of SiO(2) monomers and subsequent permanent fixing by the growth of a SiO(2) shell. Various assemblies of Au NPs such as dimer, trimer, and pearl-chain morphology were fabricated by systematically changing the concentration and injection speed of TEOS. A longitudinal plasmon resonance band was observed as a result of the assembly of Au NPs and can be tuned from visible to near-infrared by altering the length of pearl-chain morphology. In addition, single Au NP was homogeneously coated with a SiO(2) shell by means of controlling the deposition rate of SiO(2) monomers during a Sto?ber synthesis without the use of a silane coupling agent or bulk polymer as the surface primer to render the Au surface vitreophilic. The Au NPs (mean size 11.4 nm in diameter) were thus encapsulated into SiO(2) beads with a wide range of sizes (from 20 to 50 nm in diameter). These pure SiO(2)-coated Au beads with tunable shell thickness should be crucial for biosensors, particularly as Raman-tag particles.     

金核银壳纳米粒子薄膜的制备及SERS活性研究

采用柠檬酸化学还原法制备金溶胶, 通过自组装技术在石英片表面制备金纳米粒子薄膜, 在银增强剂混合溶液中反应获得金核银壳纳米粒子薄膜. 用紫外-可见吸收光谱仪和原子力显微镜(AFM)研究了不同条件下制备的金核银壳纳米粒子薄膜的光谱特性和表面形貌, 并以结晶紫为探针分子测量了金核银壳纳米粒子薄膜的表面增强拉曼光谱(SERS). 结果表明, 金纳米粒子薄膜的分布、银增强剂反应时间的长短对金核银壳纳米粒子薄膜的形成均有重要影响. 制备过程中, 可以通过控制反应条件获得一定粒径的、具有良好表面增强拉曼散射活性的金核银壳纳米粒子薄膜.     

Three-layer composite magnetic nanoparticle probes for DNA

A method for synthesizing composite nanoparticles with a gold shell, an Fe3O4 inner shell, and a silica core has been developed. The approach utilizes positively charged amino-modified SiO2 particles as templates for the assembly of negatively charged 15 nm superparamagnetic water-soluble Fe3O4 nanoparticles. The SiO2-Fe3O4 particles electrostatically attract 1-3 nm Au nanoparticle seeds that act in a subsequent step as nucleation sites for the formation of a continuous gold shell around the SiO2-Fe3O4 particles upon HAuCl4 reduction. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding properties of gold nanoparticle probes, but the magnetic properties of the Fe3O4 inner shell.     

Local structural characterization of Au/Pt bimetallic nanoparticles

In this study, we examined the amount-dependent change in morphology for a series of Au/Pt bimetallic nanoparticles synthesized using chemical reduction. The Au/Pt molar ratio was varied from 1/1 to 1/4 to synthesize Pt shell layers with different thicknesses. We have obtained that these bimetallic nanoparticles can form flower-like nanoparticles. Moreover, an extended X-ray absorption fine structure (EXAFS) analysis was used to demonstrate the structure of Au/Pt bimetallic nanoparticles. The EXAFS results confirmed the formation of a core–shell structure and inter-diffusion between Au and Pt atoms. The composition of the shell layer was found to be Pt-enriched Au/Pt alloy.     

Synthesis of aqueous Au core-Ag shell nanoparticles using tyrosine as a pH-dependent reducing agent and assembling phase-transferred silver nanoparticles at the air-water interface

We demonstrate that the amino acid tyrosine is an excellent reducing agent under alkaline conditions and may be used to reduce Ag+ ions to synthesize stable silver nanoparticles in water. The tyrosine-reduced silver nanoparticles may be separated out as a powder that is readily redispersible in water. The silver ion reduction at high pH occurs due to ionization of the phenolic group in tyrosine that is then capable of reducing Ag+ ions and is in turn converted to a semi-quinone structure. These silver nanoparticles can easily be transferred to chloroform containing the cationic surfactant octadecylamine by an electrostatic complexation process. The now hydrophobic silver nanoparticles may be spread on the surface of water and assembled into highly ordered, linear superstructures that could be transferred as multilayers onto suitable supports by the versatile Langmuir-Blodgett technique. Further, tyrosine molecules bound to the surface of Au nanoparticles through amine groups in the amino acid may be used to selectively reduce silver ions at high pH on the surface of the Au nanoparticles, thus leading to a simple strategy for realizing phase-pure Au core-Ag shell nanostructures.     

Rapid one-step synthesis, characterization and functionalization of silica coated gold nanoparticles

This paper describes a rapid, simple and one-step method for preparing silica coated gold (Au@SiO₂) nanoparticles with fine tunable silica shell thickness and surface functionalization of the prepared particles with different groups. Monodispersed Au nanoparticles with a mean particle size of 16 nm were prepared by citrate reduction method. Silica coating was carried out by mixing the as prepared Au solution, tetraethoxysilane (TEOS) and ammonia followed by microwave (MW) irradiation. Although there are several ways of coating Au nanoparticles with silica in the literature, each of these needs pre-coating step as well as long reaction duration. The present method is especially useful for giving the opportunity to cover the colloidal Au particles with uniform silica shell within very short time and forgoes the use of a silane coupling agent or pre-coating step before silica coating. Au@SiO₂ nanoparticles with wide range of silica shell thickness (5-105 nm) were prepared within 5 min of MW irradiation by changing the concentration of TEOS only. The size uniformity and monodispersity were found to be better compared to the particles prepared by conventional methods, which were confirmed by dynamic light scattering and transmission electron microscopic techniques. The prepared Au@SiO₂ nanoparticles were further functionalized with amino, carboxylate, alkyl groups to facilitate the rapid translation of the nanoparticles to a wide range of end applications. The functional groups were identified by XPS, and zeta potential measurements.     

Preparation and Characterization of Pt/Co‐Core Au‐Shell Magnetic Nanoparticles

Pt/Co‐core Au‐shell nanoparticles were synthesized via a two‐step route using NaBH₄ as a reducing agent. The nanoparticles are characterized by UV‐vis spectroscopy, transmission electron microscopy (TEM) and powder X‐ray diffraction (XRD). The results indicate that the as‐synthesized Pt/Co‐core Au‐shell nanoparticles have a disordered face centered cubic (fcc) structure, whereas the annealed Pt/Co‐core Au‐shell nanoparticles exhibit an ordered face centered tetragonal (fct) structure. Superconducting quantum interference device (SQUID) studies reveal that the coercivity of the annealed Pt/Co‐core Au‐shell nanoparticles increases to 510 Oe after heat treatment at 500 °C for 2 h.     

A General and High‐Yield Galvanic Displacement Approach to Au?M (M=Au,Pd, and Pt) Core–Shell Nanostructures with Porous Shells and Enhanced Electrocatalytic Performances

In this work, we utilize the galvanic displacement synthesis and make it a general and efficient method for the preparation of Au? M (M=Au, Pd, and Pt) core–shell nanostructures with porous shells, which consist of multilayer nanoparticles. The method is generally applicable to the preparation of Au? Au, Au? Pd, and Au? Pt core–shell nanostructures with typical porous shells. Moreover, the Au? Au isomeric core–shell nanostructure is reported for the first time. The lower oxidation states of Au^I, Pd^II, and Pt^II are supposed to contribute to the formation of porous core–shell nanostructures instead of yolk‐shell nanostructures. The electrocatalytic ethanol oxidation and oxygen reduction reaction (ORR) performance of porous Au? Pd core–shell nanostructures are assessed as a typical example for the investigation of the advantages of the obtained core–shell nanostructures. As expected, the Au? Pd core–shell nanostructure indeed exhibits a significantly reduced overpotential (the peak potential is shifted in the positive direction by 44 mV and 32 mV), a much improved CO tolerance (I_f/I_b is 3.6 and 1.63 times higher), and an enhanced catalytic stability in comparison with Pd nanoparticles and Pt/C catalysts. Thus, porous Au? M (M=Au, Pd, and Pt) core–shell nanostructures may provide many opportunities in the fields of organic catalysis, direct alcohol fuel cells, surface‐enhanced Raman scattering, and so forth.     

Synthesis of core/shell nanoparticles of Au/CdSe via Au-Cd bialloy precursor

We present a novel method for the preparation of ultrasmall Au/CdSe core/shell particles. Au-Cd bialloy particles of 4.7 nm diameter were prepared as the precursor. The Cd component in the precursor reacted with the Se source at a temperature of 205 degrees C and was heated to 250 degrees C, leading to formation of a Au/CdSe core/shell structure. The sizes of Au/CdSe nanoparticles have a narrow distribution with an average size of 6.0 nm and Au core of 2.2 nm diameter. The X-ray diffraction pattern and the images of the high-resolution electron transmission microscopy show that the Au cores and the CdSe shells of Au/CdSe core/shell nanoparticles are both well crystallized, and the CdSe shells are in a cubic phase. The absorption spectrum of the Au/CdSe nanoparticles combines the absorption behaviors of the Au cores and the CdSe shells.     

光化学合成Au核@Pd壳复合纳米粒子及其表征

在PEG-丙酮溶液体系中, 采用紫外光辐射还原Au(Ⅲ), Pd(Ⅱ)离子混合物和以Au晶种为核、紫外光辐射还原Pd(Ⅱ)使其沉积在Au晶种表面上这两种方法, 合成了Au核@Pd壳复合纳米粒子. 通过改变Au(Ⅲ)离子或Au晶种对Pd(Ⅱ)离子的摩尔比调节复合粒子的尺寸和Pd壳厚度, 分别获得了直径范围为5.6~4.6 nm和4.6~6.2 nm的复合粒子. 利用UV-Vis吸收光谱、TEM、HR-TEM和XPS等表征手段, 证明了合成的纳米粒子为核-壳复合结构. 研究了Au@Pd纳米粒子的直径随溶液中Au(Ⅲ)/Pd(Ⅱ)摩尔比的改变而变化的规律; 对Au核向Pd壳的供电子作用以及复合粒子的光化学形成机理进行了讨论.     

Fabrication of nanorattles with passive shell

This investigation describes the formation of a metal nanorattle with a pure metal shell by varying experimental parameters. The galvanic replacement reaction between silver and chloroauric acid was adopted to prepare hollow metal nanoparticles. This approach is extended to produce nanorattles of Au cores and Au shells by starting with Au(core)Ag(shell) nanoparticles as templates. The effect of temperature on the nanostructure of the final product is also considered. The composition of the shell in nanorattles can be controlled by varying the reaction temperature (to form pure gold or gold-silver alloy, for example). X-ray absorption fine structure spectroscopy is conducted to elucidate the fine structure of these nanoparticles. Partial alloying between the Au core and the Ag shell is observed by extended X-ray absorption fine structure (EXAFS).     

Strategies toward well‐defined polymer nanoparticles inspired by nature: Chemistry versus versatility

Polymeric nanoparticles are promising delivery platforms for various biomedical applications. One of the main challenges toward the development of therapeutic nanoparticles is the premature disassembly and release of the encapsulated drug. Among the different strategies to enhance the kinetic stability of polymeric nanoparticles, shell‐ and core‐crosslinking have been shown to provide robust character, while creating a suitable environment for encapsulation of a wide range of therapeutics, including hydrophilic, hydrophobic, metallic, and small and large biomolecules, with gating of their release as well. The versatility of shell‐ and core‐crosslinked nanoparticles is driven from the ease by which the structures of the shell‐ and core‐forming polymers and crosslinkers can be modified. In addition, postmodification with cell‐recognition moieties, grafting of antibiofouling polymers, or chemical degradation of the core to yield nanocages allow the use of these robust nanostructures as “smart” nanocarriers. The building principles of these multifunctional nanoparticles borrow analogy from the synthesis, supramolecular assembly, stabilization, and dynamic activity of the naturally driven biological nanoparticles such as proteins, lipoproteins, and viruses. In this review, the chemistry involved during the buildup from small molecules to polymers to covalently stabilized nanoscopic objects is detailed, with contrast of the strategies of the supramolecular assembly of polymer building blocks followed by intramicellar stabilization into shell‐, core‐, or core–shell‐crosslinked knedel‐like nanoparticles versus polymerization of polymers into nanoscopic molecular brushes followed by further intramolecular covalent stabilization events. The rational design of shell‐crosslinked knedel‐like nanoparticles is then elaborated for therapeutic packaging and delivery, with emphasis on the polymer chemistry aspects to accomplish the synthesis of such nanoparticulate systems. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Phytosynthesis of Au, Ag and Au-Ag bimetallic nanoparticles using aqueous extract and dried leaf of Anacardium occidentale

Present study reports a green chemistry approach for the biosynthesis of Au, Ag, Au-Ag alloy and Au core-Ag shell nanoparticles using the aqueous extract and dried powder of Anacardium occidentale leaf. The effects of quantity of extract/powder, temperature and pH on the formation of nanoparticles are studied. The nanoparticles are characterized using UV-vis and FTIR spectroscopies, XRD, HRTEM and SAED analyses. XRD studies show that the particles are crystalline in the cubic phase. The formation of Au core-Ag shell nanoparticles is evidenced by the dark core and light shell images in TEM and is supported by the appearance of two SPR bands in the UV-vis spectrum. FTIR spectra of the leaf powder before and after the bioreduction of nanoparticles are used to identify possible functional groups responsible for the reduction and capping of nanoparticles. Water soluble biomolecules like polyols and proteins are expected to bring about the bio-reduction.