Well‐Defined SiO2@P(EtOx‐stat‐EI) Core–Shell Hybrid Nanoparticles via Sol‐Gel Processes

Positively charged nanoparticles (NPs) are very interesting for biomedical and pharmaceutical applications, such as nonviral gene delivery. Here, the synthesis of SiO₂ nanoparticles with a covalently grafted poly(2‐ethyl‐2‐oxazoline) (PEtOx) shell (SiO₂@PEtOx) is presented. PEtOx with a degree of polymerization of 20 and 38 is synthesized via microwave supported cationic ring‐opening polymerization and subsequently end‐functionalized with a triethoxysilyl linker for subsequent grafting to silica particles with hydrodynamic radii of 7, 31, and 152 nm. The resulting SiO₂@PEtOx particles are characterized by using dynamic light scattering (DLS), transmission electron microscopy (TEM, cryoTEM), and scanning electron microscopy (SEM) to determine changes in particle size. Thermal gravimetrical analysis is used to quantify the amount of polymer on the silica surface. Subsequent in situ transformation of SiO₂@PEtOx particles into SiO₂@P(EtOx‐stat‐EI) (poly(2‐ethyl‐2‐oxazoline‐stat‐ethylene imine) grafted silica particles) under acidic conditions inverts the surface charge from negative to positive according to ζ‐potential measurements. The P(EtOx‐stat‐EI) shell could be used for the deposition of Au NP afterward.

     

Kinetics of Core‐Shell Nanoparticle Formation by Two‐Dimensional Nuclear Magnetic Resonance

We have studied the kinetics of polymeric nanoparticle formation for poly(styrene‐block‐4‐vinylpyridine) [P(S‐b‐4‐VPy)], chains in a non‐selective solvent using 1,4‐dibromobutane (DBB) as a cross‐linker by means of different nuclear magnetic resonance (NMR) spectroscopy techniques. The kinetic process was followed using ¹H, ¹³C, and 2‐D Heteronuclear Single Quantum Correlation (HSQC) NMR experiments. The kinetic data obtained from 2‐D HSQC and ¹H NMR experiments were in good agreement between them, proving the reliability of the 2‐D HSQC NMR technique for the in situ study of the kinetics of core‐shell nanoparticle formation. A value of 1.5 × 10⁻⁵ s⁻¹ was determined for the apparent kinetic constant of the P(S‐b‐4‐VPy)‐DBB core‐shell nanoparticle formation process.

     

以树形分子为模板制备银纳米颗粒

以硝酸银为原料,硼氢化钠为还原剂,PAMAM树形分子为模板兼稳定剂,制备出粒径分布范围在4～7mm的银纳米颗粒．实验发现,其他条件相同时,银纳米颗粒的粒径随着Ag^ ／树形分子摩尔比的增加而增加,并且树形分子代数越高,所起的模板作用越显著．还研究了溶液pH值的影响,发现当溶液pH值在7左右时,可以制得粒径较小、分散性较好的银纳米颗粒．用紫外-可见光谱,透射电镜(TEM)以及原子力显微镜(AFM)等测试手段对所制得的银纳米颗粒进行了表征．     

Synthesis and Characterization of Core‐Shell Selenium/Carbon Colloids and Hollow Carbon Capsules

A novel Se/C nanocomposite with core‐shell structures has been prepared through a facile one‐pot microwave‐induced hydrothermal process. The new material consists of a trigonal‐Se (t‐Se) core and an amorphous‐C (a‐C) shell. The Se/C composite can be converted to hollow carbon capsules by thermal treatment. These products were characterized by transmission electron microscopy (TEM), powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy‐dispersive X‐ray (EDX) spectroscopy, and X‐ray photoelectron spectroscopy (XPS).     

聚酰胺-胺型树形分子模板法制备Pt纳米簇

利用紫外-可见吸收光谱和红外光谱对Pt2＋与G5.5-COOCH3聚酰胺-胺型树形分子的络合机理进行了研究, 结果表明Pt2＋与G5.5-COOCH3 PAMAM的最外层叔胺基发生络合作用, 但两者之间达到络合平衡需要较长时间, 且平衡时间随Pt2＋与树形分子物质的量比增大而增长; Pt2＋与G5.5-COOCH3树形分子的最大络合数为50～55; 采用硼氢化钠还原法原位制备了G5.5-COOCH3 PAMAM包裹、平均粒径小于2 nm、多晶的球形Pt纳米簇, 并研究了Pt2＋与PAMAM物质的量比对Pt纳米簇形貌的影响, 实验结果表明, Pt2＋与PAMAM物质的量比为10时, 生成尺寸较小分布较窄的内型Pt纳米簇/树形分子复合材料, 而物质的量比为50时, 会生成部分尺寸较大、分布较宽的外型Pt纳米簇/树形分子纳米复合材料.     

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.     

Fabrication and Characterization of Sulfonate‐containing Polystyrene/CaCO3 Core‐shell Nanoparticles

Polystyrene (PSt) seed latex was first prepared via soap‐free emulsion polymerization in the presence of a small amount of methacrylic acid using ammonium persulfate as initiator, and then seeded emulsion polymerization of sodium 4‐styrenesulfonate (NaSS) and St was carried out to synthesize P(St‐NaSS) core latex using 2,2′‐azobisisobutyronitrile as initiator. After that, P(St‐NaSS)/CaCO₃ core‐shell nanoparticles were fabricated by sequentially introducing Ca(OH)₂ aqueous solution and CO₂ gas into the core latex. The morphology of the core and core‐shell nanoparticles was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and the state of CaCO₃ shell was confirmed with high‐resolution scanning transmission electron microscope (HR‐STEM) and selected area electron diffraction (SAED). Results showed that PNaSS chains were successfully grafted onto the PSt seed surface, and length of the PNaSS "hairs" could be modulated by adjusting NaSS amount. Sulfonic groups of the PNaSS hairs served as additives in the formation and stabilization of amorphous CaCO₃(ACC) and prevented ACC from sequent transformation into crystalline states. The amount of the anchored CaCO₃ increased with the growth of PNaSS hair length, and reached 51 wt% (by thermalgravimetric analysis) under the optimal encapsulating temperature of 45°C. Moreover, the forming mechanism of P(St‐NaSS)/CaCO₃ core‐shell nanoparticles was proposed.     

Biosensor Based on Self‐Assembling Glucose Oxidase and Dendrimer‐Encapsulated Pt Nanoparticles on Carbon Nanotubes for Glucose Detection

A novel amperometric glucose biosensor based on layer‐by‐layer (LbL) electrostatic adsorption of glucose oxidase (GOx) and dendrimer‐encapsulated Pt nanoparticles (Pt‐DENs) on multiwalled carbon nanotubes (CNTs) was described. Anionic GOx was immobilized on the negatively charged CNTs surface by alternatively assembling a cationic Pt‐DENs layer and an anionic GOx layer. Transmission electron microscopy images and ζ‐potentials proved the formation of layer‐by‐layer nanostructures on carboxyl‐functionalized CNTs. LbL technique provided a favorable microenvironment to keep the bioactivity of GOx and prevent enzyme molecule leakage. The excellent electrocatalytic activity of CNTs and Pt‐DENs toward H₂O₂ and special three‐dimensional structure of the enzyme electrode resulted in good characteristics such as a low detection limit of 2.5 μM, a wide linear range of 5 μM–0.65 mM, a short response time (within 5 s), and high sensitivity (30.64 μA mM^?1 cm^?2) and stability (80% remains after 30 days).     

The Electrochemical Characterization of Single Core–Shell Nanoparticles

We report the direct solution‐phase characterization of individual gold‐core silver‐shell nanoparticles through an electrochemical means, with selectivity achieved between the core and shell components based on their different redox activities. The electrochemically determined core–shell sizes are in excellent agreement with electron microscopy‐based results, successfully demonstrating the electrochemical characterization of individual core–shell nanoparticles.     

Synthesis of PEDOT Nanoparticles and Vesicles by Dispersion Polymerization in Alcoholic Media

Summary: The synthesis of PEDOT nanoparticles and vesicles by dispersion polymerization in a methanol/water mixture (3/2, v/v) is reported, using either ammonium persulfate or iron(III) p‐toluenesulfonate as oxidants and α‐EDOT‐PEO as a reactive stabilizer. The influence of the oxidant as well as the α‐EDOT‐PEO molar mass and concentration on the core‐shell particle morphology and conductivity properties have been investigated. PEDOT particles with conductivities up to 1.5 × 10⁻² S · cm⁻¹ have been obtained in high yield.

TEM image of PEDOT vesicles prepared using PEO‐based stabilizers of 25 000 g · mol⁻¹ in water/methanol mixture (2:3 v/v) at room temperature using ammonium persulfate as an oxidant.     

季铵化聚酰胺胺树状聚合物封装的RuRh双金属DENs催化聚(甲基氢硅氧烷)区域选择性改性研究

采用共络合法制备了部分季铵化的第五代聚酰胺胺树状聚合物封装的RuRh双金属纳米粒子(DENs)催化剂, 分别利用紫外-可见光谱、光散射分析和透射电镜表征了该树状聚合物封装的RuRh双金属纳米粒子的形成、粒径及其分布. 红外光谱和核磁共振谱分析表明, RuRh双金属DENs催化剂对聚(甲基氢硅氧烷)的硅氢化改性显示了较高的催化活性和良好的区域选择性.     

Molecularly Imprinted Multi‐Layer Core‐Shell Nanoparticles – A Surface Grafting Approach

Surface initiated living‐radical polymerization (SIP) based on dithiocarbamate iniferters has been used to create molecularly imprinted core‐shell (CS) nanoparticles. Using this approach, propranolol, morphine and naproxen have been successfully imprinted in particle shells (the latter could not be imprinted using conventional aqueous‐based CS methods). Rebinding properties of the imprinted particles appear to be similar to those made by alternative methods. The living radical initiation mechanism makes it possible to build complex multi‐layer particles sequentially. As a demonstration, multi‐layer propranolol‐imprinted particles were generated. Two additional functional shells were grown over the imprinted shell, while the propranolol binding was retained, albeit at a reduced level.

     

One‐Pot Synthesis and Electrocatalytic Properties of Pd@Pt Core‐Shell Nanocrystals with Tailored Morphologies

Pd@Pt core‐shell nanocrystals consisting of well‐defined Pd nanocube cores and dendritic Pt shells were prepared by a new facile aqueous one‐pot synthetic method. The prepared Pd@Pt nanocrystals exhibited efficient catalytic activity and stability toward methanol electrooxidation, and their catalytic function was highly dependent on their Pt shell thickness due to the different synergism between Pt and Pd.     

The Synthesis of Magnetic Core‐Shell Nanoparticles by Surface‐Initiated Ring‐Opening Polymerization of ε‐Caprolactone

Summary: The synthesis of core‐shell particles with a poly(ε‐caprolactone) (PCL) shell and magnetite (Fe₃O₄) contents of between 10 wt.‐% and 41 wt.‐% proceeds by surface‐initiated ring‐opening polymerization of ε‐caprolactone to give surface‐immobilized oligomers with between 1 400 g · mol⁻¹ and 11 500 g · mol⁻¹. The particles are dispersable in good solvents for the PCL shell. Magnetization experiments on the resulting superparamagnetic ferrofluids give a core‐size distribution with an average diameter, d_v, of about 9.7 nm.

TEM image of Fe₃O₄/PCL core‐shell particles cast from CHCl₃ dispersion.     

A Novel Inorganic-Organic Composite Constructed from Cobalt（Ⅱ）-Monosubstituted Polyoxometalates and Poly（amidoamine）-NH2 DendrimersA Novel Inorganic-Organic Composite Constructed from Cobalt（Ⅱ）-Monosubstituted Polyoxometalates and Poly（amidoamine）-NH2 Dendrimers

An inorganic-organic composite was prepared by poly（amidoamine） （PAMAM） dendrimer reacting with cobalt（Ⅱ）-monosubstituted polyoxometalates Na5Co^Ⅱ（H2O）PW11O39 （PW11CO） in an aqueous solution. The hybrid composite PW11Co/PAMAM was characterized by FT-IR, UV-Vis diffuse reflectance spectra （DR-UV-Vis）, XPS, XRD and TG/DTA, indicating that the PWI iCo was chemically anchored to PAMAM. The morphologies of the title composite were characterized by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The catalytic activity was evaluated by oxidation of isobutyraldehyde （IBA） to isobutyric acid （IBAc） in MeCN under mild conditions （20 ℃, ambient pressure）, showing that the title compound is a more effective and recoverable catalyst than corresponding PW11Co.     

Self‐assembly of a new class of amphiphilic poly(amidoamine) dendrimers and their electrochemical properties

Amphiphilic poly(amidoamine) (PAMAM) dendrimers consisting of a hydrophilic dendrimer core and hydrophobic aromatic dansyl or 1‐(naphthalenyl)‐2‐phenyldiazene (NPD) shells have been synthesized. These amphiphilic dendrimers from the zero generation to the third generation self‐assemble into vesicular aggregates in water. The self‐assembly behavior of these dendrimers strongly depends on their generations. The generation dependence has been further investigated by an exploration of their electrochemical properties. For the PAMAM–NPD aggregates, the photoisomerization process leads to a change in the aggregate size. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5512–5519, 2005     

New Route to Smart Core‐Shell Polymeric Microgels: Synthesis and Properties

Summary: A new method has been developed to prepare smart polymeric microgels that consist of well‐defined temperature‐sensitive cores with pH‐sensitive shells. The microgels were obtained directly from aqueous graft copolymerizations of N‐isopropylacrylamide and N,N‐methylenebisacrylamide from water‐soluble polymers containing amino groups such as poly(ethyleneimine) and chitosan. The gel diameters ranged from 300 to 400 nm. The unique core‐shell nanostructures, which had narrow size distributions, exhibited tuneable responses to pH and temperature.

Transmission electron micrograph of the poly(N‐isopropylacrylamide)/chitosan core‐shell microgels.     

Drug Target Identification Using Affinity Core‐Shell Magnetic Nanoparticles and Mass Spectrometry

Affinity core‐shell magnetic nanoparticles (MNPs) were prepared for identifying the target proteins of drugs in the cell lysate when used in combination with nano‐high‐performance liquid chromatography tandem mass spectrometry (HPLC‐MS/MS)‐based shotgun proteomic analysis. A number of new potential targets of cyclosporine A (CsA) could be identified, owing to the high efficacy of the affinity MNPs in drug target identification. To the best of our knowledge, this is the first time to reveal such an abundant target spectrum of CsA.     

Facile Synthesis of Carbon‐Supported Ultrasmall Ag@Pd Core‐Shell Nanocrystals with Superior Electrocatalytic Activity for Direct Formic Acid Fuel Cell Application

To design electrocatalysts with excellent performance, morphology, composition and structure is a decisive influential factor. In this work, ultrasmall Ag@Pd core‐shell nanocrystals supported on Vulcan XC72R carbon with different Ag/Pd atomic ratios are synthesized via a facile successive reduction approach with formaldehyde and ethylene glycol as reducing agents, respectively. The Ag‐core/Pd‐shell nanostructures are revealed by high‐resolution transmission electron microscopy (HRTEM). Ag@Pd core‐shell nanocrystals possess a narrow size distribution with an average size of ca. 4.3 nm. In comparison to monometallic Pd/C and commercial Pd black catalysts, such Ag@Pd core‐shell nanocrystals display excellent electrocatalytic activities for formic acid oxidation, which may be due to high Pd utilization derived from the formation of Ag@Pd core‐shell nanostructure and the strong interaction between Ag and Pd.     

Synthesis and Characterization of Copolymercore-Silvershell Composite Microspheres

Composite microspheres composed of monodispersed poly（St-co-MAA） latices with diameter about 260 nm as core and Ag nanocrystals as shell were prepared by an in situ reduction method. The shell thickness could be controlled in the range of 15--45 nm by this coating process. The structure and the composition of the core-shell microspheres were characterized by transmission electron microscopy （TEM）, X-ray diffractometry （XRD）, X-ray photoelectron spectroscopy （XPS）, and thermogravimetric analysis （TG）. The formation of the composite microspheres is explained by the nucleation of silver on the surface of the latices followed by growth of the silver shell.