现场紫外-可见吸收光谱研究电解二氧化锰的还原过程

应用现场紫外 可见吸收光谱研究碱性溶液中电解MnO2(EMD)放电机理.结果表明,对EMD电极的放电还原,包括两个单电子过程,其第1电子还原又分为3步:①还原MnO2颗粒表面和阳离子空位附近的Mn4+离子,②还原斜方锰矿中的Mn4+离子,③还原软锰矿中的Mn4+离子.第2电子还原是将溶解的Mn3+还原成Mn2+,进一步转化成Mn(OH)2和Mn3O4.     

One-step advanced preparation of surface-functional peptide nanospheres by the polymerization of L-phenylalanine N-carboxyanhydride with dual initiators

Surface-grafted peptide nanospheres consisting of hydrophobic poly(L-phenylalanine) with hydrophilic poly(ethylene glycol) (PEG) grafts were successfully prepared by the one-step polymerization of L-phenylalanine N-carboxyanhydride with the dual initiators of hydrophobic n-butylamine and hydrophilic NH2-monoterminated PEG (NH2-PEG). The monodispersed peptide nanospheres were stably self-assembled during polymerization in a mixture of water/dimethyl sulfoxide to create a colloidal solution, but only aggregated in water or organic solvents. When n-butylamine or NH2-PEG was used as a solitary initiator, the peptide nanospheres were not formed. The peptide nanospheres showed high dispersion-stability in water, and their diameter was approximately 300 nm. Furthermore, the peptide nanospheres were well-redispersed in water, retaining the same diameter and monodispersity even after lyophilization. Peptide nanospheres with the functional carboxylic acid on their graft layer were also successfully prepared by the one-step preparation method. This one-step preparation method of surface-grafted peptide nanospheres will be useful as an advanced technology to develop biodegradable functional nanospheres.     

Immobilization of enamel matrix derivate protein onto polypeptide multilayers. Comparative in situ measurements using ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry

The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces and the immobilization of enamel matrix derivate (EMD) protein was followed by utilizing in situ ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry (DPI). The use of the relatively new DPI technique validated earlier published ellipsometry measurements of the PLL-PGA polypeptide films. The hydrophobic aggregating EMD protein was successfully immobilized both on top of and within the multilayer structures at pH 5.0. DPI measurements further indicated that the immobilization of EMD is influenced by the flow pattern during adsorption. The formed polypeptide-EMD multilayer films are of interest since it is known that EMD is able to trigger cell response and induce biomineralization. The multilayer films thus have potential to be useful as bioactive and biodegradable coatings for future dental implants.     

Nanosphere formation in copolymerization of methyl methacrylate with poly(ethylene glycol) macromonomers

Polymeric nanospheres consisting of poly(methyl methacrylate) (PMMA) cores and poly(ethylene glycol) (PEG) branches on their surfaces were prepared by free radical copolymerization of methyl methacrylate (MMA) with PEG macromonomers in ethanol/water mixed solvents. PEG macromonomers having a methacryloyl (MMA‐PEG) and p‐vinylbenzyl (St‐PEG) end group were used. It has become clear that the obtained polymer dispersions form three kinds of states, particle dispersion (milky solution), clear solution, and gel/precipitation. It was found that the reaction parameters such as MMA concentration, molecular weight, and concentration of PEG macromonomers, and water content can affect nanosphere formation in a copolymerization system. The water volume fraction of mixed ethanol/water solvents affected the particle size of the nanospheres. These differences in the formation of nanospheres were due to the solvophilic/solvophobic balance between the copolymers and solvents during the self‐assembling process of the copolymers. The sizes of nanospheres can be controlled by varying concentration of PEG macromonomer and water content in solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1811–1817, 2000     

Hierarchical TiO2 nanospheres with dominant {001} facets: facile synthesis, growth mechanism, and photocatalytic activity

Hierarchical TiO(2) nanospheres with controlled surface morphologies and dominant {001} facets were directly synthesized from Ti powder by a facile, one-pot, hydrothermal method. The obtained hierarchical TiO(2) nanospheres have a uniform size of 400-500?nm and remarkable 78?% fraction of {001} facets. The influence of the reaction temperature, amount of HF, and reaction time on the morphology and the exposed facets was systematically studied. A possible growth mechanism speculates that Ti powder first dissolves in HF solution, and then flowerlike TiO(2) nanostructures are formed by assembly of TiO(2) nanocrystals. Because of the high concentration of HF in the early stage, these TiO(2) nanostructures were etched, and hollow structures formed on the surface. After the F(-) ions were effectively absorbed on the crystal surfaces, {001} facets appear and grow steadily. At the same time, the {101} facets also grow and meet the {101} facets from adjacent truncated tetragonal pyramids, causing coalescence of these facets and formation of nanospheres with dominant {001} facets. With further extension of the reaction time, single-crystal {001} facets of hierarchical TiO(2) nanospheres are dissolved and TiO(2) nanospheres with dominant {101} facets are obtained. The photocatalytic activities of the hierarchical TiO(2) nanospheres were evaluated and found to be closely related to the exposed {001} facets. Owing to the special hierarchical architecture and high percentage of exposed {001} facets, the TiO(2) nanospheres exhibit much enhanced photocatalytic efficiency (almost fourfold) compared to P25 TiO(2) as a benchmark material. This study provides new insight into crystal-facet engineering of anatase TiO(2) nanostructures with high percentage of {001} facets as well as opportunities for controllable synthesis of 3D hierarchical nanostructures.     

Synthesis and self-assembly of side-chain azocomplex for preparation of solid and hollow nanosphere

A new strategy based on ionic self-assembly technology was provided for design of solid and hollow nanospheres. Solid azocomplex nanospheres were constructed by ionic self-assembly of statistical ionomer and metanil yellow. The structure of azocomplex and self-assembly behaviors were examined by a variety of techniques including ¹H-NMR, ¹³C-NMR, DSC, FTIR, UV–vis, TEM, and elemental analysis. The azocomplex was subjected to solvent-induced self-assembly to construct a variety of morphologies. Solid polymeric nanospheres with the sizes of 50~100?nm in diameter were formed in aqueous solution. High-resolution transmission electron microscopes and X-ray energy dispersion spectrometer were used to study the morphology and composition of the solid nanospheres. The spherical and ordered structure was destroyed in DMF, and converted into membrane structure. Polymeric hollow nanospheres with azobenzene chromophores were formed in DMF/H₂O mixed solvent, with 62.5% H₂O in mass. The size of these hollow nanospheres was 50~120?nm in diameter.     

Interfacial Synthesis and Functionality of Self‐Stabilized Polydiaminonaphthalene Nanoparticles

A simple and effective template‐free synthesis method for nanosized conducting polymers with self‐stability and functionality is a main challenge. Herein, a strategy is reported for the facile synthesis of poly(1,5‐diaminonaphthalene) nanospherical particles by an interfacial miniemulsion oxidative polymerization of 1,5‐diaminonaphthalene at mobile microinterfaces between a stirred biphase without external emulsifiers. The size of the nanospheres was carefully optimized by controlling the polymerization conditions. Formation and self‐stabilization mechanisms of the nanoparticles are proposed. The constantly movable and refreshed microinterface is a key to successful synthesis of the nanospheres, for significantly suppressing secondary growth leading to agglomerated particles because vigorous stirring makes as‐formed self‐stabilized nanospheres instantly leave the microinterfaces. The resulting nanospheres possess several advantages: clean surface, self‐stability, redispersibility, semiconductivity, electroactivity, and fluorescence emission. The fluorescence emission can be quenched by specific quenchers, thus enabling low‐cost, high‐performance chemosensors to be obtained for the sensitive detection of Zn^II ions in a wide linear concentration range of more than five orders of magnitude with a superior detection limit down to 1 nM .     

醇/水介质对PEG大分子单体与BMA分散共聚反应的影响

通过端基反应法合成了苯乙烯单封端的聚乙二醇(St- PEG)大分子单体,使其与甲基丙烯酸丁酯(BMA)在乙醇 水混合介质中进行分散共聚,得到了聚乙二醇接枝的聚甲基丙烯酸丁酯(PBMA- g -PEG)高分子微球.PBMA- g -PEG共聚物的亲溶剂 疏溶剂平衡将影响微球的形成,反应结束时,体系随BMA浓度和介质中水含量的变化呈现出4种不同的状态,透明清液、乳液、伴有沉淀或凝胶的乳液和凝胶.用透射电子显微镜(TEM)和激光光散射(LLS)对乳液体系的粒径及其形态进行了表征,表明所得接枝高分子微球形态规整具有较好的单分散性.通过控制介质中水的含量和BMA的浓度可得粒径在4 0～5 0 0nm范围的PBMA -g -PEG微球.     

Ordered Microporous Surface Films Formed by Core‐Shell‐Type Nanospheres

Summary: Polymer nanospheres are synthesized by free‐radical dispersion copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) with a methacryloyl‐terminated polystyrene (PS‐MC) macromonomer in cyclohexane. Such polymer nanospheres are stabilized sterically with polystyrene (PS)‐grafted chains in cyclohexane at temperatures greater than 34 °C (the Θ temperature for PS). Ordered microporous surface films are constructed by casting these core‐shell‐type nanospheres from hot cyclohexane solution at 20 °C. The results indicate the possibility of fixation or encapsulation of functional materials after microporous patterning of the core‐shell‐type nanospheres.

SEM photograph of a vertical section of a hexagonal micropore film obtained here.     

One-step synthesis of hollow UO2 nanospheres via radiolytic reduction of ammonium uranyl tricarbonate

Black precipitates were successfully obtained by radiolytic reduction of ammonium uranyl tricarbonate in the aqueous solution of HCOONH_4 by one step.TEM,SAED,EDS,and XRD analysis indicated that the precipitates consist of hollow UO_2 nanospheres(φ:30-50 nm,wall thickness:8-15 nm,and cavity diameter:10-20 nm).The effect of HCOONH_4 concentration,irradiation time and dose rate on the morphology,and size of nanospheres was investigated.Then,a gas-bubble template mechanism was proposed.     

Synthesis,characterization, and application of monodisperse gelatin-stabilized silver nanospheres in reduction of aromatic nitro compounds

Monodisperse colloidal silver nanospheres were synthesized by the reaction of silver nitrate, hydroxylammonium hydrosulphate (NH₂OH)₂ · H₂SO₄ and sodium hydroxide in the presence of gelatin as stabilizer. Colloidal nanospheres were characterized by UV-vis absorption spectroscopy, transmission electron microscopy, X-ray diffraction and dynamic light scattering. X-ray diffraction data confirmed that the silver nanospheres were crystalline with face-centered-cubic structure. Transmission electron microscopy analysis revealed the formation of homogeneously distributed silver nanoparticles of spherical morphology and size of the nanoparticles was in the range of 0.7–5.2 nm. Silver nanospheres were stable for more than two months when stored at ambient temperature. Size and size distribution were studied by varying pH, reaction temperature, silver ion concentration in feed solution, concentration of reducing agent and concentration of the stabilizing agent. Catalytic activity of silver nanospheres was tested for the reduction reaction of nitro compounds in sodium borohydride solution. Monodisperse silver nanospheres showed excellent catalytic activity towards the reduction of aromatic nitro compounds. The reduction rate of aromatic nitro compounds had been observed to follow the sequence 4-nitrophenol > 2-nitrophenol > 3-nitrophenol.     

Phase diagrams of self-assembled mono-tethered nanospheres from molecular simulation and comparison to surfactants

We perform Brownian dynamics simulations on model 3-D systems of mono-tethered nanospheres (TNS) to study the equilibrium morphologies formed by their self-assembly in a selective solvent. We predict that in contrast to flexible amphiphiles the nanospheres are locally ordered and there is an increase in the local order with an increase in concentration or relative nanoparticle diameter. We present the temperature vs concentration phase diagram for a system of TNS and propose a dimensionless scaling factor F(v) (headgroup volume/tether volume) that allows a comparison between the morphologies formed from TNS and traditional surfactants.     

Highly Stable Amorphous Calcium Phosphate Porous Nanospheres: Microwave‐Assisted Rapid Synthesis Using ATP as Phosphorus Source and Stabilizer,and Their Application in Anticancer Drug Delivery

Highly stable amorphous calcium phosphate (ACP) porous nanospheres with a relatively uniform size and an average pore diameter of about 10 nm have been synthesized by using a microwave‐assisted hydrothermal method with adenosine 5′‐triphosphate disodium salt (ATP) as the phosphorus source and stabilizer. The as‐prepared ACP porous nanospheres have a high stability in the phosphate buffer saline (PBS) solution for more than 150 h without phase transformation to hydroxyapatite, and the morphology and size were essentially not changed. The important role of ATP and effects of experimental conditions on the formation of ACP porous nanospheres were also investigated. The ACP porous nanospheres were characterized by X‐ray powder diffraction (XRD), Fourier‐transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This method is facile, rapid, surfactant‐free and environmentally friendly. The as‐prepared ACP porous nanospheres are efficient for anticancer drug (docetaxel) loading and release. The ACP porous nanosphere drug‐delivery system with docetaxel shows a high ability to damage tumor cells, thus, is promising for the application in anticancer treatment.     

Denting Nanospheres with a Short Peptide

Dented nanospheres show promising potential in drug delivery,nanomotors,etc.However,it is still challenging to prepare them by homopolymer self-assembly because of the strict structural requirements of the homopolymer.Herein,we propose a strategy for preparing dented nanospheres from homopolymers by co-assembly with a short peptide.They were co-assembled from poly(2-hydroxy-3-((4-(ethoxycarbonyl)phenyl)amino)propyl methacrylate) (PHBzoMA59) and (S)-2-((S)-2-((((gH-fluoren-9-yl)methoxy)carbonyl)amino)-3-phenylpro-panamido)-3-phenylpropanoic acid (Fmoc-FF-OH).PHBzoMA homopolymers can only self-assemble into nanospheres without dent,and the addition of a short peptide introduced hydrogen bonding and complementary π-π stacking interactions led to the final dented nanosphere morphology.The weight fractions of the short peptide can be adjusted to regulate the final morphology.It was confirmed that the radius of curvature of the dent on the surface was related to the organic bubble inside the protospheres prepared at critical aggregation concentration(CAC).The organic bubble can be adjusted by altering the kind of organic solvent and solution pH,which allowed control over the dented nanosphere dimension.The use of different organic solvents with various polarities allows adjustment of the interfacial tension,and hence the denting degree.This degree can also be controlled by manipulating the solution pH to (de)protonate the short peptide and homopolymer.Furthermore,the versatility of this method was highlighted by using a different homopolymer and the applicability of the resulting dented nanospheres was demonstrated by decoration with gold nanoparticles.Overall,this study provided important insights and a new simple strategy to prepare dented nanospheres in a controlled fashion.     

受限空间内聚苯乙烯微粒的制备

以(N,N-二甲氨基-4-吡啶)五氰合铁(II)封端的聚氧丙烯聚氧乙烯共聚物(EPE-Fe)与苯乙烯在水中自组装形成纳米体系(EPE-Fe-St), 在纳米尺度受限空间内进行了苯乙烯自由基聚合, 制备了聚苯乙烯微球(EPE-Fe-PS). 用Fe³⁺对自组装体系的纳米球壳进行固化后形成Fe-EPE-Fe-St 体系, 聚合后也制备了聚苯乙烯微球(Fe-EPE-Fe-PS). 研究结果表明,制备了粒径为60～200 nm 的不同粒径单分散聚苯乙烯微球, 聚合温度对纳米Fe-EPE-Fe-St 体系粒径影响较小, 而对EPE-Fe-St 体系较大. 在受限空间内苯乙烯的自由基聚合可得到数均分子量超过70 万的聚苯乙烯; 自组装体系中引发剂量增多使聚苯乙烯分子量下降, 聚合温度上升也使分子量下降, 而增加自组装的EPE-Fe 用量可增加聚苯乙烯的分子量. 两种受限条件下的聚苯乙烯微球的玻璃化转变温度(T_g)在90～135 ℃之间, 纳米反应器壳层的硬化提高了聚苯乙烯微球的T_g.     

Electrophoretic behavior of DNA‐methyl‐CpG‐binding domain protein complexes revealed by capillary electrophoreses laser‐induced fluorescence

The free solution electrophoretic behavior of DNA‐protein complexes depends on their charge and mass in a certain experimental condition, which are two fundamental properties of DNA‐protein complexes in free solution. Here, we used CE LIF to study the free solution behavior of DNA‐methyl‐CpG‐binding domain protein (MBD2b) complexes through exploring the relationship between the mobilities, charge, and mass of DNA‐protein complexes. This method is based on the effective separation of free DNA and DNA‐protein complexes because of their different electrophoretic mobility in a certain electric field. In order to avoid protein adsorption, a polyacrylamide‐coated capillary was used. Based on the evaluation of the electrophoretic behavior of formed DNA‐MBD2b complexes, we found that the values of (μ₀/μ)‐1 were directly proportional to the charge‐to‐mass ratios of formed complexes, where the μ₀ and μ are the mobility of free DNA probe and DNA‐protein complex, respectively. The models were further validated by the complex mobilities of protein with various lengths of DNA probes. The deviation of experimental and calculated charge‐to‐mass ratios of formed complexes from the theoretical data was less than 10%, suggesting that our models are useful to analyze the DNA‐binding properties of the purified MBD2b protein and help to analyze other DNA‐protein complexes. Additionally, this study enhances the understanding of the influence of the charge‐to‐mass ratios of formed DNA‐protein complexes on their separation and electrophoretic behaviors.     

Reversible thermoresponsive aggregation/deaggregation of water-dispersed polymeric nanospheres exhibiting structural transformation

Crystalline polymeric nanospheres composed of poly{stearyl methacrylate (SMA)-co-poly(ethylene glycol) monomethacrylate (PEGm)}s were prepared by the dispersion radical polymerization of SMA and PEGm in an ethanol/water solution. Scanning electron microscopy showed that the nanospheres were highly spherical, and had a narrow size distribution. Electron spectroscopy for chemical analysis and X-ray diffraction studies of the nanospheres suggested a core-corona-type structure; the hydrophilic PEGm corona accumulated on the nanosphere surface, while the hydrophobic SMA core formed a layered structure. Heat treatment caused a melting of the SMA layers, but successive cooling allowed it to re-form. Accompanying this reversible order-disorder transition, the nanospheres also showed a reversible aggregation/deaggregation behavior in their water-dispersion state.     

锆酸钡/聚合物复合中空纳米球的水热合成

采用聚合物辅助水热合成方法, 在强碱条件下加入PAA和PVA的混合液,实现了聚合物/锆酸钡复合中空纳米球的软化学一步合成, 而且球壳为有机-无机复合材料, 有望用于吸附分离、催化剂载体、轻质陶瓷和涂料等方面.     

Direct facile approach to the fabrication of chitosan-gold hybrid nanospheres

Chitosan-gold hybrid nanospheres were prepared through a direct facile approach that utilized cross-linked composite nanospheres consisting of low-molecular-weight chitosan (LWCS) and ethylenediaminetetraacetic acid (EDTA) as a precursor reaction system. EDTA was employed not only to construct the counterion interaction-based composite nanospheres with the cationic chitosan but also as the reductant for subsequent in situ gold salt reduction within the LWCS-EDTA composite nanospheres. This approach elegantly ensured that each and every nanosphere was loaded with gold nanoparticles and no nonembedded free gold nanoparticles would exist in the dispersing medium. Moreover, becauseof the noncovalent interaction between LWCS and EDTA, the EDTA reductant can be easily removed from the cross-linked nanospheres, and "pure" chitosan-gold hybrid nanospheres can be obtained. The obtained chitosan-gold hybrid nanospheres were found to have a tunable size and good dispersing stability within a wide pH range. The embedded gold nanoparticles were in the range from several to several tens of nanometers, which may be useful for sensing and imaging. Morphology studies indicated that most of the loaded gold nanoparticles were located in the interior of the hybrid nanospheres. Taking into account the good biocompatibilities of LWCS, abundant functional (amino) groups in chitosan, and the mild preparation conditions, we find that the chitosan-gold hybrid nanospheres prepared here may have tremendous potential in advanced biomedical applications.     

Water/ionic liquid interfaces as fluid scaffolds for the two-dimensional self-assembly of charged nanospheres

Liquid-liquid interfaces formed between water and ionic liquids serve as fluid scaffolds to self-assemble anionic nanospheres two-dimensionally. When aqueous dispersions of anionic fluorescent polystyrene nanospheres (diameter ～500 nm) are layered on ionic liquids, ordered monolayers are spontaneously formed at the interface. Fluorescent nanospheres are hexagonally packed in the interfacial monolayers, as observed by confocal laser scanning microscopy (CLSM). The adsorption and alignment of nanospheres at the interface are affected by the ionic strength and pH of the aqueous phase, indicating electrostatic interaction as the primary driving force for the self-assembly. CLSM observation of the water/ionic liquid interface reveals that the lower hemisphere of nanospheres is exposed to the ionic liquid phase, which effectively alleviates lateral electrostatic repulsion between charged nanospheres and promotes their close packing. The densely packed monolayer structure of nanospheres is stably immobilized on the surface of CLSM glass dishes simply by rinsing the ionic liquid layer with pure water, probably as a consequence of the gluing effect exerted by imidazolium cations. The fluidic nature of the water/ionic liquid interface facilitates the diffusion and ordering of nanospheres into a hexagonal lattice, and these features render the interface promising soft scaffolds to self-assemble anionic nanomaterials two-dimensionally.