聚吡咯纳米粒子的制备与应用

综述了导电性聚吡咯纳米粒子的制备方法、特殊性能与应用。     

Morphology-dependent electrochemical supercapacitive characteristics of nanostructured manganese dioxide

The dependence on morphology of the supercapacitive characteristics of manganese dioxide nanospheres (NSs) and nanorods (NRs) was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and a series of electrochemical techniques. Because the nanosized pores in MnO₂ NSs resulted in high surface area, MnO₂ electrodes made of NSs had higher specific capacitance (SC) than those made of NRs at current densities less than 2.0 A g⁻¹. However, at current densities over 2.0 A g⁻¹, the power density of MnO₂ electrodes composed of NRs was better than that of NSs. The high surface area and nanosized pores in MnO₂ NSs increase the number of redox active sites, which leads to high specific capacitance. On the other hand, the small pore size in MnO₂ NSs restricts the rates of charge and discharge, thus limiting their power density.     

Network films of conducting polymer-linked polyoxometalate-modified gold nanoparticles: Preparation and electrochemical characterization

The ability of Keggin-type phosphododecamolybdate (PMo₁₂O₄₀³⁻, PMo₁₂) to undergo chemisorption on solid surfaces (including gold) is explored here to convert (by ligand place-exchange and phase transfer to aqueous solution) the alkanothiolate-modified Au nanoparticles of controlled size (prepared in toluene) into a stable colloidal solution of PMo₁₂-protected gold nanoparticles, PMo₁₂-AuNPs, the sizes of which are ca. 4-5 nm as determined by transmission electron microscopy. By dip-coating, PMo₁₂-AuNPs were assembled on carbon electrode substrates. The step-by-step assembly, by which alternate exposures to the solutions of PMo₁₂-AuNPs and either anilinium cations or pyrrole monomers, was utilized to grow in controlled manner hybrid network films in which the negatively charged PMo₁₂-AuNP deposits were linked, or electrostatically attracted, by ultra-thin, positively charged conducting polymer (polyaniline or polypyrrole) structures. The three-dimensionally distributed PMo₁₂-AuNPs immobilized within the polypyrrole-based composite film exhibited some electrocatalytic reactivity towards reduction of hydrogen peroxide.     

Electro-precipitation of magnetite nanoparticles: An electrochemical study

Nanoparticles of magnetites (Fe₃O₄) are synthesized with a new process based on electro-precipitation in ethanol medium. A mechanism pathway is proposed consisting of a Fe(OH)₃ precipitation followed by the reduction of iron hydroxide to magnetite in the presence of hydroxyl ions which are generated at the cathode.     

Synthesis and characterization of Fe-Ti nanoparticles by nitrogen plasma metal reaction

The plasma state and nanoparticle formation of Ti-Fe alloys were studied by nitrogen plasma metal reaction. The nitrogen plasma state is dependent on the nitrogen partial pressure and the master alloy composition. Synthesis of Ti-Fe nanoparticles can be carried out only when the nitrogen partial pressure is smaller than 10% or the Ti composition is larger than 50 at.%. The as-received nanoparticles are composed of TiN and Fe phases with the mean particle diameters ranging from 25 to 40 nm; the TiN and Fe nanoparticles have quadrangular and spherical appearance, respectively. The nitrogen plasma promotes Fe evaporation more strongly than Ti, and as a result the as-received nanoparticles are Fe-rich. Compared with the hydrogen plasma, the nitrogen plasma has a smaller effect on evaporation enhancement, but stronger reactivity.     

Synthesis, characterization and fine-tuning of bimodal poly(organosiloxane) nanoparticles

The acid catalyzed sol-gel type synthesis of polyorganosiloxane core-shell nanoparticles with removable PDMS core in aqueous dispersion leads to the inherent formation of a bimodal size distribution with smaller spheres having approximately 26 nm radii and larger nanoparticles with 60 nm in radius. The origin of the self-organized bimodality is investigated and finally attributed to a combination of stabilization of the growing particles due to i) a miniemulsion-type stabilization by the ultrahydrophobe PDMS and ii) by surface co-stabilization by the employed surfactant. The significant influence of temperature, pH, stirrer speed and amount of the surfactant on the particle sizes allows for the design and fine-tuning of different nanoparticles sizes and distributions.     

Synthesis and characterization of Au/TiO2 core-shell structure nanoparticles

Au/TiO₂ core-shell structure nanoparticles were synthesized by sol-gel process, and the morphology and crystallinity of TiO₂ shell were investigated by TEM and UV-vis absorption spectrometer. Au/TiO₂ core-shell structure nanoparticles could be prepared by the hydrolysis of TOAA (titanium oxide acethylacetonate) in gold sol ethanol solution with water. The thickness of TiO₂ shell on the surface of gold particles was about 1 nm. To investigate the crystallinity of TiO, shell, UV light with 254 nm and radioactive ray of⁶⁰Co were irradiated on the TiO₂-coated gold sol ethanol solution. The surface plasmon band of gold nanoparticles appeared only when the radioactive ray was irradiated on the TiO₂-coated gold sol ethanol solution. From these results, it was found that the TiO, shell was amorphous and the MUA (mercaptoundecanoic acid) layer on the Au particle for its dispersion in ethanol did not act as an obstacle to disturb the movement of electrons onto the surface of Au particles.     

纳米羟基磷灰石的制备及表征

采用化学沉淀法制备了羟基磷灰石纳米粒子,并且通过扫描电子显微镜(SEM)、X射线衍射(XRD)、红外光谱(IR)等测试手段,对其进行了表征。实验结果表明:以Ca(OH)2和H3PO4为原料所制备出的纳米羟基磷灰石纳米粒子多呈针状或短棒状,平均粒径20~25 nm,长75~80 nm,且大小均匀,分散性好。尺寸和形状更接近人体骨磷灰石结构,并能与骨形成牢固的化学结合,是一种很有应用前景的人工骨和人工口腔材料。     

Synthesis and characterization of sol-gel bioactive glass nanoparticles doped with boron and copper

In this work the sol-gel synthesis of bioactive glass nanoparticles containing both boron and copper oxides is reported for the first time in the literature. Two acid/base co-catalysed methods were compared. The obtained glasses have been characterized in terms of morphology, composition, particle surface area, phase analysis and bioactivity in acellular simulated body fluids. The almost spherical nanoparticles (<100 nm diameter) obtained are characterized by a certain degree of aggregation and have compositions, which are coherent with the theoretical ones. Each glass revealed the ability to promote the growth of hydroxyapatite on its surface during soaking in simulated body fluid, thus we can assume that the addition of boron and copper did not negatively affect the bioactivity of the sol-gel derived glasses. Future investigations will be devoted to biological characterizations for cytotoxicity, antibacterial properties and pro-angiogenetic abilities.     

PEI-assisted preparation of Au nanoparticles via reductive crystallization process

Nano-sized gold particles were prepared in a solution containing polyethylenimine (PEI) utilizing a batch reactor. PEI acts as a reducing agent as well as a stabilizing agent of nanoparticles. The effects of initial concentration of PEI on the mean particle diameter, coefficient of variation (C.V.), growth rate, nucleation rate and the number of nuclei were studied. The particle diameter of gold decreased markedly with increasing initial concentration of PEI, from 3.3 μm to a minimum value of about 5 nm. The observed decrease of particle diameter was considered to be caused by the growth-inhibiting effect of PEI, which affects the conclusive number of nuclei.     

Electrosynthesis and characterization of polypyrrole/Au nanocomposite

Polypyrrole films containing gold nanoparticles (PPy/Au) were electrosynthesized on a glassy carbon electrode. This was done by applying a constant current of 1.43 mA cm⁻² in solutions containing colloidal Au particles and pyrrole monomer. A chloroaurate medium with a citrate/tannic acid reducing/protection agent was employed for generating the Au colloids. The PPy/Au films were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Also, electrochemical behaviors of the PPy/Au films were characterized by cyclic voltammetry (CV) and AC impedance measurements. Experimental results demonstrate that PPy/Au has greater conductivity and better stability than PPy. The effect of incorporated Au nanoparticles in PPy matrix was studied and the mechanism was suggested.     

Electrocatalysis by design: Effect of the loading level of Au nanoparticles-MnOx nanoparticles binary catalysts on the electrochemical reduction of molecular oxygen

This study concerns the efficient electrochemical reduction of molecular oxygen (O₂), in O₂-saturated 0.1 M KOH solution, to OH⁻ through a four-electron reduction pathway by a novel binary catalyst that is comprised of two kinds of catalysts, i.e., Au nanoparticles (nano-Au) and manganese oxide nanoparticles (nano-MnOx) electrodeposited onto a relatively inert substrate, e.g., glassy carbon (GC) electrode. The nano-Au catalyst is efficiently used for the electro-reduction of O₂ to hydrogen peroxide through a two-electron reduction pathway at a reasonably low overpotential. While the latter (i.e., nano-MnOx) is effectively used for the subsequent catalytic decomposition of the electrogenerated hydrogen peroxide to water and molecular oxygen. The dependence of the electrocatalytic activity of the proposed binary catalysts towards the oxygen reduction on the loading level of both species has been investigated in this paper. This is done aiming at the preparation of a binary catalyst composed of the optimum amounts of both species which supports an apparent four-electron reduction of O₂ at sufficiently low overpotential in replacement of the costly Pt-based electrocatalysts.     

Formation of stable passive film on stainless steel by electrochemical deposition of polypyrrole

Stable passive film has been formed on 304 stainless steel during the electrochemical deposition of polypyrrole (PPy) from sulfuric acid solution. The stability of passive film under PPy increases with aging in H₂SO₄ and this film has much higher resistance to pitting than that formed by anodic polarization under the same condition of aging. XPS studies indicate that the content of chromium components in the oxides under PPy layer is about twice that of the anodically formed passive film with larger value of the ratio Cr₂O₃/Cr(OH)₃. Higher content of iron with a ratio of Fe²⁺/Fe³⁺ more than unity is also observed with a considerable lower hydration and sulfate content in the oxides under PPy layer. It is suggested that sulfate ion is consumed as a dopant in the formation of PPy film and the oxidation of stainless steel is achieved under the environment of lower concentration of water and sulfate molecules. This may result in the enhancement of formation of corrosion-resisting oxides rather than hydroxides and sulfates.     

Nanoassembly of CdTe nanowires and Au nanoparticles: pH dependence and reversibility of photoluminescence

Radial organized nanohybrids that are composed of Au nanoparticles (NPs) surrounding CdTe nanowires (NWs) via bioconjugation of streptavidin (SA) and D-biotin (B) were prepared to compare with the non-conjugated NWs. Two respective NW-containing hybrids with/without Au bioconjugation presented the same pH dependence except for photoluminescence (PL) reversibility. It would be explained that the chemical modification of NW surface can be retarded due to the geometric hindrance of acidic fluids in nanoscale regime and the loosely encapsulated Au NPs on NWs assisted to induce the luminescence recovery from collective resonance of excitons and plasmons in nanohybrids.     

Nanospherical particles of polypyrrole synthesized and doped by plasma

This work presents the synthesis of nano and meso spherical iodine doped particles of polypyrrole using glow discharges of pyrrole. The synthesis produced polypyrrole powder with the purpose of using the polymers in bioelectric applications. The powder was composed of homogeneous spheres of diameter between 35 and 350 nm, which arranged in agglomerates of several micrometers. A molecular simulation approach of polypyrrole nanoparticles was done considering full networking of 12 pyrrole rings joined in hexagonal arrangements. In those conditions, spherical particles can be obtained with a minimum diameter of approximately 1.4 nm. The inclusion of iodine atoms is difficult in such particles, however as the particles grow, iodine compounds produced in the chemical reactions can be trapped or adhered to the particles. The electric conductivity of polypyrrole powder as a function of relative humidity was in the interval 10⁻⁹-10⁻⁶ S/m.     

Synthesis of ultra-thin polypyrrole nanosheets for chemical sensor applications

Ultra-thin polypyrrole nanosheets (UPNSs) are fabricated by organic crystal surface-induced polymerization (OCSP) of pyrrole in an aqueous suspension containing hydrated crystals of sodium decylsulfonate (C₁₀SO₃Na) below the Krafft temperature using FeCl₃ as an oxidant. The hydrated C₁₀SO₃Na crystals are used as templates through electrostatic binding of the cationic polypyrrole (PPy) chains oxidized by Fe(III) ions on the anionic C₁₀SO₃Na crystal surface. The resulting UPNSs have a single layer thickness of ∼21 nm, widths between 2 and 6 μm, and lengths greater than 10 μm. The UPNSs are composed of a single continuous PPy domain. Moreover, the UPNSs exhibit higher conductivity (30.6 Scm⁻¹) and longer conjugation lengths than the PPy nanoparticles (2.4 Scm⁻¹) prepared using emulsion polymerization. We systematically investigate the UPNSs as gas sensors for detecting and quantifying toxic gases such as HCl and NH₃. The UPNSs exhibit much higher gas sensitivity and faster response times compared with the PPy nanoparticles.     

Colloidal Co nanoparticles supported on SiO2: Synthesis, characterization and catalytic properties for steam reforming of ethanol

Colloidal Co nanoparticles with sizes in the 3–8 nm range were obtained by thermal decomposition of Co₂(CO)₈ in the presence of ligands and impregnated on SiO₂ to prepare SiO₂-supported Co nanocatalysts. The catalysts showed activity for the steam reforming of ethanol with higher values for smaller Co particles. H₂ adsorption results and Fourier transform infrared spectroscopy of adsorbed CO suggested that the fraction of accessible Co sites also depended on the synthesis conditions. Precipitation of the Co nanoparticles with methanol instead of ethanol before impregnation had a positive effect on the density of accessible Co sites to catalysis; similar result was verified by increasing the thermal treatment temperature under H₂ flow before the reaction. Based on the distribution of products with temperature of reaction, a mechanism for steam reforming of ethanol on SiO₂-supported Co nanocatalysts is suggested.     

微波CVD法制备碳纳米球及结构表征

以甲烷为碳源气体,在不使用催化剂的条件下采用微波化学气相沉积法合成了直径为50nm左右的碳纳米球。采用X射线衍射仪、场发射扫描电镜、高分辨透射电镜和拉曼光谱等手段对碳纳米球的形貌与结构进行观察和分析。实验结果表明,本实验所合成的碳纳米球具有较高的纯度,碳球为实心结构,由围绕着中心排列组成的未闭合的石墨层构成。并结合实验结果对碳纳米球的生长机理进行了探讨。     

Synthesis and characterization of boron carbide films by plasma-enhanced chemical vapor deposition

The plasma-enhanced chemical vapor deposition of boron carbide was investigated on quartz glass and alumina substrates from a gas mixture of BCl 3 , H 2 , and CH 4 in an inductively coupled plasma (ICP) medium produced by a radio frequency (RF) discharged onto the gases passing through a tubular reactor under atmospheric pressure. A thin solid boron carbide coating with a gray color was deposited on both substrates. The results of XRD revealed that the major solid phase formed in the coating material was β-rhombohedral B 4 C. The SEM analysis showed that the surface homogeneity increased with an increase in the exposure time, and different boron carbide structures were formed at different RF powers and exposure times.     

Synthesis of nanostructured metal oxide by liquid-phase deposition

We synthesized hollow magnetite particles by liquid-phase deposition (LPD) using polystyrene (PS) particles as templates. We prepared β-FeOOH/PS composite particles by adding boric acid to an aqueous FeOOH/NH₄F·HF solution. PS particles were used as templates. Calcination of the composite particles under vacuum produced hollow magnetite (Fe₃O₄) particles that were readily attracted to a magnetic field.