Self-assembly directed synthesis of poly(ortho-toluidine)-metal(gold and palladium) composite nanospheres

Poly(ortho-toluidine) (POT)-gold (Au) and palladium (Pd) composite nanospheres were successfully synthesized by the reaction of o-toluidine with the corresponding metal (Au or Pd) colloidal solution through self-assembly process in the presence of dodecylbenzenesulfonic acid (DBSA), which acts as both a dopant and surfactant, and ammonium peroxydisulfate as an oxidizing agent. The composites (POT-DBSA/Au or Pd) were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, UV-Visible (UV-Vis) spectroscopy, and electrical conductivity measurements. TEM images of the nanocomposites reveal that metal (Au or Pd) nanoparticles were well dispersed on POT spheres. TGA and XRD results show that the composites exhibit high thermal stability and are more crystalline compared with pristine POT. It was found that the electrical conductivity of the POT-DBSA/Au or Pd composites is 2 orders of magnitude higher than that of pristine polymer. Also, the POT-DBSA/Pd composite exhibits magnetic property. The formation mechanism of the POT-DBSA/Au or Pd composite nanosphere is discussed.     

In situ prepared polypyrrole–Ag nanocomposites: optical properties and morphology

Polypyrrole–silver (PPy–Ag) nanocomposites with various silver contents have been synthesized via a kinetically favorable one-step chemical oxidative polymerization process. The oxidant, ammonium persulfate, was used to oxidize pyrrole monomer for growing chains of PPy. And AgNO₃ was used as a precursor for metallic silver nanoparticles. The detailed characterization techniques, UV–Vis–NIR, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy (TEM), have been used to reveal electronic environment, structure, and morphology of composites as well as as-synthesized PPy. The synthesis environment prior to polymerization has also been investigated by absorption spectroscopy. The TEM images of PPy–Ag nanocomposites reveal that silver nanoparticles are deeply embedded into the polymer matrix in addition to surface adsorption. It is observed that the size distribution of inorganic nanoparticles (ca. 4–10 nm, depending on the metal ion concentrations) as well as structural morphology is altered by the initial concentrations of silver ions.     

Characterization of conductive composite films based on TEMPO-oxidized cellulose nanofibers and polypyrrole

Abstract  

In this article, conductive composite films based on TEMPO-oxidized cellulose nanofibers (TOCN) and polypyrrole (PPy) were synthesized in situ by a Chemical Polymerization Induced Adsorption Process of pyrrole on the surface of TOCN in aqueous medium. Resulting composite films were investigated by X-ray photoelectron spectroscopy, scanning, and transmission electron microscopy, N₂ gas adsorption analysis, thermogravimetric analysis, mechanical tests, and conductivity measurements in the ambient air. Our results showed a stable, flexible, and highly electrically conductive composite film in which PPy nanoparticles coated the surface of the TOCN network. In addition, the advantage in using the famous material, TOCN, is clearly due to the presence of carboxylate (COOH/COO⁻Na⁺) and hydroxyl (OH) moieties on the surface of TOCN. These reactive moieties could enhance the adsorption process of positively charged PPy backbone during polymerization. TEM observations demonstrated the formation of a PPy coat along the surface of the cellulose nanofibers having a diameter of about 90 nm which is relatively higher compared to the initial diameter of pure TOCN (~9 nm). Despite the physical and chemical treatment of TOCN during polymerization, the micrometric length of the cellulosic nanomaterial was maintained. In addition, the incorporation of polyvinyl alcohol as an additive in the TOCN/PPy composite seems to enhance the flexibility of composite films (bent up to 180°) without losing the high electrical conductivity. Finally, because of the high conductivity and good mechanical properties of the TOCN/PPy composite films obtained in this work, they can be used as a promising material in applications of sensors, flexible electrodes, and other fields requiring electrically conductive flexible films.     

Facile synthesis of monodisperse superparamagnetic Fe3O4/PMMA composite nanospheres with high magnetization

Monodisperse superparamagnetic Fe(3)O(4)/polymethyl methacrylate (PMMA) composite nanospheres with high saturation magnetization were successfully prepared by a facile novel miniemulsion polymerization method. The ferrofluid, MMA monomer and surfactants were co-sonicated and emulsified to form stable miniemulsion for polymerization. The samples were characterized by DLS, TEM, FTIR, XRD, TGA and VSM. The diameter of the Fe(3)O(4)/PMMA composite nanospheres by DLS was close to 90 nm with corresponding polydispersity index (PDI) as small as 0.099, which indicated that the nanospheres have excellent homogeneity in aqueous medium. The TEM results implied that the Fe(3)O(4)/PMMA composite nanospheres had a perfect core-shell structure with about 3 nm thin PMMA shells, and the core was composed of many homogeneous and closely packed Fe(3)O(4) nanoparticles. VSM and TGA showed that the Fe(3)O(4)/PMMA composite nanospheres with at least 65% high magnetite content were superparamagnetic, and the saturation magnetization was as high as around 39 emu g(-1) (total mass), which was only decreased by 17% compared with the initial bare Fe(3)O(4) nanoparticles.     

Fe3O4/ 聚吡咯复合材料的制备及表征

以化学沉淀法制备Fe₃O₄ 纳米粒子, 采用乙醇对Fe₃O₄ 纳米粒子表面进行处理, 使其表面有机化, 然后通过乳液原位复合制备Fe₃O₄ / 聚吡咯复合材料。利用TEM, XPS, 四探针测试仪和震荡磁力计对其进行表征和检测。结果表明: 经醇处理的Fe₃O₄ 纳米粒子的分散性得到明显改善, Fe₃O₄ 纳米粒子被包覆在聚吡咯层内, 包覆层厚度为10 nm 左右, 复合材料具有优良的电性能和磁性能, 电导率e= 7. 69 s/ cm～13. 6 s/ cm, 饱和磁强度M_s= 12. 06 emu/ g～24. 38 emu/ g, 矫顽力H_c= 11 Oe～41 Oe。其环境稳定性明显优于纯聚吡咯。      

Synthesis and characterization of novel Ag-polypyrrole@poly(styrene-co-methacrylic acid) nanocomposite particles

Novel raspberry-like Ag-polypyrrole/poly(styrene-co-methacrylic acid) (Ag-PPy/P(St-co-MAA)) colloidal nanocomposite particles were prepared by aqueous oxidative polymerization of pyrrole using AgNO₃ as the oxidant. The polymerization was carried out in the pre-synthesized polymer-emulsion of P(St-co-MAA) with emulsifier-free P(St-co-MAA) latex particles serving as both the templates and the stabilizers. Without any extra surfactants or polymer stabilizers, the polymerization proceeded steadily with the in-situ produced Ag-PPy nanocomposites depositing on the surface of the template particles. The obtained product is typical of raspberry-like morphology, whose nanostructures and compositions were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and electron dispersive X-ray spectrometer (EDS), respectively. The results confirmed that the surface of the P(St-co-MAA) latex was coated by Ag-PPy nanocomposite particles with a size range from 2 nm to 50 nm. Most of Ag nanoparticles are encapsulated by the PPy sheath or dispersed in the PPy layer.     

Synthesis of core-shell Au@polypyrrole nanocomposite using a dendrimer-template approach

Conducting polymeric nanostructures have been reported recently, which were produced from polypyrrole (PPy), including hollow nanocapsules, nanofibers, nanoporous membranes, nanowires, and nanofilms. In most cases, new synthetic routes were used aimed at controlling specific properties of these conducting nanostructures at the molecular level. In this communication we present a new chemical route to synthesize polypyrrole-based nanocomposites, in which polyamidoamine (PAMAM) dendrimers encapsulating Au nanoparticles are used as template. The two-step synthesis comprises the reduction of Au nanoparticles inside PAMAM molecules followed by PPy polymerization around the PAMAM-Au nanoparticles. The structure of the core-shell PAMAM-gold@polypyrrole nanospheres comprises a 40 nm PPy shell enclosing a core of 3 nm gold nanoparticles, as revealed by Transmission Electronic Microscopy (TEM). This new, environmentally-friendly approach may be suitable to produce hybrid nanomaterials for applications in catalysis, batteries, sensors, and micro/nanoelectronic devices.     

Nano-silver mediated polymerization of pyrrole: synthesis and gas sensing properties of polypyrrole (PPy)/Ag nano-composite

Thermal polymerization of pyrrole was performed using silver nitrate as source of silver ions followed by its conversion to Polypyrrole (PPy)/Ag nano-comoposites without using any external oxidizing agent or solvent. The formation of PPy was monitored by UV-Visible absorption spectroscopy showing a band at approximately 464 nm. XRD measurement confirmed characteristic peaks for face centered cubic (fcc) silver and presence of PPy at 2 theta of approximately 23 degrees suggesting the formation of PPy/Ag nanocomposite. Transmission electron microscopy (TEM) images showed non-aggregated spherical Ag nano-particles of about 5-10 nm. PPy/Ag thick film acts as a NH3 sensor at 100 degrees C, a H2S sensor at 250 degrees C and CO2 sensor at 350 degrees C. The thick films showed capability to recognize various gases at different operating temperature.     

Gas phase hydrogenation reaction using a ‘metal nanoparticle–polymer’ composite catalyst

A facile synthesis route is described here for the preparation of a poly (anthranilic acid)-palladium nanoparticle composite material by polymerization of anthranilic acid (AA) monomer using palladium acetate (PA) as the oxidant. It was found that oxidative polymerization of AA leads to the formation of poly-AA (PAA), while the reduction of PA results in the formation of palladium nanoparticles with an average size of ~2 nm. The palladium nanoparticles were uniformly dispersed and highly stabilized within the macromolecular matrix resulting in a uniform metal–polymer composite material. The resultant composite material was characterized by means of different techniques, such as IR and Raman spectroscopy, which yielded information about the chemical structure of polymer, whereas electron microscopy images provided information concerning the morphology of the composite material and the distribution of the metal particles in the composite material. The composite material was tested as a catalyst for ethylene hydrogenation reaction and showed a catalytic activity at higher temperatures.     

Palladium infiltration in high surface area microporous silica nanoparticles

Metallic Pd clusters were embedded into a host matrix of microporous SiO₂ nanoparticles via a solution reduction of Pd(NO₃)₂ by hydrazine hydrate. The infiltration of 33 wt.% Pd leads to a 13% porosity loss of SiO₂ nanoparticles, which demonstrated an initial surface area of 748 m²/g. The presence of Pd in the pores was demonstrated by EDS spectroscopy and by X-ray diffraction. The metallic guest species presumably reside in the accessible micropores with an estimated size about 1.3 nm. Hydrogen uptake was measured for Pd-infiltrated SiO₂ nanoparticles. A possible mechanism for the formation of composite nanoparticles is proposed based on electrostatic interaction between Pd²⁺ and SiO₂ nanoparticles.     

Ammonia gas sensor based on PPy/ZnSnO3 nanocomposites

In this paper, Zinc stannate (ZnSnO₃) nanoparticles were synthesized by a sol-gel method. Then, polypyrrole (PPy)/ZnSnO₃ nanocomposites were prepared by a simple in situ chemical polymerization method. By means of X-ray diffraction, Fourier transform infrared and scanning electron microscopy, the microstructure of PPy/ZnSnO₃ nanocomposites was characterized. The XRD patterns indicate that ZnSnO₃ nanoparticles have a perovskite phase with an orthorhombic structure, and incorporation of PPy did not change the crystalline structure of ZnSnO₃. The PPy was evenly dispersed on the surface of ZnSnO₃ particles, which was endorsed by FTIR spectral analyses. SEM images indicate that the PPy was evenly dispersed on the surface of ZnSnO₃ particles without apparent agglomeration. We found that the nanocomposites exhibited a higher response to NH₃ gas.     

Synthesis of dendrimer-stabilized gold-polypyrrole core-shell nanoparticles

Core-shell composite nanoparticles consisting of a gold core and polypyrrole shell were prepared and stabilized with the poly(amidoamine) dendrimer. An in situ redox polymerization technique was used in which pyrrole reduced Au3+ to Au and then oxidized to polypyrrole. The presence of gold nanoparticles as a core was characterized by its surface plasmon absorption peak at 534 nm. Fourier transform infrared spectroscopy confirmed the presence of polypyrrole on the nanoparticle surfaces. The average diameter of the core-shell nanoparticle is 8.7 +/- 1.8 nm with a shell thickness of approximately 1.5-2.0 nm as estimated from the transmission electron microscopy image. Dissolution of the Au core using KCN enabled the formation of hollow polymer nanospheres.     

TiN/聚吡咯纳米复合材料的制备及表征

采用氨解法制备了纳米氮化钛(TiN)粉体,对纳米TiN粉体进行表面改性,使其均匀分散到吡咯单体中.采用原位聚合法制备了TiN/聚吡咯(PPy)纳米复合材料.对合成的复合材料用X射线衍射(XRD)、透射电镜(TEM)、傅立叶变换红外光谱(FT-IR)、四探针测试仪等方法进行了表征与检测.结果表明:PPy成功地包覆在TiN纳米颗粒表面,形成了纳米TiN/PPy复合材料.复合材料具有优良的电性能.     

Studies of Fe-doped SiO<Superscript>2</Superscript>/TiO<Superscript>2</Superscript> composite nanoparticles prepared by sol-gel-hydrothermal method

Fe-doped SiO²/TiO² composite nanoparticles were directly prepared by sol-gel-hydrothermal process, and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), thermal gravimetry (TG), X-Ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectra (DRS). It was found that the Fe^{3 +} was well dispersed in solid solution of SiO²/TiO² composite nanoparticles that was about 10 nm with spherical morphology and rich silica layer external surface. It could effectively offer broadband shield for both UVB (290–320 nm) and UVA (320–400 nm). The results of Photodecomposition of methylene blue showed that the photoactivity of Fe-doped SiO²/TiO² composite was minimized due to the addition of iron ion.     

Synthesis and characterization of fluorescent chitosan-ZnO hybrid nanospheres

Hybrid hollow nanospheres of chitosan-ZnO (CS-ZnO Nps) were successfully prepared by the in situ growing of ZnO quantum dots (QDs) in an aqueous solution consisting of a cationic polymer CS and an anionic monomer acrylic acid (AA), followed by the polymerization of AA and selectively crosslinking of CS with glutaraldehyde. The as-prepared nanospheres were characterized by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV-visible spectrometer (UV) and fluorescence spectrophotometer (PL). ZnO QDs were dispersed evenly in the shell of hybrid nanospheres, with its dimension less than 5 nm. These fluorescent CS-ZnO Nps were expected to be simultaneously used as biological fluorescent labeling and a carrier for guest materials.     

One-pot synthesis of ZnO/Ag nanospheres with enhanced photocatalytic activity

ZnO/Ag composite nanospheres with an average diameter of about 440 nm, were synthesized through a facile one-pot solvothermal reaction, using a kind of biomolecular sodium alginate as template, H₂O and diethanolamine as solvents, followed by the assembly of ZnO and Ag nanoparticles in-situly produced. The composite spheres were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy disperse X-ray spectrum. Moreover, the results showed that the as-made ZnO/Ag assembled nanospheres exhibited better photocatalytic performance than the pure ZnO nanoparticles and this one-pot synthesis method has great potential to be extended for the synthesis of other metallic oxide/metal spheres.     

Fabrication of multiwalled carbon nanotubes/polypyrrole/Prussian blue ternary composite nanofibers and their application for enzymeless hydrogen peroxide detection

In this article, Prussian blue (PB) covered multiwalled carbon nanotubes (MWCNTs)/polypyrrole (PPy) ternary composite nanofibers with good dispersibility in water and ethanol have been prepared by directly mixing ferric-(III) chloride and potassium ferricyanide in the presence of MWCNT/PPy coaxial nanofibers under ambient conditions. Transmission electron microscopy shows that the as-synthesized PB nanoparticles covered on the surface of MWCNT/PPy nanofibers. Fourier-transform infrared spectroscopy, UV–Visible spectroscopy, and X-ray diffraction patterns have been used to characterize the obtained MWCNT/PPy/PB ternary composite nanofibers. The MWCNT/PPy/PB ternary composite nanofibers exhibit good electrocatalytic response to detection of H₂O₂ and provide a new material to modify electrode for amperometric biosensors.     

超临界流体沉积法制备纳米Cu/SBA-15复合材料

采用超临界流体沉积法,以无机盐Cu(NO₃)₂为前驱物,超临界CO₂为溶剂,乙醇为共溶剂,在压力20 MPa左右、温度 50℃ 条件下将Cu(NO₃)₂沉积到SBA-15介孔分子筛的孔道中。反应完成后,用氢气对前驱物进行还原,得到纳米线和纳米颗粒Cu/SBA-15复合材料。用透射电镜(TEM)和X射线衍射(XRD)对Cu/SBA-15复合材料进行表征,发现在SBA-15孔道内部填充了Cu 纳米线和分散的Cu 纳米颗粒。Cu 纳米线平均直径为6nm,长度为几纳米到几微米,并且沿着孔道生长,能够随着孔道发生弯曲;Cu纳米粒子的平均尺寸为3.2nm,高度分散。同时,实验中还发现,通过控制反应条件,能够控制复合材料中纳米结构的形貌(纳米线或者纳米颗粒) 。实验结果表明,超临界流体沉积法是制备担载型复合材料的有效方法。选择合适的共溶剂可以用超临界CO₂溶解无机盐,并可以通过控制反应条件,控制所制备的复合材料中纳米结构的形貌。     

A versatile approach for the fabrication of Au hollow nanoparticles based on poly(styrene-co-2-aminoethyl methacrylate) template

The hollow Au nanospheres were successfully prepared by the template method. The poly(styrene-co-2-aminoethyl methacrylate hydrochloride) (P(St-co-AEMH)) nanoparticles synthesized by the emulsion polymerization were used as the templates. After coating by Au colloidal nanoparticles and the formation of Au shells, the interior templates were etched out by sulfuric acid, leading to the formation of Au hollow nanospheres. The structure and morphology of the nanoparticles and hollow nanospheres were carefully investigated by the fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), wide-angle X-ray diffractometer (WAXD), and thermal gravimetric analysis (TGA) techniques.     

泡沫镍负载石墨烯/钯复合电极催化H2O2电还原研究

采用简单的一步浸渍法制备了还原氧化石墨烯-贵金属Pd复合改性的泡沫镍电极,采用X射线衍射和扫描电镜对复合电极的微观结构和表面形貌进行分析,通过循环伏安法、线性伏安法、计时电流法对H₂O₂还原反应的催化活性及稳定性进行了测试。结果表明,石墨烯包覆在泡沫镍骨架表面,在石墨烯内均匀分散着贵金属Pd纳米颗粒,直径约为100nm。该复合电极对H₂O₂电还原表现出较好的催化性能。在1mol/L NaOH+0.5mol/L H₂O₂混合溶液中,电位为-0.5V时,电流密度可达164mA/cm²,同时表现出较好的稳定性。