化学合成生物降解高分子材料的研究现状

综述了国内外近年来通过化学方法合成的各种可生物降解高分子材料,对其合成方法、降解原理、研究现状及研究热点进行了简单的概述,旨在为可生物降解材料的发展作铺垫。     

pH effect on the aggregation of silver nanoparticles synthesized by chemical reduction

Silver colloidal nanoparticles were prepared according to the chemical reduction method in which the ascorbic acid was used as a reducing agent and sodium citrate as a stabilizing agent. The absorption spectra of all prepared samples obtained using the UV-Vis spectrophotometer showed a surface plasmon peak at a wavelength of about 420 nm. The size of the silver nanoparticles was controlled by changing the pH values of the reaction system. At high pH, smaller size silver nanoparticles were obtained compared to low pH values. This difference can be attributed to the difference in the reduction rate of the precursor. In addition to the inverse proportionality between the size and the pH value it is clear that increasing the pH value enables us to obtain spherical nanoparticles while at low pH, rods and triangular particle shapes were formed. Poor balance between nucleation and growth processes could be the cause of this result.     

Photocatalytic and antibacterial activities of ZnO nanoparticles synthesized by chemical method

Journal of Materials Science: Materials in Electronics - In this study, ZnO NPs were synthesized and reporting first time using capping agent SDS with Zn (NO3)2 and KOH as precipitating agent. The...     

次亚磷酸钠还原法制备纳米铜颗粒

利用液相还原两步法,油酸为萃取荆和保护剂,葡萄糖和次亚磷酸钠将五水硫酸铜分别还原为氧化亚铜和单质铜,制备得到了粒度为50～100nm左右分散均匀的球形纳米铜颗粒,并用XRD、SEM和TEM对其进行了表征.结果表明,在油酸的保护下,采用液相还原两步法可制得分散性好、具有抗氧化性能的球形纳米铜颗粒.     

Inkjet printing using copper nanoparticles synthesized by electrolysis

A modified electrolysis method was employed to synthesize copper nanoparticles for mass production. Processing parameters including electrolyte temperature, pH and reduction agents were controlled in order to synthesize the particles continuously and directly from copper plates. As a result, well-dispersed copper nanoparticles with an average diameter of 15 nm were obtained and the oxidation of these particles was prevented by controlling the parameters. Using an amphiphilic surfactant, a water-based copper nano-colloid was prepared and printed onto a polyimide substrate using a conventional ink-jet printer. Copper patterns sintered at 230 °C showed a resistivity of 5.4 μΩ-cm (bulk resistivity; 1.67 μΩ-cm).     

High-frequency magnetic properties of Ni-Zn ferrite nanoparticles synthesized by a low temperature chemical method

Spinel-structured Ni-Zn ferrite nanoparticles (NPs) have been directly synthesized by a low temperature co-precipitation method. The structure and high-frequency magnetic properties of the particles were investigated. The as-prepared Ni-Zn ferrite NPs demonstrate typical soft magnetic properties. The saturation magnetization (M_s), as high as about 60 emu/g, was achieved. The imaginary part μ^' ' of the permeability shows a broad peak in the frequency range 200 MHz~6 GHz, which indicates that the as-prepared Ni-Zn ferrite NPs have a remarkable feature of electromagnetic (EM) wave absorption in the high-frequency range. Hence, resultant Ni-Zn ferrite NPs can be used as efficient microwave absorbers and effective heating mediators for hyperthermia application in cancer therapy.     

Bimetallic nanoparticles of copper and indium by borohydride reduction

This study investigated the preparation of copper-indium bimetallic nanoparticles through the borohydride reduction in an alcohol solution for application in ink-coating and sputtering target materials. Copper, indium metal and copper-indium intermetallic materials were synthesized by reacting CuCl₂ and InCl₃ with NaBH₄ in 2-propanol (IPA) and tetraethylene glycol (TEG) at room temperature. The Cu-In samples contained Cu₂In and CuIn phases with particle sizes of 10-100 nm and 30-200 nm in both the IPA and TEG solutions, respectively. The nanoparticulate Cu-In precursor layer was coated onto a soda-lime glass through spin-casting, where the Cu-In intermetallic phases of Cu₂In and Cu₁₁In₉ were produced through heat treatment in Ar gas and a microstructured CuInSe₂ layer was produced in a selenium atmosphere. Cu, In, Cu-In intermetallic nanoparticles and the films were characterized using powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analyses.     

化学还原法制备纳米银粒子及其表征

采用化学还原法, 通过一系列条件实验,借助紫外-可见分光光度计(UV-vis)得到最佳实验条件,在最佳实验条件下制得紫黑色溶胶,在40℃下真空干燥3h,获纳米银粉.制备的纳米银粉用X射线衍射仪(XRD)和透射电镜(TEM)分析表明,其粒径大小分布范围窄,形状为单一球形,平均粒径为18nm.     

Agglomerates of amorphous carbon nanoparticles synthesized by a solution-phase method

A novel solution-phase method is developed for preparation of agglomerates of amorphous carbon nanoparticles under ambient atmosphere by the reaction of ferrocene and ammonium chloride in diglycol at 200 °C. Samples are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and N₂ adsorption-desorption isotherms. It is found that the nanoparticles are complete amorphous and agglomerate together due to the strong surface tension. The agglomerates of amorphous carbon nanoparticles with a diameter of 20-50 nm have a wide size distribution of mesopores with a Brunauer-Emmett-Teller surface area of 75.2 m² g^− 1. It is proposed that the dissolved reactants uniformly dispersing in the solutions could react at a molecular level to form uniform carbon nanoparticles.     

Visible luminescence mechanism of ZnO nanoparticles synthesized by sol-gel method

We presented our investigations on the absorption and emission properties of the nanocrystalline ZnO particles of different particle sizes (2 nm-5 nm) by sol-gel method. In the room temperature PL spectra, three emission bands, ultraviolet (UV), blue and green were observed. With increasing the particle sizes, both the UV and the visible emission bands shifted to lower energies progressively. From the size-dependency, there was a linear relationship between the energetic maxima of the UV and the green emission bands with a slope of about 0.26, which indicated that the green luminescence of ZnO was produced by the transitions of electrons from deep level to the valence band (or shallow acceptor level). A linear dependence was also found between the energetic maxima of the UV and the blue emissions with a slope of 0.15, the origin this blue emission band is not clear at present. While in van Dijken et al.'s paper, however, they identified only two emission bands in the emission spectra, an UV and a broad visible emission band, and the linear fit between the energetic maxima of these two bands in particles of different sizes has a slope of 0.6, so they proposed that the visible emission in ZnO was originated from the recombination of a shallowly trapped electron with a deeply trapped hole. We attributed this divergence to the fact that the broad visible band is actually composed of two separate emission bands originated from two different recombination processes, and should not had been treated as one emission band.     

化学气相反应制备碳化硅纳米线

用硅粉、二氧化硅和石墨粉作原料，在无催化剂的条件下，在1400℃下用高温化学气相反应法制备了碳化硅纳米线，并用高分辨扫描电镜观察了所得碳化硅纳米线的形貌。所得碳化硅纳米线直径为100-500nm，长度可达几百微米。还提出了描述碳化硅纳米线的生长机理。     

Barium hydroxyapatite nanoparticles synthesized by citric acid sol-gel combustion method

Barium hydroxyapatite (BaHAP) nanoparticles have been synthesized by citric acid sol-gel combustion method using citric acid as a reductant/fuel and nitrate as an oxidant at a relatively low temperature of 600 °C. The thermal decomposition of nitrate-citrate xerogel was investigated by thermogravimetric/differential thermal analysis (TG/DTA) technique. The yielding powders calcined at 600 °C have been characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and transmission electron microscope (TEM). The possible combustion process was presented.     

Mixed Ni/Co hydroxide nanoparticles synthesized by sonochemical method

Nickel hydroxide nanoparticles with different amounts of cobalt atoms in the structure forming a unique material, were synthesized by using ultrasonic radiation. The particles of 5 nm diameter were prepared and characterized by X-Ray diffraction, Raman and Infrared spectroscopies, and thermogravimetry. The incorporation of cobalt leads to distinct crystalline planes, showing an opened and disarranged structure, indicating the stabilization of the alpha-Ni(OH)2 phase.     

Large-scale synthesis of copper nanoparticles by chemically controlled reduction for applications of inkjet-printed electronics

Copper nanoparticles are being given considerable attention as of late due to their interesting properties and potential applications in many areas of industry. One such exploitable use is as the major constituent of conductive inks and pastes used for printing various electronic components. In this study, copper nanoparticles were synthesized through a relatively large-scale (5?l), high-throughput (0.2?M) process. This facile method occurs through the chemical reduction of copper sulfate with sodium hypophosphite in ethylene glycol within the presence of a polymer surfactant (PVP), which was included to prevent aggregation and give dispersion stability to the resulting colloidal nanoparticles. Reaction yields were determined to be quantitative while particle dispersion yields were between 68 and 73%. The size of the copper nanoparticles could be controlled between 30 and 65?nm by varying the reaction time, reaction temperature, and relative ratio of copper sulfate to the surfactant. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images of the particles revealed a spherical shape within the reported size regime, and x-ray analysis confirmed the formation of face-centered cubic (FCC) metallic copper. Furthermore, inkjet printing nanocopper inks prepared from the polymer-stabilized copper nanoparticles onto polyimide substrates resulted in metallic copper traces with low electrical resistivities (≥3.6?μΩ?cm, or ≥2.2 times the resistivity of bulk copper) after a relatively low-temperature sintering process (200?°C for up to 60?min).     

Synthesis of copper indium sulfide nanoparticles by solvothermal method

Single crystalline CuInS₂ particles with a chalcopyrite structure and a size of 7–10 nm were prepared by a convenient solvothermal reaction, and characterized by XRD, XPS, TEM (HR-TEM) and UV–vis absorption spectroscopy. The as-synthesized nanoparticles can be redispersed in organic solvents, which will facilitate the practical application of these nanoparticles under organic-solution conditions. The growth of the CuInS₂ is regarded to involve the formation and decomposition of Cu²⁺-thiourea complexes, the reduction of Cu²⁺ and a slow supply of In³⁺ ions in the crystallization solution.     

Colloidal synthesis of indium nanoparticles by sodium reduction method

Nanocrystalline indium particles are prepared by direct reaction of sodium metal with anhydrous indium trichloride in N,N′-dimethylformamide (In-1) or n-trioctylphosphine (In-2 and In-3) as a solvent at a temperature between 120 and 360 °C under the atmosphere of argon. The product was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Visible spectroscopy and thermogravimetric analysis (TGA). XRD patterns of In-1 exhibit broad peaks with particle diameter of about 15 nm while In-2 and In-3 particles have bigger particle size of about 50 nm reflecting the effect of solvents and reaction temperatures. Absorption spectroscopy measurements reveal the solvent dependence of surface plasmon resonance with the sharp absorption peaks at about 290 nm for In-1 in toluene and 260 nm for In-3 in dichloromethane.     

Shape-controlled hollow silica nanoparticles synthesized by an inorganic particle template method

Shape-controlled hollow silica nanoparticles have been successfully synthesized by an inorganic particle template method, which involves sol–gel silica coating over surfaces of the template and followed by acid-dissolution removal of the template. This work demonstrates shape control of the hollow particle using calcium carbonate as the template with a variety of shapes such as cubic, rough-surfaced spherical and rod-like particles. Inner size and shape of hollow silica nanoparticles synthesized were exactly reflected to outer size and shape of template used, and existence of micropores in the silica shell wall was verified by nitrogen gas adsorption analysis.     

Structural and optical studies of yttrium oxide nanoparticles synthesized by co-precipitation method

Yttrium oxide (yttria) nanoparticles were successfully synthesized by co-precipitation method. As-synthesized and annealed powders were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), UV-visible (UV-vis), photoluminescence (PL) spectra and Fourier transform infrared spectrometer (FTIR). The XRD results show that the as-prepared sample has mixed phase of Y(OH)₃ and yttria (Y₂O₃). However, cubic yttrium oxide phase alone is found for annealed samples. The strain values are calculated from Williamson-Hall (W-H) plot for annealed samples. SEM and TEM micrographs show that the samples are composed of aggregated nanoparticles with different shapes and sizes. From the UV-vis spectra, it is found that the position of the absorption peak is shifted towards the lower wavelength side when particle size decreases. In the PL spectra, the broad emission bands are observed between 340 and 380 nm and the presence of metal oxide is confirmed by FTIR spectra.