Rapid synthesis and characterization of silver nanoparticle/bis(o-phenolpropyl)silicone composites by platinum

The formation of silver nanoparticle/bis(o-phenolpropyl)silicone composites have been promoted by the addition of chloroplatinic acid (<2 wt%) to the reaction of silver nitrate with bis(o-phenolpropyl)silicone BPPS [(o-phenolpropyl)2(SiMe2O)n, = 2, 3, 8, 236]. TEM and FE-SEM data exhibit that the silver nanoparticles having the size of <20 nm are well dispersed throughout the BPPS matrix in the composites. XRD patterns are consistent with those for polycrystalline silver. The addition of small amount of platinum to the silver accelerated the rate of composite formation by forming a Ag-Pt bimetallic alloy. The size of silver nanoparticles increased with increasing the relative molar concentration of silver salts added with respect to BPPS. However, the addition of platinum (1-5 wt%) to the AgNO3-BPPS mixture did not affect the size distribution of silver nanoparticles appreciably. It was found that in the absence of BPPS, most of the silver nanoparticles undergo macroscopic precipitation by agglomeration, indicating that BPPS is essential to stabilize the silver nanoparticles by coordination.     

Synthesis and characterization of silver nanoparticle composite with poly(p-Br-phenylsilane)

The one-pot synthesis and characterization of silver nanoparticle-poly(p-Br-phenylsilane) composites have been carried out. The conversion of silver(+1) salt to stable silver(0) nanoparticles is promoted by poly(p-Br-phenylsilane), Br-PPS possessing both possible reactive Si-H bonds in the polymer backbone and C-Br bonds in the substituents. The composites were characterized using XRD, TEM, FE-SEM, and solid-state UV-vis analytical techniques. TEM and FE-SEM data show the formation of the composites where large number of silver nanoparticles (less than 30 nm of size) are well dispersed throughout the Br-PPS matrix. XRD patterns are consistent with that for fcc-typed silver. The elemental analysis for Br atom and the polymer solubility confirm that the cleavage of C-Br bond and the Si-Br dative bonding were not occurred appreciably at ambient temperature. Nonetheless, TGA data suggest that some sort of cross-linking was occurred at high temperature. The size and processability of such nanoparticles depend on the ratio of metal to Br-PPS. In the absence of Br-PPS, most of the silver particles undergo macroscopic aggregation, which indicates that the polysilane is necessary for stabilizing the silver nanoparticles.     

TiO2/聚苯胺复合材料的合成、结构表征及光催化性能

在室温下,以苯胺为单体、钛酸四丁酯为反应物,通过化学氧化原位聚合和溶胶-凝胶的方法制备了TiO2/聚苯胺复合材料。利用X-射线衍射仪、傅立叶变换红外光谱仪、紫外-可见吸收光谱仪、热失重分析仪等对复合材料表面的微观结构及热稳定性进行了表征。通过光催化降解甲基橙实验评价了TiO2/聚苯胺复合光催化剂在紫外光条件下的光催化活性,实验表明,TiO2/聚苯胺复合材料的催化效率大大提高,特别是TiO2/聚苯胺(质量比例为1/2)复合材料对甲基橙的降解效率最高达到85.7%。     

Efficient synthesis of PbTe nanoparticle networks

The synthesis of semiconductor nanocrystalline networks using weak capping ligands in aqueous media has been demonstrated. Carbohydrates, including ?-cyclodextrin, D-(+)-glucose, D-glucosamine, lactobionic acid, sucrose, and starch were chosen as weak ligands to facilitate the formation of PbTe nanoparticle networks. The nanoparticle size, ranging from 5 nm to 30 nm, can be tuned by manipulating the temperature and concentration. Through a similar strategy, more complicated nanostructures including carbohydrate spheres@PbTe core-shell structures and Te@carbohydrate@PbTe multilayered submicron cables have been fabricated. This is a general approach which can be easily extended to the fabrication of other semiconductor networks, including PbSe and Bi₂Te₃ using carbohydrates and ethylenediaminetetraacetic acid (EDTA), respectively, as ligands.     

Preparation and characterization of polymer/inorganic nanoparticle composites through electron irradiation

In this paper, we report a new method to prepare the polymer/inorganic nanoparticle composites using electron irradiation-induced polymerization. The mixture of nanoparticles and MMA solution were co-irradiated by 1.6 MeV electron beam to a dose of 10, 20 and 30 kGy at a dose-rate of 60 kGy/h in air at room temperature. The products after irradiation were extracted using a soxhlet extractor with boiling xylene and investigated by X-ray diffraction (XRD), Fourier transmission infrared (FTIR), X-ray photoelectron spectroscopy (XPS), optical absorption spectra (OAP) and photoluminescence (PL). The FTIR and XPS results show that there exist some unextractable PMMA in the nanocomposites after extraction, indicating a strong interaction between the PMMA and nanoparticles. PL results show that new luminescence peaks appear at 415 and 420 nm for the nanocomposites of anatase and γ-Al₂O₃.     

Facile synthesis and characterization of hydroxylapatite nanoparticle chains

The hydroxylapatite nanoparticle chains were firstly synthesized by self-assembly with sodium polymethacrylic acid as the template. These high-quality HAP nanoparticle chains showed well-defined nanoscaled structures and regular morphology. The nanoparticle chains were 1.4-2 μm in length and the nanoparticles were about 45 nm in diameter. The structure of products has been studied with XRD and FT-IR spectrum. The forming conditions and mechanism of the products have been investigated. This synthesis method is facile and effective. The products will have potential applications in many fields such as biosensor, and biomimetic bone materials etc. The experimental outcomes present here will have potential values in crystal engineering research and practical applications.     

纳米功能化石墨烯/室温硫化硅橡胶复合材料的制备与表征

用KH-550对氧化石墨进行改性, 再对其进行还原, 获得功能化石墨烯(FG), 未经干燥的FG经超声处理后可以稳定分散在质量比9∶1的丙酮/水混合液中; 在高速搅拌和超声分散条件下, 将FG分散液分散到室温硫化(RTV)硅橡胶中, 固化后得到纳米FG(nano-FG)/RTV硅橡胶复合材料。采用FTIR、TEM、SEM、XRD和DSC分析了FG及复合材料的结构和形貌。结果表明: KH-550连接到石墨烯片层表面上, 使其片层起皱、折叠, 部分发生了剥离, 层间距增大到3.46 ; FG经过超声处理后剥离成透明至半透明的片层; nano-FG/RTV硅橡胶复合材料的断面结构为褶皱结构, 不同于纯硅橡胶, 也未出现微观相分离; 与硅橡胶相比, 复合材料的T_g、T_m和结晶度均有所提高。复合材料的力学性能测试结果表明, nano-FG对RTV硅橡胶具有明显的补强效果, 当nano-FG质量分数为0.5 %时, nano-FG/RTV硅橡胶复合材料的拉伸强度比纯RTV硅橡胶提高了一倍多, 达到了0.43 MPa; 断裂伸长率也提高了52%, 达到了265%。      

壳聚糖/纤维素生物质发泡复合材料多孔结构的表征

以壳聚糖微粒为增强体,离子液体为纤维素溶剂,采用冷冻干燥法成功制备了壳聚糖/纤维素生物质发泡复合材料。利用SEM、XRD和TGA表征多孔复合材料微观结构、结晶性能以及热稳定性,测试了其孔隙率和吸水性能。实验结果表明:壳聚糖/纤维素多孔复合材料具有三维相互贯通的微孔结构,壳聚糖粉体有助于孔洞结构的形成,TGA结果显示纤维素多孔材料的热稳定性能得以提高。XRD结果显示纤维素经离子液体溶解再生后晶型结构由纤维素I转化为纤维素II。纤维素含量较低(≤4wt%)时,随1wt%壳聚糖粉体的加入,孔隙率明显提高。壳聚糖/纤维素多孔复合材料的力学性能随纤维素含量的增加而不断提高,而吸水性能有所下降。壳聚糖与纤维素质量比为1∶3时,壳聚糖/纤维素多孔复合材料孔隙率为72.7%,吸水率和相对保湿率分别为28.0g/g和17.6g/g,断裂强度和断裂伸长率分别为0.32 MPa和25.4%,能够作为一种优良的吸附材料用于制备高性能的医用敷料。     

One-pot synthesis and characterization of poly(alkoxysilane)s promoted by silver colloidal nanoparticles

Si-Si/Si-O dehydrocoupling of hydrosilanes with alcohols (1:1.5 mole ratio), catalyzed by AgNO3 which converted to Ag(0) colloidal nanoparticles, gave poly(alkoxysilane)s in one-pot in moderate to high yield. The hydrosilanes include p-X-C6H4SiH3 (X = H, CH3, OCH3, F), PhCH2SiH3, and (PhSiH2)2. The alcohols include MeOH, EtOH, (i)PrOH, PhOH, and CF3(CF2)2CH2OH. The weight average molecular weight and polydispersity of the poly(alkoxysilane)s were in the range of 1,600 approximately 8,000 Dalton and 1.4 approximately 3.5. The dehydrocoupling reactions of phenylsilane with ethanol (1:3 mole ratio) in the presence of the silver nanocolloid catalyst produced only triethoxyphenylsilane as product.     

Photochemical synthesis and characterization of Ag/TiO2 nanotube composites

TiO₂ nanotubes were fabricated by a hydrothermal method. Silver nanoparticles with diameters around 3–5 nm were loaded onto the surface of TiO₂ nanotubes via a deposition approach followed by a photochemical reduction process under ultraviolet irradiation. Transmission electron microscopy (TEM), N₂ adsorption measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy (UV-vis), and fluorescence spectroscopy (FL) were applied to characterize the as-prepared Ag/TiO₂ nanotube composites. The photocatalytic activity of the as-prepared materials was investigated by photodegrading of methyl orange. The results showed that silver particles were in zero oxidation state and highly dispersed on the surface of TiO₂ nanotubes when the concentration of Ag⁺ was low. The presence of metallic silver can help the electron-hole separation by attracting photoelectrons. The Ag/TiO₂ nanotube composites with a suitable amount of silver showed a further improvement on the photocatalytic activity for degradation of methyl orange in water.     

Microwave-assisted synthesis and characterization of zinc oxide/carbon nanotube composites

A composite material of zinc oxide and carbon nanotubes were successfully synthesized via a sol process using zinc acetate dihydrate and treated multi-wall carbon nanotubes under microwave irradiation. The morphology, microstructure and chemical bonding of as-obtained composites were well characterized using X-ray diffraction, scanning electron microscope, transmission electron microscope, and Fourier transform infrared spectroscopy. Zinc oxide nanoparticles were dispersively coated on the surface of carbon nanotube when the precursor was dried under microwave irradiation without post-annealing. X-ray diffraction results obviously showed the mixture of two phases of carbon nanotube and wurzite zinc oxide whose size is approximately 15 nm. The formation of zinc oxide nanoparticles on carbon nanotube surface in the composite prepared by microwave heating is much better than the composite heated by conventional annealing. Fourier transform infrared spectroscopic results suggest that carboxylic groups and uniform heating by microwave heating could play key roles on the nucleation of zinc oxide on carbon nanotube surface.     

Chemical synthesis of hydroxyapatite/poly(ε-caprolactone) composites

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂)—biodegradable polymer composites as bone replacement scaffolds were synthesized by a colloidal non-aqueous precipitation technique at room temperature. The starting materials used for synthesizing hydroxyapatite (HA) were Ca(NO₃)₂·4H₂O and H₃PO₄ with a Ca/P ratio of 1.67 while poly(ε-caprolactone) (PCL) was used as the biodegradable polymer. The composites were prepared containing up to 34.5 wt.% HA and PCL polymer without any evidence of phase separation. This paper describes, the synthesis and structure of the HA/PCL composites. In addition, the pH changes during precipitation, the yield of the chemical reaction, and the possible existence of any bond between the ceramic and the polymer including the microstructure of the composites were studied. Finally, the mechanical and thermal properties of the composites were investigated. The results of these studies are described and discussed.     

Surface-confined synthesis of silver nanoparticle composite coating on electrospun polyimide nanofibers

A methodology for fabricating hierarchical nanostructures by surface-confined synthesis of silver nanoparticles on electrospun polyimide nanofibers is reported. Through surface-confined imide cleavage at the dianhydride domain via immersion in an aqueous KOH solution, potassium polyamate coatings of accurately defined thickness are formed (at a rate of 25 nm h(-1) ). By utilizing the ion-exchange capability of the polyamate resin, silver ions are introduced through immersion in an aqueous AgNO3 solution. Subsequent reduction of the metal ion species leads to the formation of nanoparticles at the fiber surface. Two modes of reduction, chemical and thermal, are investigated in the report, each leading to distinct morphologies of the nanoparticle coatings. Via thermal reduction, a composite surface layer consisting of monodisperse silver nanoparticles (average diameter 5.2 nm) embedded in a re-imidized polyimide matrix is achieved. In the case of chemical reduction, the reduction process occurs preferentially at the surface of the fiber, leading to the formation of silver nanoparticles anchored at the surface, though not embedded, in a polyamic acid matrix. By regulating the modification depth, control of the particle density on the fiber surface is established. In both reduction approaches, the polyimide nanofiber core exhibits maintained integrity.     

Optical and morphological characterisation of a silver nanoparticle/fluorescent poly(phenylenethynylene) composite for optical biosensors

Thiol silver nanoparticles prepared by the phase transfer method have been mixed with a fluorescent poly(phenylenethynylene) sequenced with dithioester-diethylsulfide moieties in order to develop a nanocomposite for its possible application in optical biosensors for the detection and attack of fungi such as Paecilomyces variotii. Films have been prepared by dipping technique and characterized by AFM, XPS, UV-Visible and fluorescence spectroscopy. Optical Absorption properties of the nanocomposite are similar to those of the polymer with an absorption tail in the visible which supports the presence of silver nanoparticles. Despite the lack of fluorescence of the nanoparticles, the composite emits in the yellow green region and the intensity of the fluorescence of the nanocomposite film decreases after the immersion in the culture thus permitting the detection of the fungus by this technique. The fungus can be deposited on films of both the polymer and nanocomposite, nevertheless only in the latter case, an attack on mycelium is observed revealing the fungicidal effect of silver nanoparticles in the nanocomposite.     

Aqueous synthesis of silver nanoparticle embedded cationic polymer nanofibers and their antibacterial activity

This paper describes the one-pot, aqueous synthesis of cationic polymer nanofibers with embedded silver nanoparticles. Poly[2-(tert-butylaminoethyl) methacrylate] (PTBAM) was used as a cationic polymer substrate to reinforce the antimicrobial activity of the embedded silver nanoparticles. Electron microscope analyses revealed that the as-synthesized nanofibers had diameters of approximately 40 nm and lengths up to about 10 μm. Additionally, silver nanoparticles of approximately 8 nm in diameter were finely embedded into the prepared nanofibers. The embedded silver nanoparticles had a lower tendency to agglomerate than colloidal silver nanoparticles of comparable size. In addition, the nanofibers with embedded silver nanoparticles exhibited excellent antibacterial performance against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Interestingly, the prepared nanofibers exhibited enhanced bactericidal performance compared with the silver-embedded poly(methyl methacrylate) (PMMA) nanofibers, presumably because of the antibacterial properties of the PTBAM substrate.     

Biosynthesis and structural characterization of silver nanoparticles from bacterial isolates

This study aimed to develop a green process for biosynthesis of silver nanomaterials by some Egyptian bacterial isolates. This target was achieved by screening an in-house culture collection consists of 300 bacterial isolates for silver nanoparticle formation. Through screening process, it was observed that strains belonging to Escherichia coli (S30, S78), Bacillus megaterium (S52), Acinetobacter sp. (S7) and Stenotrophomonas maltophilia (S54) were potential candidates for synthesis of silver nanoparticles. The extracellular production of silver nanoparticles by positive isolates was investigated by UV-Vis spectroscopy, X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results demonstrated that UV-visible spectrum of the aqueous medium containing silver ion showed a peak at 420 nm corresponding to the plasmon absorbance of silver nanoparticles. Scanning electron microscopy micrograph showed formation of silver nanoparticles in the range of 15-50 nm. XRD-spectrum of the silver nanoparticles exhibited 2θ values corresponding to the silver nanocrystal that produce in hexagonal and cubic crystal configurations with different plane of orientation. In addition, the signals of the silver atoms were observed by EDS-spectrum analysis that confirms the presence of silver nanoparticles (AgNPs) in all positive bacterial isolates.     

纳米SiO2/聚氨酯/环氧树脂复合体系的合成及表征

采用活性稀释剂的环氧基团与纳米SiO2反应,以达到对纳米SiO2的表面改性、防止团聚等目的;以环氧树脂(E44)和缩水甘油(Glycidyl)同时对聚氨酯预聚体进行封端,与TDE-85环氧树脂共混,组成纳米SiO2/聚氨酯/环氧树脂复合体系。采用FT-IR、DMA、SEM和万能实验机对体系的相关性能进行表征,结果表明,与纯环氧树脂和聚氨酯/环氧树脂/活性稀释剂复合体系相比,纳米SiO2/聚氨酯/环氧树脂复合体系的相关性能更加优异;加入纳米SiO2的Tg最高为78℃;断面形貌显示体系相容性好且纳米SiO2没有发生团聚;加入3%纳米的SiO2后,体系的拉伸强度和冲击强度达到最高,室温下分别为78.23MPa和50.85kJ/m2,液氮下(-196℃)分别为93.09MPa和62.56kJ/m2。     

Solar photocatalytically active,engineered silver nanoparticle synthesis using aqueous extract of mesocarp of Cocos nucifera (Red Spicata Dwarf)

ABSTRACT

Silver nanoparticles synthesised using aqueous extract of Cocos nucifera (CN) mesocarp were evaluated for their photocatalytic activity under solar irradiation. The silver nanoparticles were synthesised by a green method of harnessing bioactive phytocomponents from the mesocarp of Cocos nucifera. Large-scale application of this process necessitates the manoeuvering of the process parameters for increasing the conversion of silver ions to nanoparticles. Process parameters influencing the morphological characteristics of silver nanoparticles such as precursor salt concentration and pH of the synthesis mixture were studied. The crystalline nanoparticles were characterised using UV-vis spectroscopy, XRD, FTIR, SEM and EDX analysis. CN extract and 5 mM silver nitrate solution at a ratio of 1:4 (v/v) in the synthesis mixture was found to be the optimum. Alkaline initial pH of the synthesis mixture was found to favour the synthesis of smaller sized monodispersed silver nanoparticles. Solar energy was harnessed for the photocatalytic degradation of Malachite green dye using silver nanoparticles obtained through the green synthesis method. Overall process aims at utilisation of naturally available resource for the synthesis of silver nanoparticles as well as the degradation of dyes using these nanoparticles, making it useful in the treatment of wastewater.     

无水型双(全氟丁基磺酰)亚胺锂的合成与表征

以全氟丁基磺酰氟为原料,经胺化、成盐、中和、置换反应合成了无水型双(全氟丁基磺酰)亚胺锂。优化了双(全氟丁基磺酰)亚胺三乙胺盐的合成条件。较优的条件为:n(C4F9SO2NH2)∶n(C4F9SO2F):n(NEt3)=1:1.04:1.4,反应温度80℃,反应时间42h。在该条件下,反应收率可达99%以上,合成双(全氟丁基磺酰)亚胺锂的总收率为53.3%。通过FT-IR、1 H-NMR、MS和ICP等对中间体及最终产物进行了表征。