溶胶-凝胶法制备环氧树脂／纳米SiO2复合材料中纳米粒子的分散性研究

用溶胶-凝胶法制备环氧树脂／纳米SiO2复合材料，研究了在脱除溶剂以及反应副产物过程中温度、表面改性剂对纳米SiO2粒子的分散性、固化后样品力学性能的影响。研究表明：纳米SiO2的引入对环氧树脂的力学性能有一定的提高；随着体系溶剂脱除温度的升高纳米粒子的团聚明显；加入表面改性剂能够阻止纳米粒子的团聚，硅烷偶联剂KH550比表面活性PEG剂能够更好地阻止纳米粒子的团聚；但是表面活性剂PEG的加入会使纳米复合材料的力学性能有一定程度的下降。     

聚苯乙烯/纳米SiO2复合颗粒制备与表征

为改善二氧化硅(SiO2)纳米粒子与聚合物基体间的亲和性,使SiO2表面功能化,将硅烷偶联剂KH-570引入C=C基团,采用乳液聚合方法在纳米SiO2粒子表面接枝苯乙烯(St)单体,实现了纳米二氧化硅表面的聚苯乙烯(PS)高分子包覆改性,制备了具有核/壳结构的SiO2-PS复合纳米粒子,产物的单体转化率和接枝效率在80%以上.研究了二氧化硅含量和偶联剂用量对聚合反应的单体转化率和接枝效率的影响,探讨了偶联剂的作用机理,利用FT-IR、TEM、TG对SiO2-PS复合粒子的表面结构进行了表征.结果表明,复合粒子具有明显的核壳结构,壳层厚度在20nm左右,乳液聚合过程可有效使二氧化硅的团聚体剥离呈纳米级颗粒.     

美制成金纳米粒子和蛋白质复合结构

美国能源部布鲁克海文国家实验室研究人员表示，他们成功地将金纳米粒子附着于蛋白质，形成了蛋白质-金纳米粒子均匀排列的薄层结构。研究人员认为，这种由纳米粒子和蛋白质组成的复合结构将能帮助人们了解蛋白质结构，确定蛋白质功能成分和组合新的蛋白质复合结构。相关研究报告将刊登在7月2日德国《应用化学》杂志上。     

模板法制备SiO2/Au复合微球及其催化性能评价

采用脲醛树脂为模板,金胶体为前体的新方法,制备了具有较大比表面积的SiO2/Au复合微球。该方法通过将金胶体与硅溶胶混合,加入尿素、甲醛溶液并在酸性条件下引发聚合反应,得到脲醛树脂(UF)/SiO2/Au复合微球;经高温煅烧除去UF模板,得到中孔SiO2/Au复合微球。采用紫外可见吸收光谱、高分辨透射电镜、原子吸收分光光度计和氮气吸附-脱附等手段对金纳米粒子在载体中的分散性、金负载量及材料比表面积和孔径分布进行了表征。该复合微球在硼氢化钠还原对硝基苯胺的反应中显示了良好的催化活性。     

纳米SiO2/PEA复合粒子的制备和表征

在经预处理的SiO2表面上通过乳液聚合反应接枝丙烯酸乙酯,用FT-IR和XPS对制备的纳米SiO2/PEA复合粒子进行了表征,研究了由复合粒子填充的PP/POE/SiO2复合材料的力学性能、结晶性能和结构形态。结果表明:通过乳液聚合反应成功地将EA接枝到纳米SiO2的表面上;由复合粒子填充的PP/POE/SiO2复合材料,纳米SiO2在基体中的分散尺寸约为100 nm,分布较均匀,复合材料的冲击强度和断裂伸长率均得到提高,在SiO2含量4%(质量分数)时,PPβ晶峰的强度最强。     

Ni-Cr—Al纳米复合镀层的制备及结构表征

采用复合电沉积技术，通过向Ni电镀液中加入一定量的Cr和Al纳米粒子制备了一种新型Ni-Cr-Al纳米复合镀层，作为比较，同时制备了Cr和Al微米粒子复合的镀层。研究了镀层中粒子尺寸对复合量的影响和镀层的微观结构。在相同的工艺参数下，纳米粒子由于在阴极的吸附少，因此较微米粒子难沉积。结构分析表明，该镀层具有纳米结构，即...     

纳米SiO2对聚丙烯酸酯乳液压敏胶性能的影响

采用原位乳液聚合法成功制备了聚丙烯酸酯/纳米SiO2复合压敏胶乳液.纳米SiO2无需表面处理,即能有效地被分散成初始粒子状态,并在纳米尺度上与原位生成的聚丙烯酸酯复合.SiO2因界面作用富集于乳胶粒子的表面,使整个粒子具有类似于"草莓"般的形貌.纳米SiO2可显著改善聚丙烯酸酯胶膜的流变性能和压敏性能,除初黏会略微下降外,持黏和180°剥离强度可同时提高,其中180°剥离强度能提高到30%以上.     

立体复合聚乳酸/SiO_2复合物的性能研究

采用溶液共混法制备了不同SiO2含量的立体复合聚乳酸/纳米SiO2复合物。DSC研究表明,纳米SiO2含量低于5%(wt,质量分数,下同)时,其对聚乳酸立体复合物的结晶有促进作用,并且在纳米SiO2添加量为1%时促进作用最为明显。随着添加量增加,材料的热稳定性明显增加,但团聚现象变得明显。XRD和FT-IR研究表明立体复合物结构并未因纳米粒子加入发生改变。     

电喷雾和二步热处理制备无硬团聚纳米氧化锌

通过电喷雾和二步热处理法制备得到无硬团聚的ZnO纳米微粒, 为制备无硬团聚氧化物纳米粉体提供了一种新方法. 试验采用添加适量PVP的Zn(CH₃COO)₂·2H2O的乙醇溶液作为电喷雾液体, 经过锥形喷雾得到均匀的微米级小液滴. 干燥后的喷雾产物先后在氮气炉和空气炉中分别600℃和400℃保温1h进行二步热处理. SEM、XRD测试结果表明, 使用该方法制备得到的ZnO纳米微粒粒度均匀, 结晶完整, 无硬团聚, 具有六角纤锌矿结构.     

溶胶-凝胶法制备环氧树脂/纳米SiO2复合材料中纳米粒子的分散性研究

用溶胶-凝胶法制备环氧树脂/纳米SiO2复合材料,研究了在脱除溶剂以及反应副产物过程中温度、表面改性剂对纳米SiO2粒子的分散性、固化后样品力学性能的影响.研究表明:纳米SiO2的引入对环氧树脂的力学性能有一定的提高;随着体系溶剂脱除温度的升高纳米粒子的团聚明显;加入表面改性剂能够阻止纳米粒子的团聚,硅烷偶联剂KH550比表面活性PEG剂能够更好地阻止纳米粒子的团聚;但是表面活性剂PEG的加入会使纳米复合材料的力学性能有一定程度的下降.     

Imaging gold nanoparticles for DNA sequence recognition in biomedical applications

The hybridization of single-stranded oligonucleotide-derivatized gold nanoparticles (Au nanoprobes) with double stranded complementary DNA was directly observed by atomic force microscopy (AFM). This specific interaction is the basis for an Au nanoprobe-based homogeneous assay for specific DNA sequence detection, based on salt-induced particle aggregation that is prevented when a complementary target is present. For long DNA targets (linearized plasmid DNA) complicated hybridized target DNA-Au-nanoprobes structures were formed, that were interpreted as the basis for stability of the Au nanoprobes against salt-induced aggregation. For shorter DNA targets (PCR amplified fragments) hybridization with the Au nanoprobes occurred, in the majority of cases, in the expected location of the DNA target fragment containing the specific sequence. The formation of the observed DNA hybridized structures provides evidence at the molecular level for specific hybridization to the target sequence as the method of binding of the Au nanoprobes.     

Direct observation of epitaxial alignment of Au on MoS2 at atomic resolution

The morphology and structural stability of metal/2D semiconductor interfaces strongly affect the performance of 2D electronic devices and synergistic catalysis. However, the structural evolution at the interfaces has not been well explored particularly at atomic resolution. In this work, we study the structural evolution of Au nanoparticles (NPs) on few-layer MoS₂ by high resolution transmission electron microscope (HRTEM) and quantitative high-angle annular dark field scanning TEM. It is found that in the transition of Au from nanoparticles to dendrites, a dynamically epitaxial alignment between Au and MoS₂ lattices is formed, and Moiré patterns can be directly observed in HRTEM images due to the mismatch between Au and MoS₂ lattices. This epitaxial alignment can occur in ambient conditions, and can also be accelerated by the irradiation of high-energy electron beam. In situ observation clearly reveals the rotation of Au NPs, the atom migration inside Au NPs, and the transfer of Au atoms between neighboring Au NPs, finally leading to the formation of epitaxially aligned Au dendrites on MoS₂. The structural evolution of metal/2D semiconductor interfaces at atomic scale can provide valuable information for the design and fabrication of the metal/2D semiconductor nano-devices with desired physical and chemical performances.

     

Morphology and surface plasma changes of Au-Pt bimetallic nanoparticles

In this study, we examined the amount-dependent change in morphology in a series of Au-Pt bimetallic nanoparticles synthesized using chemical reduction. The amount of Au precursor was kept constant throughout the experiment. The Au/Pt molar ratio was varied from 1/1 to 1/4 to synthesize Pt shell layers with different thicknesses. We observed a remarkable shift of the surface plasmon band at around 410 nm. By high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometry (EDS), the composition of the shell layer was found to be Pt-enriched Au-Pt alloy. As the concentration of Pt increases, Pt clusters (ca. 1.8 nm in diameter) form a string-like shape on the surface of nanoparticles.     

Coulomb blockade behaviors in individual Au nanoparticles as observed through noncontact atomic force spectroscopy at room temperature

Coulomb blockade behaviors in individual Au nanoparticles of 2 nm core diameter in double-barrier structures have been studied by means of noncontact atomic force spectroscopy (NC-AFS) at room temperature. The Au nanoparticles with a 1-decanethiol ligand were chemisorbed by 1,10-decanedithiol molecules of a mixed 1-octanethiol/1,10-decanedithiol self-assembled monolayer coated on a Au(111) surface; these particles were observed through NC-AFS. NC-AFS measurements of the cantilever frequency shift-sample voltage (Δf-V(S)) curves were sequentially conducted on three Au nanoparticles under the same experimental conditions; the Δf-V(S) curves were found to deviate from the parabolic (Δf(N)) curve in the cases where no extra charge existed on the Au core. The experimental Δf(CB)(=Δf-Δf(N)) and Δf(CB)/V curves agree well with the theoretical curves obtained using a golden-rule calculation and the same parabolic parameters. All the results, through NC-AFS, suggest Coulomb blockade behaviors in the Au nanoparticles at room temperature.     

Formation of nanoparticle arrays on S-layer protein lattices

Crystalline bacterial cell surface layers (S-layers) composed of identical protein units have been used as binding templates for well-organized arrangements of nanoparticles. Isolated S-layer proteins were recrystallized into monomolecular arrays on solid substrates (such as silicon wafers and SiO2-coated grids) and in suspension forming so-called self-assembly products. These S-layer assemblies were studied by atomic force microscopy and transmission electron microscopy (TEM). The orientation of the S-layer lattice, exhibiting anisotropic surface properties, on the solid surface and on the self-assembly products, was compared with the orientation on the bacterial cell. On both bacterial cells and SiO2 surfaces the outer face of the S-layer protein was exposed. On the self-assembly products occasionally the inner face was also visible. Metal- and semiconductor nanoparticles 2 to 10 nm in mean diameter were covalently or electrostatically bound to the solid-supported S-layers and self-assembly products. TEM studies reveal that upon activation of carboxyl groups in the S-layer lattice with 1-ethyl-3,3'(dimethylaminopropyl)carbodiimide (EDC), a close-packed monolayer of 4-nm amino-functionalized CdSe nanoparticles could be covalently established on the S-layer lattice. Because of electrostatic interactions, anionic citrate-stabilized Au nanoparticles (5 nm in diameter) formed a superlattice at those sites where the inner face of the S-layer lattice was exposed. In contrast, cationic semiconductor nanoparticles (such as amino-functionalized CdSe particles) formed arrays on the outer face of the solid-supported S-layer lattices.     

In situ Raman monitoring of competitive adsorption of Ag and Au nanoparticles onto a poly(4-vinyl pyridine) surface

The competitive adsorption of citrate-capped Ag and Au nanoparticles (~25 nm in diameter) onto a poly(4-vinyl pyridine) (P4VP) surface has been investigated by means of Raman scattering spectroscopy. The P4VP film prepared on a glass slide was too thin for its normal Raman spectrum to be observed, but the Raman peaks of P4VP could be detected upon the adsorption of Ag and/or Au nanoparticles onto the film, due to the surface-enhanced Raman scattering (SERS) effect associated with the localized surface plasmon of Ag and/or Au nanoparticles. Neither quartz crystal microbalance nor atomic force microscopy (AFM) nor scanning electron microscopy (SEM) methodologies can distinguish between Ag and Au nanoparticles during their adsorption onto P4VP, but it is possible through Raman scattering spectroscopy because Ag (though not Au) nanoaggregates are SERS active at 514.5 nm excitation, while both Ag and Au nanoaggregates are SERS active at 632.8 nm excitation. Coupled with the AFM data, we were thus able to infer that about 120 Ag nanoparticles per 1 μm(2) were adsorbed, along with 60 Au nanoparticles per 1 μm(2), onto the P4VP film over a period of 1.5 h from a 1 : 1 mixture of Ag and Au sols at 1.6 nM each.     

Synthesis of Hierarchical 4H/fcc Ru Nanotubes for Highly Efficient Hydrogen Evolution in Alkaline Media

Hierarchical metal nanostructures containing 1D nanobuilding blocks have stimulated great interest due to their abundant active sites for catalysis. Herein, hierarchical 4H/face‐centered cubic (fcc) Ru nanotubes (NTs) are synthesized by a hard template‐mediated method, in which 4H/fcc Au nanowires (NWs) serve as sacrificial templates which are then etched by copper ions (Cu²⁺) in dimethylformamide. The obtained hierarchical 4H/fcc Ru NTs contain ultrathin Ru shells (5–9 atomic layers) and tiny Ru nanorods with length of 4.2 ± 1.1 nm and diameter of 2.2 ± 0.5 nm vertically decorated on the surface of Ru shells. As an electrocatalyst for the hydrogen evolution reaction in alkaline media, the hierarchical 4H/fcc Ru NTs exhibit excellent electrocatalytic performance, which is better than 4H/fcc Au‐Ru NWs, commercial Pt/C, Ru/C, and most of the reported electrocatalysts.     

Dechlorination of trichloroethylene in aqueous solution by noble metal-modified iron

Bimetallic particles are extremely interesting in accelerating the dechlorination of chlorinated organics. Four noble metals (Pd, Pt, Ru and Au), separately deposited onto the iron surface through a spontaneous redox process, promoted the TCE dechlorination rate, and the catalytic activity of the noble metal followed the order of Pd>Ru>Pt>Au. This order was found to be dependent on the concentrations of adsorbed atomic hydrogen, indicating that the initial reaction was cathodically controlled. Little difference in the distribution of the chlorinated products for the four catalysts (cis-DCE: 51%; 1,1-DCE: 27%; trans-DCE: 15% and VC: 7%) was observed. The chlorinated by-products accumulated in both Pt/Fe and Au/Fe (10.3% and 2.5% of the transformed TCE, respectively), but did not accumulate in Pd/Fe and Ru/Fe. Ru/Fe was further examined as an economical alternative to Pd/Fe. The 1.5% Ru/Fe was found to completely degrade TCE within 80 min. Considering the expense, the yield of chlorinated products and the lifetime of a reductive material, Ru provides a potential alternative to Pd as a catalyst in practical applications.     

Microstructure analysis of ion beam-induced surface nanostructuring of thin Au film deposited on SiO2 glass

Effects of the irradiation dose on surface nanostructuring accompanied with the dewetting process of Au films deposited on SiO₂ glass were examined using an atomic force microscope and a scanning electron microscope. In addition, the microstructural evolution and the chemical concentration of Au films were investigated using a transmission electron microscope equipped with an energy-dispersive spectrometer. As increasing the Ar ion irradiation dose, the lattice expansion of Au nanoscale islands sustained on the SiO₂ glass was observed and irradiation-induced lattice defects together with irradiation-induced interface ion mixing were accounted for this lattice expansion. Finally a layer of photosensitive Au nanoballs with highly spherical shape embedded in a SiO₂ substrate was obtained after Ar ion irradiation to 10.0 × 10¹⁶/cm² and some of Au nanoballs were found to be single crystals. As the irradiation energy of the Ar ions increased from 100 to 150 keV, the average diameter of the Au nanoballs in the substrate increased and the red shift of the SPR peak was observed. This tendency of the experimental SPR peaks corresponded with that of the theoretically calculated SPR peaks using Mie solution.     

Au-CeO_2纳米杂聚体颗粒的合成研究

在CeO2纳米立方体颗粒存在条件下,以丁基锂还原Au前体获得了Au-CeO2纳米杂聚体。采用TEM、HRTEM、STEM、EDS、XRD对纳米颗粒的形貌、结构及成分进行了分析。考察了实验条件对杂聚体形成的影响。结果表明,丁基锂适宜用作Au的还原剂,Au还原速度不能过快以保证Au在CeO2纳米颗粒表面能以多相成核方式形核长大。Au和Au-CeO2纳米颗粒浸渍γ-Al2O3后焙烧的实验表明,Au-CeO2杂聚体结构能有效抑制Au在高温下的凝聚长大。