Gold nanoparticles incarcerated in nanoporous syndiotactic polystyrene matrices as new and efficient catalysts for alcohol oxidations

The controlled synthesis of gold nanoparticles (AuNPs), incarcerated in a semicrystalline nanoporous polymer matrix that consisted of a syndiotactic polystyrene-co-cis-1,4-polybutadiene multi-block copolymer is described. This catalyst was successfully tested in the oxidation of primary and secondary alcohols, in which we used dioxygen as the oxidant under mild conditions. Accordingly, (±)-1-phenylethanol was oxidised to acetophenone in high yields (96%) in 1 h, at 35 °C, whereas benzyl alcohol was quantitatively oxidised to benzaldehyde with a selectivity of 96% in 6 h. The specific rate constants calculated from the corresponding kinetic plots were among the highest found for polymer-incarcerated AuNPs. Similar values in terms of reactivity and selectivity were found in the oxidation of primary alcohols, such as cinnamyl alcohol and 2-thiophenemethanol, and secondary alcohols, such as indanol and α-tetralol. The remarkable catalytic properties of this system were attributed to the formation, under these reaction conditions, of the nanoporous ε crystalline form of syndiotactic polystyrene, which ensures facile and selective accessibility for the substrates to the gold catalyst incarcerated in the polymer matrix. Moreover, the polymeric crystalline domains produced reversible physical cross-links that resulted in reduced gold leaching and also allowed the recovery and reuse of the catalyst. A comparison of catalytic performance between AuNPs and annealed AuNPs suggested that multiple twinned defective nanoparticles of about 9 nm in diameter constituted the active catalyst in these oxidation reactions.     

Functionalized Soft Nanoporous Materials through Supramolecular Assembly of End‐Functionalized Polymer Blends

Supramolecular assembly through complementary interaction between molecular subgroups belonging to phase‐separating polymer species offers a great opportunity, not only for constructing nanoscale soft templates reminiscent of conventional block copolymer morphologies, but also for tailoring surface properties by facile removal of one of the structure components by cleaving complementary interactions. Herein we report the fabrication of a novel, organic, nanoporous film through supramolecular assembly of two complementarily, end‐interacting, mono‐end‐functionalized polymers under solvent annealing. The film of end‐functionalized polymer blends under solvent annealing yielded phase‐separated nanodomains that resemble nanoscopically ordered structures of block copolymers, but that are more advantageous due to easily cleavable and exchangeable links between the phase‐separated domains. The removal of one of the components of the precursor structure formed from the end‐functionalized polymers through cleavage of complementary interactions allowed us to fabricate mono‐ or multilayered nanoporous structures in which the chemically useful end‐functionalities of the remnant polymers are rich on the surface of the pores. The resultant, organic, nanoporous films with tailored surface functionality offer a useful platform for various chemical and biological applications.     

以碳纳米管为支撑电沉积制备高电活性与电催化性能的六氰合铁酸钴纳米多孔薄膜

以碳纳米管(MWNTs)修饰的碳糊电极为基底电极,通过电沉积方法制备了六氰合铁酸钴(CoHCF)纳米多孔生物传感平台。考察了MWNTs对CoHCF沉积的影响,优化了CoHCF沉积的各种实验条件(0.5mol/L KCl,1 mmol/L CoCl2和0.9 mmol/L K3Fe(CN)6混合溶液,在循环伏安电压范围0～1.1 V内扫20圈,扫速100 mV/s),借助循环伏安法、交流阻抗法和扫描电镜法对修饰电极进行了表征。由于MWNTs的支撑作用,电沉积得到的CoHCF呈现出多孔结构和良好的电化学稳定性。具有纳米多孔结构的MWNTs-CoHCF薄膜能有效地促进生物小分子在电极上的电子交换,维生素B2在纳米多孔CoHCF/MWNTs上具有优异的氧化还原行为,其测定线性范围为1.2×10-7～2.6×10-7mol/L,检出限为8.9×10-8mol/L。     

On the scaling of the interface energy of the liquid clusters in the disordered nanoporous medium

Similarity of the extrusion curves of non-wetting liquid in a nanoporous medium with different initial fill volume fractions is observed experimentally. The similarity can be explained by the scaling of the interface energy and the self-similarity of the infinite percolation cluster of fluid-filled pores. Understanding the physical processes leading to the observed phenomena is a foundation for the development of high-performance devices for damping and energy storage on the basis of such heterogeneous systems.     

以原位形成的磷酸铝骨架为模板制备纳米孔炭(英文)

以不同有机物(邻苯二酚、间苯二酚、对苯二酚、乙二醇、环己胺)为辅助炭源,通过直接炭化含柠檬酸及磷酸铝的复合物制备了一系列纳米孔炭材料(NC),采用多种表征手段研究了辅助炭源对最终炭材料性质的影响.结果表明,NC材料的结构和表面官能团性质随辅助炭源的变化而改变,其中以间苯二酚、对苯二酚、环己胺为辅助炭源制备的炭材料在空气氧化苯甲醇反应中表现有较高的催化活性.     

纳米孔模板浸润法制备聚乙烯纳米线阵列的热导率的实验研究

采用纳米孔模板润湿技术制备了直径为200 nm的低密度聚乙烯(LDPE)纳米线阵列, 并利用纳秒激光闪光法测量了20—80℃时LDPE纳米线阵列的热导率. 测量得到室温时LDPE纳米线阵列的热导率为2.2 W/mK, 大约比其体材料的热导率高1个数量级, 并且纳米线阵列的热导率随温度的升高略有增加. 忽略纳米线之间的声子散射, 估算得到室温下单根LDPE纳米线的热导率高于5 W/mK. 本文制备LDPE纳米线热导率的提高源自其分子链定向度增加导致的低维导热效应的增强, 纳米线的分子链定向度受工艺过程中流体剪切、振动、分子链迁移运动、 纳米孔约束等几种因素的综合影响.     

先驱体聚合物粘结法制备SiC纳米多孔陶瓷

采用SiC纳米粉体与聚碳硅烷(PCS)为原料低压成型低温烧结制备SiC纳米多孔陶瓷,研究了PCS含量对烧成纳米多孔陶瓷性能的影响。SEM和AFM微观形貌分析表明,PCS裂解产物将SiC纳米颗粒粘结起来,烧成陶瓷内部有大量的纳米孔存在。烧成SiC纳米多孔陶瓷孔径分布呈单峰分布、孔径分布范围窄,随着PCS含量的增大烧成多孔陶瓷强度增大,但孔隙率降低、烧结过程中坯体尺寸线收缩率增大。PCS含量为20wt%时三点弯折强度为36.8MPa,孔隙率为39.5%,平均孔径为49.3 nm。     

Multiple Interfaces Structure Derived from Metal–Organic Frameworks for Excellent Electromagnetic Wave Absorption

Hierarchical yolk–shell nanostructure (NiO/Ni/GN@Air@NiO/Ni/GN) derived from Ni‐based metal–organic frameworks (Ni‐MOFs) is synthesized by solvothermal reactions. After successive carbonization and oxidation treatments, hierarchical NiO/Ni nanocrystals covered with a graphene shell are obtained with the yolk–shell nanostructure intact. The NiO/Ni/GN@Air@NiO/Ni/GN composites are characterized by X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate that the NiO/Ni/GN@Air@NiO/Ni/GN composites exhibit superior electromagnetic wave absorption properties. A minimum reflection loss (RL_min) of ?34.5 dB is obtained at 17.2 GHz with the thin thickness of 1.7 mm. In addition, the best microwave absorption properties are achieved with a 2.0 mm absorber layer (RL_min = ?22.5 dB, bandwidth of 6.0 GHz). The outstanding absorption ability may arise from the unique yolk–shell structure and nanoporous carbon, which can tune the dielectric of the NiO/Ni/GN@Air@NiO/Ni/GN composites to acquire good impedance matching. Moreover, the interspaces can induce interfacial polarization and multiple reflections.     

生物凝胶电镀法制备铜纳米多孔膜

采用生物凝胶电镀法制备铜纳米多孔膜。 电镀电压为5 V,阳极为铜片,实验探究了电镀液成分、电镀时间、阴极衬底及沉积电压对电镀层表面形貌的影响。 采用扫描电子显微镜(SEM)和X射线衍射(XRD)对样品形貌和晶型进行表征,得出制备铜膜的最佳条件。 结果表明,电镀的铜膜颗粒尺寸在100 nm左右,晶粒平均尺寸为25 nm,存在较强的(111)织构,而且XRD结果表明,附着的壳聚糖凝胶对铜膜有保护作用,防止其被氧化。 同时采用电化学工作站对其过程中的电镀电流进行实时测量,电流变化曲线表明电镀进行到一定时间后,电流趋于一个很小的稳定值,壳聚糖凝胶阻止了镀液中铜离子的进一步沉积。