Preparation and characterization of nanoporous polyimide membrane by the template method as low‐k dielectric material

In order to decrease the resistance–capacitance delay and signal crosstalk in ultra large‐scale integrated circuits (ULSIC), dielectric materials with ultra low dielectric constants are developed to be the replacement of silicon dioxide. Introduction of air on the matrix material is an important method to reduce the dielectric constant, and polyimide (PI) is the most promising polymer to prepare porous matrix material for its distinct advantages. PI membrane with nanopores was prepared by the method of template method (i.e. thermolysis of polystyrene nanospheres in the matrix) following the synthesis of template. The nanoporous membrane was characterized by Fourier transformer infrared, scanning electron microscopy, thermogravimetric analysis, and the dielectric constant of which was measured. Results showed that uniform nanopores about 100–200 nm were formed in the PI membrane, and dielectric constant of which was decreased to 2.08 from 3.34. The nanoporous membrane can be applied as potential low‐k dielectric material in ULSIC. Copyright © 2015 John Wiley & Sons, Ltd.     

Porous polymer supported palladium catalyst for cross coupling reactions with high activity and recyclability

Porous polymer supported palladium catalyst for cross coupling reactions with high activity has been successfully prepared by coordination of Pd 2+ species with Schiff bases functionalized porous polymer. The catalyst has been systemically investi-gated by a series of characterizations such as TEM, N 2 adsorption, NMR, IR, XPS, etc. TEM and N 2 isotherms show that the sample maintains the nanoporous structure after the modification and coordination. XPS results show that chemical state of palladium species in the catalyst is mainly +2. More importantly, the catalyst shows very high activities and excellent recycla-bility in a series of coupling reactions including Suzuki, Sonogashira, and Heck reactions. Hot filtration and poison of catalysts experiments have also been performed and the results indicate that soluble active species (mainly Pd(0) species) in-situ gener-ated from the catalyst under the reaction conditions are the active intermediates, which would redeposit to the supporter after the reactions.     

Molecular organic crystals: from barely porous to really porous

Holey suitable crystals: A trisbenzimidazolone molecule self-assembles by hydrogen bonding to form a permanently porous crystal with an apparent surface area, SA(BET) , of 2796?m(2) g(-1) , demonstrating that extrinsic, intermolecular porosity is a viable strategy for highly porous materials.     

Effects of electrolytes on the fabrication of three‐dimensional nanoporous gold films by a rapid anodic potential step method for SERS

A unique one‐step anodic potential step strategy has been developed recently by our group to fabricate a three‐dimensional (3D) nanoporous gold film (NPGF) within 1 min as an efficient surface‐enhanced Raman scattering (SERS) active substrate. Gloria et al. (J. Electroanal. Chem. 2011, 656, 114–119) demonstrated that the prepared NPGF under optimum conditions (2 M HCl, 50 s) has higher SERS intensities than that of a commercial single‐use gold substrate. However, the SERS performance of 3D NPGFs fabricated in neutral KCl by this strategy have not been investigated. In this paper, SERS performances of the NPGFs fabricated in electrolytes of KCl and HCl are compared for the first time, using pyridine as a test molecule. Equivalent SERS intensities can be obtained on the 3D NPGFs prepared in these two electrolytes under respectively optimum conditions. The results suggest that hot spots of nanogaps and crevices because of the aggregation/coalescence of gold nanoparticles and the formation/removal of thin gold oxide coatings contribute greatly to the high SERS activity. Copyright © 2012 John Wiley & Sons, Ltd.     

4‐(N,N‐Dimethylamino)pyridine‐Embedded Nanoporous Conjugated Polymer as a Highly Active Heterogeneous Organocatalyst

We report herein for the first time the incorporation of a versatile organocatalyst, 4‐(N,N‐dimethylamino)pyridine (DMAP), into the network of a nanoporous conjugated polymer (NCP) by the “bottom‐up” approach. The resulting DMAP‐NCP material possesses highly concentrated and homogeneously distributed DMAP catalytic sites (2.02 mmol g^?1). DMAP‐NCP also exhibits enhanced stability and permanent porosity due to the strong covalent linkage and the rigidity of the “bottom‐up” monomers. As a result, DMAP‐NCP shows excellent catalytic activity in the acylation of alcohols with yields of 92–99 %. The DMAP‐NCP catalyst could be easily recovered from the reaction mixture and reused in at least 14 consecutive cycles without measurable loss of activity. Moreover, the catalytic acylation reaction could be performed under neat and continuous‐flow conditions for at least 536 h of continuous work with the same catalyst activity.     

Hierarchical Nanoporous Structures by Self‐Assembled Hybrid Materials Based on Block Copolymers

Hierarchical nanoporous structures are fabricated by adsorption of micelles of diblock copolymer‐templated Au‐nanoparticles onto a hydrophilic solid substrate. Gold nanoparticles are prepared using micelles (19 nm) of polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) as nanoreactors. Deposition of thin films of the micellar solution, modified with a non‐selective solvent (THF), on hydrophilic surfaces leads to the formation of hierarchical nanoporous morphologies. The thin films exhibit two different pore diameters and a total pore density of 15 × 10⁸ holes per cm². The structure was analyzed in terms of topography and chemical composition using AFM, TEM and XPS measurements. The PS‐b‐P4VP template was subsequently removed by oxygen plasma etching, to leave behind metallic nanopores that mimic the original thin film morphology.

     

核壳硅碳复合微球固定相的制备及其在糖类分离中的应用

采用一步法在二氧化硅(SiO₂)表面涂覆酚醛树脂聚合物(PF),并在氮气气氛下碳化,制备了核壳硅碳复合微球(Sil@MC)固定相。实验对Sil@MC固定相进行形貌观察和孔结构分析,表明制备出的Sil@MC固定相具有良好的单分散性,包覆后的Sil@MC材料比表面积为302 m²/g,平均孔径为9.5 nm,孔容为0.63 cm³/g,说明通过共聚反应成功地将碳材料固定在二氧化硅上。将制备的Sil@MC材料作为HPLC固定相,采用匀浆法装柱,以乙腈-水(含0.1%(v/v)甲酸)作为流动相,发现Sil@MC色谱柱在高效液相色谱-质谱中可以实现4种极性糖类化合物(D-(+)-氨基葡萄糖盐酸盐、葡萄糖、D-(+)-海藻糖二水合物和棉子糖)的分离,然而未涂覆酚醛树脂的SiO₂材料未能对这4种极性糖类化合物实现分离。实验进一步对Sil@MC固定相的性能进行了评价,代表性的低聚糖异构体松三糖和棉子糖、耐斯糖和水苏糖及乳寡糖异构体3′-唾液酸乳糖和6′-唾液酸乳糖、乳-N-四糖和乳-N-新四糖在Sil@MC色谱柱中...     

H2S gas sensor based on integrated resonant dual-microcantilevers with high sensitivity and identification capability

Detection of trace-level hydrogen sulfide(H₂ S) gas is of great importance whether in industrial production or disease diagnosis.This research presents a novel H₂ S gas sensor based on integrated resonant dual-microcantilevers which can identify and detect trace-level H₂ S in real-time.The sensor consists of two integrated resonant microcantilever sensors with different functions.One cantilever sensor can identify H₂ S by outputting positive frequency ...     

Hypercrosslinked Polymers: A Review

Hypercrosslinked polymers (HCPs) represent a class of nanoporous materials with a wide range of practical and potential applications such as gas sorption and separation, heterogeneous catalysis, drug delivery, and chromatographic separation. First introduced by Davankov and Tsyurupa in the early 1970s, HCPs have developed rapidly over the past few decades. Mostly based on Friedel-Crafts chemistry, HCP materials can be prepared from the post-crosslinking of polystyrene-type precursors in their swollen state, or from the condensation of small building blocks. HCP materials manifest numerous important advantages, including moderate synthetic conditions, an enormous stockroom of inexpensive monomers, robust structures, and good thermal and chemical stabilities. This review article aims to provide an overview of recent publications on HCPs, and the emphasis is positioned on the synthetic approaches, theoretical studies, characterizations, structure-property relationships, and applications of these HCP materials.     

二维纳米空洞方格:诺氟沙星锰(Ⅱ)配合物

The reactions of norfloxacin (H-Norf) with Mn(ClO₄)₂·6H₂O and Mn(OH)₂ yield Mn(H-Norf)(ClO₄)₂·2H₂O (1) and [Mn(Norf)₂·4H₂O]_n (2) , respectively. 1 is monomeric while 2 has a novel 2D neutral square grid with an antibacterial drug as building block. Crystal data for 1: triclinic, space group P1 (No.2), a=9.0939(3), b=9.4395(3), c=12.7182(3)?, α=111.447(2), β=90.340(2), γ=112.357(1)°, V=926.34(5)?³, Z=1, ρ_cacl=1.664g·cm^-3. MoKα radiation (λ=0.71073?), T=293(2)K, μ=0.595mm^-1, R₁=0.0692, wR₂=0.1482 for 2320 observed reflections from 4390 independent reflections, GOF=0.940; Crystal data for 2: Monoclinic, P2₁/c, a=5.7530(12), b=21.865(4), c=13.343(3)?, β=98.25(3)°, V=1661.1(6)?³, Z=2, ρ_cacl=1.527g·cm^-3, T=293(2)K, μ=0.477mm^-1, R₁=0.0531, wR₂=0.1552 for 2070 observed reflections from 2870 independent reflections, GOF=1.384. CCDC: 140819; 151063.