电子诱导金属多肽的超分子组装、化学响应释放及其催化应用

近年来,超分子组装在催化、制药、传感器、提纯、组织工程等领域获得广泛应用.为了实现超分子结构功能化,经常会将金属纳米颗粒或者金属活性位引入或共组装至有机超分子骨架中,由此获得金属化的纳米材料.例如,金属纳米颗粒修饰的多肽纤维、金属聚合物、金属负载的水凝胶和气凝胶.常见的金属化策略包括自组织、金属有机配位络合、聚合和电子...     

Fabrication and characterization of TEOS-based silica aerogels prepared using rapid supercritical extraction

Silica aerogels were prepared using the precursor tetraethylorthosilicate (TEOS) via a rapid supercritical extraction (RSCE) method. Multiple consistent batches of monolithic TEOS-based aerogels were fabricated via an 8-h RSCE process. Fabricating TEOS-based aerogels with an RSCE method offers some distinct advantages. One advantage is the relative simplicity of the RSCE approach: liquid precursors are mixed and poured into a metal mold in a hydraulic hot-press, where gelation, aging and extraction of liquid from the pores occur. The precursor recipe employs TEOS, ethanol, water, oxalic acid to catalyze hydrolysis, and ammonia to catalyze the subsequent polycondensation reactions. Another advantage is that reaction of TEOS to form sol gels yields ethanol as a byproduct. A process that releases ethanol, rather than methanol (as in tetramethylorthosilicate (TMOS)-based aerogels) may be more appealing for commercial applications, involving scale-up of the process. The significantly lower cost of TEOS, compared to TMOS, is a considerable advantage. The TEOS-based RSCE aerogels are mesoporous and optically translucent, have bulk densities of 0.099(±0.003) g/cm³ and surface areas of 460(±10) m²/g. Signals observed in infrared and Raman spectra of the aerogels are consistent with Si–O framework bonds. Using scanning electron microscopy imaging, the surface morphology of the aerogel samples was imaged at magnifications up to 150 kX.     

Advances in the electrochemical catalytic reduction of CO2 with metal complexes

Electrocatalytic CO₂ reduction has emerged as a promising strategy to effectively produce fuels and chemicals sustainably. In this regard, the study of electrochemical catalytic reduction of CO₂ with metal complexes is a powerful tool for both the development of catalysts that operated under desired conditions (low overpotentials, high catalytic rates and selectivity, and extended durability) and the understanding of basic principles in catalysis. To illustrate the state-of-the-art, this revision presents a selection of the most recent and remarkable findings reported in terms of key strategies to improve reaction rates, selectivity and mechanism understanding for the leading families of homogeneous catalysts.     

多尺度结构Ag/PA6纳米纤维膜的制备及其催化性能

随着工业的进步,废水处理特别是印染废水的处理成为亟待解决的问题.银纳米粒子因其特殊的物理化学性能而表现出催化活性,但银纳米粒子的团聚限制了其使用,所以出现了一系列新的载体材料,如微球、薄膜和纤维等.其中电纺纳米纤维由于具有高比表面积,作为载体材料具有非常大的优势,而将常规电纺纳米纤维作为载体也已有报道.但是,将具有更高比表面积的电纺纳米纤维作为载体,特别是一种类似于树枝状结构的多尺度纳米纤维作为载体还鲜有报道.本文制备了一种多尺度结构的PA6纳米纤维膜,该纳米纤维膜由直径为50?120 nm的主纤维和10?50 nm的分支纤维构成;由于分支纤维的出现,多尺度结构纳米纤维膜的比表面积得到了提高,可以为银纳米粒子的负载提供更多附着位点.制备的多尺度结构纳米纤维膜通过银胶溶液浸渍成功地负载银纳米粒子,对制备的纳米纤维膜的形态、化学结构以及对亚甲基蓝的催化性能进行了探讨.SEM,EDS和TEM结果表明,银纳米粒子成功地负载在多尺度结构纳米纤维的表面,并且银纳米粒子的粒径以及负载量可以通过变换银胶溶液的浓度合理调控.此外,与常规PA6纳米纤维膜相比,多尺度结构纳米纤维膜更有利于银纳米粒子的分散,同样通过银胶溶液A浸渍,负载在多尺度结构纳米纤维上银纳米粒子粒径为8.6 nm,而负载在普通PA6纳米纤维上银纳米粒子粒径为11.2 nm.XPS分析表明,银纳米粒子成功地负载到多尺度结构纳米纤维上,并且经不同银胶溶液处理,纳米纤维膜的载银量不同.通过O的高能XPS分析发现,银纳米粒子与PA6分子间形成了配位键,这在一定程度上有利于Ag纳米粒子的固定,阻止了Ag纳米粒子的团聚.Ag/PA6纳米纤维膜以及多尺度结构Ag/PA6纳米纤维膜催化降解实验表明,多尺度结构Ag/PA6纳米纤维膜具有较高的催化活性,反应2 h后对10 mg/L亚甲基蓝的降解率达到98.13%,并且降解过程符合伪一级动力学.不同浸渍液浓度处理纳米纤维膜催化实验表明,Ag纳米粒子的大小以及含量都会影响纳米纤维的催化活性,纳米粒子粒径越小,其催化活性越高;不同NaBH4加入量催化体系催化实验表明,随着NaBH4加入量的增大,催化体系的降解率增高,其对催化体系的催化性能起着至关重要的作用;其他条件一定,随着染料初始浓度的增大,催化体系的催化性能下降;循环实验表明,经5次循环之后,其降解率仍高达83.5%,该纳米纤维膜具有一定的循环使用性能.     

Low-temperature selective catalytic reduction of NOx with NH3 over zeolite catalysts: A review

The selective catalytic reduction (SCR) of NO_x by NH₃ is one of the most mature technologies for NO_x treatment. Catalysts are the main factors affecting denitrification efficiency. Zeolites as low-temperature NH₃-SCR catalysts have been extensively studied in the past few years. In this work, the mechanism of zeolites for NH₃-SCR reaction was reviewed and the denitrification performances of zeolite catalysts prepared by different methods were compared. The effects of sulfur and water poisoning on zeolite catalysts in NH₃-SCR reaction were also analyzed. Several ways to address the problems in low-temperature NH₃-SCR reaction were discussed. Hopefully, this review could provide a fundamental understanding of SCR reaction on zeolite catalysts and pave the way toward similar studies to realize its commercial applications.     

In situ assembly of well-dispersed gold nanoparticles on electrospun silica nanotubes for catalytic reduction of 4-nitrophenol

The tubular nanocomposite with well-dispersed distribution of small gold nanoparticles (AuNPs) assembled on the inside and outside surfaces of silica nanotubes (SNTs) was fabricated by combining the single capillary electrospinning technique and an in situ reduction approach. The AuNPs/SNTs nanocomposite exhibited a good catalytic activity for reduction of 4-nitrophenol (4-NP).     

Fabrication and characterization of superhydrophobic silica nanotrees

Superhydrophobic silica nanotrees were obtained by sol–gel method with hybrid silica sol and jelly-like resorcinol formaldehyde resin. Rough surfaces were obtained by removing the organic polymer at high temperature. After the films with rough surface were modified by trimethylchlorosilane (TMCS), the wettability of the film changed from superhydrophilic to superhydrophobic. The surface roughness of the silica nanotrees film is about 20 nm, and it is transparent and superhydrophobic with a water contact angle higher than 150°.     

Fabrication of color-tunable luminescent silica nanotubes loaded with functional dyes using a sol-gel cocondensation method

Luminescent silica nanotubes SNT-2 (loaded with coumarion laser dye 2) and SNT-3 (loaded with anthracene laser dye 3) were prepared by sol-gel cocondensation of functional dyes and TEOS in a cholesterol-based organogel system. The emission colors of silica nanotubes were tuned by using different functional dyes. Interestingly, there is a great difference in PL spectrum of silica nanotubes loaded with functional dyes between ethanol and the solid state. In ethanol, a green light emission of SNT-2 and a bluish green light emission of SNT-3 were observed at 486 and 465 nm, respectively, because of the anchoring state between the dye and the tube, whereas in the solid state, strong blue light emissions of SNT-2 and SNT-3 were observed at 482 and 483 nm, respectively, because of the intense emission of the silica nanotube (SNT) itself rather than that of 2 and 3.     

功能化含钨介孔硅材料的直接合成表征及其在多相氧化脱硫中的应用

温和条件下,燃油深度脱硫一直是非常重要的研究课题.目前,加氢脱硫(HDS)是石油工业上广泛采用的脱硫技术,它能够有效脱除燃油中的硫醚、硫醇和等无机硫化物,但对于芳香族硫化物(如二苯并噻吩、4,6-二甲基二苯并噻吩等),则效果较差.对于上述有机硫化物的深度脱除,现有的加氢脱硫技术需要更为苛刻的反应条件,如高温、高压、高活性贵金属催化剂等,这势必导致燃油成本的大幅上升.因此,世界各国科学家都加强了高效非加氢脱硫方法的研究,主要包括氧化脱硫法、吸附脱硫法、萃取脱硫法和生物脱硫法等,其中氧化脱硫法是一种公认的具有应用前景的高效脱硫技术,该技术只需在常温常压下进行,可将含硫化合物氧化成其相应的砜类物质后,再用溶剂萃取法或吸附法除去.氧化脱硫反应中所涉及氧化剂有过氧化氢、有机过氧化物和氧气等.在这些氧化剂中,过氧化氢由于其活性高,在氧化反应后的副产物只有水,而被广泛研究.
　　离子液体作为一种低温熔融盐,因其独特的理化性质,如无蒸气压、低毒性、良好的溶解性以及结构可调等,受到了广泛的关注.其中,功能化多酸基离子液体不仅具备离子液体的特点,还具备多金属氧酸盐的优势,已被用于燃油的均相氧化脱硫过程中.但是,此过程中离子液体往往用量较大,催化剂难于回收和循环利用,氧化剂用量较大,阻碍其在工业中的应用.为了克服上述缺点,本课题组以多酸基离子液体[C16mim]3PW12O40和正硅酸四乙酯为原料通过溶胶-凝胶法直接合成了一系列含钨功能化介孔复合材料 W-SiO2,其中咪唑型阳离子作为介孔模板剂,而多酸阴离子作为金属源.采用 XRD, IR, Raman, BET, DRS, TEM等测试手段对所合成的材料进行了表征.结果表明,钨活性物种是以氧化钨的形式存在,并且能够均匀地分散在载体二氧化硅上,所合成的材料比表面积为513–743 m2/g,孔体积为0.37–0.50 cm3/g,孔径为2.91–3.20 nm.将所合成的材料 W-SiO2-20应用于燃油氧化脱硫反应(过程中无需有机溶剂),结果表明,所合成的复合材料既能作为吸附剂来吸附有机硫化物,又能作为催化剂来活化过氧化氢以氧化有机硫化物.在最优条件(反应温度60oC, O/S摩尔比为2.5,反应时间40 min)下,二苯并噻吩脱除率可100%,而且反应体系易于循环使用,7次循环后脱硫率无明显降低.此外,还考察了复合材料在相同条件下对于不同硫化物的脱除效果,结果表明,反应活性顺序为4,6-DMDBT＞ DBT＞ BT＞ DT.     

Synthesis and characterization of nanocast silica NCS-1 with CMK-3 as a template

Nanocast silica (NCS-1) was synthesized by a casting process by employing the mesoporous carbon CMK-3 (the replica of SBA-15) as a template, tetraethoxysilane (TEOS) as the silica source, and hydrochloric acid (HCl) as the catalyst. The ordered carbon template was removed by employing different methods, such as calcination, thermal treatment followed by calcination, and controlled combustion. According to XRD and TEM characterization, NCS-1 exhibits an ordered structure with hexagonal symmetry and retains the morphology of the original SBA-15 used for the synthesis of CMK-3 over two replication steps on the nanometer scale. This demonstrates the well-connected porosity in CMK-3 type carbon, which can be used as a mold to synthesize mesostructured materials. The nitrogen adsorption isotherms generally show type IV shape, indicating mesoporous characteristics. The structure of NCS-1 is strongly influenced by variables of the nanocasting process, such as the loading amount of silica, hydrolysis temperature, and carbon removal methods. The surface area, pore size, and pore volume of NCS-1 can be tuned to a certain range by varying these parameters.     

Fabrication and catalytic properties of Pt and Ru decorated TiO2⧹CNTs catalyst for methanol electrooxidation

Highly ordered anodic titania nanotube arrays provide a large surface area for electrodepositing nickel nanoparticles which are used as the catalyst for carbon nanotube growth. Pt and Ru nanoparticles, approximately 3 nm in diameter, are uniformly electrodeposited on the as synthesized titania-supported carbon nanotubes (CNTs), constructing a novel catalyst for electrocatalytic oxidation of methanol. An enhanced and stable catalytic activity is obtained due to the uniformly dispersed Pt and Ru nanoparticles, and the large CNT network facilitating the electron transfer between the adsorbed methanol molecules and the catalyst substrate. An oxidation peak current density of 55 mA/cm² is achieved at a low Pt load of 0.126 mg/cm² with a Pt/Ru mole ratio of 1:1.     

Preparation and characterization of platinum (Pt) and palladium (Pd) nanoparticle decorated graphene sheets and their utilization for the elimination of basic fuchsin and indigo carmine dyes

In this study, graphene nano sheets, prepared with chemical oxidation and reduction routes via modified-Hummer method, were successfully decorated with platinum (Pt) and palladium (Pd) nanoparticles. Structural and morphological features of resulted graphene-metal nanocomposites were characterized with FT-IR, XRD, SEM and TEM methods. Anti-oxidant activity (AOA) values of nanocomposites were determined. The IC₅₀ values of Pt-graphene and Pd-graphene nanocomposites were found to be 46.1 and 90.2 μg/mL, respectively based on the ABTS method and 80.2 and 143.7 μg/mL according to the DPPH method. It was found that the graphene-metal nanocomposites exhibited superior free radical scavenging activity compared to several types of noble metal nano particles although the nanocomposites consist of much lower amount of active metal sites than the nano-crystalline metal powders. It was consequently reported that the graphene-metal nanocomposites could be successfully used for the photocatalytic elimination of fuchsin and indigo carmine dyes under light irradiation.     

自下而上法制备金-介孔二氧化硅复合纳米管用作还原4-硝基苯酚的催化剂

采用自下而上方法制备了金-介孔二氧化硅复合纳米管,其中金纳米粒子作为催化剂嵌在介孔二氧化硅纳米管管壁内侧。金纳米颗粒的团聚、脱落和晶粒尺寸生长都可以被有效限制,而且催化剂负载量和尺寸大小均可实现简单控制。管壁中的介孔孔道、纳米管末端开口以及一维中空管道可以协同促进反应物扩散,从而提高4-硝基苯酚还原反应活性。循环实验证明这种复合纳米管催化剂具有良好的可重复使用性,而且在反应过程中未出现金纳米粒子脱落或团聚现象。     

Preparation and characterization of monodisperse porous silica microspheres with controllable morphology and structure

A novel method for the preparation of monodisperse porous silica microspheres with controllable morphology and structure is reported. The starting porous polymer microspheres were first functionalized with ethylenediamine (EDA) to generate amino groups. Subsequently, silica nanoparticles were deposited in the porous polymer microsphere to form polymer/silica hybrid microspheres via a modified sol‐gel process in the presence of tetra‐n‐butylammonium bromide (TBAB) or tetramethyl ammonium hydroxide (TMAH). Upon calcination of the polymer/silica hybrid microspheres, the porous silica microspheres were obtained. The morphology, inner structure, and properties of the porous silica microspheres were studied by field emission scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis, and mercury intrusion method. The results show that the presence of TBAB or TMAH in the process not only prevents the agglomeration of the hybrid microspheres, but also governs the controllable morphology from a porous inner structure to a hollow‐cage structure. The obtained porous silica microspheres exhibit no shrinkage from the polymer microspheres with a yield of around 98%. These porous silica microspheres have potential applications in the fields of chromatography, catalyst, and biology. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Influence of selenium on the catalytic properties of ruthenium-based cluster catalysts for oxygen reduction

The favourable influence of selenium on the catalytic properties of Ru-based catalysts for the oxygen reduction reaction in acid electrolytes has been investigated by rotating disk electrode measurements. Compared to the oxygen reduction of selenium-free Ru-based catalysts, the overpotential at low current densities (ca. 10 μA cm⁻²) is not affected by the presence of selenium whereas selenium-containing catalysts show higher current densities under fuel cell relevant conditions. The kinetically controlled current density at 0.6 V versus SHE increases 4–5 fold with increasing selenium content. A maximum value is obtained at about 15 mol% Se. This effect is tentatively explained by a modification of the catalytic active centre, which is assumed to consist of Ru---C---CO complexes. IR spectroscopic investigations indicate a reaction of selenium with these complexes. This model is also supported by the study of the electrooxidation of CO. In contrast to the selenium-free catalyst, no CO oxidation is observed on the selenium-containing catalyst. Additional effects of selenium are an enhanced stability towards electrochemical oxidation and a lower amount of Ru oxides formed during synthesis, as evidenced from XRD investigations. Direct four electron oxygen reduction to water is efficient and H₂O₂ production of these catalysts is small (about 5% at potentials <0.3 V vs. SHE ).     

Structural characterization and catalytic activities of copper complexes with pyridine-amine-phosphine-oxide ligand

A new tetradentate containing pyridine, amine and phosphine oxide donor systems (1) was synthesized by the condensation of o-diphenylphosphinoaniline with 2-pyridinecarbaldehyde. Reaction of 1 with equal molar amount of CuCl₂ and Cu(ClO₄)₂ provided the formation of [CuCl₂(1)] (4) and [[Cu(1)(H₂O)](ClO₄)₂] (5), respectively. The ligand 1 behaves as a tridentate in 4, while as a tetradentate in 5. Both complexes were characterized by EPR, UV-Vis spectroscopy and X-ray diffraction. Both copper(II) complexes are in a square-pyramidal geometry. Single crystal structure of the copper complex reveals that the copper center is surrounded by three nitrogen donors and two chloride for 4; three nitrogen donors, water and oxygen donor from the moiety of phosphine oxide for 5. Complexation of 1 with CuCl in dichloromethane resulted in the formation of the corresponding copper(I) species, which catalyzed the oxidation of benzylic alcohols under aerobic conditions.     

Magnetic GO‐PANI decorated with Au NPs: A highly efficient and reusable catalyst for reduction of dyes and nitro aromatic compounds

Due to the high activity of Au nanoparticles (NPs) for various reactions, many researchers have tried to develop heterogeneous catalysts in order to prevent irreversible agglomeration of Au NPs. Herein, magnetic graphene oxide modified with polyaniline (PANI) was used as a support for Au NPs that brings together advantages including: uniform dispersal of the catalyst in water,alarge surface area related to the graphene oxide; easy electron transfer in chemical reactions and good attachment of Au NPs to the support associated with PANI; and finally facile recovery in the presence of a magnetic field. Catalytic reduction of different analytes (Congo red, methylene blue, rhodamine B and 4‐nitro phenol) was evaluated in the presence of NaBH₄ and the results show high catalytic activity of the catalyst. The catalyst was thoroughly characterized using various methods including FTIR, XRD, XPS, FE‐SEM and HRTEM analyses while its catalytic activity was evaluated via reduction of different analytes.     

Fabrication and characterization of adenine-grafted carbon-modified amorphous ZnO with enhanced catalytic activity

Sustainability has become a countersign and guiding rule for current field of nanocatalysis. Herein, we report a cost-effective, greener, clean, and proficient process for the formation of adenine-grafted carbon-modified amorphous ZnO nanocatalyst (ZnO@AC) derived from garment industry waste (waste cotton cloth). Due to adenine functionality, catalyst provides consistent dispersion of ZnO providing catalytically active sites for the synthesis of pyrano[2,3-d]pyrimidines and bis(pyrazol-5-ole) and alters the electron–hole pair recombination without notable mass-transfer limitation. The photocatalytic evaluation of ZnO@AC was performed on methyl orange (MO) dye under UV light and 87.3% degradation efficiency resulted in 75 min. Moreover, the catalyst was recyclable and could be reused up to eight runs, making it more sustainable. The morphology of ZnO@AC remained intact with the slight agglomeration of ZnO nanoparticles (nps) after eight recoveries according to the transmission electron microscopy (TEM) image of the used catalyst.     

Synthesis and characterization of chitosan-hydroxyapatite composite for bone graft applications

In the current work chitosan-hydroxyapatite composites were synthesized using the method of co-precipitation for bone grafting. The composite samples were characterized using SEM, EDS and UTM. The composites showed a good Ca:P ratio of 2.10, indicating a sufficient level of osteoconductive of the composites. The EDS peaks showed a strong presence of carbon, oxygen, calcium and phosphorous with insignificant impurities. The UTM tests revealed compressive modulus of 80 ?MPa desired for various human bones. Also, grey rational analysis was used to optimize the process parameters. The results thus obtained show an improvement over previously reported results of bone grafts using other materials and procedures. Thus, the work can serve as a viable alternative to traditional bone grafting techniques, such as allografts and autografts, which face problems of biocompatibility and affordability.