Dynamically coated silica monolith with ionic liquids for capillary electrochromatography

An ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) was introduced as dynamic coating of a silica monolithic column for capillary electrochromatography of phenols and nucleoside monophosphates. The run-to-run and column-to-column repeatability of migration time for six phenols were satisfactory on this column with relative standard deviation values less than 0.90 and 4.31%, respectively. Anodic electroosmotic flow (EOF) was observed, which increased with the increase of [BMIM][BF4] concentration within 120 mM and when [BMIM][BF4] concentration was above 120 mM, EOF leveled off due to the saturation of [BMIM][BF4] on the monolith. Efficient separation of phenols and nucleoside monophosphates on this dynamically coated monolithic column was obtained, compared with a dynamically coated fused-silica column and unmodified silica monolithic column. The retention behavior of uncharged phenols is mainly manipulated by hydrophobic interactions due to the presence of butyl groups, and that of nucleoside monophosphates is governed by the electrostatic attraction mechanism based on the interaction between positively charged [BMIM][BF4] moieties and negatively charged phosphate groups. In addition, silica matrix also contributes to the separation resolution.     

Ultra-large Scale Molecular Dynamics Simulation for Nano-engineering

In light of the special need of nano-engineering, an ultra-large scale and high-performance molecular dynamics（MD） simulation program was implemented. In many nano-engineering processes, the free boundary condition should be adopted. To meet this particular requirement, a pointer link and dynamic array data structures were employed so that both reliability and accuracy of simulation could be ensured. Using this method, one could realize the MD simulation of the nano-engineering system consisting of several million atoms per single CPU.     

动态超声萃取分光光度法在线测定红花中的总红花黄色素

用动态超声萃取分光光度法在线测定了红花中的红花黄色素, 对萃取条件进行了优化. 萃取与测定同时进行, 大大缩短了样品的分析时间, 简化了分析过程. 通过与静态超声萃取、振荡萃取和索式萃取进行比较, 不仅证明该方法耗时最短, 而且样品用量小, 萃取产率较高. 实际样品分析得到了满意的结果.     

Simultaneous separation of basic and acidic proteins using 1-butyl-3-methylimidazolium-based ion liquid as dynamic coating and background electrolyte in capillary electrophoresis

1-Butyl-3-methylimidazolium tetrafluoroborate ionic liquids (1B-3MI-TFB ILs) were employed as a coating material and BGE in CE for simultaneous separation of basic and acidic proteins such as lysozyme, cytochrome C, ribonuclease A, albumin, and alpha-lactalbumin. 1B-3MI-TFB ILs effectively reversed the surface charges on the capillary inner surface, preventing the adsorption of positively charged proteins onto the silica surface, as well as associated with proteins, thus benefiting the separation efficiencies and reproducibility. Consequently, simultaneous baseline separation of five proteins was achieved within 14 min by using 10 mM of 1B-3MI-TFB ILs as dynamic coating and the only running electrolyte at the voltage of +20 kV. The proposed coating technique is simple, less time-consuming, reproducible, and also stable enough for proteins separation without the need of additives. Symmetrical peaks with efficiencies up to 670,000 plates/m were obtained. Recoveries of proteins with RSD (for migration times) of 0.23-0.42% (run-to-run) and 2.5-3.8% (day-to-day) were achieved, respectively. The applicability of the proposed method in proteins separation was evaluated by the separation of egg white samples.     

Styrenated phenol modified nanosilica for improved thermo-oxidative and mechanical properties of natural rubber

The present work aims to prepare thermal and oxidation resistant Natural Rubber (NR) composites using antioxidant-modified nanosilica (MNS). The thermo-oxidative aging performance of the composites was evaluated by the variations in mechanical properties after aging at 100 °C for 24 h. The performance was further monitored through Scanning Electron Microscopy, Fourier Transform Infrared spectroscopy, Thermogravimetric Analysis, and Dynamic Mechanical Analysis. NR nanocomposite with 1–7.5 phr nanosilica (NS) and 3 phr MNS were prepared and its rheological properties were studied. A comparative study of the theoretical models yielded that modified Guth-Gold equation predicted Young's modulus better than other models. Thermal stability of natural rubber MNS composite was improved by 10 °C with pre-eminent mechanical properties like tensile strength and heat build-up. A linear relationship of compression set with modulus of all composites were also established. Equilibrium swelling test revealed improved crosslink density in NR MNS composite. The strong interaction between antioxidant and nanosilica enabled low migration of antioxidant in NR MNS composite. Hence its protective function after aging showed more effective than NR NS composites. These versatile functional properties of NR MNS composite suggest its potential application in electrical, electronic and high performance rubber products.     

Cellulose nanofibre enabled natural rubber composites: Microstructure,curing behaviour and dynamic mechanical properties

Traditional rubber industries rely heavily on petroleum-based materials, such as carbon black (CB). The present study aims at mitigating the environmental challenges, through partial replacement of CB, while simultaneously consuming an easily accessible agricultural waste. Accordingly, cellulose nanofibre (CNF) was extracted from wheat-straw using chemo-mechanical process, which in-turn was used for fabrication of CNF enabled rubber nanocomposites. Microstructural observation of CNF confirmed nanometric defibrillation of cellulose. A variety of tests were performed on the nanocomposites towards exploring their structure-property correlations, curing-behaviour, thermal degradability and mechanical (static and dynamic) properties. Overall, considerable enhancement in properties such as tensile strength and strain energy density could be realized, owing to synergistic use of CNF and CB in rubber, allowing for replacement of up to 15 phr CB. These were further augmented by significant improvements in dynamic rolling-resistance, traction and stress-softening behaviour. The results were especially significant, considering that the improvements could be achieved without any modification of CNF surface, thereby establishing its potential for development of environment friendly rubber nanocomposites.     

Dynamic pH barrage junction focusing of amino acids,peptides, and digested monoclonal antibodies in capillary electrophoresis–mass spectrometry

Dynamic pH barrage junction focusing in CE enables effective signal enhancement, quantitative capture efficiencies, and straightforward optimization. The method is a technical variant of dynamic pH junction focusing. CE separation with dynamic pH barrage junction focusing is compatible with both optical and mass spectrometric detection. We developed a CE–MS/MS method using hydrophilic polyethyleneimine-coated capillaries and validated it for the qualitative analysis of amino acids, peptides, and tryptic peptides of digested monoclonal antibodies. The S/N of extracted ion electropherograms of zwitterionic analytes were enhanced by approximately two orders of magnitude with a tradeoff of a shortened separation window. Online focusing improved the MS signal intensity of a diluted antibody digest, enabling more precursor ions to be analyzed with subsequent tandem mass spectrometric identification. It also broadened the concentration range of protein digest samples for which adequate sequence coverage data can be obtained. With only 0.9 ng of digested infliximab sample loaded into the capillary, 76% and 100% sequence coverage was realized for antibody heavy and light chains, respectively, after online focusing. Full coverage was achieved with 9 ng of injected digest.     

Enzyme-Driven,Switchable Catalysis Based on Dynamic Self-Assembly of Peptides

Covalent regulatory systems of enzymes are widely used to modulate biological enzyme activities. Inspired by the regulation of reactive-site phosphorylation in organisms, we developed peptide-based catecholase mimetics with switchable catalytic activity and high selectivity through the co-assembly of nanofibers comprising peptides and copper ions (Cu²⁺). Through careful design and modification of the peptide backbone structure based on the change in the free energy of the system, we identified the peptide with the most effective reversible catalytic activity. Kinase/phosphatase switches were used to control the reversible transition of nanofiber formation and depolymerization, as well as to modulate the active-site microenvironment. Notably, the self-assembly and disassembly processes of nanofibers were simulated using coarse-grained molecular dynamics. Furthermore, theoretical calculations confirmed the coordination of the peptide and Cu²⁺, forming a zipper-like four-ligand structure at the catalytically active center of the nanofibers. Additionally, we conducted a comprehensive analysis of the catalytic mechanism. This study opens novel avenues for designing biomimetic enzymes with ordered structures and dynamic catalytic activities.     

A Microporous Hydrogen Bonded Organic Framework for Highly Selective Separation of Carbon Dioxide over Acetylene

The separation of acetylene (C₂H₂) from carbon dioxide (CO₂) is a very important but challenging task due to their similar molecular dimensions and physical properties. In terms of porous adsorbents for this separation, the CO₂-selective porous materials are superior to the C₂H₂-selective ones because of the cost- and energy-efficiency but have been rarely achieved. Herein we report our unexpected discovery of the first hydrogen bonded organic framework (HOF) constructed from a simple organic linker 2,4,6-tri(1H-pyrazol-4-yl)pyridine (PYTPZ) (termed as HOF-FJU-88) as the highly CO₂-selective porous material. HOF-FJU-88 is a two-dimensional HOFs with a pore pocket of about 7.6 Å. The activated HOF-FJU-88 takes up a high amount of CO₂ (59.6 cm³ g⁻¹) at ambient conditions with the record IAST selectivity of 1894. Its high performance for the CO₂/C₂H₂ separation has been further confirmed through breakthrough experiments, in situ diffuse reflectance infrared spectroscopy and molecular simulations.     

Gold Extracted from Wastewater as an Efficient MOF-Supported Electrocatalyst

The recovery of gold from wastewater is necessary from both environmental and economic standpoints. Metal–organic frameworks (MOFs) can serve as high-capacity and selective adsorbents, as shown in a recent work by Zhao and co-workers. Their novel three-dimension cationic framework goes further than selectively adsorbing AuCl₄⁻. It also serves as a stable platform to transform adsorbed gold into an efficient catalyst for the electrochemical reduction of CO₂. This work highlights the versatility of MOFs, which can serve as selective adsorbents and as a support for nanoparticle catalysts.