Microfluidics and electrochemistry: an emerging tandem for next-generation analytical microsystems

Microfluidic and electrochemical technologies have been at the forefront of the development of emerging analytical microsystems. Microfluidics and electrochemistry show a synergistic relationship, empowering their inherent features. Thus, integration of microfluidics and electrochemical (bio)sensors is envisioned as a powerful tandem for boosting the next generation of lab-on-a-chip platforms, including point-of-care and point-of-need systems. In this review, a general overview of the advantages, drawbacks, and gaps as well as remaining challenges and future trends of coupling microfluidics and electrochemical cells is presented. Special attention is given to the manufacturing and scale-up of the integrated devices and all those aspects that can push on the development of true lab-on-a-chip platforms for reaching the industrial domain and actual commercialization.     

High-speed separation of proteins by microchip electrophoresis using a polyethylene glycol-coated plastic chip with a sodium dodecyl sulfate-linear polyacrylamide solution

In this paper, we describe a method for size-based electrophoretic separation of sodium dodecyl sulfate (SDS)-protein complexes on a polymethyl methacrylate (PMMA) microchip, using a separation buffer solution containing SDS and linear polyacrylamide as a sieving matrix. We developed optimum conditions under which protein separations can be performed, using polyethylene glycol (PEG)-coated polymer microchips and electrokinetic sample injection. We studied the performance of protein separations on the PEG-coated PMMA microchip. The electrophoretic separation of proteins (21.5-116.0 kDa) was completed with separation lengths of 3 mm, achieved within 8 s on the PEG-coated microchip. This high-speed method may be applied to protein separations over a large range of molecular weight, making the PEG-coated microchip approach applicable to high-speed proteome analysis systems.     

Catalytic C-phenylation of methyl acrylate with tetraphenylantimony(v) halides and carboxylates

Catalytic C-phenylation of methyl acrylate to methyl cinnamate with the Ph₄SbX complexes (X = F, Cl, Br, OH, OAc, O₂CEt) in the presence of the palladium compounds PdCl₂, Pd(OAc)₂, Pd₂(dba)₃, Pd(Ph₃P)₂Cl₂, and Pd(dppf)Cl₂ (dba is dibenzylideneacetone and dppf is bis(diphenylphosphinoferrocene)) was studied in organic solvents (MeCN, THF, DMF, MeOH, and AcOH). The highest yield of methyl cinnamate (73% based on the starting organometallic compound) was obtained for the Ph₄SbCl—PdCl₂ (1 : 0.04) system in acetonitrile.     

Dependence of the glass transition temperature of poly (methyl methacrylates) on their tacticity

The specific isobaric heat capacities of poly (methylmethacrylates) (PMMA) having various tacticities were measured by the DSC method within a broad range of temperatures including the glass transition. Glasses with uniform thermal history were used in the measurements and the data were treated by employing a procedure which provided the thermodynamic T_g independent of the experimental conditions. The semiquantitative validity of Boyer's empirical relationT _g ×c_p=const. was confirmed; also it was found that within the limits of experimental accuracy the c_p,g values at 298 K andC _p,l values at 400 K are independent of the tacticity of the sample.Using the data thus measured and linearized equations representing the dependence ofT _g on the content of iso-, syndio- and heterotriads, the T_g values of pure isotactic PMMA and pure syndiotactic PMMA were found to be respectively 315 K and 397 K.Dedicated to Professor Dr. F. H. Müller.     

Preparation and characterization of cationic poly(n-isopropylacrylamide) copolymer latexes

Cationic poly(N-isopropylacrylamide) (NIPAM) copolymer latexes have been prepared at 70°C using methylene-bisacrylamide (MBA) as the crosslinking agent,2-2′-azobis-(2-amidinopropane hydrochloride) (V50) as the initiator and in the presence of 2-aminoethyl-methacrylate hydrochloride (AEM). It was found that the concentration of AEM plays a major role in the polymerization kinetics and particle nucleation. However, too high a concentration (2–5 mol%/NIPAM) caused the latex to be polydispersed together with the production of large amounts of polyelectrolytes. The presence of surface amino groups on the final particles under the protected form was revealed both by an ultraviolet spectrometry and nuclear magnetic resonance methods. It was indirectly evidenced through the electrophoretic mobility behavior of the latex particles (below and above the lower critical solubility temperature of the poly(NIPAM)) as well as by their stability against a monovalent electrolyte.     

甲基丙烯酸甲酯-丙烯酸丁酯共聚物微观结构研究

用１３Ｃ ＮＭＲ研究了由基团转移共聚得到的甲基丙烯酸甲酯 丙烯酸丁酯共聚物的微观结构，共聚物中单体链节的三元组含量从季碳和羰碳的共振信号测得，实验测得的三元组分数与通过竞聚率和单体组成比按末端基效应模式的计算值相符．丙烯酸丁酯由于具有大得多的竞聚率值而呈现较强的均聚倾向．     

Phase behavior and surface tensions of amphiphilic fluorinated random copolymer aqueous solutions

Phase behavior and surface tension of aqueous solutions of fluorinated random copolymers [perfluoroalkylacrylate]–[poly(ethyleneoxide)methacrylate], [C_mRf-acrylate]-[EO_n-methacrylate] with fluroalkyl carbon number m = 8, 6, 4, 2 and number of ethyleneoxide unit, n = 9 and 4.5 were investigated as a function of composition and different combinations of m and n. Isotropic solutions are formed at lower temperatures over wide concentration range of copolymer but at higher temperature phase separation occurs. The cloud point of copolymer decreases with decreasing n as well as m, and also with decreasing the number of poly(ethyleneoxide)methacrylate chain per perfluorinatedalkylacrylate chain, suggesting that the copolymers become more hydrophobic on decreasing m and n. Equilibrium and dynamic surface tension measurements show that copolymers become increasingly surface active as m as well as n decrease but the adsorption at the air–water interface is very slow due to bulkiness of the molecules. No clear evidence of the formation of micellar aggregates could be obtained from surface tension–composition curves.     

侧链含不同功能性羟基的温敏性N-异丙基丙烯酰胺共聚物微凝胶的制备及性能比较

选择含有活性羟基的亲水单体多缩乙二醇单甲基丙烯酸酯(PEGMA)、甲基丙烯酸羟乙酯(HEMA),分别和N-异丙基丙烯酰胺(NIPAM)交联共聚,制备了侧链含有功能性羟基、链长不同的温敏性微凝胶.研究发现,亲水单体HEMA和PEGMA的引入对微凝胶的去溶胀性能有不同的影响,PEGMA的引入使得微凝胶的体积相转变温度升高,微凝胶的去溶胀比随着PEGMA投料比的增加而降低.而HEMA的引入使得微凝胶的体积相转变温度降低;微凝胶的去溶胀比随着HEMA投料比的增加先是增加然后降低,当HEMA的投料比为8mol%时,去溶胀比达到最大.     

Molybdosphoric Acid Mixed with Titania Used as a Catalyst to Synthesize Diphenyl Carbonate via Transesterification of Dimethyl Carbonate and Phenol

The 12-molybdosphoric acid mixed with titania (MPA-TiO2) was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate (DPC) via transesterification of dimethyl carbonate (DMC) and phenol. The X-ray diffraction (XRD) and infrared (IR) techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate (MPC) were obtained over MPA-TiO2 with the weight ratio of MPA to TiO2 as 5:1.     

两个含草酸根及硫氰酸根的新型三脚架钴(Ⅱ)配合物的合成、晶体结构及光谱性质(英)

本文合成了两个新型Co(Ⅱ)配合物，[LCo(μ-C₂O₄)CoL]·(ClO₄)₂·2CH₃CN (1)和[CoL(SCN)]·ClO₄ (2)，其中，L即三(3，5-二甲基吡唑甲基)胺。在配合物1中，Co与来自三脚架配体的4个氮和草酸根桥联配体的2个氧原子配位，处于扭曲八面体配位环境。由草酸根桥联两套LCo，构成了一个双核结构。在单核配合物2中，Co(Ⅱ)处于三角双锥配位构型，SCN-通过N配位与中心离子Co(Ⅱ)键联。在同一晶胞中有两个构型略微不同的分子，两个分子之间通过SCN的S原子有弱相互作用。对化合物1和2在溶液中的光谱性质做了进一步的研究和讨论。