Supramolecular Hydrogel Capsules Based on PEG: A Step Toward Degradable Biomaterials with Rational Design

Supramolecular microgel capsules based on polyethylene glycol (PEG) are a promising class of soft particulate scaffolds with tailored properties. An approach to fabricate such particles with exquisite control by droplet‐based microfluidics is presented. Linear PEG precursor polymers that carry bipyridine moieties on both chain termini are gelled by complexation to iron(II) ions. To investigate the biocompatibility of the microgels, living mammalian cells are encapsulated within them. The microgel elasticity is controlled by using PEG precursors of different molecular weights at different concentrations and the influence of these parameters on the cell viabilities, which can be optimized to exceed 90% is studied. Reversion of the supramolecular polymer cross‐linking allows the microcapsules to be degraded at mild conditions with no effect on the viability of the encapsulated and released cells.

     

Effect of Intersection Angle of Input Channels in Droplet Generators

In this paper, we studied the effects of the intersection angle between the inlet channels on the droplet diameter using a COMSOL Multiphysics^® simulation. We employed the level-set method to study the droplet generation process inside a microfluidic flow device. A flow-focusing geometry was integrated into a microfluidics device and used to study droplet formation in liquid–liquid systems. Droplets formed by this flow-focusing technique are typically smaller than the upstream capillary tube and vary in size with the flow rates. Different intersection angles were modeled with a fixed width of continuous and dispersed channels, orifices, and expansion channels. Numerical simulations were performed using the incompressible Navier–Stokes equations for single-phase flow in various flow-focusing geometries. As a result of modeling, when the dispersed flow rate and the continuous flow rate were increased, the flow of the continuous flow fluid interfered with the flow of the dispersed flow fluid, which resulted in a decrease in the droplet diameter. Variations in the droplet diameter can be used to change the intersection angle and fluid flow rate. In addition, it was predicted that the smallest diameter droplet would be generated when the intersection angle was 90°.     

Controllable Synthesis of Multicompartmental Particles Using 3D Microfluidics

A microfluidic assembly method based on a microfluidic chip and capillary device was developed to create multicompartmental particles. The microfluidic chip design endows the particles with regulable internal structure. By adjusting the microstructure of the chip, the diameter of the capillary, the gap length between the two microfluidic components, and the flow rates, the size of the particles and the number or the ratio of different regions within the particle could be widely varied. As a proof of concept, we have produced some complicated particles that even contain 20 compartments. Furthermore, the potential applications of the anisotropic particles are explored by encapsulating magnetic beads, fluorescent nanoparticles, and the cells into different compartments of the microparticles. We believe that this method will open new avenues for the design and application of multicompartmental particles.     

Controlled Release of Encapsulated Bioactive Volatiles by Rupture of the Capsule Wall through the Light‐Induced Generation of a Gas

The encapsulation of photolabile 2‐oxoacetates in core–shell microcapsules allows the light‐induced, controlled release of bioactive compounds. On irradiation with UVA light these compounds degrade to generate an overpressure of gas inside the capsules, which expands or breaks the capsule wall. Headspace measurements confirmed the light‐induced formation of CO and CO₂ and the successful release of the bioactive compound, while optical microscopy demonstrated the formation of gas bubbles, the cleavage of the capsule wall, and the leakage of the oil phase out of the capsule. The efficiency of the delivery system depends on the structure of the 2‐oxoacetate, the quantity used with respect to the thickness of the capsule wall, and the intensity of the irradiating UVA light.     

电感耦合等离子体原子发射光谱法研究锗的氢化反应机理

采用氢化物连续发生－ＩＣＰ－ＡＥＳ法研究了锗的氢化反应中各反应物之间的摩尔关系及其与锗烷产率之间的关系，提出锗的氢化反应是由中和反应所诱导或催化的反应机理，确定获得最大锗烷产率的酸碱浓度匹配原则。     

Generation of Superstable,Monodisperse Microbubbles Using a pH‐Driven Assembly of Surface‐Active Particles

Bubbling to the surface : Microscale gas bubbles can be generated in a microfluidic device by simultaneously injecting CO₂ and a dispersion of particles whose hydrophobicity increases as the pH value decreases. The CO₂ dissolves rapidly out of the bubbles, which shrink, and render the dispersion increasingly acidic. This drives the particles to the bubble surface where they form a type of “armor” against further dissolution (see picture).

     

Laser-Induced Generation of Hydrogen in Water by Using Graphene Target

A new method of hydrogen generation from water, by irradiation with CW infrared laser diode of graphene scaffold immersed in solution, is reported. Hydrogen production was extremely efficient upon admixing NaCl into water. The efficiency of hydrogen production increased exponentially with laser power. It was shown that hydrogen production was highly efficient when the intense white light emission induced by laser irradiation of graphene foam was occurring. The mechanism of laser-induced dissociation of water is discussed. It was found that hydrogen production was extremely high, at about 80%, and assisted by a small emission of O₂, CO and CO₂ gases.     

Atomic Fluorescence Determination of Selenium Using Hydride Generation Technique

Abstract

Hydride generation followed by atomic fluorescence spectrometry, a simple and very sensitive technique, has been evaluated for selenium analysis in different environmental and biological samples. Research is focused on the interfering effects of several selected anions, cations, and acids on the selenium determination and the sample preparation procedures. Besides some transition metals such as Ni²⁺ Co²⁺ and Cu²⁺ HNO₃ acid, the digestion medium used for sample preparation, shows strong interference. In order to reduce this interfering effect, matrix match or standard addition is recommended. This technique is validated by analyzing a number of standard reference materials. Results for selenium analysis in some biological samples are also presented.     

因子分析-氢化物发生原子吸收法分析砷的形态

报道了用流动注射氢化物发生原子吸收法（ＦＩ－ＨＧＡＡＳ）对砷４种形态,Ａｓ,ＤＭＡ,ＭＭＡ）的混合体系进行测量后,根据吸光度加和性原则,用因子分析法（ＴＦＡ）对测定值进行解析,从而测定了混合体系中砷存在形态的数目、种类和含量。实验结果表明,不同酸度介质中不同形态砷校正曲线的斜率可作为相应的目标检测向量,应用于μｇ／Ｌ级低浓度砷的形态分析,平均回收率为９３．９％,结果令人满意。     

Development and Application of a Hydride Generation Laser Induced Fluorescence Method for Measurements of Bismuth

A hydride generation laser induced fluorescence (HG LIF) approach has been investigated for trace level measurements of bismuth. The technique uses a tunable dye laser operating at 306.7 nm as the excitation source and bismuth fluorescence is measured at 472 nm. The optimized HCl and NaBH₄ concentrations for bismuth measurements were 1.2 M and 2.0%, respectively. The current technique has a limit of detection of 0.03 ppb and 0.01 ppb for blank measurements performed with the laser tuned on and off the bismuth excitation wavelength, respectively. Measurements of bismuth in different sample matrices have demonstrated the effectiveness of thiourea and ascorbic acid as masking agents for measuring samples containing interfering ions. Measurements of bismuth have been performed in reference materials, a bismuth-containing medication, and tea leaves. The results demonstrate that the HG LIF approach has feasibility for measuring bismuth in various samples at environmentally relevant concentrations.     

Generation of picoliter droplets of liquid for electrospray ionization with piezoelectric inkjet

We report the association of inkjet and electrospray ionization MS to detect picoliter droplet, where the liquid volume and its position onto the tip can be precisely controlled to form ultrafine droplets for successive ionization of the analyte. Single rectangle pulse was applied to piezoelectric device on inkjet microchip for the ejection of each picoliter droplet, and it was controlled by a computer. The voltage and width of driving pulse for the inkjet were optimized to make reproducible ejection of the solvent with low viscosity. The volume of each droplet was about 600 pl, and a trigger of 10 droplets was selected as the best inlet mode taking relative standard derivation of the droplets into consideration. The target substrate used with high voltage to form ionization was graphite, after several attempts with some materials. High‐speed camera was used to capture the breaking‐up process of a droplet. The distance between the inkjet nozzle and the tip was set at 2 cm to avoid short circuit. The influences on the mass intensity of the diameter of the tip, the volume and the concentration of the sample were examined. The tip with a small diameter performed greater intensity, and the limit of detection decreased, whereas the small volume of liquid played high ionization efficiency. Linear regression in the range between 1 and 200 ppm for caffeine was conducted, where internal standard theobromine was used. Some real samples were also detected with the instrument. Copyright © 2013 John Wiley & Sons, Ltd.     

高效液相色谱/氢化物发生/原子荧光快速检测尿砷形态

本文对砷形态分析方法进行了评述。提出了人尿中Ａｓ（Ⅲ）、Ａｓ（Ⅴ）、一甲基砷（ＭＭＡ）和二甲基砷（ＤＭＡ）的快速、灵敏的形态分析方法。方法基于在１５ｃｍ长、３μｍ粒径的ＨＰＬＣ柱上快速分离不同形态的砷后以灵敏的氢化物发生／原子荧光检测。常见砷的四种形态的分析只须４ｍｉｎ即可完成,检出限在μｇ／Ｌ级。标准样品尿中砷的形态分析结果与标准值吻合很好。本法已应用于摄取砷糖前、后所采集的尿样中砷的形态分析研     

氢化物发生－缝管原子捕集－原子吸收法测定钢铁和地质试样中的砷

介绍简易的氢化物发生原子吸收测砷的方法。喷雾器负压将ＫＢＨ_４吸入反应器，并将生成的ＡｓＨ_３吸入乙炔－空气焰原子化。石英缝管使灵敏度提高３．５倍。方法的检测限（３σ）为１．８ｎｇ／ｍＬ（５ｍＬ试样）。２０ｎｇ／ｍＬＡｓ（Ⅲ）标准液１０次测定的ＲＳＤ为３．８％。本法成功地应用于钢铁和地质标样中微量砷的测定。     

碱式模式氢化物发生原子荧光法测定食用菌中痕量锗

研究了碱式模式氢化物发生原子荧光法测定痕量锗。考察了HG－AFS仪器参数及氢化物发生条件对锗荧光强度的影响以及常见共存元素的干扰。在选定的最佳工作条件下,测定了真菌中的痕量锗。方法检出限（3σ）为0.76μg/L,相对标准偏差(RSD)为0.81％,回收率为94.6％－101.3％。     

氢化物负压发生器—真空无火焰原子化器的原子吸收光谱法测定碲

在负压发生器中用1％NaBH_4将Te(Ⅳ)还原成碲化氢后,再加入2mL氧气,用真空泵将氧与碲化氢的混合物吸进电热真空石英管中,同时测定原子吸收光谱。加入的氧与硼氢化钠分解产生的氢反应生成水分子,消除了氢对碲的干扰。     

不锈钢网阴极微生物燃料电池的产电性能研究

构建了一个以曝气池污泥为阳极接种微生物、碳毡为阳极、无任何修饰的不锈钢网为阴极的双室微生物燃料电池. 通过输出电压、功率密度以及电化学阻抗等考察了阴极面积对电池产电性能的影响,并对电池的长期运行稳定性进行评价. 研究结果表明,不锈钢网作为微生物燃料电池的阴极性能稳定. 当不锈钢网面积为2 × 2 cm²时,最大输出电压达到0.411 V,功率密度为0.303 W•m^-2,内阻841 Ω,极化内阻80 Ω. 增大阴极面积至2 × 4 cm²,最大输出电压能达到0.499 V,内阻减小至793 Ω. 不锈钢网价格便宜,具有长期运行稳定性,适宜做MFCs的阴极.     

重金属自产电能的电化学处理

重金属污染是最受关注的环境问题之一. 电化学处理快速、高效,因而备受关注,发展快速. 本文从重金属离子在阴极接受电子完成电化学还原的原电池和燃料电池系统角度考虑,阐述重金属离子的产电原理,结合实例介绍了重金属在阴极的还原方式,讨论了重金属自产电能处理技术的优势和存在的问题. 污染物自身产能的电化学处理是一种崭新的技术,以期早日付之实用.