Cobalt nanoparticles anchored to porous silicon as a novel modifier for the construction of enzyme‐free hydrogen peroxide screen‐printed sensor

In this work, a screen‐printed carbon electrode (SPCE) was modified with a cobalt/porous silicon (Co@PSi) nanocomposite powder to develop a nonenzymatic sensor for the detection of hydrogen peroxide. The Co@PSi nanocomposite was synthesized through the chemical reaction between silicon powder in a HF/HNO₃ solution and cobalt cations. In this process, cobalt nanoparticles were anchored on the porous silicon. The structure and morphology of the synthesized nanocomposite were investigated by X‐ray diffraction, Fourier transform infrared spectroscopy, X‐ray photoemission spectroscopy, energy dispersive X‐ray spectroscopy, and field‐emission scanning electron microscopy. The constructed nonenzymatic, screen‐printed sensors based on the Co@PSi nanocomposite showed perfect electrocatalytic oxidation response to hydrogen peroxide over the range 1–170 and 170–3,770 μmol/L with the limit of detection of 0.8 μmol/L. In addition, the Co@PSi‐SPCE sensor exhibited good selectivity for the determination of H₂O₂ in the presence of common interfering species including glucose, ascorbic acid, uric acid, dopamine, nitrate, and nitrite ions. The constructed electrochemical sensor was successfully used for the determination of H₂O₂ in real samples.     

晶体硅金刚线切割废料制备高纯氮化硅

以晶体硅金刚线切割废料为原料,通过氮化反应制得氮化硅,既回收了金刚线切割废料,又解决了环境污染的问题。 通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和X射线能量色谱仪(EDS)等技术手段研究了原料经HCl和HF酸洗净化后制备氮化产物的物相组成、组分质量分数和微观形貌的影响。 结果表明,HCl酸洗后切割废料制备的氮化产物中主要物相为Si₂N₂O和Si₃N₄,而HF酸洗后切割废料制备的氮化产物中主要物相为Si₃N₄。 氮化产物中Si₂N₂O的形成与切割废料中SiO₂的质量分数有关,降低原料中SiO₂的质量分数是切割废料经过高温氮化制得氮化硅的前提。     

Protein delivery based on uncoated and chitosan-coated mesoporous silicon microparticles

Mesoporous silicon is a biocompatible, biodegradable material that is receiving increased attention for pharmaceutical applications due to its extensive specific surface. This feature enables to load a variety of drugs in mesoporous silicon devices by simple adsorption-based procedures. In this work, we have addressed the fabrication and characterization of two new mesoporous silicon devices prepared by electrochemistry and intended for protein delivery, namely: (i) mesoporous silicon microparticles and (ii) chitosan-coated mesoporous silicon microparticles. Both carriers were investigated for their capacity to load a therapeutic protein (insulin) and a model antigen (bovine serum albumin) by adsorption. Our results show that mesoporous silicon microparticles prepared by electrochemical methods present moderate affinity for insulin and high affinity for albumin. However, mesoporous silicon presents an extensive capacity to load both proteins, leading to systems were protein could represent the major mass fraction of the formulation. The possibility to form a chitosan coating on the microparticles surface was confirmed both qualitatively by atomic force microscopy and quantitatively by a colorimetric method. Mesoporous silicon microparticles with mean pore size of 35 nm released the loaded insulin quickly, but not instantaneously. This profile could be slowed to a certain extent by the chitosan coating modification. With their high protein loading, their capacity to provide a controlled release of insulin over a period of 60-90 min, and the potential mucoadhesive effect of the chitosan coating, these composite devices comprise several features that render them interesting candidates as transmucosal protein delivery systems.     

Effect of oxidized silicon (SiOx) surfaces functionalization on real‐time PCR by Lab‐on‐a‐chip microdevices

There is a great need to improve the biocompatibility of silicon‐based lab‐on‐chip substrate materials for reliable quantitative analysis of biological solutions. These advanced microdevice surfaces need not only be biocompatible but also have surfaces of defined wettability characteristics. The inhibition of biomolecular activity due to microdevice surface interaction is common and can result in inaccurate results or decreased reaction yields. In this work we investigate different techniques for the chemical functionalization of oxidized silicon (SiO_x) surfaces in order to: (i) obtain defined hydrophobic/hydrophilic surfaces; and (ii) increase the efficiency of performing Real‐Time Polymerase Chain Reaction (PCR) on a silicon‐based lab‐on‐chip. Silicon oxide surfaces are functionalized by grafting alkylic chain silanes and poly(ethylene glycol) (PEG) chains to the surfaces, rendering them hydrophobic or hydrophilic. Functionalized surfaces are characterized through contact angle and atomic force microscopy (AFM) measurements, showing stable hydrophobic surfaces with contact angles of 69–78° and layer thicknesses of 11–15 Å and hydrophilic surfaces displaying contact angles of 5–6° and thicknesses of 22–52 Å. PCR experiments carried out directly on bare silicon oxide lab‐on‐chip surfaces show low yields of DNA amplification. Hydrophobic surfaces decrease the inhibition of PCR. Hydrophilic surfaces are a major improvement on the bare silicon oxide exhibiting the same maximum reaction yield as obtained with a standard thermocycler. We have found that the best results are associated with PEG modified surfaces, which prove very suitable for the fabrication of reliable PCR silicon lab‐on‐chips. Copyright © 2011 John Wiley & Sons, Ltd.     

Quartz crystal microbalance simulation of the directionality of Si etching in CF4 glow discharges

Two quartz crystal microbalances have been mounted in a planar rf discharge system in such a way that the potential of the microbalances with respect to the glow discharge can be varied. This apparatus allows a rapid simulation of the etching directionality that can be expected in real pattern transfer situations in that operating one microbalance at ground and one at a negative potential gives a measure of the sidewall and vertical etch rates, respectively. The voltage threshold for ion-assisted etching has been determined to be 20 V which is the approximate value of the plasma potential in this asymmetric system.     

多孔硅纳米材料的制备及在高能锂电池中的应用

多孔硅纳米材料具有巨大的比表面积,可调控的物理化学性质,在药物治疗、传感、能源储存与转化等领域拥有巨大的应用前景。尤其在高能量密度锂离子电池领域,多孔硅由于其丰富的孔道结构能有效释放充放电过程中硅体积变化带来的巨大应力以及大大地缩短锂离子传输距离,而引起了人们的广泛研究兴趣。但是,开发简便快速的方法来合成结构可调变的多孔硅纳米材料仍是当前研究的挑战。近年来,一些用来合成多孔硅纳米材料的方法已有报道。我们基于本课题组最近的研究进展和近年来相关文献,比较详细综述了近年来多孔硅纳米材料的制备方法以及重点关注其在高能锂电池领域的应用。最后,对多孔硅纳米材料的未来发展方向做了进一步的展望。     

A catalytic C?C bond‐forming reaction between aliphatic fluorohydrocarbons and arylsilanes

C? C coupling reactions between arylsilanes and alkylfluorides are efficiently catalyzed by disilyl cation 1. Primary as well as secondary alkylfluorides were quantitatively coupled with arylsilanes; however, in the case of tertiary fluorides, the hydrodefluorination reaction predominated. Primary alkylfluorides were found to give arenes with mostly rearranged alkyl substituents. In all cases subsequent Friedel–Crafts‐type chemistry occurred. Copyright © 2010 John Wiley & Sons, Ltd.