One Pot Synthesis of Surface PEGylated Core–Shell Microparticles by Suspension Polymerization with Surface Enrichment of Biotin/Avidin Conjugation

Core–shell microparticles that consist of poly(vinyl neodecanoate) (VND) crosslinked with poly(ethylene glycol dimethacrylate) (EGDMA) as the core and poly(ethylene glycol methacrylate) (PEGMA) ( = 360 or = 526 g · mol^?1) as the shell have been synthesized using suspension polymerization by a conventional free radical polymerization process. Interfacial tension and stability tests show that PEGMA acts as an amphiphilic macromonomer and is located on the oil/water interface of the suspension system, thus forming an outer layer during the polymerization. Kinetic studies of the monomers' conversion of VND, EGDMA, and PEGMA have been carried out using ¹H NMR spectroscopy. EGDMA and PEGMA were found to have faster reaction rates compared to VND. Moreover, scanning electron microscopy showed that the polymerization of these particles starts from the shell and finishes towards the core. Consequently, the resulting microsphere is found to have a multi‐layer structure. Biotin was covalently bound to the surface by the PEGMA hydroxy groups. Conjugation of biotin with streptavidin PE (phycoerythrin) was subsequently carried out. Confocal microscopy was used to confirm the presence of fluorescing streptavidin. The amount of avidin conjugated to the microspheres was calculated by the release of a 2‐(4‐hydroxyphenylazo)benzoic acid/avidin complex using UV/vis spectroscopy. One avidin molecule was found to occupy 7 nm² on the surface of the microspheres.

     

Studies on the particle size control of gelatin microspheres

A series of gelatin microspheres (GMs) were prepared through emulsification-coacervation method in water-in-oil (w/o) emulsions. The influence of preparation parameters on particle size, surface morphology, and dispersion of GMs was examined. The studied preparation parameters include concentration of gelatin solutions, concentration of the emulsifier, w/o ratio, emulsifying time, stirring speed, and so on. The surface morphology, dispersion, and particle sizes of GMs were determined by the scanning electron microscopy (SEM), SemAfore 4 Demo software, and particle size distribution graphic charts. The experimental results indicated that increasing the concentration of gelatin solution would increase the particle size of GMs. When the solution concentration increased from 0.050 to 0.200 g/mL gradually, the particle size increased correspondingly. The relationship between the two quantities was linear. On the contrary, increasing the concentration of the emulsifier would decrease the particle size of GMs. Furthermore, the particle size reduced quickly at initial time and slowed down latterly. With the increase of emulsifier concentration from 0 to 0.020 g/mL, themean diameters ofGMsdecreased from 17.32 to 5.38 μm. However, the particle size dwindled slowly when emulsifier concentration was higher than 0.020 g/mL. The excellent result was obtained with the condition of 0.050 g/mL of emulsifier concentration, 0.100 g/mL of gelatin solution concentration, 1/5 of w/o ratio, 10 min of emulsifying time, and 900 r/min of the stirring speed. The GMs prepared at this condition had the smallest sizes, the narrowest size distribution, the best spherical shape, and fluidity. The w/o ratio has the same influence on particle size of GMs as that of gelatin solution concentration. With the increase of w/o ratio, the average particle sizes increased linearly, and the surface of microspheres become smoother as well. It is supposed that w/o ratio can be used to change the diameters and surface morphologies of GMs. The emulsifying time has little influence on the mean diameters of GMs, but it affects the dispersion of GMs apparently. When the emulsifying time was shorter than 5 min, the GMs had bad dispersion. After increasing the emulsifying time to 13 min, the dispersion of GMs changed greatly, whereas the dispersion of GMs became bad again when the emulsifying time was longer than 13 min. According to the experimental results, 13 min was considered to be the best emulsifying time. The stirring speed has the similar influence on GMs’ morphologies as that of emulsifying time. Slow stirring rate made large size distribution and bad spherical shape of GMs; excessive stirring speed results in aggregation among GMs likewise. The smaller size distribution and better spherical shape of GMs were observed under the stirring rate between 500 and 1500 r/min by SEM. In conclusion, increasing the concentration of gelatin solution or w/o ratio would increase the particle sizes of GMs, increasing the concentration of the emulsifier would decrease the sizes of GMs at proper emulsifying time, and stirring speed would get the best spherical shape of GMs. These are the basic laws governing the design and manufacture of the GMs. __________ Translated from Acta Polymerica Sinica, 2008, 8 (in Chinese)     

Clean and reproducible SERS substrates for high sensitive detection by solid phase synthesis and fabrication of Ag‐coated Fe3O4 microspheres

The solid‐phase synthesis of Ag‐coated Fe₃O₄ microsphere was elaborated under argon atmosphere. This straightforward process utilized neither reducing agents nor electric current and involved the dry mixing of a precursor of CH₃COOAg with Fe₃O₄ microspheres followed by heating in an inert atmosphere. Ag nanoparticles with diameters of 30–50 nm were well‐decorated on the surfaces of Fe₃O₄ microspheres. The as‐synthesized Ag‐coated Fe₃O₄ microspheres were assembled into a surface‐enhanced Raman scattering (SERS) substrate holding clean and reproducible properties under an externally exerted magnetic force. Using these nanoprobes, analyte molecules can be easily captured, magnetically concentrated, and analyzed by SERS. This clean SERS substrate was used to detect 4‐aminothiophenol, even at a concentration as low as1.0 × 10^–12 M. In particular, the Ag‐coated Fe₃O₄ microspheres, acting as reproducible SERS substrates, were applied to detect methyl‐parathion and 4‐mercaptopyridine. Strong SERS signals were obtained with the analytes at a concentration of 1.0 × 10^–6 M. The unique, clean, and reproducible properties indicate a new route in eliminating the single‐use problem of traditional SERS substrates and show promising applications for detecting other organic pollutants. Similarly, this work may provide a new model system to a series of metal–Fe₃O₄ decorating reactions for a reproducible utilization. Copyright © 2012 John Wiley & Sons, Ltd.     

Fabrication of superhydrophobic surface of hierarchical ZnO thin films by using stearic acid

Flower-like hierarchical ZnO microspheres were successfully synthesized by a simple, template-free, and low-temperature aqueous solution route. The morphology and microstructure of the ZnO microspheres were examined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The bionic films with hydrophobicity were fabricated by the hierarchical ZnO microspheres modified by stearic acid. It was found that the hydrophobicity of the thin films was very sensitive to the added amount of stearic acid. The thin films modified with 8% stearic acid took on strong superhydrophobicity with a water contact angle (CA) almost to be 178° and weak adhersion. The remarkable superhydrophobicity could be attributed to the synergistic effect of micro/nano hierarchical structure of ZnO and low surface energy of stearic acid.     

对流自组装2维胶体晶体成膜趋势和覆盖率

从自组装理论出发, 分析对流自组装2维胶体晶体中空白、条纹区域出现的机理,并在实验上予以验证。通过研究得知, 2维胶体晶体的自组装过程呈现空白、条纹、大面积单层、双层条纹的趋势。从胶体晶体覆盖率的角度出发研究2维胶体晶体的组装参数与质量之间的关系,结果表明:胶体晶体的总覆盖率与基片提拉速度倒数呈线性正比,和粒子体积分数呈反比例函数关系; 受到多种因素的影响,大面积2维胶体晶体总是伴随着一定比例的空白区域和双层区域出现,提拉法所能获得的最大单层覆盖率为95%。     

空心球壳型V2O5的制备研究

无机空心微球含可容纳大量客体的中空部分,具有比表面积大、密度小、表面渗透能力强、稳定性好等特点,在化学、生物、材料科学和光电领域均有重要的应用,如控制释放胶囊(药物、颜料、化妆品、油墨)、催化剂及催化剂载体、分离材料、声学隔音材料以及电子学元件等。[1-3]空心球壳材料的制备方法通常有喷雾干燥法,乳液法[4],模板合成法[5]。近年来以胶体粒子为模板合成空心材料引起了人们的高度重视,其中聚苯乙烯微球(PSt)由于其形貌规整,粒径均一而被广泛用作形成空心结构的有机模板[6]。通过对锂离子电池正极材料的广泛研究,发现空心球壳型…     

具有核壳结构磁性复合微球的制备与表征

采用两步法制备了具有核壳结构的Fe3O4/P(MMA/DVB)(core)-P(St/GMA/DVB)(shell)磁性复合微球.首先,用改进的细乳液聚合制备了Fe3O4/P(MMA/DVB)微球;然后,加入总量不同的苯乙烯(St)、甲基丙烯酸缩水甘油酯(GMA)和二乙烯基苯(DVB),通过种子乳液聚合,制备了不同磁含量的核壳结构的磁性复合微球.分别用X-射线衍射(XRD)、高倍透射电镜(HR-TEM)、热重分析(TGA)、振动样品磁力计(VSM)等手段对磁性微球的性能进行了表征.实验结果表明,Fe3O4/P(MMA/DVB)微球的磁含量为84 wt%;通过改变加入壳层单体的量,核壳复合微球的磁含量可控在20 wt%~76 wt%之间.该微球具有超顺磁性,相应的饱和磁化强度为12~50Am2/kg.     

Fe3O4/交联PVA复合微球的制备与表征

以PVA为骨架材料,戊二醛为交联剂,盐酸为催化剂,通过乳化-化学交联法,在W/O型的乳状液中制备了磁性高分子微球--Fe3O4/交联PVA复合微球.并用SEM,光学显微镜,TG等技术对微球进行表征,考察了不同的盐酸加入方式对微球形貌的影响.     

Preparation of HNS microspheres by rapid membrane emulsification

In order to improve the dispersibility and loading efficiency of 2,2′,4,4′,6,6′-hexanitrostilbene (HNS), HNS microspheres were prepared by rapid membrane emulsification method with nitrocellulose (NC) as binder. The effects of NC solution concentration, stirring speed and polyvinyl alcohol (PVA) solution concentration on microspheres were investigated. It was characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), differential thermal analysis (DTA) and angle of repose analyzer. The results show that the HNS microspheres prepared with 5 wt% NC solution concentration, stirring speed of 100 rpm and 2 wt% PVA solution concentration have better regular morphology, higher sphericity, unchanged crystalline shape, increased activation energy and significantly improved dispersibility compared with the refined HNS. Rapid membrane emulsification has a series of advantages such as green, low cost and easy scale up, which provides a better way to prepare microspheres of energy materials.     

Biomimetic color-changing skin based on temperature-responsive hydrogel microspheres with the photonic crystal structure

The responsive color-changing bionic skin imitation of certain organisms such as chameleons has potential applications in the fields of chemical sensing and information transfer. Inspired by the cellular structure of the chameleon iridophores, a flexible and scalable fabrication strategy was proposed in the present study, which centers on the modular assembly of miniature color-changing pixel dots. The color-changing pixel dots were formed by self-assembling charged silica particles inside hydrogels and fabricated in bulk using microfluidic methods. The pixel dots were immobilized in hydrogels to encapsulate in a membrane structure similar to biological skin. With thermal stimulation, the bionic color-changing skin can change color from green to red and has an angle-independent color display with good environmental adaptability.