碱溶法制备高孔隙度多孔微球

提出并研究了以碱溶侵蚀提高多孔硅球孔隙度的新方法,研究了碱液浓度、处理温度、反应时间与洗除量的关系。结果表明,随着NaOH浓度的提高,不仅洗除量加大,而且硅胶的溶解速度亦少许增大,其主要原因是由于某些孔结构的塌陷导致了细屑的脱除。温度升高和处理时间延长会导致洗除量增大。随着洗除量的增加,硅胶的比孔容呈线性增大,但其外观仍为均匀的球形,且直径亦未见明显变化。选用粒径4~5 μm、孔径8 nm、比孔容1.4 cm3/g的多孔硅胶,采用1.25 mol/L NaOH水溶液、室温(25 ℃)处理3.0 h,制备了粒径4~5 μm、孔径14 nm、比孔容3.2 cm3/g的高孔隙度多孔硅胶,其孔隙度从75%增加到88%。     

Preparation of magnetite-loaded silica microspheres for solid-phase extraction of genomic DNA from soy-based foodstuffs

Solid-phase extraction has been widely employed for the preparation of DNA templates for polymerase chain reaction (PCR)-based analytical methods. Among the variety of adsorbents studied, magnetically responsive silica particles are particularly attractive due to their potential to simplify, expedite, and automate the extraction process. Here we report a facile method for the preparation of such magnetic particles, which entails impregnation of porous silica microspheres with iron salts, followed by calcination and reduction treatments. The samples were characterized using powder X-ray diffractometry (XRD), scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, and vibrating sample magnetometry (VSM). XRD data show that magnetite nanocrystals of about 27.2 nm are produced within the pore channels of the silica support after reduction. SEM images show that the as-synthesized particles exhibit spherical shape and uniform particle size of about 3 μm as determined by the silica support. Nitrogen sorption data confirm that the magnetite-loaded silica particles possess typical mesopore structure with BET surface area of about 183 m²/g. VSM data show that the particles display paramagnetic behavior with saturation magnetization of 11.37 emu/g. The magnetic silica microspheres coated with silica shells were tested as adsorbents for rapid extraction of genomic DNA from soybean-derived products. The purified DNA templates were amplified by PCR for screening of genetically modified organisms (GMOs). The preliminary results confirm that the DNA extraction protocols using magnetite-loaded silica microspheres are capable of producing DNA templates which are inhibitor-free and ready for downstream analysis.     

Molecularly imprinted polymeric shell coated monodisperse‐porous silica microspheres as a stationary phase for microfluidic boronate affinity chromatography

Molecular imprinting of cis‐diol functionalized agents via boronate affinity interaction has been usually performed using nanoparticles as a support which cannot be utilized as a stationary phase in continuous microcolumn applications. In this study, monodisperse‐porous, spherical silica particles in the micron‐size range, with bimodal pore diameter distribution were selected as a new support for the synthesis of a molecularly imprinted boronate affinity sorbent, using a cis‐diol functionalized agent as the template. A specific surface area of 158 m²/g was achieved with the imprinted sorbent by using monodisperse‐porous silica microspheres containing both mesoporous and macroporous compartments as the support. High porosity originating from the macroporous compartment and sufficiently high particle size provided good column permeability to the imprinted sorbent in microcolumn applications. The mesoporous compartment provided a large surface area for the parking of imprinted molecules while the macroporous compartment facilitated the intraparticular diffusion of imprinted target within the microsphere interior. A microfluidic boronate affinity system was first constructed by using molecularly imprinted polymeric shell coated monodisperse‐porous silica microspheres as a stationary phase. The synthetic route for the imprinting process, the reversible adsorption/ desorption behavior of selected target and the selectivity of imprinted sorbent in both batch and microfluidic boronate affinity chromatography systems are reported.     

高碳含量新型亚微米无孔二氧化硅材料的修饰方法及其在反相加压毛细管电色谱平台上的应用

亚微米无孔二氧化硅(NPS)材料具有小粒径及表面光滑形状规整等特点,是一种性能优异的色谱材料,但其存在比表面积小、修饰效率低的问题.针对此设计了一种具有高碳含量的修饰方法:以3-缩水甘油基氧基丙基三甲氧基硅烷(GPTS)作为硅烷偶联剂,聚乙烯亚胺(PEI)作为聚合物包覆层,并以硬脂酰氯修饰得到一种氨基包覆的具有C18碳...     

Simple method for preparation of porous polyimide film with an ordered surface based on in situ self-assembly of polyamic acid and silica microspheres

In this Article, we addressed a facile method for the fabrication of porous polyimide film with an ordered surface based on the solvent-evaporation-assisted in situ self-assembly of polyamic acid (PAA, precursor of polyimide) and silica microspheres during vacuum-drying of PAA/silica colloid solution. Hydroxyl groups on the surface of silica microspheres have strong hydrogen-bonding with PAA chains, which improve the dispersion of silica microspheres in PAA/DMF solution and further help the self-assembly of PAA/silica colloid solution via solvent evaporation. The approach is simple, neither the preparation of special template nor complex preparation process and precise control over condition is necessary. Furthermore, the method could be employed for mass production of ordered porous polyimide films, and by changing the content and size of silica microspheres, the pore size and porous structure of the porous polyimide films could be tunable. The wettability behavior of the as-prepared porous polyimide films is also studied; the ordered surface topography of the porous polyimide films could change the wettability from hydrophilicity to hydrophobicity.     

Photochemical construction of nanoporous polymer microspheres in Cu/Cu2O nanoparticle suspensions

Taking the poly(styrene-co-acrylamide) (P(St-AM)) as a model material, a novel two-step photochemical method was introduced to construct nanoporous polymer microspheres at room temperature. Under ultraviolet light irradiation, suspensions composed of Cu/Cu₂O nanoparticles were first prepared in an alcohol solution of acetylacetonate and benzophenone. Subsequently, the monomers were photopolymerized around the nanoparticles in the suspension-added precursor solution to form polymer–nanoparticle composite microspheres. Nanoporous polymer microspheres could then be obtained by removing the particles with acid. The products had been investigated by XRD, SEM, TEM, IR, DSC, and BET. Results showed the typical microspheres had diameters of 200~300?nm, and the specific areas and pore volume regularly varied with the quantity of the suspensions. By the optimum control, porous P(St-AM) microspheres with average pore size of 5.7?nm, pore volume of 0.18?cm³/g, and specific surface area of 123.54?m²/g could be obtained. The method represents a new, easily manipulated, cost-effective, and safe route for preparation of porous polymer microspheres using inorganic porogens.     

Preparation and adsorption property of novel inverse-opal hierarchical porous N-doped carbon microspheres

The design of pore structure is the key factor for the performance of porous carbon spheres.In this wo rk,novel micron-sized colloidal crystal microspheres consisting of fibrous silica(F-SiO_2) nanoparticles are firstly prepared by water-evapo ration-induced self-assembly of F-SiO_2 nanoparticles in the droplets of an inverse emulsion system to be used as sacrificial templates.Acrylonitrile(AN) was infiltrated in the voids of the F-SiO_2 colloidal crystal microspheres,and in-situ induced by ~(60)Co y-ray to polymerize into polyacrylonitrile(PAN).After the PAN-infiltrated F-SiO_2 colloidal crystal microspheres were carbonized and etched with HF solution,novel micron-sized inverse-opal N-doped carbon(IO-NC) microspheres consisting of hollow carbon nanoparticles with a hierarchical macro/meso-porous inner surface were obtained.The IO-NC microspheres have a specific surface area as high as 266.4 m~2/g and a molar ratio of C/N of 5.They have a good dispersibility in water,and show a high adsorption capacity towards rhodamine B(RhB) up to 137.28 mg/(g microsphe re).This work offers a way to obtain novel micron-sized hierarchical macro/meso-porous N-doped carbon microspheres,which opens a new idea to prepare high-performance hierarchical porous carbon materials.     

Controllable porous fluorinated polyimide thin films for ultralow dielectric constant interlayer dielectric applications

In this paper, silica microspheres were used as template to prepare porous fluorinated polyimide (FPI) thin films from polyamic acid (PAA, precursor of FPI) and silica colloid solution. The strong hydrogen-bonding interaction between silica microspheres and PAA chains have improved the dispersion of silica microspheres in N,N-Dimethylformamide (DMF) solution, resulting in the high weight content of silica template in PAA/silica colloid solution, and thus giving rise to the formation of porous FPI films with maximum porosity of 35%. The interior microstructures of the resultant porous FPI thin films were investigated. It is found that the porous FPI thin films have interconnected “ink-bottle-type” porous structure, and the pore size, porosity could be precisely controlled by the diameter and weight content of silica microspheres, respectively. Although both the tensile strength and young modules declined with the increasing porosity, the high level void of the porous FPI films endowed the FPI ultralow dielectric constant of 1.84 when the porosity increased to 35%. Furthermore, the mechanical and dielectric properties of the porous FPI films were closely related to the microstructures and porosity, indicating the desired properties could be controlled to meet the application in the microelectronics.     

Determination of the pore connectivity and pore size distribution and pore spatial distribution of porous chromatographic particles from nitrogen sorption measurements and pore network modelling theory

The pore connectivity, pore size distribution and pore spatial distribution of the porous structure of native and silanized silica particles were determined by matching the experimental nitrogen sorption data with the theoretical results obtained from pore network model simulations. The agreement between theory and experiment is found to be good. The results clearly indicate that the deposition of the silane layer to the pore surfaces of the native silica particles produces a silanized silica particle with a mean pore diameter and pore connectivity smaller than that of the native silica particle. Furthermore, the evaluation of the pore diffusivity of ribonuclease under unretained conditions shows that the lower values of the pore connectivity found in the samples of silanized silica particles, when compared with the values of the pore connectivity obtained for the native silica particles, increase the diffusional mass transfer resistance within the porous structure of the silanized silica particles.     

Pore structural studies of monodisperse porous polymer particles

Monodisperse polystyrene latex particles with molecular weight on the order of 10⁶ were used as inert diluents for the preparation of monodisperse porous styrene-divinylbenzene copolymer particles via seeded emulsion polymerization techniques. Mercury porosimetry and nitrogen adsorption-desorption isotherms were used to assess pore structure and pore size distribution. Pore size distribution was very sensitive to the molecular weight of the polystyrene latex particles used as inert diluent. Qualitative evidence from the techniques used indicated that the monodisperse porous polymer particles were macroporous (average pore diameter > 500 Å) in nature. As the molecular weight of the linear polymer decreased, the porous structure of the polymer particles ranged in complexity across the spectrum of macro/mesopore structures. Scanning electron microscope results indicated the existence of voids between the microspheres and their agglomerates within the porous polymer particle, and nitrogen adsorption isotherms confirmed that the pores were due to interstices between these crosslinked microspheres and agglomerates.     

Atypical silica-based column packings for high-performance liquid chromatography

Column packings widely used for high-performance liquid chromatography (HPLC) mostly are based on porous silica microspheres with certain pore sizes and pore size distributions. Such materials have the most desirable compromise of properties that provide for effective and reproducible separations over a wide range of operating conditions. To provide desired separation characteristics, several manufacturers specially synthesize the silica particles for these packings. While such column packing materials have general utility for a wide range of needs, special silica-based particles have been synthesized with different physical conformations for special separation goals. This presentation describes some atypical types of silica-based particles with unique separation properties that enlarge the capabilities of HPLC methods.     

核壳硅碳复合微球固定相的制备及其在糖类分离中的应用

采用一步法在二氧化硅(SiO₂)表面涂覆酚醛树脂聚合物(PF),并在氮气气氛下碳化,制备了核壳硅碳复合微球(Sil@MC)固定相。实验对Sil@MC固定相进行形貌观察和孔结构分析,表明制备出的Sil@MC固定相具有良好的单分散性,包覆后的Sil@MC材料比表面积为302 m²/g,平均孔径为9.5 nm,孔容为0.63 cm³/g,说明通过共聚反应成功地将碳材料固定在二氧化硅上。将制备的Sil@MC材料作为HPLC固定相,采用匀浆法装柱,以乙腈-水(含0.1%(v/v)甲酸)作为流动相,发现Sil@MC色谱柱在高效液相色谱-质谱中可以实现4种极性糖类化合物(D-(+)-氨基葡萄糖盐酸盐、葡萄糖、D-(+)-海藻糖二水合物和棉子糖)的分离,然而未涂覆酚醛树脂的SiO₂材料未能对这4种极性糖类化合物实现分离。实验进一步对Sil@MC固定相的性能进行了评价,代表性的低聚糖异构体松三糖和棉子糖、耐斯糖和水苏糖及乳寡糖异构体3'-唾液酸乳糖和6'-唾液酸乳糖、乳-N-四糖和乳-N-新四糖在Sil@MC色谱柱中被成功分离,峰形良好,展现了基于酚醛树脂衍生碳的核壳硅碳复合材料在在极性化合物色谱分离方面具有应用潜力。     

Effect of Temperature on Thermal Treatment of Silica Coated Magnetic Nanoparticles

In the quest for developing a catalyst with as many desired characteristics, a facile synthetic route was designed for the preparation of mesoporous silica coated magnetic nanoparticles(MSMNP) employing a colloid mill reactor. The composite particles were characterized by the techniques, such as nitrogen adsorption-desorption isotherms, scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction patterns (XRD), thermo-gravimetric analysis(TGA), Fourier transform infrared spectroscopy(FTIR) and vibrating sample magnetometer(VSM), etc. The analysis showed that the resulted MSMNP composites were composed of silica shell layers with open pores connecting channels and NiFe₂O₄ with spinel structure, so the thermal treatment temperature did not show significant effect on pore textural properties, and its specific surface areas were in the range of 443-474 m²/g, while pore volume of about 0.8 cm³/g with an average pore size of around 9.5 nm. The composites with super paramagnetic nature were encapsulated entirely with amorphous silica layers contributing to optimum porosity and abundant surface hydroxyl groups.     

Preparation and characterization of monodisperse porous silica microspheres with controllable morphology and structure

A novel method for the preparation of monodisperse porous silica microspheres with controllable morphology and structure is reported. The starting porous polymer microspheres were first functionalized with ethylenediamine (EDA) to generate amino groups. Subsequently, silica nanoparticles were deposited in the porous polymer microsphere to form polymer/silica hybrid microspheres via a modified sol‐gel process in the presence of tetra‐n‐butylammonium bromide (TBAB) or tetramethyl ammonium hydroxide (TMAH). Upon calcination of the polymer/silica hybrid microspheres, the porous silica microspheres were obtained. The morphology, inner structure, and properties of the porous silica microspheres were studied by field emission scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis, and mercury intrusion method. The results show that the presence of TBAB or TMAH in the process not only prevents the agglomeration of the hybrid microspheres, but also governs the controllable morphology from a porous inner structure to a hollow‐cage structure. The obtained porous silica microspheres exhibit no shrinkage from the polymer microspheres with a yield of around 98%. These porous silica microspheres have potential applications in the fields of chromatography, catalyst, and biology. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

AFM-porosimetry: density and pore volume measurements of particulate materials

We introduced the novel technique of AFM-porosimetry and applied it to measure the total pore volume of porous particles with a spherical geometry. The methodology is based on using an atomic force microscope as a balance to measure masses of individual particles. Several particles within the same batch were measured, and by plotting particle mass versus particle volume, the bulk density of the sample can be extracted from the slope of the linear fit. The pore volume is then calculated from the densities of the bulk and matrix materials, respectively. In contrast to nitrogen sorption and mercury porosimetry, this method is capable of measuring the total pore volume regardless of pore size distribution and pore connectivity. In this study, three porous samples were investigated by AFM-porosimetry: one ordered mesoporous sample and two disordered foam structures. All samples were based on a matrix of amorphous silica templated by a block copolymer, Pluronic F127, swollen to various degrees with poly(propylene glycol). In addition, the density of silica spheres without a template was measured by two independent techniques: AFM and the Archimedes principle.     

杂化硅胶整体材料研磨法制备混合型高效液相色谱固定相

以聚乙二醇（PEG）为致孔剂，四甲氧基硅烷（TMOS）和乙烯基三甲氧基硅烷（VTMS）为杂化硅胶前驱体，在乙酸催化作用下使硅烷发生水解，在尿素加热分解提供的碱性环境下水解的硅烷进一步缩聚得到杂化硅胶整体材料。将此整体材料用球磨机研磨，然后用三羟甲基氨基甲烷处理，并洗涤干燥得到粒径为3 μm左右的硅胶颗粒。探索了不同反应条件对硅胶颗粒的大小、比表面积和孔径、表面形貌和分散性的影响；当TMOS和VTMS体积比为3：1时可以得到孔径为7.5 nm和比表面积为245 m²/g的硅胶颗粒。通过对所制得的硅胶颗粒表面进行C18（十八烷基二甲基氯硅烷）键合修饰和巯基-烯点击反应，得到混合型高效液相色谱固定相。对此固定相的测试结果表明以上硅胶色谱填料的制备方法具有一定的实用性。     

Synthesis of porous poly(styrene-co-acrylic acid) microspheres through one-step soap-free emulsion polymerization: whys and wherefores

Synthesis of porous poly(styrene-co-acrylic acid) (PS-co-PAA) microspheres through one-step soap-free emulsion polymerization is reported. Various porous PS-co-PAA microspheres with the particle size ranging from 150 to 240 nm and with the pore size ranging from 4 to 25 nm are fabricated. The porous structure of the microspheres is confirmed by the transmission electron microscopy measurement and Brunauer-Emmett-Teller (BET) analysis. The reason for synthesis of the porous PS-co-PAA microspheres is discussed, and the phase separation between the encapsulated hydrophilic poly(acrylic acid) segment and the hydrophobic polystyrene domain within the PS-co-PAA microspheres is ascribed to the pore formation. The present synthesis of the porous PS-co-PAA microspheres is anticipated to be a new and convenient way to fabricate porous polymeric particles.     

Preparation and properties of magnetic alumina microspheres with a γ-Fe_2O_3/SiO_2 core and Al_2O_3 shell

Magnetic alumina composite microspheres with γ-Fe 2 O 3 core/Al 2 O 3 shell structure were prepared by the oil column method. A dense silica layer was deposited on the surface of γ-Fe 2 O 3 particles (denoted as γ-Fe 2 O 3 /SiO 2 ) with a desired thickness to protect the iron oxide core against acidic or high temperature conditions. γ-Fe 2 O 3 /SiO 2 /Al 2 O 3 particles with about 85 wt% Al 2 O 3 were obtained and showed to be suitable for practical applications as a magnetic catalyst or catalyst support due to their magnetic properties and pore structure. The products were characterized with scanning electron microscope (SEM) and transmission electron microscope (TEM), nitrogen adsorption-desorption, and vibrating sample magnetometer (VSM). The specific surface area and pore volume of the γ-Fe 2 O 3 /SiO 2 /Al 2 O 3 composite microspheres calcined at 500 ? C were 200 m 2 /g and 0.77 cm 3 /g, respectively.     

Polymer/Ag composite microspheres produced by water-in-oil-in-water emulsion polymerization and their application for a preservative

Nanosized Ag particles were entrapped successfully in multihollow porous poly(methyl methacrylate) (PMMA) microspheres by water-in-oil-in-water emulsion polymerization. The structure of the PMMA/Ag microspheres prepared was characterized by scanning electron microscopy and X-ray powder diffraction analysis. It was found that the Ag nanoparticles were impregnated in the inner voids of the microspheres and they had a face-centered cubic structure. In the preservation test, the PMMA/Ag microspheres showed a powerful antibacterial performance, indicating that the Ag ions released effectively through the nanosized pore channel of the PMMA wall.     

Cagelike polymer microspheres with hollow core/porous shell structures

Submicron‐scaled cagelike polymer microspheres with hollow core/porous shell were synthesized by self‐assembling of sulfonated polystyrene (PS) latex particles at monomer droplets interface. The swelling of the PS latex particles by the oil phase provided a driving force to develop the hollow core. The latex particles also served as porogen that would disengage automatically during polymerization. Influential factors that control the morphology of the microspheres, including the reserving time of emulsions, polymerization rate, and the Hildebrand solubility parameter and polarity of the oil phase, were studied. A variety of monomers were polymerized into microspheres with hollow core/porous shell structure and microspheres with different diameters and pore sizes were obtained. The polymer microspheres were characterized by scanning electron microscopy, transmission electron microscopy, optical microscopy, and Fourier transform infrared spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 933–941, 2007