Nanoassembly of biodegradable microcapsules for DNA encasing

A new microcontainer for DNA delivery based on biocompatible poly[beta-glucuronic acid-(1 --> 3)-N-acetyl-beta-galactosamine-6-sulfate-(1 --> 4)](chondroitin sulfate)/poly(-l-arginine) microcapsules with 40 nm thick molecularly organized shell was proposed. DNA molecules were deposited as DNA/sperimidine complex on the surface of template 4 mum core particles followed by layer-by-layer nanoassembly of protective chondroitin sulfate/poly(-l-arginine) shell. After template core dissolution, DNA molecules were captured inside microcapsules retaining a natural double-helix structure. The developed DNA encapsulation approach can be employed for targeted delivery of plasmid DNA in living cells.     

Synthesis of Hollow Mesoporous TiO2 Microspheres with Single and Double Au Nanoparticle Layers for Enhanced Visible‐Light Photocatalysis

A facile method was used to prepare hollow mesoporous TiO₂ and Au@TiO₂ spheres using polystyrene (PS) templates. Au nanoparticles (NPs) were simultaneously synthesized and attached on the surface of PS spheres by reducing AuCl₄^? ions using sodium citrate which resulted in the uniform deposition of Au NPs. The outer coating of titania via sol‐gel produced PS@Au@TiO₂ core–shell spheres. Removing the templates from these core–shell spheres through calcination produced hollow mesoporous and crystalline Au@TiO₂ spheres with Au NPs inside the TiO₂ shell in a single step. Anatase spheres with double Au NPs layers, one inside and another outside of TiO₂ shell, were also prepared. Different characterization techniques indicated the hollow mesoporous and crystalline morphology of the prepared spheres with Au NPs. Hollow anatase spheres with Au NPs indicated enhanced harvesting of visible light and therefore demonstrated efficient catalytic activity toward the degradation of organic dyes under the irradiation of visible light as compared to bare TiO₂ spheres.     

Core/shell microcapsules consisting of Fe3O4 microparticles coated with nitrogen-doped mesoporous carbon for voltammetric sensing of hydrogen peroxide

The authors describe the preparation of core/shell composites consisting of Fe₃O₄ microparticles coated with nitrogen-doped mesoporous carbon. Synthesis was accomplished by simultaneous reduction of template α-Fe₂O₃ and pyrolysis of a nitrogen-containing poly(ionic liquids). The mesoporous composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometry and adsorption/desorption isotherms. The characterizations prove successful formation of an Fe₃O₄ core and an outer shell (coating) consisting of nitrogen-doped mesoporous carbon. The material was placed on a glassy carbon electrode and synergistic catalytic effect of of N-doping, the mesoporous, core/shell structure and two types of active sites properties between Fe₃O₄ core and nitrogen-doped mesoporous carbon shell is shown to result in superior electrochemical activity towards the reduction of hydrogen peroxide. Figures of merit include (a) a sensitivity of 77.1 μA mM⁻¹ cm⁻²; (b) a linear response over the 50 μM to 33 mM H₂O₂ concentration range, (c) a 5.9 μM detection limit of (at an S/N ratio of 3), and (d) a low working voltage of −0.4 V (vs. saturated calomel electrode) which makes the method more selective.

Electrochemical method for H₂O₂ detection based on Fe₃O₄@nitrogen-doped mesoporous carbon microcapsules core/shell composites (Fe₃O₄@NMCMs), prepared by the polymerization of the ionic liquids (1-Allyl-3-ethylimidazolium tetrafluoroborate, [AEIm]BF₄) monomer (PILs) on the surface of α-Fe₂O₃ nano-peanuts and then pyrolysis.

     

Near-critical CO2 in mesoporous silica studied by in situ FTIR spectroscopy

Attenuated total reflection Fourier transform infrared spectroscopy was used to correlate the band shift of the nu2 vibrational band of carbon dioxide with the density of the fluid. Upon adsorption of CO2 on mesoporous silica and a nonporous SiO2 film, additional bands were detected due to interactions of CO2 with SiO2. Near the saturation pressure for the porous samples, the absorbance of the nu2 band increased strongly, which was concluded to be caused by liquidlike CO2 inside the pores. Integration of single-beam-sample-reference spectra between bulk CO2 and CO2 adsorbing on the mesoporous silica coated on one part of the internal reflection element revealed excess adsorption type isotherms with sharp maxima at 21 degrees C. A flatter curve shape could be observed at 25 degrees C, which allowed estimating the pore critical temperature. Moreover, the density of the fluid inside and outside the pores could be compared. Over the investigated ranges of pressure, temperature, and pore size, the results evidenced that the CO2 density was always higher in the silica pores than in the bulk, even under supercritical conditions. This has important consequences on the pressure dependence of dissolution power and diffusivity of fluids in mesoporous solids. An overview is given on the influences of fluid phase behavior in the bulk and in the pores at various conditions on solubility and diffusivity.     

One-step multicomponent encapsulation by compound-fluidic electrospray

Fabrication of sophisticated or smart materials often needs controlled integrating multiple components into a single capsule. Most of conventional microencapsulation strategies merely envelop one content into a shell every time. We report a compound-fluidic electrospray method could one-step enclose multiple components into a single microcapsule without contact. The as-prepared microcapsules have multiple compartments inside, in each of which different content can be addressably loaded. This approach gives flexibility for generating diverse microcapsules that could one-step integrate different active components in microscopic domain free of contact, which may find potential applications in multicomponent drug delivery, microreactors and others.     

Encapsulating Palladium Nanoparticles Inside Mesoporous MFI Zeolite Nanocrystals for Shape‐Selective Catalysis

Pd nanoparticles were successfully encapsulated inside mesoporous silicalite‐1 nanocrystals (Pd@mnc‐S1) by a one‐pot method. The as‐synthesized Pd@mnc‐S1 with excellent stability functioned as an active and reusable heterogeneous catalyst. The unique porosity and nanostructure of silicalite‐1 crystals endowed the Pd@mnc‐S1 material general shape‐selectivity for various catalytic reactions, including selective hydrogenation, oxidation, and carbon–carbon coupling reactions.     

“Dissolution-reassembly” for N-doped hollow micro/meso-carbon spheres with high supercapacitor performance

N-Doped hollow carbon spheres with mesoporous/microporous shells and outstanding performance in supercapacitor has been prepared by “dissolution-reassembly” method.     

Synthesis of microcapsules with polystyrene/ZnO hybrid shell by Pickering emulsion polymerization

Polystyrene/zinc oxide (ZnO) hybrid microcapsules having polystyrene as inner shell and ZnO nanoparticles as outer shell were synthesized by Pickering emulsion polymerization method. ZnO nanoparticles were used to form the colloidosomes that worked as the polymerization vessels, where both styrene monomer and crosslink agent were polymerized together. Fourier transform infrared spectra and thermogravimetric thermograms showed the existence of ZnO and polystyrene in the shell of hybrid microcapsules. The hollow structure and the different morphology under various conditions were also observed by field emission scanning electron microscopy. In addition, the shell thickness of hybrid microcapsules increased as the monomer concentration increased. The photoluminescence property of PS/ZnO hybrid microcapsules could be maintained without any noticeable variation by comparing with the pure ZnO particles. It could be reasonably deduced that hybrid hollow microspheres with multifarious polymer as inner shell and ZnO nanoparticles as outer shell would be produced for many applications.     

Assembly of MOF Microcapsules with Size‐Selective Permeability on Cell Walls

The assembly of metal–organic frameworks (MOFs) into microcapsules has attracted great interest because of their unique properties. However, it remains a challenge to obtain MOF microcapsules with size selectivity at the molecular scale. In this report, we used cell walls from natural biomaterials as non‐toxic, stable, and inexpensive support materials to assemble MOF/cell wall (CW) microcapsules with size‐selective permeability. By making use of the hollow structure, small pores, and high density of heterogeneous nucleation sites of the cell walls, uniform and continuous MOF layers could be easily obtained by inside/outside interfacial crystallization. The prepared MOF/CW microcapsules have excellent stability and enable the steady, slow, and size‐selective release of small molecules. Moreover, the size selectivity of the microcapsules can be adjusted by changing the type of deposited MOF.     

Fabrication of carbon microcapsules containing silicon nanoparticles-carbon nanotubes nanocomposite by sol-gel method for anode in lithium ion battery

Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT@C) have been fabricated by a surfactant mediated sol-gel method followed by a carbonization process. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were produced by a wet-type beadsmill method. To obtain Si-CNT nanocomposites with spherical morphologies, a silica precursor (tetraethylorthosilicate, TEOS) and polymer (PMMA) mixture was employed as a structure-directing medium. Thus the Si-CNT/Silica-Polymer microspheres were prepared by an acid catalyzed sol-gel method. Then a carbon precursor such as polypyrrole (PPy) was incorporated onto the surfaces of pre-existing Si-CNT/silica-polymer to generate Si-CNT/Silica-Polymer@PPy microspheres. Subsequent thermal treatment of the precursor followed by wet etching of silica produced Si-CNT@C microcapsules. The intermediate silica/polymer must disappear during the carbonization and etching process resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT@C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT@C microcapsules were measured with a lithium battery half cell tests.     

Preparation and Performance of Dual-functional Magnetic Phase-change Microcapsules

The fabrication of desired anti-magnetic materials for irradiation shielding remains a challenge to date. In this work, a new type of dual-functional magnetic shielding phase change microcapsules with paraffin as the core, melamine-formaldehyde (MF) resin as the shell and doped with magnetic particles in the shell were successfully prepared by in situ polymerization. The magnetic particles were dispersed in the shell layer by coating a hydrophilic emulsifier on the surface. These microcapsules were specifically applied to the field of magnetic shielding by the screen printing method. The effect of magnetic particles on the performance of phase-change microcapsules was examined by differential scanning calorimetry and thermogravimetric analyses. The magnetic type and magnetic strength of the microcapsules were studied by the vibrating sample magnetometer. Moreover, the effects of different magnetic particles (Fe₃O₄, CrO₂) on the performance of phase change microcapsules and the magnetic strength of microcapsules were compared. The results showed that these two kinds of magnetic particles can greatly improve the phase change latent heat, thermal stability, and thermal conductivity of the microcapsules. Finally, the great magnetic shielding role of these microcapsules was demonstrated in both static and pulsed magnetic fields through the screen printing of magnetic shielding ink on wallpaper. Incorporating 0.5 g Fe₃O₄ inside of microcapsules, specifically, the magnetic intensity was effectively reduced by ∼250 Oe within a short distance in the static field. We expect that these magnetic microcapsules hold great potential for the shielding of irradiations via the screen printing on various substrates.     

载有量子点的介孔二氧化硅微球的制备与性能研究

采用自组装方法制备了一种磁核/介孔二氧化硅壳的微球, 调节体系中C₁₈TMS的加入量可控制介孔硅球的比表面积; 并通过化学修饰的方法对介孔微球表面进行巯基功能化修饰. 利用巯基与量子点之间的相互作用可将一定尺寸的量子点吸附于介孔二氧化硅球的孔中, 令介孔微球具有荧光效应; 同时可以利用吸附不同粒径的量子点的荧光光谱对介孔二氧化硅微球孔径的大小进行近似考察.     

Influence of operation conditions on the microencapsulation of PCMs by means of suspension-like polymerization

Microcapsules containing PRS® paraffin wax (core) and a polystyrene shell were prepared by suspension-like polymerization. The influence of reaction temperature, stirring rate, and mass ratio of paraffin wax to styrene on the properties of phase change materials microcapsules was studied. The reaction temperature had not a significant effect on the size of the microcapsules but an increase of molecular weight and a narrow molecular weight distribution of polystyrene shell were observed when reaction temperature was increased. An exponential relationship between the stirring rate and the mean particle diameter in number has been found. It was observed that paraffin is difficultly encapsulated when the paraffin/polymer mass ratio was higher than 2.00, as a consequence of a shortage of polymer that could not completely cover the amount of paraffin added. However, when a large proportion of monomer was employed, the polymer tended to polymerize inside the droplets during the microencapsulation process forming complex inner structures. The microcapsules obtained have an interesting energy storage capacity of 153.5 J/g that makes them suitable for different applications.     

Influence of chemical shell structure on the thermal properties of microcapsules containing a flame retardant agent

Microcapsules containing ammonium phosphate as the acid source for an intumescent system were prepared by various processes. The microcapsules have different morphologies, load content and various types of polymeric shell. The polymers for our microcapsule shell are polymers considered as carbon source for intumescent formulations. In this paper we discuss the influence of polymeric shell and phosphate content of the microcapsules on the capacity to produce a thermally stable residue at high temperature, one of the characteristics for an intumescent formulation.     

Microfluidic fabrication of polysiloxane/dimethyl methylphosphonate flame‐retardant microcapsule and its application in silicone foams

A novel and versatile route for fabricating flame‐retardant microcapsules via microfluidics technology is reported. The flame‐retardant microcapsules were prepared with a dimethyl methylphosphonate (DMMP) core and an ultraviolet‐curable (UV‐curable) polysiloxane shell. Furthermore, a UV‐curable polysiloxane was synthesized. The synthesis mechanism of UV‐curable polysiloxane and the curing mechanism of flame‐retardant microcapsules were analyzed. To verify that DMMP was encapsulated in the microcapsules, X‐ray fluorescence was used before and after microencapsulation. The resulting microcapsules were well monodispersed and exhibited a good spherical shape with a smooth surface. In addition, the size of the microcapsules decreased dramatically with an increasing flow‐rate ratio of the middle‐/inner‐phase or outer‐phase flow rate. The thermal stability of the microcapsules was worse than shell materials but superior to DMMP. Silicone foams (SiFs) with microcapsules prepared using a dehydrogenation method achieved a relatively higher limiting oxygen‐index value than the pure SiF, which indicated that the microcapsules could enhance the flame retardation of SiFs effectively. Because of the polysiloxane shell, the microcapsules had good compatibility with SiFs, and the influence of microcapsules on the mechanical properties of SiFs was unremarkable.     

Self-Assembly Approach Towards MoS2-Embedded Hierarchical Porous Carbons for Enhanced Electrocatalytic Hydrogen Evolution

Transition metal-based nanoparticle-embedded carbon materials have received increasing attention for constructing next-generation electrochemical catalysts for energy storage and conversion. However, designing hybrid carbon materials with controllable hierarchical micro/mesoporous structures, excellent dispersion of metal nanoparticles, and multiple heteroatom-doping remains challenging. Here, a novel pyridinium-containing ionic hypercrosslinked micellar frameworks (IHMFs) prepared from the core–shell unimicelle of s-poly(tert-butyl acrylate)-b-poly(4-bromomethyl) styrene (s-PtBA-b-PBMS) and linear poly(4-vinylpyridine) were used as self-sacrificial templates for confined growth of molybdenum disulfide (MoS₂) inside cationic IHMFs through electrostatic interaction. After pyrolysis, MoS₂-anchored nitrogen-doped porous carbons possessing tunable hierarchical micro/mesoporous structures and favorable distributions of MoS₂ nanoparticles exhibited excellent electrocatalytic activity for hydrogen evolution reaction as well as small Tafel slope of 66.7 mV dec⁻¹, low onset potential, and excellent cycling stability under acidic condition. Crucially, hierarchical micro/mesoporous structure and high surface area could boost their catalytic hydrogen evolution performance. This approach provides a novel route for preparation of micro/mesoporous hybrid carbon materials with confined transition metal nanoparticles for electrochemical energy conversion.     

硫/介孔碳复合正极材料的制备与表征

以经加热处理的单质硫与由模板法制备的介孔碳合成一种硫/介孔碳复合材料(S/C).结构和电化学性能测试表明,介孔碳能有效提高硫电极的电化学反应活性、限制硫电极中间产物在电解液中的溶解流失,从而使S/C复合电极具有高的比容量、良好的倍率放电性能和稳定的循环性能.在800mA/g的高电流密度下,硫电极的首周放电比容量达到1234mAh/g;循环100周后,比容量仍保持在800mAh/g以上.     

Fabrication of bimodal porous silicate with silicalite-1 core/mesoporous shell structures and synthesis of nonspherical carbon and silica nanocases with hollow core/mesoporous shell structures

In this work, an attempt has been made to modify the shape and nanostructure of core-shell materials, which have been usually generated on the basis of amorphous spherical cores. Novel core-shell silicate particles, each of which consists of a silicalite-1 zeolite crystal core and mesoporous shell (ZCMS), were synthesized for the first time. The ZCMS core-shell particles are unique because they are of pseudohexagonal prismatic shape and have hierarchical porosity of both a uniform microporous core and a mesoporous shell coexisting in a particle framework. The nonspherical bimodal porous core-shell particles were then utilized as templates to fabricate a new carbon replica structure. Interestingly, the pore replication process was carried out only through the mesopores in the shell, and not through the micropores due to the narrower micropore size in the core, resulting in nonspherical carbon nanocases with a hollow core and mesoporous shell (HCMS) structure. Nonspherical silica nanocases with HCMS structure were also generated by replication using the carbon nanocases as templates, which are not possible to synthesize through other synthetic methods. Interestingly, the pseudohexagonal prismatic shape of the zeolite crystals was transferred onto the carbon and silica nanocases.     

Multifunctional hybrid materials for combined photo and chemotherapy of cancer

Combined chemo and photothermal therapy in in vitro testing has been achieved by means of multifunctional nanoparticles formed by plasmonic gold nanoclusters with a protecting shell of porous silica that contains an antitumor drug. We propose a therapeutic nanoplatform that associates the optical activity of small gold nanoparticles aggregates with the cytotoxic activity of 20(S)-camptothecin simultaneously released for the efficient destruction of cancer cells. For this purpose, a method was used for the controlled assembly of gold nanoparticles into stable clusters with a tailored absorption cross-section in the vis/NIR spectrum, which involves aggregation in alkaline medium of 15 nm diameter gold colloids protected with a thin silica layer. Clusters were further encapsulated in an ordered homogeneous mesoporous silica coating that provides biocompatibility and stability in physiological fluids. After internalization in 42-MG-BA human glioma cells, these protected gold nanoclusters were able to produce effective photothermolysis under femtosecond pulse laser irradiation of 790 nm. Cell death occurred by combination of a thermal mechanism and mechanical disruption of the membrane cell due to induced generation of micrometer-scale bubbles by vaporizing the water inside the channels of the mesoporous silica coating. Moreover, the incorporation of 20(S)-camptothecin within the pores of the external shell, which was released during the process, provoked significant cell death increase. This therapeutic model could be of interest for application in the treatment and suppression of non-solid tumors.     

Formation of Pickering emulsion by use of PCM and SiC and application to preparation of hybrid microcapsules with interfacial polycondensation reaction

It was tried to form Pickering emulsion by use of paraffin wax as a phase change material (PCM) and SiC as solid powder and to apply to the preparation of the hybrid microcapsules with the interfacial polycondensation reaction. Pickering emulsion could be formed by stirring PCM and SiC in the continuous water phase. The mean diameter of PCM droplets in the (O/W) emulsion decreased with the added amount of SiC. The SiC weight adhered on the surface of PCM droplets become the maximum in the continuous phase with pH 6.8. The hybrid microcapsules with the shell made of SiC and polyurea resin film could be prepared by using Pickering emulsion. There was a critical adhesion weight of SiC, above which the hybrid microcapsules could not be formed. Thermal conductivity of hybrid microcapsules could be improved as compared with the PCM microcapsules. Copyright © 2015 John Wiley & Sons, Ltd.