A novel method for the preparation of core‐shell nanoparticles and hollow polymer nanospheres

A one‐step method to prepare core‐shell nanoparticles and thus hollow nanospheres is reported. The process for the formation of core and shell took place during reaction. Once the core formed, it was covered with the shell substance produced in situ, and thus, the shell hindered the continued growth of the core. Based on this method, we readily obtained core‐shell nanoparticles by choosing AgCl, CuS, or Fe(III) diethyldithiocarbamate (FeDEC)₃ as model core substances and the cogel from gelatin and gum arabic as the shell substance. High‐resolution transmission electron microscopy (HRTEM) directly revealed the core‐shell structure. TEM results showed the average particle sizes were under 100 nm, depending on the core substance and the concentration of substances producing cores. After removal of the core materials, hollow nanospheres resulted, which were directly observed by TEM. The observation further verified the core‐shell structure. UV spectrophotometry also gave signals of coated structure and revealed high core content (51.1%) and nearly perfect coating (91.6%). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2594–2600, 2004     

巯基-迈克尔加成法合成温敏性PEG共聚物及凝胶化反应

巯基-迈克尔加成反应由于条件温和、迅速、高效等优点,近年来成为生物医用高分子材料合成的热点之一。双丙烯酰氧基的聚乙二醇二丙烯酸酯（PEGDA）和双巯基的3,6-二氧杂-1,8-辛二硫醇（EDT）通过巯基-迈克尔加成形成了温敏性的PEG共聚物(poly(PEGDA-alt-EDT) )。增大PEGDA 的分子量相应提高poly(PEGDA600-alt-EDT)水溶液的临界溶液温度（LCST）。1HNMR 和GPC表征了共聚物的结构和分子量。在APS的引发下poly(PEGDA-alt-EDT)末端官能团进一步发生偶合-聚合形成温敏性PEG共聚物水凝胶。SEM、流变性能测试和平衡溶胀系数结果表明,poly(PEGDA-alt-EDT)水凝胶具有典型的三维孔洞结构、良好的流变性能、溶胀能力和温度响应性。     

Improvement of hollow mesoporous silica nanoparticles synthesis by hard-templating method via CTAB surfactant

In this study, hollow mesoporous silicate nanoparticles using TEOS precursors in the presence of polystyrene template were synthesized. The process was performed in an alcohol-based chemical system and the addition of CTAB surfactant. The polystyrene template was used under controlled conditions having a spherical morphology with a uniform distribution and an average size of 50 nm. The results of the FTIR analysis showed that TEOS pre-cursor particles formed surface boundaries during the synthesis with CTAB surfactants, and also the presence of SiOSi bonds (in the 600 to 1320 cm⁻¹ range) indicates the formation of silicate chains on Polystyrene templates. Thermal analysis studies showed that by using appropriate thermal treatment and precise control, organic compounds can be removed from the system and synthesize hollow mesoporous silicate particles with minimum structural defects at 280 °C. The BET analysis showed that the specific surface area of these particles is 1180 m² g⁻¹. X-ray diffraction results demonstrated that the resulting product was amorphous silica and unwanted phases were not formed in this system. The dynamic light scattering analysis illustrated that the synthesized particles had dimensions ranging from 1 to 10 nm, and the particle size distribution occurred within a narrow range. Scanning electron microscopy images confirm the nodularity of nanoparticles with a mean size of 25–30 nm. Finally, the transmitted electron microscope images showed that the synthesized silicate particles were hollow, so that the diameter of the hollow chamber and its total diameter were about 30 and 80 nm, respectively.     

Synthesis of polystyrene/polythiophene core/shell nanoparticles by dual initiation

Polystyrene/polythiophene (PSt/PTh) core/shell nanoparticles were successfully synthesized via a one-pot Fe³⁺-catalyzed oxidative and soap-free emulsion polymerization process. A small amount of sodium styrene sulfonate (NaSS) was used to maintain the colloidal stability of the PSt/PTh nanoparticles. Hydrogen peroxide (H₂O₂) and a trace of iron chloride (FeCl₃) were used to carry out the free-radical polymerization of styrene and the oxidative polymerization of thiophene. The dual initiation characteristics of H₂O₂/FeCl₃ in the PSt/PTh core/shell nanoparticle formation were investigated by observing the time-evolution of the particle morphology. In addition, photoluminescent property, particle size distribution, core/shell morphology and the formation mechanism of the PSt/PTh nanoparticles were studied by spectrofluorophotometery, dynamic light scattering (DLS), in-situ IR, zeta-potential, and time-evolution field-emission scanning electron microscope (FE-SEM) analyses.     

Preparation of novel hybrid inorganic–organic hollow microspheres via a self‐template approach

BACKGROUND: Hollow microspheres, especially biodegradable polymeric microspheres, have attracted considerable attention due to their particular characteristics. Up to now, microspheres have been prepared via various strategies, for instance the template synthesis method and the self‐assembly process. However, economic, novel and simple methods to prepare hollow microspheres are still being sought. RESULTS: Phosphazene‐containing microspheres, which contain self‐assembled core‐shell structures, were prepared at high colloid contents using an ultrasonic bath via a self‐template approach. Along with the controlled self‐degradation of the internal core, the corresponding hybrid inorganic–organic hollow microspheres appeared. The mechanism was evidenced by means of transmission and scanning electron microscopy, cross‐polarization with magic angle spinning NMR, Fourier transform infrared spectroscopy, X‐ray diffraction and thermogravimetric analysis. CONCLUSION: It was clarified that the phosphazene‐containing microspheres could be formed and stably dispersed without aggregation even at high colloid contents using the ultrasonic bath method and the microspheres contain self‐assembled core–shell structures. Along with the controlled self‐degradation of the internal core, the corresponding hollow microspheres appeared. The mechanism of this preparation is of great significance because it is completely different from the conventional template synthesis method and the self‐assembly process. The absence of any stabilizing agent and special templates might inspire creative imagination in the design of new morphologies of micro‐ and nanostructures. Copyright © 2007 Society of Chemical Industry     

MnO2纳米空心球的制备及其电化学性能

采用水热法通过添加Ce离子制备了MnO₂纳米空心球电极材料。Ce离子对MnO₂的形貌和结晶程度有很大的影响,添加Ce离子后生成由纳米棒组成的中空球,中空球比表面积(BET)达到315.2 m²·g^-1。MnO₂电极电化学测试结果表明:当铈锰摩尔比为0.2时电极材料具有较好的电化学性能,其比电容达到178.6 F·g^-1,与未加Ce离子相比其比电容提高了2.6倍,而且经过1000次循环稳定性测试后比电容仍保留了90.5%。这些结果表明添加Ce离子有利于形成中空结构,并提高了MnO₂电极的比电容。     

New approach to hybrid materials: Functional sub-micrometer core/shell particles coated with NiS clusters by γ-irradiation

Functional sub-micrometer core/shell hybrid particles coated with inorganic components have many promising applications as new materials based on their multiphase structures with unusual features. Herein we demonstrate a novel approach to produce such particles with potential applications in the fields of magnetic materials. PSt seed latex was prepared through emulsion polymerization. Core-shell P(St-co-Am) particles with polyacryamide (PAm)-rich shell were formed through interfacial-initiated seeded emulsion polymerization. Then spherical P(St-co-AM)/NiS sub-micrometer composites were successfully prepared by the reaction of nickelous sulfate (NiSO₄) and thioacetamide (CH₃CSNH₂) under ⁶⁰Co γ-irradiation at ambient temperature and pressure. P(St-co-AM)/NiS hybrid particles were confirmed with electron microscopy, X-ray diffraction and X-ray photo-electron spectroscopy. The properties of P(St-co-Am) hybrid particles were studied with UV-vis spectroscopy, photoluminescence spectroscopy and magnetic hysteresis loop analysis.     

Controlled growth of hollow polyaniline structures: From nanotubes to microspheres

Homogeneous and fairly monosized microspherical structures of polyaniline has been synthesized using a simple soft template method with β-naphthalene sulfonic acid (β-NSA) as both the surfactant and dopant, and ammonium persulfate (APS) as the oxidant at 2–5 °C. The morphology of PANI-NSA was successfully controlled from nanotubes to microsphere, by changing the synthesis conditions (i.e. pH, the concentration of surfactant and monomer, and temperature). Some mechanistic aspects of the formation of nanotubes and hollow spheres have been discussed precisely based on SEM, TEM, DLS, FTIR and UV-visible results. Moreover, synthesis was performed under acidic environment to obtain further understanding about the formation mechanisms.     

Melt compounding of syndiotactic polypropylene nanocomposites containing organophilic layered silicates and in situ formed core/shell nanoparticles

Syndiotactic polypropylene (sPP) compounds containing organophilic layered silicates were prepared by means of melt extrusion at 220 °C using a corotating twin screw extruder in order to examine the influence of the silicate modification and the addition of maleic-anhydride-grafted isotactic polypropylene (iPP-g-MA) as compatibilizer on morphology development and mechanical properties. Synthetic sodium fluoromica was used as water-swellable layered silicate, which was rendered organophilic by means of cation exchange with protonated octadecylamine. Only compounding of the modified silicate in conjunction with iPP-g-MA afforded exfoliation and dispersion of individual silicate layers, encapsulated in an iPP-g-MA shell, within the polypropylene matrix. Interlayer distance increased with increasing content and increasing molecular weight of the compatibilizer. The Young's modulus of the nanocomposite increased fivefold from 490 to 2640 MPa. This was attributed to silicate nanoreinforcement and nucleation of sPP crystallization via the iPP-g-MA shell of the dispersed organophilic silicate nanoparticles. The yield stress was increased to 29 MPa with respect to 16 MPa for the bulk sPP. Morphology and mechanical properties were examined as a function of the silicate—and compatibilizer content.     

Factorial experimental design on synthesis of functional core/shell polymeric nanoparticles via differential microemulsion polymerization

Functionalized core/shell nanoparticles of the co‐polymer of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) could be polymerized by differential microemulsion polymerization, using a small amount of surfactant (the weight ratio of sodium dodecyl sulfate (SDS)/monomer is 1 : 24). The core/shell nanoparticles have a high conversion, high molecular weight, and small particle size (25–30 nm). The statistical analysis indicated that SDS, water, and the interactionbetween SDS and water have a significant positive interaction between the MMA conversion to form the core nanoparticles. For the core‐shell polymer, [GMA], [GMA]*[SDS], and [GMA]* [water] have significant negative effects on conversion; whereas [SDS] and [water], [SDS]*[water] and [GMA]*[SDS]*[water] have positive effects on the conversion to form core/shell nanoparticles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of novel organic/inorganic hybrid nanoparticles containing an organotin core and a polystyrene shell

A series of new well‐defined nanoparticles containing an organotin core and a polystyrene shell were obtained by crosslinking of n‐Bu₂SnO with various chain‐length amphiphilic polystyrene‐b‐poly‐(6‐(4‐vinylphenoxy) hexanoic acid. The amphiphilic copolymers were synthesized via reversible addition fragmentation chain transfer polymerization and hydrolysis. The structures of the nanoparticles were studied by the transmission electron microscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy analysis. Notably, the morphology of the crosslinked copolymer showed individual nanoparticles with regularly spherical shape. And the nanoparticle diameters decreased with increasing number of organotin carboxylate units. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphology transition control of polyaniline from nanotubes to nanospheres in a soft template method

A soft template route is reported for the fabrication of polyaniline nanospheres via the oxidative polymerization of aniline in the presence of β‐naphthalenesulfonic acid (β‐NSA) as both surfactqant and dopant, and ammonium persulfate as oxidant at 2–5 °C. Control over the morphology and size of the nanoparticles was achieved by changing the reaction medium via addition of an organic cosolvent (i.e. ethanol or ethylene glycol) and by controlling the concentrations of aniline and β‐NSA and the molar ratio of β‐NSA to aniline. By this means the size of the β‐NSA–aniline micelles and the way that aniline monomer interacts with the micelles were controlled. In fact the lower dielectric constant of organic cosolvent, due to reduction of the possibility of dissociation of ionic species, causes the monomer to exist mostly as neutral aniline molecules rather than as anilinium cations. The neutral aniline molecules form aniline‐filled micelles with β‐NSA, which act as soft templates for the formation of polyaniline nanospheres. Scanning and transmission electron microscopies, dynamic light scattering, and Fourier transform infrared and UV‐visible spectroscopies were used to characterize the products. The mechanism of morphology transition from nanotubes to nanoparticles is discussed based on the experimental observations. © 2014 Society of Chemical Industry     

Preparation and characterization of core‐shell nanoparticles containing poly(chlorotrifluoroethylene‐co‐ethylvinylether) as core

Core shell latex particles with a glassy core and a low T_g polymeric shell are usually preferred. More so, the glassy core happens to be a fluoropolymer with a shell polymer that helps in processability. We describe here the preparation and characterization of core shell nanoparticles consisting of poly(chlorotrifluoroethylene‐co‐ethylvinylether) as core encapsulated in poly(styrene‐acrylate) copolymer shell using seeded emulsion polymerization method under kinetically controlled monomer starved conditions. Properties of the emulsion using surfactants (fluoro/conventional) and surfactant free conditions were investigated. Average size (100 nm), spherical shape and core–shell morphology of the latex particles was confirmed by dynamic light scattering and transmission electron microscopy. Absence of C? F and C? Cl peaks in X‐ray photoelectron spectroscopy proves that cores are completely covered. Polymerization in the presence of fluorocarbon surfactant was found to give optimum features like narrow size distribution, good shell deposition and no traces of agglomeration. Films of core shell latex particles exhibited improved transparency and enhanced water contact angles thus making them suitable for applications in various fields including coatings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fabrication and application of hollow ZnO nanospheres in antimicrobial casein‐based coatings

ZnO hollow nanospheres with porous shells were prepared successfully via a simple hard‐template method and a calcination process. Then the obtained ZnO hollow nanospheres were encapsulated with mildew‐proof agent and modified by polydopamine. At last,antimicrobial casein‐based coatings were obtained by mixing the drug‐loaded ZnO and casein latex. Antimicrobial testing results revealed casein‐based hollow ZnO/mildew‐proof agent nanocomposite films displayed the better antimicrobial activities, and it still has antimicrobial properties after 1 year.     

Development of mesoporous SiO2/CeO2 core/shell nanoparticles with tunable structures for non-damage and efficient polishing

For abrasive particles, the type, morphology, structure, size and distribution, physio-chemical properties are usually considered as key influential factors which determine the ultra-precision polishing performance. It is commonly recognized that the structure design, surface modification, and doping treatment of abrasives contribute to achieving high-quality and high-efficiency polishing. Herein, we report the fabrication of sub-100 nm monodispersed dendritic-like mesoporous silica (D-mSiO₂) with tunable structures via an oil-water biphase stratification approach. A CeO₂ thin shell was subsequently coated on the D-mSiO₂ nanospheres forming core/shell structured D-mSiO₂/CeO₂ composites. The samples were examined via XRD, SEM, TEM, SAED, DLS, FTIR, and nitrogen adsorption-desorption measurements. The polishing characteristics of the D-mSiO₂/CeO₂ nano-abrasives over silica films were tracked by atomic force microscopy and noncontact interferometric microscopy. Compared with commercial ceria particles, the obtained D-mSiO₂/CeO₂ nano-abrasives were favorable for mechanical scratch elimination and removal rate enhancement. Furthermore, an enlarged pore volume or porosity of D-mSiO₂ cores achieved an atomic-scale surface with relatively low roughness, less variation, and enhanced removal rate. The mechanism of high-efficiency and defect-free polishing for the CeO₂-based composites was discussed. These results may provide promising guidance in the design and optimization of novel particle abrasives.     

A chemical etching route to controllable fabrication of TiO2 hollow nanospheres for enhancing their photocatalytic activity

The TiO₂ hollow nanospheres with diameters of about 230 nm were prepared by a simple and controllable route based on hydrolysis of Ti(OBu)₄ on the surfaces of the Cu₂O solid nanospheres followed by inward etching of the Cu₂O nanospheres. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The further post-heat treatment led to the high crystallization of the TiO₂ hollow nanospheres. The photocatalytic performances of these samples were evaluated for the photodegradation of rhodamine B (RhB) under UV-light irradiation. The as-prepared TiO₂ hollow nanospheres showed higher photocatalytic activity than the CuO and the CuO/TiO₂ hollow nanospheres. Effects of temperature and time for post-heat treatment of TiO₂ as well as initial RhB concentrations on the RhB photodegradation have also been studied. The results show that the TiO₂ hollow nanospheres have the good reusability as photocatalysts and are promising in waste water treatment.     

竹炭生物模板法合成空心层状纳米NiO

以竹炭作为生物模板,结合浸渍-煅烧法制备了空心纳米NiO。XRD测试结果表明,产物为立方相NiO;TEM测试结果表明样品为空心六面体结构,其平均粒径为100～150 nm,孔径为50～100 nm,且壳层结构均由片状纳米晶粒构筑而成。     

中空聚合物微球的制备及其在涂料中的应用

近年来,中空聚合物微球由于其独特的结构特点,表现出普通材料不具备的性能,引起研究者广泛的兴趣。阐述了当前合成中空聚合物微球的研究现状,并展望了中空聚合物微球在涂料中的应用前景。