For the controlled modification of sol-gel-templated polymer nanocomposites, which are transferred to a nanostructured, crystalline TiO2 phase by a calcination process, the addition of a single homopolymer was investigated. For the preparation, the homopolymer polystyrene (PS) is added in different amounts to the diblock copolymer P(S-b-EO) acting as a templating agent. The homopolymer/diblock copolymer blend system is combined with sol-gel chemistry to provide and attach the TiO2 nanoparticles to the diblock copolymer. So-called good-poor solvent-pair-induced phase separation leads to the formation of nanostructures by film preparation via spin coating. The fabricated morphologies are studied as a function of added homopolymer before and after calcination with atomic force microscopy, field emission scanning electron microscopy, and grazing incidence small-angle X-ray scattering. The observed behavior is discussed in the framework of controlling the block copolymer morphologies by the addition of homopolymers. At small homopolymer concentrations, the increase in homopolymer concentration changes the structure size, whereas at high homopolymer concentrations, a change in morphology is triggered. Thus, the behavior of a pure polymer system is transferred to a more complex hybrid system. 相似文献
In this mini‐review, we highlighted the recent progresses in the controlled synthesis of metal sulfides hollow nanostructures via hard template technique. After a brief introduction about the formation mechanism of the inorganic hollow nanostructures via hard template technique, the discussions primarily focused on the emerging development of metal sulfides hollow nanostructures. Various synthetic strategies were summarized concerning the use of the hard template engaged strategies to fabricate various metal sulfides hollow nanostructures, such as hydrothermal method, solvothermal method, ion‐exchange, sulfidation or calcination etc. Finally, the perspectives and summaries have been presented to demonstrate that a facile synthetic technique would be widely used to fabricate metal sulfides hollow nanostructures with multi‐shells and components. 相似文献
High-density arrays of titania nanoparticles were prepared using a polystyrene-b-poly(ethylene oxide) block copolymer (PS-b-PEO) as a template and a titanium tetraisopropoxide based sol-gel precursor as titania source via a spin-coating method. The hydrophilic titania sol-gel precursor was selectively incorporated into hydrophilic PEO domains of PS-b-PEO and form titania nanoparticle arrays, due to a microphase separation between the PS block and the sol-gel/PEO phase. Field emission scanning electron microscopy (FESEM) and scanning probe microscopy (SPM) images showed that the uniformity and long-range order of the titania/PEO domains improved with increasing sol-gel precursor amount. Grazing incidence small-angle X-ray scattering (GISAXS) results indicate that the ordered structures exist over large length scales. Titania nanocrystal arrays of anatase modification were obtained by calcination at 600 degrees C for 4 h. After calcination, separated particles were observed for low and medium amounts of sol-gel precursors. Films with higher precursor amounts showed wormlike structures due to the aggregation between neighboring particles. Removal of the polymer matrix via UV treatment leads to highly ordered arrays of amorphous titania while retaining the domain size and interparticle distance initially present in the hybrid films. Photoluminescence (PL) properties were investigated for samples before and after calcination. The PL intensity increases with the increasing amount of sol-gel precursor. Bands at 412 nm were ascribed to self-trapped exitons and bands at 461 and 502 nm to oxygen vacancies, respectively. Uncalcined or UV-treated samples also showed PL properties similar to calcined samples, indicating that the local environment of the titanium atoms is similar to the environment of the crystalline anatase modification. 相似文献
The phase behavior of block copolymer based supramolecular complexes polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) and amphiphilic pentadecylphenol (PDP) molecules resembles the phase behavior of conventional block copolymers. Several PS‐b‐P4VP(PDP) complexes are found to self‐assemble into gyroid nanostructures. Typically, the grains are randomly oriented with a maximal size of several micrometers. Here, the orientation of a gyroid PS‐b‐P4VP(PDP) complex upon shearing is reported. It is found that the (111) gyroid lattice direction orients parallel to the shear direction after only several seconds of large amplitude oscillatory shearing. Oriented gyroid complexes can be used as templates for the preparation of metal nanofoams with improved ordering with potentially superior properties.
Hexagonal Zn(0.9)Mg(0.1)TiO(3) (ZMT) composite fibers were successfully prepared by combining sol-gel with an electrospinning and calcination technique. The crystalline phase and microstructures of Zn(0.9)Mg(0.1)TiO(3) fibers, calcined at various temperatures for 1 h, were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetry differential thermal analysis (TG-DTA) techniques. The results showed that the crystalline phase, morphology and grain size of the ZMT fibers were influenced by the calcination temperature and the doped magnesium improved the stability of the ilmenite ZnTiO(3)-based ceramic. Fibrous, linked particles and separated hexagonal particles were obtained after being calcined at 500, 700 and 900 °C, respectively. The single phase Zn(0.9)Mg(0.1)TiO(3) was formed from 700 °C to 900 °C and the possible formation mechanism was proposed. The as-prepared samples exhibited low activities for Methylene blue (MB) photodegradation under visible-light irradiation. 相似文献
A facile method is reported to controllably fabricate one dimensional(1D) polymer nanostructures via metallogel template polymerization.The metallogel was prepared through coordination interactions between silver ions and a ligand(L) bearing three pyridyl groups in tetrahydrofuran(THF).The diameters of the metallogel nanofibers could be tuned by the gel concentration(GC).Due to its high thermal stability and facility of removal,the metallogel was used as the template for radical polymerization of diacryolyl-2,6-diaminopyridine(DADAP) to form poly-diacryolyl-2,6-diaminopyridine(PDADAP) nanostructures.The gradually eroding of the templates by PDADAP provided us an effective way to fabricate various nanostructures of the polymer.We have demonstrated that different 1D nanostructures,including nanoribbons,nanotubes and nanowires,could be selectively fabricated by adjusting polymerization time,monomer concentration and GC.The rheological properties of the gel samples were tested by a rheometer.As prolonging the reaction time,more and more polymers were formed and the strength of the resulting polymer gels became higher and higher.The simple preparation process,easy controlled microstructures and adequate gel strength would make it a facile synthetic method for different 1D polymer nanosturctures. 相似文献
Sub-micrometer-sized hollow tantalum oxide (Ta2O5) spheres with tunable shell thickness and void size have been fabricated exploiting beta-diketone-functionalized polystyrene (PS) beads as sacrificial templates in a sol-gel process. First, a controlled precipitation of Ta2O5 nanoparticles was carried out on the template surface by hydrolyzing tantalum ethoxide (Ta(OEt)5) at room temperature, and subsequently, the polymer core was removed either via chemical treatment with toluene or calcination at 650 degrees C. The thickness of the tantala shell precipitated on the PS core during the coating process was tuned between 100 and 142 nm by varying the concentration of tantala precursor in the reaction media. The obtained Ta2O5-coated PS particles and hollow microspheres were characterized by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Due to the unique optical and dielectric properties, these nanostructured materials are envisaged to be used in applications such as novel building blocks for the fabrication of advanced materials, surface coatings, catalysts, and drug delivery systems. 相似文献
Hybrid Pt/TiO(2) nanostructures with diverse morphologies from nanodot, nanowire to mesoporous structures were obtained by a one-step synthesis based on block copolymer self-assembly. The structural transformation was easily tuned by controlling the relative amount of TiO(2) sol-gel precursor to poly(styrene-block-ethylene oxide) diblock copolymer (PS-b-PEO). These Pt/TiO(2) nanocomposites were utilized as photocatalysts with enhanced activity via synergistic coupling. Key parameters including the amount of TiO(2), types of morphology of photocatalysts, and the platinization of TiO(2) discussed in this study affected photocatalytic performance given that the hybrids were well-dispersed in nanopatterned configurations. 相似文献
A novel film coating technique, template-assisted electrostatic spray deposition (TAESD), was developed for the synthesis of porous metal oxide films and tested on TiO(2). Organic templates are codeposited with the titania precursor by electrostatic spray deposition and then removed during calcination. Resultant films are highly porous with pores casted by uniformly sized templates, which introduced a new level of control over the pore morphology for the ESD method. Employing the amphiphilic block copolymer Pluronic P123, PMMA latex spheres, or a combination of the two, mesoporous, macroporous, and hierarchically porous TiO(2) films are obtained. Decoupled from other coating parameters, film thickness can be controlled by deposition time or depositing multiple layers while maintaining the coating's structure and integrity. 相似文献
By means of a plasma technique, the surfaces of monodisperse polystyrene (PS) colloids have been modified with hydroxyl groups. Using these surface-modified PS colloids as sacrificial templates, we have fabricated silica-coated PS colloids (PS@silica) and titania-coated PS colloids (PS@titania) composite microspheres as well as hollow and mesoporous silica and titania microspheres. This process not only demonstrated a facile, low-cost, environmentally benign way to fabricate hollow oxides structures but also offered a feasible alternative to the preparation of polymer/inorganic oxide composites by templating against the polymer substrate with hydrophobic surfaces. 相似文献
The surfaces of monodisperse polystyrene (PS) colloids have been modified with hydroxyl groups by means of plasma treatment
technique. By templating against these surface-modified PS colloids, the germania coating PS composite microspheres were prepared
via a sol–gel process. After removal of PS cores, the resulting composite microspheres converted into hollow germania microspheres
with mesoporous structure. The shell thickness of these hollow spheres can be controlled by varying the concentration of germania
precursor. BET results indicated that the hollow germania microspheres shell exhibits slightly broader pore size distribution
than that of corresponding composite one owing to the swelling effects of the PS core during the etching process. In addition,
the as-prepared germania exhibits amorphous phase which can be converted into crystalline phase by calcination treatment.
It is worthy to noting that this fabrication protocol demonstrated a facile, low-cost and environment-benign way for fabricating
hollow germania structures by templating method. Moreover, this protocol is not limit to germania; it also could be used to
create the other hollow inorganic oxides spheres. 相似文献
The silica/polymer hybrid hollow nanoparticles with channels and gatekeepers were successfully fabricated with a facile strategy by using thermoresponsive complex micelles of poly(ethylene glycol)-b-poly(N-isopropylacrylamide) (PEG-b-PNIPAM) and poly(N-isopropylacrylamide)-b-poly(4-vinylpyridine) (PNIPAM-b-P4VP) as the template. In aqueous solution, the complex micelles (PEG-b-PNIPAM/PNIPAM-b-P4VP) formed with the PNIPAM block as the core and the PEG/P4VP blocks as the mixed shell at 45 °C and pH 4.0. After shell cross-linking by 1,2-bis(2-iodoethoxyl)ethane (BIEE), tetraethylorthosilicate (TEOS) selectively well-deposited on the P4VP block and processed the sol-gel reaction. When the temperature was decreased to 4 °C, the PNIPAM block became swollen and further soluble, and the PEG-b-PNIPAM block copolymer escaped from the hybrid nanoparticles as a result of swelled PNIPAM and weak interaction between PEG and silica at pH 4.0. Therefore, the hybrid hollow silica nanoparticles with inner thermoresponsive PNIPAM as gatekeepers and channels in the silica shell were successfully obtained, which could be used for switchable controlled drug release. In the system, the complex micelles, as a template, could avoid the formation of larger aggregates during the preparation of the hybrid hollow silica nanoparticles. The thermoresponsive core (PNIPAM) could conveniently control the hollow space through the stimuli-responsive phase transition instead of calcination or chemical etching. In the meantime, the channel in the hybrid silica shell could be achieved because of the escape of PEG chains from the hybrid nanoparticles. 相似文献
Titania-silica mesoporous composites have been prepared using polyethylene glycol (PEG) 20,000 as a template direction reagent with the assistance of supercritical carbon dioxide (SC CO(2)). For this preparation method, the composite precursors of tetrabutyl titanate (TBTT) and tetraethyl orthosilicate (TEOS) were dissolved in supercritical CO(2) and impregnated into PEG 20,000 using SC CO(2) as swelling agent and carrier. After removal of the PEG template by calcination in air at suitable temperatures, porous titania-silica composites were obtained. Effects of CO(2) pressure and temperature have been studied on the impregnation ratio during the supercritical fluid condition. The composite products were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), FTIR spectroscopy, nitrogen sorption-desorption experiments, scanning electronic microscope (SEM), and transmission electron microscope (TEM). XRD and nitrogen sorption-desorption experimental results indicate that the titania-silica composite crystallized in anatase phase and has a preferable BET surface area up to 301.98 m(2)/g. It was also demonstrated that the microstructure and macroproperty of TiO(2)/SiO(2) composites depend strongly on the experimental pressure during the impregnation process in SC CO(2). At suitable CO(2) pressure, silica even can be found in a single crystalline structure in nature by observation of TEM. At the same time, SEM indicates that the composite product existed in a spheric form or a cubic form inserted with many holes. So this work provides a new route to control and obtain the special micrography of TiO(2)/SiO(2) composites with the aid of suitable polymer templates in supercritical CO(2). 相似文献
A new method to fabricate metal/conducting polymer composite nanowires is presented by taking silver/polypyrrole composite nanowires as an example.A silver(Ⅰ)-coordinated organogel as template was prepared firstly,and redox-polymerization of pyrrole took place on the gel fiber,giving product of silver/polypyrrole nanowires.The silver/polypyrrole nanowires were characterized by multiple techniques.This strategy could be carried out in one-step procedure at room temperature,and it proves the utility of coordinated organogels in template synthesis of polymer nanostructures. 相似文献