Fluoroalkyl end-capped vinyltrimethoxysilane oligomer/anatase titanium oxide nanocomposite-encapsulated low molecular weight aromatic compounds [RF-(VM-SiO2)n-RF/an-TiO2/Ar-H] were prepared by the sol–gel reactions of the corresponding oligomer in the presence of anatase titanium oxide nanoparticles (an-TiO2) and the aromatic compounds such as bisphenol A [BPA], 1,1′-bi(2-naphthol) [BINOL], and fullerene under alkaline conditions. Thermogravimetric analyses measurements show that RF-(VM-SiO2)n-RF/an-TiO2 nanocomposite-encapsulated BPA and BINOL, in which the theoretical contents in the composites are 25?～?32 %, were found to give no weight loss corresponding to the contents of these aromatic compounds even after calcination at 800 °C. On the other hand, the corresponding nanocomposite-encapsulated fullerene exhibited weight loss behavior related to the presence of fullerene under similar conditions; however, UV–vis spectra showed the presence of the residual fullerene in the composites even after calcination. An-TiO2 in these fluorinated nanocomposites can keep its crystalline structure without phase transformation into rutile even after calcination at 1,000 °C, although the parent an-TiO2 nanoparticles underwent a complete phase transformation into rutile under similar conditions. Notably, RF-(VM-SiO2)n-RF/an-TiO2/Ar-H nanocomposites can give a good photocatalytic activity even after calcination at 1,000 °C for the decolorization of methylene blue under UV light irradiation. More interestingly, these fluorinated nanocomposites before and after calcination were found to exhibit a higher photocatalytic activity at the initial UV light irradiation from 1 to 3 min than that of the corresponding RF-(VM-SiO2)n-RF/an-TiO2 nanocomposites under similar conditions.
Figure
Encapsulated BPA and BINOL in the nanocomposites exhibit no weight loss even after calcination at 800 °C, and RF-(VM-SiO2)n-RF/an-TiO2/Ar-H nanocomposites before and after calcination at 1,000 °C can give a higher photocatalytic activity than that of RF-(VM-SiO2)n-RF/an-TiO2 nanocomposites. Notably, the photocatalytic activity of RF-(VM-SiO2)n-RF/an-TiO2/C60 nanocomposites after calcination increased by about 2.5-fold, compared with that of RF-(VM-SiO2)n-RF/an-TiO2 nanocomposites. 相似文献
Two kinds of fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(VM)n-RF] silica nanocomposites containing biphenylene units were prepared by the sol-gel reactions of the corresponding oligomer
with biphenylene-bridged ethoxysilanes or 4,4′-biphenol under alkaline conditions, respectively. One is the fluorinated oligomer/silica
nanocomposites containing biphenylene units [RF-(VM-SiO2)n–RF/Ar-SiO2], of whose biphenylene units were incorporated into nanocomposite cores through the siloxane bondings, and the other is the
fluorinated oligomer/silica nanocomposites containing biphenylene units [RF-(VM-SiO2)n–RF/Biphenol], of whose biphenylene units were directly encapsulated into nanocomposite cores through the sol–gel process. Interestingly,
the shape of RF-(VM-SiO2)n–RF/Ar-SiO2 nanocomposites is morphologically controlled cubic particles; although the shape of RF-(VM-SiO2)n–RF/Biphenol nanocomposites is spherically fine particles. Thermogravimetric analyses 2H magic-angle spinning nuclear magnetic resonance, Ultraviolet visible, and fluorescent spectra showed that biphenylene units
in RF-(VM-SiO2)n–RF/Ar-SiO2 nanocomposites have a flammable characteristic after calcinations at 800 °C; in contrast, biphenylene units in RF-(VM-SiO2)n–RF/Biphenol nanocomposites have a nonflammable characteristic even after calcination at 800 °C. X-ray photoelectron spectroscopy analyses
of these two kinds of fluorinated nanocomposites showed that nonflammable characteristic toward biphenylene units in the silica
gel matrices is due to the formation of ammonium hexafluorosilicate during the sol–gel process. 相似文献
A variety of fluoroalkyl end-capped oligomers, such as fluoroalkyl end-capped acrylic acid oligomer [RF-(ACA)n-RF], acryloylmorpholine oligomer [RF-(ACMO)n-RF], 2-acrylamido-2-methylpropanesulfonic acid oligomer [RF-(AMPS)n-RF], 2-(methacryloyloxy)ethanesulfonic acid oligomer [RF-(MES)n-RF], and N,N-dimethylacrylamide oligomer [RF-(DMAA)n-RF], were applied to the autoreduction of gold ions to give the corresponding oligomers/gold nanocomposites, of whose sharp plasmon absorption bands are observed around 535 nm. In these fluorinated oligomers, RF-(ACA)n-RF oligomer and RF-(ACMO)n-RF were effective for the one-pot preparation of the gold nanoparticles under very mild conditions; although the other fluorinated oligomers and the corresponding non-fluorinated–(ACMO)n-oligomer were unable to afford the gold nanoparticles. RF-(ACA)n-RF/SiO2 nanocomposites and RF-(ACMO)n-RF/SiO2 nanocomposites, which were prepared by the sol–gel reactions of tetraethoxysilane in the presence of silica nanoparticles and the corresponding oligomers under alkaline conditions, were also applied to the encapsulation of gold nanoparticles into these fluorinated nanocomposite cores through the autoreduction of gold ions at room temperature. Interestingly, these fluorinated oligomers/silica nanocomposite-encapsulated gold nanocomposites before and after calcination at 800 °C were found to exhibit the same plasmon absorption band around 525 nm. RF-(MES)n-RF oligomer and RF-(AMPS)n-RF oligomer are not suitable for the autoreduction of gold ions; however, RF-(MES)n-RF[or RF-(AMPS)n-RF]/polyaniline [PAn] nanocomposites, which were prepared by the polymerization of aniline initiated by ammonium persulfate in the presence of the corresponding oligomer, enabled the formation of gold nanoparticles through the oxidation of PAn in the composites at room temperature. The reversible conformational change of PAn in the nanocomposites from the polyemeraldine salt to the oxidized pernigraniline base was observed during such oxidation process. Graphical abstract
Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomer [RF-(DOBAA)n-RF]/silica gel nanocomposite, which was prepared by reaction of the corresponding fluorinated oligomer with tetraethoxysilane
and silica gel nanoparticles under alkaline conditions, exhibited no weight loss even at 800 °C equal to the original silica
gel, although the corresponding parent RF-(DOBAA)n-RF oligomer was completely degraded at 600 °C. Thermogravimetric analyses/mass spectra of fluorinated nanocomposite showed that
this nanocomposite decomposed around 280 °C to afford CO2 and H2O as the major evolved gaseous products including some minor fluoro- and hydrocarbons. X-ray photoelectron spectroscopy analyses
also showed that the contents of C, F, and Si atoms in RF-(DOBAA)n-RF/SiO2 nanocomposite after the calcination at 800 °C were similar to those before the calcination. These findings suggest that the
evolved gaseous products should be encapsulated quantitatively into nanometer-size-controlled silica matrices to give the
fluorinated silica gel nanocomposite with no weight loss even at 800 °C equal to the original silica gel. 相似文献
Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomer [RF-(DOBAA)n-RF] reacted with hibitane in methanol at 90 °C to afford RF-(DOBAA)n-RF oligomeric nanoparticles-encapsulated hibitane in good isolated yields. These fluorinated oligomeric particles-encapsulated hibitane were nanometer size-controlled very fine particles, and were found to exhibit a good dispersibility and stability in a wide variety of traditional organic solvents including fluorinated aliphatic solvents. Each dispersed solution with fluorinated nanoparticles afforded transparent colorless solution. These fluorinated nanoparticles were also found to exhibit a good antibacterial activity, and were applied to the surface modification of traditional organic polymers such as poly(methyl methacrylate). 相似文献
Fluoroalkyl end-capped acrylic acid oligomer [RF-(ACA)n-RF]/, 2-(methacryloyloxy)ethanesulfonic acid oligomer [RF-(MES)n-RF]/, 2-acrylamido-2-methylpropanesulfonic acid oligomer [RF-(AMPS)n-RF]/polyaniline [PAn] nanocomposites were prepared by the polymerization of aniline initiated by ammonium persulfate in the presence of the corresponding oligomers, respectively. These fluorinated oligomers were also applied to the preparation of the corresponding fluorinated oligomers/phenyl-capped aniline dimer (An-dimer: N,N′-diphenyl-1,4-phenylenediamine) nanocomposites by the interaction of the fluorinated oligomers with An-dimer. These fluorinated composites thus obtained were found to afford nanometer size-controlled fine particles possessing a good dispersibility and stability in water and traditional organic media such as methanol. UV–vis spectra of RF-(MES)n-RF/PAn nanocomposites and RF-(AMPS)n-RF/PAn nanocomposites showed the similar absorption peaks around 350, 430, and 780 nm to those of the usual Brønsted acid-doped PAn; however, interestingly, RF-(ACA)n-RF/PAn nanocomposites were found to exhibit only an absorption peak around 430 nm based on the polaron transition.
We have studied on the solubilization of single-walled carbon nanotubes (SW-CNTs) into aqueous and organic media by the use of a variety of nanometer size-controlled fluorinated self-assemblies, which were formed by the aggregations of end-capped fluoroalkyl segments in fluoroalkyl end-capped acrylic acid oligomers [RF-(ACA)n-RF], N,N-dimethylacrylamide oligomers [RF-(DMAA)n-RF], acryloylmorpholine oligomers [RF-(ACMO)n-RF], and N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers [RF-(DOBAA)n-RF]. Fluorinated self assemblies formed in organic media (colorless solutions) could solubilize SW-CNTs into organic media to afford the transparent pale yellow solutions. The dynamic light scattering measurements showed that the size of fluorinated self-assemblies increased after the solubilization of SW-CNTs into organic media. It was suggested that the solubilization of SW-CNTs into organic media is due to the encapsulation of SW-CNTs into fluorinated assemblies. Fluorinated assemblies were also able to solubilize SW-CNTs into water to give the transparent gray solutions. Among a variety of fluorinated assemblies, fluorinated assemblies formed by RF-(ACMO)n-RF [RF = CF(CF3)OC6F13] oligomer was more effective for the solubilization of SW-CNTs into both aqueous and organic media. Contact angle measurements of dodecane and the fluorescence spectra for poly(methyl methacrylate) cast film modified by fluorinated self-assemblies—SW-CNTs complexes showed that SW-CNTs are dispersed above the PMMA surface. 相似文献
Cross-linked fluoroalkyl end-capped cooligomers possessing double decker-type aromatic silsesquioxane segments as core units
[RF-(Ar-SiSQ)x-(Co-M)y-RF] were prepared under mild conditions by the cooligomerizations of fluoroalkanoyl peroxide with the corresponding aromatic
silsesquioxane possessing bifunctional vinyl groups (Ar-SiSQ) and comonomers (Co-M) such as acryloylmorpholine (ACMO), N,N-dimethylacrylamide (DMAA) and N-(1,1-dimethyl-3-oxobutyl)acrylamide (DOBAA). Interestingly, these cross-linked fluorinated cooligomers thus obtained were
found to form the nanometer size-controlled nanoparticles with a good dispersibility in a variety of solvents including fluorinated
aliphatic solvents. These fluorinated cooligomeric nanoparticles were demonstrated to have red-shifted fluorescent emissions
related to the presence of aromatic silsesquioxane segments, compared with that of parent aromatic silsesquioxane, indicating
that each aromatic moiety in these nanoparticles can interact effectively with each other through the π–π stacking between
the aromatic moieties to afford the red-shifted fluorescent emissions. These fluorinated nanoparticles were also applied to
the surface modification of poly(methyl methacrylate) (PMMA) to exhibit not only a good oleophobicity imparted by fluorine
but also a fluorescent emission behavior related to aromatic silsesquioxane segments in nanoparticles on the modified PMMA
surface. More interestingly, cross-linked RF-(Ar-SiSQ)x-(DOBAA)y-RF cooligomeric nanoparticles interacted with fluorescein to give the corresponding fluorinated cooligomeric particles/fluorescein
nanocomposites in methanol. These fluorinated fluorescein nanocomposites were found to afford an extraordinarily enhanced
light absorption (λmax = 441 nm), compared with that of fluoroalkyl end-capped DOBAA oligomer [RF-(DOBAA)n-RF] possessing no aromatic silsesquioxane segments. 相似文献
Mesoporous F−-doped TiO2 powders were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) in a mixed NH4F-H2O solution. Effects of F− ion content and calcination temperatures on the phase composition and porosity of mesoporous titania were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and BET surface areas. The results showed the BET surface area (SBET) of the pure and doped powders dried at 100°C ranged from 260 to 310 m2/g as determined by nitrogen adsorption. With increasing calcination temperatures, the SBET values of the calcined titania powders decreased due to the increase in crystalline size. The pore size distribution was bimodal with fine intra-particle pore and larger inter-particle pore as determined by nitrogen adsorption isotherms. The peak pore diameter of intra-particle pore increases with increasing F− ion content. At 700°C, all the titania powders exhibit monomodal pore size distributions due to the complete collapse of the intra-particle pores. The crystallization of anatase was obviously enhanced due to F−-doping at 400°C and 500°C. Moreover, with increasing F− ion concent, F− ions not only suppressed the formation of brookite phase at low temperature, but also prevented phase transition of anatase to rutile at high temperature. 相似文献
Nanophase silica-titania particles were prepared by two different synthetic routes, namely, sol–gel and hydrothermal processing. The crystallinity and crystallographic phases, particle size and surface area of the materials were controlled by varying the calcination temperature, and/or the ratio of Si to Ti. It was determined by XRD that the crystallite sizes of SiO2-TiO2 prepared by sol–gel and hydrothermal processing decreased from 11 to 6 nm and 12 to 9 nm, respectively, as the mole fraction of silica was increased from 0.1 to 0.4. It is proposed that the presence of the amorphous silica suppresses the growth of anatase TiO2 grains and their phase transformation to rutile. The photocatalytic decomposition rate of 1,4-dichlorobenzene (DCB) in aqueous solution with the sol–gel derived SiO2-TiO2 powder prepared at 750 °C was about 10 ± 5% higher than that observed with Degussa P25, whereas the SiO2-TiO2 samples prepared by hydrothermal processing at 250 °C showed a slightly lower decomposition rate than P25. 相似文献
Thiophene monomer reacted with ferric chloride in the presence of a variety of fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers [RF-(DOBAA)x-RF] to afford nanometer size-controlled RF-(DOBAA)x-RF oligomers-polythiophene composites [RF-(DOBAA)x-RF/PTh]. RF-(DOBAA)x-RF/PTh nanocomposites thus obtained were demonstrated to have a good dispersibility and stability in methanol to give a transparent brown solution. In addition, these fluorinated nanocomposites were applied to the surface modification of common organic polymers such as poly(methyl methacrylate), and were dispersed regularly above the polymer surface. 相似文献
Synthesis of rutile pigments is based on solid state reaction and on Hedvall effect, i.e., phase transformation from anatase to rutile. Therefore, it is important to know the thermal behavior of these compounds (the temperature of this change). The goal was to prepare rutile pigments of type Ti1?3xCrxNb2xO2+x/2 by conventional solid state method from titanium dioxide TiO2 (AV-01, anatase), to determine an influence of composition (x = 0, 0.05, 0.10, 0.20, 0.30, 0.50) and calcination temperature (850; 900; 950; 1,000; 1,050; 1,100; 1,150 °C) on color properties of these compounds and to analyze other starting compounds of titanium (hydrated anatase paste TiO2·nH2O, titanyl sulfate dihydrate TiOSO4·2H2O (VKR 611), hydrated sodium titanium oxide paste Na2Ti4O9·nH2O) and their reaction mixtures for x = 0.05 by simultaneous TG–DTA analysis. According to the highest chroma C of color, the optimal conditions for synthesis of these pigments are concentration x = 0.05 and calcination temperature 1,050 °C and higher. It was observed that initial temperature 760–830 °C is needful for a formation of rutile structure. This temperature is the lowest for hydrated Na2Ti4O9 paste (760 °C) and similar for other starting compounds of titanium. 相似文献
An analysis of the effects of dopants concentration and different starting titanium compounds on the anatase to rutile phase transformation at the synthesis of rutile pigments Ti1?3xCrxNb2xO2±δ is presented in this study. The main goal was to analyze reaction mixtures for x = 0.05 (previous study) and 0.30 by simultaneous TG–DTA analysis and to determine the temperature of anatase–rutile transition. For x = 0.05, initial temperatures 760–830 °C are needful for a formation of rutile structure. The temperature is the lowest for the hydrated Na2Ti4O9 paste (760 °C) and similar for other starting compounds of titanium. But for x = 0.30, the anatase–rutile transition begins at higher temperatures 910–1,030 °C because of high-Nb content, which is the inhibitor of this modification change. In addition, we found the influence of calcination temperatures (850, 900, 950, 1000, 1050, 1100, and 1150 °C) on color properties and particle size distribution of these materials prepared from anatase TiO2 and with x = 0.30. Selected pigments were also analyzed by X-ray powder diffraction. 相似文献
Inorganic dielectrics encapsulated in an organic matrix are showing excellent promise as novel dielectric materials. In this work, firstly highly organized crystalline nanoparticles of rutile TiO2 were synthesized by acid hydrolysis of titanium isopropoxide at room temperature. Then we developed a novel dielectric material consisting of highly organized rutile TiO2/polyaniline (PAni) nanocomposites by in-situ chemical oxidative polymerization. The structural, morphological, conducting, and dielectric properties of the rutile TiO2/PAni nanoparticles have been evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution-transmission emission microscopy (HR-TEM), four-point probe technique, CV (Capacitance versus Voltage), and Impedance analyzer. The nanocomposites show 70 times higher permittivity compared to rutile nanoparticles and much higher compared to anatase/PAni (ES) nanocomposites at 10 MHz. Large interfacial polarizations, nanostructure, and dopant levels are the key factors for the large dielectric constant of the nanocomposites. The rutile/PAni (ES) nanocomposites might see potential uses in super-capacitors, gate dielectric in transistors, and capacitive-type gas sensors. 相似文献
Mesoporous titania nanoparticles (denoted as MTN) with high surface area (e.g., 252 m2 g−1) were prepared using tetrapropyl orthotitanate (TPOT) as a titania precursor and 10–20 nm or 20–30 nm silica colloids as
templates. Co-assembly of TPOT and silica colloids in an aerosol-assisted process and immediate calcination at 450 °C resulted
in anatase/silica composite nanoparticles. Subsequent removal of the silica colloids from the composite by NaOH solution created
mesopores in the TiO2 nanoparticles with pore size corresponding to that of silica colloids. Effects of silica colloids’ contents on MTN porosity
and crystallites’ growth at a higher calcination temperature (e.g., 1000 °C) were investigated. Silica colloids suppressed
the growth of TiO2 crystallites during calcination at a higher calcination temperature and controllable contents of the silica colloids in precursor
solution resulted in various atomic ratios of anatase to rutile in the calcinated materials. The mesostructure and crystalline
structure of these titania materials were characterized by transmission electron microscope (TEM), scanning electron microscope
(SEM), X-ray diffraction (XRD), differential thermal analysis (DTA)-thermo-gravimetric analysis (TGA), and N2 sorption. 相似文献
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