Two kinds of hydrophilic polymers, poly(oxyethylene methacrylate) (POEM) and poly(styrene sulfonic acid) (PSSA), were grafted from TiO2 nanoparticles via the surface-initiated atom transfer radical polymerization (ATRP) technique. Chlorine modified TiO2 nanoparticles (TiO2-Cl), the ATRP initiators, were synthesized by the reaction of -OH in TiO2 with 2-chloropropionyl chloride (CPC). FT-IR, UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS) clearly showed that the polymer chains were successfully grafted from the surface of TiO2 nanoparticles. The hydrophilically modified TiO2 nanoparticles have a better dispersion in alcohol than unmodified nanoparticles, as revealed by transmission electron microscopy (TEM). It was also found that the polymer grafting did not significantly alter the crystalline structure of the TiO2 nanoparticles according to the X-ray diffraction (XRD) patterns. Grafting amounts were 10% of the weight for both TiO2-POEM and TiO2-PSSA nanoparticles, as determined by thermogravimetric analysis (TGA). 相似文献
We synthesized titanium dioxide (TiO2) and nitrogen-doped TiO2 nanoparticles (N-TiO2 NPs) via a sol-hydrothermal method using ammonium chloride (NH4Cl) as the nitrogen (N) source. Furthermore, an N-TiO2/4-mercaptobenzoic acid (4-MBA)/silver (Ag) nanocomplex served as an active substrate for surface-enhanced Raman scattering (SERS) and was prepared by self-assembly. During SERS, the Raman signals of 4-MBA of the N-TiO2/MBA/Ag nanocomplexes exhibited higher intensity and sensitivity than pure TiO2/MBA/Ag, with 1% N doping in N-TiO2, producing the strongest Raman signals. We characterized the N-TiO2 hybrid materials by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet-visible diffuse reflectance spectra. N doping did not influence the phase of the TiO2 crystal. The doped N entered into the crystal lattice of the TiO2, replacing some oxygen (O) to form Ti-O-N or Ti-N-O linkage. The results indicated that an appropriate amount of N doping could enhance the SERS performance of the TiO2 SERS substrate via N substitution doping. These doping forms were beneficial to the molecular charge transfer (CT), and this resulted in improved SERS performance for N-doped TiO2 NPs. We attributed this improvement to the formation of N-doping energy levels that were beneficial to the process of TiO2 to MBA molecule CT. This work not only enriched the nonmetal-doped CT mechanism in SERS but also provided several reference values for practical applications.
CdSe and CdSe/TiO2 nanoparticles were synthesized under multibubble sonoluminescence (MBSL) condition. The influences of TiO2 introduced as the sensitizer on the morphology and crystal transformation were investigated. The morphology, phase and optical properties of the final products have been characterized by X-ray powder diffraction, transmission electron microscope, UV-vis absorption spectroscopy and photoluminescence spectroscopy. The results showed that as-prepared nanoparticles are well-crystallized, and the suppression of crystal pattern transition as well as the control of CdSe crystal growth can be implemented by coupling of TiO2 semiconductor. Furthermore, the possible growth mechanism for different morphologies and crystal phases of the nanocrystals were also discussed. 相似文献
In the preparation of nanocomposites, there is competition between the dispersion of nanoparticles and the formation of agglomerates. In this study, radical copolymerization of ethyl acrylate and methyl methacrylate initiated by 2,2‐azobis (isobutyro) nitrile (AIBN) was performed, in the presence of titanium oxide (TiO2) nanoparticles modified in a new approach; a good dispersion of the nanoparticles in the unsaturated polyester (UP) matrix was obtained. The TiO2 nanoparticles were exposed to 3‐(methacryloxy) propyl trimethoxy silane as the coupling agent. The presence of coupling agent‐grafted TiO2 nanoparticles in the copolymerization process resulted in the formation of a polymeric layer on the surface of the TiO2 nanoparticles (doubly modified‐TiO2). The grafting of coupling agent molecules and consequently copolymer macromolecular chains onto the surface of TiO2 nanoparticles was investigated using Fourier transform infrared (FTIR) analysis. It found that the formation of an acrylate layer on the surface of nanoparticles was successful. Then, unsaturated polyester (UP)/TiO2 nanocomposites were prepared. The morphology was studied using transmission electron microscopy (TEM). Mechanical properties and ultraviolet visible (UV/VIS) spectroscopy of various samples, including the doubly modified‐TiO2 nanoparticles, with different nanoparticle inclusions and the unmodified‐TiO2 nanoparticles, were also investigated. The results showed the doubly modified‐TiO2 nanoparticles, compared to those of unmodified‐TiO2, had better nanoparticle dispersion causing improvement in the mechanical properties and UV shielding. 相似文献
By dipping-lifting in sol-gel solution and reducing process, the graphene/TiO2 composite film on the glass plate was first prepared. Then, the Ag/graphene/TiO2 composite film was fabricated by interface reaction with AgNO3 and N2H4·H2O on the surface of graphene/TiO2 composite film. The characterization results show that the uniform porous TiO2 film is made up of the anatase crystal, and the Ag/graphene/TiO2 composite film is constructed by doping or depositing graphene sheets and Ag nanoparticles on the surface of TiO2 film. The photoelectrochemical measurement results indicate that the Ag/graphene/TiO2 composite film has an excellent photoelectrochemical conversion property. 相似文献
Poly(N-methyl pyrrole) coating was successfully electrodeposited on steel substrates in mixed electrolytes of dodecyl benzene sulphonic acid (DBSA) with oxalic acid in the absence and the presence of TiO2 nanoparticles (NPs). The morphology and compositions were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray spectroscopy (EDX). X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to calculate the size of nanoparticles. Electrode/polymer/electrolyte system was studied by Electrochemical Impedance Spectroscopy (EIS). The FESEM micrographs suggest that the incorporation of TiO2 nanoparticles affects the morphology of the film significantly and makes the TiO2 to be loosely piled up with PMPy. The results of EIS showed that synthesized PMPy in the presence of TiO2 NPs increases and decreases the Rpo and Cc of the coating respectively. The increase of the area of synthesized PMPy in the presence of nanoparticles can increase its ability to interact with the ions liberated during the corrosion reaction of steel in NaCl solution. 相似文献
Porous organic carbon-doped titania (C-TiO2) nanomaterials and their composites with Ag nanoparticles (Ag/C-TiO2) were synthesized by an eggshell membrane templating method, and their structural and photocatalytic properties were systematically
characterized. These nanomaterials, exhibiting a macroscopic morphology of a thin film, are composed of interwoven tubes,
and the tube wall consists of nanocrystals. The doped organic carbon was composed of the active carbon and carbonate species,
which could form a layer around the surface of TiO2 nanoparticles, while the silver was incorporated into Ag/C-TiO2 composites as separated Ag nanoparticles. The degradation of methylene blue under visible light irradiation was employed
to evaluate the photocatalytic activity of these as-prepared TiO2-based materials. Both C-TiO2 and Ag/C-TiO2 nanomaterials showed higher photocatalytic activity than pure TiO2 material–commercial Degussa P25. These results can be accounted for the coupling effect of the incorporation of carbon species
and Ag nanoparticles. 相似文献
TiO2 sol-gels with various Ag/TiO2 molar ratios from 0 to 0.9% were used to fabricate silver-modified nano-structured TiO2 thin films using a layer-by-layer dip-coating (LLDC) technique. This technique allows obtaining TiO2 nano-structured thin films with a silver hierarchical configuration. The coating of pure TiO2 sol-gel and Ag-modified sol-gel was marked as T and A, respectively. According to the coating order and the nature of the TiO2 sol-gel, four types of the TiO2 thin films were constructed, and marked as AT (bottom layer was Ag modified, surface layer was pure TiO2), TA (bottom layer was pure TiO2, surface layer was Ag modified), TT (pure TiO2 thin film) and AA (TiO2 thin film was uniformly Ag modified). These thin films were characterized by means of linear sweep voltammetry (LSV), X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy and transient photocurrent (Iph). LSV confirmed the existence of Ag0 state in the TiO2 thin film. SEM and XRD experiments indicated that the sizes of the TiO2 nanoparticles of the resulting films were in the order of TT > AT > TA > AA, suggesting the gradient Ag distribution in the films. The SEM and XRD results also confirmed that Ag had an inhibition effect on the size growth of anatase nanoparticles. Photocatalytic activities of the resulting thin films were also evaluated in the photocatalytic degradation process of methyl orange. The preliminary results demonstrated the sequence of the photocatalytic activity of the resulting films was AT > TA > AA > TT. This suggested that the silver hierarchical configuration can be used to improve the photocatalytic activity of TiO2 thin film. 相似文献
A tubular array of TiO2-nanotubes on a Ti substrate was used as a support for an Ag sputter-deposited layer intended for surface-enhanced Raman scattering (SERS) investigations. Composite samples of Ag/TiO2-nanotube/Ti were studied with the aid of scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) to reveal their characteristic morphological and chemical features. Raman spectra of pyridine (as a probe molecule) were measured at different cathodic potentials ranging from −0.2 down to −1.2 V after the pyridine had been adsorbed on the TiO2-nanotube/Ti substrates covered with the Ag deposit. In addition, SERS spectra on a bulk electrochemically-roughened Ag reference substrate, were also measured.The SERS activity of the composite samples was strongly dependent on the amount of Ag deposit and, in some cases, was even higher than that for the Ag reference substrate. The SERS intensity vs. electrode potential dependences measured were interpreted in terms of the modified electronic structure of the Ag deposits due to the interaction of the Ag clusters with the TiO2-nanotube/Ti substrate. 相似文献
The aqueous solutions of different stability containing silver sulfide (Ag2S) nanoparticles are studied. The stable, transparent, and turbid solutions have been subjected to daylight for 7 months, to ultraviolet and laser irradiation, as well as to an electron beam. Solar radiation is found to favor the Ag2S reduction to Ag and/or the formation of Ag2S/Ag hybrid nanoparticles in the solution. At a high amount of hybrid nanoparticles, the exciton–plasmon interaction causes asymmetry in the absorption spectra. The exposure of Ag2S particles precipitated from the solution with the electron beam leads to the reversible growth of Ag threads. The possible exciton–plasmon interplay mechanisms in Ag2S/Ag hybrid nanoparticles are considered. The physical mechanisms of the changing Ag2S stoichiometry, the formation of metallic Ag and Ag2S/Ag hybrid nanoparticles are the generation of hot carriers and the energy transfer (exciton–plasmon interaction) in a metal–semiconductor hybrid nanosystem are elucidated, as well.
This paper investigated the gaseous formaldehyde degradation by the amine-functionalized SiO2/TiO2 photocatalytic films for improving indoor air quality. The films were synthesized via the co-condensation reaction of methyltrimethoxysilane (MTMOS) and 3-aminopropyltrimethoxysilane (APTMS). The physicochemical properties of prepared photocatalysts were characterized with N2 adsorption/desorption isotherms measurement, X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FT/IR). The effect of amine-functional groups and the ratio of MTMOS/APTMS precursors on the formaldehyde adsorption and photocatalytic degradation were investigated. The results showed that the formaldehyde adsorption and photocatalytic degradation of the APTMS-functionalized SiO2/TiO2 film was higher than that of SiO2/TiO2 film due to the surface adsorption on amine sites and the relatively high of the specific surface area of the APTMS-functionalized SiO2/TiO2 film (15 times higher than SiO2/TiO2). The enhancement of the formaldehyde degradation of the film can be attributed to the synergetic effect of adsorption and subsequent photocatalytic decomposition. The repeatability of photocatalytic film was also tested and the degradation efficiency was 91.0% of initial efficiency after seven cycles. 相似文献
X-ray photoelectron spectroscopy (XPS) was used to characterise the effects of low energy (<2 eV) argon ion plasma surface modification of TiO2 thin films deposited by radio frequency (RF) magnetron sputter system. The low energy argon ion plasma surface modification of TiO2 in a two-stage hybrid system had increased the proportion of surface states of TiO2 as Ti3+. The proportion of carbon atoms as alcohol/ether (COX) was decreased with increase the RF power and carbon atoms as carbonyl (CO) functionality had increased for low RF power treatment. The proportion of C(O)OX functionality at the surface was decreased at low power and further increase in power has showed an increase in its relive proportion at the surface. The growth of S180 cells was observed and it seems that cells are uniformly spreads on tissue culture polystyrene surface and untreated TiO2 surfaces whereas small-localised cell free area can be seen on plasma treated TiO2 surfaces which may be due to decrease in C(O)OX, increase in CO and active sites at the surface. A relatively large variation in the surface functionalities with no change in the surface roughness was achieved by different RF plasma treatments of TiO2 surface whereas no significant change in S180 cell growth with different plasma treatments. This may be because cell growth on TiO2 was mainly influenced by nano-surface characteristics of oxide films rather than surface chemistry. 相似文献
UV irradiation of materials consisting of a polymer matrix that possesses precursors of noble metals followed by annealing results in creation of metal nanoparticles within the irradiated domains. Such photoinduced nanocomposites are promising for photonics applications due to the strong alteration of their optical properties compared to initial nonirradiated materials. We report our results on the synthesis and investigation of two kinds of these materials:
Photoinduced Au nanocomposites based on PMMA matrices, including bulk materials prepared by means of the polymerization technique;
photoinduced Ag nanocomposites with an organic–inorganic hybrid matrix based on TiO2 gels.
The experimental data on evolution of absorption spectra of these materials due to laser irradiation at different wavelengths are presented. The linear and nonlinear refractive index changes in these materials owing to light-induced nanonstructuring are investigated. 相似文献
An amorphous acrylic acid (AA) polymer coating was generated on TiO2 nanoparticles through pulse radio frequency (RF) plasma polymerization. The AA plasma synthesis mechanism was studied by its optical emission spectrum. The chemical structures of AA–plasma‐polymer were carefully investigated by Fourier transform infrared spectroscopy (FTIR). The dispersion behaviors of AA‐coated and uncoated TiO2 nanoparticles in glycol solution were characterized by ultraviolet absorbency and particle size distribution measurements. The results showed that the aggregation of TiO2 nanoparticles in glycol solution was effectively lowered and the dispersion was improved a lot after AA–plasma‐polymer coating. The pulse plasma coating parameters played an important role in the dispersion enhancement of TiO2 nanoparticles. By properly regulating the pulse discharge parameters, the system could gain the highest radical–monomer reactions rate, the most compatible functional groups on the nanoparticles, and the best dispersion in the background media. 相似文献
Compared to conventional film photocatalysts, fiber photocatalyst has a greater surface-to-volume ratio and a 3-D open structure that allows its surface active sites to be accessible for reactants more easily and effectively. However, TiO2 powder (Degussa P25), by itself, cannot be prepared in the form of fibers, but with the help of a polymer nanofiber, TiO2 particles can be immobilized in a fibrous network of polyelectrolyte. Here, hybrid multilayered hollow nanofibers (HMHNFs) composed of TiO2/polyelectrolyte (PE) have been prepared by a combination of a electrospinning method and layer-by-layer (LBL) technology. The results show that both the average diameter and the wall thickness of the HMHNFs can be well controlled by the template, as well as the number of coating layers. The dried morphology of the obtained HMHNFs is dependent on the inner deposited numbers of the polyelectrolyte layers. When compared with other nanostructured TiO2 materials, such as commercial TiO2 nanoparticles (P25, Degussa) and TiO2 films, the hollow TiO2/PE hybrid nanofibers exhibited higher photocatalytic activities. 相似文献
Ag/TiO2 sol with narrow particle size distribution was synthesized using TiCl4 as the starting material. TiCl4 was converted to Ti(OH)4 gel. The Ag/TiO2 sol was prepared by a process where H2O2 was added and then heated at 90–97 °C. After condensation reaction and crystallization, a transparent sol with suspended Ag/TiO2 was formed. Ag/TiO2 was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, contact angle analysis, and X-ray photoelectron spectroscopy. The photocatalytic properties of Ag/TiO2 film were evaluated by degradation of methylene blue in aqueous solution under UV light irradiation. The suspended Ag/TiO2 particles were rhombus primary particles with the major axis ca. 40 nm and the minor axis ca. 10 nm. Ag nanoparticles were well dispersed on TiO2 and the particle size was only 1–2 nm. Ag could restrain the recombination of photo-generated electrons and holes effectively. Transparent thin films could be obtained through dip-coating glass substrate in the sol. The thin film had strong hydrophilicity after being illuminated by UV light. Ag/TiO2 film showed a significant increase in photocatalytic activity compared to the TiO2 film. The high amount of surface hydroxyls on Ag/TiO2 film also played an important role in its photocatalytic activity. 相似文献
Tubular arrays of TiO2 nanotubes (ranging in diameter from 40 to 110 nm) on a Ti substrate were used as a support for Ag, Au or Cu deposits obtained by the sputter deposition technique, where the amount of metal varied from 0.01 to 0.2 mg/cm2. Those composite supports were intended for surface-enhanced Raman scattering (SERS) investigations. Composite samples were studied with the aid of scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) to reveal their characteristic morphological and chemical features. Raman spectra of pyridine (as a probe molecule) were measured at different cathodic potentials ranging from −0.2 down to −1.2 V after the pyridine had been adsorbed on the metal-covered TiO2 nanotube/Ti substrates. In addition, SERS spectra on a bulk standard activated Ag, Au and Cu substrates were also measured. The SERS activity of the composite samples was strongly dependent on the amount of metal deposit, e.g. at and above 0.06 mg Ag/cm2, the intensity of SERS signal was even higher than that for the Ag reference substrate. The high activity of these composites is mainly a result of their specific morphology. The high SERS sensitivity on the surface morphology of the substrate made it possible to monitor very small temporal changes in the Ag metal clusters. This rearrangement was not detectable with microscopic (SEM) or microanalytical (AES) methods. The SERS activity of Au or Cu clusters was distinctly lower than those of Ag. The spectral differences exhibited by the three kinds of composites as compared to the reference metal samples are discussed. 相似文献