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1.
Nanoparticles of TiO 2 were synthesised by sol–gel technique and photo deposition of about 1% noble metal (M/TiO 2, M = Ag, Au, and Pt) on TiO 2 was carried out. The catalysts were characterised by XRD, TEM, BET, FT-IR, and UV–Visible spectroscopy. Using commercial TiO 2 (P-25 Degussa), the conditions such as dye concentration, catalyst weight and pH were optimized for complete decolourisation of textile dye tartazine (TAZ) under UV and visible irradiations. Among the catalysts tested, the synthesised TiO 2 showed better photocatalytic activity than TiO 2 (P-25 Degussa). Whereas, M/TiO 2 catalysts showed remarkable photocatalytic activity towards the decolourisation of TAZ even under visible irradiation. This enhanced activity of M/TiO 2 catalyst may be attributed to the trapping of conduction band electrons by noble metals. 相似文献
2.
BACKGROUND: In this study, visible‐light‐derived photocatalytic activity of metal‐doped titanium dioxide nanosphere (TS) stacking layers, prepared by chemical vapor deposition (CVD), was investigated. The as‐grown TS spheres, having an average diameter of 100–300 nm, formed a layer‐by‐layer stacking layer on a glass substrate. The crystalline structures of the TS samples were of anatase‐type. RESULTS: Ultraviolet (UV) absorption confirmed that metallic doping (i.e. Co and Ni) shifted the light absorption of the spheres to the visible‐light region. With increasing dopant density, the optical band gap of the nanospheres became narrower, e.g. the smallest band gap of Co‐doped TS was 2.61 eV. Both Ni‐ and Co‐doped TS catalysts showed a photocatalytic capability in decomposing organic dyes under visible irradiation. In comparison, Co‐doped TiO 2 catalyst not only displays the adsorption capacity, but also the photocatalytic activity higher than the N‐doped TiO 2 catalyst. CONCLUSION: This result can be attributed to the fact that the narrower band gap easily generates electron–hole pairs over the TS catalysts under visible irradiation, thus, leading to the higher photocatalytic activity. Accordingly, this study shed some light on the one‐step efficient CVD approach to synthesize metal‐doped TS catalysts for decomposing dye compounds in aqueous solution. Copyright © 2010 Society of Chemical Industry 相似文献
3.
TiO 2 microspheres and TiO 2/carbon quantum dots (CQDs) composites with different CQDs contents were successfully synthesized via solvothermal and in situ hydrothermal method. The structure and morphology of the prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM). Results showed that carbon elements were successfully doped into the TiO 2 lattice (C-TiO 2) and CQDs were hybrid with C-TiO 2 microspheres. The X-ray photoelectron spectroscope (XPS), valence band XPS (VB-XPS) and UV–vis diffuse reflectance spectra (DRS) analyses revealed that carbon doped into TiO 2 microspheres could lead to local energy levels in the band structure and generate valence band tails to absorb visible light. The photocatalytic activities of these samples were evaluated by the photodegradation of Rhodamine B (RhB) under visible light irradiation. C-TiO 2/CQDs samples presented an enhanced photocatalytic performance compared with pristine TiO 2, which could be attributed to the present of CQDs, acting as adsorption sites for RhB molecules and charge separation centers to impede the recombination and prolong the life time of electron and hole pairs. 相似文献
4.
This study explores the significance of dopant location in a doped TiO 2 nanostructure in ascertaining its photocatalytic properties. The un-doped TiO 2, boron-doped TiO 2 (B–TiO 2) and nitrogen-doped TiO 2 (N–TiO 2) photocatalysts were synthesized (with variable dopant concentrations) via sol-gel method. The photocatalysts were further characterized for structural, surface, and physico-chemical properties in reference to their influence on photocatalytic properties. The results of X-ray diffraction (XRD), micro Raman, Energy dispersive X-ray technique (EDX), X-ray photoelectron spectroscopy (XPS), and Fourier Transform infrared spectroscopy (FTIR) confirmed the existence of B and N atoms in the TiO 2 crystal lattice. The results also indicated that the B and N doping promoted the formation of rutile phase in doped TiO 2. Further, B doping leads to decrease in the surface area whereas N doping leads to increase in surface area of TiO 2. The UV–Vis DRS analysis revealed that a red shift in absorption band edge occurs upon B and N doping. The band gap values also decreased to 2.96 and 2.27 eV in B–TiO 2 and N–TiO 2, respectively in comparison to 2.98 for un-doped TiO 2. The photocatalytic degradation studies of diclofenac sodium (DCLF) were conducted to examine the effect of dopant role on the efficiency of doped photocatalyst. B–TiO 2 exhibited maximum photocatalytic activity by degrading 98% of DCLF in comparison to N–TiO 2, which showed 95% degradation. 相似文献
5.
A series of photo-catalysts were synthesized by neodymium and fluorine doped TiO 2, and their characteristics evaluated by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (UV–vis), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Neodymium and fluorine doped TiO 2 has obvious absorption in the visible light and the absorption edge shifts toward red wavelength. In addition, compared with pure TiO 2, the doped catalyst has intense absorption at 528, 587, 750, 808, and 881 nm. The catalytic efficiency was tested by monitoring the photo-catalytic degradation of methylene blue (MB) in visible light and ultraviolet light. The results showed that the optimum doping content was Nd:F:TiO 2 = 0.5:5:100 (molar ratio) heat treated at 500 °C, and the reaction rates of MB degradation were estimated to be about 1.76 times and 1.45 times higher than undoped TiO 2 in ultraviolet light and visible light. 相似文献
6.
The aim of this research is to enhance the photocatalytic activity of TiO 2 nanoparticles for the UV–visible light by multiple-doping with Iridium, carbon and nitrogen. The tridoped TiO 2 photocatalyst were prepared by wet chemical method, and characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible light diffuse reflection spectroscopy and room temperature photoluminescence spectroscopy. Besides, the photocatalytic H 2 evolution performance of Ir-C-N tridoped TiO 2 under UV–visible light irradiation was evaluated. It was found that Ir existed as Ir 4+ by substituting Ti in the lattice of TiO 2; meanwhile, C and N were also incorporated into the surface of TiO 2 nanoparticles in interstitial mode. Meanwhile, Ir-C-N tridoping extended the absorption of TiO 2 into the visible light region and narrowed its band gap to ~3.0 eV, resulting in enhanced photocatalytic H 2 evolution under UV–visible light irradiation. This could be attributed to narrow band gap and proper electronic structure of TiO 2 after Ir-C-N tridoping. 相似文献
7.
A photocatalyst, TiO 2?xN y/AC (activated carbon (AC) supported N‐doped TiO 2), highly active in both the Vis and UV range, was prepared by calcination of the TiO 2 precursor prepared by acid‐catalyzed hydrolysis in an ammonia atmosphere. The powders were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, X‐ray diffraction, N 2 adsorption, Fourier transform infrared spectroscopy and phenol degradation. The doped N in the TiO 2 crystal lattice creates an electron‐occupied intra‐band gap allowing electron‐hole pair generation under Vis irradiation (500–560 nm). The TiO 2?xN y/AC exhibited high levels of activity and the same activity trends for phenol degradation under both Vis and UV irradiation: TiO 2?xN y/AC calcined at 500 °C for 4 h exhibited the highest activity. The band‐gap level newly formed by doped N can act as a center for the photo‐generated holes and is beneficial for the UV activity enhancement. The performance of the prepared TiO 2?xN y/AC photocatalyst revealed its practical potential in the field of solar photocatalytic degradation of aqueous contaminants. Copyright © 2007 Society of Chemical Industry 相似文献
8.
Silver and zirconium co‐doped and mono‐doped titania nanocomposites were synthesized and deposited onto polyacrylonitrile fibers via sol–gel dip‐coating method. The resulted coated‐fibers were characterized by X‐ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, thermogravimetric analysis, and BET surface area measurement. Photocatalytic activity of the TiO 2‐coated and TiO 2‐doped coated fibers were determined by photomineralization of methylene blue and Eosin Y under UV–vis light. The progress of photodegradation of dyes was monitored by diffuse reflectance spectroscopy. The XRD results of samples indicate that the TiO 2, Ag‐TiO 2, Zr‐TiO 2, and Ag‐Zr‐TiO 2 consist of anatase phase. All samples demonstrated photo‐assisted self‐cleaning properties when exposed to UV–vis irradiation. Evaluated by decomposing dyes, photocatalytic activity of Ag–Zr co‐doped TiO 2 coated fiber was obviously higher than that of pure TiO 2 and mono‐doped TiO 2. Our results showed that the synergistic action between the silver and zirconium species in the Ag‐Zr TiO 2 nanocomposite is due to both the structural and electronic properties of the photoactive anatase phase. These results clearly indicate that modification of semiconductor photocatalyst by co‐doping process is an effective method for increasing the photocatalytic activity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
9.
Transition metal (Fe, V and W)-doped TiO 2 was synthesized via the solvothermal technique and immobilized onto fiberglass cloth (FGC) for uses in photocatalytic decomposition
of gaseous volatile organic compounds—benzene, toluene, ethylbenzene and xylene (BTEX)—under visible light. Results were compared
to that of the standard commercial pure TiO 2 (P25) coated FGC. All doped samples exhibit higher visible light catalytic activity than the pure TiO 2. The V-doped sample shows the highest photocatalytic activity followed by the W- and Fe-doped samples. The UV-Vis diffuse
reflectance spectra reveal that the V-doped sample has the highest visible light absorption followed by the W- and Fe-doped
samples. The X-ray diffraction (XRD) patterns indicate that all doped samples contain both anatase and rutile phases with
the majority (>80%) being anatase. No new peaks associated with dopant oxides can be observed, suggesting that the transition
metal (TM) dopants are well mixed into the TiO 2 lattice, or are below the detection limit of the XRD. The X-ray absorption near-edge structure spectra of the Ti K-edge transition
indicate that most Ti ions are in a tetravalent state with octahedral coordination, but with increased lattice distortion
from Fe- to V- and W-doped samples. Our results show that the TM-doped TiO 2 were successfully synthesized and immobilized onto flexible fiberglass cloth suitable for treatment of gaseous organic pollutants
under visible light. 相似文献
10.
Fe 3+ doped TiO 2 deposited with Au (Au/Fe–TiO 2) was successfully prepared with an attempt to extend light absorption of TiO 2 into the visible region and reduce the rapid recombination of electrons and holes. The samples were characterized by X-ray diffraction (XRD), N 2 physical adsorption, Raman spectroscopy, atomic absorption flame emission spectroscopy (AAS), UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The photocatalytic activities of the samples were evaluated for the degradation of 2,4-chlorophenol in aqueous solutions under visible light ( λ > 420 nm) and UV light irradiation. The results of XRD, XPS and high-resolution transmission electron microscopy (HRTEM) analysis indicated that Fe 3+ substituted for Ti 4+ in the lattice of TiO 2, Au existed as Au 0 on the surface of the photocatalyst and the mean particle size of Au was 8 nm. Diffuse reflectance measurements showed an extension of light absorption into the visible region for Au/Fe–TiO 2, and PL analysis indicated that the electron–hole recombination rate has been effectively inhibited when Au deposited on the surface of Fe-doped TiO 2. Compared with Fe doped TiO 2 sample and Au deposited TiO 2 sample, the Au/Fe–TiO 2 photocatalyst exhibited excellent visible light and UV light activity and the synergistic effects of Fe 3+ and Au was responsible for improving the photocatalytic activity. 相似文献
11.
Nitrogen doped yellowish anatase phase of titania support (TiO 2?x N x ) was prepared by hydrolysis of titanium (IV) butoxide with 15% NH 4OH followed by filtration, drying and calcination at 450 °C for 3 h. For comparison, TiO 2 was prepared by hydrolysing titanium (IV) butylate with distilled water. Deposition precipitation method was used for Au loading on TiO 2?x N x and TiO 2. These were characterised by XRD, Laser Raman spectroscopy, transmission electron microscopy, BET surface area analyser, and UV–visible spectrophotometry. UV–visible (diffused reflectance) spectrum of TiO 2?x N x support shows a distinct absorption band around 450 nm wavelength indicating for N doping. Whereas, TiO 2 does not show any absorption band in the visible region. The activity of gold loaded on these supports was tested for CO oxidation reaction. Effect of different pre-treatment conditions and effect of moisture on these catalysts were studied, and the results obtained were interpreted on the basis of nitrogen doping, optoelectronic properties, ability of oxygen uptake of the support and particle size of gold. 相似文献
12.
Sulfur-doped TiO 2 catalysts were prepared by a mechanochemical method. The prepared catalysts exhibited photocatalytic activity in methylene blue degradation under visible light. The catalyst structure has been characterized using UV–visible spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry analysis (TGA) as well as Fourier transform infrared spectroscopy (FT-IR). UV–visible spectroscopy revealed that the absorption edge of the doped TiO 2 was red-shifted compared with bare TiO 2. XRD patterns suggested that the brookite phase became more prevalent with increasing ball milling duration. In addition, surface sulfate species were detected by FT-IR, XPS and TGA. We deduce the rise of catalytic activity is due to the synergetic effect between the brookite phase and the anatase phase that would probably retard the electron–hole recombination. On the other hand, methylene blue was found to be N-demethylated during the irradiation thus giving rise to blue-shifting of peak at 664 nm in UV–visible spectroscopy. 相似文献
13.
TiO 2 nanopowders doped by Cu were prepared by the sol–gel method. The effects of Cu doping on the structural, optical, and photo-catalytic properties of titania nanopowders have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Vis absorption spectroscopy. XRD results suggest that adding impurities has a significant effect on anatase phase stability, crystallinity, and particle size of TiO 2. Titania rutile phase formation in the system (Ti–Cu) was promoted by Cu 2+ doped TiO 2. The photo-catalytic activity was evaluated by photo-catalytic degradation kinetics of aqueous methylene orange (MO) under visible radiation. The results show that the photo-catalytic activity of the 5 %Cu doped TiO 2 nanopowders has a larger degradation efficiency than pure TiO 2 under visible light. Also, the minimum band gap was estimated to be ~ 1.9–2 eV from UV–Vis spectra. 相似文献
14.
An effort was made not only to demonstrate the performance of the self-cleaning coatings on building materials such as ceramic glazed tiles and glass windows, but also to understand the fundamental issues that are still alive in the field of self-cleaning surfaces based on photocatalysis. Nano TiO 2 transparent thin films were generated by dip, spray and flow coating method. The present results indicate that the inconsistent results in the self-cleaning studies may be due to the effect of aggregation of model pollutant (methylene blue) dye on TiO 2 surface. The effect of aliovalent metal ion (Ni 2+, Fe 3+, Nb 5+) doping on phase formation, polymorphic transition, visible light absorbance and optical transparency of TiO 2 film were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV visible absorption spectroscopy. The improved visible light activity of doped TiO 2 thin film was correlated to the Ti(Ni/Fe)O 3 phase formation, UV and visible light absorbance, variation in the optical energy band gap and the probable light scattering associated with grain size. 相似文献
15.
Boron-doped titanium dioxide nanoparticles (B–TiO 2 NPs) were prepared by a sol-gel method. The physicochemical properties of B–TiO 2 NPs were characterized by X-ray diffraction, transmission electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. The band structure and electrical properties of B–TiO 2 NPs were investigated using the first-principle. The effects of the concentration gradient of doping B ions on the photocatalytic antibacterial activity of B–TiO 2 NPs under visible-light irradiation were investigated by the inhibition zone method and the shaking flask method. The experimental results show that B–TiO 2 NPs are mainly composed of the anatase phase, but no B-related phase was observed. With the increase of the doping amount of boron ions, the particle size decreases and the specific surface area increases. B atoms mainly exist in the form of substitutional dopant and interstitial dopant. Theoretical calculations reveal that B atoms in the TiO 2 matrix exist much more easily as interstitial dopant, but B–TiO 2 NPs composed of B substituted dopant have better photocatalytic performance. The results of the antibacterial assays show that B–TiO 2 NPs have strong antibacterial activities and some bactericidal activities. Finally, the mechanism of the antibacterial activity of B–TiO 2 NPs are examined. 相似文献
16.
In this study, undoped and Magnesium doped TiO2 nanoparticles (Mg-TiO2 NPs) are successfully synthesized via a simple sol–gel method cost-effectively. The prepared Mg- TiO2 NPs is characterized by UV–Vis, FTIR, PL, XRD, FESEM, TEM, and EDAX. UV–Visible Spectroscopy showed that an increase in the optical bandgap concerning the concentration of dopant Mg increases. The bandgap values were found to be 3.57–3.54 eV. FTIR spectra shows that the presence of the characteristic stretching and bending vibrational band of Ti–O bonding at 468 cm?1 and shifts in vibrational bands were observed for Mg-TiO2 NPs. PL spectra of Mg- TiO2 NPs at different concentrations exhibit a strong UV emission band. X-ray diffraction confirmed the formation of the tetragonal anatase phase. The average crystallite size of synthesized samples was found to be 22–19 nm. The average crystallite size of Mg- TiO2 NPs decreases with increasing the concentration of dopant Mg. The FESEM and TEM analysis confirmed that the spherical morphology for both TiO2 and Mg-TiO2 NPs. SAED pattern confirms the crystalline nature of prepared samples. EDAX spectra confirm the presence of Ti, O, and Mg and confirm that Mg2+ ions are present in the TiO2 lattices. The prepared samples were investigated against gram-positive and gram-negative bacteria. The prepared samples exhibit potent antibacterial activity against gram-negative bacteria than the gram-positive bacteria. The prepared samples exhibit significant photocatalytic degradation for Methylene blue (MB). 相似文献
17.
TiO 2 porous ceramic/Ag–AgCl composite was prepared by incorporating AgCl nanoparticles within the bulk of TiO 2 porous ceramic followed by reducing Ag + in the AgCl particles to Ag 0 species under visible light irradiation. The porous TiO 2 ceramic was physically robust and chemically durable, and the porous structure facilitated the implantation of AgCl NPs. Compared with the bare TiO 2 ceramic, TiO 2 porous ceramic/Ag–AgCl composite exhibited higher photocatalytic performance for the degradation of MO and RhB under visible light irradiation. The reaction rate constants k of MO and RhB degradation over TiO 2 porous ceramic/Ag–AgCl composite was respectively 6.25 times and 3.62 times higher than those recorded over the bare TiO 2 porous ceramic. The photocatalytic activity showed virtually no decline after four times cyclic experiments under visible light irradiation. Scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectra and X-ray photoelectron spectroscopy were used to characterize the TiO 2 porous ceramic/Ag–AgCl composite. 相似文献
18.
The optical, electrical, and microstructurtal properties of pure and TiO 2/Poly(vinyl alcohol) (PVA) composite polymer films were carried out using FTIR, XRD, UV‐Visible, DC electrical conductivity, and Positron annihilation lifetime spectroscopy (PALS) techniques. The FTIR study reveals that the Ti + ions of TiO 2 interacts with the OH groups of PVA via intra /inter molecular hydrogen bonding and forms charge transfer complex (CTC). These formed CTC will affect the optical property of the composite film, which is reflected from UV‐Visible study. Using the observed UV–Visible spectra, optical energy band gap is estimated and its value decreases with increasing dopant concentration. The positron annihilation studies show that the considerable effect on free volume related microstructure of the PVA due to doping and complex formation. These microstructural modifications are also enhances PVA crystallinity which is reflected from XRD studies. It is also observed that the TiO 2 particle forms cluster within the PVA due to the aggregation of particles and these particle cluster size increases with dopant concentration. These microstructural variations due to doping affects the DC electrical conductivity and its variations are understood based on the intra chain one‐dimensional interpolaron hopping conduction mechanism. POLYM. COMPOS. 37:987–997, 2016. © 2014 Society of Plastics Engineers 相似文献
19.
A highly visible-light photocatalytic active Ag-modified TiO 2 (Ag–TiO 2) was prepared by a simple sol–gel process using TiOSO 4 as the starting material, AgNO 3 as a silver doping source, and hydrazine as a reducing agent. The prepared Ag–TiO 2 samples were characterized by several techniques such as X-ray powder diffraction (XRD), BET surface area measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), energy dispersive X-ray spectrometry (EDX), X-ray absorption spectroscopy (XAS) and UV–vis diffuse reflectance spectroscopy (DRS). The Ag–TiO 2 photocatalyst, a mixture of amorphous and anatase phases, has a high surface area. The silver contents in the Ag–TiO 2 samples were determined by ICP measurements. The diffused reflectance UV–vis spectra indicated that the Ag–TiO 2 samples exhibited higher red shifts compared with the undoped TiO 2 sample. Indigo carmine degradation under visible irradiation indicated that the Ag–TiO 2 catalyst gave higher photocatalytic efficiency than those of commercial P25-TiO 2 and undoped-TiO 2 samples. The Ag–TiO 2 catalyst can be reused many times without any additional treatment. 相似文献
20.
Cobalt doped amorphous mesoporous titania–silica with Ti/Si mass ratio of 0.8 (Co–TiO 2–SiO 2) was synthesized and used for the photodegradation of six cationic dyes (gentian violet, methyl violet, methylene blue, fuchsin basic, safranine T, and Rhdamine B) under UV and visible light illumination. The catalyst was characterized by a combination of various physicochemical techniques, such as N 2 physisorption, diffuse reflectance UV–vis, X-ray diffraction, and FT-IR.Co–TiO 2–SiO 2 exhibited activity under UV light and had better activity under visible light when compared with that of Degussa P25 TiO 2. The activity of Co–TiO 2–SiO 2 was also compared with that of Co-MCM-41, Co doped mesoporous titania with a crystalline framework (Co–MTiO 2) and titania-loaded Co doped MCM-41 (TiO 2/Co-MCM-41) for the degradation of gentian violet under visible light irradiation. It was also found that the degradation rates of Co–TiO 2–SiO 2 for gentian violet, methyl violet, methylene blue, fuchsin basic and safranine T were greater in alkaline media than in acid and neutral media, while it did not exhibit any significant activity for the photodegradation of Rhdamine B in alkaline media or in acid media under visible light irradiation. 相似文献
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