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1.
Nanocrystalline TiO2 powders with different morphologies and grain sizes were successfully synthesized by the hydrothermal method. Different concentrations of hydrochloric acid (HCl), ammonium chloride (NH4Cl), ammonium sulfate [(NH4)2SO4], and ammonium carbonate [(NH4)2CO3] were used as additives in the hydrothermal process to investigate the effect of the concentration of ammonium (NH 4 + ) and chloride ions (Cl?) on the phase compositions, morphologies, and grain sizes of the prepared TiO2. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy, Brunauer–Emmett–Teller analysis, and UV–Vis spectra. XRD results show that the as-synthesized powders are composed of anatase or a mixture of anatase and brookite. The grain size of the synthesized nano-TiO2 powder ranged from 5.0 to 11.3 nm, and the related BET specific surface area varied from 127.5 to 191.0 m2/g. The photocatalytic activities of the prepared TiO2 powders were evaluated by degradation of methylene blue (MB) in aqueous solution under UV light irradiation, and the results show that the photocatalytic performance of TiO2 powders synthesized with additives is improved compared with that of TiO2 prepared without any additives. 相似文献
2.
J. Chris Culberson Peter Knappe Notker Rösch Michael C. Zerner 《Theoretical chemistry accounts》1987,71(1):21-39
An intermediate neglect of differential overlap method of use for examining the electronic structure of lanthanide complexes is developed. It is characterized by a basis set obtained from relativistic Dirac-Fock atomic calculations, the inclusion of all one-center two-electron integrals, and a parameter set based on molecular geometry.Lanthanide halides MX2, MX3 and MX4 are studied here, as well as initial results for the twelve coordinate Ce(NO3)6
–2 ion. Geometries obtained are in excellent agreement with experimental values when available. Many MX3 complexes are found to be pyramidal, and EuCl2 and YbCl2 are calculated to be bent even at the SCF level. Models invoking London type forces are therefore not required. Ionization potentials are calculated for the trihalides (SCF) and are in reasonable agreement with experiment.Contrary to conclusion of others, f-orbital participation, although small, is required — at least in this model — to obtain the spread of metal to halide bond distance observed in these complexes. However f-orbital participation does not seem to be significant even in the twelve coordinate Ce(NO3)6
–2 complex: rather the large coordination number seems to be a consequence of the relatively large size of the lanthanide ion. 相似文献
3.
Kurt Rossmanith 《Monatshefte für Chemie / Chemical Monthly》1979,110(1):109-114
Using the reduction of the trichlorides by lithium metal/naphthalene in tetrahydrofurane (THF), SmCl2 and EuCl2 were prepared in solventfree state, very sparingly soluble inTHF. The reduction of YbCl3, combined with extraction to eliminate the oxide chloride content, yielded the compound YbCl2·THF, much more soluble inTHF than YbCl3. 相似文献
4.
Cationic lanthanide complexes [Ln(CH3CN)9]3+[(AlCl4)3]3–·CH3CN served as efficient catalysts for the tandem Friedel–Crafts alkylation/ketalization reaction of 2-hydroxychalcones with naphthols/substituted phenols to produce diaryl-fused 2,8-dioxabicyclo[3.3.1]nonanes in moderate to high yields. The high catalytic efficiency of the cationic lanthanide complex [Yb(CH3CN)9]3+[(AlCl4)3]3–·CH3CN compared with that of YbCl3 can be attributed to the increased Lewis acidity of the Yb species as a result of cation formation. 相似文献
5.
Liuxue Zhang 《Polymer Degradation and Stability》2006,91(9):2213-2219
A series of polyaniline-anatase TiO2 (PANI-TiO2) nanocomposite powders with different PANI:TiO2 ratios were prepared by ‘in-situ’ deposition oxidative polymerization of aniline hydrochloride using ammonium persulfate (APS) as oxidant in the presence of ultrafine grade powder of anatase TiO2 cooled in an ice bath. And the solid-phase photocatalytic degradation of PANI-TiO2 nanocomposites was investigated under the ambient air in order to assess the feasibility of developing photodegradable polymers. The photodegradation of the composite powders was compared with that of pure PANI powders by performing weight loss monitoring, elemental analysis, FT-IR and UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The PANI-TiO2 nanocomposite powders showed highly enhanced photodegradation and the photodegradation increased with decreasing ratios of PANI:TiO2. A weight loss of about 6.8% was found for the PANI-TiO2 (1:3) nanocomposite; however, the weight loss of the PANI-HCl powder was only 0.3% after being irradiated for 60 h under air. The photocatalytic degradation of the nanocomposite powders accompanied the peak intensity decrease in the FT-IR spectra at 1235 cm−1, attributed to C-N stretching mode for benzenoid unit, and the depigmentation of the powders due to the visible light scattering from growing cavities. The elemental analysis and XPS analysis of the composite showed that the bulk and surface concentrations of N decreased with irradiation. A possible mechanism for the photocatalytical oxidative degradation was also mentioned. 相似文献
6.
Sharipov G. L. Gainetdinov R. Kh. Abdrakhmanov A. M. 《Russian Chemical Bulletin》2003,52(9):1969-1973
The influence of salts (TbCl3, Tb(NO3)3, PrCl3, EuCl3, CeCl3, and DyCl3) on the spectrum and intensity of multi-bubble sonoluminescence (SL) of water was observed at a frequency of 20 kHz. Luminescence bands of the lanthanide ions were detected in the SL spectra of concentrated solutions of the CeIII, TbIII, and DyIII chlorides (0.1—1 mol L–1). No luminescence was observed for solutions of the other salts, and the shape of the spectra is due to the absorption of the water SL by the lanthanide ions. Possible mechanisms of the appearance of SL of lanthanides were considered. The first mechanism is the excitation of the lanthanide aqua ions in the solution bulk due to the absorption of the short-wave portion of glow of the excited water molecules and OH radicals emitted from the cavitation gas-vapor bubbles. The second mechanism involves the transfer of the lanthanide ions to the gas phase from the liquid layer adjacent to the cavitation bubble and their excitation in the bubble volume upon collisions with other hot or electron-excited particles. 相似文献
7.
Luminescent microspherical bridged polysilsequioxane were prepared by heating the mixture of lanthanide ions (EuCl3 or TbCl3) and bis-silylated bipyridine having dual roles, i.e. the bipyridine moieties can sensitize the luminescence of Eu3+ (or Tb3+) ions and the alkoxysilane substituent can be hydrolyzed and condensed via sol–gel process to create inorganic silica framework.
The obtained microspheres were systematically investigated by IR spectroscopy, scanning electron microscopy, absorption spectroscopy,
PL excitation and emission spectroscopy. IR spectra indicate that the silylated bipyridine has been hydrolyzed under the reaction
conditions. SEM images show the microspherical morphology of the luminescent materials. It has been confirmed that the strong
luminescence of the spherical bridged polysilsequioxanes is due to the effective energy transfer from the silylated bipyridine
to the chelated lanthanide ions. 相似文献
8.
Yuhong Zhang Huaxing Zhang Yongxi Xu Yanguang Wang 《Journal of solid state chemistry》2004,177(10):3490-3498
A systematic study of microstructure and photocatalytic properties of lanthanide doping of nanocrystalline mesoporous titanium dioxide is performed. The anatase-to-rutile (A-R) phase transformation of nanosized TiO2 was significantly inhibited by lanthanide doping and the inhibitory effect was enhanced with the increase of the rare earth radius, i.e., La3+>Gd3+>Yb3+ for different lanthanide dopants. At high calcination temperatures, different texture lanthanide titanium oxides of Ln4Ti9O24 (La3+, Pr3+, Nd3+), Ln2Ti2O7 (Eu3+, Gd3+, Tb3+, Dy3+, Er3+), and Yb2TiO5 were developed, respectively, revealing that the structures of lanthanide titanium oxide developed in Ln/TiO2 depend on the lanthanide radius. Larger radius lanthanides prefer to form higher coordination number lanthanide titanium oxide. In addition, the thermal stability of mesoporous structures of TiO2 was remarkable improved by lanthanide doping. The photocatalytic properties were studied by employing the photodegradation of Rhodamine B (RB) as a probe reaction. The results indicate that the lanthanide doping could bring about significant improvement to the photoreactivity of TiO2, and the improvement was sensitive to the atomic electronic configuration. 相似文献
9.
G. L. Sharipov R. Kh. Gainetdinov A. M. Abdrakhmanov 《Russian Chemical Bulletin》2008,57(9):1827-1830
A weak glow in the region of the Eu3+ photoluminescence spectrum was detected against the background of the continuum of the solvent emission during multibubble
sonolysis of air- or argon-saturated EuCl3 solutions (0.1 mol L−1) in heavy water. No characteristic sonoluminescence of the europium ion in aqueous solutions was observed earlier. Possible
reasons for the low yield of Eu3+ sonoluminescence compared with other lanthanide ions (Ln3+) are discussed and the influence of europium on the spectrum of the solvent continuum related, in particular, to quenching
of the electron-excited sonolysis products H2O* (D2O*) and Eu3+* in electron transfer reactions.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1793–1796, September, 2008. 相似文献
10.
Thermochemical Investigations on Mixtures of Some Lanthanoide Halides with CuCl, AgCl, and TlCl The phase diagrams CuCl/LaCl3 (GdCl3, YbCl3), AgCl/LaCl3 (GdCl3, YbCl3) and TlCl/LaCl3 (GdCl3, YbCl3) were determined by difference thermal analysis. The systems with CuCl resp. AgCl as component are eutectic, however in mixtures with YbCl3 the compounds Cu3YbCl6 and Ag3YbCl6, resp., which decompose peritectically, were observed. The systems with thallous chloride contain several compounds, namely TlLn2Cl7 (TlCl/GdCl3 resp. YbCl3), Tl2LnCl5 (TlCl/LaCl3 resp. GdCl3) and Tl3LnCl6 (TlCl/GdCl3 resp. YbCl3). The enthalpies of mixing of liquid mixtures of AgCl/LaCl3 and AgCl/YbCl3 were measured calorimetrically at 1173 K. On comparing the alkali chloride–lanthanoide chloride systems with the MCl systems presented in this paper some differences were observed. The M+ ions with d10 configuration decrease the tendency to form ternary halides in the MCl? LnCl3 systems, the enthalpies of mixing are also much less exothermic than those of the comparable NaCl + LnCl3 mixtures. The Tl+ ion with d10 s2 configuration on the other hand behaves like an alkali cation of comparable size. 相似文献
11.
《Journal of molecular catalysis. A, Chemical》2000,151(1-2):205-216
Lanthanide metal-ion-doped TiO2 nanoparticles were prepared with hydrothermal method and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma (ICP) and fluorescence spectrum. The results showed that a small part of metal ions entered into the lattice of TiO2 and others adsorbed on the surface of TiO2. The photoelectrochemical and photocatalytic properties of these lanthanide metal-ion-doped TiO2 nanoparticles were investigated and the results showed that the photoresponse of Eu3+-, La3+-, Nd3+- and Pr3+-doped TiO2 electrodes were much larger and that of Sm3+-doped TiO2 electrode was a little larger than that of undoped TiO2 electrode, indicating that the photogenerated carriers were separated more efficiently in Eu3+-, La3+-, Nd3+- and Pr3+-doped TiO2 nanoparticles than in undoped TiO2 nanoparticles. The photocatalytic degradation of rhodamine B (RB) was conducted in the suspension of lanthanide metal-ion-doped TiO2 nanoparticles, and its first-order reaction rate constant (k) and average initial rate (rini) were significantly higher in the presence of Eu3+-, La3+-, Nd3+- and Pr3+-doped TiO2 nanoparticles than those in the presence of undoped TiO2 nanoparticles. The enhanced photocatalytic degradation rate of RB in the presence of Eu3+-, La3+-, Nd3+- and Pr3+-doped TiO2 nanoparticles is attributed to increased charge separation in these systems. The effect of the content of La3+ on the reaction parameters (k and rini) was also investigated and the result showed that there was an optimal value (ca. 0.5%) of the content of La3+ to make the rate constant (k) and average initial rate (rini) reach the maxima. 相似文献
12.
(CH3NH3)4YbCl7 has been synthesized from a solution of CH3NH3Cl and YbCl3 in a mixture of ethnole/acetonitrile. The structure was solved from 1464 single crystal data by Patterson methods and refined to a final Rw = 0.035 space group P2, a = 9.972(6) Å, b = 7.605(5) Å, c = 12.866(6) Å, β = 90.53(4)°. The structure consists of alternating [YbCl6]3? octahedra and of tetrahedrally arranged [(CH3NH3)4Cl]3+ units. Raman spectra display a splitting of frequencies related to the CH3NH3+ group in agreement with the structure determination. The magnetic susceptibility shows a remarkable deviation from a Curie-Weiss law below 170 K which may be explained by crystal field effects of Yb3+. 相似文献
13.
Boron-doped TiO2 was prepared by the sol-gel method and by grinding TiO2 powder with a boron compounds (boric acid and boric acid triethyl ester followed by calcinations at temperature range 200 to 600°C. Three types of pristine TiO2: ST-01 (Ishihara Sangyo Ltd., Japan; 300 m2/g), P25 (Degussa, Germany, 50 m2/g), A11 (Police S.A., Poland 12 m2/g) were used in grinding procedure. The photocatalytic activity of obtained powders in visible light was estimated by measuring the decomposition rate of phenol (0.21 mmol/dm3) in an aqueous solution. The photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron emission spectroscopy (XPS), UV-VIS absorption and BET surface area measurements. The best photoactivity under visible light was observed for B-TiO2 modified with 2 wt% of boron prepared by grinding ST-01 with dopant followed by calcinations at 400°C. This photocatalyst contains 16.9 at.% of carbon and 6.6 at.% of boron in surface layer and its surface area is 192 m2/g. 相似文献
14.
D. A. Johnson A. G. Maddock M. Taylor 《Journal of Radioanalytical and Nuclear Chemistry》1987,119(1):43-50
When anhydrous EuCl3, GdCl3, DyCl3 or Eu2O3 are irradiated with fast neutrons and then dissolved in dilute hydrochloric acid, small amounts of reducing species, believed to be divalent lanthanide cations, are revealed. The amount produced increases with the thermodynamic stability of the Ln2+ species /Eu>Dy>Gd>/. 相似文献
15.
E. Acayanka A. Tiya Djowe S. Laminsi C. C. Tchoumkwé S. Nzali A. Poupi Mbouopda P. T. Ndifon E. M. Gaigneaux 《Plasma Chemistry and Plasma Processing》2013,33(4):725-735
The present study explores a new method of synthesis of TiO2 nano-particles in an aqueous medium from TiCl3 precursor by non-thermal plasma in humid air as feeding gas obtained at atmospheric pressure. The precursor solution, TiCl3 is oxidized by strongly reactive species generated by gliding arc plasma (HO· = 2.85 V/SHE) to produce titanium oxide powders. The synthesized powder was characterised by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, FTIR spectroscopy, nitrogen physisorption, and UV–Vis spectroscopy. The results obtained showed that the material consists of rod-shaped nanoparticles of rutile and anatase phases. The presence of TiO2 phases was confirmed by FTIR spectrum and textural analyses showed that the material is mesoporous with specific surface area of 158 m2 g?1. UV–Visible spectrum of the plasma-synthesized TiO2 sample showed that it absorbs in the UV–A region leading to effective use as a photocatalyst under visible light. 相似文献
16.
Nahomi Sakaguchi Shuji Matsuo Tsutomu Kurisaki Taku Matsuo Hisanobu Wakita 《Research on Chemical Intermediates》2006,32(2):95-101
The photocatalytic degradation of 2-propanol in D2O solution under UV irradiation was investigated. The conversion yield from 2-propanol to acetone was studied by 1H-NMR measurements. The study was carried out to elucidate effects of O2 in the reaction medium and lanthanide ion modification on the TiO2 surface. Under aerobic conditions, acetone formation was clearly increased in comparison with anaerobic conditions. On the
modification of TiO2 with lanthanide ion, the conversion yield decreased with the increase in the ionic radius. Yb3+ ion modification increased the acetone formation by approx. 5% in comparison with the unmodified case. Appreciably large
effects of the counter ion in lanthanide salts were also observed. The role of OH˙ radical formation in the first step of photocatalysis was emphasized in the experimental results. 相似文献
17.
M. R. Mohammadi M. C. Cordero-Cabrera M. Ghorbani D. J. Fray 《Journal of Sol-Gel Science and Technology》2006,40(1):15-23
Stabilised titania sols were prepared using an additive free particulate sol-gel route, via electrostatic stabilisation mechanism,
with various processing parameters. Peptisation temperature, 50°C and 70°C, and TiO2 concentration, 0.1, 0.2 and 0.4 molar, were chosen as processing parameters during sol preparation. Results from TiO2 particle size and zeta potential of sols revealed that the smallest titania hydrodynamic diameter (13 nm) and the highest
zeta potential (47.7 mV) were obtained for the sol produced at the lower peptisation temperature of 50°C and lower TiO2 concentration of 0.1 M. On the other hand, between the sols prepared at 70°C, smaller titania particles (20 nm) and higher
zeta potential (46.3 mV) were achieved with increasing TiO2 concentration up to 0.4 M. X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) results of produced powders annealed
at different temperatures showed that the 300°C annealed powder made from 0.1 M sol prepared at 50°C was a mixture of anatase
and brookite, corresponding to a major phase of anatase (∼95% estimated), with the smallest average crystallite size of 1.3 nm
and the highest specific surface area (SSA) of 193 m2/g. Furthermore, increasing TiO2 concentration up to 0.4 molar for the sols prepared at 70°C resulted in decreasing the average crystallite size (1.9 nm at
300°C) and increasing SSA (116 m2/g at 300°C) of the powders annealed at different temperatures. Anatase-to-rutile phase transformation temperature was increased
with decreasing peptisation temperature down to 50°C, whereas TiO2 concentration had no effect on this transition. Anatase percentage increased with decreasing both peptisation temperature
and TiO2 concentration. Such prepared powders can be used in many applications in areas from photo catalysts to gas sensors. 相似文献
18.
Two types of isostructural complexes of lanthanide chlorides with diglyme have been synthesized. These are mononuclear molecular complexes [LnCl3(diglyme)(THF)] (Ln = Eu ( 1 ), Gd ( 2 ), Dy ( 3 ), Er ( 4 ), Yb ( 5 ); diglyme = diethylen glycol dimethyl ether) and binuclear molecular complexes [LnCl3(diglyme)]2 (Ln = Dy ( 3d ), Er ( 4d ), Yb ( 5d )). Complex 1 was obtained by the reaction of [EuCl3(DME)2] with diglyme in THF. The complexes 2 – 5 and 3d – 5d resulted from reactions of LnCl3·6H2O, (CH3)3SiCl and diglyme in THF. The mononuclear complexes 2 – 5 crystallized directly from the solutions where the reactions of lanthanide compounds with diglyme took place. Recrystallizations of the powder products of the same reactions from dichloromethane resulted in the binuclear complexes 3d – 5d . Reactions of lanthanide bromide hydrates, (CH3)3SiBr and diglyme in THF achieved mononuclear molecular complexes [LnBr3(diglyme)(L)] (Ln = Gd, L = H2O ( 6 ); Ln = Ho, L = THF ( 7 )). Crystals of 6 and 7 were grown by recrystallization from dichloromethane. The lanthanide atoms (Ln = Eu–Yb) are seven‐coordinated in a distorted pentagonal bipyramidal fashion in all reported complexes, 1 – 7 and 3d – 5d . Four oxygen atoms and three halide ions are coordinated to lanthanide atoms in 1 – 7 , [LnX3(diglyme)(L)]. Four chloride ions, two bridging and two nonbridging, and three oxygen atoms are coordinated to lanthanide atoms in 3d – 5d , [LnCl3(diglyme)]2. 相似文献
19.
The photodegradation of an aqueous solution of methyl orange by the TiO2/SnS powders was studied in different ratios of SnS against TiO2. The effects of the initial pH value and light resource were investigated. The SnS extends the light absorption edge of the TiO2 to ~940 nm of the SnS (1.32 eV). The results indicated that the optimal SnS proportion for the maximum degradation efficiency increased in relation to a decrease in the initial pH in both sunlight and visible light, and decreased when changing from visible light to sunlight. The pure TiO2 powder had maximum efficiency in conditions of pH 9 and visible light irradiation or in conditions of pH 7 and sunlight irradiation. In visible light, the degradation efficiency on the powders containing the SnS was larger than that on the pure TiO2 powder in a range of pH 3–7. The maximum efficiency in visible light was found to be in conditions of pH 5 and TiO2:SnS = 3:2 and 2:3, beyond which the efficiency decreased. The efficiency was, overall, larger in sunlight than in visible light. The mechanism of the effects of pH and light resource was discussed in view of the surface charge of the catalysts. 相似文献
20.
Nano-sized TiO2–60 wt% SrO composite powders were synthesized from titanium isopropoxide and Sr(OH)2·8H2O by use of a sol–gel method. Ag spot-coated TiO2–60 wt% SrO composite powders containing 3, 5, or 7 wt% Ag were synthesized by hydrothermal-assisted attachment, by use of Ag hydrosol in a high-pressure bomb at 250 °C and 450 psi. Nano-sized Ag particles approximately 5–25 nm in diameter adhered to the TiO2–60 wt% SrO2 composite powders. The photocatalytic activity of Ag spot-coated TiO2–SrO powders in the degradation of phenol showed that all were highly active when irradiated with UV light. TiO2–60 wt% SrO composite powder spot-coated with 5 wt% Ag was more photocatalytically active under visible light than TiO2–SrO composite powder. 相似文献