The surface properties and the activities in catalytic wet air oxidation over CeO2-TiO2 catalysts

No-noble metal CeO₂-TiO₂ catalysts prepared by sol-gel method were developed and examined for catalytic wet air oxidation (CWAO) of acetic acid. The structure of the catalysts was measured by BET, SEM, XRD, XPS and DTA-TG. We investigated the effect of the interactions of Ce and Ti on the structure of CeO₂-TiO₂ catalysts. The mechanisms of the relationships between the different content of Ti and the activity of CeO₂-TiO₂ catalysts were discussed. The results showed that the average crystal size of CeO₂ decreased and the surface areas increased; the low valence of Ce³⁺ increase, and the chemisorbed oxygen slightly decreased with the increase of Ti content on the surface of CeO₂-TiO₂ catalysts. The order of the activity in CWAO of acetic acid followed: Ce/Ti 1/1 > Ce/Ti 3/1 > Ce/Ti 1/3 > Ce/Ti 5/1 > CeO₂ > TiO₂ > no catalyst. In CWAO of acetic acid, the optimal atomic ratio of Ce and Ti was 1, and the highest COD removal was over 64% at 230 °C, 5 MPa and 180 min reaction time over Ce/Ti 1/1 catalyst. The excellent activity and stability of CeO₂-TiO₂ catalysts was observed in our study.     

A novel method for immobilization of Co tetraphenylporphyrins on P(4VP-co-St)/SiO2: Efficient catalysts for aerobic oxidation of ethylbenzenes

In this paper, poly(4vinylpyridine-co-styrene) (P(4VP-co-St)) was grafted on silica gel particles in the manner of “grafting from”, and the grafting particle P(4VP-co-St)/SiO₂ was gained. The grafting particle P(4VP-co-St)/SiO₂ is a novel kind of supports for immobilizing metalloporphyrin catalysts. Then, the immobilization of cobalt tetraphenylporphyrin (CoTPP) on the supports P(4VP-co-St)/SiO₂ was carried out via the axial coordination reaction between CoTPP and the pyridine groups of the grafted P(4VP-co-St), resulting in the heterogenised catalysts CoTPP-P(4VP-co-St)/SiO₂. The synthesized catalysts were characterized by FTIR and the axial coordination process between CoTPP and the grafted P(4VP-co-St) was confirmed by UV-vis. The effects of various factors on the immobilization reaction of CoTPP were studied in detail. Finally, the catalytic performance of CoTPP-P(4VP-co-St)/SiO₂ in the catalytic oxidation process of ethyl benzene was investigated. The experimental results show that the axial coordination reaction is a very easy and novel method for favorably immobilizing CoTPP onto the P(4VP-co-St)/SiO₂ surfaces. During the immobilization process of CoTPP on P(4VP-co-St)/SiO₂, the most bonding amount of CoTPP (0.19 g/g) is obtained under the lower temperature (5 °C) and the higher concentration of CoTPP(6.0 mg/ml) lasting 4 h. Moreover, the supported catalyst CoTPP-P(4VP-co-St)/SiO₂ can effectively activate the dioxygen, and obviously catalyze the transform of ethylbenzene into acetophenone. So it exhibits the fine catalytic activity.     

Electronic state of ruthenium deposited onto oxide supports: An XPS study taking into account the final state effects

The electronic state of ruthenium in the supported Ru/EO_x (EO_x = MgO, Al₂O₃ or SiO₂) catalysts prepared by with the use of Ru(OH)Cl₃ or Ru(acac)₃ (acac = acetylacetonate) and reduced with H₂ at 723 K is characterized by X-ray photoelectron spectroscopy (XPS) in the Ru 3d, Cl 2p and O 1s regions. The influence of the final state effects (the differential charging and variation of the relaxation energy) on the binding energy (BE) of Ru 3d_5/2 core level measured for supported Ru nanoparticles is estimated by comparison of the Fermi levels and the modified Auger parameters determined for the Ru/EO_x samples with the corresponding characteristics of the bulk Ru metal. It is found that the negative shift of the Ru 3d_5/2 peak which is observed in the spectrum of ruthenium deposited onto MgO (BE = 279.5-279.7 eV) with respect to that of Ru black (BE = 280.2 eV) or ruthenium supported on γ-Al₂O₃ and SiO₂ (BE = 280.4 eV) is caused not by the transfer of electron density from basic sites of MgO, as considered earlier, but by the differential charging of the supported Ru particles compared with the support surface. Correction for the differential charging value reveals that the initial state energies of ruthenium in the Ru/EO_x systems are almost identical (BE = 280.5 ± 0.1 eV) irrespectively of acid-base properties of the support, the mean size of supported Ru crystallites (within the range of 2-10 nm) and the surface Cl content. The results obtained suggest that the difference in ammonia synthesis activity between the Ru catalysts supported on MgO and on the acidic supports is accounted for by not different electronic state of ruthenium on the surface of these oxides but by some other reasons.     

Efficient biomimetic aerobic oxidation of phenylethane catalyzed by P(4VP-co-St)/SiO2-supported metalloporphyrins

In this work, three kinds of metalloporphyrins (CoPs, FePs, and MnPs) were immobilized on the grafting particles P(4VP-co-St)/SiO₂ through the axial coordination reaction, respectively, and the supported biomimetic catalysts MP-P(4VP-co-St)/SiO₂ (M = Co, Fe and Mn) were prepared. The catalytic performances of various supported biomimetic catalysts for the oxidation of phenylethane in the absence of any reductant and solvent were investigated and compared detailedly. The experimental results show that the supported catalysts MP-P(4VP-co-St)/SiO₂ can effectively activate dioxygen, and obviously catalyze the oxidation of phenylethane to hypnone. When MPs are immobilized on the supports P(4VP-co-St)/SiO₂, the catalytic activity of MP-P(4VP-co-St)/SiO₂ is improved greatly. Also the catalytic activities of MP-P(4VP-co-St)/SiO₂ differ among the different metals, according to the following series: Co(II) > Fe(III) > Mn(III). Under the reaction conditions of 393 K and the ordinary pressure of oxygen, the catalyst CoP-P(4VP-co-St)/SiO₂ gave wonderful results with 24 mol% yield and 95% selectivity to the main product hypnone, and the another product, α-phenylethanol was few. All these results indicate that the grafting particles P(4VP-co-St)/SiO₂ can not only protect metalloporphyrin from oxidation, but also promote it to activate O₂. Additionally, some rules were specially found in the studies: (1) CoPs as a biomimetic catalyst had an optimum used amount, and excess addition would make the catalyst activity worse; (2) the immobilization density of CoPs on P(4VP-co-St)/SiO₂ surface still had the high-point; (3) the catalyst activity trended to steady during nine cycle.     

Benzene adsorption and oxidation on Ir(1 1 1)

Adsorption, decomposition and oxidation of benzene on Ir(1 1 1) was studied by high resolution (synchrotron) XPS, temperature programmed desorption and low energy electron diffraction. Molecular adsorption of benzene on Ir(1 1 1) is observed between 170 K and 350 K. Above this temperature both desorption and decomposition of benzene take place. An ordered adsorbate structure was observed upon adsorption around 335 K. Decomposition involves C-C bond breaking as the formation of CH_ad is observed. The presence of a saturated O_ad layer (0.5 ML) weakens molecular benzene adsorption and suppresses decomposition.     

Nanometer-scale spatial inhomogeneities of the chemical and electronic properties of an ion implanted Mn-Ge alloy

Electron energy loss spectroscopy maps using a transmission electron microscope were used to investigate with nanometer spatial resolution the Mn distribution of a Mn_xGe_1−x ion implanted alloy (x ? 4%). Mn is fully diluted in the Ge matrix in a subsurface implanted layer, showing concentration inhomogeneities at the nm scale. In the deep implanted layers the presence of Mn rich clusters—either amorphous or in the Mn₅Ge₃ phase—is directly evidenced. Scanning Tunneling Microscopy/Spectroscopy directly shows that the Mn₅Ge₃ clusters are metallic, while those smaller and amorphous are semiconducting with 0.45 ± 0.05 eV band gap. The Ge matrix with Mn dilution is semiconducting with 0.60 ± 0.05 eV gap. Electronic structure results are compared with ab-initio calculations.     

Photooxidation of different organic dyes (RB, MO, TB, and BG) using Fe(III)-doped TiO2 nanophotocatalyst prepared by novel chemical method

The nano-structured Fe(III)-doped TiO₂ photocatalysts with anatase phase have been developed for the oxidation of non-biodegradable different organic dyes like methyl orange (MO), rhodamine B (RB), thymol blue (TB) and bromocresol green (BG) using UV-Hg-lamp. The different compositions of Fe_xTi_1−xO₂ (x = 0.005, 0.01, 0.05, and 0.1) nanocatalysts synthesized by chemical method (CM), have been characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, specific surface area (BET), transmission electronic microscopy (TEM) analysis, XPS, ESR and zeta potential. From XRD analysis, the results indicate that all the compositions of Fe(III) doped in TiO₂ catalysts gives only anatase phase not rutile phase. For complete degradation of all the solutions of the dyes (MO, RB, TB, and BG), the composition with x = 0.005 is more photoactive compared all other compositions of Fe_xTi_1−xO₂, and degussa P25. The decolorization rate of different dyes decreases as Fe(III) concentration in TiO₂ increases. The energy band gap of Fe(III)-doped TiO₂ is found to be 2.38 eV. The oxidation state of iron has been found to be 3+ from XPS and ESR show that Fe³⁺ is in low spin state.     

Oxygen adsorption and oxidation reactions on Au(2 1 1) surfaces: Exposures using O2 at high pressures and ozone (O3) in UHV

Nanosized gold particles supported on reducible metal oxides have been reported to show high catalytic activity toward CO oxidation at low temperature. This has generated great scientific and technological interest, and there have been many proposals to explain this unusual activity. One intriguing explanation that can be tested is that of Nørskov and coworkers [Catal. Lett. 64 (2000) 101] who suggested that the “unusually large catalytic activity of highly-dispersed Au particles may in part be due to high step densities on the small particles and/or strain effects due to the mismatch at the Au-support interface”. In particular, their calculations indicated that the Au(2 1 1) stepped surface would be much more reactive towards O₂ dissociative adsorption and CO adsorption than the Au(1 1 1) surface. We have now studied the adsorption of O₂ and O₃ (ozone) on an Au(2 1 1) stepped surface. We find that molecular oxygen (O₂) was not activated to dissociate and produce oxygen adatoms on the stepped Au(2 1 1) surface even under high-pressure (700 Torr) conditions with the sample at 300-450 K. Step sites do bind oxygen adatoms more tightly than do terrace sites, and this was probed by using temperature programmed desorption (TPD) of O₂ following ozone (O₃) exposures to produce oxygen adatoms up to a saturation coverage of θ_O = 0.90 ML. In the low-coverage regime (θ_O ? 0.15 ML), the O₂ TPD peak at 540 K, which does not shift with coverage, is attributed to oxygen adatoms that are bound at the steps on the Au(2 1 1) surface. At higher coverages, an additional lower temperature desorption peak that shifts from 515 to 530 K at saturation coverage is attributed to oxygen adsorbed on the (1 1 1) terrace sites of the Au(2 1 1) surface. Although the desorption kinetics are likely to be quite complex, a simple Redhead analysis gives an estimate of the desorption activation energy, E_d, for the step-adsorbed oxygen of 34 kcal/mol and that for oxygen at the terraces near saturation coverage of 33 kcal/mol, values that are similar to others reported on Au surfaces. Low Energy Electron Diffraction (LEED) indicates an oxygen-induced step doubling on the Au(2 1 1) surface at low-coverages (θ_O = 0.08-0.17 ML) and extensive disruption of the 2D ordering at the surface for saturation coverages of oxygen (θ_O ? 0.9 ML). Overall, our results indicate that unstrained step sites on Au(2 1 1) surfaces of dispersed Au nanoparticles do not account for the novel reactivity of supported Au catalysts for CO oxidation.     

Semiquantitative perfusion combined with diffusion-weighted MR imaging in pre-operative evaluation of endometrial carcinoma: Results in a group of 57 patients

Purpose

To evaluate the semiquantitative DCE and quantitative DWI parameters in endometrial cancer, in order to assess the presence of neoplastic tissue and normal myometrium and to ascertain a potential relationship with tumor grade.

Methods and materials

A total of 57 patients with biopsy-proven endometrial adenocarcinoma who underwent MR imaging examination for staging purposes were retrospectively evaluated. Imaging protocol included multiplanar T₁- and T₂-weighted TSE, DCE T₁-weighted (THRIVE; 0, 30, 90 and 120 seconds after intravenous injection of gadolinium) and DWIBS sequences (b values = 0 and 1000 mm²/s). Color perfusion and ADC maps were automatically generated on dedicated software. Relative enhancement (RE, %), maximum enhancement (ME, %), maximum relative enhancement (MRE, %), time to peak (TTP, s) and mean apparent diffusion coefficient (ADC) were calculated by manually drawing a region of interest (ROI) both on the neoplastic tissue and the normal myometrium. Histopathology was used as reference standard.

Results

Histopathological analysis confirmed the presence of endometrial carcinoma in all patients. Neoplastic tissue demonstrated significantly lower (P < 0.001) values of RE (%) 63.92 ± 35.68; ME (%) 864.91 ± 429.54 and MRE (%) 75.97 ± 38.26 as compared to normal myometrium (RE (%) 151.43 ± 55.99; ME (%) 1800.73 ± 721.32; MRE (%) 158.28 ± 54.05). TTP was significantly higher (P < 0.05) in tumor lesion (385.51 ± 1630.27 vs 195.44 ± 78.69). Mean ADC value of neoplastic tissue (775.09 ± ?220.73 × 10^− 3 mm²/s) was significantly lower (P < 0.05) than in myometrium (1602.37 ± 378.54 × 10^− 3 mm²/s). The analysis of perfusion and diffusion parameters classified according to tumor grades, showed a statistically significant difference only for RE (P = 0.043) and ME (P = 0.007).

Conclusions

Perfusion parameters and mean ADC differ significantly between endometrial cancer and normal myometrium, potentially reflecting the different microscopical features of cellularity and vascularity; however a significant relationship with tumor grade was not found in our series.     

Study on immobilization of lipase onto magnetic microspheres with epoxy groups

Magnetic microspheres were synthesized by the suspension polymerization of glycidyl methacrylate (GMA), methacrylic acid (MAA) and divinyl benzene (DVB) in the presence of oleic acid-coated Fe₃O₄ nanoparticles. Triacylglycerol lipase from porcine pancreas was covalently immobilized on the magnetic microspheres via the active epoxy groups with the activity yield up to 63% (±2.3%) and enzyme loading of 39 (±0.5) mg/g supports. The resulting immobilized lipase had higher optimum temperature compared with those of free lipase and exhibited better thermal, broader pH stability and excellent reusability. Furthermore, the catalyzed capability of immobilized lipase was also investigated by catalyzing synthesis of hexyl acetate and the esterification conversion rate reached to 83% (±2.5%) after 12 h in nonaqueous solvent.     

Heterogeneous adsorption and catalytic oxidation of benzene, toluene and xylene over spent and chemically regenerated platinum catalyst supported on activated carbon

The heterogeneous adsorption and catalytic oxidation of benzene, toluene and o-xylene (BTX) over the spent platinum catalyst supported on activated carbon (Pt/AC) as well as the chemically treated spent catalysts were studied to understand their catalytic and adsorption activities. Sulfuric aqueous acid solution (0.1N, H₂SO₄) was used to regenerate the spent Pt/AC catalyst. The physico-chemical properties of the catalysts in the spent and chemically treated states were analyzed by using nitrogen adsorption-desorption isotherm and elemental analysis (EDX). The gravimetric adsorption and the light-off curve analysis were employed to study the BTX adsorption and oxidation on the spent catalyst and its modified Pt/AC catalysts. The experimental results indicate that the spent Pt/AC catalyst treated with the H₂SO₄ aqueous solution has a higher toluene adsorption and conversion ability than that of the spent Pt/AC catalyst. A further studies of H₂SO₄ treated Pt/AC catalyst on their catalytic and heterogeneous adsorption behaviours for BTX revealed that the activity of the H₂SO₄ treated Pt/AC catalyst follows the sequence of benzene > toluene > o-xylene. The adsorption equilibrium isotherms of BTX on the H₂SO₄ treated Pt/AC were measured at different temperatures ranging from 120 to 180 °C. To correlate the equilibrium data and evaluate their adsorption affinity for BTX, the two sites localized Langmuir (L2m) isotherm model was employed. The heterogeneous surface feature of the H₂SO₄ treated Pt/AC was described in detail with the information obtained from the results of isosteric enthalpy of adsorption and adsorption energy distributions. Furthermore, the activity of H₂SO₄ treated Pt/AC about BTX was found to be directly related to the Henry's constant, isosteric enthalpy of adsorption and adsorption energy distribution functions.     

The effect of heat treatment on the performance of the Ni/(Zr-Sm oxide) catalysts for carbon dioxide methanation

The active catalysts for methane formation from the gas mixture of CO₂ + 4H₂ with almost 100% methane selectivity were prepared by reduction of the oxide mixture of NiO and ZrO₂ prepared by calcination of aqueous ZrO₂ sol with Sm(NO₃)₃ and Ni(NO₃)₂. The 50 at%Ni-50 at%(Zr-Sm oxide) catalyst consisting of 50 at%Ni-50 at%(Zr + Sm) with Zr/Sm = 5 calcined at 650 or 800 °C showed the highest activity for methanation. The active catalysts were Ni supported on tetragonal ZrO₂, and the activity for methanation increased by an increase in inclusion of Sm³⁺ ions substituting Zr⁴⁺ ions in the tetragonal ZrO₂ lattice as a result of an increase in calcination temperature. However, the increase in calcination temperature decreased BET surface area, metal dispersion and hydrogen uptake due to grain growth. Thus, the optimum calcination temperature existed.     

Mesoporous (ZrO2-TiO2)/Al2O3 ternary carriers as hydrodesulfurization catalysts support

Ternary systems at various compositions were synthesized by coprecipitating Zr and Ti (to get a ZrO₂-TiO₂ 40-60 mol%) chlorides in aqueous basic media (provided by urea thermal decomposition) over an alumina substrate. Materials characterization included N₂ physisorption, X-ray diffraction, thermal analysis, high-resolution electron microscopy and Raman and UV-vis spectroscopies. High interaction among components was clearly evidenced by various techniques. Textural properties of ternary oxides could be tuned depending on composition of formulations. Mixed oxides with 10 or 20 mol% of ZrO₂-TiO₂ (at 40-60% mol, in turn) had the most suitable combination of textural properties (surface area, average pore diameter and pore volume) for the intended application (support of catalyst for hydrodesulfurization de oil-derived middle distillates). The suitability of those ternary supports was demonstrated in the dibenzothiophene hydrodesulfurization where the corresponding supported MoS₂ catalysts (at 2.8 atom Mo nm⁻²) were much more active (on a per mass of catalyst basis) than when impregnated over either alumina or zirconia-titania oxides.     

Carbon nanotubes supported Pt-Ni catalysts and their properties for the liquid phase hydrogenation of cinnamaldehyde to hydrocinnamaldehyde

The Pt-Ni catalysts supported on CNTs have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding hydrocinnamaldehyde (HCMA) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt-0.34 wt% Ni/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 70 °C under a pressure of around 2.0 MPa, and 98.6% for the conversion of CMA and 88.2% for the selectivity of CMA to HCMA, respectively. The selective hydrogenation for the CC bond in CMA would be improved as increasing the reaction temperature, and the hydrogenation for the CO bond in CMA is enhanced as increasing the H₂ pressure. In addition, these catalysts have also been characterized using TEM-EDS, XPS, H₂-TPR and H₂-TPD techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Ni would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt⁰ onto CNTs and increase the catalytic activity and selectivity of CMA to HCMA.     

Novel luminescent RE/TiO2 (RE = Eu, Gd) catalysts prepared by in-situation sol-gel approach construction of multi-functional precursors and their photo or photocatalytic oxidation properties

In this context, a novel synthesis method was used to fabricate rare earth/TiO₂ catalyst for the first time. Lanthanide (Eu, Gd) coordination polymers with picolinic acids were applied as precursors of titania oxide components, in particular, polyethylene glycol and polyacrylamide were added to assemble inorganic-organic hybrid polymeric network through an in-situation sol-gel technique. After sintering treatment of the multi-component precursor under 600 °C for 3 h, fluorescence excitation and emission spectra show that Eu/TiO₂ crystalline phosphor exhibits strong red luminescence under excitation wavelength at 394 and 464 nm. SEM and BET indicate the two hybrids are porous and homogenous. The oxidation experiments from trivalent arsenite As(III) to pentavalent arsenate As(V) by the above two catalysts substantiate that their surfaces have higher affinity to arsenate and can enhance photocatalytic oxidation activity in comparison with pure titania.     

Adsorption and desorption of Ca and PO4 species from SBFs on RF-sputtered calcium phosphate thin films

RF magnetron sputtering of calcium phosphate (CaP) coatings is a promising technique to apply thin bioactive films on bulk implant materials. In this paper the properties of the interface between RF sputtered coatings and simulated body fluids (SBFs) are related to the ability to form CaP crystals on the coating surface. Two types of coatings were compared: coatings with a low Ca over P ratio (∼0.8; CaP_low), which remain inert when immersed in SBF₂ (i.e. SBF with twice the Ca and PO₄ concentrations), and coatings with a high Ca over P ratio (1.6; CaP_high), which show the formation of CaP crystals on their surface within 2 h. Low energy ion scattering (LEIS) and radioactive labeling of the SBFs combined with liquid scintillation counting (LSC) allowed us to study very accurately the composition of the adsorbates of both coating groups after 10 min of immersion in SBF₂. For the adsorbate on CaP_high and CaP_low coatings coverages were found consistent with ionic adsorption and Ca/P ratios of 1.24 ± 0.02 and 2.17 ± 0.10, respectively. Adsorption was found to be reversible over the studied immersion period. After an induction period of 40 min a CaP precipitate started to form on the CaP_high coatings with a Ca/P ratio of 1.30 ± 0.02. Further, no significant desorption of coating species was observed during this induction period.     

Selective hydrogenation of cinnamaldehyde to cinnamyl alcohol with carbon nanotubes supported Pt-Co catalysts

The Pt-Co catalysts supported on carbon nanotubes (CNTs) have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding cinnamyl alcohol (CMO) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt-0.17 wt%Co/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 60 °C under a pressure of around 2.5 MPa, and 92.4% for the conversion of CMA and 93.6% for the selectivity of CMA to CMO, respectively. The selective hydrogenation for the CO double bond in CMA would be improved as increasing the H₂ pressure, and the selective hydrogenation for the CC double bond in CMA is enhanced as increasing the reaction temperature. In addition, these catalysts have also been characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), H₂-temperature programmed reduction (H₂-TPR) and H₂-temperature programmed desorption (H₂-TPD) techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Co would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt⁰ onto CNTs and increase the catalytic activity and selectivity of CMA to CMO.     

Influence of the physico-chemical properties of CeO2-ZrO2 mixed oxides on the catalytic oxidation of NO to NO2

Commercial and home-made Ce-Zr catalysts prepared by co-precipitation were characterised by XRD, Raman spectroscopy, N₂ adsorption at −196 °C and XPS, and were tested for NO oxidation to NO₂. Among the different physico-chemical properties characterised, the surface composition seems to be the most relevant one in order to explain the NO oxidation capacity of these Ce-Zr catalysts. As a general trend, Ce-Zr catalysts with a cerium-rich surface, that is, high XPS-measured Ce/Zr atomic surface ratios, are more active than those with a Zr-enriched surface. The decrease in catalytic activity of the Ce-Zr mixed oxided upon calcinations at 800 °C with regard to 500 °C is mainly attributed to the decrease in Ce/Zr surface ratio, that is, to the surface segregation of Zr. The phase composition (cubic or t′′ for Ce-rich compositions) seems not to be a direct effect on the catalytic activity for NO oxidation in the range of compositions tested. However, the formation of a proper solid solution prevents important surface segregation of Zr upon calcinations at high temperature. The effect of the BET surface area in the catalytic activity for NO oxidation of Ce-Zr mixed oxides is minor in comparison with the effect of the Ce/Zr surface ratio.     

Photocatalytic activity of multielement doped TiO2 in the degradation of congo red

TiO₂ although considered a promising photocatalyst for the degradation of aqueous pollutants, it suffers from poor absorption in the visible region and hence requires ultraviolet (UV) light for activation. To make TiO₂ a visible active photocatalyst, multielement (C, N, B, and F) doping has been done. The synthesised CNBF/TiO₂ catalysts were calcined at different temperatures and characterized by XRD, BET surface area, UV DRS, XPS, HRSEM-EDAX, and TEM techniques. These catalysts found to show less band gap values when compared to bare TiO₂. These catalysts were tested for their catalytic activity towards the degradation of a textile dye - congo red (CR) under different reaction conditions. It was found that the photocatalytic activity was dependent on both doping of multielement and the calcination temperature of CNBF/TiO₂. The co-doped catalysts which were calcined at 400 °C and 600 °C (100% intensity in anatase phase) were found to be the best catalysts (100% decolourisation of CR in 21/2 h and 2 h respectively). TOC analysis carried out for the samples at the reaction time of 5 h showed very high percentage (83%) degradation of CR over CNBF/TiO₂ catalysts calcined at 600 °C when compared to the other catalysts calcined at different temperatures. CNBF/TiO₂ (1000 °C) showed very less photocatalytic activity due to the formation of rutile phase.     

AFM images of G1-phase premature condensed chromosomes: Evidence for 30 nm changed to 50 nm chromatin fibers

To gain evidence for 30 nm changed to 50 nm chromatin fibers, we used atomic force microscopy (AFM) to study the ultrastructural organization of G₁-phase premature condensed chromosomes (PCC). The surface of early G₁-phase PCC is smooth and fibrous structures exist around the chromatids. The height of early G₁-phase PCC is about 410 nm and the width is 1.07 ± 0.11 μm (n = 30). At late G₁-phase, the surface becomes globular. The height of late G1-phase PCC is about 370 nm and the width is 845.04 ± 82.84 nm (n = 30). Phase image reveals that early G₁-phase PCC is composed of 50 nm (48.91 ± 6.63 nm, n = 30) chromatin fibers and these 50 nm chromatin fibers tangle together, while late G₁-phase PCC is composed of 30 nm (30.96 ± 4.07 nm, n = 30) chromatin fibers. At high magnification, fibers existing around the chromatids become clear in early G₁-phase PCC. Chromatin fibers revealed by closer view of the end of chromatid are about 50 nm. In late G₁-phase PCC, the surface presents globular structures. The shape of these globular structures is regular and the diameter is 118.96 ± 11.70 nm (n = 30). Our results clearly show that 30 nm chromatin fibers change to 50 nm chromatin fibers in G₁-phase PCC and suggest that 50 nm chromatin fibers are the basic component of the mitotic chromosomes.