Tunable luminescence and energy transfer properties of Sr₃AlO₄F:RE³+ (RE = Tm/Tb, Eu, Ce) phosphors

Sr(3)AlO(4)F:RE(3+) (RE = Tm/Tb, Eu, Ce) phosphors were prepared by the conventional solid-state reaction. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) spectra, as well as lifetimes were utilized to characterize samples. Under the excitation of UV light, Sr(3)AlO(4)F:Tm(3+), Sr(3)AlO(4)F:Tb(3+), and Sr(3)AlO(4)F:Eu(3+) exhibit the characteristic emissions of Tm(3+) ((1)D(2)→(3)F(4), blue), Tb(3+) ((5)D(4)→(7)F(5), green), and Eu(3+) ((5)D(0)→(7)F(2), red), respectively. By adjusting the doping concentration of Eu(3+) ions in Sr(3)AlO(4)F:0.10Tm(3+), 0.10Tb(3+), zEu(3+), a white emission in a single composition was obtained under the excitation of 360 nm, in which an energy transfer from Tb(3+) to Eu(3+) was observed. For Sr(3)AlO(4)F:Ce(3+),Tb(3+) samples, the energy transfer from Ce(3+) to Tb(3+) is efficient and demonstrated to be a resonant type via a dipole-quadrupole interaction by comparing the experimental data and theoretical calculation. Furthermore, the critical distance of the Ce(3+) and Tb(3+) ions has also been calculated to be 9.05 ?. The corresponding luminescence and energy transfer mechanisms have been proposed in detail. These phosphors might be promising for use in near-UV LEDs.     

Preparation and the luminescent properties of Tb3+-doped Gd2O3 fluorescent nanofibers via electrospinning

Tb(3+)-doped Gd(2)O(3) (Gd(2)O(3):Tb(3+)) nanofibers were prepared via a simple electrospinning technique using poly(ethylene oxide) (PEO) and rare-earth acetate tetrahydrates (Ln(CH(3)COO)(3)·4H(2)O (Ln = Gd, Tb)) as precursors. The obtained nanofibers have an average diameter of about 80 nm and are composed of pure cubic Gd(2)O(3) phase. A possible formation mechanism for the nanofibers is proposed on the basis of the experimental results, which reveals that PEO acts as the structure directing template during the whole electrospinning and subsequent calcination process. The luminescent properties of the nanofibers were investigated in detail. The nanofibers exhibit a favorable fluorescent property symbolized by the characteristic green emission (545 nm) resulting from the 5D4-->7F5 transition of Tb(3+). Concentration quenching occurs when the Tb(3+) concentration is 3 at.%, indicating that the Gd(2)O(3):Tb(3+) nanofibers have an optimum luminescent intensity under such a doping concentration.     

Dicationic ion-pairing agents for the mass spectrometric determination of perchlorate

Perchlorate and other hydrophobic ions can be measured with high sensitivity and selectivity by forming a positively charged ion pair with a dicationic agent. A commercially available reagent, 1,6-bis(trimethylammonium)hexane dibromide (Br(N(CH3)3)(CH2)6(N(CH3)3)Br) allows for the determination of perchlorate by electrospray ionization mass spectrometry as the [(N(CH3)3)(CH2)6(N(CH3)3)ClO4]+ ion. Limits of detection (LODs) are better than those previously observed with custom-synthesized dicationic agents. An LOD of 20 ng/L is readily attainable with a single-quadrupole mass spectrometer.     

Electrochemical studies of the interaction of metal chelates with DNA. 4. Voltammetric and electrogenerated chemiluminescent studies of the interaction of tris(2,2'-bipyridine)osmium(II) with DNA

Cyclic voltammetric and electrogenerated chemiluminescent data were used to study the binding of tris(2,2'-bipyridine)-osmium(II), Os(bpy)3(2+), an electrostatic binder, to calf thymus DNA. The oxidized form of the osmium complex, Os(bpy)3(3+), has a stronger association to DNA than the reduced form, Os(bpy)3(2+), as indicated by the negative shift of E0' of the CV waves (K3+/K2+ = 3.35). The calculated binding constant, K2+, and binding site size, s, for the Os(byp)3(2+)-DNA system depended slightly on whether a mobile or a static equilibrium was assumed. In 10 mM NaCl, 10 mM Tris pH 7, K2+ = (7.3 +/- 0.4) x 10(3) M-1 and s = 3 base pairs (mobile) and K2+ = (5.0 +/- 0.2) x 10(3) M-1 and s = 3 base pairs (static). Electrogenerated chemiluminescence (ECL) was produced upon oxidation of Os(bpy)3(2+) at a Pt electrode in a solution containing 10 mM C2O4(2-) and 10 mM phosphate at pH 5. Addition of DNA caused a decrease in the emission intensity (I); a plot of I vs relative DNA concentration yielded K2+ = (6.5 +/- 0.5) x 10(3) M-1 and s = 3 base pairs. The osmium complex produced ECL when bound to the DNA molecule with an efficiency of 30% that of the unbound chelate.     

Biological nitrate removal from wastewater of a metal-finishing industry

An upflow packed bed reactor at laboratory scale has been operated for a continuous period of 5 months to investigate the technical feasibility of biological nitrate removal applied to the effluent of the coagulation-sedimentation wastewater of a metal-finishing industry. The reactor was fed with industrial wastewater in a five-fold dilution to reproduce the global spill in the factory (20/80, industrial wastewater/domestic wastewater) with a concentration of nitrate between 141 and 210 gNO(3)-N/m(3). Methanol was added as a carbon source for denitrification. Inlet flow rate was progressively increased from 9 to 40 L/day (nitrogen input load from 45 to 250 gNO(3)-N/(m(3)h)). The highest observed denitrification rate was 135 gNO(3)-N/(m(3)h) at a nitrate load of 250 gNO(3)-N/(m(3)h), and removal efficiencies higher than 90% were obtained for loads up to 100 gNO(3)-N/(m(3)h). A mass relation between COD consumed and NO(3)-N removed around 3.31 was observed. Better results were achieved in a previous stage using tap water with nitrate added as a sole pollutant as a synthetic feed (critical load of 130 gNO(3)-N/(m(3)h) and denitrification rate of 200 gNO(3)-N/(m(3)h) at a nitrate load of 250 gNO(3)-N/(m(3)h)). This fact could indicate that the chemical composition of the industrial source hinders to some extent the performance of the biological process. Whatever case, results demonstrated the viability of the denitrification process for the global industrial wastewater. A simple model based on Monod kinetics for substrate consumption, and constant biomass concentration was applied to model the industrial wastewater treatment, and a reasonably good fitting was obtained.     

LiNi₁/₃Co₁/₃Mn₁/₃O₂-graphene composite as a promising cathode for lithium-ion batteries

The use of graphene as a conductive additive to enhance the discharge capacity and rate capability of LiNi(1/3)Co(1/3)Mn(1/3)O(2) electrode material has been demonstrated. LiNi(1/3)Co(1/3)Mn(1/3)O(2) and its composite with graphene (90:10 wt %) were prepared by microemulsion and ball-milling techniques, respectively. The structural and morphological features of the prepared materials were investigated with powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Characterization techniques depict single-phase LiNi(1/3)Co(1/3)Mn(1/3)O(2) with particle sizes in the range of 220-280 nm. Electrochemical studies on LiNi(1/3)Co(1/3)Mn(1/3)O(2) and LiNi(1/3)Co(1/3)Mn(1/3)O(2)-graphene were conducted using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy methods by constructing a lithium half-cell. Cyclic voltammograms show the well-defined redox peaks corresponding to Ni(2+)/Ni(4+). Charge-discharge tests were performed at different C rates: 0.05, 1, and 5 between 2.5 and 4.4 V. The results indicate the better electrochemical performance of the LiNi(1/3)Co(1/3)Mn(1/3)O(2)-graphene composite in terms of high discharge capacity (188 mAh/g), good rate capability, and good cycling performance compared to LiNi(1/3)Mn(1/3)Co(1/3)O(2). The improved electrochemical performance of the LiNi(1/3)Co(1/3)Mn(1/3)O(2)-graphene composite is attributed to a decrease in the charge-transfer resistance.     

Raman and infrared spectroscopic investigations on aqueous alkali metal phosphate solutions and density functional theory calculations of phosphate-water clusters

Phosphate (PO(4)(3-)) solutions in water and heavy water have been studied by Raman and infrared spectroscopy over a broad concentration range (0.0091-5.280 mol/L) including a hydrate melt at 23 degrees C. In the low wavenumber range, spectra in R-format have been constructed and the R normalization procedure has been briefly discussed. The vibrational modes of the tetrahedral PO(4)(3-)(aq) (T(d) symmetry) have been assigned and compared to the calculated values derived from the density functional theory (DFT) method for the unhydrated PO(4)(3-)(T(d)) and phosphate-water clusters: PO(4)(3-).H(2)O (C(2v)), PO(4)(3-).2H(2)O (D(2d)), PO(4)(3-).4H(2)O (D(2d)), PO(4)(3-).6H(2)O (T(d)), and PO(4)(3-).12H(2)O (T), a cluster with a complete first hydration sphere of water molecules. A cluster with a second hydration sphere of 12 water molecules and 6 in the first sphere, PO(4)(3-).18H(2)O (T), has also been calculated. Agreement between measured and calculated vibrational modes is best in the case of the PO(4)(3-).12H(2)O cluster and the PO(4)(3-).18H(2)O cluster but far less so in the case of the unhydrated PO(4)(3-) or phosphate-water cluster with a lower number of water molecules than 12. The asymmetric, broad band shape of v(1)(a(1)) PO(4)(3-) in aqueous solutions has been measured as a function of concentration and the asymmetric and broad band shape was explained. However, the same mode in heavy water has only half the full width at half-height compared to the mode in normal water. The PO(4)(3-) is strongly hydrated in aqueous solutions. This has been verified by Raman spectroscopy comparing v(2)(H(2)O), the deformation mode of water, and the stretching modes, the v(1)OH and v(3)OH of water, in K(3)PO(4) solutions as a function of concentration and comparison with the same modes in pure water. A mode at approximately 240 cm(-1) (isotropic R spectrum) has been detected and assigned to the restricted translational mode of the strong hydrogen bonds formed between phosphate and water, P-O...HOH. In very concentrated K(3)PO(4) solutions (C(0) > or = 3.70 mol/L) and in the hydrate melt, formation of contact ion pairs (CIPs) could be detected. The phosphate in the CIPs shows a symmetry lowering of the T(d) symmetry to C(3v). In the less concentrated solutions, PO(4)(3-)(aq) solvent separated ion pairs and doubly solvent separated ion pairs exist, while in very dilute solutions fully hydrated ions are present (C(0) < or = 0.005 mol/L). Quantitative Raman measurements have been carried out to follow the hydrolysis of PO(4)(3-)(aq) over a very broad concentration range. From the hydrolysis data, the pK(3) value for H(3)PO(4) has been determined to be 12.45 at 23 degrees C.     

Kinetics of Fe(3)O(4)-CoO/Al(2)O(3) catalytic ozonation of the herbicide 2-(2,4-dichlorophenoxy) propionic acid

The presence of Fe(3)O(4)-CoO/Al(2)O(3) can improve degradation efficiency significantly during the ozonation of the herbicide 2-(2,4-dichlorophenoxy) propionic acid (2,4-DP). The main factors affecting degradation efficiency, such as pH, the catalyst concentration and addition of the scavenger, were investigated. The kinetics of the catalytic ozonation are also discussed. The results indicate that two factors, the oxidation after adsorption of 2,4-DP and the oxidation of hydroxyl radicals (OH), lead to a great enhancement in ozonation efficiency during the catalytic ozonation of 2,4-DP in the presence of Fe(3)O(4)-CoO/Al(2)O(3), in which the oxidation of the OH plays an important role. Under controlled conditions, the apparent reaction rate constants for the degradation of 2,4-DP were determined to be 2.567 × 10(-4)s(-1) for O(3) and 1.840 × 10(-3)s(-1) for O(3)/Fe(3)O(4)-CoO/Al(2)O(3). The results from the analysis of the reaction kinetics using the relative method showed that O(3)/Fe(3)O(4)-CoO/Al(2)O(3) possessed a larger R(ct) (R(ct) is defined as the ratio of the ·OH exposure to the O(3) exposure, R(ct) = ∫C(t)(OH) dt/C(t)O(3)dt) than O(3), indicating that O(3)/Fe(3)O(4)-CoO/Al(2)O(3) produced more hydroxyl radicals.     

Synthesis of a nanostructured star block copolymer with a cyclotriphosphazene core

An amphiphilic star block copolymer of poly(L-lactic acid)-b-poly(ethylene glycol) (PLLA-b-PEG) was synthesized using a hexachlorocyclotriphosphazene ring (N3P3Cl6) as a core. N3P3(OC6H4-p-CHO)6 was prepared by the reaction between the hexachlorocyclotriphosphazene core and 4-hydroxybenzaldehyde sodium salt. N3P3(OC6H4-p-CH2OH)6 was then obtained by reduction of N3P3(OC6H4-p-CHO)6. N3P3(OC6H4-p-CH2OH)6 was used as an initiator to obtain a PLLA-grafted star branched polymer by polymerizing lactide, which was then treated with succinic acid to produce a carboxylated PLLA-grafted star polymer. PEG blocks were attached to a carboxylated PLLA-grafted star polymer to produce an amphiphilic PLLA-b-PEG-grafted star block polymer by additional esterification with poly(ethylene glycol methyl ether).     

Effect of CeO2 doping on catalytic activity of Fe2O3/gamma-Al2O(3) catalyst for catalytic wet peroxide oxidation of azo dyes

In order to find a catalyst with high activity and stability for catalytic wet peroxide oxidation (CWPO) process under normal condition, with Fe(2)O(3)/gamma-Al(2)O(3) and Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) catalysts prepared by impregnation method, the effect of CeO(2) doping on the structure and catalytic activity of Fe(2)O(3)/gamma-Al(2)O(3) for catalytic wet peroxide oxidation of azo dyes at 25 degrees C and atmospheric pressure is evaluated using BET, SEM, XRF, XRD, XPS and chemical analysis techniques, and test results show that, better dispersion and smaller size of Fe(2)O(3) crystal can be achieved by adding CeO(2), and the content of chemisorbed oxygen can also be increased on the surface of catalyst. CWPO experimental results indicate that azo dyes in simulated wastewater can be efficiently mineralized and the catalytic activity of Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) can be increased by about 10% compared with that of Fe(2)O(3)/gamma-Al(2)O(3) because of the promotion of the structural and redox properties of the ferric oxide by ceria doped. Leaching tests indicate that Fe(2)O(3)/gamma-Al(2)O(3) and Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) are stable with a negligible amount of irons found in the aqueous solution after reaction for 2h. It can therefore be concluded from results and discussion that in comparison with Fe(2)O(3)/gamma-Al(2)O(3), Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) is a suitable catalyst, which can effectively degrade contaminants at normal temperature and atmospheric pressure.     

Highly sensitive and selective trimethylamine sensor using one-dimensional ZnO-Cr2O3 hetero-nanostructures

Highly selective and sensitive detection of trimethylamine (TMA) was achieved by the decoration of discrete p-type Cr(2)O(3) nanoparticles on n-type ZnO nanowire (NW) networks. Semielliptical Cr(2)O(3) nanoparticles with lateral widths of 3-8 nm were deposited on ZnO NWs by the thermal evaporation of CrCl(2) at 630 °C, while a continuous Cr(2)O(3) shell layer with a thickness of 30-40 nm was uniformly coated on ZnO NWs at 670 °C. The response (R(a)/R(g): R(a), resistance in air; R(g), resistance in gas) to 5 ppm TMA of Cr(2)O(3)-decorated ZnO NWs was 17.8 at 400 °C, which was 2.4 times higher than that to 5 ppm C(2)H(5)OH and 4.3-8.4 times higher than those to 5 ppm p-xylene, NH(3), benzene, C(3)H(8), toluene, CO, and H(2). In contrast, both pristine ZnO and ZnO (core)-Cr(2)O(3) (shell) nanocables (NCs) showed comparable responses to the different gases. The highly selective and sensitive detection of TMA that was achieved by the deposition of semielliptical Cr(2)O(3) nanoparticles on ZnO NW networks was explained by the catalytic effect of Cr(2)O(3) and the extension of the electron depletion layer via the formation of p-n junctions.     

Laser spectroscopic measurement of quenching and doublet mixing rates of the Na(3P(3/2, 1/2)) doublet in a propane-air flame

We have measured the quenching rate of the Na 3P level and the doublet mixing rates of the Na 3P(3/2) and 3P(1/2) levels in a propane-air flame at atmospheric pressure. To obtain these rates, subnanosecond time-resolved fluorescence measurements were made using a mode-locked dye laser and the time-correlated single-photon counting method. Our results are 1.4 x 10(9) s(-1) for the quenching rate and 3.0 x 10(9) s(-1) for the 3P(3/2) --> 3P(1/2) mixing rate.     

Biofunctionalization of CeF(3):Tb(3+) nanoparticles

CeF(3):Tb(3+) nanoparticles (short pillar-like morphology with an average length and width of 11 and 5?nm, respectively) were successfully prepared by a polyol process using diethyleneglycol (DEG) as solvent. After being functionalized with a SiO(2)-NH(2) layer, these CeF(3):Tb(3+) nanoparticles can be conjugated with biotin molecules (activated by thionyl chloride) and further with avidin. The as-formed CeF(3):Tb(3+) nanoparticles, CeF(3):Tb(3+) nanoparticles functionalized with amino groups, biotin conjugated amino-functionalized CeF(3):Tb(3+) nanoparticles and biotinylated CeF(3):Tb(3+) nanoparticles bonded with avidin were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), UV/vis absorption spectra and luminescence spectra, respectively. The biofunctionalization of the CeF(3):Tb(3+) nanoparticles has less effect on their luminescence properties, i.e. they still show strong green emission (from Tb(3+), with (5)D(4)-(7)F(5) at 543?nm as the most prominent group), indicative of the great potential for these CeF(3):Tb(3+) nanoparticles to be used as biological fluorescence probes.     

Twinning of YBa2Cu3O7 thin films on different substrates

The twinning of YBa₂Cu₃O₇ (YBCO) thin films with c-axis orientation on (001) MgO, (001) SrTiO₃, (012) LaAlO₃, (110) NdGaO₃ and (001) NdGaO₃ substrates, prepared by laser ablation, has been examined using a combination of and θ/2θ scans at a four-circle diffractometer. On all substrates, except for (001) NdGaO₃, the tetragonal to orthorhombal phase transition results in four different orientations of YBCO twins relating to the substrate. On (001) NdGaO₃ only two different twin orientations, accompanied by a slight lattice monoclinization, has been observed.     

Luminescence study on Eu(3+) doped Y(2)O(3) nanoparticles: particle size, concentration and core-shell formation effects

Nanoparticles of Eu(3+) doped Y(2)O(3) (core) and Eu(3+) doped Y(2)O(3) covered with Y(2)O(3) shell (core-shell) are prepared by urea hydrolysis for 3?h in ethylene glycol medium at a relatively low temperature of 140?°C, followed by heating at 500 and 900?°C. Particle sizes determined from x-ray diffraction and transmission electron microscopic studies are 11 and 18?nm for 500 and 900?°C heated samples respectively. Based on the luminescence studies of 500 and 900?°C heated samples, it is confirmed that there is no particle size effect on the peak positions of Eu(3+) emission, and optimum luminescence intensity is observed from the nanoparticles with a Eu(3+) concentration of 4-5?at.%. A luminescence study establishes that the Eu(3+) environment in amorphous Y (OH)(3) is different from that in crystalline Y(2)O(3). For a fixed concentration of Eu(3+) doping, there is a reduction in Eu(3+) emission intensity for core-shell nanoparticles compared to that of core nanoparticles, and this has been attributed to the concentration dilution effect. Energy transfer from the host to Eu(3+) increases with increase of crystallinity.     

Mechanistic Investigation of Cycloreversion/Cycloaddition Reactions between Zirconocene Metallacycle Complexes and Unsaturated Organic Substrates

Treatment of the diazametallacycle Cp(2)Zr(N(t-Bu)C=N(SiMe(3))N(SiMe(3))) (4a) with diphenylacetylene resulted in the formation of the azametallacyclobutene Cp(2)Zr(N(t-Bu)C(Ph)=C(Ph)) (6a) and Me(3)SiN=C=NSiMe(3) in high yield. A kinetic study using UV-vis spectroscopy was carried out on the transformation. Saturation kinetic behavior was observed for the system, which is supportive of a mechanism that involves a reversible formal [2 + 2] retrocycloaddition of 4a to generate the transient imido species Cp(2)Zr=N-t-Bu (7a) and Me(3)-SiN=C=NSiMe(3). Trapping 7a with diphenylacetylene in an overall [2 + 2] cycloaddition reaction affords zirconacycle 6a. The study of cycloreversion/cycloaddition reactions between diazametallacycle complexes and diphenylacetylene was extended to other zirconocene systems. Detailed kinetic studies were performed for the exchange reactions between the diazametallacycle complexes Cp(2)Zr(N(2,6-Me(2)Ph)C=N(SiMe(3))N(SiMe(3))) (8a) and Cp(2)Zr-(N(2,6-Me(2)Ph)C=N(t-Bu)N(t-Bu)) (8b) with diphenylacetylene (5a) to give the corresponding azametallacyclobutene complex Cp(2)Zr(N(2,6-Me(2)Ph)C(Ph)=C(Ph)) (6c) and extruded carbodiimides (Me(3)SiN=C=NSiMe(3) for 8a and (t-Bu)N=C=N(t-Bu) for 8b). For both systems, the reactions were found to be first order in metallacycle and zero order in alkyne. Treatment of the diazametallacycle complexes Cp(2)Zr(N(2,6-i-Pr(2)Ph)C=N(Cyc)N(Cyc)) (9a) and Cp(2)Zr-(N(2,6-i-Pr(2)Ph)C=N(i-Pr(2))N(i-Pr(2))) (9b) with alkyne 5a resulted in the formation of the six-membered zirconacycles 10a,b, respectively, upon heating at 75 degrees C. The products 10a,b are generated from the overall insertion of alkyne 5a into the nitrogen-carbon bond of the zirconium-containing diazacyclobutane. Complex 10a has been characterized by an X-ray crystallographic study. When the azacyclobutene Cp(2)Zr(N(2,6-i-Pr(2)Ph)C(Ph)=C(Ph)) (6e) was treated with CycN=C=NCyc or (i-Pr)N=C=N(i-Pr), the same six-membered zirconacycle complexes 10a,b were obtained. Kinetic analysis of the reaction of 6e and (i-Pr)N=C=N(i-Pr) to yield 10b supports an associative process wherein alkyne 5a directly inserts into the zirconium-carbon bond of 6e. The diazametallacycle complex 4a underwent a stoichiometric metathetical exchange with symmetrical carbodiimides RN=C=NR (R = p-Tol, m-Tol, i-Pr, Cyc) to generate new cyclic zirconocene complexes and Me(3)SiN=C=NSiMe(3). Kinetic studies were carried out on the exchange reaction between 4a and (m-Tol)N=C=N(m-Tol) to form 4e and Me(3)SiN=C=NSiMe(3). The experimental rate data obtained are consistent with a dissociative mechanism. Additionally, the saturation rate constant derived for this system from the data is the same (within experimental error) as the saturation rate constant obtained from the kinetic study of 4a and diphenylacetylene to form 6a and Me(3)SiN=C=NSiMe(3). These findings provide additional support for a dissociative mechanistic pathway in the exchange reactions, since the rate constant in the formal [2 + 2] retrocycloaddition reaction to generate imidozirconocene species Cp(2)Zr=N-t-Bu (7a) and Me(3)SiN=C=NSiMe(3) should be the same for both reactions.     

The catalytic incineration of (CH3)2S and its mixture with CH(3)SH over a Pt/Al(2)O(3) catalyst

Catalytic incineration is one of the cost-effective technologies to solve the troublesome volatile organic compounds (VOCs). However, some sulfur containing VOCs, such as dimethyl sulfide, may deactivate the Pt catalyst that is commonly used in the catalytic incineration process. This paper provides information on the poisoning effect of (CH3)2S. The catalytic incineration of (CH3)2S, typically emitted from the petrochemical industry, over a Pt/Al(2)O(3) fixed bed catalytic reactor was studied. The effects of operating parameters including inlet temperature, space velocity, (CH3)2S concentration, O2 concentration and catalyst size were characterized. Catalytic incineration on a mixture of (CH3)2S with CH(3)SH was also tested. The results show that the conversions of (CH3)2S increase as the inlet temperature increases and the space velocity decreases. The higher the (CH3)2S concentration is, the lower its conversion is. The O2 concentration has a positive effect on the conversion of (CH3)2S. (CH3)2S has a poisoning effect on the Pt/Al(2)O(3) catalyst, especially at lower temperatures. The conversion of (CH3)2S is significantly suppressed by the existence of CH(3)SH.     

The size-controlled synthesis of uniform Mn2O3 octahedra assembled from nanoparticles and their catalytic properties

Uniform Mn(2)O(3) octahedral nanoparticles were synthesized by a mediated N, N-dimethylformamide (DMF) solvothermal route. On the basis of a time-dependent experiment, we propose that the Mn(2)O(3) octahedra were formed through oriented aggregation of primary nanocrystals. Meanwhile, poly(vinyl-pyrrolidone) (PVP) was applied as a surfactant to facilitate the oriented aggregation of small Mn(2)O(3) nanoparticles into octahedral crystallites. By tuning the amount of Mn(NO(3))(2), particles with average sizes 1 μm to 300 nm, with a narrow size distribution, could be fabricated. The catalytic test results show that the as-obtained Mn(2)O(3) octahedra exhibited desirable CO catalytic oxidation properties and the surface texture and particle size significantly affected the catalytic activity. By contrast, the larger Mn(2)O(3) octahedral nanoparticles prepared at a lower concentration of Mn(NO(3))(2) exhibited relatively high activities.     

A multiphase sodium vanadium phosphate cathode material for high-rate sodium-ion batteries

The unsatisfactory rate capability and poor cycling stability at high rate of sodium-ion batteries(SIBs) have impeded their practical applications. Herein, a Na₃V₂(PO₄)₃/Na₃V₃(PO₄)₄ multiphase cathode materials for high-rate and long cycling SIBs was successfully synthesized by regulation the stoichiometric ratio of raw materials. The combined experiment and simulation results show that the multiphase materials consisted of NASICON structural phase Na3V2(PO4)3 and layered structure phase Na₃V₃(PO₄)₄, possess abundant phase boundaries. Electrochemical experiments demonstrate that the multiphase materials maintain a remarkable reversible capacity of 69.0 mA h g^-1 even at an ultrahigh current density of 100 C with a high capacity retention of 81.25 % even after 10,000 cycles. Na₃V₂(PO₄)₃/Na₃V₃(PO₄)₄ electrode exhibits a higher working voltage, superior rate capability and better cycling stability than Na₃V₂(PO₄)₃ electrode, which indicates that the introduction of second phase can be an effective strategy for the development of novel cathode materials for SIBs.