Interaction of Au with thin ZrO2 films: influence of ZrO2 morphology on the adsorption and thermal stability of Au nanoparticles

The model catalysts of ZrO(2)-supported Au nanoparticles have been prepared by deposition of Au atoms onto the surfaces of thin ZrO(2) films with different morphologies. The adsorption and thermal stability of Au nanoparticles on thin ZrO(2) films have been investigated using synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The thin ZrO(2) films were prepared by two different methods, giving rise to different morphologies. The first method utilized wet chemical impregnation to synthesize the thin ZrO(2) film through the procedure of first spin-coating a zirconium ethoxide (Zr(OC(2)H(5))(4)) precursor onto a SiO(2)/Si(100) substrate at room temperature followed by calcination at 773 K for 12 h. Scanning electron microscopy (SEM) investigations indicate that highly porous "sponge-like nanostructures" were obtained in this case. The second method was epitaxial growth of a ZrO(2)(111) film through vacuum evaporation of Zr metal onto Pt(111) in 1 × 10(-6) Torr of oxygen at 550 K followed by annealing at 1000 K. The structural analysis with low energy electron diffraction (LEED) of this film exhibits good long-range ordering. It has been found that Au forms smaller particles on the porous ZrO(2) film as compared to those on the ordered ZrO(2)(111) film at a given coverage. Thermal annealing experiments demonstrate that Au particles are more thermally stable on the porous ZrO(2) surface than on the ZrO(2)(111) surface, although on both surfaces, Au particles experience significant sintering at elevated temperatures. In addition, by annealing the surfaces to 1100 K, Au particles desorb completely from ZrO(2)(111) but not from porous ZrO(2). The enhanced thermal stability for Au on porous ZrO(2) can be attributed to the stronger interaction of the adsorbed Au with the defects and the hindered migration or coalescence resulting from the porous structures.     

Long-range electron transfer across molecule-nanocrystalline semiconductor interfaces using tripodal sensitizers

Four tripodal sensitizers, Ru(bpy)(2)(Ad-tripod-phen)(2+) (1), Ru(bpy)(2)(Ad-tripod-bpy)(2+) (2), Ru(bpy)(2)(C-tripod-phen)(2+) (3), and Ru(bpy)(2)(C-tripod-bpy)(2+) (4) (where bpy is 2,2'-bipyridine, phen is 1,10-phenanthroline, and Ad-tripod-bpy (phen) and C-tripod-bpy (phen) are tripod-shaped bpy (phen) ligands based on 1,3,5,7-tetraphenyladamantane and tetraphenylmethane, respectively), have been synthesized and characterized. The tripodal sensitizers consist of a rigid-rod arm linked to a Ru(II)-polypyridine complex at one end and three COOR groups on the other end that bind to metal oxide nanoparticle surfaces. The excited-state and redox properties of solvated and surface-bound 1-4 have been studied at room temperature. The absorption spectra, emission spectra, and electrochemical properties of 1-4 in acetonitrile solution are preserved when 1-4 are bound to nanocrystalline (anatase) TiO(2) or colloidal ZrO(2) mesoporous films. This behavior is indicative of weak electronic coupling between TiO(2) and the sensitizer. The kinetics for excited-state decay are exponential for 1-4 in solution and are nonexponential when 1-4 are bound to ZrO(2) or TiO(2). Efficient and rapid (k(cs) > 10(8) s(-)(1)) excited-state electron injection is observed for 1-4/TiO(2). The recombination of the injected electron with the oxidized Ru(III) center is well described by a second-order kinetic model with rate constants that are independent of the sensitizer. The sensitizers bound to TiO(2) were reversibly oxidized electrochemically with an apparent diffusion coefficient approximately 1 x 10(-11) cm(2) s(-)(1).     

以表面活性剂为模板ZrO2薄膜在空气-水界面的自组装研究

采用三种阴离子表面活性剂: 十二烷基磺酸钠(SDS), 十二烷基苯磺酸钠(DBS-Na), 十二烷基苯磺酸(DBS-H)作模板, 在空气-水界面上组装ZrO₂薄膜. 结果表明, 采用SDS组装的薄膜具有良好的机械强度. 经X射线能量扫描谱原位检测以及X射线衍射(XRD)谱检测证实, 所获薄膜为层状结构, 其层间距在2.70～3.54 nm之间. 利用所建立的层状结构模型解释了各种阴离子表面活性剂组装ZrO₂薄膜并控制层间距变化的机理.     

Organic-inorganic hybrid materials constructed from inorganic lanthanide sulfate skeletons and organic 4,5-imidazoledicarboxylic acid

Five different types of the lanthanide sulfate-carboxylates family, [La(2)(SO(4))(Himdc)(2)(H2O)2] , [Gd(2)(SO(4))(2)(Himdc)(H2O)3].H2O , [Ln(2)(SO(4))(2)(Himdc)(H2O)(3)].H2O (Ln = Gd3a, Eu3b), [Eu(6)Cu(SO(4))(6)(Himdc)(4)(H2O)(14)] , and [Ln(Himc)(SO(4))(H2O)] (Ln = Eu5a, Gd5b, Tb5c, Dy5d, Er5e); H(2)imc = 4-imidazolecarboxylic acid, H(3)imdc = 4,5-imidazoledicarboxylic acid) have been obtained by hydrothermal reactions of Ln(2)O(3), transition metal sulfates and H(3)imdc at 170 degrees C and characterized by means of elemental analyses, IR, TG analysis, luminescence spectroscopy and single crystal X-ray diffraction. The 3D structure of 1 is constructed from alternately linkages of organic {La(Himdc)} layers and inorganic {La(2)O(2)(SO(4))} layers, with the La atoms as hinges. 2 and 3a/3b both contain alternately arranged 1D left- and right-handed helical {Ln(imdc)} chains bridged by SO(4)(2-) anions to form a 3D framework with 1D rectangle-like channels along the b axis. The structural differences of 2 and 3a/3b lie in the linkages of the SO(4)(2-) anions. Complex 4 consists of 2D tubular Eu-sulfate layers pillared by {Cu(Himdc)(2)} units to generate a 3D network. Complexes 5a-5e possess 2D bamboo-raft-like layer structures based on helical tubes. Interestingly, H(2)imc comes from the in-situ decarboxylation of H(3)imdc in the hydrothermal reactions. The luminescence properties of the complexes 3a, 4, 5a 5c, 5d were investigated in solid state at room temperature.     

Catalysis of SO42--ZrO2/TiO2 nanometer solid superacid

Superacid catalyst SO42--ZrO2/TiO2 was applied in esterification of Acetic Acid and Butanol. The particle size of ZrO2 in the catalyst was about 12.5 nm. In catalyst preparation conditions, the effect factor order on catalytic activity is H2SO4 concentration ＞ calcination temperature ＞ ZrO2 supported content. The optimum preparation condition is as follows: ZrO2 content 3.5g/g; calcination temperature 600℃, and H2SO4 concentration 0.5mol/L. The catalytic activity is 96.5 vol%.SO42-/MxOy solid superacid is a kind of green catalyst, whose application perspective is bright. In this paper, SO42--ZrO2/TiO2 solid superacid was prepared with nanometer compound carrying method. The acidic strength of catalysts was measured with the following Hammett indicators, 2,4-dinitrofluorobenzene (H0=-14.52) and p-nitrochlorobenzene (H0=-12.70). Catalytic activity was evaluated with esterification reaction of Acetic Acid and Butanol. Reaction temperature was at 105℃, and reaction time was only 1h. The conversion rate of Acetic Acid was analyzed by a gas chromatograph (GC-14C SHIMADZU in Japan)The experimental results showed that H2SO4 concentration had more influences on catalytic activity than other two factors, calcination temperature and ZrO2 supported content. Since sulfur absorbed on the surface of metal oxides is necessary to the acidity of SO42-/MxOy solid superacid,H2SO4 concentration in impregnation solution is needed enough high. But, it can't be too much high,otherwise, Zirconium sulfate formed on the catalyst surface will be harmful influences on catalytic activity. In researched cover, 0.5mol/L H2SO4 concentration is the most suitable, and the catalyst prepared with this concentration has very strong acidity.The optimum preparation condition is as follows: ZrO2 content 3.5g/g; calcination temperature 600℃, and H2SO4 concentration 0.5mol/L. In the catalyst prepared with above conditions, the acidic strength (H0) of the catalyst is smaller than ＜-14.52, and catalytic activity is 96.5 vol%. When it was re-used in esterification reaction, catalytic activity decreased gradually with re-used times increasing(seen in Table 1). But after catalyst is used repeatedly up to five times, catalytic activity (84.3 vol %)is still higher than that of H2SO4 catalyst.The X-ray diffraction patterns showed that ZrO2 supported in TiO2 belonged tetragonal zirconia phases. Through the calculation of Scherrer formula, the particle size of ZrO2 in the catalyst is about 12.5 nm. After SO42- promoted nanometer ZrO2/TiO2 compound carrier, the diffraction peaks of tetragonal zircoma become broader and the strength weaker. It shows that adding SO4 ions restrains the crystallization of ZrO2, diminishes the size of particles. This might be why SO42--ZrO2/TiO2 has high catalytic activity and stability in acidic catalysis reaction.     

Electrical conductances of aqueous Na2SO4, H2SO4, and their mixtures: limiting equivalent ion conductances, dissociation constants, and speciation to 673 K and 28 MPa

The electrical conductivities of aqueous solutions of Na(2)SO(4), H(2)SO(4), and their mixtures have been measured at 373-673 K at 12-28 MPa in dilute solutions for molalities up to 10(-2) mol kg(-1). These conductivities have been fit to the conductance equation of Turq et al.(1) with a consensus mixing rule and mean spherical approximation activity coefficients. Provided the concentration is not too high, all of the data can be fitted by a solution model that includes ion association to form NaSO(4)(-), Na(2)SO(4)(0), HSO(4)(-), H(2)SO(4)(0), and NaHSO(4)(0). The adjustable parameters of this model are the dissociation constants of the SO(4)(-) species and the H(+), SO(4)(-2), and HSO(4)(-) conductances (ion mobilities) at infinite dilution. For the 673 K and 230 kg m(-3) state point with the lowest dielectric constant, epsilon = 3.5, where the Coulomb interactions are the strongest, this model does not fit the experimental data above a solution molality of 0.016. Including the species H(9)(SO(4))(5)(-) gave satisfactory fits to the conductance data at the higher concentrations.     

Anion-dependent formation of helicates versus mesocates of triple-stranded M2L3 (M = Fe2+, Cu2+) complexes

A series of dinuclear triple-stranded complexes, [Fe(2)L(3)?X]X(6) [X = BF(4)(-) (1), ClO(4)(-) (2)], [Fe(2)L(3)?SO(4)](2)(SO(4))(5) (3), [Fe(2)L(3)?Br](BPh(4))(6) (4), Fe(2)L(3)(NO(3))Br(6) (5), and [Cu(2)L(3)?NO(3)](NO(3))(6) (6), which incorporate a central cavity to encapsulate different anions, have been synthesized via the self-assembly of iron(II) or copper(II) salts with the N,N'-bis[5-(2,2'-bipyridyl)methyl]imidazolium bromide (LBr) ligand. X-ray crystallographic studies (for 1-4 and 6) and elemental analyses confirmed the cagelike triple-stranded structure. The anionic guest is bound in the cage and shows remarkable influence on the outcome of the self-assembly process with regard to the configuration at the metal centers. The mesocates (with different configurations at the two metal centers) have formed in the presence of large tetrahedral anions, while helicates (with the same configuration at both metal centers) were obtained when using the relatively smaller spherical or trigonal-planar anions Br(-) or NO(3)(-).     

Acidity of mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2 materials: a combined solid-state NMR and theoretical calculation study

The acidity of mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2 materials was studied in detail by multinuclear solid-state NMR techniques as well as DFT quantum chemical calculations. The 1H MAS NMR experiments clearly revealed the presence of two different types of strong Br?nsted acid sites on both MoO(x)/ZrO2 and WO(x)/ZrO2 mesoporous materials, which were able to prontonate adsorbed pyrine-d5 (resulting in 1H NMR signals at chemical shifts in the range 16-19 ppm) as well as adsorbed trimethylphosphine (giving rise to 31P NMR signal at ca. 0 ppm). The 13C NMR of adsorbed 2-(13)C-acetone indicated that the average Br?nsted acid strength of the two mesoporous materials was stronger than that of zeolite HZSM-5 but still weaker than that of 100% H2SO4, which was in good agreement with theoretical predictions. The quantum chemical calculations revealed the detailed structures of the two distinct types of Br?nsted acid sites formed on the mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2. The existence of both monomer and oligomer Mo (or W) species containing a Mo-OH-Zr (or W-OH-Zr) bridging OH group was confirmed with the former having an acid strength close to zeolite HZSM-5, with the latter having an acid strength similar to sulfated zirconia. On the basis of our NMR experimental and theoretical calculation results, a possible mechanism was proposed for the formation of acid sites on these mesoporous materials.     

Efficient synthesis and sulfonation of ordered mesoporous carbon materials

Ordered mesoporous carbons (OMCs) with hexagonal structure were efficiently synthesized via cooperative self-assembly of phenol/formaldehyde resol and surfactant F127 under acidic aqueous conditions. Induced by HCl, a gel phase mainly containing phenol/formaldehyde resol and F127 was obtained within several hours. X-ray diffraction (XRD), transmission electron microscope (TEM) and nitrogen adsorption isotherms indicated that the synthesized samples possess 2-D hexagonal mesostructure. The influence of the synthesis conditions, including acid concentration and mass ratio of resol to F127, was investigated. When the acid concentration was fixed in the range of 0.6-2.0 M and the mass ratio of resol to F127 in the range of 3.5-4.0, highly ordered mesoporous carbon could be synthesized. The synthesized OMCs could be easily sulfonated in concentrated sulfuric acid at elevated temperature. The results indicate that the mesostructural stability and the content of the surface sulfonic acid (SO(3)H) groups depend mainly on the pyrolysis temperature of the OMCs and the sulfonation temperature, suggesting that the combination of pyrolysis and sulfonation temperature is essential for developing OMCs with high densities of SO(3)H groups.     

Construction of the multidecker anthracene-silver(I) system by intramolecular pi-pi interactions

As a continuation of the study on the construction of the multidecker aromatic compounds with pi-pi interactions, the anthracene derivatives 9,10-dimethylanthracene (dman), 9,10-diphenylanthracene (dpan), and 7,12-dimethylbenz[a]anthracene (dmban) have been studied toward complexation with the silver(I) ion. The crystal structures of [Ag(dman)(0.5)(p-xylene)(ClO(4))], [Ag(2)(dpan)(0.5)(C(6)H(6))(0.5)(CF(3)SO(3))(2)], and [Ag(2)(dmban)(2)(ClO(4))(2)](p-xylene), together with the metal-free ligand dpan, have been determined by single-crystal X-ray diffraction. These pi-electron-rich aromatic compounds are found to have great promise as an approach to the effective self-assembly of high nuclearity in a multilayer fashion.     

Light-induced metastable linkage isomers of ruthenium sulfur dioxide complexes

The irradiation of ruthenium-sulfur dioxide complexes of general formula trans-[Ru(II)(NH(3))(4)(SO(2))X]Y with laser light at low temperature results in linkage isomerization of SO(2), starting with eta(1)-planar S-bound to eta(2)-side S,O-bound SO(2). The solid-state photoreaction proceeds with retention of sample crystallinity. Following work on trans-[Ru(NH(3))(4)Cl(eta(1)-SO(2))]Cl and trans-[Ru(NH(3))(4)(H(2)O)(eta(1)-SO2)](C(6)H(5)SO(3))(2) (Kovalevsky, A. Y.; Bagley, K. A.; Coppens, P. J. Am. Chem. Soc. 2002, 124, 9241-9248), we describe photocrystallographic, IR, DSC, and theoretical studies of trans-[Ru(II)(NH(3))(4)(SO(2))X]Y complexes with (X = Cl(-), H(2)O, or CF(3)COO(-) (TFA(-))) and a number of different counterions (Y = Cl(-), C(6)H(5)SO(3)(-), Tos(-), or TFA(-)). Low temperature IR experiments indicate the frequency of the asymmetric and symmetric stretching vibrations of the Ru-coordinated SO(2) to be downshifted by about 100 and 165 cm(-1), respectively. Variation of the trans-to-SO(2) ligand and the counterion increases the MS2 decay temperature from 230 K (trans-[Ru(II)(NH(3))(4)(SO(2))Cl]Cl) to 276 K (trans-[Ru(II)(NH(3))(4)(SO(2))(H(2)O)](Tos)(2)). The stability of the MS2 state correlates with increasing sigma-donating ability of the trans ligand and the size of the counterion. Quantum chemical DFT calculations indicate the existence of a third eta(1)-O-bound (MS1) isomer, the two metastable states being 0.1-0.6 eV above the energy of the ground-state complex.     

SO_4~(2-)/ZrO_2催化剂上正丁烷异构化反应

考察了活化温度、反应温度、空速、Ｈ２／Ｃ４比和载Ｐｔ对ＳＯ２－４／ＺｒＯ２催化剂的正丁烷异构化反应活性和稳定性的影响．较高的Ｈ２／Ｃ４比可提高ＳＯ２－４／ＺｒＯ２催化剂的稳定性和稳态活性．催化剂负载Ｐｔ后，可降低反应原料中的Ｈ２／Ｃ４比．积炭是造成反应初始阶段催化剂迅速失活的主要原因，经烧炭再生以后这部分失活可以完全恢复     

Self-assembled NiO-ZrO2 nanocrystals with mesoscopic void space: an efficient and green catalyst for C-S cross-coupling reaction in water

New NiO-ZrO(2) nanocrystals (MNZ-1) with mesoscopic self-assembly have been synthesized by using a non-ionic surfactant as the structure directing agent (SDA) via evaporation induced self-assembly (EISA) method. Powder X-ray diffraction (PXRD), N(2) sorption study and transmission electron microscopic (TEM) image analyses revealed the cubic structure, mesoporosity and mesoscopic self-assembly of ca. 7.0 nm sized tiny nanocrystals in the material. MNZ-1 catalyzes the aerobic aryl-sulfur cross-coupling reactions for a series of aryl-iodides with 4-chlorothiophenol in environment friendly water medium at elevated as well as room temperature. Pure ZrO(2) mesoporous nanocrystals are inactive, whereas pure NiO nanocrystals showed much lower catalytic activity under similar reaction conditions. The MNZ-1 nanocatalyst is completely non-air sensitive, inexpensive and effective for the synthesis of a series of essential biomolecules derived from diaryl sulfides.     

Anion effect on the nanostructure of a metal ion binding self-assembling peptide

Effects of copper salts containing different anions (SO(4)(2)(-), Cl(-), and NO(3)(-)) on the self-assembly of a designed peptide EAK16(II)GGH with affinity for Cu(2+) have been investigated. The peptide secondary structure, self-assembled nanostructures, and surface activity were observed to depend strongly on the type of anion. Over a salt concentration range from 0.05 to 10.0 mM, SO(4)(2)(-) induced long fiber formation, whereas Cl(-) and NO(3)(-) caused short fiber formation. The fiber length increased with copper sulfate concentration, but the concentration of copper chloride and copper nitrate did not affect the peptide nanostructures significantly. Analysis by Fourier transform infrared spectroscopy (FTIR) revealed that the addition of the copper salts tended to cause the peptide conformation to change from alpha-helix/random coil to beta-sheet, the extent to which depended on the anion type. This evidence of the anion effect was also supported by surface tension measurements using the axisymmetric drop shape analysis-profile (ADSA-P) technique. An explanation for the effect of anions on the peptide self-assembly was proposed. The divalent anion SO(4)(2)(-) might serve as a bridge by electrostatically interacting with two lysine residues from different peptide molecules, promoting beta-sheet formation. The extensive beta-sheet formation may further promote peptide self-assembly into long fibers. On the other hand, monovalent anions Cl(-) and NO(3)(-) may only electrostatically interact with one charged residue of the peptide; hence, a mixed secondary structure of alpha-helix/random coil and beta-sheet was observed. This observation might explain the predominant formation of short fibers in copper chloride and copper nitrate solutions.     

Preparation of mesostructured barium sulfate with high surface area by dispersion method and its characterization

The spherical and cubic mesoporous BaSO(4) particles with high surface area were successfully produced via one-step process through precipitation reaction in aqueous solution of Ba(OH)(2) and H(2)SO(4) with ethylene glycol (n-HOCH(2)CH(2)OH) as a modifying agent. The BaSO(4) nanomaterial revealed that the high surface area and the mesoporous was stable up to 400 degrees C. Agglomerate mesoporous barium sulfate nanomaterials were obtained by the reaction of Ba(2+) and SO(2-)(4) with ethylene glycol aqueous solution. The ethylene glycol was used to control the BaSO(4) particle size and to modify the surface property of the particles produced from the precipitation. The dried and calcined mesoporous BaSO(4) nanomaterials were characterized by X-ray diffraction (XRD), BET surface area and N(2) adsorption-desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared resonance (FTIR) and thermogravimetric analysis (TGA). The as-prepared mesoporous dried BaSO(4) possesses a high BET surface area of 91.56 m(2) g(-1), pore volume of 0.188 cm(3) g(-1) (P/P(0)=0.9849) and pore size of 8.22 nm. The SEM indicates that the morphology of BaSO(4) nanomaterial shows shell like particles up to 400 degrees C, after that there is drastically change in the material due to agglomeration. Synthesis of mesoporous BaSO(4) nanomaterial is of significant importance for both sulphuric acid decomposition and oxidation of methane to methanol.     

Subtle role of polyatomic anions in molecular construction: structures and properties of AgX bearing 2,4'-thiobis(pyridine) (X(-) = NO(3)(-), BF(4)(-), ClO(4)(-), PF(6)(-), CF(3)CO(2)(-), and CF(3)SO(3)(-))

Studies on the subtle effects and roles of polyatomic anions in the self-assembly of a series of AgX complexes with 2,4'-Py(2)S (X(-) = NO(3)(-), BF(4)(-), ClO(4)(-), PF(6)(-), CF(3)CO(2)(-), and CF(3)SO(3)(-); 2,4'-Py(2)S = 2,4'-thiobis(pyridine)) have been carried out. The formation of products appears to be primarily associated with a suitable combination of the skewed conformers of 2,4'-Py(2)S and a variety of coordination geometries of Ag(I) ions. The molecular construction via self-assembly is delicately dependent upon the nature of the anions. Coordinating anions afford the 1:1 adducts [Ag(2,4'-Py(2)S)X] (X(-) = NO(3)(-) and CF(3)CO(2)(-)), whereas noncoordinating anions form the 3:4 adducts [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = ClO(4)(-) and PF(6)(-)). Each structure seems to be constructed by competition between pi-pi interactions of 2,4'-Py(2)S spacers vs Ag.X interactions. For ClO(4)(-) and PF(6)(-), an anion-free network consisting of linear Ag(I) and trigonal Ag(I) in a 1:2 ratio has been obtained whereas, for the coordinating anions NO(3)(-) and CF(3)CO(2)(-), an anion-bridged helix sheet and an anion-bridged cyclic dimer chain, respectively, have been assembled. For a moderately coordinating anion, CF(3)SO(3)(-), the 3:4 adduct [Ag(3)(2,4'-Py(2)S)(4)](CF(3)SO(3))(3) has been obtained similarly to the noncoordinating anions, but its structure is a double strand via both face-to-face (pi-pi) stackings and Ag.Ag interactions, in contrast to the noncoordinating anions. The anion exchanges of [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = BF(4)(-), ClO(4)(-), and PF(6)(-)) with BF(4)(-), ClO(4)(-), and PF(6)(-) in aqueous media indicate that a [BF(4)(-)] analogue is isostructural with [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = ClO(4)(-) and PF(6)(-)). Furthermore, the anion exchangeability for the noncoordinating anion compounds and the X-ray data for the coordinating anion compounds establish the coordinating order to be NO(3)(-) > CF(3)CO(2)(-) > CF(3)SO(3)(-) > PF(6)(-) > ClO(4)(-) > BF(4)(-).     

H-bonding dependent structures of (NH4+)3H+(SO4 2-)2. Mechanisms of phase transitions

The role of different H-bonds in phases II, III, IV, and V of triammonium hydrogen disulfate, (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2), has been studied by X-ray diffraction and (1)H solid-state MAS NMR. The proper space group for phase II is C2/c, for phases III and IV is P2/n, and for phase V is P onemacr;. The structures of phases III and IV seem to be the same. The hydrogen atom participating in the O(-)-H(+).O(-) H-bond in phase II of (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2) at room temperature is split at two positions around the center of the crucial O(-)-H(+).O(-) H-bonding, joining two SO(4)(2)(-) tetrahedra. With decreasing temperature, it becomes localized at one of the oxygen atoms. Further cooling causes additional differentiation of possibly equivalent sulfate dimers. The NH(4)(+) ions participate mainly in bifurcated H-bonds with two oxygen atoms from sulfate anions. On cooling, the major contribution of the bifurcated H-bond becomes stronger, whereas the minor one becomes weaker. This is coupled with rotation of sulfate ions. In all the phases of (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2), some additional, weak but significant, reflections are observed. They are located between the layers of the reciprocal lattice, suggesting possible modulation of the host (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2) structure(s). According to (1)H MAS NMR obtained for phases II and III, the nature of the acidic proton disorder is dynamic, and localization of the proton takes place in a broader range of temperatures, as can be expected from the X-ray diffraction data.     

First steps towards dissolution of NaSO4- by water

NaSO(4)(-)(H(2)O)(n) (n = 0-4) clusters have been generated in the gas phase as model systems to simulate the first dissolution steps of sulfate salts in water; photoelectron spectroscopy and theoretical calculations indicate that the first three water molecules strongly interact with both Na(+) and SO(4)(2-), forming a three-water solvation ring to start to pry apart the Na(+)SO(4)(2-) contact ion pair.     

大孔SO42-/ZrO2-SiO2复合固体酸制备及催化性能

利用浸渍水解法在大孔SiO2载体上组装固体酸制备出大孔径SO42-/ZrO2-SiO2复合固体酸催化剂。用扫描电镜、红外光谱仪和粉末X射线衍射仪等对其进行表征,结果表明:大孔SiO2载体的毛细管效应促使ZrO2以纳米薄层方式均匀地沉积在SiO2薄层表面,并抑制了ZrO2晶体的生长和晶相的转变,载体的大孔全连通的结构赋予该复合材料高的通透性(孔径在1~2μm)、两面活性点和大的比表面积(约156 m2.g-1)。Hammett指示剂法测得经550℃焙烧后产物的酸强度H0值小于-13.75,属于固体超强酸。以乙酸正丁酯的合成为探针反应考察硫酸浸渍液浓度、焙烧温度等制备条件对其催化活性的影响,结果表明,该SO42-/ZrO2-SiO2固体酸具有较好的催化活性,当焙烧温度为550℃和硫酸浸渍液浓度为1.5 mol.L-1时,超强酸对酯化反应的催化酯化率达到97%。