Adsorption of Water and Methanol on a NaZSM-5 Zeolite. A temperature-programmed desorption (TPD) study

Using temperature-programmed desorption (TPD), we have investigated the desorption behavior after subsequent co-adsorption of methanol and water and after adsorption of their mixtures on a NaZSM-5 zeolite. The course of desorption indicates that a strong mutual displacement of both components occurs. However, on the strongest adsorption sites methanol is preferentially adsorbed, and already the addition of small amounts of methanol leads to a displacement of water. Our results support the idea of a subdivision of the pore space for adsorption of water/methanol mixtures. Above all, the experiments show that in the part of the pore space where both components are adsorbed, different sites are of importance which vary significantly in their interaction strength. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of the acidic properties of zeolites by means of temperature-programmed desorption (TPD) of ammonia

Desorption energy distributions were calculated for temperature-programmed desorption (TPD) of ammonia from H zeolites of different type by means of regularization. This method does not require any limiting assumptions about the distribution function. It could be shown that the desorption energy distributions obtained are nearly independent of the experimental conditions and therefore they should represent a suitable measure for the distribution of the strength of acidic sites. The calculated desorption energy distributions for the ammonia desorption from the isolated bridging SiOHAl groups of H zeolites of different type significantly differ from each other in shape. The increase of the desorption energy of the main range of the distribution functions correlates well with the increase of the average acid strength of the SiOHAl groups with decreasing Al content of the zeolites.     

Heterogeneity of OH Groups in H-Mordenites TPD and IR studies of ammonia desorption

We have investigated the temperature-programmed desorption (TPD) of ammonia during the activation of NH4Na-mordenites of different exchange degrees. Using a regularization method, desorption energy distribution functions have been calculated. The obtained results indicate the heterogeneity of the bridging Si-OH-Al groups in HNa-mordenites. This was concluded from the width of the distribution functions and from the presence of submaxima. For HNa-mordenites of exchange degrees below 50%, containing only hydroxyls in the broad channels, two distinct submaxima are present, thus suggesting the presence of at least two kinds of bridging hydroxyls of various acid strengths. In HNa-mordenites of exchange degrees above 50%, the hydroxyls appear in narrow channels and the distribution of ammonia desorption energy broadens on the side of higher energies. This may be related to a strong stabilization of ammonium ions inside narrow channels. The maximum concentrations of hydroxyls of desorption energies between 95 and 135 kJ mol_-1 and between 135 and 165 kJ mol_-1 calculated from TPD data were 3.9 and 3.3 OH per unit cell (u.c.). These values agree well with our previous IR results of concentrations of hydroxyls in broad and in narrow channels (3.7 and 2.8 OH per u.c.). The TPD data obtained for the heterogeneity of OH groups in HNa-mordenites are in accordance with the IR data concerning ammonia desorption. The IR band of OH groups restoring upon saturation of all the hydroxyls with ammonia and subsequent step-by-step desorption at increasing temperatures shifts to lower frequencies indicating that there are hydroxyls of various acid strengths and the less acidic hydroxyls restore first at lower desorption temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of the Alkali-Metal Cations On the Protonation Constants of Myo-Inositol Hexakis(Phosphate)

Abstract

Values for the protonation constants of myo-inositol hexakis(phosphate) have been determined at 25°C and 0.1 M ionic strength by potentiometry in media containing two different concentrations of Li⁺, Na⁺, K⁺ and Cs⁺ salts.

The Alog K_yHM values, which correspond to the differences between the constants obtained with and without alkali-metal cations, are considered as being related to the binding ability of the ligand towards these cations.

Their relative behaviour is then analysed and some conclusions are drawn about the conformations which might be adopted by the complexes in different pH regions.     

原位程序升温脱附(TPD)方法的建立及其应用实例

介绍了在ＶＧＥＳＣＡＬＡＢ２１０电子能谱仪上自己研制组装的用于研究单晶金属表面吸附层的原位ＴＰＤ装置。研制的单晶样台采用钽丝加热，最高加热速度可达３０Ｋ／ｓ，线性升温范围－１００－１００℃，最高可达１０００℃以上。     

XPS,AFM, ATR and TPD evidence for terraced,dihydrogen terminated, 1×1 (100) silicon

Heating (100) silicon at high temperature (say, higher than 850 °C) in H₂, cooling to 670–700 °C in the same ambient, and quenching to room temperature in N₂ results in environmentally robust, terraced 1 × 1 (100) SiH₂. Evidence for this conclusion is based on angle‐resolved x‐ray photoelectron spectroscopy, atomic force microscopy, infrared absorption spectroscopy in the attenuated total reflection mode, thermal programmed desorption, and reflection high‐energy electron diffraction. Copyright © 2005 John Wiley & Sons, Ltd.     

Meso-四(对烷氧苯基)卟啉金属银配合物的激光解吸电离飞行时间质谱表征

通过激光解吸电离飞行时间质谱对meso-四(对烷氧苯基)卟啉金属银配合物进行了表征.样品溶解在氯仿中,以正离子方式记录谱图,结果发现除了产生目标化合物分子离子峰外,没有任何碎片峰.激光解吸电离飞行时间质谱是表征这种meso-四(对烷氧苯基)卟啉金属银配合物有效的方法.     

A study on the reduction behayior of Fe_2(MoO_4)_3 with a combined in-situ temperature-programmed reduction- Mossbauer spectroscopic technique

In H2/N2 atmosphere, the reduction behavior of the stoichiometric compound, Fe2(MoO4)3, was studied by in-situ Mossbauer spectroscopy (in-situ MBS), temperature-programmed reduction (TPR) and X-ray diffraction (XRD). The results showed that the reduction products, β-FeMoO4, Mo4O11, MoO2, Fe3O4, Fe2Mo3O8, Fe and Mo, as well as iron-molybdenum alloys, were formed subsequently when the reduction temperature was raised. It was found that when Mo6+ were reduced to Mo4+, Fe2+ were oxidized to Fe3+. Due to the interactions among the metal ions and the electron transfers, the reduction processes of the metal ions in Fe2(MoO4)3 are very complex. According to the results of XRD and MBS obtained at various TPR stages, the reaction equations for the reduction stages were proposed. The Mossbauer spectrum of an intermediate species, Fe2Mo3O8, was found to exhibit two doublets, with I.S.=0.90mm/s and Q.S. =0.58 mm/s, and I.S. = 1.02mm/s and Q.S. = 1.04mm/s, respectively.     

A calorimetric study ofN,N-dimethylformamide complexes of copper(II) in acetonitrile

Complex formation of copper(II) with N,N-dimethylformamide(DMF) has been investigated calorimetrically in acetonitrile at 25°C. Calorimetric titration curves obtained are explained in terms of formation of [Cu(dmf) _n ]²⁺ (n=1–4, 6) and their formation constants, enthalpies and entropies were determined. Formation of [Cu(dmf)₅]²⁺ is uncertain. The stepwise enthalpies S ₃ ⁰ and entropies S _n ⁰ at each consecutive step are all negative except for S ₃ ⁰ . The overall enthalpies of formation of [Cu(dmf)₆]²⁺ is –(77.8±5.4) kJ-mol^–1, which is compared with the enthalpy of transfer of copper(II) ion, H _t ^o =–79.7 kJ-mol^–1, from acetonitrile to DMF.     

TPD study of NH3 adsorption/desorption on the surface of V/Ti, V/Al based catalysts for selective catalytic reduction of NOx by ammonia 1. TPD test of γ-Al2O3, TiO2 (anatase) and alumina-supported vanadia catalysts

The effect of temperature on the adsorption/desorption of ammonia from the air mixture on the surface of γ-Al₂O₃, TiO₂ (anatase) and alumina-supported vanadia catalyst samples has been investigated using temperature-programmed desorption (TPD). When the vanadia loading was increased, the fraction of the acid sites providing the NH₃ adsorption in the high-temperature state decreased. At the same time, the fraction of the medium temperature state significantly increased.     

The interaction between n-alkyl trimethylammonium bromides with poly(l-aspartate): a thermodynamics study

Specific conductivities of a homologous series of n-alkyl trimethylammonium bromides (C₈,C₁₀,C₁₂ and C₁₄TABs) in the presence of poly(l-aspartate) in glycine buffer at pH 3.2 and 25 ^∘C have been measured over a range of C _n TAB concentrations. From the conductivity changes, the number of surfactant molecules absorbed onto the polymer, the Gibbs free energies of adsorption and the equilibrium constants have been calculated. A statistical thermodynamics analysis was used to obtain the Gibbs free energies of adsorption. The results obtained using both methods are compared and analysed. Received: 15 December 1999 Revised form: 29 February 2000 Accepted: 3 March 2000     

The influence of promoters and poisons on carbon monoxide adsorption on Rh(100): a DFT study.

Density functional theory calculations were performed to determine the pairwise lateral interaction energies between carbon monoxide and coadsorbed elements from the first three rows of the periodic table on a Rh(100) surface. The atoms were placed in a c(2x2) arrangement of fourfold hollow sites and the carbon monoxide probe molecule in a p(2x2) arrangement, so that each CO molecule had four atoms as nearest neighbours. The alkali atoms show an attractive interaction with CO while the other atoms show a repulsive interaction. For second-row elements the maximum repulsion is at nitrogen and for third-row elements at sulphur. Attempts to correlate the interaction energies with properties of the system, such as electronegativity, distances, or change in work function, failed, which implies that each combination of adsorbates needs to be calculated separately.     

A robust in vitro Anticancer,Antioxidant and Antimicrobial Agents Based on New Metal-Azomethine Chelates Incorporating Ag(I), Pd (II) and VO (II) Cations: Probing the Aspects of DNA Interaction

A novel azomethine ligand (HNAP) [HNAP = 1-(Pyridin-3-yliminomethyl)-naphthalen-2-ol] and its Ag(I), Pd (II) and VO (II) chelates have been synthesized and structurally inspected using a wide range of spectroscopic and analytical tools, including infra-red (IR), ultraviolet-visible (UV-Vis) and ¹H NMR spectroscopy techniques, CHN analysis, molar conductance, magnetic susceptibility, and thermogravimetric analysis. The molar conductance measurements reveal that the chelates are non-electrolytes. The thermal behavior of the investigated metal chelates shows that the hydrated, coordinated water molecules and the anions are removed in successive steps followed immediately by decomposition of the ligand in the subsequent steps. The activation thermodynamic parameters are calculated from the TG curves and discussed. Complexes formation study via continuous variation m molar ratio has been investigated, and results were consistent to those found in the solid complexes with a ratio of (M:L) as (1:1) or 1:2 (M:L) molar ratio for all the monolithic and bi-valent metal complexes with square planar for Pd (II), and Ag(I) cations while, square pyramidal geometry for VO (II) cation. DFT calculations for the titled different metal-chelates have been studied and showed a good correlation with the experimental data. The prepared compounds had been checked In vitro towards numerous sorts of plant pathogenic fungi and bacteria to evaluate their antimicrobial properties and compared with some known antibiotics. Significantly, all the complexes show excellent antimicrobial activity against various strains of bacteria and fungi, including both Gram-negative and Gram-positive bacteria. Besides, the complexes exhibited high cytotoxicity against various carcinoma cell lines, including HCT-116, MCF-7, and HepG-2. Moreover, the effect of the new synthesized compounds as antioxidants was determined by reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH) and compared with that of Vitamin C. Furthermore, the binding interactions of the complexes with CT-DNA were explored using UV-Vis spectroscopy, viscosity and gel electrophoreses measurements. They cooperatively bind to DNA possibly through intercalations. The binding ability of the complexes was shown as HNAPAg > HNAPPd > HNAPVO complex.     

Synthesis and Characterization of Bridged Bimetallic Complexes. I. Copper(II) Complexes with Conjugated Diimine Ligands

A series of binucleating Uganda with fully conjugated π-systems have been synthesized. Homobinuclear copper(II) complexes of the form [(Cu(dien)ClO₄)₂L]-(ClO₄)₂, where dien is diethylenetriamine and L is binucleating ligand, were prepared. Mononuclear complexes, with structure similar to that of the preceeding compounds, [Cu(dien)L′(ClO₄)](ClO₄) were synthesized as reference compounds. The infrared spectra, elctronic spectra and magnetic properties were studied. The inductive effect, steric effect and the effect of the length of the conjugated π-system on the magnetic exchange interaction between the two copper ions are discussed. The electrochemical properties of these complexes were investigated by cyclic voltammetry. The copper ions showed the cooperative phenomena and a quasi-reversible sequential transfer of two electrons at the same potential.     

On-site determination of polynuclear aromatic hydrocarbons in seawater by stir bar sorptive extraction (SBSE) and thermal desorption GC-MS

The identification and quantification of semi-volatile contaminants dissolved in water is currently done in laboratory after a sampling step. This procedure is not satisfactory first because risks of samples contamination and analytes losses remain, in particular when these are present in ultra-trace concentrations, and secondly because procedures are time-consuming. The coupling of the stir bar sorptive extraction (SBSE), a new device of extraction technique, and a new generation of gas chromatography mass spectrometry (GC-MS), the field apparatus EM 640 S from Bruker, could be an answer to the challenge of on-site analysis. This analytical system was used to analyze 24 PAHs, among them 15 EPA priority pollutants. It was shown that this coupling led to encouraging results with LODs around the sub-ppt level for most of the compounds and R.S.D. included between 1 and 48%. The existence of competition phenomena between the various analytes inside the absorbent phase was demonstrated with the release (up to 80%) of light compounds. This result shows the necessity to work on the kinetic domain rather than on the thermodynamic equilibrium that is influenced by nature and concentration of other compounds. The matrix effects were also studied through the comparative analysis of ultrapure water, artificial and natural seawaters spiked with PAHs and the influence of ionic strength and particulate organic matter was investigated.     

Counterion binding induces attractive interactions between negatively-charged self-assembled monolayer of 3-mercaptopropionic acid on Au(111) in reductive desorption

The electrochemical reductive desorption of the self-assembled monolayers of 3-mercaptopropionic acid in an aqueous alkaline solution gives a sharp peak with the full width at half maximum of about 20 mV irrespective of the type of cations in a linear scan voltammogram. This suggests that a strong attractive interaction exists between negatively charged carboxylate groups in the self-assembled monolayer surface due to the counterion binding, which not only simply stabilizes the adsorbed carboxylates but also makes the interaction between the adsorbed thiolates even attractive possibly by forming a two-dimensional ionic crystal. The effect of tetraalkylammonium ions on the shape of the voltammograms was also examined. Dedicated to Professor Oleg Petrii on the occasion of his 70th birthday.     

A MALDI‐TOF MS study of lanthanide(III)‐cored poly(phenylenevinylene) dendrimers

An extensive study by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry (MS) of some first‐generation and second‐generation lanthanide(III)‐cored poly(phenylenevinylene) dendrimers is described. The complexes were obtained by self‐assembly of suitably functionalized carboxylate dendrons around the lanthanide ion (La³⁺, Er³⁺). Fourier transform infrared (FT‐IR) spectroscopy gave reasonable evidence for the proposed structures. However, MS was used to ascertain unequivocally the complex formation. The most reliable results were found in the negative reflector mode, using 2‐[(2E)‐3‐(4‐tert‐butylphenyl)‐2‐methylprop‐2‐enylidene]malononitrile (DCTB) as matrix. Well‐defined and highly resolved base peaks corresponding to negative ions of [Gn₄La]^? and [Gn₄Er]^? were found in all cases, with an excellent match between the theoretical and observed isotope distributions. However, the 3 : 1 stoichiometry used in the synthesis guarantees an empirical formula Gn₃Ln for the complexes. Copyright © 2008 John Wiley & Sons, Ltd.     

C_（60）分子间相互作用势及其晶体压缩系数的计算

根据Ｃ（６０）晶体升华焓的实验值求得了Ｃ（６０）分子间相互作用势的解析表达式。用该表达式计算了Ｃ（６０）分别为面心立方和六方晶格时晶体的结合能，讨论了不同晶格的稳定性问题，解释了Ｃ（６０）晶体一般是面心立方的原因。本文还根据Ｃ（６０）分子间相互作用势计算了Ｃ（６０）晶体的压缩系数，并与文献的实验值进行了比较，所得结果与实验值相符合。