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Sung Hwan Yoon Chaminda M. Gamage Kent J. Gillig Vicki H. Wysocki 《Journal of the American Society for Mass Spectrometry》2009,20(6):957-964
The implementation of surface-induced dissociation (SID) to study the fast dissociation kinetics (sub-microsecond dissociation)
of peptides in a MALDI TOF instrument has been reported previously. Silicon nanoparticle assisted laser desorption/ionization
(SPALDI) now allows the study of small molecule dissociation kinetics for ions formed with low initial source internal energy
and without MALDI matrix interference. The dissociation kinetics of N(CH3)4+ and N(CD3)4+ were chosen for investigation because the dissociation mechanisms of N(CH3)4+ have been studied extensively, providing well-characterized systems to investigate by collision with a surface. With changes
in laboratory collision energy, changes in fragmentation timescale and dominant fragment ions were observed, verifying that
these ions dissociate via unimolecular decay. At lower collision energies, methyl radical (CH3) loss with a sub-microsecond dissociation rate is dominant, but consecutive H loss after CH3 loss becomes dominant at higher collision energies. These observations are consistent with the known dissociation pathways.
The dissociation rate of CH3 loss from N(CH3)4+ formed by SPALDI and dissociated by an SID lab collision energy of 15 eV corresponds to log k = 8.1, a value achieved by
laser desorption ionization (LDI) and SID at 5 eV. The results obtained with SPALDI SID and LDI SID confirm that (1) the dissociation
follows unimolecular decay as predicted by RRKM calculations; (2) the SPALDI process deposits less initial energy than LDI,
which has advantages for kinetics studies; and (3) fluorinated self-assembled monolayers convert about 18% of laboratory collision
energy into internal energy. SID TOF experiments combined with SPALDI and peak shape analysis enable the measurement of dissociation
rates for fast dissociation of small molecules. 相似文献
3.
Methanol Adsorption on TiO2 Film Studied by Sum Frequency Generation Vibrational Spectroscopy (cited:2) 下载免费PDF全文
A broadband infrared surface sum frequency generation vibrational spectroscopy (SFG-VS) and an in situ UV excitation setup devoted to studying surface photocatalysis have been constructed. With a home-made compact high vacuum cell, organic contaminants on TiO2 thin lm surface prepared by RF magnetron sputtering were in situ removed under 266 nm irradiation in 10 kPa O2 atmosphere. We obtained the methanol spectrum in the CH3 stretching vibration region on TiO2 surface with changing the methanol pressure at room temperature. Features of both molecular and dissociative methanol, methoxy, adsorbed on this surface were resolved. The CH3 symmetric stretching vibration frequency and Fermi resonance of molecular methanol is red-shifted by about 6?8 cm-1 from low to high coverage. Moreover, the recombination of dissociative methanol and H on surfaces in vacuum was also observed. Our results suggest two equilibria exist: between molecular methanol in the gas phase and that on surfaces, and between molecular methanol and dissociative methanol on surfaces. 相似文献
4.
The method of pyridine temperature-programmed desorption (TPD) was applied for the measurement of acid properties of in situ reduced copper catalysts on silicate support. A thermal-conductivity detector (TCD) was used for the detection of TPD spectra of pyridine. The combination of flame-ionization detector and thermal conductivity detector shows that the region of TPD spectrum with the peak maxima TMAX1 = 350 °C is a superposition of the TCD response on spectra of desorbed pyridine, water and carbon dioxide, desorbing simultaneously from the catalyst surface. The method for the elimination of H2O and CO2 on the layer of NaOH was tested and the pure TPD spectrum of pyridine was obtained. The exact determination of pyridine concentration allows to estimate the amount of weak and medium acid centers of the catalyst. The gas chromatography with the mass spectroscopy (GC–MS) analyses was used for the interpretation of high temperature region of the pyridine TPD spectra (TMAX2 = 620 °C). It was found that pyridine bonded on the strong acid centers is decomposed to N2 and CO under very high temperature. The available chromatographic method for the separation of components present in pyridine TPD spectrum in the high-temperature region was suggested. The method for the quantification of strong acidity of copper-supported catalyst was found. 相似文献
5.
H. Shinohara H. Sato F. Misaizu K. Ohashi N. Nishi 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):197-200
Metastable uni-cluster dissociation for several hydrogen-bonded and van der Waals cluster ions are observed via resonance-enhanced two-photon ionization reflectron time-of-flight (TOF) mass spectrometry. All of the cluster ions studied show evaporation of a single molecule from the respective parent cluster ions as dominant metastable decay processes. Furthermore, the averaged metastable evaporation rate constants (k evap) of these cluster ions in a fixed time domain of 0.2–50 µs are obtained by analyzing the relative intensity of metastable ion peaks due to evaporation in the acceleration and the field-free drift regions of the TOF mass spectrometer. An intensity anomaly in some of the observed metastable ion peaks, indicative of magic number stability of the cluster ion, is also presented. 相似文献
6.
Grady R. Blacken Michael Volný Matthew Diener Karl E. Jackson Pratistha Ranjitkar Dustin J. Maly František Tureček 《Journal of the American Society for Mass Spectrometry》2009,20(6):915-926
Zirconium, titanium, and hafnium oxide-coated stainless steel surfaces are fabricated by reactive landing of gas-phase ions
produced by electrospray ionization of group IVB metal alkoxides. The surfaces are used for in situ enrichment of phosphopeptides
before analysis by matrix-assisted laser desorption ionization (MALDI) mass spectrometry. To evaluate this method we characterized
ZrO2 (zirconia) surfaces by (1) comparison with the other group IVB metal oxides of TiO2 (titania) and HfO2 (hafnia), (2) morphological characterization by SEM image analysis, and (3) dependence of phosphopeptide enrichment on the
metal oxide layer thickness. Furthermore, we evaluated the necessity of the reactive landing process for the construction
of useful metal oxide surfaces by preparing surfaces by electrospray deposition of Zr, Ti, and Hf alkoxides directly onto
polished metal surfaces at atmospheric pressure. Although all three metal oxide surfaces evaluated were capable of phosphopeptide
enrichment from complex peptide mixtures, zirconia performed better than hafnia or titania as a result of morphological characteristics
illustrated by the SEM analysis. Metal oxide coatings that were fabricated by atmospheric pressure deposition were still capable
of in situ phosphopeptide enrichment, although with inferior efficiency and surface durability. We show that zirconia surfaces
prepared by reactive landing of gas-phase ions can be a useful tool for high throughput screening of novel phosphorylation
sites and quantitation of phosphorylation kinetics. 相似文献
7.
Shinji Tomoda Yohji Achiba Katsunori Nomoto Kenji Sato Katsumi Kimura 《Chemical physics》1983,74(1):113-120
In this paper we describe several characteristics of our supersonic nozzle beam photoelectron spectrometer recently constructed for studying hydrogen-bonded dimers in the gas phase by HeI (58.4 nm) radiation. Using this photoelectron apparatus, we have reinvestigated the HeI photoelectron spectrum of the formic-acid dimer (HCOOH)2 which is well known as a fairly strong doubly hydrogen-bonded dimer. It was found that the (HCOOH)2 spectrum deduced here from the spectrum of the monomer—dimer mixture considerably differs from that reported by Carnovale et al. in the region beyond 16.5 eV. New spectral assignments are given for four ionization bands beyond 16.5 eV. It is also indicated that the lower bound of the dissociation energy of (HCOOH)2+ is estimated to be 1.0 ± 0.1 eV from the threshold of the dimer band (11.0 eV) obtained in this experiment. This value is considerably smaller than the value of 1.7 ± 0.2 eV recently reported for the water dimer cation (H2O)2+. 相似文献
8.
Y. Zhang M. Späth W. Krätschmer M. Stuke 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,23(3):195-196
Delayed ionization is found to be absent for sub-picosecond laser excitation of free C60 and C70 at 248 nm. The autocorrelation trace obtained for C 60 + in a laser time-of-flight (TOF) mass spectrometer using two time-delayed and collinear 248 nm ultrashort laser pulses has a width of 1.1 ps (715 fs for sech2 pulses), in agreement with the laser pulse duration measurement in NO gas. Both above observations can be explained by direct ionization of C60 via coherent two-photon absorption by the high intensity sub-picosecond 248 nm laser excitation avoiding the channel leading to delayed ionization. 相似文献
9.
J. H. Liu L. P. Wang Q. M. Xiao Z. Yao H. Ding 《Plasma Chemistry and Plasma Processing》2010,30(3):349-361
This work reports laser ionization combined with Time-Of-Flight (TOF) mass spectrometry investigation on intermediate species
in the hydrocarbon plasma of atmospheric-pressure fast-flow pulsed dc-discharge. All neutral intermediate species including
transient radicals from benzene/Ar discharge have been characterized by a molecular beam sampling combined with TOF mass spectrometry.
This shows that with a hydrocarbon gas mixture of 0.3% C6H6 in Ar discharge the intermediate species consist of simple radicals (such as C2, C5H5, C7H7) and polycyclic organic molecules (C10H8, C13H10, C14H10). Theoretical studies on total energies and ionization potentials of the intermediate species have been carried out using
the hybrid density functional theory. Effect of the ionization potential on mass spectral intensity has been discussed. Based
on the observed data, the possible major neutral reaction channels of the plasma chemistry have been discussed. The developed
experimental method has implications in volatile organic compounds removing and impurities diagnosis in Tokamak edge-plasma. 相似文献
10.
Breanna M. Wong Greg Collinge Alyssa J.R. Hensley Yong Wang Jean-Sabin McEwen 《Progress in Surface Science》2019,94(2):100538
Bimetallic catalysts have demonstrated properties favorable for upgrading biofuel through catalytic hydrodeoxygenation. However, the design and optimization of such bimetallic catalysts requires the ability to construct accurate, predictive models of these systems. To generate a model that predicts the kinetic behavior of benzene adsorbed on Pt (1 1 1) and a Pt3Sn (1 1 1) surface alloy (Pt3Sn (1 1 1)), the adsorption of benzene was studied for a wide range of benzene coverages on both surfaces using density functional theory (DFT) calculations. The adsorption energy of benzene was found to correlate linearly with benzene coverage on Pt (1 1 1) and Pt3Sn (1 1 1); both surfaces exhibited net repulsive lateral interactions. Through an analysis of the d-band properties of the metal surface, it was determined that the coverage dependence is a consequence of the electronic interactions between benzene and the surface. The linear coverage dependence of the adsorption energy allowed us to quantify the influence of the lateral interactions on the heat of adsorption and temperature programmed desorption (TPD) spectra using a mean-field model. A comparison of our simulated TPD to experiment showed that this mean-field model adequately reproduces the desorption behavior of benzene on Pt (1 1 1) and Pt3Sn (1 1 1). In particular, the TPD correctly exhibits a broadening desorption peak as the initial coverage of benzene increases on Pt (1 1 1) and a low temperature desorption peak on Pt3Sn (1 1 1). However, due to the sensitivity of the TPD peak temperature to the desorption energy, precise alignment of experimental and theoretical TPD spectra demands an accurate calculation of the adsorption energy. Therefore, an analysis of the effect of the exchange-correlation functional on TPD modeling is presented. Through this work, we show the necessity of incorporating lateral interactions into theoretical models in order to correctly predict experimental behavior. 相似文献
11.
《Radiation Physics and Chemistry》2003,66(1):27-33
The adsorption of methanol on γ-irradiated and un-irradiated SiO2 surfaces pretreated at 473 K was investigated by Fourier transform infrared spectroscopy, temperature programmed desorption (TPD) and pulse methods. Methanol adsorbed only in molecular form on the un-irradiated sample. Treating the pre-irradiated silica surface with methanol at room temperature formaldehyde and hydrogen were formed. The methanol adsorbed on the irradiated silica transformed to formyl groups during a longer time at room temperature and desorbed as formaldehyde simultaneously with CH3OH (Tmax=395 K) on the TPD. 相似文献
12.
Yu. S. Nekrasov N. S. Ikonnikov Yu. A. Belousov S. S. Kiselev 《Journal of Analytical Chemistry》2011,66(13):1291-1297
We have studied the behavior of ferrocene CpFeCp (FcH), ferrocenium triiodide [FcH]+I3−, dimethylaminomethylferrocene FcCH2NMe2 and its trimethylammonium salt [FcCH2NMe3]+I− under the conventional conditions of electrospray ionization (ESI), when the substance solution is subjected to spraying,
and in two versions of desorption electrospray ionization (DESI), when the sprayed solvent bombards the surface of solid or
liquid samples. In addition to these techniques, the behavior of neutral compounds under conditions of electrospray ionization
of vapors of the studied compounds in a gas phase (ESI_V) has been investigated. It has been shown using the examples of ferrocene
and its dimethylaminomethyl derivative that the detection limits for these compounds occurring in a gas phase are comparable
within an order of magnitude with their detection limits under the ESI and DESI conditions of solid and liquid samples. The
high effectiveness of ionization of analyte vapors makes it possible to use the ESI method not only in combination with liquid
(conventional ESI technology) and thin layer chromatography (DESI), but also with gas liquid chromatography (ESI_V). Thus,
the electrospray ionization becomes a universal method allowing studies of a compound under the natural conditions in any
state of aggregation, that is, solid, liquid, and gas. With the help of statistical methods for designing experiments (complete
factorial experiment), quantitative evaluation of the influence of experimental parameters on the ion-formation processes
under different ESI conditions has been carried out, which makes it possible to purposefully select the optimal conditions
to record the ESI mass spectra with a minimum number of experiments. Moreover, analysis of the dependences of the mass spectra
on the experimental parameters can serve as an instrument for studying the details of the ion-formation mechanisms depending
upon different ways of ionization. 相似文献
13.
《Chemical physics》1987,115(3):453-459
The vacuum ultraviolet (VUV) and photoelectron spectra of SnH3CH3 were recorded between 6.20 and 11.28 eV and between 8 and 17 eV, respectively. Spectra were interpreted using ab initio CI calculations. The photoelectron spectrum confirmed the low SnC bond energy. The first two ionization potentials (IP) observed were attributed to the ionization of the a1 (10.65 eV) and e orbitals (11.15 and 11.60 eV, split by the Jahn-Teller effect), thereby showing an inversion of IPs compared with ethane. Similarly, the first two bands of the VUV spectrum (at 7.04 and 7.72–8.16 eV) were attributed to a1 and e transitions towards the Rydberg s orbital. A splitting of the same order of magnitude as that of the photoelectron spectrum could be noted in the E state. Observed transitions between 8.65 and 10 eV showed a strong interaction between the Rydberg p MO and the σ*SnC antibonding orbital. Primarilyvalence transitions were encountered beyond 10 eV. 相似文献
14.
L. M. Cotoruelo M. D. Marqués A. Leiva J. Rodríguez-Mirasol T. Cordero 《Adsorption》2011,17(3):539-550
The adsorption processes of three aromatic chemicals onto activated carbons (ACs) from aqueous solutions have been studied.
Eucalyptus kraft lignin obtained from cellulose industry as a residual biomass has been used to prepare activated carbons
by physical activation with CO2. The influences of the activation time on the surface areas and pore volumes of the ACs were analyzed. The physicochemical
properties and the surface chemical structure of the adsorbents have been studied by means of N2 and CO2 adsorption, ultimate analysis, XPS, TPD and SEM. XPS and TPD spectra of the ACs have suggested the presence of aromatic rings
and carbon-oxygen functional groups in the solid surfaces. The potential use of the ACs for the removal of acetaminophen (paracetamol),
salicylic acid and benzoic acid has been investigated at different pH, temperature and contact time. The adsorption equilibrium
data have been correlated to Langmuir isotherm model. The thermodynamic study has been developed, the values of ΔH, ΔG, and ΔS have been calculated and they indicated that the processes are endothermic for acetaminophen and exothermic for salicylic
and benzoic acids. The analysis of the kinetic experiments showed that the effective diffusivities are low; 10−12 to 10−11 cm2/s, and they are the corresponding to intraparticle mass transfer, which appears as the controlling step for the net adsorption
processes. 相似文献
15.
The reactions between SO2 and O2 were carried out in the presence of TiO2 and NiO under various partial pressures of SO2 and O2 at temperatures from 240 to 330°C. TiO2 and NiO were pretreated by applying an annealing effect from which the catalysts would have the different activity. The rates are the highest for TiO2 pretreated at high temperature in the region of 400 to 600deg;C in vacuum, 1.21 × 10?4 mmHg. In contrast, the rates are the lowest for NiO pretreated at high temperaturefrom 350 to 550°C. The data have been correlated with 1.4 and first-order kinetics for TiO2 and NiO, respectively. A reaction mechanism to explain the data was suggested. The quantities of anionic vacancies in TiO2 surfaces and of positive holes in NiO appeared to be paramount in determining the type of kinetics. 相似文献
16.
Lijuan Zhou Jichun Jiang Kun Zhao Jinxu Li Chenxin Wu Haiyang Li Di Tian Keyong Hou 《中国化学快报》2018,29(5):707-710
Radiofrequency field enhanced chemical ionization enhances the sensitivity of benzene, toluene, hydrogen sulfide and other compounds by 2–3 orders of magnitude and expanded the detection range of the compounds with ionization energy from 10.6 eV to 12.0 eV. 相似文献
17.
Qinyuan Wu Gordon A. Anderson Harold R. Udseth Michael G. Sherman Steven Van Orden Ruidan Chen Steven A. Hofstadler Michael V. Gorshkov Dale W. Mitchell Alan L. Rockwood Richard D. Smith 《Journal of the American Society for Mass Spectrometry》1996,7(9):915-922
A new in-magnetic field electrospray ionization (ESI) and Fourier transform ion cyclotron resonance mass spectrometer has been constructed and evaluated. This system is characterized by the use of multiple concentric cryopanels to achieve ultrahigh vacuum in the ion cyclotron resonance cell region, a probe-mounted internal ESI source, and a novel in-field shutter. Initial experiments demonstrate high resolution mass measurement capability at a field strength of 1 T. Mass resolution of 700,000 has been obtained for the 3+ charge state of Met-Lys-bradykinin (at m/z 440) generated by electrospray ionization. When electron impact ionization was employed, resolution in excess of 9,200,000 was achieved for nitrogen molecular ions (N 2 + ). Isotopic resolution for molecular ions of bovine ubiquitin (MW=8565 µ) also was achieved by using small ion populations. 相似文献
18.
Z. Zurek 《Journal of Thermal Analysis and Calorimetry》1993,39(1):15-20
A new thermogravimetric apparatus for studying the kinetics of metal sulphidation in a H2/H2S gas mixture is described. The main difference between this device and other equipment is the application of hydrogen to obtain a H2/H2S mixture at suitable sulphur partial pressures at a total mixture pressure of 1 atm.The use of the carrier gas allows the measurement of sulphidation kinetics under dynamic conditions and consequently over a much wider pressure range of sulphur vapour, down to 10–12 atm.The author would like to thank Dr Marek Jodko for his help in devising the chemical analysis of H2S in a H2/H2S gas mixture and for stimulating discussions relating to the design of the above apparatus. 相似文献
19.
Bernadette Charleux Michel Moreau Jean-Pierre Vairon Savvas Hadjikyriacou Rudolf Faust 《Macromolecular Symposia》1998,132(1):25-35
The use of non-homopolymerizable monomers such as 1,1-diphenylethylene (DPE) in the synthesis of functional polymers and block copolymers by cationic polymerization has been recently reported. The most important parameters in this process, the kinetics and extent of ionization and capping as well as the stability of the cation, were investigated by studying the reaction with TiCl4 of 1-methoxy-1,1-diphenyl-3,3,5,5-tetramethylhexane, a model for DPE-capped polyisobutene chain-end. This study was performed using 1H NMR and the high-purity stopped-flow device coupled with UV-visible spectroscopy. 相似文献
20.
Adsorption of Pesticides onto Granular Activated Carbon: Determination of Surface Diffusivities Using Simple Batch Experiments 总被引:1,自引:0,他引:1
The Homogeneous Surface Diffusion Model (HSDM) has been successfully used to predict the adsorption kinetics for several chemicals inside batch adsorber vessels. In addition to the adsorption equilibrium, this model is based on external mass transfer and surface diffusion. This paper presents the determination of the surface diffusion coefficient (D
s) using a differential column batch reactor (DCBR). The adsorption kinetics for three pesticides onto granular activated carbon have been established experimentally. Their corresponding three diffusion coefficients were determined by fitting the computer simulations to the experimental concentration-time data. The results show that this original apparatus increases by an order of magnitude the range of reachable diffusion coefficient compared to perfectly mixed contactors. Moreover the computed D
s values are more accurate because of the better assessment of the external mass transfer coefficient (k
f) for fixed beds. 相似文献