- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Thermal atomic layer deposition of Sn metal using SnCl <sub/>4</sub> and a vapor phase silyl dihydropyrazine reducing agent
摘要： This work explores a novel, thermal atomic layer deposition (ALD) process to deposit tin metal at a low temperature. The authors employ 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (DHP) to reduce SnCl4 on silicon substrates. The authors explored a range of temperatures between 130 and 210 °C to determine the ALD window, which was found to be 170–210 °C. The authors show that this process yields a growth rate of ～0.3 ? per cycle at 190 °C. Furthermore, X-ray photoelectron spectroscopy results showed that the ?lm impurities are reduced for depositions within the ALD window. The reaction mechanism was explored using in situ mass spectrometry and in situ quartz crystal microbalance (QCM). Within the ALD temperature window, the QCM results showed a saturated mass gain during the SnCl4 exposure and a net mass loss during the DHP dose. Consistent with the QCM results, in situ mass spectroscopy data indicate that the DHP exposure step removes surface Cl via formation of volatile trimethylsilyl chloride and pyrazine by-products, effectively reducing the oxidation state of surface-bound Sn. This work is the ?rst thermal Sn metal ALD process to be reported in literature and the oxidation/reduction chemistry presented here may be applied to other metal precursors, increasing the applicability of metal ALD use in industry.
关键词： quartz crystal microbalance,X-ray photoelectron spectroscopy,ALD window,SnCl4,mass spectrometry,tin metal,thermal atomic layer deposition,DHP
更新于2025-09-04 15:30:14
-
LC-MS Supported Studies on the in Vitro Metabolism of both Enantiomers of Flubatine and the in Vivo Metabolism of (+)-[18F]Flubatine—A Positron Emission Tomography Radioligand for Imaging α4β2 Nicotinic Acetylcholine Receptors
摘要： Both enantiomers of [18F]flubatine are promising radioligands for neuroimaging of α4β2 nicotinic acetylcholine receptors (nAChRs) by positron emission tomography (PET). To support clinical studies in patients with early Alzheimer’s disease, a detailed examination of the metabolism in vitro and in vivo has been performed. (+)- and (?)-flubatine, respectively, were incubated with liver microsomes from mouse and human in the presence of NADPH (β-nicotinamide adenine dinucleotide 2′-phosphate reduced tetrasodium salt). Phase I in vitro metabolites were detected and their structures elucidated by LC-MS/MS (liquid chromatography-tandem mass spectrometry). Selected metabolite candidates were synthesized and investigated for structural confirmation. Besides a high level of in vitro stability, the microsomal incubations revealed some species differences as well as enantiomer discrimination with regard to the formation of monohydroxylated products, which was identified as the main metabolic pathway in this assay. Furthermore, after injection of 250 MBq (+)-[18F]flubatine (specific activity > 350 GBq/μmol) into mouse, samples were prepared from brain, liver, plasma, and urine after 30 min and investigated by radio-HPLC (high performance liquid chromatography with radioactivity detection). For structure elucidation of the radiometabolites of (+)-[18F]flubatine formed in vivo, identical chromatographic conditions were applied to LC-MS/MS and radio-HPLC to compare samples obtained in vitro and in vivo. By this correlation approach, we assigned three of four main in vivo radiometabolites to products that are exclusively C- or N-hydroxylated at the azabicyclic ring system of the parent molecule.
关键词： epibatidine,liquid chromatography-mass spectrometry (LC-MS),flubatine,NCFHEB,liver microsomes,nicotinic acetylcholine receptors (nAChRs),radiometabolites,positron emission tomography (PET)
更新于2025-09-04 15:30:14
-
Encyclopedia of Spectroscopy and Spectrometry || Accelerator Mass Spectrometry (AMS)
摘要： Accelerator mass spectrometry (AMS) was developed for analyzing 14C in environmental and archeological specimens in the 1970s (although it was first demonstrated in the 1930s). It is now principally used to measure only a handful of isotopes, although it is feasible to apply it to many additional analytes. AMS represents the marriage of high-energy physics with radioanalytical chemistry and finds applications in geoscience, environmental analysis, archeology, cosmochemistry, biosciences, medicine, material science, nuclear chemistry, and physics. AMS employs a high-energy tandem accelerator to raise ion energies to the mega-electron-volt (MeV) range and enable complete destruction and avoidance of isobaric interferences. Typical AMS is thus capable of measuring very small isotope ratios, typically in the range of 10^-15 (atomic ratio). Isotopes of interest include 14C, 10Be, 26Al, 36Cl, 41Ca, and 129I. Measured rare/natural ratios for these isotopes fall well below the 1–10^-9 range measured with other mass spectrometers (except for laser-based systems with resonance ionization techniques, which can match the range of the AMS).
关键词： radioanalytical chemistry,AMS,high-energy physics,isotopes,Accelerator Mass Spectrometry
更新于2025-09-04 15:30:14
-
Encyclopedia of Spectroscopy and Spectrometry || Field Ionization Kinetics in Mass Spectrometry
摘要： The mass spectra of molecules, ionized by electron ionization (EI), field ionization (FI) or photoionization (PI) in the gas phase, usually show many peaks with varying intensities. These peaks result from fragment ions generated by a series of competing and consecutive unimolecular dissociation reactions of the molecular ions provided that the latter have obtained during their formation an amount of energy in excess of the ionization energy of the corresponding molecules. The resulting mass spectrum therefore is determined by the relative rates of these unimolecular dissociation reactions, which in their turn are related to the relative abundances of the fragment ions observed. It will be clear that studying the kinetics of ion dissociation can provide an invaluable insight into the foundation of a mass spectrum.
关键词： Gas-Phase Ion Chemistry,Unimolecular Dissociation,Ion Lifetimes,Mass Spectrometry,Field Ionization Kinetics
更新于2025-09-04 15:30:14
-
Encyclopedia of Spectroscopy and Spectrometry || Ion Dissociation Kinetics in Mass Spectrometry ☆
摘要： The ionization processes taking place in the source of a mass spectrometer and the many possible activation processes available in multi-dimensional mass spectrometry lead to ions with a broad range of internal energy which can extend well above the lowest fragmentation threshold, thus allowing the molecular ion to dissociate within the typical time frame of a mass spectrometry experiment. Dissociation is a dynamical process characterized by its associated lifetime. The following questions need to be addressed. (i) How fast does a selected fragmentation process take place under given experimental conditions (state selection, well-defined energy or temperature, for example) and how is the excess energy partitioned among the reaction products? (ii) Which information can be inferred from the experimental data about the reaction mechanism?
关键词： Ion Dissociation Kinetics,Canonical Rate Constant,Unimolecular Rate Constant,Mass Spectrometry,Microcanonical Rate Constant
更新于2025-09-04 15:30:14
-
Simultaneous determination of dissolved phenanthrene and its metabolites by derivative synchronous fluorescence spectrometry with double scans method in aqueous solution
摘要： A simple and sensitive derivative synchronous fluorescence spectrometry with double scans (DS-DSFS) method was developed for simultaneous determination of dissolved Phenanthrene (Phe) and its metabolites 1-hydroxy-2-naphthoic acid (1H2NA) and salicylic acid (SA) in aqueous solution. The value of 69 nm was selected as the optimal Δλ conditions for Phe and 1H2NA, and the Δλ value of 55 nm was selected for SA. The overlapping fluorescence emission spectra of Phe, 1H2NA and SA were resolved by DS-DSFS. The signals detected at wavelength of 296 nm for Phe, 352 nm for 1H2NA and 307 nm for SA vary linearly when the concentrations in the range of 4.0–1.0 × 103 μg L?1, 4.0–1.2 × 103 μg L?1 and 4.0–8.0 × 102 μg L?1, respectively. The detection limits were 0.08, 0.07 and 0.88 μg L?1 for Phe, 1H2NA and SA, with the relatively standard deviations less than 5.0%. The established method was successfully applied in the determination of Phe and the metabolites during the biodegradation of dissolved Phe in the lab. It was evidenced that the method has potential for the in situ investigation of PAH biodegradation.
关键词： Metabolites,PAHs,In situ,Derivative synchronous fluorescence spectrometry,Biodegradation
更新于2025-09-04 15:30:14
-
Time-of-flight spectrometry of ultra-short, polyenergetic proton bunches
摘要： A common approach for spectrum determination of polyenergetic proton bunches from laser-ion acceleration experiments is based on the time-of-flight (TOF) method. However, spectra obtained using this method are typically given in relative units or are estimated based on some prior assumptions on the energy distribution of the accelerated ions. In this work, we present a new approach using the TOF method that allows for an absolute energy spectrum reconstruction from a current signal acquired with a sub-nanosecond fast and 10 μm thin silicon detector. The reconstruction is based on solving a linear least-squares problem, taking into account the response function of the detection system. The general principle of signal generation and spectrum reconstruction by setting up an appropriate system response matrix is presented. Proof-of-principle experiments at a 12 MV Tandem accelerator using different nanosecond-short (quasi-)monoenergetic and polyenergetic proton bunches at energies up to 20 MeV were successfully performed. Within the experimental uncertainties of 2.4% and 12.1% for energy and particle number, respectively, reconstructed energy distributions were found in excellent agreement with the spectra calculated using Monte Carlo simulations and measured by a magnetic spectrometer. This TOF method can hence be used for absolute online spectrometry of laser-accelerated particle bunches.
关键词： silicon detector,time-of-flight spectrometry,energy spectrum reconstruction,polyenergetic proton bunches,laser-ion acceleration
更新于2025-09-04 15:30:14
-
Catalyst-Assisted Solution–Liquid–Solid Synthesis of CdS/CuInSe <sub/>2</sub> and CuInTe <sub/>2</sub> /CuInSe <sub/>2</sub> Nanorod Heterostructures
摘要： Axial nanowire heterostructures composed of cadmium sulfide (CdS)/copper indium diselenide (CuInSe2) and copper indium telluride (CuInTe2)/copper indium diselenide (CuInSe2) were synthesized by a solution?liquid?solid (SLS) method with the catalyzer of bismuth nanocrystals. Electron microscopy and diffraction studies show CuInTe2 and CuInSe2 segments growing along the [112] direction with a clear epitaxial interface between them. In CdS/CuInSe2 nanorod heterostructures, CuInSe2 and CdS segments grow along the [112] and [111] direction, respectively, with an obvious epitaxial interface between them. Energy-dispersive X-ray spectrometry demonstrates the alloy-free composition modulation in two nanorod heterostructures. In CuInTe2/CuInSe2 nanorod heterostructures, Te and Se are localized in CuInTe2 and CuInSe2 segments, respectively. Cu/In/Se and Cd/S are localized in the CuInSe2 and CdS sections of the CdS/CuInSe2 nanorod heterostructures. This research confirms that the SLS mechanism provides a general alternate technique to prepare multicomponent axial 1D heterostructures that have been difficult to generate by using either catalyst-free solution-phase synthesis or vapor?liquid?solid growth.
关键词： epitaxial interface,nanowire heterostructures,solution?liquid?solid (SLS) method,bismuth nanocrystals,energy-dispersive X-ray spectrometry
更新于2025-09-04 15:30:14
-
Separation and Pre–Concentration of Metal Cations – DNA/RNA Chelates Using Molecular Beam Mass Spectrometry with Tunable Vacuum Ultraviolet (VUV) Synchrotron Radiation and Various Analytical Methods
摘要： Separation and pre–concentration procedures such as Liquid–Liquid Extraction (LLE), Solid Phase Extraction (SPE) and Homogenous Liquid–Liquid Extraction (HLLE) make it feasible to determine the trace of metal cations such as Mg2+, Ca2+, Cr3+, Mn2+, Fe3+, Co2+, Co3+, Ni2+, Cu2+, Zn2+, Se2+, Mo6+, Ru4+, Rh3+, Pd2+, Ag+, Cd2+, Sn2+, Te2+, Te4+, Hg2+ and Pb2+ in natural samples using molecular beam mass spectrometry with tunable Vacuum Ultraviolet (VUV) synchrotron radiation (Figure 1) and various analytical methods [1-21]. Pre–concentration methods generally improve sensitivity and selectivity of the analysis with the additional advantage of isolation the analyte from the interfering compounds [22,23]. In the recent years, Homogenous Liquid– Liquid Extraction (HLLE) using molecular beam mass spectrometry with tunable Vacuum Ultraviolet (VUV) synchrotron radiation and various analytical methods has been extensively used in sample preparation due to speed, suitable performance, higher concentration factor and less solvent consumption in comparison with Liquid–Liquid Extraction (LLE) and Solid Phase Extraction (SPE) [24-44]. In the present editorial, an effective method is presented for pre–concentration of Mg2+, Ca2+, Cr3+, Mn2+, Fe3+, Co2+, Co3+, Ni2+, Cu2+, Zn2+, Se2+, Mo6+, Ru4+, Rh3+, Pd2+, Ag+, Cd2+, Sn2+, Te2+, Te4+, Hg2+ and Pb2+ by Homogenous Liquid–Liquid Extraction (HLLE) and using molecular beam mass spectrometry with tunable Vacuum Ultraviolet (VUV) Synchrotron radiation and various analytical methods.
关键词： Separation,Pre–Concentration,Vacuum Ultraviolet (VUV) Synchrotron Radiation,Molecular Beam Mass Spectrometry,DNA/RNA Chelates,Metal Cations,Analytical Methods
更新于2025-09-04 15:30:14
-
Satellite-like Gold Nanocomposites for Targeted Mass Spectrometry Imaging of Tumor Tissues
摘要： We have developed a simple, rapid, high-throughput cancer diagnosis system using functional nanoparticles (NPs) consisting of poly(catechin) capped-gold NPs (Au@PC NPs) and smaller nucleolin-binding aptamer (AS1411) conjugated gold NPs (AS1411–Au NPs). The AS1411–Au NPs/Au@PC NP is used as a targeting agent in laser desorption/ionization mass spectrometry (LDI-MS)-based tumor tissue imaging. Self-assembled core-shell Au@PC NPs are synthesized by a simple reaction of tetrachloroaurate(III) with catechin. Au@PC NPs with a well-defined and dense poly(catechin) shell (~40?60 nm) on the surface of each Au core (~60?80 nm) are obtained through careful control of the ratio of catechin to gold ions, as well as the pH of the reaction solution. Furthermore, we have shown that AS1411-conjugated Au NPs (13-nm) self-assembled on Au@PC NP can from a satellite-like gold nanocomposite. The high density of AS1411–Au NPs on the surface of Au@PC NP enhances multivalent binding with nucleolin molecules on tumor cell membranes. We have employed LDI-MS to detect AS1411–Au NPs/Au@PC NPs labeled nucleolin-overexpressing MCF-7 breast cancer cells through the monitoring of Au cluster ions ([Aun]+; 1 ≤ n ≤ 3). The ultrahigh signal amplification from Au NPs through the formation of a huge number of [Aun]+ ions results in a sensing platform with a limit of detection of 100 MCF-7 cells mL?1. Further, we have applied the satellite-like AS1411–Au NPs/Au@PC NP nanocomposite as a labeling agent for tumor tissue imaging by LDI-MS. Our nanocomposite-assisted LDI-MS imaging platform can be extended for simultaneous analysis of different tumor markers on cell membranes when using different ligand-modified metal nanoparticles.
关键词： tissue imaging,aptamers,laser desorption/ionization mass spectrometry,self-assembly,gold nanocomposites
更新于2025-09-04 15:30:14