Electrochemical determination of Hg(II) in aquatic solutions on bare and modified glassy carbon electrode (GCE) is reported. Optimizing the parameters used for a bare GCE, such as the electrolyte solution, the potential and time of deposition, resulted in linear response over a large range of Hg(II) concentrations (4–160 ppb) using linear sweep anodic stripping voltammetry. Modification of the electrode with 4,4′-disulfanediyldibenzenediazonium (DSBD) yielded a lowest detection limit of 1 ppb. Two procedures for DSBD synthesis are described for the first time, and the product was characterized by microanalysis, FTIR and 1H-NMR. The electrochemical attachment of DSBD to the electrode was studied and compared with the electrochemical behaviour of DSBD analogous molecules, i.e. 4-aminophenyl disulfide, p-aminothiophenol and phenyl disulfide. 相似文献
Some transition metal complexes are known to catalyze ortho/para hydrogen conversion, hydrogen isotope scrambling, and hydrogenation reactions in liquid solution. Using the example of Vaska's complex, we present here evidence by NMR that the solvent is not necessary for these reactions to occur. Thus, solid frozen solutions or polycrystalline powdered samples of homogeneous catalysts may become heterogeneous catalysts. Comparative liquid- and solid-state studies provide novel insight into the reaction mechanisms. 相似文献
Current biological studies have been advanced by the continuous development of robust, accurate, and sensitive mass spectrometric
technologies. The MALDI LTQ Orbitrap is a new addition to the Orbitrap configurations, known for their high resolving power
and accuracy. This configuration provides features inherent to the MALDI source, such as reduced spectra complexity, forgiveness
to contaminants, and sample retention for follow-up analyses with targeted or hypothesis-driven questions. Here we investigate
its performance for characterizing the composition of isolated protein complexes. To facilitate the assessment, we selected
two well characterized complexes from Saccharomyces cerevisiae, Apl1 and Nup84. Manual and automatic MS and MS/MS analyses readily resolved their compositions, with increased confidence
of protein identification compared with our previous reports using MALDI QqTOF and MALDI IT. CID fragmentation of singly-charged
peptides provided sufficient information for conclusive identification of the isolated proteins. We then assessed the resolution,
accuracy, and sensitivity provided by this instrument in the context of analyzing the isolated protein assemblies. Our analysis
of complex mixtures of singly-charged ions up to m/z 4000 showed that (1) the resolving power, inversely proportional to the square root of m/z, had over four orders of magnitude dynamic range; (2) internal calibration led to improved accuracy, with an average absolute
mass error of 0. 5 ppm and a distribution centered at 0 ppm; and (3) subfemtomole sensitivity was achieved using both CHCA
and DHB matrices. Additionally, our analyses of a synthetic phosphorylated peptide in mixtures showed subfemtomole level of
detection using neutral loss scanning. 相似文献
We designed and operated a new system of pulsed flow modulation (PFM) two dimensional comprehensive gas chromatography (GC × GC) mass spectrometry (MS). This system is based on the combination of PFM–GC × GC with a quadrupole mass spectrometer of GC–MS via a supersonic molecular beams interface and its fly-through Cold EI ion source and applied this system for the analysis of JP8 jet fuel. PFM is a simple GC × GC modulator that does not consume cryogenic gases while providing tunable second GC × GC column injection time for enabling the use of quadrupole based mass spectrometry regardless its limited scanning speed. We analyzed JP8 jet fuel with our new PFM–GC × GC–MS with Cold EI system and found that as the second dimension GC elution time is increased the observed molecular ion mass is reduced. This unique observation that helped in improved sample compounds identification under co-elution conditions was enabled via having abundant molecular ions in Cold EI for all the fuel compounds. We named this type of analysis as PFM–GC × GC × MS. We found and discuss in this paper that PFM–GC × GC–MS with Cold EI combines improved separation of GC × GC with Cold EI benefits of tailing-free ultra-fast ion source response time and enhanced molecular ions and mass spectral isomer and isotope information for the provision of increased sample identification information.
High-temperature hydrolysis of Zn(II) and Mn(II) alkoxides in a high boiling point solvent in the presence of surfactants was used to prepare surfactant-coated Zn(1-x)Mn(x)O nanocrystals with average size of 5.5 nm and x = 0.04 +/- 0.03. The magnetic properties of the nanocrystals were measured both for isolated particles diluted in a hydrocarbon matrix and for a nanocrystal powder. Nanocrystals of manganese oxide and ZnO coated with manganese oxide were prepared for comparison to the Zn(1-x)Mn(x)O nanocrystals. We find that the manganese ions primarily substitute zinc ions in the hexagonal ZnO lattice, and part of them are ferromagnetically coupled up to room temperature even in isolated noninteracting nanocrystals. The rest of the ions are magnetically disordered or uncoupled. Surprisingly, these small Zn(1-x)Mn(x)O nanocrystals poses relatively large low-temperature magnetic coercivity and relatively high blocking temperature in the isolated form, which indicate large magnetic anisotropy. In the nanocrystal powder the coercive field decreased significantly. This study highlights the advantages of working with noninteracting single domain particles of these intriguing materials. 相似文献
Journal of Solid State Electrochemistry - Manganese oxide is an important emerging electrode material for use in supercapacitor applications. Herein, we propose a new aqueous electrolyte,... 相似文献
We study, theoretically and experimentally, the evolution of patterns in a passive nonlinear cavity that is longer than the coherence length of the light circulating in it. The patterns exhibit spatial line narrowing as the feedback is increased, resembling the line narrowing in lasers. 相似文献
We formulate the theory describing the evolution and interactions between optical spatial solitons that propagate in opposite directions. We show that coherent collisions between counterpropagating solitons give rise to a new focusing mechanism resulting from the interference between the beams, and that interactions between such solitons are insensitive to the relative phase between the beams. 相似文献
We present the experimental observation of a spatial vector soliton formed by counterpropagation of coherent optical fields. This is to our knowledge the first observation of a vector soliton in which the induced waveguide (potential) is periodic in the propagation direction. This vector soliton induces a waveguide and a thick grating within the waveguide, which can be used as a tunable optical waveguide filter. 相似文献