Hydride generation atomic fluorescence spectrometry (HG-AFS) is used for the determination of hydride-forming elements due to its high sensitivity, simplicity, and low cost. A new HG-AFS method for the simultaneous determination of arsenic and lead in vegetable oil is reported. Vortex-assisted extraction with dilute nitric acid was used to isolate arsenic and lead from vegetable oil. The conditions influencing the fluorescence signal, including the carrier fluid, oxidizing agent, and reducing agent, were optimized. The interferences of coexisting ions were also evaluated. Under the optimized conditions, the limits of detection were 0.6 and 0.4?µg?kg?1 for arsenic and lead. The recoveries were from 84.4 to 105% for both metals in vegetable oil. The optimized method was used for the determination of arsenic and lead in commercial vegetable oil. The analytical results by this approach were in good agreement with values obtained by inductively coupled plasma mass spectrometry with microwave digestion. 相似文献
Research on NOx treatment is extensive in recent years due to growing environmental awareness. Selec- tive catalytic reduction (SCR) of NOx, as a proven technology, offers higher NOx control efficiency than many other NOx treatment methods. The present work reviews the recent development of SCR reactor technologies. Firstly, catalysts and mechanism of different SCRs were briefly summarized. Different SCR reactors, e.g. structured reactor, fluidized bed reactor and moving bed reactor, were then discussed. As a more advanced technology, multifunctional reactors were also developed for SCR process and could be divided into two categories: decoupled adsorption-reaction process and combined SCR system. The mechanism and properties of these processes were discussed in detail. Some recommendations were given for the future work in SCR reactor design. SCR reactor technology for emerging energy processes was also addressed, such as oxyfuel combustion and biofuel conversion processes, which put forward new requirements for SCR technologies and also open new opportunities for advanced design of SCR reactors. 相似文献
Detecting the underlying performance of hydrated electrons and hydroxyl radicals in the cationic water cluster can greatly help to understand the inter reaction mechanism in the liquid water and aqueous solutions. Based on our previous (H2O)10+ research, we have paid attention to more problems of larger cationic clusters in this work, including the existence of hemibonded type, long-range correction functions, and hydrogen-bonded site analyses. The lower-energy structures of the cationic water cluster (H2O)12+ have been comprehensively explored, and more experienced functions are introduced to check the ground state and vibration spectrum. Unlike the configuration regularity of neutral (H2O)12 clusters and small cationic water clusters, those new-found structures for (H2O)12+ are inclined to adopt three dimension (3D) cage-like structures and the H2O-OH2 structure appears in the higher energy isomer. The calculation reveals that the lowest stable isomer is the 3D cage structure W14 predicted at MP2 level, which has not been reported yet. In the thermal simulation, structure transition from the cage-like to the ring-like occurs at T?>?≈256 K, and the two dimension (2D) ring-like structure occupies a dominant position at high temperature range. The infrared spectra explain that the difference of the spectra between the 2D net structures and 3D cage-structures is mainly caused by the weight fluctuation of single acceptor-single donor (AD), double acceptor-single donor (AAD), and single acceptor-double donor (ADD) sites in these isomers. This further gives a similarity relation between (H2O)12+ and H+(H2O)12 clusters in the shape of the network and spectral characteristics. By molecular orbitals and topological analysis, we find that the lone pair orbital on hydroxyl radical dominates the reactivity and stability of cationic system. The present research may be helpful for exploring the evolution law of the larger cationic water clusters in the future.
Three ruthenium(II) polypyridyl complexes with 5-amino-1,10-phenanthroline ligands have been successfully designed and synthesized. They have been fully characterized by ESI-MS, ESI-HRMS, 1H NMR, and elemental analyses. The photophysical and electrochemical properties of the three complexes have been investigated in organic solvent. The geometrical configuration and the electron density distribution in the frontier molecular orbitals of the three complexes have been studied. The three complexes show metal-to-ligand charge transfer (1MLCT) absorption at 445 nm, and intense triplet metal-to-ligand (3MLCT) emission at around 619 nm in fluid solution at 298 K and 580 nm in low-temperature glass. Electrochemical studies of the three complexes are consistent with one RuIII/II reversible couple at around 1.31 V accompanied by three ligand-centered reduction couples.
One of the most effective ways to cope with the problems of global warming and the energy shortage crisis is to develop renewable and clean energy sources. To achieve a carbon-neutral energy cycle, advanced carbon sequestration technologies are urgently needed, but because CO2 is a thermodynamically stable molecule with the highest carbon valence state of +4, this process faces many challenges. In recent years, electrochemical CO2 reduction has become a promising approach to fix and convert CO2 into high-value-added fuels and chemical feedstock. However, the large-scale commercial use of electrochemical CO2 reduction systems is hindered by poor electrocatalyst activity, large overpotential, low energy conversion efficiency, and product selectivity in reducing CO2. Therefore, there is an urgent need to rationally design highly efficient, stable, and scalable electrocatalysts to alleviate these problems. This minireview also aims to classify heterogeneous nanostructured electrocatalysts for the CO2 reduction reaction (CDRR). 相似文献
A diastereoselectivity-controllable formal [3+2]-cycloaddition of arylvinyl oxirane 2,2-diesters with cyclic N-sulfonyl imines is developed, affording the corresponding tricyclic oxazolidine derivatives in moderate to excellent yields with excellent diastereoselectivities in the presence of palladium(0) or scandium(III) triflate. This protocol allows selective synthesis of diastereomers of tricyclic oxazolidine derivatives under switchable and mild conditions. Further transformations of the obtained products were conducted by removing ester groups and arylvinyl moieties. 相似文献
The side-on-end-on coordination of N2 can be very important to activate and functionalize this very stable molecule. However, such coordination has rarely been reported. This study reports a gas-phase species (a polynuclear vanadium nitride cluster anion [V5N5]−) that can capture N2 efficiently (12 %), and the quantum chemistry modelling suggests an unusual side-on-end-on coordination. The cluster anions were generated by laser ablation and the reaction with N2 has been characterized by mass spectrometry, photoelectron imaging spectroscopy, and density functional theory calculations. The back-donation interactions between the localized d–d bonding orbitals on the low-coordinated dual metal (V) sites and the antibonding π* orbitals of N2 are the driving forces to adsorb N2 with a high binding energy (about 2.0 eV). 相似文献