Optical characterization of CdTe/ZnSe fractional monolayer structures grown by atomic layer epitaxy

Luminescence properties of CdTe/ZnSe fractional monolayer grown by atomic layer epitaxy have been investigated. To investigate the origin of the highly efficient luminescence, various optical spectroscopic methods such as, photoluminescence (PL), temporal/spatial resolved PL, temperature dependence PL, and excitation power dependence PL have been used. It is found that structural inhomogeneities affect dominant influence on the line width and line shape of luminescence. The luminescence intensity greatly enhanced by the localization of exciton at the disorder induced localized states.     

N-heterocyclic carbenes as ligands in high-valent molybdenum and tungsten complexes

Oxometal complexes of molybdenum and tungsten in high oxidation states from stable adducts with 1,3-dimethylimidazoline-2-ylidene (L) 1. The first ‘carbene’ complexes of molybdenum(VI) [MoO₂Cl(L)₃]Cl (3a) and tungsten(VI) WO₂Cl₂(L)₂ (4b) are reported.     

Cr(VI)在Mg-Al型类水滑石上的吸附-脱附性研究I.吸附性

研究了Cr(VI)在带结构正电荷的Mg-Al型类水滑石(HTlc)上的吸附性能,考察了pH、无机电解质添加剂NaCl,NaNO3,Na2SO4和Na3PO4及有机添加剂EDTA和柠檬酸等因素的影响,并结合红外光谱和XRD实验结果探讨了吸附机理.研究表明,Mg-Al型HTlc对Cr(VI)有很强的吸附能力,其吸附动力学和吸附等温线分别符合准二级速率方程和Langmuir方程,饱和吸附量达105mg/g,有望成为一种优良的含Cr(VI)污水处理剂和Cr(VI)污染土壤修复剂.初始pH增大,吸附量降低.无机电解质和有机添加剂均能明显抑制Cr(VI)在HTlc上的吸附,其抑制吸附作用的强弱顺序分别为Na3PO4≥Na2SO4≥NaCl>>NaNO3和柠檬酸>EDTA.Cr(VI)在HTlc上的吸附可分为层间的离子交换吸附和外表面的吸附,其中外表面的吸附层在微观上又可分为因化学键合作用而形成的内络合层和因静电作用而形成的外络合层.     

Study of metal-loaded activated charcoals for the separation and determination of selenium species by energy dispersive X-ray fluorescence analysis

Conversion of adsorption properties of activated charcoal (C^∗) by metal modification towards selenite, selenate and seleno-dl-methionine (Se-Met) was studied. Several metals were included in modification studies and also a procedure was developed for the separation and independent determination of microgram quantities of these selenium species in aqueous solution. Selenium species were collected one by one from the same sample solution onto collector material by adsorbing them directly or after complex formation onto different metal-loaded activated charcoals (MgC^∗ and FeC^∗). The mass of selenium in these collectors was measured directly by energy dispersive X-ray fluorescence spectrometry (EDXRF). Detection limits for all three selenium species were better than 6 μg corresponding to concentration of 60 μg/l with 0.100 l of initial sample volume.     

ⅥB族金属叁键有机化合物的研究进展

本文对一类重要的ⅥB族金属叁键化合物R_2M_2(CO)_4(R为环戊二烯基及类环戊二烯基)近年来的研究成果进行了综述,综述重点是这类化合物的官能团M≡M参键的化学活性,全文包括R_2M_2(CO)_4的合成及结构,M≡M叁键与亲核试剂、与碳-碳重键,与氧或与金属羰基物等试剂的反应及其应用。     

Rapid—In—situ Determination of Chromium （VI） in Water Using Modified Diphenylcarbazine with Citrate

In recent years, the determination of Cr (VI) has attracted great attention because of its toxicity to human, plants and animals1-5. Usually, in the industrial waste water, the concentration of Cr (VI) is relatively high and should be determined frequently. So, an accurate, quick, and convenient method for the measurement of Cr (VI) in environmental water, as well as in river, lake, sea and tap water, is of great importance. The method for determination of Cr (VI) by diphenylcarbazine …     

Template-Reaktion von Bis(acetylacetonato)-dioxo-molybdän(VI) mit Benzoylhydrazin

Template Reaction of Bis(acetylacetonato)-dioxo-molybdenum(VI) with Benzoylhydrazone By reaction of bis(acetylacetonato)-dioxo-molybdenum(VI) with benzoylhydrazine benzoylhydrazido(2?)-acetylacetonebenzoylhydrazonato(2?)-oxo-molybdenum(VI) was formed beside another species. The compound was characterized by mass spectrometry and X-ray structural analysis. Crystallographic data see ?Inhaltsübersicht”?.     

线性变位极谱法研究 ⅩⅥ.铀(Ⅵ)-5-Br-PADAP-磺基水杨酸的配位吸附波

本文提出了铀(Ⅵ)-5-Br-PADAP-磺基水杨酸三元配合物的极谱配位吸附波。在pH为7.5-8.2的醋酸、三乙醇胺、乙醇底液中,该波的峰电位在-0.6855V(vs.SCE)。在1.00×10^-7-1.00×10^-5mol·dm^-3范围内,铀(Ⅵ)浓度与峰电流呈线性关系。对极谱波的电流、电位性质进行了研究,测定了配合物的组成、表观稳定常数和离解及生成速率常数。     

Selective flow injection analysis of ultra-trace amounts of Cr(VI), preconcentration of it by solvent extraction, and determination by electrothermal atomic absorption spectrometry (ETAAS)

A rapid, robust, sensitive and selective time-based flow injection (FI) on-line solvent extraction system interfaced with electrothermal atomic absorption spectrometry (ETAAS) is described for analyzing ultra-trace amounts of Cr(VI). The sample is initially mixed on-line with isobutyl methyl ketone (IBMK). The Cr(VI) is complexed by reaction with ammonium pyrrolidine dithiocarbamate (APDC), and the non-charged Cr(VI)–PDC chelate formed is extracted into IBMK in a knotted reactor made from PTFE tubing. The organic extractant is separated from the aqueous phase by a gravity phase separator with a small conical cavity and delivered into a collector tube, from which 55 μl organic concentrate is subsequently introduced via an air flow into the graphite tube of the ETAAS instrument. The operations of the FI-system and the ETAAS detector are synchronously coupled. A significant advantage of the approach is that matrix constituents, such as high salt contents, effectively are eliminated. The extraction procedure was optimized by a simplex approach. A central composite design was subsequently employed to verify the estimated operational optimum. An 18-fold enhancement in sensitivity of Cr(VI) was achieved after preconcentration for 99 s at a sample flow rate of 5.5 ml min⁻¹, as compared to direct introduction of 55 μl of sample, yielding a detection limit (3σ) of 3.3 ng l⁻¹. The sampling frequency was 24.2 samples h⁻¹. The proposed method was successfully evaluated by analyzing a NIST Cr(VI)-reference material, synthetic seawater and waste waters, and waste water samples from an incineration plant and a desulphurization plant, respectively.     

Removal of humic matter interference in the determination of Cr(VI) in soil extracts by the diphenylcarbazide method

Alkaline digestion of soil samples, which is recommended for minimizing Cr(III)–Cr(VI) interconversions during the extraction of Cr(VI), may also solubilize humic matter (HM). The latter is responsible for both positive and negative interference in the analysis of Cr(VI) in the extract by the diphenylcarbazide (DPC) method. Humic compounds indeed absorb light at 540 nm as the Cr-DPC product and are also able to rapidly reduce Cr(VI) under the pH conditions of the standard DPC method. To prevent any risk of interference and make the DPC method applicable to soil extracts, a new protocol is proposed. This consists of three successive steps: (1) extraction of Cr(VI) by the U.S.EPA method 3060A in the presence of Mg²⁺; (2) batch removal of solubilised HM by the XAD-7 sorbent at pH 3.0 ± 0.1 with 3–5 min contact time; (3) analysis of Cr(VI) with the DPC method at pH 3.0 ± 0.1. The application of this new protocol to the soil product SQC-012 Lot 4 certified by R.T. Corporation (RTC, USA) gave significantly lower Cr(VI) concentrations and smaller variability compared to certified values (46.5 ± 2.3 instead of 153 ± 32.6 mg/kg). The new protocol was validated by Cr(VI) and Cr(III) spikes either to the soil/extractant suspension or to the exctract. Cr(VI) results in the wide range of acceptance limits (104–202 mg/kg) reported by RTC were only obtained when the U.S.EPA method 3060A without the addition of Mg²⁺ and DPC analysis at pH 1.0 were applied. The latter procedure appears questionable since it leads to largely variable results which reflect the complex role played by humic matter in the determination of Cr(VI) and the instability of Cr(III) during the extraction.