Formation of Ad-Layers and Clusters on Condensation of Metal Vapors on Solid Surfaces

Synthesis of organometallic materials can be accomplished in many cases by cocondensation of metal atoms and organic molecules at low temperatures. The reaction kinetics is determined by the competition between metal cluster growth and formation of the organometallic compound. Interesting compounds may contain one or more metal atoms; the latter type could be obtained by reaction between a cluster containing the desired number of metal atoms and an organic molecule. A precise knowledge of the events occurring on condensation of metal atoms and cluster formation can therefore be of value in the control of chemical synthesis. These phenomena have been investigated in connection with the study of the growth of thin metallic films, both experimentally and theoretically. Direct observation of the formation of very small clusters is difficult. The good agreement between experimental results and recent calculations for the development of large clusters, however, allows reliable theoretical conclusions for the first stages of adsorption and cluster formation. The present contribution describes experimental work on film growth and relevant theoretical concepts, and an attempt is made to develop applications to organometallic synthesis.     

Luminescent dendrimers as ligands for metal ions

Suitably designed luminescent dendrimers can play a role of ligands for luminescent and non-luminescent metal ions. This combination leads to species capable of exhibiting interesting and unusual properties, including (i) shielding excited states from quenching processes, (ii) light harvesting, (iii) conversion of incident UV light into visible or infrared emission, and (iv) metal ions sensing with signal amplification.     

碱金属和重金属叠氮化物的感度和导电性研究

分别用EHCO和DV－X_α方法，计算研究了α－NaN_3、β-NaN_3和AgN_3的能带结构和原子簇电子结构. AgN_3与NaN_3相比：带隙(△Eg)较小、带宽(BW)较大，因而电导率较大. 比较前沿晶体轨道(CO)和前沿分子轨道(MO)的能级、组成及电子在其间的跃迁；预示AgN_3比NaN_3更敏感、更易分解和起爆．还从电子微观层次揭示了金属叠氮化物的导电性和爆炸性之间的联系．     

Radiation grafting from binary monomer mixtures. I. Vinyl ether of monoethanolamine and vinyl ether of ethyleneglycol

Gamma-radiation grafting of vinyl ether of monoethanolamine and vinyl ether of ethyleneglycol (VEEG) on polyethylene films has been studied from binary monomer mixtures. The effect of co-monomer composition and total exposure radiation dose on the grafting process is investigated. A combination of potentiometric and gravimetric techniques is applied to determine the grafting degree of each monomer in the final graft copolymer. The presence of more active monomer VEEG in the mixture was found to enhance the grafting of both monomers because the increasing of copolymerization rate which in turn increases the total grafting degree. The modification of the hydrophilic properties of the graft copolymer is studied by examining the grafted films for water- and copper (II) ions uptake.     

Metal furnace heated by flame as a hydride atomizer for atomic absorption spectrometry: Sb determination in environmental and pharmaceutical samples

The present work describes a metallic hydride atomizer for atomic absorption spectrometry, by evaluating the performance of the Inconel 600^® tube. For this purpose, stibine was used as the model volatile compound and antimony determination in river and lake sediments and in pharmaceutical samples was carried out to assess the metal furnace performance. Some parameters are evaluated such as those referring to the generation and transport of the hydride (such as KBH₄ and acid concentrations, carrier gas flow rate, injected volume, etc.), as well as those referring to the metal furnace (such as tube hole area, flame composition, long-term stability, etc.). The method presents linear Sb concentration from 2 to 80 μg L⁻¹ range (r > 0.998; n = 3) and the analytical frequency of ca. 140 h⁻¹. The limit of detection (LOD) is 0.23 μg L⁻¹ and the precision, expressed as R.S.D., is less than 5% (40 μg L⁻¹; n = 10). The accuracy is evaluated through the reference materials, and the results are similar at 95% confidence level according to the t-test.     

A novel intumescent flame-retardant system containing metal chelates for polyvinyl alcohol

A novel flame retardant containing phosphorous-nitrogen structure, the ammonium salt of 2-hydroxyl-5,5-dimethyl-2,2-oxo-1,3,2-dioxapho sphorinane (PNOH), was synthesized and its structure was characterized by ¹H NMR and FTIR spectra. PNOH was used together with ammonium polyphosphate (APP) to prepare a novel intumescent flame retardant (IFR) for polyvinyl alcohol (PVA). When a few amounts (0.5%) of metal chelates were added, the flame retardancy of the IFR-PVA systems was significantly improved, having a high LOI value of 34.2 in a total IFR loading of 15 wt.%. In order to have an understanding of the resulting flame retardant effects, the thermal degradation behaviors of IFR-PVA systems were investigated by thermogravimetric analysis (TGA), and the morphology and structures of residues generated in different conditions were investigated by scanning electronic microscopy (SEM) and FTIR spectra. The results show that NiSAO can promote the thermal stability of the IFR-PVA; the residual char containing polyphosphoric or phosphoric acid is formed during the combustion; the formation of a continuous and dense char layer could inhibit the transmission of heat during contacting with flame and shows good flame retardancy.     

Calix[4]crown in dual sensing functions with FRET

A new calix[4]crown chemosensor based on dual sensing probes reveals Pb²⁺ ion selectivity over other metal ions, which arises from a hypsochromic shift of azo units in UV spectrum as well as a fluorescence enhancement of pyrenyl parts in fluorescence spectrum via a suppressed FRET.     

Solid-liquid equilibrium diagrams of common ion binary salt hydrate mixtures involving nitrates and chlorides of magnesium, cobalt, nickel, manganese, and iron(III)

The solid-liquid equilibrium diagrams of binary mixtures involving magnesium nitrate hexahydrate with cobalt nitrate hexahydrate, nickel nitrate hexahydrate (partly), manganese nitrate tetrahydrate, and iron(III) nitrate nonahydrate and of magnesium chloride hexahydrate with cobalt and nickel chlorides hexahydrates and manganese chloride tetrahydrate, and the of two manganese salts were determined. Those diagrams that showed a simple eutectic were fitted by the Ott equation and where the required BET parameters were available, the magnesium salt rich parts of the liquidus were modeled by means of this method.     

金属离子对中位─四（4─N甲氧羰甲基吡啶）卟啉表面增强拉曼光谱的影响

研究了金属离子对吸附在银胶表面的中位－四（４－Ｎ甲氧羰甲基吡啶）卟啉表面增强拉曼光谱的影响。结果表明，中位－四（４－Ｎ甲氧羰甲基吡啶）卟啉可发生金属离子取代反应。金属离子嵌入卟啉大环，吸附在银胶表面的中位－四（４－Ｎ甲氧羰甲基吡啶）卟啉转变为金属配合物。给出了各种金属配合物主要拉曼峰的经验式归属。金属离子的半径，ｄ电子对卟啉环的排斥作用，金属卟啉骨架模式频率随孔穴大小，大环的平面性和π－π相互作用而相应变化的特性，都可用来解释不同金属离子配合物的结构灵敏特征峰为何存在着差异。     

Chemically-bonded stationary phases for thin-layer chromatography of metal ions

Summary A numer of bonded stationary phases were investigated for the separation of Cd²⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ by thin-layer chromatography. The effect of structure, surface loading, type of silica gel and mobile phase concentration was considered.