Synthesis and Photophysics of Some Novel Imidazole Derivatives Used as Sensitive Fluorescent Chemisensors

Some novel imidazole derivatives were developed for highly sensitive chemisensors for transition metal ions. Since these compounds are sensitive to different external stimulations such as UV irradiation, heat, increasing pressure and changing the environmental pH causing colour change and so they can be used as a ??multi-way?? optically switchable material. A prominent fluorescence enhancement was found in the presence of transition metal ions such as Hg²⁺, Pb²⁺ and Cu²⁺ and this was suggested to result from the suppression of radiationless transitions from the n-??* state in the chemisensors. The existence of C-H??.O intramolecular hydrogen bonding in dmphnpi is confirmed by the Natural Bond Orbital analysis (NBO). The Mulliken, NBO charge analysis and the HOMO-LUMO energies were also calculated. The electric dipole moment (??) and the first-hyperpolarisability (??) value of the investigated molecules have been studied both experimentally and theoretically which reveal that the synthesized molecules have microscopic non-linear optical (NLO) behaviour with non-zero values. Ground and excited state DFT calculation were carried out in order to find out dipole moment and energy.     

Ni2+—6X-络合物g因子的双自旋—轨道耦合系数模型

本文提出一个计算Ni²⁺—6X^-络合物g因子的双自旋-轨道耦合系数模型,并用以计算NaCl:Ni²⁺和NaBr:Ni²⁺的g因子。计算中采用了一种半经验方法来确定分子轨道系数。结果表明,对Br^-或I^-这类具有大的自旋-轨道耦合系数的配体离子,配体自旋-轨道耦合作用对g因子的贡献不可忽略。这表明,对某些共价晶体,g因子的计算必须用双自旋-轨道耦合系数模型的理论公式而不能用只包括 关键词：     

The fluorescence of polyamidoamine dendrimers peripherally modified with 1,8-naphthalimide groups: Effect of the rare earth ions and protons

We report the absorption spectra, fluorescent spectra and photophysical properties of G 2.0 polyamidoamine dendrimers with peripheral 1,8-naphthalimide groups with the hydrogen ions, the rare earth ions (Er³⁺, Tb³⁺, Nb³⁺, Eu³⁺, Yb³⁺ and Gd³⁺) and the mixture of the rare earth metal and hydrogen ions. The presence of the rare earth ions and hydrogen ions was found to enhance the fluorescence owing to the coordination between the rare earth metal or hydrogen ions and internal amido groups of polyamidoamine (PAMAM) from dendrimer. The result from the 3D isogram of the fluorescence spectra for the dendrimers with peripheral 1,8-naphthalimide groups show that it was obtained for the different emission fluorescence intensity and scope by varying the excitation wavelength and the different rare earth ions as well as its concentration. The results obtained reveal that the capacities of these systems might have acted as a sensitive label agent of the rare earth cations and protons.     

On the thermodynamics of phase transitions in metal hydrides

Metal hydrides are solutions of hydrogen in a metal, where phase transitions may occur depending on temperature, pressure etc. We apply Le Chatelier’s principle of thermodynamics to a particular phase transition in TiH _x , which can approximately be described as a second-order phase transition. We show that the fluctuations of the order parameter correspond to fluctuations both of the density of H⁺ ions and of the distance between adjacent H⁺ ions. Moreover, as the system approaches the transition and the correlation radius increases, we show -with the help of statistical mechanics-that the statistical weight of modes involving a large number of H⁺ ions (‘collective modes’) increases sharply, in spite of the fact that the Boltzmann factor of each collective mode is exponentially small. As a result, the interaction of the H⁺ ions with collective modes makes a tiny suprathermal fraction of the H⁺ population appear. Our results hold for similar transitions in metal deuterides, too. A violation of an -insofar undisputed-upper bound on hydrogen loading follows.     

Vibrationally assisted transitions and phonon spectra in crystalline solids

The vibrationally assisted electronic (vibronic) transitions of localized centers in crystalline solids provide relevant information regarding the phonon spectra of the host materials. We present the vibronic spectra of some compounds with particular attention to the case of the transition metal ions V²⁺ and Cr³⁺ embedded in simple ionic crystals such as MgO or more complex systems such as YAG. The vibronic spectra are interpreted in light of the radiative selection rules and are compared with phonon data obtained with other techniques such as neutron scattering, infrared and Raman spectroscopies. Conclusions regarding the effectiveness of vibronic spectra in uncovering the phonon spectral distributions are presented.     

Photodetachment of H− near a Dielectric-Covered Metal Surface

We combine a simple model potential with closed-orbit theory to study the photodetachment of H^? near a dielectric-covered metal surface. We calculate photodetachment cross sections to show that the chemisorption of a dielectric thin layer on the metal surface can significantly affect the photodetachment of negative ions. Compared to the photodetachment of hydrogen negative ions near clean metallic surfaces, our calculated cross sections show stronger oscillations, the amplitude of the oscillation growing with the layer thickness. For fixed thickness, the amplitude depends on the dielectric constant and on the metallic surface. We expect our study to guide future experimental studies of negative-ion photodetachment from dielectric-covered metallic surfaces.     

ESR OF Ti(III) in LiCl-KCl Eutectic

Study of corrosion phenomena associated with the use of molten salts as coolants raised interest in the behaviour of various metal ions in such melts. Gruen & McBeth¹, in the early sixties, studied various transition metal ions in LiCl/KCl eutectic. The purpose of the present letter is an attempt to correlate ESR data with data derived from optical spectroscopy, in particular with respect to the equilibrium between hexa- and tetra-coördinate species of Ti(III) with chlorine ions.     

Radiation effects in nanoclusters embedded in solids

Nanoclusters embedded in hard solid materials such as silica show great promise forincreased practical applications, as they combine the exciting nanosize effects with veryhigh structural stability. Ion irradiation can be used to tailor the properties of theseclusters, the perhaps most dramatic example being the use of swift heavy ions to reshapespherical metal nanoparticles to have antennas or become rods. In this article we reviewexperimental and simulation studies of ion beam processing of nanoclusters embedded insolids.     

Interfacial kinetic enhancement of metal ion adsorption on binary mixed self-assembled monolayers

The adsorption of metal ions, a type of surface reaction on binary mixed self-assembled monolayers (SAMs) on a gold surface composed of 1,6-hexanedithiol (HDT) with 11-mercaptoundecanoic acid (MUA), was monitored by in situ surface plasmon resonance (SPR) measurements. The differential SPR reflectance (ΔR) enables the kinetics of adsorption of Pt²⁺ on the mixed SAMs to be investigated. Unlike single HDT SAM, kinetic analyses of the mixed SAMs showed that the rate of adsorption of Pt²⁺ was enhanced and that it was highly dependent on the fraction of MUA present. These SPR measurements suggest that the adsorption rate of metal ions can be readily manipulated simply by using mixed SAMs.     

第一过渡金属酞菁分子的电子结构的第一性原理计算

对第一过渡金属酞菁化合物(Metal Phthalocyanine,MPc,M=Sc,Ti,V,Cr,Mn,Fe,Co,Ni和Cu)的电子结构和基本物理化学性质进行了第一性原理计算.理论模拟出来的STM图像表现出亚分子结构,与已有的实验观察结果相当吻合,且跟金属原子的d电子组态明显有关.在小偏压条件下,第一过渡金属首尾端ScPc,NiPc和CuPc分子的中央金属离子在STM图像表现为空洞,其他所有金属酞菁分子的中央金属离子均为亮斑.同时还研究了ScPc和NiPc分子的STM图像与偏压的关系,当针尖偏压分别 关键词： STM图像模拟 金属酞菁 电子结构     

Metal ion interaction with ribosomal RNA

Summary We have used UV differential spectroscopy in order to detect small modifications in the ribosomal RNA absorption spectrum due to the binding of rRNA molecules with the metal ions Na⁺, K⁺, Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺ and Ni²⁺. Our data show that all the ions, investigated are involved in ion-type bond with the phosphate groups of rRNA and cause a refolding of the molecules with an overall increase in basebase ?stacking? interactions. Besides this ion-type binding with phosphate groups, transition metal ions Mn²⁺, Co²⁺, and Ni²⁺ are also able to bond directly to the bases To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

The calculations of cell dimensions of stoichiometric phases and binary and ternary solid solutions with the A15 structure

Equations that successfully reproduce the unit cell dimensions of stoichiometric (i) transition metal-transition metal (T-T) and (ii) transition metal-non-transition metal (T-B) phases with the β-Wolfram or A15 structure in terms of the diameters of the component atoms for CN 12 [J. Less-Common Metals, 81, 161 (1981)], are hear applied to binary and ternary solid solutions with the A15 structure, to discover how well and under what conditions they reproduce the observed lattice parameter variation. That in the main, they perform satisfactorily gives further credence to the model on which they are based, which shows how the various interatomic contacts within the interpenetrating icosahedra and CN 14 polyhedra of the structure, combine together in controlling the cell dimensions of the phases. The model also indicates that it is the contacts between the transition metal atoms that are paramount in controlling a. This fact leads to a specific prediction for the lattice parameter variation in transition-metal-rich solid solutions of T-B phases, which is essentially substantiated for phases of niobium.     

Magnetic and transport properties of transition-metal implanted ZnO single crystals

ZnO single crystals were implanted with Mn, Co and Ni with fluences between 1 × 10¹⁶ cm^-2 and 1 × 10¹⁷ cm^-2 and energy of 200 keV. Results indicate that aggregation of transition metal ions in the as implanted state occurs only in the case of Ni. After an annealing stage to recover the ZnO structure aggregation occurs for the higher fluences of all implanted species. For lower concentrations paramagnetic behaviour with magnetic moments close to those of individual ions is observed. No polarised impurity band is formed as a result of the presence of transition metal ions and all samples show electrical conduction by carriers in extended states of ZnO. Significant values of magnetoresistance are measured at low temperatures, where electrical transport is described by hopping mechanisms between localized states. The sign of the magnetoresistance is dependent of the doping ion and is correlated with the observed aggregation.     

Surface states and its influence on luminescence in ZnS nanocrystallite

In this pape,r the influence of surface effects on the self-activated (SA) luminescence in ZnS nanoparticles prepared by the wet-chemical method is presented. It is observed that the luminescence of SA decreases dramatically by rinsing with methanol. In the rinsed sample, the luminescence of SA increases more by ultraviolet (UV) light irradiation. To clarify its origin, the Raman spectra and electron paramagnetic resonance (EPR) are studied. The results demonstrate that the vibrational modes assigned to organic functional groups of -OH and -COO and -CH₃ decreases remarkably by rinsing, while the EPR signal originated from the unpaired electrons of some transition metal impurity ions including Mn²⁺ increases. It is suggested that the SA centers prefer to occupy the sites near the surface and that the donor of SA emission may be partly related to the organic functional groups of -OH and -COO adsorbed on the surface. The surface-dangling bonds caused by unpaired electrons of some transition metal impurity ions play a role of surface states, leading to the quenching of the SA emissions. The organic functional groups chemically combine with these surface-dangling bonds leading to the decrease in surface states and surface nonradiative relaxation channels and to the increase in the SA emissions.     

Laser-related spectroscopy of ion-doped crystals for tunable solid-state lasers

In this work an overview of transition metal (TM) ion- and rare earth (RE) ion-doped crystals for application as tunable solid-state lasers will be given. Spectroscopic and laser results will be presented including recent research and advances in this field. Within this work tunability is defined as the possibility to achieve laser oscillation in the vibronic sideband of a transition. Tunable solid-state lasers are of interest for a wide field of applications, e.g. in scientific research, in medicine, for measurement and testing techniques, ultra short pulse generation, and communication. They can also be used as coherent light sources for second-harmonic generation, for optical parametric oscillators, and for sum- and difference-frequency generation. Tunable laser media based on 3d?3d transitions of transition-metal ions and 4f?5d transitions of rare-earth ions cover nowadays almost the whole spectral range between 270 nm and 4500 nm, see Fig. 1 [1-15]. In comparison to laser systems based on the 4f?4f transitions of trivalent rare-earth ions, tunable lasers based on 3d?3d and 4f?5d transitions are in general affected by a higher probability of excited-state absorption (ESA), a higher probability of non-radiative decay, and a higher saturation intensity leading to higher laser thresholds. Often laser oscillation cannot be obtained at all. These general topics will be considered in Sect. 1, where the basic aspects of tunable solid-state lasers are discussed: these are the preparational, the spectroscopic, and the laser aspect. In Sect. 2, the investigation of transition metal ion-doped crystals with respect to the realization of tunable laser oscillation is presented. The work is focused on transition-metal ions of the 3d row (Fe row) and divided into two subsections according to the octahedral and tetrahedral coordinations of the ion investigated. Each subsection is structured according to the electron configurations: 3d¹, 3d³, 3d⁴, and 3d⁸ for the octahedrally coordinated ions and 3d¹, 3d², and 3d⁴ for the tetrahedrally coordinated ions. Section 3 deals with interconfigurational transitions of divalent and trivalent rare-earth ions. Finally, in Sect. 4 the work is summarized. Received: 22 December 2000 / Published online: 30 March 2001     

Hofmeister series and ionic effects of alkali metal ions on DNA conformation transition in normal and less polarised water solvent

Normal and less polarised water models are used as the solvent to investigate Hofmeister effects and alkali metal ionic effects on dodecamer d(CGCGAATTCGCG) B-DNA with atomic dynamics simulations. As normal water solvent is replaced by less polarised water, the Hofmeister series of alkali metal ions is changed from Li⁺ > Na⁺ ? K⁺ ? Cs⁺ ? Rb⁺ to Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺. In less polarised water, DNA experiences the B→A conformational transition for the lighter alkali metal counterions (Li⁺, Na⁺ and K⁺). However, it keeps B form for the heavier ions (Rb⁺ and Cs⁺). We find that the underlying cause of the conformation transition for these alkali metal ions except K⁺ is the competition between water molecules and counterions coupling to the free oxygen atoms of the phosphate groups. For K⁺ ions, the ‘economics’ of phosphate hydration and ‘spine of hydration’ are both concerned with the DNA helixes changing.     

识别过渡金属离子的1,8-萘二甲酰亚胺多胺衍生物荧光传感器的研究

设计合成了用以检测过渡金属离子的荧光化学敏感器体系,它们是由1,8-萘二酰亚胺为荧光团,多胺衍生物为金属离子受体组成．在室温下对其光物理性质的研究中发现,在没有加入过渡金属离子时,由于体系内存在有效的光诱导电子转移过程使得荧光团的荧光被淬灭．加入过渡金属离子后,金属离子受体中的氮原子和过渡金属离子之间的配位作用阻断了光诱导电子转移过程,体系的荧光增强．不同的金属离子受体表现出了和过渡金属离子不同的配位识别能力,并且通过荧光的变化传递出受体-金属离子作用的信息．     

Investigation by EELS and TRIM simulation method of the interaction of Ar and N ions with the InP compound

In this study, the EELS results revealed the great sensitivity of InP compound submitted to Ar⁺ or N⁺ ions at low energy. The preliminary treatment of InP by the Ar⁺ ions was useful as part of the cleaning process of the surface. Further argon ions bombardment on cleaned InP led however to breaking of chemical bonds In–P, with desorption of phosphorus atoms and appearance of In metal distributed on InP. The damaged InP by Ar⁺ ions, constituted the diphase (In; InP) system of depth of about 30 Å, involving a superficial roughness. The In metal proportion on such a system was determined by a calculation method based on the experimental EELS spectra of pure In and InP.We submitted the heated and no heated system (In; InP) to nitrogen ions bombardment. The nitrogen reacted with the In metal to compensate the phosphorus vacancies so that InN species were formed. The heating of (In; InP) system at 450 °C, allowed the surface reconstruction with elimination of defects due to the structure and the roughness. The temperature also caused the coalescence of In metal towards the surface. Because of the physical stability of the interface of heated (In; InP) system, the nitrogen reacted with the outmost layers of In metal to form a homogeneous layer of InN of thickness estimated at 20 Å. We associated to the EELS the TRIM (Transport and Range of Ions in Matter) simulation method in order to show the mechanism of interaction Ar⁺ or N⁺ ions-InP and determine the disturbed depth as a function of the energy. The EELS alone was not able to give us with accuracy the disturbed depth of the target by these ions.     

Monoatomic and cluster beam effect on ToF-SIMS spectra of self-assembled monolayers on gold

Self-assembled monolayers represent well-defined systems that is a good model surface to study the effect of primary ion beams used in secondary ion mass spectrometry. The effect of polyatomic primary beams on both aliphatic and aromatic self-assembled monolayers has been studied. In particular, we analysed the variation of the relative secondary ion yield of both substrate metal-cluster (Au_n⁻) in comparison with the molecular ions (M⁻) and clusters (M_xAu_y⁻) by using Bi⁺, Bi₃⁺, Bi₅⁺ beams. Moreover, the differences in the secondary ion generation efficiency are discussed. The main effect of the cluster beams is related to an increased formation of low-mass fragments and to the enhancement of the substrate related gold-clusters. The results show that, at variance of many other cases, the static SIMS of self-assembled monolayers does not benefit of the use of polyatomic primary ions.