Incorporation of stable organic radicals into cyclotriphosphazene: preparation and characterization of mono- and diradical adducts

Stable cyclotriphosphazenes 4 and 5, incorporating one and two carbon radical centers, respectively, have been easily prepared and characterized. EPR spectroscopic studies in fluid solution at room temperature were carried out for both compounds and also for diradical 5 in frozen solvent matrixes. Spectral results are consistent with a triplet or degenerate singlet triplet ground state for 5. Reductive cyclic voltammetry shows a redox couple, being monoelectronic for 4 and bielectronic for 5.     

Synthesis and photoluminescent properties of 1,1'-binaphthyl-based chiral phenylenevinylene dendrimers

New chiral, soluble binaphthyl derivatives that incorporate stilbenoid dendrons at the 6,6'-positions have been prepared. The synthesis of the new enantiopure dendrimers was performed in a convergent manner by Horner-Wadsworth-Emmons (HWE) reaction of the appropriately functionalized 1,1'-binaphthyl derivative (R)-1 and the appropriate dendrons (R)(2n)G(n)-CHO. Different electroactive units were incorporated in the peripheral positions of the dendrons in order to tune both the optical and electrochemical behavior of these systems. Fluorescence measurements on the chiral dendrimers reveal a strong emission with maxima between 409 and 508 nm depending upon the substitution pattern. Finally, the redox properties of the dendrimers were determined by cyclic voltammetry, showing the influence of the functional groups at the peripheral positions of the dendrimer on the redox behavior of these systems.     

Particle and surface characterization of a natural illite and study of its copper retention

Illite clays are known to have a strong affinity for metallic pollutants in the environment and can be applied as low-cost adsorbents for industrial waste treatment. A crucial factor in the development of such applications, however, is the understanding of the chemical, mineralogical, and colloidal properties of these clays. It is also important to understand the mechanisms involved in the surface adsorption of metals by these adsorbants. In order to study the retention of transition metals on illite clays, we have applied surface characterization techniques such as FPIA, SEM-EDX, XRD, N2 (77 K) adsorption, and FTIR. In addition to these experimental techniques, we have also employed a theoretical model that accounts for the chemistry of transition metal ions, and considers the global retention process to be the sum of several single retention processes. This model adequately fits the experimental data and allows for the speciation of metal retention on illite surfaces. Between pH values of 2.53 and 3.01 the only adsorption processes are the electrostatic sorption of [Cu(H2O)6]2+, and the surface complexation of [Cu(H2O)6]2+ and [Cu(OH)(H2O)5]+ ions. Surface complexation of [Cu(OH)(H2O)5]+ ions increases with pH, overcoming [Cu(H2O)6]2+ retention, and thus contributing to the surface precipitation of Cu(OH)2.     

Electrochemical characterization of core@shell CoFe2O4/Au composite

Quantum dots (QDs) have received considerable attention due to their unique optical and electrical properties. Although substantial research has focused on the potential applications and toxicological impacts of QDs, far less effort has been directed toward understanding their fate and transport in the environment. In this work, the effect of four coatings, polyethylene glycol functionalized polymer (PEGP), carboxyl derivatized polymer (COOHP), linoleic acid (LA), and polyacrylic acid-octylamine (PAA-OA), on the transport and retention of QDs in porous media were evaluated under environmentally relevant conditions. Aqueous QD suspensions (ca. 10 nM) were introduced into water-saturated columns packed with 40–50 mesh Ottawa sand at a pore-water velocity of 7.6 m/day. At an ionic strength (IS) of 3 mM and pH of 7, PEGP-coated QDs were completely retained within the column, while more than 60 % of COOHP-coated QDs were transported through a column run under identical conditions. When PAA-OA and LA were used as coatings, effluent QD recoveries increased to more than 65 and 89 % of the injected mass, respectively. Additionally, a decrease in pH from 9.5 to 5.0, or an increase of IS from 0 to 30 mM reduced the eluted mass of PAA-OA-coated QDs by more than 2 and 15 times, respectively. The relative mobility of coated QDs (LA > PAA-OA > COOHP > PEGP) was consistent with total interaction energy profiles between QDs and sand surfaces calculated based on Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. At an IS of 3 mM (NaCl) and pH 7, a linear correlation was obtained between the fraction of eluted QDs and the magnitude of the primary interaction energy barrier. These findings demonstrate the strong dependence of QD transport on coating type and indicate that interaction energies based on DLVO theory can be used to predict the relative mobility of QDs in porous media.     

Enhancing energy harvesting by coupling monostable oscillators

The performance of a ring of linearly coupled, monostable nonlinear oscillators is optimized towards its goal of acting as energy harvester – through piezoelectric transduction – of mesoscopic fluctuations, which are modeled as Ornstein-Uhlenbeck noises. For a single oscillator, the maximum output voltage and overall efficiency are attained for a soft piecewise-linear potential (providing a weak attractive constant force) but they are still fairly large for a harmonic potential. When several harmonic springs are linearly and bidirectionally coupled to form a ring, it is found that counter-phase coupling can largely improve the performance while in-phase coupling worsens it. Moreover, it turns out that few (two or three) coupled units perform better than more.     

Shedding Light on the Origin of Solid-State Luminescence Enhancement in Butterfly Molecules

Different molecular strategies have been carefully evaluated to produce solid-state luminescence enhancement (SLE) in compounds that show dark states in solution. A set of α-phenylstyrylarene derivatives with a butterfly shape have been designed and synthesised, for the first time, with the aim of improving the solid-state fluorescence emission of their parent styrylarene compounds. Although these butterfly molecules are not fluorescent in solution, one of them (1,2,4,5-tetra(α-phenylstyryl)benzene) exhibits a fluorescence quantum yield as high as 68 % in a drop-cast sample and 31 % in its crystalline form. In contrast, 1,3,5-tris(α-phenylstyryl)benzene and 4,6-bis(α-phenylstyryl)pyrimidine do not show SLE. A range of fluorescence spectroscopy experiments and DFT calculations were carried out to unravel the origin of different photophysical behaviour of these compounds in the solid state. The results indicate that a rational strategy to control the SLE effect in luminogens depends on a delicate balance between molecular properties and inter-/intramolecular interactions in the solid state.     

能量连续传递的超分子人工光捕获系统构筑及其在光催化反应中应用

光捕获系统在自然界光合作用过程中起着至关重要的作用.模拟自然界的光捕获体系,在生物成像、发光器件、光催化以及解决人类面临的能源问题等方面均具有重要意义[1].目前,在水相中构筑高效的人工光捕获系统已取得一系列重要进展[2].然而,为了更好地理解并模拟自然界中以多通道信息通讯为特征的捕光天线系统[3],构筑具有多步连续能量转移特征并能实现光能到化学能转化的人工光捕获体系仍然是一项具有挑战性的工作.     

Layer-block dendrimers with alternating thienylenevinylene and phenylenevinylene units

A series of new hybrid, layer-block π-conjugated dendrons and dendrimers with alternating thienylenevinylene and phenylenevinylene units has been prepared by means of an orthogonal and convergent-growth methodology that made use of the Horner-Wadsworth-Emmons (HWE) reaction. The placement of the thiophene and benzene rings can be accurately controlled to afford a large variety of dendritic structures, although access to compounds of high generation proved difficult. The optical properties of the synthesized dendrimers were determined by UV/vis and fluorescence spectroscopy, and the influence of the generation and nature of the core on the behavior of these materials was evaluated.     

Preparation of polymer-supported gold nanoparticles based on resins containing ionic liquid-like fragments: easy control of size and stability

Crosslinked polymers containing covalently attached functional sites with chemical structures related to those present in ILs and having macroscopic properties very similar to the ones of the corresponding bulk ILs can be advantageously applied to the preparation of gold nanoparticles (AuNPs). The size and morphology of the resulting metal nanoparticles (MNPs) can be easily modulated through a proper combination of the synthetic method used for the generation of the NPs and the structural elements of the polymer. Additionally, the resulting supported AuNPs are demonstrated to be stable for at least eight months with the vials open to the atmosphere. Several synthetic methodologies have been studied, as well as different structural parameters for the functional polymers. Those include the chemical nature (anions and cations) and loading of the ionic liquid-like fragments and the morphology of the polymeric matrix. The results obtained show the potential to prepare supported AuNPs with narrow size distributions and small diameters that can have potential interest for application in different fields.