Highly reduced iron-doped lithium niobate for optoelectronic tweezers

We investigate the applicability of highly reduced lithium niobate samples doped with iron for the use as optoelectronic tweezers. Increasing the reduction degree of Fe-doped lithium niobate is well known to increase the photoconductivity and reduce the writing time of internal space-charge fields. Based on our measurements of the photorefractive properties, we determine the optimal conditions for dielectrophoretic trapping and present the application of Fe-doped lithium niobate as optoelectronic tweezers. For higher reduction degrees, an unexpected decrease in the photovoltaic current density and the saturation space-charge field is reported.     

Synthesis,characterization of nanosized CoAl<Subscript>2</Subscript>O<Subscript>4</Subscript> and its electrocatalytic activity for enhanced sensing application

Nanosized cobalt aluminate (CoAl₂O₄) was prepared by thermolysis of heteronuclear coordination compound, namely [Al₂Co(C₂O₄)₄(OH₂)₆]. The synthesized precursor was characterized by chemical analysis, vibrational spectra and thermal analysis. The cobalt aluminate obtained after a heating treatment of the precursor at 700 °C was characterized by IR, XRD, TEM coupled with SAED measurements. Two types of carbon-based electrodes, glassy carbon and boron-doped diamond electrodes were decorated with the obtained cobalt aluminate in order to enhance the electroanalytical performance for the tetracycline (TC) detection in the aqueous solutions. Cyclic voltammetry technique was used to determine the effect of the nanosized CoAl₂O₄ on the electrochemical oxidation of TC and as consequence, for TC detection at both carbon-based electrodes. The obtained cobalt aluminate exhibited the electrocatalytic activity toward TC detection in direct relation with the type of the carbon substrate, which allowed enhancing the electroanalytical parameters of TC detection in the aqueous solution.     

Photocatalytically-assisted electrochemical degradation of <Emphasis Type="Italic">p</Emphasis>-aminophenol in aqueous solutions using zeolite-supported TiO<Subscript>2</Subscript> catalyst

This paper reports the results of an investigation into enhancement of the electrochemical oxidation of p-aminophenol (4-AP) in an aqueous solution with a boron-doped diamond (BDD) electrode, assisted by photocatalysis using a zeolite-supported TiO₂ (Z-TiO₂) catalyst. The BDD electrode was characterised in 0.1 M Na₂SO₄-supporting electrolyte and the presence of 4-AP by open-circuit potential behaviour (OCP) and cyclic voltammetry (CV). The electrode behaviour was investigated in the dark and following UV irradiation and in the absence/presence of the Z-TiO₂ catalyst. The electro-oxidation process was carried out using chronoamperometry (CA) and multiple-pulsed amperometry (MPA) at the selected potential under potentiostatic conditions. The electrochemical degradation process of 4-AP on the BDD electrode was improved by the application of a pulsed potential, which allowed both in-situ electrochemical cleaning of the electrode and indirect oxidation of 4-AP by oxygen evolution. The application of photocatalysis using Z-TiO₂ in the 4-AP electrochemical degradation exhibited an enhanced effect when the anodic potential was set at +1.25 V vs. Ag/AgCl in the water stability region, close to the oxygen evolution potential.     

Dendritic oligothiophenes terminated with tris(alkyloxy)phenylethynyl tails: synthesis, physical properties, and self-assembly

Three-dimensional (3D) π-conjugated dendritic oligothiophenes up to a third generation have been functionalized with tris(decyloxy)phenylethynyl tails at the periphery. The first-generation compounds (3 T-p-Ph-C10 and 6 T-p-Ph-C10) were synthesized by palladium-catalyzed Sonogashira coupling reactions, whereas the higher generation products were synthesized by palladium-catalyzed Suzuki coupling reactions in a divergent approach. The optical and electrochemical properties were investigated by UV/Vis absorption, fluorescence spectroscopy, and cyclic voltammetry. The results revealed that the terminal tris(alkyloxy)phenylethynyl groups are conjugated to the branched oligothiophene core, yielding redshifted absorption and fluorescence spectra and reduced optical band gaps relative to the dendritic oligothiophene core. A structural study revealed a close relationship between the type of supramolecular organization and the size of the oligothiophene core. The first-generation compounds 3 T-p-Ph-C10 and 6 T-p-Ph-C10 displayed columnar phases in the bulk state, which was confirmed by two-dimensional wide-angle X-ray scattering (2D WAXS) measurements. The self-assembly into columnar stacks has mainly been attributed to phase separation between the rigid thiophene cores and the flexible side-chains assisted by minor π-stacking interactions between the conjugated dendritic oligothiophene units. The high-generation compounds, however, showed less ordered structures in the solid state.     

Biocompatible functionalization of polymersome surfaces: a new approach to surface immobilization and cell targeting using polymersomes

Vesicles assembled from amphiphilic block copolymers represent promising nanomaterials for applications that include drug delivery and surface functionalization. One essential requirement to guide such polymersomes to a desired site in vivo is conjugation of active, targeting ligands to the surface of preformed self-assemblies. Such conjugation chemistry must fulfill criteria of efficiency and selectivity, stability of the resulting bond, and biocompatibility. We have here developed a new system that achieves these criteria by simple conjugation of 4-formylbenzoate (4FB) functionalized polymersomes with 6-hydrazinonicotinate acetone hydrazone (HyNic) functionalized antibodies in aqueous buffer. The number of available amino groups on the surface of polymersomes composed of poly(dimethylsiloxane)-block-poly(2-methyloxazoline) diblock copolymers was investigated by reacting hydrophilic succinimidyl-activated fluorescent dye with polymersomes and evaluating the resulting emission intensity. To prove attachment of biomolecules to polymersomes, HyNic functionalized enhanced yellow fluorescent protein (eYFP) was attached to 4FB functionalized polymersomes, resulting in an average number of 5 eYFP molecules per polymersome. Two different polymersome-antibody conjugates were produced using either antibiotin IgG or trastuzumab. They showed specific targeting toward biotin-patterned surfaces and breast cancer cells. Overall, the polymersome-ligand platform appears promising for therapeutic and diagnostic use.     

Predicting the influence of a p2-symmetric substrate on molecular self-organization with an interaction-site model

An interaction-site model can a priori predict molecular self-organisation on a new substrate in Monte Carlo simulations. This is experimentally confirmed with scanning tunnelling microscopy on Fréchet dendrons of a pentacontane template. Local and global ordering motifs, inclusion molecules and a rotated unit cell are correctly predicted.     

Reactive Nanoparticles Derived from Polysaccharide Phenyl Carbonates

Polysaccharide (PS) based nanoparticles (NP) are of great interest for biomedical applications. A key challenge in this regard is the functionalization of these nanomaterials. The aim of the present work was the development of reactive PS-NP that can be coupled with an amino group containing compounds under mild aqueous conditions. A series of cellulose phenyl carbonates (CPC) and xylan phenyl carbonates (XPC) with variable degrees of substitution (DS) was obtained by homogeneous synthesis. The preparation of PS-NP by self-assembling of these hydrophobic derivatives was studied comprehensively. While CPC mostly formed macroscopic aggregates, XPC formed well-defined spherical NP with diameters around 100 to 200 nm that showed a pronounced long-term stability in water against both particle aggregation as well as cleavage of phenyl carbonate moieties. Using an amino group functionalized dye it was demonstrated that the novel XPC-NP are reactive towards amines. A simple coupling procedure was established that enables direct functionalization of the reactive NP in an aqueous dispersion. Finally, it was demonstrated that dye functionalized XPC-NP are non-cytotoxic and can be employed in advanced biomedical applications.