Detection of heavy metal ions by ISFETs in a flow injection analysis cell

An ion-selective field-effect transistor (ISFET) is chemically modified with a photopolymerizable and cyanopropyl modified polysiloxane containing N,N,N',N'-tetrabutyl-3,6-dioxaoctane-dithioamide as Cd2+ ionophore. This CHEMFET has a Nerstian response (30 mV/decade) to a change of cadmium activity in aqueous solutions. Selectivity coefficients of the CHEMFET towards potassium, calcium, copper, and lead are given. Preliminary results of the CHEMFET in a flow injection analysis cell without wire bonding and polymeric encapsulation are presented

Preparation and properties of organic dispersions of monodisperse silica receptor colloids grafted with calixarene derivatives or alkyl chains

We introduce cation-selective receptor colloids consisting of a monodisperse inorganic silica core grafted with an organic layer containing calixarene receptor molecules. The surface layer is designed to provide chemical selectivity (toward Cs+) as well as colloidal stability in organic solvents of interest in which silica spheres otherwise may flocculate. Grafting procedures for commercial- and laboratory-made silica dispersions are investigated for 25,27-bis[1-(11-hydroxyundecyl)oxy]calix[4]arene-crown-6 (designed and synthesized for this purpose), octadecyl alcohol, and mixtures ("cografting") of both compounds. Special attention is given to the nature of the solvent, which markedly influences grafting densities and colloidal stability during and after grafting procedures. NMR, elemental analysis, and light scattering are used to characterize a variety of carefully purified, grafted silica dispersions and to demonstrate, among other things, the presence of calixarene groups on the silica spheres. Preliminary complexation experiments with cesium chloride are reported. NMR and electrophoresis indicate that calixarene-silica colloids indeed are receptors for cesium cations

Detection of heavy metal ions by ISFETs in a flow injection analysis cell

An ion-selective field-effect transistor (ISFET) is chemically modified with a photopolymerizable and cyanopropyl modified polysiloxane containing N,N,N',N'-tetrabutyl-3,6-dioxaoctane-dithioamide as Cd2+ ionophore. This CHEMFET has a Nerstian response (30 mV/decade) to a change of cadmium activity in aqueous solutions. Selectivity coefficients of the CHEMFET towards potassium, calcium, copper, and lead are given. Preliminary results of the CHEMFET in a flow injection analysis cell without wire bonding and polymeric encapsulation are presented

Metal–Organic Frameworks (MOFs) as Multivalent Materials: Size Control and Surface Functionalization by Monovalent Capping Ligands

Control over particle size and composition are pivotal to tune the properties of metal organic frameworks (MOFs), for example, for biomedical applications. Particle-size control and functionalization of MIL-88A were achieved by using stoichiometric replacement of a small fraction of the divalent fumarate by monovalent capping ligands. A fluorine-capping ligand was used to quantify the surface coverage of capping ligand at the surface of MIL-88A. Size control at the nanoscale was achieved by using a monovalent carboxylic acid-functionalized poly(ethylene glycol) (PEG-COOH) ligand at different concentrations. Finally, a biotin–carboxylic acid capping ligand was used to functionalize MIL-88A to bind fluorescently labeled streptavidin as an example towards bioapplications

Reactions of enamines of cyclodecanone and cyclododecanone with dimethyl acetylenedicarboxylate in apolar and in polar solvents

Enamines of cyclodecanone and cyclododecanone (1a‐d) react with dimethyl acetylenedicarboxylate (DMAD) in an apolar solvent via (2 + 2) cycloaddition and conrotatory opening of the cyclobutene ring in 3 to give the cis,trans‐cycloalkadienes 5a‐d in yields of 44–85%. The compounds 5 do not undergo further thermal or photochemical transformation of the cis,trans moiety. In methanol, the enamines react with DMAD to give bicyclo[7.2.1]dodecene (8a) or bicyclo[9.2.1]tetradecene (8b and 8c) derivatives. These reactions take place via intramolecular nucleophilic addition of the enamine moiety to the α‐methoxycarbonyl group in 10, which is formed from the intermediate Michael adduct 9. The structure of 8b was determined by single‐crystal X‐ray analysis

Substantial rate enhancements of the esterification reaction of phthalic anhydride with methanol at high pressure and using supercritical CO2 as a co-solvent in a glass microreactor

The esterification reaction of phthalic anhydride with methanol was performed at different temperatures in a continuous flow glass microreactor at pressures up to 110 bar and using supercritical CO2 as a co-solvent. The design is such that supercritical CO2 can be generated inside the microreactor. Substantial rate enhancements were obtained, viz. a 53-fold increase was obtained at 110 bar and 60 °C. Supercritical CO2 as a co-solvent gave rise to a 5400-fold increase (both with respect to batch experiments at 1 bar at the same temperature).\ud \ud \u

Gamma-radiolytic stability of new methylated TODGA derivatives for minor actinide recycling

The stability against gamma radiation of MeTODGA (methyl tetraoctyldiglycolamide) and Me2TODGA (dimethyl tetraoctyldiglycolamide), derivatives from the well-known extractant TODGA (N,N,N′,N′-tetraoctyldiglycolamide), were studied and compared. Solutions of MeTODGA and Me2TODGA in alkane diluents were subjected to 60Co γ-irradiation in the presence and absence of nitric acid and analyzed using LC-MS to determine their rates of radiolytic concentration decrease, as well as to identify radiolysis products. The results of product identification from three different laboratories are compared and found to be in good agreement. The diglycolamide (DGA) concentrations decreased exponentially with increasing absorbed dose. The MeTODGA degradation rate constants (dose constants) were uninfluenced by the presence of nitric acid, but the acid increased the rate of degradation for Me2TODGA. The degradation products formed by irradiation are also initially produced in greater amounts in acid-contacted solution, but products may also be degraded by continued radiolysis. The identified radiolysis products suggest that the weakest bonds are those in the diglycolamide center of these molecules