Hydrophilic ion-exchanger membranes with a high ion-exchange capacity not only find numerous applications in ion separations, but also have interesting properties when used as sensing membranes of ion-selective electrodes (ISEs). As pointed out in the literature, the hydrophilic nature of these membranes may reduce biofouling of ISE sensing membranes as caused by electrically neutral, hydrophobic interferents. This work shows that hydrophilic high-capacity ion-exchanger membranes are more resistant to Donnan failure (i.e., the limitation of the upper detection limit by co-ion transfer into the sensing membrane) than both hydrophobic ionophore-doped and hydrophobic ionophore-free ion-exchanger membranes. Nernstian responses of hydrophilic anion-exchanger membranes were found for anions as large as 2.0 nm, in spite of the cross-linked nature of the anion exchanger that was used. This shows that the high resistance of hydrophilic anion-exchangers to Donnan failure caused by cations such as tetrabutylammonium is not the result of size exclusion. For typical ions, the hydrophilicity of the anion exchanger does not play a decisive factor either. Instead, the excellent resistance to Donnan failure exhibited by hydrophilic ion exchange membranes is primarily caused by the high activity of exchangeable ions in the ion exchanger phase, which disfavors partitioning of ions of opposite charge (along with target ions) from samples into these sensing membranes. The absence of Donnan failure caused by hydrophobic co-ions may be of substantial benefit for measurements in biological samples.

Silver nanoparticles and nanowires can be efficiently synthesized in high yield using the polyol synthesis method. However, there are many open questions regarding the mechanisms involved, and how the size and morphology can be effectively controlled. In this work, silver nanoparticles were characterized during and after the synthesis procedure. In the early stages, crystalline silver-silver chloride nanoparticles (Ag-AgCl NPs) were the most commonly observed particles. As the reaction progressed, the fraction of Ag-AgCl NPs decreased while the fraction of isolated silver nanoparticles (Ag NPs) increased. We hypothesize that the AgCl in Ag-AgCl NPs dissolves as Ag­(I) into the solution and is then reduced to Ag(0), leaving the Ag portion as isolated Ag NPs with similar particle size, morphology, and microstructures. These Ag NPs accounted for the majority of the final product.

Potentiometric sensors, such as polymeric membrane, ion-selective electrodes (ISEs), have been used in the past to monitor a variety of chemical processes. However, the use of these sensors has traditionally been limited to aqueous solutions and moderate temperatures. Here we present an ISE with a high-capacity ion-exchange sensing membrane for measurements of nitrate and nitrite in the organic solvent propylene glycol at 150 °C. It is capable of continuously measuring under these conditions for over 180 h. We demonstrate the usefulness of this sensor by in situ monitoring of anion concentrations during the synthesis of copper and silver nanoparticles in propylene glycol using the polyol method. Ion chromatography and a colorimetric method were used to independently confirm anion concentrations measured in situ. In doing so, it was shown that in this reaction the co-ion nitrate is reduced to nitrite.

1IntroductionWith av iew to reduced biofouling,i on-selectivee lectrodes (ISEs) [1-7] with fluorous membranes [8][9][10][11] were developed for av arietyo fi ons.T hey show large improvements in selectivities as compared to conventionalI SE membrane matrixes,s uch as plasticized PVC.F or example,i onophore-free cation-exchangeI SEs made with perfluoroperhydrophenanthrene as membrane matrix have aselectivity range of 16 orders of magnitude [12],ascompared to 8o rders of magnitude for membranes made from plasticized PVC [12].A lso,f luorous membrane ISEs with fluorophilic ionophoresf or Ag + ,C O 3 2À Keywords: Ion-selective electrode · Polymer · Silver · Potassium · Fluorous [a] J.