Tin(IV) oxide coatings from hybrid organotin/polymer nanoparticles

Tin dioxide coatings are widely applied in glasses and ceramics to improve not only optical, but also mechanical properties. In this work, we report a new method to prepare SnO(2) coatings from aqueous dispersions of polymer/organotin hybrid nanoparticles. Various liquid organotin compounds were encapsulated in polymeric nanoparticles synthesized by miniemulsion polymerization. Large amounts of tetrabutyltin and bis(tributyltin) could be successfully incorporated in cross-linked and noncross-linked polystyrene nanoparticles that served as sacrificial templates for the formation of tin oxide coatings after etching with oxygen plasma or calcination. Cross-linked polystyrene particles containing bis(tributyltin)--selected for having a high boiling point--were found to be especially suited for the oxide coating formation. The content of metal in the particles was up to 12 wt %, and estimations by thermogravimetrical indicated that at least 96% of the total organotin compound was converted to SnO(2). The resulting coatings were mainly identified as tetragonal SnO(2) (cassiterite) by X-ray diffraction, although a coexistence of this phase with orthorhombic SnO(2) was observed for samples prepared with bis(tributyltin).

Catheter-type sensor for potentiometric monitoring of oxygen, pH and carbon dioxide

The fabrication and analytical performance of a catheter-type electrode suitable for potentiometric monitoring of PO2, pH and PCO2 in flowing blood is described. The catheter electrode is based on impregnating a single segment of dual-lumen gas permeable silicone rubber tubing with the proton ionophore tridodecylamine to impart H+ permselectivity to both inner and outer walls of the tubing. One lumen is filled with an unbuffered bicarbonate solution and the other lumen is filled with a strong buffer. By inserting Ag/AgCl reference electrode wires in each lumen and a cobalt electrode in the buffered lumen, simultaneous potentiometric detection of PO2, pH and PCO2 is achieved. The response of cobalt electrode to PO2 arises from a steady-state mixed potential owing to slow oxidation of cobalt and simultaneous reduction of oxygen on the surface of the cobalt electrode. The response towards PCO2 is completely analogous to the response mechanism of a conventional Severinghaus PCO2 sensor (i.e., change in pH of the bicarbonate solution). Continuous measurements of PO2, pH and PCO2 during 4-5 h blood pump studies using the catheter electrodes correlate well with conventional bench-top blood gas analyzer (PO2: r2 = 0.992; pH: r2 = 0.940; PCO2: r2 = 0.993.