Solid-state reference electrodes based on carbon nanotubes and polyacrylate membranes

A novel potentiometric solid-state reference electrode containing single-walled carbon nanotubes as the transducer layer between a polyacrylate membrane and the conductor is reported here. Single-walled carbon nanotubes act as an efficient transducer of the constant potentiometric signal originating from the reference membrane containing the Ag/AgCl/Cl− ions system, and they are needed to obtain a stable reference potentiometric signal. Furthermore, we have taken advantage of the light insensitivity of single-walled carbon nanotubes to improve the analytical performance characteristics of previously reported solid-state reference electrodes. Four different polyacrylate polymers have been selected in order to identify the most efficient reservoir for the Ag/AgCl system. Finally, two different arrangements have been assessed: (1) a solid-state reference electrode using photo-polymerised n-butyl acrylate polymer and (2) a thermo-polymerised methyl methacrylate:n-butyl acrylate (1:10) polymer. The sensitivity to various salts, pH and light, as well as time of response and stability, has been tested: the best results were obtained using single-walled carbon nanotubes and photo-polymerised n-butyl acrylate polymer. Water transport plays an important role in the potentiometric performance of acrylate membranes, so a new screening test method has been developed to qualitatively assess the difference in water percolation between the polyacrylic membranes studied. The results presented here open the way for the true miniaturisation of potentiometric systems using the excellent properties of single-walled carbon nanotubes

Design and synthesis of porous ZnTiO<inf>3</inf>/TiO<inf>2</inf> nanocages with heterojunctions for enhanced photocatalytic H<inf>2</inf> production

Despite the tremendous potential applications of hollow micro/nanostructures, their composition has been limited to mainly single chemical compounds. Inspired by recent innovations in the areas of metal organic frameworks (MOFs) and nanocoating, here, we report the rational synthesis of mesoporous ZnTiO3/TiO2 hollow polyhedra (MZTHP) obtained by hydrothermal treatment of zeolitic imidazolate framework-8 (ZIF-8)@TiO2 core-shell polyhedral particles. The subsequent calcination of these particles caused phase transformation from TiO2 to ZnTiO3 and eventually induced the formation of Zn2TiO4. In addition, the fabrication of these hollow structures revealed a way for the preparation of hollow polyhedral photocatalysts with Pt nanoparticles deposited onto their external surface (PHS-1) or encapsulated inside their hollow structures (PHS-2). Importantly, these two types of Pt-decorated nanoparticles are shown to exhibit an improved yet distinctly different performance for photocatalytic hydrogen production, highlighting that the photocatalytic activity correlates with the Pt location and dispersion