Chemical sensing properties of ion selective electrodes made of AgGeSe and AgCuGeSe films

CONDE GARRIDO, J. M.; MARIA ANDREA UREÑA; ARCONDO, B.

Congreso; European Congress on Advanced Materials and Processes (EUROMAT2011); 2011

The chemical stability of chalcogenide glasses ensures high endurance even in aggressive acidic media and their remarkable glass forming ability enables the use of these materials, either as bulk or as thin films, in the development of sensitive membranes for ion selective electrodes (ISEs) in micro-sensors or multi-sensor arrays. The bulk chalcogenide glasses Agx(Ge0.25Se0.75)100-x (0 at.% ≤ x ≤ 25 at.%) and (Ag1-yCuy)25 (Ge0.25Se0.75)75 (y = 0.05, 0.1 0.2) have been studied as sensitive materials for ISEs. Additionally, thin films of these compositions were deposited by pulsed laser deposition (PLD) and used as membranes of ISEs. The analytical properties of the electrodes such as reproducibility, linear range, sensibility, detection limit and response time range were studied for the two ChG systems. The cross-selectivity of some interfering ions was also investigated. In the present work we found that ISEs based on the AgGeSe and AgCuGeSe system, both in bulk and film geometries, show sensitivity to the presence of Ag+ and Cu2+ ions in aqueous solutions with detection limits between 10-6 M and 10-7 M. In all the cases the sensitivity to Ag+ ions was nernstian (close to the theoretical 59 mV/dec) but it was supernernstian in the presence of Cu2+.  The study of the different compositions suggests that it’s the silver in the membranes (not the copper) that accounts for the sensibility of the ISEs. The addition of Cu to the membrane composition does not improve the sensitivity of the electrodes. Electrical conductivities of the samples were measured and it was concluded that, for this system, only membranes made of ionic conductors (more than 8 at.% Ag in their composition) exhibit good sensing properties.