Silica glass thin films containing Ru(II) tris-bipyridine
complex were deposited via a sol-gel dipping procedure on
K-glass substrates to build electrochemiluminescent
(ECL) sensors. Films were prepared starting from an
ethanolic solution of prehydrolised Si(OC2H5)4 and
Ru(bpy)3Cl2. Transparent, crack free and homogeneous
reddish Ru(II) tris-bipyridine complex doped silica layers,
200\ub120 nm thick were obtained. The films, either deposited
at room temperature or thermally annealed at 100,
200 and 300\ub0C for 30 h, were structurally and chemically
characterised. Ru(bpy)3Cl2 thermal stability was previously
checked by thermogravimetric analysis (TGA). The
films were investigated by x-ray photoelectron
spectroscopy (XPS), secondary ion mass spectrometry
(SIMS), atomic force microscopy (AFM) and UV-Vis
spectroscopy. Experimental data showed that the complex
maintains its integrity either in the as-prepared and in the
annealed films and that it is homogeneously distributed
inside the thin layer. Electrochemical and ECL characterisation
of the thin film electrodes were made by means
of cyclic voltammetry (CV) and controlled potential step
experiments. The ECL sensor showed a diffusive redox
behaviour of the Ru(bpy)3
2+/Ru(bpy)3
3+ system. Light
emission produced from the reaction between oxalic acid
and the electrogenerated Ru(bpy)3
3+ was larger and stable
when thermally treated electrodes were used after a
suitable hydrating period. The 300\ub0C treated sensor was
the best performing sample both in terms of low complex
leakage and sensitivity
