Sol-gel-Derived highly sensitive optical oxygen sensing materials using Ru(II) complex via covalent grafting strategy.

The preparation and oxygen sensing properties of Ru(ll) covalently-grafted and physically-incorporated silica based hybrid materials by sol-gel technique are described in this article. The Ru(II) complexes are successfully grafted onto the backbone of the silica via the condensation reaction of the tetraethoxysilane and the functionalized Ru(II) complex 2-[4'-{3-(Triethoxysilyl)propyl}phenyl]imidazo [4,5-f]-1,10-phenanthroline that contains the hydrolysable tri-alkoxylsilyl group. The luminescence quenching of Ru(II) complex by oxygen within the silica matrix is efficient. The oxygen quenching sensitivity of the covalently-grafted sample is higher than that of the physically-incorporated one due to the strong Si-CH2 bond that is useful to prolong the excited state lifetimes and enhance the photobleaching of the luminophore. The downward oxygen sensing Stern-Volmer plots can be well fitted using the Demas two-site model and the Lehrer model due to the heterogeneous distribution of the Ru(ll) complex within the sol-gel derived silica.