The preparation and characterisation are described of a robust, reversible, hydrogen peroxide optical sensor, based on the fluorescent quenching of the dye ion-pair [Ru(bpy)(3)(2+)(Ph(4)B(-))(2)], by O(2) produced by the catalytic breakdown of H(2)O(2), utilizing the inorganic catalyst RuO(2).xH(2)O. The main feature of this system is the one-pot formulation of a coating ink that, when dried, forms an active single-layer fluorescence-based H(2)O(2) sensor, demonstrably capable of detecting H(2)O(2) over the range of 0.01 to 1 M, with a relative standard deviation of ca. 4% and a calculated lower limit of detection of 0.1 mM. These sensors are sterilisable, using dry-heat, and stable when stored over 40 days, without exhibiting any loss in sensitivity or response characteristics.