Dual-mode oxygen-sensing based on oxygen-adduct formation at cobaltporphyrin-polymer and luminescence quenching of pyrene: An optical oxygen sensor for a practical atmospheric pressure

A dual-mode and a non-Stern-Volmer type oxygen pressure-sensitive coating was prepared by combining the cobaltporphyrin (CoP) ligated with a polymer and 1-pyrenebutyric acid (Py): the combination of the rapid and reversible oxygen (O₂)-adduct formation of the CoP was accompanied by a visible absorption spectral change and luminescence quenching of Py with oxygen. The oxygen sensor composed of CoP/Py was successfully characterized by a significantly high oxygen sensitivity under the practical atmospheric oxygen pressure of 10-21 kPa. Py was adsorbed on an anodized aluminium substrate. Its luminescence decreased by quenching with oxygen which obeyed the conventional Stern-Volmer equation. Copolymers of vinylidenechloride with 1-vinylimidazole, 1-vinyl-2-methylimidazole, and 4-vinylpyridine (1, 2 and 3, respectively) were prepared to provide both an oxygen-barrier coating for the first luminescent Py layer and CoP ligation for tuning the oxygen-adduct formation equilibrium. The luminescent Py layer was further coated with a second polymer layer: The oxygen-barrier polymer coating enhanced the Stern-Volmer type luminescence intensity from the Py layer. Visible absorption of the CoP-containing polymer second layer increased in response to the oxygen-adduct formation or oxygen partial pressure, which overlapped and reduced the luminescence from the Py layer. The sum of the luminescence decreased along with an increase in the oxygen partial pressure, yielding a non-Stern-Volmer type response or high sensitivity to the oxygen partial pressure.