A simple colorimetric luminescent oxygen sensor using a green LED with Pt octaethylporphyrin in ethyl cellulose as the oxygen-responsive element

A simple colorimetric oxygen sensor using a coloured LED and only one luminescent oxygen-sensitive emissive layer is described. A green LED acts as both a green emission source and an excitation source for a film of oxygen-sensitive Pt octaethylporphyrin (PtOEP) in ethyl cellulose containing TiO2 or ZnO as a scattering agent. This gives a sensor with a “traffic light”, red–yellow–green, response to increasing oxygen concentration. The addition of the singlet oxygen stabiliser diazobicyclo[2.2.2]octane increases the sensor stability significantly. Because of the relatively thick sensor layer used response times are long, with 90% response times of ca. 1000 s for nitrogen to oxygen and ca. 300 s for oxygen to nitrogen.