New luminescent oxygen-sensing and temperature-sensing materials based on gadolinium(III) and europium(III) complexes embedded in an acridone–polystyrene conjugate

Abstract

New sensing materials have been developed which rely on the use of luminescent europium(III) and gadolinium(III) complexes with thenoylacetylacetonate embedded in an acridone–polystyrene conjugate. Acridone acts as an antenna which efficiently absorbs violet light. Covalent coupling to the polystyrene backbone prevents aggregation and enables very high antenna loading (16 % w/w). Energy transfer from the antenna to the lanthanide complexes results in efficient red luminescence from the Eu(III) complex or green phosphorescence originating from the Gd(III) chelate. The luminescence of the material based on the Eu(III) complex is only slightly affected by oxygen but is highly sensitive to temperature under physiological conditions (20–40 °C). The Gd(III) complex has long phosphorescence decay times of approximately 1 ms and high sensitivity to oxygen. Ultra-thin (250 nm) sensing layers with sufficient absorption at the excitation wavelength enable monitoring of rapid oxygen changes virtually in real time. Immobilization of both complexes in a single matrix results in a dual-luminescence material with emissions almost ideally matching the red and green channels of a digital camera. Thus, oxygen imaging using a very simple and inexpensive set-up can be realized. Additionally, the material can be used for simultaneous sensing of oxygen and temperature.