A highly sensitive and flexible photonic crystal oxygen sensor

Oxygen sensing attracts high research interest because it is applicable to early diagnosis and health monitoring. Herein, based on photonic crystals (PCs), a novel fluorescence enhancement effect (FEE) was explored to achieve highly sensitive and accurate oxygen detection. A flexible oxygen sensor was fabricated from heterogeneous polydimethylsiloxane (PDMS) and polystyrene (PS) PCs embedded with platinum(II) octaethylporphyrin (PtOEP) oxygen-sensitive dye. Two different fluorophore incorporation (PtOEP-in and PtOEP-out) PCs were compared in terms of their FEE and oxygen-sensing performance. Simultaneously, photoluminescence enhancement was experimentally and theoretically examined and was determined to be the main factor in improving the performance of the oxygen sensor. In particular, the optimized PC oxygen sensor showed a 12-fold higher PL intensity than PS microspheres (control group). Moreover, the optimized sensor demonstrated high sensitivity to oxygen, with excellent accuracy, photostability and flexibility. This work is expected to provide a universal route to design flexible PC sensors for health monitoring through fluorescent ultratrace detection.