Preparation Of Flexible PtOEP/PS Oxygen Sensor Based On Photonic Crystal Fluorescence Enhancement And Study Of Its Oxygen Sensing

Oxygen is closely related to the metabolism of all living creatures,which is essential for humans and biological systems.With the rapid development of early medical diagnosis,numerous diseases such as cancer,tumor and burns can be monitored by oxygen sensing.Compared with Clark electrode,the optical oxygen sensor based on“phosphorescence quenching”is highly accurate,reversible and non-invasive,however its sensitivity,signal-to-noise ratio and stability is seriously limited now because of the interference by photobleaching and fluorescence from background.In order to meet these demand,photonic crystals(PCs)were introduced into oxygen sensor,thus higher oxygen sensing was obtained using the principle of fluorescence enhancement effect(FEE).Herein,two Pt OEP-in and Pt OEP-out flexible oxygen sensors were prepared,these are different in the position of Pt OEP loaded inside PCs(gap and body).This flexible oxygen sensor was made by two heterogeneous polydimethylsiloxane(PDMS)and polystyrene(PS)PCs embedded with platinum(II)octaethylporphyrin(Pt OEP)oxygen-sensitive dyes.Besides,FEE and oxygen-sensing performance of two oxygen sensor were compared by varying the amount of fluorophores.When 20?L Pt OEP was added to the PCs FEE oxygen sensor,the optimized PCs oxygen sensor showed 12-fold higher fluorescence intensity than disorderly PS microspheres(control group).Simultaneously,the oxygen sensor demonstrated a high sensitivity to oxygen(K_sv=16.13),with excellent accuracy(R²=0.9999)and photostability(99.11%).Particularly,the sensitivity of Pt OEP-in and Pt OEP-out oxygen sensors increased by 83.57%and 134.45%compared with the control group,respectively.In addition,the ordered microstructure of PCs was not destroyed and the reflectance was slightly reduced by 3%after 100 continuous stretching.The oxygen sensing sensitivity was retained by 80%,which proves that the oxygen sensor can still maintain better flexibility and stability.Finally,two different dyes,coumarin-6(C-6)and fluorescein isothiocyanate(FITC)were introduced as a reference into the PCs FEE oxygen sensor.The color range of this colorimetric oxygen sensor was studied using CIE-1931 software with the ratio of two fluorescent dyes changed.It is indicated that the color range of Pt OEP/C-6colorimetric oxygen sensor was from pink to indigo,and its sensitivity(K_sv)was 14.41.Furthermore,the sensitivity of Pt OEP/FITC colorimetric oxygen sensor was 17.65,and the color range was from red to green.Importantly,the color changing of Pt OEP/FITC oxygen sensing film was tested in a sealed chamber and photographed with a smartphone.The result shows that the appearance of the oxygen sensing film changed between red,pink and yellow as the oxygen content increased from 0%to 100%.