Dual-mode nanophotonic upconversion oxygen sensors

Nanophotonic biosensors capable of being excited in the NIR spectrum have applications in various sectors. Here, we develop a 980 nm-excitable nanophotonic sensor for real-time oxygen detection in both water and air by analyzing the photoluminescence lifetime and intensity using a nanocomposite of lanthanide-doped NaYF4:Yb3+,Tm3+ upconversion nanoparticles and a PtTFPP platinum porphyrin complex in a polystyrene matrix. Excellent overlap between the emission of the upconversion nanoparticles and the excitation band of the PtTFPP guarantees 68% efficient excitation of the PtTFPP molecules with a 980 nm NIR laser. For the first time, the oxygen sensitivity of the upconversion nanoparticles alone was reported, and it was demonstrated that the PL lifetime-based sensitivity slope was boosted more than 10 times by adding PtTFPP oxygen-sensitive molecules due to the energy transfer from the upconversion nano-emitters. In addition, the functionality of the upconversion-based sensor was investigated by analyzing its sensitivity, stability, reversibility, and temperature-dependent lifetime in both water and air, and its performance was compared with that of the sensor exposed to direct excitation at 410 nm. More importantly, the sensor was implanted under the skin of a chicken, and it was demonstrated that the PL intensity was amplified more than 12 times by employing the 980 nm excitation laser instead of 410 nm laser light. Therefore, excellent emission of the sensor under the skin paves the way for the development of implantable oxygen sensor platforms.

Automated summary

We developed a nanophotonic sensor that can be excited in the NIR spectrum for real-time oxygen detection in water and air. By analyzing the photoluminescence lifetime and intensity, we combined lanthanide-doped upconversion nanoparticles with a PtTFPP platinum porphyrin complex in a polystyrene matrix to achieve 68% efficient excitation of the PtTFPP molecules with a 980 nm NIR laser. We reported for the first time the oxygen sensitivity of the upconversion nanoparticles alone and demonstrated a more than 10-fold improvement in sensitivity by adding PtTFPP oxygen-sensitive molecules. Additionally, we investigated the functionality of the sensor and its performance compared to a sensor exposed to direct excitation at 410 nm. Furthermore, we implanted the sensor under the skin of a chicken and found that the PL intensity was amplified more than 12 times using the 980 nm excitation laser, opening up possibilities for the development of implantable oxygen sensor platforms.