A H2O2-activated NIR-II fluorescence/photothermal temperature dual-mode nanoprobe for high-contrast reporting of abiotic stress response in plants

Real-time, in-situ and non-invasive monitoring of H2O2 level is critical for studying the response of plants toward abiotic stresses. However, most of the developed imaging strategies suffer from low spatiotemporal resolution and potential false results. In this work, a complementary NIR-II fluorescence/photothermal temperature dual- mode nanoprobe was constructed for high-contrast and accurate tracking of H2O2 fluctuation in plant leaves under abiotic stress. Upon exposure to a NIR laser, the H2O2-mediated oxidation products of the nanoprobes caused "turn-off" NIR-II fluorescence and "turn-on" photothermal temperature. As for the plant imaging, both the dual signals display a high signal-to-noise ratio due to weak autofluorescence and low background absorption. Additionally, the combination of dual modes can provide complementary and self-calibrated sensing information, since the NIR-II fluorescence mode shows high sensitivity (limit of detection: 0.72 mu M), while the photo- thermal temperature mode allows point-of-care analysis of H2O2. This dual-mode nanoprobes can report H2O2 level in plants under different abiotic stresses, and the generated H2O2 was found to diffuse away from the organs and travel over a long distance to adjacent organs. This study offers an effective and promising tool to explore the signaling pathways and assess plant health status.