Cancer　is　a　serious　global　health　threat,　and　photodynamic　therapy　(PDT)　is　an　effective　treatment　method　for　cancer.　This　therapy　works　by　generating　a　large　amount　of　singlet　oxygen　(1O2)　under　the　influence　of　oxygen　and　light,　which　induces　apoptosis　in　tumor　cells,　leading　to　their　destruction.　However,　the　resistance　of　cells　to　apoptosis　limits　the　development　of　PDT,　and　thus　the　combination　of　ferroptosis　and　apoptosis　provides　a　new　perspective　for　PDT.　During　PDT　and　ferroptosis,　the　levels　of　1O2　and　the　microenvironment　(viscosity)　within　cells　often　change.　To　address　this,　this　study　developed　a　novel　fluorescent　probe,　NI-QM-OH,　based　on　the　TICT-ICT　effect,　capable　of　monitoring　changes　in　1O2　and　viscosity　during　PDT.　The　probe　exhibits　excellent　selectivity,　high　sensitivity,　and　a　low　LOD　(0.38　μM),　and　has　been　successfully　applied　for　bioimaging　in　HepG2,　HeLa,　and　MCF-7　cells,　as　well　as　for　monitoring　viscosity　and　1O2　levels　in　zebrafish.　Most　importantly,　NI-QM-OH　also　enables　the　visualization　of　the　diagnosis　of　fatty　liver　disease　(both　alcoholic　and　nonalcoholic).　©　2025　American　Chemical　Society.