The development of biocompatible nanosystems for cancer therapeutics and diagnostics(theranostics)is highly desirable for preventing over-or under-treatment during cancer treatment.It has been well recognized that the combination of strong fluorescence for diagnostics and the efficient generation of singlet oxygen for photodynamic therapy in one sensitizer used to be in conflict,because efficient excited state(S1→T1)intersystem crossing normally quenches the fluorescence.