A polymorphic SrGa2O4:Eu2+ red phosphor for warm illumination and operando visualization of H2O2 catalytic reaction

γ- to β-phase transformation was achieved in a polymorphic SrGa 2 O 4 :Eu 2+ red phosphor. The red emitter was demonstrated as a color convector in warm illumination and a fluorescent probe in operando visualization of catalytic processes.