Surface Modification of Fe2O3 Nanoparticles to Develop as Intrinsic Photoluminescent Probe and Unprecedented Photocatalyst

Herein, we demonstrate the emergence of intrinsic multicolor fluorescence in α-Fe₂O₃ nanoparticles (NPs) from blue, cyan, to green, upon functionalization and further surface modification with a small organic ligand, Na-tartrate. Furthermore, we have found an excellent photocatalytic property of the functionalized α-Fe₂O₃ NPs in the decoloration of a model water contaminant. Detailed characterization of α-Fe₂O₃ NPs before and after functionalization were carried out by X-ray diffraction and transmission electron microscopy. Proper investigation through UV-visible absorption and photoluminescence study along with theoretical support from literature reveals that ligand-to-metal charge transfer from tartrate ligand to lowest unoccupied energy level of Fe³⁺ of the NPs and d-d transitions centered over Fe³⁺ ions in the NPs play the key role in the generation of multiple fluorescence from the ligand functionalized α-Fe₂O₃ NPs. Vibrating sample magnetometry measurements exhibit magnetic behavior of Fe₂O₃ NPs changed considerably after surface modification. We believe that the developed ferromagnetic, multicolor fluorescent α-Fe₂O₃ NPs would pioneer new opportunities toward diverse applications.