Monodisperse Fe₂O₃ Supraparticles: Eco‐Friendly Fabrication, Gallic Acid Modification, Size‐Dependent Photothermal Conversion Efficiency, and Cellular Uptake

Abstract In this study, the eco‐friendly fabrication system of the hierarchical monodisperse Fe₂O₃ supraparticles (SPs) is systematically studied. First, by means of urea as pH modulator, monodisperse Fe₂O₃ SPs with 7 to 90 nm in diameters can be one‐step in situ self‐assembled in 100% water solution. Then, the SPs can be reliably fabricated by various carboxyl stabilizers, indicating the versatility of the proposed fabrication system. Third, by means of gallic acid (GA) modification, the corresponding products (denoted as Fe₂O₃@GA SPs) can be endowed near‐infrared light‐absorbing properties and photothermal therapy potentials. Fourth, the Fe₂O₃@GA SPs exhibit size‐dependent photothermal performances and cellular uptake. In terms of 8 nm sized Fe₂O₃@GA SPs, their photothermal conversion efficiency and cellular uptake are 66.63% and 8.4 pg Fe/cell, both of which are higher than that of 25 and 47 nm sized products.