Chemical Functionalization Meets Enhanced Electrical Conductivity in Iron Oxide Nanoparticles

Abstract An excellent combination of either oxides or metallic nanoparticles (NPs) and functional π‐electron rich conjugated molecules can originate a variety of intriguing phenomena convenient for technological applications. Functional π‐conjugated aromatic molecules can hold the potential to control the size, shape, morphology, and optoelectronic properties of nanoparticles through the formation of covalent interfaces. Interfacial charge transfer at the nanoparticles−molecules interfaces plays vital roles in modulating photophysical and electrical conductivity properties, which found enormous applications in catalysis, electrical, and magnetism. This work illustrates iron oxide nanoparticles (Fe ₃ O ₄ NPs) capped with in situ generated aryl radicals for tuning electrical properties. Organic molecules with different functional groups are covalently attached to the surface of Fe ₃ O ₄ NPs through radical formation. An electrical insulating pristine Fe ₃ O ₄ NPs turns into semiconductor behavior upon aryl radical functionalization, which is due to the synergistic and efficient intermolecular charge transfer between Fe ₃ O ₄ NPs of mixed valence metal ions (Fe ²⁺ , a d ⁶ electronic system, and Fe ³⁺ , a d ⁵ electronic system) and π‐electron rich aromatic molecules (donor–acceptor interactions). A theoretical framework strongly supports the experimental findings. These findings on tuning the electrical conductivity of nanoparticles using a small molecule can provide a promising avenue for a wide range of electronic applications.