Photonic Reactions Leading to Fluorescence in a Polymeric System Induced by the Photothermal Effect of Magnetite Nanoparticles Using a 780 nm Multiphoton Laser.

Recently, polymer-coated magnetite (Fe3 O4 ) nanoparticles (NPs) are extensively studied for applications in therapeutics or diagnostics using photothermal effect. Therefore, it is essential to understand the interactions between Fe3 O4 NPs and polymers when optical stimuli are applied. Herein, the photonic reactions of Fe3 O4 NPs and polymer composites upon application of a 780 nm multiphoton laser are analyzed. The photonic reactions produce unique results including fluorescence from conformationally changed polymer and low-temperature phase transformation of Fe3 O4 NPs. Typically, π-conjugated chains are formed, inducing fluorescence through a series of main and side-chain cleavage reactions of polymers with the aliphatic chain. In addition, fluorescence is detected in the cellular system by photonic reactions between Fe3 O4 NPs and biomolecules. After multiphoton laser irradiation, light emission is detected near the intracellular Fe3 O4 NPs, and a stronger intensity is observed in large-sized NPs.