Magnetic nanoparticle-polymer composites loaded with hydrophobic sensitizers for photodegradation of azoic dyes

Abstract

Oleate-protected iron oxide magnetic nanoparticles (MNPs) were encapsulated with amphiphilic comb polymer poly(maleic anhydride alt-1-octadecene) (PMAO) in order to achieve the phase transfer to aqueous media and to load the resulting MNP-PMAO assemblies with phenalenone (PN), a hydrophobic photosensitizer with a quantum yield of singlet oxygen production close to unity. Steady-state fluorescence measurements complemented with density functional theory calculations, together with emission lifetime experiments, led us to conclude that PN molecules in the hybrid nanomaterial are indeed localized in a hydrophobic environment. In addition, laser flash-photolysis assays confirmed the generation of the triplet state of PN and its quenching by O2, an indication of the formation of singlet molecular oxygen (1O2). For monodisperse magnetic nanocubes (MNCs) 23 nm in edge length, the MNC-PMAO-PN nanohybrids can be efficiently removed by magnetic decantation. We performed photodegradation experiments of azoic derivative acid black 10B (AB10B), a dye commonly used in the cosmetic industry and which is found in wastewaters. Irradiation of a 0.01 mM AB10B solution for 120 min in the presence of the MNC-PMAO-PN assemblies (200 mg L-1, expressed as iron oxide concentration) led to a 76% decomposition of the dye at pH around 6. Unlike other methods based on Fenton processes, our strategy reaches a significant photodegradation efficiency without the addition of H2O2or acids. Similar systems could be used to encapsulate hydrophobic photosensitizers for other purposes, such as bacterial inactivation and combined photodynamic and magnetic hyperthermia therapies.