title: Reactive nature of dopamine as a surface functionalization agent in iron oxide nanoparticles.
abstract: Dopamine forms an initial structure coordinated to the surface of the iron oxide nanoparticle as a result of improved orbital overlap of the five-membered ring and a reduced steric environment of the iron complex. However, through transfer of electrons to the iron cations on the surface and rearrangement of the oxidized dopamine, a semiquinone is formed. Because of free protons in the system, oxygens on the surface are protonated, which allows for the Fe2+ to be released into the solution as a hydroxide. This released fragment of the nanoparticle will then eventually oxidize in air to a form of an iron(III) oxyhydroxide. All of the reported results demonstrate that the reactivity between Fe3+ and dopamine quickly facilitates the degradation of the nanoparticles. The energetic modeling studies substantiate our proposed decomposition mechanism and thus conclude that the use of dopamine as a robust anchor for iron oxide or iron oxide shell particles will not fulfill the need for stable ferrofluids in most biomedical applications.
authors.affiliation: Departments of Chemistry and Physics, Virginia Commonwealth University, Richmond, VA 23284, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Shultz
authors.forename: J Ulises
authors.initials: JU
authors.lastname: Reveles
authors.forename: Shiv N
authors.initials: SN
authors.lastname: Khanna
authors.forename: Everett E
authors.initials: EE
authors.lastname: Carpenter
mesh_terms: D002316:Cardiotonic Agents / Q000737:chemistry*; D004298:Dopamine / Q000737:chemistry*; D004579:Electron Transport; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D008956:Models, Chemical; D053758:Nanoparticles; D010084:Oxidation-Reduction; D010316:Particle Size; D011809:Quinones / Q000737:chemistry; D013053:Spectrophotometry; D013696:Temperature
chemical_list: D002316:Cardiotonic Agents; D005290:Ferric Compounds; D005296:Ferrous Compounds; D011809:Quinones; C000499:ferric oxide; D004298:Dopamine