title: Novel guests for porous columnar thin films: the switchable perchlorinated trityl radical derivatives.
abstract: TiO(2) and SiO(2) porous thin films consisting of tilted nanocolumns prepared by glancing angle evaporation (GLAD) have been infiltrated with guest derivatives belonging to the family of perchlorinated trityl radicals, novel guest molecules presenting an open-shell electronic configuration associated with paramagnetism, fluorescence, and electroactivity. The main driving forces for infiltration from aqueous solutions of the carboxylate-substituted radical derivatives are the electrostatic interactions between their negative charge and the net positive charges induced on the film pores. Positive charges on the internal surface of the films were induced by either adjusting the radical solution pH at values lower than the point of zero charge (PZC) of the oxide or passivating the nanocolumns oxide surface with a positively charged aminosilane. The infiltrated composite thin films are robust and easy to handle thanks to the physical protection exerted by the film columns. They also keep the multifunctionality of the used guests, as confirmed by electron paramagnetic resonance (EPR), UV-vis spectroscopy, and fluorescence spectroscopy. To prove the electroactivity of the infiltrated porous films, a porous TiO(2) host layer was supported onto conductive indium tin oxide (ITO). By application of an appropriate redox potential, the guest radical molecules have been reversibly switched from their open-shell electronic configuration to their diamagnetic state and hence changed their optical properties. On the basis of these results, it is herein proposed that the appropriate surface functionalization of the pore internal surface of GLAD thin films can be used to prepare novel radical-oxide composite thin films usable for the development of robust switchable electrically driven photonic and magnetic devices.
authors: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus Universitari de la UAB, E-08193, Bellaterra, Spain.
authors: Malena
authors: M
authors: Oliveros
authors: Lola
authors: L
authors: González-García
authors: Veronica
authors: V
authors: Mugnaini
authors: Francisco
authors: F
authors: Yubero
authors: Nans
authors: N
authors: Roques
authors: Jaume
authors: J
authors: Veciana
authors: Agustin R
authors: AR
authors: González-Elipe
authors: Concepció
authors: C
authors: Rovira
mesh_terms: D005609:Free Radicals / Q000737:chemistry*; D054879:Halogenation; D008280:Magnetics; D010084:Oxidation-Reduction; D044367:Phase Transition; D016062:Porosity; D014320:Triphenylmethyl Compounds / Q000737:chemistry*
chemical_list: D005609:Free Radicals; D014320:Triphenylmethyl Compounds