title: Defect induced tunable near infrared emission of Er-CeO2 by heterovalent co-dopants.
abstract: We investigate the effects of heterovalent co-dopants on the structural and emission properties of 1% Er-CeO2 nanoparticles. The CeO2 oxide host was selected on the basis of its fairly well-understood defect chemistry in either a pure or doped state. As a luminescent activator, Er is acknowledged as an interesting element due to its rich luminescence and excitation properties spanning the visible to near-infrared range. The optically inactive trivalent La and monovalent Li metal ions with a concentration of up to 20% were chosen to presumably generate a variable amount of defects in the Er-CeO2 lattice. It was found that La and Li co-dopants induced distinct changes related to the size, lattice constant, bandgap energy, lattice and surface defects of Er-CeO2. As a result of these changes, a strong modulation of the luminescence intensity and shape was measured using a suite of excitation conditions (charge-transfer absorption band of CeO2, direct/up-conversion into Er absorptions and X-ray excitation modes). The use of Eu as a luminescent probe offered additional information concerning the effects of La/Li co-doping on the local structure surrounding the luminescent activator. Remarkably high percentages of 90 and 98% of the total emission of Er measured between 500 and 1100 nm are measured in the near-infrared region at 980 nm under X-ray and up-conversion excitation at ∼1500 nm, respectively. The optical properties suggest that Li, Er co-doped CeO2 has good potential for therapy and biological imaging.
authors.affiliation: Faculty of Chemistry, Department of Organic Chemistry, Biochemistry and Catalysis, University of Bucharest, 4-12 Regina Elisabeta Bvd., Bucharest, Romania.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Florea
authors.forename: Daniel
authors.initials: D
authors.lastname: Avram
authors.forename: Bogdan
authors.initials: B
authors.lastname: Cojocaru
authors.forename: Ion
authors.initials: I
authors.lastname: Tiseanu
authors.forename: Vasile
authors.initials: V
authors.lastname: Parvulescu
authors.forename: Carmen
authors.initials: C
authors.lastname: Tiseanu