Inorganic nanoparticles doped with optically active rare-earth ions and coated with organic ligands were synthesized in order to create fluorescent polymethyl methacrylate (PMMA) nanocomposites. Two different aromatic ligands (acetylsalicylic acid, ASA and 2-picolinic acid, PA) were utilized in order to functionalize the surface of Tb3+？:？LaF3 nanocrystals. The selected aromatic ligand systems were characterized using infrared spectroscopy, thermal analysis, rheological measurements, and optical spectroscopy. Nanoparticles produced in situ with the PMMA contained on average 10？wt% loading of Tb3+？:？LaF3 at a 6？:？1 La？:？Tb molar ratio and ~7？wt% loading of 4？:？1 La？:？Tb molar ratio for the PA and ASA systems, respectively. Measured diameters ranged from ？nm to ？nm which is indicative that agglomerates formed during the synthesis process. Both nanocomposites exhibited the characteristic Tb3+ emission peaks upon direct ion excitation (350？nm) and ligand excitation (PA？:？265？nm and ASA？:？275？nm). 1. Introduction Rare-earth (RE) ions doped into inorganic matrices have been utilized as luminescent additives in applications such as light-emitting devices, lasers, optical amplifiers, and biological fluorescence labeling [1]. RE ions are ideal additives due to their ability to produce intense narrow spectral bands in the visible range of the electromagnetic spectrum and exhibit long excited-state lifetimes as a result of f-f electronic transitions [2, 3]. With respect to many inorganic materials, polymer matrices have the potential to offer improved production rates, lower cost, and improved processability. However, polymers exhibit inherently high vibrational energies which tend to quench many of the transitions of rare-earth ions thus limiting their application as optical materials [4]. RE ions are typically incompatible with organic polymers; although, PMMA has been shown suitable when utilized as a matrix for certain RE ion ligand complexes [5]. In this research, the method utilized to overcome high vibrational energy observed in PMMA is to incorporate optically active RE ions into low vibrational energy inorganic nanoparticles which then are dispersed into a polymer matrix by the use of selective organic ligands. The inorganic component is rare-earth ion phosphor, (terbium III), doped lanthanum trifluoride (LaF3) nanocrystals. Terbium (III) (Tb3+) emits green fluorescence as a result of a strong electronic transition, 5D4 → 7F5, occurring near 543？nm. Tb3+ exhibits absorption levels at shorter wavelengths in the ultraviolet (UV) to visible color region
References
[1]
Z. L. Wang, Z. W. Quan, P. Y. Jia, et al., “A facile synthesis and photoluminescent properties of redispersible CeF3, CeF3:Tb3+, and CeF3:Tb3+/LaF3 (core/shell) nanoparticles,” Chemistry of Materials, vol. 18, no. 8, pp. 2030–2037, 2006.
[2]
P. K. Sharma, R. Nass, and H. Schmidt, “Effect of solvent, host precursor, dopant concentration and crystallite size on the fluorescence properties of Eu(III) doped yttria,” Optical Materials, vol. 10, no. 2, pp. 161–169, 1998.
[3]
V. Bekiari and P. Lianos, “Multicolor emission from terpyridine-lanthanide ion complexes encapsulated in nanocomposite silica/poly(ethylene glycol) sol-gel matrices,” Journal of Luminescence, vol. 101, no. 1-2, pp. 135–140, 2003.
[4]
E. Brunet, O. Juanes, and J. Rodriguez-Ubis, “Supramolecularly organized lanthanide complexes for efficient metal excitation and luminescence as sensors in organic and biological applications,” Current Chemical Biology, vol. 1, no. 1, pp. 11–39, 2007.
[5]
H. Jiu, L. Zhang, G. Liu, and T. Fan, “Fluorescence enhancement of samarium complex co-doped with terbium complex in a poly(methyl methacrylate) matrix,” Journal of Luminescence, vol. 129, no. 3, pp. 317–319, 2009.
[6]
R. R. Tang, G. L. Gu, and Q. Zhao, “Synthesis of Eu(III) and Tb(III) complexes with novel pyridine dicarboxamide derivatives and their luminescence properties,” Spectrochimica Acta—Part A, vol. 71, no. 2, pp. 371–376, 2008.
[7]
Z. Wang, M. Li, C. Wang, J. Chang, H. Shi, and J. Lin, “Photoluminescence properties of LaF3: Eu3+ nanoparticles prepared by refluxing method,” Journal of Rare Earths, vol. 27, no. 1, pp. 33–37, 2009.
[8]
L. G. Jacobsohn, K. B. Sprinkle, C. J. Kucera, et al., “Synthesis, luminescence and scintillation of rare earth doped lanthanum fluoride nanoparticles,” Optical Materials, vol. 33, no. 2, pp. 136–140, 2010.
[9]
B. Kokuoz, J. R. DiMaio, C. J. Kucera, D. D. Evanoff, and J. Ballato, “Color kinetic nanoparticles,” Journal of the American Chemical Society, vol. 130, no. 37, pp. 12222–12223, 2008.
[10]
B. Kokuoz, C. Kucera, J. R. DiMaio, and J. Ballato, “Organic—inorganic hybrid nanoparticles with enhanced rare-earth emissions,” Optical Materials, vol. 31, no. 9, pp. 1327–1330, 2009.
[11]
Y. Luo, X. Yu, W. Su, et al., “Energy transfer in a ternary system composed of Tb(DBM)3Phen, Eu(DBM)3Phen, and poly(N-vinylcarbazole),” Journal of Materials Research, vol. 24, no. 10, pp. 3023–3031, 2009.
[12]
S. Maji and K. S. Viswanathan, “Ligand-sensitized fluorescence of Eu3+ using naphthalene carboxylic acids as ligands,” Journal of Luminescence, vol. 128, no. 8, pp. 1255–1261, 2008.
[13]
I. G. Binev, B. A. Stamboliyska, and Y. I. Binev, “The infrared spectra and structure of acetylsalicylic acid (aspirin) and its oxyanion: an ab initio force field treatment,” Journal of Molecular Structure, vol. 378, no. 3, pp. 189–197, 1996.
[14]
L. C. Thompson, “Complexes of the rare earths. VIII. Picolinic acid,” Inorganic Chemistry, vol. 3, no. 9, pp. 1319–1321, 1964.
[15]
R. Dangtungee, J. Yun, and P. Supaphol, “Melt rheology and extrudate swell of calcium carbonate nanoparticle-filled isotactic polypropylene,” Polymer Testing, vol. 24, no. 1, pp. 2–11, 2005.
[16]
B. M. Ellerbrook, Fabrication of fluorescent nanoparticle-polymer compoites for photoactive-based materials, M.S. thesis, 2010.
[17]
L. Ravina, Everything You Want to Know about Coagulation & Flocculation, Zeta-Meter, Staunton, Va, USA, 4th edition, 1993.
[18]
R. Bird, R. Armstrong, and O. Hassager, Eds., Dynamics of Polymeric Liquids, Volume 1, Fluid Mechanics, vol. 1, John Wiley & Sons, New York, NY, USA, 1977.
[19]
H. Barnes, A Handbook of Elementary Rheology, vol. 1, The University of Wales Institute of Non-Newtonian Fluid Mechanics, Wales, UK, 2000.
[20]
S. G. Hatzikiriakos, N. Rathod, and E. B. Muliawan, “The effect of nanoclays on the processibility of polyolefins,” Polymer Engineering and Science, vol. 45, no. 8, pp. 1098–1107, 2005.
[21]
H. E. Sliney, “Rare-earth fluorides and oxides—an exploratory study of their use as solid lubricants at temperatures to F ( C),” 1–26.
[22]
Z. Zhang, L. Yu, W. Liu, and Q. Xue, “Effect of LaF3 nanocluster modified with succinimide on the lubricating performance of liquid paraffin for steel-on-steel system,” Tribology International, vol. 34, no. 2, pp. 83–88, 2001.
[23]
J. Wang, S. Bo, L. Song, J. Hu, X. Liu, and Z. Zhen, “One-step synthesis of highly water-soluble LaF3:Ln3+ nanocrystals in methanol without using any ligands,” Nanotechnology, vol. 18, no. 46, article 465606, 2007.
[24]
J. Mezyk, D. Di Nuzzo, A. Mech, R. Tubino, and F. Meinardi, “Exciton-exciton annihilation in organic lanthanide complexes,” Journal of Chemical Physics, vol. 132, article 024504, 2010.
[25]
M. A. Diaz-Garcia, S. F. De Avila, and M. G. Kuzyk, “Energy transfer from organics to rare-earth complexes,” Applied Physics Letters, vol. 81, no. 21, pp. 3924–3926, 2002.
[26]
M. D. Fairchild, “In color appearance models: CIECAM02 and beyond,” in Proceedings of the IS&T/SID 12th Color Imaging Conference, pp. 1–68, Scottsdale, Ariz, USA, November 2004.
[27]
P. R. Selvin and J. E. Hearst, “Luminescence energy transfer using a terbium chelate: improvements on fluorescence energy transfer,” Proceedings of the National Academy of Sciences of the United States of America, vol. 91, no. 21, pp. 10024–10028, 1994.
