Photoluminescence of Mesoporous Silica Film Impregnated with an Erbium Complex

1. Surface area (m2/g) Pore size(nm) ErQ undoped 920 2.1 ErQ doped 725 2.0 Mesoporous silica film ErQ EtOH 20nm 20nm Ultrasonic treatment Dissolve ErQ in EtOH Immersion of mesoporous silica film Surface Cleaning 50nm Desorption of CTACl Decomposition of CTACl Water Photoluminescence of Mesoporous Silica Film Impregnated with an Erbium Complex Oun-Ho Park†, Jae Young Bae, Ji-in Jung, and Byeong-Soo Bae Laboratory of Optical Materials and Coating (LOMC), Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea E-mail: oh-park@kaist.ac.kr http://www.sol-gel.net/lomc Research direction Sample preparation of the mesoporous silica film impregnated with ErQ • Since planar optical amplifiers have a smaller interaction length with respect to erbium-doped fiber amplifiers, higher erbium concentration is required to obtain a sufficient optical gain. • high doping levels of erbium quench the fluorescence emission and reduce the performance of the amplifier. • Theoretically, the most effective method for uniform dispersion is the periodic arrangement of erbium ions in a matrix when high doping levels of Er3+ ions are required. • In this study, we impregnate Er complex into mesoporous silica film, and then measure the photoluminescence for 1.5 m amplification. • Preparation of mesoporous silica films • - Precursor : Tetramethylorthosilicate (TMOS) • - Solvent : Methanol (CH3OH) • - Surfactant : n-Cetyltrimethylammonium Chloride [CH3(CH2)15N(CH3)3]Cl (CTACl) • Erbium 8-hydroxyquinoline (ErQ) was incorporated into the mesoporous silica films by impregnation. The silica films were placed into 10 ml of 1.5  10-3–1.5  10-2 M erbium 8-hydroxyquinoline in ethanol. Ethanol was removed by flowing nitrogen gas over the sample. References Synthesis of Mesoporous Silica Film Thermogravimetric Analysis Temperature Profile for Calcination FT-IR Spectra • FT-IR spectra of (a) as-synthesized and (b) calcined mesoporous silica films • Residual OH and organic templates are almost removed. • Abrupt weight losses take place at 280 & 310 oC due to the desorption and the decomposition of CTACl, respectively. • Temperature profile is determined to calcine the residual organic surfactants effectively. Characterization of Mesoporous Silica Film XRD Result Microstructure High Resolution TEM images Transmittance (a) (a) (b) (c) 433 ± 2 nm (b) Substrate • Obtained mesoporous silica films are optically transparent in the range of visible wavelength. • TEM cross-sectional images of perpendicular (a, b) and through (c) the pores of hexagonal mesoporous silica thin films • Pore size : ~ 2 nm Average Roughness : 2 nm • XRD patterns of (a) as-synthesized and (b) calcined hexagonal mesoporous silica films • (a) SEM & (b) ARM Images Optical Properties of Mesoporous Silica Film Impregnated with ErQ Schematic Structure Photoluminescence N2 Adsorption Er distribution & Concentration Concentration Effect • Pore size : 2 nm • Expected molecular size of ErQ : >1 nm • It is expected that the impregnated ErQ molecules are homogeneously distributed due to the periodic pore arrangement. • PL is linearly proportional to erbium atomic density., which implies • No concentration quenching was found up to ~1021 ions/cm3 of erbium concentration. • Depth profile and composition was obtained by RBS measurements. • Er is impregnated up to ~1021 ions/cm3. • PL intensity increases as the concentration of ErQ solution increases due to the impregnation of ErQ into the pore. • ErQ is impregnated into the pore! Conclusions • ErQ impregnated mesoporous silica film shows a clear 1.5 m photoluminescence. • Impregnation of ErQ into the pore is confirmed by N2 adsorption. • Homogeneous distribution of ErQ in depth is confirmed by RBS measurement. • High concentration of erbium is impregnated without concentration quenching • PL is linearly proportional to the erbium concentration. • Transparent mesoporous silica films are successfully fabricated using a sol-gel spin coating method. • The obtained mesoporous silica films have hexagonal structure with 2 nm pore size. • Er complex is homogeneously impregnated into the mesoporous silica films by an immersing technique, and its concentration can be easily controlled by changing the concentration of Er complex solution. The 5th International Meeting of Pacific Rim Ceramic Societies September 29 – October 2 2003, Nagoya Congress Center, Nagoya, Japan