Whispering Gallery Resonance from Self-Assembled Microspheres of Highly Fluorescent Isolated Conjugated Polymers

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• 作者：Soh Kushida ; Daniel Braam ; Chengjun Pan ; Thang D. Dao ; Kenichi Tabata ; Kazunori Sugiyasu ; Masayuki Takeuchi ; Satoshi Ishii ; Tadaaki Nagao ; Axel Lorke ; Yohei Yamamoto
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：June 23, 2015
• 年：2015
• 卷：48
• 期：12
• 页码：3928-3933
• 全文大小：424K
• ISSN：1520-5835

文摘

Self-assembly of highly fluorescent isolated conjugated polymers (ICPs), comprising alternating phenylene moieties with an insulating cyclic side chain and different arylene moieties, was comprehensively studied. Two out of nine ICPs were identified to form well-defined spheres of 1鈥? 渭m diameter. The degree of twisting of the main chains was found to be an important structural factor enabling formation of spheres, for which dihedral angles >50掳 between the neighboring arylene moieties were required. A single microsphere with high sphericity exhibited whispering gallery mode (WGM) photoemission upon excitation with a focused laser. In this emission, sharp and periodic emission lines were superimposed on a broad photoemission spectrum. The WGM spectral profiles were very sensitive to the integrity of the spherical geometries and surface smoothness, which depends on the self-assembling condition as well as the structure of the polymer backbone. Microspherical optical resonators consisting of such highly fluorescent conjugated polymers are novel. They also present advantages in that (i) there is no need for a light waveguide and fluorescent-dye doping, (ii) its high refractive index is beneficial for light confinement, and (iii) the fabrication process is simple, not requiring sophisticated, costly microfabrication technology.