title: Color Tuning of Core-Shell Fluorescent Microspheres by Controlling the Conjugation of Poly(p-phenylenevinylene) Backbone.
abstract: A series of poly(p-phenylenevinylene) (PPV)-coated microspheres with varied fluorescent emission colors have been prepared by controlling the average length of the conjugated segments on the polymer backbone. A modified Wessling method was used for preparing PPV with different conjugation segments. The labile sulfonium groups of the initial polymer precursor of PPV (pre-PPV) were partly substituted by relatively stable methoxyl groups. A series of precursors with different degrees of substitution were prepared by controlling the time of reaction; these precursors were adsorbed onto the negatively charged substrate spheres. Subsequently, heterogeneous thermal treatment eliminated the sulfonium groups selectively to form the conjugated segments on the PPV backbone with varied average conjugation lengths. Under UV exposure, the as-prepared PPV-coated microspheres displayed emission colors ranging from blue to green; a 65 nm shift in the emission maximum was observed in the fluorescence spectra. The gradual color change in emission of spheres was also confirmed in a confocal microscopy study. Further characterizations indicated that these microspheres possessed clear core-shell structure, good monodispersity in size, smooth surfaces, uniform emission, and superior thermal and photo stability. Flow cytometry measurements indicated that these spheres have very different patterns of intensity combination from four-signal receiving channels. The simple method reported herein, which can effectively and efficiently tune the emission color of the fluorescent microspheres, is a promising approach for preparation of microspheres used as encoded signal carrier in flow cytometry and other high-throughput techniques.
authors.affiliation: State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University , Suzhou, Jiangsu 215123, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Chen
authors.affiliation: State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University , Suzhou, Jiangsu 215123, PR China.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.affiliation: State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University , Suzhou, Jiangsu 215123, PR China.
authors.forename: Heng
authors.initials: H
authors.lastname: Zhang
authors.affiliation: State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University , Suzhou, Jiangsu 215123, PR China.
authors.forename: Li-Juan
authors.initials: LJ
authors.lastname: Fan
keywords: color tuning; conjugation length; flow cytometry; fluorescent microspheres; poly(p-phenylenevinylene)