The creation of organic heterojunctions from conjugated polymers on the nanoscale has attracted recent attention as a consequence of their considerable potential in optoelectronic devices. Herein, we report proof-of-concept results on a versatile synthetic strategy to access various linearly segmented nanowire heterojunctions with controlled dimensions using the seeded growth "living crystallization-driven self-assembly"method followed by a secondary crystallization step. Specifically, we describe the creation of coaxial and also segmented coaxial B-A-B and A-B-A nanowires with a solvophilic poly(ethylene glycol) (PEG) corona, an inner crystalline core that consists of poly(di-n-hexylfluorene) (PDHF), which functions as a donor, and an outer crystalline core of poly(3-(2′-ethylhexyl)thiophene) (P3EHT), which acts as an acceptor. The latter is present either along the entire nanowire or solely in the central or terminal segments. These assemblies were created by seeded growth of two types of π-conjugated polymeric building blocks, the triblock copolymer PDHF-b-P3EHT-b-PEG and the diblock copolymer PDHF-b-PEG, by using fiber-like seeds derived from either material. The nanowires with both solid-state donor and acceptor blocks exhibit Förster resonance energy transfer (FRET) from the PDHF inner core to the P3EHT outer core which was characterized by fluorescence spectroscopy and laser confocal scanning fluorescence microscopy (LCSM). The FRET in the solid-state coaxial heterojunctions with an inner PDHF core and an outer P3EHT core was enhanced relative to the directly analogous system in which the P3EHT block was solvated.
Bibliographical noteFunding Information:
I.M. thanks NSERC (Canada) for an NSERC Discovery Grant, the Canadian Government for a Canada 150 Research Chair, the University of Victoria for start-up funds, the Canada Foundation for Innovation (CFI), the British Columbia Knowledge Development Fund (BCKDF), and NSERC for equipment and instrumentation support. H.S. thanks NSERC for support. X.J. thanks the Engineering and Physical Sciences Research Council (EPSRC, UK) for financial support. H.S. also thanks the Biology Department Electron Microscopy Lab at the University of Victoria and the NMR facility at the University of Bristol. H.S. thanks Prof. Cornelia Bohne for the use of fluorescence spectroscopy facilities. H.S. and X.J. also thank the Bristol Chemistry Electron Microscopy Unit for the use of TEM facilities and the Wolfson Bioimaging Facility at the University of Bristol for the use of confocal microscopy facilities. We also thank Dr. Samuel Pearce, Dr. Liam R. MacFarlane, and Dr. Yifan Zhang for useful discussions on the manuscript.
Copyright © 2020 American Chemical Society.
Copyright 2020 Elsevier B.V., All rights reserved.