Morphology-Dependent Energy Transfer of Polyfluorene Nanoparticles Decorating InGaN/GaN Quantum-Well Nanopillars

Abstract

Conjugated polymer nanoparticles (CPNs), prepared in aqueous dispersion from poly[(9,9-bis{3-bromopropyl}fluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1,3}-thiodiazole)] (PFBT-Br), are incorporated into a nanopillar architecture of InGaN/GaN multiple quantum wells (MQWs) to demonstrate a new organic/inorganic class of nanostructured excitonic model system. This hybrid system enables intimate integration for strong exciton−exciton interactions through nonradiative energy transfer (NRET) between the integrated CPNs and MQW pillars. The NRET of these excitonic systems is systematically investigated at varied temperatures. In these hybrids, InGaN/GaN MQWs serve as the donor of the NRET pair, while immobilized PFBT-Br polymer serves as the acceptor. To understand morphology-dependent NRET, PFBT-Br CPNs coating InGaN/GaN MQWs are made to defold into polymer chains by in situ treatment with a good solvent (THF). The experimental results indicate that NRET is significantly stronger in the case of CPNs compared with their defolded polymer chains. At room temperature, while the NRET efficiency of open polymer chains−nanopillar system is only 10%, PFBT-Br CPNs exhibit a substantially higher NRET efficiency of 33% (preserving the total number of polymer molecules). The NRET efficiency of the nanoparticle systems is observed to be 25% at 250 K, 22% at 200 K, 19% at 150 K, and 15% at 100 K. On the other hand, the defolded polymer chains exhibit significantly lower NRET efficiencies of 17% at 250 K, 16% at 200 K, 11% at 150 K, and 5% at 100 K. This work may potentially open up new opportunities for the hybrid organic/inorganic systems where strong excitonic interactions are desired for light generation, light harvesting, and sensing applications. C onjugated polymer nanoparticles (CPNs) attract significant attention for important applications including bioimaging, 1−3 biosensing, 4,5 and optoelectronics. 6−12 One of the most attractive features of CPNs is the convenient tunability and control of their properties through the choice and functionalization of the polymer and the surface modification of nanoparticles. Furthermore, CPNs exhibit low toxicity, 13 and their mechanical stability can be enhanced through cross-linking.14 Their optical properties arise from the controlled conformational changes of the polymer and their aggregation form rather than the quantum confinement effects, in contrast with inorganic nanoparticles, for example, colloidal semiconductor quantum dots (QDs).13 As a result of these attractive properties, CPNs find use as alternative color convertors, or molecular beacons, in various biotechnology 1,3,4 and optoelectronic applications. 6,9,10,13,14 The emission of color convertors, including CPNs, can be enhanced via the Forster-type nonradiative energy transfer (NRET) (also dubbed as Forster resonance energy transfer, FRET), which basically relies on the exciton−exciton interactions between the donor and acceptor emitters. 15 For example, polymers, 16 organic dyes, 17 inorganic QDs, 18 and epitaxial quan...

Highly Luminescent CB[7]‐Based Conjugated Polyrotaxanes Embedded into Crystalline Matrices

“…These problems mainly arise from the changes in the polymer morphology upon film casting, which affects the inter and intrachain interactions. To decrease these interactions and consequently, achieve higher QYs in solid films, various approaches have been adopted including the utilization of nonradiative energy transfer to light‐emitting polymers and the incorporation of the polymers into inorganic nanoparticles . Alternatively, chemical entities such as dendrones have been attached to the polymer backbone in order to weaken the π–π stacking .…”

Construction of multi-layered white emitting organic nanoparticles by clicking polymers

“…PFBTBr was obtained through Suzuki coupling of a fluorene monomer and benzothiadiazole as reported in previous studies. 27,32,33 Finally, a red emitting polymer, PTH-N3, was synthesized by treating PTHTs with sodium azide in DMF. PTHTs were prepared by the Stille coupling of 2-(2,5-dibromothiophen-3-yl)ethyl-4-methylbenzenesulfonate and 5,5 0 -bis(tributylstannyl)-2,2 0 -bithiophene (ESI, † Scheme S1).…”

“…PFBN3 and PFBT polymers were utilized as donor and acceptor pairs, respectively, so as to study energy transfer dependent on nanoparticle morphology and design. 32 Using FRET, we seek to tune the emission of the hybrid nanoparticles to white, which has potential applications in solid state lighting. First, the photophysical properties of the donor and acceptor polymer nanoparticles were investigated in order to find out whether they are suitable for FRET studies.…”

π-Conjugated nanostructured materials: preparation, properties and photonic applications

“…Fig. 3b shows a 61,[79][80][81][82][83][84][85] Nanoparticles with diameters of 20-30 nm were prepared by using blue-emitting polyuorene as a host and doped with varying amounts of green-, yellow-, and red-emitting conjugated polymers (PFPV, PFBT, MEH-PPV, respectively) to study the energy transfer from the host polymer to the dopant polymers. 61,79 The particle size and morphology were not affected by the presence of the dopants.…”