Precise Control of Quantum Dot Location within the P3HT-b-P2VP/QD Nanowires Formed by Crystallization-Driven 1D Growth of Hybrid Dimeric Seeds

Abstract

Herein, we report a simple fabrication of hybrid nanowires (NWs) composed of a p-type conjugated polymer (CP) and n-type inorganic quantum dots (QDs) by exploiting the crystallization-driven solution assembly of poly(3-hexylthiophene)-b-poly(2-vinylpyridine) (P3HT-b-P2VP) rod-coil amphiphiles. The visualization of the crystallization-driven growth evolution of hybrid NWs through systematic transmission electron microscopy experiments showed that discrete dimeric CdSe QDs bridged by P3HT-b-P2VP polymers were generated during the initial state of crystallization. These, in turn, assemble into elongated fibrils, forming the coaxial P3HT-b-P2VP/QDs hybrid NWs. In particular, the location of the QD arrays within the single strand of P3HT-b-P2VP can be controlled precisely by manipulating the regioregularity (RR) values of P3HT block and the relative lengths of P2VP block. The degree of coaxiality of the QD arrays was shown to depend on the coplanarity of the thiophene rings of P3HT block, which can be controlled by the RR value of P3HT block. In addition, the location of QDs could be regulated at the specific-local site of P3HT-b-P2VP NW according to the surface characteristics of QDs. As an example, the comparison of two different QDs coated with hydrophobic alkyl-terminated and hydroxyl-terminated molecules, respectively, is used to elucidate the effect of the surface properties of QDs on their nanolocation in the NW.

Interfacial Crystallization‐Driven Assembly of Conjugated Polymers/Quantum Dots into Coaxial Hybrid Nanowires: Elucidation of Conjugated Polymer Arrangements by Electron Tomography

“…[ 7,28,41 ] Herein, chloroform and acetonitrile were used as a good solvent for P3HT-b -P2VP and a selective solvent for P2VP, respectively. [ 23 ] A series of optical micrographs presented in Figure 1 a (see also Figure S1, Supporting Information) shows the progression of the formation of self-aggregates through the color change of solution (0.1 mg mL −1 of CP). [ 24 ] P3HT-b -P2VP and tri-n -octyl phosphine oxide (TOPO)-capped CdSe QDs with a diameter of about 3 nm were dissolved in chloroform (bottom layer).…”

“…The QDs were co-crystallized with P3HT-b -P2VP by solvophobic interaction between the aliphatic chains on the QDs and the hexyl side chain of the P3HT block as acetonitrile diffused into the chloroform solution. [ 23 ] It should be noted that the formation of NWs in a chloroform solution containing a high concentration of CPs and QDs driven by acetonitrile diffusion was completed in a much shorter time (5 h, Figure S1b,c, Supporting Information).…”

“…Therefore, the crystallization of the CPs was found to be the main driving force for the formation of the hybrid CPs/QDs NWs. [ 23,41 ] It should be noted that no association of QDs with CPs NWs was observed when adding the QDs into the precrystallized CP NWs by solution-biphase method ( Figure S9, Supporting Information). The co-assembly of QDs and CPs contributes the generation of hybrid NWs.…”

“…Therefore, QDs acted not only as n-type chemicals but also as labeling agents for the CPs assemblies driven by the crystallization of the P3HT blocks. [ 23 ] Accordingly, the crystalline nature of the CPs attributed to the coplanarity and torsional disorder of the P3HT blocks in the hybrid assemblies might be determined by the location of QDs. Since conventional TEM experiments provide only 2D information regarding QD location within the hybrid NWs, TEM tomography (TEMT) was used to identify QDs location in three dimensions ( Figure 3 ).…”

“…[ 37 ] The intimate relationship between nanostructure and property has been studied. [ 38,39 ] Interestingly, in a previous report, [ 23 ] the structural evolution of coaxial P3HT-b -P2VP/QDs hybrid NWs was identifi ed by the formation of QDs-dimeric seeds bridged by P3HT-b -P2VP chains at the initial state of solution-assembly, before undergoing 1D growth. The QD dimers acted as labeling agents for the determination of the crystallization kinetics of the CPs.…”