Solvation of quantum dots in 1-alkyl-1-methylpyrrolidinium ionic liquids: toward stably luminescent composites

Takuya Nakashima,Kasumi Shigekawa,Shohei Katao,Fumio Asanoma,Tsuyoshi Kawai

doi:10.1080/14686996.2020.1735923

Takuya Nakashima, Kasumi Shigekawa + Show 3 more

Open Access

https://doi.org/10.1080/14686996.2020.1735923

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Abstract

ABSTRACT CdTe nanoparticles capped with a cationic thiolate ligand were stably dispersed in ionic liquids, 1-alkyl-1-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)amides with an alkyl group of n-propyl, butyl and octyl-chain, and in an ionic plastic crystal, 1-ethyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide. Dispersion behavior of CdTe nanoparticles in these ionic media was evaluated, in which the solvation of nanoparticles by the ionic components was particularly interested. The ionic media showed alkyl-chain length-dependent solvation behavior, which was suggested by the thermal analysis of nanocomposites. The longer alkyl-chains led to the greater decrease in the thermal melting enthalpy of ionic media with the introduction of nanoparticles. The ionic liquid with an octyl-chain, which is considered to form a thicker solvation layer, afforded better emission durability of CdTe nanoparticles compared to the ionic liquid with a shorter alkyl chain.

Highlights

Ionic liquids (ILs) have been studied as media for the synthesis and dispersion of nanoparticles (NPs) [1,2] from viewpoints of their uses in catalysts [3], quasi-solid state electrolytes [4], and optical [5] and luminescent materials [6]
We have studied the effect of chemical structure of ILs on the solvation behavior for NPs with charged surface
The interactions of IL-components with the charged NP-surface effectively suppressed the crystallization of IL bulk phase, which was demonstrated by the differential scanning calorimetry (DSC) study

Summary

Introduction

Ionic liquids (ILs) have been studied as media for the synthesis and dispersion of nanoparticles (NPs) [1,2] from viewpoints of their uses in catalysts [3], quasi-solid state electrolytes [4], and optical [5] and luminescent materials [6]. The solvation layer by IL-components on the surface should effectively protect the NPsurface in ILs. detailed insights into the solvation of NPs in ILs including the thickness, ordering structure and their dependence on the chemical structure of ILs have not been addressed yet for such the ligandcapped NPs with a single nanometer size. Detailed insights into the solvation of NPs in ILs including the thickness, ordering structure and their dependence on the chemical structure of ILs have not been addressed yet for such the ligandcapped NPs with a single nanometer size We expect that these characteristics should have a critical impact on the performance of NP-based composite materials. We here study the structure of solvation layer in ILs using the CdTe NPs capped with TC-Tf2 N ligand as a model colloid. The effect of solvation layer is demonstrated as luminescence durability of CdTe NPs under continuous light irradiation

Materials

Characterization

Results and discussion

Conclusions