Self-Assembly of CdSe Nanoplatelets into Stacks of Controlled Size Induced by Ligand Exchange

Artsiom Antanovich,Anatol Prudnikau,Mikhail Artemyev,Anna Matsukovich,Alexander Achtstein

doi:10.1021/acs.jpcc.5b12139

Abstract

In this paper we present a simple method for the preparation of highly stable colloidal solutions of individual nanoplatelets (NPls) with increased fluorescence quantum yield and a versatile procedure of NPls self-assembly into stacks of controlled size. Dynamic light scattering technique has been demonstrated to be simple and accurate method for in situ studies of the growth kinetics of NPls aggregates. The self-assembly method introduced in this work is based on the exchange of ligands on the surface of CdSe nanoplatelets. Hexadecylphosphonic acid allows control of the average size (length) of NPls stacks in a broad range by varying its concentration and reaction time. The main mechanism governing controlled formation of NPls stacks is based on strong van der Waals interaction between rigid brushes of alkyl chains on the surface of neighboring NPls. The interaction strength and, consequently, the length and colloidal stability of stacks have been shown to be dependent on type and concentration of differ...

Highlights

Semiconductor nanoparticles (NPs) are materials of high interest because of their unique properties which make them promising candidates for various applications that range from light-emitting technology to photocatalysis and bioimaging
We demonstrate that the dynamic light scattering (DLS) technique can be successfully applied for the analysis of NPls aggregation kinetics in situ
We noticed that heating of crude 4.5 monolayers thick (4.5 ML) CdSe NPls in chloroform or octadecene in the presence of Cd(OAc)[2] or Zn(OAc)[2] resulted in the formation of stable colloidal solutions of NPls with increased PL quantum yield (QY)

Summary

■ INTRODUCTION

Semiconductor nanoparticles (NPs) are materials of high interest because of their unique properties which make them promising candidates for various applications that range from light-emitting technology to photocatalysis and bioimaging. Current synthesis protocols allow preparation of NPs of various forms such as dots, rods, branched particles, and platelets The latter, commonly called nanoplatelets (NPls) or colloidal quantum wells, were introduced relatively recently.[1] They have an atomically flat surface, and their thickness is quantized to an integer number of monolayers.[2,3] As a consequence, if compared to quantum dots (QDs) or nanorods, they exhibit extremely narrow intense bands on both absorption and PL spectra with full width at half maximum (fwhm) as small as 10 nm and small Stokes shift. NPls were dissolved in a small amount of chloroform and drop-cast on the Si plates

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES

Stacking in Colloidal Nanoplatelets