In-Situ Preparation of CdTe Quantum Dots Capped with a β-Cyclodextrin-Epichlorohydrin Polymer: Polymer Influence on the Nanocrystal's Optical Properties.

Rudy Martin-Trasanco,Alain Tundidor-Camba,Maria Montero-Cabrera,Guadalupe Pizarro,Diego Oyarzun,Cesar Zuñiga,Pedro Ortiz,Ramiro Arratia-Pérez,Hilda Esparza-Ponce

doi:10.3390/nano8110948

Abstract

β-Cyclodextrin (βCD), the less water soluble of the cyclodextrins, has been used as a capping agent in the preparation of semiconductor nanocrystals or quantum dots (QDs). Nevertheless, no reports have been found in the use of the highly water-soluble polymer of this, prepared by the crosslinking of the βCD units with epichlorohydrin in basic medium (βCDP). This polymer, besides to overcome the low solubility of the βCD, increases the inclusion constant of the guest; two parameters that deserve its use as capping agent, instead of the native cyclodextrin. In the present manuscript, we afforded the in-situ aqueous preparation of cadmium telluride (CdTe) QDs capped with βCDP. The polymer influence on the photoluminescent properties of the nanocrystals was analyzed. The βCDP controls the nanocrystals growth during the Oswald ripening stage. Consequently, the CdTe capped βCDP QDs showed lower Stokes-shift values, higher photoluminescent efficiency, and narrower size distribution than for nanocrystals obtained in the absence of polymer. Transmission electron microscopy (TEM) micrographs and energy dispersive X-ray spectroscopy (EDS) analysis revealed the composition and crystallinity of the CdTe QDs. This βCDP capped CdTe QDs is a potential scaffold for the supramolecular modification of QDs surface.

Highlights

Quantum dots (QDs) are zero-dimensional semiconductor materials, often prepared by organometallic synthetic routes
The aqueous compatibility of these quantum dots (QDs) is accessed by replacing the trioctylphosphine oxide (TOPO) ligand via a ligand exchange methodology, a procedure that attempts against the photoluminescent efficiency [2]
Cadmium telluride nanocrystals capped with a βCD units with epichlorohydrin in basic medium (βCDP) polymer were obtained through the aqueous synthesis approach

Summary

Introduction

Quantum dots (QDs) are zero-dimensional semiconductor materials, often prepared by organometallic synthetic routes This method consists in reflux a metal-organic precursor, i.e., trioctylphosphine (TOP) in a high boiling coordinating solvent, such as trioctylphosphine oxide (TOPO) [1]. Among the three CDs, βCD is the most commercially available and its cavity is of adequate size to form stable inclusion complexes with a wide variety of drugs. It has the drawback of scarce water solubility (1.85 g/100 mL, at 25 ◦C) [20]. These βCDP capped CdTe QDs represent a breakthrough in the design of new scaffolds for preparing functionalized fluorescent nanodevices based on supramolecular interactions

Chemicals

Spectroscopy

Quantum Yield Measurements

Synthesis and Optical Properties of βCDP Capped QDs

Conclusions