NIR-Emitting Alloyed CdTeSe QDs and Organic Dye Assemblies: A Nontoxic, Stable, and Efficient FRET System.

Doris Ramírez-Herrera,Eustolia Rodríguez-Velázquez,Manuel Alatorre-Meda,Georgina Pina-Luis,Antonio Tirado-Guízar,Pablo Taboada,Francisco Paraguay-Delgado

doi:10.3390/nano8040231

Abstract

In the present work, we synthesize Near Infrared (NIR)-emitting alloyed mercaptopropionic acid (MPA)-capped CdTeSe quantum dots (QDs) in a single-step one-hour process, without the use of an inert atmosphere or any pyrophoric ligands. The quantum dots are water soluble, non-toxic, and highly photostable and have high quantum yields (QYs) up to 84%. The alloyed MPA-capped CdTeSe QDs exhibit a red-shifted emission, whose color can be tuned between visible and NIR regions (608–750 nm) by controlling the Te:Se molar ratio in the precursor mixtures and/or changing the time reaction. The MPA-capped QDs were characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and zeta potential measurements. Photostability studies were performed by irradiating the QDs with a high-power xenon lamp. The ternary MPA-CdTeSe QDs showed greater photostability than the corresponding binary MPA-CdTe QDs. We report the Förster resonance energy transfer (FRET) from the MPA-capped CdTeSe QDs as energy donors and Cyanine5 NHS-ester (Cy5) dye as an energy acceptor with efficiency (E) up to 95%. The distance between the QDs and dye (r), the Förster distance (R0), and the binding constant (K) are reported. Additionally, cytocompatibility and cell internalization experiments conducted on human cancer cells (HeLa) cells revealed that alloyed MPA-capped CdTeSe QDs are more cytocompatible than MPA-capped CdTe QDs and are capable of ordering homogeneously all over the cytoplasm, which allows their use as potential safe, green donors for biological FRET applications.

Highlights

Quantum dots (QDs) are considered an excellent alternative to organic fluorophores due to their unique optical properties, such as broad excitation spectra, high photostability, size-tunable emission, narrow and symmetric emission spectra, and high quantum yields (QYs) [1]
We report a systematic study on the synthesis of high QY NIR-emitting mercaptopropionic acid (MPA)-capped CdTeSe QDs without the use of an inert atmosphere and pyrophoric ligands in a single step and in less than an hour
Many of the synthetic methods reported using organic solvents, which involves a second step for the modification of the QD surface with thiolated ligands to make it water soluble

Summary

Introduction

Quantum dots (QDs) are considered an excellent alternative to organic fluorophores due to their unique optical properties, such as broad excitation spectra, high photostability, size-tunable emission, narrow and symmetric emission spectra, and high quantum yields (QYs) [1]. These characteristics demonstrate them as attractive materials for biomedical and technological applications, such as clinical diagnosis and labeling [2,3,4], as well as for solar energy conversion in photovoltaic devices [5,6]. A systematic study to obtain only core-doped QDs with high QYs and photostability is required

Methods

Results

Conclusion