γ-Radiation Enhanced Luminescence of Thiol-Capped Quantum Dots in Aqueous Solution.

Shuquan Chang,Haiqian Zhang,Xiaohong Zhang,Xian Wu,Jianzhang Lan,Zheng Li

doi:10.3390/nano9040506

Abstract

Quantum dots (QDs) have attracted great attention due to their unique optical properties. High fluorescence efficiency is very important for their practical application. In this study, we report a simple and efficient strategy to enhance the photoluminescence of water-dispersed thiol-capped QDs using γ-radiation. Three kinds of QDs with different surface ligands and cores (MPA-CdTe, MPA-CdSe and Cys-CdTe) were fabricated and irradiated by high-energy γ-ray in an aqueous solution. Their photoluminescence intensities were significantly enhanced after irradiation, which were closely related to the radiation dose and the structure of QDs. The positions of the fluorescence emission peaks did not shift obviously after irradiation. The mechanism of photoluminescence enhancement was discussed based on the results of photoluminescence (PL) spectra, UV-visible light absorption (UV-vis) spectra, transmission electron microscope (TEM), X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS). This method can be employed to uniformly treat large batches of QDs at room temperature and without other chemicals.

Highlights

Colloid semiconductor nanocrystals, which are known as quantum dots (QDs), exhibit unique optical and optoelectronic properties due to quantum confinement effects [1]
Water-dispersed QDs can be directly synthesized in an aqueous medium using thiols as stabilizing agents such as thioglycolic acid (TGA), mercaptopropionic acid (MPA) and cysteamine (Cys) [9]
Bao et al observed a strong photoluminescence enhancement effect of CdTe QDs stabilized by TGA under room light and concluded that the fluorescence quantum yields reached the maximum in 20 days [17]

Summary

Introduction

Colloid semiconductor nanocrystals, which are known as quantum dots (QDs), exhibit unique optical and optoelectronic properties due to quantum confinement effects [1]. Bao et al observed a strong photoluminescence enhancement effect of CdTe QDs stabilized by TGA under room light and concluded that the fluorescence quantum yields reached the maximum in 20 days [17]. Zare et al reported high-efficiency CdTe/CdS nanocrystals by growing CdS shells on CdTe cores under UV light [21] This method is considered to be an alternative way to achieve high quality QDs. the energy and penetration abilities of UV and visible light are low, which leads to a long activation time and low homogeneity. We report a simple and efficient strategy to enhance the photoluminescence of water-dispersed, thiol-capped QDs (MPA-CdTe, MPA-CdSe and Cys-CdTe) using γ-radiation. The advantage of this method is that it can be used to uniformly treat large quantities of QD solution at room temperature and without other chemicals

Materials

Characterization

Photoluminescence Properties of As-Prepared QDs Before and After Irradiation

Morphology and Structure of As-Prepared QDs Before and After γ-Irradiation

Mechanism of γ-Radiation-Induced QD Photoluminescence Enhancement