Issue 31, 2014

Highly bright water-soluble silica coated quantum dots with excellent stability

Abstract

Silica coating via a Stöber method is an effective route to render luminescent quantum dots (QDs) with great biocompatibility, low toxicity and water-solubility for bioapplications. However, the bottleneck in this route is the access of highly luminescent, colloidally stable QD dispersion in alcoholic solution. Herein, we report a facile route based on the Stöber method for the synthesis of isolated silica coated QDs (QD@SiO2) with high emission efficiencies, tunable small size (less than 30 nm) and excellent stability. Prior to silica coating, the initial oil-soluble QDs were made dispersible in alcohol–water media by replacing the native hydrophobic ligands with adenosine 5′-monophosphate (AMP). Then, 3-mercaptopropyl-trimethoxysilane (MPS) was introduced to serve as silane nucleation primers. Finally, a silica shell with controllable thickness was obtained on the QD surface by hydrolysis/condensation of tetraethyl orthosilicate (TEOS). Remarkably, the resultant QD@SiO2 had nearly the same high luminescent efficiency (50–65%) as that of initial oil-soluble QDs and exhibited excellent long-term photo and colloidal stability in harsh environments (pH range of 3–13, saturated NaCl solution and thermal treatment at 100 °C). It was demonstrated that the cytotoxicity of the resultant QD@SiO2 was significantly diminished. Moreover, the QD@SiO2 conjugated with folic acid exhibits high specific binding toward receptor-positive Hela cells over receptor-negative A549 cells, indicating the potential of our obtained QD@SiO2 as robust biomarkers in cells due to their chemical processibility and low cytotoxicity.

Graphical abstract: Highly bright water-soluble silica coated quantum dots with excellent stability

Supplementary files

Article information

Article type
Paper
Submitted
22 Mar 2014
Accepted
04 Jun 2014
First published
05 Jun 2014

J. Mater. Chem. B, 2014,2, 5043-5051

Author version available

Highly bright water-soluble silica coated quantum dots with excellent stability

Y. Ma, Y. Li, S. Ma and X. Zhong, J. Mater. Chem. B, 2014, 2, 5043 DOI: 10.1039/C4TB00458B

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