Tuning the Optical Properties of Silicon Quantum Dots via Surface Functionalization with Conjugated Aromatic Fluorophores

Mohammed Abdelhameed,Olabode O Oyeneye,Subrata Chakrabarti,William Z Xu,Eli Zysman-Colman,Shalimar Chen,Paul A Charpentier,Diego Rota Martir

doi:10.1038/s41598-018-21181-8

Mohammed Abdelhameed, Olabode O Oyeneye + Show 6 more

Open Access

https://doi.org/10.1038/s41598-018-21181-8

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Journal: Scientific Reports	Publication Date: Feb 14, 2018
Citations: 27	License type: open-access

Affiliation: Western University, University of St Andrews

Abstract

Silicon Quantum Dots (SQDs) have recently attracted great interest due to their excellent optical properties, low cytotoxicity, and ease of surface modification. The size of SQDs and type of ligand on their surface has a great influence on their optical properties which is still poorly understood. Here we report the synthesis and spectroscopic studies of three families of unreported SQDs functionalized by covalently linking to the aromatic fluorophores, 9-vinylphenanthrene, 1-vinylpyrene, and 3-vinylperylene. The results showed that the prepared functionalized SQDs had a highly-controlled diameter by HR-TEM, ranging from 1.7–2.1 nm. The photophysical measurements of the assemblies provided clear evidence for efficient energy transfer from the fluorophore to the SQD core. Fӧrster energy transfer is the likely mechanism in these assemblies. As a result of the photogenerated energy transfer process, the emission color of the SQD core could be efficiently tuned and its emission quantum efficiency enhanced. To demonstrate the potential application of the synthesized SQDs for bioimaging of cancer cells, the water-soluble perylene- and pyrene-capped SQDs were examined for fluorescent imaging of HeLa cells. The SQDs were shown to be of low cytotoxicity

Highlights

Despite some reports of aromatic fluorophores incorporated into SQDs that permit sensitization of the SQDs via energy transfer, there are still limited examples of luminescent SQDs covalently functionalized with conjugated emissive compounds obtained through a solution-based reduction method[17,18]
The functionalized SQDs were characterized by UV−Vis absorption spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, steady-state and times-resolved emission spectroscopy, high-resolution transmission electronic microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS)
SQDs functionalized with aromatic fluorophores were prepared following a solution-based reduction route as shown in Fig. 1 24

Summary

Introduction

Despite some reports of aromatic fluorophores incorporated into SQDs that permit sensitization of the SQDs via energy transfer, there are still limited examples of luminescent SQDs covalently functionalized with conjugated emissive compounds obtained through a solution-based reduction method[17,18]. SQDs covalently linked with pyrene units through a nonconjugated bridge and observed efficient energy transfer from the donor pyrene moieties to the acceptor SQD core[22]. Using a conjugated bridge may offer even improved optical properties through photogenerated energy transfer. Phenanthrene, pyrene, and perylene fluorophores were chosen for the surface passivation of SQDs due to their high stability and excellent optical properties including high fluorescence quantum yield[23]. Functionalization of the SQDS with these fluorophores is expected to improve the quantum yield of SQDs and tunability of PL emission, which can be applied in many fields such as bioimaging. The functionalized SQDs were characterized by UV−Vis absorption spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, steady-state and times-resolved emission spectroscopy, high-resolution transmission electronic microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS)

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Conclusion