Silicon quantum dot-coated onto gold nanoparticles as an optical probe for colorimetric and fluorometric determination of cysteine
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Silicon quantum dots (SiQDs) were synthesized from N-[3-(trimethoxysilyl)propyl]-ethylenediamine and catechol by a hydrothermal method. Transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the morphology and structure of quantum dots. The SiQDs were then placed on gold nanoparticles (AuNPs). When Cys is added to this solution, Cys will penetrate the SiQDs “shell” of the SiQDs/AuNP composite. This is due to the interaction and conformational differences of Cys and other substance with AuNPs and leads to the dispersion of the aggregated SiQD/AuNPs. A color change from purple to red can be visually observed, and the (green) fluorescence of SiQDs (with excitation/emission peaks at 430/520 nm) is restored. This dual-readout nanoprobe was successfully applied to the selective and sensitive detection of cysteine (Cys) in (spiked) serum and urine samples. The detection limit is 3.5 nmol·L−1 (at an S/N ratio of 3), and the method works on the 0.01 to 2 μM Cys concentration range.
KeywordsAmino acid detection Fluorescence probe Colorimetric probe Quenching FRET Stern-Volmer plot Steric hindrance effect Serum analysis Urine analysis
We acknowledge the support from the National Natural Science Foundation of China (21607061), the Opening Project of State Key Laboratory of Chemo/Biosensing and Chemometrics of Hunan University (2016017), the Priority Academic Program Development of Jiangsu Higher Education Institutions, Collaborative Innovation Center of Technology and Material of Water Treatment, and the Program of Young Backbone Teachers in Jiangsu University (2015).
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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