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ACS Sens. 2017 Sep 22;2(9):1369-1376. doi: 10.1021/acssensors.7b00522. Epub 2017 Sep 5.

High-Throughput Single-Particle Analysis of Metal-Enhanced Fluorescence in Free Solution Using Ag@SiO2 Core-Shell Nanoparticles.

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MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, Key Laboratory for Chemical Biology of Fujian Province, Collaborative Innovation Center of Chemistry for Energy Materials, Department of Chemical Biology, College of Chemistry and Chemical Engineering, and ‡Department of Physics, Xiamen University , Xiamen, Fujian 361005, P. R. China.


Metal-enhanced fluorescence (MEF) based on localized surface plasmon resonance (LSPR) is an effective strategy to increase the detection sensitivity in biotechnology and biomedicine. Because plasmonic nanoparticles are intrinsically heterogeneous, high-throughput single-particle analysis of MEF in free solution are highly demanded for the mechanistic understanding and control of this nanoscale process. Here, we report the application of a laboratory-built high-sensitivity flow cytometer (HSFCM) to investigate the fluorescence-enhancing effect of individual plasmonic nanoparticles on nearby fluorophore molecules. Ag@SiO2 core-shell nanoparticles were used as the model system which comprised a silver core, a silica shell, and an FITC-doped thin layer of silica shell. FITC-doped silica nanoparticles of the same particle size but without silver core were used as the counterparts. Both the side scattering and fluorescence signals of single nanoparticles in suspension were measured simultaneously by the HSFCM at a speed of thousands of particles per minute. The roles of silver core size (40-100 nm) and fluorophore-metal distance (5-30 nm) were systematically examined. Fluorescence enhancement factor exceeding 30 was observed at silver core size of 70 nm and silica shell thickness of 5 nm. Compared with ensemble-averaged spectrofluorometric measurements, our experimental observation at the single-particle level was well supported by the finite difference time domain (FDTD) calculation. It allows us to achieve a fundamental understanding of MEF, which is important to the design and control of plasmonic nanostructures for efficient fluorescence enhancement.


Ag@SiO2 nanostructure; flow cytometry; localized surface plasmon resonance; metal-enhanced fluorescence; single-particle analysis


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