Abstract
The performance of a metal-enhanced fluorescence (MEF) substrate is fundamentally based on the orientation of the metal nanostructures on a solid substrate. In particular, two-dimensional (2D) periodic metallic nanostructures exhibit a strong confinement of the electric field between adjacent nanopatterns due to localized surface plasmon resonance (LSPR), leading to stronger fluorescence intensity enhancement. The use of vertical vibration-assisted convective deposition, a novel, simple, and highly cost-effective technique for preparing the 2D periodic nanostructure of colloidal particles with high uniformity, was therefore proposed in this work. The influences of vertical vibration amplitude and frequency on the structure of thin colloidal film, especially its uniformity, monolayer, and hexagonal close-packed (HCP) arrangement, were also investigated. It was found that the vibration amplitude affected film uniformity, whereas the vibration frequency promoted the colloidal particles to align themselves into defect-free HCP nanostructures. Furthermore, the results showed that the self-assembled 2D periodic arrays of monodisperse colloidal particles were employed as an excellent template for a Au thin-film coating in order to fabricate an efficient MEF substrate. The developed MEF substrate provided a strong plasmonic fluorescence enhancement, with a detection limit for rhodamine 6G as low as 10−9 M. This novel approach could be advantageous in further applications in the area of plasmonic sensing platforms.
Highlights
Fluorescence spectroscopy is an analytical method based on an emission property of either single fluorescent molecule that is triggered by the absorption of excitation radiation at a particular wavelength
A novel method for preparing a large-area monolayer of 2D periodic nanopatterned arrays using the vertical vibration-assisted convective deposition technique has been successfully proven in this work
It was an alternative method for preparing 2D periodic nanopatterned arrays with relatively low costs and simplicity compared to those reported in previous works [27,28,41,42]
Summary
Fluorescence spectroscopy is an analytical method based on an emission property of either single fluorescent molecule (fluorophore) that is triggered by the absorption of excitation radiation at a particular wavelength. It is widely used in tremendous applications in medical, life science, and biotechnology fields due to its rapid, non-destructive, and sensitive analytical method for the analysis of biomolecular substances [1]. In order to detect a target biomolecular substance, the fluorophore is immobilized on the biomolecule for employment as a fluorescent probe. The methods to achieve a strong fluorescence intensity have been intensely investigated for improving sensitivity and lowering the detection limit of bioanalytical sensors [2]. A recognized powerful technology called metal-enhanced fluorescence (MEF) is an area of particular focus, due to its ability to significantly enhance the fluorescence signal in the near-field and shield fluorophores against photobleaching processes [3,4]
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