Flow-based approach for scalable fabrication of Ag nanostructured substrate as a platform for surface-enhanced Raman scattering

23 January 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


The droplet-based biphasic reaction is an efficient strategy for the fabrication of surface-bound nanostructures. Here, we developed a process of fabricating ordered micro-ring arrays of silver (Ag) nanostructures from surface nanodroplet reaction on a micro-patterned hydrophobic substrate for reproducible detection by surface-enhanced Raman spectroscopy (SERS). Our process consisted of the generation of surface nanodroplet arrays, followed by a biphasic chemical reaction between droplets and the continuous flow of silver nitrate (AgNO3) precursor solution. The parameters in the formation and reaction of the droplet array were well controlled to maintain the uniformity of Ag nanostructures throughout the substrate. By scaling up the process parameters and the size of the microchamber, we were able to produce a SERS substrate with a surface area of > 60 cm^2 in a single run. Such a large area could be sufficient for analyzing more than a thousand samples. We demonstrated the repeatability of SERS measurements using Ag nanostructures by analyzing three environmental (rhodamine 6G, chlorpyrifos, triclosan), a biological (indoxyl sulfate), and a psychoactive drug (tetrahydrocannabinol) compounds. 2D mapping of SERS intensities was also performed for both small and large-scale substrates by collecting data from more than 100 locations on the substrate. Our work demonstrated droplet-based biphasic reaction as a simple approach for the fabrication of SERS substrate with a large area. The technique may help to eliminate the requirement for sophisticated equipment for the fabrication of SERS active substrate.


Surface nanodroplet
Ag nanostructures

Supplementary materials

Flow-based appraoch for scalable fabrication of Ag nanostructured substrate as a platform for surface-enhanced Raman scattering
The supplementary data consists of information on the following: Optical image of micro-patterned Si wafer. Enhancement factor calculation. Stability test and image of the fabricated substrate. Optical images showing the stability of VE droplets in reactive flow. Vibration modes in SERS spectra of R6G, TC, CP, and THC.


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