Self-Concentrated Surface-Enhanced Raman Scattering-Active Droplet Sensor with Three-Dimensional Hot Spots for Highly Sensitive Molecular Detection in Complex Liquid Environments

Abstract

In this work, a surface-enhanced Raman scattering (SERS)-active droplet with three-dimensional (3D) hot spots prepared from a superhydrophobic SERS substrate, which is inspired by the nut wizard strategy, was developed for ultrasensitive detection in complex liquid environments. The SERS substrate was composed of silver-capped parylene C-coated carbon nanoparticles (Ag-PC@CNPs). Such a SERS substrate was prepared by candle-soot deposition to provide a porous carbon nanoparticle layer followed by deposition of a parylene C film to protect the CNPs and then sputtering of silver nanoparticles. Similar to a nut wizard, a droplet

Electrostatic tweezer for droplet manipulation

“…On such a substrate, droplets carrying highly diluted aqueous analyte could pick the silver nanoparticles during motion ( Fig. 4 D ), therefore showing an enhanced sensitivity in Raman measurement due to the plasmonic properties of silver nanoparticles ( 42 ). Such a method dramatically increases the detecting efficiency and sensitivity ( SI Appendix , Fig.…”

“…The superhydrophobic alumina substrates were obtained by successively immersing the cleaned aluminum in a 2.5 M HCl solution for 15 min, hot water (100 °C) for 5 min, and a 0.01 M perfluorooctanoic acid aqueous solution for 1 h. To render ITO-coated glass, polystyrene, gold-coated polystyrene, and other substrates superhydrophobic, these substrates were first sprayed using a commercial superhydrophobic sprayer, Glaco (purchased from Soft99 Corporation), followed by heating at 60 °C for 5 min. The SERS surface was prepared using the combined candle soot and thin-film deposition processes ( 42 ). Briefly, a candle soot layer was first formed by placing a newly prepared glass above a burning candle flame for 15 s. Then, the candle soot–coated substrate was deposited by a thin parylene C film (∼150 nm) using specialized vacuum deposition equipment (Specialty Coating Systems, Inc.) as well as a thin silver film (∼30 nm) composed of nanoparticles using a vacuum sputter coating apparatus (Denton Vacuum LLC).…”

Detection of a miRNA biomarker for cancer diagnosis using SERS tags and magnetic separation

“…26 Recent studies have also demonstrated that samples concentrated into microdroplets ($2.5-5.0 mL) can be measured with a confocal Raman spectrometer. [27][28][29] The enriched microdroplet contains 3D SERS active hotspots that can be excited more than a 2D planar SERS substrate. 27 Thus, the microdroplet is also suitable for the detection of low-abundant biological samples such as miRNA and offers the advantage of more efficient interrogation of the bulk of the sample.…”

Flexible Surface‐Enhanced Raman Scattering Substrates: A Review on Constructions, Applications, and Challenges

“…On the other hand, Raman report molecules attached on the surface of precious metal particles as SERS tags can be applied to detect the biomolecules possessing small scattering cross‐sections. [ 11–13 ]…”