Abstract
Practical application of surface-enhanced Raman scattering (SERS)-active platforms requires that they provide highly uniform and reproducible SERS signals. Moreover, to achieve highly stable and consistent SERS signals, it is important to control the nanostructured gaps of SERS-active platforms precisely. Herein, we report the synthesis of gap-controllable nanoporous plates and their application to efficient, robust, uniform, and reproducible SERS-active platforms. To prepare well-defined nanoporous plates, ultraflat, ultraclean, and single-crystalline Au nanoplates were employed. The Au nanoplates were transformed to AuAg alloy nanoplates by reacting with AgI in the vapor phase. The Ag in the alloy nanoplates was then chemically etched, thus forming well-defined SERS-active nanoporous plates. For the precise control of gaps in the nanoporous plates, we investigated the alloy forming mechanism based on X-ray photoelectron spectroscopy and transmission electron microscopy analyses. According to the mechanism, the composition of Ag was tunable by varying the reaction temperature, thus making the nanostructured gaps of the porous plates adjustable. We optimized the nanoporous plates to exhibit the strongest SERS signals as well as excellent uniformity and reproducibility. The computational simulation also supports the experimental SERS signals of nanoporous plates. Furthermore, we successfully performed label-free detection of a biocide mixture (5-chloro-2-methyl-4-isothiazolin-3-one/2-methyl-4-isothiazol-3-one) up to 10 ppm using Au nanoporous plates. The adoption of single-crystalline Au nanoplates, the novel synthesis method for alloy nanoplates in the vapor phase, and the investigation of alloy forming mechanisms synergistically contributed to the formation of well-defined nanoporous plates. We anticipate that the nanoporous plates will be useful for the practical sensing of trace chemical and biological analytes.
Highlights
Surface-enhanced Raman scattering (SERS) is a fascinating phenomenon that can enhance the Raman signals of molecules up to 106–1014.1–3 This remarkable enhancement is mainly attributed to hot spots, in which the electromagnetic eld strongly increases.[4]
The prepared Au nanoplates and AgI powder are placed in a glass reaction tube, and the reaction tube is put in the horizontal quartz tube furnace system
We report the synthesis of an intra-nanogap controllable Au plate with uniform and reproducible surface-enhanced Raman scattering (SERS) activity and the application of a nanoporous Au plate to the sensing of trace amounts of a detrimental chemical
Summary
Surface-enhanced Raman scattering (SERS) is a fascinating phenomenon that can enhance the Raman signals of molecules up to 106–1014.1–3 This remarkable enhancement is mainly attributed to hot spots, in which the electromagnetic eld strongly increases.[4]. The Ag in the alloy nanoplates was chemically etched, forming well-defined SERS-active nanoporous plates. A er chemical etching of the AuAg alloy nanoplate, we obtained an optical image of the nanoporous Au plate (top panel of Fig. 1c).
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