Spin-Coated Ag NPs SERS Substrate: Role of Electromagnetic and Chemical Enhancement in Trace Detection of Methylene Blue and Congo Red

Abstract

This work demonstrates a simple low cost and reproducible spin coating method followed by thermal reduction for the uniform growth of silver nanoparticles (AgNPs) as surface enhanced Raman scattering (SERS) substrate. In this work, cationic dye MB and anionic dye CR are selected as two different kinds of SERS probe molecules to investigate the differences between EME and CE mechanism. The results indicate that SERS spectra of MB molecule on AgNPs SERS substrate exhibit the shift in the Raman peak positions and high sensitivity (LOD ~ 10 -10 M) with large GSERS (~ 10 9 ) value, which can be attributed to the contribution from both EME and CE mechanism. It is found that Clhalide ions present in the MB molecule are forming surface complex (AgNPs@Cl -) on the surface of AgNPs SERS substrate which is confirmed by the XPS investigation, which might be responsible for the CE enhancement in MB molecule.Whereas Congo red being anionic dye showed no shift in Raman peak positions and less sensitivity (LOD ~10 -8 ) with GSERS (~ 10 7 ) value on AgNPs SERS substrate, which can be attributed to EME mechanism only. The obtained results suggest that Clhalide ions present in the MB molecule plays important role by giving large SERS enhancement for MB molecule on AgNPs SERS substrate. It is expected that this work will provide insight into role of EME and CE mechanisms for cationic dye MB and anionic dye CR.

Surface Plasmon Resonance-Induced Charge Transfer in Ag/Mercaptobenzoic Acid/Polyaniline Sandwich Structures

“…1−3 SERS is attributed mainly to the electromagnetic field enhancement mechanism (EM). 4,5 When a laser beam interacts with a metal nanostructure surface, it induces a localized electric field, leading to the polarization of electrons around the analyte and promoting surface plasmon resonance (SPR). 6,7 This resonant interaction focuses the electric field on the surface of the nanostructure, amplifying the Raman scattering intensity.…”

“…Surface-enhanced Raman scattering (SERS), which is an important tool for surface analysis and detection, utilizes the amplification effect induced on the surface of metal nanostructures to significantly enhance the Raman signal of molecules. − SERS is attributed mainly to the electromagnetic field enhancement mechanism (EM). , When a laser beam interacts with a metal nanostructure surface, it induces a localized electric field, leading to the polarization of electrons around the analyte and promoting surface plasmon resonance (SPR). , This resonant interaction focuses the electric field on the surface of the nanostructure, amplifying the Raman scattering intensity. , The important role of the EM in SERS cannot be overstated, but it has significant limitations. , In particular, the inherent heterogeneity of metal nanostructures and the limited enhancement region affect EM enhancement. , In addition, a chemical enhancement mechanism (CM), including resonance and charge-transfer (CT) enhancement, has been discovered . This CM provides an additional SERS enhancement effect that significantly enhances the SERS intensity. , …”

Simple fluorescence “turn-off” assay for Congo red using commercial 2-aminophthalic acid

“…In the past few years, some techniques have been developed for the determination of CR, such as ultraviolet-visible (UV-vis) absorption spectrometry, 2 uorescent methods, 1,4,5,7 electrochemical methods, 3,6,8 surface-enhanced Raman scattering (SERS), 9 high-performance liquid chromatography (HPLC) 10 and so on. The UV-vis absorption spectrometry is a commonly used method for quantifying CR.…”

“…Nonetheless, the stability needs to be improved. Spin-coated silver nanoparticles were employed as a SERS substrate to determine CR with a LOD of 0.1 nM 9 . Yet a stable and uniform SERS substrate is difficult to fabricate, and costly instruments are not easily affordable.…”

Ultrasensitive detection of crystal violet using a molybdenum sulfide–silver nanostructure-based sensing platform: roles of the adsorbing semiconductor in SERS signal enhancement

“…Other organic dyes, such as methylene blue, rhodamine 6G, Congo red and methyl orange, have been detected using SERS-based sensors, resulting in low detection limits (LODs). [12][13][14] Therefore, SERS is also expected to sense CV at low concentrations. However, compared to other dyes, there are few SERS-based sensing systems for CV that are described properly in the literature.…”