Interior Hotspot Engineering in Ag–Au Bimetallic Nanocomposites by In Situ Galvanic Replacement Reaction for Rapid and Sensitive Surface-Enhanced Raman Spectroscopy Detection

Abstract

Engineering of interior hotspots provides a paradigm shift from traditional surface-enhanced Raman spectroscopy (SERS), in which the detection sensitivity depends on the positioning of adsorbed molecules. In the present work, we developed an Ag–Au bimetallic nanocomposite (SGBMNC) SERS platform with interior hotspots through facile chemical syntheses. Ag nanoparticles replaced by Au via the galvanic replacement reaction (GRR) provided hotspot regions inside the SGBMNC that remarkably enhanced the plasmonic activity compared to the conventional SERS platforms without the internal hotspots. The diffusion of analytes into the proposed interior hotspots during the GRR process enabled sensitive detections within 10 s. The SERS behaviors of the SGBMNC platform were investigated using methylene blue (MB) as a Raman probe dye. A quantitative study revealed excellent detection performance, with a limit of detection (LOD) of 42 pM for MB dye and a highly linear correlation between peak intensity and concentration (R2 ≥ 0.91). The SGBMNC platform also enabled the detection of toxic benzyl butyl phthalate with a sufficient LOD of 0.09 ppb (i.e., 280 pM). Therefore, we believe that the proposed methodology can be used for SERS assays of hazardous materials in practical fields.

Gold-Deposited Graphene Nanosheets for Self-Cleaning Graphene Surface-Enhanced Raman Spectroscopy with Superior Charge-Transfer Contribution

“…In addition, the majority (∼97%) of intensity points lie within the range of 10% variation (green dashed lines) from their respective average intensity values (red dashed lines). Thus, the experimental findings represent a reasonably good reproducibility of the G-SERS signals from the tested substrate area …”

“…Thus, the experimental findings represent a reasonably good reproducibility of the G-SERS signals from the tested substrate area. 51 In order to explore the time-dependent stability of the G-SERS signal with GAu substrates, the MB G-SERS spectra were acquired every day from GAu2 substrates over a period of 7 days. The resultant average G-SERS spectra for 1 μM MB dye molecules from five different detection spots were compared with the pristine freshly prepared GAu2-based G-SERS substrates stored under ambient conditions (Figure 6e,f).…”

Hybrid Materials Obtained by Immobilization of Biosynthesized Ag Nanoparticles with Antioxidant and Antimicrobial Activity

“…There is great interest among researchers in the use of silver nanoparticles due to their broad antibacterial properties against many antibiotic-resistant microbial strains, high availability and low toxicity against human cells [11,[27][28][29]. Although Ag is considered to have the best plasmonic characteristics among the noble metals, its stability remains a challenge due to its high surface reactivity [30]. This problem can be solved by stabilizing the surface using plant extracts.…”