SERS enhancement, sensitivity and homogeneity studies on bi-metallic Ag-Cu films through tuning of broad band SPR towards red region

Bimetallic Ag–Cu Alloy Microflowers as SERS Substrates with Single-Molecule Detection Limit

“…We observed the presence of spin−orbit doublets of Cu 2p 1/2 and Cu 2p 3/2 at two different binding energies of 932.2 and 951.9 eV for Cu 0 and at 934.7 and 954.8 eV for Cu +2 , respectively. 53 However, in both peaks, the peak intensity of Cu +2 was found to be lower than that of Cu 0 , indicating the formation of Cu +2 in smaller quantities compared to Cu 0 . 62 Moreover, when we collected the XPS spectra of alloy substrates with an increasing percentage composition of Cu, we noticed a decrease in the peak intensity of the Ag 3d orbital (Figure S8, Supporting Information) with an increase in the peak intensity for the Cu 2p orbital (Figure 4d), exactly in an opposite way.…”

“…However, it can be clearly seen that the size of the alloy MFs decreased (from 66 to 19 μm) with an increase in the copper composition in the alloy (Figures 2b−g, S3 and S4, Supporting Information). 53 The average sizes of 1, 5, 7.5, 10, 12.5, and 15% alloy microflowers were determined to be ∼62, 58, 55, 45, 32, and 19 μm, respectively (Figures 2b−g). However, at 15% Cu, we observed the formation of nanospheres in addition to MFs (Figure 2h).…”

“…The highresolution narrow scan spectra of Ag (Figure 4b) in both pure Ag and alloy substrates showed characteristic peaks at 367.6 and 373.6 eV corresponding to Ag 3d 5/2 and 3d 3/2 , confirming the oxidation state of Ag as metallic Ag 0 . 53,62 However, when we collected the high-resolution spectrum of copper for the 10% alloy substrate, it showed two asymmetric peaks at 952.3 and 932.2 eV (Figure 4c). The deconvolution of these peaks indicated Cu in both elemental and oxidized states as Cu 0 and Cu +2 .…”

“…Zhang et al synthesized polymer-stabilized monometallic Cu and Ag–Cu NPs and showed that the latter produced better SERS properties . Pal et al synthesized bimetallic Ag–Cu films, and Rao et al synthesized Cu–Ag nanoparticle-embedded polymer thin films and showed their efficiency as broad-band-spectrum SERS substrates. Nandhagopal et al fabricated pure Ag and Ag–Cu bimetallic thin films and showed that the latter demonstrated a 3-fold increase in SERS efficiency .…”

SERS as a probe for the charge-transfer process in a coupled semiconductor nanoparticle system TiO2/MBA/PbS

“…Since it was discovered on a rough silver electrode in 1974, 7 the surface-enhanced Raman scattering (SERS) has seen renewed interest over the past decades because of its high sensitivity, high selectivity, and nondestructive nature. Today SERS is being widely applied to many areas, such as analytical chemistry, 8-10 electrochemistry, 11 life science, 12-14 material area 15,16 and environment monitoring. 17 There are two primary mechanisms that account for SERS: electromagnetic mechanism (EM) and chemical enhancement mechanism (CM).…”