In Situ Creation of Surface-Enhanced Raman Scattering Active Au–AuO_x Nanostructures through Electrochemical Process for Pigment Detection

Abstract

Roughing the metallic surface via oxidation–reduction cycles (ORC) to integrate the surface plasmon resonance and surface-enhanced Raman scattering (SERS) is predominant in developing sensor systems because of the facile preparation and uniform distribution of nanostructures. Herein, we proposed a distinctive ORC process: the forward potential passed through the oxidation of Au and reached the oxygen evolution reaction, and once the potential briefly remained at the vertex, the various reverse rates were employed to control the reduction state. The created hybrid Au–AuO x possessed electromagnetic and chemical enhancements concurrently, wherein the rough surface provided the strong local electromagnetic fields and significant interaction between AuO x and molecule to improve the charge transfer. The synergistic effects significantly amplified the intensity of Raman signal with an enhancement factor of 5.5 × 10 6 under the optimal conditions. Furthermore, the prepared SERS substrate can simultaneously identify and quantify the mixed edible pigments, Brilliant Blue FCF and Indigo Carmine, individually. This result suggested that the development of SERS sensor based on the proposed SERS-activated methodology is feasible and reliable.

Plasma-Induced Enhancement in Electronic Properties of Gold Nanoparticles: Application in Electrochemical Biosensing of Cortisol

“…Hence, plasma treatment could easily disrupt the bond. Further, the plasma treatment induced a change in the redox state of the surface AuNPs, which can be seen from the Au–O x peaks at 491 and 635–677 cm –1 (Figure C,D) . Raman signals observed at 590 cm –1 (Figure D) were ascribed to the surface oxide species …”

“…Further, the plasma treatment induced a change in the redox state of the surface AuNPs, which can be seen from the Au−O x peaks at 491 and 635−677 cm −1 (Figure 5C,D). 31 Raman signals observed at 590 cm −1 (Figure 5D) were ascribed to the surface oxide species. 32 The reduction in the size of AuNPs due to the plasma treatment occurred as a result of the removal of citrate capping and partial surface oxide formation.…”

Au3+ Species-Induced Interfacial Activation Enhances Metal–Support Interactions for Boosting Electrocatalytic CO2 Reduction to CO

“…Therefore, we used Raman spectra to study the metal coordination structure (Figure e). The peaks at 560 and 635 cm –1 were assigned to the M–O–Ce and M–O structures, respectively. , Au–CeO 2 –DP–B exhibited a higher signal intensity of these two peaks, indicating the higher valance state of Au species and the higher MSIs. In addition, the peak at about 600 cm –1 could be ascribed to the D mode of the Frenkel-type O vacancies from the CeO 2 support. , For comparison, the other control samples including Au–C–FR–B and Au–CeO 2 –FR–B were synthesized by a fast reduction method using NaBH 4 as the reductant (Figures S4 and S5).…”

Spectroscopic Evidence for the Involvement of Interfacial Sites in O–O Bond Activation over Gold Catalysts

“…These observations, along with reported Raman spectra of bulk Au(OH) 3 and IR spectra of gaseous Au(OH) 2 that exhibit ν(Au−OH) features between 635 and 680 cm −1 , 68 suggest that the 690 cm −1 peak corresponds to the ν(Au−OH) mode and signifies that OH* binds at appreciable coverages on er-Au during catalysis of H 2 O 2 (Figure 3). 69 Analysis of time-dependent SERS spectra indicates that er-Au stabilizes OH* groups that mediate O−O and O−H bond activations in H 2 O 2 . Figure 4b Two features signifying diatomic oxygen surface intermediates (800 and 960 cm −1 ) grow independently with H 2 O 2 concentration, which suggests they bind to distinct adsorption sites on er-Au.…”