Controlled Fabrication of Flower-Shaped Au–Cu Nanostructures Using a Deep Eutectic Solvent and Their Performance in Surface-Enhanced Raman Scattering-Based Molecular Sensing

Abstract

Controlled synthesis of anisotropic bimetallic nanostructures with tunable morphology is of great current interest for their applications in surface-enhanced Raman scattering (SERS), plasmonics, and catalysis. Despite huge effort that has been devoted so far, fabrication of bimetallic nanostructures with controlled morphology and size remained to be a great challenge, especially when their shapes are anisotropic. Here, we report a facile, one-step synthetic approach for the fabrication of anisotropic bimetallic gold–copper nanostructures (Au–Cu NSs) of the 200–300 nm size range, using choline chloride/urea (ChCl/urea)-based deep eutectic solvent (DES) as the soft template. A concentration of the CuCl2 precursor in the reaction mixture was found to impact the reduction kinetics of the metal ions, directly affecting the final morphology of the Au–Cu nanostructures and elemental distributions in them. The fabricated anisotropic Au–Cu NSs revealed a high SERS signal for crystal violet (CV) molecules adsorbed at their surfaces, with the signal enhancement factor as high as 0.21 × 106 and capacity of detecting CV molecules of concentrations as low as 10–10 M in their aqueous solutions. The growth mechanism of the anisotropic bimetallic nanostructures in DES and their SERS performance has been discussed. The simple DES-assisted synthesis strategy presented in this work can be adopted for large-scale nonaqueous fabrication of other bimetallic nanostructures in a quite “greener” way.

A label-free and selective SERS-based sensor for determination of ampicillin contamination in water using a fabric gold–silver alloy substrate with a handheld Raman spectrometer

“…It can be explained that a higher redox potential of Au 3+ than that of Ag + (Au 3+ /Au = 1.002 V and Ag + /Ag = 0.80 V) is the driving force for the formation of Au rich Au–Ag alloy NPs. 27,28…”

Sensitive and Homogeneous Surface‐Enhanced Raman Scattering Detection Using Heterometallic Interfaces on Metal–Organic Framework‐Derived Structure

“…[ 77 ] The Au 4f XPS survey spectra exhibited two significant peaks at ≈83.5 and ≈87.4 eV corresponding to the Au 4f 7/2 and 4f 5/2 characteristic signals and 1.14 eV for FWHM value of Au peak, respectively. [ 78,79 ] In addition, the high‐resolution spectra of Co 2p, O 1s, Ag 3d, and Au 4f regions of Au@ZIF‐67‐CO, Ag@ZIF‐67‐CO, and ZIF‐67‐CO are presented in Figure S5 (Supporting Information). The XPS spectra of Au@ZIF‐67‐CO and Ag@ZIF‐67‐CO demonstrate that the Co and O elements of ZIF‐67‐CO are maintained after the electrodeposition or chemical grafting process.…”

Trends in Application of SERS Substrates beyond Ag and Au, and Their Role in Bioanalysis

“…They achieved a 50-fold enhancement in SERS spectra with 10% Ag-Cu alloy microflowers, which supersedes the efficiency of pure Au-Ag MFs [ 180 ]. Bimetallic nanostructures with tunable morphology are of current interest in plasmonics, catalysis and SERS [ 175 ]. In their study, Siva et al fabricated gold−copper nanostructures (Au−Cu NSs) of 200–300 nm size range and revealed a high SERS signal for crystal violet with EF as high as 10 6 and the ability to detect crystal violet (CV) molecules of concentrations as low as 10 −10 M. In addition, Rao et al showed that modification of Cu substrate with Ag is highly dependent on the concentration of Ag [ 178 ].…”