Fabrication and SERS activity of high aspect ratio copper nanowires prepared via solid-state ionics method

Solid-state ionics method is a convenient, efficient and pollution-free method to prepare metal nanostructures with controllable morphology, size and roughness. The present work reports that the copper nanowires with the length of 5-50 mm, 1-3 mm and 2-8 mm can be prepared by solid-state ionics method at 6 mu A direct-current electric field (DCEF) with fast ionic conductor RbCu4Cl3I2 films using copper electrodes, gold electrodes and silver electrodes on the two ends of glass substrate, respectively. The surface morphologies, chemical compositions and surface-enhanced Raman scattering (SERS) effect of the copper nanowires were characterized. The results show that the diameters of copper nanowires composed of pure Cu ranged from 40 nm to 90 nm, 50 nm-80 nm and 30 nm-100 nm were prepared by using copper electrodes, gold electrodes and silver electrodes with vacuum thermal evaporation plating equipment (ZHD-300), respectively. The fractal dimensions of copper nanowires using copper electrodes is 1.406. Au+ and Ag+ in the anode displaces Cu+ of RbCu4Cl3I2 films and the part of pure RbCu4Cl3I2 films become RbCu(4-x)AuxCl3I2 (0 < x <= 4) and RbCu(4-x)AgxCl3I2 (0 < x <= 4) using gold electrodes and silver electrodes, respectively. At the initial stage of growth prepared by gold and silver electrodes, the RbCu4Cl3I2 channel for transporting copper ion is open and the growth of copper nanostructures ends with the increase of the amount of RbCu(4-x)Au/AgxCl3I2 (0 < x <= 4) and the blockage of the channel for transporting copper ions. The limiting concentrations for melamine and crystal violet (CV) detected by the prepared copper nanowires using copper electrodes are as low as 1 x 10(-11) mol/L and 1 x 10(-12) mol/L, respectively. The enhancement factor for melamine/copper nanowires and CV/copper nanowires are estimated to be 5.34 x 10(9) and 5.37 x 10(9), respectively. The discovery of the growth mechanism of copper nanowires prepared by solid-state ionics method provides the possibility to expand the types of metal nanostructures and prepare noble metal nanostructures with cheap metal electrodes by this method. The prepared copper nanowires with high aspect ratio, simple detection procedure and low detection concentration has promising and strong application prospect for SERS detection in food safety.