Centimeter level high surface roughness copper / silver nanoheterostructures for highly sensitive SERS detection

A novel method for centimeter level high surface roughness copper nanoparticles (CuNPs)/silver nanowires (AgNWs) heterostructures prepared by vacuum thermal evaporation method and solid-state ionics method under 6 ​μA direct current electric field (DCEF) using fast ionic conductor KAg4I5 was developed. The fractal dimension of the CuNPs/AgNWs heterostructures was calculated by grid-coverage method and the surface-enhanced Raman scattering (SERS) performance was detected by melamine aqueous solution as probe molecules. The results indicate that the macroscopic dendritic CuNPs/AgNWs heterostructures arranged neatly near cathode with the longest length of 6.3 ​cm were prepared, the diameters of CuNPs/AgNWs heterostructures ranged from 40 to 100 ​nm and many regularly arranged CuNPs with the diameter from 10 to 30 ​nm lie in the prepared nanoheterostructures, which lead to the CuNPs/AgNWs heterostructures have high surface roughness. The molar ratio of Ag:Cu is 11.87:1 and the fractal dimension of CuNPs/AgNWs heterostructures was 1.64 which means that there were more dentritic nanoheterostructures. The limiting concentration of melamine for the prepared high surface roughness CuNPs/AgNWs heterostructures SERS substrates is 10−16 ​mol/L, which is far below the strictest safety limits required of melamine in US and China. The EF for R6G/CuNPs/AgNWs heterostructures is estimated to be 4.82 ​× ​1012. These results indicate that the prepared CuNPs/AgNWs heterostructures with facile material synthesis, high surface roughness, low detection concentration and simple detection procedure has promising and strong application prospect for SERS detection in food safety.