Facile construction of silver nanocubes/graphene oxide composites for highly sensitive SERS detection of multiple organic contaminants by a portable Raman spectrometer

Here, we demonstrate a reliable surface-enhanced Raman scattering (SERS) substrate composed of graphene oxide (GO) nanosheets and Ag nanocubes for sensitive detection of varied organic contaminants, malachite green, methylene blue and crystal violet by a portable Raman spectrometer with the limits of detection (LODs) of 10-9, 10-10 and 10-9 M, respectively, owing to a synergistic SERS enhancement arising from electromagnetic field effect of Ag nanocubes and chemical enhancement of GO sheets. The SERS substrates also present highly uniform signal over substrates and low relative standard deviations of 6.53 %, 6.16 % and 6.70 %, respectively are obtained on each sample, which is attribute to the extremely uniform size of Ag nanocubes as well as the consistent distribution of Ag nanocubes on GO sheets. Moreover, the SERS substrate is capable of label-free detection of more complex organic pesticides such as tetramethylthiuram disulfide and diquat dibromide with the LOD of 10-8 M, which is below the safety levels regulated by United States Environmental Protection Agency. Consequently, the Ag nanocubes/GO composites are promising as efficient SERS platforms for reliable and highly sensitive monitoring of food safety and environmental pollution.