Ultrasensitive SERS substrates based on Au nanoparticles photo-decorated on Cu2O microspheres for the detection of rhodamine B and methylene blue

Integrating noble-metal and semiconductor nanomaterials for Raman signal enhancement is of great significance in the field of surface enhanced Raman spectroscopy (SERS). In this work, a SERS-active substrate composed of Au nanoparticles (NPs) on Cu2O microspheres is produced by the polyol and photochemical methods for the effective detection of organic dye molecules, rhodamine B (RhB) and methylene blue (MB). The formation of Au/Cu2O nanostructure is confirmed by X-ray diffraction, field emission scanning electron microscopy , elemental mapping and UV-Vis spectroscopy. The proposed heterogeneous nanomaterials have high SERS activity by the synergistic interaction among Au NPs, Cu2O microspheres and organic dye molecules through electromagnetic and chemical mechanisms. The photochemical parameter for the growth of Au NPs and Cu2O microspheres is optimized by elevating the SERS signal intensity to high extent. The measured analytical enhancement factors (AEFs) are as high as 2.55 × 1012 for RhB and 1.2 × 1011 for MB. The corresponding limits of detection (LOD) are 2.36 × 10-13 M for RhB and 3.40 × 10-12 M for MB. The reproducibility and the uniformity with the relative standard deviation (RSD) < 10% confirm the superiority of the proposed SERS substrate. The real-sample analysis of RhB in the chili solution and MB in the pond water gives the satisfactory recovery values > 87.8%. This reliable and facile production approach is practically applicable to produce SERS-active substrates in various real applications.