Tumor-derived exosomes (exos) closely related to the occurrence, development and treatment of tumors. However, it is not clear how exosomes affect the physical properties of the target cells, which leads...

Surface-enhanced Raman scattering (SERS) has attracted attention because of its enormous potential to detect molecules with low concentrations. The method of fabricating SERS substrates is of great importance for improving the detection resolution. However, SERS substrates with different triangular pyramid tips fabricated by using the tip-based nanoindentation method has not been reported. Here, we prepared arrayed micro/nanocavities on copper-based graphene using the continuous indentation method with a Berkovich tip and a cube-corner tip, which have different face angles. Gold nanoparticles were then sputtered onto the graphene−copper micro/nanocavities to form the Au@GR@Cu micro/ nanocavities SERS substrates. The substrates formed using the Berkovich tip and cube-corner tip were labeled B2−B9 and C2−C9, respectively, in which the numbers indicate the machining feed. Rhodamine 6G (R6G) was employed, and the Raman intensities of R6G on the differently arrayed Au@GR@Cu micro/nanocavities were measured. The Raman intensities of R6G were stronger on the pile-ups than on the inverted triangular pyramid cavities. The Raman intensities of R6G were highest on the C2 and B2 structures and lowest on the C9 and B9 structures. The Raman intensities of R6G on the arrayed Au@GR@Cu micro/nanocavities fabricated by the cube-corner tip were stronger than those on the arrayed Au@GR@Cu micro/nanocavities fabricated using the Berkovich tip with the same machining feed. In addition, the electric field intensity and distribution of the B9 and C9 arrayed Au@GR@Cu were simulated using Comsol software. Au@GR@Cu structures fabricated by the cube-corner tip were generated with higher electric field intensities. Furthermore, the relative standard deviations at 1362 cm −1 of R6G were 6.19 and 6.62% on the C2 and C4 surfaces, respectively, showing good homogeneity. The SERS spectra of 10 −9 mol/L malachite green solution and 10 −6 mol/L carbaryl solution were recognized on the C1, C2, and C4 surfaces on day 1 and after 3 months, respectively. After storage at room temperature for 3 months, the reductions in the Raman intensities were less than 10%, indicating excellent stability. The results showed that the arrayed Au@GR@Cu micro/nanocavities fabricated using the cube-corner tip performed better than those fabricated using the Berkovich tip and exhibited excellent uniformity, availability, and stability, providing great potential for detecting pesticides at low concentrations.

Nanostructures and nanoparticles are two typical structures which have already been widely employed as the Surface Enhanced Raman Scattering (SERS) substrates. In most studies, they are employed separately as SERS substrates. Recently, the hierarchical structures including nanostructures and nanoparticles present better SERS characteristics. However, how to machine such hierarchical structures is a big problem. In the present study, a novel method integrating the nanoindentation process and chemical redox reaction to machine the hierarchical SERS substrate is provided. Micro/nanostructures are formed on the Cu(110) plane first, and then Ag nanoparticles are generated on the structured Copper surface. Effects of parameters of the indentation process and the corrosion times in the AgNO3 solutions on the Raman intensities of the SERS substrate with hierarchical structures are experimentally studied. The intensity and distribution of the electric field of single and multi Ag nanoparticles on the surface of plane and micro/nanostructures are studied with the COMSOL software. The feasibility of the hierarchical SERS substrate is verified using R6G molecules. Finally, the enhancement factor of malachite green molecules can reach to 5.089×109, which proves that the method is simple, replicable and low cost method for machining the hierarchical SERS substrate.