Fig. 1. Schematic illustration of the experiment. (I–III) Microfluidic chip fabrication on Si wafer by dry etching. (IV–V) BS fabrication by laser. (VI) HF treatment on BS. (VII) AgNPs’ growth on BS. (VIII) Catalytic reaction and SERS detection on Ag-BS substrate.

Fig. 2. SEM images of the BS with (a) side view and (b) oblique view.

Fig. 3. (a) SEM image of the AgNPs on the BS protrusions. (b), (c), and (d) Enlarged SEM images of AgNPs on the area marked by red, green, and blue squares in (a).

Fig. 4. SEM images of the AgNPs grown under (a) 15°C, (b) 25°C, (c) 50°C, and (d) 75°C. The scale bars indicate 100 nm.

Fig. 5. SEM images of the AgNPs grown in (a) 0.001, (b) 0.01, (c) 0.1, and (d) 1 mol/L AgNO3 solution. The scale bars indicate 100 nm.

Fig. 6. EDS spectra of the Ag-BS (a) under different reaction temperatures, where inset shows the peak intensity versus temperature; and (b) with different AgNO3 solution concentrations, where inset shows the peak intensity versus concentration.

Fig. 7. SERS spectra taken before (black line) and after (red line) the catalytic reaction of pNP to pAP. Inset illustrates the chemical reaction process.

Fig. 8. SERS spectra of R6G with the concentrations ranging from 10−6 to 10−8  M.