2.4. SERS Measurement

First, rhodamine 6G was dissolved in purified water to obtain R6G solutions with different concentrations. By adding purified water to the cadmium nitrate solution, a 1.0 × 10⁻³–1.0 × 10⁻⁷ M solution was prepared as the probe molecule. After that, 5 μL of R6G solution (or cadmium nitrate solution) with different concentrations were dropwise dispersed on the above-mentioned silicon wafer (0.6 cm × 0.6 cm) substrate containing Ag@CuO FM and then naturally dried. The detection of SERS was carried out under a 50× objective lens and confocal Raman system with excitation wavelengths of 532 nm and 0.785 μm², respectively. Raman grating with a 1200 L/mm, the spectral data acquisition 3 times, each acquisition time is 10 s.