Fig. 1. Schematic diagram of the work study process

Fig. 2. SEM images of (a) AuNRs, (b) ZIF -8, (c, d) AuNRs@ZIF-8 of different magnifications

Fig. 3. UV–Vis absorption spectra of the as-synthesized AuNRs and AuNRs@ZIF-8

Fig. 4. Sample performance diagram. (a) SERS spectra of 10⁻⁵ mol/L R6G for AuNRs@ZIF-8 and AuNRs substrates; (b) SERS spectra of R6G with the concentration ranging from 10⁻⁹ to 10⁻⁴ mol/L for AuNRs@ZIF-8 substrates; (c) The Raman intensities at 612 cm⁻¹ versus logarithmic values of R6G concentrations; (d) Series of SERS spectra of random 10 sites of the substrates absorbing 10⁻⁴ mol/L R6G

Fig. 5. Raman spectrum of the R6G powder on silicon wafer

Fig. 6. UV–vis absorption spectra of the R6G and R6G/AuNRs@ZIF-8