Fig. 1. SEM image of Au nanoparticles monolayer film

Fig. 2. (a) Schematic diagram of experiment; (b) normal Raman spectrum of OMBA powder (Ⅰ), SERS spectrum of OMBA adsorbed on Au MLF in air (Ⅱ) and in 0.01 mol·L^-1 NaOH solution (Ⅲ), and SERS spectrum of TP adsorbed on Au MLF in air (Ⅳ)

Fig. 3. SERS spectra of OMBA adsorbed on Au MLF in air (a), in aqueous solution at pH 2 (b), pH 7 (c) and pH 12 (d)

Fig. 4. (a) SERS spectra of OMBA on Au MLF measured in aqueous solution at pH 12 with different laser power; (b) Laser power dependent normalized intensity of band at 997 cm^-1 of TP and band at 1 427 cm^-1 of OMBA
Ⅰ: 2 mW; Ⅲ: 5 mW; Ⅲ: 10 mW; Ⅳ: 20 mW

Fig. 5. (a) Time dependent SERS spectra of OMBA on Au MLF in aqueous solution with pH 12 (laser power 2 mW); (b) Time dependent normalized intensity of band at 997 cm^-1 of TP and band at 1 427 cm^-1 of OMBA