Fig. 1. Factors influencing the SERS performance^[21-27]

Fig. 2. (a) Schematic diagram of femtosecond laser-induced reduction of silver/palladium alloy^[31]; (b) Nanostructures formed by two-step femtosecond laser-induced reduction of silver ions^[32]; (c) Schematic diagram of the plasma-enhanced reduction of silver ionsat the solid-liquid interface^[33]; (d) Schematic diagram of SERS substrates prepared by laser-induced forward transfer^[35]; (e) Metal nanostructures formed by pulsed laser deposition^[37]

Fig. 3. (a) Femtosecond laser preparation of silver-based SERS substrates in air^[42]; (b) Femtosecond laser preparation of silver-based SERS substrates (S-Ag-Ar) in an argon atmosphere^[44]; (c) Femtosecond laser preparation of gold-based SERS substrates^[47]

Fig. 4. (a) Schematic of Ag/CuO NWs SERS substrate fabrication^[60]; (b) Ag/TiO₂ composite SERS substrate^[61]; (c) Schematic of the Au NP-attached SERS substrate fabrication^[62]

Fig. 5. SERS performance comparison between the hydrophilic substrate and superhydrophobic substrate^[69]

Fig. 6. Schematic of the femtosecond laser fabrication of superhydrophobic SERS^[71-72]

Fig. 7. (a) Schematic of the fabrication strategy of ultrasensitive SERS substrates^[74]; (b) Schematic of the fabrication strategy of hybrid superhydrophilic/superhydrophobic substrates^[75]; (c) Schematic of hybrid superhydrophilic/superhydrophobic microporous SERS substrates^[27]