Table 2.

The currently reported SERS substrates with different designs.

Substrate Type	Process	Sensitivity	Uniformity	Stability	Refs.
MNPs in Suspension	Easy Only have to synthesize the MNPs	High	Poor	Poor	[101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118]
MNPs on nanostructured solid substrates	Hard Fabricate the nanostructured substrate and deposit metal MNPs, time-consuming	Fair to high	Good	Good	[119,120,121,122,123,124,125,126,127]
Metal on porous materials	Complex Depends on the materials, the fabrication generally time-consuming	Fair to high	Good	Good	[81,128,129,130,131,132,133,134,135,136,137]
MNPs on biological or commercial substrate	Easy Only have to decorate the substrate with MNPs	Fair to acceptable	Fair	Fair	[98,138,139,140,141]