Fig. 1. Photographs of filter paper before and after dipping in nanoparticle solution[34]

Fig. 2. (a) Inkjet printer used in fabrication of SERS substrate; (b) printed paper obtained by inkjet printing with sample in nanoparticle zone; (c) scanning electron micrograph of Ag NPs on paper[31]

Fig. 3. Schematic of preparation of SERS paper substrate using chemical reaction method[45]

Fig. 4. Detection of (a) Rhodamine 6G on glass slide and (b) thiram from apple peel when paper substrate is used as test paper[44]