Nanoparticle (NP)-loaded filter paper (FP)-based surface-enhanced Raman scattering (SERS) substrates have been prepared using differently shaped gold (Au) NPs. The shape of Au NPs plays a significant role in the amplification ofSERS signal. Here, two differently shaped Au NPs were synthesized using two different techniques: (a) femtosecond (fs) laser ablation in liquid and (b) chemical method. Spherical shaped Au NPs were obtained using fs ablation of a bulk Autarget in distilled water and Au nanostars (NSs) were achieved through chemical process utilizing N-vinyl-2-pyrrolidone as a reducing/capping agent. The size and shapes of these synthesized NPs and NSs were investigated meticulously usingdifferent characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy and X-ray diffraction. Both the NPs and NSs were subsequently loaded onto commercially available FP by simple drop casting method. To achieve higher number of hot spots, the aggregated spherical NPs were obtained by addition of NaCl. The non-aggregated spherical, aggregated spherical, and star Au NPs loaded on FP were used for the detection of a dye (Nile blue) and an explosive molecule (Picric acid).

Flexible polymer (polyvinyl alcohol, PVA) nanofibres achieved with electrospinning and loaded with picosecond laser-ablated gold nanoparticles (Au NPs) were utilized as surface-enhanced Raman scattering (SERS) substrates.The fabricated polymer nanofibres and Au NPs were characterized by UV–Visible absorption, field emission scanning electron microscope, transmission electron microscopy and X-ray diffraction techniques. The PVA–Au NPs SERS substrates were used to detect the dye methylene blue (MB 5 $\mu$M) and a chemical warfare agent simulant (methyl salicylate) using a portable Raman spectrometer. The flexible PVA–Au NPs nanofibre exhibited a good sensitivity with enhancement factors of >10$^4$ and a high reproducibility (RSD$\sim$10%). These flexible substrates could be extended for SERS studies of various explosive and other hazardous molecules.