Multi-shape silver nanoparticles on filter paper by the chemical reduction method.

The surface plasmon resonance property of silver nanoparticles (AgNPs) makes them a top-notch material for developing sensors, especially in surface-enhanced Raman scattering (SERS). The multi-shape silver nanoparticles decorated on cellulose fiber of paper provide flexible paper-based SERS substrates with different sensitivity. The isotropic and anisotropic morphology of AgNPs on filter paper has been controlled by weak and strong reducing agents: sodium borohydride (NaBH₄), ascorbic acid (L-AA), glucose, formaldehyde (HCHO). The capping agent's chitosan and the reaction conditions like the ratio of precursors and stirring speed also influence the shape, size, stability, and dispersity of AgNPs on filter paper. Multi-shape AgNPs on paper are obtained as spherical shapes (about 50–100 nm), rods (size 100–500 nm in length, 50-nm wide), or thin wings. Depending on the reduction condition, these AgNPs can be single-dispersed or stuck together to form corals on paper. The fabricated paper-based SERS substrates were investigated the optical characterization and used to detect melamine in an aqueous solution with detection limits as low as 10⁻⁸ M with the EF = 2.3 × 10⁹. [ABSTRACT FROM AUTHOR]