Abstract: Disclosed is a method of pulsed laser ablation production of gold-platinum AuxPt1-x alloy nanoparticles in a colloidal solution. The colloidal solution of AuxPt1-x alloy nanoparticles is suitable for many biological applications including lateral flow immunoassays and other bio-detections based on optical scattering. The nanoparticles form by fragmentation of the bulk material without evaporation, minimizing oxidation of the nanoparticles. The nanoparticles conjugate with bio-molecules such as protein, antibodies, peptides, RNA oligomers, DNA oligomers, other oligomers, or polymers effectively by passive adsorption. Advantageously the AuxPt1-x alloy nanoparticles have a wide optical extinction spectrum in the visible region, appearing nearly black in both colloidal and dried form. The nanoparticles can be used for labeling bio-molecules and provide a high visual contrast in visual-based bioassays.

Abstract: Disclosed is a method for enhancing the optical signal of precious metal nanoparticles by introducing linker molecules for precious metal nanoparticles to form clusters in a stable colloidal suspension. The formation of clusters according to the present disclosure not only enhances the optical signal, but also can alter the optical spectrum, providing an alternative color for use in visual-based bioassays such as lateral flow immunoassays against the white test paper strips. The formed clusters are capable of passive adsorption of a variety of biomolecules which effectively bind onto the surface, requiring a minimum modification in the bio-assay protocol from that use for standard gold nanoparticles, which is being widely-used in lateral flow immunoassays.