Naked-Eye Biosensing using Plasmonic Nanoparticles

Since the introduction of LSPR as a transduction technique, monitoring the antibody/antigen is only possible by UV-Visible spectroscopy. Indeed, the color changes resulting from a displacement of the LSPR band during target recognition are, for spherical gold nanoparticles that often absorb around 520 nm, a few nanometers and are therefore not visible to the naked eye. Indeed, in this region of the electromagnetic spectrum, red extends over several tens of nm. A plasmon band located slightly lower in the electromagnetic spectrum would generate a much more noticeable colour change for an equivalent displacement. The combination of gold and silver in the form of an alloy or core-shell allows the position of the LSPR band to be modulated and located in the area of interest.