Surface Plasmon Resonance Spectroscopy

Surface plasmon resonance (SPR) biosensors detect binding events without any fluorescent label: instead they watch a gold nanostructure's own optical resonance move. This simulator plots that resonance directly — a reflectance-vs-wavelength spectrum with a sharp dip that red-shifts as analyte molecules accumulate on the functionalized sensor surface, driven by the real relationship Δλ = S·Δn between refractive-index change and resonance-wavelength shift. Underneath, the surface coverage θ that sets Δn is never faked: it is integrated live from the Langmuir adsorption isotherm dθ/dt = k_on·C·(1−θ) − k_off·θ, the same association/dissociation kinetics used to fit real SPR sensorgrams. Tune analyte concentration and the on/off rate constants, then switch between sample injection and buffer wash to watch the dip shift out and relax back — a live optical readout of binding kinetics, not just a schematic of it.