Copper nanoparticle UV-vis spectrum calculator

For clean copper spheres in water the plasmon peak is near 550 nm up to about 40 nm, then red-shifts: about 556 nm at 50 nm, 582 nm at 80 nm and 594 nm at 100 nm (table above). Measured colloids often peak at 560–600 nm because of size distribution, ligands and a thin oxide layer.

Copper's interband absorption (electrons excited from the d band) begins near 2.1 eV, about 590 nm, right where the plasmon sits. That extra loss damps and broadens the resonance, so copper shows a shoulder-like peak on a rising absorption background instead of the sharp line of silver.

They absorb green and yellow light around the plasmon (550–600 nm) and, through interband transitions, everything bluer; what is transmitted is mostly red, which reads as copper-red to brown (colour column in the table).

Copper oxidizes quickly in air and water. A Cu₂O or CuO skin (refractive index about 2.5–2.7) red-shifts the peak and damps it; a thick shell can wipe it out. Model it in the calculator by adding a shell with a custom refractive index, and compare with your measurement to estimate the oxide thickness.

At the peak, about 4.7 × 10⁸ M⁻¹ cm⁻¹ for 20 nm spheres, 4.3 × 10⁹ for 40 nm and 1.1 × 10¹¹ for 100 nm in water (table above). Use c = A / (ε ℓ) for the particle concentration.

Yes: Mie theory solves Maxwell's equations exactly for spheres and layered spheres, at any size. The inputs are the measured optical constants of copper and of the medium.

Yes: copper nanospheres and core–shell nanoparticles (add a shell) are available in every calculator, from spectra to optical properties: near-field enhancement maps, dimers and hot spots, nanoparticle arrays and lattice resonances, particles on a substrate, emitters and the Purcell factor, nanorods and laser heating.