Metal-Oxide Nanoparticle Photocatalysis: UV Band-Gap Excitation

Photocatalytic water and air treatment runs on a strict energy threshold: only photons carrying at least the semiconductor's band-gap energy can excite an electron-hole pair, and for TiO₂ that means UV light at or below 387 nm. This simulator renders the whole chain in 2D — a live photon-energy readout against the 3.2 eV gap, absorption (or transmission) of each incoming photon, electron/hole migration to the nanoparticle surface with a real chance of unproductive recombination along the way, hydroxyl-radical generation at the surface, and those radicals mineralizing dissolved pollutant molecules into CO₂ and H₂O. Sweep the wavelength slider across the 387 nm cutoff to see the reaction switch off exactly where the physics says it should.