“…This may be because vapor-phase CO 2 photoreduction on TiO 2 nanotubes surface-decorated by <10 nm-sized nanoparticles of Cu, Pt, Ru, Au, Pd, AuPd, ZnPd, Ag, etc. has primarily been reported to result in the dominant formation (>95% of all product molecules formed) of C 1 products such as methane, carbon monoxide, methanol, and formaldehyde, with C 2 products such as ethane and ethylene being formed as minor byproducts (<5% of all products). − In metal particles larger than 50 nm, the quasi-static approximation is no longer valid and the quadrupole plasmon mode becomes significant, which produces an antisymmetric distribution of charge density oscillations on the surface of the metal nanoparticle when excited. , In even larger nanoparticles and aggregates of dissimilar nanoparticles, multipole plasmon excitations with rapidly alternating surface charge density oscillations dominate . Multipolar plasmon resonance modes and symmetry breaking in heterodimers , afford the possibility of closely lying reaction sites having opposite charge, thus enabling a reduction in the dipole repulsion of adsorbed C 1 reaction intermediates and facilitating their C–C coupling to form C 2 products.…”