Nanospace-enhanced photoreduction for the synthesis of copper(I) oxide nanoparticles under visible-light irradiation

[Display omitted] •Cuprous oxide nanoparticles were synthesized under visible-light irradiation.•The reaction needs nano-restricted copper acetate in single-wall carbon nanotubes.•Distorted copper acetate can be photoreduced by the visible-light irradiation. Nanoparticles of copper(I) oxide (cuprous oxide; Cu2O) were able to be synthesized from nano-restricted copper acetate (Cu(OAc)2) in micropores of single-wall carbon nanotubes (SWNTs) by visible-light photoreduction. The specific structure of confined Cu(OAc)2 in the micropore is indispensable for the reduction process to Cu2O by the irradiation, because, in general, aqueous solution of Cu(OAc)2 can be reduced under UV-light irradiated conditions. The present results strongly suggest that the micropore of SWNTs whose pore width is in the micropore-size range can play as nanoreactor space for the synthesis of Cu2O through the nano-restricted precursor whose reactivity is different from that in the bulk phase.