A water-soluble composition includes reducible copper ions or copper nanoparticles complexed with a reactive polymer. The reactive polymer can be crosslinked using suitable irradiation to provide copper-containing water-insoluble complexes. The water-soluble composition can be used to provide various articles and electrically-conductive materials that can be assembled in electronic devices. The reactive polymer has greater than 1 mol % of recurring units comprising sulfonic acid or sulfonate groups, at least 5 mol % of recurring units comprising a pendant group capable of crosslinking via [2+2] photocycloaddition, and optionally at least 1 mol % of recurring units comprising a pendant amide, amine, hydroxyl, lactam, phosphonic acid, or carboxylic acid group.