Hydrothermally-synthesized CuO nanoparticles decorated on CuO sputtered thin-film for nitrite sensing application

•Cu(OH)2 nanoparticles (NPs) solutions with different CuO content were prepared.•Cu(OH)2 NPs were drop cast on ITO and CuO/ITO substrates and dehydrated.•Sputtered CuO underlayer enhances the crystallinity and adhesion of drop-coated NPs.•CuO-based nitrite sensors were tested.•The nitrite sensor has high sensitivity of 402.89 μAmM−1cm−2 and good selectivity.