The influence of surface modification on the optical and capacitive properties of NiO nanoparticles synthesized via surfactant-assisted coprecipitation

•Ultrathin NiO graphene-like morphology via surfactant-assisted coprecipitation.•Effect of pH on stabilizing superficial α-Ni(OH)2 phase on NiO.•Self-doping influences on optical, magnetic and electrochemical performance of NiO.•Room temperature ferromagnetism and narrowing in the band gap of undoped NiO.•High capacitance behavior of interconnected mesoporous sheets of NiO sample.