Photocatalytic N-doped TiO2 for self-cleaning of limestones Laura Fornasini, Laura Bergamonti, Federica Bondioli, Danilo Bersani, Laura Lazzarini, Yaron Paz and Pier Paolo Lottici Eur. Phys. J. Plus, 134 10 (2019) 539 Published online: 31 October 2019 DOI: 10.1140/epjp/i2019-12981-6