Robust ferromagnetic and fast sunlight photocatalytic properties of nanocrystalline SnO2: Co/Cu codoping

Abstract

Spintronics technology and organic pollutants removing have pushed the researchers to explore strong ferromagnetic and sunlight photocatalytic properties in oxide semiconductors. Herein, the role of Co monodoping and Co/Cu codoping on room temperature ferromagnetism and sunlight photodegradation properties of SnO2 nanoparticles was investigated. Series compositions composed of SnO2, Sn0.97Co0.03O2, Sn0.94Co0.03Cu0.03O2 and Sn0.91Co0.03Cu0.06O2 nanopowders were synthesized by coprecipitation method. The synthesized powders showed a single phase nature of tetragonal rutile structure with no sign for any impurities or secondary phases. SEM images demonstrate that the grains of the pure SnO2 consist of large aggregates which are transformed to fine particles due to Co/Cu codoping. The UV band gap of SnO2 was strongly engineered to visible light responses due to incorporation of Co/Cu ions. Integration between Co (magnetic) and Cu (nonmagnetic) ions induces clear room temperature ferromagnetism in SnO2. The exchange interactions between localized spins of Co3+-Co3+ Co3+-Cu2+ and Cu2+-Cu2+ via high-density doping-induced defects (oxygen vacancies) lead to strong ferromagnetic ordering. Sn0.94Co0.03Cu0.03O2 and Sn0.91Co0.03Cu0.06O2 nanopowders revealed a fast sunlight photocatalytic performance (~100%) for Congo red (CR), malachite green (MG) and methylene blue (MB) dyes. The partial substitution of Sn4+ by Co3+ and Cu2+ are found to augment the wavelengths absorbed, amount of oxygen vacancies and life time of the photo-generated electron hole pairs, resulting in better photocatalytic activity of Sn0.94Co0.03Cu0.03O2 and Sn0.91Co0.03Cu0.06O2 nanopowders in comparison with undoped and Co monodoped SnO2.