Non-thermal atmospheric plasma sources are at the centre of a growing new field of research that promises significant benefits in areas ranging from catalysis to medicine. The main value of atmospheric pressure sources lie in their ability to generate highly energetic and reactive species under near-ambient conditions. This characteristic makes atmospheric plasma an appealing alternative to well-established vacuum plasma processes. In this study, radio frequency atmospheric pressure plasma sources are used for modification of metal oxide surfaces and direct metal deposition. In atmospheric pressure plasma afterglow, plasma electrons are shown to be capable of reducing Cu2O films, this is proven by applying an external electric field to collect or to retard plasma electrons and observing the evolution of the oxide film. Using a micro-plasma jet, Cu2O and SnO2 are demonstrated to be completely reduced to their parent metals when exposed to helium plasma. A reducing plasma is required to induce partial reduction in TiO2, WO3 and ZnO, generating oxygen deficiencies. Oxygen deficient TiO2, also known as black titania is a well-known defective metal oxide photocatalyst. In this work, a facile method for producing black titania is developed using reducing plasma jets. This method improves photocatalyic efficiencies of nano-porous anatase up to sixfold while dispensing the need for vacuum or high pressure equipment. Deposition of conductive metals is a topic of ongoing research, with an aim to develop techniques and precursors that can enable printing of electrical circuits onto unconventional substrates. In this work, a novel technique for metal printing using plasma jets is developed. The method developed in this work enables single-step deposition of conductors from lowcost metal salt based precursors. Using aerosolized CuSO4 in the plasma jet stream, it is shown that metallic traces can be deposited on a large variety surfaces with fine spatial control
