Aerosol direct writing of titanium oxide nanoparticles synthesized by spark ablation

The need for clean energy solutions, following the principles of green chemistry is growing every day. In this work, we present a purely solid-state one-step technique to synthesize and fabricate thin films of titanium oxides. Nanoparticles of titanium oxide are formed by reactive spark ablation, a technique that rapidly sublimates titanium targets by using high temperature low-pressure plasma, which then react in the presence of oxygen under very high local temperatures. The synthesized particles are then deposited onto silicon substrates in the form of thin films via aerosol direct writing. Morphology (FE-SEM, TEM and AFM) and structural analysis (GI-XRD) confirm that spark plasma produces highly defective oxides (where Ti3+ states can be assumed), mostly corresponding to TiO2-x phases (oxygen deficient anatase and rutile) which are assembled into mesoporous thin films. Optical properties experimentally show that spark ablation has the potential to produce titanium oxide materials active in visible light, which is shown to be correlated with the saturation of oxygen during reaction. Increasing the oxygen content yielded a significant shift in optical behaviour, lowering the bandgap by ∼0.6 eV.