Highly visible-light-responsive nanoporous nitrogen-doped TiO2 (N-TiO2) photocatalysts produced by underwater plasma technology for environmental and biomedical applications

Abstract

We suggest an easy one-step underwater plasma method to generate nanoporous N-doped TiO2(N-TiO2) photocatalysts with high reactivity in the visible light range. The extreme energy input of this underwater plasma technology allowed the synthesis, crystallization, doping, and porosity of TiO2 by inducing the continuous reaction of highly energetic atomic and molecular species within a few minutes. The produced N-TiO2 demonstrated a nanoporous anatase-brookite polycrystalline structure with substitutionally doped N atoms. The N doping species led to a narrow bandgap, effective charge-carrier separation, and better light absorbing ability in the visible light region. Accordingly, N-TiO2 photocatalysts showed efficient photocatalytic activities for methylene blue(MB), rhodamine B(Rh B), and tetracycline(TC) under solar and visible light conditions, up to approximately 4.5 times higher than that of commercial TiO2. Furthermore, the superior biocompatibility (94.5%) of water purified by N-TiO2 photocatalysts proved the feasibility of these materials for practical use. Moreover, N-TiO2 photocatalysts showed excellent antibacterial ability against gram-negative Escherichia coli(E. coli) and gram-positive Staphylococcus aureus(S. aureus), which extends the applicability of N-TiO2 photocatalysts to biomedical applications and sludge purification. This study presents one of the most facile and fast methods for the production of highly visible-light-responsive and nanoporous TiO2 for environmental and biomedical applications.