Biomineralized N-doped CNT/TiO ₂ core/shell nanowires for visible light photocatalysis

We report an efficient and environmentally benign biomimetic mineralization of TiO ₂ at the graphitic carbon surface, which successfully created an ideal TiO ₂/carbon hybrid structure without any harsh surface treatment or interfacial adhesive layer. The N-doped sites at carbon nanotubes (CNTs) successfully nucleated the high-yield biomimetic deposition of a uniformly thick TiO ₂ nanoshell in neutral pH aqueous media at ambient pressure and temperature and generated N-doped CNT (NCNT)/TiO ₂ core/shell nanowires. Unlike previously known organic biomineralization templates, such as proteins or peptides, the electroconductive and high-temperature-stable NCNT backbone enabled high-temperature thermal treatment and corresponding crystal structure transformation of TiO ₂ nanoshells into the anatase or rutile phase for optimized material properties. The direct contact of the NCNT surface and TiO ₂ nanoshell without any adhesive interlayer introduced a new carbon energy level in the TiO ₂ band gap and thereby effectively lowered the band gap energy. Consequently, the created core/shell nanowires showed a greatly enhanced visible light photocatalysis. Other interesting synergistic properties such as stimuli-responsive wettabilites were also demonstrated.