A biogenic TiO₂-C-O nanohybrid grown from a Ti⁴⁺-polymer complex in green tissues of chilis, interface bonding, and tailored photocatalytic properties

A nanostructured a-TiO₂ (anatase) is well known to be a promising material for harvesting photocatalysis in ultraviolet–visible light for its applications. In this article, we report a simple biosynthesis of a stable compound a-TiO₂-C-O of small core–shells by a hydrothermal reaction of titanium tetrabutoxide in small tissues (proteins, lipids, or carbohydrates) of green chili (hot) at moderate temperature followed by burning out the organics in a flame in camphor in open air. In a proposed microscopic model, the a-TiO₂ is shown to be growing preferentially in support of an inbuilt biogenic 2D layer C–sp ² (template) in the coherent (101) facets in a controlled shape of small cuboids (8–15 nm sizes), with a joint C–sp ² charge/spin layer in an a-TiO₂-C-O hybrid composite phase. A thin residual ‘Ti⁴⁺ -O-C’ surface layer lasts, with a rocking of a ‘C-O cage’ on the Ti⁴⁺ ions of 285 cm⁻¹ frequency, in the samples heated at ≤ 600 °C in air. It is found to be promoting a markedly enhanced photocatalytic response in degrading methylene blue dye and 2-chlorophenol under a visible light irradiation. The results are described with N₂ sorption hysteresis, microscopic images, Raman/XPS (X-ray photoelectron spectroscopy) bands, and ultraviolet–visible light absorption/emission spectra in the samples prepared of varied microscopic surface layers.