Synthesis of layered protonated titanate hierarchical microspheres with extremely large surface area for selective adsorption of organic dyes

Abstract

In this paper, we report a facile synthesis of layered protonated titanate (LPT) hierarchical microspheres through a one step solvothermal reaction in the presence of hexamethylenetetramine (HMTA). Structural characterizations reveal these LPT hierarchical microspheres with a 3D flower-like morphology are built with self-assembled ultrathin nanosheets that are actually composed of several layers or even a monolayer of protonated titanate with an enlarged interlayer spacing. And it is found that these LPT hierarchical microspheres have a certain extent of absorption in the visible region, showing a yellow colour. The changes of such special LPT nanostructures in interlayer spacing and colour should be attributed to the intercalation of NH₄⁺ or other amino-derivatives generated by the decomposition of HMTA. It is exciting that these LPT hierarchical microspheres possess extremely large surface area, reaching the value of 450 m² g⁻¹, and they display specific selectivity towards methylene blue, compared to methyl orange, cresol red and rhodamine B.