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Monodisperse TiO 2 Spheres with High Charge Density and Their Self‐Assembly
Author(s) -
Xia Hongbo,
Wu Suli,
Su Xin,
Zhang Shufen
Publication year - 2017
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201601347
Subject(s) - dispersity , spheres , materials science , charge (physics) , self assembly , charge density , chemical engineering , nanotechnology , chemical physics , chemistry , physics , polymer chemistry , engineering , quantum mechanics , astronomy
Titanium dioxide (TiO 2 ) spheres are potential candidates to fabricate three‐dimensional (3D) photonic crystals owing to their high refractive index and low absorption in the visible and near‐infrared regions. Here, TiO 2 spheres with both high surface charge density and uniform size, which are necessary for the self‐assembly of TiO 2 spheres, have been prepared by means of sol–gel methods in ethanol in the presence of thioglycolic acid as ligand. Thioglycolic acid, which contains two functional groups, not only acts as coordinating ligand for stabilizing and controlling the growth of TiO 2 spheres but also endows the resulting TiO 2 spheres with high charge density as based on ζ ‐potential analysis when the pH of the TiO 2 aqueous dispersion was 6.5 or higher. The SEM images illustrate that the diameter of the prepared TiO 2 spheres can be tuned from 100 to 300 nm by simply controlling the concentration of H 2 O. FTIR spectra confirm that thioglycolic acid bonded to the surface of TiO 2 spheres through carboxylic groups. As anticipated, the obtained TiO 2 spheres could self‐assemble to form a 3D opal photonic crystal structure by means of a simple gravity sedimentation method. Then the TiO 2 spheres in the 3D opal photonic crystal structure were able to transform into a pure anatase phase by annealing at different temperatures.