The fabrication and characterization of TiO2 nanospheres with high visible light photocatalytic activity by direct carbonization of block copolymer templates

Titanium dioxide nanospheres with visible light photocatalytic activity were synthesized via a sol–gel approach using an amphiphilic diblock copolymer, polystyrene-block-polyacrylic acid (PS-b-PAA), as template at room temperature in toluene. The morphology and crystal structure of synthesized TiO2 nanospheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD pattern of TiO2 nanospheres revealed the crystal transformation, resulting in the change of photocatalytic activity. The XPS pattern revealed the formation of Ti–O–C bonds upon carbonization, as a result of visible light absorption. The TiO2 nanospheres had diameters ranging from 200 to 500 nm. The photodegradation experiments showed that such TiO2 nanospheres had pronounced visible-light photocatalytic activity.