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A simple solvothermal approach employing oleic acid has been developed to prepare anatase Ti O_2 nanocrystals with different shapes, which were tuned from nanorods to nano-ellipsoids by increasing the amount of Na F from 0 to 0.5 mmol, and the optical band gap decreased from 3.47 e V to 3.29 e V accordingly. However, when the fluoride was changed to NH_4 F, the resultant Ti O_2 nanocrystals possessed an anatase phase but were made up of smaller-sized nanocrystals and nanorods, and the band gap was increased to 3.53 e V. The X-ray photoelectron spectroscopy(XPS) results illustrated an increase of fluorine content with an increasing amount of Na F could account for the variation of the shape and optical band gap of Ti O_2 nanocrystals. Moreover, the absence of fluorine content brought about less change of shape and increase of optical band gap of the product synthesized in the presence of NH_4 F. This result may offer another way to alter the shape and band gap of metal oxide nanocrystals with the assistance of fluoride.
A simple solvothermal approach employing oleic acid has been developed to prepare anatase Ti O 2 nanocrystals with different shapes, which were tuned from nanorods to nano-ellipsoids by increasing the amount of NaF from 0 to 0.5 mmol, and the optical band gap decreased from 3.47 eV to 3.29 e V accordingly. However, when the fluoride was changed to NH_4 F, the resultant Ti O_2 nanocrystals possessed an anatase phase but were made up from smaller-sized nanocrystals and nanorods, and the band gap was increased to 3.53 e V . The X-ray photoelectron spectroscopy (XPS) results illustrated an increase of fluorine content with an increasing amount of Na F could account for the variation of the shape and optical band gap of Ti O_2 nanocrystals. Moreover, the absence of fluorine content brought about less change of shape and increase of optical band gap of the product synthesized in the presence of NH_4 F. This result may offer another way to alter the shape and band gap of metal oxide nanocrystal s with the assistance of fluoride.