Both un doped and Cr doped TiO NT

Many strategies have been employed to address such issues. One of them is to synthesize doped titania with metal additives in order to achieve new electron states or holes inside the TiO2 electronic band structure [18], [19], [20], [21] and [22]. In addition, impressive improvement of the NO2-sensing performance has been achieved by doping TiO2 with chromium to induce p-type semiconducting behaviour [13], [14] and [23].