Influence of fluorine doping on the microstructure, optical and electrical properties of SnO2 nanoparticles

Abstract

temperature and doping rate. These results show the strong correlation between the structural, morphological, optical and electrical properties of the samples depending on doping content which was well reflected on the quality of the nanoparticles.

Multi-functional MnO2 nanomaterials for photo-activated applications by a plasma-assisted fabrication route

“…6b), it was possible to extrapolate E G values as 2.5 eV, 2.2 eV, 2.0 eV and 1.8 eV for growth temperatures of 100°C, 200°C, 300°C and 400°C, respectively. These values were blue-shifted with respect to literature data for MnO 2 (typically close to 1.8 eV 1,13,60,61 ), a phenomenon that could be ascribed to the occurrence of size effects 29,46 and to a modified carrier concentration when oxygen vacancies are saturated by fluorine. This explanation also accounts for the progressive increase of band gap values at the lowest deposition temperatures, resulting in a higher F content (see above and Fig.…”

“…2f ), exerting a beneficial influence on photocatalytic activity and conductivity and suppressing, in parallel, detrimental electron-hole recombination processes. 46,49,51,53 In this case, a predominant contribution of RMS roughness could be ruled out since, as already noted, the corresponding values showed an opposite trend with respect to that shown in Fig. 7b.…”

“…In all cases, the substrate contribution was subtracted. The band gap (E G ) of the samples was evaluated using the equation: 3,46,47…”

“…The spectra were also characterized by a broadened absorption tail towards the near-infrared (NIR) region, consistent with the presence of O vacancies (see the above XPS data) and resulting in the formation of subband gap states. 46,53 From Tauc plots (Fig. 6b), it was possible to extrapolate E G values as 2.5 eV, 2.2 eV, 2.0 eV and 1.8 eV for growth temperatures of 100°C, 200°C, 300°C and 400°C, respectively.…”

“…41 In particular, our attention is devoted to the fabrication of F-doped MnO 2 nanomaterials starting from a fluorinated Mn(II) precursor. As a matter of fact, fluorine doping has been demonstrated to favourably affect the structural, optical, electrical and catalytic properties of different oxides for various applications, such as gas sensing, Li-ion batteries and photocatalysis, [46][47][48][49][50][51] but it has never been reported so far for MnO 2 -based materials. To this aim, one of the main novel characters of this work is the synthesis of nanostructured β-MnO 2 with a fine control of F content and morphology as a function of the growth temperature.…”