TY - JOUR

T1 - Introduction of oxygen vacancies and fluorine into TiO 2 nanoparticles by co-milling with PTFE

AU - Senna, Mamoru

AU - Šepelák, Vladimir

AU - Shi, Jianmin

AU - Bauer, Benjamin

AU - Feldhoff, Armin

AU - Laporte, Vincent

AU - Becker, Klaus Dieter

N1 - Funding Information: M.S. thanks Alexander von Humboldt-Foundation to enable his research stay in Braunschweig. V.S. thanks the DFG (SPP1415) for supporting this work. V.L. acknowledges N. Xanthopoulos (EPFL–Interdisciplinary Centre for Electron Microscopy) for performing XPS analyses. The authors thank Prof. B. Malic for TG-DTA measurement, and Toho Titanium Co. Ltd. for the kind donation of anatase nanoparticles, TA50.

PY - 2012/3

Y1 - 2012/3

N2 - Solid-state processes of introducing oxygen vacancies and transference of fluorine to n-TiO 2 nanoparticles by co-milling with poly(tetrafluoroethylene) (PTFE) powder were examined by diffuse reflectance spectroscopy (DRS) of UV, visual, near- and mid-IR regions, thermal analyses (TG-DTA), energy-dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The broad absorption peak at around 8800 cm -1 (1140 nm) was attributed to the change in the electronic states, viz. electrons trapped at the oxygen vacancies (Vo) and dd transitions of titanium ions. Incorporation of fluorine into n-TiO 2 was concentrated at the near surface region and amounted to ca. 40 at% of the total fluorine in PTFE, after co-milling for 3 h, as confirmed by the F1s XPS spectrum. The overall atomic ratio, F/Ti, determined by EDXS was 0.294. By combining these analytical results, a mechanism of the present solid state processes at the boundary between PTFE and n-TiO 2 was proposed. The entire process is triggered by the partial oxidative decomposition of PTFE. This is accompanied by the abstraction of oxygen atoms from the n-TiO 2 lattices. Loss of the oxygen atoms results in the formation of the diverse states of locally distorted coordination units of titania, i.e. TiO 6-nVo n, located at the near surface region. This leads subsequent partial ligand exchange between F and O, to incorporate fluorine preferentially to the near surface region of n-TiO 2 particles, where local non-crystalline states predominate.

AB - Solid-state processes of introducing oxygen vacancies and transference of fluorine to n-TiO 2 nanoparticles by co-milling with poly(tetrafluoroethylene) (PTFE) powder were examined by diffuse reflectance spectroscopy (DRS) of UV, visual, near- and mid-IR regions, thermal analyses (TG-DTA), energy-dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The broad absorption peak at around 8800 cm -1 (1140 nm) was attributed to the change in the electronic states, viz. electrons trapped at the oxygen vacancies (Vo) and dd transitions of titanium ions. Incorporation of fluorine into n-TiO 2 was concentrated at the near surface region and amounted to ca. 40 at% of the total fluorine in PTFE, after co-milling for 3 h, as confirmed by the F1s XPS spectrum. The overall atomic ratio, F/Ti, determined by EDXS was 0.294. By combining these analytical results, a mechanism of the present solid state processes at the boundary between PTFE and n-TiO 2 was proposed. The entire process is triggered by the partial oxidative decomposition of PTFE. This is accompanied by the abstraction of oxygen atoms from the n-TiO 2 lattices. Loss of the oxygen atoms results in the formation of the diverse states of locally distorted coordination units of titania, i.e. TiO 6-nVo n, located at the near surface region. This leads subsequent partial ligand exchange between F and O, to incorporate fluorine preferentially to the near surface region of n-TiO 2 particles, where local non-crystalline states predominate.

KW - Mechanochemical reaction

KW - Oxidative decomposition

KW - Oxygen vacancies

KW - Poly(tetrafluoroethylene)

KW - Titania nanoparticles

UR - http://www.scopus.com/inward/record.url?scp=84857232406&partnerID=8YFLogxK

U2 - 10.1016/j.jssc.2011.12.036

DO - 10.1016/j.jssc.2011.12.036

M3 - Article

AN - SCOPUS:84857232406

VL - 187

SP - 51

EP - 57

JO - Journal of solid state chemistry

JF - Journal of solid state chemistry

SN - 0022-4596

ER -