Novel physical sunscreen from one-dimensional TiO2 nanowire: Synthesis, characterization and the effects of morphologies and particle size for use as a physical sunscreen

The performance of the one-dimensional (1D) morphology as an inorganic UV filter for sunscreens of titanium dioxide (TiO2) was evaluated in this research. The 1D TiO2 nanowires were prepared using solid TiO2 and 10 M NaOH as precursors via a modified hydrothermal method, followed by calcination at 400–900 °C for 5 h. The influences of TiO2 loading, hydrothermal time and calcination temperature were studied on the morphologies of the as-prepared samples. The morphologies of the TiO2 nanowires were investigated using SEM and TEM techniques. The results found all the variables directly affected the particle size and shape of the TiO2 nanowires. The hydrothermal synthesis conditions using a TiO2 loading of 0.2 g at 220 °C for 24 h (HTiO2) resulted in a particle size that was the longest and narrowest in length and diameter, respectively. The first product from the hydrothermal synthesis is H2Ti3O7, which can transform into TiO2(B) (TiO2@400), anatase (TiO2@700) and rutile (TiO2@900) by calcination at 400, 700 and 900 °C, respectively. The calcined samples were selected for a porcine skin penetration study. The 1D morphology particles were localized on the stratum corneum of the skin, while the comparison spherical particle penetrated the deeper layer. From the SPF test, the highest SPF is TiO2 anatase.