Authors: M. Zou, F. Yang, J. Ma, Y. Chen, L. Cao, F. Liu
Affilation: Chinese Academy of Inspection and Quarantine, China
Pages: 510 - 513
Keywords: nanoscale titanium dioxide, particle size, crystal structure, light absorbance
Nanoscale titanium dioxide is an important physical sun-block material and is widely used in sunscreen. In our test, the influences of the particle size and crystal structure on light absorbance were examined. The experiment shows that the absorbance (Abs) of nanoscale titanium dioxide in UV-ray district is much higher than it in visible light district under the same concentration (0.04 g/L), as shown in figure 1. The Abs of nanoscale rutile keeps increasing, reaches the highest at 360 nm, and then starts to decrease as the wavelength becomes shorter. The nanoscale anatase has the similar light absorbance characteristic, with the highest Abs peak at 320 nm. In the UVA district, the rutile has stronger absorbance ability than the anatase, while in UVB and UVC, there is a similar absorbance between rutile and anatase. Compared with the bulk titanium dioxide, the nanoscale titanium dioxide can more effectively absorb the UV-ray and let the visible light easily pass through. Since the anatase is of the stronger activity than rutile and thus probably easily harms the skin, the nanoscale rutile should be the best selection used for sunscreen of the four samples in figure 1. However, when the particle size of rutile is too small, for example smaller than 10 nm, it will have much higher Abs in UVB and UVC district and lower Abs in UVA and visible light district, as shown in figure 2. Therefore the appropriate particle size and crystal structure must be considered when nanoscale titanium dioxide is applied for sun-block effect. The detailed test optimizations are being carried out in our lab.