hydrophilic and photocatalytic properties of tio2/sio2 nano-layers in dry weather

This paper describes the changes in tio2/sio2 nanolayers properties induced by ultraviolet visible spectroscopy (uv) irradiation in terms of hydrophilicity/photocatalycity. the tio2/sio2 nano particles were synthesized by the sol-gel method and deposited on sodalime glass by dipcoating. x-ray diffraction (xrd) of the tio2 particles showed that the nanoparticles were crystallized in anatase crystal structure with a crystallite size of ~12 nm. the morphology and surface roughness of tio2 nanolayer were observed by scanning electron microscope (sem) and atomic force microscopy (afm) analysis. the surface roughness (ra) for tio2/glass and tio2/sio2 was measured ~ 5 and 19 nm, respectively. the hardness of nanolayers on the glass was evaluated and scratch thickness for 1000 g sinker was measured ~150 nm. the selfcleaning properties were tested in dry condition (rh<15%) under uv irradiation by evaluating the oleic acid photodegradation and monitoring the hydrophilic properties of the surface with a contact angle measurement. the  result showed that contact angle of the layer decreases from 77 to 42° after 25 h uv irradiation. fouriertransform infrared spectroscopy attenuated total reflectance (ftir-atr) showed the elimination of c=o bonds of oleic acid on the surface after uv light irradiation. water droplet contact angle measurement on tio2 nanolayer exhibited a less hydrophilicity after uv irradiation and the contact angle changed  from 15 to 40°, which may be due to the low atmospheric humidity. adding sio2 nanoparticles increases roughness of the nanolayer, from 5 to 19 nm, without a significant effect on the photodegradation rate of oleic acid.