Photonic crystals in biology - NanoTR-VI

Poster Session, Thursday, June 17Theme F686 - N1123Humidity Sensing Properties of Titanium Dioxide (TiO 2 ) Thin FilmsMehmet KABADAYI 1 , Salih OKUR 1 ,Nesli T. YAĞMURCUKARDEŞ 11 Izmir Institute of Technology, Faculty of Science, Department of Physics, Gulbahce Koyu Kampusu, 35430,Urla, Izmir, TurkeyAbstract- Humidity sensing properties of TiO 2 nanoparticle thin film that prepared by drop casting method were investigatedby quartz crystal microbalance (QCM) and electrical characterization. The results of our experiment show that TiO 2nanoparticles have a great potential for humidity sensing applications at room temperature.Pure titanium dioxide does not occur in nature but isderived from ilmenite of leuxocene ores. The TiO 2nanoparticles generally present in three crystal phases:anatase, rutile, and brookite. Due to its highphotocatalytic activity, anatase is used as a photocatalystto treat various waste waters [2].In our study we used commercially available millenniumPC 500 TiO 2 which has 5-10nm particle size, 99%anatase form and 250 m 2 /gr BET surface area. 1gr TiO 2dispersed in 20ml distilled water and kept into ultrasoniccleaner for 30 minute at 50 0 C. After waiting 10 minutesthe semi-transparant part of the dispersion was taken.And 5μl of the dispersion is coated over a glass substrateby drop-casting method. The thickness of the film wasmeasured as 450 nm with Dektak 150 profilometer ofVeeco. SEM image of drop casted millenium PC 500TiO 2 thin film is shown in Figure1.(1)where is resonant frequency (8MHz), A is thearea of the gold disk coated onto the crystal, ρ isthe density of the crystal (2.684g/cm 3 ), and μ is theshear modulus of quartz (2.947x10 11 g/cms 2 ).F/Hz20-2-4-611%22%43%53%84%75%94%84%94%97%-80 1000 2000 3000 4000 5000 6000210(a)Time/sec43%53%75%22%11%y = 0,698 - 0,067407x R= 0,9972y = 2,2276 - 0,077601x R= 0,99245(b)-1f/Hz-2-3-4-5upwarddownward-60 20 40 60 80 100Relative Humidity (%)Figure 2(aand b):Frequency change with different RH(%) valuesFigure 1. SEM image of drop casted millenium PC 500 TiO2 thin film.For the electrical characterizations, Au metal withhigh purity (99.9%) was thermally evaporated onthe TiO 2 film with a separation of 17 μl. Keithly2420 Sourcemeter was used to investigateelectronic parameters. To estimate the frequencychange due to mass loading of water molecules,QCM with the model of CHI400A Series from CHInstruments was used. Electrical characterizationand frequency changes were obtained with theexposure of the film at different relative humidity(RH) ratios. (11%, 22%, 43%, 55%, 75%, 84%,94%, and 97% RH.)To convert the measured frequency change to themass change, Sauerbrey Equation is used [3].Figure 2 (a and b) shows the frequency changes dueto different relative humidity values .The frequencyof the TiO 2 film is decreasing and increasinghumidity values from 11% to 97%.A positive frequency observed during the resonanceoscillations because of the behaviours of TiO 2films.Our experimental results give that TiO2nanoparticle sensor is sensitive to relative humiditychanges at room temperature[1] S. Okur, M. Kus, F. Özel, V. Aybek, M. Yilmaz, Talanta,81;1-2; 2010; 248.[2] Tetsuro, K., Toshiaki, O., Mitsunobu, I., et al.,Photocatalytic Activity of Rutile–Anatase Coupled TiO2Particles Prepared by a Dissolution–ReprecipitationMethod, J.Colloid. Interf. Sci., 2003, vol. 267, no. 2, pp.377–381.[3] G. Sauerbrey, Z. Phys. 155 (1959) 206.6th Nanoscience and Nanotechnology Conference, zmir, 2010 701