Photonic crystals in biology - NanoTR-VI

Poster Session, Thursday, June 17Theme F686 - N1123Humidity Sensor applications based on Carbon Nanotubes (CNTs) modified with various Calixarenemolecules measured by a Quartz Crystal Microbalance (QCM)F. Nadi Gür 1* , S. Okur 1* , Nesli T. Yağmurcukardeş 1 , Mustafa Yılmaz 2 , Mahmut Kuş 31 Izmir Institute of Technology, Department of Physics Urla/Izmir/TURKEY2 Selçuk University, Department of Chemistry, Selçuklu/Konya/TURKEY3 Selçuk University, Department of Chemical Engineering, Selçuklu/Konya/TURKEYAbstract— We predict that CNTs modified with calixerene molecules has a strong potential to investigate as a humiditysensors. This study focuses on humidity sensing properties of CNTs modified with calixrene. The humidity adsorbtiondesorptionkinetics are tested by Quartz Crystal Microbalance (QCM) technique. According to the our experimental results,modified CNTs with calixerene film will be possible option and open new approaches for more reliable, high sensitive,reversible and cost effective electro-chemical sensor applications.The accurate measurements of humidity levels are veryimportant concerns in environmental fields, such as medical ordomestic applications for human comfort, industrial uses,agriculture, automobiles.Thus, the requirement for cheap,reliable and sensitive sensors are urgent.Across all over the world, researchers have beeninterested in CNT based sensors and CNTs have shown to bestrong potential for the revolutionary of sensors generations[1]. As can be seen from Fig.1, due to their small size, highstrength, high electrical and thermal conductivity, and largeeffective active area, CNTs have many advantages compare tothe bulk or thin films for electro-chemical sensor applications[1,2].repeatability characteristics. The adsorption-desorptionkinetics are analyzed and discussed in details. F (Hz)50%110 %22 (a)%43-50 %53-100-150%75%84%94 %94%75%84%11%22%43%53-200%97-2500 1000 2000 3000 4000 5000 6000Time (s)- F (Hz)1000100 F (Hz)500-50-100-150-200(b)%43%53%75%84%97-2500 200 400 600 800 1000 1200Time (s)y = 13.733 * e^(0.028238x) R= 0.99383y = 8.1544 * e^(0.034337x) R= 0.98145(c)downwardupwardFigure 1: SEM image of carbon nanotubes filmThin films of calixarene derivatives have been widely usedin chemical sensors. Due to their zeolite-like capacity andselectivity, calixarenes became promising materials for sensorapplications [3]. Calixarene derivatives have been used inrecent times as gas sensors applications [4]. It is also knownthat some calixarene derivatives adsorb water molecules. SalihOkur reported a humidity sensing properties of calixerenederivatives [5]. However we did not reach any application ofCNTs modified with calixerene molecules based on humiditysensor.QCM tehnique is a powerfull option to investigate sensingproperties of modified CNTs, since it is highly sensitive tomass changes 1 ng/ 2 [2]. QCM has been used widely tomonitor the change in mass loading by measuring the shift ofits resonant frequency [5].In this work, we firstly started with CNTs dissolved intoethanol and CNT film coated by drop-casting technique.Humidity measurements of CNT film were recorded andmonitored by QCM from %11 RH to %97 RH. According toFig.2 adsorbtion-desorbtion process are very fast andreversible. We have obtained very good response and high1020 30 40 50 60 70 80 90 100Relative Humidity (%)Figure 2: QCM frequency shifts (Hz) as a function of time (s) for differentincreasing and decreasing relative humidity values between 11% and 97% RH(a) and (b) The change in the QCM frequency vs varying RH values (c)In summary, both CNTs and Calixerene derivates show verygood response to humidity changes sensor applications.Modified CNTs with Calixerene molecules show highlysensitive responce to RH changes and can be used as costeffective sensor materials.*Corresponding author: salihokur@iyte.edu.tr ,fatihnadigur@gmail.com[1] Niraj Sinha, Jiazhi Ma, and John T. W. Yeow, Carbon Nanotube-BasedSensors,JNN Vol.6, 573–590, 2006[2] Y. Zhang, K. Yu, R. Xu, D. Jiang, L. Luo, Z. Zhu, Quartz crystalmicrobalance coated with carbon nanotube films used as humidity sensor,Sens. Actuators A 120 (2005) 142–146.)[3] Koshets I. A., et.al.,Sens. Actuators B 106, (2005), 177[4] Ohira, Shin-I. , et.al., Talanta 2009, 77, 1814.[5]Salih Okur, Mahmut Kus, Faruk Ozel, Mustafa Yılmaz,Humidityadsorption kinetics of water soluble calix[4]arene derivativesmeasured using QCM technique,Sensors and Actuators B 145 (2010) 93–976th Nanoscience and Nanotechnology Conference, zmir, 2010 699