| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Thin Films | Tuesday Sessions |
| Session TF-TuM |
| Session: | Interfaces in Multilayers & Nanocomposites |
| Presenter: | ShienDer Tzeng, National Dong Hwa University, Taiwan, Taiwan, Republic of China |
| Authors: | S.D. Tzeng, National Dong Hwa University, Taiwan, Taiwan, Republic of China Y.S. Li, National Dong Hwa University, Taiwan, Taiwan, Republic of China K.T. Chiang, National Dong Hwa University, Taiwan, Taiwan, Republic of China I.C. Ni, National Dong Hwa University, Taiwan, Taiwan, Republic of China |
| Correspondent: | Click to Email |
Nanocomposite structures formed by the assembly of nanoparticles with functional surface molecules have many interesting properties [1-3]. We found that these surface molecules at the interface between nanoparticles play very important role on the physical properties (e.g., resistance and Seebeck coefficient reported in this work) of the nanocomposite thin film. For instance, shorter length of surface molecules results in shorter interparticle gap distance and thus increases the electric and plasmonic coupling between nanoparticles. Besides, the barrier height could also be tuned by using different kinds of molecules. Furthermore, the interparticle gap distance or the barrier height of charge conduction could also be influenced by their surrounding gases. In this work, we show that Heme modified nanoparticle assembled films could be used for low water vapor pressure sensing (as shown in Fig. 1). From high vacuum to ~0.01 Torr water vapor, the resistance of Heme device could increase 1%. By contrast, 8-mercaptooctanoic acid (MOA) or 6-mercaptohexanoic acid (MHA) modified nanoparticle assembled films need 1 Torr water vapor to cause 1% resistance change. Besides, we found that the response is proportional to Pγ, and the characteristic energy of water adsorbed in the nanocomposite structure could be calculated from the value of γ. Furthermore, the response time of such water vapor sensors could be less than 0.2 sec, much shorter than most known humidity sensors. We also found that the thermoelectric properties of these molecule-nanoparticle composite thin films were very sensitive to surrounding gases (as shown in Fig. 2). For instance, the Seebeck coefficient of MHA-modified gold nanoparticle assembled films was about 12.5 μV/K in high vacuum (10-5 Torr), but became 120 μV/K in 600 Torr O2 gas. Such great change in Seebeck coefficient could be explain by the change of density of state contributed by the gas molecules adsorbed on the surface molecules.
References:
1. I-Chi Ni, Su-Ching Yang, Cheng-Wei Jiang, Chih-Shin Luo, Watson Kuo, Kuan-Jiuh Lin, Shien-Der Tzeng, Journal of Physical Chemistry C 116, 8095 (2012).
2. Cheng-Wei Jiang, I-Chi Ni, Shien-Der Tzeng, and Watson Kuo, Applied Physics Letters 101, 083105 (2012).
3. Cheng-Wei Jiang, I-Chi Ni, Shien-Der Tzeng, Cen-Shawn Wu, and Watson Kuo, Nanoscale 6, 5887 (2014).