Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 Synthesis and Modification of Multi-walled Carbon Nano-tubes (MWCNT) for Water Treatment Applications Mohammed Baghat 1 *, Ahmed Farghali 2 , Mohamed Khedr 2 , 1 CMRDI, Egypt 2 Banii-Sue f university Abstract-Fe-Co/CaCO 3 catalyst/support prepared by wet impregnation method is used for preparation of MWCNTs by chemical vapor deposition (CVD) of acetylene. CaCO 3 was found to be a good support as a high selective material for deposition of CNTs with high purity. Catalyst/support phases were identified by using XRD. The effect of growing time and temperature on carbon yield was studied. The structure and purity of CNTs was examined by TEM. The prepared CNTs were purified using chemical oxidation method and the effect of acid treatment on CNTs surface was studied by TEM and SEM. The functional groups produced at CNTs surface were examined by using FTIR spectroscopy. The funcationalzed CNTs were used for adsorption of some heavy metals and for removal of some organic dyes from water. *Corresponding author: m_bahgat70@yahoo.com 6th Nanoscience and Nanotechnology Conference, zmir, 2010 361
Poster Session, Tuesday, June 15 Theme A1 - B702 Fabrication and Band Gap Engineering of Te rnary Nanofilms by Electroche mical Co-depos ition 1 *and Ümit Demir 2 1 Bingöl University, Sciences and Arts Faculty, Department of Chemistry, 12000, Bingöl-Turkey 2 Atatürk University, Sciences Faculty, Department of Chemistry, 25240, Erzurum-Turkey Abstract-We report on the preparation of ternary compound (Bi x Sb 1-x ) 2 Te 3 nanofilms on single crystal Au (1 1 1) using a practical electrochemical method, based on the simultaneous underpotential deposition (UPD) of Bi, Sb and Te from the same. Nanofilms are characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and reflection absorption- FTIR (RA-FTIR). Nanofilms of bismuth-antimony-telluride with various compositions are highly crystalline and have a kinetically preferred orientation at (0 1 5) for hexagonal crystal structure. AFM studies show uniform morphology with hexagonal-shaped crystals deposited over the entire gold substrate. The compositional and structural analyses reveal that the films are pure phase with corresponding atomic ratios. The absorbance studies show that the band gap of nanofilms could be tuned as a function of composition. The binary and ternary compound semiconductors such as Bi2Te 3 , Sb 2 Te 3 and (Bi x Sb 1-x ) 2 Te 3 have also attracted considerable interest due to the requirements of environment protection and military applications [1]. Particularly for optoelectronic applications, it is important to be able to tune the band gap of the material [2]. In recent years, extensive attention has been devoted to tune the band gap of the binary compound semiconductors through the quantum confinement effect [3]. However, progress in this field has so far only allowed generating films with thickness of a limited range, in which the quantum confinement effect is prominent. The superior success of compound semiconductors in optoelectronics, integrated circuits and thermoelectric applications is largely attributed to the capability of energyband gap engineering through composition modulation of ternary compound semiconductors [4]. Most of the difficulties experienced in research on alloy films lie in devising a synthetic scheme to produce the desired ternary homogeneous structure. To achieve homogeneous ternary compounds, the growth rates of the two constituent materials (Bi2Te 3 and Sb 2 Te 3 ) must be equal and the conditions necessary for the growth of one constituent cannot impede the growth of the other. Furthermore, the structure and bonding of the two materials must be sufficiently similar to allow their facile mixing; otherwise, the formation of segregated structures such as two different binary compounds may occur [5]. Various methods have been used to synthesize ternary (BixSb 1-x ) 2 Te 3 films. In these studies, ternary compounds with only several x values were prepared. No comprehensive study has yet been conducted on (Bi x Sb 1-x ) 2 Te 3 compound in which x displays a broad variation. Here, we report on the electrochemical synthesis of homogeneous ternary films in all proportions. Recently, we have developed a simple and convenient way for electrochemical deposition of compound semiconductor materials on the basis of a combination of co-deposition and the UPD [6]. We have shown that this method could be used to grow highly crystalline binary thin films [7,8]. In this study, we report on the synthesis of homogeneous ternary nanofilms with various compositions. Nanofilms of bismuth-antimony-telluride with various compositions are highly crystalline preferred orientation at (0 1 5) for hexagonal crystal structure. Studies show uniform morphology with hexagonal-shaped nanocrystals. The films are pure phase with corresponding atomic ratios. The band gap of nanofilms could be tuned as a function of composition. (a) Figure 1. (a) Absorbance of (Bi x Sb 1-x ) 2 Te 3 nanofilms for different compositions, (b) Plot of shifting of XRD peak positions for nanofilms, with different compositions. In summary, bismuth-antimony-telluride nanofilms could be deposited underpotentially by an electrochemical codeposition method at room temperature. The prepared nanofilms with various compositions were homogeneous and in highly crystalline structure. The dependence of the band gap on the alloy composition is found to be linear and the band gap could be tuned from 0.17 eV to 0.29 eV by changing the concentration ratio of (Bi+Sb) solutions during electrochemical deposition. These results indicate that ternary compound semiconductor thin films could be successfully prepared by UPD-based electrochemical co-deposition technique. Atatürk University is gratefully acknowledged for the financial support of this work. *Corresponding author : 2Tiern@mynet.com [1] J. Yang, W. Zhu, X. Gao, S. Bao, X. Fan, X. Duan, J. Hou, J. Phys. Chem. B 110, 4599 (2006). [2] J.B. Chaudhari, N.G. Deshpande, Y.G. Gudage, A. Ghosh, V.B. Huse, R. Sharma, Appl. Surf. Sci. 254, 6810 (2008). [3] Langmuir, 22, 4415 (2006). [4] Y. Liang, L. Zhai, X. Zhao, D. Xu, J. Phys. Chem. B 109, 7120 (2005). [5] R.E. Bailey, S.M. Nie, J. Am. Chem. Soc. 125, 7100 (2003). [6] Chem Mater, 17, 935 (2005). [7 517, 5419 (2009). (b) 6th Nanoscience and Nanotechnology Conference, zmir, 2010 362
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