Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 Preparation of Ag Nanotags for SERS Applications Seda Kibar 1 , Mürvet Volkan 1, * 1 Department of Chemistry, Middle East Technical University, Ankara 06531, Turkey Abstract- For biological applications with SERS method, Ag nanotags were constructed. Through this aim, Ag nanoparticles were coated with silica and doped with a Raman-active dye, brilliant cresyl blue. Surface of these particles were functionalized with amino groups for attachment of biological molecules. Studies of preparation of SERS nanotags are focused on Ag, providing higher enhancement than Au do, due to the strong extinction and scattering spectra resulting from its localized surface plasmon resonance (SPR) [1,2]. Hence, in this study, silver NPs was prepared and, for colloidal stabilization and further surface modifications, a homogeneous shell of inorganic material, silica [3] was deposited on and labeled with brilliant cresyl blue, BCB. Ag nanoparticles were prepared by co-reduction of silver nitrate, AgNO 3 with sodium citrate [4]. Silica coated Ag NPs was constructed according to the Stöber process consisting of hydrolysis and co-condensation of tetraethylorthosilicate, TEOS, a silica precursor [5]. Different silica thickness was achieved with different molar ratio of TEOS to Ag NPs. The size and morphology of both Ag NPs and silica coated Ag NPs were measured using SEM and silica thickness was seen as ranging from 74 nm to 17 nm. Followings are the SEM images and UV spectra of Ag and silica coated-Ag Nps: Figure 3. Raman spectrum of dye-doped SiO 2 (Ag) NPs For highest BCB intensity, optimization of silica thickness was studied and optimum thickness was decided as 36 nm: Figure 4. Raman spectrum of dye-doped SiO 2 (Ag) NPs with different silica thickness For further biological applications, surface was modified with amino groups using APTS [6]. Figure 1. SEM images of Ag and SiO 2 (Ag) NPs Abs 2.000 1.800 1.600 1.400 1.200 1.000 0.800 0.600 0.400 0.200 0.000 0 200 400 600 800 1000 wavelength, nm Figure 2. UV spectrum of Ag and SiO 2 (Ag) NPs Ag NPs SiO2(Ag Dye-doping in silica matrix was studied through two different routes, embedding and impregnation. Raman studies showed that dye doped- SiO2(Ag) prepared by embedding gives higher intensity and provides more stability: Figure 5. Raman spectrum of dye-doped SiO 2 (Ag) NPs with different silica thickness *Corresponding author: murvet@metu.edu.tr [1] Y. Yang, J. Shi, G. Kawamura, M. Nogami, Scripta Materialia 58, 862 (2008). [2] L. Lu, H. Wang, Y. Zhou, S. Xi, H. Zhang, J. Hu, B. Zhao, Chem. Commun., 144 ( 2002). [3] E. Mine, A. Yamada, Y. Kobayashi, M. Konno, L. M. Liz-Marzán, J. Colloid Interface Sci. 264, 385 (2003). [4] G. V. P. Kumar, S. Shruthi, B. Vibha, B. A. A. Reddy, T. K. Kundu, C. Narayana, J. Phys. Chem. C 111,4388 (2007). [5] Y. Kobayashi, H. Katakami, E. Mine, D. Nagao, M. Konno, L. M. Liz-Marzán, J. Colloid Interface Sci. 283, 392 (2005). [6] S. L. Westcott, S. J. Oldenburg, T. R. Lee, N. J. Halas, Langmuir 14, 539 (1998). 6th Nanoscience and Nanotechnology Conference, zmir, 2010 272
Poster Session, Tuesday, June 15 Synthesis and Characterization of Palladium Nanoparticles Stabilized by Tannic Acid Emrah Bulut 1 ,Mustafa Can 2 *, Hilal Köse 1 and Mahmut Özacar 1 1 Sakarya University, Department of Chemistry, 54187 Sakarya, Turkey 2 Sakarya University, Institute of Sciences and Technology, 54187 Sakarya, Turkey Theme A1 - B702 Abstract-Palladium nanop articles were prepared with the sol-gel method using tannic acid as reducing and stabilizing agent. The OH groups of tannic acid oxidized by the reduction of palladium ions and then formed metallic palladium nanop articles stabilized by the tannic acid derivatives. Formed palladium nanop articles were characterized by XRD, SEM and EDS. Nanoscale materials have received considerable attention because the particles in the nanometric size range are thought of as a bridge between molecules and bulk materials. These nanomaterials often exhibit very interesting chemical, optical, electronic, and magnetic properties that are unachievable in bulk materials. Moreover, ultrafine particles of noble metals have attracted particular interest because their increased number of edges, corners, and faces gives them a high surface/volume ratio and therefore they are useful in various fields of chemistry. Because of these unique characteristics, metal nanoparticles are being intensively studied for applications in catalysis, optoelectronics, preservatives, and biosensing, biological labeling, controlled drug delivery, etc. [1-3]. Catalysis provides a natural application for nanoparticles because their large surface area-to-volume ratio allows effective utilization of expensive metals. Without a suitable support, however, metal particles aggregate, reducing surface area and restricting control over particle size. To overcome this problem, catalytic nanoparticles have been stabilized by capping ligands that range from small organic molecules to large polymers. Encapsulation by polymers is advantageous because in addition to stabilizing and protecting the particles, polymers offer unique possibilities for modifying both the environment around catalytic sites and access to these sites [2-5]. More recently, with the development of nanotechnology, this purpose may be achieved via stabilizing them by synthetic polymers. Ideally, the stabilizers should have moderate affinity towards metal nanoparticles, so that the aggregation of metal nanoparticles can be prevented. In this study, we describe “tannic acid-stabilized method” for the preparation of palladium nanoparticles. The general characteristic of tannic acid are able to chelate with many kinds of metal ions through their dense ortho-phenolic hydroxyls, and capable of scavenging free radicals so as to prevent metal species from oxidation. The property of tannic acid implies that it could be used as an ideal stabilizer for preparing stabilized-metal nanoparticles. It is reported that silver nanoparticles have been successfully prepared by using polyphenols as the stabilizers [6-7]. Using a tannic acid as the stabilizer, our research group also developed a facile route for the synthesis of Pd(0) nanoparticles. In the present study, palladium nanoparticles are prepared using tannic acid acting as both the reducing and stabilizing agent. A novel and facile method was applied to synthesize palladium nanoparticles that have catalysts feature by using tannic acid which have reduction effect with involving -OH groups and keeps the prepared particles stable because of its mo lecular structure. The tannic acid stabilizes the newly born Pd 0 clusters and can influence the growth of the nucleation and hence particle size. No other reducing agents were used during palladium nanoparticle synthesis. Pd 2+ 0 reaction occurs in aqueous tannic acid above 50 o C. Characterization of the resulting nanoparticles by X-Ray Diffraction (XRD) and Scanning Electron Micrographs (SEM) are presented in Figure. 1 and 2. Figure 1. SEM image of Pd nanoparticles Figure 2. XRD pattern of Pd nanoparticles * Corresponding author: mstfacan@gmail.com [1] A. Nemamcha, J.-L. Rehspringer and D. Khatmi, J. Phys. Chem. B 110, 383 (2006). [2] P.S. Roy, J. Bagchi and S.K. Bhattacharya, Transition Met. Chem. 34, 447 (2009). [3] S. Kidambi and M. L. Bruening, Chem. Mater. 17, 301 (2005). [4] N. Karousis et al., J. Phys. Chem. C 112, 13463 (2008). [5] X. Huang et al., Catal Lett. 133, 192 (2009). [6] E Bulut and M. Özacar, A Facile Aqueous-Phase Route to Synthesis of Silver Nanoparticles and Nanosheets, 4. Ulusal -13 Haziran, 2008, [7] E. Bulut, M. Özacar, Ind. Eng. Chem. Res. 48, 5686 (2009). 6th Nanoscience and Nanotechnology Conference, zmir, 2010 273
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Photonic crystals in biology

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