Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 Performance of Silver Doped PEDOT Polymer Film as a SERS Substrate Üzeyir Doğan, 1* Murat Kaya, 1 Atilla Cihaner 2 and Mürvet Volkan 1 1 Department of Chemistry, Middle East Technical University, Ankara, Turkey 2 Department of Materials Engineering, Atılım University, Ankara, Turkey Abstract - A new and simple polymer substrate for inducing Surface Enhanced Raman Scattering (SERS) has been investigated. This new SERS substrate consists of an ITO slide as a solid support electrochemically covered with poly (3,4 ethylenedioxythiophene) (PEDOT) and fine silver particles. Raman spectroscopy is an analytical technique that is widely used to characterize chemical substances in samples [1] because of having different signal patterns for different Raman active substances. However, the sensitivity of the technique is very low. Surface enhanced Raman scattering (SERS) overcomes this disadvantage of Raman spectroscopy. A major factor in the large enhancement associated with SERS is the strong electromagnetic field enhancement close to the surface produced by surface plasmons, which are the result of the coupled oscillations of the conductance electrons of metals and the electromagnetic field component of the incident light [2,3]. When an analyte is brought into contact with nanoparticles of metals such as silver [4] or gold [5] the strong field enhances the Raman effect. Conducting polymers have a wide range of applications in the field of optical, electronic, electro-chromic devices, and sensors etc. Among them, poly (3,4 ethylenedioxythiophene) (PEDOT) (Figure 1) is considered to be a good applicant for its regioregular polymerization, low bandgap, stability and optical transparency. The recent technological interests are in the synthesis of conducting polymers incorporated with metal nanoparticles for varied applications. Conducting polymers are widely employed as support materials for dispersing the metal particles [6]. Figure 2. Raman spectrum of 10 -7 M BCB Additionally, the homogeneity of the surface in terms of its SERS activity (Figure 3) and shelf life of the substrates were examined. Figure 3. Raman spectrum of 10 -7 M BCB at different points on the same substrate. Figure 1. Poly(3,4-ethylenedioxythiophene) or PEDOT In this study, we investigated a new SERS active substrate using electrochemical method. Briefly, the surface of indium tin oxide (ITO) coated glass surface covered with variable amounts of PEDOT polymer and doped with variable amounts of silver nanoparticles. The effects of several experimental conditions of preparation were investigated using low concentrations of brilliant cresyl blue (BCB). Figure2 shows the characteristic SERS signal of 10 -7 M BCB acquired with the prepared substrate. The spectral evaluations of this compound closely matched with those reported in literature. * murvet@metu.edu.tr [1] Smith, E., Dent, G., 2005. Modern Raman spectroscopy. A practical approach. Wiley, England [2] Raether, H., 1988. Surface Plasmons. Springer-Verlag, Berlin [3] Schatz, G-C., Van Duyne, R.P., 2002. Handbook of Vibrational Spectroscopy. Wiley, Chichester [4] Li, S-Y., Cheng, J., Chung, K-T,. 2008. Surface-enhanced Raman spectroscopy using silver nanoparticles on a precoated microscope slide, Spectrochimica Acta, Part A 69: 524–527 [5] Joo, S-W., 2004. Surface-enhanced Raman scattering of 4,4- bipyridine on gold nanoparticle surfaces, Vibrational Spectroscopy, 34: 269–272 [6] S. Harish , J. Mathiyarasu , K. L. N. , V. YegnaramanJ Appl Electrochem (2008) 38:1583–1588 6th Nanoscience and Nanotechnology Conference, zmir, 2010 335
Poster Session, Tuesday, June 15 Theme A1 - B702 Preparation and Characterization of Zn-Rice Husk Char Esra Alt intig 1 * 1 Department of Chemistry, Sakarya University, Sakarya 54180, Turkey Abstract- In this study, rice husk was used as precursor for the preparation of activated carbon by chemical activation with ZnCl 2 . Rice husk charcoal supporting zinc (RH/Zn) was prepared by activation and chemical reduction. The RH/Zn composites were characterized by FTIR, XRD, EDS, zinc particle size and distribution, zin ion (Zn +2 ). Scanning electron microscopy (SEM) showed that the Z n particles were distributed uniformly on the RH matrix. The Zn content and surface morphology of the RH/Zn composites depended on the initial concentration of ZnNO 3 , and the higher the Zn content, the smaller the specific surface area obtained on the RH. Rice is one of the major crops grown throughout the world, sharing equal importance with wheat as the principal staple food and a provider of nourishment for the world's population Concern about environmental protection has aroused over the years from a global viewpoint. Rice husk ash, the most appropriate representative of the high ash biomass waste, is currently obtaining sufficient attraction, owning to its wide usefulness and potentiality in environmental conservation. [1]. Activated carbons are produced through physical or chemical activation. Chemical activation can be accomplished in a single step by carrying out thermal decomposition of raw material with chemical reagents. The most widely used chemicals include zinc chloride (ZnCl 2 ), phosphoric acid (H 3 PO 4 ), and potassium hydroxide/carbonate (KOH/K 2 CO 3 ) [2]. In this study, rice husk was used as precursor for the preparation of activated carbon by chemical activation and Zn-RH active carbon was prepared by exchanging Na ions with Zn ions in active carbon. 90 %T 80 70 water bath maintained at 60 o C for one week. NaCl solution was replaced every day. This sample was washed with deionized water several times and dried in oven at 110 o C. In ion exchange study, Zn(NO 3 ) 2 .5H 2 O was used as a cation source. The experiments were conducted by treating Na-RH with a series of solutions at 0.1 N containing different proportions of two com peting cations in polyethylene bottles placed in a shaker at 25 o C for 2 days [3]. The masses of RH were varied between 0.1 and 1 g, whereas the solution volumes were changed from 5 to 25 ml to ensure evenly distributed data along the ion exchange isotherm. Solid and solution phases were separated by centrifuging at 4000 rpm. Initial and final concentrations of the exchanging zinc and sodium were determined. In addition, FTIR (Fourier Transform Infrared Spectroscopy), X-ray diffraction (XRD), and element analysis (EDS), The Brunauer Emmett Teller specific surface area (S BET ) studied the chemical characteristics of RH and Zn-RH char particles. In summary, we showed that an efficient Rice husk supporting zinc was prepared by activation and chemical reduction. The RH/Zn structures were characterized by zinc particle size. Distribution and morphology of nanoparticles have been characterized using FTIR, XRD, SBET . Scanning electron microscopy (SEM) showed that the Zn particles were distributed uniformly on the RH matrix. Rice husk carbon is thus potential alternatives to commercially available activated carbon as they have high selectivity and are efficient with low production costs. *Corresponding author: altintig@sakarya.edu.tr 4000 FTIR 3500 3000 2500 Figure 1. FTIR Spectrum of RH active carbon. 2000 1750 1500 1250 1000 750 1/cm Table 1. The elemental analysis results of Zn-RH active carbon El t. Line Intensity Error Conc Units (c/s) 2-sig C Ka 165.21 8.127 57.222 wt.% O Ka 78.35 5.596 30.754 wt.% Na Ka 14.08 2.373 0.803 wt.% Si Ka 136.03 7.374 3.782 wt.% Cl Ka 5.92 1.539 0.178 wt.% Fe Ka 3.40 1.166 0.247 wt.% Zn Ka 18.87 2.747 7.013 wt.% [1] Fooa, K.,Y. and Hameed, B., H., 2009. Utilization of rice husk ash as novel adsorbent: A judicious recycling of the colloidal agricultural waste, Advances in Colloid and Interface Science, 152: 39-47. [2] Ucar, S., Erdem , M., Tay, T., Karagoz, S., 2009. Preparation and characterization of activated carbon produced from pomegranate seeds by ZnCl 2 activation, Applied Surface Science, 255: 8890–8896. [3] Top, A., Ulku, S., 2004, Silver, zinc, and copper exchange in a Na-clinop tilolite and resulting effect on antibacterial activity, Applied Clay Science, 27: 13– 19. We first prepare the active carbon from rice husk. The rice husk powder was prepared though a carbonization treatment at 700 °C. Prior to surface modification, the husk were grinded and then sieved into a desired particle size of 10-40μm. Then RH Powder was prepared by stirring NaCl solution at 500 rpm in a 2000-ml closed beaker placed in a constant temperature 6th Nanoscience and Nanotechnology Conference, zmir, 2010 336
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