Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 Tyrosinase-Fe 3 O 4 -Chitosan Nanobiocomposite Film for Biosensor Application 1 and -Ozkan 1 * 1 Izmir Institute of Technology, Chemical Engineering Department, Gulbahce Koyu, 35430- Abstract- Tyrosinase-Fe 3 O 4 -chitosan nanobiocomposite film was prepared in order to determine the pesticide residue as a biosensor application in the following research. The immobilized tyrosinase enzyme on the Fe 3 O 4 -chitosan nanocomposite prepared by coating of chitosan onto the Fe 3 O 4 nanoparticles was also characterized by the measurements of atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectra, thermogravimetric analysis (TGA) and differential scanning calorimetric analysis (DSC). Contaminated pesticide residues for ground water, raw food materials and processed foods results form the application of organophosphate pesticides (OP) to increase the amount and quality of the product [1]. Reliable analytical procedures are required in order to determine the pesticide residue at low level. Spectrophotometric and chromatographic techniques are analytical methods commonly used [2]. These methods have a number of disadvantages such as expensive instrumentation requirement, highly trained personnel, time consumption, and difficulties in adaptation for field analysis. In recent years enzyme electrodes show remarkable advances for the detection of toxic compounds based on enzymatic reactions. Tyrosinase enzyme is one of the appropriate enzymes to detect the pesticide residue depending on the inhibition mechanism directly related to decrease in the amount of enzymatically produced quinones while substrate (catechol) is consumed [3] as shown in Figure 1. Figure 2. The illustration of tyrosinase immobilized on Fe 3 O 4 - chitosan nanocomposite The morphology of the (a) Fe 3 O 4 nanoparticles, (b) chitosan film, (c) Fe 3 O 4 nanoparticle-chitosan and (d) tyrosinase-Fe 3 O 4 -chitosan nanobiocomposite films were characterized with AFM. The binding mechanism of each material was characterized by using FTIR spectra. TGA and DSC were performed to reveal the formation of nanobiocomposite material. Corresponding author: 0Tfehimeozkan@iyte.edu.tr Figure 1. Basic reaction mechanism of tyrosinase on catecol The effective immobilization of tyrosinase on the electrode surface is the key issues for the development of tyrosinase biosensors. The immobilization methods can be classified as chemical (covalent cross-linking and covalent binding) and physical (physical entrapment, micro encapsulation, and adsorption) methods [4]. In recent years magnetic nanoparticles are becoming the focus of researchers due to lots of properties. Especially Fe 3 O 4 has significant properties such as strong superparamagnetism, low toxicity and large surface area provides high enzyme loading [5]. However this nanoparticle tends to aggregate and therefore stabilizers such as surfactants, metal nanoparticles and polymeric compounds have been used. As a natural polymer, chitosan has the characteristic of biodegradable, biocompatible, bioactive, nontoxic, film forming ability, physiological inertness and high mechanical strength [6]. In this study, Fe3O 4 -chitosan nanocomposite was prepared to immobilize the tyrosinase enzyme on it. This nanobiomaterial was characterized for the development of tyrosinase biosensor used in determination of pesticide residue as the future work. For this aim tyrosinase solution was prepared in phosphate buffer solution (PBS) at pH 6.5. Acetic acid was used for the preparation of chitosan solution. The Fe 3O 4 nanoparticle suspensions was prepared by dispersing the particle in double distilled water with ultrasonication. Then tyrosinase solutions, chitosan solutions and Fe 3 O 4 nanoparticles were mixed with a specific volume ratio in order to obtain tyrosinase-Fe 3 O 4 -chitosan nanobiocomposite film (Figure 2). [1] Ingrid Walz I., Schwack W., 2007. Cutinase inhibition by means of insecticidal organophosphates and carbamates Part 1: Basics in development of a new enzyme assay, Eur. Food. Res. Technol., 225: 593-601. [2] Poerschmann, J., Zhang, Z., Kopinke, F.D., Pawliszyn, J., 1997. Solid Phase Microextraction for Determining the Distribution of Chemicals in Aqueous Matrixes, Anal. Chem., 69: 597–600 [3] Munoz J.L.-Molina F., Varon R., Rodriguez-Lopez -Canovas F., Tudela J., 2008 Calculating molar absorptivities for quinones: Application to the measurement of tyrosinase activity, J. Comput. Aided Mol. Des., 22: 299-309. [4] Buerk D.G., 1993. Biosensors; Theory and Applications. U.S.A. [5] Gu, H. W.; Xu, K. M.; Xu, C. J.; Xu, B., 2006. Biofunctional Magnetic Nanoparticles for Protein Separation and Pathogen Detection, Chem. Commun., 941-949. [6]Barbara K. , 2004. Application of chitin- and chitosan-based materials for enzyme immobilizations: a review, Enzyme and Microbial Technology, 35: 126–139 . 6th Nanoscience and Nanotechnology Conference, zmir, 2010 331
Poster Session, Tuesday, June 15 Hydrothermal synthesis of indium tin oxide for transparent and reflective thin films Meltem Asiltürk a, * , Esin Burunkaya b,c , Nadir Kiraz b,c , Ömer Kesmez b,c , Ertuğrul Arpaç b,c a Inonu University, Department of Chemistry, Malatya, Turkey b Akdeniz University, Department of Chemistry, Antalya, Turkey c NANOen R&D Ltd, Antalya, Turkey Theme A1 - B702 Abstract- Indium tin oxide (ITO) used as optical material with high refractive index was hydrothermally synthesized from a mixture of indium(III) chloride and tin(IV) chloride. Surface of the ITO particles was modified with different modifying agents used as a copolymer for coatings and then, thin films of surface modified ITO nanoparticles was deposited on glass and silicon-wafers by the spin-coating method. It was found that particle size of ITO powder is finer than 10 nm and particles have high transmittance in visible region but it has low transmittance in infrared region. Surface of ITO particles can easily modify a ligand, and thus it can use in applications of thin film. Thickness of films is about 515 nm. Refractive index of films is 1.7-1.8. Indium tin oxide (ITO) is an advanced ceramic material with many electronic and optical applications due to its excellent properties of high conductivity (104 -1 cm -1 ) and high transparency (85–90%) to visible light [1, 2]. For many applications, especially in microelectronics and optoelectronics, with optical and IR-blocking coatings, it is important to use ITO powders comprising nanoscale particles. The high electrical property is originated from the creation of a conducting carrier–oxygen vacancy with the addition of dopant (Sn 4+ ) to the matrix (In 2 O 3 ). The oxygen vacancies act as doubly ionized donors and contribute at a maximum two electrons to the electrical conductivity. In 2 O 3 exists in two different crystallographic structures, i.e. rhombohedra and cubic forms. High electrical conductivity is normally achieved by the stabilization of the cubic phase [3–5]. For this reason, there are very large numbers of possible uses for indium tin oxide systems, and, accordingly, there have also been a very large number of investigations into their preparation. For many applications, especially in microelectronics and optoelectronics, with optical and IR-blocking coatings it is important to use ITO powders comprising nanoscale particles. Such nanoscale particles have an average particle size of preferably from 5 to 30 nm. Many techniques such as solvothermal, microemulsion, sol-gel, coprecipitation, and hydrothermal method have been used to prepare nanocrystalline ITO powders [6- 11]. Among these chemical techniques, the main advantages of hydrothermal synthesis are related to homogeneous nucleation processes, ascribed to elimination of the calcinations step to produce very low grain sizes and high purity powders [12]. In this work, we prepared ITO powders without additional heat treatment after the hydrothermal synthesis. Prior to the surface modification, ITO sol was prepared without using dispersant in ethanol and then, surface of ITO particles was modified different chemical compounds. With the coating solutions which have modified ITO particles, we coated glass substrate and Si-wafers by spin coating method. The results showed that ITO powders were well crystallized. They have dominant cubic crystalline structure. The particle size of ITO powder is < 10 nm. ITO particles have high transmittance in visible region but it has low transmittance in infrared region. Surface of ITO powders can easily modify a ligand, and thus it can use in applications of thin film. Thickness of films is about 515 nm. Refractive index of films is 1.7-1.8. Figure 1. TEM micrograph of ITO nanoparticles This study was financially supported by TÜBİTAK (Turkey) as a research projects with grand no 107M253. * masilturk@inonu.edu.tr [1] J.H. Hwang, D.D. Edward, D.R. Kammler and T.O. Mason, Solid State Ionics, 129 (2000), 135–144. [2] C. P. Udawatte and K. Yanagisawa, J. Solid State Chem., 154 (2000), 444–450. [3] P. S. Devi, M. Chatterjee, and D. Ganguli, Mater. Lett., 55 (2002), 205-210. [4] N. Nadaud, N. Legueux and M. Nanot, J. Solid State Chem., 135 (1998), 140-148. [5] N. C. Pramanik, S. Das and P. K. Biswas, Mater. Lett., 56 (2002), 671-679. [6] J.S. Lee, S.C. Choi, J. Eur. Ceram. Soc. 25 (2005) 3307- 3314. [7] M-K. Jeon, M. Kang, Mater. Lett., 62 (2008), 676-682. [8] D.H. Lee, Y.J. Chang, G.S. Herman, C.H. Chang, Adv. Mater., 19 (2007) 843-847. [9] C. Goebbert, R. Nonninger, M.A. Aegerter, H. Schmidt, Thin Solid Films, 351 (1999), 79-84. [10] J. E. Song, D.K. Lee, H.W. Kim, Y. II. Kim, Y.S. Kang, Coll. Sur. A, 257-258 (2005), 539-542. [11] K. Yanagısawa, C. P. Udawatte, J. Mater. Res., 15(6) (2000), 1404-1408. [12] F. Sayilkan, M. Asilturk, S. Erdemoglu, M. Akarsu, H. Sayilkan, M. Erdemoglu, E. Arpac, Mater. Lett., 60(2) (2006), 230-235. 6th Nanoscience and Nanotechnology Conference, zmir, 2010 332
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