Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 > µ 6th Nanoscience and Nanotechnology Conference, zmir, 2010 298
Poster Session, Tuesday, June 15 Theme A1 - B702 Effect of Toluene on Nano Calcite Production by Carbonation Route Murat Molva 1 and Ekrem Özdemir 1 * 1 -Izmir, Turkey Abstract- Nano size calcium carbonate crystals were produced in 20 mM Ca(OH) 2 by CO 2 diffusion in the presence of toluene as an or ganic additive. Based on the X-ray diffraction, the main crystal morphology was calcite with the crystallite size of 30-35 nm. Scanning electron microscopy indicated the maximum dimensions of the crystals up to 200 nm. According to the FTIR analysis, chemical structure of the precipitates had some differences after the addition of toluene and crystallinity was occurred in different chemical structures. Crystallization of calcite occurs in the presence of varying complexity of organic molecules. Those organic molecules may influence the morphology of crystals during calcium carbonate precipitation. Studies on the interaction of macromolecules with calcite suggest that these molecules can bind specifically to certain crystal planes during crystal growth, thereby modifying the final morphology attained [1]. On the other hand, solubility of CO 2 increases in the presence of some organics [2]. Amphiphilic property of some organic solvents may have a great influence on structural framework and solvating degree of additives, dielectric constant of solution, polarity, and interaction between the ions (such as Ca 2+ ) in the solution. At room temperature, some organic solvents, such as hexane, toluene, and benzene can not exhibit amphiphilic property since they are not miscible in water. Molecular structural framework and solvating degree of additive may affect the initial formation of crystallization by blocking of growth site and confining the reaction solutions with organized media and can lead to high localized accumulation of ionic charge with high spatial density, thereby, determining the size, shape and organization of the crystal forms. Thus, it can be speculated that the amphiphilic property of organic solvent plays an important role in determining the calcite crystal morphology [3,4]. Organic solvents and water have co-effect on the polymorph and morphology of CaCO 3 particles at room temperature. Various unusual crystal morphologies, such as dendriteshaped, flower-like, wheatgrass-like, needle-like, whiskers, double-taper-like, cubical, spherical etc. can be obtained depending on the experimental conditions [3]. In this study, nano size calcite crystals were produced via carbonation route, where the CO2 was diffused through the surface of a stirred reactor containing various concentrations of Ca(OH) 2 slurry in the presence of toluene (merck, >99.9 %) as an organic additive. The ratio of the mixture (toluene / water) varied fro m 5 % to 20 % (v/v) and stirring rate was 400 and 800 rpm. pH and conductivity were monitored during the tests and characterization of nano crystals was expressed by SEM, XRD and FTIR. Figure 1 shows the SEM images of the nano crystals which were obtained in the presence of 5 % (a) at 400 rpm and (c) at 800 rpm, and 20 % toluene (b) at 400 rpm and (d) at 800 rpm, respectively. The crystallite sizes were calculated fro m Debye Scherrer Equation as 30-35 nm using XRD data. Figure 2 shows the FTIR data for the calcite with and without addition of toluene and found that there are some structural diferrences in the calcite morphology as indicated in v 1 , v 2 , v 3 , and v 4 orientations. Effect of toluene on size, shape, and morphology of the produced calcite will be discussed in detail during the presentation. (a) (c) (b) (d) Figure 1. SEM images of the nano crystals in the presence of toluene: (a) 5 %, 400 rpm, (-b) 20 %, 400 rpm (c) 5 %, 800 rpm, (d) 20 %, 800 rpm abs 6 5 4 3 2 1 0 2510-2530 (v 1 +v 3 ) 2500 calcite with toluene calcite without toluene 2000 1797-1831 (v 1 +v 4 ) 1500 1000 wavelength (cm -1 ) Figure 2. FTIR spectra of the nano crystals (20 mM Ca(OH) 2 , CO 2 , H 2 O and 20 % toluene). 1420-1450 v 3 1084 -1100 875-885 v 2 711-748 v 1 v 4 0T*Corresponding author: ekremozdemir@iyte.edu.tr [1] Meldrum F.C., Hydeb S. T., Morphological influence of magnesium and organic additives on the pre precipitation of calcite, Journal of Crystal Growth 231 (2001) 544–558 [2] Brooks B.W, Shilimkan R.V, Manufacture of calcium carbonate dispersions in lubricating oil, Colloid and Polymer Science 257 (1979) 981-983 [3] Lei, M., Li, P. G., Sun, Z. B. and Tang, W. H. (2006) Effects of organic additives on the morphology of calcium carbon ate particles in the presence of CTAB. Materials Letters 60, 1261-1264 [4] Dickinson, S. R. and McGrath, K. M. (2004) Aqueous precipitation of calcium carbonate modified by hydroxyl-containing compounds. Crystal Growth & Design 4, 1411-1418 500 6th Nanoscience and Nanotechnology Conference, zmir, 2010 299
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