Photonic crystals in biology

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
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6th Nanoscience and Nanotechnology Conference, zmir, 2010 299