The effect of alkaline ion exchange time on the antibacterial property of copper/soda lime silica gel
Seyyed Mohsen Moghimi
1, Mohammad Ghorbanpour
2, Zeinab Darabi
3, Mehran Yousefi
41,3- Chemical Engineering Department,Sahand University of Technology, Tabriz, Iran 2,4- Chemical Engineering Department, University of MohagheghArdabili, Ardabil, Iran
[email protected] Abstract
The aim of this project was evolution of the antibacterial effect of copper/soda lime silica gel nanocomposites. These nanocomposites were prepared via immersion of silica gels in the molten salt of copper sulfate at 560 °C. In this investigation, the proposed method results in synthesis of nanoparticles and immobilization of them on the substrate with less than 40 min. The morphology and absorption spectra of the nanocomposites were characterized by SEM and UV-Vis spectrophotometer. The antimicrobial activity of samples was also investigated by microbial tests. Interestingly, all the prepared nanocomposites revealed the inhibitory effect against E. coli. However, the highest inhibitory effect depends on the copper content and size. According to stability test results, the nanocomposites were stable.
Keywords: Ion exchange, Copper, Silica gels, Nanocluster, Antibacterial.
1. INTRODUCTION
Antibacterial compounds have the potential of removing bacterium, bacteria fatal, or reducing the growth of them. These compounds do not disturb the surrounding structured tissues. Also, it is of high importance to note that the on hand antibacterial compounds do not affect resistant bacterium and their side effects. Nano scaled material considered as novel antibacterial property effectiveness because of their high surface/volume ratio. In todays technologies, metallic nanostructured materials like Ag, Cu, ZnO and Ti have considerable antibacterial characteristic and attracted much more attention of newest researches [1,2]. Among the so-called metals, Cu is of highest consideration because of its less toxicity, lower price, stability and easier mixing with polymers [3,4].
In water disinfection application stabled and fixed nanostructured cu have the advantageous of using in packed beds and longer period of usage. Many reference methods have been proposed for synthesis of stabled nanostructured Cu, e.g. thermal reduction, vacuum vapor deposition, microwave irradiation, chemical reduction and laser ablation [4]. These methods have their own shortage like cost consuming facilities and chemical recovery compounds.
The aim of this working is the application of alkaline ion-exchange method in preparation of stabled nanostructured Cu on sodium glass (silica gel). First silica gel and copper sulfate were put in the furnace. As the temperature increased, the structure of glass become softer. on the other hand, as atomic penetration increased, sodium atoms deport from the structure of silica gel and Cu substitute in the texture[5-7].
Alkaline ion-exchange has many advantageous in compare to other methods, advantageous of no need of expensive facilities, solution preparation and chemical factors like recovery compounds, toxic surfactant. Also, this method is easy, time saving and environmental friendly
2. M
ATERIALS AND METHODS2.1 M
ATERIALSSodium silica gel, nutrient agar with sodium chloride, copper sulfite of Merck co. Ltd and bacteria from Institute of Iranian Industrial and Scientific researches were received.
2.2 N
ANOCOMPOSITE PREPARATIONSilica gel were Soaked in the bath of molten copper sulfate with time period of 10,20,40,60 minutes at the temperature of 560-570 °C. after the limited time reached and the solution cooled, the samples were washed with water and salty water with the help of ultrasonic on continuity, the samples were dried in the oven and the produced CuO/silica gel were named 0,10,20,40,60 with respect to the preparation time.
2.3 N
ANOCOMPOSITE INVESTIGATIONThe morphology changes of nanocomposites were diagnosed by electronic microscope (LEO 1430VP, Germany). Absorbed spectra of nanocomposites were analyzed before and after nanostructured particles fixation.
2.4 A
SSESSMENT OF ANTIBACTERIAL ACTIVITYAntibacterial effective evaluation done with Disk-Diffusion Assay. At first, Mueller-Hinton agar medium prepared and divided into 5 Sterile plates. test tubes were selected and filled with 3 ml of physiology serum.
In the vicinity of the flame appropriate amount of bacterial colonies in saline and within their respective tubes were inoculated. The tube solution vortexed to achieve homogeneous suspension were equal to 1.5×108 colony-forming units/ml based on the 0.5 McFarland standard in each plate the bacterial suspension fertilized in 3 directions (the sterile swab was used). Then nanocomposite put on the surface of plate in the circular area of 5 mm diameter. Plate were put in incubator at 37 °C and incubated. After 24 hours, the diameter of the growth inhibition zones was measured.
2.5 S
TABILITY OF NANOCOMPOSITESIn order to investigate nanocomposite stabilities, samples were soaked in solution of 2 molar sodium chloride for 24 hours. By comparison of absorbed spectra which were sent to the solution, delivery of copper from samples measured.
3. R
ESULTS AND DISCUSSION3.1 C
OLORIn the process of alkaline ion-exchange, Cu ions in molten salt bath diffuse in glass structure and substituted with sodium. As a result, Na departed from silica gel structure and enter the bath and Cu ions permeated and accumulated. On the surface and in the structure of the silica gel, Cu cluster were constructed. Fig. 1 show the process with exact details. The first silica gel sample was Colorless and by promoting the ion-exchange process, the color of samples changed from light green to dark green. This change demonstrates the production of silica gel/Cu composite.
3.2 M
ORPHOLOGYFig. 2 represents pictures taken by electronic microscope. These pictures revealed the initial silica gel has few defects on its surface. There is small amount of particles on the surface that seemed to be broken parts of glass. As the time of process increased, the defects on the surface of silica gel decreased and few amount of Cu nanoparticles produced. The more time, the more diffusion of Cu particle in silica gel structure and the more fixed nanoparticles. On the other hand, time affect the size of nanoparticles and it increased by more process time. Directly speaking, time affect the amount of nanoparticles and their size.
Figure 2. SEM photos of Silica gel (A), samples of 10, 20, 40 and 60 (B-E)
Fig. 3-A represents nanocomposite absorption spectra in the range of 320 nm-520 nm. It was understood that absorption quantity of samples increased by increasing the time [8].
In absorption spectra, a peak at approximately 360 nm observed. This peak relates to the characteristic of particle surface plasmon and corresponds to the size of nanoparticles. By the increment of time from 10 to 40 min., the peak intensity increased (Fig. 3-B) because of more amount of nanoparticles on the surface and more loading of Cu. After 40 min. The increment rate of peak intensity decreased because the amount of ions on the substrate increased less. This phenomena is the result of longer distance that need to be passed by Na deport from glass and diffuse Cu, but at the starting of process, the process is different.
Figure 3. Absorption spectra of Cu/Silica gel nanocomposites (A), Maximum absorption intensity of samples (B)
3.4 A
NTIBACTERIALC
HARACTERISTICFig. 4 explains the result of pre paned nanocomposites of Cu./silica gel vs. Escherichia coli bacteria. Initial silica gel does not have the antibacterial property. Among the samples, 10 has minimum shadow of 6.76 mm.
This effect increased to 7.6 mm for sample 20. Also for sample 40 and 60, the shadow was 7.84, and no considerable difference observed for the 2 sample. This result can be analyzed with the help of absorption spectra and morphology analysis. After 40 min. the surface of Silica gel was saturated with nanoparticles and
0.72 0.76 0.8 0.84 0.88 0.92
320 370 420 470 520
Absorbance (a.u.)
Wavelength (nm)
10 min 20 min 40 min 60 min
0.83 0.84 0.85 0.86 0.87 0.88 0.89 0.9 0.91
10 20 30 40 50 60
Maximum absorbance (a.u.)
Time of ion Exchange (min)
maximum loading of substrate reached. Based on the results sample 40 has the optimum characteristics. Many papers investigated the antibacterial characteristic. The researches of shadow measurement for evaluation of antibacterial property of Ag loaded fibers [9], Cu/Silica gel nanocomposite and loaded powder of hydroxyapatite with Cu [10]. The result of their working was compared with mentioned works.
Figure 4. Shadow measurement of nanocomposites Cu/Silica gel
3.5 S
TABILITY TESTTo investigate stability Cu/ silica gel nanocomposites soaked in sodium chloride salt solution of 2 molar. The obtained results from absorption spectra showed small change of stability property that means high stability of nanocomposites. In this process the Cu nanocomposite permeate glass structure that fix after cooling and cannot deport the medium.
4. C
ONCLUSIONIn this research, synthesis of Cu/Silica gel nanocomposites with the method of ion-exchange was done.
Electronic microscope showed that the contact of silica gel with molten salt results in the production of Cu nanoparticles on the surface silica gel and the intensity of absorption increased as the time of process increased.
Investigation antibacterial property vs. Escherichia coli bacteria represented high antibacterial effect of nanocomposites. Also, stability test proved high nanocomposites stability.
5. A
CKNOWLEDGMENT6. R
EFERENCES 6.5 6.7 6.9 7.1 7.3 7.5 7.7 7.910 20 30 40 50 60
Inhibition zone diameter (mm)
Time of ion Exchange (min)
3. Shrivastava, S., et al.,(2007), “ Characterization of enhanced antibacterial effects of novel silver nanoparticles,” Nanotechnology, 18 (22): p. 225103.
4. Kim, T., et al.,(1998), “ Antimicrobial effects of metal ions (Ag+, Cu2+, Zn2+) in hydroxyapatite,”
Journal of materials science: Materials in Medicine, 9 (3): p. 129-134.
5. Stoimenov, P.K., et al.,(2002), “ Metal oxide nanoparticles as bactericidal agents,” Langmuir, 18 (17): p. 6679-6686.
6. Ren, G., et al.,(2009), “ Characterisation of copper oxide nanoparticles for antimicrobial applications,” International journal of antimicrobial agents, 33 (6): p. 587-590.
7. Ramyadevi, J., et al.,(2012) “ Synthesis and antimicrobial activity of copper nanoparticles,”
Materials Letters, 71: p. 114-116.
8. Dhas, N.A., C.P. Raj, and A. Gedanken,(1998), “ Synthesis, characterization, and properties of metallic copper nanoparticles,” Chemistry of materials, 10 (5): p. 1446-1452.
9. Yang, M. and J.-J. Zhu,(2003), “ Spherical hollow assembly composed of Cu 2 O nanoparticles,”
Journal of crystal growth, 256 (1): p. 134-138.
10. Yeh, M.-S., et al.,(1999), “ Formation and characteristics of Cu colloids from CuO powder by laser irradiation in 2-propanol,” The Journal of Physical Chemistry B, 103 (33): p. 6851-6857.
11. Zhao, Y., et al.,(2004), “ Microwave‐Induced Polyol‐Process Synthesis of Copper and Copper Oxide Nanocrystals with Controllable Morphology,” European Journal of Inorganic Chemistry, 2004 (20): p. 4072-4080.
12. Gonella, F., et al.,(2005), “ Cu-alkali ion exchange in glass: a model for the copper diffusion based on XAFS experiments,” Computational materials science, 33 (1): p. 31-36.
13. Dong, Z.-W., et al.,(2009), “ Ultrafast dynamics of copper nanoparticles embedded in soda-lime silicate glass fabricated by ion exchange,” Thin Solid Films, 517 (21): p. 6046-6049.
14. Ti, Y., et al.,(2008), “ Photoluminescence of copper ion exchange BK7 glass planar waveguides,”
Journal of materials science, 43 (22): p. 7073-7078.
15. Link, S., M. Mohamed, and M. El-Sayed,(1999), “ Simulation of the optical absorption spectra of gold nanorods as a function of their aspect ratio and the effect of the medium dielectric constant,”
The Journal of Physical Chemistry B, 103 (16): p. 3073-3077.
16. Mary, G., S. Bajpai, and N. Chand,(2009), “ Copper (II) ions and copper nanoparticles‐loaded chemically modified cotton cellulose fibers with fair antibacterial properties,” Journal of Applied Polymer Science, 113 (2): p. 757-766.
17. Grace, M., N. Chand, and S.K. Bajpai,(2009), “ Copper alginate-cotton cellulose (CACC) fibers with excellent antibacterial properties,” J Eng Fiber Fabr, 4 (3): p. 1-14.
