2 .Experimental

4. Conclusions

Nano crystalline zinc oxide can be prepared by a simple and cost-effective sol–gel process using aromatic acid ( salicylic acid) as precursors. Experimental results suggest a close relationship between the photocatalytic activity and the particles uniformity and size. The results clearly indicate that the synthesized zinc oxide nanoparticles have higher photocatalytic activity relative to ZnO bulk for the degradation of congo red dye.

4. Conclusions

Nano crystalline zinc oxide can be prepared by a simple and cost-effective sol–gel process using aromatic acid ( salicylic acid) as precursors. Experimental results suggest a close relationship between the photocatalytic activity and the particles uniformity and size. The results clearly indicate that the synthesized zinc oxide nanoparticles have higher photocatalytic activity relative to ZnO bulk for the degradation of congo red dye.

3 .Results

5.References[1] L.Q. Jing, Y.C. Qu, B.Q. Wang, S.D. Li, B.J. Jiang, L.B. Yang, W. Fu, H.G. Fu, J.Z. Sun,

Sol. Energy Mater. Sol. Cells 90 (2006) 1773–78.[2] T. Alammar, A.V. Mudring, Mater. Lett. 63 (2009) 732–735.

[3 ]J. Xie,Y. Li, W. Zhao, L. Bian, Y.Wei. Powder Technology 207 (2011) 140–144.

3.1. FTIR absorption 3.2. XRD pattern

13th Iranian Inorganic Chemistry Seminar

Investigation of photocatalytic activity properties of ZnO nanoparticles synthesized in neutral condition

Zahra Sheybani fard1, Akram Hosseinian2, Ali Reza Mahjoub*,1

*

1 Department of Chemistry, Tarbiat Modares University, 14115-175 Tehran, Iran2 Department of Engineering Science, University Colleges of Engineering, University of Tehran, P.O. Box 11365-4563 Tehran, Iran

11 . .IntroductionIntroduction

In the 1980's, photocatalysis oxidation technology was applied in the field of pollution control. This technology could effectively destroy the stable structure of refractory pollutants. Moreover, it has the advantages of wide application range, high efficiency, energy saving, low running cost, and no secondary pollution. Over the past few decades, semiconductor photocatalysis is becoming increasingly attractive due to its great potential to .solve environmental problems Among metal oxides, ZnO is a semiconductor with direct band gap energy of ( 3.37 eV) at room temperature and

.relatively large binding energy ( 60 meV)ZnO is an excellent semiconductor for photocatalytic degradation of environmental pollutants ]1-3[.

11 . .IntroductionIntroduction

In the 1980's, photocatalysis oxidation technology was applied in the field of pollution control. This technology could effectively destroy the stable structure of refractory pollutants. Moreover, it has the advantages of wide application range, high efficiency, energy saving, low running cost, and no secondary pollution. Over the past few decades, semiconductor photocatalysis is becoming increasingly attractive due to its great potential to solve environmental problems. Among metal oxides, ZnO is a semiconductor with direct band gap energy of ( 3.37 eV) at room temperature and

relatively large binding energy ( 60 meV). ZnO is an excellent semiconductor for photocatalytic degradation of environmental pollutants ]1-3[.

Aromatic acidsAromatic acids : :salicylic acidsalicylic acid Zn(II) saltsZn(II) salts

Zinc salicylate

22 . .Materials and MethodMaterials and Method

The aqueous solutions were evaporated to near dryness

in water bath.2H2O

washed with ethanol to eliminate the aliphatic acid in excess (pH=7)

and finally, decomposed at 500°C (for 2h)

and finally, decomposed at 500°C (for 2h)

All materials were purchased from Merck Chemical Company and used without further purification. In this work ZnO nanoparticles was prepared by mixing the corresponding Zn(II) salts maintained in aqueous suspension with an aliphatic acid. The aqueous solutions were evaporated to near dryness in water bath and washed with ethanol to eliminate the aliphatic acid in excess (pH=7) and decomposed at 500°C (for 2h).

The above figure shows IR spectra of product, after and before decomposition at 500oC. All the observed absorption bands confirm that the product before decomposition is zinc salicylate. ZnO nanoparticles are produced by decomposition of zinc salicylate. The sharp peak centered around 3400Cm-

1indicates the presence of water at the ZnO surface. The broad peak around 460cm-1 is attributed to Zn-O vibration.

The above figure shows X-ray diffraction patterns of dried product after decomposition at 500oC. The obtained XRD patterns match with the standard patterns of ZnO. The crystalline phases of ZnO is hexagonal (wurtzite), space groups P63mc with the lattice parameters a = 3.24982 Å, b = c = 5.20661 Å which are close to the reported values, (JCPDS cards number 36-1451). The sharp diffraction peaks of the sample indicated that well-crystallized.

3.3. SEM Characterization and EDX Analysis

The above figure shows SEM image of ZnO nanoparticles obtained by decomposition of dried sol–gel product. In this work, Uniform spherical nanoparticles with diameter of 63 nm are obtained. The chemical composition of the synthesized ZnO nanoparticles were studied using EDX. This result indicates that calcined ZnO nanoparticles contains %100 ZnO void of template.

3.4. UV-Vis Spectroscopy

To evaluate the photocatalytic activity of zinc oxide nanoparticles in presence of Congo Red dye , ZnO materials (as a catalyst) was resolved into Congo red solution. The solution was magnetically stirred and irradiated with UV light. Photodegradation of congo red in the presence and absence UV irradiation were investigated. Congo red solution exposed to ZnO without the presence of UV light for 10 min (the ZnO adsorption) and was exposed to light in the presence of ZnO for 10, 30 and 50 min (the photocatalysis condition).

Photocatalytic test

Results show that, both UV light and photocatalyst (ZnO nanoparticles) are needed for the effective destruction of Congo red. The photocatalyst is a surface reaction and depends on the active surface available for the reaction. However, the synthesized nanoparticles with this method have shown much greater photocatalytic efficiency comparable to that of commercial sample.