Investigating structural, optical and photocatalytic properties of hydrothermally synthesized ZnO nanorod arrays with various aspect ratios

Document Type: Research Paper


1 Young Researchers and Elite Club, South Tehran Branch, Islamic Azad University, Tehran, Iran

2 2Physics department, University of Kashan, Kashan, Iran.

3 3Plasma Physics Research Center, Science and Research branch, Islamic Azad University, Tehran, Iran

4 4Department of Physics, Shahrood University of Technology, Shahrood, Iran


ZnO nanorods with various aspect ratios (by changing the time of growth between 0-240 min) were synthesized using hydrothermal method and were investigated using XRD, SEM, UV–Vis and PL. It was found that growth time is directly coupled with the length, orientation and aspect ratio of the nanorod arrays. The optical transmittance of the NR arrays indicated a regular decrement of average transmittance with increasing the aspect ratio of NRs in the visible range. The optical constants (absorption coefficient, extinction coefficient and refractive index) can be account as a function of refractive index were determined. The porous ZnO nanorod with the thickness of ∼ 1560 nm and texture coefficient of 0.96 for (002) plane exhibits the average visible transmittance <60%, refractive index 1.34, packing density 0.26 and lowest optical band gap, was fabricated in the longest time of hydrothermal growth (240 min). As the growth time was increased, the photoluminescence properties was sustained a general weakening tendency and a red-shift of UV-emission peak position. The UV-assisted photocatalytic degradation of 4-Nitrophenol (4-NP) of ZnO NRs were investigated. The considerable photocatalytic performance of ZnO NRs with highest aspect ratio was explained by its porosity and optical characteristics.


Main Subjects

[1] Janotti, C. G. Van de Walle, Fundamentals of zinc oxide as a semiconductor, Rep. Prog. Phys.  2009, 72, 126501.

[2] V. Srikant, V. Sergo, D. R. Clarke, Epitaxial Aluminum-Doped Zinc Oxide Thin Films on Sapphire: I, Effect of Substrate Orientation, J. Am, Ceram. Soc. 1995, 78, 1931-1934.

[3] Y. Ryu, T.-S. Lee, J. A. Lubguban, H. W. White, B.-J. Kim, Y.-S. Park, C.-J. Youn, Next generation of oxide photonic devices: ZnO-based ultraviolet light emitting diodes, Applied Physics Letters, 2006, 88, 241108-241108.

[4] H. Fu, T. Xu, S. Zhu, Y. Zhu, Photo corrosion inhibition and enhancement of photocatalytic activity for ZnO via hybridization with C60, Environ. Sci.Technol. 2008, 21, 8064.

[5] C. Ren, C. Beifang, Y. Min, Wu, J. Xu, Z. Fu, T. Guo, Y. Zhao,C. Zhu, Synthesis of Ag/ZnO nanorods array with enhanced photocatalytic performance, J. Hazard. Mater. 2010, 182, 123.

[6] Y. Liu, H. Lv, S. Li, X. Xing, G. Xi, Preparation and photocatalytic property of hexagonal cylinder-like bipods ZnO microcrystal photocatalyst,  Dyes and Pigments, 2012, 95, 443-449.

[7] J.H. Bang, S. Kenneth, Applications of ultrasound to the synthesis of nanostructured materials, Advanced Materials, 2010, 22, 1039-1059.

[8] O. Akhavan, M. Mehrabian, K. Mirabbaszadeh, R. Azimirad, Hydrothermal synthesis of ZnOnanorod arrays for photocatalytic inactivation of bacteria, J. Phys. D: Appl. Phys. 2009, 22,225-305.

[9] J. Zhang, Y. Su, H. Wei, J. Wang, C. Zhang, J. Zhao, Z. Yang, M. Xu, L. Zhang, Y. Zhang,Double-nucleation hydrothermal growth of dense and large-scale ZnO nanorod arrays with high aspect ratio on zinc substrate for stable photocatalytic property, Mater. Lett. 2013, 107, 251.

[10]       W. Park, D. Hl Kim, S-W. Jung, Gyu-Chul Yi, Metal organic vapor-phase epitaxial growth of vertically well-aligned ZnO nanorods, Applied Physics Letters, 2002, 80, 4232.

[11]       Q. X. Zhao, P. Klason, M. Willander, Growth of nanostructures by vapor liquid solid method,Appl. Phys. A, 2007, 88, 27-30.

[12]       M. H. Huang, Y. Wu, H. Feick, N. Tran, E .Weber, P. Yang, Catalytic Growth of Zinc Oxide Nanowires by Vapor Transport, Adv. Mater., 2001, 13, 113-116.

[13]       x. Sun, G. M. Fuge, M. N. R. Ashfold, Growth of aligned ZnO nanorods arrays by catalysis-free pulsed laser deposition methods, Chem. Phys. Lett. 2004, 396, 21-26.

[14]       J.Wu, S. C. Liu, Low-Temperature Growth of Well-Aligned ZnO Nanorods by ChemicalVapor Deposition, Adv .Mater., 2002, 14, 215-218.

[15]       W. I. Park, D. H. Kim, S.W. Jung G. C. Yi, Metal organic vapor-phase epitaxial growth ofvertically well aligned ZnO nanorods, Appl. Phys. Lett., 2002, 80, 4232-4234.

[16]       H. D. Yu, Z. P. Zhang, M. Y. Han, X. T. Hao, F. R. Zhu, A general low-temperature route for large-scale fabrication of highly oriented ZnO nanorod/nanotube arrays, J. Am. Chem.Soc. 2005, 127, 2378-2379.

[17]       J. X. Wang, X. W. Sun, Y. Yang, H. Huang, Y. C. Lee, O. K. Tan, L. Vayssieres, Hydrothermally grown oriented ZnO nanorod arrays for gas sensing applications, Nanotech. 2006, 19, 4995.

[18]        A. Wei, X.W. Sun, J. X. Wang, Y. Lei, X. P. Cai, Chang Ming Li, Z. L. Dong, W. Huang, Enzymatic glucose biosensor based on ZnO nanorod array grown by hydro thermal decomposition, Appl. Phys. Lett. 2006, 12, 123902.

[19]       M. Guo, P. Diao, S. Cai, Hydrothermal growth of well-aligned ZnO nanorod arrays: Dependence of morphology and alignment ordering upon preparing conditions, SolidState Chem. 2005, 178, 1864.

[20]       A. Bakin, A. El-Shaer, A. CheMofor, M. Kreye, A. Waag, F. Bertram, J. Christen, M.Heuken, J. Stoimenos, MBE growth of ZnO layers on sapphire employing hydrogen peroxide asan oxidant, J. Cryst. Growth, 2006, 287, 7-11.

[21]       O. Akhavan, R. Azimirad, S. Safa, M. M. Larijani, Visible light photo-induced anti bacterial activity of CNT–doped TiO2 thin films with various CNT contents, J. Mater. Chem. 2010, 20,7386.

[22]       B.D. Cullity, "X-ray Diffraction." Addison-Wesley Publishing Company, 1956, 204, 158-159.

[23]       O. Akhavan, M. Mehrabian, K. Mirabbaszadeh, R. Azimirad, Hydrothermal synthesis of ZnO nanorod arrays for photocatalytic inactivation of bacteria, J. Phys. D: Appl. Phys. 2009, 42, 225305.

[24]       M. Breedon, C. Rix, K. Kalantar-zadeh, Seeded Growth of ZnO Nanorods from NaOH Solutions, Mater.Lett. 2009, 63, 249-251.

[25]       M.A. Abbasi, Y. Khan, S. Hussain, O. Nur, M. Willander, Anions effect on the low temperature growth of ZnO nanostructures, Vacuum, 2012, 86, 1998-2001.

[26]       B. J. Lawrie, R. F. Haglund, R. Mu, Enhancement of ZnO photoluminescence by localized and propagating surface plasmons, Opt. Express, 2009, 17, 2565-2572.

[27]       Y.G. Wang, S.P. Lau, H.W. Lee, S.F. Yu, B.K. Tay, X.H. Zhang, H.H. Hng, Photoluminescence study of ZnO films prepared by thermal oxidation of Zn metallic films in air,J. Appl. Phys., 2003, 94, 354–358.

[28]       R.N. Gayen, R. Bhar, A.K. Pal, Synthesis and characterization of vertically aligned ZnO nanorods with controlled aspect ratio, Indian J. pure and appl. Phys., 2010, 48, 385-393.

[29]       G.Srinivasan, J.Kumar, Effect of Mn doping on the microstructures and optical properties ofsol-gel derived ZnO thin films , J. Cryst. Growth, 2008, 310, 1841–1846.

[30]       L. Xu, X. Li, J. Yuan, Effect of K-doping on structural and optical properties of ZnO thin films, Super lattices Micro struct., 2008, 44, 276-281.

[31]       M. Vishwas, K. Narasimha Rao, K. V. Gowda, R. P. S. Chakradhar, Effect of sintering on optical, structural and photoluminescence properties of ZnO thin films prepared by sol–gelprocess, Spectrochim. Acta, Part A. 2010, 77, 330-333.

[32]       H. C. Genuino, D. T. Horvath, C. K. King'ondu, G. E. Hoag, J. B. Collins, Steven L. Suib, Effects of visible and UV light on the characteristics and properties of crude oil-in-water (O/W) emulsions, Photochemical & Photo biological Sciences, 2012, 11, 692-702.

[33]       S.W. Xue, X.T. Zu, W.G. Zheng, H.X. Deng, X. Xiang, Effects of Al doping concentration on optical parameters of ZnO:Al thin films by sol–gel technique, Physica B, 2006, 381, 209–213.

[34]       S. Ilican, Y. Caglar, M. Caglar, F. Yakuphanoglu, Structural, optical and electrical properties of F-doped ZnO nanorod semiconductor thin films deposited by sol–gel process.Appl. Surf. Sci., 2008, 255, 2353–2359.

[35]       M. Naser, S. Zaliman, Al-DouriYarub, “Investigation of the absorption coefficient, refractive index, energy band gap, and film thickness for Al0. 11Ga0. 89N, Al0. 03Ga0. 97N,and GaN by optical transmission method”, International Journal of Nano electronics and Materials, 2009, 2, 189-195.

[36]       M. Dutta, S. Maridha, D. Basak, Effect of sol concentration on the properties of ZnO thin films prepared by sol–gel technique Appl. Surf. Sci., 2008, 254, 2743–2747.

[37]       A. Moustaghfir, E. Tomasella, S.B. Amor, M. Jacquet, J. Cellier, T. Sauvaget, Structural and optical studies of ZnO thin films deposited by rf magnetron sputtering: influence of annealing, Surf. Coat. Technol., 2003, 174, 193-196.

[38]       X. Liu, L. Pan, Q. Zhao, T. Lv, G. Zhu, T. Chen, T. Lu, Z. Sun, C. Sun, UV-assiste dphotocatalytic synthesis of ZnO–reduced graphene oxide composites with enhanced photocatalytic activity in reduction of Cr(VI), Chemical Engineering Journal, 2012, 183, 238-243.

[39]       D. Li, H. Haneda, Morphologies of zinc oxide particles and their effects on photocatalysis, Chemosphere, 2003, 51, 129-137.