ZnO nanopowders were synthesized via microwave assisted hydrothermal method at different precursor solution molarities. For this, the aqueous solutions of zinc aceatate dihydrate and sodium hydroxide were prepared at different molarity as precursor materials. The synthesized ZnO nanopowders were further calcined in air at 500oC for 2 h. The effects of different precursor solution molarity on the crystalline structure of the ZnO nanopowders were investigated by X-ray diffraction study. Field emission scanning electron microscope was used to analyze the surface morphology of the ZnO nanopowders. As the NaOH solution molarity increases, the rod-like structure of ZnO begins to be seen. The optical band gap values of the ZnO nanopowders were also determined by reflectance measurements.  

Keywords - ZnO, nanorod, microwave assisted hydrothermal method, precursor molarity, FESEM

[1] S. Chala, N. Sengouga, F. Yakuphanoglu, S. Rahmane, M. Bdirina, I. Karteri, “Extraction of ZnO thin film parameters for modeling a ZnO/Si solar cell” Energy, vol. 164, pp. 871–880, Dec. 2018.
[2] L. Zhu, W. Zeng, “Room-temperature gas sensing of ZnO-based gas sensorˮ Sensors and Actuators A: Physical, vol. 267, pp.242-261, Nov. 2017.
[3] T. Chen, M. H. Wang, H. P. Zhang, Z. Y. Zhao, T. T. Liu, “Novel synthesis of monodisperse ZnO-based core/shell ceramic powders and applications in low-voltage varistorsˮ Materials & Design, vol. 96, pp. 329-334, Apr. 2016.
[4] S. Ilican, K. Gorgun, S. Aksoy, Y.Çağlar, M. Çağlar,“Fabrication of p-Si/n-ZnO:Al heterojunction diode and determination of electrical parametersˮ Journay of Molecular Structure, vol.1156, pp. 675-683, Mar. 2018.
[5] H. Huang, Q. Zhao, K. Hong, Q. Xu, X. Huang, “Optical and electrical properties of N-doped ZnO heterojunctionˮ Physica E: Lowdimensional Systems and Nanostructures, vol.57, pp. 113-117, Mar. 2014.
[6] Y. Çaglar, M. Çaglar, S. Ilican, S. Aksoy, F. Yakuphanoğlu, “ Effect of channel thickness on the field effect mobility of ZnO-TFT fabricated by sol gel processˮ Journal of Alloys and Compounds, Vol. 621, pp. 189-193, Feb. 2015.
[7] S. Park, “Enhancement of hydrogen sensing response of ZnO nanowires for the decoration of WO3 nanoparticlesˮ Materials Letters, vol. 234, pp. 315-318, Jan. 2019.
[8] R. Yatskiv, J. Grym,“Luminescence properties of hydrothermally grown ZnO nanorodsˮ Superlattices and Microstructure, vol. 99, pp. 214-220, Nov. 2016.
[9] A. O. Dikovska, G. B. Atanasova, G. V. Avdeev, N. N. Nedyalkov, “Synthesis and characterization of ZnO nanostructures on noble-metal coated substratesˮ Applied Surface Science, vol. 374, pp. 65-70, June 2016.
[10] P. Samadipakchin, H. R. Mortaheb, A. Zolfaghari, “ ZnO nanotubes: Preparation and photocatalytic performance evalutionˮ Journal of Photochemistry and Photobiology A: Chemistry, vol. 337, pp. 91-99, Mar. 2017.
[11] E. Praveen, K. Jayakumar, “Sensitivity enhancement of mechanical sensing element via self-assembled ferroelectric ZnO nanoflowersˮ Materials Chemistry and Pyhsics, vol. 223, pp. 190-195, Feb. 2019.
[12] A. O. Juma, A. Matibini, “Synthesis and structural analysis of ZnONiO mixed oxide nanocomposite prepared by homogeneous precipitationˮ Ceramic International, vol. 43, pp.15424-15430, Dec. 2017.
[13] A. Moulahi, F. Sediri, “Controlled synthesis of nano-ZnO via hydro/solvothermal process and study of their optical propertiesˮ Optik, vol. 127, pp. 7586-7593, Oct. 2016.
[14] Z. N. Kayani, M. Anwar, Z. Saddige, S. Riaz, S. Naseem, “Biological and optical properties of sol-gel derived ZnO using different percentages of silver contentsˮ Colloids and Surfaces B: Biointerfaces, vol. 171, pp. 383-390, Nov. 2018.
[15] G. Byzynski, A. P. Pereira, D. P. Volanti, C. Ribeiro, E. Longo, “ High-performance ultraviolet-visible driven ZnO morpholgies photocatalyst obtained by microwave-assisted hydrothermal methodˮ Journal of Photochemistry and Photobiology A: Chemistry, vol. 353, pp. 358-367, Feb. 2018.
[16] A. B. Murphy, “Band-gap determination from diffuse reflectance measurements of semiconductor films, and application to photoelectrochemical water-splitting Sol. Energy Mater. Sol. Cells vol. 91, pp. 326–1337,
 2007