Self-aligned nanocrystalline ZnO hexagons by facile solid-state and co-precipitation route
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In this study, we report the synthesis of well-aligned nanocrystalline hexagonal zinc oxide (ZnO) nanoparticles by facile solid-state and co-precipitation method. The co-precipitation reactions were performed using aqueous and ethylene glycol (EG) medium using zinc acetate and adipic acid to obtain zinc adipate and further decomposition at 450 °C to confer nanocrystalline ZnO hexagons. XRD shows the hexagonal wurtzite structure of the ZnO. Thermal study reveals complete formation of ZnO at 430 °C in case of solid-state method, whereas in case of co-precipitation method complete formation was observed at 400 °C. Field emission scanning electron microscope shows spherical morphology for ZnO synthesized by solid-state method. The aqueous-mediated ZnO by co-precipitation method shows rod-like morphology. These rods are formed via self assembling of spherical nanoparticles, however, uniformly dispersed spherical crystallites were seen in EG-mediated ZnO. Transmission electron microscope (TEM) investigations clearly show well aligned and highly crystalline transparent and thin hexagonal ZnO. The particle size was measured using TEM and was observed to be 50–60 nm in case of solid-state method and aqueous-mediated co-precipitation method, while 25–50 nm in case of EG-mediated co-precipitation method. UV absorption spectra showed sharp absorption peaks with a blue shift for EG-mediated ZnO, which demonstrate the mono-dispersed lower particle size. The band gap of the ZnO was observed to be 3.4 eV which is higher than the bulk, implies nanocrystalline nature of the ZnO. The photoluminescence studies clearly indicate the strong violet and weak blue emission in ZnO nanoparticles which is quite unique. The process investigated may be useful to synthesize other oxide semiconductors and transition metal oxides.
KeywordsZnO Hexagonal Nanostructured Semiconductor
The authors were grateful to University of Pune and UGC, Government of India for the financial assistance and Dr. Arun Andhale, Principal, Mahatama Phule Mavidyalaya, Pimpri Pune-411017 for providing facilities to carry out the above research. The authors also thank staff of Nanocrystalline Material laboratory of C-MET, Pune for many stimulating discussions and providing characterization facilities.
- Cullity B (1977) Elements of X-ray diffraction. Addison-Wesley, Reading MA, p 102Google Scholar
- JCPDS card No. 36.1451Google Scholar
- Khan Y, Durrani S, Mehmood M, Ahmad J, Riaz Khan M, Firdous S (2010) Low temperature synthesis of fluorescent ZnO nanoparticles. Appl Surf Sci 257(5):1756–1761 Google Scholar
- Lauf R, Bond W (1984) Fabrication of high-field zinc oxide varistors by sol–gel processing. Ceram Bull 63:278Google Scholar
- Lee N, Kim M, Chung I, Oh M (1991) Electrical characteristics and reheat-treatment effects in a ZnO varistor fabricated by two-stage heat-treatment. J Mater Sci 26:1126Google Scholar
- Manjula G, Nair M, Nirmala, Rekha K, Anukaliani A (2011) Structural, optical, photo catalytic and antibacterial activity of ZnO and Co doped ZnO nanoparticles. Mater Lett 65(12):1797–1800Google Scholar
- Silverstein R, Webster F (1997) Spectroscopic identification of organic compound, 6th edn. Wiley, New York, pp 81–97Google Scholar
- Thorat J, Kanade K, Nikam L, Chaudhari P, Kale B (2010) Nanostructured ZnO hexagons and optical properties. J Mater Sci 22(4):394–399Google Scholar
- Vanheusden K, Warren W, Seager C, Tallant D, Voigt JA, Gnade B (1996) Mechanisms behind green photoluminescence in ZnO phosphor powders. J Appl Phys 79:7983Google Scholar