One-dimensional Zno Nanostructures Hydrothermal Preparation And Its Luminescent Properties

Nanocone arrays,nanopropeller arrays,cone-,bullet-,and short rod-like nanocrystals of zinc oxide were directly synthesized on Zn foil through a simple hydrothermal method.ZnO nanorod arrays were prepared by heating zinc foil covered with ZnCl₂ solution in air.The influence of the reaction temperature,time,and precursor concentration on the size and shape of the as prepared ZnO nanostructures and their photoluminescence spectra have been studied.The possible formation mechanisms of these ZnO nanostructures were also proposed.These results would provide a base for research of physical and chemical properties of ZnO nanostructures and their applications in photonic,electronic,solar cells,sensing and photocatalysis,etc.(1) Large-scale oriented ZnO nanocone arrays were directly grown on zinc substrate through a hydrothermal reaction of Zn foil with n-butylamine aqueous solution(3 mol/L) at 100-180℃for 12 h.The synthesized products were characterized with X-ray diffraction,Raman spectra,scanning electron microscopy and transmission electron microscopy.The results showed that the ZnO nanocones were single crystalline with the wurtzite structure and grown alone the[0001]direction. The diameter of nanocones is decreased with increasing the reaction temperature.A possible growth mechanism was also proposed to account for the formation of the ZnO nanocone arrays.The photoluminescence spectra of the ZnO nanocone arrays was studied at room temperature,two UV emission bands at 377 and 396 nm assigned to free exciton emission and exciton-exciton collision, respectively,and phonon replicas associated with 2-E₂ phonon were observed in the PL spectra.(2) Zinc oxide nanopropeller arrays were fabricated on zinc foil via a hydrothermal reaction of Zn foil with 4-8 mol/L aqueous ammonia at 100℃for 18 hours.The synthesized products were single crystalline ZnO with the wurtzite structure.The possible formation mechanism was discussed.(3) Cone,bullet and rod-like ZnO nanocrystals were prepared via a hydrothermal reaction of Zn(CH₃COO)₂ with zinc foil,the bullet-like nanocryatals was prepared for the first time.The control over these ZnO nanosized crystals with different shapes was achieved by adjusting the reaction temperature and time.The as prepared products were single crystalline ZnO with the wurtzite structure.The photoluminescence spectra exhibit a strong ultraviolet emission at 388 nm and a weak blue emission peaking at 461 nm,the UV and blue emissions corresponded to the free exciton emission from the wide band gap of ZnO and related intrinsic defect structures of ZnO,respectively. The possible growth mechanism was also discussed.(4) Well-aligned ZnO nanorod arrays were directly grown on zinc foil by heating zinc foil coved with ZnCl₂ solution in air at 400℃for 1 hour.The products were characterized by scanning electron microscopy,transmission electron microscopy and X-ray powder diffraction.The results showed that the ZnO nanorods were single crystalline with the wurtzite structure,the diameters and length were 450～550 nm and 8μm,respectively.A possible mechanism was also proposed to account for the formation of ZnO nanorod arrays.The photoluminescence spectra of the ZnO nanorod arrays was studied at room temperature,an intense UV emission at 397 nm and a weak, broader blue-green emission peaking at 490 nm were observed.The UV and blue-green emissions corresponded to the near band-edge emission of the wide band-gap ZnO and related intrinsic defect structures of ZnO,respectively.