(NO 3) 2 ‧6H 2 O, ZnO-based nanowires, growth time ZnO-based nanomaterials can be used as sensors for different applications, including gas and ultraviolet (UV) ray sensors. To grow ZnO nanowires by the hydrothermal method, a ZnO seed layer was prepared by a sputtering method to deposit ZnO films on SiO 2 /Si substrates of about 200 nm thickness. Next, Zn(NO 3) 2 ‧6H 2 O and C 6 H 12 N 4 were used as reagents, and DI water was used as a solvent, and they were mixed to the designed compositions. We found that when Zn(NO 3) 2 ‧6H 2 O and C 6 H 12 N 4 were used as reagents to grow ZnO nanostructured materials, growth temperature, the concentration of the diluted solution, growth time, and the position of the substrates were four important factors affecting the synthesis results. The surface morphologies of ZnO nanowires were observed by field-emission scanning electron microscopy (FESEM), and crystalline phases were analyzed using X-ray diffraction (XRD) patterns. The FESEM images and XRD patterns were used to determine the effects of synthesis parameters on the morphologies and crystalline properties of the grown nanostructured materials. First, we found that 100 ℃ was the optimum synthesis temperature for growing pure ZnO nanowires, because ZnO-based nanowires could be successfully synthesized at different concentrations of Zn(NO 3) 2 ‧6H 2 O and C 6 H 12 N 4 and different synthesis times. The effects of growth time, the position of the substrates on the carry sheet glass, and concentrations of Zn(NO 3) 2 ‧6H 2 O and C 6 H 12 N 4 on the growth of nanostructured materials were also investigated.

ZnO films with a thickness of ~200 nm were deposited on SiO2/Si substrates as the seed layer. Then Zn(NO3)2-6H2O and C6H12N4 containing different concentrations of Eu(NO3)2-6H2O or In(NO3)2-6H2O were used as precursors, and a hydrothermal process was used to synthesize pure ZnO as well as Eu-doped and In-doped ZnO nanowires at different synthesis temperatures. X-ray diffraction (XRD) was used to analyze the crystallization properties of the pure ZnO and the Eu-doped and In-doped ZnO nanowires, and field emission scanning electronic microscopy (FESEM) was used to analyze their surface morphologies. The important novelty in our approach is that the ZnO-based nanowires with different concentrations of Eu3+ and In3+ ions could be easily synthesized using a hydrothermal process. In addition, the effect of different concentrations of Eu3+ and In3+ ions on the physical and optical properties of ZnO-based nanowires was well investigated. FESEM observations found that the undoped ZnO nanowires could be grown at 100 °C. The third novelty is that we could synthesize the Eu-doped and In-doped ZnO nanowires at temperatures lower than 100 °C. The temperatures required to grow the Eu-doped and In-doped ZnO nanowires decreased with increasing concentrations of Eu3+ and In3+ ions. XRD patterns showed that with the addition of Eu3+ (In3+), the diffraction intensity of the (002) peak slightly increased with the concentration of Eu3+ (In3+) ions and reached a maximum at 3 (0.4) at%. We show that the concentrations of Eu3+ and In3+ ions have considerable effects on the synthesis temperatures and photoluminescence properties of Eu3+-doped and In3+-doped ZnO nanowires.

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