On the basis of the SEM images, the utilization of different solvents evidently resulted in different diameters of the synthesized ZnO NRs. The ZnO NRs that were synthesized using 2-ME provided the smallest diameter, whereas those synthesized with EtOH displayed the largest diameters. The size of the ZnO NRs in diameter is strongly dependent on the grain size of the ZnO seed layer [29]. As the grain size of the seed layer increases, larger sizes of ZnO NRs in diameter are produced. Figure 3 SEM images of ZnO NRs prepared with different solvents: (a) MeOH, (b) EtOH, (c) IPA, and (d) 2-ME. XRD characterization PX-478 The crystal structure

and microstructure of the as-synthesized ZnO NRs were studied through XRD. Figure 4 shows the XRD patterns of the ZnO NRs that were synthesized on the silicon substrate with the aqueous solutions and different seeded layers. All of the diffraction peaks are consistent with the standard card Joint Committee on Powder Diffraction

Standards (JCPDS) 36–1451. The peak intensities were measured in the range of 30° to 70° at 2θ. The result showed that the ZnO NRs that were prepared through the hydrothermal growth method presented a remarkably strong diffraction peak at the (002) plane, which is located between 34.5° and 34.6° [30, 31]. This finding indicated that all of the ZnO samples possessed pure hexagonal wurtzite GSK3326595 structures with high c-axis orientations. Figure 4 X-ray diffraction patterns of ZnO NRs with hydrothermal growth selleck chemicals llc process: (a) MeOH, (b) EtOH, (c) IPA, and (d) 2-ME. Among the peaks, the ZnO NRs that were prepared with EtOH resulted in the narrowest peak of full width at half maximum (FWHM). By contrast, the ZnO NRs that were prepared with 2-ME showed the largest peak of FWHM. Simultaneously,

the 2-ME solvent also showed the highest peak intensities on the (002) plane. Compared with the standard diffraction peaks of ZnO, the clear and sharp peaks indicated that the ZnO NRs possessed an excellent crystal quality, with no other diffraction peaks and characteristic peaks of impurities in the ZnO NRs. Therefore, all of the diffraction peaks were similar to those of the bulk ZnO. Table 1 shows the ZnO XRD data from the JCPDS card compared with the measured ZnO XRD results. Table 1 XRD parameters of ZnO NRs hkl 2θ(°) JCPDS Observed MeOH EtOH IPA see more 2-ME 100 32.02 31.98 31.98 32.10 31.76 002 34.52 34.62 34.64 34.68 34.42 101 36.46 36.52 36.5 36.58 36.25 102 47.76 47.8 47.74 47.8 47.53 110 56.94 56.78 56.96 56.86 56.60 103 63.08 63.06 63.08 63.06 62.86 The average grain size of the ZnO NRs was estimated using Scherrer’s formula [32]: (1) where κ is the Scherrer constant, which is dependent on the crystallite shape and can be considered as 0.9 [33, 34]; λ is the X-ray wavelength of the incident Cu Kα radiation, which is 0.154056 nm [35]; FWHM is the full width at half maximum of the respective peak; and θ represents the diffraction peak angle.