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The thickness of ZnO thin films was measured using surface profiler (Dektak 150+).
The ZnO thin film was subsequently deposited onto the cleaned glass using high purity (99.999%) ZnO target.  
This phenomenon can be explained by the fact that the number of the sputtered ZnO molecules at the target surface increases due to the enhancement of bombardment by argon ions as the RF power increased [15].
Regardless of the RF power applied, all film shows a peak at 2q∼34.4° that correspond to the (002) hexagonal wurtzite structure of ZnO with JCPDS Card no. 36-1451.
Figure 2: XRD pattern of ZnO thin film with various RF power.

The ZnO has a wurtzite structure with the standard JCPDS card no. 36-1451 and cell parameters of a = 0.3250 nm, c = 0.5207 nm and space group: P63mc (186).
The MgO exhibits a cubic structure with the standard JCPDS card no. 77-2179 and cell parameter of a = 0.4211 nm and space group: Fm-3m (225).
The lattice spacing of 0.1624 and 0.2475 nm corresponds to the d-spacing of the (110) and (101) planes, respectively, can be ascribed to the wurtzite ZnO with the standard JCPDS card no. 36-1451.
Simultaneously, the lattice spacing of 0.1492 and 0.2109 nm corresponds to the d-spacing of the (220) and (200) planes, respectively, and can be ascribed to the cubic MgO with the standard JCPDS card no. 77-2179.
As pH increases, the number of negatively charged surface sites increases and the number of positively charged surface sites decreases.

All the diffraction peaks in Fig. 1 can be perfectly indexed as pure monoclinic phase of ZnWO4 [space group: T2/c [13]] with lattice constants of a = 4.691 Å, b = 5.720 Å and c = 4.925 Å (JCPDS card No. 15-0774).
All the diffraction peaks in Fig.2 can be perfectly indexed as pure hexagonal phase of ZnO [space group: P63/mc[186]] with lattice constants of a = b =3.249 Å, c = 5.206 Å (JCPDS card No. 36-1451).
When excited at 262 nm, the ZnO product exhibited at 396 nm and 510 nm.
At the very beginning, the direct mixing of the two solutions led to the formation of a large number of amorphous ZnWO4 particles.
When excited at 262 nm, the ZnO product exhibited at 396 nm and 510 nm.

The final product was numbered as ZnO-1.
Following the same treatment, the final product was numbered as ZnO-2.
All the diffraction peaks of the samples are consistent with pure ZnO (JCPDS Card Files, NO. 05-0664), where lattice constant a=0.3249 nm, c= 0.5205 nm.
Fig. 3 The XRD of two ZnO Powders Fig. 4 shows the DSC-TGA for the precursors of the ZnO samples.
The ZnO nanoparticles (ZnO-1) prepared by nucleation/crystallization separation shows better response compared with the sample (ZnO-2) prepared by co-precipitation.

From Fig. 1(a), one can see clearly that the products consist of a large number of sheet-like microtructures, which has two-dimensional size of tens to one hundred of micrometers.
(a) TEM and (b) HRTEM images of as-synthesized ZnO/graphene composites inserted with an enlarged HRTEM image of the ZnO nanoparticle.
The ZnO peaks are indexed and compared with standard file (JCPDS card No. 36-1451), indicates that the as-synthesized composites has ZnO components corresponding to hexagonal wurtzite structure.
The Raman spectrum of the ZnO/graphene composites is shown in Fig. 3(b), which shows Raman signals from both ZnO and GO.
SEM characterization indicate that the composites consist of a large number of sheet-like microtructures.

In the preparation of nanometer ZnO materials, people have carried out extensive and fruitful research and ZnO nanorods, ZnO nano-films[8], ZnO nano-belts[9], ZnO nano-wires array[10], ZnO nano-comb[11], ZnO nano-ring[12], ZnO nano-helix[13] have been reported.
The synthesis temperature was 220℃.It can be seen that all of the diffraction peaks can be indexed within experimental error as hexagonal ZnO phase with lattice constants a =0.32508 nm and c = 0.52069nm by comparison with the data from JCPDS cards No.36-1451.
▽—ZnO Fig.1.
Zn(OH)2 decompose to produce ZnO nuclei.
The concentration of growth units of [Zn(OH)4]2- and nucleation units of Zn(OH)2 were low, so the initial number of ZnO nuclei were less.

Based on Fig. 1, it was evident that the calcined ZnO nanoparticles exhibited the hexagonal wurtzite structure in good agreement with the JCPDS-card number of 36-1451.
The calcined samples showed pure ZnO without any secondary phase.
Table 1 Structural, optical and photocatalytic properties of ZnO nanoparticles.
The morphology of ZnO powders is presented in Fig. 2.
The pure ZnO was obtained after calcining at 600 oC in air for 1 h.

Compare infrared absorption band of as-sample with ionic liquid, it can be found that they have the same specific absorption peak, but the strength has been weakened and the peak moving toward the lower wave number.
The infrared spectrum of the power being compared with the spectrum of ionic liquid, it can be seen that the strength of ionic liquid has been weakened and the peak moving toward the lower wave number.
The reaction between ILs and ZnO lead to red shift of ILs.
Fig.2 XRD pattern of the ZnO nanorod sample All the peaks are indexed to typical hexagonal wurtzite structure ZnO, with calculated cell parameters a=3.249 Å and c=5.191 Å, consistent with the standard values for bulk ZnO (JCPDS card No. 79-0205).
In addtion, the wurtzite-structured ZnO crystal is described schematically as a number of alternating planes composed of tetrahedral coordinated O2- and Zn2+ ions, stacked alternatively along the c-axis.

Then the WO3/ZnO composite photocatalysts were obtained.
Characteristic peaks are observed for all diffraction patterns, which are indexed to the standard card (JCPDS card no. 36-1451).
The absorption plots show that both ZnO and WO3/ZnO exhibit strong absorption in the ultraviolet light region Fig.1(C) and compositing WO3 enhances the ultraviolet light absorption of the ZnO.
(C) (B) Fig.1 (A) XRD patterns of photocatalysts: (a) pure ZnO and (b) WO3/ZnO; (B) SEM picture of WO3/ZnO; (C) UV-Vis absorption spectra of photocatalysts: (a) ZnO; (b) WO3/ZnO. 3.2 Photocatalytic oxidation desulfurization 3.2.1.
So, the optimal amount of WO3/ZnO is 0.02 g in a 20 mL reaction system.

This is because large numbers of hydroxyl groups exist on the wet particle surface.
Fig. 2.Density distribution of ZnO nanoparticles.
UV spectrum of ZnO nanoparticles solution in ethanol.
X-ray diffraction peaks of ZnO nanoparticles agreed with the reported JCPDS data (JCPDS Card No. 36-1451) and compared this results with data published in many articles.
Fig. 5.XRD pattern of ZnO nanoparticles.