Figure (2), illustrates the XRD patterns of pure TiO2 and the resulted Ag\TiO2 nanocomposite sintered at 450oC, recorded in the 2θ region 10o-80o. The patterns shown that the diffractions peaks at 25.3o, 37.96o, 48.24o, 54.90o, 55.16o, 62.86o,68.94o, 75.11o match up (101), (004), (200), (105), (211), (204), (116),(220) and (215) lattice plane of Anatase stage of TiO2, correspondingly. Regarding Figure (2 a), the diffracting peaks match up the TiO2 anatase stage (JCPSD Card: 21-1272) as shown in pure TiO2 with content (0% mol) of Ag. Besides, in the case of nanocomposite, the Ag content increase to (2-6 mol)% in addition to anatase phase, there is week intensity is observed and positioned at 2θ = 38.42o correspond to (111) reflection that because of high silver contents with FCC (Face Centered Cubic) stage as shown in Figure (2b,c,d) and shown that silver content had limited impact on the anatase phase at high contents . Hence, at high content of Ag (2-6%), interpreting the XRD develops the heterophase morphology of Ag\TiO2 nanocomposite, this could not be acknowledged in pure TiO2 because of the Ag’s zero content [21-24]. Since, each of such peaks gets indexed by Ag standardized XRD patterns (JCPSD card: 03-0931) and the anatase phase of TiO2 (JCPSD Card: 21-1272). While there are no peaks observed for rutile and brookite phase in the composite as well.For the estimation of nanoparticles in the composite, the average crystalline size id achieved by using the Scherer equation (1). As well as, in state of calculate the lattice constants (unite cell) of tetragonal TiO2 for the highest peaks, it's found that the lattice constant were estimated as shown in table (1).
Table1. Structural features of pure TiO2 and Ag\TiO2 nanocomposite
Samples
|
(hkl)
|
2θ (deg.)
|
FWHM β(deg.)
|
Crystallite size D(nm)
|
Pure TiO2
|
(101)
(004)
(200)
|
25.3o
37.8o
48.0o
|
0.5760
0.0900
0.1200
|
14.77
97.49
75.72
|
2% Ag- TiO2
|
(101)
(004)
(200)
(111)
|
25.5o
37.2o
48.2o
38.1o
|
0.0720
0.0900
0.5760
0.9600
|
118.20
97.31
15.79
9.15
|
4% Ag- TiO2
|
(101)
(004)
(200)
(111)
|
25.4o
37.9o
48.1o
38.4o
|
0.0900
0.0720
0.0900
0.0900
|
94.54
121.90
101
97.66
|
6% Ag- TiO2
|
(101)
(004)
(200)
(111)
|
25.2o
37.0o
48.1o
38.3o
|
0.8640
0.0900
0.0900
0.1488
|
9.84
97.26
101
59
|
Figure 3, illustrate the optical properties of synthesized pure TiO2 as well as Ag\TiO2 nanocomposites with different concentrations of Ag by UV.Vis spectroscopy. A strong absorption edge of pure TiO2 sample was located around ʎ=320 nm, which is set to transfer the bandwidth of anatase pure TiO2 sample [25]. In state of Ag doped TiO2 with different concentrations, shifting the absorbing edge of Ag\TiO2 nanocomposites was done to the lengthier wavelength, this causes more absorption of noticeable light in range (330-360) nm and this red shifting due to interaction of silver with TiO2 during the sol-gel method. Besides, The absorption red shift result in reduction the value energy gaps Eg of Ag\TiO2 nanocomposites as illustrated by the Figure 4(a,b,c,d), respectively due to addition Ag ions which result in delay the recombination rate and enhanced the effect of Ag\TiO2 nanocomposites in photocatalytic filed[26, 27].
From the results, the values of energy band gap for indirect allowed transition are agreement with previous work [28, 29]. Since, the response of noticeable light of the Ag\TiO2 nanocomposite had been prompted because of surface plasmon resonance of Ag upon TiO2 surface. Ag\TiO2 nanocomposite strengthened at 450oC reveal analogous spectra of optical absorbance because of the Ag existent on TiO2 sol-gel is cured at low temperature.
For the purpose of examining the conduct of the intermediate and function reaction sets existent in the synthesized pure TiO2 and Ag\TiO2 nanocomposite, FTIR spectra had been registered in 400-4000 cm-1 ranging as illustrated in Figure (5). A broad band appeared in the range of 3373-3676 cm-1 related to O-H extending vibrations besides weak band at 1635 cm-1 related to O-H bend vibrations of water molecule. The existence of Hydroxyl sets at the surface of samples has a significant part within photolytic applications. Besides, the bands at region of 2887 cm-1 plus 2347 cm-1 represented the symmetric as well as anti-symmetrical vibrations mode which attribute to the presence of surfactant. A widespread absorbing bands witnessed within 450 to 850 cm-1 ranging showed Ti-O bending mode of vibrations that improves the creation of metallic oxygen bond. In addition, presence peak at 800 cm-1 in state of Ag\TiO2 nanocomposite while there is no peak in pure TiO2 due to the Ti-O-Ag stretching vibrations of nanocomposite [22]. Moreover, the results of FTIR spectrum reveal the increasing concentrations for O-H bands of Ag\TiO2 nanocomposite because of the increasing of Ag content and lead to possible interaction of TiO2 with Ag species.
Figure 6 (a,b,s,d) shows the FESEM analysis of bare TiO2 plus Ag\TiO2 nanocomposite. Regarding to in Figure 6(a), The morphology of pure TiO2 NPs was annealed at 450oC result in forming non-spherical shape (like rhombus and aggregated particles) with long particles was about 0.5-1μm and average diameters are approximately about 100-500nm. In state of Ag\TiO2 nanocomposites with different concentrations of Ag contents, Figure 6 (b, c, d) shows the development of the produced Ag\TiO2 nanocomposite structure. The nanocomposite of Ag\TiO2 powder after the addition of Ag NO3 and annelid at 450oC results in decreasing pH and forming granular particles with less size, there will be interaction amid these particles and forming an amorphous aggregate as show in figure 6 (b,c). In state of Ag content 6% the Ag\TiO2 nanocomposite formed with less aggregation and smaller size as shown in figure 6(d).
According to the obvious discussion in the offered images, the calcined form at 450 oC and addition of HNO3 resulted to reduce the aggregated, growth of particles and affecting the size distribution [19, 30].
In state of EDX analysis, the results reveal increasing Ag content after addition Ag NO3 and calcined at 450oC for 4 h and forming Ag\TiO2 nanocomposite as shown in the figure 7 ( b,c,d) as compared with pure TiO2 figure 7 (a). The atomic rate of Ag, Ti, and O are also listed in Figure 7 (a,b,c,d). As illustrated by the figure, the content of Ag added to the solution was extremely depressed and the Ag ions were dispersed and migrated alongside with the grain limits toward the surface of TiO2. Also, it's suggested that Ag ions were perhaps present upon the surface of TiO2 anatase grains, creating the Ag-O-Ti bonds. This results agreement with previous work[31], who reported that addition low content of Ag ions, resulted in forming and lighting of Ag NPs.