**3. Results and discussion**

The cross section of the samples was observed and the thickness of the TiO2 films grown on borosilicate was measured. **Figure 6a** shows the FE-SEM image of the 280 nm thick film, revealing the formation of a dense film. The AFM image (**Figure 7a**) shows that the film presents homogeneous morphology, composed of rounded grains of 124 nm mean size and of 19 nm RMS roughness, which can be considered favorable for photocatalytic applications [37], since it facilitates the contact of the adsorbed substances with the film, increasing its photocatalytic efficiency [46].

**Figure 6.** FE-SEM fracture images for TiO2 films: (a) thickness of 280 nm and (b) thickness of 468 nm.

the species near the solid surface. A *Thermo Scientific, K-Alpha model* equipment was used. After the acquisition of the high-resolution spectra, the deconvolution was done using the algorithm Smart in the software Avantage®. The binding energies were corrected considering

of methyl orange dye (MO, 5 mg L−1) in an aqueous solution (pH = 2), under UV light irradiation (Sankyo Denki Co., Ltd., 15 W, λ = 352 nm). The changes in the MO concentration were monitored using a UV-vis spectrophotometer (*Global Trade Technology*). For this purpose, the films were placed in a reactor (**Figure 5**) containing 40 mL of the dye solution and were illu-

The photocatalytic reactor consists of a glass chamber containing the MO dye solution to be

ponents of the photoreactor were arranged in a box to prevent loss of photons and to protect users against the emitted UV radiation. The distance between the photocatalyst and the UV

on borosilicate was measured. **Figure 6a** shows the FE-SEM image of the 280 nm thick film, revealing the formation of a dense film. The AFM image (**Figure 7a**) shows that the film presents homogeneous morphology, composed of rounded grains of 124 nm mean size and of 19 nm RMS roughness, which can be considered favorable for photocatalytic applications [37], since it facilitates the contact of the adsorbed substances with the film, increasing its

The cross section of the samples was observed and the thickness of the TiO2

catalyst supported in borosilicate, and the source of radiation. The com-

films were estimated by measuring the degradation

/20 wt.% O2

) was bubbled into

films grown

the C1s reference peak at 214.8 eV.

The photocatalytic activities of the TiO2

**Figure 5.** Schematic diagram of the photocatalytic reactor.

216 Titanium Dioxide - Material for a Sustainable Environment

minated by two tubular UV lamps for 300 min. Synthetic air (N2

**2.2. Photocatalytic tests**

the solution during the tests.

degraded, the TiO2

lamps was set at 25 cm.

**3. Results and discussion**

photocatalytic efficiency [46].

**Figure 7.** AFM images of TiO2 film with thickness of 280 nm: (a) topography and (b) 3D image.

The RMS (*Root Mean Square*) roughness expresses the values of a roughness profile that moves away from the midline, in other words, it is the standard deviation of the mean height *Z* [47], being mathematically expressed as:

$$RMS = \sqrt{\frac{\sum\_{i=1}^{N} (Z\_{\mathbb{N}} - Z)^2}{N - 1}} \tag{6}$$

where *N* is the number of peaks; *ZN* is the height of each peak; and *Z* is the mean height of *N* peaks.

The morphology of the surface of the TiO2 film grown with thickness of 468 nm (**Figure 8a**) presents a mean grain size of 214 nm and roughness values of the order of 16 nm (**Table 1**). It can be observed as a dense film with columnar structure (**Figure 6b**). Results presented by Krumdieck et al. [48] showed that the increase of the thickness of the films caused a decreased of the roughness, similar trend with the values exhibited in the present work. The results clearly show that the increase of the growth time (**Table 1**) caused an increase in the film thickness, as evidenced by Antunes et al. [49].

**Figure 8.** AFM images of TiO2 film with thickness of 468 nm: (a) topography and (b) 3D image.


**Table 1.** Characteristics of TiO2 films grown by MOCVD on borosilicate.

**Figure 9** shows the XRD patterns of TiO2 films grown at 400°C with different thickness. The characteristic peaks correspond to the crystalline anatase phase (JCPDS 21–1272).

**Figure 10** shows the XPS spectra of the 280 nm TiO2 thin film. The surface of the films contains high quantities of Ti and O elements and C (**Figure 10a**). According to Liu et al. [50] and Babelon et al. [51], the presence of C1s peak was ascribed to the residual carbon from the metalorganic precursor and to surface pollution provoked for the sample exposition to air before the XPS experiments. Ti2p spectrum (**Figure 10b**) appeared at 459.5 and 465.2 eV attributed, respectively, to Ti2p3/2 and Ti2p1/2 peaks of O─Ti─O in TiO2 [50, 52]. Bharti et al. [53] and Lin et al. [54] suggested that these peaks are consistent with Ti4+ in TiO2 lattice. The O1s spectrum (**Figure 10c**) reveals two peaks at 530.7 and 532.4 eV. The first one can be attributed to the oxygen present in the TiO2 lattice, and the other one represents the surface oxygen [52].

**Figure 11** exhibits the C/C0 graphs as a function of the time of exposure to UV radiation, where *C* represents the dye concentration at each time interval and *C*<sup>0</sup> is the initial concentration. The photolysis curve demonstrates that without the presence of the catalyst (TiO2 film) there was no degradation of the dye. The TiO2 film with thickness of 280 nm degraded 28% of MO dye for a total test time of 300 minutes while the TiO2 film with 468 nm of thickness, showed 69% of dye degradation in the same condition, that is, it was approximately 2.5× more efficient.

A large surface area is necessary for the light irradiation and the photocatalyst contacting with pollutant compound and, consequently, the photocatalysis efficiency of the TiO2 films

**Figure 10.** XPS spectra of the 280 nm TiO2

**Figure 9.** XRD patterns of the TiO2

films (a) survey; (b) Ti2p, and (c) O1s.

films grown on borosilicate at 400°C.

Titanium Dioxide Films for Photocatalytic Degradation of Methyl Orange Dye

http://dx.doi.org/10.5772/intechopen.75528

219

**Figure 9.** XRD patterns of the TiO2 films grown on borosilicate at 400°C.

**Figure 9** shows the XRD patterns of TiO2

218 Titanium Dioxide - Material for a Sustainable Environment

**Temperature of deposition** 

**Figure 8.** AFM images of TiO2

**Table 1.** Characteristics of TiO2

**[°C]**

attributed to the oxygen present in the TiO2

for a total test time of 300 minutes while the TiO2

oxygen [52].

**Figure 11** exhibits the C/C0

no degradation of the dye. The TiO2

**Figure 10** shows the XPS spectra of the 280 nm TiO2

**Growth time [min]**

characteristic peaks correspond to the crystalline anatase phase (JCPDS 21–1272).

films grown by MOCVD on borosilicate.

[53] and Lin et al. [54] suggested that these peaks are consistent with Ti4+ in TiO2

attributed, respectively, to Ti2p3/2 and Ti2p1/2 peaks of O─Ti─O in TiO2

photolysis curve demonstrates that without the presence of the catalyst (TiO2

*C* represents the dye concentration at each time interval and *C*<sup>0</sup>

tains high quantities of Ti and O elements and C (**Figure 10a**). According to Liu et al. [50] and Babelon et al. [51], the presence of C1s peak was ascribed to the residual carbon from the metalorganic precursor and to surface pollution provoked for the sample exposition to air before the XPS experiments. Ti2p spectrum (**Figure 10b**) appeared at 459.5 and 465.2 eV

**Film thickness** 

film with thickness of 468 nm: (a) topography and (b) 3D image.

**[nm]**

400 30 280 124 19 400 40 468 214 16

The O1s spectrum (**Figure 10c**) reveals two peaks at 530.7 and 532.4 eV. The first one can be

of dye degradation in the same condition, that is, it was approximately 2.5× more efficient.

A large surface area is necessary for the light irradiation and the photocatalyst contacting with pollutant compound and, consequently, the photocatalysis efficiency of the TiO2

films grown at 400°C with different thickness. The

**Mean grain size** 

**[nm]**

lattice, and the other one represents the surface

film with 468 nm of thickness, showed 69%

graphs as a function of the time of exposure to UV radiation, where

film with thickness of 280 nm degraded 28% of MO dye

thin film. The surface of the films con-

[50, 52]. Bharti et al.

**RMS roughness [nm]**

film) there was

films

is the initial concentration. The

lattice.

**Figure 10.** XPS spectra of the 280 nm TiO2 films (a) survey; (b) Ti2p, and (c) O1s.

**Author details**

**References**

2015;**121**:67-72

using TiO2

**170**:520-529

of dyes using TiO2

2012;**35**:889-894

Rodrigo Teixeira Bento and Marina Fuser Pillis\* \*Address all correspondence to: mfpillis@ipen.br

Pollution Research. 2017;**24**:1113-1121

(CCTM-IPEN/CNEN), Cidade Universitária, São Paulo, Brazil

photocatalysts. Comptes Rendus Chimie. 2015;**18**:23-31

Materials Science and Technology Center, Nuclear and Energy Research Institute

[1] Khaoulani S, Chaker H, Cadet C, Bychkov E, Cherif L, Bengueddach A, Fourmentin S. Wastewater treatment by cyclodextrin polymers and noble metal/mesoporous TiO2

Titanium Dioxide Films for Photocatalytic Degradation of Methyl Orange Dye

http://dx.doi.org/10.5772/intechopen.75528

221

[2] Tsoumachidou S, Lambropoulou D, Poulios I. Homogeneous photocatalytic oxidation of UV filter paraaminobenzoic acid in aqueous solutions. Environmental Science and

[3] Josephine GAS, Nisha UM, Meenakshi G, Sivasamy A. Nanocrystalline semiconductor doped rare earth oxide for the photocatalytic degradation studies on acid blue 113: A diazo compound under UV slurry photoreactor. Ecotoxicology and Environmental Safety.

[4] Horáková M, Klementová S, Kriz P, Balakrishna SK, Spatenka P, Golovko O, Hájková P, Exnar P. The synergistic effect of advanced oxidation processes to eliminate resistant

[5] Akpan UG, Hameed BH. Parameters affecting the photocatalytic degradation of dyes

[6] Reza KM, Kurny ASW, Gulshan F. Parameters affecting the photocatalytic degradation

[7] Silva MC, Corrêa AD, Torres JA, Amorim MTSP. Descoloração de corantes industriais e efluentes têxteis simulados por peroxidase de nabo (Brassica campestre). Química Nova.

[8] Jin XC, Liu GQ, Xu ZH, Tao WY. Decolorization of a dye industry effluent by *Aspergillus* 

[9] Wang C, Yediler A, Linert D, Wang Z, Kettrup A. Toxicity evaluation of reactive dyestuffs, auxiliaries and selected effluents in textile finishing industry to luminescent bac-

[10] Kasic H, Bozic AL, Koprivanace N. Heterogeneous photocatalytic treatment of textile dye effluent containing Azo dye: Direct Crysophenine G. Der Chemica Sinica. 2011;**2**:37-46

*fumigatus* XC6. Applied Microbiology Biotechnology. 2007;**74**:239-243

teria *Vibrio fischeri*. Chemosphere. 2002;**46**:339-344

: A review. Applied Water Science. 2017;**7**:1569-1578


chemical compounds. Surface & Coatings Technology. 2014;**241**:154-158

**Figure 11.** MO dye concentration as a function of the time of exposure to UV irradiation (λ = 352 nm) with and without the presence of TiO2 films grown by MOCVD.

is intensified [55, 56]. The increase in thickness is also favorable for the photocatalytic performance, since thinner films have a higher electron recombination rate than thicker films [57].
