International Research Journal of Applied and Basic Sciences
© 2015 Available online at www.irjabs.com
ISSN 2251-838X / Vol, 9 (5):648-655
Science Explorer Publications
Comparison of Ti-Ti and Ti-O bonds in nanosurfaces of rTiO2 (110) for Conversion
Dibenzodioxin to CO2
Akram salarvand , and Leila Mahdavian*
Department of Chemistry, Doroud Branch, Islamic Azad University, P.O. Box: 133. Doroud. Iran
*Corresponding Author email: Mahdavian_leila@yahoo.com
ABSTRACT: One of the very dangerous pollutants, which are produced by wet trash burning in our
cities, is dibenzodioxin, known as a carcinogenic material. The purpose of this study is eliminating
this pollutant and changing it into less dangerous material. Nanoparticles of titanium dioxide (TiO 2)
are a strong photo catalyst to change hydrocarbon compounds into carbon dioxide. In this study, this
pollutants elimination by nanoparticles of rutile titanium dioxin (110) is simulated. Titanium dioxide
has two Ti-Ti and Ti-o connection that this pollutants approaching and changing into other products
is studied through semi-empirical (ZINDO/S) method. The results show that the energy of pollutants
approaching to Ti-O connection is less than Ti-Ti, which is in practice probability of the pollutants
approaching to this connection is more, because its electron matching and connection polarity is
more.
Keywords: Nano-surface of Titanium dioxide, Dibenzodioxin, Ti-O connection, Ti-Ti connection,
semi-empirical method, ZINDO/S.
INTRODUCTION
Dioxin and furans are the big groups of carcinogenic materials in environment, which are observed
everywhere as environmental pollutants such as water, air and soil. They are so harmful for human health
because of their resistance in different environments [1-3]. These compounds are produced by different
methods such as open trash burning, using the fossil fuel with long chain like oil, tar, coal, and also by
industries, automobiles; and also this pollution can be caused by cracking the oil pipes, decaying the tankers,
seeping the surface tanks or even underground tanks, and different event that often occur producing and
transferring oil materials. In Doroud city in Iran, dioxin pollutants and Furan pollutants easily come into food
chain and human body through wet trash-burning in suburbs and wind-blowing toward farms and rivers around
the city [4].
One of the main purpose of our research is eliminating these pollutants in source, before coming into the
environment, titanium dioxide has various application, because abnormal chemical, mechanical, optical,
electrical, magnetic features [5-8]. During the recent years, using the TiO2 heterogeneous photocatalysts is
considered by researchers to decrease the environmental pollutants and to decrease the organic compounds of
air and hogwash [9, 10]. These articles are also used as semi-conductors [11].
Figure 1. The ball and stick model of a rutile TiO2 unit cell, a) front view and b) top view.
In this research, the simulation of nano-surfaces reaction of titanium dioxide and dibenzodioxin is done
Gauss View 5.0 software and its geometrical shape and structure is improved by Gaussian 09 program
Intl. Res. J. Appl. Basic. Sci. Vol., 9 (5), 648-655, 2015
package, and changing dibenzodioxin into less dangerous products on the connection of different TiO2
nanoparticles in different states is studied and calculated. Titanium dioxide (titania) can be appeared in three
crystalline form, rutile (tetragonal), anatase (tetragonal), brookite (orthorhombic) [12-15]. The structure of the
rutile is the most common form of titania, that system is the most resistant phase thermodynamically.
Figure 2. Ball and stick model of all probabilities of pollutant approaching to titanium dioxide with 2 × 2 nano-surface.
Figure 1 shows the ball and stick model of a rutile TiO2 nano-surface, which Fig.2 shown all probability of
the pollutants approaching. In this research, the pollutants approaching to Ti-Ti connection, the first probability
and Ti-O connection, the third probability (figure 2) were calculated and studied, and their thermodynamic
properties were assessed by the ZINDO/S in semi-empirical method.
COMPUTATIONAL METHODS
Chemical computations involving different mathematical methods are divided into two groups: 1Molecular mechanics, 2- Quantum mechanics.
One of the most general computer programs of chemical computations is Gaussian series, which is
developed by John A. Pople in Petersburg [16]. Computation can be happened on the systems in gas phase
case or solution case or in base form or stimulating form. Gaussian has used a wide expansion of theoretical
models of density, and male the energies, analytical parts and analytical frequencies calculable for all DFT
models [17, 18]. All of the approaching steps of dibenzodioxin to nano-surfaces of rutile TiO2 through B3LYP
method were improved on the 6-31G basis.
In order to evaluate thermodynamics features of chemical steps, semi-empirical calculations were used.
Energy and improved configuration of molecules had clear relationships to chemical phenomena and other
amounts of similar atomic charge and frontier orbitals are less defined by quality results.
Basically catalyst features are defined completely by electronica structure. So the electronica structure
design on the basis of changing in physical structure and compound is important for this purpose, ZINDO/S
method is extensively used to compute heat formation, geometric form of molecule, ionization energy,
electronic adherence, and other features.
If the calculations of this method be based on improved structure by DFT method, the result will be more
correct. Now by use of DFT method and semi empirical ZINDO/S, the attraction steps of dibenzodioxin on two
r-TiO2 (110) nano-surfaces connection are studied.
RESULTS
By the use of empirical data of X-ray diffraction from the structure of titanium dioxide nano-surfaces [19],
the angles and the link length between oxygen and titanium, Z-matrix of different forms of rutile titanium dioxide
nano-surfaces are written according to figure 1 and they are optimized by Gaussian program package, under
Linux with B3LYP/6-31G method then Z-matrix file of dibenzodioxin regarding to the structure, angles and the
length of link is written and is improved by the above method. According to the oxygen and titanium atoms
condition TiO2 surface, there are two Ti-Ti and Ti-O bridges to which the pollutants can approach, that the
considered probabilities are simulated and optimized.
It should be noted that during the pollution approaching to titania structure, the mechanism of pollution
changing to safe products in environment by this nano-catalyst is as following:
Dioxin (C12H8O2) + TiO2 (NP) → 2Phenol (C6H5OH) -rTiO2 (NP)
Phenol (C6H5OH) -rTiO2 (NP) + 9O2 → 6CO2 + 6H2O + rTiO2 (NP)
The pollutants approach to nano-surfaces of structure kind of titania and link kind, and their electrons are
exchanged and the pollutant changed to carbon dioxide according to two above-mentioned reactions.
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Intl. Res. J. Appl. Basic. Sci. Vol., 9 (5), 648-655, 2015
Figure 3. The approach of dibenzodioxin to the bridge cross Ti-Ti in r-TiO2 nano-surface and converted to phenol.
After optimized all this steps of changing, thermodynamics factures of pollutant on TiO 2 are calculated by
semi empirical computational method.
The reaction of dibenzodioxin and r-TiO2 nano-surface
Phenol production
The dibenzodioxin approaches to Ti-Ti bond in 3 steps, and in the fourth and fifth steps react with the
th
th
nano-surface; in the 6 and 7 steps, transition state and exchange of electron occur between the surface and
th
th
pollutant and in the 8 and 9 steps changes in to phenol and in the 10th step it moves away from the surface.
Figure 4. The approach of dibenzodioxin to the bridge cross Ti-O in r-TiO2 nano-surface and converted to phenol.
A linear view of each part is shown in the figure 3. For the Ti-O bond, this approaching, passing and
exchanging into phenol are planned in 8 steps, which are shown in figure 4. All steps are optimized through
using the B3LYP method with basis set 6-31G. The thermodynamic properties of these steps are computed
according to ZINDO/S as seen in table 1.
Table 1. The thermodynamic properties of interaction Dioxin on rutile TiO 2 (110) nano-surface and conversion to C6H6O at
298K (ZINDO/S).
Steps
Etotal
Dipol
(mJ /mol)
Moment (D)
The approach of dibenzodioxin to Ti-Ti
4
1
3217.02
1.21×10
4
2
3432.54
1.14×10
4
3
3569.34
1.44×10
4
4
2773.85
1.09×10
4
5
2763.31
1.09×10
4
6
2274.53
0.97×10
4
7
3478.61
1.11×10
4
8
2518.08
1.10×10
4
9
3130.67
1.29×10
4
10
2118.49
1.06×10
The approach of dibenzodioxin to Ti-O
4
1
2340.50
0.66×10
4
2
3460.87
1.28×10
4
3
3614.67
1.17×10
4
4
3203.83
1.15×10
4
5
3176.16
1.15×10
4
6
2847.04
1.13×10
4
7
2921.48
1.15×10
4
8
3191.15
1.35×10
RMS
o
kcal/mol. A
Ebin
( mJ /mol)
H
(mJ /mol )
Enuc
(mJ /mol)
Gele
(mJ /mol)
Eele
(V)
3326
3253
3571
3958
3958
3609
3545
3686
3829
3297
5400.08
5195.60
5752.40
4956.91
4946.37
4487.16
5664.20
4703.67
5316.26
4304.08
5442.68
5658.20
5795.00
4999.51
4988.97
4530.01
5707.24
4746.71
5316.26
4347.12
25971.12
26510.09
27192.93
27660.03
27649.49
28264.32
27443.43
26866.71
28108.37
26154.19
-22754.10
-23077.55
-23623.59
-24886.18
-24886.18
-25989.78
-23964.82
-24348.63
-23297.71
-24035.70
0.118
0.120
0.122
0.129
0.129
0.135
0.124
0.126
0.121
0.125
3240
3424
3699
3830
3830
3863
3678
3279
4523.56
5643.93
5797.73
538.69
5359.22
5032.63
5107.07
5376.74
4566.16
56842.53
5840.33
5429.49
5401.82
5075.67
5150.10
5419.78
25776.13
26354.71
27350.30
27544.23
27516.56
27256.02
27262.89
25981.46
-23435.63
-22893.84
-23735.63
-24340.41
-24340.41
-24408.98
-24341.42
-22790.30
0.121
0.119
0.123
0.126
0.126
0.126
0.126
0.118
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Intl. Res. J. Appl. Basic. Sci. Vol., 9 (5), 648-655, 2015
Figure 5. The approach of phenol to the bridge cross Ti-Ti in r-TiO2 nano-surface and converted to CO2.
Phenol to CO2
The phenol was created around rTiO2 nano-surface approaches to Ti-Ti, Ti-O bond and after reacting with
the nano-surface converted to CO2. This reaction is optimized and simulated in 6 steps (Figs. 5, 6) and all the
strictures are optimized through DFT method and its thermodynamic properties are computed by the ZINDO/S
method, its results is shown in the table 2.
Figure 6. The approach of phenol to the bridge cross Ti-O in r-TiO2 nano-surface and converted to CO2.
Table 2. The thermodynamic properties of interaction phenol on rutile TiO2 (110) nano-surface and conversion to CO2 at
298K (ZINDO/S).
Steps
Etotal
Dipol
RMS
o
(mJ/mol)
Moment (D) kcal/mol. A
The approach of dibenzodioxin to the bridge cross Ti-Ti
4
1
2235.28
1.33×10
4284
4
2
2551.18
1.36×10
4262
4
3
2318.03
1.69×10
4408
4
4
3089.13
1.11×10
3900
4
5
1852.00
1.12×10
3892
4
6
3495.98
1.09×10
3401
The approach of dibenzodioxin to the bridge cross Ti-O
4
1
3696.21
1.05×10
3684
4
2
2368.05
1.25×10
4094
4
3
3190.89
0.99×10
3617
4
4
2744.28
1.34×10
4274
4
5
3005.52
1.36×10
4235
4
6
3495.98
1.09×10
3401
Ebin
(mJ /mol)
H
(mJ /mol)
Enuc
(mJ /mol)
Gele
(mJ /mol)
Eele
(V)
4662.28
4978.17
4750.08
5516.12
4289.12
6053.88
4701.57
5017.47
4790.25
5555.42
4330.16
609.66
29813.88
29874.19
31366.73
30547.11
31206.23
31847.15
-27578.60
-27323.01
-29048.70
-27457.98
-29354.23
-28351.17
0.143
0.142
0.151
0.142
0.152
0.147
6130.79
4802.63
5625.47
5178.86
5442.63
6053.88
6171.40
4843.24
5666.08
5219.47
5483.68
609.66
30395.43
30500.95
30546.05
30596.54
30789.95
31847.15
-2669.92
-28132.90
-27355.27
-27852.26
-27784.43
-28351.17
0.014
0.146
0.142
0.144
0.144
0.147
DISCUSSION
Dibenzodioxin to phenol
The computed thermodynamics properties in tables 1 and 2 are about converting dibanzodioxin to phenol
on the Ti-Ti, Ti-O bonds on rTiO2 nano-surfaces.
Figure 7 is the total energy (mJ/mol) of this reaction by using the semi empirical method ZINDO/S, as can
be seen in the figure, the energy of transition state in 6th and 7th steps for the Ti-Ti bond and 4th step for the TiO bond decrease. It shows that it's an spontaneous reaction, but converted transition state to product (phenol)
is endothermic. The necessary energy for Ti-O bond is less than Ti-Ti that the occurring reaction of
dibenzodioxin with Ti-O bond is more probable.
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Intl. Res. J. Appl. Basic. Sci. Vol., 9 (5), 648-655, 2015
Figure 7. The total energy of dibenzodioxin interaction on rutile TiO 2 (110) nano-surface and conversion to phenol at 298K
(ZINDO/S).
In addition to energy computing of physical reaction between them, RMS parameter (Root-Mean Square)
of gradient was computed by using the first relation through semi-empirical ZINDO/S for the surfaces of the
potential of multidimensional object.
1
  E  2  E  2  E  2  2
  
  
 
(3 N )  1   
  X A   y A   z A  
(1)
In than reaction, RMS computational parameters are computed by the simulation software, and then if the
randomly computational time in simulation be more, it has a significant effect on this parameters amounts.
The computational results of this reaction are seen in table 1. Other thermodynamic parameters of dipolar
moment (D), RMS gradient, binding energy, formation enthalpy, electrical energy, nuclear energy are computed
by ZINDO/S method.
In order to access to this reaction electrical properties by using the electrical energy and the following
equation:
(2)
Eelec  RI
where R is the electrical resistance and I is the current intensity per (A), that I can be found from I 
equation so:
E t
R  elec
nF
q
t
(3)
Figure 8. The electrical resistance of dibenzodioxin interaction on rutile TiO 2 (110) nano-surface and conversion to phenol
at 298K (ZINDO/S).
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Intl. Res. J. Appl. Basic. Sci. Vol., 9 (5), 648-655, 2015
The electrical resistance of all steps and conversions are computed based on electrical data, (2) and (3)
equations, as can be seen in figure 8. The electrical resistance of Ti-O bond is less than Ti-Ti, so this conditions
electrical conductivity is more and electron exchange of dibenzodioxin and rutile TiO2 (110) nano-surface
occurs easier in transition state step.
Figure 9. The total energy of interaction phenol on rutile TiO 2 (110) nano-surface and conversion to CO2 at 298K
(ZINDO/S).
Phenol to CO2
After changing dibenzodioxin to phenol, phenol molecule near to nano surfaces and electron exchange
occurs between them. This change is designed in 6 steps for both two condition, which cases 3 and 4 is
transition state step of this reaction, as can be seen in figure 9, the total energy calculated by ZINDO/S method,
in transition state step shows a sudden change.
Figure 10. The electrical resistance of phenol interaction on rutile TiO2 (110) nano-surface and conversion to CO2 at 298K
(ZINDO/S).
The computed thermodynamic properties for this reaction are shown in table 2. That all parameters of this
reaction for transition state step show the most amounts and computed dipolar moment increases for the
product that is related to form and polarity of molecular.
Electrical resistance of converted phenol to CO2 in Ti-O bond is less than Ti-Ti bond, which can be seen in
figure 10, because there is a Ti-O bond and electronegativity difference between these two elements and its
conversion is easier to low-risk product.
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Intl. Res. J. Appl. Basic. Sci. Vol., 9 (5), 648-655, 2015
Thermodynamic properties of these reactions
Equation constant and other thermodynamic parameters such as Gibbs free energy, enthalpy and entropy
of the whole reactions were computed through the following equation:
 Gelec 
K  exp 

Rt 

(4)
That T is the reactions temperature that in these computation is considered 298K. In order to computed
the entropy reactions:
S elec 
H
T
(5)
Table 3. The thermodynamic properties of interaction phenol on rutile TiO 2 (110) nano-surface and conversion to low-risk
product at 298K (ZINDO/S).
∆Gelec
(mJ/mol)
The interaction of dibenzodioxin to the bridge cross Ti-Ti
Dibanzodioxin to phenol
-3235.68
Phenol to CO2 & H2O
-1470.10
The interaction of dibenzodioxin to the bridge cross Ti-O
Dibanzodioxin to phenol
-904.78
Phenol to CO2 & H2O
-24685.35
∆Helec
(mJ/mol)
∆Selec
(mJ/K.mol)
lnK
-912.67
88.68
7.80
5.23
130598.83
59336.32
863.33
-505.32
5.93
81.14
36518.82
996352.48
Function mechanism
Anatase and rutile have the same chemical formula (TiO 2) and have same geometrical symmetry
(tetragonal) but have different structures. In temperatures of higher than 915oC anatase is converted to rutile
structure automatically. The rutile is more known than anatase. Titanium dioxin molecules on the metal surface
activate by ultraviolet radiation and during some chemical processes make bacteria, algae and fungi
disappeared (figure 11). When ultraviolet ray radiates to titanium dioxide, and electrochemical reactions happen
and it frees the radical, free radicals confront to pollutants and destroy them.
Figure 11. The electron transition from valance band (VB) to conduction band (CB) in semiconductor rTiO 2 (110) nanosurfaces.
The suggested mechanism for this change is as following which its view is shown in figure 11. After
attracting the sun ultraviolet by titania nano-surfaces the electrons of capacity balances displace to guide band
balance, and an empty hole appears in capacity balance, so the following can be considered:
TiO2 + hν → TiO2 (ecb− +holevb+)
−
+
H2O → OH +H
Oxidative reaction:
holevb+OHads− → •OH
•
OH + Dioxin + O2 → C6H6O
•
OH + C6H6O + O2 → CO2 + H2O
CONCLUSION
TiO2 has a very special surface, very small size and is very reactiveative. The electrical resistance of
titanium dioxide change in confronting to a pollutant so can function as a pollution controller in cars and
industrial factories. The results show that it can be a good sensor against manufactured pollutants like dioxin.
The structure resistance, the granule size the porosity percent, the additives are the factors that influence its
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Intl. Res. J. Appl. Basic. Sci. Vol., 9 (5), 648-655, 2015
sensory degree and photo catalyst. The most important feature of titania nano-surfaces is their electrical
conduction.
Electrical conduction of titania nano-surfaces completely differs from crystalline structure to other
structure according to the kinds and angles of bonds. Every atom is vibrating in its place. When on electron (or
electric charge) comes in to a series of atoms, the atoms vibration increase, and as the result of colliding to
each other. They transfer the imposed electrical charge. The more the atoms are, the more the electrical
condition of this group of nanotubes will be.
The results show that all of the reaction are thermal receptor, and is used in changing the necessity to sun
radiation (solar energy) or other energies.
One of the manufacturing ways of dioxin is burning the home trash in open environment. The temperature
in this burning is more than 1000 ℃ , that in this temperature, all titania nano-surfaces change to rutile and the
necessary energy of this reaction is provided. It should be noted that rutile formation need less energy than
anatase does. It also works better and among the considered probability, Ti-O bond is more suitable to change
this reaction, so using this nano catalyst to change dioxin into safer products is suitable and economical.
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