**6. Technological applications of mesoporous TiO2**

#### **6.1. Environmental photocatalysis**

One of the potential applications of heterogeneous photocatalysis is the environmental remediation [8, 20, 74, 119-122]. Different semiconductor oxides have shown to be capable of triggering photocatalytic, highlighting the TiO2 [19, 20, 123]. In this context, nanostructured materials tend to favor the photocatalytic applications of these materials [60].

Kim and Kwak reported studies where the photocatalytic activity of a mesoporous TiO2 prepared using di-block copolymers via sol-gel synthesis was evaluated, using methylene blue as oxidizable substrate [50]. The materials with small crystallite size (about 5.1 nm), high surface area (about 210 m2 g-1) and small pore size distribution were the ones who exhibited the best photocatalytic activities, using ultraviolet radiation, with apparent constants of degradation around 0.093 min-1. The particles synthesized presented spherical morphology with surface areas dependent on the type of di-block copolymer used.

In [58] is related a sol-gel synthesis of a TiO2 with intermediate porosity, under hydrothermal conditions using a water-soluble cationic surfactant, obtaining a mesoporous TiO2 with maximum pore size of 6.9 nm and maximum surface area of 284 m2 g-1. The synthesized material had its photocatalytic activity evaluated on degradation of methylene blue. The synthesized product showed to be superior (95%) to TiO2 P25 (24%), using irradiation with UV radiation under the same reaction conditions. The greater photocatalytic efficiency was attributed to the higher surface area, when compared to this parameter measured to TiO2 P25 (50 m2 g-1), and the ordination of the synthesized material, attributed to the use of the surfactant.

The synthesis of a TiO2 supported on SBA-15 mesoporous silica, reported in [124], resulted in materials efficient to degrade photocatalytic phenols. SBA-15 silica presents hexagonal arrangement and bi-dimensional pores with diameter up to 30 nm. The materials obtained have surface area of 361.4 m2 g-1 and pore volume of 1.217 cm3 g-1.

#### **6.2. Hydrogen production**

Hydrogen production via heterogeneous photocatalysis based in the electronic excitation of a semiconductor material using UV-Visible radiation is promising for the production of clean and sustainable energy [19, 54, 125]. Generally speaking, this process is based on the electronic excitation of the photocatalyst. From there, the photo-generated hole at the valence band reacts readily with a sacrificial reagent, while in conduction band electrons are trapped by a cocatalyst, being used in the reduction of H+ ions, with the production of hydrogen [126].

Mesoporous TiO2 of intermediate porosity have generally high surface area and high density of active sites, which tends to facilitate the diffusion of reagents, favoring the conversion of solar energy in photocatalytic reactions [41, 93, 127].

A porous composite based on TiO2 incorporated to silica MCM-48 (Mobil Crystalline Materials n° 48) was proposed as photocatalyst for hydrogen production [128]. The authors reported that the tetrahedrically coordinated TiO2 act as active sites on photocatalysis of water reducing the potential, facilitating the formation of gaseous hydrogen, even in the absence of a cocatalyst.

Microspheres of TiO2 doped with carbonates has also been proposed for hydrogen production under visible (λ > 400 nm) irradiation [129]. A rate of H2 production of 0.2 mmol h-1 g-1 was achieved using the photocatalyst charged with 1 wt% Pt. The photocatalytic performance was attributed to the characteristics of the mesoporous structure such as the diameter of the microspheres, between 0.5 and 4 μm, pore size in the range between 3 and 11 nm and high surface area (500 m2 g-1).

A mesoporous TiO2-SiO2 mixed oxide with molar ratio of 97:3, calcined at 773 K was also proposed for hydrogen production [66]. It produced hydrogen at a rate of 0.27 cm3 h-1 g-1, an expressive value when compared to the rate achieved using TiO2 P25 (0.17 cm3 h-1 g-1). This mixed oxide has characteristics that favored its photocatalytic activity, such as a surface area of 162 m2 g-1, pore diameter of 4.3 nm and pore volume of 0.24 cm3 g-1.

#### **6.3. Electrodes in Lithium ion batteries**

**6. Technological applications of mesoporous TiO2**

One of the potential applications of heterogeneous photocatalysis is the environmental remediation [8, 20, 74, 119-122]. Different semiconductor oxides have shown to be capable of triggering photocatalytic, highlighting the TiO2 [19, 20, 123]. In this context, nanostructured

Kim and Kwak reported studies where the photocatalytic activity of a mesoporous TiO2 prepared using di-block copolymers via sol-gel synthesis was evaluated, using methylene blue as oxidizable substrate [50]. The materials with small crystallite size (about 5.1 nm), high

the best photocatalytic activities, using ultraviolet radiation, with apparent constants of degradation around 0.093 min-1. The particles synthesized presented spherical morphology

In [58] is related a sol-gel synthesis of a TiO2 with intermediate porosity, under hydrothermal conditions using a water-soluble cationic surfactant, obtaining a mesoporous TiO2 with maximum pore size of 6.9 nm and maximum surface area of 284 m2 g-1. The synthesized material had its photocatalytic activity evaluated on degradation of methylene blue. The synthesized product showed to be superior (95%) to TiO2 P25 (24%), using irradiation with UV radiation under the same reaction conditions. The greater photocatalytic efficiency was attributed to the higher surface area, when compared to this parameter measured to TiO2 P25 (50 m2 g-1), and the ordination of the synthesized material, attributed to the use of the surfactant. The synthesis of a TiO2 supported on SBA-15 mesoporous silica, reported in [124], resulted in materials efficient to degrade photocatalytic phenols. SBA-15 silica presents hexagonal arrangement and bi-dimensional pores with diameter up to 30 nm. The materials obtained

g-1 and pore volume of 1.217 cm3

Hydrogen production via heterogeneous photocatalysis based in the electronic excitation of a semiconductor material using UV-Visible radiation is promising for the production of clean and sustainable energy [19, 54, 125]. Generally speaking, this process is based on the electronic excitation of the photocatalyst. From there, the photo-generated hole at the valence band reacts readily with a sacrificial reagent, while in conduction band electrons are trapped by a co-

Mesoporous TiO2 of intermediate porosity have generally high surface area and high density of active sites, which tends to facilitate the diffusion of reagents, favoring the conversion of

A porous composite based on TiO2 incorporated to silica MCM-48 (Mobil Crystalline Materials n° 48) was proposed as photocatalyst for hydrogen production [128]. The authors reported that the tetrahedrically coordinated TiO2 act as active sites on photocatalysis of water reducing

g-1) and small pore size distribution were the ones who exhibited

g-1.

ions, with the production of hydrogen [126].

materials tend to favor the photocatalytic applications of these materials [60].

with surface areas dependent on the type of di-block copolymer used.

**6.1. Environmental photocatalysis**

98 Solar Radiation Applications

surface area (about 210 m2

have surface area of 361.4 m2

**6.2. Hydrogen production**

catalyst, being used in the reduction of H+

solar energy in photocatalytic reactions [41, 93, 127].

Mesoporosos materials have been used in the production of electrodes for Lithium ion batteries. Physical properties such as particle size, porosity and pore size determine the performance of this class of batteries [127]. The mesoporous structure favors the transport of electrolyte, facilitating the contact between the surface of the electrode and the electrolyte and shortening the path of diffusion of the Li+ ions.

These batteries have a long life cycle, rapid loading and unloading capacity, being capable to store high energy densities in a compact and lightweight container. Because of this, it has been used as power sources for portable electronic devices [127, 130, 131].

Mesoporous TiO2 is a promising material in this kind of battery by offering numerous advantages, such as high potential of ions insertion, low cost, low toxicity, easy synthesis and stability to pH variation [60]. Anatase is generally regarded as the most suitable polymorph of TiO2 for Li+ insertion, superior to rutile and with more stable structure than brookite. However, anatase with large particle sizes present poor performance due to its low capabilities to promote ionic diffusion and electronic conductivity [132, 133]. Thus, the control of particle size and porosity during its synthesis is imperative for obtaining materials with desirable characteristics.

The particle size influence on the dynamic process of storage of Li+ ions, ensuring a significant increase on battery performance when the particle size is reduced. For example, the discharge capacity of TiO2 rutile with particles of 300 nm is 110 mAh g−1, while this same parameter for particle sizes of 30 and 15 nm is, respectively, 338 and 378 mAh g−1 [134].

Studies involving the application of mesoporous microspheres of anatase with regular porosity showed that pore structure significantly influences on specific capacity, speed capability and performance cycle of the batteries [60]. The materials with higher surface area had the best performance. It was also observed that when the pore size was very small, the transport of Li + in the electrolyte was heavily restricted.

#### **6.4. Solar cells**

Solar cells have a great advantage when compared to conventional power generation systems, since in these solar energy can be directly converted into electric. The traditional solar cells are basically constituted by two layers of semiconductor materials, an n-p type pair. When photons with appropriate energy reach the semiconductor pair, electrons are excited producing electricity [135].

The first solar cells were based on crystalline silicon. Actually, studies are being conducted with the goal of developing efficient photovoltaic cells and low cost, since the crystalline silicon-based cells are of very high cost.

The solar cells can be classified as:


In the organic solar cells are used semiconductor organic polymers or small and medium organic molecules, such as phthalocyanines, fullerenes, poly-(p-phenylenevinylene) (PPV). These cells can be produced on flexible substrates, and are promising in terms of production costs. On the other hand, they still have low efficiency, as well as some limitations, such as the possibility of degradation of the organic component.

In 2009, Park and co-workers developed an organic solar cell based on a polymer-fullerene composite, with a reasonable energetic efficiency (6.5%) [138].

Dye-sensitized solar cells, DSCs, Figure 7, are devices constituted by a semiconductor material, a sensitizer (dye), a conductive glass, an electrolyte and a platinum counter-electrode. Unlike conventional systems, where semiconductor assumes both the task of absorbing light as the charge carriage, in DSCs such functions are separated: the light is absorbed by a dye anchored to the surface of a semiconductor, and the charge separation occurs at the semiconductorelectrolyte interface [139].

A great leap in this area was given by [140] by using mesoporous nanocristalline TiO2 films in place of single crystals of oxide semiconductor as substrates for the adsorption of the sensitizer dye. The use of mesoporous films resulted in a significant increase in the conversion efficiency of incident light in current, IPCE, which went from 0.13 to 88% [141]. The principal reason for this was the increase in the amount of dye adsorbed due to the greater surface area in general available in the mesoporous films. Using mesoporous films, the overall efficiency of conversion of solar cells sensitized by dye reached 7% in the decade of 90 [140]. Actually, the best cells exceed the 13% [142, 143], confirming the feasibility of commercial applications of these devices.

**Figure 7.** Simplified diagram showing the functioning of DSCs.

**6.4. Solar cells**

100 Solar Radiation Applications

electricity [135].

silicon-based cells are of very high cost.

The solar cells can be classified as:

less efficient;

**d.** Hybrid solar cells [137].

electrolyte interface [139].

devices.

possibility of degradation of the organic component.

composite, with a reasonable energetic efficiency (6.5%) [138].

Solar cells have a great advantage when compared to conventional power generation systems, since in these solar energy can be directly converted into electric. The traditional solar cells are basically constituted by two layers of semiconductor materials, an n-p type pair. When photons with appropriate energy reach the semiconductor pair, electrons are excited producing

The first solar cells were based on crystalline silicon. Actually, studies are being conducted with the goal of developing efficient photovoltaic cells and low cost, since the crystalline

**a.** First generation solar cells, where are the silicon solar cells used commercially, which

**b.** Second generation solar cells. More profitable than the first generation solar cells, but still

In the organic solar cells are used semiconductor organic polymers or small and medium organic molecules, such as phthalocyanines, fullerenes, poly-(p-phenylenevinylene) (PPV). These cells can be produced on flexible substrates, and are promising in terms of production costs. On the other hand, they still have low efficiency, as well as some limitations, such as the

In 2009, Park and co-workers developed an organic solar cell based on a polymer-fullerene

Dye-sensitized solar cells, DSCs, Figure 7, are devices constituted by a semiconductor material, a sensitizer (dye), a conductive glass, an electrolyte and a platinum counter-electrode. Unlike conventional systems, where semiconductor assumes both the task of absorbing light as the charge carriage, in DSCs such functions are separated: the light is absorbed by a dye anchored to the surface of a semiconductor, and the charge separation occurs at the semiconductor-

A great leap in this area was given by [140] by using mesoporous nanocristalline TiO2 films in place of single crystals of oxide semiconductor as substrates for the adsorption of the sensitizer dye. The use of mesoporous films resulted in a significant increase in the conversion efficiency of incident light in current, IPCE, which went from 0.13 to 88% [141]. The principal reason for this was the increase in the amount of dye adsorbed due to the greater surface area in general available in the mesoporous films. Using mesoporous films, the overall efficiency of conversion of solar cells sensitized by dye reached 7% in the decade of 90 [140]. Actually, the best cells exceed the 13% [142, 143], confirming the feasibility of commercial applications of these

today correspond to about 86% of the solar cells market [136];

**c.** Third generation solar cells, where are the dye-sensitized organic cells;

The I- /I3 redox pair dissolved in nitriles is thermodynamically capable to reduce the photo oxidized dye on the surface of TiO2. The difference between the energy of the semiconductor conduction band and the redox potential of the electrolyte determines the maximum opencircuit potential than a DSC can achieve. Additionally, the kinetics of reduction is one or two orders of magnitude faster than the process of recombination between the electron in the conduction band of the oxide and the photo oxidized dye [144]. This difference makes the charge separation process in the TiO2-sensitizer-electrolyte interface to be very efficient. The disadvantages of using liquid electrolytes based on I- /I3 redox pair include the toxicity of species of iodine and the inner filter effect caused by the strong absorption of light in the visible region by I3 - , which makes DSCs efficiency dependent on the exposed face.

The system TiO2/Ru(II) complex/(I- /I3 - ) is relatively simple and efficient, allowing a consider‐ able advance in the understanding of the charge separation process from absorption of sunlight in sensitized semiconductors. However, this system presents challenges to be overcome, to its large-scale implementation. There stands out the high cost of the Ru(II) complexes, the high toxicity of the electrolyte and the and the need for an efficient sealing of the device in order to prevent the leakage of the electrolyte and the consequent loss of activity. Even so, modules up to 6000 cm2 have been produced [145].

Alternatively, several other materials have been proposed to build DSCs. Organic compounds, such as indole and anthocyanins derivatives also have been proposed as sensitizers [146-150]. Recently, [151] described DSCs possessing efficiencies higher than 12% using a Zn(II) por‐ phyrine as sensitizer and Co(II)/(III) complexes as redox pair. Another approach that has attracted much attention involves the use of solid systems that, at first, dispense step of sealing and increase solar cell stability in real conditions of operation [152-155].

A major breakthrough in the development of solid DSCs has been achieved with the use of perovskites, as the CH3NH3PbI3, as sensitizers [156-158]. These compounds are chemical‐ ly very stable and can be produced *in situ* from precursors solutions and have a wide range of absorption, from visible to near infrared. When adsorbed on surface of TiO2 films, CH3NH3PbI3 is capable of injecting electrons efficiently and be regenerated by hole transporter materials (HTM) as spiro-MeOTAD (2,2',7,7'-tetraquis [N,N-di(4-metoxyphen‐ yl)amino]-9,9'-spirobifluorene). DSCs with efficiencies higher than 14% have been descri‐ bed using this approach [156]. It is interesting that the use of this same material in DSCs with Ru(II) complexes results in conversion efficiencies between 2 and 3% [159, 160]. This makes clear that it is not enough to simply replace one or another component in the DSCs to achieve greater efficiencies. It is necessary a good understanding of the characteristics of each part of the interfaces of the device and of the different processes of electron transfer that occur between the components.

**Figure 8.** Decrease of electronic recombination on the FTO/electrolyte interface due to the application of the blocking layer.

In all approaches described above, it is common the need to deposit multiple layers of semiconductor oxides with different functions. Besides the nanoporous layer, responsible for dye adsorption and transport of electrons, there is the blocking layer deposited on the surface of the substrate which is responsible for reduction of the electronic recombination on the substrate-electrolyte interface, Figure 8.

Additionally, scattering layers, composed of particles with size between 400 and 700 nm can be deposited, which contributes to a greater use of the incident light. Several proposals can be found in the literature in relation to different layers of metal oxides in DSCs. In these are included the use of different techniques of deposition and also various materials. The research groups working in this area agree that the deposition of different semiconductor oxide layers with different morphologies is indispensable for production of high efficiency DSCs [143, 161]. However, there is still no consensus on the best deposition technique to be employed and what better composition to be used for the different electrolytes.

Recently, we reported the production of contact-blocking layers using the *layer-by-layer* (LbL) technique, which showed excellent performance in DSCs based on liquid electrolytes [162-164]. This technique stands out for its low cost, possibility of control of composition, thickness and morphology of films and the possibility to be employed on a large scale. It was noted, for example, that the use of a mixture between TiO2 and more insulating oxides as Nb2O5 results in an increase of all the photoelectrochemical parameters of the DSCs [165].

#### **7. Conclusion**

attracted much attention involves the use of solid systems that, at first, dispense step of sealing

A major breakthrough in the development of solid DSCs has been achieved with the use of perovskites, as the CH3NH3PbI3, as sensitizers [156-158]. These compounds are chemical‐ ly very stable and can be produced *in situ* from precursors solutions and have a wide range of absorption, from visible to near infrared. When adsorbed on surface of TiO2 films, CH3NH3PbI3 is capable of injecting electrons efficiently and be regenerated by hole transporter materials (HTM) as spiro-MeOTAD (2,2',7,7'-tetraquis [N,N-di(4-metoxyphen‐ yl)amino]-9,9'-spirobifluorene). DSCs with efficiencies higher than 14% have been descri‐ bed using this approach [156]. It is interesting that the use of this same material in DSCs with Ru(II) complexes results in conversion efficiencies between 2 and 3% [159, 160]. This makes clear that it is not enough to simply replace one or another component in the DSCs to achieve greater efficiencies. It is necessary a good understanding of the characteristics of each part of the interfaces of the device and of the different processes of electron transfer

**Figure 8.** Decrease of electronic recombination on the FTO/electrolyte interface due to the application of the blocking

and increase solar cell stability in real conditions of operation [152-155].

that occur between the components.

102 Solar Radiation Applications

layer.

In this chapter, aspects related to obtaining and application of mesoporous nanostructured materials in photocatalytic processes had been addressed, emphasizing its application in advanced oxidative processes, increasing the overall efficiency of conversion in dye sensitized solar cells, manufacturing of electrodes for lithium-ion batteries and hydrogen production, with focus on TiO2. Although many advances have occurred, some challenges still needed to be overcome so that these materials become more efficient and economically viable. On the other hand, the potential that mesoporous materials demonstrated and the improvements already achieved promote the study and development of what is a promising source of technological applications.

#### **Acknowledgements**

To Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Conselho Nacional de Desen‐ volvimento Científico e Tecnológico (CNPq), Brazilian agencies for research funding and grants, by the support and funding.

### **Author details**

Antonio E. H. Machado1\*, Karen A. Borges1 , Tatiana A. Silva1 , Lidiaine M. Santos1 , Mariana F. Borges1 , Werick A. Machado1 , Bruno P. Caixeta1 , Marcela Dias França2 , Samuel M. Oliveira1 , Alam G. Trovó 1 and Antonio O.T. Patrocínio1

\*Address all correspondence to: aehmachado@gmail.com

1 Universidade Federal de Uberlândia, Instituto de Química, Laboratório de Fotoquímica e Ciência de Materiais, Minas Gerais, Brazil

2 Instituto Federal Goiano, Goiás, Brazil

#### **References**


[7] Chen KC, Wang YH. The effects of Fe-Mn oxide and TiO2/alpha-Al2O3 on the forma‐ tion of disinfection by-products in catalytic ozonation. Chemical Engineering Journal 2014;253 84-92. DOI: 10.1016/j.cej.2014.04.111.

**Author details**

104 Solar Radiation Applications

Mariana F. Borges1

Samuel M. Oliveira1

**References**

Antonio E. H. Machado1\*, Karen A. Borges1

Ciência de Materiais, Minas Gerais, Brazil

2 Instituto Federal Goiano, Goiás, Brazil

10.1007/s13233-014-2062-5.

9037-9042. DOI: 10.1021/Es5020696.

2014.05.112.

, Werick A. Machado1

, Alam G. Trovó 1

\*Address all correspondence to: aehmachado@gmail.com

, Tatiana A. Silva1

and Antonio O.T. Patrocínio1

, Bruno P. Caixeta1

1 Universidade Federal de Uberlândia, Instituto de Química, Laboratório de Fotoquímica e

[1] Bahng SH, Kwon NH, Kim HC, Siddique A, Kang HJ, Lee JY, et al. Simple Synthesis of Water-Dispersible and Photoactive Titanium Dioxide Nanoparticles Using Func‐ tionalized Poly(ethylene oxide)s. Macromolecular Research 2014;22(4) 445-456. DOI:

[2] Hidalgo D, Messina R, Sacco A, Manfredi D, Vankova S, Garrone E, et al. Thick mes‐ oporous TiO2 films through a sol–gel method involving a non-ionic surfactant: Char‐ acterization and enhanced performance for water photo-electrolysis. International

[3] Sanchez-Quiles D, Tovar-Sanchez A. Sunscreens as a source of hydrogen peroxide production in coastal waters. Environmental Science & Technology 2014;48(16)

[4] Xi BJ, Chu XN, Hu JY, Bhatia CS, Danner AJ, Yang H. Preparation of Ag/TiO2/SiO2 films via photo-assisted deposition and adsorptive self-assembly for catalytic bacteri‐ cidal application. Applied Surface Science 2014;311 582-592. DOI: 10.1016/j.apsusc.

[5] Yeh SW, Ko HH, Chiang HM, Chen YL, Lee JH, Wen CM, et al. Characteristics and properties of a novel in situ method of synthesizing mesoporous TiO2 nanopowders by a simple coprecipitation process without adding surfactant. Journal of Alloys and

[6] Wang ZY, Yao N, Hu X. Single material TiO2 double layers antireflection coating with photocatalytic property prepared by magnetron sputtering technique. Vacuum

Compounds 2014;613 107-116. DOI: 10.1016/j.jalicom.2014.05.227.

2014;108 20-26. DOI: 10.1016/j.vacuum.2014.05.009.

Journal of Hydrogen Energy 2014. DOI: 10.1016/j.ijhydene.2014.02.163.

, Lidiaine M. Santos1

, Marcela Dias França2

,

,


composites as photocatalysts for wastewater treatment using solar irradiation. Inter‐ national Journal of Photoenergy 2008;2008. DOI: 10.1155/2008/482373.

[31] Fujishima A, Honda K. Electrochemical Photolysis of Water at a Semiconductor Elec‐ trode. Nature 1972;238(5358) 37-+. DOI: 10.1038/238037a0.

[19] A. E. H. Machado, A. O. T. Patrocinio, M. D. França, L. M. Santos, K. A. Borges, L. F. Paula. Metal oxides for photoinduced hydrogen production and dye-sensitized solar cell applications. In: Méndez-Vilas A. (ed.) Materials and processes for energy: com‐ municating current research and technological developments. Badajoz: Formatex;

[20] A. E. H. Machado, L. M. Santos, K. A. Borges, P. S. Batista, V. A. B. Paiva, P. S. Müller Jr., et al. Potential Applications for Solar Photocatalysis: From Environmental Reme‐ diation to Energy Conversion. In: Babatunde E. B. (ed.) Solar Radiation. Rijeka: In‐

[21] F. Sordello, V. Maurino, C. Minero. Improved photochemistry of TiO2 inverse opals and some examples. In: Saha S (ed.) Molecular Photochemistry-Various Aspects. Ri‐

[22] M. Valenzuela. Photocatalytic deposition of metal oxides on semiconductor particles: a review. In: Saha S (ed.) Molecular Photochemistry-Various Aspects. Rijeka: InTech;

[23] Jaroenworaluck A, Pijarn N, Kosachan N, Stevens R. Nanocomposite TiO2-SiO2 gel for UV absorption. Chemical Engineering Journal 2012;181 45-55. DOI: 10.1016/j.cej.

[24] Affam AC, Chaudhuri M. Degradation of pesticides chlorpyrifos, cypermethrin and chlorothalonil in aqueous solution by TiO2 photocatalysis Journal of Environmental

[25] Chen JW, Shi JW, Wang X, Ai HY, Cui HJ, Fu ML. Hybrid metal oxides quantum dots/TiO2 block composites: Facile synthesis and photocatalysis application. Powder

[26] Hirakawa T, Sato K, Komano A, Kishi S, Nishimoto CK, Mera N, et al. Specific prop‐ erties on TiO2 photocatalysis to decompose isopropyl methylphosphonofluoridate and dimethyl methylphosphonate in Gas Phase. Journal of Photochemistry and Pho‐

tobiology a-Chemistry 2013;264 12-17. DOI: 10.1016/j.jphotochem.2013.04.012. [27] A. Eremenko, N. Smirnova, I. Gnatiuk, O. Linnik, N. Vityuk, Y. Mukha, et al. Silver and gold nanoparticles on sol-gel TiO2, ZrO2, SiO2 surfaces: optical spectra, photoca‐ talytic activity, bactericide properties. In: Cuppoletti J (ed.) Nanocomposites and Pol‐

[28] V. S. Viteri, E. Fuentes. Titanium and Titanium Alloys as Biomaterials. In: Gegner J (ed.) Tribology-Fundamentals and Advancements. Rijeka: InTech; 2013. p. 155-181. [29] Grcic I, Vujevic D, Zizek K, Koprivanac N. Treatment of organic pollutants in water using TiO2 powders: photocatalysis versus sonocatalysis. Reaction Kinetics Mecha‐

[30] Machado AEH, França MD, Velani V, Magnino GA, Velani HMM, Freitas FS, et al. Characterization and evaluation of the efficiency of TiO2/zinc phthalocyanine nano‐

nisms and Catalysis 2013;109(2) 335-354. DOI: 10.1007/s11144-013-0562-5.

Management 2013;130 160-165. DOI: 10.1016/j.jenvman.2013.08.058.

Technology 2013;246 108-116. DOI: 10.1016/j.powtec.2013.05.014.

ymers with Analytical Methods. Rijeka: InTech; 2011. p. 51-83.

2013. p. 867-879.

106 Solar Radiation Applications

2012. p. 25-41.

2011.08.028.

Tech; 2012. p. 339-378.

jeka: InTech; 2012. p. 63-87.


rials and Engineering Materials Ii 2013;683 522-525. DOI: 10.4028/www.scientific.net/ AMR.683.522.


[55] Ferreira OP, Alves OL, Macedo JD, Gimenez ID, Barreto LS. Ecomaterials: Develop‐ ment and application of functional porous materials for environmental protection. Química Nova 2007;30(2) 464-467. DOI: 10.1590/S0100-40422007000200039.

rials and Engineering Materials Ii 2013;683 522-525. DOI: 10.4028/www.scientific.net/

[44] Paula LF, Amaral RC, Iha NYM, Paniago RM, Machado AEH, Patrocinio AOT. New layer-by-layer Nb2O5-TiO2 film as an effective underlayer in dye-sensitised solar

[45] Zhu XD, Wang YJ, Zhou DM. TiO2 photocatalytic degradation of tetracycline as af‐ fected by a series of environmental factors. Journal of Soils and Sediments 2014;14(8)

[46] Kumar N, Maitra U, Hegde VI, Waghmare UV, Sundaresan A, Rao CNR. Synthesis, Characterization, Photocatalysis, and Varied Properties of TiO2 Cosubstituted with Nitrogen and Fluorine. Inorganic Chemistry 2013;52(18) 10512-10519. DOI: 10.1021/

[47] Gupta SK, Singh J, Anbalagan K, Kothari P, Bhatia RR, Mishra PK, et al. Synthesis, phase to phase deposition and characterization of rutile nanocrystalline titanium di‐ oxide (TiO2) thin films. Applied Surface Science 2013;264 737-742. DOI: 10.1016/

[48] Idigoras J, Berger T, Anta JA. Modification of Mesoporous TiO2 Films by Electro‐ chemical Doping: Impact on Photoelectrocatalytic and Photovoltaic Performance. Journal of Physical Chemistry C 2013;117(4) 1561-1570. DOI: 10.1021/Jp306954y.

[49] Ji YF, Zhou L, Ferronato C, Salvador A, Yang X, Chovelon JM. Degradation of sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid by TiO2 photocatalysis: Ki‐ netics, photoproducts and comparison to structurally related compounds. Applied Catalysis B-Environmental 2013;140 457-467. DOI: 10.1016/j.apcatb.2013.04.046.

[50] Kim DS, Kwak SY. The hydrothermal synthesis of mesoporous TiO2 with high crys‐ tallinity, thermal stability, large surface area, and enhanced photocatalytic activity. Applied Catalysis a-General 2007;323 110-118. DOI: 10.1016/j.apcata.2007.02.010.

[51] Davis ME. Ordered porous materials for emerging applications. Nature

[52] Lee ES, Lee KM, Yoon SI, Ko YG, Shin DH. Influence of CNT incorporation on the photovoltaic behavior of TiO2 films formed by high-voltage electrophoretic deposi‐

tion. Current Applied Physics 2013;13 S26-S29. DOI: 10.1016/j.cap.2013.01.013.

[53] Kondo JN, Domen K. Crystallization of mesoporous metal oxides. Chemistry of Ma‐

[54] Zheng XL, Kuang Q, Yan KY, Qiu YC, Qiu JH, Yang SH. Mesoporous TiO2 Single Crystals: Facile Shape-, Size-, and Phase-Controlled Growth and Efficient Photocata‐ lytic Performance. Acs Applied Materials & Interfaces 2013;5(21) 11249-11257. DOI:

2002;417(6891) 813-821. DOI 10.1038/Nature00785.

terials 2008;20(3) 835-847. DOI: 10.1021/Cm702176m.

cells. Rsc Advances 2014;4(20) 10310-10316. DOI: 10.1039/C4ra00058g.

1350-1358. DOI: 10.1007/s11368-014-0883-7.

AMR.683.522.

108 Solar Radiation Applications

Ic401426q.

j.apsusc.2012.10.113.

10.1021/Am403482g.


SiO2 mixed oxide photocatalysts. International Journal of Hydrogen Energy 2012;37(15) 11061-11071.


method for application in dye solar cells. Ceramics International 2011;37(3) 1017-1024. DOI: 10.1016/j.ceramint.2010.11.014.

[78] Kojima T, Sugimoto T. Formation Mechanism of Amorphous TiO2 Spheres in Organ‐ ic Solvents 3. Effects of Water, Temperature, and Solvent Composition. Journal of Physical Chemistry C 2008;112(47) 18445-18454. DOI: 10.1021/Jp802957e.

SiO2 mixed oxide photocatalysts. International Journal of Hydrogen Energy

[67] Taffa DH, Kathiresan M, Arnold T, Walder L, Erbacher M, Bauer D, et al. Dye sensi‐ tized membranes within mesoporous TiO2 Photocurrents in aqueous solution. Jour‐ nal of Photochemistry and Photobiology a-Chemistry 2010;216(1) 35-43. DOI:

[68] Tan HQ, Zhao Z, Niu M, Mao CY, Cao DP, Cheng DJ, et al. A facile and versatile method for preparation of colored TiO2 with enhanced solar-driven photocatalytic

[69] Zhang RY, Elzatahry AA, Al-Deyab SS, Zhao DY. Mesoporous titania: From synthe‐ sis to application. Nano Today 2012;7(4) 344-366. DOI: 10.1016/j.nantod.2012.06.012.

[70] Zhou XF, Lu J, Jiang JJ, Li XB, Lu MN, Yuan GT, et al. Simple fabrication of N-doped mesoporous TiO2 nanorods with the enhanced visible light photocatalytic activity.

[71] Pal N, Bhaumik A. Soft templating strategies for the synthesis of mesoporous materi‐ als: Inorganic, organic-inorganic hybrid and purely organic solids. Advances in Col‐

[72] Abdel-Azim SM, Aboul-Gheit AK, Ahmed SM, El-Desouki DS, Abdel-Mottaleb MSA. Preparation and Application of Mesoporous Nanotitania Photocatalysts Using Different Templates and pH Media. International Journal of Photoenergy 2014;2014.

[73] Song HJ, Chen T, Sun YL, Zhang XQ, Jia XH. Controlled synthesis of porous flowerlike TiO2 nanostructure with enhanced photocatalytic activity. Ceramics Internation‐

[74] Patrocinio AOT, El-Bacha AS, Paniago EB, Paniago RM, Iha NYM. Influence of the Sol-Gel pH Process and Compact Film on the Efficiency of TiO2-Based Dye-Sensi‐ tized Solar Cells. International Journal of Photoenergy 2012. DOI:

[75] Niederberger M, Garnweitner G, Buha J, Polleux J, Ba JH, Pinna N. Nonaqueous syn‐ thesis of metal oxide nanoparticles: Review and indium oxide as case study for the dependence of particle morphology on precursors and solvents. Journal of Sol-Gel

Science and Technology 2006;40(2-3) 259-266. DOI: 10.1007/s10971-006-6668-8.

[76] Ribeiro C, Malagutti, A. R., Mendonça, V. R. E Mourão, A. J. L. Nanoestruturas em fotocatálise: uma revisão sobre estratégias de síntese de fotocatalisadores em escala

[77] Muniz EC, Goes MS, Silva JJ, Varela JA, Joanni E, Parra R, et al. Synthesis and charac‐ terization of mesoporous TiO2 nanostructured films prepared by a modified sol-gel

loid and Interface Science 2013;189 21-41. DOI: 10.1016/j.cis.2012.12.002.

activity. Nanoscale 2014;6(17) 10216-10223. DOI: 10.1039/C4nr02677b.

Nanoscale Research Letters 2014;9 DOI: 10.1186/1556-276x-9-34.

al 2014;40(7) 11015-11022. DOI: 10.1016/j.ceramint.2014.03.108.

2012;37(15) 11061-11071.

110 Solar Radiation Applications

10.1016/j.jphotochem.2010.09.003.

DOI: 10.1155/2014/687597.

10.1155/2012/638571.

nanométrica. Química Nova 2009;32(8).


[101] Gao J, Li HR, Rong H, Dai YH. Large pore nanocrystalline TiO2 films for quasi-solid state dye-sensitized solar cells. Nanotechnology and Precision Engineering, Pts 1 and 2 2013;662 177-181. DOI: 10.4028/www.scientific.net/AMR.662.177.

[89] Wen ZH, Wu W, Liu Z, Zhang H, Li JH, Chen JH. Ultrahigh-efficiency photocatalysts based on mesoporous Pt-WO3 nanohybrids. Physical Chemistry Chemical Physics

[90] Wang YZ, Zhu SP, Chen XR, Tang YG, Jiang YF, Peng ZG, et al. One-step templatefree fabrication of mesoporous ZnO/TiO2 hollow microspheres with enhanced photo‐ catalytic activity. Applied Surface Science 2014;307 263-271. DOI: 10.1016/j.apsusc.

[91] Shamaila S, Khan A, Sajjad L, Chen F, Zhang JL. Mesoporous titania with high crys‐ tallinity during synthesis by dual template system as an efficient photocatalyst. Cat‐

[92] Antonelli DM, Ying JY. Synthesis of Hexagonally Packed Mesoporous TiO2 by a Modified Sol-Gel Method. Angewandte Chemie-International Edition in English

[93] Joo JB, Lee I, Dahl M, Moon GD, Zaera F, Yin YD. Controllable Synthesis of Mesopo‐ rous TiO2 Hollow Shells: Toward an Efficient Photocatalyst. Advanced Functional

[94] Lopez A, Acosta D, Martinez AI, Santiago J. Nanostructured low crystallized titani‐ um dioxide thin films with good photocatalytic activity. Powder Technology

[95] Ramasamy E, Jo C, Anthonysamy A, Jeong I, Kim JK, Lee J. Soft-template simple syn‐ thesis of ordered mesoporous titanium nitride-carbon nanocomposite for high per‐ formance dye-sensitized solar cell counter electrodes. Chemistry of Materials

[96] Tran TH, Nosaka AY, Nosaka Y. Adsorption and decomposition of a dipeptide (Ala-Trp) in TiO2 photocatalytic systems. Journal of Photochemistry and Photobiology a-

[97] Lu YF, Fan HY, Stump A, Ward TL, Rieker T, Brinker CJ. Aerosol-assisted self-as‐ sembly of mesostructured spherical nanoparticles. Nature 1999;398(6724) 223-226.

[98] Yang H, Coombs N, Sokolov I, Ozin GA. Free-standing and oriented mesoporous silica films grown at the air-water interface. Nature 1996;381(6583) 589-592. DOI:

[99] Yang XH, Fu HT, Yu AB, Jiang XC. Large-surface mesoporous TiO2 nanoparticles: Synthesis, growth and photocatalytic performance. Journal of Colloid and Interface

[100] Wu MT, Chow TJ. TiO2 particles prepared by size control self-assembly and their us‐ age on dye-sensitized solar cell. Microporous and Mesoporous Materials 2014;196

Chemistry 2007;192(2-3) 105-113. DOI: 10.1016/j.jphotochem.2007.05.011.

alysis Today 2011;175(1) 568-575. DOI: 10.1016/j.cattod.2011.03.041.

Materials 2013;23(34) 4246-4254. DOI: 10.1002/adfm.201300255.

2010;202(1-3) 111-117. DOI: 10.1016/j.powtec.2010.04.025.

2012;24(9) 1575-1582. DOI: 10.1021/Cm203672g.

Science 2012;387 74-83. DOI: 10.1016/j.jcis.2012.06.080.

354-358. DOI: 10.1016/j.micromeso.2014.05.035.

DOI:10.1038/18410.

10.1038/381589a0.

2013;15(18) 6773-6778. DOI: 10.1039/c3cp50647a.

1995;34(18) 2014-2017. DOI: 10.1002/anie.199520141.

2014.04.023.

112 Solar Radiation Applications


[124] Zhao S, Su D, Che J, Jiang BY, Orlov A. Photocatalytic properties of TiO2 supported on SBA-15 mesoporous materials with large pores and short channels. Materials Let‐ ters 2011;65(23-24) 3354-3357. DOI 10.1016/j.matlet.2011.07.053.

[112] Xu S, Zhou CH, Yang Y, Hu H, Sebo B, Chen BL, et al. Effects of Ethanol on Optimiz‐ ing Porous Films of Dye-Sensitized Solar Cells. Energy & Fuels 2011;25(3) 1168-1172.

[113] Dhungel SK, Park JG. Optimization of paste formulation for TiO2 nanoparticles with wide range of size distribution for its application in dye sensitized solar cells. Renew‐

[114] Li Y, Wang WN, Zhan ZL, Woo MH, Wu CY, Biswas P. Photocatalytic reduction of CO2 with H2O on mesoporous silica supported Cu/TiO2 catalysts. Applied Catalysis

[115] Nguyen-Phan TD, Pham HD, Kim S, Oh ES, Kim EJ, Shin EW. Surfactant removal from mesoporous TiO2 nanocrystals by supercritical CO2 fluid extraction. Journal of Industrial and Engineering Chemistry 2010;16(5) 823-828. DOI: 10.1016/j.jiec.

[116] Spataru T, Preda L, Osiceanu P, Munteanu C, Anastasescu M, Marcu M, et al. Role of surfactant-mediated electrodeposited titanium oxide substrate in improving electro‐ catalytic features of supported platinum particles. Applied Surface Science 2014;288

[117] Mali SS, Kim H, Shim CS, Patil PS, Kim JH, Hong CK. Surfactant free most probable TiO2 nanostructures via hydrothermal and its dye sensitized solar cell properties. Sci‐

[118] Rahman MYA, Umar AA, Roza L, Salleh MM. Effect of optical property of surfac‐ tant-treated TiO2 nanostructure on the performance of TiO2 photo-electrochemical cell. Journal of Solid State Electrochemistry 2012;16(5) 2005-2010. DOI: 10.1007/

[119] Hashimoto K, Irie H, Fujishima A. TiO2 photocatalysis: A historical overview and fu‐ ture prospects. Japanese Journal of Applied Physics Part 1-Regular Papers Brief Communications & Review Papers 2005;44(12) 8269-8285. DOI: 10.1143/Jjap.44.8269.

[120] Hoffmann MR, Martin ST, Choi WY, Bahnemann DW. Environmental Applications of Semiconductor Photocatalysis. Chemical Reviews 1995;95(1) 69-96. DOI: 10.1021/

[121] Ibhadon AO, Fitzpatrick P. Heterogeneous Photocatalysis: Recent Advances and Ap‐

[122] Oregan B, Gratzel M. A Low-Cost, High-Efficiency Solar-Cell Based on Dye-Sensi‐ tized Colloidal TiO2 Films. Nature 1991;353(6346) 737-740. DOI: 10.1038/353737a0. [123] Khataee AR, Zarei M, Ordikhani-Seyedlar R. Heterogeneous photocatalysis of a dye solution using supported TiO2 nanoparticles combined with homogeneous photo‐ electrochemical process: Molecular degradation products. Journal of Molecular Cat‐

alysis a-Chemical 2011;338(1-2) 84-91. DOI: 10.1016/j.molcata.2011.01.028.

plications. Catalysts 2013;3(1) 189-218. DOI: 10.3390/Catal3010189.

B-Environmental 2010;100(1-2) 386-392. DOI: 10.1016/j.apcatb.2010.08.015.

able Energy 2010;35(12) 2776-2780. DOI: 10.1016/j.renene.2010.04.031.

DOI: 10.1021/Ef101546a.

114 Solar Radiation Applications

2010.05.005.

s10008-011-1605-3.

Cr00033a004.

660-665. DOI: 10.1016/j.apsusc.2013.10.092.

entific Reports 2013;3. DOI: 10.1038/Srep03004.


sensitized solar cells. Synthetic Metals 2009;159 2342-2344. DOI: 10.1016/j.synthmet. 2009.08.027.

[150] Shahid M, Shahid ul I, Mohammad F. Recent advancements in natural dye applica‐ tions: a review. Journal of Cleaner Production 2013;53(0) 310-331. DOI: http:// dx.doi.org/10.1016/j.jclepro.2013.03.031.

[137] Ito S, Nazeeruddin MK, Liska P, Comte P, Charvet R, Pechy P, et al. Photovoltaic characterization of dye-sensitized solar cells: Effect of device masking on conversion

efficiency. Progress in Photovoltaics 2006;14(7) 589-601. DOI: 10.1002/Pip.683.

[138] Park SH, Roy A, Beaupré S, Cho S, Coates N, Moon JS, et al. Bulk heterojunction so‐ lar cells with internal quantum efficiency approaching 100%. Nature Photonics

[139] Gratzel M. Solar energy conversion by dye-sensitized photovoltaic cells. Inorganic

[140] O'Regan B, Grätzel M. A Low-Cost, High-Efficiency Solar-Cell Based on Dye-Sensi‐ tized Colloidal TiO2 Films. Nature 1991;353(6346) 737-740. 10.1038/353737a0.

[141] Gratzel M. Photoelectrochemical cells. Nature 2001;414(6861) 338-344. DOI:

[142] Chiba Y, Islam A, Watanabe Y, Komiya R, Koide N, Han LY. Dye-sensitized solar cells with conversion efficiency of 11.1%. Japanese Journal of Applied Physics, Part 2:

[143] Kroon JM, Bakker NJ, Smit HJP, Liska P, Thampi KR, Wang P, et al. Nanocrystalline dye-sensitized solar cells having maximum performance. Progress in Photovoltaics

[144] Kalyanasundaram K, Gratzel M. Applications of functionalized transition metal com‐ plexes in photonic and optoelectronic devices. Coordination Chemistry Reviews

[145] Hinsch A, Veurman W, Brandt H, Loayza Aguirre R, Bialecka K, Flarup Jensen K.

[146] Higashijima S, Miura H, Fujita T, Kubota Y, Funabiki K, Yoshida T, et al. Highly effi‐ cient new indoline dye having strong electron-withdrawing group for zinc oxide dye-sensitized solar cell (vol 67, pg 6289, 2011). Tetrahedron 2011;67(43) 8421-8421.

[147] Kuang D, Uchida S, Humphry-Baker R, Zakeeruddin SM, Grätzel M. Organic dyesensitized ionic liquid based solar cells: Remarkable enhancement in performance through molecular design of indoline sensitizers. Angewandte Chemie-International

[148] Patrocinio AOT, Murakami Iha NY. Em busca da sustentabilidade: Células solares

[149] Patrocinio AOT, Mizoguchi SK, Paterno LG, Murakami Iha NY. Efficient and low cost devices for solar energy conversion: efficiency and stability of some natural dye

sensibilizadas por extratos naturais. Quimica Nova 2010;33(3) 574-578.

types. Progress in Photovoltaics 2012;20(6) 698-710. DOI: 10.1002/pip.1213.

dye solar module proto‐

2009;3 297-302. DOI:10.1038/nphoton.2009.69.

10.1038/35104607.

116 Solar Radiation Applications

Chemistry 2005;44(20) 6841-6851. DOI: 10.1021/Ic0508371.

Letters & Express Letters 2006;45(24-28) L638-L640.

1998;177 347-414. DOI: 10.1016/S0010-8545(98)00189-1.

Worldwide first fully up-scaled fabrication of 60 × 100 cm<sup>2</sup>

2007;15(1) 1-18. DOI: 10.1002/Pip.707.

DOI: 10.1016/j.tet.2011.08.092.

Edition 2008;47(10) 1923-1927.


Sensitized Solar Cells. International Journal of Photoenergy 2012;638 5711-5717. DOI: 10.1155/2012/638571.


**Chapter 6**
