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Lanthanides Effects on TiO2 Photocatalysts

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Gustavo Lopes Colpani, Micheli Zanetti, Rubieli Carla Frezza Zeferino, Luciano Luiz Silva, Josiane Maria Muneron de Mello, Humberto Gracher Riella, Natan Padoin, Márcio Antônio Fiori and Cíntia Soares

Submitted: 02 May 2018 Reviewed: 14 August 2018 Published: 22 November 2018

DOI: 10.5772/intechopen.80906

From the Edited Volume

Photocatalysts - Applications and Attributes

Edited by Sher Bahadar Khan and Kalsoom Akhtar

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Semiconductors have been evaluated to heterogeneous photocatalysis degradation of recalcitrant contaminants in aqueous media due to the capacity of mineralizing these compounds under UV or visible light irradiation. However, this process has the inherent feature of photogenerated charges recombination and the high bandgap energy of the electronic structure of some semiconductors that can reduce the formation of reactive oxygen species, which are responsible for the compound degradation. In this context, structural modifications in semiconductors have been proposed to enhance the photocatalytic activity, such as doping processes with elements that are capable of generating superficial defects that capture the formed electrons, avoiding the recombination, or increasing the density of –OH groups or water molecules on the surface of the catalyst, which can enhance the formation of hydroxyl radicals. Therefore, this brief review is proposed to show the role of lanthanides in the TiO2 doping and the synthesis method applied, as well as the results discussed in the literature.


  • photocatalyst
  • lanthanides
  • TiO2
  • doping
  • optical properties

1. Introduction

Photocatalysis applied in gas or aqueous media involves the reactive oxygen species (ROS) formation, mainly hydroxyl radical (•OH), superoxide (•O2), and singlet oxygen (1O2), which are generated by the oxidation of water molecules or capture of electrons by oxygen. These species are very effective oxidant agents, and they are capable of degrading recalcitrant compounds due to the high potential of oxidation. These ROS are produced on the semiconductors’ surface, such as titanium dioxide (TiO2), which is considered the most promising material because it is inexpensive, nontoxic, chemically and thermally stable, abundant, and environmentally friendly. However, this semiconductor only will produce these species when it receives a minimum energy amount, called the bandgap energy (Eg), which is capable to remove an electron from the valence band (VB) and transfer it to the conduction band (CB), thus creating the electron-hole pair. For TiO2, this minimum energy is supplied by photons with frequency in the ultraviolet light region, which possess wavelengths below 400 nm [1, 2, 3, 4, 5, 6].

Despite the ability of photocatalytic processes to degrade several compounds by the use of hydroxyl radicals, their use is still not widespread, with scarce industrial applications. This is due to some inherent features of the catalysts employed, such as the recombination of photogenerated charges, which reduces the formation of radicals and, consequently, the efficiency of photocatalytic degradation. Therefore, plenty of studies have been performed to overcome this drawback, like surface modifications that allow the capture of the generated electrons and avoid the recombination. Furthermore, the bandgap energy required for the formation of the electron/vacancy pair, which for TiO2 is equal to 3.2 eV, restricts this catalyst to the use of a light source that has wavelengths in the ultraviolet region (≈390 nm). Therefore, only 5% of sunlight can be used in photocatalysis that applies this semiconductor, which makes the process more expensive. In this way, superficial modification through metal and nonmetal doping is fundamental to overcome these drawbacks [7, 8, 9, 10].

Among the possible dopants, rare earths have been investigated for their ability to increase photocatalytic activity, possibly by reducing bandgap energy due to the introduction of orbitals between the conduction and valence bands, generating impurity energy levels in the semiconductor elements. These states are generated from the 4f level, which are electron deficient. Another hypothesis for this increase in contaminant degradability is that the adsorption of these lanthanides on the surface of the semiconductors generates an imbalance of surface charges, which can produce surface defects and vacancies of oxygen and titanium. These two propositions lead to states that serve as electron scavengers and reduce the recombination of photogenerated charges, increasing the probability of •OH formation. Moreover, the lanthanides adsorbed on the surface may act as traps to water molecule and –OH (hydroxyl anion) groups, which increase their density on the photocatalyst surface and can promote more intense formation of hydroxyl radicals. Another important feature related to the use of these compounds is that they serve as a Lewis base, which could concentrate the contaminants dispersed in aqueous medium on the semiconductor surface enhancing the electron transfer for the direct degradation of the contaminant or increasing the probability of interaction between the molecules and the radicals formed [11, 12, 13, 14, 15].

The mechanisms of lanthanides doping on TiO2 proposed by different researchers have not been the same, with two ways most discussed. Rare earths can be included in the TiO2 lattice by direct linking or substitution producing a≡Ti–O–Ln–O–Ti≡arrangement, which cause distortions/defects in the lattice due to the mismatch of ionic radius of Ln3+ and Ti4+. On the other hand, some doping methods do not supply enough energy to promote the ions substitution in the lattice, and the lanthanides are located in the TiO2 surface or boundaries of the semiconductor particles, creating Ti–O–Ln bonds [16, 17, 18, 19, 20].

Different methods are currently used for doping, like solvothermal, microemulsion, electrospinning, cathodic sputtering, hydrothermal, microwave, sonochemical, and sol–gel, which is the most usual process. However, these methods usually employ reactants such as tetrabutoxide and titanium isopropoxide, which are aggressive to the environment, besides using severe conditions of temperature and pressure. Therefore, the methodology using ultrasound appears as an alternative to avoid the application of secondary reactants and extreme conditions [21, 22, 23, 24, 25].

Lanthanides have particular features when compared with other metal oxides dopants, because they inhibit the transition from the anatase phase to the rutile phase, reduce the crystalline size, can easily react with the functional groups of Lewis bases to mineralize organic compounds, and bring luminescent properties to the titanium dioxide [19, 26, 27].

Thus, titanium dioxide doped with lanthanides, which avoid the recombination mechanisms, has been studied in the sense of optimizing the capacity of radical formation due to the increased numbers of defects and oxygen vacancies on the surface of the lattice to trap e−/h+ pairs and reduce the recombination, besides that increase the density of –OH groups or water molecules attached to the surface of the catalyst. However, the excess of these dopants reduces the photocatalytic capacity of the semiconductor, possibly due to the excess of vacancies generated, which act as recombination centers instead of electrons scavenger [28, 29, 30].


2. TiO2

The crystalline structures of titanium dioxide are anatase, rutile, and brookite, which is difficult to be synthesized in laboratory. Therefore, the first two lattices are the most prominent in researches. All crystal lattices are composed of TiO6 octahedra, but with distinct connections between these structures, since anatase has four connections between the edges, brookite has three connections, and rutile has only two. This structure confers to rutile a greater thermodynamic stability among the other polymorphs, as established by the third Pauling rule [31, 32, 33].

There is a great interest in the application of titanium dioxide as a photocatalyst because this compound is nontoxic, economical, chemically inert, and photostable to corrosion, besides high thermal stability, intense photocatalytic activity, and strong oxidant power. However, not all crystalline structures have the same efficiency in the absorption of light for catalysis; for example, although rutile is the polymorph thermodynamically more stable, its photocatalytic activity is lower than anatase, possibly due to the high temperature required for its preparation, which causes an increase in particle size, a high rate of electron/vacancy recombination that reduces the number of hydroxyl groups on the surface, and lower electron mobility in relation to anatase [34, 35, 36, 37].

However, the rutile phase has a bandgap equal to 3.0 eV, having the ability to absorb radiation in the visible light spectrum, while the anatase has a bandgap of approximately 3.2 eV. Therefore, the interaction of these two crystalline structures often has better photocatalytic results than when they are purely applied, which is possibly due to the visible light absorption by the rutile, which serves as a photosensitizer for the anatase phase. An example of this phase interaction is the commercial P25® titanium dioxide from Degussa Evonik, which has a composition of 80% anatase and 20% rutile, exhibiting high photocatalytic activity [32, 38, 39].

Regarding to the electronic structure, this catalyst can be considered a semiconductor with indirect bandgap for anatase phase, meaning that the valence and conduction bands of this lattice do not have the same maximum and minimum momentum, respectively. This condition leads to a recombination of the electron/vacancy pair that only occurs if assisted by a phonon, resulting in a longer lifetime of this electron generated. Furthermore, TiO2 is an n-type semiconductor; in other words it has a greater density of electrons than vacancies produced by oxygen, because they are compensated by the presence of Ti3+, which brings the Fermi level closer to the conduction band [40, 41, 42].

Bandgap energy for the structure with the highest photocatalytic activity is approximately 3.2 eV, and the valence band, formed mainly by the 2p orbital of the oxygen, has an energy level of approximately 2.60 V, which is more positive than the oxidation potential of water to hydroxyl radicals (E0 = 2.27 V). In the case of the conduction band, which is constituted mainly by titanium 3d orbitals, the energy level is equal to −0.51 V, with a value that is negatively greater than the oxygen reduction potential of the superoxide radical (E0 = −0.33 V). As depicted in Figure 1, with these conditions titanium dioxide can degrade organic compounds through activation by UV light, which makes it a prominent catalyst [13, 32, 43, 44, 45].

Figure 1.

Redox potential of conduction and valence bands and the radical formation.


3. Lanthanides

The rare earths (RE) are a group of elements with physicochemical properties that are very similar, which is constituted by lanthanides (lanthanum to lutetium), scandium, and yttrium, totalizing 17 elements of the periodic table. This series can be separated into light rare earths that comprise low atomic mass elements (lanthanum to europium) and heavy rare earths, which are constituted from lutetium to gadolinium, besides yttrium [19, 46].

These elements have shown great potential for industrial applications because of their unique magnetic, optical, and/or redox properties, with important uses in the field of catalysis, high temperature superconductors, hybrid cars, permanent magnets, nuclear magnetic resonance, rechargeable batteries, manufacture of glass and ceramic materials, shift reagents, etc. The electronic configuration of these chemical elements assure these properties due to the distribution of the electrons with the complete levels until 5, such as xenon, but with the level f, it was incomplete and protected by orbitals 6 s and/or 5d, except for of the scandium and yttrium. Thus, the representation of the electronic configuration is described as [Xe] 4fn6s2 or [Xe] 4fn5d16s2 for lanthanides (Ln), which usually have an oxidation state equal to 3+ (Ln3+) [47, 48, 49, 50, 51].

The orbitals 4f that were partially completed are responsible for the optical properties of rare earths, since different arrangements of these orbitals generate different levels of energy, allowing the absorption in a broad spectrum of light radiation, which can vary from ultraviolet to visible. Moreover, the luminescence of some rare earth ions arises from the f-f electronic transitions within their partially filled 4f orbitals that can occur by electric or magnetic dipole [52, 53].

Another advantage of this configuration is that these orbitals are sterically shielded from the surrounding microenvironment by the filled 5s and 5p orbitals, meaning that there are almost no perturbations of these transitions by other bonding elements, which assure that the optical properties do not undergo sudden changes [48, 54, 55].


4. Surface modification by lanthanides

The surface modification of semiconductors that occurs by the addition of tiny and controlled impurities is denominated doping, and this process is applied to achieve distinct electronic properties from those raw materials. Metal doping has a main feature, the bandgap reduction, which optimizes the ability of a semiconductor to absorb wavelengths with less energy, reduce recombination of the vacancy/electron pairs, and modify the adsorptive capacity of the surface of this photocatalyst. Bandgap reduction occurs possibly due to the formation of energy levels between the conduction and valence bands, such as when transition metals are used, because these incorporate levels 3d in the TiO2 lattice, which leads to the formation of electronic levels occupied near to the conduction band. However, visible light absorption by semiconductor doped with noble metals, such as gold and silver, may be associated with the surface resonance effect of Plasmon, which is described as an oscillation of the electrons on the surface of these metals, which cause a separation of charge carriers [13, 44, 56].

Another advantage of metal doping is the decrease in photogenerated charges recombination, which is due to the Schottky barrier formation in the interface of semiconductor and metal. The electrons formed migrate, and they are captured by the metal particles, which become active sites for oxygen reduction. This barrier is formed by the electronic binding between the lanthanides and titanium dioxide, allowing the mobility of electrons formed in the semiconductor valence band to the metal, until equilibrium occurs between the Fermi levels [57, 58].

The rare earths when applied in TiO2 doping have shown one or both features above discussed, mainly due to the presence of incomplete 4f levels, surface defects, and oxygen vacancies. The first ones reduce the TiO2 bandgap due to the appearance of orbitals between the conduction and valence bands, which generates impure energy levels. This reduction provides an electron transfer from VB until the orbital created and/or from this to the CB requires less energy. In addition, these orbitals f have the ability to produce complexes with several Lewis bases, increasing the concentration of these species on the surface of the catalyst and, consequently, the photocatalytic activity. Moreover, these orbitals have the ability to trap the photogenerated electrons due to their incomplete levels, which avoids the recombination of the charge carriers [11, 12, 13, 14, 15].

Another advantage of lanthanides is the ability of some ions of these elements (Ln3+) to generate surface defects and titanium and oxygen vacancies. This occurs possibly because some lanthanides ions have an atomic radius higher than Ti4+ (0.68 Å), such as La3+ (1.15 Å) and Sm3+ (1.24 Å). In these cases, Ln3+ is not able to replace the titanium ions in the semiconductor lattice, and these ions only are adsorbed on the surface, forming Ti–O–Ln3+ bonds. This fact leads to an imbalance in the surface charges of the TiO2 crystal structure. Since titanium atom has a Pauling electronegativity value (1.54) higher than those presented by lanthanum (1,10) and samarium atoms (1,17), a transfer of electrons occur from these lanthanides to the titanium, which is converted from Ti4+ to Ti3+. The excess of negative charge disturbs the electronegativity, and it is necessary remove an ion of O2− for every two Ti3+ ions produced, which causes the formation of oxygen and titanium vacancies, generating a surface defect. Furthermore, the presence of lanthanides, dispersed as interstitial impurities on the TiO2 lattice causes surface defects. The presence of these vacancies and defects causes the capture of electrons produced on the surface of the photocatalyst and decreases the recombination of photogenerated charge carriers. However, an excess of lanthanides on the photocatalyst surface can lead to a high density of defects and vacancies, which creates recombination centers [30, 59, 60, 61, 62, 63, 64].

Rare earth application as dopant also can increase the surface area of the catalyst because it reduces the growth of the crystal structure. Besides, these elements can increase the thermal stability, since they interfere in the conversion of the anatase phase to rutile during the calcination of the doped semiconductors [12, 25, 65].

Lanthanides have been applied as TiO2 dopants in many researches, highlighting yttrium, cerium, neodymium, praseodymium, europium, samarium, and lanthanum, with promising photocatalytic activity responses, such as studies performed by Liu et al. [66] which evaluated the cerium doping on titanium dioxide using chemical coprecipitation method, with molar ratio from 0.5 to 2.5% of cerium in relation to the semiconductor to evaluate the degradation of methylene blue 2,3-dichlorophenol and benzene, under visible and UV light. The best results occur when the RE concentration was equal to 0.50% (mol∙mol−1). Xue et al. [67] evaluated the effects of cerium doping into TiO2 nanotubes by chemical impregnation and ultrasound. The molar ratio applied was 0.1–1.0% of the lanthanide in relation to the semiconductor, with subsequent calcination of all samples at 673 K. The results obtained in the degradation of glyphosate under UV light showed that the molar ratio equal 0.15% optimizes the photocatalysis.

Cerium doping was also recently evaluated by Pei et al. [68] in the titanium dioxide nanorods formation. The inclusion of cerium in the semiconductor occurred by hydrothermal method. The inclusion of this element changed the semiconductor wavelength absorption to 480 nm, with bandgap energy equal to 2.65 eV, meaning that photocatalysis can occur in visible light.

Neodymium (Nd) has attracted interest as a semiconductor dopant because of its ability to absorb and emit wavelengths in the range from UV to IR radiation, besides the usual features of RE, such as discussed above. Du et al. [69] used this element in the titanium dioxide film doping by sol–gel method. In this research, the photocatalytic effects of the mass ratios of neodymium (0.1 and 0.9%) after calcination at 823 K for 2 h were evaluated. The obtained films were used in the degradation of methylene blue under UV light, with efficiency upper of 92% in the removal of this dye when using a mass ratio of 0.10%. Possibly, this increment occurs due to a reduction in bandgap energy, since analysis showed an increase in the visible light wavelengths absorption by the doped semiconductor. Another important research was done by Thomas et al. [70] who applied molar ratios equal to 0.30, 0.50, and 0.70% of neodymium to doping titanium dioxide via sol-gel method. It evaluated the insertion of a third component, phosphotungstic acid, in the degradation of methylene blue and 4-chlorophenol under visible light. The results obtained showed an increase in the degradation in relation to the pure semiconductor, with the best result when the molar ratio was equal to 0.50%.

Another element evaluated for titanium dioxide doping is praseodymium, classified as a light rare earth with molar mass equal to 140.9 g·mol−1. Liang et al. [71] evaluated the degradation of the reactive yellow dye 4 under UV and visible radiation using TiO2 doped with different ionic ratios of praseodymium (0.50–1.80%), which was included in the crystal lattice by sol–gel method, with calcination at 773 K for 2 h. The photodegradation results demonstrated that Ln3+:TiO2 equal to 1.0 and 1.5% optimizes the photocatalytic capacity of the semiconductor in degrading the contaminant under UV and visible light, respectively. This increase in the catalytic activity of praseodymium doped semiconductors was also confirmed according to research published by Kralova et al. [72], which demonstrated that titanium dioxide doped with 0.3 mol% of praseodymium at different temperatures (723, 823 and 923 K) and calcination times (4, 8 and 12 h) promotes a reduction in bandgap energy (from 3.20 to 3.14 eV) when the photocatalyst was calcined at 723 K for 8 h. The efficiency increase in the degradation of an organochlorine pesticide under UV light (LED) possibly is related to milder temperatures joined with intermediate times, which ensure a diffusion of the lanthanide without changes in the crystalline phase.

The studies performed by Leal et al. [73] are prominent due to the extensive evaluation about lanthanides doping of TiO2 lattices. The light lanthanide series (La-Eu), besides gadolinium, were evaluated for the degradation of orange and violet methyl by UV light. The pH values (3.1 and 5.6) and the mass fraction of Ln3+:TiO2 (0.1 and 0.3%) were used as parameters for the experiments, with semiconductor doping by the sol–gel method and calcination at 773 K for 2 h. The results showed an increase (approximately 37%) in the degradation of the compounds when the doped semiconductors were applied instead of pure TiO2. Therefore, this research provides an overview of the potential application of these lanthanides to degrade different compounds under different process conditions.

Reszczyńska et al. [74] also evaluated the effects of the application of yttrium, praseodymium, erbium, and europium in the photodegradation efficiency of phenol, under visible and UV light. Furthermore, hydrothermal and sol-gel methods for semiconductor doping were compared in relation to photocatalytic activity response. It used the molar ratios of 0.25 and 0.50% of Ln3+ in relation to titanium dioxide. The results showed an increase in phenol degradation under visible light for doped photocatalysts when compared to pure TiO2. When UV light was applied as radiation source only, the hydrothermal process showed better results than the pure semiconductor. However, if the decomposition efficiencies of the contaminant are compared, it is remarkable that the hydrothermal process overcomes the sol-gel method in most cases. This possibly is related to the high surface area, low crystallite dimensions, and higher density of –OH obtained in the first method employed. In addition, the lower concentration of rare earths in doping showed the best degradation results of the molecule evaluated.

Lanthanum (La) doping has an extensive discussion about the mechanisms, which are well-known. However, different methods, as well as the optimized rare earth amount for each of these methods, are still evaluated, without being exhausted. Among the researches carried out, Li et al. [75] evaluated different amounts (0–0.50%) of lanthanum in the TiO2 doping, which are impregnated in the semiconductor by sol-gel method, with subsequent calcination (973–1173 K). The best response in methyl orange photodegradation occurred when the concentration of lanthanum was 0.05% with a calcination temperature at 973 K.

Jun et al. [76] analyzed the photocatalytic activity of TiO2 doped with different concentrations of lanthanum (from 0 to 0.90% w∙w−1) by sol–gel method followed by calcination at 823 K for 2 h. The results showed that mass ratio 0.30% (0.17% mol∙mol−1) demonstrated the best results in methylene blue removal. It was proposed that the increase in photocatalytic efficiency is due to the formation of vacancies and defects from the presence of lanthanide on the TiO2 surface. It was also possible to verify that an increase in lanthanum concentration causes a reduction in photocatalytic efficiency, possibly because La serves as a mediator in the interfacial charge transfer or as a recombination center.

Samarium (Sm) has been used to doping semiconductors because its presence causes significant improvements in the degradation of compounds, which leads the semiconductors to absorb wavelengths in the visible light spectrum, besides low cost of the compound when compared with others lanthanides. Tang et al. [77] doped titanium dioxide with different concentrations of samarium (0–2.16% mol∙mol−1) by the sol-gel method followed by different calcination temperatures (623–1123 K). The pollutants evaluated were methanol and acetone, with best results when the lowest concentrations of samarium (0.30 and 0.43%) were applied. The photocatalytic degradations achieved results of upper 90% when applied by UV light, which demonstrates that an increase in the amount of rare earths can lead these photocatalysts from electron traps to recombination centers.

Xiao et al. [78] demonstrated that methylene blue degradation under UV light showed best responses when the lowest samarium molar ratio was applied (0.50%). The sol-gel method was used for the inclusion of Sm in the TiO2 lattice, and the samples were calcined for 2 h at 873 K.

4.1. Calcination temperature effects

Calcination is a vital step for doping, since it allows the activation and/or fixation of the dopant in the semiconductor crystal structure, besides the removal of impurities and the increase in the density of vacancies due to the removal of oxygen from the photocatalyst lattice, in addition to promoting an increase in crystallization. However, an excessive increase in the calcination temperature can lead to a particle aggregation and, consequently, reduction of the surface area, besides the conversion of the anatase phase to rutile, which can affect the photocatalytic activity. Therefore, the calcination temperature control is essential to assure high photocatalytic activity [75, 79, 80, 81].

Usually anatase to rutile phase transformation occurs at temperatures between 500 and 750°C, as soon as there is an increase in the crystalline size of anatase when the calcination temperature enhances. However, the lanthanides doping shift the phase transformation to higher temperatures (above 700°C) and suppress the anatase crystalline growth between 500 and 700°C [82, 83, 84, 85, 86].

Chen et al. [87] evaluated the effect of rare earth doping (0.20, 0.50, 1.0, and 2.0% mol) by hydrothermal method and the calcination temperature (673, 773, 873 and 1073 K). The results obtained showed that the best photocatalytic activity was achieved when the temperature of calcination was 773 K for 2 h, with a crystallite size equal to 15 nm. It was possible to verify that an increase of the temperature reduces the surface area of the crystal structures formed.

Cruz et al. [88] published a research about titanium dioxide doped with samarium via sol–gel method, in which the photocatalytic degradation of a herbicide under UV light was investigated. The parameters evaluated were the calcination temperature and the samarium concentration, with the best efficiency in herbicide degradation when the samples were calcined at 773 K for 4 h. Similar results were obtained by Yang et al. [76], which showed that the degradation of the methylene blue by TiO2 doped with neodymium and fluorine via sol-gel method was optimized when the temperature and time of calcination were equal to 773 K and 3 h, respectively.

Li et al. [89] also evaluate the effect of temperature on the photocatalytic activity of titanium dioxide doped with europium via hydrothermal method. It used calcination temperatures between 573 and 1173 K. The temperature at 773 K, with a calcination time of 4 h, improves the degradability of the contaminant, probably because of the increase in crystallization and reduction of defects, which improve the ability to absorb visible light wavelengths.


5. Conclusion

The degradation of recalcitrant compounds using semiconductors doped with lanthanides, in aqueous media, is a promising area due to the increasing incidence of these compounds in water media due to the inefficiency of current processes in eliminating such molecules. Doping semiconductors with lanthanides has been an efficient strategy to generate defects in the surfaces of the materials. These defects act as active sites that capture the electrons and prevent recombination events or increase the density of hydroxyl groups and increase the amount of water molecules bound on the surface of photocatalytic materials. All these mechanisms increase the efficiency of the photodegradation processes. However, the excess of these dopants reduces the photocatalytic capacity of the semiconductor, possibly due to the excess of vacancies generated, which act as recombination centers instead of electrons scavenger.



The authors acknowledge the Community University of Chapecó and Region (Unochapecó), for technical and scientific support.


Conflict of interest

There are no conflicts to declare.


  1. 1. Devi LG, Kumar SG. Exploring the critical dependence of adsorption of various dyes on the degradation rate using Ln3+-TiO2 surface under UV/solar light. Applied Surface Science. 2012;261:137-146. DOI: 10.1016/j.apsusc.2012.07.121
  2. 2. Leong S, Ramzjou A, Wang K, Hapgood K, Zhang X, Wang H. TiO2 based photocatalytic membranes: A review. Journal of Membrane Science. 2014;472:167-184. DOI: 10.1016/j.memsci.2014.08.016
  3. 3. Fotiou T, Triantis TM, Kaloudis T, O’shea KE, Dionysiou DD, Hiskia A. Assessment of the roles of reactive oxygen species in the UV and visible light photocatalytic degradation of cyanotoxins and water taste and odor compounds using C–TiO2. Water Research. 2016;90:52-61. DOI: 10.1016/j.watres.2015.12.006
  4. 4. Ribao P, Corredor J, Rivero MJ, Ortiz I. Role of reactive oxygen species on the activity of noble metal-doped TiO2 photocatalysts. Journal of Hazardous Materials. DOI: 10.1016/j.jhazmat.2018.05.026. In press
  5. 5. Khan SA, Khan SB, Asiri AM. Layered double hydroxide of Cd-Al/C for the mineralization and de-coloration of dyes in solar and visible light exposure. Scientific Reports. 2016;6(35107):1-14. DOI: 10.1038/srep35107
  6. 6. Arshad T, Khan SA, Faisal M, Shah Z, Akhtar K, Asiri AM, et al. Cerium based photocatalysts for the degradation of acridine orange in visible light. Journal of Molecular Liquids. 2017;241:20-26. DOI: 10.1016/j.molliq.2017.05.079
  7. 7. Singh S, Mahalingam H, Singh PK. Polymer-supported titanium dioxide photocatalysts for environmental remediation: A review. Applied Catalysis A: General. 2013;462-463:178-195. DOI: 10.1016/j.apcata.2013.04.039
  8. 8. Zhao C, Pelaez M, Dionysiou DD, Pillai SC, Byrne JA, O’shea KE. UV and visible light activated TiO2 photocatalysis of 6-hydroxymethyluracil, a model compound for the potent cyanotoxin cylindrospermopsin. Catalysis Today. 2014;224:70-76. DOI: 10.1016/j.cattod.2013.09.042
  9. 9. Etacheri V, Valentin C, Schneider J, Bahnemann D, Pillai SC. Visible-light activation of TiO2 photocatalysts: Advances in theory and experiments. Journal of Photochemistry and Photobiology, C: Photochemistry Reviews. 2015;25:1-29. DOI: 10.1016/j.jphotochemrev.2015.08.003
  10. 10. Wang W, Huang G, Yu JC, Wong PK. Advances in photocatalytic disinfection of bacteria: Development of photocatalysts and mechanisms. Journal of Environmental Sciences. 2015;34:232-247. DOI: 10.1016/j.jes.2015.05.003
  11. 11. Kumaresan L, Prabhu A, Palanichamy M, Arumugam E, Murugesan V. Synthesis and characterization of Zr4+, La3+ and Ce3+ doped mesoporous TiO2: Evaluation of their photocatalytic activity. Journal of Hazardous Materials. 2011;186:1183-1192. DOI: 10.1016/j.jhazmat.2010.11.124
  12. 12. Cao Y, Zhao Z, Yi J, Ma C, Zhou D, Wang R, et al. Luminescence properties of Sm3+-doped TiO2 nanoparticles: Synthesis, characterization, and mechanism. Journal of Alloys and Compounds. 2013;553:12-20. DOI: 10.1016/j.jallcom.2012.11.149
  13. 13. Coronado JM, Fresno F, Hernández-Alonso MD, Portela R. Design of Advanced Photocatalytic Materials for Energy and Environmental Applications, Green Energy and Technology. 1st ed. London: Springer-Verlag; 2013. DOI: 10.1007/978-1-4471-5061-9_1. 351p
  14. 14. Liu Y, Fang P, Cheng Y, Gao Y, Chen F, Liu Z, et al. Study on enhanced photocatalytic performance of cerium doped TiO2-based nanosheets. Chemical Engineering Journal. 2013;219:478-485. DOI: 10.1016/j.cej.2012.12.098
  15. 15. Sudhagar P, Devadoss A, Nakata K, Terashima C, Fujishima A. Enhanced photoelectrocatalytic water splitting at hierarchical Gd3+:TiO2 nanostructures through amplifying light reception and surface states passivation. Journal of the Electrochemical Society. 2015;162(3):H108-H114. DOI: 10.1149/2.0161503jes
  16. 16. Colpani GL, Zanetti JT, Cecchin F, Dal'Toé A, Fiori MA, Moreira RFPM, et al. Carboxymethyl-β-cyclodextrin functionalization of TiO2 doped with lanthanum: Characterization and enhancement of photocatalytic activity. Catalysis Science & Technology. 2018;8:2636-2647. DOI: 10.1039/c7cy02115a
  17. 17. Dal’Toé ATO, Colpani GL, Padoin N, Fiori MA, Soares C. Lanthanum doped titania decorated with silver plasmonic nanoparticles with enhanced photocatalytic activity under UV-visible light. Applied Surface Science. 2018;441:1057-1071. DOI: 10.1016/j.apsusc.2018.01.291
  18. 18. Ali KA, Abdullah AZ, Mohamed AR. Visible light responsive TiO2 nanoparticles modified using Ce and La for photocatalytic reduction of CO2: Effect of Ce dopant content. Applied Catalysis A: General. 2017;537:111-120. DOI: 10.1016/j.apcata.2017.03.022
  19. 19. Mazierski P, Mikolajczyk A, Bajorowicz B, Malankowska A, Zaleska-Medynska A, Nadolna J. The role of lanthanides in TiO2-based photocatalysis: A review. Applied Catalysis B: Environmental. 2018;233:301-317. DOI: 10.1016/j.apcatb.2018.04.019
  20. 20. Bingham S, Daoud WA. Recent advances in making nano-sized TiO2 visible-light active through rare-earth metal doping. Journal of Materials Chemistry. 2011;21:2041-2050. DOI: 10.1039/c0jm02271c
  21. 21. Gomez V, Balu AM, Ruiz JCS, Irusta S, Dionysiou DD, Luque R, et al. Microwave-assisted mild-temperature preparation of neodymium-doped titania for the improved photodegradation of water contaminants. Applied Catalysis A: General. 2012;441-442:47-53. DOI: 10.1016/j.apcata.2012.07.003
  22. 22. Shirsath SR, Pinjari DV, Gogate PR, Sonawane SH, Pandit AB. Ultrasound assisted synthesis of doped TiO2 nano-particles: Characterization and comparison of effectiveness for photocatalytic oxidation of dyestuff effluent. Ultrasonics Sonochemistry. 2013;20:277-286. DOI: 10.1016/j.ultsonch.2012.05.015
  23. 23. Zheng JQ, Zhu YJ, Xu JS, Lu BQ, Qi C, Chen F, et al. Microwave assisted rapid synthesis and photocatalytic activity of mesoporous Nd-doped SrTiO3 nanospheres and nanoplates. Materials Letters. 2013;100:62-65. DOI: 10.1016/j.matlet.2013.02.107
  24. 24. Sathishkumar P, Mangalaraja RV, Rozas O, Mansilla HD, Pinilla MAG, Anandan S. Low frequency ultrasound (42 kHz) assisted degradation of Acid Blue 113 in the presence of visible light driven rare earth nanoclusters loaded TiO2 nanophotocatalysts. Ultrasonics Sonochemistry. 2014;21:1675-1681. DOI: 10.1016/j.ultsonch.2014.03.004
  25. 25. Yaoguang Y, Gang C, Yansong Z, Zhonghui H. Recent advances in rare earth elements modification of inorganic semiconductor based photocatalysts for efficient solar energy conversion: A review. Journal of Rare Earths. 2015;33(5):453-462. DOI: 10.1016/S1002-0721(14)60440-3
  26. 26. Shayegan Z, Lee C, Haghighat F. TiO2 photocatalyst for removal of volatile organic compounds in gas phase—A review. Chemical Engineering Journal. 2018;334:2408-2439. DOI: 10.1016/j.cej.2017.09.153
  27. 27. Zheng X, Li X, Peng H, Wen J. Ag-decorated core-shell Sm2O3@TiO2 nanocomposites with enhanced visible-light photocatalytic performance. Journal of Physics and Chemistry of Solids. 2018;123:206-215. DOI: 10.1016/j.jpcs.2018.07.022
  28. 28. Jaimy KB, Ghosh S, Warrier KG. Enhanced visible light activity of nano-titanium dioxide doped with multiple ions: Effect of crystal defects. Journal of Solid State Chemistry. 2012;196:465-470. DOI: 10.1016/j.jssc.2012.06.048
  29. 29. Samadi M, Zirak M, Naseri A, Khorashadizade E, Moshfegh AZ. Recent progress on doped ZnO nanostructures for visible-light photocatalysis. Thin Solid Films. 2016;605:2-19. DOI: 10.1016/j.tsf.2015.12.064
  30. 30. Nešić J, Manojlović DD, Anđelković I, Dojčinović BP, Vulić PJ, Krstić J, et al. Preparation, characterization and photocatalytic activity of lanthanum and vanadium co-doped mesoporous TiO2 for azo-dye degradation. Journal of Molecular Catalysis A: Chemical. 2013;378:67-75. DOI: 10.1016/j.molcata.2013.05.018
  31. 31. Marschall R, Wang L. Non-metal doping of transition metal oxides for visible-light photocatalysis. Catalysis Today. 2014;225:111-135. DOI: 10.1016/j.cattod.2013.10.088
  32. 32. Verbruggen SW. TiO2 photocatalysis for the degradation of pollutants in gas phase: From morphological design to plasmonic enhancement. Journal of Photochemistry and Photobiology, C: Photochemistry Reviews. 2015;24:64-82. DOI: 10.1016/j.jphotochemrev.2015.07.001
  33. 33. Patil RA, Devan RS, Liou Y, Ma Y. Efficient electrochromic smart windows of one-dimensional pure brookite TiO2 nanoneedles. Solar Energy Materials & Solar Cells. 2016;147:240-245. DOI: 10.1016/j.solmat.2015.12.024
  34. 34. Nakata K, Fujishima A. TiO2 photocatalysis: Design and applications. Journal of Photochemistry and Photobiology, C: Photochemistry Reviews. 2012;13:169-189. DOI: 10.1016/j.jphotochemrev.2012.06.001
  35. 35. Lan Y, Lu Y, Ren Z. Mini review on photocatalysis of titanium dioxide nanoparticles and their solar applications. Nano Energy. 2013;2:1031-1045. DOI: 10.1016/j.nanoen.2013.04.002
  36. 36. Gaya UI. Heterogeneous Photocatalysis Using Inorganic Semiconductor Solids. Inglaterra: Springer Science+Business Media Dordrecht; 2014. DOI: 10.1007/978-94-007-7775-0
  37. 37. Zangeneh H, Zinatizadeh AAL, Habibi M, Akia M, Isa MH. Photocatalytic oxidation of organic dyes and pollutants in wastewater using different modified titanium dioxides: A comparative review. Journal of Industrial and Engineering Chemistry. 2015;26:1-36. DOI: 10.1016/j.jiec.2014.10.043
  38. 38. Krishna MV, Madhavi G, Idris NF, Idris SAM, Chowdary LRK. Photocatalysis of β-blockers—An overview. Arabian Journal of Chemistry. 2014. DOI: 10.1016/j.arabjc.2014.10.044. In press
  39. 39. Monteiro RAR, Miranda SM, Silva CR, Faria JL, Silva AMT, Boaventura RAR, et al. Gas phase oxidation of n-decane and PCE by photocatalysis using an annular photoreactor packed with a monolithic catalytic bed coated with P25 and PC500. Applied Catalysis B: Environmental. 2015;165:306-315. DOI: 10.1016/j.apcatb.2014.10.026
  40. 40. Ângelo J, Andrade L, Madeira LM, Mendes A. An overview of photocatalysis phenomena applied to NOx abatement. Journal of Environmental Management. 2013;129:522-539. DOI: 10.1016/j.jenvman.2013.08.006
  41. 41. Miessler GL, Fischer PJ, Tarr DA. Química Inorgânica. 5th ed. São Paulo: Pearson Education do Brasil; 2014. 649p
  42. 42. Zhang J, Zhou P, Liu J, Yu J. New understanding of the difference of photocatalytic activity among anatase, rutile and brookite TiO2. Physical Chemistry Chemical Physics. 2014;16:20382-20386. DOI: 10.1039/C4CP02201G
  43. 43. Henderson MA. A surface science perspective on TiO2 photocatalysis. Surface Science Reports. 2011;66:185-297. DOI: 10.1016/j.surfrep.2011.01.001
  44. 44. Park H, Park Y, Kim W, Choi W. Surface modification of TiO2 photocatalyst for environmental applications. Journal of Photochemistry and Photobiology, C: Photochemistry Reviews. 2013;15:1-20. DOI: 10.1016/j.jphotochemrev.2012.10.001
  45. 45. Wen J, Li X, Liu W, Fang Y, Xie J, Xu Y. Photocatalysis fundamentals and surface modification of TiO2 nanomaterials. Chinese Journal of Catalysis. 2015;36:2049-2070. DOI: 10.1016/S1872-2067(15)60999-8
  46. 46. Jha MK, Kumari A, Panda R, Kumar JR, Yoo K, Lee JY. Review on hydrometallurgical recovery of rare earth metals. Hydrometallurgy. 2016;161:77-101. DOI: 10.1016/j.hydromet.2016.01.035
  47. 47. Turra C. Impacto dos elementos terras raras no agrossistema citrícola [Thesis]. São Paulo: Universidade de São Paulo; 2010
  48. 48. Atwood DA. The Rare Earth Elements: Fundamentals and Applications. United Kingdom: John Wiley & Sons, Ltd; 2012. 649p
  49. 49. Lima JF. Nanocompostos a base de cério com aplicações na absorção da radiação ultravioleta [thesis]. São Paulo: Universidade de São Paulo; 2013
  50. 50. Cotton S. Lanthanide and Actinide Chemistry. United Kingdom: John Wiley & Sons Ltd; 2006. DOI: 10.1002/0470010088. 263p
  51. 51. Quirino WG. Produção e caracterização de dispositivos orgânicos eletroluminescentes (OLEDs) baseados em complexos β-dicetonatos de terras-raras [Thesis]. Rio de Janeiro: Pontifícia Universidade Católica; 2007
  52. 52. Huang C. Rare Earth Coordination Chemistry Fundamentals and Applications. Singapore: John Wiley & Sons; 2010. DOI: 10.1002/9780470824870. 575p
  53. 53. Li X, Zhang F, Zhao D. Highly efficient lanthanide upconverting nanomaterials: Progresses and challenges. Nano Today. 2013;8:643-676. DOI: 10.1016/j.nantod.2013.11.003
  54. 54. Malta OL. Mechanisms of non-radiative energy transfer involving lanthanide ions revisited. Journal of Non-Crystalline Solids. 2008;354:4770-4776. DOI: 10.1016/j.jnoncrysol.2008.04.023
  55. 55. Shimizu Y, Ueda K. Lanthanide 4f energy levels in perovskite-type YAlO3. Journal of Luminescence. 2015;168:14-19. DOI: 10.1016/j.jlumin.2015.07.018
  56. 56. Fornari AMD. Atividade fotocatalítica e fotoeletroquímica de nanotubos de TiO2 impregnados com nanopartículas de metais nobres ou pontos quânticos para aplicação na produção de hidrogênio [Thesis]. Rio Grande do Sul: Universidade Federal do Rio Grande do Sul; 2014
  57. 57. Dong H, Zeng G, Tang L, Fan C, Zhang C, He X, et al. An overview on limitations of TiO2-based particles for photocatalytic degradation of organic pollutants and the corresponding countermeasures. Water Research. 2015;79:128-146. DOI: 10.1016/j.watres.2015.04.038
  58. 58. Ferreira Neto VJM. Processo fotocatalítico aplicado à geração de energia—Redução fotocatalítica de dióxido de carbono [Thesis]. Rio de Janeiro: Universidade Federal do Rio de Janeiro; 2015
  59. 59. Cai H, Chen X, Li Q, He B, Tang Q. Enhanced photocatalytic activity from Gd, La codoped TiO2 nanotube array photocatalysts under visible-light irradiation. Applied Surface Science. 2013;284:837-842. DOI: 10.1016/j.apsusc.2013.08.018
  60. 60. Lan X, Wang L, Zhang B, Tian B, Zhang J. Preparation of lanthanum and boron co-doped TiO2 by modified sol–gel method and study their photocatalytic activity. Catalysis Today. 2014;224:163-170. DOI: 10.1016/j.cattod.2013.10.062
  61. 61. Callister WD, Rethwisch DG. Materials Science and Engineering: An Introduction. 7th ed. New York: John Wiley & Sons; 2007. 721p
  62. 62. Meksi M, Turki A, Kochkar H, Bousselmi L, Guillard C, Berhault G. The role of lanthanum in the enhancement of photocatalytic properties of TiO2 nanomaterials obtained by calcination of hydrogenotitanate nanotubes. Applied Catalysis B: Environmental. 2016;181:651-660. DOI: 10.1016/j.apcatb.2015.08.037
  63. 63. Tao Z, Ding H, Chen X, Hou G, Zhang Q, Tang M, et al. The co-doping effect of Sm and In on ceria for electrolyte application in IT-SOFC. Journal of Alloys and Compounds. 2016;663:750-754. DOI: 10.1016/j.jallcom.2015.12.164
  64. 64. Zhou X, Zhang X, Feng X, Zhou J, Zhou S. Preparation of a La/N co-doped TiO2 film electrode with visible light response and its photoelectrocatalytic activity on a Ni substrate. Dyes and Pigments. 2016;125:375-383. DOI: 10.1016/j.dyepig.2015.10.044
  65. 65. Maba G. Rare earth doped titania/carbon nanomaterials composite photocatalysts for water treatment [Thesis]. Johannesburg: University of Johannesburg; 2015
  66. 66. Liu TX, Li XZ, Li FB. Enhanced photocatalytic activity of Ce3+-TiO2 hydrosols in aqueous and gaseous phases. Chemical Engineering Journal. 2010;157:475-482. DOI: 10.1016/j.cej.2009.12.010
  67. 67. Xue W, Zhang G, Xu X, Yang X, Liu C. Preparation of titania nanotubes doped with cerium and their photocatalytic activity for glyphosate. Chemical Engineering Journal. 2011;167:397-402. DOI: 10.1016/j.cej.2011.01.007
  68. 68. Pei LZ, Liu HD, Lin N, Yu HY. Hydrothermal synthesis of cerium titanate nanorods and its application in visible light photocatalysis. Materials Research Bulletin. 2015;61:40-46. DOI: 10.1016/j.materresbull.2014.09.094
  69. 69. Du J, Qi W, Shan Z, Xin G, Jiao L, Haizhi G, et al. Effect of hydroxyl groups on hydrophilic and photocatalytic activities of rare earth doped titanium dioxide thin films. Journal of Rare Earths. 2015;33(2):148-153. DOI: 10.1016/S1002-0721(14)60395-1
  70. 70. Thomas J, Radhika S, Yoon M. Nd3+-doped TiO2 nanoparticles incorporated with heteropoly phosphotungstic acid: A novel solar photocatalyst for degradation of 4-chlorophenol in water. Journal of Molecular Catalysis A: Chemical. 2016;411:146-156. DOI: 10.1016/j.molcata.2015.10.021
  71. 71. Liang C, Liu C, Li F, Wu F. The effect of praseodymium on the adsorption and photocatalytic degradation of azo dye in aqueous Pr3+-TiO2 suspension. Chemical Engineering Journal. 2009;147:219-225. DOI: 10.1016/j.cej.2008.07.004
  72. 72. Kralova M, Levchuk I, Kasparek V, Sillanpaa M, Cihlar J. Influence of synthesis conditions on physical properties of lanthanide-doped titania for photocatalytic decomposition of metazachlor. Chinese Journal of Catalysis. 2015;36:1679-1685. DOI: 10.1016/S1872-2067(15)60943-3
  73. 73. Leal EGV, Neira JPL, Avella JAP, Pérez E, Meza O. Screening of factors influencing the photocatalytic activity of TiO2:Ln (Ln = La, Ce, Pr, Nd, Sm, Eu and Gd) in the degradation of dyes. Computational Materials Science. 2015;107:48-53. DOI: 10.1016/j.commatsci.2015.05.014
  74. 74. Reszczyńska J, Grzyb T, Wei Z, Klein M, Kowalska E, Ohtani B, et al. Photocatalytic activity and luminescence properties of RE3+–TiO2 nanocrystals prepared by sol–gel and hydrothermal methods. Applied Catalysis B: Environmental. 2016;181:825-837. DOI: 10.1016/j.apcatb.2015.09.001
  75. 75. Li H, Zheng K, Sheng Y, Song Y, Zhang H, Huang J, et al. Facile synthesis and luminescence properties of TiO2:Eu3+ nanobelts. Optics and Laser Technology. 2013;49:33-37. DOI: 10.1016/j.optlastec.2012.12.007
  76. 76. Jun D, Buhui L, Jingjing H, Wenlong Z, Hailong P, Jianguo Z. Hydrophilic and photocatalytic performances of lanthanum doped titanium dioxide thin films. Journal of Rare Earths. 2013;31(10):992-996. DOI: 10.1016/S1002-0721(13)60019-8
  77. 77. Tang J, Chen X, Liu Y, Gong W, Peng Z, Cai T, et al. Samarium-doped mesoporous TiO2 nanoparticles with improved photocatalytic performance for elimination of gaseous organic pollutants. Solid State Sciences. 2013;15:129-146. DOI: 10.1016/j.solidstatesciences.2012.10.001
  78. 78. Xiao Q, Si Z, Zhang J, Xiao C, Tan X. Photoinduced hydroxyl radical and photocatalytic activity of samarium-doped TiO2 nanocrystalline. Journal of Hazardous Materials. 2008;150:62-67. DOI: 10.1016/j.jhazmat.2007.04.045
  79. 79. Giri PK, Galvagno G, Ferla A, Rimini E, Coffa S, Raineri V. Formation and annealing of defects during high-temperature processing of ion-implanted epitaxial silicon: the role of dopant implants. Materials Science and Engineering. 2000;B71:186-191. DOI: 10.1016/S0921-5107(99)00372-4
  80. 80. Mamane H, Horovitz I, Lozzi L, Camillo D, Avisar D. The role of physical and operational parameters in photocatalysis by N-doped TiO2 sol–gel thin films. Chemical Engineering Journal. 2014;257:159-169. DOI: 10.1016/j.cej.2014.07.018
  81. 81. Saharudin KA, Sreekantan S, Lai CW. Fabrication and photocatalysis of nanotubular C-doped TiO2 arrays: Impact of annealing atmosphere on the degradation efficiency of methyl orange. Materials Science in Semiconductor Processing. 2014;20:1-6. DOI: 10.1016/j.mssp.2013.12.019
  82. 82. Acevedo-Peña P, Carrera-Crespo JE, González F, González I. Effect of heat treatment on the crystal phase composition, semiconducting properties and photoelectrocatalytic color removal efficiency of TiO2 nanotubes arrays. Electrochimica Acta. 2014;140:564-571. DOI: 10.1016/j.electacta.2014.06.056 0013-4686
  83. 83. Borlaf M, Caes S, Dewalque J, Colomer MT, Moreno R, Cloots R, et al. Effect of the RE (RE = Eu, Er) doping on the structural and textural properties of mesoporous TiO2 thin films obtained by evaporation induced self-assembly method. Thin Solid Films. 2014;558:140-148. DOI: 10.1016/j.tsf.2014.03.002
  84. 84. Elghniji K, Hentati1 O, Mlaik N, Mahfoudh A, Ksibi M. Photocatalytic degradation of 4-chlorophenol under P-modified TiO2/UV system: Kinetics, intermediates, phytotoxicity and acute toxicity. Journal of Environmental Sciences. 2012;24(3):479-487. DOI: 10.1016/S1001-0742(10)60659-6
  85. 85. Armaković SJ, Grujić-Brojčin M, Šćepanović M, Armaković S, Golubović A, Babić B, et al. Efficiency of La-doped TiO2 calcined at different temperatures in photocatalytic degradation of β-blockers. Arabian Journal of Chemistry. DOI: 10.1016/j.arabjc.2017.01.001. In press
  86. 86. Ðorđević V, Milićević B, Dramićanin MD. Rare earth-doped anatase TiO2 nanoparticles. In: Janus M, editor. Titanium Dioxide. 1st ed. London: Intech Open; 2017. pp. 25-60. DOI: 10.5772/intechopen.68882
  87. 87. Chen Q, Jiang D, Shi W, Wu D, Xu Y. Visible-light-activated Ce–Si co-doped TiO2 photocatalyst. Applied Surface Science. 2009;255:7918-7924. DOI: 10.1016/j.apsusc.2009.04.167
  88. 88. Cruz D, Arévalo JC, Torres G, Margulis RGB, Ornelas C, Elguézabal AA. TiO2 doped with Sm3+ by sol–gel: Synthesis, characterization and photocatalytic activity of diuron under solar light. Catalysis Today. 2011;166:152-158. DOI: 10.1016/j.cattod.2010.08.023
  89. 89. Yang L, Liu P, Li X, Li S. The photo-catalytic activities of neodymium and fluorine doped TiO2 nanoparticles. Ceramics International. 2012;38:4791-4796. DOI: 10.1016/j.ceramint.2012.02.067

Written By

Gustavo Lopes Colpani, Micheli Zanetti, Rubieli Carla Frezza Zeferino, Luciano Luiz Silva, Josiane Maria Muneron de Mello, Humberto Gracher Riella, Natan Padoin, Márcio Antônio Fiori and Cíntia Soares

Submitted: 02 May 2018 Reviewed: 14 August 2018 Published: 22 November 2018