JBCS

INTRODUCTION

Human activities, particularly water, air, and soil pollution, have significantly disrupted the environmental balance. The pursuit of sustainable solutions for remediating contaminated environments, as well as for the storage and production of clean, renewable energy, is essential to advancing the global sustainability agenda. In this context, titanium dioxide has been the subject of intense research interest because of its central role in the development of photovoltaic devices,^1,2 catalytic and photocatalytic systems,^3-7 lithium-ion batteries,^8-12 photoelectrochemical cells,^13-16 as a cleaning agent in cement composites,¹⁶ and water treatment applications,¹⁷ among others.

The global market for TiO₂ is approximately USD 20.9 billion and is projected to reach USD 35 billion by 2034.¹⁸ This growth underscores both the high demand for the material and the need for new synthetic routes. Since nano-TiO₂ is a central nanomaterial for environmental and human well-being applications, it is logical to move forward with less harmful synthetic routes that prioritize the use of fewer toxic solvents and require lower energy inputs. In this context, the microwave-assisted hydrothermal method for nano-TiO₂ synthesis has emerged as a promising and efficient route for the synthesis.

Microwave heating prevents temperature gradients within a sample and promotes uniform thermal motion with strong molecular oscillation, which traditional heating methods cannot achieve. These characteristics result in faster synthesis, fewer byproducts, and minimal structural damage.¹⁹ Several studies have reported the successful synthesis of nano-TiO₂ through microwave-assisted sol-gel, hydrothermal, and solvothermal methods. Using an organic-free precursor for TiO₂ synthesis, Zhang et al.²⁰ prepared 5 nm anatase crystals from K₂Ti₄O₉. The resulting material exhibited a specific surface area greater than 200 m² g^-1 and showed comparable efficiency in acetaldehyde decomposition to that of the commercial reference, Degussa P25. Wilson et al.²¹ prepared smaller and more crystalline TiO₂ nanoparticles via microwave heating, significantly reducing the reaction time and energy consumption from 15 h to just 5-10 min compared with conventional heating. Simonsen et al.²² studied the influence of hydroxyl groups on the photocatalytic activity and the photoinduced hydrophilicity of microwave-assisted sol-gel TiO₂ film synthesis. Using stearic acid as a model compound, they evaluated the photoactivity of the films, which exhibited a highly homogeneous morphology with a predominant anatase crystalline phase. A strong correlation was observed between the photocatalytic performance and the density of surface hydroxyl groups on the TiO₂ films.

The advantages of using microwave radiation for nano-TiO₂ synthesis are further enhanced when the reaction is carried out in a mild solvent mixture, which is primarily composed of water. Accordingly, this study reports a one- and two-step microwave-assisted hydrothermal synthesis of nano-TiO₂. Our work is notable for employing a fast, efficient, and sustainable method that yields TiO₂ nanoparticles with a high specific surface area, more than twice that of a commercial reference, and excellent photocatalytic performance. The influence of heating duration on the morphological, structural, surface physicochemical, and photocatalytic properties of the resulting nanoparticles is also discussed.

Numerous studies have reported the synthesis of TiO₂ nanoparticles via microwave-assisted hydrothermal routes. Nevertheless, few papers have explored the impact of a two-step heating process using mild solvents under low-temperature conditions. Our work introduces a simple, low-energy, scalable synthetic strategy that combines the benefits of microwave heating with sequential thermal treatment to tailor the particle morphology, crystallinity, and surface characteristics. The novelty of this approach lies in the optimization of synthesis conditions that yield anatase TiO₂ with superior photocatalytic activity and high specific surface area and in the comprehensive analysis of how heating stages influence nanoparticle aggregation, exposed crystal facets, and dye degradation performance. These features provide new insights into controlling nanostructure properties through green processing, highlighting the potential of this method for sustainable nanomaterial production, especially for environmental applications, such as dye degradation.

 

EXPERIMENTAL

All the chemicals were analytical grade reagents and used without further purification. Isopropyl alcohol (99.9%), titanium(IV) isopropoxide (TIP, 97%) as the precursor, and tetramethylammonium hydroxide solution (TMAH, 25%) as the catalyst, were purchased from Sigma-Aldrich. Ultrapure water (18.2 MΩ cm, Direct-Q, Merck Millipore) was used for all aqueous preparations.

The synthesis began by adding 900 mL of ultrapure water and 0.6 mL of TMAH to a glass flask placed in an ice bath. Once the solution reached 2 °C, a mixture of 2.1 mL of TIP in 60 mL of isopropyl alcohol was added under vigorous stirring. The resulting mixture was then allowed to stand for 10 min. An aliquot of 40 mL of the mixture was transferred into Teflon-lined vessels, sealed, and heated in a microwave oven (MARS 6, CEM Corporation) for 2.4 h. The microwave power was set to 800 W, and the temperature was maintained at 90 °C. For the two-step synthesis, a second heating stage was performed at 160 °C for 2 h, with the microwave power adjusted to 1200 W. Reaction parameters were selected to decouple nucleation from growth. An initial microwave stage at 90 °C for 2.4 h (800 W) was used to favor nucleation of anatase under mild, water-rich conditions. A second stage at 160 °C for 2 h (1200 W) was then applied to promote crystallite growth and defect annealing while avoiding polymorphic transformation. The higher-temperature step was also chosen to tailor morphology and facet exposure. In our instrument (MARS 6), the power set point was used to achieve and maintain the target temperature; the reaction outcome was primarily dictated by the temperature-time profile. For both procedures, after the heating process, the nanoparticle dispersions were concentrated using a rotary evaporator and then centrifuged at 1740 g for 10 min. The precipitates were rinsed with ethanol thrice and dried at 80 °C for 12 h.

For X-ray diffraction (XRD) analysis, a diffractometer (D8 Advance, Bruker) with Cu Kα radiation (λ = 1.54148 Å) was used, operating at 40 kV and 30 mA. The scan was performed over a 2θ angular range of 10 to 110° at a rate of 0.02° s^-1, ensuring that TiO₂ crystalline phases, if present, would be detected. The experimentally obtained diffractograms were compared with crystal standards from the American Mineralogist Crystal Structure Database (AMCSD). The Rietveld method was applied to XRD patterns using the program FullProf, version 2023.²³ The crystal structure was refined in the space group of anatase I41/amd (141).

Transmission electron microscopy (TEM) samples were prepared by dispersing 1 mg of the synthesized TiO₂ in 1 mL of 99% isopropyl alcohol, followed by deagglomeration and homogenization in an ultrasonic bath for 10 min. Approximately 20 µL of this dispersion was drop-cast, using a 30 µL micropipette, onto a 400-mesh copper grid (0.037 mm aperture) coated with a formvar/carbon film (EMS) and then kept in a desiccator for 48 h. TEM, high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) images were taken on a JEM2100 LaB6 JEOL instrument.

The surface area and pore volume of the nanoparticles were determined from nitrogen adsorption-desorption isotherms at −195.5 °C using a physisorption analyzer (ASAP 2020 Plus, Micromeritics) over a relative pressure (P/P₀) range of 0.00-0.995. Prior to analysis, all samples were outgassed at 70 °C for 24 h until a residual pressure of 10 μTorr was reached in the sample tube. The specific surface area (S_BET) was calculated by the Brunauer-Emmett-Teller (BET) method using adsorption data in the P/P₀ interval of 0.05-0.30. The total pore volume (V_p) was obtained by the Barrett-Joyner-Halenda (BJH) procedure by converting the amount of N₂ adsorbed at P/P₀ = 0.995 to the equivalent liquid volume, and the mean pore diameter (D_p) was estimated from D_p = 4V_p/S_BET.

The hydrodynamic radius (R_h) and zeta potential (ζ) of the nanoparticles dispersed in water (0.1 mg mL^-1, pH 7) were measured via a dynamic light scattering (DLS) spectrophotometer (Zetasizer Nano ZS, Malvern) equipped with a 4 mW, 632.4 nm He-Ne laser.

Photocatalytic activity assays were conducted in a mirrored reactor equipped with a polypropylene vessel and a 15 W Hg lamp (Tovalight) with the main emission line at 254 nm, adjusted to deliver an irradiance of 100 mW cm^-2. No optical filters were used. Aqueous dispersions of the nanoparticles (0.5 g of TiO₂ in 40 mL of 10 mg L^-1 RhB solution) were prepared and transferred to the reactor vessel, and then stirred in the dark for 30 min. Upon switching on the lamp (t = 0), 4.0 mL aliquots were collected every 10 min for the first 60 min, followed by a final collection at 120 min. A blank test was performed under identical conditions, without adding TiO₂. After each time point, the aliquots were centrifuged at 1740 g for 10 min, and the absorbance of the supernatant was measured at 553 nm using a UV-Vis spectrophotometer (WUV-M51, Weblabor). The absorbance values were compared with a previously established calibration curve to quantify the extent of photocatalytic dye degradation.

 

RESULTS AND DISCUSSION

The microwave-assisted hydrothermal synthesis of nanoparticles resulted in yields of approximately 49 and 53% for samples TDN1 and TDN2, respectively. As TDN2 underwent a more extended growth period, its yield was slightly greater than that of TDN1. This minor difference may be attributed to Ostwald ripening rather than aggregation and TiO₂ polymerization from the TMAH precursor. In this case, the preformed small crystals in the TDN1 sample may have partially dissolved and subsequently redeposited onto larger particles. The ripening process occurs because smaller particles are less energetically favorable than the larger particles.^24,25

Figure 1 presents the TEM analysis of the TDN1 and TDN2 samples. The synthesis route produced nanoparticles with irregular shapes for TDN1 (Figures 1a and 1c), with an average diameter of 6.4 ± 1.6 nm. In contrast, the TDN2 sample appears more monodisperse (Figures 1b and 1d), with most nanoparticles displaying a rectangular morphology, measuring approximately 18.2 ± 2.8 nm in length and 8.9 ± 1.9 nm in width. Additionally, cuboid nanoparticles are present, with dimensions of 9.1 ± 1.54 nm × 9.2 ± 1.5 nm. Both rectangular and cuboid particles likely have the same morphology, with rectangular nanoparticles being approximately twice as long as the cuboids but having similar edge widths. This suggests that two cuboid units may have self-assembled to form rectangular structures. This observation supports the hypothesis that aggregation is more predominant than polymerization during the second heating step, which is consistent with the slight yield increase observed for TDN2 compared with TDN1. Figures 1e and 1f present HRTEM and SAED images of individual particles of samples TDN1 and TDN2, respectively. They show the presence of lattice fringes, indicating that the obtained particles are crystalline. According to the Joint Committee on Powder Diffraction Standards (JCPDS), the diffraction rings in the inset of figures (see Figures 1e and 1f) describe the anatase structure, cards 4-477.

 

 

For X-ray analysis (Figure 2), the peaks of the sample diffractograms were compared and identified with a standard structure from the American Mineralogist Crystal Structure Database and JCPDS card 4-477. This confirms that, under synthetic conditions, only the anatase polymorph was identified by its diffraction maxima (101), (103), (004), (112), (200), (105), (211), and (213). The highest intensity diffraction peak indicates that the (101) crystalline plane is the preferential orientation of the crystallites. As seen in the TEM analysis (Figure 1f), the (101) faces predominated in the TDN2 samples, as they emerged as the surface energy of the crystals decreased to the detriment of the reduction in the area of the (001) face with higher surface energy.²⁶ Several experimental parameters influence the transformation of anatase into rutile or brookite, including the synthesis method, the TiO₂ precursor, and the type of heat applied. These factors can significantly affect the phase transition behavior of anatase to other TiO₂ polymorphs.²⁷ However, no evidence of brookite or rutile polymorphs was found in the TDN1 and TDN2 samples. The Rietveld refinement of the XRD data yielded lattice parameters consistent with those of the anatase phase, as shown in Table 1. The structural parameters indicate that TDN1 exhibits distortions (defects), particularly along the c-axis. These distortions likely resulted from insufficient temperature and reaction time during the one-step synthesis, which limited the ordering of the crystal lattice. In contrast, the two-step synthesis used for TDN2 did not produce such structural distortions. According to the literature, the increase in temperature synthesis promotes the growth of anatase nano-crystallites and, consequently, enhances the crystallinity of the samples, as observed for TDN2.^28-30

 

 

 

 

The DLS analysis parameters for samples TDN1 and TDN2 are summarized in Table 2. The colloidal stability of TiO₂ nanoparticles is essential for various applications, including the shelf life of commercial products and environmental concerns, such as their interactions with living organisms.³¹ At pH 7 (0.1 mg mL^-1), both dispersions exhibit strongly negative zeta potentials (ζ ca. −52 mV), indicating that the particle surfaces are highly deprotonated under these conditions. However, colloidal stability cannot be deduced from a single ζ value. For metal-oxide dispersions such as TiO₂, the stability landscape depends on the interplay between the ζ at the working pH and the isoelectric point (IEP), the ionic strength/electrolyte composition, and non-DLVO interactions (e.g., van der Waals forces and hydrogen-bond/bridging between surface hydroxyls). Small pH shifts around the IEP can markedly alter the electrostatic contribution to stabilization, and in the range of -30 mV < ζ < +30 mV, unstable sols are formed. Because a pH-dependent ζ-titration was not carried out here, we avoid general claims about "colloidal stability" and restrict our interpretation to the measurement conditions.

 

 

Irrespective of the large |ζ| values at pH 7, the hydrodynamic radii (R_h ca. 495 nm for TDN1 and ca. 154 nm for TDN2) are substantially larger than the primary particle sizes observed by TEM, consistent with the presence of secondary aggregates in the measurement medium. Such aggregation can occur when attractive interparticle forces within clusters outweigh electrostatic repulsion between primary particles. The smaller R_h of TDN2 suggests weaker secondary aggregation under the tested conditions. For TDN1 dispersion, aggregation behavior may explain the larger hydrodynamic radius observed in the DLS measurements than in the particle sizes obtained from the TEM analysis.

Table 3 presents the results of the BET surface area analysis. This characterization allows the determination of the specific surface area (S_BET), average pore volume (V_p), average pore diameter (D_p), and average particle size (P_BET). An increase in time and temperature results in a slight decrease in the average specific surface area and an increase in the average volume of pores. The TDN1 and TDN2 samples had a larger surface area than the benchmark P25 from Evonik, one of the most commonly used commercial TiO₂ samples by research groups worldwide. Another commercial product of pure-anatase (Sigma-Aldrich, Catalog No. 637254) has a specific surface area of 45-55 m² g^-1.³² The S_BET values of TDN1 and TDN2 are comparable to those of other pure-anatase S_BET values reported in the literature (in the case of TDN1), as described by Zanardo et al.³³ (S_BET = 101 m² g^-1) and higher (in the case of both samples) than those of other pure-anatase samples prepared via a microwave-assisted hydrothermal method, as reported by Cabello et al.³⁴ (S_BET = 83 m² g^-1) and Su et al.³⁵ (S_BET = 92 m² g^-1).

 

 

Figure 3a shows the photocatalytic activity curves of the TDN1 and TDN2 samples. After 2 h of UV irradiation, the nanoparticles degraded nearly all the RhB molecules, resulting in approximately 90 and 98% degradation for TDN1 and TDN2, respectively. The UV-only experiment shows a low, nearly linear conversion, consistent with photolysis in the absence of a catalytic surface. Each reported value is the mean of three measurements; the corresponding standard deviations were consistently low (< 5%) and were therefore omitted for brevity. Figure 3b presents the kinetic curves for RhB photodegradation over the TiO₂ samples. The data were fitted using the pseudo-first order model, ln(C/C₀) = −kt, where C is the RhB concentration at time t, C₀ is the initial concentration, k is the rate constant, and t is time. The rate constants are 0.00631, 0.01841, and 0.03137 min^-1 for RhB photolysis (no catalyst), TDN1, and TDN2, respectively. The TDN2 sample exhibits the highest rate constant, which likely arises from a combination of structural, surface, and colloidal factors intrinsic to the sample.

 

 

Although TDN1 has a slightly higher S_BET (ca. 112 vs. 99 m² g^-1), TDN2 exhibits wider pores (D_p ca. 4.76 vs. 2.79 nm) and a larger pore volume (0.118 vs. 0.078 cm³ g^-1), which tends to facilitate mass transport (influx of RhB and efflux of intermediates/products) and the renewal of reactive species at the interface - an especially relevant advantage when the kinetics are partially limited by intra-/interparticle diffusion. As indicated by the DLS results, TDN1 nanoparticles appear more aggregated than TDN2, which may hinder the accessibility of RhB to their surface. Furthermore, TDN2 nanoparticles presented more exposed (101) crystal facets than TDN1. It has been reported³⁶ that anatase crystals with predominant (101) surfaces exhibit enhanced photocatalytic activity for the oxidative degradation of organic compounds compared to other crystal faces.

TDN2 sample, on the other hand, exhibits better crystallinity, since the Rietveld analysis for TDN1 shows the presence of defects along the c-axis. These distortions, attributed to the single heating step, were mitigated by the second heating stage used for TDN2, which is consistent with its higher photocatalytic activity. Such defects typically act as recombination centers for electron-hole pairs, thereby reducing the photocatalytic activity of TDN1. In a previous study,³⁷ the commercial catalyst Degussa P25 achieved 100% photodegradation of RhB under UV light within 60 min. Compared with the benchmark, the TDN2 sample demonstrated excellent degradation performance (ca. 90%) with the same reaction time. However, it is not possible to confirm whether the irradiance (i.e., the luminous power received per unit area) and other experimental conditions were identical.

Nevertheless, numerous studies^38-42 have reported the use of TiO₂ as a mediator for the degradation of organic pollutants, particularly dyes and pesticides, under UV irradiation. For example, the degradation of the carcinogenic dye Direct Red 23 (CAS No. 3441-14-3), which is widely used in the textile industry and agribusiness (cotton, leather, and seed dyeing), reached 54% with TiO₂/UV treatment. In contrast, it was only ca. 2% when using UV light alone for 180 min. Another study⁴³ reported the degradation of the pesticide Phosalone^® at approximately 60% using TiO₂ and UV, versus ca. 20% with UV light alone over 25 min.

Similarly, under UV irradiation for 120 min, the TDN1 and TDN2 samples exhibited dye degradation at least ca. 46% greater than those under UV light alone. When exposed to UV illumination (λ < 390 nm), the TiO₂ samples can promote electron transport from the valence band to the conduction band, generating electron-hole pairs. The valence band potential is sufficiently positive to generate free radicals (such as •OH) on the TiO₂ surface. In contrast, the conduction band potential is sufficiently negative to reduce molecular O₂ and H₃O⁺ dissolved in the reaction medium, generating the radicals •O₂^- and •H, respectively. Alternatively, UV light can degrade water molecules to form free radicals (•OH). The free radicals generated by the semiconductor photoexcitation and the action of UV light can promote the oxidation of organic matter adsorbed on the surface of TiO₂, reducing its concentration over time. Thus, the results of the photocatalytic experiments in the present study demonstrate that the efficient photodegradation of RhB was mainly due to the TiO₂ samples in the reaction medium.

 

CONCLUSIONS

Nano-TiO₂ samples with an anatase crystalline structure were successfully synthesized. The particle sizes ranged from approximately 6 to 18 nm, exhibiting irregular shapes for the one-step (TDN1) and cubic/rectangular morphologies for the two-step (TDN2) microwave-assisted syntheses. Compared with TDN2, the TDN1 samples showed greater aggregation in aqueous dispersions at pH 7, although both samples presented similarly high negative zeta potential values (approximately -52 mV). The specific surface areas were nearly twice those of commercial nano-TiO₂, with values of ca. 112 m² g^-1 for TDN1 and ca. 99 m² g^-1 for TDN2. Both samples demonstrated excellent photocatalytic performance and the combination of factors - (i) more exposed (101) facets, (ii) lower defect density and higher crystallinity, (iii) reduced aggregation (greater effectively accessible surface area), and (iv) a texture more favorable to diffusion - explains why TDN2 exhibits a higher rate constant than TDN1 and, therefore, achieves ca. 98% RhB degradation in 120 min, surpassing the ca. 90% of TDN1 under the same experimental conditions. These results confirm that the microwave-assisted hydrothermal method is an effective strategy for producing nanostructured TiO₂ with high photocatalytic activity, while also offering advantages such as reduced synthesis time, lower energy consumption, and the use of mild solvents. This approach represents a promising alternative for sustainable TiO₂ production, aligned with current environmental and economic demands for treating organic pollutants.

 

DATA AVAILABILITY STATEMENT

All data supporting the findings of this study are included within the article.

 

ACKNOWLEDGMENTS

The authors thank UFVJM, CAPES, MCTI/FINEP (01.22.0271.00), and FAPEMIG (APQ-03149-17, CEX-112-10, and CEX-RED-00010-14) for their financial support. The authors also acknowledge the Laboratory of Multiuser Equipment at Pontal, Universidade Federal de Uberlândia (FINEP/2013 INFR13 01.13.0371.00), for performing the BET analysis. T. P. S. and R. G. F. gratefully acknowledge UFVJM and FAPEMIG for their master's scholarships. J. L. R. and M. C. P. are research fellows of CNPq.

 

AUTHOR CONTRIBUTIONS

D. S. M. was responsible for conceptualization, formal analysis, investigation, writing (original draft, review and editing), funding acquisition, resources, supervision; R. G. F., T. P. S., M. D. V. R. R. for methodology; J. L. R., A. S. A. for formal analysis, investigation, resources; M. C. P. for formal analysis, investigation, funding acquisition, resources.

 

REFERENCES

1. Kim, Y. G.; Walker, J.; Samuelson, L. A.; Kumar, J.; Nano Lett. 2003, 3, 523. [Crossref]

2. Slooff, L. H.; Kroon, J. M.; Loos, J.; Koetse, M. M.; Sweelssen, J.; Adv. Funct. Mater. 2005, 15, 689. [Crossref]

3. Henderson, M. A.; Surf. Sci. Rep. 2011, 66, 185. [Crossref]

4. Anpo, M.; Takeuchi, M.; J. Catal. 2003, 216, 505. [Crossref]

5. Zhang, J.; Xu, Q.; Feng, Z.; Li, M.; Li, C.; Angew. Chem. 2008, 120, 1790. [Crossref]

6. Chen, C.; Ma, W.; Zhao, J.; Chem. Soc. Rev. 2010, 39, 4206. [Crossref]

7. Dhakshinamoorthy, A.; Navalon, S.; Corma, A.; Garcia, H.; Energy Environ. Sci. 2012, 5, 9217. [Crossref]

8. Wagemaker, M.; Kentgens, A. P. M.; Mulder, F. M.; Nature 2002, 418, 397. [Crossref]

9. Kavan, L.; Kalbáč, M.; Zukalová, M.; Exnar, I.; Lorenzen, V.; Nesper, R.; Graetzel, M.; Chem. Mater. 2004, 16, 477. [Crossref]

10. Hu, Y. S.; Kienle, L.; Guo, Y. G.; Maier, J.; Adv. Mater. 2006, 18, 1421. [Crossref]

11. Bruce, P. G.; Scrosati, B.; Tarascon, J. M.; Angew. Chem., Int. Ed. 2008, 47, 2930. [Crossref]

12. Hengerer, R.; Kavan, L.; Krtil, P.; Grätzel, M.; J. Electrochem. Soc. 2000, 147, 1467. [Crossref]

13. Fujishima, A.; Honda, K.; Nature 1972, 238, 37. [Crossref]

14. Grätzel, M.; Nature 2001, 414, 338. [Crossref]

15. Cho, I. S.; Lee, C. H.; Feng, Y.; Logar, M.; Rao, P. M.; Cai, L.; Kim, D. R.; Sinclair, R.; Zheng, X.; Nat. Commun. 2013, 4, 1723. [Crossref]

16. Wang, Z.; Gauvin, F.; Feng, P.; Brouwers, H. J. H.; Yu, Q.; Constr. Build. Mater. 2020, 263, 120558. [Crossref]

17. Natoli, A.; Cabeza, A.; Torre, A. G.; Aranda, M. A. G.; Santacruz, I.; J. Am. Ceram. Soc. 2012, 95, 502. [Crossref]

18. Fact.MR; Titanium Dioxide Market. [Link] accessed in October 2025

19. Wang, Y.; He, Y.; Lai, Q.; Fan, M.; J. Environ. Sci. 2014, 26, 2139. [Crossref]

20. Zhang, P.; Yin, S.; Sato, T.; Appl. Catal., B 2009, 89, 118. [Crossref]

21. Wilson, G. J.; Will, G. D.; Frost, R. L.; Montgomery, S. A.; J. Mater. Chem. 2002, 12, 1787. [Crossref]

22. Simonsen, M. E.; Li, Z.; Søgaard, E. G.; Appl. Surf. Sci. 2009, 255, 8054. [Crossref]

23. Rodríguez-Carvajal, J.; FullProf, suite 2023; Laboratoire Léon Brillouin (CEA-CNRS), France, 2023.

24. Alemán, J. V.; Chadwick, A. V.; He, J.; Hess, M.; Horie, K.; Jones, R. G.; Kratochvíl, P.; Meisel, I.; Mita, I.; Moad, G.; Penczek, S.; Stepto, R. F. T.; Pure Appl. Chem. 2007, 79, 1801. [Crossref]

25. Yang, H. G.; Zeng, H. C.; J. Phys. Chem. B 2004, 108, 3492. [Crossref]

26. Liu, G.; Yang, H. G.; Pan, J.; Yang, Y. Q.; Lu, G. Q.; Cheng, H. M.; Chem. Rev. 2014, 114, 9559. [Crossref]

27. Borkar, S. A.; Dharwadkar, S. R.; Ceram. Int. 2004, 30, 509. [Crossref]

28. Zhang, H.; Banfield, J. F.; Am. Mineral. 1999, 84, 528. [Crossref]

29. Shao, Y.; Tang, D.; Sun, J.; Lee, Y.; Xiong, W.; China Particuol. 2004, 2, 119. [Crossref]

30. Won, D. J.; Wang, C. H.; Jang, H. K.; Choi, D. J.; Appl. Phys. A: Mater. Sci. Process. 2001, 73, 595. [Crossref]

31. Vidmar, J.; Milačič, R.; Golja, V.; Novak, S.; Sčančar, J.; Anal. Methods 2016, 8, 1194. [Crossref]

32. Merck; Titanium Dioxide, Anatase. [Link] accessed in October 2025

33. Zanardo, D.; Ghedini, E.; Menegazzo, F.; Cattaruzza, E.; Manzoli, M.; Cruciani, G.; Signoretto, M.; Materials 2019, 12, 3093. [Crossref]

34. Cabello, G.; Davoglio, R. A.; Pereira, E. C.; J. Electroanal. Chem. 2017, 794, 36. [Crossref]

35. Su, C. H.; Hu, C. C.; Sun, Y. C. C.; Hsiao, Y. C.; J. Taiwan Inst. Chem. Eng. 2016, 59, 229. [Crossref]

36. Amano, F.; Yasumoto, T.; Prieto-Mahaney, O. O.; Uchida, S.; Shibayama, T.; Ohtani, B.; Chem. Commun. 2009, 2311. [Crossref]

37. Wan, X.; Ke, H.; Yang, G.; Tang, J.; Prog. Nat. Sci.: Mater. Int. 2018, 28, 683. [Crossref]

38. Daneshvar, N.; Salari, D.; Khataee, A. R.; J. Photochem. Photobiol., A 2003, 157, 111. [Crossref]

39. Daneshvar, N.; Salari, D.; Khataee, A. R.; J. Photochem. Photobiol., A 2004, 162, 317. [Crossref]

40. Jin, H.; Wu, Q.; Pang, W.; J. Hazard. Mater. 2007, 141, 123. [Crossref]

41. Hu, C.; Yu, J. C.; Hao, Z.; Wong, P. K.; Appl. Catal., B 2003, 42, 47. [Crossref]

42. Wang, W. Y.; Ku, Y.; Colloids Surf., A 2007, 302, 261. [Crossref]

43. Daneshvar, N.; Hejazi, M. J.; Rangarangy, B.; Khataee, A. R.; J. Environ. Sci. Health, Part B 2004, 39, 285. [Crossref]