Journal of Nanomaterials

Journal of Nanomaterials / 2014 / Article
Special Issue

Development and Fabrication of Advanced Materials for Energy and Environment Applications 2014

View this Special Issue

Research Article | Open Access

Volume 2014 |Article ID 835450 |

Guozhu Fu, Yanqiu Yang, Gang Wei, Xin Shu, Ning Qiao, Li Deng, "Influence of Sn Doping on Phase Transformation and Crystallite Growth of Nanocrystals", Journal of Nanomaterials, vol. 2014, Article ID 835450, 5 pages, 2014.

Influence of Sn Doping on Phase Transformation and Crystallite Growth of Nanocrystals

Academic Editor: Shao-Wen Cao
Received16 Jan 2014
Accepted02 Feb 2014
Published10 Mar 2014


Sn doped TiO2 nanocrystals were synthesized via a single-step hydrothermal method and the influences of Sn doping on TiO2 have been investigated. It is found that Sn doping not only facilitates the crystal transfer from anatase to rutile but also facilitates the morphology change from sphere to rod. The states of Sn were studied by XPS and the creation of oxygen vacancies by Sn doping is confirmed. Moreover, the HRTEM results suggest that Sn facilitates preferential growth of resulting nanocrystals along (110) axis, which results in the formation of rod-like rutile nanocrystals.

1. Introduction

In recent years, the applications of semiconductors in photocatalysis and other fields have attracted much interest [1, 2], and many semiconductor nanomaterials and their heterogeneous structures have been developed for their application in energy and environmental applications [35], for example, the investigations of TiO2 on various organic pollutants photodegradation [6] due to its excellent photocatalytic activity, physical and chemical stability, and nontoxicity [7]. Because most of the solar energy is focused on the visible light, it is important to develop the visible-light-driven photocatalysts. However, TiO2 is only sensitive to UV light because of its large band gap (3.2 eV). In order to efficiently use solar energy, many methods have been studied. An effective way is to introduce foreign ions into TiO2, including rare earth element doping [8], metals doping [9], and nonmetals doping [10, 11].

The property of TiO2 can also be affected by foreign metal ions doping. It has been shown that the photocatalytic activity of the modified TiO2 improves to different extents depending on different ion doping, such as Mn2+ [12], Zr4+ [13], and Fe3+ [14]. Moreover, the phase transformation behavior and structure of TiO2 are also affected by foreign metal ions. For example, Ag+ [15], Mn2+ [16], and Cr3+ [17] are proved to promote phase transformation from anatase to rutile, while silicon ion doping strongly restrains the phase transformation [18] and lowers the phase transition temperature [19]. But, so far, no detailed study has been reported on the influence of Sn4+ doping on the phase transformation and structure of hydrothermal synthesis TiO2.

In our work, Sn doped TiO2 nanocrystals were prepared by hydrothermal method. The existing states of Sn and its role in phase transformation as well as the morphology evolution were investigated. Sn facilitates the phase conversion from anatase to rutile and prefers the morphology evolution from spherical shape to nanorods.

2. Experimental Section

Sn doped TiO2 nanoparticles were prepared by hydrothermal method. 2.9 mL acetic acid was added to 17 mL tetrabutyl titanate and stirred for 15 min. The mixture was then poured into 73 mL of water and vigorously stirred for 1 hour. After adding 1 mL concentrated nitric acid, the mixture was heated to 80°C and peptized for 75 min. Then the volume was adjusted with water to 80 mL. The mixture was kept in a 100 mL autoclave and heated at 200°C for 12 h. For Sn doped samples, appropriate volume of tin tetrachloride was added to distilled water in advance (the feed molar ratios of Sn/Ti were modulated as 0.25/100, 0.5/100, 0.75/100, and 1.0/100, resp.).

The powder XRD experiments were performed on Bruker D8 Advance X-ray diffractometer using monochromic Cu Kα radiation ( nm). The scanning electron microscopy (SEM) images were recorded using S4700 Hitachi Ltd. The transmission electron microscopy (TEM) was performed with a Tecnai G2 20 transmission electron microscope of HongKong Co., Ltd. The X-ray photoelectron spectroscopy (XPS) experiments were carried out on Thermo ESCALAB 250 and the binding energies are calibrated by C1 photoelectron peak (284.6 eV).

3. Results and Discussion

The X-ray diffraction patterns of TiO2 samples with different Sn doping ratios are shown in Figure 1. It can be seen that the undoped TiO2 is mainly composed of anatase and weak diffraction peaks of rutile TiO2 can also be found in the XRD pattern. With the addition of Sn, the samples undergo “reutilization” to give rutile as the predominant polymorph, and the conversion from anatase to rutile is completed on 0.75% and 1.0% Sn doped samples, which suggests that the doped Sn ions can promote the formation of rutile.

The TEM results in Figure 2 show that the particle shape changed from sphere (diameter of 10–20 nm) to rod (width of ~20 nm and length of 100–200 nm) by Sn doping, which are consistent with SEM results (not shown here). The space between the lattice planes of Sn-free TiO2 (Figure 2(a)) is 0.35 nm, which corresponds well to the value of (101) plane for anatase. The lattice space of 0.33 nm displayed in Sn–TiO2 samples (Figures 2(b)2(e)) is equal to the value of (110) plane for rutile. Therefore, it is reasonable to conclude that the Sn-free TiO2 spherical nanocrystals are mainly anatase structure and the Sn doped TiO2 rod-like particles are rutile. As for our samples, with an increasing of Sn doping amount in TiO2, the content of the spherical anatase decreases and the rod-like rutile increases, illustrating that Sn doping facilitates the phase conversion from anatase to rutile, which is consistent with XRD. Furthermore, the HRTEM images reveal rod-like building units and nanocrystal growth along the [110] axis, indicating that the formation of the rod-like TiO2 is the result of the preferential growth (PG) in crystallographic orientation favored by Sn incorporation. Since Ti (IV) and Sn (IV) ions have the similar ionic radii, it is reasonable to deduce that Sn ions substitute lattice Ti, which is confirmed by our subsequent experiment. The EDX spectrum in Figure 2(e) also confirms the existence of Sn in TiO2 nanocrystals.

Figure 3 shows the XPS spectra of Sn doped TiO2 sample with Sn/Ti atomic ratio of 1%. As for Ti 2 spectrum in Figure 3(a), the two peaks at 458.1 eV and 458.7 eV could be assigned to O–Ti–O and Ti–O–Sn, respectively. Due to the electronegativity of Sn (1.96) which is larger than Ti (1.54) [20], the substitution of Sn for Ti in the lattice leads to the shift of binding energy to a higher value.

As for O1 spectrum in Figure 3(b), the peak at 532.2 eV is attributed to surface hydroxyl oxygen atoms. The peak at 529.3 eV is the binding energy of O1 in Ti–O–Ti, while the occurrence of the peak at 530 eV is the result of Sn substitute for Ti leading to the positive shift. These observations all confirm the formation of Ti−O−Sn structure in the Sn doped TiO2, owing to the substitution of Ti by Sn.

As shown in Figure 4, both anatase and rutile phase coexist at short treatment time, and the ratio of rutile/anatase increases with treatment time prolonging. A similar finding was reported by Zhang and Gao [21] who stated that phase transformation occurred simultaneously with particle growth.

It has been shown that the oxygen vacancies of TiO2 increase if foreign cations replace Ti4+ ions [22]. Vemury and Pratsinis [23] found that the formation of rutile phase was enhanced either by introducing dopant oxides with the same crystal structure as rutile or by creating oxygen vacancies by doping cations. It has been reported that the rutile fraction increases at a higher Eu3+ addition owing to the creation of oxygen vacancies by replacing the Ti4+ sites with subvalent Eu3+ ions in the TiO2 [24]. In our samples, the creation of oxygen vacancies is by replacing the Ti4+ sites with Sn4+ ions in TiO2 and therefore the rutile formation can be enhanced. Moreover, it was supposed that there is a relationship between the phase transformation and the nanocrystal growth process [25] and the preferential growth process aids phase transformation. The minimization of the area of high-energy surface faces promoted by the preferential growth process may be an extra driving force for the phase transformation from anatase to rutile phase.

4. Conclusions

In summary, the promoting roles of Sn4+ in both TiO2 phase transformation and morphology change have been confirmed in our study. The result demonstrated that morphology transition was related to the preferential growth process and the phase transformation was related to the creation of oxygen vacancies caused by Sn. Our observations of preferential growth coupled with phase transformation process led us to understand the preferential growth process aided phase transformation.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.


This work was supported by Beijing Key Laboratory of Bioprocess, State Key Laboratory of Chemical Resource Engineering, China 863 Project (nos. 2009AA03Z802 and 2009AA03Z803), and Amoy Major Scientific and Technological Innovation Project (2012S0305).


  1. S. W. Cao, X. F. Liu, Y. P. Yuan et al., “Artificial photosynthetic hydrogen evolution over g-C3N4 nanosheets coupled with cobaloxime,” Physical Chemistry Chemical Physics, vol. 15, no. 42, pp. 18363–18366, 2013. View at: Publisher Site | Google Scholar
  2. P. Hu, S. S. Pramana, S. W. Cao et al., “Ion-induced synthesis of uniform single-crystalline sulphide-based quaternary-alloy hexagonal nanorings for highly efficient photocatalytic Hydrogen evolution,” Advanced Materials, vol. 25, no. 18, pp. 2567–2572, 2013. View at: Publisher Site | Google Scholar
  3. S. W. Cao, Y. P. Yuan, J. Fang et al., “In-situ growth of CdS quantum dots on g-C3N4 nanosheets for highly efficient photocatalytic hydrogen generation under visible light irradiation,” International Journal of Hydrogen Energy, vol. 38, pp. 1258–1266, 2013. View at: Publisher Site | Google Scholar
  4. M. S. Yao, P. Hu, Y. B. Cao, W. C. Xiang, X. Zhang, and F. L. Yuan, “Morphology-controlled ZnO spherical nanobelt-flower arrays and their sensing properties,” Sensors and Actuators B: Chemical, vol. 177, pp. 562–569, 2013. View at: Google Scholar
  5. S. W. Cao, J. Fang, M. M. Shahjamali et al., “In situ growth of Au nanoparticles on Fe2O3 nanocrystals for catalytic applications,” CrystEngComm, vol. 14, pp. 7229–7235, 2012. View at: Publisher Site | Google Scholar
  6. A. Fujishima, T. N. Rao, and D. A. Tryk, “Titanium dioxide photocatalysis,” Journal of Photochemistry and Photobiology C: Photochemistry Reviews, vol. 1, no. 1, pp. 1–21, 2000. View at: Google Scholar
  7. W. X. Dai, X. Chen, X. P. Zheng et al., “Photocatalytic oxidation of CO on TiO2: chemisorption of O2, CO, and H2,” ChemPhysChem, vol. 10, no. 2, pp. 411–419, 2009. View at: Publisher Site | Google Scholar
  8. M. S. Hassan, T. Amna, O. B. Yang, H. C. Kim, and M. S. Khil, “TiO2 nanofibers doped with rare earth elements and their photocatalytic activity,” Ceramics International, vol. 38, pp. 5925–5930, 2012. View at: Publisher Site | Google Scholar
  9. Y. X. Li, S. Q. Peng, F. Y. Jiang, G. X. Lu, and S. B. Li, “Effect of doping TiO2 with alkaline-earth metal ions on its photocatalytic activity,” Journal of the Serbian Chemical Society, vol. 72, no. 4, pp. 393–402, 2007. View at: Publisher Site | Google Scholar
  10. P. Z. Si, W. Jiang, H. X. Wang et al., “Large scale synthesis of nitrogen doped TiO2 nanoparticles by reactive plasma,” Materials Letters, vol. 68, pp. 161–163, 2012. View at: Publisher Site | Google Scholar
  11. G. S. Wu, J. L. Wen, J. P. Wang, D. F. Thomas, and A. C. Chen, “A facile approach to synthesize N and B co-doped TiO2 nanomaterials with superior visible-light response,” Materials Letters, vol. 64, pp. 1728–1731, 2010. View at: Publisher Site | Google Scholar
  12. V. D. Binas, K. Sambani, T. Maggos, A. Katsanaki, and G. Kiriakidis, “Synthesis and photocatalytic activity of Mn-doped TiO2 nanostructured powders under UV and visible light,” Applied Catalysis B: Environmental, vol. 113-114, pp. 79–86, 2012. View at: Publisher Site | Google Scholar
  13. H. J. Liu, G. G. Liu, and Q. X. Zhou, “Preparation and characterization of Zr doped TiO2 nanotube arrays on the titanium sheet and their enhanced photocatalytic activity,” Journal of Solid State Chemistry, vol. 182, no. 12, pp. 3238–3242, 2009. View at: Google Scholar
  14. L. Sikong, B. Kongreong, D. Kantachote, and W. Sutthisripok, “Photocatalytic activity and antibacterial behavior of Fe3+-doped TiO2/SnO2 nanoparticles,” Energy Research Journal, vol. 1, no. 2, pp. 120–125, 2010. View at: Publisher Site | Google Scholar
  15. J.-Y. Park, J.-J. Yun, C.-H. Hwang, and I.-H. Lee, “Influence of silver doping on the phase transformation and crystallite growth of electrospun TiO2 nanofibers,” Materials Letters, vol. 64, no. 24, pp. 2692–2695, 2010. View at: Publisher Site | Google Scholar
  16. J. P. Xu, Y. B. Lin, Z. H. Lu et al., “Enhanced ferromagnetism in Mn-doped TiO2 films during the structural phase transition,” Solid State Communications, vol. 140, no. 11-12, pp. 514–518, 2006. View at: Publisher Site | Google Scholar
  17. T. H. Jun and K. S. Lee, “Cr-doped TiO2 thin films deposited by RF-sputtering,” Materials Letters, vol. 64, no. 21, pp. 2287–2289, 2010. View at: Publisher Site | Google Scholar
  18. Y.-H. Zhang and A. Reller, “Phase transformation and grain growth of doped nanosized titania,” Materials Science and Engineering C, vol. 19, no. 1-2, pp. 323–326, 2002. View at: Publisher Site | Google Scholar
  19. Y. Q. Cao, T. He, L. S. Zhao, E. J. Wang, W. S. Yang, and Y. A. Cao, “Structure and phase transition behavior of Sn4+-doped TiO2 nanoparticles,” Journal of Physical Chemistry C, vol. 113, no. 42, pp. 18121–18124, 2009. View at: Publisher Site | Google Scholar
  20. J. Li and C. Z. Hua, “Hollowing Sn-doped TiO2 nanospheres via Ostwald ripening,” Journal of the American Chemical Society, vol. 129, no. 51, pp. 15839–15847, 2007. View at: Publisher Site | Google Scholar
  21. Q. Zhang and L. Gao, “Preparation of oxide nanocrystals with tunable morphologies by the moderate hydrothermal method: insights from rutile TiO2,” Langmuir, vol. 19, no. 3, pp. 967–971, 2003. View at: Publisher Site | Google Scholar
  22. R. Arroyo, G. Córroyo, J. Padilla, and V. H. Lara, “Influence of manganese ions on the anatase–rutile phase transition of TiO2 prepared by the sol–gel process,” Materials Letters, vol. 54, pp. 397–402, 2002. View at: Publisher Site | Google Scholar
  23. S. Vemury and S. E. Pratsinis, “Dopants in flame synthesis of titania,” Journal of the American Ceramic Society, vol. 78, no. 11, pp. 2984–2992, 1995. View at: Google Scholar
  24. J. G. Li, X. H. Wang, K. J. Watanabe, and T. M. Ishigaki, “Phase structure and luminescence properties of Eu3+-doped TiO2 nanocrystals synthesized by Ar/O2 radio frequency thermal plasma oxidation of liquid precursor mists,” The Journal of Physical Chemistry B, vol. 110, no. 3, pp. 1121–1127, 2006. View at: Publisher Site | Google Scholar
  25. C. Ribeiro, C. Vila, D. B. Stroppa et al., “Anisotropic growth of oxide nanocrystals: insights into the rutile TiO2 phase,” Journal of Physical Chemistry C, vol. 111, no. 16, pp. 5871–5875, 2007. View at: Publisher Site | Google Scholar

Copyright © 2014 Guozhu Fu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Related articles

No related content is available yet for this article.
 PDF Download Citation Citation
 Download other formatsMore
 Order printed copiesOrder

Related articles

No related content is available yet for this article.

Article of the Year Award: Outstanding research contributions of 2020, as selected by our Chief Editors. Read the winning articles.