- Email: [email protected]
manganese oxide nanocrystalline films
Applied Surface Science 420 (2017) 489–495
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Full length article
Low temperature self-assembled growth of rutile TiO2 /manganese oxide nanocrystalline films Zhenya Sun a,b , Daokun Zhou a , Jianhua Du c,∗ , Yuxing Xie a a b c
School of Resources and Environmental Engineering, Wuhan University of Technology,122 Luoshi Road, Wuhan 430000, China Centre for Materials Research and Analysis, Wuhan University of Technology,122 Luoshi Road, Wuhan 430000, China GCER (Global Centre for Environmental Remediation), University of Newcastle, Callaghan, NSW 2308, Australia
a r t i c l e
i n f o
Article history: Received 24 March 2017 Received in revised form 16 May 2017 Accepted 17 May 2017 Available online 23 May 2017 Keywords: Rutile Anatase Self-assemble Manganese oxide Photocatalyst
a b s t r a c t We report formation of rutile TiO2 nanocrystal at low temperature range in the presence of ␣-MnO2 which self-assembled onto sulfanyl radical activated silicon oxide substrate. SEM, HRTEM, XPS and Raman spectroscopy were used to study the morphology and oxidation state of synthesised crystals. The results showed that when the ␣-MnO2 was reduced to Mn3 O4, it induced the formation of rutile instead of anatase phase in the TiCl4 -HCl aqueous system. The finding will promote the understanding of phase transformation mechanism when manganese oxide and titanium oxide co-exist in soil and water environment. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Titania crystal phase dominantly affects the photocatalytic properties of nanocrystals, phase control is important for the applications. The prototypical photocatalyst TiO2 exists in different polymorphs, the most common forms are the anatase and rutile [1]. Anatase phase is the metastable crystal type of titanium dioxide, generally prepared through hydrothermal [2], sol-gel [3], and selfassembly methods from inorganic or organic titanium source [4–6]; while rutile must be prepared in high temperature condition, and the phase transition process of anatase to rutile could be impacted by temperature, preparation method and the species and quantity of doping ion, etc. [7,8]. It has been reported that highly active nano anatase could be grown on goethite composite film was prepared using molecular self-assembly method [9]. Manganese is the secondly abundant transition metal element in crust which is only inferior to iron [10]. Manganese (hydrogen) oxide is a natural minerals with highly chemical reactivity and strongly adsorption ability [11]. Manganese oxide is closely related to the supergene environment iron but more active transition metal than iron [12]. There are various morphology and structure of manganese oxides, the
∗ Corresponding author. GCER, ATC Building, Callaghan Campus, University of Newcastle, 2308, Australia. E-mail addresses: [email protected], [email protected] (J. Du). http://dx.doi.org/10.1016/j.apsusc.2017.05.145 0169-4332/© 2017 Elsevier B.V. All rights reserved.
unique adsorption capacity and conductivity have attracted a lot of research attention [13–15]. However, the controllable preparation of multiphase orderly mineral composite of manganese oxide and titanium oxide nanocrystals has not been intensively investigated. In this study, we simulated the self-assembly process in the supergene minerals at low temperature range to induce the growth of nano titanium dioxide grain on the surface of manganese oxide. We also investigated how the phase change of nano manganese oxide crystal could affect the formation of rutile phase nano particles. It was found nano rutile phase was dominant instead of the usual anatase phase, while nano manganese oxide also experienced a complex phase change process from ␣-MnO2 to tetragonal crystal system hausmannite (Mn3 O4 ). These findings will promote the understanding of phase change mechanism when manganese oxide and titanium oxide co-exist in soil and water environment. The TiO2 /Mn3 O4 nano composite film will also have potential values for solar cells and photocatalysts. 2. Materials and methods 2.1. Preparation of the manganese oxide and titanium oxide nano composite film on HS/SiO2 substrate 2.1.1. Pre-treatment of silicon oxide substrate The silicon oxide glass slide substrate (purity of SiO2 is 99%) were flushed with deionized water at 293 K, then soaked 12 h in
490
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
the piranha solution (V30% H2 O2: V98% H2 SO4 = 3:7). After filtration and drying, the clean silicon oxide glass slides were washed again with distilled water until the pH value of washing liquid was 5. After that, the substrate was dried at 353 K for 4 h and stored in a desiccator for further use. 2.1.2. Preparation of sulfanyl self-assembled silicon oxide substrate 2 mL of 3-Mercaptopropyl trimethoxysilane (MPTMS) was dissolved in 100 mL of methylbenzene to derive sulfanyl radical also known as hydrosulphide/sulfanyl radical (HS). 3 pieces of pre-treated silicon oxide glass slides were immersed into MPTMS/methylbenzene solution in a 293 K water-bath for four hours then washed with anhydrous ethanol. The self-assembled HS/SiO2 substrate was obtained after dried at 353 K for 4 h. This self-assembled SAMs of the HS/SiO2 can guide the growth of the crystal and formed steady nano film materials in the low temperature aqueous system which has been widely used in nano functional materials preparation and material surface modification. It provided an economic and convenient method to induce the formation of manganese oxide and titanium oxide nano film. 2.1.3. Preparation of the manganese oxide and titanium oxide nano composite film on HS/SiO2 substrate The manganese oxide nano film was prepared by adding the selfassembled HS/SiO2 substrate into a mixture solution of 0.1 mmol/L MnSO4 and 0.2 mmol/L KMnO4 , pH was adjusted to 2.8 by adding 36% nitric acid. The mixed solution was then kept in a water-bath for 6 h at 343 K without stirring. Manganese oxide nano film on HS/SiO2 was obtained after the mixture was washed with distilled water, followed by filtering and drying. The titanium oxide nano film was prepared by immersing the self-assembled HS grafted SiO2 substrate into a solution mixture of 36% hydrochloride acid and 0.2 mol/L TiCl4 solution until the pH reached 1.0. The mixed solution was then kept in a water-bath for 4 h at 353 K without stirring. The titanium oxide nano film on HS/SiO2 was obtained after washing with distilled water, followed by filtering and drying. The manganese oxide and titanium oxide nano composite film was prepared by adding the manganese oxide nano film on HS/SiO2 substrate in the previous step which is same as obtaining the titanium oxide nano film. 2.2. Characterisations The thickness and surface morphology of the samples were observed using field emission scanning electron microscopy (SEM, Zeiss Ultra Plus, Germany), The composition and crystalline microstructure of the samples were analysed using high-resolution transmission electron microscopy (TEM, JEM-2100F STEM/EDS, Japan) with an accelerating voltage of 160 kV and Raman spectroscopy (InviaDELTA-320, UK) with 514.5 nm laser in the wavenumber range of 100–700 cm−1 . The manganese oxidation state of the samples were observed using X-ray photoelectron spectroscopy (ESCALAB 250Xi, USA). 3. Results and discussion 3.1. SEM surface morphology The surface morphology and thickness of the samples were observed by SEM as shown in Fig. 1. Fig. 1(a, d) showed that a thin manganese oxide nano film formed on HS/SiO2 substrate which was approximately 100 nm thick with irregular rough honeycomb, cellular arrangement, these surface features provided large surface area allowing the deposition of titanium oxide nano particles.
The SEM images in Fig. 1(b, e) revealed that the TiO2 nanocrystals with were 50 nm–100 nm long on HS/SiO2 presented platelet structure with a thickness of approximate 500 nm. The hybrid of manganese oxide and titanium oxide aggregation particles were about 100 nm–200 nm (Fig. 1c) with a thickness of about 1000 nm (Fig. 1f), this hybrid layer was thicker than the both the manganese oxide and titanium oxide nano films. The surface morphology of the hybrid composite film was similar to the titanium oxide nano film. The nano hybrid composite film didn’t present distinctive layered structure, and the grains of manganese oxide and titanium oxide could not be distinguished by SEM, as a result, a selected area of 20 m × 15 m titanium oxide/manganese oxide composite nano film (Fig. 1g) was further analysed by SEM/EDS to map the elemental distribution of Ti and Mn in the nano composite film. The distributions of Ti and Mn element (Fig. 1h, i) in the selected area are quite homogeneous and uniformed. Considering the depth of electron penetration into the sample, the nano composite layer should be a hybrid layers of manganese oxide and titanium oxide nanocrystals. 3.2. TEM morphology and diffraction pattern 3.2.1. TEM images of the manganese oxide nano film on HS/SiO2 The microstructure of the manganese oxide nano film on HS/SiO2 by TEM were shown in Fig. 2. Fig. 2a, the lowresolution topography, showed spherical grains of manganese oxide nanocrystals in the range of 5–10 nm. The crystal lattice matrix could be observed in high resolution lattice Fig. 2b with measured spacing of d = 0.346 nm and 0.240 nm corresponding to ␣-MnO2 ’s (220) and (211) lattice planes respectively. The electron diffraction Fig. 2c was the regional area of Fig. 2a. The interplanar distances of diffraction ring calculating from inside to outside of the ring were 3.46 Å, 2.45 Å, 1.97 Å, 1.43 Å which match the (220), (400), (321) and (002) lattice planes of ␣-MnO2 respectively (reference to JCPDS NO.44-0141). The result of TEM indicated that the manganese oxide nano film inducing by self-assembled HS silicon oxide substrate was mainly ␣-MnO2 crystal. 3.2.2. TEM figures of the titanium oxide nano film on HS/SiO2 The microstructure of the titanium oxide nano film on HS/SiO2 was observed by TEM as shown in Fig. 3. From the low resolution topography Fig. 3a, the spherical grains were attributed to titanium oxide nanocrystal. In the high resolution lattice Fig. 3b, we observed that titanium oxide crystal formed anatase (101) lattice plane and (004) lattice plane with measured spacing of 0.352 nm and 0.238 nm. The electron diffraction Fig. 3c was the regional area of Fig. 3a. The interplanar distances of diffraction ring calculating from inside to outside of the ring were 3.52 Å, 2.42 Å, 1.89 Å, 1.69 Å, 1.49 Å, 1.36 Å, 1.26 Å in turn, indexing to anatase TiO2 ’s (101), (103), (200), (105), (213), (116) and (215) lattice planes respectively (reference to JCPDS NO.21-1272). The result of TEM indicated that the crystal phase of titanium oxide inducing by self-assembled HS/SiO2 substrate was mainly anatase. 3.2.3. TEM images of manganese oxide and titanium oxide nano hybrid composite film on HS/SiO2 The microstructure of the manganese oxide and titanium oxide nano composite film on HS/SiO2 by TEM was shown in Fig. 4a showed that there were several layers of nano composite grew on the surface of the manganese oxide nanocrystal. The crystal lattice in Fig. 4b were measured at spacing of 0.308 nm corresponding to hausmannite Mn3 O4 (202) lattice plane in the darker area and the lattice spacing of d = 0.324 nm corresponding to the rutile TiO2 ’s (110) lattice plane in the lighter area. Other areas of the composite film were shown in Fig. 4f and g. The measured d-spacing in Fig. 4f were 0.340 nm, 0.226 nm and
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
491
Fig. 1. SEM images of the samples. (a,d) the manganese oxide nano film (b,e) the titanium oxide nano film (c,f) the manganese oxide and titanium oxide nano composite film (g)SEM morphology of the nano composite film (h) EDS Ti mapping in the nao composite film (i) EDS Mn mapping in the nano composite film
Fig. 2. TEM images of the ␣-MnO2 nano film on HS/SiO2 .
(a) Low resolution topography (b) high resolution lattice image (c) electron diffraction pattern
0.262 nm corresponding to hausmannite Mn3 O4 (211), (312) and (301) lattice plane in the darker area and the lattice spacing within the red circle of d = 0.218 nm corresponding to the rutile TiO2 ’s (111) lattice plane which co-existed with the Mn3 O4 (312) lattice plane. This coexistence of rutile with hausmannite could also be evidently seen in Fig. 4g where within the red circle, the lattice spacing of d = 0.230 nm corresponding to the rutile TiO2 ’s (200) lattice plane while adjacent lattice spacing of d = 0.220 nm was the
Mn3 O4 (321) lattice plane (reference to JCPDS NO. 21-1276 and JCPDS NO. 65-2776). Fig. 4c and d were the representative selected area electron diffraction patterns (SAED) of the Mn3 O4 /TiO2 nano composite film, and the interplanar distances of diffraction rings in Fig. 4c, d from inside to outside were listed in Tables 1 and 2 respectively. The SAED results further confirmed these nano composite material was a mixture of rutile and hausmannite.
492
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
Fig. 3. TEM images of the TiO2 (anatase)nano film on HS/SiO2.
(a) Low resolution topography (b) high resolution lattice image (c) electron diffraction pattern
Table 1 The data of Fig. 4c’s electron diffraction rings. d(Å)
3.403
2.613
2.292
2.182
1.781
1.550
1.420
mineralogical phase lattice plane
Mn3 O4 (211)
Mn3 O4 (301)
Rutile (200)
Rutile (111)
Mn3 O4 (332)
Mn3 O4 (305)
Rutile (221)
The EDS spectrum diagram 4e showed the elemental information of Fig. 4a, the elements of Ti, Mn, Si and O were detected which further proved that the TiO2 /Mn3 O4 nano composite film was formed on the surface of the self-assembled HS silicon oxide substrate. Therefore, it could be concluded that the ␣-MnO2 was formed by self-assembled onto the HS silicon oxide substrate in MnSO4 KMnO4 aqueous system; while the ␣-MnO2 nano film on HS/SiO2 was added in TiCl4 -HCl aqueous system, the ␣-MnO2 nano film was reduced to the hausmannite Mn3 O4 and the nano rutile phase formed rather than the usual anatase phase generated by the previous method.
that the Mn 2p3/2 and 2p1/2 peaks were observed at 642.4 eV and 654 eV, which could be assigned to ␣-MnO2 [17]. The XPS scan of the manganese oxide and titanium oxide nano composite film was supplied in Fig. 7(a), which showed the characteristic peaks of titanium, manganese, oxygen and adventitious carbon. The peak of manganese was again very weak due to the coverage by titanium oxide. The high-resolution Mn 2p and O 1s spectra were presented in Fig. 7b and c, respectively. As shown in Fig. 7b, the peaks of Mn 2p3/2 and Mn 2p1/2 were located at binding energy of 641.3 eV and 653 eV, which were consistent with the reported values of Mn3 O4 [17]. Such a conclusion was further validated by the XPS results of O 1s shown in Fig. 7c, the binding energy values of approximately 529.7, 530.2, 531.2, 532 and 532.9 eV were corresponded to the bulk oxygen of TiO2 , lattice oxygen of Mn3 O4 , the key bridge oxygen to Mn from the process of ␣-MnO2 reduced to Mn3 O4 , the lattice oxygen of SiO2 and adsorbed molecular water, respectively [18–20]. It was further confirmed that the phase transformation process of the ␣-MnO2 to Mn3 O4 which induce the synthesis of rutile TiO2 in TiCl4 -HCl aqueous system.
3.4. Raman spectra analysis Fig. 5 showed the Raman spectra of the manganese oxide nano film, the titanium oxide nano film, the manganese oxide and titanium oxide nano composite film on HS/SiO2. The Raman vibrations at 150 cm−1 assigned to the Ti-O bond stretching vibration of anatase [7]. While the Raman vibrations at 446 cm−1 and 606 cm−1 were associated with Ti O bonds in two different space symmetric stretching vibration of rutile. The Raman peak at 650 cm−1 for the manganese oxide nano film attributed to the Mn-O bond stretching vibration of MnO6 of the ␣-MnO2 [16]. The Raman scattering of Mn3 O4 nanocrystals was not detected in the composite which was due to the coverage by the thicker grains of TiO2 . These information provided further evidence that ␣-MnO2 in TiCl4 -HCl aqueous system could induce the generation of rutile. 3.5. XPS analysis X ray photoelectron spectroscopy in Fig. 6a was the survey scan of manganese oxide nano film. The binding energy of Si 2p, S 2p, C 1s, O 1s and Mn 2p were observed. Si 2p and S 2p were from the self-assembled HS/SiO2 substrate, respectively. Fig. 6b showed
3.6. Hypothesis of the transformation of anatase to rutile nanocrystal inducing by the ˛-MnO2 to Mn3 O4 phase transformation Based on the above evidence, we proposed the hypothesis of rutile formation mechanism in the low temperature TiCl4 -HCl system in Fig. 8. Manganese hydrolysate such as MnO2+ was adsorbed by the self-assembled monolayer HS/SiO2 substrate and generated the ␣-MnO2 in MnSO4 – KMnO4 aqueous system, while the TiCl4 hydrolysate such as TiO2+ was adsorbed by the HS/SiO2 substrate, it would generate the anatase TiO2 in TiCl4 -HCl aqueous system. While the ␣-MnO2 nano film on HS/SiO2 was added in TiCl4 -HCl aqueous system, part of the manganese oxide was more prone to reduction reaction caused by the quantisation effect of manganese oxide nanocrystals despite of the low concentration of TiCl4. The overall reaction equations could be summarised as: 3MnO2 + TiCl4 → Mn3 O4 + TiO2 + 2Cl2 ↑ This reaction accelerated the hydroxylation of TiCl4 to generated polynuclear hydroxyl complex titanium and continue to dehydrate to form titanium oxide octahedron.The ␣-MnO2 nano film was
Table 2 The data of Fig. 4d’s electron diffraction rings. d(Å)
3.403
2.482
2.201
1.937
1.543
1.357
1.324
1.167
mineralogical phase lattice plane
Mn3 O4 (211)
Rutile (101)
Mn3 O4 (321)
Mn3 O4 (411)
Mn3 O4 (404)
Rutile (301)
Mn3 O4 (514)
Rutile (321)
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
493
Fig. 4. TEM images and EDS spectrum diagram of the TiO2 (rutile)/Mn3 O4 nano composite film on HS/SiO2 . (a) Low resolution topography (b) high resolution lattice image (c, d) selected area electron diffraction pattern (e) EDS spectrum diagram (f, g) high resolution lattice image of rutile and hausmannite.
reduced to the hausmannite Mn3 O4 (tetragonal crystal system) which had abundant interfaces and also induced the formation of rutile instead of anatase. The titanium oxide octahedron tended to polymerise and share the top oxygen atom on these interfaces of hausmannite Mn3 O4 , which eventually induced the growth of rutile TiO2 nanocrystal. This chemical reaction was a spontaneous thermodynamic process which could pass the system’s Gibbs free energy.
4. Conclusions We investigated the formation of different titanium oxide crystal phase from anatase to rutile nanocrystal at lower temperature range on the manganese oxide self-assembled on HS/SiO2 substrate. It was found that the manganese oxide, titanium oxide, manganese oxide and titanium oxide crystals formed on HS/SiO2 substrate were in the 5–10 nm size range. The oxidation of ␣MnO2 nanocrystal led to the reduction of manganese oxide to hausmannite which induced the nucleation and formation of rutile nanocrystal instead of the usual anatase phase and therefore nano
494
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
manganese oxide and titanium oxide co-exist in soil and water environment and also be beneficial for the solar cells and photocatalysts industries. Acknowledgements This work was supported by Natural Science Foundation of China (No. 41372054). References
Fig. 5. The Raman spectra of the ␣-MnO2 , TiO2 and TiO2 /Mn3 O4 nano films on HS/SiO2.
rutile phase was the dominant crystal phase. These findings will promote the understanding of phase change mechanism when
Fig. 6. The XPS spectra of the ␣-MnO2 nano films on HS/SiO2.
Fig. 7. The XPS spectra of the TiO2 /Mn3 O4 nano films on HS/SiO2.
[1] T. Luttrell, S. Halpegamage, J. Tao, A. Kramer, E. Sutter, M. Batzill, Why is anatase a better photocatalyst than rutile? – Model studies on epitaxial TiO2 films, Sci. Rep.-UK 4 (2014) 1–8. [2] N. Liu, X. Chen, J. Zhang, J.W. Schwank, A review on TiO2 -based nanotubes synthesized via hydrothermal method: formation mechanism, structure modification, and photocatalytic applications, Catal. Today 225 (2014) 34–51. [3] H. Kang, Z. Sun, Y. Liu, Adsorption-visible photocatalytic synergy of Ag+ –TiO2 /AC composite, Chin. J. Environ. Eng. 9 (2015) 1620–1624. [4] Z. Zhang, F. Xiao, Y. Guo, S. Wang, Y. Liu, One-pot self-assembled three-dimensional TiO2 -graphene hydrogel with improved adsorption capacities and photocatalytic and electrochemical activities, ACS Appl. Mater. Interface 5 (2013) 2227–2233.
(a) Survey scan (b) Mn 2p spectra
(a) Survey scan (b) Mn 2p spectra (c) O 1s spectra
Fig. 8. The schematic diagram of the rutile TiO2 nanocrystal inducing by the ␣-MnO2 /Mn3 O4 phase transformation process.
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495 [5] S. Yuan, Q. Zhang, F. Lei, Self assembly TiO2 films on the flexible transparent conductive oxide substrates: preparation and photoelectrochemical activity, Chin. J. Inorg. Chem. 31 (2015) 1099–1104. [6] Z. Sun, X. He, J. Du, W. Gong, Synergistic effect of photocatalysis and adsorption of nano-TiO2 self-assembled onto sulfanyl/activated carbon composite, Environ. Sci. Pollut. Res. 23 (2016) 21733–21740. [7] K. Zhu, Q. Chen, Y. Deng, Phase transition of TiO2 nanocrystals investigated by low-temperature Raman, J. Light Scattering 20 (2008) 330–332. [8] D.A.H. Hanaor, C.C. Sorrell, Review of the anatase to rutile phase transformation, J. Mater. Sci. 46 (2011) 855–874. [9] Y. Zhou, Z. Sun, Preparation and characterization of FeOOH/TiO2 thin film on SiO2 self-assembly monolayer, J. Wuhan Univ. Technol. 35 (2013) 16–20. [10] A. Lu, X. Lu, Z. Ren, New advances in environmental mineralogy of natural oxides and hydroxides of iron and manganese, Earth Sci. Front. 7 (2000) 473–483. [11] C. Clarke, J. Tourney, K. Johnson, Oxidation of anthracene using waste Mn oxide minerals: the importance of wetting and drying sequences, J. Hazard. Mater. 205–206 (2012) 126–130. [12] L. Zhang, Q. Zhang, Y. Zheng, Interaction of manganese oxides with multiple valences heavy metals in environmental remediation, Acta Sci. Circumst. 33 (2013) 1519–1526. [13] Y. Meng, W. Song, H. Huang, Z. Ren, S. Chen, S.L. Suib, Structure–property relationship of bifunctional MnO2 nanostructures: highly efficient,
[14]
[15]
[16]
[17]
[18]
[19] [20]
495
ultra-stable electrochemical water oxidation and oxygen reduction reaction catalysts identified in alkaline media, J. Am. Chem. Soc. 136 (2014) 11452–11464. C. Luo, R. Wei, D. Guo, S. Zhang, S. Yan, Adsorption behavior of MnO2 functionalized multi-walled carbon nanotubes for the removal of cadmium from aqueous solutions, Chem. Eng. J. 225 (2013) 406–415. S. Devaraj, N. Munichandraiah, Effect of crystallographic structure of MnO2 on its electrochemical capacitance properties, J. Phys. Chem. C 112 (2008) 4406–4417. J. Tang, P. Cao, Y. Fu, Synthesis of a mesoporous manganese dioxide-graphene composite by a simple template-free strategy for high-performance supercapacitors, Acta Phys.-Chim. Sin. 30 (2014) 1876–1882. J. Zhao, J. Nan, Z. Zhao, N. Li, J. Liu, F. Cui, Energy-efficient fabrication of a novel multivalence Mn3 O4 -MnO2 heterojunction for dye degradation under visible light irradiation, Appl. Catal. B: Environ. 202 (2017) 509–517. H. Perron, J. Vandenborre, C. Domain, R. Drot, J. Roques, E. Simoni, J.J. Ehrhardt, H. Catalette, Combined investigation of water sorption on TiO2 rutile (110) single crystal face: XPS vs periodic DFT, Surf. Sci. 601 (2007) 518–527. L. Yang, C. Gao, M. Zheng, Synthesis and electrochemical properties of Mn3 O4 polyhedral nanocrystals, Chin. J. Inorg. Chem. 29 (2013) 381–388. C. Ge, Y. Liu, M. Ren, Formation mechanism of nanosilica film on rutile TiO2 , Chin. J. Nonferr. Metals 18 (2008) 1110–1116.
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Full length article
Low temperature self-assembled growth of rutile TiO2 /manganese oxide nanocrystalline films Zhenya Sun a,b , Daokun Zhou a , Jianhua Du c,∗ , Yuxing Xie a a b c
School of Resources and Environmental Engineering, Wuhan University of Technology,122 Luoshi Road, Wuhan 430000, China Centre for Materials Research and Analysis, Wuhan University of Technology,122 Luoshi Road, Wuhan 430000, China GCER (Global Centre for Environmental Remediation), University of Newcastle, Callaghan, NSW 2308, Australia
a r t i c l e
i n f o
Article history: Received 24 March 2017 Received in revised form 16 May 2017 Accepted 17 May 2017 Available online 23 May 2017 Keywords: Rutile Anatase Self-assemble Manganese oxide Photocatalyst
a b s t r a c t We report formation of rutile TiO2 nanocrystal at low temperature range in the presence of ␣-MnO2 which self-assembled onto sulfanyl radical activated silicon oxide substrate. SEM, HRTEM, XPS and Raman spectroscopy were used to study the morphology and oxidation state of synthesised crystals. The results showed that when the ␣-MnO2 was reduced to Mn3 O4, it induced the formation of rutile instead of anatase phase in the TiCl4 -HCl aqueous system. The finding will promote the understanding of phase transformation mechanism when manganese oxide and titanium oxide co-exist in soil and water environment. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Titania crystal phase dominantly affects the photocatalytic properties of nanocrystals, phase control is important for the applications. The prototypical photocatalyst TiO2 exists in different polymorphs, the most common forms are the anatase and rutile [1]. Anatase phase is the metastable crystal type of titanium dioxide, generally prepared through hydrothermal [2], sol-gel [3], and selfassembly methods from inorganic or organic titanium source [4–6]; while rutile must be prepared in high temperature condition, and the phase transition process of anatase to rutile could be impacted by temperature, preparation method and the species and quantity of doping ion, etc. [7,8]. It has been reported that highly active nano anatase could be grown on goethite composite film was prepared using molecular self-assembly method [9]. Manganese is the secondly abundant transition metal element in crust which is only inferior to iron [10]. Manganese (hydrogen) oxide is a natural minerals with highly chemical reactivity and strongly adsorption ability [11]. Manganese oxide is closely related to the supergene environment iron but more active transition metal than iron [12]. There are various morphology and structure of manganese oxides, the
∗ Corresponding author. GCER, ATC Building, Callaghan Campus, University of Newcastle, 2308, Australia. E-mail addresses: [email protected], [email protected] (J. Du). http://dx.doi.org/10.1016/j.apsusc.2017.05.145 0169-4332/© 2017 Elsevier B.V. All rights reserved.
unique adsorption capacity and conductivity have attracted a lot of research attention [13–15]. However, the controllable preparation of multiphase orderly mineral composite of manganese oxide and titanium oxide nanocrystals has not been intensively investigated. In this study, we simulated the self-assembly process in the supergene minerals at low temperature range to induce the growth of nano titanium dioxide grain on the surface of manganese oxide. We also investigated how the phase change of nano manganese oxide crystal could affect the formation of rutile phase nano particles. It was found nano rutile phase was dominant instead of the usual anatase phase, while nano manganese oxide also experienced a complex phase change process from ␣-MnO2 to tetragonal crystal system hausmannite (Mn3 O4 ). These findings will promote the understanding of phase change mechanism when manganese oxide and titanium oxide co-exist in soil and water environment. The TiO2 /Mn3 O4 nano composite film will also have potential values for solar cells and photocatalysts. 2. Materials and methods 2.1. Preparation of the manganese oxide and titanium oxide nano composite film on HS/SiO2 substrate 2.1.1. Pre-treatment of silicon oxide substrate The silicon oxide glass slide substrate (purity of SiO2 is 99%) were flushed with deionized water at 293 K, then soaked 12 h in
490
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
the piranha solution (V30% H2 O2: V98% H2 SO4 = 3:7). After filtration and drying, the clean silicon oxide glass slides were washed again with distilled water until the pH value of washing liquid was 5. After that, the substrate was dried at 353 K for 4 h and stored in a desiccator for further use. 2.1.2. Preparation of sulfanyl self-assembled silicon oxide substrate 2 mL of 3-Mercaptopropyl trimethoxysilane (MPTMS) was dissolved in 100 mL of methylbenzene to derive sulfanyl radical also known as hydrosulphide/sulfanyl radical (HS). 3 pieces of pre-treated silicon oxide glass slides were immersed into MPTMS/methylbenzene solution in a 293 K water-bath for four hours then washed with anhydrous ethanol. The self-assembled HS/SiO2 substrate was obtained after dried at 353 K for 4 h. This self-assembled SAMs of the HS/SiO2 can guide the growth of the crystal and formed steady nano film materials in the low temperature aqueous system which has been widely used in nano functional materials preparation and material surface modification. It provided an economic and convenient method to induce the formation of manganese oxide and titanium oxide nano film. 2.1.3. Preparation of the manganese oxide and titanium oxide nano composite film on HS/SiO2 substrate The manganese oxide nano film was prepared by adding the selfassembled HS/SiO2 substrate into a mixture solution of 0.1 mmol/L MnSO4 and 0.2 mmol/L KMnO4 , pH was adjusted to 2.8 by adding 36% nitric acid. The mixed solution was then kept in a water-bath for 6 h at 343 K without stirring. Manganese oxide nano film on HS/SiO2 was obtained after the mixture was washed with distilled water, followed by filtering and drying. The titanium oxide nano film was prepared by immersing the self-assembled HS grafted SiO2 substrate into a solution mixture of 36% hydrochloride acid and 0.2 mol/L TiCl4 solution until the pH reached 1.0. The mixed solution was then kept in a water-bath for 4 h at 353 K without stirring. The titanium oxide nano film on HS/SiO2 was obtained after washing with distilled water, followed by filtering and drying. The manganese oxide and titanium oxide nano composite film was prepared by adding the manganese oxide nano film on HS/SiO2 substrate in the previous step which is same as obtaining the titanium oxide nano film. 2.2. Characterisations The thickness and surface morphology of the samples were observed using field emission scanning electron microscopy (SEM, Zeiss Ultra Plus, Germany), The composition and crystalline microstructure of the samples were analysed using high-resolution transmission electron microscopy (TEM, JEM-2100F STEM/EDS, Japan) with an accelerating voltage of 160 kV and Raman spectroscopy (InviaDELTA-320, UK) with 514.5 nm laser in the wavenumber range of 100–700 cm−1 . The manganese oxidation state of the samples were observed using X-ray photoelectron spectroscopy (ESCALAB 250Xi, USA). 3. Results and discussion 3.1. SEM surface morphology The surface morphology and thickness of the samples were observed by SEM as shown in Fig. 1. Fig. 1(a, d) showed that a thin manganese oxide nano film formed on HS/SiO2 substrate which was approximately 100 nm thick with irregular rough honeycomb, cellular arrangement, these surface features provided large surface area allowing the deposition of titanium oxide nano particles.
The SEM images in Fig. 1(b, e) revealed that the TiO2 nanocrystals with were 50 nm–100 nm long on HS/SiO2 presented platelet structure with a thickness of approximate 500 nm. The hybrid of manganese oxide and titanium oxide aggregation particles were about 100 nm–200 nm (Fig. 1c) with a thickness of about 1000 nm (Fig. 1f), this hybrid layer was thicker than the both the manganese oxide and titanium oxide nano films. The surface morphology of the hybrid composite film was similar to the titanium oxide nano film. The nano hybrid composite film didn’t present distinctive layered structure, and the grains of manganese oxide and titanium oxide could not be distinguished by SEM, as a result, a selected area of 20 m × 15 m titanium oxide/manganese oxide composite nano film (Fig. 1g) was further analysed by SEM/EDS to map the elemental distribution of Ti and Mn in the nano composite film. The distributions of Ti and Mn element (Fig. 1h, i) in the selected area are quite homogeneous and uniformed. Considering the depth of electron penetration into the sample, the nano composite layer should be a hybrid layers of manganese oxide and titanium oxide nanocrystals. 3.2. TEM morphology and diffraction pattern 3.2.1. TEM images of the manganese oxide nano film on HS/SiO2 The microstructure of the manganese oxide nano film on HS/SiO2 by TEM were shown in Fig. 2. Fig. 2a, the lowresolution topography, showed spherical grains of manganese oxide nanocrystals in the range of 5–10 nm. The crystal lattice matrix could be observed in high resolution lattice Fig. 2b with measured spacing of d = 0.346 nm and 0.240 nm corresponding to ␣-MnO2 ’s (220) and (211) lattice planes respectively. The electron diffraction Fig. 2c was the regional area of Fig. 2a. The interplanar distances of diffraction ring calculating from inside to outside of the ring were 3.46 Å, 2.45 Å, 1.97 Å, 1.43 Å which match the (220), (400), (321) and (002) lattice planes of ␣-MnO2 respectively (reference to JCPDS NO.44-0141). The result of TEM indicated that the manganese oxide nano film inducing by self-assembled HS silicon oxide substrate was mainly ␣-MnO2 crystal. 3.2.2. TEM figures of the titanium oxide nano film on HS/SiO2 The microstructure of the titanium oxide nano film on HS/SiO2 was observed by TEM as shown in Fig. 3. From the low resolution topography Fig. 3a, the spherical grains were attributed to titanium oxide nanocrystal. In the high resolution lattice Fig. 3b, we observed that titanium oxide crystal formed anatase (101) lattice plane and (004) lattice plane with measured spacing of 0.352 nm and 0.238 nm. The electron diffraction Fig. 3c was the regional area of Fig. 3a. The interplanar distances of diffraction ring calculating from inside to outside of the ring were 3.52 Å, 2.42 Å, 1.89 Å, 1.69 Å, 1.49 Å, 1.36 Å, 1.26 Å in turn, indexing to anatase TiO2 ’s (101), (103), (200), (105), (213), (116) and (215) lattice planes respectively (reference to JCPDS NO.21-1272). The result of TEM indicated that the crystal phase of titanium oxide inducing by self-assembled HS/SiO2 substrate was mainly anatase. 3.2.3. TEM images of manganese oxide and titanium oxide nano hybrid composite film on HS/SiO2 The microstructure of the manganese oxide and titanium oxide nano composite film on HS/SiO2 by TEM was shown in Fig. 4a showed that there were several layers of nano composite grew on the surface of the manganese oxide nanocrystal. The crystal lattice in Fig. 4b were measured at spacing of 0.308 nm corresponding to hausmannite Mn3 O4 (202) lattice plane in the darker area and the lattice spacing of d = 0.324 nm corresponding to the rutile TiO2 ’s (110) lattice plane in the lighter area. Other areas of the composite film were shown in Fig. 4f and g. The measured d-spacing in Fig. 4f were 0.340 nm, 0.226 nm and
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
491
Fig. 1. SEM images of the samples. (a,d) the manganese oxide nano film (b,e) the titanium oxide nano film (c,f) the manganese oxide and titanium oxide nano composite film (g)SEM morphology of the nano composite film (h) EDS Ti mapping in the nao composite film (i) EDS Mn mapping in the nano composite film
Fig. 2. TEM images of the ␣-MnO2 nano film on HS/SiO2 .
(a) Low resolution topography (b) high resolution lattice image (c) electron diffraction pattern
0.262 nm corresponding to hausmannite Mn3 O4 (211), (312) and (301) lattice plane in the darker area and the lattice spacing within the red circle of d = 0.218 nm corresponding to the rutile TiO2 ’s (111) lattice plane which co-existed with the Mn3 O4 (312) lattice plane. This coexistence of rutile with hausmannite could also be evidently seen in Fig. 4g where within the red circle, the lattice spacing of d = 0.230 nm corresponding to the rutile TiO2 ’s (200) lattice plane while adjacent lattice spacing of d = 0.220 nm was the
Mn3 O4 (321) lattice plane (reference to JCPDS NO. 21-1276 and JCPDS NO. 65-2776). Fig. 4c and d were the representative selected area electron diffraction patterns (SAED) of the Mn3 O4 /TiO2 nano composite film, and the interplanar distances of diffraction rings in Fig. 4c, d from inside to outside were listed in Tables 1 and 2 respectively. The SAED results further confirmed these nano composite material was a mixture of rutile and hausmannite.
492
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
Fig. 3. TEM images of the TiO2 (anatase)nano film on HS/SiO2.
(a) Low resolution topography (b) high resolution lattice image (c) electron diffraction pattern
Table 1 The data of Fig. 4c’s electron diffraction rings. d(Å)
3.403
2.613
2.292
2.182
1.781
1.550
1.420
mineralogical phase lattice plane
Mn3 O4 (211)
Mn3 O4 (301)
Rutile (200)
Rutile (111)
Mn3 O4 (332)
Mn3 O4 (305)
Rutile (221)
The EDS spectrum diagram 4e showed the elemental information of Fig. 4a, the elements of Ti, Mn, Si and O were detected which further proved that the TiO2 /Mn3 O4 nano composite film was formed on the surface of the self-assembled HS silicon oxide substrate. Therefore, it could be concluded that the ␣-MnO2 was formed by self-assembled onto the HS silicon oxide substrate in MnSO4 KMnO4 aqueous system; while the ␣-MnO2 nano film on HS/SiO2 was added in TiCl4 -HCl aqueous system, the ␣-MnO2 nano film was reduced to the hausmannite Mn3 O4 and the nano rutile phase formed rather than the usual anatase phase generated by the previous method.
that the Mn 2p3/2 and 2p1/2 peaks were observed at 642.4 eV and 654 eV, which could be assigned to ␣-MnO2 [17]. The XPS scan of the manganese oxide and titanium oxide nano composite film was supplied in Fig. 7(a), which showed the characteristic peaks of titanium, manganese, oxygen and adventitious carbon. The peak of manganese was again very weak due to the coverage by titanium oxide. The high-resolution Mn 2p and O 1s spectra were presented in Fig. 7b and c, respectively. As shown in Fig. 7b, the peaks of Mn 2p3/2 and Mn 2p1/2 were located at binding energy of 641.3 eV and 653 eV, which were consistent with the reported values of Mn3 O4 [17]. Such a conclusion was further validated by the XPS results of O 1s shown in Fig. 7c, the binding energy values of approximately 529.7, 530.2, 531.2, 532 and 532.9 eV were corresponded to the bulk oxygen of TiO2 , lattice oxygen of Mn3 O4 , the key bridge oxygen to Mn from the process of ␣-MnO2 reduced to Mn3 O4 , the lattice oxygen of SiO2 and adsorbed molecular water, respectively [18–20]. It was further confirmed that the phase transformation process of the ␣-MnO2 to Mn3 O4 which induce the synthesis of rutile TiO2 in TiCl4 -HCl aqueous system.
3.4. Raman spectra analysis Fig. 5 showed the Raman spectra of the manganese oxide nano film, the titanium oxide nano film, the manganese oxide and titanium oxide nano composite film on HS/SiO2. The Raman vibrations at 150 cm−1 assigned to the Ti-O bond stretching vibration of anatase [7]. While the Raman vibrations at 446 cm−1 and 606 cm−1 were associated with Ti O bonds in two different space symmetric stretching vibration of rutile. The Raman peak at 650 cm−1 for the manganese oxide nano film attributed to the Mn-O bond stretching vibration of MnO6 of the ␣-MnO2 [16]. The Raman scattering of Mn3 O4 nanocrystals was not detected in the composite which was due to the coverage by the thicker grains of TiO2 . These information provided further evidence that ␣-MnO2 in TiCl4 -HCl aqueous system could induce the generation of rutile. 3.5. XPS analysis X ray photoelectron spectroscopy in Fig. 6a was the survey scan of manganese oxide nano film. The binding energy of Si 2p, S 2p, C 1s, O 1s and Mn 2p were observed. Si 2p and S 2p were from the self-assembled HS/SiO2 substrate, respectively. Fig. 6b showed
3.6. Hypothesis of the transformation of anatase to rutile nanocrystal inducing by the ˛-MnO2 to Mn3 O4 phase transformation Based on the above evidence, we proposed the hypothesis of rutile formation mechanism in the low temperature TiCl4 -HCl system in Fig. 8. Manganese hydrolysate such as MnO2+ was adsorbed by the self-assembled monolayer HS/SiO2 substrate and generated the ␣-MnO2 in MnSO4 – KMnO4 aqueous system, while the TiCl4 hydrolysate such as TiO2+ was adsorbed by the HS/SiO2 substrate, it would generate the anatase TiO2 in TiCl4 -HCl aqueous system. While the ␣-MnO2 nano film on HS/SiO2 was added in TiCl4 -HCl aqueous system, part of the manganese oxide was more prone to reduction reaction caused by the quantisation effect of manganese oxide nanocrystals despite of the low concentration of TiCl4. The overall reaction equations could be summarised as: 3MnO2 + TiCl4 → Mn3 O4 + TiO2 + 2Cl2 ↑ This reaction accelerated the hydroxylation of TiCl4 to generated polynuclear hydroxyl complex titanium and continue to dehydrate to form titanium oxide octahedron.The ␣-MnO2 nano film was
Table 2 The data of Fig. 4d’s electron diffraction rings. d(Å)
3.403
2.482
2.201
1.937
1.543
1.357
1.324
1.167
mineralogical phase lattice plane
Mn3 O4 (211)
Rutile (101)
Mn3 O4 (321)
Mn3 O4 (411)
Mn3 O4 (404)
Rutile (301)
Mn3 O4 (514)
Rutile (321)
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
493
Fig. 4. TEM images and EDS spectrum diagram of the TiO2 (rutile)/Mn3 O4 nano composite film on HS/SiO2 . (a) Low resolution topography (b) high resolution lattice image (c, d) selected area electron diffraction pattern (e) EDS spectrum diagram (f, g) high resolution lattice image of rutile and hausmannite.
reduced to the hausmannite Mn3 O4 (tetragonal crystal system) which had abundant interfaces and also induced the formation of rutile instead of anatase. The titanium oxide octahedron tended to polymerise and share the top oxygen atom on these interfaces of hausmannite Mn3 O4 , which eventually induced the growth of rutile TiO2 nanocrystal. This chemical reaction was a spontaneous thermodynamic process which could pass the system’s Gibbs free energy.
4. Conclusions We investigated the formation of different titanium oxide crystal phase from anatase to rutile nanocrystal at lower temperature range on the manganese oxide self-assembled on HS/SiO2 substrate. It was found that the manganese oxide, titanium oxide, manganese oxide and titanium oxide crystals formed on HS/SiO2 substrate were in the 5–10 nm size range. The oxidation of ␣MnO2 nanocrystal led to the reduction of manganese oxide to hausmannite which induced the nucleation and formation of rutile nanocrystal instead of the usual anatase phase and therefore nano
494
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495
manganese oxide and titanium oxide co-exist in soil and water environment and also be beneficial for the solar cells and photocatalysts industries. Acknowledgements This work was supported by Natural Science Foundation of China (No. 41372054). References
Fig. 5. The Raman spectra of the ␣-MnO2 , TiO2 and TiO2 /Mn3 O4 nano films on HS/SiO2.
rutile phase was the dominant crystal phase. These findings will promote the understanding of phase change mechanism when
Fig. 6. The XPS spectra of the ␣-MnO2 nano films on HS/SiO2.
Fig. 7. The XPS spectra of the TiO2 /Mn3 O4 nano films on HS/SiO2.
[1] T. Luttrell, S. Halpegamage, J. Tao, A. Kramer, E. Sutter, M. Batzill, Why is anatase a better photocatalyst than rutile? – Model studies on epitaxial TiO2 films, Sci. Rep.-UK 4 (2014) 1–8. [2] N. Liu, X. Chen, J. Zhang, J.W. Schwank, A review on TiO2 -based nanotubes synthesized via hydrothermal method: formation mechanism, structure modification, and photocatalytic applications, Catal. Today 225 (2014) 34–51. [3] H. Kang, Z. Sun, Y. Liu, Adsorption-visible photocatalytic synergy of Ag+ –TiO2 /AC composite, Chin. J. Environ. Eng. 9 (2015) 1620–1624. [4] Z. Zhang, F. Xiao, Y. Guo, S. Wang, Y. Liu, One-pot self-assembled three-dimensional TiO2 -graphene hydrogel with improved adsorption capacities and photocatalytic and electrochemical activities, ACS Appl. Mater. Interface 5 (2013) 2227–2233.
(a) Survey scan (b) Mn 2p spectra
(a) Survey scan (b) Mn 2p spectra (c) O 1s spectra
Fig. 8. The schematic diagram of the rutile TiO2 nanocrystal inducing by the ␣-MnO2 /Mn3 O4 phase transformation process.
Z. Sun et al. / Applied Surface Science 420 (2017) 489–495 [5] S. Yuan, Q. Zhang, F. Lei, Self assembly TiO2 films on the flexible transparent conductive oxide substrates: preparation and photoelectrochemical activity, Chin. J. Inorg. Chem. 31 (2015) 1099–1104. [6] Z. Sun, X. He, J. Du, W. Gong, Synergistic effect of photocatalysis and adsorption of nano-TiO2 self-assembled onto sulfanyl/activated carbon composite, Environ. Sci. Pollut. Res. 23 (2016) 21733–21740. [7] K. Zhu, Q. Chen, Y. Deng, Phase transition of TiO2 nanocrystals investigated by low-temperature Raman, J. Light Scattering 20 (2008) 330–332. [8] D.A.H. Hanaor, C.C. Sorrell, Review of the anatase to rutile phase transformation, J. Mater. Sci. 46 (2011) 855–874. [9] Y. Zhou, Z. Sun, Preparation and characterization of FeOOH/TiO2 thin film on SiO2 self-assembly monolayer, J. Wuhan Univ. Technol. 35 (2013) 16–20. [10] A. Lu, X. Lu, Z. Ren, New advances in environmental mineralogy of natural oxides and hydroxides of iron and manganese, Earth Sci. Front. 7 (2000) 473–483. [11] C. Clarke, J. Tourney, K. Johnson, Oxidation of anthracene using waste Mn oxide minerals: the importance of wetting and drying sequences, J. Hazard. Mater. 205–206 (2012) 126–130. [12] L. Zhang, Q. Zhang, Y. Zheng, Interaction of manganese oxides with multiple valences heavy metals in environmental remediation, Acta Sci. Circumst. 33 (2013) 1519–1526. [13] Y. Meng, W. Song, H. Huang, Z. Ren, S. Chen, S.L. Suib, Structure–property relationship of bifunctional MnO2 nanostructures: highly efficient,
[14]
[15]
[16]
[17]
[18]
[19] [20]
495
ultra-stable electrochemical water oxidation and oxygen reduction reaction catalysts identified in alkaline media, J. Am. Chem. Soc. 136 (2014) 11452–11464. C. Luo, R. Wei, D. Guo, S. Zhang, S. Yan, Adsorption behavior of MnO2 functionalized multi-walled carbon nanotubes for the removal of cadmium from aqueous solutions, Chem. Eng. J. 225 (2013) 406–415. S. Devaraj, N. Munichandraiah, Effect of crystallographic structure of MnO2 on its electrochemical capacitance properties, J. Phys. Chem. C 112 (2008) 4406–4417. J. Tang, P. Cao, Y. Fu, Synthesis of a mesoporous manganese dioxide-graphene composite by a simple template-free strategy for high-performance supercapacitors, Acta Phys.-Chim. Sin. 30 (2014) 1876–1882. J. Zhao, J. Nan, Z. Zhao, N. Li, J. Liu, F. Cui, Energy-efficient fabrication of a novel multivalence Mn3 O4 -MnO2 heterojunction for dye degradation under visible light irradiation, Appl. Catal. B: Environ. 202 (2017) 509–517. H. Perron, J. Vandenborre, C. Domain, R. Drot, J. Roques, E. Simoni, J.J. Ehrhardt, H. Catalette, Combined investigation of water sorption on TiO2 rutile (110) single crystal face: XPS vs periodic DFT, Surf. Sci. 601 (2007) 518–527. L. Yang, C. Gao, M. Zheng, Synthesis and electrochemical properties of Mn3 O4 polyhedral nanocrystals, Chin. J. Inorg. Chem. 29 (2013) 381–388. C. Ge, Y. Liu, M. Ren, Formation mechanism of nanosilica film on rutile TiO2 , Chin. J. Nonferr. Metals 18 (2008) 1110–1116.