TiO2 Facets Shaped by Concentration-Dependent Surface Diffusion of

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Surfaces, Interfaces, and Catalysis; Physical Properties of Nanomaterials and Materials

TiO2 Facets Shaped by ConcentrationDependent Surface Diffusion of Dopamine Li Yan, Haoze Chen, and Chuanyong Jing J. Phys. Chem. Lett., Just Accepted Manuscript • Publication Date (Web): 12 Feb 2019 Downloaded from http://pubs.acs.org on February 12, 2019

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The Journal of Physical Chemistry Letters

TiO2 Facets Shaped by Concentration-Dependent Surface Diffusion of Dopamine

Li Yan1,2, Haoze Chen1,2, Chuanyong Jing1,2,*

1State

Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for

Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China

2University

of Chinese Academy of Sciences, Beijing 100049, China

Corresponding Author: [email protected] (C. Jing)

ACS Paragon Plus Environment

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ABSTRACT

Facet engineering highlights the fundamental understanding of kinetic growth of facets with capping agents. Here, we provided a roadmap for modulating TiO2 facets using dopamine as a capping agent inspired by density functional theory calculations and molecular dynamics simulations. Our calculations revealed that the surface diffusion of dopamine and their facetspecific affinity direct the kinetic growth of TiO2 {100} and {101} facets into a non-equilibrium crystal shape. Our TiO2 synthesis agreed well with the theoretical predictions, suggesting that the concentration-dependent diffusion is central in accurately tuning a desirable ratio of mixed facets. Our findings shed a new light on the diffusion-limited kinetically-controlled facet growth mechanism, and this fine tuning of mixed facets on a single crystal provides a general approach to design and fabricate facets on metal oxides.

TOC GRAPHICS

KEYWORDS: Crystal facets, capping agent, diffusion coefficient, kinetic growth, molecular dynamics


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The dominant role of crystal facet cannot be overestimated considering the myriad applications of metal oxide crystals in catalysis, solar cells, lithium ion batteries, and sensors.1-5 The facetdependent reactivity has evoked extensive studies,6-9 but how to fabricate the desirable facet or a combination of facets on a single crystal remains a great challenge.9-10 The difficulty may be solved with a comprehensive understanding of facet growth mechanism. Crystal facets emerge from the thermodynamically-favored growth of facet with the lowest surface energy.11-12 This Wulff construction rule is often practiced using a capping agent which binds preferentially to a facet to achieve a maximum surface energy drop.13-18 Extensive studies suggest that synthesizing 100% desired facets is not as simple as prediction from thermodynamics.13,18-20 We hypothesize that the oriented diffusion of capping agents kinetically controls the evolution and growth of facets. The facet growth of rare metals has proven to be kinetically, rather than thermodynamically, controlled,21-24 and depended on concentrations of capping agents.25-28 As a proof of concept, the objective of this study was to explore how surface diffusion of capping agent affects the growth of metal oxide facets. Anatase TiO2 crystal was used as a typical metal oxide, and dopamine as a capping agent due to its strong adhesion on metal oxides.29 The discovery in this study presents a new strategy to tailor the growth dynamics for controllable exposed facets on a single crystal. The basic function of a capping agent is realized by preferential binding on a certain facet using its functional groups for a maximum surface energy drop. To study the interaction of dopamine with TiO2 facets, the change in surface energies derived from dopamine adsorption via phenolic hydroxyl (–OH) and amine (–NH2) groups was compared based on first-principles


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density functional theory (DFT) calculations (Table S1 and S2 in Supporting Information). The surface free energies of pristine {001}, {100}, and {101} facets are 0.96, 0.68, and 0.49 J/m2, respectively, agreeing well with previous studies.1,13,30 Dopamine adsorption using its two –OH groups substantially reduces the energy of the {001} facet to 0.65 J/m2 by forming two Tisurf-O and two Osurf-H bonds in bidentate and dissociative adsorption mode (Figure S1a).31 On the other hand, the –OH group only slightly reduces the surface energies of {100} (0.65 J/m2) and {101} (0.47 J/m2). When the –NH2 group is involved in dopamine adsorption, the energy of {001} facet is slightly reduced to 0.81 J/m2 with only Tisurf-N bond (Figure S1d), while the energies of {100} (0.63 J/m2) and {101} (0.45 J/m2) remain virtually unchanged (Table S2). The dynamic diffusion of a capping agent should be the initial step even before adsorption occurs.32-33 To study the diffusion of dopamine on TiO2 facets, molecular dynamics (MD) simulations were performed with dopamine coverage of 1.8 to 5.0 number/nm2 (Figure 1 and Figure S2). The calculated diffusion coefficient (D, Å2/ps) decreased from 1.09 × 10−2 on {001} to 3.82 × 10−3 on {100} and 2.32 × 10−3 on {101} facets with dopamine coverage of 1.8 molecules/nm2 (Figure 1g). With dopamine coverage up to 5.0 molecules/nm2, the D values followed the order of {001} (3.58 × 10−2) > {100} (3.57 × 10−2) > {101} (2.90 × 10−2) (Figure 1h). The results suggest that the dopamine diffusion is both facet- and concentration-dependent. In addition to the above calculation using a single periodic slab model, we constructed a TiO2 tetradecahedron model with mixed facets (Figure S3) to explore the concentrationdependent surface diffusion and competitive adsorption of dopamine on diverse facets. The MD results in Figure 2 show that a fast dopamine diffusion occurs at t < 0.5 ns, by which the coverage density changed averagely by 53% on three facets. At t = 1 ns, dopamine diffusion slows down to a reorganization stage.22 Dopamine diffusion reaches equilibrium after t > 2 ns.


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The equilibrium dopamine density increases in the order {001} < {100} < {101} when the initial dopamine molecules increased from 14, 28 up to 50. With 140 dopamine molecules, however, the density sequence is changed to {101} (1.7 number/nm2) < {001} (2.0 number/nm2) < {100} (2.2 number/nm2) (Figure 2h). The results imply that the competitive adsorption of dopamine on mixed facets is diffusion-limited, and the diffusion on each facet is concentration-dependent.

Figure 1. MD equilibrated structures for dopamine adsorption on each TiO2 {001}, {100}, and {101} facet, considering a dopamine concentration of (a-c) 20 molecules and (d-f) 56 molecules. MSD of dopamine on TiO2 facets with (g) 20 and (h) 56 molecules.


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Figure 2. Typical dopamine diffusion snapshots on the TiO2 mixed facets taken at different times of 0 ns, 0.5 ns, and 1.0 ns, considering a dopamine concentration of (a) 14 molecules, (b) 28 molecules, (c) 50 molecules, (d) 140 molecules. Arrows indicate the diffusion direction, which is 140 molecules in a case; the dopamine molecules on {101} facet are moving to {100} facet. (e–h) The coverage density curves of dopamine on each facet as a function of simulation time.

Figure 3 shows a closer inspection of time and space evolution of dopamine diffusion on TiO2 mixed facets, as well as its concentration profile at initial and equilibrium stages. Dopamine diffuses instantaneously from {001} to nearby {101}, and then to the inner layer of {100} facet after about 0.5 ns for 14 and 28 dopamine molecules (Figure 3a-b). Meanwhile, dopamine


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molecules on {100} slightly diffuse to nearby {101} facet. On the other hand, no dopamine molecule diffuses on {101} facet, where the molecules remain close to the surface even after 5 ns as evidenced by the concentration profile at equilibrium. Notably, when the number of dopamine molecules increases to 50, a slight diffusion from {101} to nearby {100} facet occurs after 4 ns (Figure 3c).

Figure 3. Distribution and concentration profile of dopamine along the normal Z direction of the cell as a function of simulation time. The concentration profiles for initial (red line) and equilibrium stages (cyan line) are shown to visualize the concentration-dependent diffusion direction, considering a dopamine concentration of (a) 14 molecules, (b) 28 molecules, (c) 50 molecules, (d) 140 molecules.


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With {101} (Figure 2h), suggesting the favorable formation of {100} facet. In fact, the coverage density of 2.0 number/nm2 should be the critical saturation concentration because further increase in dopamine concentration (>280 molecules, 4.0 number/nm2) exhibits no significant change in its distribution


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(Table S3). Therefore, we propose that adjusting dopamine concentrations may fine-tune a TiO2 crystal exposing mixed facets with non-equilibrium Wulff shape. Following the above prediction, we fabricated TiO2 mixed facets by increasing concentrations of dopamine and the resulted crystals are shown in Figure 4. The crystals expose 94% of {101} facet without dopamine. With the addition of 0.1 mL (DA0.1) and 0.25 mL (DA0.25) of 0.02-M dopamine, the {101} exposure decreased to 49% and 25%, respectively, correspondingly with 46% and 67% increase in {100} (Figure 4b, see Figure S5 and Table S4 for details). Further increasing dopamine to 0.5 mL (DA0.5) induced no noticeable change in facet ratio (Figure 4b), indicating that the equilibrium was reached with 0.08 to 0.17 mM dopamine (Figure S6). Notably, the addition of dopamine from 1 mL (DA1) to 2 mL (DA2) increased the exposure of the {101} facet from 52% to 97%, and decreased {100} exposure from 44% to 0%. This observation was attributed to the limited adsorption of dopamine because of its polymerization at high concentrations (>0.17 mM, Figure S6).34-35 The synthesized TiO2 crystals were 24–53 nm with the lattice fringe spacing of 0.35 nm and 0.47 nm corresponding to the (101) and (002) planes,16 respectively (Figure 4a). The anatase crystal form was confirmed by their X-ray diffraction (XRD) patterns and Raman characterization (Figure S7). The successful fabrication of tailored facets of {100} (0–67%) and {101} (25–97%) confirmed the theoretical prediction from our MD simulations. The TiO2 growth in the presence of dopamine is diffusion-limited, resulting in a non-equilibrium Wulff crystal with kinetically-controlled facets.


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Figure 4. (a) TEM images of synthesized faceted-TiO2 with different dopamine concentrations. (b) The analysis of facet ratio as a function of dopamine concentration. The calculation of facet ratio was detailed in Figure S5 and Table S4.

This study explains why dopamine can be used to engineer non-equilibrium TiO2 crystal with mixed facets. The concept proved by this study could be applicable to kinetically control a variety of non-equilibrium Wulff shapes. In addition, the capping agent can be extended to other molecules such as catechol (Figure S8), which contains the same aryl–OH functional group as dopamine. The roadmap proposed by this study thereby opens a new avenue for facet engineering with capping agents.


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ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at… Details of theoretical calculations, dopamine polymerization, material characterization, and movies of molecular dynamics simulation are available.

AUTHOR INFORMATION Corresponding Author [email protected] Notes The authors declare no competing financial interests.

ACKNOWLEDGMENT We acknowledge the financial support of the National Basic Research Program of China (2015CB932003), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB14020201), and the National Natural Science Foundation of China (41425016, 21337004, and 21321004).

REFERENCES


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(1) Liu, G.; Yang, H. G.; Pan, J.; Yang, Y. Q.; Lu, G. Q.; Cheng, H.-M., Titanium Dioxide Crystals with Tailored Facets. Chem. Rev. 2014, 114, 9559-9612. (2) Gao, X.; Zhang, T., An Overview: Facet-Dependent Metal Oxide Semiconductor Gas Sensors. Sensors Actuators B: Chem. 2018, 277, 604-633. (3) Wu, H.; Yang, T.; Du, Y.; Shen, L.; Ho, G. W., Identification of Facet-Governing Reactivity in Hematite for Oxygen Evolution. Adv. Mater. 2018, 30, 1804341. (4) Rong, S.; Zhang, P.; Liu, F.; Yang, Y., Engineering Crystal Facet of alpha-MnO2 Nanowire for Highly Efficient Catalytic Oxidation of Carcinogenic Airborne Formaldehyde. ACS Catal. 2018, 8, 3435-3446. (5) Wang, Q. W.; Zhou, H. X.; Liu, X. L.; Li, T.; Jiang, C. J.; Song, W. H.; Chen, W., FacetDependent Generation of Superoxide Radical Anions by ZnO Nanomaterials under Simulated Solar Light. Environ. Sci. Nano 2018, 5, 2864-2875. (6) Selcuk, S.; Selloni, A., Facet-Dependent Trapping and Dynamics of Excess Electrons at Anatase TiO2 Surfaces and Aqueous Interfaces. Nat. Mater. 2016, 15, 1107-1113. (7) Yang, D. H.; Li, Y. D.; Liu, X. Y.; Cao, Y.; Gao, Y.; Shen, Y. R.; Liu, W. T., Facet-Specific Interaction between Methanol and TiO2 Probed by Sum-Frequency Vibrational Spectroscopy. Proc. Natl. Acad. Sci. USA 2018, 115, E3888-E3894. (8) Huang, X. P.; Hou, X. J.; Zhang, X.; Rosso, K. M.; Zhang, L. Z., Facet-Dependent Contaminant Removal Properties of Hematite Nanocrystals and Their Environmental Implications. Environ. Sci. Nano 2018, 5, 1790-1806. (9) Bai, S.; Wang, L. L.; Li, Z. Q.; Xiong, Y. J., Facet-Engineered Surface and Interface Design of Photocatalytic Materials. Adv. Sci. 2017, 4, 1600216. (10) Jiang, H. B.; Cuan, Q.; Wen, C. Z.; Xing, J.; Wu, D.; Gong, X.-Q.; Li, C.; Yang, H. G., Anatase TiO2 Crystals with Exposed High-Index Facets. Angew. Chem. Int. Ed. 2011, 50, 37643768. (11) Seo, S. E.; Girard, M.; de la Cruz, M. O.; Mirkin, C. A., Non-Equilibrium Anisotropic Colloidal Single Crystal Growth with DNA. Nat. Commun. 2018, 9, 4558. (12) Wulff, G., On the Question of Speed of Growth and Dissolution of Crystal Surfaces. Z. Kristallogr. 1901, 34, 449-530. (13) Yang, H. G.; Sun, C. H.; Qiao, S. Z.; Zou, J.; Liu, G.; Smith, S. C.; Cheng, H. M.; Lu, G. Q., Anatase TiO2 Single Crystals with a Large Percentage of Reactive Facets. Nature 2008, 453, 638-641. (14) Joo, J.; Chow, B. Y.; Prakash, M.; Boyden, E. S.; Jacobson, J. M., Face-Selective Electrostatic Control of Hydrothermal Zinc Oxide Nanowire Synthesis. Nat. Mater. 2011, 10, 596-601. (15) Kaur, R.; Mehta, S. K., Metallomicelle Templated Transition Metal Nanostructures: Synthesis, Characterization, DFT Study and Catalytic Activity. Phys. Chem. Chem. Phys. 2017, 19, 18372-18382. (16) Jung, M.-H.; Ko, K. C.; Lee, J. Y., Single Crystalline-Like TiO2 Nanotube Fabrication with Dominant (001) Facets Using Poly(vinylpyrrolidone) for High Efficiency Solar Cells. J. Phys. Chem. C 2014, 118, 17306-17317. (17) Wu, B.; Zheng, N., Surface and Interface Control of Noble Metal Nanocrystals for Catalytic and Electrocatalytic Applications. Nano Today 2013, 8, 168-197. (18) Yang, S.; Yang, B. X.; Wu, L.; Li, Y. H.; Liu, P.; Zhao, H.; Yu, Y. Y.; Gong, X. Q.; Yang, H. G., Titania Single Crystals with a Curved Surface. Nat. Commun. 2014, 5, 5355.


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(19) Roy, N.; Park, Y.; Sohn, Y.; Leung, K. T.; Pradhan, D., Green Synthesis of Anatase TiO2 Nanocrystals with Diverse Shapes and Their Exposed Facets-Dependent Photoredox Activity. ACS Appl. Mater. Inter. 2014, 6, 16498-16507. (20) Boppella, R.; Anjaneyulu, K.; Basak, P.; Manorama, S. V., Facile Synthesis of Face Oriented ZnO Crystals: Tunable Polar Facets and Shape Induced Enhanced Photocatalytic Performance. J. Phys. Chem. C 2013, 117, 4597-4605. (21) Meena, S. K.; Sulpizi, M., From Gold Nanoseeds to Nanorods: The Microscopic Origin of the Anisotropic Growth. Angew. Chem. Int. Ed. 2016, 55, 11960-11964. (22) Gao, H. M.; Liu, H.; Qian, H. J.; Jiao, G. S.; Lu, Z. Y., Multiscale Simulations of Ligand Adsorption and Exchange on Gold Nanoparticles. Phys. Chem. Chem. Phys. 2018, 20, 13811394. (23) Fichthorn, K. A.; Balankura, T.; Qi, X., Multi-Scale Theory and Simulation of ShapeSelective Nanocrystal Growth. Crystengcomm 2016, 18, 5410-5417. (24) Qi, X.; Fichthorn, K. A., Theory of the Thermodynamic Influence of Solution-Phase Additives in Shape-Controlled Nanocrystal Synthesis. Nanoscale 2017, 9, 15635-15642. (25) Zhou, S.; Mesina, D. S.; Organt, M. A.; Yang, T.-H.; Yang, X.; Huo, D.; Zhao, M.; Xia, Y., Site-Selective Growth of Ag Nanocubes for Sharpening Their Corners and Edges, Followed by Elongation into Nanobars through Symmetry Reduction. J. Mater. Chem. C 2018, 6, 1384-1392. (26) Kim, M. J.; Flowers, P. F.; Stewart, I. E.; Ye, S.; Baek, S.; Kim, J. J.; Wiley, B. J., Ethylenediamine Promotes Cu Nanowire Growth by Inhibiting Oxidation of Cu(111). J. Am. Chem. Soc. 2017, 139, 277-284. (27) Hajfathalian, M.; Gilroy, K. D.; Hughes, R. A.; Neretina, S., Citrate-Induced Nanocubes: A Re-Examination of the Role of Citrate as a Shape-Directing Capping Agent for Ag-Based Nanostructures. Small 2016, 12, 3444-3452. (28) Wang, Y.; Wan, D.; Xie, S.; Xia, X.; Huang, C. Z.; Xia, Y., Synthesis of Silver Octahedra with Controlled Sizes and Optical Properties via Seed-Mediated Growth. Acs Nano 2013, 7, 4586-4594. (29) Lee, H.; Dellatore, S. M.; Miller, W. M.; Messersmith, P. B., Mussel-Inspired Surface Chemistry for Multifunctional Coatings. Science 2007, 318, 426-430. (30) Lazzeri, M.; Vittadini, A.; Selloni, A., Structure and Energetics of Stoichiometric TiO2 Anatase Surfaces. Phys. Rev. B 2001, 63, 155409. (31) Urdaneta, I.; Keller, A.; Atabek, O.; Palma, J. L.; Finkelstein-Shapiro, D.; Tarakeshwar, P.; Mujica, V.; Calatayud, M., Dopamine Adsorption on TiO2 Anatase Surfaces. J. Phys. Chem. C 2014, 118, 20688-20693. (32) Raffaini, G.; Melone, L.; Punta, C., Understanding the Topography Effects on Competitive Adsorption on a Nanosized Anatase Crystal: A Molecular Dynamics Study. Chem. Commun. 2013, 49, 7581-7583. (33) Wang, Y.; He, J.; Liu, C.; Chong, W. H.; Chen, H., Thermodynamics versus Kinetics in Nanosynthesis. Angew. Chem. Int. Ed. 2015, 54, 2022-2051. (34) Muller, M.; Kessler, B., Deposition from Dopamine Solutions at Ge Substrates: An in Situ ATR-FTIR Study. Langmuir 2011, 27, 12499-12505. (35) Della Vecchia, N. F.; Avolio, R.; Alfe, M.; Errico, M. E.; Napolitano, A.; d'Ischia, M., Building-Block Diversity in Polydopamine Underpins a Multifunctional Eumelanin-Type Platform Tunable Through a Quinone Control Point. Adv. Funct. Mater. 2013, 23, 1331-1340.


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TiO2 Facets Shaped by Concentration-Dependent Surface Diffusion of

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