Supplementary Information. A Bioinspired Interfacial Chelating-like Reinforcement Strategy toward Mechanically Enhanced Lamellar Materials

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1 Supplementary Information A Bioinspired Interfacial Chelating-like Reinforcement Strategy toward Mechanically Enhanced Lamellar Materials Ke Chen,, Shuhao Zhang, Anran Li, Xuke Tang, Lidong Li*, and Lin Guo*, Dr. K. Chen, S. Zhang, Dr. A. Li, X. Tang, Dr. L. Li, Prof. L. Guo Experimental materials and methods Materials. Graphite powder with particle size < 20 µm was used as received from Alfa Aesar, all other reagents (e.g., KMnO 4, H 2 SO 4, NaOH, C 2 H 5 OH, and acetone, analytical grade) were used without further purification. Ultrapure doubly deionized water (Resistivity >18.2 MΩ cm) in this work was obtained from a synergy UV water purification system (Millipore Corporation). Inositol hexaphosphoric acid (Phytic acid, C 6 H 18 O 24 P 6 ) or IP6, inose, sodium alginate (SA, (C 6 H 7 O 6 Na)), Polyvinyl Alcohol with molecular weight of ~145,000 (PVA, [-CH 2 CHOH-] n ) and ethylene diamine tetraacetic acid sodium (EDTA-2Na) were purchased from Aladdin industrial corporation (Shanghai, China). Cellulose nitrate-cellulose acetate (CN-CA) filter membranes (0.22 µm pore size, 47 mm diameter) from Hai Cheng Shi Jie Filter Co. Ltd (Beijing, China) were used in filtration to support fabricated paper. Sonication was performed using a KQ-300VDE

2 dual frequency ultrasonic cleaner from Kunshan Ultrasonic Instruments Co., Ltd (Jiangsu, China). A Sigma 2-16 centrifuge was employed for the centrifugation. Methods. Preparation of graphene oxide (GO): GO was prepared by following the modified Hummers method. 1-3 In a typical process, 3.0 g of natural graphite flakes (Alfa Aesar) was subjected to pre-oxidation treatment by stirring vigorously for 6 hours at 80 C in a mixture of K 2 S 2 O 8 (2.5 g), P 2 O 5 (2.5 g), and H 2 SO 4 (15 ml). The pre-oxidized graphite powder (about 3.5 g) was dried overnight before further oxidative treatment by stirring it in a mixture of 120 ml of H 2 SO 4 and 15 g of KMnO 4 in an ice bath. Notably, KMnO 4 was slowly added with vigorous stirring to avoid the temperature rising above 20 C. The solution was then transferred to 35 ± 3 C water bath and stirred for about 1 hour before adding 250 ml of water. Followed by adding 700 ml of warm water and 20 ml of H 2 O 2 (30 wt.%) to reduce KMnO 4 and MnO 2 to MnSO 4. The color of the blend solution turned to dark greenish yellow during the reduction. Then the warm solution was filtered. The GO slurry collected form membrane was then washed with 750 ml of 2 M HCl, and purified GO can be collected at the tube bottom after centrifugation, followed by centrifugation and careful washing with water to clean out remnant salt. The extracted GO was then re-dispersed in water (1 mg ml -1 ) for vacuum filtration. Fabrication of Bioinspired Lamellar Composite Papers as Nacre-Inspired Composites (PA-SA/GO, PA-PVA/GO): These bioinspired lamellar composite papers were successfully prepared by filtering the blends of the diluted composite dispersion with 20.0 vol.% of GO (SA/GO or PVA/GO) and aqueous PA solution,

3 through an CN-CA filter membrane, according to our previous VAF method. For the optimization of mechanical properties, the bioinspired composites with different chelating agent concentrations could be obtained by tuning the mass percentage of diluted composite dispersions to the aqueous chelating agent solution from 0.5 to 10.0wt.%. For comparison, the composite paper without PA (SA/GO or PVA/GO) was also prepared by the same method. After the filtration, specimens were air-dried until the paper could be peeled off for analysis. A water-circulation multi-function vacuum pump with vacuum filter holder was utilized for the vacuum filtration. Supporting Information Figures and Tables Figure S1. Molecular models constructed in the VASP calculations. (a) PA/GO. (b) Inose/GO. (c) PA-Inose/GO composites.

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5 Figure S2. Characterization of aqueous GO suspension, aqueous PA, inose, and the PA-inose blend. (a) The UV-vis spectra of pure GO, PA, inose, and the PA-inose blend, and their corresponding photographs (inset). (b) The comparison of UV-vis spectra for these aqueous suspensions including GO, PA/GO, Inose/GO, and PA-Inose/GO, and their corresponding photographs (inset). (c-e) Fourier transformation infrared (FTIR) spectra of aqueous GO suspension, PA, and inose solutions, respectively. (f) Comparison in FTIR spectra of pure GO, PA/GO, Inose/GO, and PA-Inose/GO. (g) Magnified FTIR spectrum of individual Inose/GO, corresponding to that of Inose/GO in figure f. UV-vis spectrum (Figure S2a) shows that, in an aqueous solution, the characteristic absorption peaks for GO nanosheets, PA molecules, and inose/pa complexes are located at about 230, 260, and 260 nm, respectively, nearly consistent with previous reported values, 1,2 but there is no absorption peak for inose molecules in the wavelength region from 200 to 800 nm, which can be attributed to the non-conjugated electron system. The absorption peak at 260 nm for PA molecules may be mainly attributed to the electronic transition of the π-π* electrons in the P=O bonding. No peak shift between PA and PA/inose suggests no obvious chemical bonding interactions between PA and inose molecules. However, after incorporating some small amounts of the chelating agents into an aqueous GO suspension, we found that, the characteristic absorption peak positions shifted from 230 nm in GO to 215, 225, and ~ nm in PA/GO, Inose/GO, and PA-Inose/GO, respectively, which may

6 be mainly due to the reduction in the GO-based conjugated system in electrons, giving rise to the blue shift of characteristic absorption band. In other words, non-covalently cross-linking interactions (e.g., H-bonds) between small organic molecules and GO nanosheets may lead to the change in the conjugated electron structure of GO nanosheets. Owing to the steric hindrance effect of PA molecules, we consider, the highly dense H-bonding interactions have mainly an influence on the conjugated electron structure of GO nanosheets; however, for inose molecules, relatively low-density H-bonding network plays an important role in adjusting the conjugated electron structure. Obviously, the blue-shifted trend of the absorption peak for PA/GO was greater than that of Inose/GO, suggesting that the difference in the value of shifted peak position also reflect the different bonding capabilities between different chelating agent and GO nanosheets. 3 Therefore, we presume that PA molecules can bond noncovalently with GO nanosheets by dense hydrogen bonds to obtain the strongest cross-linking capability. In Fourier transformed infrared (FTIR) spectra for structural units (GO, PA/GO, Inose/GO, and PA-Inose/GO), Figure S2c shows the characteristic bands of pure GO centered at wave-numbers of , 2865, 1735, 1621/1608, 1420, 1222, 1050, and 975 cm -1, corresponding to -O-H (hydroxyl), C-H (carbon hydrogen), C=O (carboxyl/carbonyl), C=C (aromatic for GO), C-O (carboyl), C-O (epoxy/ether), C-O (alkoxy/alkoxide), and O-C=O (carboxyl), 4,5 respectively; Figrue S2d exhibits that the main characterisitc bands of PA at 1643, 1130/1010, and 860/802 cm -1, can be ascribed to HPO 2-4, P=O, and P-O-C stretching vibration, respectively; 6,7 Figure S2e

7 presents the chief characteristic bands of inose centered at wavenumber of 2939/2910/2881, 1458/1377/1334, 1257/1053/1003, and 721 cm -1, are associated with C-H stretching vibration, C-C stretching vibration, C-O formation vibration, and C-H stretching vibration, respectively. 8 In addition, the broad characteristic bands at about 1689 cm -1 in PA/GO are obviously different from the two characteristic bands at 1730 and 1630 cm -1 in GO or a sharp band at 1643 cm -1 in PA, and several bands at 1130, 1010, 860, and 802 cm -1 are demonstrated in PA/GO, as shown in Supporting Information Figure S2f, also indicating the existence of PA molecules in the GO system and strong noncovalent cross-linking interactions (e.g., hydrogen bonds) between HPO 2-4 (hydroxyl groups) and active sites (e.g., oxygen-contained groups) of GO. The characteristic bands of PA-Inose/GO are similar to those of PA/GO. However, these characteristic bands at 2918/714 cm -1 (C-H for inose), 1720 cm -1 (C=O for GO), 1419/1354/881 cm -1 (C-C for inose), and 1245/1045/994 cm -1 (C-O for inose) shift to a lower wavenumber than those of pure GO or inose, separately, which is distinguished from the changing trend of some characterisic bands in PA/GO. Based on the above analysis, we can consider that there are strong noncovalent cross-linking interactions bewteen the hydroxyl groups on its cyclohexanehexol ring and the oxygen-contained groups of GO nanosheets by highly dense H-bonding network, similar to the bonding/reinforcing behavior of many GO-based composites and some natural materials. 9-13

8 Figure S3. Atomic force microscope (AFM) images of morphology of the assembled nanocomposite membrane on silica sheet, topography (Top) and phase (Bottom) images of the same area. (a) PA/GO (Topography: z-range: 120 nm; Phase: z-range: 26 ). (b) Inose/GO (Topography: z-range: 50 nm; Phase: z-range: 21 ). (c) PA-Inose/GO (Topography: z-range: 125 nm; Phase: z-range: 28 ). Scale bar, 1 µm. Atomic force microscope (AFM) images demonstrated, the topography of these hybrid microstructural membranes of GO nanosheets adsorbed/covered by organic molecules of PA, Inose, PA-Inose was uniform with a root-mean square (RMS) roughness of 5.2 ± 1.4, 4.1 ± 1.0, and 4.4 ± 1.2 nm within 8 µm 8 µm, respectively, as shown in Supporting Information Figure S3a-c (top), and AFM phase images with clear contrast between GO nanosheets and these organic molecules, also exhibited that a high surface absorbance/coverage of GO could be achieved for these samples

9 prepared from aqueous hybrid suspensions (Supporting Information Figure S3a-c, bottom).

10 Figure S4. The optimization for mechanical properties of the obtained layered materials by tensile tests in natural environments, including ultimate stress (σ max ), average Young s modulus (E ave ), maximum Young s modulus (E max ), and toughness (W) dependent on additive amounts of organic molecules as chelating-like reagents. (a) PA/GO. (b) Inose/GO. (c) PA-Inose/GO. Note that red box represents the optimum additive amount of chelating agent, corresponding to the best mechanical property.

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13 Figure S5. Characterization of these obtained materials. (a-d) Comparison of fracture cross-sectional SEM images of pure GO and these bioinspired lamellar composites. Details of the fracture surfaces showing densely stacked platelets by the organics-go cross-linking, the platelets stretching and pulling out. (e) Fracture cross-sectional SEM images for natural nacre from red abalone, describing the aragonite platelets stretching and pulling out. Note that red arrow indicates the filmy platelets stretching. Yellow arrow displays the small cavity from the platelets pulling out. (f) X-ray diffraction (XRD) patterns. (g) Fourier transformation infrared (FTIR) spectra. (h) Raman spectra. (i) P 2p X-ray photoelectron spectroscopy (XPS) of PA/GO. (j) Deconvoluted C1s XPS spectra. The C1s peak of the species can be fitted into five line shapes with binding energies at , , , , and ev, corresponding to the C-C/C=C, C-OH, C-O-C,

14 C=O, and O-C=O, respectively. (k) Deconvoluted O1s XPS spectra. The O1s peak of the species can be fitted into two line shapes with binding energies at and ev, respectively. With respect to the FTIR spectra (Supporting Information Figure S5g), these characteristic peaks in PA/GO composite paper shifted to the relatively high wavenumber at approximately 1404, 1253, and 1072 cm -1, corresponding to C-O (carboxyl), C-O (epoxyl/ether), and C-O (alkoxyl/alkoxide), respectively, in comparison with those of the GO paper. In addition, the peak centered at 975 cm -1 exhibits remarkably decreased O-C=O stretch intensity. 4,5 Simultaneously, the characteristic peak at ~830 cm -1, which is corresponding to the P-O-C vibration, is distinguished from that of pure PA at 802 or 860 cm -1, as show in Supporting Information Figure S2d, also reported from the literatures. 6,7 Similarly, these characteristic peaks in PA-Inose/GO are analogous with those in PA/GO; for Inose/GO, a typical small peak appears at about 1570 cm -1 and no characteristic peak of the P-O-C vibration at 830 cm -1 can be observed, which are different from those of PA/GO or PA-Inose/GO. Raman spectra (Supporting Information Figure S5h) show that the values of the I D /I G ratios ( ) for these composites were slightly lower than that of pure GO paper (1.11), indicating that organic chelating agent can enhance the noncovalent cross-linking interaction behavior between GO nanosheets. 14

15 A small XPS peak of P 2p can be observed at binding energy 135 ev which is attributed to the ultra-low content of P in the composite system, from PA/GO, confirming that small amounts of PA molecules was incorporated into the GO system (Supporting Information Figure S5i). 15 In the C1s XPS spectra (Figure S5j), the C1s component of C-O-C group shifts slightly from ev in GO to ev in PA/GO, 287.1eV in Inose/GO, and ev in PA-Inose/GO. And the values of the I C-C /I C-O-C ratio in these composites are clearly higher than that in GO paper, accompanying with the increase in the relative areas of the peak, corresponding to C-OH groups. The C-OH groups are generated and the intensities of the peak are reduced by the ring-opening of C-O-C in GO nanosheets while adding these organic chelating molecules into GO system. These phenomena can be ascribed to the strong bonding interactions between these small organic molecules and C-O-C groups of GO nanosheets. 16,17 Besides, in comparison to the O1s XPS spectra of GO (533.7 ev), the O1s component shifts to the low bonding energy of approximately ev for PA/GO, ev for Inose/GO, and ev for PA-Inose/GO, respectively, indicating the change in the electron binding energy of oxygen element in these composites, which can be mainly associated to the strong noncovalent cross-linking interactions (e.g., hydrogen bonds) again (as shown in Supporting Information Figure S5k).

16 Figure S6. Thermogravimetric-differential scanning calorimetry (TG-DSC) analysis of these lamellar materials. (a) GO. (b) PA/GO. (c) Inose/GO. (d) PA-Inose/GO. With respect to TG-DSC analysis in N 2 as shown in Supporting Information Figure S6, for these obtained materials, the small endothermic peak around 65 C can be due to the loss of free water and partial confined water. The sharp endothermic peak around C for GO can be attributed to the decomposition of oxygen functionality such as hydroxyl, epoxide, and carboxyl groups of these materials. 18,19 However, the decomposition peaks for PA/GO, Inose/GO, and PA-Inose/GO are observed between ~225.1 and C which are shifted to higher temperatures by ~3-5 C compared to pure GO paper. This could be explained as follows:the organic chelating molecules on the interlamination of GO nanosheets may slightly restrict the

17 heat transfer to GO nanosheets in these composites, causing it to decompose at higher temperatures.

18 Figure S7. Contact force (left), topography (corresponding to the profile line in the height image), and phase (right) in-situ SPM images in nanoindentation tests on these obtained samples. (a) GO. (b) PA/GO. (c) Inose/GO. (d) PA-inose/GO. Table S1. Statistic roughness of these obtained materials, based on the in-situ SPM images. Samples R q a, (nm) R q b, (nm) R a a, (nm) R a b, (nm) GO (upper c ) ± ± ± ± 23.4 GO (bottom d ) 181.5± ± ± ± 31.2 PA/GO (upper) 219.7± ± ± ± 14.2 PA/GO (bottom) 175.3± ± ± ± 30.9 Inose/GO (upper) ± ± ± ± 45.8 Inose/GO (bottom) 264.3± ± ± ± 31.6 PA-Inose/GO (upper) ± ± ± ± 6.4 PA-Inose/GO (bottom) ± ± ± ± 22.7 a The roughness is obtained at 20 µm 20 µm area. b The roughness is obtained at 10 µm 10 µm area. c upper represents the upper surface of the samples. d bottom stands for the bottom surface of the samples.

19 Figure S8. Micromechanical properties of these obtained materials. (a-c) Typical contour maps of Young s modulus (E y ) (top figures) and Hardness (H) (bottom figures) dispersion within 50 µm 50 µm areas, based on static nanoindentation tests. (d-g) NanoDMA (Nanoscale Dynamic Mechanical Analysis) nanoindentation tests of storage modulus (E, top) and tanδ coefficient (bottom) as a function of contact depth of indentation probe into the paper at w = 10, 60, 100, 200 Hz and at different dynamic loadings (F d = 0.5, 1.0, 1.5, 2.0 µn).

20 Figure S9. Mechanical properties of these obtained materials, including GO (a), PA/GO (b), Inose/GO (c), and PA-Inose/GO (d), in the special environment holding room temperature at 25 C and the higher relative humidity ( 85% RH): I, representative stress-strain curves from tensile tests under the relatively high humidity condition of minutes pre-holding time; II-V, the pre-holding time dependence of ultimate stress (σ m, II), average Young s modulus (E ave, III), maximum Young s modulus (E max, IV), and toughness (W, V), respectively. We investigate the effect of external environment on mechanical properties of these obtained materials by controlling the relative humidity under the test condition, as shown in Figure S9. In comparison, it can be clearly seen that the mechanical properties of these obtained materials obviously reduced under the relatively high humidity (Figure S9a-d, I). Figure S9a-d clearly shows that ultimate stress (σ max, II), average/maximum Young s modulus (E ave /E max, III and IV) and toughness (W, V) of the obtained material gradually decrease, respectively, with the increase of the

21 pre-holding time (from 0 to 5.0 min). For example, as for GO, the values in the ultimate stress, average/maximum Young s modulus, and toughness reduce from ~94.2 MPa/ ~2.3/3.4 GPa/~1.5 MJ m -3 (0.5 min) to 31.1 MPa/~1.2/1.6 GPa/~0.6 MJ m -3 (5.0 min), respectively; with respect to these composite paper (e.g., PA/GO), the values in the ultimate stress, average/maximum Young s modulus, and toughness gradually decrease from ~172.8 MPa/~3.8/5.5 GPa/~3.1 MJ m -3 (0.5 min) to ~98.1 MPa/~1.7/2.5 GPa/~2.3 MJ m -3 (5.0 min). Obviously, after the 5 min pre-holding time, the mechanical property values of these composites are clearly higher than those of pure GO paper, indicating the higher dense H-bonding effect. These results are highly consistent with our previous report. 17 Figure S10. Comparison of no crack and completed fracture surface for these layered materials before and after stretching, explored by the in-situ tensile testing under ESEM observation, corresponding to crack growths in Figure 4 in the main text. (a) GO. (b) PA/GO. (c) Inose/GO. (d) PA-Inose/GO. Scale bar, 2.0 µm. Details of the fracture surfaces further showing the platelets stretching and pulling out. Red arrow indicates the filmy platelets stretching. Yellow arrow displays the small cavity generated from the platelets pulling out.

22 Figure S11. Typical digital photo, microstructure, and mechanical properties for the lamellar composite material. (a) Digital image of the brown PA-SA/GO composite. (b-d) Multi-scale SEM images for the PA-SA/GO composite. (e-i) Comparison of mechanical properties of the SA/GO and PA-SA/GO composite papers. Representative stress-strain curves from tensile test (e), the content of PA dependence of ultimate stress (f), the content of PA dependence of average Young s modulus (g), the content of PA dependence of maximum Young s modulus (h), and the content of PA dependence of toughness. Note that red box represents the optimum additive amount of chelating agent, corresponding to the best mechanical property.

23 Figure S12. Typical digital photo, microstructure, and mechanical properties for the lamellar composite material. (a) Digital image of the PA-PVA/GO composite. (b-d) Multi-scale SEM images for the brown PA-PVA/GO composite. (e-i) Comparison of mechanical properties of the PVA/GO and PA-PVA/GO composite papers. Representative stress-strain curves from tensile test (e), the content of PA dependence of ultimate stress (f), the content of PA dependence of average Young s modulus (g), the content of PA dependence of maximum Young s modulus (h), and the content of PA dependence of toughness. Note that red box represents the optimum additive amount of chelating agent, corresponding to the best mechanical property. Digital photos exhibit their poor light transmittance, as observed in Figures S11a and S12a. Multi-scale cross-sectional morphology images show the interlaced close-packed lamellar microstructure in these composites (named by PA-SA/GO and

24 PA-PVA/GO) (Figures S11b-d and S12b-d). The mechanical properties of two types of lamellar composites clearly show the high strength, toughness, and Young s modulus, in comparison with those of the lamellar composites without PA (SA/GO and PVA/GO), as shown in Figures S11e-i and S12e-i. As for PA-SA/GO (Figure S11e-i), the BICR strategy strongly reinforces the mechanical properties of the composite, improving the tensile maximum stress by ~70.5% to ~374.2 MPa and the toughness by ~84.7% to 18.1 MJ m -3 ; the enhancement of average and maximum Young s modulus are up to ~73.9% and ~41.4%, respectively, when compared with SA/GO (σ max, ~219.4 MPa; W, ~9.8 MJ m -3 ; E ave, ~2.3 GPa; E max, ~2.9 GPa). Similarly, the tensile stress and average/maximum Young s modulus of PA-PVA/GO are as high as ~260.9 MPa, ~2.7/3.4 GPa, respectively, approximately 118.5% and ~800.0/70.0% higher than those of PVA/GO (σ max, ~119.4 MPa; E ave, ~0.3 GPa; E max, ~2.0 GPa)), but the decrease in toughness is ~173.0%. The reduced toughness can be attributed to the fact that the presence of a large number of H-bonds/π-π interactions often cause crystallization or clustering of polymer materials, 20 thereby making them stiff or brittle. Notably, the strong bonding/cross-linking effect from both H-bonding network/π-π interactions between the richer phosphate (hydroxyl) groups on the cyclohexanehexol ring of PA molecules and active sites in these composite matrixes greatly enable the more effective load transfer (larger energy dissipation) at the hybrid interfaces or intermolecular sites.

25 Figure S13. Comparison of mechanical properties of pure GO paper and the EDTA/GO composites. (a) Interfacial chelating-like models between GO nanosheets and EDTA-2Na. Note that: White, H; Gray, C; Red, O; pink, P. (b) Representative stress-strain curves from the tensile test for GO and EDTA/GO. (c) The content of EDTA-2Na dependence of ultimate stress. (d) The content of EDTA-2Na dependence of average Young s modulus. (e) The content EDTA-2Na dependence of maximum Young s modulus. (f) The content of DETA-2Na dependence of toughness.

26 Figure S13 clearly shows that the mechanical properties of the EDTA/GO composite possess high strength, toughness, and Young s modulus, in comparison with those of pure GO. When compared with pure GO (σ max, ~118.8 MPa; E ave, ~2.6 GPa; E max, ~4.9 GPa; W, ~2.7 MJ m -3 ;), EDTA/GO possesses a higher ultimate stress of ~219.9 MPa (in some cases up to MPa, Figure S13b), a higher average/maximum Young s modulus of ~6.4/9.0 GPa, and a higher toughness of ~3.5 MJ m -3, which are ~85.1%, ~146.1%/83.7%, and ~29.6% higher than those of pure GO, respectively. Table S2. Summary of mechanical properties for typical bioinspired lamellar composite papers by tensile tests. Adding Materials chelating agent content σ max (MPa) E ave (GPa) E max (GPa) W (MJ m -3 ) (wt.%) GO ± ± ± ± 0.3 PA/GO ± ± ± ± 0.8 Inose/GO ± ± ± ± 0.7 PA-Inose/GO ± ± ± ± 0.8 SA/GO ± ± ± ± 2.8 PA-SA/GO ± ± ± ± 4.4 PVA/GO ± ± ± ± 5.8 PA-PVA/GO ± ± ± ± 2.2 EDTA/GO ± ± ± ± 0.5

27 Table S3. Summary of the mechanical improvement of typical chelating agent-reinforced materials in comparison with those materials without any chelating agents. Adding chelating agent Materials content (wt.%) % (σ max ) % (E ave ) % (E max ) % (W) GO PA/GO 0.63 ~124.1 ~150.0 ~134.7 ~118.5 Inose/GO 0.42 ~98.4 ~119.2 ~91.8 ~25.9 PA-Inose/GO 0.42 ~94.6 ~138.5 ~116.3 ~40.7 EDTA/GO 0.63 ~85.1 ~146.2 ~ SA/GO PA-SA/GO 2.0 ~ ~ PVA/GO PA-PVA/GO 2.0 ~118.5 ~ ~ References (1) Dimiev, A.; Kosynkin, D. V.; Alemany, L. B.; Chaguine, P.; Tour, J. M. Pristine Graphite Oxide. J. Am. Chem. Soc. 2012, 134, (2) Veiga, N.; Macho, I.; Gómez, K.; González, G.; Kremer, C.; Torres, J. Potentiometric and Spectroscopic Study of the Interaction of 3d Transition Metal Ions with Inositol Hexakisphosphate. J. Mol. Struct. 2015, 1098,

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