Dual Functional Biocomposites Based on Polydopamine Modified

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Dual functional biocomposites based on polydopamine modified cellulose nanocrystal for Fe3+-pollutant detecting and auto-blocking Yangyang Han, Xiaodong Wu, Xinxing Zhang, Zehang Zhou, and Canhui Lu ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b01567 • Publication Date (Web): 01 Sep 2016 Downloaded from http://pubs.acs.org on September 3, 2016

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ACS Sustainable Chemistry & Engineering

Dual functional biocomposites based on polydopamine modified cellulose nanocrystal for Fe3+-pollutant detecting and auto-blocking Yangyang Han, Xiaodong Wu, Xinxing Zhang,* Zehang Zhou and Canhui Lu* State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, No.24 South Section 1 of First Ring Road, Cheng Du 610065, China Abstract In this work, a facile and sustainable strategy for ferric ion (Fe3+) detection was developed for the first time based on a coordination bonding between Fe3+ and polydopamine (PDA) modified cellulose nanocrystals (CNC) (PDA@CNC). PDA, as a probe molecule for Fe3+ detection, was in situ synthesized onto CNC template via one-pot oxidative polymerization of biological dopamine, yielding nano-sized and well-dispersed PDA@CNC nanohybrid. When PDA@CNC met Fe3+, the coordination bonding between PDA and Fe3+ led to rapid agglomeration of PDA@CNC, resulting in macroscopical and flocculent PDA@CNC aggregates. Interestingly, this morphology transition of PDA@CNC enabled on-site detection of Fe3+ with a minimum limit of 3 ppm by the naked eye, which could be further optimized to 0.5 ppm using dynamic light scattering method. Furthermore, we demonstrated another interesting application of the smart PDA@CNC biocomposites in automatic blockage of wastewater containing Fe3+. This easily and eco-friendly preparation method for dual functional PDA@CNC biocomposites provides a new strategy for Fe3+-pollutant detecting and auto-blocking in a simple and sustainable way.

Corresponding author: Xinxing Zhang and Canhui Lu *E-mail address: [email protected] & [email protected]

ACS Paragon Plus Environment

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Key words: cellulose nanocrystal, polydopamine, Fe3+, detection, automatic blockage Introduction The fast development of industry gives rise to the increasing environmental pollution. Excess release of metal ion from industrial wastewater has great environmental, public health, and economic impacts. Ferric ion (Fe3+), as the most abundant essential transition metal ion in human body, plays a crucial role in biological and environmental systems.1 An overload of Fe3+ can lead to serious disease, such as Huntington’s, Alzheimer’s and Parkinson’s disease.2-3 Thus, determination of Fe3+ is an important issue for both environmental monitoring and clinical research. Several mature methods for detecting Fe3+ have been established, such as inductively coupled plasma atomic emission or mass spectroscopy (ICP-AES, ICP-MS),4-5 atomic absorption spectroscopy (AAS)6 and optical methods7. However, large equipments and complex synthesis of ligands were employed in these methods, which greatly hindered their application in on-site analysis. Therefore, a convenient and quick method for Fe3+ detection is very necessary to practical application. Dopamine, a biomolecule with catechol and amine functional groups, has similar characteristics to the powerful adhesive foot protein secreted by mussels.8 Generally, dopamine can be self-polymerized to prepare polydopamine (PDA), which can spontaneously form thin polymer coatings on a variety of organic and inorganic materials, acting as a surface modification reagent.9-11 Furthermore, PDA can generate strong interactions with certain metal ions due to the coordination bonding between catechol ligands and metal ions. Recently, coordination between PDA and Fe3+ was found to be a pivotal component which is responsible for the hardness and high extensibility of the cuticle of byssal threads.12 Inspired by the byssal threads, HoltenAndersen et al. constructed self-healing gels based on coordination between Fe3+ and PDA.13 Moreover, Lu et al. prepared pollutant-absorbing supramolecular hydrogels using PDA modified montmorillonite with Fe3+ as a physical cross-linker.14 Inspired by these pioneering works, an interesting concept arises: the coordination between PDA and Fe3+ might be utilized to detect Fe3+ in aqueous waste by employing PDA as an indicator. Hitherto, this issue has been rarely explored as far as we know. Cellulose nanocrystals (CNC), which is derived from abundant cellulosic resources such as plants and microbial cellulose,15-17 has attracted great attention because of their unique properties such as excellent


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nanometric dispersity, high specific surface area, enriched surface active groups and particularly environmental sustainability.18 More importantly, CNC has eminent colloidal stability due to the interelectrostatic repulsions of the negatively charged sulfate ester groups on CNC.19 Previous works have demonstrated that CNC could serve as an excellent template and stabilizer for metal nanoparticles,20 intrinsic conducting polymers,21-23 various carbon materials,23-24 as well as PDA25. However, rare efforts, to the best of our knowledge, have taken to apply the nano-sized and well-suspended CNC-based nanohybrids into environmental monitoring fields. In this paper, dual functional PDA@CNC biocomposites were prepared for Fe3+-pollutant detecting and auto-blocking for the first time. CNC was used as a template for in situ synthesis of PDA, forming nano-sized and well-dispersed PDA@CNC nanohybrid. The PDA on CNC could serve as a ‘‘discriminator’’ for Fe3+ in water. When PDA met Fe3+, the coordination bonding between PDA and Fe3+ led PDA@CNC to conglomerate into macroscopical and flocculent aggregates, which made it possible to conveniently detect Fe3+ with a minimum limit of 3 ppm by the naked eye and 0.5 ppm by dynamic light scattering (DLS) measurement. More interestingly, this morphology transition of PDA@CNC upon Fe3+ could be utilized to auto-block Fe3+pollutant. This proposed strategy of hybridizing different natural resources might open up new possibilities for their novel application in environmental fields, such as pollutant detecting and automatical blockage of industry sewages.

Materials and Methods Materials Medical purified cotton, analytical grade sulfuric acid (H2SO4), 3,4-dihydroxyphenethylamine hydrochloride (dopamine), tris(hydroxymethyl)-aminomethane (Tris), iron chloride hexahydrate (FeCl3·6H2O) and other chemical reagents were all purchased from commercial sources and used without further purification.

Preparation of CNC CNC was prepared by hydrolyzing cotton fibers with sulfuric acid based on reference.26 Medical purified cotton (4 g) was mixed with sulfuric acid solution (70 mL, 64 wt%) and then stirred vigorously at 45 oC for 45 min. The resultant suspension was immediately diluted ten times to avoid the follow-up hydrolysis.


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Subsequently, the suspension was centrifuged and washed with deionized water for 3 times to remove all the soluble substances. Dialysis was applied to remove the residual acid in the suspension until the dialyzate changed to neutrality. The resultant CNC suspension was concentrated to a desired concentration (1.16 wt%), which was sonicated for 30 min at room temperature.

Synthesis of PDA@CNC 172 g CNC suspension (1.16 wt%, containing about 2 g CNC) was diluted to 1000 mL with distilled water and sonicated for 15 min. 1.2 g of Tris was added into the CNC suspension to adjust the pH to a predetermined value of 8.5. Subsequently, 2.0 g of dopamine (dopamine/CNC at a weight ratio of 1:1) was dissolved in the suspension and the resultant suspension was magnetically stirred for 24 h in ambient atmosphere at room temperature. During the polymerization process, the color of the dispersion slowly turned black. The product was then centrifuged at 10000 rpm for 5 min and washed with deionized water for 3 times. After dialysis, PDA@CNC nanohybrid (1.86 wt%) was dispersed by ultrasonic treatment. PDA@CNC nanohybrids with different mass ratios of dopamine/CNC (1:2 and 4:1) were prepared under the same condition as mentioned above.

Characterization The transmission electron microscopy (TEM, JEOL JEM-100CX, Japan) was carried out to observe the morphology of the synthesized CNC and PDA@CNC nanohybrid. Fourier transform infrared spectroscopy (FTIR) was conducted on a Nicolet 6700 spectrophotometer (USA) to characterize the chemical structural of CNC and PDA@CNC nanohybrid. Powdered samples of pristine CNC and PDA@CNC were mixed with KBr to produce tablets for FTIR measurement recorded from 4000 to 400 cm-1. The content of PDA in PDA@CNC nanohybrids was calculated by weighing method. Thermogravimetric analysis (TGA) measurement was performed from room temperature to 600 oC with a heating rate of 10 oC/min under steady nitrogen on a TG209 F1 instrument (NETZSCH Co., Germany). Ultraviolet-visible (UV-vis) spectra were recorded on a Shimadzu UVmini-1240 spectrophotometer using a quartz cuvette with an optical path of 1 cm. The rheological analysis was carried out at 25±0.1 oC on a strain-controlled HAAKE MARS with parallel plate geometry (20 mm diameter). 20 µL FeCl3 solution of various concentrations (40, 80 and 160 mM) was added to 1000 µL PDA@CNC nanohybrid under efficient stirring, respectively. The strain was kept at 1% with a gap


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size of 1 mm, and a dynamic frequency sweep from 0.01 to 1 Hz was conducted to measure the storage modulus G’ and loss modulus G”. Zeta potential (ϛ-potential, ZP) of the pristine CNC (1 mg/mL) and PDA@CNC (1 mg/mL) aqueous suspension under a neutral condition was measured using Zetasizer nano-ZS (Malvern, UK). X-ray photoelectron spectroscopy (XPS) experiments were performed on a Kratos XSAM 800 spectrometer using Al Kα. The fitting procedure was performed using “casa XPS” software. The optical photo micrograph of the Fe3+/PDA@CNC was taken by using a biological microscope (UB 200i, Chongqing UOP Photoelectric Technology Co., Ltd., China). Scanning electron microscope (SEM, KYKY 2800B) was performed to observe the surface morphology of the porous filter membranes after filtering 5 mL pristine PDA@CNC suspension and 5 mL Fe3+-contained PDA@CNC suspension. Raman spectra were recorded by a Raman Spectrometer (Renishaw 2000) using a 785 nm near infrared laser excitation source. A laser power of 10-20 mW, combined with a short integration time of 0.2 s was used for this measurement.

Fe3+-pollutant detection and auto-blockage Fe3+ detection: 300 µL of PDA@CNC suspension was diluted to 100 mL with deionized water. Then, a series of Fe3+ solution with different concentration was added to the PDA@CNC aqueous suspension. The size of the PDA@CNC nanohybrid was measured by DLS method using a Zetasizer nano-ZS instrument (Malvern, UK). Fe3+ auto-blockage: 5 mL of PDA@CNC suspension was diluted to 100 mL with deionized water. A 50 mL syringe equipped with microfiltration membranes (pore size, 5 µm) was packed with the diluted PDA@CNC nanohybrid under a force of 9.8 N. The suspension was continuously syringed out. After adding 30 ppm Fe3+, the Fe3+/PDA@CNC could not be smoothly syringed out under the same condition.

Results and discussion Synthesis and characterization of PDA@CNC The synthesis of PDA@CNC biocomposites is illustrated in Figure 1. As widely reported,27-28 natural cellulose fibers consist of bundle of microfibers, which have crystal region and amorphous region. By acid hydrolysis of the amorphous state of cellulose microfibers, nanometer-sized and rod-like CNC is reserved. The


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obtained CNC has good colloidal stability due to the negatively charged sulfate ester groups on the surface.19 After introducing dopamine monomer into CNC suspension, catechols are prone to react with the hydroxyl groups of CNC, resulting in the dehydration and formation of a charge-transfer complex.29 Then, dopamine gradually self-polymerizes to form a PDA cladding layer on the surface of CNC, with a color change from white to black (Figure S1). In this process, CNC acted as an excellent template for the synthesis of PDA as well as a stabilizer, yielding nano-sized and well-dispersed PDA@CNC nanohybrid suspension. The contents of PDA in the resultant PDA@CNC nanohybrid were 20.2, 29.1 and 44.5 wt% when the mass ratios of dopamine to CNC were 1:2, 1:1 and 4:1, indicating that higher mass ratio of dopamine to CNC resulted in higher content of PDA in PDA@CNC nanohybrids.

Figure 1. Schematic illustration for the preparation of PDA@CNC biocomposites. TEM was carried out to observe the morphologies of CNC before and after the PDA coating. As shown in Figure 2a, rod-like CNC is 10-20 nm in diameter and 200-400 nm in length. After polymerization of


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dopamine, a flocculent PDA layer was coated on CNC in PDA@CNC nanohybrid as revealed in Figure 2b. Moreover, white CNC turned to black after the polymerization of dopamine (Figure 2 inset). These results indicate that PDA was successfully synthesized onto the surface of CNC template. Besides, zeta potential was measured to evaluate the colloidal stability of PDA@CNC. The zeta potential value of the pristine CNC was measured to be -21 mV while the zeta potential of PDA@CNC was -26 mV. The colloidal stability of CNC is enhanced after the coating of PDA. This result may be attributed to that the PDA on the surface of CNC could weaken the interparticle hydrogen bonding of CNC and hamper its aggregation.30

Figure 2. TEM images, zeta potential and photographs of CNC (a) and PDA@CNC nanohybrid (b), scale bars: 100 nm. XPS spectroscopy was utilized to analyze the element composition and chemical structure of PDA@CNC nanohybrid. The XPS spectrum of PDA@CNC shows peak components of C 1s, N 1s, and O 1s, ascribing to C, O, and N elements in PDA@CNC (Figure 3a). The complicated nature of PDA on CNC was revealed by different chemical states of elemental C, O, and N. The C 1s core-level spectrum could be curve-fitted with five peak components as shown in Figure 3b. The main peaks at 288.3, 286.2, 285.0, 284.6, and 282.7 eV are assigned to O-C-O/C=O, C-O, C-N, C-C/C-H and aromatic C, respectively.31 In the O 1s peak (Figure 3c), two peaks were observed at 531.7 eV for C-O-H/ C-O-C and 532.5 eV for O-C-O.32 The three components of N 1s


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peak (Figure 3d) correspond to amine groups (401.7 eV), substituted amines (399.8 eV), and imino groups (398.5 eV).33 The primary amine group of dopamine was converted to secondary amine, suggesting that dopamine was converted to indolic compounds and spontaneous polymerized into PDA. The presence of minor amount of primary amine is due to the concurrent existence of noncovalently self assembled dopamine in the covalent polymerized PDA.34 In addition, UV-vis, FTIR and TGA analysis also confirm the presence of PDA on CNC template (as shown in Figure S2, Figure S3 and Figure S4, respectively). These results all indicate that PDA has been successfully polymerized onto the surface of CNC template. The strong interaction between the PDA and CNC makes it convenient to modify CNC with PDA, forming PDA@CNC biocomposites.29 35

Figure 3. XPS analyses of PDA@CNC nanohybrid: (a) survey scan, (b) C 1s, (c) O 1s, and (d) N 1s core levels. Coordination evaluation


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To elucidate the coordination interaction between Fe3+ and PDA@CNC nanohybrid, desired concentration of Fe3+ was added into PDA@CNC suspension. The original PDA@CNC suspension flew readily in the tilted vial as shown in Figure 4a. However, after the addition of Fe3+ (90 ppm), the PDA@CNC suspension did not exhibit gravitational flow in the inverted vial within 10 s (Figure 4b). The whole gelation process was recorded as shown in Supplementary Video 1. These results indicate that the Fe3+ behaved as a cross-linker in the gelation of PDA@CNC nanohybrid, which is ascribed to the catechol-Fe3+ complex interaction.14 The Fe3+ induced gelation of PDA@CNC nanohybrid was further quantified by dynamic rheological measurements. The storage modulus (G’) values of all the samples are higher than the loss modulus (G’’) values over the entire frequency range as shown in Figure 4c, revealing that the Fe3+/PDA@CNC exhibited an elastic behavior.36 Besides, increase of Fe3+ concentration caused the obvious rise of the modulus of Fe3+/PDA@CNC as given in Figure 4c, indicating that Fe3+ acted as desirable cross-linking points. These results demonstrate that a network was formed in PDA@CNC suspension via coordination interaction between PDA@CNC nanohybrid and Fe3+. In addition, this coordination interaction was further proved by UV-vis spectra and Raman spectra as shown in Figure S5 and Figure S6.

Figure 4. Photographs of PDA@CNC suspension before (a) and after (b) adding Fe3+ (90 ppm). The storage modulus G’ and loss modulus G’’ logarithmically against frequency of the corresponding samples with different Fe3+ concentration (c).


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Detection of Fe3+ As discussed above, a layer of PDA was successfully synthesized onto CNC template. The PDA layer could generate complex interaction with Fe3+. Thus, the obtained nano-sized and well-dispersed PDA@CNC nanohybrid (Figure S7, discussed in Supporting Information) might exhibit responsible behaviors (morphology or suspension property variation) to Fe3+ stimuli, which makes it possible to detect Fe3+ with this sustainable PDA@CNC biocomposites. To evaluate the feasibility of PDA@CNC biocomposites in detecting Fe3+, different concentrations of Fe3+ (0, 1, 2, 3, 4 and 5 ppm) were introduced into PDA@CNC nanohybrid suspension respectively. As shown in Figure 5a, the suspension of pure PDA@CNC (0 ppm) was clear. No particles were observed. When 1 and 2 ppm Fe3+ was added into the PDA@CNC nanohybrid, no obvious variation appeared. However, when the concentration of Fe3+ reached 3 ppm, a large number of fine aggregates presented in the suspension, which could be clearly observed by naked eye as magnified in Figure S8. This result indicates that a minimum detection limit of Fe3+ as low as 3 ppm could be realized by the naked eyes. With Fe3+ concentration further increased to 4 and 5 ppm, larger aggregates of PDA@CNC could be seen distinctly (Figure 5a). The aggregating process of PDA@CNC was quite rapid within 30 s as recorded in Supplementary Video 2. These results confirm the ability of this PDA@CNC biocomposites in detecting Fe3+ in a convenient and fast way. In addition, we employed DLS to measure the size variation of PDA@CNC biocomposites. The size change of PDA@CNC below 3 ppm Fe3+ was monitored by DLS. As depicted in Figure 5b, with the concentration of Fe3+ increased from 0.1 ppm to 0.5 ppm, the size of PDA@CNC did not show distinct change (A region). However, when Fe3+ further increased above 0.5 ppm, the size of PDA@CNC dramatically increased with Fe3+ concentration increasing (B region), which is resulted from the coordination interaction between PDA@CNC and Fe3+. Based on the data above, the Fe3+-detection mechanism using PDA@CNC nanohybrid as a discriminator is illustrated in Figure 5c. The binding interaction of Fe3+ and catechol of PDA drawn PDA@CNC nanohybrid closer, forming macroscopical and flocculent PDA@CNC aggregates finally (Figure 5a). Higher Fe3+ concentration led to more serious aggregation of PDA@CNC nanohybrid, resulting larger agglomerates. The


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agglomerates are visible to the naked eyes when the concentration of Fe3+ exceeded 3 ppm. Hence, convenient and fast determination of Fe3+ by the naked eye could be achieved by using PDA@CNC biocomposites. The detection of different metal ions by PDA@CNC nanohybrid was explored. As given in Table S1, Mg2+, Cr3+, Co2+, Mn2+, Hg2+, Ni2+, Cd2+, Zn2+ and Ag1+ did not cause rapid aggregation of PDA@CNC even when the ion content reached 20 ppm, indicating that these ions have no obvious coordination interaction with PDA@CNC. However, Cu2+ and Fe2+ caused agglomeration of PDA@CNC at 9 ppm and 14 ppm, respectively, which reveals that Cu2+ and Fe2+ have coordination interaction with PDA@CNC. Thus, Cu2+ and Fe2+could also be detected using PDA@CNC nanohybrid as an indicator with different detection limits. Based on the results above, it is verified that the aggregation of PDA@CNC was caused by the coordination bonding between metal ions and PDA@CNC, rather than charge neutralization by positively charged ions.

Figure 5. Photographs of PDA@CNC nanohybrid suspension after adding different concentrations of Fe3+ (0, 1, 2, 3, 4, and 5 ppm) (a). Dimensional evolution of PDA@CNC aggregates under different concentrations of Fe3+ (b). Schematic illustration for the detection of Fe3+ (c). Automatic blockage of Fe3+-pollutant As demonstrated above, the change of PDA@CNC morphology from nano-sized and well-dispersed nanohybrid to macroscopical and flocculent aggregates after meeting Fe3+ enabled us to detect Fe3+ by the naked eyes. Moreover, this conversion might be utilized to realize automatic blockage of Fe3+-pollutant in


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environmental fields. Specifically, by installing a microfiltration membrane with a desired pore size at drain outlet, sewages containing nano-sized PDA@CNC could smoothly pass through microfiltration membrane. However, excess Fe3+ in sewages leads to macroscopical aggregation of PDA@CNC nanohybrid, which could block the microfiltration membrane and stop the sewages letting out. Hence, the sustainable PDA@CNC nanohybrid acted as not only an indicator for Fe3+ detection, but also a blocking agent for sewages containing excess Fe3+. As a proof-of-concept, we conducted an experiment to demonstrate the potential application of this smart PDA@CNC biocomposite in automatic blockage of wastewater containing excess Fe3+. As shown in Figure 6a (left), pure PDA@CNC suspension was injected from a syringe to pass through a microfiltration membrane under a force of 9.8 N. The pore size of the microfiltration membrane was 5 µm, which is larger than the size of PDA@CNC nanohybrid. As recorded in Supplementary Video 3, PDA@CNC nanohybrid suspension was continuously injected through the microfiltration membrane under the applied force. This is attributed to the fact that the size of PDA@CNC nanohybrid is much smaller than the pore size of the membrane, and PDA@CNC nanohybrid could pass through the void of the membrane easily as illustrated in Figure 6a (right). However, after adding 30 ppm Fe3+ into PDA@CNC nanohybrid, the suspension could not be injected out under the same condition (Figure 6b left, Supplementary Video 4), resulting from the serious aggregation of PDA@CNC nanohybrid (Figure S9) which might block the porous membrane as illustrated in Figure 6b (right). The surface morphology of the porous membranes after filtering PDA@CNC and Fe3+/PDA@CNC suspensions was observed by SEM as shown in Figure S10, which can confirm the given illustrations. It is worth noting that different concentration of Fe3+ resulted in PDA@CNC aggregates with different sizes as confirmed in Figure 5b. Thus, we can use microfiltration membranes with different pore sizes to realize the selective blockage of sewages containing desired content of Fe3+. Compared to the visual colorimetry and fluorescence methods reported for Fe3+ detection,37-39 this research provided a facile but efficient approach to detect as well as automatically block Fe3+-contained sewages using sustainable PDA@CNC biocomposites.


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Figure 6. Photographs of flowing status of PDA@CNC nanohybrid and schematic illustration before (a) and after (b) meeting Fe3+. Conclusions In summary, we presented a simple and convenient method for on-site detection for Fe3+-pollutant by using environmentally friendly PDA@CNC biocomposite as an indicator. PDA@CNC nanohybrid was synthesized via in situ oxidative polymerization of dopamine using CNC as a template. The resulted PDA@CNC nanohybrid exhibited interesting responsive behavior towards Fe3+ as a result of the coordination interaction between Fe3+ and PDA@CNC. This allowed us to detect Fe3+ at a detection limit of 3 ppm by the naked eyes and 0.5 ppm by DLS. Moreover, PDA@CNC nanohybrid could effectively block pollutant which contains excess Fe3+ by installing a microfiltration membrane at drain outlet. This sustainable and low-cost PDA@CNC


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biocomposite provides new opportunities for the convenient detection and efficient auto-blockage of Fe3+pollutant, exhibiting broad application prospects in environmental fields.

Author information Corresponding author: Xinxing Zhang and Canhui Lu *E-mail address: [email protected] & [email protected] Tel: +86-28-85460607 Fax: +86-28-85402465

Acknowledgements The authors thank the National Science Foundation of China (51673121 and 51473100) and State Key Laboratory of Polymer Materials Engineering (Grant No. sklpme2015-2-02) for financial support.

Supporting Information Photographs of CNC suspension, CNC suspension after adding dopamine and CNC/dopamine suspension. UV-vis spectra of CNC and PDA@CNC nanohybrid. FTIR spectra of CNC, PDA and PDA@CNC nanohybrid. TGA curves of CNC, PDA and PDA@CNC nanohybrid. UV-vis spectra of PDA@CNC and Fe3+/PDA@CNC suspensions. Raman spectra of PDA@CNC and Fe3+/PDA@CNC. Photographs of PDA@CNC suspension before and after standing for 7 days. Photographs of PDA@CNC suspension before and after adding 3 ppm Fe3+. Detection of various metal ions with PDA@CNC biocomposites. Optical microscope image of Fe3+/PDA@CNC agglomerates. SEM images of porous membranes after filtering 5 mL PDA@CNC suspension and 5 mL Fe3+/PDA@CNC suspension. Video 1: gelation process of PDA@CNC nanohybrid. Video 2: detection of Fe3+ by PDA@CNC nanohybrid. Video 3: flowing status of PDA@CNC nanohybrid. Video 4: flowing status of PDA@CNC nanohybrid after meeting Fe3+. This material is available free of charge via the Internet at http://pubs.acs.org.

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Dual functional biocomposites based on polydopamine modified cellulose nanocrystal for Fe3+-pollutant detecting and auto-blocking Yangyang Han, Xiaodong Wu, Xinxing Zhang,* Zehang Zhou and Canhui Lu* For Table of Contents Only

A sustainable and convenient method was developed for on-site detection of Fe3+ by the naked eyes and auto-blockage of Fe3+-pollutant by using environmentally friendly PDA@CNC biocomposites


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A sustainable and convenient method was developed for on-site detection of Fe3+ by the naked eyes and auto-blockage of Fe3+-pollutant by using environmentally friendly PDA@CNC biocomposites TOC 84x57mm (300 x 300 DPI)


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Schematic illustration for the preparation of PDA@CNC biocomposites. Figure 1 114x86mm (300 x 300 DPI)



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TEM images, zeta potential and photographs of CNC (a) and PDA@CNC nanohybrid (b), scale bars: 100 nm Figure 2 139x70mm (300 x 300 DPI)


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XPS analyses of PDA@CNC nanohybrid: (a) survey scan, (b) C 1s, (c) O 1s, and (d) N 1s core levels Figure 3 115x96mm (300 x 300 DPI)



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Photographs of PDA@CNC suspension before (a) and after (b) adding Fe3+ (90 ppm). The storage modulus G’ and loss modulus G’’ logarithmically against frequency of the corresponding samples with different Fe3+ concentration (c) Figure 4 75x41mm (300 x 300 DPI)


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Photographs of PDA@CNC nanohybrid suspension after adding different concentrations of Fe3+ (0, 1, 2, 3, 4, and 5 ppm) (a). Dimensional evolution of PDA@CNC aggregates under different concentrations of Fe3+ (b). Schematic illustration for the detection of Fe3+ (c) Figure 5 160x59mm (300 x 300 DPI)



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Photographs of flowing status of PDA@CNC nanohybrid and schematic illustration before (a) and after (b) meeting Fe3+ Figure 6 152x122mm (300 x 300 DPI)


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Dual Functional Biocomposites Based on Polydopamine Modified

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