Fibers and Polymers 2015, Vol.16, No.5, 1193-1200 DOI 10.1007/s12221-015-1193-4 ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version) Communication Synthesis and Characterization of TMU-16-NH2 Metal-organic Framework Nanostructure Upon Silk Fiber: Study of Structure Effect on Morphine and Methyl Orange Adsorption Affinity Amir Reza Abbasi*, Jalal ad-Din Aali, Azadeh Azadbakht1, Ali Morsali2*, and Vahid Safarifard2 Faculty of Chemistry, Razi University, Kermanshah 67194, Islamic Republic of Iran Department of Chemistry, Faculty of Science, Islamic Azad University, Khorramabad, Islamic Republic of Iran 2 Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, Tehran 14155-4838, Islamic Republic of Iran (Received November 25, 2014; Revised March 12, 2015; Accepted March 17, 2015) 1 Abstract: Thin films of a three-dimensional porous Zn(II)-based metal-organic framework, [Zn (H N-BDC) (4-bpdh)]· 3DMF (TMU-16-NH ), containing azine-functionalized pores, were deposited on surfaces of silk fiber via a stepwise manner. The effect of sequential dipping steps in growth of TMU-16-NH upon fiber has been studied. These systems depicted a decrease in the size accompanying a decrease in the sequential dipping steps. The deposition of TMU-16-NH upon silk fiber was monitored by XRPD and FT-IR spectroscopy. The TMU-16-NH upon silk fiber can serve as a host for encapsulating morphine (Mph) and methyl orange (MO). 2 2 2 2 2 2 2 Keywords: Metal-organic framework, Silk, Nanoparticle, Methyl orange, Morphine fiber with -COOH surface functionalization. The deposited films of [Zn2(H2N-BDC)2(4-bpdh)]·3DMF (TMU-16-NH2) [17] were porous and could be loaded with different guest species. The shown porosity of the films and the known ability of MOFs to adsorb different kind of species open a wide field of possible applications, such as protection layers for working clothes and gas separation materials in the textile industry, for synthetic polymers with a MOF layered on the surface. Due to the synthesis and the additional further processing fibers made from silk are more suitable compared with other synthetic and natural fibers. The surface of silk fibers exhibits very large amounts of reactive carboxylic groups. These carboxylic groups are already able to complex Zn(II) ions and act as an anchoring group for the Zn carboxylate, which is the secondary building unit (SBU) of TMU-16-NH2 and is deposited with the first pulse of the stepwise deposition. In general, positive ions are bounded to the silk at high pH value, since the carboxylic groups are unprotonated and the electron pair on the carboxylic oxygen is available for donation to metal ions [18,19]. Introduction The field of metal-organic frameworks (MOFs), which are also called porous coordination polymers (PCPs), has been growing tremendously over the last two decades [1,2]. This fascinating class of crystalline hybrid materials, which are formed by association of metal centers or clusters linked by organic moieties, offers an unique chemical versatility combined with a designable framework and an unprecedentedly large and permanent porosity [3-5]. These materials have enormous potential for many practical structure-related applications. This includes the more traditional areas of storage, separation or controlled release of gases, catalysis, sensing, and drug delivery, as well as the adsorptive removal of hazardous materials, which are based on the pore size and shape and the host-guest interactions involved [6-11]. However, the majority of these applications are based on the ability of MOFs to behave as hosts for certain molecules [12]. Apart from their use as bulk materials, these frameworks could be processed as supported homogeneous porous thin films on various surfaces. Controlling the assembly of metal-organic frameworks thin films on different substrates is currently recognized as one of the most important issues in the synthesis of functional materials [13]. Different strategies have been developed in the literature to fabricate thin films of MOFs. These technical approaches can be grouped in several ways such as surface functionalization [14], layerby-layer (LBL) [15] and electrospun nanofibrous filters [16]. In this work we report the layer-by-layer deposition of a microporous Zn(II)-MOF material on the surface of natural Experimental Materials and Physical Techniques All reagents and solvents were used as supplied by Merck Chemical Company and used without further purification. The silk fiber was obtained from Guilan Silk Company. The natural silk fibers were pre washed using an aqueous solution containing NaOH (pH=9.5), at 25 oC for 5 min, followed by washed several times with water and dried at ambient temperature. X-ray powder diffraction (XRPD) measurements were done on a Philips X’pert diffractometer with monochromatic Cu Kα radiation. The simulated XRD *Corresponding author: [email protected] *Corresponding author: [email protected] 1193 1194 Fibers and Polymers 2015, Vol.16, No.5 Amir Reza Abbasi et al. powder pattern based on single crystal data were prepared using Mercury software. The samples were characterized with a scanning electron microscope (SEM, Philips XL 30 and S-4160) with gold coating. The average particle sizes were prepared using Microstructure measurement software. In situ fluorescence spectroscopy experiment has been carried out on a JASCO spectroflurimeter (FP 6200). Infrared spectra were taken with a FT-IR Bruker, vector 22 spectrometer using KBr pellets in the 400-4000 cm-1 range. Syntheses of TMU-16-NH2 Upon Silk Surfaces The ligand 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4bpdh) was synthesized according to previously reported methods [20]. 2.3 g (4.5 mmol) of hydrazine hydrate was added dropwise to a solution of 4-acetylpyridine (1.089 g, 9.0 mmol) dissolved in ethanol (15 ml). Two drops of formic acid were added and the mixture was stirred at room temperature for 24 h. The yellow solid that formed was filtered and washed several times with ethanol/ether (1:1). Yield: 0.536 g (50 %). The growth of TMU-16-NH2 upon silk fiber was achieved by sequential dipping in alternating bath of aqueous Zn(NO3)2·6H2O (0.297 g, 1 mmol) and a DMF solution of 4-bpdh (0.119 g, 0.5 mmol) and 2- aminobenzene-1,4-dicarboxylic acid (H2BDC-NH2) (0.181 g, 1 mmol). Before the experiment began, silk fibers were immersed in an alkaline solution. In alkaline pH, the surface of fiber becomes negatively charged due to deprotonation of the carboxylic group present at the fiber’s surface [21]. The first layer was fabricated by immersing the silk-COO− surface into an solution of Zn(II) and then in solution of ligands (1 cycle). When negative fiber was immersed in an aqueous solution of zinc(II) nitrate, Zn(II) ions are attracted to the fiber surface [18]. The dipping step in 4-bpdh/H2BDCNH2 solutions allowed the formation of TMU-16-NH2 and initiated the formation of new TMU-16-NH2 particles, as illustrated in Figure 1. The results show that sequential dipping in alternating baths of aqueous Zn(II) and 4-bpdh/H2BDC-NH2 leads to a stepwise deposition of TMU-16-NH2 multilayers. The thickness of the multilayers was increased with the increase of the deposition cycles [18]. The dipping step in each Zn(II) and 4-bpdh/H2BDC-NH2 solutions was 2 min followed by some rinses in pure DMF each for 1 min. In order to investigate the deposition of the first 15 MOF layers on the surface of the silk fiber, the substrate was dipped alternatively into SBUand linker solution with washing with DMF in between [14]. Figure 1. (A) The preparation of TMU-16-NH upon silk fiber from raw reagents and (B) the use of TMU-16-NH upon silk for encapsulating and further releasing therapeutic species. 2 2 TMU-16-NH2 MOFs@Silk Fibers Fibers and Polymers 2015, Vol.16, No.5 1195 Results and Discussion Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Powder Diffraction (XRPD) Due to the small amount and thickness of the deposited MOF film, the standard technique of FT-IR is suited for the investigation of film quality. Therefore, after each deposition cycle, an absorption spectrum of the dried substrate was recorded. The increase of the intensity of the vibrational bands (υ=776 cm-1 and υ=834 cm-1) from TMU-16-NH2 phase is proportional to the number of performed deposition cycles. It can be concluded that the characterization of MOF films with a low number of performed deposition cycles can be better achieved using the FT-IR spectra than XRPD, due to its limitation in detection of films with a thickness <40 nm [14,22]. The change of the intensity was observed after the first deposition cycle on the silk surface. Although the observed change of the intensity is small, the intensity increases continuously with each further deposition cycle (Figure 2). The linear increase of the absorbance indicates a regular assembly of the cationic and anionic building blocks. FT-IR for TMU-16-NH2 (KBr, 400-4000 cm-1): 3460 (s, broad), 3349 (s, broad), 2927 (w), 1663 (s), 1625 (s), 1579 (s), 1502 (s), 1427 (s), 1378 (s), 1257 (s), 831 (s), 768 (s) and 574 (s). To determine the crystal phase of TMU-16-NH2 formed upon silk fiber, XRPD measurements were carried out over the diffraction angle (2θ) of 3-35 o. Figure 3 shows the XRPD patterns; simulated from single crystal X-ray data of TMU-16-NH2 (a), as-synthesized TMU-16-NH2 (b), pristine silk fibers (c), TMU-16-NH2 upon silk after applying 10 (d) and 15 deposition cycles (e). The nine major peaks found at Figure 2. FT-IR spectra of pure silk fiber and silk fiber containing TMU-16-NH after applying 5 and 15 deposition cycles; (a) silk yarn, (b) 5 deposition cycles@silk yarn, and (c) 15 deposition cycles@silk yarn. 2 Figure 3. Simulated pattern based on single crystal data of XRPD pattern of TMU-16-NH (a), as-synthesized TMU-16-NH (b), the pure silk fiber (c), TMU-16-NH upon silk after applying 10 (d) and 15 deposition cycles (e), TMU-16-NH upon silk after the adsorption (f) and delivery of MO (g). 2 2 2 2 4.96 o, 8.36 o, 8.52 o, 9.36 o, 10.04 o, 10.40 o, 16.80 o, 17.12 o and 25.28 o on the 2 theta scale correspond respectively to the (002), (110), (111−), (112−), (112), (200), (220), (221) and (331−) crystal planes. Acceptable matches with slight difference in 2θ, were observed between the simulated XRPD pattern and the experimental data (Figure 3(d)) [17]. The results indicated that TMU-16-NH2 formed on the silk fiber and the crystallinity of the coated [Zn2(H2N-BDC)2(4bpdh)]·3DMF MOF films were increased by increasing the cycles of layer by layer coating of TMU-16-NH2 on the silk fibers (Figure 3(d) and (e)) [18]. Figure 3(f) shows the X-ray powder diffraction patterns of TMU-16-NH2 upon silk soaked in an aqueous solution (10-4 mol l-1) of methyl orange (MO) at room temperature for 2 h. It is worth noting that when the crystals were soaked in the solution for about 2 h, most of the peaks in the XRPD data distinctly weakened. The delivery of MO from TMU-16-NH2 upon silk performed in ethanol at room temperature under continuous stirring was determined by XRPD (Figure 3(g)). The unusual phenomenon can be well explained by the high amount of guest in TMU16-NH2, which has a significant impact on the sensitivity of the X-ray analysis. The obtained pattern match with the pattern of monoclinic TMU-16-NH2, space groups C2/c with the lattice parameters a=17.1558 (6) Å, b=13.4604 (4) Å, c=36.1586 (11) Å and z=8 [17]. The wide peak at 17-23 o corresponds to the silk substrate [18,19]. 1196 Fibers and Polymers 2015, Vol.16, No.5 Effects of Sequential Dipping Steps Particle sizes and morphology of nanoparticles are depending on sequential dipping [23]. Effect of different Amir Reza Abbasi et al. sequential dipping in growth of TMU-16-NH2 upon fiber were studied at pH=9.5. The results suggest that with increasing the fiber dipping steps into SBU- and linker Figure 4. SEM image of the pristine silk fiber. Figure 5. SEM photographs and the corresponding particle size distribution histograms of TMU-16-NH upon silk after applying 4 deposition cycles. 2 TMU-16-NH2 MOFs@Silk Fibers Fibers and Polymers 2015, Vol.16, No.5 1197 Figure 6. SEM photographs and the corresponding particle size distribution histograms of TMU-16-NH upon silk after applying 10 deposition cycles, corresponding wavelength-dispersive X-ray (WDX) analysis of TMU-16-NH upon silk after applying 10 deposition cycles. 2 2 solution, growth takes place on more nuclei, the Zn(II) and 4-bpdh/H2BDC-NH2 attraction increases, and subsequently the concentration and size of TMU-16-NH2 particles upon silk fiber increases [21]. For the sake of investigating the morphology of the prepared coating samples, the SEM images of samples were studied. The SEM images of the non-modified natural fiber (Figure 4) were compared with after applying 4 (Figure 5) and 10 deposition cycles (Figure 6) of TMU-16-NH2 upon silk fiber. The surface of the individual fibers is covered by a continuous film of separated crystals with an average size of 60 and 123 nm for 4 and 10 deposition cycles, respectively, 1198 Fibers and Polymers 2015, Vol.16, No.5 Amir Reza Abbasi et al. Figure 7. (A) Photographs showing the visual color change when TMU-16-NH upon silk was immersed in the aqueous solution of MO (10 mol l ). No further change in color occurred after 7 days, temporal evolution of fluorescence intensity spectra for the loading of Mph (B) and MO (C) from TMU-16-NH upon silk. 2 -4 -1 2 TMU-16-NH2 MOFs@Silk Fibers without defects. However, the SEM images with a low magnification also exhibit areas with big agglomerates of the deposited MOF. This can be understood by considering the possible storage effect of the unreacted material between the fibers. The wavelength-dispersive X-ray (WDX) mapping of the surface shows the uniform distribution of Zn throughout the whole substrate surface (Figure 6). Adsorption Affinity The porosity of MOF films deposited on substrate surfaces is an important point concerning the possible use of such functional materials for different purposes. TMU-16-NH2 has one-dimensional open channels (aperture size of 7.1× 4.6 Å) running along c axis which the internal surface is decorated by the azine groups of the 4-bpdh ligands [17]. For augment of porosity in TMU-16-NH2 upon silk, we successfully tested its porosity with guest molecules by suspending it in an aqueous solution of morphine (Mph) and methyl orange (MO). The silk fiber containing 1.0 g of TMU-16-NH2 was immersed in a sufficient amount of an Fibers and Polymers 2015, Vol.16, No.5 1199 aqueous solution of Mph or MO (10-4 mol l-1) in a small sealed flask at room temperature. The dark red solutions of MO fade slowly to very pale orange (Figure 7A), while the TMU-16-NH2 upon silk get darker. We tested for the amount of Mph and MO that can be inserted in the pores. Results show that 1.0 g of TMU-16-NH2 can absorb approximately 2.00 and 1.271 g of guest in Mph and MO contained TMU16-NH2 upon silk, respectively. The guest content was estimated by XRPD (Figure 3) and fluorescence intensity spectra (Figure 7(B) and (C)) [24]. The change of intensity and width indicates that the resulting solid TMU-16-NH2 upon silk retains the host framework crystallinity as MO/ Mph molecules diffused in. The rapid decline of the fluorescence intensity spectra also proves that TMU-16-NH2 can absorb Mph faster than MO. The higher sorption for Mph is attributed to the size and strong hydrogen bonding interactions. Adsorption of guest was spontaneous and endothermic, and the entropy (the driving force of the adsorption) increases with the adsorption of guest. Entropic hydrophobic interactions occur when a guest replaces the Figure 8. Temporal evolution of fluorescence intensity spectra for the delivery of Mph (A) and MO (B) from TMU-16-NH upon silk containing Mph or MO. 2 1200 Fibers and Polymers 2015, Vol.16, No.5 water within a cavity. An increase in entropy increases the favorability of the process. Release Assays The encapsulated guest could be easily removed from the frameworks upon immersion of guest@MOFs in ethanol. The temporal evolution of fluorescence intensity spectra for MO in ethanol solution, which shows λmax at 270 nm, becomes stronger with increasing MO content. The delivery of MO in ethanol increases with time, indicating that the MO release is governed by the host-guest interaction. Similar behaviors were also observed in the delivery of Mph from TMU-16-NH2 upon silk (Figure 8). The MOF-Mph interaction is stronger than MOF-MO, so the delivery of MO from TMU-16-NH2 can be faster than Mph but the amount of adsorbance is less. Conclusion In summary, we report the fabrication of [Zn2(H2N-BDC)2 (4-bpdh)]·3DMF (TMU-16-NH2) metal-organic framework (MOF) nanostructures upon silk fiber using layer-by-layer method at ambient pressure and temperature. Due to existence of -COOH groups on the surface of the silk fibers no self-assembled monolayer formation was required. XRPD analyses indicated that the prepared TMU-16-NH2 MOF on silk fibers were crystalline. The deposition of MOF thin films on natural fiber surfaces might be a new path for the fabrication of functional materials for different applications, such as protection layers for working clothes and gas separation materials in the textile industry. TMU-16-NH2 upon silk may indeed is suitable for applications requiring frequent loading and unloading of guests. Acknowledgement Support of this investigation by Iran National Science Foundation: INSF (No. 92031906) and Razi University of Kermanshah are gratefully acknowledged. References 1. F. A. Almeida Paz, J. Klinowski, S. M. F. Vilela, J. P. C. Tome, J. A. S. Cavaleiro, and J. Rocha, Chem. Soc. Rev., 41, 1088 (2012). 2. H. C. Zhou, J. R. Long, and O. M. Yaghi, Chem. Rev., 112, 673 (2012). 3. S. Kitagawa, S.-I. Noro, and T. Nakamura, Chem. Amir Reza Abbasi et al. Commun., 701 (2006). 4. D. Maspoch, D. Ruiz-Molina, and J. Veciana, Chem. Soc. Rev., 36, 770 (2007). 5. J. J. T. Perry, J. A. Perman, and M. J. Zaworotko, Chem. Soc. Rev., 38, 1400 (2009). 6. R. B. Getman, Y. S. Bae, C. E. Wilmer, and R. Q. Snurr, Chem. Rev., 112, 703 (2012). 7. H. B. Tanh Jeazet, C. Staudt, and C. Janiak, Dalton Trans., 41, 14003 (2012). 8. J. Sculley, D. Yuan, and H.-C. Zhou, Science, 4, 2721 (2011). 9. M. Yoon, R. Srirambalaji, and K. Kim, Chem. Rev., 112, 1196 (2012). 10. Z. Yin, Q. X. Wang, and M. H. Zeng, J. Am. Chem. Soc., 134, 4857 (2012). 11. L. Hashemi and A. Morsali, Crystengcomm., 14, 779 (2012). 12. S. Qiu and G. Zhu, Coord. Chem. Rev., 253, 2891 (2009). 13. D. Zacher, O. Shekhah, C. Woll, and R. A. Fischer, Chem. Soc. Rev., 38, 1418 (2009). 14. M. Meilikhov, K. Yusenko, E. Schollmeyer, C. Mayer, H.-J. Buschmann, and R. A. Fischer, Dalton Trans., 40, 4838 (2011). 15. D. Zacher, K. Yusenko, A. Betard, S. Henke, M. Molon, T. Ladnorg, O. Shekhah, B. Schupbach, T. Arcos, M. Krasnopolski, M. Meilikhov, J. Winter, A. Terfort, C. Woll, and R. A. Fischer, Chem.-Eur. J., 17, 1448 (2011). 16. J. K. Yuan, X. G. Liu, O. Akbulut, J. Q. Hu, S. L. Suib, J. Kong, and F. Stellacci, Nat. Nanotechnol., 3, 332 (2008). 17. V. Safarifard and A. Morsali, Crystengcomm., 16, 8660 (2014). 18. A. R. Abbasi, K. Akhbari, and A. Morsali, Ultrason. Sonochem., 19, 846 (2012). 19. A. R. Abbasi and A. Morsali, J. Inog. Organomet. Polym. Mater., 20, 825 (2010). 20. A. R. Kennedy, K. G. Brown, D. Graham, J. B. Kirkhouse, M. Kittner, C. Major, C. J. McHugh, P. Murdoch, and W. E. Smith, New J. Chem., 29, 826 (2005). 21. A. R. Abbasi and A. Morsali, Ultrason. Sonochem., 17, 704 (2010). 22. A. Azadbakht, A. R. Abbasi, N. Noori1, E. Rafiee1, and M. Taran, Fiber Polym., 14, 687 (2013). 23. A. R. Abbasi and A. Morsali, Ultrason. Sonochem., 17, 572 (2010). 24. P. Horcajada, C. Serre, G. Maurin, N. A. Ramsahye, F. Balas, M. Vallet-Regi, M. Sebban, F. Taulelle, and G. Ferey, J. Am. Chem. Soc., 130, 6774 (2008).
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