Photochemistry and Photobiology, 2015, 91: 814–818
Hybrid Membrane of Agarose and Lanthanide Coordination Polymer: a Selective and Sensitive Fe3+ Sensor Kai Zheng, Kai-Li Lou, Cheng-Hui Zeng*, Sha-Sha Li, Zhi-Wen Nie and Shengliang Zhong* Key Laboratory of Functional Small Organic Molecule, Ministry of Education and Jiangxi’s Key Laboratory of Green Chemistry, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, P. R. China Received 29 January 2015, accepted 14 April 2015, DOI: 10.1111/php.12460
usage. So the new strategy of making portable soft film should be devoted to satisfy more applications. The agarose membrane is convenient to take along, very appropriate to perform at outdoors, it is a kind of environmental friendly and biocompatible material, and the agarose is very cheap and easy to get (19). To the best of our knowledge, detecting species with the hybrid device of agarose and lanthanide coordination polymers was not reported, though many hybrids of lanthanide sol–gel were prepared and applied in sensing (20–23). Another disregarded point is that many sensing experiments were processed in organic solvents (24,25), but not in water, this is not applicable in environment monitoring and biosensing. Inspired by the aforementioned considerations and based on our previous work on lanthanide complexes (25–30), herein, a highly luminescent coordination polymer ([Tb(HL1)L1H2O]n (1, H2L1 = 4-methyl salicylic acid) (29), was adopted to hybrid with agarose. The membrane was characterized by Fourier transform infrared (FT-IR), powder X-ray diffraction (PXRD), scanning electron microscope (SEM) and luminescence. Ligand in 1 has two coordination groups of carboxyl and hydroxyl, might show excellent sensing properties. Therefore, a new and convenient strategy for fabricating durable thin film of hybrid material which contains 1 and agarose was developed. The sensing properties show it had highly selective and sensitive detecting effect to Fe3+ in water, which can be distinguished by visualization in daylight or irradiated by portable small UV light at the scene.
ABSTRACT A new hybrid membrane was prepared by a facile method based on a highly luminescent lanthanide coordination polymer and agarose. The soft membrane was characterized by FT-IR, PXRD, SEM and luminescence. It is found that the soft membrane is a highly selective and sensitive sensor, among 19 metal ion solutions of Fe3+, Mg2+, Li+, Ca2+, Zn2+, Cu2+, Ba2+, Mn2+, Ru3+, Cr3+, Ag+, Sr2+, Cd2+, Na+, Ni2+, Pb2+, Fe2+, Hg2+ and Ca2+, only Fe3+ quench the luminescence. The sensing results can be distinguished by the naked eye in daylight or by irradiation of a portable UV light at the scene. Mechanism studies reveal the sensing is due to the decomposition of the coordination polymer 1 which induced by slow permeation of Fe3+. Further studies found anions of BO3 , CO23 , H2 PO4 , Br , Cl , ClO4 , H2 PO4 , I , IO3 and NO3 will not quench the luminescence of the hybrid membrane, which imply that other anions in water would not disturb the detection result.
INTRODUCTION Lanthanide coordination polymers are very promising materials for their wide applications in the areas of optics, catalysis, magnetism and electrophysics because of their unique structures and properties (1,2). As optical materials, they have attracted increasing attention in up conversion emission (3–5), time-resolved microscopy and luminescent sensors due to the “antenna effect” of the ligands (6–8). Lanthanide coordination polymers have been explored to sense many species, such as CO23 , OH , HSO4 , H+, Ag+, Cu2+, Mg2+, Zn2+, acetone, halide ions, explosives, proteins, antibiotics and so on (9–15). Fe3+ is usually seen and can be detected by lanthanide MOFs (Ln-MOFs) microparticles or their suspension (16,17). Insoluble microsized lanthanide coordination polymers are usually not homogeneous in solutions (14), the detection study usually get into the trouble of nonuniform solutions, which result in unstable luminescence signal. Thus, a growing number of researches pay attention on coordination polymers thin films or coatings preparation (12,18). But these methods need expensive luminescent equipment, not suitable to use at the scene, these MOF films and coatings cannot satisfy all the application in industry or sensing
MATERIALS AND METHODS Chemicals and materials. Tb(NO3)36H2O was prepared by dissolving 99.9% Tb4O7 in concentrated HNO3 (68%) and then evaporated at 100°C until the crystal film formed. 4-methyl salicylic acid (99%) and agarose powder were purchased from Aladdin Company (Shanghai, China). NaOH was purchased from Guangzhou Chemical Reagent Factory (Guangzhou, China). Other chemicals (A.R) were commercially available and used without further purification. Physical measurements. Luminescence spectra were recorded using an RF-5301PC spectrofluorophotometer at room temperature, excited at 341 nm. PXRD spectra were obtained by a D-MAX 2200VPC diffractometer with Cu Ka radiation. The morphologies of samples were evaluated with a Quanta 400F thermal field emission environmental scanning electron microscope. Portable 365 nm UV light is made by Gongyi Instrument Company. Inductive coupled plasma (ICP) atomic emission spectrometric analysis was also measured (POEMS, TJA). Preparation of coordination polymer 1. The procedure of preparing coordination polymer 1 is similar to our previous reported basophilic method (29). In a 100 mL beaker, 0.235 g (1.5 mmol) H2L1 and 20 mL H2O were mixed, and adjusted to pH = 12 with 0.1 M NaOH, then the solution mixed with 40 mL water solution of Tb(NO3)36H2O (nL:
*Corresponding authors’ e-mails: [email protected] (Cheng-Hui Zeng) and [email protected] (Shengliang Zhong) © 2015 The American Society of Photobiology
814
Photochemistry and Photobiology, 2015, 91
815
Figure 1. Soft hybrid membrane in the gel tray. Figure 2. IR spectra of hybrid membrane, agarose and 1. nM = 3: 1) and stirred for 10 min. The resulting mixture was transferred into a 50 mL Teflon-lined stainless-steel autoclave and heated at 80°C for 48 h. After cooling to room temperature, crystals were obtained by filtration, washed with 4 mL water three times and dried at 60°C. Anal. Calcd (%): C, 40.18; H, 3.162. Found (%): C, 39.72; H, 3.197. FT-IR (KBr pellet, cm 1): 3151 (s), 1637 (m), 1612 (m), 1577 (m), 1561 (m), 1532 (m), 1495 (s), 1446 (s), 1382 (m), 1257 (m), 1247 (m), 1221 (m), 1167 (m), 861 (m), 792 (m). Preparation of hybrid membrane. About 0.10 g of agarose powder was dispersed into 5 mL H2O, heated in a water bath at 90°C, after the agarose powder was dissolved; 9.0 mg grinded 1 was dispersed in 1 mL DMF, and then mixed with agarose solution under strong magnetic stirring for 20 min. The mixture was poured into a 12 9 12 cm gel tray, stayed for 1 h at room temperature to form a soft membrane (Fig. 1).
RESULTS AND DISCUSSION Characterization The phase purity of powder 1 was characterized by PXRD, Fig. S1 shows the peaks of the experimental results corresponding well with the simulated results of single crystal structure 1 (29), which proves that the powder has the same structure as 1. In order to characterize the membrane, it was dried up in an oven at 60°C. Figure 2 shows the IR spectrum of agarose, hybrid material and coordination polymer 1. It can be seen that the spectrum of hybrid material is very similar to agarose, with very small difference of several nm of the peaks, but it is different from 1. This confirms that there is no obvious chemical bonds formed between 1 and agarose, and implies 1 is encompassed into the agarose, with weak interactions of hydrogen bond and Van der Waals force between 1 and agarose, which induces small change in the IR peaks. ICP atomic emission spectrometric analysis show the content of Tb3+ is 2.61%, which is consistent with the theoretical value of 2.75%. SEM in Fig. 3 shows the membrane is smooth, the cracking is induced during the desiccation process. Luminescence of the soft hybrid material was measured at the best excitation of 341 nm, it shows characteristic emission band at 489, 545, 586 and 622 nm, which corresponds to the transitions of 5D4–7F6, 5D4–7F5, 5D4–7F4 and 5D4–7F3, respectively (31).
Figure 3. SEM of the dehydrated hybrid membrane.
Sensor Before the sensing experiment was processed, the chunk soft membrane was cut into small blocks of 1 9 1 cm. Very interestingly; we found that the small block membrane and solution became fuchsia, after the small membrane reacted with 10 mL 10 6 M Fe3+ water solution for 2 h (Fig. 4). Other 18 metal (M) ion solutions (M(NO3)X or MClX, M = Mg2+, Li+, Ca2+, Zn2+, Cu2+, Ba2+, Mn2+, Ru3+, Cr3+, Ag+, Sr2+, Cd2+, Na+, Ni2+, Pb2+, Fe2+, Hg2+ and Ca2+) and the membranes had no obvious colour change from the eye sight (Fig. 4), after reacted for 2 h. Then small membranes were irradiated by a portable 365 nm UV light, only the membrane react with Fe3+ did not show green luminescence (Fig. 5) from eye sight. This is another convenient mode to distinguish the sensing result to Fe3+, because small UV light is portable. The luminescence test on a sophisticated RF-5301PC (at the best excitation of 341 nm) further proved the results of visualization. Overlay plot depicting luminescence spectra in Fig.
816
Kai Zheng et al.
Figure 4. The color changes of membrane (top) and metal ion water solutions (bottom) in daylight, after they reacted for 2 h.
Figure 7. LOD for sensing Fe3+, with the signal of luminescence decrease three times to the noise (MS/N = 3).
Figure 5. The picture of soft gel immersed in different metal ions for 2 h, and then excited by a portable 365 nm UV light.
Figure 8. Sensing results of the hybrid membrane to 1 lM BO3 , CO23 , H2 PO4 , Br , Cl , ClO4 , H2 PO4 , I , IO3 and NO3 .
Figure 6. Histogram of the luminescence at 544 nm of the membrane, when sensing metal ions.
S2 proves that only Fe3+ quenched Tb3+ centered luminescence of the soft membrane, the histogram show more apparently the sensing result (Fig. 6). The limit of detection (LOD) for Fe3+ was 0.1 lM, with the luminescence decrease three times to the noise (MS/N = 3) after reacting for 2 h (Fig. 7), this is lower than the LOD for Fe3+ reported by Dang(17), and a little lower than the LOD value of 3.3 9 10 7 M for Fe3+ which reported by prof. Zhou (16). The luminescence of the reaction solution would not recover even large quantity of EDTA was added, which indi-
cated the sensing is irreversible. The result show the membrane reached the maximum quenching efficiency after 2 h, this may due to the slow permeation of Fe3+ into the membrane, because the membrane is as thick as 0.4 mm. In order to investigate whether the anions would disturb the sensing effect of Fe3+, 1 lM KBrO3, K2CO3, KH2PO4, KBr, KCl, KClO4, KH2PO4, KI, KIO3 and KNO3 water solutions were selected to react with the small soft membrane. The luminescence at 545 nm shows the anions of BO3 , CO23 , H2 PO4 , Br , Cl , ClO4 , H2 PO4 , I , IO3 and NO3 had nearly no quenching effect to the Tb3+ centered luminescence (Fig. 8), the results eliminated the doubt whether the anions would disturb the Fe3+ sensing in water, because these anions usually exist in water. Furthermore, the results demonstrate that the membrane is a highly selective sensor to Fe3+. More importantly, Fig. 9 shows the normalized luminescence intensity has excellent linear relationship with the concentration of Fe3+ in the range of 0.1–2.1 lM, they fit a linear formula of
Photochemistry and Photobiology, 2015, 91
817
methyl salicylic acid, considering the similarity structures of 4methyl salicylic acid and salicylic acid, and salicylic acid has a very high binding constant with Fe3+, of the order of 1036 (32). Further study shows the upward two reaction solutions have similar absorption spectra and the same absorption peak is 299 nm (Fig. 10), which imply the sensing mechanism is due to the decomposition of 1 which induced by Fe3+ permeating into the membrane slowly.
CONCLUSIONS
Figure 9. Linear relationship of normalized luminescence of membrane and Fe3+ concentration, in the range of 0.1–2.1 lM.
A new hybrid membrane was prepared by a facile method, based on a highly luminescent lanthanide coordination polymer and agarose. Soft membrane was characterized by FT-IR, SEM and luminescence. It was found that the soft membrane is a highly selective and sensitive Fe3+ sensor, among 19 metal ion solutions of Fe3+, Mg2+, Li+, Ca2+, Zn2+, Cu2+, Ba2+, Mn2+, Ru3+, Cr3+, Ag+, Sr2+, Cd2+, Na+, Ni2+, Pb2+, Fe2+, Hg2+ and Ca2+, only Fe3+ quench the luminescence of the membrane. The sensing results can be distinguished by the naked eye in daylight or under portable UV light, at the scene. Mechanism study reveal the sensing is due to the decomposition of the coordination polymer which induced by the slow permeation of Fe3+, which due to the high binding constant of Fe3+ and 4-methyl salicylic acid. Further studies found anions of BO3 , CO23 , H2 PO4 , Br , Cl , ClO4 , H2 PO4 , I , IO3 and NO3 would not disturb the detection result. The sensing experiment was operated in water, which makes the membrane more applicable to environmental monitoring and biosensing. Acknowledgements—The authors acknowledge the financial support of Jiangxi Normal University (5616) and NSFC (21201089, 21261010).
SUPPORTING INFORMATION
Figure 10. UV-vis of solution for membrane reacted with Fe3+ and deprotonated ligand.
Y = 1.0000 0.5032X (X represents the concentration of Fe3+ and Y represents normalized luminescence intensity). It implies that we can determine the Fe3+ concentration in this range by measuring the luminescence, since the R2 value of the formula is as large as 0.9815. Besides, it was found that the luminescence of membrane decreased with the time regularly, when reacting with 1 lM Fe3+ (Fig. S3). Possible mechanism To elucidate the possible mechanism for the sensing effect to Fe3+ of membrane, powder 1 was added into Fe3+ water solution. It was found that the powder was dissolved quickly and the solution became fuchsia, the similar color as the above reaction solution of Fe3+ and hybrid membrane. This inferred the sensing mechanism may due to the high binding constant of Fe3+ with 4-
Additional Supporting Information may be found in the online version of this article: Figure S1. PXRD of powder 1 and simulated results. Figure S2. Overlay plot depicting luminescence spectra of hybrid membrane after reacting with different M ions, from inside to outside are in contrast, Mg2+, Li+, Ca2+, Zn2+, Cu2+, Ba2+, Mn2+, Ru3+, Cr3+, Ag+, Sr2+, Cd2+, Na+, Ni2+, Pb2+, Fe2+, Hg2+, Ca2+ and Fe3+ (red line), respectively. Figure S3. Luminescence change in the hybrid membrane with time at 545 nm, when reacting with 1 lM Fe3+.
REFERENCES 1. Armelao, L., S. Quici, F. Barigelletti, G. Accorsi, G. Bottaro, M. Cavazzini and E. Tondello (2010) Design of luminescent lanthanide complexes: from molecules to highly efficient photo-emitting materials. Coord. Chem. Rev. 254, 487–505. 2. Yu, J., Y. Cui, H. Xu, Y. Yang, Z. Wang, B. Chen and G. Qian (2013) Confinement of pyridinium hemicyanine dye within an anionic metal-organic framework for two-photon-pumped lasing. Nat. Commun. 4, 2719. 3. Xu, H., R. Chen, Q. Sun, W. Lai, Q. Su, W. Huang and X. Liu (2014) Recent progress in metal-organic complexes for optoelectronic applications. Chem. Soc. Rev. 43, 3259–3302.
818
Kai Zheng et al.
4. Sun, L., X. Ge, J. Liu, Y. Qiu, Z. Wei, B. Tian and L. Shi (2014) Multifunctional nanomesoporous materials with upconversion (in vivo) and downconversion (in vitro) luminescence imaging based on mesoporous capping UCNPs and linking lanthanide complexes. Nanoscale 6, 13242–13252. 5. Zhou, J., Z. Liu and F. Li (2012) Upconversion nanophosphors for small-animal imaging. Chem. Soc. Rev. 41, 1323–1349. 6. Wang, Y. and H. Li (2014) Luminescent materials of zeolite functionalized with lanthanides. CrystEngComm 16, 9764–9778. 7. Leonard, J. P., C. M. G. dos Santos, S. E. Plush, T. McCabe and T. Gunnlaugsson (2007) pH driven self-assembly of a ternary lanthanide luminescence complex: the sensing of anions using a [small beta]-diketonate-Eu(iii) displacement assay. Chem. Commun., 129– 131. 8. Gunnlaugsson, T. and J. P. Leonard (2005) Lanthanide luminescent switches: modulation of the luminescence of bis-macrocyclic based Tb(iii) conjugates in water by H+, Na+ and K+. Dalton Trans., 3204–3212. 9. Chen, B., S. Xiang and G. Qian (2010) Metal-organic frameworks with functional pores for recognition of small molecules. Acc. Chem. Res. 43, 1115–1124. 10. Zhao, L., Y. Liu, C. He, J. Wang and C. Duan (2014) Coordinationdriven nanosized lanthanide ‘Molecular Lanterns’ as luminescent chemosensors for the selective sensing of magnesium ions. Dalton Trans. 43, 335–343. 11. Wong, K. L., G. L. Law, Y. Y. Yang and W. T. Wong (2006) A highly porous luminescent terbium-organic framework for reversible anion sensing. Adv. Mater. 18, 1051–1054. 12. Bo, Q.-B., H.-T. Zhang, H.-Y. Wang, J.-L. Miao and Z.-W. Zhang (2014) Anhydrous lanthanide MOFs and direct photoluminescent sensing for polyoxometalates in aqueous solution. Chem. Eur. J. 20, 3712–3723. 13. Butler, S. J. and D. Parker (2013) Anion binding in water at lanthanide centres: from structure and selectivity to signalling and sensing. Chem. Soc. Rev. 42, 1652–1666. 14. Liu, Y., M. Chen, T. Cao, Y. Sun, C. Li, Q. Liu, T. Yang, L. Yao, W. Feng and F. Li (2013) A cyanine-modified nanosystem for in vivo upconversion luminescence bioimaging of methylmercury. J. Am. Chem. Soc. 135, 9869–9876. 15. Zhou, Z., Q. Wang, J. Lin, Y. Chen and C. Yang (2012) Nucleophilic addition-triggered lanthanide luminescence allows detection of amines by Eu(thenoyltrifluoroacetone)3. Photochem. Photobiol. 88, 840–843. 16. Zhou, X.-H., L. Li, H.-H. Li, A. Li, T. Yang and W. Huang (2013) A flexible Eu(iii)-based metal-organic framework: turn-off luminescent sensor for the detection of Fe(iii) and picric acid. Dalton Trans. 42, 12403–12409. 17. Dang, S., E. Ma, Z.-M. Sun and H. Zhang (2012) A layer-structured Eu-MOF as a highly selective fluorescent probe for Fe3 + detection through a cation-exchange approach. J. Mater. Chem. 22, 16920– 16926. 18. Bradberry, S. J., A. J. Savyasachi, M. Martinez-Calvo and T. Gunnlaugsson (2014) Development of responsive visibly and NIR lumines-
19. 20. 21. 22.
23.
24. 25.
26.
27.
28.
29.
30.
31. 32.
cent and supramolecular coordination self-assemblies using lanthanide ion directed synthesis. Coord. Chem. Rev. 273, 226–241. Zamora-Mora, V., D. Velasco, R. Hernandez, C. Mijangos and E. Kumacheva (2014) Chitosan/agarose hydrogels: cooperative properties and microfluidic preparation. Carbohydr. Polym. 111, 348–355. Zhou, Z., Y. Zheng and Q. Wang (2014) Extension of novel lanthanide luminescent mesoporous nanostructures to detect fluoride. Inorg. Chem. 53, 1530–1536. Saha, S., S. Chanda, A. Dutta and T. P. Sinha (2014) Dielectric relaxation and phonon modes of NdCrO3 nanostructure. J. Sol-Gel. Sci. Technol. 69, 553–563. Motorina, A., O. Tananaiko, I. Kozytska, V. Raks, R. Badia, M. E. Diaz-Garcia and V. N. Zaitsev (2014) Hybrid silica-polyelectrolyte films as optical sensing materials for tetracycline antibiotics. Sens. Actuators. Chem. 200, 198–205. Cao, B. S., J. L. Wu, Z. Q. Feng and B. Dong (2013) Investigation of near-infrared-to-ultraviolet upconversion luminescence of Tm3+ doped NaYF4 phosphors by Yb3+ codoping. Mater. Chem. Phys. 142, 333–338. Xu, H., F. Liu, Y. Cui, B. Chen and G. Qian (2011) A luminescent nanoscale metal-organic framework for sensing of nitroaromatic explosives. Chem. Commun. 47, 3153–3155. Zhu, Y.-M., C.-H. Zeng, T.-S. Chu, H.-M. Wang, Y.-Y. Yang, Y.X. Tong, C.-Y. Su and W.-T. Wong (2013) A novel highly luminescent LnMOF film: a convenient sensor for Hg2 + detecting. J. Mater. Chem. A 1, 11312–11319. Zeng, C.-H., J.-L. Wang, Y.-Y. Yang, T.-S. Chu, S.-L. Zhong, S. W. Ng and W.-T. Wong (2014) Lanthanide CPs: the guest-tunable drastic changes of luminescent quantum yields, and two photon luminescence. J. Mater. Chem. C 2, 2235–2242. Nie, Z.-W., S.-S. Li, C.-H. Zeng, L. Wang, Y. Li, S.-G. Yin and S.L. Zhong (2014) Hetero-metallic lanthanide CPs involving sodium: synthesis, crystal structure, and luminescence properties. Z. Anorg. Allg. Chem. 640, 2255–2260. Wang, H.-M., Y.-Y. Yang, C.-H. Zeng, T.-S. Chu, Y.-M. Zhu and S. W. Ng (2013) A highly luminescent terbium-organic framework for reversible detection of mercury ions in aqueous solution. Photochem. Photobiol. Sci. 12, 1700–1706. Zeng, C.-H., F.-L. Zhao, Y.-Y. Yang, M.-Y. Xie, X.-M. Ding, D.-J. Hou and S. W. Ng (2013) Unusual method for phenolic hydroxyl bridged lanthanide CPs: syntheses, characterization, one and two photon luminescence. Dalton Trans. 42, 2052–2061. Zeng, C.-H., Y.-Y. Yang, Y.-M. Zhu, H.-M. Wang, T.-S. Chu and S. W. Ng (2012) A new luminescent terbium 4-methylsalicylate complex as a novel sensor for detecting the purity of methanol. Photochem. Photobiol. 88, 860–866. Li, Q.-P. and B. Yan (2014) Photophysical properties of lanthanide (Eu3+, Tb3+) Hybrid soft gels of double functional linker of ionic liquid-modified silane. Photochem. Photobiol. 90, 22–28. Ogawa, K. and N. Tobe (1966) A spectrophotometric study of the complex formation between Iron(III) and salicylic acid. Bull. Chem. Soc. Jpn. 39, 227–232.
Hybrid Membrane of Agarose and Lanthanide Coordination Polymer: a Selective and Sensitive Fe3+ Sensor Kai Zheng, Kai-Li Lou, Cheng-Hui Zeng*, Sha-Sha Li, Zhi-Wen Nie and Shengliang Zhong* Key Laboratory of Functional Small Organic Molecule, Ministry of Education and Jiangxi’s Key Laboratory of Green Chemistry, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, P. R. China Received 29 January 2015, accepted 14 April 2015, DOI: 10.1111/php.12460
usage. So the new strategy of making portable soft film should be devoted to satisfy more applications. The agarose membrane is convenient to take along, very appropriate to perform at outdoors, it is a kind of environmental friendly and biocompatible material, and the agarose is very cheap and easy to get (19). To the best of our knowledge, detecting species with the hybrid device of agarose and lanthanide coordination polymers was not reported, though many hybrids of lanthanide sol–gel were prepared and applied in sensing (20–23). Another disregarded point is that many sensing experiments were processed in organic solvents (24,25), but not in water, this is not applicable in environment monitoring and biosensing. Inspired by the aforementioned considerations and based on our previous work on lanthanide complexes (25–30), herein, a highly luminescent coordination polymer ([Tb(HL1)L1H2O]n (1, H2L1 = 4-methyl salicylic acid) (29), was adopted to hybrid with agarose. The membrane was characterized by Fourier transform infrared (FT-IR), powder X-ray diffraction (PXRD), scanning electron microscope (SEM) and luminescence. Ligand in 1 has two coordination groups of carboxyl and hydroxyl, might show excellent sensing properties. Therefore, a new and convenient strategy for fabricating durable thin film of hybrid material which contains 1 and agarose was developed. The sensing properties show it had highly selective and sensitive detecting effect to Fe3+ in water, which can be distinguished by visualization in daylight or irradiated by portable small UV light at the scene.
ABSTRACT A new hybrid membrane was prepared by a facile method based on a highly luminescent lanthanide coordination polymer and agarose. The soft membrane was characterized by FT-IR, PXRD, SEM and luminescence. It is found that the soft membrane is a highly selective and sensitive sensor, among 19 metal ion solutions of Fe3+, Mg2+, Li+, Ca2+, Zn2+, Cu2+, Ba2+, Mn2+, Ru3+, Cr3+, Ag+, Sr2+, Cd2+, Na+, Ni2+, Pb2+, Fe2+, Hg2+ and Ca2+, only Fe3+ quench the luminescence. The sensing results can be distinguished by the naked eye in daylight or by irradiation of a portable UV light at the scene. Mechanism studies reveal the sensing is due to the decomposition of the coordination polymer 1 which induced by slow permeation of Fe3+. Further studies found anions of BO3 , CO23 , H2 PO4 , Br , Cl , ClO4 , H2 PO4 , I , IO3 and NO3 will not quench the luminescence of the hybrid membrane, which imply that other anions in water would not disturb the detection result.
INTRODUCTION Lanthanide coordination polymers are very promising materials for their wide applications in the areas of optics, catalysis, magnetism and electrophysics because of their unique structures and properties (1,2). As optical materials, they have attracted increasing attention in up conversion emission (3–5), time-resolved microscopy and luminescent sensors due to the “antenna effect” of the ligands (6–8). Lanthanide coordination polymers have been explored to sense many species, such as CO23 , OH , HSO4 , H+, Ag+, Cu2+, Mg2+, Zn2+, acetone, halide ions, explosives, proteins, antibiotics and so on (9–15). Fe3+ is usually seen and can be detected by lanthanide MOFs (Ln-MOFs) microparticles or their suspension (16,17). Insoluble microsized lanthanide coordination polymers are usually not homogeneous in solutions (14), the detection study usually get into the trouble of nonuniform solutions, which result in unstable luminescence signal. Thus, a growing number of researches pay attention on coordination polymers thin films or coatings preparation (12,18). But these methods need expensive luminescent equipment, not suitable to use at the scene, these MOF films and coatings cannot satisfy all the application in industry or sensing
MATERIALS AND METHODS Chemicals and materials. Tb(NO3)36H2O was prepared by dissolving 99.9% Tb4O7 in concentrated HNO3 (68%) and then evaporated at 100°C until the crystal film formed. 4-methyl salicylic acid (99%) and agarose powder were purchased from Aladdin Company (Shanghai, China). NaOH was purchased from Guangzhou Chemical Reagent Factory (Guangzhou, China). Other chemicals (A.R) were commercially available and used without further purification. Physical measurements. Luminescence spectra were recorded using an RF-5301PC spectrofluorophotometer at room temperature, excited at 341 nm. PXRD spectra were obtained by a D-MAX 2200VPC diffractometer with Cu Ka radiation. The morphologies of samples were evaluated with a Quanta 400F thermal field emission environmental scanning electron microscope. Portable 365 nm UV light is made by Gongyi Instrument Company. Inductive coupled plasma (ICP) atomic emission spectrometric analysis was also measured (POEMS, TJA). Preparation of coordination polymer 1. The procedure of preparing coordination polymer 1 is similar to our previous reported basophilic method (29). In a 100 mL beaker, 0.235 g (1.5 mmol) H2L1 and 20 mL H2O were mixed, and adjusted to pH = 12 with 0.1 M NaOH, then the solution mixed with 40 mL water solution of Tb(NO3)36H2O (nL:
*Corresponding authors’ e-mails: [email protected] (Cheng-Hui Zeng) and [email protected] (Shengliang Zhong) © 2015 The American Society of Photobiology
814
Photochemistry and Photobiology, 2015, 91
815
Figure 1. Soft hybrid membrane in the gel tray. Figure 2. IR spectra of hybrid membrane, agarose and 1. nM = 3: 1) and stirred for 10 min. The resulting mixture was transferred into a 50 mL Teflon-lined stainless-steel autoclave and heated at 80°C for 48 h. After cooling to room temperature, crystals were obtained by filtration, washed with 4 mL water three times and dried at 60°C. Anal. Calcd (%): C, 40.18; H, 3.162. Found (%): C, 39.72; H, 3.197. FT-IR (KBr pellet, cm 1): 3151 (s), 1637 (m), 1612 (m), 1577 (m), 1561 (m), 1532 (m), 1495 (s), 1446 (s), 1382 (m), 1257 (m), 1247 (m), 1221 (m), 1167 (m), 861 (m), 792 (m). Preparation of hybrid membrane. About 0.10 g of agarose powder was dispersed into 5 mL H2O, heated in a water bath at 90°C, after the agarose powder was dissolved; 9.0 mg grinded 1 was dispersed in 1 mL DMF, and then mixed with agarose solution under strong magnetic stirring for 20 min. The mixture was poured into a 12 9 12 cm gel tray, stayed for 1 h at room temperature to form a soft membrane (Fig. 1).
RESULTS AND DISCUSSION Characterization The phase purity of powder 1 was characterized by PXRD, Fig. S1 shows the peaks of the experimental results corresponding well with the simulated results of single crystal structure 1 (29), which proves that the powder has the same structure as 1. In order to characterize the membrane, it was dried up in an oven at 60°C. Figure 2 shows the IR spectrum of agarose, hybrid material and coordination polymer 1. It can be seen that the spectrum of hybrid material is very similar to agarose, with very small difference of several nm of the peaks, but it is different from 1. This confirms that there is no obvious chemical bonds formed between 1 and agarose, and implies 1 is encompassed into the agarose, with weak interactions of hydrogen bond and Van der Waals force between 1 and agarose, which induces small change in the IR peaks. ICP atomic emission spectrometric analysis show the content of Tb3+ is 2.61%, which is consistent with the theoretical value of 2.75%. SEM in Fig. 3 shows the membrane is smooth, the cracking is induced during the desiccation process. Luminescence of the soft hybrid material was measured at the best excitation of 341 nm, it shows characteristic emission band at 489, 545, 586 and 622 nm, which corresponds to the transitions of 5D4–7F6, 5D4–7F5, 5D4–7F4 and 5D4–7F3, respectively (31).
Figure 3. SEM of the dehydrated hybrid membrane.
Sensor Before the sensing experiment was processed, the chunk soft membrane was cut into small blocks of 1 9 1 cm. Very interestingly; we found that the small block membrane and solution became fuchsia, after the small membrane reacted with 10 mL 10 6 M Fe3+ water solution for 2 h (Fig. 4). Other 18 metal (M) ion solutions (M(NO3)X or MClX, M = Mg2+, Li+, Ca2+, Zn2+, Cu2+, Ba2+, Mn2+, Ru3+, Cr3+, Ag+, Sr2+, Cd2+, Na+, Ni2+, Pb2+, Fe2+, Hg2+ and Ca2+) and the membranes had no obvious colour change from the eye sight (Fig. 4), after reacted for 2 h. Then small membranes were irradiated by a portable 365 nm UV light, only the membrane react with Fe3+ did not show green luminescence (Fig. 5) from eye sight. This is another convenient mode to distinguish the sensing result to Fe3+, because small UV light is portable. The luminescence test on a sophisticated RF-5301PC (at the best excitation of 341 nm) further proved the results of visualization. Overlay plot depicting luminescence spectra in Fig.
816
Kai Zheng et al.
Figure 4. The color changes of membrane (top) and metal ion water solutions (bottom) in daylight, after they reacted for 2 h.
Figure 7. LOD for sensing Fe3+, with the signal of luminescence decrease three times to the noise (MS/N = 3).
Figure 5. The picture of soft gel immersed in different metal ions for 2 h, and then excited by a portable 365 nm UV light.
Figure 8. Sensing results of the hybrid membrane to 1 lM BO3 , CO23 , H2 PO4 , Br , Cl , ClO4 , H2 PO4 , I , IO3 and NO3 .
Figure 6. Histogram of the luminescence at 544 nm of the membrane, when sensing metal ions.
S2 proves that only Fe3+ quenched Tb3+ centered luminescence of the soft membrane, the histogram show more apparently the sensing result (Fig. 6). The limit of detection (LOD) for Fe3+ was 0.1 lM, with the luminescence decrease three times to the noise (MS/N = 3) after reacting for 2 h (Fig. 7), this is lower than the LOD for Fe3+ reported by Dang(17), and a little lower than the LOD value of 3.3 9 10 7 M for Fe3+ which reported by prof. Zhou (16). The luminescence of the reaction solution would not recover even large quantity of EDTA was added, which indi-
cated the sensing is irreversible. The result show the membrane reached the maximum quenching efficiency after 2 h, this may due to the slow permeation of Fe3+ into the membrane, because the membrane is as thick as 0.4 mm. In order to investigate whether the anions would disturb the sensing effect of Fe3+, 1 lM KBrO3, K2CO3, KH2PO4, KBr, KCl, KClO4, KH2PO4, KI, KIO3 and KNO3 water solutions were selected to react with the small soft membrane. The luminescence at 545 nm shows the anions of BO3 , CO23 , H2 PO4 , Br , Cl , ClO4 , H2 PO4 , I , IO3 and NO3 had nearly no quenching effect to the Tb3+ centered luminescence (Fig. 8), the results eliminated the doubt whether the anions would disturb the Fe3+ sensing in water, because these anions usually exist in water. Furthermore, the results demonstrate that the membrane is a highly selective sensor to Fe3+. More importantly, Fig. 9 shows the normalized luminescence intensity has excellent linear relationship with the concentration of Fe3+ in the range of 0.1–2.1 lM, they fit a linear formula of
Photochemistry and Photobiology, 2015, 91
817
methyl salicylic acid, considering the similarity structures of 4methyl salicylic acid and salicylic acid, and salicylic acid has a very high binding constant with Fe3+, of the order of 1036 (32). Further study shows the upward two reaction solutions have similar absorption spectra and the same absorption peak is 299 nm (Fig. 10), which imply the sensing mechanism is due to the decomposition of 1 which induced by Fe3+ permeating into the membrane slowly.
CONCLUSIONS
Figure 9. Linear relationship of normalized luminescence of membrane and Fe3+ concentration, in the range of 0.1–2.1 lM.
A new hybrid membrane was prepared by a facile method, based on a highly luminescent lanthanide coordination polymer and agarose. Soft membrane was characterized by FT-IR, SEM and luminescence. It was found that the soft membrane is a highly selective and sensitive Fe3+ sensor, among 19 metal ion solutions of Fe3+, Mg2+, Li+, Ca2+, Zn2+, Cu2+, Ba2+, Mn2+, Ru3+, Cr3+, Ag+, Sr2+, Cd2+, Na+, Ni2+, Pb2+, Fe2+, Hg2+ and Ca2+, only Fe3+ quench the luminescence of the membrane. The sensing results can be distinguished by the naked eye in daylight or under portable UV light, at the scene. Mechanism study reveal the sensing is due to the decomposition of the coordination polymer which induced by the slow permeation of Fe3+, which due to the high binding constant of Fe3+ and 4-methyl salicylic acid. Further studies found anions of BO3 , CO23 , H2 PO4 , Br , Cl , ClO4 , H2 PO4 , I , IO3 and NO3 would not disturb the detection result. The sensing experiment was operated in water, which makes the membrane more applicable to environmental monitoring and biosensing. Acknowledgements—The authors acknowledge the financial support of Jiangxi Normal University (5616) and NSFC (21201089, 21261010).
SUPPORTING INFORMATION
Figure 10. UV-vis of solution for membrane reacted with Fe3+ and deprotonated ligand.
Y = 1.0000 0.5032X (X represents the concentration of Fe3+ and Y represents normalized luminescence intensity). It implies that we can determine the Fe3+ concentration in this range by measuring the luminescence, since the R2 value of the formula is as large as 0.9815. Besides, it was found that the luminescence of membrane decreased with the time regularly, when reacting with 1 lM Fe3+ (Fig. S3). Possible mechanism To elucidate the possible mechanism for the sensing effect to Fe3+ of membrane, powder 1 was added into Fe3+ water solution. It was found that the powder was dissolved quickly and the solution became fuchsia, the similar color as the above reaction solution of Fe3+ and hybrid membrane. This inferred the sensing mechanism may due to the high binding constant of Fe3+ with 4-
Additional Supporting Information may be found in the online version of this article: Figure S1. PXRD of powder 1 and simulated results. Figure S2. Overlay plot depicting luminescence spectra of hybrid membrane after reacting with different M ions, from inside to outside are in contrast, Mg2+, Li+, Ca2+, Zn2+, Cu2+, Ba2+, Mn2+, Ru3+, Cr3+, Ag+, Sr2+, Cd2+, Na+, Ni2+, Pb2+, Fe2+, Hg2+, Ca2+ and Fe3+ (red line), respectively. Figure S3. Luminescence change in the hybrid membrane with time at 545 nm, when reacting with 1 lM Fe3+.
REFERENCES 1. Armelao, L., S. Quici, F. Barigelletti, G. Accorsi, G. Bottaro, M. Cavazzini and E. Tondello (2010) Design of luminescent lanthanide complexes: from molecules to highly efficient photo-emitting materials. Coord. Chem. Rev. 254, 487–505. 2. Yu, J., Y. Cui, H. Xu, Y. Yang, Z. Wang, B. Chen and G. Qian (2013) Confinement of pyridinium hemicyanine dye within an anionic metal-organic framework for two-photon-pumped lasing. Nat. Commun. 4, 2719. 3. Xu, H., R. Chen, Q. Sun, W. Lai, Q. Su, W. Huang and X. Liu (2014) Recent progress in metal-organic complexes for optoelectronic applications. Chem. Soc. Rev. 43, 3259–3302.
818
Kai Zheng et al.
4. Sun, L., X. Ge, J. Liu, Y. Qiu, Z. Wei, B. Tian and L. Shi (2014) Multifunctional nanomesoporous materials with upconversion (in vivo) and downconversion (in vitro) luminescence imaging based on mesoporous capping UCNPs and linking lanthanide complexes. Nanoscale 6, 13242–13252. 5. Zhou, J., Z. Liu and F. Li (2012) Upconversion nanophosphors for small-animal imaging. Chem. Soc. Rev. 41, 1323–1349. 6. Wang, Y. and H. Li (2014) Luminescent materials of zeolite functionalized with lanthanides. CrystEngComm 16, 9764–9778. 7. Leonard, J. P., C. M. G. dos Santos, S. E. Plush, T. McCabe and T. Gunnlaugsson (2007) pH driven self-assembly of a ternary lanthanide luminescence complex: the sensing of anions using a [small beta]-diketonate-Eu(iii) displacement assay. Chem. Commun., 129– 131. 8. Gunnlaugsson, T. and J. P. Leonard (2005) Lanthanide luminescent switches: modulation of the luminescence of bis-macrocyclic based Tb(iii) conjugates in water by H+, Na+ and K+. Dalton Trans., 3204–3212. 9. Chen, B., S. Xiang and G. Qian (2010) Metal-organic frameworks with functional pores for recognition of small molecules. Acc. Chem. Res. 43, 1115–1124. 10. Zhao, L., Y. Liu, C. He, J. Wang and C. Duan (2014) Coordinationdriven nanosized lanthanide ‘Molecular Lanterns’ as luminescent chemosensors for the selective sensing of magnesium ions. Dalton Trans. 43, 335–343. 11. Wong, K. L., G. L. Law, Y. Y. Yang and W. T. Wong (2006) A highly porous luminescent terbium-organic framework for reversible anion sensing. Adv. Mater. 18, 1051–1054. 12. Bo, Q.-B., H.-T. Zhang, H.-Y. Wang, J.-L. Miao and Z.-W. Zhang (2014) Anhydrous lanthanide MOFs and direct photoluminescent sensing for polyoxometalates in aqueous solution. Chem. Eur. J. 20, 3712–3723. 13. Butler, S. J. and D. Parker (2013) Anion binding in water at lanthanide centres: from structure and selectivity to signalling and sensing. Chem. Soc. Rev. 42, 1652–1666. 14. Liu, Y., M. Chen, T. Cao, Y. Sun, C. Li, Q. Liu, T. Yang, L. Yao, W. Feng and F. Li (2013) A cyanine-modified nanosystem for in vivo upconversion luminescence bioimaging of methylmercury. J. Am. Chem. Soc. 135, 9869–9876. 15. Zhou, Z., Q. Wang, J. Lin, Y. Chen and C. Yang (2012) Nucleophilic addition-triggered lanthanide luminescence allows detection of amines by Eu(thenoyltrifluoroacetone)3. Photochem. Photobiol. 88, 840–843. 16. Zhou, X.-H., L. Li, H.-H. Li, A. Li, T. Yang and W. Huang (2013) A flexible Eu(iii)-based metal-organic framework: turn-off luminescent sensor for the detection of Fe(iii) and picric acid. Dalton Trans. 42, 12403–12409. 17. Dang, S., E. Ma, Z.-M. Sun and H. Zhang (2012) A layer-structured Eu-MOF as a highly selective fluorescent probe for Fe3 + detection through a cation-exchange approach. J. Mater. Chem. 22, 16920– 16926. 18. Bradberry, S. J., A. J. Savyasachi, M. Martinez-Calvo and T. Gunnlaugsson (2014) Development of responsive visibly and NIR lumines-
19. 20. 21. 22.
23.
24. 25.
26.
27.
28.
29.
30.
31. 32.
cent and supramolecular coordination self-assemblies using lanthanide ion directed synthesis. Coord. Chem. Rev. 273, 226–241. Zamora-Mora, V., D. Velasco, R. Hernandez, C. Mijangos and E. Kumacheva (2014) Chitosan/agarose hydrogels: cooperative properties and microfluidic preparation. Carbohydr. Polym. 111, 348–355. Zhou, Z., Y. Zheng and Q. Wang (2014) Extension of novel lanthanide luminescent mesoporous nanostructures to detect fluoride. Inorg. Chem. 53, 1530–1536. Saha, S., S. Chanda, A. Dutta and T. P. Sinha (2014) Dielectric relaxation and phonon modes of NdCrO3 nanostructure. J. Sol-Gel. Sci. Technol. 69, 553–563. Motorina, A., O. Tananaiko, I. Kozytska, V. Raks, R. Badia, M. E. Diaz-Garcia and V. N. Zaitsev (2014) Hybrid silica-polyelectrolyte films as optical sensing materials for tetracycline antibiotics. Sens. Actuators. Chem. 200, 198–205. Cao, B. S., J. L. Wu, Z. Q. Feng and B. Dong (2013) Investigation of near-infrared-to-ultraviolet upconversion luminescence of Tm3+ doped NaYF4 phosphors by Yb3+ codoping. Mater. Chem. Phys. 142, 333–338. Xu, H., F. Liu, Y. Cui, B. Chen and G. Qian (2011) A luminescent nanoscale metal-organic framework for sensing of nitroaromatic explosives. Chem. Commun. 47, 3153–3155. Zhu, Y.-M., C.-H. Zeng, T.-S. Chu, H.-M. Wang, Y.-Y. Yang, Y.X. Tong, C.-Y. Su and W.-T. Wong (2013) A novel highly luminescent LnMOF film: a convenient sensor for Hg2 + detecting. J. Mater. Chem. A 1, 11312–11319. Zeng, C.-H., J.-L. Wang, Y.-Y. Yang, T.-S. Chu, S.-L. Zhong, S. W. Ng and W.-T. Wong (2014) Lanthanide CPs: the guest-tunable drastic changes of luminescent quantum yields, and two photon luminescence. J. Mater. Chem. C 2, 2235–2242. Nie, Z.-W., S.-S. Li, C.-H. Zeng, L. Wang, Y. Li, S.-G. Yin and S.L. Zhong (2014) Hetero-metallic lanthanide CPs involving sodium: synthesis, crystal structure, and luminescence properties. Z. Anorg. Allg. Chem. 640, 2255–2260. Wang, H.-M., Y.-Y. Yang, C.-H. Zeng, T.-S. Chu, Y.-M. Zhu and S. W. Ng (2013) A highly luminescent terbium-organic framework for reversible detection of mercury ions in aqueous solution. Photochem. Photobiol. Sci. 12, 1700–1706. Zeng, C.-H., F.-L. Zhao, Y.-Y. Yang, M.-Y. Xie, X.-M. Ding, D.-J. Hou and S. W. Ng (2013) Unusual method for phenolic hydroxyl bridged lanthanide CPs: syntheses, characterization, one and two photon luminescence. Dalton Trans. 42, 2052–2061. Zeng, C.-H., Y.-Y. Yang, Y.-M. Zhu, H.-M. Wang, T.-S. Chu and S. W. Ng (2012) A new luminescent terbium 4-methylsalicylate complex as a novel sensor for detecting the purity of methanol. Photochem. Photobiol. 88, 860–866. Li, Q.-P. and B. Yan (2014) Photophysical properties of lanthanide (Eu3+, Tb3+) Hybrid soft gels of double functional linker of ionic liquid-modified silane. Photochem. Photobiol. 90, 22–28. Ogawa, K. and N. Tobe (1966) A spectrophotometric study of the complex formation between Iron(III) and salicylic acid. Bull. Chem. Soc. Jpn. 39, 227–232.
