Selective recognition of Pr3 + based on fluorescence enhancement sensor

Materials Science and Engineering C 33 (2013) 4140–4143

Contents lists available at ScienceDirect

Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec

Selective recognition of Pr3 + based on fluorescence enhancement sensor M.R. Ganjali a,⁎, M. Hosseini b, A. Ghafarloo a, M. Khoobi c, F. Faridbod a, A. Shafiee c, P. Norouzi a a b c

Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran, Iran Department of life science engineering, Faculty of New Sciences & Technologies, University of Tehran, Tehran, Iran Department of Medicinal Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences, Tehran 14176, Iran

a r t i c l e

i n f o

Article history: Received 6 February 2013 Received in revised form 1 June 2013 Accepted 4 June 2013 Available online 13 June 2013 Keywords: Fluorescent sensor Praseodymium Enhancement Fluorescence

a b s t r a c t (E)-2-(1-(4-hydroxy-2-oxo-2H-chromen-3-yl)ethylidene)hydrazinecarbothioamide (L) has been used to detect trace amounts of praseodymium ion in acetonitrile–water solution (MeCN/H2O) by fluorescence spectroscopy. The fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to Pr3+ ions in MeCN/H2O (9/1:v/v) solution. The fluorescence enhancement of L is attributed to a 1:1 complex formation between L and Pr3+, which has been utilized as the basis for selective detection of Pr3+. The sensor can be applied to the quantification of praseodymium ion with a linear range of 1.6 × 10−7 to 1.0 × 10−5 M. The limit of detection was 8.3 × 10−8 M. The sensor exhibits high selectivity toward praseodymium ions in comparison with common metal ions. The proposed fluorescent sensor was successfully used for determination of Pr3+ in water samples. © 2013 Elsevier B.V. All rights reserved.

1. Introduction Difficulties in the quantity of determination of lanthanides result from the great chemical similarity of their ions [1,2]. Praseodymium is one of the rare chemicals that can be found in houses, in equipment such as color televisions, fluorescent lamps, energy-saving lamps and glasses. Praseodymium used as a core material for carbon arc lights is used by the motion picture industry. Praseodymium is dumped in the environment in many different places, mainly by petrol-producing industries. It can also enter the environment when household equipment is thrown away. Praseodymium will gradually accumulate in soils and water soils and this will eventually lead to increasing concentrations of Pr3+ in humans, animals and soil particles [3,4]. Available instrumental methods for this purpose including, flame photometry, atomic absorption spectrometry, electron microscope analysis and neutron activation analysis often suffer from such parameters as high cost, need for large size samples and inability for continuous monitoring [5]. Among the various detection techniques, fluorescent chemosensors, colorimetric and potentiometric sensors have been developed quickly for their simplicity and high sensitivity [6–20]. Fluorescent chemosensors are of great importance owing to their high sensitivity and low detection limit. Most literatures report use of fluorescence quenching as the readout mechanism for the sensor response. The greatest advantage of fluorescence enhancement sensors, in comparison with fluorescence quenching sensors, is the ease of measuring lowconcentration contrast relative to a “dark” background. This reduces the ⁎ Corresponding author. Tel.: +98 21 6112788. E-mail address: [email protected] (M.R. Ganjali). 0928-4931/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.msec.2013.06.005

likelihood of false positive signals and increases the sensitivity [21]. Consequently, there is an urgent need to develop new turn-on fluorescent sensors which can be advantageous. However, to the best of our knowledge, fluorescent sensors for Pr3+, especially with fluorescence enhancement technique, have not been reported. We have recently reported a number of highly selective and sensitive fluorescent sensors for some ions [22–28]. Present work; introduce a highly selective praseodymium sensor based on a novel fluorophore, for determination of Pr3+ ions over a wide concentration range. 2. Experimental 2.1. Reagents All Chemicals were of the reagent–grade from Fluka and Merck chemical companies. The nitrate and chloride salts of all cations used (all from Merck) were of the highest purity available and used without any further purification except for vacuum drying over P2O5. 2.2. Appararus TLC was conducted on silica gel 250 m, F254 plates. Melting points were measured on a Kofler hot stage apparatus and are uncorrected. The IR spectra were taken using Nicolet FT-IR Magna 550 spectrographs (KBr disks). 1H NMR spectra were recorded on a Bruker 500 MHz NMR instruments. The chemical shifts (d) and coupling constants (J) are expressed in parts per million and hertz, respectively. All fluorescence

M.R. Ganjali et al. / Materials Science and Engineering C 33 (2013) 4140–4143

4141

H2N

S

NH OH

O

OH

N

S H2N

N H

NH2

Me

EtOH, Reflux 1

O

O

O

O

L

Scheme 1. Synthesis of L.

measurements were carried out on a Perkin-Elmer LS50 luminescence spectrometer.

Cu2+, Zn2+, Ni2+, and other lanthanide ions tested except a slight changes in case of Sm3+ and Er3+ ions.

2.3. Fluorescence measurements

3.3. UV titration

A fluorimetric cell was filled with 3.0 mL fluorophore L (5.0 × 10−6 M) in MeCN/H2O) (9/1:v/v) solution. Then, an emission spectrum was taken from the solution. This solution was titrated with standardized praseodymium ion solution and the fluorescence intensity of the system was measured. The emission intensity, at an excitation wavelength of 330 nm, was measured. Spectral bandwidths of monochromators for excitation and emission were 5 nm. The fluorescence quantum yield was obtained by comparison of the integrated area of the emission spectrum and absorbance of the samples with the reference under the same excited wavelength. The concentration of the reference quinine sulfate (Ф = 0.54) in an aquoes solution was adjusted to match the absorbance of the test sample. The quantum yields were calculated with Eq. (1).

The cation binding properties were investigated by UV absorption and fluorescence spectroscopy. (Fig. 2) shows that the absorption band of L in the UV spectrum originally appears at 267, 279 and 305 nm in a solution of MeCN/H2O (9/1:v/v). As soon as Pr3+ ion was added at room temperature, there were two well-defined isosbestic points at 240 and 270 nm, respectively, indicating that a stable complex was present having a certain stoichiometric ratio between the receptor L and Pr3+ formed.

∫emissionsample Areference Asample ∫emission

ð1Þ

reference

3. Results and discussion 3.1. The procedure for the preparation of (E)-2-(1-(4-hydroxy-2-oxo2H-chromen-3-yl)ethylidene)hydrazinecarbothioamide (L) A new fluorophore L (Scheme 1) was synthesized as follow: To a mixture of 3-acetyl-4-hydroxycoumarin (2 mmol) and thiosemicarbazone (1.5 mmol) in ethanol (3 mL), catalytic amount of triethylamine (0.3 mL) was added in ambient temperature. Reaction mixture was refluxed for two hours. After completion of the reaction (which is monitored by TLC method) and formation of corresponding hydrazine, the mixture was cooled, and the resulting crude product was purified by crystallization from ethanol. The product was obtained as yellowish crystal. Mp = 194–196, 1H NMR (500 MHz, DMSO-d6):): 12.45 (br s, 1H, OH), 7.81 (d, J = 6.5, 1H, H5 coumarin), 7.63 (t, J = 6.5, 1H, H7 coumarin), 7.37–7.34 (m, 2H, H6,8 coumarin), 5.59 (s, 1H, NH), 2.07 (s, 3H, Me). IR ν max (KBr): 3549, 3473, 3413, 1697, 1616, 1561, 1308, 1102. The spectra of the characterization analysis have been provided as supplementary materials. 3.2. Preliminary studies To evaluate whether L could be used as a selective fluorescent chemosensor for praseodymium ion, the interaction of L (5 × 10−6 M) with a number of metal ions (5 × 10−4 M) was investigated spectrofluorometrically in MeCN/H2O (9/1:v/v) solution at 25.0 ± 0.1 °C. The resulting fluorescence intensities of L in presence of different metal ions are shown in Fig. 1. It can be clearly seen from Fig. 1, in case of Pr3+ ion a significant enhancement in the fluorescence intensity of L was observed. No significant fluorescence change were observed when

Fluorescence properties of L (5.0 × 10−6 M) were examined in acetonitrile–water (MeCN/H2O) (9/1:v/v) solution at room temperature. It exhibit emission with the emission maxima at 398 nm when they are excited at 310 nm. In order to evaluate whether L could be used as a selective fluorescent sensor for presidium ion, the complexation of L with a number of metal ions was investigated spectrofluorometrically in MeCN/H2O solution at 25.0 ± 0.1 °C. A 5.0 × 10−6 M solution of L in MeCN/H2O (9/1:v/v) was titrated with microliter amounts of 1.0 × 10−4 M solutions of metal ions spectrofluorometrically (at λex = 310 nm), at a constant ionic strength of 0.01 M ammonium nitrate in 25.0 ± 0.1 °C. The resulting fluorescence intensity–mole ratio data for; Na+, Mg2+, Hg2 +, Zn2+, Cu2+, Yb3+, Sm3+, Pr3+, Er3+, La3+ and Ce3+ ions are shown in Fig. 3. It can be clearly seen from (Fig. 3) that only Pr3+ ion can increase remarkable the fluorescence intensity of 1000 Pr3+

900

Fluorescence Intensity (A.U)

ϕsample ¼ ϕreference

3.4. Fluorescence Properties

800 700 Sm 3+

600

L, Ce3+,La3+, Tm3+, Lu 3+,Tb3+, Eu3+, Dy 3+,Nd3+, Gd3+,Cu2+,Ni 2+, Pb 2+, Hg 2+, Fe3+

500 400 Er3+

300 200 100 0 325

375

425

475

525

Wavelength (nm) Fig. 1. Fluorescence responses of L (5 × 10−6 M) MeOH/H2O (9/1:v/v) solution upon addition of cations (5 × 10−4 M) (λex = 310 nm).

4142

M.R. Ganjali et al. / Materials Science and Engineering C 33 (2013) 4140–4143 Table 1 The formation constants of L __ Mn+ complexes.

L 15

0.65

35 55 75

A

95 115

0.45

135 150

Cation

log Kf

Co2+ Hg2+ Zn2+ Cu2+ Sm3+ Er3+ Pr3+ Yb3+ Mg2+ Na+ Ce3+ La3+

2.35 2.05 2.15 4.15 3.85 3.15 5.86 2.86 1.85 1.68 2.44 2.11

± ± ± ± ± ± ± ± ± ± ± ±

0.10 0.10 0.11 0.11 0.11 0.11 0.17 0.17 0.17 0.17 0.11 0.11

170

0.25 230

240

250

260

270

280

290

300

310

320

330

Wavelength (nm) Fig. 2. Changes in the UV spectra of L (5 × 10−5 M) upon addition of Pr3+ (1.0×. 10−3 M) in MeCN/H2O (9/1:v/v).

and hence decrease the non-radiative decay of the excited state. The fluorescence quantum yield (Φ) was 0.23 without Pr3+ and was increased to 0.70 by Pr3+ addition. In the presence of various concentration of praseodymium ion ranging from 1.6 × 10−7 to 2.4 × 10−6 M, significant fluorescence enhancement of fluorescent probe was observed. The detection limit was calculated as 8.3 × 10−8 M based on 3δ of the blank as definition by IUPAC. In out range concentration, the intensity of L is no change due the praseodymium ion uncomplexed. 3.5. Selectivity

the ligand L. Other metal ions can no significant enhance the fluorescence intensity of L as Pr3+ ion can. From such a sharp inflection point at a molar ratio of 1, it can be immediately concluded that in the all cases a 1:2 cation complex [ML]n+ is formed in acetonitril–water (9/1:v/v) solution. The formation constants of the resulting complexes were evaluated by fitting the fluorescence intensity–metal ion molar ratio data to a 1:2 model using a nonlinear least-squares curve-fitting program, as described elsewhere [29]. The enhancement of fluorescence is attributed to the introduction of Pr3+, and the strong complexation occurs with ligands evident from large binding constant values. The results are summarized in Table 1. From Table 1, it was concluded that L was appropriate for the Pr3+ fluorescent sensor design. The change in emission spectra was observed when various concentrations of Pr3+were added to it. As can be seen in Fig. 4, the fluorescence emission spectra of L enhanced upon addition of Pr3+ without spectral changes. The system shows selective chelation enhanced fluorescence (CHEF) in the presence of Pr3+. The enhancement of fluorescence is attributed to the strong binding of Pr3+ evident from a large binding constant value (6.3 × 10−6 M−1) that would impose rigidity

The selectivity behavior is obviously one of the most important characteristics of a chemosensor, which is the relative sensor response for the primary ion over other ions present in solution. In order to test the interference for other common cations on the determination of Pr3+, a competition experiment was performed in which the fluorescent probe was added to a solution of Pr3+ (3.0 × 10−5 M) in the presence of other metal ions (3.0 × 10−5 M) (Table 2). From Table 2, one can see that the relative error of common species except Sm3+ and Er3+, such as alkali, alkaline earth, transitional and heavy metal ions, is less than ±5% which is considered as tolerated. Thus, L exhibits nice selectivity for Pr3+ over other common cations. The results obtained indicated that the proposed fluorescent sensor can be applied to the determination of traces of Pr3+ ion in real samples, in the presence of several other co-existing cationic species.

Fluorescence Intensity (A.U)

1000 900 Pr Sm Er Ce La Yb Cu Hg Zn Mg Na

800 700 600 500 400 300 200 100 0 0

0.2

0.4

0.6

0.8

[Mn+]/[L] Fig. 3. Fluorescence intensity vs. [Mn+]/[L] mole ratio plots in MeCN solution for different transition metal ions.

Fig. 4. a) Fluorescence titration of L (5 × 10−6 M) in MeCN/H2O (9/1:v/v) solution in the presence of varying concentrations of Pr3+ ion: (1) 0,(2) 1.6 × 10−7 M,(3) 5.0 × 10−7 M, (4) 8.3 × 10−7 M, (5) 1.6 × 10−6 M, (6) 2.6 × 10−6 M, (7) 3.6 × 10−6 M, (8) 4.6 × 10−6 M, (9) 5.6 × 10−6 M, (10) 6.6 × 10−6 M, (11) 7.6 × 10−6 M, (12) 8.6 × 10−6 M, (13) 1.0 × 10−5 M, (14) 1.2 × 10−5 M, (15) 2.0 × 10−5 M, (16) 2.2 × 10−5 M, (17) 3.0 × 10−5 M, λex = 310 nm. b) Visual fluorescence changes of sensor L (1.0 × 10−1 M) in the absence (A) and excess presence of Pr3+ ion (1.0 × 10−2 M) (B), The photo was taken under a handheld UV (365 nm) lamp.

M.R. Ganjali et al. / Materials Science and Engineering C 33 (2013) 4140–4143 Table 2 Interference of different metal ions to the fluorescence determination of Pr3+ ion with the proposed sensor. M

n+

Relative error(%)

La3+ Sm3+ Gd3+ Dy3+ Tb3+ Er3+ Ce3+ Ni2+ Co2+ Cd2+ Cu2+ Pb2+ Zn2+ Sr2+ Be2+ Ca2+ Cs+ Li+

3.7 5.7 3.8 3.9 3.1 5.2 3.7 2.3 2.2 2.1 2.6 2.8 2.4 2.0 2.1 2.2 1.8 1.1

3.6. Analytical application The high degree of mercury selectivity, exhibited by the proposed sensor, makes it potentially useful for monitoring low level praseodymium ion concentrations in different water samples. Ten water samples (tap and river water samples) ware taken and diluted with wateracetonitrile solution in a 25.0 mL volumetric flask. Different amounts of Pr3+ ions were added to water samples. The proposed sensor was used to determine the Pr3+ content and the calibration method was applied. The results obtained with the sensor are summarized in Table 3. It was found that the accuracy of Pr3+ detection in different solution samples is almost quantitative. 4. Conclusion In conclusion, a selective fluorescent probe for Pr3 + ion determination based on (E)-2-(1-(4-hydroxy-2-oxo-2H-chromen-3-yl) ethylidene)hydrazinecarbothioamide (L) has been reported. The fluorescence emission intensity of L is remarkably enhanced upon the addition of praseodymium ion which is attributed to the formation of 1:1 complex. The method proposed in this work is simple, rapid, sensitive and selective and it was successfully applied for determination of Pr3+ in waste water samples. Acknowledgment The authors express their appreciation to the Research Council of University of Tehran for financial support of this work. Appendix A. Supplementary data Supplementary data to this article can be found online at http:// dx.doi.org/10.1016/j.msec.2013.06.005.

Table 3 Determination of Pr3+ ion in water samples and waste water with the present sensor. Sample Tap water River water a

Added (mol L−1) 3.0(±0.1) 5.0(±0.2) 2.5(±0.2) 6.3(±0.3)

× × × ×

−6

10 10−6 10−6 10−6

Found a (mol L−1) 3.1 (±0.2) 5.1(± 0.2) 2.4 ± (0.1) 6.5(± 0.2)

Results are based on three measurements.

× × × ×

10−6 10−6 10−6 10−6

Recovery (%) 103.4 103.7 98.0 104.1

4143

References [1] V. Bekiari, P. Judeinstein, P. Lianos, A sensitive fluorescent sensor of lanthanide ions, J. Lumin. 104 (2003) 13–15. [2] W.S.H. Xia, R.H. Schmehl, C.J. Li, A Fluorescent 18-Crown-6 Based Luminescence Sensor for Lanthanide Ions, Tetrahedron 56 (2000) 7045–7049. [3] [1] http://www.lenntech.com. [4] [2] http://www.webelements.com. [5] V.S. Sastri, J.-C.G. Bunzli, V.R. Rao, G.V.S. Rayudu, J.R. Perumareddi, Modern Aspect of Rare Earth Elements, Elsevier, 2003. [6] J.V. Mello, N.S. Finney, You have full text access to this content Dual-Signaling Fluorescent Chemosensors Based on Conformational Restriction and Induced Charge Transfer, Angew. Chem. Int. Ed. 40 (2001) 1536–1538. [7] A. Coskun, E.U. Akkaya, Ion Sensing Coupled to Resonance Energy Transfer: A Highly Selective and Sensitive Ratiometric Fluorescent Chemosensor for Ag(I) by a Modular Approach, J. Am. Chem. Soc. 127 (2005) 10464–10465. [8] J. Raker, T.E. Glass, Selectivity via Cooperative Interactions: Detection of Dicarboxylates in Water by a Pinwheel Chemosensor, J. Org. Chem. 67 (2002) 6113–6116. [9] Y. Kubo, M. Yamamoto, M. Ikeda, M. Takeuchi, S. Shinkai, S. Yamaguchi, K. Tamao, A Colorimetric and Ratiometric Fluorescent Chemosensor with Three Emission Changes: Fluoride Ion Sensing by a Triarylborane– Porphyrin Conjugate, Angew. Chem. Int. Ed. 42 (2003) 2036–2040. [10] F. Sancenon, R. Martinez-Manez, M.A. Miranda, M.J. Segui, J. Soto, Towards the Development of Colorimetric Probes to Discriminate between Isomeric Dicarboxylates, Angew. Chem. Int. Ed. 42 (2003) 647–650. [11] M. Shamsipur, K. Alizadeh, M. Hosseini, C. Caltagirone, V. Lippolis, A selective optode membrane for silver ion based on fluorescence quenching of the dansylamidopropyl pendant arm derivative of 1-aza-4,7,10-trithiacyclododecane ([12]aneNS3), Sens. Actuators B 113 (2006) 892–899. [12] M. Hosseini, S. Dehghan Abkenar, M.R. Ganjali, B. Veismohammadi, P. Norouzi, M. Salavati-Niasari, Highly Selective Ratiometric Fluorescent Sensor for La(III) Ion Based on a New Schiff's Base, Anal. Lett. 42 (2009) 1029–1040. [13] M.R. Ganjalia, V. Kumar Gupta, M. Hosseini, M. Hariri, F. Faridbod, P. Norouzi, Lanthanide recognition: A dysprosium(III) selective fluorimetric bulk optode, Sens. Actuators B 171–172 (2012) 644–651. [14] M.R. Ganjali, M. Hosseini, Z. Memari, F. Faridbod, P. Norouzi, H. Goldooz, A. Badiei, Selective recognition of monohydrogen phosphate by fluorescence enhancement of a new cerium complex, Anal. Chim. Acta 708 (2011) 107–110. [15] M. Hosseini, M.R. Ganjali, M. Tavakoli, P. Norouzi, F. Faridbod, H. Goldooz, A. Badiei, Pyrophosphate Selective Recognition in Aqueous Solution Based on Fluorescence Enhancement of a New Aluminium Complex, J. Fluoresc. 21 (2011) 1509–1513. [16] M. Hosseini, Z. Vaezi, M.R. Ganjali, F. Faridbod, S. Dehghan Abkenar, Fluorescence “Turn-On” chemosensor for the selective detection of beryllium, Spectrochim. Acta A 83 (2011) 161–164. [17] L.J. fan, W.E. Jones, A Highly Selective and Sensitive Inorganic/Organic Hybrid Polymer Fluorescence “Turn-on” Chemosensory System for Iron Cations, J. Am. Chem. Soc. 128 (2006) 6784–6785. [18] M. Hosseini, M.R. Ganjali, B. Veismohammadi, S. Riahi, P. Norouzi, M. Salavati-Niasari, S.D. Abkenar, Highly Selective Ratiometric Fluorescent Sensor for La(III) Ion Based on a New Schiff's Base, Anal. Lett. 42 (2009) 1029–1040. [19] M. Hosseini, H.B. Sadeghi, M. Rahimi, M. Salavati-Niasari, S.D. Abkenar, K. Alizadeh, M.R. Ganjali, Highly selective and sensitive tin(II) membrane electrode based on a new synthesized Schiff's base, Electroanalysis 21 (2009) 859–866. [20] F. Faridbod, M.R. Ganjali, M. Hosseini, M.R. Ganjali, P. Norouzi, Potentiometric sensor for determination of clomiphene, Int. J. Electrochem. Sci. 7 (2012) 1927–1936. [21] M.R. Ganjali, M. Hosseini, M. Hariri, F. Faridbod, P. Norouzi, Sens. Actuators B 141 (2009) 90–96. [22] M.R. Ganjali, B. Veismohammadi, M. Hosseini, P. Norouzi, A new Tb3+-selective fluorescent sensor based on 2-(5-(dimethylamino)naphthalen-1-ylsulfonyl)-Nhenylhydrazinecarbothioamide, Spectrochim. Acta A 74 (2009) 575–578. [23] M. Hosseini, M.R. Ganjali, B. Veismohammadi, P. Norouzi, K. Alizadeh, S. Dehghan Abkenar, Highly selective ratiometric fluorescence determination of Eu3+ ion based on (4E)-4-(2-phenyldiazenyl)-2-((E)-(2-aminoethylimino)methyl)phenol, Mater. Sci. Eng. C 30 (2010) 929–933. [24] M. Hosseini, Z. Vaezi, M.R. Ganjali, F. Faridbod, S. Dehghan Abkenar, K. Alizadeh, M. Salavati-Niasari, Fluorescence “turn-on” chemosensor for the selective detection of zinc ion based on Schiff-base derivative, Spectrochim. Acta A 75 (2010) 978–982. [25] M. Hosseini, M.R. Ganjali, B. Veismohammadi, F. Faridbod, P. Norouzi, S. Dehghan Abkenar, Novel selective optode membrane for terbium ion based on fluorescence quenching of the 2-(5-(dimethylamino) naphthalen-1-ylsulfonyl)-Nhenylhydrazinecarbothioamid, Sens. Actuators B 147 (2010) 23–30. [26] M. Hosseini, M.R. Ganjali, F. Aboufazeli, F. Faridbod, H. Goldoozd, A. Badiei, P. Norouzi, A selective fluorescent bulk sensor for lutetium based on hexagonal mesoporous structures, Sens. Actuators B 184 (2013) 93–99. [27] S. Banthia, A. Samanta, A New Strategy for Ratiometric Fluorescence Detection of Transition Metal Ions, J. Phys. Chem. B 110 (2006) 6437–6440. [28] P. Roy, K. Dhara, M. Manassero, P. Banerjee, Synthesis, characterization and selective fluorescent zinc(II) sensing property of three Schiff-base compounds, Inorg. Chim. Acta 362 (2009) 2927–2932. [29] P. Bühlmann, E. Pretsch, E. Bakker, Carrier-Based Ion-Selective Electrodes and Bulk Optodes. 1. General Characteristics, Chem. Rev. 97 (1997) 3083–3132.