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Determination of transition metal irons based on quenching of the rare earth luminescence
Sensors and Actuators B 91 (2003) 252–255
Determination of transition metal irons based on quenching of the rare earth luminescence Tsuyoshi Arakawa*, Masami Akamine Department of Biological and Environmental Chemistry, Kyushu School of Engineering, Kinki University, Kayanomori 11-6, Iizuka, Fukuoka 820-8555, Japan
Abstract The determination of heavy metal ions was investigated by the use of rare earth ions (Eu3þ) as spectroscopic probes. A few heavy metal ions efficiently quenched the luminescence of Eu3þ in polymerized cellulose films which were obtained by sodium carboxymethyl cellulose (NaCMC) solution and EuCl3 solution or the mixed solution of EuCl3 and a heavy metal chloride. Also, the decay time of Eu3þ ions (t) in Eu3þ– Cuþ, Eu3þ–Cu2þ system was shorter than that of only Eu3þ system (t0). The linear relationship between the concentration of copper ions (Cuþ or Cu2þ) and t0/t reflected the dynamic quenching, as predicted by the Stern–Volmer equation. The method proposed appears the detection of heavy metal ions in environmental waters. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Transition metal ions; Rare earth; Luminescence; Quenching
1. Introduction Many rare earth complexes attract the interest as fluorescent probes in detection applications. The structural optimization of the rare earth complexes enhanced the availability in the molecular recognition and chirality sensing of biological substances [1,2]. It was reported that terbium chelate was used as a label in fluorescent immunoassays [3]. The polymers including the rare earth complex were synthesized, and the fluorescence were examined with the aim of the application to laser materials, etc. [4]. The hydrolysis product of the nerve agent Soman in water could be measured by the luminescence of Eu3þ–polymer complexes containing methyl-3,5-dimethylbenzoate ligand [5]. In this paper, we demonstrated the ability to detect the transition metal ions using the luminescence of polymerized cellulose films by assisting of rare earth ions.
chloride and rare earth chloride was put on the bottom of container. There was the viscous sodium carboxymethyl cellulose (Na-CMC) solution (4 mM) on a nylon cloth. Then the container was turned up side down and the solution contacted with each other through nylon cloth, followed by the formation of cellulose film containing of rare earth ions (Eu3þ) or rare earth ions and heavy metal ions. The nylon mesh cloth attaching cellulose thin film was removed from the container, washed and dried in a desciccator. The cellulose films containing of Cuþ ions were prepared by the use of degassed water and under dry nitrogen atmosphere. The emission and excitation spectra were recorded by a Hitachi recording absolute spectrofluorophotometer (F4500) at room temperature. The life times were measured with nitrogen laser (355 nm) having pulses of less than 5 ns.
3. Results and discussion 2. Experimental
3.1. The luminescence of Eu3þ in the cellulose film
The cellulose film was prepared by the use of the 30 ml glass bottle container of which two parts was separated by a 100 mesh nylon cloth. The rare earth chloride (EuCl3) solution (10–100 mM) or the mixed solution of heavy metal
The narrow emission peaks of rare earth spectra provide for highly sensitive and selective analyses. Especially, in this study, the Eu3þ ion was selected because the luminescence properties of europium chelates include large Stokes shifts (200–300 nm), sharp emission lines and long fluorescence lifetimes [6]. Fig. 1 shows the emission spectra of a Eu3þ– cellulose film together with Eu3þ–Mnþ (M: heavy metal)
* Corresponding author. Tel.: þ81-948-22-5655; fax: þ81-948-23-0536. E-mail address: [email protected] (T. Arakawa).
0925-4005/03/$ – see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0925-4005(03)00116-3
T. Arakawa, M. Akamine / Sensors and Actuators B 91 (2003) 252–255
253
Fig. 1. The emission intensity and the content of Eu3þ ions in a polymerized cellulose film vs. the concentration of EuCl3 solution.
cellulose films under the excitation of 395 nm. The emission lines at 591, 615 and 697 nm originate from 5 D0 ! 7 Fj transitions of Eu3þ. The effect of varying the Eu3þ ion concentration of cellulose films on the emission band is presented in Fig. 1. The abscissa indicates the concentration of EuCl3 when a cellulose film was prepared. At first, the intensity of emission line at 615 nm increased exponentially with the concentration of Eu3þ ions in cellulose film up to ca. 100 mM, and then became almost constant. A few fluorescence spectra of the europium ions of the cellulose film prepared using aqueous solution which changed the concentration of heavy metal the chloride by fixing of the concentration of europium chloride (100 mM), are also shown in Fig. 2. When Cr3þ or Cuþ was coexisted with Eu3þ in a cellulose film, the intensity of emission lines of Eu3þ ions was extremely decreased. Moreover, the intensity of the emission line of 615 nm, which was the strongest emission line, decreased with the concentration CuCl or CrCl3 as shown in Fig. 3. The concentration of Cuþ and Cr3þ in the cellulose membrane became almost fixed over 50 mM for the concentration of metal chloride solutions under experimental conditions. The emission intensity extremely decreased in the lower concentration of Cuþ or Cr3þ ions. The effect on the intensity of luminescence under coexistence of heavy metal ions were summarized in Table 1,
Fig. 3. Dependence of emission intensity of Eu3þ for Eu3þ–Cuþ cellulose films and Eu3þ–Cr3þ cellulose films on the content of cations. The cellulose films prepared using aqueous solution which changed the concentration of the heavy metal chloride by fixing the concentration of EuCl3 (100 mM).
together with the results of decay time as described later. When Cr3þ, Fe3þ, Cu2þ or Cuþ coexisted in the cellulose film, the luminescence was extremely decreased. It is well known that the intensity of luminescence for the europium complexes is affected by the ligand [7]. On the other hand, heavy metals are known to be strong quenchers of luminescence [8]. The quenching of perdeuterated naphthalene by paramagnetic ions (Co2þ, Cr3þ, Cu2þ, Ni2þ) was explained that the interaction between the triple state molecules and the paramagnetic is of the exchange type interaction. But, the intensity of luminescence of Eu3þ–Co2þ did not almost decrease, although Co2þ is paramagnetic. Also, in the case of Cuþ, which is nonmagnetic, the quenching phenomenon observed. Since Zn2þ or Pb2þ is not paramagnetic, it could not induce quenching by interaction from the viewpoint of Hoijtink’s mechanism [9], but it may cause quenching by spin–orbit interaction due to its large atomic number. Our measurements with Zn2þ or Pb2þ showed very slight quenching.
Table 1 The relative intensity (I0/I) of 615 nm emission line and the relative decay time (t0/t) of Eu3þ ions for Eu3þ–Mnþ system
Fig. 2. The emission spectra of cellulose films containing Eu3þ ions. The film was prepared by the use of (a) EuCl3 (100 mM) solution, (b) the mixed solution of EuCl3 (100 mM) and CrCl3 (50 mM), and (c) the mixed solution of EuCl3 (100 mM) and CuCl (50 mM).
Mnþ
I0/Ia
t0/tb
Cuþ Cu2þ Co2þ Mn2þ Cr3þ Fe3þ Zn2þ Pb2þ
2.5 2.0 1.0 1.0 8.0 6.0 1.5 1.5
4.1 2.0 1.0 1.0 1.2 1.9 1.1 1.2
a These values were compared at 0.35 mM/g of Eu3þ and 0.1 mM/g of Mnþ. b The decay time was 3:8 10 ns. These values were compared at 0.35 mM/g of Eu3þ and 0.2 mM/g of Mnþ.
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Fig. 4. Luminescence decay curves of an Eu3þ cellulose film and an Eu3þ–Cuþ cellulose film. The N2 laser (337 nm) was used.
3.2. The decay time of Eu3þ in the cellulose film The decay times and amplitudes of europium luminescence for a Eu3þ–Cuþ and Eu3þ system are shown in Fig. 4. In the presence of Cuþ ions, the decay time t (slope) was smaller than that of only Eu3þ system (t0). At the same time, the decrease of the amplitude was almost consistent with that of the luminescence intensity estimating by I0/I. The same phenomena were observed in the Eu3þ–Cu2þ system. The changes in decay time and amplitude indicate the co-existence of static and dynamic quenching. The correlation between the concentration of copper ions (Cuþ or Cu2þ) and t0/t are shown in Fig. 5. That is, the linear relationship reflects the dynamic process, as predicted by the Stern– Volmer equation [10], whereas the decreasing of amplitude (or luminescence intensity) is mainly a result of static quenching. The relative decay times (t0/t) for other heavy metal ions are summarized in Table 1. The t0/t of the Eu3þ– Cr3þ system, which the decrease of the emission intensity
was observed, was the same as that of only Eu3þ system. According to the Stern–Volmer equation, the extent of quenching is proportional to the decay time of the europium luminescence. The absorption spectrum Cr3þ or Fe3þ, which was a dynamic quencher, has a higher overlap with the emission spectrum of the europium ion. On the other hand, since none of the completely colorless ions showed dynamic quenching, it was expected that in the Eu3þ–Cuþ system the quenching and the decrease of decay time were not observed. The compounds including Cuþ ions exhibits the luminescence which is attribute to the 3d9 4s ! 3d10 interconfigurational transitions [11]. The emission band with maxima at 520 nm for Eu3þ–Cuþ cellulose film was observed under 360 nm excitation. The excitation spectrum of Cuþ has partly an overlap with that of Eu3þ. Although the mechanism of quenching for Eu3þ–Cuþ system could not be clarified, the energy transfer from the excited state to Eu3þ ions via Cuþ ions would predominately occur, comparing with the process to directly Eu3þ ions. The method presented is inferior to the most sensitive methods in the lower limit of detection of copper [12]. Especially, several europium chelates with multidentate ligands have become available, which retain their strong luminescence in aqueous solution because in these chelates the excited europium ion is efficiently protected from the aqueous environment [13]. However, specialized technology is necessary for the preparation of these chelates [14]. The operation of the method presented is simple. These results suggest that there are the ability of the detection of transition metal ions in environmental waters, including river water and industrial wastewater.
4. Conclusions The luminescence and the decay time of Eu3þ ions in cellulose polymer film, which was prepared by Na-CMC solution and EuCl3 solution or the mixed solution of EuCl3 and a heavy metal chloride, was studied. The quenching of europium luminescence depended on the heavy metal ion. In the Eu3þ–Cuþ and Eu3þ–Cu2þ system, the intensity and the decay time with the concentration of Cuþ or Cu2þ. This method based on quenching of europium luminescence may be useful for the determination of the heavy metal.
References
Fig. 5. Calibration graph for Cuþ and Cu2þ in the linearized form of a Stern–Volmer plot.
[1] E.P. Diamandis, T.K. Christopoulos, Europium chelate labels in timeresolved fluorescence immunoassays and DNA hybridization assays, Anal. Chem. 62 (1990) 1149A–1157A. [2] T. Yamada, S. Shinoda, J. Uenishi, H. Tsukube, Stereo-controlled substitution on tris(2-pyridylmethyl) amine ligands and chirality tuning of luminescence in their lanthanide complexes, Tetrahedron Lett. 42 (2001) 9031–9033. [3] M.P. Baily, B.F. Rocks, C. Riley, Terbium chelate for use as a label in fluorescent immunoassays, Analyst 109 (1984) 1449–1450.
T. Arakawa, M. Akamine / Sensors and Actuators B 91 (2003) 252–255 [4] Y. Ueba, E. Banks, Y. Okamoto, Investigation on the synthesis and characterization of rare earth metal-containing polymers. II. Fluorescence properties of Eu3þ–polymer complexes containing bdiketone ligand, J. Appl. Polym. Sci. 25 (1980) 2007–2017. [5] A.L. Jenkins, O.M. Uy, G.M. Murray, Polymer-based lanthanide luminescence sensor for detection of the hydrolysis product of the nerve agent soman in water, Anal. Chem. 71 (1999) 373–378. [6] C.C. Bryden, C.N. Relley, Europium luminescence lifetimes and spectra for evaluation of 11 europium complexes as aqueous shift reagents for nuclear magnetic resonance spectrometry, Anal. Chem. 54 (1982) 610–615. [7] P.R. Selvin, J. Jancarik, M. Li, L. Hung, Crystal structure and spectroscopic characterization of a luminescent europium chelate, Inorg. Chem. 35 (1996) 700–705. [8] C.O. Hill, S.H. Lin, Quenching of phosphorescence by paramagnetic molecules in rigid media. II. Quenching of perdeuderated naphthalene by Coþþ, Cr3þ, Cuþþ, and Niþþ, J. Chem. Phys. 53 (1970) 608–612.
255
[9] G.J. Hoijtink, The influence of paramagnetic molecules on singlet– triplet transitions, Mol. Phys. 3 (1960) 67–70. [10] O.S. Wolfbeis, in: Schulman (Ed.), Methods and Applications. Part II. Molecular Luminescence Spectroscopy, Wiley, New York, 1988, pp. 202–212. [11] J.D. Barrie, B. Dunn, O.M. Stafsudd, P. Nelson, Luminescence of Cuþ–b00 -alumina, J. Lumin. 37 (1987) 303–311. [12] J. Lin, T. Hobo, Chemiluminescence investigation of NH2OH– fluorescein–Cu2þ system and its application to copper analysis I serum, Talanta 42 (1995) 1619–1623. [13] M.A. Kessler, Determination of copper at ng ml1 based on quenching of the europium chelate luminescence, Anal. Chim. Acta 364 (1998) 125–129. [14] V. Mukkala, M. Kwiatkowski, J. Kankare, H. Takalo, Influence of chelating groups on the luminescence properties of europium (III) and terbium (III) chelates in the 2,20 -bipyridine series, Helv. Chim. Acta 76 (1993) 893–899.
Determination of transition metal irons based on quenching of the rare earth luminescence Tsuyoshi Arakawa*, Masami Akamine Department of Biological and Environmental Chemistry, Kyushu School of Engineering, Kinki University, Kayanomori 11-6, Iizuka, Fukuoka 820-8555, Japan
Abstract The determination of heavy metal ions was investigated by the use of rare earth ions (Eu3þ) as spectroscopic probes. A few heavy metal ions efficiently quenched the luminescence of Eu3þ in polymerized cellulose films which were obtained by sodium carboxymethyl cellulose (NaCMC) solution and EuCl3 solution or the mixed solution of EuCl3 and a heavy metal chloride. Also, the decay time of Eu3þ ions (t) in Eu3þ– Cuþ, Eu3þ–Cu2þ system was shorter than that of only Eu3þ system (t0). The linear relationship between the concentration of copper ions (Cuþ or Cu2þ) and t0/t reflected the dynamic quenching, as predicted by the Stern–Volmer equation. The method proposed appears the detection of heavy metal ions in environmental waters. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Transition metal ions; Rare earth; Luminescence; Quenching
1. Introduction Many rare earth complexes attract the interest as fluorescent probes in detection applications. The structural optimization of the rare earth complexes enhanced the availability in the molecular recognition and chirality sensing of biological substances [1,2]. It was reported that terbium chelate was used as a label in fluorescent immunoassays [3]. The polymers including the rare earth complex were synthesized, and the fluorescence were examined with the aim of the application to laser materials, etc. [4]. The hydrolysis product of the nerve agent Soman in water could be measured by the luminescence of Eu3þ–polymer complexes containing methyl-3,5-dimethylbenzoate ligand [5]. In this paper, we demonstrated the ability to detect the transition metal ions using the luminescence of polymerized cellulose films by assisting of rare earth ions.
chloride and rare earth chloride was put on the bottom of container. There was the viscous sodium carboxymethyl cellulose (Na-CMC) solution (4 mM) on a nylon cloth. Then the container was turned up side down and the solution contacted with each other through nylon cloth, followed by the formation of cellulose film containing of rare earth ions (Eu3þ) or rare earth ions and heavy metal ions. The nylon mesh cloth attaching cellulose thin film was removed from the container, washed and dried in a desciccator. The cellulose films containing of Cuþ ions were prepared by the use of degassed water and under dry nitrogen atmosphere. The emission and excitation spectra were recorded by a Hitachi recording absolute spectrofluorophotometer (F4500) at room temperature. The life times were measured with nitrogen laser (355 nm) having pulses of less than 5 ns.
3. Results and discussion 2. Experimental
3.1. The luminescence of Eu3þ in the cellulose film
The cellulose film was prepared by the use of the 30 ml glass bottle container of which two parts was separated by a 100 mesh nylon cloth. The rare earth chloride (EuCl3) solution (10–100 mM) or the mixed solution of heavy metal
The narrow emission peaks of rare earth spectra provide for highly sensitive and selective analyses. Especially, in this study, the Eu3þ ion was selected because the luminescence properties of europium chelates include large Stokes shifts (200–300 nm), sharp emission lines and long fluorescence lifetimes [6]. Fig. 1 shows the emission spectra of a Eu3þ– cellulose film together with Eu3þ–Mnþ (M: heavy metal)
* Corresponding author. Tel.: þ81-948-22-5655; fax: þ81-948-23-0536. E-mail address: [email protected] (T. Arakawa).
0925-4005/03/$ – see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0925-4005(03)00116-3
T. Arakawa, M. Akamine / Sensors and Actuators B 91 (2003) 252–255
253
Fig. 1. The emission intensity and the content of Eu3þ ions in a polymerized cellulose film vs. the concentration of EuCl3 solution.
cellulose films under the excitation of 395 nm. The emission lines at 591, 615 and 697 nm originate from 5 D0 ! 7 Fj transitions of Eu3þ. The effect of varying the Eu3þ ion concentration of cellulose films on the emission band is presented in Fig. 1. The abscissa indicates the concentration of EuCl3 when a cellulose film was prepared. At first, the intensity of emission line at 615 nm increased exponentially with the concentration of Eu3þ ions in cellulose film up to ca. 100 mM, and then became almost constant. A few fluorescence spectra of the europium ions of the cellulose film prepared using aqueous solution which changed the concentration of heavy metal the chloride by fixing of the concentration of europium chloride (100 mM), are also shown in Fig. 2. When Cr3þ or Cuþ was coexisted with Eu3þ in a cellulose film, the intensity of emission lines of Eu3þ ions was extremely decreased. Moreover, the intensity of the emission line of 615 nm, which was the strongest emission line, decreased with the concentration CuCl or CrCl3 as shown in Fig. 3. The concentration of Cuþ and Cr3þ in the cellulose membrane became almost fixed over 50 mM for the concentration of metal chloride solutions under experimental conditions. The emission intensity extremely decreased in the lower concentration of Cuþ or Cr3þ ions. The effect on the intensity of luminescence under coexistence of heavy metal ions were summarized in Table 1,
Fig. 3. Dependence of emission intensity of Eu3þ for Eu3þ–Cuþ cellulose films and Eu3þ–Cr3þ cellulose films on the content of cations. The cellulose films prepared using aqueous solution which changed the concentration of the heavy metal chloride by fixing the concentration of EuCl3 (100 mM).
together with the results of decay time as described later. When Cr3þ, Fe3þ, Cu2þ or Cuþ coexisted in the cellulose film, the luminescence was extremely decreased. It is well known that the intensity of luminescence for the europium complexes is affected by the ligand [7]. On the other hand, heavy metals are known to be strong quenchers of luminescence [8]. The quenching of perdeuterated naphthalene by paramagnetic ions (Co2þ, Cr3þ, Cu2þ, Ni2þ) was explained that the interaction between the triple state molecules and the paramagnetic is of the exchange type interaction. But, the intensity of luminescence of Eu3þ–Co2þ did not almost decrease, although Co2þ is paramagnetic. Also, in the case of Cuþ, which is nonmagnetic, the quenching phenomenon observed. Since Zn2þ or Pb2þ is not paramagnetic, it could not induce quenching by interaction from the viewpoint of Hoijtink’s mechanism [9], but it may cause quenching by spin–orbit interaction due to its large atomic number. Our measurements with Zn2þ or Pb2þ showed very slight quenching.
Table 1 The relative intensity (I0/I) of 615 nm emission line and the relative decay time (t0/t) of Eu3þ ions for Eu3þ–Mnþ system
Fig. 2. The emission spectra of cellulose films containing Eu3þ ions. The film was prepared by the use of (a) EuCl3 (100 mM) solution, (b) the mixed solution of EuCl3 (100 mM) and CrCl3 (50 mM), and (c) the mixed solution of EuCl3 (100 mM) and CuCl (50 mM).
Mnþ
I0/Ia
t0/tb
Cuþ Cu2þ Co2þ Mn2þ Cr3þ Fe3þ Zn2þ Pb2þ
2.5 2.0 1.0 1.0 8.0 6.0 1.5 1.5
4.1 2.0 1.0 1.0 1.2 1.9 1.1 1.2
a These values were compared at 0.35 mM/g of Eu3þ and 0.1 mM/g of Mnþ. b The decay time was 3:8 10 ns. These values were compared at 0.35 mM/g of Eu3þ and 0.2 mM/g of Mnþ.
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T. Arakawa, M. Akamine / Sensors and Actuators B 91 (2003) 252–255
Fig. 4. Luminescence decay curves of an Eu3þ cellulose film and an Eu3þ–Cuþ cellulose film. The N2 laser (337 nm) was used.
3.2. The decay time of Eu3þ in the cellulose film The decay times and amplitudes of europium luminescence for a Eu3þ–Cuþ and Eu3þ system are shown in Fig. 4. In the presence of Cuþ ions, the decay time t (slope) was smaller than that of only Eu3þ system (t0). At the same time, the decrease of the amplitude was almost consistent with that of the luminescence intensity estimating by I0/I. The same phenomena were observed in the Eu3þ–Cu2þ system. The changes in decay time and amplitude indicate the co-existence of static and dynamic quenching. The correlation between the concentration of copper ions (Cuþ or Cu2þ) and t0/t are shown in Fig. 5. That is, the linear relationship reflects the dynamic process, as predicted by the Stern– Volmer equation [10], whereas the decreasing of amplitude (or luminescence intensity) is mainly a result of static quenching. The relative decay times (t0/t) for other heavy metal ions are summarized in Table 1. The t0/t of the Eu3þ– Cr3þ system, which the decrease of the emission intensity
was observed, was the same as that of only Eu3þ system. According to the Stern–Volmer equation, the extent of quenching is proportional to the decay time of the europium luminescence. The absorption spectrum Cr3þ or Fe3þ, which was a dynamic quencher, has a higher overlap with the emission spectrum of the europium ion. On the other hand, since none of the completely colorless ions showed dynamic quenching, it was expected that in the Eu3þ–Cuþ system the quenching and the decrease of decay time were not observed. The compounds including Cuþ ions exhibits the luminescence which is attribute to the 3d9 4s ! 3d10 interconfigurational transitions [11]. The emission band with maxima at 520 nm for Eu3þ–Cuþ cellulose film was observed under 360 nm excitation. The excitation spectrum of Cuþ has partly an overlap with that of Eu3þ. Although the mechanism of quenching for Eu3þ–Cuþ system could not be clarified, the energy transfer from the excited state to Eu3þ ions via Cuþ ions would predominately occur, comparing with the process to directly Eu3þ ions. The method presented is inferior to the most sensitive methods in the lower limit of detection of copper [12]. Especially, several europium chelates with multidentate ligands have become available, which retain their strong luminescence in aqueous solution because in these chelates the excited europium ion is efficiently protected from the aqueous environment [13]. However, specialized technology is necessary for the preparation of these chelates [14]. The operation of the method presented is simple. These results suggest that there are the ability of the detection of transition metal ions in environmental waters, including river water and industrial wastewater.
4. Conclusions The luminescence and the decay time of Eu3þ ions in cellulose polymer film, which was prepared by Na-CMC solution and EuCl3 solution or the mixed solution of EuCl3 and a heavy metal chloride, was studied. The quenching of europium luminescence depended on the heavy metal ion. In the Eu3þ–Cuþ and Eu3þ–Cu2þ system, the intensity and the decay time with the concentration of Cuþ or Cu2þ. This method based on quenching of europium luminescence may be useful for the determination of the heavy metal.
References
Fig. 5. Calibration graph for Cuþ and Cu2þ in the linearized form of a Stern–Volmer plot.
[1] E.P. Diamandis, T.K. Christopoulos, Europium chelate labels in timeresolved fluorescence immunoassays and DNA hybridization assays, Anal. Chem. 62 (1990) 1149A–1157A. [2] T. Yamada, S. Shinoda, J. Uenishi, H. Tsukube, Stereo-controlled substitution on tris(2-pyridylmethyl) amine ligands and chirality tuning of luminescence in their lanthanide complexes, Tetrahedron Lett. 42 (2001) 9031–9033. [3] M.P. Baily, B.F. Rocks, C. Riley, Terbium chelate for use as a label in fluorescent immunoassays, Analyst 109 (1984) 1449–1450.
T. Arakawa, M. Akamine / Sensors and Actuators B 91 (2003) 252–255 [4] Y. Ueba, E. Banks, Y. Okamoto, Investigation on the synthesis and characterization of rare earth metal-containing polymers. II. Fluorescence properties of Eu3þ–polymer complexes containing bdiketone ligand, J. Appl. Polym. Sci. 25 (1980) 2007–2017. [5] A.L. Jenkins, O.M. Uy, G.M. Murray, Polymer-based lanthanide luminescence sensor for detection of the hydrolysis product of the nerve agent soman in water, Anal. Chem. 71 (1999) 373–378. [6] C.C. Bryden, C.N. Relley, Europium luminescence lifetimes and spectra for evaluation of 11 europium complexes as aqueous shift reagents for nuclear magnetic resonance spectrometry, Anal. Chem. 54 (1982) 610–615. [7] P.R. Selvin, J. Jancarik, M. Li, L. Hung, Crystal structure and spectroscopic characterization of a luminescent europium chelate, Inorg. Chem. 35 (1996) 700–705. [8] C.O. Hill, S.H. Lin, Quenching of phosphorescence by paramagnetic molecules in rigid media. II. Quenching of perdeuderated naphthalene by Coþþ, Cr3þ, Cuþþ, and Niþþ, J. Chem. Phys. 53 (1970) 608–612.
255
[9] G.J. Hoijtink, The influence of paramagnetic molecules on singlet– triplet transitions, Mol. Phys. 3 (1960) 67–70. [10] O.S. Wolfbeis, in: Schulman (Ed.), Methods and Applications. Part II. Molecular Luminescence Spectroscopy, Wiley, New York, 1988, pp. 202–212. [11] J.D. Barrie, B. Dunn, O.M. Stafsudd, P. Nelson, Luminescence of Cuþ–b00 -alumina, J. Lumin. 37 (1987) 303–311. [12] J. Lin, T. Hobo, Chemiluminescence investigation of NH2OH– fluorescein–Cu2þ system and its application to copper analysis I serum, Talanta 42 (1995) 1619–1623. [13] M.A. Kessler, Determination of copper at ng ml1 based on quenching of the europium chelate luminescence, Anal. Chim. Acta 364 (1998) 125–129. [14] V. Mukkala, M. Kwiatkowski, J. Kankare, H. Takalo, Influence of chelating groups on the luminescence properties of europium (III) and terbium (III) chelates in the 2,20 -bipyridine series, Helv. Chim. Acta 76 (1993) 893–899.