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Detection of butylamine by means of surface plasmon resonance
Sensors and Actuators B 108 (2005) 899–902
Detection of butylamine by means of surface plasmon resonance Tsuyoshi Arakawa∗ , Atsushi Kawabayashi, Takashi Saga Department of Biological and Environmental Chemistry, School of Humanity-Oriented Science and Engineering, Kinki University, Iizuka, Fukuoka 820-8555, Japan Received 13 July 2004; received in revised form 11 November 2004; accepted 17 November 2004 Available online 11 January 2005
Abstract The detection of butylamine as a malodorous substance was investigated by a surface plasmon resonance (SPR) sensor. When the A zeolite thin film on a gold surface via the thiol–alkoxysilane interfacial layers was formed, the resonance angle changed from 22.30◦ to 69.24◦ . Moreover, the anchored zeolite layers were exposed to butylamine, the shifts of the incident angle (θ) were observed. The θ increased linearly with the gas concentration region of 0% to about 1%. The sensitivity of butylamine was lowest among some amines. Also, the sensitivity depended on the kind of zeolite as follows; the sequence was 13X zeolite > 5A zeolite ≈ mordenite > ZSM-5. © 2004 Elsevier B.V. All rights reserved. Keywords: Zeolite; Butylamine; Surface plasmon resonance sensor
1. Introduction A lot of studies for the surface plasmon resonance (SPR) have been reported in the field of chemical sensing. In particular, the applied study of SPR sensor has drawn attention in the field of medical chemistry [1–3]. In the SPR sensor, the detecting material is greatly influenced in the substrate coated with the gold thin film of the SPR sensor head, as can be understood from the principle of SPR [4]. We have attempted to detect some gaseous species using a SPR sensor. When the polyethylene glycol thin film was coated on an Au thin film, it was found that the alcohol could be selectively detected [5]. Also, it was reported that the SPR sensor with the Apiezon–grease thin film would be effective the detection of lower hydrocarbons [6]. Moreover, it may be expected that the kind of detectable gases would be increased by the use of inorganic thin film. In this paper, we briefly describe the detection of butylamine as a malodorous substance using chemically anchored zeolite layers, as there would be appreciable interaction between butylamine and acid sites ∗
Corresponding author. Tel.: +81 948 22 5655; fax: +81 948 23 0536. E-mail address: [email protected] (T. Arakawa).
0925-4005/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2004.11.074
(Lewis or Br¨onsted acid sites) as an adsorption sites on a zeolite.
2. Experiment The apparatus for an SPR-based chemical sensor is essentially identical to that reported elsewhere [7]. The sensor head was prepared in the following way. A gold thin film with a thickness of about 55 nm was prepared by thermal evaporation of gold (purity; 99.99%) on the surface of corner cube prism. The zeolite used commercial sodium 5A zeolite, sodium 13X zeolite, mordenite and ZSM-5. The preparation of zeolite thin film on the gold surface was referred to the method as reported elsewhere [8]. The anchoring of zeolite crystals to the gold surface involved two steps: formation of the thiol monolayers and exposure to a zeolite suspension in toluene, followed by the attachment of a gas sample cell. The thiol layers were formed by immersing the gold thin film for 1 h into the solution dissolving 0.1 g of (3-mercaptopropyl) trimethoxysilane in 30 ml of toluene. Then, the thiol layers were rinsed with toluene to excess adsorbate from the gold thin film, followed by stirring in 30 ml toluene solution of dis-
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T. Arakawa et al. / Sensors and Actuators B 108 (2005) 899–902
persed zeolite (0.1 g) overnight. After attachment of the zeolite crystals, the alkoxy groups of the silane were hydrolyzed and further reacted with the zeolite by heating in air at 373 K for 1 h. In order to compare the sensitivity of butylamine, the sensitivity of some amines (ethylamine, propylamine and isopropylamine) was investigated. Butylamine gases were diluted with dry air at various concentrations and were passed through a gas sample cell. Fixed quantity of ethylamine gases was introduced from one side of a gas sample cell with a gas syringe. SEM micrographs were recorded by a Hitachi S-4300SE/N.
3. Results and discussion 3.1. Formation of the zeolite crystal Fig. 1 presents SEM micrograph of the 5A zeolite-coated gold surface on a slide glass instead of a prism. It is clear that this coating process provides a method to obtain uniform crystal distributions on the entire slide surface. The cubic shape crystal, which is feature of the crystal structure of the 5A zeolite, was observed. Also it was independently confirmed that the zeolite crystals recovered from the gold substrate gave the same X-ray diffraction pattern and peak ratios as the bulk. Thus, it was clear that the attached
particles displayed the crystalline habit of the bulk materials. 3.2. SPR spectra under adsorption of amines In the surface plasmon method, the resonance angle is very sensitive to the refractive index of the medium outside the metal thin film. When the medium on the surface of gold thin film was changed from air to a thiol–alkoxysilane thin film, the resonance angle changed from 22.30◦ to 52.94◦ . Moreover, when the zeolite layer via the thiol–alkoxysilane interfacial layer was formed, the peak of the resonance curve shifted to larger incident angle as shown in Fig. 2. The incident angle, after anchoring of zeolite crystals was dependent on the type of the zeolite, for example, the incident angle for the 5A zeolite was 69.24◦ . Next, when the amine gas was introduced into the gas sample cell, the incident angle was immediately shifted and slowly shifted to higher incident angle for about 15 min; after that the incident angle remained almost constant. Moreover, when the atmosphere was changed from amine gases to air again, θ decreased with time and the incident angle returned to the original value after 20 min. Thus, the change of the incident angle would be attributed to the adsorption or desorption of amines on the zeolite layer. In the case of the butylamine gas (0.5%) for the 5A zeolite, the incident angle was 69.54◦ .
Fig. 1. Scanning electron micrographs of 5A zeolite crystals anchored to gold surfaces via the interfacial coupling layer. Scale bar: 100 m (top part), 10 m (bottom part). The frame indicates the area of higher magnification.
T. Arakawa et al. / Sensors and Actuators B 108 (2005) 899–902
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Fig. 5. Dependence θ on the concentration of ethylamine gas for some zeolites: (a) 13X zeolite, (b) 5A zeolite, (c) mordenite, (d) ZSM-5. Fig. 2. Resonance curves for a gold film: (a) in air (22.30◦ ), (b) coated with the thiol film (52.94◦ ), (c) coated with the chemically anchored 5A zeolite layer (69.24◦ ).
Fig. 3. Calibration plots of the amines for 5A zeolite: (a) propylamine (5.08), (b) ethylamine (8.7), (c) isopropylamine (5.62), (d) butylamine (4.71). The values in parentheses are the dielectric constants.
The shift of the incident angle after gas adsorption (θ) increased linearly with the concentration of butylamine as shown in Fig. 3, together with the results of other samples. The slope of the straight line refers to the sensitivity observed for the film. The slope depends upon the species of amines and the sensitivity of butylamine was lowest among some amines; the sequence of the sensitivity was propylamine ≈ ethylamine > isopropylamine > butylamine. This sequence agrees almost with that of the magnitude of dielectric constant. The incident angle of SPR spectra is influenced by the amount and refractive index of adsorbates. The sensitivity decreases with an increase in the carbon numbers. The result of amines was similar to that of lower hydrocarbons using an isoprene rubber thin film as reported in elsewhere [6]. On the other hand, Fig. 4 shows the dependence of θ on the gas concentration of butylamine
gas using various zeolites. The θ increased linearly up to ca. 1%. However, for 13X or 5A zeolite, it became almost a flat on the incident angle with the rise of the concentration. It would be assumed that there is the difference of the saturated adsorption amounts among these zeolites. The slope of line decreases on going from 13X zeolite to ZSM-5. Also, Fig. 5 shows the results of ethylamine. Up to 2%, there was little difference of the sensitivity among 13X, 5A and mordenite, and the sensitivity of ZSM-5 was extremely low. The sequence of zeolite was the same as that of butylamine above ca. 2%. Since it would be considered that the amines mainly adsorbed at the Br¨onsted site of zeolite, the sequence of zeolite, 13X zeolite > 5A zeolite ≈ mordenite > ZSM-5, is correlated to the amounts of adsorbed amines, defining from the value of SiO2 /Al2 O3 , which is the measure of amount of Br¨onsted site for zeolites. It is seemed that the SPR sensor with the ancored zeolite layer would be effective for the detection of butylamine, although the precise measurement of the adsorbed amount of amines for each zeolite and the selective detection of butylamine must be done.
4. Conclusions The major observations of the SPR sensor with the anchored zeolite thin film on a gold surface via the thiol–alkoxysilane interfacial layers are as follows. The sensitivity depended on the species of amines and the kind of zeolite. (1) The sensitivity of butylamine was lowest among some amines; the sequence of the sensitivity was propylamine ≈ ethylamine > isopropylamine > butylamine. (2) The sensitivity decreased on going from 13X zeolite to ZSM-5.
References
Fig. 4. Dependence θ on the concentration of butylamine gas for some zeolites: (a) 13X zeolite, (b) 5A zeolite, (c) mordenite, (d) ZSM-5.
[1] M. Hendrix, E.S. Priestly, G.F. Joyce, C.H. Wong, Direct observation of aminoglycoside–RNA interactions by surface plasmon resonance, J. Am. Chem. Soc. 119 (1997) 3641–3648. [2] J. Homola, Present and future of surface plasmon resonance biosensors, Anal. Bioanal. Chem. 377 (2003) 528–539. [3] R.J. Green, R.A. Frazier, K.M. Shakesheff, M.C. Davies, C.J. Roberts, S.J.B. Tendler, Surface plasmon resonance analysis of dynamicbiological interactions with biomaterials, Biomaterials 21 (2000) 1823–1835.
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T. Arakawa et al. / Sensors and Actuators B 108 (2005) 899–902
[4] H. Raether, Surface plasmon oscillation and their applications, Physics of Thin Films, vol. 9, Academic Press, New York, 1977, p. 145. [5] S. Miwa, T. Arakawa, selective gas detection by means of surface plasmon resonance sensors, Thin Solid Films 281/282 (1996) 466–468. [6] T. Urashi, T. Arakawa, Detection of lower hydrocarbons by means of surface plasmon resonance, Sens. Actuators B 76 (2001) 32–35. [7] K. Ideta, T. Arakawa, Surface plasmon resonance study for the detection of some chemical species, Sens. Actuators B 13/14 (1993) 384–386. [8] Y. Yan, T. Bein, Molecular recognition on acoustic wave devices: sorption in chemically anchored zeolite monolayers, J. Phys. Chem. 96 (1992) 9387–9393.
Biographies Tsuyoshi Arakawa received his BEng degree in Industrial Chemistry in 1971 from Miyazaki University and Dr Eng degree in 1978 from Kyushu
University. He had been an assistant professor at Osaka University since 1977 and moved to Kinki University in Kyushu. He has been a professor there since 1992. His current research is focused on optical chemical sensors based on laser-excited surface plasmon resonance, detection of chemical species with luminescent rare earth complexes, semiconductive gas sensors having heterocontacts and preparation of new nintermetallic compounds by a mechanical alloying method. Atsushi Kawabayashi received his BEng degree in industrial chemistry in 2003 from Kinki University in Kyushu. He was a student in Graduate School of Industrial Engineering Science, Kinki University, and was interested in optical sensors based on laser-excited surface plasmon resonance. Takashi Saga received his BEng degree in industrial chemistry in 2004 from Kinki University in Kyushu. He was a student in Graduate School of Industrial Engineering Science, Kinki University, and was interested in optical sensors based on laser-excited surface plasmon resonance.
Detection of butylamine by means of surface plasmon resonance Tsuyoshi Arakawa∗ , Atsushi Kawabayashi, Takashi Saga Department of Biological and Environmental Chemistry, School of Humanity-Oriented Science and Engineering, Kinki University, Iizuka, Fukuoka 820-8555, Japan Received 13 July 2004; received in revised form 11 November 2004; accepted 17 November 2004 Available online 11 January 2005
Abstract The detection of butylamine as a malodorous substance was investigated by a surface plasmon resonance (SPR) sensor. When the A zeolite thin film on a gold surface via the thiol–alkoxysilane interfacial layers was formed, the resonance angle changed from 22.30◦ to 69.24◦ . Moreover, the anchored zeolite layers were exposed to butylamine, the shifts of the incident angle (θ) were observed. The θ increased linearly with the gas concentration region of 0% to about 1%. The sensitivity of butylamine was lowest among some amines. Also, the sensitivity depended on the kind of zeolite as follows; the sequence was 13X zeolite > 5A zeolite ≈ mordenite > ZSM-5. © 2004 Elsevier B.V. All rights reserved. Keywords: Zeolite; Butylamine; Surface plasmon resonance sensor
1. Introduction A lot of studies for the surface plasmon resonance (SPR) have been reported in the field of chemical sensing. In particular, the applied study of SPR sensor has drawn attention in the field of medical chemistry [1–3]. In the SPR sensor, the detecting material is greatly influenced in the substrate coated with the gold thin film of the SPR sensor head, as can be understood from the principle of SPR [4]. We have attempted to detect some gaseous species using a SPR sensor. When the polyethylene glycol thin film was coated on an Au thin film, it was found that the alcohol could be selectively detected [5]. Also, it was reported that the SPR sensor with the Apiezon–grease thin film would be effective the detection of lower hydrocarbons [6]. Moreover, it may be expected that the kind of detectable gases would be increased by the use of inorganic thin film. In this paper, we briefly describe the detection of butylamine as a malodorous substance using chemically anchored zeolite layers, as there would be appreciable interaction between butylamine and acid sites ∗
Corresponding author. Tel.: +81 948 22 5655; fax: +81 948 23 0536. E-mail address: [email protected] (T. Arakawa).
0925-4005/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2004.11.074
(Lewis or Br¨onsted acid sites) as an adsorption sites on a zeolite.
2. Experiment The apparatus for an SPR-based chemical sensor is essentially identical to that reported elsewhere [7]. The sensor head was prepared in the following way. A gold thin film with a thickness of about 55 nm was prepared by thermal evaporation of gold (purity; 99.99%) on the surface of corner cube prism. The zeolite used commercial sodium 5A zeolite, sodium 13X zeolite, mordenite and ZSM-5. The preparation of zeolite thin film on the gold surface was referred to the method as reported elsewhere [8]. The anchoring of zeolite crystals to the gold surface involved two steps: formation of the thiol monolayers and exposure to a zeolite suspension in toluene, followed by the attachment of a gas sample cell. The thiol layers were formed by immersing the gold thin film for 1 h into the solution dissolving 0.1 g of (3-mercaptopropyl) trimethoxysilane in 30 ml of toluene. Then, the thiol layers were rinsed with toluene to excess adsorbate from the gold thin film, followed by stirring in 30 ml toluene solution of dis-
900
T. Arakawa et al. / Sensors and Actuators B 108 (2005) 899–902
persed zeolite (0.1 g) overnight. After attachment of the zeolite crystals, the alkoxy groups of the silane were hydrolyzed and further reacted with the zeolite by heating in air at 373 K for 1 h. In order to compare the sensitivity of butylamine, the sensitivity of some amines (ethylamine, propylamine and isopropylamine) was investigated. Butylamine gases were diluted with dry air at various concentrations and were passed through a gas sample cell. Fixed quantity of ethylamine gases was introduced from one side of a gas sample cell with a gas syringe. SEM micrographs were recorded by a Hitachi S-4300SE/N.
3. Results and discussion 3.1. Formation of the zeolite crystal Fig. 1 presents SEM micrograph of the 5A zeolite-coated gold surface on a slide glass instead of a prism. It is clear that this coating process provides a method to obtain uniform crystal distributions on the entire slide surface. The cubic shape crystal, which is feature of the crystal structure of the 5A zeolite, was observed. Also it was independently confirmed that the zeolite crystals recovered from the gold substrate gave the same X-ray diffraction pattern and peak ratios as the bulk. Thus, it was clear that the attached
particles displayed the crystalline habit of the bulk materials. 3.2. SPR spectra under adsorption of amines In the surface plasmon method, the resonance angle is very sensitive to the refractive index of the medium outside the metal thin film. When the medium on the surface of gold thin film was changed from air to a thiol–alkoxysilane thin film, the resonance angle changed from 22.30◦ to 52.94◦ . Moreover, when the zeolite layer via the thiol–alkoxysilane interfacial layer was formed, the peak of the resonance curve shifted to larger incident angle as shown in Fig. 2. The incident angle, after anchoring of zeolite crystals was dependent on the type of the zeolite, for example, the incident angle for the 5A zeolite was 69.24◦ . Next, when the amine gas was introduced into the gas sample cell, the incident angle was immediately shifted and slowly shifted to higher incident angle for about 15 min; after that the incident angle remained almost constant. Moreover, when the atmosphere was changed from amine gases to air again, θ decreased with time and the incident angle returned to the original value after 20 min. Thus, the change of the incident angle would be attributed to the adsorption or desorption of amines on the zeolite layer. In the case of the butylamine gas (0.5%) for the 5A zeolite, the incident angle was 69.54◦ .
Fig. 1. Scanning electron micrographs of 5A zeolite crystals anchored to gold surfaces via the interfacial coupling layer. Scale bar: 100 m (top part), 10 m (bottom part). The frame indicates the area of higher magnification.
T. Arakawa et al. / Sensors and Actuators B 108 (2005) 899–902
901
Fig. 5. Dependence θ on the concentration of ethylamine gas for some zeolites: (a) 13X zeolite, (b) 5A zeolite, (c) mordenite, (d) ZSM-5. Fig. 2. Resonance curves for a gold film: (a) in air (22.30◦ ), (b) coated with the thiol film (52.94◦ ), (c) coated with the chemically anchored 5A zeolite layer (69.24◦ ).
Fig. 3. Calibration plots of the amines for 5A zeolite: (a) propylamine (5.08), (b) ethylamine (8.7), (c) isopropylamine (5.62), (d) butylamine (4.71). The values in parentheses are the dielectric constants.
The shift of the incident angle after gas adsorption (θ) increased linearly with the concentration of butylamine as shown in Fig. 3, together with the results of other samples. The slope of the straight line refers to the sensitivity observed for the film. The slope depends upon the species of amines and the sensitivity of butylamine was lowest among some amines; the sequence of the sensitivity was propylamine ≈ ethylamine > isopropylamine > butylamine. This sequence agrees almost with that of the magnitude of dielectric constant. The incident angle of SPR spectra is influenced by the amount and refractive index of adsorbates. The sensitivity decreases with an increase in the carbon numbers. The result of amines was similar to that of lower hydrocarbons using an isoprene rubber thin film as reported in elsewhere [6]. On the other hand, Fig. 4 shows the dependence of θ on the gas concentration of butylamine
gas using various zeolites. The θ increased linearly up to ca. 1%. However, for 13X or 5A zeolite, it became almost a flat on the incident angle with the rise of the concentration. It would be assumed that there is the difference of the saturated adsorption amounts among these zeolites. The slope of line decreases on going from 13X zeolite to ZSM-5. Also, Fig. 5 shows the results of ethylamine. Up to 2%, there was little difference of the sensitivity among 13X, 5A and mordenite, and the sensitivity of ZSM-5 was extremely low. The sequence of zeolite was the same as that of butylamine above ca. 2%. Since it would be considered that the amines mainly adsorbed at the Br¨onsted site of zeolite, the sequence of zeolite, 13X zeolite > 5A zeolite ≈ mordenite > ZSM-5, is correlated to the amounts of adsorbed amines, defining from the value of SiO2 /Al2 O3 , which is the measure of amount of Br¨onsted site for zeolites. It is seemed that the SPR sensor with the ancored zeolite layer would be effective for the detection of butylamine, although the precise measurement of the adsorbed amount of amines for each zeolite and the selective detection of butylamine must be done.
4. Conclusions The major observations of the SPR sensor with the anchored zeolite thin film on a gold surface via the thiol–alkoxysilane interfacial layers are as follows. The sensitivity depended on the species of amines and the kind of zeolite. (1) The sensitivity of butylamine was lowest among some amines; the sequence of the sensitivity was propylamine ≈ ethylamine > isopropylamine > butylamine. (2) The sensitivity decreased on going from 13X zeolite to ZSM-5.
References
Fig. 4. Dependence θ on the concentration of butylamine gas for some zeolites: (a) 13X zeolite, (b) 5A zeolite, (c) mordenite, (d) ZSM-5.
[1] M. Hendrix, E.S. Priestly, G.F. Joyce, C.H. Wong, Direct observation of aminoglycoside–RNA interactions by surface plasmon resonance, J. Am. Chem. Soc. 119 (1997) 3641–3648. [2] J. Homola, Present and future of surface plasmon resonance biosensors, Anal. Bioanal. Chem. 377 (2003) 528–539. [3] R.J. Green, R.A. Frazier, K.M. Shakesheff, M.C. Davies, C.J. Roberts, S.J.B. Tendler, Surface plasmon resonance analysis of dynamicbiological interactions with biomaterials, Biomaterials 21 (2000) 1823–1835.
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T. Arakawa et al. / Sensors and Actuators B 108 (2005) 899–902
[4] H. Raether, Surface plasmon oscillation and their applications, Physics of Thin Films, vol. 9, Academic Press, New York, 1977, p. 145. [5] S. Miwa, T. Arakawa, selective gas detection by means of surface plasmon resonance sensors, Thin Solid Films 281/282 (1996) 466–468. [6] T. Urashi, T. Arakawa, Detection of lower hydrocarbons by means of surface plasmon resonance, Sens. Actuators B 76 (2001) 32–35. [7] K. Ideta, T. Arakawa, Surface plasmon resonance study for the detection of some chemical species, Sens. Actuators B 13/14 (1993) 384–386. [8] Y. Yan, T. Bein, Molecular recognition on acoustic wave devices: sorption in chemically anchored zeolite monolayers, J. Phys. Chem. 96 (1992) 9387–9393.
Biographies Tsuyoshi Arakawa received his BEng degree in Industrial Chemistry in 1971 from Miyazaki University and Dr Eng degree in 1978 from Kyushu
University. He had been an assistant professor at Osaka University since 1977 and moved to Kinki University in Kyushu. He has been a professor there since 1992. His current research is focused on optical chemical sensors based on laser-excited surface plasmon resonance, detection of chemical species with luminescent rare earth complexes, semiconductive gas sensors having heterocontacts and preparation of new nintermetallic compounds by a mechanical alloying method. Atsushi Kawabayashi received his BEng degree in industrial chemistry in 2003 from Kinki University in Kyushu. He was a student in Graduate School of Industrial Engineering Science, Kinki University, and was interested in optical sensors based on laser-excited surface plasmon resonance. Takashi Saga received his BEng degree in industrial chemistry in 2004 from Kinki University in Kyushu. He was a student in Graduate School of Industrial Engineering Science, Kinki University, and was interested in optical sensors based on laser-excited surface plasmon resonance.