Research article Received: 12 January 2015,
Revised: 11 March 2015,
Accepted: 18 April 2015
Published online in Wiley Online Library: 27 May 2015
(wileyonlinelibrary.com) DOI 10.1002/bio.2950
N-butylamine functionalized graphene oxide for detection of iron(III) by photoluminescence quenching Javad Gholami,a Mehrdad Manteghian,b* Alireza Badiei,c Hiroshi Uedad and Mehran Javanbakhte ABSTRACT: An N-butylamine functionalized graphene oxide nanolayer was synthesized and characterized by ultraviolet (UV)– visible spectrometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Detection of iron(III) based on photoluminescence spectroscopy was investigated. The N-butylamine functionalized graphene oxide was shown to specifically interact with iron (III), compared with other cationic trace elements including potassium (I), sodium (I), calcium (II), chromium (III), zinc (II), cobalt (II), copper (II), magnesium (II), manganese (II), and molybdenum (VI). The quenching effect of iron (III) on the luminescence emission of N-butylamine functionalized graphene oxide layer was used to detect iron (III). The limit of detection (2.8 × 106 M) and limit of quantitation (2.9 × 105 M) were obtained under optimal conditions. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: N-butylamine; graphene oxide; photoluminescence; iron(III)
Introduction
Luminescence 2016; 31: 229–235
* Correspondence to: Mehrdad Manteghian, Department of Chemical Engineering, Tarbiat Modares University, P.O. Box 14115-311, Tehran, Iran. E-mail: [email protected] a
Material Engineering Department, Nano Materials Division, Tarbiat Modares University, Tehran, Iran
b
Department of Chemical Engineering, Tarbiat Modares University, P.O. Box 14115-311, Tehran, Iran
c
School of Chemistry, College of Science, University of Tehran, P.O. Box 141556455, Tehran, Iran
d
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1–18, Nagatsuta-cho, Midori-ku, Yokoyama, Kanagawa, 226-8503, Japan
e
Department of Chemistry, Amirkabir University of Technology, Tehran, Iran Abbreviations: GO, Graphene oxide; LOD, Limit of detection; LOQ, Limit of quantitation; NGO, N-butylamine functionalized graphene oxide; PET, Photoinduced electron transfer; XPS, X-ray photoelectron spectroscopy.
Copyright © 2015 John Wiley & Sons, Ltd.
229
Carbon nanomaterials have attracted attention because of their prominent electronic, optical, thermal, mechanical, and chemical properties (1,2). Graphene, carbon nanostructures has been investigated for use in many applications, such as polymer composites, energy-related materials, sensor, field-effect transistors (FET), and biomedical applications (3). Graphene oxide (GO) that is obtained from the chemical oxidation of graphene layer has drawn much attention in optical detection because of its unique optical properties for example as a platform containing a mixture of sp2/sp3 hybridized carbon atoms (4), fluorescence emission potential (5), solubility, and functionalization ability (3), which are responsible for its unique optical features. These characteristics have been applied to fluorescence-based detection of a wide range of samples including proteins (6), biomarkers (7), pathogen (8), DNA (9), RNA (10,11), dopamine (12), silver (I) (13), mercury (II) (14,15), potassium (16), and other biological analytes (17). However, as GO has low emission efficiency, overcoming this problem with chemical modification can be an effective solution (18). Metals are the main components of trace elements (i.e,, chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn)) that are required by organisms in very small quantities to maintain proper physiological and biochemical functions of our body (19). Iron is one of the most important trace elements, which exists in two different oxidation states, ferric ion (Fe3+) and ferrous ion (Fe2+) in the human body, and which plays several key roles. It is involved in the formation of red blood cells, provides for the exchange of gases between the lungs and body tissue, and supports the immune system and metabolism (20,21). Therefore, different methods have been investigated for iron detection such as atomic absorption spectroscopy (22) and inductively coupled plasma emission spectrometry (23). However, the methods based on fluorescent sensors have
received considerable attention because of their ability to detect very low concentrations of specific substances without complicated processes (24). Hence, various fluorescent sensors have been developed for the selective detection of iron (III) in recent years (24). Accordingly, the use of photoluminescence methods together with new material such as functionalized GO can be a suitable process for simple and direct detection of iron. For the current study N-butylamine functionalized graphene oxide (NGO) was synthesized with good photoluminescence emission efficiency. The detection of iron according to the quenching of NGO luminescence emission was investigated, and was found to be a simple and affordable method. Herein, good limit of detection (LOD) and limit of quantitation (LOQ) were obtained under optimal conditions.
J. Gholami et al.
Experimental Materials Graphite powder was supplied by Daejung (Korea). N-Butylamine, potassium permanganate, sodium nitrate, sulfuric acid, iron(III) nitrate nonahydrate, zinc(II) nitrate monohydrate, cobalt(II) nitrate hexahydrate, magnesium (II) nitrate hexahydrate, manganese (II) nitrate tetrahydrate, cooper(II) nitrate trihydrate, chromium (III) nitrate nonahydrate, hydrogen peroxide, thionyl chloride, ammonium heptamolybdate tetrahydrate, dimethylformamide, tetrahydrofuran, sodium hydroxide, phosphoric acid, boric acid and acetic acid were from Merck (Germany).
Instruments The UV-visible spectrum was measured using a Ray Leigh UV-1600 spectrometer. Fourier transform infrared (FT-IR) spectra were recorded with a Spectrum RX I (Perkin–Elmer). The X-ray photoelectron spectroscopy spectrum (XPS) of the sample was recorded by an ESCA-3400 Electron spectrometer (Shimadzu, Kyoto, Japan) (with silver as a standard) for which the sample was prepared by drop casting the suspension of NGO on cleaned silicon wafer, and drying at 60 °C for 2 h. The transmission electron microscopy (TEM) image was taken by an Hitachi HT-7100 (100 kV). The sample for TEM was prepared by drop casting the NGO suspension in water on a carbon-coated copper TEM grid, and the grids were left to dry at room temperature. The size of particle was measured by a Malvern Instruments Zetasizer Nano-S90. The photoluminescence spectra were obtained with a Cary Eclipse spectrophotometer (Agilent Technology).
The mixture was cooled down and dispersed in distilled water (20 mL). After that, the suspension was centrifuged at 7000 rpm for 5 min, and the supernatant was dried by rotary evaporation. Finally, the N-butylamine functionalized GO powder was redispersed in distilled water (20 mL) (Fig. 1) (18). Iron(III) detection The photoluminescence titration experiments were performed in the solution containing NGO (0.5 g/L) and Britton–Robinson buffer at a 1:2 ratio (v/v). The time-dependent fluorescence spectra were recorded after iron (III) was added to the experimental solution. The effect of pH was investigated by adding 7 μmol/L iron (III) in buffer with different pH values (i.e. 3.0, 5.0, 7.0, and 9.0). Sensitivity was measured with different concentrations of iron (III). Selectivity was examined by adding 7 μmol/L of either potassium (I), sodium (I), calcium (II), chromium (III), zinc (II), cobalt (II), copper (II), magnesium (II), manganese (II), or molybdenum (VI).
Results and discussion Characterization of NGO UV-visible spectroscopy. GO exhibited maximum absorbance at 230 nm, which corresponds to the π → π* transitions of the aromatic C = C bond, with a weak shoulder peak at 300 nm, which corresponds to the n → π* transition of the C = O bond (Fig. 2a) (26). Clearly, the absorption peak of π → π* and n → π* transitions after N-butylamine modification of GO are shifted to 280 nm and 345 nm, respectively, which can be related to nucleophilic reactions between epoxy and carboxylic groups of GO by N-butylamine (Fig. 2b). These reactions cause to remove some of
NGO synthesis GO was synthesized according to the Hummer method (25). Typically, graphite powder (1 g) and sodium nitrate (1 g) were added to sulfuric acid (46 mL) concentrate in an ice bath, while stirring the potassium permanganate (6 g) was added gradually. Then, distilled water (20 mL) and hydrogen peroxide (30%) were added to the suspension. The mixture was filtrated and washed with hydrogen chloride (0.1%) and distilled water multiple times and dried at room temperature. Next, the dried GO (0.2 g) was added to thionyl chloride (25 mL) and dimethylformamide (2 mL), and the mixture was stirred at 80 °C for 48 h. Afterwards, the mixture was centrifuged twice at 5000 rpm for 15 min and the supernatant was discarded. The remaining solid, after washing with tetrahydrofuran and drying in vacuum at room temperature, was added with N-butylamine (1 mL) and heated under nitrogen at 60 °C for 72 h.
Figure 2. UV–visible absorption spectra of GO and NGO suspensions.
230
Figure 1. Schematic illustration of the functionalizing GO with N-butylamine.
wileyonlinelibrary.com/journal/luminescence
Copyright © 2015 John Wiley & Sons, Ltd.
Luminescence 2016; 31: 229–235
N-butylamine functionalized graphene oxide for detection of Iron (III) reactive sites, which can recover sp2 domains of GO nanolayers and more extensive redistribution of π electrons (18,27). So, NGO exhibited longer wavelength and enhanced absorbance, which can be related to the conjugation of π electrons. FT- IR spectroscopy. FT-IR spectrum of GO showed a peak at 1730 cm1 due to the stretch of the C = O bond of the carboxylic acid group of GO (Fig. 3a), which disappeared after the chemical modification of GO by N-butylamine, and a new vibration band around 1648 cm1 appeared due to the C = O stretching of the amide group for NGO (Fig. 3b). Also, a new peak at 1162 cm1 is assigned to the C–N–C asymmetric stretching of the attached N-butylamine (Fig. 3b). So, the results suggest that N-butylamine is attached to the GO surface by a covalent bond through the formation of an amide group. The peaks at 1035 cm1 and 1040 cm1 in the both spectra of GO and NGO are attributed to the C–O–C
bond of the epoxy group (18). So, FT-IR spectra exhibited amide formation on the surface of GO after modification with N-butylamine. XPS spectroscopy. Based on the XPS spectrum, the curve fitting of the N 1 s was performed using a Lorentzian peak shape (Fig. 4). The peak of N 1 s spectrum at 400.9 is related to the N-C bond of the amide group, and the peak at 399.7 eV is attributed to the N–C bond of the of 1,2-amino alcohols which it can be due to ring-opening aminations of epoxides by N-butylamine (18). Transmission electron microscopy. A TEM image shows the nanolayers of NGO on the surface of a copper grid (Fig. 5). The NGO nanolayers tend to attach each other and form multilayers. The zetasizer showed that the average size of the layer in suspension was about 70 nm.
Figure 3. FT-IR spectra of (a) GO, and (b) NGO.
231
Figure 4. The N 1 s XPS spectra for NGO.
Luminescence 2016; 31: 229–235
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence
J. Gholami et al. Detection of iron (III) by NGO nanolayers
Figure 5. Transmission electron microscopy (TEM) image of NGO nanolayers.
Quenching of NGO fluorescence by iron(III). Photoluminescence spectroscopy was used to detect iron (III) by NGO nanolayers. NGO solution (0.5 g/L) at an excitation wavelength of 350 nm emitted luminescence at 433 nm (Fig. 6a, 1) that it is brighter than GO photoluminescence (Fig. 6a; 2). In GO, the photoluminescence was perhaps caused by electron–hole pairs due to sp2 domains in the sp3 matrix that the epoxide and carboxylic groups in GO often induce following non-radiative recombination of localized electron–hole pairs that leads to low emission efficiency (18,28). After modification, carboxylic and some epoxide groups of GO are reacted with N-butylamine and removed (15). Consequently, the NGO emitted brighter photoluminescence. The addition of Iron (III) significantly quenched the NGO luminescence emission at 433 nm (Fig. 6a; 3). It can be related to the photoinduced electron transfer (PET), which is the light-induced transfer of electrons from the nitrogen of NGO as a donor to the iron (III) as an acceptor (Fig. 6b). At the different pH, quenching ratio (F0 F)/F (where F0 and F are the intensity of NGO luminescence emission in the absence and presence of iron (III), respectively) is variable. For instance, 0.75 mL of NGO (0.5 g/L) was added to quartz cells with 1.5 mL Britton–Robinson buffer with
232
Figure 6. (a) Fluorescence spectra of 1. NGO (0.5 g/L), 2. GO (0.5 g/L), and 3. Quenched luminescence emission of NGO by iron (III). (b) Schematic of interaction NGO and iron (III) 3+ (Fe ) and PET. (c) Quenched luminescence emission of NGO (0.5 g/L) by iron (III) (7 μmol/L) in Britton–Robinson buffer at different pH values (λex = 350 nm, λem = 433 nm).
wileyonlinelibrary.com/journal/luminescence
Copyright © 2015 John Wiley & Sons, Ltd.
Luminescence 2016; 31: 229–235
N-butylamine functionalized graphene oxide for detection of Iron (III) different pH values (i.e,, 2.0, 5.0, 7.0, and 9.0). Then, 15 μL of iron (III) (103 mol/L) was added to each cell. The highest quenching ratio occurred at pH 7 (Fig. 6c). At the low pH, the amide and amine groups are protonated and was not quenched by iron (III). However, in the higher pH these groups become deprotonated, and quenching ratio increases due to stronger PET process (29). The interaction time between the NGO (0.5 g/L) and iron (III) (103 mol/L) was investigated (Fig. 7). Since the quenching was stabilized 3 min after mixing samples, the photoluminescence spectra were acquired at 3 min. Iron (III) dose dependency of NGO photoluminescence. The potential use of NGO for the detection of iron (III) was examined by photoluminescence titration. Microliter volumes of iron (III) were gradually added to NGO (0.5 g/L) in the solution at pH 7, and luminescence intensities were recorded after 3 min (Fig. 8a). The calibration curve of F0/F versus iron (III) concentration showed the quenching according to PET, following a typical Stern–Volmer type equation as follows (Fig. 8b):
Figure 7. Time course of NGO luminescence quenching ratio (0.5 g/L), by iron (III) (7 μmol/L) at pH 7 (λex = 350 nm, λem = 433 nm).
F 0 = F ¼ 1 þ K sv Feþ3
(1)
where F0 and F are the intensities of NGO luminescence emission in the absence and presence of iron (III), respectively; Ksv is the Stern–Volmer constant at approximately 0.009, with a regression coefficient (r2) of 0.98. LOD and LOQ were acquired using eqns (2) and (3) as follows: LOD ¼ 3 SD=m
(2)
LOQ ¼ 10 SD=m
(3)
where SD is the standard deviation for the blank and m is the slope of NGO luminescence intensity against the concentration of iron (III). Here, SD and m are 12 and 4.2 × 106, respectively. Therefore, the LOD and LOQ are calculated as 2.8 × 106 M and 2.9 × 105 M, respectively. Selectivity against other minerals. The selectivity of the sensor was examined for other cationic trace element samples in the same condition (i.e,, NGO, 0.5 g/ L; sample, 7 μmol/L; interaction time, 3 min; pH 7) (Fig. 9). As a result, NGO exhibited good iron (III) selectivity over other samples (potassium (I), sodium (I), calcium (II), chromium (III), zinc (II), cobalt (II), copper (II), magnesium (II), manganese (II), and molybdenum (VI)), which can be attributed to the high charge densities of iron (III). The charge density of the metal ions is defined as the amount of electric charge/unit volume, which is one of the most important characterizations of the relative electrophilicity of a metal ion (30). Based on the formal charge and Shannon ionic radius of cations (31), the charge densities increase in the following order: potassium (I) (0.1) < sodium (I) (0.5) < calcium (II) (0.48) < cobalt (II) (1.15) < zinc (II) (1.18) < manganese (II) (1.65) < copper (II) (1.28) < magnesium (II) (2.5) < chromium (III) (3.12) < molybdenum (VI) (3.75) < iron (III) (6.0). Accordingly, the iron (III) has biggest charge density among the cationic trace elements that cause the highest electrophilicity. As a result, the quenching effect of iron (III) is far more prominent compared with other cationic trace elements based on PET
Luminescence 2016; 31: 229–235
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence
233
Figure 8. (a) Photoluminescence emission of NGO (0.5 g/L) added with increasing concentrations of iron as shown in (b). (b) Calibration curve of F0/F versus the concentration of 6 4 iron (III) (6.6 × 10 M to 1.51 × 10 M) (time: 3 min, pH 7, λex = 350 nm, λem = 433 nm).
J. Gholami et al.
Figure 9. Photoluminescence quenching ratio of NGO (0.5 g/L) in the presence of the same concentration (7 μmol/L) of different cationic trace elements (time: 3 min, pH 7, λex = 350 nm, λem = 433 nm).
mechanism, probably because of the stronger interaction between NGO as a donor and iron (III) as an acceptor of electrons.
Conclusion The NGO nanolayer was synthesized. FT-IR and XPS spectra were used to characterize different functional groups of the graphene layer. Transmission electron image showed the nanolayer of N-butylamine functionalized graphene in suspension. Photoluminescence spectroscopy was used to detect iron (III) based on the quenching effect of iron (III). The NGO nanolayer interacted best with iron (III) at pH 7. The detection of iron (III) was performed with good selectivity in the presence of other cationic trace elements including potassium (I), sodium (I), calcium (II), chromium (III), zinc (II), cobalt (II), copper (II), magnesium (II), manganese (II), and molybdenum (VI). Therefore, this functionalized GO will be a good substrate for detecting trace amounts of iron in biological samples. Acknowledgements The Authors thank the Tokyo Institute of Technology and University of Tehran for their support in TEM, XPS, UV-visible and photoluminescence characterizations.
References
234
1. Jariwala D, Sangwan VK, Lauhon LJ, Marks TJ, Hersam MC. Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing. Chem Soc Rev 2013;42:2824–60. 2. Akhavan O. Photocatalytic reduction of graphene oxides hybridized by ZnO nanoparticles in ethanol. Carbon 2011;49:11–8. 3. Dreyer DR, Park S, Bielawski CW, Ruoff RS. The chemistry of graphene oxide. Chem Soc Rev 2010;39:228–40. 4. Chung C, Kim YK, Shin D, Ryoo SR, Hong BH, Min DH. Biomedical applications of graphene and graphene oxide. Acc Chem Res 2013; 46:2211–24. 5. Lu CH, Yang HH, Zhu CL, Chen X, Chen GN. A graphene platform for sensing biomolecules. Angew Chem Int Ed 2009;48:4785–7. 6. Lu CH, Li J, Zhang XL, Zheng AX, Yang HH, Chen X, Chen GN. General approach for monitoring peptide–protein interactions based on graphene–peptide complex. Anal Chem 2011;83:7276–82. 7. He Y, Lin Y, Tang H, Pang D. A graphene oxide-based fluorescent aptasensor for the turn-on detection of epithelial tumor marker mucin 1. Nanoscale 2012;4:2054–9.
wileyonlinelibrary.com/journal/luminescence
8. Jung JH, Cheon DS, Liu F, Lee KB, Seo TS. A graphene oxide based immuno-biosensor for pathogen detection. Angew Chem Int Ed 2010;49:5708–11. 9. Wu C, Zhou Y, Miao X, Ling L. A novel fluorescent biosensor for sequence-specific recognition of double-stranded DNA with the platform of graphene oxide. Analyst 2011;136:2106–10. 10. Zhou X, Liao Y, Xing D. Sensitive monitoring of RNA transcription levels using a graphene oxide fluorescence switch. Chin Sci Bull 2013; 58:2634–9. 11. Debin Z, Lan Z, Wenge M, Suqin L, Xiaobo X. Detection of microRNA in clinical tumor samples by isothermal enzyme-free ampli fi cation and label-free graphene oxide-based SYBR Green I fluorescence platform. Biosens Bioelectron 2015;65:152–8. 12. Chen JL, Yan XP, Meng K, Wang SF. Graphene oxide based photoinduced charge transfer label-free near-infrared fluorescent biosensor for dopamine. Anal Chem 2011;83:8787–93. 13. Wen Y, Xing F, He S, Song S, Wang L, Long Y, Li D, Fan C. A graphenebased fluorescent nanoprobe for silver(I) ions detection by using graphene oxide and a silver-specific oligonucleotide. Chem Comm 2010;46:2596–8. 14. Li M, Zhou X, Ding W, Guo S, Wu N. Fluorescent aptamer-functionalized graphene oxide biosensor for label-free detection of mercury(II). Biosens Bioelectron 2013;41:889–93. 15. Jiahao H, Xiang G, Jingjing J, Jang KK, Zhigang L. Graphene 2+ oxide-based amplified fluorescent biosensor for Hg detection through hybridization chain reactions. Anal Chem 2014; 86:3209–315. 16. Shu JZ, Yan Y, Chun Mei L, Cheng ZH. Graphene oxide amplified fluorescence anisotropy for label-free detection of potassium ion. Analyst 2015;140:353–7. 17. Wang Y, Li Z, Wang J, Li J, Lin Y. Graphene and graphene oxide: biofunctionalization and applications in biotechnology. Trends Biotechnol 2011;29:205–12. 18. Mei Q, Qingsong M, Kui Z, Guijian G, Bianhua L, Suhua W, Zhongping Z. Highly efficient photoluminescent graphene oxide with tunable surface properties. Chem Comm 2010;46:7319–21. 19. Fraga CG. Relevance, essentiality and toxicity of trace elements in human health. Mol Asp Med 2005;26:235–44. 20. Al Faris NA, Ahmad D. Distribution of trace elements like calcium, copper, iron and zinc in serum samples of colon cancer—a case control study. J King Saud Univ Sci 2011;23:337–40. 21. Hirayama T, Okuda K, Nagasawa H. A highly selective turn-on fluorescent probe for iron(II) to visualize labile iron in living cells. Chem Sci 2013;4:1250–6. 22. Gómez-Nieto B, Gismera MJ, Sevilla MT, Procopio JR. Simultaneous and direct determination of iron and nickel in biological solid samples by high-resolution continuum source graphite furnace atomic absorption spectrometry. Talanta 2013;116:860–5. 23. Whittaker PG, Lind T, Williams JG, Gray AL. Inductively coupled plasma mass spectrometric determination of the absorption of iron in normal women. Analyst 1989;114:675–8.
Copyright © 2015 John Wiley & Sons, Ltd.
Luminescence 2016; 31: 229–235
N-butylamine functionalized graphene oxide for detection of Iron (III) 24. Sahoo SK, Sharma D, Bera RK, Crisponi G, Callan JF. Iron(III) selective molecular and supramolecular fluorescent probes. Chem Soc Rev 2012;41:7195–227. 25. Hummer WS. Preparation of graphitic oxide. J Am Chem Soc 1957;80:1339. 26. Paredes JI. Graphene oxide dispersions in organic solvents. Langmuir 2008;24:10560–4. 27. Taylor KL, Liu RQ, Liang PH, Price J, Dunaway-Mariano D, Tonge PJ, Clarkson J, Carey PR. Evidence for electrophilic catalysis in the 4chlorobenzoyl-CoA dehalogenase reaction: UV, Raman, and 13C-NMR spectral studies of dehalogenase complexes of benzoyl-CoA adducts. Biochemistry 1995;34:13881–8.
28. Shang J, Ma L, Li J, Ai W, Yu T, Gurzadyan GG. The origin of fluorescence from graphene oxide. Sci Rep. 2012;2 . 29. Lakowicz JR. Principles of fluorescence spectroscopy. 3rd ed. LLC, New York, USA: Springer Science+Business Media 2006:642–644. 3+ 30. Yadavi M, Badiei A, Ziarani GM. A novel Fe ions chemosensor by covalent coupling fluorene onto the mono, di- and tri-ammonium functionalized nanoporous silica type SBA-15. Appl Surf Sci 2013;279:121–8. 31. Shannon RT. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Cryst 1976;32:751–67.
235
Luminescence 2016; 31: 229–235
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence
Revised: 11 March 2015,
Accepted: 18 April 2015
Published online in Wiley Online Library: 27 May 2015
(wileyonlinelibrary.com) DOI 10.1002/bio.2950
N-butylamine functionalized graphene oxide for detection of iron(III) by photoluminescence quenching Javad Gholami,a Mehrdad Manteghian,b* Alireza Badiei,c Hiroshi Uedad and Mehran Javanbakhte ABSTRACT: An N-butylamine functionalized graphene oxide nanolayer was synthesized and characterized by ultraviolet (UV)– visible spectrometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Detection of iron(III) based on photoluminescence spectroscopy was investigated. The N-butylamine functionalized graphene oxide was shown to specifically interact with iron (III), compared with other cationic trace elements including potassium (I), sodium (I), calcium (II), chromium (III), zinc (II), cobalt (II), copper (II), magnesium (II), manganese (II), and molybdenum (VI). The quenching effect of iron (III) on the luminescence emission of N-butylamine functionalized graphene oxide layer was used to detect iron (III). The limit of detection (2.8 × 106 M) and limit of quantitation (2.9 × 105 M) were obtained under optimal conditions. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: N-butylamine; graphene oxide; photoluminescence; iron(III)
Introduction
Luminescence 2016; 31: 229–235
* Correspondence to: Mehrdad Manteghian, Department of Chemical Engineering, Tarbiat Modares University, P.O. Box 14115-311, Tehran, Iran. E-mail: [email protected] a
Material Engineering Department, Nano Materials Division, Tarbiat Modares University, Tehran, Iran
b
Department of Chemical Engineering, Tarbiat Modares University, P.O. Box 14115-311, Tehran, Iran
c
School of Chemistry, College of Science, University of Tehran, P.O. Box 141556455, Tehran, Iran
d
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259-R1–18, Nagatsuta-cho, Midori-ku, Yokoyama, Kanagawa, 226-8503, Japan
e
Department of Chemistry, Amirkabir University of Technology, Tehran, Iran Abbreviations: GO, Graphene oxide; LOD, Limit of detection; LOQ, Limit of quantitation; NGO, N-butylamine functionalized graphene oxide; PET, Photoinduced electron transfer; XPS, X-ray photoelectron spectroscopy.
Copyright © 2015 John Wiley & Sons, Ltd.
229
Carbon nanomaterials have attracted attention because of their prominent electronic, optical, thermal, mechanical, and chemical properties (1,2). Graphene, carbon nanostructures has been investigated for use in many applications, such as polymer composites, energy-related materials, sensor, field-effect transistors (FET), and biomedical applications (3). Graphene oxide (GO) that is obtained from the chemical oxidation of graphene layer has drawn much attention in optical detection because of its unique optical properties for example as a platform containing a mixture of sp2/sp3 hybridized carbon atoms (4), fluorescence emission potential (5), solubility, and functionalization ability (3), which are responsible for its unique optical features. These characteristics have been applied to fluorescence-based detection of a wide range of samples including proteins (6), biomarkers (7), pathogen (8), DNA (9), RNA (10,11), dopamine (12), silver (I) (13), mercury (II) (14,15), potassium (16), and other biological analytes (17). However, as GO has low emission efficiency, overcoming this problem with chemical modification can be an effective solution (18). Metals are the main components of trace elements (i.e,, chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn)) that are required by organisms in very small quantities to maintain proper physiological and biochemical functions of our body (19). Iron is one of the most important trace elements, which exists in two different oxidation states, ferric ion (Fe3+) and ferrous ion (Fe2+) in the human body, and which plays several key roles. It is involved in the formation of red blood cells, provides for the exchange of gases between the lungs and body tissue, and supports the immune system and metabolism (20,21). Therefore, different methods have been investigated for iron detection such as atomic absorption spectroscopy (22) and inductively coupled plasma emission spectrometry (23). However, the methods based on fluorescent sensors have
received considerable attention because of their ability to detect very low concentrations of specific substances without complicated processes (24). Hence, various fluorescent sensors have been developed for the selective detection of iron (III) in recent years (24). Accordingly, the use of photoluminescence methods together with new material such as functionalized GO can be a suitable process for simple and direct detection of iron. For the current study N-butylamine functionalized graphene oxide (NGO) was synthesized with good photoluminescence emission efficiency. The detection of iron according to the quenching of NGO luminescence emission was investigated, and was found to be a simple and affordable method. Herein, good limit of detection (LOD) and limit of quantitation (LOQ) were obtained under optimal conditions.
J. Gholami et al.
Experimental Materials Graphite powder was supplied by Daejung (Korea). N-Butylamine, potassium permanganate, sodium nitrate, sulfuric acid, iron(III) nitrate nonahydrate, zinc(II) nitrate monohydrate, cobalt(II) nitrate hexahydrate, magnesium (II) nitrate hexahydrate, manganese (II) nitrate tetrahydrate, cooper(II) nitrate trihydrate, chromium (III) nitrate nonahydrate, hydrogen peroxide, thionyl chloride, ammonium heptamolybdate tetrahydrate, dimethylformamide, tetrahydrofuran, sodium hydroxide, phosphoric acid, boric acid and acetic acid were from Merck (Germany).
Instruments The UV-visible spectrum was measured using a Ray Leigh UV-1600 spectrometer. Fourier transform infrared (FT-IR) spectra were recorded with a Spectrum RX I (Perkin–Elmer). The X-ray photoelectron spectroscopy spectrum (XPS) of the sample was recorded by an ESCA-3400 Electron spectrometer (Shimadzu, Kyoto, Japan) (with silver as a standard) for which the sample was prepared by drop casting the suspension of NGO on cleaned silicon wafer, and drying at 60 °C for 2 h. The transmission electron microscopy (TEM) image was taken by an Hitachi HT-7100 (100 kV). The sample for TEM was prepared by drop casting the NGO suspension in water on a carbon-coated copper TEM grid, and the grids were left to dry at room temperature. The size of particle was measured by a Malvern Instruments Zetasizer Nano-S90. The photoluminescence spectra were obtained with a Cary Eclipse spectrophotometer (Agilent Technology).
The mixture was cooled down and dispersed in distilled water (20 mL). After that, the suspension was centrifuged at 7000 rpm for 5 min, and the supernatant was dried by rotary evaporation. Finally, the N-butylamine functionalized GO powder was redispersed in distilled water (20 mL) (Fig. 1) (18). Iron(III) detection The photoluminescence titration experiments were performed in the solution containing NGO (0.5 g/L) and Britton–Robinson buffer at a 1:2 ratio (v/v). The time-dependent fluorescence spectra were recorded after iron (III) was added to the experimental solution. The effect of pH was investigated by adding 7 μmol/L iron (III) in buffer with different pH values (i.e. 3.0, 5.0, 7.0, and 9.0). Sensitivity was measured with different concentrations of iron (III). Selectivity was examined by adding 7 μmol/L of either potassium (I), sodium (I), calcium (II), chromium (III), zinc (II), cobalt (II), copper (II), magnesium (II), manganese (II), or molybdenum (VI).
Results and discussion Characterization of NGO UV-visible spectroscopy. GO exhibited maximum absorbance at 230 nm, which corresponds to the π → π* transitions of the aromatic C = C bond, with a weak shoulder peak at 300 nm, which corresponds to the n → π* transition of the C = O bond (Fig. 2a) (26). Clearly, the absorption peak of π → π* and n → π* transitions after N-butylamine modification of GO are shifted to 280 nm and 345 nm, respectively, which can be related to nucleophilic reactions between epoxy and carboxylic groups of GO by N-butylamine (Fig. 2b). These reactions cause to remove some of
NGO synthesis GO was synthesized according to the Hummer method (25). Typically, graphite powder (1 g) and sodium nitrate (1 g) were added to sulfuric acid (46 mL) concentrate in an ice bath, while stirring the potassium permanganate (6 g) was added gradually. Then, distilled water (20 mL) and hydrogen peroxide (30%) were added to the suspension. The mixture was filtrated and washed with hydrogen chloride (0.1%) and distilled water multiple times and dried at room temperature. Next, the dried GO (0.2 g) was added to thionyl chloride (25 mL) and dimethylformamide (2 mL), and the mixture was stirred at 80 °C for 48 h. Afterwards, the mixture was centrifuged twice at 5000 rpm for 15 min and the supernatant was discarded. The remaining solid, after washing with tetrahydrofuran and drying in vacuum at room temperature, was added with N-butylamine (1 mL) and heated under nitrogen at 60 °C for 72 h.
Figure 2. UV–visible absorption spectra of GO and NGO suspensions.
230
Figure 1. Schematic illustration of the functionalizing GO with N-butylamine.
wileyonlinelibrary.com/journal/luminescence
Copyright © 2015 John Wiley & Sons, Ltd.
Luminescence 2016; 31: 229–235
N-butylamine functionalized graphene oxide for detection of Iron (III) reactive sites, which can recover sp2 domains of GO nanolayers and more extensive redistribution of π electrons (18,27). So, NGO exhibited longer wavelength and enhanced absorbance, which can be related to the conjugation of π electrons. FT- IR spectroscopy. FT-IR spectrum of GO showed a peak at 1730 cm1 due to the stretch of the C = O bond of the carboxylic acid group of GO (Fig. 3a), which disappeared after the chemical modification of GO by N-butylamine, and a new vibration band around 1648 cm1 appeared due to the C = O stretching of the amide group for NGO (Fig. 3b). Also, a new peak at 1162 cm1 is assigned to the C–N–C asymmetric stretching of the attached N-butylamine (Fig. 3b). So, the results suggest that N-butylamine is attached to the GO surface by a covalent bond through the formation of an amide group. The peaks at 1035 cm1 and 1040 cm1 in the both spectra of GO and NGO are attributed to the C–O–C
bond of the epoxy group (18). So, FT-IR spectra exhibited amide formation on the surface of GO after modification with N-butylamine. XPS spectroscopy. Based on the XPS spectrum, the curve fitting of the N 1 s was performed using a Lorentzian peak shape (Fig. 4). The peak of N 1 s spectrum at 400.9 is related to the N-C bond of the amide group, and the peak at 399.7 eV is attributed to the N–C bond of the of 1,2-amino alcohols which it can be due to ring-opening aminations of epoxides by N-butylamine (18). Transmission electron microscopy. A TEM image shows the nanolayers of NGO on the surface of a copper grid (Fig. 5). The NGO nanolayers tend to attach each other and form multilayers. The zetasizer showed that the average size of the layer in suspension was about 70 nm.
Figure 3. FT-IR spectra of (a) GO, and (b) NGO.
231
Figure 4. The N 1 s XPS spectra for NGO.
Luminescence 2016; 31: 229–235
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence
J. Gholami et al. Detection of iron (III) by NGO nanolayers
Figure 5. Transmission electron microscopy (TEM) image of NGO nanolayers.
Quenching of NGO fluorescence by iron(III). Photoluminescence spectroscopy was used to detect iron (III) by NGO nanolayers. NGO solution (0.5 g/L) at an excitation wavelength of 350 nm emitted luminescence at 433 nm (Fig. 6a, 1) that it is brighter than GO photoluminescence (Fig. 6a; 2). In GO, the photoluminescence was perhaps caused by electron–hole pairs due to sp2 domains in the sp3 matrix that the epoxide and carboxylic groups in GO often induce following non-radiative recombination of localized electron–hole pairs that leads to low emission efficiency (18,28). After modification, carboxylic and some epoxide groups of GO are reacted with N-butylamine and removed (15). Consequently, the NGO emitted brighter photoluminescence. The addition of Iron (III) significantly quenched the NGO luminescence emission at 433 nm (Fig. 6a; 3). It can be related to the photoinduced electron transfer (PET), which is the light-induced transfer of electrons from the nitrogen of NGO as a donor to the iron (III) as an acceptor (Fig. 6b). At the different pH, quenching ratio (F0 F)/F (where F0 and F are the intensity of NGO luminescence emission in the absence and presence of iron (III), respectively) is variable. For instance, 0.75 mL of NGO (0.5 g/L) was added to quartz cells with 1.5 mL Britton–Robinson buffer with
232
Figure 6. (a) Fluorescence spectra of 1. NGO (0.5 g/L), 2. GO (0.5 g/L), and 3. Quenched luminescence emission of NGO by iron (III). (b) Schematic of interaction NGO and iron (III) 3+ (Fe ) and PET. (c) Quenched luminescence emission of NGO (0.5 g/L) by iron (III) (7 μmol/L) in Britton–Robinson buffer at different pH values (λex = 350 nm, λem = 433 nm).
wileyonlinelibrary.com/journal/luminescence
Copyright © 2015 John Wiley & Sons, Ltd.
Luminescence 2016; 31: 229–235
N-butylamine functionalized graphene oxide for detection of Iron (III) different pH values (i.e,, 2.0, 5.0, 7.0, and 9.0). Then, 15 μL of iron (III) (103 mol/L) was added to each cell. The highest quenching ratio occurred at pH 7 (Fig. 6c). At the low pH, the amide and amine groups are protonated and was not quenched by iron (III). However, in the higher pH these groups become deprotonated, and quenching ratio increases due to stronger PET process (29). The interaction time between the NGO (0.5 g/L) and iron (III) (103 mol/L) was investigated (Fig. 7). Since the quenching was stabilized 3 min after mixing samples, the photoluminescence spectra were acquired at 3 min. Iron (III) dose dependency of NGO photoluminescence. The potential use of NGO for the detection of iron (III) was examined by photoluminescence titration. Microliter volumes of iron (III) were gradually added to NGO (0.5 g/L) in the solution at pH 7, and luminescence intensities were recorded after 3 min (Fig. 8a). The calibration curve of F0/F versus iron (III) concentration showed the quenching according to PET, following a typical Stern–Volmer type equation as follows (Fig. 8b):
Figure 7. Time course of NGO luminescence quenching ratio (0.5 g/L), by iron (III) (7 μmol/L) at pH 7 (λex = 350 nm, λem = 433 nm).
F 0 = F ¼ 1 þ K sv Feþ3
(1)
where F0 and F are the intensities of NGO luminescence emission in the absence and presence of iron (III), respectively; Ksv is the Stern–Volmer constant at approximately 0.009, with a regression coefficient (r2) of 0.98. LOD and LOQ were acquired using eqns (2) and (3) as follows: LOD ¼ 3 SD=m
(2)
LOQ ¼ 10 SD=m
(3)
where SD is the standard deviation for the blank and m is the slope of NGO luminescence intensity against the concentration of iron (III). Here, SD and m are 12 and 4.2 × 106, respectively. Therefore, the LOD and LOQ are calculated as 2.8 × 106 M and 2.9 × 105 M, respectively. Selectivity against other minerals. The selectivity of the sensor was examined for other cationic trace element samples in the same condition (i.e,, NGO, 0.5 g/ L; sample, 7 μmol/L; interaction time, 3 min; pH 7) (Fig. 9). As a result, NGO exhibited good iron (III) selectivity over other samples (potassium (I), sodium (I), calcium (II), chromium (III), zinc (II), cobalt (II), copper (II), magnesium (II), manganese (II), and molybdenum (VI)), which can be attributed to the high charge densities of iron (III). The charge density of the metal ions is defined as the amount of electric charge/unit volume, which is one of the most important characterizations of the relative electrophilicity of a metal ion (30). Based on the formal charge and Shannon ionic radius of cations (31), the charge densities increase in the following order: potassium (I) (0.1) < sodium (I) (0.5) < calcium (II) (0.48) < cobalt (II) (1.15) < zinc (II) (1.18) < manganese (II) (1.65) < copper (II) (1.28) < magnesium (II) (2.5) < chromium (III) (3.12) < molybdenum (VI) (3.75) < iron (III) (6.0). Accordingly, the iron (III) has biggest charge density among the cationic trace elements that cause the highest electrophilicity. As a result, the quenching effect of iron (III) is far more prominent compared with other cationic trace elements based on PET
Luminescence 2016; 31: 229–235
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence
233
Figure 8. (a) Photoluminescence emission of NGO (0.5 g/L) added with increasing concentrations of iron as shown in (b). (b) Calibration curve of F0/F versus the concentration of 6 4 iron (III) (6.6 × 10 M to 1.51 × 10 M) (time: 3 min, pH 7, λex = 350 nm, λem = 433 nm).
J. Gholami et al.
Figure 9. Photoluminescence quenching ratio of NGO (0.5 g/L) in the presence of the same concentration (7 μmol/L) of different cationic trace elements (time: 3 min, pH 7, λex = 350 nm, λem = 433 nm).
mechanism, probably because of the stronger interaction between NGO as a donor and iron (III) as an acceptor of electrons.
Conclusion The NGO nanolayer was synthesized. FT-IR and XPS spectra were used to characterize different functional groups of the graphene layer. Transmission electron image showed the nanolayer of N-butylamine functionalized graphene in suspension. Photoluminescence spectroscopy was used to detect iron (III) based on the quenching effect of iron (III). The NGO nanolayer interacted best with iron (III) at pH 7. The detection of iron (III) was performed with good selectivity in the presence of other cationic trace elements including potassium (I), sodium (I), calcium (II), chromium (III), zinc (II), cobalt (II), copper (II), magnesium (II), manganese (II), and molybdenum (VI). Therefore, this functionalized GO will be a good substrate for detecting trace amounts of iron in biological samples. Acknowledgements The Authors thank the Tokyo Institute of Technology and University of Tehran for their support in TEM, XPS, UV-visible and photoluminescence characterizations.
References
234
1. Jariwala D, Sangwan VK, Lauhon LJ, Marks TJ, Hersam MC. Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing. Chem Soc Rev 2013;42:2824–60. 2. Akhavan O. Photocatalytic reduction of graphene oxides hybridized by ZnO nanoparticles in ethanol. Carbon 2011;49:11–8. 3. Dreyer DR, Park S, Bielawski CW, Ruoff RS. The chemistry of graphene oxide. Chem Soc Rev 2010;39:228–40. 4. Chung C, Kim YK, Shin D, Ryoo SR, Hong BH, Min DH. Biomedical applications of graphene and graphene oxide. Acc Chem Res 2013; 46:2211–24. 5. Lu CH, Yang HH, Zhu CL, Chen X, Chen GN. A graphene platform for sensing biomolecules. Angew Chem Int Ed 2009;48:4785–7. 6. Lu CH, Li J, Zhang XL, Zheng AX, Yang HH, Chen X, Chen GN. General approach for monitoring peptide–protein interactions based on graphene–peptide complex. Anal Chem 2011;83:7276–82. 7. He Y, Lin Y, Tang H, Pang D. A graphene oxide-based fluorescent aptasensor for the turn-on detection of epithelial tumor marker mucin 1. Nanoscale 2012;4:2054–9.
wileyonlinelibrary.com/journal/luminescence
8. Jung JH, Cheon DS, Liu F, Lee KB, Seo TS. A graphene oxide based immuno-biosensor for pathogen detection. Angew Chem Int Ed 2010;49:5708–11. 9. Wu C, Zhou Y, Miao X, Ling L. A novel fluorescent biosensor for sequence-specific recognition of double-stranded DNA with the platform of graphene oxide. Analyst 2011;136:2106–10. 10. Zhou X, Liao Y, Xing D. Sensitive monitoring of RNA transcription levels using a graphene oxide fluorescence switch. Chin Sci Bull 2013; 58:2634–9. 11. Debin Z, Lan Z, Wenge M, Suqin L, Xiaobo X. Detection of microRNA in clinical tumor samples by isothermal enzyme-free ampli fi cation and label-free graphene oxide-based SYBR Green I fluorescence platform. Biosens Bioelectron 2015;65:152–8. 12. Chen JL, Yan XP, Meng K, Wang SF. Graphene oxide based photoinduced charge transfer label-free near-infrared fluorescent biosensor for dopamine. Anal Chem 2011;83:8787–93. 13. Wen Y, Xing F, He S, Song S, Wang L, Long Y, Li D, Fan C. A graphenebased fluorescent nanoprobe for silver(I) ions detection by using graphene oxide and a silver-specific oligonucleotide. Chem Comm 2010;46:2596–8. 14. Li M, Zhou X, Ding W, Guo S, Wu N. Fluorescent aptamer-functionalized graphene oxide biosensor for label-free detection of mercury(II). Biosens Bioelectron 2013;41:889–93. 15. Jiahao H, Xiang G, Jingjing J, Jang KK, Zhigang L. Graphene 2+ oxide-based amplified fluorescent biosensor for Hg detection through hybridization chain reactions. Anal Chem 2014; 86:3209–315. 16. Shu JZ, Yan Y, Chun Mei L, Cheng ZH. Graphene oxide amplified fluorescence anisotropy for label-free detection of potassium ion. Analyst 2015;140:353–7. 17. Wang Y, Li Z, Wang J, Li J, Lin Y. Graphene and graphene oxide: biofunctionalization and applications in biotechnology. Trends Biotechnol 2011;29:205–12. 18. Mei Q, Qingsong M, Kui Z, Guijian G, Bianhua L, Suhua W, Zhongping Z. Highly efficient photoluminescent graphene oxide with tunable surface properties. Chem Comm 2010;46:7319–21. 19. Fraga CG. Relevance, essentiality and toxicity of trace elements in human health. Mol Asp Med 2005;26:235–44. 20. Al Faris NA, Ahmad D. Distribution of trace elements like calcium, copper, iron and zinc in serum samples of colon cancer—a case control study. J King Saud Univ Sci 2011;23:337–40. 21. Hirayama T, Okuda K, Nagasawa H. A highly selective turn-on fluorescent probe for iron(II) to visualize labile iron in living cells. Chem Sci 2013;4:1250–6. 22. Gómez-Nieto B, Gismera MJ, Sevilla MT, Procopio JR. Simultaneous and direct determination of iron and nickel in biological solid samples by high-resolution continuum source graphite furnace atomic absorption spectrometry. Talanta 2013;116:860–5. 23. Whittaker PG, Lind T, Williams JG, Gray AL. Inductively coupled plasma mass spectrometric determination of the absorption of iron in normal women. Analyst 1989;114:675–8.
Copyright © 2015 John Wiley & Sons, Ltd.
Luminescence 2016; 31: 229–235
N-butylamine functionalized graphene oxide for detection of Iron (III) 24. Sahoo SK, Sharma D, Bera RK, Crisponi G, Callan JF. Iron(III) selective molecular and supramolecular fluorescent probes. Chem Soc Rev 2012;41:7195–227. 25. Hummer WS. Preparation of graphitic oxide. J Am Chem Soc 1957;80:1339. 26. Paredes JI. Graphene oxide dispersions in organic solvents. Langmuir 2008;24:10560–4. 27. Taylor KL, Liu RQ, Liang PH, Price J, Dunaway-Mariano D, Tonge PJ, Clarkson J, Carey PR. Evidence for electrophilic catalysis in the 4chlorobenzoyl-CoA dehalogenase reaction: UV, Raman, and 13C-NMR spectral studies of dehalogenase complexes of benzoyl-CoA adducts. Biochemistry 1995;34:13881–8.
28. Shang J, Ma L, Li J, Ai W, Yu T, Gurzadyan GG. The origin of fluorescence from graphene oxide. Sci Rep. 2012;2 . 29. Lakowicz JR. Principles of fluorescence spectroscopy. 3rd ed. LLC, New York, USA: Springer Science+Business Media 2006:642–644. 3+ 30. Yadavi M, Badiei A, Ziarani GM. A novel Fe ions chemosensor by covalent coupling fluorene onto the mono, di- and tri-ammonium functionalized nanoporous silica type SBA-15. Appl Surf Sci 2013;279:121–8. 31. Shannon RT. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Cryst 1976;32:751–67.
235
Luminescence 2016; 31: 229–235
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence
