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A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine
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A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine Xingzong Jiang a, Mingqin Shangguan a, Zhen Lu a, Sili Yi b, Xiaoyang Zeng a, Yongle Zhang a, Linxi Hou a, * a
College of Chemical Engineering, Fuzhou University, Fuzhou, 350108, PR China Institute of Food Safety and Environment Monitoring of Photocatalysis on Energy and Environment College of Chemistry, Fuzhou University, Fuzhou, 350116, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 October 2019 Received in revised form 19 December 2019 Accepted 3 January 2020 Available online xxx
Hydrazine (N2H4) has been classified as an environmental contaminant and human carcinogen owing to its high toxicity. Exposed to high concentration of hydrazine can cause irreversible damage to human bodies. Hence, it is significant to explore an effective analytical method to selectively recognize and detect it. In this work, an intramolecular charge transfer (ICT) based probe 1 was designed and synthesized by condensation of V-shaped bis-coumarin and 4-bromobutyric acid. The V-shaped biscoumarin with p-expanded system endowed the probe 1 larger stokes shift and superior tolerance to photobleaching. This “turn-on” probe exhibited a high selectivity towards hydrazine over other common ions and amine-containing species with a distinct fluorescent enhancement at 555 nm. It could rapidly detect hydrazine over a wide pH range and the detection limit was as low as 4.2 ppb. The large shift of absorption spectrum enabled it to detect hydrazine in real water samples and gas-state hydrazine by “naked-eyes". © 2020 Published by Elsevier Ltd.
Keywords: Fluorescent probe Bis-coumarin derivative Hydrazine detection Gaseous detection
1. Introduction Hydrazine (N2H4), known as a crucial weak base and a typical reducing agent, has been widely used in various fields, such as the pharmacy, chemistry, catalysis and agriculture [1e3]. Additionally, due to its high enthalpy of combustion, hydrazine is often employed as high-energy fuel in rocket-propulsion and missile systems [4,5]. Although hydrazine plays an important and positive role in production and manufacturing process, the toxicity and carcinogenicity of it shouldn’t be ignored. As a volatile and watersoluble compound, it can cause irreversible damage to the lungs, liver, kidneys, respiratory system and central nervous system of living bodies through easily absorbed by dermal, breathing or oral routes [6e8]. In fact, hydrazine has been denoted as a possible human carcinogen by the U.S. Environmental Protection Agency (EPA) with the threshold limit value (TLV) of 10 ppb [9]. Therefore, the convenient and high-efficiency detection methods for trace hydrazine have gained increasing attention.
* Corresponding author. E-mail address: [email protected] (L. Hou).
To date, various methods have been developed to determine hydrazine. Traditional analytical techniques including surfaceenhanced Raman spectroscopy [10], chromatography [11e13] electrochemistry [14,15] and titration [16,17] are inferior for detecting hydrazine due to the apparent limitations such as timeconsuming, requirement of expensive instruments and professionals, as well as complicated pre-treatments. In comparison, fluorescent probes are flourishing as promising technique in virtue of unique advantages such as real-time visual monitoring, in-situ analysis and ease to operation [18,19]. A number of fluorescent probes for detecting molecules and ions in vivo or vitro have been reported. However, the fluorescent probes for hydrazine have been reported less [20]. Until now, most of the probes for hydrazine are designed via anchoring a fluorophore with reaction sites including 4-bromobutanoate [21,22], acetyl [23e25], aldehyde [26,27], malononitrile [28,29], phthalimide [30], and trifluoroacetyl acetonate [31]. However, many of them suffer from several ineradicable defects such as narrow pH range, complicated synthesis procedures, long response time or poor selectivity. Various organic fluorophores such as benzothiazole [32,33], coumarins [34e39], rhodamine [40], 1,-8 naphthalimide [23,41] and heptamethine cyanine [24] have been utilized to design
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Please cite this article as: X. Jiang et al., A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine, Tetrahedron, https://doi.org/10.1016/j.tet.2020.130921
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fluorescent probes recent years. Among these fluorophores, coumarin and its derivatives, especially coumarin-fused heterocycles, attract more attention for their large stokes shift, superior tolerance to photobleaching and great fluorescent quantum yield [42]. In addition, due to the extension of the conjugated system and the plentifulness of electrons in coumarin-fused heterocycles, coumarins with p-expanded system show several distinguished properties, such as larger stokes shift, red shift in the excitation and emission wavelengths, and colorimetric properties compared with the traditional coumarins whose absorption and emission wavelength generally locate on short-wave band [43]. Taking significant advantages stated above into consideration, p-expanded coumarins can be applied in environmental detection and even biosensors. In this work, the V-shaped bis-coumarin was selected as fluorophore combined with 4-bromobutanoate to afford a “turn-on” fluorescent probe 1. This V-shaped bis-coumarin possessed a electron-donating group (hydroxyl) and a electron-withdrawing group (carbonyl) at the site corresponding to position 7 and 2 of the coumarin moiety respectively, which formed the push-pull electron structure and emitted fluorescent according to ICT (intramolecular charge transfer) theory [44]. In addition, it was reported that bromo-ester derivatives could react with hydrazine through nucleophilic substitution to the bromine group and nucleophilic addition to the ester carbonyl with subsequent intramolecular cyclization to release the fluorophore [45]. So we assumed that the electron-withdrawing 4-bromobutanoate could prohibit the ICT process and quench the fluorescent emission of the fluorophore by esterification. When reacted with hydrazine, the fluorophore could be released and the ICT process was recovered, which resulted fluorescent enhancement simultaneously. As expected, upon addition of hydrazine, the emission intensity distinctly increased at 555 nm in DMSO: PBS buffer solution (3:1, v/ v, pH ¼ 7.4), simultaneously, the UVeVIS absorption spectrum showed a red shift with the color changing from colorless to yellow. The color change provided a visual method of detecting hydrazine by “naked-eye”. The limit of detection value (LOD) was found to be 4.2 ppb, which was lower than the TLV (10 ppb) according to the EPA. The probe exhibited excellent selectivity and rapid response towards hydrazine. Moreover, the probe could be used for practical detection of hydrazine in real water samples and gas-state hydrazine. 2. Experimental section 2.1. Materials and instruments All chemical reagents and solvents were purchased from commercial suppliers, further purification was not required. Absorption spectra were detected on Lambda 750 UVevis spectrophotometer. Fluorescent spectra were measured on the Hitachi F-4600 spectrofluorometer. 1H NMR spectra were recorded on a Bruker Avance III 600 MHz spectrometer and referenced to the solvent signals. The mass spectra were performed on Agilent HPLC-MS. 2.2. Synthesis of probe 1 The detailed synthesis route was given in the Electronic supplementary information (Scheme. S1) [46]. Compound 1 (1.40 g, 5 mmol) and 4-bromobutyric acid (1.17 g, 7 mmol) were mixed in the dichloromethane (20 mL) with stirring. 4dimethylaminopyridine (DMAP, 0.23 g, 2 mmol) and N, N0 -dicyclohexylcarbodiimide (DCC, 0.40 g, 2 mmol) were added into the solution and stirred at room temperature for 6 h. After the reaction
finished, the solvent was removed under reduced pressure. The residue was purified by silica gel column chromatography (CH2Cl2/ CH3OH ¼ 10/1, v/v) to afford pure probe 1 as white solid (1.31 g, 62% yield). 1H NMR (600 MHz, DMSO) d 8.57 e8.41 (m, 2H), 7.87 (dd, J ¼ 8.5, 7.3, 1.4 Hz, 1H), 7.50 (ddd, J ¼ 79.4, 11.3, 8.6, 1.7 Hz, 4H), 3.67 (t, J ¼ 6.6 Hz, 2H), 2.84 (t, J ¼ 7.3 Hz, 2H), 2.23 (p, J ¼ 6.8 Hz, 2H) (Fig. S3). 13C NMR (101 MHz, DMSO) d 174.03 (s), 170.86 (s), 157.21 (s), 155.66 (s), 155.36 (s), 154.75 (s), 152.30 (s), 135.50 (s), 131.12 (s), 129.66 (s), 125.47 (s), 119.43 (s), 117.99 (s), 115.57 (s), 113.55 (s), 111.39 (s), 106.88 (s), 34.64 (s), 32.51 (s), 28.20 (s) (Fig. S6). HRMS: m/z calcd for C20H13BrO6 [MþH]þ: 428.9968, found: 428.9975 (Fig. S8). 2.3. General procedures for analysis The stock solution of probe 1 (1 mM) was prepared in DMSO, and then diluted with DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4). Stock solutions of hydrazine and other common analytes (cations: Naþ, Kþ, Ca2þ, Mg2þ, Liþ, Fe2þ, Zn2þ, Fe3þ, Mn2þ, Co2þ, 2 2 2 Al3þ; anions: Cl, HPO2 4 , CO3 , SO4 , F , NO3 , I , AcO , SO3 ; and amine-containing species: Triethylamine, Diethylamine, 2Aminoethanol, Sulfamic acid, Aniline, NH3$H2O, L-Cys, Ala, Glu, Hcy, GSH) were prepared in distilled water. The stock solutions were used freshly and were diluted to appropriate concentrations as needed. All spectral analysis experiments were carried out in DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) with probe 1 (900 mL, 200/9 mM) and hydrazine (100 mL, appropriate concentration). When conducted the fluorescent experiment, the stock solution of probe 1 was added into a quartz cuvette (1 cm 1 cm), followed by addition of 100 mL of the hydrazine stock solutions with different concentrations. The fluorescent spectra were recorded after 15 min. The process of selectivity and competition studies were same as above, except interfering substances (1 mM, 50 mL) were added in front of hydrazine (100 mL, 500 mM). The excitation wavelength was 460 nm, and the PMT voltage was 550 V. The excitation and emission slit width were 5 nm and 5 nm, respectively. 2.4. Water samples test Tap water in laboratory and Minjiang River water were selected for the practical sample analysis. The stock solution of probe 1 (900 mL, 200/9 mM) was added into a quartz cuvette (1 cm 1 cm), followed by addition of 50 mL of the water samples respectively. After that, 100 mL of different concentrations of standard hydrazine solution (100 mM, 300 mM, 500 mM) were added to the solution. The fluorescent spectra of these samples were recorded after 15 min. 2.5. Detection of gaseous hydrazine Filter papers were immersed in DMSO solution of probe 1 (2 mM) for 5 min and then dried at room temperature. Different concentrations of hydrazine solution (0, 0.5%, 1%, 5%, 10%, 20%, 30%) were prepared in test tubes. The above filter paper strips were hung in respective test tubes at room temperature for 10 min. Observing the color and fluorescent changing under the natural light and UV light (commercial hand-held 365 nm UV lamp) respectively. 3. Results and discussion 3.1. UVevis and fluorescent spectra The optical property of probe 1 was investigated first. The timedependent absorption spectra of the probe 1 (20 mM) were examined at room temperature after addition of hydrazine (100 mM) to
Please cite this article as: X. Jiang et al., A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine, Tetrahedron, https://doi.org/10.1016/j.tet.2020.130921
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Fig. 1. (a) The time-dependent UVevis absorption spectral of probe 1 (20 mM) in the presence of hydrazine (100 mM). (b) Fluorescent emission spectra of probe 1 (20 mM) with the gradually increasing concentration of hydrazine (0e100 mM) in DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4). lex ¼ 460 nm lem ¼ 555 nm. (c) Fluorescent photographs of probe 1 in the presence of increasing concentrations of hydrazine. (d) The fluorescent intensities (lem ¼ 555 nm) of probe 1 were linearly related to the concentrations of hydrazine (0e50 mM). lex ¼ 460 nm, dex ¼ 5 nm, dem ¼ 5 nm.
DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) (Fig. 1a). It can be observed that the free probe 1 showed a maximum absorption peak at 357 nm. After addition of hydrazine, the absorption peak at 357 nm was decreased gradually. Inversely, the absorption peak at 460 nm was increased dramatically. A well-defined isobestic point appeared at 390 nm. Such a large red shift of 103 nm in absorption spectrum transformed the solution from colorless and transparent to orange, suggesting hydrazine could be detected with the “nakedeyes". Subsequently, the fluorescent titration experiment of the probe 1 was carried out in the DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) (Fig. 1b). Originally, the free probe 1 solution (20 mM) exhibited a very weak emission peak at 555 nm under the excitation of 460 nm. After addition of hydrazine with increasing concentration (0 e100 mM), a significant increase of the fluorescent intensity at 555 nm was observed and reached to a plateau at the concentration of 60 mM. The fluorescent color changed from colorless to yellow gradually (Fig. 1c). Such a large Stokes shift of 95 nm in emission spectrum made it have a higher signal-noise ratio than other probes (Table S1). Meanwhile, the fluorescent intensity at 555 nm exhibited an excellent linear relationship (y ¼ 2.79 þ 52.79x, R2 ¼ 0.9960) with the concentrations of hydrazine in the range of 0 e50 mM (Fig. 1d). The detection limit was calculated to be 0.0099 mM (4.2 ppb) based on 3s/k, which was lower than TLV of 10 ppb. These results indicated that the probe 1 was competent for detecting hydrazine qualitatively and quantitatively. 3.2. Selectivity and competition studies The selectivity of fluorescent probe was an important parameter in performance evaluation. The response of the probe 1 toward common cations (Naþ, Kþ, Ca2þ, Mg2þ, Liþ, Fe2þ, Zn2þ, Fe3þ, Mn2þ, 2 2 Co2þ, Al3þ) and anion (Cl, HPO2 4 , CO3 , SO4 , F , NO3 , I , AcO ,
SO2 3 ) were performed in the DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) to prove the selectivity of probe 1 to hydrazine. Upon addition 50 mL of different analytes (1 mM) respectively, only hydrazine triggered a prominent fluorescent emission enhancement at 555 nm while other species appeared negligible variation (Fig. 2a). Moreover, competitive assays indicated that the coexistence of cations and anions had no interference on the detection of hydrazine (Fig. 2b). Subsequently, the response of the probe 1 toward amine-containing species (Triethylamine, Diethylamine, 2-Aminoethanol, Sulfamic acid, Aniline, NH3$H2O, L-Cys, Ala, Glu, Hcy, GSH) was performed in the same condition (Fig. S9). The results demonstrated the probe 1 had the same excellent selectivity and anti-interference ability to these amine-containing species. Such a high selectivity and anti-interference ability of the probe 1 indicated it could be used as a sensing platform for hydrazine detection in complex environment. 3.3. Effect of pH and reaction time In view of the importance of pH value adaptation in practical applications, the pH effects on fluorescent response of probe 1 in the absence and presence of hydrazine were investigated (Fig. 3a). The probe 1 was inert to pH in the range of 2.0e11.0 in the absence of hydrazine. Upon treatment with hydrazine (50 mM), the maximal fluorescent signal was observed in the pH range of 4.0e11.0. These results indicated that the probe 1 could exist steadily and detect hydrazine with excellent sensitivity over a wide pH range. For kinetic studies, time-dependent fluorescent intensity measurement was performed on probe 1 (20 mM) with hydrazine (50 mM) in DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) (Fig. 3b). Upon introduction of hydrazine to the probe solution, a significant enhancement of the fluorescent intensity at 555 nm arose and reached the plateau within 15 min. These results implied the probe 1 had a fast response to hydrazine.
Please cite this article as: X. Jiang et al., A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine, Tetrahedron, https://doi.org/10.1016/j.tet.2020.130921
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Fig. 2. Fluorescent emission of probe 1 (20 mM), upon the addition of different ions (50 mM) and N2H4 (50 mM), in DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4). (a) Represents the addition of hydrazine or various other ions to the solution of probe 1. (b) Represents the addition of hydrazine to the above ions-containing solutions (bars show: 0. Blank, 1. Naþ, 2. 2 2 2 Kþ, 3. Ca2þ, 4. Mg2þ, 5. Liþ, 6. Fe2þ, 7. Zn2þ, 8. Fe3þ, 9. Mn2þ, 10. Co2þ, 11. Al3þ, 12. Cl, 13. HPO2 4 , 14. CO3 , 15. SO4 , 16. F , 17. NO3 , 18. I ,19. AcO , 20. SO3 ).
Fig. 3. (a) The fluorescent intensity of probe 1 (20 mM) in the absence (black line) or presence (red line) of hydrazine (50 mM) at various pH values. (b) Reaction time profiles of probe 1 (20 mM) with hydrazine (50 mM).
Then we extended the reaction time to determined the photostability of probe 1 (Fig. S10). Under the irradiation of 460 nm UVlight, there was no change in the fluorescence intensity of probe 1 in the absence of hydrazine within 1 h. When hydrazine (50 mM) was added, as expect, the fluorescence intensity increased immediately and reached the maximum within 15 min. Additionally, the fluorescence intensity was nearly unchanged over time, which indicated the photostability of probe 1. 3.4. Proposed detection mechanism To our knowledge, bromo-ester derivatives could react with hydrazine through nucleophilic substitution to the bromo group and nucleophilic addition to the ester carbonyl with subsequent intramolecular cyclization to release the fluorophore [45]. So the electron-withdrawing group bromo-ester derivatives was introduced into the V-shaped bis-coumarin fluorophore to prohibit its
ICT process and quench the fluorescent. After reaction with hydrazine, the fluorophore was released and the ICT process was recovered, which resulted in fluorescent enhancement (Scheme 1)., In order to determine the reaction, UV eVis absorption spectra were analyzed (Fig. S11), the free probe 1 exhibited a broad absorption band at 300 e400 nm, but there was a negligible absorption at 460 nm. When reacted with hydrazine, the peak at 350 nm decreased gradually, whereas the peak at 460 nm which regarded as characteristic absorption peak of compound 1 increased sharply. Additionally, it was similar to the absorption spectra of compound 1 which confirmed our hypothesis. 1H NMR was further taken to verify the mechanism, and the results were performed in Fig. 4. After the addition of hydrazine into probe 1 in DMSO-d6, the protons of probe 1 at 8.52 ppm (a), 8.45 ppm (b), 7.87 ppm (c), 7.57 ppm (d), 7.54 ppm (e), 7.50 ppm (f), 7.36 ppm (g) remarkably shifted to 8.39 ppm (a), 8.31 ppm (b), 7.83 ppm (c), 6.84 ppm (d), 6.98 ppm (e), 7.52 ppm (f), 7.50 ppm (g). As expected,
Scheme 1. The proposed mechanism of probe 1 reacting with hydrazine.
Please cite this article as: X. Jiang et al., A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine, Tetrahedron, https://doi.org/10.1016/j.tet.2020.130921
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Fig. 4. The changes of 1H NMR spectra of probe 1 after reacted with hydrazine.
it was similar to the 1H NMR spectra of compound 1 (Fig. S4). All the above results confirmed that probe 1 could react with hydrazine to release the fluorophore. 3.5. Water samples test Hydrazine had been widely used in various industrial processes, the detection and quantification of it in real aqueous samples was significant. The probe 1 was applied to detect hydrazine in tap water and Minjiang River in Fuzhou city, respectively. The water samples (50 mL) were added into the probe 1 solution (20 mM), and there was no significant fluorescent enhancement observed. Then, an aliquot of hydrazine solution (10 mM, 30 mM, 50 mM) was added to the above real samples and recorded the fluorescent spectra. As shown in Table 1, the resultant hydrazine recoveries were in the range of 101e105%, indicating the possibility of probe 1 for hydrazine detection in practical water samples. 3.6. Detection of gaseous hydrazine
light and UV light respectively (Fig. 5). The fluorescent color from colorless to yellow were observed with the increase of hydrazine vapor concentration, meanwhile, the color clearly changed from colorless to yellow by “naked-eyes”. Furthermore, this analytic method could identify hydrazine vapor even at a concentration as low as 0.5%. Hence, it had great application value for the rough detection of gaseous hydrazine.
4. Conclusion In summary, a new type of V-shaped bis-coumarin “turn-on” fluorescent probe for hydrazine detection had been reported. It exhibited distinct changes in the intensity of both absorption and emission spectra upon addition of hydrazine. The remarkable color change can be observed visually. The sensing mechanism was elucidated by spectroscopy and 1H NMR analysis. The probe exhibits prominent selectivity and sensitivity with a low detection limit. It was a candidate for “naked-eyes” and fluorescent detection of hydrazine in real water samples and gas-state hydrazine.
To explore the practical applications of the probe, the detection of gaseous hydrazine was also performed. Primarily, the tailored filter paper strips were immersed in the probe 1 solution (2 mM) for 5 min. Then took them out and dried at room temperature. Different concentrations of hydrazine solution (0, 0.5%, 1%, 5%, 10%, 20%, 30%) were prepared in test tubes, the above filter paper strips were hung in respective test tubes at room temperature for 10 min. The color and fluorescent changing was observed under the natural Table 1 Detection of hydrazine in environmental samples.
Tap water
Minjiang River
Spiked (mM)
Detected (mM)
Recovery (%)
RSD (%)
0 10 20 30 0 10 20 30
Not detected 10.17 20.83 31.51 Not detected 10.19 20.77 31.20
e 101.7 104.2 105.0 e 101.91 103.8 104.0
e 0.41 0.28 0.30 e 0.18 0.23 0.28
Fig. 5. Photographs for probe 1 coated filter papers upon exposure to gaseous hydrazine with different concentrations. Upper: under natural light; Lower: under a hand-hold UV lamp with an excitation at 365 nm in dark.
Please cite this article as: X. Jiang et al., A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine, Tetrahedron, https://doi.org/10.1016/j.tet.2020.130921
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Declaration of competing interest There are no conflicts to declare. Acknowledgements This work was supported by the National Natural Science Foundation of China (No: 21676057), United Fujian Provincial Health and Education Project for Tackling the Key Research P.R. China (WKJ2016-2-04) and Scientific Research Topics of Traditional Chinese Medicine in Fujian Provincial Department of Health (WZZY201317). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.tet.2020.130921. References [1] U. Ragnarsson, Synthetic methodology for alkyl substituted hydrazines, Chem. Soc. Rev. 30 (4) (2001) 205e213. [2] J. Sanabria-Chinchilla, K. Asazawa, T. Sakamoto, K. Yamada, H. Tanaka, P. Strasser, Noble metal-free hydrazine fuel cell catalysts: EPOC effect in competing chemical and electrochemical reaction pathways, J. Am. Chem. Soc. 133 (14) (2011) 5425e5431. [3] L.L. Xiao, J. Tu, S.G. Sun, Z.C. Pei, Y.X. Pei, Y. Pang, et al., A fluorescent probe for hydrazine and its in vivo applications, RSC Adv. 4 (79) (2014) 41807e41811. [4] J. Waser, B. Gaspar, H. Nambu, E.M. Carreira, Hydrazines and azides via the metal-catalyzed hydrohydrazination and hydroazidation of olefins, J. Am. Chem. Soc. 128 (35) (2006) 11693e11712. [5] K. Yamada, K. Yasuda, N. Fujiwara, Z. Siroma, H. Tanaka, Y. Miyazaki, et al., Potential application of anion-exchange membrane for hydrazine fuel cell electrolyte, Electrochem. Commun. 5 (10) (2003) 892e896. [6] S. Garrod, M.E. Bollard, A.W. Nichollst, S.C. Connor, J. Connelly, J.K. Nicholson, et al., Integrated metabonomic analysis of the multiorgan effects of hydrazine toxicity in the rat, Chem. Res. Toxicol. 18 (2) (2005) 115e122. [7] C.A. Reilly, S.D. Aust, Peroxidase substrates stimulate the oxidation of hydralazine to metabolites which cause single-strand breaks in DNA, Chem. Res. Toxicol. 10 (3) (1997) 328e334. [8] S.D. Zelnick, D.R. Mattie, P.C. Stepaniak, Occupational exposure to hydrazines: treatment of acute central nervous system toxicity, Aviat. Space Environ. Med. 74 (12) (2003) 1285e1291. [9] O. o R a D a U S Environmental Protection Agency (EPA, Integrated Risk Information System (IRIS) on Hydrazine/hydrazine Sulfate, National Center for Environmental Assessment, DC, 1999. [10] X. Gu, J.P. Camden, Surface-enhanced Raman spectroscopy-based approach for ultrasensitive and selective detection of hydrazine, Anal. Chem. 87 (13) (2015) 6460e6464. [11] G.E. Collins, Gas-phase chemical sensing using electrochemiluminescence, Sens. Actuators, B 35 (1e3) (1996) 202e206. [12] O. Gyllenhaal, L. Gronberg, J. Vessman, Determination of hydrazine in hydralazine by capillary gas-chromatography with nitrogen-selective detection after benzaldehyde derivatization, J. Chromatogr. 511 (1990) 303e315. [13] M. Sun, L. Bai, D.Q. Liu, A generic approach for the determination of trace hydrazine in drug substances using in situ derivatization-headspace GC-MS, J. Pharm. Biomed. Anal. 49 (2) (2009) 529e533. [14] S.E.F. Kleijn, B. Serrano-Bou, A.I. Yanson, M.T.M. Koper, Influence of hydrazineinduced aggregation on the electrochemical detection of platinum nanoparticles, Langmuir 29 (6) (2013) 2054e2064. [15] A. Umar, M.M. Rahman, S.H. Kim, Y.-B. Hahn, Zinc oxide nanonail based chemical sensor for hydrazine detection, Chem. Commun. (2) (2008) 166e168. [16] H.E. Malone, Determination of mixtures of hydrazine and 1,1dimethylhydrazine, Anal. Chem. 33 (1961) 575e577. [17] Z.K. He, B. Fuhrmann, U. Spohn, Coulometric microflow titrations with chemiluminescent and amperometric equivalence point detection - bromimetric titration of low concentrations of hydrazine and ammonium, Anal. Chim. Acta 409 (1e2) (2000) 83e91. [18] Q. Zhai, W. Feng, G. Feng, Rapid detection of hydrazine in almost wholly water solution and in living cells with a new colorimetric and fluorescent turn-on probe, Anal. Methods. 8 (29) (2016) 5832e5837. [19] D. Cheng, Y. Pan, L. Wang, Z. Zeng, L. Yuan, X. Zhang, et al., Selective visualization of the endogenous peroxynitrite in an inflamed mouse model by a mitochondria-targetable two-photon ratiometric fluorescent probe, J. Am.
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Actuators, B 199 (2014) 93e100. [30] M.V.R. Raju, E.C. Prakash, H.-C. Chang, H.-C. Lin, A facile ratiometric fluorescent chemodosimeter for hydrazine based on Ing-Manske hydrazinolysis and its applications in living cells, Dyes Pigments 103 (2014) 9e20. [31] S. Goswami, S. Das, K. Aich, D. Sarkar, T.K. Mondal, A coumarin based chemodosimetric probe for ratiometric detection of hydrazine, Tetrahedron Lett. 55 (16) (2014) 2695e2699. [32] Y. Wang, H. Xiang, R. Zhao, C. Huang, A renewable test strip combined with solid-state ratiometric fluorescence emission spectra for the highly selective and fast determination of hydrazine gas, Analyst 143 (16) (2018) 3900e3906. [33] J. Zhou, R. Shi, J. Liu, R. Wang, Y. Xu, X. Qian, An ESIPT-based fluorescent probe for sensitive detection of hydrazine in aqueous solution, Org. Biomol. Chem. 13 (19) (2015) 5344e5348. [34] Y.-H. Xiao, G. Xi, X.-X. Zhao, S. Zhou, Z.-Q. Zhou, B.-X. 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A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine Xingzong Jiang a, Mingqin Shangguan a, Zhen Lu a, Sili Yi b, Xiaoyang Zeng a, Yongle Zhang a, Linxi Hou a, * a
College of Chemical Engineering, Fuzhou University, Fuzhou, 350108, PR China Institute of Food Safety and Environment Monitoring of Photocatalysis on Energy and Environment College of Chemistry, Fuzhou University, Fuzhou, 350116, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 October 2019 Received in revised form 19 December 2019 Accepted 3 January 2020 Available online xxx
Hydrazine (N2H4) has been classified as an environmental contaminant and human carcinogen owing to its high toxicity. Exposed to high concentration of hydrazine can cause irreversible damage to human bodies. Hence, it is significant to explore an effective analytical method to selectively recognize and detect it. In this work, an intramolecular charge transfer (ICT) based probe 1 was designed and synthesized by condensation of V-shaped bis-coumarin and 4-bromobutyric acid. The V-shaped biscoumarin with p-expanded system endowed the probe 1 larger stokes shift and superior tolerance to photobleaching. This “turn-on” probe exhibited a high selectivity towards hydrazine over other common ions and amine-containing species with a distinct fluorescent enhancement at 555 nm. It could rapidly detect hydrazine over a wide pH range and the detection limit was as low as 4.2 ppb. The large shift of absorption spectrum enabled it to detect hydrazine in real water samples and gas-state hydrazine by “naked-eyes". © 2020 Published by Elsevier Ltd.
Keywords: Fluorescent probe Bis-coumarin derivative Hydrazine detection Gaseous detection
1. Introduction Hydrazine (N2H4), known as a crucial weak base and a typical reducing agent, has been widely used in various fields, such as the pharmacy, chemistry, catalysis and agriculture [1e3]. Additionally, due to its high enthalpy of combustion, hydrazine is often employed as high-energy fuel in rocket-propulsion and missile systems [4,5]. Although hydrazine plays an important and positive role in production and manufacturing process, the toxicity and carcinogenicity of it shouldn’t be ignored. As a volatile and watersoluble compound, it can cause irreversible damage to the lungs, liver, kidneys, respiratory system and central nervous system of living bodies through easily absorbed by dermal, breathing or oral routes [6e8]. In fact, hydrazine has been denoted as a possible human carcinogen by the U.S. Environmental Protection Agency (EPA) with the threshold limit value (TLV) of 10 ppb [9]. Therefore, the convenient and high-efficiency detection methods for trace hydrazine have gained increasing attention.
* Corresponding author. E-mail address: [email protected] (L. Hou).
To date, various methods have been developed to determine hydrazine. Traditional analytical techniques including surfaceenhanced Raman spectroscopy [10], chromatography [11e13] electrochemistry [14,15] and titration [16,17] are inferior for detecting hydrazine due to the apparent limitations such as timeconsuming, requirement of expensive instruments and professionals, as well as complicated pre-treatments. In comparison, fluorescent probes are flourishing as promising technique in virtue of unique advantages such as real-time visual monitoring, in-situ analysis and ease to operation [18,19]. A number of fluorescent probes for detecting molecules and ions in vivo or vitro have been reported. However, the fluorescent probes for hydrazine have been reported less [20]. Until now, most of the probes for hydrazine are designed via anchoring a fluorophore with reaction sites including 4-bromobutanoate [21,22], acetyl [23e25], aldehyde [26,27], malononitrile [28,29], phthalimide [30], and trifluoroacetyl acetonate [31]. However, many of them suffer from several ineradicable defects such as narrow pH range, complicated synthesis procedures, long response time or poor selectivity. Various organic fluorophores such as benzothiazole [32,33], coumarins [34e39], rhodamine [40], 1,-8 naphthalimide [23,41] and heptamethine cyanine [24] have been utilized to design
https://doi.org/10.1016/j.tet.2020.130921 0040-4020/© 2020 Published by Elsevier Ltd.
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fluorescent probes recent years. Among these fluorophores, coumarin and its derivatives, especially coumarin-fused heterocycles, attract more attention for their large stokes shift, superior tolerance to photobleaching and great fluorescent quantum yield [42]. In addition, due to the extension of the conjugated system and the plentifulness of electrons in coumarin-fused heterocycles, coumarins with p-expanded system show several distinguished properties, such as larger stokes shift, red shift in the excitation and emission wavelengths, and colorimetric properties compared with the traditional coumarins whose absorption and emission wavelength generally locate on short-wave band [43]. Taking significant advantages stated above into consideration, p-expanded coumarins can be applied in environmental detection and even biosensors. In this work, the V-shaped bis-coumarin was selected as fluorophore combined with 4-bromobutanoate to afford a “turn-on” fluorescent probe 1. This V-shaped bis-coumarin possessed a electron-donating group (hydroxyl) and a electron-withdrawing group (carbonyl) at the site corresponding to position 7 and 2 of the coumarin moiety respectively, which formed the push-pull electron structure and emitted fluorescent according to ICT (intramolecular charge transfer) theory [44]. In addition, it was reported that bromo-ester derivatives could react with hydrazine through nucleophilic substitution to the bromine group and nucleophilic addition to the ester carbonyl with subsequent intramolecular cyclization to release the fluorophore [45]. So we assumed that the electron-withdrawing 4-bromobutanoate could prohibit the ICT process and quench the fluorescent emission of the fluorophore by esterification. When reacted with hydrazine, the fluorophore could be released and the ICT process was recovered, which resulted fluorescent enhancement simultaneously. As expected, upon addition of hydrazine, the emission intensity distinctly increased at 555 nm in DMSO: PBS buffer solution (3:1, v/ v, pH ¼ 7.4), simultaneously, the UVeVIS absorption spectrum showed a red shift with the color changing from colorless to yellow. The color change provided a visual method of detecting hydrazine by “naked-eye”. The limit of detection value (LOD) was found to be 4.2 ppb, which was lower than the TLV (10 ppb) according to the EPA. The probe exhibited excellent selectivity and rapid response towards hydrazine. Moreover, the probe could be used for practical detection of hydrazine in real water samples and gas-state hydrazine. 2. Experimental section 2.1. Materials and instruments All chemical reagents and solvents were purchased from commercial suppliers, further purification was not required. Absorption spectra were detected on Lambda 750 UVevis spectrophotometer. Fluorescent spectra were measured on the Hitachi F-4600 spectrofluorometer. 1H NMR spectra were recorded on a Bruker Avance III 600 MHz spectrometer and referenced to the solvent signals. The mass spectra were performed on Agilent HPLC-MS. 2.2. Synthesis of probe 1 The detailed synthesis route was given in the Electronic supplementary information (Scheme. S1) [46]. Compound 1 (1.40 g, 5 mmol) and 4-bromobutyric acid (1.17 g, 7 mmol) were mixed in the dichloromethane (20 mL) with stirring. 4dimethylaminopyridine (DMAP, 0.23 g, 2 mmol) and N, N0 -dicyclohexylcarbodiimide (DCC, 0.40 g, 2 mmol) were added into the solution and stirred at room temperature for 6 h. After the reaction
finished, the solvent was removed under reduced pressure. The residue was purified by silica gel column chromatography (CH2Cl2/ CH3OH ¼ 10/1, v/v) to afford pure probe 1 as white solid (1.31 g, 62% yield). 1H NMR (600 MHz, DMSO) d 8.57 e8.41 (m, 2H), 7.87 (dd, J ¼ 8.5, 7.3, 1.4 Hz, 1H), 7.50 (ddd, J ¼ 79.4, 11.3, 8.6, 1.7 Hz, 4H), 3.67 (t, J ¼ 6.6 Hz, 2H), 2.84 (t, J ¼ 7.3 Hz, 2H), 2.23 (p, J ¼ 6.8 Hz, 2H) (Fig. S3). 13C NMR (101 MHz, DMSO) d 174.03 (s), 170.86 (s), 157.21 (s), 155.66 (s), 155.36 (s), 154.75 (s), 152.30 (s), 135.50 (s), 131.12 (s), 129.66 (s), 125.47 (s), 119.43 (s), 117.99 (s), 115.57 (s), 113.55 (s), 111.39 (s), 106.88 (s), 34.64 (s), 32.51 (s), 28.20 (s) (Fig. S6). HRMS: m/z calcd for C20H13BrO6 [MþH]þ: 428.9968, found: 428.9975 (Fig. S8). 2.3. General procedures for analysis The stock solution of probe 1 (1 mM) was prepared in DMSO, and then diluted with DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4). Stock solutions of hydrazine and other common analytes (cations: Naþ, Kþ, Ca2þ, Mg2þ, Liþ, Fe2þ, Zn2þ, Fe3þ, Mn2þ, Co2þ, 2 2 2 Al3þ; anions: Cl, HPO2 4 , CO3 , SO4 , F , NO3 , I , AcO , SO3 ; and amine-containing species: Triethylamine, Diethylamine, 2Aminoethanol, Sulfamic acid, Aniline, NH3$H2O, L-Cys, Ala, Glu, Hcy, GSH) were prepared in distilled water. The stock solutions were used freshly and were diluted to appropriate concentrations as needed. All spectral analysis experiments were carried out in DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) with probe 1 (900 mL, 200/9 mM) and hydrazine (100 mL, appropriate concentration). When conducted the fluorescent experiment, the stock solution of probe 1 was added into a quartz cuvette (1 cm 1 cm), followed by addition of 100 mL of the hydrazine stock solutions with different concentrations. The fluorescent spectra were recorded after 15 min. The process of selectivity and competition studies were same as above, except interfering substances (1 mM, 50 mL) were added in front of hydrazine (100 mL, 500 mM). The excitation wavelength was 460 nm, and the PMT voltage was 550 V. The excitation and emission slit width were 5 nm and 5 nm, respectively. 2.4. Water samples test Tap water in laboratory and Minjiang River water were selected for the practical sample analysis. The stock solution of probe 1 (900 mL, 200/9 mM) was added into a quartz cuvette (1 cm 1 cm), followed by addition of 50 mL of the water samples respectively. After that, 100 mL of different concentrations of standard hydrazine solution (100 mM, 300 mM, 500 mM) were added to the solution. The fluorescent spectra of these samples were recorded after 15 min. 2.5. Detection of gaseous hydrazine Filter papers were immersed in DMSO solution of probe 1 (2 mM) for 5 min and then dried at room temperature. Different concentrations of hydrazine solution (0, 0.5%, 1%, 5%, 10%, 20%, 30%) were prepared in test tubes. The above filter paper strips were hung in respective test tubes at room temperature for 10 min. Observing the color and fluorescent changing under the natural light and UV light (commercial hand-held 365 nm UV lamp) respectively. 3. Results and discussion 3.1. UVevis and fluorescent spectra The optical property of probe 1 was investigated first. The timedependent absorption spectra of the probe 1 (20 mM) were examined at room temperature after addition of hydrazine (100 mM) to
Please cite this article as: X. Jiang et al., A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine, Tetrahedron, https://doi.org/10.1016/j.tet.2020.130921
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Fig. 1. (a) The time-dependent UVevis absorption spectral of probe 1 (20 mM) in the presence of hydrazine (100 mM). (b) Fluorescent emission spectra of probe 1 (20 mM) with the gradually increasing concentration of hydrazine (0e100 mM) in DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4). lex ¼ 460 nm lem ¼ 555 nm. (c) Fluorescent photographs of probe 1 in the presence of increasing concentrations of hydrazine. (d) The fluorescent intensities (lem ¼ 555 nm) of probe 1 were linearly related to the concentrations of hydrazine (0e50 mM). lex ¼ 460 nm, dex ¼ 5 nm, dem ¼ 5 nm.
DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) (Fig. 1a). It can be observed that the free probe 1 showed a maximum absorption peak at 357 nm. After addition of hydrazine, the absorption peak at 357 nm was decreased gradually. Inversely, the absorption peak at 460 nm was increased dramatically. A well-defined isobestic point appeared at 390 nm. Such a large red shift of 103 nm in absorption spectrum transformed the solution from colorless and transparent to orange, suggesting hydrazine could be detected with the “nakedeyes". Subsequently, the fluorescent titration experiment of the probe 1 was carried out in the DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) (Fig. 1b). Originally, the free probe 1 solution (20 mM) exhibited a very weak emission peak at 555 nm under the excitation of 460 nm. After addition of hydrazine with increasing concentration (0 e100 mM), a significant increase of the fluorescent intensity at 555 nm was observed and reached to a plateau at the concentration of 60 mM. The fluorescent color changed from colorless to yellow gradually (Fig. 1c). Such a large Stokes shift of 95 nm in emission spectrum made it have a higher signal-noise ratio than other probes (Table S1). Meanwhile, the fluorescent intensity at 555 nm exhibited an excellent linear relationship (y ¼ 2.79 þ 52.79x, R2 ¼ 0.9960) with the concentrations of hydrazine in the range of 0 e50 mM (Fig. 1d). The detection limit was calculated to be 0.0099 mM (4.2 ppb) based on 3s/k, which was lower than TLV of 10 ppb. These results indicated that the probe 1 was competent for detecting hydrazine qualitatively and quantitatively. 3.2. Selectivity and competition studies The selectivity of fluorescent probe was an important parameter in performance evaluation. The response of the probe 1 toward common cations (Naþ, Kþ, Ca2þ, Mg2þ, Liþ, Fe2þ, Zn2þ, Fe3þ, Mn2þ, 2 2 Co2þ, Al3þ) and anion (Cl, HPO2 4 , CO3 , SO4 , F , NO3 , I , AcO ,
SO2 3 ) were performed in the DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) to prove the selectivity of probe 1 to hydrazine. Upon addition 50 mL of different analytes (1 mM) respectively, only hydrazine triggered a prominent fluorescent emission enhancement at 555 nm while other species appeared negligible variation (Fig. 2a). Moreover, competitive assays indicated that the coexistence of cations and anions had no interference on the detection of hydrazine (Fig. 2b). Subsequently, the response of the probe 1 toward amine-containing species (Triethylamine, Diethylamine, 2-Aminoethanol, Sulfamic acid, Aniline, NH3$H2O, L-Cys, Ala, Glu, Hcy, GSH) was performed in the same condition (Fig. S9). The results demonstrated the probe 1 had the same excellent selectivity and anti-interference ability to these amine-containing species. Such a high selectivity and anti-interference ability of the probe 1 indicated it could be used as a sensing platform for hydrazine detection in complex environment. 3.3. Effect of pH and reaction time In view of the importance of pH value adaptation in practical applications, the pH effects on fluorescent response of probe 1 in the absence and presence of hydrazine were investigated (Fig. 3a). The probe 1 was inert to pH in the range of 2.0e11.0 in the absence of hydrazine. Upon treatment with hydrazine (50 mM), the maximal fluorescent signal was observed in the pH range of 4.0e11.0. These results indicated that the probe 1 could exist steadily and detect hydrazine with excellent sensitivity over a wide pH range. For kinetic studies, time-dependent fluorescent intensity measurement was performed on probe 1 (20 mM) with hydrazine (50 mM) in DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4) (Fig. 3b). Upon introduction of hydrazine to the probe solution, a significant enhancement of the fluorescent intensity at 555 nm arose and reached the plateau within 15 min. These results implied the probe 1 had a fast response to hydrazine.
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Fig. 2. Fluorescent emission of probe 1 (20 mM), upon the addition of different ions (50 mM) and N2H4 (50 mM), in DMSO: PBS buffer solution (3:1, v/v, pH ¼ 7.4). (a) Represents the addition of hydrazine or various other ions to the solution of probe 1. (b) Represents the addition of hydrazine to the above ions-containing solutions (bars show: 0. Blank, 1. Naþ, 2. 2 2 2 Kþ, 3. Ca2þ, 4. Mg2þ, 5. Liþ, 6. Fe2þ, 7. Zn2þ, 8. Fe3þ, 9. Mn2þ, 10. Co2þ, 11. Al3þ, 12. Cl, 13. HPO2 4 , 14. CO3 , 15. SO4 , 16. F , 17. NO3 , 18. I ,19. AcO , 20. SO3 ).
Fig. 3. (a) The fluorescent intensity of probe 1 (20 mM) in the absence (black line) or presence (red line) of hydrazine (50 mM) at various pH values. (b) Reaction time profiles of probe 1 (20 mM) with hydrazine (50 mM).
Then we extended the reaction time to determined the photostability of probe 1 (Fig. S10). Under the irradiation of 460 nm UVlight, there was no change in the fluorescence intensity of probe 1 in the absence of hydrazine within 1 h. When hydrazine (50 mM) was added, as expect, the fluorescence intensity increased immediately and reached the maximum within 15 min. Additionally, the fluorescence intensity was nearly unchanged over time, which indicated the photostability of probe 1. 3.4. Proposed detection mechanism To our knowledge, bromo-ester derivatives could react with hydrazine through nucleophilic substitution to the bromo group and nucleophilic addition to the ester carbonyl with subsequent intramolecular cyclization to release the fluorophore [45]. So the electron-withdrawing group bromo-ester derivatives was introduced into the V-shaped bis-coumarin fluorophore to prohibit its
ICT process and quench the fluorescent. After reaction with hydrazine, the fluorophore was released and the ICT process was recovered, which resulted in fluorescent enhancement (Scheme 1)., In order to determine the reaction, UV eVis absorption spectra were analyzed (Fig. S11), the free probe 1 exhibited a broad absorption band at 300 e400 nm, but there was a negligible absorption at 460 nm. When reacted with hydrazine, the peak at 350 nm decreased gradually, whereas the peak at 460 nm which regarded as characteristic absorption peak of compound 1 increased sharply. Additionally, it was similar to the absorption spectra of compound 1 which confirmed our hypothesis. 1H NMR was further taken to verify the mechanism, and the results were performed in Fig. 4. After the addition of hydrazine into probe 1 in DMSO-d6, the protons of probe 1 at 8.52 ppm (a), 8.45 ppm (b), 7.87 ppm (c), 7.57 ppm (d), 7.54 ppm (e), 7.50 ppm (f), 7.36 ppm (g) remarkably shifted to 8.39 ppm (a), 8.31 ppm (b), 7.83 ppm (c), 6.84 ppm (d), 6.98 ppm (e), 7.52 ppm (f), 7.50 ppm (g). As expected,
Scheme 1. The proposed mechanism of probe 1 reacting with hydrazine.
Please cite this article as: X. Jiang et al., A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine, Tetrahedron, https://doi.org/10.1016/j.tet.2020.130921
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Fig. 4. The changes of 1H NMR spectra of probe 1 after reacted with hydrazine.
it was similar to the 1H NMR spectra of compound 1 (Fig. S4). All the above results confirmed that probe 1 could react with hydrazine to release the fluorophore. 3.5. Water samples test Hydrazine had been widely used in various industrial processes, the detection and quantification of it in real aqueous samples was significant. The probe 1 was applied to detect hydrazine in tap water and Minjiang River in Fuzhou city, respectively. The water samples (50 mL) were added into the probe 1 solution (20 mM), and there was no significant fluorescent enhancement observed. Then, an aliquot of hydrazine solution (10 mM, 30 mM, 50 mM) was added to the above real samples and recorded the fluorescent spectra. As shown in Table 1, the resultant hydrazine recoveries were in the range of 101e105%, indicating the possibility of probe 1 for hydrazine detection in practical water samples. 3.6. Detection of gaseous hydrazine
light and UV light respectively (Fig. 5). The fluorescent color from colorless to yellow were observed with the increase of hydrazine vapor concentration, meanwhile, the color clearly changed from colorless to yellow by “naked-eyes”. Furthermore, this analytic method could identify hydrazine vapor even at a concentration as low as 0.5%. Hence, it had great application value for the rough detection of gaseous hydrazine.
4. Conclusion In summary, a new type of V-shaped bis-coumarin “turn-on” fluorescent probe for hydrazine detection had been reported. It exhibited distinct changes in the intensity of both absorption and emission spectra upon addition of hydrazine. The remarkable color change can be observed visually. The sensing mechanism was elucidated by spectroscopy and 1H NMR analysis. The probe exhibits prominent selectivity and sensitivity with a low detection limit. It was a candidate for “naked-eyes” and fluorescent detection of hydrazine in real water samples and gas-state hydrazine.
To explore the practical applications of the probe, the detection of gaseous hydrazine was also performed. Primarily, the tailored filter paper strips were immersed in the probe 1 solution (2 mM) for 5 min. Then took them out and dried at room temperature. Different concentrations of hydrazine solution (0, 0.5%, 1%, 5%, 10%, 20%, 30%) were prepared in test tubes, the above filter paper strips were hung in respective test tubes at room temperature for 10 min. The color and fluorescent changing was observed under the natural Table 1 Detection of hydrazine in environmental samples.
Tap water
Minjiang River
Spiked (mM)
Detected (mM)
Recovery (%)
RSD (%)
0 10 20 30 0 10 20 30
Not detected 10.17 20.83 31.51 Not detected 10.19 20.77 31.20
e 101.7 104.2 105.0 e 101.91 103.8 104.0
e 0.41 0.28 0.30 e 0.18 0.23 0.28
Fig. 5. Photographs for probe 1 coated filter papers upon exposure to gaseous hydrazine with different concentrations. Upper: under natural light; Lower: under a hand-hold UV lamp with an excitation at 365 nm in dark.
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Please cite this article as: X. Jiang et al., A “turn-on” fluorescent probe based on V-shaped bis-coumarin for detection of hydrazine, Tetrahedron, https://doi.org/10.1016/j.tet.2020.130921