Analytical Methods Volume 13 Number 11 21 March 2021 Pages 1311–1434 rsc.li/methods Duc Anh Thai and Nae Yoon Lee A paper-based colorimetric chemosensor for rapid and highly sensitive detection of sulfide for environmental monitoring I PAPER M nde ed xe lin d in e! ISSN 1759-9679 Analytical Methods View Article Online Published on 09 February 2021. Downloaded by Istanbul Technical University on 5/27/2023 12:46:04 AM. PAPER Cite this: Anal. Methods, 2021, 13, 1332 View Journal | View Issue A paper-based colorimetric chemosensor for rapid and highly sensitive detection of sulfide for environmental monitoring† Duc Anh Thai and Nae Yoon Lee * In this study, we report on paper-based colorimetric detection of sulfide using a newly synthesized chemical acting as a chemosensor, based on the deprotonation mechanism. Paper strips were also fabricated and incorporated with the chemosensor for on-site monitoring. The presence of sulfide induced deprotonation of a hydroxyl group of the chemosensor, which eventually resulted in a distinct spectral change in the tube as well as a visible color change on a paper strip. The chemosensor showed a highly selective colorimetric response to sulfide by changing its color from colorless to yellow without any interference from a mixture containing other anions. Moreover, the chemosensor effectively differentiated sulfide from other thiols, including cysteine and glutathione. The chemosensor colorimetrically detected sulfide with a fast response time of 10 s under physiological conditions. Received 13th January 2021 Accepted 9th February 2021 Practically, the paper test strip enabled colorimetric visualization of as low as 30 mM sulfide and a good recovery in quantitative analysis in water samples. The introduced paper-based chemosensor is DOI: 10.1039/d1ay00074h rsc.li/methods 1 a promising colorimetric strategy with rapid, selective, and sensitive sensing abilities for sulfide monitoring in environmental water samples. Introduction Sulde (S2) is known as a highly toxic substance, recognized by its rotten egg malodorous smell, and is widely distributed in natural water and wastewater.1 Sulde appears naturally in petroleum and hot springs, while some amounts of it are generated from the decay of organic matter (e.g. human and animal wastes) by bacterial processes.2 Furthermore, it is also produced from the industrial production of paper and pulp mills, chemical fertilizers, manufacturing of sulfuric acid, and dyes.3 In biological systems, sulde is endogenously produced from L-cysteine catalyzed by cystathionine-b-synthase, cystathionine-g-lyase, and 3-mercaptopyruvate sulfurtransferase.4–6 Sulde is involved in several physiological functions, including vascular smooth muscle cell proliferation, apoptosis, insulin signaling, and oxygen sensing.7–9 However, abnormal concentrations of sulde in bio-systems are associated with serious health problems such as Alzheimer's disease, Down's syndrome, liver cirrhosis, heart disease, and diabetes.10–12 Due to the considerable interest in sulde, there is an urgent need for the development of a novel approach for fast and sensitive detection of sulde. Department of BioNano Technology, Gachon University, 1342 Seongnam-daero, Sujeong-gu, Seongnam-si, Gyeonggi-do, 13120, Korea. E-mail: nylee@gachon.ac.kr † Electronic supplementary information (ESI) available: Experimental details, characterization and spectral studies. See DOI: 10.1039/d1ay00074h 1332 | Anal. Methods, 2021, 13, 1332–1339 Gas chromatography and high-performance liquid chromatography techniques have been known as gold standard methods for the detection and determination of sulde in various samples, including environmental water and soil samples.13 While chromatographic strategies possess the advantages of separation capability and reliability, these techniques require expensive equipment, sophisticated training for operation, high operating cost, and time-consuming analysis.14 In addition, although the methylene blue test is the most common approach for the spectroscopic analysis of sulde,15 this method is necessarily catalyzed by concentrated HCl and is poorly selective towards other thiol compounds.16 It is thus necessary to develop a simple and quick system that enables the selective detection of sulde. Recently, due to such desirable properties such as sensitivity, ease of operation, and real-time detection, chemosensors have emerged as an attractive method. Indeed, various sulde sensors and their applications have been explored following some important sensing mechanisms, including the reduction of azides to amines,17,18 nucleophilic reactions,19,20 and displacement of metal ions by sulde.21,22 However, most of the reported sensors still have drawbacks of complicated synthesis and interference by other thiols, such as cysteine and glutathione.23 In addition, most previous chemosensors are based on uorescence signaling, which still requires sophisticated excitation and read-out instruments, which makes these methods unsuitable for on-site monitoring of sulde. This journal is © The Royal Society of Chemistry 2021 View Article Online Published on 09 February 2021. Downloaded by Istanbul Technical University on 5/27/2023 12:46:04 AM. Paper Considering these limitations, a deprotonation-based colorimetric chemosensor has been consequently developed for a fast response and non-interference detection of sulde.24,25 Moreover, chemosensors containing Schiff's base have been particularly attractive due to their chromophoric characteristics and high stability. A very limited number of Schiff's base chemosensors for sulde, based on deprotonation, have recently been reported. Although these reported systems perform well, they still require multiple syntheses. Kaushik et al.26 reported an azine based chemosensor for the detection of sulde in biological uids such as human serum and mouse serum. Another colorimetric chemosensor was proposed by Ryu et al.27 to detect multiple targets: copper(II), cyanide, and sulde. Furthermore, colorimetry provides a straightforward and convenient strategy for developing paper-based sensor. Paper-based colorimetric detection has become a popular strategy due to its advantages such as portability, fast response, and minimal instrumentation. Most of all, the development of colorimetric paper strips eliminates the requirement of light sources and enables signal determination by the naked eye in the form of color change.28 This is an advantage for an in situ analysis with limited equipment in a low-resource environment. Herein, we introduce a sensitive paper-based colorimetric chemosensor for the rapid detection of sulde. By performing absorption spectroscopy, we characterized various sensing properties of the chemosensor, such as selectivity, sensitivity, pH effect, stability, and reversibility. Furthermore, the colorimetric chemosensor was incorporated in designed paper strips for rapid and selective visualization of sulde without sophisticated equipment. Moreover, we demonstrated the practicality of the colorimetric chemosensor for quantitatively monitoring sulde in water sample as a proof-of-concept test. 2 Experimental section 2.1 Materials and instrumentation All reagents and solvents were of analytical grade and used without further purication. Sulfanilamide, 2,3-dihydroxybenzaldehyde, sodium sulde, Bis–Tris, all anions in the form of tetrabutylammonium and sodium salts and amino acids (cysteine and glutathione) were purchased from Sigma-Aldrich, Korea. Dimethyl sulfoxide (DMSO) solvent was supplied by Biosesang (Seongnam, Korea). All solutions and buffers were prepared in deionized water. Glass microber lters were supplied by Chmlab Group (Barcelona, Spain). Proton Nuclear Magnetic Resonance (1H NMR) spectra were recorded on a JEOL JNM-LA400 instrument (JEOL Ltd., USA) at 400 MHz. Liquid Chromatography-Mass Spectrometry (LC-MS) with the electrospray ionization (ESI) technique was performed with an API 3200™ system (AB Sciex Pte. Ltd., USA). Fourier-transform infrared spectroscopy (FTIR) peaks were recorded on a JASCO FT/IR-4600 spectrometer (JASCO International Co., Ltd., Japan). UV-Vis absorption and uorescence spectra were recorded using an Epoch™ Microplate and Synergy™ H1 Hybrid MultiMode spectrophotometer (BioTek Instruments, Inc., USA), respectively. The pH level of a solution was measured using a digital pH meter Istek pH-200L (Istek, Inc., Korea). This journal is © The Royal Society of Chemistry 2021 Analytical Methods 2.2 Synthesis of chemosensor L The chemosensor L was prepared by a reaction of 2,3-dihydroxybenzaldehyde (1 mmol) and sulfanilamide (1 mmol) in absolute ethanol. The reaction mixture was stirred at room temperature for 24 h. Then, the tangerine orange precipitate was ltered, washed several times with cold ethanol, and dried in a vacuum. The chemosensor L was characterized by standard analytical techniques including mass spectrometry, 1H NMR spectroscopy, FTIR spectroscopy, and UV-Vis spectrophotometry. 2.3 General analytical procedure Chemosensor L stock was initially prepared in DMSO, and the solution was then diluted with the DMSO : Bis–Tris buffer (4 : 6, 10 mM, pH 7.0) solution to make a nal concentration of 50 mM. All anions such as uoride (F), chloride (Cl), bromide (Br), iodide (I), azide (N3), nitrite (NO2), nitrate (NO3), sulfate (SO42), cysteine (Cys), glutathione (GSH), and sulde (S2) were prepared in deionized water and the test solutions were mixed in an Eppendorf tube. The spectral measurements were recorded at room temperature for further analysis. The detailed procedures for selective, competitive, sensitive, pH-dependent and time-dependent, and reversible tests are described in the ESI.† 2.4 Theoretical calculations To understand the sensing mechanism of chemosensor L, theoretical computation was performed using density functional theory (DFT) calculations. The optimized structures of the ground state for chemosensor L with and without sulde were generated using GaussView embedded in the Gaussian 09 program.29 DFT calculations were evaluated and optimized with the B3LYP/6-31G* basis set.30 Moreover, the frontier molecular orbital contributions including the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) and the corresponding energies of chemosensor L with and without sulde were also simulated. 2.5 Fabrication of paper strips and detection of sulde in water samples The designed paper strip was fabricated using lter paper on which chemosensor L was coated by immersion, as shown in Fig. 1. The strip was rst designed in AutoCAD soware, and then a glass microber lter (Chmlab Group, Spain) was used to fabricate the paper strip by laser cutting. Next, the prepared strip was immersed in the DMSO solution of chemosensor L (100 mM) for 5 min allowing the chemosensor L to homogeneously distribute along the substrate. The substrate was then dried in a vacuum to obtain a ready-to-use paper strip, which could be used for the recognition of sulde. For water sample analysis, water samples from laboratory taps were collected in glass bottles. To mimic the sulde contaminated water samples, the tap water samples were spiked with various concentrations of sulde ranging from 200 to 800 mM. The chemosensor L was prepared in Bis–Tris buffer as optimized Anal. Methods, 2021, 13, 1332–1339 | 1333 View Article Online Published on 09 February 2021. Downloaded by Istanbul Technical University on 5/27/2023 12:46:04 AM. Analytical Methods Paper Fig. 1 Fabrication process of the paper strip coated with chemosensor L for the visualization of sulfide. conditions for performing a real sample test. For sample analysis, different sulde-spiked water samples were added to chemosensor L solution to perform quantitative measurements. The UV-Vis absorption was monitored at the 400 nm wavelength, and the experiments were performed four times and averaged for further calculation. 3 Results and discussion 3.1 Characterization of the synthesized chemosensor L Generally, there are three forms of sulde that exist in aqueous solution including hydrogen sulde (H2S), bisulde (HS), and sulde anions (S2). Under physiological conditions, approximately one-h exists as H2S and the remainder largely as its anions such as HS and S2.26 In this study, a mixture of H2S, HS, and S2 in solution was referred to as “sulde”. A chemosensor L was designed and developed for application to detect sulde in an aqueous solution. Chemosensor L ((Z)-4-((2,3-dihydroxybenzylidene)amino)benzenesulfonamide) was synthesized with a 56% yield, from 2,3-dihydroxybenzaldehyde and sulfanilamide with a 1 : 1 molar ratio (Scheme 1). The mass of chemosensor L was determined from the dominant peak at 293.3 m/z in the mass spectra (Fig. 2a). The content of C, H, N, O, and S elements in chemosensor L was found to be 53.42%, 4.14%, 9.58%, 21.89%, and 10.97%, respectively. The proposed chemical structure of chemosensor L is illustrated in Fig. 2b. Fig. 2c shows Scheme 1 Schematics of the synthesis of chemosensor L. 1334 | Anal. Methods, 2021, 13, 1332–1339 Structural characterization of chemosensor L. (a) Liquid chromatography-mass spectra (LC-MS) of chemosensor L. (b) Proposed chemical structure of chemosensor L. (c) 1H NMR of chemosensor L in DMSO-d6. (d) FTIR spectra of chemosensor L. Fig. 2 the 1H NMR chemical shis of chemosensor L using DMSO-d6 solvent. The peak at 8.92 ppm corresponded to benzylidene HC] N, while the proton attached to hydroxyl groups was featured at 5.77 ppm.31 The carbon next to the hydroxyl group carried the proton featured as a peak at 6.86–6.76 ppm. The peaks at 6.56– 6.54 and 6.96–6.94 ppm were related to other protons of the benzylidene moiety. In addition, the peaks at 7.81–7.85, 7.54– 7.52, 7.41–7.37, and 7.12–7.10 ppm corresponded to the aromatic protons of the benzenesulfonamide moiety.32 Furthermore, the IR band resulting from the NH2 group of the chemosensor L was observed at approximately 700 cm1. The sharp band at 1016 cm1 and doublet bands at around 1403 cm1 represented O] S]O symmetric and HC]N vibrations, respectively. Additionally, the IR spectra showed a band at 3425 cm1, which was related to aromatic O–H vibration (Fig. 2d).31 The typical aromatic hydroxyl groups, like phenols, have been well known for being deprotonated in the presence of basic anions. 3.2 Spectral properties and sensitivity of chemosensor L The spectral properties of chemosensor L were examined by both UV-Vis and uorescence titration towards different concentrations of sulde in the DMSO: Bis–Tris buffer (4 : 6, 10 mM, pH 7.0) solution. Fig. 3a shows the UV-Vis absorption spectra of chemosensor L in the wavelength range from 300 to 600 nm. The free chemosensor L displayed no certain absorption band; however, the solutions showed a gradual bathochromic shi in the successive addition of sulde. An absorption peak at 400 nm appeared with the addition of sulde, and the absorbance at 400 nm signicantly increased as the concentration of sulde increased. Sulde also induced a distinct color change of chemosensor L from colorless to yellow (inset gure). In addition, the absorbance at 400 nm was plotted as a function of sulde concentration. As a result, This journal is © The Royal Society of Chemistry 2021 View Article Online Published on 09 February 2021. Downloaded by Istanbul Technical University on 5/27/2023 12:46:04 AM. Paper Analytical Methods Fig. 4 Results of selectivity of chemosensor L to sulfide. Absorbance (a) and fluorescence intensity (b) change of chemosensor L (50 mM) in the presence of various anions. The corresponding visible color (c) and fluorescence color (d) change of chemosensor L (50 mM) in the presence of various anions (60 equivalents) in the DMSO: Bis–Tris buffer (4 : 6, 10 mM, pH 7.0) solution. UV-Vis spectra (a) and emission spectra (c) of chemosensor L (50 mM) in the presence of different concentrations of sulfide (0–60 equivalents). The inset figures show the visible and fluorescence color change of chemosensor L after reacting with sulfide in the DMSO: Bis– Tris buffer (4 : 6, 10 mM, pH 7.0) solution. Absorbance (b) and fluorescence intensity (d) plotted as a function of sulfide concentrations. Fig. 3 a linear equation was obtained with the coefficient of determination R2 ¼ 0.9996. The limit of detection (LOD) was determined to be 25.8 mM (Fig. 3b). Interestingly, during the experiment, we found that chemosensor L showed a uorescence response to sulde. The chemosensor L initially showed a non-uorescence signal when excited at 400 nm. However, when sulde was introduced into the chemosensor L solution, a new broad uorescence band emerged at around 570 nm (Fig. 3c). The uorescence emission was also recognized by orange uorescence under 365 nm UV light (inset gure). Consequently, the emission intensity gradually enhanced with an increase of sulde concentration with a detection limit of 15.6 mM (R2 ¼ 0.9843) (Fig. 3d). The LOD was considerably lower than a secondary maximum contaminant level set for sulde in water (7.8 mM) as established by the US Environmental Protection Agency (EPA).33 Therefore, chemosensor L showed a strong colorimetric and uorescence signal, which could be efficiently used for the sensitive detection of sulde in environmental systems. 3.3 The selectivity of chemosensor L for sulde detection Fig. 4 shows the selectivity of chemosensor L to sulde (S2) among various anions, such as uoride (F), chloride (Cl), bromide (Br), iodide (I), azide (N3), nitrite (NO2), nitrate (NO3), sulfate (SO42), cysteine (Cys), and glutathione (GSH), the nal two of which contained thiol. Chemosensor L (50 mM) was essentially colorless and non-uorescent in the aqueous solution; however, chemosensor L exhibited an absorption peak at 400 nm in response to sulde upon the addition of each anion. Aer the addition of sulde to chemosensor L, the absorbance increased approximately 5.4-fold compared with that of chemosensor L (Fig. 4a). In contrast, for other anions This journal is © The Royal Society of Chemistry 2021 chemosensor L showed almost no absorption spectral change. Accordingly, the chemosensor L solution showed a visible color change from colorless to yellow with sulde, while with the other anions it remained colorless (Fig. 4c). This can be explained by the fact that sulde deprotonates chemosensor L to produce a yellow color product, whereas the other anions cannot react with chemosensor L and the solution remained colorless. On the other hand, the addition of sulde to chemosensor L resulted in emission spectra change accompanied by orange uorescence and the uorescence intensity signicantly enhanced about 12.4fold compared with that of chemosensor L. However, no such obvious change was observed in the presence of other anions and thiols (Fig. 4b and d). These results demonstrate that chemosensor L was highly selective to sulde and also efficiently discriminated sulde from thiol-containing analytes. Moreover, chemosensor L exhibited the high selectivity to sulde in the presence of other interferences in the mixture, such as F, Cl, Br, I, N3, NO2, NO3, SO42, Cys, and GSH (Fig. S1, ESI†). The sulde sensing had no considerable interference from coexistent anions. Although a slight decrease in spectra was observed in competitive thiols such as Cys and GSH, the absorbance and emission signals still presented the signicant recognition of sulde in the solution. Therefore, chemosensor L was able to effectively detect sulde in the presence of foreign solutions. Sulde tends to compete for the proton and deprotonates the hydroxyl (–OH) group from chemosensor L.24,26 Although uoride can deprotonate phenolic hydroxyl in a quinolone-containing receptor,34 this has not caused any interference to our proposed chemosensor L, presumably because sulde is a stronger base than uoride. These results indicate that chemosensor L is not only highly selective for sulde, but also possesses an excellent capacity to resist disturbance from other anions and thiols. 3.4 The sensing mechanism of chemosensor L To better understand the interaction between chemosensor L and sulde, FTIR spectra of chemosensor L were successively Anal. Methods, 2021, 13, 1332–1339 | 1335 View Article Online Published on 09 February 2021. Downloaded by Istanbul Technical University on 5/27/2023 12:46:04 AM. Analytical Methods (a) FTIR spectra of chemosensor L in the presence and absence of sulfide. The optimized structures of the ground state for (b) chemosensor L and (c) chemosensor L + S2. HOMO – LUMO and energy gaps of (d) chemosensor L and (e) chemosensor L + S2. Fig. 5 recorded with and without sulde. As shown in Fig. 5a, the absorbance band in the IR spectra of chemosensor L was observed at 3425 cm1 as a result of O–H stretching. The broad chemical band was possibly due to the overlap between two aromatic –OH groups contained in chemosensor L. However, upon reaction with sulde, as a result of chemical modication at the –OH group, the O–H vibration band was converted to a sharp band and concurrently shied to 3355 cm1. The hydrogen atom in the –OH functional group was deprotonated and the chemical shi changed due to the deprotonation of the aromatic –OH by sulde. Besides, there was very little IR spectral change from the remaining structural features in chemosensor L when reacted with sulde. In addition, the change in UV-Vis absorption of chemosensor L in the presence of strong base OH anions, known as a deprotonation factor, was nearly similar to that of chemosensor L obtained with sulde (Fig. S2, ESI†). Moreover, a Job's plot was used to determine the binding mode of the complex chemosensor L and sulde. The molar fraction of sulde corresponding to the maximum absorbance change amounted to 0.5, indicating 1 : 1 stoichiometry between chemosensor L and sulde (Fig. S3, ESI†). These results conrmed that the changes in the color and absorption were due to the deprotonation of a hydroxyl functionality contained in chemosensor L. The sensing mechanism of the chemosensor L with sulde is proposed in Scheme 2. The presence of sulde Anticipated sensing mechanism of chemosensor L for sulfide detection. Scheme 2 1336 | Anal. Methods, 2021, 13, 1332–1339 Paper deprotonates the hydroxyl group in the benzylidene moiety of chemosensor L to produce a yellow color as well as spectral change (Fig. 3a). Furthermore, the optimized structure (Fig. 5b and c) and molecular orbital properties (HOMO and LUMO) (Fig. 5d and e) of chemosensor L with and without sulde were simulated by DFT calculations using the B3LYP/6-31G* basic level of theory. From the DFT calculations, the p electrons were generally located on the benzylidene moiety in the HOMO of chemosensor L both with and without sulde. In the LUMO, however, the electrons were transferred to rearrange around the HC]N linkage when chemosensor L was excited with an energy gap of 0.146 eV, which was much higher than the energy needed for deprotonating chemosensor L (0.036 eV) by sulde (Fig. 5d and e). Therefore, the tendency of releasing protons from the hydroxyl group was considered as the LUMO state of chemosensor L when reacted with sulde. The hydroxyl unit being adjacent to the Schiff's base linkage tended to be deprotonated, which eventually enhanced the intramolecular charge transfer (ICT) in the chemosensor L, resulting in the spectral and color change.35 This demonstration was in good agreement with the apparent change in both UV-Vis and uorescence spectra conforming to the deprotonation mechanism of chemosensor L toward sulde (Scheme 2). 3.5 L pH and time effects and reversibility of the chemosensor To investigate the effect of pH on sulde binding, the sensing behavior of chemosensor L was demonstrated with a series of solutions with pH values ranging from 2 to 12. Chemosensor L efficiently monitored sulde in the solution with pH ranging from 6 to 9 (Fig. 6a and S4, ESI†). In general, in acidic pH, the deprotonation is less likely to occur due to the inuence of a high concentration of H+. However, a high concentration of OH above pH 10 caused interference to chemosensor L. Moreover, H2S species are predominant at acidic pH, while an appreciable number of dissociated anions such as HS and S2 exist at physiological pH.26,36 Therefore, the natural pH was chosen as the optimum condition to evaluate the performance of the chemosensor L. These results show that chemosensor L can be effectively applied for the detection of sulde in real samples under physiological conditions. Since real-time sulde monitoring of sulde is important, we also demonstrated the response time of chemosensor L. The absorbance was measured aer adding sulde into chemosensor L solution and then recorded every minute. Fig. 6b shows the stability of chemosensor-based colorimetric detection of sulde. A quick response was observed aer adding sulde into the chemosensor L solution. In particular, a new absorption band at 400 nm immediately reached the plateau within 10 s and then remained stable for the next 30 min. The proposed chemosensor L exhibited an impressively fast response in comparison with reported chemosensors for the detection of sulde (Table S1, ESI†). This result conrmed the rapid and sustained detection ability of chemosensor L for sulde, which is probably appropriate for real-time monitoring of sulde. This journal is © The Royal Society of Chemistry 2021 View Article Online Published on 09 February 2021. Downloaded by Istanbul Technical University on 5/27/2023 12:46:04 AM. Paper Analytical Methods Fig. 7 The chemosensor L-coated paper strips for sulfide detection. (a) Visible color change and (b) mean intensity of chemosensor Lcoated paper strips (100 mM) in the presence of various anions (100 mM). (c) Visible color change and (d) mean intensity of chemosensor Lcoated paper strips in the presence of various concentrations of sulfide (0–100 mM). The absorbance of chemosensor L (50 mM) with sulfide at different pH (a) and intervals time (b) in the DMSO: Bis–Tris buffer (4 : 6, 10 mM) solution. (c) Reversibility of chemosensor L (50 mM) in the DMSO: Bis–Tris buffer (4 : 6, 10 mM, pH 7.0) solution. Fig. 6 Interestingly, the chemosensor L is also reversible for the distinct recognition of sulde over cycles of the sequential addition of sulde, followed by H+ ions (Fig. 6c). Chemosensor L displayed a yellow color and the maximum absorption at 400 nm when reacted with sulde. Upon addition of HCl to the yellow-colored chemosensor L – sulde complex, the absorption band at 400 nm disappeared and, correspondingly, the color changed from yellow to colorless. When sulde was added again, the spectra and yellow color were recovered. The spectral absorptions of chemosensor L can be reversed by the addition of sulde and HCl in succession (Fig. S5, ESI†). Therefore, the chemosensor L could be reused, and the sensing behavior could be reversible at least 3 cycles for the distinct colorimetric recognition of sulde. 3.6 Sulde detection using paper strips Aer optimizing the experiment in aqueous solution, we established the paper-based assay for the determination of sulde. Fig. 7 shows the result of chemosensor L-coated paper This journal is © The Royal Society of Chemistry 2021 strips used for colorimetric recognition of sulde. By using laser cutting techniques, paper strips were fabricated and were immersed in the chemosensor L solution to be ready-to-use colorimetric paper strips to visualize sulde (Fig. 1). Consequently, the paper strips displayed an obvious color change to yellow when sulde was present inside a solution containing various anions (Fig. 7a). Paper strips were further analyzed by using ImageJ to obtain the mean intensities. The result indicated that the intensity of the paper strip containing sulde was signicantly higher than those of the paper strip containing other anions (Fig. 7b). Additionally, the color intensity of the paper strips increased as the sulde concentration increased from 0 to 100 mM. The detection limit of paper-based chemosensor L for naked-eye visualization of sulde was as low as 30 mM (Fig. 7c and d). Therefore, the paper strips could be effectively used for simple, selective, and rapid colorimetric detection of sulde for environmental monitoring of water samples in real time in remote areas with scarce analytical instrumentation. In addition, to further test the potential of the synthesized chemosensor L for the detection of sulde in real samples, chemosensor L was applied to quantitate sulde in water contaminated with sulde. Tap water samples were collected and spiked with sulde to mimic sulde-contaminated water. Sample analysis was performed by applying the same method used for linearity experiments, with the optimized conditions. The sulde-contaminated water samples were added to chemosensor L prepared in Bis–Tris buffer to perform the quantitative measurement. Each sample was analyzed with four replicates to evaluate the reliability and accuracy of the proposed method. The results are illustrated in Table 1, and it was found that sulde was recovered, from 94 to 99%, for tap water samples. These values indicated that the introduced colorimetric approach exhibited reliable and precise sulde recovery as compared to reported sensing strategies that could be potentially applicable for the direct determination of sulde in environmental samples.37–40 Anal. Methods, 2021, 13, 1332–1339 | 1337 View Article Online Analytical Methods Published on 09 February 2021. Downloaded by Istanbul Technical University on 5/27/2023 12:46:04 AM. Table 1 Paper Determination of sulfide concentration in water samples a Sample Spiked amount (mM) Detected amount (mM) Percentage recovery Tap water 1 Tap water 2 Tap water 3 200 500 800 188.0 9.2 478.3 27.6 791.7 73.7 94% 96% 99% a Mean standard deviation. 4 Conclusions In this study, we have successfully developed a novel paperbased chemosensor for rapid colorimetric detection of sulde with high selectivity based on the deprotonation mechanism. Chemosensor L selectively detected sulde without any interference from other anions and thiols, through a color change from colorless to yellow. The paper-based colorimetric chemosensor L has an impressively fast response time of 10 s compared with previous studies (Table S1, ESI†) and a detection limit of 25.8 mM and 30 mM in aqueous solution and paper strips, respectively. A portable paper strip is potentially applied for on-site recognition of sulde in hazardous environments. Furthermore, chemosensor L was found to enable reliable quantitative determination of sulde for potential use in monitoring of sulde in environmental samples such as water. Therefore, the method introduced in this study is highly promising for on-site and real-time colorimetric monitoring of sulde in environmental and biological samples. Author contributions Duc Anh Thai: methodology, formal analysis, investigation, resources, and writing – original dra. Nae Yoon Lee: conceptualization, methodology, resources, data curation, project administration, funding acquisition, investigation, writing – review & editing, and supervision. Conflicts of interest There are no conicts to declare. Acknowledgements This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2020R1A2B5B01001971). This research was also supported by Korea Basic Institute (National Research facilities and Equipment Center) grant funded by the Ministry of Education (2020R1A6C103A050) and by the Gachon University research fund of 2019 (GCU-2019-0817). Notes and references 1 J. W. Morse, F. J. Millero, J. C. Cornwell and D. Rickard, Earth-Sci. Rev., 1987, 24, 1–42. 1338 | Anal. Methods, 2021, 13, 1332–1339 2 L. Zhang, P. De Schryver, B. De Gusseme, W. De Muynck, N. Boon and W. Verstraete, Water Res., 2008, 42, 1–12. 3 L. Tang, M. Cai, Z. Huang, K. Zhong, S. Hou, Y. Bian and R. Nandhakumar, Sens. Actuators, B, 2013, 185, 188–194. 4 O. Kabil and R. Banerjee, J. Biol. Chem., 2010, 285, 21903– 21907. 5 K. Tanizawa, Journal of Biochemistry, 2011, 149, 357–359. 6 D. Boehning and S. H. Snyder, Annu. Rev. Neurosci., 2003, 26, 105–131. 7 G. Yang, L. Wu and R. Wang, FASEB J., 2006, 20, 553–555. 8 W. Yang, G. Yang, X. Jia, L. Wu and R. Wang, J. Physiol., 2005, 569, 519–531. 9 Y. J. Peng, J. Nanduri, G. Raghuraman, D. Souvannakitti, M. M. Gadalla, G. K. Kumar, S. H. Snyder and N. R. Prabhakar, Proc. Natl. Acad. Sci. U. S. A., 2010, 107, 10719–10724. 10 K. Eto, T. Asada, K. Arima, T. Makifuchi and H. Kimura, Biochem. Biophys. Res. Commun., 2002, 293, 1485–1488. 11 S. Fiorucci, E. Antonelli, A. Mencarelli, S. Orlandi, B. Renga, G. Rizzo, E. Distrutti, V. Shah and A. Morelli, Hepatology, 2005, 42, 539–548. 12 D. J. Elsey, R. C. Fowkes and G. F. Baxter, Cell Biochem. Funct., 2010, 28, 95–106. 13 J. Radford-Knoery and G. A. Cutter, Anal. Chem., 1993, 65, 976–982. 14 S. K. Pandey and K. H. Kim, Environ. Sci. Technol., 2009, 43, 3020–3029. 15 M. Okumura, N. Yano, K. Fujinaga, Y. Seike and S. Matsuo, Anal. Sci., 1999, 15, 427–431. 16 N. S. Lawrence, J. Davis and R. G. Compton, Talanta, 2000, 52, 771–784. 17 A. R. Lippert, E. J. New and C. J. Chang, J. Am. Chem. Soc., 2011, 133, 10078–10080. 18 V. S. Lin, A. R. Lippert and C. J. Chang, Proc. Natl. Acad. Sci. U. S. A., 2013, 110, 7131–7135. 19 Y. Qian, J. Karpus, O. Kabil, S. Y. Zhang, H. L. Zhu, R. Banerjee, J. Zhao and C. He, Nat. Commun., 2011, 2, 1–7. 20 X. Li, S. Zhang, J. Cao, N. Xie, T. Liu, B. Yang, Q. He and Y. Hu, Chem. Commun., 2013, 49, 8656–8658. 21 M. G. Choi, S. Cha, H. Lee, H. L. Jeon and S. K. Chang, Chem. Commun., 2009, 47, 7390–7392. 22 Z. Guo, G. Chen, G. Zeng, Z. Li, A. Chen, J. Wang and L. Jiang, Analyst, 2015, 140, 1772–1786. 23 F. Yu, X. Han and L. Chen, Chem. Commun., 2014, 50, 12234– 12249. 24 S. Y. Lee and C. Kim, RSC Adv., 2016, 6, 85091–85099. 25 A. K. Manna, J. Mondal, R. Chandra, K. Rout and G. K. Patra, Anal. Methods, 2018, 10, 2317–2326. 26 R. Kaushik, A. Ghosh, A. Singh and D. A. Jose, Anal. Chim. Acta, 2018, 1040, 177–186. 27 K. Y. Ryu, J. J. Lee, J. A. Kim, D. Y. Park and C. Kim, RSC Adv., 2016, 6, 16586–16597. 28 W. Chen, X. Fang, H. Li, H. Cao and J. Kong, Sci. Rep., 2016, 6, 1–7. 29 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, This journal is © The Royal Society of Chemistry 2021 View Article Online Paper 30 31 Published on 09 February 2021. Downloaded by Istanbul Technical University on 5/27/2023 12:46:04 AM. 32 33 34 35 B. Mennucci, G. A. Petersson and H. Nakatsuji, Gaussian 09, Gaussian Inc. Wallingford, CT, 2009. A. D. Becke, J. Chem. Phys., 1993, 98, 1372–1377. J. W. Y. Liew, K. S. Loh, A. Ahmad, K. L. Lim and W. R. Wan Daud, Energies, 2018, 11, 1910. D. A. Jose, P. Kar, D. Koley, B. Ganguly, W. Thiel, H. N. Ghosh and A. Das, Inorg. Chem., 2007, 46, 5576–5584. Z. Li, S. Wang, L. Xiao, X. Li, X. Shao, X. Jing and L. Ren, Inorg. Chim. Acta, 2018, 476, 7–11. US Environmental Protection Agency, Fed. Regist., 1986, 51, 34014–34025. Y. C. Cai, C. Li and Q. H. Song, ACS Sens., 2017, 2, 834–841. This journal is © The Royal Society of Chemistry 2021 Analytical Methods 36 B. Tan, S. Jin, J. Sun, Z. Gu, X. Sun, Y. Zhu and Y. Z. Zhu, Sci. Rep., 2017, 7, 1–12. 37 Y. Wang, H. Sun, L. Hou, Z. Shang, Z. Dong and W. Jin, Anal. Methods, 2013, 5, 5493–5500. 38 A. Hatamie, B. Zargar and A. Jalali, Talanta, 2014, 121, 234– 238. 39 U. R. Kondekar, L. S. Walekar, A. H. Gore, P. V. Anbhule, S. H. Han, S. R. Patil and G. B. Kolekar, Anal. Methods, 2015, 7, 2547–2553. 40 S. Yan, R. Song and Y. Tang, Anal. Methods, 2016, 8, 3768– 3773. Anal. Methods, 2021, 13, 1332–1339 | 1339
