English

• Hypochlorite ion (ClO⁻) is a key reactive oxygen species (ROS), which is produced by immune cells to fight off foreign bacteria and viruses [1,2]. However, excessive amounts of ClO⁻ can damage tissues, and cause a range of diseases such as cancer, arthritis, cardiovascular disease, and neurological disease [3–6]. In addition, hypochlorite is the main ingredient in bleach and disinfectants, which is also very important for our daily life. Therefore, selective and sensitive detection of hypochlorite is extremely important.

  At present, the methods for detecting ClO⁻ include colorimetric analysis, electrochemical analysis, chromatographic analysis, nuclear magnetic resonance, and fluorescence probe techniques [7–9]. Among them, fluorescent probes have attracted particular attention for their excellent sensitivity and selectivity, real-time detection, high spectral resolution, and low cost [10,11]. Thus, various fluorescent probes with different recognition sites, such as unsaturated C = C and C = N bonds [12,13], thioether [14,15], amino group [16] and hydrazide [17], have been reported for sensing and detection of ClO⁻. However, most of these probes are somewhat hampered by their small Stokes shifts, long response times, and poor water solubility. Therefore, it is essential for development of novel fluorescent probes with simple synthesis and excellent performance for ClO⁻ ultrafast response.

  Luminescent lanthanide complexes, particularly of Eu(Ⅲ) and Tb(Ⅲ), have been widely used in sensing field for their inherent advantages such as narrow f-f emission band, long fluorescence lifetime, and large Stokes shift [18,19]. Owing to their long-lifetime emissions, lanthanide complexes are suitable for time-gated luminescence analysis, which can eliminate short-lived background autofluorescence and improve sensitivity and accuracy of probes. Some lanthanide-based probes for sensing of HOCl/OCl⁻ were also reported [20]. However, most of lanthanide complexes were selected typical aggregation-caused quenching (ACQ) type ligands, which may quench the probes emission in their aggregated state [21]. Recently, the aggregation-induced emission luminogens (AIEgens) demonstrated by Tang et al. have been attracted much attention for their particular emission characteristics, i.e., they emit weak luminescence in the solvated molecular state due to the free rotation of the aryl groups, and show strong fluorescence in the aggregated state for restriction the free rotation [22]. Thus, some groups tentatively incorporated the AIEgens into the Ln(Ⅲ) complexes [23], which can sensitize the Ln(Ⅲ) center with enhanced luminescence at the aggregated state. The AIE-active Ln(Ⅲ) complex probes may have potential applications in insoluble water solution for high emission.

  In the above context, herein we design and synthesize a novel phenylphenothiazine anchored Tb(Ⅲ)-cyclen complex PTP-Cy-Tb for ClO⁻ detection (Scheme 1). The phenylphenothiazine antenna was rationally selected for its AIE characteristics [24], and the thioether group in phenothiazine ring is also a good reaction site of ClO⁻. While the octadentate macrocyclic polyaminocarboxylate ligand exhibits high binding affinity toward Tb(Ⅲ), which make the complex high stability in aqueous solution [25,26]. We found that the AIE antenna can sensitize the Tb³⁺ ion fluorescence, and make the PTP-Cy-Tb complex a good AIE characteristic. Importantly, PTP-Cy-Tb complex shows fluorescence turn-on respond toward ClO⁻ in aqueous solution for oxidation the thioether group of PTP-Cy-Tb to sulfoxide of OPTP-Cy-Tb, which makes the energy transfer from ligand to Tb(Ⅲ) center more effectively. The recognition mechanism and the application of probe were also well discussed.

  Scheme 1

  

  Scheme 1.  Proposed detection mechanism of the PTP-Cy-Tb probe to ClO⁻.

  DownLoad: Full-Size Img PowerPoint

  The detailed synthesis route of ligand PTP-Cy and its Tb(Ⅲ) complex PTP-Cy-Tb (Scheme S1 in Supporting information). Briefly, a phenylphenthiazide anchored Tb(Ⅲ)-cyclen ligand PTP-Cy was first prepared from 4-(10H-phenothiazin-10-yl)aniline over four steps. TbCl₃·6H₂O was coordinated with the AIE fluorophore PTP-Cy in CH₃OH solution to obtain the target compound PTP-Cy-Tb as a white solid. The structure of ligand PTP-Cy was fully characterized by ¹H nuclear magnetic resonance (NMR), ¹³C NMR and time of flight mass spectrometer (TOF-MS) spectrum (Figs. S1–S7 in Supporting information), while the structure of PTP-Cy-Tb can be confirmed by TOF-MS spectrum (Fig. S8 in Supporting information) and Fourier transform-infrared (FT-IR) spectra (Fig. S9 in Supporting information). In the FT-IR spectra, the signal peaks of C=O and C—N in PTP-Cy locate at 1679 and 1104 cm⁻¹, respectively. After coordinated with Tb³⁺, these two peaks show a lower wavenumber shift to 1654 and 1080 cm⁻¹, respectively, indicating that the four N and O atoms are involved in the coordination with Tb³⁺ in PTP-Cy-Tb complex.

  The absorption spectra of PTP-Cy and PTP-Cy-Tb in 4-(2-hydroxyethyl)−1-piperazineethanesulfonic acid (HEPES) buffer solution (10 mmol/L, pH 7.4). As shown in Fig. 1a, PTP-Cy shows an absorption peak at 306 nm, while this ligand-based absorption red shifts to 312 nm in PTP-Cy-Tb. This may be attributed to the increased degree of electron delocalizetion after coordination of the ligand PTP-Cy with Tb³⁺, leading to a greater range of π-electron activity in the complex. Therefore, the energy level transition energy of PTP-Cy-Tb molecular orbital decreases, resulting in a red-shift of the absorption peak. Then, we tested emission spectra of PTP-Cy and PTP-Cy-Tb in HEPES buffer solution (10 mmol/L, pH 7.4) (Fig. 1b). With excitation at 320 nm, PTP-Cy exhibits two fluorescence emission peaks at 374 and 448 nm, respectively. The emission at 374 nm can be attributed to the localized excited (LE) state in the molecules, while the long-wavelength emission at 448 nm may originate from the intramolecular charge transfer (ICT) from phenothiazine to benzene moiety [27]. In the emission spectra of PTP-Cy-Tb, the ligand-based emission can also be observed, but its intensity largely decreases. In addition, the Tb³⁺ based emission peaks at 491 nm (⁵D₄ → ⁷F₆), 546 nm (⁵D₄ → ⁷F₅), 586 nm (⁵D₄ → ⁷F₄) and 621 nm (⁵D₄ → ⁷F₃) were observed. In order to distinguish between ligand fluorophore and Tb(Ⅲ) luminescence, we tested the time-gated emission spectra of PTP-Cy-Tb with a delay time of 0.1 ms, which exhibited clear Tb(Ⅲ) emission (Fig. S10 in Supporting information). The above results confirm that Tb³⁺ emission was sensitized through PTP-Cy.

  Figure 1

  

  Figure 1.  Normalized absorption (a) and emission (b) spectra of PTP-Cy and PTP-Cy-Tb (c = 20 µmol/L, λ_ex = 320 nm). (c) The relative emission intensity (I/I₀) of PTP-Cy-Tb at 546 nm versus the fraction of the Toluene/DMSO mixtures (λ_ex = 320 nm). Inset: Fluorescence in DMSO and in toluene. (d) Fluorescence (FL) intensity of PTP-Cy-Tb at 546 nm (20 µmol/L) with adding different concentrations of ClO⁻ versus the reaction time (λ_ex = 320 nm). (e) Fluorescence intensity of PTP-Cy-Tb at 546 nm (20 µmol/L) with increasing concentration of ClO⁻ (0–32 µmol/L). (f) Linear relationship between fluorescence intensity and ClO⁻ concentration.

  DownLoad: Full-Size Img PowerPoint

  The fluorescence lifetime of PTP-Cy-Tb was measured in H₂O and D₂O. As shown in Table S1 and Fig. S11 (Supporting information), the fluorescence lifetime of PTP-Cy-Tb in water was 0.51 ms, while value in D₂O was 0.59 ms. According to the formula q = 5.0 × (K_H − K_D − 0.06) [28], we derived the number of ligand water molecules of PTP-Cy-Tb to be one.

  Owing to the butterfly shape of the core ring, phenothiazine derivatives often show AIE features [29,30], which also observed in PTP-Cy ligand (Fig. S12 in Supporting information). Thus, we investigated the AIE properties of PTP-Cy-Tb complex in toluene/DMSO mixture, because it shows good solubility in DMSO, but is insoluble in toluene. As shown in Fig. 1c and Fig. S13 (Supporting information), PTP-Cy-Tb shows weak emission in DMSO. Upon increasing the fraction of toluene, its emission gradually increased and attained the maximum intensity in 100% toluene solution, due to the formation of molecular aggregates. Thus, PTP-Cy-Tb complex exhibits typical AIE characteristic.

  The sensing ability of PTP-Cy-Tb toward ClO^‒ was then investigated by emission spectra in HEPES buffer solution (10 mmol/L, pH 7.4). Firstly, the respond time of probe was investigated by the time-dependent fluorescence experiment of PTP-Cy-Tb (20 µmol/L) with different concentrations of ClO⁻ (5, 10 and 20 µmol/L). As shown in Fig. 1d, the fluorescence intensity of PTP-Cy-Tb for all three concentrations of ClO^‒ increased quickly and saturated within 10 s, and then remained almost constant with time. Therefore, 10 s was chosen as the optimal reaction time for PTP-Cy-Tb and ClO⁻. Subsequently, the fluorescence intensity of PTP-Cy-Tb versus the concentration of ClO^‒ was recorded by normal emission titration and also time-gated emission spectra. As shown in Fig. 1e and Figs. S14 and S15 (Supporting information), upon increasing the concentration of ClO⁻ from 0 to 32 µmol/L, both the ligand-base emission at 375 nm and Tb³⁺-central emission at 491, 546, 586 and 621 nm gradually increased and saturated after the addition of 22.4 µmol/L ClO^‒, with the maximum peak at 546 nm a 33-fold enhancement. The fluorescence response can be easily observed by the naked eyes, with the fluorescent color change from dark emission to strong green emission under a handle ultraviolet (UV) light irradiation. In addition, there was a good linear relationship between the fluorescence intensity at 546 nm and the ClO⁻ concentration in the range of 0–9.6 µmol/L (Fig. 1f), and the limit of detection (LOD) was determined to be 8.85 nmol/L according to the 3σ/K rule [31].

  The absorption of PTP-Cy-Tb before and after addition of ClO⁻ was also carried out (Fig. S16 in Supporting information). After addition of ClO⁻, two new absorption peaks at 302 and 337 nm appeared. In addition, the fluorescence lifetime of PTP-Cy-Tb after addition of ClO⁻ were also investigated (Table S1 and Fig. S17 in Supporting information). The calculated number of coordination water was also one, indicating that the Tb³⁺ coordination central is basically unchanged before and after the addition of ClO⁻. Thus, PTP-Cy-Tb can be used for absorption and emission detection of ClO^‒.

  The fluorescent sensing selectivity of PTP-Cy-Tb (20 µmol/L) was then evaluated by addition same amount (100 µmol/L) of various analytes. As shown in Fig. 2a and Fig. S18 (Supporting information), there is a clear fluorescence enhancement at 546 nm in the presence of ClO⁻, while the addition of other analytes leads to barely fluorescence change. In addition, competition experiments were also performed by first adding 100 µmol/L of other analytes, followed by the addition of same amount of ClO⁻ to PTP-Cy-Tb solution (20 µmol/L). As shown in Fig. 2b, PTP-Cy-Tb still showed a good fluorescence enhancement of ClO⁻ under the same test conditions. These experimental results indicate that PTP-Cy-Tb has good selectivity and anti-interference effect on ClO⁻.

  Figure 2

  

  Figure 2.  (a) FL histograms after addition of different analytes (100 µmol/L): 1-blank, 2-ClO⁻, 3-F⁻, 4-CN⁻, 5-NO₂⁻, 6-NO₃⁻, 7-CH₃COO⁻, 8-CO₃²⁻, 9-H₂O₂, 10-S²⁻, 11-SO₃²⁻, 12-SO₄²⁻. λ_ex = 320 nm. (b) The FL intensity of PTP-Cy-Tb (c = 20 µmol/L) at 546 nm with addition of 100 µmol/L different analytes (red bar) and then addition of 100 µmol/L ClO⁻ (blue bar): 1-blank, 2-F⁻, 3-CN⁻, 4-NO₂⁻, 5-NO₃⁻, 6-CH₃COO⁻, 7-CO₃²⁻, 8-H₂O₂, 9-S²⁻, 10-SO₃²⁻, 11-SO₄²⁻. (c) FL intensity before and after addition of ClO⁻ (100 µmol/L) at different pH values. λ_ex = 320 nm. (d) The LUMO and HOMO orbital diagrams of PTP-Cy and OPTP-Cy. (e) Schematic representation of the energy transfer process of PTP-Cy-Tb and OPTP-Cy-Tb. ISC, intersystem crossing; ET, energy transfer; S, singlet; T, triplet.

  DownLoad: Full-Size Img PowerPoint

  The appropriate pH range is crucial for the application of fluorescent probes. Thus, we also investigated the effects of pH on recognition behaviors of PTP-Cy-Tb toward ClO^‒. As shown in Fig. 2c, PTP-Cy-Tb still exhibits a good sensing ability toward ClO⁻ in wide pH range from 5.0 to 9.0, which can be used in environmental and physiological condition.

  The highly sensitive and selective sensing of PTP-Cy-Tb toward ClO⁻ may be attributed the strong oxidation property of ClO⁻, which can oxidize PTP-Cy-Tb to OPTP-Cy-Tb. This transformation can be verified by mass spectra and FT-IR. As shown in Fig. S19 (Supporting information), we found only the TOF-MS (m/z) signal of OPTP-Cy-Tb at 848.3553 after reaction of PTP-Cy-Tb with ClO^‒. In addition, a strong FT-IR peak at 979 cm⁻¹ appears after addition of ClO⁻ (Fig. S20 in Supporting information), which further confirmed the formation of the S=O bond.

  Subsequently, we calculated the energy transfer efficiency of the pre-oxidized ligand PTP-Cy and the post-oxidized ligand OPTP-Cy to the Tb³⁺ ion central. As we all known, the antenna effect of PTP-Cy-Tb/OPTP-Cy-Tb complex involves two steps: first the singlet excited state of ligand PTP-Cy/OPTP-Cy undergoes intersystem crossing to the longer-lived triplet excited state (S₁ → T₁, ΔE₁) after absorption photons; in the second step, the relatively long lifetime T₁ is then transferred to the Tb³⁺ excited states (T₁ → Tb ⁵D₄ excited state, 20,500 cm⁻¹) [32]. Both the energy gap of ΔE₁ and ΔE₂ will affect the antenna effect procedure, in which the ΔE₁ should be greater than 5000 cm⁻¹ based on the Reinhold's empirical rule, while ΔE₂ must be above 3500 cm⁻¹ to inhibit reversible energy transfer [33,34]. We used the density functional theory (DFT) calculation to get the S₁ and T₁ energy level of PTP-Cy and OPTP-Cy. As shown in Fig. 2d, presents the molecular orbital diagrams of lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of PTP-Cy and OPTP-Cy, and their energy levels (Fig. 2e and Table S2 in Supporting information). The ΔE₁ values of PTP-Cy and OPTP-Cy were found to be 3996 and 5145 cm⁻¹, respectively, indicating that the intersystem crossing from S₁ to T₁ of OPTP-Cy is more effective for antenna effect procedure than that of PTP-Cy. Meanwhile, the ΔE₂ values of PTP-Cy-Tb and OPTP-Cy-Tb were 3724 and 5732 cm⁻¹, respectively. Thus, the T₁ state of both ligands can effectively sensitize the excited state of Tb³⁺. Combining these two constraints, we can rationalize that the OPTP-Cy ligand gives more efficient antenna effect to Tb³⁺ center than PTP-Cy, which make PTP-Cy-Tb a fluorescence turn-on response after reaction with ClO^‒.

  We also compared PTP-Cy-Tb with some previous reported probes of ClO^‒ (Table S3 in Supporting information). It clearly demonstrates that PTP-Cy-Tb shows some advantages with high selectivity, rapid response, large Stokes shift, and better biocompatibility.

  The practical application of PTP-Cy-Tb for detection of environmental ClO^‒ was evaluated. We chose three real water samples (Tap water, Qianhu Lake and Ganjiang River) for the detection of ClO^‒ content. Different concentrations of ClO⁻ (0, 2, 4 and 8 µmol/L) were added to water samples containing 20 µmol/L PTP-Cy-Tb. As shown in Table S4 (Supporting information), ClO⁻ was not detected in the free real water, but can be observed with almost the same values as the addition ClO⁻ concentrations. The recoveries were in the range of 96.88%–104.50%, with the relative standard deviations (RSD) lower than 4.98%. These experimental data show that the PTP-Cy-Tb probe can be used for the detection of actual water samples in the environment.

  Meanwhile, we built a smartphone-assisted rapid detection system of ClO⁻ for its portable detection, simple and low cost. As shown in Figs. 3a and b, under UV light (365 nm), the solution gradually changes from colorless to green with increasing the concentration of ClO^‒ (0–10 µmol/L). We obtain the corresponding color information (RGB values) in the fluorescent image through the WeChat color recognition device on the smartphone. The G/G₀ (G₀ and G are the brightness of G channel before and after the addition of ClO⁻) can be used as a parameter for ClO⁻ quantification. As shown in Fig. S21 (Supporting information), there is a linear relationship between G/G₀ and ClO⁻ concentration (0–10 µmol/L), and the calculated LOD is 51.7 nmol/L. This indicates that the PTP-Cy-Tb can be used for real-time and visualized detection of ClO⁻.

  Figure 3

  

  Figure 3.  (a) Fluorescence images with addition of ClO⁻ (0–10 µmol/L). (b) RGB values analysis of fluorescence images. (c) Fluorescent photographs of different analytes added dropwise to the silica gel plates. (d) Color changes of silica gel plates under visible light (left) and 365 nm UV light (right).

  DownLoad: Full-Size Img PowerPoint

  To investigate the on-site detection of ClO⁻, we further developed silica gel plates impregnated with PTP-Cy-Tb as test strips. As shown in Fig. 3c, a drop of ClO⁻ solution (20 µmol/L) was placed on the pretreated silica gel plate, which emitted green fluorescence under UV light (365 nm). In contrast, dropwise addition of other analytes (20 µmol/L) did not fluoresce. Subsequently, we wrote with ClO⁻ on a pretreated silica gel plate, which showed green fluorescent fonts under UV light (365 nm) (Fig. 3d), whereas under visible light there was no color change. Therefore, PTP-Cy-Tb pretreated silica gel plates have the potential to safely and efficiently detect ClO⁻.

  In summary, we design and synthesize a new phenylphenthiazide anchored Tb(Ⅲ)-cyclen complex PTP-Cy-Tb for ClO⁻ detection. We found that the AIE-based phenylphenthiazide fluorephore can sensitize Tb(Ⅲ) center, which makes the PTP-Cy-Tb complex also a good AIE characteristics. PTP-Cy-Tb shows a good fluorescence turn-on response toward ClO⁻ over other test species, and the detection limit was found to be 8.85 nmol/L. The TOF-MS and FT-IR experiment confirm that the addition of ClO⁻ can oxidize the thioether group of PTP-Cy-Tb to get the sulfoxide OPTP-Cy-Tb complex. The DFT calculations analysis reveal that OPTP-Cy ligand gives more efficient antenna effect to Tb(Ⅲ) center than PTP-Cy, which make PTP-Cy-Tb a fluorescence turn-on response after reaction with ClO⁻. PTP-Cy-Tb can detect of ClO⁻ in real water samples, and the on-site and real-time detection methods were also obtained via the smartphone-assisted visualization method and test strips derived from PTP-Cy-Tb. This design strategy may be applied to other rare earth fluorescence probes for detecting ClO⁻ and other molecules with high selectivity and sensitivity.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  Acknowledgments

  This work was supported by the National Nature Science Foundation of China (Nos. 22061028 and 22361028) and Jiangxi Provincial Natural Science Foundation (No. 20224ACB203012).

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2024.109769.

  
  
• 1. [1]

     X.Q. Chen, F. Wang, J.Y. Hyun, et al., Chem. Soc. Rev. 45 (2016) 2976–3016. doi: 10.1039/C6CS00192K

  2. [2]

     Y. Koide, Y. Urano, K. Hanaoka, T. Terai, T. Nagano, J. Am. Chem. Soc. 133 (2011) 5680–5682. doi: 10.1021/ja111470n

  3. [3]

     C.Y. Chu, X.M. Lyu, Z.X. Wang, et al., Chem. Eng. J. 402 (2020) 126125. doi: 10.1016/j.cej.2020.126125

  4. [4]

     L.J. Gui, J. Yan, J.Y. Zhao, et al., Biosens. Bioelectron. 240 (2023) 115660. doi: 10.1016/j.bios.2023.115660

  5. [5]

     Q.L. Liu, M. Xiao, H.C. Ding, et al., Dyes. Pigm. 215 (2023) 111194. doi: 10.1016/j.dyepig.2023.111194

  6. [6]

     W. Ahmad, B. Ijaz, K. Shabbiri, et al., J. Biomed. Sci. 24 (2017) 76. doi: 10.1186/s12929-017-0379-z

  7. [7]

     K.J. Wang, D.Z. Xi, C.T. Liu, et al., Chin. Chem. Lett. 31 (2020) 2955–2959. doi: 10.1016/j.cclet.2020.03.064

  8. [8]

     X.J. Hea, H. Chen, C.C. Xu, et al., J. Hazard. Mater. 388 (2020) 122029. doi: 10.1016/j.jhazmat.2020.122029

  9. [9]

     Y. Zhao, X.Q. Yu, X. Liu, et al., Anal. Chem. 95 (2023) 7170–7177. doi: 10.1021/acs.analchem.2c05532

  10. [10]

      J.T. Hou, N. Kwon, S. Wang, et al., Coord. Chem. Rev. 450 (2022) 214232. doi: 10.1016/j.ccr.2021.214232

  11. [11]

      Z.Y. Hu, X.Y. Chen, Y.S. Yang, et al., Coord. Chem. Rev. 501 (2024) 215562. doi: 10.1016/j.ccr.2023.215562

  12. [12]

      J.S. Lan, L. Liu, R.F. Zeng, et al., Chem. Commun. 56 (2020) 1219–1222. doi: 10.1039/c9cc06477j

  13. [13]

      Y. Zhou, H. Xu, Q.X. Li, et al., Org. Biomol. Chem. 21 (2023) 1270–1274. doi: 10.1039/d2ob02138b

  14. [14]

      A.S. Zheng, H. Liu, C.H. Peng, et al., Talanta 226 (2021) 122152. doi: 10.1016/j.talanta.2021.122152

  15. [15]

      H.J. Wang, W.W. Xing, Z.H. Yu, Chin. Chem. Lett. 35 (2024) 109183. doi: 10.1016/j.cclet.2023.109183

  16. [16]

      B.C. Zhu, L. Wu, M. Zhang, et al., Biosens. Bioelectron. 107 (2018) 218–223. doi: 10.1016/j.bios.2018.02.023

  17. [17]

      G.J. Mao, Y.Y. Wang, W.P. Dong, et al., Spectrochim. Acta A: Mol. Biomol. Spectrosc. 249 (2021) 119326. doi: 10.1016/j.saa.2020.119326

  18. [18]

      M.C. Heffern, L.M. Matosziuk, T.J. Meade, Chem. Rev. 114 (2014) 4496–4539. doi: 10.1021/cr400477t

  19. [19]

      I.F. Costa, L. Blois, T.B. Paolini, et al., Coord. Chem. Rev. 502 (2024) 215590. doi: 10.1016/j.ccr.2023.215590

  20. [20]

      L. Tian, H. Ma, B. Song, et al., Talanta 212 (2020) 120760. doi: 10.1016/j.talanta.2020.120760

  21. [21]

      J.C. Han, Z.Y. Zhang, D.D. Liu, X. Wang, Chem. Commun. 59 (2023) 90–93. doi: 10.1039/d2cc03903f

  22. [22]

      J. Li, J.X. Wang, H.X. Li, et al., Chem. Soc. Rev. 49 (2020) 1144–1172. doi: 10.1039/c9cs00495e

  23. [23]

      Z.C. Zhu, B. Song, J.L. Yuan, C.L. Yang, Adv. Sci. 3 (2016) 1600146. doi: 10.1002/advs.201600146

  24. [24]

      J.Y. Zhang, M.N. Zhu, Y.X. Lu, et al., Chem. Eur. J. 28 (2022) e202200458. doi: 10.1002/chem.202200458

  25. [25]

      S. Aoki, H. Kawatani, T. Goto, E. Kimura, M. Shiro, J. Am. Chem. Soc. 123 (2001) 1123–1132. doi: 10.1021/ja0033786

  26. [26]

      H.R. Lei, J. Liu, J.L. Yan, S.H. Lu, Y. Fang, ACS Appl. Mater. Interfaces 6 (2014) 13642–13647. doi: 10.1021/am5031424

  27. [27]

      H. Tanaka, K. Shizu, H. Nakanotani, C. Adachi, J. Phys. Chem. C 118 (2014) 15985–15994. doi: 10.1021/jp501017f

  28. [28]

      J. Liu, M. Morikawa, N. Kimizuka, J. Am. Chem. Soc. 133 (2011) 17370–17374. doi: 10.1021/ja2057924

  29. [29]

      J. Yang, J.W. Qin, P.Y. Geng, et al., Angew. Chem. 130 (2018) 14370–14374. doi: 10.1002/ange.201809463

  30. [30]

      X.G. Song, S.G. Shen, M.Y. Lu, Y. Wang, Y. Zhang, Chin. Chem. Lett. 35 (2024) 109118. doi: 10.1016/j.cclet.2023.109118

  31. [31]

      J.M. Qin, X. Li, Q.Y. Cao, et al., Chin. Chem. Lett. 35 (2024) 108925. doi: 10.1016/j.cclet.2023.108925

  32. [32]

      L. Yu, L.X. Feng, L. Xiong, et al., J. Hazard. Mater. 434 (2022) 128914. doi: 10.1016/j.jhazmat.2022.128914

  33. [33]

      X.Z. Xie, Y.R. Zhang, Y.J. Wu, X.B. Yin, Y. Xia, J. Phys. Chem. C 127 (2023) 1220–1228. doi: 10.1021/acs.jpcc.2c07084

  34. [34]

      H.Q. Yin, X.Y. Wang, X.B. Yin, J. Am. Chem. Soc. 141 (2019) 15166–15173. doi: 10.1021/jacs.9b06755

• 

  Scheme 1  Proposed detection mechanism of the PTP-Cy-Tb probe to ClO⁻.

  下载: 全尺寸图片 幻灯片
  

  Figure 1  Normalized absorption (a) and emission (b) spectra of PTP-Cy and PTP-Cy-Tb (c = 20 µmol/L, λ_ex = 320 nm). (c) The relative emission intensity (I/I₀) of PTP-Cy-Tb at 546 nm versus the fraction of the Toluene/DMSO mixtures (λ_ex = 320 nm). Inset: Fluorescence in DMSO and in toluene. (d) Fluorescence (FL) intensity of PTP-Cy-Tb at 546 nm (20 µmol/L) with adding different concentrations of ClO⁻ versus the reaction time (λ_ex = 320 nm). (e) Fluorescence intensity of PTP-Cy-Tb at 546 nm (20 µmol/L) with increasing concentration of ClO⁻ (0–32 µmol/L). (f) Linear relationship between fluorescence intensity and ClO⁻ concentration.

  下载: 全尺寸图片 幻灯片
  

  Figure 2  (a) FL histograms after addition of different analytes (100 µmol/L): 1-blank, 2-ClO⁻, 3-F⁻, 4-CN⁻, 5-NO₂⁻, 6-NO₃⁻, 7-CH₃COO⁻, 8-CO₃²⁻, 9-H₂O₂, 10-S²⁻, 11-SO₃²⁻, 12-SO₄²⁻. λ_ex = 320 nm. (b) The FL intensity of PTP-Cy-Tb (c = 20 µmol/L) at 546 nm with addition of 100 µmol/L different analytes (red bar) and then addition of 100 µmol/L ClO⁻ (blue bar): 1-blank, 2-F⁻, 3-CN⁻, 4-NO₂⁻, 5-NO₃⁻, 6-CH₃COO⁻, 7-CO₃²⁻, 8-H₂O₂, 9-S²⁻, 10-SO₃²⁻, 11-SO₄²⁻. (c) FL intensity before and after addition of ClO⁻ (100 µmol/L) at different pH values. λ_ex = 320 nm. (d) The LUMO and HOMO orbital diagrams of PTP-Cy and OPTP-Cy. (e) Schematic representation of the energy transfer process of PTP-Cy-Tb and OPTP-Cy-Tb. ISC, intersystem crossing; ET, energy transfer; S, singlet; T, triplet.

  下载: 全尺寸图片 幻灯片
  

  Figure 3  (a) Fluorescence images with addition of ClO⁻ (0–10 µmol/L). (b) RGB values analysis of fluorescence images. (c) Fluorescent photographs of different analytes added dropwise to the silica gel plates. (d) Color changes of silica gel plates under visible light (left) and 365 nm UV light (right).

  下载: 全尺寸图片 幻灯片
•