A tetraphenylethene-based system for the detection of metal ions in water

Abstract

A tetraphenylethene-based system (100) for the detection of metal ions in water, comprising: i) a first reaction chamber (102) configured to synthesize TPE-CHO (4-(1,2,2-triphenylvinyl)benzaldehyde), the first reaction chamber (102) comprising: a) a mixing module (102a) configured to mix a specific amount of 1-bromo-1,2,2-triphenylethylene and 4-formylphenylboronic acid; b) a solvent dispensing unit (102b) configured to add tetrahydrofuran and potassium carbonate solution to the mixing module (102a); c) a catalyst addition unit (102c) configured to add Tetrakis(triphenylphosphine)palladium(0) to the mixing module (102a); ii) a second reaction chamber (104) configured for the synthesis of TPE-PVA ((E)-N-methyl-2-(4-(1,2,2-triphenylvinyl)benzylidene)hydrazinecarbothioamides), wherein the second reaction chamber (104) comprises: a) a reagent mixing unit (104a) configured to dissolve 4-methyl-3-thiosemicarbazide in ethanol; b) a mixing unit (104b) configured to add 4-methyl-3-thiosemicarbazide and acetic acid to the reagent mixing unit (104a); iii) a reflux unit (106) connected to a temperature control module (108), wherein the reflux unit (106) is configured to heat the prepared mixtures under reflux at a specific temperature for a specific period of time, the temperature control module (108) maintaining the specified temperature; iv) a nitrogen supply unit (110) connected to the first reaction chamber (102) and configured to maintain an inert atmosphere, with the mixture being stirred under a nitrogen atmosphere; (v) a purification unit (112) configured to perform column chromatography to obtain the synthesized compound separately from the first reaction chamber (102) and the second reaction chamber (104); and vi) a detection arrangement (114) configured to use the synthesized TPE-PVA for the detection of metal ions in an aqueous medium.

Description

FIELD OF THE INVENTION

[0001] The present disclosure relates to a tetraphenylethylene-based system for detecting metal ions in water. More specifically, the present invention relates to a system for synthesizing tetraphenylethylene. Hydrazinecarbothioamide (TPE-PVA) as a fluorescent chemosensor, wherein tetraphenylethylene hydrazinecarbothioamide (TPE-PVA), known as probe 1, is synthesized. The synthesized compound is then characterized with respect to its photophysical phenomena and mechanochromic properties. BACKGROUND OF THE INVENTION

[0002] Heavy metals and transition ions, particularly mercury (Hg2+) and silver (Ag+) ions, pose significant environmental and health risks due to their toxicity and widespread distribution in ecological systems. Mercury is not biodegradable and enters the environment through various industrial processes, including oil refining, mining, and the combustion of fossil fuels. The World Health Organization (WHO) stipulates that Hg2 + -content in drinking water must not exceed 6 parts per billion. Likewise, silver ions, which are frequently released during industrial processes, can cause significant biological instability by binding to thiol, amino, and carboxyl groups in enzymatic reactions.

[0003] Conventional detection methods for these metal ions, such as inductively coupled plasma mass spectrometry, atomic absorption spectrometry, and high-performance liquid chromatography, have limitations, including high instrumentation costs, complex procedures, and the need for skilled monitoring. While existing fluorescent probes offer advantages such as real-time detection and ease of use, they have disadvantages such as low sensitivity and high detection limits.

[0004] Furthermore, current detection systems typically focus on the detection of Hg2+ or Ag+ ions individually, as they are unable to detect both ions simultaneously with a single probe. While tetraphenylethylene (TPE)-based materials are promising due to their aggregation-induced emission (AIE) properties, the development of dual-sensor probes with methylenehydrazine carbothioamide receptors for enhanced metal ion detection remains largely unexplored.

[0005] Therefore, there is an urgent need to develop an efficient system for synthesizing a new dual-sensor probe that can detect both Hg 2+ - as well as Ag + -ions simultaneously with high sensitivity and selectivity, while being suitable for practical environmental monitoring applications. SUMMARY OF THE INVENTION

[0006] The present disclosure relates to a tetraphenylethene-based system for detecting metal ions in water. This invention relates to the synthesis of tetraphenylethene hydrazinecarbothioamide (TPE-PVA), designated Probe 1, which is extensively characterized using various techniques. The compound exhibits remarkable photophysical properties, including aggregation-induced emission (AIE) and mechanochromic properties. When mechanical force is applied to the solid form of Probe 1, its emission color shifts from turquoise blue to lemon yellow upon milling, then from lemon yellow to parrot green after annealing at 160 °C, and then to arctic blue after exposure to DCM vapor. The synthesized probe displays exceptional selectivity and sensitivity towards mercury(II) (Hg2 + ) and silver(I) (Ag +) ions and significantly reduces the emission in the presence of these ions compared to other ions. A detailed photophysical analysis revealed limits of detection (LOD) of only 0.18344 and 0.2384 µg mL, respectively. -1 for Hg 2+ or Ag + with a quantum yield (Φ) of 2.26. In addition, probe 1 was developed as a paper strip-based sensor and kit for Hg 2+ and Ag + Ions were tested for possible practical applications. The binding interactions of probe 1 with Hg 2+ and Ag + were additionally validated by 1 H-NMR titration. These findings are promising for the development of effective on-site fluorescent probes for Hg 2+ and Ag + - Recognition in the future.

[0007] The disclosure relates to providing a tetraphenylethylene-based system for detecting metal ions in water. The system comprises: a first reaction chamber configured for synthesizing TPE-CHO (4-(1,2,2-triphenylvinyl)benzaldehyde), wherein the first reaction chamber comprises: a mixing module configured for mixing a predetermined amount of 1-bromo-1,2,2-triphenylethylene and 4-formylphenylboronic acid; a solvent delivery unit configured for adding tetrahydrofuran and potassium carbonate solution to the mixing module; and a catalyst addition unit configured for adding tetrakis(triphenylphosphine)palladium(0) to the mixing module.The system further comprises: a second reaction chamber configured to synthesize TPE-PVA ((E)-N-methyl-2-(4-(1,2,2-triphenylvinyl)benzylidene) hydrazinecarbothioamide), the second reaction chamber comprising: a reagent mixing unit configured to dissolve 4-methyl-3-thiosemicarbazide in ethanol; and a mixture preparation unit configured to add 4-methyl-3-thiosemicarbazide and acetic acid to the reagent mixing unit.The system further comprises: a reflux unit connected to a temperature control module, the reflux unit configured to reflux the prepared mixtures at a specific temperature for a specific period of time, the temperature control module maintaining the specific temperature; a nitrogen supply unit connected to the first reaction chamber and configured to maintain an inert atmosphere, the mixture being stirred under a nitrogen atmosphere; a purification unit configured to perform column chromatography to obtain the synthesized compound separately from the first reaction chamber and the second reaction chamber; and a detection assembly configured to use the synthesized TPE-PVA to detect metal ions in aqueous media.

[0008] In one embodiment, the first reaction chamber further comprises a monitoring unit configured to monitor the reaction progress using DC.

[0009] In one embodiment, the second reaction chamber further comprises a product collection unit configured to collect a pale yellow precipitate upon cooling after the mixture of 4-methyl-3-thiosemicarbazide, ethanol, and acetic acid is heated to reflux using a reflux unit.

[0010] In one embodiment, the temperature control module includes a feedback system configured to maintain precise temperature control under reflux conditions.

[0011] In one embodiment, the nitrogen supply unit comprises a gas flow regulator configured to maintain a constant inert atmosphere throughout the synthesis process.

[0012] In one embodiment, the detection device (114) uses test strips made of Whatman paper dipped in acetonitrile solution with probe 1 (TPE-PVA) for the selective and sensitive detection of Hg2 +- and Ag + - ions to other metal ions through a fluorescence shutoff mechanism, using the synthesized TPE-PVA in a mixed aqueous medium of ACN:H2O in a ratio of 1:9 v / v as a dual-sensor chemosensor.

[0013] An object of the invention is to provide a tetraphenylethene-based system for detecting metal ions in water.

[0014] Another object of the present disclosure is to provide a system for synthesizing tetraphenylethene hydrazinecarbothioamide (TPE-PVA) as a fluorescent chemosensor.

[0015] Another object of the present invention is to provide a system for synthesizing a TPE-PVA dual sensor probe with a quantum yield (Φ) of 2.26.

[0016] Another object of the present invention is to provide a chemosensor that can selectively and sensitively detect Hg2+ and Ag+ over other metal ions through a fluorescence shutoff mechanism.

[0017] Another object of the present invention is to provide a system for synthesizing a dual sensor probe from which test strips for the on-site detection of metal ions can be produced using Whatman filter paper.

[0018] Another object of the present invention is to provide a system for synthesizing a dual sensor probe that functions effectively in mixed aqueous media (ACN:H2O in the ratio 1:9 v / v).

[0019] To further clarify the advantages and features of the present disclosure, a more detailed description of the invention will be given with reference to specific embodiments thereof illustrated in the accompanying drawings. It should be noted that these drawings represent only typical embodiments of the invention and are therefore not to be considered limiting its scope. The invention will be described and explained in additional detail and in greater detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE CHARACTERS

[0020] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout. Fig. 1 shows a block diagram of a tetraphenylethene-based system for detecting metal ions in water according to an embodiment of the present disclosure; and Fig. 2A and Fig. 2B illustrate Scheme 1 and Scheme 2, which show the synthetic route to TPE-CHO and TPE-PVA, respectively, according to an embodiment of the present disclosure.

[0021] Furthermore, those skilled in the art will appreciate that elements in the drawings are shown for convenience and may not necessarily be drawn to scale. For example, the flowcharts illustrate the method by key steps to enhance understanding of aspects of the present disclosure. Moreover, with respect to device construction, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details relevant to understanding embodiments of the present disclosure in order not to clutter the drawings with details that would be readily apparent to those skilled in the art who would benefit from the description herein. DETAILED DESCRIPTION:

[0022] To facilitate an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and described in specific language. It is to be understood, however, that this is not intended to limit the scope of the invention, as such changes and further modifications to the illustrated system and such further applications of the principles of the invention as illustrated therein are contemplated as would normally occur to one skilled in the art to which the invention pertains.

[0023] It will be understood by one skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be limiting thereof.

[0024] References in this specification to "one aspect," "another aspect," or similar language mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Therefore, occurrences of the phrase "in one embodiment," "in another embodiment," and similar language throughout this specification may or may not all refer to the same embodiment.

[0025] The terms "comprises," "comprising," or other variations thereof are intended to cover non-exclusive inclusion, such that a process or method comprising a list of steps not only includes those steps, but may also include other steps not expressly listed or inherent in such process or method. Likewise, one or more devices or subsystems or elements or structures or components preceded by "comprises...a" does not preclude, without further limitation, the existence of other devices or other subsystems or other elements or other structures or other components or additional devices or additional subsystems or additional elements or additional structures or additional components.

[0026] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are for illustrative purposes only and should not be considered limiting.

[0027] Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0028] Fig. 1 shows a block diagram of a tetraphenylethene-based system (100) for detecting metal ions in water according to an embodiment of the present disclosure.

[0029] With reference to Fig. 1, the system (100) comprises a first reaction chamber (102) configured to synthesize TPE-CHO (4-(1,2,2-triphenylvinyl)benzaldehyde), the first reaction chamber (102) comprising: a mixing module (102a) configured to mix a predetermined amount of 1-bromo-1,2,2-triphenylethylene and 4-formylphenylboronic acid; a solvent delivery unit (102b) configured to add tetrahydrofuran and potassium carbonate solution to the mixing module (102a); and a catalyst addition unit (102c) configured to add tetrakis(triphenylphosphine)palladium(0) to the mixing module (102a).The system (100) further comprises: a second reaction chamber (104) configured to synthesize TPE-PVA ((E)-N-methyl-2-(4-(1,2,2-triphenylvinyl)benzylidene) hydrazinecarbothioamide), the second reaction chamber (104) comprising: a reagent mixing unit (104a) configured to dissolve 4-methyl-3-thiosemicarbazide in ethanol; and a mixture preparation unit (104b) configured to add 4-methyl-3-thiosemicarbazide and acetic acid to the reagent mixing unit (104a).The system (100) further comprises: a reflux unit (106) connected to a temperature control module (108), the reflux unit (106) being configured to reflux the prepared mixtures at a specific temperature for a specific period of time, the temperature control module (108) maintaining the specific temperature; a nitrogen supply unit (110) connected to the first reaction chamber (102) and configured to maintain an inert atmosphere, the mixture being stirred under a nitrogen atmosphere; a purification unit (112) configured to perform column chromatography to obtain the synthesized compound separately from the first reaction chamber (102) and the second reaction chamber (104); and a detection assembly (114) configured to use the synthesized TPE-PVA to detect metal ions in an aqueous medium.

[0030] In one embodiment, the first reaction chamber (102) further comprises a monitoring unit (102d) configured to monitor the reaction progress by means of TLC.

[0031] In one embodiment, the second reaction chamber (104) further comprises a product collection unit (104c) configured to collect a pale yellow precipitate upon cooling after the mixture of 4-methyl-3-thiosemicarbazide, ethanol, and acetic acid has been refluxed using the reflux unit (106).

[0032] In one embodiment, the temperature control module (108) comprises a feedback system (108a) configured to maintain precise temperature control during reflow conditions.

[0033] In one embodiment, the nitrogen supply unit (110) comprises a gas flow regulator (110a) configured to maintain a constant inert atmosphere throughout the synthesis process.

[0034] In one embodiment, the detection device (114) uses test strips made of Whatman paper dipped in acetonitrile solution with probe 1 (TPE-PVA) for the selective and sensitive detection of Hg2 +- and Ag + -ions to other metal ions through a fluorescence shut-off mechanism, using the synthesized TPE-PVA in a mixed aqueous medium of ACN:H2O in a ratio of 1:9 v / v as a dual-sensor chemosensor.

[0035] The present invention relates to a system for the synthesis of tetraphenylethene hydrazinecarbothioamide (TPE-PVA) as a novel dual-sensor probe 1. The synthesized probe 1 has a quantum yield (Φ) of 2.26 with a pendant methylenehydrazinecarbothioamide receptor region. The synthesized probe 1 exhibits impressive photophysical phenomena such as aggregation-induced emission (AIE) and mechanochromic properties when mechanical force is applied to the solid of the probe 1.

[0036] In one embodiment, the connecting probe 1, known as TPE-PVA, is synthesized by the reaction of 4-(1,2,2-triphenylvinyl)benzaldehyde and 4-methyl-3-thiosemicarbazide in the presence of ethanol and acetic acid as solvents. The synthesized AIE luminogens were characterized by various characterization techniques.

[0037] The synthesis of said probe 1 is carried out in two steps, the first step comprising the synthesis of TPE-CHO (4-(1,2,2-triphenylvinyl) benzaldehyde) and the second step comprising the synthesis of TPE-PVA ((E)-N-methyl-2-(4-(1,2,2-triphenylvinyl) benzylidene) hydrazinecarbothioamide).

[0038] Fig. 2A and Fig. 2B illustrate Scheme 1 and Scheme 2, which show the synthetic route to TPE-CHO and TPE-PVA, respectively, according to an embodiment of the present disclosure. In the first step, 1-bromo-1,2,2-triphenylethylene (335.24 mg, 1.0 mmol) and 4-formylphenylboronic acid (179.9 mg, 1.2 mmol) were dissolved in 20 ml of tetrahydrofuran and 7 ml of a 2 M aqueous potassium carbonate solution. The mixture was stirred for 0.5 hours at room temperature under a nitrogen atmosphere (N2). Tetrakis(triphenylphosphine)palladium(0) (0.010 g) was then added, and the reaction mixture was heated to reflux at 80 °C overnight. The reaction was monitored by TLC, and after completion of the reaction, the solvent was removed under reduced pressure, yielding a residue. This residue was purified by chromatography on a silica gel column using n-hexane / dichloromethane (v / v 3:1) as eluent to obtain TPE-CHO as a light yellow powder (346.0 mg, 96% yield).

[0039] The characterization results of TPE-CHO showed: 1H-NMR (400 MHz, CDC13) δ / ppm: 9.90 (s, 1H, -CHO), 7.62 (d, J = 8.5 Hz, 2H, - Ar -H), 7.20 (d, J = 8.3 Hz, 2H, - Ar -H), 7.15-7.09 (m, 9H, - Ar -H), 7.06-6.99 (m, 6H, - Ar -H). 13C NMR: (101 MHz, CDCl3) δ / ppm: 191.93, 150.56, 143.04, 142.99, 142.89, 139.74, 134.25, 131.95, 131.30, 131.28, 131.23, 129.17, 127.93, 127.74, 127.05, 126.89, 126.86, 124.46. HR-ESI-MS calculated for C7H 20 O [M + H ]+ : 361.1548; found: 361.1546. IR (ATR): 691, 1018, 1210, 1554, 1691, 2724, 2824, 3050 cm - 1 ; the structure of probe 1 was confirmed by a combination of characterization techniques, including IR, 1 H-NMR and 13 C-NMR spectroscopy and HR-MS spectrometry.

[0040] In relation to Fig., which shows the synthesis route for (E)-methyl-2-(4-(1,2,2-triphenyl)benzylidene) hydrazinecarbothioamide (TPE-PVA) in the second step, 4-methyl-3-thiosemicarbazide was dissolved in 10 ml of ethanol. 4-methyl-3-thiosemicarbazide and 1 ml of acetic acid were then added to this solution. The entire solution was then refluxed at 80 °C for 30 minutes. Upon cooling to room temperature, the pale yellow solute precipitated. The completion of the reaction was confirmed by TLC, and the final pale yellow product was then purified by column chromatography with petroleum ether / ethyl acetate (v / v = 30 / 1) to afford (E)-methyl 2-(4-(1,2,2-triphenylvinyl)benzylidene)hydrazinecarbothioamide (147.0 mg, 66% yield).

[0041] The characterization results of TPE-PVA showed: 1H-NMR (400 MHz, CDCl 3) δ / ppm: 9.56 (s, 1H), 7.72 (s, 1H), 7.37 (d, J = 8.5 Hz, 2H), 7.11 (qd, J = 3.9, 1.8 Hz, 9H), 7.07 - 7.00 (m, 9H), 3.23 (d, J = 4.9 Hz, 3H). 13C-NMR: (101 MHz, CDC13) δ / ppm: 178.15, 146.32, 143.38, 143.34, 143.20, 142.26, 142.05, 140.05, 131.85, 131.34, 131.32, 131.27, 131.14, 127.85, 127.81, 12 7.69, 126.77, 126.69, 126.65, 31.15, 29.71, 29.37. IR (ATR): 691, 748, 818, 1022, 1080, 1249, 1546, 1691, 2853, 2924, 3624, 3742, cm-1; HR-ESI-MS calculated for C29H25N3S [M + H] +: 448.1803; found: 448.1895. Various characterization techniques such as IR, 1 H-NMR and 13 C-NMR spectroscopy and HRMS spectrometry were used to confirm the structure of probe 1.

[0042] The synthesized AIE luminogens were characterized by various characterization techniques such as infrared (IR) attenuated total reflection (ATR), 1 H-NMR and 13C-NMR spectroscopy and high-resolution mass spectrometry (HRMS). IR spectra were recorded on a Bruker, Germany (α), spectrometer in the range of 4000-400 cm -1 recorded 1H NMR spectra were recorded on a 400 MHz Bruker Advance spectrometer and 13C NMR with 101 MHz spectrometers using CDCl3-d or DMSO-d6 as solvent (trimethyl silane as internal standard). DEPT-135 NMR spectra were recorded on a 400 MHz Bruker Advance spectrometer. Mass spectrometry (HR-MS) data were obtained using a Waters Micromass Q-Tof Micro in electrospray ionization (ESI)-MS mode. UV-vis absorption spectra were recorded using the Specord plus UV-vis. The reaction was carried out using a double-beam spectrophotometer (Analytik Jena), and fluorescence emission was measured using an FP-8300 (Jasco) fluorescence spectrometer. The progress of all reactions was monitored by TLC (on a silica-coated aluminum plate).

[0043] To perform UV-Vis and fluorescence experiments, all stock solutions of the cations (100 µg mL -1) by dissolving the required amount of metal salts in double distilled water. The stock solution of probe 1 (1 × 10 -4 M) was prepared in acetonitrile. For spectral analysis, test solutions were prepared by adding 1.0 ml (1 × 10 -4 M) of probe 1 with 1.0 ml (100 µg mL -1 ) of each cation was mixed in a test tube, the mixture was diluted to 10 ml with distilled water, and allowed to stand at room temperature for 10 minutes. Absorption and fluorescence (emission) spectra were then recorded at room temperature.

[0044] For fluorescence titration to detect Hg 2+ - and Ag + - cations, 1 ml of probe 1 (10 -4 mol / 1) in acetonitrile solution in each test tube of different sets and aqueous solutions of Hg 2+ - and Ag +-ions (1 ppm) were added at different concentrations. All solutions were diluted to a constant volume, and each test tube solution was then subjected to sequential absorption and emission measurements at room temperature. The fluorescence spectra were recorded at an excitation wavelength (λ ex ) of 270 nm with a bandwidth of 10.

[0045] To prepare the paper strips for probe 1, paper strips were prepared by cutting Whatman paper, which was then immersed in an acetonitrile solution of probe 1 (1 × 10 -4 ). These strips were left to air dry. Their purpose was to absorb Hg 2+ - and Ag + ions in the presence of other cations. The test strips were examined under UV irradiation at 365 nm, allowing easy detection with the naked eye.

[0046] For dynamic light scattering (DLS) analysis, a solution of probe 1 in acetonitrile (1 × 10 -4 ), while water mixtures and metal ion solutions were prepared in double distilled water. DLS measurements were initially performed with the probe only and subsequently in the presence of Hg 2+ - and Ag + -metal ion solutions in a ratio of 1:0.5.

[0047] To fully characterize it, phytochemical and spectroscopic analyses were performed. To confirm the purity and structure of the probe, FT-IR, 1H NMR, 13C NMR, and HRMS spectra were performed. This invention revealed the successful synthesis of TPE-PVA.

[0048] The solid powder of Probe 1 emits bright yellow fluorescence, and its aggregation-induced emission (AIE) properties were investigated by analyzing its emission spectra in various solvents. Probe 1, upon excitation at 270 nm, exhibited fluorescence peaks at 420 nm and 426 nm in THF and acetonitrile, respectively, with weaker emission intensity in acetonitrile. THF was selected for further AIE studies because the solvent plays a crucial role in the emission behavior, likely due to a solvophobic effect.

[0049] The concept of AIE explains that luminogens become emissive when aggregated under certain conditions. The TPE-PVA synthesized in this invention is soluble in THF but insoluble in water, so its AIE properties can be studied by increasing the water content in THF. TPE-PVA aggregation began when the water content reached 60% or more, with the fluorescence intensity gradually increasing with water contents up to 70% and then rising steeply. When the water content reached 99%, the THF solution showed a significant fluorescence enhancement, suggesting that TPE-PVA is an AIE-active compound.

[0050] Further fluorescence measurements showed that probe 1 in THF produced a weak emission at 431 nm, which increased upon addition of water, peaking at 466 nm at 99% water content. This enhanced fluorescence in the aggregated state results from restricted intramolecular rotations and enhanced π-conjugation in TPE-PVA molecules. In THF, TPE-PVA molecules remain isolated and exhibit minimal emission due to non-radiative decay from free rotations. However, when molecular aggregates form upon addition of water, the emission increases due to restricted rotations.

[0051] The UV-visible absorption spectrum of Probe 1 in THF and THF / H2O mixtures showed an absorption maximum at 358 nm in THF, which shifted to 368 nm upon addition of water, indicating the formation of J-aggregates in the presence of water. This confirms that Probe 1 exhibits strong AIE properties with maximum fluorescence in THF / H2O at 99% water content.

[0052] The investigation of on / off fluorescence emission for metal ion detection, especially Hg 2+ - and Ag + -ions, showed that probe 1 exhibits low emission in organic solvents, but the photoluminescence emission (PL) increases upon addition of water and forms aggregates due to AIE. After addition of aqueous analyte solutions, the PL emissions were measured in the presence of Hg 2+ and Ag + selectively switched off, demonstrating the probe's potential as a selective fluorescence sensor.

[0053] The mechanochromic luminescence (MC) properties of Probe 1 (TPE-PVA) in its solid state were investigated due to its aggregation-induced emission (AIE). When solid Probe 1 was ground with a mortar and pestle, its emission color under UV light (365 nm) changed dramatically from turquoise blue to lemon yellow. Furthermore, heating and exposure to solvent vapors further altered the color of Probe 1. Upon annealing at 160 °C, it changed from lemon yellow to parrot green, and upon vapor deposition with dichloromethane (DCM) vapor, it changed to arctic blue. The mechanochromic properties of Probe 1 were further analyzed by powder X-ray diffraction (PXRD). Before grinding, the PXRD pattern showed several sharp peaks between 20 = 10° and 25°, with a broad peak at 20 = 20°, corresponding to the (101) plane of carbonaceous materials containing nitrogen and sulfur atoms. Another broad peak at 20 = 42.5° was observed, which coincided with the (034) plane and confirmed the monoclinic phase of Sample 1 before milling. After two minutes of milling, all sharp peaks disappeared, leaving only broad peaks at 20 = 12.5° and 20°, indicating a completely amorphous state. When the milled TPE-PVA was subjected to vapor deposition with dichloromethane, the PXRD pattern showed numerous sharp diffraction peaks, indicating a transition back to a crystalline form. However, the peak positions indicated that it did not completely return to its original crystalline state. This phase transition between crystalline and amorphous forms is responsible for the mechanochromic luminescence observed in Sample 1.

[0054] Fluorescence and UV spectroscopic studies of probe 1 (TPE-PVA) were conducted to investigate its metal recognition properties in the presence of various biologically and environmentally relevant cations. A 1 × 10 -5 M solution of probe 1 in acetonitrile was treated with various cations such as Zn 2+ , Co 2+ , Ed. 2+ , Ca 2+ , Ag + , Mg 2+ , Sn 2+ , Fe 3+ , Ni 2+ , Cu 2+ , Li + , Pb 2+ , Fe 2+ , Mn 2+ and Cr 6+ in an aqueous medium. The emission spectra for probe 1 showed a peak at 466 nm upon excitation at 270 nm, and the addition of 100 µg mL -1 solutions of each cation resulted in variations in the fluorescence emission of probe 1. Of all the cations tested, Hg 2+ - and Ag +ions significantly quenched the fluorescence of Probe 1, indicating the strong selectivity and sensitivity of the probe to these ions in a mixed aqueous environment. Although other cations slightly reduced the fluorescence, the effect was minimal compared to the dramatic fluorescence quenching observed with Hg 2+ - and Ag + -ions was observed. This pronounced quenching effect underlines the stronger affinity of probe 1 to Hg 2+ - and Ag + -ions. Fluorescence changes were also observed under ambient and UV light. Under ambient light, probe 1 showed less emission in the presence of various cations, while under UV light, all test samples except those with Hg 2+ - and Ag + ions, intense fluorescence was observed. This reaction suggests that the reduced fluorescence in the presence of Hg 2+ and Ag +could be due to specific interactions with probe 1, in contrast to other cations, which did not result in significant changes. These results confirm that probe 1 is effective in detecting Hg 2+ - and Ag + -ions compared to other cations, making it a suitable fluorescence sensor for these ions.

[0055] The UV-Vis spectra of the synthesized probe 1 (TPE-PVA) were recorded in a mixed solvent of acetonitrile and water at room temperature and showed a maximum absorption at a wavelength of 362 nm. When tested with various cations in an aqueous medium, the absorption of probe 1 showed a significant increase upon addition of all cations except mercury(II) (Hg 2+ ) and silver(I) ions (Ag + ) only minimal changes. The introduction of Hg 2+ - and Ag +-ions led to significant changes in the absorption spectra; the original absorption maximum at 362 nm disappeared completely and new bands appeared at 352 nm and 354 nm respectively. This change indicates that the complex formation between Hg 2+ - and Ag + ions and probe 1 probably led to the formation of these new peaks, which reflect the interactions between the metal ions and the organic part of the probe.

[0056] The sensor performance of probe 1 was evaluated based on its response to Hg 2+ - and Ag + -ions in a mixed aqueous medium of acetonitrile and water. Upon excitation at 270 nm, probe 1 showed a fluorescence emission band at 466 nm. The addition of different concentrations of Hg 2+ - and Ag + -ions resulted in a decrease in fluorescence intensity, which at a concentration of 1.6 µg mL -1for both ions almost disappeared. This indicates that probe 1 Hg 2+ - and Ag + ions in solution. To establish an analytical method for quantifying these analytes, the relationship between analyte concentration and fluorescence signal intensity was determined using the Stern-Volmer quenching equation. The analysis revealed a linear correlation between the fluorescence response and the ion concentration in the range of 0–1.4 µg mL. -1 for Ag + and 0-1.2 µg mL -1 for Hg 2+ . The obtained linear regression coefficients were 0.9785 for Ag + and 0.9834 for Hg 2+ , indicating a strong correlation and the potential for accurate quantification of these metal ions with Probe 1.

[0057] The limit of detection (LOD) for the developed method was determined for Hg 2+ - and Ag +-ions using a formula that takes into account the slope of the emission intensity ratio diagram and the standard deviation of blank measurements. The detection limits determined for the sensor system were 0.18344 µg mL -1 for Hg 2+ and 0.2384 µg mL -1 for Ag + These values ​​are well below the permissible levels for both ions in drinking water. The achieved linearity, correlation coefficient, and detection limit indicate a reasonable level of accuracy for the sensor system and suggest its potential for testing both ions in actual samples.

[0058] The on-site detection of Hg 2+ - and Ag +-ions developed paper-based strips demonstrated effective visual verification. These strips were prepared by dipping paper into an acetonitrile solution of Probe 1 and then drying it. When tested under UV light, the paper of Probe 1 showed a bright blue fluorescence. However, the fluorescence decreased upon addition of Hg 2+ - and Ag + ions, indicating a successful response to these specific cations. In contrast, competing cations did not affect the fluorescence. These results indicate that Probe 1 has excellent selectivity and sensitivity for the detection of Hg 2+ - and Ag + -ions as well as stability, speed and ease of use without the need for complex devices.

[0059] The sensor mechanism of the TPE-PVA probe for the detection of Hg 2+ - and Ag +The quenching of ions was evaluated by analyzing the decrease in fluorescence intensity upon addition of these ions. It was assumed that the fluorescence quenching was due to complex formation between the probe and the ions. The sensing mechanism was confirmed using various techniques.

[0060] 1 H-NMR experiments performed in DMSO-d6 showed sharp peaks corresponding to the NH proton, which after addition of Hg 2+ - and Ag + ions gradually disappeared and shifted downward, indicating strong complexation through the NH bond. FT-IR spectra showed a weakening of the NH stretching peak, further confirming stable complexation with the ions and suggesting the involvement of NH in the complexation process.

[0061] Dynamic light scattering (DLS) measurements showed that the size of the sample solution was initially large due to aggregation, but this size decreased after the addition of Ag + - and Hg 2+ ions decreased significantly, indicating that complexation with these ions led to the breakdown of aggregation and the formation of smaller particles.

[0062] Time-correlated single-photon counting (TCSPC) measurements showed that the quenching mechanism was static, as evidenced by the ratio of fluorescence lifetimes before and after the addition of the quencher. This suggested that complexation between the probe and the ions occurred in the ground state.

[0063] Binding parameters, including the binding constant and the number of binding sites, were calculated from fluorescence quenching data, indicating the presence of a single class of binding sites for the probe. Binding stoichiometry was determined by Job's plot analysis and revealed a ratio of 1:2 for the probe and Ag. + complex and a ratio of 2:1 for the probe and the Hg 2+ -Complex.

[0064] Finally, the fluorescence quantum yield of the probes was determined in the absence of Hg2+ and Ag + -ions using quinine sulfate as a reference, which provides insight into the photophysical properties of the probe.

[0065] The above results show that TPE-PVA synthesized as Sample 1 in this invention exhibits a quantum yield (Φ) of 2.26 and an aggregation-induced emission activity (AIE) in addition to remarkable mechanochromic photophysical phenomena. The mechanochromic luminescence properties arise from the transition of the probe from a crystalline to an amorphous state. The synthesized Probe 1 proved to be effective for metal ion detection in mixed aqueous media and acted as a fluorescence sensor for the selective and sensitive detection of Hg. 2+ - and Ag + -ions in an ACN :H2O mixture. The presence of only Hg 2+ - and Ag +-ions significantly quenched the fluorescence of probe 1 and enabled the development of a detection method that utilizes these quenching properties to distinguish both ions with a single probe. In addition to the application in paper strip-based detection, the on-site detection of Hg 2+ and Ag + in real samples. Due to the selectivity and sensitivity of the probe to these ions, there is potential for the future development of kits for the detection of Hg 2+ - and Ag + -ions.

[0066] The drawings and the foregoing description provide examples of embodiments. Those skilled in the art will recognize that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be separated into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of the processes described herein may be changed and are not limited to the manner described herein. Furthermore, the actions of any flowchart need not be implemented in the order shown; nor do all actions necessarily need to be performed. Also, those actions that are not dependent on other actions may be performed in parallel with the other actions. The scope of the embodiments is in no way limited by these specific examples.Numerous variations, whether explicitly stated in the specification or not, such as differences in structure, dimensions, and material use, are possible. The scope of the embodiments is at least as broad as indicated in the following claims.

[0067] Advantages, other benefits, and solutions to problems have been described above with reference to specific embodiments. However, the advantages, benefits, solutions to problems, and any components that may cause an advantage or solution to occur or become more apparent are not to be construed as a critical, required, or essential feature or component of any or all of the claims. REFERENCES 100 A tetraphenylethylene-based system for the detection of metal ions in water. 102 First reaction chamber 102a mixing module 102b Solvent dosing unit 102c Catalyst addition unit 102d monitoring unit 104 Second reaction chamber 104a Reagent mixing unit 104b Mixture preparation unit 104c Product collection unit 106 backflow preventers 108 Temperature control module 108a Feedback system 110 Nitrogen supply unit 110a gas flow regulator 112 cleaning system 114 Detection module

Claims

[1] A tetraphenylethene-based system (100) for detecting metal ions in water, comprising: i) a first reaction chamber (102) configured to synthesize TPE-CHO (4-(1,2,2-triphenylvinyl) benzaldehyde), the first reaction chamber (102) comprising: a) a mixing module (102a) configured to mix a specific amount of 1-bromo-1,2,2-triphenylethylene and 4-formylphenylboronic acid; b) a solvent dispensing unit (102b) configured to add tetrahydrofuran and potassium carbonate solution to the mixing module (102a); c) a catalyst addition unit (102c) configured to add tetrakis(triphenylphosphine)palladium(0) to the mixing module (102a); ii) a second reaction chamber (104) configured for the synthesis of TPE-PVA ((E)-N-methyl-2-(4-(1,2,2-triphenylvinyl)benzylidene) hydrazinecarbothioamide), the second reaction chamber (104) comprising: a) a reagent mixing unit (104a) configured to dissolve 4-methyl-3-thiosemicarbazide in ethanol; b) a mixture preparation unit (104b) configured to add 4-methyl-3-thiosemicarbazide and acetic acid to the reagent mixing unit (104a); iii) a reflux unit (106) connected to a temperature control module (108), the reflux unit (106) being configured to reflux the prepared mixtures for a specific period of time at a specific temperature, the temperature control module (108) maintaining the specific temperature; iv) a nitrogen supply unit (110) connected to the first reaction chamber (102) and configured to maintain an inert atmosphere, wherein the mixture is stirred under a nitrogen atmosphere; v) a purification unit (112) configured to perform column chromatography to obtain the synthesized compound separately from the first reaction chamber (102) and the second reaction chamber (104); and vi) a detection arrangement (114) configured to use the synthesized TPE-PVA to detect metal ions in an aqueous medium. [2] The system of claim 1, wherein the first reaction chamber (102) further comprises a monitoring unit (102d) configured to monitor the reaction progress by TLC. [3] The system of claim 1, wherein the second reaction chamber (104) further comprises a product collection unit (104c) configured to collect a pale yellow precipitate upon cooling after the mixture of 4-methyl-3-thiosemicarbazide, ethanol, and acetic acid is refluxed using the reflux unit (106). [4] The system of claim 1, wherein the temperature control module (108) comprises a feedback system (108a) configured to maintain precise temperature control during reflux conditions. [5] The system of claim 1, wherein the nitrogen supply unit (110) comprises a gas flow regulator (110a) configured to maintain a constant inert atmosphere throughout the synthesis process. [6] The system of claim 1, wherein the detection arrangement (114) uses test strips of Whatman paper dipped in acetonitrile solution with probe 1 (TPE-PVA) for the selective and sensitive detection of Hg2 +- and Ag + -ions to other metal ions through a fluorescence shut-off mechanism, using the synthesized TPE-PVA in a mixed aqueous medium of ACN:H2O in a ratio of 1:9 v / v as a dual-sensor chemosensor.

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