Paper Test Strips Research Articles

Colorimetric reversibility: Aqueous phase recognition of cyanide using smart phone-based device with real sample analysis

A novel colorimetric 2-hydrazinobenzothiazole based probe (BTHP) was successfully synthesized and employed as an optical cyanide sensor. The interaction of CN− with BTHP produced a distinct color variation (dark pink color) with a red shift (96 nm) in its absorption spectra. The probe was selective, sensitive and robust towards cyanide ion sensing even in the presence of other competing ions. It could detect cyanide ion upto 0.77 µM, even lower than the limit recommended by WHO (1.9 µM). The binding stoichiometry for BTHP-CN− complex (1:1) was confirmed via Job’s plot. A binding constant of 3.19*102 M−1 was calculated in the recognition process. The cyanide ion recognition mechanism was confirmed using 1H NMR titration and DFT calculation. The probe coated filter paper test strips displayed dark pink color upon cyanide exposure. BTHP can be used reversibly for the visible detection of cyanide in liquid (real water) as well as solid phase (soil). Further, the practical applications of the developed sensor include smartphone based sensing, logic gate fabrication, molecular keypad lock and write-read-erase-read devices.

Trace level detection of putrescine and cadaverine in food samples using a novel rhodanine-imidazole dyad and evaluation of its biological properties

Biogenic amines are important indicators of food spoilage and quality. Food safety is significantly influenced by biogenic amines such as Putrescine and Cadaverine, produced by microbes during food spoilage. Herein, a colorimetric probe for detecting Putrescine and Cadaverine based on a chemo-dosimeter strategy has been proposed. The probe L1 irreversibly binds with Putrescine and Cadaverine through an aza-Michael addition reaction in which the dicyanomethyl group of the probe is substituted by the primary amine group from the biogenic amines. This chemical reaction rapidly changes color from colorless to pale green. The probe could detect Putrescine and Cadaverine in trace levels of 52 nM and 18 nM, without much interference from other common biogenic amines. The binding mechanism of probe L1 with biogenic amines was confirmed using 1H NMR, IR, and DFT studies. The detection procedure is made portable and affordable by using a smartphone camera to capture colorimetric changes and convert them into RGB coordinates. Test paper strips coated with the probe were developed to illustrate its real-world analytical application. The potential application of probe L1 in real samples was demonstrated using in-vivo models of Prawn and Beef using test paper strips. Probe L1 showed satisfactory performance for detecting Putrescine and Cadaverine in the vapor phase.

Chromogenic Chemosensor for Simultaneous Detection of PO4 3- and CO3 2- Anions in Organo-Aqueous Solutions: Application in Arduino Based Electronic Color Sensor Device and Logic Gate.

Three new chromogenic receptors have been synthesized with the primary objective of facilitating the selective recognition of PO4 3-and CO3 2- ions in an organo-aqueous medium. R1 and R2 exhibit an extraordinary detection limit aligning with both EPA and WHO guidelines. R1 shows LOD of 0.135 ppm for PO4 3- and 0.175 ppm for CO3 2-, while R2 sets forth a LOD of 0.427 ppm for PO4 3- and 0.729 ppm for CO3 2-. The binding mechanism involves intramolecular charge transfer (ICT) band are substantiated by comprehensive studies that include UV-Vis titration, 1H-NMR titration, DFT studies and electrochemical studies. Chemosensors were employed in the formulation of logic gate, the fabrication of a paper strip test kit and its application in RGB color sensor device.

AIE active hydroxycoumarin-anthranilic acid coupled enamine: Sequential detection of Cu2+/S2− ions and live cell imaging application

In this contribution, we designed and developed 7-diethylamino-4-hydroxycoumarin coupled anthranilic acid-based enamine (DHCBA) and its Cu2+ complex (DHCBA-Cu)via simple synthetic strategy. DHCBA shows solvatochromic effect, aggregation induced emission feature at 80 % methanol–water mixture and colorimetric as well as fluorescence turn-off sensing features towards Cu2+ ions. The DHCBA-Cu2+ ensemble has been utilized as a turn-on fluorescence sensor for the detection of S2− through a decomplexation approach. The formation of a 1:1 DHCBA-Cu2+ ensemble was further supported by 1H NMR studies, HRMS analysis and Density Functional Theory (DFT) calculation. The detection limit for Cu2+ was found to be 6.5 nM and then the binding affinity and binding stoichiometry of the probe towards Cu2+ ion was calculated using the online BindFit v0.5 supramolecular software. Moreover, the 1:1 stoichiometric ratio between DHCBA and Cu2+ ions were confirmed via single crystal X-ray analysis. The structural analysis of DHCBA-Cu2+ indicates that it forms an interesting one-dimensional coordination polymeric chain-like structure, further transformed into a two-dimensional polymeric network through hydrogen bonding interactions. The reversible on–off–on emission character of the probe, DHCBA was successfully applied for the construction of the IMPLICATION logic gate as well as on-site detection applications using paper strip and cotton-swab tests. Furthermore, the sensing feature of the enamine against Cu2+/S2− ions were validated by intracellular imaging applications.

Design and synthesis of phenothiazine-based D–A molecules with ICT characteristics as efficient fluorescent probes for detecting hypochlorite in water

Phenylthiazide compounds are frequently utilized to construct electron donor–acceptor (D–A) dyes, exhibiting excellent fluorescence and colorimetric analysis performance due to their electron-rich properties. Three D-A type compounds 5a–c, featuring intramolecular charge transfer (ICT) characteristics, were designed and synthesized using phenothiazine as the donor and various aryl-substituted imidazoles as acceptors for the detection of hypochlorite. Additionally, the ICT properties of the compounds can be fine-tuned by introducing various substituents to achieve a more sensitive optical response to HClO/ClO−. Among these, compound 5c, which contains the electron-withdrawing group –CN, demonstrated high sensitivity (3.5 nM), high selectivity, and a rapid response to HClO/ClO−. Experimental results indicated that the strategy based on structural tuning presents a promising approach for optimizing fluorescent probes. To broaden practical applications, compound 5c was fabricated into paper test strips and thin-layer chromatography (TLC) plates for on-site analysis and detection of HClO/ClO−. The compound was capable of detecting HClO/ClO− not only in actual water samples but also in complex environmental water samples, thereby providing a convenient tool for real-time HClO/ClO− detection.

A PET based colorimetric/fluorescent dual-signal probe for selective detection of hypochlorite in real water samples

As a potent oxidizing agent, hypochlorite is pervasive across various terminal disinfection processes, including water treatment, household blenching and medical sterilization. Thus, the specific visualization identification of hypochlorite in real water samples is crucial for assessing water quality safety and pollutant toxicity. Herein, a novel turn-on colorimetric/fluorescent dual-signal probe AMXM based on 6‑methoxy-2,3-dihydro-1H-xanthene-4-carboxaldehyde scaffold has been successfully designed and synthesized for highly selective and sensitive detection of ClO− in real water sample. Upon the addition of hypochlorite, the solution's color visibly changes from red to yellow to the naked eye, and a strong yellowish green fluorescence is observed under UV light at 365 nm. AMXM demonstrates an excellent linear response (R2 = 0.9922), with a low detection limit of 56.2 nM, and is unaffected by other potential interfering substances. The mechanism of AMXM’s response to hypochlorite ions was confirmed through 1H NMR spectroscopy and density functional theory (DFT) calculations. Furthermore, AMXM was successfully applied to paper test strips and used for the quantitative determination of hypochlorite ions in four real water samples.

New phenanthridine-based multi-functional chemosensor for selective detection of Th4+ and Hg2+ ions in both aqueous and solid state

A new phenanthridine-based multifunctional chemosensor (L), was synthesised via a green synthetic route and characterised using FT-IR, NMR and HRMS analysis. The sensing application of L towards metal ions in both solution and solid-state was studied using UV–vis and fluorescence spectroscopy, which exhibits dual-sensing behaviour for Th4+ and Hg2+ ions with good recyclability. In aqueous acetonitrile, L showed rapid response for the detection of environmental toxic metal ions and has a very low analytical detection limit of 125.5 pM and 1.94 nM for Th4+ and Hg2+ions respectively, which is remarkably lower than the World Health Organization standard. The cation binding property of the L with Th4+ and Hg2+ions was investigated by Job plot, 1H NMR titration, HR-MS and DFT calculation. The in-situ formed ensemble L-Hg2+ was further applied in the naked-eye detection of Cys (Cystine) and His (Histidine) over other common amino acids. The utility of L for real-time detection of Hg2+ and Th4+ ions was explored in various sources of environmental water samples, test paper strips, fingerprint imaging, fluorescent ink and smartphone-assisted sensing techniques, demonstrating the promising on-site visualization of the probe in controlling the toxicity levels in wastewater sources without resorting to expensive instruments.

Photochemical and electrochemical behavior of a molecular probe: Fluorescence on-off-on response to detect multiple ions (Cu2+, ClO− and CN−) with different rate of reaction

A molecular probe 3 containing phenyl substituted imidazolyl unit and diaminomaleonitrile (DAMN) moiety has been synthesized and characterized. Photophysical and electrochemical behavior probe 3 were studied in partial aqueous medium (ACN/H2O, 9.5:0.5 v/v). Probe 3 upon interaction with different class of ions showed sensitivity for Cu2+, ClO− and CN− ions with different response time and reaction rates due to variation in intramolecular charge transfer (ICT) process. Both Cu2+ and ClO− ions displayed enhanced emission due to hydrolysis of imine bond to form compound 2 in the medium whereas, with CN− fluorescence quenching was observed due to the deprotonation of –OH/–NH2 functions. The kinetic and optical behavior of the probe suggested that interaction occurred in two steps with Cu2+ (complexation and hydrolysis; absk1,2,3(Cu2+) = 1.17, 0.74 and 0.06 s−1) and ClO− (hydrolysis and deprotonation; absk1,2(ClO−) = 3.0 and 0.60 s−1) ions while CN− (absk1,2(CN−) = 2.13 and 1.66 s−1) induces deprotonation in one step. The interaction of probe 3 with ClO− was relatively fast than with Cu2+/CN− ions. Job's plot analysis between probe 3 and ions revealed a 1:1 (Cu2+/ClO−) and 1:2 (CN−) ratio stoichiometry with good limit of detection (nM) and binding affinity (LOD, 17; KCu2+ = 3.23 × 106 M−1; LOD, 18.5; KClO− = 5.23 × 105 M−1 and LOD, 23.2; KCN− = 5.50 × 109 M−2) respectively. Probe 3 displayed a naked–eye sensitive fluorescence response to detect tested ions on test paper strips and good recovery percentage of ions in real water sample analysis.

A spatial hue smartphone-based colorimetric detection and discrimination of carmine and carminic acid in food products based on differential adsorptivity

A novel, portable, disposable, affordable, and environmentally friendly paper-based analytical device (PAD) was designed for on-site determination of carmine and carminic acid. This platform utilized paper test strips with a chitosan coating as an adsorption layer, which was characterized using scanning electron microscope, energy-dispersive X-ray analysis, and water contact angle measurement. Carmine and carminic acid could be efficiently adsorbed on chitosan-coated paper test strips, producing distinct colors that could be captured using a smartphone camera without the need for an elution step. Notably, by utilizing the Hue component of the HSL model, it was possible to differentiate between carmine and carminic acid, confirming their presence in a sample. Furthermore, the color saturation intensity changed in a concentration-dependent manner, allowing for the determination of carmine and carminic acid concentrations in the ranges of 200–800 μg/mL and 20–100 μg/mL, respectively. Additionally, the created test strip could be used to measure the percentage of carminic acid in the presence of carmine. The developed PAD enabled the quantification of carmine in various food samples without the need for reagents or complex equipment. The environmental impact of this method was found to be positive based on assessments using GAPI and AGREE tools.

Dual-channel fluorescent sensor for rapid Cu2+ and Fe3+ detection: Enhanced sensitivity and selectivity with triazole-substituted acridinedione derivative

The AR-2 sensor, derived from a triazole-substituted acridinedione, exhibits distinct responses to Cu2⁺ and Fe³⁺ ions. It shows fluorescence enhancement in the presence of Cu2⁺ ions and a reduction in fluorescence with Fe³⁺ ions. This sensor is distinguished by its high sensitivity, selectivity, rapid response time, reversibility, and broad operating pH range, with shallow detection limits for both ions. Structural and photophysical analyses of AR-2 were conducted using density functional theory (DFT) and various spectroscopic techniques. The binding modes and recognition mechanisms for Cu2⁺ and Fe³⁺ ions were elucidated through multiple experimental approaches. Additionally, AR-2 demonstrated efficacy in the rapid, visual detection of these ions via paper test strips and swab tests. It successfully identified Cu2⁺ and Fe³⁺ ions in real water and food samples, achieving notable recovery rates. The AR-2 sensor also excelled in fluorescence imaging, effectively visualizing iron and copper pools in seed sprouts.

A Dicyanoisophorone-based Fluorescent Turn-on Probe for Rapid Detecting Thiophenol in Aqueous Medium and Living Cell Imaging

A novel colorimetric and fluorescent thiophenol probe based on dicyanoisophorone has been successfully achieved, which has low-cost, easy operation, high selectivity, sensitivity and stability. The chemosensor shows a large Stokes shift and approximately 170 nm when excited at 510 nm. ISO-DiNO2 could be utilized as “Turn-on” and a naked-eyes chemosensor to detect PhSH, which is accompanied by a distinct color shift from red to dark purple with strong red fluorescence at 365 nm UV-light. Its limit of detection was determined to be 1.15 μM. More importantly, ISO-DiNO2 can react instantaneously (<10 s) with PhS−. In addition, ISO-DiNO2 has been utilized in test paper strips, water sample together with imaging of PhS− in living Raw264.7 cells, demonstrating that ISO-DiNO2 has excellent and promising applications.

Precise intramolecular-charge-transfer property modulation of D-A-type fluorescent probes for bifunctional detection of phosgene and nerve agent

Chemical warfare agents such as phosgene and nerve agents pose severe threats to national defense and public safety, yet the development of bifunctional ratiometric fluorescent probes for them is still in its infancy. Aimed at this target, an intramolecular-charge-transfer (ICT) modulation strategy via incorporating donors with varied electron-donating ability, is put forward. Based on it, a series of donor(D)-acceptor(A)-type fluorescent probes are designed and synthesized. It is found that as the ICT strength of probes weakens, a ratiometric fluorescent probe with bi-analyte identification of phosgene and diethylchlorophosphate (DCP, the mimic of nerve agent sarin) is gained. Upon exposure to phosgene and DCP, 3-(benzo[d]thiazol-2-yl)-4′-(1,2,2-triphenylvinyl)-[1,1′-biphenyl]-4-amine (BTTPE), with the weakest ICT property, presents discriminative bathochromic shifts (Δλem = 58 nm for phosgene and Δλem = 152 nm for DCP) and favorable limits of detection (LODs in solution: 6.42 nM for phosgene; 6.80 µM for DCP). Besides, the prepared BTTPE-based paper test strips combined with a smartphone can detect phosgene vapor under the colorimetric-fluorescent dual-mode sensing and enable the visual recognition and quantitative detection of DCP vapor, with LODs in the vapor phase of 0.29 ppm for phosgene and 0.49 ppm for DCP. Hereby, this work not only provides the ICT modulation strategy for the first time to realize the ratiometric fluorescence detection of phosgene/DCP but also opens up a new avenue for tailoring multifunctional fluorescent probes.

Detecting dissolved mercury(ii) ions using chitosan-AgNP strips integrated with smartphones.

A simple preparation of a paper strip test with a smartphone-based instrument for detecting dissolved mercury is still in development. This study aims to develop a smartphone-based colorimetric paper strip test using chitosan-stabilized silver nanoparticles for detecting dissolved mercury. The method demonstrated high sensitivity and selectivity for Hg2+ ions, with detection limits comparable to UV-vis spectrophotometry. Silver ions embedded in the chitosan matrix were reduced by either sodium NaBH4 or N2H4. Both chi-AgNP colloidal and chi-AgNP paper strips were tested for sensitivity of mercury(ii) solution detection with and without ion interference. The accuracy of colour change responding to the mercury concentration was recorded with several smartphones in a handmade cubical and a T-shape micro-studio. Only NaBH4 gives colloidal chi-AgNPs relatively dispersed, and the colloidal chi-AgNPs become aggregated when AgNP interacts with mercury(ii) ions. The colour change of chi-AgNP paper strips responding to the concentration of mercury(ii) and quantified using a smartphone is consistent when confirmed with UV-vis spectrophotometric determination with a comparable limit of detection (0.76 μM). The inferring ions do not significantly affect mercury(ii) analyses. Therefore, the paper strip integrated with the smartphone is effectively used for mercury(ii) detection in water as long as the mercury concentration is >1 μM. This finding might inspire advanced technology with a larger number of data references, and machine learning involvement to develop more compatible and simple mercury detection.

Colorimetric detection of alkaline phosphatase on paper microfluidic test strip based on the in-situ formation of gold nanoparticles

Affordable alkaline phosphatase enzyme detection methods are essential for diagnosing hepatic diseases. In this work, an in-situ formation of gold nanoparticles was utilized to develop a colorimetric method to detect alkaline phosphatase. Alkaline phosphatase dephosphorylates the substrate 2-phospho-L-ascorbic acid and produces ascorbic acid. Ascorbic acid, thus formed, is a good reducing agent that reduces Au3+ ions to gold nanoparticles. Alkaline phosphatase concentrations from 20 U/L to 400 U/L were spectrophotometrically detected using the surface plasmon resonance properties of the in-situ formed gold nanoparticles. The detection shows a sensitivity of 0.004 ± 0.0002 (a.u)/(U/L), a limit of detection of 2.8 mU/L, and a limit of quantification of 9.5 mU/L. A three-dimensional microfluidic paper test strip was fabricated to translate this detection method into a point-of-care testing device. The blue color formed on the paper was scanned, and the color intensities were analyzed using image processing. The three-dimensional microfluidic paper-based analytical devices could detect alkaline phosphatase concentration from 20 U/L to 400 U/L with an improved sensitivity of 0.0980 ± 0.0016 (a.u)/(U/L). The limit of detection and limit of quantification of the analysis on the paper strip was 0.748 U/L and 2.49 U/L, respectively.

Visual‐Detection of Cu2+ in DMSO aAqueous Solution Based on Benzimidazole Azo‐dye as a Colorimetric Chemosensor

AbstractIn this work, a novel colorimetric chemosensor (BIAD) containing azo chromophore, 1,5dihydroxynaphthalene, and benzimidazole was synthesized and characterized by using IR, 1H,13C NMR, and mass spectral data, and elemental analysis. The cation recognition studies (including fourteen metal cations) exhibited that the synthesized azo dye can act as a rapid, sensitive, and selective colorimetric chemosensor for detecting Cu2+ ions. The addition of Cu2+ ions to the BIAD solution, changed immediately the solution color from purple to blue‐green, which could be observed by the naked eye. Comparison of the UV/Visible spectra of BIAD and (BIAD+Cu2+) revealed a red shift from 543 nm to 616 nm, which confirms the formation of a complex between Cu2+ cations and BIAD molecules. The result of Job's plot indicated that the stoichiometry binding ratio of BIAD to Cu2+ is 1 : 1. The limit of detection (LOD) was found for BIAD toward Cu2+ ion to be 0.10 μM. Furthermore, the BIAD‐based test paper strips were successfully used for the rapid detection of Cu2+ ions (&lt;1 sec) in the aqueous solution (H2O‐DMSO, 9 : 1).

A self-assembled nanoprobe for rapid detection of hypochlorite in pure water and its application in living cells, food and environmental systems

As an important ROS species participating in various physiological and pathological processes, high level of hypochlorite (ClO−) poses significant health and safety concerns, necessitating efficient detection methods. Herein, this study introduces a water-soluble fluorescent nanoprobe Nano-SJD, effectively detect ClO− in both food samples and living cells. The small molecular probe SJD with N, N-dimethylthiocarbamyl (DMTC) as recognition moiety was constructed based on a naphthalene derivative. To further improve the water solubility, SJD was assembled with an amphiphilic copolymer (mPEG-DSPE) to prepare a water soluble fluorescent nanoprobe Nano-SJD. Fortunately, the nanoprobe preserves the excellent properties of small molecules and performs very well optical response to ClO− in aqueous solution, possessing the advantages including ultra-rapid response (within 1 s), minimal interference, low detection limits (0.39 μM) and good pH stability. What's more important, we have also developed smartphone-compatible test paper strips for convenient on-site detection of ClO− in real-water samples. Additionally, the robust fluorescent imaging behavior of Nano-SJD for visualization of ClO− in living cells highlights its broad potential in biosystem applicability.

A Ratiometric Fast-Response Fluorescent Probe Based on Dicyanoisophorone for Monitoring HClO in Paper Test Strips and Living Mice.

A new dicyanoisophorone-based ratiometric fluorescent probe NOSA was synthesized and characterized. It showed a fast fluorescence response to HClO with the emission color change from dark green to bright red. NMR, IR, and HRMS suggested that the detection of NOSA to HClO may originate from the hydroxyl deprotection reaction by HClO on the molecule NOSA, which caused a red-shift of fluorescence. The probe NOSA displayed high selectivity and excellent anti-interference performance with a limit of detection at 3.835 × 10-7M. The convenient paper test strips were successfully obtained and applied to the detection of HClO based on fluorescence color change with the varied NaClO concentration. Moreover, spiked recovery experiments in real water samples indicated that the probe NSOA could quantitatively detect HClO, and the fluorescence bio-imagings in vivo were carried out, and HClO detection in biosystems using NOSA was realized.

Dual-emissive gold nanocluster / polylysine complex for ratio and visual luminescent detection

Heavy metals pollution shows a serious threat to global human and animal populations. Especially, mercury ions (Hg2+) are non-biodegradable and could accumulated through the food chain, causing severe damage to central nervous system and immune system. The sensitive and rapid detection of Hg2+ is important for human safety. In this study, based on the host–guest interaction between D-penicillamine (DPA) modified AuNCs and polylysine (PLL), a AuNCs@PLL complex system is constructed. The network of PLL enhances the luminescence properties of AuNCs through electrostatic interaction and hydrogen bonding. In combination with the blue emission of PLL, the AuNCs@PLL complex exhibits dual-emitting luminescence, which could be employed as a promising luminescent probe for Hg2+ detection. The high-affinity metallophilic Hg2+-Au+ interactions leads to the decomposition of AuNCs and consequently quenches the red emission, but the blue emission originating from PLL is unaffected. Based on this characteristic, a ratio luminescent probe targeted for quick accurate detection of Hg2+ is developed. Furthermore, paper test strips were fabricated employing the AuNCs@PLL luminescent probe for visual semi-quantitative Hg2+ detection. In addition to the benefits for sustainable development of the environment, health of the human, this study also has theoretical values for understanding the mechanism of NCs self-assembly.

An investigation of the Excitation Wavelength-Dependent Dynamic Changes in the Mechanism of Detection of Picric Acid using Pyrene-Based Donor-Acceptor Systems.

Picric acid (PA) is an important industrial feedstock and hence the release of industrial effluents without proper remediation results in its buildup in soil and water bodies. The adverse effects of PA accumulation in living beings necessitate the development of efficient methods for its detection and quantification. Herein, we describe pyrene-based fluorescent sensors for PA, where pyrene is appended with electron-withdrawing groups, malononitrile, and 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene) malononitrile (DCDHF). These molecules displayed the typical emission of pyrene monomers, as well as a broad red-shifted emission resulting from an intramolecular charge transfer (ICT) in the excited state. Both the emissions displayed a turn-off response to PA with high selectivity and sensitivity and the lowest limit of detection was estimated as 27 nM. To prove the feasibility of on-site detection, test paper strips were prepared, which could detect PA up to 4.58 picograms. Using a combination of experimental and theoretical studies the mechanism of the detection was identified as primary/secondary inner filter effect, oxidative photoinduced electron transfer, or a combination of both depending on the excitation wavelength. Interestingly, the contribution of each of these mechanisms to the total quenching process varied with a change in the excitation wavelength.

Ultra-selective pyrene-based fluorescent sensor for detection of Fe+3 in neat aqueous medium

Transition metals, particularly Fe+3, play vital roles in biological and environmental systems, yet their chronic elevation can lead to severe diseases. Early detection of Fe+3 is crucial for diagnosing associated ailments. While traditional detection methods have drawbacks, fluorescent sensors offer promising alternatives due to their ease of use, cost-effectiveness, and real-time monitoring capability. Pyrene-based sensors have demonstrated notable sensitivity and selectivity for Fe+3, but challenges remain in achieving applicability in neat aqueous systems. We present two novel turn-off pyrene-based sensors, APTS (sodium 8-aminopyrene-1,3,6-trisulfonate) and APSS (sodium (E)-4-hydroxy-3-((pyren-1-ylimino)methyl)benzenesulfonate), incorporating sulfonate groups to enable their use in pure water samples and achieve nanomolar-level detection limits. Through meticulous experimental and characterization efforts, we elucidate the significance of the imine linkage in enhancing selectivity towards Fe+3 ions. Our sensors exhibit exceptional selectivity and sensitivity, with LODs of 45.6 nM and 45.9 nM for APTS and APSS, respectively, surpassing environmental protection guidelines. Additionally, binding stoichiometry studies reveal insights into the interaction mechanisms, supported by fluorescence lifetime analysis and DFT studies. APSS particularly stands out for its lack of interference from other metal ions, notably Cu2+ as well as Fe2+, offering promising potential for real-time applications and development of paper strip tests. The practical applicability of our sensors is demonstrated through successful Fe+3 detection in various water samples with recoveries ranging from 94 % to 104 %. Overall, our study highlights the effectiveness of APTS and APSS as robust fluorescent probes, with implications for environmental monitoring and biomedical diagnostics.