Sensing of aluminum and cyanide ions utilizing a novel bis-phenol a based fluorogenic probe: Applications in test stripts

A highly efficient, selective, reversible and ultra-sensitive fluorescence "Turn-ON" chemosensor for aluminium ions by a novel Schiff base

The synthesis of a Schiff base-based chemosensor, denoted as H6L, was accomplished through the condensation reaction of Isophthalohydrazide and 2,6-dihydroxybenzaldehyde in an ethanol solvent. The resulting compound was further characterized using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, as well as high-resolution mass spectrometry (HRMS). Extensive research has been conducted on several facets of metal sensing phenomena, revealing that the Schiff base H6L demonstrates discerning and expeditious fluorescence sensing characteristics specifically towards Al (III) in acetonitrile. The purported method detects Al (III) can be ascribed to the suppression of photo-induced electron transfer (PET) and the enhanced chelation-induced fluorescence (CHEF). The stoichiometry of metal-ligand complexes (2:1) was determined using Job's plots titrations, HRMS and subsequently confirmed using NMR titration studies. The H6L sensors demonstrated remarkable fluorescence sensing capabilities in acetonitrile, with a low detection limit (LOD) of 0.44 μM. This LOD is suitably low for the detection of Al3+, which is commonly found in many environmental and biological systems. Fluorescence lifetime measurement provides additional evidence of complexation of H6L with Al (III). The reversibility of the sensor was demonstrated through the introduction of pyrophosphate (PPi), which forms a complex with aluminium ions, thereby releasing the chemo sensor for subsequent utilization. The findings suggest that H6L has the potential to serve as a viable probe for the detection and identification of Al3+ ions.

Development of a bisphenol A based chemosensor for Al3+ and its application in cell imaging and plant root imaging

Bisphenol A is a fluorophoric platform that is used to develop chemosensors for various species. Herein, we report a bisphenol A based Schiff-base molecule, 4,4'-(propane-2,2-diyl)bis(2-((E)-((2-hydroxy-5-methylphenyl)imino)methyl)phenol) (Me-H4L), as a selective chemosensor for Al3+. Among the several metal ions, it shows a significant increment in its fluorescence intensity (50 fold) at 535 nm in the presence of Al3+ ions. The enhanced fluorescence was attributed to the CHEFF mechanism and inhibition of CN isomerization. The limit of detection value of Me-H4L for Al3+ was determined to be 9.65 μM. Its quantum yield and lifetime increased considerably in the presence of the cation. Some theoretical calculations were performed to explain the interaction between Al3+ and the probe. Furthermore, Me-H4L was applied in cell imaging studies using animal cells and plant roots.

A red fluorescent carbon dots with good water solubility for rapid detection of Al3+ in actual samples

We developed a facile strategy for the fabrication of red fluorescent carbon nanodots (R-CDs) and demonstrated their applications for Al3+ sensing. Red-emission carbon dots (CDs) were synthesized using a simple hydrothermal treatment with citric acid and urea as precursors, manifesting intriguing red-emission behaviour at 610 nm. With increasing Al3+ concentration, the fluorescence band at 610 nm decreased gradually. Monitoring the intrinsic fluorescence variation (I610nm ), as-prepared CDs were developed as an effective platform for fluorescent Al3+ sensing, with a linear range of 0.5-60.0 μM and a detection limit of 3.0 nM. More importantly, R-CDs have been applied successfully to the analysis of Al3+ in actual samples with satisfactory recoveries in the range 97.12-102.05%, which indicated that obtained CDs could be implemented as an effective tool for the identification and detection of Al3+ in actual samples.

A photochromic salicylaldehyde hydrazone derivative based on CN isomerization and ESIPT mechanisms and its detection of Al3+ in aqueous solution

A simple photochromic Schiff base was successfully prepared by the condensation of salicylaldehyde and benzoyl hydrazine. This compound has reversible photochromic properties based on isomerization and ESIPT mechanisms. In organic solvents, after irradiation with 365 nm UV light for 2 min, the absorption peak at 367 nm of the compound showed a significant decrease, while a double absorption peak appeared at 418 nm and 438 nm, accompanied by a significant change of the solution color from colorless to yellow. The compound can also complex with Al³⁺ at the molar ratio of 2:1 in the water solution (acetonitrile/water, v/v, 1:99), resulting in significantly enhanced fluorescence of the compound, so as to achieve fluorescence detection of Al³⁺ in living cells and water samples.

Aggregation induced emission based fluorenes as dual-channel fluorescent probes for rapid detection of cyanide: applications of smartphones and logic gates

Rational modification of molecular structure by incorporating electron donating groups can play a potential role for designing aggregation induced emission (AIE) active fluorescent probes. Based on this principle, fluorescent probes (1a–c) were synthesized, and they displayed excellent aggregation induced emission (AIE) behavior in a H₂O/DMF (4 : 1, v/v) mixture due to restrictions in intramolecular charge transfer (ICT). As a comparison, probe 1d was synthesized by installing an electron withdrawing (–NO₂) group that surprisingly quenched the aggregation behaviour. Additionally, AIE active probes 1a–c displayed a highly sensitive dual channel (fluorometric and colorimetric) response towards rapid detection of CN⁻, which is an active toxic material. Probes 1a–c showed selectively enhanced fluorescence emission behavior towards CN⁻ with detection limits of 1.34 ppb, 1.38 ppb, and 1.54 ppb, respectively. The sensing mechanism involves Michael type adduct formation due to the nucleophilic addition reaction of cyanide with probes and was confirmed through ¹H NMR titration experiments. In contrast, probe 1d containing an electron withdrawing moiety showed insensitivity towards CN⁻. Therefore, this study provides the efficient strategy to induce AIE character in fluorescent probes and expands the mechanistic approach toward the sensing of toxic CN⁻.

Rational modification of molecular structure by incorporating electron donating groups can play a potential role for designing aggregation induced emission (AIE) active fluorescent probes.

Quinoline based thiosemicarbazones as colorimetric chemosensors for fluoride and cyanide ions and DFT studies

High toxicity and extensive accessibility of fluoride and cyanide ions in diverse environmental media encouraged attention for scheming well-organized probes for their detection. Keeping in mind we have designed and synthesized thiosemicarbazone-based chemosensors RB-1, RB-2 and RB-3 for the detection of fluoride and cyanide ions. The structural elucidation of the synthesized chemosensors is done by employing different analytical techniques including nuclear magnetic resonance and electronic absorption specrtoscopies. Admirable detection limit, binding constant and fast response time (2 s) to F- and CN- ions enlarged the applications of these chemosensors. Additional confirmation of the sensing ability of these chemosensors is derived from DFT and TDDFT calculations with M06/6-311G(d,p) method by performing FMO, UV-Vis, QTAIM and global reactivity parameters elucidation. Overall results point out that investigated chemosensors are suitable candidates for sensing the F- ions. These chemosensors were successfully applied to detect F- ions in a commercial toothpaste sample.

A Zn(II)-Based Sql Type 2D Coordination Polymer as a Highly Sensitive and Selective Turn-On Fluorescent Probe for Al3

A luminescent coordination polymer with the overall formula {[Zn(tr2btd)(bpdc)]∙DMF}n (where tr2btd = 4,7-di(1H-1,2,4-triazol-1-yl)-2,1,3-benzothiadiazole; bpdc = 4,4'-biphenyldicarboxylate) was synthesized and characterized by single-crystal and powder X-ray diffraction, thermogravimetric, infrared spectroscopy, and elemental analyses. Luminescent properties of the obtained compound were studied in detail both in the solid state and as a suspension in N,N-dimethylacetamide (DMA). It was found that {[Zn(tr2btd)(bpdc)]∙DMF}n exhibits bright turquoise luminescence with excellent quantum efficiency and demonstrates turn-on fluorescence enhancement effect upon soaking in DMA Al3+ solution. Fluorescence titration experiments were carried out and the detection limit for Al3+ ions was calculated to be 120 nM, which is among the lowest reported values for similar materials. Moreover, compound demonstrated excellent selectivity and reusability, and the mechanism of the response is discussed. These results indicate that {[Zn(tr2btd)(bpdc)]∙DMF}n is a promising probe for sensitive fluorescent Al3+ detection.

A Novel Schiff Base-Modified Dialdehyde Cellulose-Based Fluorescent Probe for Al3+ and Its Application in Environmental Analysis

Cellulose is the most abundant natural polymer with good biodegradability and biocompatibility. In this paper, a novel fluorescent probe DAC-SD-NA for aluminum (Al³⁺ ) detection is successfully synthesized based on dialdehyde cellulose (DAC). DAC-SD-NA exhibited a remarkable "turn-on" fluorescence response to Al³⁺ in a wide pH range, and the fluorescence color of DAC-SD-NA solution turned from colorless to bright blue at the presence of Al³⁺ . The detection limit for Al³⁺ is computed to be 6.06×10^-7 m. The reaction mechanism of DAC-SD-NA towards Al³⁺ is confirmed by Job's plot, X-ray photoelectron spectroscopy, and density functional theory (DFT) calculations. In view of DAC-SD-NA exhibited good sensitivity and selectivity, it is applied to detect Al³⁺ in real water. What's more, DAC-SD-NA-loaded fluorescent hydrogel can serve as a convenient tool for the detection of Al³⁺ .

Cyanobiphenyl-spiropyrane and -hemicyanine conjugates for cyanide detection in organic/aqueous media through reverse ICT direction: Their practical applications

Cyanide is one of the most known toxic substances. It is used in many industries and threats human health and environment through releasing with wastewater. Therefore, it is very important to detect its accurate amount, rapidly. Herein, turn-on and turn-off fluorescence sensors of hybrid cyanobiphenyl-spiropyrane and -hemicyanine were developed for the detection of CN^- ions on the basis of nuchleophilic addition to indolium moiety. Detection behavior of the both probes toward a series of anions was investigated by means of fluorescence, UV-vis, NMR and TOF-MS techniques. The results obviously indicate that both probes show remarkable spectral changes and high selectivity toward CN^- with respect to other tested anions. Cyanide levels in water samples up to 0.208 μM could be quantitatively detected as practical application. A smartphone imaging application was successfully constructed for CN^- detection. Noticeably, production of cotton kids and PSF capsules revealed that the probe could be conveniently used for on-site measurement of cyanide without complicated instruments.

Phenolphthalein Conjugated Schiff Base as a Dual Emissive Fluorogenic Probe for the Recognition Aluminum (III) and Zinc (II) Ions

In this study, a new phenolphthalein derivative, FFIZNA, has been planned and successfully prepared in an uncomplicated way. The probe FFIZNA could selectively monitor Al³⁺ and Zn²⁺ among other relevant cations with diverse colors through a turn-on emission response in EtOH:HEPES (9/1;v/v) media owing to the chelation enhanced fluorescence (CHEF), prevention of ESIPT, -C=N- isomerization and PET of the probe FFIZNA. The interactions of Al³⁺ and Zn²⁺ with the probe FFIZNA were confirmed by emission spectroscopy, Job's plot and ¹H-NMR titration substantiated 1:2 reaction stoichiometry between FFIZNA and Al³⁺ and Zn²⁺. The time-response study displayed that the emission of FFIZNA with Al³⁺ and Zn²⁺, rapidly boosted and reached the stable value in less than 3.0 and 4.0 min, respectively. Therefore, the FFIZNA has successfully been utilized to the dual recognition of Al³⁺ and Zn²⁺ in solutions. Phenolphthalein conjugated schiff base as a dual emissive fluorogenic probe for the detection aluminum (III) and zinc (II) ions.

1,8-Naphthalimide appended propiolate-based fluorescent sensor for selective detection of cysteine over glutathione and homocysteine in living cells

A novel 1,8-naphthalimide-based fluorogenic chemoprobe NASP was designed and developed as a sensor platform for the selective detection of biologically important cysteine over glutathione and homocysteine in living-cells.