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Herein, oxygen-doped g-C3N4 quantum dots (OCNQDs) were fabricated through sintering and ultrasonic-assisted liquid-phase exfoliation methods. The obtained OCNQDs with uniform size show high crystalline quality, and the average diameter is 6.7 ± 0.5 nm. Furthermore, the OCNQDs display excellent fluorescence properties, good water solubility, and excellent photo stability. The OCNQDs as fluorescence probe show high sensitivity and selectivity to Fe3+ ions. Furthermore, the fluorescent OCNQDs are applied for live cell imaging and Fe3+ ions detecting in living cells with low cytotoxicity, good biocompatibility, and high permeability. Overall, the fluorescent OCNQDs fabricated in this work can be promising candidates for a range of chemical sensors and bioimaging applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple single step multicomponent ugi type reaction was carried out to yield N-(tert-butyl)-2-(furan-2-yl)imidazo[1,2- a ]pyridine-3-amine (TBFIPA). • The synthesized TBFIPA was characterized using 1H NMR, 13C NMR and HRMS spectroscopic methods. • The selective & sensitive detection was identified using hypsochromic shift (lab : 335nm → 285nm) & fluorescence quenching. • The proposed mechanism is evident from Job plot, 1H NMR titration, ESI-MS data and theoretical DFT calculation. • The Cr3+ ion-selective TBFIPA was successfully applied in the design of a user-friendly silica-based portable test kits. • Also, the fluorescence quenching ability of TBFIPA in presence of Cr3+ ions are validated by imaging onion epidermal cells. • Real samples contaminated with Cr3+ ions were identified using TBFIPA with an appropriated relative error percentage. A simple single step one pot multicomponent reaction was performed to synthesize N-(tert -butyl)-2-(furan-2-yl)imidazo[1,2- a ]pyridine-3-amine (TBFIPA). The synthesized TBFIPA was subjected to library of cations to study its ability for selective and sensitive detection of specific metal ions. Selective detection of chromium ions by TBFIPA were found from the significant hypsochromic shift (335 nm → 285 nm) in the UV–Visible spectra. The fluorescent TBFIPA displays complete quenching of fluorescence under UV lamp (365 nm) only in the presence of chromium without the interference of common metal ions. Binding constant (k a) obtained from Benesi-Hildebrand plot is 0.21 × 105 M−1, limit of detection (LOD) and limit of quantification (LOQ) of TBFIPA toward Cr3+ ions are 4.70 × 10−7 M and 1.56 × 10−7 M, respectively. The mechanism proposed during complex formation were supported by stoichiometric Job continuous variation plot, 1H NMR titration and ESI-MS spectroscopic data. All the experimental confirmation for complex formation were corroborated with theoretical DFT studies optimized using RB3LYP/6-31G(d) basis set. The selectivity and sensitivity of TBFIPA toward Cr3+ ions are found suitable to design a user-friendly silica based portable test kit. Alongside, TBFIPA was successfully utilized for imaging onion epidermal cells. Furthermore, the results obtained for biological, environmental, and industrial samples provided solid evidence to estimate chromium ions using TBFIPA in these real samples. [ABSTRACT FROM AUTHOR]

A general synthetic method was improved to synthesize a chemosensor based on a tripodal Bodipy (t-BODIPY) structure. The product and its intermediate products were successfully prepared and fully characterized. The metal ion sensing performance of the tripodal compound was evaluated by UV/Vis and fluorescence spectroscopies. According to the obtained data, t-BODIPY is a selective and sensitive fluorescence probe for detection of Cu2+ ions in the presence and in the absence of competing ions. This chemosensor presents relatively a low detection limit of 5.4 x10-7 M for Cu2+. Bio-imaging studies on living yeast cells suggest that t- BODIPY has some advantages over other chemosensors to recognize copper (II) ions. [ABSTRACT FROM AUTHOR]

A commercially available probe (RS) has been reported for instantaneous selective colorimetric detection of Cu(II) and fluorescent detection of Al(III) ions in H2O:DMSO (90:10% v/v) medium. The probe displays a color change from pale yellow (kab 352 nm) to yellowish-green (kab 411 nm) with Cu(II) and a change in emission from green (tex 340nm; tem 522 nm) to bluish-green (tem 489nm) with Al(III) ions. The optical detection of these metal ions by RS is via the formation of tetragonally distorted octahedral RS-Cu(II) and tetrahedral RS-Al(III) complexes as evidenced from the results of UV-Vis, 27Al & ¹H NMR, HRMS, EPR and thermal analysis studies. Job's method indicates that the stoichiometry of both these complexes is 1:1. The probe's corresponding optical changes are particular for Cu(II) and Al(III) ions in the presence of other metal ions. RS displays high selectivity to these ions in a wide pH range. The limits of the detection of Cu(II) and Al(III) are as low as 66nM and 0.83 mM, respectively. Further, RS could be applied as a fluorescent probe for observing Al(III) ions in living HeLa cells by carrying out cell image studies.A commercially available probe (RS) has been reported for instantaneous selective colorimetric detection of Cu(II) and fluorescent detection of Al(III) ions in H2O:DMSO (90:10% v/v) medium. The probe displays a color change from pale yellow (kab 352 nm) to yellowish-green (kab 411 nm) with Cu(II) and a change in emission from green (kex 340nm; kem 522 nm) to bluish-green (kem 489nm) with Al(III) ions. The optical detection of these metal ions by RS is via the formation of tetragonally distorted octahedral RS-Cu(II) and tetrahedral RS-Al(III) complexes as evidenced from the results of UV-Vis, 27Al & 1H NMR, HRMS, EPR and thermal analysis studies. Job's method indicates that the stoichiometry of both these complexes is 1:1. The probe's corresponding optical changes are particular for Cu(II) and Al(III) ions in the presence of other metal ions. RS displays high selectivity to these ions in a wide pH range. The limits of the detection of Cu(II) and Al(III) are as low as 66nM and 0.83 mM, respectively. Further, RS could be applied as a fluorescent probe for observing Al(III) ions in living HeLa cells by carrying out cell image studies. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) are drawing tremendous attention due to their unique photoluminescence property and fascinating functions. Herein, we prepared novel CQDs functionalized with amino acids (AA-CQDs) by a one-pot hydrothermal method for selective detection of Al3+ ions and fluorescence imaging. The prepared AA-CQDs exhibit a novel triple-excitation and single-colour emission for fluorescent property. In addition, the AA-CQDs have a high absolute quantum yield (24.23%) and quantum lifetime (13.29 ns). Moreover, the AA-CQDs exhibit high selectivity and sensitivity for Al3+ by fluorescence enhancement. In pH 7.4 PBS solution, there was a good linear relation between the fluorescence intensity and the concentration of Al3+ in the range of 1–20 μmol L−1; the limit of detection (3σ) was only 0.32 μmol L−1. Furthermore, an AA-CQD probe was also utilized for detection of Al3+ in living cells based on excellent biocompatibility and endocytosis. Based on the concentration of Al3+ ions in cells and apoptosis data, there will be a quick reflect of apoptosis induced by aluminium ions via the fluorescence intensity of the AA-CQD probe. This work will set the stage for developing novel CQD-based biosensors in cell research. [ABSTRACT FROM AUTHOR]

[Display omitted] • PET based Probe 7 showed selectivity for Hg2+ and H+ ion in phosphate buffer (10 % DMSO). • Probe 7 displayed "turn – On - Off" emission in acidic and alkaline medium • Probe 7 exhibited sensitivity to visualize lysosomes and Hg2+ ion in live cells. • Probe 7 on test paper strips, showed naked-eye sensitive green color with Hg2+. A 1,5–bis(1,4-piperazinyl–naphthalimide– N –ethylmorpholine) pyridine based flexible fluorescence probe 7 is designed, synthesized, and its photophysical behavior has been examined in different media. The photophysical behavior of probe 7 in phosphate (PBS) buffer (10 % DMSO) showed pH sensitivity and selectivity for Hg2+ ion in solution and live cell with a change in naked-eye sensitive visible color. In acidic medium (pH ≤ 6) probe 7 showed enhanced (∼21 fold) "turn–On" emission, while at pH ≥ 7.4 probe 7 remained in the "turn–Off" state. The observed fluorescence "turn–On" response is attributed to inhibition in photoinduced electron transfer (PET) process. Jobs plot analysis revealed a 1:2 stoichiometry for an interaction between probe 7 and Hg2+ ion with good limit of detect (LOD) 5.78 × 10−8 M (57 nM). The reversibility in complexation and the mode of interaction were confirmed by EDTA and through NMR and HRMS spectroscopic data. MTT assay and cell imaging studies showed biocompatibility of the probe 7 to detect lysosomes and Hg2+ ion in A549 cells. For analytical application paper strip test was performed to detect Hg2+ ion with naked-eye sensitive visible color change. [ABSTRACT FROM AUTHOR]

A novel boron dipyrromethene (BODIPY)‐based fluorescent probe BDP−Pd was designed and synthesized. Upon coordination with Pd2+, the emission of the probe at 508 nm significantly increased, showing an 'OFF‐ON' fluorescence response. The complexation of BDP−Pd with Pd2+ in both acetonitrile and aqueous solution were then studied by absorption and fluorescence spectra. The binding stoichiometry between the probe and Pd2+ was found to be 1 : 2, and the binding constant was determined to be 8.5×1010 M−2 and 8.2×1010 M−2 in acetonitrile and aqueous solution, respectively. The probe exhibited a detection limit as low as 0.72 ppb toward Pd2+ with no obvious interference from up to 21 species of common metal ions, suggesting BDP−Pd as a sensitive and selective fluorescent probe for Pd2+ detection. The fast fluorescence 'OFF‐ON' phenomenon of the probe upon coordination with Pd2+ ions could be easily observed by a hand‐hold UV lamp under naked eye in solution as well as on homemade test trips. Density functional theory (DFT) calculations were carried out to give the optimized structure of complex BDP−Pd : 2Pd2+ and rationalize the detection mechanism through a prohibited intramolecular photoinduced electron transfer (PET) process. The bio‐imaging application of the probe was investigated and it showed excellent cell permeability for fluorescent imaging of Pd2+ ions in A549 human non‐small cell lung cancer cells. [ABSTRACT FROM AUTHOR]

The synthesis of a novel, and highly selective Fe3+ ion sensor based on anthrone‐spirolactam and its quinoline hybrid ligand is reported. The designed ligand displayed selective detection of Fe3+ ions with enhanced fluorescence emission. The complexation of Fe3+ ion led to a red shift of 32 nm from 420 nm to 452 nm, and a several fold increase in intensity with fluorescent green emission. The complexation (detection) of Fe3+ ions with ligand resulted in chelation enhanced fluorescence and intramolecular charge transfer through the inhibition of C=N isomerization. This hybrid sensor shows high sensitivity and selectivity, spontaneous response, and works on a wide pH range a minimum detection limit of 6.83 × 10−8 M. Importantly, the sensor works through the fluorescence turn‐on mechanism that overcomes the paramagnetic effect of Fe3+ ions. The binding mechanism between the ligand and the Fe3+ ions was established from the Job's plot method, optical studies, Fourier transfor infrared spectroscopy, NMR titration, fluorescence life‐time studies, and density functional theory optimization. The sensor displayed excellent results in the quantification of Fe3+ ions from real water samples. Furthermore, due to its biocompatibility nature, fluorescent spotting of Fe3+ ions in live cells revealed its bioimaging applications. [ABSTRACT FROM AUTHOR]

A near-infrared ratiometric fluorescent probe CR-Ac based on a coumarin–benzopyrylium platform has been developed for selective detection of Cu2+. The cell imaging data revealed the capabilities of CR-Ac in monitoring the dynamic changes of subcellular Cu2+ and the quantification of Cu2+ levels in living cells. [ABSTRACT FROM AUTHOR]

A novel quinoline‐imidazole hybrid conjugate chromophore, 2‐(4,5‐diphenyl‐1H‐imidazol‐2‐yl)‐4‐phenylquinoline (DIPQ), is designed, synthesized, characterized using NMR, ESI‐MS and ESI‐HRMS analyses and explored for its ability in detecting a range of biologically relevant cations. Among the various metal ions, DIPQ responds selectively to the addition of Zn2+ with a change in color from colorless to pale yellow along with characteristic green fluorescence at 564 nm. Zn2+ induced absorption and fluorescence changes of DIPQ are not affected by other commonly coexistent metal ions and anions. DIPQ‐Zn2+ binding interactions are thoroughly studied using NMR and MALDI‐MS analyses. DIPQ is capable to detect Zn2+ even at the nano‐molar levels with a limit of detection (LOD) and limit of quantification (LOQ) of 2.7×10−8 M and 8.1×10−8 M, respectively. Sample matrices have trivial impact on the Zn2+ detection ability of DIPQ. The quantitative results obtained from the DIPQ method are comparable with the ICP‐OES method. Moreover, DIPQ has a wide pH range of operation, exhibited good cell permeability and low toxicity for biological applications. Furthermore, DIPQ is suitable to detect Zn2+ ions present in biological tissues. [ABSTRACT FROM AUTHOR]

An effective ratiometric fluorescent probe based on silicon particles/gold nanoclusters (SiNPs/AuNCs) nanohybrid has been fabricated and applied to be a "on-off-on" switch sensing platform for detection of Hg2+ and cysteine. In this elaborated sensing platform, the SiNPs just acted as internal reference signal, providing a build-in correction for background interferences and environmental effects, to which the AuNCs as a signal report unit for Hg2+ response was covalently grafted by amidation reaction. The fluorescence intensity of SiNPs/AuNCs could be effectively quenched upon adding Hg2+, accompanied with an easily distinguishable fluorescent color change. The ratiometric fluorescence signal (F 649 /F 511) of the established nanoprobe was linearly proportional to the concentration of Hg2+ ranging from 0.02 to 24 μM with a low detection limit of 5.6 nM, which is below the guideline value of Hg2+ in drinking water set by the World Health Organization. Interestingly, upon addition of cysteine, the Hg2+-quenched fluorescence intensity was recovered gradually. Furthermore, the approach developed has also been utilized for Hg2+ detection in real complex biological samples with satisfactory results. More importantly, benefiting from the good water-solubility and excellent biocompatibility, this nanoprobe can monitor the intracellular Hg2+ and cysteine in living cells, indicating its potential applications in advanced biosensing and bioimaging. Herein, we reported an effective dual-emission ratiometric probe for "on-off-on" detection of Hg2+ and cysteine. Image 1 • An efficient dual-emission fluorescent probe for simultaneously and visual detecting Hg2+ and L-Cys was constructed. • The probe could simultaneously detection of Hg2+ in human serum and urine samples. • Due to the ratiometric fluorescence model, the background interference was extincted. • The developed probe was successfully used for the fluorescence bioimaging of Hg2+ and L-Cys in live cells. [ABSTRACT FROM AUTHOR]

A rhodamine based chemosensor, 3-(((2-(3′,6′-bis(ethylamino)-2′,7′-dimethyl-3-oxospiro[isoindoline-1,9′-xanthen]-2-yl)ethyl)imino)methyl)-2-hydroxy-5-methylbenzaldehyde (HL-CHO), has been developed for the detection of Al3+, Cr3+ and Fe3+ ions. The absorbance of HL-CHO at 528 nm increases significantly in HEPES buffer in methanol : water (9 : 1, v/v) (pH 7.4) in the presence of Al3+, Cr3+ and Fe3+ ions with the alteration of solution color from colorless to pink. The fluorescence intensity of the probe at 550 nm enhances by 1465, 588 and 800 fold in the presence of Al3+, Cr3+ and Fe3+ ions, respectively. To the best of our knowledge, this huge increase in fluorescence intensity with Al3+ and Cr3+ has not been observed for other rhodamine based chemosensing systems. The weak fluorescence and no coloration of the probe are due to the existence of a spirolactam ring. The trivalent cations induce the opening of the spirolactam ring and consequently change the color and the fluorescence intensity followed by the 1 : 1 complex formation with HL-CHO which are evident from Job's analysis, ESI mass spectral analysis and elemental analysis. The quantum yield and lifetime of HL-CHO have increased considerably in the presence of the trivalent cations. The high sensitivity of the probe towards all the cations is evident from the nM order of LOD values. This has been used in living cell imaging studies with the human neuroblastoma SH-SY5Y cell line. Having appended –CHO groups for Schiff-base condensation with other amines, HL-CHO could be a potential precursor for future chemosensors. [ABSTRACT FROM AUTHOR]

A novel recyclable ratiometric fluorescent probe based on MOFs was designed and synthesized by a one-step approach, which was realized by assembling Al-MOFs in an aqueous solution containing rhodamine B (RhB) as a fluorescent reagent and Fe3O4 as a magnetically recyclable reagent. The obtained fluorescent probe (Fe3O4/RhB@Al-MOFs) has two emissions under excitation at 330 nm, in which the emission at 440 nm is attributed to the Al-MOFs and the emission at 610 nm presumably originates from the RhB dye. It was noted that the probe displays responses to Mg2+ ions with fluorescence enhancement at 440 nm, whereas the fluorescence at 610 nm would be a constant reference fluorescence signal. The existence of RhB significantly improves the detection accuracy and broadens the linear range. As a result, the selectivity of Fe3O4/RhB@Al-MOFs towards Mg2+ compared to other metal ions is excellent. When the Mg2+ ions (262.5 ppm) are added, the ratio of fluorescence intensity (I440/I610) is changed from 2.47 to 11.5. The Fe3O4/RhB@Al-MOFs show a rapid detection process (90 s), high fluorescence enhancement (up to 5-fold) and a low detection limit of Mg2+ ions (8 × 10−7 M). In particular, the magnetic Fe3O4 endows Fe3O4/RhB@Al-MOFs with a high magnetic responsiveness, thus, facilitating the separation procedures. As expected, it can be easily separated and recycled without a significant loss of recognition performance after being used many times, and thus, exhibits good reusability. Meanwhile, the cell cytotoxicity experiments suggest that Fe3O4/RhB@Al-MOFs is nearly non-toxic and in vitro cell imaging experiments demonstrate that the probe is capable of successfully enhancing fluorescence from the intracellular area in HL-7702 and A375 cellular systems. Hence, it has the potential for the detection of Mg2+ ions inside biosystems. [ABSTRACT FROM AUTHOR]

We report a triazole appended imidazopyridine based chemosensor (probe 1) for sequential detection of Cu2+ and CN− ions using fluorometry. Probe 1 is fluorescent in aqueous acetonitrile (H2O‐CH3CN, 1:1, v/v) when common metal ions are present, but the fluorescence is quenched when Cu2+ is present. The binding mechanism, quantitative determination and the mode of interaction of Cu2+ with probe 1 are explained using fluorescence spectroscopy, electrospray ionization mass spectrometry and Density Functional Theory (DFT) calculations. The observed detection limit for Cu2+ is found to be (18.17×10−6 M) and it is comparable with those reported for other Cu2+ chemosensors. Further, the 1–Cu2+ complex formation is found to be reversible, and this property has been successfully exploited for the quantitative determination of CN− ions in aqueous acetonitrile. Addition of CN– leads to a complete recovery of fluorescence from 1–Cu2+ complex, permitting the real time detection with the lower limit of detection of CN− being 33.57×10−6 M. The observed experimental results are supported by DFT calculations. A possible application of 1–Cu2+ in fluorescence imaging of Rhizoctonia solani mycelia cells, contaminated with CN− ions, is also represented. [ABSTRACT FROM AUTHOR]

A new coumarin-based probe 3-acetyl-7-diethylaminocoumarinthiosemicarbazone (DCT) is synthesized for Al3+ fluorescence detection in CH 3 CH 2 OH/H 2 O (6 : 4, v / v). The fluorescence intensity at 428 nm was enhanced about 15-fold with the fluorescence changed from colorless to blue. The binding constantof Al3+ with DCT is 5.04 × 106 M−1. The limit of detection (LOD) of Al3+ is calculated to be 82 nM. Furthermore, the binding details are determined by Job's plot and ESI - MS studies, which indicated that a stoichiometric ratio of 1 : 1 complex is formed between Al3+ and DCT. Cell imaging confirmed that DCT could useful for detecting Al3+ in HepG2 cells. • Probe DCT is highly selective and sensitive towards Al3+in aqueous solution phase with LOD is 82 nM,which could monitor intracellular Al3+ levels. • The mechanism indicated that a ratio of 1 : 1 complex is formed between Al3+ and DCT. [ABSTRACT FROM AUTHOR]

A novel Schiff base fluorescence probe (HL) was synthesized by the condensation of salicylaldehyde and an 8-aminoquinoline derivative. This probe acts as a "turn-on" dual selectivity fluorescence probe for Zn2+ and Al3+ ions, providing different colors and detection limits (DL) of 11.5 and 23.5 nM, respectively. Moreover, when Zn2+ and Al3+ co-exist, HL exhibits a preference for Al3+ by displacing Zn2+ from the HL-Zn2+ complex, realizing a dual-channel signal output for Al3+. The HL-Al3+ system could further discern F− by a "turn-off" fluorescence response with a DL of 86.0 nM. Furthermore, the probe HL was capable of monitoring intracellular Al3+, Zn2+ and F− in living PC12 cells in vitro through fluorescence imaging, which proved its value in potential in vivo applications. [ABSTRACT FROM AUTHOR]

A new, bis -thiophene based Schiff base receptor A2 has been synthesized and rationally designed as rapid and highly selective fluorescence sensor for Cu2+ ion in a semi-aqueous medium. Structural characterization of A2 was confirmed by NMR, FT-IR and HRMS spectral techniques. The receptor A2 shows the colorimetric response from yellow to colorless and fluorescence "turn-on" with Cu2+ ions under visible and UV light. Both the UV–Vis and fluorescence studies were confirmed the formation of 1:1 stoichiometry complex with an estimated association constant of 1.07 × 10−5 M−1. The sensor could work in the pH range of 4.0–8.0 without interference in the presence of other interfering ions. The lowest detection limits by colorimetric and fluorescence techniques were found to be 1.18 × 10−7 M and 8.8 × 10−8 M respectively. Further, the probe was applied to image the intracellular Cu2+ ions in the HeLa cell line. The sensing mechanism was studied by ESI-mass analysis and DFT calculations. Unlabelled Image • Synthesized Schiff base receptor A2 exhibited superb selectivity for Cu2+ ion. • The lowest detection limit of Cu2+ (UV–Vis =1.18 × 10−7 M and FL = 8.8 × 10−8 M) for receptor A2 reported. • DFT calculations supported the experimental data. • The receptor A2 was used to observe Cu2+ ion in live cell imaging. • A "Turn-on" Cu2+ sensor with 19-fold fluorescence enhancement was observed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel imidazole derived bithiophene benzothiazole based sensor for the detection of Al3+ ions was developed. • The sensor DIBT effectively detect Al3+ ions with low LOD (13.7 nM). • Sensor DIBT was employed for the practical application in pharmaceutical samples. • The sensor DIBT can track Al3+ ions in live cells. Owing to the extensive application of aluminium ions (Al3+) in numerous industrial platforms, it is vital to design a chemosensor for the selective detection of Al3+ ions. Hence, we have attempted to introduce new imidazole appended bithiophene benzothiazole-based fluorescent sensor 2-(5′-(4,5-diphenyl-1H-imidazol-2-yl)-[2,2-bithiophen]-5-yl)benzo[d]thiazole (DIBT) , for the fluorescence ratiometric recognition of Al3+ ions in an aqueous medium (acetonitrile/water 8:2 v/v). We employed Job's plot experiments to study the mode of complexation of the sensor DIBT with Al3+ ions. The ratio of binding stoichiometry of the DIBT + Al3+ complex was found to be 1:1. The mode of binding was further verified using the 1H NMR titration experiments and HRMS analysis. The detection limit of DIBT with Al3+ was found to be 13.7 nM. We performed DFT and TD-DFT calculations to get in-depth insights into the mechanical aspects. The chelation-enhanced fluorescence type sensor DIBT was analyzed for its practical application in real water and pharmaceutical samples. The sensor DIBT can effectively track Al3+ ions in live Escherichia coli (E-coli) bacterial cells. [ABSTRACT FROM AUTHOR]

A simple relay identification fluorescence probe for Fe 3 + and phosphate anion with “on-off-on” switching was designed and synthesized based on the phenylthiazole and biphenylcarbonitrile. Probe 1 displayed highly selective and sensitive recognition to Fe 3 + in HEPES aqueous buffer (EtOH/H 2 O = 2:8, v/v, pH = 7.4) solutions. The optimized structures and HOMO and LUMO of probe 1 and [1-Fe 3 + ] complex were obtained by the density functional theory (DFT) calculations with B3LYP as the exchange and correlation functional using a suite of Gaussian 09 programs. The [1-Fe 3 + ] complex solution also showed a high selectivity toward PO 4 3 − . The lower limits of detection of probe 1 to Fe 3 + and [1-Fe 3 + ] complex to PO 4 3 − were estimated to 1.09 × 10 − 7 M and 1.86 × 10 − 7 M. Besides, the probe 1 also was used to detected the target ions in real water sample and living cells successfully. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorescein dye derived sensor for fluoride ions. • Naked eye detection of fluoride ions. • Very fast Turn-on fluorescence with fluoride ions. • Fluoride ions detection in aqueous solution. • NMR titrations reveals N H and fluoride adduct formation. • Applicable for live cell imaging via fluorescence imaging. Imidazole functionalized on fluorescein dye was developed as an efficient probe for naked eye and fluorescence determination of fluoride ions. The probe is dramatic color change and very exciting fluorescence turn-on response with the addition fluoride ions. Moreover, fluoride ions triggering leads to the fissure of the spirolactam ring that causes drastic color makes feasible for the naked eye detection of fluoride ions. The mode of binding of fluoride with the probe was proved by 1H NMR titration experiments and the observed photophysical changes were rationalized by use of DFT calculations. This sensor was more applied to detect fluoride ions in real samples and imaging of fluoride ions through fluorescence imaging in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorescein dye derived sensor for fluoride ions. • Naked eye detection of fluoride ions. • Very fast Turn-on fluorescence with fluoride ions. • Fluoride ions detection in aqueous solution. • NMR titrations reveals N H and fluoride adduct formation. • Applicable for live cell imaging via fluorescence imaging. Imidazole functionalized on fluorescein dye was developed as an efficient probe for naked eye and fluorescence determination of fluoride ions. The probe is dramatic color change and very exciting fluorescence turn-on response with the addition fluoride ions. Moreover, fluoride ions triggering leads to the fissure of the spirolactam ring that causes drastic color makes feasible for the naked eye detection of fluoride ions. The mode of binding of fluoride with the probe was proved by 1H NMR titration experiments and the observed photophysical changes were rationalized by use of DFT calculations. This sensor was more applied to detect fluoride ions in real samples and imaging of fluoride ions through fluorescence imaging in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly selective and sensitive chemosensor (L) for detection of Hg2+ ion in semi-aqueous medium. • The chemosensor can detect Hg2+ ions as low as 11.8 nM by spectrofluorometric by turn-off mechanism. • The practical utility of probe L was studied on the test strip, real water analysis and live cell imagaing. We have developed a new chromogenic and fluorogenic chemosensor (L) based on benzothiazole conjugated with quinolinyl acrylate for the detection of Hg2+ ions with excellent selectivity and sensitivity. In the presence of Hg2+, the fluorescence of L was quenched from light blue to colorless. The L could work in the wide pH range of 5.0–8.0 without considerable interference from other tested ions. UV–Visible and fluorometric investigations revealed that the limit of detection (LOD) for Hg2+ was 1.0 μM (202 ppb) and 11.8 nM (2.38 ppb), respectively. Further, the applicability of probe L in the determination of Hg2+ in various water samples and biological samples were tested. Human Bone Osteosarcoma cell lines (HOS) were utilized for this study and satisfying results were obtained. These cell line results also further support the 'on-off' properties of probe L. Based on the colorimetric and fluorescent results we have designed a Boolean logic gate for futuristic applications. [ABSTRACT FROM AUTHOR]

Mitochondria-targetable fluorescent chemosensors, Rhodamine-B and rhodamine 6G bearing syringaldehyde based receptors were designed and synthesized for efficient chemosensing of Zinc(II) ions. The probes showed the very selective naked eye color change to pink from colorless upon addition of Zinc(II) ions, further these probes showing turn-on fluorescence enhancement with Zn(II) ions by opening of rhodamine spirolactam. The probes are very sensitive towards Zn(II) ions among other ions. These probes RBS and R6S will be applicable to detect zinc ions upto the low level concentration 0.18 and 0.19 nano molar respectively. The affinity of these sensors RBS and R6S for Zinc (II) ions was found to be in the range of 1.12 × 104 M−1 and 7.28 × 104 M−1 respectively. 1H-nmr titrations of the probes with Zn(II) ions clearly indicating the spiroring opening of the spirolactam. DFT calculations supporting that the perceived photophysical changes of the probes on appendage of the zinc ions. Probes RBS and R6S are useable for selective staining mitochondria. Both of the probes are applicable to reveal labile Zn(II) in live Hela and MCF-7 cells via fluorescence imaging. RBS and R6S are also finding application on quantification of Zinc(II) ions inside mitochondria via fluorescence imaging. [Display omitted] • Rhodamine dye derived sensor for Zinc(II) ions • Colorimetric changes detectable using Naked eyes • NMR titrations showing spiroring opening • Applicable for live cell imaging via fluorescence imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrazinecarbothioamide appended 1,8-naphthalimide based probe (L) was synthesized. • Detection limits of L were in nanomolar range for both ions through a "turn-on" fluorescence response. • Easily observable color changes were observed after addition of Hg2+ and Ag+ ion into a solution of L. • "Turn-on" fluorescence response was due to restriction of PET and operation of CHEF processes. • Intracellular detection of Hg2+ and Ag+ ions in MDA-MB-231 and HDF cells was assessed. The probe (L) having hydrazinecarbothioamide and 1,8-naphthalimide moieties was synthesized and evaluated for its metal ion sensing ability. It exhibits a selective and sensitive colorimetric as well as fluorescent recognition of Hg2+ and Ag+ ions in CH 3 OH - HEPES buffer solution (5 mM, 7:3, v/v , pH = 7.4) in presence of other metal ions. Probe L is weakly fluorescent upon excitation with 410 nm light, but after gradual addition of HgCl 2 and AgNO 3 enhancement in fluorescent intensity was observed. Detection limits of Hg2+ and Ag+ using L have been found to be 20 nM (Hg2+) and 40 nM (Ag+) over the pH range of 6 – 10 that is suitable for practical application under physiological pH conditions. The reversibility of interaction of L with Hg2+ ion was monitored using Na 2 EDTA by emission titration. The "OFF-ON" fluorescence switching can be observed with naked eye, in which fluorescent " OFF " is due to operation of PET process in free L. Whereas upon complexation with these two metal ions, PET is restricted and CHEF process becomes operational. Mass spectral analysis and Job's plot yielded a binding ratio of 1:1 for both metal ions. NMR titration studies are consistent with binding of Hg2+ or Ag+ to NH group (attached with naphthalimide moiety) and sulfur atom of hydrazinecarbothioamide group. From cytotoxicity assay, 5 μM solution of L was considered in cellular imaging study and the potentiality of the probe L was established by using human breast cancer cell line (MDA-MB-231) and primary human dermal fibroblasts (HDF), through fluorescence cell imaging experiments for tracking both Hg2+ and Ag+ in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Schiff base molecule (L) having pyrene and coumarin moieties was synthesized. • L is highly selective colorimetric and fluorometric probe for Al(III), Cr(III) and Fe(III) with very low detection limit. • Fluorescence response is an "OFF-ON" mechanism through inhibition of PET and operation CHEF processes. • Cell imaging and cytotoxicity studies performed using MDA-MB-231 and HDF cells indicate that L is biologically safe. A Schiff base (L) containing coumarin and pyrene moieties was synthesized and characterized. It showed excellent selective recognition of M(III) ions (M = Al, Cr and Fe) in presence of monovalent, divalent and other trivalent metal ions. Sensor L itself is non-fluorescent upon excitation with 353 nm light (λ ex = 353) but a very large enhancement in fluorescence intensity was observed during the addition of these three trivalent metal ions into a CH 3 OH/aqueous HEPES buffer (5 mM, pH = 7.4, 6:4, v/v) solution of L. This prominent "OFF-ON" fluorescence switching can be observed with naked eye, in which "OFF" is due to operation of PET process in free L but PET is inhibited upon complexation thereby allowing CHEF (chelation enhanced fluorescence) process to operate. Detection limits of Al3+, Cr3+ and Fe3+ using L have been found to be 0.79 nM, 1.15 μM, and 1.28 μM respectively in the pH range of 6‒10. Additionally, "OFF-ON" fluorescence can be reversed by sequestering M(III) ions using [EDTA]4– solutions. Analysis of mass spectra and Job's plot revealed a binding ratio of 1:1 for all three metal ions with L. The imine nitrogen and carbonyl oxygen atoms of L are involved in binding with Al3+, Cr3+ and Fe3+ ions, as revealed by NMR titration and IR spectroscopic analysis. Results of quantum yield (Φ), time resolved photoluminescence (TRPL) and computational studies (DFT/TDDFT) studies were also reported. Fluorescence intensity of these M(III) bound L complexes is quenched by fluoride ions. From cytotoxicity analysis, 7.5 μM of probe L was selected to analyze its fluorescence attributes in cellular imaging. Using human breast cancer cell line (MDA-MB-231) and primary human dermal fibroblasts (HDF), the potentiality of the probe L was confirmed through fluorescence cell imaging experiments. [ABSTRACT FROM AUTHOR]

A Schiff base, 1-[2-(1,3-benzothiazol-2-yl)hydrazinylidene]methyl-naphthalen-2-ol (BTHN) have been synthesized by the condensation of 2-hydrazinobenzothiazole and 2-hydroxy-1-naphthaldehyde. Structure of BTHN has been determined with the help of spectroscopic techniques and elemental analysis. Photophysical parameters of the BTHN were studied in the different solvents of varying polarity. The photophysical parameter were largely affected by the varying polarity and absorption as well as emission spectra showed strong bathochromic shift. Further, interactions of the BTHN dye with metal ions were also explored by spectrofluorimetry and BTHN found to be an excellent off-on chemosensor for Cd2+ in DMF-H 2 O solution. The molecular coordination complex between BTHN with Cd2+ is 1:1, confirmed by Benesi-Hildebrand and Job-plot method. In addition, the BTHN has been effectively employed for the fluorescence imaging of cadmium ions in the living cells. Unlabelled Image • Synthesis of 1-(2-benzo (d) thiazol-2-yl-hydrazono) methyl naphthalene-2-ol (BTHN). • Spectroscopic and photophysical investigations of BTHN. • Turn-on fluorometric chemosensor for detection Cd2+ ion. [ABSTRACT FROM AUTHOR]

• Hydrazide based fluorescence probe for detection of Al3+ ions. • Therotical calculations (DFT) were carried out for probe (SCH) and Al3+-SCH. • Life time decay were carried out. • SCH and Al3+-SCH used for cellular imaging sensor in MCF-7 cells Development of highly specific and susceptible sensors for aluminium (Al3+ ions) determination in water medium is still a remarkable task. Herein, a fluorescence probe (SCH) is derived from the condensation of salicyaldehyde and carbohydrazide in 2:1 M ratio and promising chemical sensing of Al3+ ions is investigated. Examinations of the emission features of SCH in CH 3 OH:H 2 O (1:2, v/v) solution showed excellent turn on behaviour of Al3+ ions, which is due to 1:1 complex formation between SCH and the Al3+ ions at ambient conditions. The lowest limit of detection was estimated by emission titration experiments and found to be 32 nM which is much more 1000-fold lower than that WHO suggested maximum tolerable concentration. The present probe SCH was highly specific for the detection of Al3+ ions over other potential interfering metal cations. Based on the reversible emission behaviour, an INHIBIT logic gate was assembled with EDTA and Al3+ ions as two inputs. In addition, prospective application of SCH as cellular imaging sensor of Al3+ ions in MCF-7 cells was monitored using optical fluorescence microscopic images and real water samples. [ABSTRACT FROM AUTHOR]

Three novel and facile calixarene derivatives (5 , 6 and 7), which were appended with four rhodamine units at the upper rim of calixarene skeleton, were firstly prepared and evaluated for selective detection of metal ions in solution. Receptors (5) and (7) indicated immediate turn on fluorescence output toward Hg2+ ions over other most competitive metal ions with the ultralow detection limits, indicating their high efficiency and reliability. The binding response to Hg2+ ions in solution was also observed through a chromogenic change (from colorless to pale pink). Furthermore, in vitro and bio-imaging studies with MCF-7 or MIA PaCa-2 cell lines were also performed to investigate the use of receptors in biological systems in order to monitor of mercury ions. Results showed that new receptors (5) or (7) were cell permeable and suitable for real-time imaging of Hg2+ in living cells (MCF-7) or (MIA PaCa-2) without any damage to healthy cell lines (HEK 293). Unlabelled Image • Three novel rhodamine based calixarene fluorescent probes (5 - 7) were synthesized for highly selective detection of Hg2+ ions. • The probe (7) could quantitatively detect Hg2+ ions with a low detection limit of 3.4 nM. • Cytotoxicity and cell imagine studies against MCF-7 and MIA PaCa-2 cell lines were performed. [ABSTRACT FROM AUTHOR]

A bisphenol based fluorescence "turn-on" chemosensor 4,4′-(propane-2,2-diyl)bis(2-((E)-(2-(benzo[d]thiazol-2-yl)hydrazineyldene)methyl)phenol) (BHMP) has been synthesized and its sensing behavior was tested towards various ionic species. The chemo-sensing behavior of BHMP has been established through absorption, fluorescence, NMR, and mass spectroscopic techniques. The probe BHMP selectively detects zinc ions over other metal ions and the resulting BHMP + Zn2+ ensemble serves as a secondary probe for the detection of pyrophosphate (PPi) anion specifically over other anions. The spectroscopic studies reveal the fluorescence enhancement of BHMP in association with Zn2+ ions was quenched in the presence of pyrophosphate (PPi) anions. A probable mechanism of this selective sensing behavior was described on the basis of "OFF-ON-OFF" strategy for detection of both cations and anions. Moreover, the biological applicability of the chemosensor BHMP was examined via cell imaging studies. A bisphenol based fluorescence "turn-on" chemosensor (BHMP) has been synthesized and its sensing behavior was tested towards various ionic species. The probe BHMP selectively detects zinc ions over other metal ions and the resulting Zn2+-BHMP ensemble serves as a secondary probe for the detection of PPi anion. The biological applicability of the chemosensor BHMP was examined via cell imaging studies. Unlabelled Image • The probe BHMP selectively detects zinc ions and the resulting Zn2+- BHMP ensemble is applied for the detection of PPi ions. • The probe detects Zn2+ and PPi ions with low detection limit of 0.28 and 0.87 nM respectively. • The probe was successfully applied to detect Zn2+ and PPi ions in live cells. [ABSTRACT FROM AUTHOR]

A newly synthesized compound, 5-methyl-1-phenyl-1H-1,2,3-triazole-4- carboxylic acid (MPC) was analyzed for its quantum chemical parameters and theoretical spectrum by computational chemistry. The calculated spectrum was in accord with the experimental measurements in a great degree. Then MPC was successfully designed and synthesized to a novel rhodamine B derivative RMPC. The RMPC exhibited about a 4000-fold increase in fluorescence intensity in the presence of Hg2+ ions over most other competitive metal ions. The triazole appended colorless chemodosimeter RMPC turns to pink upon the complex formation only with Hg2+ ions as a 1: 2 M ratio and enables naked-eye detection. The coordination mechanism of turning on/off fluorescence for Hg2+ ions were well proposed by explaining Hg2+ inducing the ring-opened rhodamine B moiety. The fluorescence imaging experiments of Hg2+ in HeLa cell demonstrated that the probe was labeled and it could be used in biological systems. Image 1 • The structural and photophysical properties of a new 1, 2, 3-triazole MPC were computed. • zMPC was synthesised a novel rhodamine based fluorescent chemosensors RMPC. • MPC selectively responds to Hg2+ by off-on fluorescence mechanisms with "naked-eye" detection of Hg2+. [ABSTRACT FROM AUTHOR]

A simple imine based receptor NA-1 has been synthesized for detection of Zinc ions. Probe NA-1 showed the selective colorimetric changes with Zinc (II) ions whereas other metal ions didn't showed any observable colorimetric changes. The probe showed the very selective turn-on fluorescence response with Zn(II) ions among other rival metal ions like Cd(II) and Hg(II). The mode of binding was studied by 1H-nmr titrations and fluorescence spectroscopy. Jobs plot analysis confirming that the probe NA-1 forms 1:1 complex with Zn(II). The observed fluorescence and absorption change further supported by theoretical calculations. The turn-on fluorescence of the probe NA-1 is probably attributable to the interruption of intramolecular charge transfer as well as ESIPT. The limit of detection of the probe for Zn(II) sensing is in the range of 14 nano molar. Cytotoxicity (MTT) assay of the probe in live HeLa cells is showing that the probe is least toxic to cells. The probe NA-1 is effectively applied to detect Zn(II) ions in HeLa cells and suggesting the probe is NA-l permeable to cell wall and viable for Zinc(II) ions imaging in live cells. • Simple imine based sensor for Zinc(II) ions • Colorimetric and turn-on fluorescence sensor • Internal charge transfer process • Applicable for live cell imaging [ABSTRACT FROM AUTHOR]

In this work, a highly selective fluorescent chemosensor N-(2-(2-butyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)hydrazine-1-carbonothioyl)benzamide (L) was prepared and characterized. An assay to detect the presence of cobalt(II) ions was developed by utilizing turn-on fluorescence enhancement with visual colorimetric response. Upon treatment with Co2+, a remarkable fluorescence enhancement located at 450 nm was visible to naked eyes accompanied with a distinct color change (from pink to colorless) in a CH3CN/HEPES (4/1, v/v, pH = 7.4) solution due to the formation of a 1:1 complex at room temperature. In addition, the linear concentration range for Co2+ was 0–25 µM with the limit of detection down to 0.26 µM. Thus, a highly sensitive fluorescent method based on chelation-assisted fluorescence enhancement was developed for the trace-level detection of Co2+. The sensor was found to be highly selective toward Co2+ ions with a large number of coexisting ions. Furthermore, the L probe can serve as a fluorescent sensor for Co2+ detecting in biological environments, demonstrating its low toxic properties to organisms and good cell permeability in live cell imaging. [ABSTRACT FROM AUTHOR]