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Mercury is highly toxic, and appropriate amounts of the mercury-selenium complex can protect plasma. However, when excessive mercury (II) ions (Hg 2+ ) are exposed to human skin or ingested directly, it can lead to irreversible accumulation in the body. Therefore, detecting the presence of Hg 2+ in cells is important. A novel fluorescent probe BTD-Hg-Lyso was designed and constructed based on the intramolecular charge transfer mechanism. Thiotaldehyde could specifically recognize Hg 2+ so that the probe could produce a fluorescence enhancement effect. In addition, the fluorescent probe BTD-Hg-Lyso exhibited the advantages of large Stokes shift (210 nm) and good selectivity. More importantly, the probe BTD-Hg-Lyso could be used for the determination of Hg 2+ in cellular lysosomes. BTD-Hg-Lyso was able to image Hg 2+ in HeLa cells, zebrafish, and tobacco seedlings (rhizome and stem) successfully., (© 2024 Wiley-VCH GmbH.)

The improved solubility of cellulose, and the enlargement of its application is of importance. Herein, we have synthesized cellulose probes with aggregation-induced emission (AIE) effect, which demonstrates high efficiency and sensitivity in detecting Hg 2+ /Hg + ions. The cellulose underwent esterification with a 11‑carbon chain using pyridine as both catalyst and reaction medium, leading to break off H bonds and a significant decrease in crystallinity. This modification allowed the cellulose to be soluble in dichloromethane (DCM) and toluene. Additionally, long-chain oil-soluble BODIPY fluorescent polymers were synthesized using 2-(dimethylamino) ethyl methacrylate (DMAEMA) as monomer via BODIPY containing RAFT reagent. The oil-soluble BODIPY fluorescent polymers were connected to cellulose through the Heck reaction, leading to the preparation of cellulose fluorescent probes. These probes could be easily dissolved in strong polar organic solvents like N, N-dimethylformamide (DMF) and ethanol, but also in DCM and toluene. They can be made into films and gels. Furthermore, the probe utilizes BODIPY as the fluorophore and CO as the binding recognition site for Hg 2+ and Hg + . The detection limits are 50 nM and 60 nM, respectively. The cellulose solubility was improved, and the cellulose based probes could be employed to detect and separate Hg 2+ and Hg + ., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Xinjian cheng, phd reports financial support was provided by National Natural Science Foundation of China. No reports a relationship with no that includes:. No has patent no pending to no. The authors declare no competing financial interest. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Mercury ion (Hg 2+ ) is considered a harmful neurotoxin, and real-time monitoring of Hg 2+ concentrations in environmental and biological samples is critical. Fluorescent probes are a rapidly emerging visualization tool owing to their simple design and good selectivity. Herein, a novel fluorescence (FL) probe 2-(4-((6-((quinolin-8-yloxy)methyl)pyridin-2-yl)methyl)piperazin-1-yl)anthracene-9,10-dione (QPPA) is designed using piperazine as a linker between the anthraquinone group, which serves as a fluorophore, and N 4 O as the Hg 2+ ligand. The probe exhibits FL "turn-on" sensing of Hg 2+ because the complex inhibits the photo-induced electron transfer (PET) process. Moreover, QPPA can overcome the invasion by other possible cations, resulting in a clear color change from orange to colorless with the addition Hg 2+ . The chelation of QPPA with Hg 2+ in a 1:1 ratio. Subsequently, the theoretically determined binding sites of the ligand to Hg 2+ are validated through 1 H NMR titration. The in situQPPA-Hg 2+ complex can be subjected to Hg 2+ extraction following the introduction of S 2- owing to its robust binding capacity. The exceptional limit of detection values for Hg 2+ and S 2- are obtained as 63.0 and 79.1 nM (S/N = 3), respectively. Moreover, QPPA can display bright red FL in the presence of Hg 2+ in different biological specimens such as HeLa cells, zebrafish, onion root tip tissues, and water flea Daphnia carinata, further providing an effective strategy for environmental monitoring and bioimaging of Hg 2+ in living organisms., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Declaration of competing interest The authors declare that there are no competing financial interests or personal relationships that influence our work., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A reusable fluorescent nanoprobe was developed using DNA-functionalized metal-organic framework (MOF) for ratiometric detection of Hg 2+ . We utilized a zirconium-based MOF (UiO-66) to encapsulate tris(bipyridine) ruthenium(II) chloride (Ru(bpy) 3 2+ ), resulting in Ru(bpy) 3 2+ @UiO-66 (RU) with red fluorescence. The unsaturated metal sites in UiO-66 facilitate the attachment of thymine-rich single-strand DNA (T-ssDNA) through Zr-O-P bond, producing T-ssDNA-functionalized RU complex (RUT). The T-ssDNA selectively binds to Hg 2+ , forming stable T-Hg 2+ -T base pairs and folding into double-stranded DNA, which permits the intercalation of SYBR Green I (SGI) and activates its green fluorescence. In the presence of Hg 2+ , SGI fluorescence increases in a dose-dependent manner, while Ru(bpy) 3 2+ fluorescence remains constant. This fluorescence contrast enables RUT to serve as an effective ratiometric nanoprobe for Hg 2+ detection, with a detection limit of 3.37 nM. Additionally, RUT demonstrates exceptional reusability due to the ability of cysteine to remove Hg 2+ , given its stronger affinity for thiol groups. The RUT was successfully applied to detect Hg 2+ in real water samples. This work advances the development of ratiometric fluorescence nanoprobe based on DNA-functionalized MOFs., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Hg 2+ contamination poses a serious threat to the environment and human health. Although gold nanoclusters (Au NCs) have been utilized as fluorescence probes or colorimetric nanozymes for performing Hg 2+ assays by using a single method, designing multifunctional nanoclusters as fluorescent nanozyme remains challenging. Herein, Ce-aggregated gold nanoclusters (Ce-Au NCs) were reported with "three in one" functions to generate strong fluorescence, excellent peroxidase-like activity, and the highly specific recognition of Hg 2+ via its metallophilic interaction. A portable fluorescence and colorimetric dual-mode sensing device based on Ce-Au NCs was developed for on-site visual analysis of Hg 2+ . In the presence of Hg 2+ , fluorescence was effectively quenched and the paper-based chips gradually darkened from green till they became completely absent, while peroxidase-like activity was significantly enhanced. Two independent signals were captured by one identification unit, which provided self-validation to improve reliability and accuracy. Therefore, this work presents a simple synthesis of a multifunctional fluorescent nanozyme, and the developed portable device for on-site visual detection has considerable potential for application in the rapid on-site analysis of heavy metal ions in the environment., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The DNA-based biosensor utilises a thymine/guanine(T/G)-rich ODN-4 scaffold with 4',6-diamidino-2-phenylindole(DAPI) as a fluorescent emissary to monitor mercury/lead(Hg(II)/Pb(II)) ions simultaneously. Key to its bifocal detection capability is the twin unbound cytosine(C) bases strategically bridging the G-quadruplex and T-rich sequences, enabling their synergistic interplay. It facilitates the recognition of Hg(II)/Pb(II) ions, characterised by high specificity, and effectively mitigates interference from silver(Ag(I)). The G-quadruplex, guided by the C bases, induces a conformational transition in T-Hg(II)-T complexes, resulting in intense fluorescence. Pb(II) causes a spatial shift in the G-quadruplex, relaxing the T-Hg(II)-T base pairs and attenuating the fluorescence signal. The ODN-4 exhibits a robust, linear correlation with Hg(II) concentration (4.09 nmol/L to 1000 nmol/L) and Pb(II) concentration (3.22 nmol/L to 5 μmol/L). Recovery rates in milk, tap water, and rice water specimens with both ions validate method accuracy (Hg(II): 95.19% to 104.68%, Pb(II): 98.20% to 103.46%). It holds promising prospects for practical food analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Due to the highly toxic nature of mercury ions to living organisms, accurately detecting Hg 2+ in water samples and biological systems is of great significance. In this study, we designed and synthesized a novel red-to-near-infrared Aggregation-Induced Emission (AIE) fluorescent probe (named as DS) based Fluorene derivatives on specifically for Hg 2+ detection. Probe DS can visually identify Hg 2+ through an red-to-near-infrared fluorescence enhancement change, characterized by a large Stokes shift (130 nm) and AIE feature. This probe offers a fast response, high selectivity and sensitivity. The Hg 2+ -induced deprotection reaction of the thioketal mechanism was thoroughly investigated using nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS) and density functional theory (DFT) calculation. Additionly, dynamic light scattering (DLS) results indicated that the aggregation states changes of the molecular play a crucial role in the AIE fluorescence response of probe DS toward Hg 2+ . The red-to-near-infrared response with AIE feature not only avoids the interference of auto-fluorescence signals in complex environments, but also reduces the fluorescence quenching caused by probe molecular aggregation. This makes probe DS highly suitable for high-quality imaging detection of Hg 2+ in aqueous environments. Furthermore, probe DS demonstrates the capability for visual fluorescence detection of Hg 2+ concentrations in water sample, plant roots and living cells., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Carbon dots (CDs), as a fascinating carbon nanomaterial, have important applications in various fields due to their unique properties. The physical and chemical properties of CDs can be fine-tuned using heteroatom doping and surface functionalisation. Here, we synthesised N-doped carbon dots (N-CDs) by reacting Citric acid, which serve as the carbon core, with twenty amino acids under microwave irradiation. The fluorescence quenching of each amino acid doped CDs by Hg(II) ions was experimentally measured. Then the effect of the molecular features and chemical properties of amino acids on the fluorescence quenching of N-CDs by Hg(II) ions was investigated by using the quantitative structure-property relationship (QSPR) method. Applying different machine learning techniques including correlation-based and ReliefF algorithm feature selection approaches to choose relevant descriptors, multi-linear regression, and support vector machine to construct QSPR model, some reliable and predictive models were developed. Based on the variables used throughout the final QSPR models, hydrophobic interactions, in addition to hydrogen bonding interactions, can be considered a major factor governing the photoluminescence behaviour of different N-CDs quenched by Hg(II) ions. N-CDs derived from amino acids bearing larger hydrophobic surfaces show greater fluorescence quenching, indicating that a greater capacity to interact with Hg(II) metal ions resulting in further fluorescence quenching.

The past decades have witnessed the feat of fluorescent probes for Fe 3+ detection, where eliminating the interference by other metal ions plays a pivotal role in its detection by probes in complex environments. Herein, by taking advantage of the substituent effects, the electron-withdrawing group (EWG) -CF 3 and electron-donating group (EDG) -CH 3 were introduced to 2-(1-pyrenyl)pyridine (pypyr) to prepare two turn-off fluorescence probes, 5-trifluoromethyl-2-(1-pyrenyl)pyridine (pypyr-CF3) and 5-methyl-2-(1-pyrenyl)pyridine (pypyr-CH3). Intriguingly, both probes displayed novel aggregation-induced emission (AIE) characteristics in MeCN/H 2 O mixtures and the size and morphology of the aggregated particles were studied via DLS and TEM. By the modulation strategy, pypyr-CF3 can detect Fe 3+ in the presence of 29 different metal ions without interference. Comparatively, pypyr-CH3 experienced serious interference from other metal ions such as Hg 2+ and Zr 4+ . Besides, pypyr-CF3 not only demonstrated a higher photoluminescence quantum yield (PLQY) of 65.25% and wider pH adaptability but is also capable of Fe 3+ detection over a wide pH range of 2-11 with a short response time (5 seconds). A plausible quenching mechanism based on the inner filter effect has also been demonstrated. More importantly, the versatile applications of pypyr-CF3, such as the quantitative analysis of Fe 3+ in actual water samples, anti-forgery ink, fingerprint identification, etc. , further corroborate its superb capabilities. This study aims to lend concrete support to the design and selectivity modulation of probes.

The development of fluorescent dyes has been a continuing attractive research topic in the field of fluorescence sensing and bioimaging technologies, most of them were subject to a single signal change. In this work, a novel colorimetric and ratiometric fluorescent probe 1 based on rhodamine and anthracene groups was designed and synthesized via the fluorescence resonance energy transfer (FRET) mechanism. Probe 1 showed excellent selectivity, higher sensitivity and ratiometric response to Hg 2+ in the CH 3 CN/H 2 O (1/1, v/v) system, with a fast response time (less than 30 s); The fluorescent color changed from purple to orange and the solution visible to the naked-eye changed from colorless to pink. The Pseudo-Stokes shift was 174 nm upon addition of Hg 2+ . The limit of detection (LOD) was calculated to be 0.81 μM and 0.38 μM according to fluorescence and UV/vis measurements, respectively. Furthermore, a possible mechanism for the detection of Hg 2+ by probe 1 was verified by using 1 H NMR, ESI-MS, and HPLC spectra. Meanwhile, probe 1 was successfully used for cell imaging for the detection of Hg 2+ in living cells., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A BOPHY-based organotellurium-containing probe was synthesized and characterized via single crystal XRD for the selective and sensitive detection of Hg 2+ over other metal ions. The probe detects Hg 2+ in less than 1 s with a 2.5-fold enhancement in fluorescent intensity. Due to the chalcogenophilicity of mercury, Hg 2+ was facilely trapped in the NTe 2 chelating cavity of the probe. The probe can detect Hg 2+ in the nanomolar range (62 nM) and it showed reversibility with S 2- ions. The sensitivity of the probe for the detection of Hg 2+ was confirmed in living HeLa cells.

Rare studies provided evidence for the real-time monitoring of stress response cysteine fluctuations. Here, we have successfully designed and synthesized a cysteine-selective fluorescent probe 1 to monitor stress response Cys fluctuations, providing visual evidence of Hg2+ regulated cysteine fluctuations for the first time, which may open a new way to help researchers to reveal the mechanism of heavy metal ion poisoning.

A small organic molecule P was synthesized and characterized as a fluorometric and colorimetric dual-modal probe for Hg 2+ . The sensing characteristics of the proposed probe for Hg 2+ were studied in detail. A fluorescent enhancing property at 583 nm (>30 fold) accompanied with a visible colorimetric change, from colorless to pink, was observed with the addition of Hg 2+ to P in an ethanol-water solution (8:2, v / v , 20 mM HEPES, pH 7.0), which would be helpful to fabricate Hg 2+ -selective probes with "naked-eye" and fluorescent detection. Meanwhile, cellular experimental results demonstrated its low cytotoxicity and good biocompatibility, and the application of P for imaging of Hg 2+ in living cells was satisfactory.

A BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) based pioneering sensing material (HL Py ) having 2-amino pyridine as receptor was synthesized and used for the selective detection of Hg 2+ ions. The synthesized HL Py features a high affinity towards Hg 2+ (k a = 2.04 × 10 5 M -1 ), accompanied by effective quenching of fluorescence in DMF:H 2 O (1:9 v/v, 10 mM HEPES buffer, pH 7.4) with 54 nM limit of detection (LOD). The emission titration experiments (Job's plot) in the presence of varying mole-fraction of Hg 2+ ions reveals the formation of non-fluorescent 2:1 coordination complex [Hg(L Py ) 2 ]. The resulting non-fluorescent [Hg(L Py ) 2 ] was thoroughly characterized using various spectroscopic techniques and analyses. Interestingly, the non-fluorescent complex [Hg(L Py ) 2 ] is able to specifically respond towards Cys over other biothiols and amino acids through a reversible de-complexation mechanism. As a result, the remarkable recovery of the fluorescence can be observed. The limit of detection (LOD) for Cys detection is estimated to be 29 nM in DMF:H 2 O (1:9 v/v, 10 mM HEPES buffer, pH 8.0). The reversibility and reusability of [Hg(L Py ) 2 ] were achieved by the sequential addition of Cys and Hg 2+ ions up to five cycles. Moreover, the removal of Hg 2+ ions up to 89% from aqueous samples using HL Py was successfully demonstrated.

A highly sensitive AIE fluorescent chemosensor, N'-((4'-(6,6-dimethyl-4,5,6,7-tetrahydro-1H-5,7-methanoindazol-3-yl)-[1,1'-biphenyl]-4-yl)methylene)picolinohydrazide (PBPHS), for the detection of Hg2+ and Cu2+ ions in near 100% aqueous solution was developed based on the renewable β-pinene derivative nopinone. The probe PBPHS was designed and synthesized via a four reaction steps, including condensation, cyclization, Suzuki coupling reaction, and Schiff-base reaction. PBPHS could recognize Hg2+ and Cu2+ over other competitive metal ions via specific complexation ability towards them. The detection limits of PBPHS for Hg2+ and Cu2+ were 15 nM and 17 nM, respectively. The fluorescent probe PBPHS could also be utilized to detect S2- and Hg2+/Cu2+ reversibly for five cycle. Moreover, the different binding mechanisms of PBPHS with Hg2+ and Cu2+ were confirmed by HRMS analysis, 1H NMR titration, DFT calculation, and molecular logic gate. Furthermore, the probe PBPHS was applied for the analysis of real water and soil samples and living HeLa cells and zebrafish bioimaging.

Gold nanoparticles (AuNPs) conjugated with Cy3-tagged aptamer which can specifically recognize chloramphenicol (CAP) (referred to as AuNPs-AptCAP) are described. CAP can trigger the configuration change of CAP binding aptamer, and thus switching the fluorescence of AuNPs-AptCAP through changing the efficiency of the fluorescence resonance energy transfer (FRET) system with Cy3 as donors and AuNPs as recipients. AuNPs-AptCAP exhibits a linear range of CAP concentrations from 26.0 to 277 μg L -1 with a limit of detection of 8.1 μg L -1 when Cy3 was excited at 530 nm and emission was measured at 570 nm. More importantly, AuNPs-AptCAP can be utilized as signal transducers for the build-up of a series of logic gates including YES, PASS 0, INH, NOT, PASS 1, and NAND. Utilizing the principle of a metal ion-mediated fluorescence switch together with a strong metal ion chelator, the fluorescence of AuNPs-AptCAP could be modulated by adding metal ions and EDTA sequentially. Therefore, a "Plug and Play" logic system based on AuNPs-AptCAP has been realized by simply adding other components to create new logic functions. This work highlights the advantages of simple synthesis and facile fluorescence switching properties, which will provide useful knowledge for the establishment of molecular logic systems. Graphical abstract.

We report a new 7-nitrobenzo-2-oxa-1, 3-diazolyl (NBD)-based chemosensor containing a piperazine derivative, NBDP, for detection of mercury ions in almost 100% aqueous medium. The chemosensor shows sensing exclusively toward Hg 2+ with a switch-on fluorescence response at 543 nm, which could be attributed to the blocking of PET (photo-induced electron transfer) process upon complexation with mercury ions. The molar ratio of Hg(Ⅱ) to NBDP in the complex is 1:1 based on the Job's plot and HRMS studies. Optimized configurations of NBDP and NBDP-Hg 2+ complexes were simulated by means of DFT calculations. The reversible fluorescence response with low detection limit (19.2 nM) in the pH range of 6.0-7.5 renders NBDP a promising candidate for Hg 2+ detection in neutral aqueous environments. For the practical application of the chemosensor, test strips were successfully fabricated for rapid detection of Hg 2+ ions. Moreover, the utility of NBDP showing the mercury recognition in Human liver cancer cells (SMMC-7721) and zebrafish as well as in live tissues of Arabidopsis thaliana has been demonstrated as monitored by fluorescence imaging., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Detection of glutathione in human serum is of great importance for clinical diagnosis of various diseases, such as AIDS, diabetes mellitus, Alzheimer disease and cancer. In this work, a new water-soluble bismacrocyclic polyamine-derived compound, namely L, which contains two molecules of 4-nitro-1,2,3-benzoxa-diazole as the fluorophores, was designed and prepared. The experiments of selectivity of L toward metal ions showed it could rapidly and sensitively detect Hg 2+ with a detection limit of 27 nM. Furthermore, the cell imaging and co-staining experiments in HeLa cells demonstrated that the L-Hg 2+ probe had selectivity for the Golgi apparatus to a certain degree. Moreover, it had excellent selectivity for biothiols, especially for glutathione. Finally, the probe was successfully applied to sensitively detect glutathione (GSH) in human serum and fetal bovine serum., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A new fluorescent "on-off-on" probe (BIPQ) is designed and developed which selectively binds with Hg 2+ ; its emission intensity is quenched almost 40-fold at 455 nm without interference from other metal cations. On gradual addition of I - to the solution of BIPQ-Hg 2+ , the emission reverts to its original intensity. The limits of detection of BIPQ for Hg 2+ and I - are found to be on the order of 3.12 × 10 -9 and 5.48 × 10 -8 M, respectively, which shows clearly that BIPQ can sense Hg 2+ at a very minute level. DFT and TDDFT studies are conducted with the probe to establish similarity between theoretical and experimental outcomes. Finally, to demonstrate its practical benefit in biological fields, live cell imaging experiments with BIPQ are carried out to detect Hg 2+ in human AGS gastric cancer cell lines.

Sensing the most toxic heavy metal (mercury) has attracted a lot of attention in recent years due to its extreme harmfulness to both human health and the environment. Thus, we reported herein the synthesis, spectroscopic and kinetic characterization, and biological evaluation of a new thioxothiazolidin coumarin derivative (ILA92), which undergoes a desulfurization reaction induced by mercuric ions (Hg 2+ ). This process is the origin of a selective sensing of Hg 2+ ions in aqueous solution by colorimetric and fluorescent methods. Furthermore, the probe showed great potential for imaging Hg 2+ in living cells., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this work, a simulated enzyme inhibition-based strategy was transplanted from natural peroxidase-based sensing methods for colorimetric nanoperoxidase-based biothiol detection. This work might provide some new perspectives for the construction and biomimetic regulation of mimicked biological signalling systems based on nanoperoxidases.

A rapid and label-free fluorescence sensing strategy has been established for the sensitive determination of melamine (MA) on the basis of poly(adenine) (poly (A))-templated Au nanoclusters (AuNCs). The poly(A)-templated AuNCs possessed excellent luminescence and photo-stability. In the presence of Hg 2+ , the luminescence of AuNCs was quenched by Hg 2+ through the metallophilic interactions between Au + and Hg 2+ . When melamine was introduced, the fluorescence intensity of sensing system could be recovered. There was a greater coordination interaction between Hg 2+ and melamine, which blocked the Hg 2+ -mediated fluorescence quenching of AuNCs. The assay allowed sensitive determination of melamine with a linear detection range from 50 nM to 100 μM. The limit of detection was as low as 16.6 nM. Furthermore, the label-free strategy was successfully employed for the detection of melamine concentration in real samples., (Copyright © 2019 Elsevier B.V. All rights reserved.)

DNA-templated silver nanoclusters (DNA-Ag NCs) with cytosine (C)-rich sequences (four or more segments of consecutive (2-5) C-bases) were synthesized. They display green and/or orange/red emissions under different excitation wavelengths. There is indication that more consecutive C-bases lead to longer emission wavelengths. The ratio of the red and green emissions of the DNA-Ag NCs depends on whether the NCs were synthesized under acidic or basic conditions. We also prepared the DNA copper/silver nanoclusters (DNA-Cu/Ag NCs) which can be synthesized in shorter time and display higher stability. The DNA-Cu/Ag NCs, under 470 nm photoexcitation, always display green emission, with a peak at 550 nm, irrespective of whether being prepared under acidic or basic conditions. The fluorescence of the Cu/Ag NCs is selectively quenched by Hg(II) ions which can be quantified by this nanoprobe with a detection limit as low as 2.4 nM. The quenching mechanism was studied by Stern-Volmer plots and lifetime studies which revealed that both static and dynamic quenching are operative. Graphical abstract Schematic presentation of fluorescent DNA-Ag nanoclusters (NCs) exhibiting red and green emission under different pH values, and green emissive DNA-Cu/Ag NCs for sensitive and rapid detection of Hg 2+ .

Synthesis of a highly responsive fluorescent ribonucleoside analogue based on a 5-methoxybenzofuran uracil core, enzymatic incorporation of its triphosphate substrate into RNA transcripts, and its utility in the specific detection and estimation of Hg 2+ -ion-mediated metallo-base pair formation in DNA-RNA and RNA-RNA duplexes are described.

In this study, a novel dual-emission ratiometric fluorescent nanoprobe (RFN) was synthesized and ultilized for highly sensitive determination of mercury ions. In this nanoprobe, fluorescein isothiocyanate (FITC) doped silica (SiO 2 ) served as a reference signal, FITC-SiO 2 microspheres were synthesized and modified with amino groups, and then Au Nanoclusters (AuNCs) were combined with the amino groups on the surface of the FITC-SiO 2 microspheres to obtain the RFN. The selectivity, stability, and pH of the RFN were then optimized, and the determination of mercury ions was performed under optimal conditions. The probe fluorescence intensity ratio (F 520 nm/F 680 nm) and Hg 2+ concentration (1.0 × 10 -10 mol/L to 1.0 × 10 -8 mol/L) showed a good linear relationship, with a correlation coefficient of R 2 = 0.98802 and a detection limit of 1.0 × 10 -10 mol/L, respectively. The probe was used for the determination of trace mercury ion in water samples, and the recovery rate was 98.15~100.45%, suggesting a wide range of applications in monitoring pollutants, such as heavy metal ion and in the area of environmental protection.

Since the accumulation of mercury (II) ions in the environment and ecosystem causes serious problems to environment and disease, the recognition of Hg 2+ ions and its bio-imaging is of high importance. In sight of the advantages of fluorescence probes, a new probe ( PMH ) was facilely synthesized by incorporating phenylimidazole fluorophore and 3-methyl-2- benzothiazolinone hydrazone hydrochloride monohydrate. The PMH probe exhibited a ratiometric response for Hg 2+ ions with fluorescence intensity increasing at 520 nm and decreasing at 445 nm simultaneously. The PMH probe interacted with Hg 2+ ions in seconds with high optical stability and showed good selectivity over other metal ions. In addition, the probe has excellent biocompatibility and imaging performance in cells and zebrafish.

This paper presents the synthesis and evaluation of physicochemical behavior of a new series of N -alkyl-bis- o -aminobenzamides (BOABs) in aqueous solution. The study was targeted to the complexing capacity of five metal ions (Fe 2+ , Cu 2+ , Cd 2+ , Hg 2+ and Pb 2+ ) of environmental concern as the medullar principle of a liquid phase sensor for its application in the determination of these metal ions due to its versatility of use. Molecular fluorescence, UV-visible and Zeta potential were measured for five BOABs and the effect of alkyl groups with different central chain length ( n = 3, 4, 6, 8 and 10) on physicochemical performance determined. The results have shown that these derivatives present higher sensibility and selectivity for Cu 2+ even in the presence of the other metal ions. An additional application test was done adding a pectin (0.1 wt %) solution to the BOAB-Cu +2 complex to obtain a precipitate (flocs) as a potential selective separation process of Cu from aqueous solution. The solid was then lyophilized and analyzed by SEM-EDS, the images showed spheric forms containing Cu +2 with diameter of approximately of 8 μm and 30 wt %.

Here, we found that Thioflavin T (ThT) could specifically bind with a G-GGG unit (named as "Guanine Island") in double stranded DNA (ds-DNA). Through stacking with G base via hydrogen bonds, the rotation of ThT was restricted and concurrently its planarization was enforced. Such a binding mode produced a significantly enhanced ThT fluorescence. Based on this discovery, with ThT as a lighting-up probe for "Guanine Island" in ds-DNA, the fluorescent detection of single-nucleotide mutation (C mutation) was investigated. With C base in target DNA mutating to G, A or T and further hybridizing with a probe DNA containing a GGG unit at the mutated point, ds-DNA including G-GGG, A-GGG or T-GGG islands was formed, respectively. After binding with ThT, C mutation was clearly recognized. With C mutating to G as an example, the detection limit was as low as 3 nM. Importantly, the developed assay could be applied to recognize C mutating to G in a DNA sequence related to dilated cardiomyopathy for diluted human serum. As a sensing unit ("Guanine Island" in ds-DNA lighting up ThT), it is expected to be applied for various biological or environmental systems.

The detection of ionic mercury (Hg2+) is very important because it is a highly toxic environmental pollutant that could cause serious diseases and threaten human health. Herein, we designed a new carbonothioate-based far-red fluorescent probe, CBRB, with a seminaphthorhodafluor dye as the fluorophore for the detection of Hg2+. The CBRB probe by itself exhibited very weak fluorescence due to the enhanced photo-induced electron transfer (PET) effect and inhibited the intramolecular charge transfer (ICT) process caused by the carbonothioate moiety. Upon addition of Hg2+, a tremendous fluorescence enhancement was achieved, attributed to the removal of the carbonothioate group via a specific mercury-promoted desulfurization reaction. Moreover, the probe displayed a large Stokes shift (about 105 nm) and was used to quantitatively measure the concentration of Hg2+ for concentrations ranging from 0 to 1 μM (DL = 3.6 nM). In addition, CBRB in our experiments responded exclusively to Hg2+, even in the presence of high concentrations other ions. Gratifyingly, this probe was successfully used to monitor Hg2+ in environmental water samples and to image Hg2+ in living cells as well as in zebrafish.

Owing to the extreme toxicity of mercury, methods for its selective and sensitive sensing in solutions, and in live cells and tissues are in great demand. In this study, we developed a naphthalimide-based diphenylphosphinothioyl group-containing fluorescent and colorimetric probe that selectively detects mercury (Hg2+). Upon addition of mercury (Hg2+) to a solution of the probe, both a colorimetric change from colorless to yellow and a fluorescence change from blue to green (under a 365 nm hand-held UV lamp) occur, both of which can be observed using the "naked-eye". Furthermore, the probe possesses the capability of sensing intracellular mercury in both live cells and tissues using dual-emission channels and two-photon microscopy.

A label-free fluorescent aptasensing platform was fabricated and a simple and rapid method to detect Hg 2+ ion in aqueous solution was put forward by means of berberine and Hg 2+ ion-aptamer are as the fluorescence probe and the recognition element, respectively. Various factors including the concentration of berberine, Hg 2+ ion and Hg 2+ ion-aptamer, pH effect and the reaction time were investigated in detail. Under the optimal experimental conditions, in the sensing system, the fluorescence intensity changes displayed a calibration response for Hg 2+ ion in the range of 0.1 μM to 10.0 μM and the detection limit was of 7.7 nM (S/N = 3). The fabricated label-free fluorescence aptasensor is not only conveniently but also effectively applicable used for analysis of Hg 2+ ion in blood serum and tap water samples and the recovery range is of 96.0%-105.7%. In brief, this study offers an easy, economical and stable assay system for detecting Hg 2+ ion in rough condition., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Detection of heavy metals is of great importance for food safety and environmental analysis. Among various heavy metal ions, mercury ion is one of the most prevalent species. The methods for detection of mercury were numerous, and the T-Hg-T based assay was promising due to its simplicity and compatibility. However, traditional T-Hg-T based methods mainly relied on multiple T-Hg-T to produce enough conformational changes for further detection, which greatly restrained the limit of detection. Hence, we established a branch-migration based fluorescent probe and found that single T-Hg-T could produce strong signals. The sensing mechanism of our method in different reaction modes was explored, and the detection limits were determined to be 18.4 and 14.7 nM in first-order reaction mode and mixed reaction mode, respectively. Moreover, coupled with Endonuclease IV assisted signal amplification, the detection limit could be 1.2 nM, lower than most DNA based fluorometric assays. For practicability, the specificity of our assay toward different interfering ions was investigated and detection of Hg 2+ in deionized water and lake water was also achieved with similar recoveries compared to those of atomic fluorescence spectrometry, which demonstrated the practicability of our method in real samples. Definitely, the proposed branch migration probe would be a promising substitution for current DNA probes based on recognition of multiple T-Hg-T and we anticipate it to be widely adopted in food and environmental analysis.

A red-emitting fluorescent probe has been developed for the selective and sensitive detection of Hg2+. With the addition of Hg2+, the solution of probe 1 displayed a remarkable fluorescence enhancement (102 fold) with λemmax = 625 nm and a large Stokes shift (150 nm). The detection limit of this probe was as low as 7.1 nM based on S/N = 3. This probe exhibited a good performance in detecting Hg2+ in real water samples, living cells and organisms.

In the present study, we are reporting the synthesis of a triazoles incorporated fluorescent hexahydroquinoline appended calix[4]arene 7 and its highly selective optical recognition ability towards Hg 2+ . The optical sensor 7 was synthesized via two different synthetic pathways and unambiguously characterized by mass spectrometry and NMR spectroscopy. The stoichiometric ratio between 7 and Hg 2+ was determined as 1:1 based on Job's plot and ESI-MS analysis. The chemosensor 7 selectively recognized Hg 2+ in the presence of competitive cations such as Cu 2+ , Cu 1+ , Co 3+ , Ni 2+ , Ag 1+ , Fe 2+ , Fe 3+ , Cr 3+ , Pb 2+ , Cd 2+ , Zn 2+ , Sn 2+ , Ti 4+ , Sb 3+ , In 3+ , Ba 2+ , Ca 2+ , and K 1+ . The limit of detection (LOD) was established as 0.5 μM on spectrofluorimetric analysis. According to world health organization (WHO) in guidelines for drinking-water quality, the mercury level in natural occurring ground and surface water is about ∼0.5 μM (μg/L). The supra molecule 7 with LOD (0.5 μM) could potentially serve effective receptors for Hg 2+ cation. The probe 7 was applied effectively for detection of Hg 2+ in real water samples (i.e. tap and deionized water), spiked with Hg 2+ (10 μM) solution. Moreover, the compound 7 showed non-toxicity during cytotoxic assay against human B cells as they retain their morphology. The supramolecule 7 in living cells showed selectivity towards Hg 2+ in cytotoxic assay with T lymphocytes, evident by morphological changes observed via AFM analysis., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A novel and adjustable lamp based on competitive interaction among dsDNA-SYBR Green I (SGI), ion quencher, and analyte was designed for bioanalysis. The "filament" and switch of the lamp could be customized by employing different dsDNA and ion quencher. The poly(AT/TA) dsDNA was successfully screened as the most effective filament of the lamp. Two common ions, Hg 2+ and Fe 3+ , were selected as the model switch, and the corresponding ligand molecules cysteine (Cys) and pyrophosphate ions (PPi) were selected as the targets. When the fluorescence-quenched dsDNA/SGI-ion complex was introduced into a target-containing system, ions could be bound by competitive molecules and separate from the complex, thereby lighting the lamp. However, no light was observed if the biomolecule could not snatch the metal ions from the complex. Under the optimal conditions, sensitive and selective detection of Cys and PPi was achieved by the lamp, with practical applications in fetal bovine serum and human urine. This ion quencher regulated lamp for fluorescent bioassays is simple in design, fast in operation, and is more convenient than other methods. Significantly, as many molecules could form stable complexes with metal ions selectively, this ion quencher operated lamp has potential for the detection of a wide spectrum of analytes. Graphical abstract A novel and adjustable lamp on the basis of competitive interaction among dsDNA-SYBR Green I, ions quencher and analyte was designed for bioanalysis. The filament and switch of lamp could be customized by employing different dsDNA and ions quencher.

This work reports a facile strategy for the synthesis of water-soluble fluorescent probes Pyr1 and Pyr2, which have carboxyl and hydroxyl group in the side chain of thioacetal moiety, respectively. Pyr1-2 exhibit exclusively selective turn-on fluorescence response towards Hg 2+ over other cations, based on intramolecular charge transfer (ICT) mechanism. Upon addition of Hg 2+ , the thioacetal moiety in Pyr1-2 can be converted to aldehyde group, which is confirmed by 1 H NMR titrations. The detection limits for Pyr1-2 are less than 1.80nM in aqueous media, lower than the maximum allowable level of Hg 2+ in drinking water by EPA. Moreover, Pyr2 have been successfully used for fluorescence imaging of Hg 2+ in living cells, demonstrating potential application in biological science., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A fluorescence probe has been designed and synthesized, and applied with a combined theoretical and experimental study. Research suggests that the probe can be used to sense Zn 2+ and Hg 2+ through selective turn-on fluorescence responses in the aqueous HEPES buffer (0.05M, pH=7.4). The limit of detection (LOD) were determined as 1.46×10 -7 M (Zn 2+ ) and 2.50×10 -7 M (Hg 2+ ). Moreover, based on DFT, the geometry optimizations of probe 1, [1-Hg 2+ ] complex and [1-Zn 2+ ] complex were carried out using the Gaussian 09 program, in which the B3LYP function was used. The electronic properties of free probe 1 and the metal complexes were studied based on the Natural Bond Orbital (NBO) analyses. The probe 1 has also been successfully applied to detection of Zn 2+ and Hg 2+ in living cells., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A novel water-soluble fluorescent probe FLS2 based on the thiooxofluorescein derivative has been firstly designed and synthesized. UV-vis absorption and fluorescence spectra studies showed that the FLS2 as a colorimetric and ratiometric fluorescent probe exhibited high selectivity and sensitivity towards Hg 2+ , which was mainly attributed to the special binding with the receptor unit accompanied with the spirolactam ring-opening progress. In addition, the probe FLS2 could be used as a naked-eye indicator for Hg 2+ with reversible response. It displayed approximate 37-fold fluorescent enhancement at 529nm in the presence of only 2.0 equiv. Hg 2+ and the detection limit was calculated at about 39nM. What's more, cellular imaging experiment revealed that the sensor had excellent biocompatibility and low cytotoxicity that could be utilized for monitoring Hg 2+ in living cells., (Copyright © 2017 Elsevier B.V. All rights reserved.)

To improve the water-solubility of heavy-metal sensing materials, a modified fluorescein-based derivative, acryloyl fluorescein hydrazine (ACFH), was designed and developed by incorporating a non-hydrogen-bonding group into the conjugated molecule for weakening intermolecular hydrogen-bonding interactions. In neutral water environments, ACFH presented a fluorescence-enhancement performance at λ max =512nm in the presence of Hg 2+ , which could be visualized by naked-eyes. Under the optimized conditions, the linear range of Hg 2+ detection was 1.0-100×10 -9 molL -1 with a correlation coefficient of 0.9992 and a detection limit of 0.86×10 -9 molL -1 . The recognition mechanism was confirmed to be a stable and irreversible 1:1 five-member ring complex between ACFH and Hg 2+ with a coordination constant of 3.36×10 9 . ACFH would possess a potential application in detecting Hg 2+ for biological assay with low cytotoxicity., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Carbamodithioate-based compound C1 was designed and synthesized as a new fluorescent probe for Hg 2 + ions. Upon the addition of Hg 2 + ions, it displayed a rare staged response: the emission spectra of C1 first showed an apparent red-shift, followed by a dramatic decrease. To investigate the sensing mechanism, control compounds C2 with the same phenanthroimidazole unit and C3 with the same carbamodithioate functionality were synthesized. On comparison, the first step sensing process was ascribed to decreasing photoinduced electron transfer on the coordination of Hg 2 + with the lone pair electrons of the nitrogen atom on the phenanthroimidazole ring. The affinity of Hg 2 + and the carbamodithioate unit with four sulfur atoms then induced changes in intramolecular charge transfer efficiency and the second step fluorescent response., (Copyright © 2016 John Wiley & Sons, Ltd.)

A near-infrared fluorescent probe NIR-Hg, for the detection of Hg 2+ ion, has been synthesized directly by condensing Changsha dye with 4-Phenyl-3-thiosemicarbazide and the structure has fully characterized by 1 HNMR, 13 CNMR, and ESI-MS. The probe has been designed on the basis of the reaction that Hg 2+ ion promotes thiosemicarbazide to oxazole in aqueous media and had been induced to produce turn-on fluorescence via an irreversible spirolactam ring-opening process. The probe NIR-Hg has exhibited fast response (1 min), high sensitivity with 44-fold fluorescence intensity enhancement under six equivalent amounts of Hg 2+ added, high selectivity over other related metal ions and a low detection limit of 5.8 × 10 -8 M in the phosphate buffer. The linear response range covers the concentration of Hg 2+ from 5 × 10 -7 to 5 × 10 -6 M. In addition, the probe has good cell-membrane permeability, which is suitable for fluorescence imaging for Hg 2+ in living cells and in vivo mice.

In this work, a turn on fluorescent sensor, based on Hg 2+ coordination conjugated polymer, was developed to detect cysteine-containing compounds. The fluorescence of conjugated polymer (poly(2,5-bis (sodium 4-oxybutyrate) -1,4 - phenylethynylene-alt-1,4-phenyleneethynylene; PPE-OBS) would be quenched by Hg 2+ because of the coordination-induced aggregation and electron transfers of PPE-OBS toward Hg 2+ . When there were some cysteine-containing compounds in PPE-OBS-Hg 2+ system, the fluorescence of PPE-OBS would be recovered. It indicated that the PPE-OBS-Hg 2+ system could be used to detect cysteine-containing compounds. Under the optimized conditions, the experiment results showed that there were particularly linear range, high sensitivity and selectivity over other amino acids. The limit of detection (LOD) of cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) were 0.725μmolL -1 , 0.982μmolL -1 and 1.21μmolL -1 by using this sensor. In addition, Cys standard recovery in several green tea drink and honey samples was also demonstrated. The recovery of Cys was range from 96.3 to 105.0% and RSD was less than 3.25%. The satisfactory results demonstrated that the proposed method could be as a potential fluorescent method for determining cysteine-containing compounds in real samples., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A novel coumarin derivatives based fluorescent chemosensor CBH was designed and synthesized by Schiff base reaction, which was connected by 7-(N,N-diethylamino) coumarin-3-aldehyde and 3-methyl-2-benzothiazolinone hydrazone through C=N. X-ray single crystal structure analysis indicated that two aromatic groups of the CBH were almost in the same plane. It displayed enhancement of the fluorescent intensity and absorbance when the sensor CBH interacted with Hg 2+ ions. The chemosensor CBH exhibited a good sensitive and selective recognition towards Hg 2+ ions in the presence of other important relevant metal ions., (Copyright © 2016. Published by Elsevier B.V.)

The inclusion of the fluorescent organic dye, ethyl 3-(7-hydroxy-2-oxo-2H-chromen-3-yl)-3-oxopropanoate (1) by the host β-cyclodextrin (β-CD), and its response toward mercuric ions (Hg 2+ ), was studied by UV/Vis, fluorescence, and 1 H NMR spectroscopic analyses, mass spectrometry and molecular modeling studies. 1 H NMR measurements together with molecular modeling studies for dye 1 demonstrate that it exhibits two tautomeric forms (keto and enol); however, when the dye is included into the β-CD cavity, the enol form predominates. Moreover, by using spectroscopic and spectrometry techniques, a 1:1 stoichiometry was determined for the complexes formed between dye 1 (enol form) and β-CD, with a binding constant (K b1 =1.8×10 4  m -1 ) and for the dye 1 (keto form)-Hg 2+ (K b2 =2.3×10 3  m -1 ). Interestingly, in the presence of 1-β-CD complex and mercuric ions, a ternary supramolecular system (Hg-1-β-CD complex) was established, with a 1:1:1 stoichiometry and a K b3 value of 4.3×10 3  m -1 , with the keto form of the dye being the only one present in this assembly. The three-component system provides a starting point for the development of novel and directed supramolecular assemblies., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A probe based on 2-(2'-hydroxyphenyl) benzothiazole (HBT) and thiophosphate has been synthesized and used for the ratiometric detection of Hg(2+). The probe was designed in such a way that the excited state intramolecular proton transfer (ESIPT) of the HBT moiety get blocked. The probe exhibited a strong fluorescence enhancement upon addition of Hg(2+) while showing almost no response to other cations in CH3CN/HEPES buffer solution. The probe exhibited fast selectivity towards Hg(2+) and could be completed in 1 min. Fluorescence imaging experiments of Hg(2+) in living TE-1 cells demonstrated its value of practical applications in biological systems.

Naphthalimide-based fluorescent probes 1 and 2 were synthesized, and were designed to form probe-Hg complexes through Hg(2+) ions coordinated to the amide group and imidazole group. They showed high sensitivity and were selective 'naked-eye' chemosensors for Hg(2+) in phosphate buffer. The fluorescence of compounds 1 and 2 could be quenched up to 90% by the addition of Hg(2+) . Reversible probes can detect Hg(2+) ions over a wide pH range (7.0-10.0). Copyright © 2015 John Wiley & Sons, Ltd., (Copyright © 2015 John Wiley & Sons, Ltd.)

In this work, we presented a simple, label-free and rapid-responsive fluorescence assay for iodide (I(-)) detection based on "molecular beacon (MB)"-hosted thioflavin T (ThT), achieving a limit of detection as low as 158 nM. The proposed method exhibited very good selectivity to I(-) ions over other anions interference due to the strong binding force between I(-) ions with Hg(2+). Upon the addition of I(-) ions, it would capture Hg(2+) from a T-Hg(2+)-T complex belonging to the MB-like DNA hairpin structure, which eventually quenched the initial fluorescence as output. In addition, it was successfully applied for operation of an integrated DNA logic gate system and to the determination of I(-) in real samples such as human urine., (Copyright © 2016 Elsevier B.V. All rights reserved.)

This work presented the design, syntheses and photophysical properties of a rhodamine B-based fluorescence probe, which exhibited a sensitive and selective recognition towards mercury (II). The chemosensor RA (Rhodamine- amide- derivative) contained a 5-aminoisophthalic acid diethyl ester and a rhodamine group, and the property of spirolactone of this chemosensor RA was detected by X-ray crystal structure analyses. Chemosensor RA afforded turn-on fluorescence enhancement and displayed high brightness for Hg(2+), which leaded to the opening of the spirolactone ring and consequently caused the appearance of strong absorption at visible range, moreover, the obvious and characteristic color changed from colorless to pink was observed. We envisioned that the chemosensor RA exhibited a considerable specificity with two mercury (II) ions which was attributed to the open of spirolactone over other interference metal ions., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A new type of easily synthesized rhodamine-based chemosensor L(3), with potential NO2 donor atoms, selectively and rapidly recognizes Hg(2+) ions in the presence of all biologically relevant metal ions and toxic heavy metals. A very low detection limit (78 nM) along with cytoplasmic cell imaging applications with no or negligible cytotoxicity indicate good potential for in vitro/in vivo cell imaging studies. SEM and TEM studies reveal strongly agglomerated aggregations in the presence of 5 mM SDS which turn into isolated core shell microstructures in the presence of 9 mM SDS. The presence of SDS causes an enhanced quantum yield (φ) and stability constant (Kf) compared to those in the absence of SDS. Again, the FI of the [L(3)-Hg](2+) complex in an aqueous SDS (9 mM) medium is unprecedentedly enhanced (∼143 fold) compared to that in the absence of SDS. All of these observations clearly manifest in the enhanced rigidity of the [L(3)-Hg](2+) species in the micro-heterogeneous environment significantly restricting its dynamic movements. This phenomenon may be ascribed as an aggregation induced emission enhancement (AIEE). The fluorescence anisotropy assumes a maximum at 5 mM SDS due to strong trapping (sandwiching) of the doubly positively charged [L(3)-Hg](2+) complex between two co-facial laminar microstructures of SDS under pre-miceller conditions where there is a strong electrostatic interaction that causes an improved inhibition to dynamic movement of the probe-mercury complex. On increasing the SDS concentration there is a phase transition in the SDS microstructures and micellization starts to prevail at SDS ≥ 7.0 mM. The doubly positively charged [L(3)-Hg](2+) complex is trapped inside the hydrophobic inner core of the micelle which is apparent from the failure to quench the fluorescence of the complex on adding 10 equivalents of H2EDTA(2-) solution but in the absence of SDS it is quenched effectively.

In this paper, a simple fluorescent probe, rhodamine B derivatives (RS), was designed and prepared for sensitive detection of Hg(2+) in CH3CN/H2O (5/5, v/v). RS exhibits high selectivity and sensitivity toward Hg(2+) over other common metal ions, displaying a significant color change from colorless to pink in the presence of Hg(2+). The fluorescence responses remain stable over a broad pH range (5.0 to 9.0) and are suitable for detection under physiological conditions. Experimental results of HeLa cells and zebrafish show that RS is cell and organism permeable. We also demonstrate the acquisition of images of Hg(2+) in HeLa cells and zebrafish by using a simple fluorescence confocal imaging technique.