Fluorogenic Chemosensor Research Articles

Nanomolar Hg2+ detection via phenothiazine fluorogenic chemosensor: Applications in water analysis and intracellular imaging

A Knoevenagel condensation reaction paved the way for the development of the PTZ-BCN probe namely (z)-2-(1H-benzo[d]imidazole-2-yl)-3-(10-ethyl-10H-phenothiazin-3-yl) acrylonitrile. PTZ-BCN’s spectral characteristics were verified through the application of IR, 1H NMR, 13C NMR, and HRMS techniques. The PTZ-BCN probe showed a high selectivity and sensitivity toward Hg2+ ions over other interfering competing metal ions in CH3CN: HEPES buffer (9:1, v/v) system. The addition of Hg2+ results in a notable redshift and fluorescence quenching of the PTZ-BCN probe. An examination of the interaction between the PTZ-BCN probe and Hg2+ involved recoding 1H NMR titration spectra, HRMS, DFT analysis, and Job’s plot respectively. Quantification of the lowest detectable Hg2+ concentration at 2.3 nM, exhibiting a correlation coefficient of R2 = 0.9985. PTZ-BCN probe has proven effective in quantitatively determining the existence of Hg2+ in real-time water samples, test strips, solid state, and Hela living cells.

Engineering a new quinoline based chromo − fluorogenic chemosensor for consecutive sensing of Cu2+ and N–acetyl–L–cysteine: Applications in Smartphone platform, real samples and living cell bioimaging

A new quinoline based chromo − fluorogenic chemosensor (QMEH) was designed for the sequential recognition of Cu2+ and N–acetyl–L–cysteine (NAC) in DMSO:H2O (50:50, v/v) medium. Excellent visual color changing and fluorescence quenching of QMEH with gradually adding of Cu2+ were monitored with highly selective binding stoichiometry (1:1), which might be resulted from a chelation enhanced quenching (CHEQ) phenomenon. Next, the Cu2+−enhanced absorbance and − quenched emission of QMEH were fully recovered by NAC through the displacement approach. The QMEH−Cu2+ complex structures showed obvious color changes by the adding of NAC from ’’bright yellow’’ to ’’noncolored’’ under daylight and from ’’noncolored’’ to ’’blue’’ under UV−cabinet, respectively. The gradual addition of NAC to the QMEH−Cu2+ solution induced its absorbance and emission recovery with low detection limits of 65.88 μM and 6.32 μM, respectively. To assess the importance of method parameters, the validation study was carried out using diverse analytical parameters. Moreover, thanks to the superior sensing performance and the low cytotoxicity ability of QMEH, it was used for the Smartphone platform, natural spring waters and the sequential bioimaging of Cu2+ and NAC in hepatocellular carcinoma cells.

Fluorescent Sensors for Tetracycline Detection in Aqueous Medium: A Mini-Review.

Tetracycline (TC) is a commonly used antibiotic in human therapy and animal husbandry. Public concerns about TC residues inflated due to their negative impact on the environment, food, and human health concerns. To ensure human health and safety, there is a need for fluorogenic chemosensors that can easily detect TC antibiotics with high selectivity and sensitivity in the aqueous medium. This mini-review discusses the progress and achievements in several fluorometric antibiotic tetracycline detection methods. Fluorogenic chemosensors for tetracycline antibiotics with easy-to-use, high selectivity, and sensitivity have been essentially required to regulate food safety and secure human health and safety. Moreover, we gave more attention to the practical applicability of chemosensors for tetracycline antibiotics in food and water quality assessment. This article starts with a section that constitutes an overview of the problems of antibiotics and the typical features of traditional techniques of antibiotic detection. It then goes on to describe up-to-date optical methods for the selective detection and efficient removal of TC. These methods involve a variety of platforms, like tetraphenylethylene polymers, metal complexes, self-assembled CuNCs, and hydrogel. The article also discusses the practical applicability of chemosensors for tetracycline antibiotics in food and water quality.

An AIE dynamic a highly selective and expeditious benzothiazole-pyrazine based colorimetric chemosensor for Ni2+and fluorogenic chemosensor for Cu2+ and Al3+ detection

Considerable research focus has been devoted to the advancement of single-component sensors that can identify several analytes. In this regard, a complex chemosensor called BPA was created by building an imine link between benzothiazole and pyrazine. On the flexible imine link, the nitrogen atoms with lone pair electrons were arranged as possible coordination sites to enable changes in molecular configurations and charge transfer. In the aqueous acetonitrile environment, BPA displayed the discriminative identification of Ni2+ by a chromogenic response (color transition from colorless to yellow) and a fluorescence “decreasing” response for Cu2+ via ligand–metal charge transfer. Additionally, BPA exhibited recognition of Al3+ through a “turn-on” fluorogenic response facilitated by the chelation-enhanced fluorescence effect. The detection limits for Ni2+, Al3+, and Cu2+ were remarkably low, measuring 5.19 nM, 16 nM, and 214 nM, respectively. A 1:1 binding stoichiometry and precise complex modes between BPA and the target metal ions were successfully determined using extensive investigations, which encompassed the utilization of Job's plot, mass spectra, NMR, and DFT analysis. The deduced coordination mechanisms were corroborated by computational and experimental methodologies. BPA's potential practical uses were demonstrated by subsequently evaluating its ability to identify Ni2+, Al3+, and Cu2+ in actual water samples and validating its performance on-site using test strips.

An Adenine‐Based Chromone‐Coupled ‘Off‐On‐Off’ Fluorogenic Dyad for Cascade Detection of Zn2+ and HSO₄− Ions or Zn2+ Ions and Picric Acid

AbstractA chromone‐coupled adenine‐based fluorogenic chemosensor (BD1) has been introduced for cascade detection of Zn2+ and HSO4−ions or Zn2+ and picric acid (PA) based on the fluorescence ‘OFF‐ON‐OFF’ mechanism. A momentous fluorescence improvement has been observed due to the accumulation of Zn2+ ions in the BD1 solution because of the formation of the Zn2+ chelated BD1 complex. A cyan color fluorescence enhancement is visible under the exposure of a 365 nm UV lamp, which is also manifested in the CIE diagram. The detection limit of our developed sensor BD1 and Zn2+−BD1 complex towards the identification of Zn2+ and HSO4− ions are in the nM and μM range, respectively, in the solution phase. Among the several explosive nitroaromatic compounds (NACs), only PA quenches the fluorescence of the Zn2+ chelated BD1 complex, and the nature of quenching is both static and dynamic. A paper strips‐based test kit experiment is performed for on‐spot identification of Zn2+ ions and PA. Based on these chemically encoded inputs and the fluorescence intensity as optical output, we have constructed an INHIBIT molecular logic circuit. The present report evokes a new approach for the development of new chemosensors from bioinspired materials such as adenine, a purine nucleobase.

Ratiometric fluorescence-based and chromogenic sensors for the detection of fluoride ions and their application in real samples.

This review focuses on the results of synthetic ratiometric fluorescent and colorimetric probes, which have been applied to qualitatively and quantitatively detect fluoride anions in cells, living organisms, and real samples. Primary attention is given to progress made in the working mechanism and applications of these probes to detect fluoride ions in living systems. In addition, design strategies and detection limit for these probes are discussed. This review aims to deliver a comprehensive compilation of the examples reported from 2005 to 2021 on the developments of ratiometric chromogenic and fluorogenic chemosensors for fluoride anions. A total of 20 different ratiometric/colorimetric sensors have been selected for the novelty in their design, sensitivity, detection limit, dynamic range, and speed of detection based on the three fundamental principles of F- ion detection, namely Si-O bond cleavage; excimer emission; and intramolecular charge transfer emission through the B-F monomer, B-F-B bridged dimers, and deprotonation of the amide N-H. Special emphasis has been given to categorize the fluorophores that work in aqueous media, and possible strategies that might be adopted to design green sensors are discussed. Finally, a tabular summary of the comparative studies of all the sensors based on their sensitivity, detection limit, working solvent, and applications is provided. This extensive review may expedite improvements in the development of advanced fluorescent probes for vast and stimulating applications in the future.

A triphenylamine scaffold for fluorogenic sensing of noxious cyanide via the ICT mechanism and its bioimaging application

A novel triphenylamine benzimidazole-based fluorogenic chemosensor (PBIA) has been developed for the selective and efficient detection of CN−.

Naphthalene derived Schiff base as a reversible fluorogenic chemosensor for aluminium ions detection

Schiff base (HNPD) was achieved by reacting 2-hydroxy-1-naphthaldehyde with N-phenyl-o-phenylenediamine in enthanol medium. The spectroscopic analyses were done to establish the formation of Schiff base apparently. Further, synthesized Schiff base conjugate was successfully used as a fluorogenic chemosensor to detect aluminium ions (Al3+) with high fluorescence amplification among the other interfering various metal ions. The limit of detection of 0.0248 × 10−6 M and a binding constant of 6.19 × 103 M−1 were obtained by the receptor HNPD for Al3+ detection. A high influence of intramolecular charge transfer kinetics was established to realize the selective responsiveness towards Al3+ ions. Density functional theory approximation formulated the band energy modulation and localization and delocalization of electron density for the HNPD and Al3+ complexation. The developed sensor ultimately inspected on the real soil and water samples and ascertained the practical ability of Al3+ ions detection of HNPD chemosensor.

Highly Selective and Rapid "Turn-On" Fluorogenic Chemosensor for Detection of Salicylic Acid in Plants and Food Samples.

Salicylic acid (SA) is one of the chemical molecules, involved in plant growth and immunity, thereby contributing to the control of pests and pathogens, and even applied in fruit and vegetable preservation. However, only a few tools have ever been designed or executed to understand the physiological processes induced by SA or its function in plant immunity and residue detection in food. Hence, three Rh6G-based fluorogenic chemosensors were synthesized to detect phytohormone SA based on the "OFF-ON" mechanism. The probes showed high selectivity, ultrafast response time (<60 s), and nanomolar detection limit for SA. Moreover, the probe possessed outstanding profiling that can be successfully used for SA imaging of callus and plants. Furthermore, the fluorescence pattern indicated that SA could occur in the distal transport in plants. These remarkable results contribute to improving our understanding of the multiple physiological and pathological processes involved in SA for plant disease diagnosis and for the development of immune activators. In addition, SA detection in some agricultural products used probes to extend the practical application because its use is prohibited in some countries and is harmful to SA-sensitized persons. Interestingly, the as-obtained test paper displayed that SA could be imaged by ultraviolet (UV) and was directly visible to the naked eye. Given the above outcomes, these probes could be used to monitor SA in vitro and in vivo, including, but not limited to, plant biology, food residue detection, and sewage detection.

Mono o‐nitrobenzyl dihydrofluorescein as a photoactivatable ROS sensor for oxidative stress in live cells

AbstractThe confocal interpretation of organelle‐selective fluorogenic chemosensors can be ambiguous because of inconsistency between the sensor localization and reaction site. To overcome this limitation, we implemented the photoactivation strategy which refers to light‐controlled probe activation within cells at the desired time. In this study, we synthesized a photoactivatable dihydrofluorescein probe (1) and its cell‐permeable derivative (3, acetoxymethyl ester of 1). We confirmed their reactivity to reactive oxygen species (ROS) and photoactivation in both solution and cells. The photoactivation of probe 3 facilitated temporal control between probe treatment and the occurrence of fluorogenic events. We conducted organelle colocalization studies and cellular ROS imaging, clearly showing that the probe primarily localized to early/late endosomes and reacted with intracellular ROS at these endosomes. These findings highlight the effectiveness of the photoactivation strategy for fluorogenic ROS probes in mitigating ambiguities associated with conventional fluorogenic ROS sensing approaches.

Shedding Novel Photophysical Insights Toward Discriminative Detection of Three Toxic Heavy Metal Ions and a hazard class 1 nitro-explosive By Using a Simple AIEE Active Luminogen.

In this work, we introduced a simple aggregation-induced emission enhancement (AIEE) sensor (PHCS) which can selectively detect and discriminate three environmentally and biologically imperative heavy metal ions (Cu2+, Co2+ and Hg2+) and a hazard class 1 categorized nitro-explosive picric acid (PA) in differential media. By virtue of its weak fluorescence attributes in pure organic medium owing to the synergistic operation of multiple photophysical quenching mechanisms, the molecular probe showcased highly selective 'TURN ON' fluorogenic response towards hazardous Hg2+ with a limit of detection (LOD) as low as 97nM. Comprehensive investigation of binding mechanism throws light on the cumulative effect of probe-metal complexation induced chelation enhanced fluorescence (CHEF) effect and subsequent AIEE activation within the formed probe-metal adducts. Noteworthily, the probe (PHCS) can be readily used in real water samples for the quantitative determination of Hg2+ in a wide concentration range. In addition, the probe displayed modest colorimetric recognition performances to selectively detect and discriminate two essential heavy metal ions (Cu2+ and Co2+) with a LOD of 96nM and 65nM for Cu2+ and Co2+ respectively, in semi-aqueous medium. Intriguingly, based on high photoluminescence efficiency, the AIEE active nano-aggregated PHCS displayed a remarkable propensity to be used as a selective and ultra-sensitive 'TURN-OFF' fluorogenic chemosensor towards PA with LOD of 34.4ppb in aqueous medium. Finally, we specifically shed light on the interaction of PHCS hydrosol towards PA using some unprecedented techniques, which helped uncover new photophysical insights of probe-explosive molecule interaction.

Alternative boronic acids in the detection of Mycolactone A/B using the thin layer chromatography (f-TLC) method for diagnosis of Buruli ulcer

BackgroundMycobacterium ulcerans is the causative agent of Buruli ulcer. The pathology of M. ulcerans disease has been attributed to the secretion of a potent macrolide cytotoxin known as mycolactone which plays an important role in the virulence of the disease. Mycolactone is a biomarker for the diagnosis of BU that can be detected using the fluorescent-thin layer chromatography (f-TLC) technique. The technique relies on the chemical derivatization of mycolactone A/B with 2-naphthylboronic acid (BA) which acts as a fluorogenic chemosensor. However, background interferences due to co-extracted human tissue lipids, especially with clinical samples coupled with the subjectivity of the method call for an investigation to find an alternative to BA.MethodsTwenty-six commercially available arylboronic acids were initially screened as alternatives to BA using the f-TLC experiment. UV–vis measurements were also conducted to determine the absorption maximum spectra of mycolactone A/B and myco-boronic acid adducts followed by an investigation of the fluorescence-enhancing ability of the boronate ester formation between mycolactone A/B and our three most promising boronic acids (BA15, BA18, and BA21). LC–MS technique was employed to confirm the adduct formation between mycolactone and boronic acids. Furthermore, a comparative study was conducted between BA18 and BA using 6 Polymerase Chain Reaction (PCR) confirmed BU patient samples.ResultsThree of the boronic acids (BA15, BA18, and BA21) produced fluorescent band intensities superior to BA. Complexation studies conducted on thin layer chromatography (TLC) using 0.1 M solution of the three boronic acids and various volumes of 10 ng/µL of synthetic mycolactone ranging from 1 µL – 9 µL corresponding to 10 ng – 90 ng gave similar results with myco-BA18 adduct emerging with the most visibly intense fluorescence bands. UV–vis absorption maxima (λmax) for the free mycolactone A/B was observed at 362 nm, and the values for the adducts myco-BA15, myco-BA18, and myco-BA21 were at 272 nm, 270 nm, and 286 nm respectively. The comparable experimental λmax of 362 nm for mycolactone A/B to the calculated Woodward-Fieser value of 367 nm for the fatty acid side chain of mycolactone A/B demonstrate that even though 2 cyclic boronates were formed, only the boronate of the southern side chain with the chromophore was excited by irradiation at 365 nm. Fluorescence experiments have demonstrated that coupling BA18 to mycolactone A/B along the 1,3-diols remarkably enhanced the fluorescence intensity at 537 nm. High-Resolution Mass Spectrometer (HR-MS) was used to confirm the formation of the myco-BA15 adduct. Finally, f-TLC analysis of patient samples with BA18 gave improved BA18-adduct intensities compared to the original BA-adduct.ConclusionTwenty-six commercially available boronic acids were investigated as alternatives to BA, used in the f-TLC analysis for the diagnosis of BU. Three (3) of them BA15, BA18, and BA21 gave superior fluorescence band intensity profiles. They gave profiles that were easier to interpret after the myco-boronic acid adduct formation and in experiments with clinical samples from patients with BA18 the best. BA18, therefore, has been identified as a potential alternative to BA and could provide a solution to the challenge of background interference of co-extracted human tissue lipids from clinical samples currently associated with the use of BA.

Synthesis and investigation of bis(phenyl)fluorene and carbazole appended dipodal Schiff base for fluorescence sensing towards Sn(II) ion and its regioselective polymerization

One-pot condensation reaction between 9,9-Bis(4-aminophenyl)fluorene and 9-Ethyl-9H-carbazole-3-carbaldehyde afforded a chemosensor ((N,N′)-4,4′-(9H-fluorene-9,9-diyl)bis(N-((9-ethyl-9H-carbazol-2-yl)methylene)aniline, SB) having Schiff base skeleton. The further step was the synthesis of the polymer (P-SB) via oxidative polycondesation reaction of SB. FT-IR, 1H NMR and 13C NMR instruments were used to characterize the functional groups on the monomer and polymer. Thermal stability and electrochemical features of SB and P-SB were characterized by thermogravimetric analysis-differential thermal analyses (TG-DTA) and cyclic voltammetry (CV), respectively. The glass transition and surface image of P-SB were determined from DSC and SEM measurements, respectively. UV–vis and photoluminescence spectroscopy (PL) allowed to determine the optical properties of SB and P-SB. The obtained polymer, which had the weight average molecular weight of 8400 Da identified by gel permeation chromatography (GPC), exhibited fluorescence property. The synthesized turn-on fluorogenic chemosensor SB showed high selectivity and sensitivity towards Sn2+ among the cations of Ag+, K+, Hg2+, Mn2+, Cd2+, Sn2+, Ca2+, Pb2+, Zn2+, Co2+, Ni2+, Cu2+, Fe3+, Al3+, Cr3+ and Cr6+. The fluorescence turn-on recognition process for the detection of Sn2+ was related to the restriction of CN isomerization, followed by inhibiting intramolecular charge transfer (ICT), with consequent chelation-enhanced fluorescence (CHEF) mechanism. The stoichiometry ratio of the analyte-sensor adduct in the solution was found to be 1:1 by Job's plot method concomitant with a dramatic increase in fluorescent signal at 471 nm and a marked color change from colorless to turquoise blue upon addition of Sn2+ ions. Limit of detection value for the formation of SB-Sn2+ chelation was calculated as 3.37 nM. No change in PL intensity of SB-Sn2+ chelation was observed in the company of other metal ions. Reversibility of the chemosensor in its binding towards Sn2+ was demonstrated in the presence of chelating agent EDTA. The synthesized SB could effectively detect Sn2+ ion as a fluorescent sensor.

Paradoxical fluorescein-naphthalene Salamo-Salen-Salamo Zn(II) complex as a H2PO4−-targeted chemosensor and its application in water samples

Chemical materials with different properties could be directionally synthesized by introducing various functional groups into a molecular system. Here, an unusual naphthalene-fluorescein Salamo-Salen-Salamo-type Zn(II) complex was first developed as a fluorogenic chemosensor (ZnSS) based on a grafting design strategy. The in situ chemosensor ZnSS exhibits selective and efficient fluorogenic detection towards dihydrogen phosphate ion (H2PO4−) with off-on style in DMSOHEPES buffer. The synthesized chemosensor ZnSS could be applied to quantitatively analyze H2PO4− ion in rain water and tap water. Fluorescence quantum yield calculation was performed to study the luminescent properties of these compounds. Moreover, the mutual equilibrium of H2PO4− ion was studied by the transition state theory and vibration analysis of density functional theory (DFT). Time-dependent DFT (TDDFT) and electrostatic potential (ESP) calculations further explain the fluorescence emission characteristics and electronic excitation behavior in the sensing process.

A biphenyl thiosemicarbazide based fluorogenic chemosensor for selective recognition of Cd2+: application in cell bioimaging.

A diversified biphenyl thiosemicarbazide based chemosensor (HBMC) has been fabricated and reported for the specific detection of Cd2+ in a MeOH : H2O (4 : 1) solution. We observed a chromogenic change from colorless to light yellow colour, and it showed a "turn-on" fluorogenic change from non fluorescent to blooming cyan colour. In fluorometric titration a sharp "turn-on" emission for Cd2+ was observed with a ∼16 fold increase in fluorescence intensity value at 496 nm by incremental addition of Cd2+ ions in the MeOH : H2O (4 : 1) solution. The reversibility of the chemosensor (HBMC) was confirmed by a sequential addition of the EDTA solution. Again the binding stoichiometry of HBMC with Cd2+ was found to be 2 : 1, as confirmed by Job's plot analysis and HRMS spectra of the HBMC-Cd2+ complex. The mechanism for Cd2+ sensing in MeOH : H2O (4 : 1) is based upon the inhibition of CN isomerization and ESIPT process and simultaneously turning on the CHEF (chelation enhanced fluorescence) process. The limit of detection for Cd2+ was found to be in the order of 10-8 (M), which implies that HBMC is an efficient probe to detect Cd2+ at the microscopic level. A reusability study was performed and on-sight detection of cadmium ions by the chemosensor (HBMC) was established by dip-stick experiment. In vitro detection of Cd2+ in human breast cancer cells (MDA-MB-231) by HBMC discloses its cell permeability and biocompatible nature. Computational studies (DFT and TDDFT) with the probe HBMC and HBMC-Cd2+ complex were also performed.

Unconventional OFF-ON Response of a Mono(calix[4]arene)-Substituted BODIPY Sensor for Hg2+ through Dimerization Reversion.

A new selective fluorogenic chemosensor for Hg2+, which combines a calixarene derivative with a BODIPY core as a fluorescent reporter, is described. The remarkable change in its fluorogenic properties in DMSO and CHCl3 has been analyzed. A study of its spectral properties on dilution, along with molecular modeling studies, allowed us to explain that this behavior involves the formation of a J-dimer, as well as how the sensing mechanism of Hg2+ proceeds.

Hybrid films composed of ethyl(hydroxyethyl)cellulose and silica xerogel functionalized with a fluorogenic chemosensor for the detection of mercury in water

Ethyl(hydroxyethyl)cellulose (EHEC) and a silica–based xerogel (SBX) were functionalized with a (18–crown–6)–styrylpyridine precursor (1) to obtain the modified polymers EHEC–1 and SBX–1, respectively. Films were obtained and the resulting materials were used as fluorogenic devices for the detection of Hg2+ in water. The films produced from EHEC–1 showed high water retention, making it difficult to apply as a reusable optical chemosensor. Since SBXs are recognized in the literature for their hydrophobicity, a hybrid film composed of EHEC and SBX–1 which did not show water retention was produced and characterized. This system showed rapid response time, outstanding selectivity compared to several other studied metal ions, and sensitivity for the detection of Hg2+ in water. The detection limit for this material using fluorescence technique was 2 ppb (∼10−8 mol L−1). The reversibility of the complex formed between EHEC-SBX–1 film and Hg2+ was demonstrated by the addition of cysteine to the medium. The result obtained also allowed the assembly of INHIBIT and IMPLICATION molecular logic gates, using Hg2+ and cysteine as inputs. The results described in this article have important significance in the development of novel reversible fluorogenic chemosensors and adsorbent materials for the effective removal of Hg2+ ions.

Synthesis and Fluorimetric Application of Novel Schiff Base Compound Containing Imidazole

This study describes the synthesis and application of 2-(2-hydroxy-5-(1H-phenanthro [9,10-d]imidazol-2-yl)benzylidene)-N-phenylhydrazine-1-carboxamide (TC) as a fluorogenic chemosensor toward for Zn2+ sensing in EtOH-H2O (9:1, v/v) media. The chemosensor TC could sensitively determine Zn2+ ions with a low detection limit (LOD) and LOD value was found to be 5.73 nM. The fluorogenic titration spectrum indicated that the Zn2+ concentration was proportional to emission and gave a good linear alteration in emission in response to the equivalent of Zn2+, the complexation ratio between chemosensor TC and Zn2+ was calculated as 1:1 by the method of continuous variation (Job's plot) from the obtained titration study. Moreover, the Ka value for the TC-Zn2+ complexation was found as 6.7×10−3 M−1 according to the Benesi–Hildebrand value of the changess in the titration of the chemosensor TC against Zn2+ ions. As a result of obtained data, chemosensor TC could be utilized to be an effective fluorogenic chemosensor for recognizing Zn2+ ions.

Selective chromogenic and fluorogenic signalling of Hg2+ ions using a benzothiazole-quinolinyl acrylate conjugate and its applications in the environmental water samples and living cells

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.

A novel “on-off-on” halogen-substituted bis(salamo)-like fluorogenic chemosensor for sequentially identifying Cu2+ ions and cysteine

A novel bis(salamo)-like fluorogenic chemosensor (BDS) was designed for recognition Cu2+ ions through fluorescence “off” in DMSO/H2O (v/v = 9:1) Tris-HCl (pH = 7.26) buffer system to form a 1:2 BDS-Cu2+ complex. Significantly, the product BDS-Cu2+ for recognition Cu2+ could relay identify cysteine (Cys) in the same solvent system. In this process, the Cys captured Cu2+ in BDS-Cu2+ due to competitive coordination and released BDS, accompanied by the fluorescence recovery (“turn on”) of the system. Interestingly, the chemosensor BDS shows orange fluorescence in solid phase but blue fluorescence in liquid phase (DMSO/H2O, v/v = 9:1). The chemosensor BDS presents high sensitivity and selectivity to Cu2+ ions and Cys with the limits of detection (LOD) toward Cu2+ and Cys of 191 nM and 211 nM separately. Furthermore, the chemosensor BDS can be practical applied in detecting Cu2+ ions on medical swab platform via the naked eye and fluorescence dual channel. Finally, the fluorescence “on-off-on” recognition mechanism of the chemosensor BDS to Cu2+ ions and sequentially Cys was rationally explained by performing density functional theory (DFT) calculations.