Fluorescent Sensor For Selective Detection Research Articles

Novel rapid “turn on” tetrahydro-[5]helicene-based fluorescence sensor for selective detection of Cd2+ with a remarkable large Stokes shift and its applications in food samples and living cell

A new tetrahydro-[5]helicene-based fluorescence sensor (PM) was conveniently synthesized for rapid detection of cadmium ion (Cd2+). PM, which has a tetrahydro-[5]helicene derivative, provided a highly sensitive “turn on” fluorescence sensing recognition for Cd2+, with a remarkable large Stokes shift of 163 nm (1.01 eV). The sensor exhibited a fluorescence enhancement toward Cd2+ via photo-induced electron transfer (PET) quenching, a process related to Cd2+-sensor complexation. PM permitted a high selective response to Cd2+ over other interfering metal ions, such as Zn2+. The application of sensor for detection of Cd2+ in commercial food products, including drinking water and rice, were performed and acceptable results were obtained. In addition, this fluorescence sensor could be efficiently applied as a fluorogenic label for tracking Cd2+ in living cells. The potential Cd2+ determination of PM ensures that this sensor can be utilized as fluorescence materials or devices for the real-time monitoring and control of Cd2+ contamination outbreak.

Phenanthridine based rapid “turn-on” fluorescent sensor for selective detection of Th4+ ion and its real-time application

A new and highly sensitive and selective phenanthridine based sensor, 9-(7,8,13,14-tetrahydrodibenzo[a,i]phenanthridin-5-yl)benzo[h]quinolin-10-ol (PHBQ), was developed for the fluorescent ‘‘turn-on’’ detection of Th4+ ion in acetonitrile: water (8:2) medium. The fluorescence intensity of PHBQ diminished in the region of pH 1 to 3 and could be recovered by adjusting the pH to above 4. The sensor PHBQ showed distinct spectral changes in response to Th4+ ion over other competitive metal ions. The fluorescence displayed good linearity with the Th4+ concentration in the equivalence of 0–0.5 equivalents. The detection limit was calculated to be as low as 99 nM, which was less than that of previously reported sensors. The recognizing mechanism of PHBQ towards Th4+ was investigated in detail using HR-MS, NMR, and IR spectroscopy. The economically viable Whatman filter paper was fabricated with PHBQ to develop a paper-based fluorescence kit to detect the Th4+ in an aqueous medium efficiently. Furthermore, the application of sensor ligand in fluorescence imaging was studied in E-coli cells due to its minimal cytotoxicity and good optical properties. The obtained data suggest that the ligand PHBQ can be used as a fluorescent sensor for tracking Th4+ in multiple applications.

An effective and reliable fluorescent sensor for selective detection of methylamine gas based on in-situ formation of MAPbBr3 perovskite nanocrystals in electrospun fibers

The development of fluorescent sensor based on lead-based perovskite nanomaterials is of the most intriguing for the design of quick check with low concentration. In the present work, a rapid, stable, and sensitive fluorescent sensor for selective detection of methylamine (MA) gas is firstly constructed based on in-situ formation of MAPbBr3 (methylamine lead bromide, that is CH3NH3PbBr3) perovskite nanocrystals (PNCs) in electrospun fibers by reacting MA gas with DMAPbBr3@PVDF (dimethylammonium lead bromide@poly (vinylidene fluoride), that is (CH3)2NH2PbBr3@PVDF) fibers. In this strategy, not only is the stability of PNCs significantly enhanced, but also does it retain the sensing efficiency due to the excellent permeability of the membrane. The sensor can maintain its stability after storage for two months due to its superior resistance to moisture, which is highly important for real-world applications. Finally, the nanofibers show a dual-mode sensor response to 5–200 ppm MA gas with a limit of detection (LOD) of 0.8 ppm.

Leftover Kiwi Fruit Peel-Derived Carbon Dots as a Highly Selective Fluorescent Sensor for Detection of Ferric Ion

Recently, the use of natural products for the synthesis of carbon dots (CDs) has received much attention. Herein, leftover kiwi (Actinidia Deliciosa) fruit peels were successfully turned into beneficial fluorescent carbon dots (KN-CDs) via the hydrothermal-carbonization route. KN-CDs 1 and KN-CDs 2 were prepared without and with ammonium hydroxide, respectively. KN-CDs 1 and KN-CDs 2 were systematically characterized by various analytical techniques. Synthesized KN-CDs showed spherical-shaped morphology with narrow size distribution and excellent optical properties with excitation-independent behaviors. The quantum yields of KN-CDs 1 and KN-CDs 2 were calculated as 14 and 19%, respectively. Additionally, the KN-CDs possess excellent prolonging and photostability. Because of the excellent optical properties of KN-CDs, they were utilized as fluorescent sensors. The strong fluorescence of the KN-CDs was selectively quenched by Fe3+ ion, and quenching behavior showed a linear correlation with the concentrations of Fe3+ ion. KN-CDs 1 and KN-CDs 2 showed the detection of Fe3+ ions within the concentration range of 5–25 µM with the detection limit of 0.95 and 0.85 µM, respectively. Based on the turn-off sensing by the detection of Fe3+ ions, KN-CDs would be a promising candidate as a selective and sensitive fluorescent sensor.

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

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

A highly selective fluorescent sensor for ratiometric detection of cyanide in aqueous solution and solid states

Designing fluorescent sensors for selective detection of CN− in aqueous and even solid states are still rarely reported due to the aggregation-caused quenching (ACQ) effect. In this paper, we report a novel fluorescent probe C-1. Due to the AIE effect, C-1 displayed obvious orange-red fluorescence with emission peak centered at 597nm in aqueous solution and solid state. Under the influence of electron withdrawing cyano and ester groups, the vinyl C=C bond was easy to be attacked by nucleophilic CN−, which destroyed the conjugated bridge and also blocked the ICT process between the donor and the acceptor. The emission band shifted from 597 nm to 475 nm consequently. Other anions have no effect on the fluorescence of C-1. Thus, C-1 could be used as a selective CN− sensor. The UV-visible and fluorescent measurement confirmed the interactions between C-1 and CN−. 1H NMR titration method further demonstrated the detection mechanism. The sensitivity and detection limit of C-1 were measured to be 5.97 × 104 M−1 and 1.2 μM respectively. Due to the solid-state emission nature, C-1 immersed test strip was prepared and used as an effective test kit to detect CN¯ ion.

Prediction of stability constants of Cu2+ complexes with organic fluorescent ligands using thermodynamic cycle in combination with DFT theory and SMD solvent model

Accurately predicting the stability constant ( ) of the Cu2+ complex with organic fluorescent ligands provides an important basis to design molecular fluorescent sensors for selective detection of Cu2+. With appropriate reference complexes, the calculated stability constants are in good agreement with experimental values. The values of the predicted stability constants of Cu2+ complexes with Calcein blue (H3Cb) and FluoZin-1 (H2Fz) are 13.33 (exp. 14.27) and 6.59 (exp. 6.01), respectively. More importantly, the results could be applied to the investigation of complexes.

Multifunctional rhodamine B appended ROMP derived fluorescent probe detects Al3+ and selectively labels lysosomes in live cells

There a few reports of rhodamine-based fluorescent sensors for selective detection of only Al3+, due to the challenge of identifying a suitable ligand for binding Al3+ ion. The use of fluorophore moieties appended to a polymer backbone for sensing applications is far from mature. Here, we report a new fluorescent probe/monomer 4 and its ROMP derived polymer P for specific detection of Al3+ ions. Both monomer 4 and its polymer P exhibit high selectivity toward only Al3+ with no interference from other metal ions, having a limit detection of 0.5 and 2.1 µM, respectively. The reversible recognition of monomer 4 and P for Al3+ was also proved in presence of Na2EDTA by both UV–Vis and fluorometric titration. The experimental data indicates the behavior of 4 and P toward Al3+ is pH independent in medium conditions. In addition, the switch-on luminescence response of 4 at acidic pH (0 < 5.0), allowed us to specifically stain lysosomes (pH ~ 4.5–5.0) in live cells.

One-pot green synthesis of optical fluorescent sensor for selective detection of Ni2+ ions and hydro gel studies

Abstract A Schiff base chemosensor derived from 2-aminophenol and 9-anthracenecarboxaldehyde (APAI) was designed and synthesized in a greener approach. It was prepared by microwave irradiation using few drops of acetic acid. The synthesized chemosensor was characterized by 1H NMR and HR-LCMS mass analysis. Its excellent selectivity towards Ni2+ was examined by both colorimetric and fluorometric sensing techniques. A rapid colour change from yellow to dark brown was observed when Ni2+ was added. Among the employed metals only Ni2+ has notable colour change. In the UV–Visible spectrum a new peak apart from the sensor appeared which confirms the selectivity in sensing. A significant enhancement in fluorescence was observed in presence of Ni2+. Among the various metals Cu2+, Co2+, Zn2+, Cr3+,Mg2+, Hg2+, Fe2+, Fe3+, Cd2+, Pb2+ Al3+, Pd2+, K+, Na+, Cr2O42− investigated no major interference was observed even in higher concentration of analytes with a comparatively lowest detection limits of 0.04 μM. The experimental results are further supported by the DFT studies. The chemosensor is likely to find application in the recovery of contaminated water and hydrogel experiments were carried out in order to support the selective colorimetric detection of Ni2+ by APAI.

Functionalized mesoporous silica as a fluorescence sensor for selective detection of Hg2+ in aqueous medium.

We combined the virtues of mesoporous silica and organic functional groups to develop a hybrid fluorescent sensor, PyU-SBA-15, with excellent ability to detect Hg2+ in aqueous medium with high selectivity. In this sensor, the pyrene fluorophore acts as the reporter and the urea unit acts as the receptor during Hg2+ determination. The control material, PyH-SBA-15, which lacks a carbonyl group in the receptor portion, did not display metal-ion selectivity, thereby demonstrating that introducing an additional metal-chelating unit is necessary to improve the metal-ion selectivity of the hybrid sensor. When the concentration of Hg2+ was increased, the fluorescence emission intensities of PyU-SBA-15 at 379, 398, and 476nm gradually decreased. The emission intensity at 379nm was linearly proportional to Hg2+ concentrations in the range of 0-1.0×10-4M, and the sensor was determined to have a detection limit of 9.92×10-8M. This work provides an effective strategy for improving or modulating the metal-ion selectivity of fluorescent sensors based on organic-inorganic hybrid mesoporous silica systems.

One-Pot, In-Situ Synthesis of 8-Armed Poly(Ethylene Glycol)-Coated Ag Nanoclusters as a Fluorescent Sensor for Selective Detection of Cu2.

Fluorescent nanomaterials, such as quantum dots, have developed rapidly in recent years and have been significantly developed. Herein, we demonstrate a facile, one-pot, and in-situ synthesis strategy to obtain fluorescent silver nanoclusters (AgNCs) coated with eight-armed poly (ethylene glycol) polymers (8PEG-AgNCs) via a direct gel-mediated process. During the synthesis, ammonium (NH3) served as the crosslinker for the gel formation via a amine-type Michael addition reaction. This hydrogel can be used as a template to synthesize AgNCs using its volume-limiting effect. The in-situ generation of AgNCs takes place inside the nanocages of the formed gels, which guarantees the homogenous distribution of AgNCs in the gel matrix, as well as the efficient coating of PEG on the nanoclusters. After the degradation of gels, the released 8PEG-AgNCs nanohybrids showed strong blue fluorescence and exhibited long-term stability in aqueous solution for nearly one year. Results showed that the fabricated sensor revealed excellent fluorescent sensitivity for the selective detection of Cu2+ with a detection limit of 50 nM and a wide linear detection range of 5–100 μM. It is proposed that the greater cross-linking density leads to smaller gel pores and allows the synthesis of AgNCs with fluorescent properties. These results indicate that this novel hydrogel with certain biodegradation has the potential to be applied as a fluorescent sensor for catalytic synthesis, fluorescence tracing in cells, and fluorescence detection fields. Meanwhile, the novel design principle has a certain versatility to accelerate the development and application of other kinds of metal nanoclusters and quantum dots.

A fluorescent sensor for selective detection of hypochlorite and its application in Arabidopsis thaliana

Hypochlorite, as one of reactive oxygen species, has drawn much attention due to its essential roles in special biological events and disorders. The exogenous hypochlorite remains a risk for human, animals and plants. In this work, a novel water soluble quinolin-containing nitrone derivative T has been developed for fluorometric sensing hypochlorite. The response mechanism of T towards ClO- was reported for the first time. In comparison with the reported sensors for ClO-, the sensor T in this work exhibited advantages including high selectivity (80 fold over other analytes), rapid response (within 5s) and lipid-water distribution transformation (LogP from 2.979 to 6.131). Further biological applications suggested that T was capable of monitoring both exogenous and endogenous ClO- in living cells. The imaging in Arabidopsis thaliana indicated that the absorption and transmission of ClO- in plant could be monitored by this sensor through the chlorine-related mechanism. This work might raise referable information for further investigations in the physiological and pathological events in both tumor and plants.

Turn-on fluorescence sensor for selective detection of fluoride ion and its molecular logic gates behavior

Loutonin based emissive probe (L) for the dual sensing of fluoride (F−) and bisulphate (HSO4−) anions in aqueous media. The development is based on reports that the interaction between fluoride and loutonin based fluorescent probe exhibits rapid and remarkable color changes in both colorimetrically as well as fluorimetrically. More amusingly, on the introduction of bisulphate ion into the medium containing loutonin fluoride ion complex (L-F−) which shows both the color and fluorescence has been recovered. The limit of detection for fluoride ions by the probe was determined as 8.62 × 10−7 M by fluorescence titrations. Further the probe L can be employed for the removal of fluoride ions. The need for a dual anion detection system with such an outstanding reversible and reproducible process characteristics led us to consider loutonin as a feasible nominee for the construction of molecular keypad lock and molecular logic circuits. The fluorescence change of loutonin after appendage of fluoride ions is mainly due to the hydrogen bonding interaction. Further, the probe could be potentially incorporated into the test strips and silica gel plates, with better selectivity for fluoride and bisulphate anions in aqueous media.

Development of the PANI/MWCNT Nanocomposite-Based Fluorescent Sensor for Selective Detection of Aqueous Ammonia.

The present work reported the polyaniline (PANI) and multiwalled carbon nanotube (MWCNT)-based nanocomposite as a sensing material for the determination of aqueous ammonia by the enhanced fluorescence method. The excitation wavelength-dependent photoluminescence (PL) intensity has shown dual emission peaks at 340 and 380 nm that correspond to two different excitation energy states. The pH-based PL intensity and zeta potential variation were analyzed to optimize the suitable medium for aqueous ammonia sensing. Zeta potential was found to shift from 4 to −21 mV upon changing the pH of the the solution from acidic to alkaline medium. The fluorescence intensity of PANI/MWCNTs was found to increase upon increasing the pH from 3.0 to 6.0 (acidic region) and exhibits a plateau upon further increasing the pH from 7.0 to 12 (basic region). The PANI/MWCNT composite has shown a linear response to aqueous ammonia concentration varying from 25 to 200 μM with a correlation coefficient (R2) of 0.99 and a limit of detection of 15.19 μM. The presence of relevant interference molecules and physiological ions had no influence on the detection of aqueous ammonia. Field-level study demonstrated that the level of aqueous ammonia can be determined selectively by using the PANI/MWCNT composite for various applications. The mechanism for the selective detection of aqueous ammonia is deliberated in detail.

A benzimidazole-based turn-off fluorescent sensor for selective detection of mercury (II)

In this study, potential fluorescent sensing ability of a donor-acceptor-donor type conjugated molecule over various metal ions (Ni(II), Zn(II), Cu(II), Cd(II), Pb(II), Fe(II), Fe(III), As(III), Se(IV), Hg(I) and Hg(II)) was investigated. The sensor basically includes benzimidazole and 3,4-propylenedioxythiophene as the acceptor and donor units, respectively. Solution of the sensor in tetrahydrofuran exhibits an emission with having a maximum at 632 nm. Since having insolubility of some ions in tetrahydrofuran, ion solutions were prepared in deionized water and titrations were performed by stepwise additions of ions into sensor solution in tetrahydrofuran. The control experiment including only deionized water resulted in 7 nm red-shift and 71 % quenching in the emission band. On the other hand, upon 1.07 eq. addition of Hg(II), 25 nm red-shift and 88 % fluorescent quenching were observed, exhibiting a difference among other ions. The corresponding spectral-shift and quenching amounts in the emission were found to be time-dependent and reach to equilibrium after 10 min. Studies showed that Hg(II) in aqueous solutions can be selectively detected even in the presence of other ions. Moreover, presence of Hg(II) (0.36 eq or beyond) changed the color of the sensor solution from pink to pale violet, which can be followed by the naked eye. In the light of these results, the reported sensor can be assigned as a fluorescent and a chromogenic sensor for Hg(II) detection. Limit of quantification was found to be 39.2 nM, which is comparable to the most of the fluorescent Hg(II) sensors in the literature.

A reversible, benzothiazole-based “Turn-on” fluorescence sensor for selective detection of Zn2+ ions in vitro

Temperature-driven, highly sensitive and selective “TURN-ON” fluorometric detection of Zn2+ by benzothiazole-based probes (L1 and L2) was reported in physiological pH in the present work. Iron(II) acted as the reversible switch or trigger for the reversible detection of Zn2+ ions by the probes resulting in “TURN-OFF” fluorescence at room temperature. However, selective detection of Zn2+ in the presence of Fe2+ was irreversible at 0–5 °C. Such temperature dependence on reversible fluorometric detection of Zn2+ in the presence of Fe2+ was explained from the thermodynamic perspective as well as DFT calculations in which the absolute enthalpy (H) and Gibbs free energy (G) of the resultant complexes and the fluorophores (L1 and L2) at different temperatures were determined. Enhanced fluorescence of the Zn2+ bound probes was due to the inhibition of excited-state intramolecular proton transfer (ESIPT). Effect of solvents, pH, and temperature on the fluorometric detection of Zn2+ was also probed in the present work. The results were translated into the visual detection of Zn2+ on paper-based fluorescence probe and later we demonstrated the sensing of mobile Zn2+ ions by the probes in living HeLa cells as the proof of concept of our present investigations. A benzothiazole-based, “TURN-ON” fluorescent sensor was developed for selective and reversible detection of Zn2+in vitro, in which Fe2+ acted as the reversible switch.

CNTs based Water soluble fluorescent sensor for selective detection of Fe3+ ion

Herein, a fluorescence sensor based on the fluorescence quenching phenomena was developed by the functionalization of Pyranine molecules over the surface of carbon nanotubes (Pry-CNTs) for quick, selective and sensitive detection of Fe3+ ion. The change in the emission along with the Fluorescence Quenching response was found linearly comparative to the Fe3+ ion concentration in the range of 0.1−10 μM, with the limit of detection of 0.2 μM. The Fluorescence study proved the coordination interaction between Fe3+ ion and Pry-CNTs lead to the recognition process. The developed fluorescence sensor is the simple and selective link for the determination of Fe3+ ion. The recovery of this method in the determination of Fe3+ ion in real water samples was found to be 99.5–100 %. This fluorescence sensor (Pyr-CNTs) can be used as a sensor for Fe3+ ion and promote for many applications in the environmental, chemical and biological systems.

A rhodamine-based fluorescent sensor for selective detection of Cu2+ in aqueous media: Synthesis and spectroscopic properties

Two new chemosensors, rhodamine B derivative bearing 3-formyl-6-nitrochromone (L1) and 3-formyl-6-methylchromone (L2) units were designed and synthesized using microwave irradiation for the selective detection of Cu2+ in aqueous media. Copper triggers the formation of highly fluorescent ring-open spirolactam. The fluorescence intensity was remarkably increased upon the addition of Cu2+ within a minute, while the other metal ions caused no significant effect. More importantly, the resulting complexes can be used as a reversible fluorescence sensor for CN−. The recognition ability of the sensors was investigated by fluorescence titration, Job’s plot, 1H NMR spectroscopy and density functional theory (DFT) calculations.

Study on synthesis and fluorescence property of rhodamine-naphthalene conjugate.

In this study, a novel ligand (HL) consisting of 2-methyl quinoline-4-carboxylic acid, rhodamine and naphthalene moiety, was designed and synthesized, it could be developed a ratiometric fluorescent sensor for selective detection of Al3+ via fluorescence resonance energy transfer (FRET) from naphthalimide moiety to rhodamine moiety. The addition of Al3+ trigger the significant fluorescence enhancement of HL at 550nm at the expense of the fluorescent emission of HL centered at 524nm.

A turn-on fluorescent sensor for selective detection of hydrazine and its application in Arabidopsis thaliana.

In this work, a primary method was constructed for detecting hydrazine in plant, thus accomplished the closed-loop monitoring of hydrazine circulation within manufacture, environment, plants, animals and human. From a series of sensors, QYL-1 was selected to present the hydrazine sensing properties. As a preliminary tool, QYL-1 suggested the ultra-wide linear range (0-20.0 equivalent) and high selectivity, which were extremely essential for linking the monitoring in various scale and field. For the first time, concentration-dependent tracking of hydrazine was successfully performed in Arabidopsis Thaliana root tips. Afterwards applications in water samples and living MCF-7 cells then fulfilled the demonstration of closing the loop by linking both the upstream and downstream nodes. More than raising a practical method, this work offered initial information for the closed-loop monitoring of hydrazine circulation, which might be significant for the ideal systematic managing in future.