A colorimetric and fluorescent turn-on chemosensor for Zn based on an azobenzene-containing compound

This paper presents a new colorimetric reversible fluorescent turn-on chemosensor molecule for zinc ion based on an azobenzene derivative. The basal fluorescence intensity of the chemosensor molecule is little affected under physiological pH 5-9, whilst the excitation (507 nm) and emission (610 nm) wavelength of the molecular probe for zinc ion is in the visible range.     

A coumarin-based fluorescent and colorimetric chemosensor for rapid detection of fluoride ion

A novel coumarin-based compound 1 featuring thiosemicarbazone as binding unit, was reported as a colorimetric and fluorescent probe for the detection of fluoride anion. The addition of F^? to a solution of probe 1 in tetrahydrofuran resulted in evident naked-eye color change from green-yellow to orange-red under daylight and obvious fluorescence quenching within 3 s. And the detection limit toward F^? was calculated to be as low as 2.16 × 10^?7 mol/L. ¹H NMR titrations proved that the interaction between 1 and fluoride ion: hydrogen bond at low fluoride ion concentration, deprotonation at high fluoride ion concentration. Besides, it exhibited highly sensitivity and selectivity for F^? over other examined ions (Cl^?, Br^?, I^?, AcO^?, NO₃^?, HSO₄^?, H₂PO₄^?) in tetrahydrofuran solution.     

A fluorescent and colorimetric chemosensor for selective detection of aluminum in aqueous solution

We have synthesized a new Schiff base 1, which detects Al³⁺ through fluorescence and naked eye in aqueous solution. The sensor 1 exhibited selective and sensitive recognition toward Al³⁺ via significant fluorescence enhancement (31-fold). Moreover, it showed a significant color change from colorless to yellow. The complex formation was proposed to be 1:1 ratio, based on the Job plot, ESI-mass spectrometry analysis, ¹H NMR titration, and IR analysis. The detection limit was 1.00 μM, which is below the WHO acceptable limit (1.85 μM) in drinking water. In addition, the sensor 1 could be recyclable simply through treatment with a proper reagent such as EDTA.     

A selective colorimetric chemosensor for lanthanide ions

The synthesis and complexing properties of a calix[4]arene derivate (6) carrying two spirobenzopyran moieties are described. The addition of lanthanide ions resulted in significant UV-vis spectral shifts (68-84 nm) in visible region. It indicates that the synthetic receptor can recognize lanthanide ions by naked eyes over other cations including Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe³⁺, Cu²⁺ and Zn²⁺. The mechanism of recognition was studied with ¹H NMR, UV-vis spectra and emission spectra. The receptor may be applied to sense lanthanide ions.     

An enhanced colorimetric chemosensor for the detection of various nitro-explosives

A simple and rapid colorimetric chemosensor for the detection of several nitro-explosives is presented. The method is based on the oxidation of colorless ABTS to its intense blue–green colored radical cation ABTS⁺ by nitrogen dioxide, which can be generated from nitro-explosives by one of the following two methods: (i) digestion of very small amounts of explosives with alkali hydroxide, yielding nitrite anions, which in acidic medium generate nitrogen dioxide, or (ii) by thermal decomposition of nitro-explosives, which generates directly nitrogen dioxide. In these processes nitrogen dioxide acts as a catalytic intermediate, thus enhancing the detection.     

A colorimetric and fluorescent turn-on chemosensor for Al and its application in bioimaging

The sensing properties of a boron dipyrromethene derivative 1 containing a N,N-(dimethylamino)styryl group at its α-position and an aniline moiety at meso-position were investigated by steady-state UV-vis absorption and fluorescence spectroscopy, which were found to exhibit wavelength ratiometric and large fluorescence enhancement in the presence of Al³⁺ with specific selectivity over other metal ions in aqueous media. Furthermore, confocal fluorescence microscopy experiments demonstrated that 1 could be used as a fluorescent probe for Al³⁺ in living cells.     

Acridinium salt based fluorescent and colorimetric chemosensor for the detection of cyanide in water

A new, selective chemosensor has been developed to detect cyanide in water at micromolar concentrations. The acridinium salt used in this sensor system is prepared in a single step from an acridine orange base. Detection is based on the irreversible, 1:1 stoichiometric, nucleophilic addition of cyanide to the 9-position of the acridinium ion. This process induces a large decrease in fluorescence intensity and a marked color change. The selectivity of the system in aqueous media for CN- over other anions is remarkably high. Also, the sensitivity of both the fluorescence- and colorimetric-based assay is below the 1.9 microM suggested by the World Health Organization (WHO) as the maximum allowable cyanide concentration in drinking water. Thus, the chemodosimeter should be applicable as a practical system for the monitoring of CN- concentrations in aqueous samples. [structure: see text]     

A novel colorimetric and fluorescent chemosensor: synthesis and selective detection for Cu and Hg

A novel two-channel metal ion sensor has been synthesized from macrocyclic dioxotetraamine and 1,8-naphthalimide derivative. The metal ion-selective signaling behaviors of the sensor were investigated. The sensor presented the selective coloration for Cu²⁺ and Hg²⁺ that can be detected by the naked-eye, respectively. Besides, the addition of Cu²⁺ and Hg²⁺ quenched the fluorescence of 1 obviously and the detection limit was found to be 3 × 10⁻⁷ M for Cu²⁺ and 7 × 10⁻⁷ M for Hg²⁺. This sensor can be utilized for the visual and spectroscopic detection of Cu²⁺ or Hg²⁺ in the presence of the other competing metal ions.     

A new colorimetric and fluorescent chemosensor based on thiacalix[4]arene for fluoride ions

A new thiacalix[4]arene based fluorescent chemosensor thiacalix[4]arene-N-(quinolin-8-yl)acetamide (TCAN8QA) has been synthesized. TCAN8QA has been found to exhibit highly selective behavior for F⁻ ions among all other anions, that is, Cl⁻, Br⁻, I⁻, PO₄⁻³, OH⁻, H₂PO₄⁻, and CH₃COO⁻ in the absorption spectra as well as in the emission spectra. Red shift and quenching in emission spectra constituting the signature for fluoride detection are due to photoinduced charge transfer (PCT) which can be attributed to deprotonation of acidic NH proton in the presence of fluoride ions.     

A pyrene-based dual chemosensor for colorimetric detection of Cu2+ and fluorescent detection of Fe3+

A pyrene based chemosensor was designed and synthesized. The pyrene fluorophore was connected with a pyridine unit through a Schiff base structure to give the sensor (L). L was tested with a variety of metal ions and exhibited high colorimetric selectivities for Cu²⁺ and Fe³⁺ over other ions. Upon binding with Cu²⁺ or Fe³⁺, L showed an obvious optical color change from colorless to pink for Cu²⁺ or orange for Fe³⁺ over a wide pH range from 3 to 12. Moreover, the fluorescence of L at 370 nm decreased sharply after bonding with Fe³⁺, while other metal ions including Cu²⁺ had no apparent interference. Thus, using such single chemosensor, Cu²⁺ and Fe³⁺ can be detected independently with high selectivity and sensitivity. The limits of detection toward Cu²⁺ and Fe³⁺ were 8.5 and 2.0 μM, respectively. DFT calculation results also proved the formation of stable coordination complexes and the phenomenon of fluorescence quenching by Fe³⁺. Furthermore, L was also successfully used as a bioimaging reagent for detection of Fe³⁺ in living cells.     

Ratiometric, colorimetric and fluorescent chemosensor for "turn-on" detection of cyanide (CN-)

Herein, we unveiled the first zinc complex based chemosensor for cyanide (CN(-)). The changed visual color from light reddish orange to dark reddish orange, the enhanced fluorescence intensity at approximately 600 nm and the near-linear correlation A(495)/A(325)versus the cyanide concentration were observed after adding CN(-).     

A colorimetric and fluorescent chemosensor for the detection of an explosive--2,4,6-trinitrophenol (TNP)

A fluorescent and colorimetric receptor (L) for specific recognition of TNP was described. The origins of this remarkable affinity was disclosed by the crystal structure of corresponding host-guest complex L·TNP.     

A highly selective fluorescent chemosensor for lead ions

A simple fluorescent chemosensor 1 exhibits a 40-fold fluorescence enhancement upon addition of lead ion and yet is insensitive to most of univalent and divalent metal ions. The high affinity of 1 toward Pb2+ presumably results from the cooperative binding behaviors of two potential metal binding sites: the dicarbonyl and the 15-monoazacrown-5 ether.     

4,7-Diaryl indole-based fluorescent chemosensor for iodide ions

Simple and selective indole based fluorescent sensors for iodide anions are reported. A series of 4,7-diaryl indole derivatives (DAIs) are designed and synthesized using Suzuki coupling. These DAIs shows significant changes in UV-vis and fluorescent intensity only with addition of iodides and not with other anions. The ability of these DAIs to function as selective iodide chemosensor is reported.     

A new fluorescent PET chemosensor for fluoride ions

A new anthracene derivative bearing two phenylurea group at the 1,8-position of anthracene shows a selective fluorescence quenching effect with fluoride ion via a PET mechanism.     

A colorimetric and fluorescent chemosensor for detection of Hg2+ using counterion exchange of cationic polydiacetylene

In this study, a colorimetric and fluorescent chemosensor for mercury ions (Hg²⁺) was developed. Cationic polydiacetylene (PDA) vesicles with a quaternary ammonium cation and iodide as a counterion show a blue-to-red color transition; the color change is accompanied by a fluorescence enhancement in selective response to Hg²⁺ ions because of a perturbation of the ene–yne conjugated backbone induced by counterion exchange. It allows for selective detection of Hg²⁺ with the naked eye and the sensor is used to determine Hg²⁺ concentrations in tap water samples.     

A fluorescent chemosensor for wide-range pH detection

Simple polyamines, L1-L3, bearing anthracene and benzophenone units at the respective ends, behave as a fluorescent pH sensor applicable to wide-range pH detection.     

Recent progress in fluorescent and colorimetric sensors for the detection of ions and biomolecules

Optical sensors are widely used in the field of analytical sensing and optical imaging because of their high sensitivity, fast response time, and technical simplicity. This review focuses on recent contributions concerning the ions, neutral molecules and especially tumor micro-environment-related parameters based fluorescent or colorimetric sensors and is organized according to their target classifications.