Both visual and fluorescent sensors for Zn(2+) based on bis(pyrrol-2-yl-methyleneamine) platform

A highly selective sequential recognition probe for Zn2+ and HSO4-/H2PO4- based on a diarylethene chemosensor

A novel diarylethene derivative chemosensor DTP-o connected to Schiff base unit for fluorescent detection of Zn²⁺ and relay-detection of HSO₄^-/H₂PO₄^- was designed and synthesized successfully. DTP-o displayed excellent photochromism and fluorometric sensing toward Zn²⁺ to form DTP-o-Zn²⁺ complex in acetonitrile with the detection limit of 5.62 × 10^-7 M. And the form of DTP-o combined with Zn²⁺ could further be verified by Job's plot titrations and mass spectrometry analysis. Furthermore, the complex of DTP-o-Zn²⁺ showed an excellent characteristic of fluorescent relay-response toward HSO₄^- and H₂PO₄^- with high sensitivity and selectivity. The detection limits for HSO₄^- and H₂PO₄^- were as low as 3.04 × 10^-8 M and 3.41 × 10^-8 M, respectively. Moreover, the sensor DTP-o could also be applied to detect Zn²⁺ on practical samples and test strips with high accuracy.

Pyrrole-quinazoline derivative as an easily accessible turn-off optical chemosensor for Cu2+ and resultant Cu2+ complex as a turn-on sensor for pyrophosphate in almost neat aqueous solution

A simple chemosensor, 6-(1H-pyrrol-2-yl)-5,6-dihydro-benzo[4,5]imidazo[1,2-c]quinazoline (1), was synthesized via simple nucleophilic addition reaction coupled with Schiff base condensation. The probe 1 is aggregation-induced emission-active and could be used as an on-off fluorescence sensor toward Cu²⁺ in H₂O/CH₃CN (99.5%, v/v) solution. Furthermore, the resultant Cu²⁺ complex selectively responded to pyrophosphate (PPi) among various anions based on fluorescent on-off signal. In addition, the probe could be used for detecting Cu²⁺ and PPi in HeLa cells.

AIE active salicylaldehyde-based hydrazone: A novel single-molecule multianalyte (Al3+ or Cu2+) sensor in different solvents

A simple asymmetric hydrazone 1 based on salicylaldehyde was designed and prepared, and exhibited an evident aggregation-induced emission (AIE) at a long wavelength of 570 nm in aqueous medium. Probe 1 can selectively sense Al³⁺ in CH₃OH solution through the chelation-enhanced fluorescence mechanism and also recognize Cu²⁺ via fluorescence quenching in H₂O solution through the Cu²⁺-induced assembly of aggregates. In addition, the probe can be applied for detecting Cu²⁺ in biological samples.

Ratiometric fluorescent probe based on pyrrole-modified rhodamine 6G hydrazone for the imaging of Cu2+ in lysosomes

A novel rhodamine-based Schiff base derivative was obtained via the simple condensation of substituted formyl-1H-pyrrole and rhodamine 6G hydrazone. Fluorescence resonance energy transfer enabled the subsequent use of the derivative as a naked-eye colorimetric and ratiometric fluorescent sensor for Cu²⁺ in semi-aqueous solution, and the existence of the morpholine group enabled the further application of the sensor in imaging Cu²⁺ in the lysosomes of HeLa cells.

Quinoline containing acetyl hydrazone: An easily accessible switch-on optical chemosensor for Zn2

A simple chemosensor, namely, N-((quinolin-8-yl)methylene)acetohydrazide (1) was synthesized and used as an off-on fluorescence sensor, which exhibits high selectivity toward Zn²⁺ in aqueous media. The probe has large Stokes shift of >200nm, and its detection limit for Zn²⁺ is 89.3nM. The binding process was confirmed through UV-vis absorption analysis, fluorescence measurements, mass spectroscopy study, ¹H NMR spectra and density functional theory calculation. The crystal structures of Zn²⁺, Ni²⁺, and Cu²⁺ complexes based on 1 were determined through X-ray crystallographic analysis. The fluorescent probe was then applied to monitor intracellular Zn²⁺ in HeLa cells.

A highly sensitive and selective off-on fluorescent chemosensor for hydrazine based on coumarin β-diketone

A coumarin-based sensor C1, namely 3-acetoacetylcoumarin was designed, synthesized and applied for hydrazine detection. Hydrazinolysis of the chemosensor gives a fluorescent coumarin-pyrazole product C1-N₂H₄ [3-(3-methyl-1H-pyrazol-5-yl)coumarin], and thus resulting in a prominent fluorescence off-on response toward hydrazine under physiological conditions. The probe is highly selective toward hydrazine over cations, anions and other biologically/environmentally abundant analytes. The detection limit of the probe is 3.2ppb. The sensing mechanism was supported by ¹H NMR, IR, MS and DFT calculation. The application of the fluorescent probe in monitoring intracellular hydrazine in glioma cell line U251 was also demonstrated.

An ‘‘off–on–off’’ sensor for sequential detection of Cu2+ and hydrogen sulfide based on a naphthalimide–rhodamine B derivative and its application in dual-channel cell imaging

A novel colorimetric and fluorometric sensor with unique dual-channel emission to sequentially detect Cu²⁺ and hydrogen sulfide (H₂S) was synthesized from naphthalimide–rhodamine B through the PET and FRET mechanism. The sensor showed a selective “off–on” fluorescence response with a 120-fold increase toward Cu²⁺, and its limits of detection were 0.26 μM and 0.17 μM for UV-vis and fluorescence measurements, respectively. In addition, 1–Cu²⁺ was an efficient “on–off” sensor to detect H₂S with detection limits of 0.40 μM (UV-vis measurement) and 0.23 μM (fluorescence measurement), respectively. Furthermore, the sensor can also be used for biological imaging of intracellular staining in living cells. Therefore, the sensor should be highly promising for the detection of low level Cu²⁺ and H₂S with great potential in many practical applications.

A novel colorimetric and fluorometric sensor with unique dual-channel emission to sequentially detect Cu²⁺ and hydrogen sulfide (H₂S) was synthesized from naphthalimide–rhodamine B through the PET and FRET mechanism.

A simple hydrazone as a multianalyte (Cu2+, Al3+, Zn2+) sensor at different pH values and the resultant Al3+ complex as a sensor for F−

A new colorimetric and fluorescence molecular chemosensor based on triazole hydrazone can be used as a multi-probe for selective detection of Al³⁺, Zn²⁺, and Cu²⁺ by monitoring changes in the absorption and fluorescence spectral patterns. Results show that Al³⁺ and Zn²⁺ ions can induce remarkable fluorescence enhancement at pH 6.0 and pH 10.0, respectively, while the addition of Cu²⁺ ions leads to a significant UV-visible absorption enhancement in the visible range at pH 6.0. In addition, the resultant Al³⁺ complex could act as an ‘on–off’ fluorescence sensor for F⁻. The fluorescence sensor was also used to monitor intracellular Al³⁺, Zn²⁺, and F⁻ in Hela cells.

A fluorescent probe for Al³⁺ and Zn²⁺ was synthesised, and the resultant Al³⁺-complex was used for the detection of F⁻.

Rhodamine 6G hydrazone with coumarin unit: a novel single-molecule multianalyte (Cu2+ and Hg2+) sensor at different pH value

An effective colourimetric and ratiometric fluorescent probe for Cu²⁺ in neutral aqueous media was synthesised. Moreover, the probe could sense Hg²⁺ with fluorescence enhancement at high pH.