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Abstract: A newly synthesized and characterized naphthalimide derivative (L1) acts as a highly sensitive chemosensor for aqueous sulfide ions in water/DMSO (3:1, v/v) medium as L1 offers distinctive reactive properties toward aqueous sulfide ions to be converted to L1A of potential turn‐on fluorescent properties over other competitive anions. Gradual addition of aqueous sulfide ions led to the formation of in situ L1A compound which showed a single point fluorescence enhancement based on intramolecular charge transfer (ICT). To establish this new interesting pathway in favor of ICT for sensing sulfide ions, the detailed spectroscopic studies of other three similar type new 1,8‐naphthalimide based organic probes (L2, L3 and L4) duly structurally characterized including theoretical (DFT) studies have been carried out systematically. The probe (L1) detects aqueous sulfide ions as low as 2.4 μM in at biological pH within a very short responsive time (15‐20 s) and this non‐cytotoxic the probe, L1 is also useful in acquiring the fluorescent image of the distribution of sulfide ions in living cells using fluorescence microscope. [ABSTRACT FROM AUTHOR]

A rhodamine–pyrene hybrid molecule acts as a colorimetric and fluorimetric sensor for Al3+ through time dependent PET–CHEF and FRET processes associated with tri-color emission. Intracellular Al3+ has been visualized through time dependent blue–green–red emission. The lowest limit of detection for Al3+ is 0.02 μM. [ABSTRACT FROM AUTHOR]

A visible light excitable rhodamine based probe operates as a SCN− selective fluorescent “turn-on” sensor for living cell imaging with a detection limit of 0.01 μM, which is much lower than the normal SCN− level in the human body. A “lock” and “key” model has been proposed to explain the fluorescence enhancement of the rhodamine probe in the presence of SCN−. [ABSTRACT FROM AUTHOR]

Polyvinyl-pyrrolidone capped spherical cadmium sulphide quantum dots (CdS-PVP QDs), 2–6 nm in size, were developed as a selective turn-on fluorescence nanosensor for monohydrogen phosphate ion (HPO 4 2−) in aqueous medium. Fluorescence intensity of CdS-PVP QDs significantly increased with addition of HPO 4 2− ions, whereas the other common inorganic ions had very little effect on the fluorescence intensity. The proposed sensor may be efficiently used for the detection of HPO 4 2− ions at a low level of concentration up to 213 nM in real urine sample. Cell imaging study indicates that the CdS-PVP QDs are cell permeable and can detect the intracellular distribution of HPO 4 2− ions under fluorescence microscope. The CdS-PVP QDs showed considerable activity against Staphylococcus aureus also. Unlabelled Image • First report of a new fluorescent nanosensor highly selective for phosphate ion (PO 4 3-) has been developed with a low detection limit upto 213 nM. • Synthesis method is simple and robust • The probe is also useful for the detection of PO 4 3- ions in real urine samples. • The sensor CdS nanoparticles can act as highly potential biomarkers to recognize the intercellular distribution of phosphate ions in living cells under fluorescence microscope. • Cytotoxicity study indicates that the nanoparticles have high antimicrobial activity against S. aureus. [ABSTRACT FROM AUTHOR]

Abstract We present here the synthesis of a simple and low-cost Schiff base chemosensor (HL) for selective detection of both Zn(II) and Cu(II) ions in HEPES buffer pH = 7.4. The chemosensor HL exhibits quick response through fluorescence and colorimetric changes for both Zn(II) and Cu (II) ions as examined by fluorescence and absorption titrations. Both the metal ions form 1:1L– Zn(II) (complex 1) and 1:1L– Cu(II) (complex 2) complexes, confirmed by Job's Plot. We are successful to elucidate the structure of complex 1 through X-ray diffraction analysis. Reversibility of the chemosensor in its binding with Zn(II) and Cu (II) ions separately is also examined in presence of Na 2 EDTA solution. The enhancement of fluorescence intensity of the chemosensor is based on the chelation-enhanced fluorescence (CHEF) effect of L–Zn(II) with the inhibition of both photoinduced electron transfer (PET) effect and C˭N isomerization in excited state and the quenching effect is due to the paramagnetic nature of Cu(II) to the L–Zn(II) system. Furthermore, the geometry and spectral property of HL and both the metal complexes have been studied by DFT, TD-DFT calculations. The limit of detection (LOD) values of both the ions are 2.29 × 10-9 M and 3.67 × 10-9 M, respectively. These values clearly suggests that HL is a promising chemosensor in monitoring Zn(II) and Cu(II) ions in the biological and environmental study with excellent accuracy and precision. The propensity of the chemosensor to detect intracellular Cu(II) and Zn(II) ions in Candida albicans cell lines by fluorescence imaging is also demonstrated in this study. Furthermore, molecular logic gates have been developed based on the idea where chemically encoded information as the input is converted into fluorescent signals as the output. In this work, the designed fluorescent chemosensor exhibits dual logic gates (XOR, AND) involving Zn(II), Cu(II) and Na 2 EDTA. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Highlights: [•] Fluorometric and colorimetric detection of Hg2+ at nano-molar level. [•] Computational studies (DFT calculation) nicely support the experimental findings. [•] LOD was 1×10−9 M in HEPES buffer (0.1 M in EtOH/water, 1/1, v/v, pH 7.4). [•] Trace level Hg2+ can be detected in living cells under fluorescence microscope. [ABSTRACT FROM AUTHOR]

Abstract: A naphthalene based fluorescent probe, 1-((Z)-(naphthalene-4-ylimino)methyl)naphthalene-2-ol (L) has been synthesized by condensing 1-naphthyl amine with 2-hydroxy naphthaldehyde. The structure of L has been established by single crystal X-ray structure. It selectively binds Al3+ with a binding constant (K a) of 1.83×105 M−1/2 and detection limit of 1.0×10−7 M. Moreover, [L–Al3+] complex can detect NO2 − ion as low as 5.7×10−8 M. Binding of L to Al3+ and [L–Al3+] complex to NO2 − ion has been established by different spectroscopic studies. The probe is very effective for detection of intracellular Al3+ through fluorescence microscopic imaging. [Copyright &y& Elsevier]

Abstract: Visible light excitable rhodamine B derivative (TARDHD) has been developed for fluorescence and naked eye detection of histidine in aqueous medium. TARDHD shows 45 fold fluorescence enhancement in the presence of histidine. It forms Schiff base with histidine and stabilizes via intra-molecular H-bonding. TARDHD can efficiently detect intracellular histidine. [Copyright &y& Elsevier]