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A multiple turn-on fluorophore (FHCS), combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone into a molecule, was identified and developed based on density functional theoretical calculation. It was expected that FHCS could express exclusive fluorescent signals and improved Stokes shifts when chelating Al3+ or Zn2+. After it was synthesized and characterized in detail, it was noted that FHCS could turn-on fluorescently discriminate trace Al3+ and Zn2+ under the optimized conditions, i.e., from no-fluorescence to strong blue fluorescence for Al3+ and to green fluorescence for Zn2+ with low detection limits of 5.37 × 10−8 M and 7.90 × 10−8 M respectively. Owing to its low toxicity, FHCS was successfully applied for quantitative determination of Al3+ and Zn2+ in natural aqueous samples and toxicity evaluation of Al3+ and Zn2+ in living cells and bio-tissues with excellent linear relationships. The action mechanisms for FHCS with Al3+ and Zn2+ were confirmed to form stable 5-member-co-6-member condensed rings between Al3+/Zn2+ and N/O atoms in FHCS by both theoretic and experimental methods, which resulted in turn-on fluorescence with different dipolar moments and improved Stokes shifts. A multiple turn-on fluorophore, combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone into a molecule (FHCS), was identified and developed for turn-on fluorescently discriminate trace Al3+ and Zn2+ in natural aqueous, living cells and bio-tissue samples with quite low detection limits of 5.37 × 10−8 M and 7.90 × 10−8 M respectively. The action mechanisms for FHCS with Al3+ and Zn2+ were confirmed by both theoretic and experimental methods to form stable 5-member-co-6-member condensed rings between Al3+/Zn2+ and N/O atoms, which resulted in turn-on fluorescence with different dipolar moments and improved Stokes shift. Image 1 • A multiple turn-on fluorophore combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone was developed. • It could turn-on fluorescently monitor Al3+ and Zn2+ in aqueous. • It was applied for cell imaging of Al3+ and Zn2+ in bio-samples. • The reaction mechanism was to form stable 5-member-co-6-member condensed rings with improved Stokes shift. [ABSTRACT FROM AUTHOR]

Nanoscale metal-organic frameworks (NMOFs) have been widely employed in biological diagnosis and treatment system. In this work, glutathione stabilized gold nanoclusters (GSH-AuNCs) were successfully encapsulated in NMOFs and the as-obtained nanocomposites (named as AuNCs@NMOFs) showed nearly 10 times enhancement in fluorescence intensity and longer fluorescence lifetime relative to GSH-AuNCs. In addition, the fluorescence intensity of AuNCs@NMOFs was quenched by highly reactive oxygen species (hROS) due to their strong oxidation ability. Based on the fact, the nanocomposites were used for the detection of hROS with a linear range from 80 nM to 1.0 μM toward hypochlorite (as the representative of hROS). The limit of detection (LOD) was about 30 nM, which was about 30 times lower than that of GSH-AuNCs (LOD = 0.96 μM). With the features of good biocompatibility, excellent luminescence and efficient cellular uptake, AuNCs@NMOFs were successfully applied in fluorescence imaging of hROS in living cells. Au nanoclusters@NMOF nanocomposites were prepared and further applied for hROS detection with high sensitivity in living cells. Image 1 • Au nanoclusters@NMOF composites were prepared as nanoprobe for hROS through a facile in-situ growth method. • The nanoprobe was developed to detect hROS with a fast response time and nearly 30 times sensitive than AuNCs. • The nanoprobe had been successfully applied in the imaging of exogenous and endogenous hROS in living cells. [ABSTRACT FROM AUTHOR]

A new colorimetric and fluorogenic probe ( RN 3 ) based on rhodamine-B has been successfully designed and synthesized. It displays a selective response to Hg 2+ in the aqueous buffer solution over the other competing metals. Upon addition of Hg 2+ , the solution of RN 3 exhibits a ‘naked eye’ observable color change from colorless to red and an intensive fluorescence with about 105-fold enhancement. The changes in the color and fluorescence are ascribed to the ring-opening of spirolactam in rhodamine fluorophore, which is induced by a binding of the constructed receptor to Hg 2+ with the association and dissociation constants of 0.22 × 10 5 M −1 and 25.2 μM, respectively. The Job's plot experiment determines a 1:1 binding stoichiometry between RN 3 and Hg 2+ . The resultant “turn-on” fluorescence in buffer solution, allows the application of a method to determine Hg 2+ levels in the range of 4.0–15.0 μM, with the limit of detection (LOD) calculated at 60.7 nM (3σ/slope). In addition, the fluorescence ‘turn-off’ and color ‘fading-out’ happen to the mixture of RN 3 -Hg 2+ by further addition of I − or S 2− . The reversible switching cycles of fluorescence intensity upon alternate additions of Hg 2+ and S 2− demonstrate that RN 3 can perform as an INHIBIT logic gate. Furthermore, the potential of RN 3 as a fluorescent probe has been demonstrated for cellular imaging. [ABSTRACT FROM AUTHOR]

Copper (II) is one of the most important metal ions for the human body that act as a catalytic cofactor for many metalloenzymes and proteins, and its homeostasis disruption could lead to many neurological diseases. The reported probes for Cu (II) determination are mostly based on fluorescence quenching mechanism, which provides low precision and reliability. In the present work, a turn-on fluorescence probe, (Z)-1-[2-oxo-2-[2-[1-oxoaceanthrylen-2 (1 H)-ylidene]hydrazinyl]ethyl]-pyridinium (OAHP), for highly selective detection of Cu2+ was developed. Hydrazide moiety of OAHP quenches probe fluorescence; however, upon its reaction with Cu, oxidative cleavage of the hydrazide moiety and intramolecular cyclization occurs, forming oxadiazole derivative with strong fluorescent properties. In this context, OAHP displayed significant fluorescence enhancement with increasing levels of Cu2+. OAHP could detect Cu2+ selectively with a detection limit of 18 nM (1.1 ppb). This is the first report for a probe that uses the ability of Cu2+ to induce oxidative decomposition of hydrazide with intramolecular cyclization, and it showed exceptional selective performance and exquisite sensitivity. Next, the method was applied successfully for monitoring Cu2+ in tap water samples with good accuracy (found% of 95.8–101.5%) and precisions (RSD<10%). Finally, OAHP was successfully applied for imaging Cu2+ in living cells, and this result indicates the potential of OAHP for selective detection of Cu2+ in complicated matrices. [Display omitted] • OAHP, a hydrazide derivative of phenanthrenequinone, was successfully used as a turn-on fluorescence probe for Cu2+. • Cu2+ induces oxidative cleavage of the hydrazide moiety and intramolecular cyclization forming oxadiazole derivative. • OAHP showed excellent selectivity to Cu2+ even vs. Cu+. • The new probe could detect Cu2+ selectively with sensitivity down to 1.1 ppb in tap water. • OAHP was successfully applied for imaging Cu2+ in Hep G2 cells. [ABSTRACT FROM AUTHOR]