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Carbon quantum dots (CQDs) are drawing tremendous attention due to their unique photoluminescence property and fascinating functions. Herein, we prepared novel CQDs functionalized with amino acids (AA-CQDs) by a one-pot hydrothermal method for selective detection of Al3+ ions and fluorescence imaging. The prepared AA-CQDs exhibit a novel triple-excitation and single-colour emission for fluorescent property. In addition, the AA-CQDs have a high absolute quantum yield (24.23%) and quantum lifetime (13.29 ns). Moreover, the AA-CQDs exhibit high selectivity and sensitivity for Al3+ by fluorescence enhancement. In pH 7.4 PBS solution, there was a good linear relation between the fluorescence intensity and the concentration of Al3+ in the range of 1–20 μmol L−1; the limit of detection (3σ) was only 0.32 μmol L−1. Furthermore, an AA-CQD probe was also utilized for detection of Al3+ in living cells based on excellent biocompatibility and endocytosis. Based on the concentration of Al3+ ions in cells and apoptosis data, there will be a quick reflect of apoptosis induced by aluminium ions via the fluorescence intensity of the AA-CQD probe. This work will set the stage for developing novel CQD-based biosensors in cell research. [ABSTRACT FROM AUTHOR]

A novel boron dipyrromethene (BODIPY)‐based fluorescent probe BDP−Pd was designed and synthesized. Upon coordination with Pd2+, the emission of the probe at 508 nm significantly increased, showing an 'OFF‐ON' fluorescence response. The complexation of BDP−Pd with Pd2+ in both acetonitrile and aqueous solution were then studied by absorption and fluorescence spectra. The binding stoichiometry between the probe and Pd2+ was found to be 1 : 2, and the binding constant was determined to be 8.5×1010 M−2 and 8.2×1010 M−2 in acetonitrile and aqueous solution, respectively. The probe exhibited a detection limit as low as 0.72 ppb toward Pd2+ with no obvious interference from up to 21 species of common metal ions, suggesting BDP−Pd as a sensitive and selective fluorescent probe for Pd2+ detection. The fast fluorescence 'OFF‐ON' phenomenon of the probe upon coordination with Pd2+ ions could be easily observed by a hand‐hold UV lamp under naked eye in solution as well as on homemade test trips. Density functional theory (DFT) calculations were carried out to give the optimized structure of complex BDP−Pd : 2Pd2+ and rationalize the detection mechanism through a prohibited intramolecular photoinduced electron transfer (PET) process. The bio‐imaging application of the probe was investigated and it showed excellent cell permeability for fluorescent imaging of Pd2+ ions in A549 human non‐small cell lung cancer cells. [ABSTRACT FROM AUTHOR]

A near-infrared ratiometric fluorescent probe CR-Ac based on a coumarin–benzopyrylium platform has been developed for selective detection of Cu2+. The cell imaging data revealed the capabilities of CR-Ac in monitoring the dynamic changes of subcellular Cu2+ and the quantification of Cu2+ levels in living cells. [ABSTRACT FROM AUTHOR]

An effective ratiometric fluorescent probe based on silicon particles/gold nanoclusters (SiNPs/AuNCs) nanohybrid has been fabricated and applied to be a "on-off-on" switch sensing platform for detection of Hg2+ and cysteine. In this elaborated sensing platform, the SiNPs just acted as internal reference signal, providing a build-in correction for background interferences and environmental effects, to which the AuNCs as a signal report unit for Hg2+ response was covalently grafted by amidation reaction. The fluorescence intensity of SiNPs/AuNCs could be effectively quenched upon adding Hg2+, accompanied with an easily distinguishable fluorescent color change. The ratiometric fluorescence signal (F 649 /F 511) of the established nanoprobe was linearly proportional to the concentration of Hg2+ ranging from 0.02 to 24 μM with a low detection limit of 5.6 nM, which is below the guideline value of Hg2+ in drinking water set by the World Health Organization. Interestingly, upon addition of cysteine, the Hg2+-quenched fluorescence intensity was recovered gradually. Furthermore, the approach developed has also been utilized for Hg2+ detection in real complex biological samples with satisfactory results. More importantly, benefiting from the good water-solubility and excellent biocompatibility, this nanoprobe can monitor the intracellular Hg2+ and cysteine in living cells, indicating its potential applications in advanced biosensing and bioimaging. Herein, we reported an effective dual-emission ratiometric probe for "on-off-on" detection of Hg2+ and cysteine. Image 1 • An efficient dual-emission fluorescent probe for simultaneously and visual detecting Hg2+ and L-Cys was constructed. • The probe could simultaneously detection of Hg2+ in human serum and urine samples. • Due to the ratiometric fluorescence model, the background interference was extincted. • The developed probe was successfully used for the fluorescence bioimaging of Hg2+ and L-Cys in live cells. [ABSTRACT FROM AUTHOR]

A novel recyclable ratiometric fluorescent probe based on MOFs was designed and synthesized by a one-step approach, which was realized by assembling Al-MOFs in an aqueous solution containing rhodamine B (RhB) as a fluorescent reagent and Fe3O4 as a magnetically recyclable reagent. The obtained fluorescent probe (Fe3O4/RhB@Al-MOFs) has two emissions under excitation at 330 nm, in which the emission at 440 nm is attributed to the Al-MOFs and the emission at 610 nm presumably originates from the RhB dye. It was noted that the probe displays responses to Mg2+ ions with fluorescence enhancement at 440 nm, whereas the fluorescence at 610 nm would be a constant reference fluorescence signal. The existence of RhB significantly improves the detection accuracy and broadens the linear range. As a result, the selectivity of Fe3O4/RhB@Al-MOFs towards Mg2+ compared to other metal ions is excellent. When the Mg2+ ions (262.5 ppm) are added, the ratio of fluorescence intensity (I440/I610) is changed from 2.47 to 11.5. The Fe3O4/RhB@Al-MOFs show a rapid detection process (90 s), high fluorescence enhancement (up to 5-fold) and a low detection limit of Mg2+ ions (8 × 10−7 M). In particular, the magnetic Fe3O4 endows Fe3O4/RhB@Al-MOFs with a high magnetic responsiveness, thus, facilitating the separation procedures. As expected, it can be easily separated and recycled without a significant loss of recognition performance after being used many times, and thus, exhibits good reusability. Meanwhile, the cell cytotoxicity experiments suggest that Fe3O4/RhB@Al-MOFs is nearly non-toxic and in vitro cell imaging experiments demonstrate that the probe is capable of successfully enhancing fluorescence from the intracellular area in HL-7702 and A375 cellular systems. Hence, it has the potential for the detection of Mg2+ ions inside biosystems. [ABSTRACT FROM AUTHOR]

A simple relay identification fluorescence probe for Fe 3 + and phosphate anion with “on-off-on” switching was designed and synthesized based on the phenylthiazole and biphenylcarbonitrile. Probe 1 displayed highly selective and sensitive recognition to Fe 3 + in HEPES aqueous buffer (EtOH/H 2 O = 2:8, v/v, pH = 7.4) solutions. The optimized structures and HOMO and LUMO of probe 1 and [1-Fe 3 + ] complex were obtained by the density functional theory (DFT) calculations with B3LYP as the exchange and correlation functional using a suite of Gaussian 09 programs. The [1-Fe 3 + ] complex solution also showed a high selectivity toward PO 4 3 − . The lower limits of detection of probe 1 to Fe 3 + and [1-Fe 3 + ] complex to PO 4 3 − were estimated to 1.09 × 10 − 7 M and 1.86 × 10 − 7 M. Besides, the probe 1 also was used to detected the target ions in real water sample and living cells successfully. [ABSTRACT FROM AUTHOR]

Three novel and facile calixarene derivatives (5 , 6 and 7), which were appended with four rhodamine units at the upper rim of calixarene skeleton, were firstly prepared and evaluated for selective detection of metal ions in solution. Receptors (5) and (7) indicated immediate turn on fluorescence output toward Hg2+ ions over other most competitive metal ions with the ultralow detection limits, indicating their high efficiency and reliability. The binding response to Hg2+ ions in solution was also observed through a chromogenic change (from colorless to pale pink). Furthermore, in vitro and bio-imaging studies with MCF-7 or MIA PaCa-2 cell lines were also performed to investigate the use of receptors in biological systems in order to monitor of mercury ions. Results showed that new receptors (5) or (7) were cell permeable and suitable for real-time imaging of Hg2+ in living cells (MCF-7) or (MIA PaCa-2) without any damage to healthy cell lines (HEK 293). Unlabelled Image • Three novel rhodamine based calixarene fluorescent probes (5 - 7) were synthesized for highly selective detection of Hg2+ ions. • The probe (7) could quantitatively detect Hg2+ ions with a low detection limit of 3.4 nM. • Cytotoxicity and cell imagine studies against MCF-7 and MIA PaCa-2 cell lines were performed. [ABSTRACT FROM AUTHOR]