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The development of mercury ion selective fluorescent probe is significant because it is one of toxic heavy metals and poses great risks and hazards to human health. Herein, we develop a mercury ion-selective fluorescent probe, namely IB, based on imidazole decorated benzothiadiazole that obtained by a facile palladium catalytic C-N coupling reaction. IB exhibits high selectivity and sensitivity towards mercury ion in water with nearly 32-fold fluorescent enhancement. The detection limit is calculated to be 0.93 nmol/L. In addition, the sensing of mercury ion can be conducted in a wide pH scope ranging from 4.0 to 10.0. Subsequently, the mercury ion elicits fluorescence of IB solution can be quenched by the addition of cyanide anions, showing "off-on-off" fluorescence transformation with at least 5 cycles, demonstrating the reversible sensing ability of IB. Furthermore, an INHIBIT logical detector has been developed using mercury ion and cyanide anions as inputs and fluorescence of IB as output. Significantly, IB can be utilized for mercury ion detection in real water sample. [ABSTRACT FROM AUTHOR]

A probe based on the phenothiazine–acridine orange conjugate (Ptz–AO) has been designed and synthesized for the sensitive and selective detection of HOCl. Ptz–AO has excellent properties, including pH-independence of fluorescence, high resistance to photobleaching, and response in real time. The value of Ptz–AO was confirmed by exogenous, endogenous and the real-time imaging of HOCl in vitro using a fluorescence microscope. [ABSTRACT FROM AUTHOR]

A simple phenothiazine-hemicyanine based probe PTZ-2Cy for selective in vitro and in vivo detection of ClO− was obtained. The detection mechanism was elucidated by absorption spectroscopy, emission spectroscopy, and ESI-MS analysis. With the increase in ClO− concentration, PTZ-2Cy first oxidize into sulfoxide product OPTZ-2Cy , and the additional concentration of hypochlorite ion leads to the cleavage of one or two C C bonds (OPTZ-Cy-CHO or OPTZ-2CHO). This is accompanied by the color change from light pink to light yellow, absorption spectra shift from 580 to 493 nm, and significant enhancement of fluorescence emission at 595 nm. The low limit of detection of ClO− ions (LOD = 0.038 μM) was obtained for the PTZ-2Cy probe in the 0–20 μM concentration range. The probe shows excellent selectivity for ClO− ions owing to dual-wavelength fluorimetric detection at 488 and 600 nm. The probe is applicable for imaging HClO in L929 cells and is a promising candidate for the development of a fluorescence sensor for hypochlorite ions detection in biological samples. A simple phenothiazine-hemicyanine based probe PTZ-2Cy was developed. The probe shows excellent selectivity for hypochlorite (ClO−) ions owing to dual-wavelength fluorimetric detection at 488 and 600 nm. The probe is applicable for imaging ClO− ions in L929 cells. [Display omitted] • A simple phenothiazine-hemicyanine based probe PTZ-2Cy for selective in vitro and in vivo detection of ClO− was obtained. • The detection mechanism was elucidated by absorption spectroscopy, emission spectroscopy, and ESI-MS analysis. • The low limit of detection of ClO− ions (LOD = 0.038 μM) was obtained for the PTZ-2Cy probe in 0–20 μM concentration range. [ABSTRACT FROM AUTHOR]

[Display omitted] • AIEgens-based Tb3+ complex was designed and synthesized for the first time. • TPE-Tb could self-assemble into novel TPE-Tb nanoparticles (TPE-Tb NPs). • TPE-Tb NPs were used as fluorescent probes for detection of DPA. • The limit of detection (LOD) of TPE-Tb NPs was as low as 0.187 nM in water. • The LOD of TPE-Tb NPs was 1.64 × 104 spores/mL in actual spore samples. Luminescent rare-earth (RE) complexes usually present outstanding advantages of long-lived emissions and high emission efficiency in aggregate and solid states. However, the combination of aggregation-induced emission (AIE)-based materials and RE complexes with excellent luminescent properties is rarely reported. Herein, AIE luminogens (AIEgens)-based Tb3+ complex (TPE-Tb) was designed and synthesized for the first time, which can self-assemble into novel TPE-Tb nanoparticles to be used as ratiometric fluorescent probe for sensitive and rapid detection of anthrax spore biomarker in aqueous solution or actual spores. The results indicated that the limit of detection (LOD) of this ratiometric fluorescent probe was as low as 0.187 nM and 1.64 × 104 spores/mL in water solution or actual spore samples, respectively. This work explored a new method for the combination of AIEgens-based materials and RE complexes by coordination mode and provided a versatile nanoprobe candidate for anthrax biomarker detection. [ABSTRACT FROM AUTHOR]

• Water-soluble fluorescent probes PTZ-TPP and PTZ-MP based on phenothiazine moiety were developed. • The sensing mechanism of probe with HOCl was elucidated. • The detection limit (LOD) of probe PTZ-TPP and PTZ-MP was evaluated to be 14.7 and 19.4 nM respectively. • The probe PTZ-MP was further used for the detection of viscosity. Due to the important role of hypochlorous acid (HOCl) in immune prevention of bacteria towards living organisms and its variations may be related to the change of intracellular viscosity, it is significant to design fluorescent probe to accurately analyze changes for detecting HOCl and viscosity simultaneously. In this paper, water-soluble, very fast-responsive fluorescent probes PTZ-TPP and PTZ-MP based on phenothiazine moiety were developed. The sensing mechanism of the probe with HOCl was elucidated by emission spectra at long and short excited wavelength 480 and 380 nm, and the oxidation structure OPTZ-TPP , sulfur peroxide structure O 3 PTZ-TPP as well as carbon-carbon double bond cleavage structure OCy-TPP were confirmed by ESI-MS analysis. The detection limit (LOD) of probe PTZ-TPP and PTZ-MP was evaluated to be 14.7 and 19.4 nM respectively. Moreover, the probe PTZ-MP was further used for the detection of viscosity. Furthermore, cell imaging of PTZ-TPP towards HOCl was conducted. And it is expected to be used in simultaneous determination of HOCl and viscosity in intracellular. A novel water-soluble, very fast-responsive fluorescent probes PTZ-TPP and PTZ-MP based on phenothiazine moiety were developed. The sensing mechanism of probe with HOCl was elucidated by emission spectra at different excited wavelength, and the oxidation structure OPTZ-TPP , sulfur peroxide structure O 3 PTZ-TPP as well as carbon-carbon double bond cleavage structure OCy-TPP were confirmed by ESI-MS analysis. The detection limit (LOD) of probe PTZ-TPP and PTZ-MP was evaluated to be 14.7 and 19.4 nM respectively. Moreover, probe PTZ-MP was further used for the detection of viscosity, and PTZ-TPP can be employed for specific detection of NaClO in living INS-1 cells. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A terpyridyl-rhodamine based probe has been designed and prepared for the sensitive and discriminative detection of Hg2+ and Cu2+ in water by dual/single emission change and applications in constructing a combinatorial logic gate and cell imaging. [Display omitted] • A new terpyridyl-rhodamine hybrid dye TR and sensor TRH have been facilely prepared. • TRH can discriminatively sense Hg2+ and Cu2+ in water with high sensitivity. • TRH can be employed for the construction of a combinatorial logic gate. • TRH can be applied for the discriminative sensing of Hg2+ and Cu2+ in living cells. Sensitive and discriminative sensing of more than one analyte with a single fluorescent probe is significant and challenging. Herein a new terpyridyl-rhodamine hybrid, namely TRH, has been rationally designed and prepared with two responsive groups in the molecular structure, which facilitate the discriminative detection of Hg2+ and Cu2+ ions in water with detection limits of 4.9 and 53.3 nM by ratiometric fluorescence change (F 595 /F 485) and fluorescence quenching, respectively. Investigations show that the selectivity to Hg2+ ions can be attributed to Hg2+-promoted spirolactam ring opening and further hydrolysis, followed by a through-bond energy transfer (TBET) process. The selective fluorescence quenching to Cu2+ ions probably can be ascribed to the binding Cu2+ to terpyridyl that triggers a ligand-to-metal charge transfer (LMCT) process, which can also efficiently inhibit the TBET process induced by Hg2+ ions and promotes the discriminative sensing of Cu (II) and Hg (II). In addition, the fluorescent responses to Hg2+ and Cu2+ ions cover a wide pH range. Moreover, a combinatorial logic gate with the functions of NOR and INHIBIT has been fabricated by using Hg2+ and Cu2+ ions as chemical input signals, and fluorescence at 485 and 595 nm as output signals. Besides, TRH also exhibits sensitive and discriminative sensing ability to Hg2+ and Cu2+ ions by the fluorescence of rhodamine fluorophore. Significantly, based on the fluorescence signal output of rhodamine moiety, TRH can be used as a tracer for the discriminative sensing of Hg2+ and Cu2+ ions by using living cells. [ABSTRACT FROM AUTHOR]

• Morpholine and thiomorpholine decorated probe Ly-OCl has been facilely synthesized. • Ly-OCl shows specific fluorescence off-on toward OCl−. • The limit of detection for OCl− is evaluated to be 2.9 nM. • Ly-OCl can trace endogenous and exogenous HOCl in lysosomes of living cells. The development of efficient probes for tracing the subcellular HOCl is significant because HOCl involves some physiological and pathological processes. In this work, a thiomorpholine and morpholine functionalized naphthalimide probe Ly-OCl has been facilely prepared and determined. Ly-OCl could be used for HOCl sensing with performances of high selectivity, high sensitivity (LOD of 2.9 nM), real-time (10 s) and wide pH range applicability (3.0–11.0). The sensing mechanism could be mainly ascribed to the oxidation of thiomorpholine by HOCl which inhibited the PET process. In addition, Ly-OCl could be applied for tracing the exogenous and endogenous HOCl in living cells by fluorescence imaging. In particular, Ly-OCl showed excellent lysosomal targeting ability with a Pearson's coefficient of 0.951. A morpholine and thiomorpholine functionalized naphthalimide has been designed and prepared with excellent performance in tracing endogenous and exogenous HOCl in lysosomes of living cells. [Display omitted] [ABSTRACT FROM AUTHOR]

• Two thiazole-fused fluoran-based fluorescent probes for copper ions have been prepared. • The two probes show high selectivity and sensitivity for copper ions. • MTFH achieves red emission (632 nm) towards copper ions due to the methyl functionalization. • The two probes can be utilized for tracing intracellular copper ions. In this work, two thiazole-fused fluoran-based fluorescent probes 8′-(diethylamino)-2-((2-hydroxyethyl) amino)spiro[isoindoline-1,11′-xantheno[2, 1- d ]thiazol]-3-one (TFH) and (8′-(diethylamino)-2-((2-hydroxyethyl)amino)-3′-methyl-3-oxospiro[isoindoline-1,11′-xantheno[2,1- d ]thiazol]-3′-ium).BF 4 (MTFH) have been prepared for copper ions. It should be noted that MTFH achieves red emission (632 nm) compared with TFH in the presence of copper ion, which mainly can be attributed to the methylation of molecule MTFH that induced more stronger ICT effect. The two probes show selective fluorescence off-on signal changes towards copper ions with detection limits of 8.8 and 60.8 nM. Copper ion detection can be conducted in a wide pH range including the physiological pH environment. Both TFH and MTFH exhibit suitable cytotoxicity and have been used for copper ion tracing in living cells. However, no other significant improvements of MTFH in sensing performance can be observed when compared with TFH. Two thiazole-fused fluoran-based fluorescent probes have been prepared for selectively and sensitively sensing copper ions, in particular, the methyl functionalization probe achieves red emission mainly due to a stronger ICT effect. [Display omitted] [ABSTRACT FROM AUTHOR]

Developing fluoran dyes for fluorescent material is significant but challenging because they are notorious for terrible luminescent efficiency. In this manuscript, two fluoran dyes (F3 and F4) were synthesized by the introduction of thiazole and indazole into the fluoran skeleton, which showed colored and fluorescent spirolactone opening form in a wide pH range (F3 : 1–10, F4 : 1–13). In addition, the absorption and emission spectra of methyl esterification products F3Me and F4Me showed large Stokes shifts (over 75 nm) in water and achieved an improved fluorescence quantum yield of 30.1% in CHCl 3. Based on the dye F4Me, a new fluorescent probe F4HP was developed, which showed high selectivity and high sensitivity (LOD of 2.0 nM) to copper ions in H 2 O/CH 3 CN (v/v, 3/2) system. Moreover, the sensing experiment was allowed in the pH range of 4.0–7.5. Furthermore, the F4HP exhibits suitable cell cytotoxicity and can be applied for imaging intracellular copper ions by confocal fluorescence imaging technology. Thiazole and indazole functionalized fluoran dyes were prepared with improved fluorescence and application in the construction of a novel copper-selective and sensitive fluorescent probe. [Display omitted] • Two modified fluoran dyes were prepared with stable fluorescence in water. • F4Me achieved a fluorescence quantum yield of 30.1% in CHCl 3. • A novel probe F4HP for Cu2+ was prepared with high selectivity and sensitivity. • F4HP could be employed as a tool for imaging intracellular Cu2+. [ABSTRACT FROM AUTHOR]

A novel indazole fused rhodamine fluorescent dye with large Stokes shift and stable fluorescence in water for constructing an Hg2+-selective probe and cell imaging applications. [Display omitted] • A indazole fused rhodamine dye InRh has been prepared with stable fluroescence in water. • Probe InRhH can respond to Hg2+ with high selectivity and sensitivity by fluorescence and absorption spectra. • Probe InRhH shows promising application in tracing Hg2+ in living cells. Developing selective and sensitive probes for mercury ion (Hg2+) is of great significance because Hg2+ exhibits high toxicity and poses a potential threat to public health and the environment. Herein, a newly designed indazole fused rhodamine dye InRh has been prepared, which shows stable fluorescent signals in water at a wide pH range of 1.0–10.0. Based on the dye InRh, a novel fluorescent probe InRhH for Hg2+ is further developed by modifying the spirolactone ring of InRh to form a closed spirolactam ring. The probe shows selective fluorescence "off–on" signal changes to Hg2+ with a visible color change and response time of 40 min in H 2 O/CH 3 CN (pH = 6.0, v/v = 4/1), and the detection limit for Hg2+ is measured to be 0.33 nM. The recognition mechanism for Hg2+ can be ascribed to the binding interactions between Hg2+ and probe in a 2: 1 coordination mode, which promotes the occurrence of spirolactam ring opening and further hydrolysis. In addition, the InRhH can be applied for test strip experiments and tracing 10−6 M level Hg2+ with visible color change. Furthermore, the suitable cytotoxicity allows the probe to apply for sensing Hg2+ in living HeLa cells by fluorescence imaging. [ABSTRACT FROM AUTHOR]

• A novel quinoline-fluoran hybrid fluorescent dye QF has been easily prepared. • A copper ion-selective fluorescent probe QFH has been developed based on QF. • QFH shows good performance in tracing intracellular copper ions by fluorescence imaging. Developing fluoran dyes as fluorescent probes is interesting because it is of great significance to extend their applications from the printing industry to other fields such as fluorescence analysis and medicine. We here present a new quinoline-fluoran hybrid dye QF , which delivers fluorescent signals in water (pH: 4.0 - 9.0) with the maximum absorption and emission centered at 514 nm and 597 nm, respectively. In addition, a large Stokes shift (83 nm) can be observed when compared to that of rhodamine B. QF is further employed for the preparation of a new fluorescent probe QFH , which exhibits high selectivity towards copper ions with the limit of detection down to 1.54 nM via a Cu2+-triggered spirolactam ring opening and hydrolysis process. Significantly, QFH can be applied for the detection of copper ions at physiological pH conditions (pH: 6.0 - 9.0) and shows low cell cytotoxicity, which allows it to be a candidate for tracing Cu2+ by cell imaging. A novel quinoline-fluoran hybrid fluorescent probe for copper ion-selective detection and application in cell imaging. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel pyridyl functionalized rhodamine dye with large Stokes shift and stable fluorescence in water was facilely prepared and utilized for a Hg2+-selective probe. [Display omitted] • A Rhodamine derivative PR has been prepared with Stokes shift of 81 nm. • Probe PRHg is synthesized, presenting high selectivity and sensitivity (LOD: 8.5 nM) to Hg2+. • PRHg exhibits great potential for tracing Hg2+ in living cells. Rhodamines gain sustained attention owing to their great potential for probe design applications. Herein, the facile preparation of a new pyridyl functionalized rhodamine dye PR is reported, which has stable fluorescence signal in water with maximum emission peak at 594 nm and Stokes shift of 81 nm. Based on dye PR , a new fluorescent probe PRHg has been developed by modifying the spirolactone of PR with hydrazine hydrate so as to produce spirolactam recognizing group for sensing of Hg2+. PRHg exhibits high selectivity and sensitivity towards Hg2+ in water/ethanol (v/v = 4/1, pH = 7.0) by a specific Hg2+-binding promoted spirolactam ring opening and hydrolyzing process. And, the detection limit for Hg2+ is evaluated to be 8.5 nM. Besides, the probe can respond to Hg2+ within 40 min and over a wide pH range from 4.0 to 10.0. Moreover, PRHg (40 µM) performs low cytotoxicity to HeLa cells (over 91.0 % cell survival rate), which allows the probe to be employed for tracing intracellular Hg2+ by fluorescence imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel quinoline-rhodamine hybrid probe P7RHg has been facilely prepared. • P7RHg can be used for raitiomet-ricly sensing of Hg2+ in water with well separated emission peaks. • P7RHg exhibits selectivity to Hg2+ with nearly 90-fold fluorescent ratio enhancement. • P7RHg shows promising potential in tracing intracellular Hg2+. To develop efficient tools for monitoring toxicant Hg2+ in aqueous solution attracts great attention because the abnormal distribution of Hg2+ in environment poses great threat to human health. We here report the preparation of a novel quinoline-rhodamine hybrid fluorescent probe P7RHg for ratiometricly sensing of Hg2+ in water, with a spirolactam-thiosemicarbazide reaction group. Upon treatment by Hg2+, the ratio of fluorescence intensity (F 600 /F 460) exhibits nearly 90-fold enhancement, presenting two well-resolved emission peaks (140 nm). Meanwhile, the specific Hg2+-induced desulfurization provides probe P7RHg an excellent selectivity to Hg2+, with a detection limit of 8.6 nM. Moreover, the low cytotoxicity allows P7RHg to be employed for tracing Hg2+ in living cells by confocal fluorescence imaging. [ABSTRACT FROM AUTHOR]

Rare earth (RE) complexes have found a variety of applications in materials science and biomedicine because of their unique luminescence properties. However, the poor stability and solubility in water of multicomponent RE assemblies significantly limit their practical applications. We rationally designed and developed a novel Eu3+/Tb3+ supramolecular assembly hybrids (Eu/Tb-SAH) by supramolecular host-guest recognition and coordination recognition with the excellent characteristics of water dispersion stability, biocompatibility and luminous properties. As anthrax spore biomarker, 2,6-pyridinedicarboxylic acid (DPA) can coordinate with Tb3+ and sensitize Tb3+, resulting in a proportional change of fluorescence intensity and lifetime on the ms timescales, thereby realizing rapid and sensitive detection of DPA in water media or actual spores. To confirm our prediction, accurate and selective detection of DPA was achieved with Eu/Tb-SAH as a nanoprobe through steady-state ratiometric fluorescence and time-resolved technology, of which the limit of detection (LOD) are 27.3 nM and 1.06 nM, respectively. This was obviously lower than the amount of anthrax spores infecting the human body (60 μM). Besides, the filter paper was used to carry out visual detection of DPA and read the corresponding data through smart phones. This work paves a new way to fabricate luminescent RE nanomaterials and provides new ideas for the design of ratiometic lifetime imaging biosensors in the meantime. Image 1 • Eu3+/Tb3+ bimetallic self-assembled nano-probes Eu/Tb-SAH were constructed. • The supramolecular host-guest recognition and coordination recognition were used. • Time-resolved detection technology was implemented. • DPA in aqueous solution or actual spores were detected sensitively. • The filter paper was used to carry out visual detection of DPA. [ABSTRACT FROM AUTHOR]

Although biothiols, including cysteine (Cys), glutathione (GSH), and homocysteine (Hcy) can be used to diagnose many diseases and research physiological metabolism in many physiological processes, in situ real-time detection and differentiation of biothiols is still challenging because their similar chemical properties and molecular structures. Herein, we utilized the native chemical ligation (NCL) reaction mechanism to develop a Förster resonance energy transfer (FRET) strategy for designing a cell penetration peptide TAT-modified ratiometric two-photon biothiols probe (TAT-probe). The TAT-probe can not only rapidly enter into mitochondria assisted by TAT peptide, but also simultaneously detect biothiols and sequentially distinguish GSH. When the TAT-probe was excited with 404/820 nm wavelength light, it showed a change in the ratio of fluorescence after adding biothiols, including a quenched red fluorescence intensity (λ em = 585 nm) and an enhanced signal in green fluorescence intensity (λ em = 520 nm). Excitingly, the TAT-probe excited at 545 nm could display a red fluorescence (λ em = 585 nm) towards GSH and a quenched signal towards Hcy or Cys. This specific fluorescence response indicated the TAT-probe could effectively detect biothiols and differentiate GSH from Cys/Hcy in mitochondria. This work pioneered a new approach to design and synthesize biothiol-probes based on peptides and NCL reaction mechanism. Image 1 • A novel peptide-based ratiometric two-photon fluorescent probe for detecting biothiols has been designed. • The TAT-probe displayed high selectivity and sensitivity, mitochondrial targeting, and good water solubility. • The TAT-probe can rapidly enter into mitochondria assisted by TAT peptide. • The TAT-probe can detect biothiols and sequentially distinguishing GSH in Mitochondria of living cells. [ABSTRACT FROM AUTHOR]

A new fluorescent probe Lyso-Fl has been facilely prepared by an esterification reaction of spironolactone fluoran dye Rdi with ethanol, which shows viscosity-selective response by fluorescence. The new probe delivers obvious fluorescence signal enhancement when environmental viscosity changes from 1.01 cP (water) to 1256 cP (98% glycerol). And, both the emission intensity (575 nm) and fluorescence lifetime of Lyso-Fl exhibit individually good linear relationships with the solution viscosity. Besides, Lyso-Fl gives a selective response to viscosity among various biological species and exhibits pH-independent (1–10) fluorescent signals towards viscosity. More importantly, Lyso-Fl shows low cytotoxicity and can be utilized for monitoring of dexamethasone-stimulated viscosity enhancement by cell imaging with excellent lysosome-targeted performance, promoting it a promising fluorescent probe for lysosomal viscosity detection. A fluoran-based fluorescent probe Lyso-Fl for viscosity has been conveniently prepared with excellent performance in monitoring of lysosomal viscosity changes via fluorescence imaging. Unlabelled Image • A fluoran-based fluorescent probe Lyso-Fl has been facilely prepared. • Lyso-Fl delivers obvious fluorescence enhancement with viscosity increase. • Lyso-Fl shows low cytotoxicity. • Lyso-Fl can be utilized for monitoring of viscosity enhancement by cell imaging with excellent lysosome-targeted performance. [ABSTRACT FROM AUTHOR]