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• A ratiometric probe for the quantitative detection of L-Cys was prepared. • Detecting L-Cys with high sensitivity (0.32 μM) and fast response time (90 s). • Smartphone fluorescence imaging and fluorescent test strips. Cysteine is an important thiol involved in the vital activities of the human body, and many physiological processes in the body are associated with it. Accurate detection of cysteine is of great importance in monitoring the development of diseases. In this paper, we prepared a ratiometric flavonoid fluorescent probe, HDFA, that exhibits specific selectivity for L-cysteine. HDFA was the first fluorescent probe that can distinguish between L-cysteine and D-cysteine. When detecting L-cysteine, the fluorescence color changed from blue to yellow, and the fluorescence quantum yield increased from 16.96 % to 21.30 %. The probe has a short response time (90 s) to L-cysteine, a large Stokes shift (186 nm), good selectivity, and anti-interference, and the detection limit was 0.32 μM. The detection mechanism was confirmed by mass spectrometry. In addition, HDFA has good applications in cell imaging, smartphone fluorescence imaging and fluorescence test strip detection. [Display omitted] [ABSTRACT FROM AUTHOR]

• The two novel fluorescent probes Z 1 and Z 2 based have been designed and synthesized base on pyrazole derivative to recognize hydrazine • The probe Z 1-2 have ICT characteristics with large Stokes shifts. • The probe Z 1-2 could be made into test paper strips for detection of hydrazine. • The probe Z 1-2 can be used in detection of N 2 H 4 in environmental soil samples and cell imaging. Here, the two novel fluorescent probes Z 1 and Z 2 have been designed and synthesized based on pyrazole derivative to recognize hydrazine, and the molecular structure was determined by 1H NMR, 13C NMR, and ESI-MS. The obtained probe molecules have AIE and ICT characteristics. Nuclear magnetic resonance analysis (NMR) and theoretical calculations were used to confirm the identification mechanism. Probes Z 1 and Z 2 have good selectivity, low detection limits (0.197 µM and 0.185 µM, respectively), and high sensitivity. Probes Z 1 and Z 2 have large Stokes shifts of 198 nm and 211 nm, respectively. The probes also could be made into test paper strips for the detection of hydrazine. Furthermore, the probes can be used in the detection of N 2 H 4 in environmental soil samples and cell imaging. The results showed that the synthetic probe had good biocompatibility. Cell imaging experiments were performed to apply probes to the detection of hydrazine hydrate in HeLa cells. [Display omitted] [ABSTRACT FROM AUTHOR]

The novel fluorescent probe NXZ is sensitive for Zn2+. It has been successfully used for making Zn2+ fluorescent test paper and imaging detection of imaging Zn2+ in bean sprouts sample and Hela cells. [Display omitted] The fluorescent probe NXZ was synthesized by introducing –OH at position 1, 8-naphthalimide 4-position and benzimidazole unit at 3-position. The Stokes shift (λ em − λ ex) of NXZ can up to 148 nm, when Zn2+ was added to the probe solution, NXZ can quickly form the complex NXZ -Zn2+ with Zn2+ in a ratio of 1: 1 within 55 s, and then quench the fluorescence intensity by 4.4 times. The complexation constant of NXZ and Zn2+ was 1.2 × 104 M−1, and the detection limit for Zn2+ was 40.3 nM, which is much lower than the maximum Zn2+ content (76 µM) stipulated in the World Health Organization (WHO). Exploring the practical application of the probe NXZ found that NXZ can be used for the quantitative detection of Zn2+ in actual water samples and qualitatively detect Zn2+ in bean sprouts samples and Hela cells. In addition, NXZ can also be made into Zn2+ test paper. [ABSTRACT FROM AUTHOR]

[Display omitted] • BTCMN is constructed by coupling of 2-(2́-hydroxyphenyl) benzothiazole (HBT) scaffold to dicyanoisophorone through a C C bond bridge based on ESIPT mechanism. • BTCMN showed super-fast response to H 2 S as compared to other current probes. • BTCMN displayed specific selection and low detection limit towards to H 2 S. • BTCMN has been successfully used for visualizing endogenous and exogenous H 2 S in the HepG2 cells with low cytotoxicity. Hydrogen sulfide (H 2 S) plays a crucial role in various physiological processes and is implicated in the pathogenesis of several diseases. The fluorescent probe (E)-2-(3-(3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylstyryl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (BTCMN) has been designed to image H 2 S in living cells using the excited-state intramolecular proton transfer (ESIPT) mechanism. This probe is developed by coupling 2-(2′-hydroxyphenyl) benzothiazole (HBT) with dicyanoisophorone through a H 2 S-responsive C C bond. Upon interaction with H 2 S, BTCMN exhibits a remarkable fluorescent change from red to green. BTCMN , which has shown exceptional performance in detecting hydrogen sulfide (H 2 S) with super-fast response times, large Stokes shifts (252 nm), specific selection towards H 2 S, and low detection limits. Importantly, BTCMN has been successfully used for visualizing endogenous and exogenous H 2 S in HepG2 cells with low cytotoxicity. These features collectively contribute to its effectiveness as a fluorescent probe for detecting H 2 S in living cells. [ABSTRACT FROM AUTHOR]

• A tetraphenyl ethylene-fused rhodamine dye TPE-RhMe has been facilely synthesized. • TPE-RhMe exhibits large Stoke shifts and red emission. • TPE-RhMe can be used as a viscosity tracer in invitro and in vivo. • TPE-RhMe exhibits excellent performance in mitochondria targeting. Long-wavelength (>600 nm) luminescent organic dyes with organelle targeting function attract much attention because they can effectively avoid interference from the biological background fluorescence, etc. In this manuscript, tetraphenyl ethylene (TPE)-fused rhodamine dye, namely TPE-RhMe, has been facilely constructed with large Stokes shifts (58–199 nm) and red emission (601–718 nm) by the introduction of a multi-rotor-functionalized TPE moiety. The multi-rotor-contained structure of TPE-RhMe makes it a viscosity probe, which shows an emission enhancement in glycerol/water mixture with the increase of glycerol. Meanwhile, TPE-RhMe shows high selectivity towards glycerol among various analytes and the sensing measurement can be conducted over a board pH range (1.0–8.0). In addition, TPE-RhMe can also monitor viscosity enhancement through fluorescence lifetime changes. Significantly, TPE-RhMe exhibits a distinct fluorescence enhancement in 4T1 and HeLa cells compared with LO2 cells and presents a promising application in distinguishing normal and tumor cells. Furthermore, TPE-RhMe can be utilized for tracing the stimulated viscosity enhancement by using HeLa cells. Importantly, TPE-RhMe displays excellent performance in mitochondria targeting with a Pearson's correlation coefficient (PCC) value of 0.96. A tetraphenyl ethylene-fused rhodamine dye with large Stokes shift and red emission has been constructed for viscosity sensing and mitochondria-targeted cell imaging. [Display omitted] [ABSTRACT FROM AUTHOR]

Based on dehydroabietic acid (DA) derived from natural rosin, two aggregation-induced emission luminogens (BioAIEgens) labeled as 12-DTPA-2pTPE and 13-DTPA-2pTPE were synthesized by introducing tetraphenylethylene (TPE) groups to dehydroabietic acid triarylamine (DTPA). Their structures were optimized, the spectral properties and AIE characteristics were investigated, and the compounds were prepared into nanoparticles (NPs) as fluorescent probes for cell imaging. The results show that the two BioAIEgens have typical AIE characteristics and large Stokes shifts (＞ 120 nm). Due to the electronic and spatial effects of the isopropyl group, the molecular configuration of 12-DTPA-2pTPE is more distorted, and the electron cloud distribution is also different from 13-DTPA-2TPE. The absorption and the emission peaks of 12-DTPA-2TPE are blue-shifted, and the fluorescence quantum yield in the solid is higher. In addition, the 13-DTPA-2TPE nanoparticles (NPs) have low cytotoxicity and good cell imaging effects in vitro. [Display omitted] • Two BioAIEgens based on dehydroabietic acid (DA) and tetraphenylethene were synthesized. • The effect of isopropyl group on (DA) skeleton was investigated by theoretical calculation and spectral behavior. • BioAIEgens can be prepared into nanoparticles (NPs) as fluorescent probes for cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ratiometric peptide-based fluorescent probe DKA with large Stokes shift (230 nm) was developed. • DKA demonstrated absorbance ratiometric and fluorescent "off-on" sensing for Hg2+ with low LOD of 13.4 nM. • DKA -Hg2+ complex was applied to sequential detect S2− with good selectivity and excellent sensitivity.. • DKA performed well in sequential detecting the distribution of Hg2+ and S2− in living cells. • DKA was used to visually and semi-quantitatively recognize Hg2+ and S2− by smartphone-assisted detection platform. In this work, a new ratiometric fluorescent probe DKA was synthesized based on the double sides of lysine backbone conjugated with alanine and dansyl groups. DKA exhibited fluorescence ratiometric response for Hg2+ with high sensitivity (13.4 nM), specific selectivity (only Hg2+), strong anti-interference ability (no interference), fast recognition (within 60 s) and wide pH range (5–10). The stoichiometry of binding of DKA and Hg2+ was determined to be 1:1 via Job's plot, ESI-HRMS and 1HNMR titration analysis. Subsequently, the in situ formation of DKA -Hg2+ complex was used for highly selective detection of S2− as a novel fluorescence "on–off" probe, and the lowest detection limit for S2− was 12.9 nM. In addition, DKA possessed excellent cells permeation and low toxicity, and fluorescence imaging of Hg2+ and S2− was performed in living Hacat cells. Most importantly, the digital imaging using a smartphone color recognition APP indicated that DKA could semi-quantitatively and visually detected Hg2+ and S2− without expensive equipment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbazolyl embellished BODIPY (CarBDP) with large Stokes-shift (157 nm) and long fluorescence life time (44.54 ns) was prepared. • CarBDP was pH-insensitive and unresponsive for other competitive ions. • CarBDP exhibited excellent AIE property together with good lysosome localization. A large number of studies have shown that lysosomal microcircumstances changes can affect many physiological and pathological processes at the cellular level. However, the visual detection of lysosomal microcircumstances is relatively difficult due to low pH (4.5–6.0) value in lysosomal that require the probe not only stable under acidic condition but also has a good localization effect to lysosomal. Obviously, novel fluorescent which possessed both acidic stability and lysosomal-target property together with lysosomal viscosity active is highly demanded. Herein, a novel BODIPY molecular CarBDP based on carbazole group was rationally designed and synthesized for the lysosomal imaging. CarBDP exhibited AIE feature with a large Stokes shift of up to 157 nm. More importantly, co-localization assay of the CarBDP -treated MCF-7 cells indicated that CarBDP has a good localization effect on lysosomal (R r = 0.7109) due to the carbazole group while the normal BODIPY that without carbazole group (PhBDP) shows poor localization performance, this was the first time that a small molecule can locate lysosomes only based on carbazole group. CarBDP exhibits strong solid emission with long fluorescence decay lifetime (τ = 44.54 ns) and was stable under acid condition.The probe CarBDP assembled with carbazole group was successfully utilized for lysosomal localization and mapping lysosomal viscosity in live cells, which provides a novel candidate tool for the determination of lysosomal microcircumstances. [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−) is an important reactive oxygen species, and excess ONOO− in the body can lead to a range of diseases. Addressing the need for sensitive detection ONOO−, in this work, a highly sensitivity and selectivity long-wavelength fluorescent probe (named CIS) was designed for tracking ONOO− in biological cells. Probe CIS featured carbazole as the fluorophore and the C C double bond with two electron withdrawing –CN groups as the recognition site. The probe CIS exhibited the typical aggregation-induced emission (AIE) and intramolecular charge transfer (ICT) characteristics with the bright red fluorescent emission in high water fraction (f w ≥ 50 %) and negligible emission in low water fraction. The fluorescence emission wavelength of probe CIS is 631 nm, with a large Stokes shift (151 nm), which can sensitively detect ONOO− in DMSO: H 2 O (7:3, v/v) environment. Notably, the probe CIS exhibited a wide pH detection range (pH = 3–10), a low detection limit of 36.66 nM, high selectivity and minimal interference. Furthermore, probe CIS demonstrated excellent biocompatibility and low cytotoxicity, and can be used for the detection of exogenous ONOO− in 4T1 cells (Mouse breast cancer cells). These research results indicate that probe CIS has potential application prospects in the biological aspects. [Display omitted] • A long-wavelength (λ em = 631 nm) fluorescent probe CIS with AIE characteristics and a large Stokes shift (151 nm) was designed and synthesized for the identification of ONOO−. • Probe CIS has a wide pH range (3−10), low detection limit (36.66 nM) and strong anti-interference for the identification of ONOO−. • Probe CIS has been successfully applied to the dual-channel detection of ONOO− in 4T1 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fifteen 9 H -carbazoles were synthesized from 2-nitrochalcones via cyclization reaction. • Carbazole with naphthyl group (PPM-17) showed the highest Stokes shift in DMSO. • DFT study demonstrated the highest stability of PPM-14. • In-silico & fluorescence-based BSA binding study revealed the BSA binding of PPM-14. • PPM-14 showed Fe3+ fluorescence ' turn off' response & applied in MCF-7 cell imaging. In the present study, fluorophores based on 9 H -carbazole have been synthesized from readily accessible 2-nitrochalcones in a single-step reductive cyclization reaction with methyl acetoacetate. The molecular geometry was confirmed based on IR, NMR and mass analysis. The ground state geometry for all the synthesized compounds was optimized using DFT-based methods to explore the localization of frontier molecular orbitals in electronically diverse carbazoles. The photophysical studies revealed a higher Stokes shift for PPM 17 due to the presence of the naphthyl group at C-1 of carbazole. The high stability of PPM14 , as evidenced by high chemical hardness, prompted us to explore its BSA binding affinity using fluorescence titration, synchronous,3-D fluorescence and energy transfer analysis. The probe (PPM 14) displayed a " turn-off" response in the presence of Fe3+ ions. The less cytotoxic behavior of PPM 14, its " turn-off " fluorescence response with Fe3+, and its utility in cell imaging application establish it as a potential small organic framework-based bio-sensor. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new fluorescent probe for ratiometric detection of Zn2+ ion at physiological pH. • The probe displays red emission, large stokes shift and fast response time. • Vivid color change for naked-eye recognition. • Capable of imaging exogenous/endogenous Zn2+ levels in live cells. A novel ratiometric fluorescent probe, namely 5-[(3-dicyanoylidene −5.5-dimethyl) cyclohexenyl-1-ethenyl] salicylaldehyde-3′-hydroxybenzohydrazone (DCSH) is presented for the selective sensing of Zn2+ ion in acetonitrile/water (2/3, pH 7.4) solution. Introducing Zn2+ ions notably caused the peak emission of DCSH to shift from 560 nm to 646 nm, accompanied with a significant enhancement of its intensity. A vivid change in fluorescence color from yellow to red facilitated the immediate identification of Zn2+ ions by visual observation. DCSH exhibits substantial Stokes shifts (110 and 196 nm), rapid detection capability (within 10 s) and high sensitivity to Zn2+ ions, achieving a limit of detection of 31.2 nM. The response mechanism is supposed to involve the block of C = N bond isomerization and excited state intramolecular proton transfer (ESIPT) along with the enhancement of fluorescence through chelation (CHEF) effect. DCSH was effectively utilized for ratiometric fluorescence imaging to monitor exogenous Zn2+ concentrations in HeLa cells. Significantly, DCSH is capable of monitoring elevated levels of Zn2+ ion during apoptosis induced by L-Buthionine sulfoximine (BSO). [ABSTRACT FROM AUTHOR]

A new near-infrared (NIR) fluorescent probe WX-HS was designed for the selective detection and imaging of H 2 S. [Display omitted] • A "turn-on" NIR phenothiazine-based fluorescent probe (WX-HS) was prepared. • WX-HS could quickly, selectively and sensitively detect H 2 S with large Stokes shift (220 nm). • WX-HS could be used to detect the freshness of food samples (pork, chicken, beef and fish). • WX-HS also be confirmed could detect exogenous H 2 S in living cells. Hydrogen sulfide (H 2 S) is a pungent gas that is one of the key mediators of signal transduction in biological systems, and its presence is related to the freshness of some protein foods. Using phenothiazine derivatives as fluorophores and 2, 4-dinitrobenzene sulfonate (DNBS) fragments as reaction groups, a near-infrared (NIR) probe WX-HS for H 2 S identification was designed. With the addition of H 2 S, WX-HS appeared a strong fluorescence signal at 660 nm with short reaction time (90 s) and high sensitivity, and fluorescence state change from non-fluorescent to orange-red. In addition, WX-HS could effectively detect H 2 S produced during food oxidation. Based on its low cytotoxicity, the WX-HS probe further enabled the detection and imaging of H 2 S in A549 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A red-emitting fluorescent probe for biothiols has been designed and synthesized. • DIcou-DNBS can be used for the screening of drug inhibitors. • DIcou-DNBS exhibits large Stokes shift in detecting Cys/Hcy/GSH. Biothiols, comprising cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play a pivotal role in maintaining the delicate redox balance essential for life processes, intricately intertwined with the well-being of living organisms. Deviations in their concentrations can precipitate a range of diseases. Herein, we presented a novel fluorescent probe, DIcou-DNBS , derived from coumarin, which possessed red emission and a substantial Stokes shift (122 nm), tailored for biothiol detection. DIcou-DNBS demonstrated rapid-responsiveness (6 min) towards Cys, Hcy and GSH with detection limits of 0.015 µM, 0.032 µM and 0.059 µM, respectively. Furthermore, its excellent biocompatibility enabled successful applications in biothiol fluorescence imaging of living cells and zebrafish. Beyond biothiol sensing, DIcou-DNBS leveraged its unique property to indirectly detect β-lactamases, making it a valuable tool in inhibitor screening and susceptibility testing of both sensitive (Staphylococcus aureus ATCC 29213) and resistant (Enterobacter cloacae ATCC 13047) bacterial strains. This assay system anticipates to furnish a potent instrument for visualization studies across biological and medical domains. [ABSTRACT FROM AUTHOR]

A novel series of pentacyclic-fused pyranoquinoliziniums bearing diverse substituents synthesized by one-pot and stepwise rhodium(III)-catalyzed C–H annulation reactions in a modular approach were disclosed. Excellent photophysical properties were obtained via tuning of donor and acceptor moieties allowing the selective bioimaging of mitochondria and lysosome. [Display omitted] • Modular synthetic strategies were rationally designed based on Rh(III) catalysis to build a new series of pentacyclic-fused pyranoquinoliziniums (4a-4i) with novel N and O atom arragnement. • In an one-pot reaction approach, reaction of 2-aryl-4-quinolones (1) with 1,2-diarylalkynes (2) generated two novel products including quinolinone-fused isoquinolines (3) and pyranoquinoliziniums (4). • The isolation of 3 allows the preparation of pyranoquinoliziniums (4) bearing diverse substituents through stepwise synthesis. • By installation of different substituents, these novel pyranoquinoliziniums (4) exhibited tunable absorption and emission properties, and fluorescence quamtum yields. • The newly synthesized pyranoquinoliziniums (4a-4g and 4i) were successfully applied to target mitochondria of living cells while 4h was specific to lysosome. On basis of their unique chemical and photophysical properties, and excellent biological activities, quinoliziniums have been widely used in various research fields. Herein, modular synthetic strategies for efficient synthesis of novel fluorescent quinoliziniums by using one-pot and stepwise rhodium(III)-catalyzed C–H annulations were developed. In the one-pot synthesis, the reaction between 2-aryl-4-quinolones (1) and 1,2-diarylalkynes (2) proceeded in a chemo- and regioselective manner to give quinolinone-fused isoquinolines (3) and pentacyclic-fused pyranoquinoliziniums (4). The structural diversity of pentacyclic-fused pyranoquinoliziniums (4) was expanded by the stepwise synthesis from 3 and 2 , allowing the strategic incorporation of electron-donating (OMe and OH) and electron-withdrawing (Cl) substituents on the top and bottom parts of the pyranoquinoliziniums (4). These newly synthesized pyranoquinoliziniums (4) exhibited tunable absorptions (455–532 nm), emissions (520–610 nm), fluorescence lifetime (0.3–5.6 ns), large Stokes shifts (up to 120 nm), and excellent fluorescence quantum yields (up to 0.73) upon adjusting the different substituents. The the unique arrangement of N and O atoms and extended π-conjugation of 4 could cause the relocation of HOMO comparing with our previous quinoliziniums. Importantly, pyranoquinoliziniums (4a-4g and 4i) targeted the mitochondria, while 4h was localized in lysosome. Due to the remarkable photophysical properties and the potential for organelle targeting of the novel class of quinoliziniums, they could be further applied for biological, chemical and material applications. [ABSTRACT FROM AUTHOR]

• The probe XCCC is a near infrared probe(λ em = 696 nm) with a large Stokes shift value (196 nm). • The probe XCCC is sensitive (LOD = 11.4 nM) and fast for HSO 3 − (within 30 s). • The probe XCCC has been successfully applied to detect HSO 3 − in natural environment and biological system. A colorimetric near-infrared fluorescent probe was designed and synthesized in this paper. The probe XCCC was obtained by simple condensation of 6-(diethylamino)-2,3-dihydro-1 H -xanthene-4-carbaldehyde and 3-cyanoacetyl indoles. XCCC detects HSO 3 − through 1, 4-nucleophilic addition reaction, with obvious near-infrared fluorescence quenching (λ em = 696 nm), and the solution color changes from pink to pale yellow under natural light to realize naked eye recognition. In addition, XCCC has a super large Stokes shift value (196 nm) by calculation. The sensitivity of XCCC and HSO 3 − in the concentration range of 0 ∼ 60 μM is excellent, and the LOD value is as low as 11.4 nM. It is very fast for XCCC to detect HSO 3 − in real time (30 s), and the reversible cycle of HSO 3 −- H 2 O 2 is realized (5 times). In practical application, XCCC successfully detected HSO 3 − qualitatively and quantitatively in actual water samples. Furthermore, we made XCCC into fluorescent test strips to qualitatively detect HSO 3 − in red wine. In particular, XCCC was used to realize exogenous cell imaging of HSO 3 − with different concentrations and reversible cell imaging of HSO 3 −-H 2 O 2 in A549 cells. It shows that probe XCCC has a potential application prospect in food samples and life systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs), as intracellular lipid storage organelles, play an important role in maintaining lipid balance. The imbalance of lipid may lead to diseases, therefore, it is of great significance to monitor and evaluate the characteristics of LDs. Herein, we report the design and synthesis of a small molecular fluorescent probe MDXB (2-(2-(6-methoxy-2,3-dihydro-1H-xanthen-4-yl) vinyl) benzothiazole), which facilitates the detection of the viscosity change of intracellular LDs. MDXB follows the motion-induced change in emission (MICE) effect, wherein the –C C- bond is used as a rotation axis, and the fluorescence maybe enhanced with the increase of viscosity. MDXB exhibits a red emission at 640 nm with a large Stokes shift of ca. 180 nm, in addition to excellent photostability, which endow it with the capability of long-term imaging. The cellular imaging investigations illustrated the enhancement on the reactive oxygen species (ROS) content and the increment on LDs viscosity in the constructed cell models, e.g., cell inflammation and heavy metal ion stimulation. We thus expect MDXB to be a potential tool for the monitoring the viscosity changes of LDs and the evaluation of concurrent intracellular biological processes. • A NIR fluorescent probe for the detection of lipid droplets viscosity was synthesized. • The probe has a large Stokes shift, good anti-interference ability and excellent light stability. • The viscosity of lipid droplets and intracellular ROS were simultaneously imaged. [ABSTRACT FROM AUTHOR]

[Display omitted] • A convenient approach to construct excimer emissive luminogens was established. • A double-bond linker between π-moiety and side-moiety is essential for AIE. • The structure-luminescence relationship was elucidated. • The high-resolution image of living Hela cells was observed. The excimer emission based on discrete π-stacked dimers of polycyclic π-systems has generated significant interest in the structure-luminescence relationship of excimers owing to their ultra-large Stokes shift. Herein, a series of excimer emissive luminogens were obtained by conjugating different polycyclic aromatic aldehydes (anthraldehyde, pyrenealdehyde and perylenealdehyde) with triphenylmethylamine. In crystalline states, all the molecules were arranged in the form of π-stacked arene dimers which were spatially isolated from each other by the bulky triphenylmethyl groups, and thus emitted bright excimer emission. The anthracene and pyrene derivatives showed fluorescence enhancement responses to grinding and the enhanced fluorescence could recover to the original state upon heating. The aggregation-induced emission (AIE) properties of them were dependent on the shapes and sizes of the polycyclic aromatic groups. The pyrene derivative showed the most excellent excimer-based AIE behavior among them. All of them were more apt to exhibit the excimer emission when formed nanoparticles with pluronic F-127 than that without pluronic F-127. Furthermore, PETP was utilized for bioimaging of living Hela cells and the high-resolution image was observed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A phenothiazine coumarin based fluorescent probe (WX-Lyso) for the detection of ClO– was synthesized. • WX-Lyso displayed a low LOD (0.99 µm) and rapid responsive time to ClO– (<5 s). • WX-Lyso was proved successfully has good lysosomal-targeting and imaging abilities to ClO– in Hela cells. A new phenothiazine coumarin based probe WX-Lyso for detection of ClO– was developed. The probe showed obvious aggregation-induced emission (AIE) characteristic and exhibited a highly selective and sensitive turn-on fluorescence signal at 544 nm for ClO– with a large Stokes shift of 144 nm. The limit of detection (LOD) of ClO– was measured as low as 0.99 μM and a good line equation was obtained in the 0–50 μM concentration range. The detection mechanism was elucidated FT-IR, ESI-MS analysis and DFT. Furthermore, the probe had been demonstrated successfully has good lysosomal-targeting and high-contrast imaging abilities, which has the potential to become a new chemical tool and provide help for detecting ClO– in living systems. [ABSTRACT FROM AUTHOR]

This work presented a FRET-ICT based fluorescent probe (named NTC) composed of coumarin-benzothiazole as the acceptor and 4-nitrobenzo[ c ][1,2,5] oxadiazole (NBD) as the donor for the detection of SO 2 derivatives in NIR. Probe NTC possessed superior performance including selectivity, quickly response toward SO 3 2−/HSO 3 − and high energy transfer efficiency (94 %). The test strips provided a simple and effective tool in detecting the presence of bisulfite. Besides, NTC was applied to test the sulfur dioxide derivatives in food samples and cells. [Display omitted] • A NIR ratiometric fluorescent probe NTC was developed to detect sulfur dioxide derivatives. • NTC had a large Stokes shift of 150 nm and 94 % energy transfer efficiency. • NTC possessed good selectivity and sensitivity toward sulfur dioxide derivatives. • NTC was applied to detect sulfur dioxide derivatives in test strips, food samples and cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • The hydrogen sulfide NIR fluorescence probe (DCM-H 2 S) was designed and synthesized. • The probe DCM-H 2 S can specifically recognize H 2 S with a large emission wavelength (681 nm) and a large Stokes shift (121 nm). • The probe DHPC showed rapid response and high sensitivity (0.13 μM). • The probe DCM-H 2 S has been successfully applied to live cell imaging for real-time, dynamic tracking of exogenous and endogenous H 2 S. The signalling molecules of hydrogen sulphide (H 2 S) play an important role in a variety of physiological and pathological processes, and its abnormal concentration causes Down's syndrome, Alzheimer's disease and diabetes mellitus. Thus, the development of an effective detection tool is of vital importance and challenge. In this paper, we synthesized a new "turn-on" hydrogen sulfide near-infrared fluorescent probe (DCM-H 2 S). Remarkably, this probe demonstrated an unanticipated level of selectivity for hydrogen sulfide (H 2 S) over other analytes, rendering it suitable for the precise determination of H 2 S in both in vitro and in vivo settings. Expectedly, the probe exhibited unexpectedly heightened selectivity for H 2 S compared to other analytes, making it a viable option for the specific determination of H 2 S in both in vitro and in vivo applications. With the addition of H 2 S, the probe exhibited distinct turn-on near-infrared (NIR) fluorescence intensity alterations in the DMSO/H 2 O system, together with a high sensitivity (LOD = 0.13 μM) and large Stokes shift (121 nm). More importantly, the probe has been successfully applied to bioimaging for real-time, dynamic tracking of exogenous and endogenous H 2 S. The outcomes showed that the probe (DCM-H 2 S) provides a rapid and effective detection tool for monitoring H 2 S in vivo. [ABSTRACT FROM AUTHOR]

In most biophysiological processes, sulfur dioxide (SO 2) is an important intracellular signaling molecule that plays an important role. The change of SO 2 in cells are closely related to various diseases such as neurological disorders and lung cancer, so it is necessary to develop fluorescent probes with the ability to accurately detect SO 2 during physiological processes. In this work, we designed and synthesized a multifunctional fluorescent probe TIS. TIS has excellent properties such as near-infrared emission, large stokes shift, excellent SO 2 detection capabilities, low detection limit, high specificity and visualization of color change before and after reaction. Simultaneously, TIS has low cytotoxicity, good biocompatibility, clear cell imaging capability and mitochondrial targeting ability. In addition, the ability of TIS to be applied to different material surfaces for latent fingerprint fluorescence imaging was also explored. TIS provides an excellent method for the accurate detection of SO 2 derivatives and shows great potential applications in near-infrared cellular imaging and latent fingerprint fluorescence imaging. (a) TIS response mechanisms for HSO 3 −. (b) application of TIS. [Display omitted] • A NIR emission fluorescent probe with AIE characterization. • TIS has long emission wavelength (795 nm) and large Stokes shift (265 nm). • Dual detection channel for SO 2 derivatives accurate detection. • Superior colocalization effect on mitochondrial (0.86). • Clear three-level finger imaging capability. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel ratiometric peptide-based fluorescent probe DWPH was developed. • DWPH showed highly selective ratiometric response to Hg2+ and S2− in 100 % aqueous solutions. • Low detection limits for Hg2+ (24.6 nM) and S2− (23.3 nM) were obtained. • DWPH were successfully used to determine Hg2+ and S2− in living cells and zebrafish. • Smartphone-assisted detection platform could achieve visual assay of different Hg2+ and S2− concentrations. A new ratiometric peptide-based fluorescent probe DWPH was designed and synthesized, comprising dansyl fluorophore as a fluorescent dye, and tripeptide backbone (Trp-Pro-His-NH 2) as a recognition group. The addition of Hg2+ caused the maximum emission peak of DWPH to blue shift from 560 nm to 510 nm. DWPH exhibited large Stokes shift (230 nm), satisfactory water solubility (100 % aqueous medium), good selectivity (only Hg2+), high sensitivity (24.6 nM), rapid response (within 50 s) and strong anti-interference ability for Hg2+ detection over a wide pH range (7–11). Additionally, the complex DWPH -Hg2+ as a relay response probe could also be applied to S2− according to displacement approach. Notably, the detection limit for S2− was calculated as 23.3 nM, exhibiting that DWPH showed great potential for environmental monitoring and bioimaging. In addition, DWPH were successfully used to determine Hg2+ and S2− in living cells and zebrafish based on excellent permeability and low cytotoxicity. What's more, the gradient concentration color changes of Hg2+ and S2− were combined with the smartphone APP to obtain red–green–blue (RGB) values, thus enabling rapid semi-quantitative detection of Hg2+ and S2− without expensive instruments. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe EDPH specializes in the detection of H 2 S with high selectivity, high sensitivity and good detection limits. • The probe EDPH has been shown to have applications in intracellular fluorescence imaging. • Purine-based fluorescent probes for the detection of H 2 S are a new direction. Hydrogen sulfide (H 2 S) is a gas with a toxic odor that plays an irreplaceable role in physiological activities within the mammalian body. Therefore, it is important to do the distribution and quantitative detection of H 2 S in mammalian cells. In this paper, a fluorescence probe (EDPH) based on purine scaffold was designed and synthesized with high sensitivity and good selectivity. H 2 S induced ether bond breakage in EDPH , resulting in a significant redshift of the absorption band (from 370 nm to 500 nm) with a Stokes shift of 130 nm. After the addition of H 2 S, the fluorescence intensity of EDPH showed a good linear correlation with the concentration of H 2 S, which enabled the quantitative detection of H 2 S with a low limit of detection (41 nM). Finally, the EDPH was applied to the cellular Hele, and the probe has good cellularity imaging capability for the detection of H 2 S in living systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two TPE fluorescence probes with morpholine/pyrrolidone group were synthesized. • TPE-Ma and TPE-Py exhibited AIE character and lysosome targeting capability. • Two-photon fluorescence nanoprobes labels lysosomes in MCF-7 cells. Lysosomes are essential cellular organelles, serving vital functions in cellular metabolism and degradation. The design of specifically targeting lysosomes probes with aggregation-induced emission (AIE) characteristics using two-photon excitation techniques is significance and challenging work. Here we designed and synthesized two tetraphenylethylene (TPE)-based AIE fluorescence probes, naming TPE-Ma and TPE-Py , with TPE as the matrix and morpholine (Ma) or pyrrolidone (Py) as the targeting group. These probes exhibit a significant Stokes shift, low cytotoxicity, two-photo fluorescence imaging and lysosome-specific targeting capability ensuring their suitability for fluorescence imaging applications. To enhance the water solubility and cellular accumulation of TPE-Ma and TPE-Py in tumor cells, we employed a biocompatible polymer 1,2-distearoyl- sn -glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-mPEG 2000) as a nanocarrier. By encapsulating TPE-Ma and TPE-Py within DSPE-mPEG 2000 , we successfully developed two AIE fluorescent nanoprobes known as DSPE@ TPE-Ma and DSPE@ TPE-Py. The results demonstrated that fluorescent nanoprobes DSPE@ TPE-Ma and DSPE@ TPE-Py possess excellent cell permeability, biocompatibility, superior photostability and specific targeting towards lysosomes in MCF-7 cells. Our findings highlight the potential of these fluorescent nanoprobes as effective tools for two-photon fluorescence imaging and targeted detection of lysosomes in cancer cells. [ABSTRACT FROM AUTHOR]

The filamentous protein 'actin' plays an essential role in maintaining a proper cellular health and any disruption in its structure and dynamics may induce the growth and metastasis of cancerous cells. Recent studies have shown that, actin can serve as a potential therapeutic target and an indicator to examine the efficacy of modern chemotherapeutic agents. In this regard, the microscopy imaging of actin using fluorescent dyes can pave the way toward development of efficient drugs for cancer treatment. Herein, we report the synthesis of an organic fluorescent dye (BCH) which shows good selectivity toward F-actin at physiological pH. The dye displays a large Stokes shift (∼232 nm), strong emission intensity, good photostability and great sustainability over a wide pH range of 2–10. The dye can directly bind and localize in the actin-rich region of gut, testes and eye of a model organism, Drosophila melanogaster in both living and fixed cells and enable their confocal microscopy imaging without using any actin binding domain. Interestingly, the BCH dye is proved to be nontoxic in the tested organism and has been successfully employed as a potential tool to visualize cellular actin in living tissues of larva and pupa of the organism. [Display omitted] • A benzil biscoumarinyl hydrazone based fluorescent dye has been synthesized. • The dye can bind and image cellular filamentous actin directly without any binding domain. • The dye is proved to be nontoxic in model organism Drosophila melanogaster. • The dye has been successfully employed to visualize cellular actin in living tissues of larva and pupa of the organism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tetraphenylimidazole (TPI)-based styryl dyes TPI-In , TPI-Bt , and TPI-Qu exhibited polarity sensitivity. • TPI-Qu and TPI-Bt were viscosity-sensitive with extremely high fluorescence quantum yields in a dense environment. • The hues of TPI-In , TPI-Qu , and TPI-Bt solutions changed in response to their acidic and basic nature. • Only TPI-Qu and TPI-Bt fluoresced more brightly in high-viscosity cellular environments. Fluorescence probes have grown to be incredibly popular tools for measuring viscosity because of their high sensitivity, ease of use, and capacity to detect a microscopic scale. In this study, we developed a new line of excited-state intramolecular proton transfer (ESIPT)-based styryl fluorescent dyes based on tetraphenylimidazole (TPI) for measuring cellular viscosity. These dyes have good photophysical properties, including significantly large Stokes shifts and sensitivity to the hydrogen-bonding donor/acceptor solvent, according to the ESIPT characteristic. By observing variations in fluorescence, TPI-Bt , and TPI-Qu demonstrated exceptional sensitivity to viscosity in a water/glycerol system and substantial sensitivity to pH in a buffered water system. Furthermore, first-principles computations, crystallography, and application in living cells all supported the behaviors of the dyes in viscous environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new benzobodipy based fluorescent probe for HOCl has been designed and developed. • The probe has excellent sensitivity with a fast response to HOCl. • The probe was applied to the fluorescence imaging of HOCl in HeLa cells and zebrafish. Hypochlorous acid (HOCl) is a significant reactive oxygen species within biological systems, and its anomalous metabolism has been linked to a range of diseases. Therefore, it is crucial to track and monitor the concentration of HOCl in living organisms to understand its biological functions and study its pathogenic mechanisms. In this study, we developed a photoinduced electron transfer (PeT) mechanism-based benzo-fused bodipy fluorescence probe, named BBy-Se , for highly sensitive and selective detection of HOCl in aqueous solutions. BBy-Se demonstrated a good turn-on fluorescence response to HOCl by specifically oxidizing the selenium atom. It exhibited significant Stokes shift (82 nm), low detection limit (10.9 nM) and rapid response (less than 10 s). Furthermore, the probe was successfully employed for real-time fluorescence imaging of HOCl in living HeLa cells and zebrafish, as demonstrated by the bioimaging results. The development of BBy-Se presents a new approach to explore the biological roles of HOCl and offers a valuable tool for studying its function in diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe based on 1,3,5-Triazine was designed and synthesized to detect Hg(Ⅱ). • The novel fluorescent probe exhibited high selectivity, good stability, large Stokes shift (100 nm). • The novel fluorescent probe has been successfully used for cell and zebrafish imaging. • The novel fluorescent probe has successfully detected Hg(II) in tobacco. Non-biodegradable, bioaccumulative, and highly toxic, mercury(II) poses a significant threat to both ecosystems and human health. Extensive data indicates that even extremely low levels of Hg(II) can cause significant harm to human health. In this paper, the thiocarbonate specific recognition site was used for the detection of Hg(II), which was successfully synthesized by the hydroxyl group of 1,3,5-Triazine with phenyl chlorothiocarbonate. The probe exhibited advantages of high sensitivity (0.253 μM), good selectivity, large Stokes shift (100 nm), and good biocompatibility. The probe TzAr-Nap-Hg successfully fluorescently imaged Hg(II) in cells, zebrafish and tobacco, making it possible to detect the content of Hg(II) in agricultural and sideline products. [ABSTRACT FROM AUTHOR]

[Display omitted] • An "off–on" long-wavelength fluorescent probe is synthesized for Cys detection. • The probe has a large Stokes shift (211 nm) and reacted with Cys specifically. • The probe can monitor Cys fluctuations caused by redox imbalance in HepG2 cells. • The probe can be used for fluorescence imaging in cells and mice. In this research, an "off–on" long-wavelength fluorescent probe (DCMN-Cl) based on (E)-2-(3-(2-(6-hydroxynaphthalen-2-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (DCMN) is designed and synthesized for cysteine (Cys) detection. DCMN-Cl exhibits a large Stokes shift (211 nm) and shows rapid response and high specificity to Cys. The fluorescence initensity at 635 nm reveals a good linear relationship with Cys concentration in the 0 to 50 μM range, and the detection limit is as low as 159 nM. The probe is also used for fluorescence imaging of Cys in cells and mice. Moreover, the probe provided visual evidence of Cu2+ and curcumin-induced intracellular Cys fluctuations. [ABSTRACT FROM AUTHOR]

A deep-red emission and lipid droplets-targeted fluorescence probe (named ZFPy) for effective bioimaging of bisulfite was developed from flavone moiety and benzoindole derivative based on intramolecular charge transfer (ICT) and Förster resonance energy transfer (FRET) platform. ZFPy displayed promising fluorescence parameters including bright deep red fluorescence (615 nm), large Stokes shift (205 nm), extended emission window gap (140 nm), high absolute fluorescence quantum yield (4.1%) and stable emission signal output. In addition, ZFPy realized ratiometric fluorescence monitoring for SO 2 derivatives with low detection limit (30 nM), preferable linearity, high sensitivity and selectivity. Interestingly, dual fluorophores (i.e. the donor moiety and 1,1,2,3-tetra-substituent-1H-benzo[e]indol-3-ium iodide moiety) released the same emission band about 475 nm to enhance the emission signal when ZFPy reacted with SO 2 derivatives, to the best of our knowledge, this is the first synergetic FRET/ICT platform for fluorescence probe, which might effectively offer ZFPy a high sensitivity and low detection limit in the detection of SO 2 derivatives. More importantly, ZFPy could image exogenous and endogenous SO 2 derivatives in living HeLa, HepG2 and L-O2 cells with good biocompatibility and photostability. ZFPy also preferred to load on lipid droplets with high Pearson's coefficient (0.95). Image 1 • A ratiometric fluorescent probe (ZFPy) for rapidly monitoring SO 2 derivatives was developed. • FRET-based ZFPy displayed larger gap (140 nm) between two emission spectra. • This is a first synergetic FRET/ICT platform for fluorescence probe. • ZFPy was applied to image exogenous and endogenous SO 2 derivatives in living Hela, HepG2 and L-O2 cells. • ZFPy showed lipid droplets-targeted ability (Pearson's coefficient 0.95). [ABSTRACT FROM AUTHOR]

A water-soluble probe with p-hydroxybenzyl quaternary ammonium linker, FR-2a, for selective imaging in senescent cells is reported. Probe FR-2a integrated water-soluble fluorophore (HT-4a) and β-galactosidase (β-gal) trigger into one entity by a p-hydroxybenzyl quaternary ammonium linker. HT-4a is a styryl-based push–pull benzothiazole fluorophore with attractive properties, including excellent water-solubility, intense fluorescence emission and a large Stokes shift (161 nm), characterized by an intramolecular charge transfer (ICT) excited state. The formation of quaternary ammonium deactivated the ICT state, resulting in fluorescence quenching of FR-2a. In the presence of β-gal, the glycosidic bond was hydrolyzed and fluorophore HT-4a was released through self-immolative process, resulting in effective fluorescence recovery. FR-2a shows high affinity to β-gal (K m = 1.33 μM), exhibiting good sensitivity, selectivity and stability for imaging in senescent cells. Image 1 • Fluorescent probe FR-2a with self-immolative p-hydroxybenzyl quaternary ammonium linker was developed. • FR-2a selectively and rapidly responses to β-gal in PBS buffer. • FR-2a has excellent water solubility, avoiding ACQ of fluorescence in PBS. • FR-2a was capable of selective imaging in senescent cells. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H 2 O 2) plays a significant role in regulating a variety of biological processes. Dysregulation of H 2 O 2 can lead to various diseases. Although numerous fluorescent imaging probes for H 2 O 2 have been reported, the development of H 2 O 2 ratiometric fluorescent probe with large Stokes shift remains rather limited. Such probes have shown distinct advantages, such as minimized interference from environment and improved signal-to noise ratio. In this work, we reported a new pyrene-based compound Py-VPB as H 2 O 2 fluorescent probe in vitro. The probe demonstrated ratiometric detection behavior, large Stokes shift and large emission shift. In addition, the probe showed high sensitivity and selectivity towards H 2 O 2 in vitro. Based on these excellent properties, we successfully applied Py-VPB to the visualization of exogenous and endogenous H 2 O 2 in living cells. Cell imaging study also showed that our probe was localized in the mitochondria. We envision that the probe can provide a useful tool for unmasking the biological roles of mitochondrial H 2 O 2 in living systems. Image 1 • The first pyrene-based fluorescent probe for H 2 O 2 detection with ratiometric readout was presented. • The probe has shown prominent properties in detecting H 2 O 2 , such as high sensitivity & selectivity and large Stokes shift. • The probe was successfully applied to visualizing exogenous and endogenous H 2 O 2 in living cells. [ABSTRACT FROM AUTHOR]

Neutrophil elastase (NE), a representative protease which is closely related to many diseases, acts an indispensable role in inflammatory diseases and clinical medicine. In this work, one activity-based non-peptide ratiometric fluorescent probe DCDF was designed with pentafluoropropionic anhydride as identification group. To our knowledge, this is the first probe capable of detecting NE in ratio. After the addition of the NE, the emission spectrum of DCDF has obvious bathochromic-shift phenomenon, and there is large Stokes shifts of ∼60 nm. Compared to only a few reported NE probes, DCDF is sensitive and selective and has very low detection limit (0–14 μg/mL, DL = 30.8 ng/mL). A possible response mechanism was proposed and verified by HPLC and HRMS spectra. What's more, DCDF is capable of endogenous recognition imaging in biological cells without interference from other enzymes under the ratio signal. A549 and HeLa cells were used for endogenous cell imaging experiments of NE and the feasibility of DCDF for the specific detection of NE in cells was proved. This experimental result makes probe DCDF a very promising tool for the clinical diagnosis and treatment of NE related diseases. Two ratiometric probe DCDF was synthesized to detect NE with a ratio signal. Probe DCDF can respond to NE in a very short time, ideal detection limit (30.8 ng/mL) and good selectivity. Probe DCDF can use to detect endogenously produced NE in A549 and HeLa with a ratio signal. Image 1 • DCDF synthesized based on ICT mechanism and the first small molecule probes capable of detecting NE in ratio. • DCDF has obvious bathochromic-shift phenomenon, and has a large Stokes shift of ∼ 60 nm. • DCDF shows highly selectivity and sensitivity, the LOD, low cytotoxicity and good biocompatibility. • The mechanism of DCDF reacted with NE was proposed and verified by HPLC and HRMS spectra. • The DCDF was successfully used for cell imaging in A549 and HeLa cells. [ABSTRACT FROM AUTHOR]

A smart fluorescent probe DPAS-Cys has been rationally designed based on a typical AIEgen DPAS and an acrylate moiety. The probe DPAS-Cys not only can be used for the detection of cysteine (Cys) selectively with large Stokes shift (200 nm) and relatively low detection limit (2.4 μM), but also shows lipid droplets (LDs) targeting property. The response mechanism for Cys was carefully verified. Importantly, due to the aggregation-induced emission characteristic, the introduction of considerable percentage of traditional organic solvent is avoidable, which makes it suitable for bioimaging in physiological systems. In addition, the confocal fluorescence imaging demonstrates that DPAS-Cys is able to detect Cys in LDs of different cell lines with universality. Our study opens a new avenue to understand the importance of LDs in biosystem, for which the gap between the essential biothiol Cys and the energy storage organelle LDs was bridged for the first time. Image 1 • A smart fluorescent probe DPAS-Cys is developed for selective detection of cysteine. • DPAS-Cys shows aggregation-induced emission characteristic and large Stokes shift. • DPAS-Cys exhibits lipid droplets targeting property with universality. [ABSTRACT FROM AUTHOR]

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]

Conventional organic dyes and inorganic fluorescent contrast agents have been hampered in bioimaging and biomedical purposes due to their intrinsic drawbacks. Thus there is a pressing need to develop novel classes of fluorescent contrasts with merits of high photostability and good biocompatibility for biomedical applications. In this study, we report the fabrication of a nanosized contrast agent (T nano) loaded with a novel organic fluorescent dye (TPACN) and evaluation of its performance for cellular imaging. This nanocontrast agent not only preserved the optical characters of TPACN, including superior fluorescence quantum yield (QY) of 67% and large Stokes shift of 165 nm, but also exhibited remarkable colloidal and fluorescence stabilities compared to free TPACN, and superior biocompatibility and enhanced cellular imaging capacity as well. Given these favorable properties, our TPACN-loaded nanocontrast agent might potentially be applied for bioimaging and biomedical use in the future. Unlabelled Image • A novel fluorescent dye with large Stokes shift and high quantum yield is synthesized. • Dye-loaded nanocontrast agent exhibits superior fluorescence property and stability. • A biocompatible fluorescent nanoprobe shows enhanced cellular imaging potential. [ABSTRACT FROM AUTHOR]

In this paper, a new strategy was presented for fluorescence labeling and imaging Al3+ in live cells with excess aluminum ions using thiolated fluorescence gold nanoclusters (Au NCs). The glutathione (GSH)-capped Au NCs were prepared via a green, facile one-pot method in aqueous solution and displayed excellent stability, ultrasmall size, monodispersity, and larger Stokes shift, which exhibits a relatively weak fluorescence at 650 nm Al3+-induced fluorescence enhancement of the GSH-Au NCs can be observed due to Al3+-triggered aggregation-induced emission (AIE) effect, which allows the role of GSH-Au NCs as a fluorescence light-up probe for detection of Al3+. Moreover, it was demonstrated that the fluorescence probe for Al3+ showed a wide detection range from 100 to 600 μM and good selectivity against other metal ions and common biomolecule. Furthermore, due to the advantages of excellent biocompatibility, low toxicity, red emission and high specificity, the proposed GSH-Au NCs fluorescence probes are suitable for the imaging of high concentrations of aluminum ions in cells, which can be applied to the diagnosis of cellular aluminum poisoning. Schematic illustration of the synthesis process of GSH-Au NCs and the fluorescence enhancement of GSH-Au NCs after adding Al ion due to the Al3+ triggered aggregation of the GSH-Au NCs. Image 1 • First report of the Al3+ rapid fluorescence detection in live cells with excess aluminum ions using thiolated Au NCs. • Al3+ as linkers can induce photoluminescence boost of thiolated Au NCs nearly 40-fold through AIE. • The biosensor is suitable for imaging of excess aluminum ions in cells due to their hypotoxicity, red emission of 650 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] • The conjugated structures of fluorescent dyes (NapPAs) were extended by the introduction of phenylethynyl, and the effects of different substituents at the p -position of phenylacetylene on the geometry, frontier orbital electron distribution, energy gap and photophysical properties of the dyes were studied. • Correlating the theoretical calculation results with the experimentally measured spectra, it was found the dyes exhibited the characteristics predicted by theoretical calculations, and various properties of the dyes could be regulated through structural modification during molecular design. • Two dyes (NapPA-LDs and NapPA-LDs-Lyso) with excellent photophysical properties (large Stokes shift, high polarity-viscosity sensitivity, good biocompatibility) were selected as fluorescent probes for bioimaging. • NapPA-LDs exhibited remarkable affinity towards LDs with excellent imaging effect, and enabled monitor the dynamic changes and movements of LDs in real time, helping to uncover previously unexplored cellular mechanisms. • NapPA-LDs-Lyso enabled simultaneous two-color imaging of LDs and lysosomes, which could monitor the dynamic changes, movements and dynamic behavior (aggregation, dissociation and fusion) of LDs and lysosomes in real time, and could serve as a potential tool to study the interactions and potential functions between LDs and lysosomes. A series of fluorescent dyes (NapPAs) based on 4-phenylacetylene-1,8-naphthalimide were synthesized and characterized, whose conjugated structures were extended by the introduction of phenylethynyl. Furthermore, changes in the photophysical properties of the dyes when substituents with varying electron richness were introduced at the p -position of phenylacetylene were studied. The theoretical calculation of the dye molecules was carried out by B3LYP functional and 6-31G(d,p) basis set, and the effects of different substituents at the p -position of phenylacetylene on the electronic structure and photophysical properties of the dyes were studied by theoretical calculation results. Theoretical calculations provided a reliable means of predicting the properties of dyes, which could help in the design of more efficient and novel dyes. To verify the practicability of the dyes, two dyes with excellent photophysical properties (large Stokes shift, high polarity-viscosity sensitivity, good biocompatibility) were selected as fluorescent probes for visualization of LDs and two-color imaging of LDs and lysosomes. Cell imaging showed that NapPA-LDs and NapPA-LDs-Lyso serve as excellent imaging tools to monitor the dynamic changes, movements, and behaviors of LDs and lysosomes in real time. Notably, NapPA-LDs-Lyso held promise as a potential tool to study the interaction between LDs and lysosomes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Probe FBC-DS performed sufficient selectivity, fast response time, high sensitivity and a large Stokes shift to HClO. • FBC-DS was applied for imaging of exogenous and endogenous HClO in living HeLa cells and zebrafish with satisfactory performances. • FBC-DS was applied for corroborating that HClO could be an efficient marker for APAP-induced hepatotoxicity in the mice liver injury models. Drug-induced liver injury (DILI), as a classic acute inflammation, has attracted widespread concern due to its unpredictability and severity. Among the various reactive oxygen species, HClO has been used as a marker for the detection of DILI process. Thus, we designed and synthesized a "turn-on" fluorescent probe FBC-DS by modifying 3'-formyl-4'-hydroxy-[1,1'-biphenyl]-4-carbonitrile (FBC-OH) with N, N-dimethylthiocarbamate group for sensitively sensing HClO. Probe FBC-DS showed a low detection limit (65 nM), fast response time (30 s), an enormous Stokes shift (183 nm) and 85-fold fluorescence enhancement at 508 nm in the detection of HClO. Probe FBC-DS could monitor exogenous and endogenous HClO in living HeLa cells, HepG2 cells and zebrafish. In addition, probe FBC-DS has been successfully utilized in biological vectors for imaging acetaminophen (APAP)-induced endogenous HClO. Moreover, DILI caused by APAP is evaluated by probe FBC-DS through imaging over-expression of endogenous HClO in the mice liver injury models. All in all, we have every reason to believe that probe FBC-DS can be a potential tool to study the complex biological relationship between HClO and drug-induced liver injury. [ABSTRACT FROM AUTHOR]

[Display omitted] • Probes 1a-b for detection of thiophenols by ESIPT mechanism were constructed with diethylcoumarin–salicylaldehyde units. • They showed large Stokes shift (greater than100 nm) and one of them displayed NIR-emitting (670 nm) when detecting thiophenols. • Probes 1a-b could form inclusion complexes with M-β-CD. • The presence of M-β-CD reduced the detection limits of probes 1a - b towards thiophenols. Thiophenol and its derivatives are compounds with high toxicity to organisms and environmental pollution, so it is necessary to detect the level of thiophenols in the environment and biological samples. The probes 1a-b were obtained by introducing the 2,4-dinitrophenyl ether group into diethylcoumarin–salicylaldehyde based compounds. And they can form host-guest compounds with methylated β-cyclodextrin (M-β-CD), the association constants of inclusion complexes are 49.2 M−1, 125 M−1 respectively. The fluorescence intensities of probes 1a-b at 600 nm (1a) and 670 nm (1b) increased significantly in thiophenols detection. Meanwhile, with the addition of M-β-CD, the hydrophobic cavity of M-β-CD significantly increased the fluorescence intensity of probes 1a-b , thus the detection limits of probes 1a-b to thiophenols were reduced from 410 nM, 365 nM to 62 nM, 33 nM respectively. Whereas, the good selectivity and short response time of probes 1a-b towards thiophenols was not affected in the presence of M-β-CD. Moreover, probes 1a-b were used for further water sample detection and HeLa cell imaging experiments due to their good response to thiophenols and the results suggested that probes 1a-b had the potential to detect the content of thiophenols in water samples and living cells. [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−), as an important reactive oxygen species (ROS), plays a significant role in pathological and physiological processes, and abnormal levels of ONOO− will lead to many diseases. Thus, novel fluorescent probe for detecting ONOO− is in urgent need. Herein, we constructed a probe TPPB with aggregation-induced emission (AIE) characteristic based on triphenylamine and boronate group. The probe TPPB possesses remarkable performances including high selectivity in the presence of other ROSs, low detection limit (32 nM) and large Stokes shift (215 nm) toward ONOO−. Besides, probe TPPB shows low cytotoxicity and good imaging ability of ONOO− in living cells. [Display omitted] [ABSTRACT FROM AUTHOR]

This study reported a unique mitochondria-targetable phosphorescent 'on-off-on' probe, Ir-DPA, based on an iridium(III) complex derivative for the sequential and specific detection of Cu2+ and Cys in vitro and in vivo. Probe Ir-DPA was constructed by a lipophilic cation unit as the chromophore as well as the mitochondria biomarker and a dipicolylamine (DPA) group as the recognition unit for Cu2+, followed by removal of Cu2+ specifically in the presence of Cys. The probe itself was strongly emissive at 570 nm. Upon addition of Cu2+, marked quenching occurred as result of the binding of Cu2+ with DPA moiety of this probe, accompanied by a distinct naked-eye luminescence color change from orange yellow to colorless. Additionally, further addition of Cys, the displacement of Cu2+ from in situ generated Ir-DPA-Cu ensemble because of the large nucleophilicity of cysteine toward Cu2+ led to the release of probe, giving rise to the luminescence recovery, as well as a relevant chromogenic change from colorless to orange yellow. Ir-DPA showed a large Stokes shift of 200 nm and high selectivity and sensitivity for the rapid detection of Cu2+ and Cys under physiological conditions, with low detection limits of 0.04 μM and 1.21 μM for Cu2+ and Cys, respectively. More importantly, the probe successfully targeted mitochondria, sensitively detected Cu2+ and exogenously or endogenously generated Cys both in mitochondria of living cells and zebrafish. Finally, Ir-DPA was capable of quantifying Cu2+ level in water samples and the in situ generated ensemble identifying Cys in human serum. These results indicated the great potential of Ir-DPA for monitoring Cu2+ and Cys in environmental, biological systems, and mitochondrial processes. A mitochondria-targetable phosphorescent 'on-off-on' probe for sequentially and selectively detecting Cu2+ and cysteine has been achieved based on Cu2+-displacement reaction. [Display omitted] • A mitochondria-targetable phosphorescent 'on-off-on' probe for the specific detection of Cu2+ and cysteine was developed. • The probe exhibited a sequential orange yellow-colorless-orange yellow phosphorescent response to Cu2+ and cysteine. • The probe was successfully used for imaging Cu2+ and cysteine both in mitochondria of living cells and animals. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel open-type NIR fluorescent probe was reported for the detection of PhSH. • The probe shows high sensitivity and selectivity to thiophenol. • Probe shows a large Stoke shift and significant fluorescence enhancement. • Probe has been applied to the detection of PhSH in living cells and water samples. In this study, a NIR fluorescent probe based on ICT principles was developed for the detection of phenylthiophenol. An excellent fluorescent mother nucleus is constructed with tricyano groups, and benzenesulfonate was introduced as a specific recognition site for thiophene, which can be used for rapid detection of thiophenol. The probe has a significant Stokes shift (220 nm). Meanwhile, it had rapid response to thiophene and high specificity. The fluorescence intensity of the probe at 700 nm showed a good linear relationship with thiophene concentration in the range of 0 to 100 μM, and the detection limit was as low as 45 nM. The probe had also been successfully applied to the detection of thiophene in real water samples. MTT assay showed low cytotoxicity and excellent fluorescence imaging in live cells. [ABSTRACT FROM AUTHOR]

On the basis of classical Schiff base reaction, two novel and efficient fluorescent probes (DQNS , DQNS1) were designed and synthesized by introducing Schiff base structure into dis-quinolinone unit for structural modification, which can be used to detect Al 3+ and ClO −. [Display omitted] • The double-recognition fluorescent probes with the same site designed based on ICT and PET mechanism has the characteristics of simple synthesis method. • Preliminary speculation, the probe (DQNS) has continuity in identifying Al3+and ClO−. • The probes (DQNS) can primarily screen and analyze environmental samples and living cells containing Al3+and ClO−. On the basis of classical Schiff base reaction, two novel and efficient fluorescent probes (DQNS , DQNS1) were designed and synthesized by introducing Schiff base structure into dis-quinolinone unit for structural modification, which can be used to detect Al3+ and ClO−. Because the power supply capacity of H is weaker than that of methoxy, DQNS shows better optical performance: a large Stokes Shift (132 nm), identify Al3+ and ClO− with high sensitivity and selectivity, low detection limit (29.8 nM and 25 nM) and fast response time (10 min and 10 s). Through the working curve and NMR titration experiment, the recognition mechanism of Al3+ and ClO− (PET and ICT) probes are confirmed. Meanwhile, it is speculated that the probe has continuity for the detection of Al3+ and ClO−. Furthermore, DQNS detection of Al3+ and ClO− was applied to real water samples and living cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel probe BD-C based on the FRET-ICT mechanism was designed to detect cysteine. • Probe BD-C had superior selectivity without the interference of other biological thiols. • Probe BD-C had large Stokes shift and the energy transfer efficiency reached 98.8%. • Probe BD-C had superior endoplasmic reticulum-targeting. Cysteine is an important thiol amino acid that is abundantly present in cells and has an important function in various life processes of the human body. Therefore, it is of great significance to develop an accurate method for monitoring cysteine concentration in cells. We designed and synthesized a novel FRET-ICT-based ratiometric fluorescence and colorimetric probe (BD-C) for detecting cysteine. As cysteine was gradually added, the fluorescence intensity of probe BD-C in buffer solution decreased at 614 nm and increased at 428 nm. The logarithm of the fluorescence intensity ratio to cysteine exhibited favorable linearity in the concentration range of 0.5–14.0 μM, with a detection limit of 395 nM. The energy transfer efficiency of this FRET system is up to 98.8%. BD-C demonstrated preeminent selectivity for cysteine and could specifically react with cysteine, though other sulfhydryl amino acids, such as GSH and Hcy, were present. Furthermore, BD-C exhibited outstanding targeting ability to the endoplasmic reticulum (ER) and was successfully applied in cellular imaging. [ABSTRACT FROM AUTHOR]

The abnormality of Cys concentration in organism could lead to a series of diseases, so its effective detection is of great importance in disease diagnosis. Here we developed a novel ESIPT fluorescent probe HBT-IDAc based on the classic ESIPT fluorophore 2-(2′-hydroxyphenyl)benzothiazole (HBT) and indanone, which could selectively and sensitively detect Cys with a large Stokes shift up to 210 nm and the detection limit to 0.89 μM. In addition, the probe exhibited good anti-interference and low cytotoxicity, and has been successfully applied to monitor Cys in cells. • A novel ESIPT fluorescent probe for selective and sensitive detection of Cys was developed. • The probe has the large stokes shift (210 nm) and good LOD (0.89 μM) in aqueous environment. • The probe exhibits low cytotoxicity and has been applied for imaging Cys in cells. [ABSTRACT FROM AUTHOR]

Mercury ion (Hg2+) is highly toxic to the environment and organisms, therefore, monitoring and quantitative detection of Hg2+ is of great significance. In this work, a new fluorescent probe TPEH that integrated tetraphenylethene (TPE) and 2-(2 ′ -hydroxyphenyl)benzothiazole was designed and synthesised. In EtOH/HEPES (2:8, v/v, pH = 7.2) solution, TPEH displays fluorescence turn on detection of Hg2+ with the advantages of swift response (<100 s), high selectivity and strong disturbance-resistant, a large Stokes shift (220 nm), and low limit of detection (81.7 nM). The sensing mechanism was proved to be Hg2+-triggered releasing of the aggregation-induced emission (AIE)-active precursor compound 2. TPEH has been successfully applied to detect Hg2+ in seafood and tea, and image Hg2+ in living cells. In addition, TPEH can be used to detect the content of Hg2+ in actual water samples with the aid of smartphone. [Display omitted] • A new AIE-based fluorescent probe TPEH for Hg2+ detection has been developed. • TPEH has the advantages of rapid response (<100 s), a large Stokes shift (220 nm), and a low detection limit (81.7 nM). • TPEH can detect Hg2+ in seafood and tea, and image Hg2+ in living cells. • TPEH can detect Hg2+ in actual water samples with the help of smartphone. [ABSTRACT FROM AUTHOR]

The fluorescent probe with both aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) shows significant advantages, such as no self-quenching at high concentration, large Stokes shift, high selectivity towards analyte etc. Based on tetraphenylethene and ESIPT structural modules, three AIE-ESIPT molecules containing one different atom (S, O, N) have been constructed in this paper. The effects of three atoms on the optical properties of fluorescent molecules have been investigated by fluorescence spectroscopy and X-ray crystallographic analyses. Interestingly, the cyclic detection of HCl and NH 3 gases can be achieved with the BTY-TPE -based portable test paper. In addition, BOY-TPE and HBIY-TPE can detect ClO− by naked eye with low detection limit, good biocompatibility. Three AIE-ESIPT fluorescent probes respectively containing S, O, N atoms have been synthesized. The effects of S, O, and N atoms on the optical properties of fluorescent molecules have been investigated by fluorescence spectroscopy and X-ray crystallographic analyses and DFT calculation. The results indicate that all three exhibit AIE and ESIPT properties, X-ray crystallographic analysis indicate a significant difference in molecular packing, which should be the dominant factor in the polymorph dependence of ESIPT luminescence. It is interesting to note that BTY-TPE -based test paper can be used for cyclic detection of HCl and NH 3 gases. In addition, BOY-TPE and HBIY-TPE can be used as intracellular probes for detecting ClO−.[ [Display omitted] ] • Three AIE-ESIPT double-mechanism fluorescent crystals have been synthesized. • Effects of S, O, and N on the properties of three fluorescent crystals were discussed. • BTY-TPE -based test strip could repeatable detect HCl and NH 3 gases. • Both BOY-TPE and HBIY-TPE with extremely low detection limit for detecting ClO−. • Both BOY-TPE and HBIY-TPE could detect ClO− in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A red-emissive fluorescent probe HBTI for reversible recognition of HSO 3 − and H 2 O 2 has been developed. • HBTI showed fluorescence on–off-on variations upon sequential addition of HSO 3 − and H 2 O 2. • HBTI is applicable to detect HSO 3 − in real food samples. • HBTI is mitochondria-targetable and can be used in cell imaging. Reducing agent SO 2 and oxidant H 2 O 2 are two essential substances in cells, and the balance between them is closely related to the survival of cells. SO 2 derivative HSO 3 − is often used as food additive. Therefore, simultaneous detection of SO 2 and H 2 O 2 is of great significance in biology and food safety. In this work, we successfully developed a mitochondria-targeted red fluorescent probe (HBTI), which has excellent selectivity, high sensitivity and large Stokes shift (202 nm). HBTI and HSO 3 −/SO 3 2− undergo Michael addition on the unsaturated C=C bond, and the addition product (HBTI-HSO 3 −) can react with H 2 O 2 to restore the conjugated structure. Fluorescence changes from red to non-emissive and then restores to red, and can be detected quickly and visually. In addition, HBTI has been successfully targeted mitochondria, and achieved dynamic reversible response to SO 2 /H 2 O 2 in living cells, and has been successfully applied to detect SO 2 in food samples. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl) is a crucial reactive oxygen species in biological systems, and its abnormal metabolism is associated with various diseases. Therefore, it is essential to accurately detect HOCl to understand its biological function and develop related therapeutic strategies for diseases. In this work, we developed a novel fluorescence probe, BCy-S , based on the twisted intramolecular charge transfer (TICT) mechanism for rapid and sensitive detection of HOCl in an aqueous solution. The probe exhibited a significant turn-on fluorescence response to HOCl, with high selectivity, rapid kinetics (less than 40 s), large Stokes shift (about 170 nm), and low detection limit (35.2 nM), based on the specific oxidation reaction of HOCl with sulfur atoms. Additionally, the outcomes of the bioimaging experiment showed that BCy-S was capable of real-time fluorescence visualization of HOCl in living HeLa cells and zebrafish. The development of BCy-S presents a new tool for investigating the physiological function of HOCl and its pathological role in diseases. [Display omitted] • A new TICT-based HOCl fluorescent probe has been designed and developed. • The probe exhibits an excellent sensitivity, large Stokes Shift and low detection limit to HOCl. • The probe could be applied for real-time fluorescence imaging of HOCl in live HeLa cells and zebrafish. [ABSTRACT FROM AUTHOR]