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A new strategy of thermally activated delayed fluorescence (TADF) material-sensitized circularly polarized luminescence (CPL) has been proposed for improving the efficiencies of fluorescent circularly polarized organic light-emitting diodes (OLEDs) (CP-OLEDs). Consequently, a pair of helicene enantiomers, (P)-HAI and (M)-HAI, were synthesized. The helicene enantiomers with the rigid helical π-skeleton had highly thermal and enantiomeric stabilities, and they also showed excellent photophysical properties, especially, intense mirror-image CPL activities with large luminescence dissymmetry factor (|glum|) values of about 6 × 10−3. Notably, the CP-OLEDs with the helicene enantiomers as emitters and a TADF molecule as sensitizer not only displayed better performance of lower turn-on voltage (VT) of 2.6 V, four-fold maxmium-external quantum efficiency (EQEmax) of 5.3%, and lower efficiencies roll-off of 1.9% at 1000 cd m−2, than those of the devices without TADF sensitizer, but also exhibited intense circularly polarized electroluminescence (CPEL) with the electroluminescence dissymmetry factor (gEL) values of −2.3 × 10−3 and +3.0 × 10−3. Meanwhile, this study also represents the first thermally activated sensitized fluorescent CP-OLEDs with markedly enhanced efficiencies and intense CPEL.

Hydrogen sulfide (H2S) is a kind of gaseous signal molecule in many physiological processes. In order to detect H2S, a novel “turn on” fluorescent probe 6,12-dihydroxyperylene-1,7-dione (DPD) was designed and synthesized. The probe DPD is fluorescence silence, while the addition of H2S induces an obvious green fluorescence with an obvious color change from dark blue to yellow-green. The probe shows excellent selectivity, fast response (2.5 min) and linear curve (0–90 μM) in wide effective pH range (4–10). Competition experiments are also revealed in corresponding studies and the detection limit is 3.6 μM. The response mechanism is proved to be the reduction of the probe by H2S, which is confirmed by 1H NMR. Furthermore, through the fluorescence turn-on signal toward H2S in Hela cells, probe DPD was successfully applied to monitor H2S in living Hela cells.

Stimuli responsive luminescent materials have attracted increasing attention for their potential application in many fields. In this work, dimethylamine substituted bisbenzocoumarins amides (DBCE and DBCP) are synthesized and their optical properties are investigated. These molecules show solvatochromic properties. The orange fluorescence emission of DBCE in crystalline state is blue-shifted to yellow emission upon grinding. The orange color could be recovered by recrystallization process. Powder wide-angle X-ray diffraction and DSC experiments reveal that the transformation from crystalline states to amorphous states under external stimuli is responsible for the mechanochromic properties. This work developed a new kind of binaphthane-type luminescent materials with blue-shifted mechanochromic properties.

A thiophene-rhodamine dyad (BYY) was easily synthesized as a fluorescence probe from 2-thiopheneacetic acid and N-(rhodamine-B)lactam-ethylenediamine. The probe showed high response speed and sensitivity toward Fe3+ in ethanol/water (2/3, v/v, pH = 7.2), and the limit of detection was as low as 10−7 M. From the Job's plot, mass spectrum, 1H NMR spectra and the theoretical calculation, the 1:2 complex ratio of Fe3+-probe was obtained and the response mechanism was determined. Significantly, the reversible binding of BYY to Fe3+ was achieved through the strong Fe3+ affinity of Na4P2O7, and the probe showed well antijamming abilities in the presence of common metal ions. Moreover, the probe was cell-permeable and could sensitively response to Fe3+ in living cells with satisfying resolution.

Luminescent organic materials with tunable emission color have attracted much attention for their potential application in multiple fields. Herein, we designed and synthesized a series of dimethylamine substituted binaphthanol based organic fluorophores. Decorating with substituents at the alkene moiety on the binaphthanol core backbone led to organic solid emitters with color tunability from the blue to red regions. These fluorophores exhibited solvatochromic properties and two compounds (DB-4 and DB-5) showed aggregation-induced emission properties. The binaphthanol core structure induced a twisted molecular conformation and special intermolecular packing mode in a single crystal structure, which was beneficial for the inhibition of the strong intermolecular π–π stacking interaction and induced the AIE feature as well as the fluorescence emission in the solid state. The absorption and emission changes of these molecules under acidic and basic conditions revealed that they had acidochromic properties and could be used as security ink. This work provided a new strategy for the synthesis of organic solid emitters with tunable emissions based on the simple binaphthanol core backbone.

Organic fluorescent molecules with π-conjugated system have shown great importance in numerous applications including bioimaging and optoelectronics. Planar aggregation-induced emissive (AIE) organic compounds with efficient solid-state luminescence are rarely developed and urgently needed in various applications. In this work, highly planar 4-styrylbenzonitrile derivatives have been synthesized. Most of these compounds show strong AIE properties with hundred-fold fluorescent enhancement. Moreover, these molecules are deep blue emissive in solid state, exhibiting good to excellent fluorescence quantum efficiency. The single crystal analysis shows that adjacent molecules could form special J-type aggregation. The intramolecular rotations are efficiently restricted by various noncovalent interactions. These molecular arrangements could be essential for the observed strong emission in aggregated and solid state. This work has paved a new path to efficient AIE-active organic emitters with highly planar conformations from 4-styrylbenzonitrile structure.

A new fluorescent probe tetrahydro[5]helicene-malononitrile derivative was designed and synthesized for selective detection of bisulfite. This fluorescent probe exhibites high response speed and selectivity toward HSO3− in PBS solution over other coexisting species accompanied by a distinct fluorescence color change from yellow to blue, which can be visually identified. The probe shows excellent sensitivity to HSO3− and the detection limit is as low as 0.27 μM. Once reacted with HSO3−, the signal-to-background ratio of fluorescence intensity can reach a 45-folds enhancement and the quantum yield dramatically increases from 1.9% to 52.3%. The response mechanism proved to be a nucleophilic addition reaction of probe with HSO3−, which was confirmed by 1H NMR, Mass titration and theory calculation. Additionally, the preliminary cell imaging experiments demonstrated that the probe could be used for intracellular bisulfite detection.

A new fluorescent probe based on coumarin conjugate has been synthesized which shows high quantum yield because of strong ICT effect. The absorption and fluorescence spectra of probe were measured in a variety of solvents and the Stokes shifts were found to be in linear relationship with the orientation polarizability of the solvents. The fluorescence intensity of probe decreased with a rise in water content which could be an effective fluorescence water sensor in organic solvents. Moreover, the probe presents a highly linear ratiometric fluorescence response to water content under the excitation of ultraviolet light. The detection results by the ratiometric fluorescence probe are in good agreement with that by the well-established standard Karl Fischer method. This ratiometric fluorescent probe provides another accessible tool for the quantitative determination of water content and may replace the Karl Fischer method for specific applications.

Studies have shown that changes in the redox state of cells might be closely related to pathological and physiological processes. Sulfur dioxide and hydrogen peroxide, as a significant redox couple in living cells, are endogenously produced by cells. Here, we report a long-wavelength fluorescent probe to reversibly monitor sulfur dioxide and hydrogen peroxide. This probe (NBD) displayed high selectivity and sensitivity, which could be accumulated in mitochondria for real-time imaging of SO2/H2O2. These results indicated that NBD would be an ideal tool for monitoring the redox cycle state in living cells.

An easily available novel fluorescent probe has been synthesized by reacting rhodamine hydrazide and 2-(thiophen-2-yl)acetyl chloride. Upon mixed with Fe 3+ in aqueous solution, the dramatic enhancement of fluorescence intensity as well as the color change of the solution were observed. Significantly, the probe displayed highly selective and sensitive recognition ability toward Fe 3+ with a limit of detection (LOD) down to 10 −7 M. The Job’s plot indicated the formation of 1:1 complex between the probe and Fe 3+ , and the complexation stability constant can be calculated as 2.95 × 10 4 M −1 . The presence of common coexisting alkali, alkaline earth, and transition metal ions showed small or no interference to the detection of Fe 3+ . All these unique features make it particularly favorable for cellular Fe 3+ imaging applications. The confocal fluorescent images demonstrated that the probe was cell-permeable and could be used for highly sensitive monitoring of Fe 3+ levels in living cells with satisfying resolution.

A novel visible light excitable chemosensor based on a rhodamine 6G naphthylurea conjugate was successfully synthesized, which shows highly selective and sensitive recognition ability toward H2PO4− in H2O-CH3CN (1/1, v/v). In response to H2PO4−, the probe provided remarkable fluorescence intensity change and clear color change from colorless to pink and the background anions showed small or no interference. The confocal fluorescent images demonstrated that the probe was cell-permeable and could effectively detect intracellular dihydrophosphate in living cells.

Emissive molecules which not only emit at low concentrations, but also are fluorescent in aggregated state, have attracted considerable interests. Herein, we report an emissive molecule 1 based on tetraphenylethylene (TPE) in which two diacetylenes (DAs) are induced to restrict the rotation of phenyl rings in TPE, and consequently preserves the fluorescence in diluted solution, while it still shows aggregation-induced emission (AIE) effect in the solid state. Crystalline microfibers of 1 with DAs well-aligned are also constructed upon vapor diffusion method. Furthermore, the thermal induced polymerization of DAs in 1 could occur via heating the single crystals of 1 to afford a new porous polymer.

Biological thiols including homocysteine (Hcy), cysteine (Cys), hydrogen sulfide (H2S) and glutathione (GSH) play crucial roles in various pathological and physiological processes. The development of optical probes for biothiols has been an active research area in recent years. Herein, a new turn-on fluorescence probe (HD-NBD) was designed and synthesized by fusing tetrahydro[5]helicene and 7-nitro-2,1,3-benzoxadiazole (NBD) for simultaneous discrimination of Hcy/Cys, H2S and GSH in aqueous solution. This probe is able to show unique absorbance enhancement at 548 nm for H2S and additional fluorescence enhancement at 536 nm only for Cys/Hcy, which can be used to discriminate H2S, Cys/Hcy and GSH simultaneously. In addition, HD-NBD also shows low background without any self-fluorescence, as well as high selectivity toward common biothiols. The low detection limits of this probe are about 0.15 μM for Hcy with a wide linear range (1–80 μM), 0.36 μM for Cys (linear range: 1–45 μM), 0.79 μM for H2S (linear range: 1–80 μM) and 4.44 μM for GSH (linear range: 1–60 μM). Moreover, HD-NBD can identify Hcy/Cys, H2S from GSH and other amino acids with high sensitivity and selectivity, therefore it could be used for detecting endogenous and exogenous Hcy/Cys under biological condition.

The extracellular SspA protease of the human pathogen S. aureus is essential for evading the host immune defence system. Two novel FRET probes for selective real-time ratiometric imaging of SspA activity in live S. aureus cells are reported.

A novel fluorescent probe (BC-PN-2) for the detection of ONOO− was synthesized by conjugating dicyano-vinyl with benzopyran-chromone. The dicyano-vinyl group can be destructed by ONOO− to generate an aldehyde group resulting in strong fluorescence. Compared with the general fluorescence probes, a novel reactive site to detect ONOO− in mitochondria is used in this probe and the results show short response time, high sensitivity and excellent selectivity toward ONOO− among reactive oxygen species (ROS) and reactive nitrogen species (RNS) in PBS. Subsequent fluorescence imaging shows the high membrane permeability, a certain mitochondrial targeting and localization effect of the probe. In addition, the product BC-aldehyde cannot permeate through the membrane. Meanwhile, BC-PN-2 can accurately identify ONOO− in mitochondria by imaging of exogenous ONOO− in HepG2 cells and prove detected ONOO− are from mitochondria.

Herein, a new “turn on” fluorescent probe C-1 is developed to specifically detect hydrazine using coumarin nucleus as the fluorophore and β-diketone as the recognition group. The probe shows high selectivity towards hydrazine over other common ions and amine-containing species, as well as good water solubility and quantitative detectability of hydrazine in concentration range of 1–200 μM. The detection limit is as low as 1.89 ppb, which is lower than the threshold set by EPA (10 ppb). Probe-coated filter papers are confirmed to detect gaseous hydrazine successfully through obvious fluorescence color changes. In addition, the probe has been verified to detect hydrazine in actual water environment and living cells.

The design and exploration of efficient organic fluorophores have attracted significant scientific interest for their various potential applications. As blue fluorescent materials are essential for the achievement of a full-color display and white emission, the development of new efficient organic blue-emitting materials is of great importance. In this work, we found that simple organic molecules 2-aryloxybenzo[d]oxazoles could act as novel organic fluorophores with special AIE properties and efficient blue fluorescent emission in the solid states. Compounds 3 and 4 possess moderately high quantum yields at 10.3% and 11.4%, respectively. The CIE coordinates indicate that most of these compounds are deep-blue emitters. The single crystal structure of compound 3 shows that it has a twisted V-shape molecular structure with J-type aggregation. Noncovalent interactions widely exist in the crystal structures, while π-π stacking interactions are not observed between adjacent aromatic rings. The special fluorescent properties of these new emitters could ascribe to the unique molecular packing mode in the crystal structure. This work provides a new strategy to access organic solid-state fluorophores with deep-blue emission.

A coumarin-appended rhodamine derivative was prepared by reacting rhodamine hydrazide and coumarin-3-carboxylic acid, which fluorescence sensing behavior toward Zn2+ against other metal ions was investigated in CH3CN. Significantly, the rodamine-coumarin derivative exhibited highly selective and sensitive recognition toward Zn2+ with a limit of detection (LOD) down to 10−9 M. Upon addition of Zn2+, remarkable fluorescent intensities enhanced and also clear color changed from colorless to pink. The Job’s plot indicated the formation of 1:1 complex between the rhodamine-coumarin derivative and Zn2+. The presence of common coexisting alkali, alkaline earth, and transition metal ions showed small or no interference with the detection of Zn2+. The conjugate dye could be used for “naked-eye” detection of Zn2+.

A novel fluorescence probe (TIA) is designed and synthesized by grafting acryl on hydroxyl and diazabenzo[ghi]perylene, respectively. The acryl groups on hydroxyl act as a recognition site and fluorescence quencher. After a conjugated addition/cyclization reaction of Cys with TIA, the acryl groups on hydroxyl fall off and acryl conjugated perylene (TIA−OH) is released as the fluorophore with 70-fold increment of fluorescence in PBS. The short response time (less than 5 min) and high signal-noise-ratio endow the probe with fast detection, high sensitivity, low detection limit (0.11 μM) and wide linear range (10−100 μM). Interestingly, compared with the parent dihydroxy 1,2-diazabenzo[ghi]perylene, the introduction of acryl group on the perylene can modulate the fluorescence and increase the fluorescence quantum yield of TIA−OH by more than 10-fold (41 % in PBS). The TD-DFT calculations also reveal that the acryl group conjugated on the perylene can result intramolecular charge transfer and the calculated fluorescence is in good agreement with the experimental values. What’s more, the high cell membrane permeability and specificity for Cys of the probe ensure the application in fluorescence imaging of living cells to detect intracellular Cys.

To develop new dyes with mitochondria staining capacity, a series of zwitterionic dyes of hybrid coumarin-difluoroboron have been synthesized. The hybrid dyes are conjugated by 7-diethylaminocoumarin, difluoroboron (BF2) β-diketone and electron-donating group. The dyes show deep-red emission (600–680 nm) and high fluorescence quantum yield in organic solvents. The nature of ICT and zwitterion has been fully researched by TD-DFT and ESP calculations. Co-staining with the Mito–Tracker Green shows staining capability to mitochondria in living cells by confocal cell imaging experiments. This work can provide a new strategy for the design of neutral cellular probes for mitochondria staining.

In this work, we have designed and synthesized a dinitrobenzene-sulfonate tetrahydro[5]helicene (H-DNP) as an effective fluorescent probe for detection of hydrogen sulfide (H2S). Upon the addition of H2S, a significant fluorescence enhancement (75-fold) at 495 nm can be observed with a distinct color change from colorless to yellow. Additionally, H-DNP shows low background spectroscopic signal, large Stokes Shift up to ~140 nm, good sensitivity, rapid response time less than 2 min, low detection limit (48 nM) and high selectivity toward common bio-thiols (Cysteine, Homocysteine and Glutathione). Compared with the previous dinitrophenoxy tetrahydro[5]helicene, this probe has shorter response time and lower detection limit. Most importantly, this probe H-DNP has low toxicity to cells and excellent cell permeability, which can be applied to visualize H2S in living cells.

In this study, a new coumarin-based fluorescent and chromogenic dual channel probe (DC) was used for the selective detection of homocysteine (Hcy) over other amino acids, especially for cysteine (Cys) and glutathione (GSH). When Hcy is present in the solution, the remarkable fluorescence enhancement and obvious blue shift in UV–vis spectra can be observed. In addition, the color change from purple to yellow can be observed clearly by unaided eyes. This probe DC has fast response time, excellent sensitivity and selectivity to Hcy. A linear relationship exists between the ratio of emissions at 486 and 625 nm, and Hcy can be detected in a wide concentration range (0–200 μM). The signal-to-background ratio of fluorescence at 486 nm can reach 8.4, and the detection limit is calculated to be 3.5 µM. The response mechanism is proved to be the Michael addition reaction by Hcy. Preliminary results on cell imaging enable the practical application of Hcy tracing in living cells.

Endogenous hydrogen sulfide plays an important role in various physiological and pathological processes and the convenient and selective recognition of hydrogen sulfide has become a research hotspot. We designed and synthesized a tetrahydro[5]helicene and 2,4-dinitrobenzene conjugate (HD-DNP) as an effective fluorescent probe for selective detection of H2S. The selective deprotection of 2,4-dinitrophenyl ether group of HD-DNP by H2S led to a dramatic fluorescent enhancement (101-fold) at 500 nm and colorimetric change in DMSO–PBS solution. HD-DNP displays many advantages including low background without any self-fluorescence, as well as high selectivity towards common bio-thiols such as Cysteine, Homocysteine and Glutathione. The detection limit of this probe for H2S was found to be about 2.4 μM with a wide linear range (10–70 μM). The response mechanism of the probe with HS− is confirmed to be thiolysis of the dinitrophenyl ether induced by HS− through 1H NMR comparison investigations.

A selective and sensitive method to detect glutathione (GSH) based on the complex of a coumarin-based probe and Cu2+ is reported. In response to GSH, the system provides remarkable fluorescence intensity change with the color change from colorless to yellow, and the detect limit is determined to be 3.6 × 10−7 M. The background amino acids show small or no interference on the detection of GSH. Moreover, this probe could be applied to detect GSH via intracellular fluorescent imaging.

The thiophene-modified rhodamine 6G (GYJ) has been synthesized as a novel chemosensor. The sensor has sufficiently high selectivity and sensitivity for the detection of Fe3+ and Al3+ ions (M3+) by fluorescence and ultraviolet spectroscopy with a strong ability for anti-interference performance. The binding ratio of M3+-GYJ complex was determined to be 2:1 according to the Job’s plot. The binding constants for Fe3+ and Al3+ were calculated to be 3.91 × 108 and 5.26 × 108 M−2, respectively. All these unique features made it particularly favorable for cellular imaging applications. The obvious fluorescence microscopy experiments demonstrated that the probes could contribute to the detection of Fe3+ and Al3+ in related cells and biological organs with satisfying resolution.

Recently, more and more rhodamine derivatives have been used as fluorophores to construct sensors due to their excellent spectroscopic properties. A rhodamine-based fluorescent and colorimetric Fe(3+) chemosensor 3',6'-bis(ethylamino)-2-acetoxyl-2',7'-dimethyl-spiro[1H-isoindole-1,9'-[9H]xanthen]-3(2H)-one (RAE) was designed and synthesized. Upon the addition of Fe(3+), the dramatic enhancement of both fluorescence and absorbance intensity, as well as the color change of the solution, could be observed. The detection limit of RAE for Fe(3+) was around 7.98 ppb. Common coexistent metal ions showed little or no interference in the detection of Fe(3+). Moreover, the addition of CN(-) could quench the fluorescence of the acetonitrile solution of RAE and Fe(3+), indicating the regeneration of the chemosensor RAE. The robust nature of the sensor was shown by the detection of Fe(3+) even after repeated rounds of quenching. As iron is a ubiquitous metal in cells and plays vital roles in many biological processes, this chemosensor could be developed to have applications in biological studies.

We report that a previously found fluorescent chemodosimeter for Hg(II) ions can also be used as a fluorescent probe for hypochlorous acid (HClO) in that its fluorescence intensity (excited at 520 nm and measured at 563 nm) is linearly proportional to the concentration of HClO in the 1–100 μM range and with a 0.1 μM detection limit. The probe can detect HClO with virtually no interference by Hg(II) and other metal ions. The mechanism for the high selectivity for HClO has been studied. The probe was applied to image hypochlorite in E. coli cells.

A rhodamine-based fluorescent and colorimetric chemosensor (RTSB) for Fe 3+ ion was designed and synthesized, which displayed highly selective and sensitive Fe 3+ -amplified fluorescence emission and absorbance above 500 nm in aqueous solution with the color change from colorless to pink. Moreover, it also showed highly selective and sensitive recognition toward cyanide ion upon addition of Fe 3+ with the color change back to colorless in the same solution. The detection limit of the system for CN − was around 7.2 × 10 −8 M (S/N = 3). The chemosensor may be found its potential applications in environmental and biological systems.

Stimuli-responsive organic luminescent materials have attracted increasing attention for their specific chemical and physical properties and potential application in many fields, such as sensing materials, optoelectronic devices and security papers. In this work, we designed and synthesized three new organic smart materials with dimethylamino naphthalene and cyanostyrene moieties. These fluorescent molecules show solvatochromic properties. With solvent polarity increased, their fluorescent emissions are red shifted. These molecules also exhibited aggregation-induced emission enhancement properties. The emission wavelength of these materials in solid state was red-shifted upon stimuli with external mechanic force, which could be recovered after addition of dichloromethane solvent. The PXRD and DSC experiments revealed that the mechanochromic properties could be ascribed to the phase transition between crystalline and amorphous states. The switch of optical properties of these molecules under acid stimuli was also studied. The fluorescent emissions show blue-shifted when exposed to trifluoroacetic acid, and these organic materials were further utilized as security ink.

A novel efficient one-pot four-component regioselective synthesis of pyrrolo[1,2-a][1,10]phenanthrolines in excellent yields has been developed by 1,3-dipolar cycloaddition of aldehydes, malononitrile, and isocyanides with 1,10-phenanthroline under solvent-free conditions within 3 min without using any catalyst or activation. The products were preliminarily investigated as chromogenic and fluorescent sensors for Cu(2+) ions.

A highly sensitive fluorescent acidic pH probe based on rhodamine B-2-aminobutenedioate conjugate, was designed and synthesized. When the H + concentration falls within the pH range of 4.0–6.5, the spirolactam unit of rhodamine B-2-aminobutenedioate was opened, which resulted in the dramatic enhancement of both fluorescence and absorbance intensity as well as the color change of the solution. Background metal ions showed small or no interference with the detection of H + . Confocal laser scanning microscopy experiments showed that rhodamine B-2-aminobutenedioate can be applied to detect acidic pH variations in living cells with a turn-on signal.

A Rhodamine-based fluorescent and colorimetric chemosensor for Fe3+ ion, acetyl rhodamine-hydroxamate (ARH), was designed and synthesized. Upon mixed with Fe3+ in CH3CN–H2O (1:1, v/v), the spirolactam of ARH was opened, which resulted in the dramatic enhancement of both fluorescence and absorbance intensity as well as the color change of the solution. Background metal ions showed small or no interference with the detection of Fe3+. The Job's plot indicated the formation of 1:1 complex between ARH and Fe3+. Confocal laser scanning microscopy experiments showed that ARH could be used to detect Fe3+ in living cells.

A novel, sulfonyl rhodamine hydrazide chemodosimeter displayed highly selective and sensitive recognition of Cu2+ in aqueous media, via colour change from colorless to pink. The colour change that occurred as a result of complexation with Cu2+ can be attributed to spirolactam ring-opening and hydrolysis of the hydrazide unit to afford C.I. Acid Red 52 (Rhodamine B) in the presence of Cu2+. An analytical method was developed and successfully used for the determination of the copper content in a sample.

New 1,8-anthrancene disulfonamide derivative 1 was designed and synthesized as a selective fluorescent sensor for Hg2+ over miscellaneous metal ions in aqueous media. Upon mixing with Hg2+ in DMSO:H2O (2:98, v/v), the decrease of fluorescence intensity and a bathochromic shift of absorbance of 1 could be observed. The Job plot indicated the formation of 1:1 complex between 1 and Hg2+. Background metal ions showed small or no interference with the detection of Hg2+. The binding mode and effect of N-substituent groups were also investigated.

A new fluorescent sensor 1 for F− was designed and synthesized through the condensation of 1,8-anthracene diamine and indole-2-carboxylic acid via DCC. Upon mixing with F− in DMSO:CH2Cl2 (1:9, v/v), the increases in fluorescence could be observed. No obvious changes could be found upon the addition of other anions such as Cl−, Br−, I−, NO3−, HSO4−, H2PO4−, AcO−. Job plots indicated the formation of 1:1 complex of 1 and F− with association constant K = 7.3 × 104 M−1. 1H NMR titration experiments indicated that fluoride anion had strong hydrogen bonding interactions not only with the N–H of the amide but also with the indole N–H and the 9-H of anthracene. This rigidified the structure and led to the reduction of the efficiency of the PET process and the enhancement of fluorescence intensity.

A novel colorimetric and fluorescent iminocoumarin-based turn-off chemosensor for acetate ion was designed and synthesized. The chemosensor could fast detect acetate ion in a 1:1 ratio within 150 ms, which could not be affected by various coexisting anions, even F(-). Futher studies showed that the detect limit was as low as 2.05×10(-7) M, and the binding constant was determined to be 1.02×10(8) M(-1). Due to these unique properties, the chemosensor showed potential application in intracellular imaging.

A novel colorimetric and fluorescent chemosensor based on a rhodamine 6G phenylurea conjugate showed highly selective and sensitive recognition toward acetate ions in H(2)O-CH(3)CN (1:1, v/v) with fluorescence intensity change and also clear color change from pink to colorless in the presence of Fe(III) ions.

A novel easily available turn-on fluorescent chemosensor RPU based on a rhodamine-phenylurea conjugate was synthesized, which showed highly selective and sensitive recognition toward Pb(2+) in CH(3)CN and Hg(2+) in aqueous media over a wide range of tested metal ions with remarkably enhanced fluorescent intensities and also clear color changes from colorless to pink.