Tetraphenylethene-based mononuclear aggregation-induced emission (AIE)-active mechanofluorochromism gold(I) complexes with different auxiliary ligands.

In this study, a series of tetraphenylethene-containing gold(I) complexes with different auxiliary ligands have been synthesized. These complexes were characterized using a variety of techniques including nuclear magnetic resonance spectroscopy, mass spectrometry, and single crystal X-ray diffraction. Their aggregation-induced emission (AIE) behaviors were investigated through ultraviolet/visible and photoluminescence spectrum analyses, and dynamic light scattering measurements. Meanwhile, their mechanofluorochromic properties were also studied via solid-state photoluminescence spectroscopy. Intriguingly, all these mononuclear gold(I) molecules functionalized by tetraphenylethene group demonstrated AIE phenomena. Furthermore, five gold(I) complexes possessing diverse auxiliary ligands exhibited distinct fluorescence changes in response to mechanical grinding. For luminogens 2-5, their solids showed reversible mechanofluorochromic behaviors triggered by the mutual transformation of crystalline and amorphous states, while for luminogen 1, blue-green-cyan three-color solid fluorescence conversion was realized by sequential mechanical grinding and solvent fumigation. Based on this stimuli-responsive tricolored fluorescence feature of 1, an information encryption system was successfully constructed.

A mitochondrial targeted dual ratiometric near-infrared fluorescent probe based on ICT effect for the detection of SO2 derivative and its bioimaging.

SO2 derivatives play an important role in many metabolic processes, excessive ingestion of them can lead to serious complications of various diseases. In this work, a novel dual ratiometric NIR fluorescent probe XT-CHO based on ICT effect was synthesized for detecting SO2 derivative. In the design of the probe, the α, ß-unsaturated bond formed between benzopyran and coumarin was used as the reaction site for SO2, meanwhile, the extended π-conjugate system promoted maximum emission wavelength of the probe up to 708 nm. Notably, the probe exhibited high selectivity and sensitivity for detecting SO2, the limit of detection reached 2.13 nM and 58.5 nM in fluorescence spectra and UV-Vis absorption spectra, respectively. The reaction mechanism of SO2 and XT-CHO had been verified by 1H NMR, ESI-MS spectra and DFT calculation. Moreover, the probe was successfully applied in detecting endogenous and exogenous SO2 in living cells and proved possessed the mitochondrial targeted ability.

Near-infrared fluorescent probe for detection of hydrogen sulfide in water samples and food spoilage.

Hydrogen sulfide (H2S) is a common toxic gas that threatens the quality and safety of environmental water and food. Herein, a new near-infrared fluorescent probe DTCM was synthesized and characterized by single crystal X-ray diffraction for sensing H2S. It exhibited a remarkable "turn-on" near-infrared (NIR) emission response at 665 nm with a remarkably massive Stokes shift of 175 nm, super-rapid detection ability (within 30 s), excellent photostability, high selectivity and sensitivity (limit of detection, LOD = 58 nM). Additionally, the probe was successfully utilized for the detection of H2S in environmental water samples. The DTCM-loaded test papers enabled convenient and real-time monitoring of H2S produced by food spoilage.

Hierarchical Porous Amidoximated Metal-Organic Framework for Highly Efficient Uranium Extraction.

With the rapid development of industry and technology, high-efficiency extraction of uranium from seawater is a research hotspot from the aspect of nuclear energy development. Herein, a new amidoximated metal-organic framework (UiO-66-DAMN-AO) constructed through a novel organic ligand of 2-diaminomaleonitrile-terephthalic acid (BDC-DAMN) is designed via one-step post-synthetic methods (PSM), which possess the merit of abundant multiaffinity sites, large specific surface area, and unique porous structure for efficient uranium extraction. Adopting one-step PSM can alleviate the destruction of structural stability and the reduction of the conversion rate of amidoxime groups. Meanwhile, introducing the BDC-DAMN ligand with abundant multiaffinity sites endow UiO-66-DAMN-AO with excellent adsorption ability (Qm = 426.3 mg g-1) and selectivity. Interestingly, the UiO-66-DAMN-AO has both micropores and mesopores, which may be attributed to the partial etching of UiO-66-DAMN-AO during the amidoximation. The presence of mesopores improves the mass transfer rate of UiO-66-DAMN-AO and provides more exposed active sites, favoring the adsorption of uranium on UiO-66-DAMN-AO. Thus, this study provides a feasible strategy for modifying metal-organic framework (MOFs) with plentiful amidoxime groups and the promising prospect for MOF-based materials to adsorb uranium from ocean.

Development of europium(III) complex fluorescent probe for hydrogen sulfide detection and its application in water samples.

Hydrogen sulfide (H2 S) is a crucial endogenous signaling component in organisms that is involved in redox homeostasis and numerous biological processes. Modern medical research has confirmed that hydrogen sulfide plays an important role in the pathogenesis of many diseases. Herein, a fluorescent probe Eu(ttbd)3 abt based on europium(III) complex was designed and synthesized for the detection of H2 S. Eu(ttbd)3 abt exhibited significant quenching for H2 S at long emission wavelength (625 nm), with rapid detection ability (less than 2 min), high sensitivity [limit of detection (LOD) = 0.41 µM], and massive Stokes shift (300 nm). Additionally, this probe showed superior selectivity for H2 S despite the presence of other possible interference species such as biothiols. Furthermore, the probe Eu(ttbd)3 abt was successfully applied to detect H2 S in water samples.

A novel diarylethene-based fluorescence sensor for Zn2+ detection and its application.

A series of fluorometric sensors of Zn2+ have been synthesized due to the significant function of Zn2+ in the human body and environment. However, most of probes reported for detecting Zn2+ have high detection limit or low sensitivity. In this paper, an original Zn2+ sensor, namely 1o, was synthesized by diarylethene and 2-aminobenzamide. When Zn2+ was added, the fluorescence intensity of 1o increased by 11 times within 10 s, along with a fluorescence color change from dark to bright blue, and the detection limit (LOD) was calculated to be 0.329 µM. According to Job's plot curves, the binding mode of 1o and Zn2+ was measured as 1:1, which was further proved by 1H NMR spectra, HRMS and FT-IR spectra. The logic circuit was designed to take advantage of the fact that the fluorescence intensity of 1o can be controlled by Zn2+, EDTA, UV and Vis. In addition, Zn2+ in actual water samples were tested, in which the recovery rate of Zn2+ was between 96.5 % and 109 %. Furthermore, 1o was successfully made into a fluorescent test strip, which could be used to detect Zn2+ in the environment economically and conveniently.

Mitochondria-targeted fluorescent probe with long wavelength emission for detecting H2S and its application in foodstuff, water and living cells.

Hydrogen sulfide (H2S) is crucial to cellular energy production, apoptosis, and redox homeostasis in mitochondria of living cells. In this work, a unique mitochondria-targeting fluorescence probe (DDMI) was established for H2S determination based on styrylpyridinium scaffold. When DDMI was treated with H2S, it showed significant fluorescence enhancement at 623 nm, with good selectivity, and high sensitivity. In addition, the "turn-on" fluorescent probe DDMI could detect H2S in water samples with good recoveries in the range of 95.4 %-105.6 % and track the degree of food spoilage by visualizing the change of DDMI-loaded test strips. Furthermore, the established probe DDMI was successfully used for monitoring exogenous H2S in living cells and mitochondria targeting. These results paved the way for success in developing a technology that could be used to identify H2S in environment, foodstuff, and living cells.

Multiresponsive tetrarylethylene-based fluorescent dye with multicoloreded changes: AIEE properties, acidichromism, Al3+ recognition, and applications.

A novel fluorescent sensor BTAE-PA containing two tetrarylethylene (TAE) units linked through pyrimidine-2-amine was prepared, and its optical properties were systematically studied. BTAE-PA exhibited a typical aggregation-induced emission enhancement behavior, and its fluorescent properties could be efficiently modulated by acid/base and metal ions in THF. The protonated effect could induce significant acidichromism and 'turn-on' near-infrared emission with a large Stokes shift (Δλ = 225 nm). Furthermore, BTAE-PA was highly selective toward Al3+ with significant absorption (yellow → orange) and fluorescence (green → red) changes. A Job's plot established the 1 : 1 stoichiometry of the complex formation between BTAE-PA and Al3+, and the limit of detection for Al3+ was determined to be 1.30 × 10-7 mol L-1. Finally, we also demonstrated that BTAE-PA could be made into test paper strips for 'naked-eye' detection of acid/Al3+, and fluorescence imaging experiments proved that BTAE-PA is capable of achieving cell imaging with good biocompatibility. Therefore, the multi-stimuli-responsive and multicoloured display performance of BTAE-PA endows the material with potential applications in security ink, acid/Al3+ sensing, and bio-imaging.

A New High Selective and Sensitive Fluorescent Probe for Al3+ based on Photochromic Salicylaldehyde Hydrazyl Diarylethene.

A new diarylethene derivative 1O decorated with a salicylaldehyde hydrazine moiety was designed and synthesized successfully, and its structure was confirmed by NMR. Diarylethene 1O showed eminent photochromism and high selectivity and sensitivity for Al3+ with turn-on fluorescent performance. As the concentration of Al3+ in 1O solution increased, the color of solution remarkably changed from dark to bright green with 313-fold fluorescent emission intensity enhancement. The 1:1 combination stoichiometry between 1O and Al3+ was verified by Job's plot and MS analysis. The association constant between 1O and Al3+ was 3.9 × 102 mol-1 L, and the limit of detection toward Al3+ was 7.98 × 10-9 mol L-1. Meanwhile, the probe can be utilized in practical water and logic circuits.

A Highly Selective Hg2+ Fluorescent Chemosensor Based On Photochromic Diarylethene With Quinoline Unit.

A novel diarylethene-based fluorescent chemosensor containing a quinoline unit (1o) had been designed and synthesized. 1o showed good photochromic ability and fluorescence switching properties by alternating UV/vis light irradiation. The chemosensor showed high "Turn-off" fluorescent selectivity for Hg2+ by competitive tests of the fluorescence reaction in the presence other ions in acetonitrile solution. The stoichiometry between the compound 1o and Hg2+ was 1:1 by Job's plot curve and HRMS analysis. In addition, the LOD for Hg2+ was calculated as 60 nM. The fluorescence emission can be back to the "Turn-on" state by adding EDTA. Based on these facts, a molecular logic gate that including four input signals (UV/vis and Hg2+/EDTA) and one output signal (fluorescent intensity at 491 nm) was designed.

Dual-ligand lanthanide metal-organic framework for ratiometric fluorescence detection of the anthrax biomarker dipicolinic acid.

Dipicolinic acid (DPA) is a unique biomarker of Bacillus anthracis. Development of a simple, fast, sensitive and timely DPA detection method is of great importance and interest for preventing mass disease outbreaks and treatment of anthrax. In this work, a novel lanthanide-doped fluorescence probe was constructed by coordination of Eu3+ with bifunctional UiO-66-(COOH)2-NH2 MOFs materials for efficient monitoring DPA. UiO-66-(COOH)2-NH2 MOFs were prepared using Zr4+ as a metal node, 1,2,4,5-benzenetetracarboxylic acid (H4BTC) and 2-aminoterephthalic acid (NH2-BDC) as bridging ligand through a simple one-pot synthesis method. By virtue their abundant carboxyl groups, UiO-66-(COOH)2-NH2 can readily grasp Eu3+ to form UiO-66-(COOH)2-NH2/Eu with coordinated water molecules at Eu sites. Upon interaction with DPA molecules, the coordinated H2O molecules were replaced by DPA molecules which transfer energy to Eu3+ in UiO-66-(COOH)2-NH2/Eu and sensitize Eu3+ luminescence. Meanwhile, DPA has a characteristic absorption band at 270 nm, which overlapped with the excitation spectrum of NH2-BDC, allowing the fluorescence of UiO-66-(COOH)2-NH2/Eu at 453 nm to be greatly quenched by DPA through inner filter effect (IFE). Therefore, the rationally designed UiO-66-(COOH)2-NH2/Eu complex not only exhibits strong hydrophilicity and high dispersion, but also serves as ratiometric fluorescence sensing platform for monitoring DPA concentration. This sensing platform showed a satisfactory linear relationship from 0.2 µM to 40 µM with a limit of detection of 25.0 nM and a noticeable fluorescence color change from blue to red, holding a great promise in practical applications.

A highly selective colorimetric and fluorescent probe Eu(tdl)2abp for H2S sensing: Application in live cell imaging and natural water.

Using 4-([2,2': 6', 2'- terpyridin] -4'-yl) -N, N-dimethylaniline (tdl) as auxiliary ligand and 6-azido-2,2'-bipyridine (abp) as recognition ligand, a europium complex fluorescent probe Eu(4-([2,2': 6', 2'-terpyridin] -4' -yl) -N, N-dimethylaniline)2-6-azido-2,2'-bipyridine Eu(tdl)2abp for efficient and specific recognition of hydrogen sulfide (H2S) was successfully synthesized and characterized by NMR and MS. Eu(tdl)2abp represented "on-off" fluorescence signals for H2S and its color changes could be identified with naked eyes. Eu(tdl)2abp had short response time (2 min) to H2S, high selectivity and good anti-interference, large stokes shift (207 nm). In various samples, when H2S existed, the azide group was reduced to amine group, resulting in closed fluorescence signal, and the fluorescence intensity reached the degree of quenching without being affected by other interference. At the same time, there was a good linear relationship between relative fluorescence intensity and H2S concentration with the detection limit (LOD) of 0.64 µM. The sensing mechanism of Eu(tdl)2abp to detect H2S was characterized by 1H NMR and HR-MS. Eu(tdl)2abp was used with success for the sensitive detection of H2S in natural water and living cells.

A coumarin-based fluorescent probe for specific detection of cysteine in the lysosome of living cells.

Cysteine (Cys), the only amino acid in the 20 natural amino acids that contains a reduced sulfhydryl group, plays important roles in the balance of redox homeostasis in biological systems. Lysosome is an important organelle containing a variety of hydrolases and has been proved to be the decomposition center of a variety of exogenous and endogenous macromolecular substances. In this research, a coumarin-based fluorescent probe MCA for the detection of Cys in lysosomes of living cells was developed. Due to the acrylate moiety, this probe exhibited high sensitivity (detection limit = 6.8 nM) and selectivity towards Cys superior to other analytes. Moreover, the probe was proved to be lysosome-targetable and showed good cell imaging ability and low cell toxicity.

Silver nanoparticles combined with amino-functionalized UiO-66 for sensitive detection of glutathione.

Herein, a fluorescent nanosensor has been constructed for detection of glutathione (GSH) based on NH2-UiO-66 and AgNPs. The NH2-UiO-66 was synthesized where 2-amino-terephthalic acid as the organic ligand and Zr4+ as the center metal ions. The AgNPs can enhance the fluorescence of NH2-UiO-66 based on metal enhanced fluorescence (MEF) effect. Moreover, in the present of GSH, the fluorescence of NH2-UiO-66@AgNPs was quenched via electrostatic interaction and Ag-S reaction. The present sensing strategy shows good linear relation with the concentration of GSH in the range of 0.2-1.0 µM and 1.0-30 µM, and the limit of detection is 79 nM. Furthermore, our fluorescent nanosensor was utilized to detect GSH in human serum with a recovery of 96.8-102.5%. The results indicated that NH2-UiO-66@AgNPs is successfully applied for high sensitive and selective detection of GSH in human serum.

Luminol-Eu-based ratiometric fluorescence probe for highly selective and visual determination of tetracycline.

In this work, a ratiometric fluorometric method based on luminol-Europium complex (luminol-Eu) was constructed for the detection of tetracycline (TC). Luminol-Eu, synthesized by self-assembly reaction, displayed a strongly emission peak at 453 nm under excitation at 360 nm which was derived from the aggregation-induced emission (AIE) of the luminol-Eu. In the present of TC, the fluorescence of luminol-Eu at 453 nm was quenched based on inner filter effect (IFE). Meantime, the characteristic emission peak of Eu3+ at 626 nm can be observed thank to antenna effect (AE). Therefore, we proposed a ratiometric fluorometric method for detection of TC, which allowed detection of TC from 0.5 to 80 µM with the detection limit of 39 nM. In addition, the luminol-Eu-based test paper was prepared for visual semi-quantitative detection of TC in real samples based on the color of luminol-Eu change from blue to red under 365 nm ultraviolet light. All of those results indicated that the ratiometric fluorometric strategy was fast, sensitive, and visual for detection of TC.

A Novel Diarylethene-rhodamine Unit Based Chemosensor for Fluorimetric and Colorimetric Detection of Hg2.

A novel fluorimetric and colorimetric chemosensor (1O) was synthesized with diarylethene-rhodamine unit and characterized by ESI-MS, 1H NMR, and 13C NMR. The chemosensor can selectively recognize extremely low concentrations of Hg2+ over a variety of metal ions with remarkable colorimetric and fluorescent responses. The colorimetric and fluorescent changes were ascribed the reaction between 1O and Hg2+ destructed the rhodamine hydrazide into open-ring form which was proved by mass spectrometry and nuclear magnetic titration analyses. The detection limits of the UV absorption and fluorescence methods for Hg2+ were found to be 0.708 µM and 24.6 nM, respectively. Moreover, the chemosensor exhibited excellent photochromism and outstanding fatigue resistance property under alternating UV and visible light irradiation. The application potential of the chemosensor was demonstrated with the qualitative detection of Hg2+ in real water samples.

Ratiometric fluorescence for sensitive detection of phosphate species based on mixed lanthanide metal organic framework.

Phosphate (PO43-) plays a major role in aquatic ecosystems and biosystems. Developing a highly sensitive and selective ratiometric fluorescence probe for detection of PO43- is of great significance to the ecological environment and human health. In this work, a novel dual lanthanide metal organic framework was synthesized via hydrothermal reaction based on Tb3+ and Ce3+ as the center metal ions and terephthalic acid as the organic ligand (designated as Tb-Ce-MOFs). The fluorescence of Tb-Ce-MOFs shows emission at 375 nm. In the presence of PO43-, with increased concentration of PO43-, the fluorescence intensity of Tb-Ce-MOFs at 500 nm and 550 nm increased, while the intensity at 375 nm was reduced. Hence, ratiometric fluorescence detecting of PO43- can be achieved by measuring the ratio of fluorescence at 550 nm (FL550) to 375 nm (FL375) in the fluorescent spectra of the Tb-Ce-MOFs. In this sensing approach, the Tb-Ce-MOFs probe exhibits highly sensitive and selective for detection of PO43-. The limit of detection is calculated to be 28 nM and the detection range is 0.1 to 10 µM. In addition, the Tb-Ce-MOFs were used in the detection of PO43- in real samples. We design and synthesize a mixed lanthanide metal organic framework fluorescence probe (Tb-Ce-MOFs) for ratiometric fluorescence for the detection of PO43- based on Tb3+ and Ce3+ as the center metal ions and terephthalic acid as the organic ligand.

Europium(III) complex fluorescent sensor for dual channel recognition of Sn2+ and Cu2+ ions in water.

A new europium(III) complex Eu(tta)3L1 (1a) (L1 = (2-(3,5-dimethoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), tta = 2-thenoyltrifluoroacetone) has been prepared and synthesized. The structure of complex was completely determined by several different analytical techniques including single-crystal X-ray diffraction, 1H and 13C NMR. The crystal structure of the complex 1a belonged to monoclinic system with the space group P21/n. Its fluorescent properties were systematically studied in details by adding different metal ions in deionized water. Upon addition of Sn2+, its fluorescence intensity was strengthened and centered at 460 nm. And when Cu2+ was added, its fluorescence emission intensity was quenched quickly. The LODs for Sn2+ and Cu2+ were calculated to be 4.52 × 10-7 mol L-1 and 1.11 × 10-7 mol L-1, respectively. Furthermore, this sensor was successfully employed to monitor Sn2+ and Cu2+ in practical samples.

A highly selective sequential recognition probe for Zn2+ and HSO4-/H2PO4- based on a diarylethene chemosensor.

A novel diarylethene derivative chemosensor DTP-o connected to Schiff base unit for fluorescent detection of Zn2+ and relay-detection of HSO4-/H2PO4- was designed and synthesized successfully. DTP-o displayed excellent photochromism and fluorometric sensing toward Zn2+ to form DTP-o-Zn2+ complex in acetonitrile with the detection limit of 5.62 × 10-7 M. And the form of DTP-o combined with Zn2+ could further be verified by Job's plot titrations and mass spectrometry analysis. Furthermore, the complex of DTP-o-Zn2+ showed an excellent characteristic of fluorescent relay-response toward HSO4- and H2PO4- with high sensitivity and selectivity. The detection limits for HSO4- and H2PO4- were as low as 3.04 × 10-8 M and 3.41 × 10-8 M, respectively. Moreover, the sensor DTP-o could also be applied to detect Zn2+ on practical samples and test strips with high accuracy.

A novel full symmetric diarylethene-based ratiometric fluorescent sensor for lysine and the application for a logic circuit.

A novel diarylethene-based ratiometric fluorescent sensor with full symmetric structure, 1o, was designed and synthesized successfully. 1o could identify lysine (Lys) with high selectivity and sensitivity and the fluorescence emission peak was red shifted 85 nm upon addition of Lys, which could realize ratio recognition. It exhibited excellent anti-interference performance in the presence of various amino acids in CH3 CN/H2 O (7/3, v/v) solution. Moreover, the limit of detection of 1o to Lys could reach 0.019 µM based on a good linear range of 0-40 µM. In addition, the fluorescence emission intensity of 1o could be turned off/on by ultraviolet/visible light due to the special structure of diarylethene. A logic circuit was designed with three inputs. The ratiometric fluorescent sensor 1o could be as a new tool and provide a new method for detection of Lys.