Trace analysis of uranyl ion (UO2) in aqueous solution by fluorescence turn-on detection via aggregation induced emission enhancement effect

A sensitive fluorescence turn-on method for trace amounts of uranyl ion (UO₂²⁺) in solution has been developed in this study, based on aggregation induced emission enhancement (AIEE) characteristics of 4-pethoxycarboxyl salicylaldehyde azine (PCSA) induced by complex interaction between UO₂²⁺ and PCSA. Under optimized conditions, a fluorescence enhancement at 540 nm could be observed, which was linearly related to the concentration of UO₂²⁺ in the range of 1–25 ppb (part per billion). Analytical data showed that a detection limit of 0.2 ppb was achieved with the relative standard deviation (R.S.D.) 1.3% (n = 5). The proposed method was successfully utilized in quantifying UO₂²⁺ in fuel processing wastewaters.     

Study of aggregation induced emission of cyano-substituted oligo (p-phenylenevinylene) by femtosecond time resolved fluorescence

The aggregation induced emission (AIE) mechanism of the cyano-substituted oligo (p-phenylenevinylene)1,4-bis [1-cyano-2-(4-(diphenylamino) phenyl) vinyl] benzene (TPCNDSB) is investigated by time resolved fluorescence technique. By reconstructing the time resolved emission spectra (TRES), it is found that in solvent of low polarity, the emission is mainly from the local emission (LE) state with high quantum yield, but in high polarity solvent, the emission is mainly from the intramolecular charge transfer (ICT) state, which is a relatively dark state, with low quantum yield. In crystal form, the restriction of transfer from LE state to ICT state results in efficient AIE.     

Turn-on fluorescence sensor based on the aggregation of pyrazolo[3,4-b]pyridine-based coumarin chromophores induced by Hg

We developed a new fluorescent sensor (PPC-S) for Hg²⁺ based on the aggregation-induced emission (AIE) of pyrazolo[3,4-b]pyridine-based coumarin chromophore (PPC-O). Given the desulfurization reaction with Hg²⁺, AIE inactive PPC-S can be transformed into PPC-O with AIE activity, which can be employed for the fluorescence turn-on detection of Hg²⁺ with satisfactory selectivity and sensitivity in aqueous solutions.     

A tetraphenylethene based polarity dependent turn-on fluorescence strategy for selective and sensitive detection of Hg in aqueous medium and in living cells

A turn-on fluorescent chemosensor strategy based on the change in the polarity of aggregation induced emission active tetraphenylethene is presented for the detection of Hg²⁺ in aqueous medium and in living cells. The sensing mechanism involves the formation of nonpolar fluorescent aggregates of tetraphenylethene molecules by elimination of polar moieties of TPE with Hg²⁺ interaction.     

A novel off-on fluorescent probe for specific detection and imaging of cysteine in live cells and in vivo

Cysteine(Cys) plays a pivotal role in many physiological and pathological processes,including detoxification and protein synthesis.The abnormal levels of Cys are linked to many diseases.In this study,a novel red-emitting off-on fluorescent probe Cys-TCF was masterly constructed for discriminative detection of Cys.After a series of experimental assessment,Cys-TCF displayed higher selectivity and sensitivity for Cys over other biothilols with a low detection limit(0.04 μmol/L).More notably,the pro...     

A chloroacetate based ratiometric fluorescent probe for cysteine detection in biosystems

The specific detection of cysteine (Cys) over homocysteine (Hcy), glutathione (GSH) and other amino acids is of great significance for studying its biological functions as well as for the diagnosis of related diseases. Chloroacetyl group was often used as a reaction site for cysteine fluorescent probes for its sensitivity and selectivity. However, high background fluorescence and low stability are common problems encountered by such probes. Here, four chloroacetyl group based fluorescent probes (C1, C2, C3, and H4) was synthesized for a comparative study. We found that the inefficient quenching ability of chloroacetyl group turned into an advantage when connected with a ratiometric fluorophore. With the modification of chloroacetyl group, probe H4 displayed excellent ratiometric property and great selectivity for Cys, the stability was also improved. Additionally, the probe was successfully applied for quantitative detection of Cys in fetal bovine serum and real-time imaging in living HeLa cells with low toxicity.     

A Novel Fluorescence Tool for Monitoring Agricultural Industry Chain Based on AIEgens

With the development of the global economy,the safety of agricultural production has attracted intense attention.To minimize the risk of harmful ingredients in the whole industry chain,it is very necessary to cover the entire process of safety inspections from planting to production to environmental management.Fluorescence sensing as a promising and powerful screening tool is widely used for the detection of ions,toxic gases,biological molecules and so on.However,traditional fluorescent probes often suffer from aggregation-induced quenching(ACQ)effects,which limits their practical applications.In this regard,aggregation-induced emission luminogens(AIEgens)can perfectly address this notorious issue and have shown great potential in agricultural safety analysis.In this review,we briefly summarize their applications in agricultural safety monitoring,including the fabrication of agricultural film,agricultural sewage treatment and selective detection of harmful residues in agricultural products.The challenge and future development of AIEgens in this field are also discussed and highlighted.Hopefully,this review can inspire more researchers to participate in this fascinating area.     

A novel fluorescent assay for edaravone with aqueous functional CdSe quantum dots

Aqueous thiol-capped CdSe QDs with a narrow, symmetric emission were prepared under a low temperature. Based on the fluorescence enhancement of thiol-stabilized CdSe quantum dots (QDs) caused by edaravone, a simple, rapid and specific quantitative method was proposed to the edaravone determination. The concentration dependence of fluorescence intensity followed the binding of edaravone to surface of the thiol-capped CdSe QDs was effectively described by a modified Langmuir-type binding isotherm. Factors affecting the fluorescence detection for edaravone with thiol-stabilized CdSe QDs were studied, such as the effect of pH, reaction time, the concentration of CdSe QDs and so on. Under the optimal conditions, the calibration plot of C/(I − I₀) with concentration of edaravone was linear in the range of (1.45–17.42) μg/mL (0.008–0.1 μmol/L) with correlation coefficient of 0.998. The limit of detection (LOD) (3σ/κ) was 0.15 μg/mL (0.0009 μmol/mL). Possible interaction mechanism was discussed.     

Piezochromic luminescence and aggregation induced emission of 9,10- bis[2-(2-alkoxynaphthalen-1-yl)vinyl]anthracene derivatives

Four derivatives of 9,10-bis[2-(2-alkoxynaphthalen-1-yl)vinyl]anthracene (BNAs) were designed, successfully synthesized and characterized by spectrofluorometer, powder wide-angle X-ray diffraction (PXRD) and differential scanning calorimetry experiments (DSC), etc. It was found that these compounds exhibited aggregation-induced emission phenomenon. Moreover, these target compounds displayed reversible color change from yellow to orange upon pressing and annealing process. Interestingly, all of BNAs obviously presented red-shifted piezofluorochromic (PFC) properties and behaved mainly length dependence of alkoxy group, in which, BNA displayed the largest PFC spectral shift (Δl_PFC=26 nm). The PXRD profiles demonstrated the transformation from crystalline to amorphous state upon grinding, and the mechanism of PFC behaviors was proposed. Thus, changing the length of alkoxyl chain could be an alternative way to tune their PFC behaviors.     

聚集诱导发光现象的理论研究

本文系统介绍了本课题组发展的分子辐射跃迁和无辐射跃迁速率常数的热振动关联函数理论方法的最新进展及其在聚集诱导发光领域的典型应用. 基于第一性原理计算, 定量考察了位阻、温度、聚集等因素对分子体系发光性质的影响. 从微观角度给出了分子聚集诱导发光机理： 分子激发态的无辐射能量衰减通道主要是对应于低频模式的芳香环扭转和高频模式的碳碳伸缩振动. 当位阻增加、温度降低或者分子聚集时, 芳香环的转动受限, 无辐射能量衰减通道被抑制, 导致无辐射跃迁速率常数降低, 而其对辐射跃迁速率常数影响不大, 从而提高分子的荧光量子产率, 荧光增强.     

具有聚集诱导发光特性的咔唑衍生物的合成及其理化性质研究

以咔唑、亚芴基肼等为原料,通过suzuki反应合成了2个新型咔唑衍生物:N-乙基-3,6-双(亚芴基肼基-5-亚甲基-2-噻吩)咔唑(S1)和N-(亚芴基肼基-4-亚甲基苯基)-3,6-双(亚芴基肼基-5-亚甲基-2-噻吩)咔唑(S2)。用FTIR、1HNMR、元素分析对S1和S2的结构进行表征,并考察其紫外吸收光谱、荧光光谱、电化学行为和热稳定性。结果表明:S1和S2薄膜的最大发射波长分别在637和649nm处,均发射红色荧光,且S1和S2均具有良好的聚集诱导发光(AIE)特性;S1和S2的HOMO能级分别是-5.26和-5.29e V,与正电极(ITO)的功函数(-4.8 e V)相匹配,可有效降低空穴注入能垒,有利于空穴的传输;S1和S2的热分解温度分别是351和360℃,均具有良好的热稳定性。     

Colorimetric and fluorimetric detection of cysteine: Unexpected Michael addition–elimination reaction

The synthesis of three isomers based on Michael addition mechanism for the detection of sulfurcontaining species in aqueous solution is described. These compounds are constructed by conjugating an enone to a coumarin fluorophore. A substituted-phenyl (o, m, or p-) was appended at the carbonyl carbon to adjust the reactivity. The experimental results showed that (E)-7-(diethylamino)-3-(3-(3-hydroxyphenyl)-3-oxoprop-1-en-1-yl)-2H-chromen-2-one (m-QPS) and (E)-7-(diethylamino)-3-(3-(4-hydroxyphenyl)-3-oxoprop-1-en-1-yl)-2H-chromen-2-one (p-QPS) barely react with sulfur-containing nucleophiles, while (E)-7-(diethylamino)-3-(3-(2-hydroxyphenyl)-3-oxoprop-1-en-1-yl)-2H-chromen-2-one (o-QPS) exhibited a fast response toward sulfite, sulfide and thiols in DMSO/phosphate buffer (2:1). The above results are probably due to the intramolecular H-bonding activated Michael addition. More interestingly, cysteine triggered unusual photophysical responses of o-QPS:the original absorption (488 nm) and emission peaks (573 nm) underwent significant blue shifts initially and then recovered, which might be caused by the Michael addition and elimination reaction, respectively.     

Quantum chemical insights into the aggregation induced emission phenomena: A QM/MM study for pyrazine derivatives

There have been intensive studies on the newly discovered phenomena called aggregation induced emission (AIE), in contrast to the conventional aggregation quenching. Through combined quantum mechanics and molecular mechanics computations, we have investigated the aggregation effects on the excited state decays, both via radiative and nonradiative routes, for pyrazine derivatives 2,3‐dicyano‐5,6‐diphenylpyrazine ( DCDPP ) and 2,3‐dicyanopyrazino phenanthrene ( DCPP ) in condensed phase. We show that for DCDPP there appear AIE for all the temperature, because the phenyl ring torsional motions in gas phase can efficiently dissipate the electronic excited state energy, and get hindered in aggregate; while for its “locked”‐phenyl counterpart, DCPP , theoretical calculation can only give the normal aggregation quenching. These first‐principles based findings are consistent with recent experiment. The primary origin of the exotic AIE phenomena is due to the nonradiative decay effects. This is the first time that AIE is understood based on theoretical chemistry calculations for aggregates, which helps to resolve the present disputes over the mechanism. © 2012 Wiley Periodicals, Inc.     

An ESIPT-based fluorescent probe for sensitive and selective detection of Cys/Hcy over GSH with a red emission and a large Stokes shift

An ESIPT-based fluorescent probe (Probe 1) using acrylate as recognition group for the selective and sensitive detection of cysteine/homocysteine (Cys/Hcy) has been developed. In the presence of Cys/Hcy, this probe was transformed into 1,3-bis(bispyridin-2ylimino)isoindolin-4-ol (dye 4) which displayed red fluorescence with a large Stokes shift (217 nm) when excited. The detection limits are as low as 5.4 nM and 7.0 nM for Cys and Hcy respectively (based on S/N = 3). Importantly, this probe has been successfully demonstrated for the detection of intracellular Cys/Hcy in living cells.     

Highly efficient organic photosensitizer with aggregation-induced emission for imaging-guided photodynamic ablation of cancer cells

We design an organic photosensitizer with a donor-π-acceptor configuration. The photosensitizer exhibits aggregation-induced emission characteristics and efficient singlet oxygen production in the aggregated state. It is then enveloped into the water-soluble micelle to afford a nanoprobe. The water-soluble nanoprobe keeps the photosensitizer in the aggregation state and is used for imaging-guided photodynamic ablation of cancer cells.     

A novel AIEE and EISPT fluorescent probe for selective detection of cysteine

We designed and synthesized a simple and readily available fluorescent probe 3 for cysteine (Cys) based on naphthalene derivative. The probe is composed of a new class of aggregation-induced emission enhancement (AIEE) active dye 2 based on excited-state intramolecular proton transfer (ESIPT) and an acrylate group as the Cys recognition unit as well as the ESIPT blocking agent, which can be cut off by Cys from the probe in aqueous solution with mild conditions. The probe had great sensitivity and selectivity for the detection of Cys over homocysteine (Hcy) and glutathione (GSH) with a detection limit of 0.05 µM. In addition, we have successfully applied the probe for bioimaging studies of Cys in living cells, indicating that the probe holds great potential for biological applications.     

A selective coumarin-based “turn-on” fluorescent sensor for the detection of cysteine and its applications for bioimaging

A coumarin-based compound (1) was designed and synthesized as a new turn-on fluorescent probe for the detection of cysteine. The in vivo imaging of Hi5 cell and Caenorhabditis elegans had further confirmed the cysteine detection by compound 1.     

Electrochemical,fluorescence, and UV detection for HPLC analysis of various cysteine derivatives

Electrochemical (ECD), fluorescence (FLD), and UV spectrophotometric (UVD) detection were used to monitor various S-alk(en)yl-L -cysteines and their corresponding sulfoxide isomers following pre-column derivatization with o-phthaldialdehyde-tert-butylthiol and separation by reversed-phase HPLC. Recording of hydrodynamic voltammograms, FLD stop-flow scanning, and on-line captured UV spectra were methods used for establishing optimal detector settings which were defined as a compromise between favorable selectivity and high sensitivity. Optimal detector settings were found at: (A) 750 mV vs. Ag/AgCl for ECD; (B) excitation at 230 nm and emission at 420 nm for FLD; and (C) 337 nm for UVD. Various aspects of detector practicability such as selectivity, baseline disturbances due to excessive reagent, scanning possibilities, as well as detection limits were evaluated and compared. Minimal detectable amounts of the compounds were in the range of 130-160 fmol for ECD, and 2.5-3.5 pmol and 13-16 pmol for FLD and UVD. In addition, the possibilities and benefits of detector coupling were examined.     

Total organochloride and organobromide determinations in aqueous samples by microwave induced plasma-optical emission spectrometry

The element specific detection of the adsorbable organic halogen (AOX) parameter in waters has been investigated by adsorption of the halogenated analytes on activated carbon, incineration to yield carbon dioxide and hydrogen halide, trapping of the halide on a 0.01 M sodium hydroxide solution and online introduction of the halogen formed by continuous oxidation into a microwave induced plasma (MIP). Detection has been carried out by optical emission spectrometry (OES) in the visible spectral region.The performance of three microwave cavities for MIP-OES running at atmospheric pressure (Beenakker, Surfatron and Microwave Plasma Torch) as well as a reduced pressure Surfatron were investigated for halide analysis. The Surfatron device operated at 30 torr provided the best detection limits: 3ng.ml^–1 for chloride and 8 ng.ml^–1 for bromide; consequently, it was the plasma chosen for AOX analysis.On-line continuous oxidation of organic compounds using KMnO₄ in H₂SO₄ medium and in batch catalytic dechlorination with a Fe/Pd system were investigated as alternatives to the incineration method for the destruction of organic halogens to render inorganic halides are also investigated.Finally, the optimized method has been applied successfully to the determination of organochloride and organobromide in spiked river waters, being the recoveries in the interval 92–105%.     

Selectively colorimetric detection of cysteine with triangular silver nanoprisms

Triangular silver nanoprisms were prepared and applied to make colorimetric detection of cysteine based on our findings that cysteine could lead to the blue shift of the dipole plasmon resonance absorption,but other 19 kinds of natural amino acids could not.Cysteine with a concentration 160 nmol/L can result in a color change that can be discerned with naked eyes.