8-羟基喹啉衍生物对某些阴离子的双重光谱响应

本文以5-甲酰基-8-羟基喹啉(5M8Q)作为阴离子识别探针,通过紫外、荧光等光谱仪考察其对阴离子识别作用。实验显示:在乙腈溶液中5M8Q对F-、CH3COO-和H2PO4-等阴离子有灵敏的识别作用:F-、CH3COO-和H2PO4-可诱导5M8Q吸收光谱红移,吸收峰位置由322nm红移至400nm。当F-、CH3COO-和H2PO4-浓度为5M8Q两倍当量时,5M8Q荧光显著增强且分别增强至103、60和13倍。结果表明:5M8Q对F-、CH3COO-和H2PO4-有灵敏的双重光谱响应,并且表现出荧光增强型识别性质。     

Label free fluorescence turn-on detection of polynucleotide kinase activity with a perylene probe

A single stranded oligonucleotide could induce aggregation of a perylene probe, the probe's monomer fluorescence was efficiently quenched. However, when the oligonucleotide was 5'-phosphorylated by polynucleotide kinase, it could be very efficiently degraded by lambda exonuclease, probe monomers were released, and a turn on fluorescence signal was detected.     

A highly selective fluorescence turn-on detection of Al3+ and Ca2+ based on a coumarin-modified rhodamine derivative

A fluorescent chemosensor 1 was synthesized containing a coumarin moiety bound to rhodamine B hydrazide. Compound 1 displayed different fluorescence emission responses to Al³⁺ and Ca²⁺ ions with high quantum yields (0.64 and 0.15, respectively) and low detection limits (3.0 × 10^–8 and 9.4 × 10^–8 M, respectively). The possible binding modes of compound 1 with Al³⁺ and Ca²⁺ ion were calculated using a Job plot, HRMS, ¹H NMR spectroscopic titration and IR spectroscopy. Moreover, the calcium in 1-Ca²⁺ could be displaced by Al³⁺ ions, resulting in another ratiometric sensing signal output, which indicates that 1-Ca²⁺ could detect Al³⁺ ions in a ratiometric way. Bioimaging results also demonstrated that compound 1 could act as an intracellular Al³⁺ ion imaging sensor.     

Selective fluorescence turn-on of a prefluorescent azomethine with Zn

A prefluorescent conjugated azomethine (4) was prepared by condensing 8-hydroxyquinoline-5-carbaldehyde with 2-amine thiophene. The fluorescence of the azomethine was quenched in organic solvents including dichloromethane, methanol, DMSO, and DMF. However, the fluorescence of 4 was selectively revived in the presence of zinc and an absolute quantum yield Φ_fl = 0.15 was measured.     

Label-free fluorescence turn-on detection of microRNA based on duplex-specific nuclease and a perylene probe

A novel fluorescence turn-on microRNA (miRNA) detection method based on duplex-specific nuclease (DSN) and a perylene probe is presented in this study. A positively charged perylene derivative (compound 1) was used as the fluorescent probe. Compound 1 exhibits strong monomer fluorescence in an aqueous buffer solution. It is well known that single-stranded DNA is a polyanion in nature. Thus, it can induce the aggregation of compound 1 through strong electrostatic, hydrophobic and π−π stacking interactions. As a result, the fluorescence of compound 1 was efficiently quenched. When the target miRNA was added, the formation of DNA-RNA hybridized duplex initiated the cleavage of the DNA strand by DSN cycle reaction, which resulted in disaggregation of compound 1. A fluorescence turn-on signal was detected, and a novel miRNA sensing method was therefore established. The presented method is label-free, simple, cost effective, sensitive and selective.     

Modulating DNA-templated silver nanoclusters for fluorescence turn-on detection of thiol compounds

Based on the fact that the fluorescence response pattern of a silver nanocluster to a specific analyte is highly dependent on the nature of the DNA template, we develop a novel fluorescence turn-on assay for thiol compounds with high specificity and sensitivity by modulating DNA-templated silver nanoclusters.     

Label-free detection of nucleic acids by turn-on and turn-off G-quadruplex-mediated fluorescence

In this study we have used two fluorescent probes, tetrakis(diisopropylguanidino)-zinc-phthalocyanine (Zn-DIGP) and N-methylmesoporphyrin IX (NMM), to monitor the reassembly of “split” G-quadruplex probes on hybridization with an arbitrary “target” DNA. According to this approach, each split probe is designed to contain half of a G-quadruplex-forming sequence fused to a variable sequence that is complementary to the target DNA. Upon mixing the individual components, both base-pairing interactions and G-quadruplex fragment reassembly result in a duplex–quadruplex three-way junction that can bind to fluorescent dyes in a G-quadruplex-specific way. The overall fluorescence intensities of the resulting complexes were dependent on the formation of proper base-pairing interactions in the duplex regions, and on the exact identity of the fluorescent probe. Compared with samples lacking any “target” DNA, the fluorescence intensities of Zn-DIGP-containing samples were lower, and the fluorescence intensities of NMM-containing samples were higher on addition of the target DNA. The resulting biosensors based on Zn-DIGP are therefore termed “turn-off” whereas the biosensors containing NMM are defined as “turn-on”. Both of these biosensors can detect target DNAs with a limit of detection in the nanomolar range, and can discriminate mismatched from perfectly matched target DNAs. In contrast with previous biosensors based on the peroxidase activity of heme-bound split G-quadruplex probes, the use of fluorescent dyes eliminates the need for unstable sensing components (H₂O₂, hemin, and ABTS). Our approach is direct, easy to conduct, and fully compatible with the detection of specific DNA sequences in biological fluids. Having two different types of probe was highly valuable in the context of applied studies, because Zn-DIGP was found to be compatible with samples containing both serum and urine whereas NMM was compatible with urine, but not with serum-containing samples.     

Chromo-fluorogenic detection of aldehydes with a rhodamine based sensor featuring an intramolecular deoxylactam

A chromogenic and fluorogenic detection of aldehydes was achieved via analyte triggered opening of the deoxylactam of N-(rhodamine B)-deoxylactam-ethylenediamine (dRB-EDA). The utility of the sensor was demonstrated by fluorescent labeling of aldehyde-displaying sialoproteins on cell surfaces.     

Sensitive turn-on fluorescent detection of tartrazine based on fluorescence resonance energy transfer

We introduce a sensitive, rapid, label-free and general fluorescent method for the determination of tartrazine by competitive binding to reduced graphene oxide (rGO) against fluorescein, and the fluorescence recovery upon fluorescein desorption from rGO provides a quantitative readout for tartrazine, giving a detection limit of 0.53 ng mL(-1).     

Sensitive turn-on fluorescent detection of melamine based on fluorescence resonance energy transfer

We here report a novel fluorescent method for the detection of melamine based on the high fluorescence quenching ability of gold nanoparticles. The fluorescence was significantly quenched via fluorescence resonance energy transfer when fluorescein molecules were attached to the surface of gold nanoparticles by electrostatic interaction. Upon addition of melamine, the fluorescence was enhanced due to the competitive adsorption of gold nanoparticles between melamine and fluorescein. Under the optimum conditions, the fluorescence enhancement efficiency [(I-I(0))/I(0)] showed a linear relationship with the concentration of melamine in the range of 1.0 × 10(-7) mol L(-1)~4.0 × 10(-6) mol L(-1), and the detection limit was calculated to be 1.0 × 10(-9) mol L(-1). The proposed method showed several advantages such as high sensitivity, short analysis time, low cost and ease of operation.     

Selective turn-on fluorescence detection of cyanide in water using hydrophobic CdSe quantum dots

The ability of 2,2'-bipyridine-bound copper(ii) ions to quench the photoluminescence of hydrophobic CdSe quantum dots is used to create a novel, selective turn-on fluorescence cyanide sensor.     

Aqueous fluorescence turn-on sensor for Zn2+ with a tetraphenylethylene compound

A new sensitive and selective fluorescence turn-on sensor for Zn(2+) (1) was developed by taking advantage of the aggregation-induced emission of the tetraphenylethylene framework. In addition, the corresponding ester precursor of 1 was successfully used for intracellular Zn(2+) imaging.     

Highly selective fluorescence turn-on chemodosimeter based on rhodamine for nanomolar detection of copper ions

A highly selective fluorescent chemodosimeter based on rhodamine is synthesized which undergoes Cu(2+) driven hydrolysis in aqueous media to produce fluorescence turn-on changes with a detection limit up to the nanomolar range.     

A new fluorometric turn-on detection of L-lactic acid based on the cascade enzymatic and chemical reactions and the abnormal fluorescent behavior of silole

By making use of the aggregation-induced emission feature of silole 1 and the cascade reactions among l-lactic acid (LA), lactate oxidase (LOD), and dodecanoic hydrazine (DH), a new fluorometric "turn-on" method is developed for the detection of LA.     

New organogels based on an anthracene derivative with one urea group and its photodimer: fluorescence enhancement after gelation

By coupling the features of anthracene and urea, a new low-molecular-weight gelator (LMWG, 1) with anthracene and urea moieties was designed and synthesized. A nontransparent gel of LMWG 1 in 1,2-dichloroethane was formed and characterized. Of particular interest is the observation of significant fluorescence enhancement after gelation, which is referred as to gelation-induced enhanced fluorescence emission. UV light irradiation of the THF solution of LMWG 1 yielded a photodimer with the h-t conformation. The photodimer can gel several organic solvents, including cyclohexane, n-hexane, and n-heptane. It should be mentioned that the gel based on the photodimer is rather stable. Our studies indicate that neither the gel phase based on LMWG 1 nor that based on the photodimer can be transformed to the solution by respective UV light irradiation or visible light irradiation/heating.     

Cytidine-stabilized gold nanocluster as a fluorescence turn-on and turn-off probe for dual functional detection of Ag and Hg

In this study, we have developed a label-free, dual functional detection strategy for highly selective and sensitive determination of aqueous Ag⁺ and Hg²⁺ by using cytidine stabilized Au NCs and AuAg NCs as fluorescent turn-on and turn off probes, respectively. The Au NCs and AuAg NCs showed a remarkably rapid response and high selectivity for Ag⁺ and Hg²⁺ over other metal ions, and relevant detection limit of Ag⁺ and Hg²⁺ is ca. 10 nM and 30 nM, respectively. Importantly, the fluorescence enhanced Au NCs by doping Ag⁺ can be conveniently reusable for the detection of Hg²⁺ based on the corresponding fluorescence quenching. The sensing mechanism was based on the high-affinity metallophilic Hg²⁺–Ag⁺ interaction, which effectively quenched the fluorescence of AuAg NCs. Furthermore, these fluorescent nanoprobes could be readily applied to Ag⁺ and Hg²⁺ detection in environmental water samples, indicating their possibility to be utilized as a convenient, dual functional, rapid response, and label-free fluorescence sensor for related environmental and health monitoring.