Suppressing Non-Radiative Relaxation through Single-Atom Metal Modification for Enhanced Fluorescence Efficiency in Molybdenum Disulfide Quantum Dots.

To enhance the fluorescence efficiency of semiconductor nanocrystal quantum dots (QDs), strategies via enhancing photo-absorption and eliminating non-radiative relaxation have been proposed. In this study, we demonstrate that fluorescence efficiency of molybdenum disulfide quantum dots (MoS QDs) can be enhanced by single-atom metal (Au, Ag, Pt, Cu) modification. Four-fold enhancement of the fluorescence emission of MoS QDs is observed with single-atom Au modification.

Two similar Schiff-base receptor based quinoline derivate: Highly selective fluorescent probe for Zn(II).

As is known, Zn plays a vital role in a variety of biological processes but excessive exposure of Zn to human beings can cause toxicity, inducing a series of overt poisoning symptoms and neurodegenerative disorders. Thus, we designed and synthesized two quinoline-derived Schiff-bases HL and HL, and investigated the fluorescence emission responses of these two Schiff-bases to various metal ions. A significant enhancement in fluorescence emission band centered at 450 nm was observed in the ethanolic solution of HL with addition of Zn, while remarkably lower fluorescence emission enhancement was obtained in the case of HL in which one methyl group was introduced to the azomethine carbon.

A Schiff-base receptor based chromone derivate: Highly selective fluorescent and colorimetric probe for Al(III).

Upon excitation of the visible light, probes show colorimetric and fluorescent responses to the specific metal ion, which can be easily detected by the naked eye. Owing to the excitation of the visible light at 423 nm, a novel and simple Schiff-base receptor based chromone derivative called 7-methoxychromone-3-carbaldehyde-(indole-3-formyl) hydrazone (MCIH2) had been investigated as a selective and sensitive probe for Al with colorimetric and fluorescent responses. Upon addition of Al to compound MCIH2 solution, compound MCIH2 could respond to Al with a good selective colorimetric signal, which was easily observed from colorless to yellow-green by the naked eye.

A novel chromone and rhodamine derivative as fluorescent probe for the detection of Zn(II) and Al(III) based on two different mechanisms.

In this study, a novel fluorescent probe, 6‑hydroxychromone‑3‑carbaldehyde‑(rhodamine B carbonyl) hydrazine (L), for Zn and Al was designed and synthesized. Initially, this probe L exhibited inferior fluorescence emission peak centered at 488 nm in EtOH/HEPES solution (3/1, 10.0 μM HEPES, pH 7.

Electrochemical immunoassay for the carcinoembryonic antigen based on the use of a glassy carbon electrode modified with an octahedral CuO-gold nanocomposite and staphylococcal protein for signal amplification.

The authors describe an electrochemical immunoassay for ultrasensitive direct determination of the carcinoembryonic antigen (CEA). A nanocomposite consisting of octahedral Cu2O nanocrystals covered with gold nanoparticles was utilized to modify a glassy carbon electrode which gives a strongly enhanced chronoamperometric signal for HO which is used as an electrochemical probe. The morphology and elemental composition of the the nanocomposite was studied by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy.

A voltammetric immunosensor for clenbuterol based on the use of a MoS-AuPt nanocomposite.

An ultrasensitive immunosensor for the direct detection of the illegally used livestock feed clebuterol (CLB) is described. It is based on the use of a glassy carbon electrode modified with an MoS-AuPt nanocomposite and on biotin-streptavidin interaction. The use of MoS-AuPt accelerates electron transfer, and this leads to a sharp increase in the electrochemical signal for the electrochemical probe hydrogen peroxide.

Theoretical Insights into Imidazolidine Oxidation of Imidacloprid by Cytochrome P450 3A4.

The metabolic mechanisms for imidazolidine oxidation of imidacloprid (IMI) by cytochrome P450 3A4 (CYP3A4) have been investigated using quantum mechanical/molecular mechanical (QM/MM) calculations. The binding mode of CYP3A4 with IMI is examined by molecular docking in collaboration with molecular dynamics (MD) simulations. The results show that there are six amino acid residues, involving Arg192, Phe195, Ile349, Ala285, Phe284 and Phe88, closely distributed around the IMI.

A highly selective and sensitive fluorescent chemosensor and its application for rapid on-site detection of Al.

In this paper, a simple naphthalene-based derivative (HL) has been designed and synthesized as a Al-selective fluorescent chemosensor based on the PET mechanism. HL exhibited high selectivity and sensitivity towards Al over other commonly coexisting metal ions in ethanol with a detection limit of 2.72nM.

Development of a coumarin-furan conjugate as Zn ratiometric fluorescent probe in ethanol-water system.

In this study, a novel coumarin-derived compound bearing the furan moiety called 7-diethylamino-3-formylcoumarin (2'-furan formyl) hydrazone (1) has been designed, synthesized and evaluated as a Zn ratiometric fluorescent probe in ethanol-water system. This probe 1 showed good selectivity and high sensitivity towards Zn over other metal ions investigated, and a decrease in fluorescence emission intensity at 511nm accompanied by an enhancement in fluorescence emission intensity at 520nm of this probe 1 was observed in the presence of Zn in ethanol-water (V : V=9 : 1) solution, which provided ratiometric fluorescence detection of Zn. Additionally, the ratiometric fluorescence response of 1 to Zn was nearly completed within 0.

A Novel Chromone Schiff-Base Fluorescent Chemosensor for Cd(II) Based on C=N Isomerization.

A new chromone Schiff-base fluorescent probe 7'-methoxychromone-3'-methylidene-1,2,4-triazole-3-imine (L) was designed and synthesized for selective recognition Cd(2+). With the fluorescence titration and the ESI-MS data, we reach the conclusion that the binding mode of the ligand-metal (L-Cd (2+) ) complex is 1:1. The sensor showed a strong fluorescence enhancement in ethanol system of Cd(2+) (excitation 409 nm and emission 462 nm) and the sensing mechanism based on the fact that C=N isomerization can be used to explain this phenomenon.

A Chromone-Derived Schiff-Base Ligand as Al(3+) "Turn on" Fluorescent Sensor: Synthesis and Spectroscopic Properties.

In this study, a novel chromone-derived Schiff-base ligand called 6-Hydroxy-3-formylchromone (2'-furan formyl) hydrazone (HCFH) has been designed and synthesized as a "turn on" fluorescent sensor for Al(3+). This sensor HCFH showed high selectivity and sensitivity towards Al(3+) over other metal ions investigated, and most metal ions had nearly no influences on the fluorescence response of HCFH to Al(3+). Additionally, the significant enhancement by about 171-fold in fluorescence emission intensity at 502 nm was observed in the presence of Al(3+) in ethanol, and it was due to the chelation-enhanced fluorescence (CHEF) effect upon complexation of HCFH with Al(3+) which inhibited the photoinduced electron transfer (PET) phenomenon from the Schiff-base nitrogen atom to chromone group.

A novel electrochemical immunosensor for highly sensitive detection of aflatoxin B1 in corn using single-walled carbon nanotubes/chitosan.

A sensitive electrochemical immunosensor for aflatoxin B1 (AFB1) detection based on single-walled carbon nanotubes/chitosan was presented. The immunosensor was based on an indirect competitive binding to a fixed amount of anti-AFB1 between free AFB1 and AFB1-bovine serum albumin, which conjugate immobilized on covalently functionalized nanotubes/chitosan laid on the glass carbon electrode. Then, the anti-mouse immunoglobulin G secondary antibody labeled with alkaline phosphatase was bound to the electrode surface through reacting with primary antibody.