"Naked-eye" colorimetric and "turn-on" fluorometric chemosensors for reversible Hg2+ detection

Strategic Substitution of -OH/-NR2 (R=Et, Me) Imparts Colorimetric Switching between F- and Hg2+ by Salicyaldehyde/Benzaldehyde-Quinoxaline Conjugates

We herein report two salicyaldehyde-quinoxaline (HQS and HQSN) conjugates and a benzaldehyde-quinoxaline (QBN) conjugate to fabricate selective chemosensors for F^- and Hg²⁺ in the micromolar range. This work demonstrates how sensing outcomes are affected by modulating proton acidity by introducing an electron donating group, -NEt₂ , in the probe backbone. Interestingly, the un-substituted probe HQS can selectively detect F^- , whereas HQSN and QBN are selective for Hg²⁺ . In order to gain insights into the mechanism of sensing, geometry optimizations have been carried out on QS^(-1) , QS^(-1) ⋅⋅⋅HF, QSN^(-1) and QSN^(-1) ⋅⋅⋅HF and the experimental data are validated in terms of free energy and pK_a values. Detailed DFT and TD-DFT analyses provide ample support towards the mechanism of sensing of the analytes.

Synthesis of novel AIEE active pyridopyrazines and their applications as chromogenic and fluorogenic probes for Hg2+ detection in aqueous media

A series of AIEE active novel pyridopyrazine derivatives showing selective and sensitive detection of Hg²⁺ in aqueous media is reported.

Real-time probing of mercury using an efficient “turn-on” strategy with potential as in-field mapping kit and in live cell imaging

Based on a rhodamine scaffold as a fluorophore and 2-aminothiazole as a receptor, we present a highly selective and sensitive sensor (TS).

Colorimetric and fluorescent sensing of a new FRET system via [5]helicene and rhodamine 6G for Hg2+ detection

A “visually colorimetric” and fluorometric sensor based on [5]helicene connected to rhodamine 6G via a hydrazide moiety was designed and prepared for the highly sensitive and selective detection of Hg²⁺.

Triple detection modes for Hg2+ sensing based on a NBD-fluorescent and colorimetric sensor and its potential in cell imaging

The sensor provides highly Hg²⁺-sensitivity and can enhance the emission in live cell.

New water soluble Hg2+ selective fluorescent calix[4]arenes: Synthesis and application in living cells imaging

The present study demonstrates the synthesis of water-soluble fluorescent calix[4]arenes (6 and 7) and its application in living cell imaging for Hg²⁺ detection at a low level. The synthesized fluorescent ligands 6 and 7 were characterized by ¹H NMR technique. The fluorescent study showed both water soluble ligands were Hg²⁺ selective and follow photo-induced electron transfer (PET) process. From the fluorimeter titration experiment detection limit was calculated as 1.14×10^-5 and 3.42×10^-5 for ligand 6 and 7, respectively. From the Benesi-Hildebrand plot binding constant values were evaluated as 666.7 and 733.3M^-1 for 6 and 7, respectively. The interactions between ligands 6 and 7 and Hg²⁺ were also demonstrated in living cells, SW-620, using Fluorescent Cell Imager. While ligands 6 and 7 alone show fluorescent properties, they loss their action with the presence of Hg²⁺ in SW-620 cells.

Near-infrared aza-BODIPY fluorescent probe for selective Cu2+detection and its potential in living cell imaging

A near-infrared (NIR) fluorescent sensor1composed of an aza-boron-dipyrromethene (aza-BODIPY) core covalently bound to two di-2-picolylamine moieties was prepared for Cu²⁺detection in aqueous solutions.

Highly Hg2+-sensitive and selective fluorescent sensors in aqueous solution and sensors-encapsulated polymeric membrane

The sensors in solutions and sensors encapsulated polymeric membranes exhibited high sensitivity and selectivity for Hg²⁺ detection, with detection limits of 0.2–49 ppb.

A metal-enhanced fluorescence sensing platform based on new mercapto rhodamine derivatives for reversible Hg(2+) detection

A new metal-enhanced fluorescence (MEF) chemosensor HMS-Ag-R-2SH for Hg(2+) has been prepared via a simple and effective method. The fluorescent chemosensor was based on a mercapto rhodamine derivatives linked with Ag nanoparticles, and the Ag nanoparticles were supported on hexagonal mesoporous silica material (HMS). Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), absorption spectroscopy and fluorescence spectroscopy techniques were employed to characterize morphology, mesostructure and spectral features of the chemosensor. This chemosensor works in a nearly pure aqueous solution with a broad pH range. The output signals include color change and fluorescence. Moreover, HMS-Ag-R-2SH presents excellent anti-disturbance ability when exposed to a series of competitive cations such as Ag(+), K(+), Li(+), Na(+), Ba(2+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+), Zn(2+), Al(3+), Cr(3+) and Fe(3+). The selectivity of this chemosensor was significantly improved due to the introduction of the sulphydryl. The chemosensor showed a lower detection limit of 2.1ppb for Hg(2+). Importantly, HMS-Ag-R-2SH could be regenerated with sodium sulfide solution for several cycles and maintain a high sensitivity.

Synthesis of Novel Fluorescent Sensors Based on Naphthalimide Fluorophores for the Highly Selective Hg2+-Sensing

With an aim to develop the new sensors for optical detection of Hg2+ions, two novel fluorometric sensors were designed and successfully prepared using 2-(3-(2-aminoethylsulfanyl)propylsulfanyl)ethanamine and one or twoN-methylnaphthalimide moieties (1and2). Sensor1was obtained viaN-alkylation,N-imidation and a one-pot nucleophilic aromatic substitution, andN-formylation of the amine, while sensor2was prepared viaN-alkylation,N-imidation, and nucleophilic aromatic substitution. The characterization, including1H NMR,13C NMR, and mass spectrometry, was then performed for1and2. The Hg2+-binding behaviors of the sensors were investigated in terms of sensitivity and selectivity by fluorescence spectroscopy. Sensor1especially provided the reversible and highly Hg2+-selective ON-OFF fluorescence behavior by discriminating various interfering ions such as Pb2+, Co2+, Cd2+, Mn2+, Fe2+, K+, Na+, and in particular Cu2+and Ag+with a detection limit of 22 ppb toward Hg2+ions.

Fluorescent graphene quantum dot nanoprobes for the sensitive and selective detection of mercury ions

Graphene quantum dots were prepared by ultrasonic route and served as a highly selective water-soluble probe for sensing of Hg(2+). The fluorescence emission spectrum of graphene quantum dots was at about 430nm. In the presence of Hg(2+), the fluorescence of the quantum dots significantly quenched. And the fluorescence intensity gradually decreased with the increasing concentration of Hg(2+). The change of fluorescence intensity is directly proportional to the concentration of Hg(2+). Under optimum conditions, the linear range for the detection of Hg(2+) was 8.0×10(-7) to 9×10(-6)M with a detection limit of 1.0×10(-7)M. In addition, the preliminary mechanism of fluorescence quenching was discussed in the paper. The constructed sensor with high sensitivity and selectivity, simple, rapid properties makes it valuable for further application.