Two hexaazatriphenylene based selective off–on fluorescent chemsensors for cadmium(II)

pH-controlled preferential binding of cucurbit[7]uril-coated iron-oxide nanoparticles to 6-mercaptonicotinic acid for fluorescent detection of cadmium ions in the solid state

A host-guest complex of 6-mercaptonicotinic acid (MNA) and cucurbit[7]uril (CB7) was prepared and conjugated to γ-Fe₃O₄ nanoparticles (NPs) to detect toxic cadmium ions in water as a solid-state sensor. The formation of an inclusion host-guest complex with CB7 was confirmed by UV-vis absorption and proton NMR spectroscopy. CB7 preferentially binds the protonated MNA form compared to the neutral form, demonstrated by a binding constant for the protonated form that is four orders of magnitude higher than that of the neutral form. An increase in the pK_a of MNA by 1.2 units was demonstrated after the addition of CB7, which further supports preferential binding between MNA and CB7. The NMR results confirm binding to cadmium via the carboxylic acid moiety. Stationary and time-resolved fluorescence results, in solution and in the solid state, indicate that cadmium and CB7 cause a blue shift in the MNA emission bands and extend its excited-state lifetime due to dissociation of the MNA dimer. In the solid state, switching the emission signals between Cd²⁺-MNA/CB7NPs (ON state) and MNAH⁺/CB7NPs (OFF state) was achieved by controlling the pH. An efficient, regenerable, and stable sensor device was fabricated for sensitive and selective detection of Cd²⁺ in contaminated water samples. Graphical abstract Regeneration of MNA/CB7 nanoparticles for the detection of cadmium ions in the solid state by a visible blue emission signal upon suppression of photoinduced electron transfer (PET).

Synthesis of a novel hexaazatriphenylene derivative for the selective detection of copper ions in aqueous solution

A hexaazatriphenylene (HAT) derivative, naphtho[2,3-h]naphtho[2',3':7,8]quinoxalino[2,3-a]naphtho[2',3':7,8]quinoxalino[2,3-c]phenazine-5,10,15,20,25,30-hexaone (NQH) was synthesized, characterized, and found to have novel properties in being selective toward the detection of copper (Cu2+) ions. The capability of NQH to be employed as a colorimetric, chemo-fluorescence and electrochemical sensor for the detection of Cu2+ was demonstrated by performing UV-Vis absorbance, fluorescence intensity, and cyclic voltammetry (CV) measurements. The interaction between NQH and Cu2+ was initially observed with an obvious color change from yellow to brown upon the addition of Cu2+ ions to NQH. The interaction was also confirmed by UV-Vis absorbance, fluorescence intensity, and mass spectroscopy (MS/MS) measurements. UV absorbance, fluorescence and CV of NQH toward Cu2+ showed good linearity with a detection limit of 3.32 μM, 2.20 μM and 0.78 μM, respectively, which are lower than the toxicity levels of copper in drinking water (20-30 μM) set by the U.S. Environmental Protection Agency (EPA) and World Health Organization (WHO). A 1 : 2 stoichiometry complexation between NQH and Cu2+ was confirmed by Job's plot and MS/MS. In addition, the selectivity and sensitivity of the NQH compound towards Cu2+ ions were further confirmed by performing CV on a screen printed flexible and planar electrochemical sensor.

Fluorescent Polyion Complex for the Detection of Sodium Dodecylbenzenesulfonate

Polyion complexes have been known about for decades, with their applications mainly restricted to drug and gene delivery. In this study, we show that by the introduction of fluorescent charged molecules into a polyion complex, it can be used as a specific detection system for surfactants. The fluorescence of 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS) is quenched in the ionic complex, while it can be recovered with the addition of the surfactant sodium dodecylbenzenesulfonate (SDBS), due to the stronger interaction between SDBS and the polyelectrolyte. This leads to a drastic color change of the solution, and a recovery of the strong emission of HPTS. Specifically, the fluorescence is linearly proportional to the concentration of SDBS, thus it can be used for the qualitative detection of SDBS. Furthermore, the detection limit for SDBS can be up to the order of 10-10 M. We believe that competitive dissociation of the ionic complex can be used as a general approach for the construction of new functional materials.

Synthesis, Photophysical and Electrochemical Properties, and Self-assembly Behavior of Two Hexaazatriphenylene Derivatives: A Single Bond Makes a Big Difference

A hexaazatriphenylene (HAT) derivative (compound 1) that bears four n-octyl chains and two thienyl groups was designed and synthesized. Further light-induced oxidation coupling reaction led to thienyl-fused compound 2. Their photophysical and electrochemical properties and self-assembly behavior have been investigated by UV/Vis, fluorescence, and (1)H NMR spectroscopies, cyclic voltammetry (CV), scanning electron microscopy (SEM), and powder X-ray diffraction (PXRD). Although the difference in compounds 1 and 2 only lie in one single bond that connects the two thienyl segments, they displayed remarkably different properties, revealing an interesting structure-property relationship.

A selective fluorescent probe for the detection of Cd2+ in different buffer solutions and water

A fluorescent probe NHQ, which exhibited excellent selectivity toward Cd²⁺ in different buffer solutions such as Tris-HCl buffer solution, HEPES buffer solution, and PBS buffer solution, and even in water, was developed.

Two hexaazatriphenylene-pyrene based Hg2+ fluorescent chemosensors applicable for test paper detection

Two chemosensors with large hexaazatriphenylene-pyrene chromophores exhibited fluorescence response to Hg²⁺, and they were successfully applied for test paper detection.

Hexaazatriphenylene (HAT) derivatives: from synthesis to molecular design, self-organization and device applications

The creativity and inventiveness of chemists working with the 1,4,5,8,9,12-hexaazatriphenylene (HAT) building block is highlighted in this review.