An ultrasensitive fluorescent probe for rapid determination of thiophenols

Theoretical Investigation on the "ON-OFF" Mechanism of a Fluorescent Probe for Thiophenols: Photoinduced Electron Transfer and Intramolecular Charge Transfer

In this study, the sensing mechanism of (2E,4E)-5-(4-(dimethylamino)phenyl)-1-(2-(2,4dinitrophenoxy)phenyl)penta-2,4-dien-1-one (DAPH-DNP) towards thiophenols was investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT). The DNP group plays an important role in charge transfer excitation. Due to the typical donor-excited photo-induced electron transfer (d-PET) process, DAPH-DNP has fluorescence quenching behavior. After the thiolysis reaction between DAPH-DNP and thiophenol, the hydroxyl group is released, and DAPH is generated with the reaction showing strong fluorescence. The fluorescence enhancement of DAPH is not caused by an excited-state intramolecular proton transfer (ESIPT) process. The potential energy curves (PECs) show that DAPH-keto is less stable than DAPH-enol. The frontier molecular orbitals (FMOs) of DAPH show that the excitation process is accompanied by intramolecular charger transfer (ICT), and the corresponding character of DAPH was further confirmed by hole-electron and interfragment charge transfer (IFCT) analysis methods. Above all, the sensing mechanism of the turn-on type probe DAPH-DNP towards thiophenol is based on the PET mechanism.

Visual and quantitative monitoring of thiophenol by a novel deep-red emitting fluorescent probe in environmental and biological systems

Detection of highly toxic thiophenols in biological or environmental systems is of great importance. Therefore, fast, reliable, and sensitive probes are needed to detect thiophenols. Herein, a novel triphenylamine conjugated dicyanoisophorone-based near infrared fluorescence probe is reported to determine trace thiophenol (PhSH) levels. The probe demonstrates a distinct "turn-on" fluorescence response to thiophenol among the tested analytes and its quantum yield (Φ) increases from 0.011 to 0.142. It has low cytotoxicity with cell viability of 90-100% up to 10.0 μM of the probe, a strong anti-interference capability, a large Stokes shift (150 nm), and a fast response time (<1 min). In addition, the probe exhibits a good linear response to PhSH over the range from 0 to 15.0 μM with a detection limit of 32.3 nM (R² = 0.9978). The detection process is also confirmed through HPLC. The practical applicability of the probe is proved by a smartphone platform, TLC kit, plant tissue imaging, soil assay, tap, and lake water analysis with good recovery values (92.3-117%), and concentration-dependent live cell bioimaging PhSH from 5.0 to 15.0 μM. Therefore, the present probe is a robust candidate for monitoring PhSH levels in biological and environmental systems.

A ratiometric fluorescent probe for selective detection of thiophenol derivatives

Though a number of on-off or off-on fluorescent probes have been developed for the detection of thiophenol by using its unique recognition groups, such as 2, 4-dinitrophenyl ether, 2, 4-dinitrophenyl sulfonamide, and 2, 4-dinitrophenyl sulfonate, up to now, there are few probes that can detect thiophenol by the proportional fluorescence signal. We developed a ratiometric fluorescent probe with coumarin pyridine derivative as fluorophore and 2, 4-dinitrophenyl ether moiety as the sensing unit which could be used to detect thiophenol derivatives by the aromatic nucleophilic substitution reaction. This probe (CPBPN) displayed significant change in fluorescence ratio (256 fold) to result in a more reliable analysis by self-calibration and a relatively low detection limit of 24 nM toward 4-methylthiophenol (MTP) within 30 min to achieve more sensitivity. Besides, the probe was also applied to detect the presence of thiophenol derivatives in actual water samples and fluorescence imaging in living cells. The present work is of great importance for monitoring environmental pollutants and studying their biological function.

A fluorescent probe based on ICT for selective detection of benzenethiol derivatives

This work presented a benzothiazole-based fluorescent probe for the detection of benzenethiol derivatives using 2, 4-dinitrobenzene moiety as a sensing unit. This probe (NCABT) was able to instantaneously respond to 4-methylbenzenethiol (MTP) within 5 min. In detecting MTP, this probe displayed a low limit of detection (49 nM). Furthermore, the probe has been proved to have the potential to detect benzenethiol derivatives with electron-donating group in real water samples.

A reaction-based ratiometric fluorescent probe for mercury ion detection in aqueous solution

Mercury ions are crucially harmful to ecosystem and human being due to their characters of bioaccumulation and difficulty of biochemical degradation. Therefore, development of mercury ion detection methods has attracted increasing interests recently. In this study, we successfully synthesized a hydroxyphenylbenzothiazole (HBT)-based fluorescent probe HBT-Hg in an extremely simple manner for mercuric ions detection. The spectral studies revealed that the probe HBT-Hg could react with Hg²⁺ selectively and sensitively in PBS buffer (10 mM, pH = 7.40), showing ratiometric fluorescent changes from blue to light green. The response mechanism of the probe HBT-Hg and Hg²⁺ was finally confirmed by HPLC analysis, viz., the probe HBT-Hg converted to its precursor compound 1. Finally, the probe HBT-Hg was successfully applied in monitoring Hg²⁺ in living A549 cells.

A highly sensitive Ru(ii) complex-based phosphorescent probe for thiophenol detection with aggregation-induced emission characteristics

A novel AIEE-active Ru(ii) based phosphorescent probe was designed for the detection of thiophenol in aqueous solution and on test paper.

An ultrasensitive and visible lighting-up probe for imaging thiophenols in water samples, in serum and visualizing thiophenols-induced oxidative stress process in live cells

Thiophenols, a class of significant industrial materials, are extremely toxic in environmental as well live cells. However, the process of live cells responding to thiophenols is not well understood. Herein, an innovative "OFF-ON" probe FY for thiophenols selectively in 100% aqueous solution was reported. It featured rapid response (~150 s), prominent sensitivity (detection limit: 5 nM), and large Stokes shift (~104 nm), which assured specific detection of thiophenols in A375 cells, HeLa cells and environment. Especially, it proved that thiophenols in live cells can be eliminated by endogenous reactive oxygen species (ROS), indicating that thiophenols may result in cellular oxidative stress. As well, it was resoundingly put into recognizing of thiophenols quantitatively in actual water samples and in serum.

Recent Progress in the Development of Fluorescent Probes for Thiophenol

Thiophenol (PhSH) belongs to a class of highly reactive and toxic aromatic thiols with widespread applications in the chemical industry for preparing pesticides, polymers, and pharmaceuticals. In this review, we comprehensively summarize recent progress in the development of fluorescent probes for detecting and imaging PhSH. These probes are classified according to recognition moieties and are detailed on the basis of their structures and sensing performances. In addition, prospects for future research are also discussed.

Ultrafast 2,7-Naphthyridine-Based fluorescent probe for detection of thiophenol with a remarkable Stokes shift and its application In vitro and in vivo

2,7-Naphthyridine derivatives were developed as fluorophores for the first time to design two fluorescence probes, AND-DNP and ND-DNP, which can be applied for detecting thiophenol in aqueous media. Comparing with ND-DNP, AND-DNP showed more favorable properties such as lower background, larger Stokes shift, and higher fluorescence quantum yield for detecting thiophenol. Moreover, the experimental results were verified by theoretical calculations. Hence, AND-DNP was selected as the superior fluorescence probe to detect thiophenol because of its high sensitivity and selectivity. Based on the experimental results, AND-DNP showed a remarkably larger Stokes shift (225 nm), faster response speed (30 s) and higher fluorescence enhancement (240-fold) than most other fluorescent probes for thiophenol reported in the literature. For an extended application, AND-DNP was applied to detect thiophenol quantitatively in real water samples. Meanwhile, AND-DNP also detected thiophenol via red emission in living A549 cells and zebrafish. All these results proved AND-DNP's potential value as an accurate probe for imaging thiophenol in different environments.

A novel fluorescence turn-on probe for the selective detection of thiophenols by caged benzooxazolidinoindocyanine

Based on a strategy involving 2,4-dinitrophenyl ether and functionalized caged benzooxazolidinoindocyanine, a fluorescence turn-on probe for the selective detection of thiophenols was developed.