Fluorescent Probe with Dual Energy Transfer Process for Selective Fe3+ Detection and Cellular Imaging

A ratiometric fluorescent probe based on benzothiazole with a large Stokes shift for fluoride ion sensing in living cells, animals and plants.

A novel near-infrared ratiometric fluorescent probe designed and synthesized by rationally linking dicyanoisophorone with 2-(2-hydroxyphenyl)benzothiazole provides a reliable and versatile tool for the visual monitoring of fluoride ions in both environmental and biological contexts.

Red-emissive fluorescent probes based on PET mechanism for highly sensitive detection and multi-scenario imaging of thiophenol.

Thiophenol (PhSH) is a highly toxic aromatic thiol endangering ecosystems, food safety, and human health. Traditional detection methods are limited by instrument dependence and inability for real-time imaging. This study developed a red-emitting fluorescent probe, TTCP-DN, based on the PET mechanism. The probe employs 5-(4-diphenylamino)benzothiophene as the fluorophore and 2,4-dinitrophenoxy as the PhSH-specific recognition moiety, achieving mitochondrial targeting via a pyridine salt. Without PhSH, fluorescence is quenched; upon PhSH-induced reaction, fluorescence restores at 623 nm. The probe has low detection limit (37.8 nM), large Stokes shift (153 nm), good biocompatibility, and high selectivity. It was applied for mitochondrial imaging in 4 T1 cells, qualitative detection and semi-quantitative concentration trend analysis of PhSH in zebrafish, plant tissues, environmental, food and biological samples (recoveries 95-105%), and fabricated into portable paper-based test strips. This work provides a versatile PhSH detection tool and a paradigm for targeted probes of toxic aromatic pollutants.

A dual-state emissive fluorescent probe for 2D and 3D intracellular picric acid sensing.

Dual-state emissive (DSE) fluorophores, which exhibit efficient fluorescence in both solution and aggregated states, are attractive candidates for sensing and bioimaging applications. Herein, we report LY26, an aromatized imidazole-based DSE fluorophore for picric acid (PA) sensing in colloidal systems and intracellular environments. LY26 displayed pronounced solvatochromic fluorescence arising from intramolecular charge transfer (ICT). In tetrahydrofuran (THF)/water mixtures, LY26 underwent a characteristic twisted intramolecular charge transfer (TICT)-to-aggregation-induced emission (AIE) transition, exhibiting fluorescence quenching at intermediate water fractions followed by substantial fluorescence recovery in highly aggregated states. Strong fluorescence was maintained in solution (ΦTHF = 10.3%), nanoaggregates (Φnanoaggregate = 10.1% at fw = 99%), and solid powder (Φsolid = 32.1%), confirming its DSE characteristics. LY26 exhibited selective fluorescence quenching toward PA with a Stern-Volmer quenching constant (KSV) of 5.27 × 104 M-1 and a limit of detection (LoD) of 2.98 μM. Spike-and-recovery experiments in real water samples afforded recoveries of 91.4-96.3%, demonstrating the practical applicability of LY26 for environmental PA detection. Encapsulation of LY26 within amphiphilic F127 polymers yielded LY26@F127 nanoparticles with excellent colloidal stability, photostability, low cytotoxicity, and efficient cellular uptake. Furthermore, concentration- and time-dependent intracellular PA sensing was successfully demonstrated in both 2D cell cultures and 3D cell-laden hydrogels. These findings establish LY26 as a promising DSE fluorophore for intracellular sensing and bioimaging in physiologically relevant cellular microenvironments.

Elucidating the sensing mechanism of a fluorescent probe for formaldehyde detection: A computational study under acidic and neutral conditions.

The probe HBT-BA1 based on excited-state intramolecular proton transfer (ESIPT) can achieve rapid optical responses and show promising potential for formaldehyde (FA) detection. However, the ESIPT-mediated luminescence regulation mechanism remains completely unexplored, particularly regarding how environmental conditions determine the subsequent reaction pathways of key intermediates. In this work, the systematic theoretical study on the environment-dependent, dual-pathway FA sensing mechanisms was performed by using quantum chemical methods. Under neutral condition, the probe captures FA and undergoes spontaneous photocyclization to emit strong deep-red light at 711 nm, with a large Stokes shift of up to 392 nm. Frontier molecular orbitals (FMOs) analysis confirms that cyclization reduces the energy gap of electronic transition and enhances electronic delocalization, thereby facilitating long-wavelength emission. In acidic environments, the intermediate undergoes acid-catalyzed hydrolysis to release the classic ESIPT fluorophore HBT, which spontaneously protonates to yield HBT+ with bright blue-violet emission at 413 nm. Overall, this work fully elucidates the environment-dependent recognition mechanism at molecular level, which provides important theoretical guidance for developing environment-adaptive probes for precise FA detection.

Recent Advances in the ESIPT-based Responsive Probes for the Detection of Bio-Active Molecules CO, NO and H₂S.

A novel rhodamine-based dual-mode fluorogenic probe for sensitive determination of Hg²+

Mercury ions (Hg2+) are highly toxic and persistent heavy metal pollutants that pose serious threats to environmental systems and human health. Therefore, developing sensitive and selective detection strategies for Hg2+ is of great significance. In this study, a rhodamine-based dual-mode fluorescent probe (RB-HG) was developed utilizing dimethylthiocarbamate groups as recognition sites. Upon undergoing specific interaction with Hg2+, leading to the dissociation of the C–O bond and subsequently triggering an opening-ring reaction to form a ketone structure (RB-C=O), thereby activating the intramolecular charge transfer (ICT) process and generating both fluorescence and colorimetric signals, thereby activating both colorimetric and fluorescence dual—channel signals. In vitro experiments demonstrate that RB-HG (5.0 μM) exhibits high selectivity and sensitivity toward Hg2+. The limits of detection for the fluorescence and colorimetric detection modes are 1.16 μM and 3.22 μM, respectively. RB-HG was successfully applied to detect Hg2+ in food samples with excellent recovery rates and to image exogenous Hg2+ in living cells, highlighting its potential for food monitoring and bioimaging applications.