A Naphthalimide-Based Fluorescent Probe for the Detection and Imaging of Mercury Ions in Living Cells

A rapid and specific fluorescent probe based on ESIPT-AIE-active for copper ion quantitative detection in food and environmental samples

In the field of food safety, the identification and measurement of active components in food is a pressing issue. The concentration of copper ions (Cu2+) in the environment is closely linked to food safety, and overall biological health. Therefore, developing rapid and accurate analytical techniques to monitor Cu2+ in food is of great significance. In this study, two fluorescent probes L-2 and L-3 were synthesized through a simple Schiff base condensation reaction. And L-3 demonstrated better anti-interference ability to Cu2+ than that of L-2. Meanwhile, spectroscopic experiments showed that L-3 possessed an extremely low detection limit (LOD) and low limits of quantification (LOQ) (LOD = 92.79 nM, LOQ = 309.33 nM), and quickly respond time (<30 s). Probe L-3 for monitoring effectively quantitatively identified Cu2+ in food and environmental samples, achieving an accuracy rate ranging from 84.42% to 117.45% and precision with a relative standard deviation (RSD) of less than 6.0%. The accuracy had been validated using the inductively coupled plasma-mass spectrometry (ICP-MS). Simultaneously, a WeChat Mini Program has been developed to detect total copper content in food samples based on fluorescence values, enabling consumers to evaluate food safety more intuitively. Moreover, L-3 also facilitated the quantitative visualization of Cu2+ in biological systems, underscoring its compatibility and practicality.

Monitoring of mercury ion in environmental media and biological systems using a red emissive fluorescent probe with a large Stokes shift

The development of practical fluorescent probe for detecting toxic mercury ions (Hg2+) is desirable for environmental assurance and public health. In this study, a new red emissive fluorescent probe (KJL) was designed and synthesized for monitoring trace Hg2+ both in vitro and in vivo with distinct features including ideal response rate (within 4 min), red emission (596 nm), large Stokes shift (162 nm), highly sensitivity (LOD = 4.79 nM) and excellent specificity. KJL also validated the good capability for accurately monitoring trace Hg2+ levels in actual samples (faucet water, drinking water, river water, lake water, urine and serum) and possessed the eye-catching ability in visualization of Hg2+ under environmental/biological conditions, which revealed the great potential of this red-emitting fluorescent probe for practical applications in complex environmental and biological systems.

An Anthracene-Based Hg2+ Fluorescent Probe with Dithioacetal: Simple Synthesis, High Selectivity and Sensitivity, and Dual-Mode Detection Capability

With the development of the chemical industry, the threat of mercury pollution to human health is increasing. Therefore, it is necessary to develop a low-cost, convenient and efficient Hg2+ detection method. In this study, anthracene-based Hg2+ fluorescent probes AN-2S and AN-4S were synthesized by a dithioacetal reaction for the rapid and efficient detection of the Hg2+ concentration in water. Through molecular structure design and synthesis route optimization, the complexity and cost of the probe synthesis were greatly reduced. AN-2S and AN-4S had good water solubility, rapid response abilities and anti-interference abilities, and could specifically detect Hg2+ using "turn-off" or "turn-on" detection modes within 1 min. The AN-4S probe showed a wide linear response range (0~40 μmol/L) and high sensitivity (4.93 × 10-8 mol/L) to Hg2+ in 99% aqueous solutions, over a pH range of 5~13. The reaction mechanism between the probe and Hg2+ was determined using 1H NMR and FT-IR spectra and Job's curves. It was proven that the AN-2S and AN-4S probes react with Hg2+ in a molar ratio of 1:1 or 1:2. The dual-detection mode enabled the probes to be used not only for the accurate quantitative detection of Hg2+ under a fluorescence spectrometer, but also for rapid qualitative analysis using a UV flashlight as a test strip, showing a broad practical application potential.

Sign Inversion of Circularly Polarized Luminescence in Cholesteric Liquid Crystals Induced by Mercury Ions through Binaphthyl Dopants' Conjugation Control

Stimuli-responsive circularly polarized luminescence (CPL) materials based on cholesteric liquid crystal (CLC) platforms show great promise for applications in information encryption and anticounterfeiting. In this study, we constructed a mercury ion-responsive CPL system in CLCs by controlling the conjugation degree of axially chiral binaphthyl derivatives. Two chiral binaphthyl derivatives (R/S-1 and R/S-2) were initially used as chiral dopants to demonstrate that CPL inversion (glum values from 0.5/-0.44 to -0.53/0.48) in CLCs could be achieved by modulating the conjugation degree of the chiral binaphthyls. Based on this concept, the thioacetal binaphthyl R-2S was developed and used as a mercury-responsive chiral dopant in CLCs. Under Hg ion treatment, the CPL sign inverted (glum value changed from 0.22 to -0.29) due to the transformation of the thioacetal into an aldehyde group. Additionally, the mercury ion-responsive CPL material was applied in information encryption.

Fluorescent polymers for environmental monitoring: Targeting pathogens and metal contaminants with naphthalimide derivatives

Monitoring Hg2+ levels in aqueous environments is crucial to assess the potential methylmercury contamination via bacterial conversion, however, existing methods often require extensive sample treatment and expensive equipment. To mitigate this issue, this study examines the synthesis and application of three naphthalimide-based compounds, with significant fluorescent and solvatochromic behavior (C1, C2, and C3). Compounds C1 and C2 demonstrated a strong affinity for Hg2+ metal ions, with C2 showing selectivity and a strong antibacterial profile, particularly against S. aureus (MIC50 (C2) = 0.01 µg/mL). Moreover, these compounds were incorporated into three polymeric matrices, namely polyvinyl chloride (PVC), poly (methyl methacrylate-co-methacrylic acid) (PMMMA), and Starch, allowing for the development of solid-support sensors/surfaces with a strong antibacterial profile, highlighting the inherent dual-functionality of the compounds. Interestingly, the C2-doped Starch biopolymer detected low concentrations of Hg2+ ions, such as 23 nM in tap water (value within the WHO standards for drinking water), through a rapid spectroscopic evaluation without sample treatment. This biopolymer was generated via a sustainable, green-chemistry-oriented, temperature-dependent water/Starch synthetic route, without the addition of plasticizers and any associated ecotoxicity. The study used sustainable methods for environmental monitoring and antibacterial applications, advancing material science to offer effective, accessible, and eco-friendly solutions for detecting and mitigating mercury pollution and bacterial contaminations, enhancing environmental and health safety.

A Novel Fluorescent Sensor for Detecting Ag+ and Hg2+ ions: A Combination of Theoretical and Experimental Studies

A new fluorescent sensor based on diethylaminosalicylaldehyde-thiosemicarbazide (DST) was studied using a combination of density functional theory calculations and experimental investigations. DST was able to detect the metal ions Ag+ and Hg2+ in the presence of various competing metal ions and anions, with detection limits of 0.45 and 0.34 µM, respectively. The DST sensor could operate in a fully aqueous environment and within a wide pH range from 5 to 9. Density functional theory studies supported the experimental findings in determining the stable structures of the DST sensor and the complexes between DST and the Ag+ and Hg2+ ions, as well as elucidating the fluorescence ON-OFF mechanism in the DST sensor and the complexes.

Chromoionophoric molecular probe infused bimodal porous polymer rostrum as solid-state ocular sensor for the selective and expeditious optical sensing of ultra-trace toxic mercury ions

This study presents a distinctive solid-state naked-eye colorimetric sensing approach by encapsulating a chromoionophoric probe onto a hybrid macro-/meso-pore polymer scaffold for fast and selective sensing of ultra-trace Hg(II). The customized structural/surface properties of the poly(VPy-co-TM) monolith are attained by specific proportions of 2-vinylpyridine (VPy), trimethylolpropane trimethacrylate (TM), and pore-tuning solvents. The interconnected porous network of poly(VPy-co-TM), inherent superior surface area and porosity, is captivating for the homogeneous/voluminous incorporation of probe molecules, i.e., 7-((4-methoxyphenyl)diazenyl)quinoline-8-ol (MPDQ), for the target-specific colorimetric detection. The structural morphology, surface topography, and phase characteristics of the bare poly(VPy-co-TM) monolith and MPDQ@poly(VPy-co-TM) sensor are examined using HR-TEM-SAED (High-Resolution Transmission Electron Microscopy - Selected Area Electron Diffraction), FE-SEM-EDAX (Field Emission Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy), XPS (X-ray Photoelectron Spectroscopy), p-XRD (Powder X-Ray Diffraction), FT-IR (Fourier Transform Infrared Spectroscopy), UV-Vis-DRS (Ultraviolet-Visible Diffuse Reflectance Spectroscopy), and BET/BJH (Brunauer-Emmett-Teller / Barrett-Joyner-Halenda) analysis. The distinctive properties of the sensor reveal a constrained geometrical orientation of the MPDQ probe onto the long-range continuous monolithic network of meso-/-macropore template, enabling selective interaction with Hg(II) with peculiar color transfiguration from pale yellow to deep brown. The sensor demonstrates a linear spectral-color alliance in the 0-200 ppb concentration range for Hg(II), with quantification and detection limits of 0.63 and 0.19 ppb. The sensor efficacy is verified using certified contaminated water and tobacco samples, with excellent reusability, reliability, and reproducibility of ≥ 99.23 % (RSD ≤1.89 %) and ≥ 99.19 % (RSD ≤1.94 %) of Hg(II), respectively.

Ratiometric fluorescence detection of Hg2+ based on gold nanocluster/carbon quantum dots nanohybrids

Ratiometric fluorescence sensing methods are widely used in analysis and detection due to their high sensitivity and stability. In this work, a ratiometric fluorescence method for sensitive detection of Hg2+ was established using a gold nanoclusters/carbon quantum dots (AuNCs/CQDs) nanohybrid probe. The AuNCs/CQDs nanohybrids probe were simply constructed by mixing blue-light-emitting gold nanoclusters (AuNCs) with an orange-emissive carbon quantum dots (CQDs). The probe had two fluorescence emission peaks at 434 nm and 561 nm when the excitation wavelength was 375 nm. With the addition of Hg2+, the fluorescence at 434 nm decreased and the fluorescence at 561 nm remained unchanged; the fluorescence intensity ratio Δ(F434/F561) and Hg2+ concentration have a good linear relationship in the range of 8.32 × 10-7 to 7.69 × 10-5 mol L-1, and the limit of detection (LOD) is 3.58 × 10-7 mol L-1. The method was applied in the detection of Hg2+ in cosmetics and wastewater, and has potential applications for detecting Hg2+ in other samples.

Solid Fluorescence pH Sensors Based on 1,8-Naphthalimide Copolymers Synthesized by UV Curing

Novel water-swollen photo-crosslinked membranes were obtained by copolymerization of the N-vinylpyrrolidone, butyl acrylate and ethyl methacrylate monomers functionalized with naphthalimide groups, as pH sensitive fluorescence probes. For that purpose, two monomers with pending naphthalimide groups anchored to ethyl methacrylate through alkyl chains with different length, were previously synthesized. The membranes were characterized using different techniques. The pH dependence of absorbance and the corresponding quenching of fluorescence were investigated and related to the structure of naphthalimide substituents linked to the membrane. The new solid sensors exhibited sensitive fluorescence changes at pH < 3, and lower time response was determined for membranes where the sensing group was linked through longer alkyl chain to the polymer matrix. The membranes were solid, thermally stable and easily handled to be applied as sensor materials, and showed a reversible behavior, which is an important feature for further fabrication of an economical on-site tool for the acidity detection in aqueous environments.

A novel water-soluble naphthalimide-based turn-on fluorescent probe for mercury ion detection in living cells and zebrafish

Mercury (Hg), as the only heavy metal that can complete the cycle in the biosphere, can further accumulate in the human body through the food chain, causing irreversible damage to...