Shedding Light on Heavy Metal Contamination: Fluorescein-Based Chemosensor for Selective Detection of Hg2+ in Water

Thymine-capped mesoporous silica nanoparticles as ion-responsive release system: A paper-based colorimetric sensing platform for rapid and selective mercuric identification

In this study, a convenient method was proposed for the synthesis of thymine-capped mesoporous silica nanoparticles (MSN) using strong hydrogen bonding in non-protonic solvent. Furthermore, application of the functionalized MSN for the recognition of mercuric ion (Hg2+) based on a paper-based platform with smartphone-assisted colorimetric detection was developed. The synthesized materials were characterized by techniques including X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FTIR), N2 adsorption-desorption, particle size analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). Through the specific and robust interaction between thymine and Hg2+, thymine molecules were uncapped in the presence of Hg2+, leading to the substantial release of Rhodamine B and the rapid production of a purple color on paper-based analytical devices within 30 s. The results were captured using a smartphone and subsequently analyzed using Photoshop software or a smartphone App developed by us. The RGB value increased linearly in the 0.74-44.2 mM Hg2+ concentration range (R = 0.9920), with a detection limit of 73.7 nM. Interference deviations of metal ions and anions to Hg2+ were in the range of -5% to +5%. The method was applied to determine Hg2+ in five Chinese herbal medicines, showing a recovery between 98.3% and 101.5% and demonstrating its superior reliability. The work highlights the potential of the method to detect Hg2+ in real samples with low cost and high efficency.

Highly selective and sensitive ratiometric detection of Hg2+ ions with NFS co-doped carbon dots: Real sample analysis, antibacterial properties, and cellular imaging applications

A simple, low-cost hydrothermal method was employed to synthesize highly fluorescent nitrogen-, fluorine-, and sulfur-co-doped carbon dots (NFS-CDs) using flufenamic acid and L-cysteine as precursors. The synthesized NFS-CDs exhibited dual emission peaks at 490 and 580 nm with a quantum yield of 24.7 %. They exhibit excellent stability, excitation-dependent fluorescent, and particle sizes ranging from 2 to 8 nm. The fluorescent chemosensor probe, NFS-CDs, showed strong selectivity and sensitivity for Hg2+ over other metal ions investigated in aqueous solutions (pH ∼ 7.4). Strong fluorescent enhancement at 490 nm and considerable quenching at 580 nm was observed in the presence of Hg2+ ions. The stoichiometric ratio of the NFS-CDs/Hg2+ complex was optimized to 1:1 according to the Benesi-Hildebrand and Stern-Volmer plot methods. The NFS-CDs exhibited a linear dynamic detection range from 0 to 10 × 10-6 M for Hg2+ ions with a lower detection limit of 18.0 and 67.5 × 10-9 M, respectively, at 490 and 580 nm. Practical applications of NFS-CDs in detecting Hg2+ ions in natural water samples showed high recovery rates (98.9-104.6 %) and low relative standard deviation (RSD ≤ 2.47 %). The NFS-CDs/Hg2+ achieved 78.7 ± 2.6 % and 83.4 ± 2.3 % antibacterial activity against E. coli and S. aureus as NFS-CDs/Hg2+ could damage the bacterial walls when they entered the bacteria. Furthermore, the NFS-CDs were used to detect Hg2+ ions intracellularly in HCT116 cells with low toxicity using live cell imaging.

Hydrazone fluorescent sensors for the monitoring of toxic metals involved in human health from 2014-2024

Hydrazone-based fluorescent sensors have been instrumental for the detection of toxic metals over the past decade due to their ease of synthesis and unique properties. This review summaries the diverse range of sensors reported for toxic metals (Al3+, Fe3+, Cu2+, Zn2+ and Hg2+) highlighting the key role this class of sensors will play in the foreseeable future.

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.