Selective sensing of Hg²⁺ using rhodamine-thiophene conjugate: red light emission and visual detection of intracellular Hg²⁺ at nanomolar level

Coumarin derivative-functionalized nanoporous silica as an on-off fluorescent sensor for detecting Fe3+ and Hg2+ ions: a circuit logic gate

A highly efficient fluorescent sensor (S-DAC) was easily created by functionalizing the SBA-15 surface with N-(2-Aminoethyl)-3-Aminopropyltrimethoxysilane followed by the covalent attachment of 7-diethylamino 3-acetyl coumarin (DAC). This chemosensor (S-DAC) demonstrates selective and sensitive recognition of Fe3+ and Hg2+ in water-based solutions, with detection limits of 0.28 × 10-9 M and 0.2 × 10-9 M for Hg2+ and Fe3+, respectively. The sensor's fluorescence characteristics were examined in the presence of various metal ions, revealing a decrease in fluorescence intensity upon adding Fe3+ or Hg2+ ions at an emission wavelength of 400 nm. This sensor was also able to detect ferric and mercury ions in spinach and tuna fish. The quenching mechanism of S-DAC was investigated using UV-vis spectroscopy, which confirmed a static-type mechanism for fluorescence quenching. Moreovre, the decrease in fluorescence intensity caused by mercury and ferric ions can be reversed using trisodium citrate dihydrate and EDTA as masking agents, respectively. As a result, a circuit logic gate was designed using Hg2+, Fe3+, trisodium citrate dihydrate, and EDTA as inputs and the quenched fluorescence emission as the output.

A methionine biomolecule-modified chromenylium-cyanine fluorescent probe for the analysis of Hg2+ in the environment and living cells

The objective of the study is, for the first time, to construct a new near infrared (NIR) fluorophore, spectrophotometric, colorimetric, ratiometric, and turn-on probe (CSME) based on chromenylium cyanine platform decorated with methionine biomolecule to provide an efficient solution for critical shortcoming to be encountered for analysis of hazardous Hg²⁺ in environment and living cell. The CSME structure and its interaction with Hg²⁺ ion were evaluated by NMR, FTIR, MS, UV-Vis and fluorescence methods as well as Density Functional Theory (DFT) calculations. The none fluorescence CSME having spirolactam ring only interacted with Hg²⁺ in aqueous solution including competing ions. This interaction caused the fluorescence CSME with opened spirolactam form which exhibited spectral and colorimetric changes in the NIR region. The probe based on UV-Vis and fluorescence techniques respond in 90 s, has wide linear ranges (for UV-Vis: 6.29 × 10^-8 - 1.86 × 10^-4 M; for fluorescence: 9.49 × 10^-9 - 1.13 × 10^-5 M), and has a lower Limit of Detection (LOD) value (for fluorescence: 4.93 × 10^-9 M, 0.99 ng/mL) than the value predicted by the US Environmental Protection Agency (EPA) organization. Hg²⁺ analysis was performed in drinking and tap water with low Relative Standard Deviation (RSD) values and high recovery. Smartphone and living cell applications were successfully performed for colorimetric sensing Hg²⁺ in real samples and 3T3 cells, respectively.

A new Fe3+-selective, sensitive, and dual-channel turn-on probe based on rhodamine carrying thiophenecarboxaldehyde: Smartphone application and imaging in living cells

A new dual-channel probe based on rhodamine B derivative (MSB) was successfully designed, synthesized, characterized by Nuclear Magnetic Resonance (NMR) Spectroscopy, Fourier Transform Infrared Spectrophotometer (FTIR), Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS), X-ray Photoelectron Spectroscopy (XPS), and Single Crystal X-rayDiffraction, and the sensing abilities toward Fe³⁺ cation have been demonstrated and the probe was successfully utilized for fluorescence imaging of Fe³⁺ in living cells. The probe demonstrated quite fast, sensitive, and selective response to Fe³⁺ by causing an extreme enhancement in UV-vis and fluorescence spectroscopy techniques in the buffered aqueous media which makes MSB a dual-channel probe. While the color of MSB solution was initially light yellow, it turned pink in the presence of Fe³⁺, which provided highly selective naked-eye determination among several ions as alkaline, alkaline-earth, and transition metal ions. After that, the probe was easily applied to paper strips and real samples such as drinking waters and supplementary iron tablets for sensing Fe³⁺ in an aqueous solution. The detection limit (LOD) and the response time of the probe were determined as 4.85x10^-9 M and 4 min, respectively, which are quite lower compared with other rhodamine based Fe³⁺ sensors in the literature. According to Job's plot, ¹H NMR titration, MALDI-TOF MS, XPS, and DFT study techniques, the complexation ratio between MSB and Fe³⁺ was found as 1:1. Moreover, the spectral response was reversible with alternately addition of Fe³⁺ or Na₂EDTA to the MSB solution. In addition, fluorescence imaging in NIH/3T3 mouse fibroblast cells and studies in real samples with a quite high recovery rate exhibited that the probe is qualified for detection of Fe³⁺ ion with multiple practical usages.

A simple organic probe for ratiometric fluorescent detection of Zn(II), Cd(II) and Hg(II) ions in aqueous solution via varying emission colours to distinguish one another

A bis (thiosemicarbazone) based probe has been synthesized and structurally characterized. The probe exhibits good selectivity towards Zn(II), Cd(II) and Hg(II) ions in an aqueous solution containing 95% water with ratiometric fluorescence changes. The modes of coordination of the probe with these metal ions and binding properties have been examined using different spectral techniques. The binding constants, determined using fluorescence titration data, are found to be 9.8 × 10³, 1.39 × 10⁵ and 2.03 × 10¹³ M^-1, respectively for Zn(II), Cd(II) and Hg(II) complexes. The high sensitivity of the probe has been demonstrated by the very low limit of detection i.e. 5.1, 3.4 and 0.51 μM for Zn(II), Cd(II) and Hg(II) ions, respectively. Different coordination mode of these metal ions with the probe has resulted in varying intra-ligand fluorescence (λ_em nm, Zn(II): 488, Cd(II): 470 and Hg(II): 578) among these metal complexes.

A selective N,N-dithenoyl-rhodamine based fluorescent probe for Fe3+ detection in aqueous and living cells

A novel N,N-dithenoyl-rhodamine based fluorescent and colorimetric Fe³⁺ probe 1 was designed and synthesized by only one step from Rhodamine B hydrazide and 2-thiophenecarbonyl chloride. The structure of probe 1 was characterized by ¹H NMR/¹³C NMR spectroscopy, IR spectroscopy, and HRMS spectrometry. Accompanying with significant changes in visual color and fluorescent spectrum, probe 1 displayed good sensitivity for Fe³⁺ with an abroad pH span. The detection limit (3.76 μmol/L, 0.2 mg/L) for Fe³⁺ was lower than WHO recommended value (0.3 mg/L) for drinking water. Using two thiophene carbonyl groups as coordinating functional recognition group, probe 1 showed excellent selectivity towards Fe³⁺ over diverse coexistent metal ions and anions. The sensing mechanism between dithenoyl-substituted probe 1 and Fe³⁺ was further confirmed by ¹H NMR and IR titration experiments, binding constants study, and Job's plot analysis. Furthermore, probe 1 also exhibited good cell membrane permeability and could be used as an efficient Fe³⁺ probe in living human cells.

A highly sensitive and selective fluorescent probe for determination of Cu (II) and application in live cell imaging

A highly sensitive fluorescent probe, 2‑butyl‑6‑(2‑ethylidenehydrazinyl)‑1H‑benzo[de]isoquinoline‑1,3(2H)‑dione (P) has been designed and synthesized to detect Cu²⁺ in CH₃CN-HEPES (4:1, v/v, pH = 7.4) solution. This probe functions via a distinctive hydrolysis mechanism through Cu²⁺-promoted accompany by extinction of the fluorescent and other competing metal ions did not showed any interference. The limit of detection toward Cu²⁺ was calculated of 320 nM. Probe P was not only successfully used for the determination of trace level Cu²⁺ in the CH₃CN-HEPES (4:1, v/v, pH = 7.4) solution, but also valid for fluorescence imaging of Cu²⁺ in lysosomes of 293T cells and it was applied in real water samples. This work indicated that P would be of great application prospect in environmental monitoring and medical diagnosis.

Dual-Emission Fluorescent Microspheres for the Detection of Biothiols and Hg2

Dual-emission nanosensor for Hg²⁺ detection was prepared by coupling CA-AEAPMS on the surface of RBS-doped modified silica microspheres. The CA-AEAPMS was synthesized by using N-(β-aminoethyl)-γ-aminopropyl methyldimethoxysilane (AEAPMS) and citric acid as the main raw material. The obtained nanosensor showed characteristic fluorescence emissions of Rhodamine B (red) and CA-AEAPMS (blue) under a single excitation wavelength (360 nm). Upon binding to Hg²⁺, only the fluorescence of CA-AEAPMS was quenched, resulting in the ratiometric fluorescence response of the dual-emission silica microspheres. This ratiometric nanosensor exhibited good selectivity to Hg²⁺ over other metal ions, because of the amide groups on the surface of CA-AEAPMS serving as the Hg²⁺ recognition sites. The ratio of F₄₅₀/F₅₈₀ linearly decreased with the increasing of Hg²⁺ concentration in the range of 0 to 3 × 10^-6 M, and a detection limit was as low as 97 nM was achieved. Then, the addition of three thiol-containing amino acids (Cys, Hcy, GSH) to the quenched fluorescence solution with Hg²⁺ can restore the fluorescence, and the detection limits of the three biothiols (Cys, Hcy, GSH) are 0.133 μM, 0.086 μM, and 0.123 μM, respectively.

Recent Developments in the Speciation and Determination of Mercury Using Various Analytical Techniques

This paper reviews the speciation and determination of mercury by various analytical techniques such as atomic absorption spectrometry, voltammetry, inductively coupled plasma techniques, spectrophotometry, spectrofluorometry, high performance liquid chromatography, and gas chromatography. Approximately 126 research papers on the speciation and determination of mercury by various analytical techniques published in international journals since 2013 are reviewed.

Multifunctional Fe3O4@SiO2nanoparticles for selective detection and removal of Hg2+ion in aqueous solution

A multifunctional magnetic core–shell Fe₃O₄@SiO₂nanoparticle decorated with rhodamine-based receptor has been successfully synthesized, aiming to detect and remove Hg²⁺from aqueous media.

Multifunctional fibrous silica composite with high optical sensing performance and effective removal ability toward Hg2+ions

A multifunctional organic–inorganic hybrid sensing material (RB-KCC-1) decorated with rhodamine-based receptor has been successfully synthesized, aiming to detect and remove Hg²⁺from aqueous media.

An anion induced multisignaling probe for Hg2+ and its application for fish kidney and liver tissue imaging studies

A highly efficient binder for the selective recognition and determination of Hg(NO₃)₂ concentration in kidney and liver tissues of fish using a fluorescence method is described.

Highly selective colorimetric sensing of Hg(ii) ions in aqueous medium and in the solid state via formation of a novel M–C bond

For the first time an easy-to-make receptor 2-chloro-3-(thiazol-2-ylamino)naphthalene-1,4-dione (R1) for highly selective sensing of Hg(ii) ions in aqueous solution and in the solid state through the formation of an Hg–C bond was developed.

Rhodamine derived colorimetric and fluorescence mercury(ii) chemodosimeter for human breast cancer cell (MCF7) imaging

Condensation of rhodaminehydrazone with naphthalene-1-carboxaldehyde generates a colourless probe, RDHDNAP that can selectively detect Hg²⁺through generation of a pink color along with significant fluorescence enhancement.

Fluorescent graphene quantum dot nanoprobes for the sensitive and selective detection of mercury ions

Graphene quantum dots were prepared by ultrasonic route and served as a highly selective water-soluble probe for sensing of Hg(2+). The fluorescence emission spectrum of graphene quantum dots was at about 430nm. In the presence of Hg(2+), the fluorescence of the quantum dots significantly quenched. And the fluorescence intensity gradually decreased with the increasing concentration of Hg(2+). The change of fluorescence intensity is directly proportional to the concentration of Hg(2+). Under optimum conditions, the linear range for the detection of Hg(2+) was 8.0×10(-7) to 9×10(-6)M with a detection limit of 1.0×10(-7)M. In addition, the preliminary mechanism of fluorescence quenching was discussed in the paper. The constructed sensor with high sensitivity and selectivity, simple, rapid properties makes it valuable for further application.