Multi-signaling thiocarbohydrazide based colorimetric sensors for the selective recognition of heavy metal ions in an aqueous medium

Highly selective chemosensor for the sensitive detection of Hg2+ in aqueous media and its cell imaging application

The deleterious toxicity of Hg²⁺ on ecological and biological system makes it crucial for the precise monitoring of Hg²⁺. Herein, we prepared a novel "turn-on" chemosensor N'-(4-(methylthio)butan-2-ylidene) rhodamine B hydrazide (denoted as MTRH) by a simple two-step reaction. MTRH exhibited an ultra-low detection limit (LOD) in fluorescence measurement of Hg²⁺ in pure aqueous media, which was estimated to be 1.3 × 10^-9 mol·L^-1. Moreover, the proposed chemosensor holds the ability of visualizing Hg²⁺ by the distinct color change of the solution. The corresponding recognition mechanism was investigated by Job's plots, mass spectrometry and DFT calculation analysis. Importantly, the characteristics such as high sensitivity, low cytotoxicity and good biocompatibility of MTRH exhibited in the application of detecting Hg²⁺ in real water sample and bioimaging of intracellular Hg²⁺ prove that MTRH is a promising tool to evaluate the levels of Hg²⁺ in complex biological systems.

A color reaction for the determination of Cu2+ in distilled beverages employing digital imaging

In this work, we describe for the first time the synthesis of a thiocarbazone for the selective determination of Cu²⁺ in distilled beverages. The method was based on the complexation reaction of Cu²⁺ with the thiocarbazone, and the colored product was analyzed using a smartphone application. The thiocarbazone reacts with Cu²⁺ to form a 1:1 (metal:ligand) complex. The Cu²⁺ complex was characterized by UV, IR and NMR spectral analyses. The proposed reaction yields a yellow color, and therefore, channel B of the RGB system was used in the analysis. After optimizing the reaction conditions, an analytical curve was obtained to determine Cu²⁺ concentrations ranging between 0.25 and 6.75 mg L^-1; the use of 400 μL sample volumes led to a relative standard deviation (n = 5) of 3.2% and a detection limit of 0.18 mg L^-1. Recovery experiments were performed with sugar cane spirits, whiskies and tequilas to evaluate the accuracy of the method, and the recovery obtained ranged from 80.5 to 112.2%.

Recent progress in cadmium fluorescent and colorimetric probes

Cadmium is a heavy metal which exists widely in industrial and agricultural production and can induce a variety of diseases in organisms. Therefore, its detection is of great significance in the fields of biology, environment and medicine. Fluorescent probe has been a powerful tool for cadmium detection because of its convenience, sensitivity, and bioimaging capability. In this paper, we reviewed 98 literatures on cadmium fluorescent sensors reported from 2017 to 2021, classified them according to different fluorophores, elaborated the probe design, application characteristics and recognition mode, summarized and prospected the development of cadmium fluorescent and colorimetric probes. We hope to provide some help for researchers to design cadmium fluorescent probes with higher selectivity, sensitivity and practicability.

Cadmium is a heavy metal which exists widely in industrial and agricultural production and can induce a variety of diseases in organisms.

Nanocellulose in biomedical and biosensing applications: A review

Cellulose is abundant in the nature and nanocellulose (NC) in particular is regarded as a credible green substrate to be used in bio nanocomposites for various applications. NC exhibits excellent mechanical reinforcement properties comparable to conventionally used materials due to its high specific surface area and tunable surface chemistry. Additionally, low toxicity, biodegradability and biocompatibility of NC deem it a promising material for use in different biomedical applications. In this review, we highlight the biomedical applications of NC based hydrogels and aerogels/nanocomposites and advancements of their employment in the areas of wound dressing, drug delivery, tissue engineering, scaffolds and biomedical implants. This review also explores the recent use of NC in making biosensors for the detection of cholesterol, various enzymes and diseases, heavy metal ions in human sweat and urine, and for general health monitoring.

Recent Progress on Luminescent Metal-Organic Framework-Involved Hybrid Materials for Rapid Determination of Contaminants in Environment and Food

The high speed of contaminants growth needs the burgeoning of new analytical techniques to keep up with the continuous demand for monitoring and legislation on food safety and environmental pollution control. Metal-organic frameworks (MOFs) are a kind of advanced crystal porous materials with controllable apertures, which are self-assembled by organic ligands and inorganic metal nodes. They have the merits of large specific surface areas, high porosity and the diversity of structures and functions. Latterly, the utilization of metal-organic frameworks has attracted much attention in environmental protection and the food industry. MOFs have exhibited great value as sensing materials for many targets. Among many sensing methods, fluorometric sensing is one of the widely studied methods in the detection of harmful substances in food and environmental samples. Fluorometric detection based on MOFs and its functional materials is currently one of the most key research subjects in the food and environmental fields. It has gradually become a hot research direction to construct the highly sensitive rapid sensors to detect harmful substances in the food matrix based on metal-organic frameworks. In this paper, we introduced the synthesis and detection application characteristics (absorption, fluorescence, etc.) of metal-organic frameworks. We summarized their applications in the MOFs-based fluorometric detection of harmful substances in food and water over the past few years. The harmful substances mainly include heavy metals, organic pollutants and other small molecules, etc. On this basis, the future development and possible application of the MOFs have prospected in this review paper.

Macrocyclic "tet a" derived colorimetric sensor for the detection of mercury cations and hydrogen sulphate anions and its bio-imaging in living cells

A mono-N-substituted probe L containing a bromosalicylaldehyde pendant arm attached to a tetraazamacrocyclic "tet a" moiety was synthesized via straight forward reaction. The probe L crystallizes in a monoclinic P2₁/n space group. The probe L displayed quick sensitivity and selectivity towards Hg²⁺ ions due to its hopeful Chelation Enhancement Quenching (CHEQ) feature. Interestingly, the probe L exhibits turn-off fluorescence response to Hg²⁺ ion and turn-on fluorescence signals to HSO₄^- ions. When the probe L was complexed with HSO₄^- in 1:1 mode (L + HSO₄^- formation), improved turn-on fluorescence emission was detected due to the chelation enhanced fluorescence effect through sensor complex. The macrocyclic "tet a" probe L exhibited a binding constant value of 3.89 × 10⁶ M^-1 and 5.58 × 10⁵ M^-1 for Hg²⁺ and HSO₄^-, respectively. Probe L exhibited good selectivity to Hg²⁺ rather than other common metal ions and HSO₄^- over other common anions. The limit of detection (LOD) of Hg²⁺ and HSO₄^- were found to be 1 nM and 7 μM, respectively. The time-resolved fluorescence emission single-photon counting study was used to determine the average lifetime value for the probe L and L + HSO₄^- ions as 0.47 and 1.02 ns, respectively. The practical application of the probe in visualizing intracellular Hg²⁺ and HSO₄^- ions distribution in live Artemia salina was demonstrated. Furthermore, the probe L with Hg²⁺cations was found to be cytotoxic against breast cancer cells in nature and can be delivered as an anticancer agent. Besides the probe L with HSO₄^- exhibit strong fluorescence emission with low cytotoxicity, and it can be recommended for live-cell imaging.

Hg2+ induced hydrolysis of thiazole amine based Schiff base: Colorimetric and fluorogenic chemodosimeter for Hg2+ ions in an aqueous medium

Simple pyrene-based chemosensors 1 to 3, were synthesized from pyrene-1-carboxaldehyde and they were characterized using various spectroscopic techniques like UV-Vis, FT-IR, Mass, ¹H NMR and ¹³C NMR. Among synthesized receptors, the receptor 1 shows high selectivity towards Hg²⁺ ions. Further, the high selectivity of receptor 1 towards Hg²⁺ ions in the presence of various other interfering metal ions like Ni²⁺, Zn²⁺, Mn²⁺, Co²⁺, Cu²⁺, Cr³⁺, Fe³⁺, Al³⁺, Ag⁺, Fe²⁺, Cd²⁺, Mg²⁺, Pb²⁺, Ca²⁺, Na⁺, K⁺ was confirmed by UV-Vis and fluorescence methods. The detection limit for Hg²⁺ ions was found to be 0.270 μM. The chemodosimetric irreversible hydrolysis of the receptor 1 in the presence of Hg²⁺ was studied by UV/Vis, fluorescence, FT-IR, LC-MS, ¹H NMR and theoretical DFT study. Further, the real life applications of receptor 1 for the determination of Hg²⁺ ions were demonstrated by UV-Vis method.

Chitosan–gold nanocomposite and its functionalized paper strips for reversible visual sensing and removal of trace Hg2+ in practice

To eliminate mercury contamination in aqueous environment, chitosan–gold nanocomposite and its functionalized paper strips were designed and developed for visual sensing and removal of trace Hg²⁺.

Synthesis and application of a highly selective copper ions fluorescent probe based on the coumarin group

A highly selective copper ions fluorescent probe based on the coumarin-type Schiff base derivative 1 (probe) was produced by condensation reaction between coumarin carbohydrazide and 1H-indazole-3-carbaldehyde. The UV-vis spectroscopy showed that the maximum absorption peak of compound 1 appeared at 439nm. In the presence of Cu²⁺ ions, the maximum peak decreased remarkably compared with other physiological important metal ions and a new absorption peak at 500nm appeared. The job's plot experiments showed that complexes of 1:2 binding mode were formed in CH₃CN:HEPES (3:2, v/v) solution. Compound 1 exhibited a strong blue fluorescence. Upon addition of copper ions, the fluorescence gradually decreased and reached a plateau with the fluorescence quenching rate up to 98.73%. The detection limit for Cu²⁺ ions was estimated to 0.384ppm. Fluorescent microscopy experiments demonstrated that probe 1 had potential to be used to investigate biological processes involving Cu²⁺ ions within living cells.

Detection of mercury ions in water using a membrane-based colorimetric sensor

The effectiveness of a colorimetric sensor is highly influential by the morphology characteristics of a membrane platform that affect the color change responses.

Design of Research on Performance of a New Iridium Coordination Compound for the Detection of Hg2

Heavy metal pollution has become one of the most significant pollution problems encountered by our country in terms of environment protection. In addition to the significant effects of heavy metals on the human body and other organisms through water, food chain enrichment and other routes, heavy metals involved in daily necessities beyond the level limit could also affect people’s lives, so the detection of heavy metals is extremely important. Ir (III) coordination compound, considered to be one of the best phosphorescent sensing materials, is characterized by high luminous efficiency, easy modification of the ligand and so on, and it has potential applications in the field of heavy metal detection. This project aims to product a new Ir (III) functional coordination compound by designing a new auxiliary ligand and a main ligand with a sulfur identification unit, in order to systematically investigate the application of iridium coordination compound in the detection of the heavy metal Hg²⁺. With the introduction of the sulfur identification unit, selective sensing of Hg²⁺ could be achieved. Additionally, a new auxiliary ligand is also introduced to produce a functional iridium coordination compound with high quantum efficiency, and to diversify the application of iridium coordination compound in this field.