Colorimetric Detection of Cu2+ and Fluorescent Detection of PO43– and S2– by a Multifunctional Chemosensor

A rhodamine-conjugated fluorescent and colorimetric receptor for the detection of Cu2+ ions: environmental utility and smartphone integration

A new rhodamine based turn on florescent probe (Z)-3',6'-bis(ethylamino)-2-(((6-methoxy-2-oxo-1,2-dihydroquinolin-3-yl)methylene)amino)-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one (RME) was efficiently synthesized through a simple condensation reaction of 2-amino-3',6'-bis(ethylamino)-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one and 6-methoxy-2-oxo-1,2-dihydroquinoline-3-carbaldehyde. The receptor RME is highly non-fluorescent and when copper ions (Cu2+ ions) are added in DMF/water (1 : 2, v/v) medium, the receptor RME exhibits a specific "turn-on" colorimetric and fluorometric response. Moreover, RME binding with Cu2+ ions produced a remarkable color variation that was perceptible to the human eye, changing from colorless to pink. The binding stoichiometry was 1 : 1, confirmed through theoretical DFT, Job's plot, and mass spectral analysis. RME showed good sensing capability for Cu2+ ions, with LOD values of 11.25 nM for ratiometric colorimetry, 1.42 nM for fluorometry, and 107 nM for smartphone-based detection. These LOD values are significantly lower than WHO's acceptable threshold of 2 μM. Additionally, developing portable techniques based on paper-based test strips and smartphone assistance allowed for qualitative and quantitative detection of Cu2+ ions. These portable and economical methods eliminate the need for expensive laboratory apparatus, enabling precise and affordable on-site assessments. In addition, the developed sensing protocol for the detection of Cu2+ ions was extended to real water samples such as tap, dam, and drinking water samples. These results demonstrated the effectiveness of RME in detecting Cu2+ ions in complex matrices, making it a promising tool for environmental monitoring and water quality assessment.

A Sensor for Detecting Aqueous Cu2+ That Functions in a Just-Add-Water Format

There is growing concern around the negative health impacts associated with contamination of drinking water by harmful chemicals. Technology that enables fast, cheap, and easy detection of ions and small molecules in drinking water is thus important for reducing the incidence of these negative health impacts. Here, we describe a sensor for detecting Cu2+ in water that provides colorimetric results in 15 min or less and functions in a just-add-water format. The sensor contains cheap reagents including salts, buffer, oxidant, chromogen, surfactant, and optionally a chelating agent. The sensor is assembled and lyophilized for shelf-stability and field-deployment. Rehydrating the sensor with water containing Cu2+ results in chromogen oxidation and blue color formation to visually indicate the presence of Cu2+. The sensor demonstrates high selectivity toward Cu2+ against other metal cations, functionality in field samples, shelf-stability, and can be tuned to activate at different Cu2+ threshold concentrations. This sensor thus has the potential to meet a variety of needs, such as point-of-need testing for Cu2+ to ensure water supplies meet health guidelines, such as the United States Environmental Protection Agency's Lead and Copper Rule.

Curcumin-Derived Turn-Off Fluorescent Probe for Copper (II) Ion Detection and Live Cell Imaging Applications

A curcumin-derived chemosensor 4,4'-((1E,3Z,5Z,6E)-3,5-bis((2hydroxyphenyl)imino) hepta-1,6-diene-1,7-diyl)bis(2-methoxyphenol) (HIBMP) was developed from curcumin and o-aminophenol using Schiff base condensation method. HIBMP selectively recognizes Cu (II) ion (Cu (II)) relative to other tested metal ions. Selective binding of Cu (II) ion turns off the fluorescent property of HIBMP and shows no interference with other metal ions. Moreover, the favourable binding of Cu (II) with HIBMP was noticed by a good linearity between the fluorescence intensity and concentration of Cu (II) with a range of 0-15.6 × 10-7 M, and the limit of detection was determined to be as low as 30.1 nM. Furthermore a 1:1 stoichiometry was identified from the results of Job's plot and HR-MS. Density functional theory (DFT) calculation results expressed that the intramolecular charge transfer (ICT) during chelation is responsible for quenching of fluorescence. Besides, the fluorescence life time measurement and ethylenediaminetetraacetic acid (EDTA) titration method revealed the stability and reversibility of the sensor. Practical use of the sensor was achieved through the quantitative analysis of spiked Cu (II) ion in real water samples with good recoveries, and biological experiments exposed that the sensor was less toxic and could be applied in fluorescence imaging of Cu (II) in living cells.

Luminous Insights: Exploring Organic Fluorescent "Turn-On" Chemosensors for Metal-Ion (Cu+2, Al+3, Zn+2, Fe+3) Detection

There are several metal ions that are vital for the growth of the environmental field as well as for the biological field but only up to the maximum limit. If they are present in excess, it could be hazardous for the human health. With the growing technology, a series of various detection techniques are employed in order to recognize those metal ions, some of them include voltammetry, electrochemical methods, inductively couples, etc. However, these techniques are expensive, time consuming, requires large storage, advanced instrumentation, and a skilled person to operate. So, here comes the need of a sensor and it is defined as a miniature device which detects the substance of interest by giving response in the form of energy change. So, from past few decades, many sensors have been formulated for detecting metal ions with some basic characteristics like selectivity, specificity, sensitivity, high accuracy, lower detection limit, and response time. Detecting various metal ions by employing chemosensors involves different techniques such as fluorescence, phosphorescence, chemiluminescence, electrochemical, and colorimetry. The fluorescence technique has certain advantages over the other techniques. This review mainly focuses on the chemosensors that show a signal in the form of fluorescence to detect Al+3, Zn+2, Cu+2, and Fe+3 ions.

A Terbium Ion-Based Dual-Ligand Fluorescent Probe for Highly Selective and Sensitive Detection of Cu2+ Ions

In this study, a fluorescent probe (GMP-Tb-SSA) utilizing lanthanide coordination polymer nanoparticles, GMP-Tb, as a sensing platform, and 5-sulfosalicylic acid (SSA) as a cofactor ligand was proposed for the detection of copper ions (Cu2+). GMP-Tb was synthesized by the self-assembly of guanine monophosphate (GMP) and terbium ion (Tb3+), and SSA was introduced as a sensitizer into the GMP-Tb network. Cu2+ could efficiently inhibit the electron transfer from the ligand GMP to the central ion, Tb3+, leading to a significant quench of fluorescence of Tb3+. The method is highly selective with a linear range of 0 to 21 µM and a detection limit of 300 nM. It is not interfered by metal ions, amino acids, and other species, and can be successfully applied to the detection of Cu2+ in real water samples.

Recent Advances in Thiourea Based Colorimetric and Fluorescent Chemosensors for Detection of Anions and Neutral Analytes: A Review

Thioureas and their derivatives are organosulfur compounds having excellent biological and non-biological applications. These compounds contain S- and N-, which are nucleophilic and allow for establishing inter-and intramolecular hydrogen bonding. These characteristics make thiourea moiety a very important chemosensor to detect various environmental pollutants. This article covers a broad range of thioureas and their derivatives that are used for highly sensitive, selective, and simple fluorimetric (turn-off and turn-on), and colorimetric chemosensors for the detection and determination of different types of anions, such as CN-, AcO-, F-, ClO- and citrate ions, etc., and neutral analytes such as ATP, DCP, and Amlodipine, etc., in biological, environmental, and agriculture samples. Further, the sensing performances of thioureas-based chemosensors have been compared and discussed, which could help the readers for the future design of organic fluorescent and colorimetric sensors to detect anions and neutral analytes. We hope this study will support the new thoughts to design highly efficient, selective, and sensitive chemosensors to detect different analytes in biological, environmental, and agricultural samples.

Synthesis of N-aminophalimides derived from α-amino acids: Theoretical study to find them as HDAC8 inhibitors by docking simulations and in vitro assays

Phthalimides are valuable for synthesis and biological properties. New acetamides 3(a-c) and 4(a-c) were synthesized and characterized as precursors for novel N-aminophalimides 5(a-c) and 6(a-c). Structures of 4a, 5(a-b), and 6(a-b) were confirmed by single crystal X-ray. Docking studies identified compounds with favorable Gibbs free energy values for binding to histone deacetylase 8 (HDAC8), an enzyme targeted for anticancer drug development. These compounds bound to both the orthosteric and allosteric pockets of HDAC8, similar to Trichostatin A (TSA), an HDAC8 inhibitor. 6(a-c) contain hydroxyacetamide moiety as a zinc-binding group, a phthalimide moiety as a capping group, and aminoacetamide moiety as a linker group, which are important for ligand-receptor binding. ΔG values indicated that compounds 5b, 6b, and 6c had higher affinity for HDAC8 in the allosteric pocket compared to TSA. In vitro evaluation of inhibitory activities on HDAC8 revealed that compounds 3(a-c) and 5(a-c) showed similar inhibitory effects (IC50 ) ranging from 0.445 to 0.751 μM. Compounds 6(a-c) showed better affinity, with 6a (IC50  = 28 nM) and 6b (IC50  = 0.18 μM) showing potent inhibitory effects slightly lower than TSA (IC50  = 26 nM). These findings suggest that the studied compounds hold promise as potential candidates for further biological investigations.

Design and Development of Inexpensive Paper-Based Chemosensors for Detection of Divalent Copper

Simple, portable, and low-cost paper-based sensors are alternative devices that have the potential to replace high-cost sensing technologies. The compatibility of the paper base biosensors for both chemical and biochemical accentuates its feasibility for application in clinical diagnosis, environmental monitoring, and food quality monitoring. High concentration of copper in blood serum and urine is associated with diseases like liver diseases, carcinomas, acute and chronic infections, rheumatoid arthritis, etc. Detection of copper concentration can give an early sign of Alzheimer disease. Apart from that genetic Wilson's disease can be detected by evaluating the concentration of copper in the urine. In view of the above advantages, a novel and the highly sensitive paper-based sensor has been designed for the selective detection of Cu2+ ions. The fast and highly sensitive chemiresistive multi-dye system sensor can detect Cu2+ ions selectively in as low as 2.23 ppm concentration. Least interference has been observed for counter ion in the detection of Cu2+. Copper chloride, nitrate, and acetate were used to validate the detection process. This assay provides a very high selectivity of Cu2+ ion over other metal cations such as Na+, Mg2+, Ca2+, etc. The easy preparation and high stability of dye solutions, easy functionalization of the paper-based sensors, high selectivity over other cations, low interference of counter anion, and significantly low detection limit of 2.23 ppm make it an effective Cu2+ ion sensor for real-time application in near future.

Nanoporous ZIF-8 Microparticles as Acetylcholinesterase and Alkaline Phosphatase Mimics for the Selective and Sensitive Detection of Ascorbic Acid Oxidase and Copper Ions

In this study, the alkaline phosphatase (ALP)-like activity of zeolitic-imidazolate framework-8 (ZIF-8) is reported for the first time. Then, colorimetric sensors for the ascorbic acid oxidase (AAO) and copper ion (Cu²⁺) detection were developed based on the acetylcholinesterase (AChE)- and ALP-like activities of ZIF-8. The ZIF-8 has good mimetic enzyme activity and exhibits high affinity to the substrates. Its AChE- and ALP-like activities also have good reusability and storage stability. Good linear dependences are obtained in the range of 1.3-250.0 μM (AChE-like activity-based) and 4.5-454.5 μM (ALP-like activity based) for Cu²⁺ detection. Furthermore, good linear dependence is also obtained based on the ALP-like activity of ZIF-8 for AAO detection in the range of 2.3-454.5 U/L. Their limits of detection (LODs) are calculated to be 0.7 µM, 2.8 µM, and 1.8 U/L, respectively. Finally, the sample spiked recoveries of Cu²⁺ in tap water, Cu²⁺, and AAO in human serum and rabbit plasma were measured, and the results are in the range of 80.0-119.3%. In short, the preparation of ZIF-8 is simple, environmentally friendly, and harmless, and can realize highly selective detection of AAO and Cu²⁺ in an efficient and fast process.

A Sensitive and Selective Colorimetric Method Based on the Acetylcholinesterase-like Activity of Zeolitic Imidazolate Framework-8 and Its Applications

In this study, a simple colorimetric method was established to detect copper ion (Cu²⁺), sulfathiazole (ST), and glucose based on the acetylcholinesterase (AChE)-like activity of zeolitic imidazolate framework-8 (ZIF-8). The AChE-like activity of ZIF-8 can hydrolyze acetylthiocholine chloride (ATCh) to thiocholine (TCh), which will further react with 5,5′-dithiobis (2-nitrobenzoic acid) (DTNB) to generate 2-nitro-5-thiobenzoic acid (TNB) that has a maximum absorption peak at 405 nm. The effects of different reaction conditions (buffer pH, the volume of ZIF-8, reaction temperature and time, and ATCh concentration) were investigated. Under the optimized conditions, the value of the Michaelis-Menten constant (K_m) is measured to be 0.83 mM, which shows a high affinity toward the substrate (ATCh). Meanwhile, the ZIF-8 has good storage stability, which can maintain more than 80.0% of its initial activity after 30 days of storage at room temperature, and the relative standard deviation (RSD) of batch-to-batch (n = 3) is 5.1%. The linear dependences are obtained based on the AChE-like activity of ZIF-8 for the detection of Cu²⁺, ST, and glucose in the ranges of 0.021–1.34 and 5.38–689.66 µM, 43.10–517.24 µM, and 0.0054–1.40 mM, respectively. The limit of detections (LODs) are calculated to be 20.00 nM, 9.25 µM, and 5.24 µM, respectively. Moreover, the sample spiked recoveries of Cu²⁺ in lake water, ST in milk, and glucose in strawberry samples were measured, and the results are in the range of 98.4–115.4% with the RSD (n = 3) lower than 3.3%. In addition, the method shows high selectivity in the real sample analysis.

A chemosensing approach for the colorimetric and spectroscopic detection of Cr3+, Cu2+, Fe3+, and Gd3+ metal ions

Metal cations are present in domestic and industrial wastewater and have adverse effects on human and aqueous life. The present study describes the development of the molecular probe 9-anthracen-9-ylmethylene)hydrazineylidene)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol (AMHMPQ) to detect Cr³⁺, Cu²⁺, Fe³⁺, and Gd³⁺ ions by using UV-visible, fluorescence, colorimetric and excitation-emission matrix (EEM) spectroscopy techniques. The interaction of Cr³⁺, Cu²⁺, Fe³⁺, and Gd³⁺ can be observed by the absorption maxima shift, turn-off, colour changes, and EEM shifts. In addition, fluorescence limits of detection 17.66 × 10^-6 M, 6.44 × 10^-9 M, 28.87 × 10^-8 M, and 12.49 × 10^-6 M in wide linear ranges, low limits of quantifications, high values of Stern-Volmer constant, Job's plot and Benesi-Hildebrand plot justify the 1:1 association affinity with association constants of 1.46 × 10⁴ M^-1, 1.86 × 10⁷ M^-1, 2.69 × 10⁵ M^-1, 2.13 × 10⁴ M^-1 for AMHMPQ-metal ions (Cr³⁺, Cu²⁺, Fe³⁺, and Gd³⁺ ions), respectively. Paper- and mask-based kits are developed to explore the utility of the designed chemosensor. Additionally, AMHMPQ acts as a reusable sensor for two, seven, two, and zero cycles for Cr³⁺, Cu²⁺, Fe³⁺, and Gd³⁺ ions, respectively, when checked with EDTA.

Verbascoside extracted from Clerodendrum inerme: A natural monomer for the fabrication of a sensitive electrochemical Cu(II) sensor

Verbascoside is isolated from the whole plants of the Verbenaceae family and demonstrates significant levels of bioactivity. In this work, we report on the isolation of verbascoside, a phenolic glycoside, from the stems of Clerodendrum inerme collected in Vietnam and verify its structure by comparing its spectroscopic data with those reported in the literature. Verbascoside is then applied as a monomer for the electrochemical deposition of a layer of polyverbascoside onto glassy carbon electrodes toward Cu2+ sensing. Electrochemical results demonstrate that the polyverbascoside-modified glassy carbon electrode is highly selective for Cu2+ ions compared to other evaluated ions including Ni2+ and Co2+. The developed sensor can detect Cu2+ in a concentration range from 0 to 175 μM with a sensitivity of 0.372 µA µM−1 and a limit of detection of 50 nM Cu2+ ions.

Real time sensor for Fe3+, Al3+, Cu2+ & PPi through quadruple mechanistic pathways using a novel dipodal quinoline-based molecular probe

A quinoline-based small molecular probe, H₂L was designed, synthesized and characterized by different spectroscopic methods. It was utilized as a multi-responsive probe for the detection of Fe³⁺, Al³⁺, Cu²⁺ and PPi. It showed very selective instant turn-on fluorimetric response towards Fe³⁺and Al³⁺ with a detection limit in nanomolar range. Solutions of H₂L containing Fe³⁺ or Al³⁺ could sequentially sense PPi by a turn-off mechanism. Also, H₂L could determine the presence of Cu²⁺ very selectively among a series of other metal ions by a sharp change in colour. Detection of Cu²⁺ through colorimetry was further investigated by systematic UV-Vis studies and the potential of H₂L to act as a potential colorimetric sensor for Cu²⁺ was suitably established. Filter-paper strip experiments were conducted to demonstrate the practical utility of the proposed sensor. Potential applications of H₂L as a sensor for pH in the acidic range has also been explored.

An IMPLICATION-logic-based fluorescent probe for sequential detection of Cu2+ and phosphates in living cells

In this manuscript, we developed an IMPLICATION logic fluorescent probe, HL, for the sequential detection of Cu2+ and phosphate anions in extracellular and intracellular environments.

Europium(III) complex fluorescent sensor for dual channel recognition of Sn2+ and Cu2+ ions in water

A new europium(III) complex Eu(tta)₃L₁ (1a) (L₁ = (2-(3,5-dimethoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), tta = 2-thenoyltrifluoroacetone) has been prepared and synthesized. The structure of complex was completely determined by several different analytical techniques including single-crystal X-ray diffraction, ¹H and ¹³C NMR. The crystal structure of the complex 1a belonged to monoclinic system with the space group P2₁/n. Its fluorescent properties were systematically studied in details by adding different metal ions in deionized water. Upon addition of Sn²⁺, its fluorescence intensity was strengthened and centered at 460 nm. And when Cu²⁺ was added, its fluorescence emission intensity was quenched quickly. The LODs for Sn²⁺ and Cu²⁺ were calculated to be 4.52 × 10^-7 mol L^-1 and 1.11 × 10^-7 mol L^-1, respectively. Furthermore, this sensor was successfully employed to monitor Sn²⁺ and Cu²⁺ in practical samples.

An oxacalix[4]arene-derived dual-sensing fluorescent probe for the relay recognition of Hg2+ and S2− ions

A rhodamine B-functionalized oxacalix[4]arene architecture has been designed as a dual-responsive probe for the sequential recognition of Hg2+ and S2− ions.

Turn-on detection of assorted phosphates by luminescent chemosensors

This review illustrates a variety of luminescent chemosensors for the selective detection of assorted phosphates via the “Turn-On” emission mechanism with focus on their design aspects, chemical structures and sensing mechanism.

A turn-on red-emitting fluorescent probe for determination of copper(II) ions in food samples and living zebrafish

Herein, we developed a turn-on red-emitting fluorescent probe for the sensitive and selective detection of copper ions (Cu²⁺) in food samples and living zebrafish. The probe employs a hemicyanine scaffold as the fluorophore and a 2-pyridinecarbonyl group as the recognition receptor and quenching moiety. The 2-pyridinecarbonyl moiety can be specifically cleaved by Cu²⁺ and results in an approximately 18-fold fluorescence enhancement of the probe, thereby providing a fluorescence turn-on assay for Cu²⁺. Additionally, the probe exhibited excellent selectivity, high sensitivity, a broad linear relationship (0.020 to 8.0 μM), and a low limit of detection (4.0 nM, S/N = 3) for Cu²⁺. Concomitantly, the probe exhibited satisfactory analytical performance when used with actual food samples. Moreover, the probe could be used for in situ determination of Cu²⁺ in both living plant tissues and in living zebrafish.

A New bis(rhodamine)-Based Colorimetric Chemosensor for Cu2

A novel sensor (RD) bearing rhodamine B and 4-tert-Butyl phenol unit have been designed and synthesized using microwave irradiation. The sensor allows selective detection of Cu2+ by forming absorptive complex and trigger the formation of highly colored ring-open spirolactam. The recognition ability of the sensor was investigated by absorbance, Job's plot, infrared (IR) and time dependent-density functional theory (TD-DFT) calculations.

Sensitive detection of sulfide ions in red region based on luminescence resonance energy transfer between upconversion nanoparticles and dye-670

Many sulfides are toxic substances that easily harm the respiratory tract, therefore affecting respiratory function or damaging other organs of the body, leading to its failure. Therefore, there is a pressing need to develop methods for sensitive detection of sulfur ions (S^2- ). Based on luminescence resonance energy transfer (LRET) theory, we report the construction of a near-infrared (NIR) excitation luminescence probe using NaGdF₄ :Yb³⁺ ,Er³⁺ @NaYF₄ upconversion nanoparticles (UCNPs) as the donor and dye-670 as the receptor for detection of S^2- . When UCNPs and dye-670 molecules were combined using ligand exchange and electrostatic attraction, LRET occurred and UCNP luminescence was quenched. When S^2- was added to the system, sulfide ions were able to destroy the double bond of the dye, inhibiting LRET and restoring UCNP luminescence. Under optimum condition, the linear range of S^2- detection was 0.65-18.2 μM, and the detection limit was 34.2 nM. This method was applied for determination of S^2- in water with satisfactory results.

A simple pyrimidine based colorimetric and fluorescent chemosensor for sequential detection of copper (II) and cyanide ions and its application in real samples

In this study, a new pyrimidine-based chemosensor (PyrCS) has been developed for sequential detection of copper (II) and cyanide ions. The PyrCS has revealed high sensitivity and selectivity toward copper ion over other metal ions in aqueous media. The PyrCS as an optical probe exhibited a distinct color change and a bathochromic shift in UV spectra in the presence of copper ion in a few seconds due to the formation of stable complex (PyrCS-Cu²⁺). The results confirmed that the PyrCS has a widely linear detection range of 0.3-30 μM toward Cu²⁺. The calculated limit of detection for Cu²⁺ ions was low as 0.116 μM. Moreover, the fluorescent intensity of PyrCS at 507 nm was significantly quenched in the presence of Cu²⁺ and Fe²⁺ ions. Additionally, complex PyrCS-Cu²⁺ was successfully used to detect cyanide ions via Cu²⁺ displacement approach. The free PyrCS was recovered after adding the CN‾ ions in a few seconds due to the formation of the stable copper cyanide complex Cu(CN)_x. The calculated LOD for CN‾ ions was low as 0.320 μM. The data also clarified that the other competing anions did not create a clear color change in solutions. Since the proposed method could provide a vivid colorimetric response in the presence of detected analytes within the pH range of 3-9, we can claim that the developed chemosensor can be utilized in any physical and biological conditions.

Fluorescence "Turn On-Off" Sensing of Copper (II) Ions Utilizing Coumarin-Based Chemosensor: Experimental Study, Theoretical Calculation, Mineral and Drinking Water Analysis

Herein, we report the preparation of a fluorescent sensor based on coumarin derivative for copper (II) ion sensing in CH₃CN/HEPES media. 6,7-dihydroxy-3-(4-(trifluoro)methylphenyl)coumarin (HMAC) sensor was fabricated and analyzed by spectroscopic techniques. The sensor demonstrates "turn on-off" fluorescence quenching in the presence of copper (II) ions at 458 nm. A clear complex between the chemosensor HMAC and copper (II) ions was characterized by ESI-MS as well as the Job's method. Also, the limit of detection (LOD, 3σ/k) value was determined as 24.5 nM in CH₃CN/HEPES (95/5, v/v) buffer media (pH = 7.0). This value is lower than the admissible level of copper (II) ions in drinking water (maximum 31.5 μM) reported by EU Water Framework Directive (WFD) and World Health Organization (WHO) guidelines. The theoretical calculations (density functional theory, DFT) have been performed for the geometric optimized structures. As a final stage, real sample analyses have successfully been performed by using HMAC, as well as ICP-OES method. The relative standard deviation for copper (II) in mineral and drinking water samples has been determined to be below 0.15% and recovery values are in the range of 95.48-109.20%.

Three Novel Zn-Based Coordination Polymers: Synthesis, Structure, and Effective Detection of Al3+ and S2- Ions

Three novel Zn-based coordination polymers (CPs), [Zn(MIPA)]_n (1), {[Zn(MIPA)(4,4′-bipy)_0.5(H₂O)]·1.5H₂O}_n (2), and {[Zn(MIPA)(bpe)]·H₂O}_n (3) (MIPA = 4-methoxyisophthalic acid, 4,4′-bipy = 4,4′-bipyridine, bpe = (E)-1,2-di(pyridine-4-yl)ethane), were constructed by ligand 4-methoxyisophthalic acid under solvothermal conditions. Compound 1 features a beaded 2D-layer architecture, while compound 2 presents a 2-fold interpenetrating structure with a uninodal three-connected hcb topology. Compound 3 has a 3-fold interpenetrated four-connected dmp topology. Photoluminescence investigations of compound 2 were explored in detail, by which ions were detected, and it was observed to have the highest quenching efficiency toward Al³⁺ and S²⁻ ions. The possible fluorescence quenching mechanisms of 2 toward Al³⁺ and S²⁻ ions were also explored. To the best of our knowledge, this is the first potential dual-responsive luminescent probe based on a Zn(II) coordination polymer for detecting Al³⁺ and S²⁻ ions via a luminescence quenching effect in ethanol.

A luminescent terbium coordination polymer as a multifunctional water-stable sensor for detection of Pb2+ ions, PO43− ions, Cr2O72− ions, and some amino acids

It is the first Ln-CP fluorescence probe for synchronous determination of Tyr and Trp in the presence of other amino acids.

A dual-responsive colorimetric probe for the detection of Cu2+ and Ni2+ species in real water samples and human serum

The monitoring of heavy transition metals has increasingly attracted great attention because they pollute the environment and have unique physiological functions. Chemosensors are useful tools for monitoring heavy transition metals due to their simple visualization, excellent sensitivity and high selectivity. Herein, we have developed a novel chemosensor for the detection of water-soluble Cu2+ and Ni2+ species with different mechanisms, and low detection limits of 2.1 nM for Cu2+ and 1.2 nM for Ni2+ were obtained. The colorimetric probe CPH has been applied to qualitative and quantitative detection of Cu2+ and Ni2+ species in real samples.

Highly Selective and Sensitive Detection of PO4 3- Ions in Aqueous Solution by a Luminescent Terbium Metal-Organic Framework

A luminescent terbium metal-organic framework [Tb(HPIA-)(PIA2-)(H2O)2] (Tb-MOF), synthesized by a lanthanide metal ion (Tb3+) and nitric heterocyclic carboxylic acid ligands H2PIA (H2PIA = 5-(1H-pyrazol-3-yl)isophthalic-acid), was structurally characterized as a three-dimensional skeleton structure in which layered coordination frameworks are connected by hydrogen bonds. Based on the antenna effect, Tb-MOF can emit bright green fluorescence under 254 nm excitation, and the fluorescence emission presents excellent durability in aqueous solutions among a wide pH range. Moreover, the structure of Tb-MOF also possesses outstanding thermal stabilities. In some ways, PO4 3- and its derivatives are thought to be a kind of pollutant ion causing series environmental and health problems. The as-synthesized Tb-MOF exhibits prominent selectivity and remarkable sensitivity for detecting PO4 3- as an easy-to-use fluorescent probe with low detection limit, fast response, and wide detection range. Therefore, Tb-MOF has significant applications in the fields of human health and environmental monitoring.

A new phthalimide based chemosensor for selective spectrophotometric detection of Cu(II) from aqueous medium

A new phthalimide based chemosensor 2-(Pyridin-2-yl-(pyridine-2-ylimino)methyl)isoindoline-1,3-dione (PP3) was synthesized and characterized by IR, LCMS and NMR spectroscopic methods. The metal ions sensing ability of PP3 was examined by naked-eye and UV-Vis absorption techniques. The colorless solution of PP3 turned to yellow upon addition of Cu²⁺ and a new absorption band appeared at 434 nm. The Job's plot and HR-MS data confirms the formation of a new complex species between PP3 and Cu²⁺ in 1:1 binding stoichiometry. The sensor PP3 allowed the detection of Cu²⁺ down to 1.65 μM without any remarkable interference from the other tested metal cations.