Selective Ion Detection Research Articles

Near-infrared fluorescence probes for the selective and sensitive detection of sulfur ions based on glutathione capped gold nanoclusters

The excellent anti-interference ability of near-infrared (NIR) fluorescent materials derived from long-wavelength emission has made them one of the most fascinating fluorescence probes.

Glowing discoveries: Schiff base-cyanostilbene probes illuminating metal ions and biological entities.

Schiff bases featuring cyanostilbene units have emerged as versatile and highly effective probes for the selective detection of various metal ions as well as biologically important species. This review comprehensively highlights recent advances in the development and application of the probes, which exhibit remarkable Aggregation-Induced Emission (AIE), Twisted Intramolecular Charge Transfer (TICT), and Excited-State Intramolecular Proton Transfer (ESIPT) properties. These unique structural characteristics facilitate their potential applications in the detection of biologically important metal ions such as Zn2+, Fe3+, Cu2+, Hg2+ and Co2+ ions with high sensitivity and selectivity. Furthermore, these probes have demonstrated significant potential in the recognition of vital biological species, including arginine, hydrazine and hypochlorite (ClO-). The present review discusses the underlying detection mechanisms, emphasizing the role of the Schiff base and cyanostilbene moieties for the selective detection of particular biologically important entities. Moreover, this discussion highlights the practical applications, problems, and future directions in this fast-growing field, emphasizing the vital importance of these probes in both analytical chemistry and bioassays.

Excited-state intramolecular proton transfer (ESIPT) active interwoven polycatenated coordination polymer for selective detection of Al3+ and Ag+ ions along with water detection in less polar solvents.

The external stimuli-responsive excited-state intramolecular proton transfer (ESIPT) on/off mechanism is a unique and expedient sensing method that offers easy monitoring through the transition between dual and single-peak emissions. To avail this advantage of ESIPT-based sensing for selective metal ion detection and trace water detection, we have synthesized a 2,5-dihydroxyterephthalate (dht)-based interwoven polycatenated coordination polymer (1). The synthesized compound has been thoroughly characterized using single-crystal and powder X-ray diffraction techniques, along with other physicochemical methods. The synthesized compound exhibits a visual luminescence color change from faint yellow to bright green under UV irradiation in the presence of Al3+ ions. This change is attributed to a blue shift in fluorescence maxima of the keto form of the dht ligand in contact with Al3+ ions. Additionally, the material detects Ag+ ions through an ESIPT-off mechanism. These significant changes in ESIPT - blue shifting for Al3+ and ESIPT-off for Ag+ - start in just 1 mM aqueous solutions of these ions. Significantly, the ESIPT-off for Ag+ is evident even in the presence of other interfering ions. Beyond metal ion detection, this material also offers both qualitative and quantitative sensing of trace amounts of water in various polar organic solvents, such as ethanol (EtOH), tetrahydrofuran (THF), isopropanol (IPA), acetone, and acetonitrile (ACN), through the ESIPT-on/off phenomenon. The activated framework of compound 1 (1') can detect 2%, 4%, 4%, 3%, and 3% water in acetone, ACN, EtOH, IPA, and THF, respectively; through the conversion from a single to dual hump emission alteration. The respective ESIPT peak shift and ESIPT-on/off in the presence of metal ions and water is explained by the interaction between the host coordination polymer and guest analytes.

A library of benzimidazole based amide and urea derivatives as supramolecular gelators – A comparative study

We present a set of alkyl chain functionalized benzimidazole based compounds containing amide and urea functional groups which were screened for their gelation behaviour. Both the sets bear similar molecular scaffolds, making them an excellent tool for determining the role of the supramolecular interactions involved in the gelation process. All the compounds were characterised using physico-chemical techniques like NMR and FT-IR. The gels were subjected to small angle neutron scattering studies (SANS), rheological studies, SEM and FT-IR. In order to rationalize the gelation behaviour, solvent parameter studies were conducted. The results show a dependence on refractive index of solvent, polarizability and dispersion interactions. The respective orientation of amide and conformation in urea based compounds were explored and studied using computational calculations and their corresponding effect on the resulting supramolecular superstructures was scrutinized. The compounds were also explored to act as chemosensor for selective detection of mercuric ions with exceptionally low LOD (limit of detection) values.

Ratiometric fluorescence sensor based on europium-organic frameworks for selective and quantitative detection of cerium ions

BackgroundDue to the unavoidable use of cerium in daily life, the accumulation of cerium in the environment increases health risks for humans. Therefore, it is crucial to develop a chemical sensing technology for the rapid, sensitive, and selective detection of cerium ions. ResultsIn this research work, a novel two-dimensional chain structure of a europium-based metal organic framework (Eu-MOF) [Eu2(tcpa)(Htcpa)2] was synthesized by using 3,4,5,6-tetrachloro-1,2-benzenedicarboxylic acid (H2TCPA) as the ligand and europium nitrate as the metal source. The results of powder X-ray diffraction and thermogravimetric analysis show that the synthesized Eu-MOF has excellent chemical and thermal stability. When the Eu-MOF suspension was excited by ultraviolet light at 292 nm, four fluorescence emissions were observed at 420, 595, 620 and 705 nm. It was particularly interesting that when cerium ions (Ce3+/Ce4+) were added to the Eu-MOF suspension, the fluorescence intensity at 420 nm was enhanced, while the fluorescence at 620 nm was quenched. On this basis, a ratiometric fluorescent sensor for detecting cerium ions was constructed, which has a good linear relationship in the range of 0.05–15 μM and a detection limit of 16 nM. The plausible mechanism of the change in the fluorescence characteristics of Eu-MOF caused by cerium ions was discussed in detail. Through the study of fluorescence lifetime and ultraviolet absorption, it was proven that the mechanism of Ce3+-quenching Eu-MOF fluorescence is the inner filter effect. Photoinduced electron transfer and internal filtering effects lead to fluorescence quenching at 620 nm, while redox reactions lead to fluorescence enhancement of the ligand at 420 nm. SignificanceThe proposed ratiometric fluorescence sensor was successfully employed for the detection of cerium ions in real water samples, confirming that it can be used as an alternative method for the detection of Ce3+ and Ce4+ in environmental samples.

Ultra-sensitive mercury detection from surface wrapping of carbon dots reduced and decorated silver nanoparticles on SERS fiber probes

Highly selective and sensitive detection of toxic mercury ions (Hg2+) has become a critical issue in recent decades, due to increasing environmental and health requirements. Herein, carbon dots reduced and decorated Ag (CDs/Ag) nanoparticles based fiber probes were fabricated, providing a “turn-off” surface-enhanced Raman spectroscopy (SERS) for low-concentration Hg2+ ions detection. The CDs/Ag nanoparticles fiber probe exhibits better SERS performance than that of Ag nanoparticles fiber, attributed to the stronger electromagnetic intensities induced by localized surface plasmon resonance (LSPR) and larger hot-spot areas resulting from the interaction between silver nanoparticles and carbon dots, under 532 nm beam excitation. As low as 10−11 M Hg2+ ions can be detected through the decrease in Raman scattering intensities of CV molecules, due to the SERS inactive Hg metal layer wrapping the surface of silver nanoparticles, through the reduction of Hg2+ ions by carbon dots. The dropping of silver nanoparticles’ LSPR induced absorption peak, EDS elemental mapping, and XPS analysis all confirm that the wrapping decreases the LSPR effect and corresponding Raman intensity. Furthermore, the detection shows high selectivity and can only be applied for detecting Hg2+ ions, owing to the reduction capability of carbon dots. The close analysis results obtained using SERS fiber probes and commercial inductively coupled plasma-mass spectrometry (ICP-MS) for detecting Hg2+ ions in real water sample confirm the reliability of this detection method. This research indicates the CDs/Ag fiber probe has a great potential application for environmental Hg2+ ions detection.

Synthesis, Sensing Performance and DFT Studies of a Novel Coumarin-based Schiff Base As a Turn-on Fluorescence Probe for Zinc Ion Detection.

The design and development of novel efficient fluorescent chemical sensors for the selective detection of ions is currently of significant importance in supramolecular chemistry. Since zinc is a ubiquitous, indispensable and the second most abundant metal ion in the human body, developing chemosensors that can accurately discriminate between Zn2+ and Cd2+ ions has been a challenge due to their similar properties as they are in the same group of the periodic table. Therefore, a technique to trace and visualize free zinc ions is demanded. In this study, an innovative coumarin-based Schiff base (L) was synthesized and characterized by 1H NMR, 13C NMR and mass spectroscopy. A novel "Turn On" fluorescence chemosensor platform was developed for trace amounts of Zn2+ ions. The fluorescence Job's plot measurement was used to determine the complexation ratio between the probe and Zn2+ ion, which showed a maximum point indicating the formation of a ML2 adduct. Additionally, the geometrical parameters calculated using DFT and TD-DFT calculations were in close agreement with the experimentally observed values.

Phenazine-based fluorescence probes for simultaneous sensing of silver and iodide ions

The selective and sensitive detection of silver ions (Ag+) and iodide ions (I−) is of paramount importance in various scientific and industrial domains. In this paper, we present phenazine-based fluorescence probes, synthesized through a scalable and straightforward procedure, for the simultaneous sensing of Ag+ and I−ions in solution phase. The introduction of Ag+ led to ratiometric changes, manifesting in alterations of both solution color (from colorless to yellow) and fluorescence signal (from blue to cyan). Mechanistic investigations unveil that Ag+ coordinate with the phenazine nitrogen ends, forming self-assembled nanostructures characterized by significant charge-transfer properties. Moreover, we observed that the nature of the terminal alkyl residue played a pivotal role in governing the binding interaction with Ag+, with aliphatic residues featuring positively charged quaternary nitrogen ends exhibiting notably reduced responses. Additionally, the in-situ formed metal complex, comprising 1.Ag+, proved to be highly effective in selectively analyzing I− ions. The exceptional binding affinity of Ag+ for I− ions, marked by an exceptionally low solubility product constant, facilitated the sequestration of Ag+, ultimately leading to the formation of free probe in the reaction medium. Our research showcases the capability of phenazine-based probes in selective ion sensing applications, and their adjustable properties position them as promising options for a range of analytical and diagnostic uses.

Indole-based Fluorometric and Colorimetric Chemosensors for the Selective Detection of Cu2+: A Brief Review From the Year 2011-2021

The development of chemosensors has been driven by concurrently advanced research in fluorescence and colorimetric chemosensing. Over the last few decades, the development of copper ion-selective fluorogenic and chromogenic chemosensors has been extensively studied due to their high sensitivity, low cost, and simplicity. They can interact with the metal ion in a unique manner and create measurable color, fluorescence, or redox potential changes. Copper (Cu2+) ion is deemed the third most prevalent transition metal in human beings owing to its various biological and physiological processes. It has drawn a great deal of attention from many researchers in various disciplines such as biology, medicine, and environmental studies. However, an excessive buildup of copper in the body has been linked to several diseases. Thus, more recent research is being focused on developing fluorometric and colorimetric chemosensors for the selective detection of copper ions. Recently, there have been a lot of studies reported in this field of study that describe highly sensitive and sophisticated indole-based chemosensors for various metal ions of interest. In addition, indole derivatives possess inherent fluorescence properties due to their electron-rich nature caused by the π-excessive system of indole, and therefore they can be employed in chemosensors for metal ion detection. Both cations and anions employ it as a molecular recognition system. This review summarizes selective and sensitive Cu2+ ion detection accomplished byvarious indole-based chemosensors between the years 2011 to 2021. Furthermore, sensor design, sensing methods, ligand-metal binding stoichiometry, association constant, and the detection limit by the chemosensors are all summarized and explored.
 Keywords: Indole, Fluorescent chemosensors, Colorimetric chemosensors, Cu2+, Turn-on, Turn-off

Red-Emitting AIEE-Active Rhodamine-Based Ionic Liquid for the Ultrasensitive and Selective Detection of Mercury Ions.

A highly fluorescent, red-emitting rhodamine-based imidazolium ionic liquid (RhB-IL) was synthesized, and its structure was extensively verified using various spectroscopic techniques. The novel molecule showed exceptional selectivity toward Hg2+ ions over other competitive metal ions. Additionally, inspired by the solution results, a paper-based device was fabricated by embedding RhB-IL on paper strips and tested for the on-site detection of Hg2+ ions using a portable UV light source. Significantly, the device displayed excellent PL sensing behavior toward Hg2+ with a detection limit of 0.21 nM. In addition, RhB-IL showed the phenomena of aggregation-induced enhanced emission. In fact, when compared to the pure THF solution of RhB-IL, a remarkable 7.7-fold increase in PL intensity was seen for the 90% water fraction. Evidently, this is the first report of a paper-based Hg2+ detection system that uses a red fluorescent ionic liquid.

Spectroscopic and Theoretical Studies on the Selective Detection of Cyanide Ions by a Turn-On Fluorescent Chemo-Dosimeter and its Application in Living Cell Imaging.

A new chemo-dosimeter AK4 containing quinoline fluorophore has rationally been designed, synthesised and characterized using 1H and 13C NMR and mass spectral techniques. The probe senses explicitly CN- ion through a dramatic enhancement in fluorescence over other commonly coexistent anions in H2O:DMSO (9:1 v/v) medium over a broad pH range (4-10). 1H NMR titration revealed the deprotonation followed by nucleophilic addition reaction of CN-, which was supported by 13C NMR and mass spectral examinations. The Job's continuous variation method indicated the formation of a 1:1 adduct between AK4 and CN- with a binding constant of 1.62 × 104M-1. A limit of detection (LOD) towards CN- of 0.69 µM has been determined, which is much lower than the World Health Organization (WHO) recommended limit of CN- in drinking water (1.9 µM). The changes in the optical properties of AK4 upon reaction with CN- were delineated using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations. Moreover, fluorescence microscopic studies established that AK4 could be an effective probe for imaging intracellular CN- in HeLa cells.

A Schiff base chemical sensor for selective detection of hexavalent chromium ions: Real sample application

In this study, a straightforward Schiff base (2-(phenylmethyl-1-hydrazine formamide)) was synthesized via ionic liquid catalysis using benzaldehyde and aminourea hydrochloride. This approach represents a simple, efficient, and environmentally friendly synthesis method, with the added benefit of recyclability and reusability of the ionic liquid catalyst. Additionally, the Schiff base exhibits considerable capability for anion detection and demonstrates selective identification of CrO42− and Cr2O72− across different pH environments. The stoichiometric ratio was determined to be 2:1 through UV–vis absorption titration, with detection limits for CrO42− and Cr2O72− measured at 6 × 10−5 M and 7 × 10−5 M, respectively. To assess the probe's complexation mechanism with hexavalent chromium ions, infrared spectroscopy, and hydrogen nuclear magnetic resonance spectroscopy were employed.

Electrochemical and Colorimetric Nanosensors for Detection of Heavy Metal Ions: A Review.

Human exposure to acute and chronic levels of heavy metal ions are linked with various health issues, including reduced children's intelligence quotients, developmental challenges, cancers, hypertension, immune system compromises, cytotoxicity, oxidative cellular damage, and neurological disorders, among other health challenges. The potential environmental HMI contaminations, the biomagnification of heavy metal ions along food chains, and the associated risk factors of heavy metal ions on public health safety are a global concern of top priority. Hence, developing low-cost analytical protocols capable of rapid, selective, sensitive, and accurate detection of heavy metal ions in environmental samples and consumable products is of global public health interest. Conventional flame atomic absorption spectroscopy, graphite furnace atomic absorption spectroscopy, atomic emission spectroscopy, inductively coupled plasma-optical emission spectroscopy, inductively coupled plasma-mass spectroscopy, X-ray diffractometry, and X-ray fluorescence have been well-developed for HMIs and trace element analysis with excellent but varying degrees of sensitivity, selectivity, and accuracy. In addition to high instrumental running and maintenance costs and specialized personnel training, these instruments are not portable, limiting their practicality for on-demand, in situ, field study, or point-of-need HMI detection. Increases in the use of electrochemical and colorimetric techniques for heavy metal ion detections arise because of portable instrumentation, high sensitivity and selectivity, cost-effectiveness, small size requirements, rapidity, and visual detection of colorimetric nanosensors that facilitate on-demand, in situ, and field heavy metal ion detections. This review highlights the new approach to low-cost, rapid, selective, sensitive, and accurate detection of heavy metal ions in ecosystems (soil, water, air) and consumable products. Specifically, the review highlights low-cost, portable, and recent advances in smartphone-operated screen-printed electrodes (SPEs), plastic chip SPES, and carbon fiber paper-based nanosensors for environmental heavy metal ion detection. In addition, the review highlights recent advances in colorimetric nanosensors for heavy metal ion detection requirements. The review provides the advantages of electrochemical and optical nanosensors over the conventional methods of HMI analyses. The review further provides in-depth coverage of the detection of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) ions in the ecosystem, with emphasis on environmental and biological samples. In addition, the review discusses the advantages and challenges of the current electrochemical and colorimetric nanosensors protocol for heavy metal ion detection. It provides insight into the future directions in the use of the electrochemical and colorimetric nanosensors protocol for heavy metal ion detection.

Synthesis of Mesoporous Eu3+-Doped Zinc/Silicate Phosphors for Highly Selective and Sensitive Detection of Sulfide Ions.

A mesoporous Eu3+-doped zinc/silicate phosphor with a large surface area (>100 m2g-1) and amorphous structure was prepared in an aqueous solution without using any organic template. The residual concentration of the Zn2+ ion in the filtrate is lower than the standard of effluent 3.5 ppm under a pH 8-11 preparation condition. When a sulfide ion (S2-) is present in aqueous solution, the phosphor can react with the sulfide ion to transform from the amorphous structure to the crystalline ZnS, which causes structural transformation and a subsequent decrease in luminescent intensity. This distinct phosphor with a high surface area and amorphous structure can be applied through the structure transformation mechanism for highly selective and sensitive detection of the sulfide ions at low concentrations. In addition, the luminescent efficiency was obtained from adjustments in the pH value, calcination temperature, and Eu3+ ion concentration. The quenching efficiency, the limit of detection (CLOD), S2- ion selectivity, and phosphor regeneration ability were systematically explored in sulfide ion detection tests. Due to the novel S2- ion-induced structural transformation, we found that the amorphous Eu3+-doped zinc/silicate phosphors demonstrate a CLOD sensitivity as low as 1.8 × 10-7 M and a high Stern-Volmer constant (KSV) of 3.1 × 104 M-1. Furthermore, the phosphors were easily regenerated through simple calcination at 500 °C and showed a KSV value of 1.4 × 104 M-1. Overall, the Eu3+-doped zinc/silicates showed many advantageous properties for detecting sulfide ions, including low toxicity, green synthesis, good selectivity, high sensitivity, and good renewability.

Simultaneous detection of Pb2+ and Cu2+ based on catalytic etching of AgNTs@AuNHs colorimetric nanoprobe

A colorimetric gold nanohexagonals coated silver nanotriangles (AgNTs@AuNHs) nanoprobe has been constructed for the ultrasensitive detection of trace Pb2+ and Cu2+, based on the fact that Pb2+ and Cu2+ as the catalyzer can selectively enhance the etching rate of AgNTs@AuNHs by S2O32−. In the presence of Pb2+, the inner AgNTs within the AgNTs@AuNHs undergo complete etching to form the hollow AuNHs, leading to the marked decrease in both absorbance and chrominance at 585 nm. In contrast, Cu2+ initiates an etching reaction on the AgNTs, subsequently extending to the AuNHs. These transformations give rise to the formation of hollow gold nanotriangles, accompanied by pronounced red-shifts in the absorption peaks of the detection system. The distinct optical responses induced by Pb2+ and Cu2+ in the AgNTs@AuNHs nanoprobe enable the sensitive and selective detection and quantification of these heavy metal ions. Furthermore, we successfully extracted RGB data from the color changes of AgNTs@AuNHs nanoprobe, enabling a straightforward visual readout for detection of Pb2+ and Cu2+. This method yields satisfactory recoveries when applied to the analysis of Pb2+ and Cu2+ in river water, rice, and onion samples, with detection results closely matching those obtained using ICP-MS. These results collectively underscore the practical applicability of the AgNTs@AuNHs nanoprobe.

Highly selective and sensitive photoelectrochemical detection of silver ions in complex industrial wastewater

Substandard discharge of industrial wastewater leads to abundant silver ions (Ag+) emission into water and soil, causing serious environmental threat. Precise and reliable detection of Ag+ is vital for environmental surveillance, while it remains a great challenge in complex actual environment. Herein, a lab-to-factory adoptable photoelectrochemical (PEC) approach for highly selective and sensitive detection of Ag+ in industrial wastewater has been first demonstrated. BiOI nanosheets (NSs) were prepared as photocathode and showed a spontaneous and selective ion-exchange process with Ag+ ions when it immersed into complicated industrial wastewater. The in situ generated AgI/Ag exhibits unique localized surface plasmonic resonance (LSPR) effect to modulate PEC signals for highly selective and sensitive Ag+ detection. As a result, the prepared photocathode delivers an ultralow detection limit (0.21 nM) and a broad linear range (up to 300 μM), outperforming most reported results. This work opens a feasible avenue for Ag+ monitoring in actual environment.

Electroactive poly(thionine) as imprinted polymer and reference probe simultaneously for ratiometric ion imprinted electrochemical Pb2+ sensor

In this work, an electrochemical sensor based on ion-imprinted polymer/Au nanoparticles/porous biochar (IIP/AuNPs/PBC) composite was proposed for the highly selective and sensitive detection of Pb2+. In this work, poly (thionine) (pTHI) served simultaneously as imprinted polymer and reference probe. It could not only realize the specific detection of Pb2+, but also provide an internal reference signal to eliminate the influence of human and environmental factors on the detection signal and further improve the stability of the sensor. In addition, the AuNPs/PBC composite with large specific surface area, excellent electron transport and electrocatalytic performance could effectively enhance the detection signal as a carrier material. At the same time, the AuNPs on the PBC surface would promote the formation of uniform and stable IIP through Au–S bonds. The synergistic effect between IIP, AuNPs/PBC and ratiometric signal mode gave the Pb2+ sensor excellent performance, including a wide linear range (0.1–1000 μg l−1), low detection limit (0.03 μg l−1, S/N = 3), excellent selectivity and stability. All these results indicate that the proposed sensor could provide a meaningful reference for highly selective detection of heavy metal ions (HMIs).

A coumarin-based fluorescent probe for highly selective detection of hazardous mercury ions in living organisms

In recent years, heavy metal mercury (II) pollutants have caused serious harm to human health and ecosystems. It has become critical to develop simple and highly selective sensing solutions for monitoring mercury (II). In this work, we designed and developed a novel fluorescent probe Coa-SH using the Hg2+-induced chemical reaction as a sensing mechanism. The probe Coa-SH showed high selectivity for the detection of Hg2+ by desulfurization reactions in solution. The test strips prepared with this probe could be applied to detect mercury ions in aqueous solutions. In addition, the probe Coa-SH provided a tool to detect Hg2+ in living systems. In living cells and zebrafish, the probe turned on bright red fluorescent signals in the presence of mercury ions. Importantly, the probe Coa-SH enabled Hg2+ detection in plant onion roots. This work provides an effective method for monitoring mercury ions in the environment and in living organisms.

A porphyrin-based metal-organic framework Al-TCPP for highly selective sensing of copper ions with exceptional low limit of detection

Sensitive and selective detection of copper ions (Cu2+) using fluorometric methods is of growing significance due to their widespread industrial use, which poses severe environmental and health risks. Here, we reported a porphyrin-based luminescent metal-organic framework (labelling LMOF), Al-TCPP, which exhibits dual emission peaks at 467 and 646 nm upon excitation by a single wavelength. When exposed to Cu2+ ions, the fluorescence peak at 646 nm reduces while the intensity of the 467 nm remains steady. This intriguing property enables the construction of a ratio-metric fluorescence sensor that utilizes an internal standard, significantly enhancing Cu2+ sensing accuracy. Our study establishes a linear relationship (y = 0.0454x + 0.3081) between the fluorescence intensity ratio I467/I646 and the Cu2+ concentration, with a high correlation coefficient R2 = 0.9943. Impressively, the present Al-TCPP achieves a low limit of detection (LOD) of 5.28 nM, one of the lowest reported values for Cu2+ detection. The mechanism underlying this phenomenon involves charge transfer from TCPP ligands in Al-TCPP to Cu2+ ions, as revealed by solid-state NMR and X-ray photoelectron spectroscopy analysis. Utilizing Al-TCPP, we successfully developed test strips for the practical Cu2+ detection. Furthermore, the present Al-TCPP has also effectively applied to determine low Cu2+ content in various samples, including water, tea and serum. This study demonstrates the versatility and practical applicability of present Al-TCPP LMOF for selective detection of Cu2+ ions in diverse environments.

A reaction-based carbazole-dicyanovinyl conjugated colorimetric and ratiometric fluorescent probe for selective detection of cyanide ions

In the present work, 4-(9′-hexylcarbazol-3′-yl)benzylidenemalononitrile 5 (probe L) was tested as a colorimetric and ratiometric fluorescent probe in dimethyl sulfoxide (DMSO) medium towards anions, cations and neutral molecules. The sensing properties of probe L were investigated by using UV–Vis absorption and fluorescence spectroscopy techniques. Probe L showed selectivity and sensitivity towards cyanide ions (CN–) in the presence of analytes used. Upon the addition of CN–, intramolecular charge transfer (ICT) band at 425 nm in UV spectrum disappeared. In addition, ICT emission intensity at 593 nm decreased and ligand-centred (LC) emission intensity at 480 nm increased. These findings indicate that nucleophilic conjugate addition of CN– to the dicyanovinyl group of probe L successfully occurs, hence forming a new adduct between probe L and CN–. In this adduct, π-conjugation was partially blocked, and the ICT transfer was hindered. Adduct formation was proved by Job’s plot, 1H NMR and FT-IR analysis. Probe L showed very low limit of detection (LOD) value of 1.467 nM towards CN–. Probe L was also applied to the CN– detection in real-world water samples by the spike and recovery method. The maximum relative standard deviation (RSD) value was 4.24, indicating this method works successfully. Therefore, probe L could find a potential use in detection of CN– in liquid media.