Ions In Environmental Samples Research Articles

A new oligo(N,O-donor)-like ratiometric fluorescent probe with FRET effect for dual-channel recognition of B4O72- ions in practical water samples

B4O72- ions are widely found in various production and living environments, and can cause serious effects on human health. For this reason, it is necessary to develop a high-efficiency method for the detection of B4O72- ions. Here a oligo(N,O-donor)-like dual-channel ratiometric fluorescence probe H3L was designed and synthesized for the detection of B4O72- ions in environmental samples. The recognition of B4O72- is based on the FRET effect by the probe H3L, the naphthalene ring partially serves as an energy donor, benzene ring partially serves as an energy acceptor, and phenolic oxygen acts as a reaction site for B4O72-. The probe H3L mainly displays the blue fluorescence of the donor; the presence of the B4O72- ions turns on the FRET effect, which will lead to yellow fluorescence of the benzene ring acceptor, enabling a ratiometric fluorescence recognition process. The probe has a large Stokes red shift (Δλ = 123 nm), which makes the emission wavelength after red shift more than 500 nm, and the obvious colourless to yellow color change can be observed by naked eyes, which solves the background fluorescence interference problem of short-wavelength fluorescence probe. At the same time, the probe has high selectivity and high sensitivity (low detection limit of 17.3 nM). In addition, we have successfully used this probe to detect B4O72- ions in actual samples. These results showed that the probe has a broad application prospect.

Fluorescent multichannel sensor array based on three carbon dots derived from Tibetan medicine waste for the quantification and discrimination of multiple heavy metal ions in water.

Afluorescent multichannel sensor array has been establishedbased on three carbon dots derived from Tibetan medicine waste for rapid quantification and discrimination of six heavy metal ions. Due to the chelation between metal ions and carbon dots (CDs), this fluorescence "turn off" mode sensing array can quantify six metal ions as low as "μM" level. Moreover, the six heavy metal ions display varying quenching effects on these three CDs owing to diverse chelating abilities between each other, producing differential fluorescent signals for three sensing channels, which can be plotted as specific fingerprints and converted into intuitive identification profiles via principal component analysis (PCA) and hierarchical cluster analysis (HCA) technologies to accurately distinguish Cu2+, Fe3+, Mn2+, Ag+, Ce4+, and Ni2+ with the minimum differentiated concentration of 5μM. Valuably, this sensing array unveils good sensitivity, exceptional selectivity, ideal stability, and excellent anti-interference ability for both mixed standards and actual samples. Our contribution provides a novel approach for simultaneous determination of multiple heavy metal ions in environmental samples, and it will inspire the development of other advanced optical sensing array for simultaneous quantification and discrimination of multiple targets.

Rationally designed dual channel reversible probe for cyanide recognition in aqueous medium with solid-state sensing abilities

A novel chromogenic azo-azomethine chemosensor, namely 2-((E)-(2-(benzo[d]thiazol-2-yl) hydrazineylidene)methyl)-4-((E)-phenyldiazenyl)phenol (referred to as L), was rationally designed and synthesized. The molecular structure of L was established using various spectroscopic and spectrometry techniques including NMR, FT-IR and mass. The spectral profile including absorption and fluorescence were recorded in solvents of varying polarity. The sensor responsiveness towards different anions was evaluated visually and established using UV–vis spectroscopy and NMR studies. A binary solution of DMSO/H2O (6:4, v:v) was used for anion recognition studies. A color change from colorless to yellow was noticed upon addition of CN– ion to the probe (L) solution. The developed probe was found to be very sensitive towards CN– ion with a detection limit of 21 nM. Benesi-Hildebrand plot revealed a binding constant of 1.2*103 and the binding stoichiometry of 1:2 was confirmed using Job’s plot. 1H NMR studies were utilised to ascertain the recognition mechanism which revealed the CN– ion assisted deprotonation of N-H and O-H group of L. The recognition mechanism established using NMR technique has been supported theoretically by DFT based studies. Additionally, cost-effective paper strips coated with L has been proved to be a convenient tool for detecting CN– ion in aqueous solutions. The reversibility and reusability of the developed probe was also investigated in both solution as well as solid state using trifluoroacetic acid (TFA) without any loss of the sensitivity of the developed probe. Moreover, the developed probe recognises cyanide ion in environmental samples with around 100 % recovery. The practical application of the Logic gate response of L was confirmed by paper strip experiment.

Dual detection of Hg2+ and Pb2+ by a coumarin-functionalized Schiff base in environmental and biosystems

Fluorescent chemosensors are often preferred for tracking toxic ions because of their non-destructive measurement and ease of use in environmental real samples and biosystems. Exploring high selectivity, great sensitivity, and biocompatible fluorophores with facile, accessible and dual-responsive features is currently highly demanding. A coumarin-based naphthol hydrazone Schiff base chemosensor, NaChro, is designed and synthesized in a two-step process to detect toxic metal ions with strong emission. Fluorescence spectra analysis demonstrates that the probe binds to Hg2+ and Pb2+ ions with a 1:1 and a 2:1 stoichiometry, respectively, with high sensitivity, short response time and minimal interference from other metal ions. The observed reversible turn-on reaction was attributed to the inhibition of C = N isomerization and excited-state intramolecular proton transfer (ESIPT) processes once the ions were introduced. The practical applications of NaChro are successfully addressed in paper strips, various water samples, HeLa cells and Zebrafish, demonstrating that the probe can detect and track Hg2+ and Pb2+ ions in environmental samples and biosystems.

Synthesis and Application of 3-[3-Phenylpyrazylazo]-2,7-Naphthalendiol for Improved Palladium Determination in Environmental Samples and Enhanced ZnO Nanoparticle Performance

In this study, a spectrophotometric method for the determination of low levels of palladium (II) was developed by forming a complex with the new reagent 3-(3-phenyl pyrazyl azo)-2,7-naphthalendiol (3PPAN). The complex showed maximum absorption at 612 nm with a maximum molar absorptivity of 4.911?104 L/mol/cm, and a linear correlation was established between absorbance and concentration. The accuracy and repeatability of the method were evaluated and found to be precise (RSD 1.22%) and accurate (relative error 0.157%). The method?s selectivity was also tested by evaluating the effect of various ions. The stability constant of the complex was determined to be 2.759?107 L/mol. The method was successfully applied to the determination of Pd (II) ions in environmental samples of water and soil. In addition, the new ligand (3PPAN) was used to improve the properties of nano ZnO through a ligand exchange reaction on nanoparticles.. KEYWORDS :Azo, Palladium, Spectrophotometric, ZnO nanoparticles.

Zinc nitride quantum dots as an efficient probe for simultaneous fluorescence detection of Cu2+ and Mn2+ ions in water samples.

The exceptional ascending heights of graphene (carbon) and boron nitride nanostructures have invited scientists to explore metal nitride nanomaterials. Herein, Zn3N2 quantum dots (QDs) were prepared via a simple hydrothermal route from the reaction between zinc nitrate hexahydrate and ammonia solution that possess efficient strength towards sensing applications of metal ions (Cu2+ and Mn2+). The as-prepared Zn3N2 QDs show bright fluorescence, displaying an emission peak at 408nm upon excitation at 320nm, with a quantum yield (QY) of 29.56%. It was noticed that the fluorescence intensity of Zn3N2 QDs linearly decreases with the independent addition of Cu2+ and Mn2+ ions, displaying good linearity in the ranges 2.5-50µM and 0.05-5µM with detection limits of 21.77nM and of 63.82nM for Cu2+ and Mn2+ ions, respectively. Theprobe was successfully tested for quantifying Cu2+ and Mn2+ in real samples including river, canal, and tap water, providinggood recoveries with a relative standard deviation  < 2%. Furthermore, the masking proposition can successfully eliminate the interference if the twometal ions exist together. It was found that thiourea is efficiently able to mask Cu2+ and selectively quenches Mn2+, and L-cysteine is able to halt the quenching potential of Mn2+ and is selectively able to sense Cu2+. The Zn3N2 QDs provide a simple way for the simultaneous detection of both Cu2+ and Mn2+ ions in environmental samples at lowsample preparationsrequirements.

New solid state contact potentiometric sensor based on a thiosemicarbazone derivative molecule for determination of copper(II) ions in environmental samples

Thiosemicarbazone derivative molecules have proven to be good sensor materials in studies using various analytical methods. In this study, new ion–selective sensors were prepared using 2–furaldehyde thiosemicarbazone and their potentiometric properties were then tested. The prepared sensors exhibited a very good selectivity towards copper(II) ions over various ions. Surface images and mappings of the prepared sensors were examined by scanning electron microscopy. Copper(II)–selective sensors had a Nernstian response of 28.5 ± 1.5 mV/decade, and a low detection limit of 6.89 × 10-6 mol L-1 over a wide concentration range of 1.0 × 10-5–1.0 × 10-1 mol L-1 (R2 = 0.9992). The newly prepared copper(II)–selective sensors were shown to be produced reproducibly, stable and economically. The sensors, which can operate in a wide pH range of 5.0–9.0 without being affected by pH changes, had a fast response time of 5 s. The newly developed copper(II)–selective sensors were used as indicator electrodes for the potentiometric titration of copper(II) ions with ethylenediaminetetraacetic acid and were successfully applied for the determination of copper(II) ion content in various environmental samples with very good performance. The data obtained with the developed sensor were compared with atomic absorption spectroscopy and it was determined that the results of both methods were compatible with each other.

Extraction and detection of mercury in electronic waste using efficient modified MOF

The harmful effects of heavy metal ions on human health and the ecosystem have made the detection of these ions in environmental samples increasingly important in recent years. There has been significant attention on the development of sensors that are selective and sensitive in detecting heavy metal ions. Due to their wide presence in the environment and high toxicity, the detection of Hg2+ ions is of great interest. MIL-101(Al)-N = 2NAPHT (2NAPHT = 3-hydroxy-2-naphthaldehyde, N = imine nitrogen) is a novel chemosensor that was solvothermally synthesized and characterized. A limit of detection of 5.48 ppb (2.73 ×10−8 M) was found for the chemosensor, which is highly selective and sensitive to Hg2+ ion detection. The fluorescence emission properties of MIL-101(Al)-NH2 were improved and more binding sites for analytes were introduced after functionalization with 2-hydroxy naphthaldehyde. The formation of the novel chemosensor was confirmed by using Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), TEM, SEM, thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Moreover, this chemosensor showcased a regenerative emission feature, retaining its detection ability for six successive cycles. The study revealed that the sorbent had a considerable Hg2+ capacity, amounting to 133.2 mg per gram of MIL-101(Al)-N = 2NAPHT chemosensor. The chemosensor MIL-101(Al)-N = 2NAPHT was also assessed for its capability to identify Hg2+ ions in electronic waste samples (silver oxide button cells). According to the results mentioned above, the chemosensor exhibited a high degree of sensitivity and selectivity towards Hg2+ ions. The MIL-101(Al)-N = 2NAPHT chemosensor is an effective and promising technology for the detection and removal of mercury from electronic waste, in conclusion.

Constructing an eco-friendly and ratiometric fluorescent sensor for highly efficient detection of mercury ion in environmental samples.

Mercury ion (Hg2+) is a highly toxic and ubiquitous pollutant, whose effective detection has aroused widespread concern. A novel ratiometric fluorescent sensor has been designed to rapidly and efficiently detect Hg2+ based on blue/red carbon dots (CDs) with environmental friendliness. This sensor was well characterized via TEM, FTIR, XPS, UV-vis, and zeta potential analysis and displayed excellent fluorescence properties and stability. The fluorescence of blue CDs at 447nm was significantly quenched with the addition of Hg2+ resulted from the static quenching, whereas that of red CDs at 650nm remained invariable. A sensitive method for Hg2+ determination was constructed in the range of 0.05-7.0nmolmL-1 with optimal conditions, and the detection limit was down to 0.028nmolmL-1. Meanwhile, compared to other 17 metal ions, the ratiometric fluorescent sensor exhibited high selectivity for Hg2+. Furthermore, satisfied recoveries had also been obtained for measuring trace Hg2+ in practical environmental samples. This developed ratiometric fluorescent sensor provided a reliable, environmental-friendly, rapid, and efficient platform for the detection of Hg2+ in environmental applications.

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.

Biosynthesized silver nanoparticles based on bitter orange bloom extract and its application for the determination of cyanide ion in environmental samples

Developing new methods for detecting and determining toxic anions is an essential parameter from waste sources for industrial and environmental scientists. This study presented, a new process for the biosynthesis of silver nanoparticles (AgNPs) based on the bitter orange bloom extract and its potential as a highly selective and sensitive chemosensor for detecting and quantifying cyanide ions. These biosynthesized AgNPs have a sharp and intense surface plasmon resonance (SPR) peak around 405 nm. AgNPs with a yellow color can be changed to colorless in the presence of a certain concentration of cyanide ions due to forming a new adduct between AgNPs and cyanide ions. Hence, the SPR intensity of AgNPs decreases, and the color of the solution becomes colorless. The sensor response to cyanide ions was linear in the concentration range of 49.7 to 1208.8 nM, and the detection limit was equal to 7.9 nM. As an applicable alternative, this assay is highly capable of qualitative and quantitative measurements of cyanide ions in the waste and toxic samples.

Sonochemical synthesis of nickel tungstate (NiWO4) nanoparticles for dye degradation and electrochemical sensing of lead ions in environmental samples

Here we have synthesised Nickel Tungstate (NiWO4) nanoparticles via sonochemical method. The structural and morphological studies were examined using XRD, FTIR, UV–Vis, SEM and TEM analysis. XRD pattern confirms the monoclinic wolframite structure of NiWO4 nanoparticles. FTIR spectrum reveals that strong absorption peaks at 450 cm−1 to 1000 cm−1 for stretching and bending vibrational frequencies of the Ni–W-O peaks in NiWO4. UV–Vis spectrum shows maximum intensity peak at ∼ 473 nm corresponding to the band gap of 3.0 eV. The SEM and TEM images show irregular shapes of nanoparticles. BET analysis shows a surface area 31.811 m2/g for NiWO4 nanomaterials. Methylene Blue (MB) and Rhodamine B (RhB) dyes were used as model pollutants for the analysis of photocatalytic activity under UV and visible light irradiations and it has proved as a fine photocatalyst. The electrochemical activity of the samples was studied by cyclic voltammetry (CV) and Electrochemical Impedance spectroscopy (EIS) in 1 M KOH aqueous electrolyte. EIS measurements showed a reduction in the charge transfer resistance in acidic electrolyte. Modified carbon paste electrode employing NiWO4 nanoparticles has sensed lead in alkaline electrolyte. The electrode displayed high sensitivity for lead detection under varying concentrations. These results confirm that the NiWO4 nanoparticles are promising electrode material for sensing lead with high electrode reversibility.

Electrocatalytic self-assembled multilayer structures based on thiolated Fc-DAB dendrimers: Determination of heavy metal ions by enzymatic inhibition

The development of sensitive and rapid inhibition-based biosensors for monitoring trace levels of heavy metals such as lead and copper ions in environmental samples is of high interest. In this work, we describe the fabrication of HRP sensitive peroxide biosensors based on ferrocenyl thiolated DAB dendrimers as bonding-layer between electrodeposited and colloidal gold nanoparticles and compare their electrocatalytic properties with those of thiolated DAB homologues. The complete electrochemical, kinetic and analytical characterization of these new heavy metals’ inhibition-biosensors are investigated.

Thermodynamics of Ag(I) Complex Formations with 2-Mercaptoimidazole in Water−Dimethyl Sulfoxide Solvents

The stability of coordination compounds of metal ions with ligands is of fundamental importance for elaborating upon practical sensors for the detection and quantification of metal ions in environmental samples. In this work, the stability constants of silver(I) complexes with 2-mercaptoimidazole (2MI) in a mixed water–dimethyl sulfoxide (DMSO) solvent were determined at 298.15 K and 308.15 K. It was found that with increasing temperature, the stability of the complexes decreases. The dependence of lgβ1 on the water−DMSO solvent compositions has its minimum at a concentration of dimethyl sulfoxide of 0.1 mol. fr. To explain the effect of the solvent, the solvation characteristics of the reagents were analyzed. In this regard, the 2MI Gibbs energy of transfer from water to aqueous dimethyl sulfoxide solvents was determined, and the influence of the aqueous DMSO solvent on the thermodynamics of 2MI protonation was analyzed. The stabilization of the silver ion and 2MI during the transition from water to a water–DMSO solvent makes a negative contribution to the change in the Gibbs energy of complexation, while the solvation of a complex particle promotes the complex formation. As a result, the Gibbs energy transfer values are slightly increased. The results of these thermodynamic studies could be useful for the development of sensor materials based on mercaptoimidazoles.

Tree-based machine learning models assisted fluorescent sensor array for detection of metal ions based on silver nanocluster probe

The growing concern over heavy metal pollution and its impact on the environment and human health has led to a proliferation of research on the detection and differentiation of heavy metal ions. A novel fluorescent sensor array utilizing only one single Ag-nanoclusters (Ag NCs) was developed for the efficient detection of six metal ions. The Ag NCs probe was prepared by using poly(methyl vinyl ether-alt-maleic acid) (PMVEM) as the ligand and has different fluorescence properties in water and dimethyl sulfoxide (DMSO). The interaction between metal ions and Ag NCs resulted in a characteristic fluorescence variation pattern which was subsequently analyzed using various tree-based machine learning models. We have compared different combinations of classification models and pre-processing methods of which the K-Nearest Neighbors Classifier with the first five linear discriminants has the highest accuracy. Through the integration of concentration models within a tree-based pipeline optimization framework, six unique concentration regression models were selected for each metal ion. In addition, the developed sensor array could identify metal ions in binary mixtures. And it still kept high accuracy for the classification of six target metal ions in river water. In conclusion, the proposed framework was found to be effective in the detection of heavy metal ions in environmental samples, thus providing a promising approach for addressing heavy metal pollution.

Development of an Fe2+ sensing system based on the inner filter effect between upconverting nanoparticles and ferrozine.

The ferrozine (FZ) assay is a vital oxidation state-specific colorimetric assay for the quantification of Fe2+ ions in environmental samples due to its sharp increase in absorbance at 562 nm upon addition of Fe2+. However, it has yet to be applied to corresponding fluoresence assays which typically offer higher sensitivites and lower detection limits. In this article we present for the first time its pairing with upconverting luminescent nanomaterials to enable detection of Fe2+via the inner filter effect using a low-power continuous wave diode laser (45 mW). Upon near infra-red excitation at 980 nm, the overlap of the upconversion emission of Er3+ at approximately 545 nm and the absorbance of the FZ:Fe2+ complex at 562 nm enabled measurement in the change of UCNP emission response as a function of Fe2+ concentration in a ratiometric manner. We first applied large, ultra-bright poly(acrylic acid) (PAA)-capped Gd2O2S:Yb3+,Er3+ UCNPs upconverting nanoparticles (UCNPs) for the detection of Fe2+ using FZ as the acceptor. The probe displayed good selectivity and sensitivity for Fe2+, with a low limit of detection (LoD) of 2.74 μM. Analogous results employing smaller (31 nm) PAA-capped hexagonal-phase NaYF4:Yb3+,Er3+ UCNPs synthesised in our lab were achieved, with a lower LoD towards Fe2+ of 1.43 μM. These results illustrate how the ratiometric nature of the system means it is applicable over a range of particle sizes, brightnesses and nanoparticle host matrices. Preliminary investigations also found the probes capable of detecting micromolar concentrations of Fe2+ in turbid solutions.

An ESIPT solvatochromic fluorescent and colorimetric probe for sensitive and selective detection of copper ions in environmental samples and cell lines.

Copper is one of the most important transition metals in our body for various physiological functions. An imbalance in the homeostasis of copper in our body can lead to various neurological disorders such as Alzheimer's disease, Parkinson's, and Menkes disease. As a result, there is a need for the detection of excess copper present in the environment and the human system. In this work, we have designed a quinoline-based fluorescent/colorimetric probe (QHS) for rapid and selective detection of copper ions via quenching of fluorescence/color change from yellow to peach which is visible to the naked eye. The probe displayed high selectivity towards copper(II), i.e., Cu(II) in the presence of different metal analytes in water samples. The sensing mechanism of the probe was confirmed by NMR, HRMS, IR spectroscopy, and SEM. The detection limit of Cu(II) ions was found to be 0.493 μM which is lower than the tolerable limit of copper (20 μM) in drinking water as per the EPA. The probe was also utilized for the visualization of Cu(II) in cell lines. The probe was also demonstrated for its application in real-time detection of aqueous samples using portable paper strips.

Disposable luminescent kit based on dithizone-functionalized waste blue-phosphor as field-deployable sensor for environment monitoring

A new disposable sensor based on waste blue-phosphor (BaMgAl10O17:Eu2+, BAM) embedded in polyvinyl alcohol (PVA) support and modified dithizone (Dz) was designed and fabricated for the determination of Pb2+ ions in environmental samples. Dz is used as the modifier to give indirect sensing property through interacting with BAM particles via surface coordinating reactions to form Dz-BAM conjugates resulting in quenching of natural fluorescence of BAM by fluorescence resonance energy transfer (FRET) mechanism. The Box-Behnken response surface factorial design was used to optimize the prepared sensor using two spectrophotometric and spectrofluorimetric approaches. The calibration curve was found to be linear in the range of 500–4500 nmol/L (R2 = 0.9986) with LOD of 150 nmol/L and LOQ of 500 nmol/L. The potential interference ions were studied and the applicability of the sensor was successfully evaluated by determination of the target ion in real tap and river water samples containing potential interferences.

Unravelling mechanism for detecting chromium on functionalized gold nanoparticles via a smartphone and spectrophotometric-based systems supported by CIEL*a*b* colour space and molecular dynamics

This paper demonstrates the application of smartphones as well as spectrophotometers as tools to demystify the mechanism leading to colour variation of 1,5-diphenylcarbazide functionalized gold nanoparticles (DPC-AuNPs) due to chromium addition. Colour Grab 3.6.1 app was used to capture and decode colours from samples containing DPC-AuNPs with different concentrations of hexavalent Chromium [Cr(VI)] standards. The presence of Cr(VI) aggregated DPC-AuNPs resulted in a colour change from pink to blue and a decrease in the peak intensity as accompanied by a red shift of the SPR peak to 670 nm.The R colour coordinates decreased as Cr(VI) concentration was increased to 16 µM then a rapid decrease was noted between 18–25 µM and G and B colour coordinates followed the same trend. Colour difference (∆E) increased significantly as the Cr(VI) concentration increased. A rapid decrease was noticed in the hue angle between 16–25 µM while chroma decreased significantly as the Cr(VI) concentration increased. Molecular dynamics calculation of a gold cluster was used to simulate the aggregation process. The calculated radial distribution [g(r)] from cluster models of the Cr-DPC complex was two-fold more than Cr-AuNPs. This was associated with the aggregation of gold nanoparticles leading to the appearance of the blue colour of AuNPs solution which was also supported by the intensity obtained from colour Grab. This study will potentially be applied in the future for the fabrication of a Lovibond photometer for the detection of metal ions in environmental samples.

Pyridinecarbohydrazide-based fluorescent chemosensor for In3+ ions and its applications in water samples, live cells, and zebrafish imaging

Herein, we synthesized and characterized a new probe N',N'-bis((E)-2-hydroxy-3-methyl benzylidene)pyridine-2,6-dicarbohydrazide (L) for the detection and quantification of In3+ ions. Probe L exhibits a significant fluorescence ON upon the addition of In3+ in DMSO:H2O (2:8, v/v) media with a detection limit as low as 62.7 nM. The key sensing ability of L towards In3+ was attributed to the chelation-enhanced fluorescence (CHEF). The binding stoichiometry between L and In3+ was found to be 1:2 by Job’s plot, nuclear magnetic resonance (NMR), and mass analysis, with the calculated association constant of (Ka), 1.42 × 103 M−2 by Benesi-Hildebrand (BH) method. Various techniques such as 1H NMR, FTIR, ESI mass, and DFT analysis were used to determine the mechanism by which L binds to the In3+ ions. The detection of In3+ in water samples demonstrates that L might be used to detect In3+ ions in environmental samples. Notably, the bio-imaging revealed that L successfully detected In3+ ions in DrG cells and zebrafish larvae.