Poly(vinyl) chloride membrane copper-selective electrode based on 1-phenyl-2-(2-hydroxyphenylhydrazo)butane-1,3-dione

Surface characterization and electroanalytical applications of the newly developed copper(II)-selective potentiometric sensor

In this work, we developed a new copper(II)-selective potentiometric sensor and investigated its surface with scanning electron microscopy (SEM). Besides the surface images of the sensors conditioned in copper(II) solutions, energy-dispersive X-ray (EDX) and mapping studies were carried out. According to the results obtained, it was determined that copper(II) ions adhered to the porous areas on the sensor surface, and that Cu2+ ions showed a wide distribution on the sensor surface in mapping studies. The new sensor had a Nernstian response of 29.3 ± 0.5 mV/decade in the concentration range of 1.0 × 10-1-1.0 × 10-5 M and a low detection limit of 8.56 × 10-6 M. The proposed sensor had fast response time (< 10 s), wide pH working range (5.0-10.0), good repeatability and stability. Finally, the sensor performed the determination of copper(II) ions in various water samples with very high recoveries (96.0-102.0%).

Synthesis, Computational and cytotoxicity studies of aryl hydrazones of β-diketones: Selective Ni2+ metal Responsive fluorescent chemosensors

A new fluorescent sensor 2-(2-(3-chloro-4-fluorophenyl)hydrazono)-5,5-dimethyl cyclohexane-1,3-dione (A) and 2-(2-(4-chloro-2-nitrophenyl)hydrazono)-5,5-dimethyl cyclohexane-1,3-dione (B) composed of a β-diketones of aryl hydrazones synthesized by simple and cost-effective method. Various analytical tools analyzed the structural investigations of the synthesized substituted β-diketones of aryl hydrazones like FT-IR, ¹H, ¹³C NMR and UV-Vis techniques, Single-crystal X-ray diffraction studies (SCXRD) (for A), Scanning electron microscopy (SEM), and fluorescence spectroscopy. SEM also investigates surface morphology modifications of aryl hydrazones and Ni²⁺ complex. Furthermore, the metal sensing (Chemo sensing) behavior of newly prepared aryl hydrazones of β-diketones derivatives was further studied by fluorescence spectroscopy. The aryl hydrazones sensor materials show admirable fluorescence selectivity with enrichment to Ni²⁺ over different cations in an aqueous ethanol solution with a recognition extremity of 4 μM-7 μM. A joint experimental and theoretical investigation was led on the chemical structure employing a density functional theory (DFT) (B3LYP), engaging a 6-31G basis set. The DFT technique's enhanced geometrical bond angles and lengths exhibited great covenant with the experimental results. The highest occupied molecular (HOMO) orbital and lowest unoccupied (LUMO) molecular orbital energy has been concluded. The cytotoxicity studies show these compounds impede the growth of KB cells highly and from the studies to evaluate their capability to accurately dock aryl hydrazones to antibodies of cancer protein such as 4LRH, 4L9K, 4 EKD and 4GIW cancer proteins.

Recent Advances in Chemical Sensors for Soil Analysis: A Review

The continuously rising interest in chemical sensors’ applications in environmental monitoring, for soil analysis in particular, is owed to the sufficient sensitivity and selectivity of these analytical devices, their low costs, their simple measurement setups, and the possibility to perform online and in-field analyses with them. In this review the recent advances in chemical sensors for soil analysis are summarized. The working principles of chemical sensors involved in soil analysis; their benefits and drawbacks; and select applications of both the single selective sensors and multisensor systems for assessments of main plant nutrition components, pollutants, and other important soil parameters (pH, moisture content, salinity, exhaled gases, etc.) of the past two decades with a focus on the last 5 years (from 2017 to 2021) are overviewed.

Exploitation of 2D Cu-MOF nanosheets as a unique electroactive material for ultrasensitive Cu(II) ion estimation in various real samples

Herein, hybrid carbon sensor has been developed with graphite sheets as a matrix, tricresyl phosphate (TCP) as a plasticizer and nanosheets of 2D Cu-MOF (metal-organic framework) as an electroactive material for the ultrasensitive Cu(II) ion detection in various real samples. Where, the present study proves the efficiency of 2D Cu-MOF as a promising sensing material for the development of Cu(II) ion selective carbon sensor. The developed 2D Cu-MOF nanosheets based sensor containing 2D Cu-MOF: TCP: graphite in the ratio of 2.67: 30.54: 66.79 (% wt/wt) displayed unique Nernstian behavior over two linearity ranges of 1.0 × 10^-11-1.0 × 10^-9 and 1.0 × 10^-5-1.0 × 10^-1 mol L^-1 with slopes of 29.5 ± 0.25 and 29.6 ± 0.13 mV decade^-1, respectively. The fabricated carbon sensor achieved a widely pH independency, fast response time and superior thermal stability with highly selective and ultrasensitive performance. Moreover, It has been efficiently applied for the Cu(II) ion potentiometric estimation in human hair, sesames seeds, two different tea infusions and tap water real samples.

Lignosulfonate-Based Conducting Flexible Polymeric Membranes for Liquid Sensing Applications

In this study, lignosulfonate (LS) from the acid sulfite pulping of eucalypt wood was used to synthesize LS-based polyurethanes (PUs) doped with multiwalled carbon nanotubes (MWCNTs) within the range of 0.1-1.4% w/w, yielding a unique conducting copolymer composite, which was employed as a sensitive material for all-solid-state potentiometric chemical sensors. LS-based PUs doped with 1.0% w/w MWCNTs exhibited relevant electrical conductivity suitable for sensor applications. The LS-based potentiometric sensor displayed a near-Nernstian or super-Nernstian response to a wide range of transition metals, including Cu(II), Zn(II), Cd(II), Cr(III), Cr(VI), Hg(II), and Ag(I) at pH 7 and Cr(VI) at pH 2. It also exhibited a redox response to the Fe(II)/(III) redox pair at pH 2. Unlike other lignin-based potentiometric sensors in similar composite materials, this LS-based flexible polymeric membrane did not show irreversible complexation with Hg(II). Only a weak response toward ionic liquids, [C2mim]Cl and ChCl, was registered. Unlike LS-based composites comprising MWCNTs, those doped with graphene oxide (GO), reduced GO (rGO), and graphite (Gr) did not reveal the same electrical conductivity, even with loads up to 10% (w/w), in the polymer composite. This fact is associated, at least partially, with the different filler dispersion abilities within the polymeric matrix.

Soil Sensors and Plant Wearables for Smart and Precision Agriculture

Soil sensors and plant wearables play a critical role in smart and precision agriculture via monitoring real-time physical and chemical signals in the soil, such as temperature, moisture, pH, and pollutants and providing key information to optimize crop growth circumstances, fight against biotic and abiotic stresses, and enhance crop yields. Herein, the recent advances of the important soil sensors in agricultural applications, including temperature sensors, moisture sensors, organic matter compounds sensors, pH sensors, insect/pest sensors, and soil pollutant sensors are reviewed. Major sensing technologies, designs, performance, and pros and cons of each sensor category are highlighted. Emerging technologies such as plant wearables and wireless sensor networks are also discussed in terms of their applications in precision agriculture. The research directions and challenges of soil sensors and intelligent agriculture are finally presented.

Ligands as copper and nickel ionophores: Applications and implications on wastewater treatment

Modern society depends on many finite natural resources, from which metals are of great importance. Copper and nickel's relevance is due to their vast applications, resulting in high market value and demand. As such, their polluting emissions are also significant and their removal from wastewaters is imperative. Moreover, effluent treatment techniques can be used to recover the metallic cations, via selective processes. In this review, copper and nickel selective ligands in the literature are surveyed. These are most commonly Schiff bases, along with crown ethers and porphyrins. They are usually employed in ion sensing (colorimetric chemosensors or electrodes) with great success - the disruption in response of colorimetric sensors is up to 7% and binding constants are usually at least one order of magnitude greater with the desired cation than with interferents. However, modified adsorbents are also reported. The possibilities of using ionophores in wastewater cleaning, allowing the treatment of effluents and the selective recovery of valuable materials, and their implications on new green policies is discussed.

A novel copper selective sensor based on ion imprinted 2-vinylpyridine polymer

A novel potentiometric Cu2+-selective microsensor has been developed that is based upon ion imprinted 2-vinylpyridine polymer. The polymer was synthesized using Cu(II) ions, 2-vinylpyridine, methacrylic acid, and ethylene glycol dimethacrylate as a template, functional monomer, and cross-linker, respectively. The resultant polymer was used as ionophore to obtain a selective potentiometric response towards Cu(II) ions in the structure of the PVC membrane. The detection limit of the microsensor was determined to be 8.4 × 10−7 mol/L, and its response time was considerably short (less than 15 s). The prepared microsensor exhibited a near-Nernstian response for Cu(II) ions over the concentration range of 10−1 to 10−6 mol/L, with a slope of 28.5 mV per decade over 2 months, and without any considerable divergence in potentials. The microsensor was effectively performed in a pH range between 4.0 and 7.0 and used as an indicator electrode in the potentiometric titration of Cu(II) ions with EDTA. The proposed microsensor has been successfully demonstrated for the determination of copper in a number of environmental water samples. The obtained potentiometric results were in good harmony with the results obtained by the AAS method.

High selective potentiometric sensor for determination of nanomolar con-centration of Cu(II) using a polymeric electrode modified by a graphene/7,7,8,8-tetracyanoquinodimethane nanoparticles

In this paper we present several possibilities for modification of the all-solid-state copper(II)-selective electrodes in order to obtain high stability and selectivity potentiometric sensor signal. The copper(II)-selective electrodes were modified in a simple way by introducing solid contact layer based on graphene or graphene oxide, 7,7,8,8-tetracyanoquinodimethane or its copper salt. Each of electrodes shown a Nernstian response, wide linear range of Cu²⁺ concentration and a low detection limit. Nevertheless, some differences between the groups of electrodes have been noticed and resulted from application of intermediate layers of various compositions. The electrode modified with graphene and 7,7,8,8-tetracyanoquinodimethane nanocomposite exhibited the best potential reproducibility and detection limit. Moreover, prepared sensors were characterized by an improved selectivity for copper(II) in relation to non-modified electrodes. The developed electrodes were successfully used for the Cu²⁺ determination in different samples and results were comparable with those obtained using voltammetry.

Rapid determination of trace level copper in tea infusion samples by solid contact ion selective electrode

A new solid contact copper selective electrode with a poly (vinyl chloride) (PVC) membrane consisting of o-xylylenebis(N,N-diisobutyldithiocarbamate) as ionophore has been prepared. The main novelties of constructed ion selective electrode concept are the enhanced robustness, cheapness, and fastness due to the use of solid contacts. The electrode exhibits a rapid (< 10 seconds) and near-Nernstian response to Cu²⁺ activity from 10^-1 to 10^-6 mol/L at the pH range of 4.0-6.0. No serious interference from common ions was found. The electrode characterizes by high potential stability, reproducibility, and full repeatability. The electrode was used as an indicator electrode in potentiometric titration of Cu(II) ions with EDTA and for the direct assay of tea infusion samples by means of the calibration graph technique. The results compared favorably with those obtained by the atomic absorption spectroscopy (AAS).

A novel fluorescein-based colorimetric probe for Cu2+ detection

A new colorimetric probe, 5-chlorosalicylaldehyde fluorescein hydrazone (CSFH), has been synthesized and characterized by, FT-IR, NMR, mass elemental analysis and X-ray single crystal diffraction.

Spectral and thermal characterization of salophen type Schiff base and its implementation as solid contact electrode for quantitative monitoring of copper(II) ion

Salophen templated Schiff base 2,3-bis(salicylaldimino)pyridine (H2IF) has been synthesized and fully characterized by a series of different spectroscopic methods and thermogravimetric analysis (TGA). It has been also further probed electrochemically and explored as a cation recognition ionophore in the form of a polymeric membrane as selective sensor for quantitative monitoring of Cu(2+). Dielectric properties of the membrane have been studied by electrochemical impedance spectroscopy (EIS). The potentiometric results have demonstrated that the sensor exhibits very good selectivity and sensitivity towards Cu(2+) over a wide variety of cations. The electrode has a linear response to Cu(2+) with a detection limit of 4.46×10(-8) and displays a Nernstian slope (29.14 mV/decade) between pH 3.0 and 6.0 with a fast response time less than 10s. The solid contact electrodes have been exploited over five mounts period with good reproducibility. The analytical availability of the proposed electrode has been evaluated by applying in the determination of Cu(2+) ions in water samples. The structural features and complexation of ionophore with Cu(2+) have been monitored by UV-Vis spectroscopy and spectral findings have been further supported by DFT and TD-DFT calculations.

Dynamic potential and surface morphology study of sertraline membrane sensors

New rapid, sensitive and simple electrometric method was developed to determine sertraline hydrochloride (Ser-Cl) in its pure raw material and pharmaceutical formulations. Membrane sensors based on heteropolyacids as ion associating material were prepared. Silicomolybdic acid (SMA), silicotungstic acid (STA) and phosphomolybdic acid (PMA) were used. The slope and limit of detection are 50.00, 60.00 and 53.24 mV/decade and 2.51, 5.62 and 4.85 μmol L⁻¹ for Ser-ST, Ser-PM and Ser-SM membrane sensors, respectively. Linear range is 0.01–10.00 for the three sensors. These new sensors were used for the potentiometric titration of Ser-Cl using sodium tetraphenylborate as titrant. The surface morphologies of the prepared membranes with and without the modifier (ion-associate) were studied using scanning and atomic force microscopes.

Antimicrobial activity and molecular analysis of azoderivatives of β-diketones

The emergence and increase in the number of multidrug resistant microorganisms have highly increased the need of therapeutic trials, necessitating a deep exploration on novel antimicrobial response tactics. This study is intended to screen and analyze the activity of a novel set of azoderivatives of β-diketones and their known analogs for antimicrobial properties. The compounds were analyzed to determine their minimum inhibitory concentration. Hit compounds 5-(2-(2-hydroxyphenyl)hydrazono)pyrimidine-2,4,6(1H,3H,5H)-trione (C5), 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxybenzenesulfonic acid (C8), 2-(2-carboxyphenylhydrazo)malononitrile (C11) were then considered in evaluating their effect on transcription, translation and cellular oxidation impact. All three compounds were found to have in vitro inhibitory action on E.coli cell growth. The study also revealed that those compounds have a notable impact on cellular activities. It is determined that the newly synthesized azoderivative of barbituric acid (C8) have maximum growth inhibitory activity among the three compounds considered, characterized by a MIC50 of 0.42mg/ml. The MS2 reporter system was used to detect the transcriptional response of the bacteria to the treatment with the selected drugs. All three compounds are found to down regulate the transcriptional pathway. The novel compound, C8, showed maximum inhibition of transcription mechanism, followed by C5 and C11. The effect of the compounds on translation was analyzed using a Yellow Fluorescent protein reporter system. All the compounds displayed reductive impact on translation of which C8 was found to the best, exhibiting 8.5-fold repression followed by C5 and C11, respectively. Fluctuations of the Reactive Oxygen Species (ROS) concentrations were investigated upon incubation in hit compounds using ROS sensor protein. All the three compounds were found to contribute to oxidative pathway. C8 is found to have the best oxidative effect than C5 and C11. All experiments were repeated at least twice, the results being verified to be significant using statistical analysis.

Solid-contact polyvinyl chloride membrane electrode based on the bis[(2-(hydroxyethylimino)phenolato]copper(II) complex for trace level determination of copper ions in wastewater

A miniaturized solid-contact polyvinyl chloride membrane electrode based on the bis[(2-(hydroxyethylimino)phenolato]copper(II) complex has been prepared for the determination of Cu(II) ion in real samples. The influence of coating membrane composition, pH, and possible interfering cations on the response of the ion-selective electrode was investigated. A number of membranes at different compositions were prepared and their Cu2+ sensing capabilities were investigated. The best results for Cu2+ sensing was obtained for the electrode membrane containing ionophore − 2-nitrophenyloctyl ether – polyvinyl chloride and potassium tetrakis(p-chlorophenyl)borate in a ratio of 4:65:30:1 (w/w, mg), respectively. The prepared electrode exhibited a near-Nernstian response (28.3 mV/decade) to Cu2+ in the concentration range from 1.0 × 10−6 to 1.0 × 10−1 mol/L with a limit of detection of 8.3 × 10−7 mol/L. The potentiometric response of the electrode was independent from the pH of the test solution in the pH range of 3.0–6.0. The electrode has a very short response time, about 15 s, and it can be used over a period of 3 months without any divergence in potential. The electrode has been successfully applied as an indicator electrode in potentiometric titration of Cu(II) ions with ethylenediaminetetraacetic acid and in the determination of Cu(II) in wastewater of the copper processing industry.

Electrochemical Analysis of Some Toxic Metals by Ion-Selective Electrodes

An overview of potentiometric sensors that are capable of detecting toxic heavy metal ions in environmental samples is presented and discussed. Notwithstanding the tremendous work performed so far, it is obvious that still several limitations do exist in terms of selectivity, limits of detection, dynamic ranges, applicability to specific problems, and reversibility. A survey on important advances in potentiometric sensors with regard to high selectivity, lower detection limit, fast response time, and on-line environmental analysis is presented in this review article. [Supplemental materials are available for this article. Go to the publisher's online edition of Critical Reviews in Analytical Chemistry to view the free supplemental file.].

Quantum chemical simulations of solvent influence on UV-vis spectra and orbital shapes of azoderivatives of diphenylpropane-1,3-dione

The DFT modeling of novel synthesized azoderivatives of β-diketones - 2-(2-(2-hydroxyphenyl)hydrazono)-1,3-diphenylpropane-1,3-dione (1), 2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1,3-diphenylpropane-1,3-dione (2), 3-(2-(1,3-dioxo-1,3-diphenylpropan-2-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzene sulfonic acid (3), 2-(2-(1,3-dioxo-1,3-diphenylpropan-2-ylidene)hydrazinyl)benzenesulfonic acid (4), 2-(2-(1,3-dioxo-1,3-diphenylpropan -2-ylidene)hydrazinyl)benzoic acid (5), 2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1-phenylbutane-1,3-dione (6) were performed. The collected information confirms that 1-5 exist in hydrazo form, being stabilized by the intramolecular hydrogen bonds in DMSO solution and solid phase, while 6 exists in mixed enol-azo and hydrazo tautomeric forms, the latter dominating in more polar solvents. The relative stability of various tautomeric and izomeric forms of the symmetric 1-5 and unsymmetric 6 azoderivatives of β-diketones is calculated based on the density functional theory (DFT). Polarizable Continuum Model was used to simulate solvatochromic effects. Solvents of different polarities were used to collect experimental spectra, and the same solvents were chosen for the PCM calculations. The optical properties of 1-6 have been investigated by density functional theory and its electronic absorption bands have been assigned by time-dependent density functional theory (TD-DFT).