A highly selective voltammetric sensor for sub-nanomolar detection of lead ions using a carbon paste electrode impregnated with novel ion imprinted polymeric nanobeads

Ion-Imprinted Polymeric Materials for Selective Adsorption of Heavy Metal Ions from Aqueous Solution

The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle of molecular imprinting methodology, have emerged as an innovative solution. Recent advances in IIPs have shown that they exhibit higher selectivity coefficients than non-imprinted ones, which could support a large range of environmental applications starting from extraction and monitoring of HMIs to their detection and quantification. This review will emphasize the application of IIPs for selective removal of transition metal ions (including HMIs, precious metal ions, radionuclides, and rare earth metal ions) from aqueous solution by critically analyzing the most relevant literature studies from the last decade. In the first part of this review, the chemical components of IIPs, the main ion-imprinting technologies as well as the characterization methods used to evaluate the binding properties are briefly presented. In the second part, synthesis parameters, adsorption performance, and a descriptive analysis of solid phase extraction of heavy metal ions by various IIPs are provided.

A Critical Review on the Use of Molecular Imprinting for Trace Heavy Metal and Micropollutant Detection

Molecular recognition has been described as the “ultimate” form of sensing and plays a fundamental role in biological processes. There is a move towards biomimetic recognition elements to overcome inherent problems of natural receptors such as limited stability, high-cost, and variation in response. In recent years, several alternatives have emerged which have found their first commercial applications. In this review, we focus on molecularly imprinted polymers (MIPs) since they present an attractive alternative due to recent breakthroughs in polymer science and nanotechnology. For example, innovative solid-phase synthesis methods can produce MIPs with sometimes greater affinities than natural receptors. Although industry and environmental agencies require sensors for continuous monitoring, the regulatory barrier for employing MIP-based sensors is still low for environmental applications. Despite this, there are currently no sensors in this area, which is likely due to low profitability and the need for new legislation to promote the development of MIP-based sensors for pollutant and heavy metal monitoring. The increased demand for point-of-use devices and home testing kits is driving an exponential growth in biosensor production, leading to an expected market value of over GPB 25 billion by 2023. A key requirement of point-of-use devices is portability, since the test must be conducted at “the time and place” to pinpoint sources of contamination in food and/or water samples. Therefore, this review will focus on MIP-based sensors for monitoring pollutants and heavy metals by critically evaluating relevant literature sources from 1993 to 2022.

Construction and application of a novel electrochemical sensor for trace determination of uranium based on ion-imprinted polymers modified glassy carbon electrode

In the present work, a novel electrochemical sensor modified glassy carbon electrode with ion-imprinted polymers (IIP-GCE) was applied for uranyl ions (UO₂²⁺) determination. Surface modifier was synthesized through precipitation polymerization method, using acrylic acid as a monomer, benzoyl peroxide (BPO) as initiator, and trimethylolpropane triacrylate (TMPTA) as cross-linker. A new uranyl-trans-3-(3-pyridyl) acrylic acid complex was employed, serving as an active and specific site on the synthesized modifier. Next, the synthesized modifier was characterized using X-ray diffraction (XRD), Scanning Electron microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. UO₂²⁺ ions were detected using a differential pulse adsorptive anodic stripping voltammetry method. Under the optimized conditions (pH = 8.0, pre-concentration time = 10 min and pre-concentration potential = -0.30 V), the modified electrode exhibited linear behavior in the interval of 1.27-95.49 μg.L^-1 with a limit of detection (LOD) of 0.43 μg.L^-1. Also, the constructed ion-imprinted sensor showed a successful application for determining UO₂²⁺ ions with recovery range of 97.6-101% in real samples.

Novel Chemoresistive Sensor for Sensitive Detection of Pb2+ Ions Using an Interdigital Gold Electrode Fabricated with a Reduced Graphene Oxide-Based Ion-Imprinted Polymer

This study presents novel chemoresistive reduced graphene oxide-ion-imprinted polymer (IIP-rGO)-based sensors for detection of lead (Pb2+) ions. The ion-imprinted polymer was synthesized by bulk polymerization and modified with a variable amount of rGO incorporated to form an IIP-rGO composite. The amount of rGO in the polymer matrix affected the sensor's relative response, and 1:3 mass ratio produced excellent results, with a consistent trend as the concentration of Pb2+ ions increased in the solution. The decrease in relative resistance (ΔR/R o) followed an exponential decay relationship between the ΔR/R o response and the concentration of Pb2+ ions in aqueous solutions. After solving the exponential decay function, it is observed that the sensor has the upper limit of ΔR/R o >1.7287 μg L-1, and the limit of detection of the sensor is 1.77 μg L-1. A nonimprinted polymer (NIP)-based sensor responded with a low relative resistance of the same magnitude although the concentration was varied. The response ratio of the IIP-based sensor to the NIP-based sensor (ΔR/R o)IIP/(ΔR/R o)NIP as a function of the concentration of Pb2+ ions in the solution shows that the response ratios recorded a maximum of around 22 at 50 μg L-1 and then decreased as the concentration increased, following an exponential decay function with the minimum ratio of 2.09 at 200 μg L-1 but never read 1. The sensor showed excellent selectivity against the bivalent cations Mn2+, Fe2+, Sn2+, and Ti2+. The sensor was capable of exhibiting 90% ΔR/R o response repeatability in a consecutive test.

Acid-etched Fe/Fe2O3 nanoparticles encapsulated into carbon cloth as a novel voltammetric sensor for the simultaneous detection of Cd2+ and Pb2

A portable electrode with usability, availability, and high-sensitivity is of great significance for effective on-site detection in practical situations. In this paper, a novel flexible, disposable sensor for Cd²⁺ and Pb²⁺ with ultrahigh sensitivity and a fast response, based on acid-etched Fe/Fe₂O₃ encapsulated into a disposable carbon cloth electrode, has been successfully fabricated. Differential pulse anode stripping voltammetry (DPASV) was used to investigate the stripping behavior of Cd²⁺ and Pb²⁺, achieving high sensitivity for Cd²⁺ and Pb²⁺ (338.7 and 408.0 μA mM^-1 cm^-2) with limits of detection (LODs) of 0.42 ppb and 0.50 ppb, respectively. Meanwhile, remarkable stability and reproducibility were obtained. Such an electrode can detect Cd²⁺ and Pb²⁺ in actual water samples so this is a good candidate to act as a simple and convenient sensor for general applications. More importantly, the novel disposable electrode exhibited the unique advantages of convenience, portability, and reliability compared to a conventional electrode, which may make it an alternative advantageous choice for practical on-site detection.

A Critical Review on the Synthesis and Application of Ion-Imprinted Polymers for Selective Preconcentration, Speciation, Removal and Determination of Trace and Essential Metals from Different Matrices

The presence of toxic trace metals and high concentrations of essential elements in the environment presents a serious threat to living organism. Various methods have been used for the detection, preconcentration and remediation of these metals from biological, environmental and food matrices. Owing to the complexicity of samples, methods with high selectivity have been used for detection, preconcentration and remediation of these trace metals. These methods are achieved by the use of ion-imprinted polymers (IIPs) due to their impressive properties such as selectivity, high extraction efficiency, speciation capability and reusability. Because of the increase of toxic trace and essential metals in the environment, IIPs have attracted great use in analytical chemistry. This review, provide a brief background on IIPs and polymerization method that are used for their preparation. Recent applications of IIPs as adsorbents for preconcentration, removal, speciation and electrochemical detection of trace and essential metal is also discussed.

Novel magnetic ion-imprinted polymer: an efficient polymeric nanocomposite for selective separation and determination of Pb ions in aqueous media

A novel ion-imprinted polymer (IIP) toward Pb(II) recognition was synthesized on the surface of magnetic multi-walled carbon nanotubes (magnetic MWCNTs). In order to prepare magnetic functionalized-MWCNT/IIP (magnetic f-MWCNT/IIP), copolymerization of methylenebisacrylamide (MBAm) and acrylamide (AM) in the presence of dithizone-Pb(II) complex was carried out on the surface of the magnetic f-MWCNTs. Selectivity of the new synthesized sorbent toward Pb(II) and the influence of a variety of foreign ions on the recognition, preconcentration, and removal of Pb(II) were evaluated using adsorption experiments in aqueous solution. The synthesized sorbent exhibited a good affinity with high adsorption capacity (Q = 80.81 mg/g) and an excellent selectivity toward Pb(II) in comparison with other common cations including alkaline, alkaline earth, and transition metals such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Cd²⁺, and Ni²⁺. The parameters such as adsorption and desorption time, adsorption capacity, effect of the sorbent mass, eluent type, concentration and volume, and also pH of the solutions were investigated. The result demonstrated that the proposed sorbent provided a fast removal and higher maximum binding capacity compared to other reported synthesized sorbents. The characteristics of the magnetic f-MWCNT/IIP were analyzed using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), vibrating sample magnetometer (VSM), and elemental analysis (EA). Graphical abstract ᅟ.

Competitive adsorption behavior toward metal ions on nano-Fe/Mg/Ni ternary layered double hydroxide proved by XPS: Evidence of selective and sensitive detection of Pb(II)

Hypersensitive and highly selective nanomaterials for the measurement of heavy metal ions (HMIs) hold a key to electro-analysis. Various works improved the results of analysis but without scientific understanding. Herein, Fe/Mg/Ni-layered double hydroxide (LDH) has been successfully prepared and its electrochemical behavior for Pb(II) detection is also studied using square wave anodic stripping voltammetry (SWASV). The well performance of electrochemistry suggest that the modification with Fe/Mg/Ni-LDH significantly promotes the selectivity and sensitivity toward Pb(II). The sensitivity on Fe/Mg/Ni-LDH modified glassy carbon electrode (GCE) is 68.1μAμM^-1 over the range from 0.03 to 1.0μM under the optimized conditions. Otherwise, the selectivity, anti-interference, stability measurements and practical implications of Fe/Mg/Ni-LDH modified GCE are also performed. What^,s more, a reasonable mechanism of detection for Pb(II) including selectivity and sensitivity is proposed based on adsorption and characterized using XPS and XRD. These findings provide a potentially excellent material to improve the sensitivity and selectivity for toxic metal ions as well as a deep understanding of detection.

Novel PVA/MOF Nanofibres: Fabrication, Evaluation and Adsorption of Lead Ions from Aqueous Solution

Plain polyvinyl alcohol (PVA) nanofibres and novel polyvinyl alcohol benzene tetracarboxylate nanofibres incorporated with strontium, lanthanum and antimony ((PVA/Sr-TBC), (PVA/La-TBC) and (PVA/Sb-TBC)), respectively, where TBC is benzene 1,2,4,5-tetracarboxylate adsorbents, were fabricated by electrospinning. The as-prepared electrospun nanofibres were characterized by scanning electron microscope (SEM), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). Only plain PVA nanofibres followed the Freundlich isotherm with a correlation coefficient of 0.9814, while novel nanofibres (PVA/Sb-TBC, PVA/Sr-TBC and PVA/La-TBC) followed the Langmuir isotherm with correlation coefficients of 0.9999, 0.9994 and 0.9947, respectively. The sorption process of all nanofibres followed a pseudo second-order kinetic model. Adsorption capacity of novel nanofibres was twofold and more compared to that of plain PVA nanofibres. The thermodynamic studies: apparent enthalpy (ΔH°) and entropy (ΔS°), showed that the adsorption of Pb(II) onto nanofibres was spontaneous and exothermic. The novel nanofibres exhibited higher potential removal of Pb(II) ions than plain PVA nanofibres. Ubiquitous cations adsorption test was also investigated and studied.

Selective Solid-Phase Extraction of Lead Ions in Water Samples Using Three-Dimensional Ion-Imprinted Polymers

Ion-imprinted polymers (IIPs) have drawn much attention in the selective determination of heavy metals. In this study, 8-hydroxyquinoline-grafted gelatin with different types of functional groups was first introduced as a biomolecular monomer to enhance the selectivity of imprinted cavities. Based on its swelling and film-forming properties, a simple strategy containing formation of the hydrogel film, swelling/folding followed by cross-linking, was proposed to prepare three-dimensional IIPs with high adsorption capacity (235.7 mg g(-1)), strong selectivity (imprinted factor was 2.9), and rapid kinetics. Based on the different swelling container, different morphologies of IIPs could be prepared to satisfy the requirements of practical application. Consequently, the IIPs extraction coupled with a spectrophotometric method was applied for determination of lead ions, and the limit of detection was 0.2 ng mL(-1), which could be used for monitoring of Pb(II) in drinking water and surface water.

An atomically thick titanium phosphate thin layer with enhancing electrochemical sensitivity toward Pb(ii)

An atomically thick titanium phosphate thin layer is synthesized and used for sensitive electrochemical detection for Pb(ii) with a high sensitivity and low limit of detection.

Synthesis of a Ni(ii) ion imprinted polymer based on macroporous–mesoporous silica with enhanced dynamic adsorption capacity: optimization by response surface methodology

In this study, a Ni(ii) ion imprinted polymer (Ni(ii)-IIP) based on macroporous–mesoporous silica (MMS) was optimally synthesized using a response surface methodology (RSM) approach for enhanced dynamic adsorption capacity.

Synthesis of ion imprinted polymeric nanoparticles for selective pre-concentration and recognition of lithium ions

A new Li⁺–IIP has been prepared for the fast determination and selective separation of lithium ions in aqueous samples.

Synthesis and application of nano-sized ionic imprinted polymer for the selective voltammetric determination of thallium

A simple and selective thallium imprinted polymer was synthesized as a chemical modifier for the stripping voltammetric determination of Tl ions. The polymerization process (bulk polymerization) was performed with ethylene glycol dimethacrylate (crosslinking monomer) and methacrylic acid (functional monomer) in the presence of 2,2'-azobis(isobutyronitrile) (initiator). The electrochemical method was based on the accumulation of thallium ions at the surface of a modified carbon paste electrode with Tl imprinted polymer and multi-walled carbon nanotubes. After preconcentration process, the voltammetric measurements were carried out via electrolysis of the accumulated Tl ions in a closed circuit. Under the optimized conditions, a linear response range from 3.0 to 240 ng mL(-1) was obtained. The detection limit and RSD (100.0 ng mL(-1) of Tl) were calculated as 0.76 ng mL(-1) and ±2.7%, respectively. The suggested modified electrode has good characteristics such as excellent selectivity, high sensitivity and suitable stability. Also, it was successfully applied for the electrochemical determination of trace amounts of Tl in the environmental and biological samples.

Highly selective monitoring of metals by using ion-imprinted polymers

Ion imprinting technology is one of the most promising tools in separation and purification sciences because of its high selectivity, good stability, simplicity and low cost. It has been mainly used for selective removal, preconcentration, sensing and few miscellaneous fields. In this review article, recent methodologies in the synthesis of IIPs have been discussed. For several applications, different parameters of IIP including complexing and leaching agent, pH, relative selectivity coefficient, detection limit and adsorption capacity have been evaluated and an attempt has been made to generalize. Biomedical applications mostly include selective removal of toxic metals from human blood plasma and urine samples. Wastewater treatment involves selective removal of highly toxic metal ions like Hg(II), Pb(II), Cd(II), As(V), etc. Preconcentration covers recovery of economically important metal ions such as gold, silver, platinum and palladium. It also includes selective preconcentration of lanthanides and actinides. In sensing, various IIP-based sensors have been fabricated for detection of toxic metal ions. This review article includes almost all metal ions based on the ion-imprinted polymer. At the end, the future outlook section presents the discussion on the advancement, corresponding merits and the need of continued research in few specific areas. Graphical Abstract IIPs for the selective monitoring of metals.

Green synthesis of gold nanoparticles and its application for the trace level determination of painter's colic

The green synthesis of metal nanoparticles is found to be more attractive in various disciplines, including in analytical chemistry for heavy metal ion sensing.

Synthesis and characterization of diphenylcarbazide-siliceous mesocellular foam and its application as a novel mesoporous sorbent for preconcentration and trace detection of copper and cadmium ions

We are introducing diphenylcarbazide functionalized siliceous mesocellular foam as a novel mesoporous solid-phase for the extraction of heavy metal ions including copper(ii) and cadmium(ii).

Silver ion imprinted polymer nanobeads based on a aza-thioether crown containing a 1,10-phenanthroline subunit for solid phase extraction and for voltammetric and potentiometric silver sensors

A new nano-sized silver(I) ion-imprinted polymer (IIP) was prepared via precipitation copolymerization using ethyleneglycol dimethacrylate, as a cross-linking agent in the presence of Ag(+) and an aza-thioether crown containing a 1,10-phenanthroline subunit as a highly selective complexing agent. The imprint silver(I) ion was removed from the polymeric matrix using a 1.0M HNO3 solution. The resulting powder material was characterized using IR spectroscopy and scanning electron microscopy. The SEM micrographs showed colloidal nanoparticles of about 52 nm and 75 nm in diameter and slightly irregular in shape for leached and unleached IIPs, respectively. The optimal pH for quantitative enrichment was 6.0 and maximum sorbent capacity of the prepared IIP for Ag(+) was 18.08 μmol g(-1). The relative standard deviation and limit of detection (LOD=3Sb/m) for flame atomic absorption spectrometric determination of silver(I) ion, after its selective extraction by the prepared IIP nanobeads, were evaluated as 2.42% and 2.2×10(-8) M, respectively. The new Ag(+)-IIP was also applied as a suitable sensing element to the preparation of highly selective and sensitive voltammetric and potentiometric sensors for ultra trace detection of silver(I) ion in water samples, with limits of detection of 9.0×10(-10) and 1.2×10(-9) M, respectively.

Nanomaterials-based electrochemical detection of chemical contaminants

Recent advances in the development of nanomaterials-based electrochemical sensors for environmental monitoring and food safety applications are assessed.

A novel ion-imprinted electrode prepared by in situ polymerization for detection of platinum

A novel ion imprinted electrode with high sensitivity and specific recognition to Pt(iv) was obtained byin situpolymerization.