Square Wave Anodic Stripping Voltammetry Research Articles

Designed 3D porous core-shell vanadium oxide microspheres for the simultaneous electrochemical sensing of toxic metal ions

The novel 3D porous core-shell vanadium oxide microspheres (CS–V2O5) were successfully prepared through a simple in-situ hydrothermal growth strategy followed by annealed in the air. The obtained CS-V2O5 with high porosity was assembled by many nanoparticles, which can not only provided more active sites, possessed highly enrichment ability, but also offered abundant ions transport channels, effectively shortened the ions diffusion distance and facilitated the rapid transport of electrolyte ions. Square wave anodic stripping voltammetry (SWASV) study showed the CS-V2O5 modified electrode (CS–V2O5/GCE) displayed enhanced electrochemical activity for detecting thallium (Tl+) and indium (In3+) ions synchronously due to the desirable structural property compared with V2O5 nanoparticles (NPs) and V2O5 nanorods (NRs). As a result, the linear range of Tl+ and In3+ was from 1.0 μg L−1 to 50.0 μg L−1 and the detection limit (LOD, S/N = 3) can arrived at 0.1 μg L−1. Furthermore, the developed sensor exhibited superior stability, satisfactory reproducibility, and provided a new approach for the construction of high-performance electrochemical sensor towards toxic metal ions.

Fully integrated battery-free and flexible electrochemical tag for on-demand wireless in situ monitoring of heavy metals

Migration of heavy metals from food contact materials to contained foods and drinks will cause severe health problems. The in situ analysis of the heavy metal ions inside these containers is in high demand. In this study, a fully integrated battery-free and flexible electrochemical tag is presented for wireless in situ detections of heavy metal ions in various containers. The circuit part of the tag is integrated with square wave anodic stripping voltammetry (SWASV) technique and near field communication (NFC) module, enabling on-board electrochemical sensing, wireless data transmission, and power harvesting. The circuits showed high consistency with commercial electrochemical workstation in SWASV analysis. A screen-printed flexible electrode array is connected with the circuit board. The working electrodes were modified with gold and bismuth nanoparticles respectively, which showed high sensitivity, selectivity, linearity, and reproducibility in the detections of lead and cadmium. The tag achieved quantitative detections of heavy metal ions in various containers, including enamelled cup, ceramic teapot, and dark-red enameled pottery. With proper encapsulation, the miniaturized passive and flexible tag can be attached to the inside surface of various containers for a long time. The wireless detections of heavy metal ions can be achieved just with an NFC-enabled smartphone outside the container. The platform provides a simple and effective solution for in situ analysis of toxic and harmful substances, which can be widely used in the areas of food safety and water quality monitoring.

Multi-channel electroanalysis of As (III), Hg and Cu in the complex matrix of Bombyx batryticatus after pre-purification

The resources of animal medicinal materials have gradually attracted the attention of people around the world, however, the increase of heavy metals in animal medicine possesses a serious threat to human health. A multi-channel analysis technique with high accuracy and sensitivity become more urgent and necessary, particularly in such complex animal matrix which contains various interference components. Here, a multi-channel analysis strategy for the detection of As (Ⅲ), total Cu and Hg at trace level in Bombyx batryticatus was established by using square wave anodic stripping voltammetry (SWASV) on prepared Au nanoparticles (AuNPs) combined with four different purification procedures. Firstly, a nano-sized uniform spherical AuNPs material was electro-deposited onto a bare Au substrate, which leads to the enhancement of effective working area at 6.98% after modification. Secondly, the animal matrix was purified by electrochemical deposition (ED) and special removal materials for the methodology study in positive samples, which proved that above purification procedure can reduce interference and lower the current baseline of Bombyx batryticatus matrix successfully. Thirdly, the electrochemical property of As (Ⅲ), Cu and Hg was obtained successfully, and the validation result was demonstrated that the intensity of the significant anodic peaks of As, Cu and Hg at −0.045 V, 0.177 V and 0.322 V were proportional (R2 = 0.9996, 0.9929, 0.9987) to their concentrations in the purified sample solution in the range of 0.01–0.10 mg L−1, with a satisfactory recovery rate (97.50%–103.00%) and detection limits (0.0004 mg L−1, 0.0013 mg L−1 and 0.0035 mg L−1). Therefore, the proposed SWASV technique combined with purification procedure would have wide application prospect especially on the online monitoring of multiple heavy metals in other animal drugs.

Improved electrochemical detection of metals in biological samples using 3D-printed electrode: Chemical/electrochemical treatment exposes carbon-black conductive sites

This work shows that the electrochemical activity of a 3D-printed electrode fabricated using a conductive composite of polylactic acid (PLA) containing carbon black (CB) can be substantially improved through a simple and fast chemical/electrochemical pretreatment in 0.5 mol L−1 NaOH. Scanning electron microscopy and infrared spectroscopy data showed that the pretreatment process promotes the removal of the non-conductive PLA material, providing greater exposure of the conductive particles. Cyclic voltammetry of the redox probe ferricyanide/ferrocyanide indicated faster electron transfer on the treated 3D-printed surface and increase in electroactive area. Moreover, electrochemical impedance spectroscopic results also confirmed faster electron transfer after surface pretreatment. As a proof-of-concept, a low-cost and sensitive method for the determination of cadmium and lead in real urine and saliva samples by square-wave anodic stripping voltammetry was developed. The chemical/electrochemical treatment provided an impressive 30-fold current increase in the detection of both metals. Acceptable limits of detection (2.9 μg L−1 for Cd2+ and 2.6 μg L−1 for Pb2+), wide linear ranges for both metals (30 μg L−1 to 270 μg L−1; R = 0.997), high stability (RSD lower than 4.5%; n = 10), and adequate recovery values (between 93% and 112%) for the analysis of spiked samples were achieved. Additionally, interday (n = 3), intra-day (n = 3), inter-electrode (n = 2) and inter-treatment (n = 2) experiments revealed RSD values lower than 6.5%, which indicates high reproducibility of the proposed treated 3D-printed electrode. The strategy here proposed opens up new applications for 3D-printed electrode in analytical electrochemistry with improved electrochemical sensing properties in comparison to screen-printed electrodes.

Ultrasensitive Platform for Electrochemical Sensing of Copper and Antimony Based on Poly(1,5-Diaminoanthraquinone)/Multiwalled Carbon Nanotubes/Carbon Paste Electrode

A new sensor for the detection of copper (II) (Cu2+) and antimony (III) (Sb3+) metal ions is described herein. The sensor is based on multi-walled carbon nanotubes mixed with a carbon paste electrode modified by poly(1,5-diaminoanthraquinone) (p-1,5-DAAQ). The Cu2+ and Sb3+ ions were effectively detected by square wave anodic stripping voltammetry (SWASV) both individually and simultaneously. The proposed modified electrode was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Poly(1,5-diaminoanthraquinone)/multi-walled carbon nanotubes/carbon paste electrode (p-1,5-DAAQ/MWCNT/CPE) was utilized for electrochemical determination of Cu2+ and Sb3+ under pre-optimized conditions (i.e., deposition potential, deposition time, square wave frequency, and concentration of HCl). For simultaneous detection, a linear range of 1–180 μ l−1 was employed with a limit of determination (LOD) of 1.3 and 1.4 ng l−1 for Cu2+ and Sb3+, respectively. Moreover, for individual detection, a linear range of 2–30 μg l−1 was used for Sb3+, while for Cu2+ it was set at 0.5–25 μg l−1, with a limit of detection of 205.7 ng l−1 and 1.9 ng l−1 for Cu2+ and Sb3+, respectively. The effects of Tween 80 (nonionic surfactant) and humic acid on the metal peak current were also studied. Water samples spiked with both Cu2+ and Sb3+ were analyzed utilizing the proposed method as well as by inductively coupled plasma-mass spectroscopy (ICP-MS). Overall, good recovery values were achieved, demonstrating the applicability of the described approach for the detection of metal ions in real water samples.

Ultrasensitive and Simultaneous Electrochemical Determination of Pb2+ and Cd2+ Based on Biomass Derived Lotus Root-Like Hierarchical Porous Carbon/Bismuth Composite

A green and effective strategy to prepare a novel lotus root-like three-dimensional (3D) bismuth/biomass derived activated carbon (Bi@BAC) composite was developed for simultaneous electrochemical sensing of Pb2+ and Cd2+. The BAC supports herein were prepared from naturally-abundant Platanus seeds chemically activation by KOH, with dense and uniform bismuth micro/nano-sized particles successfully anchored on the carbon substrate through microwave-assisted hydrothermal treatment and subsequent carbothermal reduction process. Simultaneous electrochemical detection of Pb2+ and Cd2+ using square wave anodic stripping voltammetry (SWASV) was performed with the novel composite modified carbon paste electrode (CPE). Under optimized experimental conditions, the Bi@BAC/CPE demonstrated good linear response for both two target metal ions in the concentration range of 0.5 to 50 μg L−1, with limits of detection (LOD, S/N = 3) of 0.13 and 0.08 μg L−1 for Pb2+ and Cd2+, respectively. Moreover, the modified electrode displayed high resistance to interference, long-term stability and good reproducibility. The Bi@BAC/CPE also demonstrated satisfactory recovery level for the detection of target metal ions in real water samples.

Detection of Copper Ions by a Simple, Greener and Cost Effective Sensor with GCE Modified with L-Tryptophan

Metal ions contamination is the leading cause of many health and environmental problems. In order to rectify and remediate the environment from metal ions contamination, simple, efficient and easy to fabricate sensors for the onsite detection of metals ions is obligatory. However, devising a practically applicable sensor that could be compatible to the environment which contains a plethora of other ions than the target metal ions, is very challenging. In this work we report a highly sensitive and selective yet simple and greener electrode for copper ions detection by modifying GCE with amino acid-L-tryptophan. The modifier brings about increase in active surface area of the GCE and effectively binds to the metal ions through the process of chelation utilizing its amino and carboxylic acid functional groups. Cyclic voltammetry (CV), square wave voltammetry (SWV) and square wave anodic stripping voltammetry (SWASV) along with electrochemical impedance spectroscopy (EIS) was conducted to investigate the surface of the electrode and its sensitivity towards detection of Cu1+ and Cu2+ ions. A number of experimental parameters such as pH, supporting electrolyte, concentration of the modifier, accumulation time and deposition potential were investigated to achieve best response of the metal ions towards the modified electrode. The designed sensor exhibited excellent electrocatalytic activity and sensitivity towards Cu1+ ions even in the presence of 5-fold higher concentration of different interferents. The LOD (Limit of detection) of 3.13 pM as determined by the calibration curve was found to be much lower than permissible values suggested by the WHO (World Health Organization) and US EPA (Environmental Protection Agency). % age recoveries as estimated from real water samples was found to be within 3% RSD value and proved the validity of the proposed methodology for the designed sensor. Computational studies were carried out using hyperchem 7.5 software with semi empirical PM3 method. The negative value of binding energy of the merged molecule i.e., −3024.181 kcal mol−1 point towards significant interactions between L-tryptophan and Cu2+ ions which is evident from the change in physicochemical properties upon merging of L-tryptophan with Cu2+ ions. Our computational studies agree well with the experimental results.

Improved anodic stripping voltammetric detection of zinc on a disposable screen-printed gold electrode

Herein, we report the improved detection of Zn2+ via square-wave anodic stripping voltammetry utilizing an electrochemically treated screen-printed gold electrode. Surface analysis of the gold surface revealed increase in rugosity, removal of residual polymeric ink, and consequent higher access to gold microparticles after electrochemical treatment which resulted in improved response for Zn2+ (detection limit of 2.5 μg L− 1). The intra- and inter-electrode precision values were calculated as 3% (n = 10) and 12.5% (n = 3), respectively, applying − 0.9 V for 90 s under stirring of 1000 rpm for pre-concentration of Zn2+ (step potential: 4 mV; amplitude: 50 mV, frequency: 50 Hz) in 0.04 mol L− 1 Britton-Robinson buffer (pH 7.0) as the background electrolyte. Satisfactory recovery values ranging 96 to 104% were achieved for the analysis of struvite (spiked sample). Therefore, the proposed sensor provides precise and accurate direct analyses, without interference from other metals, with rapid responses enabling on-site analyses.

Rapid and simultaneous electrochemical method to measure copper and lead in canine liver biopsy

The conventional analytical techniques used for the quantitative analysis of heavy metals in animal tissues are the atomic absorption spectroscopy (AAS) and the inductively-coupled plasma mass spectrometry (ICP-MS). These methods involve high cost, skilled personnel and long analysis times. Several studies have shown the applicability of electrochemical transducer coupled to disposable screen-printed electrodes (SPE) for measuring metals. The aim of the present study was to applicate and validate a simple and fast protocol for the simultaneous measurement of Cu and Pb concentrations in canine liver biopsy, coupling a simple digestion procedure with electrochemical stripping analysis. Square wave anodic stripping voltammetry (SWASV) coupled to disposable SPE was employed as fast and sensitive method for metals detection. Samples were digested with hydrogen peroxide/hydrochloric acid mixture for 1 h coupled to solid phase purification with carbon columns. Instrumental precision, digestion procedure accuracy and limits of detections were evaluated. To validate the proposed method the metal concentrations have also been determined by AAS. Instrumental precision and digestion method accuracy were less than 15.3% and 16.8% for Cu and Pb, respectively. The limits of detection were 10 and 6 mg/kg dry weight in liver samples for Cu and Pb, respectively. The results obtained by the electrochemical method are in agreement with those of the reference method. The obtained results showed a reliable approach for Cu and Pb detection simultaneously with good sensitivity, accuracy and precision. The simple sample pre-treatment together with the low cost makes this approach particularly appealing for Cu and Pb quantification for diagnostic purposes.•Simultaneous determination of Cu and Pb concentrations in canine liver biopsy.•Square wave anodic stripping voltammetry (SWASV) with screen-printed electrodes (SPE) coupled to an acid digestion protocol.•Cu and Pb were measured with a very good sensitivity and accuracy.•Good agreement with AAS reference method.•Low cost, fast and sensitive method for diagnostic purposes.

Synthesis of bismuth nanoparticle-loaded cobalt ferrite for electrochemical detection of heavy metal ions.

As an efficient modified electrode material for the detection of heavy metal ions, bismuth nanoparticles (BiNPs) were loaded on cobalt ferrite (CoFe2O4), a unique magnetic photocatalytic material, to fabricate a highly sensitive sensor. The obtained BiNPs@CoFe2O4 nanocomposites showed excellent adsorption and electrical conductivity using a Square Wave Anodic Stripping Voltammetry (SWASV) detection method. Under optimized conditions, the BiNPs@CoFe2O4/GCE sensor could simultaneously determine Pb2+ and Cd2+, with detection limits of 7.3 and 8.2 nM, respectively. In addition, the BiNPs@CoFe2O4 exhibited acceptable reproducibility and good stability, which indicated great potential for the detection of heavy metal ions in reality.

Facile Trace Mercury (II) Sensor Using Statistically Optimized Electrochemical Co-deposited Gold Nanofilm Modified Screen-Printed Carbon Electrodes

Rapid detection of trace mercury (II) in water is very challenging. A novel sensor for the facile detection of mercury (II) was developed using electrochemically co-deposited gold nanofilm modified screen-printed carbon electrodes (EcoD-AuNF/SPCE). Because a monolayer of gold nanofilm is freshly co-deposited during the mercury (II) preconcentration period, no additional modification on an electrode is required prior to a test. Central composite design (CCD) and response surface methodology (RSM) were used to evaluate the effects of the critical testing parameters simultaneously (i.e., the co-deposited gold concentration of $350\,\,\mu \text{g}\,\,\text{L}^{-1}$ , deposition potential of −0.75 V, and testing pH of 3.50). The response of square-wave anodic stripping voltammetry (SWASV) showed a linear relationship with the mercury (II) concentration over a range of 1 to $40~\mu \text{g}$ /L (ppb), with an LoD of $0.29~\mu \text{g}$ /L and sensitivity of $0.37~\mu \text{A}$ /ppb. Significant influences on the mercury (II) stripping peak potential, peak height, and peak shape were observed in the presence of chloride. Therefore, an optimized amount of chloride (i.e., 600 mg/L) was preemptively added to minimize the potential effect of naturally occurring chloride and to improve further the detection sensitivity (i.e., LoD of $0.16~\mu \text{g}$ /L and sensitivity of $0.55~\mu \text{A}$ /ppb). Validation testing using real-world water samples indicated reliable prediction of mercury (II) concentration could be obtained in complex media. In summary, this newly developed voltammetric approach has excellent detection performance and practical significance for potential on-site voltammetric determination of trace mercury (II) in water.

Determination of 8-hydroxy-7-iodo-5-quinoline sulfonic acid (HIQSA) at renewable electrode with Sb2O3/MWCNT-TiO2 nanohybrid

8-hydroxy-7-iodo-5-quinoline sulfonic acid (HIQSA) was determined using square wave anodic stripping voltammetry (SWASV) at the surface of carbon paste electrode modified with Sb2O3 and multi-walled carbon nanotubes-titanium dioxide nanohybrid (Sb2O3/TiO2-MWCNTPE) in aqueous media. To estimate the properties and morphology of the modified electrode, field emission-scanning electron microscopy (FE-SEM) coupled by energy dispersive spectroscopy (EDS) was applied. The linear concentration range was found to be 1.0 to 100 μM by using accumulation potential of −0.8 V and accumulation time of 150 s. Under these conditions, LOD and LOQ were obtained at 1.2 and 3.9 μM, respectively. This newly developed method was successfully applied for the determination of HIQSA in tap water.

Amino Acid-Fabricated Glassy Carbon Electrode for Efficient Simultaneous Sensing of Zinc(II), Cadmium(II), Copper(II), and Mercury(II) Ions.

Herein, we present a greener approach to achieve an ultrasensitive, selective, and viable sensor engineered by amino acids as a recognition layer for simultaneous electrochemical sensing of toxic heavy metals (HMs). Electrochemical techniques like electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square-wave anodic stripping voltammetry (SWASV) were applied to demonstrate sensing capabilities of the designed analytical tool. The comparative results of different amino acids demonstrate alanine’s superior performance with a well-resolved and enhanced current signal for target metal ions due to strong complexation of its functional moieties. The working conditions for alanine-modified GCE were optimized by investigating the effect of alanine concentration, different supporting electrolytes, pH values, accumulation potentials, and time. The limits of detection for Zn2+, Cd2+, Cu2+, and Hg2+ were found to be 8.92, 5.77, 3.01, and 5.89 pM, respectively. The alanine-modified electrode revealed absolute discrimination ability, stability, and ultrasensitivity toward metal ions even in the presence of multifold interfering species. Likewise, greener modifier-designed electrodes possessed remarkable electrocatalytic activity, cost affordability, reproducibility, and applicability for picomolar level detection of HM ions in real water sample matrixes. Theoretical calculations for the HM–amino acid interaction also support a significantly improved mediator role of the alanine modifier that is consistent with the experimental findings.

Square Wave Anodic Stripping Voltammetric Determination of Paracetamol at Poly Luminol/Functionalized Multi-Walled Carbon Nanotubes Modified Glassy Carbon Electrode

In the present study an electrochemical sensor, based on glassy carbon electrode (GCE) modified by polyluminol (PLum)/functionalized multi-walled carbon nanotube (f-MWCNTs) was introduced for the determination of paracetamol. Modified electrode was made by casting the f-MWCNTs on GCE and electropolymerization of luminol on its surface. The surface morphology was investigated by scanning electron microscopy (SEM) and impedance electrochemical spectroscopy (EIS). The effective parameters on the response of the modified electrode were optimized, and the square wave anodic stripping voltammetry (SWASV) was applied for drug determination. Under the optimized conditions, at least two linear dynamic ranges (0.04–32.2 and 32.2–172.2 µM) were observed between the anodic peak currents and concentrations of PCM when PLum/f-MWCNTs/GCE was used, and its detection limit was 25 nM. The proposed electrode was successfully applied to determine PCM in pharmaceutical formulations, urine and serum samples.

Assembling reduced graphene oxide with sulfur/nitrogen- “hooks” for electrochemical determination of Hg(II)

Herein the sulfur/nitrogen contained groups, serving as the “hooks” for electrochemical determination of Hg(II), were assembled on the reduced graphene oxide (hereafter SN-rGO) via a one-step facile hydrothermal method. The thiourea acts as a precursor for sulfur/nitrogen doping and partial reduction of graphene oxide. The SN-rGO was used to modify the glassy carbon electrode (GCE) for electrochemical detection of Hg(II) by square wave anodic stripping voltammetry (SWASV). The sulfur/nitrogen doping significantly improves the Hg(II) complexation by SN-rGO due to the creation of multifunctional groups on the graphene nanosheet. The SN-rGO modified electrode has excellent sensitivity (20.48 μA/μM) and limit of detection (LOD 8.93 nM) for Hg(II) detection. The newly developed Hg(II) sensing electrode possesses minimal interference for other ions typically found in natural waters. Therefore, it can be used for routine water quality monitoring. The fabrication of the SN-rGO electrode is rapid and low cost; hence, it offers a potential platform for environmental monitoring of toxic metal ions.

Simultaneous electrochemical determination of Sb(III) and Sb(V) in Water samples: Deposition potential differences and Sb(III) photooxidation characteristics

Many theoretical studies on the photooxidation characteristics of Sb(III) have been performed in recent years, but these characteristics haven’t been well used by now. This research, based on the photooxidation characteristics of Sb(III) and the electrochemical activity difference between Sb(III) and Sb(V), realized the determination of Sb species in a single electrolyte solution by square-wave anodic stripping voltammetry (SW-ASV) without adding any external oxidant or using complex calculations. The electrolyte solution used in this research was 2.0 mol/L HCl, which could promote both the photooxidation of Sb(III) and the electroreduction of Sb(V) by forming chlorination complexes with Sb. Under this condition, Sb(III) had an obvious anodic stripping peak at an enrichment potential of −0.4 V, while Sb(V) was not detected at this enrichment potential. The whole system was exposed to ultraviolet light for a suitable time to ensure that all Sb(III) was oxidized to Sb(V) after the determination of Sb(III). Then, Sb(V) was detected at an enrichment potential of −0.9 V, which represented the total Sb concentration (Sb(tot)) in solution. The original Sb(V) concentration was calculated from the difference between the concentrations of Sb(tot) and Sb(III). Sb(III) photooxidation mechanism investigation proved that O2 play an important role in the photooxidation process and photoinduced H2O2 was the major oxidant of Sb(III). The linear ranges of Sb(III) and Sb(V) were 0.6–1.5 and 0.7–10.0 μmol/L, with detection limits of 4.21 and 5.05 nmol/L, respectively. This method has been successfully applied to Sb speciation and concentration determination in water samples.

Functionalization of PET Track-Etched Membranes by UV-Induced Graft (co)Polymerization for Detection of Heavy Metal Ions in Water

Nowadays, water quality monitoring is an essential task since environmental contamination and human exposure to heavy metals increased. Sensors that are able to detect ever lower concentrations of heavy metal ions with greater accuracy and speed are needed to effectively monitor water quality and prevent poisoning. This article shows studies of the modification of flexible track-etched membranes as the basis for the sensor with various polymers and their influence on the accuracy of detection of copper, cadmium, and lead ions in water. We report the UV-induced graft (co)polymerization of acrylic acid (AA) and 4-vinylpyridine (4-VPy) on poly(ethylene terephthalate) track-etched membrane (PET TeMs) and use them after platinum layer sputtering in square wave anodic stripping voltammetry (SW-ASV) for detection of Cu2+, Cd2+, and Pb2+. Optimal conditions leading to functionalization of the surface and retention of the pore structure were found. Modified membranes were characterized by SEM, FTIR, X-ray photoelectron spectroscopy (XPS) and colorimetric analysis. The dependence of the modification method on the sensitivity of the sensor was shown. Membrane modified with polyacrylic acid (PET TeMs-g-PAA), poly(4-vinylpyridine) (PET TeMs-g-P4VPy), and their copolymer (PET TeMs-g-P4VPy/PAA) with average grafting yield of 3% have been found to be sensitive to µg/L concentration of copper, lead, and cadmium ions. Limits of detection (LOD) for sensors based on PET TeMs-g-PAA are 2.22, 1.05, and 2.53 µg/L for Cu2+, Pb2+, and Cd2+, respectively. LODs for sensors based on PET TeMs-g-P4VPy are 5.23 µg/L (Cu2+), 1.78 µg/L (Pb2+), and 3.64 µg/L (Cd2+) µg/L. PET TeMs-g-P4VPy/PAA electrodes are found to be sensitive with LODs of 0.74 µg/L(Cu2+), 1.13 µg/L (Pb2+), and 2.07 µg/L(Cd2+). Thus, it was shown that the modification of membranes by copolymers with carboxylic and amino groups leads to more accurate detection of heavy metal ions, associated with the formation of more stable complexes.

Kelp-Derived Activated Porous Carbon for the Detection of Heavy Metal Ions via Square Wave Anodic Stripping Voltammetry

Biomass-derived porous carbon materials with environmental adaptability and superior specific surface area have become one of the most promising materials in 21st era, especially in the electrochemical application. Herein, we proposed a kelp-derived carbon material (KPC) with a unique highly disordered graphite layer structure as an outstanding sensor via facile KOH activation method. The BET adsorption-desorption isotherm of KPC shows a typical IUPAC I type, and KPC possesses a high specific surface area with 2064 m2 g−1. Morphology observation and pore size analysis indicate that its porous-rich structure comprises countless micropores and mesopores. This unique structure of KPC not only provides massive active sites but exhibits high sensitivity in the detection of heavy metal by square wave anodic stripping voltammetry (SWASV), with Pb2+ at 53.4 μA μM−1 and Cd2+ at 26.5 μA μM−1 in simultaneous detection. This study reports a new strategy for the detection of heavy metal ions using porous metal-free carbon materials.

A Novel Electrochemical Sensor Based on A Glassy Carbon Electrode Modified with GO/MnO2 for Simultaneous Determination of Trace Cu(II) and Pb(II) in Environmental Water

AbstractIn this study, manganese dioxide hybridized with graphene oxide (GO/MnO2) nanocomposite was prepared by a facile synthesis method, which was applied to modify the glassy carbon electrode (GCE) in an electrochemical sensor of Cu(II) and Pb(II) for the first time. The morphology and structure of the nanocomposite were investigated by scanning electron microscopy, transmission electron microscopy and X‐ray diffraction, which exhibited MnO2 had been uniformly attached to the lamellar structure of GO, resulting in more adsorptive sites. Electrochemical properties of GO/MnO2/GCE were characterized by cyclic voltammetry and electrochemical impedance spectroscopy and the result confirmed GO/MnO2/GCE had an excellent electrochemical performance. Furthermore, the important factors affecting on the sensor sensitivity, including pH value, deposition potential, deposition time and material proportion were systematically investigated using square wave anodic stripping voltammetry (SWASV). The interferences from other ions on the target ion have also been discussed in this study. Under the optimal conditions, the GO/MnO2/GCE exhibited the linear ranges of 0.05 ∼ 1 μM for Cu(II) and Pb(II) with the detection limits of 1.67 nM and 3.33 nM, respectively, which was much lower than some electrochemical methods in reported literatures. The work provides a novel, simple and fast method for the simultaneous determination of Cu(II) and Pb(II).

A high-sensitive electrochemical DNA biosensor based on a novel ZnAl/layered double hydroxide modified cobalt ferrite-graphene oxide nanocomposite electrophoretically deposited onto FTO substrate for electroanalytical studies of etoposide

The combination of layered double hydroxides (LDHs), cobalt ferrite (CoFe2O4) and graphene oxide (GO) creates a ternary nanocomposite that can incredibly improve advantages of each compound; this is an impressive way to attain multifunctional materials with attractive properties. In this study, a new high-sensitive electrochemical DNA biosensor was fabricated for the electroanalytical studies of etoposide using a novel ZnAl/layered double hydroxide modified cobalt ferrite-graphene oxide nanocomposite (GO/CoFe2O4/ZnAl-LDH) that was electrophoretically deposited (EPD) on the fluorine tin oxide (FTO) substrate. This DNA biosensor was prepared via electrostatic adsorption of DNA onto the GO/CoFe2O4/ZnAl-LDH/FTO electrode. The electrochemical behavior of electrodes was characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). EIS plot obviously demonstrated a rapid electron transport at low frequencies for GO/CoFe2O4/ZnAl-LDH. Differential pulse voltammetry (DPV) and square wave anodic stripping voltammetry (SWASV) were employed for the electrochemical detection of ETO. The results revealed that DNA/GO/CoFe2O4/ZnAl-LDH/FTO bioelectrode had ultrahigh sensitivity to ETO with the detection limit of 0.0010 μM in the linear range of 0.2–10 μM. In addition, the developed biosensor revealed precise reproducibility and excellent stability of about 95% of the initial activity after 6–7 weeks. On the other hand, the present bioelectrode was also capable of discriminating different interferences and was also used to detect etoposide in real samples such as human blood plasma, serum and urine with good recoveries, ranging from 97.0% to 104.0%. The obtained results of the excellent performance of this biosensor could be assigned to the active reaction sites and good electrochemical activity of nanocomposites, hence helping increase the DNA immobilization and accelerate the electron transfer more effectively on the surface electrode.