Anodic Stripping Research Articles

Increasing Sensitivity and Selectivity for Heavy Metal Sensing through Microfluidic Electrochemical Sensor

Introduction Cadmium usually exists in nature as a compound and under normal environmental conditions, its small content will not affect human health. Nevertheless, with human society's development, heavy metal ions pollution has become substantially serious, and they have serious biological toxicity. Hence, it is important to develop simple, rapid, sensitive, and portable devices for Cd2+ sensing [1].In the present work, we show how paper based microfluidic sensors improve sensitivity and limit of detection (LOD) in comparison to classical screen-printed carbon-based electrode (SPCE). Furthermore, the presented microfluidic electrochemical carbon-based sensor (μCS) do not employ critical metals and rely on graphite foil that is modified by N-doped carbon nanoonions (N-CNOs) N-CNOs. Experimental For the synthesis of N-doped CNOs the Kuznetsov method was employed [2]. The alignment of the component for μCS device is sketched below. After providing the analyte solution through the sponge the electrochemical detection is carried out through accumulation of the metal at the working electrode for varying times and cathodic potentials. The final detection is carried out through square wave anodic stripping voltammetry (SWASV) of the accumulated metal. Results and discussion To realize a sensitive measurement, some experimental conditions including the optimal amount of the employed N-doped CNOs and Nafion in the nanocomposite, deposition time and potential, and the effect of pH of supporting electrolyte were studied. By increasing the deposition time ranging from 0 to 5 min, the SPCE/N-CNOs signal was increased and after that, it remains roughly constant because the WE surface is being saturated and also the amount of analyte in the droplet was reduced due to the presence of a stagnant flow. However, for μCS/N-CNOs by increasing the accumulation time ranging from 0 to 10 min the signal was increased which shows that the electrode surface is still far from being saturated (because of the live flow). A linear concentration range from 1.0 to 100.0 μg L- 1 was achieved using SWASV. Also, the LOD and sensitivity are calculated to be 0.5 μg L- 1 and 1.02 μA µM-1 cm-2, respectively. Additionally, the method was successfully employed for measurements of Cd2+ in different real samples, which demonstrated the excellent applicability of the device for the adsorption and detection of heavy metal ions. Conclusion The μCS/N-CNOs offers several core advantages over SPCE/N-CNOs in terms of cost, simplicity, analysis time, and sensitivity. These unique advantages are due to the combined microfluidic configuration, 3D electrode layout, and a unique modifier. We believe our findings would have significant implications in developing other portable, fast, and cost-effective electrochemical detection platforms, such as clinical diagnosis and security inspection.

Microelectrode Set Made of Carbon Nanotubes for the Detection of Biomolecules and Neurotransmitters

Electrode miniaturization is an alternative path for the development of sensitive electrochemical sensors. The low charging current, enhanced mass transport and their suitability to be employed in resistive mediums has made microelectrodes attractive for detection of biomolecules. Carbon nanotubes (CNTs) are unique nanomaterials with high electrical conductivity and mechanical strength. They are known for their chemical stability and the ability to assemble them into nano and microelectrodes makes them an appealing alternative electrode material compared to metals. This talk will report the fabrication of an electrochemical-set that has CNT microelectrode assemblies as working, reference, and counter electrode components and have been tested for the detection of heavy metals (Pb2+), neurotransmitters (dopamine), and other biomolecules (nicotinamide adenine dinucleotide (NADH), furosemide). Limits of detection of 0.5 nM for dopamine, 18 nM for NADH, 2 nM for Furosemide, and 0.4 ppt for Pb2+ have been achieved. Different voltammetric techniques were employed during the study: cyclic voltammetry (CV), square wave voltammetry (SWV), amperometry, and square wave anodic stripping voltammetry (SWASV). The robustness of the electrodes and the simplicity of its fabrication have been demonstrated. Furthermore, a simple method for the fabrication nanoelectrode arrays that can be employed as working electrodes will be presented. The background and key components that are considered important to achieve this performance will be reported.

Electrochemical Method for Detection and Quantification of Lead Particulate in Tap Water

Quantification of lead particulates requires laborious sample acidification and/or digestion in acidic environment, therefore lead quantification is limited to laboratories with trained personnel and expensive instrumentation. These technologies are not easily accessible to the public, and the large number of portable methods available to public today are characterized by their qualitative nature, and requirement of additional reagents. Unlike labor intense expensive instruments, electrochemical methods are inexpensive, fast and portable but they are blind to non-electroactive lead species or particulate forms of lead. They are limited to the detection of ionic or electroactive analytes. This talk will report an electrochemical method for the detection and quantification of lead contaminant in drinking waters that results from particulate forms of lead, mostly present as scales. We will present the fundamentals of membrane electrolysis for reagent-free sample preparation and detection of Pb2+. Also, we will present the characterization of real particulates/scales extracted from lead service lines from the Cincinnati area. We think this method will contribute to the development of on-site, quantitative methods of lead detection, and can assist to the research and understanding of drinking water contamination. Perhaps it could help to determine what triggers lead intermittent release to residential tap water. This work has the potential to address the lack of that instrumentation because it employs a robust technology based on anionic exchange membrane and controlled electrolysis for in-situ generation of nitric acid, that eliminates the need of external reagent or sample treatments. For its trace detection, it employs a well stablished Anodic Striping Voltammetry method.

Dual ion specific electrochemical sensor using aminothiazole-engineered carbon quantum dots

A novel electrochemical sensor capable of concurrently detecting Pb2+ and Hg2+ ions has been innovatively engineered. This sensor utilizes the anodic stripping voltammetry technique (ASV) with a composite consisting of carbon quantum dots and aminothiazole (CQD-AT). In this composite, both the carbon quantum dots and aminothiazole contribute significantly to the electroactive surface area, boasting an abundance of functional groups that include oxygen and nitrogen atoms. These functional groups serve as active sites that enhance sensor sensitivity by facilitating the electrostatic interaction-based adsorption of heavy metal ions. Aminothiazole surface is evenly covered with CQDs, which are essential for metal gets reoxidized into metal ions for stripping analysis. Due to this unique modification, the Pb2+ and Hg2+ electrochemical sensor using the CQD-AT composite coated on carbon fiber paper electrode (CQD-AT/CFP) exhibits superior analysis performance such as wide linear range (0.6 × 10–11–160 × 10–6 M) for Pb2+ and Hg2+ with a limit of detection (LOD) of 3.0 pM and 6.2 pM for Pb2+ and Hg2+. CQD-AT/CFP modified electrode can be considered as a potential material for electrochemical simultaneous determination of Pb2+ and Hg2+ in different water samples.

Determination of Some Heavy Metals in European and Polish Coal Samples.

This work presents coal analyses for heavy metal content (Tl, Cu, Zn, Cd, Fe). The tested coal samples came from a Russian deposit in the Kuzbass Basin (Novosibirsk and Kemerovo Oblasts, near Kazakhstan) and from Poland. The concentration of thallium in coal was determined using DPASV-differential pulse anodic stripping voltammetry-and other metals were examined with FAAS, i.e., flame atomic absorption spectrometry. The study confirmed the presence of thallium in the tested coal sample. The coal samples from outside the European Union contained four times more thallium (the maximum content of thallium in coal has been determined to be 0.636 mg·kg-1) than the samples of Polish coal (where the maximum content of thallium was 0.055 mg·kg-1). Cadmium concentration was on average 1.99 mg·kg-1 in the samples from outside the European Union, and 1.2 mg·kg-1 in the samples of Polish coal. Zinc concentration in the samples from outside the European Union was on average 11.27 mg·kg-1, and in the samples of Polish coal approx. 7 mg·kg-1. In addition, iron concentration in all coal samples was determined as 14.96 mg·kg-1, whereas copper concentration in the samples from outside the European Union averaged as 3.96 mg·kg-1. The obtained results do not show any correlation between the presence of thallium and the presence of other metals. It is worth noting that heavy metals pose a threat to living organisms due to their persistence and bioaccumulation, particularly in the context of dust emissions to the atmosphere.

Preparation of Gold Nanoparticles via Anodic Stripping of Copper Underpotential Deposition in Bulk Gold Electrodeposition for High-Performance Electrochemical Sensing of Bisphenol A.

Bisphenol A is one of the most widely used industrial compounds. Over the years, it has raised severe concern as a potential hazard to the human endocrine system and the environment. Developing robust and easy-to-use sensors for bisphenol A is important in various areas, such as controlling and monitoring water purification and sewage water systems, food safety monitoring, etc. Here, we report an electrochemical method to fabricate a bisphenol A (BPA) sensor based on a modified Au nanoparticles/multiwalled carbon nanotubes composite electrocatalyst electrode (AuCu-UPD/MWCNTs/GCE). Firstly, the Au-Cu alloy was prepared via a convenient and controllable Cu underpotential/bulk Au co-electrodeposition on a multiwalled modified carbon nanotubes glassy carbon electrode (GCE). Then, the AuCu-UPD/MWCNTs/GCE was obtained via the electrochemical anodic stripping of Cu underpotential deposition (UPD). Our novel prepared sensor enables the high-electrocatalytic and high-performance sensing of BPA. Under optimal conditions, the modified electrode showed a two-segment linear response from 0.01 to 1 µM and 1 to 20 µM with a limit of detection (LOD) of 2.43 nM based on differential pulse voltammetry (DPV). Determination of BPA in real water samples using AuCu-UPD/MWCNTs/GCE yielded satisfactory results. The proposed electrochemical sensor is promising for the development of a simple, low-cost water quality monitoring system for the detection of BPA in ambient water samples.

Development of Microfluidic Paper-Based Analytical Devices (µPADs) for Determination of Cd2+, Pb2+, and Cu2+ Ions in Mineral Water

Microfluidic paper-based analytical devices (µPADs) have been successfully developed using dual detection: electrochemical and colorimetric systems. The µPADs have the potential to be used as Pb(II), Cd(II), and Cu(II) sensors to test the quality of water. The fabrication process uses hot embossing and screen-printing methods. The working electrode in the electrochemical zone was enhanced by the bismuth metal deposition process, while in the colorimetric zone, the gold nanoparticles modified with thioctic acid and dansylhydrazine (TA-Au-DNS) were used as a colorimetric sensor to detect Cu. The basic material of µPADs was characterized using a Fourier-transform infrared (FTIR) and a contact angle meter (CAM). In the electrochemical zone, the signals of square wave anodic stripping voltammetry (SWASV) resulted in good detection of Pb(II) and Cd(II) (from 0 to 100 ppb) with a limit of detection of 1.588 and 1.42 ppb, respectively. In the colorimetric zone, the performance of TA-Au-DNS for detecting Cu metal was obtained from readings through the red-green-blue (RGB) sensor as a miniature of µPADs reader. The LOD, LOQ, and average Vx0 (linearity values) in the detection of Cu(II) (from 58 to 100 ppb) are 8.51 ppb, 28.36 ppb, and 0.41%, respectively.

MoS2 Quantum Dots-based Low-cost and Disposable Electrochemical Sensor for the Detection of Lead (II) Ions

After the discovery of graphene, two-dimensional (2D) nanomaterials have received great attention due to their excellent physico-chemical properties. Application of 2D-nanomaterials as receptors of a sensor can achieve high sensitivity and specificity as every atom of the material directly interacts with the analyte. In the present work, MoS2 quantum dots (MSQD) for the ultrasensitive electrochemical detection of lead (Pb2+) ions. MSQDs were prepared by mechanical shear exfoliation method. Size of the QDs and inter planar distance of the crystalline QDs were studied using transmission electron microscope (TEM). The prepared quantum dots were drop casted on a shiny surface of well-polished pencil graphite electrode (PGE). In order to obtain the highest sensitivity for Pb2+-ion sensing, anodic stripping DPV (ASDPV) was employed and consequently, the effect of pH, deposition potential and time were optimized. The sensor shows a linear range from 5.66 10−9 M to 491.93 10−9 M with a calculated detection limit 1.96 10−9 M for the detection of Pb2+-ion. The sensor’s response for Pb2+-ion was unaffected in the presence of any other metal ions. A remarkable average recovery percentage around 99.50% from the Pb2+-ion spiked agriculture soil and ground water samples proves the practical applicability of the sensor.

Development of smartphone-controlled and machine-learning-powered integrated equipment for automated detection of bioavailable heavy metals in soils

Rapid and accurate on-site detection of crop-absorbable cadmium (Cd) and lead (Pb) in soils is important for food security and human health. The automated soil sample pretreatment method, including the ultrasonic extraction of weakly acid-soluble heavy metals, suction-filtration, and UV photolysis, was proposed to achieve the high-efficiency preparation from soil sample to extract solution. Bismuth-film-modified glass carbon electrode combined with the homemade potentiostat was fabricated to implement the square-wave anodic stripping voltammetry (SWASV) measurements of soil extracts. The peak-information-acquisition algorithm was designed to automatically obtain peak heights and widths of Zn2+, Cd2+, Pb2+, Bi3+, and Cu2+ stripping currents, and then which were used as input variables for establishing machine-learning models to enhance the detection accuracy of SWASV to Cd2+ and Pb2+ under the coexistence of multiple heavy metal ions. Eventually, the smartphone-controlled integrated-automated detection equipment was developed and successfully applied to the automatic pretreatment of soil samples and the determination of weakly acid-soluble Cd2+ and Pb2+ in real soil samples. The detection speed was 75 min/sample, and the detection results were close to the standard method (BCR-ICP-MS). This equipment can provide powerful technical support for on-site rapid and accurate determination of crop-absorbable heavy metals in soils.

Detection Methods of Mercury and Lead Ions

Heavy metals ions are substances that can cause irreversible damage to the human body. These elements are often contained in raw materials and equipment in industrial production. These heavy metal ions, especially lead and mercury ions, can cause serious diseases when they enter the human body. Therefore, in order to avoid the excessive accumulation of mercury and lead ions in human body, it is very important to detect the heavy metal ions in products. The inductively coupled plasma mass spectrometry (ICP-MS) for detecting mercury ions has been discussed in this work. In addition, electrochemical sensor which used to detect mercury ions was also introduced in this work. As for detection of lead ions, flame atomic absorption spectrometery (FAAS) and anodic stripping voltammetry (ASV) were discussed respectively. This work will promote the understanding of lead and mercury ions detection. At the same time, more research on portable and inexpensive detection methods has become a focus of future research.

Simultaneous quantification of lead, cadmium and zinc in superficial marine sediments using a carbon-fiber microelectrode modified with bismuth film

Marine sediments are a useful environmental assessment matrix as they naturally trap toxic substances of anthropogenic origin and thus have higher concentrations of these than the surrounding water. Therefore, developing methods for the sensitive, accurate, and inexpensive quantification of these substances is important, as the traditional techniques have various disadvantages. The current study evaluated the effectiveness of an in situ bismuth-modified carbon-fiber microelectrode (voltamperometric sensor) to simultaneously detect Pb, Cd, and Zn in marine sediments from Puerto Jeli in El Oro Province, Ecuador. This site is representative of the contamination levels present along the coast in this province. Differential pulse anodic stripping voltammetry was applied, and the resulting linear regression for the metal quantification ranged from 12 to 50 μg mL−1, with quantification limits for Pb(II), Cd(II), and Zn(II) of 18.69, 12.55, and 19.29 μg mL−1, respectively. Thus, the quantification with the sensor was successful. According to the preliminary results, Cd and Pb values exceeded the permissible limits established by Ecuador (Texto Unificado de la Legislación Secundaria del Ministerio del Ambiente) and the US Environmental Protection Agency, respectively.

Engineered CoFe2O4@NiFe LDH nanocomposite based electrochemical sensor for the detection of Cr, As, Sb and Tl in various supporting electrolytes

The early detection and timeous monitoring of trace metals within the environment is crucial, especially with the need to develop mitigating strategies that help reduce health challenges. In this context, the electrochemical detection of Cr(VI), Sb(V), As(III), As(V) and Tl(III) has been performed using differential pulse anodic stripping voltammetry (DPASV) on a glassy carbon electrode modified with CoFe2O4@NiFe LDH. The anticipated active sites, such as the surface hydroxyl and oxide groups on the highly mesoporous nanoflower-like CoFe2O4@NiFe LDH composite that can readily interact with trace metal ions, were identified through physiochemical characterisation. The electrochemical characterisation revealed that the electrical conductivity was improved upon modifying the glassy carbon electrode with the CoFe2O4@NiFe LDH modifier. Subsequently, the developed sensor demonstrated a remarkable response on the detection of Cr(VI), Sb(V), As(III), As(V) and Tl(III), with good linearity (0.13–50 µg/L), low limit of detection (0.14, 0.15, 0.09, 0.12 and 0.19, respectively), low limit of quantification and high sensitivity. Significant parameters critical to the sensor's performance, such as type of electrolyte solution, deposition potential, deposition time and pH, were optimised. The DPASV results suggested that the developed sensor was repeatable and reproducible with intra-day and interday precision below 5 %. The proposed electrochemical sensor performed very well in tap and river water samples and could, therefore, open new avenues for the selective detection of trace metals in various matrices.

Multistage pore structure legume-like UiO-66-NH2@carbon nanofiber aerogel modified electrode as an electrochemical sensor for high sensitivity detection of HMIs

Electrode material is the core component of electrochemical sensor, which has a decisive influence on the detection performance of heavy metal ions. A novel electrochemical sensor based on amino modified metal-organic frameworks loaded three-dimensional carbon nanofiber aerogel composite material was proposed. The UiO-66-NH2 was embedded into nanofibers through one-step electrospinning technology to forming a legume-like structure, ensuring the number of active sites N coordination with HMIs, which improved enrichment capacity of the sensor. 3D carbon nanofiber aerogel with multistage pore structure was developed by one-dimensional nanofibers as unit modules, which increases conductive path and HMIs transport channel. Accordingly, the UiO-66-NH2 @carbon nanofiber aerogel modified electrode (N-U@CFA/GCE) as an electrochemical sensor exhibited an ultra-high sensitivity and the low limit of detection for the simultaneous detection of Cd2+ (0.52 nM) and Pb2+ (0.46 nM) using the differential pulse anode stripping voltammetry and was feasible and accurate for the detection of actual environmental water. The novel sensor platform has high sensitivity, stability and anti-interference, which showing great potential on HMIs monitoring.

Design and Analysis of Photon Imaging Detector Based on Printed Circult Board Technology Cross Strip Anode

Detectors with cross strip (XS) anodes have high application value in deep space exploration, quantum communications, space astronomical telescopes, etc. In this article, a single-layer XS anode based on Printed Circult Board (PCB) technology is proposed, which can conveniently realize large-area array detection with a simple process and low cost. We theoretically studied the electron motion principle and equivalent model of the XS anode and established a model of the XS anode through the finite element method. The model allows us to determine the anode geometry, such as anode strip width, inter-strip distance, and substrate thickness, to optimize the output signal on the XS anode, thereby indirectly affecting the resolution of the detector. The optimal parameters of the detector were processed with the help of our model, such as a strip width of 110 μm, strip spacing of 550 μm, and substrate thickness of 150 μm. The model shows that the strip charge collection ratio is 1:1. Comparing model predictions with experimental measurements reveals key parameters, such as the manufacturing is convenient and simple and can provide some ideas for subsequent large-area array detector imaging.

A square-wave anodic stripping voltammetric method for determining carbendazim in pineapple and orange juices without sample pre-treatment

Carbendazim is a fungicide used for pest control in fruit crops. However, carbendazim is dangerous to human health and the environment, requiring monitoring by appropriate analytical methods. For this, a square-wave anodic stripping voltammetric method was developed for the first time for determining carbendazim in orange and pineapple juices. As a sensor, the proposed method uses a carbon paste electrode modified with cobalt phthalocyanine. The optimized voltammetric parameters were: rest time = 5 s, pulse amplitude = 30 mV, potential increment = 1.0 mV, frequency = 20 s−1, potential window ranging from + 0.6 to + 1.1 V, peak potential (+0.90 V) and deposition time = 45 s. The method presented a linear response (r2 = 0.994, n = 8, limits of detection = 0.57 nmol L−1) from 49.7 to 384.6 nmol L−1 carbendazim, good reproducibility (relative standard deviation = 2.4 %) and accuracy (recovery rates = 93.3–107.9 %). The proposed method is superior to other methods reported in the literature because the preparation of the sensor is faster, as well as being simple, sensitive, selective, low-cost, high-frequency analysis, and eco-friendly as it does not use any sample pre-treatment (sonication, centrifugation, filtration, pre-concentration, dilution and/or extraction with organic solvents).

Electrochemical determination of sorafenib by chronopotentiometry and ASDPV based on novel molecularly imprinted polymer and their applications in oncology patients

A promising selective and sensitive biosensor was fabricated for the first time to monitor trace amounts of sorafenib (SORF), a multi-target kinase inhibitor, based on the electropolymerization of pyrrole on a carbon paste electrode (CPE). To prepare a modified CPE, the prepared metal organic framework (NH2-MIL-101(Fe)) was mixed with graphite powder in the presence of an appropriate amount of paraffin oil before it was packed into a plastic tube containing a copper wire. Computational studies appreciate the use of pyrrole as the functional monomer for electropolymerization at the CPE surface using chronopotentiometry in the presence of SORF as a template. After the leaching of SORF, the imprinted sensor was characterized using FT-IR, SEM, and AFM, while NH2-MIL-101(Fe) was investigated by XRD, XPS, and SEM analysis. Under optimum conditions, SORF was detected using anodic stripping differential pulse voltammetric and chronopotentiometric techniques. High sensitivity (6.40 × 10−12 mol/L), excellent selectivity, and a wide linear range (4.20 × 10−11–7.10 × 10−3 mol/L) were recorded. Furthermore, the proposed sensor exhibited good repeatability (RSD = 2.40 % for n = 7) and high lifetime stability (∼7 weeks). Based on the above-mentioned merits, the designed electrochemical sensor was properly utilized for SORF determination in different oncology patients with satisfactory results (recovery = 94.40–99.90 %).

Validating Electrochemical Active Surface Area Determination of Nanostructured Electrodes: Surface Oxide Reduction on AuPd Nanoparticles

Accurate normalization of electrochemical active surface area (ECSA) of nanostructured catalysts and nanoparticles is of utmost importance for catalyst activity determination and comparability. AuxPdy nanoparticles are a highly interesting example, as electrocatalysts for selective oxygen reduction reaction and alcohol oxidation. Most techniques used today for ECSA determination lack accurate validation for nanostructured electrodes and instead rely on reference values determined for macroelectrodes. This includes ECSA determination for AuxPdy nanoparticles, most commonly done by potentiodynamic surface oxide reduction. Here we suggest a versatile approach to validate different ECSA determination techniques for nanoparticle-modified or nanostructured electrodes, using surface oxide reduction of AuxPdy as an illustrative example. Combining this with volume determination by anodic stripping, we electrochemically estimate the NP diameter, which serves as an indication of the accuracy of the obtained ECSA values. Showcasing this for different nanoparticle compositions, we provide experimental conditions for determining AuxPdy nanoparticle ECSA using surface oxide reduction and compare those to parameters reported for macroelectrodes. The approach we introduce herein can be readily applied to a number of different alloy systems, thus, providing a widely applicable approach to determine electrochemical surface areas and validate the transferability of existing macroelectrode characterization techniques to nanostructured or nanoparticle-modified electrodes.

Ultrasensitive Electroanalytical Detection of Pb2+ and H2O2 Using Bi and Fe-Based Nanoparticles Embedded into Porous Carbon Xerogel-The Influence of Nanocomposite Pyrolysis Temperatures.

Multifunctional materials based on carbon xerogel (CX) with embedded bismuth (Bi) and iron (Fe) nanoparticles are tested for ultrasensitive amperometric detection of lead cation (Pb2+) and hydrogen peroxide (H2O2). The prepared CXBiFe-T nanocomposites were annealed at different pyrolysis temperatures (T, between 600 and 1050 °C) and characterized by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption, dynamic light scattering (DLS), and electron microscopies (SEM/EDX and TEM). Electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWV) performed at glassy carbon (GC) electrodes modified with chitosan (Chi)-CXBiFe-T evidenced that GC/Chi-CXBiFe-1050 electrodes exhibit excellent analytical behavior for Pb2+ and H2O2 amperometric detection: high sensitivity for Pb2+ (9.2·105 µA/µM) and outstanding limits of detection (97 fM, signal-to-noise ratio 3) for Pb2+, and remarkable for H2O2 (2.51 µM). The notable improvements were found to be favored by the increase in pyrolysis temperature. Multi-scale parameters such as (i) graphitization, densification of carbon support, and oxide nanoparticle reduction and purification were considered key aspects in the correlation between material properties and electrochemical response, followed by other effects such as (ii) average nanoparticle and Voronoi domain dimensions and (iii) average CXBiFe-T aggregate dimension.

Nano-Needle Boron-Doped Diamond Film with High Electrochemical Performance of Detecting Lead Ions

Nano-needle boron-doped diamond (NNBDD) films increase their performance when used as electrodes in the determination of Pb2+. We develop a simple and economical route to produce NNBDD based on the investigation of the diamond growth mode and the ratio of diamond to non-diamond carbon without involving any templates. An enhancement in surface area is achievable for NNBDD film. The NNBDD electrodes are characterized through scanning electron microscopy, Raman spectroscopy, X-ray diffraction, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse anodic stripping voltammetry (DPASV). Furthermore, we use a finite-element numerical method to research the prospects of tip-enhanced electric fields for sensitive detection at low Pb2+ concentrations. The NNBDD exhibits significant advantages and great electrical conductivity and is applied to detect trace Pb2+ through DPASV. Under pre-deposition accumulation conditions, a wide linear range from 1 to 80 µgL−1 is achieved. A superior detection limit of 0.32 µgL−1 is achieved for Pb2+, which indicates great potential for the sensitive detection of heavy metal ions.

NiFe2O4/G-C3N4 modified pencil graphite electrode for mercury(II) detection

The design and development of composite electrodes towards the trace-level detection of Hg(II) ions has triggered paramount importance in the area of electrochemistry. In this context, pencil graphite electrode was modified with NiFe2O4/G-C3N4, wherein bimetallic oxides were heterogeneously grown over the g-C3N4 sheets through a wet chemical approach. The results derived from transmission electron microscopy and X-ray diffraction analysis indeed reflected that NiFe2O4 were uniformly distributed over the sheet surface and complemented with effective interactions between them. The composites were coated over a pencil graphite electrode (PGE) and were used for the electrochemical detection of Hg(II) ions under various conditions. The cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) reveal better electrochemical performance of modified electrodes compared to bare PGE, G-C3N4/PGE, and NiFe2O4/PGE. The improved charge transfer kinetics at the electrode-electrolyte interface were the dominant factor to exhibit higher performance. The proposed sensor showed acceptable reproducibility and stability under the optimal reaction conditions. Additionally, the sensor showed a broad linear range from 10 to 800 nM with a limit of detection (LOD) of 2.49 nM. Further, the fabricated sensor has been successfully employed to determine Hg(II) contents in real water sample matrices.