Electrochemical Sensor Applications Research Articles

Design of highly defective Zn-doped CeO2 solid solution quantum dots for accurate monitoring of ciprofloxacin

Water quality monitoring requires new water sensors with highly sensitive and low-power consumption to detect the increasingly widespread contamination of antibiotics. Quantum dots (QDs), typically solid solution quantum dots (SSQDs), are emerging as promising sensing materials candidates owing to their unique structure with extremely small size and extraordinary electronic properties. In this work, Zn-doped CeO2 solid solution quantum dots with 2–6 nm grain size were embedded into biocarbon sheets and constructed as modified sensing electrode to detect trace ciprofloxacin (CIP). Biocarbon skeleton and the highly defective SSQDs structure enables them to be ideal reactors for electro-redox of CIP. The proposed strategy offers a powerful and feasible way to fabricate SSQDs modified electrode, suggesting potential application of electrochemical sensor for antibiotic.

Application of nanomaterial-modified electrochemical sensors in pesticide residue detection

Nowadays, the frequent application of insecticides leads to pesticide remnants detected in plentiful amounts of many foods, such as fruits and edibles. Even though the remains of the compounds produced by pesticides are tracked, the tremendous toxicity is sufficient to endanger human life and health. Thus, detecting pesticide residue in different vegetable and fruit foods is essential. Determine the number of leftover pesticides in different vegetable and fruit foods to avoid serious illnesses brought about by exposure to pesticides so that people’s physical and mental health and product quality and safety are ensured. Therefore, this article is about nano-porous materials based-electrochemical sensors used to detect pesticide residues in food. This article briefly introduces the mechanism and composition of electrochemical sensors, the classification of electrochemical nanomaterials, and the utilization of nanomaterials in electrochemical sensors. Nano-porous materials have a high specific surface area, adsorption, and catalytic properties to ensure accurate, accurate, and reliable detection. This article discusses metal nanomaterials with variable sizes, shape, surface, and physical and chemical features and their implementation in the detection of electrochemical sensors. It also introduces metal oxide nanomaterials with the characteristics of cheap and easy preparation and the detection range of this material. It also introduces the properties of carbon nanomaterials, carbon nanotubes, graphene, and carbon dots. Subsequently, this article summarizes the progress of nano-porous materials based on electrochemical sensors in pesticide residues. It also introduces the opportunities and challenges that nanomaterial-modified electrochemical sensors will face in pesticide detection and looks forward to reducing the harm of pesticides to the environment and human health in the future.

Modifying platinum microelectrodes with electrochemically reduced graphene oxide for application in electrochemical ascorbic acid sensor

Graphene oxide drop-casted on a platinum microelectrode was successfully changed to reduced graphene oxide by using a cyclic voltammetry method. The presence of an electrochemically reduced graphene oxide layer on the platinum electrode was proved by using scanning electron microscopy images, Raman and Fourier-transform infrared spectroscopy spectra. Cyclic voltammetry and linear sweep voltammetry results indicated that the platinum microelectrode modified with electrochemically reduced graphene oxide can be used as an electrochemical sensor for detection of ascorbic acid in aqueous solutions. In a cyclic voltammetry scan and a linear sweep voltammetry curve corresponding to the presence of ascorbic acid, a peak related to the direct oxidation of ascorbic acid appears. The electrochemical sensor based on the electrochemically reduced graphene oxide material works effectively with a detection limit of 0.04 mM, a detection linear range from 0.04 mM to 1.0 mM, a good repeatability, and especially, a rapid detection time thanks to a direct ascorbic acid detection based on the oxidation of ascorbic acid.

Synthesis, characterization, and utilization of NiCeO2@f-MWCNT/EDA nanoparticles as electrode materials for supercapacitor application

Metal oxide and carbon nanotube-based materials are widely preferred in supercapacitor and electrochemical sensor applications due to their interesting physicochemical structure. In this paper, we report the synthesis, characterization, and utilization of NiCeO2@f-MWCNT/EDA nanoparticles as electrode materials for supercapacitor applications. The characterization studies of NiCeO2@f-MWCNT/EDA nanomaterials were performed using X-ray diffraction (XRD), Transmission electron microscope (TEM), and Raman spectroscopy apparatus. The characterization methods revealed a good distribution of NiCeO2 on f-MWCNT/EDA and formed a new structure of NiCeO2@f-MWCNT/EDA nanoparticles. Electrochemical studies of NiCeO2@f-MWCNT/EDA nanoparticles showed a significant specific capacitance of between 2385 and 603 Fg−1 with good cyclic stability of 1000 cycles with capacity retention between 42% and 1.4% at 10 mV/s scan rate. The obtained results reveal that the prepared NiCeO2@f-MWCNT/EDA nanoparticles are promising electrode materials for supercapacitor devices.

Excellent photoluminescence and electrochemical properties of Sm3+ doped Ca2MgSi2O7 nanophosphor: Display and electrochemical sensor applications

A series of orange-red light emitting Ca2MgSi2O7:Sm3+ nanopowders were fabricated via low-cost eco-friendly green combustion technique using Aloe vera gel as fuel. The phase purity of the samples were confirmed by the powder X-ray diffraction (PXRD) technique. Pure single-phase tetragonal structure is observed from the PXRD results with no additional impurity peaks. The band gap energy of the fabricated powders was estimated by diffuse reflectance spectra (DRS) and is found to be in the range of 4.01–5.98 eV. A high resolution scanning electron microscope (SEM) was used to study the morphological behaviour of the samples. Honeycomb-like structures are observed from the SEM results. The particle size was evaluated by transmission electron microscopy (TEM) and is found to be ∼50 nm. The interplanar distance is found to be 0.53 nm. Photoluminescence properties were systematically studied in detail. The phosphors are successfully excited at 403 nm NUV light, producing reddish-orange characteristic emission. The emission peaks are centered at 558 (4G5/2 → 6H5/2), 607 (4G5/2 → 6H7/2) and 645 nm (4G5/2 → 6H9/2), respectively. Among the observed peaks the red emanation (4G5/2 → 6H7/2) is stronger than the orange emission (4G5/2 → 6H5/2) in the current investigation. The photoluminescent concentration quenching is noticed above 5 mol% Sm3+ ion doping content. The dipole–dipole interaction resulting in cross relaxation is found to be the principal cause of concentration quenching mechanism. The color features such as Commission Internationale de l’Eclairage (CIE) and correlated color temperature (CCT) were studied in detail. The optimized chromaticity coordinates were estimated to be (0.6363, 0.3632), which fall in the reddish-orange region. The average CCT value obtained is 3362 K. The average color purity is found to be ∼82%. Sm3+ incorporated Ca2MgSi2O7 samples are possible contender for single white light generation commercial candidates owing to their strong hypersensitivity of Sm3+ ions through host, least possibility for re-absorption of blue-green emission owing to poor direct f–f excitation of Sm3+ ions, and high color purity (reddish-orange emission). The prepared powders exhibit excellent electrochemical redox properties and CPE modified optimized powders show outstanding sensitive response which indicates its use in the potential electrochemical sensor materials for drug sensing studies.

Optimized synthesis, structural and electrical enhancement of Zinc sulfide nanoparticles for electrochemical sensor applications

A potentiostat with three electrode configurations was used to conduct electrochemical experiments on the successfully produced zinc sulfide nanoparticles. The results of the X-ray diffraction investigation showed that ZnS is polycrystalline and has a rhombohedral system. Using a well-known Williamson-Hall analysis, the average values of mean crystallite size and microstrain were found to be 1.56 nm and 3.7 × 10−2, respectively. The visible part of the photoluminescence spectrum of ZnS showed a noticeable emission peak at around 620 nm that was ascribed to the forbidden energy gap that gives rise to the electron-hole pair in ZnS. The FT-IR spectrum also revealed the structure of ZnS nanoparticles. A thermogravimetry graphic was used to prove ZnS's thermal stability. Energy dispersive spectroscopy coupled with transmission electron microscopy was used to verify the stoichiometry of ZnS, and the results show a roughly stoichiometric structure. With the aid of this electrode, ZnS@Ni, ethanol, and water could be found in both mediums. The electrochemical behavior of ZnS with varied concentrations of methanol on media was displayed by the Cyclic Voltammetry. Here, ZnS performs even with low methanol levels. As the methanol concentration was raised, the electrochemical peak raised. Additionally, ZnS's cyclic voltammetry demonstrated distinct feature peaks that might be used in fuel cell-type sensor applications. Electrochemical impedance spectroscopy was used to validate ZnS's capacity to make a wide variety of physical and electrochemical systems. Herein devised efficient ZnS -based electrochemical sensor for methanol detection is cost-efficient with the perspective of being scaled-up for point-of-care sensors required for monitoring methanol from environmental experiments.

Amperometry sensor for real time detection of hydrogen peroxide adulteration in food samples

Porous and defective nanomaterials lead to higher adsorption and are widely used in electrochemical sensor applications. The rGO-MoS2 tailored defect rod shapes provide rapid electron conduction thanks to redox reactions in the sensing medium. Modified polyethylene terephthalate (PET) flexible carbon screen-printed electrode (SPE) shows H2O2 sensing in food samples. We measured linear current amperometry signals in various sensing mediums of 0.1 M phosphate buffer solution (PBS), raw apple juice, and raw milk in the 1 to 50 μM range. Synergistic effects improved the sensing performance by sensitivity (S) of ∼ 773.33 μA/cm2 μM and limit of detection (LOD) of 0.017 μM (S/N, 3:1) in 0.1 M PBS. The observed LODs in the juice and milk samples are 0.025 μM (S = 324.33 μA/cm2 μM) and 0.046 μM (S = 138 μA/cm2 μM), respectively. This non-enzymatic research is fit to employ H2O2 sensing, implementing handheld, real-time controlled units in liquid food samples.

Molecularly Imprinted Polymer-Based Biomimetic Systems for Sensing Environmental Contaminants, Biomarkers, and Bioimaging Applications

Molecularly imprinted polymers (MIPs), a biomimetic artificial receptor system inspired by the human body’s antibody-antigen reactions, have gained significant attraction in the area of sensor development applications, especially in the areas of medical, pharmaceutical, food quality control, and the environment. MIPs are found to enhance the sensitivity and specificity of typical optical and electrochemical sensors severalfold with their precise binding to the analytes of choice. In this review, different polymerization chemistries, strategies used in the synthesis of MIPs, and various factors influencing the imprinting parameters to achieve high-performing MIPs are explained in depth. This review also highlights the recent developments in the field, such as MIP-based nanocomposites through nanoscale imprinting, MIP-based thin layers through surface imprinting, and other latest advancements in the sensor field. Furthermore, the role of MIPs in enhancing the sensitivity and specificity of sensors, especially optical and electrochemical sensors, is elaborated. In the later part of the review, applications of MIP-based optical and electrochemical sensors for the detection of biomarkers, enzymes, bacteria, viruses, and various emerging micropollutants like pharmaceutical drugs, pesticides, and heavy metal ions are discussed in detail. Finally, MIP’s role in bioimaging applications is elucidated with a critical assessment of the future research directions for MIP-based biomimetic systems.

Machine learning-guided the fabrication of nanozyme based on highly-stable violet phosphorene decorated with phosphorus-doped hierarchically porous carbon microsphere for portable intelligent sensing of mycophenolic acid in silage

Violet phosphorene (VP) have been proved to be more stable than black phosphorene, but few reports for its application in electrochemical sensors. In this study, a highly-stable VP decorated with phosphorus-doped hierarchically porous carbon microsphere (PCM) with multiple enzyme-like activities as a nanozyme sensing platform for portable intelligent analysis of mycophenolic acid (MPA) in silage with machine learning (ML) assistance is successfully fabricated. The pore size distribution on the PCM surface is discussed using N2 adsorption tests, and morphological characterization indicates that the PCM is embedded in the layers of lamellar VP. The affinity of the VP-PCM nanozyme obtained under the guidance of the ML model reaches Km = 12.4 μmol/L for MPA. The VP-PCM/SPCE for the efficient detection of MPA exhibits high sensitivity, a wide detection range of 2.49 μmol/L - 71.14 μmol/L with a low limit of detection of 18.7 nmol/L. The proposed ML model with high prediction accuracy (R2 = 0.9999, MAPEP = 0.0081) assists the nanozyme sensor for intelligent and rapid quantification of MPA residues in corn silage and wheat silage with satisfactory recoveries of 93.33%–102.33%. The excellent biomimetic sensing properties of the VP-PCM nanozyme are driving the development of a novel MPA analysis strategy assisted by ML in the context of production requirements of livestock safety.

Ultralight 3D Graphene Oxide Aerogel Decorated with Pd-Fe Nanoparticles for the Simultaneous Detection of Eight Biomolecules.

In this proof-of-concept study, an ultralight graphene oxide aerogel (GOx-Aero) decorated with bimetallic palladium-iron nanoparticles (Pd-Fe) was synthesized and immobilized on a glassy carbon electrode (GCE) for electrochemical sensor applications. The main objective of this work was to develop a sensitive electrochemical sensor capable of simultaneously detecting eight biomolecules, including ascorbic acid (AA), dopamine (DA), uric acid (UA), 8-hydroxyguanine (8HG), guanine (G), adenine (A), thymine (T), and cytosine (C). To the best of our knowledge, this is the first time that an electrochemical sensor has been able to detect eight biomolecules simultaneously. The bimetallic GOx aerogel significantly enhanced the performance of the sensor by increasing the electroactive area, conductivity, and anodic peak current response. The sensor demonstrated sharp, well-defined, and continuous oxidation peaks for all eight analytes of interest and wide linear ranges of 5.0-1750, 0.25-100.0, 0.5-500.0, 0.5-375.0, 0.5-500.0, 0.5-500.0, 5.0-1500.0, and 5.0-1500.0 μM for AA, DA, UA, 8HG, G, A, T, and C, respectively. The prepared sensor also exhibited excellent stability, reproducibility, and sensitivity with a very low limit of detection (LOD) of 553.7, 1.8, 69.6, 43.2, 42.9, 72.3, 57.2, and 318.4 nM for AA, DA, UA, 8HG, G, A, T, and C, respectively. The Pd-Fe-GOx-Aero-GCE was also tested in various real samples such as artificial saliva, artificial cerebrospinal fluid (CSF), salmon sperm DNA, and genomic DNA from calf thymus, where it demonstrated good recovery values. Additionally, the novel developed sensor was used to monitor the interaction between the anticancer drug, cisplatin, which has well-described binding affinity with the G and A bases in DNA. Overall, Pd-Fe-GOx-Aero-GCE displayed an extremely promising platform not only for the simultaneous detection of eight biomolecules in complex biological matrices but also for DNA-drug interaction studies toward the development of electrochemical high-throughput drug screening assays, which is of great importance in the field.

Development of bismuth sulfide nanorods and polyamidoamine dendrimer on reduced graphene oxide as electrode nanomaterials for electrochemical determination of salbutamol

Dendrimers, a new class of nanomaterials, are receiving more attention in various fields. In this study, by combining the advantages of polyamidoamine (PAMAM) dendrimer with reduced graphene oxide (rGO) and bismuth sulfide (Bi2S3), we came to design a new composite and its application for electrochemical sensors was investigated for the first time. As a new approach in the preparation of the composite, PAMAM was used for the first time to increase the surface of Bi2S3 with rGO, which ultimately led to an increase in the active surface area of the sensor (5 times compared to the bare electrode). For the first time, we used the sonochemical method for interaction between PAMAM with Bi2S3 and rGO, which was a simpler and faster method to prepare the composite. The purposeful design of the composite was done by using the experimental design method to obtain the optimum composition of components. The new nanocomposite was successfully applied for simple and sensitive electrochemical sensing of salbutamol for controlling the health of food. Salbutamol is used as a prohibited additive in animal and poultry feed. The sensor has good sensitivity (35 times increase compared to the bare electrode) and a low detection limit (1.62 nmol/L). Moreover, it has acceptable selectivity, good repeatability (1.52–3.50%), good reproducibility (1.88%), and satisfactory accuracy (recoveries: 84.6–97.8%). An outstanding feature of the sensor is its broad linear range (5.00–6.00 × 102 nmol/L). This sensor is well suited for the determination of salbutamol in milk, sausage, and livestock and poultry feed samples.

Front Cover: Versatile Metalloporphyrin‐Based Electrochemical Sensing Applications: From Small Gasotransmitters to Macromolecules (Eur. J. Inorg. Chem. 17/2023)

The Front Cover shows an engaging platform for electrochemical sensor development: Metalloporphyrins. Although the last years have been times of numerous technological transitions, porphyrins have been and currently are critical building blocks in the development of micro-/nanosensors. In recent years, not only have small molecules been detected and quantified, but it is now also possible to measure relevant macromolecules with high precision in intricate samples. This work presents an up-to-date list of reports in which metalloporphyrins are used as electrochemical sensors. Most of them are developed with a blend of porphyrin rings and metals of the first transition series. Renewed efforts in the synthesis, improved electronics, and data analysis will lead to better performance and new applications of metalloporphyrin-based electrochemical sensors in the coming years. More information can be found in the Review by S. A. Suarez and co-workers.

A Novel Rare Earth and Covalent Organic Framework Composite for Rapid and Highly Sensitive Electrochemical Analysis of Sulfadiazine in Fish Muscle

The misuse of sulfadiazine (SFZ) has led to great hazard to the environment and human safety; therefore, a simple, rapid, and sensitive method to detect sulfadiazine is urgently needed. Herein, we report a simple fabrication method for rare earth vanadate samarium (SmV)-doped covalent organic framework COFTDBA-TTL nanocomposites (SmV/COFTDBA-TTL), which were used to construct a sulfadiazine (SFZ) electrochemical sensor. The synergistic effect arising from the combination of SmV and COFTDBA-TTL accelerates the charge transfer kinetics, along with the creation of more surface-active sites that benefit effective detection. Compared with other electrochemical sensors, this electrochemical sensor exhibits low detection limit (2.40 nM), wide linear range (7.32–12.0 μM), good reproducibility (RSD = 0.823%), and stability (RSD = 3.60%). It provides a novel method and theoretical basis for the application of rare earth COF-based electrochemical sensors to detect environmentally destructive pollutants.

Recent advances in electrochemical sensors and biosensors for monitoring drugs and metabolites in pharmaceutical and biological samples.

Various applications of electrochemical sensors and biosensors have been reported in many fields. These include pharmaceuticals, drug detection, cancer detection, and analysis of toxic elements in tap water. Electrochemical sensors are characterised by their low cost, ease of manufacture, rapid analysis, small size and ability to detect multiple elements simultaneously. They also allow the reaction mechanisms of analytes, such as drugs, to be taken into account, giving a first indication of their fate in the body or their pharmaceutical preparation. Several materials are used in the construction of sensors, such as graphene, fullerene, carbon nanotubes, carbon graphite, glassy carbon, carbon clay, graphene oxide, reduced graphene oxide, and metals. This review covers the most recent progress in electrochemical sensors used to analyze drugs and metabolites in pharmaceutical and biological samples. We have highlighted carbon paste electrodes (CPE), glassy carbon electrodes (GCE), screen-printed carbon electrodes (SPCE) and reduced graphene oxide electrodes (rGOE). The sensitivity and analysis speed of electrochemical sensors can be improved by modifying them with conductive materials. Different materials used for modification have been reported and demonstrated, such as molecularly imprinted polymers, multiwalled carbon nanotubes, fullerene (C60), iron(III) nanoparticles (Fe3O4NP), and CuO micro-fragments (CuO MF). Manufacturing strategies and the detection limit of each sensor have been reported.

Gold nanoparticles-decorated peptide hydrogel for antifouling electrochemical dopamine determination.

A reliable and brief ultralow fouling electrochemical sensing system capable of monitoring targets in complex biological media was constructed and validated based on gold nanoparticles-peptide hydrogel-modified screen-printed electrode. The self-assembled zwitterionic peptide hydrogel was prepared by a newly designed peptide sequence of Phe-Phe-Cys-Cys-(Glu-Lys)3 with the N-terminal modified with a fluorene methoxycarbonyl group. The thiol groups on cysteine of the designed peptide are able to self-assemble with AuNPs to form a three-dimensional nanonetwork structure, which showed satisfactory antifouling capability in complex biological media (human serum). The developed gold nanoparticles-peptide hydrogel-based electrochemical sensing platform displayed notably sensing properties for dopamine determination, with a wide linear range (from 0.2 nM to 1.9 μM), a low limit of detection (0.12 nM), and an excellent selectivity. This highly sensitive and ultralow fouling electrochemical sensor was fabricated via simple preparation with concise components that avoid the accumulation of layers with single functional material and complex activation processes. This ultralow fouling and highly sensitive strategy based on the gold nanoparticles-peptide hydrogel with a three-dimensional nanonetwork offers a solution to the current situation of various low-fouling sensing systems facing impaired sensitivity and provides a potential path for the practical application of electrochemical sensors.

Single‐atom metal‐nitrogen‐carbon catalysts energize single molecule detection for biosensing

AbstractBiosensors featuring single molecule detection present huge opportunities as well as challenges in food safety inspection, disease diagnosis, and environmental monitoring. Single‐molecule detection is largely lacking of high enough activity, precision molecule selectivity, and understanding in the exact operating mechanism. Single‐atom catalysts (SACs), especially those metals‐nitrogen‐carbon that mimic the natural metalloenzyme structure, and with well‐defined metal atom bond configurations, high level of molecular selectivity, and easy fabrication, endow single molecule detections with practical‐use feasibilities. The recent advances in single‐atom catalysts also present new pathways in the key mechanism understandings. In this short review, we will first visit the brief history and advantages of SACs that have been explored only recently for molecule‐scale biosensors, where they are analogous and also differentiated from those nanozymes and natural metalloenzymes. Their applications in electrochemical, photochemical, and photoelectrochemical sensors are then discussed comprehensively by focusing on the different molecule‐scale sensing modes in achieving local coordination‐modulated signal amplifications. Finally, we identify new opportunities and challenges faced by these SACs‐based single molecule detections in the further development of biosensors.image

Application of a new electrochemical sensor for voltammetric determination of p-nitrophenol and betulin

A highly sensitive electrochemical sensor based on a Surface Active Modifier (SAM) consisting of Taunit-M carbon nanotubes and mesoporous carbon (NanoTechCenter LLC, Tambov, Russia) is developed for the voltammetric determination of betulin and p-nitrophenol. The effect of the modifier concentration on the electrode surface on the analytical signal of betulin was studied, and a method for modifying the surface of the SAM graphite electrode was developed. The developed method is easy to use, fast, stable, sensitive, and cost-effective procedure, which can be used to detect these analytes in real samples. Voltammograms of p-nitrophenol were obtained for the first time on the developed modified electrochemical sensor and the dependence of the height of its analytical signal on the pH of a phosphate buffer thus obtained was studied in a wide pH range from 4 to 12, a background electrolyte with optimal pH was also chosen. Proceeding from the calibration dependences of the height of the betulin analytical signal on the concentration obtained for various background electrolytes with different pH and cation-anion composition, a background electrolyte with the maximum sensitivity of the analytical signal was selected on a modified electrochemical sensor. Study of cyclic voltammograms was carried out to understand the electrode processes, exhibiting a pronounced peak of anodic oxidation observed in a potential range from 0.7 to 0.9 V. However, there was no peak in the cathodic direction which indicates the irreversible nature of the electrode process. When determining the nature of currents, the Semerano criterion equal to 1.6 was calculated, which indicates the absence of the contribution of the diffusion component of the current. Verification of the correctness of the voltammetric method for determining betulin on a new electrochemical sensor was carried out using the «spike-test» method. The data obtained show that the voltammetric determination of betulin can be carried out with a measurement error not exceeding 15%. The proposed modified electrodes were compared with previously known electrodes for the determination of pentacyclic triterpenoids and pesticides at concentrations of 0.5 × 10–3 – 8.0 × 10–3 mg/dm3.

Recent advances in nanomaterials-based electrochemical sensors for tramadol analysis.

Tramadol is a centrally-acting analgesic used for treating moderate to severe acute and chronic pain. Pain is an unpleasant sensation that occurs most commonly as a result of tissue injury. Tramadol possesses agonist actions at the μ-opioid receptor and effects reuptake at the noradrenergic and serotonergic systems. In the last years, several analytical procedures have been published in the literature for the determination of tramadol from pharmaceutical formulations and biological matrices. Electrochemical methods have attracted tremendous attention for the quantification of this drug owing to their demonstrated potential for quick response, real-time measurements, elevated selectivity and sensitivity. In this review, we highlighted the recent advances and applications of nanomaterials-based electrochemical sensors for the analysis and detection of tramadol, which is extremely important for the indication of effective diagnoses and for quality control analyses in order to protect human health. Also, the main challenges in developing nanomaterials-based electrochemical sensors for the determination of tramadol will be discussed. At last, this review offers prospects for the future research and development needed for modified electrode sensing technology for the detection of tramadol.

Green engineered synthesis of PbxZn1-xO NPs: An efficient electrochemical sensor and UV light-driven photocatalytic applications

The present work deals with preparation of PbxZn1-xO nanoparticles (NPs) (x = 0, 0.1, 0.3 & 0.5 M) first time using Zingiber officinale leaf as green fuel by solution combustion route and its structural confirmation was achieved by different spectral techniques. Powder-X-ray diffraction (P-XRD) analysis confirmed the switching of dopant Pb ions into host lattice without altering hexagonal wurtzite phase of host ZnO. The impact of Pb dopant directly affects crystallinity of ZnO host lattice changes the surface morphology with noticeable voids and pores with agglomeration examined by Scanning Electron Microscopy (SEM). The decreasing energy band gap of prepared nanoparticles from 3.3 eV − 2.4 eV due to increasing Pb content examined by UV–Visible absorption spectral technique hinders the recombination of electron-holes pairs by trapping e- and h+, which influence the enhanced photocatalytic activities. This optical characterization influences the achieved NPs used as excellent photocatalyst to remove malachite green (MG) dye under visible-light irradiation, which shows 98.5 % dye degradation at 160 min confirmed by its low kinetic constants of photocatalytic degradation of MG dye for Pb doped ZnO (17.42x10-3 min−1) than host ZnO (10.82×10-3 min−1) nanoparticles. The thermodynamics of redox reaction and capacitance measurement of prepared NPs-graphite paste electrode was investigated by electrochemical analysis in a 3-electrode system using 0.1 M KCl in the different scan rates 0.01–0.05 V/s. The excellent variation of redox peak potentials performance on sensor detections, the Pb-ZnO NPS shows an excellent chemical (Paracetamol) and biomolecule (Dextrose) sensing activity due to the region of Pb+2 ions effect.

Design and Application of Thymol Electrochemical Sensor Based on the PtNPs-CPOFs-MWCNTs Composite.

In this study, the preparation of covalent polyoxometalate organic frameworks (CPOFs) is introduced using the idea of polyoxometalate and covalent organic frameworks. Firstly, the prepared polyoxometalate was functionalized with an amine group (NH2-POM-NH2), and then the CPOFs were prepared by a solvothermal Schiff base reaction with NH2-POM-NH2 and 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) as monomers. After the incorporation of PtNPs and MWCNTs into the CPOFs material, the PtNPs-CPOFs-MWCNTs nanocomposites, which possess excellent catalytic activity and electrical conductivity, were formed and utilized as new electrode materials for the electrochemical thymol sensors. The obtained PtNPs-CPOFs-MWCNTs composite exhibits excellent activity toward thymol, which is attributable to its large special surface area, good conductivity and the synergistic catalysis of each component. Under optimal experimental conditions, the sensor presented a good electrochemical response to thymol. The sensor shows two good linear relationships between the current and thymol concentration in the range of 2-65 μM (R2 = 0.996) and 65-810 μM (R2 = 0.997), with the corresponding sensitivity of 72.7 μA mM-1 and 30.5 μA mM-1, respectively. Additionally, the limit of detection (LOD) was calculated to be 0.2 μM (S/N = 3). At the same time, the prepared thymol electrochemical sensor revealed superior stability and selectivity. The constructed PtNPs-CPOFs-MWCNT electrochemical sensor is the first example of thymol detection.