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Fabrication of Electrochemical Sensor for the Detection of Mg Ions Using CeOsub.2 Microcuboids as an Efficient Electrocatalyst
In human blood serum, the concentration of magnesium ions typically ranges from 0.7 mM to 1.05 mM. However, exceeding the upper limit of 1.05 mM can lead to the condition known as hypermagnesemia. In this regard, a highly sensitive and selective electrochemical sensor for Mg(II) ion detection was successfully fabricated by immobilizing cerium oxide (CeO[sub.2] ) microcuboids, synthesized via microwave radiation method, onto the surface of glassy carbon electrode (GCE). Cyclic voltammetry studies revealed the exceptional electrocatalytic effect of CeO[sub.2] microcuboid-modified GC electrode, particularly in relation to the irreversible reduction signal of Mg(II). The microcuboid-like structure of CeO[sub.2] microparticles facilitated enhanced adsorption of Mg(II) ion (Γ=2.17×10[sup.−7] mol cm[sup.−2] ) and electron transfer (k[sub.s] =8.94 s[sup.−1] ) between the adsorbed Mg(II) ions and GCE. A comprehensive analysis comparing the performance characteristics of amperometry, differential pulse voltammetry, cyclic voltammetry, and square wave voltammetry was conducted. The square wave voltammetry-based Mg(II) sensor exhibited remarkable sensitivity of 2.856 μA mM[sup.−1] , encompassing a broad linear detection range of 0–3 mM. The detection and quantification limits were impressively low, with values of 19.84 and 66.06 μM, respectively. Remarkably, the developed electrode showed a rapid response time of less than 140 s. Multiple linear regression and partial least squares regression models were employed to establish a mathematical relationship between magnesium ion levels and electrochemical parameters. Notably, the proposed sensor exhibited excellent anti-interferent ability, repeatability, stability, and reproducibility, enabling the fabricated electrode to be used effectively for Mg(II) ion sensing in real-world samples.
Journal Article
Development and Application of an Electrochemical Sensor with 1,10-Phenanthroline-5,6-dione-Modified Electrode for the Detection of IEscherichia coli/I in Water
The routine monitoring of bacterial populations is crucial for ensuring water quality and safeguarding public health. Thus, an electrochemical sensor based on a 1,10-phenanthroline-5,6-dione-modified electrode was developed and explored for the detection of E. coli. The modified electrode exhibited enhanced NADH oxidation ability at a low potential of 0.1 V, which effectively eliminated the interference from other redox compounds in bacteria. The sensitivity for NADH was 0.222 μA/μM, and the limit of detection was 0.0357 μM. Upon cell lysis, the intracellular NADH was released, and the concentration of E. coli was determined through establishing the relationship between the oxidation current signal and NADH concentration. The performance of the electrochemical sensor in the detection of NADH and E. coli suspensions was validated using the WST-8 colorimetric method. The blank recovery experiment in real water samples exhibited good accuracy, with recovery rates ranging from 89.12% to 93.26% and relative standard deviations of less than 10%. The proposed electrochemical sensor realized the detection of E. coli without the usage of biomarkers, which provides a promising approach for the broad-spectrum detection of microbial contents in complex water environments.
Journal Article
Bisub.2WOsub.6@g-Csub.3Nsub.4 Heterostructure for Cathodic Photoelectrochemical Dopamine Sensor
A simple and low-cost cathodic photoelectrochemical (PEC) sensor based on Bi[sub.2] WO[sub.6] @g-C[sub.3] N[sub.4] was designed for dopamine (DA) detection. The Bi[sub.2] WO[sub.6] nanoflower was first prepared using a simple hydrothermal method followed by the combination with g-C[sub.3] N[sub.4] nanosheet to form the Bi[sub.2] WO[sub.6] @g-C[sub.3] N[sub.4] heterostructure. The heterostructure can extend the absorbance to the visible region and accelerate the transfer of charge carriers. Furthermore, DA easily coordinates with exposed Bi[sup.3+] on the Bi[sub.2] WO[sub.6] surface and forms the charge-transfer complex to further enhance the cathodic photocurrent. Under optimal conditions, there are two linear relationships between the concentration of DA and photocurrent intensity. The linear ranges are 0.1–10 µM and 10–250 µM, with a sensitive detection limit (LOD) of 28 nM. Notably, the real sample of human blood serum analysis further revealed the accuracy and feasibility of the Bi[sub.2] WO[sub.6] @g-C[sub.3] N[sub.4] -based PEC platform. Convincingly, the heterostructure of Bi[sub.2] WO[sub.6] and g-C[sub.3] N[sub.4] opened up a new avenue for the construction of DA analysis.
Journal Article
Colorimetric Sensors for Chemical and Biological Sensing Applications
Colorimetric sensors have been widely used to detect numerous analytes due to their cost-effectiveness, high sensitivity and specificity, and clear visibility, even with the naked eye. In recent years, the emergence of advanced nanomaterials has greatly improved the development of colorimetric sensors. This review focuses on the recent (from the years 2015 to 2022) advances in the design, fabrication, and applications of colorimetric sensors. First, the classification and sensing mechanisms of colorimetric sensors are briefly described, and the design of colorimetric sensors based on several typical nanomaterials, including graphene and its derivatives, metal and metal oxide nanoparticles, DNA nanomaterials, quantum dots, and some other materials are discussed. Then the applications, especially for the detection of metallic and non-metallic ions, proteins, small molecules, gas, virus and bacteria, and DNA/RNA are summarized. Finally, the remaining challenges and future trends in the development of colorimetric sensors are also discussed.
Journal Article
Organic Luminescent Sensor for Mercury Ions in Aqueous Solutions
The substrate N[sup.1] , N[sup.3] , N[sup.5] -tris(2-hydroxyphenyl)benzene-1,3,5-tricarboxamide (Sensor A) was prepared in the reaction of 1,3,5-benzenetricarboxylic acid (trimesic acid) and o-aminophenol in ethanol. The prepared organic sensor fulfills the chemiluminescent requirements including a luminophore, spacer, and suitable binding receptor that distress the probe’s luminescent features, providing selective and sensitive detection of mercury and iron ions in aqueous solutions. The sensor selectively detects mercury and iron ions in a water matrix containing various metal ions, including sodium, calcium, magnesium, zinc, and nickel. Strong and immediate binding was observed between mercury ions and the substrate at pH 7.0 with a binding affinity toward Hg[sup.2+] 9-fold higher than that observed for iron sensor binding affinity, which makes the substrate a distinctive luminescence sensor for mercury detection at ambient conditions. The sensor shows a linear response toward Hg[sup.2+] in the concentration range from 50 ppb to 100 ppm (2.0 × 10[sup.−8] to 4.2 × 10[sup.−5] M) with a limit of detection of 2 ppb (1.0 × 10[sup.−8] M). Further, Sensor A provides linear detection for iron ions in the range from 10 ppb to 1000 ppm (1.5 × 10[sup.−8] to 1.5 × 10[sup.−3] M). The measured adsorption capacity of Sensor A toward mercury ions ranged from 1.25 to 1.97 mg/g, and the removal efficiency from water samples reached 98.8% at pH 7.0. The data demonstrate that Sensor A is an excellent probe for detecting and removing mercury ions from water bodies.
Journal Article
Electrochemical Sensors and Their Applications: A Review
The world of sensors is diverse and is advancing at a rapid pace due to the fact of its high demand and constant technological improvements. Electrochemical sensors provide a low-cost and convenient solution for the detection of variable analytes and are widely utilized in agriculture, food, and oil industries as well as in environmental and biomedical applications. The popularity of electrochemical sensing stems from two main advantages: the variability of the reporting signals, such as the voltage, current, overall power output, or electrochemical impedance, and the low theoretical detection limits that originate from the differences in the Faradaic and nonFaradaic currents. This review article attempts to cover the latest advances and applications of electrochemical sensors in different industries. The role of nanomaterials in electrochemical sensor research and advancements is also examined. We believe the information presented here will encourage further efforts on the understanding and progress of electrochemical sensors.
Journal Article
Fesub.3Osub.4-Nanoparticle-Modified Sensor for the Detection of Dopamine, Uric Acid and Ascorbic Acid
A simple electrochemical sensor based on electrochemically synthesized Fe[sub.3] O[sub.4] nanoparticles was constructed by an ink with the nanoparticles, isopropanol, NAFION and carbon Vulcan to detect dopamine, uric acid and ascorbic acid. The electrocatalytic activity of the nanoparticles for the oxidation of the analyte molecules was examined by means of cyclic voltammetry and square wave voltammetry. The parameters controlling the performance of the sensor were optimized, such as the amount of Fe[sub.3] O[sub.4] nanoparticles (1, 2, 3, 5, 8, 10 mg), amount of binder (5, 10, 15 µL) and carbon Vulcan in the ink (4, 6, 8 mg). The temperature was maintained at 25 °C and the pH was 7.5 with buffer phosphate. The optimal sensor conditions were 8 mg magnetite, 4 mg carbon Vulcan and 5 µL of NAFION@ 117. The calibration curves for the three analytes were determined separately, obtaining linear ranges of 10–100, 20–160 and 1050–2300 µM and limits of detection of 4.5, 14 and 95 µM for dopamine, uric acid and ascorbic acid, respectively. This electrochemical sensor has also shown significant sensitivity and selectivity without interference from the three analyte molecules presented simultaneously in solution. This sensor was applied for the detection of these molecules in real samples.
Journal Article
Adsorbed Oxygen Ions and Oxygen Vacancies: Their Concentration and Distribution in Metal Oxide Chemical Sensors and Influencing Role in Sensitivity and Sensing Mechanisms
Oxidation reactions on semiconducting metal oxide (SMOs) surfaces have been extensively worked on in catalysis, fuel cells, and sensors. SMOs engage powerfully in energy-related applications such as batteries, supercapacitors, solid oxide fuel cells (SOFCs), and sensors. A deep understanding of SMO surface and oxygen interactions and defect engineering has become significant because all of the above-mentioned applications are based on the adsorption/absorption and consumption/transportation of adsorbed (physisorbed-chemisorbed) oxygen. More understanding of adsorbed oxygen and oxygen vacancies (VO•,VO••) is needed, as the former is the vital requirement for sensing chemical reactions, while the latter facilitates the replenishment of adsorbed oxygen ions on the surface. We determined the relation between sensor response (sensitivity) and the amounts of adsorbed oxygen ions (O2(ads)−, O(ads), −O2(ads)2−, O(ads)2−), water/hydroxide groups (H2O/OH−), oxygen vacancies (VO•, VO••), and ordinary lattice oxygen ions (Olattice2−) as a function of temperature. During hydrogen (H2) testing, the different oxidation states (W6+, W5+, and W4+) of WO3 were quantified and correlated with oxygen vacancy formation (VO•, VO••). We used a combined application of XPS, UPS, XPEEM-LEEM, and chemical, electrical, and sensory analysis for H2 sensing. The sensor response was extraordinarily high: 424 against H2 at a temperature of 250 °C was recorded and explained on the basis of defect engineering, including oxygen vacancies and chemisorbed oxygen ions and surface stoichiometry of WO3. We established a correlation between the H2 sensing mechanism of WO3, sensor signal magnitude, the amount of adsorbed oxygen ions, and sensor testing temperature. This paper also provides a review of the detection, quantification, and identification of different adsorbed oxygen species. The different surface and bulk-sensitive characterization techniques relevant to analyzing the SMOs-based sensor are tabulated, providing the sensor designer with the chemical, physical, and electronic information extracted from each technique.
Journal Article
A Dinitrophenol-Based Colorimetric Chemosensor for Sequential Cusup.2+ and Ssup.2− Detection
A dinitrophenol-based colorimetric chemosensor sequentially sensing Cu[sup.2+] and S[sup.2−] , HDHT ((E)-2-(2-(2-hydroxy-3,5-dinitrobenzylidene)hydrazineyl)-N,N,N-trimethyl-2-oxoethan-1-aminium), was designed and synthesized. The HDHT selectively detected Cu[sup.2+] through a color change of yellow to colorless. The calculated detection limit of the HDHT for Cu[sup.2+] was 6.4 × 10[sup.−2] μM. In the interference test, the HDHT was not considerably inhibited by various metal ions in its detection of Cu[sup.2+] . The chelation ratio of the HDHT to Cu[sup.2+] was determined as 1:1 by using a Job plot and ESI-MS experiment. In addition, the HDHT–Cu[sup.2+] complex showed that its color selectively returned to yellow only in the presence of S[sup.2−] . The detection limit of the HDHT–Cu[sup.2+] complex for S[sup.2−] was calculated to be 1.2 × 10[sup.−1] μM. In the inhibition experiment for S[sup.2−] , the HDHT–Cu[sup.2+] complex did not significantly interfere with other anions. In the real water-sample test, the detection performance of the HDHT for Cu[sup.2+] and S[sup.2−] was successfully examined. The detection features of HDHT for Cu[sup.2+] and the HDHT–Cu[sup.2+] for S[sup.2−] were suggested by the Job plot, UV–Vis, ESI-MS, FT-IR spectroscopy, and DFT calculations.
Journal Article