Engineered tenorite structure of barium-enriched copper oxide for on-site monitoring of cytotoxic methotrexate in environmental samples.

Emerging pharmaceutical pollutants pose a threat to both human and environmental health. The removal and monitoring of such pollutants necessitate the use of practical on-site monitoring devices; however, the designs of such devices are underdeveloped. This study involves the fabrication of a low-cost sensor based on barium-incorporated copper oxide (Ba-CuO) for the on-site monitoring of the cytotoxic drug methotrexate (MTRX) in water and sediment samples. The tenorite structure of CuO was slightly enriched with Ba ions at the td sites, distorting the tetrahedron and enhancing its electrochemical properties. Ba-CuO was obtained from Cu(NO3)2 and Ba(OH)2 by a ligand exchange protocol and was characterized using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray analysis. In addition, the Ba-CuO sensor was tested under various conditions, and it could detect MTRX at concentrations as low as 0.4 nM, with a high sensitivity of 1.3567 µA µM-1 cm-2. On-site monitoring yielded recoveries of greater than 93 % from spiked samples, thus exhibiting excellent reproducibility and stability. Therefore, the developed method is practical and has no matrix effect on the MTRX sensor.

Ultrasensitive detection of ineradicable and harmful antibiotic chloramphenicol residue in soil, water, and food samples.

Chloramphenicol (CAP) is a harmful antibiotic that inevitably enters our food chain through natural or manmade means. Its ineradicable residue pollutes soils and water, accumulates in plants and animal products, and eventually affects human health. An ultrasensitive method for detecting and monitoring CAP is therefore urgently required. Herein, we report an ultrafast extraction and amperometry detection method based on a graphite-sulfate-modified electrode for detecting CAP in soil, water, and food samples. The graphite sulfate is prepared by the oxidation method and its structural properties are comprehensively investigated. The developed sensor electrode showed a wider linear range of 0.3-32.0 µg kg-1 and an ultralow detection limit of 0.1 µg kg-1, both of which meet the European Commission Reg 1871/2019 reference points for action. The method works well with both meat and plant samples, achieving CAP recoveries ranging from 90.8 to 99.1% even at low concentrations. Moreover, the sensor electrode shows more than 95% selectivity toward CAP detection in the soil, water, and food matrices. The developed method exhibits good repeatability and reproducibility in the analysis of real samples.

Lanthanum tin oxide-modified sensor electrode for the rapid detection of environmentally hazardous insecticide carbaryl in soil, water, and vegetable samples.

The growing population and global food demands have encouraged the use of pesticides to increase agricultural yields; however, the irrational use of pesticides threatens human health and the environment. Carbaryl (CRBL) is the most widespread insecticide and severely affects soil, water systems, and human health. Thus, it is crucial to monitor CRBL residues in the environment and vegetable samples. This study reports the rapid and sensitive electrochemical detection of CRBL based on a pyrochlore-type lanthanum tin oxide (LSO) nanoparticles (NPs)-modified screen-printed carbon electrode (SPCE). A low-temperature hydrothermal method was employed to prepare the LSO NPs. The structural properties of the LSO NPs were characterized by X-ray diffraction, Raman, and X-ray photoelectron spectroscopy analyses. The LSO NPs/SPCE demonstrated good electroanalytical performance for CRBL detection, with a low detection limit of 0.4 nM (0.08 µg/L) and a sensitivity of 1.05 µA/(µM cm2). Furthermore, the LSO NPs/SPCE exhibited high selectivity among highly interfering carbamate and organophosphorus pesticides, which share similar mechanisms of action. Additionally, the LSO NPs/SPCE sensor achieved > 90% recovery for the detection of CRBL in soil, water, and vegetable samples, thus verifying its suitability for the rapid detection of CRBL.

Effect of the Ni3TeO6 phase in a Ni2Te3O8/expanded graphite composite on the electrochemical monitoring of metribuzin residue in soil and water samples.

Growing food demand and climate change have led to the development of various pest control agents to increase crop yields. Although pesticides help meet the food demand, they cause harm to human health and the environment. Metribuzin (MTBZ) is one of the common herbicides used for controlling weeds. Therefore, monitoring MTBZ residues in soil and water bodies is essential for decreasing risk to the environment and human health. This paper reports a highly selective and sensitive electrochemical sensor electrode based on a Ni3TeO6-phase-integrated Ni2Te3O8/expanded graphite (referred to here as NTO-eGR) composite for the detection of MTBZ. The NTO-eGR composite was prepared by a one-step low-temperature hydrothermal method and characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and electron microscopy techniques. The Ni3TeO6 phase was found to be an active component in the NTO/eGR composite, which exhibited satisfactory analytical performance in MTBZ detection with a sensitivity of 1.454 µA µM-1 cm-2. Moreover, the NTO-eGR electrode exhibited high selectivity to MTBZ even in the presence of a five-fold excess of interfering species in water and soil samples. The studies on practical applicability revealed that NTO-eGR exhibits good reproducibility with a relative standard deviation of 2.67% (n = 5). Moreover, good recoveries of greater than 90% were achieved in the determination of MTBZ in soil and water samples. Hence, the NTO-eGR sensor electrode is highly suitable for the rapid on-site determination of MTBZ.

Graphene Nanosheet-Wrapped Mesoporous La0.8Ce0.2Fe0.5Mn0.5O3 Perovskite Oxide Composite for Improved Oxygen Reaction Electro-Kinetics and Li-O2 Battery Application.

A novel design and synthesis methodology is the most important consideration in the development of a superior electrocatalyst for improving the kinetics of oxygen electrode reactions, such as the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in Li-O2 battery application. Herein, we demonstrate a glycine-assisted hydrothermal and probe sonication method for the synthesis of a mesoporous spherical La0.8Ce0.2Fe0.5Mn0.5O3 perovskite particle and embedded graphene nanosheet (LCFM(8255)-gly/GNS) composite and evaluate its bifunctional ORR/OER kinetics in Li-O2 battery application. The physicochemical characterization confirms that the as-formed LCFM(8255)-gly perovskite catalyst has a highly crystalline structure and mesoporous morphology with a large specific surface area. The LCFM(8255)-gly/GNS composite hybrid structure exhibits an improved onset potential and high current density toward ORR/OER in both aqueous and non-aqueous electrolytes. The LCFM(8255)-gly/GNS composite cathode (ca. 8475 mAh g-1) delivers a higher discharge capacity than the La0.5Ce0.5Fe0.5Mn0.5O3-gly/GNS cathode (ca. 5796 mAh g-1) in a Li-O2 battery at a current density of 100 mA g-1. Our results revealed that the composite's high electrochemical activity comes from the synergism of highly abundant oxygen vacancies and redox-active sites due to the Ce and Fe dopant in LaMnO3 and the excellent charge transfer characteristics of the graphene materials. The as-developed cathode catalyst performed appreciable cycle stability up to 55 cycles at a limited capacity of 1000 mAh g-1 based on conventional glass fiber separators.

Studies on the sonochemical polymorphism of Sb2O3 on activated graphite for the electrochemical determination of imipramine.

This work reports the simultaneous sonochemical activation of graphite and sonohydrolysis of antimony chloride (SbCl3) in the alkaline medium. The experiments conducted by bath sonicator operated at 37 kHz of frequency and a maximum power of 150 W. The simple sonohydrolysis of SbCl3 alone produced an orthorhombic phase of Sb2O3, whereas, it produced mixed phases of cubic and orthorhombic Sb2O3 when introduced with graphite. Herein, the activated graphite (aGR) provides the best support to the growth of cubic phase. This cubic Sb2O3 is grown only on the graphite basal planes, which confirmed by scanning electron microscope. Moreover, the phase changes have identified by the X-ray diffraction, Raman and X-ray photoelectron analysis. The prepared aGR-Sb2O3 composite has applied to the electroanalytical studies of anti-depressant drug imipramine (IMP). The results showed that aGR-Sb2O3 revealed better activity than Sb2O3; the reasons are discussed comprehensively. Furthermore, aGR-Sb2O3 exhibited comparable analytical results for the determination of IMP.

Effect of cavitation erosion in the sonochemical exfoliation of activated graphite for electrocatalysis of acebutolol.

This study mainly covered the cavitation erosion in probe sonication and its electrochemical behavior. The activated graphite was exfoliated by the probe sonication wherein the titanium alloy (TA) is used as a probe (micro-tip). The sonication performed in the aqueous solution contains a mixture of sulfuric acid and nitric acid (1:1). The exfoliated graphite (EG) was examined by field emission scanning electron microscope, Raman and X-ray diffraction pattern analysis. The results showed that some TA particles dissolute from the TA micro-tip accompanied with graphite exfoliation. This dissolution experienced from the cavitation erosion, because the acoustic cavitation makes severe deformation on probe tips due to the bubble collapse. The dissolution rate increased when increasing sonication time; the resultant TA particles are randomly distributed over the EG. These EGTAs applied to the electrochemical oxidation of acebutolol which revealed an appreciable electrochemical performance and also exhibited better analytical performances to the electrochemical determinations. The obtained analytical parameters viz., sensitivity (0.234 µA µM-1 cm-2), linear range (0.01-15.1 µM), and limit of detection (0.003 µM) are highly comparable with the previous reports. Moreover, it has an acceptable tolerance with the interfering substances.

Sonochemical Synthesis of Sulfur Doped Reduced Graphene Oxide Supported CuS Nanoparticles for the Non-Enzymatic Glucose Sensor Applications.

Over the present material synthesis routes, the sonochemical route is highly efficient and comfortable way to produce nanostructured materials. In this way, the copper sulfide (CuS-covellite) and sulfur doped reduced graphene oxide (S-rGO) nanocomposite was prepared by sonochemical method. Interestingly, the structure of the as-prepared S-rGO/CuS was changed from the covellite to digenite phase. Herein, the S-rGO was act as a mild oxidizer and liable for the structural transformations. These structural changes are sequentially studied by various physicochemical characterizations such as Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). After scrupulous structural evaluations, the transformation of CuS phase was identified and documented. This oxidized CuS has an excellent electrocatalytic activity when compare to the bulk CuS. This S-rGO/CuS was further used for the determination of glucose and acquired good electrocatalytic performances. This S-rGO/CuS was exhibited a wide linear concentration range, 0.0001-3.88 mM and 3.88-20.17 mM, and a low-level detection limit of 32 nM. Moreover, we have validated the practicability of our developed glucose sensor in real biological samples.

Electrochemical preparation of activated graphene oxide for the simultaneous determination of hydroquinone and catechol.

This paper describes the electrochemical preparation of highly electrochemically active and conductive activated graphene oxide (aGO). Afterwards, the electrochemical properties of aGO was studied towards the simultaneous determination of hydroquinone (HQ) and catechol (CC). This aGO is prepared by the electrochemical activation of GO by various potential treatments. The resultant aGOs are examined by various physical and electrochemical characterizations. The high potential activation (1.4 to -1.5) process results a highly active GO (aGO1), which manifest a good electrochemical behavior towards the determination of HQ and CC. This aGO1 modified screen printed carbon electrode (SPCE) was furnished the sensitive detection of HQ and CC with linear concentration range from 1 to 312µM and 1 to 350µM. The aGO1 modified SPCE shows the lowest detection limit of 0.27µM and 0.182µM for the HQ and CC, respectively. The aGO1 modified SPCE reveals an excellent selectivity towards the determination of HQ and CC in the presence of 100 fold of potential interferents. Moreover, the fabricated disposable aGO1/SPCE sensor was demonstrated the determination of HQ and CC in tap water and industrial waste water.

A voltammetric determination of caffeic acid in red wines based on the nitrogen doped carbon modified glassy carbon electrode.

We reported an electrochemical determination of caffeic acid (CA) based on the nitrogen doped carbon (NDC). The described sensor material was prepared by the flame synthesis method, which gave an excellent platform for the synthesis of carbon nanomaterials with the hetero atom dopant. The synthesized material was confirmed by various physical characterizations and it was further characterized by different electrochemical experiments. The NDC modified glassy carbon electrode (NDC/GCE) shows the superior electrocatalytic performance towards the determination of CA with the wide linear concentration range from 0.01 to 350 µM. It achieves the lowest detection limit of 0.0024 µM and the limit of quantification of 0.004 µM. The NDC/GCE-CA sensor reveals the good selectivity, stability, sensitivity and reproducibility which endorsed that the NDC is promising electrode for the determination of CA. In addition, NDC modified electrode is applied to the determination of CA in red wines and acquired good results.

Rapid synthesis of ethyl cellulose supported platinum nanoparticles for the non-enzymatic determination of H2O2.

Cellulose derivatives are one of the carbohydrate polymers which received a great interest in the construction of nanostructured materials. Particularly, the ethyl cellulose provides an enormous support to the metal nanoparticles. To the best of our knowledge, this is the first time report for the simple and rapid synthesis of ethyl cellulose (EC) supported platinum nanoparticles (PtNPs) for the determination of non-enzymatic hydrogen peroxide (H2O2). The PtNPs/EC composite was confirmed by various characterizations such as fourier transform infra-red spectra, energy dispersive X-ray spectra, field emission scanning electron microscope and cyclic voltammetry. Further, the PtNPs/EC composite modified glassy carbon electrode (GCE) was successfully determined the H2O2 with the linear concentration range from 0.05µM to 2.22mM and the lowest detection limit of 0.01µM. Moreover, the PtNPs/EC/GCE sensor electrode manifested an acceptable sensitivity, selectivity and reproducibility. In addition, we have determined the H2O2 in contact lens solution and human blood serum samples.

Synthesis and characterizations of biscuit-like copper oxide for the non-enzymatic glucose sensor applications.

We described the synthesis of biscuit-like copper oxide (CuO) by the precipitation cum thermal annealing process. The biscuit-like CuO microstructures were successfully obtained by template free synthesis process. Thereby, the oxalic acid was used as the shape forming agent. Herein, the role of the sonic wave was quite important to controlling the shape. The CuO microstructures were characterized by the X-ray diffraction pattern, scanning electron microscope and energy dispersive X-ray analysis. The as-prepared CuO was used to fabricate the disposable sensor electrode using screen printed carbon electrode (SPCE). The CuO modified SPCE was successfully determined the glucose with the linear concentration ranging from 0.0005 to 4.03mM and the lowest detection limit of 0.1µM. The biscuit-like CuO microstructures based glucose sensor displayed appreciable analytical performance than the other CuO nanostructures. Moreover, the disposable CuO/SPCE was applied to determine the glucose in human blood serum, saliva and urine samples. The developed glucose sensor attained good recoveries in real sample analysis, hence, it is applicable for the commercial applications.

Studies on the influence of ß-cyclodextrin on graphene oxide and its synergistic activity to the electrochemical detection of nitrobenzene.

The impact of the ß-cyclodextrin (ß-CD) on the graphene oxide (GO) was considerably altered the activity of electrochemical sensors. Hence, the present study, we scrutinized the electrocatalytic determination of nitrobenzene (NB) by changing the different loading level of ß-CD on GO modified electrodes. The composites were prepared by the simple ultrasonication method and characterized by UV-Visible spectroscopy, infrared spectroscopy and scanning electron microscope. Interestingly, the synergistic electrocatalytic activity was appeared for the 1.2mg ß-CD loaded GO (ß-CD1.2mg/GO) to the determination of NB whereas bare SPCE, GO and other ß-CD loaded GO/SPCE exhibited the lower electrocatalytic activity. The ß-CD1.2mg/GO composite modified SPCE was furnished the linear concentration range from 0.5-1000µM and showed the lowest detection limit of 0.184µM. Moreover, it exhibited high sensitivity, acceptable reproducibility and good stability. Besides, the proposed sensor was demonstrated its practicability in real water samples.

Three-Dimensional Fibrous Network of Na0.21 MnO2 for Aqueous Sodium-Ion Hybrid Supercapacitors.

Sodium-ion hybrid supercapacitors are potential energy-storage devices and have recently received enormous interest. However, the development of cathode materials and the use of nonaqueous electrolyte remain a great challenge. Hence, aqueous Na-ion hybrid supercapacitors based on a three-dimensional network of NaMnO2 were developed. The cathode material was synthesized by the electro-oxidation of potassium manganese hexacyanoferrate nanocubes. The oxidized compound was confirmed to be Na0.21 MnO2 by various physical characterization methods. Manganese dioxide is a well-characterized material for aqueous asymmetric pseudocapacitors, but its usage at high operating voltages is limited due to the electrochemical stability of water. Nevertheless, high-potential and high-performance aqueous supercapacitors exhibiting a cell potential of 2.7 V were developed. Further, the practical applicability of an asymmetric supercapacitor based on NaMnO2 (cathode) and reduced graphene oxide (anode) was demonstrated by powering a 2.1 V red LED.

Modern Approach to the Synthesis of Ni(OH)2 Decorated Sulfur Doped Carbon Nanoparticles for the Nonenzymatic Glucose Sensor.

As a growing aspect of materials science, there are an enormous number of synthesis routes that have been identified to produce materials, particularly through simple methodologies. In this way, the present study focuses on the easiest way to prepare sulfur doped carbon nanoparticles (SDCNs) using a flame synthesis method and has also demonstrated a novel route to synthesize Ni(OH)2 decorated SDCNs by a simple adsorption cum precipitation method. The SDCNs are alternative candidates to prestigious carbon materials such as graphene, carbon nanotubes, and fullerenes. Moreover, SDCNs provide excellent support to the Ni(2+) ion adsorption and initiate the formation of Ni(OH)2. The formation of Ni(OH)2 on the SDCN matrix was confirmed by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), selected area diffraction pattern (SAED), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). After these meticulous structural evaluations, we have described the mechanism for the formation of Ni(OH)2 on an SDCN matrix. The as-prepared Ni(OH)2 decorated SDCN nanocomposites were used as an electrode material for nonenzymatic glucose sensors. The fabricated glucose sensor exhibited a wide linear concentration range, 0.0001-5.22 mM and 5.22-10.22 mM, and a low-level detection limit of 28 nM. Additionally, it reveals excellent selectivity in the potentially interfering ions and also possesses a good stability. The practicality of the fabricated glucose sensor was also demonstrated toward glucose detection in biological samples.

Electrochemical properties of the acetaminophen on the screen printed carbon electrode towards the high performance practical sensor applications.

Acetaminophen is a non-steroidal anti-inflammatory drug used as an antipyretic agent for the alternative to aspirin. Conversely, the overdoses of acetaminophen can cause hepatic toxicity and kidney damage. Hence, the determination of acetaminophen receives much more attention in biological samples and also in pharmaceutical formulations. Here, we report a rapid and sensitive detection of the acetaminophen based on the bare (unmodified) screen printed carbon electrode (BSPCE) and its electrochemistry was studied in various pHs. From the observed results, the mechanism of the electro-oxidation of acetaminophen was derived for various pHs. The acetaminophen is not stable in strong acidic and strong alkaline media, which is hydrolyzed and hydroxylated. However, it is stable in intermediate pHs due to the dimerization of acetaminophen. The kinetics of the acetaminophen oxidation was briefly studied and documented in the schemes. In addition, the surface morphology and disorders of BSPCE was probed by scanning electron microscope (SEM) and Raman spectroscopy. Moreover, the BSPCE determined the acetaminophen with the linear concentration ranging from 0.05 to 190µM and the lower detection limit of 0.013µM. Besides that it reveals the good recoveries towards the pharmaceutical samples and shows the excellent selectivity, sensitivity and stability. To the best of our knowledge, this is the better performance compare to the previously reported unmodified acetaminophen sensors.