Current Applications of Magnetic Nanomaterials for Extraction of Mycotoxins, Pesticides, and Pharmaceuticals in Food Commodities.

Environmental pollutants, such as mycotoxins, pesticides, and pharmaceuticals, are a group of contaminates that occur naturally, while others are produced from anthropogenic sources. With increased research on the adverse ecological and human health effects of these pollutants, there is an increasing need to regularly monitor their levels in food and the environment in order to ensure food safety and public health. The application of magnetic nanomaterials in the analyses of these pollutants could be promising and offers numerous advantages relative to conventional techniques. Due to their ability for the selective adsorption, and ease of separation as a result of magnetic susceptibility, surface modification, stability, cost-effectiveness, availability, and biodegradability, these unique magnetic nanomaterials exhibit great achievement in the improvement of the extraction of different analytes in food. On the other hand, conventional methods involve longer extraction procedures and utilize large quantities of environmentally unfriendly organic solvents. This review centers its attention on current applications of magnetic nanomaterials and their modifications in the extraction of pollutants in food commodities.

Deep eutectic solvent as an efficient modifier of low-cost adsorbent for the removal of pharmaceuticals and dye.

Waste from biomass was used to prepare a low-cost biochar-clay hybrid adsorbent. The hybrid adsorbent was synthesised by combining Kaolin with biomass (Vitex doniana), thereafter, modified with Deep Eutectic Solvent (DES). The materials were characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), Thermal gravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET), also, pHpzc of the materials were studied. The resultant adsorbents were used for both column and batch adsorption of organic pollutants; dye (Acid Blue 74; AB74) and pharmaceuticals (ciprofloxacin; CIP and acetaminophen; ACTE). Column adsorption capacity, effect of pollutant concentration and effect of flow rate were studied, also, the column was modelled using Thomas, Yoon-Nelson and Adams-Bohart model. Furthermore, batch adsorption experiments were performed, effect of change in pH, time, dose and concentration were studied. Batch adsorption data were fitted with isotherm and kinetic models. The experiment showed tremendous increase in adsorption capacity when the hybrid adsorbent (HYD) was modified with DES (HYD-DES). Acid Blue 74 on HYD-DES has the highest column sorption capacity followed by ciprofloxacin and acetaminophen. Adsorption was favoured at pH range of 2-10 for both AB74 and ACTE as there is no significant changes in the % removal performance, while adsorption was best at pH 6 and above for CIP. AB74 and CIP are best described by Langmuir isotherm, whereas ACTE adsorption was best explained by Freundlich isotherm equilibrium. The DES modified HYD has shown it can be effectively utilised as possible adsorbent for adsorbing organic dyes and pharmaceuticals.

Brief bibliometric analysis of "ionic liquid" applications and its review as a substitute for common adsorbent modifier for the adsorption of organic pollutants.

The importance of improving adsorbent's adsorption efficiency in organic pollutants has been reported by many researchers. Surfactant-based modified adsorbents were a tasteful choice. As a result, the use of surfactants as a modifier for removing organic pollutants has shown to play a very big role in enhancing the adsorption efficiency of different materials. Ionic liquids are receiving extensive interest as green multipurpose compounds, primarily as a replacement for traditional chemicals that are used in many chemical processes. This work gives a brief bibliometric analysis of application of ionic liquid from 1930 to 2017, documents were collected from Scopus database and keywords from the abstracts and titles were analyzed using VOSviewer software. Furthermore, the work presents a review of conventionally known surfactants and the recent likelihood of ionic liquids for modifying adsorbents for adsorption of organic pollutants. Over the period of years between 1930 and 2017, 13,144 documents were published on the application of ionic liquids. VOSviewer software further confirms that adsorption is one of the leading areas in applications of ionic liquids. Review also showed that ionic liquid is a good modifier of adsorbents.

Theoretical and experimental adsorption studies of sulfamethoxazole and ketoprofen on synthesized ionic liquids modified CNTs.

The adsorption of sulfamethoxazole (SMZ) and ketoprofen (KET) using carbon nanotubes (CNTs) and CNTs modified with ionic liquids (ILs) was investigated. Two ionic liquids (1-benzyl, 3-hexyl imidazolium, IL1 and 1-benzyl, 3-decahexyl imidazolium, IL2) were synthesized, and characterized by nuclear magnetic resonance (1H and 13C NMR) and high resolution-mass spectrometry (HR-MS). CNTs and modified CNTs were characterized using FT-IR, X-ray diffraction (XRD), surface area and porosity analysis, thermal gravimetric analysis (TGA), Zeta potential, Raman and scanning electron microscopy (SEM). Kinetics, isotherm and computational studies were carried out to determine the efficiency and adsorption mechanism of SMZ and KET on modified CNTs. A density functional theory (DFT) method was applied to shed more light on the interactions between the pharmaceutical compounds and the adsorbents at the molecular level. The effects of adsorbent dosage, concentration, solution pH, energetics and contact time of SMZ and KET on the adsorption process were investigated. The adsorption of SMZ and KET on CNTs and modified CNTs were pH dependent, and adsorption was best described by pseudo-second-order kinetics and the Freundlich adsorption isotherm. Ionic liquid modified CNTs showed improved adsorption capacities compared to the unmodified ones for both SMZ and KET, which is in line with the computational results showing performance order; CNT+KET/SMZ < CNT-ILs+SMZ < CNT-ILs+KET.

Quantitative analyses of selected polychlorinated biphenyl (PCB) congeners in water, soil, and sediment during winter and spring seasons from Msunduzi River, South Africa.

The lack of information and the need for knowledge on the organic pollutants within the area of KwaZulu-Natal together with the global problem of water supply have prompted our investigation into the analyses of eight polychlorinated biphenyl (PCB) congeners in the Msunduzi River of KwaZulu-Natal, South Africa. Soil, sediment, and water samples were collected at ten different sites along the river during winter and spring seasons. Soil and sediment samples were extracted using ultra sonication with dichloromethane while water samples were liquid-liquid extracted using dichloromethane. All sample extracts were cleaned-up using a multi-layer silica gel column and analyzed with gas chromatography-mass spectrometry. Quality assurance measures were also determined. The percentage recoveries for water were 53-128 for all the PCBs analyzed, while sediment recoveries ranged between 69 and 105%. The highest total concentrations of the PCBs in sediment were 214.21-610.45 ng/g dw at the Du Toit sampling site and 30.86-444.43 ng/g dw basis at the wastewater treatment inlet for winter and spring, respectively. Soil PCB concentrations were 76.53-397.75 ng/g dw at the Msunduzi Town sampling site and 20.84-443.49 ng/g (dry weight) at the Du Toit sampling site for winter and spring, respectively. In addition, high PCB concentrations were found in effluent of the wastewater treatment inlet compared to other sampling sites, which ranged between 0.68-22.37 and 2.53-35.69 ng/mL for winter and spring seasons, respectively. In all the sampling sites selected for this study, Du Toit afforded the highest PCB concentration levels and the lowest was after chlorination at the Darvill wastewater treatment plant. The results presented are new and it is the first study of organic pollutants such as PCBs that has been carried out on this river.

Occurrence and significance of polychlorinated biphenyls in water, sediment pore water and surface sediments of Umgeni River, KwaZulu-Natal, South Africa.

The Umgeni River is one of the main sources of water in KwaZulu-Natal, South Africa; however; there is currently a lack of information on the presence and distribution of polychlorinated biphenyls (PCBs) in its sediment, sediment pore water and surface water. This study aims to determine the occurrence and significance of selected PCBs in the surface water, sediment pore water and surface sediment samples from the Umgeni River. Liquid-liquid and soxhlet extractions were used for water or pore water, and sediments, respectively. Extracts were cleaned up using a florisil column and analysed by gas chromatography-mass spectrometry. The total concentrations of eight polychlorinated biphenyls were 6.91-21.69 ng/mL, 40.67-252.30 ng/mL and 102.60-427.80 ng/g (dry weight), in unfiltered surface water, unfiltered sediment pore water and surface sediments, respectively. The percentage contributions of various matrices were 4, 36 and 60 % for unfiltered surface water, unfiltered pore water and sediment, respectively. The highest concentrations of PCBs were found in water, pore water and sediment collected from sampling sites close to the Northern Wastewater Treatment Works. The highest chlorinated biphenyl, PCB 180, was the most abundant at almost all sampling sites. To our knowledge, this is the first report on occurrence of polychlorinated biphenyls in the Umgeni River water, pore water and sediment system and our results provide valuable information regarding the partitioning of the PCBs between the water and sediment systems as well as the organic chemical quality of the water.

Mesoporous Mn-substituted MnxZn1-xCo2O4 ternary spinel microspheres with enhanced electrochemical performance for supercapacitor applications.

Extensive investigations have been carried out on spinel mixed transition metal oxide-based materials for high-performance electrochemical energy storage applications. In this study, mesoporous Mn-substituted MnxZn1-xCo2O4 (ZMC) ternary oxide microspheres (x = 0, 0.3, 0.5, 0.7, and 1) were fabricated as electrode materials for supercapacitors through a facile coprecipitation method. Electron microscopy analysis revealed the formation of microspheres comprising interconnected aggregates of nanoparticles. Furthermore, the substitution of Mn into ZnCo2O4 significantly improved the surface area of the synthesized samples. The electrochemical test results demonstrate that the ZMC3 oxide microspheres with an optimal Mn substitution exhibited enhanced performance, displaying the largest specific capacitance of 589.9 F g-1 at 1 A g-1. Additionally, the ZMC3 electrode maintained a capacitance retention of 92.1% after 1000 cycles and exhibited a significant rate capability at a current density of 10 A g-1. This improved performance can be ascribed to the synergistic effects of multiple metals resulting from Mn substitution, along with an increase in the surface area, which tailors the redox behavior of ZnCo2O4 (ZC) and facilitates charge transfer. These findings indicate that the incorporation of Mn into mixed transition metal oxides holds promise as an effective strategy for designing high-performance electrodes for energy storage applications.

Oxyhalogen-sulfur chemistry: kinetics and mechanism of oxidation of captopril by acidified bromate and aqueous bromine.

By nature of their nucleophilicity, all thiol-based drugs are oxidatively metabolized in the physiological environment. The key to understanding the physiological role of a hypertension drug, (2S)-1-[(2S)-2-methyl-3-sulfanylpropanoyl]pyrrolidine-2-carboxylic acid, medically known as captopril is through studying its oxidation pathway: its reactive intermediates and oxidation products. The oxidation of captopril by aqueous bromine and acidified bromate has been studied by spectrophotometric and electrospray ionization techniques. The stoichiometry for the reaction of acidic bromate with captopril is 1:1, BrO3(-) + (C4H6N)(COOH)(COCHCH3CH2)-SH → (C4H6N)(COOH)(COCHCH3CH2)-SO3H + Br(-), with reaction occurring only at the thiol center. For the direct reaction of bromine with captopril, the ratio is 3:1; 3Br2 + (C4H6N)(COOH)(COCHCH3CH2)-SH + 3H2O → (C4H6N)(COOH)(COCHCH3CH2)-SO3H + 6HBr. In excess acidic bromate conditions the reaction displays an initial induction period followed by a sharp rise in absorbance at 390 nm due to rapid formation of bromine. The direct reaction of aqueous bromine with captopril was much faster than oxidation of the thiol by acidified bromate, with a bimolecular rate constant of (1.046 (±0.08) × 10(5) M(-1) s(-1). The detection of thiyl radicals confirms the involvement of radicals as intermediates in the oxidation of Captopril by acidified BrO3(-). The involvement of thiyl radicals in oxidation of captopril competes with a nonradical pathway involving 2-electron oxidations of the sulfur center. The oxidation product of captopril under these strong oxidizing conditions is a sulfonic acid as confirmed by electrospray ionization mass spectrometry (ESI-MS), iodometric titrations, and proton nuclear magnetic resonance ((1)H NMR) results. There was no evidence from ESI-MS for the formation of the sulfenic and sulfinic acids in the oxidation pathway as the thiol group is rapidly oxidized to the sulfonic acid. A computer simulation analysis of this mechanism gave a reasonably good fit to the experimental data.

The double-stranded ladder-like structure of poly[[bis(µ2-acetato-κ(2)O:O')bis(acetato-κO)bis(µ-4,4'-bipyridine-κ(2)N:N')dicopper(II)] 4-nitrophenol disolvate tetrahydrate].

The reaction of 4,4'-bipyridine with copper acetate in the presence of 4-nitrophenol led to the formation of the title compound, {[Cu(CH3COO)2(C10H8N2)]·C6H5NO3·2H2O}n. The complex forms a double-stranded ladder-like coordination polymer extending along the b axis. The double-stranded polymers are separated by 4-nitrophenol and water solvent molecules. The two Cu(II) centres of the centrosymmetric Cu2O2 ladder rungs have square-pyramidal coordination environments, which are formed by two acetate O atoms and two 4,4'-bipyridine N atoms in the basal plane and another acetate O atom at the apex. The ladder-like double strands are separated from each other by one unit-cell length along the c axis, and are connected by the water and 4-nitrophenol molecules through a series of O-H···O and C-H···O hydrogen-bonding interactions and two unique intermolecular π-π interactions.

Exploration of the Different Dimensions of Wurtzite ZnO Structure Nanomaterials as Gas Sensors at Room Temperature.

In this work, we report on the synthesis of four morphologies of ZnO, namely, nanoparticles, nanorods, nanosheets, and nanoflowers, from a single precursor Zn(CH3COO)2·2H2O under different reaction conditions. The synthesised nanostructured materials were characterised using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy, UV-Vis, XPS analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and nitrogen sorption at 77 K. The XRD, FTIR, and Raman analyses did not reveal any significant differences among the nanostructures, but differences in the electronic properties were noted among the different morphologies. The TEM and SEM analyses confirmed the four different morphologies of the ZnO nanostructures. The textural characteristics revealed that the specific surface areas were different, being 1.3, 6.7, 12.7, and 26.8 m2/g for the nanoflowers, nanoparticles, nanorods, and nanosheets, respectively. The ZnO nanostructures were then mixed with carbon nanoparticles (CNPs) and cellulose acetate (CA) to make nanocomposites that were then used as sensing materials in solid-state sensors to detect methanol, ethanol, and isopropanol vapour at room temperature. The sensors' responses were recorded in relative resistance. When detecting methanol, 6 out of 12 sensors were responsive, and the most sensitive sensor was the composite with a mass ratio of 1:1:1 of ZnO nanorods:CNPs:CA with a sensitivity of 0.7740 Ω ppm-1. Regarding the detection of ethanol vapour, 9 of the 12 sensors were responsive, and the 3:1:1 mass ratio with ZnO nanoparticles was the most sensitive at 4.3204 Ω ppm-1. Meanwhile, with isopropanol, 5 out of the 12 sensors were active and, with a sensitivity of 3.4539 Ω ppm-1, the ZnO nanoparticles in a 3:1:1 mass ratio were the most sensitive. Overall, the response of the sensors depended on the morphology of the nanostructured ZnO materials, the mass ratio of the sensing materials in the composites, and the type of analyte. The sensing mechanism was governed by the surface reaction on the sensing materials rather than pores hindering the analyte molecules from reaching the active site, since the pore size is larger than the kinetic diameter of the analyte molecules. Generally, the sensors responded well to the ethanol analyte, rather than methanol and isopropanol. This is due to ethanol molecules displaying a more enhanced electron-donating ability.

Effect of seawater acidification on physiological and energy metabolism responses of the common Cockle (Anadara antiquata) of Gazi Bay, Kenya.

Ocean acidification (OA) is becoming a potential threat to marine organisms, especially in calcifying marine invertebrates. So far, along the Kenya Coast, there has been little research on the impact of OA on cockle (Anadara antiquata), particularly on their physiological impacts induced by exposure to acidified seawater. Hence, this study aimed to investigate the physiological and biochemical responses of Anadara antiquata under present and future predicted seawater pH. In this study, the Anadara antiquata was exposed to three pH treatments (pH 7.90, 7.60, and 7.30) for 8 weeks to mimic future OA and to understand the physiological and biochemical effects on the organisms. Condition index, energy reserves (glycogen and protein), and cellular damage (e.g., lipid peroxidation level) were measured. Condition index (CI) showed no significant difference at different pH treatments (pH 7.90, 7.60, and 7.30), whereas the survival Anadara antiquata was slightly reduced after 8 weeks of exposure to pH 7.30. Glycogen and protein content were not affected at reduced pH (7.60 and 7.30). However, after 8 weeks of exposure to pH 7.60 and 7.30, Anadara antiquata showed a slight decrease in lipid peroxidation, an indication of cellular damage. The physiological and biochemical parameters analyzed (glycogen and protein content; lipid peroxidation levels) showed useful biomarkers to assess ocean acidification impacts in cockle.

Zeolitic imidazolate framework as humidity-resistant solid state-chemiresistive gas sensors: A review.

With significant technological advances, solid-state gas sensors have been extensively applied to detect toxic gases and volatile organic compounds (VOCs) in confined areas such as indoor environments and industries and to identify gas leakage. Semiconductor metal oxides are the primary sensing materials, although their major drawbacks include a lack of sensitivity, poor performance at high humidity, and operating at high temperatures ranging between 140 and 400 °C. Recently, the use of zeolitic imidazolate frameworks (ZIFs) in gas sensors has received considerable attention as a promising material to overcome the drawbacks possessed by semiconductor metal oxide-based gas sensors. Because of their unique properties, including size tunability, high surface area, and stability in humidity, ZIF becomes a preferred candidate for sensing materials. The use of ZIF materials in gas sensors is limited because of their high-temperature operation and low gas responses. This review outlines the strategies and developments in the utilization of ZIF-based materials in gas sensing. The significant influence of the addition of carbon additives in ZIF materials for temperature operation sensors is discussed. Finally, ZIF-carbon additives and SMO@ZIFs/carbon additives are the proposed materials to be studied for future prospects for the detection of VOCs at low temperatures and exhibiting good selectivity towards the gas of interest.

A humidity-resistant and room temperature carbon soot@ZIF-67 composite sensor for acetone vapour detection.

Zeolitic imidazolate framework-67 (ZIF-67), carbon nanoparticles (CNPs), and the CNPs@ZIF-67 composite were prepared and used to fabricate sensors for the detection of acetone vapour. The prepared materials were characterized using transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and Fourier-transform infrared spectroscopy. The sensors were tested using an LCR meter under the resistance parameter. It was found that the ZIF-67 sensor did not respond at room temperature, the CNP sensor had a non-linear response to all analytes, and the CNPs/ZIF-67 sensor had an excellent linear response to acetone vapour and was less sensitive to 3-pentanone, 4-methyl-1-hexene, toluene and cyclohexane vapours. However, it was found that ZIF-67 improves carbon soot sensor sensitivity by 155 times, wherein the sensitivity of the carbon soot sensor and carbon soot@ZIF-67 sensor on acetone vapour was found to be 0.0004 and 0.062 respectively. In addition, the sensor was found to be insensitive to humidity and the limit of detection was 484 ppb at room temperature.

Occurrence, distribution, and environmental risk of pharmaceutical residues in Mombasa peri-urban creeks, Kenya.

The information on pharmaceutical compounds' distribution and their possible risks in marine ecosystems along the Kenya coast is limited especially in the peri-urban creeks. Hence, this study aimed to determine pharmaceutical residue levels and distribution in selected peri-urban creeks in Mombasa and Gazi bay. The target compounds were analgesic (acetaminophen), antibiotics (trimethoprim and sulfamethoxazole), antiepileptic (carbamazepine), and antiretroviral (nevirapine). Pharmaceutical residues in grab surface seawater in wet and dry seasons ranged from below detection limit (BDL)-1065.6 µg L-1 and BDL-71.3 µg L-1, respectively. The concentration of the pharmaceutical residues was high in Tudor creek in the dry and wet seasons with a mean concentration of 63.3 µg L-1 and 233.1 µg L-1 respectively compared to Makupa creek (dry season, 54.2 µg L-1; wet season 16.2 µg L), and Mtwapa creek (dry season, 43.1 µg L-1; wet season, 15.0 µg L-1). Gazi Bay being used as a control site had a mean concentration of 21.3 µg L-1 and 3.1 µg L-1 during the dry season and wet season respectively. Acetaminophen and nevirapine were the most ubiquitous compounds in seawater since they were found in all seawater samples collected. Risk quotients (RQ) for invertebrates and algae based on the mean concentrations of the analytes were estimated to provide a preliminary environmental risk assessment. The results suggest that the studied acetaminophen, trimethoprim, sulfamethoxazole, and carbamazepine in seawater pose low (0.01 ≤ RQ < 0.1) to medium (0.1 ≤ RQ < 1) ecological risk whereas nevirapine poses medium to high (RQ ≥ 1) ecological risk to the ecosystems of Mombasa periurban creeks and Gazi bay. Further research, however, is encouraged on the distribution of pharmaceuticals in the marine environment and the long-term synergistic effects of mixtures of these compounds on marine biota.

An evaluation of adverse drug reactions and outcomes attributed to kratom in the US Food and Drug Administration Adverse Event Reporting System from January 2004 through September 2021.

Kratom is a widely used Asian botanical that has gained popularity in the United States due to a perception that it can treat pain, anxiety, and opioid withdrawal symptoms. The American Kratom Association estimates 10-16 million people use kratom. Kratom-associated adverse drug reactions (ADRs) continue to be reported and raise concerns about the safety profile of kratom. However, studies are lacking that describe the overall pattern of kratom-associated adverse events and quantify the association between kratom and adverse events. ADRs reported to the US Food and Drug Administration Adverse Event Reporting System from January 2004 through September 2021 were used to address these knowledge gaps. Descriptive analysis was conducted to analyze kratom-related adverse reactions. Conservative pharmacovigilance signals based on observed-to-expected ratios with shrinkage were estimated by comparing kratom to all other natural products and drugs. Based on 489 deduplicated kratom-related ADR reports, users were young (mean age 35.5 years), and more often male (67.5%) than female patients (23.5%). Cases were predominantly reported since 2018 (94.2%). Fifty-two disproportionate reporting signals in 17 system-organ-class categories were generated. The observed/reported number of kratom-related accidental death reports was 63-fold greater than expected. There were eight strong signals related to addiction or drug withdrawal. An excess proportion of ADR reports were about kratom-related drug complaints, toxicity to various agents, and seizures. Although further research is needed to assess the safety of kratom, clinicians and consumers should be aware that real-world evidence points to potential safety threats.

A Novel BiOCl Based Nanocomposite Membrane for Water Desalination.

In this study, BiOCl based nanocomposites were used as photocatalytic membranes for a simulated study on water desalination in reverse osmosis membrane systems. Through molecular dynamic simulation, the molecular structure of BiOCl, BiOCl/Ag2S and BiOCl/Bi2O3 heterojunctions were designed and their electronic properties, mechanical properties, and membrane performance for water desalination were evaluated for the first time. The molecular structure was created, and a geometry optimization task was used to optimize it. Material Studio 2019 CASTEP was used for simulation of the electronic and mechanical properties and water desalination was performed by ReaxFF software under pressures between 0 and 250 MPa. The novel BiOCl based nanocomposites showed improved electronic and mechanical properties and, most importantly, improvements in salt rejection and water permeability as compared to well-known materials such as graphene and MoS2. BiOCl and BiOCl/Ag2S had a bandgap around two, which is the ideal bandgap for semiconductor photocatalysts. A salt rejection of 98% was achieved under an applied pressure of 10 MPa. Salt rejection was higher for BiOCl/Bi2O3, while water permeability was higher for BiOCl/Ag2S. The monolayer BiOCl was unstable under pressures higher than 50 MPa, but the mechanical stability of BiOCl/Ag2S increased twofold and increased fourfold for BiOCl/Bi2O3, which is even higher than MoS2. However, between the three nanocomposites, BiOCl/Ag2S was found to be the most ideal photocatalytic nanocomposite membrane.

Nickel Oxide-Carbon Soot-Cellulose Acetate Nanocomposite for the Detection of Mesitylene Vapour: Investigating the Sensing Mechanism Using an LCR Meter Coupled to an FTIR Spectrometer.

Nanocomposite sensors were prepared using carbon soot (CNPs), nickel oxide nanoparticles (NiO-NPs), and cellulose acetate (CA), which was used to detect and study the sensing mechanism of mesitylene vapour at room temperature. Synthesised materials were characterised using high-resolution transmission electron microscopy (HR-TEM), powder x-ray diffraction (PXRD), Raman spectroscopy, and nitrogen sorption at 77 K. Various sensors were prepared using individual nanomaterials (NiO-NPs, CNPs, and CA), binary combinations of the nanomaterials (CNPs-NiO, CNPs-CA, and NiO-CA), and ternary composites (NiO-CNPs-CA). Among all of the prepared and tested sensors, the ternary nanocomposites (NiO-CNPs-CA) were found to be the most sensitive for the detection of mesitylene, with acceptable response recovery times. Fourier-transform infrared (FTIR) spectroscopy coupled with an LCR meter revealed that the mesitylene decomposes into carbon dioxide.

Selective detection of methanol vapour from a multicomponent gas mixture using a CNPs/ZnO@ZIF-8 based room temperature solid-state sensor.

Methanol vapour is harmful to human health if it is inhaled, swallowed, or absorbed through the skin. Solid-state gas sensors are a promising system for the detection of volatile organic compounds, unfortunately, they can have poor gas selectivity, low sensitivity, an inferior limit of detection (LOD), sensitivity towards humidity, and a need to operate at higher temperatures. A novel solid-state gas sensor was assembled using carbon nanoparticles (CNPs), prepared from a simple pyrolysis reaction, and zinc oxide@zeolitic imidazolate framework-8 nanorods (ZnO@ZIF-8 nanorods), synthesised using a hydrothermal method. The nanomaterials were characterized using scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy Raman spectroscopy, and Fourier transform infrared spectroscopy. The ZnO@ZIF-8 nanorods were inactive as a sensor, the CNPs showed some sensor activity, and the CNPs/ZnO@ZIF-8 nanorod composite performed as a viable solid-state sensor. The mass ratio of ZnO@ZIF-8 nanorods within the CNPs/ZnO@ZIF-8 nanorod composite was varied to investigate selectivity and sensitivity for the detection of ethanol, 2-propanol, acetone, ethyl acetate, chloroform, and methanol vapours. The assembled sensor composed of the CNPs/ZnO@ZIF-8 nanorod composite with a mass ratio of 1.5 : 6 showed improved gas sensing properties in the detection of methanol vapour with a LOD of 60 ppb. The sensor is insensitive to humidity and the methanol vapour sensitivity was found to be 0.51 Ω ppm-1 when detected at room temperature.

Design of Multi-Layer Graphene Membrane with Descending Pore Size for 100% Water Desalination by Simulation Using ReaxFF.

The performance of a desalination membrane depends on a specific pore size suitable for both water permeability and salt rejection. To increase membrane permeability, the applied pressure should be increased, which creates the need to improve membrane stability. In this research article, a molecular dynamics (MD) simulation was performed using ReaxFF module from Amsterdam Modeling suite (AMS) software to simulate water desalination efficiency using a single and multi-layer graphene membrane. The graphene membrane with different pore sizes and a multi-layer graphene membrane with descending pore size in each layer were designed and studied under different pressures. The stability of the membrane was checked using Material Studio 2019 by studying the dynamics summary. The single-layer graphene membrane was evaluated under pressures ranging from 100 to 500 MPa, with the salt rejection ranging from 95% to 82% with a water permeability of 0.347 × 10-9 to 2.94 × 10-9 (mm.g.cm-2s-1.bar-1), respectively. Almost 100% salt rejection was achieved for the multi-layer graphene membrane. This study successfully demonstrated the design and optimization of graphene membrane performance without functionalization.

Prediction of electronic properties of novel ZnS-ZnO-recycled expanded polystyrene nanocomposites by DFT.

DFT calculations using Material Studio (2019) were used to ascertain the changes in electronic properties of recycled expanded polystyrene (rEPS) after modification with nanoparticles of ZnS and ZnO. The nanocomposites were obtained using rEPS and suitable metal salt precursors via a solvothermal method. The XRD analysis was conducted to obtain the crystallography data of the new rEPS-based nanocomposites. Using Material Studio simulation software, the potential photocatalytic properties of the new prepared material was predicted and information on the electronic band structure was extracted. The calculated band gap values for rEPS and ZnS-ZnO-rEPS nanocomposite were 4.217 eV and 2.698 eV, respectively. Furthermore, our results showed that the nanocomposite is a p-type semiconductor. From the electronic structure and the band gap narrowing, these nanocomposites obtained from a waste material may have some potential in photocatalytic applications.