Sustainable Coating Materials: Exploring the Influence of Adjuvants on Kaolinite Suspension with Insights from Five Local Mining Clays.

Herein, we presented a comprehensive case study on the kaolin suspension derived from mining powder, with a specific emphasis on its mineral constituents within the size range of 2-5 µm and its suitability in spray applications. We have systematically investigated the influence of adjuvants, existing in both organic molecules and polymers, on the sedimentation behavior of clay suspensions. The investigations included the analysis of turbidity, dispersion weight, pH, and surface charge as key parameters. Our findings revealed that the specific presence of PEG-PPG-PEG, PAA, and PSAMA had a notable effect on delaying the suspension of sedimentation by the actual sediment weight as well as enhancing the uniformity of clay coating by the reflection efficiency of coating materials in PPFD units. To enhance sustainability in coating materials, it was essential to elucidate the optimal amounts of adjuvants and the pH levels as they are closely related to the efficacy of tree-coated spraying and soil conditions.

Reduced graphene oxide/zinc oxide composite as an electrochemical sensor for acetylcholine detection.

Acetylcholine (ACh) plays a pivotal role as a neurotransmitter, influencing nerve cell communication and overall nervous system health. Imbalances in ACh levels are linked to neurodegenerative diseases, such as Alzheimer's and Parkinson's. This study focused on developing electrochemical sensors for ACh detection, utilizing graphene oxide (GO) and a composite of reduced graphene oxide and zinc oxide (rGO/ZnO). The synthesis involved modified Hummers' and hydrothermal methods, unveiling the formation of rGO through deoxygenation and the integration of nano-sized ZnO particles onto rGO, as demonstrated by XPS and TEM. EIS analysis also revealed the enhancement of electron transfer efficiency in rGO/ZnO. Cyclic voltammograms of the electrode, comprising the rGO/ZnO composite in ACh solutions, demonstrated prominent oxidation and reduction reactions. Notably, the composite exhibited promise for ACh detection due to its sensitivity, low detection threshold, reusability, and selectivity against interfering compounds, specifically glutamate and gamma-aminobutyric acid. The unique properties of rGO, such as high specific surface area and electron mobility, coupled with ZnO's stability and catalytic efficiency, contributed to the composite's potential in electrochemical sensor applications. This research, emphasizing the synthesis, fabrication, and characterization of the rGO/ZnO composite, established itself as a reliable platform for detecting the acetylcholine neurotransmitter.

Sugar molasses as a sustainable precursor for the synthesis of graphene sand composite adsorbent for tetracycline and methylene blue removal.

Sugar molasses from agricultural waste could be a sustainable carbon source for the synthesis of graphene adsorbent introduced in this work. The sugar molasses was successfully converted to graphene-like material and subsequently coated on the sand as graphene sand composite (GSC), as proven by XRD, XPS, Raman spectroscopy, and SEM with EDX mapping analyses. The adsorption performance of GSC was evaluated against the removal of Tetracycline (TC) and methylene blue (MB) pollutants from an aqueous solution in a fixed bed column continuous-flow adsorption setup. The effect of different process conditions: bed height (4-12 cm), influent flow rate (3-7 mL/min), and contaminants' concentration (50-150 ppm) was investigated. The results revealed that column performance was improved by increasing the bed depth and lowering the flow rate and concentration of the pollutants. The best removal efficiency was obtained when the bed height was 12 cm, the influent flow rate of 3 mL/min, and the pollutants' initial concentration was 50 mg/L. Thomas, Adams-Bohart, and Yoon-Nelson models were attempted to fit the breakthrough curves. Regeneration of the GSC indicated the decline of breakthrough time from 240-280 to 180 min, reflecting the decrease in adsorptive sites due to the incomplete regeneration process. Overall, sugar molasses was shown to be a low-cost precursor for synthesizing valuable graphene material in the form of GSC, which can reduce the problem for industrial waste management of sugar molasses, and the GSC could be used as an adsorbent for environmental application.

Introducing micropores into carbon nanoparticles synthesized via a solution plasma process by thermal treatment and their charge storage properties in supercapacitors.

Carbon materials synthesized via a solution plasma process (SPP) have recently shown great potential for various applications. However, they mainly possess a meso-macroporous structure with a lack of micropores, which limits their applications for supercapacitors. Herein, carbon nanoparticles (CNPs) were synthesized from benzene via SPP and then subjected to thermal treatment at different temperatures (400, 600, 800, and 1000 °C) in an argon environment. The CNPs exhibited an amorphous phase and were more graphitized at high treatment temperatures. A small content of tungsten carbide particles was also observed, which were encapsulated in CNPs. An increase in treatment temperature led to an increase in the specific surface area of CNPs from 184 to 260 m2 g-1 through the development of micropores, while their meso-macropore structure remained unchanged. The oxygen content of CNPs decreased from 14.72 to 1.20 atom% as the treatment temperature increased due to the degradation of oxygen functionality. The charge storage properties of CNPs were evaluated for supercapacitor applications by electrochemical measurements using a three-electrode system in 1 M H2SO4 electrolyte. The CNPs treated at low temperatures exhibited an electric double layer and pseudocapacitive behavior due to the presence of quinone groups on the carbon surface. With increasing treatment temperature, the electric double layer behavior became more dominant, while pseudocapacitive behavior was suppressed due to the quinone degradation. Regarding cycling stability, the CNPs treated at high temperatures (with a lack of oxygen functionality) were more stable than those treated at low temperatures. This work highlights a way of introducing micropores into CNPs derived from SPP via thermal treatment, which could be helpful for controlling and adjusting their pore structure for supercapacitor applications.

Electrochemical paraquat sensor based on lead oxide nanoparticles.

1,1-Dimethyl-4,4-bipyridinium dichloride known as paraquat is a popular well-known herbicide that is widely used in agriculture around the world. However, paraquat is a highly toxic chemical causing damage to vital organs including the respiratory system, liver, heart, and kidneys and death. Therefore, detection of paraquat is still necessary to protect life and the environment. In this work, an electrochemical sensor based on lead oxide nanoparticles (PbO-NPs) modified on a screen-printed silver working electrode (SPE) has been fabricated for paraquat detection at room temperature. The PbO-NPs have been synthesized by using a sparking method via two Pb metal wires. The electrochemical paraquat sensors have been prepared by a simple drop-casting of PbO-NPs solution on the surface of the SPE. The PbO-NPs/SPE sensor exhibits a linear response in the range from 1 mM to 5 mM with good reproducibility and high sensitivity (204.85 µA mM-1 cm-2) for paraquat detection at room temperature. The PbO-NPs/SPE sensor shows high selectivity to paraquat over other popular herbicides such as glyphosate, glufosinate-ammonium and butachlor-propanil. The application of the PbO-NPs/SPE sensor is also demonstrated via the monitoring of paraquat contamination in juice and milk.

Hydroxyapatite coating on an aluminum/bioplastic scaffold for bone tissue engineering.

Three-dimensional printing can produce scaffolds with shapes and dimensions tailored for practical clinical applications. Enhanced osteoconductivity of such scaffolds is generally desired. Hydroxyapatite (HA) is an inorganic ceramic that can be used to coat such scaffolds and to accelerate healing during the bone restoration process. In this study, HA-coated aluminum/bioplastic scaffolds were fabricated, and their structural characteristics and osteoconductivity were evaluated. Aluminum/bioplastic scaffolds were fabricated by three-dimensional printing, and HA slurries with solids loadings of 10-20 vol% were used for coating. As solids loadings increased, the thickness of the coating layers slightly increased, whereas pore sizes decreased. The average compressive strength was comparable to that of cancellous bone. Potential osteoconductivity was tested by simulated body fluid immersion for 28 days, and the formation of the HA phase on the surface along with a weight increase indicates the potential bioactivity of the samples.

Au nanoparticle-decorated TiO2 hollow fibers with enhanced visible-light photocatalytic activity toward dye degradation.

TiO2 hollow fibers (THF) were prepared by a template method using kapok as a biotemplate and subsequently decorated by plasmonic Au nanoparticles using a solution plasma process. The THF exhibited an anatase phase and a hollow structure with a mesoporous wall. Au nanoparticles with a diameter of about 5-10 nm were uniformly distributed on the THF surface. Au nanoparticles-decorated TiO2 hollow fibers (Au/THF) have enhanced photocatalytic activity toward methylene blue degradation under visible light-emitting diode (Vis-LED) as compared to pristine THF and P25. This could be attributed to combined effects including effective light-harvesting by a hollow structure, large surface area due to a mesoporous wall of THF, and visible-light absorption and efficient charge separation induced by Au nanoparticles. The Au/THF also showed good recyclability and separation ability.

Titanium dioxide and fluoropolymer-based coating for smart fabrics with antimicrobial and water-repellent properties.

In the coronavirus disease 2019 pandemic, protective clothing is required for medical staff at risk of infection. This study proposes functional smart fabrics with antimicrobial and water-repellent properties, using titanium dioxide (TiO2) and fluoropolymer-based precursors as coating materials. Experimental results indicated a uniform distribution of TiO2 particles with an average size below 200 nm throughout the fabric. A zone of inhibition test revealed that the fabric inhibited bacterial growth, specifically of Staphylococcus aureus and Klebsiella pneumoniae, before and after 10 wash cycles of the fabric. In wetting angle measurements, the contact angles of water droplets on the fabric ranged from 120° to 139°. A water repellency test confirmed that the coated fabrics retained their water-repellent property after 10 wash cycles.