Alkyl-capped copper oxide nanospheres and nanoprolates for sustainability: water treatment and improved lubricating performance

Synthesis and in situ oxidation of copper micro- and nanoparticles by arc discharge plasma in liquid

This work presents a one-step controlled method for the synthesis of copper oxide nanoparticles using an arc discharge in deionized water without subsequent thermal annealing. The synthesis conditions were varied by changing the arc discharge current from 2 to 4 A. Scanning electron microscopy images of samples synthesized at discharge current of 2 A revealed the formation of tenorite (CuO) nanopetals with an average length of 550 nm and a width of 100 nm, which had a large surface area. Arc discharge synthesis at 3 and 4 A current modes provides the formation of a combination of CuO nanopetals with spherical cuprite (Cu2O) nanoparticles with sizes ranging from 30 to 80 nm. The crystalline phase and elemental composition of the synthesized particles were identified by X-ray diffraction analysis, Raman spectroscopy and Energy dispersive analysis. As the arc discharge current was raised from 2 to 4 A, two notable changes occurred in the synthesized particles: the Cu/O ratio increased, and the particle sizes decreased. At 4 A, the synthesized particles were from 30 to 80 nm in size and had a spherical shape, indicating an increase in the amount of cuprite (Cu2O) phase. The optical band gap of the aqueous solutions of copper oxide particles also increased from 2 to 2.34 eV with increasing synthesis current from 2 to 4 A, respectively. This suggests that the proposed synthesis method can be used to tune the band gap of the final material by controlling the Cu/O ratio through the current of arc discharge. Overall, this work demonstrates a novel approach to the synthesis of copper oxide nanoparticles with controllable CuO/Cu2O/Cu ratios, which has the potential to be useful in a variety of applications, particularly due to the significant enhancement of photocatalytic abilities and widen the working spectral range.

Genesis of copper oxide nanoparticles from waste printed circuit boards and evaluation of their photocatalytic activity

Discarded Printed Circuit Boards (PCBs) are one of the secondary resources of high-purity copper, and precious materials, which if disposed off inappropriately may present several environmental risks. This study focuses on the production of copper oxide nanoparticles (CuO NPs) from reclaimed copper via a facile precipitation route to obtain a value-added nanoproduct. The synthesis involved the dissolution of downsized PCBs, leaching of Cu into the solution phase and the precipitation of nanoparticles (NPs) in an alkaline medium. XRD analysis confirmed the as-synthesized NPs were monoclinic CuO of size 19.23 nm without any impurity. HRTEM analysis confirmed that the NPs were nearly round spheres with average particle size of 19.973 ± 6.036 nm. The NPs have a specific surface area of 200 m²/g and mesoporous structure with mean pore diameter of 18.051 nm. The CuO NPs photocatalyzed the degradation of Congo Red under visible light irradiation. Hence, the PCB e-waste was utilized to produce nanomaterials with added-values, decreasing environmental problems.

Oxidative Stability of Vegetal Oil-Based Lubricants

Lipids are widely distributed in nature and are one of the most important components of natural foods, synthetic compounds, and emulsions. To date, there is a strong social demand in the industrial sector for the use of sustainable products with a minimal environmental impact. Depending on their origin and composition, lipids can be employed as a plausible alternative as biodegradable lubricants in order to reduce the use of conventional mineral oil lubricants and mitigate their environmental impact. This perspective provides an overview of the advantages and constrains of vegetal oils under different lubrication regimes and the tribochemical reactions that can take place. Also, the different factors and pathways that influence their oxidation, the key role of moisture, and the changes of physical properties under pressure and temperature are reviewed. Special emphasis is devoted to the oxidation instability of fatty acids and vegetal oils and the physical and chemical approaches to improve oxidative and thermal stability are described in detail.