Ultrasound assisted facile synthesis of Mn(II) and Cu(II) coordination polymers and their use as precursors for α-Mn3O4 and CuO nanoparticles: Synthesis, characterization and catalytic properties

Structural, optical and photocatalytic properties of mesoporous CuO nanoparticles with tunable size and different morphologies

Nanomaterials with controllable particle size and shape have fascinating properties. Herein, CuO nanoparticles (NPs) with controlled particle size and morphology are obtained via a simple co-precipitation approach. Variation of the reaction medium composition steers the variation of both particle size and morphology of the CuO NPs. The reaction was performed in ethanol–water solutions with different volume to volume ratios (v/v%) i.e. 0, 25, 50, and 100%. XRD of the obtained samples revealed a drop in their particle size from ∼13 to ∼7 nm when the aqueous medium is entirely replaced by the ethanolic medium. TEM and HR-TEM investigations have pointed to the formation of CuO NPs with rod-like shapes in water (diameter = 15 nm and length = 200 nm). Whereas, spherical NPs with a diameter of 7.2 nm are obtained in ethanol. Structural analysis of CuO samples obtained in different media was done applying the Rietveld method. The volume of the monoclinic unit cell of CuO is increased to 81.869 ų when water (81.207 ų) is completely substituted by ethanol. Moreover, the internal local strain (ε) and the dislocation density (δ) values increase from 2.78 × 10⁻³ to 4.64 × 10⁻³ and 0.592 × 10⁶ to 1.93 × 10⁶ line per m², respectively by changing from aqueous to ethanolic medium. The optical band gap (E_g) determined using Tauc's equation for the direct transition is increased from 2.2 to 2.65 eV when water is totally replaced by ethanol. The feasibility of both CuO samples as photocatalysts for the degradation of Congo red was tested. CuO prepared in pure water showed remarkably high efficiency during the first 25 min of illumination. Both samples showed complete dye removal after 35 min. Ultimately, this work presents a simple and green approach for the preparation of CuO NPs with tunable particle size, varied morphological shapes, high surface area, and different structural and optical properties merely through controlling the ethanol content in water.

Ethanol/water percentage plays a crucial role in tuning of the particle size and morphology, hence the structural, optical and photocatalytic properties of the synthesized CuO nanomaterials.

Enhancement of catalytic activity in NH3-SCR reaction by promoting dispersibility of CuCe/TiO2-ZrO2 with ultrasonic treatment

A series of CuCe-modified TiO₂-ZrO₂ catalysts synthesized by stepwise impregnation method and ultrasonic-assisted impregnation method were investigated to research the removal of NO in the simulated flue gas. Results showed that the CuCe/TiO₂-ZrO₂ catalyst prepared by ultrasonic-assisted impregnation method exhibited the superior NO conversion, in which higher than 85% NO was degraded at the temperature range of 250-400 °C and the highest NO conversion of 94% at 350 °C. It proves that ultrasonic treatment can markedly improve the performance of catalysts. The effect of ultrasonic enhancement on CuCe/TiO₂-ZrO₂ was comprehensively studied through being characterized by physicochemical characterization. Results reveal that the ultrasonic cavitation effect improves the distribution of active species and the synergistic interaction between Cu with Ce components (Cu⁺ + Ce⁴⁺ ↔ Cu²⁺ + Ce³⁺) on the catalysts significantly, thus resulting in better dispersibility as well as a higher ratio of Cu²⁺ and Ce³⁺ of the catalysts. Moreover, it was found that the CuCe/TiO₂-ZrO₂ catalyst prepared by the ultrasonic-assisted impregnation method represented a higher degree of ultrafine metal particles and evenness. The above results were described with the generalized dimension and singularity spectra in multifractal analysis and validated by the comparative test. Therefore, it can be concluded that ultrasonic treatment facilitates the particle size and distribution of active sites on the catalysts.