Sonochemical decomposition of noble metal oxides and sonochemical alloying of gold–silver systems

Recently, environmental problems, such as global warming, have become more severe; thus, there is a requirement to implement sustainable development goals in materials processing. In this study, we investigated a low-cost and environmentally-friendly sonochemical process for the synthesis of metal nanoparticles with large specific surface areas and catalysis effects. Au₂O₃ hydrate and Ag₂O were reduced to Au and Ag, respectively, at room temperature in a short time when irradiated with ultrasound in ethanol. Furthermore, when a mixed powder of Au₂O₃ hydrate and Ag₂O was irradiated in ethanol, Au–Ag alloys were obtained in only 10 min. This fast and environmentally friendly alloying technique, known as sonochemical alloying, is promising for alloy syntheses.     

Enhanced sonochemical degradation of bisphenol-A by bicarbonate ions

Sonochemical elimination of organic pollutants can take place through two degradation pathways. Molecules with relatively large Henry’s law constants will be incinerated inside the cavitation bubble, while nonvolatile molecules with low Henry’s law constants will be oxidised by the OH ejected from the bubble of cavitation. Taking bisphenol-A as a model pollutant, this study points out an alternate degradation route, mediated by bicarbonate ions, which is significant for the elimination of micro-pollutants at concentrations present in natural waters. In this process, OH radicals react with bicarbonate ions to produce the carbonate radical, which, unlike the OH radical, can migrate towards the bulk of the solution and therefore induce the degradation of the micro-pollutants present in the bulk solution. As a consequence, initial degradation rate is increased by a factor 3.2 at low concentration of bisphenol-A (0.022 μmol l⁻¹) in presence of bicarbonate in water.     

Superiority of sonochemical processing method for the synthesis of barium titanate nanocrystals in contrast to the mechanochemical approach

The results indicated that the ultrasonic sonochemistry which brings into play the acoustic cavitation phenomenon is more powerful and feasible in synthesizing the mixed oxides in contrast to the conventional solid-state approaches. The obtained results demonstrated that the sonochemical approach is able to obtain highly pure powder product at a much lower processing temperature of about 323 K (50 °C) in contrast to 1173 K (900 °C) which is essential for the synthesis by the mechanochemical approach. Sonochemical synthesis benefits from homogenous ordering the reactant ions (which have been dissolved in the solution mixture) into perovskite structure using ultrasonication. This indicates that the acoustic cavitation phenomenon is much more powerful and cost-effective than high energy ball milling in synthesizing nanopowders of the mixed oxide materials. Moreover, the sonochemical processing method is able to prepare the final powder products in a much shorter time by a one-step synthesis approach without the need for the successive calcination in contrast to the solid-state approach.     

Three-dimensional organometallic thallium(I) supramolecular polymer nanostructures synthesized with sonochemical process

A new three-dimensional thallium(I) supramolecular polymer, [Tl₂(μ₂-ATA)]_n (1), [H₂ATA = 2-aminoterephthalic acid]_, has been synthesized and characterized. The single-crystal X-ray data of compound 1 shows one type of Tl^I ion with a low coordination number. Compound 1 was self-assembled from Tl⋯C, Tl⋯O and Tl⋯N secondary interactions in thallium(I) coordination and the active lone pair on Tl^I in this compound may be involved in donor bonding. Two sides of the aromatic ring of ATA²⁻ anion have been involved in two types of secondary Tl⋯C approaches. Three samples of 1 were synthesized with three different concentrations of initial reagents under ultrasonic irradiation. The thermal stability of compound 1 samples were studied by thermo gravimetric (TG) and differential thermal analyses (DTA). These nano-structures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).     

Ultrasonic-assisted synthesis of porous S-doped carbon nitride ribbons for photocatalytic reduction of CO2

A series of porous S-doped carbon nitride ribbons (PSCN) were prepared by one-pot hydrothermal and sonochemical synthesis techniques. The morphologies and nanostructures of the catalysts were characterized by SEM, XRD and IR, which confirmed the pristine graphitic structures of carbon nitrides retained in the products. Due to sonication treatment, PSCN has porous structures in the thin ribbon and larger specific surface areas (PSCN 43.5 m²/g, SCN 26.6 m²/g and GCN 6.5 m²/g). XPS and elemental mappings verified that sulfur atoms were successfully introduced into the carbon nitride framework. Diffuse reflectance spectroscopy (DRS) results showed S-doping in the carbon nitride reduced the bandgap energy and enhanced their capability of the utilization of visible light, which contributed to higher photo-generated current. Photoluminescence (PL) analysis indicates the recombination of photogenerated carriers was suppressed in PSCN. Moreover, the photocatalytic performance showed that S-doping and porous and thin ribbon nanostructures may effectively boost the CO₂ reduction rate (to as much as 5.8 times of GCN) when illuminated by visible light (>420 nm) without the need of sacrificial materials. The preliminary mechanisms of the formation of PSCN and its applications in photocatalytic CO₂ reduction are proposed. It highlights the potential of the current technique to produce effective, nonmetal-doped carbon nitride photocatalysts.     

Sonochemical construction of hierarchical strontium doped lanthanum trisulfide electrocatalyst: An efficient electrode for highly sensitive detection of ecological pollutant in food and water

Herbicides are used constantly in agriculture to enhance productivity across the globe. This herbicide monitoring requires utmost importance since its high dose leads to ecological imbalance and a negative impact on the environment. Moreover, a quantification of toxic herbicide is one of the important problems in the food analysis. In this work, deals with the development of a simple, and facile one-pot sonochemical synthesis of strontium doped La₂S₃ (Sr@La₂S₃). Morphological and structural characterization confirms the doping of Sr@La₂S₃ to generate a hierarchical layered structure. The electrochemical performance of modified with rotating disk electrode (RDE) using Sr@La₂S₃ composite is high, compared to La₂S₃ and bare electrodes towards the quantitative detection of mesotrione (MTO) in phosphate buffer. Sr@La₂S₃/RDE showed good sensitivity for MTO detection and it exhibit a range of 0.01–307.01 μM and limit of detection of 2.4 nM. Besides, the selectivity of fabricated electrode is high as it can electrochemically reduce MTO particularly, even in the presence of other chemicals, biological molecules and inorganic ions. The repeatability of MTO detection is high even after 30 days with a lower RSD values. Hence, simple fabrication of Sr@La₂S₃/RDE could be a novel electrode for the sensitive, selective, and reproducible determination of herbicides in real-time applications.     

Ultrasound-assisted green syntheses of novel pyrimidine derivatives and their comparison with conventional methods

Ultrasound-assisted green syntheses of novel potentially bioactive pyrimidine derivatives have been carried out. The same compounds were obtained by conventional methods of synthesis, and the reaction times and yields of final products obtained by these two methods were compared. It was found that the time of utrasound-promoted reactions was reduced by almost 6–96 times, and their yields were equal or turn out to be greater compared to the traditional approach. The synthesized compounds showed a pronounced stimulating effect on plant growth. The most active derivatives were selected for deeper biological studies and subsequent field trials.     

Simple sonochemical synthesis,characterization of TmVO4 nanostructure in the presence of Schiff-base ligands and investigation of its potential in the removal of toxic dyes

Thulium vanadate (TmVO4) nanorods were successfully prepared by a simple sonochemical approach using Schiff-base ligands. Additionally, TmVO₄ nanorods were employed as a photocatalyst. The most optimal crystal structure and morphology of TmVO4 have been determined and optimized by varying Schiff-base ligands, the molar ratio of H2Salen, the sonication time and power, and the calcination time. A Eriochrome Black T (EBT) analysis revealed that the specific surface area was 24.91 m2/g. A bandgap of 2.3 eV was determined by diffuse reflectance spectroscopy (DRS) spectroscopy, which makes this compound suitable for visible photocatalytic applications. In order to assess the photocatalytic performance under visible light, two anionic dyes (EBT) and cationic dyes (Methyl Violet (MV)) were used as models. A variety of factors have been studied in order to improve the efficiency of the photocatalytic reaction, including dye type, pH, dye concentration, and catalyst loading. Under visible light, the highest efficiency was achieved (97.7%) when 45 mg TmVO4 nanocatalysts were present in 10 ppm Eriochorome Black T at pH = 10.