Isocyanide-based synthesis of spirorhodanine-cyclopentadiene and spirorhodanine-iminobutenolide conjugates from Winterfeldt's zwitterions and 5-ylidene rhodanines.

An ultrasonic-assisted isocyanide-based protocol to access a series of functionalized spirorhodanine-cyclopentadiene and spirorhodanine-iminobutenolide conjugates from alkyl isocyanides and dialkyl acetylenedicarboxylates in the presence of 5-ylidene rhodanines in MeCN, is described. The reaction proceeds via interception of the reactive Winterfeldt's zwitterions by 5-ylidene rhodanine derivatives. The structures of the target compounds were confirmed by X-ray diffraction studies.

Ultrasonic-Assisted Conversion of Micrometer-Sized BiI3 into BiOI Nanoflakes for Photocatalytic Applications.

This work describes a novel method for converting bismuth triiodide (BiI3) microplates into bismuth oxyiodide (BiOI) nanoflakes under ultrasonic irradiation. To produce BiOI nanoflakes with a high yield and high purity, the conversion process was carefully adjusted. Rapid reaction kinetics and increased mass transfer are benefits of the ultrasonic-assisted approach that result in well-defined converted BiOI nanostructures with superior characteristics. The produced BiOI nanoflakes were examined utilizing a range of analytical methods, such as Transmission Electron Microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The progress in the ultrasonic conversion process with time was monitored through diffuse reflectance spectroscopy (DRS). The outcomes demonstrated the effective conversion of BiI3 microplates into crystalline, homogeneous, high-surface-area BiOI nanoflakes. Additionally, the degradation of organic dyes (methylene blue) under ultraviolet (UV) light irradiation was used to assess the photocatalytic efficacy of the produced BiOI nanoflakes. Because of their distinct morphology and electrical structure, the BiOI nanoflakes remarkably demonstrated remarkable photocatalytic activity, outperforming traditional photocatalysts. The ability of BiOI nanoflakes to effectively separate and utilize visible light photons makes them a viable option for environmental remediation applications. This work not only shows the promise of BiOI nanoflakes for sustainable photocatalytic applications but also demonstrates a simple and scalable approach to their manufacturing. The knowledge gathered from this work opens up new avenues for investigating ultrasonic-assisted techniques for creating sophisticated nanomaterials with customized characteristics for a range of technological uses.

Naked-Eye Detection of Morphine by Au@Ag Nanoparticles-Based Colorimetric Chemosensors.

In this study, we report a novel and facile colorimetric assay based on silver citrate-coated Au@Ag nanoparticles (Au@AgNPs) as a chemosensor for the naked-eye detection of morphine (MOR). The developed optical sensing approach relied on the aggregation of Au@Ag NPs upon exposure to morphine, which led to an evident color variation from light-yellow to brown. Au@Ag NPs have been prepared by two different protocols, using high- and low-power ultrasonic irradiation. The sonochemical method was essential for the sensing properties of the resulting nanoparticles. This facile sensing method has several advantages including excellent stability, selectivity, prompt detection, and cost-effectiveness.

Bimetallic TiO2 Nanoparticles for Lignin-Based Model Compounds Valorization by Integrating an Optocatalytic Flow-Microreactor.

The challenge of improving the activity of TiO2 by modifying it with metals and using it for targeted applications in microreactor environments is an active area of research. Recently, microreactors have emerged as successful candidates for many photocatalytic reactions, especially for the selective oxidation process. The current work introduces ultrasound-assisted catalyst deposition on the inner walls of a perfluoro-alkoxy alkane (PFA) microtube under mild conditions. We report Cu-Au/TiO2 and Fe-Au/TiO2 nanoparticles synthesized using the sol-gel method. The obtained photocatalysts were thoroughly characterized by UV-Vis diffuse-reflectance spectroscopy (DRS), high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and N2 physisorption. The photocatalytic activity under UV (375 nm) and visible light (515 nm) was estimated by the oxidation of lignin-based model aromatic alcohols in batch and fluoropolymer-based flow systems. The bimetallic catalyst exhibited improved photocatalytic selective oxidation. Herein, four aromatic alcohols were individually investigated and compared. In our experiments, the alcohols containing hydroxy and methoxy groups (coniferyl and vanillin alcohol) showed high conversion (93% and 52%, respectively) with 8% and 17% selectivity towards their respective aldehydes, with the formation of other side products. The results offer an insight into ligand-to-metal charge transfer (LMCT) complex formation, which was found to be the main reason for the activity of synthesized catalysts under visible light.

Ultrasound-assisted synthesis of heterocyclic compounds.

In this review, we tried to underscore the synthesis of the heterocyclic compounds under assisted ultrasonic irradiation. The ultrasonic irradiation has been applied for medicinal chemistry and drug discovery process since it dramatically reduces reaction times, from days or hours to minutes. Also, ultrasonic irradiation provides lower cost, excellent yields, greater purity, and simple workups as compared to lower yields, longer reaction times, lesser purity and in the conventional methods. In this review, we have compared synthesis of the heterocyclic compounds under ultrasonic irradiation with other methods.

Ultrasound-assisted bottom-up synthesis of Ni-graphene hybrid composites and their excellent rhodamine B removal properties.

In this paper, a facile one-pot bottom-up approach has been developed for the rapid preparation (≤5 min) of graphene nanostructures and Ni-graphene hybrid composites. Under the aid of ultrasonic irradiation, the graphene nanostructures were prepared via reducing hexachloro-benzene(C6Cl6) with sodium (Na) in non-polar organic solvent n-tetradecane (C14H30). On the basis of this route, the Ni-graphene hybrid composites were easily synthesized by adding Ni nanoparticles (NPs) into reaction system. The whole reaction was carried out at low temperature (100-120 °C) and in air atmosphere. Despite the absence of nitrogen protection, the result from surface analysis still shows a relatively high C/O ratio (10:1). The effect of the Ni NPs content and size on the specific surface area (SSA) of the products is also investigated. The synthesized samples exhibit large SSA, which is significantly affected by the Ni NPs content rather than their size. The adsorption performances of the samples are evaluated for the removal of organic dyes such as rhodamine B (RhB) from aqueous solutions. The testing results show great adsorption capacity (qmax = 963.04 mg g-1), rapid adsorption rate (~99.88%, 2 min), high adsorption efficiency (>99.7%) and good chemical stability in a wide pH range (3-13), high salt tolerance (>80 mg mL-1), and good recyclability (>99.5%, 20 cycles).

Diastereoselective Sonochemical Synthesis of Spirocyclopropaneoxindoles and Evaluation of Their Antioxidant and Cytotoxic Activities.

An efficient diastereoselective synthesis of spirocyclopropaneoxindoles is reported using three-component reactions of various phenacylidenetriphenylphosphorane, isatins and phenacyl bromide under ultrasonic irradiation. The structures of synthesized spirocyclopropaneoxindoles were characterized by their spectral data. The antioxidant activities of the synthesized compounds were evaluated by 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay. Among the products, those with NH group in their structure exhibited higher antioxidant activities than other derivatives. Also, in vitro cytotoxicity of compounds 4b, 4e, 4j, 4k were examined against heLa cancer cell lines using MTT assay. The results revealed that compound 4j with chlorine substituent on phenyl group displayed higher cytotoxicity activity (IC50 =4.50±0.30 µg/mL) after 48 h.

Ethyl Butyrate Synthesis Catalyzed by Lipases A and B from Candida antarctica Immobilized onto Magnetic Nanoparticles. Improvement of Biocatalysts' Performance under Ultrasonic Irradiation.

The synthesis of ethyl butyrate catalyzed by lipases A (CALA) or B (CALB) from Candida antarctica immobilized onto magnetic nanoparticles (MNP), CALA-MNP and CALB-MNP, respectively, is hereby reported. MNPs were prepared by co-precipitation, functionalized with 3-aminopropyltriethoxysilane, activated with glutaraldehyde, and then used as support to immobilize either CALA or CALB (immobilization yield: 100 ± 1.2% and 57.6 ± 3.8%; biocatalysts activities: 198.3 ± 2.7 Up-NPB/g and 52.9 ± 1.7 Up-NPB/g for CALA-MNP and CALB-MNP, respectively). X-ray diffraction and Raman spectroscopy analysis indicated the production of a magnetic nanomaterial with a diameter of 13.0 nm, whereas Fourier-transform infrared spectroscopy indicated functionalization, activation and enzyme immobilization. To determine the optimum conditions for the synthesis, a four-variable Central Composite Design (CCD) (biocatalyst content, molar ratio, temperature and time) was performed. Under optimized conditions (1:1, 45 °C and 6 h), it was possible to achieve 99.2 ± 0.3% of conversion for CALA-MNP (10 mg) and 97.5 ± 0.8% for CALB-MNP (12.5 mg), which retained approximately 80% of their activity after 10 consecutive cycles of esterification. Under ultrasonic irradiation, similar conversions were achieved but at 4 h of incubation, demonstrating the efficiency of ultrasound technology in the enzymatic synthesis of esters.

Some Features of the Ultrasonic Liquid Extraction of Metal Ions.

The non-linear equation of the radial oscillations of a liquid ball in an immiscible liquid under the exposure of time-varying sound pressure was obtained. The behavioral features of a liquid spherical drop placed in such a media were analyzed in the presence of ultrasound irradiations. The slowing-down effect of the extracted metal ions under its exposure has been studied for the first time, using theoretical and experimental approaches. This phenomenon mechanism was revealed, and analytical equations for the mass transfer rate as a function of the sound pressure oscillations amplitude and the substrate ultrasonic treatment time are presented. Experimental studies of Fe3+ ions extracted from chloride and nitrate solutions in systems based on water-soluble polymers were carried out, and a convincing coincidence with the results of theoretical calculations was established. The conditions for achieving the desired extraction efficiency when applying the ultrasonic stimulating effect are specified. The derived result opens the complementary possibility in operations, with the separateness of extraction processes, that which has the essential practical importance.

Influence of Synthesis Method on LTA Time-Dependent Stability.

Time-stability of LTA zeolite formed by hydrothermal method with or without the action of ultrasonic irradiation was investigated by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The results show that 6 months after the synthesis by hydrothermal process with continuous sonication, LTA evolves into a more stable sodalite, whereas no differences are detected 12 months after LTA synthesis by conventional pre-fused hydrothermal process. These data confirm that using the two approaches, different mechanisms control both zeolite crystallization and time-stability of the newly-formed mineral at solid state. The results are particularly important in the light of the synthetic zeolite application.

Effects of Low-Frequency Ultrasound on Microcystis aeruginosa from Cell Inactivation to Disruption.

Ultrasound can be used to induce cell resonance and cavitation to inhibit cyanobacterial growth, but it can also lead to increase in dissolved nutrients because of cell disruption. This study investigated the process from cell inactivation to disruption of Microcystis aeruginosa. Algal cells were sonicated (at 35 kHz) under various intensities and durations. Results showed that chlorophyll a content and Fv/Fm values decreased slightly within the first 5 min. Superoxide dismutase activity was stimulated and its peak value appeared at the fifth minute. After 20 min, considerable number of ruptured cells were observed and the concentrations of dissolved nitrogen and phosphorus increased rapidly. Finally, ammonia and nitrate merely composed a small portion of dissolved nitrogen. This study demonstrated that excessive ultrasound treatment can significantly rupture algal cells and lead to the release of cellular inclusions, which may cause ecological issues or public health problems. Based on our findings, ultrasonic intensity controlled at 0.035 W/mL and applied for a duration of 20 min delivers the optimal result in effectively inhibiting physiological activities of Microcystis aeruginosa without marked cell disruption. This will ultimately help to achieve algal control, while conserving energy and preserving the environment and human health.

Enhancement of ultrasonic disintegration of sewage sludge by aeration.

Sonication is an effective way for sludge disintegration, which can significantly improve the efficiency of anaerobic digestion to reduce and recycle use of sludge. But high energy consumption limits the wide application of sonication. In order to improve ultrasonic sludge disintegration efficiency and reduce energy consumption, aeration was introduced. Results showed that sludge disintegration efficiency was improved significantly by combining aeration with ultrasound. The aeration flow rate, gas bubble size, ultrasonic density and aeration timing had impacts on sludge disintegration efficiency. Aeration that used in later stage of ultrasonic irradiation with low aeration flow rate, small gas bubbles significantly improved ultrasonic disintegration sludge efficiency. At the optimal conditions of 0.4 W/mL ultrasonic irradiation density, 30 mL/min of aeration flow rate, 5 min of aeration in later stage and small gas bubbles, ultrasonic sludge disintegration efficiency was increased by 45% and one third of ultrasonic energy was saved. This approach will greatly benefit the application of ultrasonic sludge disintegration and strongly promote the treatment and recycle of wastewater sludge.

Inactivation of Escherichia coli and Staphylococcus aureus by ultrasound.

OBJECTIVES: The aim of this study was to obtain valuable information about the effect of ultrasonic irradiation with a frequency of 30 kHz frequency and power of 100 W on the inactivation capability of two bacterial groups, namely, Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, in physiologic water samples. METHODS: Ultrasonic irradiation of bacterial samples with different populations of 5 × 10(3), 1.5 × 10(4), and 3 × 10(4) colony-forming units/mL was performed at a constant frequency with various treatment times. The specific energy (γ) values were calculated for these different concentrations of E coli and S aureus. The rate constant for ultrasonic inactivation was estimated in the linear region of a plot representing a survival ratio logarithm versus sonication time. RESULTS: Although a significant death rate for E coli was observed with ultrasound treatment, in contrary to expectations, an increase in S aureus populations was observed. CONCLUSIONS: Considering the widespread use of ultrasound for sterilization of tools and equipment used in hospitals, the results obtained in this study indicate that ultrasonic irradiation is not a suitable method for the elimination of the major hospital pathogen S aureus.

Ultrasonic oil recovery and salt removal from refinery tank bottom sludge.

The oil recovery and salt removal effects of ultrasonic irradiation on oil refinery tank bottom sludge were investigated, together with those of direct heating. Ultrasonic power, treatment duration, sludge-to-water ratio, and initial sludge-water slurry temperature were examined for their impacts on sludge treatment. It was found that the increased initial slurry temperature could enhance the ultrasonic irradiation performance, especially at lower ultrasonic power level (i.e., 21 W), but the application of higher-power ultrasound could rapidly increase the bulk temperature of slurry. Ultrasonic irradiation had a better oil recovery and salt removal performance than direct heating treatment. More than 60% of PHCs in the sludge was recovered at an ultrasonic power of 75 W, a treatment duration of 6 min, an initial slurry temperature of 25°C, and a sludge-to-water ratio of 1:4, while salt content in the recovered oil was reduced to <5 mg L(-1), thereby satisfying the salt requirement in refinery feedstock oil. In general, ultrasonic irradiation could be an effective method in terms of oil recovery and salt removal from refinery oily sludge, but the separated wastewater still contains relatively high concentrations of PHCs and salt which requires proper treatment.

Reductive dechlorination of 2,4-dichlorophenol by using MWCNTs-Pd/Fe nanocomposites prepared in the presence of ultrasonic irradiation.

The research on developing a purification technology for 2,4-dichlorophenol (2,4-DCP) polluted water with high efficiency and the low energy consumption is crucial for achieving several Sustainable Development Goals (SDGs). In order to achieve these goals, MWCNTs-Pd/Fe nanocomposites were prepared by Fe nanoparticles modified with multi-walled carbon nanotubes (MWCNTs) and palladium (Pd) in the presence of ultrasonic irradiation. The MWCNTs-Pd/Fe nanocomposites were characterized by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-Ray Diffraction (XRD), and others. Characterization results confirmed that the MWCNTs-Pd/Fe was successfully prepared, with the particle size of 80 nm and the specific surface area of 89.5 m2/g confirmed. We studied the reductive dechlorination of 2,4-Dichlorophenol (2,4-DCP) by MWCNTs-Pd/Fe nanocomposites under different conditions, and the optimized experimental results were found when the Pd loading was 0.4 %, the pH was 3, and the temperature was 30 °C. The phenol yield increased from 76.5 % (without ultrasonic irradiation) to 92.3 % (with ultrasonic irradiation) in 300 min and the 2,4-DCP removal rate reached 98.7 % under the optimal conditions. Therefore, ultrasonic irradiation enhanced the performance of MWCNTs-Pd/Fe nanocomposites for 2,4-DCP removal. We also established the degradation mechanism of chlorophenol by analyzing the intermediates, and proposed the degradation kinetics model. The degradation of 2,4-DCP followed the pseudo-first-order kinetics with the rate constant of 0.05988 min-1. Also, this study demonstrated the potential of using ultrasonic irradiation to improve the properties and recovery of MWCNTs-Pd/Fe nanocomposites, contributing to achievement of the Sustainable Development Goals (SDGs), including SDG-3, SDG-6.

The Evolution of Sonochemistry: From the Beginnings to Novel Applications.

Sonochemistry is the use of ultrasonic waves in an aqueous medium, to generate acoustic cavitation. In this context, sonochemistry emerged as a focal point over the past few decades, starting as a manageable process such as a cleaning technique. Now, it is found in a wide range of applications across various chemical, physical, and biological processes, creating opportunities for analysis between these processes. Sonochemistry is a powerful and eco-friendly technique often called "green chemistry" for less energy use, toxic reagents, and residues generation. It is increasing the number of applications achieved through the ultrasonic irradiation (USI) method. Sonochemistry has been established as a sustainable and cost-effective alternative compared to traditional industrial methods. It promotes scientific and social well-being, offering non-destructive advantages, including rapid processes, improved process efficiency, enhanced product quality, and, in some cases, the retention of key product characteristics. This versatile technology has significantly contributed to the food industry, materials technology, environmental remediation, and biological research. This review is created with enthusiasm and focus on shedding light on the manifold applications of sonochemistry. It delves into this technique's evolution and current applications in cleaning, environmental remediation, microfluidic, biological, and medical fields. The purpose is to show the physicochemical effects and characteristics of acoustic cavitation in different processes across various fields and to demonstrate the extending application reach of sonochemistry. Also to provide insights into the prospects of this versatile technique and demonstrating that sonochemistry is an adapting system able to generate more efficient products or processes.

Contact-Electro-Catalysis-Assisted Separation via a Dancing PTFE Membrane for Fouling Control.

Advanced oxidization processes (AOPs) offer promising solutions for addressing the fouling issues in membrane separation systems. However, the high energy requirements for electrical or light power in the AOPs can be a drawback. In this study, we present a contact-electro-catalysis (CEC)-based approach for controlling membrane fouling, which is stimulated by mild ultrasonic irradiation. During this process, electrons are transferred between a dancing polytetrafluoroethylene membrane and water or oxygen molecules, resulting in the formation of free radicals •OH and •O2-. These free radicals are capable of degrading or inactivating foulants, eliminating the need for additional chemical cleaners, secondary waste disposal, or external stimuli. Furthermore, the time-dependent voltage spikes/oscillations (peak, +7.8/-8.2 V) generate a nonuniform electric field that drives dielectrophoresis, effectively keeping contaminants away from the membrane surface and further enhancing the antifouling performance of the dancing membrane. Therefore, the CEC-assisted membrane separation system offers a green and effective strategy for controlling membrane fouling through mild mechanical stimulation.

Ultrasonic-driven chemical reduction synthesis of alizarin complexone-modified gold nanoparticles for dual-signal colorimetric and fluorometric sensing of histamine in seafood products.

Alizarin complexone-modified gold nanoparticles (Au0-NPsALz) were synthesized using a proposed ultrasonic irradiation-assisted chemical reduction method. Ultrasonic irradiation powers, reaction time and alizarin complexone concentration had been proven to be the main parameters for controlling the nucleation and growth of Au0-NPsALz. In the synthesized ultrasonic irradiation-assisted chemical reduction conditions, Au0-NPsALz had a spherical oriented morphology with a uniform size of 17.84 ± 1.37 nm and are shiny red with a surface plasmon resonance (SPR) of 535 nm. A rapid colorimetric and fluorometric dual-mode detection strategy for selective detection of histamine in seafood was developed based on the self-assembly of Au0-NPsALz-Ni (II) complexes. Ni (II) can capture the histamine molecules close to Au0-NPsALz surfaces, making changes in the colorimetric and fluorometric responses of the solution. The quantitative analysis of histamine was realized through the variation of dual-signal colorimetric and fluorometric responses. Such Au0-NPsALz sensor offered good detection sensitivity for histamine with a detection limit (LOD) of 59.32 µmol L-1 and 116.20 µmol L-1 and wide linear response within the range of 10-10000 µmol L-1 (R2 = 0.9952) and 100-5000 µmol L-1 (R2 = 0.9947) for colorimetric and fluorometric measurement, respectively. Recoveries ranging from 94.99 to 103.29 % and 97.67-106.88 % for colorimetric and fluorometric assay were obtained, showing low levels of matrix effects. Particularly, the results of the dual-mode sensor were also validated by comparing with the HPLC method for improving the assay accuracy and dependability. Ultimately, the developed Au0-NPsALz colorimetric and fluorometric probe performs excellently in practical applications, with promising results for detecting histamine in seafood products.

Facilitating polymorphic crystallization of HMX through ultrasound and trace additive assistance.

Low sensitivity octahydro-1,3,4,7-tetranitro-1,3,5,7-tetrazocine (HMX) has garnered significant attention from researchers due to its reduced shock sensitivity. However, the crystallization process poses challenges due to the high solidity and viscosity of the metastable α phase. Despite efforts to address this with additional energy sources like ultrasonic irradiation, prolonged exposure duration often results in small particle sizes, hindering the production of HMX with a consistent particle size distribution, thus limiting its applicability. To overcome these challenges, a method combining ultrasonic irradiation and trace H+ additive was proposed and investigated for their impact on the polymorphic transformation of HMX. The H+ additive was found to modify barriers, thus there was a lack of competitive driving force for the nucleation or growth of the metastable α form, thereby shortening the transformation pathway and duration. Moreover, the H+ additive significantly accelerated the nucleation rate of the ß form (67.7 orders of magnitude faster with 0.10 wt ‰ H+) and the growth rate of ß form HMX (5.8 orders of magnitude faster with 0.10 wt ‰ H+). While H+ additive alone was insufficient to induce spontaneous nucleation of the ß form, combining it with short-duration ultrasonic irradiation further promoted ß nucleation and shortened the polymorphic transformation duration (almost 20 orders of magnitude shorter). This rational approach led to effective control of the transformation process. The resulting low sensitivity HMX crystals exhibited varying mean sizes ranging from 20 to 340 µm, with purity exceeding 99.6 %, an apparent density greater than 1.8994 g/cm3, and few internal defects, fully meeting the requirements of low-sensitivity HMX, thus significantly expanding its potential applications. Our study sheds light on the mechanisms governing HMX polymorphic transformation in the presence of additives and ultrasonic irradiation, offering guidance for the rational control of this complex transformation.

Radical generation and bactericidal activity of nanobubbles produced by ultrasonic irradiation of carbonated water.

Our previous study showed that nanobubbles (NBs) encapsulating CO2 gas have bactericidal activity due to reactive oxygen species (ROS) (Yamaguchi et al., 2020). Here, we report that bulk NBs encapsulating CO2 can be efficiently generated by ultrasonically irradiating carbonated water using a piezoelectric transducer with a frequency of 1.7 MHz. The generated NBs were less than 100 nm in size and had a lifetime of 500 h. Furthermore, generation of ROS in the NB suspension was investigated using electron spin resonance spectroscopy and fluorescence spectrometry. The main ROS was found to be the hydroxyl radical, which is consistent with our previous observations. The bactericidal activity lasted for at least one week. Furthermore, a mist generated by atomizing the NB suspension with ultrasonic waves was confirmed to have the same bactericidal activity as the suspension itself. We believe that the strong, persistent bactericidal activity and radical generation phenomenon are unique to NBs produced by ultrasonic irradiation of carbonated water. We propose that entrapped CO2 molecules strongly interact with water at the NB interface to weaken the interface, and high-pressure CO2 gas erupts from this weakened interface to generate ROS with bactericidal activity.