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Copper (I) oxide (cuprite) is a material widely used nowadays, and its versatility is further amplified when it is brought to the nanometric size. Among the possible applications of this nanomaterial, one of the most interesting is that in the medical field. This paper presents a cuprite nanopowder study with the aim of employing it in medical applications. With regards to the environmental context, the synthesis used is related to green chemistry since the technique (out-of-phase pulsed electrochemistry) uses few chemical products via electricity consumption and soft conditions of temperature and pressure. After different physico-chemical characterizations, the nanopowder was tested on the Candida albicans to determine its fungicide activity and on human blood to estimate its hemocompatibility. The results show that 2 mg of this nanopowder diluted in 30 µL Sabouraud broth was able to react with Candida albicans. The hemocompatibility tests indicate that for 25 to 100 µg/mL of nanopowder in an aqueous medium, the powder was not toxic for human blood (no hemolysis nor platelet aggregation) but promoted blood coagulation. It appears, therefore, as a potential candidate for the functionalization of matrices for medical applications (wound dressing or operating field, for example). [ABSTRACT FROM AUTHOR]

Copper (I) oxide (cuprite) is a material widely used nowadays, and its versatility is further amplified when it is brought to the nanometric size. Among the possible applications of this nanomaterial, one of the most interesting is that in the medical field. This paper presents a cuprite nanopowder study with the aim of employing it in medical applications. With regards to the environmental context, the synthesis used is related to green chemistry since the technique (out-of-phase pulsed electrochemistry) uses few chemical products via electricity consumption and soft conditions of temperature and pressure. After different physico-chemical characterizations, the nanopowder was tested on the Candida albicans to determine its fungicide activity and on human blood to estimate its hemocompatibility. The results show that 2 mg of this nanopowder diluted in 30 µL Sabouraud broth was able to react with Candida albicans. The hemocompatibility tests indicate that for 25 to 100 µg/mL of nanopowder in an aqueous medium, the powder was not toxic for human blood (no hemolysis nor platelet aggregation) but promoted blood coagulation. It appears, therefore, as a potential candidate for the functionalization of matrices for medical applications (wound dressing or operating field, for example).

Developing effective strategies for the flexible control of fluid is vital for microfluidic electrochemical biosensing. In this study, a gigahertz (GHz) acoustic streaming (AS) based sonoelectrochemical system was developed to realize an on-chip surface modification and sensitive hydrogen peroxide (H2O2) detection from living cells. The flexible and controlled fluid surrounding the electrochemical chip was optimized theoretically and applied in the sonoelectrochemical deposition of Au nanoparticles (AuNPs) first. Under the steady and fast flow stimulus of AS, AuNPs could be synthesized with a smaller and evener size distribution than the normal condition, allowing AuNPs to show an excellent peroxidase-like activity. Moreover, the AS also accelerated the mass transport of target molecules and improved the catalytic rate, leading to the enhancement of H2O2 detection, with an extremely low detection limit of 32 nM and a high sensitivity of 4.34 μA/ (mM·mm2). Finally, this system was successfully applied in tracking H2O2 release from different cell lines to distinguish the cancer cells from normal cells. This study innovatively integrated the surface modification and molecules detection process on a chip, and also proposed a simple but sensitive platform for microfluidic biosensing application.

In this report, the synergetic sonoelectrochemical method was utilized to produce magnetite nanoparticles was doped with MnO2 with the assistance of ultrasound to form nanoarchitectonic magnetic crystals with a mesoporous magnetite @ manganese dioxide (m-Fe3O4@MnO2) hybrid nanostructure. The hybrid nanocomposite was rapidly produced based on the nucleation and growth of pure iron-oxide nanocrystals in the electrochemical system. The nanocomposite was pure, highly amorphous, and mesoporous in nature; the magnetite was spherical in shape, with an average diameter of 45 ± 10 nm and a MnO2-plane length of 420 ± 30 nm. The stability of the pure m-Fe3O4 was enhanced from 89.61 to 94.04% with negligible weight loss after adding manganese dioxide and the stable formation of the hybrid nanostructure. Based on the superior results of the material, it was utilized as an anode material in Li-ion batteries. The m-Fe3O4@MnO2 hybrid nanostructure had a highly active surface area, which enhanced the interfacial interaction between the Li-ion and the metal surface; it delivered 1513 mAh g−1 and 1290 mAh g−1 as the first specific discharge and charge capacity, respectively, with 85% coulombic efficiency, and it showed an excellent cyclic reversibility of 660 mAh g−1 with a coulombic efficiency of almost 99% at current density of 1.0 A g−1. [ABSTRACT FROM AUTHOR]

In this report, the synergetic sonoelectrochemical method was utilized to produce magnetite nanoparticles was doped with MnO2 with the assistance of ultrasound to form nanoarchitectonic magnetic crystals with a mesoporous magnetite @ manganese dioxide (m-Fe3O4@MnO2) hybrid nanostructure. The hybrid nanocomposite was rapidly produced based on the nucleation and growth of pure iron-oxide nanocrystals in the electrochemical system. The nanocomposite was pure, highly amorphous, and mesoporous in nature; the magnetite was spherical in shape, with an average diameter of 45 ± 10 nm and a MnO2-plane length of 420 ± 30 nm. The stability of the pure m-Fe3O4 was enhanced from 89.61 to 94.04% with negligible weight loss after adding manganese dioxide and the stable formation of the hybrid nanostructure. Based on the superior results of the material, it was utilized as an anode material in Li-ion batteries. The m-Fe3O4@MnO2 hybrid nanostructure had a highly active surface area, which enhanced the interfacial interaction between the Li-ion and the metal surface; it delivered 1513 mAh g−1 and 1290 mAh g−1 as the first specific discharge and charge capacity, respectively, with 85% coulombic efficiency, and it showed an excellent cyclic reversibility of 660 mAh g−1 with a coulombic efficiency of almost 99% at current density of 1.0 A g−1.

The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) occurring at the Raney-Ni mesh electrode in 30 wt.-% aqueous KOH solution were studied in the absence (silent) and presence of ultrasound (408 kHz, ∼54 W, 100% acoustic amplitude) at different electrolyte temperatures (T = 25, 40 and 60 °C). Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) experiments were performed to analyse the electrochemical behaviour of the Raney-Ni electrode under these conditions. Under silent conditions, it was found that the electrocatalytic activity of Raney-Ni towards the HER and the OER depends upon the electrolyte temperature, and higher current densities at lower overpotentials were achieved at elevated temperatures. It was also observed that the HER activity of Raney-Ni under ultrasonic conditions increased at low temperatures (e.g., 25 °C) while the ultrasonic effect on the OER was found to be insignificant. In addition, it was observed that the ultrasonic effect on both the HER and OER decreases by elevating the temperature. In our conditions, it is suggested that ultrasound enhances the electrocatalytic performance of Raney-Ni towards the HER due to principally the efficient gas bubble removal from the electrode surface and the dispersion of gas bubbles into the electrolyte, and this effect depends upon the behaviour of the hydrogen and oxygen gas bubbles in alkaline media.

In electrochemical processes, gas bubbles on the electrode can cause an increase in both overpotential and ohmic voltage drop which leads to higher energy consumption. Applying power ultrasound during water electrolysis can help to reduce the overpotential, enhance mass transfer, and save energy. In this study, we investigated the effect of ultrasound (20 kHz) on the hydrogen evolution reaction (HER) on a stainless steel plate with varying concentrations of NaOH solutions at 298 K, using linear sweep voltammetry (LSV). We especially focused on understanding the bubble behavior on the stainless steel plate during HER using high-speed imaging in ultrasonic field. When ultrasound was applied to solutions with NaOH concentrations of 0.1, 0.5, 1 M, the current density increased by about 9.0, 5.9, 2.8 %, respectively. As the ultrasound irradiation began, the bubbles tended to hover around on the electrode surface, coalescing with other bubbles, rather than rising. When the size of the coalesced bubbles became too large to stay on the surface of the electrode, they were expelled from the ultrasonic field. The repeated collapse and coalescence of these bubbles was observed while they were rising. The velocity increased about 2 times when ultrasound irradiation began, and increased by more than 6 times in the ultrasonic field. More nucleation of bubbles was observed on the electrode in the ultrasonic field. Using ultrasound reduced the critical diameter of bubbles which detached from the electrode, from 58.0 to 15.9 μm, and the residence time of the bubbles, from 533 to 118 ms. Further, when the ultrasound was applied, the mean diameter of bubbles decreased from 71.8 to 17 μm. Hence, bubble coverage on the electrode surface decreased from 8.3 to 1 % despite an increase in the total number of bubbles. As a result, ultrasound was found to be effective for hydrogen production during water electrolysis, increasing current by the faster removal of gas from the stainless steel plate.

In thin layer sonoelectrochemistry (TLS), constructive interference is established in a thin layer of electrolyte with a low power, ultrasonic quartz crystal oscillator (QCO). No cavitation, no temperature increase, and no impacts on mass transport are observed. In this first report of TLS experiments without cavitation, voltammetric morphologies are not disrupted. Interfacial electron transfer for three transition metal species are evaluated with established cyclic voltammetric diagnostics. For Ru(bpy) 3 2 + with inherently fast (reversible) interfacial electron transfer, voltammograms are unchanged on sonication at 41 kHz. For Fe3＋ with slow heterogeneous electron transfer, interfacial rate increases with sonication, where increases in rate persist without diminution for minutes postsonication. For a cobalt phenanthroline probe, changes in voltammetric morphology at higher QCO intensity are consistent with chemical changes of ligand loss. Constructive interference in TLS imparts sound pressure to the electrode solution interface to increase electron transfer rates without mass transport disruption. TLS may provide means to electrocatalyze interfacial rates. [ABSTRACT FROM AUTHOR]

• Sonochemistry has demonstrated the ability alter chemical reactions and change physical properties under mild reaction conditions. • Ultrasound has found its way into diverse industries but limitedly in the biomedical field. • In the (bio-)medical field ultrasonic cleaning and imaging are most established but use in sonodynamic therapy (SDT) and drug delivery systems is emerging. • To pave the way for sonochemically application-driven advancements, various fundamental aspects need to be addressed. Sonochemistry, although established in various fields, is still an emerging field finding new effects of ultrasound on chemical systems and are of particular interest for the biomedical field. This interdisciplinary area of research explores the use of acoustic waves with frequencies ranging from 20 kHz to 1 MHz to induce physical and chemical changes. By subjecting liquids to ultrasonic waves, sonochemistry has demonstrated the ability to accelerate reaction rates, alter chemical reaction pathways, and change physical properties of the system while operating under mild reaction conditions. It has found its way into diverse industries including food processing, pharmaceuticals, material science, and environmental remediation. This review provides an overview of the principles, advancements, and applications of sonochemistry with a particular focus on the domain of (bio-)medicine. Despite the numerous benefits sonochemistry has to offer, most of the research in the (bio-)medical field remains in the laboratory stage. Translation of these systems into clinical practice is complex as parameters used for medical ultrasound are limited and toxic side effects must be minimized in order to meet regulatory approval. However, directing attention towards the applicability of the system in clinical practice from the early stages of research holds significant potential to further amplify the role of sonochemistry in clinical applications. [ABSTRACT FROM AUTHOR]

• GHz acoustic resonator based microfluidic sonoelectrochemical platform was developed. • Flexibly and accurately controlling the fluid flow in microfluidic channel was achieved. • On-chip sonoelectrochemical deposition of nanoparticles and sensing of H 2 O 2 was improved. • Tracking intracellular H 2 O 2 release to identify the cancer cells from normal cells was evaluated. Developing effective strategies for the flexible control of fluid is vital for microfluidic electrochemical biosensing. In this study, a gigahertz (GHz) acoustic streaming (AS) based sonoelectrochemical system was developed to realize an on-chip surface modification and sensitive hydrogen peroxide (H 2 O 2) detection from living cells. The flexible and controlled fluid surrounding the electrochemical chip was optimized theoretically and applied in the sonoelectrochemical deposition of Au nanoparticles (AuNPs) first. Under the steady and fast flow stimulus of AS, AuNPs could be synthesized with a smaller and evener size distribution than the normal condition, allowing AuNPs to show an excellent peroxidase-like activity. Moreover, the AS also accelerated the mass transport of target molecules and improved the catalytic rate, leading to the enhancement of H 2 O 2 detection, with an extremely low detection limit of 32 nM and a high sensitivity of 4.34 μA/ (mM·mm2). Finally, this system was successfully applied in tracking H 2 O 2 release from different cell lines to distinguish the cancer cells from normal cells. This study innovatively integrated the surface modification and molecules detection process on a chip, and also proposed a simple but sensitive platform for microfluidic biosensing application. [ABSTRACT FROM AUTHOR]

Nanopowders of copper (I) oxide (Cu 2 O, cuprite) were synthesized by out-of-phase pulsed sonoelectrochemical method and characterized by several physico-chemical techniques (X-ray diffraction, transmission electronic miscroscopy, energy-dispersive x-ray spectroscopy, centrifugal liquid sedimentation, zeta potentials and specific area measurements). The same analyses were done on commercial cuprite and copper nanopowders for comparison. Once the chemical nature and morphology of the three materials have been determined, bactericidal assays were performed on methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli) in Trypto-Casein-Soy medium. The results show that sonoelectrochemical Cu 2 O nanopowders are good antibacterial material as compared to the two commercial nanopowders while using a synthesis method that is inexpensive and adaptable to the industrial scale. [Display omitted] • Sonoelectrochemical Cu 2 O nanopowders are efficient bactericide materials in tryptocasein-soy. • Antibacterial activity is better against Staphylococcus aureus than Escherichia coli. • The nanopowder is bactericide at low mass concentration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sonoelectrochemistry shows promise for removing organic pollutants from water. • This method can rapidly mineralise many persistent organic pollutants in water. • Highly oxidising radicals are the main agents performing mineralisation. • Fundamentals of sonoelectrochemical organic pollutant degradation are reviewed. • An in-depth analysis of recent examples in this field is provided. The combination of electrochemistry and ultrasonic irradiation (sonoelectrochemistry) has gained increasing attention in recent years as a method for removing dissolved pollutants from water. This interest stems from the potential for sonoelectrochemical approaches to completely mineralise dissolved pollutants, converting them into harmless mineral species such as water and carbon dioxide. In many cases, the electrochemical and ultrasonic inputs into a sonoelectrochemical pollutant degradation process are found to be synergistic, producing a faster rate of degradation than that produced by the sum of the purely electrochemical or purely sonochemical inputs on their own. This synergism has several causes, with enhanced production of powerfully oxidising radicals and improved mass transport to and from the electrode surface being the two most often cited. In this review, we first give an overview of the various factors that impact on sonoelectrochemical pollutant degradation studies (including reactor design, sonochemical and electrochemical parameters and reaction conditions), before then discussing in detail examples of sonoelectrochemical processes for the degradation of persistent organic pollutants in water from 2015 onwards. [ABSTRACT FROM AUTHOR]

The electrochemical advanced oxidation processes (EAOPs) have received significant attention among the many other water and wastewater treatment technologies. However, achieving a desirable removal effect with a single technique is frequently difficult. Therefore, the integration of ultrasound technique with other processes such as electrocoagulation, electro-Fenton, and electrooxidation is a critical way to achieve effective organic pollutants decomposition from wastewater. This review paper is focused on ultrasound-assisted electrochemical (US/electrochemical) processes, so-called sonoelectrochemical processes of various organic pollutants. Emphasis was given to recently published articles for discussing the results and trends in this research area. The use of ultrasound and integration with electrochemical processes has a synergistic impact owing to the physical and chemical consequences of cavitation, resulting in enhancing the mineralization of organic pollutants. Various types of sonoelectrochemical reactors (batch and continuous) employed in the US/electrochemical processes were reviewed. In addition, the strategies to avoid passivation, enhanced generation of reactive oxygen species, and mixing effect are reviewed. Finally, concluding remarks and future perspectives on this research topic are also explored and recommended. • Recent trends of ultrasound-assisted electrochemical processes are reviewed. • Mechanisms of pollutants mineralization from wastewater using ultrasound-assisted electrochemical processes are described. • Ultrasound-assisted electrochemical processes have been proved to remove efficiently pollutants from wastewater. • Synergistic effect, reactor strategies, and generation of reactive oxygen species are assessed. • The challenges and perspectives for future studies and applications are proposed. [ABSTRACT FROM AUTHOR]

• Under silent conditions, the HER and OER activities of Raney-Ni in weak alkaline media improve when the electrolyte temperature is increased. • The HER activity of Raney-Ni in weak alkaline media under ultrasonic conditions (408 kHz) increases at 25 °C while the OER activity of Raney-Ni under ultrasonic conditions is not affected. • Combining ultrasonication (408 kHz) at high electrolyte temperatures do not improve the HER and OER activities of Raney-Ni in weak alkaline media. • Ultrasound (408 kHz) has no influence on the stability of the Raney-Ni coating. The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) occurring at the Raney-Ni mesh electrode in 30 wt.-% aqueous KOH solution were studied in the absence (silent) and presence of ultrasound (408 kHz, ∼54 W, 100% acoustic amplitude) at different electrolyte temperatures (T = 25, 40 and 60 °C). Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) experiments were performed to analyse the electrochemical behaviour of the Raney-Ni electrode under these conditions. Under silent conditions, it was found that the electrocatalytic activity of Raney-Ni towards the HER and the OER depends upon the electrolyte temperature, and higher current densities at lower overpotentials were achieved at elevated temperatures. It was also observed that the HER activity of Raney-Ni under ultrasonic conditions increased at low temperatures (e.g., 25 °C) while the ultrasonic effect on the OER was found to be insignificant. In addition, it was observed that the ultrasonic effect on both the HER and OER decreases by elevating the temperature. In our conditions, it is suggested that ultrasound enhances the electrocatalytic performance of Raney-Ni towards the HER due to principally the efficient gas bubble removal from the electrode surface and the dispersion of gas bubbles into the electrolyte, and this effect depends upon the behaviour of the hydrogen and oxygen gas bubbles in alkaline media. [ABSTRACT FROM AUTHOR]

• Gas removal process in HER under sonication was recorded by high-speed camera. • Bubbles experience fragmentation, collision and attraction under sonication. • Ultrasound reduces the critical size and residence time of bubbles in HER. • Ultrasound enables the faster removal of bubbles from the electrode surface. • Ultrasound improves water electrolysis efficiency. In electrochemical processes, gas bubbles on the electrode can cause an increase in both overpotential and ohmic voltage drop which leads to higher energy consumption. Applying power ultrasound during water electrolysis can help to reduce the overpotential, enhance mass transfer, and save energy. In this study, we investigated the effect of ultrasound (20 kHz) on the hydrogen evolution reaction (HER) on a stainless steel plate with varying concentrations of NaOH solutions at 298 K, using linear sweep voltammetry (LSV). We especially focused on understanding the bubble behavior on the stainless steel plate during HER using high-speed imaging in ultrasonic field. When ultrasound was applied to solutions with NaOH concentrations of 0.1, 0.5, 1 M, the current density increased by about 9.0, 5.9, 2.8 %, respectively. As the ultrasound irradiation began, the bubbles tended to hover around on the electrode surface, coalescing with other bubbles, rather than rising. When the size of the coalesced bubbles became too large to stay on the surface of the electrode, they were expelled from the ultrasonic field. The repeated collapse and coalescence of these bubbles was observed while they were rising. The velocity increased about 2 times when ultrasound irradiation began, and increased by more than 6 times in the ultrasonic field. More nucleation of bubbles was observed on the electrode in the ultrasonic field. Using ultrasound reduced the critical diameter of bubbles which detached from the electrode, from 58.0 to 15.9 μm, and the residence time of the bubbles, from 533 to 118 ms. Further, when the ultrasound was applied, the mean diameter of bubbles decreased from 71.8 to 17 μm. Hence, bubble coverage on the electrode surface decreased from 8.3 to 1 % despite an increase in the total number of bubbles. As a result, ultrasound was found to be effective for hydrogen production during water electrolysis, increasing current by the faster removal of gas from the stainless steel plate. [ABSTRACT FROM AUTHOR]