In this study, a novel microextraction technique termed as ultrasound-assisted microextraction (UAME) has been proposed for preconcentration of trace metal ions from water samples. UAME is performed in two steps based on ultrasonic emulsification and ultrasound-accelerated phase separation phenomena upon different ultrasound frequencies. UAME thus can be taken place in a single closed vessel to avoid unnecessary risks of contamination, and it is successfully applied in the fluorometric analysis of trace aluminium (III).

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Ultrasonic irradiation to a liquid generates cavitation bubbles with high temperature and high pressure. In this study, the formation of NO₂^- and NO₃^- during the sonolysis of air-saturated water was investigated to discuss the effects of the bubble temperature and pressure on the reactions of nitrogen with oxygen. It was suggested that the ratio of NO₂^- and NO₃^- is changed by the bubble temperature and pressure.

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Acoustic cavitation concentrates and releases a very large amount of energy in localized areas, which can be used for various environmental engineering processes using sonophysical and sonochemical effects. Even though acoustic cavitation has been studied widely for decades, only few studies have been devoted to optimization of medium to large scale reactors. For the industrial use of ultrasound technology following topics should be intensively investigated: (i) the limitation of power density in large-scale sonoreactors, (ii) the hybrid processes of ultrasonic processes and other advanced oxidation processes (AOPs) and the use of catalysts for the increase in removal efficiency, (iii) the quantification of radical-induced reactions, and (iv) the measurement of appropriate input and ultrasound energy should be intensively investigated.

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Sonoluminescence (SL) and sonochemiluminescence (SCL) have been used to generate molecular hydrogen in a photocatalytic process using colloidal platinum, Ru(bipy)^<2+>_3 as a photosensitiser, and methyl viologen as an electron relay agent. SL and SCL and various radicals were generated in water using 355 kHz ultrasound. The efficiency of the photocatalytic hydrogen production was to some extent limited by sonochemical side reactions, however the in situ photon generation was sufficiently intense for relatively pronounced H2 generation above the background sonochemical processes.

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We observed multi-bubble sonoluminescence spectra from sodium dodecyle-sulfate solutions saturated with Ar at 148 kHz. The spectra revealed that the Na emission consists of two components, one of which is broadened lines which are shifted from original D lines, and the other is unshifted narrow lines. Sonication-time dependence of the Na emission was also measured for the total sonication time of 30 minutes. The unshifted narrow lines gradually disappeared with sonication time, and the only shifted broad lines remained after 12 minutes. We showed that the effects are caused by accumulation of impurity gases such as CO, which are originated from decomposition of the solutes in bubbles. The unshifted narrow lines are easily affected by the impurity gases. The results suggest that the two components originated from different environments, although both of them come from gas phase.

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Acoustic cavitation was investigated in a microreactor containing micromachined pits. A 200 kHz transducer attached to the microreactor generated localized cavitation that originated from the micropits. Both sonoluminescence (SL) and sonochemiluminescence (SCL) were used for quantifying the caviation activity under different experimental conditions. At low power levels, the cavitation activity was limited to the pit region. At high power levels, cavitation streamers from the pits (for 2 and 3 pits setups) tend to approach each other that resulted in an increased cavitation activity in the region between the pits. Key results that will be discussed include (i) significant differences observed in SL and SCL activities under different experimental conditions and (ii) experimental proof for the transient nature of the cavitation bubbles, by measuring SL in propanol solutions.

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This research studied the mechanical effects of various frequencies by the degradation of Polyethylene oxide and Polystyrene at different solvents, concentration. In order to exclude the influence of sonochemical apparatus, different types were used. The power delivered into solution was set at the same (5W). In water solution, t-BuOH was used as a radical scavenger to suppress the chemical effects. The results showed that there is nearly the same trend in degradation of polymer despite of the type of polymer or the solvents: the mechanical effects decreases as the frequency increases. The maximum and minimum mechanical effects are at around 40 kHz and 500 kHz, respectively.

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The versatility of biological effects induced by low-intensity ultrasound across a wide range of applications paint ultrasound a positive light as a tool in cancer therapy and drug delivery. However, further understanding of how changing ultrasound parameters can alter the acoustic environment and hence, the cellular responses, is required to help promote the translational research of therapeutic ultrasound. In this respect, we will summarize here our studies on the biological and sonochemical effects at different acoustic conditions and their implications in ultrasound-aided macromolecular delivery, drug sonosensitization and reversal of multidrug resistance. From the results shown here we will present a discussion on how ultrasound can be a "two-edged sword" which necessitates treading new roads in understanding the interaction between US and biological systems, especially when it approaches a genetic level.

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Acoustic streaming is an important phenomenon observed in sonochemical reactor at high frequency which controls the physical effects of the cavitation and further influence on sonochemical reaction performance. The distribution of liquid flow field has been studied. The absorption coefficient in water inducing acoustic streaming has been quantified. Variation of oscillation plate radius has been investigated. Simulation results indicate that there exists a best oscillation plate radius to enhance liquid flow in sonochemical reactor.

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The enhancement in the rate of bubble growth via rectified diffusion in surfactant solutions during acoustic cavitation has been investigated. Dodecyl trimethyl ammonium chloride (DTAC) caused a greater increase in the growth rate than equivalent concentrations of the surfactants sodium dodecyl sulphate (SDS) and dodecyl dimethyl ammonium propane sulfonate (DDAPS). However, if the electrostatic charge was suppressed by the addition of salt, DDAPS showed the highest growth rate. Particle-image velocimetry (PIV) has been used to characterize the microstreaming around a bubble in aqueous solutions of these surfactants. Results indicate an enhancement of microstreaming velocities in the vicinity of the bubble when surfactant of any form is present in the solution and the results correlate with the enhanced bubble growth rates. A clear difference can also be observed when bubbles undergo surface mode oscillations that dramatically increase the streaming velocities, resulting in a chaotic flow.

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One of the major criteria in developing industrial applications of sonochemistry is the optimization of various experimental factors in order to achieve maximum efficiency at a minimum energy cost. There are two key parameters that control the primary sonochemical reaction efficiency: (i) bubble temperature that determines the amount of primary radicals generated inside a single bubble and (ii) the total number of active cavitation bubbles, which determines the overall chemical activity. However, these two parameters depend upon various experimental conditions, namely, acoustic frequency, acoustic power, reactor design, etc. The chemical reactivity is also dependent upon the mass transfer events and other physical effects of acoustic cavitation. The facts and factors involved in optimizing sonochemical reactions have been discussed.

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The mass flow rate of ultrasonic atomization was estimated by measuring the vaporization amount from a bulk liquid with a fountain. The effects of ultrasonic frequency and intensity on the atomization characteristics were investigated when the directivities of the acoustic field from a transducer were almost the same. The sample was water. The mass flow rate of ultrasonic atomization increased with increasing ultrasonic intensity and decreasing ultrasonic frequency. At the same apparent surface area of the fountain, the number of atomized droplets became larger as the ultrasonic frequency increased.

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Artemisinin suppresses the life-cycle of the plasmodium parasite which causes malaria. It is found naturally occurring within the trichome glands of the Artemisia annua plant. It was shown that the use of ultrasound as an aid to the extraction process decreased the temperature required for extraction however increased the yield of the target extract in a faster extraction time when compared to conventional thermal extractions under similar conditions. It is thought that this occurs through effective cavitation and the production of acoustic streaming and micro jets coupled with greater solvent penetration into the plant material which aid in the extraction

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Simultaneous irradiation of ultraviolet light and ultrasound to titania photocatalysis has been studied recently, where the titania particles suspended in aqueous medium and 20〜200 kHz ultrasound are generally used. In this work, we employed fibrous titania prepared by a sol-gel coating on a metal fiber and high frequency ultrasound driven at 2.4 MHz. In the presence of titania fiber, the synergy index was found to be very high compared to the other process.

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The amount of hydroxyl radicals produced from a single cavitation bubble was quantified by terephthalate dosimetry at various frequencies and pressure amplitudes, while the dynamics of the single bubble was observed by stroboscopic and light-scattering methods. Also, sonoluminescence (SL), sonochemiluminescence (SCL) of luminol, and sodium atom emission (Na^*) in the cavitation field were observed. The amount of hydroxyl radicals per cycle as well as the intensity of SL was proportional to pressure amplitude at every frequency performed, and it decreased with increasing frequency. When the single bubble was dancing with a decrease in pressure amplitude, however, the amount of hydroxyl radicals was greater than that for the stable bubble at the higher pressure amplitude and did not significantly decrease with frequency. Furthermore, SCL and Na^* were detected only under unstable bubble conditions. These results imply that the instability of bubbles significantly enhances sonochemical efficiency for non-volatile substances in liquid phase.

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Cavitational reactors are a novel and promising form of multiphase reactors, based on the principle of release of large magnitude of energy due to the violent collapse of the cavities. The present work gives an overview of the different areas of application such as chemical synthesis including nanomaterials, water and effluent treatment and biotechnology. Some experimental case studies using industrially important reactions have been presented, highlighting the degree of intensification achieved as compared to the conventional approaches. Comparison of the energy efficiencies and cavitational yields for the sonochemical and hydrodynamic cavitation reactors will also be presented based on the recent work carried out at Institute of Chemical Technology, Mumbai. Also possible limitations hampering the successful installations of cavitational reactors at commercial scale operations will also be discussed.

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Sonochemistry has been widely used to synthesize different nanomaterials. Recently, sonochemical method was used to shape-controlled synthesize various nanoparticles, such as gold nanocluster, Au@Ag, ZnO/CdS core/shell nanostructures, BaF_2 hollow nest-like and 8-hydroxyquinoline aluminum nanoflowers and so on. Sonoelectrochemical technique has also been proven to be a fast, simple and effective route for the synthesis of nanomaterials. A series of semiconductor, metal nanoparticles and their composites were facilely synthesized by this method. The shape and size could be controlled by adjusting parameters such as current density, time of deposition and sonication, temperature and sonic power, et al. The formation mechanism was proposed.

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Olivine phase LiFePO_4 was successfully synthesized via an amorphous FePO_4・2H_2O which was synthesized by sonochemical oxidation. The amorphous FePO_4・2H_2O was prepared from a solution including (NH_4)_2HPO_4 and FeSO_4・7H_2O using sonochemical oxidation. The particle size and relative surface area of the amorphous FePO_4・2H_2O were submicron and 23.5 m^2g^<-1>. The amorphous FePO_4・2H_2O was changed to an amorphous FePO_4 (350℃) and a crystalline FePO_4 (700℃) by heating in air atmosphere. The battery performances of amorphous FePO_4・2H_2O, amorphous FePO_4, crystalline FePO_4, and LiFePO_4 were investigated using a galvanostatic discharge-charge cycler. These cathode materials showed good discharge capacities. LiFePO_4 showed a first discharge capacity of 146mAhg-1, 86% of the theoretical capacity.

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Although rings of carbon nanotubes (CNTs) are predicted to have interesting magnetic properties, facile preparation or isolation methods of the rings with high purity are not yet reported. We describe here a convenient method for the isolation of circular single-walled carbon nanotubes (c-SWCNTs) using ultrasonic atomization.

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We have modelled the sonochemical production of BaTiO_3 nanoparticles under the experimental condition of Dang et al. Numerical simulations based on the model have revealed that only primary particle aggregate with other particles. According to Dang et al., sonochemically synthesized BaTiO_3 nanocrystals of 5 nm in diameter were attached each other with their crystal axes aligned, which is known as mesocrystal. The mean diameter of the aggregates was 100-400 nm. In the present study, electric dipole-dipole interaction model is studied for oriented attachment of BaTiO_3 nanocrystals. It is suggested that there may be electric dipole moment in the sonochemically synthesized BaTiO_3 nanocrystals, while it was reported that the dipole moment disappeared below 20 nm in diameter of BaTiO_3 nanocrystals prepared by the two-step thermal decomposition of barium titanyl oxalate and postheating treatment.

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Electrochemical oxidation of water-insoluble amines (n-octylamine and n-decylamine) was successfully accomplished in aqueous electrolytes using acoustic emulsification. Ultrasonication to the water-insoluble organic substrate/aqueous electrolyte mixtures allowed a formation of very stable emulsions having the characteristic of giving narrow monomer droplet size distributions in the submicrometer range in aqueous electrolytes without added surfactants and the smooth electrochemical reaction in the emulsions took place via direct electron transfer between the electrode and the water-insoluble organic droplets. In this kind of electron-transfer system, supporting electrolyte should be dissolved not only in the aqueous phase but also in the organic droplets and contribute to the formation of an electric bilayer inside the droplets.

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We focus on a compact continuous flow system to generate nanoemulsion in microchannels with ultrasonic vibration. This device is fabricated by the easily-stackable microchannel plates and an ultrasonic vibrating plate. Optimized oscillation frequency is 2.25 MHz. The cross-sectional pattern of the microchannels affects on not only the residence time but the efficiency of nanoemulsification. By optimizing the microchannels, we have succeeded in the production of nanoemulsion with 80 nm in a diameter.

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To investigate the effects of low-intensity ultrasound on human malignant melanoma (C-32), cells in vitro and C-32 tumor in mice were exposed to 0.1-0.5 W/cm^2 (1.011-MHz) ultrasound. In another experiments, cells in vitro and in vivo were sonotransfected with the following genes: GFP, IFN-beta, and GFP tagged IFN-beta gene, after micro-bubbles were added. Two minutes daily sonication resulted in growth inhibition. Neither significant cell killing nor change in cell migration activity was observed, but several genes were either up- or down-regulated. Sonotransfection with IFN-beta resulted in cell killing, apoptosis induction and overall growth inhibition of melanoma. While GFP sonotransfection did not significantly affect cell growth, it was shown that cells transfected with GFP-tagged IFN-beta genes were more likely to undergo apoptosis. In addition, growth of cells sub-cultured with sonotransfected cells was also inhibited. These findings suggest the potential use of low-intensity ultrasound against malignant melanoma.

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microRNA (miRNA) is involved in many life phenomena through gene expression regulation. We found that sonication changed miRNA expressions significantly. To examine if the phenomenon could be applied for ultrasound mediated gene regulation (UMGR), we prepared 16 DNA fragments by random ligation of target sequences of four miRNAs whose expressions decreased by sonication. The fragments were introduced into a 3'UTR of the luciferase gene, constructing a gene cassette library. When cells transfected with gene cassettes were sonicated, two cassettes increased luciferase activities over two fold. The target fragments of these gene cassettes were then introduce the luciferase gene under control of a sonication responsive promoter and introduced into cells. Without sonication, one of them decreased luciferase activity to 30% of that of identical cells without the target fragment while it didn't much decrease luciferase activity (〜90%) of that of identical cells without the target fragment at the peak after sonication. When the luciferase gene was replaced with a suicide gene, cell death was lowered without sonication (23% to 4%) while keeping high cell death rate after sonication (60% to 49%). These results indicate that sonication affected miRNA expressions and that target sequences could be useful for UMGR.

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Paper reports on production and focusing of micro-underwater shock waves for medical applications. Shock wave focusing has various scientific, industrial and medical applications. For precise shock wave therapies near sensitive organs, a micro-shock wave source is required. A half-ellipsoidal cavity was designed and constructed as an extracorporeal shock wave (ESW) source. Underwater shock waves were generated a magnetic pulse compression (MPC) unit and an electrode. The whole sequences of the shock wave generation, propagation, focusing, and cavitation generation were observed by time-resolved high speed shadowgraph visualization method.

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Our previous study suggested new sonodynamic therapy for cancer cells based on the delivery of titanium dioxide (TiO_2) nanoparticles (NPs) modified with a protein specifically recognizing target cells and subsequent generation of hydroxyl radicals from TiO_2 NPs activated by external ultrasound irradiation (called TiO_2/US treatment). The present study first examined the uptake behavior of TiO_2 NPs modified with pre-S1/S2 (model protein-recognizing hepatocytes) by HepG2 cells for 24 h. Next, the effect of the TiO_2/US treatment on HepG2 cell growth was examined for 96 h after the 1 MHz ultrasound was irradiated (0.1 W/cm^2, 30 s) to the cells which incorporated the TiO_2 NPs. Although no apparent cell-injury was observed until 24 h after the treatment, the viable cell concentration had deteriorated to 46% of the control at 96 h. Finally, the TiO_2/US treatment was applied to a mouse xenograft model. The pre-S1/S2-immobilized TiO_2 (0.1 mg) was directly injected into tumors, followed by 1 MHz ultrasound irradiation at 1.0 W/cm^2 for 60 s. As a result of the treatment repeated 5 times within 13 days, tumor growth could be hampered up to 28 days compared with the control conditions.

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The study was performed in order to examine the chemical and biological effects induced by pulsed low intensity ultrasound using a 1 MHz generator with 50% duty factor and pulse repetition frequency (PRF) range from 0.5 to 100 Hz in vitro. The study shows that changing PRF in this range changed the acoustic environment resulting in a domination of "ultrasound streaming" (convection) or standing waves. Thus the work compares between the two factors and their roles in determining the biological and chemical effects.

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Applied pressure dependence of the sonochemical power was examined. The range of pressure is 0 Pa-several hundreds of kPa. The relation between cavitation power and sonochemical power was also discussed. Cavitation behavior is responsible for chemical reaction under ultrasonic irradiation and it is influenced by many parameters. In this presentation, we demonstrated the sonolysis of KI solution by 200 kHz ultrasound at 25 ℃ under various pressures. The sonochemical power increased with increasing pressure up to 0.075 MPa. Then, it fell down over the pressure.

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A convenient chemical conversion method that allows the direct preparation of nanocrystalline ZnE (E=O, S, Se) semiconductor spheres and hollow spheres, as well as their core/shell structures, is reported. By using monodispersed ZnO nanospheres as a starting reactant and in situ template, ZnS, ZnSe solid and hollow nanospheres, and ZnO/ZnS and ZnO/ZnSe core/shell nanostructures have been obtained through an ultrasound-assisted solution-phase conversion process. Another core/shell-type ZnO nanosphere/CdS nanorod and ZnO nanosphere/CdS nanoparticle composites have also been successfully synthesized via a facile sonochemical route. Different sulfur sources used in reaction systems resulted in different surface coating statuses. The photoluminescence and electrogenerated chemiluminescence properties of the as-prepared nanocrystals were investigated. Ultrasonic irradiation has also been used to obtain uniform PbS nanospheres, SrMoO_4 3D spherical superstructure, BaF_2 hollow nest-like nanostructure, and so on. The ultrasound-induced self-assembly growth procedure has been proposed for the possible formation mechanism of above products.

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High-speed shadowgraphy of cavitation bubbles was observed in SDS surfactant solutions at various concentrations at ultrasonic frequencies of 37 kHz, 87 kHz and 123 kHz. Maximum diameter of cavitation bubbles was estimated from the movies at the frame rate of a million per second. The histogram of the maximum diameter showed significant decrease in the number of large-size bubbles in surfactant solutions compared to in water. This decrease was pronounced at higher frequencies at 1 mM SDS solutions. The concentration dependence indicated that the decrease was most marked at 5 mM at the frequency of 87 kHz. The results were elucidated in terms of the inhibition of bubble coalescence, which are in agreement with previous works by Ashokkumar's group.

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Formation of nitric ion during ultrasonic irradiation was examined under various conditions. Source of oxidation power in sonolysis is acoustic cavitation. The cavitation occurs in a liquid irradiated with ultrasound. Some kinds of active species are produced during cavitation. Radicals and hydrogen peroxide are typical oxidizing agents in noble gases or oxygen. In the air, on the other hand, nitric acid is also produced when sonolysis is carried out in an aqueous solution. It plays an important role in oxidation. It is not saying, nitric acid or nitric ions are also useful in organic reaction, mainly synthesis. To increase yield of nitrate ion, we irradiate pulsed waves of ultrasound. In this presentation, effects of rest time of irradiation and atmospheric gas on yield of nitric ion were reported.

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Strong emission in liquid is observed by radio frequency irradiation using a submerged electrode. Plasma is generated in liquid, and because the liquid around the plasma is evaporated instantly, the plasma seems as if to be generated in a bubble. We measured the spectrum of the plasma emission, analyzed the produced gas by plasma in water and also measured the production rate of hydrogen gas. The mole ratio of hydrogen to the produced gas is 90 to 99% and the rate of hydrogen gas is 1.2 to 2.3 larnol/s at 150 W. The rate of the hydrogen gas decreases with increase of the pressure from 60 to 100 kPa. To clarify the gas production mechanism, we carried out numerical simulations of the chemical reactions inside and outside the bubble. As a result, the mole ratio of the produced gas is .approximately agreeable to the experimental result.

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In the present study, the effects of pressure and temperature on sonochemical reaction were investigated using a flow-type sonochemical reactor equipped with a PZT transducer which effectively oscillates in the frequency range of 470-500 kHz. The gauge pressure and temperature conditions ranged from 0.03 to 0.2 MPa and from 313 to 373 K, respectively. All the experiments were carried out at the frequencies determined from respective frequency-transducer impedance curves which were obtained under different pressure and temperature conditions, and the effects of pressure and temperature on sonochemical reaction were evaluated by the rate constant of KI oxidation. The results demonstrated that the reaction rate constant decreased with an increase in the pressure at 313 and 333 K. On the other hand, however, it was found that the reaction rate constant slightly increased with the pressure at 373 K

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Using ultrasonication in oraganic reaction various ketones were reductively coupled to give the corresponding pinacol type dimer. Ketones were substituted with methyl, hydroxyl, acetoxy, halogen and amine on the benzene ring. Using ultrasonication, the reaction time changed shorter and the yields of the reductive coupling reaction changed better. The pinacol was converted to the corresponding pinacolone using strong acid, but pinacol did not change easily to pinacolone using ultrasonication with TiCl_4 in short time. In the case of acetophenone, the corresponding pinacol was obtained in 75% for 2h without using ultrasonication, however by using ultrasonication the same reductive coupling reaction of acetophenone was achieved in 90% only for 10 min. When acetophenone substituted with nitro group was used as the substitute, the nitropinacol produced in the reaction was easily reduced to aminopinachol in the reductive couppliung. Reductive coupling of fluoroacetophenone showed high yield in this reaction.

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Ultrasound (US) was used to investigate change of the viscosity of aqueous solutions of copolymer having Acrylic Acid (AA) and N-hydroxyethyl acrylamide (HEAA) segments. The US effect on the shear viscosity of the copolymer containing 25mol % HEAA group was examined at different US intensities (10-50 W) of frequencies (23, 43, 96 and 143 kHz) for several exposure times (1- 5 min). The US effect showed decrease of the shear viscosity in the exposure to each US. The FT-IR spectra showed a substantial change to 23 that 43, 96 and 141kHz.

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Interpenetrated polymer hydrogels of polyvinylalcohol (PVA) and polyhydroxyethyl methacrylate (PHEMA) were prepared for studying effect of ultrasound (US) on their hydrogen bonding networks of in hydrogels. Fourier transform infrared spectroscopy (FT-IR) of the PVA/PHEMA hydrogels was used to investigate in the absence and presence of US. It was noted that the US influenced Interpenetrating Polymer Network (IPN) in which hydrogen bondings in the gels broke by the US exposure and then reformed without US.

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Amphiphilic block copolymer films having phase separation layer of polyethylene oxide (PEO) segments and azobenzene ones were exposed to ultrasound (US) (43kHz, 28W) in water (25℃ and 80℃) for 30min. Then, the surface morphology was measured with Atomic Force Microscopy (AFM). It was observed that the PEO moiety in the block copolymer was effectively swelled by the US exposure. It meaning that the US enhanced swelling of the PEO segments of the film.

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A novel, mild an unsual "sono-halogenation" of various aromatic compounds with potassium halide salts was investigated under ultrasound in a biphasic carbon tetrachloride/water medium. The feasibility study was first undertaken with the potassium bromide salt and then extended to chloride and iodide analogues. This methodology could be considered as a new expansion of the ultrasonic advanced oxidation processes (UAOPs) into a synthetic aspect as the developed methodology is linked to the sonolytic disappearance of carbon tetrachloride. Advantages of the present method are not only that the handling of the bromination is simple but also that the halogenating agents used are readily available, inexpensive, and easy-handling.

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Saccharification of cellulosic biomass is important from the perspective of food protection in order to produce bio-based fuel as ethanol from non-food resources. Therefore, it can become a new chemical industrial process as an alternative exhaustible resource instead of oil. It is well known that saccharification from biomass can be accomplished by enzymatic reaction or sulfuric acid method. However, they have some disadvantages, for example, the former reaction is slow and uneconomical, and the latter method cannot recycle the liquid acid catalyst. Ultrasonic wave has a physical action as stirring and a chemical action as radical reaction by selecting the frequency appropriately. In this study, saccharification of cellulosic biomass was investigated with various recyclable solid acid catalysts. Cellulose was saccharified to low-molecular sugar with the solid acid catalyst under irradiation of an ultrasonic wave. It was found that the saccharification ratio depends on the property of the solid catalyst.

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