In this study we demonstrate formation of nitric oxide in aqueous nitrogen-containing solutions exposed to 50 kHz cavitation-producing ultrasound using electron paramagnetic resonance (EPR) spectroscopy. Formation of ^・NO by ultrasound was independent of the pH of the sonicated water throughout the measured range (pH 3-8.5). The presence of dissolved oxygen was not essential for production of ^・NO: the highest yields of ^・NO (〜 1.2 μM ^・NO/minute) were found under an atmosphere of 40% N_2 and 60% argon. The formation of ^・NO by ultrasound in aqueous solutions can be understood in terms of combustion chemistry- type reactions occurring inside the "hot" collapsing cavitation bubbles. Other N-containing molecules can also serve as a source of nitrogen for ^・NO production.

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In this work we use a sensitive method for detecting the presence of hydrated electrons in argon-saturated water exposed to 50 kHz ultrasound. This method is based on the fact that hydrated electrons, but not hydrogen atoms, can be scavenged by Cd^<2+> to prevent their reaction with the nitrone spin trap α-(4-pyridyl-l-oxide)-N-t-butylnitrone(POBN) to form the EPR-detectable adduct POBN/^・H. No detectable yield of hydrated electrons in argon-saturated aqueous solutions at neutral pH was found. These results are evidence against the formation of hydrated electrons as reactive intermediates in the sonochemistry of neutral aqueous solutions.

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Sonochemical decomposition of surface active agent DBS and SDS in water under argon or air atmosphere was investigated. The rate of decomposition of SDS under air was faster than that under argon indicative the participation of oxygen in oxidation process. Amethylene blue method was used for the determination of surfactants. The decomposition rates of 1OOμM of DBS were 2.5μM/min under argon and 3.7μM/min under air and were slower than expected values.

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The absorption and fluorescence properties of pheophorbide-a (Phd-a) or its derivatives (sodium salt of Phd-a: NaPhd-a) were investigated in micellar aqueous solutions before and after ultrasound irradiation (50kHz, 10min). The absorption spectra changed depending on the surfactant (cetyltrimethyl ammonium bromide=CTAB or sodium dodecyl sulfate=SDS) concentrations. The molecular formation in various micellar solutions was estimated from the analysis of absorption spectra. The absorption bands resulted from an aggregate form of the chromophore present in 50mM phosphate buffer and pre-micellar (lower concentration than the c.m.c.=critical micellar concentration; 1OmM CTAB or 2mM SDS) solutions. The specific bands of the aggregate disappeared with a simultaneous increase of the bands of monomer in normal micellar (higher concentration than the c.m.c.; 2mM CTAB or 1OmM SDS) solution. The fluorescence spectra, the lifetime and the fraction of each lifetime components of the chromophore in the micellar solutions significantly changed before and after the ultrasound irradiation although the changes in absorption spectra was small. The fluorescence emission band at 710nm due to the aggregate disappeared almost in the pre-micellar solution after the irradiation. The fraction of the short-lifetime (1.4ns of NaPhd-a and 1.8ns of Phd-a in H2O; 1.3ns of NaPhd-a in 2mM CTAB) component estimated for the aggregates decreased 55% in H2O or 85% in 2mM CTAB increasing with that of the long-lifetime (4.9ns of NaPhd-a and 4.7ns of Phd-a in H2O; 4.3ns of NaPhd-a in 2mM CTAB) component after the ultrasound treatment. From these fluorescence properties, it was considered that the aggregate molecules actually were monomerized in stable by the ultrasound irradiation.

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Power ultrasound of 20 kHz was applied to the synthesis of silica spheres via the controlled hydrolysis of tetraethoxysilane (TEOS). Silica spheres of about 0.3μm were agglomerated to form tolerably uniform, dense particles of about 2μm through 90 min's sonication. This agglomeration behavior was examined by laser diffraction particle size analysis and transmission electron microscopy. It was found that the agglomeration process involves (I) incubation period where no agglomeration occurs, (II) rapid formation of ramified particles and (III) their densification. It was inferred that sonication enhances the collision among silica spheres.

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Multi-layered carbon nanotubes and related nano materials were produced in liquid benzene chlorides with chemical assistants under ultrasonic irradiation. The reaction was operated in a glass beaker at ambient temperature and pressure. The reaction products depended on the chemical assistants. When it was zinc, zinc chloride or nickelocene, a certain amount of carbon nanotubes were produced. When it was zinc oxide, nickel, nickel chloride or no use, few or no nanotubes were produced. The chemical assistants of low melting point might be effective for the nanotube production. Concerning the source materials, o-dichlorobenzene was more suitable for it than chlorobenzene and benzene.

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An ultrasonic wave improves a solid electrode voltammetry in sensibility and reproducibility. Ultrasonic effects on an electrochemical reaction are mainly mass transport. The reaction, however, might not be facilitated only by the effective mass transport of reactant in the case of slow reaction. The relationship between the reaction velocity and ultrasonic vibrating effect was studied by examining how much dependence redox current in the voltammogram had on the potential scan rate.

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Chemical application of ultrasounds has received much attention so far. However, the application to electrochemistry, particularly to electroorganic processes has been relatively limited. From the above point of view, we aimed to explore effects of ultrasounds on variety of electroorganic processes. In this work, clear and significant effects of the ultrasonic irradiation on reaction rates could be demonstrated in electrocatalytic processes such as photocatalytic and -mediatory reactions, and it was found that reaction rates in both electrocatalytic processes were greatly enhanced by ultrasonic waves.

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A new separation method, using ultrasonic atomization, for ethanol-water solution is discussed. This method has a high efficiency and separation ability, comparing with distillation. 100% ethanol is obtained from several mol.% ethanol-water solution, at 10℃ of solution temperature. And, more than 30℃, required energy for separation about 1/5〜1/7 comparing with distillation. Ultrasonic separation is not a thermal separation method, which will be used for separation, with avoiding thermal effects.

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For therapeutic application of cavitational effects, it is very important to obtain the effects at low acoustic intensity. We are approaching in two ways. One is finding chemicals which lowers cavitation threshold and the other is optimized ultrasonic waveforms for inducing cavitation. We previously reported that organic compounds with multiple chlorine can lower cavitation thresh- old in water. Unfortunately, such chemicals require too high concentration to be administrated into human bodies. This time we investigated the effect of xanthens, a dye family with multiple halogen atoms, for reducing cavitation threshold in both water and living mice livers. In the presence of Erythrosine or Rose bengal, cavitation thresholds in water and mice livers were about five times and ten times smaller than in the absence of the xantenes, respectively.

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The effect of the acoustic cavitation in organic liquids was investigated. Aliphatic and aromatic hydrocarbons, alcohols .aldehydes, ethers and ketones were sonicated. These organic liquids seemed to decompose at the high temperature site formed from adiabatic collapse of the cavities. The decomposition products from aliphatic and aromatic hydrocarbons were hydrogen, methane, ethylene, acetylene and higher alkanes and alkenes, and hydrogen, methane, ethylene, carbon monoxide, carbon dioxide and aldehydes from alcohols. Hydrocarbons involved aromatic and cyclic compounds having high vapor pressure more than lOmmHg have not been decomposed, however, alcohols having high vapor pressure up to 40mmHg have decomposed. Methanol solution of DPPH (1,1-diphenyl-2-picrylhydrazyl), radical scavenger, was sonicated to investigated the behavior of sonochemically formed radicals. It is considered that DPPH has too low vapor pressure to enter the cavity and scavenges free radicals migrated from the cavity at the interface region. The major product from DPPH was DPPH2 (1,1-diphenyl-2-picrylhydrazine) and three kind of unknown products were observed The rate of formation of products from methanol in the presence DPPH was almost same as that in the absence of DPPH. So, the decomposition of methanol mostly completed in the cavity.

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It is known that the bio-materials are not only physically droken but also chemically degraded by ultrasonic irradiation. In this report, we try to degrate organnic phosphate using ultrasound. As the result, the mineralization of organic phosphate proceeded and phosphate ion was produced. After one hour sonication, about forty percent of phosphorus was ionized. This technique should be applied to the quantitative analysis of phosphorus in organic phosphate.

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The oxidative degradation of chloroform by heterogeneous photocatalysis and by sonolysis have been investigated. The photocatalysis using TiO_2(P25) resulted in the formation of carbon dioxide and chloride ion as the main products as well as some organic chlorides as minor products. Simultaneous irradiation of ultrasound with the photo-irradiation enhanced the mineralization to form CO_2and Cl^-,suggesting that the products of the sonolysis,which were organic chlorides such as chloroacetic acids, are oxidized more rapidly to be mineralized than original compound. The same experiments were performed for mono,di and tri chloroacetic acids as for chloroform and the similar results were obtained.

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Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) have been reported to be produced from low temperature (<800℃) waste incineration process of chlorine-containing compounds such as PCB. PCDD/F and PCB are toxic and stable compounds, and it is difficult to decompose these compounds. On the other hand, sonochemical process can be produced hot bubbles (〜5000K) and surrounding (〜2000K), therefore, sonochemical decomposition of these chlorinated compounds may successfully proceed without production of PCDD/F. The sonochemical degradiation of 4-chlorobiphenyl and PCB related compounds (chlorobenzene, dichlorobenzene, benzene and biphenyl) in aqueous solution was performed and decomposition rate and decomposition products were investigated. The decomposition relatively readily proceeded and PCDD/F were not detected from 100 times condensed sonicated sample solution.

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Sonoluminescence (SL) intensity from cavitation-bubble fields has been measured for a well-defined standing-wave sound field in a rectangular cell filled with distilled water, when ultrasonic frequency, the water height and temperature were systemically changed. Optics was designed to ensure all the sonoluminescencing positions in the cell were detectable by a PMT. The temperature was controlled by a cooling bath, in which the cell was sunk. In order to obtain an overall view of SL intensity dependence on resonance situation in cell, a 3D SL intensity-water height-ultrasonic frequency contour map was obtained. The SL intensity is strongly influenced by the modes of acoustic standing wave formed in the cell and resonance properties of transducer. Although the basic trend was confirmed that the SL intensity decreases when the temperature increases, it was found that SL intensity was further modulated by the appearance of resonance mode of standing wave during the rise of temperature. [Work supported by Japan Small Business Corporation through Creative and Fundamental R&D Program for SMEs].

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The low-Q method for generating single-bubble sonoluminescence developed in our laboratory is examined from the perspective of chemical applications. The method utilizes two Langevin transducers sandwiching a flask and produces as many as four sonoluminescing bubbles symmetrically in the plane at the center of the flask. Compared with the sonoluminescence in the ordinary resonant, high-Q method, the present luminescence is dimmer, which suggests that the bubbles may have lower temperature and that they may be dancing around in the neighborhood of the average position. It is argued that the apparent low quality is by no means a drawback from the standpoint of chemical reactions, since chemical reactions seem to be more likely to take place within such poor cavitation bubbles, as suggested by the recent pioneering discovery by T. and F. Lepoint.

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The sonochemical reactions usually take place in a cell in which sound field has very complicated form. The reaction field also becomes very complicated, and it is very difficult to obtain reliable and reproducible results. In this study , the form of the sound field (running wave, standing wave, diverging wave and converging wave) and that of the reaction field were compared each other. The sound field was visualized by the shlieren technique while the reaction field was done by the sonic chemi-luminescence of lumiol solution. A disk shaped piezoelectric ceramic transducer(PZT) was used as transmitter (diameter; 40mm). The transducer was attached to the bottom of water bath. The ultrasound frequency was 1MHz. The running wave was formed by sponge absober which was attached on the water surface. On the other hand, the standing wave was formed by blast reflector. The effect of the sound field forms was studied using the concave transducer (diameter; 100mm, focusing point; 180mm and frequency ; 500kHz). Continuous sinusoidal signal was generated by the function generator (Hewletpackard co.) to drive the transducer. The laser beam was diffracted on the sound field in the shlieren system. The light intensity of the order 0 and 1 were measured by CCD camera. The sound pressure was estimated by the light intensity. During the sonication, the luminescence emitted from the solution was measured by the photo-multiplier (HAMAMATSU photonics k.k.) and recorded on photographic films by the camera (lens; canon macro lens FD 50mm, light exposure time; 5min, diaphragm; 3.5 and film; ASA3200). The distance between the luminescence and the photo-multiplier or the lens was kept to be 10cm. Temperature of the water circulated around the glass cell was kept to be 20℃. The concentration of the luminol solution was 1.5 × 10^<-5>M. Since the shlieren technique and sonic chemi-luminescence don't mix the sound field, we measured the certain sound presure during the sonochmical reaction.

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[Introduction] We have studied mechanism of sonochemical reaction in liquid benzene. We already found the production of C_<60> by ultrasonic irradiation to liquid benzene, so that we have also studied the application of sonochemical process to the synthesis of new carbon materials. Here we present our recent result related to the mechanism of sonochemical process of liquid benzene. [Experimental] Samples were irradiated with a ultrasonic homogenizer (SMT, UH-600.) equipped with a titanium tip 20 mm in diameter. The ultrasonic irradiation was carried out in an open glass vessel with Ar gas bubbling through liquid. The glass vessel was cooled using an ice bath. [Results and Discussion] Liquid benzene turned yellow, when strong ultrasound irradiated. The coloring of benzene is due to polymerization of benzene. In order to know the mechanism in detail, we analysed the methanol soluble product with a HPLC. Main product was biphenyl. Biphenyl may produce through phenyl radical which can be considered to an intermediate for high temperature pyrolysis of benzene. We measured relative rate of the polymerization reaction in various benzene derivatives. The rate is apparently proportional to the inverse of the vapour pressure of the liquids. From this relation, we analyzed the reaction rate of benzene / chlorobenzene mixture. As a results, we conclude that the sonochemical polymerization occurs at the vapour phase of a bubble. Recently we also measured sonoluminescence during ultrasonic irradiation. The spectrum may include the information for the primary process of sonochemical process.

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The phenolic compounds related to tocopherols were synthesized and oxidized by various oxidants such as Fremy's salt under the condition of ultrasonic irradiation. 2-Hydroxyethylchromans were synthesized from trimethylbenzoquinone and 5,6-dihydro-4-methyl-2H-pyran and aluminum trichloride as catalyst in the solvent of nitrobenzene. In this synthesis , ultrasonic irradiation was very useful for the increase of the reaction yields. Oxidation with Fremy's Salts were also useful for the acceleration of the reaction and the product selectivity.[chemical formula]

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It is important for mankind to diminish carbon dioxide in the atmosphere. We attempt to utilize ultrasound for reducing C02. As the result, the amount of C02 decreased to about half for one hour sonication. Carbon monooxide and hydrogen were evolved during sonication. The behavior of CO was related to that of C02. On the other hand, H2 behaved independently. Temperature dependence of the decreasing rate for C02 was observed. The decreasing rate was down with increasing temperature in the range of 5-45℃. Thus, the efficiency of sonication was down in the high temperature region. The effect of dissolved (or satulated) gas in the solution on sonolysis was also observed. The decreasing rate for C02 followed the order Ar>He>H2>N2.

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It is necessary to specify the cavitation or ultrasonic intensity in a reaction vessel. The cavitation intensity depends on experimental conditions under sonication: sample volume, dissolved gases frequency and so on. We have proposed the method for quantification of ultrasonic intensity based on decomposition of porphyrin. Porphyrin is one of sensitive analytical regents. The purpose of this work is to investigate the effects of the sample volume and frequency on decomposition of porphyrin under sonication. The ultrasonic processor with a planar PZT oscillator of radius 2.5cm was used in order to generate the ultrasound of 500kHz. Experiment was carried out with cylindrical sample cells which were made of Pyrex. The sample volume changes with the cell radius and liquid height Power ultrasound was irradiated into solution saturated with air for 30min. All experiments were carried out at 25 ± 1 ℃. Decomposition of porphyrin depends on the cell radius and the liquid height. When the cell radius is larger than the oscillator radius, the amount of decomposed porphyrin unit volume decreases with increasing the cell radius. We found from the logarithm plot of (1-R_<TPPS>) vs r that the following relation between the cell radius and (l-R_<TPPS>) holds. 1-R_<TPPS>=K_1・r^<-1.4±0.1> (1) where r(cm) is the cell radius and R_<TPPS> is defined as the ratio for the absorption of porphyrin in solutions before and after ultrasonic irradiation. The amount of decomposed porphyrin unit volume decreases with increasing the liquid height. The effect of the sample volume on decomposition of porphyrin under sonication is expressed by the following equation. 1-R_<TPPS>=k_2・V^<-0.55±0.05> (2) where V(cm^3) is the sample volume. The relation is similar to volume dependence of cavitation threshold reported by G. Iernetti.

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There have been many study on chemical reaction induced by ultrasound sonication, however,in the most of the studies continuous wave have been used. In this study,we investigated effect of driving interval of the wave using burst waves. To quantity amount of the ultrasonic induced radicals, DMPO of 20μl was dissolved in water of 8500μl. The solution was placed into a cylindrical grass cell (20mm in diameter and 30mm height) and was sonicated by PZT transducer attached at the bottom of the cell. The sonication frequency was 1MHz and the voltage applied on the transducer was 100V. During sonication, a small amount of sample was picked up from the cell at a certain time intervals,and the concentration of the OH-DMPO radicals was measured by ESR. We measured production of OH-DMPO radicals with varying the sonication time and the interval time. It was found that i) the smaller rate of the interval time gives the larger amount of the radicals and that ii) though the sonication time is fixed, the radical production per wave cycle decreases with increasing of the interval time.

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A quantitative study of the sonolysis and the addition to olefins of bromotrichloromethane was performed. Under ultrasonic irradiation, bromotrichloromethane is cleaved to a bromine atom and a trichloromethyl radical (1) followed by the recombination to either bromotrichloromethane (2) or molecular bromine and hexachloroethane (3). Br-CCl_3 -)))→Br・ + ・CCL_3 (1) Br・+ -CCl_3 → Br-CCl_3 (2) 2・CCl_3 → Cl_3C-CCl_3 2Br・ → Br_2 (3) An addition of a small amount of n-octane to bromotrichloromethane decreased a yield of hexachloroethane. Since n-octane was added in the amount with little effect on the vapor pressure, the decrease in the yield of hexachloroethane is not due to the decrease in the sonolysis of BrCCl_3 but is due to the increase in the recombination (2). In the presence of 1-octene, BrCCl_3 gives the one-to-one addition product via the radical chain reaction with trichloromethyl radical (4) and (5). ・CCl_3 + C_6H_<13>-CH=CH_2 → C_6H_<13>-CH・-CH_2CCl_3 (4) C_6H_<13>-CH・-CH_2CCl_3 + Br-CCl_3 → C_6H_<13>-CHBr-CH_2CCl_3 + ・CCl_3 (5) When the mole fraction of the sum of n-octane and 1-octene was kept constant, the yield of bromotrichlorononane increased as increasing the concentration of 1-octene. The yields of hexachloroethane were almost constant in the presence of 1-octene, though the lower yield was obtained without 1-octene. Again, the change in mole ratio of n-octane to 1-octene does not affect the vapor pressure of the system. Therefore, the increased yield of hexachloroethane with 1-octene may be due to the suppression of the reaction (2) by 1-octene.

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It is well known that H_2O_2, HNO_2 and HNO_3 are produced when power ultrasound is irradiated into water saturated with air. Several works have investigated the concentration dependence of the chemical species for the irradiation time. However, little study on the change in pH has been reported. Especially, the effect of the dissolved gases on the pH change is not cleared. The purpose of this work is to investigate quantitativety the pH change in water saturated with different gases under sonication. Sonication was carried out under atmosphere of air, oxygen, nitrogen, and argon. The value of pH in water for different dissolved gases was obtained under a constant ultrasonic intensity. The pH measurement was carried out by Expandable Ionanalyzer (Model EA 940, Orion). The ultrasonic intensity in a reaction vessel was determined on the basis of decomposition of porphyrin (tetraphenylporphine tetrasulfonic acid, hereafter abbreviated as TPPS). In this work, we pay sufficiently attention to degassing. Under air atmosphere, the pH value changed from 7 to 4.3 for irradiation time of 30 min and after that the value approached to 3.7. On the other hand, the pH values for water saturated with Ar, N_2 and O_2 were almost independent of irradiation time. In general, the decrease of pH in water saturated with air is considered to be responsible for production of HNO_3, since production of H_2O_2 and HNO_2 does not contribution to the change in the pH. On the other hand, in water saturated with only Ar or O_2, HNO_2 and HNO_3 should not be produced for lack of nitrogen. However, slightly decrease of the pH for Ar and O_2 was observed. The amounts of decomposed TPPS in solutions saturated with O_2 and air are two times as large as that saturated with N_2. In the case of Ar, the value is about three times as large as that for N_2. The ultrasonic effect on TPPS decomposition reaction for different dissolved gases is in the order of Ar > air = O_2 > N_2, which corresponds to that of the luminescence intensity.

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Ultrasonic hyperthermia has been employed as a modality for cancer therapy because of the feasibility of penetration and focusing.The absorbed-dose of ultrasound depends on frequency, intensity and sonication time and estimating dose-distribution is crucial for the clinical application of ultrasound. This study was performed to improve a chemical dosimeter using the Weissler reaction (determination of iodine liberated from potassium iodide due to ultrasonic cavitation). A KI-starch solution containing chloral hydrate (CH) or trichloroacetic acid (TCA) saturated with air in a polystyrene dish was irradiated with 1.0 MHz ultrasound.For measurement of liberated iodine, absorbance at 555 nm was measured with a spectrophotometer. A "lattice" vessel consisting of 100 small containers was used for the estimation of dose-distribution. The absorbed-dose was calculated as a"Gy-equivalent" from the relation between radiation dose (Gy) and the change in absorbance by X-rays. When KI-starch solutions containing TCA instead of CH were sonicated, the absorbance increased at a higher rate by a factor of approximately 2. However, almost no difference in threshold-intensity was observed. When KI-starch solutions containing CH were sonicated after adjustment of the pH to 2.0, almost equal enhancement of the absorbance increase was recognized. These results indicate that pH during sonication is an important factor in KI-chemical dosimetry. When a "lattice" vessel containing KI-starch solution with TCA was sonicated to determine the dose-distribution using a large transducer for therapeutic use,. the two-dimensional distribution of the absorbed-dose was easily visualized and estimated. These methods appear to be useful for the estimation of ultrasonic absorbed-dose.

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