Sonochemical and photosonochemical degradation of 4-chlorophenol in aqueous media

The degradation of 4-chlorophenol (4-CP) in aqueous media by 516 kHz ultrasonic irradiation was investigated in order to clarify the degradation mechanism. The degradation of concentrated 4-CP solution by means of ultrasound, UV irradiation and their combined application was also studied. The obtained results indicate that *OH radical are the primary reactive species responsible for 4-CP ultrasonic degradation. Very little 4-CP degradation occurs if the sonolysis is carried out in the presence of the *OH radical scavenger tert-butyl alcohol, also indicating that little or no pyrolysis of the compound occurs. The dominant degradation mechanism is the reaction of substrate with *OH radicals at the gas bubble-liquid interface rather than high temperature direct pyrolysis in ultrasonic cavities. This mechanism can explain the lower degradation rate of the ionic form of 4-CP that is partly due to the rapid dissociation of *OH radicals in alkaline solutions. The sonochemical destruction of concentrated 4-CP aqueous solution is obtained with low rate. Coupling photolysis with ultrasound irradiation results in increased efficiency compared to the individual processes operating at common conditions. Interestingly, the photosonochemical decomposition rate constant is greater than the additive rate constants of the two processes. This may be the result of three different oxidative processes direct photochemical action, high frequency sonochemistry and reaction with ozone produced by UV irradiation of air, dissolved in liquid phase because of the geyser effect of ultrasound streaming. Additionally, the photodecomposition, at 254 nm, of hydrogen peroxide produced by ultrasound generating *OH radical can partly explain the destruction enhancement.     

气液两相滑动弧放电中自由基的光谱研究

气液两相滑动弧放电是近年来出现的一种新型低温等离子体废水处理技术,对高浓度有机废水具有很好的降解效果。为了认识气液两相滑动弧放电降解有机废水的机理,用发射光谱法对气液两相滑动弧在空气中放电所产生的主要自由基进行了实验研究,分析了自由基持续再生的化学过程。通过对光谱线强度变化的分析,得到了OH和NO自由基谱线强度在放电反应空间的分布特点,以及输入电压和液相(水)流量因素对OH和NO自由基产生过程的影响。结果表明：OH是气液两相滑动弧放电的主导自由基;OH和NO自由基谱线强度沿着电极中轴均先增后减;在非平衡区域,自由基谱线强度随着输入电压的增大而增大;OH自由基谱线强度随水流量的增大而增大,NO自由基谱线强度则随着水流量的增大而减小。     

Physicochemical process of non-thermal plasma at gas-liquid interface and synergistic effect of plasma with catalyst

An atmospheric-pressure plasma jet (APPJ) was directly irradiated at a gas-liquid interface under ambient conditions. The reactive oxygen species (ROS) like hydroxyl radicals (•OH), hydrogen peroxide (H₂O₂) and ozone (O₃) and also reactive nitrogen species (RNS) such as nitrogen oxides (NO_x) and nitric acid (HNO₃) formed during the plasma discharge were quantified under various experimental parameters. In a chemical dosimetry method, terephthalic acid (TA) was employed for the quantification of •OH and titanium sulfate was used to quantify the H₂O₂. Quantitative determination of NO₃⁻ was carried out by using Ion chromatography (IC). The changes in the solution pH were studied during the plasma treatment. Strong acidification along with the production of dominant reactive nitrogen species and ozone formation were observed with air. The effect of various gases, gas flow rate, various applied voltage and catalyst were studied to optimize the experimental conditions for the best performance. The influence of catalyst Fe²⁺ salt, TiO₂ on the formation of reactive species were studied. The efficiency of the plasma device for the degradation of crystal violet (CV) was also investigated with TiO₂ and Fe²⁺ salt.     

Spectroscopic Investigation on the Synergistic Effects of Ultrasound and Dioxopromethazine Hydrochloride on Protein

The bovine serum albumin (BSA) was selected as a target molecule, the sonodynamic damage to protein in the presence of dioxopromethazine hydrochloride (DPZ) and its mechanism were studied by means of absorption and fluorescence spectra. The results of hyperchromic effect of absorption spectra and quenching of intrinsic fluorescence spectra indicated that the synergistic effects of ultrasound and DPZ could induce the damage of BSA molecules. The damage degree of BSA molecules increased with the increase of ultrasonic irradiation time and DPZ concentration. The results of synchronous fluorescence and three-dimensional fluorescence spectra further confirmed that the synergistic effects of ultrasound and DPZ induced the damage of BSA molecules. The results of oxidation-extraction photometry with several reactive oxygen species (ROS) scavengers indicated that the damage of BSA molecules could be mainly due to the generation of ROS, in which both ¹O₂ and ·OH were the important mediators of the ultrasound-inducing BSA molecules damage in the presence of DPZ.     

The influence of ultrasound on the fluoroquinolones antibacterial activity

In this work, the antibacterial effect of fluoroquinolones (FQs) upon Escherichia coli (E.coli) was measured with and without application of 40 kHz ultrasound (US) stimulation. The research results demonstrated that simultaneous application of 40 kHz US apparently enhanced the antibacterial effectiveness of FQs. That is, the synergistic effect was observed and the bacterial viability was reduced when FQs and US were combined. In addition, various influencing factors, such as FQs drug concentration, US irradiation time and solution temperature, on the inhibition of E.coli were also investigated. The antibacterial activity was enhanced apparently with increasing of FQs drug concentration, US irradiation time and solution temperature. Furthermore, we discussed preliminarily the mechanism of US enhanced antibacterial activity. Results show that US can activate FQs to produce reactive oxygen species (ROS) indeed, which are mainly determined as superoxide radical anion (·O(2)(-)) and hydroxyl radical (·OH).     

脉冲放电等离子体/TiO2协同体系中氧自由基的光谱分析

基于脉冲放电等离子体/TiO2的协同作用效果,研究利用脉冲放电过程中产生的紫外光效应,建立以玻璃珠负载的TiO2膜作为光催化剂的脉冲放电等离子体/TiO2协同体系,并从氧自由基(·O)光谱分析的角度说明脉冲放电等离子体/TiO2光催化的协同作用机理.研究结果表明,·O主要在777 um处形成特征发射光谱,对应跃迁为3p...     

微波液相放电等离子体发射光谱研究

液相放电能够产生各种活性物质,其中羟基自由基(OH),氢自由基(H)被认为是引发液相化学反应的主要活性物种,但由于其活性强寿命短的特点,测量比较困难,由于缺少标准样品,定量测量更为困难。用光学方法测量自由基是一种直接测量方法,其特点是瞬时在线测量,能立即获得数据,进行时间和空间分布测量。为了研究微波水中放电产生的自由基特性,利用发射光谱诊断技术对微波水中放电产生的活性物质进行了在线检测,考察了微波功率、反应器内部压强对OH自由基相对光谱强度的影响,并观测了等离子体中OH自由基强度的空间分布;同时,估算了微波液相等离子体中的电子激发温度。实验结果表明,微波水中放电可以产生大量的OH,H,O自由基,其中OH自由基的相对光谱强度最强,并随微波功率的增加呈现明显上升的趋势,随反应器内部压强的增大而迅速减弱;以OH为主的自由基主要产生于电极尖端附近。微波液相等离子体的电子激发温度约为0.33×104 K。     

Simultaneous hydrodynamic cavitation and glow plasma discharge for the degradation of metronidazole in drinking water

In this study, a novel hydrodynamic cavitation unit combined with a glow plasma discharge system (HC-GPD) was proposed for the degradation of pharmaceutical compounds in drinking water. Metronidazole (MNZ), a commonly used broad-spectrum antibiotic, was selected to demonstrate the potential of the proposed system. Cavitation bubbles generated by hydrodynamic cavitation (HC) can provide a pathway for charge conduction during glow plasma discharge (GPD). The synergistic effect between HC and GPD promotes the production of hydroxyl radicals, emission of UV light, and shock waves for MNZ degradation. Sonochemical dosimetry provided information on the enhanced formation of hydroxyl radicals during glow plasma discharge compared to hydrodynamic cavitation alone. Experimental results showed a MNZ degradation of 14% in 15 min for the HC alone (solution initially containing 300 × 10⁻⁶ mol L⁻¹ MNZ). In experiments with the HC-GPD system, MNZ degradation of 90% in 15 min was detected. No significant differences were observed in MNZ degradation in acidic and alkaline solutions. MNZ degradation was also studied in the presence of inorganic anions. Experimental results showed that the system is suitable for the treatment of solutions with conductivity up to 1500 × 10⁻⁶ S cm⁻¹. The results of sonochemical dosimetry showed the formation of oxidant species of 0.15 × 10⁻³ mol H₂O₂ L⁻¹ in the HC system after 15 min. For the HC-GPD system, the concentration of oxidant species after 15 min reached 13 × 10⁻³ mol H₂O₂ L⁻¹. Based on these results, the potential of combining HC and GPD systems for water treatment was demonstrated. The present work provided useful information on the synergistic effect between hydrodynamic cavitation and glow plasma discharge and their application for the degradation of antibiotics in drinking water.     

脉冲放电等离子体/活性炭联合体系中OH自由基的发射光谱研究

基于OH自由基的强氧化性(2.8 V)及脉冲放电等离子体(pulsed discharge plasma, PDP)与活性炭(activated carbon, AC)联合体系的协同作用,依托于光谱检测技术简单、准确性高、灵敏度高等优点,利用发射光谱技术测量了以O2作为载气的PDP/AC联合体系中产生的OH自由基的相对发射光谱,用以表征体系中OH自由基相对生成量的变化。通过考察PDP水处理体系中不同AC添加量、脉冲峰值电压、电极间距对OH自由基相对发射光谱强度的影响,分析了影响OH自由基生成量的因素;通过比较,分析去离子水和酸性橙II(acid orange, AO7)溶液中OH自由基发射光谱强度的变化规律,表征了OH自由基生成量的变化,以说明PDP/AC的协同作用机理及OH自由基对有机物的氧化作用。研究结果表明,增加AC的添加量可以增强其在PDP体系中的催化效果,导致PDP/AC联合体系中OH自由基的相对发射光谱强度的增加;随着脉冲峰值电压的升高,注入PDP体系中的能量增加,从而增加了体系中OH自由基的产量;电极间距增加导致PDP体系能量效率降低,降低了OH自由基的产生量;无论是以去离子水还是以AO7溶液为溶液相,PDP/AC联合体系中OH自由基的产量均高于其在单独PDP体系中的生成量,且在PDP/AC联合体系和单独的PDP作用体系中,去离子水中OH自由基的相对发射光谱强度均高于其在AO7溶液中的强度值,这证明了AC对PDP体系中OH自由基生成的协同作用和有机物对OH自由基的消耗。     

Degradation of Acid Blue 25 in aqueous media using 1700 kHz ultrasonic irradiation: ultrasound/Fe(II) and ultrasound/H2O2 combinations

In this work, the sonolytic degradation of an anthraquinonic dye, C.I. Acid Blue 25 (AB25), in aqueous phase using high frequency ultrasound waves (1700 kHz) for an acoustic power of 14 W was investigated. The sonochemical efficiency of the reactor was evaluated by potassium iodide dosimeter, Fricke reaction and hydrogen peroxide production yield. The three investigated methods clearly show the production of oxidizing species during sonication and well reflect the sonochemical effects of high frequency ultrasonic irradiation. The effect of operational conditions such as the initial AB25 concentration, solution temperature and pH on the degradation of AB25 was studied. Additionally, the influence of addition of salts on the degradation of dye was examined. The rate of AB25 degradation was dependent on initial dye concentration, pH and temperature. Addition of salts increased the degradation of dye. Experiments conducted using distilled and natural waters demonstrated that the degradation was more efficient in the natural water compared to distilled water. To increase the efficiency of AB25 degradation, experiments combining ultrasound with Fe(II) or H₂O₂ were conducted. Fe(II) induced the dissociation of ultrasonically produced hydrogen peroxide, leading to additional OH radicals which enhance the degradation of dye. The combination of ultrasound with hydrogen peroxide looks to be a promising option to increase the generation of free radicals. The concentration of hydrogen peroxide plays a crucial role in deciding the extent of enhancement obtained for the combined process. The results of the present work indicate that ultrasound/H₂O₂ and ultrasound/Fe(II) processes are efficient for the degradation of AB25 in aqueous solutions by high frequency ultrasonic irradiation.     

Origin of Antibacterial Activity of ZnO Nanoparticles: The Roles of Protonic and Electronic Conductions

To elucidate the origin of antibacterial activity of ZnO nanoparticles, a reactive oxygen species (ROS) mechanism is systematically investigated based on electronic and protonic conductions. While the enhancement of antibacterial activity by an increase in electronic conductivity is marginal, an apparent improvement is observed by in the increase of protonic conductivity in terms of the surface basicity. This study first demonstrates that antibacterial activity can be enhanced by controlling the surface basicity of solid particles. The basicity of ZnO can be modulated by doping alkaline‐earth oxides such as MgO and CaO, and it results in the increase of hydroxyl defects on the surface of solid particles. The basicity shows a strong dependency on mobile OH concentrations. The increase of ROS hydroxyl radicals is confirmed by Mg (ZMO) or Ca‐doping (ZCO), which shows high antibacterial activity, and Ca‐doped ZnO exhibits the highest performance. It is clearly observed that the antibacterial activity is proportional to the basicity, which is controlled by the mobile OH formation. While both electrons and hydroxyl species are required for ROS reactions, it is concluded that the formation of hydroxyl species is a key factor in improving the antibacterial activity in ZnO.     

Flow-mode water treatment under simultaneous hydrodynamic cavitation and plasma

Over the last two decades, the scientific community and industry have made huge efforts to develop environmental protection technologies. In particular, the scarcity of drinking water has prompted the investigation of several physico-chemical treatments, and synergistic effects have been observed in hyphenated techniques. Herein, we report the first example of water treatment under simultaneous hydrodynamic cavitation and plasma discharge with the intense generation of radicals, UV light, shock waves and charged particles. This highly reactive environment is well suited to the bulk treatment of polluted water (i.e. E. coli disinfection and organic pollutant degradation). We have developed a new prototype and have efficiently applied this hybrid technology to water disinfection and the complete degradation of methanol in water with the aim of demonstrating its scalability. We have analyzed the mechanisms of water disinfection under the abovementioned conditions and verified them by measuring cavitation noise spectra and plasma emission spectra. We have also used the degradation of textile dyes and methanol solutions as an indicator for the formation of radicals.     

Visible light induced sonophotocatalytic degradation of Reactive Red dye 198 using dye sensitized TiO2

In this paper we are reporting the accelerated sonophotocatalytic degradation of Reactive Red (RR) 198 dye under visible light using dye sensitized TiO(2) activated by ultrasound. The effect of sonolysis, photocatalysis and sonophotocatalysis under visible light has been examined to study the influence on the degradation rates by varying the initial substrate concentration, pH and catalyst loading to ascertain the synergistic effect on the degradation techniques. Ultrasonic activation at 47kHz contributes through cavitation leading to the splitting of H(2)O(2) produced by both photocatalysis and sonolysis. This results in the formation of oxidative species, such as singlet oxygen ((1)O(2)) and superoxide (O2-*) radicals in the presence of oxygen. Sonication increases the amount of reactive radical species, inducing faster oxidation of the substrate and degradation of intermediates and also the deaggregation of the photocatalyst which are responsible for the observed synergy. Further, the photocatalytic activity of RR 198 dye sensitized TiO(2) is demonstrated by the degradation of phenol under visible light and ultrasound. A comparative study using TiO(2), Hombikat UV 100 and ZnO was also carried out.     

New insights on the role of ROS in the mechanisms of sonoporation-mediated gene delivery

Reactive oxygen species (ROS) are hypothesized to play a role in the sonoporation mechanisms. Nevertheless, the acoustical phenomenon behind the ROS production as well as the exact mechanisms of ROS action involved in the increased cell membrane permeability are still not fully understood. Therefore, we investigated the key processes occurring at the molecular level in and around microbubbles subjected to ultrasound using computational chemistry methods. To confirm the molecular simulation predictions, we measured the ROS production by exposing SonoVue® microbubbles (MBs) to ultrasound using biological assays. To investigate the role of ROS in cell membrane permeabilization, cells were subjected to ultrasound in presence of MBs and plasmid encoding reporter gene, and the transfection level was assessed using flow cytometry. The molecular simulations showed that under sonoporation conditions, ROS can form inside the MBs. These radicals could easily diffuse through the MB shell toward the surrounding aqueous phase and participate in the permeabilization of nearby cell membranes. Experimental data confirmed that MBs favor spontaneous formation of a host of free radicals where HO was the main ROS species after US exposure. The presence of ROS scavengers/inhibitors during the sonoporation process decreased both the production of ROS and the subsequent transfection level without significant loss of cell viability. In conclusion, the exposure of MBs to ultrasound might be the origin of chemical effects, which play a role in the cell membrane permeabilization and in the in vitro gene delivery when generated in its proximity.     

检测活性氧的荧光探针新进展

活性氧对于人体是十分重要的。然而,过量的活性氧是相当有害的,它们会对人体产生氧化损伤,导致细胞死亡。活性氧现在已经引起了化学、生物、医药等多个领域学者的浓厚兴趣,它们被认为和多种病理条件有密切的联系。由于活性氧寿命短、反应活性高,并且大部分都存在于体内很难被捕获,因此它们的分析测定是一项国际性难题。荧光探针作为活性氧的高灵敏的检测分析物,已经得到越来越广泛和深入的研究。由于每一种活性氧都有它独特的生理学活性,因此设计高选择性的,能够检测具体一种活性氧的荧光探针分子就显得十分重要。本文主要对近三年来检测单线态氧、过氧化氢、超氧阴离子和羟自由基这四种活性氧的荧光探针的研究进展进行综述,关注这类荧光探针的检测机理以及具体应用。     

喷嘴-平板直流电晕放电中的OH(A2S+→X2P, 0-0)光谱研究

 为更深入地认识电晕放电低温等离子体中自由基的生成机理，以发射光谱测量为基础并结合背景气体淬灭率影响，研究了常压下喷嘴-平板电晕自由基簇射过程中放电参数、背景气体、电极气成分等因素对OH(A²S⁺→X²p, 0-0)发光的影响。结果表明：在放电参数影响中，放电电压及放电电流都会影响OH生成量，OH发光随功率增加而大大增强；在加湿氮气直流电晕放电中有明显的OH(A²S⁺→X²p, 0-0)光谱存在，但加湿空气条件下OH生成较少；载气增湿后OH生成量明显增多，而Ar和O­2的存在分别增强和减弱了OH(A²S⁺→X²p, 0-0)发光，可能的原因是这两种物质影响了放电和OH(A²S⁺)的淬灭。     

Availability of indirect atmospheric plasma from a dielectric barrier discharge device on biofilm-forming bacteria

An investigation of the treatment effect of atmospheric cold plasma (ACP)-generated reactive oxygen species (ROS) against problematic bacteria of chronic wounds is presented. To study ROS effects specifically, a vacuum chamber with a flowmeter to control the background gas composition and a mesh electrode for a dielectric barrier discharge (DBD) device were used. In addition, a numerical modeling was developed to simulate the amount of ROS flux transported from the mesh electrode to determine which of the ROS species was the main factor in the treatment effect. Considering the experimental and computational results and the effective transport distance of each species, ozone could be the main factor in the experimental results.     

碱性介质电催化体系活性氧的生成及其光谱学研究

亚熔盐液相氧化技术可在相对低温下实现难分解两性金属矿物的高效转化,基于此进一步提出了碱性介质电化学活性氧协同强化新方法。利用紫外-可见光光谱和电子自旋共振波谱等手段对电催化体系活性氧的生成与转化机理进行了系统解析。通过阴极电催化的作用,在电极表面定向进行两电子氧气还原反应,原位产生大量的活性氧组分。研究发现过渡金属离子与两电子氧气还原产物HO-₂之间的“自诱发”效应,可生成具有更高氧化活性的羟基自由基,大幅促进两性金属转化过程,实现了碱性介质电化学高级氧化过程。利用紫外-可见光光谱检测到电化学体系活性氧催化氧化低价两性金属氧化物(Cr₂O₃和V₂O₃)的转化过程。与此同时,根据标准自由能变化的热力学数据计算可知,V₂O₃比Cr₂O₃更易在活性氧存在的条件下发生溶出反应。采用电子自旋共振波谱(ESR)对电催化体系内的羟基自由基进行检测,结果表明由V₂O₃引发的电化学-类Fenton反应激发产生的羟基自由基ESR信号比Cr₂O₃信号强。利用猝灭剂实验验证了具有高氧化电位的羟基自由基可以对两性金属液相氧化起到促进作用。该研究为碱性介质电化学矿物溶出实际反应提供理论参考。     

大气环境下氩气空心针-板放电中OH和O的空间分布

研究了大气环境下氩气空心针-板放电等离子体中OH和O的空间分布。利用空心针-板放电装置,得到了3cm长的等离子体炬。首先采集了300～800nm范围内的光发射谱,发现除了ArⅠ谱线、N2第二正带系谱线C3Πu(ν′=0)→B3Πg(ν″=0)外,还出现了OH自由基的谱带、OⅠ谱线和较弱的H谱线。由于含氧活性粒子在材料表面改性中具有重要作用,实验选取了OH发射的309nm附近的谱带和激发态O发射的777.4nm谱线,分析了它们的相对强度,得到了粒子的空间分布。结果表明:沿等离子体从弧根到弧梢位置,OH自由基数量迅速减少,O原子数量呈现先增多后减少的规律。     

Spectroscopic study on the sonodynamic and sonocatalytic damage of anthraquinone derivants to bovine serum albumin under ultrasonic irradiation

In this work, three anthraquinone derivants (Alizarin: 1,2-dihydroxy-9, 10-anthraquinone, Alizarin–DA: 1,2-dihydroxy-9, 10-anthraquinone-3-aminomethyl-N, N-diacetic acid and Alizarin–DA–Fe: 1,2-dihydroxy-9, 10-anthraquinone-3-aminomethyl-N, N-diacetate-Ferrous(III)) were used to study the sonodynamic and sonocatalytic damage of bovine serum albumin (BSA) molecules according to the hyperchromic effect of UV–vis spectra and quenching effect of intrinsic fluorescence. Meanwhile, some influencing factors such as ultrasonic irradiation time, anthraquinone derivants concentration and ionic strength on the damage of BSA molecules were also considered. The results show that the synergetic effect of anthraquinone derivants and ultrasonic irradiation can efficiently damage the BSA molecules. Finally, some special radical scavengers were used to determine the kind of generated reactive oxygen species (ROS) in the presence of three anthraquinone derivants under ultrasonic irradiation. The results show that the ROS, at least, including singlet oxygen (¹O₂) and hydroxyl radicals (OH) are generated during the sonodynamic and sonocatalytic processes. It is wished that this paper could offer some valuable references for the application of anthraquinone derivants in sonodynamic therapy (SDT) and sonocatalytic therapy (SCT) for tumor treatment.