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本文合成了磁性金属有机骨架材料Fe3O4@[Cu3(btc)2],并作为分散微固相萃取的吸附剂用于四环素类抗生素的富集. 对萃取的条件,包括萃取时间、溶液pH和洗脱溶剂对四环素类抗生素萃取效率的影响进行了研究. 结果显示Fe3O4@[Cu3(btc)2]可以有效富集四环素类抗生素,而四环素类抗生素与Fe3O4@[Cu3(btc)2]之间的静电相互作用主导了这一过程. 利用分散微固相萃取结合液相色谱-串联质谱法对天然水中的四种四环素类抗生素(土霉素,四环素,金霉素和多西环素)残留进行了测定. 四种抗生素的检出限(S/N=3)为0.01∽0.02 μg/L,定量限(S/N=10)为0.04∽0.07 μg/L. 河水和养殖水中四环素三个水平的加标回收率为70.3%∽96.5%,相对标准偏差为3.8%∽12.8%. 结果表明,基于磁性金属有机骨架材料的分散微固相萃取可以从水中简单、快速、高效地富集四环素类抗生素. 相似文献
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光催化降解有机污染物由于其具有低能耗和绿色环保的特点,已经成为研究的热点. 氧化铋纳米晶体的带隙在2.0∽2.8 eV之间,利用它催化可见光降解有机污染物具有较高的活性,从而引起了越来越多的关注. 尽管近年来已经开发了几种制备Bi2O3基半导体材料的方法,但是仍然难以用简单的方法大规模地制备高活性的Bi2O3催化剂. 因此,开发简单可行的大规模制备Bi2O3纳米晶体的方法对于工业废水处理的潜在应用具有重要意义. 本文通过蚀刻商用BiSn粉末,然后进行热处理,成功地大规模制备了多孔Bi2O3. 获得的多孔Bi2O3在亚甲基蓝(MB)的光催化降解中表现出优异的活性和稳定性. 对该机理的进一步研究表明,多孔Bi2O3合适的能带结构允许生成活性氧物种,例如O2-·和·OH,可有效降解MB. 相似文献
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制备了Bi7Ti4NbO21,Bi4Ti3O12及Nb掺杂Bi4Ti3O12(Nb-Bi4Ti3O12)层状结构铁电陶瓷材料.结合Nb-Bi 4Ti3O12的介电温谱和 退极化实验结果,研究了Bi7Ti4NbO21的晶体结构 对其介电、压电性能的影响 .高分辨透射电镜结果表明,在Bi7Ti4NbO21中, 沿着c轴方向,(Bi2Ti3O10)2-和(BiTiNbO7)2-两个类钙钛矿层分别 与(Bi2O2)2+层叠加堆积而成.这种晶体结构决定了Bi7Ti4NbO21的 介电温谱在668℃和845℃出现介 电双峰.结合极化样品的退化实验分析,说明材料在这两个温度附近发生了铁电—铁电相变 、铁电—顺电相变,分别是(Bi2Ti3O10)2-< /sup>和(BiTiNbO7)2-层状 结构发生微观结构相变的结果.在退极化过程中,由于受热时钙钛矿层内空位引起的缺陷偶 极子的定向排列受到破坏,引起材料部分退极化,表现为300℃热处理后Bi7Ti 4NbO 21的压电活性降低了10%,显示了室温下材料的压电性能来源于自发极化的固有电 偶极子和缺陷偶极子的共同贡献. 相似文献
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采用柠檬酸作燃烧剂用燃烧合成法制备了Gd2O3:Eu3+纳米晶.用X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)和荧光分光光度计等对Gd2O3:Eu3+纳米晶的结构、形貌和发光性能进行了分析.结果表明:不同柠檬酸与稀土离子配比(C/M)制备的样品经800℃ 退火1 h后,均得到了纯立方相的Gd2O3:Eu3+纳米晶,晶粒尺寸约为30 nm,尺寸分布较窄,其中以C/M=1.0时制备的纳米晶结晶性最好,发光强度最大.Gd2O3:Eu3+纳米晶主发射峰位置均在612 nm处 (5D0→7F2跃迁),激发光谱中电荷迁移态发生红移,观察到Gd3+向Eu3+的有效能量传递.对柠檬酸与稀土离子配比(C/M)对结晶度、发光性质等的影响也进行了分析和讨论. 相似文献
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以传统的浸渍法,在不同焙烧温度下制备了用于CO氧化反应的Co3O4/SiO2催化剂.通过激光拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、程序升温还原(TPR)和X射线吸收精细结构谱(XAFS)表征了该系列催化剂的结构.在所有的催化剂中,XRD和Raman光谱都只检测到了Co3O4晶相的存在.与Co3O4体相相比,XPS结果表明在200 oC焙烧的(Co3O4(200)/SiO2)催化剂中Co3O4表面上存在着过量的Co2+.与XPS的结果一致,TPR结果表明Co3O4(200)/SiO2催化剂中Co3O4表面上存在氧缺陷, 并且XAFS结果也表明Co3O4(200)/SiO2催化剂中Co3O4具有更多的Co2+.提高焙烧温度使得过量的Co2+进一步氧化为Co3+,同时降低了表面氧缺陷浓度,从而得到计量比的Co3O44/SiO2催化剂.在所有的负载催化剂中Co3O4(200)/SiO2催化剂表现出了最好的CO氧化催化性能,表明过量Co2+和表面氧缺陷的存在能够促进Co3O4催化CO氧化反应的活性. 相似文献
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A two-channel thermal dissociation cavity ring down spectroscopy (CRDS) instrument has been built for in situ, real-time measurement of NO2 and total RNO2 (peroxy nitrates and alkyl nitrates) in ambient air, with a NO2 detection limit of 0.10 ppbv at 1 s. A 6-day long measurement was conducted at urban site of Hefei by using the CRDS instrument with a time resolution of 3 s. A commercial molybdenum converted chemiluminescence (Mo-CL) instrument was also used for comparison. The average RNO2 concentration in the 6 days was measured to be 1.94 ppbv. The Mo-CL instrument overestimated the NO2 concentration by a bias of +1.69 ppbv in average, for the reason that it cannot distinguish RNO2 from NO2. The relative bias could be over 100% during the afternoon hours when NO2 was low but RNO2 was high. 相似文献
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Laboratory measurements of the absorption coefficients of NO2 at wavelengths suitable for the operation of differential absorption lidar (DIAL) systems, at around 446 nm and 489 nm are reported. Such measurements are necessary for the valid determination of absolute levels of concentration of NO2 in the atmosphere and have been made in order to assess anomalies in existing data. A theoretical assessment of some of the optional systems currently available for the application of DIAL to the measurement of atmospheric concentrations of SO2 is described. 相似文献
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利用一个空间零维大气等离子体模型对其中的氮氧化物在不同电离度情况下的变化规律进行了数值模拟,得到了放电后不同初始电子密度下的氮氧化物(包括NO,NO+,NO2,NO2+,N2O,N2O+,NO3和N2O5)及影响其产消的主要反应物N和O3的密度随时间的演化规律.结果表明,电子初始密度ne0=109 cm-3时,NO和NO2的去除率较高,氮氧化物总密度较小,最适合消除氮氧化物污染.同时,还对N和O3随电离度变化的行为进行了分析.
关键词:
大气等离子体
氮氧化物
电离度
数值模拟 相似文献
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Ignition enhancement by addition of NO and NO2 from a N2/O2 plasma torch in a supersonic flow 总被引:1,自引:0,他引:1
Kenichi Takita Naoyuki Abe Goro Masuya Yiguang Ju 《Proceedings of the Combustion Institute》2007,31(2):2489-2496
The effects of NO and NO2 produced by using a plasma jet (PJ) of a N2/O2 mixture on ignition of hydrogen, methane, and ethylene in a supersonic airflow were experimentally and numerically investigated. Numerical analysis of ignition delay time showed that the addition of a small amount of NO or NO2 drastically reduced ignition delay times of hydrogen and hydrocarbon fuels at a relatively low initial temperature. In particular, NO and NO2 were more effective than O radicals for ignition of a CH4/air mixture at 1200 K or lower. These ignition enhancement effects were examined by including the low temperature chemistry. Ignition tests by a N2/O2 PJ in a supersonic flow (M = 1.7) for using hydrogen, methane, and ethylene injected downstream of the PJ were conducted. The results showed that the ignitability of the N2/O2 PJ is affected by the composition of the feedstock and that pure O2 is not the optimum condition for downstream fuel injection. This result of ignition tests with downstream fuel injection demonstrated a significant difference in ignition characteristics of the PJ from the ignition tests with upstream fuel injection. 相似文献
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D. Feldmann 《Optics Communications》1979,29(1):67-72
The change of the discharge voltage when laser light crossing the discharge is tuned to a molecular transition has been measured. Experiments have been performed in the wavelength region between 570 nm and 620 nm with discharges in NH3, NO2, H2, N2, O2 and argon. Transitions from the ground states of NH2 and NO2 and transitions from metastable states of N2 and H2 have been detected. The spacial dependence of the opto galvanic in a low pressure dc-discharge of H2 and N2 has been studied. 相似文献
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T. Stacewicz J. Wojtas Z. Bielecki M. Nowakowski J. Mikołajczyk R. Mędrzycki B. Rutecka 《Opto-Electronics Review》2012,20(1):53-60
We describe several applications of cavity ring-down spectroscopy (CRDS) for trace matter detection. NO2 sensor was constructed in our team using this technique and blue-violet lasers (395–440 nm). Its sensitivity is better than
single ppb. CRDS at 627 nm was used for detection of NO3. Successful monitoring of N2O in air requires high precision mid-infrared spectroscopy. These sensors might be used for atmospheric purity monitoring
as well as for explosives detection. Here, the spectroscopy on sharp vibronic molecular resonances is performed. Therefore
the single mode lasers which can be tuned to selected molecular lines are used. Similarly, the spectroscopy at 936 nm was
used for sensitive water vapour detection. The opportunity of construction of H2O sensor reaching the sensitivity about 10 ppb is also discussed. 相似文献
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In this paper we report structural and magnetic properties of Fe3O4 nanoparticles synthesized by thermal decomposition of ball milled iron nitrate and citric acid in N2 and air ambient. The XRD pattern of samples which are prepared in air shows some impurity phases, while the samples synthesized in the N2 atmosphere are almost pure Fe3O4 phase. The result shows that by increasing the particle size, the magnetization of the samples increases. The increase of magnetization by increasing the particle size could be attributed to the lower surface spin canting and surface spin disorder of the larger magnetic nanoparticles. The results of ac magnetic susceptibility measurements show that the susceptibility data are not in accordance with the Néel -Brown model for superparamagnetic relaxation, but fit well with conventional critical slowing down model which indicates that the dipole-dipole interactions are strong enough to cause superspin-glass like phase in these samples. 相似文献
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Cavity ring-down spectroscopy is a relatively new and quite sensitive technique for the measurement of gas-phase optical extinction.
It holds the potential for simple, direct and sensitive measurement of the concentrations of a variety of trace gases in the
atmosphere. For example, detection of the nitrate radical, NO3, and its companion, dinitrogen pentoxide, N2O5, has been demonstrated with a sensitivity of 0.25 pptv (1σ). This paper considers several of the requirements for the application
of cavity ring-down spectroscopy to concentration measurements of trace gases in ambient air. These include detection sensitivity,
measurement of an accurate zero in the presence of competing absorbers, cavity stability and mirror cleanliness, laser line-width
effects, saturation effects, Rayleigh scattering, the influence of atmospheric aerosols and sampling issues for reactive species.
Examples drawn from our work on NO3 and N2O5 detection in the field illustrate these considerations.
Received: 1 April 2002 / Revised version: 5 June 2002 / Published online: 12 September 2002
RID="*"
ID="*"Corresponding author. Fax: +1-303/497-5822, E-mail: sbrown@al.noaa.gov 相似文献
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This paper reports on the influence of the sintering temperature and atmosphere and transition-metal doping on the magnetic properties of nanocrystalline and bulk In2O3. Undoped nanocrystalline In2O3 is diamagnetic whatever the sintering temperature and atmosphere. All single-phase transition-metal-doped In2O3 samples are paramagnetic, with a paramagnetic effective moment originating from weakly interacting transition metal ions. No trace of ferromagnetism has been detected even with samples sintered under argon, except extrinsic ferromagnetism for samples with magnetic dopant concentrations exceeding the solubility limit. 相似文献
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To study surface behaviors, MgFe2O4 ferrite materials having different grain sizes were synthesized by two different chemical methods, i.e., a polymerization method and a reverse coprecipitation method. The single phase of the cubic MgFe2O4 was confirmed by the X-ray diffraction method for both the precursors decomposed at 600-1000 °C except for a very small peak of Fe2O3 was detected for the samples calcined at 600 and 700 °C by the polymerization method. The crystal size and particle size increased with an increase in the sintering temperature using both methods. The conductance of the MgFe2O4 decreased when the atmosphere was changed from ambient air to air containing 10.0 ppm NO2. The conductance change, C = G(air)/G(10 ppm NO2), was reduced with an increase in the operating temperature. For the polymerization method, the maximum C-value was ca. 40 at 300 °C for the samples sintered at 900 °C. However, the samples sintered at 1000 °C showed a low conductance change in the 10 ppm NO2 gas, because the ratio of the O2 gas adsorption sites on the particle surface is smaller than those of the samples having a high C-value. The low Mg content on the surface affects the low ratio of the gas adsorption sites. For the reverse coprecipitation method, the particle size was smaller than that of the polymerization method. Although a stable conductance was obtained for the sample sintered at 900 and 1000 °C, its conductance change was less than that of the polymerization method. 相似文献