Low-Temperature_Oxidation_of_CO_over_Gold_Supported_on_TiO2,_α-Fe2O3,_and_Co3O4

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Low-Temperature Solution Processed Tin Oxide Efficient Perovskite

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Low-Temperature Solution-Processed Tin Oxide as an Alternative Electron Transporting Layer for Eﬃcient Perovskite Solar Cells
O
making it not the ultimate ETL material. For example, the electron mobility of TiO2 is not high enough. Zhou et al. showed that Y-doping can increase the electron mobility and electrical conductivity of TiO2 and therefore improve the eﬃciencies for perovskite cells.7 However, doping may not be able to completely overcome the intrinsic low electron mobility issue. Moreover, Snaith et al. reported that perovskite solar cells using mesoporous TiO2 are sensitive to ultraviolet (UV) illumination.24 There exist other transparent metal oxides, such as ZnO, In2O3, and SnO2, that exhibit similar or even better electrical and optical properties as compared to TiO2. Especially, these oxides exhibit a much higher electron mobility than TiO2.25 Recently, Liu et al. reported that a planar perovskite solar cell using a low-temperature solution-processed nanoparticle (ZnO) ETL achieved a high PCE of 15.7%.26 The results suggest that metal oxides other than TiO2 can be good ETL materials for high-eﬃciency perovskite solar cells. SnO2 is a metal oxide that has not only a much higher electron mobility but also a wider band gap than TiO2.25,27 Because ETLs absorb photons with energies higher than the band gap but do not contribute to photocurrents, such absorptions cause only a small current loss. Therefore, SnO2 should lead to a smaller ETL-induced current loss than TiO2. For ultra-high-eﬃciency cells, every potential energy loss should be eliminated. Moreover, SnO2, with a wider band gap, is more stable than TiO2 under UV illumination.25 Fluorine-doped SnO2 (FTO) is a robust transparent conducting electrode that has been widely used in the thin- ﬁ lm solar cell industry. Gelled SnO2 nanoparticles have been used as ETLs for polymer-based solar cells.28 Dye-sensitized solar cells using high-temperature prepared mesoporous SnO2 particles coated with TiO2 and MgO have achieved high eﬃciencies.27 However, there is no report on eﬃcient perovskite solar cells using SnO2 as both ETLs and antireﬂection ﬁlms. Here, we report on low-cost and low-temperature solutionprocessed SnO2 as an ETL material for achieving highly eﬃcient planar perovskite solar cells. The best-performing planar cell using a SnO2 ETL has achieved PCEs of 17.21% and 14.82% when measured under reverse and forward voltage scans, respectively. The perovskite solar cells using SnO2 ETLs

CeO_2_ACFN低温选择性催化还原烟气中的NO

CHEMICAL INDUSTRY AND ENGINEERING PROGRESS 2008年第27卷第3期·412·化工进展CeO 2/ACFN 低温选择性催化还原烟气中的NO韦正乐，黄碧纯，黄华存，叶代启（华南理工大学环境科学与工程学院，广东广州 510006）摘要：制备了CeO 2/ACFN （硝酸氧化处理的改性活性碳纤维）催化剂，对低温选择性催化还原（SCR ）NO 性能进行了考察。

用SEM 、BET 和XRD 进行催化剂结构特性表征，结果显示CeO 2微粒高度分散在ACF 的表面。

实验表明，ACF 先经过硝酸预氧化，然后再负载CeO 2，能明显提高对NO 的转化效率，CeO 2负载量为9％（质量分数），180 ℃、空速为11 000 h －1时，CeO 2/ACFN 的NO 脱除率为93.96％。

关键词：低温选择性催化还原；CeO 2；活性碳纤维中图分类号：X 701.7 文献标识码：A 文章编号：1000–6613（2008）03–0412–05Low-temperature selective catalytic reduction of NO on CeO 2/ACFNWEI Zhengle ，HUANG Bichun ，HUANG Huacun ，YE Daiqi（College of Environmental Science and Engineering ，South China University of Technology ，Guangzhou 510006，Guangdong ，China ）Abstract ：ACFN (activated carbon fibers modified by nitric acid) supported cerium catalyst was prepared. The structure of such catalyst prepared was characterized by SEM ，BET and XRD methods. The results indicated that cerium particles were highly dispersed on the surface of ACFN. The performance of CeO 2/ACFN in low temperature selective catalytic reduction (SCR) of NO was studied. The activated carbon fibers (ACF) was pre-oxidized by nitric acid firstly ，and then loaded with CeO 2. The de-NO efficiency could be greatly enhanced. The highest de-NO efficiency could be obtained with aloading of 9％ CeO 2. In the cases of high space velocity(11 000 h －1)，a high catalytic activity was observed at 180 ℃，and NO reduction conversion was 93.96％.Key words ：low-temperature selective catalytic reduction ；CeO 2；activated carbon fiber在有氧情况下，以NH 3为还原剂的催化还原NO （SCR-NO ）技术已经工业化，目前普遍使用的商用催化剂体系为钒系催化剂，如V 2O 5/TiO 2、V 2O 5-WO 3/TiO 2，其工作温度范围为300～400 ℃；在温度低于200 ℃时，则不具备良好的催化活性。

Low Temperature Electronic Absorption Spectra of Oxidized and Reduced

Contributed by Harry B. Gray, October 5, 1973
The electronic absorption spectra of oxiABSTRACT dized and reduced spinach ferredoxins have been measured between 1200 and 600 nm at low temperature in D2O/ ethylene glycol glasses. Relatively weak absorption bands are observed at 720, 820, and 920 nm in oxidized ferredoxin, and at 652, 820, and 920 nm in reduced ferredoxin. The spectral results show that the two Fe(III) centers in oxidized ferredoxin are not equivalent, and that the 820- and 920-nm bands are associated with the nonreducible site. Assignment of the reducible site as tetrahedral Fe(Il) is indicated. The 720-nm (13.9 kcm-1) band in oxidized ferredoxin is attributed to an intensity-enhanced 6A, - 4T, d-d transition, whereas the 652-nm (15.3 kem-') feature of reduced ferredoxin could be due either to 5E -3T, in tetrahedral Fe(II)S4 or an Fe(II) Fe(III) intervalence excitation.

219401833_两种包装材料结合真空贮藏对油炸脆枣货架期的预测

杜雨桐，陈恺，承春平，等. 两种包装材料结合真空贮藏对油炸脆枣货架期的预测[J]. 食品工业科技，2023，44（13）：349−355. doi:10.13386/j.issn1002-0306.2022040219DU Yutong, CHEN Kai, CHENG Chunping, et al. Prediction of the Shelf Life of Fried Crispy Dates by Combining Two Packaging Materials with Vacuum Storage[J]. Science and Technology of Food Industry, 2023, 44(13): 349−355. (in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2022040219· 贮运保鲜 ·两种包装材料结合真空贮藏对油炸脆枣货架期的预测杜雨桐1，陈　恺1, *，承春平1，许铭强2，王雪妃1，王　田1，李焕荣1（1.新疆农业大学食品科学与药学学院，新疆果品精深加工与贮运保鲜工程技术研究中心，新疆乌鲁木齐 830052；2.新疆农业科学院农产品贮藏加工研究所，新疆乌鲁木齐 830091）摘　要：为探究低温油炸脆枣贮藏过程中品质劣变规律，采用PET 真空包装、PET 真空+脱氧剂包装、铝箔真空包装、铝箔真空+脱氧剂四种包装方式，分析不同贮藏温度（25、35、45 ℃）下酸价和过氧化值的变化，结合Arrhenius 公式建立低温油炸脆枣货架期的预测模型。

结果表明：不同贮藏温度下四种包装方式的油炸脆枣的酸价、过氧化值呈上升趋势，25 ℃变化速率低。

从包装效果来看，铝箔真空+脱氧剂包装方式油炸脆枣的氧化速率最低（酸价动力学模型K 值=0.0131，过氧化值动力学模型K 值=0.0147），预测货架期模型R 2>0.90，拟合度良好，货架期预测值模型误差小于10%。

潜山油藏减氧空气驱室内实验研究——以辽河油田S625区块为例

石油地质与工程2021年11月PETROLEUM GEOLOGY AND ENGINEERING 第35卷第6期文章编号：1673–8217（2021）06–0068–05潜山油藏减氧空气驱室内实验研究——以辽河油田S625区块为例张鸿1，2，王岐3，马宝全1（1．中国石油大庆油田有限责任公司勘探开发研究院，黑龙江大庆163712；2．国家能源稠（重）油开采研发中心，辽宁盘锦124010；3．中国石油大庆油田有限责任公司第二采油厂，黑龙江大庆163414）摘要：为改善辽河油田潜山油藏S625区块注水开发中后期产量递减快、采收率低、注水难度大等问题，在室内采取不同含氧量减氧空气配置实验方法，并借助物理模型、高温高压PVT等实验装置，开展减氧空气驱实验。

结果表明，地层温度压力下，静态低温氧化后原油中轻质组分减少，重质组分增加；随含氧量增多，氧化程度增强，O2利用率与转化率升高，产出气中CO2含量增加，但不高于0.6%。

油藏温度较低时（110 ℃），随含氧量增多，低温氧化作用对驱油效率贡献率增大，但含氧量变化对气驱驱油效率影响不明显。

在地层温度下注减氧空气比单纯注氮气对原油膨胀性能好，低于饱和压力时，随着压力增加，原油溶解能力增强；同一压力下，含氧量越多，原油溶解能力越强，体积系数越大，有利于提高原油采收率。

关键词：潜山油藏；减氧空气驱；低温氧化；溶胀实验中图分类号：TE357 文献标识码：ALaboratory experimental study on oxygen reducing air flooding in buried hill reservoirAll Rights Reserved.--by taking S 625 block of Liaohe oilfield as an exampleZHANG Hong1, 2, WANG Qi3, MA Baoquan1(1. Exploration& Development Research Institute of Liaohe Oilfield Company, PetroChina, Panjin, Liaoning 124010, China;2.National Energy Heavy Oil R&D Center, Panjin, Liaoning 124010, China;3.No.2 Oil Production Plant of DagangOilfield Co., Ltd., PetroChina, Daqing, Heilongjiang 163414, China)Abstract: In order to solve the problems in the middle and late stage of water injection development in blockS625 of Liaohe oil field, such as rapid production decline, low recovery great difficulty on water injection andetc., the experimental methods of oxygen reducing air configuration with different oxygen content were adoptedin laboratory. By means of physical model, high-temperature and high-pressure PVT and other experimentaldevices, the experimental study on oxygen reducing air flooding is carried out. The experimental results show:after static low-temperature oxidation under formation temperature and pressure, the light components incrude oil decrease and the heavy components increase; with the increase of oxygen content, the oxidationdegree becomes obvious, the oxygen utilization and conversion rates increase, and CO2 concentration in theproduced gas increases, not more than 0.6%. When the reservoir temperature is low (110 ℃), with the increaseof oxygen content, the contribution rate of low-temperature oxidation to oil displacement efficiency increases,but the change of oxygen content has no obvious effect on gas displacement efficiency. Under the formationtemperature, oxygen reducing air injection is better than nitrogen injection on the expansion performance ofcrude oil. Below the saturation pressure, the solubility of crude oil increases with the increase of pressure.Under the same pressure, the higher the oxygen content, the stronger the crude oil solubility and the larger the收稿日期：2021–04–22；修订日期：2021–05–19。

一种醋酸甲酯羰基化合成醋酐新催化系统的优化研究_张华西_曾健_谭平华_李荣_陈群

[7] 吕志凤, 战风涛. 用 H2O2-有机酸氧化脱除催化裂化柴油中的硫化物[J]. 石油大学学报(自然科学版), 2001, 25 (3): 26-29.
[8] 陈兰菊, 赵地顺, 郭绍辉. 改性氧化铝负载氧化物催化氧化噻吩的脱硫研究[J]. 化学学报, 2007, 65(16): 17181722.
[5] 王鹏, 傅军. 含噻吩烷烃在分子筛上裂化脱硫的研究[J]. 石油炼制与化工, 2000, 31(3): 58-62.
[6] Carniti P, Gervasini A, Biella S, et al. Niobic acid and niobium phosphate as highly acidic viable catalysts in aqueous medium: Fructose dehydration reaction [J].Catal Today,2006,118(3):373-378.
铑质量浓度对反应的影响实验结果如图 3 所示。
于醋酐生成有促进作用，由图 4 可见，碘甲烷质量分数在 15%左右时醋酐生成速率最大，继续提高碘甲烷含量对碘甲烷和 Rh (CO)2I2-的氧化加成作用意义已不大。 2.2.3 锂盐浓度的影响
锂盐质量浓度对反应的影响实验结果如图 5 所示。
图 5 锂盐质量浓度对醋酐生成速率的影响
Catalytic oxidative desulfurization of gasoline over niobium acid modified USY molecular sieve JI Gui-jie, SHEN Jian
(College of Petrochemical Technology, Liaoning University of Petroleum and Chemical Technology, Fushun 113001, China) Abstract: A Nb/USY catalyst with 15% of Nb by mass was prepared by impregnation method, and characterized by XRD and BET. The catalytic oxidative desulfurization performances of the catalyst for gasoline were investigated by using the isooctane containing thiophene as the simulated gasoline and H2O2 as oxidant. The results showed that the Nb/USY catalyst had very good dispersion of Nb on the surface of USY, and exhibited excellent performance of catalytic oxidation desulfurization. Under the conditions of reaction temperature of 50℃, reaction time of 90min, the molar ratio of the oxidant to thiophene of 10:1, and the mass ratio of the catalyst to the gasoline of 1:100, the desulfurizition rate of the simulated gasoline was up to 83%. Keywords: Nb/USY; catalyst; thiophene; gasoline; oxidative desulfurization; hydrogen peroxide

CO低温氧化催化剂研究进展

CO低温氧化催化剂研究进展杨德强;周庆华【摘要】The CO oxidation,which involving duwhstrial, environmental, military, and many aspects of human life, has been one of the hot catalytic field. Noble metal catalysts have high activity, good stability, long life, etc., but with the very expensive price,it is necessary to search for the non-noble metal catalyst which have good catalytic activity and lower price. This paper gives a review of CO oxidation catalysts which including noble metal and non-noble metal catalysts.%CO催化氧化涉及工业、环保、军事和人类生活的多个方面,一直是催化领域的热点之一.贵金属催化剂有活性高,稳定性好,寿命长等优点,但价格昂贵,研究开发价格低廉,活性较好的非贵金属催化剂也越来越受到了人们的重视.本文将CO氧化催化剂分为贵金属和非贵金属两类进行了综述.【期刊名称】《化学工程师》【年(卷),期】2011(000)008【总页数】3页(P36-38)【关键词】CO氧化;贵金属;非贵金属【作者】杨德强;周庆华【作者单位】黑龙江中医药大学,黑龙江哈尔滨150040;黑龙江中医药大学,黑龙江哈尔滨150040【正文语种】中文【中图分类】O643.32空气污染是当今社会的重要环境问题之一，CO又是释放到空气中最多的气态染物之一。

低热-NaOH联合处理剩余污泥释放碳源的效果

第30卷第6期2022年12月V ol.30 No.6Dec.2022安徽建筑大学学报Journal of Anhui Jianzhu UniversityDOI：10.11921/j.issn.2095-8382.20220609低热-NaOH联合处理剩余污泥释放碳源的效果唐玉朝1，2，蔡丽丽1，2，陈园1，2，刘俊3（1. 安徽建筑大学环境与能源工程学院，安徽合肥 230601；2. 环境污染控制与废弃物资源化利用安徽省重点实验室，安徽合肥 230601；3. 安徽中环环保科技股份有限公司，安徽合肥 230071）摘要：为了研究低热-NaOH联合处理剩余污泥，获得胞内碳源释放的最佳方案，测定破解后污泥上清液中的SCOD、蛋白质和多糖浓度，分析其随NaOH投加量、水浴温度、以及反应时间的变化。

结果表明，低热-NaOH联合处理剩余污泥的最佳条件是NaOH投加量3.0 g/L、水浴温度60 ℃、反应时间24 h。

在此条件下，上清液中SCOD、蛋白质和多糖浓度分别达18 341.4 mg/L、1 434.53 mg/L、324.8 mg/L。

经污泥破解前后粒度对比分析，污泥破解前后中值粒度分别为30.2 μm和8.71 μm，相差荧光显微镜观显示污泥絮体被破坏。

研究显示，低热-NaOH联合处理可在较低能耗下充分释放剩余污泥碳源，研究结果可为优化热碱法预处理剩余污泥提供依据。

关键词：低热；NaOH；剩余污泥；SCOD中图分类号：X703 文献标识码：A 文章编号：2095-8382（2022）06-062-06Effect of Low Temperature Thermal and NaOH Treatment on Carbon Release fromExcess SludgeTANG Yuchao1，2，CAI Lili1，2，CHEN Yuan1，2，LIU Jun3（1. School of Environment and Energy Engineering，Anhui Jianzhu University，Hefei 230601，China；2. Anhui Provincial Key Laboratory of Environmental Pollution Control and Resource Reuse，Hefei 230601，China；3. Anhui Zhonghuan Environmental Protection Technology Co.LTD，Hefei 230071，China）Abstract：To study the optimal scheme to obtain the intracellular carbon release from excess sludge with low temperature thermal and NaOH treatment，the concentrations of SCOD， protein and polysaccharide in the treated sludge supernatant were determined，and their relationship with NaOH dosage，water bath temperature and reaction time were analyzed. The results show that the optimal scheme of low grade fever and NaOH treatment for the excess sludge were a NaOH dosage of 3.0 g/L，a water bath temperature of 60 ℃，a reaction time of 24 h，and the concentrations of SCOD，protein and polysaccharide in the supernatant reached 18 341.4 mg/L，1 434.53 mg/L and 324.8 mg/L，respectively. The median particle size before and after sludge treatment was 30.2 μm and 8.71 μm， respectively. The phase-contrast and fluorescence microscopy showed that the floc sludge was destroyed. The study proved that the combined low temperature thermal and NaOH treatment can fully release the carbon of excess sludge with low energy consumption，and provides references for optimizing the thermo-alkaline pretreatment of excess sludge.Keywords：low thermal；NaOH；excess sludge；SCOD收稿日期：2021-07-08基金项目：国家自然科学基金项目（51978003；51578002）作者简介：唐玉朝（1975-），男，副教授，博士，主要研究方向为水处理理论与技术；蔡丽丽（1996-），女，硕士研究生，主要研究方向为水处理理论与技术。

Support Low-temperature_oxidation_of_CO_catalysed_by_Co3O4

Part Ⅰ Supplementary FiguresFigure S1 TEM images of the cobalt hydroxide carbonate precursor obtained by the precipitation of cobalt acetate tetrahydrate dissolved in ethylene glycol with aqueous sodium carbonate solution at 160 ℃. This nanorod-shaped solid precursor has a diameter of 10–20 nm and a length of 200–300 nm.SUPPLEMENTARY INFORMATIONdoi: 10.1038/nature07877Figure S2 TEM images of Co3O4 nanoparticles synthesized following the same procedure as the nanorods but precipitated at 80 ℃.a, Low-magnification. b-c, High-magnifications. d, HRTEM image. e-f, HRTEM images viewed along the [110] and [100] orientations with inserted micro-diffraction patterns. g, Schematic 3-D representation of a truncated octahedron, and its projection along the [110] (h) and [100] (i) orientations. When viewed along the [110] orientation, the nanoparticle is bound by four {111} and two {001} facets. When viewed along the [100] orientation, the nanoparticle shows {001} facets (two (001) and two (010)). Hence, the morphology of the nanoparticle is a truncated octahedron, surrounded by eight {111} and six {001} planes.Figure S3 Desorptions of H2O and CO2 from the Co3O4 nanorods used for CO oxidation at -77 ℃ for 12 h on stream. The sample (200 mg) just after the reaction was purged with a 20 vol% O2 / He mixture (50 ml/min), and the temperature was naturally increased from -77 ℃ to room temperature by removing the dry-ice cooling bath and then gradually increased to 450 ℃ at a rate of 10 ℃/min and kept at that level for 30 min. The effluent gas was monitored by a mass spectrometer. The desorption of CO2 at -77 ~ -60 ℃ represents the very weakly adsorbed CO2 on the catalyst surface, while the desorption of CO2 at ~100 ℃ corresponds to the decomposition of carbonates and/or bicarbonates. It is estimated that ~98% of the produced CO2 leaves the catalyst surfaces and appears in the outlet stream, and only ~2% of the CO2 that is formed is weakly adsorbed and/or deposits as carbonates on the catalyst surfaces. Desorption of water takes place mainly at 250-380 ℃, suggesting a strong adsorption on the surface. This indicates that the carbonates and H2O/OH- species are formed during the course of the reaction and block the active sites gradually, hindering the adsorption of CO and oxygen. The carbonate species might be chemically, but only weakly, adsorbed and can be easily removed, whereas the H2O/OH- species might be strongly adsorbed, thereby requiring a higher temperature for desorption.Figure S4 Effects of water, carbon dioxide and propane on the oxidation of CO over Co3O4 nanorods.a, 0.50 vol% CO / 0.26 vol% O2 / 8.20 vol% H2O / He. b, 0.51 vol% CO / 0.51 vol% C3H8 / 0.26 vol% O2 / 8.33 vol% H2O / 15.33 vol% CO2 / He. c, 0.51 vol% CO / 0.49 vol% C3H8 / 2.89 vol% O2 / 8.62 vol% H2O / 15.42 vol% CO2 / He (a stoichiometric amount of O2 for the combustion of both CO and propane). d, Propane oxidation in the feed stream of (c). CO is readily oxidized to CO2 at 200 ℃, but propane is only marginally oxidized to CO2 and H2O. The total oxidation of propane is achieved at 350 , and the reaction is rather stable at 400 for 32 h on-stream. 200 mg (40-60 mesh) catalyst sample was pre-treated with a 20 vol% O2 / He mixture (50 ml/min) at 450 for 30 min. The feed gas flow rate was 50 ml/min, and the concentrations of CO, H2O, CO2, C3H8 and O2 in the feed streams were chosen according to the exhaust gas composition emitted from a gasoline-fuel engine.Figure S5 TEM images of the used Co3O4 samples in Figure S4. a-b, Run (a). c-d, Run (b). e-f, Run (c). g-h, Run (d). All the used samples show well-maintained nanorod-shaped structures, demonstrating the high thermal stability of the Co3O4 nanorods even in the presence of large amounts of H2O and CO2 at 200-400 ℃.Part Ⅱ Calculation of Turnover FrequencyTable S1. Turnover frequency of the Co3+ site and apparent activation energy for CO oxidation over Co3O4 nanorods and nanoparticles.Temperature (℃)(s-1)Reaction rate* (mol g-1 s-1) TOFNanorods Nanoparticles Nanorods Nanoparticles** -86 1.69 × 10-6 2.76 × 10-7 1.01 × 10-20.83 ~ 1.66 ×10-2-77 3.91 × 10-6 4.66 × 10-7 2.33 × 10-2 1.40 ~ 2.80 × 10-2-65 7.98 × 10-6 1.01 × 10-6 4.75 × 10-2 3.03 ~ 6.07 × 10-2-56 1.25 × 10-5 1.81 × 10-67.45 × 10-20.54 ~ 1.09 × 10-1 Ea (kJ mol-1) *** 22 21A (molecule g-1 s-1) 8.0 × 1024 5.7 × 1023*The reaction rates were measured with a feed stream of 1.0 vol% CO / 2.5 vol% O2 / He, and the hourly gas space velocity was in the range of 6.0 × 104 - 9.0 × 105 ml g-1 h-1, through which the conversion of CO was adjusted to below 15% in order to calculate the reaction rates under differential reactor conditions.**Assuming a mean particle size of 20 nm and a fraction of surface defects of 5-10%.***Ea: Apparent activation energy; A: Pre-exponential factor.Co3O4 nanorods. TEM images of the Co3O4 nanorods (Fig. 1a-b) indicate that the length of a single rod is 200-300 nm, and the average value is approximately 250 nm. The widths of the {110} and {001} planes in the single rod are 10 and 15 nm, respectively, estimated from the HRTEM images (Fig. 1c-f). The surface area of the {110} plane is (10 × 15) × 2 + (10 × 250) × 2 = 5300 nm2, while the surface area of the {001} plane is (15 × 250) × 2 = 7500 nm2. So, the surface area of the {110} plane occupies about 41% of the total surface area of a single rod.According to the surface atomic configuration of the {110} plane in a unit cell (Fig. S6), there are eight O2- ions, four Co3+ ions and four Co2+ ions. The area of the {110} unit plane is estimated to be 0.808 nm × 1.143 nm = 0.9233 nm2. Thus, the total number of {110} unit plane in a single rod is 5300 / 0.9233 = 5740, and the total number of Co3+ ions is 22960. Since 1 g of Co3O4 nanorodscontains 4.4 × 1015 rods, the surface of one gram of Co3O4 nanorods has 2.52 × 1019 {110} unit planes, equaling to 1.01 × 1020 Co3+ ions. Together with the measured reaction rates, the TOFs based on the Co3+ site on the Co3O4 nanorods are calculated and summarized in Table S1.Figure S6 Atomic configuration of the {110} unit plane.Co3O4 nanoparticles. As shown in Fig. S2, the size of the Co3O4 nanoparticles is in the range of 10-30 nm; thus an average size of 20 nm is taken. The morphology of the nanoparticle is a truncated octahedron, surrounded by eight {111} and six {001} planes. Unlike the nanorod, the nanoparticle does not expose the reactive {110} plane. The exposed {111} and {100} planes do not contain octahedrally coordinated Co3+, but their sub-layers do. As illustrated in the atomic configurations (Fig. S7), the sub-layer of the {100} plane contains four Co3+ cations, while there are three or one Co3+ cation(s) above or below the {111} plane.Since the active sites are usually the surface defects located in the corners and edges of the spherical particles in heterogeneous catalysts, it is highly possible that the atoms on the sub-layers are easily exposed in these defects and thus contribute considerably to the catalysis. Assuming a mean particle size of 20 nm and a fraction of surface defects of 5-10%, the maximum number of Co3+ site exposed on the surface of one gram Co3O4 nanoparticles is approximately 1.0 ~ 2.0 ×1019. Accordingly, the TOFs of the Co3+ site are estimated and also summarized in Table S1.Figure S7 Atomic projections of the {100} and {111} planes in Co3O4 nanoparticle showing the atomic configurations in the sub-layers.It is interesting to note that the turnover frequencies of the Co3+ site are approximately in the same level for the nanorods and the nanoparticles. This is further evidenced by the fact that the apparent activation energy for both cases is essentially the same (21-22 kJ mol-1). Therefore, the difference in the reaction rate constants between the nanorods and the nanoparticles is due merely to the variation in the number of the active Co3+ site.。

氧化锌纳米棒阵列的生长

Aligned ZnO Nanorod Arrays Grown Directly on Zinc Foils andZinc Spheres by a Low-Temperature Oxidization Method用低温氧化方法直接在锌箔和锌颗粒培养排列有序的氧化锌纳米棒阵列ABSTRACT Vertically aligned, dense ZnO nanorod arrays were grown directly on zinc foils by a catalyst-free,low-temperature (450_500 °C) oxidization method. The zinc foils remain conductive even after the growth of ZnOnanorods on its surface. The success of this synthesis largely relies on the level of control over oxygen introduction.By replacing zinc foils with zinc microspheres, unique and sophisticated urchin-like ZnO nanorod assemblies can be readily obtained.摘要垂直有序密排的氧化锌纳米棒阵列直接通过无催化剂，低温（450~500°C）氧化法在锌箔上生长。

在氧化锌纳米棒生长在它表面上后，锌箔仍然具有导电性。

合成能够成功在很大程度上依赖于对引导氧气控制程度。

通过将锌箔更换成锌微球，独特和复杂的海胆样氧化锌纳米棒组件很容易获得。

Z inc oxide (ZnO) is recognized as oneof the most important photonic materialsfor applications in the blue_ultraviolet region owing to its directwide band gap (_3.37 eV) and large excitationbinding energy (60 meV at roomtemperature).Stimulated by the recentdiscovery of belt like morphology and therealization of room-temperature UV lasingfrom ZnO nanowires,ZnO nanostructuresin the form of nanorods, nanowires, andnanobelts have attracted a great deal of attentionfrom the research community.Especially,substantial effort has been devotedto the fabrication of vertically aligned ZnOnanowire arrays because these arrays demonstratedsuperior optical and field emissionproperties that make them promisingcandidates for applications in UV lasers,light-emitting diodes (LED),solar cells,and field emission displays.To fabricate vertically aligned ZnO nanorodarrays, three main techniques were usuallyused so far. The first technique is basedon the well-known vapor_liquid_solid(VLS) growth mechanism,10 in which goldnanoparticles were used as the catalyst todirect the nanowire growth, a-plane sapphirewhich has perfectlattice matchupwith ZnO c plane wasused as the growthsubstrates, and thegrowth was conductedat relativelyhigh temperatures of由于其直宽禁带和大的激励结合能，氧化锌是公认的应用于蓝紫外地区最重要的光子材料之一,由于带状形态发现的促进和室温紫外激光发射的实现，氧化锌纳米线，以纳米棒，纳米线，和纳米带形式存在的纳米氧化锌吸引了研究机构大量的注意力。

LOW TEMPERATURE CO OXIDATION CATALYST

专利名称：LOW TEMPERATURE CO OXIDATION CATALYST发明人：SUNG, Shiang,KOEGEL, Markus申请号：EP20773823.8申请日：20200319公开号：EP3941620A1公开日：20220126专利内容由知识产权出版社提供摘要：The present disclosure is directed to a low temperature carbon monoxide (LT-CO) oxidation catalyst composition for abatement of exhaust gas emissions from a lean burn engine. The LT-CO oxidation catalyst composition includes an oxygen storage component (OSC), a first platinum group metal (PGM) component, and a promoter metal, wherein the OSC is impregnated with the first PGM component and the promoter metal and the LT-CO oxidation catalyst composition is effective for oxidizing carbon monoxide (CO) and hydrocarbons (HC) under cold start conditions. Further provided are catalytic articles including the LT-CO oxidation catalyst composition, which may optionally further include a diesel oxidation catalyst (DOC) composition (giving an LT-CO/DOC article). Further provided is an exhaust gas treatment system including such catalytic articles, and methods for reducing a HC or CO level in an exhaust gas stream using such catalytic articles.申请人：BASF Corporation地址：100 Park Avenue Florham Park, NJ 07932 US国籍：US代理机构：Finnegan Europe LLP 更多信息请下载全文后查看。

Pd(100)氧化表面上低温丙烷氧化的活性相研究

物理化学学报Acta Phys. -Chim. Sin. 2023, 39 (10), 2305033 (1 of 8)Received: May 16, 2023; Revised: June 12, 2023; Accepted: June 13, 2023; Published online: June 28, 2023. *Correspondingauthors.Emails:*************.cn(K.W.);*****************.cn(X.Z.);Tel.:+86-10-62754005(K.W.).The project was supported by the National Natural Science Foundation of China (22222102, 21821004, 21927901). 国家自然科学基金(22222102, 21821004, 21927901)资助项目© Editorial office of Acta Physico-Chimica Sinica[Communication] doi: 10.3866/PKU.WHXB202305033 Active Phase on Oxidized Pd(100) for Low-Temperature Propane OxidationMeijia Xu, Yuchen Zhang, Yifan Zhu, Changlin Li, Zi-Ang Wu, Xiong Zhou *, Kai Wu *College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.Abstract: Palladium, a key component of three-way catalysts used in automobile exhaust treatment, plays a pivotal role in complete oxidation of alkanes and low-temperature oxidation of CO. Under oxygen-rich conditions, a thin oxide layer spontaneously forms on the palladium surface. To understand the influence of the oxidized palladium surface on the active phase of low-temperature hydrocarbon oxidation, we have conducted a comprehensive study of the oxidation process on Pd(100) and its impact on propane oxidation. Our experimental results reveal that under varying oxidation conditions, the Pd(100) surface sequentially forms three different monolayered oxide phases, namely, (2 × 2)-O, (5 × 5)-PdO and (√5 × √5) R 27°-PdO. The oxygen coverage correspondingly increases in the order of 0.25 monolayer, 0.56 monolayer and 0.8 monolayer. Notably, (5 × 5)-PdO is identified for the first time by high-resolution scanning tunneling microscopy. Experiments show this structure exhibits typical chiral features with its two enantiomers observed in the experiments. The chiral features of the (5 × 5)-PdO structure may bear significant implications in practical applications like chiral catalysis. Based on high-resolution atomic imaging, we have proposed a new (5 × 5)-PdO structure model. In addition, it’s experimentally revealed that upon thermal treatments the (5 × 5)-PdO structure decomposes into the (√5 × √5) R 27°-PdO and the (2 × 2)-O structures, and the (√5 × √5) R 27°-PdO decomposes into the (2 × 2)-O structure as well. These results suggest that the thermal stability of these oxide phases is in the order of (2 × 2)-O > (√5 × √5) R 27°-PdO > (5 × 5)-PdO. We have also compared the catalytic activities of these three oxidation phases in low-temperature propane oxidation. The results show that only the (√5 × √5) R 27°-PdO could catalyze propane oxidation near room temperature. We have observed a significant number of oxygen defects in the (√5 × √5) R 27°-PdO, which also forms the reduced (2 × 2)-O phase. Both complete oxidation products H 2O and CO 2 are detectable by temperature-programmed desorption within two main temperature slots around 285 and 315 K. Neither the (2 × 2)-O nor the (5 × 5)-PdO phase shows an obvious catalytic activity. The superior oxidation activity of the (√5 × √5) R 27°-PdO phase might be associated with its higher O density and hence more active O species within the structure. Our study indicates that the (√5 × √5) R 27°-PdO serves as the active phase for the low-temperature propane oxidation. These insights would help understand the working mechanisms of three-way catalysts and should be of great importance for the development of efficient and low-temperature three-way catalysts.Key Words: Palladium oxide; Chiral oxide; Low-temperature propane oxidation; Scanning tunneling microscopyPd(100)氧化表面上低温丙烷氧化的活性相研究徐美佳，张宇琛，朱一帆，李昌林，吴子昂，周雄*，吴凯*北京大学化学与分子工程学院，北京 100871摘要：钯作为汽车尾气处理的三效催化剂的关键成分，在烷烃的完全氧化和CO低温氧化中扮演着重要催化角色。

低熔点琼脂糖分子量

低熔点琼脂糖分子量英文回答：Low melting point agarose is a type of agarose that has a lower melting temperature compared to regular agarose. It is commonly used in molecular biology techniques such as gel electrophoresis. The molecular weight of low melting point agarose can vary depending on the manufacturer and specific product.One of the advantages of using low melting point agarose is that it allows for easy recovery of DNA or RNA from the gel after electrophoresis. Since it has a lower melting temperature, the gel can be melted at a lower temperature, which helps to preserve the integrity of the nucleic acids. This is particularly useful when working with sensitive samples or when the DNA or RNA needs to be further analyzed or purified.For example, let's say I am conducting a PCR experimentand I want to analyze the amplified DNA fragments using gel electrophoresis. I can prepare a gel using low melting point agarose and load my PCR products onto the gel. After electrophoresis, I can visualize the DNA bands under UV light. If I want to extract a specific DNA band for further analysis, I can simply cut out the band from the gel and melt it at a low temperature to recover the DNA. This allows me to isolate the DNA without the need foradditional purification steps, saving time and effort.Another advantage of low melting point agarose is that it can be used to embed living cells or tissues for histological analysis. Since it has a lower melting temperature, it is less likely to damage or denature the biological samples compared to regular agarose. This is particularly important when studying delicate tissues or cells that are sensitive to heat or mechanical stress.For example, let's say I am studying the morphology of a specific tissue in a mouse model. I can embed the tissue in a gel made of low melting point agarose and then perform histological staining and analysis. After the analysis, Ican simply melt the gel at a low temperature to recover the tissue for further studies or preservation. This allows meto study the tissue in its native state without the risk of damaging or altering its structure.中文回答：低熔点琼脂糖是一种相对于普通琼脂糖具有较低熔点的琼脂糖。

高卤染料废水采用UV

生态毒理学报Asian Journal of Ecotoxicology第18卷第6期2023年12月V ol.18,No.6Dec.2023㊀㊀基金项目:国家自然科学基金资助项目(52070111)㊀㊀第一作者:任航(1996 ),男,硕士,研究方向为废水中有机卤代物的高级还原脱卤,E -mail:********************* ㊀㊀*通信作者(Corresponding author ),E -mail:*******************.cnDOI:10.7524/AJE.1673-5897.20230513001任航,熊富忠,李菲菲,等.高卤染料废水采用UV/SO 2-3工艺减毒过程中的中间产物及其毒性变化规律研究[J].生态毒理学报,2023,18(6):225-236Ren H,Xiong F Z,Li F F,et al.Variation of intermediates and toxicity in high halogen dye wastewater during UV/SO 2-3process for detoxification [J].A -sian Journal of Ecotoxicology,2023,18(6):225-236(in Chinese)高卤染料废水采用UV /SO 2-3工艺减毒过程中的中间产物及其毒性变化规律研究任航1,熊富忠2,李菲菲1,陈吕军1,*1.清华大学环境学院,北京1000842.北京大学环境科学与工程学院,北京100871收稿日期:2023-05-13㊀㊀录用日期:2023-08-13摘要:染料废水含有大量难降解有机污染物,其中的有机卤代物通常具有较大的毒性和生态风险,但这类物质在常规的生物处理和化学处理工艺中的去除效果不佳㊂针对染料废水的脱卤困境,研究采用UV/SO 2-3高级还原工艺对染料废水进行还原脱卤㊂在初始pH 为8.5,SO 2-3投加量为40mmol ㊃L -1的条件下,废水中52.2%的可吸附有机卤素(adsorbable organic halogens,AOX)可以在反应开始6h 后被去除,更高的初始pH 和更大的SO 2-3投加量均有利于提升AOX 的去除率㊂中间体的定性和半定量研究揭示了染料废水中部分氯代苯胺类物质的还原脱卤路径,发现苯胺很可能是这些物质还原脱卤的主要产物㊂废水中有机物的平均预测毒性揭示了还原过程中废水急性毒性的变化趋势㊂这一趋势与T 3发光杆菌和小球藻的急性毒性评价结果一致㊂此外,染料废水的AOX 浓度与T 3发光杆菌的发光抑制率呈现正相关关系,而且染料废水经过还原脱卤后,尽管水中盐含量有所增加,其EC 50由1.26mg ㊃L -1增加到5.94mg ㊃L -1,这也证明了还原脱卤过程可以降低出水的急性毒性㊂因此,UV/SO 2-3过程可以通过对水中有机卤代物的还原脱卤降低出水中的AOX ,降低废水急性毒性和生态风险㊂关键词:染料废水;可吸附有机卤素;毒性评价;高级还原;UV/SO 2-3文章编号:1673-5897(2023)6-225-12㊀㊀中图分类号:X171.5㊀㊀文献标识码:AVariation of Intermediates and Toxicity in High Halogen Dye WastewaterDuring UV /SO 2-3Process for Detoxification Ren Hang 1,Xiong Fuzhong 2,Li Feifei 1,Chen Lyujun 1,*1.School of Environment,Tsinghua University,Beijing 100084,China2.College of Environmental Sciences and Engineering,Peking University,Beijing 100871,ChinaReceived 13May 2023㊀㊀accepted 13August 2023Abstract :Many refractory organic contaminants are contained in dye wastewater,especially the organic halogens,which are considered toxic and ecologically risky.Their removal is unsatisfactory by conventional bioreactors andchemical process.In this study,UV/SO 2-3,one of the advanced reduction processes,was selected to address this de -halogenation trouble in dye wastewater treatment.When the initial pH of dye wastewater is 8.5and SO 2-3dosage is40mmol ㊃L -1,52.2%of adsorbable organic halogens (AOX)will be removed within 6h.Higher initial pH value226㊀生态毒理学报第18卷and higher SO2-3dosage are favorable to dehalogenation.The identification and relative quantification of intermedi-ates revealed the dehalogenation pathway of polychlorinated aniline,and aniline may be the main reducing product. The toxicity reduction was indicated by the variation of average predicted acute toxicity value of multiple organiccompounds,which was complied with the result of acute toxicity evaluation by Photobacterium phosphoreum T3 and Chlorella pyrenoidosa.The positive correlation between the luminescence inhibition rate and AOX concentra-tion is verified,and the EC50of this high-halogen dye wastewater increases from1.26mg㊃L-1to5.94mg㊃L-1afterdehalogenation,accompanied with increasing salinity.Acute toxicity reduction during UV/SO2-3process is revealed.Therefore,the UV/SO2-3process has been proven to decrease AOX and acute toxicity in dye wastewater.Keywords:dye wastewater;adsorbable organic halogens(AOX);toxicity assessment;advanced reduction process; UV/SO2-3㊀㊀染料废水是染料生产工艺中各工段排水组成的混合废水,其中主要的污染物包含染料分子㊁染料原辅料㊁中间体以及副产物等㊂未经处理的染料废水具有难降解有机物含量高[1-3]㊁无机盐离子含量高[1]的显著特征,常规生物处理和化学处理的效率很低,特别是对有机卤代物的去除效果较差,工艺出水将表现出较强的毒性和生态风险[4-6]㊂我国是全球最大的染料生产国和消费国,2020年总产量达76.9万t,占全世界总产量的70%,产品种类达到1000种之多[7-8],其中分散染料和活性染料的产量超过世界的50%㊂染料废水中的有机卤代物普遍具有持久性(persistence,P)㊁生物累积性(bioaccumulation,B)以及毒性(toxicity,T),具有巨大的生态风险,其中的许多物质已被列入美国环境保护局(United States En-vironmental Protection Agency,US EPA)的优先控制污染物㊁欧盟的高关注物质(substances of very high concern,SVHC)㊁中国严格限制有毒化学品名录等㊂仅杭州湾附近的一个工业园区的染料生产企业,每年就要排放>60t的可吸附有机卤素(adsorbable or-ganic halogens,AOX)[1]㊂Gellert[9]和Emmanuel等[10]的研究也发现,一些废水中AOX的含量与发光细菌㊁淡水藻和大型蚤等受试生物表征的生物毒性具有很强的相关性㊂为了应对高卤染料废水的有机卤代物去除困境,降低排水毒性和生态风险,新工艺的开发势在必行㊂尽管高级氧化工艺(advanced oxidation proces-ses,AOPs)产生的自由基具有较高的氧化还原电位(oxidation-reduction potential,ORP)和选择性[11-14],对难降解有机物有较好的去除效果,但当废水中含有浓度较高的卤离子(Cl-㊁Br-等)时,将产生氧化性较弱的含卤自由基或氧化物[15-18],降低有机物矿化率的同时也会产生次生有机卤代物,增加出水中AOX 的含量㊂而且,随着废水中Cl-含量的增加,AOPs 出水中的AOX浓度与急性毒性将同时增加[19-20]㊂高卤废水经过AOPs的处理后,尽管有机物有所减少,但常出现排水毒性不降反升的现象[16,21]㊂高级还原工艺(advanced reduction processes, ARPs)因产生的还原性自由基普遍具有很低的ORP,在与有机物反应的同时并不会活化水中的卤离子,对水中卤代物具有很好的去除作用[22-24],在有机物风险控制的研究中得到关注㊂还原性自由基同样可以与有机卤代物发生反应,将有机物分子中的有机卤原子转化为游离的无机卤离子㊂相比其他还原工艺,仅有采用UV作为激发方式时才会产生e-aq (ORP=-2.9~-2.6V)[25-26],因此,UV/SO2-3去除有机卤代物的动力学和反应机理在近年来得到广泛研究,其对卤代脂肪烃氯乙酸[23]和卤代芳香族化合物2,5-二氯硝基苯[24]等都有很高的去除效率,还原中间体的毒性也会逐渐降低[24]㊂不过,尽管UV/SO2-3过程对染料废水中卤代芳香族化合物具有很强的还原脱卤潜力,但尚无在废水中应用的先例,其对脱卤和毒性控制的效果有待研究㊂排水急性毒性的升高是采用AOPs处理高卤染料废水时面临的风险[21],而应用ARPs进行还原脱卤的最终目标是为了降低排水毒性㊂生物毒性试验在工业废水毒性评价中一直发挥着重要作用㊂发光细菌[9,27]和淡水藻[2829]等具有世代时间短㊁对环境敏感以及成本相对较低的特点,因而常被用于废水的毒性检测㊂不同的受试生物通常对污染物具有不同的敏感度,开展多种毒性试验有利于全面研究废水毒性的变化,特别是小球藻作为生态系统的初级生产者,能够更好地反映废水的生态风险[30-31]㊂因此,本研究选择某染料生产企业的染料废水二级处理出水为研究对象,采用UV/SO2-3过程对废第6期任航等:高卤染料废水采用UV/SO 2-3工艺减毒过程中的中间产物及其毒性变化规律研究227㊀水进行深度处理,研究ARPs 在废水还原脱卤中的应用潜力,分析这一过程中有机物种类和毒性的变化,并采用T 3发光杆菌和蛋白核小球藻评价出水毒性㊂1㊀材料与方法(Materials and methods )1.1㊀主要试剂本研究使用的主要药品:无水亚硫酸钠(Na 2SO 3,98%,上海麦克林)㊁氯化钠(NaCl ,99.5%,上海泰坦)㊁无水硫酸钠(Na 2SO 4,99%,中国国药集团)㊁硝酸(HNO 3,65%,北京现代东方)㊁硫酸(H 2SO 4,98%,北京通广化工)㊁盐酸(HCl ,36%,北京通广化工)㊁氢氧化钠(NaOH ,96%,上海泰坦)㊁二氯甲烷(CH 2Cl 2,99.9%,北京迈瑞达)㊂综合毒性试验的受试生物为发光细菌和蛋白核小球藻㊂明亮发光杆菌(Photobacterium phosphoreum T 3)的冻干粉由浙江清华长三角研究院提供,保存在-80ħ下㊂蛋白核小球藻(Chlorella pyrenoidosa )购自南京海洱斯生物科技有限公司㊂研究选用的高卤染料废水为某染料生产企业污水处理设施的处理出水,废水有机组成多样,且大多数含有苯环结构㊂企业采用的处理工艺为AAO ,废水在开始还原反应前预先经过铁粉/亚硫酸盐(Fe/PDS)工艺处理㊂通过GC -MS 谱图与美国国家标准技术研究院(NIST)提供的参考化合物谱库进行对比,选择可靠度在70%以上的物质,作为废水的主要有机组分,这些物质如表1所示㊂表1㊀UV /SO 2-3进水中主要有机物Table 1㊀Main organic substances in UV/SO 2-3influent序号No.保留时间/min Retention time/min污染物Contaminant 峰面积Peak area CAS 可靠度/%Reliability/%1 4.6984苯甲醛Benzaldehyde553209100-52-7942 4.9199苯胺Aniline37765962-53-3933 6.87492,3-环戊烯并吡啶2,3-cyclopentenopyridine99277533-37-99648.49274-氯苯胺4-chloroaniline 53794106-47-89758.8733N,N -二乙基苯胺N,N -diethylaniline89297991-66-79669.98082-(1-甲基环丙基)苯胺2-(1-methylcyclopropyl)aniline10952171579-33-690711.21832,4-二氯苯胺2,4-dichloroaniline248874554-00-797811.63732-叔丁基对甲苯酚2-amino -6-chlorobenzothiazole2394602409-55-476912.5281苯甲砜Methyl phenyl sulfone 829283112-85-4811012.65332-丙氧基苯甲醛2-propyloxybenzaldehyde 153********-12-5951112.83152,4,6-三氯苯胺2,4,6-trichloroaniline 851739634-93-5981213.264-丙氧基苯甲醛4-propyloxybenzaldehyde 1780135736-85-6871313.34674-氯-N,N -二乙基苯胺4-chlorophenyl -N,N -diethylamine1024732873-89-4911413.48633,4-二氯苯胺3,4-dichloroaniline21114195-76-1961514.09312,6-二叔丁基苯醌2,6-di -tert -butyl -p -benzoquinone39716719-22-2871614.45423,4-二乙基苯酚3,4-diethylphenol 228624875-85-4701715.19582,5-叔丁基酚2,5-di -tert -butylphenol 130********-45-6951815.3983-二乙基氨基酚3-diethylaminophenol15367891-68-9961915.5906N,N -二乙基-1,4-苯二胺N,N -diethyl -1,4-phenylenediamine368634593-05-0832017.06892,6-二异丙基苯甲醚2,6-diisopropyl anisole173********-52-7862117.56012,4,6-三溴苯胺2,4,6-tribromoaniline301016147-82-0962217.6901二乙基苯胺Dibenzylamine1580037103-49-1952318.3452-氨基-6-氯苯并噻唑2-amino -6-chlorobenzothiazole69421095-24-974228㊀生态毒理学报第18卷1.2㊀实验方法1.2.1㊀实验装置研究中的还原脱卤试验均在如图1所示的自制双层玻璃反应器中进行,玻璃夹层供冷却水通过,反应器顶盖开口,分别安装紫外灯㊁传感器以及取样口㊂试验开始前打开反应器的冷却水,预热紫外灯(253.7nm 处的光子流为0.5μEinstein ㊃s -1)20min 以上㊂废水的初始pH 通过硫酸和氢氧化钠溶液(0.1mol ㊃L -1)进行调节㊂在试验过程中通过传感器对反应器内的温度和溶解氧浓度进行监测,调节冷却水的流量使反应器内流体温度保持在(20ʃ0.5)ħ㊂在反应开始后按照预设时间通过反应器的取样口进行取样,取出的液体样品经过0.45μm 的水系滤膜过滤后,立即放入4ħ下避光保存,并在取样后的24h 内完成分析,每个样品至少重复2次㊂图1㊀自制高级还原反应器(ARPs )Fig.1㊀Self -made reactor for advancedreduction processes (ARPs)1.2.2㊀发光细菌发光抑制试验菌种复苏方法参考‘水质急性毒性的测定发光细菌法“(GB/T 15441 1995)进行㊂将1mL 在4ħ下保存的2.5%氯化钠溶液加入盛有0.5g T 3发光杆菌冻干粉的安瓿瓶,摇匀后在4ħ下复苏2min ㊂使用2.5%的氯化钠溶液稀释菌液,调节发光杆菌浓度使发光量在200~600万光子单位之间㊂测定发光强度前,将180μL 的水样和20μL 的菌悬液混合后,通过微孔板振荡器(Titramax 1000,海道尔夫,德国)在20ħ下混合15min ㊂振荡完成后,通过酶联免疫检测仪(Infinite M200PRO ,帝肯,美国)测定完全混合后的相对发光强度,并根据式(1)计算相对发光抑制率㊂将4ħ下保存的2.5%氯化钠溶液作为空白对照,每组试验重复3次㊂相对抑制率=L 0-L eL 0ˑ100%(1)式中:L 0为对照组相对发光强度;L e 为试验组相对发光强度㊂1.2.3㊀小球藻生长抑制试验试验方法参考迟彤彤等[21]的研究,为获得对数生长期的小球藻,将5mL 含有小球藻的藻液接种到100mL 淡水小球藻培养基中(2mL 浓缩培养基用超纯水稀释至1L ,加入3ɢ海盐)进行扩培㊂接种后的藻液置于(25ʃ1)ħ的恒温光照培养箱(SPX -250B -Z ,博迅,上海,中国),控制每天光照和黑暗周期分别为14h 和10h ,早晚摇藻一次促进生长,并监测小球藻种群密度的变化㊂测定生长抑制率前,将1mL 待测水样与4mL 含有对数生长期小球藻的培养基混合均匀,测定并记录小球藻的初始密度,随后采用扩培的条件继续培养小球藻㊂在培养96h 后,测定不同样品中小球藻的密度㊂根据式(2)和式(3)计算小球藻生长抑制率㊂将模拟天然水作为空白对照,每组试验重复3次㊂μ=r 0-r er e ˑ100%(2)式中:μ为小球藻的生长抑制率;r 0为对照组小球藻平均生长率;r e 为试验组小球藻平均生长率㊂r =ln N t -ln N 0t(3)式中:r 为小球藻平均生长率;t 为小球藻的培养时间;N t 为培养t (d)后的藻细胞浓度;N 0为藻细胞的初始浓度㊂1.3㊀当量毒性单一有机物的急性毒性采用LC 50与EC 50进行描述,为衡量废水中多种有机物对一种受试生物的毒性效应,采用式(4)计算平均急性毒性㊂SMA V i =nATV i,1ˑ ˑATV i,n(4)式中:SMA V 为种平均急性毒性值;ATV 为急性毒性值;n 为有机物种类数㊂有机物急性与慢性毒性的预测数据均通过IRFMN 模型进行预测,预测通过VEGA 软件进行㊂1.4㊀仪器分析水中AOX 浓度采用总有机卤素测定仪(MultiX 2500,耶拿,德国)进行分析,分析方法参考颉亚第6期任航等:高卤染料废水采用UV/SO 2-3工艺减毒过程中的中间产物及其毒性变化规律研究229㊀玮[32]的研究㊂废水中有机组分的分析采用气相色谱质谱联用(GC -MS ,7890A -5795C ,安捷伦,美国)进行,分析方法详见此前研究[24]㊂1.5㊀相关性分析废水中AOX 浓度与受试生物抑制作用之间的相关性通过Spearman 相关性分析进行检验,显著性检验方式为双尾检验㊂假设AOX 浓度与受试生物的抑制率不相关,当P <0.05时,拒绝原假设,认为AOX 浓度与受试生物的抑制率相关㊂2㊀结果与讨论(Results and discussion )2.1㊀还原脱卤效能不同条件下UV/SO 2-3过程对废水中AOX 的去除效果如图2所示,UV 辐照和SO 2-3同样是废水高效还原脱卤的必要条件,更长的反应时间㊁更高的初始pH 以及更大的SO 2-3投加量都有利于提升AOX的去除,改善AOX 的去除效果㊂当初始pH 为8.5(未调节),SO 2-3投加量为40mmol㊃L -1时,6h 的反应可以去除废水中52.2%的AOX ㊂不同来源的废水在不同工艺下的AOX 去除情况如图2(a)所示,经过Fe/PDS 的处理后,废水中的AOX 可以在UV/SO 2-3工段去除52.2%,仅投加SO 2-3的对照组只去除了7.5%,而未经Fe/PDS 的废水,在UV/SO 2-3过程仅能去除8.3%㊂Fe/PDS 过程对脱卤效果的提升可能是通过降低废水色度,减少吸光物质与SO 2-3之间的紫外光子的竞争实现的[24,33-34]㊂初始pH 与SO 2-3投加量对还原过程的促进作用与其他合成废水的研究一致[22,35],这一规律在含图2㊀不同反应条件对还原脱卤效能的影响注:(a)不同系统,(b)pH ,(c)SO 2-3浓度,(d)AOX 残余浓度对反应时间的线性拟合;AOX 表示可吸附有机卤代物㊂Fig.2㊀Reducing dehalogenation under different conditionsNote:(a)Different system,(b)pH value,(c)SO 2-3concentration,(d)Linear fitting for AOX concentration to reaction time;AOX means adsorbable organic halogens.230㊀生态毒理学报第18卷有更加复杂成分的实际染料废水中并没有发生变化㊂SO 2-3投加量为40mmol㊃L -1时,随着初始pH 由3增加到12,AOX 的去除速率逐渐提升,1h 的反应对AOX 的去除由8%上升至18%,提升超过1倍;初始pH 为8.5时,随着SO 2-3投加量有由0增加到60mmol ㊃L -1,AOX 在6h 内的去除率由38.8%提升至56.5%㊂更高的初始pH 值提升了SO 2-3在S (Ⅳ)中的比重,更大的SO 2-3投加量则直接增加了S(Ⅳ)的总量,这2种方式都有助于提升关键还原性自由基e -aq 的产生量㊂在反应初期,AOX 在脱卤反应中的去除速率会随着剩余AOX 的减少而不断降低,表现出准一级反应的特征,这也与单一卤代物去除的过程一致㊂不过,相比单一目标卤代物短则几分钟,长则几十分钟的去除时间[36-37],染料废水还原脱卤的速率相对较慢,52.2%的AOX 去除就需要几百分钟的时间㊂这可能是水中无机盐离子的影响,特别是NO -3引起的竞争性抑制㊂NO -3及其还原产物可以通过对紫外光子的直接捕获和对e -aq 的消耗产生强烈的抑制作用,100mg ㊃L -1的NO -3就能通过竞争性抑制将目标卤代物的去除速率降低到不足原来的50%[24]㊂此外,即便SO 2-3的投加量已经达到了60mmol㊃L -1,反应开始3h 后AOX 的去除速率也逐渐趋于稳定㊂如图2(d)所示,近乎线性的AOX 浓度变化更加符合零级反应的特征,剩余SO 2-3在反应开始3h 后的浓度可能已经非常低了,脱卤效率也因此降低㊂2.2㊀还原脱卤路径染料废水的有机组成多样,且大多数含有苯环结构,在UV/SO 2-3过程中的变化非常复杂㊂为分析还原脱卤过程中有机组分及其毒性变化,通过GC -MS 对废水中主要有机组分进行定性分析,并根据有机物峰面积的相对变化分析有机物的转化㊂进水中主要有机物的相对含量在UV/SO 2-3过程中的变化如图3(a)所示,经过UV/SO 2-3过程的处理后,进水中可检出的主要有机物种类不断减少,特图3㊀废水主要有机组分的相对含量(a )㊁在UV /SO 2-3过程中的变化(b )和预测还原路径(c )Fig.3㊀Relative content (a)and variation (b)of main organic substances,and predicted reduction pathway (c)during UV/SO 2-3process第6期任航等:高卤染料废水采用UV/SO2-3工艺减毒过程中的中间产物及其毒性变化规律研究231㊀别是其中的有机卤代物,由进水中的7种减少到出水中的3种,且分子中卤原子的含量也呈现减少的趋势㊂值得注意的是,在众多有机物相对含量都持续降低的过程中,苯胺(aniline,AN)与4-氯苯胺(4-chloroaniline,4-CAN)的相对含量在反应过程中出现升高的现象,特别是AN,其在出水中的浓度甚至接近进水浓度的40倍㊂由图3(b)可知,中间体鉴定结果指示了几种主要有机物在还原反应中的变化㊂其中,水中的卤代芳香族化合物在还原反应开始前可以被检出的2,4, 6-三氯苯胺(2,4,6-trichloroaniline,2,4,6-TCAN),在反应开始3h后就无法检出了,并且在之后的反应过程中也没有再次检出㊂与之对应的是,在反应开始时几乎无法被检出的AN在UV/SO2-3过程开始后出现了强烈的信号㊂这表明2,4,6-TCAN很可能在UV/SO2-3过程中发生了还原脱卤反应,苯环上的Cl 被H直接取代㊂值得注意的是,4-CAN在不同历时下的废水中均有检出,而且相对含量持续增加,很可能是2,4,6-TCAN的还原脱卤过程中的一个中间体,随后经过进一步脱卤生成AN㊂此外,N,N-二乙基对苯二胺(N,N-diethyl-1,4-benzenediamine)的信号也在反应开始后消失了,N,N-二乙基苯胺(N,N-diethyl-benzenamine)的信号则在还原后才被检出,这表明AN的结构可能也会在还原反应中被破坏,其并不是还原反应的最终产物,这与此前的研究结果一致[24],因而最终产物的毒性效应可能会更低㊂根据定性与半定量分析的结果,可以得到如图3(c)所示的有机卤代物脱卤还原的预测路径㊂2.3㊀出水综合毒性2.3.1㊀毒性预测有机废水的毒性效应主要取决于水中有机组分的性质,采用VEGA软件预测废水中主要有机物的毒性效应值,得到包括鱼类LC50㊁大型蚤EC50和藻类EC50在内的预测结果㊂不同时间出水的平均急性毒性数值变化如图4所示,经过UV/SO2-3过程的处理,出水的SMA V普遍升高㊂其中,鱼类的SMA V数值大于藻类和大型蚤,而且随着处理时长的延长快速增加,说明出水中有机物对鱼类的急性毒性效应相对较弱㊂藻类和大型蚤的SMA V在处理过程中的变化相对较小,而且数值较低,水中有机物对其急性毒性效应较大㊂这一结果表明,有机卤代物在UV/SO2-3过程中整体上向着毒性降低的方向转化,还原脱卤可以降低出水对鱼类㊁藻类以及大型蚤的急性毒性效应,对鱼类的急性毒性具有显著的控制作用㊂2.3.2㊀发光细菌T3发光杆菌的受抑制情况如图5所示,尽管已经过处理,废水在进入UV/SO2-3反应前仍然表现出一定的急性毒性,经过还原脱卤后,出水对T3发光杆菌的发光抑制率由原来的50%降低至33%,说明急性毒性被减弱㊂值得注意的是,急性毒性的降低主要出现在还原反应开始2h之后,尽管此前废水中AOX的去除速率较快(图2(a)),但发光抑制作用图4㊀废水主要有机组分的种平均急性毒性值(SMAV)在UV/SO2-3过程中的变化Fig.4㊀Species mean acute toxicity value(SMA V)of mainorganic matter during UV/SO2-3process图5㊀UV/SO2-3过程出水对T3发光杆菌的发光抑制Fig.5㊀Luminescence inhibition of Photobacteriumphosphoreum T3by UV/SO2-3effluent232㊀生态毒理学报第18卷的变化并不显著㊂这表明废水中主要有机物在脱卤的过程中可能产生了少量毒性较强的还原中间体,而从第3小时开始才开始降低的发光抑制率,表明高毒性的中间体可能已经被去除㊂此后,随着更多卤代物的去除和AOX 浓度的持续降低,废水的急性毒性也不断降低㊂尽管毒性预测结果并非是T 3发光杆菌的毒性效应浓度,但鱼类㊁藻类以及大型蚤的效应浓度变化趋势与T 3发光杆菌是一致的,降低的速率也表现出慢-快-慢的规律,这表明T 3发光杆菌可能受有机物毒性的影响较大㊂2.3.3㊀小球藻小球藻生长抑制试验的结果如图6所示,废水经过UV/SO 2-3过程的处理后,对小球藻的生长抑制作用持续下降,这表明UV/SO 2-3过程对废水的还原脱卤有助于降低出水对水生态的影响㊂脱卤反应开始前,废水对小球藻的生长抑制率约为40%,在初始pH 为8.5的条件下,经过6h 的还原脱卤后,废水对小球藻的生长抑制作用几乎可以忽略不计,特别是在反应已经进行到5h 时,甚至还观察到了出水对小球藻生长的促进作用,这一趋势与SMA V 持续上升反映的变化是一致的㊂值得注意的是,尽管此时出水中仍含有约1.8mg ㊃L -1的AOX ,但是对小球藻的抑制作用已经几乎完全解除,这与T 3发光杆菌存在较大差异㊂这种差异表明,小球藻可能只对部分有机物敏感,随着这部分有机物的去除,小球藻受到的抑制作用持续降低,图6㊀UV /SO 2-3工艺出水对小球藻的生长抑制Fig.6㊀Growth inhibition of Chlorella pyrenoidosaby UV/SO2-3effluent因而并非废水全部的有机污染物都能对小球藻产生显著的急性毒性效应[21,31]㊂尽管如此,废水对小球藻的急性毒性效应在经过UV/SO 2-3过程的处理后得到控制,而且随着处理时间的增加,抑制作用持续降低,说明出水的急性毒性持续下降,还原脱卤有利于降低出水对小球藻的毒性效应㊂2.3.4㊀AOX 的毒性指示作用废水经过UV/SO 2-3过程的处理后,AOX 浓度与急性毒性均降低㊂废水有机组分的分析结果表明,一些高毒性有机卤代物在还原过程中被除去,但不同受试生物在毒性试验中有着不同的表现㊂为了验证这2种变化之间的相关性,研究AOX 浓度与急性毒性的关系,选择了不同处理条件下的出水AOX 和对应的受试生物抑制率作为数据集,进行Spearman 相关性分析,结果如图7所示㊂如图7(a)所示,AOX 浓度与T 3发光细菌发光抑制率呈现显著的正相关关系(P <0.01)㊂尽管不同反应条件下出水的水质条件各有差异,但AOX 浓度的变化趋势整体上与抑制率相同,AOX 可以指示染料废水的急性毒性㊂这与Gellert [9]和Emmanuel 等[10]的发现一致,这种正相关关系在染料废水的急性毒性上可能同样成立㊂不过,不同于T 3发光细菌,染料废水AOX 浓度与小球藻生长抑制率之间并未表现出显著的相关关系(图7(b)),相比AOX 浓度的变化,小球藻可能对其他条件的变化更加敏感㊂小球藻对于染料废水中有机卤代物毒性效应的指示作用相对较弱,这一结果与2.3.3中相关分析的结果一致㊂也正因此,小球藻作为一种初级生产者,其生长抑制试验能够作为T 3发光细菌毒性试验的补充,更加全面地评价出水毒性和生态风险㊂因此,染料废水的AOX 浓度可以指示染料废水的急性毒性,不过单一毒性试验的结果可能是片面的,综合运用多种受试生物进行毒性评价是非常必要的㊂染料废水在还原脱卤前后T 3发光杆菌的EC 50如图7(c)与图7(d)所示,还原脱卤前废水的AOX 浓度为3.26mg ㊃L -1,EC 50为1.26mg ㊃L -1,而经过还原脱卤后,废水的AOX 浓度降低至1.56mg ㊃L -1,而EC 50增加到5.94mg ㊃L -1㊂这一变化证明了UV/SO 2-3过程通过对废水中有机物的还原,在改变有机物种类的同时,降低了废水的急性毒性㊂此外,这一现象也进一步证实了染料废水的AOX 浓度与急性毒性之间存在正相关关系㊂第6期任航等:高卤染料废水采用UV/SO 2-3工艺减毒过程中的中间产物及其毒性变化规律研究233㊀图7㊀废水AOX 浓度与(a )T 3发光细菌发光抑制率㊁(b )小球藻的生长抑制率的相关性以及(c )进水和(d )出水的EC 50Fig.7㊀Correlation between AOX concentration and (a)luminescence inhibition rate of Photobacterium phosphoreum T 3and (b)growth inhibition rate of Chlorella pyrenoidosa ,and EC 50of (c)influent and (d)effluent2.4㊀排水生态风险评估多种有机物的预测SMA V 表明不同物种对有机物变化的响应强度存在差异,这种差异可能导致废水对水环境特定营养级的冲击,进而对水生态产生影响㊂染料废水经UV/SO 2-3过程处理后出水中的主要有机物及其毒性效应浓度如表2所示㊂首先,一些出水中残余的有机卤代物仍可对3种受试生物表现出较大的毒性,这表明废水脱卤对降低毒性和生态风险是必要的㊂其次,有机物对大型蚤的NOEC 一般低于鱼类和藻类,特别是有机卤代物,其NOEC 的数值远低于其他2种生物,说明大型蚤受到的长期影响可能较大㊂藻类的EC 50和NOEC 相对较大,受到的影响应该较小,这符合2.3.3中小球藻生长抑制试验的结果㊂这表明部分藻类作为初级生产者对有机污染的响应可能弱于直接捕获水中有机物的消费者(大型蚤),这可能是由于藻类主要吸收水中的无机物,对有机物的变化相对不敏感㊂因此,废水中有机物对消费者的影响大于作为初级生产者的藻类㊂无机离子也会表现出对多种水生生物的影响[38-39],进而产生对水生态的影响㊂经过还原脱卤后,染料废水中主要的无机盐离子为Cl -和SO 2-4,其浓度分别可达5150mg ㊃L -1和7800mg ㊃L -1㊂不过,这一浓度的无机离子在综合毒性试验中对发光细菌和小球藻表现出的抑制作用还不显著,其对水生态的影响也会相应较低㊂此外,这一浓度废水进入纳污区或综合污水处理厂后将得到大幅稀释,对水生态的影响将更加微弱㊂综上所述,UV/SO 2-3技术对染料废水中多种有机卤代物均具有还原脱卤的作用,可以减少水中。

Nanoparticulate gold catalysts for low-temperature CO oxidation

Journal of New Materials for Electrochemical Systems 7, 163-172 (2004) © J. New. Mat. Electrochem. SystemsNanoparticulate Gold Catalysts for Low-Temperature CO OxidationM. HarutaResearch Institute for Green Technology, National Institute of Advanced Industrial Science and Technology (AIST) 16-1 Onogawa, Tsukuba 305-8569, Japan(Received November 27, 2003; received revised form December 29, 2003) Abstract: Gold can be deposited as nanoparticles on a variety of support materials by coprecipitation, deposition-precipitation of Au(OH)3 , grafting of organo-gold complexes such as dimethyl-Au(III)-acetylacetonate, mixing of colloidal Au particles, and vacuum deposition. The unique and practically useful catalytic performance of Au emerges by the strong contact with the support, the selection of support materials, and the size control of Au particles. The oxidation of CO can take place even at a temperature as low as 200 K, owing to the moderate adsorption of CO on the edges and corners of Au nanoparticles and to the activation of O2 , probably at the perimeter interface with the supports. However, an exception is that acidic supports such as Al2O3-SiO2 and activated carbon do not lead to low temperature CO oxidation, which imposes an essential scientific question related to polymer electrolyte fuel cells. A comprehensive mechanism for low-temperature CO oxidation is presented that can account for the whole catalytic behavior of supported gold catalysts : an increase in TOF with a decrease in the diameter of Au particles, large difference in the enhancing effect of moisture among support metal oxides, zeroth order kinetics at concentrations of CO and O2 above 0.1 vol%, and low apparent activation energies. Key words: gold, nanoparticles, CO oxidation, catalyst preparation, structure sensitivity1. INTRODUCTIONGold was regarded to be catalytically inert, however, it is now well known that Au is about 1000 times more active than Pt in the electrochemical and catalytic oxidation of CO under basic but not acidic encironments[1-7]. Gold can also promote many other reactions when stabilized in the form of nanoparticles attached to metal oxide and activated carbon supports [8-12]. Since Au/Fe2O3 supported on zeolite-coated paper honeycomb was commercially used for an odor eater in modern Japanese rest rooms in 1992, R&D activity on the catalysis of Au has been rapidly growing in the world, expanding the frontiers of sciences and applications of the noblest metal of Au [9]. Over supported nanoparticulate Au catalysts, H2 oxidation and hydrogenation reactions of unsaturated hydrocarbons are structure insensitive and the rates per surface exposed metal atom (turn*To whom correspondence should be addressed: Fax:+81-29-861-8458; E-mail: m.haruta@aist.go.jpover frequencies, TOFs) are almost independent of the size and shape of Au particles [13]. In contrast, other reactions, typically CO oxidation and propylene epoxidation are markedly structure sensitive. Both the rate and selectivity are defined by the three major factors: contact structure of Au particles (the length of perimeter interface), selection of the support, and the size of Au particles. This means that catalyst preparation is crucially important for the catalysis by Au nanoparticles. Accordingly, the first attempt in this paper is to make a comprehensive overview of the techniques currently available for preparing nanoparticulate Au catalysts. The oxidation of CO is one of the simplest reactions, while it covers a wide range of applications from gas masks, gas sensors, indoor air quality control to hydrogen purification for polymer electrolyte fuel cells. The reaction attracts renewed interest both in fundamental [14] and applied research of catalysis and electrochemistry [1-3,7,15]. As summarized in Table 1, supported Au catalysts are superior to both the other supported noble metal163164M. Haruta / J. New. Mat. Electrochem. Systems 7, 163-172 (2004)catalysts and base metal oxides in room temperature catalytic activity and moisture enhancement. In this context, the second attempt in this paper is to deliver answers to the general questions why the combination of inactive components for the adsorption of CO and O2, Au with Al2O3 or TiO2, for example, can bring surprisingly high catalytic activity for CO oxidation [16] and why moisture enhances the catalytic activity [17]. The discovery of highly active Au catalysts was led by a simple assumption based on a volcano-like relation between the catalytic activity of metal oxides for the oxidation and the heat of metal oxide formation per one oxygen atom which corresponds to the metal-oxygen (M-O) bonding strength [11,18]. It had been expected that the combination of metals located at the opposite sides of the volcano plots, Ag or Au which has weaker M-O bonding than PtO2 with Mn, Fe, Co, Ni which have stronger bonding, might bring about complex oxides as active as PtO2 which has optimum M-O bonding strength. In fact, some gold composite oxides (later they were found to be Au nanoparitcles supported on transition metal oxides) were much more active than PtO2 in CO oxidation. Jaksic has intensively studied the nature, causes, and consequences of volcano plots of transition metals for hydrogen electrode reactions in an attempt to explore optimum synergetic intermetallic systems [19-21]. He has also extended his work to metal-oxide electrocatalytic systems for simultaneous anodic hydrogen and CO oxidation [15]. These achievements will surely flourish in the near future in providing novel electrode catalysts in fuel cell applications, as in the case of nanoparticulate Au catalysts. This article, devoted to the 70th anniversary of Professor Jaksic, therefore, will also convey acalcination of HAuCl4 crystallites dispersed on the support surfaces. Table 2 lists four categories of techniques that can deposit Au nanoparticles with diameters below 10 nm [22]. A suitable technique should be chosen depending on the kind of support materials such as basic or acidic metal oxides, carbonaceous materials, or single crystals.Table 2. Preparation techniques for nanoparticulate Au catalysts.Categories Preparation of mixed precursors of Au and the metal component of supports Preparation techniques Coprecipitation (hydroxides or carbonates) CP co-sputtering (oxides) in the presence of O2 CS amorphous alloy (metals) AA Support materials Be(OH)2, TiO2*, Mn2O3, Fe2O3, Co3O4, NiO, ZnO, In2O3, SnO2 Co3O4 ZrO2 Ref. 4, 23-26 2728Strong interaction of Au precursors with support materialsdeposition-precipitation Mg(OH)2*, Al2O3, TiO2, (aqueous HAuCl4 Fe2O3, Co3O4, NiO, ZnO, solution) DP ZrO2, CeO2, Ti-SiO2 liquid phase grafting (organogold complex in organic solvents) LG gas phase grafting (organogold complex) GG TiO2, MnOx, Fe2O329-3334, 35all kinds, including SiO2, Al2O3-SiO2, and activated C TiO2, activated C36, 37Mixing colloidal Au with support materials Model catalysts using single crystalcolloid mixing CMvacuum deposition VD Defects are the sites for (at low temperature) deposition. MgO, Si, TiO212, 38, 39 40-46Table 1. Comparison of performances of three classes of catalysts for CO oxidation at room temperature.The addition of Mg citrate during or after coprecipitation or deposition-precipitation is indispensable for depositing Au as nanoparticles.Catalyst Nanoparticulate gold Other noble metals Base metal oxidesActivity Excellent Poor GoodMoisture Activated Activated Deactivatedcomprehensive overview of the requirements and the working mechanism of Au catalysts.The first category is characterized by the preparation of wellmixed precursors, for example, hydroxide and/or carbonate, oxide, or metal mixtures of Au with the metal component of the support by coprecipitation (CP)[4,23-26], co-sputtering by Ar containing O2 (CS)[27], or amorphous alloying (AA)[28], respectively. These precursor mixtures are calcined in air at temperatures above 550K. Since Au tends to become metallic while the support metal forms crystalline oxide phase, Au is gradually excluded to the surfaces of the support to form metallic Au particles strongly attached to the crystalline metal oxides such as α-Fe2O3, Co3O4, and ZrO2. Among the three techniques, coprecipitation is the most useful and simplest way of preparation. An aqueous solution of HAuCl4•4H2O and water soluble metal salts, most preferably nitrates, such as Fe(NO3)2•9H2O is poured into an aqueous alkaline solution under agitation in a few minutes. After aging for 1 hour, the precipitate is washed with water for more than 5 times until the pH of the supernatant reaches a steady value around 7 and then filtrated. This procedure makes the coprecipitation2. PREPARATION OF NANOPARTICULATE GOLD CATALYSTSIt is difficult to deposit Au as nanoparticles on metal oxides by the impregnation method (IMP) mainly because Au has lower melting point (Au: 1336 K, Pd: 1823 K, Pt: 2042 K) and much lower affinity to oxygen than Pd and Pt. Another reason is that chloride ion markedly enhances the coagulation of Au particles duringNanoparticulate Gold Catalysts for Low-Temperature ... / J. New. Mat. Electrochem. Systems 7, 163-172 (2004)165method different from the impregnation method in that the catalyst precursor is almost free from Na and Cl ions (several tens ppm). The removal of Cl ions is indispensable for preventing Au nanoparticles from coagulation. The hydroxide and/or carbonate mixture is dried overnight and calcined in air to obtain powder catalysts. The following conditions are important to obtain homogeneous dispersion of Au nanoparticles. 1) Concentration of metal salt solution : 0.1~0.4M/l. 2) Neutralizer : Na2CO3 or K2CO3 Since gold hydroxide, Au(OH)3, is amphoteric, its solubility increases due to the formation of Au(OH)4- anion when pH is too high. Therefore, precipitation is the most efficient in the pH range of 7-10. When metal salt solution is added to Na2CO3 or K2CO3 solution within a few minutes, precipitate can be formed at a relatively constant pH in the range of 8-9, resulting in the homogeneous distribution of Au nanoparticles and thus better reproducibility of catalytic performance. When NaOH solution is used, the pH widely changes during coprecipitation. The use of NH4OH solution usually results in the formation of Au particles larger than 10 nm in diameter. 3) Temperature : 320-360K for precipitation and 550-670K for calcination Aqueous solutions for coprecipitation should be warmed to a temperature in the range of 320-360K in order to promote the exchange of chloride in AuCl4- ion with OH to transform into Au(Cl)4-n(OH)n- . To prepare Au/Co3O4, coprecipitation should be carried out in the temperature range of 270-300K so as to depress the reduction of AuCl4- ion with the oxidation of Co2+ ion to Co3+ ion. The catalytic activity for low-temperature CO oxidation of coprecipitates reaches a maximum when they are calcined at a temperature around 570K, where hydroxide species of Au mostly changes to metallic Au particles [25]. Above 670K the coagulation of Au nanoparticles becomes accelerated. Figure 1 shows a TEM photograph for Au/α-Fe2O3 prepared by coprecipitation. Gold nanoparticles are homogeneously dispersed on α-Fe2O3 particles, with a standard deviation of the diameter of about 30%. The applicability of coprecipitation is limited to metal hydroxides or carbonates that can be coprecipitated with Au(OH)3. Actually, Au can be supported in the form of welldispersed nanoparticles on α-Fe2O3, Co3O4, NiO, and ZnO while not on TiO2, Cr2O3, MnOx, and CdO [24]. In the case of TiO2, the addition of Mg citrate during or after coprecipitation is necessary to obtain good dispersion of Au nanoparticles [29], while in the case of Mn2O3 precipitation in aqueous LiCO3 solution leads to better catalytic activity for selective CO oxidation in H2 stream[26]. The second category is based on the deposition or adsorption of Au compounds, for example, Au hydroxide by depositionprecipitation (DP)[29-33] or organogold complex by liquid phase grafting (LG) [34,35] and by gas phase grafting (GG)[36,37]. The DP method is the easiest to handle and is used now for producing commercial Au catalysts. The pH of aqueous HAuCl4 solution is20nmFigure 1. TEM photograh for Au/α-Fe2O3 prepared by coprecipitation followed by calcinationi at 673K. Au/Fe=1/19 (atomic ratio).adjusted at a fixed point in the range of 6 to 10, and is selected primarily based on the isoelectric points (IEP) of the metal oxide supports shown in Figure 2. As for the neutralizer, NaOH or KOH is preferable to Na2CO3 or K2CO3. This is probably because hydroxides can adjust the pH of HAuCl4 solution with smaller amount than carbonates and accordingly bring weaker ionic strength of the solution. As in the case of coprecipitation, NH4OH or urea is, in principle, not recommended because of the formation of larger Au particles with wider size distribution. It has recently been reported that aging for 16 hours leads to a high loading of about 8 wt% of small Au nanoparticles over TiO2 when homogeneous precipitation using urea as a neutralizer is applied [32]. Another example is Au/θ-Al2O3 prepared by ion exchange with AuCl4- in acidic aqueous solution, followed by washing and by neutralization with ammonia aqueous solution [33].Figure 2. Isoelectric points for various metal oxides.166M. Haruta / J. New. Mat. Electrochem. Systems 7, 163-172 (2004)Careful control of the concentration around 10-3M/l, pH in the range of 6 to 10, and temperature in the range of 320K to 360K of the aqueous HAuCl4 solution enables selective deposition of Au(OH)3 only on the surfaces of support metal oxides without precipitation in the liquid phase. It is easier to deposit Au(OH)3 on metal oxide supports if their specific surface areas are larger than 10 m2/g. Because the precursor can be washed before drying, Na and Cl ions are removed to a level of a few tens ppm, as in the case of coprecipitation. The only drawback of DP is that it is not applicable to metal oxides, the IEPs of which are below 5 (see Fig. 2), and to activated carbon. Gold hydroxide cannot be deposited on SiO2 (IEP=2), SiO2-Al2O3 (IEP=1), or WO3 (IEP=1). Gold deposited on the hydroxides of alkaline earth metals exhibits the highest catalytic activity for CO oxidation at 200 K only when Au is small clusters with diameters below 1.0 nm [31]. Magnesium citrate is indispensable to prepare such tiny Au clusters. When BeO or MgO powder is dispersed in an aqueous solution of HAuCl4 at 343 K, the oxide is transformed into hydroxide and is partly dissolved to change the pH of the solution toward 10. At this pH and at 343 K, an aqueous solution of magnesium citrate is added in an amount of about 6 times as the molar of Au. After aging at 343 K for 1h, the solid precursor is washed for several times, dried overnight, and is calcined in air at a temperature ranging from 523 K to 553 K. When the precursor is calcined at temperatures above 553 K, the hydroxide support is transformed into crystalline metal oxide, being accompanied by the formation of large Au particles. This causes the loss of catalytic activity for CO oxidation even at 473 K. The role of magnesium citrate is schematically drawn in Figure 3. Since the concentration of dissociated free citrate anion is automatically controlled at pH=10 by the dissociation equilibrium, the reduction of AuCln(OH)4-n- (“n” depends on pH) into metallic Au can be avoided. In contrast, the reduction of Au anions proceeds in Na citrate solution due to its complete dissociation. Because citrate anion is trivalent anion, it can adsorbstrongly on metal oxide surfaces, probably surrounding the Au hydroxide precipitates. Through DTA and TG it has been proved that during calcination the thermal decomposition of Au hydroxide takes place earlier than the desorption and combustion of citrate anion. This suggests that citrate anion might act as a barrier which prevents Au clusters and particles from coagulation. Liquid phase grafting (LG) using organo-gold complexes such as phenylphoshine-gold nitrate in organic solvent can produce Au/ MnOx catalyst active for CO oxidation [34]. It has also the same limitation as that of DP in its applicability to the type of metal oxide supports [35]. Furthermore, it needs freshly prepared metal hydroxides [34] probably because the concentration of surface OH groups in organic solvent should be high enough for the interaction with the organo-gold complex. In contrast, gas phase grafting (GG) using dimethyl-Au(III)-aceytylacetonate is unique in that it can deposit Au nanoparticles on almost all kinds of supports, for example, SiO2 and SiO2-Al2O3 , and activated carbon [36,37]. Before introducing the vapor of organic gold complex, metal oxide support is usually evacuated at 523 K followed by oxygen treatment at the same temperature to remove hydrocarbon contaminants over the surfaces. This pretreatment improves the reproducibility of Au deposition. Dimethy-Au(III)acetylacetonate has a planar structure and its adsorption structure was estimated by DFT (Density Functional Theory) calculations to have a chemical interaction with OH groups of metal oxide surfaces at its oxygen atoms in the acetylacetonate ring. The horizontal adsorption might lead to the better contact of Au nanoparticles with the support and the homogeneous distribution of the gold complex over the metal oxide surfaces,. The third category is to use monodispersed Au colloids stabilized by organic ligands or polymer compounds [12,38-39]. Among the former six techniques, only GG is effective for depositing Au nanoparticles on activated carbon, however, the sizes of Au particles are relatively large and around 10 nm. Precise control of dispersion and size (within 5 nm in diameter) of Au nanoparticles can be accomplished by dipping the support in Au sols stabilized with polyvinyl pyrrolidone or tetrakis(hydroxymethyl) phosphonium chloride [12]. The last category is the preparation of model catalysts using single crystals of MgO, TiO2 (rutile), FeO, Fe3O4, and Si as a support. Size selected Au anion clusters can be deposited with homogeneous dispersion at temperatures below 273 K [40-46], and then they are annealed at higher temperatures to stabilize them. Surface defects or specific surface cages are suggested as sites for stabilizing the Au clusters. In future applications gold catalysts may be used in combination with other transition metal catalysts and base metal oxide catalysts, especially in electrochemical systems [47] and environmental pollutant abatement [48,49]. Even a mechanical mixture of Au/Fe2O3 catalyst with Pt black led to improved performance in the electrochemical oxidation of MeOH and CO [50]. It has been demonstrated by us that the most prosperous way is to integrate a few different supported precious metal catalysts inFigure 3. Schematic illustration for the role of Mg citrate in depositing Au on rare earth metal hydroxides.Nanoparticulate Gold Catalysts for Low-Temperature ... / J. New. Mat. Electrochem. Systems 7, 163-172 (2004)167nm scale, as schematically shown in Figure 4. The idea is to combine synergetically the different performances of each precious metal by choosing the most suitable support respectively for a target reaction and then by integrating them into a single catalytic system. An integrated catalyst composed of Pd or Pt/ SnO2, Au/Fe2O3, and Ir/La2O3 exhibited enhanced catalytic activities not only for dioxin decomposition but also for the oxidation of H2 and (CH3)3N [49].Dioxin Decomposition below 423 KO Cl O Au Pt Ir Fe2O3 SnO2 Cl CO, HCL HCHO etc. CO2catalysts prepared by DP, photochemical deposition (PD), and IMP methods [6]. The DP method yields hemispherical metal particles with their flat planes strongly attached to the TiO2 support, often by epitaxial contact, Au (111) to anatase TiO2 (112) as shown in Figure 5 and rutile TiO2 (110), while PD and IMP methods yield spherical particles, which are simply loaded on the TiO2 support and, therefore, are much larger, particularly in the case of Au. Over Pt/TiO2, the reaction of CO with O2 takes place mainly on the Pt surfaces with or without decoration of TiO2 and the metal oxide support itself is less involved in the reaction. This can explain why different methods of preparation do not make any appreciable difference in the TOF of Pt catalysts. In contrast, the TOF of Au/TiO2 markedly depends on the methods of preparation and changes by four orders of magnitude. The TOF of strongly attached hemispherical Au particles exceeds that of Pt by one order of magnitude. The dramatic difference in TOFs suggests that the contact structure is the most critical factor in supported Au catalysts. The sharp contrast between Pt and Au metal catalysts in CO oxidation suggests that the reactions might take place at the perimeter interfaces around the Au particles. To confirm this hypothesis, Vannice prepared an inversely supported catalyst, namely, TiO2 layers deposited on a Au substrate, and observed appreciable catalytic activity [51]. Another type of Au/TiO2 catalyst was prepared by mechanically mixing a colloidal solution‫ޓ‬CarrierLa2O3Figure 4. Schematic representation of a multi-functional catalyst integrating three supported precious metal catalysts.A mixture of SnO2 and Fe2O3 was prepared by coprecipitation from an aqueous solution of SnCl4 and Fe(NO3)2, followed by calcination in air at 673K. Palladium is first deposited by DP in an aqueous solution of Pd(CH3COO)2 at pH=7, where Pd2+ cation can approach negatively charged SnO2, but is not allowed to approach Fe2O3 which is positively charged. After washing and calcination at 673K, the sample composed of PdO/SnO2 and Fe2O3 was aged in an aqueous solution of HAuCl4 at pH7.5. Gold hydroxide Au(OH)3 is selectively deposited from AuCl4-n(OH)n anion on positively charged Fe2O3, without precipitation on negatively charged SnO2. After washing and calcination, the Figure 5. TEM for Au/TiO2 prepared by deposition-precipitation method, sample composed of PdO/SnO2 and Au/Fe2O3 is dispersed in an aqueous solution of Na2CO3, to which an aqueous solution of IrCl4 and La(NO3) is poured to obtain finally a mixture of Pd/ Table 3. CO oxidation over Pt/TiO2 and Au/TiO2 prepared by different methods [6]. through washing, SnO2+Au/Fe2O3+Ir/La2O3 calcination, and reduction in H2 stream.Metal3. STRUCTURE SENSITIVITY OF CO OXIDATIONThe catalytic activity of supported Au catalysts for the low-temperature oxidation of CO strongly depends on preparation methods and conditions. This is because the catalytic activity is defined by the contact structure of Au particles with support, the type of support, and the size of Au particles.PtPreparation methodsMetal loading (wt %) 1.0 1.0 0.9 0.7 1.8 1.0Diameter of Au (nm)T1/2* (K)Rate at 300K (mol s−1 g-cat−1) 1.4 x 10−7 1.9 x 10−7 2.4 x 10−8 6.9 x 10−7 5.5 x 10−6TOF at 300K (s−1)Ea (kJ/ mol)DP IMP PD DP Au DP IMP PD1.3 ± 0.3 1.4 ± 0.3 2.4 ± 0.6 3.1 ± 0.7 2.7 ± 0.6 10 < 4.6 ± 1.5334 339 363 282 253 481 4772.7 x 10−3 3.8 x 10−3 9.2 x 10−3 3.4 x 10−2 1.2 x 10−149 60 53 19 18 583.1. Contact Structure of Gold ParticlesTable 3 lists TOFs and apparent activation energies for CO oxidation at 300K over Pt/TiO2 and Au/TiO21.7 x 10−10ሪ9.6 x 10−61.01.5 x 10−1056* T1/2 : temperature for 50% conversion of 1 vol.% CO in air under a space velocity of 2 x 104 h−1 ml/g-cat. Preparation methods : DP deposition-precipitation, IMP Impregnation, PD photochemical deposition.168M. Haruta / J. New. Mat. Electrochem. Systems 7, 163-172 (2004)of 5nm Au particles with TiO2 powder and by calcination in air at different temperatures [52]. Calcination at 873K promotes the coagulation of Au particles in forming larger particles with diameters above 10nm, but at the same time, with stronger contact (observed by TEM), leading to much higher catalytic activity than calcination at 573K.3.2. Type of Metal Oxide SupportFor CO oxidation, many oxides except for strongly acidic materials such as Al2O3-SiO2 and activated carbon can be used as a support to induce catalytic activity at temperatures below 300K. For Pd and Pt, semiconductive metal oxides lead to enhanced catalytic activities but at temperatures above 300K (see T1/2 in Table 3). Semiconductive metal oxides such as TiO2, Fe2O3, and NiO provide more stable Au catalysts than insulating metal oxides such as Al2O3 and SiO2. The difference also appears in the enhancing effect of moisture: the concentration of H2O required by Al2O3 and SiO2 supports is at least 100 ppm higher than that by TiO2, for CO oxidation to proceed at room temperature [53,54]. Alkaline earth metal hydroxides such as Be(OH)2 and Mg(OH)2 lead to the highest activity at a temperature as low as 196K [23,31]. In contrast, when an acidic material such as Al2O3-SiO2, WO3, or activated carbon is used as a support, gold exhibits poor activity; even at temperatures above 473K the conversions are far below 100% [37]. As clearly seen in Figure 6, low-temperature CO oxidation under acidic environment has not yet been accomplished by any catalysts. This reaction is very important in relation to polymer electrolyte fuel cells, which are operated at relatively low temperatures around 373K [55]. In order to use methanol directly as a fuel, the anode should also be active for the electrochemical oxidation of CO, for which, however, the present Pt electrode is not only inactive but also deactivated. Low-temperature CO oxidation under an acidic environment is an essential scientific issue in opening a new stage of fuel cell development.decreasing or steady TOF [7]. The rates over Au/TiO2 were about one order of magnitude greater when measured as the temperature was lowered from 353K than when measured as the temperature was raised from 203K [56]. This difference is assumed to occur from the accumulation of carbonate species on the surfaces of the support at low temperatures resulting in the loss of the activating power of the perimeter interfaces for O2. Therefore, the steady state rate over Au/TiO2, which was deactivated during experiments at lower temperatures, is regarded to be close to the rate of CO reaction with O2 over the surfaces of the Au particles with the least contribution of O2 activation at the perimeter interfaces. The one order of magnitude difference in the rate between fresh (obtained by high temperature measurements) and deactivated Au/ TiO2 can be ascribed to the contribution of the TiO2 support. Accordingly, the increase in the TOF can be explained if the adsorption sites for CO are edge, corner, or step sites, and the reaction zone is the periphery around the Au particles, the fractions of which increase in hemispherical Au particles with a decrease in their size [57].3.3. Size of the Au ParticlesFigure 7 plots the TOFs of CO oxidation over Pt/SiO2 and Au/ TiO2 as a function of the mean diameter of metal particles. A sharp increase in the TOF is observed with a decrease in the diameter from 4 nm. In contrast, the Pt group of metals shows aFigure 7. Turnover frequency of CO oxidation over Au/TiO2 and Pt/SiO2 as a function of the mean diameter of metals.4. REACTION PATHWAYS IN CO OXIDATIONFigure 8 shows Arrhenius plots for CO oxidation over noble metal catalysts. A unique feature of Au catalysts is that apparent activation energies (Ea) are very low. At temperatures below 300K, the value of Ea is 20 to 40 kJ/mol and is nearly zero at temperatures above 300K. In contrast, Pt group metals have a value of Ea ranging from 50 kJ/mol (see Table 3) to 170 kJ/mol [58] and are more active than Au but only at temperatures above 500K. At room temperature, Au is more active by 1-4 orders of magnitude. The rate of CO oxidation over Au/TiO2, Au/Fe2O3, Au/Co3O4 is independent of the concentration of CO and is only slightly dependent on the concentration of O2 (on the order of 0 to 0.25) in the range of concentrationdown to 0.1 vol% [5]. This independence suggests that CO and O2 are adsorbed on the catalyst surfaces nearly to saturation and that the reaction of the two adsorbed species is the rate-determining step.Reaction Temperature (K)Acidity/Basicity of the SupportFigure 6. Temperature for CO oxidation (50% conversion) as a function of acidity and basicity of support materials. Reaction conditions : CO 1 vol% in air, SV=2 X 104h-1/ml•g-cat.。

低温胁迫对高山离子芥试管苗膜脂过氧化及AsA-GSH 循环系统的影响

低温胁迫对高山离子芥试管苗膜脂过氧化及AsA-GSH 循环系统的影响杨宁;丁芳霞;李宜珅;王程亮【摘要】Using a natural cold resistance species ,Chorisporabungeana plantlets in vitro as material ,this study investigated the effects of products of lipid peroxidation , active oxygen and ascorbate-glutathione cycle response to the different low temperature stresses aiming to reveal the partial physiological mechanism . The results show that the relative electrolytic leakage , malonaldehyde (MDA ) , hydrogenperoxide(H2O2)and glutathione(GSH)contents are increased under different low temperature stresses(4℃ ,0 ℃ ,- 4 ℃) . Ascorbate peroxidase (APX ) , mondehydroascorbate reductase (MDHAR ) and glutathione reductase glutathione reductase(GR) activities are fluctuated around the comparison whe n C . bungeana is exposure to 4 ℃ and 0 ℃ . When C . bungeana is exposure to -4 ℃ , the APX and MDHAR activities are inhibited than control ( P < 0.05 ) , as well as the GR activity increased firstly , then decreased . Our research reveal that under different low temperature stresses , C . bungeana plantlets in vitro performed the membrane lipid peroxidation in some degrees , and may increase its oxidation resistance protection ability by increasing the H2 O2 content . Antioxidant enzymes (APX ,MDHAR ,GR ) and antioxidant (GSH ) in ascorbate-glutathione cycle worke together and coordinated to reduce the low temperature damage .%通过研究高山离子芥细胞在不同低温胁迫中活性氧代谢及AsA-GSH循环中生理指标的动态变化，揭示其响应低温胁迫的部分生理机制．以天然抗寒性植物高山离子芥试管苗为材料，研究了脂质过氧化产物，活性氧和抗坏血酸-谷胱甘肽（AsA-GSH）循环系统对其冷冻低温胁迫（4℃、0℃和-4℃）的反应．结果显示低温胁迫下，高山离子芥细胞中相对电导率、丙二醛（MDA）、H2O2含量和GSH不同程度的提高；抗坏血酸过氧化酶（APX）、单脱氢抗坏血酸还原酶（MDHAR）及谷胱甘肽还原酶（GR）活性在4℃和0℃胁迫下呈波动性变化，在-4℃胁迫下， APX 和MDHAR活性处于抑制状态，显著低于对照（P＜0.05），而GR活性则呈现出先升高后降低的变化趋势．结果表明低温胁迫下，高山离子芥试管苗发生不同程度的膜脂过氧化，并可能通过增加细胞内H2 O2含量来促进其抗氧化保护能力；同时AsA-GSH循环代谢中抗氧化酶（APX ，MDHAR ，GR）与抗氧化剂（GSH）共同协调作用，以减轻低温所造成的伤害．【期刊名称】《西北师范大学学报（自然科学版）》【年(卷),期】2014(000)005【总页数】7页(P79-84,105)【关键词】低温胁迫;高山离子芥试管苗;活性氧;AsA-GSH循环【作者】杨宁;丁芳霞;李宜珅;王程亮【作者单位】西北师范大学生命科学学院，甘肃兰州 730070;西北师范大学生命科学学院，甘肃兰州 730070;西北师范大学生命科学学院，甘肃兰州 730070;西北师范大学生命科学学院，甘肃兰州 730070【正文语种】中文【中图分类】Q945.78高山离子芥是高山冰缘植物的典型代表，属于十字花科离子芥属多年生草本植物.它生长于天山雪线附近的高山流石堆，苏联、巴基斯坦、阿富汗也有分布，生长期在每年的6月至9月，具有先锋植物的特点，能适应低氧分压、高山冻融过程中剧烈的气温波动和强紫外线辐射的环境，是改良十字花科作物抗冷冻性的宝贵野生种质资源，也是研究植物抗逆机理最为理想的材料[1].细胞膜在植物抗逆性方面起着重要作用，膜系统的稳定性与植物的抗逆性密切相关[2-4].在低温胁迫下，细胞内活性氧代谢的平衡被破坏，产生过多的活性氧，引发或加剧膜质过氧化作用，造成细胞膜系统的损害[5].因此，活性氧的清除是细胞膜保持良好稳定性的关键.抗坏血酸-谷胱甘肽(Ascorbate-glutathione，AsA-GSH)循环在清除活性氧过程中发挥着极其重要的作用[6]，其抗坏血酸过氧化物酶(Ascorbate peroxidase，APX)以抗坏血酸(AsA)为底物将H2O2还原成H2O，同时生成单脱氢抗坏血酸(Mondehydroascorbate，MDHA)，由于MDHA不稳定，一部分可被单脱氢抗坏血酸还原酶(Mondehydroascorbate reductase，MDHAR)还原为AsA，另一部分可进一步氧化生成脱氢抗坏血酸(Dehydroascorbate，DHA).DHA又可以还原型谷胱甘肽(Glutathione，GSH)为底物，在脱氢抗坏血酸还原酶(Dehydroascorbate reductase，DHAR)的作用下生成AsA，同时产生氧化型谷胱甘肽(Oxidized glutathione，GSSG)，GSSG又可在谷胱甘肽还原酶(Glutathione reductase，GR)的催化下被还原成GSH[7].Rao[8]等认为适度的逆境条件能够刺激植物AsA-GSH循环中酶活性升高，增强对活性氧的清除能力.刘正鲁等[9]的研究结果也表明维持AsA-GSH 循环的快速有效运行是嫁接苗耐盐性优于自根苗的一个重要方面.因此本试验以高山离子芥试管苗为研究材料，探讨低温胁迫下其膜脂过氧化以及AsA-GSH循环中相关酶等生理指标的动态变化，旨在揭示高山离子芥细胞响应低温胁迫的部分生理机制，为进一步探讨高山冰缘植物高山离子芥的低温适应性机制，并为农作物的抗低温育种、改善作物抗冻性提供理论依据.1 材料与方法1.1 试验材料与处理1.1.1 高山离子芥试管苗的培养本研究采用的高山离子芥取材于新疆天山乌鲁木齐河源区.将高山离子芥(Chorispora bungeana)去皮种子用70%乙醇浸泡30 s，然后用0.1%升汞浸泡6～8 min，无菌水冲洗3次，子叶直接接种于含有3%蔗糖的MS培养基中(不含任何激素)，在光照培养架上(25 ℃,2 000 lx,12 h光照)培养.待种子萌发，长至4 cm左右时，试管苗转移至含蔗糖3%，1 mg·L-16-BA的MS培养基中，在光照培养架上(25 ℃、2 000 lx、12 h光照)继代培养3～4次后，用于试验.1.1.2 试验材料处理将在25 ℃培养的高山离子芥试管苗放置到4 ℃、0 ℃和-4 ℃进行低温胁迫，胁迫时间分别为6 h,12 h,24 h,48 h和72 h，收集不同胁迫时段的叶片用于指标的测定，每次试验3个重复.以25 ℃条件下培养的未胁迫处理的高山离子芥试管苗为对照.1.2 测定方法相对电导率(REC)的测定参照龚富生和张嘉宝[10]的方法；硫代巴比妥酸(TBA)法测定丙二醛(MDA)含量[11]，单位以μmol·L-1表示；过氧化氢(H2O2)含量的测定参照张治安和陈展宇[12]的方法，单位以μmol·g-1表示；抗坏血酸过氧化物酶(APX)活性测定参照李忠光等[13]的方法，以毎消耗1 μmol·L-1的抗坏血酸为1个酶活单位；单脱氢抗坏血酸还原酶(MDHAR)活性测定参照孙园园等[14]的方法，以1 min内OD340值变化0.01为1个酶活力单位、谷胱甘肽还原酶(GR)活性测定参照刘正鲁等[9]的方法，以1 min内OD340值变化0.1为 1个酶活单位，单位均以Ug-1 fresh weight(FW)表示.谷胱甘肽(GSH)含量的测定参照陈沁和刘友良[15]的方法，单位以μg·g-1表示.1.3 数据分析采用SPSS 17.0统计软件进行数据统计，用Duncan方法进行单因素方差分析，用Coreldraw 9.0作图.2 结果与分析2.1 低温胁迫对高山离子芥试管苗叶片相对电导率的影响细胞膜通透性的大小可间接的用组织的相对电导率衡量，组织相对电导率越高，说明细胞膜完整性遭到破坏的程度就越大.如图1所示，高山离子芥试管苗叶片细胞在4 ℃和-4 ℃胁迫初期(0～24 h)，相对电导率低于对照水平，胁迫后期(48～72 h)相对电导率升高至与对照相当的水平；而0 ℃胁迫则显著高于对照水平(P<0.05)，且在胁迫24 h时出现峰值，约为对照水平的300.00%，之后，相对电导率保持在较高水平.同色柱形图中不同字母表示差异显著P<0.05(下同)(Different letters in the same color histogram indicate significant differences P<0.05)图1 低温胁迫对高山离子芥试管苗叶片相对电导率的影响Fig 1 Effects of Low temperature treatment on REC of C.bungeana plantlets leaves2.2 低温胁迫对高山离子芥试管苗叶片MDA含量的影响MDA是膜脂过氧化作用的最终产物,是膜系统受害的重要标志之一.如图2所示，高山离子芥试管苗在4 ℃和0 ℃胁迫过程中，细胞中MDA含量围绕对照组上下波动，呈现先下降后上升的趋势，最终保持了与对照相当的水平；并且在4 ℃胁迫时，24 h出现峰值，约为对照的147.86%，并维持该水平至48 h；在0 ℃胁迫时，MDA含量于48 h达到最大值，为对照的190.60%；而-4 ℃胁迫时，MDA含量在6 h内快速升高，为对照的164.96%，并维持该水平至12 h，随后，MDA含量降至与对照相当的水平，随着胁迫时间的延长，在胁迫进行的48 h达到峰值，为对照的185.47%，并维持该水平至72 h.图2 低温胁迫对高山离子芥试管苗叶片丙二醛含量的影响Fig 2 Effects of Low temperature treatment on MDA content of C.bungeana plantlets leaves2.3 低温胁迫对高山离子芥试管苗叶片H2O2含量的影响H2O2是细胞有氧代谢的产物，激素等信号以及生物、非生物胁迫刺激均可诱导植物细胞内H2O2的大量积累.由图3可以看出，4 ℃、-4 ℃两种温度胁迫下，较之对照组H2O2含量都显著上升(P<0.05)，且均在48 h达到最大值，分别为对照的175.62%，282.31%；0 ℃胁迫时，0～12 h，H2O2含量保持在与对照相当的水平，在24 h达到最高，为对照的151.05%.图3 低温胁迫对高山离子芥试管苗叶片过氧化氢含量的影响Fig 3 Effects of Low temperature treatment on H2O2 content of C.bungeana plantlets leaves 2.4 低温胁迫对高山离子芥试管苗叶片AsA-GSH循环中APX活性的影响APX对H2O2的亲和力很高，是细胞中清除H2O2的重要酶类之一.如图4所示，高山离子芥试管苗细胞在4 ℃和0 ℃胁迫的整个进程中，APX活性始终围绕对照值上下波动；-4 ℃胁迫下，APX的活性显著低于对照(P<0.05)，酶活性处于抑制状态.图4 低温胁迫对高山离子芥试管苗叶片抗坏血酸过氧化物酶活性的影响Fig 4 Effects of Low temperature treatment on APX activity of C.bungeana plantlets leaves2.5 低温胁迫对高山离子芥试管苗叶片AsA-GSH循环中MDHAR活性的影响由图5可知，不同低温处理对高山离子芥试管苗细胞中MDHAR的活性有显著性的影响(P<0.05).4 ℃,0 ℃两种温度胁迫下，MDHAR活性呈现出先升高后降低的变化趋势，但随着胁迫时间的增加，不同温度胁迫下的MDHAR活性变化有差异，4 ℃胁迫下在12 h达到了MDHAR活性的最大值，为对照的136.20%，而在0 ℃胁迫下，MDHAR活性12h时出现峰值，为对照的122.94%；在胁迫后期，无论是4 ℃还是0 ℃，MDHAR活性均降至低于对照的水平.-4 ℃胁迫下，MDHAR活性显著低于对照(P<0.05)，酶活性处于抑制状态.图5 低温胁迫对高山离子芥试管苗叶片单脱氢抗坏血酸还原酶活性的影响Fig 5 Effects of Low temperature treatment on MDHAR activity of C.bungeana plantlets leaves2.6 低温胁迫对高山离子芥试管苗叶片AsA-GSH循环中GR活性的影响如图6所示，4 ℃,-4 ℃两种温度胁迫下，GR活性呈现出先升高后降低的变化趋势，但随着胁迫时间的增加，不同温度胁迫下的GR活性变化有差异，4 ℃胁迫下在24 h达到了GR活性的最大值，为对照的314.11%，而在-4 ℃胁迫下，GR活性6 h时出现峰值，为对照的192.03%；0 ℃胁迫下，GR活性表现为先升高后降低再升高的趋势.图6 低温胁迫对高山离子芥试管苗叶片谷胱甘肽还原酶活性的影响Fig 6 Effectsof Low temperature treatment on GR activity of C.bungeana plantlets leaves2.7 低温胁迫对高山离子芥试管苗叶片GSH含量的影响GSH是AsA-GSH循环中重要的抗氧化物质，从图7可以看出，在整个胁迫进程中，GSH含量都比对照组有所提高，且在不同低温胁迫过程中呈现不同的变化趋势.4 ℃胁迫初期(0～6 h)GSH含量增加迅速，随后降至与对照相当的水平，胁迫48 h时达到最大值，为对照的216.07%，之后，GSH含量下降至高于对照的水平.0 ℃胁迫时，GSH含量在6 h内达到最大，为对照的171.47%，之后，GSH含量始终围绕峰值上下波动.-4 ℃胁迫时，GSH的含量随胁迫时间的延长呈持续上升的趋势，在72 h时达到最大值，为对照的166.32%.图7 低温胁迫对高山离子芥试管苗叶片谷胱甘肽含量的影响Fig 7 Effects of Low temperature treatment on GSH content of C.bungeana plantlets leaves3 讨论3.1 低温胁迫下高山离子芥试管苗细胞中膜脂过氧化程度及H2O2含量的变化逆境胁迫下植物细胞内活性氧代谢失衡，导致自由基的积累和膜脂过氧化，引起植物细胞水平的氧化伤害[16].相对电导率的变化可以反映植物细胞膜的伤害程度，可作为抗寒性大小的重要指标应用[17].本试验中，高山离子芥试管苗叶片细胞在4 ℃和-4 ℃胁迫初期(0～24 h)，相对电导率低于对照水平，胁迫后期(48～72 h)相对电导率均升高至与对照相当的水平，推测可能是由于高山离子芥试管苗在初期接受冷及冻胁迫时应激产生特殊机制，关闭部分离子通道引起的，而在胁迫后期其对4 ℃和-4 ℃的低温胁迫产生了适应，表现为相对电导率维持在与对照相当的水平.孔淑贞[18]在研究香蕉幼苗的低温生理时发现在5 ℃低温下，香蕉幼苗冷害严重，叶片电解质渗出率明显增大；仲强等[19]在研究浙江天童常绿木本植物的叶片抗寒性时发现，在-5 ℃低温处理下，各植物叶片相对电导率均显著增大，这与本试验结果中相对电导率的反应不同，说明高山离子芥细胞响应低温胁迫时在电导率的反应方面存在不同于上述植物的响应机制，这可能与物种特异性有关.在本试验中，0 ℃胁迫的相对电导率的反应有别于4 ℃和-4 ℃的冷冻胁迫，显著高于对照水平(P<0.05)，分析认为，0 ℃作为临界温度，相对电导率来自物理和化学方面的多种因素影响了细胞膜的完整性，包括细胞间隙可能形成冰核造成原生质脱水，甚至细胞结冰等，从而导致膜完整性的破坏和选择透性的丧失，引起质膜透性的显著升高.MDA是细胞原生质膜在不适宜的生长条件下发生脂质过氧化的产物，能够抑制细胞保护酶活性和降低抗氧化物的含量，从而加剧膜脂过氧化[20].高山离子芥试管苗在4 ℃和0 ℃胁迫过程中，细胞中MDA含量围绕对照组上下波动，呈现先下降后上升的趋势，最终保持了与对照相当的水平，这与高福元[21]在-10 ℃低温下研究紫叶矮樱和美国红栌丙二醛含量的变化所得出的结果一致.胁迫初期MDA含量表现出略微下降的趋势，可能是在低温胁迫初始时植物保护酶产生的一种防御反应，酶活力增强，清除活性氧和自由基的能力增强，植物体内MDA含量也随之下降；随着低温胁迫时间的延长，胁迫程度加强，酶活力也随之下降，清除活性氧和自由基的能力减弱，体内MDA含量相对升高.总体来看，整个胁迫过程中，冻害温度(-4 ℃)下的MDA含量明显高于非冻害温度(4 ℃和0 ℃)下，说明MDA对温度胁迫的反应与胁迫程度正相关.Janda及Chen等提出，植物体内H2O2的积累会使植物产生抗逆反应，增加的H2O2被认为是引起植物系统获得抗性的重要信号分子，同时H2O2含量的增加可能还有助于植株诱导其他保护机制[22-23].本试验中，三种胁迫温度(4 ℃,0 ℃,-4 ℃)下H2O2含量均不同程度的提高，且随胁迫程度的增加，在冻胁迫时(-4 ℃)的H2O2含量积累程度明显高于冷害胁迫(4 ℃和0 ℃)，反映出H2O2含量积累与温度胁迫程度相关，因此推测高山离子芥试管苗在低温胁迫下通过增加细胞内H2O2含量来促进其抗氧化的保护能力.3.2 低温胁迫下高山离子芥试管苗细胞中AsA-GSH循环的变化AsA-GSH循环各组分主要涉及APX、DHAR和GR等几种抗氧化酶及AsA、GSH二种非酶抗氧化剂[24].APX是叶绿体中清除H2O2的重要酶，在植物逆境胁迫中具有重要的抗氧化作用.对APX响应低温胁迫的研究表明，4 ℃和0 ℃胁迫的整个进程中，APX活性始终围绕对照值上下波动；-4 ℃胁迫下，APX活性被显著抑制.说明APX对低温非常敏感，随着胁迫程度的加深APX活性降低，这与本试验中-4 ℃胁迫下H2O2含量显著积累的结果一致，所以APX活性降低部分造成了细胞中H2O2的过多积累.APX 要发挥正常的催化作用，需要依赖MDHAR和DHAR 源源不断地再生AsA[25]，本试验中，-4 ℃胁迫下，MDHAR活性显著低于对照(P<0.05)，该酶活性处于抑制状态而无法有效再生足够的AsA，所以我们认为这也是-4 ℃胁迫下，APX活性被抑制的原因之一.4 ℃,0 ℃两种温度胁迫下，MDHAR活性呈现出先升高后降低的变化趋势，在胁迫后期，MDHAR活性均降至低于对照的水平.说明在一定的低温范围内，机体可以通过MDHAR清除植物体内由胁迫产生的活性氧，不致造成膜脂过氧化；但当温度过低或低温持续时间延长，MDHAR活性被抑制，由此可以看出MDHAR活性与低温胁迫强度及胁迫时间存在相关性.GSH具有能直接清除H2O2以及间接减少和HO-·的作用，对于维持生物体内合适的氧化还原环境起着至关重要的作用[26].作为高山离子芥中的功能性物质和抗氧化剂，GSH除了可以自身合成外，也可由GR催化GSSG还原成，促进生物体内GSH的循环再生，维持细胞内GSH的水平并间接参与生物体对自由基的清除[27].本研究中，高山离子芥试管苗细胞在三种低温胁迫下，GSH含量均高于对照组水平，反应出高山离子芥试管苗细胞通过增加GSH以减少氧自由基伤害作为手段之一来积极响应了胁迫；GR活性在4 ℃,-4 ℃两种温度胁迫下，呈现出先升高后降低的变化趋势，0 ℃胁迫下，GR活性始终围绕对照值上下波动.可见，在低温胁迫下，高山离子芥试管苗细胞内GSH含量的提高与GR活性的增加并不同步，GSH的增幅远远大于GR活性增加，因此认为，低温胁迫下，GSH的一部分来源是GR将GSSG还原为GSH，但最主要的来源仍是高山离子芥试管苗自身合成能力的增强.这一结论也支持了朱为民等[28]在研究Cd2+ 胁迫对番茄幼苗抗坏血酸-谷胱甘肽循环代谢的影响时所得出的观点.综上所述，高山离子芥试管苗在受到低温胁迫时，随胁迫强度的加深及胁迫时间的延长，高山离子芥试管苗通过统一协调机体细胞内的膜脂过氧化、活性氧和AsA-GSH循环系统等多因素共同作用，完成抵御低温胁迫的生理响应.值得关注的是，本研究的几种测试指标(H2O2含量、APX活性、GR活性和GSH含量)在0 ℃胁迫时没有表现出明显规律，呈波动变化，这可能与0 ℃这种特殊的临界温度下细胞响应不同有关，而关于低温胁迫的研究报道很多，但关注0 ℃胁迫的却少见报道，本研究中所发现的现象说明对0 ℃胁迫下细胞响应机制尚不明确，这为我们揭示植物抵抗低温胁迫机理提出了新的深入研究的方向.参考文献:[1]杨宁，强治金，陈霞，等.高山离子芥磷脂酶Dα编码区基因序列克隆与表达载体构建[J].西北师范大学学报：自然科学版，2014，50(3):94-98.[2]姜述君,常缨,范文艳,等.温度逆境锻炼对低温胁迫下番茄幼苗细胞膜脂过氧化产物及抗氧化酶活性的影响[J].植物生理科学,2007,23(10):444-448.[3]徐跃进,李艳春,俞振华.西葫芦抗冷性生理生化指标分析[J].湖北农业科学,2006，45(2):211-213.[4]郁继华,张国斌,冯致,等.低温弱光对辣椒幼苗抗氧化酶活性与质膜透性的影响[J].西北植物学报,2005,25(12):2478-2483.[5]韩冰,贺超兴,闫妍,等.AMF对低温胁迫下黄瓜幼苗生长和叶片抗氧化系统的影响[J].中国农业科学,2011,44(8):1646-1653.[6]MANISHA G,ANN C,JACO V,et al.Copper affects the enzymes of ascorbate-glutathione cycle and its related metabolites in the roots of Phaseolus vulgaris[J].Physiologia Plantarum,1999,106(3):262-267.[7]罗娅,汤浩茹,张勇.低温胁迫对草莓叶片SOD和AsA-GSH循环酶系统的影响[J].园艺学报,2007,34(6):1405-1410.[8]RAO M V,HALE B A,ORMROD D P.Amelioration of ozone induced oxidative damage in wheat plants grown under high carbon dioxide[J]PlantPhysiology,1995,109(2):421-432.[9]刘正鲁,朱月林,魏国平,等.NaCl 胁迫对茄子嫁接幼苗叶片抗坏血酸和谷胱甘肽代谢的影响[J].西北植物学报,2007,27(9):1795-1800.[10]龚富生,张嘉宝.植物生理学实验[M].北京:中国气象出版社,1995:254-256.[11]李合生.植物生理生化实验原理和技术[M].北京:高等教育出版社,2000:134-137.[12]张治安,陈展宇.植物生理学实验技术[M].长春:吉林大学出版社,2008:182-185.[13]李忠光,李江鸿,杜朝昆,等.在单一提取系统中同时测定五种植物抗氧化酶[J].云南师范大学学报:自然科学版,2002,22(6):44-48.[14]孙园园,林成永,金崇伟,等.氮素形态对菠菜体内抗坏血酸含量及其代谢的影响[J].浙江大学学报:农业与生命科学版,2009,35(3):292-298.[15]陈沁,刘友良.谷胱甘肽对盐胁迫大麦叶片活性氧清除系统的保护作用[J].作物学报,2000,26(3):365-372.[16]WU F B,ZHANG G P,DOMIN Y P.Fourbarley genotypes respond differently to cadmium:lipid peroxidation and activities of antioxidant capacity[J].Environmental and Experimental Botany,2003,50(2)：67-78. [17]SCHAFF T,LEVIN L,BLAIR N,et al.Spatial heterogeneity of benthos on the Carolina continental slope:large(100 km) scale variation[J].Marine Ecology Progress Series,1992,88:143-160.[18]孙淑贞.香蕉幼苗的低温生理及抗冷性研究[D].广州:华南师范大学,2003.[19]仲强,康蒙,郭明,等.浙江天童常绿木本植物的叶片相对电导率及抗寒性[J].华东师范大学学报：自然科学版,2011(4):45-52.[20]PRASAD T K.Role of calalase in inducing chilling tolerance in pre-emergentmaize seedlings[J].Plant Physiology,1997,114(4):1369-1376. [21]高福元,张吉立,刘振平,等.持续低温胁迫对园林树木电导率和丙二醛含量的影响[J].山东农业科学,2010,81(2):47-49.[22]JANDA T,SZALAI G,TARI I,et a1.Hydroponic treatment with salicylic acid decreases the effects of chilling injnry in maize(Zea mayL)plants[J].Planta,1999，208(2):175-180.[23]CHEN Z,SIVA H,KLESSIG D F.Active oxygen species in the induction of plant systemic acquired resistance by salicylic acid[J].Science,1993,262：1883-1886.[24]FOYER C H,HALLIWELL B.The presence of glutathione and glutathione reductase in chloroplasts:a proposed role in ascorbic acidmetabolism[J].Planta,1976,133(1)：21-25.[25]高永生,陈集双.盐胁迫下镧对小麦幼苗叶片抗氧化系统活性的影响[J].中国稀土学报,2005,23(4):490-495.[26]陈坤明,宫海军,王锁民.植物谷胱甘肽代谢与环境胁迫[J].西北植物学报,2004,24(6):1119-1130.[27]SMITH I K,VIERHALLER T L,THORNE C A.Properties and functions of glutathione reductase in plants[J].Physiologia Plantarum,1989,77(3):449-456.[28]朱为民,丁海东,齐乃敏,等.Cd2+胁迫对番茄幼苗抗坏血酸-谷胱甘肽循环代谢的影响[J].华北农学学报,2005,20(3):50-53.。

氧化石墨烯动态光散射

氧化石墨烯（Graphene Oxide，简称GO）是一种具有特殊结构和性质的碳材料，其在动态光散射方面表现出一些有趣的特点。

动态光散射是指当光通过一个粒子或材料时，由于光与粒子之间的相互作用，导致光的传播方向和强度发生变化的现象。

在氧化石墨烯中，动态光散射主要涉及到以下几个方面：
1. 布朗运动：氧化石墨烯的层状结构使得其在溶液中表现出布朗运动。

这种运动使得氧化石墨烯颗粒在溶液中随机运动，并导致光的散射方向和强度的变化。

2. 多普勒效应：当氧化石墨烯颗粒以一定速度相对于观察者运动时，会引起多普勒效应，即光的频率发生变化。

这种频率变化可以通过光的散射来观察到，从而提供了关于氧化石墨烯颗粒运动状态的信息。

3. 光学激发：氧化石墨烯在受到光的激发时，其电子结构会发生变化，导致光的散射特性发生改变。

通过调控氧化石墨烯的激发方式和条件，可以实现对光的散射行为的控制。

通过对氧化石墨烯动态光散射的研究，可以获得关于氧化石墨烯颗粒运动、聚集态和光学性质的信息。

这些信息对于深入理解氧化石墨烯的物理特性以及在光学传感、光学器件和生物医学应用等领域的应用
具有重要意义。

金属载体强相互作用

肉桂醇是香料、药物及其他精细化工产品生产过程中的重要原料和反应中间体，目前工业上生产肉桂醇的方法多局限在均相计量还原法上，但其反应条件苛刻、还原剂用量大、反应后产物分离繁琐、产生大量废弃物，不符合可持续经济发展的要求，而采用多相催化加氢的方法具有反应条件温和、还原剂(氢气)绿色无污染、催化剂易于分离、可循环使用等特点，因此研制经济高效的肉桂醛选择加氢催化剂具有重要的学术意义和经济价值。

【2】599肉桂醇可作为医药原料，常用于心脑血管药物的合成，如脑益嗦等，对病毒引起的肺瘤能有效抑制；临床用于血癌、子宫癌、卵巢肿瘤、食管癌等多种肿瘤。

【8】Chambers A, Jaekson S D, Stirling D,Webb G Selective Hydroge natio n of Cinn amaldehyde over Supported Copper Catalysts[J].J Catal,1997,168(2):301 —314.载体1. Fe离子沉积增加了催化剂有效比表面积，减小了Au颗粒尺寸.[5]K.M. Parida et al. Low temperature CO oxidation over gold supported mesoporous Fe-TiQ. J. Mol. Catal. A319 (2010) 92- 972. 具有大比表面积的载体是金颗粒高度分散的前提，而载体的浸润性决定了金催化剂在焙烧过程中是否会团聚成大的金颗粒，若团聚其催化活性降低。

[6]8983. 载体与纳米金颗粒之间的相互作用强度也是影响催化活性的关键因素。

(几何效应)当金颗粒以半球状附着在载体表面时与载体表面的相互作用较强，由于半球状附着在载体表面上的金的自由能要比球状附着在载体表面上的自由能大，所以半球状的金颗粒更容易吸附反应介质以降低其自由能，因此，其催化活性一般较高；而以球状附着在载体表面时金颗粒难吸附反应介质，使得其催化活性较低。