MnO2/Poly(3,4-ethylenedioxythiophene)Coaxial Nanowires by One-Step Coelectrodeposition for Electrochemical Energy Storage
Ran Liu and Sang Bok Lee*
Department of Chemistry and Biochemistry,Uni V ersity of Maryland,College Park,Maryland20742
Received December19,2007;E-mail:slee@https://www.doczj.com/doc/ce1029171.html,
One-dimensional(1D)nanostructured materials have been
intensively investigated as building components in electrochemical
energy storage1and solar energy conversion2devices because they
provide short diffusion path lengths to ions and excitons,leading
to high charge/discharge rates1and high solar energy conversion
efficiency.2More recently,coaxial nanowires have attracted
greater attention in this field due to their added synergic properties
(e.g.,high conductivity)3a or functionalities(e.g.,core/shell p-n
junction)3b,c arising from the combination of different materials.3
Various materials such as semiconductor/semiconductor,metal/
metal oxide,and metal oxide/metal oxide,have been employed
as core/shell in coaxial nanowires.3However,there have been
few studies on the coaxial nanowires with transition metal oxide and conductive polymer,although both of them are important electroactive materials used in electrochemical energy storage.4 The combination of these two materials at1D nanostructures may exhibit excellent electrical,electrochemical,and mechanical properties for electrochemical energy storage.To date,only a few reports have been published on the synthesis of metal oxide/ conductive polymer with core/shell structures.5In all of these reports,a stepwise synthetic approach was adopted:metal oxide nanoparticles,5a nanostrands,5b or nanotubes5c were first synthesized and subsequently coated chemically by conductive polymers as shells.
In this paper,we introduce a simple one-step method to synthesize MnO2/poly(3,4-ethylenedioxythiophene)(PEDOT)co-axial nanowires by coelectrodeposition in a porous alumina template.6MnO2is one of the most popular electrochemical energy storage materials because of its high energy density,low cost, environmental friendliness,and natural abundance,7but it has poor conductivity.4c PEDOT has merits of excellent conductivity,high stability,and mechanical flexibility,8but it provides low electro-chemical energy density.Electrodeposition is used here because it is a simple yet versatile method in controlling structures and their composition by tuning applied potentials and electrolyte ingredi-ents.9In this report,MnO2/PEDOT coaxial nanowires are found to be promising electrochemical energy storage materials.The core MnO2provides high energy storage capacity,while the highly conductive,porous,and flexible PEDOT shell facilitates the electron transport and ion diffusion into the core MnO2and protects it from structurally significant collapsing and breaking.These combined properties enable the coaxial nanowires to have very high specific capacitances at high current densities.
Scheme1illustrates the growth of MnO2/PEDOT coaxial nanowires.Under a constant potential(typically0.75V vs Ag/ AgCl),Mn2+(10mM manganese acetate)is converted to its higher oxidization state,which can readily undergo hydrolysis to yield MnO2.7Simultaneously,EDOT monomer(80mM)is electropo-lymerized into PEDOT in the pores of the template.10Very interestingly,this coelectrodeposition gives rise to formation of coaxial nanowires.
Figure1a shows the SEM image of free-standing coaxial nanowires grown at0.75V after removal of template.Figure1b shows the TEM image of a single coaxial nanowire.Although the core MnO2and shell PEDOT can be easily distinguished by their morphologies in TEM images,energy dispersive X-ray spectro-scopic(EDS)elemental maps of S and Mn(Figure1c and d)from the designated area in Figure1b clearly confirms the coaxial nanostructure.The electron diffraction pattern reveals that the core MnO2is amorphous(see Supporting information).
We can easily control the structures of coaxial nanowires such as PEDOT shell thickness and nanowire length by varying the applied potential.This should provide us with the ability to tune electrochemical properties of the coaxial nanowires.Since the onset growth potential of MnO2(0.5V)is lower than that of PEDOT (0.75V),MnO2nanowires can be selectively grown below0.6V, while PEDOT nanowires are grown at the potentials above0.85V due to the higher growth rate of PEDOT given that the concentration of EDOT monomer is8times that of Mn2+.Between these two extreme potentials,coaxial nanowires with various PEDOT shell thicknesses(25-100nm)can be obtained,as shown in Figure1e. After the MnO2cores in these coaxial nanowires are selectively removed by wet etching,PEDOT nanotubes with different wall thicknesses are obtained and clearly observed by TEM(Supporting information).Interestingly,the inner surface morphology of PEDOT nanotubes appears somewhat rough and spiky.It suggests the PEDOT may have grown into the MnO2core layer.This can be supported further by an EDS line-scan profile on a single coaxial nanowire(Supporting information).Such PEDOT penetrations may play important roles in further improving the core conductivity. The growth mechanism of coaxial nanowires,although not completely understood,is briefly suggested as follows.We have previously proved that the sputtered ring-shape Au electrodes at the bottom of the pores can direct the growth of PEDOT nanotubes at low overpotential.11This may explain the preferential formation of the PEDOT shell.In addition,MnO2and PEDOT tend to have phase segregation when coelectrodeposited at bulk electrode surface (Supporting information).The phase segregation of these two materials may force the MnO2to grow in the spaces left by the PEDOT shells as the cores.
Scheme1.One-Step Synthesis of MnO2/PEDOT Coaxial
Nanowires
Published on Web02/15/2008
29429J.AM.CHEM.SOC.2008,130,2942-294310.1021/ja7112382CCC:$40.75?2008American Chemical Society
Finally,we investigate electrochemical properties of the coaxial nanowires for an electrochemical supercapacitor,an electrochemical energy storage device required to provide high power while it maintains its energy density (or specific capacitance)at a high charge/discharge rate.Specific capacitance values of coaxial nanowires (grown at 0.75V),MnO 2nanowires,PEDOT nano-wires,and MnO 2thin film at different current densities are shown in Figure 2.
Coaxial nanowires not only exhibit high specific capacitance values but also maintain them well at high current density compared to the others.As shown in Figure 2,the coaxial nanowires preserved 85%of its specific capacitance (from 210to 185F/g)as the current density increases from 5to 25mA/cm 2.These specific capacitance values are comparable to those of electrodeposited MnO 2films (190-240F/g),which however decreased significantly with increased current densities (e.g.,from 210to 40F/g at current density of 1-10mA/cm 2).7The specific capacitance of coaxial nanowires is higher than that of PEDOT nanowires as a result of the inclusion of MnO 2as cores.The well-maintained specific capacitance is mainly due to short paths of ion diffusion in the nanowires.Therefore,even at high current density (high power demand),the nanowire materials can be fully utilized.The porous nature of the PEDOT shell allows such fast ion diffusion into the core MnO 2of the coaxial nanowires.In addition,the highly electrical conductive PEDOT shell facilitates electron transport to the core MnO 2,which has low conductivity 4c that can limit its charge/discharge rate 7(cyclic voltammogram in Supporting infor-
mation).It also explains the significant decrease of specific capacitance of pure MnO 2nanowires.With regard to mechanical stability,the solid core MnO 2and the flexible PEDOT shell prevent,synergistically,the coaxial nanowires from significant collapsing and breaking after removal of the template and the drying process that downgrades their electrochemical performance (Supporting information).
In conclusion,MnO 2/PEDOT coaxial nanowires were fabricated by a one-step coelectrodeposition method.The structures of the coaxial nanowires could be controlled by applied potential.The combination of MnO 2and PEDOT into 1D nanostructures showed excellent electrochemical and mechanical properties for energy storage applications.The synthetic method presented here will be further investigated for the extension to fabricating other hetero-geneous 1D nanocomposite structure with other metal oxides 12and conductive polymers,which may lead to new types of materials in electrochemical energy storage devices.
Acknowledgment.The work was supported by the Laboratory for Physical Sciences,UMD-NSF-MRSEC under grant DMR 05-20471and University of Maryland.
Supporting Information Available:Electron diffraction pattern and EDS line-scan,TEM of PEDOT nanotubes,phase segregation,SEM of MnO 2nanowires,and other detailed electrochemical characteriza-tions.This material is available free of charge via the Internet at https://www.doczj.com/doc/ce1029171.html,.References
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JA7112382
Figure 1.(a)SEM image of MnO 2/PEDOT coaxial nanowires (0.75V).(b)TEM image from a single coaxial nanowire (0.75V).(c and d)EDS maps of S and Mn from the boxed area in Figure 1b.(e)PEDOT shell thickness variation with applied potential.Scale bar,50
nm.
Figure 2.Specific capacitance of MnO 2nanowires (closed blue square),PEDOT nanowires (open purple dots),MnO 2thin film (open green square)and MnO 2/PEDOT coaxial nanowires (closed red dots)at difference charge/discharge current densities.
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3分钟简单英语演讲稿 3分钟简单英语演讲稿1 We’ve all been taught that we should help people. It is the right thing to do and will make us popular with others. It may even win us favors in return. However， we must be realistic. We can’t say yes to every request. If we did， we would fail or go crazy for sure. Sometimes we simply don’t have the time to help. In this case， we must know how to say no politely. When we need to say no， here is one method we can try. First， we should tell the truth. If we really can’t do something， we should just say so. Second，we should remember to refuse requests politely. We must communicate clearly， but must also be sincere and sympathetic. A true friend will understand. Finally，we must not feel guilty about saying no. Sometimes refusing others is the right thing to do. It can save ourselves， and them， a lot of trouble. In short， we cannot please everyone all the time. Refusing favors is a part of life. 3分钟简单英语演讲稿2
英语即兴演讲稿（带翻译）3分钟3篇 英语即兴演讲稿（带翻译）3分钟篇1 My Definition of Success By Bao Jinlong(鲍金龙) It is easy to describe success in terms of money,fame and reputation. But I believe that success is not external.I believe that success comes from within.My definition of success is to be true to yourself,and be true to others.That means,that you must cherish your personal ideal even in the face of adversity.I also believe that success is not discriminatory. Success is not restricted to such a class of people,in fact,it may be achieved by any person irrespective of his race,creed,gender and economic background.A good example of success is that of Beethoven.He is one of the world's most famous composers,yet he was deaf.He could not hear the majestic pieces of music that he created.Yet,in the face of this adversity,he was able to maintain his ideals--that of composing music. To exemplify what success means to me,I pose a question to all of you.What brings us together here today?I believe that it is the beauty of the spoken word.The effect of pause and the sound of rhetoric are unique to the spoken word.I believe the beauty of the spoken word is even stronger for those who have difficulty in expressing themselves. These people are reclusive and had their emotions hidden within them. I once went to Australia and I saw two pictures,Once was drawn by a normal child,the other was drawn by a child with social inhibitions.The picture drawn by the normal child was simple and plain.The other was life-like,
简单英语演讲稿3分钟 【英语演讲稿一】 the footsteps of the xx world expo is getting closer and closer to us, civilized and harmonious call is still ringing in my ears. shanghai, china obtained the right to host the world expo xx, expo xx shanghai china will be a world event, the development of shanghai's new round of golden opportunity, as it is an important embodiment of our national spirit. world expo is a great influence and a long history of international activities, is the largest gathering of human beings. people from around the world gathered in one place display their products and skills, boast of their hometown and motherland. expo set the culmination of human civilization, which has a unique appeal, make you feel surging. world expo is a platform, we are the masters. she put up a platform for us to let the world know us; she built a bridge for us, so we better communicate with the world. this platform may let us display self wantonly. we are the masters here, we have to landlord, let guest experience enthusiasm and happiness. everyone to contribute for the expo, we are no exception, as a living piece of fertile land in pudong's teachers, we are proud and pride. in the vision of a better tomorrow , we have to do for the world expo will own a wonderful ability, we
常用食物中的脂肪酸及其含量
常用食物中的脂肪酸及其含量 * 1-4當用食辆中的脂肪酸及其含 注*根躬中国陕学料学疑卩牛册究斯编著农食物成分表*19&5年版计算㈣再。
饱和脂肪酸 不含双键的脂肪酸称为饱和脂肪酸，大部分动物油都是饱和脂肪酸。膳食中饱和脂肪酸多存在于动物脂肪及乳脂中，这些食物也富含胆固醇。故进食较多的饱和脂肪酸也必然进食较多的胆固醇。实验研究发现，进食大量饱和脂肪酸后肝脏的3- 羟基-3- 甲基戊二酰辅酶A( HMG-CoA ) 还原酶的活性增高，使胆固醇合成增加，植物中富含饱和脂肪酸的有椰子油、棉籽油和可可油。 单不饱和脂肪酸 单不饱和脂肪酸，分子中只有一个双键，其余为单键。单不饱和脂肪酸是属于不必需脂肪酸，可以在体内合成，常见的这类脂肪包括棕榈烯酸及油酸，是橄榄油的最主要成分；而芥花籽油、花生油、菜籽油、果仁及牛油果均相对含有较多这类脂肪
酸。单不饱和脂肪酸在室温下呈液体状。 多不饱和脂肪酸 多不饱和脂肪酸，分子中有多个双键。它必须从食物中摄取，故称为必需脂肪酸。常见的多不饱和脂肪酸包括亚麻油酸及次亚麻油酸。红花籽油、粟米油、大豆油、葵花籽油及果仁均相对含有较多这类脂肪酸。多不饱和脂肪酸在室温下呈液体状。 动物脂肪与植物油 人们在日常饮食中离不开动物脂肪与植物油，应如何去认识和应用呢?油脂的营养价值并不在于它的来源。人们常认为动物脂肪就是饱和脂肪，就不好，而植物脂肪就是不饱和脂肪，所以就好，其实这并不确切。譬如，鱼肝油是动物脂肪，但不饱和脂肪酸很多，而椰子油是植物油，饱和脂肪酸却很多。因此，衡量动物脂肪与植物油的好坏，关键在于它本身所含脂肪酸的种类及其饱和程度、维生素含量、消化率的高低、储存性能等。下面比较动物脂肪（猪油、牛油、羊脂、黄油、奶油）和植物油（芝麻油又名香油、豆油、花生油、菜籽油、玉米油、葵花籽油、茶油）的特性与作用。 （1）必需脂肪酸及胆固醇含量：植物油富含必需脂肪酸，不含胆固醇，相反，动物脂肪中必需脂肪酸含量很少，饱和脂肪酸和胆固醇含量较高。必需脂肪酸有降血脂作用，而饱和脂肪酸和胆固醇则有升高血脂的作用，所以从预防动脉粥样硬化和心脑 血管疾病的角度来 看，一般说来植物油比动物脂肪好 (2)脂肪的消化率：与它的熔点有关。脂肪中含多不饱和脂肪酸越多熔点越低，消化率越高，植物油消化率几乎为100％。牛、羊脂肪消化率为80％-90% 。 (3)脂溶性维生素含量：动物肝脏、奶和蛋类中的脂肪富含维生素A和维生素D;植物油则富含维生素E,这些维生素对维持人体健康都是不可少的。
my chinese dream 我的中国梦 i am very glad to stand here to give thier a short speech.today my topic is that the youth are the future of motherland 很高兴站在这里做这篇短小的演讲，我演讲的主题是青年是祖国的未来。 在准备英语演讲比赛的时候，我本想简单地从网上搜索一些文章作为我演讲的内容。我 看过很多文章，有著名主持人的、北大教授的、大学生的，也有初中生的。但是看完之后， 我放弃了当初的想法，我甚至为当初的想法感到有一些羞愧。因为今天我站在这里向大家演 讲的主题，是一个庄重而严肃的主题；是一个充满荣耀与自豪的主题；是每一个中华儿女共 同期盼的主题。每个人都有属于他们自己的中国梦，而我，当然也有一直萦绕在心怀只属于 我的中国梦。 so what?s my chinese dream ? finally i will announce. we had learned a lot of knowledge and understood a lot of truth in the book. we had a basic concept to our country at that time. we know that our country is full of sunshine , and we are the future of our country, and our dreams are to be the hope of our motherland. 我的中国梦是什么样的？先卖个关子。 记得刚刚上学那会儿，我们天真无邪。在课本里，我们学到了很多很多知识，也明白了 很多很多道理，我们对祖国也有了一个最基本的概念。我们知道我们的祖国到处充满阳光， 正在慢慢发展，而我们，就是祖国未来的花朵，未来的希望。我们梦想将来能够成为祖国的 希望。 这，是我们最初的中国梦。最真诚的我们，最真诚的梦。 但是，不知道什么时候开始，我们长大了，生活似乎一下子变得和以前不太一样了，与 此同时，虽然我们很不想承认但是却又不得不承认的是，我们的思想，我们的为人处世观， 我们对我们祖国的看法，也潜移默化中慢慢开始了转变。我们的社会变得到处充满欺骗、冷 漠、勾心斗角、压力、腐败、险恶，我们变得暴躁，不冷静，愤世嫉俗。我们的国家，似乎 也开始变得千疮百孔。而好多我们亲爱的祖国委以重任培养的青年学生们变得轻浮、急躁， 更别提什么梦想，什么中国梦了？ are we sick, or is our dear motherland sick? 我很惊讶，当大街上有老人摔倒，我们不敢再去扶起；我很难过，当有人做了好事被报 道，更多的人说他做作；我很伤心，当我看到我们众多的青年人变得冷漠、市侩、欺诈以及 缺乏理想。 到底是我们病了，还是我们亲爱的祖国病了？ i dont want to talk about the construction of our country politics, and also speak impassioned speech on the diaoyu island event .i just want to appeal young people,showing the side of youth,good and confidence.we must learn to organize our own thoughts, correct our own concept, and change our direction to the right side in future life. china dream actually lies in our young generation, especially of the intellectuals. 我的中国梦，不想大谈政治，也不想对钓鱼岛事件发表慷慨激昂的演讲。我只想呼吁， 呼吁我们年轻人，呼吁我们祖国的希望能够将我们的青春一面，将我们的善良一面，将我们 的自信一面好好展现出来。我们要学会整理自己的思想，端正自己看问题的观念，摆正自己 的人生方向。我们的中国梦实际上正掌握在我们自己手上，掌握在我们年青一代，尤其是知 识分子手上。
AMAMFSAc23033 谷类脂肪酸度滴定法 AM-AM-FS-Ac-23033 脂肪酸度——谷类 1.仪器和试剂 1.1 仪器 (a)谷物研磨机—适用于磨碎小样品。 (b)脂肪提取设备—Soxhlet或其它适合的型号(耐用的纸套筒或铝质RA-360套筒适合提取用)。 1.2 试剂 (a)甲苯-乙醇-酚酞溶液—0.02%。向IL甲苯中加1L乙醇和0.4g酚酞。 (b)乙醇-酚酞溶液—0.04%。向1L乙醇中加0.4g酚酞。 (c)氢氧化钾标准溶液0.0178N。无碳酸盐的。1ml=1mgKOH。 2.试验过程 2.1.方法Ⅰ 用人工四分法或利用机械采样装置取得大约50g谷物(玉米200g)的代表性样品，尽量磨碎以便使不少于90%的样品能通过40号筛 (某些较粗颗粒不会明显地影响结果)。如果样品太湿不易磨碎，在约10O℃干燥到足以除去多余的水分。 在提取器中，用石油醚提取10±0.1g磨碎的样品大约16h。样品磨碎后尽快着手提取，切勿将磨碎的样品放置过夜。在蒸气浴上将溶剂从提取物中全部蒸发掉。在提取烧瓶中用5Oml甲苯-乙醇-酚酞溶液溶解残渣并用标准KOH溶液滴定到明显的粉色，或将黄色溶液滴定到桔红色。如果滴定中有乳状物形成，加入第二份5Oml甲苯-乙醇-酚酞来消除。终点颜 色应显示与向5Oml和滴定开始时原始溶液颜色相同的适当浓度的K 2Cr 2 O 7 溶液中加 2.5ml0.0l%KmnO 4。溶液得到的溶液颜色相同。(把0.5%的K 2 Cr 2 O 7 溶液滴到5OmlH 2 O中直到颜 色相当，然后加25ml0.0l%KMnO 4 溶液)。 用5Oml甲苯-乙醇-酚酞溶液进行空白滴定，从样品滴定值中减去空白值。如果加入了另一份5Oml甲苯-乙醇-酚酞溶液，则进行双份空白滴定。将脂肪酸度以中和从1OOg谷物(干成份)中分离出的脂肪酸所需要KOH的mg数报告。脂肪酸度=l0×(滴定值-空白值)。 2.2.方法Ⅱ 测定玉米的快速法 (可在1h内得到结果) 按2.1制备样品，称20±0.01g放入玻璃塞烧瓶或一般瓶中，准确加入5Oml苯，塞好瓶，摇几秒钟使苯蒸气饱和瓶内的空气，临时松塞降压后再塞好。在机械振荡器内振荡烧瓶3Omin，或用手定期振荡45min。将瓶子倾斜不少于3min使粗粉沉积在一个角上。小心地尽可能多地把液体倾泻入l5cm插在8cm玻璃漏斗中的折叠滤纸，用表面皿盖上漏斗减少蒸发。在25m1容量瓶中准确收集25ml滤液。将此滤液转入950ml平底烧瓶中，再用乙醇-酚酞溶液将容量瓶充至25ml刻度并转到含苯提取物的烧瓶中。 按C制备所用的色标，用标准KOH溶液滴定提取物。对白玉米滴定到明显粉色，对黄玉米滴到桔红色。如果滴定过程中有乳状液形成，加入苯和乙醇-酚酞溶液各95ml来消除。测定25ml苯和25m1乙醇-酚酞混合溶液空白滴定值。如果再次加了苯和乙醇，则重复空白滴定。将脂肪酸度报告为中和从1OOg玉米(干料)中的游离脂肪酸所需KOH的mg数。 脂肪酸度=10×(滴定值-空白值)。以干样计算。
Win7系统绕过开机密码的具体操作方法 怎么才能绕过系统开机密码？如何不破解密码直接进入加密电脑？下面就给大家介绍Win7系统绕过开机密码的具体操作方法。 第一步： 首先进入windows错误恢复界面，选择启动启动修复（推荐），至于这个怎么进去很关键，这里小编教大家一个方法，就是在Windows启动时，就是启动电脑后显示Windows旗帜登录界面时按下主机的开关机键断电（把握好断电时机是成功与否的关键），人工造成异常关机之后，然后再开机就会出现这样的界面了。 第二步： 在进入“启动修复”界面之后，会自动“正在尝试修复”，这里需要几分钟大家稍等下。 第三步： 在扫描完之后，后弹出【启动修复】小窗口界面，窗口中选择“查看问题详细信息”，接着将滚动条拉下来，找到“如果无法获取联机隐私声明，请脱机阅读我们的隐私声明”点击下方的连接。
第四步： 在弹出【erofflps-记事本】中，点击“文件”选择打开，你也可使用组合键Ctrl+O进行打开。 第五步： 在弹出的【打开】窗口中，打开“计算机”选择C盘—Windows—System32。在窗口下面的“文件类型”选择“所有文件”。
第六步： 选择完“所有文件”类型之后，在列表中找到“Utilman”，右键点“重命名”更改为“Utilman1”，接着继续在列表中找到“cmd”右键点击“重命名”更改为“Utilman”。
第七步： 都改好名字之后，关闭“打开窗口”—“erofflps-记事本”—“启动修复”窗口。接着最后一个窗口注意要点击“取消”不要点击“完成”，电脑将会自动重启。 第八步： 在重启之后，点击登录界面的左下角“小按钮”，将会弹出“cmd”运行与命令。 第九步： 在cmd的窗口中，输入以下操作命令：
简单英语演讲稿3分钟6篇 简单英语演讲稿3分钟篇一 Ladies and Gentlemen： Good morning! I’m very glad to stand here and give you a short speech. Man’s life is a process of growing up, actually I’m standing here is a growth. If a person’s life must constituted by various choices, then I grow up along with these choices. Once I hope I can study in a college in future, however that’s passed, as you know I come here, now I wonder what the future holds for me. When I come to this school, I told to myself: this my near future, all starts here. Following I will learn to become a man, a integrated man, who has a fine body, can take on important task, has independent thought, an open mind, intensive thought, has the ability to judge right and wrong, has a perfect job. Once my teacher said :” you are not sewing, you are stylist; never forget which you should lay out to people is your thought, not craft.” I will put my personality with my interest and ability into my study, during these process I will combine learning with doing. If I can achieve this “future”, I think that I really grow up. And I deeply believe kindred, good-fellowship and love will perfection and happy in the future. How to say future? Maybe it’s a nice wish. Lets make up our minds,
3分钟简短英语演讲稿 3分钟简短英语演讲稿 演讲稿的’内容要根据具体情境、具体场合来确定，要求情感真实，尊重观众。在当下社会，演讲稿的使用越来越广泛，那要怎么写好演讲稿呢？下面是小编收集整理的3分钟简短英语演讲稿，欢迎大家分享。 1.Agree or disagree: Advertising aiming at children should be restricted. I disagree. It’s fair to advertize to children even children are always said to be unable to distinguish between reality and fiction, between entertainment and advertising. A supposed consequence of advertising is that children are being persuaded to demand things that they don’t need and to adopt consumerist values and attitudes in their formative years. However, it’s up to the parents to determine what should and should be bought for their children. Children need to know how to see these ads and realize how a certain product would affect them and thus balance
小学生三年级英语演讲稿2分钟 篇一：小学开学英语演讲稿两分钟带翻译 学生两分钟英语演讲稿 good morning everyone, today is my turn to the speech. first of all, i would like to say that a quick test, we hope that the good preparation, good test for all, is the only way home for a good year. my english is not high, i wish i could within the next two years to learn english well. i hope you will be able to learn english after graduation to have a good future. finally, i wish the students and teachers a happy new year, further study and work. well! i finished the speech. thank you for listening。大家早上好，今天是轮到我讲话。首先，我要说的是，快速测试，我们希望很好的准备，良好的测试的所有，是唯一回家的路上有一个良好的一年。我的英语水平不高，我希望我能在未来两年内学好英语。我希望，你将能够学习英语毕业后有一个美好的未来。最后，我祝愿学生和教师的快乐新的一年里，进一步研究和工作。好!我完成了讲话。谢谢你听。篇二：XX希望之星小学组英语演讲稿6篇 1.学生两分钟英语演讲稿 good morning everyone, now is my turn to the speech.
食品中脂肪酸的测定 基础知识: 油脂就是食品的重要组分与营养成分。油脂中脂肪酸组分的测定最常用的方法就是气相色谱法。样品前处理采用酯交换法(甲酯化法),图谱解析采用归一化法。 气相色谱(GC) 就是一种把混合物分离成单个组分的实验技术它被用来对样品组分进行鉴定与定量测定。 一个气相色谱系统包括: ? 可控而纯净的载气源能将样品带入GC系统 ? 进样口同时还作为液体样品的气化室 ? 色谱柱实现随时间的分离 ? 检测器当组分通过时检测器电信号的输出值改变从而对组分做出响应 ? 某种数据处理装置 氢火焰离子化检测器(FID) :氢气与空气燃烧所生成的火焰产生很少的离子。在氢火焰中,含碳有机物燃烧产生CHO+离子,该离子强度与含量成正比。该检测器检出的就是有机化合物,无机气体及氧化物在该检测器无响应。 当纯净的载气(没有待分离组分)流经检测器时产生稳定的电信号就就是基线。
1——载气(氮气); 2——氢气; 3——压缩空气; 4——减压阀(若采用气体发生器就可不用减压阀); 5——气体净化器(若采用钢瓶高纯气体也可不用净化器); 6——稳压阀及压力表; 7——三通连接头; 8——分流／不分流进样口柱前压调节阀及压力表; 10——尾吹气调节阀; 11——氢气调节阀; 12——空气调节阀; 13——流量计(有些仪器不安装流量计); 14——分流／不分流进样口; 15——分流器; 16——隔垫吹扫气调节阀; 17——隔垫吹扫放空口; 18——分流流量控制阀; 19——分流气放空口; 20——毛细管柱; 21——FID检测器; 22——检测器放空出口;
方法来源: GB 5009、168-2016 食品安全国家标准食品中脂肪酸的测定 1、范围 本方法规定了食品中脂肪酸含量的测定方法。 本方法适用于游离脂肪酸含量不大于2%的油脂样品的脂肪酸含量测定。 2、原理 样品中的脂肪酸经过适当的前处理(甲酯化)后,进样,样品在汽化室被汽化,在一定的温度与压力下,汽化的样品随载气通过色谱柱,由于样品中组分与固定相间相互作用的强弱不同而被逐一分离,分离后的组分到达检测器(detceter)时经检测口的相应处理(如FID 的火焰离子化),产生可检测的信号。根据色谱峰的保留时间定性,归一化法确定不同脂肪酸的百分含量。 3、试剂与材料 除非另有说明,本方法所用试剂均为分析纯,水为GB/T6682规定的一级水。 3、1石油醚:沸程30℃~60℃。 3、2甲醇(CH3OH):色谱纯。 3、3正庚烷[CH3(CH2)5CH3]:色谱纯。 3、4无水硫酸钠(Na2SO4)。 3、5异辛烷[(CH3)2CHCH2C(CH3)3]:色谱纯。 3、6硫酸氢钠(NaHSO4)。 3、7氢氧化钾(KOH)。 3、8氢氧化钾甲醇溶液(2mol/L):将13、1g氢氧化钾溶于100mL无水甲醇中,可轻微加热,加入无水硫酸钠干燥,过滤,即得澄清溶液,有效期3个月。 3、9混合脂肪酸甲酯标准溶液:取出适量脂肪酸甲酯混合标准移至到10mL容量瓶中,用正庚烷稀释定容,贮存于-10℃以下冰箱,有效期3个月。 3、10单个脂肪酸甲酯标准溶液:将单个脂肪酸甲酯分别从安瓿瓶中取出转移到10mL容量瓶中,用正庚烷冲洗安瓿瓶,再用正庚烷定容,分别得到不同脂肪酸甲酯的单标溶液,贮存于-10 ℃以下冰箱,有效期3个月。 3、11丙酮:色谱纯。 5、仪器与设备 5、1实验室用组织粉碎机或研磨机。 5、2气相色谱仪:具有氢火焰离子检测器(FID)。 5、3毛细管色谱柱:聚二氰丙基硅氧烷强极性固定相,柱长100m,内径0、25mm,膜厚0、2μm。
己酸(caproic acid) 辛酸(caprylic acid) 癸酸(capric acid) 月桂酸(1auric acid) 肉豆蔻酸(myristic acid) 棕榈酸(palmitic acid) 棕榈油酸(palmitoleic acid) 硬脂酸(stearic acid) 油酸(oleic acid) 反油酸(elaidic acid) 亚油酸(1inoleic acid) α-亚麻酸(α-1inolenic acid) γ-亚麻酸(γ-1inolenic acid) 花生酸(arachidic acid) 花生四烯酸(arachidonic acid) 二十碳五烯酸(timnodonic acid ，EPA ) 芥子酸(erucic acid) 二十二碳五烯酸(鰶鱼酸)(clupanodonic acid) 二十二碳六烯酸(docosahexenoic acid ，DHA) 二十四碳单烯酸(神经酸)(nervonic acid) C 4：0 C 6：0 C 8：0 C10：0 C12：0 C14：0 C16：0 C16：1，n-7 cis C18：0 C18：1，n-9 cis C18：1，n-9 trans C18：2，n-6,9,all cis C18：3，n-3，6，9，all cis C18：3，n-6，9，12 all cis C20：0 C20：4，n-6,9,12,15 all cis C20：5，n-3，6，9,12，15 all cis C22：1，n-9 cis C22：5，n-3，6，9，12，15 all cis C22：6，n-3，6，9，12，15，18 all cis C24：1，n-9 cis 碳水化合物(carbohydrate) 分类：
初中英语演讲稿3分钟（一） As you slowly open your eyes, look around , notice where the light comes into your room; listen carefully, see if there are new sounds you can recognize; feel with your body and spirit, and see if you can sense the freshness in the air. Yes, yes, yes, it’s a new day, it’s a different day, and it’s a bright day! And most importantly, it is a new beginning for your life, a beginning where you are going to make new desicisions, take new actions, make new friends, and take your life to a totally unprecedented level! You know all this is real as long as you are confident,passionate and committed! And you are confident, you are passionate, you are committed! You will no longer fear making new sounds, showing new facial expressions, using your body in new ways,approaching new people, and asking new questions. You will live every single day of your life with absolute passion, and you will show your passion through the words you speak and the actions you take. You will focus all your time and effort on the most important goals of your life. You will never succumb to challenges of hardships. You will never waver in your pursuit of excellence. After all,you are the best, and you deserve the best! As your coach and friend, I can assure you the door to all the best things in the world will open to you, but the key to that door is in your hand. You must do your part, you must faithfully follow the plans you make and take the actions you plan, you must never quit, you must never fear. I know you must do it, you can do it, you will do it, and you will succeed! Now stand firm and tall, make a fist, get excited, and yell it out: I must do it! I can do it! I will do it! I will succeed! I must do it! I can do it! I will do it! I will succeed! I must do it! I can do it! I will do it! I will succeed! 初中英语演讲稿3分钟（二） It’s a very intresting topic today. I think my dad was a hero for me when i was a young child. we'd go fishing, walks, and other fun things for a kid. Every child has a good and great father, and so do i. my dad played a very important role in my daily life——exactly speaking, in my past 16 years. My father always stands in the center of my life，from past till now and possibly in the future. My family was rather poor when i was in my childhood. we didn't have our own house and had to live in a shabby，small room rented from my father's factory. the room was so small that there was little space for people to walk. i didn't have my own bed and had to sleep with my parents. this is terrible both for my parents and me. But father made this all different！he works very hard on his own business, now we have our own 2 housese,surly,i have my own room.and he take our family so much happiness, richer and richer. When i was little, i did everything with my dad. you could always find me sitting on his knee or walking and doing everything with him. every night he would read me a bed time story and make the voices of each character.
3分钟简短英语演讲稿 1.Agree or disagree: Advertising aiming at children should be restricted. I disagree. It’s fair to advertize to children even children are always said to be unable to distinguish between reality and fiction, between entertainment and advertising. A supposed consequence of advertising is that children are being persuaded to demand things that they don’t need and to adopt consumerist values and attitudes in their formative years. However, it’s up to the parents to determine what should and should be bought for their children. Children need to know how to see these ads and realize how a certain product would affect them and thus balance out the pros and cons and see if it’s in their best interest. In my opinion, the parents as well as the world need to stop babying children and let them learn lessons for life, because certain things can’t be restricted well. Temptation is always at children’s side. They have to learn to resist and make responsible decisions. 2.Agree or disagree: Junk food should be taxed. I agree that junk food should be taxed. In modern society, many people are attracted to eat in KFC or MacDonald’s. Everyday, many hamburgers, fried chips and so on are sold out. Despite the good sale, it can’t be denied that all these are junk food. Just as the word junk, they bring great harm to our healthy. So, there comes a appeal that junk food should be taxed.