Name: quantification of hydrogen concentrations in surface and interface layers and bulk materials through depth profiling with nuclear reaction analysis
Uploaded: 2016-03-29T13:00:00.000+00:00
Duration: 14 min 11 s
Description: Watch this Scientific Journal Video about Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis at JoVE.co

我们非常赞赏分枝松本用于实现通过远程控制从数据采集计算机的麦芽加速器参数使得能够NRAħ深度分布的自动测量软件。我们感谢K.难波为进行巧妙的Pd（110）样品制备和NRA和TDS测量的BL-1E特高压系统和C.野在加速器操作技术援助。在SiO 2 /硅（100）样品感激地接受为NEC公司，日本的Z.刘的礼貌。这项工作部分由日本学术振兴会（JSPS），以及通过赠款在资助科学研究在创新领域的授予在援助科学研究（批准号24246013和26108705）的支持"材料设计通过Computics:复杂的关联和非平衡Dynamics的教育，文化，体育，科学部，技术部日本。

1.实验计划<ol><li>确定根据测量任务（BL-1E为表面氢，BL-2C为散装或界面氢）感兴趣的MALT加速器束线。联系协助科学家（目前MW或KF）讨论NRA测量及其必要的准备工作的细节。 </li><li>下载束流时间申请表格，并观察MALT网站31日提交的最后期限。 注:麦芽设施分别每三月和九月的夏季（4月至9月）和冬季（10月 - 月）上半年而言，诚邀新的项目建议。 </li><li>写光束时建议，并提交MALT网站上的说明。 </li><li>该提案的批准后，确认为即将到来的半年任期梁时间表为MALT网站31日公布。安全培训需要在学期开始的新用户。 </li><li>准备在ADVA梁时间NCE。考虑所需的材料的运输实验的所有细节，以及时间，对样品安装，尤其是用于在特高压原位表面处理（如果需要）。对于NRA测量就绪的目标样本梁时间开始之前。 </li></ol> 2.准备在BL-1E NRA测量（UHV） 注:在处理用于在真空中使用的仪器和材料，包括清洁工具时，一定要戴上手套。 <ol><li> 安装单晶样品放入超高真空（参见图1（B））。 <ol><li>设置点焊机电源3.5。将单晶样品到干净，平坦，不导电的工作表面和点焊两个4厘米长的片钽（Ta）的线（0.3毫米直径）平行采样的边缘。 </li><li>轻轻弯曲的电线，以适应周围的晶体边缘形状而在点焊点对付弯曲力用镊子或钳子。上的约1cm每侧的长度，一个pply 2-4额外点焊点线对沿着晶体边缘。 </li><li>弯曲的线端从晶体中心在平行于工作表面水平面点之遥。放置样品架具有支持导线到钽板样品（0.3mm厚）。对准样品，以覆盖背面灯丝加热器上方的孔并通过点焊所有四个支撑金属丝端部到板固定检体的位置。如果可能的话，将多个焊接点每根导线年底，丝尖走向样本。 </li><li>切掉任何过多的线材长度从固定板边缘突出。设置点焊机的功率最小，并通过点焊钳释放一个脉冲关闭空。点焊K型（镍铬 - 镍铝）热电偶（0.2毫米直径）的晶体样品的上边缘。 </li><li>确认样品的正确的连接通过在低温恒温器头测量馈电触点之间的电阻安装:长丝与样本（二IAS接触线连接到样品架板）&gt; 20MΩ;灯丝与地面（低温恒温器体）&gt; 20MΩ;灯丝引线（0.3毫米直径W的）&lt;3Ω;热电偶导线:〜16Ω;热电偶与地面&gt; 20MΩ;热电偶与样品〜20Ω和〜8Ω（取决于线材，镍铬或镍铝）。 </li><li>注意样品和光束轮廓显示器（石英板）的中心之间的距离。 </li><li>特高压操纵头更换垫片铜和小心地插入安装用低温恒温器样品。拧紧法兰螺栓和疏散系统，特高压下从协助科学家的指令。 </li><li>特高压准备室，用于通过连接器磁带和铝箔的烘烤。保证所有的涡轮分子泵的正常操作，至少30分钟，一个压力&lt;2×10 -4帕。打开加热器室烘烤特高压系统24小时。 </li><li>下面确认1×10 -5帕离子规读数。关闭加热器烘烤秒。激活非蒸发吸气剂（NEG）与内部加热器元件泵在400-450℃下进行30分钟，同时腔室仍是热的。 </li><li>让凉爽的室内3-4小时，然后重新装QMS电子和电源电缆离子枪和光学LEED。 QMS，离子枪，以及LEED的德加细丝。确认室基础压力为&lt;1×10 -8帕充分冷却到室温（在12-24小时）之后。 </li></ol></li><li> 特高压准备单晶表面（参见图1（a））。 <ol><li>在与机械手的x，y，z台室中心位置的样品，并旋转以视口和离子枪（面向气体定量配给器）之间对齐表面。接通离子枪电源和调整"排放"控制到20 mA。看通过视口的样品并使得发光的离子枪灯丝的镜像是在样品表面上可见细调整样品旋转角度。 </li><li>设置"束能量"上的离子枪婆WER提供800伏特。在室底部关闭NEG泵闸阀引进6×10 -3帕的氩气成通过可变泄漏阀特高压室。确认约2微安溅射离子电流（数字测试仪，从样本到地）和溅射表面，在室温下10分钟。 </li><li>液氮添加到机械手低温恒温器。在操纵头，连接灯丝加热导致电源和数字测试仪（20毫伏范围）热电偶馈通。接地灯丝。 </li><li>连接样品接触到偏压电源。应用1千伏的样本偏差。使用灯丝加热器电流达6.6，一种用于退火，氧化，和闪光灯加热在下一工序（2.2.5），同时监测热电偶电压（样品温度）与该数字测试仪。 注意:切勿触摸数字测试仪或操纵头，而样本是有偏差的（致命电击危险！）。 </li><li>特高压退火样品1000 K中10分钟，保证压力仍然低于2×10 -7帕。氧化在750 K的5.0×10 -5帕O 2的5分钟，然后在室温（RT）下在5.0×10 -5帕的 H 2降低。特高压进行最后的闪烁到600ķ。 </li><li>观察LEED模式，并重复步骤2.2.1至2.2.2（溅射）和2.2.3。 2.2.5（退火/氧化/ H 2 -还原），直到与低背景的结果（ 图3）和无杂质亮点清晰（1×1）结构保持在俄歇电子谱32。溅射在重复的溅射/退火周期只有2-3分钟。 </li><li> （可选）液态氮添加到操纵器低温恒温器冷却样品至90 K和暴露于H 2气的几Langmuirs（L）（1:L = 1.33×10 -4帕）。执行TDS测量，最后确认H 2热脱附谱与文献数据符合15。 注:必要的准备前进中的NRA束时间已完成。干净的水面目标，现在可以经常〜2-3小时内通过与2.2.6 2-3分钟溅射周期重复步骤2.2.1准备。 </li></ol></li></ol><img alt="图3" src="/files/ftp_upload/53452/53452fig3.jpg" /> 在BL-1E特高压系统图3. LEED的清洗钯模式（223伏特）（110）表面 ，清除（1×1）图案鲜艳的衍射斑点在低背景标志着一种原子秩序井然的表面结构。 <a href="https://www.jove.com/files/ftp_upload/53452/53452fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <ol start="3"><li>对齐15 N离子束单晶目标。 <ol><li>在特高压1E室，在室内中心位置样品（x = 25，y = 26，用眼睛来QMS前孔的高度调整Z）和旋转面对15 N离子束线。带来石英板束分布监视器（ 图1（B））插入NRA测量位置由在步骤2.1.5测定样品监视器距离降低样品架。关于窗口凸缘设置操纵器下面数码相机上石英板在加速器控制室TV监视器发送束轮廓图像。 </li><li>删除所有其他电气触点在机械手头部进行采样和信号线连接到控制室数字电流积分。在BL-1E静电偏转电压设为8500 V.公开赛特高压室和弯曲磁铁BM04之间的BL-1E三个手动闸阀。 </li><li>获得辅助科学家的指令来熟悉中控室油门控制系统。 注意:加速器参数（如光束能源和方向限定磁铁字段和聚焦透镜）被设置与中央控制面板上的可分配的拨号。束线阀门和法拉第杯子远程开/鼠标点击和气动执行机构关闭。 </li><li>在控制室，开关从"待机"模式为"操作"电流积分。集成的模拟输出连接到电流指标。在油门控制面板，在狭缝反馈模式加速调整15 N离子束能量为5,535高斯（参数:NMR03）的能量分析仪磁场搭配弯曲磁场（参数HPB04）到〜-6,033.4高斯直接离子束在上特高压1E目标室。设置磁四极透镜参数（MQ04）到XCC = 4.64 A和YCC = 5.15 A到大约聚焦光束。 </li><li>在中控室，加速器和束线1E之间打开两个闸阀。打开法拉第杯（FC）FC04，并在电视屏幕上靶室的石英片观察离子束轮廓。微调BM04和MQ04的参数设置来获得轮廓监控板中心精心聚焦离子束。石英调整显示器的样品manipulat z位置或者，如果必要的。 </li><li>关闭法拉第杯FC04和采样监测距离再次抬起样品z位置。注意NMR03 / HPB04 / MQ04（XCC，YCC）参数，并将其保存在一个新的MagparNNN.xls文件的束流时间（NNN，一个三位数字）。 注意:在此基础上参考NMR03 / HPB04输入，MagparNNN.xls计算能量分析（BM03）和方向开关（BM04）匹配磁场参数磁体必须保持一个15 N中，在目标上的离子束的位置能量扫描。 </li></ol></li></ol> 3.准备测量NRA在BL-2C <ol><li>抬起从束线位置的任何以前使用的样品引入到所述操纵器传递棒，与固定螺钉的安全高度，并以光束线紧密闸阀。 </li><li>在分离在机械手的KF法兰连接馈电和回转泵在线样品当前行。从分离的闸阀法兰操纵者。 </l我&gt; <li>将机械手到准备表和幻灯片样品架出传输管。机械手旋转轴水平放置样本。 </li><li>松开样品夹的两颗M2螺栓（ 图2（B）），并删除旧的目标。设置新的样品，对齐平行轴机械手，并拧紧螺丝钳。收回样品放入输送管，并与固定螺钉的安全位置。 </li><li>在闸阀更换垫片铜并重新安装机械手的束线。安装旋转泵线机械手。关闭在回转泵线到涡轮分子泵（TMP）阀。 </li><li>打开机械手的旋转泵管线阀，疏散输送管10-15分钟以恢复旋转底座的压力。关闭机械手泵管路阀门和旋转泵行TMP开阀。慢慢打开闸阀操纵和撤离20-30分钟，以恢复2-3×10 -3帕。 </li><li>较低的采样光束线的位置和排列表面上没有光束剖面监视器（玻璃板）的RMAL与BL-2C摄像头和附近的电视监控的援助入射光束的方向。然后BL-2C摄像头信号线连接到电视监控控制室。对NRA室和弯曲磁铁BM04之间的BL-2C打开两个气动闸阀。 </li><li>连接样品操盘馈电和数字电流积分（控制室）之间采样电流信号线。在加速器控制室，从切换模式为&#39;操作&#39;袖手旁观&#39;和连接集成模拟输出电流积分器电流监控器。 </li><li>粗略地对准15 N离子束通过设置弯曲磁场（参数HPB04）的BL-2C为目标，以〜0.6高斯（极性:正），磁四极透镜MQ04参数XCC = 4.64 A和YCC = 5.15 A，和四极透镜MQ-2C参数为a = 3.3和B = 3.6 A至约聚焦光束。 </li><li>微调HPB04 / MQ04（XCC，YCC）/ MQ-2C（A，B）参数来优化梁输电工程离子（通畅的通道目标）和目标光束剖面（使用光束轮廓监控BPM-1C和BPM-2C和BL-2C摄像机图像），并注意最佳设置。 </li></ol> 4.测量NRA在BL-1E <ol><li> Flash的热钯样品600 K，从任何污染物吸附自由表面。在145 K的灯丝加热（〜3.6）和运行压缩，他低温恒温器（或液氮冷却）稳定样品的温度。 </li><li>闭阀到加速器和NEG泵和暴露样品到2,000 LH 2在145 K。让样品（2.66×10 -3帕×100秒）冷却至80 K和调整为1×10 -6 Pa的H 2背景压力。 </li><li>在控制室，在BM03的能量扫描（通常NMR03 = 5525高斯）设定为15N离子束的能量来所需的开始值，并根据MagparNNN.xls表调整BM04。 </li><li>油门CONTRO加载NRA数据采集软件（NRAmain.vi）在BL-2C升PC。选择深度剖析常规"AutoScanLinuxUHVfb3.vi"。在AutoScanLinuxUHVfb3.vi，推动"阅读的当前值"当前的磁铁参数设置传送到控制PC软件。 </li><li>再次验证上的BL-1E所有阀都打开，使样品电流信号线连接，即当前的数字化仪被设置为&#39;操作"，而理想的15±5 nA的的15 N光束可 ​​以用FC04。 </li><li>设置统计的启动，停止和（分别为典型的5525高斯5,600高斯和高斯1，）能量扫描的BM03参数的步长值并打开选项&#39;强制TVC到GVM"。对于15 N 2+〜15 nA的光束中，"采集时间"参数设置为50秒。 </li><li>点击AutoScanLinuxUHVfb3.vi控制台中的"执行"箭头开始自动采集深度剖面（最多〜35纳米的深度为钯STOP = 5600高斯）。在扫描结束时（或为较早TERMIN通货膨胀），点击"停止测量"关闭数据文件。 </li><li>开关电流数字化仪模式"袖手旁观"，从分离样品操纵穿心采样电流线，而特​​高压室之前关闭的BL-1E最后闸阀。 </li><li>通过关闭可变漏阀停止后台H 2气用量。打开在特高压腔底部的NEG闸阀。 （可选:取样品的H 2 TDS谱）。 </li><li>有关其他NRA测量（可选），重新露出的Pd（110）表面H 2的说明步骤4.2并重复步骤4.3通过4.9。 </li></ol> 5.测量NRA在BL-2C <ol><li>在中控室，在BM03设置15 N离子束能量为能量扫描（通常NMR03 = 5525高斯开始在表面分析）所需的启动值。 </li><li>在加载BL-2C油门控制PC上的NRA数据采集软件（NRAmain.vi）。选择深度剖析程序"AutoScanLinux11.vi"。输入自动能量扫描（START，STOP，STEP），匹配的开始到在步骤5.1设定的BM03值所需的BM03参数。对于目前的SiO 2 / Si的样品，"采集时间"设置为50秒。 </li><li>再次验证上的BL-2C所有阀都打开，使样品电流信号线连接，即当前的数字化仪被设置为&#39;操作"，而一个15 N 2+ 50-100 nA的的光束可 ​​在FC04。 </li><li>单击"AutoScanLinux11.vi&#39;执行&#39;箭头收购，在BM03参数的停止值将自动终止深度剖面。在扫描结束（或提前终止），点击"停止测量"关闭数据文件。 </li></ol> 6.数据分析<ol><li>复制*从收购PC /家用/ csadmin / DataTaking / BTNNN .nra原始数据文件（NNN是当前束流时间数）到一个USB记忆棒和TRansfer数据分析PC。 </li><li>启动自制软件的NRA数据分析和公开程序"NRA-Linux的-2C-v3.ipf"。获取程序NRA分析-2C-v4.ipf，LinuxAddOn -3- v3.ipf，和菜单NRA.ipf，并将其复制到包含伊戈尔用户例程的数据文件夹。 </li><li>编译程序，并从出现的"NRA"菜单中选择"加载NRA数据"。选择数据文件在第4或5测量，然后点击"继续"在出现的弹出对话框。 注意:软件从测量的数据产生两个图表的输出:"原始数据"（原始γ-计数（GRS）与NMR03磁场数据采集期间所显示），以及&#39;NRA光谱"中，对应于激发曲线（背景-减去事件负责标准化γ收益（ 我 常模 ）与15 N离子能量）。 </li><li>从"NRA"菜单中选择"正确的采样电流读数"，然后选择"重新计算乌拉特ISC（全波）从平均ISC / IFAR比例（ 如样品W / O偏置）"，从下拉菜单选项来重新调整离子束的电荷从目前的数字化阅读以实际尺寸（μC），参考平均FC04梁整个数据集的当前读数。从"NRA谱"图中删除"Inorm_by_Faraday"痕迹。 注:归到这一规模的综合事件负责是最好（超过正常化法拉第电流），因为它能更好地反映实际命中目标比FC04电流15 N离子电荷。后者被测量一次法拉第杯打开之前（交付光束到目标），因此没有考虑，在采集时间为每个数据点总是发生在一定程度上的电子束电流的波动。重新调整样品费是必要的，因为目前的数字化阅读高估实际的事件离子束的电荷因继发埃尔从目标ectron发射。 </li><li>确定分别对应为E RES的NMR03值（表面共振峰在"原始数据"积最大位置）。如果从5,535高斯的软件默认值不同，更正条目（如果需要的话也停止功率值）从"NRA"菜单中选择"NMR，能源和深度规模"程序。 </li><li>如果背景率（CPS）更正就显得十分必要，先用"正确法拉第读数"功能修改背景值，进入1的修正系数后，重新计算从原始（GRS）数据归一化γ-收益率（为FC04电流）。然后再次运行"正确的样品电流读数"功能（步骤6.4）也重新计算收费标准化γ-产量与正确缩放相对于FC04法拉第修订的背景。 </li><li>情节充电归γ-产量与深度顶轴显示卷积水电根深度分布（ 图4）。 </li><li>添加误差线用从&#39;NRA"菜单中的各自的功能的曲线图。只要有可能，喜欢充正常化。 注:计数统计定义错误的NRAγ-产量ΔI，I = GRS - 背景 ，通过测量的原始计数的错误传播的不确定性， <img alt="式（1）" src="/files/ftp_upload/53452/53452eq1.jpg" />和背景， <img alt="式（1）" src="/files/ftp_upload/53452/53452eq2.jpg" />因此，计算如下: <img alt="式（1）" src="/files/ftp_upload/53452/53452eq3.jpg" /> 。在深度分布图（ 图4和5）是Δ 我 规范 =ΔI /入射离子束的电荷的误差棒。 </li><li> （可选）与合适的模型功能3执行数据的拟合分析。 </li></ol>

<ol>
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The authors declare that they have no competing financial interests.

图4显示在钯（110）在BL-1E超高真空系统单晶的例子中，有效的区分和表面吸附通过15 N NRA从散装吸收氢的定量。在这三个轮廓的表面H的峰的高再现性证明了原位 UHV样品制备的可靠性和对NRA测量的非破坏性的性质。与预期的原子的饱和密度进一步确定ħ覆盖的定量协议显示NRA测量的精度。接近的H 2的NRA型材之间预曝光的Pd（110）和在Pd只有表面的氢的两个激发曲?...

氢作为杂质或作为一个庞大的各种材料构成和的氢引起的相互作用现象的财富的普及使揭示的许多领域中的表面附近区域，并在固体埋入界面的重要任务的氢气分配工程和基础材料科学。突出的上下文包括在氢气能源的应用，燃料电池，光电，和加氢催化，氢保留和脆化在核和聚变反应堆的工程，在外延生长制造和氢氢引起的表面活性剂效果的储存和净化材料吸氢的研究半导体器件技术有关的电气可靠性问题。 尽管它的无所不在和简单的原子结构，氢的定量检测构成分析挑战。氢气仅包含单个电子，否则通用的元素analys是电子能谱呈现无效。通过质量分析，光学，或核共振技术如冶金熔接，热脱附，红外线吸收或核磁共振光谱共同氢气检测方法主要是不敏感的氢的深度位置。这排除， 例如 ，表面吸附和散装吸收氢而在其物理和化学物质的相互作用基本上不同区分，因此它们的区别变得对于包含小体积和大表面积的纳米结构材料的分析日益重要。通过二次离子质谱法氢谱，尽管提供深度分辨定量ħ浓度，同样破坏性分析的目标作为冶金融合，以及溅射效应可能使表面不可靠附近获得的深度信息。 在狭窄的核反应分析能量共振通过1 H的（E RES）（15 N，αγ）12下 ​​以6.385兆电子伏1-3反应，另一方面，结合了高的深度分辨率无损氢定量的优点在少数的顺序纳米的表面附近。该方法确定表面H的coverage与在10 13 cm -2的顺序的灵敏度（〜典型原子单层密度的1％）。在材料的内部的氢浓度可与几个10 18 cm -3的（〜100在。ppm的）和大约2微米的探测深度范围内的检测限进行评估。近表面深度分辨率是通常在15 N离子束的表面垂直入射2-5纳米到分析靶。在表面掠射的几何形状，分辨率可以进一步跌破1纳米增强值。见参考文献。 3详细介绍。 这些功能已被证明1 H（ <s达&gt; 15 N，αγ）12 C NRA作为一个强大的技术，阐明了大量的各种工艺和材料3氢在表面和界面的静态和动态行为。通过兰福德4于1976年成立，15 N NRA最初主要用于定量测定散装材料和薄膜卷^ h的浓度。除其他目的，通过15 N NRA获得的绝对氢浓度已被用于校准其它，不能直接定量，氢气检测技术5,6。 15也与层状薄膜结构定义良好的接口的目标ñNRA氢谱已被描述7-10。最近，已取得很大进展，在化学上清洁和结构明确目标的近表面区域学习氢由15 N NRA用表面分析超高真空（UHV）仪器组合以prepar实现ê原子控制原位表面对H分析3。 通过量化在单晶表面上的氢覆盖，NRA已显著氢吸附相的电流微观理解，许多材料作出了贡献。1 H（15 N，αγ）12 C NRA是另外的唯一的实验技术来直接测量零点表面吸附H原子11， 即振动能量，它可以揭示在入射离子束的方向吸附的H原子的量子力学的振动运动。通过表面吸附和批量吸收之间纳米级判别的能力H，15 N NRA可以通过材料的表面，如相关的水合约会12或观察的H面下方氢化成核提供有价值的洞察氢入口-absorbing金属13-15。高-Resolution 15 N NRA应用已经证明，以检测吸附层16的亚单层的厚度变化，并区分表面吸附从体积吸收的氢在钯纳米晶体17的潜力。与热脱附谱（TDS）的组合允许的H 2热解吸特征明确的标识和用于吸附的热稳定性的深度分辨的评估和吸收的氢的状态对解吸和扩散13,15,18。由于它的非破坏性的性质和高的深度分辨率1 H（15 N，αγ）12 C NRA也检测氢的理想方法埋在完整的接口，其允许在金属/金属19-22和金属研究氢捕集/半导体界面16,23-25 ​​和堆叠薄膜系统9跟踪氢扩散。通过直接可视化氢再分配phenomen，涉及到电气设备退化/硅基二氧化硅接口之间的金属氧化物半导体（MOS）结构，NRA做出了器件可靠性研究26特别宝贵的贡献。 在NRA氢气检测原理是照射所分析的目标至少有Ë 解析度 = 6.385兆电子伏的15 N离子束诱导在15 N和1小时之间的谐振1 H（15 N，αγ）12 C核反应材料。该反应释放出的是与附近的样品一闪烁检测器测得的4.43兆电子伏特性γ射线。所述γ-产量成比例的目标的一定深度的H +浓度。由事件15 N离子的数量归这个信号转换它到γ检测系统已校准用已知的H +浓度的标准目标之后绝对ħ密度。15 </sup&gt;ñ达E RES离子事件可以与目标表面上氢反应。埋氢的浓度在高于ë 水库能量（E I）具有15 N离子入射测定。目标材料内部，15 N离子遭受由于电子制动能量损失。此效果提供了高深度分辨率，因为1 H（15 N，αγ）12 C核反应共振有一个很窄的宽度（洛伦兹宽度参数Γ= 1.8千电子伏）和6.4 N之间范围的材料阻止本领MeV的15 1-4千电子伏/ nm时，使得15 N离子的通过只有几个原子层的通路是足够将其能量转移共振窗口之外。因此，共振反应检测埋H在E I&gt;的 ​​探测深度D E 解析度 =（E I - 电子 RES）/ S，其中S是电子停止分析材料3的功率。 通过测量γ产量，而在小的增量扫描所述入射15 N离子能量，可以得到包含在目标中的氢的浓度深度分布的核反应激发曲线。在这种激励曲线（γ-收益率与15 N能源），实际的^ h深度分销是卷积，增加了一个主要高斯扩大和对于深度分辨率3的主要限制的NRA工具的功能。在表面（ 即在E I = E RES）的高斯宽度由多普勒效应是由于相对于目标表面的H原子的零点振动11,27,28为主。检测埋氢的收益率曲线E I&gt; 电子 资源是由于随机15 N离子能量straggli受到额外高斯加宽组件target内纳克。正比于离子轨迹长度的平方根的歧离宽度增加在材料29,30及成为支配分辨率限制上述探测10-20纳米深度的因素。 为了证明一些非常典型的氢分析应用程序与15 N NRA，我们在这里示范性地描述:（1）表面H覆盖的定量评价，并在H 2暴露钯（Pd）单晶，大宗吸收氢浓度和（2）的深度位置和氢层的密度在的 SiO 2 / Si的（100）堆叠的埋入界面的评价。全国步枪协会的测量是在麦芽5东京大学，它提供了一个高度稳定和良好的单色（ΔE 我 ≥2千电子伏）的6-13 MeV的15 N离子束的MV范-德-格拉夫串列加速器31进行。作者已经开发出一种计算机控制系统的accelerat或使氢分析自动化能量扫描和数据采集。反映了h以上分析的应用提出了两种不同的NRA测量任务，麦芽设施提供了两种离子束线，专业实验站:（1）特高压表面分析系统，单锗酸铋（BGO，毕4个 GE 3 O 12 ）致力于氢表面覆盖度的定量NRAγ-闪烁探测器，以零点振动谱，并在与TDS一个独特的组合原子控制的单晶目标^ h深度剖析;和（2）装备有两个BGO检测器的高真空腔室定位非常接近目标增加γ-检测效率，为低级ħ检测限和更快的数据采集。这种设置有没有样品制备设备，但允许快速样品交换（约30分钟），因此对于吞吐量较高的目标而精心CONTROLLED表面层不是分析任务，如在掩埋界面ħ分析或散装ħ浓度的定量的一个重要部分。在这两个光束线，BGO探测器方便地放置在真空系统之外，因为γ射线穿透可忽略的衰减薄室壁。 <img alt="图1" src="/files/ftp_upload/53452/53452fig1.jpg" /> 图1. NRA设置在BL-1E超高真空系统（A） 的示意性顶视图到装有溅射离子枪，低能量电子衍射（LEED）和俄歇电子能谱（AES）对在 BL-1E超高真空系统-situ安装在一个线性平移阶段制备的原子有序的和化学清洁单晶表面靶和组合NRA和TDS测量结果与一个四极质谱仪（QMS）。安装在T（B）钯单晶样品他品尝低温机械手的持有人。 <a href="https://www.jove.com/files/ftp_upload/53452/53452fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> 图1（a）所示的束线（BL）-1E，这是设备齐全的原位制备有序原子单晶表面，并具有基本压力&lt;10-8帕，以保持表面洁净度超高真空系统。提供用于表面分析工具样品访问时，4"BGO闪烁体放置在〜目标后面30mm以下。该样品安装在4轴操纵阶段进行精确的15 N离子束轴线（X，Y， Z，Θ）的定位，并且可以用液氮冷却至〜80 K或与压缩他至〜20 K 图1（B）示出安装在由点焊接钽支撑导线到他压缩低温恒温器钯单晶目标。石英表间隔绝缘SAMPL<html>从低温恒温器机体E座板电。这使所需数量NRA入射15 N离子束电流测量并允许从样品架的背面的钨灯丝电子轰击加热。 K型热电偶点焊到钯试样边缘。附着在样品上方操纵轴线A石英板是用来监测该离子束轮廓和样品光束的对准。 图2（A）表示在BL-2C具有两个4"BGO检测器的安装布置在相对 ​​于90°的到15 N光束与其前表面没有比从光束轴相距19.5毫米，样品保持器（ 图2（B））提供了用于快速样品交换简单夹紧机构并允许绕垂直轴的样品的旋转调整为15N入射角。 尔斯/ ftp_upload / 53452 / 53452fig2.jpg"/&gt; 图2. NRA设置在BL-2C。（A）的示意性顶视图成BL-2C中的高真空室配备有两个BGOγ探测器靠近目标位置。 （B）和SiO 2构成的大芯片目标样本保持器/硅（100）夹紧在。雾与水汽这个样本类型NRA分析的可视化是由15 N离子束照射的点之后， <a href="https://www.jove.com/files/ftp_upload/53452/53452fig2large.jpg" target="_blank">请点击这里查看该图的放大版本。</a>

<table><tbody><tr><td>&lt;strong&gt;Material&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Pd single crystal&amp;nbsp;</td><td>SPL (Surface Preparation Laboratory), http://www.spl.eu/products.html, or any other suitable supplier</td><td>Order made to specification</td><td>Disk, 9 mm diam., (110) oriented, aligned to &amp;lt; 0.5 degree or less, one side polished to &amp;lt; 0.3 mm roughness, self-prepared specimen&amp;nbsp;</td></tr><tr><td>H&lt;sub&gt;2&lt;/sub&gt; gas</td><td>Joutou Gas Corporation, Ltd., Japan, http://www.jyotougas.co.jp/item/gas.html</td><td></td><td>(99.9995%), or any other suitable supplier</td></tr><tr><td>O&lt;sub&gt;2&lt;/sub&gt; gas</td><td>Joutou Gas Corporation, Ltd., Japan, http://www.jyotougas.co.jp/item/gas.html</td><td></td><td>(99.99%), or any other suitable supplier</td></tr><tr><td>Ar gas</td><td>Joutou Gas Corporation, Ltd., Japan, http://www.jyotougas.co.jp/item/gas.html</td><td></td><td>(99.99995%), or any other suitable supplier</td></tr><tr><td>Tantalum / Wire</td><td>The Nilaco Corporation, http://nilaco.jp/en/order.php</td><td>TA-411325</td><td>(99.95%), 0.3 mm diam., or any other suitable supplier</td></tr><tr><td>Alumel / Wire&amp;nbsp;</td><td>The Nilaco Corporation, http://nilaco.jp/en/order.php</td><td>851266</td><td>0.2 mm diam., or any other suitable supplier</td></tr><tr><td>Chromel / Wire (Chromel)</td><td>The Nilaco Corporation, http://nilaco.jp/en/order.php</td><td>861266</td><td>0.2 mm diam., or any other suitable supplier</td></tr><tr><td>&lt;strong&gt;Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>3 keV Raster Ion Bombardment Gun and Control</td><td>VARIAN, http://www.eurovac.se/docs/varian1.htm</td><td>981-2046 Power Supply, 981-2043 Ion Gun</td><td>or equivalent product of any other suitable manufacturer</td></tr><tr><td>LEED-AUGER Optics</td><td>OCI, http://www.ocivm.com/spectrometer_bdl800ir.html</td><td>BDL600IR</td><td>or equivalent product of any other suitable manufacturer</td></tr><tr><td>Quadrupole Mass Spectrometer</td><td>Pfeiffer Vacuum, http://www.pfeiffer-vacuum.com/</td><td>Prisma QMS 200</td><td>or equivalent product of any other suitable manufacturer</td></tr><tr><td>Palladium Hydrogen Purifier</td><td>Power + Energy Inc., http://www.powerandenergy.com</td><td>PE-3001</td><td>99.9999999% purity; P+E H2 purifiers are now business of SAES Pure Gases Inc., http://www.saespuregas.com/Products/Gas-Purifier/Hydrogen/Palladium-Membrane/Palladium-Purifier-PE2100.html</td></tr></tbody></table>

quantification of hydrogen concentrations in surface and interface layers and bulk materials through depth profiling with nuclear reaction analysis

经由谐振1小时核反应分析（NRA）（15 N，αγ）12 C反应是深度剖析的一个非常有效的方法，该方法定量和非破坏性地揭示了在表面上的氢密度分布，在接口和在体积固体材料具有很高的深度分辨率。该技术适用于通过静电加速器提供6.385兆电子伏15N的离子束和特异性检测在深度通过1 H同位素为从靶表面约2微米。表面H的coverage与在〜10 13厘米的量级灵敏度测量-2（〜典型原子单层密度的1％）H体积和浓度为〜10 18厘米的检测限-3（〜100在。ppm的）。近表面深度分辨率为表面法线15 N离子入射2-5纳米到目标并且可以提高到值低于1毫微米用于通过ADOP非常平坦的目标婷表面掠入射几何。该方法是通用的并易于适用于任何在高真空兼容均质材料具有光滑的表面（无孔）。导电目标通常容忍忽略不计降解离子束照射。氢定量和正确的深度分析所需要的基本组合物（除氢）和靶材料的质量密度的知识。特别是在超高真空方法原位目标制备和表征，1H组合（15 N，αγ）12 C NRA在原子控制表面和纳米界面非常适合氢分析。我们示例性地在这里展示15 N NRA在东京大学（1）定量测定表面覆盖率和氢在暴露的Pd一个的 H 2的近表面区域中的体相浓度的麦芽串联加速器设施的应用（110）的单晶，和（2）确定薄的 SiO 2薄膜的界面附近在Si（100）氢的深度位置和层密度。

图4显示了近地表的H 2 NRA ^ h型材-exposed钯在90 K A样品温度在BL-1E特高压系统测量（110）1.33×10 -6 Pa的H 2的背景压力。在15 N离子入射能量已被转换成使用钯（S = 3.90千电子伏/纳米）的制动功率探测深度。后预曝光的钯（110）样品至2,000 LH 2在145 K至诱导氢吸收到钯本体15得到开放符号轮廓。此轮廓可以达E ...

Watch this Scientific Journal Video about Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis at JoVE.co

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

我们说明1 H的应用（15 N，αγ）12 C共振核反应分析（NRA）定量评价的表面上的氢原子的密度，在体积，并在固体材料的界面层。钯（110）单晶2 / Si的（100）堆叠的和SiO的近表面氢深度剖面进行说明。

通过与核反应分析深度剖面的表面和界面层和颗粒材料氢含量的定量

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

quantification-hydrogen-concentrations-surface-interface-layers-bulk

Research

JoVE Journal

Engineering

26.4K 次观看.  The University of Tokyo. 我们说明1 H的应用（15 N，αγ）12 C共振核反应分析（NRA）定量评价的表面上的氢原子的密度，在体积，并在固体材料的界面层。钯（110）单晶2 / Si的（100）堆叠的和SiO的近表面氢深度剖面进行说明。 

视频: Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX.

In this paper, a procedure for quantifying the mass transport parameters of chemicals in various materials is presented. This process involves employing an inverse-analysis based diffusion model to vapor emission profiles recorded by real-time, mass spectrometry in high vacuum.

一个反分析方法化工运输的油漆表征

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in ...

科研

化学

Atomically Traceable Nanostructure Fabrication

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process being used in order to maintain exquisite control over both feature size and feature density. Here, we demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. Hydrogen depassivation lithography is the first step of the nanoscale fabrication process followed by selective atomic layer deposition of up to 2.8 nm of titania to make a nanoscale etch mask. Contrast with the background is shown, indicating different mechanisms for growth on the desired patterns and on the H passivated background. The patterns are then transferred into the bulk using reactive ion etching to form 20 nm tall nanostructures with linewidths down to ~6 nm. To illustrate the limitations of this process, arrays of holes and lines are fabricated. The various nanofabrication process steps are performed at disparate locations, so process integration is discussed. Related issues are discussed including using fiducial marks for finding nanostructures on a macroscopic sample and protecting the chemically reactive patterned Si(100)-H surface against degradation due to atmospheric exposure.

We report a protocol for combining the atomic metrology of the Scanning Tunneling Microscope for surface patterning with selective Atomic Layer Deposition and Reactive Ion Etching. Using a robust process involving numerous atmospheric exposures and transport, 3D nanostructures with atomic metrology are fabricated.

原子纳米结构可追溯制造

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process ...

工程学

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates.

The study of methods to generate on-demand hydrogen for fuel cells continues to grow in importance. However, systems to measure hydrogen evolution from the reaction of chemicals with water can be complicated and expensive. This article details a simple, low-cost, and robust method to measure the evolution of hydrogen gas.

一种简单，低成本和强大的系统来测量氢气与水溶液化学反应放出的音量

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) ...

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. They offer new possibilities for the characterization of living systems and are particularly appropriate for detecting, localizing and quantifying the presence of metal oxide nanoparticles both in biological specimens and the environment. Indeed, these techniques all meet relevant requirements in terms of (i) sensitivity (from 1 up to 10 &#181;g.g-1 of dry mass), (ii) micrometer range spatial resolution, and (iii) multi-element detection. Given these characteristics, microbeam chemical element imaging can powerfully complement routine imaging techniques such as optical and fluorescence microscopy. This protocol describes how to perform a nuclear microprobe analysis on cultured cells (U2OS) exposed to titanium dioxide nanoparticles. Cells must grow on and be exposed directly in a specially designed sample holder used on the optical microscope and in the nuclear microprobe analysis stages. Plunge-freeze cryogenic fixation of the samples preserves both the cellular organization and the chemical element distribution. Simultaneous nuclear microprobe analysis (scanning transmission ion microscopy, Rutherford backscattering spectrometry and particle induced X-ray emission) performed on the sample provides information about the cellular density, the local distribution of the chemical elements, as well as the cellular content of nanoparticles. There is a growing need for such analytical tools within biology, especially in the emerging context of Nanotoxicology and Nanomedicine for which our comprehension of the interactions between nanoparticles and biological samples must be deepened. In particular, as nuclear microprobe analysis does not require nanoparticles to be labelled, nanoparticle abundances are quantifiable down to the individual cell level in a cell population, independently of their surface state.

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

We describe a procedure for the detection of chemical elements present in situ in human cells as well as their in vitro quantification. The method is well-suited to any cell type and is particularly useful for quantitative chemical analyses in single cells following in vitro metal oxide nanoparticles exposure.

原位金属氧化物纳米粒子的核探针检测与单细胞定量研究

Micro-analytical techniques based on chemical element imaging enable the localization and quantification of chemical composition at the cellular level. ...

3D Depth Profile Reconstruction of Segregated Impurities Using Secondary Ion Mass Spectrometry

The presented protocol combines excellent detection limits (1 ppm to 1 ppb) using secondary ion mass spectrometry (SIMS) with reasonable spatial resolution (~1 &#181;m). Furthermore, it describes how to obtain realistic three-dimensional (3D) distributions of segregated impurities/dopants in solid state materials. Direct 3D depth profile reconstruction is often difficult to achieve due to SIMS-related measurement artifacts. Presented here is a method to identify and solve this challenge. Three major issues are discussed, including the i) nonuniformity of the detector being compensated by flat-field correction; ii) vacuum background contribution (parasitic oxygen counts from residual gases present in the analysis chamber) being estimated and subtracted; and iii)&#160;performance of all steps within a stable timespan of the primary ion source. Wet chemical etching is used to reveal the position and types of dislocation in a material, then the SIMS result is superimposed on images obtained via scanning electron microscopy (SEM). Thus, the position of agglomerated impurities can be related to the position of certain defects. The method is fast and does not require sophisticated sample preparation stage; however, it requires a high-quality, stable ion source, and the entire measurement must be performed quickly to avoid deterioration of the primary beam parameters.

The presented method describes how to identify and solve measurement artifacts related to secondary ion mass spectrometry as well as obtain realistic 3D distributions of impurities/dopants in solid state materials.

使用二次离子质谱法重建分离杂质的 3D 深度剖面

The presented protocol combines excellent detection limits (1 ppm to 1 ppb) using secondary ion mass spectrometry (SIMS) with reasonable spatial ...

Studying Soft-matter and Biological Systems over a Wide Length-scale from Nanometer and Micrometer Sizes at the Small-angle Neutron Diffractometer KWS-2

The KWS-2 SANS diffractometer is dedicated to the investigation of soft matter and biophysical systems covering a wide length scale, from nm to &#181;m. The instrument is optimized for the exploration of the wide momentum transfer Q range between 1x10-4 and 0.5 &#197;-1 by combining classical pinhole, focusing (with lenses), and time-of-flight (with chopper) methods, while simultaneously providing high-neutron intensities with an adjustable resolution. Because of its ability to adjust the intensity and the resolution within wide limits during the experiment, combined with the possibility to equip specific sample environments and ancillary devices, the KWS-2 shows a high versatility in addressing the broad range of structural and morphological studies in the field. Equilibrium structures can be studied in static measurements, while dynamic and kinetic processes can be investigated over time scales between minutes to tens of milliseconds with time-resolved approaches. Typical systems that are investigated with the KWS-2 cover the range from complex, hierarchical systems that exhibit multiple structural levels (e.g., gels, networks, or macro-aggregates) to small and poorly-scattering systems (e.g., single polymers or proteins in solution). The recent upgrade of the detection system, which enables the detection of count rates in the MHz range, opens new opportunities to study even very small biological morphologies in buffer solution with weak scattering signals close to the buffer scattering level at high Q.
In this paper, we provide a protocol to investigate samples with characteristic size levels spanning a wide length scale and exhibiting ordering in the mesoscale structure using KWS-2. We present in detail how to use the multiple working modes that are offered by the instrument and the level of performance that is achieved.

Here, we present a protocol to investigate soft matter and biophysical systems over a wide mesoscopic length scale, from nm to &#181;m that involves the use of the KWS-2 SANS diffractometer at high intensities and an adjustable resolution.

在小角度中子衍射仪KWS-2研究软物质和生物系统在广泛的长度尺度从纳米，微米尺寸

The KWS-2 SANS diffractometer is dedicated to the investigation of soft matter and biophysical systems covering a wide length scale, from nm to &#181;m. ...

生物工程

Neutron Crystallography Data Collection and Processing for Modelling Hydrogen Atoms in Protein Structures

Neutron crystallography is a structural technique that allows determination of hydrogen atom positions within biological macromolecules, yielding mechanistically important information about protonation and hydration states while not inducing radiation damage. X-ray diffraction, in contrast, provides only limited information on the position of light atoms and the X-ray beam&#160;rapidly induces radiation damage of photosensitive&#160;cofactors and metal centers. Presented here is the workflow employed for the IMAGINE and MaNDi beamlines at Oak Ridge National Laboratory (ORNL) to obtain a neutron diffraction structure once a protein crystal of suitable size (&#62; 0.1 mm3) has been grown. We demonstrate mounting of hydrogenated protein&#160;crystals in quartz capillaries for neutron diffraction data collection. Also presented is the vapor exchange process of the mounted crystals with D2O-containing buffer to ensure replacement of hydrogen atoms at exchangeable sites with deuterium. The incorporation of deuterium reduces the background arising from the incoherent scattering of hydrogen atoms and prevents density cancellation caused by their negative coherent scattering length. Sample alignment and room temperature data collection strategies are illustrated using quasi-Laue data collection at IMAGINE at the High Flux Isotope Reactor (HFIR). Furthermore, crystal mounting and rapid freezing in liquid nitrogen for cryo-data collection to trap labile reaction intermediates is demonstrated at the MaNDi time-of-flight instrument at the Spallation Neutron Source (SNS). Preparation of the model coordinate and diffraction data files and visualization of the neutron scattering length density (SLD) maps will also be addressed. Structure refinement against neutron data-only or against joint X-ray/neutron data to obtain an all-atom structure of the protein of interest will finally be discussed. The process of determining a neutron structure will be demonstrated using crystals of the lytic polysaccharide monooxygenase Neurospora crassa LPMO9D, a copper-containing metalloprotein involved in the degradation of recalcitrant polysaccharides via oxidative cleavage of the glycosidic bond.

Neutron protein crystallography is a structural technique that permits the localization of hydrogen atoms, thereby providing important mechanistic details of protein function. We present here the workflow for mounting a protein crystal, neutron diffraction data collection, structure refinement and analysis of the neutron scattering length density maps.

中子晶体学数据收集和处理，用于蛋白质结构中氢原子的建模

Neutron crystallography is a structural technique that allows determination of hydrogen atom positions within biological macromolecules, yielding ...

Quantitative Atomic-Site Analysis of Functional Dopants/Point Defects in Crystalline Materials by Electron-Channeling-Enhanced Microanalysis

A novel elemental and chemical analysis scheme based on electron-channeling phenomena in crystalline materials is introduced, where the incident high-energy electron beam is rocked with the submicrometric pivot point fixed on a specimen. This method enables us to quantitatively derive the site occupancies and site-dependent chemical information of impurities or intentionally doped functional elements in a specimen, using energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy attached to a scanning transmission electron microscope, which is of significant interest to current materials science, particularly related to nanotechnologies. This scheme is applicable to any combination of elements even when the conventional Rietveld analysis by X-ray or neutron diffraction occasionally fails to provide the desired results because of limited sample sizes and close scattering factors of neighboring elements in the periodic table. In this methodological article, we demonstrate the basic experimental procedure and analysis method of the present beam-rocking microanalysis.

We provide a general outline of quantitative microanalysis methods for estimating the site occupancies of impurities and their chemical states by taking advantage of electron-channeling phenomena under incident electron beam-rocking conditions, which reliably extract information from minority species, light elements, oxygen vacancies, and other point/line/planar defects.

通过电子引导增强微分析对晶体材料中功能性多裤/点缺陷的定量原子场分析

A novel elemental and chemical analysis scheme based on electron-channeling phenomena in crystalline materials is introduced, where the incident ...

Measuring the Time-Evolution of Nanoscale Materials with Stopped-Flow and Small-Angle Neutron Scattering

This paper presents the use of a stopped-flow small-angle neutron-scattering (SANS) sample environment to quickly mix liquid samples and study nanoscale kinetic processes on time scales of seconds to minutes. The stopped-flow sample environment uses commercially available syringe pumps to mix the desired volumes of liquid samples that are then injected through a dynamic mixer into a quartz glass cell in approximately 1 s. Time-resolved SANS data acquisition is synced with the sample mixing to follow the evolution of the nanostructure in solution after mixing. 
To make the most efficient use of neutron beam time, we use a series of flow selector valves to automatically load, rinse, and dry the cell between measurements, allowing for repeated data collection throughout multiple sample injections. Sample injections are repeated until sufficient neutron scattering statistics are collected. The mixing setup can be programmed to systematically vary conditions to measure the kinetics at different mixing ratios, sample concentrations, additive concentrations, and temperatures. The minimum sample volume required per injection is approximately 150 &#181;L depending on the path length of the quartz cell. 
Representative results using this stopped-flow sample environment are presented for rapid lipid exchange kinetics in the presence of an additive, cyclodextrin. The vesicles exchange outer-leaflet (exterior) lipids on the order of seconds and fully exchange both interior and exterior lipids within hours. Measuring lipid exchange kinetics requires in situ mixing to capture the faster (seconds) and slower (minutes) processes and extract the kinetic rate constants. The same sample environment can also be used to probe molecular exchange in other types of liquid samples such as lipid nanoparticles, proteins, surfactants, polymers, emulsions, or inorganic nanoparticles. Measuring the nanoscale structural transformations and kinetics of exchanging or reacting systems will provide new insights into processes that evolve at the nanoscale.

This protocol presents the use of a stopped-flow sample environment to quickly mix multiple liquid solutions in situ during a small-angle neutron scattering measurement and to study kinetic processes on nanometer length scales and second time scales.

利用停流和小角中子散射测量纳米材料的时间演化

This paper presents the use of a stopped-flow small-angle neutron-scattering (SANS) sample environment to quickly mix liquid samples and study nanoscale ...

High-Resolution Neutron Spectroscopy to Study Picosecond-Nanosecond Dynamics of Proteins and Hydration Water

Neutron scattering offers the possibility to probe the dynamics within samples for a wide range of energies in a nondestructive manner and without labeling other than deuterium. In particular, neutron backscattering spectroscopy records the scattering signals at multiple scattering angles simultaneously and is well suited to study the dynamics of biological systems on the ps-ns timescale. By employing D2O-and possibly deuterated buffer components-the method allows monitoring of both center-of-mass diffusion and backbone and side-chain motions (internal dynamics) of proteins in liquid state.
Additionally, hydration water dynamics can be studied by employing powders of perdeuterated proteins hydrated with H2O. This paper presents the workflow employed on the instrument IN16B at the Institut Laue-Langevin (ILL) to investigate protein and hydration water dynamics. The preparation of solution samples and hydrated protein powder samples using vapor exchange is explained. The data analysis procedure for both protein and hydration water dynamics is described for different types of datasets (quasielastic spectra or fixed-window scans) that can be obtained on a neutron backscattering spectrometer.
The method is illustrated with two studies involving amyloid proteins. The aggregation of lysozyme into &#181;m sized spherical aggregates-denoted particulates-is shown to occur in a one-step process on the space and time range probed on IN16B, while the internal dynamics remains unchanged. Further, the dynamics of hydration water of tau was studied on hydrated powders of perdeuterated protein. It is shown that translational motions of water are activated upon the formation of amyloid fibers. Finally, critical steps in the protocol are discussed as to how neutron scattering is positioned regarding the study of dynamics with respect to other experimental biophysical methods.

Neutron backscattering spectroscopy offers a nondestructive and label-free access to the ps-ns dynamics of proteins and their hydration water. The workflow is presented with two studies on amyloid proteins: on the time-resolved dynamics of lysozyme during aggregation and on the hydration water dynamics of tau upon fiber formation.