This work was part of the research programme of the Foundation for Fundamental Research on Matter (FOM), which is part of the Netherlands Organisation for Scientific Research (NWO). Authors of this work thank M. J. F. van de Sande for skillful technical assistance, M. A. Verheijen for TEM images, and the group of Tom Gregorkiewicz for PL measurements.

1.规划实验<ol><li>合成或获得的利息13（ 图1a）的纳米晶体。 </li><li>通过确保在基片材料不具有在纳米晶体（图1a）的喇曼光谱重叠峰避免与背景信号的任何混淆。 </li><li>打开拉曼光谱设置的激光。等待足够的时间（约15分钟）的激光强度稳定。 </li><li>测量纳米材料的散装参考待分析12（图1b），以下在步骤2中从散装材料的峰值位置中所述的测量步骤，估计相对移位12。 </li><li>估算所需要的激光功率使用上要被测量的纳米晶体不同的功率拉曼测量。开始具有最低可能的功率的测量，以获得足够的信号（峰强度的对比率背景噪声应至少50），而且如果需要增加激光功率，只要该纳米晶体拉曼峰值保持相同12,13的位置和形状。 </li></ol>利息的纳米2.拉曼光谱<ol><li>加载与纳米晶体的粉末沉积在衬底导入测量室在样品上。 注意:基板尺寸不是关键的（可从毫米到数十厘米），只要它适合于样品支架阶段。的粉末或薄膜的厚度应至少为几十纳米到具有从拉曼光谱仪可检测的信号。对于平面基板保持台，只需放置在光学元件（ 图1b）的衬底。 <ol><li>确保"激光"和"激活"灯都关了，为了从操作激光的不必要的照明是安全的开门之前。如果这些灯不关，执行步骤的操作20.5和2.6。在"联锁"的牌子始终岿然不动。 </li><li>按"盖松开"，并打开测量室的门，并把样品到样品架台（ 图1b）。 </li></ol></li><li>样品的调整的聚焦被测量，以获得最高可能的信号。 <ol><li>选择50X的目标和重点纳米晶粉（ 图1b）的表面上。 </li><li>使用样本保持器的z方向操纵带来下焦点的样品。检查聚焦图像的清晰度从计算机屏幕上的直播相机视图。 </li><li>关闭测量室的门。 </li><li>通过点击从Renishaw的软件的"快门离"钮去掉快门，并让被测定激光光线照到样品。观察到"激光"和"积极"的迹象，现在绿色闪烁，呈红色闪烁，分别。在从S实时图像creen，激光器将是可见的（图1c）。 </li><li>从实时图像，微调使用滚轮机器人，直到最小的激光点，这是最好的重点，是在实时图像上观察到的样品聚焦。 </li></ol></li><li>从Renishaw的分析软件设置测量如下所述（ 图1d）。 <ol><li>从"测量"选择新的光谱采集选项。 </li><li>从弹出窗口，设置测量范围从150至700厘米-的1，设置时间测量为30秒，获得作为2×的总数，和激光功率的0.5％的比例（在测量过程中使用的25毫瓦的激光）。接受的参数插入，窗口将被关闭。 </li><li>通过点击菜单栏上的收购开始按钮开始测量。在测量过程中的"激光"和"活动"指示灯将保持上。 </li></ol></li><li>不要打开测量室时，这些灯是作为激光在操作和正在执行的测量。 </li><li>经过测量完成后，把快门按一下"快门"按钮，从雷尼绍软件。观察到，"激光"和"活动"的关灯。按"盖松开"，然后打开测量室的门。 </li><li>前服用样品流出，降低样品架台与z操纵器，直到有测定样本和放大透镜的表面，以去除样品之间的安全距离。然后，将样品返回到其容器。 </li><li>关闭激光。 </li><li>保存在雷尼绍软件格式，".wxd"中的数据，并在文本文件格式，名为".txt"。后者将用于实验数据的分析。 </li></ol> 3.尺寸Distribut离子测定利息的纳米晶的<ol><li>打开测量为纳米晶体测量的文本文件，和体参考。 </li><li>前绘图数据，但使用三次样条平滑它们，将数据标准化为1处于它们的最高峰的位置，以具有相对峰位移的良好比较。 </li><li>积在硅纳米晶体和硅基准数据，确定参考硅的峰值位置，并估计偏移的量，如果有的话，从521厘米-1的实际峰值位置12然后保存处理的硅纳米晶体的数据作为.TXT文件中。 </li><li>启动拟合程序。 <ol><li>对于装修过程中，请在图2F所示为一个分析程序，如数学拟合函数。 </li><li>导入规格化和校正数据作为输入使用"导入"命令非线性拟合模型。 </li><li>确保间隔对偏斜度为0.1〜1.0，且平均尺寸间隔为2纳米至20纳米之间。 </li><li>如果需要的话，插入下测得的峰的附加的峰使用拟合函数，并重复步骤3.4.2和3.4.3以适合其他子分发（多个）。 </li><li>按"Shift + Enter"来执行拟合程序。 </li><li>在此之后，插入所获得的值的平均大小以及在图2b中所示的预先定义的通用分布函数的偏度。 </li><li>在此之后，插入所获得的值的平均大小，D 0，偏度，σ，在图2b中所示的预先定义的一般分布函数。 </li><li>设置的积分的下边界为1纳米。设置集成的上限任何尺寸不表现出在拉曼光谱的任何变化（20纳米的硅NCS）12到。 </li><li>整合在图2b的分布函数</stron克&gt;作为纳米晶体的大小，使用的积分函数定义一个数据分析，并通过设置的较低和较高的尺寸为整体的边界（1-20纳米的硅NCS）绘图程序的功能。剧情Φ（D）对丁给大小分布。可替换地，发现了一组Φ（D）的值的D（表示的Si-NC的，例如，从1至20纳米，具有1纳米的增量）和情节Φ（D）中对丁，的每个值是尺寸分布。 </li><li>如果多模态粒度分布存在，首先定义要安装用于进行其它尺寸分布的峰值。然后，通过首先找到的测定数据的反卷积后获得（与大小分布确定过程）各峰的面积，然后计算每个峰的面积比相对于估计不同尺寸分布的其体积分数相对于彼此总的拉曼峰值。 </li></ol></li></ol>

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The authors have nothing to disclose.

首先讨论的焦点是协议中的关键步骤。为了不具有与所关注的材料重叠的峰，它使用另一种类型的衬底材料中提到的步骤1.2是很重要的。例如，如果硅的NC感兴趣，不使用硅衬底的拉曼测量。 图 1中，例如，硅的NC上合成有机玻璃基板，其具有完全平面信号大致围绕感兴趣的范围内， 即 480-530厘米- 1。除了测量堆积的参考信号来估计纳米晶体相关的峰值的移位中提到的步骤1.4，它也很关键来定位块体的峰的精确位置，因为它也可以错开根据操作和环境拉曼光谱仪的条件。对硅-NC的的情况下，参照样品是晶体硅晶片，这是已知吨Ó有横向光学（TO）模式在521厘米- 1 12然而，这可以被移动作为操作激光器，这是很喜欢与环境条件，和强度的温度的结果。因此，在测量前，每次记录一个基准数据，并相对于从文献已知的峰值位置纠正它们是重要的。高的激光功率可以加热的纳米晶体，并改变它们的大小，这导致在拉曼光谱的激光诱导的移位。因此，关键是要确定的最大激光功率，可安全地使用下列在步骤1.5中的说明。如果插入在步骤3.4.3估计的平均大小和偏斜入装配功能不能不能涵盖所测量的拉曼光谱的形状，这意味着所分析的材料是由子分布。然后再次重复步骤3.4.2和3.4.3增加额外的峰拟合。积分奔的确定daries（步骤3.4.7）的粒度分布是另一个临界点。积分中的​​分布函数的边界表示最小和最大尺寸的纳米晶体的尺寸分布。 1纳米的最小尺寸稳定的大部分纳米晶体的系统。17作为尺寸相关偏移量的增加而减小的纳米晶体的尺寸，设置集成到任何尺寸的上限，不表现出在任何移拉曼光谱（步骤3.4.8）。例如，硅的NC确定尺寸大于20纳米的不表现出在拉曼光谱的任何变化，它们像散样行为。10,12因此，对于硅的NC设定积分的上边界的任何尺寸大于20纳米不会改变的结果。 将PCM描述了通过一个复杂的表达式纳米晶体的尺寸相关的拉曼峰。事实上，在PCM取决于声子的分散性，该限制功能，和VIB定量的频率，而这一切隐含取决于大小，D。另外，PCM为特定的大小，并确定尺寸分布，其具有被投影到一个通用的分布函数并获得上积分的尺寸范围。此过程是复杂的，到现在为止，实验者用拉曼光谱大多从作为测量的拉曼峰值的偏移确定的Si-NC的平均大小。另一方面，多粒子分析-PCM，我们已经公式化包含大小，D，作为显式参数和使得可能不仅确定的平均尺寸，但也完全分布，并以简单的方式塑造使用拉曼光谱。 如已经注意到的，拉曼光谱能够确定纳米晶体的约束限制，这是约20nm为硅内的粒度分布。更大的尺寸，不能为他们的大小分布分析，因为它们不表现出大小 -在拉曼光谱中， 即依赖特性，它们具有相似的峰形状和本体晶体Si位置。此限制保持为任何类型的纳米晶体体系表现出尺寸相关峰移在拉曼光谱。然而，该限制的限制可以根据纳米晶体的系统而异。例如，约束限制革NCS是约15纳米。18 在纳米晶体的大小分析的关注是因为辅助的原因，这可能导致使用拉曼光谱尺寸错误解释的纳米晶体的拉曼峰的位移。这些次级原因是结构上的修改下过度的激光功率纳米晶体的拉曼测定时（颗粒生长或形状变化），和诱导的基质，其中纳米晶体嵌入（如果有的话）的应力。为了避免过度的激光加热，建议开始测量以尽可能低的激光功率，并增加它逐步建立了明确的信号。只要峰的形状和位置保持稳定所用的激光功率的独立的，可以认为，所使用的激光功率是在安全极限。13此外，限制超出其中，拉曼峰的加热相关的增宽是观察到的是在文献中所述的Fano加宽只要未达到的Fano扩大限制限定。12,19，纳米颗粒不受到加热相关的修改。如果压力相关的峰移存在时，它是不可避免的，并且具有确定尺寸相关峰移之前占。应力的量可以使用X射线衍射（XRD），其中在该衍射峰值位置的移位是应力的量度来确定。所估计的应力然后可占在拉曼光谱与加入应力依赖性峰移项。18如果没有应力从​​X射线衍射观察到的，可以进行粒度分布的直接分析从作为测量的拉曼光谱。由于所有的纳米颗粒具有稳定的结构，如前面所观察到的，14的结晶性很好地建立，和与差的晶体结构有关的问题被排除的拉曼分析。 多粒子分析-PCM表明在图2中一个是柔性的，在分布函数和所使用的限制功能的条款。例如，任何类型的通用的分布函数可以与对数正态分布函数来代替， 即它可以是一个对数正态分布，正常的，或一个逻辑函数，在不影响声子约束功能。此外，分析-PCM表现在图2 C可以根据所使用的材料的类型重新定义。表现出尺寸相关拉曼峰的变化（有些纳米系统，使它们的尺寸分布可以还利用拉曼光谱）的葛NC的，20的SnO 2 -NCS，21 TiO 2的-NCS，22和钻石NC的决定。23

半导体纳米晶体提请注意为他们的电子和光学特性可以通过简单地改变它们的范围大小相比，他们各自的激子玻尔半径进行调整。1这些独特的大小相关的功能，使这些纳米晶体相关的各种技术应用。例如，载体乘法效果，观察到当一个高能量光子被的CdSe，Si和葛的纳米晶体吸收，可以在频谱变换在太阳能电池应用的概念被使用; 2 - 4或尺寸相关的光发射PBS-NC的和Si-NC的所用的光可以使用发光二极管（LED）的应用程序。5,6-对纳米晶体尺寸分布的精确知识和控制，因此将发挥上的可靠性的决定因素的作用，这些技术的应用程序基于所述性能在纳米晶体。 常用技术的尺寸d纳米晶体的istribution和形态学分析可以被列为X射线衍射（XRD），透射电子显微镜（TEM），光致发光光谱（PL）和拉曼光谱。 X射线衍射是一种结晶技术，揭示了分析材料的形态信息。从衍射峰的扩大，估计该纳米晶体的大小是可能的，但是7，从而获得清晰的数据通常是耗时的。此外，X射线衍射只能使平均纳米晶体尺寸分布的计算。在多模态粒度分布的存在，大小分析用X射线衍射可以是误导性的，导致错误的解释。 TEM是一个功能强大的技术，使纳米晶体成像8虽然TEM能够揭示在多模态粒度分布各自的分布的存在下，制样问题始终努力的测量之前要花费。此外，工作在密密麻麻纳米晶体合奏不同尺寸是由于个别纳米成像的困难挑战。光致发光光谱（PL）是光学分析技术，和光学活性的纳米晶体可以诊断。从尺寸相关发射得到的纳米晶体的尺寸分布。9由于间接带隙的纳米颗粒，大纳米晶体是不受到限制效应，和缺陷富含小的纳米晶体的差的光学性能不能由PL和观察到的大小来检测分布仅限于纳米晶体具有良好的光学性能。虽然这些上述技术都有其自身的优点，他们都没有满足的期望的能力（即，速度快，非破坏性，并可靠）从和理想化大小分析技术。 的纳米晶体的尺寸分布分析的另一种手段是拉曼光谱。拉曼光谱是广泛使用在大多数实验室的，而且它是一个快速和非破坏性技术。此外，在大多数情况下，是不需要的样品制备。拉曼光谱是一种振动分析的材料的技术，它可用于获得不同的形态（晶体或无定形）的信息，和大小相关的信息（从出现在频谱的声子模式的尺寸相关的移） 10拉曼光谱的独特之处在于，虽然尺寸依赖性变化观察到作为移位的频谱，声子峰的形状（扩大，不对称）给出了关于纳米晶体尺寸分布的形状的信息。因此，在原则上是可能的，以提取必要的信息 ，即，平均尺寸和形状因子，从拉曼光谱得到纳米晶体分析的尺寸分布。在多模态粒度分布的情况下的子分布，也可以单独通过deconvolu识别化实验拉曼光谱。 在文献中，这两种理论通常称为建模纳米晶体尺寸分布上的拉曼光谱的形状的效果。债券极化模式（BPM）11描述了从规模内的所有债券的贡献纳米晶体的极化。单粒子声子约束模型（PCM）10使用尺寸相关的物理变量， 即 ，晶体动量，声子频率和分散性，并限制的程度，以限定纳米晶体的拉曼光谱具有特定的大小。由于这些物理变量取决于大小，PCM的可明确地公式化为纳米晶体尺寸的函数的解析表示可以被定义。因此投射在一个通用尺寸分布函数此表达式将能够考虑尺寸分布的PCM内的效果，它可以用来确定nanocr从实验拉曼光谱ystal尺寸分布。12

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Raman Spectroscopy</td>
			<td>Renishaw</td>
			<td>In Via</td>
			<td>Equipped with 514 nm Ar ion laser</td>
		</tr>
		<tr>
			<td>Wire 3.0</td>
			<td>Renishaw</td>
			<td></td>
			<td>Raman spectroscopy record tool</td>
		</tr>
		<tr>
			<td>Mathematica</td>
			<td>Wolfram</td>
			<td></td>
			<td>For fitting function and size determination</td>
		</tr>
		<tr>
			<td>Substrate</td>
			<td></td>
			<td></td>
			<td>Plexiglass (to avoid signal coincidence with Si-NCs)</td>
		</tr>
		<tr>
			<td>Si wafer</td>
			<td></td>
			<td></td>
			<td>Reference to Si-NC peak position</td>
		</tr>
		<tr>
			<td>Photoluminescence Spectroscopy</td>
			<td></td>
			<td></td>
			<td>334 nm Ar laser. For optical size distribution.</td>
		</tr>
		<tr>
			<td>Transmission Electron Microscopy</td>
			<td></td>
			<td></td>
			<td>Beam intensity 300 kV. For nanocrystal size and morphology determination.</td>
		</tr>
	</tbody>
</table>

characterization of nanocrystal size distribution using raman spectroscopy with a multi-particle phonon confinement model

纳米晶体的尺寸分布的分析是它们的大小依赖特性的处理和优化的关键要求。用于大小分析的常用技术是透射电子显微镜（TEM），X射线衍射（XRD）和光致发光光谱（PL）。这些技术，然而，不适合于分析在同一时间以快速，非破坏性的纳米晶体尺寸分布和可靠的方式。我们在这一工作的目的是表明半导体纳米晶体是受尺寸相关声子限制效应的该大小分布，利用拉曼光谱法可以定量估计在非破坏性的，快速和可靠的方式。此外，混合的大小分布可以分别探测，和它们各自的体积比可以使用这种技术来估计。为了分析的粒度分布，我们已形式化的单粒子的PCM和p的解析表达式rojected它到通用分布函数将表示分析纳米晶体的尺寸分布。作为一个模型的实验中，我们已经分析的自由站立的硅纳米晶体（硅NCS）与多模态粒度分布的粒度分布。估计的大小分布是在用TEM和PL结果非常一致，揭示了模型的可靠性。

对于使用拉曼光谱作为一种尺寸的分析工具，模型来提取所需的测量拉曼光谱的大小相关的信息。 图2总结了分析多粒子声子约束模型12全尺寸相关声子约束功能 （图2 c）的投影到一个通用尺寸分布函数（ 图2b），其被选择为对数正态分布函数。给定的幅度（图2 d）中，全宽半值（图2 e）和所述频移（图2 F）值，该模型可成功地用于确定尺寸分布。 图3设想使用多部分的ICLE声子限制模型来确定的Si-NC的尺寸分布（详细内容如下）。在本分析中使用的Si-NC的具有小的和大的Si-NC的双峰尺寸分布中所示的TEM照片。13通过TEM大小分析（此处未示出），小的Si-NC的具有范围2-分布10纳米，和大的Si-NC的具有范围40-120纳米的分布。拉曼光谱在左侧面板的分析表明，小的Si-NC的尺寸分布是确实是在范围2-10纳米。分布是对数正态分布为4.2纳米的平均尺寸，并与0.27斜度（形状各向异性因子）。 图4表示Si-NC的一个详细的比较分析使用不同的前体合成用等离子体增强化学气相沉积（PECVD）系统流动。对于拟合作为测量的拉曼光谱数据，我们使用了两种拟合函数知道我们在硅NC混合物有两个子分布。由于硅不显示尺寸相关峰移为大于20nm的尺寸，堆积状洛伦兹峰可以分配给大的Si-NC的，这是在这种情况下的范围40-120纳米（表示为"大型硅在情节-NCS"）。对于小的Si-NC的，我们使用的多声子粒子约束模型作为拟合函数（表示为"小的Si-NC的"中的情节）。平均尺寸，并且粒度分布的偏度从这个贴合，这是必要的参数绘制在图2b展示了尺寸分布获得。该嵌合功能可以集成到从该峰移没有观察到任何更多的大小， 即 20纳米的硅纳米晶。结果表明，我们能够成功地确定平均尺寸，偏度和Si-NC的使用拉曼光谱的完整尺寸分布（图c和d）。此外，小的Si-NC的和大的Si-NC的体积分数可通过积分的峰面积之比来确定。对于使用3 SCCS的的SiH 4流速 ，小的Si-NC的体积分数（每秒标准立方厘米）的Si-NC的合成率为80％，而对于10 SCCS的SiH 4流量的情况下，小的Si-NC体积分数是88％。 图5表明的硅-NC的测得的平均粒径从各种技术的比较。首先，我们的分析-PCM 12（分）是在与PCM非常吻合。10其次，从拉曼光谱得到的结果与从透射电子显微镜（TEM）和光致发光光谱（PL）中获得的结果一致（使用Delerue 等人 16）的模型中得到的PL尺寸分布。这证明使用拉曼光谱与解析-PCM对硅-NC的尺寸分析的可靠性。此外，我们还证明了BPM，11，其也用于半导体纳米晶体的大小分析。图5总结还注意，PCM从其尺寸相关拉曼位移优于BPM确实预测的Si-NC的尺寸。 <img alt="图1" src="/files/ftp_upload/53026/53026fig1.jpg" /> 图1.纳米颗粒表征和拉曼光谱仪。A）的Si-NC的上利用PECVD工具有机玻璃基板沉积在Ar / 4的SiH气体混合物。的Si-NC的是粉末的形式。在基板上的音调差异是由于在形态和厚度的Si-NC粉末的差异，这在合成13期间暴露于不同的等离子体区域。由于硅-NC的沉积形态已经准备好拉曼光谱测量。基板的短边是2厘米。b）基准样品， 即 ，晶体Si晶片，在为了观察体Si的拉曼峰值位置测量。这informatio将n从其散装峰位置确定的Si-NC的相对移动时，可以用作一个参考点。用于确定大小研究。d）该软件用于执行和记录数据到所述的屏幕截图的拉曼光谱仪的三）的图像进行分析。 <img alt="图2" src="/files/ftp_upload/53026/53026fig2.jpg" /> 图2中的Si-NC的硅-NC的。一个 ）的拉曼强度与尺寸分布。 二）通用尺寸分布函数来确定的一维的Si-NC的尺寸分布。 三）分析表示的尺寸分布的分析中使用的公式为形成Si的NC颗粒的PCM与粒径 D。4）振幅，e）该半峰全宽， 和 f）的Si-NC的具有大小D，它明确地振动频率表示出现在C）。 <img alt="图3" src="/files/ftp_upload/53026/53026fig3.jpg" /> 图3。从拉曼光谱的分析，以纳米尺寸分布 。作为测量的数据从拉曼光谱可以被转换为使用多粒子分析-PCM纳米晶体的定量尺寸分布。 <img alt="图4" src="/files/ftp_upload/53026/53026fig4.jpg" /> 图4尺码和Si-NC的体积分数的分析。的Si-NC的拉曼光谱合成使用一PECVD工具）3 SCCS 和 b），10 SCCS的SiH 4（硅烷）气体流量的各部位。a）和b）演示了去卷积路线为小型和大型的Si-NC的。使用散装般大的Si-NCS和多粒子分析-P洛伦兹峰反卷积做的是CM为小型硅纳米晶。相应尺寸分布和小的Si-NC的体积分数为3和10 SCCS的SiH 4流量中演示c）和d），分别。小的Si-NC的平均尺寸为0.26对面板c进行偏斜度4.2纳米）和3.7纳米，具有0.30 分图d斜度）。的体积分数分别估计为80％和88％对板c）和d），...。 <img alt="图5" src="/files/ftp_upload/53026/53026fig5.jpg" /> 图5。比较硅-NC的各种技术的粒径分布 。用Si-NC的使用拉曼光谱各种技术（TEM和PL 16），大小分析，大小分析，得出非常一致。结果还表明，在PCM导致更精确的尺寸确定相对于所述的BPM。这个数字已经是EN修改的参考。 12由美国物理研究所的许可。

Watch this Scientific Journal Video about Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model at JoVE.com

Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model

我们展示了如何使用拉曼光谱法采用一种解析定义的多声子粒子约束模型，以确定以定量方式的半导体纳米晶体的尺寸分布。得到的结果与像透射电子显微镜和光致发光光谱的其它大小分析技术非常吻合。

使用拉曼光谱与多颗粒的声子坐月子型号纳米大小分布的特征

Analysis of the size distribution of nanocrystals is a critical requirement for the processing and optimization of their size-dependent properties. The ...

characterization-nanocrystal-size-distribution-using-raman

Nanyang Technological University

Research

JoVE Journal

Engineering

13.4K 次观看.  Eindhoven University of Technology. 我们展示了如何使用拉曼光谱法采用一种解析定义的多声子粒子约束模型，以确定以定量方式的半导体纳米晶体的尺寸分布。得到的结果与像透射电子显微镜和光致发光光谱的其它大小分析技术非常吻合。 

视频: Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult1. At the same time, the ability to do so is highly important in view of a number of applications in functional soft matter including electronics, biomedical engineering, and sensors. In the past, successful strategies to control the size and shape of supramolecular polymers typically focused on the use of templates2,3, end cappers4 or selective solvent techniques5. 
Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing electrostatic repulsive interactions on the hydrophilic rim and attractive non-covalent forces within the hydrophobic core of the polymerizing building block, we manage to create small and discrete spherical objects6,7. Increasing the salt concentration to screen the charges induces a sphere-to-rod transition. Intriguingly, this transition is expressed in an increase of cooperativity in the temperature-dependent self-assembly mechanism, and more stable aggregates are obtained. 
For our study we select a benzene-1,3,5-tricarboxamide (BTA) core connected to a hydrophilic metal chelate via a hydrophobic, fluorinated L-phenylalanine based spacer (Scheme 1). The metal chelate selected is a Gd(III)-DTPA complex that contains two overall remaining charges per complex and necessarily two counter ions. The one-dimensional growth of the aggregate is directed by &pi;-&pi; stacking and intermolecular hydrogen bonding. However, the electrostatic, repulsive forces that arise from the charges on the Gd(III)-DTPA complex start limiting the one-dimensional growth of the BTA-based discotic once a certain size is reached. At millimolar concentrations the formed aggregate has a spherical shape and a diameter of around 5 nm as inferred from 1H-NMR spectroscopy, small angle X-ray scattering, and cryogenic transmission electron microscopy (cryo-TEM). The strength of the electrostatic repulsive interactions between molecules can be reduced by increasing the salt concentration of the buffered solutions. This screening of the charges induces a transition from spherical aggregates into elongated rods with a length &gt; 25 nm. Cryo-TEM allows to visualise the changes in shape and size. In addition, CD spectroscopy permits to derive the mechanistic details of the self-assembly processes before and after the addition of salt. Importantly, the cooperativity -a key feature that dictates the physical properties of the produced supramolecular polymers- increases dramatically upon screening the electrostatic interactions. This increase in cooperativity results in a significant increase in the molecular weight of the formed supramolecular polymers in water.

The goal of this experiment is to determine and control the size, shape and stability of self-assembled discotic amphiphiles in water. For aqueous based supramolecular polymers such level of control is very difficult. We apply a strategy using both repulsive and attractive interactions. The experimental techniques applied to characterize this system are broadly applicable.

控制的大小，形状和稳定性超分子聚合物在水

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult1. At the same time, the ability to do ...

科研

工程学

Synthesis of Phase-shift Nanoemulsions with Narrow Size Distributions for Acoustic Droplet Vaporization and Bubble-enhanced Ultrasound-mediated Ablation

High-intensity focused ultrasound (HIFU) is used clinically to thermally ablate tumors. To enhance localized heating and improve thermal ablation in tumors, lipid-coated perfluorocarbon droplets have been developed which can be vaporized by HIFU. The vasculature in many tumors is abnormally leaky due to their rapid growth, and nanoparticles are able to penetrate the fenestrations and passively accumulate within tumors. Thus, controlling the size of the droplets can result in better accumulation within tumors. In this report, the preparation of stable droplets in a phase-shift nanoemulsion (PSNE) with a narrow size distribution is described. PSNE were synthesized by sonicating a lipid solution in the presence of liquid perfluorocarbon. A narrow size distribution was obtained by extruding the PSNE multiple times using filters with pore sizes of 100 or 200 nm. The size distribution was measured over a 7-day period using dynamic light scattering. Polyacrylamide hydrogels containing PSNE were prepared for in vitro experiments. PSNE droplets in the hydrogels were vaporized with ultrasound and the resulting bubbles enhanced localized heating. Vaporized PSNE enables more rapid heating and also reduces the ultrasound intensity needed for thermal ablation. Thus, PSNE is expected to enhance thermal ablation in tumors, potentially improving therapeutic outcomes of HIFU-mediated thermal ablation treatments.

Phase-shift nanoemulsions (PSNE) can be vaporized using high intensity focused ultrasound to enhance localized heating and improve thermal ablation in tumors. In this report, the preparation of stable PSNE with a narrow size distribution is described. Furthermore, the impact of vaporized PSNE on ultrasound-mediated ablation is demonstrated in tissue-mimicking phantoms.

相移窄粒度分布的纳米乳液的合成声波液滴蒸发和泡增强的超声介导消融

High-intensity  focused ultrasound (HIFU) is used clinically to thermally ablate tumors. To  enhance localized heating and improve thermal ablation in ...

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives. The extremely bright and tunable x-rays produced by synchrotron radiation allow rapid acquisition of high-resolution data that provide information about these processes. Transformations in the bulk materials, such as phase transitions, can be directly observed using X-ray diffraction (XRD), while X-ray absorption spectroscopy (XAS) gives information about the local electronic and geometric structures (e.g.&#160;changes in redox states and bond lengths). In situ experiments carried out on operating cells are particularly useful because they allow direct correlation between the electrochemical and structural properties of the materials. These experiments are time-consuming and can be challenging to design due to the reactivity and air-sensitivity of the alkali metal anodes used in the half-cell configurations, and/or the possibility of signal interference from other cell components and hardware. For these reasons, it is appropriate to carry out ex situ experiments (e.g.&#160;on electrodes harvested from partially charged or cycled cells) in some cases. Here, we present detailed protocols for the preparation of both ex situ and in situ samples for experiments involving synchrotron radiation and demonstrate how these experiments are done.

We describe the use of synchrotron X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques to probe details of intercalation/deintercalation processes in electrode materials for Li-ion and Na-ion batteries. Both in situ and ex situ experiments are used to understand structural behavior relevant to the operation of devices

正极材料的同步辐射技术锂离子和钠离子电池表征

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. ...

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.
As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz&frac12; at 0.3 K 5.

Scanning-probe single-electron capacitance spectroscopy facilitates the study of single-electron motion in localized subsurface regions. A sensitive charge-detection circuit is incorporated into a cryogenic scanning probe microscope to investigate small systems of dopant atoms beneath the surface of semiconductor samples.

扫描探针单电子电容谱

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states are indeed the resources for implementing various protocols, ranging from enhanced metrology to quantum communication and computing. A variety of devices can be used to generate non-classical states, such as single emitters, light-matter interfaces or non-linear systems3. We focus here on the use of a continuous-wave optical parametric oscillator3,4. This system is based on a non-linear &#967;2 crystal inserted inside an optical cavity and it is now well-known as a very efficient source of non-classical light, such as single-mode or two-mode squeezed vacuum depending on the crystal phase matching. 
Squeezed vacuum is a Gaussian state as its quadrature distributions follow a Gaussian statistics. However, it has been shown that number of protocols require non-Gaussian states5. Generating directly such states is a difficult task and would require strong &#967;3 non-linearities. Another procedure, probabilistic but heralded, consists in using a measurement-induced non-linearity via a conditional preparation technique operated on Gaussian states. Here, we detail this generation protocol for two non-Gaussian states, the single-photon state and a superposition of coherent states, using two differently phase-matched parametric oscillators as primary resources. This technique enables achievement of a high fidelity with the targeted state and generation of the state in a well-controlled spatiotemporal mode.

We describe the reliable generation of non-Gaussian states of traveling optical fields, including single-photon states and coherent state superpositions, using a conditional preparation method operated on the non-classical light emitted by optical parametric oscillators. Type-I and type-II phase-matched oscillators are considered and common procedures, such as the required frequency filtering or the high-efficiency quantum state characterization by homodyning, are detailed.

光与连续波光学参量振荡器的量子态工程

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states ...

Surface Enhanced Raman Spectroscopy Detection of Biomolecules Using EBL Fabricated Nanostructured Substrates

Fabrication and characterization of conjugate nano-biological systems interfacing metallic nanostructures on solid supports with immobilized biomolecules is reported. The entire sequence of relevant experimental steps is described, involving the fabrication of nanostructured substrates using electron beam lithography, immobilization of biomolecules on the substrates, and their characterization utilizing surface-enhanced Raman spectroscopy (SERS). Three different designs of nano-biological systems are employed, including protein A, glucose binding protein, and a dopamine binding DNA aptamer. In the latter two cases, the binding of respective ligands, D-glucose and dopamine, is also included. The three kinds of biomolecules are immobilized on nanostructured substrates by different methods, and the results of SERS imaging are reported. The capabilities of SERS to detect vibrational modes from surface-immobilized proteins, as well as to capture the protein-ligand and aptamer-ligand binding are demonstrated. The results also illustrate the influence of the surface nanostructure geometry, biomolecules immobilization strategy, Raman activity of the molecules and presence or absence of the ligand binding on the SERS spectra acquired.

We describe the fabrication and characterization of nano-biological systems interfacing nanostructured substrates with immobilized proteins and aptamers. The relevant experimental steps involving lithographic fabrication of nanostructured substrates, bio-functionalization, and surface-enhanced Raman spectroscopy (SERS) characterization, are reported. SERS detection of surface-immobilized proteins, and probing of protein-ligand and aptamer-ligand binding is demonstrated.

表面增强拉曼光谱检测生物分子利用EBL装配纳米衬底

Fabrication and characterization of conjugate nano-biological systems interfacing metallic nanostructures on solid supports with immobilized biomolecules ...

Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the presence of carbon nanotubes. These nanowires are extreme in the sense that they are the limit of miniaturization of nanowires and their behavior is not always a simple extrapolation of the behavior of larger nanowires as their diameter decreases. The paper then describes the methods required to obtain Raman spectra from extreme nanowires and the fact that due to the van Hove singularities that 1D systems exhibit in their optical density of states, that determining the correct choice of photon excitation energy is critical. It describes the techniques required to determine the photon energy dependence of the resonances observed in Raman spectroscopy of 1D systems and in particular how to obtain measurements of Raman cross-sections with better than 8% noise and measure the variation in the resonance as a function of sample temperature. The paper describes the importance of ensuring that the Raman scattering is linearly proportional to the intensity of the laser excitation intensity. It also describes how to use the polarization dependence of the Raman scattering to separate Raman scattering of the encapsulated 1D systems from those of other extraneous components in any sample.

The paper describes a method for producing extreme nanowires by melt infiltration into carbon nanotubes and how 1D systems may be characterized and investigated using Resonance Raman Spectroscopy to determine vibrational and optical excitation energies.

至尊纳米线和其他维系统的共振拉曼光谱

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the ...

Characterization of Full Set Material Constants and Their Temperature Dependence for Piezoelectric Materials Using Resonant Ultrasound Spectroscopy

During the operation of high power electromechanical devices, a temperature rise is unavoidable due to mechanical and electrical losses, causing the degradation of device performance. In order to evaluate such degradations using computer simulations, full matrix material properties at elevated temperatures are needed as inputs. It is extremely difficult to measure such data for ferroelectric materials due to their strong anisotropic nature and property variation among samples of different geometries. Because the degree of depolarization is boundary condition dependent, data obtained by the IEEE (Institute of Electrical and Electronics Engineers) impedance resonance technique, which requires several samples with drastically different geometries, usually lack self-consistency. The resonant ultrasound spectroscopy (RUS) technique allows the full set material constants to be measured using only one sample, which can eliminate errors caused by sample to sample variation. A detailed RUS procedure is demonstrated here using a lead zirconate titanate (PZT-4) piezoceramic sample. In the example, the complete set of material constants was measured from room temperature to 120 &#176;C. Measured free dielectric constants <img alt="Equation 1" src="/files/ftp_upload/53461/image001.jpg" /> and&#160;<img alt="Equation 2" src="/files/ftp_upload/53461/image002.jpg" /> were compared with calculated ones based on the measured full set data, and piezoelectric constants d15 and d33 were also calculated using different formulas. Excellent agreement was found in the entire range of temperatures, which confirmed the self-consistency of the data set obtained by the RUS.

This protocol describes the procedure of measuring the temperature dependence of the full set material constants of piezoelectric materials using resonant ultrasound spectroscopy (RUS).

全套材料常数表征及其温度依赖性的压电材料使用共振超声波谱

During the operation of high power electromechanical devices, a temperature rise is unavoidable due to mechanical and electrical losses, causing the ...

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we demonstrate an optical spectroscopy method that is capable of resolving spectral features beyond that of the spin fine structure and homogeneous linewidth of single quantum dots (QDs) using a standard, easy-to-use spectrometer setup. This method incorporates both laser and photoluminescence spectroscopy, combining the advantage of laser line-width limited resolution with multi-channel photoluminescence detection. Such a scheme allows for considerable improvement of resolution over that of a common single-stage spectrometer. The method uses phonons to assist in the measurement of the photoluminescence of a single quantum dot after resonant excitation of its ground state transition. The phonon&#39;s energy difference allows one to separate and filter out the laser light exciting the quantum dot. An advantageous feature of this method is its straight forward integration into standard spectroscopy setups, which are accessible to most researchers.

The manuscript describes a method of phonon-assisted quasi-resonant fluorescence spectroscopy that incorporates both laser-limited resolution and photoluminescence (PL) spectroscopy. This method utilizes optical phonons to provide linewidth-limited resolution spectra of atom-like semiconductor structures in the energy domain. The method is also easily realized with a single spectrometer optical spectroscopy setup.

高分辨率声子辅助准共振荧光光谱仪

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we ...

Fabrication of Fully Solution Processed Inorganic Nanocrystal Photovoltaic Devices

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal inks. For the photoactive absorber layer, colloidal CdTe and CdSe nanocrystals (3-5 nm) are synthesized using an inert hot injection technique and cleaned with precipitations to remove excess starting reagents. Similarly, gold nanocrystals (3-5 nm) are synthesized under ambient conditions and dissolved in organic solvents. In addition, precursor solutions for transparent conductive indium tin oxide (ITO) films are prepared from solutions of indium and tin salts paired with a reactive oxidizer. Layer-by-layer, these solutions are deposited onto a glass substrate following annealing (200-400 &#176;C) to build the nanocrystal solar cell (glass/ITO/CdSe/CdTe/Au). Pre-annealing ligand exchange is required for CdSe and CdTe nanocrystals where films are dipped in NH4Cl:methanol to replace long-chain native ligands with small inorganic Cl- anions. NH4Cl(s) was found to act as a catalyst for the sintering reaction (as a non-toxic alternative to the conventional CdCl2(s) treatment) leading to grain growth (136&#177;39 nm) during heating. The thickness and roughness of the prepared films are characterized with SEM and optical profilometry. FTIR is used to determine the degree of ligand exchange prior to sintering, and XRD is used to verify the crystallinity and phase of each material. UV/Vis spectra show high visible light transmission through the ITO layer and a red shift in the absorbance of the cadmium chalcogenide nanocrystals after thermal annealing. Current-voltage curves of completed devices are measured under simulated one sun illumination. Small differences in deposition techniques and reagents employed during ligand exchange have been shown to have a profound influence on the device properties. Here, we examine the effects of chemical (sintering and ligand exchange agents) and physical treatments (solution concentration, spray-pressure, annealing time and annealing temperature) on photovoltaic device performance.

This protocol describes the synthesis and solution deposition of inorganic nanocrystals layer by layer to produce thin film electronics on non-conductive surfaces. Solvent-stabilized inks can produce complete photovoltaic devices on glass substrates via spin and spray coating following post-deposition ligand exchange and sintering.

全面解决方案处理的无机纳米晶体光伏器件的制造

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal ...