我们感谢 Prof. Alivisatos 在加州大学伯克利分校和 Prof. Taeghwan 在首尔国立大学进行了有益的讨论。这项工作得到了 IBS-R006-D1 的支持。W.C.L. 感谢汉阳大学研究基金 (HY-2015-N) 的支持。

1. 纳米颗粒的合成 <ol> <li> 合成铂纳米粒子 <ol> 组合17.75 毫克铵铂 (iv) (NH <li> 4 ) 2 Pt (iv) Cl 6 ), 3.72 毫克酸铵 (ii) (NH 4 ) 2 Pt (ii) Cl 4 ), 115.5 毫克四甲基溴化铵, 109 毫克聚 (基) (兆瓦: 2.9万), 10 毫升的乙二醇, 在100毫升 3-颈圆底烧瓶中搅拌棒配有橡胶隔膜. </li>
		<li> 将烧瓶与回流冷凝器一起装备, 并在真空下清洗。搅拌的反应混合物与磁性搅拌棒在 1000 rpm. </li>
		<li> 将反应混合物加热到180和 #176; 在加热地幔中, 以10和 #176 的速率; 在氩流动下的 c/分钟. </li>
		<li> 保持温度 (180 和 #176; C) 为20分钟。该溶液变成深褐色的颜色. </li>
		<li> 从加热地幔中取出烧瓶, 使其冷却到室温. </li>
		<li> 将产品转移到50毫升离心管。在产品中加入30毫升丙酮, 以沉淀纳米颗粒, 将样品在 2400 x g 离心10分钟. 
		注意: 为安全起见, 此过程应在通风罩中执行. </li>
		<li> 用10毫升乙醇丢弃上清和 re-disperse 黑沉淀. </li>
		<li> 沉淀的产品与30毫升的甲苯和离心机的悬浮在 2400 x g 10 分钟. 丢弃上清和 re-disperse 的黑色沉淀与10毫升乙醇。重复此过程3次. </li>
		<li> 将5毫升的油加入铂纳米颗粒, 并将分散体转移到100毫升的圆底烧瓶中。在 1000 rpm 的磁搅拌下过夜分散, 使配体交换反应发生. </li>
		<li> 将配体交换的纳米粒子在 1万 x g 离心30分钟, 将它们与溶液分离. </li>
		<li> 丢弃上清液, 在10毫升的疏水溶剂中分散铂纳米颗粒, 如甲苯、己烷或氯仿. </li>
	</ol> </li> <li> 合成的硒化铅纳米粒子 <ol> 制备油酸铅的758毫克醋酸铅 (铅 (Ac) <li> 2 <ol> 和 #183; 3H <li> 2 O), 2.5 毫升油酸性, 和10毫升的二苯基醚与一个搅拌酒吧在100毫升3颈圆底烧瓶配备了橡胶隔膜. </li>
			<li> 将烧瓶与回流冷凝器一起装备. </li>
			<li> 加气在70和 #176; C 在真空条件下为 2 h, 搅拌与磁性搅拌棒在 1000 rpm. </li>
			<li> 用氩气清洗烧瓶, 然后冷却到室温. </li>
		</ol> </li> <li> 在一个单独的容器中制备膦硒化物 (TOPSe) <ol> <li>, 在惰性气氛下结合474毫克硒和6毫升的膦 (顶), 使用手套防止试剂暴露在空气中. </li>
			<li> 将硒粉溶解在顶部, 超声波在 110 W, 40 赫, 混合使用旋流混合器, 直到溶液变得明显透明. </li>
		</ol> </li> <li> 在单独的250毫升3颈圆底烧瓶中, 在120和 #176 上加气15毫升的二苯基醚; C 在真空条件下与磁性搅拌在1000分钟的 30 min. </li>
		<li> 用氩气清洗烧瓶, 然后将二苯基醚加热到230和 #176; C. </li>
		<li> 将油酸铅和 TOPSe 溶液迅速注入预热二苯醚。注射时温度会下降到一定程度。将老化温度设置为170和 #176; C. </li>
		<li> 将混合物的温度保持在170和 #176; C 为10分钟, 并进行剧烈搅拌, 以使硒化铅纳米颗粒的生长发生. </li>
		<li> 从加热地幔中取出烧瓶, 使其冷却到室温. </li>
		<li> 准备两个50毫升离心管, 将产品分成相等的体积并转移到管子。在每根管子上加入30毫升乙醇, 沉淀纳米颗粒, 并将悬浮液在 2400 x g 上离心10分钟. </li>
		<li> 丢弃上清和 re-disperse 10 毫升的甲苯. </li>
		<li> 沉淀30毫升乙醇和离心悬浮在 2400 x g 10 min. 丢弃上清和 re-disperse 的黑色沉淀与10毫升甲苯。重复此过程3次. </li>
		<li> 丢弃上清液, 将硒化铅纳米微粒分散在10毫升的疏水溶剂中, 如甲苯、己烷或氯仿. </li>
	</ol> </li> </ol> 2。液芯制作 <ol> <li> 氮化硅液体电池 ( 图 3a ) <ol> 沉积氮化硅层 <li> <ol> 将低氮化硅薄膜存入100和 #181. 由低压化学气相沉积 (LPCVD) 在835和 #176; C 和 140 mTorr 的压力, 100 sccm 烷和 50 sccm 氨的流动, m 厚硅片 (4 英寸)。通过改变沉积时间来控制氮化硅层厚度为 25 nm。沉积率为 2.5-3.0 nm/分钟, 但每个 CVD 的轻微变化. </li>
		</ol> </li> <li> 顶部和底部芯片 注: 有关微细加工过程的详细说明, 请参阅参考 25 。
		<ol> <li> 自旋涂层10毫升的正光刻胶在氮化硅/硅片上的 3000 rpm 为三十年代, 使用足够的光刻胶完全润湿晶片. 
			注: 在纺纱过程中, 超薄硅片容易破碎。我们通常将超薄晶片贴在另一硅片上, 厚度为500和 #181; m 使用光刻胶以避免破损。经旋涂后, 将薄晶圆片与浓晶片分离, 浸入丙酮中。该技术还可用于超薄硅片上的自旋涂层. </li>
			<li> 在85和 #176 的热板上烘烤硅片; C. 六十年代. 
			注意: 不要在 #62 的温度下烘烤准备好的晶片; 110 和 #176; c. 在高温下烘烤光刻胶会使光刻胶从正极变成负光刻胶. </li>
			<li> 通过铬面膜 ( 图 1a ) 将光刻胶涂层硅片暴露于十年代的紫外线 (365 nm). </li>
			<li> 将光刻胶涂覆的硅片浸入到50毫升的显影液中, 四十年代. 在50毫升的去离子水中浸泡1分钟冲洗晶片。重复洗涤过程两次. </li>
			<li> 使用活性离子蚀刻蚀刻氮化硅1分钟, 其流量为50的六氟化硫的 sccm. </li>
			<li> 将顶部芯片和底部芯片浸入丙酮中2分钟以除去光刻胶。用手轻轻摇动碟, 有效去除光刻胶. </li>
			<li> 用氢氧化钾 (30 毫克/毫升) 的水溶液在85和 #176 上蚀刻硅; C 为 1.5-2 h. 使用水浴, 以确保蚀刻溶液具有均匀的温度剖面。不均匀的温度会导致一些区域过度的 etched, 而有些是不完全蚀刻. </li>
			<li> 当窗口看起来完全被肉眼蚀刻时, 停止蚀刻并将电池从蚀刻液中取出。将电池从蚀刻液中取出时, 将其倾斜, 以避免窗口因浮力而破裂的可能性, 如果水平提升, 则可能发生. </li>
			<li> 使用底部芯片的掩码重复这些过程 ( 图 1b ). 
			注: 由于顶部和底部芯片的窗口非常薄, 大约 25 nm, 它们非常脆弱。因此, 在处理时应格外小心。当芯片停留在表面上时, 窗口的一侧应始终朝向向上. </li>
		</ol> </li> <li> 粘接顶部和底部芯片 <ol> <li> 自旋涂层在氮化硅/硅片上的正光刻胶10毫升, 在三十年代为 3000 rpm. </li>
			<li> 在90和 #176 的热板上烘烤硅片; C. 六十年代. </li>
			<li> 通过铬面膜 ( 图 1c ) 将光刻胶涂层硅片暴露于十年代的紫外线 (365 nm). </li>
			<li> 将光刻胶涂覆的硅片浸入到50毫升的显影液中, 四十年代. 在50毫升的去离子水中浸泡1分钟冲洗晶片。重复洗涤过程两次. </li>
			<li> 使用热蒸发器将 100 nm 厚的铟层沉积到底部芯片上。铟层用作垫片和密封材料. </li>
			<li> 将芯片浸入丙酮中2分钟以除去光刻胶。用手轻轻摇动碟, 有效去除光刻胶. </li>
			<li> 使用器将底部和顶部的芯片对齐, 并在100和 #176 之间进行粘合. </li>
		</ol> </li> </ol> </li> <li> 硅液-单元格 ( 图 3b ) <ol> <li> 准备顶部和底部芯片 <ol> <li> 使用具有层厚度的 p 型硅 (SOI) 硅片100 nm, 400 nm, 600 和 #181; m 为顶部的硅, 被埋没的 2 , 和处理硅层, 分别. </li>
			<li> 在 950-1100 和 #176 的氧化炉中进行 SOI 晶圆片的湿氧化; C. 以 170 nm 的厚度生长一层氧化硅. </li>
			<li> 在室温下将 SOI 硅片浸入到缓冲氧化物蚀刻 (BOE) 溶液中, 将硅氧化物蚀刻为2分钟, 这是一个湿蚀刻的氧化硅。步骤2.2.1.2 和2.2.1.3 的目的是将 SOI 硅片的顶部硅层厚度降低到 25 nm. </li>
			<li> 使用与步骤2.1.1.1 相同的工艺条件, 在 SOI 晶片 (4 英寸) 上沉积一层低氮化硅, 厚度为 25 nm. </li>
			<li> 使用与步骤 2.1.2.1 2.1.2.4 相同的进程和掩码模式来对氮化硅进行图案处理. </li>
			<li> 将硅片浸入丙酮中2分钟以除去光刻胶。用手轻轻摇动碟, 有效去除光刻胶. </li>
			<li> 在三十年代使用京东方解决方案蚀刻氧化硅. </li>
			<li> 用氢氧化钾 (500 毫克/毫升) 的水溶液在80和 #176 上蚀刻硅; C 为 7-12 h. 三甲胺 (TMAH) 水溶液也可用于硅蚀刻. </li>
			<li> 用85% 磷酸在160和 #176 上蚀刻氮化硅; C 为 10 min. </li>
			<li> 在室温下用京东方溶液蚀刻硅氧化物3分钟. </li>
			<li> 使用底部芯片的掩码重复步骤 2.2.1.1 2.2.1.10 ( 图 1b ). </li>
		</ol> </li> <li> 粘接顶部和底部芯片 <ol> <li> 自旋涂层在氮化硅/硅片上的正光刻胶10毫升, 在三十年代为 3000 rpm. </li>
			<li> 在90和 #176 的热板上烘烤硅片; C. 六十年代. </li>
			<li> 通过铬面膜 ( 图 1c ) 将光刻胶涂层硅片暴露于十年代的紫外线 (365 nm). </li>
			<li> 将光刻胶涂覆的硅片浸入到50毫升的显影液中, 四十年代. 在50毫升的去离子水中浸泡1分钟冲洗晶片。重复洗涤过程两次. </li>
			<li> 使用热蒸发器将 100 nm 厚的铟层沉积到底部芯片上。铟层用作垫片和密封材料. </li>
			<li> 将芯片浸入丙酮中2分钟以除去光刻胶。用手轻轻摇动碟, 有效去除光刻胶. </li>
			<li> 使用器将底部和顶部的芯片对齐, 并在100和 #176 之间进行粘合. </li>
		</ol> </li> </ol> </li> </ol> 3。液-细胞 TEM <ol> <li> 加载解决方案 <ol> <li> 添加20和 #181; L 的纳米颗粒分散 (协议1.1 和 1.2) 变成5毫升的小瓶, 在空气中晾干10分钟. 将纳米粒子分散在溶剂混合物中 (1 毫升的邻二氯苯,250、#181、烷、10、#181、油的 l). 
		注: 在极端条件下干燥, 如高温、低压和延长时间, 可能导致微粒分散。由于 ligand-to-particle 相互作用是动态的, 在极端条件下, 在配体脱离后, 颗粒团聚的几率很高。由于邻二氯苯、烷和油具有不同的蒸气压, 在加载过程前应立即进行干燥过程, 以保持溶剂比恒定. </li>
		<li> 使用光学显微镜检查液体细胞. 
		注: 如果任何一个液体细胞的窗户被打破, 不要使用该细胞. </li>
		<li> 将纳米颗粒分散的 100 nL 载入储层 ( 图 2a 和 2b ) 的液体细胞。配备有超薄毛细管 ( 图 2c ) 的注射器可以有效地将少量的色散加载到液细胞的储层中. 
		注: 一般情况下, 纳米颗粒分散的注入量超过了储层的容量。如果分散物溢出从水库, 液体细胞可能不完全地密封。因此, 在储层外的任何溢出的分散体都必须被滤纸的尖端吸收为扇形形状。在吸收过程中避免与窗户接触. </li>
		<li> 将液体电池暴露在空气中10分钟以使邻二氯苯干燥. </li>
		<li> 将真空油脂应用于铜孔径网格的一侧, 其大小为 2 mm, hole-size 为600和 #181; m, 并将液体电池覆盖在孔径网格的润滑一侧, 以创建密封环境. 
		注: 在窗户上沉积的真空油脂大大降低了 TEM 的分辨率。因此, 在第一次尝试时, 不应更正铜孔径网格与单元格窗口的孔匹配问题;相反, 该单元格应被丢弃, 并准备了一个新的. </li>
	</ol> </li> <li> tem 测量 <ol> <li> 将液体电池置于标准 tem 支架中。该液体电池设计成符合标准的持有人. 
		注意: 使用手套避免 TEM 支架的污染. </li>
		<li> 在连续图像获取模式下设置 TEM。在 200 kV 的加速度电压下捕获 TEM 图像, 电流密度为 ~ 700 米/秒 2 . 
		注: 经常检查 TEM 压力水平。如果压力水平不正常, 立即停止成像, 并尽快从 TEM 室中取出支架。液胞 TEM 的低对比度使图像聚焦困难。良好的对准和对焦可以很容易地执行初始粗糙的焦点在窗口的边缘。通过改变电流密度可以控制干燥速率。2D 干燥速率可以通过跟踪不断变化的干燥补丁的大小来测量。然而, 很难数量按容积计算干燥率. </li>
		<li> 使用 ImageJ 软件包打开原始 TEM 图像。选择该程序的多点图标, 并分配图像中所有单个纳米粒子的中心, 然后提取所选粒子的 x 和 y 坐标. </li>
		<li> 计算径向分布函数 (RDF): 
		<img alt="Equation 1" src="/files/ftp_upload/56335/56335eq1.jpg"/> 其中, r 是间距离, N 是粒子数, A 是粒子所覆盖的区域, 和 #961; 是2D 的面积密度粒子 ( N / A ), <img alt="Equation 2" src="/files/ftp_upload/56335/56335eq2.jpg"/> 是从粒子 j 到粒子 k 的位置向量, 和 #948; ( r ) 是狄拉克δ函数。我们使用和 #160; <img alt="Equation 3" src="/files/ftp_upload/56335/56335eq3.jpg"/> where = 0.8 nm 作为狄拉克δ函数进行实际计算. </li>
	</ol>
	</li>
</ol>

<ol>
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作者没有什么可透露的。

以铂铵 (IV) 和酸铵 (II) 为原料, 用聚 (基) (PVP) 作为配体和乙二醇作为溶剂和还原剂, 合成了 7 nm 的铂纳米颗粒.27.用油进行配体交换反应, 在疏水溶剂中分散颗粒。以硒为原料, 将铅油酸酯配合物的热分解, 合成了铅化硫纳米颗粒,28 (参见参考29 , 用于详细合成的纳米晶)。由于合成的铅硒化物纳米颗粒已经被长链配体所覆盖, 这些微粒不需要配基交...

胶体纳米粒子的自组装是有兴趣的, 因为它提供了一个机会来获得单个纳米粒子的集体物理性质11。在实际的设备规模应用中, 自组装最有效的方法之一是在基板上通过挥发性溶剂的蒸发来自我组织,6,7,8,9,10,11. 这种溶剂蒸发法是一种非平衡过程, 主要受蒸发速率和纳米粒子-基体相互作用的变化等动力学因素的影响。然而, 由于难以估计和控制的动力学因素, 机械理解纳米粒子自组装的溶剂蒸发不完全成熟。虽然原位X 射线散射研究提供了非平衡纳米粒子自组装过程的集合平均信息,12,13,14, 此技术不能确定单个纳米粒子的运动, 它们与整体轨迹的联系不能轻易地被访问。
液体细胞 TEM 是一种新的工具, 跟踪单个纳米粒子的轨迹, 使我们能够理解纳米粒子运动的不均匀性及其对合奏行为的贡献15,16, 17,18,19,202122,2324,25 26。我们以前用液体细胞 TEM 跟踪单个纳米粒子在溶剂蒸发过程中的运动, 表明溶剂边界的运动是诱导纳米粒子自组装的主要推动力18,19. 本文介绍了利用液-细胞 TEM 观察纳米粒子自组装过程的实验。首先, 我们提供了合成铂和硒化铅纳米粒子的协议, 然后介绍了 TEM 中的液细胞的制备方法, 以及如何将纳米微粒加载到液细胞中。作为代表性的结果, 我们展示了由溶剂干燥驱动的纳米粒子自组装的 TEM 电影的快照图像。通过跟踪这些电影中的单个粒子, 我们可以了解在单个纳米粒子水平上的溶剂-干燥-介导的自组装的详细机制。在自组装过程中, 氮化硅窗口上的铂纳米粒子主要跟随蒸发溶剂前缘的运动, 因为在薄溶剂层上的强毛细管力作用。其他的纳米粒子 (硒化铅) 和基体 (硅) 也有类似现象, 这表明溶剂锋的毛细管力是粒子在基底附近迁移的一个重要因素。

<table>
	<tbody>
		<tr>
			<td>ammonium hexachloroplatinate (IV)</td>
			<td>Sigma-Aldrich</td>
			<td>204021</td>
			<td></td>
		</tr>
		<tr>
			<td>ammonium tetrachloroplatinate (II)</td>
			<td>Sigma-Aldrich</td>
			<td>206105</td>
			<td></td>
		</tr>
		<tr>
			<td>tetramethylammonium bromide, 98%</td>
			<td>Sigma-Aldrich</td>
			<td>195758</td>
			<td></td>
		</tr>
		<tr>
			<td>poly(vinylpyrrolidone) powder</td>
			<td>Sigma-Aldrich</td>
			<td>234257</td>
			<td>Mw ~29,000</td>
		</tr>
		<tr>
			<td>ethylene glycol, anhydrous, 99.8%</td>
			<td>Sigma-Aldrich</td>
			<td>324558</td>
			<td></td>
		</tr>
		<tr>
			<td>n-hexane, anhydrous, 95%</td>
			<td>Samchun Chem.</td>
			<td>H0114</td>
			<td></td>
		</tr>
		<tr>
			<td>ethanol, anhydrous, 99.5%</td>
			<td>Sigma-Aldrich</td>
			<td>459836</td>
			<td></td>
		</tr>
		<tr>
			<td>oleylamine, 70%</td>
			<td>Sigma-Aldrich</td>
			<td>O7805</td>
			<td>Technical grade</td>
		</tr>
		<tr>
			<td>lead(II) acetate trihydrate, 99.99%</td>
			<td>Sigma-Aldrich</td>
			<td>467863</td>
			<td></td>
		</tr>
		<tr>
			<td>oleic acid, 90%</td>
			<td>Sigma-Aldrich</td>
			<td>364525</td>
			<td>Technical grade</td>
		</tr>
		<tr>
			<td>diphenyl ether, 99%</td>
			<td>Sigma-Aldrich</td>
			<td>P24101</td>
			<td>ReagentPlus</td>
		</tr>
		<tr>
			<td>selenium powder, 99.99%</td>
			<td>Sigma-Aldrich</td>
			<td>229865</td>
			<td></td>
		</tr>
		<tr>
			<td>tri-n-octylphosphine, 97%</td>
			<td>Strem</td>
			<td>15-6655</td>
			<td>Air sensistive</td>
		</tr>
		<tr>
			<td>Toluene, anhydrous, 99.9%</td>
			<td>Samchun Chem.</td>
			<td>T2419</td>
			<td></td>
		</tr>
		<tr>
			<td>acetone 99.8%</td>
			<td>Daejung Chem.</td>
			<td>1009-2304</td>
			<td></td>
		</tr>
		<tr>
			<td>potassium hydroxide, 95%</td>
			<td>Samchun Chem.</td>
			<td>P0925</td>
			<td></td>
		</tr>
		<tr>
			<td>p-type silicon-on-insulator wafers</td>
			<td>Soitec</td>
			<td>Power-SOI</td>
			<td>for liquid cells with silicon windows</td>
		</tr>
		<tr>
			<td>tetramethylammonium hydroxide, 25% in H2O</td>
			<td>J.T.Baker</td>
			<td>02-002-109</td>
			<td></td>
		</tr>
		<tr>
			<td>AZ 5214 E</td>
			<td>AZ Electronic Materials</td>
			<td>AZ 5214 E</td>
			<td>Positive photorest</td>
		</tr>
		<tr>
			<td>AZ-327</td>
			<td>AZ Electronic Materials</td>
			<td>AZ-327</td>
			<td>AZ 5214 develper</td>
		</tr>
		<tr>
			<td>indium pellets 99.98-99.99%</td>
			<td>Kurt J. Lesker Company</td>
			<td>EVMIN40EXEB</td>
			<td>thermal evaporator target</td>
		</tr>
		<tr>
			<td>1,2-dichlorobenzene, &#62;99%</td>
			<td>TCI</td>
			<td>D1116</td>
			<td></td>
		</tr>
		<tr>
			<td>pentadecane, &#62;99%</td>
			<td>Sigma-Aldrich</td>
			<td>P3406</td>
			<td></td>
		</tr>
		<tr>
			<td>buffered oxide etch 7:1</td>
			<td>microchemicals</td>
			<td>BOE 7-1 VLSI</td>
			<td></td>
		</tr>
		<tr>
			<td>phosphoric acid, 85%</td>
			<td>Samchun Chem.</td>
			<td>P0449</td>
			<td></td>
		</tr>
	</tbody>
</table>

liquid-cell transmission electron microscopy for tracking self-assembly of nanoparticles

干燥纳米粒子的分散是建立纳米微粒自组装结构的一种通用方法, 但这一过程的机制还没有完全被理解。我们用液-细胞透射电镜 (TEM) 追踪了单个纳米粒子的运动轨迹, 以研究其组装过程的机理。在此, 我们提出的协议用于液体细胞 TEM 研究的自组装机制。首先, 我们介绍了详细的合成协议, 用于生产均匀大小的铂和硒化铅纳米颗粒。接下来, 我们介绍了用氮化硅或硅窗生产液态细胞的微细加工过程, 然后描述了液-细胞 TEM 技术的加载和成像过程。包括一些说明, 为整个过程提供有用的提示, 包括如何管理脆弱的细胞窗口。通过液-胞 TEM 跟踪的纳米粒子的单个运动表明, 蒸发引起的溶剂边界的变化影响了纳米粒子的自组装过程。溶剂的边界驱使纳米颗粒主要形成无定形的聚合体, 其次是聚集体的扁平化以产生2维 (2D) 自组装结构。这些行为也观察到不同的纳米颗粒类型和不同的液体细胞组成。

该液芯由一个顶部芯片和一个底部芯片组成, 它装有氮化硅窗口, 对电子束具有25纳米厚度的透明。顶部芯片有一个储存样品溶液和蒸发溶剂的储罐。这些芯片是通过传统的微细加工处理25。用于顶部和底部芯片的掩码分别显示在图 1a和 1b中。图 2a和 2b分别显?...

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Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles

用于跟踪纳米粒子自组装的液体细胞透射电子显微镜

在这里, 我们介绍了实验协议的 real-time 观察的自组装过程中使用液体细胞透射电镜。

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully ...

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12.6K 次观看.  Institute for Basic Science (IBS). 在这里, 我们介绍了实验协议的 real-time 观察的自组装过程中使用液体细胞透射电镜。

视频: Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles

Origami Inspired Self-assembly of Patterned and Reconfigurable Particles

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two dimensional (2D) structures. These technologies are mature, offer high precision and many of them can be implemented in a high-throughput manner. We leverage the advantages of planar lithography and combine them with self-folding methods1-20 wherein physical forces derived from surface tension or residual stress, are used to curve or fold planar structures into three dimensional (3D) structures. In doing so, we make it possible to mass produce precisely patterned static and reconfigurable particles that are challenging to synthesize.
In this paper, we detail visualized experimental protocols to create patterned particles, notably, (a) permanently bonded, hollow, polyhedra that self-assemble and self-seal due to the minimization of surface energy of liquefied hinges21-23 and (b) grippers that self-fold due to residual stress powered hinges24,25. The specific protocol described can be used to create particles with overall sizes ranging from the micrometer to the centimeter length scales. Further, arbitrary patterns can be defined on the surfaces of the particles of importance in colloidal science, electronics, optics and medicine. More generally, the concept of self-assembling mechanically rigid particles with self-sealing hinges is applicable, with some process modifications, to the creation of particles at even smaller, 100 nm length scales22, 26 and with a range of materials including metals21, semiconductors9 and polymers27. With respect to residual stress powered actuation of reconfigurable grasping devices, our specific protocol utilizes chromium hinges of relevance to devices with sizes ranging from 100 &mu;m to 2.5 mm. However, more generally, the concept of such tether-free residual stress powered actuation can be used with alternate high-stress materials such as heteroepitaxially deposited semiconductor films5,7 to possibly create even smaller nanoscale grasping devices.

We describe experimental details of the synthesis of patterned and reconfigurable particles from two dimensional (2D) precursors. This methodology can be used to create particles in a variety of shapes including polyhedra and grasping devices at length scales ranging from the micro to centimeter scale.

折纸灵感的图案和可重构颗粒自组装

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two ...

科研

化学

Formation of Ordered Biomolecular Structures by the Self-assembly of Short Peptides

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control self-assembly and mimicking this process in vitro will bring about major advances in the areas of materials science and nanotechnology. Among the available biological building blocks, peptides have several advantages as they present substantial diversity, their synthesis in large scale is straightforward, and they can easily be modified with biological and chemical entities1,2. Several classes of designed peptides such as cyclic peptides, amphiphile peptides and peptide-conjugates self-assemble into ordered structures in solution. Homoaromatic dipeptides, are a class of short self-assembled peptides that contain all the molecular information needed to form ordered structures such as nanotubes, spheres and fibrils3-8. A large variety of these peptides is commercially available.
This paper presents a procedure that leads to the formation of ordered structures by the self-assembly of homoaromatic peptides. The protocol requires only commercial reagents and basic laboratory equipment. In addition, the paper describes some of the methods available for the characterization of peptide-based assemblies. These methods include electron and atomic force microscopy and Fourier-Transform Infrared Spectroscopy (FT-IR). Moreover, the manuscript demonstrates the blending of peptides (coassembly) and the formation of a &#34;beads on a string&#34;-like structure by this process.9 The protocols presented here can be adapted to other classes of peptides or biological building blocks and can potentially lead to the discovery of new peptide-based structures and to better control of their assembly.

This paper describes the formation of highly ordered peptide-based structures by the spontaneous process of self-assembly. The method utilizes commercially available peptides and common lab equipment. This technique can be applied to a large variety of peptides and may lead to the discovery of new peptide-based assemblies.

生物分子有序结构由短肽的自组装形成

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control ...

Self-assembly of Complex Two-dimensional Shapes from Single-stranded DNA Tiles

Current methods in DNA nano-architecture have successfully engineered a variety of 2D and 3D structures using principles of self-assembly. In this article, we describe detailed protocols on how to fabricate sophisticated 2D shapes through the self-assembly of uniquely addressable single-stranded DNA tiles which act as molecular pixels on a molecular canvas. Each single-stranded tile (SST) is a 42-nucleotide DNA strand composed of four concatenated modular domains which bind to four neighbors during self-assembly. The molecular canvas is a rectangle structure self-assembled from SSTs. A prescribed complex 2D shape is formed by selecting the constituent molecular pixels (SSTs) from a 310-pixel molecular canvas and then subjecting the corresponding strands to one-pot annealing. Due to the modular nature of the SST approach we demonstrate the scalability, versatility and robustness of this method. Compared with alternative methods, the SST method enables a wider selection of information polymers and sequences through the use of de novo designed and synthesized short DNA strands.

DNA tiling is an effective approach to make programmable nanostructures. We describe the protocols to construct complex two-dimensional shapes by the self-assembly of single-stranded DNA tiles.

复杂的二维形状的从单链DNA的瓷砖自组装

Current methods in DNA nano-architecture have successfully engineered a variety of 2D and 3D structures using principles of self-assembly. In this ...

Obtaining 3D Chemical Maps by Energy Filtered Transmission Electron Microscopy Tomography

Energy filtered transmission electron microscopy tomography (EFTEM tomography) can provide three-dimensional (3D) chemical maps of materials at a nanometric scale. EFTEM tomography can separate chemical elements that are very difficult to distinguish using other imaging techniques. The experimental protocol described here shows how to create 3D chemical maps to understand the chemical distribution and morphology of a material. Sample preparation steps for data segmentation are presented. This protocol permits the 3D distribution analysis of chemical elements in a nanometric sample. However, it should be noted that currently, the 3D chemical maps can only be generated for samples that are not beam sensitive, since the recording of filtered images requires long exposure times to an intense electron beam. The protocol was applied to quantify the chemical distribution of the components of two different heterogeneous catalyst supports. In the first study, the chemical distribution of aluminum and titanium in titania-alumina supports was analyzed. The samples were prepared using the swing-pH method. In the second, the chemical distribution of aluminum and silicon in silica-alumina supports that were prepared using the sol-powder and mechanical mixture methods was examined.

This paper describes a protocol to achieve 3D chemical maps combining energy filtered imaging and electron tomography. The chemical distribution of two catalyst supports formed by elements that are difficult to distinguish by other imaging techniques was studied. Each application consists of mapping overlapped chemical elements - respectively spaced-ionization edges.

通过能量过滤透射电镜成像获得3D 化学图

Energy filtered transmission electron microscopy tomography (EFTEM tomography) can provide three-dimensional (3D) chemical maps of materials at a ...

Analysis of Minerals Produced by hFOB 1.19 and Saos-2 Cells Using Transmission Electron Microscopy with Energy Dispersive X-ray Microanalysis

This video presents the use of transmission electron microscopy with energy dispersive X-ray microanalysis (TEM-EDX) to compare the state of minerals in vesicles released by two human bone cell lines: hFOB 1.19 and Saos-2. These cell lines, after treatment with ascorbic acid (AA) and &#946;-glycerophosphate (&#946;-GP), undergo complete osteogenic transdifferentiation from proliferation to mineralization and produce matrix vesicles (MVs) that trigger apatite nucleation in the extracellular matrix (ECM).
Based on Alizarin Red-S (AR-S) staining and analysis of the composition of minerals in cell lysates using ultraviolet (UV) light or in vesicles using TEM imaging followed by EDX quantitation and ion mapping, we can infer that osteosarcoma Saos-2 and osteoblastic hFOB 1.19 cells reveal distinct mineralization profiles. Saos-2 cells mineralize more efficiently than hFOB 1.19 cells and produce larger mineral deposits that are not visible under UV light but are similar to hydroxyapatite (HA) in that they have more Ca and F substitutions.
The results obtained using these techniques allow us to conclude that the process of mineralization differs depending on the cell type. We propose that, at the cellular level, the origin and properties of vesicles predetermine the type of minerals.

We present a protocol to compare the state of minerals in vesicles released by two human bone cell lines: hFOB 1.19 and Saos-2. Their mineralization profiles were analyzed by Alizarin Red-S (AR-S) staining, ultraviolet (UV) light visualization, transmission electron microscopy (TEM) imaging and energy dispersive X-ray microanalysis (EDX).

透射电镜 hFOB 1.19 和 Saos-2 细胞产生的能量色散 X 射线显微分析

This video presents the use of transmission electron microscopy with energy dispersive X-ray microanalysis (TEM-EDX) to compare the state of minerals in ...

Using Graphene Liquid Cell Transmission Electron Microscopy to Study in Situ Nanocrystal Etching

Graphene liquid cell electron microscopy provides the ability to observe nanoscale chemical transformations and dynamics as the reactions are occurring in liquid environments. This manuscript describes the process for making graphene liquid cells through the example of graphene liquid cell transmission electron microscopy (TEM) experiments of gold nanocrystal etching. The protocol for making graphene liquid cells involves coating gold, holey-carbon TEM grids with chemical vapor deposition graphene and then using those graphene-coated grids to encapsulate liquid between two graphene surfaces. These pockets of liquid, with the nanomaterial of interest, are imaged in the electron microscope to see the dynamics of the nanoscale process, in this case the oxidative etching of gold nanorods. By controlling the electron beam dose rate, which modulates the etching species in the liquid cell, the underlying mechanisms of how atoms are removed from nanocrystals to form different facets and shapes can be better understood. Graphene liquid cell TEM has the advantages of high spatial resolution, compatibility with traditional TEM holders, and low start-up costs for research groups. Current limitations include delicate sample preparation, lack of flow capability, and reliance on electron beam-generated radiolysis products to induce reactions. With further development and control, graphene liquid cell may become a ubiquitous technique in nanomaterials and biology, and is already being used to study mechanisms governing growth, etching, and self-assembly processes of nanomaterials in liquid on the single particle level.

Using Graphene Liquid Cell Transmission Electron Microscopy to Study in Situ Nanocrystal Etching

Graphene liquid cell electron microscopy can be used to observe nanocrystal dynamics in a liquid environment with greater spatial resolution than other liquid cell electron microscopy techniques. Etching premade nanocrystals and following their shape using graphene liquid cell Transmission Electron Microscopy can yield important mechanistic information about nanoparticle transformations.

用石墨烯液细胞透射电镜研究原位纳米晶蚀刻

Graphene liquid cell electron microscopy provides the ability to observe nanoscale chemical transformations and dynamics as the reactions are occurring in ...

Performing Spectroscopy on Plasmonic Nanoparticles with Transmission-Based Nomarski-Type Differential Interference Contrast Microscopy

Differential interference contrast (DIC) microscopy is a powerful imaging tool that is most commonly employed for imaging microscale objects using visible-range light. The purpose of this protocol is to detail a proven method for preparing plasmonic nanoparticle samples and performing single particle spectroscopy on them with DIC microscopy. Several important steps must be followed carefully in order to perform repeatable spectroscopy experiments. First, landmarks can be etched into the sample substrate, which aids in locating the sample surface and in tracking the region of interest during experiments. Next, the substrate must be properly cleaned of debris and contaminants that can otherwise hinder or obscure examination of the sample. Once a sample is properly prepared, the optical path of the microscope must be aligned, using Kohler Illumination. With a standard Nomarski style DIC microscope, rotation of the sample may be necessary, particularly when the plasmonic nanoparticles exhibit orientation-dependent optical properties. Because DIC microscopy has two inherent orthogonal polarization fields, the wavelength-dependent DIC contrast pattern reveals the orientation of rod-shaped plasmonic nanoparticles. Finally, data acquisition and data analyses must be carefully performed. It is common to represent DIC-based spectroscopy data as a contrast value, but it is also possible to present it as intensity data. In this demonstration of DIC for single particle spectroscopy, the focus is on spherical and rod-shaped gold nanoparticles.

The goal of this protocol is to detail a proven approach for the preparation of plasmonic nanoparticle samples and for performing single particle spectroscopy on them with differential interference contrast (DIC) microscopy.

基于传输的野武学型差分干涉对比显微镜对等离子体纳米粒子的光谱处理

Differential interference contrast (DIC) microscopy is a powerful imaging tool that is most commonly employed for imaging microscale objects using ...

Preparation of Graphene-Supported Microwell Liquid Cells for In Situ Transmission Electron Microscopy

The fabrication and preparation of graphene-supported microwell liquid cells (GSMLCs) for in situ electron microscopy is presented in a stepwise protocol. The versatility of the GSMLCs is demonstrated in the context of a study about etching and growth dynamics of gold nanostructures from a HAuCl4 precursor solution. GSMLCs combine the advantages of conventional silicon- and graphene-based liquid cells by offering reproducible well depths together with facile cell manufacturing and handling of the specimen under investigation. The GSMLCs are fabricated on a single silicon substrate which drastically reduces the complexity of the manufacturing process compared to two-wafer-based liquid cell designs. Here, no bonding or alignment process steps are required. Furthermore, the enclosed liquid volume can be tailored to the respective experimental requirements by simply adjusting the thickness of a silicon nitride layer. This enables a significant reduction of window bulging in the electron microscope vacuum. Finally, a state-of-the-art quantitative evaluation of single particle tracking and dendrite formation in liquid cell experiments using only open source software is presented.

Preparation of Graphene-Supported Microwell Liquid Cells for In Situ Transmission Electron Microscopy

A protocol for preparation of graphene-supported microwell liquid cells for in situ electron microscopy of gold nanocrystals from HAuCl4 precursor solution is presented. Furthermore, an analysis routine is presented to quantify observed etching and growth dynamics.

石墨烯支持的微井液体细胞制备,用于原位透射电子显微镜

The fabrication and preparation of graphene-supported microwell liquid cells (GSMLCs) for in situ electron microscopy is presented in a stepwise protocol. ...

Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers

The production of monodisperse cylindrical micelles is a significant challenge in polymer chemistry. Most cylindrical constructs formed from diblock copolymers are produced by one of three techniques: thin film rehydration, solvent switching or polymerization-induced self-assembly, and produce only flexible, polydisperse cylinders. Crystallization-driven self-assembly (CDSA) is a method which can produce cylinders with these properties, by stabilizing structures of a lower curvature due to the formation of a crystalline core. However, the living polymerization techniques by which most core-forming blocks are formed are not trivial processes and the CDSA process may yield unsatisfactory results if carried out incorrectly. Here, the synthesis of cylindrical nanoparticles from simple reagents is shown. The drying and purification of reagents prior to a ring-opening polymerization of &#949;-caprolactone catalyzed by diphenyl phosphate is described. This polymer is then chain extended by methyl methacrylate (MMA) followed by N,N-dimethyl acrylamide (DMA) using reversible addition&#8722;fragmentation chain-transfer (RAFT) polymerization, affording a triblock copolymer that can undergo CDSA in ethanol. The living CDSA process is outlined, the results of which yield cylindrical nanoparticles up to 500 nm in length and a length dispersity as low as 1.05. It is anticipated that these protocols will allow others to produce cylindrical nanostructures and elevate the field of CDSA in the future.

Crystallization-driven self-assembly (CDSA) displays the unique ability to fabricate cylindrical nanostructures of narrow length distributions. The organocatalyzed ring-opening polymerization of &#949;-caprolactone and subsequent chain extensions of methyl methacrylate and N,N-dimethyl acrylamide are demonstrated. A living CDSA protocol that produces monodisperse cylinders up to 500 nm in length is outlined.

通过结晶驱动生物降解块共聚物的自组装合成单分散圆柱状纳米粒子

The production of monodisperse cylindrical micelles is a significant challenge in polymer chemistry. Most cylindrical constructs formed from diblock ...

Self-Assembly of Hybrid Lipid Membranes Doped with Hydrophobic Organic Molecules at the Water/Air Interface

Because of their unique properties, including an ultrathin thickness (3-4 nm), ultrahigh resistivity, fluidity and self-assembly ability, lipid bilayers can be readily functionalized and have been used in various applications such as bio-sensors and bio-devices. In this study, we introduced a planar organic molecule: copper (II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPc) to dope lipid membranes. The CuPc/lipid hybrid membrane forms at the water/air interface by self-assembly. In this membrane, the hydrophobic CuPc molecules are located between the hydrophobic tails of lipid molecules, forming a lipid/CuPc/lipid sandwich structure. Interestingly, an air-stable hybrid lipid bilayer can be readily formed by transferring the hybrid membrane onto a Si substrate. We report a straightforward method for incorporating nanomaterials into a lipid bilayer system, which represents a new methodology for the fabrication of biosensors and biodevices.

We report a protocol for producing a hybrid lipid membrane at the water/air interface by doping the lipid bilayer with copper (II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPc) molecules. The resulting hybrid lipid membrane has a lipid/CuPc/lipid sandwich structure. This protocol can also be applied to the formation of other functional nanomaterials.

在水/空气界面上掺杂与疏水有机分子混合脂膜的自组装

Because of their unique properties, including an ultrathin thickness (3-4 nm), ultrahigh resistivity, fluidity and self-assembly ability, lipid bilayers ...