作者想感谢香港易在埃默里大学综合显微镜核心的电子显微成像。这项工作是由美国国立卫生研究院拨款赞助（PN2EY018244，R01 CA108468，U54CA119338的，1K99CA154006-01）。

以下的合成程序涉及标准的无空气的技术和使用的真空/惰性气体歧管;参考文献10和11中可以找到详细的方法。所有潜在的有毒和易燃物质的MSDS应咨询在使用之前，所有的易燃和/或空气不稳定的化合物应分装到隔垫密封的小瓶，在手套箱中或手套袋。 1。合成的汞硒化镉量子点（汞X CD-X SE）核心<ol><li>准备辛基膦（TOP）为0.4的溶液中的硒。硒（0.316克，4毫摩尔）加入到一个50毫升三颈烧瓶中，然后进行抽真空和填写使​​用的Schlenk线用氩气。在无空气的条件下（干燥的氮气或氩气气氛下），加入10 ml的TOP和热至100°C，同时搅拌1小时，得到一种清澈，无色的溶液。溶液冷却至室温，并设置将烧瓶放在一边。 </li><li>在一个250毫升的三颈烧瓶中，添加氧化镉（CdO的0.0770克，0.6毫摩尔），tetradecylphosphonic磺酸（TDPA0.3674克，1.32毫摩尔），和十八碳烯（ODE，27.6毫升），并撤离溶液，搅拌的同时使用的Schlenk线。的温度上升至100℃，另外的15分钟，以除去低沸点杂质和疏散。 </li><li>在氩气或氮气下，将混合物加热到300℃1小时，充分溶解的CdO的。该解决方案将一个红色的颜色为无色透明。溶液冷却至室温。 </li><li>十六烷基（HDA，7.0克）的镉溶液，加热至70°C，并撤离。一旦达到一个恒定的压力，提高温度至100-110℃，回流该溶液30分钟。将舒伦克线阀切换到惰性气体和热电偶直接插入到溶液中。 </li><li>在无空气的条件下，添加二苯基膦（DPP，100微升）到该溶液的温度上升至310℃。取出7.5毫升0.4 M TOP-SE解决方案（3毫摩尔硒）在连接到一个16号针头的一次性使用的塑料注射器。 </li><li>一旦温度平衡在310℃，温度控制器设置为0℃，迅速注入的TOP硒溶液直接进入镉溶液。该解决方案将改变从无色到黄色，橙色和温度会迅速下降，再次增加〜280°C。反应1分钟后，从加热套中取出烧瓶中，并迅速冷却空气流中，直到温度小于200℃。 </li><li>当温度达到〜40℃，用30毫升己烷稀释;大部分剩余的镉前体的溶液将沉淀出来。移除该沉淀物，通过离心分离（5,000 xg离心10分钟）。 </li><li>六个50ml聚丙烯离心管中，在每个稀释的粗的纳米晶体溶液12毫升，用40毫升丙酮，离心（5,000×g离心10分钟），并仔细滗析并丢弃上清液。 </li><li>溶解nanocr石英晶体粒料的己烷溶液（25毫升的总体积）。提取此溶液3次，用等体积的甲醇中，保持最佳的相位。对于第三次抽提，甲醇的体积可以被调整，以〜15毫升纯CdSe量子点，获​​得浓缩的己烷溶液，在大约200μM。该反应的典型产率是3μmol的CdSe纳米晶体的直径为2.3纳米（50〜60％的反应收率）。 </li><li>确定的纳米晶体的直径和浓 ​​度通过测量的UV-Vis吸收光谱和咨询的马瓦尼和同事12和消光的Bawendi和同事13的相关性的大小配合图表。有关详细信息，请参阅附录。 </li><li>汞阳离子交换部分交换的纳米晶体可以与汞的吸收和荧光发射红移。以下混合在一起，以便在与搅拌棒的20毫升玻璃小瓶中（该反应可根据需要缩放）：3毫升己烷，2毫升氯仿，1毫升200μM镉硒QD溶液（为200 nmol），15微升的油胺（OLA），汞（OT）2在氯仿中的0.1M溶液和500μl。可以准备，水星octanethioate（HgOT 2）反应在甲醇醋酸汞和辛硫醇（见附录）。作为阳离子交换反应的进行，红移的程度可能会被监控采用UV-Vis吸收分光光度测定法。后已经达到所需的吸收带，测量在350 nm处的吸收的纳米晶体溶液，并确定新的消光系数，假设的纳米晶体的浓度并没有改变（30.7μM在这个例子中）。淬灭反应，通过除去未反应的汞：添加癸烷，5毫升10毫升己烷，和7毫升甲醇中，并提取该溶液中，保持最佳的相，含有纳米晶体。提取两次以上，用己烷和甲醇中，并调整体积的甲醇中，使最高相〜7毫升。如果相位是缓慢分离，可将溶液离心（5,000 xg离心，10分钟）。添加100μl的顶部，100微升OLA，和100μl油酸其次是40毫升丙酮以生成沉淀的纳米晶体。通过离心收集的纳米晶体，并分散在3 mL正己烷。再次离心除去不溶物，并再次确定的纳米晶体的浓度，使用新的在350nm处的消光系数。允许年龄的纳米晶体溶液在室温下至少24小时，然后进行到下一步骤。 </li></ol> 2。锌镉硫化物增长（CDŸ锌1-Y S）壳牌<ol><li>准备0.1M的壳前体溶液，在50毫升的三颈烧瓶中。镉的前体：醋酸镉水合物（230.5毫克，1毫摩尔）和10毫升油胺（OLA）。锌前驱物：醋酸锌（183.5毫克，1毫摩尔）和10毫升OLA。硫前体：硫（32.1毫克，1毫摩尔）和10毫升ODE。真空条件下，加热回流1小时，每个解决方案得到明确的解决方案，然后充以氩气。硫的解决方案可能待冷却至室温，但镉和锌的前体保持在约50℃下壳前体的数量的计算，可以在参考文献14中找到。 </li><li> 3颈烧瓶中加入：汞柱X CD 1-x Se的量子点（120 nmol，直径为2.3纳米），ODE（2毫升），及三辛基氧化膦（TOPO中，250毫克）。疏散己烷在室温下使用的Schlenk线。的温度上升到100℃，回流15分钟。更改的Schlenk线阀的氩气或氮气和插入热电偶的纳米晶体溶液中。 </li><li>的温度上升至120℃，加入0.5单层硫前体溶液（140微升），并让反应继续进行15分钟。小等分试样（&lt;50微升），可以使用的玻璃注射器除去监视使用荧光和/或UV-Vis吸收分光光度法测定的反应的进展。的温度上升至140℃，添加0.5镉单层的前体溶液（140微升），然后使反应继续进行15分钟。加入500μl无水OLA向反应溶液。 </li><li>在160℃下添加0.5单层硫前体溶液（220微升），接着由同等数量的锌前体溶液在170℃下用15分钟每次加入之间。然后在180℃下添加0.25单层硫前体溶液（150微升）和锌的前体溶液，在15分钟的间隔。 </li><li>溶液冷却至室温，并再次计算出一个新的消光系数为这些颗粒使用的UV-Vis光谱，假设不改变纳米晶体的数目（120 nmol在3.8毫升的反应溶液）。粗混合物的反应溶液作为存放在冷冻柜;纳米晶体可以解冻，并根据需要使用的第1.8节和1.9节中描述的方法相同的方法纯化。 </li><li>的纳米晶体的特征可使用电子显微镜，UV-Vis吸收光谱和荧光光谱。量子产率可计算绝对使用积分球或相对比较，使用参考文献15的方法，公知的标准。 </li></ol> 3。相转移<ol><li>加入纯化的芯/壳汞X CD 1-X SE /镉Ŷ锌1-Y S量子点（5毫升，20μM），一个50毫升三颈烧瓶中，并在高真空下，以得到干燥的膜中除去己烷。填充用氩气的烧瓶中，加入无水吡啶（3ml）中的纳米颗粒薄膜和热的淤浆至80℃。超过1-2小时的过程中，纳米粒子将完全溶解。 </li><li> 1 - 硫代甘油（1毫升）加入到该溶液中，并在80℃下搅拌2小时。然后冷却溶液至室温，并添加三乙胺（0.5毫升）中去质子化硫甘油。搅拌30分钟。该解决方案可能会变得混浊，加入三乙胺后由于极性纳米晶体在该溶剂混合物中的溶解性差。 </li><li>的QD的溶液转移到50毫升锥形离心管续癌宁20毫升己烷和20ml丙酮的混合物，搅拌均匀。通过离心（5,000×g离心10分钟），分离析出的纳米晶体，并用丙酮洗涤沉淀。 </li><li>溶解在DMSO（5ml）中的QD颗粒与浴中超声处理，然后离心（7,000 xg离心，10分钟），以除去可能的聚集体。确定的纳米粒子的浓度，从UV-Vis吸收光谱。应当使用这种纯量子点的溶液在3小时之内，作为表面硫醇可以慢慢地在环境条件下在空气中氧化。 </li><li>稀释至10μM或更少用DMSO的QD的溶液，并转移到50毫升的烧瓶中。准备5毫克/毫升的溶液（在附录中的所述合成）在DMSO中的巯基化的聚丙烯酸。添加的聚合物溶液（0.15毫克每nmol量子点的聚合物）滴加到QD的溶液中，同时搅拌和脱气的溶液，在室温下5分钟。 </li><li>吹扫QD /聚合物溶液用氩气并加热到80℃下进行90分钟。然后冷却至室温的溶液ð逐滴加入等体积的50mM硼酸钠，pH值为8。搅拌10分钟。 </li><li>净化量子点通过透析（20 kDa的截止频率）在50mM硼酸钠，pH 8，然后使用离心过滤器（10 kDa的截止频率）的粒子集中。从UV-Vis吸收光谱确定的浓度。 </li></ol> 4。聚乙二醇涂层<ol><li>在一个4毫升玻璃小瓶中，用搅拌棒，1纳摩尔量子点在硼酸盐缓冲液混合，用40,000×750沓单氨基-聚乙二醇（30毫克，40微摩尔）的摩尔过量的。如果一个特定的化学功能是要添加到的纳米晶体（ 例如，酰肼或马来酰亚胺），它可引入的取代的氨基-PEG与异型双氨 ​​基-PEG（30％摩尔分数通常运作良好）的一小部分。的纳米晶体溶液稀释至1μM用硼酸盐缓冲液。该反应可以根据需要进行缩放。 </li><li>准备一个新鲜DMTMM（20毫克，72微摩尔）在DMSO（144微升）溶液中。该解决方案可以简单地加热ü各州温暖的自来水或淹没在洗澡超声波仪，充分溶解DMTMM的流。快速添加25,000×摩尔过量的产品0.5M的DMTMM溶液（50微升）到QD的溶液中，并在室温下搅拌30分钟。 </li><li>重复步骤4.2四次PEG纳米晶体表面饱和。最后，加入200μl1 M Tris缓冲液，淬灭反应，并使用透析，离心过滤器，或超速离心纯化的纳米晶体。 </li><li>可分析的单分散性，水动力的大小，和表面电荷，使用液相色谱法，琼脂糖凝胶电泳，和荧光显微镜的纳米晶体。为了确定使用一个自动化的液相色谱系统（GE AKTAprime Plus）的流体动力学尺寸和粒度分布，使用的Superose 6柱，用PBS缓冲液洗脱剂，流速为0.5毫升/分钟，并在260或280 nm处的吸收检测。比较纳米粒子洗脱时间与分子量标准。琼脂糖凝胶电泳电阻，制备0.5％的琼脂糖凝胶在50mM硼酸钠缓冲液（pH8.5）或50mM磷酸钠缓冲液（pH7.4），10％甘油和加载到井1μM的样品混合，并运行在100 V 30分钟。图片中的纳米晶体的凝胶，使用UV手棒或UV透射仪和荧光激发。图像用荧光显微镜在单分子水平的纳米晶体，在10mM磷酸盐缓冲液稀释为0.2nM的颗粒，下降2.5微升该溶液的玻璃盖玻片上，并小心地将顶部的液珠上的第二盖玻片传播电影之间的盖玻片。图像的表面结合的使用高数值孔径的物镜（理想情况下至少1.40）的粒子在任一落射荧光或的TIRF模式与在400-580 nm和电子倍增CCD相机之间的波长的激发。精确的成像显微镜设置参数之间会有所不同。 </li></ol>

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Phys. 8, 3895-3903 (2006).</li><li>Zhang, X., Mohandessi, S., Miller, L. W., Snee, P. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+functionalization+of+aqueous+CdSe/ZnS+nanocrystals+using+small-molecule+chemical+activators.">Efficient functionalization of aqueous CdSe/ZnS nanocrystals using small-molecule chemical activators.</a> Chem. Comm. 47, 3532-3534 (2011).</li><li>Bucio, L., Souza, V., Albores, A., Sierra, A., Chavez, E., Carabez, A., Guiterrez-Ruiz, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cadmium+and+mercury+toxicity+in+a+human+fetal+hepatic+cell+line+(WRL-68+cells).">Cadmium and mercury toxicity in a human fetal hepatic cell line (WRL-68 cells).</a> Toxicol. 102, 285-299 (1995).</li><li>Han, S. G., Castranova, V., Vallyathan, V. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+cytotoxicity+of+cadmium+and+mercury+in+a+human+bronchial+epithelial+cell+line+(BEAS-2B)+and+its+role+in+oxidative+stress+and+induction+of+heat+shock+protein+70.">Comparative cytotoxicity of cadmium and mercury in a human bronchial epithelial cell line (BEAS-2B) and its role in oxidative stress and induction of heat shock protein 70.</a> J. Toxicol. Environ. Health Part A. 70, 852-860 (2007).</li><li>Strubelt, O., Kremer, J., Tilse, A., Keogh, J., Pentz, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+studies+on+the+toxicity+of+mercury,+cadmium,+and+copper+toward+the+isolated+perfused+rat+liver.">Comparative studies on the toxicity of mercury, cadmium, and copper toward the isolated perfused rat liver.</a> J. Toxicol. Environ. Health Part A. 47, 267-283 (1996).</li></ol>

没有利益冲突的声明。

相对于传统的CdSe量子点，三元合金汞X CD-X SE纳米晶体可调谐的大小和荧光波长独立。在合成过程中的CdSe纳米晶体核的大小是第一次选择，和荧光的波长选择在二次汞阳离子交换步骤中，基本上不改变纳米晶体尺寸9。重要的是要允许纯化汞X CD 1-X SE纳米晶体在室温下孵育，在至少24小时前封盖。这允许一些弱吸附汞阳离子扩散到的纳米晶体晶格。不使这个过程中发生，在近...

<table border="1"><tbody><tr><td> 的试剂的名称 </td><td> 公司 </td><td> 目录编号 </td><td> 评论（可选） </td></tr><tr><td>硒</td><td> Sigma-Aldrich公司</td><td> 229865 </td><td></td></tr><tr><td>三-n-辛基</td><td> STREM </td><td> 15-6655 </td><td>纯度为97％，在空气中不稳定</td></tr><tr><td>氧化镉</td><td> Sigma-Aldrich公司</td><td> 202894 </td><td>剧毒：谨慎使用</td></tr><tr><td> Tetradecylphosphonic酸</td><td> PCI合成</td><td> 4671-75-4 </td><td></td></tr><tr><td>十八</td><td>阿法埃莎</td><td> L11004 </td><td>工业级</td></tr><tr><td>十六胺</td><td> Sigma-Aldrich公司</td><td> H7408 </td><td></td></tr><tr><td>二苯基</td><td> Sigma-Aldrich公司</td><td> 252964 </td&gt; <td>发火的</td></tr><tr><td>醋酸汞</td><td> Sigma-Aldrich公司</td><td> 456012 </td><td>剧毒：谨慎使用</td></tr><tr><td> 1 - 辛硫醇</td><td> Sigma-Aldrich公司</td><td> 471836 </td><td>强烈的气味</td></tr><tr><td>油酸</td><td> Sigma-Aldrich公司</td><td> W281506 </td><td></td></tr><tr><td>醋酸锌</td><td>阿法埃莎</td><td> 35792 </td><td></td></tr><tr><td>醋酸镉水合物</td><td> Sigma-Aldrich公司</td><td> 229490 </td><td>剧毒：谨慎使用</td></tr><tr><td>油胺</td><td> Fisher Scientific则</td><td> AC12954 </td><td>在空气中不稳定</td></tr><tr><td>硫</td><td> Sigma-Aldrich公司</td><td> 344621 </td><td></td></tr><tr><td>三正辛基氧</td><td> STREM </td><td> 15-6661 </td><td> 99％ </td></tr><tr><td>吡啶</td><td> VWR </td><td> EM-PX2012-6 </td><td>无水</td></tr><tr><td>甘油</td><td> Sigma-Aldrich公司</td><td> M1753 </td><td>强烈的气味</td></tr><tr><td>三乙胺</td><td> Sigma-Aldrich公司</td><td> 471283 </td><td>无水</td></tr><tr><td>透析管</td><td>光谱实验室</td><td> 131342 </td><td> 20 kDa的截止</td></tr><tr><td>离心式过滤器</td><td>密理博</td><td> UFC801024 </td><td> 10 kDa的截止</td></tr><tr><td>单氨基-PEG </td><td>拉普Polymere </td><td> 12 750-2 </td><td> 750大</td></tr><tr><td> DMTMM，4 - （4,6 - 二甲氧基-1,3,5 - 三嗪-2 - 基） - 4 - 甲基吗啉鎓水合物</td><td>阿法埃莎</td><td> H26333 </td><td></td></tr><tr><td> AKTAprime加色谱系统</td><td> GE医疗集团</td><td></td><td></td></tr><tr><td> SUPEROSE 6 10/300 GL层析柱</td><td> GE医疗集团</td><td> 17-5172-01 </td><td></td></tr><tr><td>琼脂糖，OmniPur </td><td> VWR </td><td> EM-2120 </td><td></td></tr><tr><td></td><td></td><td></td><td>附录 合成硫醇的汞 ：慢慢加入乙酸汞的甲醇溶液（1当量）1 -辛硫醇（3当量）和氢氧化钾（3当量），在室温下在甲醇中的搅拌溶液。汞（II）硫醇的沉淀通过过滤分离，用甲醇和一次，用乙醚洗两次，然后在真空下干燥。 多齿聚合物的合成 ：将聚丙烯酸（1克，1773沓）溶解在25毫升二甲基甲酰胺（DMF）中，在一个150毫升的三颈烧瓶中，并用氩气泡30分钟。添加无水半胱胺（374毫克，4.87毫摩尔）在10毫升DMF中的溶液。在室温下，在剧烈搅拌下，慢慢加入无水二异丙基（DIC，736毫克，5.83毫摩尔）超过30分钟，然后加入三乙胺（170微升，1.22毫摩尔），使反应继续进行72小时，在60℃下加入巯​​基乙醇（501毫克，6.41毫摩尔），以便淬灭反应，并在室温下搅拌2小时。通过旋转蒸发除去DMF，和隔离的聚合物为2:1的混合物加入冰冷的丙酮：氯仿，随后离心。 〜5毫升无水DMF中，过滤器中的聚合物溶解，沉淀再次用二乙醚，并重复。干燥产物在氩气下在真空下和存储。 CdSe核直径的测定 ：从UV-Vis吸收光谱确定的波长，所述第一激子峰（λ，以nm为单位），这是最长的波长峰值（ 例如，在图2a中的大约498纳米的CdSe），并使用上浆曲线马瓦尼和他的同事12： <img src="/files/ftp_upload/4236/4236eq1.jpg" alt=“式（1）”/&gt; 硒化镉纳米晶体浓度的测定 ：从背景中减去的紫外-可见光谱的CdSe纳米晶体的光学透明的解决方案，确定在350 nm波长的吸收。系列稀释液，可以使用，以确定是否是光吸收Beer定律的线性范围内。的纳米晶体的浓度（QD，M）可以通过以下来确定插入的纳米晶体的直径（D，单位为nm）的光吸收值（A 3SA），和比色皿的路径长度（l，单位：cm）变成下面的等式从的经验关系的Bawendi和他的同事13： <img src="/files/ftp_upload/4236/4236eq2.jpg" alt="公式2" /></td></tr></tbody></table>

compact quantum dots for single-molecule imaging

单分子成像是一个重要的工具，对于理解生物分子功能的机制和可视化的空间和时间异质性的分子行为的基础细胞生物学1-4。要图像的个别分子的利益，它是典型的共轭到一个荧光标记（染料，蛋白质，小珠，或量子点），并与落射荧光或总内部反射荧光显微镜（TIRF）观察。它们的荧光染料和荧光蛋白质已被几十年来的荧光成像的主体，是不稳定的必要观察单个分子的高光子通量下，得到信号完全丧失之前只需要几秒钟的观察。乳胶珠和染料标记的珠提供改进的信号的稳定性，但在急剧放大的流体动力学尺寸，它可以有害地改变所研究的分子的扩散和行为的牺牲。 ntent“量子点（量子点）之间的平衡这两个问题的制度。这些纳米粒子组成的半导体材料，可以设计一个水动力紧凑的尺寸，优异的抗光降解5。因此，近年来，量子点已经在使长期观察单分子水平上的复杂大分子的行为。然而，这些粒子仍然表现出受损的扩散分子在拥挤的环境中，如细 ​​胞的细胞质和神经元突触间隙，它们的尺寸仍然过大，4,6 ，7。 最近，我们已设计的流体动力学尺寸最小化的量子点的芯和表面涂层，而平衡的偏移量的胶体稳定性，耐光性，亮度，和在过去8,9阻碍紧凑量子点的实用程序的非特异性结合。这篇文章的目的是展示这些优化的纳米晶的合成，修饰和表征，由汞的合金X CD-X SE核心涂有绝缘CDŸ锌1-Y的外壳，再涂上一多与短聚乙二醇修饰的高分子配体（ PEG）链（ 图1）。与传统的CdSe纳米晶体相比，汞X CD 1-X SE合金提供了更大的荧光量子产率，在增强的信号噪声在细胞中，和在非细胞毒性的可见光波长的激发的红光和近红外波长的荧光。多齿聚合物涂层的纳米晶体的表面，在一个封闭的和平面的构象结合的流体动力学尺寸最小化，并，PEG中和表面电荷，以尽量减少非特异性结合的细胞和生物分子。最终的结果是一个明亮的荧光纳米晶与排放之间550-800 nm和总的水动力大小近12处。这是在sAME许多可溶性的球形细胞中的蛋白质，远小于传统的聚乙二醇化量子点（25-35纳米）的尺寸范围。

图2描述了有代表性的吸收光谱和荧光光谱CdSe纳米晶，汞X CD-X SE阳离子交换后，汞纳米晶X CD 1-X SE / CDŸ锌1-Y S纳米晶后壳的增长。核心CdSe纳米晶有一个荧光量子产率接近15％（包括深阱长波长发射），但这样的效率下降到不到1％，汞交换，可能是由于引入通过表面原子扰乱9充电载流子陷阱。然而，增长的薄壳CDŸ锌1-Y S提高了?...

Watch this Scientific Journal Video about Compact Quantum Dots for Single-molecule Imaging at JoVE.com

Compact Quantum Dots for Single-molecule Imaging

我们描述了准备的胶体量子点与最小化的流体力学尺寸为单分子荧光成像。相比传统的量子点，这些纳米颗粒的尺寸类似于球状蛋白质单分子反对光降解，亮度，稳定性和耐非特异性结合的蛋白质和细胞进行了优化。

紧凑型量子点的单分子成像

Single-molecule imaging is an important tool for  understanding the mechanisms of biomolecular function and for visualizing the  spatial and temporal ...

compact-quantum-dots-for-single-molecule-imaging

Research

JoVE Journal

Engineering

18.0K 次观看.  Emory University. 我们描述了准备的胶体量子点与最小化的流体力学尺寸为单分子荧光成像。相比传统的量子点，这些纳米颗粒的尺寸类似于球状蛋白质单分子反对光降解，亮度，稳定性和耐非特异性结合的蛋白质和细胞进行了优化。

视频: Compact Quantum Dots for Single-molecule Imaging

Gradient Echo Quantum Memory in Warm Atomic Vapor

Gradient echo memory (GEM) is a protocol for storing optical quantum states of light in atomic ensembles. The primary motivation for such a technology is that quantum key distribution (QKD), which uses Heisenberg uncertainty to guarantee security of cryptographic keys, is limited in transmission distance. The development of a quantum repeater is a possible path to extend QKD range, but a repeater will need a quantum memory. In our experiments we use a gas of rubidium 87 vapor that is contained in a warm gas cell. This makes the scheme particularly simple. It is also a highly versatile scheme that enables in-memory refinement of the stored state, such as frequency shifting and bandwidth manipulation. The basis of the GEM protocol is to absorb the light into an ensemble of atoms that has been prepared in a magnetic field gradient. The reversal of this gradient leads to rephasing of the atomic polarization and thus recall of the stored optical state. We will outline how we prepare the atoms and this gradient and also describe some of the pitfalls that need to be avoided, in particular four-wave mixing, which can give rise to optical gain.

The gradient echo memory is a protocol for storing optical quantum states of light in atomic ensembles. Quantum memory is a key element of a quantum repeater, which can extend the range of quantum key distribution. We outline the operation of the scheme when implemented in a 3-level atomic ensemble.

梯度回波量子存储在温暖的原子蒸气

Gradient  echo memory (GEM) is a protocol for storing optical quantum states of light in  atomic ensembles. The primary motivation for such a technology ...

科研

工程学

Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and entanglement, to solve certain problems exponentially faster than with the best known algorithms on a classical computer. Gate-defined lateral quantum dots on GaAs/AlGaAs are one of many avenues explored for the implementation of a qubit. When properly fabricated, such a device is able to trap a small number of electrons in a certain region of space. The spin states of these electrons can then be used to implement the logical 0 and 1 of the quantum bit. Given the nanometer scale of these quantum dots, cleanroom facilities offering specialized equipment- such as scanning electron microscopes and e-beam evaporators- are required for their fabrication. Great care must be taken throughout the fabrication process to maintain cleanliness of the sample surface and to avoid damaging the fragile gates of the structure. This paper presents the detailed fabrication protocol of gate-defined lateral quantum dots from the wafer to a working device. Characterization methods and representative results are also briefly discussed. Although this paper concentrates on double quantum dots, the fabrication process remains the same for single or triple dots or even arrays of quantum dots. Moreover, the protocol can be adapted to fabricate lateral quantum dots on other substrates, such as Si/SiGe.

This paper presents a detailed fabrication protocol for gate-defined semiconductor lateral quantum dots on gallium arsenide heterostructures. These nanoscale devices are used to trap few electrons for use as quantum bits in quantum information processing or for other mesoscopic experiments such as coherent conductance measurements.

纳米加工门定义的GaAs / AlGaAs多量子点横向

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and ...

Analysis of Contact Interfaces for Single GaN Nanowire Devices

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit a strong degradation after annealing due to the occurrence of void formation at the contact/SiO2 interface. This void formation can cause cracking and delamination of the metal film, which can increase the resistance or lead to a complete failure of the NW device. In order to address issues associated with void formation, a technique was developed that removes Ni/Au contact metal films from the substrates to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN NW devices. This procedure determines the degree of adhesion of the contact films to the substrate and NWs and allows for the characterization of the morphology and composition of the contact interface with the substrate and nanowires. This technique is also useful for assessing the amount of residual contamination that remains from the NW suspension and from photolithographic processes on the NW-SiO2 surface prior to metal deposition. The detailed steps of this procedure are presented for the removal of annealed Ni/Au contacts to Mg-doped GaN NWs on a SiO2 substrate.

A technique was developed that removes Ni/Au contact metal films from their substrate to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN nanowire devices.

单氮化镓纳米线设备分析接触界面

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit  a strong degradation after annealing due to the  occurrence of void formation at the ...

Construction and Characterization of External Cavity Diode Lasers for Atomic Physics

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs1,2. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling1,2 makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman3, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included.

This is an instructional paper to guide the construction and diagnostics of external cavity diode lasers (ECDLs), including component selection and optical alignment, as well as the basics of frequency reference spectroscopy and laser linewidth measurements for applications in the field of atomic physics.

外腔半导体激光器的原子物理的构建与鉴定

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and ...

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 ...

Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. At the same time the AFM tip is passivated to prevent unspecific interactions between the tip and the substrate, which is a prerequisite to study single molecules attached to the AFM tip. Analyses to determine the adhesion force, the adhesion length, and the free energy of these molecules on solid surfaces and bio-interfaces are shortly presented and external references for further reading are provided. Example molecules are the poly(amino acid) polytyrosine, the graft polymer PI-g-PS and the phospholipid POPE (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine). These molecules are desorbed from different surfaces like CH3-SAMs, hydrogen terminated diamond and supported lipid bilayers under various solvent conditions. Finally, the advantages of force spectroscopic single molecule experiments are discussed including means to decide if truly a single molecule has been studied in the experiment.

A protocol to couple a large variety of single molecules covalently onto an AFM tip is presented. Procedures and examples to determine the adhesion force and free energy of these molecules on solid supports and bio-interfaces are provided.

调查单分子粘附的原子力谱

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

硅表面润湿性的选择区域改性脉冲紫外激光照射在液体环境

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization.

The fabrication process and experimental characterization techniques relevant to single-electron pumps based on silicon metal-oxide-semiconductor quantum dots are discussed.

硅金属 - 氧化物 - 半导体量子点单电子泵

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by ...

Use of a Multi-compartment Dynamic Single Enzyme Phantom for Studies of Hyperpolarized Magnetic Resonance Agents

Imaging of hyperpolarized substrates by magnetic resonance shows great clinical promise for assessment of critical biochemical processes in real time. Due to fundamental constraints imposed by the hyperpolarized state, exotic imaging and reconstruction techniques are commonly used. A practical system for characterization of dynamic, multi-spectral imaging methods is critically needed. Such a system must reproducibly recapitulate the relevant chemical dynamics of normal and pathological tissues. The most widely utilized substrate to date is hyperpolarized [1-13C]-pyruvate for assessment of cancer metabolism. We describe an enzyme-based phantom system that mediates the conversion of pyruvate to lactate. The reaction is initiated by injection of the hyperpolarized agent into multiple chambers within the phantom, each of which contains varying concentrations of reagents that control the reaction rate. Multiple compartments are necessary to ensure that imaging sequences faithfully capture the spatial and metabolic heterogeneity of tissue. This system will aid the development and validation of advanced imaging strategies by providing chemical dynamics that are not available from conventional phantoms, as well as control and reproducibility that is not possible in vivo.

A multi-compartment dynamic phantom is used to simulate some biology of interest for metabolic studies using hyperpolarized magnet resonance agents.

一个多腔动态单一酶幻影超极化磁共振剂研究的用途

Imaging of hyperpolarized substrates by magnetic resonance shows great clinical promise for assessment of critical biochemical processes in real time. Due ...

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

We present a compact reflection digital holographic system (CDHM) for inspection and characterization of MEMS devices. A lens-less design using a diverging input wave providing natural geometrical magnification is demonstrated. Both static and dynamic studies are presented.

紧凑的镜头少数字全息显微镜的MEMS检测与表征

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and ...