Name: reverse microemulsion-mediated synthesis of monometallic and bimetallic early transition metal carbide and nitride nanoparticles
Uploaded: 2015-11-27T14:00:00.000+00:00
Duration: 7 min 47 s
Description: Watch this Scientific Journal Video about Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles at JoVE.com

This work was sponsored by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, grant no. DE-FG02-12ER16352. S.T.H. thanks the National Science Foundation for financial support through the National Science Foundation Graduate Research Fellowship under Grant No. 1122374.

1.合成二氧化硅封装的单金属或金属合金的金属氧化物纳米颗粒的<ol><li>准备反相微乳液<ol><li>加将240ml无水正庚烷到一个干净的，烘箱干燥的1L圆底烧瓶（RBF）使用干净，烘箱干燥量筒含有烘箱干燥的磁力搅拌棒。 </li><li>添加54 ml的聚氧乙烯（4）月桂基醚，以在恒定搅拌下的正庚烷。 注意:由于高粘度和此表面活性剂的低表面张力的，干净的，干燥的60毫升注射器应该用来获得精确的体积，而不是一个量筒。 </li><li>添加7.8 ​​ml的超纯去离子（DI）水的恒定搅拌下使用移液管。密封用橡胶塞和封口膜蜡RBF。让对RME混合至少10分钟。 </li><li>添加0.1〜0.5 ml的试剂级的NH 4 OH的到乳液中，如果它希望降低水解时间。 注意:某些金属醇盐前驱水电lyze慢慢在中性pH。让RME加入NH 4 OH混合后，至少还要10分钟。作为代表例，加入0.5ml 的 NH 4 OH的建议涉及钛（IV）异丙合成。 </li></ol></li><li>制备金属醇盐前体，醇，和正庚烷溶液<ol><li>一个干净的，烘箱干燥的250个ml的RBF连接到在Schlenk线，并用氮气冲洗。或者，将清洁，烘干250毫升RBF的成干燥的氮气手套箱。 </li><li>加入12ml含5％w / v的异丙醇钨（WIPO）的异丙醇使用干净，干燥的注射器。在此阶段，其他金属醇盐也可以加入，如钽（V）的异丙醇（大埔），钼（V）的异丙醇（MoIPO），铌（V）的异丙醇（NbIPO），钛（IV），异丙醇（TiIPO），镍（Ⅱ），甲氧基乙醇（NiMEO），钴（II），异丙醇（CoIPO）等。 注:金属醇盐可以商业购买或通过加入脱水的合成我们醇使用的Schlenk线如别处所描述的相应的金属氯化物盐。（注意:金属醇盐合成从金属氯化物释放气体HCl，并且必须在通风良好的通风橱中进行）27 </li><li>使用干净的，烘箱干燥的插管，转移120毫升无水正庚烷至250 ml的RBF含有金属醇盐溶液</li></ol></li><li>使用干净的，烘箱干燥的套管，转移在10分钟的跨度下恒定搅拌的金属醇盐 - 醇 - 正庚烷溶液进RME。 注意:对于与水反应剧烈金属醇盐，如碲（Ⅳ），增加了一个慢得多的滴加速率是必需的。最终溶液应当是光学透明的考虑所使用的金属醇盐前体的，但也可以是根据所使用的金属醇盐和它们的氧化状态不同的颜色。我们注意到，该乳液是透明或半透明的是取决于粒径而色彩是依赖于金属的氧化态。 </li><li> 4小时后，用干净的，干燥的注射器注射1.4 ml的试剂级的NH 4 OH的进入溶液的溶液。然后，使用另一个干净，干燥的注射器，注入1.2毫升试剂级四乙基原硅酸盐（TEOS）中的溶液。 注意:钠氢氧化钠（NaOH）不应被使用，因为它会导致在渗碳/氮化二氧化硅壳的致密化，并导致在最终纳米颗粒的晶格钠杂质。残留的NH 4 OH，另一方面在热处理方便分解。 </li><li>后16.5小时，除去橡胶塞，并使用干净，干燥的量筒添加300ml甲醇中，以在恒定搅拌下的溶液中。 </li><li>后搅拌10分钟，取出搅拌棒，并使溶液沉降。 注意:将有两个液相存在:一个庚烷富有的上层相和富甲醇更低的相位。二氧化硅封装的金属O西德纳米颗粒，指定以SiO 2 / MO x将沉淀从下层相的烧瓶的底部。 </li><li> 1小时后，滗出液相成有机废物容器和收集固体相的 SiO 2 / MO 中的x清洁的50ml离心管中。 注意:如果正在使用的聚丙烯或聚苯乙烯离心管中，沉淀剂不能存储长期在该状态下为残留庚烷将缓慢溶解离心管，使其伸长。此外，残留的 NH 4 OH和TEOS可引起在SiO 2继续增长超过了什么期望。 </li><li>离心2,056 xg离心5分钟，在SiO 2 / MO 个第一阶段 ，然后弃去上清液成一个有机废弃物容器。 </li><li>添加10-30毫升丙酮中，以每50ml离心管中，并通过摇动或超声处理分散粉末进入丙酮。这有助于在煅烧前除去多余的表面活性剂。 </li><li> CentrifugE中的 SiO 2 / MO x和丙酮的混合物在4626×g离心10分钟，然后倒出上清液成有机废物容器中。允许在SiO 2 / MO x凝胶干燥过夜。 </li></ol>将该合成粉末2.热处理警告声明:氢气，甲烷和氨气是非常易燃。氨气是有毒的。彻底泄漏检查应所有的热处理之前进行，且治疗应在石英管状炉保持在通风良好的通风橱有一个油鼓泡在气体出口来执行。所有气瓶应配备阻火和存放在远离炉。如果法律要求或机构规定，过量的氨气应通过大量的水进行鼓泡，要么丢弃废物碱或使用的HCl中和至pH 7氯化铵溶液。 <ol><li>的二氧化硅 / MO x powde煅烧中R空气<ol><li>粉碎干燥的 SiO 2 / MO x凝胶成使用玻璃搅拌棒或研钵和杵细粉。放入氧化铝坩埚船和负载的粉末放入石英管炉中。 </li><li>使用2℃/ min的加热速率，煅烧下100sccm的空气的的 SiO 2 / MO x粉末在450℃下1小时。这消除了任何残留的表面活性剂并且还提高了二氧化硅壳的微孔。后炉冷却，取出在环境条件下煅烧的SiO 2 / MO x粉末和商店。 </li></ol></li><li>在SiO 2 / MO x粉末在甲烷/氢气气氛的渗碳<ol><li>加载煅烧过的 SiO 2 / MO x粉末成无釉氧化铝坩埚舟，并放入石英管式炉。冲洗石英管炉用氮气至少30分钟以除去氧气。通过喷洒所有关节用肥皂水进行泄漏检查。 </li><li>使用2℃/ min的加热速率，渗碳在氢气120sccm的和33标准立方厘米甲烷在850℃下4小时，以形成的 SiO 2 / MC x中的SiO 2 / MO x粉末。 </li><li> 4小时后，停止甲烷的流动并保持该粉末在850℃下1小时，在短短120sccm的氢气以清除任何过量的表面碳。 </li><li>允许炉内慢慢下120sccm的氢气冷却到室温。然后，冲洗炉用氮气至少30分钟，以除去氢。 </li><li>流95标准立方厘米氮气和5sccm气过粉末3小时暴露于空气之前缓慢钝化碳化物。 </li><li>除去从炉和存储在SiO 2 / MC x粉末在真空干燥器或在干燥的氮气手套箱防止长期堆积在空气中氧化的金属碳化物纳米颗粒。 </li></ol></li><li>在SiO 2 / MO x粉末的在氨气氛中氮化<ol><li>罗亚D中的煅烧过的 SiO 2 / MO x粉末放进氧化铝坩埚舟，并放入石英管式炉。 </li><li>冲洗石英管炉用氮气至少30分钟以除去氧气。 </li><li>使用2℃/ min的加热速率，nitridize在SiO 2 / MO X的 100sccm的氨在800℃粉末4小时，以形成的 SiO 2 / MN 的X. </li><li>允许炉缓慢冷却至室温。然后，冲洗炉用氮气至少30分钟，以除去氨。 </li><li>流95标准立方厘米氮气和5sccm气过粉末3小时暴露于空气之前缓慢钝化氮化物。 </li><li>除去从炉和存储在SiO 2 / MN x粉末在真空干燥器或在干燥的氮气手套箱防止长期堆积在空气中氧化的金属氮化物的纳米颗粒。 </li></ol></li></ol> 3.取出硅胶壳和支持纳米颗粒警告声明:氟化氢铵（ABF）是剧毒。在通风良好的通风橱中使用适当的个人防护装备，包括丁基橡胶手套，面罩和抗HF labcoat具有耐氢氟酸袖子时，才应处理。玻璃和金属的实验室设备不应该处理ABF时使用。 <ol><li>硅溶解在氟化氢铵对酸稳定金属碳化物和氮化物（如WC和W 2 N） <ol><li>称取200毫克的 SiO 2 / MC x或SiO 2的/ MN x的并放入30ml的可密封聚丙烯容器有聚四氟乙烯涂覆的磁性搅拌棒。 </li><li>如果期望，以支持在一个高表面积催化剂载体上的纳米颗粒，如碳黑或碳纳米管，称出料，并将其添加到可密封的聚丙烯容器中。 注意:质量称出将取决于纳米颗粒在th所期望的负载电子书支持。为催化剂的支持体是不稳定的ABF，如氧化铝，载体可以添加二氧化硅已被除去之后和在ABF被中和。如果不支持添加，纳米分散体将获得。 </li><li>加入20毫升的超纯去离子水，并开始混合以形成悬浮液。或者，预先制作20重量％ABF溶液添加20毫升</li><li>称取5克的ABF，然后添加到搅拌混合物中。添加后，密封聚丙烯容器。 注:ABF在水中溶解是吸热的，所以，溶液的温度会下降。 </li><li>为了确保二氧化硅和在催化剂载体上的纳米颗粒的分散性好完全溶解，停止16小时后，反应通过加入试剂级的NH 4 OH逐滴以中和ABF溶液至pH 6-7。注意:该反应是放热的。 </li><li>空中和的混合物放入离心管中并在离心机2056 xg离心10分钟。 </li><li>清空苏佩rnatant成为碱性废液容器（以确保总的中和）和再分散催化剂粉末在20ml超纯去离子水。 </li><li>离心4626 xg离心10分钟，弃去上清液，并做一最后20毫升去离子水冲洗。多达12850×g离心可能需要不受支持纳米颗粒。 </li><li>干燥粉末在真空下，然后存储在真空干燥器中或干燥的氮气手套箱防止长期堆积氧化金属碳化物或氮化物的纳米颗粒。 </li></ol></li><li>硅溶解在氢氧化钠碱性稳碳化物和氮化物（如TAC和钽3 N 5） <ol><li>称取200毫克的 SiO 2 / MC x或SiO 2的/ MN x的并放入50ml玻璃RBF有磁力搅拌棒。称出并根据需要添加的催化剂载体。 </li><li>加入30毫升的至少0.1M的NaOH水溶液。安装冷凝器的RBF或密封用橡胶塞和封口膜蜡。 </li><li>热，在60℃下持续搅拌16小时。冷却后，离心该溶液在2056×g离心10分钟。 </li><li>清空上清液成为碱性废液容器和再分散的催化剂粉末在20ml超纯去离子水。 </li><li>离心4626 xg离心10分钟，弃去上清液，并做一最后20毫升去离子水冲洗。多达12850×g离心可能需要不受支持纳米颗粒。 </li><li>干燥粉末在真空下，然后存储在真空干燥器中或干燥的氮气手套箱防止长期堆积氧化金属碳化物或氮化物的纳米颗粒。 </li></ol></li></ol>

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E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal+Carbides+as+Alternative+Electrocatalyst+Supports.">Metal Carbides as Alternative Electrocatalyst Supports.</a> ACS Catal. 3, 1184-1194 (2013).</li><li>Nie, M., Shen, P. K., Wei, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanocrystaline+tungsten+carbide+supported+Au&#8211;Pd+electrocatalyst+for+oxygen+reduction.">Nanocrystaline tungsten carbide supported Au&#8211;Pd electrocatalyst for oxygen reduction.</a> J. Power Sources. 167 (1), 69-73 (2007).</li><li>Ham, D. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Palladium-nickel+alloys+loaded+on+tungsten+carbide+as+platinum-free+anode+electrocatalysts+for+polymer+electrolyte+membrane+fuel+cells.">Palladium-nickel alloys loaded on tungsten carbide as platinum-free anode electrocatalysts for polymer electrolyte membrane fuel cells.</a> Chem Commun (Camb). 47 (20), 5792-5794 (2011).</li><li>Yan, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Template-free+pseudomorphic+synthesis+of+tungsten+carbide+nanorods.">Template-free pseudomorphic synthesis of tungsten carbide nanorods.</a> Small. 8, 3350-3356 (2012).</li><li>Esposito, D. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-cost+hydrogen-evolution+catalysts+based+on+monolayer+platinum+on+tungsten+monocarbide+substrates.">Low-cost hydrogen-evolution catalysts based on monolayer platinum on tungsten monocarbide substrates.</a> Angew. Chem. Int. Ed. 49, 9859-9862 (2010).</li><li>Esposito, D. V., Hunt, S. T., Kimmel, Y. C., Chen, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+class+of+electrocatalysts+for+hydrogen+production+from+water+electrolysis:+metal+monolayers+supported+on+low-cost+transition+metal+carbides.">A new class of electrocatalysts for hydrogen production from water electrolysis: metal monolayers supported on low-cost transition metal carbides.</a> J. Am. Chem. Soc. 134, 3025-3033 (2012).</li><li>Kelly, T. G., Hunt, S. T., Esposito, D. V., Chen, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monolayer+palladium+supported+on+molybdenum+and+tungsten+carbide+substrates+as+low-cost+hydrogen+evolution+reaction+(HER)+electrocatalysts.">Monolayer palladium supported on molybdenum and tungsten carbide substrates as low-cost hydrogen evolution reaction (HER) electrocatalysts.</a> Int. J. Hydrogen Energy. 38, 5638-5644 (2013).</li><li>Hunt, S. T., Nimmanwudipong, T., Roman-Leshkov, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+non-sintered,+metal-terminated+tungsten+carbide+nanoparticles+for+catalysis.">Engineering non-sintered, metal-terminated tungsten carbide nanoparticles for catalysis.</a> Angew. Chem. Int. Ed. Engl. 53 (20), 5131-5136 (2014).</li><li>Mehrota, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alkoxides+and+Alkylalkoxides+of+Metals+and+Metalloids.">Alkoxides and Alkylalkoxides of Metals and Metalloids.</a> Inorg. Chim. Acta. 1, 99-112 (1967).</li><li>Munoz-Aguado, M., Gregorkiewitz, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sol-Gel+Synthesis+of+Microporous+Amorphous+Silica+from+Purely+Inorganic+Precursors.">Sol-Gel Synthesis of Microporous Amorphous Silica from Purely Inorganic Precursors.</a> J. Colloid Interface Sci. 185, 459-465 (1997).</li></ol>

The authors have nothing to disclose.

甲程序用于合成非烧结，金属端过渡金属碳化物和氮化物的纳米颗粒与可调谐的尺寸和结构在这里提出的方法26的关键步骤包括:使用无湿气的RBF以包含稀释金属醇盐前体，避免了碱金属在所有步骤的杂质，而不是丙酮或异丙醇，渗碳或氮化的组件，并用氟化氢铵工作时使用合适的PPE之前执行适当的泄漏检查沉淀用过量的甲醇对RME。 该方法可以在几个方面进行修改。表...

前过渡金属碳化物（差旅管理）是低成本的，表现出高的热稳定性和电化学稳定性以及特有的催化活性地球上资源丰富的材料。1-3具体地，碳化钨（WC）和碳化钼（钼2℃）有被广泛地研究其催化相似之处铂族金属（铂族金属）。4,5-由于这些有利的性质，差旅管理已被确定为候选替换昂贵的PGM催化剂在新兴的可再生能源技术，如生物质转化，燃料电池，和电解槽6,7 为了最大限度地提高催化活性，工业催化剂几乎总是配制成超小纳米颗粒（直径&lt;10纳米）分散在高表面积载体，例如炭黑。8然而，差旅管理的合成需要温度高于〜700℃以上。这导致了nanopartic广泛烧结LES（NPS），多余的表面积炭（焦炭）和热降解的支持。这两种粒子烧结和支持的降解导致材料的表面积下降。过量表面杂质附着块活性金属位点，这已被证明能大大减少或在某些情况下，完全消除的差旅管理。9,10作为这样的催化活性，主要是在散装微粒或薄膜与进行TMC反应性的基础研究精细地控制表面，而不是在高表面积的TMC纳米材料。 许多方法已经发展到合成TMC纳米粒，但这些方法不适合于合成催化剂活性TMC纳米粒。传统的湿法浸渍技术使用浸渍在高表面积载体金属盐溶液。在热，湿热浸渍法可以暴露于破坏性的渗碳条件导致支持退化的催化剂载体。此外，烧结Ç一个仅在载体上的金属的低重量％负荷被减轻，并且它也不能使用湿法浸渍合成不受支持TMC纳米粉末。几个较新的方法包括混合的金属前体与碳前体和施加传统和非传统的加热技术11-18过量碳被用来防止烧结，但是这过量的碳会导致广泛的表面碳，使得这些材料不适合于催化用途。 由于这些合成难题，差旅管理传统上被研究作为助催化剂11为铂族金属，催化剂载体为铂族金属，19-22或支持活性铂族金属单层23-25 ​​这里介绍的方法提供了以合成两个非烧结的能力与金属终止TMC纳米颗粒和过渡金属氮化物（TMN）纳米粒子具有可调尺寸，晶相和金属构成。26的方法提出还提供ABility获得TMC或TMN纳米分散体或沉积的TMC和TMN纳米粒上在室温高表面积的催化剂载体，从而缓解热支持降解。此方法因此适合于TMC和TMN纳米粒，先进的多金属TMC和TMN纳米粒，或需要精确地控制颗粒尺寸和表面的其他应用程序的开发独立催化应用。26 这里介绍的方法使用一个三步式协议来合成TMC和TMN纳米颗粒。在第一步骤中，一个反相微乳液（RME）被用于涂敷前过渡金属氧化物（TMO）的NP在二氧化硅纳米球。该乳液是通过使用市售非离子表面活性在非极性介质中分散的水滴制备。二氧化硅包封TMO纳米粒然后经过任渗碳或氮化热处理。这里，二氧化硅微粒防止烧结在高温下，同时允许反应气体扩散到吨他TMO纳米粒子，并将它们转换为TMC或TMN的NP。在最后的步骤中，二氧化硅壳是使用酸性或碱性处理，得到TMC或TMN纳米分散体可以在一个高表面积载体进行分散，如炭黑除去。

<table><tbody><tr><td>n-heptane</td><td>Sigma-Aldrich</td><td>246654</td><td></td></tr><tr><td>polyoxyethylene (4) lauryl ether</td><td>Sigma-Aldrich</td><td>235989</td><td>Brij&amp;reg; L4</td></tr><tr><td>tungsten (VI) isopropoxide</td><td>Alfa Aesar</td><td>40247</td><td>W(VI)IPO</td></tr><tr><td>tungsten (VI) chloride</td><td>Sigma-Aldrich</td><td>&lt;a href=&quot;http://www.sigmaaldrich.com/catalog/product/aldrich/241911?lang=en&amp;amp;region=US&quot;&gt;241911&lt;/a&gt;</td><td>To prepare W(VI)IPO, homemade</td></tr><tr><td>tungsten (IV) chloride</td><td>Strem Chemicals</td><td>74-2348</td><td>To prepare W(IV)IPO, homemade</td></tr><tr><td>tantalum (V) isopropoxide</td><td>Alfa Aesar</td><td>&lt;a href=&quot;http://www.alfa.com/en/catalog/40038&quot;&gt;40038&lt;/a&gt;</td><td>Ta(V)IPO</td></tr><tr><td>niobium (V) isopropoxide</td><td>Alfa Aesar</td><td>&lt;a href=&quot;http://www.alfa.com/en/catalog/36572&quot;&gt;36572&lt;/a&gt;</td><td>Nb(V)IPO</td></tr><tr><td>nickel (II) methoxyethoxide</td><td>Alfa Aesar</td><td>42377</td><td>Ni(II)MEO</td></tr><tr><td>titanium (IV) isopropoxide</td><td>Sigma-Aldrich</td><td>&lt;a href=&quot;http://www.sigmaaldrich.com/catalog/product/aldrich/87560?lang=en&amp;amp;region=US&quot;&gt;87560&lt;/a&gt;</td><td>Ti(IV)IPO</td></tr><tr><td>molybdenum (V) isopropoxide</td><td>Alfa Aesar</td><td>&lt;a href=&quot;http://www.alfa.com/en/catalog/39159&quot;&gt;39159&lt;/a&gt;</td><td>Mo(V)IPO</td></tr><tr><td>molybdenum (V) chloride</td><td>Sigma-Aldrich</td><td>&lt;a href=&quot;http://www.sigmaaldrich.com/catalog/product/aldrich/208353?lang=en&amp;amp;region=US&quot;&gt;208353&lt;/a&gt;</td><td>To prepare Mo(V)IPO, homemade</td></tr><tr><td>tetraethyl orthosilicate</td><td>Sigma-Aldrich</td><td>333859</td><td>TEOS</td></tr><tr><td>ammonium hydroxide</td><td>Sigma-Aldrich</td><td>320145</td><td></td></tr><tr><td>methanol</td><td>Sigma-Aldrich</td><td>34860</td><td></td></tr><tr><td>anhydrous isopropanol</td><td>Sigma-Aldrich</td><td>&lt;a href=&quot;http://www.sigmaaldrich.com/catalog/product/sial/278475?lang=en&amp;amp;region=US&quot;&gt;278475&lt;/a&gt;</td><td>To prepare homemade alkoxides</td></tr><tr><td>ammonium bifluoride</td><td>Sigma-Aldrich</td><td>224820</td><td></td></tr><tr><td>carbon black</td><td>Cabot Corp.</td><td>Vulcan&amp;reg; XC72R</td><td></td></tr><tr><td>Methane</td><td>AirGas</td><td>ME R300</td><td></td></tr><tr><td>Hydrogen</td><td>AirGas</td><td>HY UHP300</td><td></td></tr><tr><td>Ammonia</td><td>AirGas</td><td>AM AH80N705</td><td></td></tr><tr><td>Quartz Tube Furnace</td><td>MTI Corp.</td><td>OTF-1200X-S-UL</td><td></td></tr></tbody></table>

reverse microemulsion-mediated synthesis of monometallic and bimetallic early transition metal carbide and nitride nanoparticles

反相微乳液用于封装单金属或双金属前过渡金属氧化物纳米颗粒在微孔二氧化硅壳。二氧化硅包封的金属氧化物纳米颗粒然后渗碳在甲烷/氢气气氛中在温度超过800℃，以形成二氧化硅 - 包封的早过渡金属碳化物纳米颗粒。在渗碳处理中，二氧化硅壳防止相邻碳化物纳米颗粒的烧结，同时也防止了过量表面碳的沉积。可替代地，硅石包封的金属氧化物纳米颗粒的温度下可氮化在氨气氛中超过800℃形成氧化硅 - 包封的早过渡金属氮化物纳米颗粒。通过调整反相微乳参数，二氧化硅壳的厚度，和所述渗碳/氮化的条件下，过渡金属碳化物或氮化物的纳米颗粒可以被调谐到各种尺寸，组合物，一次晶相。渗碳或氮化后，将二氧化硅壳然后使用一个室温水氟化氢铵溶液或在40-60℃的0.1至0.5M的NaOH溶液中除去。而在二氧化硅壳被溶解，一个高表面积载体，如炭黑，可以加入到这些溶液以获得支持的前过渡金属碳化物或氮化物的纳米颗粒。如果没有高表面积载体被添加，​​那么纳米颗粒可以被存储为一个或纳米分散体离心分离，得到纳米粉末。

在该协议的第一步骤中，目标是封装内微孔二氧化硅球的单金属或双金属的过渡金属氧化物（TMO）的NP。 图1示出了代表性的合成的前和沉淀用甲醇后拍摄的图像。期间，似乎是取决于在合成中使用的金属此步骤两次重现的形态的结果已经观察到:该TMO的NP可以单独涂覆有二氧化硅球体（图2b）或多个TMO的NP可以在一个单一的硅球被涂覆（图2a）。单独使用涂覆TMO...

Watch this Scientific Journal Video about Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles at JoVE.com

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

A &#8220;removable ceramic coating method&#8221; is presented in visual format for the synthesis of non-sintered and metal-terminated monometallic and bimetallic early transition metal carbide and nitride nanoparticles with tunable sizes and crystal structures.

单金属和双金属前过渡金属碳化物和氮化物纳米粒子的反相微乳液介导的合成

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The ...

reverse-microemulsion-mediated-synthesis-monometallic-bimetallic

Research

JoVE Journal

Chemistry

10.8K 次观看.  Massachusetts Institute of Technology. A “removable ceramic coating method” is presented in visual format for the synthesis of non-sintered and metal-terminated monometallic and bimetallic early transition metal carbide and nitride nanoparticles with tunable sizes and crystal structures.

视频: Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

Preparation and Reactivity of Gasless Nanostructured Energetic Materials

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the balls. Among other applications, it is a versatile technique that allows for effective preparation of gasless reactive nanostructured materials with high energy density per volume (Ni+Al, Ta+C, Ti+C). The structural transformations of reactive media, which take place during HEBM, define the reaction mechanism in the produced energetic&#160;composites. Varying the processing conditions permits fine tuning of the milling-induced microstructures of the fabricated composite particles. In turn, the reactivity, i.e., self-ignition temperature, ignition delay time, as well as reaction kinetics, of high energy density materials depends on its microstructure. Analysis of the milling-induced microstructures suggests that the formation of fresh oxygen-free intimate high surface area contacts between the reagents is responsible for the enhancement of their reactivity. This manifests itself in a reduction of ignition temperature and delay time, an increased rate of chemical reaction, and an overall decrease of the effective activation energy of the reaction. The protocol provides a detailed description for the preparation of reactive nanocomposites with tailored microstructure using short-term HEBM method. It also describes a high-speed thermal imaging technique to determine the ignition/combustion characteristics of the energetic materials. The protocol can be adapted to preparation and characterization of a variety of nanostructured energetic composites.

This protocol describes the preparation of gasless nanostructured energetic materials (Ni+Al, Ta+C, Ti+C) using the short-term high-energy ball milling (HEBM) technique. It also describes a high-speed thermal imaging method to study the reactivity of mechanically fabricated nanocomposites. These protocols can be extended to other reactive nanostructured energetic materials.

准备和无气腹纳米结构的反应含能材料

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the ...

科研

工程学

Generation of Zerovalent Metal Core Nanoparticles Using n-(2-aminoethyl)-3-aminosilanetriol

In this work, a facile one-pot reaction for the formation of metal nanoparticles in a water solution through the use of n-(2-aminoethyl)-3-aminosilanetriol is presented. This compound can be used to effectively reduce and complex metal salts into metal core nanoparticles coated with the compound. By controlling the concentrations of salt and silane one is able to control reaction rates, particle size, and nanoparticle coating. The effects of these changes were characterized through transmission electron microscopy (TEM), UV-Vis spectrometry (UV-Vis), Nuclear Magnetic Resonance spectroscopy (NMR) and Fourier Transform Infrared spectroscopy (FTIR). A unique aspect to this reaction is that usually silanes hydrolyze and cross-link in water; however, in this system the silane is water-soluble and stable. It is known that silicon and amino moieties can form complexes with metal salts. The silicon is known to extend its coordination sphere to form penta- or hexa-coordinated species. Furthermore, the silanol group can undergo hydrolysis to form a Si-O-Si silica network, thereby transforming the metal nanoparticles into a functionalized nanocomposites.

Generation of Zerovalent Metal Core Nanoparticles Using n-2-aminoethyl-3-aminosilanetriol

A novel method for metal core nanoparticle synthesis using a water stable silanol is described.

使用N-零价金属芯纳米粒子的生成（2-氨基乙基）-3- aminosilanetriol

In this work, a facile one-pot reaction for the formation of metal nanoparticles in a water solution through the use of ...

化学

The Synthesis of [Sn10(Si(SiMe3)3)4]2- Using a Metastable Sn(I) Halide Solution Synthesized via a Co-condensation Technique

The number of well-characterized metalloid tin clusters, synthesized by applying the disproportionation of a metastable Sn(I) halide in the presence of a sterically demanding ligand, has increased in recent years. The metastable Sn(I) halide is synthesized at&#160;&#34;outer space conditions&#34; via the preparative co-condensation technique. Thereby, the subhalide is synthesized in an oven at high temperatures, around 1,300 &#176;C, and at reduced pressure by the reaction of elemental tin with hydrogen halide gas (e.g., HCl). The subhalide (e.g., SnCl) is trapped within a matrix of an inert solvent, like toluene at -196 &#176;C. Heating the solid matrix to -78 &#176;C gives a metastable solution of the subhalide. The metastable subhalide solution is highly reactive but can be stored at -78 &#176;C for several weeks. On heating the solution to room temperature, a disproportionation reaction occurs, leading to elemental tin and the corresponding dihalide. By applying bulky ligands like Si(SiMe3)3, the intermediate metalloid cluster compounds can be trapped before complete disproportionation to elemental tin. Hence, the reaction of a metastable Sn(I)Cl solution with Li-Si(SiMe3)3 gives [Sn10(Si(SiMe3)3)4]2- 1 as black crystals in high yield. 1 is formed via a complex reaction sequence including salt metathesis, disproportionation, and degradation of larger clusters. Further, 1 can be analyzed by various methods like NMR or single crystal X-ray structure analysis.

The Synthesis of [Sn10SiSiMe334]2- Using a Metastable SnI Halide Solution Synthesized via a Co-condensation Technique

The disproportionation reaction of a metastable Sn(I) chloride solution, obtained via the preparative co-condensation technique, is used for the synthesis of a metalloid tin cluster compound.

的合成[锡<sub&gt; 10</sub&gt;（SI（SIME<sub&gt; 3</sub&gt;）<sub&gt; 3</sub&gt;）<sub&gt; 4</sub&gt;]<sup&gt; 2</sup<sup&gt; -</sup&gt;使用亚稳锡（I）卤溶液通过共缩聚合成技术

The number of well-characterized metalloid tin clusters, synthesized by applying the disproportionation of a metastable Sn(I) halide in the presence of a ...

Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are demonstrated here. The catalyst forms a substitutional solid solution structure, with a small and uniform particle size around 2 nm. This is realized by careful control over the impregnation, calcination, and reduction steps during catalyst preparation and is identified by advanced in situ synchrotron techniques. The catalyst propane dehydrogenation performance continuously improves with increasing Cu:Pt atomic ratio.

A convenient method for the synthesis of 2 nm supported bimetallic nanoparticle Pt-Cu catalysts for propane dehydrogenation is reported here. In situ synchrotron X-ray techniques allow for the determination of the catalyst structure, which is typically unobtainable using laboratory instruments.

用于丙烷脱氢的负载型Pt-Cu固溶体纳米粒子催化剂的合成与测试

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

化学沉淀法合成铌2O5改性高比表面积镍催化剂

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution of capping ligands during the synthesis reaction, their role in regulating the nucleation and growth rates of colloidal nanoparticles is not well understood. In this work, we demonstrate a mechanistic investigation of the role of trioctylphosphine (TOP) in Pd nanoparticles in different solvents (toluene and pyridine) using in situ SAXS and ligand-based kinetic modeling. Our results under different synthetic conditions reveal the overlap of nucleation and growth of Pd nanoparticles during the reaction, which contradicts the LaMer-type nucleation and growth model. The model accounts for the kinetics of Pd-TOP binding for both, the precursor and the particle surface, which is essential to capture the size evolution as well as the concentration of particles in situ. In addition, we illustrate the predictive power of our ligand-based model through designing the synthetic conditions to obtain nanoparticles with desired sizes. The proposed methodology can be applied to other synthesis systems and therefore serves as an effective strategy for predictive synthesis of colloidal nanoparticles.

The main goal of this work is to elucidate the role of capping agents in regulating the size of palladium nanoparticles by combining in situ small angle x-ray scattering (SAXS) and ligand-based kinetic modeling.

配体介导成核与钯金属纳米粒子的生长

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution ...

Synthesis of Bimetallic Pt/Sn-based Nanoparticles in Ionic Liquids

We demonstrate a method for the synthesis of bimetallic nanoparticles consisting of Pt and Sn. A synthesis strategy is used in which the particular physico-chemical properties of ionic liquids (ILs) are exploited to control both nucleation and growth processes. The nanoparticles form colloidal sols of very high colloidal stability in the IL, which is particularly interesting in view of their use as quasi-homogeneous catalysts. Procedures for both nanoparticle extraction in conventional solvents and for nanoparticle precipitation are presented. The size, structure and composition of the synthesized nanocrystals are confirmed using inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDX). By this, we show that the nanocrystals are random-type alloy and of small (2-3 nm) size. The catalytic activity and selectivity in the hydrogenation of &#945;,&#946;-unsaturated aldehydes is tested in a semi-continuous batch-type reactor. In this context, the bimetallic Pt/Sn-based nanoparticles reveal a high selectivity towards the unsaturated alcohol.

A protocol for the synthesis of bimetallic nanoparticles in ionic liquids and the procedure of their catalytic testing in the selective hydrogenation of unsaturated aldehydes are described.

离子液体中双金属 Pt/锡基纳米粒子的合成

We demonstrate a method for the synthesis of bimetallic nanoparticles consisting of Pt and Sn. A synthesis strategy is used in which the particular ...

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. Here, we introduce the molten-salt synthesis (MSS) method for making metal oxide nanomaterials. Advantages over other methods include its simplicity, greenness, reliability, scalability, and generalizability. Using pyrochlore lanthanum hafnium oxide (La2Hf2O7) as a representative, we describe the MSS protocol for the successful synthesis of complex metal oxide nanoparticles (NPs). Furthermore, this method has the unique ability to produce NPs with different material features by changing various synthesis parameters such as pH, temperature, duration, and post-annealing. By fine-tuning these parameters, we are able to synthesize highly uniform, non-agglomerated, and highly crystalline NPs. As a specific example, we vary the particle size of the La2Hf2O7&#160;NPs by changing the concentration of the ammonium hydroxide solution used in the MSS process, which allows us to further explore the effect of particle size on various properties. It is expected that the MSS method will become a more popular synthesis method for nanomaterials and more widely employed in the nanoscience and nanotechnology community in the upcoming years.

Here, we demonstrate a unique, relatively low-temperature, molten-salt synthesis method for preparing uniform complex metal oxide lanthanum hafnate nanoparticles.

复合金属氧化物纳米粒子的熔融盐合成

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. ...

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared according to the methodology developed by surface organometallic chemistry (SOMC). In this framework, catalytic cycles can be determined by isolating crucial intermediates. All air-sensitive materials are handled under inert atmosphere (using gloveboxes or a Schlenk line) or high vacuum lines (HVLs, &#60;10-5 mbar). The preparation of SiO2-700 (silica dehydroxylated at 700 &#176;C) and subsequent applications (the grafting of complexes and catalytic runs) requires the use of HVLs and double-Schlenk techniques. Several well-known characterization methods are used, such as Fourier-transform infrared spectroscopy (FTIR), elemental microanalysis, solid-state nuclear magnetic resonance spectroscopy (SSNMR), and state-of-the-art dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP-SENS). FTIR and elemental microanalysis permit scientists to establish the grafting and its stoichiometry. 1H and 13C SSNMR allows the structural determination of the hydrocarbon ligands coordination sphere. DNP SENS is an emerging powerful technique in solid characterization for the detection of poorly sensitive nuclei (15N, in our case). SiO2-700 is treated with about one equivalent of the metal precursor compared to the amount of surface silanol (0.30 mmol&#183;g-1) in pentane at room temperature. Then, volatiles are removed, and the powder samples are dried under dynamic high vacuum to afford the desired materials [(&#8801;Si-O-)Hf(&#951;2&#960;-MeNCH2)(&#951;1-NMe2)(&#951;1-HNMe2)]. After a thermal treatment under high vacuum, the grafted complex is converted into metal imido silica complex [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)]. [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] effectively promotes the metathesis of imines, using the combination of two imine substrates, N-(4-phenylbenzylidene)benzylamine, or N-(4-fluorobenzylidene)-4-fluoroaniline, with N-benzylidenetert-butylamine as substrates. A significantly lower conversion is observed with the blank runs; thus, the presence of the imido group in [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is correlated to the catalytic performance.

A new group IV metal catalyst for imine metathesis is prepared by grafting amine metal complex onto dehydroxylated silica. Surface metal fragments are characterized using FT-IR, elemental microanalysis, and solid-state NMR spectroscopy. Further dynamic nuclear polarization surface enhanced NMR spectroscopy experiments complement the determination of the coordination sphere.

利用表面有机金属化学方法，利用硅支持的催化剂进行Imine金属分析

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared ...

A Salt-Templated Synthesis Method for Porous Platinum-based Macrobeams and Macrotubes

The synthesis of high surface area porous noble metal nanomaterials generally relies on time consuming coalescence of pre-formed nanoparticles, followed by rinsing and supercritical drying steps, often resulting in mechanically fragile materials. Here, a method to synthesize nanostructured porous platinum-based macrotubes and macrobeams with a square cross section from insoluble salt needle templates is presented. The combination of oppositely charged platinum, palladium, and copper square planar ions results in the rapid formation of insoluble salt needles. Depending on the stoichiometric ratio of metal ions present in the salt-template and the choice of chemical reducing agent, either macrotubes or macrobeams form with a porous nanostructure comprised of either fused nanoparticles or nanofibrils. Elemental composition of the macrotubes and macrobeams, determined with x-ray diffractometry and x-ray photoelectron spectroscopy, is controlled by the stoichiometric ratio of metal ions present in the salt-template. Macrotubes and macrobeams may be pressed into free standing films, and the electrochemically active surface area is determined with electrochemical impedance spectroscopy and cyclic voltammetry. This synthesis method demonstrates a simple, relatively fast approach to achieve high-surface area platinum-based macrotubes and macrobeams with tunable nanostructure and elemental composition that may be pressed into free-standing films with no required binding materials.

A synthesis method to obtain porous platinum-based macrotubes and macrobeams with a square cross section through chemical reduction of insoluble salt-needle templates is presented.

多孔铂基微波和宏管的盐模板合成方法

The synthesis of high surface area porous noble metal nanomaterials generally relies on time consuming coalescence of pre-formed nanoparticles, followed ...

单金属和双金属前过渡金属碳化物和氮化物纳米粒子的反相微乳液介导的合成

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