作者感谢 Deryn 在气凝胶技术方面的灵感和技术洞察力, 以及陆军研究实验室-传感器和电子设备局, 克里斯托弗. 海恩斯博士在军备研究中的博士。开发和工程中心, 美国陆军 RDECOM-ARDEC, 和斯蒂芬博士 Bartolucci 在美国陆军贝尼特实验室为他们提供援助。这项工作得到了美国陆军学院西点军校教师发展研究基金的资助。

警告: 使用前请查阅所有相关的安全数据表 (SDS)。在进行化学反应时, 使用适当的安全措施, 包括使用油烟机和个人防护设备。快速的氢气演化会导致反应管产生高压, 从而导致瓶盖的弹出和溶液喷出。确保反应管帽保持在协议规定的状态下打开。
1. 金属凝胶制剂
<ol><li>
金属离子溶液的制备。
	<ol>
<li>准备2毫升以下盐的 0.1 M 解答: HAuCl4· 3H2O 和 Na2PdCl4在去离子水。在 1:1 (v/v) 水和乙醇溶剂中制备2毫升的0.1 米 K2PtCl6 。大力摇动和涡流解决方案, 以帮助在盐的溶解。</li>
	</ol>
</li>
	<li>
制备还原剂溶液。
	<ol>
<li>制备10毫升的以下还原剂 0.1 M 溶液: 二甲胺硼烷 (DMAB) 和 NaBH4 (硼化钠)。</li>
	</ol>
</li>
	<li>
金凝胶的制备。
	<ol>
<li>吸管0.5 毫升0.1 米 HAuCl4· 3H2O 溶液成1.7 毫升或2.0 毫升离心管。强力吸管0.5 毫升 DMAB 进入离心管与金溶液, 以确保快速混合盐和还原剂溶液。一旦溶液混合, 把离心管垂直放置在管架与管帽打开。 注: 如果管帽左关闭, 氢气的演变将导致内部压力, 迫使顶部弹出开放, 并有可能喷雾的减少混合物。</li>
	</ol>
</li>
	<li>
钯凝胶的制备。
	<ol>
<li>吸管0.5 毫升0.1 米 Na2PdCl4溶液成1.7 毫升或2.0 毫升离心管。强力吸管0.5 毫升的 NaBH4进入离心管与钯溶液。将离心管垂直放置在管架上, 管帽打开。</li>
	</ol>
</li>
	<li>
铂凝胶的制备。
	<ol>
<li>吸管0.5 毫升0.1 米 K2PtCl6溶液成1.7 毫升或2.0 毫升离心管。强力吸管0.5 毫升 DMAB 进入离心管与铂溶液。将离心管垂直放置在管架上, 管帽打开。</li>
	</ol>
</li>
	<li>
管反演。
	<ol>
<li>在大约5分钟, 盖离心管和轻轻地反转3-5 倍, 以帮助金属颗粒的聚结, 而不是金属凝胶的一部分。确保管帽在换向管后立即名额, 并更换机架中的管, 以保持管的垂直方向。</li>
	</ol>
</li>
	<li>
平衡。<ol>
<li>虽然金, Pd 和 Pt 凝胶最初形成在几分钟内, 留下新生凝胶在减少剂溶液的 3-6 小时, 以允许完全还原金属离子和表面自由能最小化发生。 注: 金属凝胶的体积比混合金属离子和还原剂溶液的初始体积小。一些额外的轻微体积收缩可以观察在平衡时间, 并更明显的黄金凝胶, 并认为是由于奥斯特瓦尔德成熟25。</li>
	</ol>
</li>
	<li>
凝胶冲洗。<ol>
<li>对于金、钯、铂凝胶在平衡期后, 去除过量的还原剂溶液, 但留下足够的溶液体积, 使金属凝胶保持浸没。确保溶液半月板不接触金属凝胶。 注: 虽然金属凝胶的稳定性足以在溶液与刮刀之间传递, 但由于与溶液的接触而产生的毛细管力会变形和压缩凝胶, 从而增加最终的气凝胶密度。这需要一些还原剂溶液留在管中, 凝胶被淹没时, 转移到去离子水。</li>
		<li>慢慢地将去离子的水吸到反应离心管的顶端。将离心管浸没在50毫升的锥管中, 装满了去离子水, 使凝胶滑出离心管。</li>
		<li>将凝胶放在去离子水中24小时, 用12小时的水代替。不要让液体半月板接触到凝胶。</li>
	</ol>
</li>
</ol>2. 电化学表面面积 (欧洲) 对湿金属凝胶的表征
注: 在进行冷冻干燥之前, 对湿金属凝胶进行电化学表征。由此产生的欧洲是最终的气凝胶结构表面的估计。氮气吸附测量用于估算干气凝胶的表面积。
<ol><li>
溶剂交换。<ol>
<li>从非盟、Pd 和 Pt 中去除尽可能多的去离子水, 并确保液体半月板不与凝胶接触。</li>
		<li>加入50毫升, 0.5 米氯化钾到锥形管, 以交换的去离子水与支持电解质内的凝胶毛孔。将凝胶留在氯化钾溶液中24小时。</li>
	</ol>
</li>
	<li>
工作电极制备。
	<ol>
<li>用无反应漆涂1毫米铂丝电极, 使用细刚毛刷或其它应用装置, 使导线尖端的4-5 毫米长度暴露。</li>
		<li>让漆干20分钟。</li>
		<li>至少涂两层漆。</li>
	</ol>
</li>
	<li>
3电极细胞设置。
	<ol>
<li>使用3电极电池设置与 Ag/AgCl (3 米饱和) 参考电极, 一个0.5 毫米直径 Pt 线辅助/计数器电极, 和漆涂层工作电极。</li>
		<li>将塑料50毫升圆锥管切成两半, 用作电化学瓶。</li>
		<li>用工作电极与凝胶接触, 用两种方法之一: 1) 刺穿凝胶, 或 2) 接触模式。<ol>
<li>
工作电极刺穿凝胶。<ol>
<li>用凝胶在修改后的50毫升圆锥管底部, 轻轻地将漆膜电极插入凝胶中。 注: 穿刺凝胶法对金凝胶更有效, 而 Pd 和铂凝胶在电极插入时更常见。</li>
			</ol>
</li>
			<li>
工作电极-接触模式。<ol>
<li>将漆膜工作电极插入锥形管内表面, 并将金属凝胶放在工作电极外露的 Pt 线的顶部。</li>
			</ol>
</li>
		</ol>
</li>
	</ol>
</li>
	<li>
电化学阻抗谱 (EIS)。<ol>
<li>执行恒电位 EIS 扫描, 频率介于 100 mhz 和1兆赫之间, 使用 10 mV 振幅正弦波。在电流溢出的情况下, 使用相同频率范围和 100-200 mA 振幅正弦波的恒电流 EIS。</li>
	</ol>
</li>
	<li>
从 EIS 数据中测定电化学表面面积 (欧洲)。<ol>
<li>对于Z ", 在最低 EIS 频率f为1兆赫的阻抗的虚分量, 除以样本质量m, 使用以下等式确定特定电容, Csp: Csp = 1/(2π)"m"(1) 注: 鉴于欧洲是在下面步骤3冷冻干燥之前从湿凝胶中确定的, 通过假设溶液中的所有金属离子都被还原成凝胶来确定质量。根据这种假设, 任何实际产量少于100% 将导致低估 Csp。</li>
	</ol>
</li>
	<li>
循环伏安法 (CV)。<ol>
<li>对 CV 测量使用100、75、50、25、10、5和 1 mV 的扫描速率。使用-0.2 到 0.2 v (vs Ag/AgCl) 的电压范围为 Au 凝胶, 并选择0.1 到 0.4 v 的 Pd 和 Pt 凝胶, 以避免氢吸附和解吸, 并氧化还原的金属。</li>
	</ol>
</li>
	<li>
从 CV 数据中测定电化学表面面积 (欧洲)。<ol>
<li>使用 1 mV 中最慢的 CV 扫描速率, 并计算特定的电容与等式: Csp = (∫ivdv)/(2μmΔV) (2) 注: 在这里i和v是当前和潜力在 CV 扫描 (A 和 v), 扫描率是μ (v/秒), 大量的凝胶是m (g) 和ΔV是潜在的放电窗口 (vs Ag/AgCl)。</li>
	</ol>
</li>
</ol>3. 气凝胶的制备和表征。
<ol><li>去除步骤1.8 中的 Au、Pd 和 Pt 凝胶的去离子冲洗水, 确保水半月板不与金属凝胶接触。</li>
	<li>将凝胶放在-80 摄氏度冷藏库中, 不少于30分钟. 将冷冻金属凝胶转移到冷冻干燥机上, 设置点压力为 4 Pa 或更低。</li>
</ol>

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Computations from Nitrogen Isotherms.</a> Journal of the American Chemical Society. 73, 373-380 (1951).</li><li>Brunauer, B., Emmett, P., Teller, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adsorption+of+Gases+in+Multimolecular+Layers.">Adsorption of Gases in Multimolecular Layers.</a> Journal of the American Chemical Society. 60, 309-319 (1938).</li><li>Herrmann, A., 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=Multimetallic+Aerogels+by+Template-Free+Self-Assembly+of+Au,+Ag,+Pt,+and+Pd+Nanoparticles.">Multimetallic Aerogels by Template-Free Self-Assembly of Au, Ag, Pt, and Pd Nanoparticles.</a> Chemistry of Materials. 26, 1074-1083 (2014).</li><li>Kornyshev, A., Irbakh, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Double-layer+capacitance+on+a+rough+metal+surface.">Double-layer capacitance on a rough metal surface.</a> Physical Review E. 53, 6192-6199 (1996).</li><li>Bisquert, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+the+boundaries+in+the+impedance+of+porous+film+electrodes.">Influence of the boundaries in the impedance of porous film electrodes.</a> Physical Chemistry Chemical Physics. 2, 4185-4192 (2000).</li><li>Bisquert, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theory+of+the+Impedance+of+Electron+Diffusion+and+Recombination+in+a+Thin+Layer.">Theory of the Impedance of Electron Diffusion and Recombination in a Thin Layer.</a> Journal of Physical Chemistry B. 106, 325-333 (2002).</li><li>Lu, K., Yuan, L., Xin, X., Xu, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hybridization+of+graphene+oxide+with+commercial+graphene+for+constructing+3D+metal-free+aerogel+with+enhanced+photocatalysis.">Hybridization of graphene oxide with commercial graphene for constructing 3D metal-free aerogel with enhanced photocatalysis.</a> Applied Catalysis B. 226, 16-22 (2018).</li><li>Nystron, G., Roder, L., Fernandez-Ronco, M., Mezzenga, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amyloid+Templated+Organic+Inorganic+Hybrid+Aerogels.">Amyloid Templated Organic Inorganic Hybrid Aerogels.</a> Advanced Functional Materials. , 1703609-1703620 (2017).</li></ol>

作者没有什么可透露的。

这里提出的贵金属气凝胶合成方法, 导致了多孔, 高表面积石柱的快速形成, 可比较慢的合成技术。1:1 (v/v) 金属离子溶液, 以降低剂溶液比是至关重要的, 以促进拟议的凝胶形成模型。快速氢气体演化作为金属离子电化学还原的副产品, 作为二次还原剂, 促进了凝胶形成过程中生长纳米粒子的致密化和融合。考虑到表 1中所示的许多合成组合不会导致凝胶的形成, 选择金属离子类型和还原?...

广泛的能量存储和转换, 催化和传感器应用得益于三维金属纳米结构, 提供控制化学反应性, 和大众运输性能1,2, 3,4,5。这样的3维金属纳米结构进一步提高电导率, 延性, 延展性和强度8,9。集成到设备需要材料是自由的或与支持材料结合。将纳米材料纳入支撑结构提供了一种尽量减少活性材料的方法, 但在设备操作10、11期间可能会受到弱吸附和最终结块的影响。
虽然有各种合成方法来控制单个纳米粒的大小和形状, 但很少有方法能够控制连续的3维纳米材料12、13、14。贵金属3维纳米结构已形成通过 dithiol 连接单分散纳米粒子, 溶胶-凝胶形成, 纳米粒子聚结, 复合材料, 纳米链, biotemplating15,16,17,18. 这些方法中有许多需要在几天到几周的时间内合成所需材料。从直接还原前体盐溶液中合成的贵金属 nanofoams, 合成时间较快, 且长度为上百微米的短量程, 但需要机械压制以进行设备集成。19,20。
第一次报告的基斯特勒, 气凝胶提供了一个合成途径, 以实现多孔结构的高比表面积, 是数量级低于其散装材料相对密度小于21,22,23.将3维结构扩展到散装材料的宏观长度尺度, 比需要支持材料或机械加工的纳米颗粒骨料或 nanofoams 具有优势。虽然气凝胶提供了一种控制孔隙度和颗粒特征大小的合成途径, 但是, 延长合成时间, 在某些情况下使用封盖剂或连结分子, 增加了整体加工步骤和时间。
本文提出了一种通过快速直接溶液还原法合成金、钯、铂气凝胶的方法24。将各种前体贵金属离子与还原剂相结合, 在 1:1 (v/v) 比值下, 在几秒到几分钟内形成金属凝胶, 与其他技术如溶胶-凝胶相比, 合成时间更长。使用离心管或小容积圆锥管, 利用积极的氢气演化作为副产品的减少步骤, 促进提出的核, 生长, 致密化, 融合, 平衡模型的凝胶形成。用扫描电镜图像分析、X 射线衍射、氮气吸附、电化学阻抗谱和循环伏安法确定气凝胶纳米结构特征尺寸的密切关系。用电化学阻抗谱和循环伏安法确定了溶剂可接近的比表面积。本发明的贵金属气凝胶的合成方法表明, 采用快速直接还原法可实现高比表面积石柱。

<table><tbody><tr><td>HAuCl&lt;sub&gt;4&lt;/sub&gt;&amp;Yuml;&amp;bull;3H&lt;sub&gt;2&lt;/sub&gt;O&amp;nbsp;</td><td>Sigma-Aldrich</td><td>16961-25-4</td><td></td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;PdCl&lt;sub&gt;4&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>13820-40-1</td><td></td></tr><tr><td>K&lt;sub&gt;2&lt;/sub&gt;PtCl&lt;sub&gt;6&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>16921-30-5</td><td></td></tr><tr><td>Pd(NH&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;4&lt;/sub&gt;Cl&lt;sub&gt;2&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>13933-31-8</td><td></td></tr><tr><td>K&lt;sub&gt;2&lt;/sub&gt;PtCl&lt;sub&gt;4&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>10025-99-7</td><td></td></tr><tr><td>Pt(NH&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;4&lt;/sub&gt;Cl&lt;sub&gt;2&lt;/sub&gt;&amp;Yuml;&amp;bull;H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma-Aldrich</td><td>13933-31-8</td><td></td></tr><tr><td>dimethylamine borane (DMAB)</td><td>Sigma-Aldrich</td><td>74-94-2</td><td></td></tr><tr><td>NaBH&lt;sub&gt;4&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>16940-66-2</td><td></td></tr><tr><td>NaH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;2&lt;/sub&gt;&amp;Yuml;&amp;bull;H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma-Aldrich</td><td>10039-56-2</td><td></td></tr><tr><td>Ethanol</td><td>Sigma-Aldrich</td><td>792780</td><td></td></tr><tr><td>Snap Cap Microcentrifuge Tubes, 2.0 mL</td><td>Cole Parmer</td><td>UX-06333-70</td><td></td></tr><tr><td>Snap Cap Microcentrifuge Tubes, 1.7 mL</td><td>Cole Parmer</td><td>UX-06333-60</td><td></td></tr><tr><td>Conical Centrifuge Tubes 15mL</td><td>Stellar Scientific</td><td>T15-101&amp;nbsp;</td><td></td></tr><tr><td>Ag/AgCl Reference Electrode</td><td>BASi</td><td>MF-2052</td><td></td></tr><tr><td>Pt wire electrode</td><td>BASi</td><td>MF-4130</td><td></td></tr><tr><td>Miccrostop Lacquer</td><td>Tober Chemical Division</td><td>NA</td><td></td></tr><tr><td>Potentiostat</td><td>Biologic-USA</td><td>VMP-3</td><td>Electrochemical analysis-EIS, CV</td></tr><tr><td>Freeze Dryer</td><td>Labconco</td><td>Freezone 2.5 Liter</td><td>Aerogel freeze drying</td></tr><tr><td>XRD</td><td>PanAlytical</td><td>Empyrean</td><td>X-ray diffractometry</td></tr><tr><td>Surface and Pore Analyzer</td><td>Quantachrome</td><td>NOVA 4000e</td><td>Nitrogen gas adsorption</td></tr><tr><td>ImageJ, Image analysis software</td><td>National Institute of Health</td><td>NA</td><td>SEM image analysis</td></tr></tbody></table>

a rapid synthesis method for au, pd, and pt aerogels via direct solution-based reduction

本文提出了一种通过快速直接溶液还原法合成金、钯、铂气凝胶的方法。在 1:1 (v/v) 比值中, 各种前体贵金属离子与还原剂的结合导致金属凝胶在几秒到几分钟内形成, 与其他技术如溶胶-凝胶相比, 合成时间更长。在离心管或小容积锥形管中进行还原步骤, 有利于形成凝胶成型的成核、生长、致密化、融合、平衡模型, 最终凝胶几何小于初始反应体积。这种方法利用积极的氢气演化作为还原步骤的副产品, 并作为试剂浓度的结果。用电化学阻抗谱和循环伏安法确定了溶剂可接近的比表面积。经冲洗和冷冻干燥后, 用扫描电镜、X 射线衍射和氮气吸附法对产生的气凝胶结构进行了检测。合成方法和表征技术导致气凝胶韧带大小的密切对应。本发明的贵金属气凝胶的合成方法表明, 采用快速直接还原法可实现高比表面积石柱。

金属离子和还原剂溶液的加入, 使溶液立即变成深黑色, 并有剧烈的气体演化。观察反应进展表明, 建议的凝胶形成机制如图 1所示。凝胶形成通过五步骤 1) 纳米粒核, 2) 生长, 3) 致密化, 4) 融合, 和 5) 平衡。前四步被观察到发生在反应的头几分钟, 与平衡第五步在 3-6 h 期间进行, 而凝胶保持在还原剂解决方案, 并继续在去离子水冲洗。图...

Watch this Scientific Journal Video about A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction at JoVE.com

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

直接溶液还原法快速合成金、钯、铂气凝胶的研究

提出了一种快速、直接的基于溶液的还原合成方法, 用于获得金、钯和 Pt 气凝胶。

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

a-rapid-synthesis-method-for-au-pd-pt-aerogels-via-direct-solution

Research

JoVE Journal

Chemistry

8.6K 次观看.  United States Military Academy, West Point. 提出了一种快速、直接的基于溶液的还原合成方法, 用于获得金、钯和 Pt 气凝胶。

视频: A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10-3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.

This article describes a rapid supercritical extraction method for fabricating silica aerogels. By utilizing a confined mold and hydraulic hot press, monolithic aerogels can be made in eight hours or less.

通过快速超临界萃取法制备二氧化硅气凝胶巨石

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The ...

科研

化学

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties of the materials were investigated. We used a one pot sol-gel approach to intercalate gold nano particles in the walls of mesoporous silica. To start with the synthesis, P123 was used as template to form micelles. Then TESPTS was used as a surface modification agent to intercalate gold nano particles. Following this process, TEOS was added in as a silica source which underwent a polymerization process in acid environment. After hydrothermal processing and calcination, the final product was acquired. Several techniques were utilized to characterize the porosity, morphology and structure of the gold intercalated mesoporous silica. The results showed a stable structure of mesoporous silica after gold intercalation. Through the oxidation of benzyl alcohol as a benchmark reaction, the GMS materials showed high selectivity and recyclability.

Here, we present a protocol with a sol-gel process to synthesize gold intercalated in the walls of mesoporous materials (GMS), which is confirmed to possess a mesoporous matrix with gold intercalated in the walls imparting great stability and recyclability.

合成和金插在介孔二氧化硅的墙壁催化性能

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties ...

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated &#62;300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.

We describe a simple method for producing highly stable oligomeric clusters of gold nanoparticles via the reduction of chloroauric acid (HAuCl4) with sodium thiocyanate (NaSCN). The oligoclusters have a narrow size distribution and can be produced with a wide range of sizes and surface coats.

根据环境条件的金纳米粒子的稳定低聚簇的大小控制合成的一种简便方法

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like ...

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 ...

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (&#60;6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Here we present protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms. Methods for preparing materials using copper salts and copper-containing nanoparticles are featured. Catalytic testing protocols demonstrate the effectiveness of these aerogels for three-way catalysis applications.

快速超临界萃取制备催化气凝胶的制备与试验研究

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three ...

Synthesis Method for Cellulose Nanofiber Biotemplated Palladium Composite Aerogels

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often result in fragile aerogels with poor shape control. The use of carboxymethylated cellulose nanofibers (CNFs) to form a covalently bonded hydrogel allows for the reduction of metal ions such as palladium on the CNFs with control over both nanostructure and macroscopic aerogel monolith shape after supercritical drying. Crosslinking the carboxymethylated cellulose nanofibers is achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in the presence of ethylenediamine. The CNF hydrogels maintain their shape throughout synthesis steps including covalent crosslinking, equilibration with precursor ions, metal reduction with high concentration reducing agent, rinsing in water, ethanol solvent exchange, and CO2 supercritical drying. Varying the precursor palladium ion concentration allows for control over the metal content in the final aerogel composite through a direct ion chemical reduction rather than relying on the relatively slow coalescence of pre-formed nanoparticles used in other sol-gel techniques. With diffusion as the basis to introduce and remove chemical species into and out of the hydrogel, this method is suitable for smaller bulk geometries and thin films. Characterization of the cellulose nanofiber-palladium composite aerogels with scanning electron microscopy, X-ray diffractometry, thermal gravimetric analysis, nitrogen gas adsorption, electrochemical impedance spectroscopy, and cyclic voltammetry indicates a high surface area, metallized palladium porous structure.

A synthesis method for cellulose nanofiber biotemplated palladium composite aerogels is presented.The resulting composite aerogel materials offer potential for catalysis, sensing, and hydrogen gas storage applications.

纤维素纳米纤维生物模板复合气凝胶的合成方法

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often ...

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 ...

Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination

Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles (NPs) can accelerate and control the selectivity of a variety of molecular transformations. This opens possibilities for the use of visible or near-IR light as a sustainable input to drive and control reactions when plasmonic nanoparticles supporting LSPR excitation in these ranges are employed as catalysts. Unfortunately, this is not the case for several catalytic metals such as palladium (Pd). One strategy to overcome this limitation is to employ bimetallic NPs containing plasmonic and catalytic metals. In this case, the LSPR excitation in the plasmonic metal can contribute to accelerate and control transformations driven by the catalytic component. The method reported herein focuses on the synthesis of bimetallic silver-palladium (Ag-Pd) NPs supported on ZrO2 (Ag-Pd/ZrO2) that acts as a plasmonic-catalytic system. The NPs were prepared by co-impregnation of corresponding metal precursors on the ZrO2 support followed by simultaneous reduction leading to the formation of bimetallic NPs directly on the ZrO2 support. The Ag-Pd/ZrO2 NPs were then used as plasmonic catalysts for the reduction of nitrobenzene under 425 nm illumination by LED lamps. Using gas chromatography (GC), the conversion and selectivity of the reduction reaction under the dark and light irradiation conditions can be monitored, demonstrating the enhanced catalytic performance and control over selectivity under LSPR excitation after alloying non-plasmonic Pd with plasmonic metal Ag. This technique can be adapted to a wide range of molecular transformations and NPs compositions, making it useful for the characterization of the plasmonic catalytic activity of different types of catalysis in terms of conversion and selectivity.

Presented here is a protocol for the synthesis of silver-palladium (Ag-Pd) alloy nanoparticles (NPs) supported on ZrO2 (Ag-Pd/ZrO2). This system allows for harvesting energy from visible light irradiation to accelerate and control molecular transformations. This is illustrated by nitrobenzene reduction under light irradiation catalyzed by Ag-Pd/ZrO2 NPs.

在可见光照射下为质子催化准备银-铂合金纳米粒子

Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles (NPs) can accelerate and control the selectivity of a variety of molecular ...

Aesthetically Enhanced Silica Aerogel Via Incorporation of Laser Etching and Dyes

A procedure for aesthetically enhancing silica aerogel monoliths by laser etching and incorporation of dyes is described in this manuscript. Using a rapid supercritical extraction method, large silica aerogel monolith (10 cm x 11 cm x 1.5 cm) can be fabricated in about 10 h. Dyes incorporated into the precursor mixture result in yellow-, pink- and orange-tinged aerogels. Text, patterns, and images can be etched onto the surface (or surfaces) of the aerogel monolith without damaging the bulk structure. The laser engraver can be used to cut shapes from the aerogel and form colorful mosaics.

This protocol describes a method for etching text, patterns, and images onto the surface of silica aerogel monoliths in native and dyed form and assembling the aerogels into mosaic designs.

通过将激光蚀刻和染料结合，美学增强硅气凝胶

A procedure for aesthetically enhancing silica aerogel monoliths by laser etching and incorporation of dyes is described in this manuscript. Using a rapid ...

工程学

Gold Nanoparticle Synthesis

Gold nanoparticles (Au nanoparticles) that are ~12 nm in diameter were synthesized by rapidly injecting a solution of 150 mg (0.15 mmol) of tetrachloroauric acid in 3.0 g (3.7 mmol, 3.6 mL) of oleylamine (technical grade) and 3.0 mL of toluene into a boiling solution of 5.1 g (6.4 mmol, 8.7 mL) of oleylamine in 147 mL of toluene. While boiling and mixing the reaction solution for 2 hours, the color of the reaction mixture changed from clear, to light yellow, to light pink, and then slowly to dark red. The heat was then turned off, and the solution was allowed to gradually cool down to room temperature for 1 hour. The gold nanoparticles were then collected and separated from the solution using a centrifuge and washed three times; by vortexing and dispersing the gold nanoparticles in 10 mL portions of toluene, and then precipitating the gold nanoparticles by adding 40 mL portions of methanol and spinning them in a centrifuge. The solution was then decanted to remove any remaining byproducts and unreacted starting materials. Drying the gold nanoparticles in a vacuum environment produced a solid black pellet; which could be stored for long periods of time (up to one year) for later use, and then redissolved in organic solvents such as toluene.

A protocol for synthesizing ~12 nm diameter gold nanoparticles (Au nanoparticles) in an organic solvent is presented. The gold nanoparticles are capped with oleylamine ligands to prevent agglomeration. The gold nanoparticles are soluble in organic solvents such as toluene.