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 border="0" cellpadding="0" cellspacing="0" width="691">
	<tbody>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">HAuCl4&#376;&#8226;3H2O&#160;</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">16961-25-4</td>
			<td style="width:229px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">Na2PdCl4</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">13820-40-1</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">K2PtCl6</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">16921-30-5</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Pd(NH3)4Cl2</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">13933-31-8</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">K2PtCl4</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">10025-99-7</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Pt(NH3)4Cl2&#376;&#8226;H2O</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">13933-31-8</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">dimethylamine borane (DMAB)</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">74-94-2</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">NaBH4</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">16940-66-2</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">NaH2PO2&#376;&#8226;H2O</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">10039-56-2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Ethanol</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td>792780</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Snap Cap Microcentrifuge Tubes, 2.0 mL</td>
			<td style="width:128px;">Cole Parmer</td>
			<td>UX-06333-70</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Snap Cap Microcentrifuge Tubes, 1.7 mL</td>
			<td style="width:128px;">Cole Parmer</td>
			<td>UX-06333-60</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Conical Centrifuge Tubes 15mL</td>
			<td style="width:128px;">Stellar Scientific</td>
			<td>T15-101&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Ag/AgCl Reference Electrode</td>
			<td style="width:128px;">BASi</td>
			<td style="width:119px;">MF-2052</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Pt wire electrode</td>
			<td style="width:128px;">BASi</td>
			<td style="width:119px;">MF-4130</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Miccrostop Lacquer</td>
			<td style="width:128px;">Tober Chemical Division</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Potentiostat</td>
			<td style="width:128px;">Biologic-USA</td>
			<td style="width:119px;">VMP-3</td>
			<td>Electrochemical analysis-EIS, CV</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Freeze Dryer</td>
			<td style="width:128px;">Labconco</td>
			<td style="width:119px;">Freezone 2.5 Liter</td>
			<td>Aerogel freeze drying</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">XRD</td>
			<td style="width:128px;">PanAlytical</td>
			<td style="width:119px;">Empyrean</td>
			<td>X-ray diffractometry</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Surface and Pore Analyzer</td>
			<td style="width:128px;">Quantachrome</td>
			<td style="width:119px;">NOVA 4000e</td>
			<td>Nitrogen gas adsorption</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">ImageJ, Image analysis software</td>
			<td style="width:128px;">National Institute of Health</td>
			<td style="width:119px;">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, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

合成，表征和混合金/硫化镉和Au / ZnS核/壳纳米颗粒功能化

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension.
Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries.
Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( &#820;500 mN/m to near zero). Furthermore, this method requires only a very modest potential (&#60; 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

方法通过表面氧化还原操纵液态金属的表面张力

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

蛋白质生物缀合物的合成<em&gt;通过</em&gt;半胱氨酸马来酰亚胺化学

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica glass ampules). Reduction of such phases by elemental alkaline metals in amines affords crystalline chalcogenidoplumbate(II) salts comprised of [PbTe3]2- or [Pb2Ch3]2- anions, depending upon which sequestering agent for the cations is present: crown ethers, like 18-crown-6, or cryptands, like [2.2.2]crypt. Reactions of solutions of such anions with transition-metal compounds yield (poly-)chalcogenide anions or transition-metal chalcogenide clusters, including one with a &#181;-PbSe ligand (i.e., the heaviest-known CO homolog).
In contrast, the solid-state synthesis of a phase of the nominal composition &#34;K2PbSe2&#34; by successive reactions of the elements and by the subsequent solvothermal treatment in amines yields the first non-oxide/halide inorganic lead(IV) compound: a salt of the ortho-selenidoplumbate(IV) anion [PbSe4]4-. This was unexpected due to the redox potentials of Pb(IV) and Se(-II). Such methods can further be applied to other elemental combinations, leading to the formation of solutions with binary [HgTe2]2- or [BiSe3]3- anions, or to large-scale syntheses of K2Hg2Se3 or K3BiSe3 via the solid-state route.
All compounds are characterized by single-crystal X-ray diffraction and elemental analysis; solutions of plumbate salts can be investigated by 205Pb and 77Se or 127Te NMR techniques. Quantum chemical calculations using density functional theory methods enable energy comparisons. They further allow for insights into the electronic configuration and thus, the bonding situation. Molecular Rh-containing Chevrel-type compounds were found to exhibit delocalized mixed valence, whereas similar telluridopalladate anions are electron-precise; the cluster with the &#181;-PbSe ligand is energetically favored over a hypothetical CO analog, in line with the unsuccessful attempt at its synthesis. The stability of formal Pb(IV) within the [PbSe4]4- anion is mainly due to a suitable stabilization within the crystal lattice.

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of ChalcogenidoplumbatesII or IV

The synthesis of chalcogenidoplumbates(II,IV) via the in situ reduction of nominal "PbCh2" (Ch = Chalcogen) and via a solid-state reaction and subsequent solvothermal reactions is presented. Additionally, reactivities of plumbate(II) solutions are portrayed, which yield the heaviest-known CO homolog known to date: the &#181;-PbSe ligand.

结合固态和基于解决方案的技术合成及Chalcogenidoplumbates的反应（II或IV）

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica ...

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 ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

铂镍纳米线的合成及减氧性能优化

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

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 and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity in aqueous CO2 reduction. Different from traditional metal nanocrystals, the synthesis of metal single atoms involves a matrix material that can confine those single atoms and prevent them from aggregation. We report an electrospinning and thermal annealing method to prepare Ni single atoms dispersed and coordinated in a graphene shell, as active centers for CO2 reduction to CO. During the synthesis, N dopants play a critical role in generating graphene vacancies to trap Ni atoms. Aberration-corrected scanning transmission electron microscopy and three-dimensional atom probe tomography were employed to identify the single Ni atomic sites in graphene vacancies. Detailed setup of electrochemical CO2 reduction apparatus coupled with an on-line gas chromatography is also demonstrated. Compared to metallic Ni, Ni single atom catalyst exhibit dramatically improved CO2 reduction and suppressed H2 evolution side reaction.

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Here, we present a protocol for the synthesis and electrochemical testing of transition metal single atoms coordinated in graphene vacancies as active centers for selective carbon dioxide reduction to carbon monoxide in aqueous solutions.

电化学 CO2还原的过渡金属单原子催化剂的合成及性能表征

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

直接溶液还原法快速合成金、钯、铂气凝胶的研究

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