作者感谢本科生绿岛谢，为的气凝胶材料的物理特性，和奥德Bechu，用于测试程序草案。我们感谢联合学院工程实验室用于加工不锈钢模具。在联合学院气凝胶实验室已经由美国国家科学基金会（NSF MRI CTS-0216153，美国国家科学基金会芮CHE-0514527，美国国家科学基金会的MRI CMMI-0722842，美国国家科学基金会芮CHE-0847901，美国国家科学基金会芮DMR-1206631，和NSF MRI CBET补助-1228851）。这种材料是基于由美国国家科学基金会批准号CHE-0847901支持工作。

安全注意事项 ：安全眼镜或护目镜，应随时与解决方案和液压热压机的准备工作期间佩戴。当制备化学试剂的溶液，当将溶液倒入在热压模具实验室必须戴上手套。 TMOS，甲醇和浓氨和含有这些试剂的溶液，必须在通风橱内进行处理。超临界提取过程中释放的热的甲醇，因此，有必要既泄的油压式热压机，并确保有热压的通风路径内没有点火源。此外，我们建议安装在左右热压防护罩的。中的一个垫圈故障的情况下，屏蔽将有助于抑制由此产生的垫圈件，从而保护任何人靠近该热压力加工。 1。准备试剂和其他用品<ol><li>收集所需的配方试剂：四甲基ylorthosilicate，甲醇，去离子水和氨水。 </li><li>使100.0毫升的1.5 M氨水。这样做，稀10.1毫升14.8 M浓氨水至100毫升去离子水。 </li><li>收购方不锈钢模具，12.7厘米x 12.7厘米×高1.9厘米，2.2厘米直径的9个圆形孔（ 见图3）。擦拭模具用干净的湿抹布，以除去表面油污或灰尘。互喷圆形良好，高温脱模喷雾剂缓解去除气凝胶从处理后的模具内。 </li><li>准备三组从1/16（1.6毫米）厚的石墨片和0.0005（0.0010毫米）厚的不锈钢箔密封垫圈。切成三块各材料的足以完全覆盖模具（&gt;12.7厘米X&gt;12.7厘米）。 </li></ol> 2。准备工具<ol><li>程序中的热压密封和提取程序。首先成立了一个密封的程序，将使用d，来密封所述敞开的模具的底部。请参阅表1为必要的程序价值。接下来的设置与使用上述模具中的二氧化硅气凝胶的正确参数的提取程序。 见表2这些参数。 </li><li>准备玻璃器皿。为了避免污染，四，玻璃烧杯中，将需要一个可容纳250毫升烧杯中标记为“前驱体溶液，”1个100毫升烧杯中标记为“甲醇”，一瓶20毫升的烧杯标有“去离子水”，和一个10毫升的烧杯标记&#39;1 .5 M氨“。确保所有的烧杯中是清洁和干燥。 </li><li>准备移液器。数字移液器应该用于缓解。将10ml的数字吸管和一个1000微升移液器将被使用。确保多个移液器吸头可供选择。 </li><li>通过添加水来填充线准备超声波仪。 </li></ol> 3。封模底<ol><li>将模具和衬垫材料在热压。 F开始步骤居中的石墨片上的下压板，添加的不锈钢箔片，并放置在模具上的不锈钢箔的顶部上。添加另一组垫圈材料（然后不锈钢石墨）在模具的上面。 （注：所用的衬垫材料可在此步骤中使用的顶部，但新的衬垫材料必须在底部使用。） </li><li>启动热压密封程序，使用表1所示的参数。这个程序密封在模具的底部，以防止所述液体前体化学品从当模具充满前体溶液泄漏。 </li></ol> 4。使前体解决方案几招TMOS为基础的二氧化硅气凝胶见表3。所有的解决方案的准备工作在通风橱中进行。 <ol><li> TMOS的第一等分移液器共计17.0毫升从试剂瓶放入250毫升的玻璃烧杯中，标记为“前驱体溶液”。 </li><li>倒一些甲醇放入100毫升的玻璃烧杯中，然后吸管甲醇等份共55.0毫升到250ml玻璃烧杯中，标记为“前体溶液”。 </li><li>倒一些去离子水到20毫升烧杯中标记为“去离子水”，并从烧杯吸管7.2毫升水倒入250毫升烧杯中。 </li><li>最后，倒入一些1.5米的NH 3进10毫升烧杯中，并从烧杯中吸270微升的溶液加入到250毫升烧杯中。 </li><li>轴封采用塑料石蜡膜将烧杯。 </li><li>混合的试剂，以确保发生水解通过声波处理至少5分钟的前体溶液。在超声处理之前，两个液层，有时在该前体混合物中可见。继5分钟超声处理后，溶液应显示为单相。如果不是这样，超声处理需额外混合物5分钟。 </li></ol> 5。倒易制毒化学解决方案为在热压模具<oL&gt; <li>在模具密封节目的最后的热压板将打开。卸下顶侧衬垫材料，并预留。离开模具的是在热压机，使模具的底侧保持密封。 </li><li>完全与前体溶液填充模具的各孔中。 （注：会有约10ml气凝胶前驱体溶液的填充模具后遗留下来这可以被丢弃或环境条件，使干凝胶下处理。） </li><li>把新鲜的衬垫材料在模具的顶部：不锈钢箔，然后再在上面所说的石墨。 </li><li>运行热压萃取程序（在表2中示出）。这个程序密封模具，加热的内容，以超临界状态，进行超临界萃取，然后冷却模具。 </li></ol> 6。从模具中取出气凝胶<ol><li>当萃取过程完成后，取出从所述热压模具和衬垫材料。 </li&gt; <li>从模具中取出顶部的衬垫材料。抛开这一点。 </li><li>轻轻地从底部衬垫材料松开模具。 </li><li>小心地从模具，一次一个删除每个气凝胶，通过从一个侧面力推他们通过用戴手套的手指。 </li><li>当气凝胶是从模具中取出，则过程就完成了。 </li></ol>

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作者宣称，他们有没有竞争的财务权益。

该RSCE法生产的单片二氧化硅气凝胶采用自动化，工艺简单一致的批次。如这里介绍的方法需要8小时的处理步骤。它可以加快加热和冷却步骤，使单片气凝胶在短短的3小时22，然而，当一8小时的过程应用中，气凝胶整料的更一致的批次的结果。的微小变化的过程中参数不影响所得气凝胶的物理性质，这表明该过程的鲁棒性22。 这里所用的前体配方导致单片二?...

氧化硅气凝胶材料具有低密度，高表面积和低的导热和导电性结合的纳米多孔结构，具有优良的光学性能。在一种材料这些特性的结合使得气凝胶有吸引力的大量应用1。在最近的一篇综述文章，Gurav 等 。详细描述二氧化硅气凝胶材料的现有的和潜在的应用，无论是在科研和工业产品2的发展。例如，二氧化硅气凝胶已被用作吸收剂，传感器，在低介电材料，作为存储介质为燃料，以及用于热绝缘应用2广泛。 气凝胶通常制作中，采用一个两步骤的过程。第一步骤涉及混合适当的化学前体，然后进行缩合和水解反应，以形成湿凝胶。为了准备硅胶，在水和含二氧化硅的前体之间的水解反应发生，在这种情况下，四甲酯（TMOS，硅（OCH 3）4），在酸或碱催化剂的存在下进行。 的Si（OCH 3）4 + H 2 O <img alt="箭头" fo:content-width=".2in" src="/files/ftp_upload/51421/arrow.jpg" width="20" />的Si（OCH 3）4-N（OH）N + N CH 3 OH TMOS是不溶于水。为了促进水解，这是必要的，包括其它溶剂，在这种情况下甲醇（MeOH中，CH 3 OH），并搅拌或超声处理的混合物。接着碱催化的缩聚反应的水解的二氧化硅物种之间发生： ，R 3的SiOH + HOSiR 3 <img alt="箭头" fo:content-width=".2in" src="/files/ftp_upload/51421/arrow.jpg" width="20" /> ，R 3的Si-O-SIR 3 + H 2 O ，R 3的SiOH + CH 3 </子&gt; 3 OSIR <img alt="箭头" fo:content-width=".2in" src="/files/ftp_upload/51421/arrow.jpg" width="20" /> ，R 3的Si-O-SIR 3 + CH 3 OH 缩聚反应导致的湿凝胶，由多孔的SiO 2固体基质，其中所述孔被填充在反应溶剂的副产物，在这种情况下的甲醇和水的形成。第二个步骤涉及干燥湿凝胶形成气凝胶：从孔而不改变固体基质中除去溶剂。干燥过程是气凝胶的形成是至关重要的。如果没有进行正确的脆弱纳米结构崩塌和干凝胶形成为在图1中示意性示出。 有三种基本方法用于干燥溶胶 - 凝胶的材料，以产生气凝胶：超临界萃取法，冷冻干燥和常压干燥。超临界萃取方法一空隙渡液 - 汽相线，使得表面张力的作用不会导致凝胶的纳米结构坍塌。超临界萃取方法可在高温（250-300℃），并用直接提取的缩合和水解反应3-7的醇溶剂的副产物的压力下进行。另外，可以执行一组的交流，并与液体二氧化碳，其具有低的超临界温度（〜31℃）代替醇的溶剂。提取然后可以在相对 ​​低的温度下进行8,9，尽管在高压下。冷冻干燥方法10,11首先冻结在低温下的湿凝胶，然后使溶剂直接升华成蒸气形式，又避免了交叉的液-汽相一致。环境压力的方法使用表面活性剂来降低表面张力作用或聚合物增强纳米结构，其次是湿凝胶的干燥在室温pressu重12-16。 在联合学院的快速超临界萃取（RSCE）过程是一步（前体气凝胶）方法17-19。该方法使用高温的超临界提取，这使得单片气凝胶的制备在小时，而不是天至通过其它方法需要几周。该方法利用一个密闭的金属模具和一个可编程的液压热压机。化学前体混合并直接倒入模具中，其放置的油压式热压机的压盘之间。热压被编程以关闭并应用的抑制力，以密封所述模具。热压然后以指定的速率加热所述模具的温度，T 高 ，高于溶剂的临界温度（参见图2的过程的曲线图）。在开始升温期间的化学反应形成凝胶和凝胶强化剂和年龄。当模具被加热的压力也上升，最终达到超临界压力。在到达T 高 ，热压住在一个固定的状态，而系统达到平衡。下一个热压力减小和超临界流体逸出，留下了热气凝胶。压然后冷却模具和其内容至室温。在该过程（其可以采取3-8小时）的端部压打开和单片气凝胶是从模具中取出。 这RSCE方法提供了比其他气凝胶制备方法显著优点。它速度快（&lt;8小时总数），而不是劳动密集型，通常只需要15-20分钟的准备时间后3-8小时的处理时间。它不需要溶剂交换，这意味着该过程中产生相对较少的溶剂废物。 在下面的章节中，我们描述了一个协议，用于通过联盟RSCE方法从母体混合物包括制订一套圆柱二氧化硅气凝胶巨石的D TMOS，甲醇和水以用作催化剂的水解和缩聚反应氨水（用TMOS：甲醇：H 2 O：的1.0:12:3.6:3.5×10 -3的NH 3的摩尔比）。我们注意到，该联盟RSCE方法可用于制备各种不同尺寸和形状的气凝胶，根据​​金属模具和油压式热压机使用。这RSCE方法也被用于从不同的前体配方20制备其它类型的气凝胶（二氧化钛，氧化铝等 ）。

<table border="0" cellpadding="0" cellspacing="0" width="1344">
	<colgroup>
		<col />
		<col span="2" />
		<col />
	</colgroup>
	<tbody>
		<tr height="61">
			<td height="61" style="height:61px;width:504px;">Tetramethylorthosilicate&#160; (TMOS)</td>
			<td style="width:252px;">Sigma Aldrich&#160;&#160; www.sigmaaldrich.com</td>
			<td style="width:252px;">218472-500G</td>
			<td style="width:336px;">98% purity, CAS 681-84-5&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:504px;">Methanol&#160; (MeOH)</td>
			<td style="width:252px;">Fisher Scientific&#160; www.fishersci.com</td>
			<td style="width:252px;">A412-20</td>
			<td style="width:336px;">Certified ACS Reagent Grade, &#8805;99.8%</td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:504px;">Ammonium Hydroxide (aqueous ammonia)</td>
			<td style="width:252px;">Fisher Scientific&#160; www.fishersci.com</td>
			<td style="width:252px;">A669S212</td>
			<td style="width:336px;">Certified ACS Plus, about 14.8N, 28.0-20.0 w/w%</td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:504px;">Deionized Water</td>
			<td style="width:252px;">On tap in house</td>
			<td style="width:252px;"></td>
			<td style="width:336px;"></td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:504px;">Flexible Graphite Sheet</td>
			<td style="width:252px;">Phelps Industrial Products</td>
			<td style="width:252px;">7500.062.3</td>
			<td style="width:336px;">1/16&#34; thick</td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:504px;">Stainless Steel Foil</td>
			<td style="width:252px;">Various</td>
			<td style="width:252px;"></td>
			<td style="width:336px;">.0005&#34; thick, 304 Stainless Steel</td>
		</tr>
		<tr height="110">
			<td height="110" style="height:111px;width:504px;">High Temperature Mold Release Spray</td>
			<td style="width:252px;">Various&#160; (for example, CRC Industrial Dry PTFE Lube)</td>
			<td style="width:252px;"></td>
			<td style="width:336px;">Should be able to withstand high temperatures.</td>
		</tr>
	</tbody>
</table>

preparing silica aerogel monoliths via a rapid supercritical extraction method

一个程序的八个小时或更少的单片二氧化硅气凝胶通过一个快速的超临界萃取工艺的制作说明。该过程需要15-20分钟的准备时间，在此期间，液体前体的混合物制备并倒入金属模具的孔中，放置在油压式热压机的压板之间，然后热压内几个小时的处理。前体溶液由四甲酯的1.0:12.0:3.6:3.5×10 -3摩尔比（TMOS）：甲醇：水：氨。在模具中，多孔二氧化硅的溶胶 - 凝胶基质形成的各孔中。作为模具和其内容物的温度升高时，模具内的压力上升。后的温度/压力条件高于超临界点的矩阵（在此情况下，用甲醇/水混合物）的细孔内的溶剂，超临界流体被释放，单片气凝胶保持在模具的孔中。在此过程中使用的模具，2.2厘米直径的1.9厘米高的圆柱形巨石生产。通过这种快速方法形成气凝胶具有相当的性能（低堆积和骨架密度，高表面积，中孔形态）来制备的那些涉及任何附加的反应步骤或溶剂萃取等方法（即产生更多的化学废物冗长的进程）的快速超临界萃取法，也可应用到基于其它前体配方气凝胶的制造。

下面这里描述的结果在单片硅气凝胶一致的分批过程， 图4示出了通过该方法制备的典型的二氧化硅气凝胶的图像。每个气凝胶需要对井的形状和尺寸在加工模具与无收缩。这些图像表明，二氧化硅气凝胶是半透明的。 这些气凝胶的物理性质总结于表4中 。他们可以媲美二氧化硅气凝胶采用低温超临界萃取21。 图5相似的前体配方?...

Watch this Scientific Journal Video about Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method at JoVE.com

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

本文介绍了一种快速超临界萃取法制造二氧化硅气凝胶。通过利用一个密闭的模具和液压热压机，单片气凝胶可以在8小时以​​内进行。

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 ...

preparing-silica-aerogel-monoliths-via-rapid-supercritical-extraction

Research

JoVE Journal

Chemistry

20.0K 次观看.  Union College. 本文介绍了一种快速超临界萃取法制造二氧化硅气凝胶。通过利用一个密闭的模具和液压热压机，单片气凝胶可以在8小时以​​内进行。 

视频: Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan &#948; solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials&#39; morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

科研

化学

Preparing Adherent Cells for X-ray Fluorescence Imaging by Chemical Fixation

X-ray fluorescence imaging allows us to non-destructively measure the spatial distribution and concentration of multiple elements simultaneously over large or small sample areas. It has been applied in many areas of science, including materials science, geoscience, studying works of cultural heritage, and in chemical biology. In the case of chemical biology, for example, visualizing the metal distributions within cells allows us to study both naturally-occurring metal ions in the cells, as well as exogenously-introduced metals such as drugs and nanoparticles. Due to the fully hydrated nature of nearly all biological samples, cryo-fixation followed by imaging under cryogenic temperature represents the ideal imaging modality currently available. However, under the circumstances that such a combination is not easily accessible or practical, aldehyde based chemical fixation remains useful and sometimes inevitable. This article describes in as much detail as possible in the preparation of adherent mammalian cells by chemical fixation for X-ray fluorescent imaging.

Here, we present a protocol on how to determine the quantity and distribution of metals in a sample using synchrotron X-ray fluorescence. We focus on adherent cells, and describe the chemical fixation method to prepare this sample. We then describe how to mount and image the sample using synchrotron X-rays.

化学固定准备贴壁细胞的X射线荧光成像

X-ray fluorescence imaging allows us to non-destructively measure the spatial distribution and concentration of multiple elements simultaneously over ...

Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml-1, modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 &#197;. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride.

Nitrogen is an effective supercritical fluid for extraction or drying processes due to its small molecular size, high density in the near-liquid supercritical regime, and chemical inertness. We present a supercritical nitrogen drying protocol for the purification treatment of reactive, porous materials.

超临界氮处理的活性多孔材料的净化

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. ...

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 ...

A Straightforward Method for Glucosinolate Extraction and Analysis with High-pressure Liquid Chromatography (HPLC)

Glucosinolates are a well-studied and highly diverse class of natural plant compounds. They play important roles in plant resistance, rapeseed oil quality, food flavoring, and human health. The biological activity of glucosinolates is released upon tissue damage, when they are mixed with the enzyme myrosinase. This results in the formation of pungent and toxic breakdown products, such as isothiocyanates and nitriles. Currently, more than 130 structurally different glucosinolates have been identified. The chemical structure of the glucosinolate is an important determinant of the product that is formed, which in turn determines its biological activity. The latter may range from detrimental (e.g., progoitrin) to beneficial (e.g., glucoraphanin). Each glucosinolate-containing plant species has its own specific glucosinolate profile. For this reason, it is important to correctly identify and reliably quantify the different glucosinolates present in brassicaceous leaf, seed, and root crops or, for ecological studies, in their wild relatives. Here, we present a well-validated, targeted, and robust method to analyze glucosinolate profiles in a wide range of plant species and plant organs. Intact glucosinolates are extracted from ground plant materials with a methanol-water mixture at high temperatures to disable myrosinase activity. Thereafter, the resulting extract is brought onto an ion-exchange column for purification. After sulfatase treatment, the desulfoglucosinolates are eluted with water and the eluate is freeze-dried. The residue is taken up in an exact volume of water, which is analyzed by high-pressure liquid chromatography (HPLC) with a photodiode array (PDA) or ultraviolet (UV) detector. Detection and quantification are achieved by conducting comparisons of the retention times and UV spectra of commercial reference standards. The concentrations are calculated based on a sinigrin reference curve and well-established response factors. The advantages and disadvantages of this straightforward method, when compared to faster and more technologically advanced methods, are discussed here.

A Straightforward Method for Glucosinolate Extraction and Analysis with High-pressure Liquid Chromatography HPLC

Here, we describe in great detail an established and robust protocol for the extraction of glucosinolates from ground plant materials. After an on-column sulfatase treatment of the extracts, the desulfoglucosinolates are eluted and analyzed by high-pressure liquid chromatography.

简捷方法对硫甙的提取与分析用高压液相色谱法（HPLC）

Glucosinolates are a well-studied and highly diverse class of natural plant compounds. They play important roles in plant resistance, rapeseed oil ...

A Convenient Method for Extraction and Analysis with High-Pressure Liquid Chromatography of Catecholamine Neurotransmitters and Their Metabolites

The extraction and analysis of catecholamine neurotransmitters in biological fluids is of great importance in assessing nervous system function and related diseases, but their precise measurement is still a challenge. Many protocols have been described for neurotransmitter measurement by a variety of instruments, including high-pressure liquid chromatography (HPLC). However, there are shortcomings, such as complicated operation or hard-to-detect multiple targets, which cannot be avoided, and presently, the dominant analysis technique is still HPLC coupled with sensitive electrochemical or fluorimetric detection, due to its high sensitivity and good selectivity. Here, a detailed protocol is described for the pretreatment and detection of catecholamines with high pressure liquid chromatography with electrochemical detection (HPLC-ECD) in real urine samples of infants, using electrospun composite nanofibers composed of polymeric crown ether with polystyrene as adsorbent, also known as the packed-fiber solid phase extraction (PFSPE) method. We show how urine samples can be easily precleaned by a nanofiber-packed solid phase column, and how the analytes in the sample can be rapidly enriched, desorbed, and detected on an ECD system. PFSPE greatly simplifies the pretreatment procedures for biological samples, allowing for decreased time, expense, and reduction of the loss of targets. 
Overall, this work illustrates a simple and convenient protocol for solid-phase extraction coupled to an HPLC-ECD system for simultaneous determination of three monoamine neurotransmitters (norepinephrine (NE), epinephrine (E), dopamine (DA)) and two of their metabolites (3-methoxy-4-hydroxyphenylglycol (MHPG) and 3,4-dihydroxy-phenylacetic acid (DOPAC)) in infants' urine. The established protocol was applied to assess the differences of urinary catecholamines and their metabolites between high-risk infants with perinatal brain damage and healthy controls. Comparative analysis revealed a significant difference in urinary MHPG between the two groups, indicating that the catecholamine metabolites may be an important candidate marker for early diagnosis of cases at risk for brain damage in infants.

We present a convenient solid-phase extraction coupled to high-pressure liquid chromatography (HPLC) with electrochemical detection (ECD) for simultaneous determination of three monoamine neurotransmitters and two of their metabolites in infants' urine. We also identify the metabolite MHPG as a potential biomarker for the early diagnosis of brain damage for infants.

用高压液相色谱法提取和分析儿茶酚胺神经递质及其代谢物的简便方法

The extraction and analysis of catecholamine neurotransmitters in biological fluids is of great importance in assessing nervous system function and ...

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 ...

Preparation of Functional Silica Using a Bioinspired Method

The goal of the protocols described herein is to synthesize bioinspired silica materials, perform enzyme encapsulation therein, and partially or totally purify the same by acid elution. By combining sodium silicate with a polyfunctional bioinspired additive, silica is rapidly formed at ambient conditions upon neutralization. 
The effect of neutralization rate and biomolecule addition point on silica yield are investigated, and biomolecule immobilization efficiency is reported for varying addition point. In contrast to other porous silica synthesis methods, it is shown that the mild conditions required for bioinspired silica synthesis are fully compatible with the encapsulation of delicate biomolecules. Additionally, mild conditions are used across all synthesis and modification steps, making bioinspired silica a promising target for the scale-up and commercialization as both a bare material and active support medium.
The synthesis is shown to be highly sensitive to conditions, i.e., the neutralization rate and final synthesis pH, however tight control over these parameters is demonstrated through the use of auto titration methods, leading to high reproducibility in reaction progression pathway and yield. 
Therefore, bioinspired silica is an excellent active material support choice, showing versatility towards many current applications, not limited to those demonstrated here, and potency in future applications.

Here, we present a protocol to synthesize bioinspired silica materials and immobilize enzymes therein. Silica is synthesized by combining sodium silicate and an amine &#39;additive&#39;, which neutralize at a controlled rate. Material properties and function can be altered either by in situ enzyme immobilization or post-synthetic acid elution of encapsulated additives.

用 Bioinspired 法制备功能性二氧化硅

The goal of the protocols described herein is to synthesize bioinspired silica materials, perform enzyme encapsulation therein, and partially or totally ...

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

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

直接溶液还原法快速合成金、钯、铂气凝胶的研究

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

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 ...