这项工作得到了哈佛大学罗兰研究所的罗兰研究员计划的支持。这项工作是在纳米系统中心 (CNS) 的一部分进行的, 这是国家纳米技术基础设施网络的一个成员, 它得到国家科学基金会的支持。ECS-0335765。中枢神经系统是哈佛大学的一部分。

1. 镍单原子催化剂的制备 (GS)
<ol><li>静电纺丝前体溶液的制备<ol>
<li>取20毫升闪烁瓶, 溶解0.5 克聚丙烯腈 (Mw= 15万), 0.5 克 polypyrrolidone (Mw= 130万), 0.5 克 Ni (无3)2· 6H2O, 0.1 毫升氰 (DCDA)甲基酰胺 (DMF)。</li>
		<li>将 DMF 混合物加热到80摄氏度, 将混合物保持在80摄氏度, 持续搅拌直至所有聚合物和盐溶解, 并观察到一个清晰的溶液。</li>
	</ol>
</li>
	<li>静电纺丝生产高分子纤维<ol>
<li>设置传统的静电纺丝参数为:15 伏的静电电压, 15 厘米的气隙距离, 集衬底 8 x 8 厘米碳纤维纸 (CFP) 与-4 伏电压。</li>
		<li>提取5毫升的前体溶液成5毫升注射器, 启动注射器泵的流速为1.2 毫升 h−1, 然后启动静电纺丝。 注: 采用高压静电纺丝。尽管在纺纱过程中, 系统的电流很低, 但还是提出了一个隔热的木柜。</li>
		<li>当静电纺丝工艺完成后, 取出 CFP 基体。聚合物纤维膜覆盖 CFP 表面。</li>
	</ol>
</li>
	<li>将聚合物纤维退火成碳纳米管<ol>
<li>将所制备的聚合物纤维薄膜/CFP 在箱式炉内1.5 小时内加热至300摄氏度, 并保持0.5 小时的温度以氧化聚合物。 注: 氧化过程后, 纳米纤维 (NFs) 是自分离的碳纸产生的独立薄膜。</li>
		<li>用剪刀把这些纳米纤维切成小块 (0.5 厘米 x 2cm), 然后把它们放进石英船里。</li>
		<li>将石英船放入管式炉内, 并将其 deaerate 在形成气体 (5% H2的 Ar) 大气中。保持气体流量为 100 sccm 和压力为 1 Tor。</li>
		<li>在10分钟内加热至300摄氏度, 2 h 斜向750摄氏度, 在那里保持另1小时, 然后自然降温。</li>
	</ol>
</li>
	<li>球磨机作为合成的5分钟到纳米粉催化和表征的一般 GS 催化剂。</li>
</ol>2. 电化学 CO2还原测量
<ol><li>电池和电极<ol>
<li>要准备 0.1 M KHCO3电解质为以下测量, 首先溶化 2.5 g KHCO3在250毫升纯净的水, 然后通过电解净化电解质用二个石墨杆在 0.1 mA 为 24 h 去除任何痕量金属离子。</li>
		<li>采用新鲜 (电化学) 抛光玻碳 (1 厘米 x 2 厘米), 并覆盖其背面与电化学惰性, 疏水性蜡, 作为工作电极基板。</li>
		<li>采取4毫升闪烁瓶, 混合5毫克的正准备的 GS 催化剂与1毫升乙醇和100µL 的离子溶液 (5% 在 2-proponal) 在瓶内, 油脂实验20分钟得到一个均匀的催化剂墨水悬浮。</li>
		<li>吸管80µL 的催化剂墨水到 2 cm2玻碳表面 (0.2 毫克 cm-2质量装货) 和真空干燥催化剂被盖的电极在干燥在使用之前。</li>
		<li>分别使用铂箔和饱和甘汞电极 (SCE) 作为计数器和参考电极。</li>
		<li>使用自定义的气密 H 型玻璃细胞, 由质子交换膜分离, 用于上述3电极组装以及电化学测试运行。</li>
		<li>将工作电极和 SCE 参考电极放在 H 细胞的一个隔间中, 并将 Pt 箔电极置于另一腔内。在 H 细胞的每个隔间注入25毫升的电解质。</li>
		<li>将 H 细胞中的3电极连接到电化学工作台进行潜在控制。</li>
		<li>将电解液与 n2在 50.0 sccm (由质量流控制器监视) 中气泡30分钟向 N2饱和 0.1 M KHCO3。</li>
		<li>选择循环伏安法 (CV) 技术在 EC 实验室软件, 设置 "E 范围 (潜力)" 作为 "-10 v 到 10 v", "I 范围 (当前)" 作为 "自动", 执行5连续 CV 扫描从-0.5 v 到-1.8 V (vs. SCE) 扫描率为 50 mV/秒在 N2-饱和 0.1 M KHCO3。</li>
		<li>更改为 50 sccm CO2气体流, 等待30分钟向 CO2饱和 0.1 M KHCO3电解质, 并保持相同的 CO2流贯穿以下电解。</li>
		<li>在 EC 实验室软件中选择 CV 技术, 将 "E 范围 (潜在)" 设置为 "-10 v 到 10 v", "I 范围 (当前)" 作为 "自动", 执行5连续 CV 扫描从-0.5 v 到-1.8 V (与 SCE) 在 CO2饱和 0.1 M KHCO3的扫描率 50 mV/秒。</li>
		<li>使用 ph 计来确定电解质的 ph 值, i. e, 0.1 M KHCO3饱和的 N2或 CO2。</li>
		<li>使用 e (vs) = e (vs SCE) + 0.244 V + 0.0591 x pH 值, 将与 sce 相对应的所有电位转换为可逆氢电极刻度。</li>
		<li>通过选择恒电位电化学阻抗谱 (PEIS) 技术, 在 EC 实验室软件中确定解决方案电阻 (R u), 然后将频率范围从 0.1 Hz 设置为200赫, 记录电阻值.</li>
		<li>手动补偿ir降为 e (ir 校正 vs) = e (vs) Ru x I (安培平均电流)。</li>
	</ol>
</li>
	<li>CO2还原产品在线气相色谱分析 (GC)<ol>
<li>采用 GC, 配以分子筛5A 和 micropacked 柱的组合, 用于 CO2RR 期间的气体产品分析。 注意: 在附加的材料表中可以找到详细的 GC 列类型。</li>
		<li>使用导热系数检测器 (TCD) 来量化 H2浓度, 和一个火焰电离探测器 (methanizer), 以定量分析 CO 含量和/或任何其他烷烃物种。</li>
		<li>对 H2和 CO 浓度的校准曲线使用两种不同标准气体 (h2: 100 和 1042 ppm;CO: 100 和 496.7 ppm;与氩气平衡)。</li>
		<li>在电解过程中, 维护 co2气体流速在 50.0 sccm, 将 co2传递到包含 co2饱和 0.1 M KHCO3电解质的阴极间隔, 并将排气口排放到 GC 中。</li>
		<li>逐步调整工作电极上的电压, 范围从-0.3 到-1.0 伏, 每个电位保持15分钟, 并记录相应的 chronoamperimetric 曲线。</li>
		<li>分别测定 TCD 和 FID 信号排气中的 H2和 CO 含量。 注: 气体产品在每种电位下连续电解10分钟后取样。50 sccm CO2气体与连续产生的 H2和 CO 混合, 在电解过程中流经 GC 的取样回路 (1 毫升)。</li>
		<li>计算给定气体产品的局部电流密度, 如下所示: <img alt="Equation" src="/files/ftp_upload/57380/57380eq2.jpg"> 其中xi 是由来自两个标准气体样本 (斯科特和 Airgas) 的校准曲线所参照的在线 GC 确定的某些产品的体积分数, v是 50 sccm 的流量, ni 是数字涉及的电子, p0 = 101.3 帕, F是法拉第常数, R 是气体常数。</li>
		<li>在每个潜在的中计算相应的法拉第效率 (FE). <img alt="Equation" src="/files/ftp_upload/57380/57380eq7.jpg"> </img> 注: 由于气体流速、电流密度、气相浓度分析等误差, 整体法拉第效率可在90至110% 范围内。</li>
	</ol>
</li>
</ol>

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在上述静电纺丝过程中, 在材料合成过程中应注意两个重要步骤: 1) 加热 DMF 混合物 (步进 1.1.2) 和 2) 泵速调整 (步进 1.2.2) 以匹配纺丝速率。图 1A中的 SEM 图像显示了获得的碳纳米纤维相互连接 (直径约200纳米)。它们被分成了小块, 通过球铣削来进行刻画, 如图 1B所示。纳米粒子在碳纳米纤维中均匀分布。在高温下, 用镍合金化的碳原子会析出, 并在冷却过...

将 CO2转换为化学品或使用清洁电的燃料变得越来越重要, 作为一种潜在的途径, 以防止进一步 CO2排放1,2,3,4, 5,6。然而, 由于高动能障碍和与氢进化反应 (她) 在水中的竞争而导致 co2还原反应 (co2RR) 的低活动性和选择性, 这一实际应用目前受到挑战。媒体。大多数传统的过渡金属催化剂, 如 Fe、Co 和镍, 由于其精湛的活动78, 表现出低 Co2RR 选择性。有效调整其材料性能以改变这些过渡金属催化剂的反应通路, 对于提高它们的 CO2RR 选择性至关重要。在改变催化剂电子性能的不同方法中, 将金属原子分散到单原子形态中, 由于它们的催化行为与体积相对应显著地变化, 因而受到了强烈的关注。9,10,11. 然而, 由于无界原子的高机动性, 在不存在支持材料的情况下获得单一金属原子是相当有挑战性的。因此, 有必要建立一个与过渡金属原子进行限制和协调的缺陷的主矩阵材料。这可能开辟了新的机会: 1) 调整过渡金属的电子性质为 CO2RR 活动站点, 和 2) 同时保持相对简单的原子协调为基础机制研究。此外, 那些被困在密闭环境中的过渡金属原子在催化过程中不能轻易移动, 防止在许多情况下观察到的表面原子成核或重建12,13 ,14。
二维层状石墨烯作为金属单原子的宿主, 由于其高的电子电导率、化学稳定性和惰性对 CO2的还原和她的催化反应特别感兴趣。更重要的是, 铁、钴和镍金属被称为能够催化在其表面的碳石墨化过程15。简而言之, 这些过渡金属在高温热退火过程中会产生碳合金。当温度下降时, 碳开始从合金化阶段沉淀出来, 并被催化在过渡金属表面形成石墨烯层。在此过程中, 随着石墨烯缺陷的产生, 金属单原子将被困在这些石墨烯缺陷作为 CO2RR16,17,18,19的活动站点。在这里, 我们报告这一详细的协议, 旨在帮助新的从业者在单原子催化领域, 以及提供一个明确的示范在线 CO2减少产品分析。更多信息可以在我们最近发布的文章19和一系列相关工作20,21,22,23中找到。

<table border="0" cellpadding="0" cellspacing="0" width="829">
	<tbody>
		<tr height="23">
			<td height="23" style="height:23px;width:216px;">syringe pump&#160;</td>
			<td style="width:164px;">KD Scientific</td>
			<td style="width:151px;">KDS-100</td>
			<td style="width:299px;"></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:216px;">tube furnance</td>
			<td style="width:164px;">Lindberg/Blue M</td>
			<td style="width:151px;">TF55035A-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">ball miller</td>
			<td style="width:164px;">SPEX SamplePrep</td>
			<td style="width:151px;">5100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">electrochemical work station</td>
			<td style="width:164px;">BioLogic</td>
			<td style="width:151px;">VMP3</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">pH meter</td>
			<td style="width:164px;">Orion</td>
			<td style="width:151px;">320 PerpHecT&#160;</td>
			<td>2 points calibration before use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">gas chromatograph</td>
			<td style="width:164px;">Shimadzu</td>
			<td style="width:151px;">GC-2014</td>
			<td>a combined seperation system consisting of molecular sieve 5A, Hayesep Q, Hayesep T, and Hayesep N</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mass flow controller</td>
			<td>Alicat Scientific&#160;</td>
			<td style="width:151px;">MC-50SCCM-D/5M</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">ultrapure water system</td>
			<td>Millipore</td>
			<td>Synergy</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">vacuum desiccator&#160;</td>
			<td>PolyLab</td>
			<td>55205</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">polyacrylonitrile</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td style="width:151px;">181315</td>
			<td>Mw=150,000</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">polypyrrolidone</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td style="width:151px;">437190</td>
			<td>Mw=1,300,000</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Ni(NO3)26H2O</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td style="width:151px;">244074</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">dicyandiamide</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td style="width:151px;">D76609</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">dimethylformamide</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td style="width:151px;">227056</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">carbon fiber paper&#160;</td>
			<td style="width:164px;">AvCarb</td>
			<td style="width:151px;">MGL370</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Nafion 117 membrane</td>
			<td style="width:164px;">Fuel Cell Store</td>
			<td style="width:151px;">117</td>
			<td>used as proton exchange membrane in H-cell</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">KHCO3</td>
			<td style="width:164px;">Sigma-Aldrich</td>
			<td style="width:151px;">431583</td>
			<td>further purified by electrolysis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">platinum foil&#160;</td>
			<td style="width:164px;">Beantown Chemical</td>
			<td style="width:151px;">126580</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">saturated calomel electrode</td>
			<td style="width:164px;">CH Instruments</td>
			<td style="width:151px;">CHI150</td>
			<td></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:216px;">glassy carbon electrode</td>
			<td style="width:164px;">HTW GmbH</td>
			<td style="width:151px;">SIGRADUR</td>
			<td>1 cm &#215; 2 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">wax</td>
			<td>Apiezon</td>
			<td style="width:151px;">W-W100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nafion 117 solution</td>
			<td>Sigma-Aldrich</td>
			<td>70160</td>
			<td>used as ionomer in catalyst ink preparation&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">forming gas</td>
			<td>Airgas</td>
			<td>UHP</td>
			<td>5% H2 balanced with Ar</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">carbon dioxide</td>
			<td>Airgas</td>
			<td>LaserPlus</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">sandard gas</td>
			<td>Airgas</td>
			<td>customized</td>
			<td>500 ppm CO, 500 ppm CH4, 1000 ppm H2 balanced with Ar</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">sandard gas</td>
			<td>Air Liquide</td>
			<td>customized</td>
			<td>100 ppm H2, 100 ppm CO and other alkanes balanced with Ar</td>
		</tr>
	</tbody>
</table>

synthesis and performance characterizations of transition metal single atom catalyst for electrochemical co2 reduction

该协议既提供了镍单原子催化剂的合成方法, 又介绍了其在水 CO2还原中的催化活性和选择性的电化学检测。与传统金属纳米晶不同的是, 金属单原子的合成涉及一种基体材料, 它可以限制这些单一原子并防止它们聚集。我们报告的静电纺丝和热退火方法, 以准备镍单原子分散和协调在石墨烯壳, 作为活性中心的 co2减少到 co。在合成过程中, N 掺杂在产生石墨烯空缺以捕获 Ni 原子方面起着关键作用。采用畸变校正扫描透射电镜和三维原子探针层析成像技术识别石墨烯空缺中的单个镍原子点。同时还介绍了电化学 CO2还原装置与在线气相色谱联用的详细设置。与金属镍相比, 镍单原子催化剂显著改善 CO2的还原和抑制 H2演化侧反应。

扫描电镜 (SEM), 扫描透射电镜 (茎) 和能量色散 X 射线光谱学 (EDX) 映射图像, 显示在图 1中的形态学特征的 GS。三维原子探针层析成像 (3 维易测) 结果显示在图 2中, 用于直接识别单个 Ni 站点分布及其邻近的化学环境。在线电化学 GC 测量的设置和结果显示在图 3中, 用于量化 CO2RR 气体产品。
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Watch this Scientific Journal Video about Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction at JoVE.com

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

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

在这里, 我们提出了一个协议, 以合成和电化学测试的过渡金属在石墨烯空缺协调合作的活性中心, 选择性二氧化碳还原到一氧化碳的水溶液。

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

synthesis-performance-characterizations-transition-metal-single-atom

Research

JoVE Journal

Chemistry

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

18.0K 次观看.  Harvard University. 在这里, 我们提出了一个协议, 以合成和电化学测试的过渡金属在石墨烯空缺协调合作的活性中心, 选择性二氧化碳还原到一氧化碳的水溶液。

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

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; therefore their preparation should be conducted under an inert atmosphere. Evaluation of the anticancer activity of these complexes can be achieved by the MTT assay.
The MTT assay is a colorimetric viability assay based on enzymatic reduction of the MTT molecule to formazan when it is exposed to viable cells. The outcome of the reduction is a color change of the MTT molecule. Absorbance measurements relative to a control determine the percentage of remaining viable cancer cells following their treatment with varying concentrations of a tested compound, which is translated to the compound anticancer activity and its IC50 values. The MTT assay is widely common in cytotoxicity studies due to its accuracy, rapidity, and relative simplicity.
Herein we present a detailed protocol for the synthesis of air sensitive metal based drugs and cell viability measurements, including preparation of the cell plates, incubation of the compounds with the cells, viability measurements using the MTT assay, and determination of IC50 values.

A method for synthesis of air-sensitive titanium and vanadium anticancer agents is described, along with the evaluation of their cytotoxic activity towards human cancer cell line by the MTT Assay.

抗癌金属配合物的合成与细胞毒性评价MTT法

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; ...

科研

化学

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

功能化的合成与表征金属 - 有机骨架

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

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

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 &#176;C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder.

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

单金属和双金属前过渡金属碳化物和氮化物纳米粒子的反相微乳液介导的合成

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

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 ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

科大-1作为香兰素的合成的非均相催化剂

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

使用Photoredox催化剂蠕虫状胶束的简便合成可见光介导的分散聚合

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

Synthesis of a Water-soluble Metal&#8211;Organic Complex Array

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.

A potential general method for the synthesis of water-soluble multimetallic peptidic arrays containing a predetermined sequence of metal centers is presented.

一个水溶性金属 - 有机络合物阵列合成

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as ...

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 ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

半导体回转金属硫框架结晶的硫醇构建块的合成

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

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 ...