这项工作主要是支持该研究所的关键技术和应用科学（ICTAS）在弗吉尼亚理工大学，弗吉尼亚理工大学研究生院的博士学者的方案支持可持续纳米技术计划，也农业部美国农业部，NIFA授权号码2010-65504-20429。作者还感谢里克·考迪尔，斯蒂芬·麦卡特尼，和W特拉维斯教会对这项工作作出的贡献。

1，纳米原纤维素制备55 <ol><li>设置一个3升三颈烧瓶中加入2升去离子水，顶置式搅拌器和pH探头。 </li><li>添加脱去木质素的牛皮纸浆，88％的亮度（20克，1％（w / v的，干重为基准）），​​2,2,6,6 - 四甲基哌啶1 - 氧基（TEMPO）（0.313克，0.1毫摩尔/克纤维素）和溴化钠（溴化钠，2.0克，1毫摩尔/克纤维素）到烧瓶中。 <ol><li>用顶置式搅拌器混合的纸浆纤维，直到纤维被分散并且没有聚集体可以在反应中可以看出。 注：分散可以通过将在水中的淤浆加入到纸浆的3升烧瓶中之前来辅助。 </li></ol></li><li>通过缓慢加入次氯酸钠（次氯酸钠51.4毫升，5毫摩尔每克的纤维素）为12％溶液至反应混合物中开始氧化。 注意：对于整个反应的一致性，使用注射器泵交付的NaClO为1.5毫升/分钟的喷射速率。 </li><li>填写第二注射器无线第氢氧化钠（NaOH，0.5M）并手动米的碱溶液到烧瓶中逐滴以维持pH值在10±0.2。 </li><li>监测pH值随时间的变化，一旦所有的纤维素可访问的羟基基团被氧化的pH值不再降低，反应完成。 </li><li>添加过量的乙醇消耗剩余的次氯酸钠。大约6毫升200标准乙醇将消耗所有100毫摩尔原次氯酸钠。 </li><li>过滤器和净化水彻底清洗氧化纤维去除试剂，直到pH为中性。使用篮式离心机或过滤一些设备，如：布氏漏斗以回收纤维。存储光纤在4°C，直到进一步使用。 注意：在完成实验后，纤维应具有的羧酸含量，如由电导滴定法测定，每克纤维的1.0〜1.5毫摩尔。应该有TEMPO氧化后在外观上，纤维的差别不大。 </li><li>创建的TEMPO氧化纸浆的3％（w / v的，干重为基准）的浆料并混合在一战国搅拌器，直到浆料变得粘稠和叶片启动，因为该悬浮液的凝胶纺丝在空气中。 注：较低浓度不作为有效的工作原纤化纤维素。 <ol><li>稀混合浆液至0.1％（重量/体积），并继续混合，直到悬浮液变成透明的。 </li></ol></li></ol> 2，层 - 层薄膜沉积为QCM-D的实验<ol><li>制备下列水溶液并调整各溶液用0.1M的NaOH至pH为10.5：含水缓冲液（水和NaOH）; 0.5％（重量/体积）的聚二甲基二氯化物（PDDA）水溶液;和0.01％（重量/体积）的木质素。调整为0.1％的NFC悬浮液的pH至8.0。 注：pH值对这些实验中被提升，因为它以前被显示，木质素吸附在一个不太凝聚状态，在碱性pH值56。 </li><li>清洁镀金的石英晶体下使用base食人鱼的解决方案[注意]制造商的建议（3:1浓NH 4 OH：H 2 O 2在60℃）10分钟。 <ol><li>冲洗晶体，纯净水，在N 2气流吹干，并立即插入石英晶体微天平流动池，以避免污染的空气。 </li></ol></li><li>通过缓冲器通过流动池，以获得谐振晶体暴露于液体的基线响应。 <ol><li>通过使石英晶体，以5分钟的PDDA溶液沉积层PDDA上的石英晶体。 </li><li> 5分钟后，切换到缓冲溶液中。 注意：此过程在步骤2.3创建单个层的响应，其中可以在不将聚合物溶液粘度的效果来确定聚合物沉积的量。 </li><li>用缓冲液R重复其它聚合物的吸附按照以下顺序樱雪各步骤之间：PDDA（+）（步骤2.3.1）;木质素（ - ）; PDDA（+）;和NFC（ - ）。重复循环4倍沉积聚合物和纳米粒子的共16层。 </li></ol></li></ol> 3，层 - 层薄膜沉积为AFM和椭偏实验<ol><li>胶云母的圆盘，以使用快速环氧树脂粘合剂的玻璃显微镜载片上。粘合剂固化后，贴上一块胶布云母光盘。剥离胶带离开造成的云母表面切割。 <ol><li>清洗硅片酸食人鱼[注意事项]（3:1 H 2 SO 4：H 2 O 2）20分钟后，以层沉积之前显著冲洗水。 </li></ol></li><li>用在2.1制备的溶液，浸要么是连接到在下面的协议在2.3.3中概述的相同顺序的各溶液载玻片或刚清洗干净的硅晶片新鲜剥离云母。 注意：此方法将创建PO层lymers在每个这些表面可以分别插入的原子力显微镜或椭率计，的。 </li><li>图像的淀积层用原子力显微镜。采集样本的图像时使用间歇接触模式和悬臂与10纳米半径硅尖（弹簧常数42牛顿/米）。设置扫描尺寸为2.5×2.5微米，扫描点为512和10积分增益来收集特定的样本图像。 </li><li>用于与干燥的LbL膜的AFM层的厚度测量，使用柔软的塑料移液管尖端和疤痕的线横跨在云母表面制备的LbL膜的表面上。 </li><li>存款LBL薄膜椭偏测量到硅片上。测量干膜厚度与相位调制椭偏仪在632.8nm使用的发生率模式的多角度的波长。变化85°和65°之间的角度在1°的间隔。 </li></ol> 4，制备自由站立LBL电影<ol><li>一个切醋酸纤维素25.4 x7.6毫米矩形（CA）膜（DS 2.5）的为0.13毫米厚，并连接到自动瓢手臂。 注：DS 3.0的乙酸纤维素是不溶于丙酮，以便DS 2.5，优选以恢复层状薄膜。 </li><li>根据浓度和pH值，在步骤2.1填写各500毫升烧杯中以PDDA，木质素和纳米纤维素的解决方案。 <ol><li>填三个额外的烧杯用含水缓冲液作为每个沉积循环冲洗溶液来使用。 </li><li>编程瓢手臂继续在同一顺序中所报2.3.3。 注意：使用每个相应聚合物溶液后不同的清洗溶液是很重要的，因为在层 - 层的过程中，一些聚合物是不紧密结合到表面将解吸。漂洗溶液的交叉污染，导致迅速的聚电解质复合物，它可吸附的“缺陷”，以在膜表面析出。 </li></ol></li><li>更改解决方案在250次定期烧杯中，他们开始出现，因为胶体复合体的混浊。一种选择是通过使用蠕动泵，以提供新鲜的溶液或缓冲液，以定制的聚氯乙烯（PVC）容器的入口和出口以自动化解决方案的更新。 注：在容器中搅动解决方案帮助提高聚电解质的扩散到表面。 </li><li>小心地修剪干燥样品的边缘与剪刀露出CA边缘，并放入有盖玻璃培养皿装有丙酮溶解的CA。 注：两个薄膜本实验从CA的前面和背面后分离。 </li><li>浸泡隔离薄膜在丙酮中24小时，反复冲洗胶片用丙酮最大限度地去除残留的CA。 </li></ol>

作者什么都没有透露。

纳米纤维素的制备对于纳米纤维素制造的纸浆纤维的成功氧化是必要的轻便颤动。氧化是通过使用次氯酸钠，在已知量基于纤维素的量应缓慢加入控制。原因之一限定氧化源自长时间的次氯酸钠溶液的储存。这降低了氧化效率可以在反应过程中应注意;纸浆液应通过在成功的氧化反应变成浅黄色的颜色，一部分的方式。如果这不发生，该纤维的羧酸含量通常低于水平，使易于原?...

有极大的兴趣，从生物质中获得额外的化学品和燃料，如碳光合作用过程中螯合植物是当前的CO 2循环的一部分。大部分固碳（42-44％）是在纤维素的形式，一个β1-4-连接的吡喃葡萄糖单元组成的聚合物;当水解时，葡萄糖可被用作主要的反应物用于发酵成基于酒精的燃料。然而，木本植物细胞壁架构已经进化了数千年创造能抵抗降解在自然环境中1的材料。这种稳定延续到工业加工的木质材料，如能源作物使得纤维素难以进入，隔离和分解成葡萄糖。仔细看看次生壁的超微结构表明，它是嵌入在木质素和下摆的无定形基质分层次晶纤维素微纤维组成的聚合物纳米复合材料icelluloses 2-4。纵取向的纤维素微纤丝的直径为约2-5纳米，这是与其它杂多糖聚合在一起，形成更大的纤维束5的单元。原纤维束被嵌入在木质素半纤维素复合体的苯基丙醇单位的某些联系到其它杂多糖像glucoronoxylan 4的无定形聚合物构成。此外，这种结构进一步组织成层，或片状结晶，整个木质化次生壁6-8。酶，如纤维素酶，有一个非常困难的时间的细胞壁内访问纤维素，因为它被发现在它的原纤维形式和嵌入在木质素。真正使生物基燃料和可再生化学平台成为现实的关键是开发流程，在经济允许的纤维素的原生形式的糖化。 新的化学和成像技术正在帮助在ST参与纤维素9,10的糖化的机制UDY。许多工作都集中在拉曼共焦成像11和原子力显微镜12来研究细胞壁的化学组成和形态。如果能够紧跟脱木素和糖化机制是一个显著的进步，影响纤维素转化为葡萄糖。模型表面的纤维素糖化，通过测量酶动力学速率与石英晶体微量天平与散热监控（QCM-D）13分析。然而，原生细胞壁如上面所指出的高度复杂的，并且这创造了不同的转换过程是如何改变植物细胞壁（聚合物的分子量，化学连接，孔隙率）的结构，歧义。细胞壁物质与已知结构组成的自立式机型会解决这个问题，并允许样品融入最先进的化学和想象力NG设备。 有细胞壁模型的缺乏和几个可用的可归类为聚合物材料的共混物和再生纤维素或细菌纤维素14，酶促聚合木质素-多糖复合物15-17，或模型表面18-21。一些开始像细胞壁模型是含有木质素前体或类似物的纤维素在其微纤丝的形式存在酶聚合的样品。然而，这些材料遭受缺乏组织层结构。为创造纳米复合材料与有组织架构的简单途径是层-层（层层）组装技术，基于聚合物或纳米粒子具有互补收费或官能团而形成有组织的多层复合膜22-25连续吸附。高强度自立混合纳米复合材料，由聚合物层层沉积和做呐noparticles，已报告了科托夫等人 26-30。在许多其它应用中，膜的LbL还研究了其在治疗递送31，燃料电池膜32,33，电池34，和木质纤维素纤维表面改性35-37的潜在用途。在纳米纤维素的近期利益基复合材料导致纳米微晶纤维素（CNC）的制备纤维素纤维的硫酸水解，带正电荷的聚电解质层层38-43多层膜的制备和表征。类似的研究也已开展与海洋tunicin和阳离子聚电解质44，CNC和木葡聚糖45获得纳米微晶纤维素，以及CNC和壳聚糖46。层层叠层形成羧化纳米原纤维素（NFCS），由纸浆纤维与阳离子聚电解质的高压均质得到的也一直研究47-49。的制备，性能和应用的CNC和纳米原纤维详细50-53审阅。 本研究涉及层层技术，因为在一个有序的方式组装孤立的木质纤维素聚合物（如纳米纤维素和木质素）作为实现仿生木质纤维复合材料层状结构的第一步一种潜在方式的检验。的层层技术被选为其良性的加工条件，诸如环境温度，压力，和作为溶剂的水，这是自然形成的复合材料54的条件。在本研究中，我们报告的多层叠合构木构件，即从四甲基哌啶1 - 氧基（TEMPO），纸浆和分离木质素的媒介氧化成自由站立的层状膜的纤维素微纤丝的。两种不同的木质素是从不同的提取技术使用，一个技术从邻木质素rganosolv制浆过程和分离过程中的其它的木质素分离自球磨​​以较少的修改。这些化合物相结合，与合成的聚电解质在此初步研究证明使稳定的自立式薄膜的体系结构类似于天然细胞壁的可行性。

<table border="0" cellpadding="0" cellspacing="0" width="699">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">sulfate pulp</td>
			<td style="width:108px;">Weyerhaeuser&#160;</td>
			<td style="width:119px;">donated</td>
			<td style="width:215px;">brightness level of 88%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">organosolv lignin</td>
			<td style="width:108px;">Sigma Aldrich</td>
			<td style="width:119px;">371017</td>
			<td>discontinued</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:257px;">hardwood milled wood lignin</td>
			<td style="width:108px;">see reference in paper</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">polydiallyldimethylammonium chloride&#160;</td>
			<td style="width:108px;">Sigma Aldrich</td>
			<td style="width:119px;">409022</td>
			<td style="width:215px;">Mn = 7.2&#215;10^4, Mw=2.4&#215;10^5</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO)&#160;</td>
			<td style="width:108px;">Sigma Aldrich</td>
			<td style="width:119px;">214000</td>
			<td>catalytic oxidation of primary alcohols to aldehydes with a purity of 98%, molecular weight is 156.25g/mol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">sodium bromide</td>
			<td style="width:108px;">Sigma Aldrich</td>
			<td style="width:119px;">S4547</td>
			<td>purity &#8805;99.0%, molecular weight 102.89</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">sodium hypochlorite</td>
			<td style="width:108px;">Sigma Aldrich</td>
			<td style="width:119px;">425044</td>
			<td>reagent grade, available chlorine 10~15%, molecular weight 74.44g/mol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">sodium hydroxide</td>
			<td style="width:108px;">VWR</td>
			<td style="width:119px;">BDH7221-4</td>
			<td>0.5N aqueous solution, density 1.02g/ml, molecular weight 40 g/mol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">sodium hydroxide</td>
			<td style="width:108px;">Acros Organics</td>
			<td style="width:119px;">AC12419-0010</td>
			<td>0.1N aquesous solution, specific gravity 1.0 g/ml, molecular weight 40 g/mol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">ammonium hydroxide</td>
			<td style="width:108px;">Acros Organics</td>
			<td style="width:119px;">AC39003-0025</td>
			<td>25% solution in water, pH 13.6, density 0.89, molecular weight 35.04 g/mol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">hydrogen peroxide</td>
			<td style="width:108px;">Fisher Scientific</td>
			<td style="width:119px;">H325-100</td>
			<td>30.0~32.0% certified ACS, pH 3.3, density 1.11</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">Mica sheets</td>
			<td style="width:108px;">TED Pella</td>
			<td style="width:119px;">NC9655733</td>
			<td>Pelco, grade V5, 10&#215;40mm, 23mm T, minimum air and bubbles, very clean</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">sulfuric acid</td>
			<td style="width:108px;">Fisher Scientific</td>
			<td style="width:119px;">A300-212</td>
			<td>95.0~98.0 w/w%, certified ACS plus, molecular weight 98.08 g/mol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">cellulose acetate</td>
			<td style="width:108px;">McMaster Carr</td>
			<td style="width:119px;">8564K44</td>
			<td>degree of substitution 2.5</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:257px;">ethanol</td>
			<td style="width:108px;">Decon Laboratories</td>
			<td style="width:119px;">04-355-223</td>
			<td>200 proof (100%), USP</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">acetone</td>
			<td style="width:108px;">Fisher Scientific</td>
			<td style="width:119px;">A18-4</td>
			<td>purity &#8805;99.5%, certified ACS reagent grade, density 0.79 g/ml, molecular weight 58.08 g/mol</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:257px;">syringy pump</td>
			<td style="width:108px;">Harvard Apparatus</td>
			<td style="width:119px;">552226</td>
			<td>pump 22 infusion/withdraw with standard syringe holder, flow rate 0.002 ul/h~55.1ml/min</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">Mill-Q water purification system</td>
			<td style="width:108px;">EMD Millipore</td>
			<td style="width:119px;">D3-UV</td>
			<td>Direct-Q, UV, water conductivity 18.5 M&#937; cm with 20 liter reservair</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">pH meter</td>
			<td style="width:108px;">Mettler Toledo</td>
			<td style="width:119px;"></td>
			<td style="width:215px;">SeverMulti</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">balance</td>
			<td style="width:108px;">Mettler Toledo</td>
			<td style="width:119px;">AB135-S</td>
			<td>accuracy 0.1mg</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:257px;">atomic force microscope</td>
			<td style="width:108px;">Asylum Research</td>
			<td style="width:119px;"></td>
			<td>MFP-3D, Olympic fluorescent microscope stage</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:257px;">ellipsometer</td>
			<td style="width:108px;">Beaglehole Instruments</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">fiber centrifuge</td>
			<td style="width:108px;">unknown</td>
			<td style="width:119px;"></td>
			<td>basket style centrifuge</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">Warring blender</td>
			<td style="width:108px;">Warring</td>
			<td style="width:119px;"></td>
			<td>Commercial</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">ultrasonic processor</td>
			<td style="width:108px;">Sonics</td>
			<td style="width:119px;"></td>
			<td>Sonics 750W, sound enclosure</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:257px;">Quartz crystal microbalance with dissipation monitoring (QCM-D)</td>
			<td style="width:108px;">Q-Sense Inc.&#160;</td>
			<td style="width:119px;">E4</td>
			<td>measure fundamental frequency of 5MHz, and monitor odd number overtones/harmonics from 3~13, use gold-coated piezoelectric quartz crystals</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:257px;">automatted dipper arm</td>
			<td style="width:108px;">Lynxmotion</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

towards biomimicking wood: fabricated free-standing films of nanocellulose, lignin, and a synthetic polycation

木质材料是由含有层状次生细胞壁多糖和木质素的结构的聚合物组成的植物细胞壁。层 - 层（层层）装配方法，其依赖于从水溶液中带相反电荷的分子的装配来建立木质素和氧化nanofibril纤维素（NFC）的孤立木聚合物的一个独立的复合膜。为方便这些带负电荷的聚合物的组装，带正电荷的聚电解质，聚（diallyldimethylammomium氯化物）（PDDA），被用来作为连接层，以创建该简化模型的细胞壁。分层吸附过程是用石英晶体微量天平与散热监控（QCM-D）和椭偏仪定量研究。结果表明，每一层吸附层的质量/厚度增加，层的总数的函数。吸附层的表面覆盖度，研究了原子力显微镜（AFM）。与木质素在所有的沉积循环的表面的完全覆盖，发现该系统，但是，表面覆盖由NFC随层数。吸附过程进行了250个周期（500个双层）的醋酸纤维素（CA）的衬底。透明自由站立LBL组装纳米复合薄膜，获得当CA衬底后溶解于丙酮中。断裂横截面的扫描电子显微镜（SEM）显示出层状结构，并且每个吸附循环（PDDA-木质素PDDA-NC）的厚度估计为17纳米的研究中使用了两种不同类型的木素。数据表明与高度控制的体系结构，其中纳米纤维素和木质素在空间上沉积的纳米级（聚合物 - 聚合物纳米复合材料），类似的是，在本机细胞壁观察到的膜。

木质结构聚合物膜的制备QCM-D解析木质素的层层吸附，NFC和PDDA被实时地在2涉及两种类型的木质素的不同实验监测与QCM-D。这种分析方法是非常敏感的检测频率变化时的分子吸附到石英的表面图1包含在一个沉积循环，其中包括两个双层（PDDA的QCM-D反应的详细描述：HMWL和PDDA： NC）。该数据表示在频率和第七泛音（仪器检测的基频和3-13奇次谐波泛音）的损耗归一化的变...

Watch this Scientific Journal Video about Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation at JoVE.com

Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

本研究的目的是使用纳米纤维素纤维的层 - 层组装和分离木质素从稀的水性悬浮液组合，以形成合成的植物细胞壁组织。石英晶体微量天平和原子力显微镜的表面测量技术被用来监测聚合物 - 聚合物纳米复合材料的形成。

朝仿生学木：纳米纤维素，木质素的装配式自由站立电影和合成聚阳离子

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and ...

towards-biomimicking-wood-fabricated-free-standing-films

Research

JoVE Journal

Chemistry

16.4K 次观看.  Virginia Tech. 本研究的目的是使用纳米纤维素纤维的层 - 层组装和分离木质素从稀的水性悬浮液组合，以形成合成的植物细胞壁组织。石英晶体微量天平和原子力显微镜的表面测量技术被用来监测聚合物 - 聚合物纳米复合材料的形成。 

视频: Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and scalable technique efficiently functionalizes metallic nanoparticles with thiol-ligands in a miscible water/organic solvent mixture allowing for rapid grafting of thiol groups onto the gold nanoparticle surface. The hydrophobic ligands on the nanoparticles then quickly phase separate the nanoparticles from the aqueous based suspension and confine them to the air-fluid interface. This drives the ligand-capped nanoparticles to form monolayer domains at the air-fluid interface.&#160; The use of water-miscible organic solvents is important as it enables the transport of the nanoparticles from the interface onto template-free substrates.&#160; The flow is mediated by a surface tension gradient3,4 and creates macroscopic, high-density, monolayer nanoparticle-ligand films.&#160; This self-assembly technique may be generalized to include the use of particles of different compositions, size, and shape and may lead to an efficient assembly method to produce low-cost, macroscopic, high-density, monolayer nanoparticle films for wide-spread applications.

A simple, robust and scalable technique to functionalize and self-assemble macroscopic nanoparticle-ligand monolayer films onto template-free substrates is described in this protocol.

一种技术，功能化和自组装纳米宏观 - 配体单层膜模板上无基材

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and ...

科研

化学

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

原子定义模板复合氧化物薄膜的外延生长

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

Fabrication of Large-area Free-standing Ultrathin Polymer Films

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films. Typically, ultrathin films are prepared using either sacrificial layers, which may damage the film or affect its mechanical properties, or they are made on freshly cleaved mica, a substrate that is difficult to scale. Further, the size of ultrathin film is typically limited to a few square millimeters. In this method, we modify a surface with a polyelectrolyte that alters the strength of adhesion between polymer and deposition substrate. The polyelectrolyte can be shown to remain on the wafer using spectroscopy, and a treated wafer can be used to produce multiple films, indicating that at best minimal amounts of the polyelectrolyte are added to the film. The process has thus far been shown to be limited in scalability only by the size of the coating equipment, and is expected to be readily scalable to industrial processes. In this study, the protocol for making the solutions, preparing the deposition surface, and producing the films is described.

We describe a method for the fabrication of large-area (up to 13 cm diameter) and ultrathin (as thin as 8 nm) polymer films. Instead of using a sacrificial interlayer to delaminate the film from its substrate, we use a self-limiting surface treatment suitable for arbitrarily large areas.

大面积的制造自立性的超薄聚合物薄膜

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films.  Typically, ultrathin films are prepared ...

From Constructs to Crystals &#8211; Towards Structure Determination of &#946;-barrel Outer Membrane Proteins

Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% percent of known structures. There are two types of membrane proteins, &#945;-helical and &#946;-barrel. While &#945;-helical membrane proteins can be found in nearly all cellular membranes, &#946;-barrel membrane proteins can only be found in the outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria. One common bottleneck in structural studies of membrane proteins in general is getting enough pure sample for analysis. In hopes of assisting those interested in solving the structure of their favorite &#946;-barrel outer membrane protein (OMP), general protocols are presented for the production of target &#946;-barrel OMPs at levels useful for structure determination by either X-ray crystallography and/or NMR spectroscopy. Here, we outline construct design for both native expression and for expression into inclusion bodies, purification using an affinity tag, and crystallization using detergent screening, bicelle, and lipidic cubic phase techniques. These protocols have been tested and found to work for most OMPs from Gram-negative bacteria; however, there are some targets, particularly for mitochondria and chloroplasts that may require other methods for expression and purification. As such, the methods here should be applicable for most projects that involve OMPs from Gram-negative bacteria, yet the expression levels and amount of purified sample will vary depending on the target OMP.

From Constructs to Crystals &amp;#8211; Towards Structure Determination of &amp;#946;-barrel Outer Membrane Proteins

&#946;-barrel outer membrane proteins (OMPs) serve many functions within the outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts. Here, we hope to alleviate a known bottleneck in structural studies by presenting protocols for the production of &#946;-barrel OMPs in sufficient quantities for structure determination by X-ray crystallography or NMR spectroscopy.

从构造到晶体 - 迈向β桶外膜蛋白的结构解析

Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% ...

Highly Stable, Functional Hairy Nanoparticles and Biopolymers from Wood Fibers: Towards Sustainable Nanotechnology

Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While metal-based nanoparticles are associated with synthetic and environmental hassles, cellulose introduces a green, sustainable alternative for nanoparticle synthesis. Here, we present the chemical synthesis and separation procedures to produce new classes of hairy nanoparticles (bearing both amorphous and crystalline regions) and biopolymers based on wood fibers. Through periodate oxidation of soft wood pulp, the glucose ring of cellulose is opened at the C2-C3 bond to form 2,3-dialdehyde groups. Further heating of the partially oxidized fibers (e.g., T = 80 &#176;C) results in three products, namely fibrous oxidized cellulose, sterically stabilized nanocrystalline cellulose (SNCC), and dissolved dialdehyde modified cellulose (DAMC), which are well separated by intermittent centrifugation and co-solvent addition. The partially oxidized fibers (without heating) were used as a highly reactive intermediate to react with chlorite for converting almost all aldehyde to carboxyl groups. Co-solvent precipitation and centrifugation resulted in electrosterically stabilized nanocrystalline cellulose (ENCC) and dicarboxylated cellulose (DCC). The aldehyde content of SNCC and consequently surface charge of ENCC (carboxyl content) were precisely controlled by controlling the periodate oxidation reaction time, resulting in highly stable nanoparticles bearing more than 7 mmol functional groups per gram of nanoparticles (e.g., as compared to conventional NCC bearing &#60;&#60; 1 mmol functional group/g). Atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) attested to the rod-like morphology. Conductometric titration, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), electrokinetic-sonic-amplitude (ESA) and acoustic attenuation spectroscopy shed light on the superior properties of these nanomaterials.

Synthesis schemes to prepare highly stable wood fiber-based hairy nanoparticles and functional cellulose-based biopolymers have been detailed.

高稳定性，功能性毛纳米粒子和木纤维生物聚合物：迈向可持续纳米技术

Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While ...

Reactive Vapor Deposition of Conjugated Polymer Films on Arbitrary Substrates

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. Conductive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-propylenedioxythiophene) (PProDOT), and a semiconducting polymer, poly(thieno[3,2-b]thiophene) (PTT), were deposited on unconventional highly-disordered and textured substrates with high surface areas, such as paper, towels and fabrics. This reported deposition chamber is an improvement of previous vapor reactors because our system can accommodate both volatile and nonvolatile monomers, such as 3,4-propylenedioxythiophene and thieno[3,2-b]thiophene. Utilization of both solid and liquid oxidants are also demonstrated. One limitation of this method is that it lacks sophisticated in situ thickness monitors. Polymer coatings made by the commonly used solution-based coating methods, such as spin-coating and surface grafting, are often not uniform or susceptible to mechanical degradation. This reported vapor phase deposition method overcomes those drawbacks and is a strong alternative to common solution-based coating methods. Notably, polymer films coated by the reported method are uniform and conformal on rough surfaces, even at a micrometer scale. This feature allows for future application of vapor deposited polymers in electronics devices on flexible and highly textured substrates.

This paper presents a protocol for reactive vapor deposition of poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), and poly(thieno[3,2-b]thiophene) films on glass slides and rough substrates, such as textiles and paper.

任意基底上共轭聚合物薄膜的反应气相沉积

We demonstrate a method of conformally coating conjugated polymers on arbitrary substrates using a custom-designed, low-pressure reaction chamber. ...

Gene-therapy Inspired Polycation Coating for Protection of DNA Origami Nanostructures

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in physiological fluids induce denaturation and degradation of self-assembled DNA nanostructures. In non-viral gene delivery, enzymatic degradation of DNA is overcome by the encapsulation of the negatively charged DNA in a cationic shell. Herein, inspired by gene delivery advancements, a simple, one-step and robust methodology is presented for the stabilization of DNA origami nanostructures by coating them with chitosan and linear polyethyleneimine. The polycation coating efficiently protects DNA origami nanostructures in Mg-depleted and nuclease-rich media. This method also preserves the full addressability of enzyme- and aptamer-based functionalization of DNA nanostructures.

Here, a protocol for the protection of DNA origami nanostructures in Mg-depleted and nuclease-rich media using natural cationic polysaccharide chitosan and synthetic linear polyethyleneimine (LPEI) coatings is presented.

基因治疗诱导聚化涂层保护 dna 折纸纳米结构

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in ...

Niobium Oxide Films Deposited by Reactive Sputtering: Effect of Oxygen Flow Rate

Reactive sputtering is a versatile technique used to form compact films with excellent homogeneity. In addition, it allows easy control over deposition parameters such as gas flow rate that results in changes on composition and thus in the film required properties. In this report, reactive sputtering is used to deposit niobium oxide films. A niobium target is used as metal source and different oxygen flow rates to deposit niobium oxide films. The oxygen flow rate was changed from 3 to 10 sccm. The films deposited under low oxygen flow rates show higher electrical conductivity and provide better perovskite solar cells when used as electron transport layer.

Here, we present a protocol for niobium oxide films deposition by reactive sputtering with different oxygen flow rates for use as an electron transport layer in perovskite solar cells.

活性溅射沉积的氧化氮薄膜：氧气流速效应

Reactive sputtering is a versatile technique used to form compact films with excellent homogeneity. In addition, it allows easy control over deposition ...

Applying Dynamic Strain on Thin Oxide Films Immobilized on a Pseudoelastic Nickel-Titanium Alloy

Direct alteration of material structure/function through strain is a growing area of research that has allowed for novel properties of materials to emerge. Tuning material structure can be achieved by controlling an external force imposed on materials and inducing stress-strain responses (i.e., applying dynamic strain). Electroactive thin films are typically deposited on shape or volume tunable elastic substrates, where mechanical loading (i.e., compression or tension) can affect film structure and function through imposed strain. Here, we summarize methods for straining n-type doped titanium dioxide (TiO2) films prepared by a thermal treatment of a pseudo-elastic nickel-titanium alloy (Nitinol). The main purpose of the described methods is to study how strain affects electrocatalytic activities of metal oxide, specifically hydrogen evolution and oxygen evolution reactions. The same system can be adapted to study the effect of strain more broadly. Strain engineering can be applied for optimization of a material function, as well as for design of adjustable, multifunctional (photo)electrocatalytic materials under external stress control.

Dynamic, tensile strain is applied on TiO2 thin films to study the effects of strain on electrocatalysis, specifically proton reduction and water oxidation. TiO2 films are prepared by thermal treatment of the pseudo-elastic NiTi alloy (Nitinol).

将动态应变应用于固定在伪弹性镍钛合金上的薄氧化物薄膜

Direct alteration of material structure/function through strain is a growing area of research that has allowed for novel properties of materials to ...

Designed for Molecular Recycling: A Lignin-Derived Semi-aromatic Biobased Polymer

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make a positive effort to solve the issue of polymer materials in the disposal phase after the use phase. In this paper, the production of biobased semi-aromatic polyesters, which can be extracted entirely from biomass such as lignin, is described and visualized. The polymer poly-S described in this paper has thermal properties similar to certain commonly used plastics, such as PET. We developed a Green Knoevenagel reaction, which can efficiently produce monomers from aromatic aldehydes and malonic acid. This reaction has been proven to be scalable and has a remarkably low calculated E-factor. These polyesters with ligno-phytochemicals as a starting point show an efficient molecular recycling with minimal losses. The polyester poly(dihydrosinapinic acid) (poly-S) is presented as an example of these semi-aromatic polyesters, and the polymerization, depolymerization, and re-polymerization are described.

An example of a closed-loop approach towards a circular materials economy is described here. A whole sustainable cycle is presented where biobased semi-aromatic polyesters are designed by polymerization, depolymerization, and then re-polymerized with only slight changes in their yields or final properties.

专为分子回收而设计：一种褐宁衍生的半芳烃生物基聚合物

The development of chemically recyclable biopolymers offers opportunities within the pursuit of a circular economy. Chemically recyclable biopolymers make ...