这项工作得到中国国家基础研究计划 (2014CB932400)、中国国家自然科学基金 (51525204 号和 U1607206) 和深圳基础研究项目 (no。JCYJ20150529164918735)。此外, 我们还要感谢二价酸福辛普利拉-Allnex 有限公司和 JSR 公司, 为亲切提供聚氨酯和苯乙烯丁橡胶, 分别。

1. 制备 1 wt% 22、66-Tetramethylpiperidin-1-oxyl (速度) 介导的氧化纤维素碳纤维 (TOCN) 溶胶
注: 溶胶被定义为在连续液体介质中非常小的固体颗粒的胶体悬浮。
<ol><li>悬浮66.7 克 Nadelholz 漂白硫酸盐浆 (NBKP, 含12克纤维素) 在700毫升的去离子 (DI) 水与机械搅拌器在 300 rpm 为20分钟。</li>
	<li>将20毫升水速溶液 (含0.15 克速度) 和20毫升水 NaBr 溶液 (含1.5 克 NaBr) 缓慢地添加到上述 NBKP 悬浮14,15。</li>
	<li>将上述悬浮液的 pH 值调整到大约 10.5 (用 pH 值计), 慢慢加入3.0 米氢氧化钠溶液。</li>
	<li>慢慢地添加大约63.8 克水次氯酸钠溶液 (与 6-14 wt% 活性氯) 与吸管到上述混合物开始速度介导的氧化。</li>
	<li>添加次氯酸钠时, 继续添加氢氧化钠溶液, 使系统的 pH 值保持在10.0 到10.5 之间。这个过程大约需要2.5 小时。</li>
	<li>用 di 水冲洗速度介导的氧化纤维素纤维3次 (每次1200毫升的底水), 以除去残留的次氯酸钠、氢氧化钠和其他化学物质。</li>
	<li>用强大的机械搅拌器处理糊状物, 将氧化纤维素纤维分解成纳米纤维。仔细地进行机械处理几次, 加上等量的水。最后, 获得了 1 wt% 速度介导的氧化纤维素碳纤维 (TOCN) 溶胶。TOCNs 的直径为4到 ~ 6 nm, 长度为0.5 到 ~ 2 微米。</li>
	<li>将 1 wt% TOCN 溶胶保存在4摄氏度 (纤维素纤维在室温下趋于腐烂)。</li>
</ol>2. TOCN-苯乙烯丁二烯橡胶 (SBR) 混合溶胶的制备
<ol><li>在11.7 毫升玻璃容器中加入0.21 克 SBR 胶体 (48.5 wt%) 到10克 1 wt% TOCN 溶胶 (步骤 20)。</li>
	<li>搅动上述混合物为3分钟与漩涡搅拌机在功率水平6达到均匀地分散的溶胶. 在使用前将上述混合物溶胶保存在4摄氏度。</li>
</ol>3. TOCN2混合溶胶的制备
<ol><li>在1毫升玻璃容器中添加0.1 克的2纳米粒子 (平均粒径为 20 nm) 到10克的 20 wt% TOCN 溶胶中。</li>
	<li>将上述混合物与均质机搅拌10分钟, 以达到均匀混合的溶胶. 间歇性地执行这10分钟过程, 因为过程中产生了大量的热量, 导致温度升高, 这可能会降低 TOCNs。使用前将混合物溶胶贮存在4摄氏度。</li>
</ol>4. TOCN 表面氧化炭纤维 (SOCF) 混合溶胶的制备
<ol><li>回流1.7 克碳纤维 (300 目, 直径5.5 到 ~ 6.0 微米和长度约50微米) 在150毫升浓硝酸在60摄氏度为 6 h 达到 SOCF16。将上述 SOCF 的0.01 克添加到20毫升玻璃容器内10克的 1 wt% TOCN 溶胶中。</li>
	<li>摇动混合上述混合物, 并超油脂实验混合物5分钟, 以达到均匀混合溶胶. 在使用前将混合物溶胶保存在4摄氏度。</li>
</ol>5. 从 1 wt% TOCN 溶胶 (表示 MHM-TOCN) 制备 Microhoneycomb 巨石
<ol><li>加载聚丙烯 (PP) 管 (内径为13毫米, 外径为15毫米, 长度为150毫米), 并填充管的底部5厘米部分13。</li>
	<li>负载一定量 (每次不控制量, 但通常大于2.7 毫升, 以确保随后的切割过程) 的 1 wt% TOCN 溶胶进入上述 PP 管含有玻璃珠。 注: TOCN 溶胶直接填充在聚丙烯管中, 不注入玻璃珠, 用于研究单向冻结过程中所涉及的距离效应。在这种情况下, TOCN 溶胶的用量为11毫升。</li>
	<li>小心删除在溶胶加载过程中可能产生的气泡。在使用前, 将含有 TOCN 溶胶的 PP 管保持在4摄氏度。</li>
	<li>将含有 TOCN 溶胶的上述 PP 管附着在用于单向冻结的浸渍机上。设置相关参数并开始将 PP 管浸入到含有液态氮气 (-196 °c) 的热水壶中, 其恒定速度为50厘米 h-1 (图 1)。</li>
	<li>用锯子切割 PP 管部分, 将冷冻 TOCN 溶胶部分分成几个部分。冷冻干燥这些部分与冷冻干燥机在-10 °c 1 天, 然后在-5 °c 1 天, 最后在0°c 1 天。MHM TOCN 以白色石柱 (图 1) 获得。</li>
</ol>6. 从 TOCN-SBR 混合溶胶 (表示 MHM-TOCN/SBR) 和 TOCN2混合溶胶 (表示 MHM-TOCN/Microhoneycomb2 ) 中制备巨石
<ol><li>负载聚丙烯 (PP) 管 (内径为13毫米, 外径为15毫米, 长度为150毫米), 玻璃珠, 填补了底部 5 cm 部分的管。 注: 玻璃珠用于覆盖不稳定冰晶生长的区域, 从而达到样品的均匀形貌。玻璃珠的尺寸和表面性质都不影响结果样品的形貌。</li>
	<li>加载一定量 (每次不控制金额, 但通常大于2.7 毫升, 以确保随后的切割过程) TOCN-SBR 混合溶胶或 TOCN2混合溶胶进入含有玻璃珠的 PP 管中。</li>
	<li>小心删除在溶胶加载过程中可能产生的气泡。在使用前, 将含有上述混合溶胶的 PP 管保持在4摄氏度。</li>
	<li>将含有上述混合溶胶的 PP 管附着在用于单向冻结的浸渍机上。设置相关参数, 并开始将 PP 管浸入一个含有液氮 (-196 °c) 的水箱中, 其恒定速度为20厘米 h-1。</li>
	<li>用锯切 PP 管部分, 将冷冻 TOCN-SBR 混合溶胶部分裂成几部分。</li>
	<li>冷冻干燥这些部分与冷冻干燥机在-10 °c 1 天, 然后在-5 °c 1 天, 最后在0°c 1 天。MHM-TOCN/SBR 和 MHM TOCN/2作为白石柱获得。</li>
</ol>7. TOCN-SOCF 混合溶胶制备 Microhoneycomb 巨石 (指 MHM TOCN/SOCF)
<ol><li>装载聚丙烯 (PP) 管 (内径为13毫米, 外径为15毫米, 长度为150毫米), 玻璃珠, 填充管底部5厘米的部分。</li>
	<li>负载一定量 (每次不控制量, 但通常大于2.7 毫升, 以确保随后的切割过程) 的 TOCN-SOCF 混合溶胶进入上述 PP 管含有玻璃珠。</li>
	<li>小心删除在溶胶加载过程中可能产生的气泡。在使用前, 将含有上述混合溶胶的 PP 管保持在4摄氏度。</li>
	<li>将含有上述混合溶胶的 PP 管附着在用于单向冻结的浸渍机上。设置相关参数, 并开始将 PP 管浸入一个含有液氮 (-196 °c) 的水箱中, 其恒定速度为20厘米 h-1。</li>
	<li>用锯子切割 PP 管部分, 将冷冻 TOCN SOCF 溶胶部分裂成几部分。冷冻干燥这些部分与冷冻干燥机在-10 °c 1 天, 然后在-5 °c 1 天, 最后在0°c 1 天。MHM-TOCN/SOCF 是一个白色灰色的巨石。</li>
</ol>

<ol>
	<li>Nishihara, H., Mukai, S. R., Yamashita, D., Tamon, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ordered+macroporous+silica+by+ice+templating.">Ordered macroporous silica by ice templating.</a> Chem. Mater. 17, 683-689 (2005).</li><li>Mukai, S. R., Nishihara, H., Yoshida, T., Taniguchi, K., Tamon, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphology+of+resorcinol-formaldehyde+gels+obtained+through+ice-templating.">Morphology of resorcinol-formaldehyde gels obtained through ice-templating.</a> Carbon. 43 (7), 1563-1565 (2005).</li><li>Mukai, S. R., Nishihara, H., Tamon, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porous+microfibers+and+microhoneycombs+synthesized+by+ice+templating.">Porous microfibers and microhoneycombs synthesized by ice templating.</a> Catal. Surv. Asia. 10 (3-4), 161-171 (2006).</li><li>Nishihara, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+monolithic+SiO2-Al2O3+cryogels+with+inter-connected+macropores+through+ice+templating.">Preparation of monolithic SiO2-Al2O3 cryogels with inter-connected macropores through ice templating.</a> J. Mater. Chem. 16 (31), 3231-3236 (2006).</li><li>Mukai, S. R., Mitani, K., Murata, S., Nishihara, H., Tamon, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assembling+of+nanoparticles+using+ice+crystals.">Assembling of nanoparticles using ice crystals.</a> Mater. Chem. Phys. 123 (2), 347-350 (2010).</li><li>Cui, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-assembled+microhoneycomb+network+of+single-walled+carbon+nanotubes+for+solar+cells.">Self-assembled microhoneycomb network of single-walled carbon nanotubes for solar cells.</a> J. Phy. Chem. Lett. 4 (15), 2571-2576 (2013).</li><li>Xu, T., Wang, C. -. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+two-step+sintering+on+micro-honeycomb+BaTiO3+ceramics+prepared+by+freeze-casting+process.">Effect of two-step sintering on micro-honeycomb BaTiO3 ceramics prepared by freeze-casting process.</a> J. Eur. Ceram. Soc. 36 (10), 2647-2652 (2016).</li><li>Yoshida, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CO2+Separation+in+a+flow+system+by+silica+microhoneycombs+loaded+with+an+ionic+liquid+prepared+by+the+ice-templating+method.">CO2 Separation in a flow system by silica microhoneycombs loaded with an ionic liquid prepared by the ice-templating method.</a> Ind. Eng. Chem. Res. 56 (10), 2834-2839 (2017).</li><li>Mukai, S. R., Nishihara, H., Tamon, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+monolithic+silica+gel+microhoneycombs+(SMHs)+using+pseudosteady+state+growth+of+microstructural+ice+crystals.">Formation of monolithic silica gel microhoneycombs (SMHs) using pseudosteady state growth of microstructural ice crystals.</a> Chem. Commun. (7), 874-875 (2004).</li><li>Gutie&#180;rrez, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macroporous+3D+Architectures+of+Self-Assembled+MWCNT+Surface+Decorated+with+Pt+Nanoparticles+as+Anodes+for+a+Direct+Methanol+Fuel+Cell.">Macroporous 3D Architectures of Self-Assembled MWCNT Surface Decorated with Pt Nanoparticles as Anodes for a Direct Methanol Fuel Cell.</a> J. Phys. Chem. C. 111, 5557-5560 (2007).</li><li>Mukai, S. R., Nishihara, H., Tamon, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphology+maps+of+ice-templated+silica+gels+derived+from+silica+hydrogels+and+hydrosols.">Morphology maps of ice-templated silica gels derived from silica hydrogels and hydrosols.</a> Micropor. Mesopor. Mat. 116 (1-3), 166-170 (2008).</li><li>Okaji, R., Taki, K., Nagamine, S., Ohshima, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+porous+honeycomb+monolith+from+UV-curable+monomer/dioxane+solution+via+unidirectional+freezing+and+UV+irradiation.">Preparation of porous honeycomb monolith from UV-curable monomer/dioxane solution via unidirectional freezing and UV irradiation.</a> J. Appl. Polym. Sci. 125 (4), 2874-2881 (2012).</li><li>Pan, Z. -. Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellulose+nanofiber+as+a+distinct+structure-directing+agent+for+xylem-like+microhoneycomb+monoliths+by+unidirectional+freeze-drying.">Cellulose nanofiber as a distinct structure-directing agent for xylem-like microhoneycomb monoliths by unidirectional freeze-drying.</a> ACS Nano. 10 (12), 10689-10697 (2016).</li><li>Saito, T., Nishiyama, Y., Putaux, J. -. L., Vigon, M., Isogai, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Homogeneous+Suspensions+of+Individualized+Microfibrils+from+TEMPO-Catalyzed+Oxidation+of+Native+Cellulose.">Homogeneous Suspensions of Individualized Microfibrils from TEMPO-Catalyzed Oxidation of Native Cellulose.</a> Biomacromolecules. 7 (6), 1687-1691 (2006).</li><li>Saito, T., Kimura, S., Nishiyama, Y., Isogai, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellulose+Nanofibers+Prepared+by+TEMPO-Mediated+Oxidation+of+Native+Cellulose.">Cellulose Nanofibers Prepared by TEMPO-Mediated Oxidation of Native Cellulose.</a> Biomacromolecules. 8, 2485-2491 (2007).</li><li>Bekyarova, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiscale+carbon+nanotube&#8722;+carbon+fiber+reinforcement+for+advanced+epoxy+composites.">Multiscale carbon nanotube&#8722; carbon fiber reinforcement for advanced epoxy composites.</a> Langmuir. 23, 3970-3974 (2007).</li><li>Nishihara, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Study on the simultaneous control of the nanostructure and morphology of the porous materials prepared via the ice-templating method [D]. , (2005).</li><li>Zhang, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+porous+graphene+sponges+assembled+with+the+combination+of+surfactant+and+freeze-drying.">Three-dimensional porous graphene sponges assembled with the combination of surfactant and freeze-drying.</a> Nano Research. 7 (10), 1477-1487 (2014).</li><li>Tao, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+ultrahigh+volumetric+capacitance:+graphene+derived+highly+dense+but+porous+carbons+for+supercapacitors.">Towards ultrahigh volumetric capacitance: graphene derived highly dense but porous carbons for supercapacitors.</a> Sci. Rep. 3, 2975 (2013).</li></ol>

作者没有什么可透露的。

实现 MHMs 的最关键步骤是单向冻结步骤, 其间水凝固形成柱状冰晶, 并将分散体推到一边形成框架。单向冻结过程主要涉及前驱体溶胶与冷却剂之间的热传递。在我们的设置中, 使用浸渍机将含有前驱溶胶的 PP 管插入到冷却剂 (液氮) 中, 并具有恒定的速度。由于液态氮一直在蒸发, 因此在氮气液位以上产生脉动温度梯度。在接触氮气液位之前, pp 管在氮气液位以上的冷空气中不可避免地经历了热交?...

作为一种全新的材料, microhoneycomb 巨石 (指 MHM) 最近吸引了多学科领域的巨大关注1,2,3,4,5,6,7,8. MHM 最初是由美国 Mukai et . 通过改良的单向冷冻干燥 (UDF) 方法制备的, 它是一个带有蜂窝状剖面9的直微阵列的整体。MHM 具有蜂窝结构的一般优点,即, 高效镶嵌, 高强度-重量比, 低压降。此外, 与较大通道尺寸的蜂窝巨石相比, MHM 具有更大的特定表面积。UDF 方法包括冰晶的单向生长和冻结时的同时相分离。在冰晶体去除之后, 得到了由冰晶塑造的固体成分。相分离形成的形态学取决于前驱体 (溶胶或凝胶) 的固有性质, 在大多数情况下, 薄片10、光纤11和鱼骨12结构很可能形成而不是 MHMs。因此, MHMs 的形成只在有限的前体中报告, 这大大阻碍了它们的化学性质的多样性。我们最近发现, 纤维素纳米纤维具有强大的结构导向功能, 通过 UDF 过程13形成 MHM 结构。只要将纤维素纳米纤维与其他水分散组分混合, 就有可能制备出各种不同化学性质的 MHMs。此外, 它们的外部形状和通道尺寸灵活且易于控制13。因此, MHMs 有望被用作过滤器, 催化剂支持, 流型电极, 传感器和生物材料支架。
本文从纤维素纳米纤维的水分散过程中, 详细介绍了 MHMs 的基本制备技术。此外, 我们还演示了几种不同类型的复合 MHMs 的制备方法。

<table><tbody><tr><td>Nadelholz Bleached Kraft Pulp</td><td>Seioko PMC company</td><td>CSF=600</td><td></td></tr><tr><td>TEMPO</td><td>Macklin Inc.</td><td>T819129</td><td>98%</td></tr><tr><td>NaBr</td><td>Macklin Inc.</td><td>S818075</td><td>AR, 99%</td></tr><tr><td>NaClO</td><td>Aladin Inc.</td><td>S101636</td><td>6-14 wt% active chlorine basis</td></tr><tr><td>SBR colloid</td><td>JSR corp.</td><td>TRD102A</td><td>48.5 wt%</td></tr><tr><td>TiO&lt;sub&gt;2&lt;/sub&gt;</td><td>Sinopharm Chemical Reagent Co., Ltd.</td><td>A63725402</td><td>crystalline anatase phase</td></tr><tr><td>carbon fiber</td><td>Shenzhen Xian&amp;rsquo;gu Ltd.</td><td>XGCP-300</td><td></td></tr><tr><td>Nitric acid</td><td>Huada Reagent Ltd.</td><td>7697-37-2</td><td>65-68 wt%</td></tr><tr><td>Mixer</td><td>Scientific Industries, Inc</td><td>G-560</td><td>the mixer&amp;nbsp;</td></tr><tr><td>Mechanical blender</td><td>Waring Lab Ltd.</td><td>MX1000XTX</td><td>For disintegrating cellulose bundles into nanofibers.</td></tr><tr><td>Homogenizer</td><td>Scientz Ltd.</td><td>HXF-DY</td><td>For dispersing TiO&lt;sub&gt;2&lt;/sub&gt; nanoparticles</td></tr><tr><td>pH meter&amp;nbsp;</td><td>Horiba Ltd.</td><td>F-74BW</td><td></td></tr></tbody></table>

microhoneycomb monoliths prepared by the unidirectional freeze-drying of cellulose nanofiber based sols: method and extensions

单片蜂窝结构由于其高强度与重量比, 对多学科领域具有吸引力。特别地, microhoneycomb 石柱 (MHMs) 以微米级的渠道被期望作为高效率的平台为反应和分离由于他们的大表面区域。到目前为止, MHMs 是由单向冷冻干燥 (UDF) 方法, 只有从非常有限的前体制备。在此, 我们报告了一个协议, 其中包括一系列由不同的组件组成的 MHMs 可以得到。最近, 我们发现纤维素纳米纤维作为一个独特的结构导向剂的作用, 通过 UDF 过程形成 MHMs。通过将纤维素纤维与不产生 MHMs 的水溶性物质混合, 可以制备各种复合 MHMs。这极大地丰富了 MHMs 的化学组成对多功能应用。

研究了 MHM-TOCN 沿单向冻结方向的不同位置的形貌, 并在图 2中显示。随着位置远离 MHM-TOCN 的底部, 显示了一个渐进的形态学变化 (图 2,讨论)。通过引入 TOCN 溶胶中的第二组分形成均匀的混合物溶胶, 可以制备各种复合 MHMs。例如, 编写了包括 SBR (图 3a)、MHMs2 (图 3b),...

Watch this Scientific Journal Video about Microhoneycomb Monoliths Prepared by the Unidirectional Freeze-drying of Cellulose Nanofiber Based Sols: Method and Extensions at JoVE.com

Microhoneycomb Monoliths Prepared by the Unidirectional Freeze-drying of Cellulose Nanofiber Based Sols: Method and Extensions

在这里, 我们提出了一个通用的协议, 以准备各种 microhoneycomb 石柱 (MHMs), 其中流体可以通过与极低的压力下降。MHMs 获得的可作为过滤器, 催化剂支持, 流型电极, 传感器和支架的生物材料。

纤维素碳纤维溶胶单向冷冻干燥制备 Microhoneycomb 石柱: 方法和外延

Monolithic honeycomb structures have been attractive to multidisciplinary fields due to their high strength-to-weight ratio. Particularly, microhoneycomb ...

microhoneycomb-monoliths-prepared-unidirectional-freeze-drying

Research

JoVE Journal

Bioengineering

8.8K 次观看.  Tsinghua University. 在这里, 我们提出了一个通用的协议, 以准备各种 microhoneycomb 石柱 (MHMs), 其中流体可以通过与极低的压力下降。MHMs 获得的可作为过滤器, 催化剂支持, 流型电极, 传感器和支架的生物材料。

视频: Microhoneycomb Monoliths Prepared by the Unidirectional Freeze-drying of Cellulose Nanofiber Based Sols: Method and Extensions

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

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

The objective of this research was to form synthetic plant cell wall tissue using layer-by-layer assembly of nanocellulose fibrils and isolated lignin assembled from dilute aqueous suspensions.&#160; Surface measurement techniques of quartz crystal microbalance and atomic force microscopy were used to monitor the formation of the polymer-polymer nanocomposite material.

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 ...

科研

化学

Easy Manipulation of Architectures in Protein-based Hydrogels for Cell Culture Applications

Hydrogels are recognized as promising materials for cell culture applications due to their ability to provide highly hydrated cell environments. The field of 3D templates is rising due to the potential resemblance of those materials to the natural extracellular matrix. Protein-based hydrogels are particularly promising because they can easily be functionalized and can achieve defined structures with adjustable physicochemical properties. However, the production of macroporous 3D templates for cell culture applications using natural materials is often limited by their weaker mechanical properties compared to those of synthetic materials. Here, different methods were evaluated to produce macroporous bovine serum albumin (BSA)-based hydrogel systems, with adjustable pore sizes in the range of 10 to 70 &#181;m in radius. Furthermore, a method to generate channels in this protein-based material that are several hundred microns long was established. The different methods to produce pores, as well as the influence of pore size on material properties such as swelling ratio, pH, temperature stability, and enzymatic degradation behavior, were analyzed. Pore sizes were investigated in the native, swollen state of the hydrogels using confocal laser scanning microscopy. The feasibility for cell culture applications was evaluated using a cell-adhesive RGD peptide modification of the protein system and two model cell lines: human breast cancer cells (A549) and adenocarcinomic human alveolar basal epithelial cells (MCF7).

Different methods to manipulate three-dimensional architecture in protein-based hydrogels are evaluated here with respect to material properties. The macroporous networks are functionalized with a cell-adhesive peptide, and their feasibility in cell culture is evaluated using two different model cell lines.

便于操作的体系结构基于蛋白质的凝胶中为单元格文化应用程序

Hydrogels are recognized as promising materials for cell culture applications due to their ability to provide highly hydrated cell environments. The field ...

生物化学

Fabrication of the Thermoplastic Microfluidic Channels

In our lab, we have successfully isolated nucleic acids directly from microliter and submicroliter volumes of human blood, urine and stool using polymer/nanoparticle composite microscale lysis and solid phase extraction columns. The recovered samples are concentrated, small volume samples that are PCRable, without any additional cleanup. Here, we demonstrate how to fabricate thermoplastic microfluidic chips using hot embossing and heat sealing. Then, we demonstrate how to use in situ light directed surface grafting and polymerization through the sealed chip to form the composite solid phase columns. We demonstrate grafting and polymerization of a carbon nanotube/polymer composite column for bacterial cell lysis. We then show the lysis process followed by solid phase extraction of nucleic acids from the sample on chip using a silica/polymer composite column. The attached protocols contain detailed instructions on how to make both lysis and solid phase extraction columns.

Here we demonstrate how to fabricate thermoplastic microfluidic chips using hot embossing and heat sealing. Then we demonstrate how to use in situ light directed surface grafting and polymerization through the sealed chip to form the composite solid phase columns.

制备热塑性微流体通道

In our lab, we have successfully isolated nucleic acids directly from microliter and submicroliter volumes of human blood, urine and stool using ...

生物学

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 ...

Cell Culture on Silicon Nitride Membranes and Cryopreparation for Synchrotron X-ray Fluorescence Nano-analysis

Very little is known about the distribution of metal ions at the subcellular level. However, those chemical elements have essential regulatory functions and their disturbed homeostasis is involved in various diseases. State-of-the-art synchrotron X-ray fluorescence nanoprobes provide the required sensitivity and spatial resolution to elucidate the two-dimensional (2D) and three-dimensional (3D) distribution and concentration of metals inside entire cells at the organelle level. This opens new exciting scientific fields of investigation on the role of metals in the physiopathology of the cell. The cellular preparation is a key and often complex procedure, particularly for basic analysis. Although X-ray fluorescence techniques are now widespread and various preparation methods have been used, very few studies have investigated the preservation of the elemental content of cells at best, and no stepwise detailed protocol for the cryopreparation of adherent cells for X-ray fluorescence nanoprobes has been released so far. This is a description of a protocol that provides the stepwise cellular preparation for fast cryofixation to enable synchrotron X-ray fluorescence nano-analysis of cells in a frozen hydrated state when a cryogenic environment and transfer is available. In case nano-analysis has to be performed at room temperature, an additional procedure for freeze-drying the cryofixed adherent cellular preparation is provided. The proposed protocols have been successfully used in previous works, most recently in studying the 2D and 3D intracellular distribution of an organometallic compound in breast cancer cells.

Presented here is a protocol for cell culture on silicon nitride membranes and plunge-freezing prior to X-ray fluorescence imaging with a synchrotron cryogenic X-ray nanoprobe. When only room temperature nano-analysis is provided, the frozen samples can be further freeze-dried. These are critical steps to obtain information on the intracellular elemental composition.

硅氮化物膜的细胞培养和同步加速器X射线荧光纳米分析的冷冻制备

Very little is known about the distribution of metal ions at the subcellular level. However, those chemical elements have essential regulatory functions ...

Multiscale Structures Aggregated by Imprinted Nanofibers for Functional Surfaces

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing challenge in the field is the fabrication of hybrid micro-nano structures using a facile, cost-effective, and high-throughput method. To overcome these challenges, this paper proposes a protocol to fabricate multiscale structures using only an imprint process with an anodic aluminum oxide (AAO) filter and an evaporative self-aggregation process of nanofibers. Unlike previous attempts that have aimed to straighten nanofibers, we demonstrate a unique fabrication method for multiscale aggregated nanofibers with high aspect ratios. Furthermore, the surface morphology and wettability of these structures on various liquids were investigated to facilitate their use in multifunctional surfaces.

Presented is an easy method to fabricate nano-micro multiscale structures, for functional surfaces, by aggregating nanofibers fabricated using an anodic aluminum oxide filter.

功能表面用印迹纳米纤维聚合的多尺度结构

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing ...

工程学

Synthesis Method for Cellulose Nanofiber Biotemplated Palladium Composite Aerogels

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

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

纤维素纳米纤维生物模板复合气凝胶的合成方法

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

Preparation and Cryo-FIB micromachining of Saccharomyces cerevisiae for Cryo-Electron Tomography

Today, cryo-electron tomography (cryo-ET) is the only technique that can provide near-atomic resolution structural data on macromolecular complexes in situ. Owing to the strong interaction of an electron with the matter, high-resolution cryo-ET studies are limited to specimens with a thickness of less than 200 nm, which restricts the applicability of cryo-ET only to the peripheral regions of a cell. A complex workflow that comprises the preparation of thin cellular cross-sections by cryo-focused ion beam micromachining (cryo-FIBM) was introduced during the last decade to enable the acquisition of cryo-ET data from the interior of larger cells. We present a protocol for the preparation of cellular lamellae from a sample vitrified by plunge freezing utilizing Saccharomyces cerevisiae as a prototypical example of a eukaryotic cell with wide utilization in cellular and molecular biology research. We describe protocols for vitrification of S. cerevisiae into isolated patches of a few cells or a continuous monolayer of the cells on a TEM grid and provide a protocol for lamella preparation by cryo-FIB for these two samples.

Preparation and Cryo-FIB micromachining of Saccharomyces cerevisiae for Cryo-Electron Tomography

We present a protocol for lamella preparation of plunge frozen biological specimens by cryo-focused ion beam micromachining for high-resolution structural studies of macromolecules in situ with cryo-electron tomography. The presented protocol provides guidelines for the preparation of high-quality lamellae with high reproducibility for structural characterization of macromolecules inside the&#160;Saccharomyces cerevisiae.

冷冻电子断层扫描 的糖核 酸的准备和冷冻-FIB微加工

Today, cryo-electron tomography (cryo-ET) is the only technique that can provide near-atomic resolution structural data on macromolecular complexes in ...

Fabrication of Micro-Patterned Chip with Controlled Thickness for High-Throughput Cryogenic Electron Microscopy

A major limitation for the efficient and high-throughput structure analysis of biomolecules using cryogenic electron microscopy (cryo-EM) is the difficulty of preparing cryo-EM samples with controlled ice thickness at the nanoscale. The silicon (Si)-based chip, which has a regular array of micro-holes with graphene oxide (GO) window patterned on a thickness-controlled silicon nitride (SixNy) film, has been developed by applying microelectromechanical system (MEMS) techniques. UV photolithography, chemical vapor deposition, wet and dry etching of the thin film, and drop-casting of 2D nanosheet materials were used for mass-production of the micro-patterned chips with GO windows. The depth of the micro-holes is regulated to control the ice thickness on-demand, depending on the size of the specimen for cryo-EM analysis. The favorable affinity of GO toward biomolecules concentrates the biomolecules of interest within the micro-hole during cryo-EM sample preparation. The micro-patterned chip with GO windows enables high-throughput cryo-EM imaging of various biological molecules, as well as inorganic nanomaterials.

A newly developed micro-patterned chip with graphene oxide windows is fabricated by applying microelectromechanical system techniques, enabling efficient and high-throughput cryogenic electron microscopy imaging of various biomolecules and nanomaterials.

用于高通量低温电子显微镜的可控厚度微图案芯片的制备

A major limitation for the efficient and high-throughput structure analysis of biomolecules using cryogenic electron microscopy (cryo-EM) is the ...

用单层石墨烯包覆 CryoEM 网格以改善冷冻样品制备

Application of Monolayer Graphene to Cryo-Electron Microscopy Grids for High-resolution Structure Determination

In cryogenic electron microscopy (cryoEM), purified macromolecules are applied to a grid bearing a holey carbon foil; the molecules are then blotted to remove excess liquid and rapidly frozen in a roughly 20-100 nm thick layer of vitreous ice, suspended across roughly 1 &#181;m wide foil holes. The resulting sample is imaged using cryogenic transmission electron microscopy, and after image processing using suitable software, near-atomic resolution structures can be determined. Despite cryoEM&#39;s widespread adoption, sample preparation remains a severe bottleneck in cryoEM workflows, with users often encountering challenges related to samples behaving poorly in the suspended vitreous ice. Recently, methods have been developed to modify cryoEM grids with a single continuous layer of graphene, which acts as a support surface that often increases particle density in the imaged area and can reduce interactions between particles and the air-water interface. Here, we provide detailed protocols for the application of graphene to cryoEM grids and for rapidly assessing the relative hydrophilicity of the resulting grids. Additionally, we describe an EM-based method to confirm the presence of graphene by visualizing its characteristic diffraction pattern. Finally, we demonstrate the utility of these graphene supports by rapidly reconstructing a 2.7 &#197; resolution density map of a Cas9 complex using a pure sample at a relatively low concentration.

作者聚焦：在显微镜网格上使用石墨烯单层增强 CryoEM 样品制备 

The application of support layers to cryogenic electron microscopy (cryoEM) grids can increase particle density, limit interactions with the air-water interface, reduce beam-induced motion, and improve the distribution of particle orientations. This paper describes a robust protocol for coating cryoEM grids with a monolayer of graphene for improved cryo-sample preparation.

单层石墨烯在冷冻电子显微镜网格中的应用，用于高分辨率结构测定

In cryogenic electron microscopy (cryoEM), purified macromolecules are applied to a grid bearing a holey carbon foil; the molecules are then blotted to ...

纤维素碳纤维溶胶单向冷冻干燥制备 Microhoneycomb 石柱: 方法和外延

摘要

探索更多视频

此视频中的章节

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

便于操作的体系结构基于蛋白质的凝胶中为单元格文化应用程序

制备热塑性微流体通道

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

硅氮化物膜的细胞培养和同步加速器X射线荧光纳米分析的冷冻制备

功能表面用印迹纳米纤维聚合的多尺度结构

纤维素纳米纤维生物模板复合气凝胶的合成方法

冷冻电子断层扫描的糖核酸的准备和冷冻-FIB微加工

用于高通量低温电子显微镜的可控厚度微图案芯片的制备

单层石墨烯在冷冻电子显微镜网格中的应用，用于高分辨率结构测定

纤维素碳纤维溶胶单向冷冻干燥制备 Microhoneycomb 石柱: 方法和外延

摘要

探索更多视频

此视频中的章节

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

便于操作的体系结构基于蛋白质的凝胶中为单元格文化应用程序

制备热塑性微流体通道

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

硅氮化物膜的细胞培养和同步加速器X射线荧光纳米分析的冷冻制备

功能表面用印迹纳米纤维聚合的多尺度结构

纤维素纳米纤维生物模板复合气凝胶的合成方法

冷冻电子断层扫描 的糖核 酸的准备和冷冻-FIB微加工

用于高通量低温电子显微镜的可控厚度微图案芯片的制备

单层石墨烯在冷冻电子显微镜网格中的应用，用于高分辨率结构测定

冷冻电子断层扫描的糖核酸的准备和冷冻-FIB微加工