从东风集团的资金支持（SM项目82 / 13-1）表示感谢。

1.酰胺化果胶原液的制备<ol><li>混合20克酰胺化果胶980克水（2.0重量％）。酰胺化的程度是25％（重量）。 </li><li>均质用高速搅拌器（10,000rpm下）的溶液2分钟以获得均匀的粘稠溶液。 </li><li>用pH条或pH计测量pH值。如果pH低于6.5，滴定用0.5M的NaOH以中和溶液（pH至7.0）。 </li><li>添加碳酸钙的每克干酰胺化果胶（Q = 1）的0.1825克的比率。 "Q"表示交联度。 </li><li> :每千克2.0％（重量）酰胺化果胶溶液，加入3.65克碳酸钙（Q = 1），7％20.0克干果胶。 </li><li>对于更大的交联，添加每克干酰胺化果胶（Q = 2）的0.3650克碳酸钙。 </li></ol> 2.生产的水凝胶<ol><li>使用高速均化器（10,000rpm下），以获得一个均匀的酰胺化果胶/碳酸钙混合物白色均匀分散。 </li><li>转移到悬挂开放聚丙烯模具或玻璃培养皿。 </li><li>放置模具在高压釜。密封该高压釜中。 </li><li>加压用气态CO 2的高压釜达到在RT 5兆帕。参阅Gurikov 等 7进一步的信息。维持24小时的压力。 </li><li>在0.2MPa /分钟慢慢减压高压釜中。 </li><li>打开高压釜并取出模具。通过把它们通过除去从模具的水凝胶。如果有必要，用刮刀。 </li></ol> 3.溶剂交换程序<ol><li>制备出10克10:90（重量/重量），每克水凝胶的乙醇/水混合物中。 </li><li>沉浸在10:90的水凝胶（W / W）12小时乙醇/水混合物中。 </li><li>继续增加的乙醇浓度， 即该方法中，从10:90（重量/重量）的乙醇/水混合物中以30:70（重量/重量）的乙醇/水混合物中。 12小时后，转移至5零点50（W / W）乙醇/水混合物中，然后至70:30（12小时），然后90:10（12小时），然后至100％的乙醇溶液（12小时）。 </li><li>进一步浸泡凝胶在纯乙醇使凝胶内的最终浓度为98％以上（重量/重量）。用密度计测量浓度。该醇凝胶现在准备超临界CO 2干燥。 </li></ol> 4.生产气凝胶的超临界CO 2干燥<ol><li>放置样品用于凝胶制剂相同的高压釜（见步骤2.3）。 </li><li>填用另外的乙醇（高压釜容积的2-10％）的高压釜，以防止过早溶剂蒸发从凝胶。不需要在溶剂凝胶完全浸没。 </li><li>密封该高压釜中。打开高压釜加热。设置高压釜工作温度至323 K.加压使用压缩机或泵的高压釜与二氧化碳12兆帕。 </li><li>定期更换的 CO 2高压釜10,11新鲜的CO 2保持压力恒定内。 6-7居住卷都必须经过一段6小时。参阅Gurikov 等 7进一步的信息。 </li><li>在0.2MPa /分钟慢慢减压高压釜中。 </li><li>打开高压釜，收集气凝胶。存储在一个exicator或密封容器中的气凝胶。 </li></ol>

<ol>
	<li>Kistler, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coherent+expanded-aerogels.">Coherent expanded-aerogels.</a> J. Phys. Chem. 36 (1), 52-64 (1932).</li><li>Aegerter, M. A., Leventis, N., Koebel, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Aerogels Handbook. , (2011).</li><li>Raman, S. P., Gurikov, P., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hybrid+alginate+based+aerogels+by+carbon+dioxide+induced+gelation:+Novel+technique+for+multiple+applications.">Hybrid alginate based aerogels by carbon dioxide induced gelation: Novel technique for multiple applications.</a> J. Supercrit. Fluids. 106, 23-33 (2015).</li><li>Draget, K. I., Skj&#229;k-Br&#230;k, G., Smidsr&#248;d, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alginate+based+new+materials.">Alginate based new materials.</a> Int. J. Biol. Macromol. 21 (1), 47-55 (1997).</li><li>Garc&#237;a-Gonz&#225;lez, C. A., Alnaief, M., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polysaccharide-based+aerogels-Promising+biodegradable+carriers+for+drug+delivery+systems.">Polysaccharide-based aerogels-Promising biodegradable carriers for drug delivery systems.</a> Carbohydr. Polym. 86 (4), 1425-1438 (2011).</li><li>Alnaief, M., Alzaitoun, M. A., Garc&#237;a-Gonz&#225;lez, C. A., Smirnova, I. <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+biodegradable+nanoporous+microspherical+aerogel+based+on+alginate.">Preparation of biodegradable nanoporous microspherical aerogel based on alginate.</a> Carbohydr. Polym. 84 (3), 1011-1018 (2011).</li><li>Gurikov, P., Raman, S. P., Weinrich, D., Fricke, M., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+approach+to+alginate+aerogels:+carbon+dioxide+induced+gelation.">A novel approach to alginate aerogels: carbon dioxide induced gelation.</a> RSC Adv. 5, 7812-7818 (2015).</li><li>Meyssami, B., Balaban, M. O., Teixeira, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prediction+of+pH+in+model+systems+pressurized+with+carbon+dioxide.">Prediction of pH in model systems pressurized with carbon dioxide.</a> Biotechnol. Prog. 8 (2), 149-154 (1992).</li><li>Subrahmanyam, R., Gurikov, P., Dieringer, P., Sun, M., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+Road+to+Biopolymer+Aerogels-Dealing+with+the+Solvent.">On the Road to Biopolymer Aerogels-Dealing with the Solvent.</a> Gels. 1 (2), 291-313 (2015).</li><li>Garc&#237;a-Gonz&#225;lez, C. A., Camino-Rey, M. C., Alnaief, M., Zetzl, C., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+drying+of+aerogels+using+CO2:+Effect+of+extraction+time+on+the+end+material+textural+properties.">Supercritical drying of aerogels using CO2: Effect of extraction time on the end material textural properties.</a> J. Supercrit. Fluids. 66, 297-306 (2012).</li><li>&#214;zbak&#305;r, Y., Erkey, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+and+theoretical+investigation+of+supercritical+drying+of+silica+alcogels.">Experimental and theoretical investigation of supercritical drying of silica alcogels.</a> J. Supercrit. Fluids. 98, 153-166 (2015).</li><li>Rudaz, 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=Aeropectin:+Fully+Biomass-Based+Mechanically+Strong+and+Thermal+Superinsulating+Aerogel.">Aeropectin: Fully Biomass-Based Mechanically Strong and Thermal Superinsulating Aerogel.</a> Biomacromolecules. 15 (6), 2188-2195 (2014).</li><li>Quraishi, 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=Novel+non-cytotoxic+alginate-lignin+hybrid+aerogels+as+scaffolds+for+tissue+engineering.">Novel non-cytotoxic alginate-lignin hybrid aerogels as scaffolds for tissue engineering.</a> J. Supercrit. Fluids. 105, 1-8 (2015).</li><li>Martins, M., 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+macroporous+alginate-based+aerogels+for+biomedical+applications.">Preparation of macroporous alginate-based aerogels for biomedical applications.</a> J. Supercrit. Fluids. 106, 152-159 (2015).</li><li>Davidovich-Pinhas, M., Bianco-Peled, 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+quantitative+analysis+of+alginate+swelling.">A quantitative analysis of alginate swelling.</a> Carbohydr. Polym. 79 (4), 1020-1027 (2010).</li><li>Mallepally, R. R., Bernard, I., Marin, M. A., Ward, K. R., McHugh, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superabsorbent+alginate+aerogels.">Superabsorbent alginate aerogels.</a> J. Supercrit. Fluids. 79, 202-208 (2013).</li><li>Porta, G. D., Del Gaudio, P., De Cicco, F., Aquino, R. P., Reverchon, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+Drying+of+Alginate+Beads+for+the+Development+of+Aerogel+Biomaterials:+Optimization+of+Process+Parameters+and+Exchange.">Supercritical Drying of Alginate Beads for the Development of Aerogel Biomaterials: Optimization of Process Parameters and Exchange.</a> Ind. Eng. Chem. Res. 52 (34), 12003-12009 (2013).</li><li>Brown, Z. K., Fryer, P. J., Norton, I. T., Bridson, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drying+of+agar+gels+using+supercritical+carbon+dioxide.">Drying of agar gels using supercritical carbon dioxide.</a> J. Supercrit. Fluids. 54 (1), 89-95 (2010).</li><li>Betz, M., Garc&#237;a-Gonz&#225;lez, C. A., Subrahmanyam, R. P., Smirnova, I., Kulozik, U. <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+novel+whey+protein-based+aerogels+as+drug+carriers+for+life+science+applications.">Preparation of novel whey protein-based aerogels as drug carriers for life science applications.</a> J. Supercrit. Fluids. 72, 111-119 (2012).</li><li>Antonyuk, S., Heinrich, S., Gurikov, P., Raman, S., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+coating+and+wetting+on+the+mechanical+behaviour+of+highly+porous+cylindrical+aerogel+particles.">Influence of coating and wetting on the mechanical behaviour of highly porous cylindrical aerogel particles.</a> Powder Technol. 285, 34-43 (2015).</li></ol>

作者宣称，他们没有竞争的经济利益。

通过使用CO 2的诱导凝胶技术，可以消除对化学代用品（例如乙酸或葡糖酸-δ-内酯（GDL））用于诱导所述生物聚合物的交联所需的需要。该酰胺化果胶气凝胶的表面积在文献值5的较高范围，但是孔体积比在文献5中要高得多。较高的孔隙体积也由二氧化碳诱导凝胶7海藻酸钠制成气凝胶观察。但是，它仍然待验证此高孔体积（4-150纳米孔径范围）的原因是否是由于凝胶化技术或先前在文献中没有解决的生物聚合物的固有性质。果胶气凝胶已报道在文献具备superinsulating属性12和由该技术制备的藻气凝胶还具有在superinsulating范围的热导率3,7。因此，用这种技术生产的酰胺化果胶气凝胶也可以设想具有superinsulating属性。 减压的协议第2节的速率是在水凝胶制剂中的重要一步。快速减压，能够增加凝胶的大孔性。这个现象可应用于组织工程应用，其中与互联的材料的大孔性为细胞13,14的生长和增殖的重要特征。另外，在协议部分1的交联度起着脱水收缩的酰胺化果胶凝胶中的重要作用，溶胀性。这类似于海藻酸钠水凝胶的溶胀行为由交联剂浓度的影响，以及15。由此通过酰胺化果胶制成的气凝胶也可以被调谐至具有类似于那些报道的藻气凝胶16超吸收属性。 &lt;P类="jove_content"&gt;通过使用作为主系统的CO 2的诱导凝胶考虑酰胺化果胶（或藻），进一步分集可以通过引入不同交联剂和生物聚合物的组合掺入气凝胶。几个金属碳酸盐（ 例如，锌，镍，钴，铜，锶，钡）可用于交联3，其中阳离子可以通过pH值的水性介质中降低与加压的 CO 2（3-5兆帕）被释放。然而，其中一些阳离子的不溶盐可以不形成用于降低生物聚合物的浓度稳定的分散体，并且可以在底部导致不均匀的凝胶沉淀下来。这是与内部设定凝胶化方法，其包括CO 2的诱导凝胶3，由此，该技术的一个应用的可用性应到个案基础上进行评估的一般问题。 各种混合物使用水溶性生物制备聚合物，如淀粉，角叉菜胶，甲基和羧甲基纤维素，结冷胶，木质素，明胶及其他;水溶性合成聚合物，例如聚乙二醇（PEG），聚乙烯醇（PVA），聚醚的P-123及其他;和水溶性无机前体，如硅酸钠可以用酰胺化果胶以产生类似于藻酸盐2与调谐性能混合气凝胶可以还混合。 作为超临界二氧化碳干燥（SCCO 2干燥）是一个典型的步骤中气凝胶生产，预处理步骤，例如使用CO 2 7可以提供溶剂交换并干燥使用的 CO 2 17,18或凝胶化，溶剂交换并干燥的任何组合一个明确的处理优势。其优点是设想为集成一锅法:其中生物聚合物分散体可以被转换成以CO 2作为在单个高压釜主处理平台生物聚合物气凝胶。对于在使用CO 2作为处理介质的单个高压釜凝胶，溶剂交换，超临界干燥和活性成分装载5,19过程:某些药物应用，可以还想象到执行一个四步骤。后处理如在某些情况下药物加载气凝胶的保护涂层是必要的靶向药物释放20。 总之，目前的工作演示了基于酰胺化果胶体系的凝胶化利用加压的二氧化碳 。另外，作为用于前体产品转化为在一个单一的高压釜目标应用程序的通用平台使用加压的 CO 2的设想。

气凝胶是一类的多孔材料，可以使用各种前体从无机（如二氧化硅，二氧化钛，氧化锆等），合成的（如间苯二酚甲醛，聚氨酯等）或生物聚合物（多糖，蛋白质和其他的制备）2。什么它们区别于传统的多孔材料是他们的能力，同时具有所有三个特点;即高表面积，超低密度和中孔的孔径分布（ 即从2-50纳米的孔径）。具有上述特性，气凝胶被广泛在绝缘，生物医药，催化，吸附和吸收的应用，药物和neutraceuticals 2领域的应用。考虑到上述可能性，生产生物聚合物凝胶系统及其随后的转化气凝胶开辟了向高价值的机会众多加入生物材料。这种努力溶于在这项研究中使用酰胺化果胶，例如， 气凝胶通常是由溶胶 - 凝胶技术产生的。凝胶是自由的以矩阵截留液系统，可以通过共价的，离子的，pH值诱发的，热或低温交联3来制备。对于这个特定的系统，我们利用离子交联， 即，二价阳离子（ 如钙），以生物聚合物链交联在一起。执行生物聚合物如酰胺化果胶或藻酸盐的可控离子交联，可以利用扩散法或内部设置方法4。在扩散方法中，凝胶化发生在第一外层，随后通过扩散传播，作为阳离子从外部解成酰胺化果胶或藻酸盐微滴或层4扩散。在内部设置的方法，所述交联剂的不溶形式被均匀地分散在该生物聚合物搜索解决方案n和阳离子通过启动pH变化4,5,6释放。然而，这两种技术面临板或整体形式制造时有关的最终凝胶的均匀性的问题。这项工作表明生产酰胺化果胶水凝胶藻酸盐凝胶3,7进一步对以前的作品建筑使用高压CO 2（5兆帕）的。简而言之，它是一个内部设定凝胶化技术，其利用加压的 CO 2来降低pH值，而不是弱酸，以产生均匀的凝胶。与增加的压力，二氧化碳在水中的溶解度增加伴随着pH值降低到3.0 8。这会导致碳酸钙溶解，释放出钙离子。钙离子与酰胺化果胶生物聚合物交联，得到水凝胶。稳定均匀的凝胶降到很低的生物聚合物的浓度（0.05重量％）可使用该技术7制备。 由于GELAT离子发生在含水介质中，溶剂交换的有机溶剂是必需的，由于在CO 2 /水系统中的溶解度间隙。典型的低分子量醇（甲醇/乙醇/异丙醇）和酮（丙酮）可被用于该溶剂交换过程。然而，与纯乙醇或其他有机溶剂的浴直接浸泡导致显著不可逆的收缩。为了避免这种缺点，逐步溶剂交换进行5,9。当凝胶内的溶剂浓度达到&gt; 98％时，有机溶剂与超临界的 CO 2（12兆帕），留下的气凝胶后面干燥。

<table border="0" cellpadding="0" cellspacing="0" width="1321">
	<tbody>
		<tr height="26">
			<td height="26" style="height:26px;width:289px;">Equipment</td>
			<td style="width:196px;"></td>
			<td style="width:240px;"></td>
			<td style="width:596px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ultraturrax homogenizer</td>
			<td>IKA, Germany</td>
			<td>T 25 Digital</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Polypropylene molds</td>
			<td>TH. Geyer, Germany</td>
			<td>9,033,201</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">High pressure autoclave&#160;</td>
			<td>Ernst Haage, Germany</td>
			<td>custom made</td>
			<td>Setup constuction done in-house</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Compressor</td>
			<td>Andreas Hofer</td>
			<td>MKZ 185-40</td>
			<td>Setup constuction done in-house</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Nitrogen adsorption</td>
			<td>Quantachrome</td>
			<td>Nova 4000e</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Density meter</td>
			<td>Anton Paar</td>
			<td>DMA 4000</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:289px;">Chemicals</td>
			<td style="width:196px;"></td>
			<td style="width:240px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Amidated pectin</td>
			<td>Herbstreith and Fox, Germany</td>
			<td>CU 025</td>
			<td>CAS # 56645-02-4; provided by company for research purposes</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium Hydroxide</td>
			<td>Sigma Aldrich, Germany</td>
			<td style="width:240px;">S8045</td>
			<td>CAS # 1310-73-2; required only in case the pectin solution needs to be neutralized to pH 6.5-7.5</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Calcium carbonate</td>
			<td>Magnesia GmbH, Germany</td>
			<td style="width:240px;">4421 Calcium carbonat, leicht, pr&#228;zipitiert, EP, E170</td>
			<td>CAS # 471-34-1</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ethanol, 99.8 %</td>
			<td>Sigma Aldrich, Germany</td>
			<td>32205</td>
			<td>CAS # 64-17-5</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Carbon dioxide, 99.9 %</td>
			<td>AGA Gas GmbH, Germany</td>
			<td></td>
			<td>CAS # 124-38-9; in-house tank available (3 ton)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Deionised Water</td>
			<td></td>
			<td></td>
			<td>CAS # 7732-18-5;&#160; available in-house (6.4-7.0 pH)</td>
		</tr>
	</tbody>
</table>

preparation of biopolymer aerogels using green solvents

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers (gelatin, agar, cellulose), only recently have biomasses been recognized as an abundant source of chemically diverse macromolecules for functional aerogel materials. Biopolymer aerogels (pectin, alginate, chitosan, cellulose, etc.) exhibit both specific inheritable functions of starting biopolymers and distinctive features of aerogels (80-99% porosity and specific surface up to 800 m2/g). This synergy of properties makes biopolymer aerogels promising candidates for a wide gamut of applications such as thermal insulation, tissue engineering and regenerative medicine, drug delivery systems, functional foods, catalysts, adsorbents and sensors. This work demonstrates the use of pressurized carbon dioxide (5 MPa) for the ionic cross linking of amidated pectin into hydrogels. Initially a biopolymer/salt dispersion is prepared in water. Under pressurized CO2 conditions, the pH of the biopolymer solution is lowered to 3 which releases the crosslinking cations from the salt to bind with the biopolymer yielding hydrogels. Solvent exchange to ethanol and further supercritical CO2 drying (10 - 12 MPa) yield aerogels. Obtained aerogels are ultra-porous with low density (as low as 0.02 g/cm3), high specific surface area (350 - 500 m2/g) and pore volume (3 - 7 cm3/g for pore sizes less than 150 nm).

（如在协议部分2指示）在图1中示出具有更高的交联度（Q = 2）凝胶化步骤后得到的典型水凝胶。将样品在左侧（样品A和B）是2重量％和1％（重量）用CO 2诱导凝胶获得果胶凝胶。通过降低生物聚合物浓度（0.5％（重量）或更低），凝胶变得透明（样品C）。在生物聚合物的浓度（0.25％重量）进一步减少也产生稳定的水凝胶（样品D），但这些凝胶非常脆弱，操作时可以打破。当溶解的CO 2离开，由于在CO 2的溶解性降低凝胶的水系统中的水凝胶内观察到的气泡被减压期间创建的。 该酰胺化果胶气凝胶特性在表1中。将所得的气凝胶的超多孔低巢穴<html>减到（低至0.013克/厘米3）作为气凝胶和其体积的质量之间的比率。表面积通过氮吸附测定的。为果胶气凝胶，它产生了350之间的比表面积- 400米2 /克。在4-150纳米范围内的孔径的细孔容积是通过使用氮（BJH法）孔隙填充的Kelvin模型测定。细孔容积为酰胺化的果胶气凝胶是3之间-第7 毫升 /克4和150纳米之间的孔尺寸。 <img alt="图1" src="/files/ftp_upload/54116/54116fig1.jpg" /> 图1.酰胺化果胶的水凝胶具有较高的交联度（Q = 2）左上:2％（重量）（样品A）。右上:1％（重量）（样品B）;左下:0.5％（重量）（样品C）;右下:0.25％（重量）（样品D）。凝胶成为透明的生物聚合物降低浓度。气泡是二氧化碳减压过程中产生的。https://www.jove.com/files/ftp_upload/54116/54116fig1large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 <table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody><tr><td> 果胶含量[重量％] </td><td> 交联度q </td><td> 堆积密度[克/厘米3] </td><td> 比表面积[米2 /克] </td><td> 比孔体积[厘米3 / g 的 ] </td><td> 平均孔尺寸（直径）[nm]的 </td></tr><tr><td> 2.00 </td><td> 1 </td><td> 0.081 </td><td> 502 </td><td> 4.1 </td><td> 14 </td></tr><tr><td> 1.00 </td><td> 1 </td><td> 0.044 </td><td> 491 </td><td> 7.1 </td><td> 27 </td></tr><tr><td> 0.50 </td><td> 1 </td><td> 0.035 </td><td> 357 </td><td> 3.8 </td><td> 27 </td></tr><tr><td> 0.25 </td><td> 1 </tD&gt; <td> 0.013 </td><td> 335 </td><td> 4.9 </td><td> 41 </td></tr><tr><td> 2.00 </td><td> 2 </td><td> 0.069 </td><td> 447 </td><td> 3.1 </td><td> 13 </td></tr><tr><td> 1.00 </td><td> 2 </td><td> 0.048 </td><td> 441 </td><td> 3.6 </td><td> 26 </td></tr><tr><td> 0.50 </td><td> 2 </td><td> 0.030 </td><td> 429 </td><td> 5.8 </td><td> 25 </td></tr><tr><td> 0.25 </td><td> 2 </td><td> 0.017 </td><td> 347 </td><td> 5 </td><td> 24 </td></tr></tbody></table> 表1.酰胺化果胶气凝胶的特点。

Watch this Scientific Journal Video about Preparation of Biopolymer Aerogels Using Green Solvents at JoVE.com

Preparation of Biopolymer Aerogels Using Green Solvents

A new way for the production of biopolymer-based aerogels by carbon dioxide (CO2) induced gelation is shown. The technique utilizes pressurized carbon dioxide (5 MPa) for the production of biopolymer hydrogels and supercritical CO2 (12 MPa) to convert gels into aerogels. The only solvents needed besides CO2 are water and ethanol.

生物聚合物气凝胶制备使用绿色溶剂

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers ...

preparation-of-biopolymer-aerogels-using-green-solvents

Research

JoVE Journal

Chemistry

17.5K 次观看.  Hamburg University of Technology. A new way for the production of biopolymer-based aerogels by carbon dioxide (CO2) induced gelation is shown. The technique utilizes pressurized carbon dioxide (5 MPa) for the production of biopolymer hydrogels and supercritical CO2 (12 MPa) to convert gels into aerogels. The only solvents needed besides CO2 are water and ethanol.

视频: Preparation of Biopolymer Aerogels Using Green Solvents

Exploring the Radical Nature of a Carbon Surface by Electron Paramagnetic Resonance and a Calibrated Gas Flow

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date back to the early 1980s the focus of these early papers primarily characterized the changes to the structures under extremely harsh conditions (pH or temperature)1-3. It is also known that paramagnetic molecular oxygen undergoes a Heisenberg spin exchange interaction with stable radicals that extremely broadens the EPR signal4-6. Recently, we reported interesting results where this interaction of molecular oxygen with a certain part of the existing stable radical structure can be reversibly affected simply by flowing a diamagnetic gas through the carbon samples at STP7. As flows of He, CO2, and N2 had a similar effect these interactions occur at the surface area of the macropore system.
This manuscript highlights the experimental techniques, work-up, and analysis towards affecting the existing stable radical nature in the carbon structures. It is hoped that it will help towards further development and understanding of these interactions in the community at large.

Stable radicals that are present in carbon substrates interact with paramagnetic oxygen through a Heisenberg spin exchange. This interaction can be significantly reduced under STP conditions by flowing a diamagnetic gas over the carbon system. This manuscript describes a simple method to characterize the nature of those radicals.

通过电子顺磁共振和校准气体流量探索碳表面的激进性质

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date ...

科研

化学

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible to ensure consistent product quality over time using this technique. We here show how to interface a commercially available flow unit with a Raman spectrometer. The Raman flow cell is placed after the back-pressure regulator, meaning that it can be operated at atmospheric pressure. In addition, the fact that the product stream passes through a length of tubing before entering the flow cell means that the material is at RT. It is important that the spectra are acquired under isothermal conditions since Raman signal intensity is temperature dependent. Having assembled the apparatus, we then show how to monitor a chemical reaction, the piperidine-catalyzed synthesis of 3-acetylcoumarin from salicylaldehyde and ethyl acetoacetate being used as an example. The reaction can be performed over a range of flow rates and temperatures, the in-situ monitoring tool being used to optimize conditions simply and easily.

Real-time monitoring allows for fast optimization of reactions performed using continuous-flow processing. Here the preparation of 3-acetylcoumarin is used as an example. The apparatus for performing in-situ Raman monitoring is described, as are the steps required to optimize the reaction.

反应执行使用连续流处理的实时监控:3  - 乙酰基香豆素的制备为例

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible ...

Synthetic Methodology for Asymmetric Ferrocene Derived Bio-conjugate Systems via Solid Phase Resin-based Methodology

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. The most common techniques utilized are imaging modalities such as Magnetic Resonance Imaging (MRI), Positron Emission Topography (PET), and Computed Topography (CT) and are optimal for understanding the physical structure of the disease but can only be performed once every four to six weeks due to the use of imaging agents and overall cost. With this in mind, the development of &#8220;point of care&#8221; techniques, such as biosensors, which evaluate the stage of disease and/or efficacy of treatment in the clinician&#8217;s office and do so in a timely manner, would revolutionize treatment protocols.1 As a means to exploring ferrocene based biosensors for the detection of biologically relevant molecules2, methods were developed to produce ferrocene-biotin bio-conjugates described herein. This report will focus on a biotin-ferrocene-cysteine system that can be immobilized on a gold surface.

The synthesis of asymmetric species of ferrocene is challenging using solution techniques. This report focuses on the methods carried out to produce a ferrocene-biotin bioconjugate using facile and clean reactions accomplished via solid-phase synthesis. Incorporation of a thiolate moiety is shown to impart the ability for immobilization on gold surfaces.

合成方法通过固相树脂为基础的方法不对称二茂铁产生的生物共轭系统

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. ...

Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids (BPCA)

Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as char and soot. PyC is ubiquitous in the environment due to its long persistence, and its abundance might even increase with the projected increase in global wildfire activity and the continued burning of fossil fuel. PyC is also increasingly produced from the industrial pyrolysis of organic wastes, which yields charred soil amendments (biochar). Moreover, the emergence of nanotechnology may also result in the release of PyC-like compounds to the environment. It is thus a high priority to reliably detect, characterize and quantify these charred materials in order to investigate their environmental properties and to understand their role in the carbon cycle.
Here, we present the benzene polycarboxylic acid (BPCA) method, which allows the simultaneous assessment of PyC&#39;s characteristics, quantity and isotopic composition (13C and 14C) on a molecular level. The method is applicable to a very wide range of environmental sample materials and detects PyC over a broad range of the combustion continuum, i.e., it is sensitive to slightly charred biomass as well as high temperature chars and soot. The BPCA protocol presented here is simple to employ, highly reproducible, as well as easily extendable and modifiable to specific requirements. It thus provides a versatile tool for the investigation of PyC in various disciplines, ranging from archeology and environmental forensics to biochar and carbon cycling research.

Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids BPCA

We present the benzene polycarboxylic acid (BPCA) method for assessing pyrogenic carbon (PyC) in the environment. The compound-specific approach uniquely provides simultaneous information about the characteristics, quantity and isotopic composition (13C and 14C) of PyC.

表征，气相炭用苯聚羧酸的定量和特定化合物同位素分析（BPCA）

Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as ...

Green and Low-cost Production of Thermally Stable and Carboxylated Cellulose Nanocrystals and Nanofibrils Using Highly Recyclable Dicarboxylic Acids

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils (CNF) from bleached eucalyptus pulp (BEP) and unbleached mixed hardwood kraft pulp (UMHP) fibers using highly recyclable dicarboxylic solid acids. Typical operating conditions were acid concentrations of 50 - 70 wt% at 100 &#176;C for 60 min and 120 &#176;C (no boiling at atmospheric pressure) for 120 min, for BEP and UMHP, respectively. The resultant CNCs have a higher thermal degradation temperature than their corresponding feed fibers and carboxylic acid group content from 0.2 - 0.4 mmol/g. The low strength (high pKa of 1.0 - 3.0) of organic acids also resulted in CNCs with both longer lengths of approximately 239 - 336 nm and higher crystallinity than CNCs produced using mineral acids. Cellulose loss to sugar was minimal. Fibrous cellulosic solid residue (FCSR) from the dicarboxylic acid hydrolysis was used to produce carboxylated CNFs through subsequent mechanical fibrillation with low energy input.

Here we demonstrate a novel method for green and sustainable productions of highly thermally stable and carboxylated cellulose nanocrystals (CNC) and nanofibrils (CNF) using highly recyclable solid dicarboxylic acids.

热稳定和羧基化纤维素纳米晶和纳米原纤维使用高度可回收的二元羧酸绿色和低成本生产

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils ...

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry

Pre-targeting combined with bioorthogonal chemistry is emerging as an effective way to create new radiopharmaceuticals. Of the methods available, the inverse electron demand Diels-Alder (IEDDA) cycloaddition between a radiolabeled tetrazines and trans-cyclooctene (TCO) linked to a biomolecule has proven to be a highly effective bioorthogonal approach to imaging specific biological targets. Despite the fact that technetium-99m remains the most widely used isotope in diagnostic nuclear medicine, there is a scarcity of methods for preparing 99mTc-labeled tetrazines. Herein we report the preparation of a family of tridentate-chelate-tetrazine derivatives and their Tc(I) complexes. These hitherto unknown compounds were radiolabeled with 99mTc using a microwave-assisted method in 31% to 83% radiochemical yield. The products are stable in saline and PBS and react rapidly with TCO derivatives in vitro. Their in vivo pre-targeting abilities were demonstrated using a TCO-bisphosphonate (TCO-BP) derivative that localizes to regions of active bone metabolism or injury. In murine studies, the 99mTc-tetrazines showed high activity concentrations in knees and shoulder joints, which was not observed when experiments were performed in the absence of TCO-BP. The overall uptake in non-target organs and pharmacokinetics varied greatly depending on the nature of the linker and polarity of the chelate.

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry

Here, we describe a protocol for radiolabeling and in vivo testing of tridentate 99mTc(I) chelate-tetrazine derivatives for pre-targeting and bioorthogonal chemistry.

制备和评价<sup&gt;99米</sup&gt;锝标记的三齿螯合物预靶向使用生物正交化学

Pre-targeting combined with bioorthogonal chemistry is emerging as an effective way to create new radiopharmaceuticals. Of the methods available, the ...

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (&#60;6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Here we present protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms. Methods for preparing materials using copper salts and copper-containing nanoparticles are featured. Catalytic testing protocols demonstrate the effectiveness of these aerogels for three-way catalysis applications.

快速超临界萃取制备催化气凝胶的制备与试验研究

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three ...

Preparation of Functional Silica Using a Bioinspired Method

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

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

用 Bioinspired 法制备功能性二氧化硅

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

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

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

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

直接溶液还原法快速合成金、钯、铂气凝胶的研究

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

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for specialized equipment to achieve modest pressures, and can even be used to achieve higher pressures in more specialized equipment and sturdier reaction vessels. At the end of the reaction, the vials can be easily depressurized by opening at room temperature. In the present example CO2 serves as both a putative directing group as well as a way to passivate amine substrates, thereby preventing oxidation during the organometallic reaction. In addition to being easily added, the directing group is also removed under vacuum, obviating the need for extensive purification to remove the directing group. This strategy allows the facile &#947;-C(sp3)-H arylation of aliphatic amines and has the potential to be applied to a variety of other amine-based reactions.

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Here we present a protocol for performing reactions in simple reaction vessels under low-to-moderate pressures of CO2. The reactions can be performed in a variety of vessels simply by administering the carbon dioxide in the form of dry ice, without the need for costly or elaborate equipment or set-ups.

用干冰作为固体 CO2源实现密封容器中的适度压力

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for ...