Charlotte M. Wentz would like to acknowledge funding through NIST Award # 70NANB8H165. Zois Tsinas would like to acknowledge funding through NIST Award # 70NANB22H140.

Impregnation and Grafting of Aminated Compounds onto Silica Substrates

<ol>
	<li>Zhu, X., 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=Recent+advances+in+direct+air+capture+by+adsorption.">Recent advances in direct air capture by adsorption.</a> Chemical Society Reviews. 51 (15), 6574-6651 (2022).</li><li>Zhao, P., Zhang, G., Yan, H., Zhao, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+latest+development+on+amine+functionalized+solid+adsorbents+for+post-combustion+CO2+Capture:+Analysis+review.">The latest development on amine functionalized solid adsorbents for post-combustion CO2 Capture: Analysis review.</a> Chinese Journal of Chemical Engineering. 35 (8), 17-43 (2021).</li><li>Chen, D., Zhang, S., Row, K. H., Ahn, W. -. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amine-silica+composites+for+CO2+capture:+A+short+review.">Amine-silica composites for CO2 capture: A short review.</a> Journal of Energy Chemistry. 26 (5), 868-880 (2017).</li><li>Nie, L., Mu, Y., Jin, J., Chen, J., Mi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+developments+and+considerations+issues+in+solid+adsorbents+for+CO2+capture+from+flue+gas.">Recent developments and considerations issues in solid adsorbents for CO2 capture from flue gas.</a> Chinese Journal of Chemical Engineering. 26 (11), 2303-2317 (2018).</li><li>Nithyashree, N., Manohara, G. V., Maroto-Valer, M. M., Garcia, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advanced+high-temperature+CO2+sorbents+with+improved+long-term+cycling+stability.">Advanced high-temperature CO2 sorbents with improved long-term cycling stability.</a> American Chemical Society Applied Material Interfaces. 12 (30), 33765-33774 (2020).</li><li>Song, 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=Alternative+pathways+for+efficient+CO2+capture+by+hybrid+processes-A+review.">Alternative pathways for efficient CO2 capture by hybrid processes-A review.</a> Renewable and Sustainable Energy Review. 82, 215-231 (2018).</li><li>Rochelle, G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amine+scrubbing+for+CO2+capture.">Amine scrubbing for CO2 capture.</a> Science. 325 (5948), 1625-1654 (2009).</li><li>Vaidye, P. D., Kenig, E. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CO2-alkanolamine+reaction+kinetics:+A+review+of+recent+studies.">CO2-alkanolamine reaction kinetics: A review of recent studies.</a> Chemical Engineering &amp; Technology. 30 (11), 1467-1474 (2007).</li><li>Veawab, A., Tontiwachwuthikul, P., Chakma, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corrosion+behavior+of+carbon+steel+in+the+CO2+adsorption+process+using+aqueous+amine+solutions.">Corrosion behavior of carbon steel in the CO2 adsorption process using aqueous amine solutions.</a> Industrial &amp; Engineering Chemical Research. 38 (10), 3917-3924 (1999).</li><li>Chen, S., Bhattacharjee, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trimodal+nanoporous+silica+as+a+support+for+amine-based+CO2+adsorbents:+Improvement+in+adsorption+capacity+and+kinetics.">Trimodal nanoporous silica as a support for amine-based CO2 adsorbents: Improvement in adsorption capacity and kinetics.</a> Applied Surface Science. 396, 1515-1519 (2017).</li><li>Jiao, J., Cao, J., Xia, Y., Zhao, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improvement+of+adsorbent+materials+for+CO2+capture+by+amine+functionalized+mesoporous+silica+with+worm-hole+framework+structure.">Improvement of adsorbent materials for CO2 capture by amine functionalized mesoporous silica with worm-hole framework structure.</a> Chemical Engineering Journal. 306, 9-16 (2016).</li><li>Guo, X., Ding, L., Kanamori, K., Nakanishi, K., Yang, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functionalization+of+hierarchically+porous+silica+monoliths+with+polyethyleneimine+(PEI)+for+CO2+adsorption.">Functionalization of hierarchically porous silica monoliths with polyethyleneimine (PEI) for CO2 adsorption.</a> Microporous and Mesoporous Materials. 245, 51-57 (2017).</li><li>Fatima, S. S., Borhan, A., Ayoub, M., Ghani, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+progress+of+functionalized+silica-based+adsorbents+for+CO2+capture.">Development and progress of functionalized silica-based adsorbents for CO2 capture.</a> Journal of Molecular Liquids. 338, 116913 (2021).</li><li>Cheng, J., Liu, M., Hu, L., Li, Y., Wang, Y., Zhou, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polyethyleneimine+entwine+thermally-treated+Zn/Co+zeolitic+imidazolate+frameworks+to+enhance+CO2+adsorption.">Polyethyleneimine entwine thermally-treated Zn/Co zeolitic imidazolate frameworks to enhance CO2 adsorption.</a> Chemical Engineering Journal. 364, 530-540 (2019).</li><li>Zagho, M. M., Hassan, M. K., Khraisheh, M., Al-Maadeed, M. A. A., Nazarenko, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+on+recent+advances+in+CO2+separation+using+zeolite+and+zeolite-like+materials+as+adsorbents+and+fillers+in+mixed+matrix+membranes+(MMMs).">A review on recent advances in CO2 separation using zeolite and zeolite-like materials as adsorbents and fillers in mixed matrix membranes (MMMs).</a> Chemical Engineering Journal Advances. 6, 100091 (2021).</li><li>Wang, J., Wang, M., Zhao, B., Qiao, W., Long, D., Ling, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesoporous+carbon-supported+solid+amine+sorbents+for+low-temperature+carbon+dioxide+capture.">Mesoporous carbon-supported solid amine sorbents for low-temperature carbon dioxide capture.</a> Industrial &amp; Engineering Chemistry Research. 52 (15), 5437-5444 (2013).</li><li>&#220;nveren, E. E., Monkul, B. O., Sario&#287;lan, S., Karademir, N., Alper, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solid+amine+sorbents+for+CO2+capture+by+chemical+adsorption:+A+review.">Solid amine sorbents for CO2 capture by chemical adsorption: A review.</a> Petroleum. 3 (1), 37-50 (2017).</li><li>Demir, H., Aksu, G. O., Gulbalkan, H. C., Keskin, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MOF+membranes+for+CO2+capture:+Past,+present+and+future.">MOF membranes for CO2 capture: Past, present and future.</a> Carbon Capture Science &amp; Technology. 2, 100026 (2022).</li><li>Xu, X., Song, C., Andresen, J. M., Miller, B. G., Scaroni, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+polyethylenimine-modified+mesoporous+molecular+sieve+of+MCM-41+type+as+high-capacity+adsorbent+for+CO2+capture.">Novel polyethylenimine-modified mesoporous molecular sieve of MCM-41 type as high-capacity adsorbent for CO2 capture.</a> Energy &amp; Fuels. 16 (6), 1463-1469 (2002).</li><li>Gelles, T., Lawson, S., Rownaghi, A., Rezaei, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+development+of+amine+functionalized+adsorbents+for+CO2+capture.">Recent advances in development of amine functionalized adsorbents for CO2 capture.</a> Adsorption. 26 (94), 5-50 (2020).</li><li>Rao, N., Wang, M., Shang, Z., Hou, Y., Fan, G., Li, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CO2+adsorption+by+amine-functionalized+MCM-41:+A+comparison+between+impregnation+and+grafting+modification+methods.">CO2 adsorption by amine-functionalized MCM-41: A comparison between impregnation and grafting modification methods.</a> Energy Fuels. 32 (1), 670-677 (2018).</li><li>Anyanwu, J. T., Wang, Y., Yang, R. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amine-grafted+silica+gels+for+CO2+capture+including+direct+air+capture.">Amine-grafted silica gels for CO2 capture including direct air capture.</a> Industrial &amp; Engineering Chemistry Research. 59 (15), 7072-7079 (2020).</li><li>Anyanwu, J. -. T., Wang, Y., Yang, R. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CO2+capture+(including+direct+air+capture)+and+natural+gas+desulfurization+of+amine-grafted+hierarchical+bimodal+silica.">CO2 capture (including direct air capture) and natural gas desulfurization of amine-grafted hierarchical bimodal silica.</a> Chemical Engineering Journal. 427 (14), 131561 (2022).</li><li>Sanz, R., Calleja, G., Arencibia, A., Sanz-P&#233;rez, E. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amino+functionalized+mesostructured+SBA-15+silica+for+CO2+capture:+Exploring+the+relation+between+the+adsorption+capacity+and+the+distribution+of+amino+groups+by+TEM.">Amino functionalized mesostructured SBA-15 silica for CO2 capture: Exploring the relation between the adsorption capacity and the distribution of amino groups by TEM.</a> Microporous and Mesoporous Materials. 158, 309-317 (2012).</li><li>Moon, H. J., 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=Understanding+the+impacts+of+support-polymer+interactions+on+the+dynamics+of+poly(ethyleneimine)+confined+in+mesoporous+SBA-15.">Understanding the impacts of support-polymer interactions on the dynamics of poly(ethyleneimine) confined in mesoporous SBA-15.</a> Journal of the American Chemical Society. 144 (26), 11664-11675 (2022).</li><li>Xu, X., Song, C., Andresen, J. M., Miller, B. G., Scaroni, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+and+characterization+of+novel+CO2+&amp;#34;molecular+basket&amp;#34;+absorbents+based+on+polymer-modified+mesoporous+molecular+sieve+MCM-41.">Preparation and characterization of novel CO2 &amp;#34;molecular basket&amp;#34; absorbents based on polymer-modified mesoporous molecular sieve MCM-41.</a> Microporous and Mesoporous Materials. 62 (1-2), 29-45 (2003).</li><li>Sousa, J. A. 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=H2S+and+H2O+combined+effect+on+CO2+capture+by+amino+functionalized+hollow+microsphere+silicas.">H2S and H2O combined effect on CO2 capture by amino functionalized hollow microsphere silicas.</a> Industrial &amp; Engineering Chemistry Research. 60 (28), 10139-10154 (2021).</li><li>Rim, G., 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=Sub-ambient+temperature+direct+air+capture+CO2+using+amine-impregnated+MIL-101(Cr)+enables+ambient+temperature+CO2.">Sub-ambient temperature direct air capture CO2 using amine-impregnated MIL-101(Cr) enables ambient temperature CO2.</a> JACS Au. 2 (2), 380-393 (2022).</li></ol>

All authors disclose no competing conflicts of interest. The full description of the procedures used in this paper requires the identification of certain commercial products and their suppliers. The inclusion of such information should in no way be construed as indicating that such products or suppliers are endorsed by NIST, or are recommended by NIST, or that they are necessarily the best materials, instruments, software or suppliers for the purposes described.

The methods described herein are intended to provide a protocol for preparing impregnated and grafted amine silica-composite adsorbents. The procedures we have documented are based on review of techniques reported in the literature and those refined in our laboratory.1,2,3. Preparation of these materials is useful within the field of carbon dioxide removal research to develop or benchmark other materials that may be used to lowe...

The anthropogenic CO2 emissions over the past several decades have been widely implicated as the main factor driving the greenhouse gas effect and consequently, related climate change1,2,3,4. There are two general methods for CO2 capture, point source and direct air capture. For more than 50 years, wet-scrubbing CO2 capture technologies have been utilized for point source capture within the industry to mitigate CO2 emissions5,6. These technologies are based on liquid-phase amines that react with CO2 to form carbamates under dry conditions and hydrogen carbonates in the presence of water7,8, see Figure 1. The main reason that carbon capture and storage is utilized at large point (industrial) sources is to prevent the further release of large quantities of CO2, thus having a neutral effect on total CO2 concentration in the atmosphere. However, point-source carbon capture systems suffer from several drawbacks, such as equipment corrosion, solvent degradation, and high energy requirements for regeneration9. Direct air capture (DAC) goes beyond emission reduction and can facilitate the removal of CO2 from the atmosphere. The removal of this existing CO2 is necessary to limit continued climate change. DAC is an emerging methodology and must address the difficulties of removing low concentrations of CO2 in atmospheric conditions (400 to 420 ppm), operate in a variety of different environmental conditions, and address the need for cost-effective materials that can be reused many times1,2,3. Significant work is needed to identify materials that meet these requirements, which will accelerate the adoption of DAC and improve its economic feasibility. Most importantly, community consensus on critical parameters of measurement needs to be established, which is essential for benchmark materials to be developed.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65845/65845fig01.jpg" /> 
Figure 1: Schematic of the expected liquid amine adsorbent CO2 capture mechanism. The top reaction is in dry conditions, and the bottom reaction is in the presence of moisture. <a href="https://www.jove.com/files/ftp_upload/65845/65845fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In an effort to remedy these drawbacks, considerable research and development of novel porous material technology have resulted in a wide array of promising materials that have the potential to be utilized as either capture materials or substrates for DAC. Some examples of such materials include mesoporous silica species10,11,12,13, zeolites14,15, activated carbon16,17, and metal-organic frameworks18. Many solid-supported amine adsorbents also show a higher tolerance to water, which is a vital consideration in CO2 removal through DAC approaches. For DAC applications, researchers must consider wet/dry environmental conditions, hot/cold temperatures, and an overall dilute atmospheric CO2 concentration. Amongst the various substrate materials, silica is commonly used because of its adjustable pore sizes, ability to surface functionalize, and large surface area1,2,3. Typical synthetic procedures and primary features of both impregnated and grafted amine-silica composites are described within this work (Figure 2). Direct synthesis, where the material is made in situ with both components, substrate and amine, is another commonly used methodology2.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/65845/65845fig02.jpg" /> 
Figure 2: Schematic representations of impregnation. Mixing of PEI and silica substrate in methanol through diffusion (top) and grafted amine-silica composites through covalent tethering (bottom). <a href="https://www.jove.com/files/ftp_upload/65845/65845fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Impregnation&#160;is a method in which an amine is physically adsorbed onto a surface, in this case, a porous silica medium, through van der Waals forces and hydrogen bonding between the amine and silica surface19,&#160;see Figure 2. Solvents such as ethanol and methanol are commonly used to promote the diffusion of the molecules into the porous structure of the substrate material. The solution can also be heated to increase the solubility of the high molar mass polyamines, thereby increasing the homogeneity of amine penetration within the pores. In the case of impregnated materials, the amount of amine introduced to a silica substrate is determined by the initial quantity of the amine and the surface area of the substrate. If the amount of amine introduced exceeds the available surface area of the silica substrate, the amine species will agglomerate on its surface. This agglomeration is readily apparent, as the impregnated material will appear to have a gel-like coating, often yellow, rather than the expected white and powdery appearance1. Among the many types of amine-base solid adsorbents, polyethyleneimine (PEI) and tetraethylene pentamine (TEPA) are the most widely used due to their high stability and high nitrogen content20. For physically impregnated systems, the theoretical loading quantity of amine can be calculated from the pre-weighted amounts of the substrate and the density of the amine. The obvious advantage of physical impregnation lies in the straightforward synthesis procedure to prepare it, as well as the potential for a large amine content due to the high porosity of the silica substrate. Conversely, the stability of the amine within the silica is limited because there is no covalent bonding between the amine and silica support. Therefore, after multiple cycles of CO2 uptake and regeneration through heat or steam, the amine can leach out of the pores. Despite these drawbacks, the implementation of such materials for DAC holds great promise for removing CO2 from the atmosphere.
Another option for the preparation of DAC materials is grafting. Grafting is a method through which amines are immobilized onto a porous silica substrate through a chemical reaction, as shown in Figure 2. This reaction proceeds by reacting an aminosilane with the surface&#39;s silanol functional group, resulting in a covalent bond. Therefore, the number of functional groups on the surface of the silica substrate impacts the grafted amine density21,22. Compared to amine-impregnated adsorbents, chemical grafting methods have had lower CO2 adsorption capacity mainly due to the low amine loading21. Conversely, chemically-grafted amines have increased thermal stability due to their covalently bound structure. This stability can be useful in the regeneration of the material as adsorbents (such as grafted silica) are heated and pressurized to remove the captured CO2 for reuse to save material and cost. In a typical synthesis procedure, the mesoporous silica substrate is dispersed in a solvent (e.g., anhydrous toluene), which is then followed by the addition of aminosilanes. The resulting sample is then washed to remove unreacted aminosilanes. Improvements in aminosilane density are reported to have been achieved through water addition, specifically with SBA-15, to expand pore size23. The procedure for grafting that will be described herein uses moisture-sensitive techniques. Therefore, additional water will not be used. Implementation of grafted aminosilane materials for DAC is promising due to their expected stability during CO2 adsorption and desorption processes. However, the major drawbacks of this methodology include the complex reactions/preparation of these materials, leading to increased cost, and their overall low CO2 adsorption capacity, meaning larger quantities are required.
Overall, results of many previous studies indicate that the structure of the substrate and amine-related modification has a significant impact on the adsorption performance with specific studies utilizing techniques such as transmission electron microscopy (TEM) and quasi-elastic neutron scattering (QENS) to fully characterize these materials24,25. In other words, the structural properties (e.g., porosity and surface area) of the substrate material determine the amine loading, so increasing these parameters can improve CO2 capacity24,25. Continued research into the optimization and design of substrate materials and preparation processes is critical to the development of high-performance adsorbents for DAC. The goal of this work is to provide guidance on impregnation and grafted amine synthesis in hopes of facilitating better transparency of synthetic techniques. Within the literature, specific details on the amounts of solvent, substrate, and amines are not always described, making it difficult to understand the correlation between experimental loading amounts and quantitative measurements of amine-silica composites. The exact loading amounts and a detailed description of the experimental procedures will be provided herein to better facilitate these types of comparisons.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Anhydrous methanol</td>
			<td>Sigma-Aldrich</td>
			<td>322415</td>
			<td>Does not come with sure-seal</td>
		</tr>
		<tr>
			<td>Anhydrous toluene</td>
			<td>Sigma-Aldrich</td>
			<td>244511</td>
			<td>Comes with sure-seal</td>
		</tr>
		<tr>
			<td>Ceramic Stirring Hot Plate</td>
			<td>NA</td>
			<td>NA</td>
			<td>The size, watage, and thermal capabilities of the stirr plate will differ depending on individual lab facilities.</td>
		</tr>
		<tr>
			<td>Fourier Transform Infrared Spectroscopy (FTIR)&#160;</td>
			<td>Nicolet i550 series spectrometer</td>
			<td>NA</td>
			<td>Run on OMNIC standard software</td>
		</tr>
		<tr>
			<td>Gastight syringe&#160;</td>
			<td>NA</td>
			<td>NA</td>
			<td>As long as the gas tight syringe has a PTFE plunger and luer tip, is suited for air sensitive technique and can be used in this protocol.&#160;</td>
		</tr>
		<tr>
			<td>Glass vial</td>
			<td>NA</td>
			<td>NA&#160;</td>
			<td>As long as the vial is made if borosilicate glass and has a screw based cap the brand name, size, or general shape does not matter for the protocol.</td>
		</tr>
		<tr>
			<td>MCM-41 silica</td>
			<td>ACS Material&#160;</td>
			<td>MSM41A01&#160;</td>
			<td>Cas no. 7631-86-9</td>
		</tr>
		<tr>
			<td>Metal needle</td>
			<td>NA</td>
			<td>NA</td>
			<td>Syringe needles need to be stainless steel. It is recommended to determine length and outerdiameter of needle by what will be transferred using the gas tight syringe. For large quantities of liquid a larger outer diameter will improve transfer rates.&#160;</td>
		</tr>
		<tr>
			<td>N&#8217;-(3-trimethylsilyl propyl) diethyleneamine (DAS)</td>
			<td>Sigma-Aldrich</td>
			<td>104884</td>
			<td>Comes with sure-seal&#160;</td>
		</tr>
		<tr>
			<td>Polyethyleneimine (PEI)</td>
			<td>Sigma-Aldrich</td>
			<td>408719</td>
			<td>Does not come with sure-seal</td>
		</tr>
		<tr>
			<td>Schlenk round bottom flask</td>
			<td>ChemGlass AirFree</td>
			<td>NA</td>
			<td>As long as the flask is suited for high pressure and temperture but the brand name, size, or general shape does not matter for the protocol</td>
		</tr>
		<tr>
			<td>Thermogravemetric Anlysis (TGA)&#160;</td>
			<td>TA Advantage</td>
			<td>NA</td>
			<td>550 series from Waters and TA Instruments</td>
		</tr>
	</tbody>
</table>

a synthetic methodology for preparing impregnated and grafted amine-based silica composites for carbon capture

Recently, there has been a significant effort towards reducing or mitigating CO2 emissions through the use of carbon capture materials for point source or direct air capture (DAC) methods. This work focuses on amine-functionalized CO2 adsorbents for DAC. These materials show promise for CO2 removal because they have low regeneration energy consumption and high adsorption capacity. The incorporation of amine species into a porous substrate combines the advantages of the amine species&#39; affinity to CO2 with the large pore volumes and surface areas of the porous substrate. There are three methods commonly used to prepare amine-based CO2 sorbents, depending on the selection of the amine species, material support, and preparation method. These methods are impregnation, grafting, or chemical synthesis. Silica is a prevalent choice of substrate material because of its adjustable pore size, moisture tolerance, temperature stability, and ability to adsorb CO2 in low concentrations for DAC applications. Typical synthetic procedures and primary attributes of both impregnated and grafted amine-silica composites are described herein.

TGA is commonly used to quantify the amount of amine loaded or grafted to the silica surface for these materials. The obtained TGA curves show a loss of residual solvent and water between 60 &#176;C to 100 &#176;C, which is shown in the derivate weight (weight %/&#176;C) curve as the first peak, and a loss of amine, which is shown in the derivate weight curve (weight %/&#176;C) as the second peak. For PEI-impregnated silica, this loss of amine is expected to appear around 200 &#176;C to 300 &#176;C, which appears as the ...

Watch this Scientific Journal Video about Standardizing the Development of Amine-Based Silica Composites as CO2 Adsorbents for Direct Air Capture at JoVE.com

Author Spotlight: Standardizing the Development of Amine-Based Silica Composites as CO2 Adsorbents for Direct Air Capture 

This work aims to facilitate the development of standardized techniques for impregnating or grafting aminated compounds onto silica substrates, which are often broadly described in the literature. Specific amounts of solvent, substrate, amines, and the values of other important experimental parameters will be discussed in detail.

A Synthetic Methodology for Preparing Impregnated and Grafted Amine-Based Silica Composites for Carbon Capture

Recently, there has been a significant effort towards reducing or mitigating CO2 emissions through the use of carbon capture materials for point source or ...

Scientists here at NIST are developing critical measurement science and benchmark materials to accelerate innovation and explore timely, effective, and scalable direct air capture, or DAC, for carbon-dioxide removal from the atmosphere. This work focuses on promoting best practices for preparation, measurement, and reporting of amine-functionalized silica composites for DAC applications. This protocol addresses outstanding research challenges and reproducible synthetic procedures for DAC materials by providing clear guidelines and conditions while identifying critical steps.In addition, we aim to enable a meaningful comparison of carbon-dioxide capabilities of these materials through clear documentation of specific adsorption experimental parameters. We are turning our efforts towards characterizing benchmark materials and developing standard techniques to foster greater comparability and confidence in reported results.

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Research

JoVE Journal

Chemistry

1.6K Views.  National Institute of Standards and Technology (NIST). Scientists here at NIST are developing critical measurement science and benchmark materials to accelerate innovation and explore timely, effective, and scalable direct air capture, or DAC, for carbon-dioxide removal from the atmosphere. This work focuses on promoting best practices for preparation, measurement, and reporting of amine-functionalized silica composites for DAC applications. This protocol addresses outstanding research challenges and reproducible synthetic procedures for DAC mate...

Video: Author Spotlight: Standardizing the Development of Amine-Based Silica Composites as CO2 Adsorbents for Direct Air Capture 

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

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

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

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

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.

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

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10-3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.

This article describes a rapid supercritical extraction method for fabricating silica aerogels. By utilizing a confined mold and hydraulic hot press, monolithic aerogels can be made in eight hours or less.

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The ...

Manufacturing of Three-dimensionally Microstructured Nanocomposites through Microfluidic Infiltration

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite in&#64257;ltration of 3D interconnected microfluidic networks. The manufacturing of the reinforced beams begins with the fabrication of microfluidic networks, which involves layer-by-layer deposition of fugitive ink filaments using a dispensing robot, filling the empty space between filaments using a low viscosity resin, curing the resin and finally removing the ink.&#160;Self-supported 3D structures with other geometries and many layers (e.g.&#160;a few hundreds layers) could be built using this method. The resulting tubular micro&#64258;uidic networks are then infiltrated with thermosetting nanocomposite suspensions containing nanofillers (e.g.&#160;single-walled carbon nanotubes), and subsequently cured. The infiltration is done by applying a pressure gradient between two ends of the empty network (either by applying a vacuum or vacuum-assisted microinjection). Prior to the infiltration, the nanocomposite suspensions are prepared by dispersing nanofillers into polymer matrices using ultrasonication and three-roll mixing methods. The nanocomposites (i.e.&#160;materials infiltrated) are then solidified under UV exposure/heat cure, resulting in a 3D-reinforced composite structure. The technique presented here enables the design of functional nanocomposite macroscopic products for microengineering applications such as actuators and sensors.

Three-dimensional (3D) microstructured composite beams are fabricated through the directed and localized infiltration of nanocomposites into 3D porous microfluidic networks. The flexibility of this manufacturing method enables the utilization of different thermosetting materials and nanofillers in order to achieve a variety of functional 3D reinforced nanocomposite macroscopic products.

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite ...

Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing and maintaining primary and pluripotent stem cell derived hepatocytes. While biological matrices are useful, they permit short term culture of hepatocytes, limiting their widespread application. We have attempted to overcome the limitations using a synthetic polymer coating. Polymers represent one of the broadest classes of biomaterials and possess a wide range of mechanical, physical and chemical properties, which can be fine-tuned for purpose. Importantly, such materials can be scaled to quality assured standards and display batch-to-batch consistency. This is essential if cells are to be expanded for high through-put screening in the pharmaceutical testing industry or for cellular based therapy. Polyurethanes (PUs) are one group of materials that have shown promise in cell culture. Our recent progress in optimizing a polyurethane coated surface, for long-term culture of human hepatocytes displaying stable phenotype, is presented and discussed.

This article will focus on developing polymer coated surfaces for long-term, stable culture of stem cell derived human hepatocytes.

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing ...

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

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

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

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

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.

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. ...

Optimization of Synthetic Proteins: Identification of Interpositional Dependencies Indicating Structurally and/or Functionally Linked Residues

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional units (e.g., domains). Traditional consensus-building models fail to account for interpositional dependencies &#8211; functionally required covariation of residues that tend to appear simultaneously throughout evolution and across the phylogentic tree. These relationships can reveal important clues about the processes of protein folding, thermostability, and the formation of functional sites, which in turn can be used to inform the engineering of synthetic proteins. Unfortunately, these relationships essentially form sub-motifs which cannot be predicted by simple &#8220;majority rule&#8221; or even HMM-based consensus models, and the result can be a biologically invalid &#8220;consensus&#8221; which is not only never seen in nature but is less viable than any extant protein. We have developed a visual analytics tool, StickWRLD, which creates an interactive 3D representation of a protein alignment and clearly displays covarying residues. The user has the ability to pan and zoom, as well as dynamically change the statistical threshold underlying the identification of covariants. StickWRLD has previously been successfully used to identify functionally-required covarying residues in proteins such as Adenylate Kinase and in DNA sequences such as endonuclease target sites.

Synthetic protein sequences based on consensus motifs typically ignore co-evolving residues, that imply interpositional dependencies (IPDs). IPDs can be essential to activity, and designs that disregard them may result in suboptimal results. This protocol uses StickWRLD to identify IPDs and help inform rational protein design, resulting in more efficient results.

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional ...

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

Color Spot Test As a Presumptive Tool for the Rapid Detection of Synthetic Cathinones

Synthetic cathinones are a large class of new psychoactive substances (NPS) that are increasingly prevalent in drug seizures made by law enforcement and other border protection agencies globally. Color testing is a presumptive identification technique indicating the presence or absence of a particular drug class using rapid and uncomplicated chemical methods. Owing to their relatively recent emergence, a color test for the specific identification of synthetic cathinones is not currently available. In this study, we introduce a protocol for the presumptive identification of synthetic cathinones, employing three aqueous reagent solutions: copper(II) nitrate, 2,9-dimethyl-1,10-phenanthroline (neocuproine) and sodium acetate. Small pin-head sized amounts (approximately 0.1-0.2 mg) of the suspected drugs are added to the wells of a porcelain spot plate, and each reagent is then added dropwise sequentially before heating on a hotplate. A color change from very light blue to yellow-orange after 10 min indicates the likely presence of synthetic cathinones. The highly stable and specific test reagent has the potential for use in the presumptive screening of unknown samples for synthetic cathinones in a forensic laboratory. However, the nuisance of an added heating step for the color change result limits the test to laboratory application and decreases the likelihood of an easy translation to field testing.

Here we present a simple, inexpensive, and selective chemical spot test protocol for the detection of synthetic cathinones, a class of new psychoactive substances. The protocol is suitable for use in various areas of law enforcement that encounter illicit material.

Synthetic cathinones are a large class of new psychoactive substances (NPS) that are increasingly prevalent in drug seizures made by law enforcement and ...