Characterization of Functionalized Chromatographic Nanoporous Silica Materials by Coupling Water Adsorption and Intrusion with Nuclear Magnetic Resonance Relaxometry
Characterization of Functionalized Chromatographic Nanoporous Silica Materials by Coupling Water Adsorption and Intrusion with Nuclear Magnetic Resonance Relaxometry
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DOI：
10.1021/acsanm.3c04330
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发表时间：
2024-01
影响因子：
5.9
通讯作者：
Carola Schlumberger;Carlos Cuadrado Collados;Jakob Söllner;Christoph Huber;D. Wisser;Hsiao-Feng Liu
中科院分区：
文献类型：
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作者：
Carola Schlumberger;Carlos Cuadrado Collados;Jakob Söllner;Christoph Huber;D. Wisser;Hsiao-Feng Liu
纳米多孔二氧化硅在色谱分离和催化应用中广泛用作化学结合固定相的支撑材料。调整固定相材料（SPMs）的结构性质和表面化学性质对于提高其对某些化合物的选择性和由此产生的工艺效率至关重要。纳米多孔二氧化硅载体是有益的，因为可以用各种亲疏水官能团进行表面修饰，但它们对表面性质的影响尚未得到详细评估。从这个意义上说，接触角是评估表面化学的关键参数，但其在孔隙中的量化具有挑战性，需要多种实验技术的结合。这项工作表明，将水吸附和侵入测量相结合，可以使用功能化亲水和疏水二氧化硅spm作为模型材料，确定在润湿、部分润湿和非润湿情况下，孔壁上吸附水的有效接触角。此外，核磁共振弛豫实验表明，吸附水膜的自旋晶格（T1）与自旋自旋（T2）弛豫时间（T1,ads.film/T2,ads.filmratio）可以与水在表面的有效吸附强度相关。实际上，观察到负逆弛豫时间比（- T2,ads.film/T1,ads.film）与接触角之间存在线性相关。我们的工作表明，水蒸气吸附和水侵入实验与核磁共振弛豫测量相结合，可以作为辅助工具来量化纳米多孔材料的润湿性和表面化学。这种方法可以在材料合成的背景下解决纳米级润湿性的重要方面，以及它们在色谱分离过程和催化中的应用。
Nanoporous silica is widely used as a support material for chemically bound stationary phases in chromatographic separations as well as for catalytic applications. Tuning of textural properties and surface chemistry of stationary phase materials (SPMs) is crucial to enhance their selectivity to certain compounds and the resulting process efficiency. Nanoporous silica supports are beneficial, as surface modifications are possible with a large variety of hydrophilic and hydrophobic functional groups, but their influence on the surface properties has not been evaluated in detail. In this sense, the contact angle is a key parameter for the assessment of surface chemistry, but its quantification in pores is challenging and requires a combination of various experimental techniques. This work demonstrates that combining water adsorption and intrusion measurements allows for the determination of the effective contact angle of adsorbed water on the pore walls for wetting, partial wetting, and nonwetting situations using functionalized hydrophilic and hydrophobic silica SPMs as model materials. Furthermore, NMR relaxometry experiments reveal that the ratio of the spin–lattice (T1) to spin–spin (T2) relaxation time of the adsorbed water film (T1,ads.film/T2,ads.filmratio) can be correlated with the effective adsorption strength of water on the surface. Indeed, a linear correlation between the negative inverse relaxation time ratio (−T2,ads.film/T1,ads.film) and the contact angle is observed. Our work demonstrates that water vapor adsorption and water intrusion experiments coupled with NMR relaxometry can be used as complementary tools to quantify the wettability and surface chemistry of nanoporous materials. This approach allows for addressing important aspects of nanoscale wettability in the context of material synthesis as well as for their application in chromatographic separation processes and catalysis.