Since their discovery, carbon nanotubes and other related nanomaterials are in the spotlight due to their unique molecular structures and properties, having a wide range of applications. The cage-like structure of carbon nanotubes is especially appealing as a route to confine molecules, isolating them from the solvent medium. This study aims to explore and characterize, through density functional theory (DFT) calculations, covalent tip-functionalization of single-walled carbon nanotubes (SWCNTS) with carboxymethyl moieties that establish pH sensitive molecular gates. The response of the molecular gate to pH fluctuations arises from variations in the noncovalent interactions between functionalized groups, which depend on the extent of protonation, leading to conformational changes. Overall, the hydrogen bonds present in the molecular models under study, as evaluated through topological analysis and pK_a calculations, suggest that functionalized SWCNTs may be suitable for the design of drug delivery systems to enhance the efficiency of some pharmacological treatments, or even in the area of catalysis and separation processes, through their incorporation in nanocomposites.

中文翻译：

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尖端功能化单壁碳纳米管中的分子内氢键作为pH敏感门

自发现以来，碳纳米管和其他相关的纳米材料因其独特的分子结构和性能而备受关注，具有广泛的应用范围。碳纳米管的笼状结构作为限制分子，将其与溶剂介质隔离的途径特别吸引人。这项研究旨在通过密度泛函理论（DFT）计算来探索和表征单壁碳纳米管（SWCNTS）与建立pH敏感分子门的羧甲基部分的共价末端官能化。分子门对pH波动的响应来自官能化基团之间非共价相互作用的变化，这取决于质子化的程度，从而导致构象变化。总体，K _a计算表明，功能化的SWCNT可能适合于药物输送系统的设计，以通过将其掺入纳米复合材料中来提高某些药理治疗的效率，甚至在催化和分离工艺领域。