The surface terminations (=O, -OH, and -F) play a key role in determining the physical and chemical properties of MXenes, which have been demonstrated with significant potential in field-effect transistors, humidity sensors, energy storage, and photocatalysis, etc. It is therefore crucial to modify these active functional groups on the surface of MXenes in order to optimize the applicability of these materials. In this study, we introduce a covalent modification strategy to successfully construct a porphyrin-functionalized Ti3C2Tx organic-inorganic nanohybrid (TPP-Ti3C2Tx) by covalently attaching porphyrin molecules to the surface groups on Ti3C2Tx nanosheets for the first time. As revealed by steady-state fluorescence spectra, transient fluorescence spectra, and DFT calculations, the robust covalent bonds between TPP and Ti3C2Tx can effectively promote the photon-induced electron and/or energy transfer within the TPP-Ti3C2Tx nanohybrid. The investigation on the nonlinear optical (NLO) properties of TPP-Ti3C2Tx nanohybrid as well as its precursors, reveals that the TPP-Ti3C2Tx nanohybrid exhibits the highest nonlinear absorption coefficient and the lowest optical limiting threshold among the tested samples at both 532 and 1064 nm, indicating its great potential as a broadband optical limiter for visible and near-infrared wavelengths. This work not only demonstrates the significant promise of covalently-linked TPP-Ti3C2Tx nanohybrid in optical limiting applications but also provides a paradigm for engineering high-performance NLO MXenes-based materials through the covalent modification strategy.

中文翻译：

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通过卟啉的表面共价官能化增强 MXene （Ti3C2Tx） 的非线性光学特性


表面终端（=O、-OH 和 -F）在决定 MXenes 的物理和化学性质方面起着关键作用，这在场效应晶体管、湿度传感器、储能和光催化等方面已被证明具有巨大的潜力。因此，为了优化这些材料的适用性，对 MXenes 表面的这些活性官能团进行改性至关重要。在这项研究中，我们引入了一种共价修饰策略，通过将卟啉分子共价连接到Ti3C2Tx纳米片上的表面基团，成功构建了卟啉官能化的Ti3C2Tx有机-无机纳米杂化物（TPP-Ti3C2Tx）。稳态荧光光谱、瞬态荧光光谱和 DFT 计算表明，TPP 和 Ti3C2Tx 之间的稳健共价键可以有效促进 TPP-Ti3C2Tx 纳米杂化物内光子诱导的电子和/或能量转移。对 TPP-Ti3C2Tx 纳米杂化物及其前驱体的非线性光学 （NLO） 特性的研究表明，TPP-Ti3C2Tx 纳米杂化物在 532 nm 和 1064 nm 处均表现出最高的非线性吸收系数和最低的光限制阈值，表明其作为可见光和近红外波长的宽带光限制器具有巨大潜力。这项工作不仅证明了共价连接的 TPP-Ti3C2Tx 纳米杂化在光限制应用中的重要前景，而且还为通过共价修饰策略设计高性能 NLO MXenes 基材料提供了一种范式。