Journal article
Band-like Optical Signatures of Ti 3 C 2 T x MXenes
Journal of physical chemistry. C, v 130(6), pp 2294-2306
27 Jan 2026
Abstract
<p>MXenes have shown great potential in electronic and optoelectronic applications. However, the optical properties of these highly conductive two-dimensional materials are not fully understood. The broad near-infrared (IR) optical extinction (similar to 1.5 eV) in Ti3C2Tx with mixed terminations (T-x: & boxH;O, -OH, -F, -Cl) has been widely attributed to a localized surface plasmon resonance (LSPR). However, previous simulations suggest this peak may be due to an interband transition (IBT). Here, we show that the real component of the dielectric constant of Ti3C2Tx at this peak is positive (epsilon(1) > 0), as measured by spectroscopic ellipsometry (SE), ruling out the possibility of LSPR. Moreover, this band nearly vanishes for experimentally synthesized chlorine-terminated Ti3C2Cl2. Density functional theory (DFT) calculations confirm an IBT origin for this band, specifically due to the oxygen terminations (Ti3C2O2). Metallic behavior is only experimentally observed below 1 eV (epsilon(1) < 0), and DFT calculations predict surface plasmon polaritons (SPPs) in the mid-IR (similar to 0.5 eV, outside the optical domain) and only for Ti3C2O2, but not for Ti3C2Cl2 or other terminations. Additionally, we demonstrate that making thicker Ti3C2Tx MXene films and/or removing the intercalated water can induce a blue shift in this IBT due to the influence of water in facilitating the out-of-plane conductivity. The IBT assignment is critical because its light-matter interaction is fundamentally different from that of an LSPR, providing a new foundation for designing innovative MXene-based optoelectronic materials, which can be tailored through their termination states, while an LSPR would be insensitive to such synthetic variations.</p>
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Details
- Title
- Band-like Optical Signatures of Ti 3 C 2 T x MXenes
- Creators
- Hui Fang - California University of PennsylvaniaZhenyao Fang - California University of PennsylvaniaAnupma Thakur - Purdue University West LafayetteVahid Rad - Drexel UniversityNithin Chandran Balachandran SajithaPaweł P. Michałowski - Łukasiewicz Research NetworkMasoud Soroush - Drexel UniversityBabak Anasori - Purdue University West LafayetteAndrew M. Rappe - California University of PennsylvaniaZahra Fakhraai (Corresponding Author) - California University of Pennsylvania
- Publication Details
- Journal of physical chemistry. C, v 130(6), pp 2294-2306
- Publisher
- ACS Publications
- Number of pages
- 13
- Grant note
- Narodowe Centrum Badan i Rozwoju: LIDER/8/0055/L-12/20/NCBR/2021 University of Pennsylvania: NA Narodowe Centrum Nauki: 14 2024/54/E/ST11/00171 National Science Foundation: CHE-2303044
The authors acknowledge funding support from the US National Science Foundation, award numbers CMMI-2134607 and CHE-2318105 (M-STAR CCI). Zh.F. acknowledges funding from the US National Science Foundation, award number CHE-2303044. P.P.M. was supported by the National Science Centre, Poland, within the SONATA BIS 14 2024/54/E/ST11/00171 project and the National Centre for Research and Development, Poland, with the LIDER/8/0055/L-12/20/NCBR/2021 project. The authors acknowledge Dr. Lianne Beltran for professional editing. Za.F. and H.F. thank Prof. Alexandra Vojvodic for her helpful insight and discussions. H.F. acknowledges the School of Arts and Sciences at the University of Pennsylvania for the Postdoctoral Fellowship.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Chemical and Biological Engineering
- Web of Science ID
- WOS:001673904300001
- Scopus ID
- 2-s2.0-105030277014
- Other Identifier
- 991022158359304721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Chemistry, Physical
- Materials Science, Multidisciplinary
- Nanoscience & Nanotechnology