Unravelling the Thickness Dependence and Mechanism of Surface-Enhanced Raman Scattering on Ti3C2TXMXene Nanosheets

Tej B. Limbu, Basant Chitara, Martha Y. Garcia Cervantes, Yu Zhou, Shengxi Huang, Yongan Tang, Fei Yan

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

MXenes have attracted great attention as promising substrates for surface-enhanced Raman scattering (SERS) applications. However, the underlying SERS mechanism has not been a focus of any investigation. Herein, we report the first systematic experimental study on the SERS activity of titanium carbide (Ti3C2TX) nanosheets with thicknesses ranging from 5 to 120 nm, using methylene blue (MB) as a probe molecule. The experimental and mathematical modeling results show that the Raman enhancement factor (EF) increases monotonically with the increasing thickness of Ti3C2TX nanosheets; however, it falls drastically around a sheet thickness of 0.8 and 1.0 μm under 532 and 633 nm laser excitations, respectively. The Raman EF reaches a maximum value around a thickness of 2.0 μm, suggesting that a maximum EF can be achieved with a 2.0 μm-thick Ti3C2TX film substrate. The thickness dependence of the Raman enhancement can be accounted for by the adsorption and intercalation of MB molecules into the interlayer spacing of Ti3C2TX. Furthermore, by combining experimental observations and numerical calculation, we confirm that the charge-transfer mechanism is dominantly responsible for Raman enhancement on Ti3C2TX. Additionally, we report an observation of resonance coupling of charge transfer and molecular transition as a contributing factor to the higher EF obtained with a 633 nm laser excitation. Taken together, these findings have significant implications for cost and performance optimization in designing MXene-based SERS substrates for next-generation chemical and biological sensing platforms.

Original languageEnglish (US)
Pages (from-to)17772-17782
Number of pages11
JournalJournal of Physical Chemistry C
Volume124
Issue number32
DOIs
StatePublished - Aug 13 2020

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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