Remarkable surface-enhanced Raman scattering of highly crystalline monolayer Ti3C2 nanosheets

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  • ReceivedFeb 27, 2020
  • AcceptedFeb 28, 2020
  • PublishedMar 25, 2020


Funded by

This wor was supported by the National Key Research and Development Program of China(2017YFF0210003)

and the Science Foundation of Chinese Academy of Inspection and Quarantine(2019JK004)


This work received financial support from the Science Foundation of Chinese Academy of Inspection and Quarantine (2019JK004), the National Key Research and Development Program of China (2017YFF0210003), and the high performance computing center of Qufu Normal University.

Interest statement

The authors declare that they have no conflict of interest.

Contributions statement

Ye Y and Xi G designed and performed the experiments; Yi W calculated the electronic structure; Liu W, Zhou Y and Bai H discussed partial experimental data; Li J and Xi G wrote the paper. All authors contributed to the general discussion.

Author information

Yuting Ye is currently a MSc candidate in material chemistry under the supervision of Prof. Guangcheng Xi at Chinese Academy of Inspection and Quarantine. His research centers on developing the excellent SERS materials for chemical sensing devices.

Wencai Yi received his BSc degree in 2013 from Tianjin Normal University. In 2018, he received his PhD degree from Jilin University, China. Then, he joined Qufu Normal University as a lecturer. His research interests focus on the algorithm of structure prediction, low dimensional gas-sensing materials, SERS and high energy density materials.

Guangcheng Xi received his BSc degree in 2002 from Fuyang Normal University, China. In 2007, he received his PhD degree from the University of Science and Technology of China. Then, he joined Chinese Academy of Inspection and Quarantine as an assistant professor. He became an associate professor in 2011 and a full professor in 2017. Currently, his research interests focus on the SERS, chemical sensing, and the nanostructure-based analysis for harmful substances.


Supplementary information

Supplementary methods and data are available in the online version of the paper, including Raman enhanced factor calculation, electronic structure calculation, photograph of the dispersion of the monolayer Ti3C2 nanosheets, XRD patterns of the Ti3C2 monolayers and Ti3AlC2, XEDS and XPS spectra of the Ti3C2 monolayers, UV-Vis absorption spectra of the obtained monolayer Ti3C2 nanosheets with high crystallinity and low crystallinity, the standard Raman spectrum of R6G reference material, and the crystal structure of Ti3C2.


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  • Figure 1

    Schematic diagram for the synthesis of highly crystalline monolayer Ti3C2 nanosheets. Note: HF and HClO4 are corrosive and should be used with extra care.

  • Figure 2

    Morphology and structure characterizations of the Ti3AlC2 precursor and the monolayer Ti3C2 nanosheets. (a) The commercial Ti3AlC2 powders after grinding. (b) The multilayer Ti3C2 nanosheets obtained by HClO4 and HF etching. (c) The SEM image of the monolayer Ti3C2 nanosheets. (d) TEM image of the monolayer Ti3C2 nanosheets. (e) AFM image of the Ti3C2 nanosheets. (f) HRTEM image of the monolayer Ti3C2 nanosheets, inset: FFT pattern of the nanosheet.

  • Figure 3

    (a) XPS spectrum of the monolayer Ti3C2 nanosheets. (b) XPS spectrum of the monolayer Ti3C2Tx nanosheets without microwave heating. (c) HRTEM image of the as-synthesized multilayer Ti3C2 nanosheets. (d) HRTEM image of the obtained monolayer Ti3C2 nanosheets without microwave heating.

  • Figure 4

    SERS properties of the flexible Ti3C2 nanosheets. (a) Flexible SERS substrate based on the Ti3C2 ultrathin nanosheets. (b) Raman spectra of 10−6–10−11mol L−1 R6G obtained in the flexible SERS substrate. (c) The average Raman EFs obtained by counting the peak intensities (R1 and R2) at three different concentration levels. (d) SERS signals collected from 20 randomly selected points on the substrate. (e) The signal intensity distribution at 612 cm−1 of 10−8 mol L−1 R6G recorded from 10,000 sites. (f) The signal intensity distribution recorded by SERS mapping at 612 cm−1 of 10−8 mol L−1 R6G in the substrate. (g) Single-molecule SERS spots recorded from 10−11 mol L−1 R6G. (h) SERS spectra of Ti3C2 ultrathin nanosheets stored in air for 3–12 months. (i) SERS spectra of a series of harmful substances: butyl hydroxy anisd (BHA), melamine, BPA, 2,4,5-TCP, and acid fuchsin (AF).

  • Figure 5

    Enhancement mechanism of the monolayer Ti3C2 nanosheets. (a) The electronic local function (ELF) of Ti3C2 with a scale bar from zero at the low end to one at the high end. (b) The DOS of Ti3C2 near the Fermi levels. (c) Side views of the electron density differences for R6G chemisorbed onto the Ti3C2 surface, in which the isosurface was set to 2×10−3 e Å−3, and the Bader charge analysis indicates there are 3.43 e transferring from Ti3C2 surface to R6G. (d) The DOS of R6G adsorbed on the Ti3C2 surface. (e) Absorption spectra for R6G on the monolayer Ti3C2 nanosheets compared with pure monolayer Ti3C2 nanosheets and R6G. (f) The measured surface potential difference profiles. (g) Energy level distribution and PICT in the R6G-Ti3C2 complex. (h) Structure diagram of the Ti3C2 nanosheets and Ti3C2Tx nanosheets. (i) Comparison of the SERS performance of the Ti3C2 nanosheets and Ti3C2Tx nanosheets.

  • Figure 6

    Toxicity of monolayer Ti3C2 nanosheets. (a) Cell vialibilities after 24 and 48 h exposure to monolayer Ti3C2 nanosheets. (b–d) Cell apoptosis in Hela cells exposed to (b) control, (c) positive control (55°C for 10 min), and (d) 1000 μg mL−1 Ti3C2 nanosheets for 48 h. Live cells were stained with AO (green), late apoptotic and dead cells were stained EB (red) and early apoptotic cells were both stained by AO and EB (orange). Magnification is 200× for all panels.