Dynamic Study of Intercalation/Deintercalation of Ionic Liquids in Multilayer Graphene Using an Alternating Current Raman Spectroscopy Technique

Zhi Cai; Haley Weinstein; Indu Aravind; Ruoxi Li; Sizhe Weng; Boxin Zhang; Jonathan L Habif; Stephen B Cronin

doi:10.1021/acs.jpclett.3c01686

Dynamic Study of Intercalation/Deintercalation of Ionic Liquids in Multilayer Graphene Using an Alternating Current Raman Spectroscopy Technique

J Phys Chem Lett. 2023 Aug 17;14(32):7223-7228. doi: 10.1021/acs.jpclett.3c01686. Epub 2023 Aug 8.

Authors

Zhi Cai¹, Haley Weinstein², Indu Aravind³, Ruoxi Li¹, Sizhe Weng², Boxin Zhang¹, Jonathan L Habif², Stephen B Cronin^{3

4

2}

Affiliations

¹ Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089, United States.
² Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089, United States.
³ Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States.
⁴ Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States.

Abstract

We report Raman spectra and infrared (IR) imaging collected during the intercalation-deintercalation half cycles in a multilayer graphene (MLG) device (∼100 layers) operating at 0.2-10 Hz. The device consists of a MLG/alumina membrane/copper stack, in which the alumina membrane is filled with ionic liquid [DEME][TFSI], forming an electrochemical cell. Upon the application of a positive voltage, the TFSI^- anions intercalate into the interstitial spaces in the MLG. The incident laser light is modulated using an optical chopper wheel that is synchronized with (and delayed with respect to) a 0.2-10 Hz alternating current (AC) voltage signal. Raman spectra taken just 200 ms apart show the emergence and disappearance of the intercalated G band mode at around 1610 cm^-1. By integration of over hundreds of cycles, a significant Raman signal can be obtained. The intercalation/deintercalation is also monitored with thermal imaging via voltage-induced changes in the carrier density, complex dielectric function ε(ω), and thermal emissivity of the device.