(Invited) On the Optical Response of Layered Materials Exfoliated in Liquid Phase: Evidence of Functional Groups and Size-Dependent Features

Liquid phase exfoliation of layered materials has proven successful for a range of applications [1]. However, the range of organic solvents needed, and the broad distribution of thicknesses [2] can be aided by applying intercalation steps such as electrochemical or solvothermal expansion which leads to thinner crystals in the dispersion [2, 3]. In this talk I will present the effect of electrochemical exfoliation on the basal functionalization of graphene and a proposal for a more accurate determination of the optical extinction coefficient based on oxidation levels for standardization [4]. I will also present a few examples of MoS2 and WS2 exfoliated via ultrasonication which display non-linear optical effects in fluorescence spectroscopy [5] and the effect of crystal-size selection on the piezoresistive and photoconduction response of MoS2 and WS2 exfoliated via lithium intercalation. [1] Yenny Hernandez, et al, Nature Nanotechnology, 3, 563–568 (2008) [2] Jonathan N. Coleman et al. Science 331, 568-571 (2011) [3] Zhongfen Ding, et al, J. Mater. Chem., 2009, 19, 2588-2592 (2009) [4] Khaled Parvez, et al, ACS Nano 2013, 7, 4, 3598–3606 (2013) [5] J Rico, et al, J. Phys.: Condens. Matter 34 105701 (2022) [6] Gabriel Cardenas-Chirivi, et al, Optical Materials, 133,112890 (2022)