Density Functional Theory Examination of Electronic and Optical properties of Two-Dimensional Transition Metal Dichalcogenides Functionalized with Forever Chemicals

Polyfluoroalkyl substances (PFAS), also known as “forever chemicals,” are a class of manufactured chemicals that pose long-term health risks to those exposed. In processes such as battery recycling, where PFAS are commonly released, detection of PFAS is crucial and made possible through portable surface-enhanced Raman spectroscopy (SERS), so long as a proper substrate is chosen. Functionalized two-dimensional (2D) transition metal dichalcogenides (TMDs) are a fast-emerging SERS substrate candidate. We use density functional theory (DFT) to evaluate substrate fitness via the electronic, and adsorptive properties of 2D TMDs functionalized with single Au atoms when laden with PFAS. From calculations of finite difference method phonon dispersions, Born-effective charge tensors, and time-dependent DFT, we simulate both off-resonance and resonance Raman spectra to compare optical properties of MoS₂ and WS₂ monolayer substrates to the more typical substrate choices of graphene and Au-functionalized silicon.