Phenylalanine and Tyrosine Interactions with the WSe2 Nanosheet: A Comparative Analysis Based on DFT Calculation and Experimental Confirmation

In this work, the interactions and subsequent optical transductions of phenylalanine (PHE) and tyrosine (TYR) amino acids on tungsten diselenide (WSe2) nanoflakes are systematically investigated using a complementary approach involving density functional theory (DFT) based ab initio calculation and experimental characterization. The WSe2 nanoflakes are synthesized using a low-cost hydrothermal method and are subsequently characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HRSEM). The strength and efficacy of PHE and TYR interactions at different molecular conformations (namely, C1, C2, and C3) with WSe2 are theoretically quantified using binding energy and charge transfer with energy band gap modulation, respectively. Next, the major theoretical predictions were finally confirmed experimentally after examining the UV–visible spectroscopy and NMR data. The interaction mechanism was also confirmed experimentally through FT-IR and EPR studies with varying WSe2 concentrations in the solution. The key findings reveal that the presence of selenium (Se) vacancy in as-synthesized WSe2 acts as a favorable molecular interaction site for both PHE and TYR, manifested in the notable improvement in binding energies, i.e., −0.59 eV to −0.70 eV for PHE and −0.82 eV to −0.95 eV for TYR. For both PHE and TYR, the physiosorbed amino acids show a moderate (0.01 to 0.04 e–) charge transfer for pristine and Se-vacant WSe2, wherein an acceptor type charge transfer for PHE and donor type charge transfer for TYR are observed in the molecular conformations representing their respective strongest interactions with Se-vacant WSe2. The results suggest that TYR and PHE are also appealing choices for use in environmental monitoring, food safety applications, and medical diagnostics due to their high sensitivity, selectivity, and miniaturization potential. Finally, the study opens pathways for complementary investigation of other similar amino acids on other transition metal dichalcogenides (TMDs), which can also be investigated as sensor materials, and a more robust sensing mechanism can be developed for utilizing similar potential molecules for large-scale sensor development.