Abstract:
The use of diphenylalanine peptide nanotubes (FF PNTs) as an active substrate for surface-enhanced Raman spectroscopy (SERS) is studied by the computer modeling and semi-empirical quantum calculations. For the PNT interacting with one of the analyte molecules Methylene blue or Thymine, the calculations revealed significant changes in the total energy of the system, the energies of the electronic levels $E_{\mathrm{HOMO}}$ and $E_{\mathrm{LUMO}}$, and the band gap. It has been found that at large distances (above 30 $\mathring{\mathrm{A}}$) between the molecular structures, the $E_{\mathrm{HOMO}}$ level of the total system is localized on FF PNT, whereas it moves to MB molecule at closer distances. The characteristic change in the SERS signal intensity and vibrational modes of MB molecule indicate the possibility of enhancing the SERS signal at FF PNTs. On the other hand, the width of the band gap about 4 eV established for FF PNT turns out to be suitable for detecting light in the solar-blind ultraviolet range (SBUV) and thus makes FF PNTs suitable for creating SBUV-sensors. The capabilities of such sensors can be further extended by the band gap tuning via the control of the adsorbed water in the FF PNTs nanochannels or application of an external electric field produced, e.g., by a PVDF-TrFE ferroelectric polymer, and by the choice of the chirality of diphenylalanine enantiomers for the selective detection of circularly polarized light, which is highly important for modern photonics.
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