Effect of the mechanism of interaction between single-layer carbon nanotubes of different diameters and albumin in solid nanocomposites on fluorescence spectra

Background and Objectives: Experimental registration of fluorescence spectra in the visible region of solid nanocomposites based on bovine serum albumin and single-walled carbon nanotubes, depending on their diameter and concentration, has been performed. Results: For nanocomposites with “thick” (average diameter 4.10 nm) nanotubes, fluorescence quenching is observed in the experimental fluorescence spectra with an increase in their concentration (from 0.001 to 0.01 g/L) under laser excitation with wavelengths of 240, 270 and 290 nm. In the case of “thin” (average diameter 1.04 nm) nanotubes in the experimental spectra of the nanocomposite, the fluorescence intensity increases by an order of magnitude as compared with the spectra of both albumin and nanotubes. Using molecular modeling, it has been shown that the surface of “thin” nanotubes forming covalent bonds with aspartic and glutamic amino acids located on the surface of albumin takes a wave-like shape. Conclusions: Electron motion is localized inside small regions of thin nanotubes, leading to the formation of “quantum dots”, which is the cause for a significant increase in the fluorescence intensity of solid nanocomposites of albumin-“thin” nanotubes.