Infrared Spectroscopic Studies of C60 and C70 Nanoparticle Interactions With 2-Pyrrolidone
Fourier transform infrared spectroscopy was used to investigate the interactions between C60 and C70 nanoparticles and 2-pyrrolidone (2-pyrrolidinone, y-lactam) in a toluene solvent environment. Infrared spectra were collected for 2-pyrrolidone in toluene, 2-pyrrolidone in toluene saturated with C60, and 2-pyrrolidone in toluene saturated with C70 over a concentration range of 200 to 2 microliters (μL) of 2- pyrrolidone per mL of toluene or toluene saturated with the nanoparticles. At the higher concentrations of this range, small broadenings of the 2-pyrrolidone carbonyl stretching absorptions on the lower wavenumber side were observed when the 2-pyrrolidone was treated with C60 and C70. A significant shift was observed for the carbonyl absorption of 2-pyrrolidone when the 2-pyrrolidone was treated with C60 at 5 and 2 μL of 2- pyrrolidone per mL of toluene saturated with C60. These observed shifts suggest a 2-pyrrolidone–C60 nanoparticle interaction or complex formation. A small broadening of the carbonyl absorption on the low wavenumber side was observed when the 2-pyrrolidone was treated with C70 at 5 and 2 μL of 2-pyrrolidone per mL of toluene saturated with C70. Spectral subtraction was used to reveal the carbonyl absorption for the 2-pyrrolidone–C60 complex that exists at the higher concentration range, but is covered up by the intense absorption of the excess 2-pyrrolidone not interacting with C60. The spectrum of 2-pyrrolidone in toluene (100 μL of 2-pyrrolidone per mL of toluene) was subtracted from the spectrum of 2-pyrrolidone in toluene saturated with C60 (100 μL of 2-pyrrolidone per mL of toluene saturated with C60). The subtraction process yielded a spectrum containing a spectral absorption very near the shifted absorption for 2-pyrrolidone treated with C60 at the lower concentrations.