On the nature of UV/vis absorption spectra of asphaltenes

New experimental data show that previously reported UV/vis spectra of asphaltenes/crude oils may have been strongly distorted by artifacts, affecting not only quantitative parameters (spectra's slopes), but also qualitative features (a presence of strong UV peaks). In a popular revised "amorphous semiconductor" (AS) model, the properties of UV/vis spectra are defined by population distribution of higher aromatics. This interpretation is obviously incompatible with the newly observed concentration effects in toluene solutions. Possibly, some specific features of UV/vis absorbance in asphaltenes/crude oils may be better described by the traditional AS model, taking into account the distribution of defects in chromophore carriers, e.g., nanosized carbonaceous species of the graphene family.