Asphaltenes are made of polycyclic aromatic hydrocarbon rings with peripheral alkane chains and are among the most surface-active and polarizable components of crude oil. They are characterized as a solubility class that is insoluble in n-heptane but soluble in aromatics such as toluene. Molecular structure analysis using atomic force and scanning tunneling microscopy methods show poly-disperse asphaltenes with a variety of molecular structures . Following the widely accepted Yen-Mullins model for asphaltenes, the average molecular weight of a molecule is around 750 g/mol and the asphaltenes can exist as a monomer, nano aggregate or clusters based on their concentration in oil .