Formation of Noncovalent Complexes between Complex Mixtures of Polycyclic Aromatic Hydrocarbons (Asphaltenes) and Substituted Aromatics Studied by Fluorescence Spectroscopy

Abstract

Quantification of the formation of molecular complexes between simple organic aromatic molecules is straightforward for pure components of definite composition; however, it becomes challenging when the interacting species are complex, intractable mixtures of thousands of polycyclic aromatic hydrocarbons (PAHs). Using the example of asphaltenes, a complex mixture of oil-derived PAHs, we demonstrate the potential of fluorescence spectroscopy for quantification of molecular processes that are at the core of their aggregation. It is found that small electron-deficient aromatic additives, especially surfactant-like additives with electron-withdrawing functional groups, interact strongly with the PAHs and lead to the formation of molecular complexes. Computational modeling revealed that as we increase the number of PAH molecules in the cluster, cohesive π–π stacking interactions between PAHs dominate in preference to adhesive hydrogen bonding or π–π stacking interactions between the PAHs and additives.

Applications of Noncontact Atomic Force Microscopy in Petroleum Characterization: Opportunities and Challenges

“…Numerous techniques can be used to characterize molecular structures today, and these are predominantly spectroscopic methods (Figure ), including UV–vis spectroscopy for electronic structures, vibrational spectroscopy (FTIR or Raman) for functional groups, mass spectrometry for molecular weight and elemental formulas, and NMR spectroscopy for atomic connections or chemical structures. Many other techniques can help, for example: X-ray diffraction for crystal structures, fluorescence spectroscopy for fluorescent molecules, and electron spin resonance spectroscopy (EPR) for paramagnetic species . In conjunction with physical techniques, chemical degradation can also be used to infer structures from the building blocks of larger molecules, especially before the advent of advanced techniques. − In addition, chemical synthesis is often considered the ultimate confirmation of structure .…”

Evaluation of the Effectiveness of Inhibitors for Middle Eastern Asphaltenes by Quartz Crystal Microbalance with Dissipation

“…The behavior discussed above is in strong contrast to that of additive molecules that contain electron-withdrawing nitro groups. Although these molecules might interact with asphaltenes in solution, 46 the experimental results indicate that there is no significant interaction with those deposited onto the surface. The swelling indicates an interaction with the deposit; however, there is no evidence of a chemical reaction with the sensor.…”

Non-destructive real-time monitoring and investigation of the self-assembly process using fluorescent probes

“…Another important aspect of uorescent probes is monitoring the assembly of very complex natural mixtures of chemically similar molecules. [74][75][76] The traditional detection methods for the aggregation process extremely depend on the combination of multiple methods, such as small-angle X-ray scattering, dynamic light scattering, and atomic force microscopy. However, each method has its limitations.…”