Caio Matheus Ferreira

The incorporation of essential oils (EOs) into layered charged matrices is a commonly pursued method for encapsulation and controlled-release applications. However, the interfacial mechanism governing their colloidal interactions in water-based dispersions and the resulting colloidal microstructure remains poorly understood. Here, the impact of chemically distinct EOs in the intermolecular interactions, hierarchical organization, and aging structural evolution of an aqueous synthetic Laponite (Lap) dispersion is investigated. With a combination of dynamic light scattering, electrophoretic measurements, ultra-small-angle X-ray scattering, and gas chromatography coupled with mass spectrometry, a correlation of how EOs molecular composition influences the colloidal interactions and Lap multi-level structural organization is established across a wide range of Lap and EOs concentrations. The results demonstrate that the presence of EO molecules significantly changes the electric double layer around Lap discs, with EOs adsorption leading to the transition from dispersed nanodiscs to complex, stable, hierarchically organized clusters with both mass- and surface-fractal morphologies, spanning from nano- to micro-scale. Moreover, aging restructures the large-scale cluster backbone, progressively going to an arrested colloidal network, evidencing structural changes related to face-to-face and face-to-edge interactions that are amplified by the presence of the EOs. These findings establish fundamental relationships between EOs chemistry, interfacial electrostatics, and hierarchical assembly in synthetic smectite Lap dispersions, providing mechanistic principles for using charged layered materials as colloidal EOs encapsulation systems.

Photo-oxidation remains a challenge for achieving long-term stability in organic electronic devices. Rubrene (Rub), a small-molecule semiconductor known for its exceptional optoelectronic properties, illustrates this problem as its highly sensitive to light and oxygen. In addition, its limited processability, requiring the use of halogen solvents or thermal evaporation for its deposition, further restricts its practical use in large-area processing . This works shows how both problems can be addressed by a colloidal approach where Rub is encapsulated through a miniemulsion method, producing stable, water-dispersible nanoemulsions (NPs). Their emission and absorption properties in the liquid, and solid films, show that nanoencapsulation preserves the intrinsic vibronic fingerprint of Rub, while inducing spectral shifts and emission narrowing, enhancing molecular ordering and stronger intermolecular coupling, quantified by calculating the Huang–Rhys factor. Systematic investigation of photo-oxidation kinetics reveals a modulation effect: in dispersion, Rub NPs oxidize faster than molecular Rub in chloroform, due to enhanced oxygen access from their large surface area, while maintaining colloidal stability. In contrast, NP-based Rub films exhibits significantly improved photostability, preserving over twice the residual absorbance of annealed neat Rub films under 11 W/m2 irradiation. Atomic Force Microscopy and Fourier Transform Infrared Spectroscopy confirm the synergistic role of excess surfactant and nanoencapsulation in Rub oxidation, while thermal annealing fine-tunes film morphology, improving stability and reducing oxygen diffusion pathways. This work establishes nanoemulsion-based confinement as an effective strategy to modulate photo-oxidation in highly reactive organic semiconductors, offering new design rules for environmentally processed, photostable optoelectronic materials and oxygen-sensing platforms.