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Rigorous Accounting for Dependent Scattering in Thick and Concentrated Nanoemulsions.
Ricardo Martinez1, Abhinav Bhanawat1, Refet Ali Yalçin2
1Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Science, University of California, 420 Westwood Plaza, Los Angeles, California 90095, United States.
Concentrated nanoemulsions become more transparent with higher oil content due to dependent scattering effects. This study validates a new method to accurately model light transfer in these systems, crucial for applications in drug delivery, food, and cosmetics.
Area of Science:
- Colloid and Interface Science
- Optical Physics
- Materials Science
Background:
- Concentrated oil-in-water nanoemulsions exhibit counterintuitive transparency increases with higher oil fractions.
- Existing models for light transfer in colloids often rely on far-field approximations, potentially missing crucial near-field scattering effects.
- Understanding light-matter interactions in nanoemulsions is vital for optimizing their performance in various applications.
Purpose of the Study:
- To rigorously investigate the phenomenon of enhanced transparency in concentrated nanoemulsions.
- To validate the accuracy of the radiative transfer with reciprocal transactions (R²T²) method, which includes near-field effects, in modeling light transfer.
- To compare the R²T² method with traditional approaches like dense medium radiative transfer (DMRT) and independent scattering assumptions.
Main Methods:
- Preparation of oil-in-water nanoemulsions with varying oil volume fractions (1–20%) and a peak droplet radius of 16 nm.
- Experimental measurement of spectral normal-hemispherical transmittance across the 400–900 nm range.
- Numerical simulations using the R²T² method to model light transfer, accounting for dependent scattering and near-field effects.
Main Results:
- Experimental measurements showed excellent agreement with numerical predictions from the R²T² method.
- The R²T² method accurately captured the unusual transparency increase with oil volume fraction, unlike independent scattering models.
- Simulations indicated that dependent scattering effects become significant at lower volume fractions than predicted by DMRT, especially for droplets >10 nm and volume fractions >10%.
Conclusions:
- Dependent scattering, including near-field effects, is the primary cause of increased transparency in concentrated nanoemulsions.
- The R²T² method provides a highly accurate tool for characterizing nanoemulsions and understanding their optical properties.
- This research enables the design of nanoemulsions for specific optical behaviors (backscattering or absorption) and has implications for drug delivery, food, and cosmetic industries.
