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Publisher DOI: 10.1021/acs.langmuir.1c00559
Title: Synergistic and competitive adsorption of hydrophilic nanoparticles and oil-soluble surfactants at the oil-water interface
Language: English
Authors: Smits, Joeri 
Giri, Rajendra P. 
Shen, Chen 
Mendonça, Diogo 
Murphy, Bridget M. 
Huber, Patrick  
Rezwan, Kurosch 
Maas, Michael 
Issue Date: 27-Apr-2021
Publisher: ACS Pub
Source: Langmuir 37 (18): 5659-5672 (2021)
Journal: Langmuir : the ACS journal of surfaces and colloids 
Abstract (english): 
Fundamental insights into the interplay and self-assembly of nanoparticles and surface-active agents at the liquid-liquid interface play a pivotal role in understanding the ubiquitous colloidal systems present in our natural surroundings, including foods and aquatic life, and in the industry for emulsion stabilization, drug delivery, or enhanced oil recovery. Moreover, well-controlled model systems for mixed interfacial adsorption of nanoparticles and surfactants allow unprecedented insights into nonideal or contaminated particle-stabilized emulsions. Here, we investigate such a model system composed of hydrophilic, negatively, and positively charged silica nanoparticles and the oil-soluble cationic lipid octadecyl amine with in situ synchrotron-based X-ray reflectometry, which is analyzed and discussed jointly with dynamic interfacial tensiometry. Our results indicate that negatively charged silica nanoparticles only adsorb if the oil-water interface is covered with the positively charged lipid, indicating synergistic adsorption. Conversely, the positively charged nanoparticles readily adsorb on their own, but compete with octadecyl amine and reversibly desorb with increasing concentrations of the lipid. These results further indicate that with competitive adsorption, an electrostatic exclusion zone exists around the adsorbed particles. This prevents the adsorption of lipid molecules in this area, leading to a decreased surface excess concentration of surfactants and unexpectedly high interfacial tension.
DOI: 10.15480/882.3593
ISSN: 1520-5827
Institute: Material- und Röntgenphysik M-2 
Document Type: Article
Funded by: Deutsche Forschungsgemeinschaft (DFG) 
More Funding information: The authors acknowledge research grant Verbundforschung BMBF/05KS7FK3/05KS10FK2 and Verbundforschung BMBF/05K16FK1 for financing LISA instrument and the Lambda GaAs detector, respectively. M.M. acknowledges support by DFG (Deutsche Forschungsgemeinschaft) project 278836263. P.H. acknowledges support by the DFG Graduate School GRK 2462 “Processes in natural and technical Particle-Fluid-Systems (PintPFS)” (Project number 390794421).
Project: SFB 986: Teilprojekt B7 - Polymere in grenzflächenbestimmten Geometrien: Struktur, Dynamik und Funktion an planaren und in porösen Hybridsystemen 
Graduiertenkolleg 2462: Prozesse in natürlichen und technischen Partikel-Fluid-Systemen (PintPFS) 
License: CC BY-NC-ND 4.0 (Attribution-NonCommercial-NoDerivatives) CC BY-NC-ND 4.0 (Attribution-NonCommercial-NoDerivatives)
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