Fischer I, Morhardt C, Heissler S, Franzreb M. Partitioning behavior of silica-coated nanoparticles in aqueous micellar two-phase systems: evidence for an adsorption-driven mechanism from QCM-D and ATR-FTIR measurements.
LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012;
28:15789-15796. [PMID:
23078043 DOI:
10.1021/la303313m]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Quartz crystal microbalance with dissipation (QCM-D), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and total organic carbon detection (TOC) are employed to examine the cause of the differences in the partitioning of silica-coated nanoparticles in an aqueous micellar two-phase system based on nonionic surfactant Eumulgin ES. The particles partition into the micelle-rich phase at pH 3 and into the micelle-poor phase at pH 7. Our results clearly show that the nonionic surfactants are adsorbed to the silica surface at pH 3. Above the critical temperature, a stable surfactant bilayer forms on the silica surface. At pH 7, the surfactants do not adsorb to the particle surface; a surfactant-loaded particle is therefore drawn to the micelle-rich phase but otherwise repelled from it. These results suggest that the partitioning in aqueous micellar two-phase systems is mainly driven by hydrogen bonds formed between the surfactants and the component to be partitioned.
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