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Determination of surface ζ ‐potential and isoelectric point of carbon surfaces using tracer particle suspensions
Author(s) -
Vasconcelos Joana M.,
Zen Federico,
Stamatin Serban N.,
Behan James A.,
Colavita Paula E.
Publication year - 2017
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.6223
Subject(s) - isoelectric point , chemistry , surface charge , particle (ecology) , tracer , electrokinetic phenomena , analytical chemistry (journal) , carbon fibers , amorphous carbon , chemical engineering , nanotechnology , amorphous solid , organic chemistry , materials science , oceanography , physics , composite number , nuclear physics , engineering , composite material , enzyme , geology
Carbon materials are widely used in a range of applications from biomaterials to sensing and electronics. Many of these applications rely on the ability to control carbon/water interfacial properties, in particular, surface charge density. This work reports a study of the electrokinetic properties of amorphous carbon thin films as a function of pH and surface chemistry. Surface ζ ‐potential (SZP) and isoelectric point were determined using the tracer particle method. Initially, the use of sulfonated and amine‐terminated latex bead suspensions as tracer particles for the determination of SZP of reference polymer surfaces was validated. The tracer particle method was then applied to the determination of SZP and isoelectric point of macroscopic carbon surfaces with different surface chemistry. Highly graphitic and sp 3 ‐rich hydrogenated carbon surfaces were found to display negative SZP, as expected for hydrophobic surfaces. The isoelectric point of the most highly graphitic surface was found to be pH iso = 3.7. Surface oxidation of these films resulted in a decrease of SZP at all pH values and in a downshift of pH iso to values lower than 1.5, consistently with the presence of surface acidic groups arising from oxidation. Results indicate that the specific choice of acid/base chemistry for the tracer particles does not significantly affect either SZP or pH iso determinations. These results show that the tracer particle method in combination with widely available latex beads as tracers can be applied for the determination of carbon SZP as a function of pH. Copyright © 2017 John Wiley & Sons, Ltd.