Stability of ZnO Nanoparticles in Solution. Influence of pH, Dissolution, Aggregation and Disaggregation Effects
In this study, the zeta potential and z-average hydrodynamic diameter of zinc oxide (20 nm, 99.5% purity) were investigated as a function of pH and time. The nanoparticles readily formed aggregates and could not be disintegrated to its primary size eventhough ultrasonication
was applied. In zinc oxide suspensions (25 mgL and 100 mg/L) the nanoparticles were examined for electrophoretic mobility and aggregation behaviour within the pH range of 3 to 11 and time duration of 60 minutes. In this study, the particle size and zeta potential were measured by dynamic light
scattering technique. The application of nanoparticle tracking analysis was demonstrated as well to observe the aggregation and disaggregation of zinc oxide nanoparticles at various pH values. The NTA results obtained in this work were compared and validated by the DLS. The z-average
hydrodynamic diameter of the particles was 389 d · nm with an average zeta potential value of +23 mV using the DLS compared to mean particle size of 365 d · nm by NTA. DLS analysis also identified the pH of the point of zero charge (pH
PZC
) and the isoelectric
point (IEP) at pH 9.4 and pH 6.4 respectively. It was found that the zeta potential remained unaffected by the concentration of the suspension. However, results show that pH does have a pronounced effect on the stability of zeta potential, pH and particle size as a function of time in pH regions
where dissolution (< pH 6.4 and 8.3 < pH < 10.5) and aggregation (pH 6.4 and 9.4) occurs. It is apparent that the pH of the suspension strongly influences the zeta potential of ZnO nanoparticles without external factors which will consequently govern their behaviour, agglomeration
state and their interactions with each other and surfaces in the environment.
Keywords: DYNAMIC LIGHT SCATTERING; NANOPARTICLE STABILITY; NANOPARTICLE TRACKING ANALYSIS; PH; ZETA POTENTIAL; ZNO
Document Type: Research Article
Publication date: 01 March 2014
- Journal of Colloid Science and Biotechnology is an international multidisciplinary peer- reviewed journal covering all aspects of colloid science including colloids preparation, characterization, structure-property relationships, spectroscopy, chemical and physical properties and applications of colloids in biotechnology, medicine and pharmaceuticals. This journal deals with interdisciplinary research areas of chemistry, physics, biology, materials science, polymer science, nanotechnology covering all topics related to colloids such as latexes, emulsions, suspensions, micellar systems, gels, composites, hybrids, surfactants, aerosols, foams, minerals, soft matter, microfluidics, encapsulation processes of active molecules, biomolecules, surfacial and interfacial processes, catalysis, electrochemistry, theoretical aspects, computer simulations and colloids in biotechnology and medicine.
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