Zeta potential (a) and Dynamic Light Scattering (DLS) (b) measurements are commonly used techniques for characterizing nanofluids. Let’s explore each measurement in the context of nanofluids:
(a) Zeta Potential Measurements: Zeta potential measurements in nanofluids help determine the surface charge and stability of nanoparticles dispersed in a liquid medium. Nanoparticles tend to aggregate or agglomerate due to attractive forces between them, which can lead to a loss of stability and altered fluid properties. The zeta potential provides information about the electrostatic repulsion or attraction between nanoparticles, which influences their dispersion and prevents or promotes aggregation.
A higher absolute zeta potential indicates greater electrostatic repulsion, promoting the stability of nanofluids by inhibiting particle agglomeration. Conversely, a low or near-zero zeta potential suggests weak repulsion, making nanoparticles more prone to aggregation.
Zeta potential measurements can be performed using techniques such as electrophoretic mobility or electrophoresis. These methods involve applying an electric field to the nanofluid and measuring the velocity of nanoparticles as they migrate. From this velocity, the zeta potential can be determined using mathematical models.
(b) Dynamic Light Scattering (DLS) Measurements: Dynamic Light Scattering is a technique used to analyze the size distribution of nanoparticles in a nanofluid. DLS measures the fluctuations in scattered light caused by the Brownian motion of nanoparticles suspended in a liquid medium. These fluctuations are related to the size of the nanoparticles.
By analyzing the intensity autocorrelation function of the scattered light, DLS provides information about the diffusion coefficient and hydrodynamic size of the nanoparticles. The hydrodynamic size takes into account both the particle’s physical size and the effect of the surrounding fluid.
DLS is particularly useful for assessing the particle size distribution in nanofluids, including the presence of aggregates or agglomerates. It can provide information about the average particle size, polydispersity index (PDI), and the presence of larger particles or clusters.
Combining Zeta Potential and DLS Measurements: The combination of zeta potential and DLS measurements is valuable for understanding and optimizing the stability and behavior of nanofluids. The zeta potential analysis helps assess the electrostatic stability and provides insight into the forces that influence particle interactions. DLS complements this by characterizing the particle size distribution and identifying the presence of larger aggregates or clusters.
By correlating zeta potential and DLS data, researchers can gain a comprehensive understanding of the nanofluid’s stability, dispersion quality, and potential applications. This knowledge is crucial for areas such as heat transfer enhancement, nanomedicine, and advanced materials, where nanofluids are employed.