1. Overview
The is a high-performance analytical instrument designed for measuring particle size, zeta potential, and molecular weight of dispersed systems. It is widely used in research and industrial laboratories for characterizing nanoparticles, colloids, proteins, and emulsions.
The Zetasizer Nano ZS integrates Dynamic Light Scattering (DLS), Electrophoretic Light Scattering (ELS), and Static Light Scattering (SLS) techniques in one compact system, offering high sensitivity, repeatability, and user-friendly operation.
Features:
2. Principle
The system uses a laser light source and backscatter detection (173°) to minimize multiple scattering effects and improve measurement accuracy for a wide range of sample concentrations.
- Dynamic Light Scattering (DLS):
Dynamic Light Scattering (DLS) is used to measure particle and molecule size. This technique measures the diffusion of particles moving under Brownian motion, and converts this to size and a size distribution using the Stokes-Einstein relationship. Measurement of size as a function of concentration enables the calculation of kD, the DLS interaction parameter. - Electrophoretic Light Scattering (ELS):
Laser Doppler Micro-electrophoresis is used to measure zeta potential. An electric field is applied to a solution of molecules or a dispersion of particles, which then move with a velocity related to their zeta potential. An available surface zeta potential accessory uses tracer particles to measure electro-osmosis close to a sample surface to calculate the zeta potential of the surface. - Static Light Scattering (SLS):
Static Light Scattering is used to determine the molecular weight of proteins and polymers. In this technique, the scattering intensity of a number of concentrations of the sample is measured, and used to construct a Debye plot. From this the average molecular weight and second virial coefficient A2 can be calculated, which gives a measure of molecule solubility.
3. Data Interpretation
- Particle Size (DLS):
Reported as the Z-average diameter (intensity-weighted mean) and Polydispersity Index (PDI), indicating the uniformity of particle size distribution.- Z-average: Sensitive to larger particles; used for comparison between samples.
- PDI: Values <0.1 indicate monodisperse samples; >0.3 indicate broad distributions.
- Zeta Potential (ELS):
Expressed in mV, representing the electrostatic potential at the slipping plane of particles. Typically, values >|30 mV| suggest good colloidal stability; values near 0 indicate potential aggregation. - Molecular Weight (SLS):
Determined from light scattering intensity vs. concentration; provides absolute molecular weights without reference standards.
Attentions:
1. Sample concentration affects results: Optimal measurements require appropriate sample concentrations, which may vary depending on the sample. Ideally, the sample should be a clear solution. It is recommended to bring your own solvents in case dilution or sample preparation is needed. And check index of your solution before testing.
• Effect on particle size measurement: The concentration of the suspension affects light scattering behavior. If the concentration is too high, multiple scattering occurs, light is scattered more than once before reaching the detector, leading to artificially larger or unstable particle size results. If the concentration is too low, the signal intensity becomes weak and data noise increases, reducing the accuracy and repeatability of the measurement.
• Effect on zeta potential measurement: The zeta potential depends on the ionic strength and conductivity of the medium. At high concentrations, strong interparticle interactions and high ionic strength can compress the electric double layer, resulting in lower apparent zeta values. At very low concentrations, insufficient particle number and low conductivity can lead to unstable electrophoretic mobility signals, affecting precision.
2. Particle size measurement cuvettes: We provide plastic cuvettes and quartz cuvettes (reusable; must be cleaned after use and returned to the testing center). If using plastic cuvettes, it is recommended to use solvents such as ethanol or DI water, which will not dissolve or damage the plastic and affect the measurement.
3. Zeta potential cuvettes: We provide zeta potential cuvettes ($30 each, reusable, can be taken away). When testing multiple samples with different solvents, it is recommended to bring your own solvents to clean the cuvette between samples.
4. Example Application
- Nanomaterials: Evaluation of size distribution and stability of nanoparticles, nanocomposites, and quantum dots.
- Biopharmaceuticals: Analysis of protein aggregation, formulation stability, and antibody interactions.
- Polymers: Determination of polymer molecular weight and solubility behavior.
- Colloids and Emulsions: Monitoring emulsion stability and formulation optimization in cosmetics, food, and coatings.
- Environmental Science: Characterization of colloidal pollutants and microplastics in aqueous media.