NANO-PARTICLE SIZE / ZETA POTENTIAL ANALYZER FACILITY OF BU ADVANCED TECHNOLOGIES R & D CENTER
Tel: +90 212 359 74 20
Contact: Sinan Şen
In the “Nano-particle
size / Zeta potential analyzer” facility of BU Advanced
Tecnologies R&D Center, a Brookhaven Instruments 90Plus Particle Size /Zeta
Analyzer is now in service.
PARTICLE SIZE ANALYSIS
The 90Plus performs fast, routine
submicron particle size measurements on a wide variety of samples and concentrations.
It is an ideal instrument for measuring colloids, latexes, micelles,
mi-croemulsions, proteins, and other nanoparticles. Based on the principles of
dynamic light scattering (DLS), also known as QELS (quasi elastic light
scattering), most measurements only take a minute or two.
Principles of Operation
The sample materials (polymers, proteins, col-loids, or
nanoparticles) will scatter incoming laser light. Due to the random motion of
these particles, the scattered light intensity fluctuates in time. Proc-essing
the fluctuating signal with a state-of-the-art digital autocorrelator yields
the particle’s diffusion coefficient, from which the equivalent spherical
parti-cle size is calculated using the Stokes-Einstein equation. Molecular weights
can also be calculated
Reproducibility
Figure 1 shows the results from multiple runs on a test
sample. Notice the standard error of the Effec-tive (or Average) Diameter is
much less than 1% of the mean of 10 repeated runs.
Figure 1. Run-to-run reproducibility.
Data Analysis and Presentation
The 90Plus
offers three choices. For routine determinations, an average diameter (Eff.
Dia.) and a distribution width (Polydispersity) are sufficient. The second choice
is to show a lognormal distribution using these values, allowing the user to
visualize the size distribution and to display cumulative and differential
results at 5% intervals. The third choice, suitable for more complicated,
multimodal size distributions is the use of advanced algorithms to obtain the
particle size distribution. Here, a numerical algorithm, including Mie theory,
is used. Results of this analysis for a mixture of latex particles are shown in
Figure 2.
Figure 2 Bimodal particle size distribution.
Features :
• Particle sizing from 2 nm to 3 μm
• Multimodal and unimodal size dis-tribution software:
Average size & size distribution width, lognormal fit, and multimodal size
distribution provided as standard
• Two scattering angles: 15° and 90°.
• 35 mW laser with high sensitivity detector.
• Zeta potential measurements.
Typical Applications
•Proteins/complexes/DNA
•Polymer Latexes
•Pharmaceutical Preparations
•Oil/Water and Water/Oil Emulsions
•Paints and Pigments
•Inks and Toners
•Cosmetic Formulations
ZETA POTENTIAL OPTION
This
instrument also has zeta potential measurement option. Besides particle size,
zeta potential is the next most common parameter needed to understand colloidal
behavior. Zeta potential is a measure of surface charge on a particle and is
readily measured with the BI-Zeta option.
Since zeta
potential is a measure of the repulsive forces in electrostatically-stabilized
systems, it is an excellent indicator of relative stability. The sign and
magnitude of zeta potential, as a function of pH, salt, or dispersing agent
concentration are indicators of stability against flocculation or coagulation.
Applications include waste water
treatment and stability of pigments, latexes, ceramics, and other colloidal
dispersions.
ZetaPALS mode is based on Phase
Analysis Light Scattering (PALS), for the determination of zeta potential of
colloidal suspensions. The ZetaPALS is used in all dilute suspensions including
under high salt conditions and in solvents. In addition, every ZetaPALS can
operate in the ELS (electrophoretic light scattering) mode, just like
Brookhaven’s ZetaPlus. The ELS mode is useful in low to moderate salt
conditions in aqueous samples.
ZETAPLUS mode
measures complete electrophoretic mobility distributions in
seconds, including multi modals, from which zeta potential distribution is
calculated. The ZetaPlus utilizes electrophoretic laser light scattering in the
reference beam mode with realtime, on-screen data acquisition and display. The
measured frequency shift provides the highest resolution without the operator
bias found in manual systems.