WorksheetsNanomaterial Characterization - DLS + Zeta
Total questions: 14
Worksheet time: 14mins
In DLS, the particle size is determined from
Absorption of UV light
Rate of Brownian motion of particles
Magnetic resonance of particles
Chemical composition
DLS can measure nanoparticle size only if the particles are suspended in a liquid
True
False
A polydisperse sample in DLS will typically show:
A single sharp peak in size distribution
Multiple peaks or a broad distribution
No signal
Only Zeta potential
Which curve corresponds to larger particles?
Figure A
Figure B
Which factor affects the accuracy of DLS measurement?
Sample concentration
Viscosity of the medium
Temperature
All of the above
What does this indicate about the sample?
It is monodisperse
It is polydisperse
The sample is highly fluorescent
There is no scattering signal
Why do large nanoparticles produce larger fluctuations in scattered intensity over time compared to small nanoparticles?
They move faster
They scatter light more strongly
They absorb more light
They change the medium viscosity
Zeta potential measures:
Particle size
Surface charge of nanoparticles
Refractive index
Viscosity
High magnitude of zeta potential (either positive or negative) generally indicates:
Particles are unstable
Particles are likely to aggregate
Particles are stable due to electrostatic repulsion
No relationship with stability
At which pH is the nanoparticle suspension most likely to aggregate?
pH 5.5
pH 8.1
pH 9.2
pH 11
The isoelectric point (IEP) of a nanoparticle suspension is:
The pH where zeta potential is maximum
The pH where zeta potential is zero
The point where all particles are negatively charged
The point where all particles are positively charged
Zeta potential measurements can be directly compared between different media (e.g., water vs cell culture medium) without considering pH or ionic strength
True
False
Increasing ionic strength of the solution (adding salt) usually:
Increases zeta potential
Decreases zeta potential
Has no effect
Reverses particle charge
You measure the zeta potential of a nanoparticle suspension at pH 4 and again at pH 8. You notice the zeta potential changes from –5 mV at pH 4 to –35 mV at pH 8. What can you infer about the particle behavior?
The particles are most likely to aggregate at pH 8
The particles are more stable at pH 8 due to higher absolute zeta potential
The particles have no change in stability
The zeta potential indicates the particles are positively charged at both pH
