I used two different zetasizer instruments to determine nanoparticles' size and I got 2 different Z-averages, Z-average (d.nm) and Z-average (r.nm). What are the differences? Which one shows the particle size?
D=diameter and r= radius indeed. However, the Z average is the grand average of (usually) all of the intensities that the DLS picks up. This may not be the actual size of your nanoparticle as there may be aggregates. If your machine can do backscatter and forwardscatter this will tell you the degree of aggregation. Check your intensity PSD, volume PSD (if you have empirical measurements of light properties i.e. refractive index) and number PSD. I like number PSD because it takes into account the most common size signature while accounting for high intensity aggregates. In an ideal situation where you have only a single particle suspension number PSD, intensity PSD, volume PSD and z-average would all be the same. This is not the usual case however as there is usually a degree of heterogeneity. Best of luck!
Agree with Zi Teng.
Diameter= d
Radius= r
So (d) is your particle size.
I think so but the instrument operator says that they are the same and the letter "r" is shown due to a problem in instrument software set up!!!
D=diameter and r= radius indeed. However, the Z average is the grand average of (usually) all of the intensities that the DLS picks up. This may not be the actual size of your nanoparticle as there may be aggregates. If your machine can do backscatter and forwardscatter this will tell you the degree of aggregation. Check your intensity PSD, volume PSD (if you have empirical measurements of light properties i.e. refractive index) and number PSD. I like number PSD because it takes into account the most common size signature while accounting for high intensity aggregates. In an ideal situation where you have only a single particle suspension number PSD, intensity PSD, volume PSD and z-average would all be the same. This is not the usual case however as there is usually a degree of heterogeneity. Best of luck!
Can any body explain the meaning of Z in "z-average" or this is a commercial name raised fron zetasizer?
Dear Vinod,
The Z-Average size or Z-Average mean used in dynamic light scattering
is a parameter also known as the cumulants mean. It is the primary and
most stable parameter produced by the technique. The Z-Average mean
is the best value to report when used in a quality control setting as it is
defined in ISO 13321 and more recently ISO 22412 which defines this
mean as the ‘harmonic intensity averaged particle diameter’.
The Z-average size will only be comparable with the size measured
by other techniques, if the sample is monomodal (i.e. only one peak),
spherical or near-spherical in shape, monodisperse (i.e. very narrow width
of distribution), and the sample is prepared in a suitable dispersant, as
the Z-Average mean size can be sensitive to even small changes in the
sample, e.g. the presence of a small proportion of aggregates. It should
be noted that the Z-average is a hydrodynamic parameter and is therefore
only applicable to particles in a dispersion or molecules in solution.
If the d.nm is the diameter of the particle then what is the particle size ...... what is the particle size in terms of nano meter?
I want to know if i have 235d.nm per particle then what is the conversion for nano meter?
In the Zetasizer software, the user can switch between displaying radius values in nanometers (which Malvern calls "r.nm") and diameter values in nanometers (which Malvern calls "d.nm"). The switch is achieved from within the records view (the table where the records and results are listed), placing the mouse over the z-average column heading, and then switching between "r.nm" and "d.nm" , i.e. radius or diameter. The only difference is a factor two. The reason for having both is that in some research fields diameter is prefered whereas in other radius is the more common parameter.
The Z-average is a specific parameter from light scattering, and defined in ISO13321/22412, and this post may be helpful as well:
http://www.materials-talks.com/blog/2014/07/10/faq-peak-size-or-z-average-size-which-one-to-pick-in-dls/
PS: there are some screen/print reports that can fix radius or diameter, so it could be a customized report that displays diameter even though radius has been selected in the records view. Contact the Malvern Panalytical help desk if in doubt. http://www.materials-talks.com/blog/2014/08/19/faq-how-can-i-submit-a-data-file-to-the-help-desk/
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