I am evaluating the effect of nanoparticle on emulsions. It was observed that when the increasing the concentration of the nanoparticles changes the mean droplet size (morphology). What is the best possible explanation for this observation.
Thanks in Advance
Dear Foster,
Does the droplet size of emulsion increase with an increase in concentration of solid particles?
I guess yes!
If the droplet size increases then it is possibly due to the increased agglomeration/ aggregation of particles with increased concentration. This would ultimately result in larger particles (lumps) and hence larger droplet size.
Please check the agglomeration/ aggregation fundamentals including the particle interaction forces involved for more detailed scientific explanation.
All the best
Rehan
In this case, the mean droplet size decreases with increasing concentration . Will the explanatin be the same as the one here?
That's surprise for me,
Lets wait for some other experts to comment as I would personally be looking forward to learn/ understand this myself now.
In presence of this nanoparticles help to generate emulsions with high stability. Also, there is a general role that, smaller droplet sizes are mostly stabilized emulsions. So I am trying to find out why the nanoparticles reduces the droplet size too
I suggest you start here: https://en.wikipedia.org/wiki/Pickering_emulsion and then look at other sources. There's a book dedicated to particle-stabilized emulsions: https://www.technology.matthey.com/article/59/4/298-302/
you should not expect relevant explanation leaving the details in dark.
What is continous and what is dispersed phase composition. In which steps do you prepare the emulsion. Conditions of emulsification. How do you measure droplet size.
in addition to what Titus wrote: and whyt nanoparticles did you add, how did you disperse those (did you use any tenside?)
Anyway, what you will have done was you changed the surface tensioon of the continuous phase in a direction enabling it to better emulsify the droplets.
You need to understand the surface tensions of the components involved here, so to understand the interfacial tension, then yoou can find the explanation for the phenomenon you observed.
For a theoretical background, you may want to read this:
Article Critical Shear Rate - the Instability Reason for the Creatio...
(although elaborated for polymer based dispersions, they theory is applicable for all dispersions and emulsions)
@Titus, the system is pH-responsive emulsion, that this the system undergoes phase inversion in response the presence of H+/OH- in the system. Conventional, when the emulsion is prepared with no acid or base treating, W/O emulsion with formed. OIil continuous phase and the Water as the dispersed phased. When the concentration of the silica nanoparticles is increased, the mean droplet size decreases even with no acid or base treating. (NB; The acid or base treating is done to change the emulsion from one type of the emulsion to the other)
@Wessling, the silica nanoparticles was stirred in the water with a high speed stirrer at a speed of 15000rpm.
Foster, I also saw your answer to Titus; are you using any tenside / emulsifier? under which conditions do you prepare the O/W emulsion? which shear rate?
re your silica nanoparticles - ok, and I would assume that some tenside is used, or?
anyway, the high speed stirrer may already be the reason for decreasing emulsion droplet size; plus my statement about the interfacial energy which can already also be changed by adding silica nanoparticles!
@Wessling, Please, can you explain to me what is meant by tenside? The emulsion, was prepared by intially stiring the emulsifier+nanoparticles+water at a speed of 15000 rpm for 3 minutes and afterwards, the oil is added to the mixture and stirred at the same rate for further 7 mins. The emulsion formed is normally W/O. In order to obtain O/W, about 2.5ml of HCL is added to the emulsion and stirred , it then changes the emulsion from W/O to O/W.
if you add oil into water in every case first o/w forms, which after receiving a critical amount of oil will switch to w/o. Multiple phase emulsions may be present.
It seems your 'emulsifier' is a base maybe an amine, which forms a surfactant (tenside as meant by Bernhard). This likely forms also a surface complex with silica. Both complex and 'emulsifier' will act as emulsifier.
At the end you will have a terribly complex system. Still unanswered - how do you then determine droplet size in this complex system?
@Titus, Thanks you so much for your response. The optical microscope images were taken and ImageJ software was used to analyze the droplet size.
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