Microemulsion is an old, ill-defined, term. To me microemulsion is a system in which one phase (say dispersed phase) is solubilised in another one through formation of a third component (emulsifier) micelles. Therefore the size of microemulsions is restricted to the micellar size of the third component (emulsifier) that can be in range of few to hundred nanometers. You don't need any energy input to produce a microemulsion. microemulsions are thermodynamically stable (as micelles are thermodynamically stable systems, i.e. washing up liquid).

Nanoemulsion is a thermodynamically unstable system in which one phase is dispersed in another one through energy input (energy intensive techniques) or chemical/thermodynamic changes (known as low-energy techniques). Conventionally, nanoemulsions have drops lower than 1 micron (or 600nm), though some researchers try to give it a smaller range to make publications more appealing.

The size measurement does not reveal whether a system is a micro or nanoemulsion, the formulation of a system define it. you can have a microemulsion with 150 nm size (say using 50wt% tween 20 as emulsifier) and also a nanoemulsion with the same size range (say using 5wt% tween 20 as emulsifier).

"emulsions" are dispersions of at least 2 liquids, where 1 of the 2 liquids is continuous, the other one is dispersed; the dispersed liquid forms droplets (there are also bi-continuous emulsion, but I ignbore them here)

- nano-emulsions have dispersed liquid droplets size of between a few up to 100 nm diameter

- micro-emulsions have dispersed droplets with a size of more than 100 nm up to a few µm.

Dear Sir,

Your answer is right for basis on size and logically but actual i am find some controversy that is :

the term ‘microemulsion’ is still used for systems with droplets < 100 nm. and ‘nanoemulsion’ is sometimes used for globule size > 100 nm.

(Reference:- Ste´phane Gibaud & David Attivi, "Microemulsions for oral administration and their therapeutic applications", Expert Opin. Drug Deliv. (2012) 9(8):937-951)

Now Sir, What is right ?

Thanks.

It's in fact the case that terms in colloidal science are often not properly used.

Thanks for answer.

I read some review article in this they are distinguish that microemulsion are thermodynamic stable while nanoemulsion not.

Sir, now my question is that if I prepare micro/nanoemulsion are more than 100 nm as well as thermodynamically stable then what I called nano or micro?

from my viewpoint, both statements are wrong; my position is that any emulsion (which all are at least 2-phase systems) are thermodynamically spoken non-equilibrium systems, hence *unstable*; but many of them are kinetically stable, i.e., during we are observing them we can not *see* that they are unstable, maybe they are kinetically stable even "forever" ;

this is somewhat analogous with a ball which you throw high into air: due to gravity, it will fall down to earth due to gravitational "instability" and will come to its "equilibrium position" at sea level, if you are standing on sea level.

If you thjrow the ball somewhat high onto some trap, maybe on a roof, it will stay there forever (for as long as the roof will exist in that form), unless you invest some work and remove it from there.

But anyway, you have invested energy / work to throw the ball to that high position, so then on the roof, regarding gravitation potential energy, the ball is not in equilibrium, but will be stable. But not stable referring to gravitation potential; if for instance the roof is wooden, degrading, then some years later all of a sudden, the ball will fall down towards sea level.

Any emulsion is a system which contains a lot of interfaces which you have created by investing work (the amount is equal to surface tension multiplied with surface area); therefore these are thermodynamically spoken non-equilibrium systems.

Nanoemulsions if well prepared are kinetically more stable than microemulsions.

Thank you sir. I have problem to understand thermodynamically law but i clear understand the law.

Once again Thanks.

Microemulsion is an old term used to indicate emulsions with sub micron disperse phase structures typically in form of swollen micelles or bicontinuous phases.

The suffix micro- was used to indicate that micro emulsions have smaller droplets with respect to "conventional" emulsions (that have typically droplets of 5-50 microns)

Since now the term "nano" is increasingly popular some authors started to use the term nanoemulsions to give a new appeal to their papers. Nanoemulsions are in many respect very very similar to micro emulsions.

there may be people who are using the term "nano" (-emulsions) although the droplet size is above 100 nm, but as in other nanotechnology areas, the "correct" use of this term is for those types of emulsions where the droplet size is below 100 nm. Insofar, these emulsions are different from "micro"-emulsions, again: if the term "micro" is properly used for those emulsions with a droplet size above 100 nm (and even better: around and above 1 µm)

Even some review article the differentiate nano and micro-emulsion by this way..

In Nano-emulsion: concentration of surfactant low while in micro is high even they say that nano is kinetically stable while micro is thermodynamically stable.....

My viewpoint is, that both are (thermodynamically spoken) non.equilibrium systems and hence at best kinetically stable.

Microemulsion is an old, ill-defined, term. To me microemulsion is a system in which one phase (say dispersed phase) is solubilised in another one through formation of a third component (emulsifier) micelles. Therefore the size of microemulsions is restricted to the micellar size of the third component (emulsifier) that can be in range of few to hundred nanometers. You don't need any energy input to produce a microemulsion. microemulsions are thermodynamically stable (as micelles are thermodynamically stable systems, i.e. washing up liquid).

Nanoemulsion is a thermodynamically unstable system in which one phase is dispersed in another one through energy input (energy intensive techniques) or chemical/thermodynamic changes (known as low-energy techniques). Conventionally, nanoemulsions have drops lower than 1 micron (or 600nm), though some researchers try to give it a smaller range to make publications more appealing.

The size measurement does not reveal whether a system is a micro or nanoemulsion, the formulation of a system define it. you can have a microemulsion with 150 nm size (say using 50wt% tween 20 as emulsifier) and also a nanoemulsion with the same size range (say using 5wt% tween 20 as emulsifier).

with the first part of your comment, I agreed. With the 2nd part., I did not. Why?

Because the droplet size in micro / nano emulsions is not determined by the amount of emulsifier / tenside, but by the colloidal system you work on AND the shear you apply.

The measurement finally tells you whether you have a micro- or nano-emulsion, not the amount of emulsifier!

I do agree, the amount of stabiliser/emulsifier does not determine whether the system is nano or microemulsion, though the ratio between dispersed phase and emulsifier which can be used as a hint. I just provide the values as a comparison to show that you might have a microemulsion while the size measurement is in range of 150nm. As you mentioned, the best way is that you need energy to produce nanoemulsion and it is better to verify that the mixture remains as a two phase system with out applying energy.

I do not agree with the size measurement as the criterion to distinguish these systems. You can easily produce nanoemulsion with drop sizes in range of 50 nm which is known to be the range of a microemulsion.

To my experience, nanoemulsions with very small drop sizes can be bluish or yellowish (specially in white light) while microemulsions are transparent/clear.

check this article: 

https://www.researchgate.net/publication/255765585_Nanoemulsions_versus_microemulsions_terminology_differences_and_similarities

Article Nanoemulsions versus microemulsions: Terminology, difference...

Thank you, Victor sir. It is excellent article.

that is to say, the size of emulsions is not a criterion for characterizing micro-emulsions and nano-emulsions. My emulsions are turbid, and will layering after several days keeping, Any way to improve these?

what are you preparing microeulsion or emulsion ? describe your problem in detail.

the oil phase is soybean oil, the water phase is alkaline soluble starch plus STMP solution, and surfactant is Tween/Span 80

Try following way;

find out the RHLB value of emulsion based on example given in link:

https://www.researchgate.net/publication/283781768_Calculation_of_Required_HLB_Value_for_OW_Emulsion

Data Calculation of Required HLB Value for O/W Emulsion

I would like to suggest you tha paper: " Nanoemulsions versus microemlusions:terminology, differences and similarities."" D.J.McClements .DOI:10.1039/c2sm06903b . Which appeared in "Soft Matter" , 2012,8,1719. The paper clearly explains why the particle size criterion is a not reliable parameter for a significant discrimination between micro and nano emulsions

see also Nanoemulsions:formation, properties and applications.

A.Gupta et al. Soft Matter, 2016.12, 2826

It depends on the colloidal system u work on

Dear Dignesh Khunt

Pls read this article..maybe you can get some ideas from it:

Preparation and in vitro evaluation of montelukast sodium oral nanoemulsion

Regards

Also you can see this a chapter in this book talk about Microemulsion

Microemulsions

Chapter · June 2018 with 100 Reads

DOI: 10.1002/9781119247159.ch9

In book: Emulsion-Based Systems for Delivery of Food Active Compounds: Formation, Application, Health, and Safety, Edition: First Edition, Chapter: 9, Publisher: John Wiley & Sons Ltd, Editors: Shahin Roohinejad, Ralf Greiner, Indrawati Oey, Jingyuan Wen, pp.231-262

Regards

Dear Anas Tarik Alhamdany Sir,

Thanks for your suggestion.

What a bunch of nonsense. A microemulsion is not a poorly-defined term. It's very specific - if people bother to read the literature beyond ten years ago. A nanoemulsion is an emulsion with a ridiculous money-grabbing nano prefix. What was colloid science has been taken over by nano- this and nano- that in order to get grant money. And it shows in the deterioration of the quality of research in this area both published and presented at conferences.

Nanodispersions supposedly are defined by nanoparticles < 100nm yet a nanoemulsion is defined by droplets < 1000nm. Really? Seriously, who decided to change the term and what gave them that divine right?

It is ridiculous and confusing. What was wrong with the original term?

I despair for my beloved discipline. Very sad.

John, I don't agree to what you wrote, at least not to all of it.

(I agree that quite often, and too often, research is too superficial, empty with hollow words, exaggerating and and and ...)

I do not agree with your omment to ther wording. First, you yourself are using the term "nano-" in your profile, and I think such terms are better characterizing what we are dealing with because with the terms "micro-" and "nano-", the scale with which one is operating is described, better than only saying "colloidal".

(I like the word "colloidal" as well, but for many people, this does not tell too much, but with "micro" and "nano", one can easier imagine what the discussion is about)

I use nano in my profile because I have to. Go to a colloid conference and count how many times the word colloid appears in abstracts compared to nano. Nano isn't easier when on one hand it means