Another way to look at this ... a surfactant lowers the surface tension at the interface between materials. Your nanoparticles can only grow bigger than a few tens of nanometers by successfully growing larger than their Kelvin barrier. This barrier is determined by the available surface energy and the radius of curvature of the particle. So when the particle is too small and doesn't have enough surface energy to exceed the Kelvin barrier, the low surface tension due to the high radius of curvature won't allow the particle to grow any larger. But if the particle successfully grows larger than the barrier, then the radius of curvature decreases, making a flatter particle with a larger radius, and the surface tension allows the particle to grow even larger into the mesoscopic domain.

The surfactant modulates the available surface energy of the particles so that the surface tension decreases, and the Kelvin barrier moves, allowing more particles to escape the aggregation process and generally lowering the mean particle size.

I think surfactants (Surface acting agents) are used in order to get reduced size nanoparticles and to avoid agglomeration..Hope this is right.. If you find any other explanation kijndly post this...

I think it is to prevent aggregation and micelles will be observed.

Hi Magesan, can you tell what Nano particles you are talking about ?

Surfactant can be used to introduce mesostructural order and controlled mesoporosity in the material.

Hi Ms.Shakila, are you sure surfactants reduce the size of Nano particles ? If yes, could you please explain the possible mechanism.....

Can we use surfactnts in case of gold nanoparticles while synthesizing from plant extracts?

Surfactants are used either to form mesostructured material (pore size define by the molecular weight and the concentration of the surfactant) or to control the growth of nanoparticles by adsorption on the surface.

The surfactant is an agent used mainly to limit agglomeration of nanoparticles and therefore acts in the reducing of their sizes. It can also control the structural form of nanoparticles. According to its molecular nature, it can also get into the structure of nanoparticles (functionalization) leading to functionalized nanoparticles. The latter possess interesting properties especially in the biological field, such as: victorisation drugs ....

surfactant act as a template for nano-particle formation during synthesis and it limit agglomeration with increase in formation of micelles.

Thank u so much ur suggestion

Gud morning Mr. Rakesh,

I m trying to synthesize some metal oxides -TiO2 like Fe2O3-TiO2, CdO-TiO2 etc.,

Surfactants may be used to prevent aggregate formation during synthesis by sol-gel method and also efficiently reduces aggregate during dialysis.

Another way to look at this ... a surfactant lowers the surface tension at the interface between materials. Your nanoparticles can only grow bigger than a few tens of nanometers by successfully growing larger than their Kelvin barrier. This barrier is determined by the available surface energy and the radius of curvature of the particle. So when the particle is too small and doesn't have enough surface energy to exceed the Kelvin barrier, the low surface tension due to the high radius of curvature won't allow the particle to grow any larger. But if the particle successfully grows larger than the barrier, then the radius of curvature decreases, making a flatter particle with a larger radius, and the surface tension allows the particle to grow even larger into the mesoscopic domain.

The surfactant modulates the available surface energy of the particles so that the surface tension decreases, and the Kelvin barrier moves, allowing more particles to escape the aggregation process and generally lowering the mean particle size.

Michael Wofsey, I read your comments with great appreciation of your detail explanation on the role of surfactant. Is it possible to manipulate the available surface energy in order to produce a nanoparticles with homogeneous diameter per batch of profuction?

Hi Syamsul, thanks for the compliment on my explanation. Your need to make very consistent-sized nanoparticles by modulating the available surface energy near the Kelvin barrier is a bit tricky, I need to think about it for a bit, and my explanation may be completely worthless in anything other than a theoretical sense. Are you growing these particles on a surface or can you sort these particles after growth?

Dear Micheal,

As far as the synthesis goes, we synthesis the nanoparticles in a bioreactor and the final product after membrane dialysis is analyse via UV-VIS and TEM. The results show a homogeneous nanoparticles were produced but personally I felt that the TEM results do not give conclusive results.

What surfactant is recommended for an acidic solution such as phosphoric acid or dilute nitric acid?

We have so many surfactants,each surfactant having its own properties. Generally the SURFACTANT as a surface active material, using in synthesis of nano particles or fabrication of thin films to reduce the agglomerations in the reactions

Surfactants are surface active agents and in Sol Gel method they act as scavengers for the synthesis of nanoporous materials.They first get interacted with the metal salt and after strong heating (calcination), they are scavenged (removed) for the synthesis of nanoparticals. they are used as templates for the synthesis of nanoparticals.But we have to know first the melting point and solubility of metal salt and of surfactant. Generally more the molecular weight of the surfactant larger is the pore size and volume of the nanoporous material. The basic motto of using surfactants in sol gel method is to make the pore size of the nanoparticals within the range of nanometer dimensions

Without surfactants can not we synthesize nanoporous materials in sol gel method?

Not like that . If u supposed to use means u can prevent aggregate formation during synthesis by sol-gel method

It is very nice to follow this very interesting discussion. Although we have used a non aqueous sol-based method for synthesis of LiFePO4 nano particles we have not used sol-gel method per se to make particulate stuff or thin films. The role of surfactants seems to be tricky but important. We have two control parameters surfactant amount and the overall viscosity of the sol. I think the most important aspect is the right choice of the surfactant itself. Control of surface tension though theoretical in nature can be used effectively. The simplest thing to do is to make a measurement of ST. We do such a measurement on water in our Integrated MSc Mechanics Laboratory

Hmm the discussion is getting interesting. CS Sunandana, can you explain how to control and measure surface tension via surfactant?

Usually the ST is measured by accurately measuring the rise of a liquid in a capillary tube. Details can be had in website like Wikipedia. Important thing is surfactant solution is till a homogeneous kind of solution. Real life example: add a spoonful of "Tide" detergent powder to 100 ml water. One could measure capillary rise by dipping a capillary into this solution and waiting for the solution to rise. Application of standard formula get us the number. As I am away from Hyderabad I dont have immediate access to details.

One small correction: line 2 read 'still' not 'till'

Nano-particles are known to have a very large surface to volume ratio. This large surface distinguish them from the bulk material. A surfactant is a material that is surface active.This means that a surfactant will lower the surface tension of the surface of the nanoparticles. Thus it depend on what kind of surfactant you are dealing with.

The discussion turns an interesting mode, the main aim of surfactant is to provide the required energy for the reaction so as to guide the particles towards the desired shape. It prevents the nanoparticles from agglomeration by making dative bonds with the surface of the desired metal particles.

Happy to read Michael Wofsey. So one needs a useful tradeoff between interfacial tension and Kelvin barrier to grow size and perhaps shape controlled nanoparticles. However the growth of nanoparticles at the interface between a metal thin film and air/vacuum by oxidation is an equally interesting and perhaps a simpler affair.

how are you Guys

am student PhD and hope to keep in touch each other for knowledge, i need your help in nano porous question i want ask about desalination using Diatomic, what's materials mixing with diatomic for get nonporous, thank you very much

with you

mohamen

Tell me the novelity of copper nanoporous materials.

dear Gowhar , my main material is diatomite and substrate is glass or silicon and using sol-gel method , so need materials mixing with diatomite for get to nano porous

Valuable question well discuss.

Diatomites and diatomaceous rock are important

as carriers of catalysts. They are characterized by high

surface area of pores and could retention capacity of the de-

posited catalyst. Used together with copper, vana-

dium, chromium, nickel, and other salts. In the oxidation of

toluene, anthracene, alcohol. Why? To accelerate poly-

merization of hydrocarbons.

sir can you please give me study material related to this answer "effect of surfactant on nanomaterial synthesis"(@ Michael Wofsey )