There are different parameters which can affect the shape of nanoparticles. You did not mention by which method you are doing your synthesis but in most of the cases magnetic stirrers are used inside the vessels and they have significant influence on shape of nanoparticles.

Also the temperature changes may have influence on it. If you carried your reaction above RT then the better would be if you record the temperature profiles for all the reactions by attaching a thermocouple to the reaction vessel.

It is surprising that you are reporting no effect of surfactants, which usually have impact on particle size and morphology.

Concentration affects nucleation and crystal growth of nano-structures. It has both thermodynamic and kinetic consequences thus observing different morphologies is not an unfamiliar result.

Naeem Sir thanks for your suggestion, as you had mentioned i did it using a magnetic hot plate only and and the solution was maintained at 60 deg prior adding the reducing agent and after adding it the solution temperature for further increased upto 90 deg, but the particles where formed even before that. so the reaction was stopped.

I know this affects sir and i maintained the temperature carefully.

May be i will try one more time.

Talal sir thanks for your reply but yeah initially i thought that throny rod shape structure was due to tween 80 presence in the solution, recently i found a paper where they have achieved the same structure even with out tween 80 just by adding different ml of hydrazine hydrate to the solution. so i repeated my same experiments in the same way and found it to be true, now that's why i need to know more about this surfactant and what it does to my synthesis process. i feel it is something to do with the crystallinity of the particles, i mean i feel that its making the particle crystalline but not sure though.

can you please give any suggestion regarding tween 80?

You may check the CMC (critical micelle conc.) value of this surfactant and repeat the experiment at different concentrations of the surfactant.

Sir its CMC is 12mM and i did it for actual CMC, ten times more also sir but no difference may be i should do for still higher concentrations and check.

Deepa, It is strange that the surfactant you used has not displayed any effect. I would suggest try to use another surfactant and check it out.

According to Wikipedia the CMC of this surfactant is 0.012 mM. You should check the surfactant concentration applied in similar studies. Good luck

Yeah sir you are right sorry i made the mistake above but have used 0.012 mM only. anyways i will try again sir.

Thanks alot for your valuable suggestion and time.

Farooq sir sure i will try with another surfactant but just was curious to know the role of this one

I am sorry to write about a peripheral point, but this is something I am both amused and frustrated about. You see, a "mole" is a little furry animal -- or as a second meaning in English, it is a small skin defect (a name not unrelated to the animal: like a small "molehill" on the skin). But the abbreviation for the chemical parameter is "mol"...

At least it used to be, until in the last 20-30 years the native English-speaking people starting what is called "phonetic spelling", and of course it's more natural to write {mole} for this phonetics. And by now even some textbooks (let alone research papers) started copying this funny spelling. Every time I read about a "mole", I can't stop visualising this mole digging the tunnel ...

Deepa i would agree with Talal sir CMC and other parameters of surfactants matter alot, also temperature effect plays a vital role with surfactants, also the unfamiliar results is nothing unusual as talal sir said about nucleation site formation and nano crystal growth formation. In certain reaction even your stirring effect (rpm) of the stirrer plays a vital role in controlling the kinetic's of a reaction.

Note : Suggestion Don't do a reaction by just picking up a surfactant understand the chemistry of surfactant and the reaction mechanism and the vital role of surfactant various properties. Also just don't keep changing surfactant just because you wanna establish a result with surfactant kindly understand the chemistry behind a reaction during Nanosynthesis.

You are synthesizing magnetic nanoparticle's (Ni nanoparticle) in dispersion medium (Distill water) they are magnetic, they have there own aggregation ratio to undergo aggregation effect too. Also hydrazine hydrate is a powerful reducing agent, Even the time period for reaction to take place during using a strong or weak (i.e fast or slow) reducing agent matter alot, it is different for both and also temperature and stirring effect (rpm) plays a vital role. Surfactant such as Tween 80 is a hydrophilic nonionic surfactant (even triton X 100 is similar if i am not wrong). In certain reaction even the surface area given for the reaction to take place matters.

Note: Nanoparticle is a very sensitive system so a proper and calculated synthesis is useful.

Mahesh sir thanks for your suggestion, it really helped a lot i will surely try to understand the mechanism of it!

sorry eugene sir, i didn't know i shouldn't use mole instead of mol as i have always seen it with the spelling mole only. thanks for making me understand it.

Hai Deepa, how are you? First i congratulates you. This is very good research. I think that the change due to Size dependence of the dispersion.

Have a nice day

Interesting way to put it gokul thanks for your aswer i will think in this way.

By the  way am fine hope you are doing good too. Thanks for your encouragement

I personally feel that there must always be a check on the type of surfactant being used - hydrophilic or hydrophobic. Next it has to be about the zeta potential that has to be maintained for the surfactant to play its role.

But when gravitational forces driven by particle size and density dominate the system, the electrostatic interactions are no longer sufficient to provide stability and another means of stabilization is therefore required. One way of doing this is to increase the kinetic stability of the suspension by slowing down the rate of sedimentation. This can be achieved by increasing the viscosity of the continuous phase.

The principle ‘surface active properties’ exhibited by surfactants are

·         Wetting

·         Foaming/defoaming

·         Dispersion/aggregation of solids

·         Solubility and solubilisation (hydrotropic properties)

·         Adsorption

Many surfactants possess a combination of these properties.

In addition, depending on the chemical composition of a particular surfactant, some products may possess important ancillary properties including

·         Biocidal properties

·         Lubricity

·         Stability in highly acidic or alkaline media

·         Viscosity modification