Coaxial electrospinning is one way.. but there are other methods too. See this paper:

dx.doi.org/10.1016/j.polymer.2010.07.042 and DOI: 10.1002/marc.200600384

electrospinning is an easier method. One can do it using one needle/syringe setup or two syringes setup. Hydro-thermal is another approach but a bit tedious. we have been trying to form core-shell structures by HT method but it is taking long time.

There is a system that incorporate two syringes as be one that could be a solution....the other is the use of emulsions that is other method to obtain core-shell fibres with just one solution.

Co-axial electrospinning is the best to produce core-shell nanofibers

Thank you all for your suggestion. But Sridhar Sir I am unable to get that paper which you have suggested me to refer. Could you please send me the soft copy of that papers please?

Thank you...

@Pallavi...

your e-mail ID

Polyaniline nanofibres are no true fibres: under any circumstance, polyaniline will form globular primary particles of about 10 nm size, and any fibres spun from Polyaniline dispersions are just more or less linear aggregates of these nanoparticles (not bad though, but you should not think such fibres are comparable with some polyester fibre, only more nanoscopic - no, it is totally different).

https://www.researchgate.net/publication/49593603_New_Insight_into_Organic_Metal_Polyaniline_Morphology_and_Structure?ev=prf_pub

In case you believe that polyaniline / solvent mixtures are "solutions", I suggest you to read this here:

https://www.researchgate.net/publication/202290125_Conductive_Polymer__Solvent_Systems_Solutions_or_Dispersions

All such systems are dispersions, hence when you are spinning, you just give the nanoparticles a new macroscopic orientation, so it looks like a fibre.

Article New Insight into Organic Metal Polyaniline Morphology and Structure

Article Conductive Polymer / Solvent Systems: Solutions or Dispersions?

Very nice info @ Bernard...I just wondered...

However, I prefer coaxial needle with two different solutions to form core-shell nanofibers.

a coherent "needle" made from polyaniline with no particle/particle contact interfaces inside the "nanofibre" is not possible so far, as long as published techniques are used. (I would never exclude somebody invents something completely new and unimaginable, but so far this has not been invented to my knowledge, see my above comment).

If you are content with a nanoscopic structure being composed of ca 10 nm nanoparticles which then agglomerate and align to form something people call a "nanofibre", and then you coat this with another shell polymer, yes, why not? (I don't know what to do with it, but you probably know..)

Dear Bernard, In the case of PANI I agree with you. In some other cases the materials that or not prone to electrospinning (eg. P3HT), we do core-shell spinning, where we put P3HT solution in the core and an easily electrospinnable solution in the shell. After spinning we can remove the shell part by dissolving it in an appropriate solvent. This solvent must be a non solvent of the material in the core, so that we get the nanofiber (as you said nano particle array) of core material.

may I ask, what is the "solvent" for the P3HT? is it doped P3HT or undoped? what are the properties of the resulting fibres?

Dear Prof.Bernard: you can use chloroform...P3HT doped with PCBM. finally you can use cyclopentanone to selectively remove the shell part. If you are interested. please refer the attached paper...this is for the application of organic solar cells.

Thanks for the paper; as far as I know, P3HT / CHCl3 systems are not true solutions; P3HT behaves more like a soap does in water. Basically, it builds a colloidal system of (at least to me) unknown structure. Even more in presence of PCBM.

The paper claims that the higher efficiency is due to alignment of P3HT chains, but they present no evidence for that at all.

I would assume that the higher efficiency of the fiber based organic solar cells is due to a higher surface area which can absorb light compared with a dense film (maybe also the PCBM dopant distribution / arrangement is different = somehow more advantageous? who knows).

The paper does not deliver any information for clarifying this question.

Thanks for the paper; as far as I know, P3HT / CHCl3 systems are not true solutions; P3HT behaves more like a soap does in water. Basically, it builds a colloidal system of (at least to me) unknown structure. Even more in presence of PCBM.

The paper claims that the higher efficiency is due to alignment of P3HT chains, but they present no evidence for that at all.

I would assume that the higher efficiency of the fiber based organic solar cells is due to a higher surface area which can absorb light compared with a dense film (maybe also the PCBM dopant distribution / arrangement is different = somehow more advantageous? who knows).

The paper does not deliver any information for clarifying this question.

I agree with the more surface area of P3HT after spinning than a dense film. It is not easy to spin P3HT /CHCl3 may be because of your suggested properties. That is why they used coaxial spinning with PCL...I have a paper in which I have fabricated nanorods from nanofibers and I found much more efficiency for solar cells fabricated using nanorods. electron transfer might be easy in nanorods than in nanofibers.