Dear Sir. Concerning your issue about the method that can be used for reduction of potassium tetrachloroplatinate. Platinum nanoparticles stabilized by linear polyethyleneimine were prepared by the liquid-phase reduction of chloroplatinic(IV) acid with sodium borohydride. The particle sizes were 3.26 nm and 1.76 nm when the molecular weights of linear polyethyleneimine were 25000 and 2150, respectively. These nanoparticles were well-dispersed in water in the range of pH 1-6. Branched polyethyleneimine also provided nanoparticles that dispersed in water in the range of pH 0-8. Linear poly(ethyleneimine-co-N-methylethyleneimine) gave nanoparticles that dispersed in water in the range of pH 0-10. The dispersibility of the nanoparticles decreased with increasing content of the N-methyl group. I think the following below links may help you in your analysis:

http://nptel.ac.in/courses/103103033/module9/lecture2.pdf

http://www.rsc.org/suppdata/c5/ta/c5ta07504a/c5ta07504a1.pdf

https://www.hindawi.com/journals/jnp/2014/285954/

 http://www.ch.ic.ac.uk/local/projects/s_liu/Html/Synthesis.html

https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/preparation-of-platinum-nanoparticles-using-linear-polyethyleneimine-as-a-stabilizer-by-liquidphase-reduction-method/E2E012AA11DD21FB3B52AE9A4159A342

Thanks

 Thank you Sir