use Aurochloric acid for electrodepostion of gold thin films....................

Please try reading any specific books before asking others this kind of questions...

Simple search using "Google" will provide good answer for your question

First, you have to decide what the way you want to synthesize, by chemical or physical or by electrochemical route. Simply, you can use some gold salt and use electrode deposition or by heat treatment at  a reasonable temperature you could end up with gold nanoparticles. The following references may help you which I just got by google "simple synthesis of gold nanoparticles".

DOI: 10.1039/C3RA40280K

doi:10.1088/0957-4484/20/18/185606

doi:10.1016/j.colsurfa.2012.10.059

Best wishes!

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Instead of using chemical methods,  laser ablation of a gold target in a liquid is an efficient and simple procedure to obtain stable gold nanoparticles.

Look at the literature on gold catalysis - especially since about 1990. deposition-precipitation leads to good results and nanoparticles of about 2-6 nm diameter.