Use the link to find plenty of software to perform indexing. All you need are accurate peak positions.
Nano-particles may cause you problems as they are often poorly crystalline and may not show good peaks, or they may consist of broad overlapped peaks which are difficult to deconvolve.
There is a software called "Unicell". You just need to know the accurate 2 theta values and its corresponding miller indices of ur sample. It gives u the a,b,c values and unit cell volume. You can check it in the link provided by Prof. Ian. If u need any help with that software, you can ask me.