to get nanoparticle size by spray pyrolysis you need to reduce the rate of deposition and increase time stop , but not guarantee to get low size you can get about 30 nm but if you able to use CBD method this is perfect way and you can get 10 nm

Dear Hersh,

In general, spray pyrolyzed thin films composed of nanoscale grains. If you like to obtain nanoporous films (like titania) by spray pyrolysis you can find numerous studies explaining the recipe and system requirements for it. It is commonly used in mesoporous perovskite-based solar cells. On the other hand, if you like to fabricate nanoparticles I strongly suggest you to designing a flame spray pyrolysis system (FSP).  FSP process is a highly promising and versatile technique for the rapid and scalable synthesis of nanostructured materials with engineered functionalities. In this context, you can explore our comprehensive book chapter including all these topics via Google Books.

All the best.

Chapter Spray Pyrolysis of Nano-Structured Optical and Electronic Materials

you can change the nozzle size of the spray system for good quality of nano sized particles. Of course the  the rate of deposition will also affect the size of deposited films 

In general, spray pyrolyzed thin films composed of nanoscale grains .