Follow these steps

Drying: After washing, allow the silver nanoparticles to dry completely. This can be achieved through air-drying or using a gentle drying method, such as lyophilization (freeze-drying), to prevent aggregation.Dispersing Agent: Consider using a dispersing agent to prevent agglomeration of the nanoparticles during the drying process. Common dispersing agents include surfactants or stabilizing agents.Grinding or Milling: Once dried, you can use a mortar and pestle or a ball mill to grind the nanoparticles into a fine powder. This helps break down any remaining aggregates and ensures a homogeneous powder.Sieving: If necessary, you can sieve the powder to obtain a more uniform particle size distribution.Storage: Store the resulting silver nanoparticle powder in a dry and inert atmosphere to prevent oxidation.

Thank you for your response, Mr. Muhammad. I have already lyophilized and oven-dried the silver nanoparticles for many days but still, they are sticky.