Hello,This "de" is not a particle as usuall,it is used for a grammar "shi...de",In chinese,if we want to emphasize something we will use this.
zhè běn shū shì wǒ zuó tiān mǎi de.This sentence want to emphasize "wo zuo tian mai".For example,"the ben shu shi wo de" want to emphasize this book is mine not others'.Hope can help you!
-Dali college of Eastern language
Teacher Quan