Despite my persistent arguments, I failed to talk my brother out of investing in that risky venture.

talk 在这里是动词，意思是"谈话、劝说"。 out 是副词，表示"离开、不参与"的状态。 of 是介词，表示"关于、涉及"的关系。 talk sb out of sth 是一个固定短语，意思是"说服某人不要做某事"，通过谈话让对方放弃某个想法或行动。