not that I know of

​

used when answering a question to mean that, judging from the information you have, the answer is no

据我所知并非如此，据我所知没有

A: Is she especially unhappy at school?

她在学校特别不高兴吗?

B: Not that I know of.

据我所知没有。

A: Are you going to Washington next month?

你下个月要去华盛顿吗?

B: Not that I know of.

没这回事。