Danny Sullivan from Google has said on Twitter that there is no search operator for sentiment simply because Google does not recognize sentiment in search. The question was if there was a way to see how sentiment plays into account with Google search rankings, which Danny shot down pretty quickly.
Danny said "It [Google search] does not recognize sentiment. So, no operator for that."
Here are those tweets:
It does not recognize sentiment. So, no operator for that.
— Danny Sullivan (@dannysullivan) July 23, 2018
10 months ago, there was confusion that Google did use sentiment analysis for rankings but that was clarified later that Google does not.
Forum discussion at Twitter.