Use 'scintilla' to emphasize how incredibly small an amount is. He doesn't have a scintilla of interest in starting a debate.
Pro Tip 2/3
Expressing Doubt
In context, 'scintilla' often signifies a strong skepticism or a lack of belief. There's not a scintilla of doubt in my mind that she'll succeed.
Pro Tip 3/3
Negative Evidence
Commonly used in legal and formal texts to denote an absence of evidence. The jury found him not guilty as there was not a scintilla of evidence against him.