The black phosphorus is relatively stable. Water? Do you mean a humid atmosphere?

Thanks, Daniela. I want to know whether black phosphorus/phosphorene quantum dots stable in water or not .

Phosphorus is very reactive. It react with oxygen despite the allotropic form. Of course, white phosphorus is much more reactive than black one. Nevertheless, black phosphorus reacts with air at normal conditions also. For a chemist with experience, the smell serves as a indicator of reaction. Our noses are no less sensitive than modern equipment. What smells? In case of elemental phosphorus - phosphorus oxides only...

Moreover, it would strange to talk about black phosphorus in the form of quantum dots. Black phosphorus is a phase, with a long-range order etc.