None can be used with a singular or a plural verb, depending on the meaning. If you want to emphasize the individuals in a group, you use the singular, and none is equivalent to ‘not one’: None of them is a professional actor. When you want to emphasize a group or collection of people or things, the plural is more usual and none is equivalent to the plural meaning of ‘not any’: None of them are professional actors. A singular construction can often sound formal or pedantic: None of them is over eighteen. When none is used of non-countable things, it is treated as singular and is equivalent to the singular meaning of ‘not any’: None of the cheese is left