Contrary to popular misconceptions, none may be either singular or plural.

When the sense is plural (as indicated by a plural noun or pronoun in the following prepositional phrase – "none of [plural entity]"), none is plural; when the sense is singular (as indicated by a singular noun or pronoun in the following prepositional phrase – "none of [singular entity]"), none is singular.

For further discussion, see Does "None" Take a Singular or Plural Verb? in the Grammar FAQs.