Abstract: A method for sorting of items (1) based on material type, comprising: —depositing an array of nanostructures (3) onto a surface portion of an item (1) to form a material identification tag (2), the nanostructures having an optical response dependent on the material type of the item onto which they are deposited, —illuminating the material identification tag using a light source (30), —determining at least one optical extinction and/or reflectance peak of the illuminated material identification tag, which peak is dependent on a material type of the item, —categorizing the item based on the detected optical extinction and/or reflectance spectrum, and —sorting the item in accordance with the categorization.