“…NPs are also actively mixed into consumer bulk products to enhance the properties of the matrix materials to which they are added (for instance, carbon black in tires, and titanium dioxide NPs in food products, toothpaste, and cosmetics 1,2 ). An interesting aspect of NPs is that their electromagnetic, 3 optical, 4,5 mechanical, and various other material responses often a Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands † Electronic Supplementary Information (ESI) available: [details of any supplementary information available should be included here].…”