2, University of California, Riverside, Riverside, California, United States
3, University of California, Riverside, Riverside, California, United States
In recent years, viruses have been investigated as versatile, hierarchical templates with site-specific affinity. Peptides displayed via genetic or chemical modification can facilitate the selective synthesis of one or more inorganic materials on viral surface proteins, while viral structure can control the long-range assembly of these materials. In particular, the M13 bacteriophage, measuring approximately one micron in length and 6 nm in diameter, has been studied extensively. This virus is composed of five structural proteins including the p3 located at its proximal tip and the p8 found along its length. Each of these proteins can be modified to create a comparatively low-symmetry template with peptide affinity for two different materials. Moreover, using simple chemical exposure, this filamentous template can undergo a shape transformation to form 60 nm spheres, while maintaining peptide affinity. The capacity for extreme modification of morphology combined with the asymmetric placement of the p3 and p8 on the viral surface make the M13 bacteriophage a potentially powerful scaffold for metal-semiconductor Janus particle assembly. Unlike core-shell metal-semiconductor structures in which the core material is isolated from the surrounding environment (and therefore chemically inactive), two-faced particles preserve the chemical activity of both materials. Exposure of both the metal and semiconductor to the surrounding environment is beneficial for photocatalytic processes as it allows for electron/hole exchange between catalyst and reactant. While the filamentous form has seen extensive use as a template, its spheroidal counterpart is relatively unstudied. This work characterized the shape change transformation then employed the spheroid as a template for a Janus-like particle composed of ZnS and Au. The novel nanoparticle was used in the photo-degradation of methylene blue, and the photo-generated electron pathway was studied. This work represents one of the first examples of application of the genetically and morphologically modified M13.