Production of Metallic Alloy Nanowires and Particles Templated Using Tomato Mosaic Virus (ToMV).

We demonstrate a simple, low-energy method whereby tomato mosaic virus (ToMV) particles can be used to template the production of nanowires and particles consisting of alloys of gold (Au), platinum (Pt) and palladium (Pd) in various combinations. Selective nanowire growth within the inner channel of the particles was achieved using the polymeric capping agent polyvinylpyrrolidone (PVPK30) and the reducing agent ascorbic acid. The reaction conditions also resulted in the deposition of alloy nanoparticles on the external surface of the rods in addition to the nanowire structures within the internal cavity. The resulting materials were characterized using a variety of electron microscopic and spectroscopic techniques, which revealed both the structural and chemical composition of the alloys within the nanomaterials.

Designer-length palladium nanowires can be templated by the central channel of tobacco mosaic virus nanorods.

We have developed methods for the templated synthesis of palladium nanowires (Pd NWs) within the central channel of tobacco mosaic virus (TMV) nanorods of various lengths. We show that uniform 4 nm diameter Pd NWs can be produced by selective growth within these channels by including the capping reagent, poly(vinyl-pyrrolidone) (PVP30K) and reducing the metal precursor to metallic palladium with ascorbic acid. The length of the Pd NWs can be controlled either by varying the length of the nanorod templates and/or through alterations to the reaction conditions. We have also demonstrated bimetallic gold (Au)-palladium (Pd) in-situ metallization of TMV nanorods resulting in the production of Pd NWs 6 nm gold nanoparticles attached to their ends. The materials produced have many potential applications in the construction of nanoscale devices.

The Use of a Replicating Virus Vector For in Planta Generation of Tobacco Mosaic Virus Nanorods Suitable For Metallization.

The production of designer-length tobacco mosaic virus (TMV) nanorods in plants has been problematic in terms of yields, particularly when modified coat protein subunits are incorporated. To address this, we have investigated the use of a replicating potato virus X-based vector (pEff) to express defined length nanorods containing either wild-type or modified versions of the TMV coat protein. This system has previously been shown to be an efficient method for producing virus-like particles of filamentous plant viruses. The length of the resulting TMV nanorods can be controlled by varying the length of the encapsidated RNA. Nanorod lengths were analyzed with a custom-written Python computer script coupled with the Nanorod UI user interface script, thereby generating histograms of particle length. In addition, nanorod variants were produced by incorporating coat protein subunits presenting metal-binding peptides at their C-termini. We demonstrate the utility of this approach by generating nanorods that bind colloidal gold nanoparticles.

Virus-Templated Near-Amorphous Iron Oxide Nanotubes.

We present a simple synthesis of iron oxide nanotubes, grown under very mild conditions from a solution containing Fe(II) and Fe(III), on rod-shaped tobacco mosaic virus templates. Their well-defined shape and surface chemistry suggest that these robust bionanoparticles are a versatile platform for synthesis of small, thin mineral tubes, which was achieved efficiently. Various characterization tools were used to explore the iron oxide in detail: Electron microscopy (SEM, TEM), magnetometry (SQUID-VSM), diffraction (XRD, TEM-SAED), electron spectroscopies (EELS, EDX, XPS), and X-ray absorption (XANES with EXAFS analysis). They allowed determination of the structure, crystallinity, magnetic properties, and composition of the tubes. The protein surface of the viral templates was crucial to nucleate iron oxide, exhibiting analogies to biomineralization in natural compartments such as ferritin cages.

Chemically-coupled-peptide-promoted virus nanoparticle templated mineralization.

The external surface of the plant virus Cowpea mosaic virus (CPMV) can be chemically modified with peptides that direct specific mineralization processes. Subsequent mineralization of the peptide-CPMV conjugates produces monodisperse nanoparticles of ca. 32 nm diameter coated with, for example, cobalt-platinum, iron-platinum or zinc sulfide, which cannot be readily prepared by other methods. This route is particularly attractive as it avoids the need to genetically engineer the protein surface of the virus to provide chimaeras for templated-mineralization. The synthetic procedure is environmentally friendly, as it proceeds at ambient temperature and pressure, in aqueous solvent. Further, the methodology is demonstrated to be generally applicable by the mineralization of a peptide-modified multiwalled carbon nanotube.

Environmentally benign synthesis of virus-templated, monodisperse, iron-platinum nanoparticles.

The use of an engineered variant of a plant virus, Cowpea mosaic virus (CPMV), as a template for directed mineralization provides an environmentally benign route to monodisperse iron-platinum nanoparticles of approximately 30 nm diameter.