The bio-inspired synthesis of hierarchical hybrid nanomaterials using biological objects as a template attracts growing interest for the design of new technologically relevant nanostructured materials. To ensure control over the shape and properties of the fabricated hybrid structures, understanding of the growth mechanism is required. In nature, biominerals are produced as a result of heterogeneous nucleation of the inorganic material onto a biological template. As an example, CaCO3 is formed in specialized organic structures with acidic protein domains, which induce directed nucleation. Despite diversity and growing number of recently designed bio/inorganic hybrid nanomaterials, understanding of the mechanism for deposition of inorganic phases onto biotemplates is restricted to a few model systems, such as CaCO3 and SiO2, as well as on hydroxyapatite, which is promising for medical uses.
With respect to the synthesis of more technologically relevant materials, ZnS is among the first discovered semiconductors, used in fabrication of devices such as solar cells, field effect transistors (FETs) and light emitting materials. In recent years, the tobacco mosaic virus (TMV) has been proven to be an excellent biotemplate with its rigid rod-like structure. It forms a hollow rod 300 nm in length with an inner diameter of 4 nm and an outer diameter of 18 nm. The rigid structure and high aspect ratio of TMV offers a variety of pre-structuring options to grow monolayers, stripes and nanowires. It is relatively stable in a broad temperature and pH range, as well as in several organic solvents, which makes it ideal for the deposition of inorganic materials such as the non-metallic inorganic oxides SiO2 and ZnO and the chalcogenides CdS and PbS.
In this work, wildtype TMV is used as a template to direct the synthesis of ZnS forming bio/inorganic nanostructures at ambient conditions, different pH and from additive-free aqueous solution. The contribution of heterogeneous nucleation at the bio/inorganic interface is examined. The growth mechanism is studied comparing the optical properties, band gap (Eg) and particle size of ZnS particles mineralized onto substrate-immobilized TMV templates and of solution-grown ZnS nanoparticles.
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