Diatoms, photosynthetic microalgae that are ubiquitous in aquatic systems, have attracted significant attention from researchers over the past several decades. The exoskeleton structures (frustules) that encloses their cytoplasm, consist of hierarchical micro/nano-structures that are composed of pure silica. The morphology of these structures gives rise to their excellent mechanical properties, surface area and optical properties. By utilizing these properties, frustules has been employed in applications ranging from sensors in chemical/bio-sensing to light scatterers in solar cells for enhanced sensitivity and energy harvesting performances, respectively. Silica nanowires, on the other hand, has long been studied as sensor materials for bio and gas sensing. Many synthesis methods including hydrothermal method, oxide assisted growth method and vapor-liquid-solid (VLS) method have been proposed for the growth of the silica nanowires. It has been proposed that the nanowires can be used for sensing purposes and light emission applications. In this paper, we propose to use VLS method to grow silica nanowires on the surface of diatom frustules. The resultant composite material particles are easy to transfer, possess enormous surface area, making them to be potential components light scattering/energy applications. In this paper, frustules from Coscinodiscus sp. (C. sp.) diatoms were cleaned with concentrated sulfuric acid under 60 °C for 40 min. P-type 100 silicon wafers are used and the substrate to hold diatom frustules and the source of silicon. ~20 nm of gold was first deposited on the bare silicon substrate through sputtering. Frustules were then dispensed to the surface before another layer of gold deposition (~10 nm). The prepared samples were then heated with a continuous Ar flow (500 sccm) under 1100 °C for 40 min before cooled with the furnace. Through SEM observation, it was found that on both types of the frustules nanowires was grown out of the surface. The nanowires have a Si to O ratio of around 1:2. The diameter of the nanowires ranges from 100 nm to 200 nm. The length of the nanowires is up to 18 µm. At the tips of the nanowires, gold nano spheres are observed, corresponding well with the as reported VLS synthesis of the silica nanowires. The scattering performance of the nanowires have been greatly improved. The resultant composite materials have the potential to be used as the materials light scattering/energy harvesting applications.

Growth of silica nanowires on diatom frustules via vapor-liquid-solid process

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.