Gold nanoparticles produced in a microalga
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An efficient biological route to production of gold nanoparticles which allows the nanoparticles to be easily recovered remains elusive. Live cells of the green microalga Chlorella vulgaris were incubated with a solution of gold chloride and harvested by centrifugation. Nanoparticles inside intact cells were identified by transmission electron microscopy and confirmed to be metallic gold by synchrotron based X-ray powder diffraction and X-ray absorption spectroscopy. These intracellular gold nanoparticles were 40–60 nm in diameter. At a concentration of 1.4% Au in the alga, a better than 97% recovery of the gold from solution was achieved. A maximum of 4.2% Au in the alga was obtained. Exposure of C. vulgaris to solutions containing dissolved salts of palladium, ruthenium, and rhodium also resulted in the production of the corresponding nanoparticles within the cells. These were surmised to be also metallic, but were produced at a much lower intracellular concentration than achieved with gold. Iridium was apparently toxic to the alga. No nanoparticles were observed using platinum solutions. C. vulgaris provides a possible route to large scale production of gold nanoparticles.
KeywordsNanoparticles Chlorella vulgaris Gold Platinum Palladium Iridium Ruthenium Rhodium Nanobiotechnology
Jianyu Chen, Manawatu Microscopy Centre, Palmerston North, Massey University, New Zealand, assisted with the TEM study. Some of the measurements were made at the Australian Synchrotron, Melbourne, Australia. Travel funds were provided by the New Zealand Synchrotron Group Ltd. Melissa Basil-Jones and Katie Sizeland assisted with the synchrotron data collection.
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