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Paris – Mimicking nature, scientists have devised a way to convert the delicate, glass-like exoskeleton of a single-cell algae into silicon, the gold standard of electronics.
The ability to replicate nanoscale structures made of silica – found in nature in sand and quartz, and the main ingredient of manufactured glass – could yield pathbreaking applications ranging from ultra-precise sensing devices to optoelectronics.
The study by Zhihao Bao and a team of a dozen scientists in the United States, published in Nature, contributes to a growing body of research on new materials that can be manipulated on an atomic scale.
"This new work shows that glass can be transformed into silicon at relatively low temperatures while preserving a complex structure," noted David Norris, a professor in chemical engineering at the University of Minnesota, by e-mail.
A 'significant new trick'
"Because glass structures are very common, both in natural and man-made materials, this is a significant new trick," added Norris, who also penned a commentary in Nature, the weekly British science journal.
Starting with the biologically-derived cell walls of single-cell algae called diatoms, the scientists exposed silica to magnesium gas at 650'C to obtain a solid in which silicon is partially trapped by magnesia.
Because the temperatures needed are relatively low compared to other processes – the thermometre exceeds 2 000'C when producing silicon from glass using carbon – "the original shape of the silica is largely preserved," explains Norris.
The magnesia is then removed by bathing the sold in hydrochloric acid, leaving behind a silicon replica with all the intricate architecture of the original template intact.
Silicon a good semiconductor
Compared to the compound silica, silicon is a far better semiconductor for electronics applications. The complicated structures borrowed from the diatoms are also well-suited for certain technical applications.
Silica, or silicon dioxide, is formed when silicon and oxygen – the two most common elements in Earth's crust – come into contact with each other.
To test the new materials, Bao and his colleagues attached miniscule wires to a single diatom replica and used it as a micro-sensor.
The results suggest that the structure provides a much more efficient sensor for certain gases than conventional techniques. – Sapa-AFP