Scientists discover oldest known human-made nanostructures

New Delhi: Scientists have discovered the oldest known human-made nanomaterials in the “unique black coatings” of ancient pottery shards — dated to 600 BC — unearthed from archeological site in Keeladi, Tamil Nadu.

The research, published recently in the journal Scientific Reports, revealed that these coatings are made of carbon nanotubes (CNTs) which have enabled the layer to last more than 2600 years, raising questions on the tools used during those periods to achieve high temperatures for making earthenwares.

According to the scientists, including those from Vellore Institute of Technology (VIT) in Tamil Nadu, the coatings are “the oldest nanostructures observed till now.” “Until this discovery, to our knowledge, the most ancient known nanostructures in human-made artifacts are from the eighth or ninth century AD,” study co-author Vijayanand Chandrasekaran from VIT told PTI. CNTs are tubular structures of carbon atoms arranged in an ordered manner, Chandrasekaran said, adding that coatings in ancient artifacts may not usually last this long due to wear and tear caused by changing conditions.

“But the robust mechanical properties of the CNT based coating has helped the layer sustain more than 2600 years,” he added. Carbon nanotubes have superlative properties, including high thermal and electrical conductivity, and very high mechanical strength, explained nanomaterial scientist M. M. Shaijumon from IISER Thiruvananthapuram, who was unrelated to the study.

“But the people of this time may not have intentionally added CNTs, instead, during the processing at high temperatures, these would have just formed accidentally,” Shaijumon told PTI. “If there is some processing of the potteries, which probably would have involved some high-temperature treatment, then it will add more justification to the findings,” he added.

According to Chandrasekaran, the closest scientific explanation for the finding is that some “vegetal fluid or extract” might have been used in the coatings of these pots which may have led to the formation of CNTs during high-temperature processing.