Water quality sensors created from human hair
Researchers from Griffith University and the Queensland University of Technology (QUT) have synthesised carbon dots from human hair waste that can detect trace amounts of chloroform in water — a major by-product of water disinfection. Their research has been published in the journal Sustainable Materials and Technology.
Carbon dots are small carbon nanoparticles (less than 10 nm in size) with varying functional groups on the surface and the ability to fluoresce when exposed to a range of chemical and biochemical contaminants. The intensity of the fluorescence changes when surface functional groups on the carbon dot interact with the particular chemical species, making them suitable for chemical sensor applications.
“It might sound strange, but hair is an extremely valuable waste product,” said Griffith’s Professor Qin Li, who led the project.
“Being rich in protein and full of carbon and nitrogen, it is an excellent precursor for transformation into useful materials like carbon dots.”
The researchers created highly fluorescent carbon dots in a sustainable chemical-free process by heating up the hair at 180°C in an oxygen-deficient environment.
“Because hair is rich in nitrogen, when we altered the thermal treatment conditions, we produced carbon dots with different nitrogen-containing functional groups on their surface which bind specific contaminants,” Prof Li said. Remarkably, the researchers also found that different coloured hair produced carbon dots that responded preferentially to differing pollutants.
“The dark hair showed a high specificity for sensing chloroform pollution in water, while the blonde hair we tested was more sensitive to metal species like magnesium,” said former Griffith University Research Fellow Dr Ehsan Eftekhari. The dark hair-derived carbon dots, with nitrogen-based sensing antennas on the surface, were so sensitive that they could detect chloroform present in as few as three molecules per billion water molecules.
“Chlorination is a widely adopted disinfection method in water treatment used to reduce pathogen risks and waterborne diseases, but it also creates by-products that have been linked to higher cancer rates,” said study co-author Professor Fred Leusch, who chairs the Australian Water Quality Advisory Committee.
“So developing sensors to monitor the amount of chlorine used in treatment and the by-product concentrations in real time is of critical importance to public health.”
The carbon dot sensors could even tell the difference between very similar chemical contaminants. Prof Li said, “In this study, we found the nitrogen-based sensing antennae on the carbon dots’ surface was sensitive to chloroform, but not to the chemically similar contaminant bromoform, due to the subtle difference in their electronic structures.
“Using biowaste to make carbon dots for water quality sensors, without employing any harmful solvents, makes it a sustainable technology that truly adheres to the principles of green chemistry.”
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