Spinning webs to catch indoor pollutants

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A 3D polyamide net structure as a highly sensitive sensor for detecting formaldehyde

Chinese and US scientists have designed a nanofibre net structure to coat a quartz crystal microbalance to be used as a sensor to detect low levels of indoor gaseous pollutants. The device could be an optimal candidate for applications ranging from sensors to filtration and tissue engineering.

Formaldehyde is used in the manufacture of many polymers, resins and other construction materials. It is also used as an intermediate in soaps and detergents and is widely using in pharmacology and medicine. Formaldehyde is, however, a carcinogenic compound, which has a safe indoor exposure limit of between 60-80 parts per billion over a time period of 30 min. Conventional formaldehyde detection methods, such as chromatography, calorimetry, fluorescence and spectroscopy, suffer from long detection times and low sensitivity and are often expensive. Therefore there is a need for a rapid, low cost and sensitive method for formaldehyde detection.

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The sticky nanofibre net membranes catch the pollutants and can be compared to a spider’s web

Bin Ding at Donghua University, Shanghai, China, and colleagues deposited polyamide membranes on a quartz crystal microbalance using an electro-spinning netting technique. The team found that the nanofibre nets had a large surface area and high porosity coupled with a large stacking density and high adhesive force, which allowed for detection of low levels of formaldehyde (50 parts per billion). The system was also found to show rapid response times with high reproducibility and selectivity.

’Electro-spun nanofibres typically have diameters in the range 100-500nm, but properties such as surface area and porosity become more significant when the fibre diameter falls below 20nm. The major challenge for us was to come up with a robust strategy for manufacturing extremely small nanofibres in large quantities and with a uniform size,’ explains Ding. ’What’s most exciting is that the nets also have potential applications as ultra-fine filters to intercept viruses and bacteria,’ he adds.

Bingyun Li, an expert in nano-sized sorbents at West Virginia University, US, comments: ’The most interesting part of this work is the high sensitivity and rapid response to formaldehyde. The challenge faced by the team will be the systems’ reproducibility and multiple cycle performance.’

The team will now focus on understanding the formation mechanisms of the nets and to apply the structures for filtration methods as well as environmental sensing.

Carl Saxton

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