A recipe for 'green' electronics? Stir volcanic H2O at 0 degrees celsius

Japanese researchers unearth an 'ultra-cool' recipe for green manufacturing.
Sade Agard
Volcanic spring exploding
Volcanic spring exploding


When you think of how to produce electrical components, water might not top your list of raw materials. Yet, researchers from the University of Tsukuba have used volcanic spring water to help develop the plastic that's a crucial ingredient of many modern technologies, according to a recent study published in Water Chemistry and Technology.

Significantly, the research may improve the sustainability of manufacturing numerous consumer and industrial goods.

Can electronics be produced from water?

In many modern technologies, plastics—polyaniline (PANI)—hold electronic components together.

PANI is used on millions of square meters annually for this and other applications. Therefore, producing it with an environmentally friendly solvent has clear advantages.

There are numerous solvents available today that can be used to create PANI. Still, most are toxic and incompatible with standard mass-production device fabrication procedures, such as inkjet printing.

"We recently reported the use of ethanol, with a small quantity of iodine additive, for preparing polyaniline," said Professor Hiromasa Goto, senior author, in a press release

"Nevertheless, water is the ultimate environmentally friendly solvent, and thus would be an even better option."

He said pure water wouldn't work because aniline is often converted into PANI using an acid and an oxidizer. Sulfate and a large number of mineral ions in volcanic spring water, however, are, in fact, adequate for polymerization. The goal of the study was to examine this idea.

Just stirring their mixtures overnight at 0 degrees celsius allowed the researchers to create PANI, nanoscale PANI particles, and PANI/silk composites. They boosted the PANI's conductivity and verified that the conductivity was not coming from trace minerals.

"Scanning electron microscopy indicates that each thread of a fabricated silk fabric was coated with PANI, and the shape of the fibers was unchanged," explained Professor Goto. 

"Thus, we have developed a straightforward means of preparing textiles that can conduct electricity."

'The pinnacle of green chemistry'

These PANI composites have numerous more potential uses. For instance, the researchers removed about 75 percent of the trace iodine from a water sample using filter paper infused with PANI.

This effort successfully prepared PANI in volcanic spring water at a low temperature - perhaps one of the most environmentally friendly methods.

The team claimed that finding the ideal mineral content, pH, and sulfate concentration for this synthesis would be simple, allowing water from any source to be a workable solvent for PANI production. 

Ultimately, they believe PANI's synthesis for electronics may be regarded as the pinnacle of green chemistry since it generates no oil waste and has no flammability risk.

The complete study was published in Water Chemistry and Technology on March 17 and can be found here. 

Study abstract:

Geothermal water is an abundant resource that springs from underground and contains many minerals or ions. Geothermal water has not yet been applied to industrial uses. In this research, synthesis of polyaniline and polyaniline/fiber composites were carried out in natural spring water. Aniline salt can be prepared with mix of aniline and geothermal water having sulfuric acid ions. The chemical structure of the products was evaluated by infrared and UV-Vis spectroscopy. The Fourier transform infrared signals derived from both benzenoid and quinonoid structures of polyaniline were observed. UV-Vis spectra of polyanilines were measured in N-methyl-2-pyrrolidone. The UV-Vis signals of π–π* transition of the main-chain, doping bands as polarons (radical cations) and bipolarons (dications) of the polyaniline were observed. Conductivity was measured by 4-probe method. High conductivity was obtained when low pH geothermal water was used for the polymerization of aniline. Conductivity was further increased with quantity of ammonium persulfate in the reaction as an initiator for the polymerization. The surface structure of the polyaniline/fiber composites was observed by scanning electron microscopy. The structure of silk fibers was exactly maintained after composites synthesis. A series of syntheses of polyaniline, a conductive polymer in geothermal water, requires no addition of sulfuric acid. This simple synthetic method could lead to the integration of polymer synthesis and geology.

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