New Solution for High-Yield Nanowire Production from Zinc Oxide

Nanowires are meeting the requirements of the market for novel, smaller, flexible electronic devices by powering electronic circuits on the molecular scale; however, the arrangement of nanowires into functional materials is still a challenge.

Dr Simas Rackauskas, KTU Institute of Materials Science. (Image credit: Kaunas University of Technology)

A team of scientists from Kaunas University of Technology (KTU), Lithuania, are providing an innovative solution for high-yield nanowire production from zinc oxide—less expensive and more eco-friendly material than the rare earth elements like arsenic, indium, or gallium usually used in electronics production.

Researchers state that the production of nanowires is mostly restricted by the surface of growth, hampering their broad application. Furthermore, several applications necessitate properties that are contradictive and thus cannot be effectively achieved in a single material.

The innovative technique for zinc oxide nanowires production, developed by the research team from KTU Institute of Materials Science, solves these issues. Therefore, the broader application of nanowires in new electronic devices, which are even smaller, flexible, and involving different surface materials, is turning out to be achievable.

The new method was created while I was researching simple ways to grow metal oxide nanostructures. The method, which we now call combustion synthesis, allows producing high levels of a controlled nanostructure. Nanowires are being grown in the gas phase, the final product collected as powder and then dispersed in various solutions. Simple coating methods such as spraying allow placing zinc oxide nanowires on various surfaces.

Dr Simas Račkauskas, Researcher, Institute of Materials Science, Kaunas University of Technology

Owing to their semiconductor properties, zinc oxide nanowires show great promise for application in optics or electronics. Furthermore, the properties of zinc oxide coated surfaces enable their use in medicine.

Presently, scientists are examining two promising applications of the zinc oxide nanowires: a multifunctional anti-reflecting solar cell coating and multifunctional gas sensor array, selective and sensitive to gases, stimulated by light.

Solar elements currently used in the market are reflecting light, thus the light, which could be turned into energy, is partly lost. Nanowire solar cell coatings improve the performance of solar cells by reducing their reflective qualities, by transforming UV rays into light and by rendering the solar elements self-cleaning properties,” explains Dr Račkauskas.

Early research shows that the efficiency of solar elements is enhanced by 6% by using zinc oxide nanowire coating. The coating is water-repellent and it decomposes the organic pollutants, thereby realizing the self-cleaning effect of a solar cell.

Currently, in the laboratory conditions, the KTU group of researchers can make about 100 g of zinc oxide nanoparticles per hour, priced at about EUR 8. The amount would be sufficient to cover the 2.5 m2 of solar elements.

In addition, KTU scientists are examining the properties of an exclusive UV sensor that can be sprayed on any surface. Two materials are used in the production of the sensor: zinc oxide nanoparticles and a conductor (wire), like graphite or metal paint.

It is possible to sketch a complete electronic scheme including wire and sensor on any surface, for example, paper, textile, or plastic. According to Dr Račkauskas, it is possible to use a light sensor as any other switch that is just triggered by light, like a simple laser pointer beam.

The application possibilities of such a UV sensor are virtually inexhaustible, however, we need to wait for the market demand and the further development of flexible electronics. Our product might be interesting for functional design as it allows integrating electronics into clothing items, walls, interior design objects. Also, our UV switch can be placed in hard-to-access locations.

Dr Simas Račkauskas, Researcher, Institute of Materials Science, Kaunas University of Technology

Highlighting the low cost and eco-friendliness of zinc in electronics production, he said: “Most electronic production uses rare earth elements, such as indium, arsenic and gallium, which are hard to extract, the process is expensive and harmful to the environment. On the other hand, Zinc is very popular, cheap and even beneficial for the human organism”.

According to the KTU scientist, the use of zinc oxide as an alternative to the rare earth elements in electronics would pave the way for economical and eco-friendly solutions.

This study is funded by the European Regional Development Fund according to the 2014–2020 Operational Programme for the European Union Funds’ Investments, under the measures No. 01.2.2-LMT-K-718 activity Attracting Foreign Researchers for Research Implementation, Project No. 01.2.2-LMT-K-718-02-0011.


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