A piece of deep frozen ice and electronic gadgets may seem to have little connection (except that they are both 'cool' to have on you), but ice could now play a role in opening a new era in the electronic industry where conducting polymers, simply put plastics with electrical properties, are in great demand for practical applications.
Chemists at Pohang University of Science and Technology (POSTECH), Korea, have discovered an innovative method to form two-dimensional polyaniline (PANI) nanosheets using ice as a hard template. The product, called PANI-ICE, is reported to have distinctly outstanding electrical properties of low resistivity and high conductivity. PANI-ICE nanosheets show high electronic current flows twice as high as that of graphene, widely known as a next generation dream material, and over 40 times higher conductivity of PANI materials produced by existing established synthetic procedures.
Among various conducting polymers, PANI has long been a promising candidate for practical applications, in particular for microelectronics and battery electrodes, due to its relatively facile chemical synthesis and easy doping process at a low financial and environmental cost compared to other materials. As PANI's electrical properties are known to largely depend on its structure, previous studies have focused on the successful fabrication of two-dimensional PANI nanosheets using graphene oxide (GO) as a hard template. Despite improved electrical properties, however, the high cost, complexity of synthetic procedures, and unreliability of electrical properties over a large area are pointed out as the downside of PANI-GO composite nanosheets. Difficulties in removing the graphene oxide template also hinder versatile formation of the products.
Dr. Moon Jeong Park, a professor of the Department of Chemistry at POSTECH, and her two doctoral students, Il Young Choi and Joungphil Lee, have recently presented an innovative method that effectively overcomes the disadvantages of existing approaches. Selected as a "Highly Important Paper" of Angewandte Chemie, an internationally acclaimed peer-reviewed journal, Park et al.'s study is drawing much attention.
Park et al. fabricate PANI nanosheets on a smooth surface of deep frozen ice, causing preferential vertical growth and molecular orientation of PANI that significantly enhances its electrical properties. The superior conductivity of PANI-ICE, in particular, outperforms that of any other existing PANI ever reported. Moreover, the fabricated nanosheets can be easily transferred to various types of substrates as they float off on the surface of an ice template. It is also noteworthy that nanosheets can be patterned into any shape when using prearranged masks.
By simply introducing an easily removable, environment-friendly ice template, Park et al. successfully tackled a major challenge in the commercialization of conducting polymers, which is to improve both electrical properties and processability. What is more impressive about Park et al.'s original approach is that the synthesis of a large area only takes a few minutes and allows the production of one square meter of PANI-ICE nanosheet at a cost lower than $8 (USD).
"We believe that these unique, unprecedented advantages of PANI-ICE can expedite the eventual convenient and inexpensive application of conducting polymers in versatile electronic devices," said Park, the leader of study. Park et al. next plan to experiment on small pitch sizes of the nanosheets and further develop their research on the applications for electrodes in various electronic devices such as actuators.
This work was supported by the Samsung Research Funding Center of Samsung Electronics.