Exploring physical chemistry of interacting matters

B. Plasma-assisted freeze-casting

Freezing is a ubiquitous phenomena which we can observe in our dairy life. In recent years, freezing is attracting much attention for materials processing because of its fascinating self-organized structure of frozen suspension. Cryoplasma can introduce chemical reactivity to the frozen self-organized structure, which enables the development of a novel type of functional thin films and structural materials for catalysts, biosensors, electrodes of batteries and capacitors, and stretchable transparent conductors, for the sustainable development and energy management in harmony with our environment. Such plasma processing combining with freezing phenomena is termed as plasma-assisted freeze-casting. [N. Sakakibara et al., Langmuir 35 (2019) 3013; N. Sakakibara et al., JAP 129 (2021) 244903.]

C. Plasma, water, supercritical fluids and functional particles

Plasma interacting with condensed solvents such as aqueous solution and supercritical fluid is next-generation processing for materials design, agriculture and medical applications. However, plasma induces highly complicated chemical reactions in the condensed phases, which hinders the understanding further development of the plasma processing. By using cutting-edge measurement system (femtosecond laser, soft X-ray, and so on), significantly unique phenomena have been revealed, such as prolonged apparent lifetime of solvated electrons influenced by abundant free electrons, and hybridization of the electronic states between oxygen-containing functional groups on plasma surface modified carbon nanotubes and water molecules. Novel colloidal suspensions are also proposed, which is three-dimensionally self-organized plasma crystal in supercritical fluid. [N. Sakakibara and E. Miura et al., PRE 102 (2020) 053207; N. Sakakibara and Y. Harada et al., PCCP 23 (2021) 10468; N. Sakakibara and Y. Matsubayashi et al., PoP 25 (2018) 010704.]