Graphene oxide nanosheets help regulate ice formation

Fish, insects, and bacteria are just a few examples of organisms that utilize antifreeze proteins (AFPs) to regulate ice formation and protect themselves from freezing. A variety of biomedical and commercial applications, such as synthesizing cryoprotectants to conserve tissues, cells, and food storage, can benefit from a similar mechanism.

One way to regulate ice formation in a controlled environment is through the utilization of nanomaterials, such as graphene oxide (GO). By using aqueous dispersions of GO nanosheets, Zhang et al. monitored how ice nucleation can be regulated.

When the nanosheets were larger than a critical size, the researchers found an intermediate state in the freezing process appeared, which had been previously predicted theoretically but never experimentally observed. This occurs due to changes in the dynamics of the water’s hydrogen atoms in the presence of the GO. As the larger GO nanosheets cause the hydrogen motion to slow down and reduce the energy requirement for ice nucleation, ice can begin to form at higher temperatures.

“Since the size of natural proteins cannot be changed freely, while the size of synthesized GOs can be controlled precisely over a wide range, it is a great advantage to use GOs to systematically study the size effect in ice formation and build up our understanding from [a] fundamental science point of view,” said author Xiang-Qiang Chu.

The group utilized aqueous dispersions of GO nanosheets of two different sizes and rapidly cooled the samples to measure their properties using quasi-elastic neutron scattering.

“As the extraction of natural AFPs are costly, laborious and difficult for mass production, the designing of synthetic products analogous to AFPs is a better alternative,” Chu said.

Source: “Investigations of structural and dynamical mechanism of ice formation regulated by graphene oxide nanosheets,” by Shengkai Zhang, Jingjing Han, Xiang Luo, Zhixin Wang, Xudong Gu, Na Li, Nicolas R. de Souza, Victoria García Sakai, and Xiang-Qiang Chu, Structural Dynamics (2021). The article can be accessed at https://doi.org/10.1063/4.0000111 .