5:15 PM - 6:45 PM
[MIS18-P07] Formation conditions of graphene liquid cells and current status of cell development for pure water encapsulation
It is important to directly observe phenomena such as phase transitions, crystal growth and dissolution that occur in liquids in order to understand formation processes of materials. For the direct observation, transmission electron microscopy (TEM) has some advantages due to relatively high spatial resolution. Since TEM uses electron as a probe, it is necessary to keep the specimen chamber in high vacuum condition. The most common way is to encapsulate targeted liquid specimen between two amorphous silicon nitride membranes. Although this commercially well-developed technique has enabled us to elucidate many interesting phenomena such as ice crystal polymorphism in water [1] and nucleation of lysozyme crystal [2], it has been difficult to observe electron-sensitive materials with higher spatial resolution for some reasons, including the thickness of the silicon nitride membranes.
Graphene liquid cell (GLC) that use graphene to prevent the evaporation of liquids have been advocated as an alternative to the conventional liquid cells [3]. While the higher spatial resolution and radical scavenging ability, the formation of the previously reported pure water GLCs were low reproducibility based on our replicated experiments. Additionally, a significant concentration increase of an encapsulated solution have been recently pointed out [4]. By directly scooping a sheet of ‘free-standing’ graphene floating on an etching solution (0.4 M aqueous (NH4)2S2O8 solution), we have found the formation of the etching solution GLCs with high reproducibility as reported at the last conference.
We are now trying to clarify the conditions for the formation of the GLCs. We found that highly concentrated salt solutions are easily encapsulated in GLCs. Characteristic behaviors such as bubble formation due to radiolysis observed for the etching solution GLC were also confirmed for a 0.4 M ammonium sulfate solution and a 0.4 M ammonium phosphate solution. Possible mechanism for the formation of the GLCs in the case of the highly concentrated salt solutions will be discussed. We show changes in the probability of the GLCs formation with decreasing concentrations of the salt solutions.
A key point for improving the reproducibility of pure water GLCs is how to prevent a leakage of water molecules from graphene’s defects. Aluminum oxide is known to be preferentially deposited onto the graphene’s defects by ALD (atomic layer deposition). We designed modified pure water GLCs by using the graphene defect sealed by the aluminum oxide. To improve sealing and create gaps between graphene, gallium, a liquid metal, was melted and dropped down or deposited on the graphene-transferred TEM grid. It was then sandwiched by another graphene-transferred TEM grid. In the presentation, we will include results of observations using the fabricated GLCs at room temperature and below the freezing point of water. We provide what is needed to strategically design GLCs depending on targeted liquids, especially pure water.
[1] K. Tai et al., Microsc Microanal. 20, 330–337 (2014).
[2] T. Yamazaki et al., Proc Natl Acad Sci USA. 114, 2154–2159 (2017).
[3] J. M. Yuk et al., Science. 336, 61–64 (2012).
[4] M. F. Crook et al., J Am Chem Soc. 145, 6648–6657 (2023).
Graphene liquid cell (GLC) that use graphene to prevent the evaporation of liquids have been advocated as an alternative to the conventional liquid cells [3]. While the higher spatial resolution and radical scavenging ability, the formation of the previously reported pure water GLCs were low reproducibility based on our replicated experiments. Additionally, a significant concentration increase of an encapsulated solution have been recently pointed out [4]. By directly scooping a sheet of ‘free-standing’ graphene floating on an etching solution (0.4 M aqueous (NH4)2S2O8 solution), we have found the formation of the etching solution GLCs with high reproducibility as reported at the last conference.
We are now trying to clarify the conditions for the formation of the GLCs. We found that highly concentrated salt solutions are easily encapsulated in GLCs. Characteristic behaviors such as bubble formation due to radiolysis observed for the etching solution GLC were also confirmed for a 0.4 M ammonium sulfate solution and a 0.4 M ammonium phosphate solution. Possible mechanism for the formation of the GLCs in the case of the highly concentrated salt solutions will be discussed. We show changes in the probability of the GLCs formation with decreasing concentrations of the salt solutions.
A key point for improving the reproducibility of pure water GLCs is how to prevent a leakage of water molecules from graphene’s defects. Aluminum oxide is known to be preferentially deposited onto the graphene’s defects by ALD (atomic layer deposition). We designed modified pure water GLCs by using the graphene defect sealed by the aluminum oxide. To improve sealing and create gaps between graphene, gallium, a liquid metal, was melted and dropped down or deposited on the graphene-transferred TEM grid. It was then sandwiched by another graphene-transferred TEM grid. In the presentation, we will include results of observations using the fabricated GLCs at room temperature and below the freezing point of water. We provide what is needed to strategically design GLCs depending on targeted liquids, especially pure water.
[1] K. Tai et al., Microsc Microanal. 20, 330–337 (2014).
[2] T. Yamazaki et al., Proc Natl Acad Sci USA. 114, 2154–2159 (2017).
[3] J. M. Yuk et al., Science. 336, 61–64 (2012).
[4] M. F. Crook et al., J Am Chem Soc. 145, 6648–6657 (2023).