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Surface evolution of manganese chloride aqueous droplets resulting in self-suppressed evaporation.

Zeng X, Zhang Y, Xia Z, Wang L, Wang C, Huang Y, Shen R, Wen W - Sci Rep (2015)

Bottom Line: A fantastic and extraordinary phenomenon was observed during the evaporation of a water droplet doped with manganese chloride.The MnCl2-doped water droplets were maintained in a relative humidity (RH) of 50% at 40 °C for more than a week and for longer than two months at a temperature of 25 °C.In contrast, a pure water droplet can only be sustained for a few minutes.

View Article: PubMed Central - PubMed

Affiliation: Nano Science and Technology Program / Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.

ABSTRACT
The exchange kinetics of liquid water, which are of fundamental interest and have potential applications, remain unclear. A fantastic and extraordinary phenomenon was observed during the evaporation of a water droplet doped with manganese chloride. As observed from the evolution of this type of droplet, a thin film was formed on the surface with an exothermic phase transition, resulting in self-suppressed evaporation. The MnCl2-doped water droplets were maintained in a relative humidity (RH) of 50% at 40 °C for more than a week and for longer than two months at a temperature of 25 °C. In contrast, a pure water droplet can only be sustained for a few minutes. The self-suppressed evaporation of doped water may be due to the special hydration of the accumulated manganese and chloride ions at the surface, decreasing the surface tension.

No MeSH data available.


Related in: MedlinePlus

Investigation of the surface of the droplets using AFM.An AFM tip was inserted approximately 2 μm into the surface of the droplets and then drawn out. The relationship between the force and the vertical displacement was recorded.
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f5: Investigation of the surface of the droplets using AFM.An AFM tip was inserted approximately 2 μm into the surface of the droplets and then drawn out. The relationship between the force and the vertical displacement was recorded.

Mentions: AFM was also used to confirm the formation of the thin film on the droplet, as shown in Fig. 5. The droplet was pre-heated at 40 °C for approximately 35 minutes. Then, the AFM probe was pierced 2 μm into the droplet from the top and then slowly drawn out. The relationship between the drawing force and the vertical displacement was recorded. Based on the results for the pure water droplet, the force became more negative in the initial stage due to the adhesion force between the water and the tip, and then, the force suddenly returned to zero, which indicates that the water was detached from the tip surface. In contrast, there were two sudden changes observed in the plot for the manganese chloride droplet. The first change corresponded to the liquid beneath the film detaching from the tip, and the second one corresponded to the film detaching from the tips. Therefore, based on these results, the film thickness is approximately 1 μm, which is approximately equal to the width between the two steps.


Surface evolution of manganese chloride aqueous droplets resulting in self-suppressed evaporation.

Zeng X, Zhang Y, Xia Z, Wang L, Wang C, Huang Y, Shen R, Wen W - Sci Rep (2015)

Investigation of the surface of the droplets using AFM.An AFM tip was inserted approximately 2 μm into the surface of the droplets and then drawn out. The relationship between the force and the vertical displacement was recorded.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4544006&req=5

f5: Investigation of the surface of the droplets using AFM.An AFM tip was inserted approximately 2 μm into the surface of the droplets and then drawn out. The relationship between the force and the vertical displacement was recorded.
Mentions: AFM was also used to confirm the formation of the thin film on the droplet, as shown in Fig. 5. The droplet was pre-heated at 40 °C for approximately 35 minutes. Then, the AFM probe was pierced 2 μm into the droplet from the top and then slowly drawn out. The relationship between the drawing force and the vertical displacement was recorded. Based on the results for the pure water droplet, the force became more negative in the initial stage due to the adhesion force between the water and the tip, and then, the force suddenly returned to zero, which indicates that the water was detached from the tip surface. In contrast, there were two sudden changes observed in the plot for the manganese chloride droplet. The first change corresponded to the liquid beneath the film detaching from the tip, and the second one corresponded to the film detaching from the tips. Therefore, based on these results, the film thickness is approximately 1 μm, which is approximately equal to the width between the two steps.

Bottom Line: A fantastic and extraordinary phenomenon was observed during the evaporation of a water droplet doped with manganese chloride.The MnCl2-doped water droplets were maintained in a relative humidity (RH) of 50% at 40 °C for more than a week and for longer than two months at a temperature of 25 °C.In contrast, a pure water droplet can only be sustained for a few minutes.

View Article: PubMed Central - PubMed

Affiliation: Nano Science and Technology Program / Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.

ABSTRACT
The exchange kinetics of liquid water, which are of fundamental interest and have potential applications, remain unclear. A fantastic and extraordinary phenomenon was observed during the evaporation of a water droplet doped with manganese chloride. As observed from the evolution of this type of droplet, a thin film was formed on the surface with an exothermic phase transition, resulting in self-suppressed evaporation. The MnCl2-doped water droplets were maintained in a relative humidity (RH) of 50% at 40 °C for more than a week and for longer than two months at a temperature of 25 °C. In contrast, a pure water droplet can only be sustained for a few minutes. The self-suppressed evaporation of doped water may be due to the special hydration of the accumulated manganese and chloride ions at the surface, decreasing the surface tension.

No MeSH data available.


Related in: MedlinePlus