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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

Evaporation process of a water droplet with 0.5 M manganese chloride.The scale bar is 2 mm.
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f1: Evaporation process of a water droplet with 0.5 M manganese chloride.The scale bar is 2 mm.

Mentions: The cleaned glass slides modified with n-decyltrimethoxysilane via chemical vapour deposition were used as the substrates, and the contact angle of pure water on this substrate was 90 ± 3°. The RH was maintained at 50 ± 5% in all of the experiments. The entire evaporation process was recorded using a homemade horizontal optical system and a commercial CCD. When the substrate temperature was maintained at 40 °C, a 20-μl droplet dries up in approximately 30 minutes, which is a common phenomenon. A water droplet with the same volume containing 0.5 M sodium chloride was sustained slightly longer for approximately 40 minutes, which was predicted based on classical Raoult’s law reported in 1882. Surprisingly, the droplet existed for more than one week when it contained 0.5 M manganese chloride. In addition, the droplet could be maintained for more than two months when stored at room temperature (25 °C). However, a pure water droplet and a sodium chloride droplet dry up in two hours under the same conditions. As shown in Fig. 1, the manganese chloride droplet (20 μl) shrank on the substrate in the initial stage, and the shape of the droplet did not change after approximately 30 minutes.


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)

Evaporation process of a water droplet with 0.5 M manganese chloride.The scale bar is 2 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Evaporation process of a water droplet with 0.5 M manganese chloride.The scale bar is 2 mm.
Mentions: The cleaned glass slides modified with n-decyltrimethoxysilane via chemical vapour deposition were used as the substrates, and the contact angle of pure water on this substrate was 90 ± 3°. The RH was maintained at 50 ± 5% in all of the experiments. The entire evaporation process was recorded using a homemade horizontal optical system and a commercial CCD. When the substrate temperature was maintained at 40 °C, a 20-μl droplet dries up in approximately 30 minutes, which is a common phenomenon. A water droplet with the same volume containing 0.5 M sodium chloride was sustained slightly longer for approximately 40 minutes, which was predicted based on classical Raoult’s law reported in 1882. Surprisingly, the droplet existed for more than one week when it contained 0.5 M manganese chloride. In addition, the droplet could be maintained for more than two months when stored at room temperature (25 °C). However, a pure water droplet and a sodium chloride droplet dry up in two hours under the same conditions. As shown in Fig. 1, the manganese chloride droplet (20 μl) shrank on the substrate in the initial stage, and the shape of the droplet did not change after approximately 30 minutes.

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