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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

Far ATR-IR spectra with Gaussian fitting (the smooth line) for water as well as the sodium chloride aqueous solution and manganese chloride aqueous solution.
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f7: Far ATR-IR spectra with Gaussian fitting (the smooth line) for water as well as the sodium chloride aqueous solution and manganese chloride aqueous solution.

Mentions: To determine the influence of ions on the hydration water, especially the hydrogen bond, far infrared spectra were adapted to investigate the binding. Because the molar absorptivity of water is too high to examine the solutions by common transmission spectroscopy, the application of an attenuated total reflection (ATR) unit was employed for the experiments. ATR affects the peak of the absorption spectra due to anomalous dispersion, resulting in decreased wavenumbers in the ATR spectrum compared to the absorption spectrum2930. As shown in Fig. 7, the hydrogen bond stretching (181 cm−1) shifted by approximately 2 cm−1 and 27 cm−1 when sodium chloride and manganese chloride were added, respectively. The hydrogen bonds in the aqueous sodium chloride droplets are slightly stronger than those in pure water. Due to the more robust interaction between the water molecules in the sodium chloride droplets, the sodium chloride droplets were maintained for a slightly longer period of time than the pure water droplets. Manganese chloride caused a larger increase in the hydrogen bonds than sodium chloride, which indicates that the water molecules are held more strongly in the solution. In the evaporation process of the droplets with manganese chloride, the accumulating ions at the surface coordinate with water molecules, which interrupts the hydrogen bonds between the non-coordinated water31. Thus, the energy releases as shown in the inset of Fig. 2a, resulting in a decrease in the surface tension. Manganese bromide exhibited phenomena similar to those of manganese chloride due to the presence of the same cations, and the Br− anions were even more prone to accumulating at the surface of the water than the Cl− anions2532.


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)

Far ATR-IR spectra with Gaussian fitting (the smooth line) for water as well as the sodium chloride aqueous solution and manganese chloride aqueous solution.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f7: Far ATR-IR spectra with Gaussian fitting (the smooth line) for water as well as the sodium chloride aqueous solution and manganese chloride aqueous solution.
Mentions: To determine the influence of ions on the hydration water, especially the hydrogen bond, far infrared spectra were adapted to investigate the binding. Because the molar absorptivity of water is too high to examine the solutions by common transmission spectroscopy, the application of an attenuated total reflection (ATR) unit was employed for the experiments. ATR affects the peak of the absorption spectra due to anomalous dispersion, resulting in decreased wavenumbers in the ATR spectrum compared to the absorption spectrum2930. As shown in Fig. 7, the hydrogen bond stretching (181 cm−1) shifted by approximately 2 cm−1 and 27 cm−1 when sodium chloride and manganese chloride were added, respectively. The hydrogen bonds in the aqueous sodium chloride droplets are slightly stronger than those in pure water. Due to the more robust interaction between the water molecules in the sodium chloride droplets, the sodium chloride droplets were maintained for a slightly longer period of time than the pure water droplets. Manganese chloride caused a larger increase in the hydrogen bonds than sodium chloride, which indicates that the water molecules are held more strongly in the solution. In the evaporation process of the droplets with manganese chloride, the accumulating ions at the surface coordinate with water molecules, which interrupts the hydrogen bonds between the non-coordinated water31. Thus, the energy releases as shown in the inset of Fig. 2a, resulting in a decrease in the surface tension. Manganese bromide exhibited phenomena similar to those of manganese chloride due to the presence of the same cations, and the Br− anions were even more prone to accumulating at the surface of the water than the Cl− anions2532.

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