Crystallization at the hexadecane/water interface observed under acoustic levitation.

Area of Science:

• Environmental Chemistry
• Physical Chemistry
• Materials Science

Background:

• Atmospheric alkanes, often as aerosols, interact with water, forming new interfaces.
• Traditional methods for studying these interfaces are limited by container interference.
• Acoustic levitation offers a contact-free method to study interfacial phenomena, mimicking atmospheric conditions.

Purpose of the Study:

• To investigate interfacial crystallization of hexadecane using acoustic levitation.
• To characterize the phase transition of alkanes at liquid-liquid interfaces.
• To demonstrate the utility of acoustic levitation for studying immiscible liquid interactions.

Main Methods:

• Acoustic levitation was used to bring water and hexadecane droplets into contact.
• Raman spectroscopy was employed for real-time characterization of the phase transition.
• Controlled humidity and temperature conditions were maintained during experiments.

Main Results:

• Interfacial crystallization of hexadecane was observed at the hexadecane/water interface.
• Crystallization occurred up to 3 K above hexadecane's melting temperature and below 30% relative humidity.
• A hexadecane:water volume ratio above 1:2 resulted in full surface crystallization.
• Solid alkane crystals were detected upon water evaporation.

Conclusions:

• Acoustic levitation is suitable for studying contact-free interfacial phenomena between immiscible liquids.
• The study provides insights into alkane interfacial crystallization relevant to atmospheric processes.
• This technique allows for real-time observation of phase transitions under controlled conditions.