• Molecular interactions at liquid-air interfaces were studied from Agnes Pockels times.
• Assembled structures at these interfaces have contributed to understanding 2D films, even with diverse materials like nanoparticles.
• Stable molecules and particles arrange at interfaces due to surface tension. The direct creation of nanostructures is possible at interfaces using atomic precursors.
• Methodologies for metal nanoparticles (NPs) on solid surfaces with ambient electrolytic spray and electrospray is adapted for liquid surfaces, allowing synthesis & assembly.
• An electrical double layer at the liquid-air interface, along with its response to moderate electric fields, can induce motion in both surface and bulk liquid, guiding suspended NPs into organized arrangements.
• Traditional methods to create thin metal sheets in vacuum conditions use thermal and electron beam evaporation, and magnetron sputtering, but require high vacuum, sophisticated tools, and elevated temperature.
• Thus, there is a need for a new method that can address the above mentioned issues. The present invention introduces an ambient method for creating thin metal films.

The present patents core idea is producing nanometer-thin metal films on liquids without vacuum or high temperatures.

Method

1. This is achieved by depositing nanometer-scale droplets onto liquid surfaces under the influence of an electric field.
2. With this objective, experiments are done by which NPs of Pd+ were synthesized on the surface of water reservoir that is self-assembled to form nanoparticle-nanosheets. Fig 1, 2.
3. A method of making nanometer thin, <100 nm free standing 2D metal sheets at air-liquid interface – the said method comprises:

• at least one metal salt precursor dissolved in a solvent;
• electrospraying of the solvated metal salt precursor at a voltage 1000-2000 V from 10-15 mm distance over the liquid surface;
• gently depositing nanometer scale droplets over the liquid surface at room temperature, which are then self- assembled to form nanoparticle-nanosheets.

Wherein, the charged metal ion reduced to neutral metal atom without using any external reducing agents during the course of deposition, that aggregates to form nanoparticles at the interface and arrange to form nanoparticle-nanosheets over the liquid surface.

Wherein

• The metal is palladium and the metal salt is palladium chloride.
• The metals are selected from various salts of gold, silver, platinum, palladium, nickel and copper.
• The thin film is made of different alloys including silver-palladium and gold-palladium.
• The solvent of the precursor solution includes methanol, ethanol, water, acetonitrile and combination thereof with different proportions.
• The liquid reservoir contains liquids including water, ionic liquid and ethylene glycol.
• The liquid reservoir contains liquid metals or semiconductors which are solids at room temperature.
• The electrospray deposition of films occurs along with other stimuli including light, temperature and magnetic field.
• The modification of the electrospray occurs during solvent evaporation of the droplets using temperature, light, electric & magnetic fields.
• The thin metal films are used as a catalyst, sensor, gas adsorbing medium and electrodes for electrochemical reactions.