Producing Nanoparticles Using Supercritical Fluids

Traditional means
Traditional means of making specifically sized material involves several techniques. These include:
• Milling
• Grinding or
• Crushing

But each of these has problems such as thermal and chemical degradation. Crystallization by adjusting supersaturation, using anti-solvents, or employing reactions and precipitations also have shortcomings:
• Product contamination
• High energy requirements
• Waste solvents
• Low yields
• Non-uniform particles

Using Supercritical Fluids
The use of Supercritical Fluids to make particles eliminates these shortcomings. There are number of SCF techniques to produce particles of controlled size and morphology for organic molecules in the sub micron range:
• RESS-Rapid Expansion of a Supercritical Solution
• GAS- Gas Anti-Solvent
• PCA- Precipitation by Compressed Fluid Anti-Solvent
• SEDS -Solution Enhanced Dispersion of Supercritical Fluids

RESS-Rapid Expansion of a Supercritical Solution
With RESS, material is dissolved in the SCF and then depressurized though a nozzle.

GAS- Gas Anti-Solvent
Here the compound is dissolved in an organic solvent, a supercritical fluid is introduced, expanding the volume and lowering the solvents solvent strength causing the compound to precipitate under controlled conditions of particle formation.

PCA- Precipitation by Compressed Fluid Anti-Solvent
With PCA, the compound dissolved in an organic solvent is sprayed into a SCF, casuing supersaturation and solute precipitation.

SEDS -Solution Enhanced Dispersion of Supercritical Fluids
Using SEDS, the compound is dissolved in an aqueous solution and the simultaneously sprayed through a coaxial nozzle with an organic solvent into the supercritical fluid. The water is dissolved into the solvent and SCF causing supersaturation and precipitation.

Nanoparticles of inorganic compounds can also be produced using supercritical fluids and sub-critical fluids. Thermal decomposition and hydrothermal syntheses are but two ways to accomplish this.

Applied Separations can provide you with the means to make both organic and inorganic particles.