(I) Transformation to monomers → (II) Supersaturation → (III) Nucleation/ Precipitation → (IV) Growth → (V) Ostwald Ripening → (VI) Aggregation
(I) Transformation of chemical precursors into active atomic or molecular species (monomers) via selected method (e.g. chemical, photochemical etc)
E.g. AgNO3 + Reducing Agent → Ag(0) [Chemical Reduction]
AgNO3 + hv → Ag(0) [Laser Ablation]
(II) Supersaturation - For particular solvent, there is a certain solubility of solute; In the presence of excess solute, precipitation occurs (supersaturation of monomers).
(III) Nucleation - When the concentration of monomers (atoms, ions, molecules) is sufficiently high, they aggregate into small clusters (or nuclei). Nucleation is thermodynamically driven i.e. supersaturated solution is not stable in energy.
(IV) Growth - Nuclei grow by molecular addition (soluble species deposit on the solid surface) relives the supersaturated step. When concentration drop below critical level, nucleation stop and particle continue to grow until equilibrium concentration of species reached.
(V) Ostwald Ripening - When reactants are depleted, particles grow by Ostwald ripening (large particles continue to grow at the expense of smaller ones). Smaller particles have higher surface energy which promotes dissolution.
(VI) Secondary Growth (Aggregation) - Rate of particle growth by aggregation is larger than by molecular addition. For nanocrystal growth, this step is stemmed by the addition of surface adsorbing species (e.g. surfactants) to afford stabalization (steric or electronic).
(I) Transformation of chemical precursors into active atomic or molecular species (monomers) via selected method (e.g. chemical, photochemical etc)
E.g. AgNO3 + Reducing Agent → Ag(0) [Chemical Reduction]
AgNO3 + hv → Ag(0) [Laser Ablation]
(II) Supersaturation - For particular solvent, there is a certain solubility of solute; In the presence of excess solute, precipitation occurs (supersaturation of monomers).
(III) Nucleation - When the concentration of monomers (atoms, ions, molecules) is sufficiently high, they aggregate into small clusters (or nuclei). Nucleation is thermodynamically driven i.e. supersaturated solution is not stable in energy.
(IV) Growth - Nuclei grow by molecular addition (soluble species deposit on the solid surface) relives the supersaturated step. When concentration drop below critical level, nucleation stop and particle continue to grow until equilibrium concentration of species reached.
(V) Ostwald Ripening - When reactants are depleted, particles grow by Ostwald ripening (large particles continue to grow at the expense of smaller ones). Smaller particles have higher surface energy which promotes dissolution.
(VI) Secondary Growth (Aggregation) - Rate of particle growth by aggregation is larger than by molecular addition. For nanocrystal growth, this step is stemmed by the addition of surface adsorbing species (e.g. surfactants) to afford stabalization (steric or electronic).
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