Formation of Unique Nanoparticle Agglomerates During Laser Ablation of CaO Powders in Ethanol

We conducted laser ablation of calcined shell powder and CaO powder dispersed in ethanol. Results showed that laser ablation induced the formation of nanoparticles and the formation of gel-like structures. Observations of the temporal change of the colloidal solution during laser ablation revealed that the gel-like structures formed rapidly after laser ablation for ca. 30 min, suggesting that the gel-like structures form via the agglomeration of CaO nanoparticles formed by laser ablation. Results showed that the gel-like structures (CaO nanoparticle agglomerates) were positively charged, suggesting that the balance between the positive charge of CaO nanoparticles which comes from the source CaO powders and the negative charge provided by ethanol during laser ablation plays a key role in NP agglomeration. It was also demonstrated that the gold-CaO and platinum-CaO nanocomposites are obtainable simply by mixing colloids of positively charged CaO gel-like structures and colloids of negatively charged gold or platinum nanoparticles.