Controlling the Morphology of Copper-Silica Nanocomposites from Laser Ablation in Liquid
Synthesis of copper-silica nanocomposites with controllable morphology and composition were produced with a one-step femtosecond reactive laser ablation in liquid (fs-RLAL) technique. The composite nanomaterials were generated by focusing femtosecond near-IR laser pulses onto a silicon wafer immersed in an aqueous copper(II) nitrate solution, with the solution pH adjusted using nitric acid or potassium hydroxide. Under acidic conditions (pH 3.0 and 5.4), little copper was incorporated in the predominantly silica product (1.4 and 1.5 wt.%). These acidic conditions yielded large ~30-80 nm silica particles, with some particles consisting of copper core/silica shell. In contrast, increasing the solution pH to 10.4 resulted in extremely high Cu loading of 31.5 wt.% and a composite product consisting of 1.5 nm copper clusters distributed throughout a matrix of amorphous silica and copper phyllosilicate. The relationship between the precursor solution pH and the product morphology and copper loading is attributed to the point of zero charge (PZC) of silica, in which the high solution pH allows for electrostatic adsorption to occur between the deprotonated silica clusters from the ablated silicon wafer and the copper hydroxide dimer formed in solution.