Laser-induced photochemical reduction of aqueous [AuCl₄]^- is a green synthesis approach requiring no chemical reducing agents or stabilizers; but size control over the resulting gold nanoparticles remains a challenge. Under optical breakdown conditions producing hydrated electrons (e_aq^-) and hydroxyl radicals (OH^•) through decomposition of water, [AuCl₄]^- reduction kinetics follow an autocatalytic rate law, which is governed by rate constants: nucleation rate k₁, dependent on e_aq^-; and growth rate k₂, dependent on the OH^• recombination product, H₂O₂. In this work, we add the hydroxyl radical scavengers isopropyl alcohol and sodium acetate to limit H₂O₂ formation. Higher scavenger concentrations both lowered k₂ values and produced smaller gold nanoparticles with Gaussian size distributions and remarkably narrow mass-weighted size distributions. With sufficiently high scavenger concentrations, the mean nanoparticle size could be tuned from 3.8 to 6.1 nm with polydispersity indices below 0.08. Both the higher surface area-normalized catalytic activity of the gold nanoparticles synthesized in the presence of scavengers, and FTIR measurements, indicate no capping ligands on the nanoparticle surfaces. These results demonstrate that the size distributions of "naked" gold nanoparticles produced by photochemical [AuCl₄]^- reduction can be effectively tuned by controlling the reaction kinetics.

#	Concept	H-Index	Publications	Citations
1	Medicine	2	2	35
2	Pharmacology	2	2	35
3	Biochemistry	1	1	17
4	Immunology	1	1	17
5	Pathology	1	1	17

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