discussionIn a typical experiment, dopamine hydrochloride (0.18 g) andpoly(vinylpyrrolidone) (PVP) (0.27 g) were dissolved in 55 mL ofdeionized water, and the pH of the mixed was adjusted using1 M NaOH and 1 M HCl. Subsequently, an aqueous solution AgNO3(3.5 wt%) was injected into the solution to give a final volume of60 mL and then vigorously stirred for 30 min.