The color and the intensity of the peak were dependent on
consumption of hydrazine hydrate. With the dosage of hydrazine
hydrate 1.0–5.0 mL, there was neither a change in color nor a characteristic
peak (Table 1A–B). A yellow color and intense peak were
observed with the consumption 10.0–15.0 mL (Table 1C, figure not
shown). When the hydrazine hydrate consumption was more than
15.0 mL, gray precipitate was observed. Changes in color were also
associated with well-defined peaks characterized by maxima centered
around 430 nm (Table 1A–B). Such peaks were known to be
the plasmon resonance displayed by silver nanoparticles [16]. As
we all know, hydrazine hydrate was with high pH (>8), it would
generate coagulation when hydrazine hydrate too much. Under the