followed by immediate addition of 1 mL of 2.5% NH3·H2O dropwise to
control the pH around 8 and continued stirring for 3 min and a yellow
homogeneous collosol was formed. After centrifugation at 8000 rpm for
15 min, the AgNPs were washed by ethanol twice and deionized water
three times and then redispersed in DDW by ultra-sonication for 3 min.
The AgNPs were dried in vacuum at 60 °C for 24 h followed for X-ray powder
diffraction analysis. The same procedure was followed to prepare
AgNPs in 65 mL of DDW without ALE