Nano ZnO was prepared according to the procedure reported
in our previous work [29]: 2.216 g of zinc acetate (ZnAc2·2H2O)
and 1.400 g of urea were dissolved in 100 mL of distilled water by
ultrasonication, respectively. The ZnAc2 andurea aqueous solutions
were mixed in a beaker. The beaker was covered by polyethene
film, placed in an electrical oven, heated to 90 ◦, and kept at the
temperature for 12 h. The formed precipitate was filtered, washed
thoroughly with distilled water, dried at 90 ◦C for 12 h, finally calcined
at 300 ◦C for 5 h.
PbS/ZnO nanocomposite: 0.814 g of the nano ZnO was added to
30.0 mL of distilled water in a beaker and ultrsonicated. 0.276 g of
Pb(NO3)2 was added to the ZnO suspension under magnetic stirring.
Then 0.200 g of Na2S·9H2O was added to the mixture under
magnetic stirring. The precipitate was filtered, washed thoroughly
with distilled water, and dried at 120 ◦C for 2 h. The obtained
PbS/ZnO nanocomposite is denoted as PbS/ZnO-A.
Another PbS/ZnO nanocomposite was prepared by the same
procedure as PbS/ZnO-A except for reversing the sequence of
adding Pb(NO3)2 and Na2S: first adding Na2S to the ZnO suspension,
then adding Pb(NO3)2 to the mixture. The obtained PbS/ZnO
nanocomposite is denoted as PbS/ZnO-B.
Pure PbS was prepared according to the same procedure as that
of PbS/ZnO-A except without nano ZnO.