Figure 13.3 illustrates the computer-controlled double-jet precipitation apparatus
for preparing AgBr crystals, by which the concentration of Ag
+ and X
À during the
whole precipitation process can be precisely controlled [38–40]. As displayed in
Fig. 13.3, the concentrations of Ag
+ and X
À ions are detected by ion selective
electrodes and the injecting rates of Ag
+ and X
À ions are adjusted on the basis of
the detecting results. Beneficial from this apparatus, the concentration can be
controlled to below the C
*
min after nucleation process to control the uniformity of
crystal size. By the double-jet precipitation apparatus, AgCl and AgBr crystals with
different morphologies have been successfully synthesized [36, 41–44].
13.3.2 In Situ Oxidation Transformation
Different to the liquid–solid precipitation, the Ag source used in oxidation transformation is usually metallic silver (Ag
0 ) [45]. As shown in Fig. 13.4, the oxidant is
Fig. 13.3 Illustration of the apparatus for double-jet precipitation
Fig. 13.4 Illustration of in
situ oxidation
transformation process
310
13 Syntheses and Applications of Silver Halide-Based Photocatalysts