The pH is another important factor for P-Ag@AgCl. Different initial
pH values were used to fabricate P-Ag@AgCl. Fig. 2 presentsfield
emission scanning electron microscopy (FESEM) images of the PAg@AgCl.
As soon as the AgNO3 solution was added to dopamine
solutions with different pH values, the mixed solution turned into
different colors (Fig. S1). The color of the dispersed particles deepens
as the solution pH increases. Fig. 1(A–D) shows the P-Ag@AgCl
synthesized atpH value of 2.1, 7.8, 9.0 and 11.0, and theproducts are
noted as P–Ag@AgCl–PVP–2.1 to 11.0. Interestingly,these nanoparticles
exhibit clearly different shapes and compositions with the
pH value increasing. P-Ag@AgCl spheres with diameters of approximately
100 nm and 80 nm can be found in Fig. 2A(pH 2.1) and B (pH
7.8), respectively. Whereas some of the photocatalysts exhibit an
ideal sphere-like shape, other P-Ag@AgCl composites show shapedeformation.
When the pH value increases to an alkaline value
(pH 9.0), silver cubic cages are mixed in the product, as shown in
Fig. 2C. Compared with photocatalysts produced in acidic and weak
alkaline reaction environment, P-Ag@AgCl formed at pH 11.0 are
mostly nanoparticles that exhibit cubic morphologies and uniform
sizes with an average edge length of 200 nm. Elemental analysis
of the Ag:AgCl hybrid nanoparticles is carried out with energy dispersive
X-ray spectroscopy (EDS) (Supporting information, Fig. S2).
The results show the rate of Ag to AgCl and the amount of nitrogen
and carbon in the products increase with the increase in pH value.
This phenomenon may be attributed to the reducing capacity and
the polymerization rate of dopamine in different pH solutions