The POMs were firstly reduced photochemically. A 500 W Hg lamp
was used as a ultra-violet (UV) light source. In a typical synthesis,
POMs (100 mL, 1 mM) were added to a quartz bottle and mixed with
isopropanol (700 μL). Then, the resulting solution was irradiated under
the UV light for 30 min with stirring. The concentration of the
reduced POMs was controlled by varying the irradiation time. This
solution of reduced POMs was mixed with prepared OMC suspension
(10 mL, 2 mg mL1
) and aqueous solution of HAuCl4 3H2O (1 mL) at
room temperature, and then stirred for 10 min; the tri-component
nanohybrids were prepared. The suspension was isolated by centrifugation
at 8000 rpm, followed by consecutive washing/centrifugation
cycles several times with doubly distilled water. The obtained
Au@POMs/OMC-x was dried in a vacuum oven at 60 °C for
36 h. For optimization of the nanocomposite, different concentrations
of HAuCl4 3H2O (2.5 mM, 50 mM, and 1 M) were selected to be added
to the mixture. The Au@POMs/OMC-x materials are referred to as
Au@POMs/OMC-1, Au@POMs/OMC-2, and Au@POMs/OMC-3, where 1,
2, and 3 represent the different concentrations of HAuCl4 3H2O
(2.5 mM, 50 mM, and 1 M) in the synthesis procedure, respectively.
F