Then 0.28 g of DDA was dissolved in the mixture under stirring. After stirring for 10 min, 1 mL of TTIP was added dropwisely and stirred for 12 h. Then the particles were washed with methanol three times and were calcined in tubular furnace under nitrogen flow for 2 h at 600 °C, and then the black TiO2 particles were obtained. For the magnetic Au@Ni@TiO2 particles, the monolayers of TiO2 particles were prepared first by dropping 200 μL of suspension onto glass slides. Then 10 nm of nickel layer was first deposited on the top of TiO2 particles via thermal deposition. Then 30 nm of Au layer was deposited. Finally, the magnetic Au@Ni@TiO2 particles were released by ultra-sonication.