Fabrication of Pt–Ag–Au heterogeneous truncated hollow sub-microspheres for chemically self-propelled colloidal motors

Colloidal motors with cavity structure, which have advantages over solid motors in catalytic efficiency, cargo capacity and biocompatibility, are still expected. Here, we design and fabricate a type of truncated hollow sub-microsphere via organic colloidal template etching/heating and layer-by-layer isotropic deposition. The as-prepared truncated hollow sphere is of one circular open pore through the shell layer and built of Pt, Ag and Au shell layers from inside to outside. They are controllable in sphere diameter, circular open pore size and shell thickness, which depend on the template and deposition conditions. Further experiments have shown that the Ag sandwich layer and post-deposition ageing process are crucial to obtaining strong and complete truncated hollow sub-microspheres. Their formation is attributed to the template geometry and nearly isotropic deposition. Due to the catalytic Pt layer on the inner surface and the truncated hollow spherical structure, such Pt–Ag–Au hollow spheres are demonstrated to be chemically propelled colloidal motors, which can directionally move in H2O2-containing solutions. This study presents a controllable route for mass-fabricating heterogeneous multi-layer truncated hollow sub-microspheres, and provides a new type of chemically self-propelled colloidal motor.