Pt-TiO₂ Bilayered Hemispherical Nanoshells with Tunable Pt Distribution for Chemically Self-Propelled Colloidal Motors

Abstract

The control of colloidal motors' motion is crucial for their practical applications. The modulation of the active component distribution on the motors is one of the effective routes to controlling their motion but still in challenge. Here, Pt-TiO 2 bilayered hemispherical nanoshells (BHNSs) with different Pt distributions are designed and fabricated via etching an organic colloidal template and depositing TiO 2 and Pt in different angles and sequences. The obtained nanoshells include the BHNSs with complete Pt outer and inner layers (or TiO 2 /Pt and Pt/TiO 2 BHNSs) and the partially bilayered hemispherical nanoshells (P-BHNSs) with incomplete Pt outer and inner layers (or TiO 2 /Pt and Pt/TiO 2 P-BHNSs). All these Pt-TiO 2 BHNSs can move, in H 2 O 2 -containing solutions, in Pt coating-pushed way, exhibiting Pt distribution-dependent motion modes, speeds, and postures. Typically, the TiO 2 /Pt (or Pt/TiO 2 ) BHNSs move at the posture of the opening forward (or backward), exhibiting well-directional motion with a relatively low speed, while the TiO 2 /Pt (or Pt/TiO 2 ) P-BHNSs move at the posture of the opening forward (or backward) with a tilted angle, showing the quasi-circular motion with a relatively high speed. A Pt coating catalysis-induced diffusiophoresis mechanism is proposed, which can well describe the Pt distribution-dependent self-propelled behaviors. This work provides a flexible route for fabricating Pt distribution-tunable nanoshells and deepens our understanding of Pt distributiondependent chemically self-propelled behaviors.

Micro-/nanoscale robotics for chemical and biological sensing

“…Self-diffusiophoretic motion (Fig. 2A) 15 is caused by the presence of concentration gradients (which stem from the asymmetric release of reaction products) around the micro-/nanomotors which work to drive the motors forward. 16 Janus particles have long been associated with this propulsion model – receiving their name from having two hemispheres with distinct chemical/catalytic characteristics.…”

A Versatile Method for Synthesis of Light-Activated, Magnet-Steerable Organic–Inorganic Hybrid Active Colloids

“…Active colloids are synthetic microparticles that can convert various forms of energy, such as light [ 1 , 2 , 3 , 4 , 5 ], chemical [ 6 , 7 ], magnetic [ 8 , 9 ], electrical [ 10 , 11 ], and acoustic energy [ 12 ] into mechanical motion. Active colloids are found many applications at the microscale, including cargo delivery [ 5 , 13 , 14 ], biosensing [ 15 ], pollution monitoring [ 16 , 17 ], and environmental remediation [ 18 , 19 ], as well as acting as model systems to study the physics of active matter [ 20 , 21 ].…”