Go-and-Stop Nanovehicles Enabled by Counterbalanced NIR Optical Engines

Abstract

Nanomotors are promising for diverse applications due to their ability to convert energy into directional motion. However, precise control of their motion is still difficult because creating required asymmetric nanostructures presents significant synthetic challenges. Inspired by automotive engine control, this study reports a general strategy for constructing optical nanomotors with programmable motion. For the first time, this approach implements a “Go and Stop” concept, leveraging dissimilar near-infrared (NIR) responsivities of upconversion nanoparticle (UCNP) to accelerate (“Go”) or brake (“Stop”) motion on demand. Specifically, the nanovehicle is designed via interface-guided anisotropic growth strategy, where half of a single upconversion nanoparticle (UCNP) is coated with a hydrophilic silica shell containing Au nanoseeds, while the other is covered by a hydrophobic periodic mesoporous organosilica (PMO) loaded with Roussin’s black salt (RBS). This dual hydrophilic/hydrophobic design is also applicable to other optical materials, thus demonstrating great flexibility. When excited at 980 nm, blue light emitted by the UCNP activates the RBS to release nitric oxide (NO), propelling the nanomotor forward. Conversely, light at 808 nm induces gold-mediated thermophoresis, which reduces and eventually stops NO-driven motion. Such “pull–push” effect enables the nanomotor to start, accelerate, decelerate, and stop simply by switching the excitation light. As a proof of concept, the nanovehicle is further used to noninvasively regulate cellular endocytosis and has demonstrated great potentials for programmable tumor treatment.