Reversed Janus Micro/Nanomotors with Internal Chemical Engine

Abstract

Self-motile Janus colloids are important for enabling a wide variety of microtechnology applications as well as for improving our understanding of the mechanisms of motion of artificial micro- and nanoswimmers. We present here micro/nanomotors which possess a reversed Janus structure of an internal catalytic “chemical engine”. The catalytic material (here platinum (Pt)) is embedded within the interior of the mesoporous silica (mSiO2)-based hollow particles and triggers the decomposition of H2O2 when suspended in an aqueous peroxide (H2O2) solution. The pores/gaps at the noncatalytic (Pt) hemisphere allow the exchange of chemical species in solution between the exterior and the interior of the particle. By varying the diameter of the particles, we observed size-dependent motile behavior in the form of enhanced diffusion for 500 nm particles, and self-phoretic motion, toward the nonmetallic part, for 1.5 and 3 μm ones. The direction of motion was rationalized by a theoretical model based on self-phoresis. For the 3 μm particles, a change in the morphology of the porous part is observed, which is accompanied by a change in the mechanism of propulsion via bubble nucleation and ejection as well as a change in the direction of motion.

A Compartmentalized Out-of-Equilibrium Enzymatic Reaction Network for Sustained Autonomous Movement

“…Besides particle motion through local O 2 production, we hypothesize that the final reaction in our network, the decomposition of H 2 O 2 into O 2 and H 2 O, can locally (in the lumen of these nanoreactors) create density fluctuations which contribute to the particle propulsion via diffusiophoresis as well. 34,35 The movement of the nanomotors and the behavior of the resulting MSD curves (e.g., Figure 4E) are in agreement with a self-diffusiophoretic model, 35−38 showing clearly nonlinear fitting according to the equation ⟨ r 2 ⟩ = 4 D Δ t + ( v Δ t ) 2 , and from which the velocity of our stomatocytes particles was extracted.…”

Hydrophilic Ultralong Organic Nanophosphors

“…HMSNPs were synthesized according to literature protocols with slight modifications . In a typical procedure, 40 mg of TEOA (as a base catalyst), 75 mg of CTAB (as a porogenic agent), and 50 mg of as‐prepared PS particles (as a template) were dispersed in 20 mL of DI H 2 O.…”

“…To confirm the universality of our approach to achieve HPPs, more UOP materials with different molecular structures including CzDClT, DCzEO, MCzT, and CPhCz were chosen. As Small 2020, 16,1906733 anticipated, a series of HPPs were successfully obtained following the preparation procedure of BCz-loaded HPPs (Figure 4a). As the photographs shown, the bright afterglow emission of these HPPs in solutions can be observed by the naked eye obviously.…”

“…HMSNPs were first synthesized according to a modified method reported previously. [16] Polystyrene (PS) nanospheres with a diameter of 358 ± 10 nm (N = 100, average size ± standard deviation (SD), Figure S1a, Supporting Information) were first synthesized as templates. Then, a mesoporous silica shell was formed on the PS template by sol-gel chemistry.…”

“…Besides, we did not find any obvious aggregates of BCz molecules in the SEM image of the BCzloaded HMSNPs (Figure S1c, Supporting Information), indicating no large-scale leakage of the phosphors. According to the DLS measurements, the average hydrodynamic sizes of BCz-loaded HPPs were 548 ± 28 nm (N = 3, average ± SD, Small 2020, 16,1906733 Figure 1. Schematic illustration of the fabrication of hollow mesoporous silica nanoparticles loaded with phosphors.➀,➁) The HMSNPs were first prepared by using polystyrene (PS) spheres as templates.…”