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1.
Angew Chem Int Ed Engl ; 58(35): 12200-12205, 2019 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-31282598

RESUMO

Inspired by the dynamics of bacterial swarming, we report a swarm of polymer-brush-grafted, glucose-oxidase-powered Janus gold nanoswimmers with a positive, macroscale chemotactic behavior. These nanoswimmers are prepared through the grafting of polymer brushes onto one side of gold nanoparticles, followed by functionalization with glucose oxidase on the other side. The resulting polymer-brush-functionalized Janus gold nanoswimmers exhibit efficient propulsion with a velocity of up to approximately 120 body lengths s-1 in the presence of glucose. The comparative analysis of their kinematic behavior reveals that the grafted polymer brushes significantly improve the translational diffusion of Janus gold nanoswimmers. Particularly, these bacteria-mimicking Janus gold nanoswimmers display a collectively chemotactic motion along the concentration gradient of a glucose resource, which could be observed at the macroscale.

2.
Angew Chem Int Ed Engl ; 58(13): 4184-4188, 2019 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-30701642

RESUMO

We report a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) brush functionalized Janus Au-Pt bimetallic micromotor capable of modulating the direction of motion with the change of the ambient temperature. The PNIPAM@Au-Pt micromotor moved along the Au-Pt direction with a speed of 8.5 µm s-1 in 1.5 % H2 O2 at 25 °C (below the lower critical solution temperature (LCST) of PNIPAM), whereas it changed the direction of motion (i.e., along the Pt-Au direction) and the speed decreased to 2.3 µm s-1 at 35 °C (above LCST). Below LCST, PNIPAM brushes grafted on the Au side were hydrophilic and swelled, which permitted the electron transfer and proton diffusion on the Au side, and thus the motion is regarded as a self-electrophoretic mechanism. However, PNIPAM brushes above LCST became hydrophobic and collapsed, and thus the driving mechanism switched to the self-diffusiophoresis like that of Pt-modified Janus silica motors. These motors could reversibly change the direction of motion with the transition of the hydrophobic and hydrophilic states of the grafted PNIPAM brushes. Such a thermoresponsive polymer brush functionalization method provides a new strategy for engineering the kinematic behavior of phoretically driven micro/nanomotors.

3.
Chem Asian J ; 14(14): 2450-2455, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-30556963

RESUMO

The engineering of self-propelled micro-/nanomotors (MNMs) with continuously variable speeds, akin to macroscopic automobiles equipped with a continuously variable transmission, is still a huge challenge. Herein, after grafting with salt-responsive poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes, bubble-propelled Janus microcapsule motors with polyelectrolyte multilayers exhibited adjustable speeds when the type and concentration of the counterion was changed. Reversible switching between low- and high-speed states was achieved by modulating the PMETAC brushes between hydrophobic and hydrophilic configurations by ion exchange with ClO4 - and polyphosphate anions. This continuously variable regulation enabled control of the speed in an accurate and predictable manner and an autonomous response to the local chemical environment. This study suggests that the integration of polymer brushes with precisely adjustable responsiveness offers a promising route for motion control of smart MNMs that act like their counterparts in living systems.

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