Self-Propelled Micromotors for Cleaning Polluted Water

Soler, Lluís; Magdanz, Veronika; Fomin, V. M.; Sánchez, Samuel; Schmidt, Oliver G.

doi:10.1021/nn405075d

Cited by 521 publications

(489 citation statements)

References 74 publications

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“…The reaction produces radicals that cause the rapid degradation and bleaching of fluorescent dyes present in solution. A similar effect is observed by Soler et al [22], who used Fenton reactions over Fe-Pt nanorods to degrade rhodamine 6G in a solution of hydrogen peroxide. In this paper, we present particles with two different SC as photoactive materials.…”

Section: Photo-activated Colloids (A) Photocatalytic Materialssupporting

confidence: 78%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

131

133

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Light-activated self-propelled colloids are synthesized and their active motion is studied using optical microscopy. We propose a versatile route using different photoactive materials, and demonstrate a multiwavelength activation and propulsion. Thanks to the photoelectrochemical properties of two semiconductor materials (α-Fe 2 O 3 and TiO 2 ), a light with an energy higher than the bandgap triggers the reaction of decomposition of hydrogen peroxide and produces a chemical cloud around the particle. It induces a phoretic attraction with neighbouring colloids as well as an osmotic selfpropulsion of the particle on the substrate. We use these mechanisms to form colloidal cargos as well as self-propelled particles where the light-activated component is embedded into a dielectric sphere. The particles are self-propelled along a direction otherwise randomized by thermal fluctuations, and exhibit a persistent random walk. For sufficient surface density, the particles spontaneously form 'living crystals' which are mobile, break apart and reform. Steering the particle with an external magnetic field, we show that the formation of the dense phase results from the collisions heads-on of the particles. This effect is intrinsically non-equilibrium and a novel principle of organization for systems without detailed balance. Engineering families of particles self-propelled by different wavelength demonstrate a good understanding of both the physics and the chemistry behind the system and points to a general route for designing new families of self-propelled particles.

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Section: Photo-activated Colloids (A) Photocatalytic Materialssupporting

confidence: 78%

Light-activated self-propelled colloids

Palacci

Sacanna

Kim

et al. 2014

Phil. Trans. R. Soc. A.

131

133

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“…They are seen as promising candidates for novel techniques in chemical sensing [4] or water treatment [5]. The motion of active colloidal particles has been the subject of numerous experimental [1][2][3]6,7] and theoretical [8][9][10][11][12] studies.…”

mentioning

confidence: 99%

Effective Interaction between Active Colloids and Fluid Interfaces Induced by Marangoni Flows

et al. 2016

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We show theoretically that near a fluid-fluid interface a single active colloidal particle generating, e.g., chemicals or a temperature gradient experiences an effective force of hydrodynamic origin. This force is due to the fluid flow driven by Marangoni stresses induced by the activity of the particle; it decays very slowly with the distance from the interface, and can be attractive or repulsive depending on how the activity modifies the surface tension. We show that, for typical systems, this interaction can dominate the dynamics of the particle as compared to Brownian motion, dispersion forces, or self-phoretic effects. In the attractive case, the interaction promotes the self-assembly of particles into a crystal-like monolayer at the interface. DOI: 10.1103/PhysRevLett.116.078301 Significant attention has been paid lately to micrometer sized particles capable of self-induced motility [1][2][3]. They are seen as promising candidates for novel techniques in chemical sensing [4] or water treatment [5]. The motion of active colloidal particles has been the subject of numerous experimental [1][2][3]6,7] and theoretical [8][9][10][11][12] studies. One realization is a particle with a catalytic surface promoting a chemical reaction in the surrounding solution [13]. For an axisymmetric particle lacking fore-and-aft symmetry, the distributions of reactant and product molecules may become nonuniform along its surface and the particle could move due to self-induced phoresis [14]. If the particle is spherically symmetric, it will remain immobile in bulk solution but can be set into motion by the vicinity of walls or other particles (not necessarily active) which break the spherical symmetry [10,[13][14][15][16].A relevant case corresponds to the movement of active particles bounded by a fluid-fluid interface. This situation raises new issues, in particular if the reactants or the products have a significant effect on the properties of the fluid interface implying tensioactivity. For example, it has been recently predicted that catalytically active, spherical particles which are trapped at the interface may be set into motion along the interface by Marangoni flows, selfinduced via the spatially nonuniform distribution of tensioactive molecules [17][18][19]. (A similar motility mechanism can originate from thermally induced Marangoni flows if, e.g., the particle contains a metal cap which is heated by a laser beam [20].) Furthermore, self-induced Marangoni flows, combined with a mechanism of triggering spontaneous symmetry breaking, have also been used to develop self-propelled droplets [21][22][23].However, another category of experimental situations occurs if the particles are not trapped at the interface but may reside in the vicinity of the interface or get near it during their motion. In this study we provide theoretical evidence that such catalytically active or locally heated spherical particles, although immobile in bulk, experience a very strong, long-ranged effective force field due to the Marangoni stresses...

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“…(a) only Fe tubes, (b) non-iron containing motors, i.e, Ti/Pt and (c) immobilized Fe/Pt microcleaners [26] . Figure 1D show dye degradation by a single micro-cleaner considering that all micro-cleaners present in the solution contribute equally to the total degradation.…”

Section: Size Effect Of Micro-cleaners On Dye Degradation and Reusabimentioning

confidence: 99%

Reusable and Long‐Lasting Active Microcleaners for Heterogeneous Water Remediation

Parmar

Vilela

Pellicer

et al. 2016

Adv Funct Materials

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Self‐powered micromachines are promising tools for future environmental remediation technology. Waste‐water treatment and water reuse is an essential part of environmental sustainability. Herein, we present reusable Fe/Pt multi‐functional active microcleaners that are capable of degrading organic pollutants (malachite green and 4‐nitrophenol) by generated hydroxyl radicals via a Fenton‐like reaction. Various different properties of microcleaners, such as the effect of their size, short‐term storage, long‐term storage, reusability, continuous swimming capability, surface composition, and mechanical properties, are studied. It is found that these microcleaners can continuously swim for more than 24 hours and can be stored more than 5 weeks during multiple cleaning cycles. The produced microcleaners can also be reused, which reduces the cost of the process. During the reuse cycles the outer iron surface of the Fe/Pt microcleaners generates the in‐situ, heterogeneous Fenton catalyst and releases a low concentration of iron into the treated water, while the mechanical properties also appear to be improved due to both its surface composition and structural changes. The microcleaners are characterized by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), nanoindentation, and finite‐element modeling (FEM).

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Self-Propelled Micromotors for Cleaning Polluted Water

Cited by 521 publications

References 74 publications

Light-activated self-propelled colloids

Light-activated self-propelled colloids

Effective Interaction between Active Colloids and Fluid Interfaces Induced by Marangoni Flows

Reusable and Long‐Lasting Active Microcleaners for Heterogeneous Water Remediation

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