Cu@TiO₂ Janus microswimmers with a versatile motion mechanism

Abstract

We report novel metal-capped TiO2 photochemically-active colloids endowed with a 'hybrid drive': directional motion is achieved in water upon UV illumination, as well as in dilute peroxide solutions upon illumination with UV or visible light. From the different behaviours of nearby particles, we infer that distinct reaction pathways affect the local composition and flow of the solution.

Tailoring Metal/TiO2 Interface to Influence Motion of Light‐Activated Janus Micromotors

“…This coupling was due to interactions between sized‐matched UV active micromotors and passive TiO 2 microparticles which stayed unsputtered in the solution . Simmchen and co‐workers previously reported the emergence of clusters based on the pumping interaction between active Cu/TiO 2 and passive SiO 2 associated with fluid flow . Under UV irradiation, these clusters exhibit directionality in observed motion and the highest average velocity was achieved by Pt/TiO 2 dimer and trimer micromotors.…”

“…[32] Simmchen and co-workers previously reported the emergence of clusters based on the pumping interaction between active Cu/TiO 2 and passive SiO 2 associated with fluid flow. [33] Under UV irradiation, these clusters exhibit directionality in observed motion and the highest average velocity was Adv. Funct.…”

Clustering-induced velocity-reversals of active colloids mixed with passive particles

“…Besides a range of theoretical studies focusing on motility-induced phase separation in active-passive mixtures [11][12][13][14] occurring at moderate densities, recent experiments [15][16][17][18][19] have observed the formation of various self-assembled structures even at very low active particle densities. Since these structures resemble those of ordinary molecules, the emerging clusters are called heteronuclear active colloidal molecules [20][21][22][23][24][25][26][27][28][29][30][31][32][33] .…”

Theory of light-activated catalytic Janus particles

“…[26,31,32,36] In this context, particular attention has been devoted to the development of photo-active colloids. [5,6,11,12,14,[37][38][39][40][41] Typically, the catalytic region of a photo-active particle is made of a semiconducting material, and catalyzes the decomposition of molecular "fuel" only when exposed to light of wavelength corresponding to the material's electronic bandgap. Therefore, the trajectory of a photo-active particle can be controlled through the intensity and direction of an external illumination source.…”