Copper colloids typically demonstrate excellent catalytic and electric properties, but their synthetic approaches lag behind their more expensive cousins. In this manuscript we investigate the synthesis of Cu colloids using a polyol-based method. We employ phthalonitrile as an additive, leading to competing reactions during the nucleation step and finally resulting in distinct sizes and properties of the copper particles. Even though during the polyol synthesis, the copper particles are partially protected from the high tendency of copper to oxidize, further treatment leads to the formation of a thin passivating and semiconducting Cu x O layer. Cu x O is known to be a visible light photocatalyst. We therefore investigate the size-dependent (photo)­catalytic activity of these colloids using rhodamine B (RhB) as a model organic pollutant. Following asymmetrization via deposition of a thin Au layer on one hemisphere, we also demonstrate the applicability as a photocatalytic micromotor.

In this manuscript we want to expand the strategies on tuneable phoretic interactions. Previously, we had kept the swimmer body fixed and varied fuel and light source. In this report we fix the fuel to hydrogen peroxide and change the species that favours its degradation, i.e. the 'catalytic' half on the Janus particles. Many materials are known to degrade hydrogen peroxide and our selection includes copper and silver, which present interesting effects besides the well known platinum.

Although many biological fluids like blood and mucus exhibit high viscosities, there are still many open questions concerning the swimming behavior of microswimmers in highly viscous media, limiting research to idealized laboratory conditions instead of application‐oriented scenarios. Here, we analyze the effect of viscosity on the swimming speed and motion pattern of four kinds of microswimmers of different sizes which move by contrasting propulsion mechanisms: two biological swimmers (bovine sperm cells and Bacillus subtilis bacteria) which move by different bending patterns of their flagella and two artificial swimmers with catalytic propulsion mechanisms (alginate microtubes and Janus Pt@SiO2 spherical microparticles). Experiments consider two different media (glycerol and methylcellulose) with increasing viscosity, but also the impact of surface tension, catalyst activity and diffusion coefficients are discussed and evaluated.

Since the highly cited paper by Purcell postulating the “Scallop theorem” almost 50 years ago, asymmetry is an unavoidable part of micromotors. It is frequently induced by self‐shadowing or self‐masking, resulting in so‐called Janus colloids. This strategy works very reliably, but turns into a bottleneck once up‐scaling becomes important. Herein, existing alternatives are discussed and a novel synthetic pathway yielding active swimmers in a one‐pot synthesis is presented. To understand the resulting mobility from a single material, the geometric asymmetry is evaluated using a python based algorithm and this process is automated in an open access tool.

We present a simple undergraduate level experiment dealing with the preparation and characterization of a colloidal Langmuir−Blodgett (LB) film. The experiment is designed to invoke an interdisciplinary understanding of colloid chemistry and surface science. It will allow the students to develop the concepts of wettability, hydrophobicity, and surface structuring with colloidal nano-and microparticles. In this experiment, the student prepares an LB film of submicron colloidal particles on a well-cleaned glass slide. The contact angle, surface morphology, and packing efficiency of the LB film are later characterized by a goniometer and an optical microscope. The students learn a very useful method of making colloidal LB films and further understanding their surface properties. It will help to broaden their knowledge in chemistry and materials science.