Pulsed laser fragmentation of microparticles (MPs) in liquid is a synthesis method for producing high‐purity nanoparticles (NPs) from virtually any material. Compared with laser ablation in liquids (LAL), the use of MPs enables a fully continuous, single‐step synthesis of colloidal NPs. Although having been employed in several studies, neither the fragmentation mechanism nor the efficiency or scalability have been described. Starting from time‐resolved investigations of the single‐pulse fragmentation of single IrO2 MPs in water, the contribution of stress‐mediated processes to the fragmentation mechanism is highlighted. Single‐pulse, multiparticle fragmentation is then performed in a continuously operated liquid jet. Here, 2 nm‐sized nanoclusters (NCs) accompanied by larger fragments with sizes ranging between several ten nm and several µm are generated. For the nanosized product, an unprecedented efficiency of up to 18 µg J−1 is reached, which exceeds comparable values reported for high‐power LAL by one order of magnitude. The generated NCs exhibit high catalytic activity and stability in oxygen evolution reactions while simultaneously expressing a redox‐sensitive fluorescence, thus rendering them promising candidates in electrocatalytic sensing. The provided insights will pave the way for laser fragmentation of MPs to become a versatile, scalable yet simple technique for nanomaterial design and development.

Noble metal alloy nanoclusters (NCs) are interesting systems as the properties of two or more elements can be combined in one particle, leading to interesting fluorescence phenomena. However, previous studies have been exclusively performed on ligand-capped NCs from wet chemical synthesis. This makes it difficult to differentiate to which extent the fluorescence is affected by ligand-induced effects or the elemental composition of the metal core. In this work, we used laser fragmentation in liquids (LFL) to fabricate colloidal gold-rich bi-metallic AuPt NCs in the absence of organic ligands and demonstrate the suitability of this technique to produce molar fraction series of 1nm alloy NC. We found that photoluminescence of ligand-free NCs is not a phenomenon limited to Au. However, even minute amounts of Pt atoms in the AuPt NCs lead to quenching and red-shift of the fluorescence, which may be attributed to the altered surface charge density.

Active and Redox‐Sensitive Colloidal Nanoclusters In article number 2206485, Stephan Barcikowski, Heinz Paul Huber, and co‐workers track microparticle laser fragmentation processes all along the timescale from picoseconds to milliseconds. They discover the unprecedented efficiency to yield ultrasmall particles, exceeding current laser synthesis’ productivities by one order of magnitude. (Cover art shows AI‐painted “Advanced Nanoparticle Generation and Excitation by Lasers in Liquids”, created by J. Barcikowski, F. Barcikowski, and S. Barcikowski using DiscoArt‐DiscoDiffusion.)

The possibilities of nanoadditivation to achieve finer, more equiaxed grains unlock huge potential for the application field of functional materials, e.g. Nd-Fe-B magnets, where the control of the microstructure and the composition is of significant importance. The surface modification of hard magnetic microparticles by non-magnetic nanoparticles (NPs) opens a novel field of research. Here, especially Cu NPs with low amounts of oxides are of high relevance as colloidal nano-additive material. To increase the productivity of surfactant-free, laser-generated Cu NPs, we performed a process parameter study via laser ablation in acetone aiming for the highest possible productivity, increasing the throughput of NP additivation on the surface of functional feedstock micro powders. By optimizing the process parameters of laser power, laser fluence, repetition rate, volume flow, and spot size, a productivity of 0.19 µg/J of Cu NPs in acetone was achieved. Then we investigated how a fine microstructure of the magnet powder MQP-S can be retained to some extent along the process chain, throughout the melting and resolidification process during suction casting. A loading series of Cu NP nanoadditivation on magnet micro powders of 0.1, 0.5, 1.0, and 2.5 wt.% was analyzed regarding magnetic properties and microstructure of the as-built part. Using full melting conditions of MQP-S by producing samples via suction casting modified with different amounts of Cu NP additions leads to finer grains, but increasing α-Fe content. Overall, the results enable higher production rates of Cu NPs in acetone and provide insights into the influence of NP-supporting characteristics on the properties of permanent magnet micro powders after full melting and resolidification.