Fragmentation converts twenty times more energy into new particle surface
In laboratories where light meets matter at the edge of human perception, a researcher has spent years decoding the conversation between laser pulses and gold suspended in liquid — seeking to understand how nanoparticles, those invisibly small architects of modern medicine and energy, can be made more deliberately and with less waste. Maximilian Spellauge's work at Munich University of Applied Sciences, conducted in collaboration with partners across Germany, has mapped the physical mechanisms governing nanoparticle formation with enough precision to suggest that the future of green chemistry may be written in picoseconds. By revealing that fragmenting existing particles converts twenty times more energy into usable surface area than conventional ablation, his findings offer a path toward scalable, additive-free production — a quiet but consequential step in humanity's long effort to shape the very small in service of the very large.
- Nanoparticle production has long been hobbled by inefficiency — liquid-based laser ablation wastes the vast majority of its energy, converting only a fraction of a percent into the new particle surfaces that actually matter.
- Spellauge's pump-probe microscopy revealed three competing mechanisms at work during laser fragmentation — phase explosion, spallation, and pressure focusing — each pulling particle size in a different direction and making controlled output elusive.
- The discovery that fragmentation achieves two percent energy-to-surface conversion, versus 0.1 percent for solid ablation, reframes which technique deserves industrial investment and why.
- Pulse durations between 10 picoseconds and 1 nanosecond have emerged as the sweet spot for liquid ablation, offering tighter control over particle size without the need for chemical additives.
- Beam shaping and pulse splitting are now on the table as practical tools for scaling these gains, pointing toward greener, more precise manufacturing in catalysis and sustainable energy sectors.
- The next frontier — real-time observation paired with computer simulation — promises to close the gap between what lasers do in the lab and what equations can reliably predict.
Nanoparticles are a thousand times smaller than a human hair, yet they underpin catalysts, energy storage systems, and medical devices. The persistent challenge has been producing them efficiently, without chemical waste, and with meaningful control over their size. Maximilian Spellauge devoted years to this problem, firing lasers at gold suspended in liquid and watching what happened at timescales measured in picoseconds.
Using pump-probe microscopy, Spellauge tracked the full exchange between laser and matter — observing how vaporized gold condenses into particles smaller than ten nanometers, or how mechanical forces tear away surface layers that break into larger ones. He also identified a fundamental inefficiency: liquid-based production loses much of its ablated material to settling, making it four times less productive than ablation in air.
The more striking discovery came when he turned to fragmentation — breaking apart existing gold microparticles with a laser. Three mechanisms emerged: photothermal phase explosion, spallation, and pressure focusing, where overlapping pressure waves shatter particles from within. Crucially, fragmentation converted roughly two percent of absorbed energy into new particle surface area, compared to just 0.1 percent for solid ablation in liquid — a twentyfold advantage.
The practical path forward became legible. Pulse durations between 10 picoseconds and 1 nanosecond optimize liquid ablation, while pulse splitting and beam shaping can boost both productivity and size control across both methods. No chemical additives are required, placing the work squarely within green chemistry principles.
Completed at Munich University of Applied Sciences in collaboration with the University of Duisburg-Essen and the Karlsruhe Institute of Technology, Spellauge's dissertation does more than describe what lasers do to gold — it shows how to steer the outcome. Real-time observation combined with simulation will define the next phase, narrowing the distance between physical reality and predictive models.
Nanoparticles are impossibly small—a thousand times tinier than a human hair—yet they have become essential to how we make catalysts, store energy, and build medical devices. The challenge has always been making them efficiently, without chemical waste, in a way that lets you control their size. A researcher named Maximilian Spellauge spent years firing lasers at gold to figure out how to do exactly that.
Spellauge's approach was methodical. He isolated single laser pulses and watched what happened to gold in liquid, using a technique called pump-probe microscopy that can track physical processes happening in picoseconds—billionths of a second. By measuring how much light the material absorbed and reflected, he could see the entire conversation between laser and matter. He was trying to understand two different ways nanoparticles form when you hit gold with a laser in liquid: sometimes the vaporized material condenses into tiny particles smaller than ten nanometers; other times, the laser mechanically tears away a surface layer that breaks into larger particles, tens of nanometers across. The catch is that liquid-based production is four times less efficient than doing it in air, because some of the ablated material just falls back down instead of forming new particles.
Then Spellauge looked at what happens when you fragment particles that are already there—microparticles of gold that the laser breaks apart. He found three distinct mechanisms at work. The first is photothermal phase explosion, where the particle suddenly turns to gas. The second is spallation, where flakes of gold peel off the surface. The third is pressure focusing, a phenomenon where overlapping pressure waves create a local spike in pressure inside the particle, forcing it to shatter into larger pieces. Here's where things got interesting: when fragmenting existing particles, about two percent of the absorbed energy went into creating new particle surface area. Compare that to solid ablation in liquid, which converts only 0.1 percent of energy into new surface. Fragmentation was twenty times more efficient.
The practical implications became clear. For liquid ablation, using shorter pulses—between 10 picoseconds and 1 nanosecond—gave the best results. Splitting the laser pulse or stretching its duration could boost productivity and tighten control over particle size. For fragmentation, shaping and splitting the laser beam itself could achieve similar gains. None of this requires chemical additives. The process aligns with green chemistry principles, which matters for industries trying to reduce their environmental footprint.
Spellauge's work opens doors in catalysis and sustainable energy technology, fields where nanoparticles are already critical but where better control and efficiency could unlock new applications. His dissertation, completed at Munich University of Applied Sciences in collaboration with researchers at the University of Duisburg-Essen and the Karlsruhe Institute of Technology, maps the physical mechanisms that determine particle size—and more importantly, shows how to deliberately steer them. The next phase will involve real-time observation of particle formation combined with computer simulations, a way of closing the gap between what the laser does and what the equations predict.
Citas Notables
The fragmentation of individual particles is much more energetically efficient than the ablation of a solid in liquid. At the same time, it becomes clear which physical mechanisms determine the particle size—and how we can specifically influence these in the future.— Maximilian Spellauge, researcher at Munich University of Applied Sciences
La Conversación del Hearth Otra perspectiva de la historia
Why does it matter that fragmentation is twenty times more efficient than ablation?
Because efficiency translates to cost and scale. If you can make the same nanoparticles with a fraction of the energy, you can produce them faster and cheaper. That changes whether the technology is viable for industry.
But you're still using a laser. Isn't that expensive?
It is, but laser-based production doesn't need chemical additives or solvents. You're not generating toxic waste. Over a full lifecycle, that can be cheaper and cleaner than traditional chemistry.
The pulse duration matters—10 picoseconds to 1 nanosecond. Why such a narrow window?
It's about timing. Too short and you don't transfer enough energy. Too long and you lose efficiency to heat and unwanted side effects. That window is where the physics aligns with what you're trying to do.
What happens if you get the pulse duration wrong?
You either waste energy or you get particles that are too large or too small. You lose control over size distribution, which matters enormously if you're trying to use these particles for something specific.
So this research is really about control, not just efficiency?
Exactly. Efficiency matters, but what Spellauge mapped out is the mechanism. Once you understand the mechanism, you can tune it. That's what makes this work valuable beyond just one application.
What comes next?
Simulations. Real-time imaging combined with computer models. The goal is to predict what will happen before you fire the laser, so you can design the process instead of just discovering it by trial and error.