It was a pretty explosive premiere for a movie about a chemical reaction. A microscopic droplet drifted across the screen — almost in homage to the panning gun barrel of the James Bond movies — and then: bang!

Scientists watching the scene last week at a meeting of the Materials Research Society (MRS) in Boston, Massachusetts, were gripped, because the death of the droplet was also an act of creation. Lutz Mädler, a process engineer at the University of Bremen in Germany, had, for the first time, captured on camera a process that makes beautifully homogeneous metal oxide nanoparticles (see ‘Blow up’). His goal is to pave the way for faster, cheaper ways to make these fragments of matter, measuring just billionths of a metre across, which are finding uses as catalysts, medical imaging probes and more.

Mädler’s presentation was part of the first MRS session ever to be dedicated to the combustion synthesis of nanoparticles. The technique aims to improve the process of making nanoparticles, which generally requires multiple, complex steps from expensive precursors. The solution, say Mädler and others, is to create the particles in bulk by simply igniting tiny droplets of precursor materials — a strategy that industry has used for decades to make carbon black for tyres and silica for optic fibres.

“This is a field that mushroomed out of industry, and didn’t have an academic following,” says Sotiris Pratsinis, a process engineer at the Swiss Federal Institute of Technology (ETH) Zurich. “These are beautiful fundamental studies.”

Mädler’s work aims to overcome a key drawback of combustion synthesis: the process is little understood and tends to be poorly controlled. In 2002, and working with Pratsinis, Mädler developed a way to make metal oxide nanoparticles by burning organometallic complexes dissolved in organic solvents (L. Mädler et al. J. Aerosol Sci. 33, 369–389; 2002). The approach worked well in the lab, but the ingredients were too expensive for most commercial applications. Mädler resolved to pick apart the process so that he could replicate it with cheaper precursors, such as metal nitrates, which can be produced directly from ores.

At present, metal nitrates yield nanoparticles that are inhomogeneous — often with hollow areas inside — but Mädler says that his high-speed videos reveal how mixing processes in the combustion of organic droplets help to make the particles more homogeneous. That should enable researchers to choose better precursors and additives that could improve combustion, and yield better-quality end products, says Karsten Wegner, a process engineer and consultant also at ETH Zurich. More and more chemicals companies are asking Wegner for advice on ways to scale up nanoparticle combustion-synthesis processes, he says, and the range of nanomaterials they want to make in large quantities is growing exponentially.

As industry explores the commercial appeal of the technique, researchers are turning to it to create specialized nanoparticles that can be tailored to medical imaging, sensing or toxicity studies. Ian Kennedy, a mechanical engineer at the University of California, Davis, is using combustion to make nanoparticles that contain europium, an exotic and expensive element that phosphoresces strongly. At the MRS meeting, Kennedy described how attaching an antibody to the particles can turn them into detectors that flag up environmental and biological toxicity. “These are exotic materials that haven’t been made this way before,” says Margaret Wooldridge, a mechanical engineer working on combustion synthesis at the University of Michigan, Ann Arbor.

Exploding droplets are themselves nothing new, says Kennedy — he was studying them in diesel fuel in the 1970s. But imaging techniques like Mädler’s will give materials scientists a better understanding of how the explosions affect the properties of the materials produced. “This field is a bridge between combustion research and materials science,” says Wooldridge. “It’s growing, and you see a lot of younger people coming in.”