Scientists use ‘atomic stencils’ to make designer nanoparticles

Inspired by an artist’s stencil, a team of scientists has developed a groundbreaking method to ‘paint’ microscopic gold particles with polymer patches, giving them new and exciting functions.

The technique, detailed in a paper published in Nature, could allow scientists to create intricate patterns on the surface of nanoparticles with atomic precision.

Imagine trying to build a complex machine using LEGO bricks that are all the same. It would be very difficult. Scientists face a similar challenge in nanotechnology.

Nanoparticles, which are particles thousands of times smaller than the width of a human hair, are the building blocks for revolutionary technologies in medicine, electronics, and energy. However, to create truly complex and functional materials, scientists need nanoparticles with different surface domains, or patches, that can guide how they connect together and organise in particular patterns. Creating these patchy nanoparticles with precision and in large quantities has been a major hurdle.

The breakthrough came from an unexpected place: an art class. Researchers, from the US and South Korea, realised they could adapt the simple concept of stenciling to the nanoscale. Their process, called “atomic stencilling,” works in two main steps. In the first step, iodide atoms are used as a microscopic stencil. These atoms stick selectively to certain flat faces of the small, gem-like gold nanoparticles, creating a mask that covers specific areas.

Next, they introduce long-chain molecules called polymers. These polymers act like paint, but they can only attach to the unmasked regions of the gold nanoparticle.

By carefully controlling the amount of the iodide ‘mask’, the scientists could precisely control the size, shape, and location of the polymer “paint” patches. This simple but elegant method allowed them to create a large variety of custom-made nanoparticles.

Using the same stencilling technique, the team successfully created more than 20 types of patchy nanoparticles with unique patterns, such as patches on their corners, faces, and even forming web-like designs.

Perhaps most remarkably, the patches were so uniform that the nanoparticles could spontaneously organise themselves into large, highly ordered 3D crystals known as superlattices. This process, called self-assembly, is a holy grail in nanomaterials science. For years, the creation of such complex, non-closely packed structures from patchy nanoparticles was largely theoretical. The new study has reportedly brought this theory to life, showing that by designing the patches correctly, scientists can direct the particles to build themselves into specific large-scale architectures.

This new level of control over nanoparticle design is a crucial step toward creating metamaterials, which are engineered materials with unique properties not found in nature, such as the ability to manipulate light and sound in new ways. The applications are vast, potentially leading to advances in targeted drug delivery, ultra-efficient catalysts, next-generation electronics, and new classes of smart materials.

The team’s technique “can extend to other nanoparticle systems, in which the tunability of core nanoparticle composition, shape, size as well as patch polymer chemistry is limitless,” the paper read. “For example, gold nanorods are promising candidates worth further study owing to their rich faceting behaviours determined by particle size and synthesis conditions.”