Sep 05, 2025

Gold quantum needles reveal a new side of nanocluster growth

Scientists uncovered gold quantum needles, a new nanoscale structure with unique optical properties that could transform imaging and energy research.

(Nanowerk News) A team at the University of Tokyo has captured the earliest moments of gold nanocluster formation, offering a rare look at how these tiny structures take shape. In the process, the researchers stumbled upon something entirely new: elongated, needle-like nanoclusters they’ve dubbed “gold quantum needles.”

These nanoscale needles respond strongly to near-infrared light, a property that could open doors for sharper biomedical imaging and more efficient light-based energy technologies. The discovery was detailed in the Journal of the American Chemical Society ("X-ray Crystallographic Visualization of a Nucleation and Anisotropic Growth in Thiolate-Protected Gold Clusters: Toward Targeted Synthesis of Gold Quantum Needles").

Structural evolution of gold nanoclusters: From anisotropic nucleation to growth into gold quantum needles. The structures were determined by X-ray crystallography. Organic residues of the surface ligands were omitted for clarity. Color code: Au (gold): yellow; S: red. (Image: Takano et al 2025)

Gold may be best known for jewelry and luxury, but at the nanoscale it behaves in unusual ways that make it a cornerstone of modern nanotechnology. Clusters of fewer than 100 gold atoms can display remarkable optical and electronic properties, yet controlling their growth into precise shapes and sizes has remained one of the field’s toughest challenges.

“Understanding how clusters form has been like peering into a black box,” said Tatsuya Tsukuda, who led the study. “We believed that by capturing their earliest stages, we could find new strategies to design them more deliberately.”

To make that possible, the team adjusted synthesis conditions so that gold clusters could be “frozen” at the very first steps of growth. Using single-crystal X-ray diffraction, they mapped out their evolving structures. The analysis revealed that instead of forming symmetrically, the clusters grew at uneven rates along different directions—ultimately giving rise to pencil-like forms built from triangular and tetrahedral building blocks.

That unusual growth path led to the gold quantum needles, whose electrons show quantum behavior by settling into specific energy states rather than continuous ones.

While the team could explain how smaller clusters developed under their experimental conditions, the appearance of the needles came as a surprise. “The triangular base structure was far beyond what we imagined,” Tsukuda said.

These insights offer scientists a clearer picture of nanocluster formation and could guide the design of new materials. Looking ahead, Tsukuda hopes to refine the synthesis process further and work with collaborators to explore practical uses for gold quantum needles, taking advantage of their striking optical properties.

Source: The University of Tokyo (Note: Content may be edited for style and length)