Shape-Controlled Synthesis of Metal Nanostructures

The geometry of metal nanostructures underpins their optical, electronic and catalytic behaviour by dictating surface‐atom coordination, plasmonic response and active facet exposure. Shape‐controlled synthesis employs strategies such as seed‐mediated growth, facet‐selective capping, oxidative etching and photochemical modulation to steer nucleation and anisotropic growth. In a typical approach, small crystalline seeds are generated under reducing conditions and then grown into cubes, rods, bipyramids or more complex morphologies by judicious choice of surfactants, halide ions and reductant strength. Oxidative etchants selectively dissolve high‐energy facets to accentuate others, while light‐driven hot electrons can accelerate reduction and introduce twinning defects that evolve morphology. Control of ligand identity and coverage further tunes surface energies and colloidal stability, enabling the preparation of uniform nanocrystals with prescribed sizes and shapes. Such nanostructures find broad application in surface‐enhanced Raman scattering, metamaterials, photocatalysis, sensing, printed electronics and nanomedicine, where shape‐dependent properties can be harnessed for enhanced sensitivity, catalytic turnover or light‐matter coupling.

Research from Nature Portfolio

Recent studies have revealed that the wavelength and intensity of excitation light during polyol synthesis not only accelerate metal‐ion reduction but also induce twin defects that transform initial seeds into cubes, rods or bipyramids. In particular, high‐energy irradiation generates plasmon‐driven hot electrons that shift growth kinetics and promote facet‐selective development, while the polymeric surfactant acts as a photochemical relay to guide anisotropic assembly. Foundational work on halide‐mediated synthesis has demonstrated that varying bromide‐ion concentration in a polyol medium enhances oxidative etching of certain facets, enabling high‐yield production of uniform silver nanocubes. By tuning the balance between reduction and etching, this approach elegantly links ionic strength to nanocrystal geometry and yields reproducible batches for plasmonic applications.

Shape-Controlled Synthesis of Metal Nanostructures publication trend

The graph below shows the total number of articles in shape-controlled synthesis of metal nanostructures across all publications each year (not limited to Nature Index journals).

Technical terms

Seed‐mediated growth: A two‐step process in which small crystalline seeds are formed first and subsequently grown into larger anisotropic nanostructures under controlled conditions.

Oxidative etching: Selective dissolution of specific crystallographic facets by controlled oxidation, sharpening or removing undesired faces to refine nanoparticle shape.

Polyol synthesis: A reduction method using polyhydric alcohols (e.g. ethylene glycol) that serve as both solvent and reducing agent, enabling uniform nucleation and growth of metal nanocrystals.

Surface ligands: Organic molecules or ions adsorbed on nanoparticle surfaces that stabilise colloids, direct facet growth and influence interparticle interactions.

Twin plane: A planar defect within a crystal where two regions of the lattice share a symmetrical mirror orientation, often serving as a locus for anisotropic growth.

Localized surface plasmon resonance (LSPR): Collective oscillation of conduction electrons in a metal nanoparticle excited by light, leading to intense electromagnetic fields at its surface and unique optical signatures.

References

1. Quantification, Exchange, and Removal of Surface Ligands on Noble-Metal Nanocrystals. Accounts of Chemical Research (2023).
2. Seeing is believing: what is on the surface of silver nanocrystals suspended in their original reaction solution. Chemical Science (2024).
3. Bromide (Br) - Based Synthesis of Ag Nanocubes with High-Yield. Scientific Reports (2015).
4. Customizable Ligand Exchange for Tailored Surface Property of Noble Metal Nanocrystals. Research (2020).
5. Silver Nanocubes: From Serendipity to Mechanistic Understanding, Rational Synthesis, and Niche Applications. Chemistry of Materials (2023).
6. Shape‐Controlled Metal Nanoparticles and Their Assemblies with Optical Functionalities. Journal of Nanomaterials (2013).
7. Effect of light at different wavelengths on polyol synthesis of silver nanocubes. Scientific Reports (2022).