Nanocrystal Quantum Dots and Their Optical Properties

Nanocrystal quantum dots (QDs) are semiconductor particles with dimensions on the order of a few nanometres, small enough that electrons and holes are confined in all three spatial dimensions. This quantum confinement gives rise to discrete electronic energy levels and size-dependent optical absorption and emission spectra. By varying composition, size and surface chemistry, QDs can be engineered to emit across the visible and near-infrared spectrum with narrow linewidths, high photostability and tunable quantum yields. Their core–shell architectures, in which a higher-band-gap shell material encapsulates a lower-band-gap core, suppress non-radiative surface traps and enhance charge-carrier confinement. Advances in synthetic control have led to highly monodisperse QDs with crystal phases selectively tailored for desired optoelectronic properties. These optical features underpin applications in light-emitting diodes, solar concentrators, lasing media and bioimaging probes. Recent work has also elucidated the interplay between crystal structure, surface ligands and charge-transfer dynamics under external stimuli, providing routes to further optimise brightness, stability and colour purity. Collectively, this research establishes nanocrystal QDs as versatile platforms for next-generation photonic and energy technologies.

Research from Nature Portfolio

Recent studies have demonstrated the ability to engineer excitonic wavefunctions in core–shell QDs by manipulating shell thickness to transition between Type-I and Type-II exciton confinement. By systematically varying shell growth, researchers uncovered intermediate “pseudo Type-II” states in which partial delocalisation of holes into the shell gives rise to dual absorption bands and blue-shifts in emission energy, highlighting design principles for photovoltaic and LED applications. In parallel, optical spectroscopy combined with first-principles calculations has enabled unambiguous determination of cubic and hexagonal crystal phases in II–VI nanocrystals. High-energy absorption features serve as rapid, non-destructive proxies for phase identification in sub-3 nm QDs, offering a high-throughput alternative to diffraction methods and improving reproducibility in nanocrystal synthesis.

Nanocrystal Quantum Dots and Their Optical Properties publication trend

The graph below shows the total number of articles in nanocrystal quantum dots and their optical properties across all publications each year (not limited to Nature Index journals).

Technical terms

Quantum confinement effect: The phenomenon by which charge carriers are spatially confined in nanoscale structures, leading to discrete energy levels and size-tunable optical transitions.

Exciton: A bound state of an electron and a hole attracted by Coulomb interaction, whose spatial distribution influences absorption and emission properties.

Core–shell structure: A nanoscale architecture in which a semiconductor core is surrounded by a shell of wider band-gap material to passivate surface defects and enhance carrier confinement.

Photoluminescence: The emission of light from a material following absorption of photons, characterised by emission wavelength, intensity and quantum yield.

Band gap: The energy difference between the valence band and conduction band in a semiconductor, determining the wavelength of absorbed and emitted light.

References

1. The Bright and Enlightening Science of Quantum Dots. Nano Letters (2023).
2. Wavefunction Engineering of Type-I/Type-II Excitons of CdSe/CdS Core-Shell Quantum Dots. Scientific Reports (2019).
3. Optical determination of crystal phase in semiconductor nanocrystals. Nature Communications (2017).
4. Three Millennia of Nanocrystals. ACS Nano (2022).
5. High-quantum yield alloy-typed core/shell CdSeZnS/ZnS quantum dots for bio-applications. Journal of Nanobiotechnology (2022).