Silicon Nanomaterials and Their Optical Properties

Silicon nanomaterials—including quantum dots, porous nanostructures and colloidal nanocrystals—exhibit unique optical phenomena arising from their reduced dimensions and surface chemistry. Quantum confinement in particles smaller than 5 nm produces size-dependent shifts of the absorption and emission spectra into the visible and near-infrared. Surface passivation and functionalisation critically influence radiative efficiency, enabling photoluminescence quantum yields exceeding 60 % in red–green emitters and even faster blue–green bands. Strategies to overcome silicon’s intrinsic indirect bandgap include dedicated surface engineering that restores phonon-less transitions analogous to direct bandgap semiconductors. In porous silicon nanoparticles, unusually long excited-state lifetimes allow temporal discrimination of signal against background autofluorescence. Advances in synthesis—from colloidal routes to laser ablation—have yielded biocompatible, oxide-passivated quantum dots for in vivo imaging and telecommunication-compatible light emitters. These developments underpin applications in biosensing, optoelectronic devices, light-emitting diodes, photovoltaics and time-resolved bioimaging, demonstrating the global and practical significance of tunable silicon nanophotonics.

Research from Nature Portfolio

Porous silicon nanoparticles with microsecond-scale photoluminescence lifetimes have been employed for time-gated fluorescence imaging, achieving over twenty-fold improvement in signal-to-background contrast in live animal models. Engineering of surface oxide layers and control of excited-state decay have enabled multiplexed imaging via differentiated lifetime tags. Examination of colloidal silicon nanocrystals revealed a critical limit in photoluminescence tunability at around 2.1 eV: in larger dots quantum confinement dominates, while in sub-2 nm regimes surface-related trap states curtail further blue‐shift and reduce quantum yield. Ultrapure, laser-synthesised silicon quantum dots endowed with oxide passivation exhibit bright exciton emission near 800 nm in physiological media, demonstrating zero cytotoxicity and efficient cellular uptake, and thus offering a new platform for theranostic applications in living systems.

Silicon Nanomaterials and Their Optical Properties publication trend

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

Technical terms

Quantum confinement: Restriction of electron and hole motion in nanoscale structures, leading to discrete energy levels and size-dependent optical transitions.

Photoluminescence: Emission of light by a material following absorption of photons, characterised by emission spectrum, lifetime and quantum yield.

Photoluminescence quantum yield (PLQY): Ratio of emitted photons to absorbed photons, indicating efficiency of radiative recombination.

Surface passivation: Chemical treatment of nanomaterial surfaces to eliminate non-radiative trap states and stabilise optical emission.

Time-gated imaging: Technique that discriminates long-lived emission from short-lived background autofluorescence by delaying detection after excitation.

References

1. In vivo time-gated fluorescence imaging with biodegradable luminescent porous silicon nanoparticles. Nature Communications (2013).
2. Surface brightens up Si quantum dots: direct bandgap-like size-tunable emission. Light: Science & Applications (2013).
3. Tunability Limit of Photoluminescence in Colloidal Silicon Nanocrystals. Scientific Reports (2015).
4. Phosphorus Doping in Si Nanocrystals/SiO2 Multilayers and Light Emission with Wavelength Compatible for Optical Telecommunication. Scientific Reports (2016).
5. Laser-synthesized oxide-passivated bright Si quantum dots for bioimaging. Scientific Reports (2016).