Plasmonic Nanostructures for Sensing Applications

Plasmonic nanostructures harness the collective oscillation of conduction electrons at metal–dielectric interfaces to concentrate electromagnetic fields into nanoscale volumes. This field localisation gives rise to sharp spectral features that shift in response to minute changes in the surrounding environment, enabling highly sensitive detection of chemical and biological analytes. Key architectures include metallic nanoparticles, nanohole arrays, nanorings and nanowires, each offering distinct resonance modes and near-field distributions. Surface-enhanced Raman spectroscopy (SERS), refractive-index sensing and label-free molecular assays all exploit these resonances, which can be tailored by varying size, shape, interparticle spacing or substrate coupling. Owing to their rapid response, compatibility with microfluidics and potential for on-chip integration, plasmonic sensors are finding applications in medical diagnostics, environmental monitoring, food safety and point-of-care testing. Current research focuses on improving sensitivity, reducing linewidths for higher resolution, increasing tolerance to unpolarised or broadband light and developing cost-effective, large-area fabrication methods.

Research from Nature Portfolio

Recent studies have demonstrated that rotationally symmetric gold nanostructures can deliver robust sensing performance under unpolarised illumination. By fabricating gammadion, star-shaped and other internally symmetric geometries, researchers have shown that multiple longitudinal plasmon modes couple constructively to yield up to a threefold increase in optical contrast. These designs achieve enhanced sensitivity and quality-factors without the need for polarisation control, offering a simplified read-out for practical sensing platforms. A rigorous figure-of-merit analysis confirms that increasing internal rotational symmetry systematically improves detection limits while maintaining narrow resonance linewidths.

Research from all publishers

Advances in nanopatterned silicon–metal hybrids have led to surface-enhanced Raman substrates with unprecedented signal intensities. Vertically aligned silicon nanowire dimers decorated with gold nanoparticles exhibit strong hot-spot formation within 40 nm gaps, delivering record SERS enhancements at near-infrared excitation and validating electromagnetic simulations of field confinement. In parallel, studies of gold–silica–gold optical cavities incorporating nanohole arrays have achieved refractive-index sensitivities of 5–7 nm per refractive index unit by optimising cavity thickness and inter-hole spacing, thereby narrowing resonance widths and boosting the sensor’s figure-of-merit. Furthermore, scalable colloidal lithography has enabled large-area gold nanohole arrays that exploit Rayleigh anomaly–plasmon mode hybridisation to produce high-order resonances with quality-factors exceeding conventional designs. Such platforms have reached refractive-index sensitivities above 400 nm/RIU and have been integrated into lens-free smartphone read-out schemes, demonstrating label-free detection of biomolecules at nanomolar concentrations in compact, cost-effective formats.

Plasmonic Nanostructures for Sensing Applications publication trend

The graph below shows the total number of articles in plasmonic nanostructures for sensing applications across all publications each year (not limited to Nature Index journals).

Technical terms

Localized surface plasmon resonance (LSPR): Collective oscillation of conduction electrons in metallic nanostructures when excited by light, resulting in intense, spatially confined electromagnetic fields highly sensitive to changes in the local dielectric environment.

Surface-enhanced Raman spectroscopy (SERS): Analytical technique that utilises plasmonic “hot spots” to amplify Raman scattering signals, enabling molecular fingerprinting at extremely low concentrations.

Refractive index sensitivity (RIS): Quantitative measure of the shift in resonance wavelength or intensity per unit change in surrounding refractive index, serving as an indicator of sensor responsiveness.

Figure-of-merit (FoM): Ratio of refractive index sensitivity to the full-width at half-maximum of the plasmonic resonance, reflecting the overall resolution and performance of a sensing device.

References

1. Au Nanoparticles@Si Nanowire Oligomer Arrays for SERS: Dimers Are Best. ACS Applied Materials & Interfaces (2024).
2. Impact of Optical Cavity on Refractive Index Sensitivity of Gold Nanohole Arrays. Biosensors (2023).
3. Rayleigh anomaly-enabled mode hybridization in gold nanohole arrays by scalable colloidal lithography for highly-sensitive biosensing. Nanophotonics (2022).
4. Polarization invariant plasmonic nanostructures for sensing applications. Scientific Reports (2017).