Dispersion and shape engineered plasmonic nanosensors

Abstract

Biosensors based on the localized surface plasmon resonance (LSPR) of individual metallic nanoparticles promise to deliver modular, low-cost sensing with high-detection thresholds. However, they continue to suffer from relatively low sensitivity and figures of merit (FOMs). Herein we introduce the idea of sensitivity enhancement of LSPR sensors through engineering of the material dispersion function. Employing dispersion and shape engineering of chiral nanoparticles leads to remarkable refractive index sensitivities (1,091 nm RIU−1 at λ=921 nm) and FOMs (>2,800 RIU−1). A key feature is that the polarization-dependent extinction of the nanoparticles is now characterized by rich spectral features, including bipolar peaks and nulls, suitable for tracking refractive index changes. This sensing modality offers strong optical contrast even in the presence of highly absorbing media, an important consideration for use in complex biological media with limited transmission. The technique is sensitive to surface-specific binding events which we demonstrate through biotin–avidin surface coupling.

Advances in optoplasmonic sensors – combining optical nano/microcavities and photonic crystals with plasmonic nanostructures and nanoparticles

“…The sensitivity can be calculated to be / ( / )/( / ) 2 /( / ) , =− ε ε and the factor χ puts shape into account (i.e. χ = 2 for spheres) [10,11]. Judicious choice of morphology and material hence allows for optimisation of the magnitude of λ * with n, strategies for which are discussed in the next section of this review.…”

“…Specific shapes such as that in Figure 2G, however, lead to natural chirality [11,37]. This enables LSPRs that are detectable via circular dichroism spectra, which are typically more feature-rich than extinction spectra and can be used for sensing more spectral signatures in complex biological systems with maximised sensitivity [11].…”

“…Specific shapes such as that in Figure 2G, however, lead to natural chirality [11,37]. This enables LSPRs that are detectable via circular dichroism spectra, which are typically more feature-rich than extinction spectra and can be used for sensing more spectral signatures in complex biological systems with maximised sensitivity [11]. Coupling and bridging single nanoparticles and the creation of dimers with controlled gap distances establishes constructive coupling between plasmon resonances of adjacent nanoparticles and regions of intense local fields in the gaps between the nanoparticles.…”

Corrosion‐Protected Hybrid Nanoparticles

“…” The method permits control over both the shape and material composition of 3D hybrid nanostructures that have been used as plasmonic nanoantennas for nanorheology11 and chiral sensing 12. However, many of the materials that can be grown with this technique are not chemically stable when exposed to air or water.…”

Artificial molecular and nanostructures for advanced nanomachinery

“…111 The active rheology probe can be actuated using a weak magnetic field and operates using a novel optical sensing scheme based on circular dichroism (CD). 112 Owing to the intense chiroptical properties of the nanohelices, this sensing scheme is practically background-free and allows optical signal identification in optically dense media (OD as high as 3). By analysing the time-and angle-dependent CD signal of the actively actuating nanohelices, direct viscosity measurement in full blood (50% v/v red blood cells) samples has been achieved.…”