Plasmonic metaresonances: harnessing nonlocal effects for prospective biomedical applications

Abstract

Metal nanoparticles (MNPs) possess optical concentration capabilities that can amplify and localize electromagnetic fields into nanometer length scales. The near-fields of MNPs can be used to tailor optical response of luminescent semiconductor quantum dots (QDs), resulting in fascinating optical phenomena. Plasmonic metaresonances (PMRs) form a class of such optical events gaining increasing popularity due to their promising prospects in sensing and switching applications. Unlike the basic excitonic and plasmonic resonances in MNP-QD nanohybrids, PMRs occur in the space/time domain. A nanohybrid experiences PMR when system parameters such as QD dipole moment, MNP-QD centre separation or submerging medium permittivity reach critical values, resulting in the plasmonically induced time delay of the effective Rabi frequency experienced by the QD asymptotically tending to infinity. Theoretical analyses of PMRs available in the literature utilize the local response approximation (LRA) which does not account for the nonlocal effects of the MNP, and neglect the MNP dependence of the QD decay and dephasing rates which hinder their applicability to QDs in the close vicinity of small MNPs. Here, we address these limitations using an approach based on the generalized nonlocal optical response (GNOR) theory which has proven to yield successful theoretical explanations of experimentally observed plasmonic phenomena. Our results indicate that, omission of the MNP nonlocal response and the associated decay/ dephasing rate modifications of the QD tend to raise implications such as significant overestimation of the QD dipole moment required to achieve PMR, under-estimation of the critical centre separation and prediction of significantly lower near-PMR QD absorption rates, in comparison to the improved GNOR based predictions. In light of our observations, we finally suggest two prospective applications of PMR based nanoswitches, namely, aptamer based in vitro cancer screening and thermoresponsive polymer based temperature sensing. To demonstrate the latter application, we develop and utilize a proof of concept (two dimensional) skin tumor model homogeneously populated by MNP-QD nanohybrids. Our simulations reveal a novel near-PMR physical phenomenon observable under perpendicular illumination, which we like to call the margin pattern reversal, where the spatial absorption pattern reverses when the near-PMR QDs switch from the bright to dark state.

A Superspace Formalism for the Electromagnetism of Generic Nonlocal Continuous Metamaterials: Principal Structures and Applications

“…The idea of exploiting nonlocality to design and develop a new generation of metamaterials (MTMs) exhibiting novel EM behaviour has also received a revival in recent years, though the basic concept in itself is not completely new, going back to at least [4] and possibly earlier. Recent examples of research focused in explicating nonlocal behaviour to harness the associated new physics include spatial dispersion in photonic crystals [69], wire media [70]- [73], semiconductor nanoparticles [74]- [77], optically nonlinear liquids [78], hyperbolic metamaterials [79], layered dielectric-metal structures [80], [81] and thin films [82], plasma-based metamaterials [83]- [85], quantum wells [86], soliton interactions with matter [87]- [92], superconducting films [93] and circuits [94], plasmonic devices and structures [95]- [97], nanocubes [98], cloaking [99], Chern metamaterials [100] and superconductors [101], dispersion management profiles [22], [102], biomedical applications in materials [103], and nonlocal uniaxial metamaterials [104].…”

On the Topology of Nonlocal Field Theories of Material Continua

“…VIII. dispersion management profiles [51], [164], biomedical applications in materials [165], nonlocal antennas [166], [167], and nonlocal uniaxial metamaterials [168]. Due to the practical importance of this area of research, we provide additional information in Appendices I and C.…”

Influence of a planar metal nanoparticle assembly on the optical response of a quantum emitter

“…Plasmonic metal nanoparticles (MNPs) [3] and quantum emitters (QEs) [4] are two categories of widely studied nanoparticles whose fascinating optoelectronic properties are often expected to synergize when combined [5][6][7][8]. Due to the tunability of the optical properties using their size and structure, MNPs and QEs possess a wide array of applications in a variety of fields such as biosensing [9,10], photothermal cancer therapy [11,12], optoelectronic nanodevices [13][14][15][16][17] and photovoltaics [18,19]. When a QE is kept in nanoscale proximity to a small MNP, a dipole-dipole coupling occurs between the two nanoparticles forming a highly tunable hybrid nanosystem exhibiting interesting optical signatures [1,2,20].…”

“…When a QE is kept in nanoscale proximity to a small MNP, a dipole-dipole coupling occurs between the two nanoparticles forming a highly tunable hybrid nanosystem exhibiting interesting optical signatures [1,2,20]. It has been shown theoretically, as well as experimentally that hybrid superstructures where one or more MNPs are attached to QEs have the potential to be utilized as versatile sensors and actuators which can surpass the capabilities of the individual constituents [11,21]. Therefore, hybrid molecules made of MNPs and QEs have captured the attention of both theorists and experimentalists.…”

“…The resonant condition of this phenomenon is termed a localized surface plasmon resonance [3]. In frequency regions close to their plasmonic peaks, MNPs can be used to tailor the optical response of nearly resonant QEs [11,30,31].…”