Quantum Plasmonics Research Articles

Recent Applications of Quantum Plasmonic Techniques for Detection of Toxic Materials

Recent Applications of Quantum Plasmonic Techniques for Detection of Toxic Materials

Phonon-Induced Geometric Chirality.

Chiral properties have seen increasing use in recent years, leading to the emerging fields of chiral quantum optics, plasmonics, and phononics. While these fields have achieved manipulation of the chirality of light and lattice vibrations, controlling the chirality of materials on demand has yet remained elusive. Here, we demonstrate that linearly polarized phonons can be used to induce geometric chirality in achiral crystals when excited with an ultrashort laser pulse. We show that nonlinear phonon coupling quasistatically displaces the crystal structure along phonon modes that reduce the symmetry of the lattice to that of a chiral point group corresponding to a chiral crystal. By reorienting the polarization of the laser pulse, the two enantiomers can be induced selectively. Therefore, geometric chiral phonons enable the light-induced creation of chiral crystal structures and therefore the engineering of chiral electronic states and optical properties.

Charge Transfer Plasmons Enabled by Supramolecular Plug: From Optoelectronic Switching to Enhanced Chiral Sensing.

Miniaturization and integration of plasmonic nanodevices are fundamentally limited by quantum tunneling, which leads to quantum plasmonics with reduced local E-field intensity. Despite significant efforts devoted to modeling and deterring the detrimental effect of quantum plasmonics, the modulation and application of electron transport through the subnanometer gaps seems rarely exploited due to the limited tunability of conventional quantum materials. Here, we establish a supramolecular plasmonic system made of pillar[5]arene complexes and plasmonic resonators (nanoparticle-on-mirror, NPoM). The supramolecular assemblies significantly enhance the gap conductance of NPoM, which results in a blue-shift of the coupled plasmons. Plasmonic hot-electron transport with laser excitation further modulates the gap plasmons, which are fully reversible and beneficial for enhanced chiroptic sensing. Such a conductive supramolecular plasmonic system not only suggests an optoelectronic switching strategy for charge transfer plasmons but also provides a superior sensing platform for single molecules.

Quantum mechanical effects in plasmonic sub-nanometer cavities formed by a tip and substrate structure

Enhancing local field intensity through light field compression is one of the core issues in surface plasmon-enhanced spectroscopy. The theoretical framework for the nanostructure composed of a tip and a substrate has predominantly relied on classical electromagnetic models, ignoring the electron tunneling effect. In this paper, we investigate the plasmonic near-field characteristics in the sub-nanometer cavity formed by the tip and the substrate using a quantum-corrected model. Additionally, we analyze the local electric field and Raman enhancement when hexagonal boron nitride (h-BN) monolayer is used as a decoupling layer for the nanocavity. The results indicate that classical electromagnetic theory fails to accurately describe the plasmonic electric field in smaller sub-nanometer gaps. When the gap is reduced to 0.32 nm, the quantum-corrected model shows that the local electric field in the sub-nanometer cavity is significantly reduced due to the tunneling current, aligning more closely with experimental results. Moreover, adding a high-barrier h-BN layer effectively prevents the occurrence of tunneling current, allowing for a strong local electric field even when the gap is less than 0.32 nm. The calculated maximum Raman enhancement reaches up to 15 orders of magnitude. Our research results provide a deep understanding of quantum mechanical effects in tip-enhanced spectroscopy systems, enabling the potential applications based on quantum plasmons in nanocavity.

Theoretical investigation of the optical and plasmonic properties of the nanocomposite media composed of silver nanoparticles embedded in rubidium

This theoretical study investigates, the optical response of a metal-dielectric nanocomposite of silver and rubidium (Ag/Rb) is theoretically studied via Maxwell-Garnett Model by varying the size, shape and volume ratio of the silver nanoparticles (AgNPs) in the coherently driven four levels rubidium dielectric atomic media. The rubidium being an alkali metal behaves as dielectric under quantum coherence effect. It was found that the optical response of this nanocomposite media strongly depends on the coherent driving fields applied in the atomic ensemble, the volume fraction of the AgNPs as well as their size and the applied frequencies. It was found that the dielectric function decreases with the increase in AgNPs’ size, while increase in Rabi frequency increases the refractive index. Similarly, the dispersion and absorption decrease with decrease in volume fraction of the AgNPs. Our results suggest important applications of this nanocomposite in various fields such as energy harvesting, photovoltaics and quantum plasmonics. The modeling approach developed in this study provides great freedom for tuning optical properties of the metal-dielectric nanocomposites.

Imaging the distribution of a surface plasmon induced electromagnetic field at the nanoscale with MFSM

Surface plasmons play a crucial role in the fields of microscopic imaging, spectroscopy, semiconductor devices, nonlinear optics, and so on. However, there is still no robust method for characterizing the surface plasmon at the nanoscale. Here, an approach for the characterization of the surface plasmon at the nanoscale was proposed by imaging the distribution of surface plasmon-induced electromagnetic field using magnetic force spectroscopy microscopy (MFSM), and the visualization of its induced electromagnetic field is demonstrated by combining magnetic force spectroscopy with a 3D reconstruction algorithm. Furthermore, an inhomogeneous electromagnetic field caused by nanostructure defects is identified by 3D imaging. The experimental method and results are of great significance for the study of surface plasmon and their effect at the nanoscale. This technique proves invaluable for investigating surface plasmon and has great prospects in the testing and application for plasmon excitation, quantum dots, and nanosensors.

Asymmetricity in fluorescence peaks of a three level Λ-type quantum emitter placed near a spherical metal nanoparticle

Abstract A generalized master equation is derived here for a hybrid three level Λ-type quantum emitter-metal nanoparticle (MNP) system in the presence of strong external fields. With this new master equation, we show the spectral reshaping of the fluorescence peaks leading to asymmetric peak heights. This asymmetricity is attributed to dressed state-reservoir coupling and strong coherent fields. The coupling of reservoir with dressed states results in different sampling of local density of states (LDOS) of the vacuum field by dressed state transitions, giving different transition probabilities to each peak. We have further explored the directional features of the resonance fluorescence spectrum in the hybrid system. These observations of spectral reshaping in a three-level-MNP system opens new directions for studying tunable electromagnetically induced transparency utilizing ‘tailored vacuum’ in quantum plasmonics.

Room-temperature quantum nanoplasmonic coherent perfect absorption

Light-matter superposition states obtained via strong coupling play a decisive role in quantum information processing, but the deleterious effects of material dissipation and environment-induced decoherence inevitably destroy coherent light-matter polaritons over time. Here, we propose the use of coherent perfect absorption under near-field driving to prepare and protect the polaritonic states of a single quantum emitter interacting with a plasmonic nanocavity at room temperature. Our scheme of quantum nanoplasmonic coherent perfect absorption leverages an inherent frequency specificity to selectively initialize the coupled system in a chosen plasmon-emitter dressed state, while the coherent, unidirectional and non-perturbing near-field energy transfer from a proximal plasmonic waveguide can in principle render the dressed state robust against dynamic dissipation under ambient conditions. Our study establishes a previously unexplored paradigm for quantum state preparation and coherence preservation in plasmonic cavity quantum electrodynamics, offering compelling prospects for elevating quantum nanophotonic technologies to ambient temperatures.

Resonant Plasmon-Assisted Tunneling in a Double Quantum Dot Coupled to a Quantum Hall Plasmon Resonator.

Edge magnetoplasmon is an emergent chiral bosonic mode promising for studying electronic quantum optics. While the plasmon transport has been investigated with various techniques for decades, its coupling to a mesoscopic device remained unexplored. Here, we demonstrate the coupling between a single plasmon mode in a quantum Hall plasmon resonator and a double quantum dot (DQD). Resonant plasmon-assisted tunneling is observed in the DQD through absorbing or emitting plasmons stored in the resonator. By using the DQD as a spectrometer, the plasmon energy and the coupling strength are evaluated, which can be controlled by changing the electrostatic environment of the quantum Hall edge. The observed plasmon-electron coupling encourages us for studying strong coupling regimes of plasmonic cavity quantum electrodynamics.

Strong coupling between plasmonic nanocavity gold nanorods and quantum dots emitter

The discovery of hybrid states in strong coupling interaction has gained growing attention in cavity-quantum electrodynamics research owing to its fundamental directives and potential in advanced optical applications. The ultra-confined mode volume of plasmonic cavity gold nanorods (AuNRs), particularly at the nanorod tip “hotspot” provides a large coupling strength, a prerequisite for a coherent energy exchange in the strong coupling regime. Here, we reported a remarkable Rabi splitting of ∼231 meV between gold nanorods longitudinal localized surface plasmon resonance (LLSPR) mode and quantum dots (QDs) at ambient conditions, monitored by dielectric medium tuning. Numerical simulations confirmed the result, displaying absorption spectral splitting.

Quantum-informed plasmonics for strong coupling: the role of electron spill-out

The effect of nonlocality on the optical response of metals lies at the forefront of research in nanoscale physics and, in particular, quantum plasmonics. In alkali metals, nonlocality manifests predominantly as electron density spill-out at the metal boundary, and as surface-enabled Landau damping. For an accurate description of plasmonic modes, these effects need be taken into account in the theoretical modeling of the material. The resulting modal frequency shifts and broadening become particularly relevant when dealing with the strong interaction between plasmons and excitons, where hybrid modes emerge and the way they are affected can reflect modifications of the coupling strength. Both nonlocal phenomena can be incorporated in the classical local theory by applying a surface-response formalism embodied by the Feibelman parameters. Here, we implement local surface-response corrections in Mie theory to study the optical response of spherical plasmonic–excitonic composites in core–shell configurations. We investigate sodium, a jellium metal dominated by spill-out, for which it has been anticipated that nonlocal corrections should lead to an observable change in the coupling strength, appearing as a modification of the width of the mode splitting. We show that, contrary to expectations, the influence of nonlocality on the anticrossing is minimal, thus validating the accuracy of the local response approximation in strong-coupling photonics.

Colour-Passive radiative cooling in optoelectronics with Silver/Quantum dot decorated silica multifunctional hybrid structures

The integration of solar cells into the architectural design is hindered by challenges such as passive cooling and colouration appeal. The present study proposes an approach to overcome these obstacles by developing colourful solar cells that maintain optimal performance while addressing limitations related to heat accumulation from plasmon metal nanoparticles and quantum dots (QDs). To attain this, silver/silica microsphere composites combined with CdSe/ZnS core/shell QDs are fabricated with two distinct sizes of Ag nanoparticles embedded around SiO2 microspheres. Upon coating CIGS cells with this hybrid structure, a visually striking vivid green colouration is observed, while ensuring performance efficiency. Furthermore, the radiative cooling capability of these cells is evaluated through indoor and outdoor experiments. Significantly, a substantial temperature reduction of up to 3.2 °C in CIGS cells is achieved when the hybrid structures were applied to the cell's surface under high solar irradiance. The study represents a significant contribution to innovative strategies targeted at achieving passive cooling effect and enhancing aesthetic integration in building-integrated photovoltaics applications.

Classical vs. quantum plasmon-induced molecular transformations at metallic nanojunctions

Chemical transformations near plasmonic metals have attracted increasing attention in the past few years. Specifically, reactions occurring within plasmonic nanojunctions that can be detected via surface and tip-enhanced Raman (SER and TER) scattering were the focus of numerous reports. In this context, even though the transition between localized and nonlocal (quantum) plasmons at nanojunctions is documented, its implications on plasmonic chemistry remain poorly understood. We explore the latter through AFM-TER-current measurements. We use two molecules: i) 4-mercaptobenzonitrile (MBN) that reports on the (non)local fields and ii) 4-nitrothiophenol (NTP) that features defined signatures of its neutral/anionic forms and dimer product, 4,4'-dimercaptoazobenzene (DMAB). The transition from classical to quantum plasmons is established through our optical measurements: It is marked by molecular charging and optical rectification. Simultaneously recorded force and current measurements support our assignments. In the case of NTP, we observe the parent and DMAB product beneath the probe in the classical regime. Further reducing the gap leads to the collapse of DMAB to form NTP anions. The process is reversible: Anions subsequently recombine into DMAB. Our results have significant implications for AFM-based TER measurements and their analysis, beyond the scope of this work. In effect, when precise control over the junction is not possible (e.g., in SER and ambient TER), both classical and quantum plasmons need to be considered in the analysis of plasmonic reactions.

Plasmonic quantum dots modulated nano-mineral toward photothermal reduction of CO2 coupled with biomass conversion

Plasmonic quantum dots modulated nano-mineral toward photothermal reduction of CO2 coupled with biomass conversion

Green Synthesis and Characterization of Zinc Oxide Using Carica papaya Leaf Extract

AbstractEnvironmental methodologies are gaining recognition in this modern world. Environmental nanotechnology plays a major role in improving modern fields of environmental engineering and science. Metal oxide nanoparticles have exceptional properties due to their small size, including quantum confinement, surface‐to‐volume ratio, plasmon excitation, high biocompatibility, and surface modifiability. The biosynthesis of nanoparticles using fungi, bacteria, and plants through various biotechnological techniques is currently a new paradigm for environmental protection. Synthesis of nanoparticles through plant extract is good because it eliminates the dangers of toxic chemicals, it is environmentally friendly, simpler, and safer as the reaction time is reduced and it can also be increased in size for higher operation. The present study is based on the development of zinc oxide nanoparticles from papaya leaf extract where zinc nitrate is used as a precursor. The biosynthesized nanoparticles are characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, electron microscopy, energy‐dispersive X‐ray analysis, UV‐visible spectroscopy, and dynamic light scattering analysis. The crystalline phase determination of the zinc oxide nanoparticles is analyzed by X‐ray diffraction and the formation of polycrystalline zinc oxide nanoparticles is confirmed. FT‐IR spectrum reveals the main functional groups and chemical information in zinc oxide nanostructures. Morphological analysis is performed using SEM at different magnification levels. EDAX analysis shows the purity of the composite samples. Optical characterization is performed using a UV–vis spectrophotometer. DLS analysis shows that the nanoparticles formed have a relatively well‐defined dimension.

Nanoparticles as Catalysts: Exploring Potential Applications

Abstract: Nanoparticles have emerged as highly promising catalysts due to their unique physical and chemical properties arising from their small size and high surface area–to–volume ratio. This review delves into the diverse applications of nanoparticles as catalysts in various chemical reactions. A key advantage lies in their substantial surface area–to–volume ratio, facilitation, enhanced accessibility of reactants, and heightened interaction with the catalyst surface. This distinctive characteristic results in improved catalytic activity and efficiency. Additionally, size-dependent properties, such as surface plasmon resonance and quantum confinement effects, offer opportunities for tailoring catalytic behavior. Despite their immense potential, challenges such as synthesis, stability, toxicity, aggregation, and recyclability require attention. Future research should prioritize scalable and sustainable synthesis methods, improve catalyst stability under harsh conditions, and ensure safe handling and disposal. This review provides an overview of the role of nanoparticles as catalysts and highlights their significance in various fields, highlighting their exceptional performance, versatility, and environmental benefits.

Surface-enhanced photoluminescence and Raman spectroscopy of single molecule confined in coupled Au bowtie nanoantenna

Optical nanoantennas possess broad applications in the fields of photodetection, environmental science, biosensing and nonlinear optics, owing to their remarkable ability to enhance and confine the optical field at the nanoscale. In this article, we present a theoretical investigation of surface-enhanced photoluminescence spectroscopy for single molecules confined within novel Au bowtie nanoantenna, covering a wavelength range from the visible to near-infrared spectral regions. We employ the finite element method to quantitatively study the optical enhancement properties of the plasmonic field, quantum yield, Raman scattering and fluorescence. Additionally, we systematically examine the contribution of nonlocal dielectric response in the gap mode to the quantum yield, aiming to gain a better understanding of the fluorescence enhancement mechanism. Our results demonstrate that altering the configuration of the nanoantenna has a significant impact on plasmonic sensitivity. The nonlocal dielectric response plays a crucial role in reducing the quantum yield and corresponding fluorescence intensity when the gap distance is less than 3 nm. However, a substantial excitation field can effectively overcome fluorescence quenching and enhance the fluorescence intensity. By optimizing nanoantenna configuration, the maximum enhancement of surface-enhanced Raman can be turned to 9 and 10 magnitude orders in the visible and near-infrared regions, and 3 and 4 magnitude orders for fluorescence enhancement, respectively. The maximum spatial resolutions of 0.8 nm and 1.5 nm for Raman and fluorescence are also achieved, respectively. Our calculated results not only provide theoretical guidance for the design and application of new nanoantennas, but also contribute to expanding the range of surface-enhanced Raman and fluorescence technology from the visible to the near-infrared region.

Quantum plasmonics pushes chiral sensing limit to single molecules: a paradigm for chiral biodetections

Chiral sensing of single molecules is vital for the understanding of chirality and their applications in biomedicine. However, current technologies face severe limitations in achieving single-molecule sensitivity. Here we overcome these limitations by designing a tunable chiral supramolecular plasmonic system made of helical oligoamide sequences (OS) and nanoparticle-on-mirror (NPoM) resonator, which works across the classical and quantum regimes. Our design enhances the chiral sensitivity in the quantum tunnelling regime despite of the reduced local E-field, which is due to the strong Coulomb interactions between the chiral OSs and the achiral NPoMs and the additional enhancement from tunnelling electrons. A minimum of four molecules per single-Au particle can be detected, which allows for the detection of an enantiomeric excess within a monolayer, manifesting great potential for the chiral sensing of single molecules.

Hot carrier creation in a nanoparticle dimer-molecule composite.

Light-matter interactions have garnered considerable interest owing to their burgeoning applications in quantum optics and plasmonics. Utilizing first principles calculations, this work explores the hot carrier (HC) generation and distribution within a composite system made up of a plasmonic nanoparticle dimer and linear polycyclic aromatic hydrocarbon (PAH) molecules. We examine the spatial and energetic distributions of HCs by initiating photoexcitation and allowing localized surface plasmon dephasing. By positioning PAH molecules within the plasmonic nanodimer's gap region, our investigation uncovers HC tuning. Notably, depending on the size of the PAH molecules, there are significant alterations in the HC distribution. Hot electrons (HEs) are distributed across both the nanodimer and the PAH molecule, while hot holes (HHs) become entirely localized on the PAH as the PAH grows larger. These findings improve our understanding of plasmon-molecule coupled states and provide guidance on how to customize HC distributions through the creation of hybrid plasmonic materials.

Heterostructures made from bone-like plasmonic Au nanoantennas and ZnO quantum dots for broadband photodetectors

The BLAuNAs/ZnO heterostructures not only improve the photoresponse to UV light but also extend the photoresponse to the visible light region due to the plasmonic properties of BLAuNAs and their material nature.