Dual Plasmon Research Articles

Biomimetic Plasmonic Nanophages by Head/Tail Self-Assembling: Gold Nanoparticle/Virus Interactions.

Gold nanoparticles (AuNPs), because of their dual plasmonic and catalytic functionalities, are among the most promising nanomaterials for the development of therapeutic and diagnostic tools for severe diseases such as cancer and neurodegeneration. Bacteriophages, massively present in human biofluids, are emerging as revolutionary biotechnological tools as they can be engineered to display multiple specific binding moieties, providing effective targeting ability, high stability, low cost, and sustainable production. Coupling AuNPs with phages can lead to an advanced generation of nanotools with great potential for biomedical applications. In the present study, we analyzed the interactions between differently sized AuNPs and filamentous M13 phages, establishing an advanced characterization platform that combines analytical techniques and computational models for an in-depth understanding of these hybrid self-assembling systems. A precise and structurally specific interaction of the AuNP-M13 hybrid complexes was observed, leading to a peculiar head/tail "tadpole-like" configuration. In silico simulations allowed explaining the mechanisms underlying the preferential assembly route and providing information about AuNPs' size-dependent interplay with specific M13 capsid proteins. The AuNP-M13 structures were proven to be biomimetic, eluding the formation of biomolecular corona. By keeping the biological identity of the virion, hybrid nanostructures maintained their natural recognition/targeting ability even in the presence of biomolecular crowding. In addition, we were able to tune the hybrid nanostructures' tropism toward E. coli based on the AuNP size. Overall, our results set the fundamental basis and a standard workflow for the development of phage-based targeting nanotools, valuable for a wide spectrum of nanotechnology applications.

A tunable graphene-based dual PIT device with dual-polarization excitation capability

A simple dual plasmon induced transparency (PIT) device based on “Z” type and “circle-strip” combination is designed, which is composed of monolayer graphene. This structure has the capability to excite double PIT simultaneously in the x polarization and y polarization directions. The polarization direction of the incident light will change the resonance frequency of the horizontal and vertical bands, but the resonance frequency of the circular graphene in the middle is not affected by the polarization direction of the light. After comparing the transmission spectra of the single structure and the combined structure, combined with the analysis of the surface electric field, it is determined that the structure adopts the coupling method of bright-bright-bright mode to realize the double PIT function. In both x and y polarization directions, the three components of the device are capable of inducing dipole resonance. Additionally, simulation results fit well with the theoretical transmittance calculations. When the device is utilized as a light sensor, it has been observed that sensitivity tends to increase alongside Fermi level elevation. Specifically, under x polarization, sensitivity can reach 1.888THz/RIU with a maximum FOM of 9.28 when the refractive index of the analyte is 1.7. Meanwhile, under y polarization, sensitivity can reach 1.943THz/RIU with a maximum FOM of 7.61 when the refractive index of the analyte is 1.3. In its capacity as an optical switch, the device has demonstrated a maximum modulation depth of 80.6 % at 2.64THz under x polarization, and 73.29 % at 1.92THz under y polarization. All modulations are achieved by adjusting the Fermi level.

Drug-Free Antimicrobial Nanomotor for Precise Treatment of Multidrug-Resistant Bacterial Infections.

Manufacturing heteronanostructures with specific physicochemical characteristics and tightly controllable designs is very appealing. Herein, we reported NIR-II light-driven dual plasmonic (AuNR-SiO2-Cu7S4) antimicrobial nanomotors with an intended Janus configuration through the overgrowth of copper-rich Cu7S4 nanocrystals at only one high-curvature site of Au nanorods (Au NRs). These nanomotors were applied for photoacoustic imaging (PAI)-guided synergistic photothermal and photocatalytic treatment of bacterial infections. Both the photothermal performance and photocatalytic activity of the nanomotors are dramatically improved owing to the strong plasmon coupling between Au NRs and the Cu7S4 component and enhanced energy transfer. The motion behavior of nanomotors promotes transdermal penetration and enhances the matter-bacteria interaction. More importantly, the directional navigation and synergistic antimicrobial activity of the nanomotors could be synchronously driven by NIR-II light. The marriage of active motion and enhanced antibacterial activity resulted in the expected good antibacterial effects in an abscess infection mouse model.

Dual plasmon-Induced transparency in two-dimensional metamaterials with coupled resonators

We herein report a numerical investigation of dual plasmon induced transparency (PIT) effect in two-dimensional plasmonic metamaterials composed of two C-shaped resonators and one U-shaped resonator. The finite difference time domain (FDTD) method is herein introduced to analyze transmission properties and electromagnetic field distributions of certain resonance wavelengths. It was found that, the PIT spectral response was affected by parameters of plasmonic metamaterials, such as the widths of C-shaped resonator and U-shaped resonator, and edge-to-edge distance between the adjacent resonators. The dual PIT effect can be attributed to the near field coupling between the dark and bright modes. The plasmonic nanostructures can provide useful guidelines for dual PIT effect in metamaterials, to support applications in selective storage, bio-chemical nanosensors, plasmonic-based all-optical information processing and optical switches.

Au-Cu2-xTe Plasmonic Heteronanostructure Photoelectrocatalysts.

Semiconductor nanocrystals coupled with plasmonic Au nanoparticles have been widely studied as photoelectrocatalysts for solar water splitting. Among these, heterostructures of copper chalcogenides with Au remained a unique category for their dual plasmon character. However, while sulfides and selenides of copper have been extensively reported, heterostructures of copper tellurides with Au have not been explored. Herein, the plasmonic semiconductor Cu2-xTe disks grown on Au nanoparticles (disk-on-dot) were explored as efficient photoelectrocatalysts for hydrogen evolution reactions (HER). This has been successfully designed by growing Cu2-xTe disks on presynthesized Au nanoparticles under optimized reaction conditions. The resulting heterostructured nanocrystals acted as efficient photoelectrocatalysts for the H2 evolution reaction with a low Tafel slope and less cathodic overpotential in the presence of light. Details of their synthesis, characterization, optical properties, and electrocatalytic activities are studied and reported in this letter.

Excellent sensing based on dual-plasmon induced transparency in graphene metasurface

Focusing on the realization of excellent sensing for graphene-based metasurface in the terahertz band. A planar monolayer graphene metasurface is proposed for sensing. Dual plasmon induced transparency (dual-PIT) phenomenon is realized in our proposed metasurface by use of the finite-difference time-domain (FDTD) method. This dual-PIT transmission spectrum can be effectively modulated by Fermi energies and positional parameters, and triple-PIT phenomenon can be realized. Interestingly, the excellent sensing performance can be achieved in terahertz band. The maximum sensitivity and Figure of Merit (FOM) are of 4.1884 THz /RIU and 43.31, respectively. These results may play an important role for designing excellent plasmonic graphene-based modulators and sensors in terahertz.

Dual Plasmon Resonances and Tunable Electric Field in Structure-Adjustable Au Nanoflowers for Improved SERS and Photocatalysis.

Flower-like metallic nanocrystals have shown great potential in the fields of nanophononics and energy conversion owing to their unique optical properties and particular structures. Herein, colloid Au nanoflowers with different numbers of petals were prepared by a steerable template process. The structure-adjustable Au nanoflowers possessed double plasmon resonances, tunable electric fields, and greatly enhanced SERS and photocatalytic activity. In the extinction spectra, Au nanoflowers had a strong electric dipole resonance located around 530 to 550 nm. Meanwhile, a longitudinal plasmon resonance (730~760 nm) was obtained when the number of petals of Au nanoflowers increased to two or more. Numerical simulations verified that the strong electric fields of Au nanoflowers were located at the interface between the Au nanosphere and Au nanopetals, caused by the strong plasmon coupling. They could be further tuned by adding more Au nanopetals. Meanwhile, much stronger electric fields of Au nanoflowers with two or more petals were identified under longitudinal plasmon excitation. With these characteristics, Au nanoflowers showed excellent SERS and photocatalytic performances, which were highly dependent on the number of petals. Four-petal Au nanoflowers possessed the highest SERS activity on detecting Rhodamine B (excited both at 532 and 785 nm) and the strongest photocatalytic activity toward photodegrading methylene blue under visible light irradiation, caused by the strong multi-interfacial plasmon coupling and longitudinal plasmon resonance.

Single particle dual plasmonic effect for efficient organic solar cells

Incorporating localized surface plasmon resonance (LSPR) into organic solar cells (OSCs) is a popular method for improving the power conversion efficiency (PCE) by introducing better light absorption. In this work, we designed a one-pot synthesis of Ag@SiO2@AuNPs dual plasmons and observed an immense increase in light absorption over a wide range of wavelengths. Ag@SiO2 plays the main role in enhancing light absorption near the ultraviolet band. The silica shell can also further enhance the LSP resonance effect and prevent recombination on the surface of AgNPs. The AuNPs on the Ag@SiO2 shell exhibited strong broad visible-light absorption due to LSP resonance and decreased light reflectance. By utilizing Ag@SiO2@AuNPs, we could enhance the light absorption and photoinduced charge generation, thereby increasing the device PCE to 8.57% and Jsc to 17.67 mA cm−2, which can be attributed to the enhanced optical properties. Meanwhile, devices without LSPR nanoparticles and Ag@SiO2 LSPR only showed PCEs of 7.36% and 8.18%, respectively.

Effect of additive acid on seeded growth of gold nanobipyramids

The presence of sharp tips and edges of gold nanobipyramids (GNBPs) lead to strong local electromagnetic field enhancement. Herein for the first time we present a study on efficacy of additive acid on the formation of GNBPs. The effect of additive acid type and its concentration in growth solution were investigated to obtain various yield and aspect ratio of GNBPs. Morphological characterization shows the nanoseeds that were grown in growth solution prepared using HCl, H2SO4, and HF at concentration from 0 to 1 mL produced GNBPs with yield ranges from 5.21 ± 0.44 to 91.46 ± 3.32% and aspect ratio from 2.00 ± 0.02 to 2.76 ± 0.05. The optical response of GNBPs exhibit dual plasmon band at wavelength around 550 nm–570 nm, corresponding to transverse surface plasmon resonance (t-SPR) and at wavelength around 700 nm–800 nm, corresponding to longitudinal surface plasmon resonance (l-SPR). The presented approach may be used to produce tunable morphological GNBPs nanostructures which potentially used in sensors, SERS, catalysis, and photonics.

Erratum “Effect of quantum charge screening on dual plasmon scattering” [Phys. Plasmas 26, 112102 (2019)

Erratum “Effect of quantum charge screening on dual plasmon scattering” [Phys. Plasmas <b>26</b>, 112102 (2019)

Tunable slow light effect based on dual plasmon induced transparency in terahertz planar patterned graphene structure

We have studied a simple novel graphene ribbon structure. A very excellent and prominent dual graphene plasmon induced transparency phenomenon could be achieved by the destructive interference resulted from the excited plasmonic modes in terahertz band. Using the simple relationship between graphene and applied voltage, a good tunable effect of this structure can be achieved. The transmission of this proposed structure is theoretically investigated by using the equivalent resonator coupled mode method. The theoretical data from our proposed method are in good agreement with the numerical simulation results. Moreover, utilizing the high dispersion property, we have also researched the slow light effect for this proposed system. The results of theoretical research have indicated that the group refractive index of our proposed structure can maintain an excellent numerical value. This investigation can play a significant role in the tunable graphene-based slow light devices.

Effect of quantum charge screening on dual plasmon scattering

In this paper, we investigate the resonant scattering of driven linear oscillations in an isothermal electron gas with an arbitrary degree of degeneracy. The coupled pseudoforce system is obtained from the quantum hydrodynamic model and is extended to include the driving pseudoforce and pseudodamping effect in order to study the quantum charge shielding on the resonant scattering, heat capacity, and Friedel oscillations around an impurity charge. It is shown that the resonant scattering phenomenon takes place when the driver wavelength matches either scale lengths of plasmon excitations, which arise due to single electron oscillations and collective electron plasma excitations. It is remarked that in the presence of a periodic density structure such as in metals, plasmon interactions with a periodic lattice structure can lead to resonant Bragg-like scattering. A generalized energy dispersion relation for pseudodamped plasmon excitations is obtained, which indicates a critical screening point beyond which the plasmon excitations behave only particlelike. It is shown that the heat capacity of plasmon excitations and the static quantum charge screening are strongly affected by interaction between the plasmon and the charge screening scale lengths.

Dual plasmons-promoted electron-hole separation for direct Z-scheme Bi3O4Cl/AgCl heterojunction ultrathin nanosheets and enhanced photocatalytic-photothermal performance

The dual plasmons (Bi, Ag)-based direct Z-scheme Bi3O4Cl/AgCl heterojunction ultrathin nanosheets are successfully synthesized by hydrothermal combined with solid-state reduction strategy. The plasmons Ag and Bi are formed during solid-state reduction process, which are firmly anchored on surface of Bi3O4Cl and AgCl, respectively, and favors the charge transfer obviously. Experiments results confirm the formation of heterojunction ultrathin nanosheets with the main size of 200∼300 nm and the thickness of <10 nm. The obtained dual plasmons-based direct Z-scheme Bi3O4Cl/AgCl heterojunction ultrathin nanosheets with the band gap of ∼1.66 eV exhibit excellent photothermal performance. 98.3% of Cr (VI) can be photocatalytic reduced and TOC removal rate of ceftriatone sodium reached 98.9% within 210 min, respectively. Due to the surface plasma resonance, the catalyst temperature increases obviously, indicating the enhanced photothermal performance, which is favorable for promoting the photocatalytic performance. Moreover, the cyclic stability experiment also proves the high stability and has advantages in practical applications. The excellent property can be ascribed to the direct Z-scheme accelerating charge transfer and prolonging the lifetimes, the dual plasmons enhancing photothermal performance and the spatial separation of photogenerated charge carriers.

Tunable Charge Transfer and Dual Plasmon Resonances of Au@WO3−x Hybrids and Applications in Photocatalytic Hydrogen Generation

We synthesized Au@WO3−x hybrids with dual plasmon resonances in visible and near-infrared (NIR) regions induced by two counterparts for enhancing photocatalytic activity. Au cores slightly influence hetero-morphology, significantly modify semiconductor plasmon, and prominently enhance H2 generation of WO3−x shells. As atom ratio of ρW:Au increases from 2 to 10, visible plasmon resonance is weakened with peak blueshifting from 540 to 490 nm, while NIR plasmon resonance strength prominently increases, and eventually average enhancement factor of photocatalytic H2 generation of the Au@WO3−x hybrids with white light illuminations increases from 1.76 to 2.85. Furthermore, the wavelength dependence of H2 generation reveals that the dominant physical mechanism of enhancing the photocatalytic activity of the hybrids is varied from excitation energy transfer to electron transfer from Au cores to WO3−x shells as ρW:Au increases. The construction of this metal-semiconductor hetero-nanostructure with dual plasmon resonances has immediate importance for the applications in solar energy conversions.

Low Power Single Laser Activated Synergistic Cancer Phototherapy Using Photosensitizer Functionalized Dual Plasmonic Photothermal Nanoagents.

Combination therapy, especially photodynamic/photothermal therapy (PDT/PTT), has shown promising applications in cancer therapy. However, sequential irradiation by two different laser sources and even the utilization of single high-power laser to induce either combined PDT/PTT or individual PTT will be subjected to prolonged treatment time, complicated treatment process, and potential skin burns. Thus, low power single laser activatable combined PDT/PTT is still a formidable challenge. Herein, we propose an effective strategy to achieve synergistic cancer phototherapy under low power single laser irradiation for short duration. By taking advantage of dual plasmonic PTT nanoagents (AuNRs/MoS2), a significant increase in temperature up to 60 °C with an overall photothermal conversion efficiency (PCE) of 68.8% was achieved within 5 min under very low power (0.2 W/cm2) NIR laser irradiation. The enhanced PCE and PTT performance is attributed to the synergistic plasmonic PTT effect (PPTT) of dual plasmonic nanoagents, promoting simultaneous release (85%) of electrostatically bonded indocyanine green (ICG) to induce PDT effects, offering simultaneous PDT/synergistic PPTT. Both in vitro and in vivo investigations reveal complete cell/tumor eradication, implying that simultaneous PDT/synergistic PPTT effects induced by AuNRs/MoS2-ICG are much superior over individual PDT or synergistic PPTT. Notably, synergistic PPTT induced by dual plasmonic nanoagents also demonstrates higher in vivo antitumor efficacy than either individual PDT or PTT agents. Taken together, under single laser activation with low power density, the proposed strategy of simultaneous PDT/synergistic PPTT effectively reduces the treatment time, achieves high therapeutic index, and offers safe treatment option, which may serve as a platform to develop safer and clinically translatable approaches for accelerating cancer therapeutics.

The Sensing Applications in U-Shape Structure Based on Dual Transparency Windows

We have researched a U-shape structure that consists of three vertical cavities coupled with bus wave-guide. The theoretical results based on the coupled mode theory are consistent with simulation results. We demonstrate that the interaction among two bright and one dark modes lead to dual plasmon induced transparency. Meanwhile, it is found that the lateral displacement S plays an important role in the transmission property, and the transmission dip with different transmittance in various lateral displacement S has been explained theoretically. Moreover, the nano sensor has a sensitivity of 1225 nm shift per refractive index unit, and the figure of merit is up to 62.5. The proposed structure has the advantages of simple and compact structure, easy fabrication, and the ultra-compact structure holds great potential to the control of light in highly integrated optical circuits and nano sensor.

Strong Fano Resonance Excited in an Array of Nanoparticle-in-Ring Nanostructures for Dual Plasmonic Sensor Applications

A large-area (over 1 cm2) nanoparticle-in-ring array (NPIRA) with strong Fano resonance is fabricated by a low-cost shadow sphere lithography (SSL) method. Controlled narrow nanogaps of 8–20 nm are formed between the nanoparticles (NPs) and rings. Quadrupole modes are excited in the nanogaps and interact with the dipole mode of the NPs and ring, resulting in two Fano resonances. The two Fano resonances are in the visible and near-infrared region, respectively, and show a maximum refractive index sensitivity of 425 nm/RIU and a figure of merit of 4.7–7.1 RIU–1. In addition, the NPIRAs show enhanced Raman intensity due to the strong electric fields confined in the nanogaps. The structure has great potential for the dual plasmonic sensor applications, i.e., surface-enhanced Raman scattering and refractive index sensing, and provides a robust sensing performance for each.

Au/Ag Bimetallic Nanocomposites as a Highly Sensitive Plasmonic Material

We report Au/Ag bimetallic nanocomposites as a highly sensitive plasmonic material. A unit approach via a three-dimensional numerical modeling is introduced to observe collective plasmon resonance in Au/Ag bimetallic nanocomposites as well as Au mono-metallic nanoensembles. Au nanoensembles provide consistently identical plasmon wavelength, independent of inter-unit distance. In analogy with mono-metallic nanoensembles, Au/Ag bimetallic nanocomposites distinctly feature converging dual plasmon resonance peaks to a single plasmon resonance peak, strongly depending on the packing density and the unit size. An effective unit size of bimetallic nanocomposites is below 2.5 nm in a subwavelength structure, which is small enough to feature bimetallic nanocomposites. As a result, the Au/Ag bimetallic nanocomposites clearly show exceptionally high sensitivity and figure-of-merit (approximately 3-fold of conventional plasmon sensitivity and 4.3-fold of conventional plasmon FOM), resulting from coupled Au-Ag quadrupole bimetallic nanounits. This study provides essential rationales for Au/Ag bimetallic nanocomposites serving as a desirable and alternative plasmonic material for advanced nanoplasmonic-sensing technologies.

A superior bright NIR luminescent nanoparticle preparation and indicating calcium signaling detection in cells and small animals

BackgroundNear-field fluorescence (NFF) effects were employed to develop a novel near-infrared (NIR) luminescent nanoparticle (LNP) with superior brightness. The LNP is used as imaging contrast agent for cellular and small animal imaging and furthermore suggested to use for detecting voltage-sensitive calcium in living cells and animals with high sensitivity.ResultsNIR Indocyanine green (ICG) dye was conjugated with human serum albumin (HSA) followed by covalently binding to gold nanorod (AuNR). The AuNR displayed dual plasmons from transverse and longitudinal axis, and the longitudinal plasmon was localized at the NIR region which could efficiently couple with the excitation and emission of ICG dye leading to a largely enhanced NFF. The enhancement factor was measured to be about 16-fold using both ensemble and single nanoparticle spectral methods. As an imaging contrast agent, the ICG–HSA-Au complex (abbreviate as ICG-Au) was conjugated on HeLa cells and fluorescence cell images were recorded on a time-resolved confocal microscope. The emission signals of ICG-Au complexes were distinctly resolved as the individual spots that were observed over the cellular backgrounds due to their strong brightness as well as shortened lifetime. The LNPs were also tested to have a low cytotoxicity. The ICG-Au complexes were injected below the skin surface of mouse showing emission spots 5-fold brighter than those from the same amount of free ICG–HSA conjugates.ConclusionsBased on the observations in this research, the excitation and emission of NIR ICG dyes were found to be able to sufficiently couple with the longitudinal plasmon of AuNRs leading to a largely enhanced NFF. Using the LNP with super-brightness as a contrast agent, the ICG-Au complex could be resolved from the background in the cell and small animal imaging. The novel NIR LNP has also a great potential for detection of voltage-gated calcium concentration in the cell and living animal with a high sensitivity.

Dual plasmonically tunable slow light based on plasmon-induced transparency in planar graphene ribbon metamaterials.

We propose a simulated terahertz design based on planar graphene ribbons. With numerical simulation, we can achieve a very obvious dual plasmon-induced transparency phenomenon through the destructive interference in this structure. Moreover, due to the simple design of this structure and the complete continuous graphene ribbons, the Fermi level of graphene can be regulated by voltage. Thus, the dual plasmon-induced transparency phenomenon can be easily tuned in the numerical simulation. Further structural analysis shows that the two graphene chips on the side of the graphene ribbons play a crucial role in the dual plasmon-induced transparency phenomenon. As the length of the two chips is close, the dual plasmon-induced transparency phenomenon gradually becomes a single plasmon-induced transparency phenomenon. The theoretical analysis of this structure shows that this system has a very high group index, and its maximum value is 800, which is far greater than that of other types of slow light devices. This work may open up a new way for designing tunable terahertz graphene-based devices and slow light devices.