Plasmonic Interactions Research Articles

Combined Au/Ag nanoparticle creation in ZnO nanopillars by ion implantation for optical response modulation and photocatalysis

ZnO nanopillars were implanted with Au-400 keV and Ag-252 keV ions with ion fluences from 1 × 1015 cm−2 to 1 × 1016 cm−2. We compared ZnO nanopillars solely implanted with Au-ions and dually-implanted with Au and Ag-ions. Rutherford Back-Scattering spectrometry (RBS) confirmed Ag and Au embedded in ZnO nanopillar layers in a reasonable agreement with theoretical calculations. A decreasing thickness of the ZnO nanopillar layer was evidenced with the increasing ion implantation fluences. Spectroscopic Ellipsometry (SE) showed a decrease of refractive index in the nanopillar parts with embedded Au, Ag-ions. XRD discovered vertical domain size decreasing with the proceeding radiation damage accumulated in ZnO nanopillars which effect was preferably ascribed to Au-ions. SE and diffuse reflectance spectroscopy (DRS) showed optical activity of the created nanoparticles at wavelength range 500 – 600 nm and 430 – 700 nm for the Au-implanted and Au, Ag-implanted ZnO nanopillars, respectively. Photoluminescence (PL) features linked to ZnO deep level emission appear substantially enhanced due to plasmonic interaction with metal nanoparticles created by Ag, Au-implantation. Photocatalytic activity seems to be more influenced by the nanoparticles presented in the layer rather than the surface morphology. Dual implantation with Ag, Au-ions enhanced optical activity to a larger extent without significant morphology deterioration as compared to the solely Au-ion implanted nanopillars.

Perspectives in Quantum Coupling, Interferences, and Enhanced Properties on Graphene Derivatives

Background: Highly conjugated carbon-based molecules and nanostructures could show interesting quantum properties for different developments. Quantum emission, encryption, and participation in signal transmissions could contribute to new quantum and nanotechnology. Methods: Quantum properties were analyzed from experimental data recorded with different optical setup configurations and appropriate lasers. The data discussed were correlated and compared with calculations. Results: In this review, we discuss the quantum properties of graphene and its derivatives produced by their high electronic densities from highly organized carbon-based structures. We also evaluate their coupling properties by combining other nanomaterial sources with atomic compositions that generate different energy levels of quantized states. Quantum emissions, pseudoelectromagnetic field interactions, quantum interferences in Fermi and Landau levels, conduction bands, plasmonic interactions, opto-electronics, electron conductions, and transference implications are also analyzed. Conclusion: The coupling of quantum properties formed from the sub-atomic level towards the transference and transduction to larger scales beyond the nano- and microscale was reviewed. We refer to the future perspectives of the phenomena discussed and their potential applications.

Fiber-Based Surface Plasmon Resonance Biosensor for Leptospira DNA Detection

Fiber-based surface plasmon resonance (SPR) sensors are the ideal configuration for rapid and label-free biomolecule detection. Gold-coated tapered optical fiber was used to excite the SPR mode that propagates at the metal–dielectric interface. By forming self-assembled monolayers (SAMs) of active chemical functional groups, the deoxyribonucleic acid (DNA) probe targeting the secY gene of Leptospira was immobilized onto the sensor surface. Red shifts in the SPR wavelengths were observed at different concentrations of leptospiral DNA target against the immobilized DNA probe due to the ability of plasmonic interaction to sensitively detect the binding of biomolecules on the sensor area. The developed sensor showed satisfactory linear responses at two target concentration ranges; low (1.0 fM to 1.0 pM) and high (0.1 nM to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.0~\mu \text{M}$ </tex-math></inline-formula> ), with the highest sensitivity of 1.22 nm per log M. The negative control test also revealed high sensor specificity toward the complementary DNA strand. This sensor will represent a significant step toward laboratory-free diagnosis of leptospirosis.

In‐situ Integrated Plasmonic TiN@ZIF‐67 Composites for the Photoreduction of CO2into Solar Fuels: Insights into their Plasmonic Interaction and Mechanism

AbstractPlasmonic materials (PMs) essentially equip the photocatalysts to harvest energy from visible light photons. Interestingly, these PMs also support the photocatalysts, which has been realized upon the advent of non‐noble metals‐based PMs. In this context, this study reveals an interesting feature of TiN@ZIF‐67 plasmonic composite photocatalysts towards CO2reduction under solar irradiation. The composite is prepared via anin‐situand direct integration process, where the plasmonic TiN nanoparticles are surface‐modified using 3‐aminopropyl‐triethoxysilane/H‐Imidazole‐2‐carbaldehyde in the former and polyvinylpyrrolidone in the latter process to construct the 1H2ImCHO‐TiN@ZIF‐67 and TiN/PVP@ZIF‐67 composites, respectively. The structural and functional properties in these composites are confirmed using XRD and FTIR spectroscopy techniques. It is observed from the TEM images that the in‐situ integration leads to deep‐surface attachments of TiN on ZIF‐67, which exerted a major impact in the CO2photoreduction. The 1H2ImCHO‐TiN@ZIF‐67 shows the simultaneous production of ∼0.11 and 0.15 mmol g−1 h−1of methanol and ethanol, respectively; whereas, the TiN/PVP@ZIF‐67 produces only ∼0.31 mmol g−1h−1of methanol. The obtained results demonstrate that developed in‐situ synthetic approach is promising for the synthesis of efficient plasmonic photocatalysts and the product formation during CO2photoreduction can be dependent on how PMs are integrated with the host photocatalysts.

Materials Perspectives of Integrated Plasmonic Biosensors

With the growing need for portable, compact, low-cost, and efficient biosensors, plasmonic materials hold the promise to meet this need owing to their label-free sensitivity and deep light–matter interaction that can go beyond the diffraction limit of light. In this review, we shed light on the main physical aspects of plasmonic interactions, highlight mainstream and future plasmonic materials including their merits and shortcomings, describe the backbone substrates for building plasmonic biosensors, and conclude with a brief discussion of the factors affecting plasmonic biosensing mechanisms. To do so, we first observe that 2D materials such as graphene and transition metal dichalcogenides play a major role in enhancing the sensitivity of nanoparticle-based plasmonic biosensors. Then, we identify that titanium nitride is a promising candidate for integrated applications with performance comparable to that of gold. Our study highlights the emerging role of polymer substrates in the design of future wearable and point-of-care devices. Finally, we summarize some technical and economic challenges that should be addressed for the mass adoption of plasmonic biosensors. We believe this review will be a guide in advancing the implementation of plasmonics-based integrated biosensors.

Far-field sub-diffraction optical imaging using near-field illumination by optoplasmonic hybrid materials

Here, we propose a method to fabricate large-scale optoplasmonic hybrid materials (OHMs) as a near-field illumination source for sub-diffraction imaging through a traditional optical microscope. An OHM is comprised of a metal/dielectric multilayer coated substrate and a microcylinder (MC) placed on top of the multilayer. Under the dark-field illumination of a traditional optical microscope, the photonic nanojet (PNJ) generated by the MC and the electric field produced on the substrate surface by the photonic–plasmonic interaction work as the near-field illumination source for an object placed on the substrate near the PNJ. High spatial frequencies of the object can be shifted to the passband of the optical microscope and weak scattering signals of the object can be enhanced upon the near-field illumination. Low-contrast objects, such as a 300-nm-diameter SiO2 nanoparticle array, two 100-nm-diameter polystyrene nanoparticles spaced ∼86 nm apart, and Escherichia coli can be resolved using the optical microscope. In addition, the field of view (FOV) is rectangular, the length of the FOV depends on the length of the MC, and the width relates to the diameter of the MC. The proposed method is wide-field, label-free, direct, noninvasive, and far-field, and it presents the potential of super-resolution imaging of unlabeled biological samples using a traditional optical microscope.

Investigation into Micro-Polishing Photonic Crystal Fibers for Surface Plasmon Resonance Sensing

In this work, we propose and demonstrate a micro-polishing-fiber (MPF)-based surface plasmon resonance (SPR) sensor. The structure of the sensor is simple and consists of three layers of regular air holes and two small air holes. The sensitivity seldom depends on the sizes of the air holes, which leads to a sensor with high structure tolerance. A tiny polishing depth ensures the mechanical strength of the polished fiber. There are three decisive factors for mass production and application of the sensor. A thin layer of indium tin oxide (ITO) film is applied to the polished surface to excite plasmonic interactions and facilitate refractive index (RI) detection. The SPR sensor is designed and analyzed by the finite element method (FEM), and optimized in terms of the air holes’ diameter, the ITO film thickness, and the core-to-surface interval. In the wide detection range between 1.32 and 1.39, the wavelength sensitivity can reach up to 11,600 nm/RIU. The MPF–SPR sensor exhibits great potential in the fields of optics, biomedicine, and chemistry.

Optical spectra of bilayer borophene synthesized on Ag(1 1 1) film

In this paper, we theoretically investigated electronic structures, density of states (DOS), optical absorption, dielectric function of bilayer borophene synthesized on Ag(111) film, stimulated by the recent experimental report [Nature materials 2022, 21:35]. The results show that there is strong coupling between the Ag film and borophene layers. In the absorption spectra of BL borophene on Ag(111) substrate, there are strong absorption peaks in visible and infrared (IR) regions, which reveals strong plexciton peaks in visible and IR regions, which is contributed from the plasmonic and excitonic coupling interaction by the hybrid between Ag film and BL borophene. Raman modes of strongest vibration directly reflects the interlayer interaction of interlayer chemical bond. Our results not only provide physical insight into BL borophene synthesized on Ag(111) film, but also propose the potential applications of BL borophene in optoelectronic devices.

Femtosecond Laser Direct‐Write Plasmonic Nanolithography in Dielectrics

Plasmon‐based devices have founded numerous applications in photonics based on optically excited strong near‐field effect at nanoscale. So far, the large‐area fabrication of periodic plasmonic nanostructures is still challenging due to a small write‐field limitation of lithography‐based techniques, especially for metallic substrates. A novel strategy is proposed to fabricate millimeter‐sized patterns of periodic plasmonic nanostructures inside dielectric materials (glass) through a femtosecond laser direct‐write plasmonic nanolithography approach. Noble metal nanoparticles are formed by the ion implantation in glass and reshaped into a nanowire‐like nanoparticles’ assembly by direct writing with femtosecond laser harnessing plasmonic interaction. As‐designed patterns at nanoscale are inscribed by this type of plasmonic lithography to form wires composed of nanoparticles. Examples for applications, the linear dichroism response, and structural color have been achieved by the plasmonic nanogratings buried inside glass (i.e., at subsurface regions). The work opens a new avenue to manipulate metallic nanoparticles in solids by direct plasmonic nanolithography and offers a reliable implementation of large‐area fabrication of plasmonic nanostructures for diverse range of photonic applications.

Electron emission from plasmonically induced Floquet bands at metal surfaces

We explore the possibility of the existence of plasmonically generated electronic Floquet bands at metal surfaces by studying the gauge transformed electron-surface plasmon interaction in the prepumped plasmonic coherent state environment. These bands may promote non-Einsteinian electron emission from metal surfaces exposed to primary interactions with strong electromagnetic fields. Resonant behavior and scaling of emission yield with the parent electronic structure and plasmonic state parameters are estimated for Ag(111) surface. The obtained relative yield intensities from non-Einsteinian emission channels in photoelectron spectra offer the means to calibrate the mediating plasmonic fields and the therefrom ensuing surface Floquet bands.

Modulation of Casimir Force between Graphene-Covered Hyperbolic Materials.

A flexible method for modulating the Casimir force is proposed by combining graphene and hyperbolic materials (HMs). The proposed structure employs two candidates other than graphene. One is hexagonal boron nitride (hBN), a natural HM. The other is porous silicon carbide (SiC), which can be treated as an artificial HM by the effective medium theory. The Casimir force between graphene-covered hBN (porous SiC) bulks is presented at zero temperature. The results show that covering HM with graphene increases the Casimir force monotonically. Furthermore, the force can be modulated by varying the Fermi level, especially at large separation distances. The reflection coefficients are thoroughly investigated, and the enhancement is attributed to the interaction of surface plasmons (SPs) supported by graphene and hyperbolic phonon polaritons (HPhPs) supported by HMs. Moreover, the Casimir force can be controlled by the filling factor of porous SiC. The Casimir force can thus be modulated flexibly by designing desired artificial HMs and tuning the Fermi level. The proposed models have promising applications in practical detection and technological fields.

Plasmonic interactions at the Pb/SeO2 interfaces designed as terahertz/gigahertz optical receivers

Herein semitransparent lead substrates of thicknesses of 200 nm are employed as plasmonic interfaces to enhance the optoelectronic performance of SeO2 thin films. Pb/SeO2 interfaces are fabricated by the physical vapor deposition technique under a vacuum pressure of 10-5 mbar. The structural analyses showed that Pb substrates can induce the evolution of tetragonal phase of selenium oxide. The phase comprises 1.27% cubic PbSe in its structure. Surface morphology studies show that Pb substrates prefer formation of grains of sizes of 250 nm resulting from the accumulation of lead crystallites of sizes of 37 nm. Optically, Pb substrates increased the light absorbability in the visible range of light without altering the value of the energy band gap, improved the dielectric response by 4% at 1.15 eV and by 40% at 1.87 eV. In addition, Durde-Lorentz modeling of the optical conductivity spectra of SeO2 has shown that Pb plasmonic resonators increase the plasmon frequency and free carrier density of Pb/SeO2 interfaces allowing it reaching 5 G/6 G technology needs. Moreover, evaluation of the terahertz cutoff frequency spectra indicated the applicability of the Pb/SeO2 as optical receivers responsive to infrared, visible and ultraviolet bands of light at terahertz cutoff frequency values of 17–160 THz. Furthermore, the capacitance and conductance spectral studies in the frequency domain of 0.01–1.80 GHz indicated the suitability of Pb/SeO2/C devices as negative conductance sources beneficial for signal amplification in the microwave frequency domain.

Investigation of Plasmonic-Enhanced Solar Photothermal Effect of Au NR@PVDF Micro-/Nanofilms.

Gold nanospheres (Au NSs) and gold nanorods (Au NRs) are traditional noble metal plasmonic nanomaterials. Particularly, Au NRs with tunable longitudinal plasmon resonance from the visible to the near-infrared (NIR) range were suitable for highly efficient photothermal applications due to the extended light-receiving range. In this work, we synthesized Au NRs and Au NSs of similar volumes and subsequently developed them into Au NR/poly(vinylidene fluoride) (PVDF) and Au NS/PVDF nanofilms, both of which exhibited excellent solar photothermal performance evaluated by solar photothermal experiments. We found that the Au NR/PVDF nanofilm showed a higher solar photothermal performance than the Au NS/PVDF nanofilm. Through detailed analysis, such as morphological characterization, optical measurement, and finite element method (FEM) modeling, we found that the plasmonic coupling effects inside the aggregated Au NR nanoclusters contributed to the spectral blue shifts and intensified the photothermal performance. As compared to Au NS/PVDF nanofilms, the Au NR/PVDF nanofilm exhibited a higher efficient light-to-heat conversion rate because of the extended light-receiving range and high absorbance, as a result of the strong plasmonic interactions inside nanoclusters, which was further validated by monochromatic laser photothermal experiments and FEM simulations. Our work proved that the Au NRs have huge potential for plasmonic solar photothermal applications and are envisioned for novel plasmonic applications.

Machine Learning Approach for Application-Tailored Nanolubricants' Design.

The fascinating tribological phenomenon of carbon nanotubes (CNTs) observed at the nanoscale was confirmed in our numerous macroscale experiments. We designed and employed CNT-containing nanolubricants strictly for polymer lubrication. In this paper, we present the experiment characterising how the CNT structure determines its lubricity on various types of polymers. There is a complex correlation between the microscopic and spectral properties of CNTs and the tribological parameters of the resulting lubricants. This confirms indirectly that the nature of the tribological mechanisms driven by the variety of CNT–polymer interactions might be far more complex than ever described before. We propose plasmonic interactions as an extension for existing models describing the tribological roles of nanomaterials. In the absence of quantitative microscopic calculations of tribological parameters, phenomenological strategies must be employed. One of the most powerful emerging numerical methods is machine learning (ML). Here, we propose to use this technique, in combination with molecular and supramolecular recognition, to understand the morphology and macro-assembly processing strategies for the targeted design of superlubricants.

Cost-Effective Bull's Eye Aperture-Style Multi-Band Metamaterial Absorber at Sub-THz Band: Design, Numerical Analysis, and Physical Interpretation.

Theoretical and numerical studies were conducted on plasmonic interactions at a polarization-independent semiconductor–dielectric–semiconductor (SDS) sandwiched layer design and a brief review of the basic theory model was presented. The potential of bull’s eye aperture (BEA) structures as device elements has been well recognized in multi-band structures. In addition, the sub-terahertz (THz) band (below 1 THz frequency regime) is utilized in communications and sensing applications, which are in high demand in modern technology. Therefore, we produced theoretical and numerical studies for a THz-absorbing-metasurface BEA-style design, with N-beam absorption peaks at a sub-THz band, using economical and commercially accessible materials, which have a low cost and an easy fabrication process. Furthermore, we applied the Drude model for the dielectric function of semiconductors due to its ability to describe both free-electron and bound systems simultaneously. Associated with metasurface research and applications, it is essential to facilitate metasurface designs to be of the utmost flexible properties with low cost. Through the aid of electromagnetic (EM) coupling using multiple semiconductor ring resonators (RRs), we could tune the number of absorption peaks between the 0.1 and 1.0 THz frequency regime. By increasing the number of semiconductor rings without altering all other parameters, we found a translation trend of the absorption frequencies. In addition, we validated our spectral response results using EM field distributions and surface currents. Here, we mainly discuss the source of the N-band THz absorber and the underlying physics of the multi-beam absorber designed structures. The proposed microstructure has ultra-high potentials to utilize in high-power THz sources and optical biomedical sensing and detection applications based on opto-electronics technology based on having multi-band absorption responses.

Improving Photostability of Photosystem I-Based Nanodevice by Plasmonic Interactions with Planar Silver Nanostructures.

One of the crucial challenges for science is the development of alternative pollution-free and renewable energy sources. One of the most promising inexhaustible sources of energy is solar energy, and in this field, solar fuel cells employing naturally evolved solar energy converting biocomplexes—photosynthetic reaction centers, such as photosystem I—are of growing interest due to their highly efficient photo-powered operation, resulting in the production of chemical potential, enabling synthesis of simple fuels. However, application of the biomolecules in such a context is strongly limited by the progressing photobleaching thereof during illumination. In the current work, we investigated the excitation wavelength dependence of the photosystem I photodamage dynamics. Moreover, we aimed to correlate the PSI–LHCI photostability dependence on the excitation wavelength with significant (ca. 50-fold) plasmonic enhancement of fluorescence due to the utilization of planar metallic nanostructure as a substrate. Finally, we present a rational approach for the significant improvement in the photostability of PSI in anoxic conditions. We find that photobleaching rates for 5 min long blue excitation are reduced from nearly 100% to 20% and 70% for substrates of bare glass and plasmonically active substrate, respectively. Our results pave promising ways for optimization of the biomimetic solar fuel cells due to synergy of the plasmon-induced absorption enhancement together with improved photostability of the molecular machinery of the solar-to-fuel conversion.

Boosting Cycling Stability and Rate Capability of Li–CO2Batteries via Synergistic Photoelectric Effect and Plasmonic Interaction

AbstractSluggish CO2reduction/evolution kinetics at cathodes seriously impede the realistic applications of Li–CO2batteries. Herein, synergistic photoelectric effect and plasmonic interaction are introduced to accelerate CO2reduction/evolution reactions by designing a silver nanoparticle‐decorated titanium dioxide nanotube array cathode. The incident light excites energetic photoelectrons/holes in titanium dioxide to overcome reaction barriers, and induces the intensified electric field around silver nanoparticles to enable effective separation/transfer of photogenerated carriers and a thermodynamically favorable reaction pathway. The resulting Li–CO2battery demonstrates ultra‐low charge voltage of 2.86 V at 0.10 mA cm−2, good cycling stability with 86.9 % round‐trip efficiency after 100 cycles, and high rate capability at 2.0 mA cm−2. This work offers guidance on rational cathode design for advanced Li–CO2batteries and beyond.

Boosting Cycling Stability and Rate Capability of Li-CO2 Batteries via Synergistic Photoelectric Effect and Plasmonic Interaction.

Sluggish CO2 reduction/evolution kinetics at cathodes seriously impede the realistic applications of Li-CO2 batteries. Herein, synergistic photoelectric effect and plasmonic interaction are introduced to accelerate CO2 reduction/evolution reactions by designing a silver nanoparticle-decorated titanium dioxide nanotube array cathode. The incident light excites energetic photoelectrons/holes in titanium dioxide to overcome reaction barriers, and induces the intensified electric field around silver nanoparticles to enable effective separation/transfer of photogenerated carriers and a thermodynamically favorable reaction pathway. The resulting Li-CO2 battery demonstrates ultra-low charge voltage of 2.86 V at 0.10 mA cm-2 , good cycling stability with 86.9 % round-trip efficiency after 100 cycles, and high rate capability at 2.0 mA cm-2 . This work offers guidance on rational cathode design for advanced Li-CO2 batteries and beyond.

Plasmonic Superlattice Membranes Based on Bimetallic Nano-Sea Urchins as High-Performance Label-Free Surface-Enhanced Raman Spectroscopy Platforms.

On the basis of an abundance of elemental plasmonic nanocrystals identifiable by their unique morphology and intrinsic optoelectronic properties, it is necessary to rationally tailor the structural parameters to optimize the functionalities of nanoassemblies for application as plasmonic circuits/devices. Among them, the plasmonic superlattice membrane has emerged as a novel optically active metamaterial, which is constructed by nanocrystals at a two-dimensional (2D) plane with a highly ordered structure and strong plasmonic coupling interactions. Here, we report on the fabrication of a novel plasmonic superlattice membrane using bimetallic core-shell nano-sea urchins (Nano-SEUs) as meta-atoms. Under the guidance of soft-ligand balancing in conjugation with drying-mediated self-assembly at the air/water interface, well-defined giant 2D superlattices with total lateral dimensions of up to 5 mm wide and 80 nm thick have been synthesized, corresponding to an aspect ratio of 62 500. Programmable morphology control over the Nano-SEUs has been achieved in high yield by rationally tuning the spiky branches as well as the thickness of the silver shell, allowing systematic variation of the plasmonic properties of the membrane. Such superlattice membranes exhibited a strong and reproducible surface-enhanced Raman spectroscopy (SERS) signal that originates from interparticle coupling and electric (E)-field enhancement, enabling an enhancement factor of up to 106. We also demonstrated that the fabricated membrane allows the label-free SERS detection of dopamine from 0.1 nM to 1 μM. Thus, this giant Nano-SEU assembled superlattice membrane can be used as a SERS substrate for on-spot biomarker detection, which paves a robust and inexpensive avenue for highly sensitive and reliable biomedical sensing and diagnostics.

Design considerations of gold nanoantenna dimers for plasmomechanical transduction.

Internal optical forces emerging from plasmonic interactions in gold nanodisc, nanocube and nanobar dimers were studied by the finite element method. A direct correlation between the electric-field enhancement and optical forces was found by observing the largest magnitude of optical forces in nanocube dimers. Moreover, further amplification of optical forces was achieved by employing optical power of the excitation source. The strength of optical forces was observed to be governed by the magnitude of polarisation density on the nanoparticles, which can be varied by modifying the nanoparticle geometry and source wavelength. This study allows us to recognise that nanoparticle geometry along with the inter-dimer distance are the most prominent design considerations for optimising optical forces in plasmonic dimers. The findings facilitate the realisation of all-optical modulation in a plasmomechanical nanopillar system, which has promising applications in ultra-sensitive nanomechanical sensing and building reconfigurable metamaterials.