Intrinsic Plasmon Research Articles

Ferroelectric Superdomain Controlled Graphene Plasmon for Tunable Mid-Infrared Photodetector with Dual-Band Spectral Selectivity

Dual-band infrared photodetectors (DBIPs) can discriminate desired signals from complex scenes and thus are highly expected for threat-warning, remote sensing, and astronomy applications. Conventional DBIPs with high-performances are, however, typically based on semiconductor thin films, but remain the challenges of complex spatial align, expensive growth and cooling requirement. Here, we report a tunable graphene plasmonic photodetector with dual-band infrared spectral selectivity driven by ferroelectric superdomain. The periodic ferroelectric polarization array with nanoscale ring shapes provides ultrahigh electrostatic field for spatially doping of monolayer graphene to desired patterns, and is further used to excite and confine intrinsic graphene plasmons. Our devices exhibit tunable resonance photoresponse in both two bands of 3.7-16.3 um and 15.1-52.1 um. The numerical calculations show that our devices own ultrahigh responsivities of 667-1080 A W-1 at room temperature in range of 5-50 um. Our devices make possible the applications of infrared imaging system and both stationary and motion state of objects detection. These investigations provide a novel approach for advanced infrared system construction by employing simple, low-cost, uncooling multispectral detectors array.

Operando Studies of the Electrochemical Dissolution of Silver Nanoparticles in Nitrate Solutions Observed With Hyperspectral Dark-Field Microscopy.

Since nanoparticles are frequently used in commercial applications, there is a huge demand to obtain deeper insights into processes at the nanoscale. Especially, catalysis, chemical and electrochemical reaction dynamics are still poorly understood. Thus, simultaneous and coupled opto-and spectro-electrochemical dark-field microscopy is used to study in situ and operando the electrochemically driven dissolution mechanism of single silver nanoparticles in the presence of nitrate ions as non-complexing counter-ions, herein. Hyperspectral imaging is used to probe the intrinsic localized surface plasmon resonance of individual silver nanospheres before, during and after their electrochemical oxidation on a transparent indium tin oxide (ITO) electrode. Furthermore, optical video imaging was performed for additional information. Based on the complete loss of spectral information and intensity, a dissolution of the particles during the reaction was concluded. This way it is revealed that the dissolution of individual particles proceeds over several seconds, indicating a hindrance by the nitrate ions. Only electrochemical analysis does not provide this insight as the measured current does not allow distinguishing between successive fast dissolution of one particle after another or slow dissolution of several particles in a concerted manner. For comparison, experiments were performed in the presence of chloride ions. It was observed that the silver chloride formation is an instantaneous process. Thus, it is possible to study and define the reaction dynamics on the single nanoparticle level in various electrochemical systems and electrolyte solutions. Accordingly, operando opto- and spectro-electrochemical studies allow us to conclude, that the oxidation of silver to solvated silver cations is a kinetically slow process, while the oxidation to silver chloride is fast. We propose this approach as a new method to study electrocatalyst materials, their transformation and degradation under operando conditions.

Plasmonically enabled two-dimensional material-based optoelectronic devices.

Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, black phosphorus and hexagonal boron nitride, have been intensively investigated as building blocks for optoelectronic devices in the past few years. Very recently, significant efforts have been devoted to the improvement of the optoelectronic performances of 2D materials, which are restricted by their intrinsically low light absorption due to the ultrathin thickness. Making use of the plasmonic effects of metal nanostructures and intrinsic plasmon excitation in graphene has been shown to be one of the promising strategies. In this minireview, recent progress in 2D material-based optoelectronics enabled by the plasmonic effects is highlighted. A perspective on more possibilities in plasmon-assisted 2D material-based optoelectronic applications will also be provided.

Nanoplasmonic Light Trapping Metascreen Encompassing Spectrally Dense Region of Solar Spectrum

An energy efficient nanoplasmonic metascreen is tailored to support near perfect absorption of sunlight around visible frequency range. To efficiently tap sunlight source, the metascreen is designed to perfectly absorb a spectrally dense region of solar spectrum. The absorption efficiency depends upon the choice of plasmonic material and optical thickness of the dielectric substrate between the metascreen and ground reflector. Alternative plasmonic materials including copper and aluminum are evaluated for their absorption characteristics, and their performance is compared to that of conventional gold and silver. Intrinsic surface plasmon resonance damping in copper-based metascreen platform is ideally suited to absorb an overall 72% of solar spectral irradiance between 400 and 1800 nm wavelength. The proposed polarization independent metascreen absorber can efficiently trap light to improve overall efficiency of solar cell.

Dual‐Electromagnetic Field Enhancements through Suspended Metal/Dielectric/Metal Nanostructures and Plastic Phthalates Detection in Child Urine

AbstractPlasmonic nanostructures exhibit intriguing optical properties due to spectrally selective plasmon resonance and thus have broad applications, including biochemical sensing and photoelectric detections. However, excited plasmons are often strongly influenced by the substrates supporting the metallic nanostructures, which not only weakens the intrinsic plasmon coupling effect, but also results in a great reduction of optical near‐field enhancement. Here, a plasmonic nanostructure combining collapsible Au‐nanofingers with selective‐etching that enables Au to be suspended is demonstrated, thus avoiding the undesirable influence of the substrates on the local near‐field distribution and forming symmetric electromagnetic‐field enhancements at both the top and bottom surfaces. The polymer support of the Au‐nanofingers is selectively etched by oxygen plasma, while the Au‐cap retains its original size. After an ultrathin dielectric coating is applied on the Au‐nanofingers, suspended Au‐caps with extremely small dielectric gaps are formed via the collapse of neighboring Au‐nanofingers by exposing them to ethanol. These nanostructures can provide a surface‐enhanced Raman scattering (SERS) enhancement of up to ≈109, which is nearly twice that in the nonsuspended system. As a highly active SERS substrate, the label‐free detection of low‐concentration harmful plastic phthalates in a child's urine without any pretreatment is successfully demonstrated, which suggests that this method is suitable for medical prediagnosis.

Optical and electronic properties of high quality Sb-doped SnO2 thin films grown by mist chemical vapor deposition

Transparent Sb-doped epitaxial SnO2 (101) thin films were grown via mist chemical vapor deposition, a nonvacuum solution-based technique that involves the gas-assisted transport of ultrasonically-generated aerosols from simple aqueous Sn and Sb precursors. The electrical properties (at 300 K) of the resulting films could be varied from insulating to semimetallic via Sb doping, with a minimum resistivity of 8×10−4Ωcm, carrier concentrations up to 3.93×1020cm−3, and a maximum mobility of 48.1±0.1cm2V−1s−1, results similar to those achieved using molecular beam epitaxy and other more-sophisticated high vacuum techniques. Secondary ion mass spectrometry and Hall effect measurements revealed that 14% of Sb in the precursor solution incorporates into the Sb:SnO2 films, with almost all the Sb atoms forming shallow substitutional donors on the Sn-site. The increase in the carrier concentration with Sb doping produced a Burstein-Moss shift of the optical gap of 0.49 eV, without significantly reducing the more than 90% transparency of the films in the visible region. X-ray photoemission spectroscopy (hν=1486.6eV) showed an asymmetric Sn3d5/2 core-level emission characterized by a carrier concentration-dependent peak splitting. This effect was modeled in terms of the creation of an intrinsic plasmon loss satellite from which a conductivity effective electron mass of (0.49±0.11)me was determined.

Utilizing niobium plasmonic perfect absorbers for tunable near- and mid-IR photodetection.

With the fast development of single photon-based technologies such as quantum computing and quantum cryptography, conventional avalanche photodiodes as single photon detectors are not the optimum tools anymore. They are currently replaced by Superconducting Nanowire Single Photon Detectors (SNSPDs) based on the superconducting to normal conducting phase transition. The current challenge with SNSPDs lies in overcoming the trade-off between detection efficiency and recovery time. While a large active area will lead to high detection efficiency, the associated high kinetic inductance causes a long recovery time. Plasmonic effects can play an important role in the absorption enhancement of SNSPDs. Nanostructuring with a suitable geometry can provide a high-absorption cross-section at the intrinsic nanowire surface plasmon resonance, which can be significantly larger than their geometric cross-section. We present a photodetector based on the intrinsic localized surface plasmon resonance of a niobium nanowire, which is one of the common superconductors with low kinetic inductance. Additionally, we are increasing the absorption of our nanostructures even further using a plasmonic perfect absorber scheme. We fabricated a plasmonic perfect absorber superconducting photodetector, investigated its response to external light at resonance, and proved its plasmonic behavior as evidenced by its polarization dependence.

A new insight into Au/TiO2-catalyzed hydrogen production from water-methanol mixture using lamps containing simultaneous ultraviolet and visible radiation

Different amounts of Au NPs were deposited on a modified-TiO2 using the deposition-precipitation method with urea and used for hydrogen production via water splitting at room temperature and atmospheric pressure. Methanol and simultaneous UV and visible radiation were used as sacrificial reagent and excitation sources, respectively. Both modified-support and photocatalysts were characterized by XRD, HRTEM or STEM-HAADF, FE-SEM-EDS, N2 physisorption and UV–vis DRS. The emission spectra of the excitation sources were also obtained by spectrofluorometry. XRD, HRTEM and UV–vis DRS results showed that TiO2 anatase was the predominant crystalline phase, with a relative high specific surface area. STEM-HAADF and FE-SEM-EDS techniques revealed that the average Au NPs size was increased with Au loading from 3.2 to 14.9 nm and that the estimated Au contents were close to the expected theoretical values. On the other hand, the photo-generated hydrogen was significantly increased with Au NPs incorporation and it could be associated to a slightly decrease of the energy band gap and the intrinsic localized surface plasmon resonance that can suppress the high rate of electron-hole pair recombination. The photocatalytic performance also depended on multiples experimental factors, such as: stirring speed, amount and size of Au NPs, as well as the radiation source. The highest hydrogen production rate (2336 μmol-H2/gcat⋅h) was obtained using the Au/TiO2 photocatalyst with 0.5 wt% Au, a stirring speed of 800 rpm and purple lamp (13 W) simultaneously emitting UV (52%) and visible (48%) radiation.

Enhancement of the Electron–Phonon Scattering Induced by Intrinsic Surface Plasmon–Phonon Polaritons

We investigate light-matter coupling in metallic crystals where plasmons coexist with phonons exhibiting large oscillator strength. We demonstrate theoretically that this coexistence can lead to strong light-matter interactions without external resonators. When the frequencies of plasmons and phonons are comparable, hybridization of these collective matter modes occurs in the crystal. We show that the coupling of these modes to photonic degrees of freedom gives rise to intrinsic surface plasmon-phonon polaritons, which offer the unique possibility to control the phonon properties by tuning the electron density and the crystal thickness. In particular, dressed phonons with reduced frequency and large wave vectors arise in the case of quasi-2D crystals, which leads to large enhancements of the electron-phonon scattering in the vibrational ultrastrong coupling regime. This suggests that photons can play a key role in determining the quantum properties of certain materials. A non-perturbative self-consistent Hamiltonian method is presented that is valid for arbitrarily large coupling strengths.

New Family of Plasmonic Photocatalysts without Noble Metals

Efficient photocatalysis is important for sustainable energy. Recently, an unconventional photocatalyst based on intrinsic plasmon, called intrinsic plasmonic photocatalyst (IPP), seems promising f...

Realization of mid-infrared broadband absorption in monolayer graphene based on strong coupling between graphene nanoribbons and metal tapered grooves

In this paper, we theoretically propose an effective broadband absorption architecture in mid-infrared region based on strong coupling between the plasmonic resonance of graphene nanoribbons and the waveguide mode of a metal tapered groove. The special architecture facilitates two new hybrid modes splitting with very strong energy distribution on graphene ribbon, which results in the broadband absorption effect. To well explain these numerical results, an analytical dispersion relation of waveguide mode is obtained based on the classical LC circuit model. The fluctuating range of absorption passband is investigated by adjusting the filled medium inside of the grooves. Leveraging the concept and method, a broadband flat-top (bandwidth ≈2.5 µm) absorption with absorption rate over 60% is demonstrated. Such a design not only enhances the intrinsic weak plasmons resonance in mid-infrared spectral region, but also reduces the absorption fluctuations caused by coupling, which are the key features for developing next-generation mid-infrared broadband optical devices.

Effect of dielectric environment on plasmonic resonance absorption of graphene nanoribbon arrays

The plasmonic resonance absorption properties of a periodic graphene nanoribbon array are studied in this paper. We discuss the effect of the asymmetricity of the dielectric environment on the plasmonic resonance of the graphene nanoribbon array in order to know which combination of the two dielectric materials surrounding the graphene is most advantageous. The results show that, regardless of the graphene in symmetric and asymmetrical environments, the absorption peak of plasmon resonance shifts to longer wavelengths (shifts red) with the increase of the changing permittivity (permittivities) on one or both sides. This absorption characteristic of the graphene periodic array to external electromagnetic waves originates from the wavelength dependence of the intrinsic graphene plasmons on the environmental medium.

Ultra-long wavelength Dirac plasmons in graphene capacitors

Graphene is a valuable 2D platform for plasmonics as illustrated in recent THz and mid-infrared optics experiments. These high-energy plasmons however, couple to the dielectric surface modes giving rise to hybrid plasmon-polariton excitations. Ultra-long wavelengths address the low energy end of the plasmon spectrum, in the GHz–THz electronic domain, where intrinsic graphene Dirac plasmons are essentially decoupled from their environment. However experiments are elusive due to the damping by ohmic losses at low frequencies. We demonstrate here a plasma resonance capacitor (PRC) using hexagonal boron-nitride (hBN) encapsulated graphene at cryogenic temperatures in the near-ballistic regime. We report on a 100 μm quarter-wave plasmon mode, at 40 GHz, with a quality factor Q ≃ 2. The accuracy of the resonant technique yields a precise determination of the electronic compressibility and kinetic inductance, allowing to assess residual deviations from intrinsic Dirac plasmonics. Our GHz frequency capacitor experiment constitutes a first step towards the demonstration of plasma resonance transistors for microwave detection in the sub-THz domain for wireless communication and sensing. It also paves the way to the realization of doping-modulated superlattices where plasmon propagation is controlled by Klein tunneling.

Mapping lattice-induced plasmon modes in metallic nanoantenna arrays using fluorescence decay of semiconductor quantum dot bioconjugates

We use the fluorescence decay of quantum dot bioconjugates and their size distribution as near field probes to investigate lattice-induced plasmonic resonances and their interaction with excitons. The quantum dots are biologically immobilized on gold nanoantenna arrays while their spontaneous emission decay rates are spectrally resolved. Our results show that the periodic arrangement of the nanoantennas can generate or optically activate certain plasmonic resonances, different from their intrinsic plasmon modes. This includes formation of a hybrid photonic-plasmonic dipole mode that can strongly couple with the quantum dots, making their decay rates anisotropic and wavelength dependent. The anisotropic decay is decided by the shapes and sizes of the nanoantennas and by the direction of the quantum dot dipoles. The results suggest lattice-induced plasmonic resonances can be used as engineered states to drive transfer of energy between quantum dots at certain wavelengths.

Overexpressed HDAC8 in cervical cancer cells shows functional redundancy of tubulin deacetylation with HDAC6

BackgroundHistone deacetylases (HDACs) are involved in epigenetic gene regulation via deacetylation of acetylated lysine residues of both histone and non-histone proteins. Among the 18 HDACs identified in humans, HDAC8, a class I HDAC, is best understood structurally and enzymatically. However, its precise subcellular location, function in normal cellular physiology, its protein partners and substrates still remain elusive.MethodsThe subcellular localization of HDAC8 was studied using immunofluorescence and confocal imaging. The binding parterns were identified employing immunoprecipitation (IP) followed by MALDI-TOF analysis and confirmed using in-silico protein-protein interaction studies, HPLC-based in vitro deacetylation assay, intrinsic fluorescence spectrophotometric analysis, Circular dichroism (CD) and Surface Plasmon Resonance (SPR). Functional characterization of the binding was carried out using immunoblot and knockdown by siRNA. Using one way ANOVA statistical significance (n = 3) was determined.ResultsHere, we show that HDAC8 and its phosphorylated form (pHDAC8) localized predominantly in the cytoplasm in cancerous, HeLa, and non-cancerous (normal), HEK293T, cells, although nucleolar localization was observed in HeLa cells. The study identified Alpha tubulin as a novel interacting partner of HDAC8. Further, the results indicated binding and deacetylation of tubulin at ac-lys40 by HDAC8. Knockdown of HDAC8 by siRNA, inhibition of HDAC8 and/or HDAC6 by PCI-34051 and tubastatin respectively, cell-migration, cell morphology and cell cycle analysis clearly explained HDAC8 as tubulin deacetylase in HeLa cells and HDAC6 in HEK 293 T cells.ConclusionsHDAC8 shows functional redundancy with HDAC6 when overexpressed in cervical cancer cells, HeLa, and deacetylaes ac-lys40 of alpha tubulin leading to cervical cancer proliferation and progression.

Photoelectron Energy Loss in Al(002) Revisited: Retrieval of the Single Plasmon Loss Energy Distribution by a Fourier Transform Method

A Fourier transform (FT) algorithm is proposed to retrieve the energy loss function (ELF) of solid surfaces from experimental X-ray photoelectron spectra. The intensity measured over a broad energy range towards lower kinetic energies results from convolution of four spectral distributions: photoemission line shape, multiple plasmon loss probability, X-ray source line structure and Gaussian broadening of the photoelectron analyzer. The FT of the measured XPS spectrum, including the zero-loss peak and all inelastic scattering mechanisms, being a mathematical function of the respective FT of X-ray source, photoemission line shape, multiple plasmon loss function, and Gaussian broadening of the photoelectron analyzer, the proposed algorithm gives straightforward access to the bulk ELF and effective dielectric function of the solid, assuming identical ELF for intrinsic and extrinsic plasmon excitations. This method is applied to aluminum single crystal Al(002) where the photoemission line shape has been computed accurately beyond the Doniach–Sunjic approximation using the Mahan–Wertheim–Citrin approach which takes into account the density of states near the Fermi level; the only adjustable parameters are the singularity index and the broadening energy Г (inverse hole lifetime). After correction for surface plasmon excitations, the q-averaged bulk loss function, q , of Al(002) differs from the optical value Im[− 1 / e(E, q = 0)] and is well described by the Lindhard–Mermin dispersion relation. A quality criterion of the inversion algorithm is given by the capability of observing weak interband transitions close to the zero-loss peak, namely at 0.65 and 1.65 eV in e(E, q) as found in optical spectra and ab initio calculations of aluminum.

A peptide derived from enzymatic digestion of globulins from amaranth shows strong affinity binding to the replication origin of Tomato yellow leaf curl virus reducing viral replication in Nicotiana benthamiana

Tomato yellow leaf curl virus (TYLCV; genus Begomovirus; family Geminiviridae) infects mainly plants of the family Solanaceae, and the infection induces curling and chlorosis of leaves, dwarfing of the whole plant, and reduced fruit production. Alternatives for direct control of TYLCV and other geminiviruses have been reported, for example, the use of esterified whey proteins, peptide aptamer libraries or artificial zinc finger proteins. The two latter alternatives affect directly the replication of TYLCV as well as of other geminiviruses because the replication structures and sequences are highly conserved within this virus family. Because peptides and proteins offer a potential solution for virus replication control, in this study we show the isolation, biochemical characterization and antiviral activity of a peptide derived from globulins of amaranth seeds (Amaranthus hypochondriacus) that binds to the replication origin sequence (OriRep) of TYLCV and affects viral replication with a consequent reduction of disease symptoms in Nicotiana benthamiana. Aromatic peptides obtained from papain digests of extracted globulins and albumins of amaranth were tested by intrinsic fluorescent titration and localized surface resonance plasmon to analyze their binding affinity to OriRep of TYLCV. The peptide AmPep1 (molecular weight 2.076 KDa) showed the highest affinity value (Kd = 1.8 nM) for OriRep. This peptide shares a high amino acid similarity with a part of an amaranth 11S globulin, and the strong affinity of AmPep1 could be explained by the presence of tryptophan and lysine facilitating interaction with the secondary structure of OriRep. In order to evaluate the effect of the peptide on in vitro DNA synthesis, rolling circle amplification (RCA) was performed using as template DNA from plants infected with TYLCV or another begomovirus, pepper huasteco yellow vein virus (PHYVV), and adding AmPep1 peptide at different concentrations. The results showed a decrease in DNA synthesis of both viruses at increasing concentrations of AmPep1. To further confirm the antiviral activity of the peptide in vivo, AmPep1 was infiltrated into leaves of N. benthamiana plants previously infected with TYLCV. Plants treated with AmPep1 showed a significant decrease in virus titer compared with untreated N. benthamiana plants as well as reduced symptom progression due to the effect of AmPep1 curtailing TYLCV replication in the plant. The peptide also showed antiviral activity in plants infected with PHYVV. This is the first report, in which a peptide is directly used for DNA virus control in plants, supplied as exogenous application and without generation of transgenic lines.

Tunable Intrinsic Plasmons due to Band Inversion in Topological Materials.

Band inversion has led to rich physical effects in both topological insulators and topological semimetals. It has been found that the inverted band structure with the Mexican-hat dispersion could enhance the interband correlation leading to a strong intrinsic plasmon excitation. Its frequency ranges from several meV to tens of meV and can be effectively tuned by the external fields. The electron-hole asymmetric term splits the peak of the plasmon excitation into double peaks. The fate and properties of this plasmon excitation can also act as a probe to characterize the topological phases even in lightly doped systems. We numerically demonstrate the impact of band inversion on plasmon excitations in magnetically doped thin films of three-dimensional strong topological insulators, V- or Cr-doped (Bi,Sb)_{2}Te_{3}, which support the quantum anomalous Hall states. Our work thus sheds some new light on the potential applications of topological materials in plasmonics.

Intrinsic Plasmon-Phonon Interactions in Highly Doped Graphene: ANear-Field Imaging Study.

As a two-dimensional semimetal, graphene offers clear advantages for plasmonic applications over conventional metals, such as stronger optical field confinement, in situ tunability, and relatively low intrinsic losses. However, the operational frequencies at which plasmons can be excited in graphene are limited by the Fermi energy EF, which in practice can be controlled electrostatically only up to a few tenths of an electronvolt. Higher Fermi energies open the door to novel plasmonic devices with unprecedented capabilities, particularly at mid-infrared and shorter-wave infrared frequencies. In addition, this grants us a better understanding of the interaction physics of intrinsic graphene phonons with graphene plasmons. Here, we present FeCl3-intercalated graphene as a new plasmonic material with high stability under environmental conditions and carrier concentrations corresponding to EF > 1 eV. Near-field imaging of this highly doped form of graphene allows us to characterize plasmons, including their corresponding lifetimes, over a broad frequency range. For bilayer graphene, in contrast to the monolayer system, a phonon-induced dipole moment results in increased plasmon damping around the intrinsic phonon frequency. Strong coupling between intrinsic graphene phonons and plasmons is found, supported by ab initio calculations of the coupling strength, which are in good agreement with the experimental data.

Optically Tunable Plasmonic Two-Dimensional Ag Quantum Dot Arrays for Optimal Light Absorption in Polymer Solar Cells

The application of localized surface plasmon resonance (LSPR) phenomena is an effective strategy to enhance the performance of polymer solar cells (PSCs) because of their ability to efficiently scatter light and dramatically increase light absorption in the active layer of PSCs. Unlike previous reports investigating LSPR materials in PSCs, we have approached the LSPR phenomenon from a physical perspective by examining the influence of the surrounding environment on LSPR properties. Uniformly ordered two-dimensional 10 nm Ag quantum dot arrays (2D Ag QAs) were prepared and utilized in PSCs. The 2D Ag QAs were incorporated into electron transport layers with different refractive indices, which showed a significant bathochromic shift as the refractive index increased and excellent agreement with theoretical calculations taking intrinsic size effects, nonlocal response, and plasmon coupling effects into account. When incorporated into PSCs, power conversion efficiencies of up to 8.51% were realized—a 12.5% en...