Resonant Excitation Research Articles

Stretchable Metamaterials with Tunable Infrared Emissivity for Dynamic Thermal Management.

Manipulation of infrared emissivity, which is closely related to surface structure and optical parameters of materials, is a crucial approach for realizing dynamic thermal management. In this study, we design a metamaterial consisting of an array of aluminum disks embedded on a surface of a stretchable elastomeric substrate. Mechanical stretching-induced deformation allows dynamic modification of the surface structure and equivalent optical parameters, thus enabling dynamic control of the emissivity. By utilizing the elastomer polydimethylsiloxane (PDMS) as the substrate, the microstructure interdisk gap can be altered by stretching the PDMS. Through theoretical calculations, the plausibility of this approach is explained by the excitation of plasmon resonance and the variation in the exposed area of highly absorbent PDMS, and the optimal structures for tuning the infrared emissivity are revealed to be 6 μm in diameter and 100 nm in height. Based on this design, we prepare samples with periods of 7 and 7.9 μm and experimentally demonstrate that a change in the period can cause a change in the emissivity and thus tunability in thermal control performance. The temperature difference between the two samples reaches 44.1 °C at a heating power of 0.28 W/cm2 for both samples. Furthermore, we construct a stretching platform that enables in situ mechanical stretching to realize dynamic changes in emissivity. The integral infrared emissivity of the sample increases from 0.32 to 0.5 at a biaxial tensile strain of 13%, achieving a 56% modulation rate of the integral infrared emissivity. The material is expected to enable dynamic thermal management.

Metallic nanoentities: Bio-engineered silver, gold, and silver/gold bimetallic nanoparticles for biomedical applications

This present study reports the biogenic synthesis of silver nanoparticles (AgNPs), gold nanoparticles (AuNPs) and Ag/Au bimetallic nanoparticles (BNPs) using bark extract of plant Tamarix aphylla (T.A). The bark extract contained total polyphenolic compounds and total flavonoids as 0.0362 mg/mg and 0.2928 mg/mg of the dried bark extract respectively. Silver nitrate (AgNO3) and hydrogen tetra chloroaurate trihydrate (HAuCl4.3H2O) were used as precursors while deionised water and methanol (CH3OH) were used as solvents. Synthesized nanoparticles were characterized through UV–visible spectroscopy, SEM (scanning electron microscopy), TEM (transmission electron microscopy) and FTIR (Fourier transform infrared) for their morphology, structure, and identification of different functional groups. The UV–visible spectra of AgNPs, AuNPs and Ag/Au BNPs showed peaks at 436, 532 and 527 nm respectively due to the excitation of Surface Plasmon Resonance. SEM and TEM images showed spherical and well distributed nanoparticles (NPs) with particle size as 29 nm (AgNPs), 13 nm (AuNPs) and 26 nm (Ag/Au BNPs). The synthesized NPs are significantly active against inhibition of free radicals, α-amylase, α-glucosidase and have anti inflammatory potential with AgNPs having the highest percent activity at 400 μg/ml, followed by Ag/Au BNPs. The same trend (AgNPs > Ag/AuBNPs > AuNPs) has been observed at all concentrations i.e. 100 μg/ml, 200 μg/ml and 400 μg/ml. AuNPs have shown lowest activity at all concentrations. So the current study strongly confirms use of T.A bark extract as reducing agent for synthesis of metal NPs and opens up a new possibility of using these green synthesized NPs as biomedicines. We also suggest further in vivo investigation to report any side effects if present.

Green Synthesis of CuO Nanoparticles Mediated Rhazya Stricta Plant Leaves Extract Characterization and Evaluation of their Antibacterial and Anticancer Activity (in vitro Study)

In this study, a straightforward, expeditious, and environmentally friendly approach to synthesize copper oxide nanoparticles (CuONPs) utilizing an aqueous extract of Rhazya Stricta (R. stricta) leaves was employed. The CuONPs underwent various analytical techniques for characterization, including X-ray diffractometer (XRD), field emission scan electron microscope (FESEM), energy dispersive X-ray (EDX) analyses, UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and zeta potential. The XRD analysis authenticated the monoclinic crystal nature, revealing an average crystallite size of 15.6 nm. FESEM images depicted semi-spherical and cubic shapes, with particle sizes ranging from 56.64 to 86.95 nm. The formation of CuONPs was initially confirmed by the observable change in colour, attributed to the excitation of surface Plasmon resonance at 280 nm in the UV-Vis spectra. FTIR analysis affirmed the presence of functional groups in the R. Stricta leaves extract, serving as both reducing and stabilizing agents, facilitating the formation of CuONPs. Zeta potential measurements indicated substantial stability with a value of 46.6 mV. The biosynthesized CuONPs were further evaluated for their antibacterial properties against Klebsiella Pneumoniae (K. pneumoniae) and Staphylococcus aureus (S. aureus), yielding inhibition zones of 21 mm and 30 mm, respectively. Additionally, the cytotoxicity assessment of CuONPs against A549 cell lines revealed higher cytotoxicity of 81.47 ± 1.517 at a CuONP concentration of 100 μg/ml. This work is the first attempt at R. stricta-facilitated synthesis of CuONPs as antibacterial and anticancer agents. It can subsequently be exploited as a potential candidate for these agents and might be utilized further in vivo studies.

Elevating electron energy gain and betatron x-ray emission in proton-driven wakefield acceleration

The long proton beams present at CERN have the potential to evolve into a train of microbunches through the self-modulation instability process. The resonant wakefield generated by a periodic train of proton microbunches can establish a high acceleration field within the plasma, facilitating electron acceleration. This paper investigates the impact of plasma density on resonant wakefield excitation, thus influencing the acceleration of a witness electron bunch and its corresponding betatron radiation within the wakefield. Various scenarios involving different plasma densities are explored through particle-in-cell simulations. The peak wakefield in each scenario is calculated by considering a long pre-modulated proton driver with a fixed peak current. Subsequently, the study delves into the witness beam acceleration in the peak wakefield and its radiation emission. Elevated plasma density increases both the number of microbunches and the accelerating gradient of each microbunch, consequently resulting in heightened resonant wakefield. Nevertheless, the scaling is disrupted by the saturation of the resonant wakefield due to the nonlinearities. The simulation results reveal that at high plasma densities, an intense and broadband radiation spectrum extending into the domain of the hard x-rays and gamma rays is generated. Furthermore, in such instances, the energy gain of the witness beam is significantly enhanced. The impact of wakefield on the witness energy gain and the corresponding radiation spectrum is clearly evident at elevated densities.

Broadband light trapping in perovskite solar cells: Optimization and enhancement through exploiting multi-resonant Mie resonators

We present multi-resonant Mie resonators comprising dielectric nanopyramid arrays (DNPAs) for efficient broadband light trapping (LT) in perovskite solar cells (PSCs). Absorption in a 100 nm-thick active layer is significantly enhanced over a broad range of wavelengths through the simultaneous resonant excitation of electric and magnetic moments. Through optimization, a PSC integrated with a front-located DNPA LT structure having a base edge of 320 nm and a spacing of 180 nm at an aspect ratio of 1.5 yields a short-circuit current density (Jsc) of 18.13 mA/cm2, which is about 29 % higher than that of a planar PSC. Multipole resonance contributions and radiation patterns of DNPs are also investigated. The spectral overlap of the multipole resonances of the DNPAs can be easily tuned, thereby providing performance enhancements in diverse applications, such as nanoantennas, metasurfaces, photodiodes, and other solar cells.

Topological Optical Waveguiding of Exciton‐Polariton Condensates

Abstract1D models with topological non‐trivial band structures are a simple and effective way to study novel and exciting concepts in topological photonics. In this work, the propagation of light‐matter quasi‐particles, so‐called exciton‐polaritons, is studied in waveguide arrays. Specifically, topological states are being investigated at the interface between dimer chains, characterized by a non‐zero winding number. In order to exercise precise control over the polariton propagation, non‐resonant laser excitation, as well as resonant excitation, are studied in transmission geometry. The results highlight a new platform for the study of quantum fluids of light and non‐linear optical propagation effects in coupled semiconductor waveguides.

Development of an Earth-Field Nuclear Magnetic Resonance Spectrometer: Paving the Way for AI-Enhanced Low-Field Nuclear Magnetic Resonance Technology.

Today, it is difficult to have a high-field nuclear magnetic resonance (NMR) device due to the high cost of its acquisition and maintenance. These high-end machines require significant space and specialist personnel for operation and offer exceptional quality in the acquisition, processing, and other advanced functions associated with detected signals. However, alternative devices are low-field nuclear magnetic resonance devices. They benefit from the elimination of high-tech components that generate static magnetic fields and advanced instruments. Instead, they used magnetic fields induced by ordinary conductors. Another category of spectrometers uses the Earth's magnetic field, which is simple and economical but limited in use. These devices are called Earth-Field Nuclear Magnetic Resonance (EFNMR) devices. This device is ideal for educational purposes, especially for engineers and those who study nuclear magnetic resonance, such as chemistry or other experimental sciences. Students can observe their internal workings and conduct experiments that complement their education without worrying about damaging equipment. This article provides a detailed explanation of the design and construction of electrical technology devices for the excitation of atomic spin resonance using Earth's magnetic fields. It covers all necessary stages, from research to analysis, including simulation, assembly, construction of each component, and the development of comprehensive software for spectrometer control.

Enhanced light confinement in nonlocal resonant metasurfaces with weak multipolar scatterers

Stronger light confinement can be enabled by nanoantennas in the nanostructure and result in efficient control of the directionality of the scattering. We report on an observation of the well-pronounced multipolar resonances from nickel nanoantennas originating from collective effects. We show that the collective coupling of multipolar modes from weak scatterers can substantially enhance the electric dipole and quadrupole resonances. We also demonstrate the generalized lattice Kerker effect in this nanoantenna array. Resonant multipolar excitations within nickel nanoantenna arrays can significantly enhance phenomena such as magneto-optical effects, indicating promising potential for advanced applications in the field of nanophotonics and sensing.

Enhanced intrinsic chiroptical response of resonant metallic metasurfaces.

The physics of resonant metasurfaces underpins many electromagnetic functionalities with enhanced performance by virtue of resonant excitations. Resonances originating from bound states in the continuum (BICs) were recently recognized in photonics for their superior optical properties, strong local field enhancement, and suppression of radiative losses. Very recently, a concept of intrinsically chiral dielectric BIC metasurfaces was proposed that combines strong narrowband resonant features with the polarization control of scattered light. Here, we design a resonant chiral metallic metasurface supporting a BIC resonance in the microwave wavelength range. In our structure, the metasurface units (meta-atoms) are characterized with rotational and mirror spatial symmetries. We numerically characterize metasurface mode properties in eigenmode calculations and scattering spectra for linearly polarized excitation under oblique incidence. Then, we investigate intrinsic chiroptical effects for transmission of normally propagating excitation beams by breaking the meta-atom in-plane mirror symmetries. We predict that the intrinsic circular dichroism in such structures may exceed 0.74.

Dynamical phase-field model of cavity electromagnonic systems

Cavity electromagnonic system, which simultaneously consists of cavities for photons, magnons (quanta of spin waves), and acoustic phonons, provides an exciting platform to achieve coherent energy transduction among different physical systems down to single quantum level. Here we report a dynamical phase-field model that allows simulating the coupled dynamics of the electromagnetic waves, magnetization, and strain in 3D multiphase systems. As examples of application, we computationally demonstrate the excitation of hybrid magnon-photon modes (magnon polaritons), Floquet-induced magnonic Aulter-Townes splitting, dynamical energy exchange (Rabi oscillation) and relative phase control (Ramsey interference) between the two magnon polariton modes. The simulation results are consistent with analytical calculations based on Floquet Hamiltonian theory. Simulations are also performed to design a cavity electro-magno-mechanical system that enables the triple phonon-magnon-photon resonance, where the resonant excitation of a chiral, fundamental (n = 1) transverse acoustic phonon mode by magnon polaritons is demonstrated. With the capability to predict coupling strength, dissipation rates, and temporal evolution of photon/magnon/phonon mode profiles using fundamental materials parameters as the inputs, the present dynamical phase-field model represents a valuable computational tool to guide the fabrication of the cavity electromagnonic system and the design of operating conditions for applications in quantum sensing, transduction, and communication.

Coherent control of rare earth 4f shell wavefunctions in the quantum spin liquid Tb2Ti2O7

The resonant excitation of electronic transitions with coherent laser sources creates quantum coherent superpositions of the involved electronic states. Most time-resolved studies have focused on gases or isolated subsystems embedded in insulating solids, aiming for applications in quantum information. Here, we focus on the coherent control of orbital wavefunctions in the correlated quantum material Tb2Ti2O7, which forms an interacting spin liquid ground state. We show that resonant excitation with a strong THz pulse creates a coherent superposition of the lowest energy Tb 4f states. The coherence manifests itself as a macroscopic oscillating magnetic dipole, which is detected by ultrafast resonant x-ray diffraction. We envision the coherent control of orbital wavefunctions demonstrated here to become a new tool for the ultrafast manipulation and investigation of quantum materials.

Amplitude analysis and branching fraction measurement of B+→D∗−Ds+π+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}^{+}\ o {D}^{\\ast -}{D}_s^{+}{\\pi}^{+} $$\\end{document} decays

The decays of the B+ meson to the final state D∗−Ds+π+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}^{\\ast -}{D}_s^{+}{\\pi}^{+} $$\\end{document} are studied in proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb−1. The ratio of branching fractions of the B+→D∗−Ds+π+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}^{+}\ o {D}^{\\ast -}{D}_s^{+}{\\pi}^{+} $$\\end{document} and B0→D∗−Ds+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}^0\ o {D}^{\\ast -}{D}_s^{+} $$\\end{document} decays is measured to be 0.173 ± 0.006 ± 0.010, where the first uncertainty is statistical and the second is systematic. Using partially reconstructed Ds∗+→Ds+γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}_s^{\\ast +}\ o {D}_s^{+}\\gamma $$\\end{document} and Ds+π0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}_s^{+}{\\pi}^0 $$\\end{document} decays, the ratio of branching fractions between the B+→D∗−Ds∗+π+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}^{+}\ o {D}^{\\ast -}{D}_s^{\\ast +}{\\pi}^{+} $$\\end{document} and B+→D∗−Ds+π+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}^{+}\ o {D}^{\\ast -}{D}_s^{+}{\\pi}^{+} $$\\end{document} decays is determined as 1.31 ± 0.07 ± 0.14. An amplitude analysis of the B+→D∗−Ds+π+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}^{+}\ o {D}^{\\ast -}{D}_s^{+}{\\pi}^{+} $$\\end{document} decay is performed for the first time, revealing dominant contributions from known excited charm resonances decaying to the D*−π+ final state. No significant evidence of exotic contributions in the Ds+π+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}_s^{+}{\\pi}^{+} $$\\end{document} or D∗−Ds+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}^{\\ast -}{D}_s^{+} $$\\end{document} channels is found. The fit fraction of the scalar state Tcs¯0∗2900++\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {T}_{c\\overline{s}0}^{\\ast }{(2900)}^{++} $$\\end{document} observed in the B+→D−Ds+π+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}^{+}\ o {D}^{-}{D}_s^{+}{\\pi}^{+} $$\\end{document} decay is determined to be less than 2.3% at a 90% confidence level.

The Vibration Characteristics Analysis of Fiber-Reinforced Thin-Walled Conical–Cylindrical Composite Shells with Artificial Spring Technique

In this paper, the vibration characteristics (free vibration and forced vibration) of fiber-reinforced thin-walled conical–cylindrical composite shells (FTCCS) are analyzed by combining theory and experiment. Based on the classical shell theory and Kirchhoff–Love assumption, the overall structure of the FTCCS is theoretically modeled. The artificial spring technology is used to simulate the arbitrary boundary conditions at the joint, which is divided into a main spring and a secondary spring. At the same time, the displacement functions of the two sub-structure shells of the FTCCS are established by the orthogonal polynomial method, and the energy function of the FTCCS is constructed according to the continuity condition of the bolt joint. Then, the vibration characteristics of the FTCCS are solved using the Rayleigh–Ritz method and the modal superposition method. Finally, the TC300/epoxy resin-based fiber-reinforced thin-walled conical–cylindrical composite shells are selected as the research object, and the rationality of the mathematical model is verified by pulse, frequency sweeping and resonance excitation tests. The experimental results show that the errors between the natural frequency and the resonance displacement calculated by the theory and the experimental results are 1.75–4.76% and 3.79–9.28%, which confirms the rationality of the proposed model. By changing the length of the shell, the lamination angle and the semi-cone angle of the conical shell, the vibration characteristics parameters under different conditions are calculated to evaluate the influence of three physical parameters on the vibration characteristics of the FTCCS.

Coupled-channel J−− meson resonances from lattice QCD

We extend an earlier calculation within lattice QCD of excited light meson resonances with JPC=1−−,2−−,3−− at the SU(3) flavor point in the representation, by considering the representation. In this case the resonances appear in coupled-channel amplitudes, which we determine, establishing the relative strength of pseudoscalar-pseudoscalar to pseudoscalar-vector decays. Combining the new octet results with the prior results for the singlet, we perform a plausible extrapolation to the physical quark mass, and compare to experimental ρJ⋆,KJ⋆,ωJ⋆ and ϕJ⋆ resonances. Published by the American Physical Society 2024

Frequency Comb With High Tunability via Coexistence State Excitation and Cavity Modulation in Microelectromechanical Resonators

Frequency Comb With High Tunability via Coexistence State Excitation and Cavity Modulation in Microelectromechanical Resonators

(Invited) Optical Probes for Resonance-Enhanced Gold Growth on Nanooptical Substrates

We investigate light-stimulated growth of gold metal lines to technically mimic the growth of long-range axonal connections for neuromorphic computing architectures. Photocatalytic gold growth from an aqueous gold chloride precursor solution (HAuCl4) on a photoactive titanium dioxide layer is used. It is known that local gold growth may be obtained by UV illumination through a shadow mask [1]. To obtain a wavelength and angle dependent growth of metal lines – and thus stimulus-dependent resistances – we suggest to employ a nanooptical template. Inspired by the typical number of 2 to 10 connections to a node found, e.g., in the neuronal system of the biological species Hydra, we decided on the implementation of a hexagonal design. The edges are formed by periodic grating nanostructures with 10 to 20 periods and a grating pitch of 170 nm to 210 nm for excitation in the UV. In order to investigate the resonant optical enhancement, we employ optical probes. It is well known that colloidal quantum dots show enhanced fluorescence emission on photonic crystal surfaces due to resonant excitation and resonant outcoupling [2]. In our initial experiments for investigation of the resonant enhancement, we use 4,4’-Bis(2,2-diphenylvinyl)-1,1’-biphenyl (DBVBi) as the emitter material. Its absorption maximum matches the excitation laser at 355 nm and fluorescence in the visible spectrum around 455 nm may be monitored with our camera and spectrometer setup.The nanostructure master was fabricated by electron-beam lithography (Kelvin Nanotechnology Ltd.) according to our design. We transfer the nanostructure pattern onto 1.1 mm thick soda-lime glass substrates by UV-nanoimprint lithography. Subsequently, a 100 nm titanium dioxide layer is deposited. The 150 nm emissive DBVBi layer is then added by thermal evaporation. The samples are characterized optically with a camera setup and magnifying optics on an in-plane rotatable xy-stage. We use a Cobolt Zouk 355 nm 10 mW laser to excite the emissive layer. The output power of the laser is set to 2 mW and its output beam is widened with a collimating lens setup to a diameter of approximately 1.5 mm². The widened beam is essential to obtain a homogeneous excitation. We observe the successful resonant excitation by the higher emission intensity of DPVBi in specific regions of the nanostructure at specific excitation angles. Already for 10 periods of the grating structure resonance effects are observed. A stronger enhancement is obtained for 20 periods. Further, the enhancement depends on the grating pitch as connections with nanograting pitches below 190 nm are no longer visible. They do not meet the criteria for resonant excitation.This method of using optical probes on the nanooptical template works well for initial characterization of the resonance enhancement at different excitation angles. Now the setup is ready for performing gold growth under different excitation conditions. Without the additional emissive layer, the waveguide thickness change needs to be compensated with an increased titanium dioxide layer thickness. For online monitoring of the resonant enhancement during growth optical probes may be employed below the photoactive titanium dioxide layer. It is expected that the resonance enhancement is reduced with the addition of gold due to the increased absorption and thus reduced quality factor as was previously studied in the context of nanostructured OLEDs [3].We acknowledge funding by the DFG (German Research Foundation) with the CRC 1461- Neurotronics (Project-ID 434434223 – SFB 1461).[1] S. Veziroglu et al. (2018). Photocatalytic growth of hierarchical au needle clusters on highly active TiO2 thin film. Advanced Materials Interfaces, 5(15), 1800465.[2] N. Ganesh et al. (2007). Enhanced fluorescence emission from quantum dots on a photonic crystal surface. Nature nanotechnology, 2(8), 515-520.[3] J. Buhl et al. (2023). Resonance‐Based Directional Light Emission from Organic Light‐Emitting Diodes: Comparing Integrated Nanopatterns and Color Conversion Waveguide Gratings. Advanced Photonics Research, 4(2), 2200143. Figure 1. (Left) Fluorescence image of optical probe layer on nanooptical substrate for 355 nm laser excitation. (Middle) Schematic of nanooptical substrate with grating pitch (in nm) and number of periods given. Same colors represent identical grating features. (Right) Field emission scanning electron microscopy (FESEM) image of one node with 6 connections. Figure 1

(Invited) Plasmon-Driven Nitrogen Photofixation

Ammonia is one of the most important chemicals as well as an efficient energy carrier. The nitrogen element is indispensable for nearly all living species on the earth. However, dinitrogen molecules that are abundant in the atmosphere cannot be used directly by living species. They need to be converted into ammonia or nitrate for use. Such conversion is known as nitrogen fixation. Because natural nitrogen fixation is insufficient for sustaining all population on the earth, the industrial Haber-Bosch process has been developed for producing ammonia from dinitrogen and dihydrogen. The process consumes a large amount of energy and generates a large amount of carbon dioxide. Photocatalytic nitrogen fixation can operate under mild conditions and uses solar energy and water. It offers an intriguing alternative approach for the conversion of atmospheric dinitrogen into ammonia.Plasmonic metal nanocrystals can effectively absorb light and efficiently generate hot charge carriers. Compared to traditional interband excitation in semiconductors, plasmon excitation offers a new approach for generating hot charge carriers, which can thereafter be utilized for various physical and chemical processes. The use of plasmonic hot charge carriers for photocatalysis has become a hot research topic in the recent years. Plasmonic hot charge carriers can not only enhance the reaction yield and selectivity, but also introduce new reaction pathways. Moreover, the plasmon resonance wavelengths of various nanoparticles can be synthetically adjusted over a broad range that surpasses the solar spectrum.We have demonstrated the powerfulness of localized plasmon resonance on driving photocatalytic reduction of atmospheric nitrogen, where plasmonic hot electrons play an essential role. First, Au nanoparticles are anchored on ultrathin titania nanosheets with oxygen vacancies. The oxygen vacancies chemisorb and activate nitrogen molecules, which are subsequently reduced to ammonia by plasmonic hot electrons generated from the Au nanoparticles. Our synthesized all-inorganic hybrid structures mimic the function of biological nitrogenase enzymes, where the plasmonic Au nanoparticles play the role of the Fe proteins and the titania nanosheets play the role of the MoFe proteins. Second, we have extended the biomimetic idea into another popular semiconductor. A plasmonic hybrid catalyst is produced by uniformly embedding Au nanoparticles in the mesopores of nitrogen-deficient hollow carbon nitride spheres. The carbon nitride spheres possess abundant nitrogen vacancies, which serve as the sites for nitrogen chemisorption and activation, and capture photoexcited electrons stemmed from the carbon nitride spheres and the plasmon resonance of the embedded Au nanoparticles for the efficient reduction of the adsorbed nitrogen molecules to ammonia. Third, when metal-semiconductor hybrid nanostructures are designed as photocatalysts for nitrogen fixation, the introduction of a Schottky barrier at the junction is unavoidable. This Schottky barrier will undoubtedly lower the utilization efficiency of plasmonic charge carriers because only plasmonic hot charge carriers with sufficient energies and appropriate momenta can overcome the barrier and inject into the semiconductor. In addition, noble metals are well-known to be expensive. We have synthesized different metal oxide nanoparticles that are degenerately doped and thus exhibit strong plasmon resonance and demonstrated Schottky-barrier-free plasmonic photocatalysts for nitrogen fixation. The excitation of the plasmon resonance in these metal oxide nanoparticles can efficiently generate hot charge carriers. Because of the abundance of defects in these degenerately doped semiconductor nanoparticles, the photogenerated hot charge carriers can rapidly migrate to the defect sites and get trapped there. In this way, the lifetime of the plasmonic hot charge carriers is Moreover, these metal oxide nanoparticles possess active sites for adsorbing and activating dinitrogen molecules. Therefore, they function in a “one-stone-two-birds” manner. As a result, a record-high solar-to-chemical energy conversion efficiency has been achieved.

(Invited) Plasmonic and Electrochemical Approaches to the Synthesis of Tailored Catalyst Materials

The development of novel photo- and electrocatalytic processes requires the design of catalyst materials that are specifically optimized to take advantage of these driving forces. This talk will describe approaches developed in our lab for (1) using visible light stimulus to control the structure of plasmonically responsive and hybrid materials and (2) using electrodeposition to grow shape-controlled nanostructures on electrode surfaces. In the first case, the reduction of more catalytically active metals onto plasmonically active metals requires fine control over competing reductive and oxidative chemical processes. Differentially modulating the rates of these reactions using only chemical and thermal parameters can be prohibitively challenging. However, excitation of the plasmon resonance of the growing nanoparticles using visible light can yield hybrid structures that are not accessible via standard colloidal approaches. In the second case, while particles synthesized in colloidal solution can be processed and cast onto electrodes, this adds an additional fabrication step—increasing time and cost—and faces challenges in controlling particle dispersion on the surface. Meanwhile, direct chemical reduction-based synthesis of well-defined nanoparticles on electrodes has proven difficult. We have developed an integrated electrochemical approach that enables directed synthesis of shaped nanoparticles on electrode surfaces. Our approach links metal nanoparticle synthesis with real-time monitoring of chemical changes in the reaction solution using a combination of colloidal particle synthesis, electrochemical particle synthesis, and electrochemical measurements. This provides a pathway for the directed adaptation of the extensive library of existing shaped colloidal nanoparticle syntheses to growth on a surface—something that remains a non-trivial challenge.

(Digital Presentation) Cooperative Quantum Dynamics of Excitons in Colloidal Quantum Dots for Novel Optoelectronic Applications

Colloidal semiconductor quantum dots (QDs) are excellent materials for combining photonics and nanoscience. They have been extensively studied to understand the photophysics of quantum confined excitons and to develop efficient optoelectronic devices such as QD solar cells and light-emitting diodes. The photophysical processes of QD devices are governed by a large number of QDs constructing the devices. Therefore, cooperative quantum dynamics of QDs, i.e., synchronous responses of QD ensembles, have a great potential for boosting optoelectronic device performances.Before the use of cooperative quantum dynamics in QD devices, the understanding of quantum dynamics of excitons, i.e., coherent properties of multiexcitons, is required to draw out quantum cooperativity from QD ensembles. In order to elucidate coherent dynamics of multiexcitons during resonant laser-pulse excitation, we performed a quantum interference spectroscopy of QD responses. We found that multiexcitons generate the high-frequency coherent oscillations with integer multiples of the exciton resonance frequency, which is called harmonic quantum coherence, and that the coherent responses govern the microscopic processes in the resonant multiphoton absorption [1-3]. Furthermore, it was demonstrated that the coherent responses were detectable as photocurrent signals in thin films of QD ensembles [4]. These developments build up an essential base of quantum cooperativities emerging in optoelectronics.Here, we report recent investigations of cooperative quantum dynamics in QDs. In optoelectronic devices, electronic couplings between QDs are expected to generate a new type of quantum cooperativities. To generate electronic coupling, we fabricated closely packed PbS QDs by using a ligand exchange method. We found that nonlinear photocurrent signals are strongly enhanced in the QD solids. The comparison analysis of different ligands clarified that the enhancement ratio increases monotonically with the decrease of the inter-QD distance [5]. This means that the signal enhancement originates from the electronic coupling and cooperative behavior of QDs. These findings show that the cooperative quantum dynamics provide a new route to advanced optoelectronic technology such as nonlinear amplifiers.Part of this work was supported by JSPS KAKENHI (JP19H05465, JP22H01990, and JP23K17877), JST PRESTO (JPMJPR23H3), and JST CREST (JPMJCR21B4).

Resolving plasmon-mediated high-order multiphoton excitation pathways in dolmen nanostructures using ultrafast nonlinear optical interferometry.

The multiphoton excitation pathways of plasmonic nanorod assemblies are described. By using dolmen structures formed from the directed assembly of three gold nanorods, plasmon-mediated three-photon excitation is resolved. These high-order multiphoton excitation channels were accessed by resonantly exciting a hybrid mode of the dolmen structure that was resonant with the 800-nm carrier wavelength of an ultrafast laser system. Rotation of the exciting field polarization to a non-resonant configuration did not generate third-order responses. Hence, the multiphoton excitation and resultant non-equilibrium electron distributions were generated by structure- and mode-selective excitation. Correlation between high-order and resonant plasmon excitation was achieved through sub-cycle time-resolved interferometric detection of incoherent nonlinear emission signals. The results illustrate the advantages of nonlinear optical interferometry and Fourier analysis for distinguishing plasmon-mediated processes from those that do not require plasmon excitation.