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Nanogap Plasmonic Structures Fabricated by Switchable Capillarya??Force Driven Selfa??Assembly for Localized Sensing of Anticancer Medicines with Microfluidic SERS
摘要： Nanogap plasmonic structures, which can strongly enhance electromagnetic fields, enable widespread applications in surface-enhanced Raman spectroscopy (SERS) sensing. Although the directed self-assembly strategy has been adopted for the fabrication of micro/nanostructures on open surfaces, fabrication of nanogap plasmonic structures on complex substrates or at designated locations still remains a grand challenge. Here, a switchable self-assembly method is developed to manufacture 3D nanogap plasmonic structures by combining supercritical drying and capillary-force driven self-assembly (CFSA) of micropillars fabricated by laser printing. The polymer pillars can stay upright during solvent development via supercritical drying, and then can form the nanogap after metal coating and subsequent CFSA. Due to the excellent flexibility of this method, diverse patterned plasmonic nanogap structures can be fabricated on planar or nonplanar substrates for SERS. The measured SERS signals of different patterned nanogaps in fluidic environment show a maximum enhancement factor ≈8 × 107. Such nanostructures in microchannels also allow localized sensing for anticancer drugs (doxorubicin). Resulting from the marriage of top-down and self-assembly techniques, this method provides a facile, effective, and controllable approach for creating nanogap enabled SERS devices in fluidic channels, and hence can advance applications in precision medicine.
关键词： anticancer drugs,doxorubicin,nanogap plasmonic structures,capillary-force driven self-assembly,surface-enhanced Raman spectroscopy,SERS,laser printing
更新于2025-09-23 15:19:57
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Potential energy shift of the Fermi level at plasmonic structures for light-energy conversion determined by graphene-based Raman measurements
摘要： Single layer graphene was used to determine the electrochemical potential of plasmonic nano-structures for photoelectrochemical energy conversions. From electrochemical Raman measurements of the graphene layer under near-infrared light, illumination has revealed the relationship between the photoenergy conversion ability and the Fermi level of the plasmonic structure. The determination is based on in situ monitoring of G and 2D Raman bands of the graphene layer on plasmonic structures. The correlation plots of G and 2D bands show the dependence on the photoconversion ability. The present electrochemical Raman measurements provide detailed understanding of the plasmon-induced charge transfer process for further developments on the ability.
关键词： plasmonic structures,Raman measurements,graphene,Fermi level,photoelectrochemical energy conversion
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Light Manipulation with Plasmonic Structures using Phase Change Materials
摘要： Over the past decade intensive research has focused on the use of plasmonic structures and metamaterials for the control of electromagnetic radiation. Response of such structures is highly dependent on factors set during fabrication, such as the combination of materials used and as well as their structural dimensions. Despite having many promising optoelectronic applications, the inability to tune the optical response of such structures post fabrication presents serious limitations. To overcome this, we present tunable plasmonic elements formed of plasmonic nanostructures on a thin film of vanadium dioxide (VO2), a phase change material. VO2 is an attractive option as a phase change material due to its large, reversible transition from a semiconducting to a metallic phase at a critical temperature of 68°C, close to room temperature. While much research on VO2 is centred on the large changes in the optical properties occurring in the NIR spectral range (above 1μm) upon the phase transition, in this work we focus on the changes in the dielectric function of VO2 in the visible spectral range. In particular, we experimentally and numerically investigate the possibility to use the phase change of VO2 to dynamically tune the plasmonic properties of noble metal nanostructures as well as to manipulate the emission properties of quantum emitters near plasmonic nanostructures. We observe a drastic change in the plasmonic properties of gold nanorods arrays fabricated on a thin layer of VO2 as the phase transition from the semiconducting to metallic phase of VO2 is thermally triggered. Upon phase transition, a >50% decrease in scattering in the red spectral region, especially around 650 nm, was detected in dark field scattering experiments (Figure 1a). Moreover, our spectrally and time resolved measurements reveal that the emission properties of quantum dots (CdSeS/ZnS) in the vicinity of the gold nanorod arrays can be modified through the thermal phase change of the underlying thin layer of VO2 (Figure 1b). When VO2 is in its semiconducting phase the photoluminescence (PL) of QDs on the nanorods array is quenched compared to the PL of QDs on the same VO2 thin film but off the array. In contrast, we observe an enhanced light emission of QDs on the array when the VO2 layer is in its thermally actuated metallic phase. Additionally, the main PL emission peaks of QDs on the nanorod arrays as well as off the arrays red shift by 15 nm, as an effect of heating. The experimental results are accompanied by supporting FDTD simulations.
关键词： photoluminescence,vanadium dioxide,plasmonic structures,quantum dots,phase change materials
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Scanning Resonant Nano-Antenna High Resolution Imaging and Emission Control of hBN Defect Photon Emission
摘要： Single atomic defects in hexagonal boron nitride (hBN) are particularly interesting due to their stability of emission and absence of blinking and bleaching, at ambient conditions. Furthermore, they show exceptional robustness of emission, even at high temperatures of operation. Therefore, hBN defects have emerged as promising candidates for novel robust single photon sources. Several attempts have been done to induce hBN defects in a controlled manner. Because of their ease of accessibility and, due to the nanometer scale thickness of the hBN flakes, these defects are attractive to couple to plasmonic structures in order to increase their photon emission. However efficient coupling requires a high precision of positioning (<20 nm) and so far the methods adopted lack this level of control, both in assembling and imaging. Also, they present static configurations of coupled emitter-particles and no strategy is adopted in order to discern between the photons emitted by the hBN defects and the luminescence of the metallic particles. Here we present first systematic and simultaneous coupling and imaging of hBN emission centers with resonant optical antennas, with nanometer control and optical resolution of 45 nm. We show the capability of nano-antennas to manipulate hBN defects by depleting their emission 30-70%. Our setup is a near-field microscope working in scattering configuration, where we fabricate a single dipolar nano-antenna as a near-field probe that we can independently scan over hBN defects controlling the coupling and the fluorescence emission with nanometer resolution. We employ a photon time-gating technique in order to discriminate the light emitted by the metallic antenna by the one radiated by the hBN emitters. Finally, we report on a lifetime shortening of 2x, due to coupling emitter--antenna.
关键词： nano-antennas,single photon sources,plasmonic structures,near-field microscope,hBN defects
更新于2025-09-16 10:30:52
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Plasmonic nanosensor based on multiple independently tunable Fano resonances
摘要： A novel refractive index nanosensor with compound structures is proposed in this paper. It consists of three different kinds of resonators and two stubs which are side-coupled to a metal–dielectric–metal (MDM) waveguide. By utilizing numerical investigation with the finite element method (FEM), the simulation results show that the transmission spectrum of the nanosensor has as many as five sharp Fano resonance peaks. Due to their different resonance mechanisms, each resonance peak can be independently tuned by adjusting the corresponding parameters of the structure. In addition, the sensitivity of the nanosensor is found to be up to 1900 nm/RIU. For practical application, a legitimate combination of various different components, such as T-shaped, ring, and split-ring cavities, has been proposed which dramatically reduces the nanosensor dimensions without sacrificing performance. These design concepts pave the way for the construction of compact on-chip plasmonic structures, which can be widely applied to nanosensors, optical splitters, filters, optical switches, nonlinear photonic and slow-light devices.
关键词： metal–dielectric–metal (MDM) waveguide,nanosensor,on-chip plasmonic structures,Fano resonance,surface plasmon polaritons (SPPs)
更新于2025-09-16 10:30:52
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Improving the performance of light-emitting diodes via plasmonic-based strategies
摘要： Light-emitting diodes (LEDs), featuring long lifetime, small size, and low energy consumption, are increasingly popular for displays and general light sources. In the past decades, new light-emitting materials and novel device configurations are being continuously investigated to obtain highly efficient LEDs. Nevertheless, the unsatisfying external quantum efficiency severely limits their commercial implementation. Among all the approaches to boost the efficiency of LEDs, the incorporation of plasmonic structures exhibits great potential in increasing the spontaneous emission rates of emitters and improving the light extraction efficiency. In this Perspective, the methods to deal with challenges in quantum-well-based LEDs and organic LEDs by employing plasmonic materials are described, the mechanisms of plasmonic-based strategies to improve the light generation and extraction efficiency are discussed, and the plasmonic control over directional emission of phosphors is introduced as well. Moreover, important issues pertaining to the design, fabrication, and manipulation of plasmonic structures in LEDs to optimize the device performance, as well as the selection roles in finding appropriate plasmonic materials and structures for desired LED devices, are explained. This perspective lists the challenges and opportunities of plasmonic LEDs, with the aim of providing some insights into the future trends of plasmonic LEDs.
关键词： spontaneous emission rates,light-emitting diodes,light extraction efficiency,external quantum efficiency,plasmonic structures
更新于2025-09-16 10:30:52
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[IEEE 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama) - Toyama (2018.8.1-2018.8.4)] 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama) - Characterization of Terahertz Plasmonic Structures Based on Metallic Wire Woven Meshes
摘要： A THz plasmonic structure based on metallic wire woven meshes to support Fano resonance is presented in numerical calculation. The structure unit of the woven metal wire is critical to perform this resonance ?eld due to its asymmetry, which is compared with the symmetry of metal-hole-array. Using di?erent bent wires with various curvatures on the woven metal wire structure can modulate the spectral properties of resonance ?eld in the frequency and bandwidth. High Q-factor resonance are thus optimized via the dimensions of the wire bending section and realized to con?ne a large volume of resonance ?eld.
关键词： Fano resonance,Terahertz,plasmonic structures,metallic wire woven meshes
更新于2025-09-11 14:15:04
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Hot-electron photodetector with wavelength selectivity in near-infrared via Tamm plasmon
摘要： Tamm plasmonic (TP) structures, consisting of a metallic film and a distributed Bragg reflector (DBR), can exhibit pronounced light confinement allowing for enhanced absorption in the metallic film at the wavelength of the TP resonance. This wavelength dependent absorption can be converted into an electrical signal through the internal photoemission of energetic hot-electrons from the metallic film. Here, by replacing the metallic film at the top of a TP structure with a hot-electron device in a metal-semiconductor-ITO (M-S-ITO) configuration, for the first time, we experimentally demonstrate a wavelength-selective photoresponse around the telecommunication wavelength of 1550 nm. The M-S-ITO junction is deliberately designed to have a low energy barrier and an asymmetrical hot-electron generation, in order to guarantee a measurable net photocurrent even for sub-bandgap incident light with a photon energy of 0.8 eV (1550 nm). Due to the excitation of TPs between the metallic film in the M-S-ITO structure and the underlying DBR, the fabricated TP coupled hot-electron photodetector exhibits a sharp reflectance dip with a bandwidth of 43 nm at a wavelength of 1581 nm. The photoresponse matches the absorptance spectrum, with a maximum value of 8.26 nA/mW at the absorptance peak wavelength that decreases by more than 80% when the illumination wavelength is varied by only 52 nm (from 1581 to 1529 nm), thus realizing a high modulation wavelength-selective photodetector. This study demonstrates a high-performance, lithography-free, and wavelength-selective hot-electron near-infrared photodetector structure.
关键词： hot-electron photodetector,near-infrared,wavelength-selective photodetection,Tamm plasmonic structures,telecommunication wavelength
更新于2025-09-11 14:15:04
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Surface enhanced perfect absorption in metamaterials with periodic dielectric nanostrips on silver film
摘要： Integrated dielectric metamaterials with plasmonic structures can cause drastic optical resonances and strengthen the capacity of light absorption. Here, we describe the optical properties of silicon nanoarrays on a thin silver film for extreme light confinement at subwavelength nanoscales. We attain the nearly total absorption in silicon nanostrips, which support magnetic quadruple Mie-type resonances in the visible regions. The Mie resonant field of the dielectric nanostrip engages the screening response of the silver film, resulting in plasmon resonance configuration and thus achieving perfect light absorption in the dielectric nanostrip. Moreover, we can attain similar results in other nanostructures, such as silicon cylinder and rhombus column arrays. Because it can sustain hybridized plasmon modes and magnetic modes, the combined system will benefit the application of solar energy accumulation.
关键词： surface plasmon polaritons,plasmonic structures,dielectric metamaterials,Mie resonances,perfect absorption
更新于2025-09-10 09:29:36