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Correlative Study of Enhanced Excitonic Emission in ZnO Coated with Al Nanoparticles using Electron and Laser Excitation
摘要： Recently, metal nanoparticle surface coatings have been found to significantly enhance the ultra-violet luminescence intensity from ZnO, providing a viable means to mitigate optical losses and improve LED performance. Although there is general agreement that resonantly excited Localized Surface plasmons (LSps) in metal nanoparticles can directly couple to excitons in the semiconductor increasing their spontaneous emission rate, the exact mechanisms involved in this phenomenon are currently not fully understood. In this work, LSP-exciton coupling in bulk and nanostructured ZnO coated with a 2 nm Al nanoparticle layer is investigated using correlative photoluminescence and depth-resolved cathodoluminescence and time-resolved photoluminescence spectroscopy. Temperature-resolved cathodoluminescence and photoluminescence measurements from 10 K to 250 K show free exciton (FX) emission enhancement factors up to 12x at 80 K, and reveal that the FX couple more efficiently to the LSPs compared to the localized donor-bound excitons. A strong polarization dependence between the LSPs and FX is observed where FX transitions are more strongly enhanced when polarized in the same direction as the electric field of the incident excitation, which is different for laser and electron beam sources. This result indicates that selective enhancement of the excitonic emission peaks in the ZnO coated with Al nanoparticles can be achieved by choosing the appropriate ZnO substrate orientation.
关键词： Localized Surface plasmons,metal nanoparticle,ZnO,exciton coupling,luminescence
更新于2025-09-23 15:21:01
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Ultralow-Power Electrically Activated Lab-on-a-Chip Plasmonic Tweezers
摘要： We propose ultralow-power plasmonic tweezers with no external optical source. They consist of a one-dimensional array of graphene-based plasmonic units driven by the optical transitions within the underlying array of (Al, In)As/(Ga, In)As/(Al, In)As/(Ga, In)As/(Al, In)As quantum cascaded heterostructures (QCHs), electrically biased in series. Each QCH unit formed in a nanopillar can act as a built-in optical source required for exciting the localized surface plasmons (LSPs) at the surface of the overlying circular graphene nanodisk. The stimulated emission due to intersubband transition within each optical source evanesces through the top (Al, In)As cladding layer and interacts with the overlying graphene nanodisk, inducing the LSPs required for the formation of the plasmonic tweezers. Numerical simulations show, under 145–170 mV applied voltages, that the tweezers with graphene nanodisks of 16–30 nm in diameter and chemical potentials of 0.5–0.7 eV can trap polystyrene nanoparticles of 9 nm in diameter and larger, demonstrating acceptable sensitivities for variations in the nanoparticle diameter and refractive index. These lab-on-a-chip plasmonic tweezers, bene?ting from their small footprints and ultralow power consumptions, which are capable of sensing and trapping nanoparticles without requiring expensive external optical sources, open up a di?erent horizon for developing compact on-chip plasmonic tweezers.
关键词： plasmonic tweezers,localized surface plasmons,graphene,lab-on-a-chip,quantum cascade heterostructures
更新于2025-09-16 10:30:52
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Plasmonic Metamaterials for Nanochemistry and Sensing
摘要： Plasmonic nanostructures were initially developed for sensing and nanophotonic applications but, recently, have shown great promise in chemistry, optoelectronics, and nonlinear optics. While smooth plasmonic films, supporting surface plasmon polaritons, and individual nanostructures, featuring localized surface plasmons, are easy to fabricate and use, the assemblies of nanostructures in optical antennas and metamaterials provide many additional advantages related to the engineering of the mode structure (and thus, optical resonances in the given spectral range), field enhancement, and local density of optical states required to control electronic and photonic interactions. Focusing on two of the many applications of plasmonic metamaterials, in this Account, we review our work on the sensing and nanochemistry applications of metamaterials based on the assemblies of plasmonic nanorods under optical, as well as electronic interrogation.
关键词： field enhancement,sensing,localized surface plasmons,optical antennas,nanochemistry,optical resonances,electronic interrogation,surface plasmon polaritons,metamaterials,Plasmonic nanostructures
更新于2025-09-12 10:27:22
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Gain‐Assisted Active Spoof Plasmonic Fano Resonance for High‐Resolution Sensing of Glucose Aqueous Solutions
摘要： Fano resonance has received much attention in recent years due to its promising applications in surface enhanced phenomena, sensing, and nonlinear optics. However, it is challenging to achieve both high quality (Q) factor and high intensity using the Fano resonance. Different from active switching/tuning of plasmonic Fano resonances, gain-assisted active spoof plasmonic Fano resonance is for the first time proposed to enhance both the Q factor and resonance intensity significantly, in which a subwavelength amplifier chip is incorporated into a passive plasmonic structure composed of two stacked corrugated metal rings. Experimental results show that the Q factor of the Fano resonance is increased from 49 to 2802, and the resonance intensity is improved from 19.89 to 37.42 dB. The high performance of the active plasmonic structure makes the limit of detection reach to 10 mg dL?1, and thus the minute change of glucose aqueous solutions has been successfully detected.
关键词： active plasmonic Fano resonance,localized surface plasmons,metamaterials
更新于2025-09-12 10:27:22
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Two dimensional sinusoidal Ag nanograting exhibits polarization-independent surface-enhanced Raman spectroscopy and its surface plasmon polariton and localized surface plasmon coupling with Au nanospheres colloids
摘要： A reproducible surface‐enhanced Raman scattering (SERS) substrate based on two dimensional (2D) sinusoidal Ag nanograting is presented. This SERS substrate with large area can be easily fabricated by maskless laser interference photolithography. The potential SERS polarization‐independent performance of 2D sinusoidal Ag nanograting is deduced by finite difference time domain and demonstrated by SERS detection experiments. A double‐enhanced Raman scattering (DERS) substrate by coupling 2D sinusoidal Ag nanograting with Au nanospheres colloids is created. With the optimal DERS substrate, SERS enhancement factor can be 10 orders of magnitude as possible. The DERS substrate was fabricated and an extra SERS effect was proved by experiments. This DERS substrate will be fabricated in a microfluidics‐based sensor in the next work and used for in situ, real‐time, continuous monitoring of trace water soluble gas‐phase or airborne agents, such as trace explosives in air.
关键词： surface plasmon polaritons,surface enhanced Raman scattering,localized surface plasmons,two dimensional sinusoidal nanograting,polarization‐independent
更新于2025-09-10 09:29:36
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Nonlinear emission from silver-coated 3D hollow nanopillars
摘要： High aspect ratio metal nanostructures have been the subject of a number of studies in the past, due to their pronounced resonances in the infrared that can be exploited to enhance vibrational spectroscopies. In this work, we investigate the nonlinear optical response of both individual and closely-packed assemblies of vertical hollow Ag nanopillars upon excitation with ultrafast laser pulses. In particular, the analysis of their nonlinear emission spectra evidences an intense two photon photoluminescence (TPPL) emission and a neat signature of second harmonic generation (SHG). Given the relatively low background, this pronounced nonlinear emission could be employed as a local probe for analytes trapped at the surface of the nanopillar or flowing through it. For this reason, these nanostructures may become appealing building blocks in multi-purpose devices for nonlinear photonics and sensing.
关键词： Two Photon Photoluminescence,Ag Nanopillars,Localized Surface Plasmons,3D nanofabrications,Second Harmonic Generation
更新于2025-09-09 09:28:46