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Coupling of Fluorophores in Single Nanoapertures with Tamm Plasmon Structures
摘要： Metal nanostructures (such as plasmonic antennas) have been widely demonstrated to be excellent devices for beaming and sorting the fluorescence emission. These effects rely on the constructive scattering or diffraction from different elements (such as metal corrugations or nanorings) of the nanostructures. However, subwavelength-size nanoholes, without nearby nanoscale features, results in an angularly dispersed emission from the distal surface. Herein, we demonstrate for the first time the emission redirection capabilities of a single isolated nanoaperture milled in a thick silver film deposited on a dielectric multilayer. Specifically, we show that a dye dissolved in ethanol filling in the nanoaperture can couple to Tamm Plasmon Polariton (TPP) modes of the structure. Due to the small in-plane wavevectors of the TPPs, the fluorescence from Tamm-coupled dyes within the nanoaperture is emitted normally to the sample surface, with a minimum angular width of about 12.54o. This kind of fluorescence manipulation has proven to be effective with various nanoaperture shapes, such as circles, squares, and triangles. Our work is also the first experimental demonstration of lateral coupling of fluorophores with TPPs in nanoholes, with potential applications in bioanalysis and biosciences.
关键词： Optical,Plasmonics,and Hybrid Materials,Magnetic
更新于2025-09-23 15:23:52
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Angular-Dependent Spontaneous Emission in Cholesteric Liquid Crystal Films
摘要： Due to the presence of a selective reflection band, cholesteric liquid crystals (CLCs) strongly modify the emission of fluorescent guest molecules. While emission along the helical axis is well understood, the emission properties at oblique angles with respect to the cholesteric helix have so far have not been explored in detail. We present a systematic study of the angular-dependent spontaneous emission properties of dye-doped cholesteric films, including a full Stokes analysis of the emitted light. Variation of the cholesteric pitch allows us to probe the effect of the photonic band structure on spontaneous emission in a wide angular range. We find exceptional angular-dependent intensity and polarization variations of the emitted light, and give experimental proof for the splitting of the first-order reflection band as well as its overlap with the second-order band at large detection angles.
关键词： and Hybrid Materials,Optical,Cholesteric Liquid Crystal,Stokes Analysis,Angular-Dependent,Plasmonics,Spontaneous Emission,Magnetic
更新于2025-09-23 15:23:52
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Enhanced Photocatalytic Hydrogen Evolution with TiO <sub/>2</sub> -TiN Nanoparticle Composites
摘要： Metal nitrides have potential in energy applications due to their physical and optical properties. Nanoparticle composites of titanium nitride (TiN) and titanium dioxide (TiO2) were investigated for their photocatalytic hydrogen (H2) activity via methanol reformation. Physical mixing of the nanoparticulate TiO2 and TiN was employed to prevent the oxy-nitride formation and particle aggregation observed in thermal preparations. This convenient combination of TiO2 and TiN demonstrated a substantial synergistic effect with enhanced activity (9.4 μmol/h TiO2-TiN vs 1.8 μmol/h TiO2) under combined UV/Vis light. Irradiation under only UV light resulted in a similar enhancement factor compared to using combined UV/Vis light, demonstrating that the enhanced activity of the composites occurs essentially for UV-driven photocatalysis. No activity/enhancement was observed with only visible light irradiation, however, minor enhancement was observed when switching between UV and UV/Vis irradiation, suggesting a contribution from the TiN plasmon. We propose that the plasmonic contribution is dependent on the band gap excitation of TiO2, which reduces the degree of band bending at the TiO2/TiN interface. This promotes the migration of hot electrons from TiN away from the TiO2/TiN interface to be used for H2 evolution.
关键词： TiO2-TiN Nanoparticle Composites,Plasmonics,Optical,Magnetic,and Hybrid Materials,Photocatalytic Hydrogen Evolution
更新于2025-09-23 15:22:29
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Periodic ZnO-Elevated Gold Dimer Nanostructures for Surface-Enhanced Raman Scattering Applications
摘要： The electron beam lithography-defined periodic ZnO-elevated gold dimer nanostructures for surface-enhanced Raman spectroscopy with strong electromagnetic field enhancements were fabricated in the present work. The ZnO nanorods (NRs) were grown on the patterned substrate using the hydrothermal process and Au dimers were deposited on the top surface of ZnO NRs, forming suspended gold dimers and providing plasmonic hot-spots with nanocavity effect. The effects of dimer radius, gap size and ZnO NR height on the dark-field scattering spectra and surface-enhanced Raman scattering (SERS) were investigated experimentally and theoretically. The SERS response was enhanced with increasing dimer radius and decreasing gap size. The SERS enhancement factor (EF) due to the localized surface plasmon resonance was calculated from simulation results. The calculated EF as a function of ZnO NR height showed the periodic trend of electric field intensity with the periodicity of about half of the exciting laser wavelength, and was in agreement with SERS measurements. Our hybrid substrates combining plasmonic nanocavity effect with charge transfer across the heterojunction denoted the potential candidate for SERS applications.
关键词： Plasmonics,Surface-Enhanced Raman Scattering,ZnO-Elevated Gold Dimer Nanostructures,Magnetic,Optical,and Hybrid Materials
更新于2025-09-23 15:21:01
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Extraordinarily Large Third-Order Optical Nonlinearity in Au Nanorods under Nanowatt Laser Excitation
摘要： Size and operating energy are two key parameters that constrain the integration capability of a nonlinear optical device. Here, we report a 60-nm thin film made of randomly distributed gold nanorods that demonstrates extraordinarily large third-order nonlinear optical absorption under an excitation power as low as 100 nanowatts. Where the effective nonlinear optical absorption (NLA) coefficient is calculated to be 8x109 cm/GW with the corresponding optical susceptibility (Imχ(3)) of 7.6x10-2 esu, which is 3-4 orders larger than that of other metallic nanostructures. The sign of the NLA could be controlled by changing the excitation wavelength or varying the pump power. The optical Kerr effect measurement also shows that the intrinsic χ(3) of our sample is quite large compared to other nanostructures. Our work eliminates the requirements of strong operation power and large physical size of nonlinear optical materials and offers new opportunities for plasmonic nanostructures in applications of on-chip nonlinear optical devices.
关键词： Nanowatt Laser Excitation,and Hybrid Materials,Optical,Plasmonics,Magnetic,Au Nanorods,Third-Order Optical Nonlinearity
更新于2025-09-19 17:13:59
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Direct Detection of Bacteria Using Positively-charged Ag/Au Bimetallic Nanoparticles: A Label-Free SERS Study Coupled with Multivariate Analysis
摘要： Rapid detection and discrimination of pathogenic bacteria for food safety, environmental pollution, medical diagnoses, and chemical and biological threats remains a considerable challenge. In the present work, we demonstrate positively charged Ag/Au bimetallic nanoparticles (Ag/Au bmNPs) as a potential surface-enhanced Raman scattering (SERS) substrate for label-free detection and discrimination of three bacteria, viz., Escherichia coli, Salmonella typhimurium and Bacillus subtilis with excellent reproducibility. The approach relies on a priori synthesis of Ag/Au bmNPs and subsequent SERS studies on bacteria. The positive surface charge on Ag/Au bmNPs offers significant advantages of short acquisition time at very low power, high sensitivity, and simple operating procedure without the need of very specific procedures/protocols used to capture the bacteria. The reproducible and specific intrinsic fingerprint of the cell wall and intracellular components of three bacteria obtained by label-free SERS enables precise discrimination and classification of three bacteria using multivariate analysis such as principal component analysis and canonical discriminant analysis.
关键词： SERS,multivariate analysis,Optical,Magnetic,label-free study,and Hybrid Materials,bacteria detection,Ag/Au bimetallic nanoparticles,Plasmonics
更新于2025-09-11 14:15:04