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Multipole Radiations from Large Gold Nanospheres Excited by Evanescent Wave
摘要： We proposed the use of the evanescent wave generated in a total internal reflection configuration to excite large gold nanospheres and investigated the radiations of the high-order plasmon modes supported in gold nanospheres. It was revealed that the evanescent wave excitation is equivalent to the excitation by using both the incident and reflected light, offering us the opportunity to control the orientation of the electric field used to excite nanoparticles. In addition, it was found that the scattering light intensity is greatly enhanced and the background noise is considerably suppressed, making it possible to detect the radiations from high-order plasmon modes. Moreover, the influence of the mirror images on the scattering induced by a metal substrate is eliminated as compared with the surface plasmon polariton excitation. By exciting a gold nanosphere with s-polarized light and detecting the scattering light with a p-polarized analyzer, we were able to reveal the radiation from the electric quadrupole mode of the gold nanosphere in both the spatial and the frequency domains. Our findings are important for characterizing the radiations from the high-order modes of large nanoparticles and useful for designing nanoscale photonic devices.
关键词： scattering,plasmon mode,electric dipole,radiation pattern,gold nanosphere,evanescent wave,electric octupole,electric quadrupole
更新于2025-11-21 11:24:58
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Photo-Modification of Melanin by a Mid-Infrared Free-Electron Laser
摘要： Melanin is rigidly constructed by several nitrogen-containing aromatic rings, and its excess accumulation in skin tissue is closely associated with melanosis. Although visible lasers (wavelength: 600–1000 nm) are conventionally used for the photo-thermolysis of melanocyte, several pigmented nevi are difficult to be treated. Here, we propose an alternate method for targeting the molecular structure of melanin using an infrared free electron laser (FEL) tuned to 5.8 μm that corresponds to the stretching vibrational mode of carboxylate group. A drastic morphological change on the black-colored surface of melanin powder were observed after the pulse irradiation with a power of 500 mJ/cm2, and the minimum irradiation time for damage to the morphology was 1.4 seconds. Analyses by mass spectroscopy, infrared spectroscopy, and 13C-nuclear magnetic resonance implied that a pyrrole group was removed by the FEL irradiation. In addition, the FEL irradiation dispersed almost all of the melanoma cells from a culture solution without any influence on other ingredients in the medium, and one-cell analysis by infrared microscopy showed that the structure of melanoma could be substantially damaged by the irradiation. This study proposes the potency of intense mid-infrared laser as novel alternative way to reduce melanin.
关键词： Infrared free electron laser,Melanoma,Vibrational mode,Melanin,Photo-modification
更新于2025-11-21 11:03:13
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Dual-mode luminescent core-shell nanoarchitectures for highly sensitive optical nanothermometry
摘要： Currently, FIR-based luminescent nanothermometry has aroused wide concern for its promising applications in fast-moving objects, harsh environments and microscopic temperature. Synchronously promoting the absolute and relative sensitivities of optical thermometers is one of the significant issues at present. In this work, a new nanothermometry strategy to possess both high absolute and relative sensitivities have been proposed by coupling of thermally-coupled-levels-based technique with non-thermally-coupled-levels method in the core-shell designed nanomaterials. Following this strategy, the core-shell-structured NaGdF4:Yb,Er@ NaYF4:Ce,Tb,Eu nanocrystals have been successfully prepared. Remarkably, the adverse cross-relaxation among different activators is extremely suppressed owing to the spatial separation of Er3+ and Eu3+/Tb3+ activators, being conducive to the realization of both intense green upconverting emissions and yellow downshifting luminescence. Moreover, the temperature-sensitive dual-mode luminescent behaviors of core-shell nanomaterials are systematically studied to probe the possible application in FIR-related luminescent thermometry. Specially, the thermally-coupled-levels-based FIR of Er3+ : 2H11/2 / 4I15/2 to Er3+ : 4S3/2 / 4I15/2 and non-thermally-coupled-levels-based FIR of Eu3+ : 5D0 / 7F2 to Tb3+ : 5D4 / 7F6 are proved to be applicable as temperature probes, leading to the achievement of dual-mode temperature sensing. Using the pre-designed core@shell nanoarchitectures, the absolute sensitivity can reach up to 1.02% K-1 based on Eu3+/Tb3+ Stokes emissions and the relative sensitivity could reach as high as 1.12% K-1 based on Er3+ anti-Stokes luminescence. We believe that this study provides a valid approach for developing high-performance optical nanothermometers.
关键词： Optical nanothermometry,Rare-earth luminescent materials,Dual-mode emission,Core-shell nanoarchitectures
更新于2025-11-20 15:33:11
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Beta-lead oxide quantum dot (β-PbO QD)/polystyrene (PS) composite films and their applications in ultrafast photonics
摘要： Polymer composite films, particularly those based on polymers and layered nanomaterials, are attractive materials for exploiting the properties of multiple materials for applications in electronics and photonics. In this work, a beta-lead oxide quantum dot (β-PbO QD)/polystyrene (PS) composite film is successfully fabricated by a solution blending method. The β-PbO QDs are well-distributed within a β-PbO QD/PS composite film and the composite film is transparent and flexible. Owing to the almost complete insolubility of both β-PbO QDs and PS, the as-fabricated β-PbO QD/PS composite film holds the nonlinear photonic response from 540 nm to 1060 nm under complete water immersion, confirming its excellent stability to high humidity. Additionally, the β-PbO QD/PS composite film exhibits a considerable capacity for optical modulation owing to a strong nonlinear absorption coefficient compared with those of other two-dimensional (2D) materials. On the basis of a home-made β-PbO QD/PS composite film saturable absorber, stable mode-locked pulses at 1060 nm are generated under humid conditions. It is anticipated that the β-PbO QD/PS composite films enable the exploitation of new waterproof, flexible photonic devices based on functional 2D materials and polymers.
关键词： composite films,mode-locked pulses,ultrafast photonics,polystyrene,nonlinear absorption,beta-lead oxide quantum dot
更新于2025-11-19 16:56:42
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Plasmonic Metasurfaces with Tunable Gap and Collective SPR Modes
摘要： Optical properties of a plasmonic metasurface made of a monolayer of gold nanoparticles in close proximity to an aluminum thin film were studied numerically and experimentally. Extinction spectra of the plasmonic metasurface were studied as functions of the thickness of a dielectric spacer between the monolayer of gold nanoparticles and the aluminum film in the visible wavelength range. The goal was to understand the excitation of a collective surface plasmon resonance (SPR) mode and a gap plasmon mode as well as their dependence on the spacer thickness, nanoparticles spacing and their size. By using finite-difference-time-domain (FDTD) calculations we find that the SPR extinction peak first red-shifts and then splits into two peaks. The first extinction peak is associated with the collective SPR mode of the monolayer and it shifts to shorter wavelengths as the spacer layer decreases. As the spacer layer decreases from 35 nm to 7.5 nm, the second peak gradually appears in the extinction spectra of the metasurface. We assign the second peak to the gap mode. The gap mode first appears at around 620 nm or greater and it shifts to larger wavelength for larger nanoparticle spacing and size. The FDTD simulations are confirmed by an experimental examination of the dispersion curves of a similar multilayer system. The computational results match the experimental results and confirm the excitation of the two modes.
关键词： gap plasmon mode,surface plasmon resonance,Plasmonic metasurfaces,aluminum thin film,FDTD,gold nanoparticles
更新于2025-11-19 16:56:42
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Plasmonic Nanocavity Metasurface Based on Laser-Structured Silver Surface and Silver Nanoprisms for the Enhancement of Adenosine Nucleotide Photoluminescence
摘要： A reliable photoluminescence (PL) spectroscopy and imaging of biomolecules at room temperature is a challenging and important problem of biophysics, biochemistry, and molecular genetics. A unique effect of strong plasmonic enhancement of the PL by metal nanostructures is one of the most effective approaches for this purpose. The highest enhancement is provided by metal nanostructures with densely packed sharp tips, periodically arranged metal nanostructures, and plasmonic cavities. All of these features have been realized in the plasmonic cavity metasurface based on the silver (Ag) laser-induced periodic surface structure and Ag triangular nanoprisms studied in the present work. The strong plasmon-enhanced PL of 5′-deoxyadenosine monophosphate deposited on such metasurfaces has been revealed at room temperature. The observed enhancement of more than 1000-fold has been interpreted as a result of synergetic action of the generation of a high concentration of hot spots near the sharp edges of the laser-induced surface structure and nanoprisms together with excitation of the collective gap mode of the cavity due to strong near-field plasmonic coupling. Correspondingly, the plasmonic cavity metasurfaces consisting of metal laser-induced periodic surface structures and nonspherical metal nanoparticles with sharp edges have been shown to be crucial for the highly sensitive detection and imaging of biomolecules at room temperature without consuming any dye labels.
关键词： hot spots,plasmon gap mode,plasmonic metasurface,near-field coupling,nucleotide photoluminescence enhancement
更新于2025-11-19 16:46:39
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Planar plasmonic nanocavity for efficient enhancement of photoluminescence of molecular emitters
摘要： Effects of plasmonic gap mode formation due to coupling between metal nanoparticles and thin metal film separated by thin dielectric luminescent film-spacer (gap) have been studied by means of light extinction and photoluminescence in three-layer planar Au NPs monolayer/shellac-dye film/Au film nanostructure with spacer thickness varied in the range 8–47 nm. The 3-fold enhancement of light extinction and 90 nm red shift of the plasmon mode have been observed in extinction spectra. The 37-fold enhancement of dye photoluminescence and the significant (48 nm) red shift of dye photoluminescence band have been observed for Au NPs monolayer/shellac-dye film/Au film nanostructure in comparison with bare shellac-dye film for the spacer thickness of 8 nm. The decrease of the spacer thickness causes the increase of the enhancement factor of dye photoluminescence indicating the strengthening of the gap mode field. FDTD calculations of the dependence of the intensity of the field of gap mode on the gap thickness have demonstrated good quantitative agreement with experimental data that proves the key role of gap mode in the enhancement of the electromagnetic field in planar metal NPs monolayer/dielectric film/metal film plasmonic nanocavity nanostructures. The variation of the gap thickness provides the possibility to tune controllably the spectral position and enhancement factor of the light emission from the molecular emitters located in the gap that can be used in the novel nanophotonics devices and for highly sensitive detection of the single molecules.
关键词： Near field coupling,Gap thickness dependence,Molecular emitters,Gap mode,Plasmonic nanocavity,Photoluminescence enhancement
更新于2025-11-19 16:46:39
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N-arylated bisferrocene pyrazole for dual-mode detection of hydrogen peroxide: AIE-active fluorescent “turn on/off” and electrochemical non-enzymatic sensor
摘要： A series of new N?arylated bisferrocene pyrazole (D-π-A-π-D) chromophores have been synthesized by the Chan?Lam cross-coupling (1, 2) and Buchwald–Hartwig amination (3, 4) reactions. The compounds 1-4 were characterized with the aid of analytical and spectroscopic methods. The solvatochromism behaviour of compounds (1, 3) showed positive solvatochromism and later (2, 4) exhibited negative solvatochromism. The compounds 1-4 interestingly showcased high-enhanced fluorescent intensity in their aggregate state while in the solution state they exhibited low fluorescent intensity behaviour. The origin of enhanced emission in the aggregated state is due to a restriction of intramolecular rotation, especially in the ratio of mixture 40:60 (CH3CN/H2O). The aggregation-induced emission(AIE) properties were utilized to detect the H2O2 which show quick response in a linear range of 10-50 μM with a detection limit of 38.8 nM (1) and 15.9 nM (3). Furthermore, the electrochemical reduction of hydrogen peroxide in the same linear range as above showed and a limit of detection (3σ) of 14.4 mM (1) and 11.6 mM (3).
关键词： Dual-mode detection of H2O2,Electrochemical non?enzymatic sensor,AIE-active luminogens
更新于2025-11-14 15:29:11
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Lossy Mode Resonance Generation by Graphene Oxide Coatings onto Cladding-Removed Multimode Optical Fiber
摘要： In this work, we have studied the suitability of graphene oxide-based thin films to be not only excellent sensitive coatings but also lossy mode resonance (LMR)-generating materials. Thin films of graphene oxide (GO) and polyethylenimine (PEI) fabricated by means of layer-by-layer assembly were selected in this study. Two optical fiber devices with 8 and 20 bilayers of the LMR-generating coating were fabricated and characterized as refractometers. Both devices show no hysteresis and high sensitivity, improving previously reported values. This research opens very promising and exciting possibilities in the field of optical fiber sensors based on LMR, strategically including specific recognition groups to the device surface to exploit this high sensitivity for monitoring a range of target analytes. The carboxylate functional groups at the edges of the GO sheets should provide excellent attachment sites for the required coupling chemistry to realize such devices.
关键词： optical fiber sensor,thin films,Dip-assisted layer by layer,lossy mode resonance,refractometer,graphene oxide
更新于2025-11-14 15:19:41
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Study of visible-light photocatalytic degradation of 2,4-dichlorophenoxy acetic acid in batch and circulated-mode photoreactors
摘要： Purpose The consumption of pesticides and chemical fertilizers is one of the major environmental and health problems. In this report, 2,4-dichlorophenoxyacetic acid (2,4-D) was chosen to evaluate the impact of photodegradation using LED (Light-emitting diode) (400 and 365 nm) sources in batch and programmable circulated-mode photoreactors respectively. Methods A β-cyclodextrin (β-CD) grafted titanium dioxide P25 (P25/β-CD) and complexation of 2,4-D and β-CD were synthesized via photoinduced and spray-drying methods, respectively. The structures were characterized. Moreover, we investigated the effects of the amount of catalyst, the β-CD amount on bed catalyst, irradiation time, kind of photoreactor on the photocatalytic degradation efficiency. Results Based on the results of experiments in batch reactor, the optimum amount of TiO2, β-CD grafted by catalyst were 1 and 0.1 g/L, respectively. In batch-mode the photodegradation efficiency of 2,4-D after 5 h with P25, P25/β-CD as a photocatalyst and 2,4-D/β-CD complex with P25 photocatalyst were approximately 81, 85 and 95% respectively. After 8 h of irradiation in circulated-mode reactor, degradation yields with P25, P25/β-CD and 2,4-D/β-CD complex along with P25 were 89, 91 and 96% respectively. On the other hand, the circulated-mode photoreactor with high efficiency was appropriate to degradation of the high concentration of 2,4-D solution (200 mg/L). After 5 successive cycles with 25 h of irradiation, P25 and P25/β-CD maintained as high 2,4-D removal efficiency as 82.6, 84% respectively, with excellent stability and reusability. Conclusion The photodegradation method can be used as an effective and environmental friendly process in the degradation of organic compound.
关键词： 2,4-D/β-CD complex,Batch-mode photoreactor,Light-emitting diode (LED),Circulated-mode photoreactor,2,4-Dichlorophenoxyacetic acid (2,4-D)
更新于2025-11-14 15:18:02