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Rectangular Pulse Generation from a Mode Locked Raman Fiber Laser
摘要： Rectangular and step-like pulses are generated in a mode locked Raman fiber laser with a nonlinear optical loop mirror. The Raman laser has a typical figure-8 configuration. Stable rectangular pulses with a fundamental repetition rate of 733 kHz are obtained. As the increasing of the pump power, the Raman pulse evolves to a step-like rectangular pulse. The maximum pulse energy is 64.1 nJ with a pulse width of 25.1 ns. After spectrally resolved measurements, the step-like pulse is proved to be induced by the dual wavelength oscillation. It is the first report of rectangular pulsed output in mode-locked Raman fiber laser to the best of our knowledge.
关键词： Laser mode locking,Raman scattering,Fiber lasers
更新于2025-11-28 14:24:03
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Diode-pumped single-pass tunable mid-infrared gas Raman source by methane-filled hollow-core fiber
摘要： We report here, to the best of our knowledge, the first diode-pumped single-pass tunable mid-infrared fiber gas Raman laser source using methane-filled hollow-core fibers. Pumped by a homemade tunable high peak-power amplified diode laser, whose wavelength covers the range of 1540 nm to 1560 nm, the mid-infrared laser emission over the range of 2796 nm to 2863 nm is generated by the stimulated Raman scattering of methane molecules. The highest average output power of ~34 mW at 2829 nm is achieved with 14.2 m fiber at 16 bar when pumped at 1550 nm. This paper opens new opportunities for compact tunable mid-infrared fiber lasers.
关键词： gas lasers,Raman lasers,fibre lasers,stimulated Raman scattering
更新于2025-11-28 14:23:57
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Atmospheric Pressure Plasma Synthesized Gold Nanoparticle/Carbon Nanotube Hybrids for Photo-thermal Conversion
摘要： In this work, a room temperature atmospheric pressure direct-current plasma has been deployed for the one-step synthesis of gold nanoparticle/carboxyl group functionalized carbon nanotube (AuNP/CNT-COOH) nanohybrids in aqueous solution for the first time. Uniformly distributed AuNPs are formed on the surface of CNT-COOH, without the use of reducing agents or surfactants. The size of the AuNP can be tuned by changing the gold salt precursor concertation. UV-Vis, ζ-potential and X-ray photoelectron spectroscopy suggest that carboxyl surface functional groups on CNTs served as nucleation and growth sites for AuNPs and the multiple potential reaction pathways induced by the plasma-chemistry have been elucidated in detail. The nanohybrids exhibit significantly enhanced Raman scattering and photothermal conversion efficiency, properties that are essential for potential multi-modal cancer treatment applications.
关键词： Surface Enhanced Raman Scattering,Gold Nanoparticles,Photothermal Conversion,Carbon Nanotubes,Plasma Synthesis
更新于2025-11-19 16:56:35
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Facile Interface Self-Assembly of Gold Nanoparticles as Surface-Enhanced Raman Scattering Substrate for Monitoring the Reduction of p-Nitrophenol
摘要： A facile interface self-assembly method was proposed to fabricate the gold monolayer film without any specific molecular cross-linkers. The film was served as a surface-enhanced Raman scattering substrate, which exhibited high enhancement and reproducibility to the 1 × 10-9 M rhodamine 6G aqueous solution. Based on the substrate, the in situ and real-time monitoring for the reduction of p-nitrophenol to p-aminophenol was demonstrated successfully.
关键词： Interfaces,Surface-enhanced Raman scattering,Self-assembly,Nanoparticles
更新于2025-11-14 17:03:37
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Au@Cu Nanoarrays with Uniform Long-Range Ordered Structure: Synthesis and SERS Applications
摘要： The nanostructures with uniform long-range ordered structure are of crucial importance for performance standardization of high-quality surface-enhanced Raman scattering (SERS) spectra. In this paper, we described the fabrication and SERS properties of Au decorated Cu (Au@Cu) nanoarrays. The Cu nanoarrays with uniform long-range ordered structure were first synthesized by in-situ electrochemistry assembly on insulated substrate. The Cu nanoarrays can reach a size of centimeters with strictly periodic nano-microstructure, which is beneficial for the production and performance standardization of SERS substrates. Then Au nanoparticals were decorated on the Cu nanoarrays by galvanic reaction without any capping agent. The obtained Au@Cu nanoarrays exhibit excellent SERS activity for 4-Mercaptopyridine, and the sensitivity limit is as low as 10?8 M. Therefore, this facile route provides a useful platform for the fabrication of SERS substrates based on nano ordered arrays.
关键词： Au nanoparticles,Cu nanoarrays,surface decoration,surface-enhanced Raman scattering (SERS)
更新于2025-09-23 15:23:52
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Silver nanoparticles with reduced graphene oxide for surface-enhanced vibrational spectroscopy of DNA constituents
摘要： Composite of silver nanoparticles with reduced graphene oxide flakes is proposed for surface enhanced vibrational spectroscopy, particularly for detection of adenine and thymine as constituents of deoxyribonucleic acid. Composite was formed by original method implying simultaneous reduction of silver ions and graphene oxide by discharge plasma at the gas–liquid interface. Combination of nanosized silver with reduced graphene oxide provided greater enhancement of Raman light scattering and infrared light absorption in comparison with separately used components. Addition of the composite to water solutions of adenine and thymine allowed detection of these analytes at micromolar concentrations. Composite of nano-silver with reduced graphene oxide can be prospective for surface enhanced spectroscopy as an alternative to the expensive lithographically prepared noble metal substrates.
关键词： Adenine,Surface Enhanced InfraRed Absorption (SEIRA),Thymine,Reduced graphene oxide,Discharge plasma,Silver nanoparticles,Surface Enhanced Raman Scattering (SERS)
更新于2025-09-23 15:23:52
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Size and dimension dependent surface-enhanced Raman scattering properties of well-defined Ag nanocubes
摘要： Understanding the role of the morphology and particle–particle interactions on the plasmonic properties is of significant importance for the development of nanomaterials with excellent optical properties. However, the preparation of precisely defined nanomaterials with sizes that span a large range and their controllable self-assembly still remain a great challenge. Here, a multistep seed-mediated method has been established for preparing uniform Ag nanocubes over a broad size range from nanoscale (50 nm) to microscale (1400 nm) and with different hierarchical nanostructures range from “zero-dimension” (“0D”) to “three-dimension” (“3D”). The influence of the size and the interactions between the Ag nanocubes on their surface-enhanced Raman scattering (SERS) properties have been systematically and quantitatively investigated. It is demonstrated through experiments and finite-difference time-domain (FDTD) calculations that the SERS activity is dependent on the matching of the nanocube size to the excitation wavelength. The optimal combinations are 80, 110 and 130 nm nanocubes with respect to 532, 638 and 785 nm excitation wavelength, respectively. Furthermore, the Raman enhancement of the Ag nanocube hierarchical nanostructures increases rapidly from “0D” to “3D”, due to the extra increase of the hot spots that is attributed to the out-of-plane plasmonic coupling realized in the “3D” hierarchical nanostructures. This work clearly illustrates the quantitative role of the size and dimension of Ag nanocubes on their SERS properties and provides fundamental information for the design of advanced nanomaterials with higher SERS sensitivity.
关键词： Silver nanocubes,Self-assembly,Surface-enhanced Raman scattering,Seed-mediated method
更新于2025-09-23 15:23:52
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Gold Nanorod-Coated Capillaries for the SERS-Based Detection of Thiram
摘要： Surface enhanced Raman scattering (SERS)-based capillary system is a promising route towards fast, real-time and in-situ detection using a facile sampling process. Here, we demonstrate for the first time resonance-tunable SERS-active capillaries with high sensitivity, reproducibility and stability. The strong signal consistency independent of measurement spots or storage time supports the long-term storage and signal tracking of analytes in practical use. The capillaries were successfully applied to the in-situ detection of pesticide residues, and the sampling process provides operation conveniency compared to conventional methods. These results indicate that our SERS-active capillaries have great potentials in fast in-situ detection for many practical applications.
关键词： surface enhanced Raman scattering,stability,thiram detection,gold nanorod,capillary tube,tunable plasmon resonance
更新于2025-09-23 15:23:52
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Reproduction of surface-enhanced resonant Raman scattering and fluorescence spectra of a strong coupling system composed of a single silver nanoparticle dimer and a few dye molecules
摘要： The spectral changes in surface-enhanced resonant Raman scattering (SERRS) and surface enhanced fluorescence (SEF) of single silver nanoparticle dimers adsorbed by near-single dye molecules are reproduced under strong coupling regimes. For the reproduction, the enhancement and quenching factors in SERRS and SEF are derived from the Purcell factors including both radiative and nonradiative plasmon modes. The Purcell factors are estimated using the coupling energies obtained by analyzing the spectral changes in plasmon resonance during SERRS and SEF decay processes on the basis of a classical hybridization model. The model is composed of a plasmon and a molecular exciton with phonon replicas accurately representing the molecular multi-level system. The reproduced SERRS spectral changes are consistent with the experimental ones. Furthermore, the calculated SEF spectral changes can reproduce the experimental ones by phenomenologically assuming transitions from ultra-fast SEF to conventional SEF with decreasing coupling energies.
关键词： strong coupling,hybridization model,silver nanoparticle dimer,dye molecules,Purcell factors,surface enhanced fluorescence,surface-enhanced resonant Raman scattering
更新于2025-09-23 15:23:52
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Developing cysteamine-modified SERS substrate for detection of acidic pigment with weak surface affinity
摘要： In this paper, we developed cysteamine-modified surface-enhanced Raman scattering (SERS) substrate for detecting detect trace amount of acidic pigment that shows weak affinity with gold nanoparticles (Au NPs). To realize sensitive and reproducible detection of pigment with weak affinity, the SERS substrate was prepared by attaching cysteamine (CA) to the Au NPs, the acidic pigment molecule could rapidly reached to the surface of Au NPs because of the formation of multi-hydrogen-bond and electrostatic interaction between the pigment and CA molecule. The proposed method allowed us to detect five kinds of acidic pigment with a limit of 1.0 ppm, which is below the strictest safety limit. Compared with the previous methods, the advantages of the present substrate were its simple substrate preparation, high reproducibility and good universality. Furthermore, the reliable and enough accurate results had been obtained by using of the proposed substrates in the assay of trace pigment in real samples.
关键词： surface-enhanced Raman scattering,hydrogen bond interaction,cysteamine-modified,acidic pigment,weak affinity
更新于2025-09-23 15:23:52