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Controlled etching of silica nanospheres monolayer for template application: A systematic study
摘要： Monolayers of silica nanospheres (SNs), via self- or guided-assembly has been extensively used for template fabrication in thin films, employed in the areas of plasmonics, photonic crystals, and solar cells. We report on a versatile, rapid, and controllable process to obtain non-close-packed structure by restructuring the SNs geometry at two-particle level. A geometrical model has been proposed to quantify parameters that control the final morphology of the monolayer. SNs of different sizes (viz. 140 nm, 170 nm, and 220 nm) were self-assembled as a close-packed monolayer on a silicon substrate using a three-step spin coating method and then sintered at 950oC before being exposed to an etchant. We investigate the dependence of particle radius, neck (formed due to sintering) parameters and distance between the SNs, on etching time and etchant concentration. The intermediate and final morphology of the restructured monolayer is used as a template to grow silicon nanowires using metal-assisted chemical etching. We provide quantitative estimates of the parameters pertaining to the restructuring of the monolayer of SNs, which can be used as tunable templates for the growth of nanowires. The optimized process can be scaled-up for industrial application because of its faster and controllable rate of production.
关键词： Silica Nanospheres,Sintering,Etching,Non-Close-Packed Monolayer,Self-Assembly
更新于2025-09-12 10:27:22
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Controlling Surface Chemical Heterogeneities of Ultrasmall Fluorescent Core–Shell Silica Nanoparticles as Revealed by High-Performance Liquid Chromatography
摘要： Ultrasmall (diameter below 10 nm) fluorescent core?shell silica nanoparticles have garnered increasing attention in recent years as a result of their high brightness and favorable biodistribution properties important for applications including bioimaging and nanomedicine. Here, we present an in-depth study that provides new insights into the physical parameters that govern full covalent fluorescent dye encapsulation within the silica core of poly(ethylene glycol)-coated core?shell silica nanoparticles referred to as Cornell prime dots (C′ dots). We use a combination of high-performance liquid chromatography (HPLC), gel-permeation chromatography, and fluorescence correlation spectroscopy to monitor the result of ammonia concentration in the synthesis of C′ dots from negatively and positively charged versions of near-infrared dyes Cy5 and Cy5.5. HPLC, in particular, allows the distinction between cases of full versus partial dye encapsulation in the silica particle core leading to surface chemical heterogeneities in the form of hydrophobic surface patches, which, in turn, modulate biological response in ferroptotic cell death experiments. Our results demonstrate that there is a complex interplay between dye?dye and dye?silica cluster interactions originally formed in the sol?gel synthesis governing optimal dye encapsulation. We expect that the reduced surface chemical heterogeneities will make the resulting nanoparticles attractive for a number of applications in biology and medicine.
关键词： gel-permeation chromatography,ferroptotic cell death,high-performance liquid chromatography,fluorescent core?shell silica nanoparticles,fluorescence correlation spectroscopy
更新于2025-09-11 14:15:04
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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) - All-Fiber High-Average-Power 4.42-μm Raman Laser Based on Silica Fiber
摘要： Mid-infrared lasers operating at wavelengths above ~3 μm are required for many applications. The lasers of a particular interest are those that can provide high average power and high quality of the output beam. A promising approach to realize such lasers is the use of gas-filled hollow-core fibers (HCF), which combine mid-infrared light guidance with all the advantages of well-established silica fiber technology. Recent progress in silica HCFs for mid-infrared spectral range has resulted in demonstration of various gas fiber lasers at wavelengths from 2.8 to 4.6 μm [1-5]. However, those lasers use bulk elements to couple the pump into a HCF, thus losing such advantages as compactness and alignment-free operation, which are expected from fiber lasers. In this work we demonstrate an all-fiber gas Raman laser operating in a single transversal mode at 4.42 μm and generating average output power as high as 360 mW. The Raman laser was constructed using silica-based fibers only (Fig.1a). A pump source was a high-power erbium-doped fiber laser emitting 2-ns pulses with 75-kHz repetition rate at 1.56 μm. The output fiber of the pump laser was fusion spliced to a revolver-type HCF. In spite of a large difference in mode field diameters of the solid-core and hollow-core fibers (20 and 55 μm, respectively), a 3-dB splice losses were obtained. The splice point was mechanically stable and no splice loss degradation was observed when HCF was filled by molecular hydrogen up to pressure of 50 atm. By using a 3.2-m-long hydrogen-filled revolver-type HCF we realized an efficient 1.56 to 4.42 μm Raman conversion in a single-pass single-cascade scheme. When 2.3 W of the pump average power was coupled to the HCF, the Raman laser generated as high as 360 mW of average power at 4.42 μm (Fig.1b). The quantum conversion efficiency was as high as 46 %. A beam quality factor of the output radiation at λ=4.42 μm was evaluated to be M2=1.4. Our results demonstrate that gas fiber Raman lasers based on revolver hollow-core silica fibers are a viable solution for the development of all-fiber mid-infrared lasers that combine a compact alignment-free design with high power single mode operation. An application area of such laser sources includes, but is not limited to, a high-average-power mid-infrared supercontinuum generation, which is of high importance for numerous applications in science, biomedicine and technology.
关键词： gas-filled hollow-core fibers,silica fiber,mid-infrared lasers,Raman laser,high power
更新于2025-09-11 14:15:04
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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) - Multi-Watt Operation of a Holmium Doped Silica Fibre Laser at 2.2 μm
摘要： Laser sources operating in the atmospheric transmission window between 2.1 and 2.25 μm are of interest for a range of applications (e.g. remote sensing, free-space communication and defence). Holmium fibre lasers provide good coverage of the lower part of this spectral region [1], but operation towards 2.2 μm is much more challenging due to a reduced emission cross-section and higher propagation losses associated with the IR absorption edge of fused silica. Furthermore, OH--contamination can cause additional absorption around 2.2 μm. Here we investigate the limits of long-wavelength tuning of a holmium-doped fibre laser, and report, to the best of our knowledge, the first watt-level (4.1 W) output from a silica fibre laser operating at 2.2 μm.
关键词： silica fibre laser,multi-watt operation,2.2 μm,holmium-doped fibre laser
更新于2025-09-11 14:15:04
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CO2 laser-induced micro-plume treatment of silicon: technique and application
摘要： A method for treating the surface of crystalline silicon (α-Si) covered with a fused silica (SiO2) plate by a laser-induced plume arising from the absorption of CO2 laser radiation in glass is presented. The mechanism of micro-plume formation and the effect of this micro-plume on α-Si sample are considered. The α-Si processing regimes were determined that relate the depth of the formed relief to the radiation power density, the temperature of the micro-plume formed during SiO2 irradiation was measured and reached 3000 K. The diffraction phase gratings were designed, manufactured on silicon, and tested, they successfully split 10.6 μm laser beam at 0 and ± 1 diffraction orders. The method belongs to the group of direct writing methods and is easily adapted to different types of diffraction elements on the surface of Si and other materials transparent to 10 μm irradiation.
关键词： Diffraction phase grating,Fused silica,Laser-induced treatment,CO2 laser,Silicon
更新于2025-09-11 14:15:04
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[IEEE 2018 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) - Boston, MA (2018.7.8-2018.7.13)] 2018 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) - Robust Multi-Layer Graphene-Based Plasmonic Cloaking
摘要： In this paper, a plasmonic cloak is designed at 1.55 μm in an epsilon-near-zero (ENZ) comprised of alternating layers of a graphene-silica stack. Because the inclusion is covered by Au and moreover, the ENZ’s boundaries are sealed by this material with optimized thicknesses, such a cloak can only work for TM incidence. This cloak is robust against the inclusion shape which is capable of working in an exceedingly large bandwidth.
关键词： TM incidence,graphene-silica stack,epsilon-near-zero,plasmonic cloak,robust,large bandwidth
更新于2025-09-11 14:15:04
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Out of plane stacking of InSe-based heterostructures towards high performance electronic and optoelectronic devices using a graphene electrode
摘要： Supramolecular chirality has attracted significant attention because of its critical roles in the life and material sciences. In this study, a natural triterpenoid-tailored amphiphilic molecule C4-MOP was designed and synthesized, in which the pyridinium head group was modified on the skeleton of triterpenoid through an alkyl linker. The introduction of pyridinium not only offers a hydrophilic cation to promote the assembly process but also renders itself as the nucleation point to adsorb silica precursors. The results showed that by adjusting the solvent compositions and the concentration of C4-MOP, well-ordered helical nanoribbons with both right- and left-handedness were fabricated by the assembly of C4-MOP, where the hydrophilic pyridinium cations were helically displayed on the surface of ribbons. Subsequently, by taking advantage of electrostatic interactions between pyridinium and the silica precursor, the supramolecular chirality of C4-MOP was successfully imprinted onto the silica nanostructures using the gel–sol mineralization process. Our work provides a simple yet useful strategy to prepare chiral silica, which could promote the applications of chiral natural products in material science.
关键词： triterpenoid,helical ribbons,silica,biomineralization,supramolecular chirality
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - The damage mitigation process for Si nanopillar structure using silica nanosphere lithography and metal assisted chemical etching
摘要： This work focuses on mitigating the damage from nanostructure fabrication using silica nanosphere lithography (SNL) and metal assisted chemical etching (MACE). Metal contamination and plasma damage are the two main factors to limit the Si wafer's minority carrier lifetime. Ni/Au and Ti/Au metal layers on bare Si wafer are compared using lifetime recovery test. Ti/Au shows to be more suitable for the MACE process. Samples deposited with Ni/Au and Ti/Au show lifetimes of 7 μs and 1200μs, respectively. The silicon surface is degraded significantly by the RIE plasma during the nanosphere etching process. SiO2 protective layer was added to the process, mitigating significantly the plasma damage on the silicon surface. Lifetime measurements shows an improvement over 1 ms when SiO2 protective layer on planar Si wafer is used. Lifetimes of 353 μs and implied open circuit voltages of 651mV were accomplished on nanopillar structured wafers using SiOx protective layer and Ti/Au.
关键词： lifetime recovery,silica nanosphere lithography,metal assisted chemical etching,Si nanopillar structure,damage mitigation
更新于2025-09-11 14:15:04
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Synthesis of Plasmonic Photonic Crystal SiO2–Ag Nanostructures by Ion Beam Deposition of Silver Clusters onto Silica Microspheres
摘要： The synthesis of plasmonic photonic crystal SiO2–Ag nanostructures by deposition of silver nanoparticles is considered. The technique includes the physical sputtering of a silver target with a kiloelectronvolt argon ion beam onto silica microspheres obtained according to St?ber. The plasmon resonance effect is shown to be interrelated with the optical properties of nanostructured supports and the morphology of aggregate structures of silver nanoparticles (clusters).
关键词： silica microspheres,ion beam deposition,plasmonic photonic crystal,SiO2–Ag nanostructures,silver clusters
更新于2025-09-11 14:15:04
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Manufacture and spectroscopic analysis of Tm<sup>3+</sup>-doped silica glass and microstructure optical fiber through the laser sintering technique
摘要： We demonstrated Tm3+-doped silica glass rod was successfully manufactured by laser sintering technique and it was made into Tm3+-doped microstructure optical fiber by stack-capillary-draw method. Based on the absorption spectrum, the core glass shows outstanding spectroscopic properties through Judd-Ofelt analysis. Fiber core-cladding structure was preserved completely without any crystallization in the core. Besides, a self-built fiber laser at 1.95 μm produces 740 mW output power with a slope efficiency of 16.73 %. The results prove that our laser sintering technique is a promising preparation method to acquire fiber materials for 2.0 μm laser.
关键词： microstructure optical fiber,fiber laser,Judd-Ofelt analysis,laser sintering technique,Tm3+-doped silica glass
更新于2025-09-11 14:15:04