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Investigation of Strongly Hydrophobic and Thick Porous Silicon Stain Films Properties
摘要： Porous silicon (PSi) structures with strong hydrophobicity have been achieved by chemical etching of p-type silicon substrates in a solution based on hydrofluoric acid solution (HF) and vanadium oxide (V2O5). The surface morphology and microstructure of the elaborated structured silicon surfaces were investigated using Scanning Electron Microscope (SEM), contact angle and Fourier Transform Infrared spectroscopy (FTIR). The results show that the obtained structures exhibit hierarchically porous surfaces with porous pillars of silicon (PPSi) and an important hydrophobicity of the surface. The electrical properties of those PPSi structures were investigated in presence of 10 ppm of NO2 gas. The response time was about 30s at room temperature. Our results demonstrate that PPSi/Si are highly hydrophobic for long time and suitable for applications in the field of self-cleaning and may be a good candidate in elaborating practical NO2 sensors.
关键词： Porous silicon,Hydrophobicity,Gas sensing applications,Pillars structures
更新于2025-09-23 15:23:52
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Carbon and graphene quantum dots: a review on syntheses, characterization, biological and sensing applications for neurotransmitter determination
摘要： Neuro-transmitters have been considered to be essential biochemical molecules, which monitor physiological and behavioral function in the peripheral and central nervous systems. Thus, it is of high pharmaceutical and biological significance to analyze neuro-transmitters in the biological samples. So far, researchers have devised a lot of techniques for assaying these samples. It has been found that electro-chemical sensors possess features of robustness, selectivity, and sensitivity as well as real-time measurement. Graphene quantum dots (GQDs) and carbon QDs (CQDs) are considered some of the most promising carbon-based nanomaterials at the forefront of this research area. This is due to their characteristics including lower toxicity, higher solubility in various solvents, great electronic features, inertness, high specific surface areas, plenty of edge sites for functionalization, and strong chemical versatility, in addition to their ability to be modified via absorbent surface chemicals and the addition of modifiers or nano-materials. Hence in the present review, the synthesis methods of GQDs and CQDs has been summarized and their characterization methods also been analyzed. The applications of carbon-based QDs (GQDs and CQDs) in biological and sensing areas, such as biological imaging, drug/gene delivery, antibacterial and antioxidant activity, photoluminescence sensors, electrochemiluminescence sensors and electrochemical sensors, have also been discussed. This study then covers sensing features of key neurotransmitters, including dopamine, tyrosine, epinephrine, norepinephrine, serotonin and acetylcholine. Hence, issues and challenges of the GQDs and CQDs were analyzed for their further development.
关键词： Carbon quantum dots,Graphene quantum dots,Neurotransmitters,Biological applications,Sensing applications,Electrochemical sensors
更新于2025-09-23 15:19:57
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Narrow plasmonic surface lattice resonances with preference to asymmetric dielectric environment
摘要： Plasmonic surface lattice resonances (SLRs) supported by metal nanoparticle arrays exhibit narrow linewidths and enhanced localized ?elds and thus are attractive in diverse applications including nanolasers, biochemical sensors and nonlinear optics. However, it has been shown that these SLRs have much worse performance in a less symmetric environment, hindering their practical applications. Here, we propose a novel type of narrow SLRs that is supported by metal-insulator-metal nanopillar arrays and that has better performance in a less symmetric dielectric environment. When the dielectric environment is as asymmetric as the air/polymer environment with a refractive index contrast of 1.0/1.52, the proposed SLRs have high quality factors of 62 under normal incidence and of 147 under oblique incidence in the visible regime. We attribute these new SLRs to Fano resonance between an in-plane dipole and an out-of-plane quadrupole (or dipole) that are respectively supported by the two metal ridges under normal (or oblique) incidence. We also show that the resonance wavelength can be tuned by varying the geometric sizes or by changing the angle of incidence. By doing this, we clarify the conditions for the formation of the proposed SLRs and illustrate their attractive merits in sensing applications. We expect that this new SLR can open up applications in asymmetric dielectric environments.
关键词： sensing applications,asymmetric dielectric environment,Plasmonic surface lattice resonances,metal-insulator-metal nanopillar arrays,Fano resonance
更新于2025-09-23 15:19:57
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Plasmonic Nanolenses Produced by Cylindrical Vector Beam Printing for Sensing Applications
摘要： Interaction of complex-shaped light fields with specially designed plasmonic nanostructures gives rise to various intriguing optical phenomena like nanofocusing of surface waves, enhanced nonlinear optical response and appearance of specific low-loss modes, which can not be excited with ordinary Gaussian-shaped beams. Related complex-shaped nanostructures are commonly fabricated using rather expensive and time-consuming electron- and ion-beam lithography techniques limiting real-life applicability of such an approach. In this respect, plasmonic nanostructures designed to benefit from their excitation with complex-shaped light fields, as well as high-performing techniques allowing inexpensive and flexible fabrication of such structures, are of great demand for various applications. Here, we demonstrate a simple direct maskless laser-based approach for fabrication of back-reflector-coupled plasmonic nanorings arrays. The approach is based on delicate ablation of an upper metal film of a metal-insulator-metal (MIM) sandwich with donut-shaped laser pulses followed by argon ion-beam polishing. After being excited with a radially polarized beam, the MIM configuration of the nanorings permitted to realize efficient nanofocusing of constructively interfering plasmonic waves excited in the gap area between the nanoring and back-reflector mirror. For optimized MIM geometry excited by radially polarized CVB, substantial enhancement of the electromagnetic near-fields at the center of the ring within a single focal spot with the size of 0.37λ2 can be achieved, which is confirmed by Finite Difference Time Domain calculations, as well as by detection of 100-fold enhanced photoluminescent signal from adsorbed organic dye molecules. Simple large-scale and cost-efficient fabrication procedure offering also a freedom in the choice of materials to design MIM structures, along with remarkable optical and plasmonic characteristics of the produced structures make them promising for realization of various nanophotonic and biosensing platforms that utilize cylindrical vector beam as a pump source.
关键词： plasmonic nanostructures,cylindrical Vector Beam printing,Sensing Applications,nanofocusing,plasmonic nanolenses
更新于2025-09-12 10:27:22