Optical Responses of Localized and Extended Modes in a Mesoporous Layer on Plasmonic Array to Isopropanol Vapor
Shunsuke MuraiElena Cabello‐OlmoRyosuke KamakuraMauricio E. CalvoGabriel LozanoTaisuke AtsumiHernán MíguezKatsuhisa Tanaka
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Mesoporous silica features open and accessible pores that can intake substances from the outside. The combination of mesoporous silica with plasmonic nanostructures represents an interesting platform for an optical sensor based on the dependence of plasmonic modes on the refractive index of the medium in which metallic nanoparticles are embedded. However, so far only a limited number of plasmonic nanostructures are combined with mesoporous silica, including random dispersion of metallic nanoparticles and flat metallic thin films. In this study, we make a mesoporous silica layer on an aluminum nanocylinder array. Such plasmonic arrangements support both localized surface plasmon resonances (LSPRs) and extended modes which are the result of the hybridization of LSPRs and photonic modes extending into the mesoporous layer. We investigate in situ optical reflectance of this system under controlled pressure of isopropanol vapor. Upon exposure, the capillary condensation in the mesopores results in a gradual spectral shift of the reflectance. Our analysis demonstrates that such shifts depend largely on the nature of the modes; that is, the extended modes show larger shifts compared to localized ones. Our materials represent a useful platform for the field of environmental sensing.Keywords:
Plasmonic Nanoparticles
plasmonic 结构的实现通常要求昂贵的制造技术，例如电子横梁和集中的离子横梁平版印刷术，允许低维的结构的自顶向下的制造。以一种自底向上的方式做 plasmonic 结构的另一条途径是胶体的合成，它对液体状态应用或聚集问题是重要挑战的很薄的稳固的电影方便。用这些方法准备的体系结构典型地不为容易的处理和方便集成是足够柔韧的。因此，开发没有不利地影响 plasmonic，有大规模尺寸的柔韧的站台展示的新 plasmonic 在高需求。作为一个答案，这里我们在场合成结构由金 nanoparticles (Au NP ) 组成在大规模上合并了到蔗糖 macrocrystals 的新 plasmonic，当保存 Au NP 的 plasmonic 性质并且在同时处理提供坚韧性时。作为概念示范的一个证明，我们在场经由在蔗糖晶体结合这些 Au NP 的 plasmonic 的绿 CdTe 量点(QD ) 的荧光改进。获得的合成材料展览厘米规模尺寸和产生的量效率(QE ) 被 58% 经由在 Au NP 和 CdTe QD 之间的相互影响提高(从 24% ～ 38%) 。而且，一从 11.0 ～ 7.40 在光致发光一生弄短 ns，对应于 2.4 的一个地改进因素，在 Au NP 的介绍之上被观察进 QD 合并 macrocrystals。这些结果建议如此的香甜的 plasmonic 晶体是有希望的让大规模柔韧的平台嵌入 plasmonic nanoparticles。
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Noble metal nanoparticles have been extensively studied to understand and apply their plasmonic responses, upon coupling with electromagnetic radiation, to research areas such as sensing, photocatalysis, electronics, and biomedicine. The plasmonic properties of metal nanoparticles can change significantly with changes in particle size, shape, composition, and arrangement. Thus, stabilization of the fabricated nanoparticles is crucial for preservation of the desired plasmonic behavior. Because plasmonic nanoparticles find application in diverse fields, a variety of different stabilization strategies have been developed. Often, stabilizers also function to enhance or improve the plasmonic properties of the nanoparticles. This review provides a representative overview of how gold and silver nanoparticles, the most frequently used materials in current plasmonic applications, are stabilized in different application platforms and how the stabilizing agents improve their plasmonic properties at the same time. Specifically, this review focuses on the roles and effects of stabilizing agents such as surfactants, silica, biomolecules, polymers, and metal shells in colloidal nanoparticle suspensions. Stability strategies for other types of plasmonic nanomaterials, lithographic plasmonic nanoparticle arrays, are discussed as well.
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Plasmonic nanocrystals with hot spots are able to localize optical energy in small spaces. In such physical systems, near-field interactions between molecules and plasmons can become especially strong. This paper considers the case of a nanoparticle dimer and a chiral biomolecule. In our model, a chiral molecule is placed in the gap between two plasmonic nanoparticles, where the electromagnetic hot spot occurs. Since many important biomolecules have optical transitions in the UV, we consider the case of Aluminum nanoparticles, as they offer strong electromagnetic enhancements in the blue and UV spectral intervals. Our calculations show that the complex composed of a chiral molecule and an Al-dimer exhibits strong CD signals in the plasmonic spectral region. In contrast to the standard Au- and Ag-nanocrystals, the Al system may have a much better spectral overlap between the typical biomolecule's optical transitions and the nanocrystals' plasmonic band. Overall, we found that Al nanocrystals used as CD antennas exhibit unique properties as compared to other commonly studied plasmonic and dielectric materials. The plasmonic systems investigated in this study can be potentially used for sensing chirality of biomolecules, which is of interest in applications such as drug development.
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Plasmonic nanocrystals with hot spots are able to localize optical energy in small spaces. In such physical systems, near-field interactions between molecules and plasmons can become especially strong. This paper considers the case of a nanoparticle dimer and a chiral biomolecule. In our model, a chiral molecule is placed in the gap between two plasmonic nanoparticles, where the electromagnetic hot spot occurs. Since many important biomolecules have optical transitions in the UV, we consider the case of Aluminum nanoparticles, as they offer strong electromagnetic enhancements in the blue and UV spectral intervals. Our calculations show that the complex composed of a chiral molecule and an Al-dimer exhibits strong CD signals in the plasmonic spectral region. In contrast to the standard Au- and Ag-nanocrystals, the Al system may have a much better spectral overlap between the typical biomolecule's optical transitions and the nanocrystals' plasmonic band. Overall, we found that Al nanocrystals used as CD antennas exhibit unique properties as compared to other commonly studied plasmonic and dielectric materials. The plasmonic systems investigated in this study can be potentially used for sensing chirality of biomolecules, which is of interest in applications such as drug development.
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