Launching and Control of Graphene Plasmons by Nanoridge Structures

The unique properties of graphene plasmons show great potential for plasmonic nanodevice applications such as sensors and modulators. Graphene plasmon launching, propagation control, and ultimately launching with directional control are therefore crucial for the development of such devices. However, previous studies have used foreign objects or external influencing factors to attain directional plasmon launching on graphene, which introduce defects and add complexity to the system. This study introduces a theoretical framework for a graphene-only approach to direction-controlled plasmon launching. We use graphene nanoridges, a defect-free natural structure of graphene, as a plasmon launcher. Through proper arrangement of the nanoridges, unidirectional, bidirectional, and wavelength-sorted plasmon launching with normal illumination can be achieved

Launching and Control of Graphene Plasmons by Nanoridge Structures

The unique properties of graphene plasmons show great potential for plasmonic nanodevice applications such as sensors and modulators. Graphene plasmon launching, propagation control, and ultimately launching with directional control are therefore crucial for the development of such devices. However, previous studies have used foreign objects or external influencing factors to attain directional plasmon launching on graphene, which introduce defects and add complexity to the system. This study introduces a theoretical framework for a graphene-only approach to direction-controlled plasmon launching. We use graphene nanoridges, a defect-free natural structure of graphene, as a plasmon launcher. Through proper arrangement of the nanoridges, unidirectional, bidirectional, and wavelength-sorted plasmon launching with normal illumination can be achieved

Launching and Control of Graphene Plasmons by Nanoridge Structures

The unique properties of graphene plasmons show great potential for plasmonic nanodevice applications such as sensors and modulators. Graphene plasmon launching, propagation control, and ultimately launching with directional control are therefore crucial for the development of such devices. However, previous studies have used foreign objects or external influencing factors to attain directional plasmon launching on graphene, which introduce defects and add complexity to the system. This study introduces a theoretical framework for a graphene-only approach to direction-controlled plasmon launching. We use graphene nanoridges, a defect-free natural structure of graphene, as a plasmon launcher. Through proper arrangement of the nanoridges, unidirectional, bidirectional, and wavelength-sorted plasmon launching with normal illumination can be achieved

Nanoscale pH Profile at a Solution/Solid Interface by Chemically Modified Tip-Enhanced Raman Scattering

A nanoscale pH profile on a 4 × 4 μm² area of NH₂-anchored glass slide in an aqueous solution is constructed using chemically modified tip-enhanced Raman scattering (TERS). <i>p</i>-Mercapto­benzoic acid (<i>p</i>MBA) and <i>p</i>-amino­thiophenol (<i>p</i>ATP) are bonded to the tip surface. A pH change can be detected from a peak at 1422 cm^–1 due to the −COO^– stretching vibration from <i>p</i>MBA and that at 1442 cm^–1 due to the NN stretching vibration arising from the formation of 4,4′-dimercapto­azobenzene (DMAB) on the <i>p</i>ATP-modified tip. The <i>p</i>MBA- and <i>p</i>ATP-modified tip can be used to determine pH in the range of 7–9 and 1–2, respectively. The spatial resolution to differentiate pH of two areas can be considered as ∼400 nm. The measured pH becomes the pH of the bulk solution when the tip is far by ∼200 nm from the surface. This technique suggests a possibility for the pH sensing in wet biological samples. TERS tips could also be chemically modified with other molecules to determine other properties in a solution

Distribution of Polymorphic Crystals in the Ring-Banded Spherulites of Poly(butylene adipate) Studied Using High-Resolution Raman Imaging

Poly­(butylene adipate) (PBA), an important biodegradable polymer, can crystallize into a particular type of ring-banded spherulite, in each of which two crystal forms, α and β, coexist. However, the distribution of the polymorphic crystals and the molecular chains orientation within the ring-banded PBA spherulites are still unclear. To determine these, in our present study, Raman spectroscopy and high spatial resolution Raman imaging were used. Characteristic Raman peaks were identified for both the α- and β-forms and for amorphous structures. Using these peaks, we investigated the polymorphic crystal distribution and molecular chain orientation within the spherulites through Raman imaging. The two crystal forms are found to be unevenly distributed in the center, ring-banded, and out-layer ringless region. The results of this study also suggested that the two crystal forms can nucleate and grow in the same temperature range (31–33 °C), but the relative content of the α-form in the ring-banded region becomes higher with the higher crystallization temperature. The image based on the Hermans orientation function for the ring-banded spherulite shows both bow-tie and ring-banded patterns, which means that the molecular chains in the ring-banded region orient not only about the radial direction of the spherulites but also about the substrate plane. Moreover, the molecular chain orientations also show periodically change along the radial direction of the ring-banded spherulite. The present study shows that Raman imaging is a very powerful technique in polymer crystal structure research