Silver Double Nanorings with Circular Hot Zone

et al. 2021

Advanced Materials

Self Cite

sharp-tip structures with a highly focused field at the end of the tip. [7] In particular, plasmonic gap nanostructures (PGNs) are among the most promising materials for diverse applications with highly localized field and amplified optical signals in the gap including sensing, spectroscopy, optics, biomedicine, electronics, and energy applications. [8][9][10][11][12][13] The development of bottom-up or top-down synthetic methods enabled the access to numerous nanogap structures with diverse gap sizes, morphologies, and compositions. [14][15][16][17][18] The highly localized electric field inside the plasmonic nanogap and the appearance of plasmonic coupling in closely neighboring structures have been studied, leading to the discovery of interesting optical phenomena and advances in sensing such as ultrasensitive spectroscopy, singlemolecule sensing methods, and in situ detection techniques. [19][20][21] As small changes in the distance, morphology, and composition of the nanogap lead to significant variations in the optical responses, the highly precise, controllable, and high-yielding preparation of PGNs is important to achieve reproducible and reliable results. However, although numerous pioneering studies on basic synthetic methods, characteristics, and applications enabled the understanding and control over plasmonic nanogaps, key challenges still remain for the practical use and applications of PGNs. In particular, the sub-nanometer, atomic-level control of the nanogap, coupled with the scaling-up issue, and its fundamental understanding have not yet been fully accomplished. For example, in surfaceenhanced Raman spectroscopy (SERS) using plasmonic gaps, early research focused on a high enhancement factor (EF). In contrast, recent studies revealed that a deep understanding at atomic scale is required, as differences in the small regime such as picocavities or molecular orientation can have a large effect on the signal. [22][23][24] Hence, a comprehensive understanding of the nanogap is critical to the further development of the field.This progress report addresses emerging issues and challenges in the field of nanogap-based plasmonics and plasmonic nanomaterials. We first describe the challenges in the creation of intra-or intergaps by bottom-up or top-down synthesis, and discuss breakthroughs that allow for overcoming these obstacles. Next, optical properties according to gap size, morphology, and composition are summarized to provide insight into the nature of gap plasmonics. The discussion of applications in this article mainly highlights surface-enhanced Plasmonic gap nanostructures (PGNs) have been extensively investigated mainly because of their strongly enhanced optical responses, which stem from the high intensity of the localized field in the nanogap. The recently developed methods for the preparation of versatile nanogap structures open new avenues for the exploration of unprecedented optical properties and development of sensing applications relying on the amplification of various optical signals....

Section: Sersmentioning

confidence: 99%

Synthesis, Assembly, Optical Properties, and Sensing Applications of Plasmonic Gap Nanostructures

Kim

et al. 2021

Advanced Materials

Self Cite

“…Furthermore, the observed enhancement factor of Au nanolens in this report is higher than the previously reported value with Ag double nanorings. 19 Interestingly, when the rim size further increased to 56 nm (and the inner domain concomitantly decreased down to 35 nm), their enhancement further increased but exhibited a broad distribution in the enhancement factors ranging from 1.8 × 10 8 to 2.9 × 10 9 . Once we found the Au nanolens with a “turned-on” status, the measured enhancement was stronger than the case of sample panel (d); however, the sample-by-sample reproducibility was not as good as the other case.…”

Section: Resultsmentioning

confidence: 98%

“…[3][4][5][6][7] It is now well understood that surface plasmons of noble metal nanoparticles, particularly at the narrow gaps or junctions between nanoparticles, localize and enhance the E-eld near noble metal nanoparticles (referred to as "hot spots") for amplifying the Raman scattering of target molecules. [8][9][10][11] To generate hotspots, nanostructures with interparticle gaps, [12][13][14] intraparticle gaps, [15][16][17][18][19][20][21] sharp tips, [22][23][24] or rough surfaces 25,26 were synthesized. Nanoparticles with intraparticle gaps have attracted considerable attention due to their homogeneity and tunability in hotspots, leading to enhanced SERS signal sensitivity and reproducibility.…”

Section: Introductionmentioning

confidence: 99%

“…37,38 In a previous study, we reported Ag double nanorings for efficient single-particle SERS. 19 Herein, we suggest a novel methodology for synthesizing Au nanolens nanostructures with a central "hot area" within a single entity. We synthesized Au nanolens structure by integrating Au nanoporous structure at the inner domain of a Pt@Au nanoring through an eccentric growth of Ag, and a subsequent nanoscale Galvanic exchange reaction.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Au nanolenses for near-field focusing

Kim

et al. 2021

Chem. Sci.

Self Cite

“…In this regard, integrating multiple nanoframes in a single entity can be considered as a new paradigm for e ciently amplifying the structural characteristics of nanoframes. However, the synthetic strategies for complex nanoframes with different multiple internal geometries are rare, and the synthesis of complex multiple nanoframes in a controllable fashion (especially in a solution phase with a high yields and homogeneity in size and shape) remains a great challenge [24][25][26][27][28][29][30] . Herein, we develop rationally designed on-demand multi-step chemical reactions for 4D complex nanoframes with a high degree of structural controllability, which we denoted such unprecedented nanoframes as "N-th nanoframes".…”

Section: Introductionmentioning

confidence: 99%

N-th Nanoframes

Yoo

Hilal

et al. 2022

Preprint

Self Cite

Herein, we report unprecedented four-dimensional complex nanoparticles by embedding various kinds of three-dimensional polyhedral nanoframes within a single entity. This synthetic strategy is based on the selective deposition of metal atoms on high surface energy facets and subsequent growth into solid platonic nanoparticles, followed by the etching of inner metals, leaving complex nanoframes. Our synthetic routes are rationally designed and executable on-demand with a high structural controllability. Diverse Au solid nanostructures (octahedra, truncated octahedra, cuboctahedra, and cubes) evolved into complex multi-layered nanoframes with different numbers/shapes/sizes of internal nanoframes. We refer to the resulting four-dimensional complex nanoframes as “N-th nanoframes”. After coating the surface of the N-th nanoframes with plasmonically active metal (like Ag), the materials exhibited highly enhanced electromagnetic near-field focusing embedded within the internal complicated rim architecture.