The influence of edge and corner evolution on plasmon properties and resonant edge effect in gold nanoplatelets.

In this paper a simulation of the properties of surface plasmons on gold nanoplatelets with various cross-sections inscribed in a circle and an investigation of their field distributions to assign multiple SPRs are described. The manipulated propagation can be obtained through the evolution of edges and corners. Furthermore, the particle morphology and the associated spectral positions alone do not uniquely reflect the important details of the local field distribution or the resonance modes. The plasmon modes were investigated and found to be mainly excited along the edges and in the side and sloped side surfaces. The strong field distributions can generally be found around the corners and how the plasmons transmit through the corners to adjacent edges was also investigated. Besides the plasmons excited along the edges as were found for the triangular nanoplatelets, plasmons were excited in the interior region of the triangular surfaces and were also investigated. Despite this in the infrared region, plasmon modes were found to be along the edges for the hexagonal nanoplatelets. Also, it can be seen that the change of nanoplatelet thickness can support different plasmon modes ranging from dipolar resonance mode to quadrupole resonance mode. The thickness far below the skin depth can display complex plasmon modes along the edges and on the side and sloping side surfaces as well as the strong coupling between the top and bottom surfaces. The observed plasmon resonance modes in this simulation reflect the interference of all these contributions including the plasmons along the edges and on the side surfaces. This is an essential step towards a thorough understanding of plasmon modes and the effect of edge and corner evolution in polygonous nanoplatelets.

[Visual analysis of literature knowledge structure and acupoint matching rules of acupuncture for depression].

OBJECTIVE: To analyze the literature knowledge structure and acupoint matching rules of acupuncture for depression. METHODS: The articles regarding acupuncture for depression published from January 1 of 1984 to October 19 of 2020 were searched in CNKI database. CiteSpace5.7.R2 software was used to import the literature data, and the keyword cluster analysis, emergence analysis and time-zone analysis of articles and acupoints were conducted, and the map of scientific knowledge was draw. RESULTS: A total of 3524 articles were included to the knowledge structure analysis, while 601 articles into the acupoint matching rules analysis. There were 13 keyword clusters of acupuncture for depression, with "post-stroke depression" and "electroacupuncture treatment" as high-frequency keywords, and "electroacupuncture treatment" and "Hamilton depression scale" had high centrality, and "electroacupuncture treatment" had the highest emergence intensity. The keywords such as "electroacupuncture treatment" and "Hamilton depression scale", etc. appeared the earliest, followed by "post-stroke depression", "fluoxetine" and "auricular point therapy", etc. According to traditional Chinese medicine theory, acupoint keywords were divided into four clusters: ①core acupoint, ②replenishing-spleen and dispelling phlegm, dispersing-liver and relieving depression, reinforcing qi and nourishing blood, ③back-shu points, five-zhi points, ④inducing-resuscitation and opening-closes. CONCLUSION: The main knowledge structure of acupuncture for depression includes five parts: treatment method, depression type, TCM-related diseases, literature type and curative effect index. Clinical acupoint matching should adhere to the principle of "focusing the disease before syndrome" and "combination of disease and syndrome", and treatment should be modified for the syndromes of phlegm stagnation blocking, liver-stagnation and qi-stagnation, and deficiency of both qi and blood.

Discrete Dipole Approximation Simulation of Nearly Touching Plasmonic Au Dimers and Influence of Particle Shape Assembly on Optical Response.

The method Discrete Dipole Approximation (DDA) is used to calculate the extinction spectra and field distribution of three types of dimers. In the paper we provide a systematic analysis of the optical response of different nanoscopic dimer structures with relatively small gap distances. A description is given about how the energy and excitation cross sections of dimer plasmons depend on nanoparticle separation. Resonance peaks of dimers show red-shift compared with single nanoparticle. Dimers formed by different single particle display distinct optical response. Interaction junctions in dimers can serve as hot spots for field enhancement. Field distribution in gaps made of two flat planes is nearly continuous. Changing gaps between two particles in dimers can tune the resonance wavelength effectively as well as different particle ensembles. Existence of sharp corners can attract and change field distribution. It is not effective volume but the effective cross-section that dominates the extinction efficiency.