Abstract

The hollow nanostructures are conducive to applications including drug delivery, energy storage and conversion, and catalysis. In the present work, a versatile type of Au nanoparticles, i.e. nanocage with hollow interior, was studied thoroughly. Simulation of the optical properties of nanocages with different sizes and shapes was presented, which is essential for tuning the localized surface plasmon resonance peak. The edge length, side length of triangle, and wall thickness were used as structural parameters of truncated Au nanocage. The dependence of absorption efficiency, resonant wavelength, and absorption quantum yield on the structural parameters were discussed. Meanwhile, the applications of absorption quantum yield in biomedical imaging and laser induced thermal therapy were investigated. It was found that the phenomenon of multipolar plasmon resonances exists on truncated Au nanocage. Furthermore, the electric field distribution at different resonant wavelengths was also investigated. It is found that the electromagnetic field corresponds to the dipolar mode in an individual nanocage is largely distributed at the corners. Whereas, the electromagnetic field corresponds to the multipolar region is mainly located in the internal corners and edges.

Highlights

  • Since the optical properties of Au colloids were firstly observed by Faraday,[1] the phenomenon known as localized surface plasmon resonance (LSPR) induced by the interaction of light and nanoparticles has attracted considerable interest in various fields, such as biology, energy harvesting, and medicine/pharmacology.[2,3,4,5]

  • A truncated Au nanocage with all the eight corners replaced by triangular holes was investigated

  • The edge length, side length of triangle and wall thickness were used as structural parameters of nanocage

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Summary

Introduction

Since the optical properties of Au colloids were firstly observed by Faraday,[1] the phenomenon known as localized surface plasmon resonance (LSPR) induced by the interaction of light and nanoparticles has attracted considerable interest in various fields, such as biology, energy harvesting, and medicine/pharmacology.[2,3,4,5] When the size of metal nanoparticles is under subwavelength, free electrons in the nanoparticles oscillate collectively.[6]. For biomedical imaging, the LSPR of nanoparticles can enhance the optical signal characteristics of certain organizations so as to improve the contrast of imaging,[7,8] which has important application in early cancer detection and diagnosis. To reduce the undesired damage to surrounding healthy tissue, the cancerous tissue must have a relatively high absorption compared to the surrounding healthy tissues.[9] In order to apply Au nanoparticles to in vivo analysis, especially involving the excitation and transformation of optical signals, the LSPR peaks of Au nanoparticles must be tuned to the near infrared band so as to achieve the maximum penetration depth of the healthy tissue.[10] In the near infrared region, the optical attenuation caused by blood and biological tissues is weak which is beneficial for the detection and treatment of deep tissue lesions.[11] The target of tuning LSPR peaks to the near infrared band rules out some kinds of nanoparticles, such as nanosphere

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