Abstract

Plasmonic light absorption properties of bimetallic Au–Pt core–shell nanorod are investigated theoretically. The plasmonic absorption intensity comparison between the longitudinal peak corresponding to outer Pt surface (denoted as band \(\hbox {Pt}_{\mathrm {L}})\) and the transverse peak corresponding to Au–Pt interface (denoted as band \(\hbox {Au}_{\mathrm {T}})\) is sensitive to the environmental dielectric constant. By increasing the environmental dielectric constant, the band \(\hbox {Pt}_{\mathrm {L}}\) fades down, whereas the band \(\hbox {Au}_{\mathrm {T}}\) gets intense. So the absorption discrepancy between \(\hbox {Pt}_{\mathrm {L}}\) and \(\hbox {Au}_{\mathrm {T}}\) bands could be greatly enhanced by increasing the environmental dielectric constant, which is more sensitive to the environmental refractive index than single plasmonic band. This refractive index sensing based on two bands’ absorption discrepancy could be further improved by increasing the Pt coating thickness or the aspect ratio of inner Au nanorod. The refractive index sensing based on red shift of the longitudinal peak corresponding to Au–Pt interface is also competitive, which can also be improved by increasing the Pt coating thickness or aspect ratio of inner Au nanorod. A mechanism based on media polarization-related electric field discontinuity and distribution of surface charge density was investigated to illuminate the absorption intensity-dependent refractive index sensing.

Graphic abstract

In this Au–Pt core–shell nanorod, the \(\hbox {Pt}_{\mathrm {L}}\) band fades down, whereas the \(\hbox {Au}_{\mathrm {T}}\) band gets intense as the environmental dielectric constant is increased. So the absorption discrepancy between \(\hbox {Pt}_{\mathrm {L}}\) and \(\hbox {Au}_{\mathrm {T}}\) bands could be greatly enhanced by increasing the environmental dielectric constant, which is more sensitive to the environmental refractive index than single plasmonic band.

中文翻译：

---

通过 Pt 涂层提高 Au 纳米棒的等离子体光学可调性：在折射率传感中的应用

摘要

从理论上研究了双金属 Au-Pt 核-壳纳米棒的等离子体光吸收特性。对应于外 Pt 表面的纵向峰（表示为带\(\hbox {Pt}_{\mathrm {L}})\）和对应于 Au-Pt 界面的横向峰（表示为带）之间的等离子体吸收强度比较\(\hbox {Au}_{\mathrm {T}})\)对环境介电常数敏感。通过增加环境介电常数，带\(\hbox {Pt}_{\mathrm {L}}\)逐渐减弱，而带\(\hbox {Au}_{\mathrm {T}}\)得到激烈的。所以\(\hbox {Pt}_{\mathrm {L}}\)和\(\hbox {Au}_{\mathrm {T}}\)之间的吸收差异通过增加环境介电常数可以大大增强波段，环境介电常数比单个等离子体波段对环境折射率更敏感。通过增加 Pt 涂层厚度或内部 Au 纳米棒的纵横比，可以进一步改善基于两个波段吸收差异的折射率传感。基于对应于 Au-Pt 界面的纵向峰红移的折射率传感也具有竞争力，这也可以通过增加 Pt 涂层厚度或内部 Au 纳米棒的纵横比来改善。研究了一种基于介质极化相关电场不连续性和表面电荷密度分布的机制，以阐明吸收强度相关的折射率传感。

图形摘要

在这个 Au-Pt 核壳纳米棒中，\(\hbox {Pt}_{\mathrm {L}}\)带逐渐减弱，而\(\hbox {Au}_{\mathrm {T}}\) )带随着环境介电常数的增加而变强。因此\(\hbox {Pt}_{\mathrm {L}}\)和\(\hbox {Au}_{\mathrm {T}}\)带之间的吸收差异可以通过增加环境介电常数来大大增强常数，它比单个等离子体带对环境折射率更敏感。