School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore.
Nanoscale. 2017 Oct 19;9(40):15356-15361. doi: 10.1039/c7nr03171h.
Silver nanoprisms (AgNPrs) exhibit localized surface plasmon resonance (LSPR) in the near infrared (NIR) region of the electromagnetic spectrum. LSPR-driven electric field enhancement around AgNPr edges has been investigated in various studies. A coating of dielectric materials such as silica on the surface of the AgNPrs is employed to extend the application of these nanoparticles under biocompatible conditions and to increase the thermal stability. Upon interactions with optical excitation (pulsed laser excitation), the AgNPrs undergo light intensity field enhancement (LIFE) at the corners. In the cases of hybrid hetero-structures of AgNPrs with silica coatings (AgNPr@SiO), LIFE leads to nano-structural deformations. In this study, we demonstrate that, depending on the intensity of the light excitation, the medium properties and the geometrical sharpness of the corners of the prisms, LIFE could induce localized damage or abrasion at the edges of the immediate dielectric contact, which in this case was the silica coating. A theoretical study was conducted to establish the influence of the finite radius of curvature (ROC) of the corners on the plasmonic interactions to generate LIFE during optical excitation. Experiments were performed on AgNPr@SiO using nanosecond pulsed laser excitation at 900 nm and electron microscopic analysis of the nanostructures revealed the localized edge abrasion of the silica at the prism corners. To further study the effect of the direct plasmonic excitation during LIFE, pulsed laser excitation on ultra-thin graphene oxide (GO) wrapped AgNPr@SiO (GO-AgNPr@SiO) was conducted. Due to the GO wrapping and subsequent changes in light absorption, the extent of the LIFE at the corners diminishes, which leads to structural stability and preservation of the hetero-structure morphology.
银纳米棱镜（AgNPrs）在电磁光谱的近红外（NIR）区域表现出局域表面等离激元共振（LSPR）。在各种研究中，已经研究了 AgNPr 边缘周围的 LSPR 驱动的电场增强。在 AgNPrs 的表面上涂覆介电材料（如二氧化硅），以在生物相容条件下扩展这些纳米粒子的应用，并提高热稳定性。在与光激发（脉冲激光激发）相互作用时，AgNPrs 在角处经历光强场增强（LIFE）。在 AgNPrs 与二氧化硅涂层的杂化异质结构（AgNPr@SiO）的情况下，LIFE 导致纳米结构变形。在这项研究中，我们证明，取决于光激发的强度、介质特性和棱镜角的几何尖锐度，LIFE 可能会在直接介电接触的边缘处引起局部损伤或磨损，在这种情况下，是二氧化硅涂层。进行了理论研究，以确定角的有限曲率半径（ROC）对等离子体相互作用的影响，以在光激发期间产生 LIFE。在 900nm 的纳秒脉冲激光激发下对 AgNPr@SiO 进行了实验，对纳米结构的电子显微镜分析揭示了在棱镜角处的二氧化硅的局部边缘磨损。为了进一步研究 LIFE 期间直接等离子体激发的影响，对超薄膜氧化石墨烯（GO）包裹的 AgNPr@SiO（GO-AgNPr@SiO）进行了脉冲激光激发。由于 GO 的包裹以及随后的光吸收变化，角处的 LIFE 程度减小，这导致结构稳定性和异质结构形态的保持。
