Nanotemplate-Guided Self-Assembly of Gold Nanoparticles and its Application to Plasmonic Bio/Chemical Sensing

Abstract

This paper presents a high-precision and high-yield nanotemplate-guided self-assembly process for spherical gold nanoparticles. This process enables us to arrange particles in designated patterns on a substrate with nanotemplates. These particles are trapped on the nanotemplate by liquid-air interfacial force during drying of the colloidal solution. In this method, particle concentration and electrostatic interaction between particles have a considerable effect on the assembly yield. The particle concentration should be optimized based on the template pattern. A nanogap-controlled particle arrangement with a high yield is achieved by controlling the electrostatic interaction, which is accomplished by adding an electrolyte. This technique enables control of the plasmonic resonance properties of metal nanoparticles on substrates for many emerging applications. Among them, this paper discusses the application of nanotemplate-guided self-assembly to an ultrasensitive nanostructure for surface-enhanced Raman spectroscopy. The gold nanoparticle dimer, which has been reported as the highest Raman enhancing structure, is directionally arrayed on a substrate. The highest enhancement can be achieved when the direction of a particle connection for a dimer is matched to the polarization direction of incident light. A considerable enhancement can be achieved at all dimers. The fabricated structures are evaluated by focusing on the polarization angle. The 10-11-M limit of detection and a 0.05-s rapid detection are achieved by using 4,4-bipyridine molecules with single-molecule sensitivity.