Abstract
Introduction: One of metal fine particles’ applications is Surface Enhanced Raman Scattering; SERS) with their surface plasmon resonance. It is usually performed on the substrates which have gold or silver clusters on their surface. It can be enhanced at the gap between two clusters much more than at the surface of a cluster. However, this enhancement at the gap of clusters was limited because these clusters were usually placed on the plate substrate. Placed these nanoparticles on the surface of the larger particles, the enhanced point can be moved on any place.In this study, we tried to prepare polystyrene (PS) particles which have smaller metal particles deposited by the electroplating on their surface. Experimental: PS beads (<1.0 μm) were used as template particles. The PS dispersion in 50 % ethanol aqueous solution was put on indium tin oxide coated glass substrate to form the colloidal crystalline template.The flash electroplating was performed with DC power supply with 1 – 10 V in aqueous solutions containing silver ions. After rinsed with distilled water, the particles were observed by scanning electron microscopy.Photoabsorption spectrum of Ag deposited samples were measured for evaluation of LSPR. Results and Discussions: SEM images of Ag electroplated with 3 V for 5 s in 0.001 M AgNO3 aqueous solution on the template by 1.0 μm PS beads were shown in Fig. 1. With lower voltage, 1 V, less Ag clusters were generated. With higher voltage, the clusters were rapidly grown and covered the PS beads’ surface so that it is not found the gap between the clusters. Same tendency was found the results with more concentrated silver solution. It is suggested that the optimal condition for placing Ag clusters on the PS beads was the electroplating with 3 or 5 V. It is also indicated that the Ag particles’ size can be controlled by the applied DC voltage and applied period of electrodeposition. In addition, the Ag cluster induced photoabsorption with surface plasmon resonance (SPR) around 480 nm region. The photoabsorption was observed particularly strongly in the brushy structure (using 1.0 μm PS beads and 5 V applied), and it was shown that it was due to the strong electromagnetic field derived from the nanogap structure in the Ag clusters. This also shows that SPR is localized. We have succeeded in preparing the localized surface plasmon resonance (LSPR) active structure and found that its optical properties can be controlled using a very simple method with an electroplating process. These results suggest that one of the possibilities of the helpful to high sensitivity the sensor using the surface enhanced method (Raman, IR, photoluminescence (PL) and more). Acknowledgement: This work was supported by JSPS KAKENHI Grant Number JP19K05191. Figure 1
Published Version
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