Presentation Information
[17p-WL2_201-14]Silicon Core-Polymer Shell Nanoparticles for Fabrication of Silicon Metasurface with Controlled Inter-Particle Distance
〇(D)VU THI OANH1, Mojtaba Karimi Habil1, Hiroshi Sugimoto1, Minoru Fujii1 (1.Kobe Univ.)
Keywords:
Mie resonance,silicon nanosphere,core-shell particle
Surface-enhanced fluorescence (SEF) sensors based on dielectric nanostructures exploit low-loss Mie resonances to amplify local electromagnetic fields, enabling efficient fluorescence enhancement with reduced quenching compared to metallic counterparts. Silicon (Si) with high refractive index (n~4) and low loss is one of the most widely employed dielectric materials in SEF. Although Si shows high compatibility with modern nanofabrication processes, especially electron beam lithography, it is quite expensive to produce large-scale devices. Bottom-up assembly using colloidal suspensions of Si nanospheres (NSs) can offer a cost-effective alternative, enabling the formation of various ordered nanostructures, e.g. close-packed monolayer, via self-assembly methods like Langmuir–Blodgett. FDTD simulations show that 150 nm-diameter Si NSs in a close-packed hexagonal monolayer show a poor field enhancement with a broad transmittance dip around the magnetic dipole (MD) and electric dipole (ED) Mie resonance wavelengths, limiting their effectiveness as substrates for SEF. By introduction of a gap between Si NSs (g), well-defined MD and ED modes in the transmittance spectra start to appear clearly when g~100 nm, the field enhancement around Si NSs can be up to 6 times when g~200 nm at 494 nm, indicating their potential SEF. We introduce a thermoresponsive polymer shell (PNIPAM) around Si NS core (Si@PNIPAM), exhibiting a temperature-dependent volume phase transition around its lower critical solution temperature of 32°C. By using Si@PNIPAM particles with tunable hydrodynamic shell thicknesses, hexagonal monolayers of 150 nm-diameter Si NSs with center-to-center distances ranging from ~350 to ~550 nm are achieved by controlling the assembly temperature. This strategy enables scalable fabrication of Si NS arrays with tunable interparticle gaps, providing a practical platform for enhancing local electromagnetic fields and, consequently, fluorescence emission.