19 April 2016 Deterministic embedding of a single gold nanoparticle into polymeric microstructures by direct laser writing technique
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Abstract
We have precisely positioned and embedded a single gold nanoparticle (Au NP) into a desired polymeric photonic structure (PS) using a simple and low-cost technique called low one-photon absorption direct laser writing (LOPA DLW), with a two-step process: identification and fabrication. First, the position of the Au NP was identified with a precision of 20 nm by using DLW technique with ultralow excitation laser power (μW). This power did not induce the polymerization of the photoresist (SU8) due to its low absorption at the excitation wavelength (532 nm). Then, the structure containing the NP was fabricated by using the same DLW system with high excitation power (mW). Different 2D photonic structures have been fabricated, which contain a single Au NP at desired position. In particular, we obtained a microsphere instead of a micropillar at the position of the Au NP. The formation of such microsphere was explained by the thermal effect of the Au NP at the wavelength of 532 nm, which induced thermal polymerization of surrounding photoresist. The effect of the post-exposure bake on the quality of structures was taken into account, revealing a more efficient fabrication way by exploiting the local thermal effect of the laser. We studied further the influence of the NP size on the NP/PS coupling by investigating the fabrication and fluorescence measurement of Au NPs of different sizes: 10, 30, 50, 80, and 100 nm. The photon collection enhancements in each case were 12.9 ± 2.5, 12.6 ± 5.6, 3.9 ± 2.7, 5.9 ± 4.4, and 6.6 ± 5.1 times, respectively. The gain in fluorescence could reach up to 36.6 times for 10-nm gold NPs.
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Dam Thuy Trang Nguyen, Aurélien Pelissier, Kevin Montes, Quang Cong Tong, Hoang Minh Ngo, Isabelle Ledoux-Rak, Ngoc Diep Lai, "Deterministic embedding of a single gold nanoparticle into polymeric microstructures by direct laser writing technique", Proc. SPIE 9884, Nanophotonics VI, 98842C (19 April 2016); doi: 10.1117/12.2225936; https://doi.org/10.1117/12.2225936
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