Direct Printing of Micropatterned Plasmonic Substrates of Size-Controlled Gold Nanoparticles by Precision Photoreduction

Although the extraordinary optical property of gold nanoparticles (AuNPs) has been known for a long time, the anticipated applications of AuNPs in plasmonically enhanced substrates and photonic microdevices are still under development. In this paper, a method for the direct printing of micrometer-scale patterns of size-controlled AuNPs is presented for plasmonic substrates and microsensor development. Using in-house digital ultraviolet lithography, a precision photoreduction technology is developed for light-controlled growth of AuNPs to create micrometer-scale micropatterns on a titanium dioxide photocatalytic layer. The titanium dioxide thin layer not only enables a photocatalytic reduction process for high-precision printing of size-controlled AuNPs in an additive manner, but also introduces a Fano resonance that can sharpen spectral width of localized surface plasmon resonance peak and increase its peak-to-valley value. This printing technology can be used to cost-effectively fabricate size-scalable micropatterned plasmonic substrates of size-controlled AuNPs and thus offers new opportunities to develop various types of miniature plasmonic devices ranging from plasmonic biochemical sensors to plasmonically enhanced photothermal and photovoltaic microdevices.