Plasmon assisted two-photon direct laser writing of micro-structures composed of chiral Ag nanoparticles

We present an approach to produce micropatterns of metallic nanoparticles (NPs) that preserve key optical properties of the individual NPs. The technique uses a photothermal reaction induced by two-photon direct laser writing. The studied NP property is plasmon chirality, which was obtained via chemical conjugation of Ag NPs with chiral ligands: N-(tertbutoxycarbonyl)-L-cysteine methyl ester. The ligand cleavage initiated by a femtosecond pulsed laser induced thermal reaction results in a significant change in dispersiblility of the nanocrystals, thereby enabling a solvent selective development process after photo-patterning. We analyzed the optical chirality of the Ag NP films before and after micropatterning by two-photon lithography. We show that this patterning technique allows the patterned film to maintain this predefined optical property. In contrast, we show the disadvantage of the common use of a photo-acid generator for the cleavage of solubilizing groups via protonation. In this case, the ligand protonation results in the loss of the chiral behavior.