• Eng, Lukas
• Oertel, U.
• Reichenbach, P.
• Georgi, U.
• Nitzsche, B.
• Kämpfe, T.

Abstract

<p>We performed a series of nonlinear-optical, photochemically-induced ex-periments using different copolymers which were UV-sensitized at around 400 nm through various chemical side groups (e.g. NVOC-protected amines). Our approach focuses on inducing very localized photoreactions on an area much smaller than the diffraction-limited optical spot, using nonlinear optical effects in the near-fields of metallic nanoparticle (NP) antennae embedded in the polymer thin film. We thus illuminated the copolymers with 100 fs pulses at a 790 nm exciting wavelength in order to trigger photoreactions through nonlinear optical effects at around 400 nm. Spin coating the copolymers onto both y-cut lithium niobate (LNO) sample surfaces (which is an excellent SHG amplifier) and onto bare glass surfaces (no SHG) and then comparing the as-induced nonlinear optical photoreactions showed a direct two-photon absorption to be the dominant photoreaction mechanism, while SHG radiation (as emitted by LNO) did not show any significant influence. High efficiency of this process can be achieved by the near-field enhancement close to metallic NPs present in the polymer thin film. First evidence is given here with protected amine side groups when spin coating the copolymer over sharp gold edges as obtained from triangular metallic NPs (i.e. so-called Fischer pattern); after laser exposure at 790 nm, the photochemically deprotected amines were successfully photo-labeled and then imaged by STORM microscopy.</p>

Topics

• nanoparticle
• impedance spectroscopy
• surface
• thin film
• glass
• glass
• gold
• Lithium
• copolymer
• amine
• microscopy
• spin coating