Second-Order Active NLO Chromophores for DNA Based Electro-Optics Materials

摘要

The recent investigations of deoxyribonucleic acid (DNA) for use in non-linear optics (NLO) are an important breakthrough. Excellent optical quality thin films of DNA were obtained by Ogata in Japan and researchers at AFRL. Recent studies suggest that DNA may prove to be a more suitable material than the polymer currently used for optical waveguide devices, due to its optical and electromagnetic properties, resistance to solvents used in device fabrication, and it is biodegradable and inexpensive. The objective was to introduce active molecules within thin films of DNA in view of obtaining highly luminescent systems by three-photon absorption (3PA) and four-photon absorption (4PA), comparing results with analog poly(methyl methacrylate) (PMMA)-based host materials, in order to advance the understanding of DNA for non-linear optics. Eight chromophores of different structures (push-pull, quadrupole, bi- chromophore) were synthetised. Most these chromophores present an absorption band around 500 nm, allowing to expect 3PA properties. Spectroscopic properties are preserved in DNA-CTMA and PMMA thin films with fluorescence properties in the NIR. Unlike in PMMA, chromophores fluorescence efficiency in DNACTMA seems to depend strongly on the size of the molecule. The fluorescence efficiency decreases in DNA-CTMA for large molecules, leading to a higher efficiency in PMMA, while shortest molecules with a similar charge transfer present higher response in DNA. The confirmation of these results by 3PA should be performed in the group of Dr. James Grote (US Air Force Research Laboratory). These results are promising for the design of DNA-based highly fluorescent displays by multiphotonic excitation.