[Show abstract][Hide abstract] ABSTRACT: DNA nanotechnology holds great promise for the
fabrication of novel plasmonic nanostructures and the potential to
carry out single-molecule measurements using optical spectroscopy.
Here, we demonstrate for the first time that DNA origami
nanostructures can be exploited as substrates for surface-enhanced
Raman scattering (SERS). Gold nanoparticles (AuNPs) have been
arranged into dimers to create intense Raman scattering hot spots in
the interparticle gaps. AuNPs (15 nm) covered with TAMRA-modified
DNA have been placed at a nominal distance of 25 nm to demonstrate
the formation of Raman hot spots. To control the plasmonic coupling
between the nanoparticles and thus the field enhancement in the hot
spot, the size of AuNPs has been varied from 5 to 28 nm by electroless
Au deposition. By the precise positioning of a specific number of
TAMRA molecules in these hot spots, SERS with the highest sensitivity down to the few-molecule level is obtained.
[Show abstract][Hide abstract] ABSTRACT: The combination of the Ugi four-component reaction (Ugi-4CR) with acyclic diene metathesis (ADMET) or thiol-ene polymerization led to the formation of poly-1-(alkylcarbamoyl) carboxamides, a new class of substituted polyamides with amide moieties in the polymer backbone, as well as its side chains. 10-Undecenoic acid, obtained by pyrolysis of ricinoleic acid, the main fatty acid of castor oil, was used as the key renewable building block. The use of different primary amines, as well as isonitriles (isocyanides) for the described Ugi reactions provided monomers with high structural diversity. Furthermore, the possibility of versatile post-modification of functional groups in the side chains of the corresponding polymers should be of considerable interest in materials science. The obtained monomers were polymerized by ADMET, as well as thiol-ene, chemistry and all polymers were fully characterized. Finally, ortho-nitrobenzylamide-containing polyamides obtained by this route were shown to be photoresponsive and exhibited a dramatic change of their properties upon irradiation with light.