Raman microscopy analysis of graphene-based nanocomposite materials under UV-C exposure

In this work, we focused on the investigation of UV-C radiation effects on novel nanomaterials structured with graphene nanoplatelets (GNPs) and DNA. Multifunctional nanocomposites were realized by combining the good electrical conductivity of GNPs with the biocompatibility and UV sensitivity of double-stranded DNA. GNP/DNA nanostructures were prepared by sonication-driven self-assembly in aqueous solution, and then dispersed into a PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) matrix. The UV-sensitivity of the GNP/DNA/PEDOT:PSS samples was investigated by exposing them to the energetic UV-C band, and investigating their morphology, surface wettability, chemical and electrical properties before and after irradiation using several techniques (scanning electron microscopy, Raman spectroscopy, electrical impedance spectroscopy). In particular, Raman imaging was used as suitable technique to analyze the chemical arrangements and their modifications upon irradiation on selected surface areas. This technique allowed appreciating chemical changes caused by the UV-C interaction with the nanocomposite original structure. Results give information about the potential applications of GNP/DNA/PEDOT:PSS nanomaterials in all environments affected by UV radiations, for example for chemical reactions or sterilization purposes, or where they are naturally present, such as in space. In reference to space environment, the GNP/DNA/PEDOT:PSS nanocomposites were also tested under UV-C while reducing the amount of oxygen reaching the sample surface, in order to separate the effects due to the atmosphere from those of the irradiation.