Hydrophobic painting materials fast detection using temperature dependence SERS on simple or PEGylated Ag nanoparticles

Abstract

In conservation and restauration efforts, fast, sensitive and reliable identification of authentic materials is crucial. We provide here the first report on the possibility to unambiguously detect hydrophobic painting materials within one second acquisition time using a compact, portable Raman instrument and surface enhanced Raman scattering (SERS) technique. SERS detection of organic materials used in artwork was improved by a simple control of the colloid application temperature. Pure citrate- and hydroxylamine-reduced silver nanoparticles (AgNPs), as well as their polyethylene glycol (PEG) functionalized version were tested at different substrate temperatures by using a conventional, largely used SERS sensitizer molecule, p-amionothiophenol (pATP). It was shown that SERS efficiency increased with temperature in all cases. Best results regarding stability and enhancement were obtained for PEGylated NPs. Such NPs were further used to detect a cochineal extract, one of the natural organic dyes employed in painting/textile manufacturing, as well as for oleic acid, one of the main constituents of linseed oil and major indicator of any oil-based painting technique.