Every one of the 45 banknotes sampled tested positive for trace quantities of cocaine, according to the research results published in the Royal Society of Chemistry's journal, the Analyst.
Traces of heroin were also detected on three of the notes.
PhD student, Jonathan Bones, who carried out the research working under the supervision of Professor Brett Paull at DCU's National Centre for Sensor Research (NCSR) described the results as "surprising".
"This is the largest sample of notes ever used in an experiment of this kind in Ireland", Bones said.
"The most recent survey carried out in the US showed 65 percent of dollar notes were contaminated with cocaine. However, the 100 percent rate uncovered in this project was surprising.
"Although not a quantitative measure, the presence of illicit substances on banknotes in general