AbstractThis work investigates the effect of plasmonic gold nanoparticle (AuNP) size on the rate of thermal release of single‐stranded oligonucleotides under femtosecond (fs)‐pulsed laser irradiation sources. Contrary to the theoretical predictions that larger AuNPs (50–60 nm diameter) would produce the most solution heating and fastest DNA release, it is found that smaller AuNP diameters (25 nm) lead to faster dsDNA denaturation rates. Controlling for the pulse energy fluence, AuNP concentration, DNA loading density, and the distance from the AuNP surface finds the same result. These results imply that the solution temperature increases around the AuNP during fs laser pulse optical heating may not be the only significant influence on dsDNA denaturation, suggesting that direct energy transfer from the AuNP to the DNA (phonon–phonon coupling), which is increased as AuNPs decrease in size, may play a significant role.