For many years researchers have said that DNA and RNA do not fluoresce without help from other chemicals.   But now some researchers are discovering how to make DNA (and RNA) to fluoresce naturally.

Researchers discover that DNA naturally fluoresces

Researchers Discover that DNA Naturally Fluoresces  

Fluorescence of Natural DNA: From the Femtosecond to the Nanosecond Time Scales

Powerful optical imaging technology catches DNA naturally fluorescing

In this research article, they add infrared (IR) to enhance the florescence.  Dark State-Modulated Fluorescence Correlation Spectroscopy For Quantitative Signal Recovery – DNA

Superresolution intrinsic fluorescence imaging of chromatin utilizing native, unmodified nucleic acids for contrast