“…The chemical and physical similarities of D 2 O to regular water make it difficult to quantify it in the D 2 O–H 2 O mixture. The prevailing methods for the quantitative determination of D 2 O, namely, gas chromatography–mass spectrometry, , nuclear magnetic spin resonance spectroscopy, , and Fourier transformed infrared spectroscopy, − have several drawbacks, such as nonportable setup, need of expensive instrumental design and specialized operators, time-consuming analysis, and complicated operations, leading to inconvenience in rapid point-of-need detection. Apart from that, there are fluorescence-based sensors for heavy water, which have been reported and are listed in Table .…”