Role of Heavy Water in the Synthesis and Nanocatalytic Activity of Gold Nanoparticles

Heavy water (D₂O) has found extensive application as a moderator in nuclear reactors. Additionally, it serves as a substitute for regular water (H₂O) in biological or spectroscopic experiments, providing a deuterium source and addressing challenges related to solvent opacity or contrast. This is particularly relevant in experiments involving neutron scattering, infrared absorption, or nuclear magnetic resonance. However, replacing H₂O with D₂O is not always a straightforward or harmless substitution and can instead have unintended chemical consequences. In this study, we highlight the significant impact of solvent deuteration on two common gold nanoparticle syntheses-borohydride reduction and ascorbic acid reduction-by comparing reactions in D₂O and H₂O and mixtures thereof. The resulting colloids exhibit differences in size and spectral characteristics, and their effectiveness as nanocatalysts in the widely used 4-nitrophenol reduction benchmark reaction is adversely affected by the presence of D₂O during both particle synthesis and as the catalytic medium. Ultimately, these results underscore a critical awareness often overlooked by scientists and engineers: despite its widespread and sometimes indispensable use in analytical spectroscopy, cellular imaging, biophysics, and organic chemistry, D₂O cannot truly replace H₂O without significantly altering the chemical environment of a reaction.