Reduction of Au³⁺ in the presence of just adenosine 5′-monophosphate (AMP) and a zwitterionic organic chemical buffering agent, specifically 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), combined with light exposure, gives rise to luminescent, water-soluble Au⁺ nanoclusters (Au⁺ NCs). The photoluminescence of these NCs is considerably enhanced by adding Y³⁺ or the chemically similar Yb³⁺ lanthanide that leads to Au⁺/Y³⁺ and Au⁺/Yb³⁺ NCs, respectively. These NCs are characterised by absorption (steady-state), photoluminescence (steady-state and time-resolved), and X-ray photoelectron spectroscopy.