Synthesis of fluorescent nanocrystals (NCs) of type GdVO4 and doped with varying fractions of Eu(III) ions. The NCs are shown to be viable fluorescent probes for hydrogen peroxide. The NCs can be used as probes for sensing glucose via the hydrogen peroxide produced by enzymatic action of glucose oxidase. Detection limits are as low as 1.6 μM for H2O2 and 2.1 μM for glucose.