Monodisperse spindle-like FeWO4 nanoparticles: Controlled hydrothermal synthesis and enhanced optical properties

► Monodisperse spindle-like FeWO4 were synthesized with hydrothermal method. ► Citric acid plays key roles in the hydrothermal synthesis. ► Their morphology can be tuned with pH value of the precursor medium. ► They show enhanced photocatalytic activities with irradiation of UV light.