Increasing awareness of the potentially harmful impacts of nanomaterials on human health has led to a high demand for low-toxicity lanthanide (Ln)-doped nanophosphors in life science fields. The present study introduces a conceptually new approach based on a microplasma technique to produce high quality crystalline lanthanide doped nanophosphors. By selecting Eu 3+ doped yttria as a model for study, systematic experiments are carried out to synthesize Y 2 O 3 :Eu 3+ nanophosphors of controllable size and various Eu 3+ doping concentrations. The plasma-liquid interaction and the obtained products are examined by complementary analytical methods. Results demonstrate that ultra-high purity crystalline Y 2 O 3 :Eu 3+ nanophosphors can be successfully prepared from merely an aqueous solution of Y(NO 3 ) 3 ·6H 2 O and Eu(NO 3 ) 3 ·6H 2 O at an extremely low plasma power consumption (3-5.5 W), without involving any hazardous chemicals. Moreover, the Eu 3+ ions prove to be efficiently and homogeneously doped into the yttria matrix, and their luminescence performance can be tuned to a large extent by adjusting the processing conditions. Due to the high degree of flexibility, this approach can be readily expanded to the green synthesis and engineering of various lanthanide doped/co-doped nanophosphors.