A new direct route for the “bottom up” syntheses of phases in the La n +1 Ni n O 3 n +1 series (n=1, 2, 3 and ∞) has been achieved via single-step heat treatments of nanosized co-crystallized precursors. The co-crystallized precursors were prepared using a continuous hydrothermal flow synthesis system that uses a superheated water flow at ca. 400°C and 24.1MPa to produce nanoparticulate slurries. Overall, a significant reduction in time and number of steps for the syntheses of La 3 Ni 2 O 7 and La 4 Ni 3 O 10 was achieved compared with more conventional synthesis methods, which typically require multiple homogenization and reheating steps over several days.