Hydrated vanadium pentoxide (V
2O
5·
nH
2O) nanotube arrays with outer diameters of 200 nm and lengths ofmore than 5
m have been synthesized via template-based physical wetting of V
2O
5 sols. The V
2O
5·
nH
2Onanotube arrays were characterized by scanning electron microscopy, X-ray diffraction, and high-resolutiontransmission electron microscopy . The field emission (FE) of the V
2O
5·
nH
2O nanotube arrays shows a turn-on field of about 6.35 V/
m at a current density of 10
A/cm
2 and an emission current density up to 2.1mA/cm
2 at a field of 9.20 V/
m. The corresponding Fowler-Nordheim plot shows a linear behavior. Thesefeatures make the V
2O
5·
nH
2O nanotube array a promising candidate for FE emitters.