Doping-free bandgap tuning in one-dimensional Magnéli-phase nanorods of Mo4O11.

We synthesized one-dimensional (1D) Magnéli-phase nanorods of Mo4O11 using the hot filament metal-oxide vapor deposition technique. The 1D Magnéli-phase Mo4O11 nanorods synthesized at 1000, 1050, 1100, 1150, and 1200 °C contain varying combinations of two orthorhombic (α) and monoclinic (η) phases, and various mixtures of Mo(4+), Mo(5+) and Mo(6+) cations, while those synthesized at a higher temperature look bluer. The shifts of the transmittance maximum and absorbance minimum of the 1D Magnéli-phase Mo4O11 nanorods are inversely and linearly proportional to the elevated temperature, verifying that the bandgaps (Eg) are inversely proportional to the elevated temperature. The bandgap (Eg) of the 1D Magnéli-phase Mo4O11 nanorods can be tuned by simply controlling the synthesis temperature without doping with other materials, giving the 1D Magnéli-phase Mo4O11 nanorods good potential for use in optoelectronic nanodevices and bandgap engineering.