Redox Multiphoton Polymerization for 3D Nanofabrication

We report for the first time on the redox multiphoton polymerization of an organic–inorganic composite material, in which one of the components, a vanadium metallo-organic complex, initiates the polymerization. The composite employs multiphoton absorption to self-generate radicals by photoinduced reduction of the metal species from vanadium (V) to vanadium (IV). We exploit this material for the fabrication of fully 3D structures by multiphoton polymerization with 200 nm resolution, employing a femtosecond laser operating at 800 nm, in the absence of a photoinitiator. Nonlinear absorption measurements indicate that the use of an 800 nm laser initiates the photopolymerization due to three-photon absorption of the vanadium alkoxide. The laser power required to induce this three-photon polymerization is comparable to what is required for inducing two-photon polymerization in materials using standard two-photon absorbers, most likely due to the high content of vanadium in the final composite (up to 50% mole).