One-step synthesis of oxygen-deficient MoO3-x nanostructures by pulsed laser ablation in liquid

Abstract

Two-dimensional (2D) α-MoO3-x colloidal solutions were synthesized for the first time by pulsed laser ablation of bulk crystals in a water medium. The obtained α-MoO3-x colloidal solutions exhibit a blue color and a strong absorption band in the visible region, indicating the presence of defects in the MoO3-x nanostructures in suspension. Indeed, coupled with exfoliation, the high energy deposited by the laser can also promote the intercalation of H+ ions into MoO3, inducing defects in the material, particularly oxygen vacancies. This process enables the formation of sub-stoichiometric MoO3-x nanostructures with optical properties distinct from those of bulk crystals. The potential of the MoO3-x colloidal solutions for detecting biological material is demonstrated using a bio-optical system, with bovine serum albumin (BSA) as a model protein. A clear decrease in the intensity of the absorption band in the visible region is observed as the BSA concentration increases, which is related to the immobilization of the protein on the surface of the nanocrystals. Total immobilization of the protein appears to be a quick process, with incubation times of less than 1 min. Contrary to the conventional liquid-phase exfoliation processes, the Pulsed Laser Ablation in Liquid (PLAL) technique offered a double advantage by enabling both exfoliation and modification of the optical properties of MoO3 in a single step. The resulting modified nanostructures showed a high potential for biosensing applications.