Controlled Release of Molecular Intercalants from Textured Two-Dimensional Nanosheet Films for Antiviral Coatings

Two-dimensional (2D) materials possess outstanding flexibility, mechanical performance, and high specific surface area, making them promising delivery platforms for drug and antiviral payloads. Encapsulation and controlled release over long periods are essential for designing next-generation drug-eluting or antiviral coatings. Current progress in loading and releasing active ingredients focuses on physical absorption/desorption and chemical functionalization of 2D material surfaces. In our study, we explore the 2D nanochannels between sheet-like nanolayers as delivery vessels and develop them into antiviral-loaded, controlled-release coatings. Solution co-deposition of 2D nano-sheets with chemical solutes yields nanosheet−molecular heterostructures. A feature of these macroscopic layered hybrids is their ability to release the intercalated molecular agent to express chemical functionality on their surfaces or in their near surroundings. Systematic design methods are needed to control this molecular release to match the demand for rate and lifetime in specific applications. We hypothesize that release kinetics are controlled by transport processes within the layered solids, which primarily involve confined molecular diffusion through nanochannels formed by intersheet van der Waals gaps. Here a variety of graphene oxide (GO)/molecular hybrids are fabricated and subject to transient experiments to characterize release kinetics, locations, and mechanisms. The measured release rate profiles can be successfully described by a numerical model of internal transport processes, and the results used to extract effective Z-directional diffusion coefficients for various film types. The diffusion coefficients are found to be 8 orders of magnitude lower than those in free solution due to nanochannel confinement and serpentine path effects, and this retardation underlies the ability of 2D materials to control and extend release over useful time scales. In-plane texturing of the heterostructured films by compressive wrinkling or crumpling is shown to be a useful design tool to control the release rate for a given film type and molecular intercalant. The potential of this approach is demonstrated through case studies on the controlled release of chemical virucidal agents.