The exfoliation and colloidal stabilization of layered transition metal dichalcogenides (TMDs) in an aqueous medium using functional biomolecules as dispersing agents have a number of potential benefits toward the production and practical use of the corresponding two-dimensional materials, but such a strategy has so far remained underexplored. Here, we report that DNA and RNA nucleotides are highly efficient dispersants in the preparation of stable aqueous suspensions of MoS and other TMD nanosheets at significant concentrations (up to 5-10 mg mL). Unlike the case of common surfactants, for which adsorption on 2D materials is generally based on weak dispersive forces, the exceptional colloidal stability of the TMD flakes was shown to rely on the presence of relatively strong, specific interactions of Lewis acid-base type between the DNA/RNA nucleotide molecules and the flakes. Moreover, the nucleotide-stabilized MoS nanosheets were shown to be efficient catalysts in the reduction of nitroarenes (4-nitrophenol and 4-nitroaniline), thus constituting an attractive alternative to the use of expensive heterogeneous catalysts based on noble metals, and exhibited an electrocatalytic activity toward the hydrogen evolution reaction that was not impaired by the possible presence of nucleotide molecules adsorbed on their active sites. The biocompatibility of these materials was also demonstrated on the basis of cell proliferation and viability assays. Overall, the present work opens new vistas on the colloidal stabilization of 2D materials based on specific interactions that could be useful toward different practical applications.

The ability to use RNA/DNA nucleotides as colloidal stabilizers for graphene would be an important asset, as a close graphene-nucleotide association would facilitate access to hybrid systems where the rich covalent and supramolecular chemistry of these biomolecules could be exploited alongside graphene in a number of applications. Unfortunately, single RNA/DNA nucleotides are inefficient graphene dispersants. Here we propose and demonstrate a supramolecular strategy which overcomes this limitation, affording aqueous dispersions of high quality graphene flakes with much improved colloidal stability. A nucleotide is combined with its complementary nucleobase yielding stable hydrogen-bonded supramolecular entities that adsorb more strongly on the graphene surface than their individual components. Based on this approach, graphene-nucleotide hybrid hydrogels could be readily obtained, where the graphene flakes were intimately and uniformly intermixed with the nucleotide-based gel phase. Such hydrogels exhibited higher uptakes and/or slower release profiles of dyes and drugs (rhodamine B, methylene blue and tetracycline) than their graphene-free counterparts. Cell proliferation tests suggested the graphene materials obtained with nucleotide-nucleobase stabilizers to be biocompatible. The present results constitute a novel strategy in the processing and molecular integration of graphene that could be extended to other (bio)molecules of interest towards the realization of functional materials for different applications.