MXenes are among the most extensively studied materials nowadays due to their functional versatility stemming from their tunable chemical and physical properties. MXenes have been predominantly synthesized by selective wet-chemical etching of parent MAX phases, followed by Li+ intercalation and subsequent delamination. This study demonstrates the substitution of Li+ with Na+ in the preparation of Ti-based MXenes for biomedical and biocatalytic applications, where biologically active Li+ is undesirable. Here, a MILD (Minimally Intensive Layer Delamination) synthesis method of Ti3C2Tx and Ti3CNTx is modified by replacing LiF with nontoxic and cost-effective NaF. The produced samples had flake sizes and surface chemistries comparable to those of LiF-MILD samples. The electrical conductivity of Ti3C2Tx films made from those flakes exceeded 5500 S/cm. Multiple acid mixtures were investigated, with 12 M HCl producing stable MXene colloids after 48 h of etching without sonication, yielding flakes significantly larger than those obtained using 9 M HCl. The Ti3C2Tx flakes exhibited a conventional 2D morphology, while Ti3CNTx scrolled, forming cylindrical nanostructures. With the proper adjustments to the etching conditions, the proposed approach may apply to the synthesis of other Ti-based MXenes.
Kanas et al. (Mon,) studied this question.