Sodium-Ion-Assisted Minimally Intensive Layer Delamination of Ti-Based MXenes: Implications for Biomedical...

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 Ti₃C₂T _x and Ti₃CNT _x 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 Ti₃C₂T _x 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 Ti₃C₂T _x flakes exhibited a conventional 2D morphology, while Ti₃CNT _x 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.