The monolayer MXene nanosheets were

The monolayer MXene nanosheets were prepared as previously described9.Ti3AlC2 was added to 20 mL solution of 9M HCl that contained 2 g of LiF and the solution was stirred at 35 °C for 24 h. After completely reaction, the MXene product was washed with deionized water for five cycles, which involved 5 min of centrifugation at 3500 rpm for each cycle. This produced a dark-green supernatant solution of MXene nanosheets having a pH of ≈7. After a final separation of the MXene from the solution using the centrifuge, the MXene was added to deionized water and sonicated for 1 h in an ice bath. After centrifugation at 3500 rpm for 1 h, the obtained exfoliated supernatant had a MXene concentration of ~1.0 mgmL−1.