Cation-induced Ti3C2Tx MXene@melamine sponge aerogels with large layer spacing and high strength for high-performance supercapacitors.

The self-assembled aerogels are considered as an efficient strategy to address the aggregation and restacking of Ti3C2Tx MXene nanosheets for high-performance supercapacitors. However, the low mechanical strength of the MXene aerogel results in the structural collapse of the self-standing supercapacitor electrode materials. Herein, a low-cost melamine sponge (MS) absorbed different cations (H+, K+, Mg2+, Fe2+, Co2+, Ni2+ and Al3+), serves as a carrier and crosslinker for loading MXene hydrogel induced by the absorbed cations on the skeleton surface and the pores of MS, resulting in the high loading mass MXene aerogels with high mechanical strength. The experimental results show that the Mg-Ti3C2Tx@MS aerogel exhibits the maximum area capacitance of 702.22 mF cm-2 at 3 mA cm-2, and the area capacitance is still 603.12 mF cm-2 even at 100 mA cm-2, indicating the high rate capability with a capacitance retention of 85.89 %. It is worth noting that the constructed asymmetric supercapacitor with activated carbon achieves high energy densities of 104.53 µWh cm-2 and 93.87 µWh cm-2 at 800 µW cm-2 and 7999 µW cm-2, respectively. Furthermore, the asymmetric supercapacitor shows the high cycling stability with 90.2 % capacity retention after 10,000 cycles. This work provides a feasible strategy to prepare Ti3C2Tx MXene aerogels with large layer spacing and high strength for high-performance supercapacitors.

Improving the sensitivity of SPR sensors based on gratings by double-dips method (DDM).

The sensitivity of surface plasmon resonance (SPR) sensors based on gratings using angular interrogation is improved by optimizing the 1st-order diffraction dip recently but still can not exceed the prism-based systems. To improve the sensitivity of grating-based systems in another way, we realize sharp dips of the higher diffraction orders and propose double-dips method (DDM), a new way using the separation of two sharp dips of different orders to improve the sensitivity of SPR sensors based on gratings with good linearity. By DDM, the grating-based systems' sensitivity is improved into more than 237 deg/RIU, more sensitive than the prism-based systems in the same condition, and the quality parameter (Chi) factor reaches more than 95. In different performance comparisons, DDM has roundly better performances than other methods. Moreover, when the grating profile errs from rectangle, DDM still works well.