No abstract

With the continuous demands for wearable electronics, the embeddable power sources have drawn attention to develop advanced electrode materials and feasible manufacture procedures. Fiber‐based flexible energy storage devices have the potential to be practically integrated by utilizing the high‐performance materials with precisely constructed structures. Herein, a novel approach is presented to achieve an outstanding fiber‐based supercapacitor by simultaneous wet‐spinning of mesoporous MXene (Ti3C2Tx) nanoflakes. The volumetric capacitance of the porous fiber is enhanced up to ≈145% when the content of mesoporous MXene reaches 15 wt%. The symmetric all‐solid‐state fiber supercapacitor shows an extraordinary capability of 821.5 F cm–3 at a current density of 0.5 A cm–3, which reflects an enormous improvement to that of a nonporous MXene fiber‐based supercapacitor. The measured energy density is 8.9 mWh cm–3 at a power density of 401 mW cm–3, which also indicates the effective synergy of the constructed pathways for ions and electrons. This work demonstrates the feasibility of scalable production of fiber‐based electrode materials with porous MXene for powering wearable applications.

Water-soluble carbon quantum dots were hydrothermally produced using corn straw as the starting material and nitric acid solution as solvent, then they were introduced as fluorescent probes for the detection of Cu2+. High-resolution transmission electron microscopy and X-ray diffraction showed that the carbon quantum dots were spherical amorphous particles with a diameter of 5 nm. The surface functional groups of carbon quantum dots were observed via Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. A new approach for Cu2+ detection was designed using carbon quantum dots based on fluorescence quenching. Linear relationships between the fluorescence variation and the Cu2+ level (1 mg·L-1 to 20 mg·L-1 and 20 mg·L-1 to 500 mg·L-1) were obtained, with coefficients of determination of 0.9960 and 0.9923, respectively. The Cu2+ detection limit was 4.26 mg·L-1. The probable quenching principle between Cu2+ and the carbon quantum dots was attributed to charge transfer.