The rapid development of smart wearable and integrated electronic products has urgently increased the requirement for high‐performance microbatteries. Although few lithium ion microbatteries based on organic electrolytes have been reported so far, the problems, such as undesirable energy density, poor flexibility, inflammability, volatility toxicity, and high cost restrict their practical applications in the above‐mentioned electronic products. In order to overcome these problems, a low cost quasi‐solid‐state aqueous zinc ion microbattery (ZIMB) assembled by a vanadium dioxide (B)‐multiwalled carbon nanotubes (VO2 (B)‐MWCNTs) cathode, a zinc nanoflakes anode, and a zinc trifluoromethanesulfonate‐polyvinyl alcohol (Zn(CF3SO3)2‐PVA) hydrogel electrolyte is exploited. As expected, the ZIMB exhibits excellent electrochemical performance, e.g., a high capacity of 314.7 µAh cm−2, an ultrahigh energy density of 188.8 µWh cm−2, and a high power density of 0.61 mW cm−2. Furthermore, the ZIMB also shows high flexibility and excellent high temperature stability: the capacity has no obvious decay when the bending angle is up to 150° and the temperature reaches 100 °C. The ZIMB provides a way to develop next‐generation miniature energy storage devices with high performance.
Four types of carbon dots (CDs) with various color (blue, green, yellow, and red) emissions have been synthesized under solvent‐free conditions from citric acid and different nitrogen sources (DMF, urea, ethanamide, and formamide). By detailed characterization and comparison, it is confirmed that the graphitized sp2 conjugated domain and surface functional groups such as C−O and C=N play synergetic roles in adjusting the fluorescence properties. Notably, the size effect is not the dominant mechanism to achieve multi‐color fluorescence emissions in this work. The structural configuration of the carbon dots further influences the energy band structure, as demonstrated in simplified energy level diagrams. An absorption peak at approximately 560 nm appears in the visible light region for red‐emitting CDs, assigned to an n→π* transition of the aromatic structure, thus introducing a new surface state energy level, resulting in a reduction in the energy of electron transition and the expansion into the visible region of the UV/Vis spectrum. Taking advantage of the diverse absorption and emission properties, different CDs/TiO2 binary composites are obtained for photocatalytic degradation of organic dyes, and it is found that the absorption range in terms of visible light and the band gap of the carbon dots make a difference to the photocatalytic performance of the composites.
Micro‐supercapacitors (MSCs) with excellent flexibility and high electrochemical performance are essential for portable and miniaturized electronics. In this paper, a laser etching technology with advantages of simple process, low cost, and high machining accuracy is used to directly etch the free‐standing MXene‐molybdenum disulfide (MoS2) film for MSC. As adding MoS2 in MXene effectively improves the electrochemical performance, such as a higher specific capacitance (about 60% higher than pure MXene). Eventually, the maximum specific capacitance of this MSC (based on the total volume of positive and negative electrodes) is 173.6 F cm−3 (1 mV s−1), and the maximum energy density and maximum power density are 15.5 mWh cm−3 and 0.97 W cm−3, respectively. In addition, the MSC also shows the excellent cycle stability and flexibility, e.g., after 6000 charge–discharge cycles and bending up to 150°, the capacitances of the MSC still retain about 98% and 89% of its initial capacitance, respectively. The laser‐etched MSC based on MXene‐MoS2 offers a new idea for future high‐performance micro energy storage devices.
In this work, two hydrostable Cr-based metal− organic frameworks (MOFs), MIL-101(Cr) and MIL-101(Cr)-SO 3 H, were successfully synthesized and applied in the adsorption and separation of ionic dye fluorescein sodium (FS) and cationic dye safranine T (ST). Interestingly, MIL-101(Cr) can efficiently adsorb FS dye but hardly adsorbs ST dye, and MIL-101(Cr)-SO 3 H exhibits the thoroughly opposite phenomenon. More importantly, the reversed adsorption with high selectivity on the two MOFs can also be attained in the mixed solutions of the dyes. Finally, a mechanism analysis indicates that this significant reversal in performance for the dyes is mainly attributed to the opposite surface charges of the two MOFs caused by −SO 3 H groups.
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