Outstanding sodium and lithium storage capability is successfully demonstrated in ultrathin NiO nanosheets (4-5 nm in thickness) synthesized via a facile solvothermal process followed by annealing in ...air. For sodium storage, the NiO nanosheets deliver a high reversible specific capacity of 299 mA h g super(-1) at a current density of 1 A g super(-1), and the capacity still remains up to 154 mA h g super(-1) at 10 A g super(-1). Upon charge/discharge cycling, the specific capacity maintains to be as high as 266 mA h g super(-1) during the 100th cycle at 1 Ag super(-1). Such sodium storage capability of NiO nanosheets is by far one of the best reported for transition metal oxides. For lithium storage, the cell achieves a high reversible specific capacity of 1242 and 250 mA h g super(-1) at 0.2 and 15 A g super(-1), respectively. The capacity for lithium storage maintains to be 851 mA h g super(-1) during the 170th cycle at 2 A g super(-1). The present results demonstrate that ultrathin NiO nanosheets are highly attractive for fast sodium/lithium diffusion with high-rate capability for rechargeable sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs).
Two-dimensional Ti3C2Tx MXenes have been extensively studied as pseudocapacitive electrode materials. This Letter aims at providing further insights into the charge storage mechanism of the Ti3C2Tx ...MXene electrode in the acidic electrolyte by combining experimental and simulation approaches. Our results show that the presence of H2O molecules between the MXene layers plays a critical role in the pseudocapacitive behavior, providing a pathway for proton transport to activate the redox reaction of the Ti atoms. Also, thermal annealing of the samples at different temperatures suggests that the presence of the confined H2O molecules is mainly controlled by the surface termination groups. These findings pave the way for alternative strategies to enhance the high-rate performance of MXenes electrodes by optimizing their surface termination groups.
The construction of ionic conductive hydrogels with high transparency, excellent mechanical robustness, high toughness, and rapid self-recovery is highly desired yet challenging. Herein, a ...hydrogen-bonding network densification strategy is presented for preparing a highly stretchable and transparent poly(ionic liquid) hydrogel (PAM-r-MVIC) from the perspective of random copolymerization of 1-methyl-3-(4-vinylbenzyl) imidazolium chloride and acrylamide in water. Ascribing to the formation of a dense hydrogen-bonding network, the resultant PAM-r-MVIC exhibited an intrinsically high stretchability (>1000%) and compressibility (90%), fast self-recovery with high toughness (2950 kJ m
), and excellent fatigue resistance with no deviation for 100 cycles. Dissipative particle dynamics simulations revealed that the orientation of hydrogen bonds along the stretching direction boosted mechanical strength and toughness, which were further proved by the restriction of molecular chain movements ascribing to the formation of a dense hydrogen-bonding network from mean square displacement calculations. Combining with high ionic conductivity over a wide temperature range and autonomous adhesion on various surfaces with tailored adhesive strength, the PAM-r-MVIC can readily work as a highly stretchable and healable ionic conductor for a capacitive/resistive bimodal sensor with self-adhesion, high sensitivity, excellent linearity, and great durability. This study might provide a new path of designing and fabricating ionic conductive hydrogels with high mechanical elasticity, high toughness, and excellent fatigue resilience for skin-inspired ionic sensors in detecting complex human motions.
1D hierarchical tubular MnO2 nanostructures have been prepared through a facile hydrothermal method using carbon nanofibres (CNFs) as sacrificial template. The morphology of MnO2 nanostructures can ...be adjusted by changing the reaction time or annealing process. Polycrystalline MnO2 nanotubes are formed with a short reaction time (e.g., 10 min) while hierarchical tubular MnO2 nanostructures composed of assembled nanosheets are obtained at longer reaction times (>45 min). The polycrystalline MnO2 nanotubes can be further converted to porous nanobelts and sponge-like nanowires by annealing in air. Among all the types of MnO2 nanostructures prepared, tubular MnO2 nanostructures composed of assembled nanosheets show optimized charge storage performance when tested as supercapacitor electrodes, for example, delivering an power density of 13.33 kW·kg–1 and a energy density of 21.1 Wh·kg–1 with a long cycling life over 3000 cycles, which is mainly related to their features of large specific surface area and optimized charge transfer pathway.
Hydrogen sulfide (H2S) is an important gaseous signaling agent mediated by many physiological processes and diseases. In order to explore its role in biological signaling, much effort has been ...focused on developing organic fluorescent probes to image H2S. However, these downconversion H2S probes are impractical for bio‐imaging beyond a certain depth because of the short tissue penetration of UV/visible light (as an excitation source). In most circumstance, these probes are also not suitable for long‐term assay due to photo‐bleaching. Herein, a new design to detect H2S based on the coumarin‐hemicyanine (CHC1)‐modified upconversion nanophosphors is reported. This inorganic–organic integrated nanoprobe is demonstrated to display a fast response time with a large ratiometric upconversion luminescence (UCL) enhancement, and extraordinary photo‐stability. CHC1‐UCNPs not only can be used for ratiometric UCL monitoring of pseudo‐enzymatic H2S production in living cells, but can also be used to identify the risk of endotoxic shock through ratiometric UCL imaging of tissue and measurement of endogenous H2S levels in plasma. The first ratiometric UCL H2S nanoprobe reported here may be further developed as the next‐generation diagnostic tool for the detection of inflammatory‐related diseases.
Coumarin‐hemicyanine (CHC1)‐modified upconversion nanophosphors are developed for ratiometric upconversion luminescence detection of H2S. This probe can be used not only for ratiometric UCL monitoring of the generation of pseudo‐enzymatic H2S in living cells, but also to identify the risk of endotoxic shock in mice through ratiometric UCL imaging of tissue and measurement of the endogenous H2S levels in plasma.
► Solution–liquid–solid growth of Ge nanowires in gold-seeded porous carbon. ► Simple and highly scalable production process. ► Porous carbon matrix improve electrical conductivity and buffer volume ...change. ► Synergistic effect between porous carbon and Ge nanowires enhances capacities. ► High reversible capacity of 789mAhg−1 during the 50th cycle at a current density of 160mAg−1.
Lithium-ion batteries have been actively researched in recent years due to it being one of the most promising energy storage systems. Herein, we report a novel approach where germanium nanowires (Ge NW) are grown in gold-seeded porous carbon via the solution–liquid–solid mechanism, and the corresponding improvement observed in terms of the specific capacity of this porous carbon–germanium nanowires (PC–Ge NW) composite anode. At a current density of 160mAg−1 and voltage window of 0.001–1.5V, a specific capacity of 789mAhg−1 during the 50th cycle for PC–Ge NW is achieved as compared to 624mAhg−1 during the 50th cycle for pure Ge NW. Even though the content of the Ge is only 53.5 weight percent in the PC–Ge NW composite, it yields a better stability and higher specific capacity, indicating a synergistic effect between porous carbon and Ge nanowires. There is also potential cost savings since the use of a lower amount of Ge can bring about good cycling properties.
We report a simple approach to prepare the nitrogen-modified few-layer graphene (FLG) directly from graphite flakes. With the aid of melamine, graphite flakes can be directly ultrasonicated into FLG ...in acetone. The subsequent annealing process further transforms the melamine absorbed on the surface of graphene into melon (C6N9H3)x, which is one type of condensation product of melamine, and simultaneously dopes the graphene with nitrogen. When tested as a supercapacitor electrode, the nitrogen-modified FLG shows a much higher specific capacitance (e.g., 227F/g at 1A/g) than that of reduced graphene oxide (rGO) (e.g., 133F/g at 1A/g).
Ultrathin vanadium oxide (V2O5) nanosheets with lateral sizes of up to tens of micrometers were synthesized, and then incorporated into multi-walled carbon nanotube (MWCNT) fibers. The solid-state ...supercapacitor based on such hybrid fibers exhibited an improved volumetric capacitance of 31 F cm-3 at 1.0 A cm-3, and a volumetric energy density of 2.1 mW h cm-3 at 1.5 W cm-3.
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