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The proposal of pseudocapacitive materials breaks the barriers between batteries and capacitors, allowing for the possible achievement of a balanced energy-power performance. However, the limited reserve of lithium restricts the practical applications of pseudocapacitive materials in lithium-based systems, whereas sodium resources are abundant with the similar properties to lithium, but there is a lack of suitable pseudocapacitive materials for sodium-based systems. The exploitation of pseudocapacitive materials for Na+ storage is urgent. This study, for the first time, reports a sonochemical approach, involving intercalation and ultrasonic exfoliation processes, to prepare composite K2Mo4O13/α-MoO3 (i.e., KMO) nanorods, and the possible applications of the KMO nanorods in Li+/Na+ pseudocapacitance were evaluated. The as-synthesized KMO possessed a uniform rod-like morphology formed by assembling nanoneedles (or nanobelts) with a large apparent aspect ratio of more than 10. Both in lithium ion batteries (LIBs) and sodium ion batteries (SIBs), the KMO nanorods exhibited efficient pseudocapacitance, which was not observed in the pristine MoO3–Na system. In SIBs, the as-synthesized KMO delivered a capacity of 895 mA h g−1 at 0.02 A g−1, which was much higher than that of the pristine MoO3–Na system. Moreover, it was found that the b values of KMO (i = avb, current i and scan rate v in the CV curves) were over 0.9 at potentials ranging from 1 V to 2 V in SIBs, indicating an obvious pseudocapacitive process. Benefiting from the layered K2Mo4O13 nanorods built with edge-shared distorted MoO6 octahedra, the Na+ ions with a larger size could be intercalated into the spaces between the double MoO6 plates. This sonochemical approach based on the intercalation and exfoliation chemistry opened a new path to prepare molybdenum-based nanostructures for superior Li+/Na+ pseudocapacitance applications on a large scale in a low-carbon and environment-friendly manner. [ABSTRACT FROM AUTHOR]

A novel efficient way to realize high performance TiO2 self-powered UV photodetectors (PDs) with enhanced responsivity is proposed in this work. By constructing asymmetric electrodes consisting of a commercial mixed silver paste and two different forms of Ag nanostructures (nanofilms and nanowires) on the active layer of TiO2, respectively. Both PD devices exhibited attractive photovoltaic characteristics in a self-powered mode (at 0 V bias). Interestingly, the responsivity of the TiO2 UV PDs is found to be enhanced by 9 times at the wavelength of 350 nm without any power supply when the configuration of the Ag nanostructure electrode was changed from nanofilms to transparent nanowires. The enhanced photoelectric conversion efficiency is mainly attributed to a modified Schottky barrier through reducing hole traps and a higher light absorptivity through using a transparent electrode according to the experimental results and physical models based on the energy band theory. In addition, TiO2 UV PDs with a Ag nanowire electrode also exhibited excellent photoelectric properties in terms of a high linear dynamic range of 103.7 dB, a fast response speed (rise time of 2 ms and fall time of 41 ms), and excellent stability. The design solutions proposed here may provide additional opportunities for further development of Schottky junction-based self-powered UV PDs with high efficiencies. [ABSTRACT FROM AUTHOR]

Abstract: Graphene nanodots (GNDs) are one of the most attractive graphene nanostructures due to their tunable optoelectronic properties. Fabricated by polystyrene‐nanosphere lithography, uniformly sized graphene nanodots array (GNDA) is constructed as an ultraviolet photodetector (PD) with ZnO nanofilm spin coated on it. The size of GNDA can be well controlled from 45 to 20 nm varying the etching time. It is revealed in the study that the photoelectric properties of ZnO/GNDA PD are highly GNDA size‐dependent. The highest responsivity (R) and external quantum efficiency of ZnO/GNDA (20 nm) PD are 22.55 mA W−1 and 9.32%, almost twofold of that of ZnO PD. Both ZnO/GNDA (20 nm) PD and ZnO/GNDA (30 nm) PD exhibit much faster response speed under on/off switching light and have shorter rise/decay time compared with ZnO PD. However, as the size of GNDA increase to 45 nm, the PD appears poor performance. The size‐dependent phenomenon can be explained by the energy band alignments in ZnO/GNDA hybrids. These efforts reveal the enhancement of GNDs on traditional photodetectors with tunable optoelectronic properties and hold great potential to pave a new way to explore the various remarkable photodetection performances by controlling the size of the nanostructures. [ABSTRACT FROM AUTHOR]

Due to the low density of nanostructured materials, it is still a big challenge to realize high volumetric performance instead of high specific gravimetric capacity with many state-of-the-art electrodes for compact electrochemical energy storage. Moreover, developing high-performance flexible and binder-free electrode materials is also crucial for their future applications in diverse fields, such as portable electronics and wearable devices. In this work, we designed and synthesized a Ni3V2O8/carbon cloth (CC) hierarchical structure as a flexible anode for sodium-ion batteries. Morphology-controllable growth of different Ni3V2O8/CC hierarchical structures is achieved by optimizing the synthesis parameters (e.g. the growth temperatures). The high mass loading (4 mg cm−2), ultra-high areal specific capacity (2.6 mA h cm−2 at a current density of 500 mA g−1), no addition of binders or other additives and good flexibility facilitate their application in sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Intrinsically p-type conductivity and a wide bandgap of ≈3.6 V endow inorganic delafossite CuGaO2 with great promise for fabricating high-performance UV photodetectors. Nevertheless, CuGaO2-based optoelectronic devices hindered because the intrinsic direct transitions are symmetry forbidden in CuGaO2. This study reports a large-area synthesis of 'CuGaO2 nanoplate/ZnS microsphere' heterostructure arrays using a facile solution-based strategy associated with an oil/water interfacial self-assembly approach. It is found that a large number of ZnS microspheres with a polycrystalline structure grow on the top surface of CuGaO2 hexagonal platelets through Ostwald ripening mechanism, forming high-density p-n heterojunctions. A parabolic dependence between the size of ZnS microsphere and the growth time is confirmed in this growth. The UV light adsorption of the heterostructure CuGaO2/ZnS thin film is two times higher than that of the pristine CuGaO2 thin film. Furthermore, the as-designed 'CuGaO2 nanoplate/ZnS microsphere' heterostructure arrays exhibit enhanced photoresponse properties. This work offers a new insight into the rational design of optoelectronic devices from the synergetic effect of p-type 2D nanoplates as well as n-type nanostructures such as ZnS, ZnO, CdS, and CdO. [ABSTRACT FROM AUTHOR]