High-Speed and High-Responsivity Blue Light Photodetector with an InGaN NR/PEDOT:PSS Heterojunction Decorated with Ag NWs.

InGaN nanorods possessing larger and wavelength selective absorption by regulating In component based visible light photodetectors (PDs) as one of the key components in the field of visible light communication have received widespread attention. Currently, the weak photoelectric conversion efficiency and slow photoresponse speed of InGaN nanorod (NR) based PDs due to high surface states of InGaN NRs impede the actualization of high-responsivity and high-speed blue light PDs. Here, we have demonstrated high-performance InGaN NR/PEDOT:PSS@Ag nanowire (NW) heterojunction blue light photodetectors utilizing surface passivation and a localized surface plasmon resonance effect. The dark current is significantly reduced by passivating the InGaN NR surface states using PEDOT:PSS. The photoelectric conversion efficiency is significantly increased by increasing light absorption due to the electromagnetic field oscillation of Ag NWs. The responsivity, external quantum efficiency, detectivity, and fall/off time of the InGaN NR/PEDOT:PSS@Ag NW PDs are up to 2.9 A/W, 856%, 6.64 × 1010 Jones, and 439/725 µs, respectively, under 1 V bias and 420 nm illumination. The proposed device design presents a novel approach toward the development of low-cost, high-responsivity, high-speed blue light photodetectors for applications involving visible light communication.

High-speed graphene/InGaN heterojunction photodetectors for potential application in visible light communication.

Due to the wavelength-selective absorption characteristic of indium gallium nitride (InGaN) ternary alloy, the InGaN-based photodetectors (PDs) show great potential as high signal-to-noise ratio (SNR) receivers in the visible light communication (VLC) system. However, the application of InGaN-based PDs with simple structure in the VLC system is limited by slow speed. Integration of graphene (Gr) with InGaN is an effective strategy for overcoming the limitation. Herein, we report on a high responsivity and fast response PDs based on Gr/InGaN heterojunctions. It finds that the three-layer Gr (T-Gr) can effectively improve the InGaN-based PDs photoelectric properties. The T-Gr/InGaN PDs show a high responsivity of 1.39 A/W@-3 V and a short rise/fall time of 60/200 µs, which are attributed to the combination of the high-quality InGaN epitaxial films and finite density of states of three-layer graphene. The fast response with high responsivity endows the T-Gr/InGaN PDs with great potential for selective detection of the VLC system.

Temporal and spatial evolution and obstacle diagnosis of resource and environment carrying capacity in the Loess Plateau.

Natural resources are scarce in the Loess Plateau, and the ecological environment is fragile. Sustainable development requires special attention to resource and environmental carrying capacity (RECC). This study selected 24 representative cities in five natural areas of the Loess Plateau; used the entropy-weight-based TOPSIS method to evaluate and analyze the RECC of each city and region from 2013 to 2018; established a diagnosis model to identify the obstacle factors restricting the improvement of RECC; and constructed the theoretical framework of the RECC system mechanism. The results show that the RECC of the Loess Plateau is increasing in general but is relatively small. The environmental and social subsystems have the highest and lowest carrying capacities, respectively. There is an evident contradiction between economic development and the environment. Population density, investment in technological innovation, per capita sown area, and per capita water resources are the main obstacles affecting the improvement of RECC in the Loess Plateau. Such evaluations and diagnoses can support ecological civilization and sustainable development.

Highly Efficient InGaN Nanorods Photoelectrode by Constructing Z-scheme Charge Transfer System for Unbiased Water Splitting.

Unbiased photoelectrochemical water splitting for the promising InGaN nanorods photoelectrode is highly desirable, but it is practically hindered by the serious recombination of charge carrier in bulk and surface of InGaN nanorods. Herein, an unbiased Z-scheme InGaN nanorods/Cu2 O nanoparticles heterostructured system with boosted interfacial charge transfer is constructed for the first time. The introduced Cu2 O nanoparticles pose double-sided effect on photoelectrochemical (PEC) performance of InGaN nanorods, which enables a robust hybrid structure and induces weakened light absorption capability simultaneously. As a result, the optimized InGaN/Cu2 O-1.5C photoelectrode with the uniform morphology exhibits an enhanced photocurrent density of ≈170 µA cm-2 at 0 V versus Pt, with 8.5-fold enhancement compared with pure InGaN nanorods. Comprehensive investigations into experimental results and theoretical calculations reveal that the electrons accumulation and holes depletion of Cu2 O facilitate to form a typical Z-scheme band alignment, thus providing a large photovoltage to drive unbiased water splitting and enhancing the stability of Cu2 O. This work provides a novel and facile strategy to achieve InGaN nanorods and other catalyst-based PEC water splitting without external bias, and to relieve the bottlenecks of charge transfer dynamics at the electrode bulk and electrode/electrolyte interface by constructing Z-scheme heterostructure.

High responsivity and high speed InGaN-based blue-light photodetectors on Si substrates.

Due to the adjustable band gap, the excellent radiation stability, and the high electron mobility of InGaN, the InGaN-based blue-light photodetectors (PDs) show great potential in visible light communication (VLC) systems. However, the applications of InGaN-based blue-light PDs in VLC systems are limited by the poor performance caused by the poor crystalline quality of InGaN materials. Herein, we report on the fabrication of high responsivity and high response speed InGaN-based metal-semiconductor metal (MSM) blue-light PDs using high-quality InGaN epitaxial films grown on Si substrates by the combination of low-temperature pulsed laser deposition (LT-PLD) and high-temperature metal organic chemical deposition (HT-MOCVD). The technology can not only suppress the interfacial reactions between films and substrates by LT-PLD growth, but also promote the lateral overgrowth of InGaN and improve the crystalline quality of InGaN-based epitaxial films by HT-MOCVD growth. Based on the high-quality InGaN-based materials, high-performance InGaN-based blue-light PDs are fabricated accordingly with a high responsivity of 0.49 A W-1 and a short rise/fall response time of 1.25/1.74 ms at an applied bias of -3 V. The performance is better than the results for the InGaN-based PDs previously reported. The InGaN-based blue-light PDs shed light on the potential for VLC system applications.

Synergetic dielectric loss and magnetic loss towards superior microwave absorption through hybridization of few-layer WS2 nanosheets with NiO nanoparticles.

WS2 nanomaterials have attracted great attention in the field of electromagnetic wave absorption due to their high specific surface area, layered structure, and peculiar electronic properties. However, further improvements on their limited electromagnetic absorbing (EMA) capacity and bandwidth are urgently required for their practical application as EMA absorbents. In this work, WS2/NiO hybrids with heterostructures are prepared by a hydrothermal method and developed into EMA absorbents. The maximum reflection loss of the hybrids with 20% NiO loading could reach -53.31 dB at a thickness of 4.30 mm; the bandwidth with a reflection loss value of less than -10 dB is determined to be 13.46 GHz (4.54-18 GHz) when the thickness of the absorbent is between 3.5 and 5.5 mm. It is found that the enhanced EMA performance of WS2/NiO hybrids is caused by the addition of magnetic NiO, which could result in the interfaces between WS2 and NiO being responsible for the synergetic magnetic loss and dielectric loss in the hybrids. This work provides a new approach for the design of excellent EMA materials for practical applications.

Light-weight and low-cost electromagnetic wave absorbers with high performances based on biomass-derived reduced graphene oxides.

Rational structure design of microwave absorption material is extremely significant from the perspectives of enhancing the electromagnetic microwave absorption (EMA) performance and adapting to cost-effective and sustainable industrial applications. Here, reduced graphene oxides (rGOs) with curl structures derived from corn stover are applied for the absorption of electromagnetic waves. The results suggest that biomass-rGO show the maximum reflection loss of -51.7 dB and an effective absorption bandwidth 13.5 GHz (4.5-18 GHz) at a thickness of 3.25 mm, implying the unique critical role of the microstructure in adjusting the EMA performance. Moreover, the successful conversion of waste biomass into widely used electromagnetic wave absorbing materials could solve the problems of environmental pollution caused by straw burning.

Highly effective photocatalytic performance of {001}-TiO2/MoS2/RGO hybrid heterostructures for the reduction of Rh B.

Effective separation and rapid transfer of photogenerated electron-hole pairs are key features of photocatalytic materials with high catalytic activity, which could be achieved in co-catalysts. It is reported that the two-dimensional (2D) MoS2 is a promising co-catalyst due to its unique semi-conductive properties and graphene-like layered structure. However, the application of MoS2 as a co-catalyst is limited by its poor electrical conductivity. On the other hand, it is worth noting that TiO2 possesses reactive crystal facets, which is one of the dominant mechanisms for the separation of photogenerated electron-hole pairs. In this work, we prepared MoS2/RGO hybrids as co-catalysts which were doped to TiO2 with highly reactive {001} planes via the hydrothermal method. It was found that the {001}-TiO2/MoS2/RGO photocatalysts with 7 wt% MoS2/RGO co-catalyst show the highest photodegradation activity for the degradation of Rh B under visible light irradiation (λ > 400 nm), which could result from the synergy of the effective separation of electron-hole pairs by the {001} facets in TiO2 and the rapid transfer of electron-hole pairs in MoS2/RGO. The results show that the {001}-TiO2/MoS2/RGO hybrid is a low-cost and stable photocatalyst for the effective degradation of Rh B under visible light.

Magnetic-field-induced dielectric behaviors and magneto-electrical coupling of multiferroic compounds containing cobalt ferrite/barium calcium titanate composite fibers.

Multiferroics have broad application prospects in various fields such as multi-layer ceramic capacitors and multifunctional devices owing to their high dielectric constants and coupled magnetic and ferroelectric properties at room temperature. In this study, cobalt ferrite (CFO)/barium calcium titanate (BCT) composite fibers are prepared from BCT and CFO sols by an electrospinning method, and are then oriented by magnetic fields and sintered at high temperatures. The effects of magnetic fields and CFO contents on the nanostructures and magnetoelectric properties of the composites are investigated. Strong coupling between magnetic and ferroelectric properties occurs in CFO/BCT composites with magnetic orientation. More interestingly, the dielectric constants of CFO/BCT composites with magnetic orientation are found to be enhanced (by ∼1.5-3.5 times) as compared with those of BCT and CFO/BCT without magnetic orientation. The boost of dielectric constants of magnetic-field orientated CFO/BCT is attributed to the magneto-electrical coupling between CFO and BCT, where the polar domains of BCT are pinned by the orientated CFO. Therefore, this work not only provides a novel and effective approach in enhancing the dielectric constants of ceramic ferroelectrics, which is of tremendous value for industrial applications, but also elucidates the interaction mechanisms between ferromagnetic phase and ferroelectric phase in multiferroic compounds.

Self-assembly of 2D-metal-organic framework/graphene oxide membranes as highly efficient adsorbents for the removal of Cs+ from aqueous solutions.

The potential toxicity and irreversibility of radionuclide Cs place severe pressure on the natural environment, which has become one of the most forefront pollution problems in nuclear energy utilization. To solve this problem, novel self-assembled membranes consisting of two-dimensional (2D) metal-organic frameworks (MOFs) and graphene oxide (GO) were prepared by a facile filtration method, which can efficiently absorb Cs+ from aqueous solutions. The batch experimental results showed that the sorption of Cs+ on the GO/Co-MOF composite membrane was strongly dependent on the addition mass and the membrane compositions. Thus, the dominant interaction mechanism was interface or surface complexation and electrostatic interaction. The maximum sorption efficiency of Cs+ on GO/Co-MOF was 88.4% with 8 mg addition mass at pH = 7.0 and 299 K. Detailed FT-IR and XPS analyses suggested that the efficient synergistic effects in the unique architectures of GO/Co-MOF play an important role in the high sorption capacity of Cs+. The facile preparation method and the highly-efficient Cs+ removal behaviour of GO/Co-MOF make the novel membrane a promising candidate for the elimination of radionuclide contamination.

Facile synthesis of highly conductive MoS2/graphene nanohybrids with hetero-structures as excellent microwave absorbers.

Two-dimensional (2D) MoS2/graphene nanosheet (MoS2/GN) hybrids have been demonstrated to be promising microwave absorption (MA) materials due to their unique chemical and physical properties as well as rich impedance matching. However, the reported strategies for preparing MoS2/GN hybrids have limited their application potential due to the complex, high-cost and inefficient preparation processes. On the other hand, it is of note that the main source of graphene is based on converting insulating graphene oxides (GO) back to conductive reduced graphene oxides (RGO). Thus, the MA performance of obtained MoS2/RGO nanohybrids is greatly affected by the conversion process of GO. In this work, we prepared the MoS2/GN hybrids by a facile hydrothermal method with directly introducing highly pure and electroconductive GNs. It is found that the highest reflection loss value of the sample-wax containing 40% MoS2/GN is -57.31 dB at a thickness of 2.58 mm, and the bandwidth of RL values less than -10 dB can reach up to 12.28 GHz (from 5.72 to 18 GHz) when an appropriate absorber thickness between 1.5 and 4 mm is chosen. The excellent MA performances emanate from effective conjugation of MoS2 with GN (Mo-C bond between the interfaces), which provides the dielectric loss caused by multi-relaxation, conductance, and polarization. Taking into account the facile synthesis route and their excellent MA performance, the MoS2/GNs hybrid nanosheets and those composite materials with similar isomorphic hetero-structures are very promising for a wide range of MA applications.