Surface Microstructure Engineering in MAPbBr3 Microsheets for Performance-Enhanced Photodetectors

Metal halide-perovskite-based photodetectors have recently emerged as a class of promising optoelectronic devices in various fields. Meanwhile, nano/microstructuring perovskite-based photodetectors are a facile integration with complementary metal-oxide semiconductors for miniaturized imaging systems. However, there are still challenges to be overcome in reducing the losses caused by light reflection on the surface of microstructural perovskites. In this work, surface microstructure engineering is employed in MAPbBr3 microsheets for reducing light reflection and improving light absorption, resulting in high-performance perovskite photodetectors. MAPbBr3 microsheets, which possess different surface morphologies of flat, upright hemisphere arrays and inverted hemisphere arrays (IHAs), are fabricated by a simple microstructure template-assisted space confinement process. The light absorption capacity of IHA MAPbBr3 is significantly higher than that of the other two structures. Hence, IHA photodetectors with excellent figures of merit, including low dark current, decent responsivity, and fast speed, are achieved. Furthermore, the noise of the IHA photodetectors is only ∼10-13 A/H z , which results in the superior sensitivity for weak light detection with a specific detectivity up to 1011 Jones. Our results demonstrate that surface engineering is a simple, low-cost, yet effective approach to improve the performance of nano-/micro-optoelectronic devices.

Template-Assisted Synthesis of 2D Perovskite Grating Single Crystal Films at Low Temperatures for UV Polarization-Sensitive Photodetectors

2D perovskites have attracted tremendous attention due to their superior optoelectronic properties and potential applications in optoelectronic devices. Especially, the larger bandgap of 2D perovskite means that they are suitable for UV photodetection. However, the layered structure of 2D perovskites hinders the interlayer carrier transport, which limits the improvement of device performance. Therefore, nanoscale structures are normally used to enhance the light absorption ability, which is an effective strategy to improve the photocurrent in 2D perovskite-based photodetectors. Herein, a template-assisted low-temperature method is proposed to fabricate 2D perovskite ((C6 H5 C2 H4 NH3 )2 PbBr4 , (PEA)2 PbBr4 ) grating single crystal films (GSCFs). The crystallinity of the (PEA)2 PbBr4 GSCFs is significantly improved due to the slow evaporation of the precursor solution under low temperatures. Based on this high crystalline quality and extremely ordered microstructures, the metal-semiconductor-metal photodetectors are assembled. Finite-different time-domain (FDTD) simulation and experiment indicate that the GSCF-based photodetectors exhibit significantly improved performance in comparison with the plane devices. The optimized 2D perovskite photodetectors are sensitive to UV light and demonstrate a responsivity and detectivity of 28.6 mA W-1 and 2.4 × 1011 Jones, respectively. Interestingly, the photocurrent of this photodetector varies as the angle of the incident polarized light, resulting in a high polarization ratio of 1.12.

Room-Temperature Diffusion-Induced Extraction for Perovskite Nanocrystals with High Luminescence and Stability

Metal halide perovskite nanocrystals (NCs) serve as a kind of ideal semiconductor for luminescence and display applications. However, the optoelectronic performance and stability of perovskite NCs are mainly subjected to current ligand strategies since these ligands exhibit a highly dynamic binding state, which complicates NC purification and storage. Herein, a method named diffusion-induced extraction is developed for crystallization (DEC) at room temperature, in which silicone oil serves as a medium to separate the solvent from perovskite precursors and diethyl ether promotes the nucleation, leading to highly emissive perovskite NCs. The formation mechanism of NCs using this approach is elucidated, and their optoelectronic properties are fully characterized. The resultant NCs ink exhibits a high photoluminescence quantum yield (PLQY) over 90% with a narrow full width at half maximum of 17 nm. The DEC method strengthens the interaction between ligand and NCs via the hydrophobic silicone oil. Therefore, the NCs maintain almost 95% of their initial PLQYs after aging more than seven months in air. The findings will be of great significance for the continued advancement of high PLQY perovskite NCs through a better understanding of formation dynamics. The DEC strategy presents a major step forward for advancing the field of perovskite semiconductor nanomaterials.

High-Rubidium-Formamidinium-Ratio Perovskites for High-Performance Photodetection with Enhanced Stability

Formamidinium lead trihalide perovskites have emerged as promising photovoltaic materials owing to their superior absorption coefficient properties. However, one big challenge is the material phase stability and thermal stability at high temperature. In this work, a large quantity of rubidium (Rb) ions is incorporated into formamidinium (FA) perovskite thin films to improve the material phase stability and thermal stability. Photodiodes based on optimized FA_0.7Rb_0.3PbI₃ perovskites deliver a high responsivity of 0.43 A W^-1, a detectivity of >10¹² Jones, a relatively large linear dynamic range of 125 dB, and an ultrafast response speed of approximately 300 ns. Moreover, these photodiodes present lower dark current and higher photocurrent after baking at high temperature. These results are very promising for photodetection at high operational temperature. In addition, the high-ratio rubidium-incorporated perovskite films may have great potential in fabricating other high-performance optoelectronic devices, i.e., light-emitting diodes and solar cells with excellent phase stability and high temperature thermostability.

Space-Confined Growth of Individual Wide Bandgap Single Crystal CsPbCl3 Microplatelet for Near-Ultraviolet Photodetection

Perovskite photodetectors (PDs) with tunable detection wavelength have attracted extensive attention due to the potential application in the field of imaging, machine vision, and artificial intelligence. Most of the perovskite PDs focus on I- or Br-based materials due to their easy preparation techniques. However, their main photodetection capacity is situated in the visible region because of their narrower bandgap. Cl-based wide bandgap perovskites, such as CsPbCl₃ , are scarcely reported because of the bad film quality of the spin-coated Cl-based perovskite, due to the poor solubility of the precursor. Therefore, ultraviolet detection using high-quality full inorganic perovskite films, especially with high thermal stability of materials and devices, is still a big challenge. In this work, high-quality single crystal CsPbCl₃ microplatelets (MPs) synthesized by a simple space-confined growth method at low temperature for near-ultraviolet (NUV) PDs are reported. The single CsPbCl₃ MP PDs demonstrate a decent response to NUV light with a high on/off ratio of 5.6 × 10³ and a responsivity of 0.45 A W^-1 at 5 V. In addition, the dark current is as low as pA level, leading to detectivity up to 10¹¹ Jones. Moreover, PDs possess good stability and repeatability.

A 3D self-supported coralline-like CuCo2S4@NiCo2S4 core-shell nanostructure composite for high-performance solid-state asymmetrical supercapacitors

Rational construction of three dimensional (3D) composite structure is an important method to flexible supercapacitor electrodes and has been extensively developed. In this work, a 3D self-supported CuCo₂S₄@NiCo₂S₄ core-shell nanostructure grown on Nickel (Ni) foam, constructed by a hydrothermal method, was used as a novel supercapacitor electrode material. The unique structure possesses a large, specific surface area, rapid diffusion of electrolyte ions by numerous channels and avoids the use of additives and adhesives. The high electrical conductivity of the CuCo₂S₄ nanoneedle arrays can speed up electronic transmission. At a current density of 1 A g^-1, the electrode material exhibits a high specific capacity of 539.2 C g^-1 and cycling stability with 100% capacity retention after 5000 cycles in 3 M KOH. Furthermore, when the obtained CuCo₂S₄@NiCo₂S₄ was used as the positive electrode and an activated carbon was used as the negative electrode, a solid-state asymmetric supercapacitor was assembled. More importantly, the obtained solid-state asymmetric supercapacitor demonstrated excellent electrochemical performance. When the power density was 400 W kg^-1, it delivered a high density of 23.4 W h kg^-1 with a high voltage window of 1.6 V, thus demonstrating that the material has the potential for use as an efficient electrode for electrochemical capacitors. Due to its comprehensive electrochemical performance, the CuCo₂S₄@NiCo₂S₄ solid-state asymmetric supercapacitor effectively operated a red LED.

Bifunctional bamboo-like CoSe2 arrays for high-performance asymmetric supercapacitor and electrocatalytic oxygen evolution

Bifunctional bamboo-like CoSe₂ arrays are synthesized by thermal annealing of Co(CO₃)_0.5OH grown on carbon cloth in Se atmosphere. The CoSe₂ arrays obtained have excellent electrical conductivity, larger electrochemical active surface areas, and can directly serve as a binder-free electrode for supercapacitors and the oxygen evolution reaction (OER). When tested as a supercapacitor electrode, the CoSe₂ delivers a higher specific capacitance (544.6 F g^-1 at current density of 1 mA cm^-2) compared with CoO (308.2 F g^-1) or Co₃O₄ (201.4 F g^-1). In addition, the CoSe₂ electrode possesses excellent cycling stability. An asymmetric supercapacitor (ASC) is also assembled based on bamboo-like CoSe₂ as a positive electrode and active carbon as a negative electrode in a 3.0 M KOH aqueous electrolyte. Owing to the unique stucture and good electrochemical performance of bamboo-like CoSe₂, the as-assembled ACS can achieve a maximum operating voltage window of 1.7 V, a high energy density of 20.2 Wh kg^-1 at a power density of 144.1 W kg^-1, and an outstanding cyclic stability. As the catalyst for the OER, the CoSe₂ exhibits a lower potential of 1.55 V (versus RHE) at current density of 10 mA cm^-2, a smaller Tafel slope of 62.5 mV dec^-1 and an also outstanding stability.

Rational Construction of Hollow Core-Branch CoSe2 Nanoarrays for High-Performance Asymmetric Supercapacitor and Efficient Oxygen Evolution

Metal selenides have great potential for electrochemical energy storage, but are relatively scarce investigated. Herein, a novel hollow core-branch CoSe₂ nanoarray on carbon cloth is designed by a facile selenization reaction of predesigned CoO nanocones. And the electrochemical reaction mechanism of CoSe₂ in supercapacitor is studied in detail for the first time. Compared with CoO, the hollow core-branch CoSe₂ has both larger specific surface area and higher electrical conductivity. When tested as a supercapacitor positive electrode, the CoSe₂ delivers a high specific capacitance of 759.5 F g^-1 at 1 mA cm^-2 , which is much larger than that of CoO nanocones (319.5 F g^-1 ). In addition, the CoSe₂ electrode exhibits excellent cycling stability in that a capacitance retention of 94.5% can be maintained after 5000 charge-discharge cycles at 5 mA cm^-2 . An asymmetric supercapacitor using the CoSe₂ as cathode and an N-doped carbon nanowall as anode is further assembled, which show a high energy density of 32.2 Wh kg^-1 at a power density of 1914.7 W kg^-1 , and maintains 24.9 Wh kg^-1 when power density increased to 7354.8 W kg^-1 . Moreover, the CoSe₂ electrode also exhibits better oxygen evolution reaction activity than that of CoO.

In situ grown Ni9S8 nanorod/O-MoS2 nanosheet nanocomposite on carbon cloth as a free binder supercapacitor electrode and hydrogen evolution catalyst

Transition metal sulfide nanostructure composites have received significant attention as energy conversion and storage devices. In this work, we report a three-dimension (3D) nanostructure with the Ni₉S₈ nanorods embedded in oxygen-incorporated MoS₂ (O-MoS₂) nanosheets for supercapacitors and hydrogen evolution catalysts. The in situ grown Ni₉S₈/O-MoS₂ nanocomposite on carbon cloth can be used as a free binder supercapacitor electrode and hydrogen evolution catalyst. The Ni₉S₈/O-MoS₂ nanocomposite exhibits electrochemical behaviors with a specific capacitance of 907 F g^-1 (at 2 A g^-1) and good cycle stability after 1200 cycles due to its unique mutual embedding 3D nanostructure. Furthermore, the Ni₉S₈/O-MoS₂ nanocomposite also shows highly electrocatalytic features for hydrogen production with an onset overpotential of ∼150 mV and a low Tafel slope of ∼81 mV dec^-1. The oxygen incorporation of MoS₂ provides more active sites to participate in the catalytic process for the hydrogen evolution reaction.

Metal-Organic Framework Template Derived Porous CoSe2 Nanosheet Arrays for Energy Conversion and Storage

Porous CoSe₂ on carbon cloth is prepared from a cobalt-based metal organic framework template with etching and selenization reaction, which has both a larger specific surface area and outstanding electrical conductivity. As the catalyst for oxygen evolution reaction, the porous CoSe₂ achieves a lower onset potential of 1.48 V versus the reversible hydrogen electrode (RHE) and a small potential of 1.52 V (vs RHE) at an anodic current density of 10 mA cm^-2. Especially, the linear sweep voltammogram curve of the porous CoSe₂ is in consist with the initial curve after durability test for 24 h. When tested as an electrode for supercapacitor, it can deliver a specific capacitance of 713.9 F g^-1 at current density of 1 mA cm^-2 and exhibit excellent cycling stability in that a capacitance retention of 92.4% can be maintained after 5000 charge-discharge cycles at 5 mA cm^-2. Our work presents a novel strategy for construction of electrochemical electrode.

High performance, self-powered ultraviolet photodetector based on a ZnO nanoarrays/GaN structure with a CdS insert layer

A self-powered photodetector based on a ZnO nanoarrays/CdS/GaN structure with a responsivity as high as 176 mA W⁻¹ at 300 nm.

Self-powered, ultraviolet-visible perovskite photodetector based on TiO2 nanorods

A self-powered, ultraviolet-visible perovskite photodetector based on TiO₂ nanorods/CH₃NH₃PbI₃ heterojunction was reported.

Evaluation of constructed wetlands by wastewater purification ability and greenhouse gas emissions

Domestic wastewater is a significant source of nitrogen and phosphorus, which cause lake eutrophication. Among the wastewater treatment technologies, constructed wetlands are a promising low-cost means of treating point and diffuse sources of domestic wastewater in rural areas. However, the sustainable operation of constructed wetland treatment systems depends upon a high rate conversion of organic and nitrogenous loading into their metabolic gaseous end products, such as N2O and CH4. In this study, we examined and compared the performance of three typical types of constructed wetlands: Free Water Surface (FWS), Subsurface Flow (SF) and Vertical Flow (VF) wetlands. Pollutant removal efficiency and N2O and CH4 emissions were assessed as measures of performance. We found that the pollutant removal rates and gas emissions measured in the wetlands exhibited clear seasonal changes, and these changes were closely associated with plant growth. VF wetlands exhibited stable removal of organic pollutants and NH3-N throughout the experiment regardless of season and showed great potential for CH4 adsorption. SF wetlands showed preferable T-N removal performance and a lower risk of greenhouse gas emissions than FWS wetlands. Soil oxidation reduction potential (ORP) analysis revealed that water flow structure and plant growth influenced constructed wetland oxygen transfer, and these variations resulted in seasonal changes of ORP distribution inside wetlands that were accompanied by fluctuations in pollutant removal and greenhouse gas emissions.

Regulation of ion channels by protein tyrosine phosphorylation

Ion channels are regulated by protein phosphorylation and dephosphorylation of serine, threonine, and tyrosine residues. Evidence for the latter process, tyrosine phosphorylation, has increased substantially since this topic was last reviewed. In this review, we present a comprehensive summary and synthesis of the literature regarding the mechanism and function of ion channel regulation by protein tyrosine kinases and phosphatases. Coverage includes the majority of voltage-gated, ligand-gated, and second messenger-gated channels as well as several types of channels that have not yet been cloned, including store-operated Ca2+ channels, nonselective cation channels, and epithelial Na+ and Cl- channels. Additionally, we discuss the critical roles that channel-associated scaffolding proteins may play in localizing protein tyrosine kinases and phosphatases to the vicinity of ion channels.

Protective effect of rhubarb on endotoxin-induced acute lung injury

To approach the mechanism of lipopolysaccharide (LPS) in causing acute lung injury (ALI) and the protective effect of rhubarb and dexamethasone, lung specimens were examined with macroscopy, microscopy, electron microscopy and the biological markers of ALI including lung wet/dry weight, the rate of neutrophils and protein content in the pulmonary alveolar lavage fluid, pulmonary capillary permeability and pulmonary alveolar permeability index were observed. The mechanism of the ALI is mainly due to direct injury of alveolar epithelium and pulmonary vascular endothelium. Rhubarb and dexamethasone could significantly reduce the edema of the lung tissue, decrease the red blood cell exudation, neutrophil infiltration and plasma protein exudation in the alveoli and all the biological markers in comparison with the ALI model rats, indicating they have protective action on vascular endothelium and alveolar epithelium.

Actions of NO and INOS on endotoxin induced rat acute lung injury and effect of rhubarb on them

This study is to explore the actions of nitric oxide (NO) and inducible nitric oxide synthase (iNOS) on endotoxin (lipopolysaccharide, LPS) induced rat acute lung injury (ALI) and effect of Rhubarb on them. LPS was injected into the sublingual vein of male Wistar rats to prepare ALI animal models. The rats were divided into 4 groups: LPS, control, Rhubarb, and dexamethasone. Macroscopic and histopathological examinations of the lung specimens were performed and the biological indexes of lung, including wet weight/dry weight, the rate of neutrophils and protein content in the pulmonary alveolar lavage fluid, pulmonary vascular permeability and pulmonary alveolar permeability were observed. In the mean time, the contents of serum NO and the activities of lung tissue homogenate iNOS were measured. The results showed that in the LPS group, the injury and celluar infiltration in the pulmonary stroma and alveoli were more prominent than that in the control group. Lung wet weight/dry weight, the rate of neutrophils, protein content, pulmonary alveolar permeability, pulmonary vascular permeability were significantly increased (P < 0.01); NO and iNOS were also markedly elevated (P < 0.01). In the groups of dexamethasone and Rhubarb, the histopathological changes were significantly milder, and all the above biological indexes of lung injury and the contents of NO and the activities of iNOS were correspondingly decreased (P < 0.05). The above data demonstrate that NO and iNOS play an important role in the onset of ALI; dexamethasone and Rhubarb interfering treatment can ameliorate lung injury and decrease the concentrations of NO and the activities of iNOS, showing that through inhibiting the levels of NO and the activities of iNOS, these 2 agents exert protective effect on ALI induced LPS.