Intrinsic defect engineered Janus MoSSe sheet as a promising photocatalyst for water splitting

The Janus MoSSe sheet has aroused significant attention due to its band edge position and intrinsic dipole moment, making it a strong candidate for water splitting photocatalysis. However, weak water adsorption seriously prevents its further application. Here, first-principles calculations are used to explore the effect of intrinsic defects on water adsorption and conversion at the Janus MoSSe sheet. First-principles calculation results clearly show that intrinsic defects (S_vac, Mo_anti, and Mo_int) can effectively alter the interaction between water and the MoSSe sheet. Except for S_vac defects, the adsorption energy of water at Mo_anti or Mo_int defects can be significantly increased by −1.0 to −1.5 eV with respect to the weak water adsorption on a pristine MoSSe sheet of about −0.24 eV. More importantly, the energy barrier for water conversion can be dramatically lowered by 48% to 0.7 eV at Mo_anti or Mo_int defects, together with a more stable final state. Such significant enhancement of the adsorption energy is attributed to the red shift of water energy levels, resulting from the strong interaction between O2p orbitals and Mo3d orbitals. It is shown that the intrinsic defects have the potential to change the photocatalytic reactivity of the surface, and thus this may serve as an important way to design photocatalysts for water splitting.

The Janus MoSSe sheet has aroused significant attention due to its band edge position and intrinsic dipole moment, making it a strong candidate for water splitting photocatalysis.     

The characterization and evaluation of the synthesis of large-ring cyclodextrins (CD9–CD22) and α-tocopherol with enhanced thermal stability

Large-ring cyclodextrins LR-CDs (CD₉–CD₂₂) were obtained from rice starch using cyclodextrin glycosyltransferase (CGTase), and were used as a wall material for embedding α-tocopherol. Complexes of α-tocopherol and LR-CDs were prepared by co-precipitation. A molar ratio of α-tocopherol/LR-CD of 1 : 2 showed the highest encapsulation efficiency. The surface morphology of the complex particles was observed to vary from irregular flakes to the formation of smaller clusters of particles using scanning electron microscopy (SEM). Based on ¹H NMR and FT-IR observations, the inclusion complexes exhibited significant chemical shifts of 0.3 ppm and decreased peak signals. In addition, thermal analysis showed that the microcapsules improved the thermostability of the α-tocopherols. Antioxidant activity analysis proved the stability of α-tocopherol during storage. This study could serve as a reference for the more effective use of LR-CDs as wall materials.

Large-ring cyclodextrins LR-CDs (CD₉–CD₂₂) were obtained from rice starch using cyclodextrin glycosyltransferase (CGTase), and were used as a wall material for embedding α-tocopherol.     

Heavy metal adsorption using structurally preorganized adsorbent

Heavy metal pollution is an essential environmental issue in the world. The current methods present limitations for the removal of low concentration divalent heavy metals from wastewater, such as high cost, unsatisfactory adsorption capacity, and poor reusability. Herein, we designed and prepared a novel chelating adsorbent. The adsorbent was prepared using chloromethyl polystyrene microsphere as a framework material modified by ethylenediaminetetraacetic acid (EDTA) with two types of functional groups and six binding sites in one coordination unit. Each coordination unit of the adsorbent prepared provides two negative charges of two carboxyl groups to balance the two positive charges of the divalent heavy metal ion, and forms coordination bonds through its two nitrogen atoms and two amidic carbonyl groups. This synergistic adsorption effect produced by electrostatic interaction and chelation significantly improves the adsorption capacity. The adsorption of some environmental heavy metals was tested, and high adsorption capacity for Pb(ii) was obtained. The saturated adsorption capacity for Pb(ii) was as high as 352.1 mg g⁻¹, and the effluent concentration of the column experiment was less than 0.20 ppm. Simultaneously, the presence of the amide group shows good anti-interference to alkali metals and alkali soil metals. The result is of considerable significance to the actual wastewater treatment.

The adsorbent had two types of functional groups and six binding sites in one coordination unit. The presence of the amide group shows good anti-interference to alkali metals and alkali soil metals.     

A thermal energy storage composite by incorporating microencapsulated phase change material into wood

Phase change energy storage wood (PCESW) was prepared by using microencapsulated phase change materials (MicroPCM) as thermal energy storage (TES) materials and wood as the matrix. The incorporation of MicroPCM and wood was realized using a vacuum impregnation method. The morphology and microstructure of MicroPCM, delignified wood (DLW) and PCESW were observed by scanning electron microscopy (SEM); the thermal properties including phase change temperature, enthalpy, thermal stability, thermal conductivity of MicroPCM and PCESW were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and laser flash analysis (LFA). The results showed that: (1) delignification improved the porosity of wood and enhanced the impregnation effect, MicroPCM got into the delignified wood successfully and mainly distributed in the vessels; (2) PCESW had excellent energy storage capacity and suitable phase transition temperature for regulating indoor temperature; (3) PCESW had prior thermal stability at room temperature and great durability after 100 heating–cooling cycles; (4) addition of graphene greatly improved the thermal conductivity of PCESW. The TES composite can be used as an indoor temperature regulating material for building energy conservation.

Phase change energy storage wood (PCESW) was prepared by using microencapsulated phase change materials (MicroPCM) as thermal energy storage (TES) materials and wood as the matrix.     

Catalytic activity of porous carbon nitride regulated by polyoxometalates under visible light

A series of porous carbon nitrides modified by different polyoxometalates (POMs) were prepared by the ultrasonic method. POMs were assembled on the surface of mpg-C₃N₄via electrostatic attraction. The catalyst has visible light degradation activity for phenol (λ > 420 nm). mpg-C₃N₄ modified by H₄SiW₁₂O₄₀ with a mass ratio of 1 : 5 showed the highest catalytic activity, which was 3.5 times higher than that of mpg-C₃N₄. As an electron acceptor, polyoxometalate can capture the photoelectron of C₃N₄, which can promote the separation of photocharge and improve the photocatalytic activity. ESR also confirmed that the superoxide radicals play a major role in degradation. The results show that the charge separation efficiency and catalytic activity can be enhanced by polyacids.

A porous composite catalyst is prepared by modifying mpg-C₃N₄ with polyacids through ultrasound. When the mass ratio of SiW₁₂ to mpg-C₃N₄ was 1 : 5, the degradation of phenol showed the best catalytic activity, which was 3.5 times that of mpg-C₃N₄.     

A new oxygen-rich energetic salt dihydrazine tetranitroethide: a promising explosive alternative with high density and good performance

A novel high-energy salt with good oxygen balance, dihydrazine tetranitroethide (5), has been synthesized and characterized by FT-IR spectroscopy, NMR spectroscopy, elemental analysis, and X-ray single crystal diffraction. Compound 5 exhibits high crystal density (1.81 g cm⁻³) and impressive detonation velocity (9508 m s⁻¹) and detonation pressure (37.9 GPa), showing potential applications as a high performance explosive and a promising additive of propellants.

A novel high-energy salt with good oxygen balance, dihydrazine tetranitroethide (5), has been synthesized and characterized by FT-IR spectroscopy, NMR spectroscopy, elemental analysis, and X-ray single crystal diffraction.

For applications in propellants, explosives and pyrotechnics, new energetic materials are required with high energy, insensitivity, high thermal stability and environment-friendly decomposition gases.¹ To achieve these goals, chemists have adopted a variety of strategies, such as construction of nitrogen-rich compounds,² energetic salts,³ metal organic framework (MOFs)⁴ and cage structure molecules.⁵ Oxygen balance (OB) is an important parameter to weigh the detonation performance of the nitrogen-rich compounds. Generally explosives may exhibit good performance when the OB close to zero.⁶ One conventional method of increasing the OB of energy materials is to introduce nitro groups, a typical high-energy and oxygen-rich substituent.⁷ Recently, gem-nitro and poly-nitro fragments, such as dinitromethyl,⁸ trinitroethyl⁹ and trinitromethyl,¹⁰ have been of interest to researchers. The compounds consisting of poly-nitro groups exhibit good OB, which largely improves their detonation velocities and pressures.¹¹ In our recent study,¹² we considered using tetranitroethylene instead of nitro as a pre-packaged module, linked to insensitive backbones, just like building blocks. The tetranitroethylene fragment has a high nitrogen content, a positive OB, and high energy within the molecule.¹³ The molecules consisting of the tetranitroethylene fragment are expected to be excellent energetic materials with superior properties.¹² But tetranitroethylene is an unstable intermediate, which is difficult to isolate.¹⁴ Hexnitroethane,¹⁵ a stable tetranitroethylene derivative, can be effectively used to synthetize poly-nitro bridged compound (Scheme 1). Previously, we discussed the possibility of constructing poly-nitro bridged-ring compounds with nitrogen-containing heterocycles and tetranitroethylene by using the Diels–Alder reaction.^12,16Open in a separate windowScheme 1Synthetic pathway for poly-nitro bridged compound.¹⁴Dipotassium tetranitroethide,¹⁷ another tetranitroethylene derivative, lead another thought to synthesize high energy salts with the tetranitroethane anion. The salt-based energetic materials often exhibit lower vapour pressure and higher densities than the non-ionic energetic materials.^3c In addition, the energetic salt can improve the properties by selecting different constituent ions.¹⁸ Based on the advantages of high-energy salt, we chose tetranitroethane anion and hydrazine cation to construct energetic salt by considering both energy and sensitivity. The synthetic route can be seen in Scheme 2. The good OB and large amounts of hydrogen-bonds prompt the target compound (dihydrazine tetranitroethide, 5) with suitable sensitivity and good performance. 5 possesses a crystal density of 1.81 g cm⁻³, detonation velocity of 9508 m s⁻¹ and detonation pressure of 37.9 GPa, which are higher than those of RDX. In addition, the salt-formation improves the carcinogenic and high toxic properties of hydrazine.Open in a separate windowScheme 2The route to synthesis of 5.The intermediate dipotassium tetranitroethide (3) was prepared from tetraiodoethylene (1) after two nitrification reactions, according to literature.¹⁹ The suspension of 3 in dichloromethane dissolves in concentrated sulfuric acid to give the solution of tetranitroethane (4) in dichloromethane. Treatment of the solution of 4 with hydrazine hydrate resulted in dihydrazine tetranitroethide (5), a yellow solid precipitated, that was confirmed by single crystal X-ray diffraction. Single crystal 5 is crystallized by using the method of the evaporation of water.Tetranitroethane 4 is also an unstable compound that is soluble in dichloromethane and difficult to isolate. It decomposed and released a brown gas as the solvent removed. Thus, we analysed the UV spectrum of the solution of 4, instead of the pure compound 4. Compared with the experimental and calculated UV spectrum of solution 4 (Fig. 1), we find that the maximum absorption wavelengths of the two curves match well, 240 nm (tested) and 239.5 nm (calculated). It can be inferred that compound 4 would be tetranitroethane.Open in a separate windowFig. 1The UV spectrum curve of tetranitroethane 4.Dihydrazine tetranitroethide 5 in the monoclinic space group C2/c with a good density of 1.81 g cm⁻³ (298 K). The gem-dinitro group is nearly planar, with the torsion angle of O5–N3–C2–N4, 179.52(17)°. However, the torsion angle of N3–C2–C2′–N4′ and N4–C2–C2′–N3′ are 77.57 (255)° and 77.57 (255)°, respectively, which shows the twist of adjacent dinitromethyl groups is caused by the steric effect. The strong hydrogen-bond interactions are presented between ammonium and nitro groups (Fig. 2b). The details of donor–acceptor distance are given in the ESI.^† Many studies have shown that the hydrogen-bonds enhance the stability of energetic molecules. At the molecular level, intermolecular hydrogen bonds between hydrazine cation and nitro groups play an important role in stabilizing energetic compounds. This kind of hydrogen-bonding interaction and cation–anion contact in the energetic salt is suggested as part of the explanation for closer packing, which causes the good density. As seen in Fig. 2c, the tetranitroethide anions are found in cross-stacking arrangements and layer by layer. While the hydrazine cation in the crystal, as the adhesive between the bricks, help to create a better stacking arrangement.Open in a separate windowFig. 2(a) Molecular structure of 5; (b) hydrogen-bonding interactions of 5 between hydrazine cation and tetranitroethide anion; (c) packing diagram of 5 (unit cell viewed along the b axis).The physical properties and calculated detonation performances are summarized in 20 Compound 5 has a detonation velocity of 9508 m s⁻¹ and a detonation pressure of P: 37.9 GPa, which is better than RDX (8748 m s⁻¹; 34.9 GPa) and similar to HMX (9320 m s⁻¹; 39.5 GPa). The sensitivities to impact and friction are 1.25 J and 34 N, respectively.Physical properties of dihydrazine tetranitroethide 5 and comparison with ADN, RDX and HMX

Two-dimensional aluminum phosphide semiconductor with tunable direct band gap for nanoelectric applications

More and more attractive applications of two-dimensional (2D) materials in nanoelectronic devices are being achieved successfully, which promotes the rapid and extensive development of new 2D materials. In this work, the structural and electronic properties of the V structure aluminum phosphide (V-AlP) monolayer are examined by density functional calculations, and its electronic properties under strain and an electric field are also explored in detail. The computation results indicate that it has good stability. Interestingly, it possesses a wide direct gap (2.6 eV), and its band gap exhibits a rich behavior depending on the strain, E-field and layer stacking. Under biaxial strain, its band gap can be tuned from 1 eV to 2.6 eV. And a direct-indirect band gap transition is found when external tension is applied. The V-AlP monolayer also exhibits anisotropic behavior as its band structure variation trends under strains along different directions are obviously different. When the external E-field is changed from 0.5 V Å⁻¹ to 1 V Å⁻¹, the band gap of the V-AlP monolayer can be tuned linearly from 0 eV to 2.6 eV. Layer stacking narrows the band gap of the 2D V-AlP material. It is concluded that strain, E-field and layer stacking can all be used effectively to modify the electronic property of the V-AlP monolayer. Thus, these results indicate that the V-AlP monolayer will have promising applications in nanoelectric devices.

More and more attractive applications of two-dimensional (2D) materials in nanoelectronic devices are being achieved successfully, which promotes the rapid and extensive development of new 2D materials.     

急性白血病不同时期PICC置管所致并发症比较

目的 了解急性白血病患者不同时期PICC置管并发症的发生情况,以针对性避免或减少导管并发症,控制非计划性拔管的发生.方法 223例PICC置管的急性白血病患者分别于非缓解期置管122例(非缓解组)和缓解期置管101例(缓解组),比较两组置管30 d内导管并发症发生和非计划性拔管情况.结果 两组机械性静脉炎、可疑导管相关感染和非计划性拔管发生率比较,差异有统计学意义(均P＜0.01).结论 急性白血病非缓解期置管患者导管相关并发症明显高于缓解期置管患者,导致非计划性拔管率高.对急性白血病非缓解期置管患者须加强机械性静脉炎、导管相关感染和非计划性拔管的预防护理干预.     

中文版服药信念特异性问卷用于换瓣术后抗凝患者的信效度检验

目的检验服药信念特异性问卷(BMQ-Specific)在我国机械瓣膜置换术后华法林抗凝患者中应用的信度和效度。方法翻译并修订BMQ-Specific,用中文版BMQ-Specific问卷对164例机械瓣膜置换术后出院患者进行电话调查,对测定结果进行信、效度分析。结果中文版BMQ-Specific问卷内容效度为0.90;问卷必要性和顾虑2个维度与总分的相关系数分别为0.75和0.82(均P<0.01);因子分析萃取了2个公因子,方差累积贡献率为61.47%。问卷的Cronbach′sα系数为0.77,重测信度为0.83,评定者间的一致性信度为0.93。结论中文版BMQ-Specific问卷信、效度较好,可用于机械瓣膜置换术后患者华法林服药信念的评估。     

外科护士疾病手术治疗相关知识培训需求调查分析

目的了解外科护士疾病手术治疗相关知识培训现状与需求,为制定针对性培训机制提供参考。方法采用自行设计的外科护士疾病手术治疗相关知识培训现状与需求调查问卷对120名外科护士进行调查。结果现有的培训内容以手术治疗相关并发症为主(74.07%)、方式以专题讲座为主(100%)、时机为科内培训为主(100%);培训需求除保留以往9项中的8项外,分别新增了手术流程,现场手术观摩、观看录像、模拟教学及跟台手术5项,需求率达64.61%～100%;学历越高培训需求越强烈。结论现有培训不能满足外科护士对相关知识的需求,其对培训内容的扩展、方式的多样化及多种时机的提供有强烈需求。医院管理者应高度重视,建立培训机制满足其需求,以提高外科护理人员专业素质和外科护理水平。