Modified halloysite nanotube filled polyimide composites for film capacitors: high dielectric constant,low dielectric loss and excellent heat resistance

In this work, halloysite nanotubes (HNTs) were chosen as the fillers and high performance polyimide (PI) as the matrix to form a series of dielectric composite materials with high dielectric constant, low dielectric loss and excellent heat resistance. Firstly, KH550 was used to modify the surface of HNTs to make sure of a good dispersion of HNTs into the polymer. The results showed that the addition of KH550 modified HNTs (K-HNTs) can improve the dielectric constant of the composite films while maintaining their excellent dielectric loss properties. To further increase the dielectric constant of the HNTs/PI composites, conductive polyaniline (PANI) was used to coat the surface of HNTs to obtain PANI modified HNTs (PANI-HNTs). Compared with the K-HNTs filled systems, the dielectric constant of the PANI-HNTs/PI nanocomposite films is greatly enhanced. The highest dielectric constant of the PANI-HNTs/PI films can achieve 17.3 (100 Hz) with a low dielectric loss of 0.2 (100 Hz). More importantly, the as-prepared composite films have high breakdown strengths (>110.4 kV mm⁻¹) and low coefficients of thermal expansion, as low as 7 ppm per °C, and a maximum discharge energy density of 0.93 J cm⁻³. Also, such properties are maintained stably up to 300 °C, which is critical for manufacturing heat-resisting film capacitors.

Halloysite nanotubes (HNTs) were chosen as the fillers and polyimide (PI) as the matrix to form a series of composites with excellent dielectric properties and thermostabilities.     

Ternary composites of Ni–polyaniline–graphene as counter electrodes for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs), different in principle from the conventional solar cells based on p–n junctions, are competitively cost-effective. For development of this kind of emerging solar cell, it is very significant to reduce their cost and improve their energy conversion efficiency to the maximum extent. In this article, ternary composites (Ni–PANI–G composites) consisting of nickel nanoparticles, polyaniline (PANI), and graphene (G) were prepared for the first time and used as counter electrodes to replace the noble metal Pt in DSSCs. In the case of PANI, the introduction of Ni nanoparticles can improve the electrocatalytic ability for the reduction of triiodide ions in the counter electrode, while in the meantime, the addition of graphene in the Ni–PANI–G composites can increase the electrical conductivity of the counter electrode. The optimized DSSCs fabricated by using the Ni–PANI–G composites as the counter electrode exhibit an overall power conversion efficiency of 5.80% compared to 5.30% for reference platinum (Pt) counter-electrodes. Electrochemical impedance spectra (EIS) show that the charge-transfer resistance at the interface between electrolyte and counter-electrode in the case of the ternary composite is obviously decreased. These results are significant to develop low-cost counter electrode materials for DSSCs.

In this article, ternary composites (Ni–PANI–G composites) consisting of nickel nanoparticles, polyaniline (PANI), and graphene (G) were prepared for the first time and used as counter electrodes to replace the noble metal Pt in DSSCs.     

Using biomimetically mineralized collagen membranes with different surface stiffness to guide regeneration of bone defects

Because guided bone regeneration (GBR) process is pronouncedly affected by the micro‐environment in the defect, the surface stiffness of collagen membranes as a constituent part of the micro‐environment was investigated in this study. The objective of this study was to manufacture biomimetically mineralized collagen membranes with controllable surface stiffness based on biomimetic strategy and to investigate the influences of surface stiffness on GBR process. The characterization and biocompatibility of membranes were examined in vitro. The mechanical properties of membranes were evaluated on macro and micro levels using tensile test and atomic force microscope, respectively. The critical‐size cranial defect model and ectopic osteogenesis were chosen to employ their performances in vivo. The results indicated that the biomimetically mineralized collagen membranes with controllable surface stiffness were manufactured based on the biomimetic theory. The in vitro experiments showed that the mineralized collagen membrane with satisfactory surface stiffness can better promote the adhesion, proliferation, and osteogenic differentiation of mesenchymal stem cells. The membranes can perform excellently in both osteoinduction and osteoconduction, which results in effective manifestations in aspects of ectopic osteogenesis and GBR in vivo. Therefore, this biomimetically mineralized collagen membrane is a promising candidate for GBR treatment in future.     

Y‐27632 simplifies the isolation procedure of human primary epidermal cells by selectively blocking focal adhesion of dermal cells

Primary skin epidermal cells isolation and in vitro expansion culture have been widely used for laboratory research and clinical applications. The conventional methods involving sequential enzymatic digestion of adult tissues have given low cell recovery rate and reduced cell viability. We report here an advanced method for human primary epidermal progenitor cells isolation from skin tissues including the Rho kinase inhibitor Y‐27632. Compared with traditional protocols, the current protocol is simple, easy, and faster; moreover, it gives a greater yield of integrin‐expressing epithelial stem cells. In addition, our new methodology does not require a separation of epidermis from dermis because the medium selectively blocks focal adhesion and growth of dermal cells. Importantly, the cells isolated from this method can maintain their regeneration potential and quickly reconstitute a mature human skin in vivo after grafting onto nude mice. In brief, we describe here a simple (one step) and serum‐free method for isolating primary epidermal stem cells from adult tissues. The isolated cells may be widely used for both laboratory studies and clinical application, especially in the field of tissue engineering and regeneration.     

N-doped carbon dots from phenol derivatives for excellent colour rendering WLEDs

To achieve competitive fluorescence carbon dots (CDs), studies on regulating fluorescence of CDs under controlled, comparable conditions are in great demand. Herein, by changing the functional groups and nitrogenous existence forms in the precursors, three efficient yellow-green emissive N-doped CDs which have the same fluorescence peak wavelength but different photoluminescence quantum yields were realized through a facile hydrothermal method. The as-prepared CDs exhibit not only excited-independent emissions but also similar surface states. The best-performing CDs among the three products exhibits photoluminescence quantum yields of up to 24.4% in water and 53.3% in ethanol, abundant surface functional groups and its high N-doping degree would be the reason for its excellent performances. By washing and reduction processes, the emission evolution of the CDs was studied linking the changes of surface states. The fluorescence can certainly be attributed to the surface of the carbon dots, and the surface states control the photoluminescence features. Serving as a yellow-green colour conversion layer, the best CDs in the three products was used to fabricate a white light-emitting diode. The white light-emitting diode shows an excellent colour rendering index up to 93.3, suggesting broad application prospects of the CDs in lighting and display fields.

Yellow-green photoluminescence carbon dots with different quantum yields were realized and used to fabricate white LEDs.     

透明帽辅助内镜下取出食管异物疗效的Meta分析

目的评价透明帽辅助内镜下取出食管异物的临床价值。方法通过计算机检索Pubmed、CNKI数据库、Web of Knowledge、Cochrane图书馆对照试验注册库和万方数据库从建库至2017年的有关透明帽辅助内镜取出食管异物的相关文献,采用Cochrane协作网提供的RevMan 5.0版软件进行统计处理,对纳入资料的异质性进行分析,计算OR值和95%可信区间。结果按照入选标准,纳入了9项临床试验,共1 103例患者。Meta分析结果显示:透明帽辅助内镜异物取出术成功率更高(OR=8.58,95%CI:4.49～16.38,P 0.05)、视野更清晰(OR=7.35,95%CI:5.20～10.40,P 0.05)、并发症发生率低(OR=0.34,95%CI:0.25～0.46,P 0.05)、患者耐受性好(OR=2.78,95%CI:2.08～3.72,P 0.05)。结论透明帽辅助内镜下食管异物取出术是一种安全有效的内镜下取异物的方法,其患者耐受性好,可提供更好的内镜下操作视野,有利于提高手术成功率,值得进一步推广应用。     

超声在新生儿肺炎诊断中的应用

新生儿肺炎作为新生儿常见疾病,严重危害新生儿健康,是导致其死亡的重要原因。目前临床诊断新生儿肺炎的主要方法为X线摄片。随着超声技术的发展,其在肺部疾病诊断中的应用也越来越多。本文就超声在新生儿肺炎的辅助诊断及治疗随访中的应用现状与进展进行综述。     

Acetone vapour-assisted growth of 2D single-crystalline organic lead halide perovskite microplates and their temperature-enhanced photoluminescence

We adopt an acetone vapour-assisted method to grow high quality single-crystalline microplates of two-dimensional (2D) perovskite, 2-phenylethylammonium lead bromide [(C₆H₅C₂H₄NH₃)₂PbBr₄]. The microplates, converted from the spin-coated films, are well-defined rectangles. Temperature dependent photoluminescence (PL) spectroscopy shows that the band gap PL is enhanced markedly with increasing temperature up to 218 K, accompanied by the quenching of the PL related to the trap states, which perhaps results from the exciton–phonon couplings. The optical phonon energy around 50 meV and the exciton binding energy around 120 meV are derived by fitting the band gap PL linewidths and intensities at different temperatures, respectively.

We report an acetone vapour-assisted method to grow single-crystalline 2D perovskite microplates and find their temperature-enhanced photoluminescence.     

Layer-by-layer assembled polyaniline/carbon nanomaterial-coated cellulosic aerogel electrodes for high-capacitance supercapacitor applications

Traditional layer-by-layer (LbL) assembled electrodes are mostly multilayer composites formed on two-dimensional membrane materials. In this case, the electroactive material cannot enter the interior of the substrate. With porous aerogels as the substrate, the LbL assembly of the electroactive material into the three-dimensional aerogel skeleton can be realised, greatly improving the utilisation and the electrochemical performance of the electroactive material. To create a promising aerogel electrode for high-performance energy storage devices, we herein report an aerogel based on wood pulp fibre (WPF) and cellulose nanocrystals (CNC), for use as a porous substrate for LbL assembly of nanostructural polyaniline (PANI) and graphene oxide (GO) or carboxylic multi-walled carbon nanotubes (CMCNT). Owing to the uniformly distributed multilayer nanoarchitecture, interpenetrating channels, and hydrophilic character of the cellulosic aerogel substrate, the produced electrodes of (PANI/CMCNT)₁₀ and (PANI/CMCNT)₁₀ both display high specific capacitances, favourable capacitance retention, good cycling stabilities, and structural flexibility. In the three-electrode test, their gravimetric specific capacitances are as high as 716.62 and 636.63 F g⁻¹, respectively. In addition, the assembled symmetric supercapacitors show good areal specific capacitances (1.95 and 1.49 F cm⁻²) in addition to high areal specific energies (168.64 and 113.57 mW h cm⁻², respectively). These results demonstrate that the integration of the LbL-assembled electroactive materials and porous cellulosic aerogel substrate can be a promising strategy to design high-efficiency green energy storage devices.

Cellulosic aerogel was used as a porous lightweight substrate to layer-by-layer assembly polyaniline and carbon nanomaterials for high capacitance supercapacitor applications.