Highly mass activity electrocatalysts with ultralow Pt loading on carbon black for hydrogen evolution reaction

Pt-based nanocatalysts offer excellent prospects for various industries.However,the low loading of Pt with excellent performance for efficient and stable nanocatalysts still presents a considerable challenge.In this study,nanocatalysts with ultralow Pt content,excellent performance,and carbon black as support were prepared through in-situ synthesis.These~2-nm particles uniformly and stably dispersed on carbon black because of the strong s-p-d orbital hybridizations between carbon black and Pt,which suppressed the agglomeration of Pt ions.This unique structure is beneficial for the hydrogen evolution reaction.The catalysts exhibited remarkable catalytic activity for hydrogen evolution reaction,exhibiting a potential of 100 mV at 100 mA·cm^(-2),which is comparable to those of commercial Pt/C catalysts.Mass activity(1.61 A/mg)was four times that of a commercial Pt/C catalyst(0.37 A/mg).The ultralow Pt loading(6.84wt%)paves the way for the development of next-generation electrocatalysts.

Multi-site occupancies and dependent photoluminescence of Ca_(9)Mg_(1.5)(PO_(4))_(7):Eu^(2+) phosphors:A bifunctional platform for optical thermometer and plant growth lighting

Herein,we demonstrate an optical thermometer based on single Eu^(2+)doped Ca_(9)Mg_(1.5)(PO_4)_7 phosphors,which were prepared by traditional solid-state reaction technique under a reduction atmosphere.Considerations on the bond length obtained by the crystal structure refinement and the dependent photoluminescence performances allow to assign the two distinct emission bands to Eu^(2+)ions occupied Cal-Ca3 and Mg2 sites.Moreover,the blue and red emitting bands perfectly match with the photosynthetic action spectrum,which can enhance the indoor plant photosynthesis.The optimal doping content of Eu^(2+)ions in this Ca_(9)Mg_(1.5)(PO_(4))_(7)system is 3 mol%.The corresponding concentration quenching effect is verified as dipole-dipole interaction with the critical distance of 3.315 nm.Furthermore,by exploiting the fluorescence intensity technique,the optical thermal resistance properties of Ca_(9)Mg_(1.5)(PO_4)_7:Eu^(2+)are identified based on the temperature dependent emission spectra in a range of 303-523 K.In detail,the maximum absolute and relative sensitivity S_(a)and S_(r)of Ca_9Mg_(1.5)(PO_(4))_(7):Eu^(2+)thermometer are as high as 0.637%/K and 0.3155 K^(-1),respectively.Consequently,the Eu^(2+)doped Ca_(9)Mg_(1.5)(PO_(4))_(7)phosphors establish a bifunctional platfo rm for both optical the rmometer and plant growth lighting via multi-site occupancies.

A high-tortuosity holey graphene in-situ derived from cytomembrane/cytoderm boosts ultrastable potassium storage

The sluggish K^(+)kinetics and structural instability of the generally-used graphite and other carbon-based materials hinder the development of potassium-ion batteries(PIBs)for high-rate capability and long-term cycling.Herein,inspired by the unique flake structure and chemical composition of cytomembrane and cytoderm,we design high-tortuosity holey graphene as a highly efficient anode for PIBs.The flake cytomembrane and cytoderm shrink into wrinkled morphology during drying and sintering and then convert into high-tortuosity graphene after oxidative exfoliating and thermal reducing process.Mean-while,the proteins,sugars,and glycolipids embedded in cytomembrane and cytoderm can in-situ form nanoholes with highly abundant oxygenic groups and heteroatoms around,which can be easily removed and finally the high-tortuosity holey graphene is obtained after a thermal reducing process.The stress distribution after K^(+)intercalation confirms the optimized release of strain caused by the volume change through the finite element method.Benefiting from the unique nanoholes shortening the ion-diffusion length,the synergy of wrinkled and holey structure stabilizing volume fluctuation,and the enhanced electronic conductivity and specific surface area,the high-tortuosity holey graphene demonstrates high reversible capacities of 410 mAh g^(-1)at 25 mA g^(-1)after 150 cycles and retains 91.5%at 2 A g^(-1)after 2500 cycles.

Single-cell profiling reveals Müller glia coordinate retinal intercellular communication during light/dark adaptation via thyroid hormone signaling

Light adaptation enables the vertebrate visual system to operate over a wide range of ambient illumination.Regulation of phototransduction in photoreceptors is considered a major mechanism underlying light adaptation.However,various types of neurons and glial cells exist in the retina,and whether and how all retinal cells interact to adapt to light/dark conditions at the cellular and molecular levels requires systematic investigation.Therefore,we utilized single-cell RNA sequencing to dissect retinal cell-type-specific transcriptomes during light/dark adaptation in mice.The results demonstrated that,in addition to photoreceptors,other retinal cell types also showed dynamic molecular changes and specifically enriched signaling pathways under light/dark adaptation.Importantly,Müller glial cells(MGs)were identified as hub cells for intercellular interactions,displaying complex cell‒cell communication with other retinal cells.Furthermore,light increased the transcription of the deiodinase Dio2 in MGs,which converted thyroxine(T4)to active triiodothyronine(T3).Subsequently,light increased T3 levels and regulated mitochondrial respiration in retinal cells in response to light conditions.As cones specifically express the thyroid hormone receptor Thrb,they responded to the increase in T3 by adjusting light responsiveness.Loss of the expression of Dio2 specifically in MGs decreased the light responsive ability of cones.These results suggest that retinal cells display global transcriptional changes under light/dark adaptation and that MGs coordinate intercellular communication during light/dark adaptation via thyroid hormone signaling.

Large-scale blow spinning of heat-resistant nanofibrous air filters

Particulate matter(PM)pollution has become a serious problem worldwide and various kinds of nanofibrous filters aiming to solve the problem have been developed.It is urgent to remove PM from high-temperature pollution sources,such as industrial emissions,coal furnaces,and automobile exhaust gases.However,filtration at pollution sources remains challenging because most existing air filters are not resistant to high temperature.Herein,heat-resistant polyimide(PI)nanofibrous air filters are fabricated via a simple and scalable solution blow-spinning method.These air filters show excellent thermal stability at high temperature up to 420℃.They exhibit a filtration efficiency as high as 99.73%at ambient temperature and over 97%at 300℃.In addition,a field test shows that the filters remove>97%of PM from the car exhaust fumes.Hence,the blow-spun PI nanofibrous membranes combined with the facile preparation strategy have great potential in high temperature air filtration fields and other similar applications such as water purification and protein separation.

Potential benefits of precise corticosteroids therapy for severe 2019-nCoV pneumonia

Dear Editor,Since last December,the outbreak of 2019-nCoV in Wuhan has caused ever-increasing attention and public panic all over the world.Up to February 9,2020,40,171 patients had been diagnosed with 2019-nCoV infection,including 6484(16.14%)severe cases and 908 deaths(2.27%).Compared to SARS and MERS,2019-nCoV appears to be much more contagious but less lethal,as most patients have mild symptoms and good prognosis1,2.However,according to the Chinese government’s daily report,13.2–21.3%of patients with 2019-nCoV infection developed into severe or fatal illness(Fig.S1a),which is characterized by the rapid development to acute respiratory distress syndrome(ARDS)or septic shock.Along with an increasing number of confirmed cases,the cumulative total of severe patients with 2019-nCoV is growing(Fig.S1b).Treatment of these critically ill patients is becoming one of the major challenges we are facing.

Porous Si/C composite as anode materials for high-performance rechargeable lithium-ion battery

A novel porous silicon was synthesized through a magnesiothermic reduction method of molecular sieve for the first time, Si/C composite was synthesized by using pitch as carbon source. The porous Si/C composite shows a high initial specific capacity of 2018.5 mAh/g with current density of 0.1 A/g. When the current density increases to 2 A/g, it still exhibits high average specific capacity of 640.3 mAh/g. The porous structure can remit the Si particle pulverization during the lithiation]delithiation process. This article can provide a reference for the research of the porous Si anode for the high performance rechargeable lithium-ion battery.

Preparation,structure,luminescence properties of europium doped zinc spinel structure green-emitting phosphor ZnAl_2O_4:Eu^(2+)

The Zn1-xAl2 O4：xEu2＋ phosphor powders were synthesized by the solid-state reaction method.The synthesis temperature for ZnAl2 O4 was optimized,whereas the phase structure,TEM images,photoluminescence（PL） properties,the concentration quenching mechanism,the fluorescence decay curves,as well as the CIE chromaticity coordinates of the samples were investigated in details.Under the excitation at 379 nm,the phosphor exhibits an asymmetric broad-band green emission with a peak at 532 nm,which is ascribed to the 5 d-4 f transition of Eu2＋.When the doping concentration of Eu2＋ ions is 0.01,the luminescence intensity of the sample reaches the maximum value.It is further proved that the exchange interaction results in the concentration quenching of Eu2＋ in the Zn1-xAl2 O4：xEu2＋ phosphor powders.The thermal quenching property of ZnAl2 O4：Eu2＋phosphor was investigated and the quantum efficiency（QE） values of the selected Zn0.99Al2 O4：0.01 Eu2＋ phosphor was measured and determined as 54.85%.The lifetime of the optimized sample Zn0.99Al2 O4：0.01 Eu2＋ is 3.0852 μs and the CIE coordinate of the sample was calculated as（0.3323,0.5538） with high-color-purity green emission.All properties indicate that the green-emitting ZnAl2 O4：Eu2＋ phosphor powder has potential application in white LEDs.

Color tunable Ba0.79Al10.9O17.14∶xEu phosphor prepared in air via valence state control

A series of luminescent Ba0.79Al10.9O17.14∶xEu (x=0.005-0.12) phosphors were prepared by high-temperature solid-state reaction in air atmosphere.The coexistence of Eu2+ and Eu3+ was observed and verified by photoluminescence (PL) and photoluminescence excitation (PLE) spectra,X-ray photoelectron spectra (XPS),and diffuse reflection spectra.The band emission peaking at 430 nm was assigned to 4F65D-4F7 transition of Eu2+,and another four emissions peaking at 589,619,655,and 704 nm were attributed to 4F-4F transitions of 5D0-7FJ(J=1,2,3,4) of Eu3+.The related mechanism of self-reduction was discussed in detail.The color of the Ba0.79Al10.9O17.14∶xEu phosphors could be shifted from blue (0.23,0.10) to red (0.42,0.27) by doping Li+ ions,and the temperature dependence properties were investigated.