Polyoxovanadate-based MOFs Microsphere Constructed from 3-D Discrete Nano-sheets as Supercapacitor

A novel polyoxovanadate-based MOFs microsphere,[Ni(phen)V2O7]·H2O(phen=1,10-phenanthroline),constructed from 3-D discrete nano-sheets has been prepared and characterized by XRD,FT-IR,SEM and TEM.Electrochemical properties as supercapacitor of the as-prepared sample,such as CV,EIS,GCD and the cycle life test have also been studied.The as-prepared MOF(V,Ni)showed a high specific capacitance of 178.09 F×g^(-1) at 1 A×g^(-1) as well as good cycling stability and coulombic efficiency.This work proved that the novel MOFs based on polyoxovanadate hybrid material may serve as a promising electrode material for high-performance supercapacitor.

Structure Engineered g-C3N4 Nano-Sheets by Switching the Pyrolysis Gas Atmosphere for Enhanced Photo-Catalytic Degradation

We developed a new one step approach to synthesize g-C3N4 nano-sheets by direct thermal pyrolysis process of urea in NH3 atmosphere. For the first time, the influence of the preparation gas atmosphere on the composition, crystalline and polymerization degree, and the activity of the g-C3N4 synthesized from thermal condensation of urea was investigated. Impressively, the g-C3N4 nano-sheets obtained under NH3 gas atmosphere exhibited much superi- or photo-catalytic activities to the prepared g-C3N4 in air or N2, and the rate of the g-C3N4-NH3 was about 5 times higher than that on g-C3N4-N2 sample. The detailed characterization analysis revealed that NH3 thermal pyrolysis atmosphere contributed to the polymerization degree and the formation of the layer with a more regular structure due to the efficiently extending of the conjugated π-conjugative system, which was favorable to the transfer of the photo-induced charge carriers. Furthermore, we studied in depth the structure-performance relationship in the sys- tem, and it was found that the synergistic effect of the larger surface area, the adjusted band energy structure and the well crystallization may be conductive to the higher separation of the electron-hole pair, thus leading to the won- derful performance for the g-C3N4-NH3. Notably, the method has the merits of low cost, scalable production and environmental friendliness.

Tribological behaviour of Ti_(3)C_(2)T_(x) nano-sheets: Substrate-dependent tribo-chemical reactions

MXenes,a newly emerging class of layered two dimensional(2D)materials,are promising solid lubricants due to their 2D structure consisting of weakly-bonded layers with a low shear strength and ability to form beneficial tribo-layers.This work aims at evaluating for the first time MXenes lubrication performance and tribofilm formation ability on different metallic substrates(mirror-lapped Fe and Cu discs).After depositing MXenes via ethanol(1 wt%)on the substrates,pronounced differences in the resulting substrate-dependent frictional evolution are observed.While MXenes are capable to reduce friction for both substrates after the full evaporation of ethanol,MXenes lubricating effect on Cu is long-lasting,with a 35-fold increased lifetime compared to Fe.Raman spectra acquired in the wear-tracks of the substrates and counter-bodies reveal notable differences in the friction-induced chemical changes depending on the substrate material.In case of Fe,the progressive failure of MXenes lubrication generates different Fe oxides on both the substrate and the ball,resulting in continuously increasing friction and a poor lubrication effect.For Cu,sliding induces the formation of a Ti_(3)C_(2)-based tribofilm on both rubbing surfaces,enabling a long-lasting lubricating effect.This work boosts further experimental and theoretical work on MXenes involved tribo-chemical processes.

A nano-sheet graphene-based enhanced thermal radiation composite for passive heat dissipation from vehicle batteries

In response to thermal runaway(TR)of electric vehicles,recent attention has been focused on mitigation strategies such as efficient heat dredging in battery thermal management.Thermal management with particular focus on battery cooling has been becoming increasingly significant.TR usually happened when an electric vehicle is unpowered and charged.In this state,traditional active battery cooling schemes are disabled,which can easily lead to dangerous incidents due to loss of cooling ability,and advanced passive cooling strategies are therefore gaining importance.Herein,we developed an enhanced thermal radiation material,consisting of~1μm thick multilayered nano-sheet graphene film coated upon the heat dissipation surface,thereby enhancing thermal radiation in the nanoscale.The surface was characterized on the nanoscale,and tested in a battery-cooling scenario.We found that the graphene-based coating's spectral emissivity is between 91% and 95% in the mid-infrared region,and thermal experiments consequently illustrated that graphene-based radiative cooling yielded up to15.1% temperature reduction when compared to the uncoated analogue.Using the novel graphene surface to augment a heat pipe,the temperature reduction can be further enlarged to 25.6%.The new material may contribute to transportation safety,global warming mitigation and carbon neutralization.

SnO_2 nano-sheet as an efficient catalyst for CO oxidation

Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR＋NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active （110） facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.

Enhanced field emission characteristics of thin-Au-coated nano-sheet carbon films

This paper reports that the nano-sheet carbon films （NSCFs） were fabricated on Si wafer chips with hydrogen- methane gas mixture by means of quartz-tube-type microwave plasma chemical vapour deposition （MWPCVD）. In order to further improve the field emission （FE） characteristics, a 5-nm Au film was prepared on the samples by using electron beam evaporation. The FE properties were obviously improved due to depositing Au thin film on NSCFs. The FE current density at a macroscopic electric field, E, of 9 V/μm was increased from 12.4 mA/cm2 to 27.2 mA/cm2 and the threshold field was decreased from 2.6 V/μm to 2.0 V/μm for Au-coated carbon films. A modified F-N model considering statistic effects of FE tip structures in the low E region and a space-chavge-limited-current effect in the high E region were applied successfully to explain the FE data of the Au-coated NSCF.

Field emission characteristics of nano-sheet carbon films deposited by quartz-tube microwave plasma chemical vapour deposition

Nano-sheet carbon films are prepared on Si wafers by means of quartz-tube microwave plasma chemical vapour deposition （MPCVD） in a gas mixture of hydrogen and methane. The structure of the fabricated films is investigated by using field emission scanning electron microscope （FESEM） and Raman spectroscopy. These nano^carbon films are possessed of good field emission （FE） characteristics with a low threshold field of 2.6 V/μm and a high current density of 12.6 mA/cm^2 at an electric field of 9 V/μm. As the FE currents tend to be saturated in a high E region, no simple Fowler-Nordheim （F-N） model is applicable. A modified F N model considering statistic effects of FE tip structures and a space-charge-limited-current （SCLC） effect is applied successfully to explaining the FE data observed at low and high electric fields, respectively.

Effect of graphene on mechanical properties of cement mortars

Functionalized graphene nano-sheets(FGN) of 0.01%-0.05%(mass fraction) were added to produce FGN-cement composites in the form of mortars. Flow properties, mechanical properties and microstructure of the cementitious material were then investigated. The results indicate that the addition of FGN decreases the fluidity slightly and improves mechanical properties of cement-based composites significantly. The highest strength is obtained with FGN content of 0.02% where the flexural strength and compressive strength at 28 days are 12.917 MPa and 52.42 MPa, respectively. Besides, scanning electron micrographs show that FGN can regulate formation of massive compact cross-linking structures and thermo gravimetric analysis indicates that FGN can accelerate the hydration reaction to increase the function of the composite effectively.

FeCoNiCrMo high entropy alloy nanosheets catalyzed magnesium hydride for solid-state hydrogen storage

The catalytic effect of FeCoNiCrMo high entropy alloy nanosheets on the hydrogen storage performance of magnesium hydride(MgH_(2))was investigated for the first time in this paper.Experimental results demonstrated that 9wt%FeCoNiCrMo doped MgH_(2)started to dehydrogenate at 200℃and discharged up to 5.89wt%hydrogen within 60 min at 325℃.The fully dehydrogenated composite could absorb3.23wt%hydrogen in 50 min at a temperature as low as 100℃.The calculated de/hydrogenation activation energy values decreased by44.21%/55.22%compared with MgH_(2),respectively.Moreover,the composite’s hydrogen capacity dropped only 0.28wt%after 20 cycles,demonstrating remarkable cycling stability.The microstructure analysis verified that the five elements,Fe,Co,Ni,Cr,and Mo,remained stable in the form of high entropy alloy during the cycling process,and synergistically serving as a catalytic union to boost the de/hydrogenation reactions of MgH_(2).Besides,the FeCoNiCrMo nanosheets had close contact with MgH_(2),providing numerous non-homogeneous activation sites and diffusion channels for the rapid transfer of hydrogen,thus obtaining a superior catalytic effect.

N‑Doped Graphene‑Decorated NiCo Alloy Coupled with Mesoporous NiCoMoO Nano‑sheet Heterojunction for Enhanced Water Electrolysis Activity at High Current Density

Developing highly effective and stable non-noble metalbased bifunctional catalyst working at high current density is an urgent issue for water electrolysis(WE).Herein,we prepare the N-doped graphene-decorated NiCo alloy coupled with mesoporous NiCoMoO nano-sheet grown on 3D nickel foam(NiCo@C-NiCoMoO/NF)for water splitting.NiCo@C-NiCoMoO/NF exhibits outstanding activity with low overpotentials for hydrogen and oxygen evolution reaction(HER:39/266 mV;OER:260/390 mV)at±10 and±1000 mA cm^(−2).More importantly,in 6.0 M KOH solution at 60℃ for WE,it only requires 1.90 V to reach 1000 mA cm−2 and shows excellent stability for 43 h,exhibiting the potential for actual application.The good performance can be assigned to N-doped graphene-decorated NiCo alloy and mesoporous NiCoMoO nano-sheet,which not only increase the intrinsic activity and expose abundant catalytic activity sites,but also enhance its chemical and mechanical stability.This work thus could provide a promising material for industrial hydrogen production.

Passively mode-locked erbium-doped fiber laser via a D-shape-fiber-based MoS_2 saturable absorber with a very low nonsaturable loss

We report on the generation of conventional and dissipative solitons in erbium-doped fiber lasers by the evanescent field interaction between the propagating light and a multilayer molybdenum disulfide（MoS_2） thin film. The MoS_2 film is fabricated by depositing the MoS_2 water–ethanol mixture on a D-shape-fiber（DF） repetitively. The measured nonsaturable loss, saturable optical intensity, and the modulation depth of this device are 13.3%, 110 MW/cm^2, and 3.4% respectively.Owing to the very low nonsaturable loss, the laser threshold of conventional soliton is as low as 4.8 mW. The further increase of net cavity dispersion to normal regime, stable dissipation soliton pulse trains with a spectral bandwidth of 11.7 nm and pulse duration of 116 ps are successfully generated. Our experiment demonstrates that the MoS_2-DF device can indeed be used as a high performance saturable absorber for further applications in ultrafast photonics.

Multifunctional oxygen-enriching nano-theranostics for cancer-specific magnetic resonance imaging and enhanced photodynamic/photothermal therapy

The combination of photodynamic therapy(PDT)and photothermal therapy(PTT)has attracted much interest in recent years,but non-specific distribution of photosensitizers and intrinsic tumor hypoxic microenvironment have continued to limit its therapeutic efficiency.We herein report a nano-theranostic system,denoted as Ce6-CuS/MSN@PDA@MnO2-FA NPs,which combines PDT,PTT,magnetic resonance(MR)imaging with hypoxia-relieving and tumor-targeting functionalities.Central to this design is the use of mussel-inspired polydopamine(PDA)coating to encapsulate the chlorin e6(Ce6)and copper sulfide nanoparticles(CuS NPs)loaded mesoporous silica nanoparticle(MSN)core.The PDA coating not only acts as pH sensitive gatekeeper to prevent the premature release of Ce6 under non-acidic tumor microenvironment(TME),but also facilitates post-functionalization so that hypoxia-relieving MnO2 nano-sheets and tumor-targeting ligand folic acid-PEG-thiol(FA-PEG-SH)can be decorated on the outer part of the drug system.In vitro and in vivo measurements clearly demonstrated that all these functionalities worked synergistically as expected.The system,having a low dark cytotoxicity,can be effectively internalized by 4T1 cells and decrease the cell viability to 2%upon 660 nm/808 nm laser irradiation.Tumors in 4T1 tumor-bearing mice can almost be completely destroyed in 2 weeks via combined PDT/PTT.Together with the TME-sensitive MR imaging performance demonstrated,Ce6-CuS/MSN@PDA@MnO2-FA NPs represent a multifunctional prototype which holds great potential to be developed into clinical theranostics.