Effect of metal nanoparticle doping concentration on surface morphology and field emission properties of nano-diamond films

Nano-diamond particles are co-deposited on Ti substrates with metal(Ti/Ni) nanoparticles(NPs) by the electrophoretic deposition(EPD) method combined with a furnace annealing at 800℃ under N_(2) atmosphere. Modifications of structural and electron field emission(EFE) properties of the metal-doped films are investigated with different metal NPs concentrations. Our results show that the surface characteristics and EFE performances of the samples are first enhanced and then reduced with metal NPs concentration increasing. Both the Ti-doped and Ni-doped nano-diamond composite films exhibit optimal EFE and microstructural performances when the doping quantity is 5 mg. Remarkably enhanced EFE properties with a low turn-on field of 1.38 V/μm and a high current density of 1.32 mA/cm^(2) at an applied field of 2.94 V/μm are achieved for Ni-doped nano-diamond films, and are superior to those for Ti-doped ones. The enhancement of the EFE properties for the Ti-doped films results from the formation of the TiC-network after annealing. However, the doping of electron-rich Ni NPs and formation of high conductive graphitic phase are considered to be the factor, which results in marvelous EFE properties for these Ni-doped nano-diamond films.

Synthesis,Crystal Structure and Photoluminescence of a TADF Cuprous Complex

A cuprous mononuclear copper complex [Cu(adpypz)CH3CNPPh3]BF4·CH2Cl2(1, adpypz = 9,9-dimethyl-10-(6-(3-phenyl-1H-pyrazol-1-yl)pyridin-2-yl)-9,10-dihydroacridine) was synthesized and characterized by Elemental Analysis, NMR, UV-Vis and X-ray single-crystal structure analysis. It crystallizes in triclinic, space group P1 with a = 11.3388(4), b = 13.4569(4), c = 16.2561(6) ?, α = 97.154(3), β = 92.187(3), γ = 114.119(4)°, V = 2235.38(13) ?3, Z = 2, Mr = 967.12, Dc = 1.437 g/cm^3, F(000) = 996, μ = 2.62 mm^(–1), GOOF = 1.031, the final R = 0.0417, and w R = 0.1024 for 8043 observed reflections with I > 2σ(I). The Cu(I) atoms in the complex are four-coordinated and adopt a tetrahedral coordination geometry. In the solid state, the complex exhibits bluish-green photoluminescence with emission peaks λmax = 492 nm(1), lifetimes 235 μs and quantum yields(ф = 0.279) at room temperature. The studies of varied temperature emission spectra and decay behaviours of the complex indicate that the complex displays thermally activated delayed fluorescence(TADF) at room temperature. The results of the experimental and DFT calculations suggest that the emission in the solid state originates from the ILCT excited states.

Synthesis,Crystal Structure and Photoluminescence of a Dinuclear Cuprous Complex with Thiocyanate Bridges

A cuprous dinuclear copper complex [PPh_2PAr_2Cu(μ-SCN)_2CuPPh_2PAr_2](1,PPh_2PAr_2 =(1-bis(2-methylphenyl)-phosphine-2-diphenylphosphino)benzene) was synthesized from the reaction of Cu SCN and PPh_2PAr_2 in CH_3CN at room temperature. The compound was characterized by Elemental Analysis,NMR,UV-Vis and X-ray single-crystal structure analysis. It crystallizes in triclinic,space group P1 with a = 10.225(2),b = 11.360(2),c = 13.420(3) ?,α = 95.81(3),β = 93.45(3),γ = 113.78(3)°,V = 1410.4(5) ?~3,Z = 1,Mr = 1192.21,Dc = 1.404 g/cm^3,F(000) = 616,μ = 3.029 mm^(–1),GOOF = 1.052,the final R = 0.0359,and w R = 0.0964 for 4878 observed reflections with I > 2σ(I). The Cu(I) atoms in the complex are four-coordinated and adopt a tetrahedral coordination geometry. The copper centers in the molecular structure are bridged by two thiocyanate anions and each Cu(I) is chelated further terminally by a PPh_2PAr_2 ligand. The [Cu(μ-SCN)_2Cu] cores have essential planar configurations. In the solid state,the complex exhibits blue photoluminescence with emission peaks λ_(max)= 478 nm(1),lifetimes 4.7 μs and quantum yields(ф = 0.43) at room temperature. The studies of varied temperature emission spectra and decay behaviours of the complex indicate that it displays thermally activated delayed fluorescence at room temperature. The results of the experimental and DFT calculations suggest that the emission in the solid state originates from the ^(1,3)MLCT excited states.

Acoustic emissions evaluation of the dynamic splitting tensile properties of steel fiber reinforced concrete under freeze-thaw cycling

This study empirically investigated the influence of freeze-thaw cycling on the dynamic splitting tensile properties of steel fiber reinforced concrete(SFRC).Brazilian disc splitting tests were conducted using four loading rates(0.002,0.02,0.2,and 2 mm/s)on specimens with four steel fiber contents(0%,0.6%,1.2%,and 1.8%)subjected to 0 and 50 freeze-thaw cycles.The dynamic splitting tensile damage characteristics were evaluated using acoustic emission(AE)parameter analysis and Fourier transform spectral analysis.The results quantified using the freeze-thaw damage factor defined in this paper indicate that the degree of damage to SFRC caused by freeze-thaw cycling was aggravated with increasing loading rate but mitigated by increasing fiber content.The percentage of low-frequency AE signals produced by the SFRC specimens during loading decreased with increasing loading rate,whereas that of high-frequency AE signals increased.Freeze-thaw action had little effect on the crack types observed during the early and middle stages of the loading process;however,the primary crack type observed during the later stage of loading changed from shear to tensile after the SFRC specimens were subjected to freeze-thaw cycling.Notably,the results of this study indicate that the freeze-thaw damage to SFRC reduces AE signal activity at low frequencies.

Carbon-Nanotube-Based Normally-on-Driving Under-Gate Field Emission Display Panel

A carbon-nanotube-based normally-on-driving under-gate field emission display(FED)panel and its operation principle are presented.In this panel,field emission electrons are extracted directly from the cathode by the high anode voltage.The image is realized by modulating the voltage of under-gate,whose value is less than the cathode voltage,to stop the cathode producing field emission electrons.The electric field inside the emission region is calculated by the finite element method.The emission property of the cathode is also studied by numerical calculation method.The results indicate that a uniform and large emission area can be obtained in this new under-gate FED panel.This study provides powerful theoretic support for the feasibility of this new kind of under-gate FED panel.

Synthesis, Structure and Photoluminescence of a Cu2I2 Complex with an Acridine-modified Diimine Ligand

A dinuclear cuprous complex[(mapypz)Cu(μ-I)2 Cu(mapypz)](1,mapypz=9,9-dimethyl-10-(6-(3-phenyl-1H-pyrazol-1-yl)-pyridin-3-yl)-9,10-dihydroacridine)was synthesized from the reaction of equivalent CuⅠand mapypz at room temperature.The compound crystallizes in monoclinic space group P21/c with a=13.8300(4),b=9.5365(2),c=19.0833(5)?,β=103.017(3)o,V=2452.23(11)?3,Z=2,Mr=1237.92,Dc=1.677 g/cm3,F(000)=1232,μ=11.334 mm^–1,GOOF=1.001,the final R=0.0330,and wR=0.0741 for 4627 observed reflections withⅠ>2σ(Ⅰ).The Cu(I)atoms in the complex are four-coordinated with a distorted tetrahedral coordination geometry.The copper centers in the molecular structure are bridged by two iodide anions and each Cu(I)is chelated further terminally by a diimine ligand.The[Cu(μ-I)2 Cu]core is planar.Ⅰn the solid state,the complex exhibits orange photoluminescence with emission peakλmax=568 nm,lifetimeτ=16μs and quantum yieldф=0.22 at room temperature.The studies of varied temperature emission spectra and decay behaviours of the complex indicate that it displays thermally activated delayed fluorescence at room temperature.The results of experimental and DFT calculations suggest that the emission in the solid state originates from the 1,3 MLCT excited states.