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A general approach is introduced to calculate field emission properties of any kind of nanostructure based on the first-principles local density of states (LDOS) and effective potentials. The experimental field emission spectroscopy images are explained as LDOS at the structure-vacuum barrier, weighted by the probability of electron tunneling. The method excellently reproduces the experimental field emission patterns of pristine capped carbon nanotubes. We show that cesium adsorbates even with a low doping ratio of one dopant per nanotube increase the emission current around 2.5 times, due to a generated dipole field.  相似文献   
2.
Here, we report two novel water‐stable amine‐functionalized MOFs, namely IISERP‐MOF26 ([NH2(CH3)2][Cu2O(Ad)(BDC)]?(H2O)2(DMA), 1 ) and IISERP‐MOF27 ([NH2(CH3)2]1/2[Zn4O(Ad)3(BDC)2]?(H2O)2(DMF)1/2, 2 ), which show selective CO2 capture capabilities. They are made by combining inexpensive and readily available terephthalic acid and N‐rich adenine with Cu and Zn, respectively. They possess 1D channels decorated by the free amine group from the adenine and the polarizing oxygen atoms from the terephthalate units. Even more, there are dimethyl ammonium (DMA+) cations in the pore rendering an electrostatic environment within the channels. The activated Cu‐ and Zn‐MOFs physisorb about 2.7 and 2.2 mmol g?1 of CO2, respectively, with high CO2/N2 and moderate CO2/CH4 selectivity. The calculated heat of adsorption (HOA=21–23 kJ mol?1) for the CO2 in both MOFs suggest optimal physical interactions which corroborate well with their facile on‐off cycling of CO2. Notably, both MOFs retain their crystallinity and porosity even after soaking in water for 24 hours as well as upon exposure to steam over 24 hours. The exceptional thermal and chemical stability, favorable CO2 uptakes and selectivity and low HOA make these MOFs promising sorbents for selective CO2 capture applications. However, the MOF′s low heat of adsorption despite having a highly CO2‐loving groups lined walls is quite intriguing.  相似文献   
3.
The quantum transport of a gated polythiophene nanodevice is analyzed using density functional theory and nonequilibrium Green's function approach. For this typical molecular field effect transistor, we prove the existence of two main features of electronic components, i.e., negative differential resistance and good switching. Ab initio based explanations of these features are provided by distinguishing fixed and shifting conducting states, which are shown to arise from the interface and functional molecule, respectively. The results show that proper functional molecules can be used in conjunction with metallic electrodes to achieve basic electronics functionality at molecular length scales.  相似文献   
4.
The reaction of MnCl2 with TMP (TMP = Trimethyl phosphate) in THF (THF = tetrahydroforan), led to the coordination polymer [Mn23‐DMP)2(μ‐DMP)2]n (1) (DMP = dimethyl phosphate). This complex was characterized by elemental analysis, IR spectroscopy and single‐crystal structure of 1 . Crystal data for 1 at ?173 °C: triclinic, space group , a = 9.7071(11), b = 10.4482(11), c = 10.6242(11) Å, α = 88.892(2)°, β = 80.829(2)°, γ = 87.572(2)°, Z = 2, R1 = 0.0441.  相似文献   
5.
Transport properties of doped nanotube-based double junctions forming a nanotransistor are investigated within the tight binding formalism. The effects of doping, gate length and gate-source hopping have been considered. It is found that in addition to the importance of rotational symmetry in determining transport properties, large gains can be achieved for semiconducting doped tubes. Received 30 November 2000  相似文献   
6.
Covalent organic frameworks are a new class of crystalline organic polymers possessing a high surface area and ordered pores. Judicious selection of building blocks leads to strategic heteroatom inclusion into the COF structure. Owing to their high surface area, exceptional stability and molecular tunability, COFs are adopted for various potential applications. The heteroatoms lining in the pores of COF favor synergistic host–guest interaction to enhance a targeted property. In this report, we have synthesized a resorcinol‐phenylenediamine‐based COF which selectively adsorbs CO2 into its micropores (12 Å). The heat of adsorption value (32 kJ mol?1) obtained from the virial model at zero‐loading of CO2 indicates its favorable interaction with the framework. Furthermore, we have anchored small‐sized Ag nanoparticles (≈4–5 nm) on the COF and used the composite for chemical fixation of CO2 to alkylidene cyclic carbonates by reacting with propargyl alcohols under ambient conditions. Ag@COF catalyzes the reaction selectively with an excellent yield of 90 %. Recyclability of the catalyst has been demonstrated up to five consecutive cycles. The post‐catalysis characterizations reveal the integrity of the catalyst even after five reaction cycles. This study emphasizes the ability of COF for simultaneous adsorption and chemical fixation of CO2 into corresponding cyclic carbonates.  相似文献   
7.
In this paper, we have investigated the structural properties of rotating neutron stars using the numerical RNS code and equations of state which have been calculated within the lowest order constrained variational(LOCV)approach. In order to calculate the equation of state of nuclear matter, we have used UV_(14) +TNI and AV_(18) potentials.We have computed the maximum mass of the neutron star and the corresponding equatorial radius at different angular velocities. We have also computed the structural properties of Keplerian rotating neutron stars for the maximum mass configuration, M_K, R_K, f_K and j_(max).  相似文献   
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