Influence of V-shaped plasmonic nanostructures on beam propagation

The influence of V-shaped plasmonic nanostructures caused by focused ion beam milling on transmission properties are addressed in this paper. In order to evaluate the influence, a finite-difference and time-domain numerical method is employed for simulation of the plasmonic structures flanked with the corrugations with equal groove depth at the exit side of a metal film which is coated on a quartz substrate. Our simulation results have shown that a V-shaped subwavelength central slit/aperture is helpful for beam shaping. It plays a positive and dominant role in transmissivity. However, the V-shaped grooves cause a red shift of the peak wavelength and a broadening of the cut-off wavelength. This leads to the beam diverging in the region of the far field. In the case of the existence of both the V-shaped central slit and the V-shaped grooves, the influence of the grooves is less compared to that of the central slit, and can be ignored theoretically. PACS 02.60.Cb; 02.70.Bf; 07.79.Fc; 42.25.Bs     

Effect of (H2O)n (n = 1–3) clusters on H2O2 + HO → HO2 + H2O reaction in tropospheric conditions: competition between one-step and stepwise routes

ABSTRACT

Effects of (H₂O)_n (n?=?1–3) on the H₂O₂?+?HO?→?HO₂?+?H₂O reaction have been investigated by the reactions of H₂O₂L(H₂O)_n (n?=?1–3)?+?HO and H₂O₂?+?HOL(H₂O)_n (n?=?1–3) at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory, coupled with rate constant calculations by using canonical variational transition state theory. Interestingly, for the former reactions, one-step process and stepwise mechanism are involved, where one-step processes occurring though cage-like hydrogen bonding network complexes and the transition states are favourable. Due to larger effective rate constants, these favourable processes are also favourable than the corresponding latter reactions. Meanwhile, the catalytic effect of (H₂O)_n (n?=?1–3) is mainly taken from water monomer, because the effective rate constant (k'(R_WM2)) of H₂O₂···H₂O?+?HO reaction is, respectively, larger by 3, 6–10 orders of magnitude than that of H₂O₂···(H₂O)₂?+?HO (k'(R_WD1)) and H₂O₂···(H₂O)₃?+?HO (k'(R_WT1)) reactions. Furthermore, the enhancement factor of water molecular (k'(R_WM2)/k_tot) is only 0.28% at 240?K, while at high temperature (such as at 425?K), the positive water vapour effect enhances up to 27.13%. This shows that at high temperatures the positive water effect is obvious under atmospheric conditions.     

Comparisons of numerical methods with respect to convectively dominated problems

A series of numerical schemes: first‐order upstream, Lax–Friedrichs; second‐order upstream, central difference, Lax–Wendroff, Beam–Warming, Fromm; third‐order QUICK, QUICKEST and high resolution flux‐corrected transport and total variation diminishing (TVD) methods are compared for one‐dimensional convection–diffusion problems. Numerical results show that the modified TVD Lax–Friedrichs method is the most competent method for convectively dominated problems with a steep spatial gradient of the variables. Copyright © 2001 John Wiley & Sons, Ltd.     

Peristaltic flow of a Johnson-Segalman fluid through a deformable tube

To understand theoretically the flow properties of physiological fluids we have considered as a model the peristaltic motion of a Johnson–Segalman fluid in a tube with a sinusoidal wave traveling down its wall. The perturbation solution for the stream function is obtained for large wavelength and small Weissenberg number. The expressions for the axial velocity, pressure gradient, and pressure rise per wavelength are also constructed. The general solution of the governing nonlinear partial differential equation is given using a transformation method. The numerical solution is also obtained and is compared with the perturbation solution. Numerical results are demonstrated for various values of the physical parameters of interest.      

A quick algorithm of exposure distribution for fabrication of micro-optical structures

An approximate algorithm of exposure distribution on photoresist for the case of large exposure dose is obtained on the basis of the algorithm reported in [X. Dong, C. Du, S. Li, C. Wang, Y. Fu, Control approach for form accuracy of microlenses with continuous relief, Opt. Express 13 (2005) 1353-1360] via analyzing a PAC concentration distribution inside the photoresist. We analyzed the fabrication errors of the micro-optical structures which are caused by the approximate algorithm. The relief form error originating from the measurement errors of characteristics parameters of the photoresist is analyzed as well. A valid approach for a quick and accurate design of the exposure distribution is provided accordingly. As an example, a saw-tooth grating with 75 μm relief depth was designed and fabricated so as to verify the new algorithm. Our measurement results show that root mean square (rms) value is less than 0.81 μm. The quick algorithm can satisfy the requirements of micro-optical systems for practical applications.     

Minority carrier lifetime control in power semiconductor devices by fast neutron irradiation

A new technology for controlling reduction of minority carrier lifetime of power semiconductor devices was given in this paper, using fast neutron irradiation in nuclear reactor. The effects of high frequency thyristor by fast neutron irradiation is mainly discussed. Furthermore, a comparison is made with electron irradiated, ⁶⁰Co-gamma irradiated and gold diffused devices. The conclusion shows, the trade-off of forward voltage drop and turn-off time of fast neutron irradiated devices is alike with gold diffused devices, while the leakage current is less than that of gold diffused devices, and not different from the electron or Gamma irradiated devices. Moreover, the deep energy levels of fast neutron irradiation in silicon was shown in this paper, and a single dominant level of Ec-0.44eV is identified for controlling minority carrier lifetime.     

MoS2 nanosheets and bulk materials altered lipid profiles in 3D Caco-2 spheroids

MoS₂ nanosheets（NSs） are novel 2 D nanomaterials（NMs） with potential uses in many areas, and therefore oral exposure route to MoS₂ NSs is plausible. Currently, MoS₂ NSs are considered as biocompatible NMs, but there is lacking of systemic investigations to study the interactions of MoS₂ NSs with intestinal cells. In this study, we exposed the 3D Caco-2 spheroids to MoS₂ NSs or MoS₂ powders（denoted as MoS₂-bulk）, and inv...     

以氨基酸酯为轴向配体的铁、锰卟啉配合物的合成及表征

The new six-coordinate complexes (TPP)Fe^Ⅱ(Gly-OMe)₂ C₅₀H₄₂FeN₆O₄ and (TPP)Fe^Ⅱ(β-Ala-OMe)₂ (C₅₂H₄₆FeN₆O₄) wbere TPP=meso-tetraphenyl porphyrinate, Gly-OMe=glycine methyl ester, β-Ala-OMe=β-alanine methyl ester and five-coordinte complex (TPP)Mn^(Ⅱ)(Gly-OMe) (C₄₇H₃₅MnN₅O₂) have been prepared by sodium borohydride method.These complexes were characterized by UV-Vis, IR, ESR, spectra and by elemental analysis. The synthesized divalent iron porphyrins are d⁶ low spin states and their UV-Vis spectra are Hypso type; while divalent manganese porphyrin is d⁵ high spin state and its UV-Vis spectrum is pseudo-Normal type.     

The Pacman effect: a supramolecular strategy for controlling the excited-state dynamics of pillared cofacial bisporphyrins

The molecular recognition properties of dizinc(II) bisporphyrin anchored by dibenzofuran (DPD), Zn2(DPD) (1), were evaluated as a strategy for utilizing the Pacman effect to control the excited-state properties of cofacial bisporphyrin motifs. Crystallographic studies establish that DPD furnishes a cofacial system with vertical flexibility and horizontal preorganization. The structure determination of a substrate-bound DPD species, Zn2(DPD)(2-aminopyrimidine) (2), completes a set of structurally homologous zinc(II) porphyrin host and host-guest complexes, which offer a direct structural comparison for the Pacman effect upon substrate complexation. Binding studies reveal that pyrimidine encapsulation by the DPD framework is accompanied by a markedly reduced entropic penalty (approximately 60 J mol(-1)K(-1)) with respect to traditional face-to-face bisporphyrin systems, giving rise to a smaller conformational energy cost upon substrate binding. Transient absorption spectroscopy reveals that substrate encapsulation within the DPD cleft dramatically affects excited-state dynamics of cofacial bisporphyrins. The emission lifetime of host-guest complex 2 increases by more than an order of magnitude compared to free host 1. In the absence of the guest, the excited-state dynamics are governed by torsional motion of the porphyrin rings about the aryl ring of the DPD pillar. Host-guest binding attenuates this conformational flexibility, thereby removing efficient nonradiative decay pathways. Taken together, these findings support the exceptional ability of the DPD system to structurally accommodate reaction intermediates during catalytic turnover and provide a novel supramolecular approach toward developing a reaction chemistry derived directly from the excited states of Pacman constructs.     

A convergent synthetic approach using sterically demanding aryldipyrrylmethanes for tuning the pocket sizes of cofacial bisporphyrins

Meso substitution opposite to the spacer provides a convenient approach for tuning the pocket sizes of pillared cofacial bisporphyrins. The synthesis and coordination chemistry of xanthene and dibenzofuran anchored platforms structurally modified with 2,6-dimethoxyaryl groups are described. Comparative structural analysis of xanthene derivatives confirms the ability of the trans-aryl groups to adjust the vertical dimension of the cofacial cleft: 7 (C(97)H(106)Cl(4)N(8)O(5)), monoclinic, space group P2(1)/c, a = 28.8353(12) A, b = 17.1139(7) A, c = 17.5978(7) A, beta = 98.826(1) degrees, Z = 4; 8 (C(101)H(123)Cl(2)N(8)O(11.5)Zn(2)), monoclinic, space group P2(1)/n, a = 14.5517(6) A, b = 22.9226(10) A, c = 28.5155(13) A, beta = 90.312(14) degrees, Z = 4; 12 (C(99)H(102)Cl(14)N(8)O(5)Mn(2)), monoclinic, space group P2/c, a = 19.5891(3) A, b = 15.0741(2) A, c = 33.2019(6) A, beta = 91.947(10) degrees, Z = 4. The convenience and versatility of this synthetic method offers intriguing opportunities to specifically tailor the binding pockets of cofacial bisporphyrins for the study of small-molecule activation within a proton-coupled electron transfer framework.