Theoretical Study of Endohedral Fullerenes M@C60 (M = Li,Na, or K) in Periodic Boundary Conditions

Journal of Experimental and Theoretical Physics - Density functional calculations in periodic boundary conditions (PBCs) were performed to investigate the structural and electronic properties of...     

Channel drop filter using photonic crystal ring resonators for CWDM communication systems

In this paper, a new optical channel drop filter (CDF) using photonic crystal ring resonators (PCRRs) is presented. Using the two-dimensional (2D) finite-difference time-domain (FDTD) method in triangular lattice photonic crystal (PC) silicon rods, 100% forward dropping efficiency and a quality factor of more than 1000 can be achieved in third communication window while the resonant wavelength is 1550 nm. Through this novel (CDF), a multi-CDF operation with 100% drop efficiencies across all channels can be obtained. The proposed device could be used in future coarse wavelength division multiplexing (CWDM) communication systems.     

PBE–DFT theoretical study of organic photovoltaic materials based on thiophene with 1D and 2D periodic boundary conditions

Conjugated organic systems such as thiophene are interesting topics in the field of organic solar cells. We theoretically investigate π-conjugated polymers constituted by n units (n = 1–11) based on the thiophene (Tn) molecule. The computations of the geometries and electronic structures of these compounds are performed using the density functional theory (DFT) at the 6–31 G(d, p) level of theory and the Perdew–Burke–Eenzerhof (PBE) formulation of the generalized gradient approximation with periodic boundary conditions (PBCs) in one (1D) and two (2D) dimensions. Moreover, the electronic properties (HOCO, LUCO, E _gap, V _oc, and V _bi) are determined from 1D and 2D PBC to understand the effect of the number of rings in polythiophene. The absorption properties—excitation energies (E _ex), the maximal absorption wavelength (λ_max), oscillator strengths, and light harvesting—efficiency are studied using the time-dependent DFT method. Our studies show that changing the number of thiophene units can effectively modulate the electronic and optical properties. On the other hand, our work demonstrates the efficiency of theoretical calculation in the PBCs.     

Optical channel drop filters based on photonic crystal ring resonators

A new optical channel drop filters (CDFs) configuration based on photonic crystals ring resonators (PCRRs) is provided. The transmission characteristics for single-ring and multiple-ring configurations have been investigated by using the two-dimensional (2D) finite-difference time-domain (FDTD) technique in triangular lattice photonic crystal (PC) silicon rods. Both forward and backward dropping were achieved in dual-ring PCRR structures. In this filter, 100% drop efficiency and acceptable quality factor can be obtained at 1550 nm. The present device can be used in the future photonic integrated circuits.     

Synthesis and Anti‐proliferative Activity of Novel Polysubstitued Indazole Derivatives

A simple and efficient process is developed for the synthesis of new N‐(1‐alkyl‐3‐chloro‐4‐ethoxy‐1H‐indazol‐5‐yl)‐arylsulfonamides 4a – d and N‐(1‐alkyl‐3‐chloro‐1H‐indazol‐5‐yl)‐arylsulfonamides 5a – d through the reduction of 1‐alkyl‐3‐chloro‐5‐nitroindazoles 2a , b with SnCl₂ in ethanol followed by coupling the corresponding amine with arylsulfonyl chlorides in pyridine. All the newly synthesized compounds have been characterized by elemental analysis and spectroscopic data. Some compounds were tested for their in vitro antiproliferative activities against two selected human cancer cell lines A2780 and A549. Among all of these derivatives, compound 5d showed the most potent antiproliferative activity against A2780 (IC₅₀ = 5.47 ± 1.45 μM) and A549 (IC₅₀ = 7.73 ± 1.66 μM) cell lines.