Coumarin-based D–π–A dyes for efficient DSSCs: DFT and TD-DFT study of the π-spacers influence on photovoltaic properties

Research on Chemical Intermediates - A series of D–π–A architectures dyes with Coumarin-based derivatives as difluorenylaminocoumarin (DF) and diphenylaminocoumarin (DP) have been...     

Additive preservers of Drazin invertible operators with bounded index

Let B(X) be the algebra of all bounded linear operators on an infinite-dimensional complex or real Banach space X. Given an integer n ≥ 1, we show that an additive surjective map Φ on B(X)preserves Drazin invertible operators of index non-greater than n in both directions if and only if Φ is either of the form Φ(T) = αATA~(-1) or of the form Φ(T) = αBT~*B~(-1) where α is a non-zero scalar,A:X → X and B:X~*→ X are two bounded invertible linear or conjugate linear operators.     

Synthesis,magnetic properties and microstructure of Ni–Zn ferrite by sol–gel technique

In the study, the Ni–Zn ferrite powder of a Ni_0.3Zn_0.7Fe₂O₄ composition was synthesized by sol–gel route using metal acetates at low temperatures. Both the scanning electron microscope and X-ray diffraction analyses of various gel samples heated at different temperatures were used to identify the reaction stages where the amorphous-gel-to-crystalline phase transition occurred. The electrical, magnetic and microstructural properties of the toroidal cores were studied. It was found that the initial permeability increased with a large frequency band (0.1–31.39 MHz) and the magnetic loss was small. The electrical resistivity was higher as compared to the ones which were obtained by the conventional process. Therefore, well–defined polycrystalline microstructure nickel–zinc ferrite and a short processing time of gel preparation have become the major achievements of this study.     

Syntheses and X-ray diffraction, photochemical, and optical characterization of Cu2SixSn1-xS3 (0.4 < or = x < or = 0.6) for photovoltaic applications

The study of the pseudobinary system Cu(2)SnS(3-)Cu(2)SiS(3) shows that a solid solution (Cu(2)Si(x)Sn(1-x)S(3)) exists in the range 0.4 < or = Si/(Sn+Si) < or = 0.6. Based on diffuse reflectance and photoelectrochemical measurements these compounds show potential as absorber materials for photovoltaic devices. The compounds were prepared at 850 degrees C from copper sulfide, silicon, tin, and sulfur and were analyzed with single-crystal (for x approximately 0.40) and powder diffraction techniques. Optical band gaps of 1.25, 1.35, and 1.45 eV were observed for the three compositions x = 0.39, 0.48, and 0.61; cathodic photocurrent occurring is significant.     

Nonlinear preservers involving quadratic operators

Analysis Mathematica - Given two different complex numbers a and b, a bounded linear operator T acting on an infinite-dimensional complex Hilbert space H is said to be {a, b}-quadratic if (T...     

Experimental and Computational Studies on Cobalt(I)-Catalyzed Regioselective Allylic Alkylation Reactions

Here, we report the development of cobalt(I)-catalyzed regioselective allylic alkylation reactions of tertiary allyl carbonates with 1,3-dicarbonyl compounds. A family of well-defined tetrahedral cobalt(I) complexes bearing commercially available bidentate bis(phosphine) ligands [(P,P)Co(PPh₃)Cl] are synthesized and explored as catalysts in allylic alkylation reactions. The catalyst [(dppp)Co(PPh₃)Cl] (dppp=1,3-Bis(diphenylphosphino)propane) enables the alkylation of a large variety of tertiary allyl carbonates with high yields and excellent regioselectivity for the branched product. Remarkably, this methodology is selective for the activation of tertiary allyl carbonates even in the presence of secondary allyl carbonates. This contrasts with the selectivity observed in cobalt-catalyzed allylic alkylations enabled by visible light photocatalysis. Mechanistic insights by means of experimental and computational investigations support a Co(I)/Co(III) catalytic cycle.     

Structural investigation of the Cu2Se-In2Se3-Ga2Se3 phase diagram, X-ray photoemission and optical properties of the Cu1−z(In0.5Ga0.5)1+z/3Se2 compounds

Structures of compounds in the Cu₂Se-In₂Se₃-Ga₂Se₃ system have been investigated through X-ray diffraction. Single crystal structure studies for the so-called stoichiometric compounds Cu(In,Ga)Se₂ (CIGSe) confirm that the chalcopyrite structure (space group I4¯2d) is very flexible and can adapt itself to the substitution of Ga for In. On the other hand a structure modification is evidenced in the Cu_1−z(In_0.5Ga_0.5)_1+z/3Se₂ series when the copper vacancy ratio (z) increases; the chalcopyrite structure turns to a modified-stannite structure (I4¯2m) when z≥0.26. There is a continuous evolution of the structure from Cu_0.74(In_0.5Ga_0.5)_1.09Se₂ to Cu_0.25(In_0.5Ga_0.5)_1.25Se₂ ((i.e. Cu(In_0.5Ga_0.5)₅Se₈), including Cu_0.4(In_0.5Ga_0.5)_1.2Se₂ (i.e. Cu(In_0.5Ga_0.5)₃Se₅). From this single crystal structural investigation, it is definitively clear that no ordered vacancy compound exists in that series. X-ray photoemission spectroscopy study shows for the first time that the surface of powdered Cu_1−z(In_0.5Ga_0.5)_1+z/3Se₂ compounds (z≠0) is more copper-poor than the bulk. The same result has often been observed on CIGSe thin films material for photovoltaic applications. In addition, optical band gaps of these non-stoichiometric compounds increase from 1.2 to 1.4 eV when z varies from 0 to 0.75.