Theoretical study on halide and mixed halide Perovskite solar cells: Effects of halide atoms on the stability and electronic properties

Increasing the stability of perovskite solar cells is one of the most important tasks in the photovoltaic industry. Thus, the structural, energetic, and electronic properties of pure CH₃NH₃PbI₃ and fully doped compounds (CH₃NH₃PbBr₃ and CH₃NH₃PbCl₃) in cubic and tetragonal phases were investigated using density functional theory calculations. We also considered the effects of mixed halide perovskites CH₃NH₃PbI₂X (where X = Br and Cl) and compared their properties with CH₃NH₃PbI₃. The DFT results indicate that the phase transformation from tetragonal to cubic phase decreases the band gap. The calculated results show that the X‐site ion plays a vital role in the geometrical stability and electronic levels. An increase in the band gap and a reduction in the lattice constants are more apparent in CH₃NH₃PbI₂X compounds (I > Br > Cl).     

Further search for selectivity of positron annihilation in the skin and cancerous systems

Positronium annihilation lifetime (PAL) spectroscopy and Doppler broadening energy spectra (DBES) have been used to search for selectivity and sensitivity for cancerous skin samples with and without cancer. This study is to further explore the melanoma cancerous system and other different types of skin samples. We found that the S parameter in melanoma skin samples cut at 0.39 mm depth from the same patient's skin is smaller than near the skin surface. However in 10 melanoma samples from different patients, the S parameters vary significantly. Similarly, among 10 normal skin samples without cancer, the S parameters also vary largely among different patients. To understand the sensitivity of PAS as a tool to detect cancer formation at the early stage, we propose a controlled and systematic study of in vivo experiments using UV-induced cancer skin from living animals.     

Synthesis and biological evaluation of some new class of benzothiazole–pyrazole ligands containing arene ruthenium,rhodium and iridium complexes

Transition Metal Chemistry - Metal complexes 1–9 have been synthesized by reacting the benzothiazole–pyrazole derivative ligands (L1, L2 and L3) with the metal precursors of ruthenium...     

Preparation of self-assembled porous flower-like nanostructured magnetite (Fe3O4) electrode material for supercapacitor application

Journal of Solid State Electrochemistry - Nanostructured electrode materials for supercapacitors have attracted research interest due to their high power density and long cycle life. Herein, porous...     

Water Soluble Nickel – metformin ternary complexes: Thermal,DNA binding and molecular docking studies

The Nickel (II) complexes [Ni(Cl)₂(metf)(o-phen)] (1), [Ni(Cl)₂(metf)(opda)] (2) , [Ni(Cl)₂(metf)(en)] (3) , [Ni(Cl)₂(metf)(2,2'-bipy)] (4) , (metf = metformin, o-phen = ortho-phenanthroline, opda = ortho-phenylenediamine, en = ethylenediamine, 2–2′ bipy = 2–2′ bipyridyl) were synthesized and characterized using LC–MS, elemental analysis, molar conductance measurements, TGA-DTA, IR spectroscopy, magnetic moment measurements and electronic spectroscopy. The central Ni²⁺ was found to be in octahedral geometry. The DNA interaction of these complexes have been studied by UV–visible absorption studies, fluorescence emission technique and viscosity measurement. The complexes showed absorption hyperchromism in UV–visible spectra with calf thymus DNA. The binding constants from UV–visible absorption studies were 7.42 × 10⁴, 0.74 × 10⁴, 3.19 × 10⁴, 5.9 × 10⁴ M⁻¹ for 1 , 2 , 3 and 4 , respectively and Stern-Volmer quenching constants from fluorescence studies were 0.16, 0.41, 0.23, 0.18, respectively. Viscosity measurements revealed that the binding of the complexes with DNA could be surface binding, mainly due to groove binding. The highest DNA cleavage activity of the complexes is recorded for complex 1 . The complexes were docked in to B-DNA sequence, 5′(D*AP*CP*CP*GP*AP*CP* GP*TP*CP*GP*GP*T)-3′ retrieved from protein data bank (PDB ID: 423D), using Discovery Studio 2.1 software. C Docker Intectraction energy of 1 , 2 , 3 and 4 complexes is 32.027, 31.427, 35.393 and 30.521 respectively. The highest docking score is seen for complex 3 .     

Enantioseparation of DPP-4 Inhibitors on Immobilized Crown Ether-Based Chiral Stationary Phase

A group of DPP-4 inhibitors such as alogliptin, linagliptin and saxagliptin were selected for enantioseparation for this study. Crown ether columns contain a chiral crown ether ring as a chiral selector is suitable for the compounds having primary amino groups. Since the selected compounds contain free amino groups, a crown ether column was selected for enantiomeric separation of dipeptidyl peptidase-4 inhibitors. Dipeptidyl peptidase-4 inhibitors are a class of oral hypoglycemics that block dipeptidyl peptidase-4 enzyme and can be used to treat diabetes mellitus type 2. A sensitive HPLC method was developed to separate the enantiomers of each dipeptidyl peptidase-4 inhibitor. Effects of various parameters such as type of solvents, selection of additives, effect of pH and column temperature on chromatographic results were studied. The optimal conditions for the chiral separation of dipeptidyl peptidase-4 inhibitors without any derivatization were investigated.     

Synthesis and molecular structure analysis of venlafaxine intermediate and its analog

1-(cyano-(4-methoxyphenyl) methyl cyclohexanol(2), C₂₄H₃₂N₂O₂, a Venlafaxine intermediate is found to crystallize in both monoclinic(2a) and orthorhombic(2b) crystal systems. The form2a crystallizes in the space groupC2/c with the cell parametersa = 23.506(3),b = 5.550(3),c = 23.192(3), and β = 115.116(2)^∘.2b crystallizes in space groupP2₁2₁2₁ with cell parametersa = 5.7850(6),b = 11.2680(6), andc = 20.6730(19). The intermolecular hydrogen bonding in the case of the monoclinic polymorph leads to the formation of dimer. The synthesis, characterization, and crystal structure studies of Venlafaxine analog 1-[2-1-(4-dimethylamino-phenyl)-ethylideneamino]-1-(4-methoxy-phenyl)-ethyl]-cyclohexanol(4) is reported.4 crystallizes inP―1 space group with cell parametersa = 10.801(7),b = 12.078(7),c = 9.928(5), α = 96.12(5)^∘, β = 110.49(5)^∘, and γ = 112.42(6)^∘.     

An efficient copper-aluminum hydrotalcite catalyst for asymmetric hydrosilylation of ketones at room temperature

A catalyst system consisting of a copper-aluminum hydrotalcite-chiral diphosphine ligand effects asymmetric hydrosilylation of several ketones, using polymethylhydrosiloxane (PMHS) as the stoichiometric reducing agent at room temperature, with moderate-to-excellent enantioselectivities. The catalyst is recovered by simple centrifugation, and the efficiency of the catalyst remains almost unaltered even after several cycles.     

The charge-transfer properties of the S2 state of fucoxanthin in solution and in fucoxanthin chlorophyll-a/c2 protein (FCP) based on stark spectroscopy and molecular-orbital theory

Fucoxanthin chlorophyll-a/c 2 protein (FCP), the membrane-intrinsic light harvesting complex from the diatom Cyclotella meneghiniana, is characterized by Stark spectroscopy to obtain a quantitative measure of the excited-state dipolar properties of the constituent pigments. The electro-optical properties of the carotenoid fucoxanthin (Fx), the primary light harvester in FCP, were determined from the Stark spectrum measured in a MeTHF glass (77 K) and compared to the results from electronic-structure calculations. On photon absorption by Fx, a 17 D change in the static dipole moment (|Delta mu|exp), and a somewhat larger |Delta mu|exp at the red edge, are measured for the S 0 --> S 2 (1 (1)A g (-)-like -->1 (1)B u *+-like) transition. The large change in dipole moment indicates that Fx undergoes photoinduced charge transfer (CT), and underscores the influence of the S 2 state on the polarity-dependent excited-state dynamics of Fx that has so far been attributed to, and discussed in terms of, the S 0 and the S 1/ICT states. MNDO-PSDCI and SACCI-CISD calculations indicate that the 1 (1)B u (*+)-like state intrinsically possesses a dipole moment much smaller than the 2 (1)A g (*-)-like state, suggesting that solvent fields promote the mixing of these two states and could account for the large dipole moments measured here for the S 0 --> S 2 transition. These CT properties of the 1 (1)B u (*+)-like state of Fx are further enhanced in the protein and underpin its photosynthetic capabilities for light harvesting and energy transfer (ET). In FCP, the CT properties of the Fx's vary according to the energetic position: between 450 and 500 nm there appear to be two sets of Fx's that exhibit |Delta mu| exp values on the order of 5 and 15 D, whereas the red-most Fx's, that are very efficient in ET to chlorophyll-a (Chl-a), exhibit strikingly large |Delta mu| exp values on the order of 40 D. Such magnitudes of |Delta mu| exp suggest a mechanism that enhances Coulombic coupling to promote ET from the S 2 state of Fx to Chl-a. These three sets of Fx's, including a fourth red Fx, are identified by fitting the Stark spectrum of FCP with the Stark spectrum of Fx in MeTHF. In contrast to the Fx's in the protein, the electrostatic properties of the Chl's in FCP are comparatively much smaller. Notably, for the Q y band of Chl-a, a |Delta mu| exp of 0.92 D and a change in polarizability ( Delta alpha exp) of 20 A (3), indicate that the Chl-a's are monomeric in nature and decoupled from each other.     

Direct asymmetric aldol reactions catalyzed by nanocrystalline copper(II) oxide

The direct asymmetric aldol reactions of aromatic and heteroaromatic aldehydes with acetone to afford chiral β-hydroxy carbonyl compounds in good yields and good to moderate enantioselectivities are realized using nanocrystalline copper(II) oxide in the presence of (1S,2S)-(−)-1,2-diphenylethylenediamine at −30 °C. The catalyst can be reused for four cycles with consistent activity and enantioselectivity.